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FIELD OF THE INVENTION
This invention relates to power saving in a communication unit operating in a communication system. The invention is applicable to, but not limited to saving processing power in the management of radio link admission control and/or scheduling, and/or overload or flow control, in a wireless communication system.
BACKGROUND OF THE INVENTION
Wireless communication systems, for example cellular telephony or private mobile radio communication systems, typically provide for radio telecommunication links to be arranged between a plurality of base transceiver stations (BTSs) and a plurality of subscriber units, often termed mobile stations (MSs). Base station contollers (BSCs) are provided, each BSC controlling one or more BTS.
Wireless communication systems are distinguished over fixed communication systems, such as the public switched telephone network (PSTN), principally in that mobile stations move between BTS (and/or different service providers) and in doing so encounter varying radio propagation environments.
In a wireless communication system, each BTS has associated with it a particular geographical coverage area (or cell). A particular range defines the coverage area where the BTS can maintain acceptable communications with MSs operating within its serving cell. Often these cells combine to produce an extensive coverage area.
Present day communications systems, both wireless and wire-line, have a requirement to transfer data between communications units. Data, in this context, includes speech communication. Such data transfer needs to be effectively and efficiently provided for, in order to optimise use of limited communication resources.
One such wireless communication system is the third generation partnership project (3GPP) standard supporting wide-band code-division multiple access (WCDMA) relating to the Universal mobile telecommunication system (UMTS) radio access network (RAN) known as UTRAN. The European Telecommunications Standards Institute (ETSI) is defining the 3GPP standard.
Within UMTS nomenclature, the base transceiver station (BTS) is called a node B, and a base station controller (BSC) is called a radio network controller (RNC).
Within the UTRAN, many communication resources need to be managed effectively, for example:
(i) The air interface (i.e. CDMA power and code) resource, with separate air interface resources for, say, each cell. (ii) The backhaul resource supporting, for example limited capacity E1 links, with separate resources for, say, each Node B. (iii) Node B hardware/software resources, for example managing the Node B's processing capability (e.g. as defined by the microprocessors, back-plane networking, etc.), may limit the throughput of data that is achievable within a cell. (iv) RNC Hardware/software resources.
In some conventional systems, the same (or at least a similar) set of QoS management algorithms must be applied to each resource. These QoS management algorithms include:
(i) Admission control: performed when a new call enters the system/cell. Admission control has an objective of determining whether QoS will be maintained for all connections, if the new call is admitted. (ii) Scheduling: performed every frame. Scheduling has an objective of ensuring that the number of data packets submitted for transmission will not exceed the capacity available over a short time period, such as a 10 msec. frame. (iii) Overload control: used if the aforementioned admission control and/or scheduling mechanisms fail in their function, in order to rectify the situation. Actions might include ‘call pre-emption’ in which low priority calls are thrown off the system. (iv) Flow control: This could be considered a sub-category of overload control, and is at least related to overload control. Flow control causes the source rate to be decreased in order that the system does not become congested.
Running all four of these QoS control mechanisms, for each of the many UTRAN resources, consumes a significant amount of processing power in terms of mega instructions per second (MIPS). The processing impact is felt principally in the radio network controller (RNC) in the 3GPP system, but also in the Node B.
The inventors of the present invention have recognised and appreciated that current QoS management algorithms address all resources with equal regard. Hence, there is no consideration as to their relative importance in limiting the data throughput of the network. It is possible that in some, perhaps even most, instances, a few of the UTRAN resources will be over-dimensioned with respect to the others. For these (relatively speaking) over-dimensioned resources, the MIPS consumed in performing the QoS management functions will be wasted, since other resources will represent a bottleneck in limiting a data throughput performance.
Thus, there exists a need in the field of this invention, to provide an improved QoS management methodology, particularly in cellular base-site resources in a wireless communication system (where transmission delay is a constraint), wherein the abovementioned disadvantages may be alleviated.
STATEMENT OF INVENTION
In accordance with a first aspect of the present invention, there is provided a communication system, as claimed in claim 1 .
In accordance with a second aspect of the present invention, there is provided a method of reducing power consumption in a system management function (e.g. an RNC) in a communication system, as claimed in claim 15 .
In accordance with a third aspect of the present invention, there is provided a 3GPP wireless communication system, as claimed in claim 23 .
In accordance with a fourth aspect of the present invention, there is provided a radio network controller, as claimed in claim 24 .
In accordance with a fifth aspect of the present invention, there is provided a storage medium, as claimed in claim 25 .
In accordance with a sixth aspect of the present invention there is provided a radio network controller, as claimed in claim 26 .
The inventive concepts of the present invention provide a mechanism for identifying the bottleneck resources in a wireless communication system. In this regard, the provision and management of access to the resources is focused on primarily the bottleneck resources. Management of other resources can be adapted accordingly, such that processing power (in terms of MIPS) can be saved. When applied to a 3GPP system, processing power in an RNC (and, to a lesser extent, a Node B) can be saved, such that the RNC (and/or Node B) could be designed to operate more efficiently and effectively. In this manner, the improved RNC (and/or Node B) is able to serve the same number of Erlangs as a similar element in a conventional system, but for less cost due to the reduced processing capabilities required.
In summary, the inventive concepts of the present invention provide a mechanism for identifying a resource bottleneck in a communication system. Additionally, the inventive concepts propose a mechanism for prioritising management algorithms to focus primarily on the bottleneck resource. Once access to the bottleneck resource performance has been managed, a reduced (if any) level of management algorithm MIPS is applied to other resources. Thus, by circumventing management of resources when no benefit can be gained due to the bottleneck limitations incurred by another resource, processing power can be saved.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:
FIG. 1 illustrates a schematic diagram of an example of a throughput capability of each of the UTRAN resources, determined and responded to according to a preferred embodiment of the present invention;
FIG. 2 shows a block diagram of a 3GPP cellular radio communications system adapted to support the various inventive concepts of a preferred embodiment of the present invention;
FIG. 3 illustrates a flowchart of a scheduler scheduling data packets for transmission dependent upon a number of resources used in the transmission in accordance with the inventive concepts of a preferred embodiment of the present invention; and
FIG. 4 illustrates a flowchart of admission control for transmission of data packets dependent upon a number of resources used in the transmission according to a preferred embodiment of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
In the context of the present invention, any reference to power saving should be viewed as encompassing saving of processor resources, for example in terms of mega instructions per second (MIPS).
The preferred embodiments of the present invention selectively apply QoS algorithms to one or more system resources, but notably not all system resources to the same degree. The preferred application of the present invention is a 3GPP wireless communication system architecture. In this regard, the present invention introduces a concept of an ‘active set’. The ‘active set’ is a list of the bottleneck UTRAN resources for which a substantial number, and preferably all, QoS management algorithms will be run. The QoS management algorithms in this context preferably comprise: scheduling and admission control.
In summary, the inventive concepts of the present invention provide a mechanism for identifying a resource bottleneck in a communication system. A mechanism for prioritising the QoS management algorithms is proposed, to focus on the bottleneck resource. Once the bottleneck resource performance has been optimised, a reduced (if any) level of management is applied to the other resources. By avoiding running management algorithms for resources when no benefit can be gained due to the bottleneck limitations incurred by another resource, processing power can be saved.
Referring now to FIG. 1 , a schematic diagram 100 illustrates a throughput capability of each of the UTRAN resources. In this illustration, the throughout of each resource may be visualised as a pipe of a given size. In the illustration of FIG. 1 , the I ub /I ur backhaul resource 115 is clearly the bottleneck in the delivery of communication services as this resource has the smallest diameter (data throughput) pipe, when compared to the RNC or Node B hardware/software resource 105 , 110 , or the air-interface resource 120 .
In accordance with the preferred embodiments of the present invention, once the ‘bottleneck’ has been identified, the efficiency improvement algorithms such as running admission control and scheduling algorithms are applied to this ‘bottleneck’ resource alone. In this manner, the ‘system’ is able to save on its processing requirements, when compared to current systems, and still provide the same level of service.
Referring now to FIG. 2 , a cellular-based telephone communication system 210 supporting a Universal Mobile Telecommunications Standard (UMTS) air-interface is illustrated, in outline, in accordance with a preferred embodiment of the invention. In particular, the described embodiment relates to the Third Generation Partnership Project (3GPP) specification for wide-band code-division multiple access (WCDMA) standard relating to UTRAN.
A plurality of subscriber units 212 – 216 communicates over the selected air-interface 218 – 221 with a plurality of Node Bs 222 – 232 . A limited number of subscriber units 212 – 216 and Node Bs 222 – 232 are shown for clarity purposes only. Each Node B 222 – 232 contains one or more transceiver units and communicates with the rest of the cellular system infrastructure via I ub interface 235 . The Node Bs 222 – 232 may be connected to external networks, for example, the public-switched telephone network (PSTN) or the Internet 234 through Radio Network Controller stations (RNC) 236 – 240 and any number of mobile switching centers (MSCs) 242 and Serving GPRS Support Nodes (SGSN) 244 .
Each RNC 236 – 240 may control one or more Node Bs 222 – 232 . Each MSC 242 (only one shown for clarity purposes) provides a gateway to the external network 234 , whilst the SGSN 244 links to external packet data networks.
The Operations and Management Center (OMC) 246 is operably connected to RNCs 236 – 240 and Node Bs 222 – 232 (shown only with respect to Node B 226 and Node B 228 for clarity), and administers and manages functions within the cellular telephone communication system 210 , as will be understood by those skilled in the art.
In accordance with a preferred embodiment of the present invention, one or more RNCs 236 – 240 has been adapted to include a bottleneck detector function. The functionality of the bottleneck detector function is described below, particularly with regard to the decision process of adding an identified bottleneck resource to an ‘active set’, or removing an identified bottleneck resource from an ‘active set’.
In addition, a scheduler typically run in the one or more RNCs 236 – 240 to schedule the transmission of data packets has also been adapted. The scheduler is operably coupled to the bottleneck detector function and has been adapted to schedule data packets according to a determined prioritisation. In particular, the data packets are scheduled according to whether a bottleneck resource, as identified by the RNC, will allow the data packet to pass therethrough.
Furthermore, in the preferred embodiment of the present invention, an admission control function/algorithm typically run in the one or more RNCs 236 – 240 has also been adapted. The admission control function/algorithm is operably coupled to the bottleneck detector function and has been adapted to admit a user requesting access according to a determined prioritisation. In particular, the admission control function/algorithm is based on whether a bottleneck resource, as identified by the RNC, will support the transmissions of the requesting user.
More generally, one or more RNCs effectively perform an improved system management function, where the RNCs are programmed, in any suitable manner, according to the preferred embodiment of the present invention. For example, new apparatus may be added to a conventional communication unit (for example RNC 236 ). Alternatively existing parts of a conventional communication unit may be adapted, for example, by reprogramming one or more processors therein. As such the required adaptation (to introduce a bottleneck detector or adapt a scheduler and/or an admission control function) may be implemented in the form of processor-implementable instructions stored on a storage medium, such as a floppy disk, hard disk, programmable read only memory (PROM), random access memory (RAM) or any combination of these or other storage media.
Although the preferred embodiment of the present invention is described with reference to a bottleneck detector and improvements to the efficient usage of, say, one or more QoS management algorithms such as a scheduler and/or an admission control function/algorithm relating to an RNC's operation, it is envisaged that these functions/algorithms may reside in other network elements. For example, it is envisaged that the inventive concepts in adapting the system's performance in response to a detected bottleneck resource may be implemented daily or weekly. In this regard, the aforementioned functions/algorithms may be located in, say, the OMC 246 , in contrast to the dynamic adaptation provided when the aforementioned functions/algorithms are preferably located in the RNC.
It is also within the contemplation of the invention that such aforementioned functions/algorithms may reside in other network elements, or alternatively be distributed amongst two or more such network elements in wireless communication systems. Furthermore, alternative radio communication architectures could benefit from the inventive concepts described herein, and the inventive concepts are not considered as being limited to the specific configuration illustrated in FIG. 2 .
In a first embodiment of the present invention, the ‘active set’ is configured to include all UTRAN resources. The QoS algorithms are optimised to exploit the findings of the bottleneck detector in the RNC. In this first embodiment, all resources are considered within the ‘active set’. The RNC determines the likelihood of each resource being a data throughput bottleneck, which limits the data throughput performance of the system. The determination is preferably made using one of the following measurements, which are further described later:
(i) The frequency at which the overload control function is initiated; or (ii) Through measurements of the percentage utilisation of the resource.
Let us now consider how the respective QoS mechanisms have been adapted to support the inventive concepts of the present invention.
Scheduler Algorithm
In the preferred embodiment of the present invention, the scheduler algorithm in the UTRAN runs, for example, every radio frame and schedules all the queued data packets for transmission in the next frame.
A known scheduler operation takes a data packet at a head of a data queue and determines, in a serial, per-data packet manner, whether the introduction of that data packet will overload any of a number of resources. All resources are checked in the known scheduler operation, with equal importance allocated to the resources. The resources could be, for example, code consumption, power consumption, backhaul bit-rate consumption, etc.
If the scheduler determines that the introduction of the data packet will overload a particular resource, the scheduler terminates the scheduling operation. Alternatively, the scheduler operation is terminated when the data packet queue is exhausted.
A problem with this known approach is that unnecessary checks are made for every data packet, checking per-data packet consumption for each and every resource. The inventors of the present invention have identified this as wasteful, particularly in scenarios where the resource is plentiful. For example, a downlink scheduler may be code limited, i.e. it stops scheduling when the code resource is exhausted. When the scheduler stops, the power and backhaul utilisation may be very low, say at 50%, but a determination has been made as to the consumption of these resources for every data packet scheduled. Thus, this adds unnecessary loading onto the scheduler processor.
The improved scheduler operation, adapted in accordance with a preferred embodiment of the present invention, is illustrated in the flowchart 300 of FIG. 3 . First, the RNC identifies a primary bottleneck resource, for example resource ‘A’, in step 302 . Then, the scheduler operation commences by taking a data packet at the head of a queued data stream, as shown in step 305 .
In the preferred embodiment of the present invention, a determination is first made as to the resource that is most likely to limit the data packet throughput, i.e. the resource that would typically reach 100% utilisation before the others. Thus, this (bottleneck) resource is allocated the highest priority in the scheduling determination process. The limitation imposed by the bottleneck resource, termed resource ‘A’, is determined in step 310 . Notably, the scheduler assesses the impact of each received data packet only against this resource ‘A’, as data packets are added to the schedule, as in step 315 . This process of introducing further data packets from the queue is continued until resource ‘A’ is fully utilised.
Thereafter, once resource ‘A’ is exhausted, the process checks the consumption of the second resource, ‘B’, as shown in step 320 . It is expected that resource ‘B’ would be the next highest priority resource, i.e. the second worst bottleneck identified from the number of resources. Resource ‘B’ is therefore likely operating below full utilisation at this point, as resource ‘A’ is typically the limiting resource. However, this relationship may not necessarily be true, so preferably the remaining resources are checked. If resource ‘B’ is fully utilised, data packets are removed from the schedule, in step 325 until the utilisation of resource ‘B’<=100%. Notably, consumption of resource ‘A’ will now be <100%.
In an enhanced embodiment of the present invention, an intelligent decision is made as to which data packet(s) is/are removed from the schedule. In this context, it is envisaged that it would be better to remove data packets that have the greatest use of resource ‘B’. For example, if resource ‘B’ is backhaul bandwidth, the data packets that consume the greatest size (in bits) are removed from the schedule.
This process continues, as shown for example in steps 330 , 335 , taking the next highest priority resource until a schedule is found for which all resources are at <=100% usage. The scheduler process is then complete, as shown in step 345 .
It is clear that the above scheduling algorithm may involve as few as 1/n process steps of the known consumption-checking algorithm, where n is the number of resources to be checked. Furthermore, as shown in the mapping table, the bottleneck detector has employed, in step 340 , a ‘mean utilisation’ as a metric to order/prioritise the respective resources. In this manner, the bottleneck resource is the resource that has the highest percentage mean utilisation. It is envisaged that in other embodiments a peak or a variable or fixed percentile loading could be used.
Admission Control Algorithm
Admission control is a process for determining whether, or not, resources are to be granted to a requesting communication device. Inefficient operation of admission control is possible when the admission control algorithm does not examine, in an optimum sequence, the admission request against the resources that are currently available. A preferred mechanism for implementing admission control is illustrated in the flowchart 400 of FIG. 4 .
The preferred mechanism commences in step 402 with the RNC identifying resource ‘A’ as a primary bottleneck resource. The RNC receives a request, in step 405 , of a call admission attempt. A determination is then made as to whether the admission of the call requires allocation of resource; say resource ‘A’ in step 410 , which is greater than the available capacity of resource ‘A’. If the requested amount of resource ‘A’ is greater than the capacity of resource ‘A’ the call is not admitted, as shown in step 430 . Resource ‘A’ has been previously identified by the RNC as being the likely bottleneck resource in terms of data throughput. Consequently, resource ‘A’ is allocated the highest priority in the admission control process.
If resource ‘A’ has sufficient capacity to accommodate the call in step 410 , a determination is made as to whether the requirements of a second resource, say resource ‘B’ in step 415 , is greater than the capacity provided by resource ‘B’. If the requested amount of second resource ‘B’ is greater than the available capacity of resource ‘B’, the call is not admitted, as shown in step 430 .
Similarly, if resource ‘B’ has sufficient capacity to accommodate the call in step 415 , a determination is made as to whether the requirements of a third resource, say resource ‘C’ in step 420 , is greater than the available capacity of resource ‘C’. If the requested amount of resource ‘C’ is greater than the available capacity provided by resource ‘C’ the call is not admitted, as shown in step 430 . This process continues until all resources have been checked, at which time the call is admitted, as shown in step 425 .
In accordance with the preferred embodiment of the present invention, a tracking process is introduced to count a failure rate of admission attempts for a particular resource. If the proportion of admission failures on a certain resource, compared to the total number of admission requests as measured over some preceding time interval, exceeds a given threshold, then the resource should be moved further up the list of resources to be checked. In this manner, the resource will be checked earlier in future. Furthermore, in the same manner as the above scheduling operation, the resources ‘A’, ‘B’ and ‘C’ (and any others) are prioritised in an order of the likelihood of an admission failure. This ordering process is preferably based on the failure count statistics.
In this manner, the number of checks required for a call admission attempt that will ultimately fail is minimised, i.e. the ordering of the resource checks has been configured such that the admission control process would likely fail at the first step of checking resource ‘A’.
Advantageously, this algorithm delivers a significant benefit during periods of high load, when blocking is occurring regularly and when the RNC processors are already under a heavy load stress.
In accordance with a second embodiment of the present invention, the active set is deemed a subset of the UTRAN resources. In this context, the reduction in MIPS is achieved by performing QoS management only on those resources in the active set, i.e. the one or more resources that have been identified as bottleneck UTRAN resources. It is noteworthy that, in the second embodiment, overload detection and reaction mechanisms are in place for all UTRAN resources and will be in an ‘active’ operational mode all of the time.
Also, in this second embodiment, the active set of UTRAN resources most preferably is configured to be adaptable in that the resources could be dynamically added to, or removed from, the active set. Preferably, at cell set-up (i.e. Node B power on) all UTRAN resources will be configured to be in the active set.
Thereafter, it is envisaged that a UTRAN resource will be added to the active set list if, over some preceding time interval or over some preceding number of scheduling/admission control events, one or more overload alarms were raised corresponding to that particular UTRAN resource.
In a similar manner, it is envisaged that a UTRAN resource will be removed from the active set if a limitation due to that particular resource has NOT been logged as one of the reasons that prevented a packet to be scheduled, or a call to be admitted. Again, this determination is carried out over some preceding time interval or over some preceding number of scheduling and/or admission control events. In addition, it is preferred that at least one UTRAN resource remains in the ‘active set’ list. In this case, for the one remaining UTRAN resource in the active set list, all the relevant QoS mechanisms (admission control, scheduling, flow control, overload control) will be applied.
TABLE 1
Indication of UTRAN resources versus QoS
algorithm for one ‘active set’
Perform
Perform
UTRAN
admission
Perform
flow
resource
control
scheduling
control
in active
for the
for the
for the
UTRAN resources
set?
resource?
resource?
resource?
RNC hardware/
Yes
Yes
Yes
Yes
software
Backhaul
Yes
Yes
Yes
Yes
resource (Iub,
Node B #1)
Backhaul
No
No
No
No
resource (Iub,
Node B #2)
Backhaul
Yes
Yes
Yes
Yes
resource (Iur,
RNC n–RNC p)
Backhaul
No
No
No
No
resource (Iur,
RNC n–RNC q)
Node B
No
No
No
No
hardware/
software
(Node B#1)
Node B
Yes
Yes
Yes
Yes
hardware/
software
(Node B#2)
Air interface
Yes
Yes
Yes
Yes
resource (Cell
#1)
Air interface
No
No
No
No
resource (Cell
#2)
If a UTRAN resource is in the active set then all QoS management functions are run. Note that in a practical system there will be many more UTRAN resources than the limited number shown in Table 1.
In an enhanced feature of the second embodiment of the present invention, an active set is associated with each of the QoS management mechanisms: admission control, scheduling. The particular QoS mechanism is ‘run’ only for those UTRAN resources in the active set. Preferably, each QoS management mechanism is configured to operate on their respective timescale, for example:
(i) An admission control function may be configured to manage an average number of resources on a relatively long time scale (say, in terms of seconds), whereas (ii) A scheduler may manage schedule resources on a shorter timescale (say, of the order of 10 msec).
It is also envisaged that different overload control mechanisms can be triggered over different timescales. In the case of some resources (in this example we will consider the air interface), the notional resource pipe size may be subject to relatively large fluctuations on a short timescale, whilst being reasonably constant over a longer timescale. Hence, for example, it might be important to perform air interface scheduling, whilst it might not be necessary to perform air interface admission control.
TABLE 2
Indication of UTRAN resources versus Qos
algorithm with one ‘active set’ per QoS algorithm
UTRAN
UTRAN
resources in
UTRAN
resources in
“admission
resources in
“flow
control”
“scheduling”
control”
UTRAN resource
active set
active set
active set
RNC hardware/
Yes
Yes
Yes
software
Backhaul
Yes
Yes
No
resource
Node B hardware/
No
Yes
No
software
Air interface
No
No
No
resource
Table 2 indicates three active sets for this enhancement to the second embodiment, one for each QoS mechanism. Again, in a practical system, there will be many more UTRAN resources than the limited number shown in Table 2.
Alternatively, one could define the set of QoS mechanisms that manages resources on a given timescale. Then, for each timescale, it is possible to define the UTRAN resources for which the applicable QoS mechanisms will be applied, as shown below in Table 3.
TABLE 3
Indication of UTRAN resources versus QoS
algorithm with timer implications
UTRAN
UTRAN
UTRAN resources
resources in
resources in
in a 1 sec. Qos
“10 ms QoS
“100 ms QoS
mgmt timescale
mgmt
mgmt
active set.
timescale”
timescale”
Admission
active set
active set
control/
UTRAN
scheduling
flow control
overload control
resource
applied
applied
applied
RNC hardware/
Yes
Yes
Yes
software
Backhaul
Yes
Yes
No
resource
Node B
No
Yes
No
hardware/
software
Air interface
No
No
No
resource
Table 3 illustrates three active sets, one for each QoS management timescale, where different QoS mechanisms are applied for each timescale.
In this enhancement of the second embodiment, it is envisaged that a UTRAN resource may be added to the active set list, for a QoS mechanism/QoS management timescale, if an overload control alarm is triggered for that resource. The measurement is preferably performed over the corresponding QoS management time period. Similarly, a UTRAN resource may be removed from the active set list for a given QoS mechanism/QoS management timescale if a limitation in the resource has NOT been logged as one of the reasons that prevented a packet to be scheduled or a call to be admitted. Again, it is envisaged that this determination is performed over some preceding time interval or over some preceding number of scheduling and/or admission control events.
Furthermore, the above mechanisms for adding resources to, or removing resources from, the active list would require that there had been no overload alarm raised corresponding to that particular UTRAN resource over the preceding time interval or number of scheduling and/or admission control events. In addition, it is preferred that at least one UTRAN resource remains in the ‘active set’ list, for that QoS management mechanism or the QoS management mechanism timescale.
In a yet further enhancement of the second embodiment, it is envisaged that reliance on overload control alarm triggering as a mechanism for modifying the active set could be reduced or removed. The alternative approach could be to perform regular measurements of the loading on each of the resources, and to make add or drop decisions on the basis of the current loading. Such a mechanism will beneficially reduce the (unwanted) occurrence of overload.
For simplicity reasons only, let us consider a case where there is just one active set. At cell set-up (i.e. Node B power on), all UTRAN resources will be in the active set. Regular measurements of the load on each of the UTRAN resources are then performed. It is envisaged that the load measurement could be averaged or could, for example, be the x th percentile. Either way, in this example, measures of load would be expressed as a percentage of the total UTRAN resource capacity.
Thus, a UTRAN resource will be removed from the active set if, for example, the UTRAN resource load is less than, say, Threshold_ 1 and has been for some time period T_ 1 . Furthermore, a UTRAN resource will be added to the active set list if, for example, the UTRAN resource load is greater than, say, Threshold_ 2 , and has been for some time period T_ 2 .
It is also within the contemplation of the present invention that any combination of the above inventive concepts could be employed. For example, it is envisaged that there could be an active set per QoS mechanism or per QoS mechanism timescale. In this regard, say at regular intervals, the particular loading as measured over certain timescales (e.g. 10, 100 or 1000 msec's) is determined for all UTRAN resources. If a certain loading criteria (threshold) is met, then a UTRAN resource will be added to, or removed from, the active set list.
Furthermore, it is envisaged that whenever an overload on a resource is identified, the resource could be immediately added to the active set.
It is also within the contemplation of the present invention that a decision on the specific QoS management mechanisms to apply for a given resource could be made ‘off-line’. In this context, the decision may be encoded as an OMC parameter. Off-line dimensioning calculations and/or experience through trial and error and/or expert systems could be used to as part of this process.
Although the preferred embodiment of the present invention has been described with reference to a bottleneck identifier in the context of a UTRAN 3GPP system, it is envisaged that the inventive concepts are equally applicable to other telecommunication systems, wireless or wire line, including for example core networks or backbone networks.
For completeness, it is worth clarifying how the reduced complexity (power in terms of MIPS) requirement may be exploited in practice. However, a skilled artisan would appreciate that the inventive concepts described herein can be exploited in a number of other ways, and therefore the inventive concepts are not limited to the mechanisms described below.
When a wireless communication network is currently installed, it is necessary that an RNC has a processing capability approximately equal to that deemed necessary to support the worst-case scenario. In this regard, the RNC needs to be configured sufficiently to accommodate all UTRAN resources. This typically results in some inefficiency on initial network installation, since it is to be expected that typically the RNC would be under-utilised in some respects. Furthermore, as the network load increases and more Node Bs are added, the inefficiencies of the RNC processor increase.
Therefore, it will be understood that the improved QoS management methodology where the bottleneck detection algorithm is running, as described above, provides at least the following advantages:
(i) Decisions on whether to add additional RNC processor resource can be taken at the OMC by monitoring the load on the RNC's processor resource. (ii) The rate at which RNC cards would have to be added in order to support a higher network load would be reduced. (iii) Where some of the QoS processing is performed in the Node B (e.g. hardware/software admission control), the technique will also result in a reduction in signalling and call set-up delays on the occasions where the Node B hardware/software resource is not a bottleneck resource.
Whilst the specific and preferred implementations of the embodiments of the present invention are described above, it is clear that one skilled in the art could readily apply variations and modifications to the preferred embodiments that fall within the inventive concepts.
Thus, a communication system and method for reducing power consumption in a communication system have been provided wherein the aforementioned disadvantages of the prior art have been substantially alleviated. | A communication system ( 200) comprises a system management function ( 246) for managing base-site resources and system throughput of data. The system management function ( 246) defines a number of resources. The system management function ( 236), such as a radio network controller, comprises a data throughput identification function to identify one or more bottleneck resources from a sub-set of system resources involved in the system's data throughput. A method of reducing power consumption (MIPS) in a system management function ( 236) and a radio network controller ( 236) are also provided. The identification of a bottleneck resource helps determine whether MIPS could be saved by not performing one or more QoS management algorithms, the benefit from which is reduced due to the bottleneck resource. |
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to PCT/EP2013/054769 filed Mar. 8, 2013, which claims priority to European application 12162180.9 filed Mar. 29, 2012, both of which are hereby incorporated in their entireties.
TECHNICAL FIELD
[0002] The present invention relates to the technology of combined cycle power plants with CO2 capture and storage capability. It refers to a method for operating a combined cycle power plant according to the preamble of claim 1 . It further refers to a combined cycle power plant for using the method.
BACKGROUND
[0003] FIG. 1 shows a simplified diagram of a combined cycle power plant (CCPP) with an integrated carbon capture and storage (CCS) facility. The combined cycle power plant 10 of FIG. 1 comprises a gas turbine 11 , the water/steam cycle 12 , a flue gas cooling circuit 13 and a CO2 capture unit 14 .
[0004] The gas turbine 11 is of the sequential combustion type and comprises a compressor 15 , which compresses ambient air 18 , a first combustor 16 , a first turbine 17 , a second combustor 16 ′ and a second turbine 17 ′. The exhaust gas of the second turbine 17 ′ passes a heat recovery steam generator 19 , which is part of the water/steam cycle 12 . The heat of the exhaust gas is used to generate steam within the heat recovery steam generator 19 . The steam drives a set of steam turbines, which comprises a high-pressure steam turbine 20 , and according to requirements an intermediate-pressure steam turbine and furthermore according to requirements a low-pressure steam turbine. The steam, which exits the last steam turbine, is condensed in the condenser 24 , and the resulting water is pumped back to the heat recovery steam generator 19 by means of feedwater pump 25 .
[0005] An intermediate extraction steam from the steam turbine 20 is introduced into the CO2 Absorber 33 , as the line 23 shows.
[0006] After having passed the heat recovery steam generator 19 , the exhaust gas is divided in a subsequent stack damper 26 into a first part, which enters a stack 28 , and a second part, which passes a louvre damper 27 and enters the flue gas cooling circuit 13 , where it is cooled down in a cooler 29 . The cooler 29 as part of the cooling water circuit comprising according to requirements a heat exchanger and a pump.
[0007] After being cooled down, the exhaust gas is fed by means of a blower 32 into a CO2 absorber 33 within the CO2 capture unit 14 . The captured CO2 leaves the CO2 absorber 33 to be compressed by means of a compressor 34 . The compressed CO2 35 is then ready to be stored.
[0008] The CO2 absorber 33 is operated with steam extracted with pressure according to requirements at a steam extraction 23 from the steam turbine 20 , or preferable between intermediate-pressure steam turbine and low-pressure steam turbine. Remaining gas from the absorber 33 is conducted to a stack 37 , while condensate 36 is fed back into the water/steam cycle 12 .
[0009] In case that a flue gas recirculation is provided, a flue gas recirculation path 38 leads from the CO2 capture unit 14 to the inlet of the gas turbine 11 . The typical pressures p 1 to p 7 at various points of the power plant 10 according to FIG. 1 are:
[0000]
p1 (gas turbine back-pressure)
35
mbar
p2 (HRSG exit)
0
mbar
p3 (after louvre damper 27)
−5
mbar
p4 (at cooler exit)
−25
mbar
p5 (at blower inlet)
−30
mbar
p6 (at blower exit)
65
mbar
p7 (at absorber exit)
0
mbar.
[0010] In a power plant configuration as shown in FIG. 1 , the required power for the blower 32 can be of the order of several MW (e.g. 8.5 MW). This has a large, negative impact on plant performance, when CO2 is captured. Furthermore, blower efficiency typically falls significantly when running off-design, meaning that part-load operation is penalized.
[0011] The capture rate of the CO2 capture unit 14 is also affected by deviation from the design point. As a concrete example, when a unit is designed for 90% CO2 capture at ISO conditions, the capture rate falls to 85% at the higher ambient temperatures encountered in summer. Guaranteeing 90% CO2 capture at all times of the year would entail over-designing the capture unit, leading to excessive costs and performance penalties.
[0012] An extreme off-design condition driving the overall system design is a gas turbine trip. Investigations have shown that the long run-out time of the blower 32 results in a strong vacuum in the upstream flue gas path (up to 100 mbar below ambient), thereby causing structural damage.
[0013] Within a combined cycle power plant with carbon capture and storage flue gas must be transported from the exhaust of the HRSG 19 to the absorber 33 of the CO2 capture unit 14 . Traditionally, the blower 32 is utilized to overcome all the pressure losses in the flue gas path, thereby enabling the gas turbine 11 to operate at design conditions (i.e. a standard gas turbine exit pressure of typically 35 mbarg). The absorber pressure is essentially atmospheric. In this example, the blower head is approximately 100 mbar.
[0014] Prior art regarding similar configurations recommends improving the CO2 capture efficiency by increasing the pressure in the absorber of the CO2 capture unit.
[0015] Document EP 1 688 173 A2 1 proposes using a blower to achieve this goal. In detail, a carbon dioxide recovery system is disclosed comprising a turbine which is driven and rotated by steam, a boiler which generates the steam supplied to the turbine, a carbon dioxide absorption tower which absorbs and removes carbon dioxide from a combustion exhaust gas of the boiler by an absorption liquid, and a regeneration tower which heats and regenerates a loaded absorption liquid with carbon dioxide absorbed therein. The regeneration tower is provided with plural loaded absorption liquid heating means in multiple stages, which heat the loaded absorption liquid and remove carbon dioxide in the loaded absorption liquid. The turbine is provided with plural lines which extract plural kinds of steam with different pressures from the turbine and which supply the extracted plural kinds of steam to the plural loaded absorption liquid heating means as their heating sources. The plural lines are connected to make the pressure of supplied steam increased from a preceding stage of the plural loaded absorption liquid heating means to a post stage of the plural loaded absorption liquid heating means.
[0016] Further, on the combustion exhaust gas outlet side of the boiler, a blasting blower which pressurizes of a combustion exhaust gas, a cooler which cools the combustion exhaust gas, and a CO2 absorption tower which is filled with CO2 absorption liquid for absorbing and removing CO2 from the combustion exhaust gas are successively arranged in this sequence from the side of the boiler.
[0017] Document WO 2008/090168 A1 teaches the use of the gas turbine to increase the absorber pressure. In detail, it discloses a process for reducing CO2 emission in a power plant, wherein the power plant comprises at least one gas turbine coupled to a heat recovery steam generator unit and the CO2 capture unit comprises an absorber and a regenerator, the process comprising the steps of: (a) introducing hot exhaust gas exiting a gas turbine having a certain elevated pressure into a heat recovery steam generator unit to produce steam and a flue gas stream comprising carbon dioxide; (b) removing carbon dioxide from the flue gas stream comprising carbon dioxide by contacting the flue gas stream with absorbing liquid in an absorber having an elevated operating pressure to obtain absorbing liquid enriched in carbon dioxide and a purified flue gas stream, wherein the settings and/or construction of the gas turbine are adjusted such that the hot exhaust gas exiting the gas turbine has a pressure of at least 40% of the elevated operating pressure of the absorber. A blower for the exhaust gas is not used.
[0018] A special situation is given, when the combined CCPP uses flue gas recirculation (FGR) to increase CO2 concentration in the exhaust gas.
[0019] There is the proposal to enrich the CO2 concentration at the gas turbine exhaust by means of a flue gas recirculation (FGR) system, in combination with post-combustion CO2 capture (see for instance document WO 2006/018389 A1). Flue gas recirculation is beneficial for the CO2 capture process because both the concentration of carbon dioxide is increased and the overall mass flow to the CO2 capture unit is reduced. These two aspects result in a smaller CO2 capture and in a more efficient capture process.
[0020] In the proposed flue gas recirculation system the CO2 enriched flue gas is cooled and cleaned before being mixed with ambient air, and then supplied to the compressor inlet of the gas turbine.
[0021] There is further a proposal disclosed in DE 100 01 110 A1, to recover water from the flue gas exiting the HRSG. This is achieved via a droplet catcher, which is placed at the exit of a power turbine. The power turbine receives exhaust gas from the HRSG at a pressure of 2-5 bar. Unlike conventional gas turbines, this turbine is specifically designed to deliver this increased pressure (2-5 bar instead of the typical 1 bar) to the HRSG.
[0022] The prior art disclosed in the WO 2006/018389 A1 has various disadvantages:
Blower auxiliary power consumption→loss in performance of plant; Blower Control→The control system of such a plant would carry more complexities, as the control of the blower would represent an additional functional block in the start up, shut down and normal operation of the flue gas path; Increase in flue gas temperature over blower→loss in performance of plant; Maintenance of blower→increased maintenance intervals, increased downtime; Following GT trip→large underpressure of system caused by blower→major hazard. Therefore the design of ducting and HRSG must be more robust (than if hazard was not present) thus increasing design and first cost.
[0028] The blower consumes power of approximately 2.6 MW, costs a lot and has sizeable footprint of roughly 10 m×5 m×7 m (L×W×H). Furthermore, the blower causes an increase in temperature of the flue gas flow by approx 3-4K. This increase causes a loss in performance of the plant. Finally, a trip of the GT whilst the blower is fully loaded could cause a severe underpressure in the flue gas path (approx. 70 mbar). This represents a major hazard.
[0029] A reliable control system is necessary in order for the blower to follow gas turbine operation. Given the potentially extreme flow non-uniformities in the ducting up-stream of the blower (including potential flow entrainment from a partially open stack (a measure applied to minimize the risk of under-pressure during extreme transients), it is also difficult to provide reliable measurements for the blower control system.
SUMMARY
[0030] It is an object of the present invention to provide a method for operating a combined cycle power plant with flue gas treatment means, which substantially reduces the effort necessary in the flue gas treatment part of the power plant.
[0031] It is a further object of the invention to disclose a combined cycle power plant for using the method according to the invention.
[0032] These and other objects are obtained by a method according to claim 1 and a combined cycle power plant according to claim 10 .
[0033] The invention relates to a method for operating a combined cycle power plant, wherein flue gas of a gas turbine is led along an flue gas path through a heat recovery steam generator to a flue gas treatment means, whereby the gas turbine is operated with a back-pressure at its exit, which compensates most or all of a pressure loss of the flue gas along the flue gas path.
[0034] According to an embodiment of the invention the gas turbine is operated to have a back-pressure at its exit, which compensates all of the pressure loss of the flue gas along the flue gas path.
[0035] Specifically, the gas turbine is operated with a back-pressure of 150 mbar to approximately 250 mbar.
[0036] According to another embodiment of the invention the gas turbine is operated to have a back-pressure at its exit, which compensates most of the pressure loss of the flue gas along the flue gas path, and that the remaining pressure loss is compensated by a blower being arranged in the flue gas path.
[0037] Specifically, the gas turbine is operated with a back-pressure of approximately 100 mbar, and the blower) is operated with a duty of approximately 50 mbar.
[0038] According to a further embodiment of the invention the flue gas treatment means comprises a flue gas cooling circuit and an integrated CO2 capture unit with a CO2 absorber.
[0039] According to just another embodiment of the invention flue gas treatment means comprises NOx reducing means.
[0040] Specifically, at least part the flue gas is recirculated to the inlet of the gas turbine on a flue gas recirculation path, and the pressure loss of the flue gas along the flue gas recirculation path is completely compensated by the back-pressure of the gas turbine.
[0041] According to another embodiment of the invention the back-pressure of the gas turbine is generated and controlled by means of a pressurized heat recovery steam generator.
[0042] The combined cycle power plant according to the invention comprises a gas turbine, a water/steam cycle with a heat recovery steam generator, through which the flue gas of the gas turbine flows along a flue gas path, whereby the gas turbine is designed to be operated with a back-pressure, which compensates most or all of the pressure loss of the flue gas along the flue gas path.
[0043] According to an embodiment of the invention a blower is arranged in said flue gas path, the duty of which is smaller than the back-pressure of the gas turbine.
[0044] According to another embodiment of the invention a pressurized heat recovery steam generator with a throttling damper in a HRSG stack is provided for generating said back-pressure.
[0045] According to a further embodiment of the invention a flue gas recirculation path is provided for recirculating flue gas back to the inlet of the gas turbine, and the gas turbine is designed to be operated with a back-pressure, which compensates the pressure loss of the flue gas along the flue gas recirculation path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawing.
[0047] FIG. 1 shows a simplified diagram of a combined cycle power plant with integrated CO2 capture and storage capabilities, which can be used with the invention;
[0048] FIG. 2 shows a further simplified diagram of a combined cycle power plant with integrated CO2 capture and storage capabilities, which can be used with the invention; and
[0049] FIG. 3 shows a simplified diagram of a combined cycle power plant with a flue gas recirculation path and a pressurized HRSG according to an embodiment of the invention.
DETAILED DESCRIPTION
[0050] The present invention proposes to reduce the duty of the flue gas blower (from 100 to around 50 mbar) and at the same time to increase the gas turbine back-pressure (p 1 in FIG. 1 , from 40 to approximately 100 mbar), compared to the state of the art configuration shown in FIG. 1 . Such a configuration permits an increase in overall net performance (because the gas turbine compressor 15 is more efficient than the blower 32 ) and reduces cost.
[0051] Furthermore, such a kind of operation permits additional, desirable features:
Slightly increasing the absorber pressure (above the standard atmospheric pressure) when the capture unit runs off-design (e.g. on hot days), so as to maintain the design CO2 capture rate without having to overdesign the unit. This can be achieved by a blower equipped with efficient mass flow control, e.g. inlet guide vanes (where efficiency varies slightly over the load range 80-100%) or variable pitch blades (high efficiency over much larger load range), adjusting the guide vanes (or blade pitch) permits maximum load when the higher absorber pressure is requested. Purging functions. Standard gas turbines can be used (no large modifications needed for 100 mbar back-pressure). The vacuum normally created (in the flue gas path) due to a gas turbine trip, is much smaller.
FIRST EMBODIMENT
[0056] According to a first embodiment of the invention it is proposed to completely eliminate the flue gas blower 32 and to operate the gas turbine 11 at a higher back-pressure (e.g. 150 mbar would be suitable in the CCPP/CCS plant of FIG. 1 ) in order to transport the exhaust gas to the CO2 capture unit 14 . The absorber pressure remains approximately constant at a given gas turbine operating point. This embodiment is ideal for system simplification and cost reduction.
[0057] Thermodynamic calculations, heat balances and cost assessments for the above-described plant of FIG. 1 conclude that implementing the invention results in the following benefits:
Overall plant output is 3.2 MW higher. Hardware costs are reduced substantially. Removing the blower leads to a more robust and more easily controllable system. The problem of vacuum creation during a gas turbine trip is completely avoided.
SECOND EMBODIMENT
[0062] The inventive concept can also be used in a CCPP/CCS employing flue gas recirculation. In this case, the gas turbine back-pressure is increased by approximately 30 mbar (corresponding to the pressure loss along the flue gas recirculation path 38 ) A small blower 32 is used for the COS stream, to overcome the pressure losses induced by the CO2 capture unit 14 . The recirculation path 38 leads from the CO2 capture unit 14 , downstream of the pump 32 and upstream of the CO2 absorber, to the inlet of the gas turbine 11 , by way of at least one subordinated path 38 a, 38 b.
[0063] In the case of a CCPP with flue gas recirculation the flue gas path is generally optimized by removing the blower. This optimization can be applied to flue gas re-circulation in the combination with carbon capture and sequestration (CCS) and flue gas recirculation for the purpose of NOx reduction.
[0064] The solution involves the provision of a pressurized HRSG in a combined cycle with a gas turbine with a flue gas recirculation system for the purposes of CCS and NOx reduction.
[0065] The solution involves designing the HRSG such that the velocity levels are higher than in a “standard” HRSG. To do so the HRSG design is smaller than the “standard” giving a higher pressure drop (dp) and a higher exit pressure. The higher exit pressure can be used to overcome the pressure losses experienced over the flue gas path without the need for an additional pressure recovery device, i.e. blower.
[0000] (A) FGR with CCS:
[0066] As has been told already, the pressure losses incurred over the flue gas path shown in WO 2006/018389 A1 must be recovered by means of a blower.
[0067] According to the present invention a pressurized HRSG is provided such that the exit pressure is sufficient to overcome the aforementioned pressure loss. By doing so the HRSG will be significantly smaller, and hence will have lower first cost and smaller footprint.
[0068] A smaller HRSG results in a larger backpressure on the turbine. This increase in backpressure on the turbine, which would be equivalent to the pressure drop across the flue gas path (i.e.: from exit of gas turbine to inlet of gas turbine).
[0069] This assumes the following:
dp over HRSG: 35 mbar dp over a DCC: 25 mbar dp over a mixer: 5 mbar dp over ducting: 5 mbar
[0074] The net increase of backpressure on the turbine is equal to sum of the dp of the DCC, mixer and ducting, i.e. 35 mbar.
[0075] FIG. 2 shows various modifications of FIG. 1 , namely relating to the operating cycle. path 38 leads from the CO2 capture unit 14 to the inlet of the gas turbine 11 . After having passed the heat recovery steam generator 19 , the exhaust gas is divided in a subsequent stack damper 26 into a first part, which enters a stack 28 to a louver damper 50 and forwards as exhaust gas 51 . A second part, which passes a louvre damper 52 and enters the flue gas cooling circuit 13 , where it is cooled down in a cooler 29 . The cooler 29 as part of the cooling water circuit comprising according to requirements a heat exchanger and a pump. After having passed the gas cooling circuit 13 the exhaust gas is compressed by means of a pump 32 a and subsequently introduced to a gas turbine 11 . Downstream of the pump 32 and upstream of the turbine 11 a part of the exhaust gas to be compressed by means of a compressor 34 . The compressed exhaust gas 35 is then ready to be stored.
[0076] An intermediate extraction steam from the steam turbine 20 is not provided.
[0077] A schematic of a respective plant layout can be seen in FIG. 3 . The combined cycle power plant 40 , as a punctuated version of previous systems, shown in FIG. 3 , comprises a gas turbine 41 with an air inlet 42 , a mixer 43 , a compressor 44 and a turbine 46 , which is driven by hot gases generated by the combustion of a fuel 45 . The exhaust gas of the gas turbine 41 passes a heat recovery steam generator 41 , which is part of a water/steam cycle, not shown.
[0078] At the exit of the HRSG, the exhaust gas can be emitted through a HRSG stack 48 with an integrated throttling damper 61 and/or flow through a flue gas line 39 , which can be shut off by means of a shutter 49 . The exhaust gas 51 flowing through the flue gas line 39 can pass a first louvre damper 50 to reach a CCS facility (not shown) and/or a second louvre damper 52 to be recirculated to the mixer 43 of the gas turbine 41 via flue gas recirculation lines 59 and 60 .
[0079] Between flue gas recirculation lines 59 and 60 a direct contact cooler (DDC) 58 is provided having a separate cooling water cycle comprising pumps 54 , 55 and 57 , a cooling tower 53 and a water treatment device 56 .
[0080] The operation of the system of FIG. 3 can be as follows:
(a) CCS Offline, FGR Ratio=0%:
[0081] Shutter 49 is closed, HRSG stack 48 is open, louvre damper 50 (CCS) is closed, louvre damper 52 (FGR path) is closed.
(b) CCS Online, FGR Ratio=0%:
[0082] Shutter 49 is open, HRSG stack 48 (throttling damper 61 ) controls the required pressure level, louvre damper 50 is open, louvre damper 52 is closed.
(c) CCS Offline, FGR Ratio=30% (for Example):
[0083] Shutter 49 is open, HRSG stack (throttling damper 61 ) controls the required pressure level, louvre damper 50 is closed, louvre damper 52 is open.
(d) CCS Online, FGR Ratio=30% (for Example):
[0084] Shutter 49 is open, HRSG stack 48 (throttling damper 61 ) controls the required pressure level, louvre damper 50 is open, louvre damper 52 is closed.
[0085] A comparison of the plant performance with and without blower gives:
Blower Consumption:
[0086] The power consumed by a blower required to overcome the pressure loss of the system in FIG. 3 was estimated based on the following parameter:
Maximum mass flow passing through the FGR path blower: 345 kg/s; Pressure increase required: 35 mbar; Corresponding blower power consumption: 2.6 MW.
Impact of Increased Backpressure on Plant Performance:
[0090] The increased of back-pressure of 35 mbar on the turbine results in a CC loss in gross power of approximately 2 MW.
(B) FGR for NOx Reduction:
[0091] As in part (A) above, a pressurized HRSG may be used such that the exit pressure is sufficient to overcome the pressure loss in the flue gas path. Similarly the increase in backpressure on the turbine will be equivalent to the dp over the flue gas path components (DCC, ducting and mixer 43 ), i.e. 35 mbar.
[0092] The deviation from the proposal in part (A) concerns the splitting of the exhaust gas after the HRSG 41 . In this case 30-40% of exhaust from the HRSG 41 shall be recirculated to the gas turbine 41 . The remaining 60-70% shall be released to an exhaust stack via the louvre damper 50 . In order to maintain the increased pressure within the flue gas path the louvre damper 50 must be throttled.
[0093] Thus, the proposed solution with respect to FIG. 3 has the following characteristics:
A control of the pressure drop across a flue gas recirculation path is realized through the application of a pressurized HRSG in combination with a throttling damper. The FGR is used for the purpose of NOx reduction and for carbon capture technologies. A throttling damper ( 61 ) in the exhaust stack ( 48 ) is used to control the pressure level in the flue gas path. The HRSG is pressurized with a delta pressure dp>60 mbar. | The invention discloses a method for operating a combined cycle power plant with an integrated CO2 capture unit, wherein flue gas of a gas turbine is led along an flue gas path through a heat recovery steam generator, a flue gas cooling circuit and a CO2 absorber. A reduction in effort is achieved by operating the gas turbine to have a back-pressure at its exit, which compensates most or all of the pressure loss of the flue gas along the flue gas path. |
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method of providing a subset of SQL (Structured Query Language) relational-database functions to existing applications.
2. Discussion of Related Art
There still exist a variety of commercially available databases with SQL interface, providing an exhaustive set of functions, but they are highly hardware resource consuming.
As a result, computer programs written for one computer with a software platform including a commercial SQL relational-database are frequently unsuitable for use with computers having a reduced hardware configuration.
In the past many existing applications had to be rewritten in order to enable them to interface with a proprietary database resident on that equipment.
Furthermore proprietary databases are usually equipment dependent and cannot be used for the same or other applications on other equipment.
One of the major problems that application developers are faced with when porting existing applications, developed on a different hardware and software platforms and using an SQL relational-database, toward equipment with reduced hardware configuration, for example communication servers, other network apparatus etc., is the need to rewrite part of the applications in order to enable them to interface with a proprietary database resident on that equipment, otherwise the applications could not be used or must be rewritten completely. Sometimes the destination equipment has a reduced availability of hardware resources because of the installation of other resource consuming applications (e.g., communication software like ISO/OSI stack protocols, TCP/IP and others) and since commercial SQL relational-databases are highly hardware resources consuming it could be desirable to avoid installing it, for example in the case of the porting of an application toward one or more communication servers.
It will be recognized that an SQL database running on any equipment with any configuration is essential in order to allow an existing application using an SQL database to be ported toward an equipment and to function correctly, when a commercial database has not been installed.
SUMMARY OF INVENTION
It is an object of the present invention to provide a method and means of porting/supplying a set of SQL database functions to an existing application on any equipment, without a significant consumption of hardware resources.
The object is attained by methods with the features according to claim 1 or claim 5 and by means according to claim 7.
The invention as claimed enables the porting of existing user software applications using an SQL database toward any reduced hardware configuration on which a commercial resource consuming SQL relational-database cannot be installed, by only copying, recompiling and executing the application files, without any source code modification.
By using the invention, the waste of time to modify existing source code is avoided, where sometimes such source code is not easily modifiable and would require a big effort.
Furthermore, it is sometimes preferable to save hardware resources for other run time applications, in these cases the emulator object of the invention enables the saving in a configuration phase.
Furthermore, the emulator can be customized to be used with different platforms on any different equipment.
Further advantageous features of the invention are defined in the subclaims.
Advantageously, security of user data can be guaranteed, when necessary, by using an encryption/decryption module to access data files.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 shows the use of the emulator during a porting phase;
FIG. 2 enumerate all parts which make up the software architecture of the emulator;
FIG. 3 shows how an SQL statement is converted into an interface function which is then translated into a sequence of emulation library functions accessing the ASCII files;
FIG. 4 shows the implementation of how an SQL statement is converted into an interface function which is then translated into a sequence of emulation library functions accessing the ASCII files; and
FIG. 4-B shows a special example of FIG. 4;
FIG. 5 shows a system for managing a telephone network, implemented using a LAN network comprising communication servers of reduced hardware configuration which can carry out the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
This invention focuses on a database emulation approach, as shown in FIG. 1. In what follows, particular attention will be paid to the service provided to the application needing the database though it should be understood that emulator might implement a different set of functions which will be the minimum required by the application in order to work.
With the present invention an original method to provide the performances of an SQL commercial database in a different way is given, by using an emulator 1.
Said emulator is a modular database: only the functions needed to satisfy the requirements of an existing user application An are configured and installed, so to enable the maximum flexibility in order to reduce the consumption of hardware resources, in particular memory and CPU time.
The emulator manages configuration and user data ASCII files F1 . . . Fn by using a modular library of functions and predefined data structures. The simple modular structure enables an easy configuration upgrade and maintenance, in order to reduce the emulator size taking into consideration the application requirements and the hardware configuration of an equipment.
Said application An has, for example, been developed on a first hardware platform HW1 interfacing the application An toward the SQL relational database with a software configuration SW1, and it is supposed to be used on a second hardware platform HW2 where the SQL database is not available and thus SW1 is not usable.
The software architecture of the emulator 1 is shown in FIG. 2.
The emulator 1 is composed of the following parts:
an Interface Module M1 providing the applications with an SQL interface (it takes the place of the SW1 platform). This module is application dependent and should be customized depending on the type of SQL statements used, with particular regard to query statement having a complex syntax. It includes a set of functions, one for each specific SQL statement used by the application An;
a modular Emulation Library M2, expandable and application independent, including a set of functions performing basic operations on the ASCII files, invoked by M1 in order to implement the SQL statements used by the application An;
an error management module (not shown in the figure);
an Encryption Module M3 (not mandatory);
configuration ASCII files including the database and tables definition F1 . . . Fm-1; and
ASCII user data files Fm . . . Fn (which can be encrypted) including the user data inserted according to the tables definition.
The emulator manages a number of ASCII files containing the tables definition and the user applications data.
For security reasons data can optionally be encrypted.
Using the emulator, the CPU time dedicated and the amount of RAM memory and hard disk number of Mbytes required is highly reduced, compared to existing SQL databases.
The SQL relational-database emulator provides the user applications with a modular library including a set of functions to:
creating SQL tables and defining fields;
storing, modifying and deleting data on created tables, where a type check is performed according to the field definition; and
retrieving such data by using SQL filters;
The emulator implements the SQL commands in two different ways:
1. to define the database structure, the following table configuration commands can be implemented by using an editor to update configuration files:
x create table
x modify table configuration
x drop table
x description
insert row to pre-populate the table
2. to use the defined database, the run-time modification of table content is realized by using the Module Interface functions IF1 . . . IFn, as shown in FIG. 3:
select rows;
insert one row;
delete rows;
update one row.
This description will continue to take as an example an SQL database whose services are to be emulated.
Before proceeding to a detailed description of the invention, it would be helpful to outline certain relevant aspects of the tables configuration phase.
It will be described in the manner in which the following SQL statements are handled:
create table (II),
modify table configuration (alter/drop/create)(I, III, II),
delete (alter/drop)(I, III),
description (IV)
insert row to pre-populate the table (V).
The SQL syntax of the aforesaid statements is the following:
I) to modify a database:
ALTER DATABASE database -- name;
II) to define a new table structure:
CREATE TABLE table -- name (field -- name1 NUMBER (9),
field -- name2 CHAR (14));
III) to delete a table:
DROP TABLE table -- name
IV) to see the table definition:
DESC table -- name
V) data inserted as default:
INSERT INTO table -- name (field -- name1, field -- name2) VALUES (`field -- value1`, `field -- value2`);
The aforesaid mentioned SQL statements can be emulated by using an ASCII configuration file written and modified by using an editor.
For each new table an ASCII file is created.
Each row defines a column of the table.
The following is an example of table on an emulator table configuration ASCII file, where the first part is the table structure definition and the second part is the user data inserted as default.
The characters "", "-" and "*" are used to divide data.
The character "#" indicates that there is a comment line.
In the first part the table structure is defined.
The data included between H . . . H represents the table definition, and each row starting with a C is a column of the defined table.
The specified parameters define for each table column the:
x type,
x length,
x if the field can be null,
x if the field is a unique index to access to the records.
In the second part of this example, rows with data are inserted into the table.
A type check is performed according to the previous table definition.
______________________________________# Table ASH.sub.-- STATES#H This table has 4 columns.linevert split.4.linevert split.#C Application Service Id. .linevert split.NUMBER.linevert split.3.linevert split.NOT NULL.linevert split.UNIQUE INDEX.linevert split.C Appiication Entity Name .linevert split.CHAR.linevert split.32.linevert split.NOT NULL.linevert split.UNIQUE INDEX.linevert split.C Sequence Number .linevert split.NUMBER.linevert split.3.linevert split.NOT NULL.linevert split.UNIQUE INDEX.linevert split.C StateName .linevert split.CHAR.linevert split.20.linevert split.NOT NULL.linevert split.H#* 1.linevert split.dh.sub.-- 1.linevert split. 0.linevert split.IDLE.linevert split.* 1.linevert split.dh.sub.-- 1.linevert split. 1.linevert split.START.sub.-- INT.sub.-- DIAL.sub.-- PEND .linevert split.* 1.linevert split.dh.sub.-- 1.linevert split. 2.linevert split.INT.sub.-- DIAL.sub.-- EXP .linevert split.* 1.linevert split.dh.sub.-- 1.linevert split. 3.linevert split.INT.sub.-- DIAL.sub.-- PEND .linevert split.* 1.linevert split.dh.sub.-- 1.linevert split. 4.linevert split.WAIT.sub.-- FOR.sub.-- CONT .linevert split.* 1.linevert split.dh.sub.-- 1.linevert split. 5.linevert split.WAIT.sub.-- FOR.sub.-- LAST .linevert split.* 1.linevert split.dh.sub.-- 1.linevert split.998.linevert split.PROVIDER.sub.-- ABORT .linevert split.* 1.linevert split.dh.sub.-- 1.linevert split.999.linevert split.SUCCESFUL.sub.-- COMPLETED .linevert split.#* 2.linevert split.bh.sub.-- 1.linevert split. 0.linevert split.IDLE.linevert split.* 2.linevert split.bh.sub.-- 1.linevert split. 1.linevert split.COMMAND.sub.-- EXPECTED .linevert split.* 2.linevert split.bh.sub.-- 1.linevert split.998.linevert split.PROVIDER_ABORT .linevert split.* 2.linevert split.bh#1.linevert split.999.linevert split.SUCCESFULCOMPLETED .linevert split.#______________________________________
The skilled man will be aware of still further configuration mode.
By way of further explanation, reference is directed to FIG. 3 which is in diagrammatic form.
An SQL statement, included in the user application, cause the activation of an emulator interface functions IFi, which invokes a sequence, depending on the specific SQL statement, of emulation library functions LF1 . . . LFm accessing the ASCII files AF1 . . . AFk containing the user data.
For example when the SQL statement INSERT INTO Tab2 (field -- name1,field -- name2) VALUES (`field -- value1`, `field -- value2`); is invoked by the user application An, the INSERT emulator interface function IF1 is activated; it calls a sequence of emulation library functions accessing the Tab2 ASCII file AF2 containing the user data, as it will be explained in more detail later.
Another example is the following: when the SQL statement SELECT FROM Tab2 is invoked by the user application An, the SELECTn emulator interface function IFn is activated; it calls a sequence of emulation library functions accessing the Tab2 ASCII file.
A modular emulation library is available providing a set of functions LF1 . . . LFm.
A subset of said functions can be combined to implement an SQL statement.
An example of library functions is the following:
______________________________________F1 .sub.-- get.sub.-- table.sub.-- descrF2 .sub.-- open.sub.-- tableF3 .sub.-- close.sub.-- tableF4 .sub.-- search.sub.-- first.sub.-- rowF5 .sub.-- search.sub.-- next.sub.-- rowF6 .sub.-- fetch.sub.-- row.sub.-- at.sub.-- curr.sub.-- posF7 .sub.-- fetch.sub.-- row.sub.-- at.sub.-- abs.sub.-- posF8 .sub.-- write.sub.-- rowF9 .sub.-- delete.sub.-- rowF10 .sub.-- refresh.sub.-- table.sub.-- file______________________________________
A detailed description of each function is provided later.
In FIG. 4 it is shown in details the implementation of one of the interface functions IF1 . . . IFn aforesaid listed and shown in FIG. 3.
Said function is translated into a sequence of emulation library functions LF1 . . . LFm accessing the ASCII files.
Table Description A and Access Description B are defined in the data area of the function IFi; they are implemented as an array of records having an element for each database table column.
Table Description A is a build up of the following configuration data:
1=column type,
2=column length,
3=whether the field can be null or not,
4=whether the field is an index to access to the records or not.
Access description B includes data about the access type and mode depending on the origin SQL statement type.
It is a build up of the following data, filled in by the emulator Interface Function IFi depending on which columns the SQL statement uses:
1=use flag to indicate if the column is used (T=true, F=false)
2=string size,
and the following fields where to read/write the result of the operation (written by the -- fetch -- row or read by the -- write -- row):
3=a flag indicating whether the field can be null or not (T=true, F=false),
4=a flag indicating whether the field contains a numeric value,
5=a flag indicating whether the field contains an alphanumeric value (char=character/ptr=pointer).
The first operation performed in RAM memory is the -- get -- table -- description function activation to retrieve from the database files the user table definition and copy it in the Table Description A. Subsequently all the emulator library functions will use the Table Description A to read/write the Access Description B.
An example of a system to manage a telephone network, implemented using a LAN network comprising communication servers of reduced hardware configuration which can carry out the invention, is shown in FIG. 5. The system includes two Application Servers AS1 and AS2, one active and the other stand-by, performing management operations for a network; these equipment have a full hardware and software configuration including duplicated disks HD.
An Operator can interface the management system by using a so-called X -- Terminal connected to a X -- Terminal Server providing a graphical operator interface.
A plurality of possible Communication Servers CS1 . . . CSn of reduced hw configuration are installed and can carry out the invention. The number of communication servers CS1 . . . CSn with different hardware configuration can increase in future upgrades of the network. On the communication server CS should be installed applications developed on different hardware configuration equipment having a complete software platform including a commercial database. As the reduced communication server CS software platform should include also communication software and since commercial SQL relational-databases are highly hardware resources consuming, the emulation approach enables to spare memory and CPU time.
An example of a telephone network management system architecture comprising network management systems according to FIG. 5, including equipment which can carry out the invention.
The emulator approach can be useful in view of future extension of the network by inserting an increasing number of equipment of different hardware configuration on which applications needing an SQL relational-database should be executed.
As the complexity of a network topology increases, the network management systems are supposed to be upgraded in terms of number of equipment installed in applications running on said equipment.
The architecture of the network management system shown in FIG. 5 can be split up in a plurality of cooperating sub-systems interconnected through a network.
Network management systems SYSTEM1 SYSTEM2 and SYSTEM3 including equipment having different configuration are interconnected to a network to be managed in order to cooperate exchanging management information.
The emulation approach enables the porting of applications developed on full hardware and software platforms toward any network equipment.
It has been mentioned above that every interface function IF1 . . . IFn aforesaid listed and shown in FIG. 3, is translated into a sequence of emulation library functions LF1 . . . LFm accessing the ASCII files.
By way of further explanation, an SQL statement in the user application is converted into a IF function each IF function is associated to a sequence of functions of the emulation library, where the sequence depends from the SQL statement the output of the SQL command is returned to the user application, as described above.
In the following will be examined in more detail:
1) IF functions
2) emulation library
3) ASCII files
An example of set of IF functions can be the following:
insert;
delete;
update;
select1; . . . ; and
selectn.
A SELECT statement, according to SQL syntax, can have a different WHERE clause. Here are some examples of different complexity. The character "*" means "ALL".
______________________________________SELECT f1, f2 FROM tab1;SELECT*FROM tab1;SELECT f1, f5 FROM tab1 WHERE (f1=0 AND f2=`string`);SELECT f1, f5 FROM tab1WHERE (F1=0 AND f2 NOT IN(SELECT f3, f4 FROM tab2 WHERE (f1=10 AND f2=`String1`)));((SELECT f1, f5 FROM tab1WHERE (F1=0 AND f2 NOT IN(SELECT f3, f4 FROM tab2 WHERE (f1=10 ANDf2=`string1`)))UNION(SELECT f1, f5 FROM tab1WHERE (F1=0 AND f2 NOT IN(SELECT f3, f4 FROM tab2 WHERE (f1=10 ANDf2=`string1`)));));______________________________________
The user application An interfaces the database using SQL statement and passing parameters (pointers to data structure containing data sent to the database and pointers to data structure in which the output of the SQL commands will be returned).
There will be described one of the aforesaid IF function, the one correspondent to the SELECT SQL statement, as far as its implementation is concerned.
TAB1 is an example of database table having 6 columns defined C1 . . . C6.
Two data lines have been inserted in TAB1; only the data relevant for the example are written, the other field can have any value. TAB1:
______________________________________C1 C2 C3 C4 C5 C6______________________________________5 70 0 string10 100 200 string______________________________________
The following SQL statement can come from the user application An: SELECT c2, c4, c5 FROM tab1 WHERE (c2=10 AND c6=`string`);
There will be described how the emulator works to get results.
In this SELECT statement with this WHERE clause, the Access Description Table B defined in FIG. 4, is duplicated in
Access Description Select B1 (not shown in figure),
Access Description Where B2 (not shown in figure).
In this case two different accesses to user data are made by using two Access Description tables. As explained before, every row of the Table Description A and Access Description B or B1 and B2 corresponds to a column of the defined database table at the creation phase.
The Access Description Select B1 defines which fields among C1 . . . C6 are to be retrieved for each data row selected from the ones present in TAB1 and should be sent to the application An, by tagging with T the fields of interest, in this case c1, c4, c5:
______________________________________1 2 3 4 5______________________________________ useC1 FC2 T 10C3 FC4 T 100C5 T 200C6 F______________________________________
The Access Description Where B2 defines the clause to identify which rows present in TAB1 should be selected, by tagging with T the fields cited in the WHERE (c2=10 AND c6=`string`) clause:
______________________________________1 2 3 4 5______________________________________ useC1 FC2 T 10C3 FC4 FC5 FC6 T 5 string______________________________________
Another solution in a different SELECT statement, for example SELECT f1,f2 FROM tab1; could be performed by using a single access and a single Access Description B. In FIG. 4-B is shown a special case of FIG. 4. This is the case of the implementation of the following SQL statement.
______________________________________((SELECT f1,f5 FROM tab1WHERE (F1=0 AND f2 NOT IN(SELECT f3, f4 FROM tab 2 WHERE (f1=10 ANDf2=`string1`)))UNION(SELECT f1,f5 FROM tab1WHERE (F1=0 AND f2 NOT IN(SELECT f3,f4 FROM tab2 WHERE (f1=10 and f2=`string`)));));______________________________________
which could be performed by using:
a multiple Table Description A1 and A2
a multiple Access Description B1 and B2.
In the following paragraph it will be explained how different steps are executed by the IFn SELECT function, by calling a definite sequence of emulator library functions.
When the user application An asks the IFn for retrieving data from the database, it sends to the emulator a pointer to a data structure containing parameters of the SQL SELECT statement and at the end of the operation will be given back a pointer to the retrieved data result of the query.
A way for the IFn to perform the aforesaid task is the following:
1) the Table Description A, in the data area of FIG. 4, is initialized according to the table description read from the ASCII file containing the configuration data, by calling the emulator library function -- get -- table -- descr() LF in particular the array of structure of Table Description A is filled in, one row for each table column;
2) the ASCII file containing user data related to the previously accessed table configuration is opened the function verify whether the file has not been opened before. If the file is opened for the first time:
opens the file
moves to the first row by calling the function -- search -- next -- row().
If not, a pointer to the file moves to the row by calling -- search -- next -- row() and return a pointer to the row, cycling till:
the end of the file, or
the specified number of rows has been read;
3) for each row, it reads the row at current position by calling the function -- fetch -- row -- at -- curr -- pos()
and verify if the WHERE clause written in B2 is satisfied for that row, in this case the required fields of that user data row are copied in B1 (SELECT Access Description), filling in the last three columns (null, long/int, char/ptr) according to the data type;
4) at the end close the user data table file.
As result of this function, the output of the SELECT clause will be available in the Access Description table (last three columns of B1) and will be returned to the application An.
An example of EMULATION LIBRARY, as listed above, can be the following.
A subset of the functions can be combined to implement an SQL statement. In the following, a more detailed description of each function is given.
F1
NAME: -- get -- table -- descr
DESCRIPTION: It gets the table description for a specified table (input parameter -- table -- name), filling in the "row description" structure (output parameter -- row -- desc). The proper table file is opened and closed after the completion of the table description reading. It logs a message when an error occurs.
F2
NAME: -- open -- table
DESCRIPTION: It opens a table file for a specified table (input parameter -- table -- name). The file can be opened for read, update or append depending on the specified "action type" (SELECT, DELETE and INSERT as specified by the input parameter -- action -- type). It gives back to the calling function the pointer to the opened file (output parameter -- file -- ptr). It logs a message when an error occurs.
F3
NAME: -- close -- table
DESCRIPTION: It closes a table file for a specified table name (input parameter -- table -- name). The file pointer is given by the calling function (input parameter -- file -- ptr). It logs a message when an error occurs.
F4
NAME: -- search -- first -- row
DESCRIPTION: It searches for the first row in a table. That means: the Table Description lines are skipped, as comment lines, till the second Header line (closing the Table Description) is found. It gets from the calling function the file pointer (input parameter -- file -- ptr) and the table name (input parameter -- table -- name) that is inserted in the error messages. If the row is correctly found it gives back to the calling function the position of the row in the table file (output parameter -- file -- pos): it is the position of the line type char. It assumes the initial value of the file pointer is pointing to the first byte of a file line, otherwise the search fails.
Last char got from the file:
first char of the row (when it has been correctly found
end-of-file found at the beginning of a line (no rows in the table)
an unexpected line first char
an unexpected end-of-file.
It logs a message when an error occurs.
F5
NAME: -- search -- next -- row
DESCRIPTION: It searches for the next row in a table. That means: Table Description lines, if found, are treated as "unexpected lines". It gets from the calling function the file pointer (input parameter -- file -- ptr) and the table name (input parameter -- table -- name) that is inserted in error messages. If the row is correctly found, it gives back to the calling function the position of the row in the table file (output parameter -- file -- pos): it is the position of the line type char. It assumes the initial value of the file pointer is pointing to the first byte of a file line, otherwise the search fails.
Last char got from the file:
first char of the row (when it has been correctly found)
end-of-file found at the beginning of a line (no more rows in the table)
an unexpected line first char
an unexpected end-of-file.
It logs a message when an error occurs.
F6
NAME: -- fetch -- row -- at -- curr -- pos
DESCRIPTION: It fetches a table row starting from the current position in the table file (position given by the calling function in the file pointer -- file -- ptr). To scan the row it uses the row description given by the calling function in the input parameter -- row -- desc. It fills in the "access structure" in the memory area of the calling function (parameter -- row -- access). For more details, See the internal function -- fetch -- row. It logs a message when an error occurs.
F7
NAME: -- fetch -- row -- at -- abs -- pos
DESCRIPTION: It fetches a table row starting from the position explicitly given by the calling function with the input parameter -- file -- pos (in addition to the file pointer -- file -- ptr). To scan the row it uses the row description given by the calling function in the input parameter -- row -- desc. It fills in the "access structure" in the memory area of the calling function (parameter -- row -- access). For more details, See the internal function -- fetch -- row. It logs a message when an error occurs.
F8
NAME: -- write -- row
DESCRIPTION: It logs a message when an error occurs. Input A and B. It inserts a row in a table (the row is appended at the bottom of the file table). It uses the row description given by the calling function as input parameter. It takes the data to be written from the Access Description structure B given by the calling function as input parameter. It opens and close the table file. It checks whether a row with the UNIQUE INDEX already exists in the table.
F9
NAME: -- delete -- row
DESCRIPTION: It logically deletes a row in a table. The calling function must give the position of the row in the table. It updates the counter of deleted lines.
F10
NAME: -- refresh -- table -- file
DESCRIPTION: It checks, for a specified table, whether the deleted lines counter has reached the threshold or not. If yes, it rewrites the table files without all lines that have been previously logically deleted. The counter is reset to 0 when the threshold is overcome and maintains the same value when the value is less than the threshold.
F11
NAME: -- fetch -- row
DESCRIPTION: It fetches a table row starting from the current position in the table file (position given by the calling function in the file pointer -- file -- ptr). To scan the row it uses the row description given by the calling function in the input parameter -- row -- desc. It fills in the "access structure" in the memory area of the calling function (parameter -- row -- access). It gets from the calling function the table name (parameter -- table -- name) and the row number (parameter -- row -- nbr) that are inserted in the error messages. If no error occurs, the scanning terminates at the end-of-line after the last column. Otherwise, the scanning is aborted when the first error is detected. It assumes the initial value of the file pointer is pointing to char immediately after the special char initiating the row.
Last char got from the file:
end-of-line terminating the last (or the unique) line composing the row (fetching successfully terminated),
column terminator of the last column fetched or bad char initiating a line or unexpected end-of-line or unexpected end-of-file (fetching aborted).
It logs a message when an error occurs.
The described method of emulating an SQL relational-database in order to simplify the porting of an existing application toward a destination equipment is felt to have considerable advantages in terms of memory and CPU time saving. | Method and means for porting an existing application (An) using a relational-database with SQL interface toward a hardware platform (HW2) with a reduced software configuration which does not include an SQL relational-database. The invention emulates an SQL database enabling hardware resources saving and providing a subset of functions for: creating SQL tables and defining fields; storing, modifying and deleting data on created tables, with a type check, retrieving such data by using SQL filters. Functions can be subdivided into levels (M1, M2, M3) in order to: convert an SQL statement, coming from an existing user application (An), into a sequence of elementary interface functions (IF1... IFn), use said interface functions to read/write data files (F1... Fn), process output data to be supplied to the requesting user application (An). |
This invention relates to switchmode power converters, and is particularly concerned with such converters for generating controlled voltages in telephone subscriber line interface circuits.
BACKGROUND OF THE INVENTION
Rosenbaum et al. U.S. Pat. No. 5,103,387 issued Apr. 7, 1992, entitled "High Voltage Converter", and U.S. Pat. No. 5,323,461 issued Jun. 21, 1994, entitled "Telephone Line Interface Circuit With Voltage Switching", relate to a switchmode power converter and its arrangement and functioning in a line interface circuit for a two-wire telephone subscriber line.
As described in these patents, an individual line interface circuit includes the power converter, also referred to as a controlled voltage generator, a driver circuit, and a switching arrangement between the driver circuit, the power converter, the line, and a telephone central office (C.O.) battery. A control circuit is programmed to control the switching arrangement and the power converter to provide various operating functions which may be required of the line interface circuit. These functions include, in particular, providing relatively high voltage signalling, such as ringing, on the line, and providing a controlled d.c. feed to the line.
For example, for supplying a ringing signal on the ring wire of the line, the power converter is operated from the C.O. battery to generate at its output a high voltage ringing signal waveform, determined by the control circuit, and the switching arrangement connects this output to the ring wire of the line. A ground return for the ringing signal is provided via the switching arrangement and an output of the driver circuit, which in this case is powered by the C.O. battery. Voltages at the outputs of the driver circuit are controlled or steered by the control circuit in a manner which is described and claimed in Rosch et al. U.S. patent application Ser. No. 07/868,893 filed Apr. 16, 1992, entitled "Telephone Line Interface Circuit With Voltage Control" and which is also described in Rosch et al. U.S. Pat. No. 5,274,702 issued Dec. 28, 1993, entitled "Wideband Telephone Line Interface Circuit".
For providing a controlled d.c. feed (loop current) to the line, the control circuit controls the switching circuit to couple the outputs of the driver circuit to the line, and to provide a supply voltage to the driver circuit from either the C.O. battery or, preferably, from the output of the power converter. In the latter case the control circuit controls the power converter to generate a d.c. supply voltage which is typically lower than the C.O. battery voltage, and also controls the driver circuit so that a desired d.c. feed or loop current is maintained on the line in an off-hook state of a subscriber's telephone connected to the line.
Providing the power converter as a part of each individual line interface circuit in this manner provides distinct advantages, for example in that different high voltage signalling waveforms, e.g. ringing signal waveforms and cadences, message waiting signalling, and coin signalling, can be readily provided under software control, and d.c. feed or loop currents can be tailored to the characteristics of, and to the telephone services provided on, each subscriber line. It also presents several challenges.
For example, because the power converter is provided as a part of the individual line interface circuit and hence on a line card which must be accommodated within a predetermined limited physical space, the power converter itself must be physically small and efficient. In addition, the line interface circuit must meet criteria for spectral energy transmitted on the two-wire line; in particular spectral energy transmitted on the line in a frequency band from 4 kHz to 270 kHz must be very low to meet accepted standards.
In order to meet these challenges, the power converter as described in the patents referred to above is a switchmode power converter operating at a fixed high frequency (640 kHz) with a variable pulse width or duty cycle. The use of a switchmode power converter promotes efficiency. The use of a fixed frequency enables control signals to be easily generated and synchronized from clock signals used by other parts of the line interface circuit. The use of a fixed frequency also ensures that undesired switching energy is limited to the region of this fixed frequency and its harmonics, and thus can be removed by narrow band filtering so that it does not disturb other subscriber lines (due to crosstalk) or subscriber equipment coupled to the line. Narrow band filtering has fewer side effects on service performance than wide band filtering. The use of a high frequency allows the energy storage components of the power converter to be small and relatively inexpensive, and enables operation above the critical frequency band mentioned above.
The power converter must have a relatively high power capability, because high voltage signalling functions such as ringing typically require power levels of 5 to 20 W for full compliance with performance specifications over a wide range of subscriber telephone and terminal loads. However, for most of the time the operation of the power converter involves the delivery of relatively low power levels, for example less than 0.5 W for on-hook situations (idle or on-hook transmission), 0.5 to 1.5 W for off-hook POTS (plain old telephone service) situations, and less than 2.5 W for ISDN (integrated services digital network) services. Message waiting also involves the delivery of a relatively low power level for prolonged periods, but requires high voltage operation of the power converter.
Switching losses in switchmode power converters typically increase in proportion to increase in the switching or operating frequency. The high operating frequency is desired as discussed above in order to meet the requirements for high voltage signalling such as ringing; the periods of such signalling are relatively short so that the power consumption and dissipation due to switching losses are not major concerns. However, during the low power and relatively prolonged operating states discussed above, it is desirable to reduce the switching losses in the power converter, thereby reducing power consumption and power dissipation, and increasing long-term reliability as a consequence of lower operating temperatures.
An object of this invention, therefore, is to provide an improved switchmode power converter for a telephone subscriber line interface circuit which can operate with reduced switching losses.
SUMMARY OF THE INVENTION
According to one aspect of this invention there is provided a switchmode power converter including a switching transistor having a controlled path connected in series with an inductor, a control circuit for controlling the transistor to conduct during pulses of a variable pulse width signal thereby to control an output voltage of the power converter, and a circuit for providing as the variable pulse width signal selectively either a first PWM (pulse width modulated) signal at a first fixed frequency or a second PWM signal at a second fixed frequency lower than the first fixed frequency, the second PWM signal having a smaller duty cycle than the first PWM signal.
Preferably the power converter includes a logic circuit for producing the second PWM signal from the first PWM signal by periodically masking pulses, for example alternate pulses, of the first PWM signal. In this case the first fixed frequency is a harmonic of the second fixed frequency.
For use of the power converter in a telephone subscriber line interface circuit, preferably the second fixed frequency is greater than 270 kHz, this being an upper limit of a critical frequency band in which there is a requirement for very low transmission of spectral energy to the subscriber line. It follows that the first fixed frequency is also greater than 270 kHz in this case.
The invention also provides a telephone subscriber line interface circuit including a power converter as recited above for selectively generating a ringing signal waveform for supply to a telephone subscriber line or a supply voltage for a driver circuit for supplying loop current on the line, and a control circuit for supplying the power converter with the first PWM signal for generating the ringing signal waveform and the second PWM signal for generating the supply voltage for the driver circuit.
According to another aspect of this invention there is provided a telephone subscriber line interface circuit comprising: a driver circuit for supplying loop current on a telephone subscriber line; a power converter for selectively generating either a high voltage ringing signal waveform for supply to the line or a supply voltage for the driver circuit, the power converter including a switching transistor having a controlled path for supplying current to an inductor and a PWM (pulse width modulated) circuit for controlling the switching transistor thereby to control a voltage generated by the power converter; and a control circuit for selectively supplying from the PWM circuit to the switching transistor a first PWM signal having a first fixed frequency when the power converter is generating the high voltage ringing signal and a second PWM signal having a second fixed frequency, less than the first fixed frequency, when the power converter is generating the supply voltage for the driver circuit.
The invention also provides a method of reducing power dissipation in a power converter which is used in a telephone subscriber line interface circuit for selectively generating either a high voltage signalling waveform, at a relatively high power level for supply to a telephone subscriber line, or a supply voltage, at a relatively lower power level for a driver circuit for providing loop current on the telephone subscriber line, the power converter comprising a switching transistor responsive to a PWM (pulse width modulated) control signal for controlling a voltage generated by the power converter, comprising the steps of: providing a first PWM signal at a first fixed frequency as the PWM control signal for generating the high voltage signalling waveform at a relatively high power level; and providing a second PWM signal at a second fixed frequency, lower than the first fixed frequency, as the PWM control signal for generating the supply voltage at a relatively lower power level.
The method preferably further comprises the step of selectively generating a high voltage message waiting signal at a relatively low power level for supply to the telephone subscriber line by providing the second PWM signal as the PWM control signal. This provides the advantage of low power operation of the power converter for possibly prolonged periods while a message waiting signal is provided on the line, even though this is a high voltage signal.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be further understood from the following description with reference to the accompanying drawings, in which:
FIG. 1 schematically illustrates a fixed frequency variable pulse width switchmode power converter which is substantially known from U.S. Pat. No. 5,103,387 referred to above;
FIG. 2 schematically illustrates part of a control circuit for the power converter of FIG. 1 provided in accordance with an embodiment of this invention;
FIG. 3 is a signal timing diagram with reference to which the operation of the circuit of FIG. 2 is explained; and
FIG. 4 is a block diagram illustrating a known arrangement of a telephone line interface circuit including the power converter.
DETAILED DESCRIPTION
Referring to FIG. 1, a fixed frequency variable pulse width (and hence duty cycle) switchmode power converter includes a transformer 10 having a primary winding and two secondary windings with senses or polarities as represented in FIG. 1 in conventional manner by dots adjacent to the windings. The primary winding is an inductor which is connected to a battery 12, constituted by the 48 V battery of a telephone C.O., via the controlled path of a power switching FET (field effect transistor) 14 and a diode 16 to prevent reverse conduction in this primary circuit. The FET 14 is controlled by a control pulse signal CP supplied to its gate via an inverting driver circuit (D) 18.
The two secondary windings of the transformer 10 are connected via respective diodes 20 and 22 and the controlled paths of respective power switching FETs 24 and 26 thereby to supply voltages with opposite polarities to a load represented by a resistor 28. An energy storage capacitor 30 is connected in parallel with the load resistor 28 to smooth the output voltage of the power converter. The FETs 24 and 26 are controlled by respective pulse signals PG and NG supplied to their gates via respective drive circuits (D) 32 and 34.
Except for the addition of the diode 16, the power converter of FIG. 1 is the same as described with reference to FIG. 3 of U.S. Pat. No. 5,103,387 already referred to above. Reference is directed to that patent for a complete description of the power converter, its operation, and the signals CP, PG, and NG. It is observed here that, as described in that patent, the signal CP (signal PCDB in the patent) is a periodic high frequency signal having negative-going pulses whose width determines the duty cycle or conductive period of the FET 14. The high frequency enables the capacitor 30 to be of a relatively small size while still satisfying the peak power requirements of the power converter, for example for supplying a ringing signal to the load represented by the resistor 28 and in that case constituted by the subscriber line and subscriber telephone equipment connected to it. For example, the high frequency can be 640 kHz and a signal at this frequency can be derived from higher frequency clock signals used in the line interface circuit.
Referring now to FIG. 2, a frequency divider 40 is illustrated which is supplied with a high frequency, e.g. 2.56 MHz, clock signal CK and produces from this by frequency division a pulse signal CH for example having a frequency of 640 kHz. A pulse width modulator (PWM) 42 is supplied with the signal CH and produces a PWM control pulse signal CTP. The width of the negative-going pulses of the signal CTP is determined in dependence upon an error signal VE representing differences between the output voltage of the power converter of FIG. 1 and a desired value of this output voltage, as described in detail in U.S. Pat. No. 5,103,387. As described by that patent, the signal CP in the present FIG. 1 would be constituted directly by the signal CTP in the present FIG. 2. Again, reference is directed to U.S. Pat. No. 5,103,387 for a full description of the manner in which the PWM 42 operates.
The control circuit of FIG. 2 further includes an AND gate 44 and an OR gate 46. The frequency divider 40 also produces a further frequency-divided pulse signal CL, for example having a frequency of 320 kHz, which is supplied to one input of the AND gate 44. A second input of this gate 44 is supplied with a binary signal L as described further below. The AND gate 44 produces at its output a pulse mask signal PM which is supplied to one input of the OR gate 46, the control pulse signal CTP from the PWM 42 being supplied to a second input of this gate 46. An output of the OR gate 46 forms a masked control pulse signal MCP, which in this embodiment of the invention is used to constitute the signal CP in the power converter of FIG. 1.
The signal timing diagram in FIG. 3 illustrates the signals CK, CH, CL (and hence the signal PM for the case when the signal L is a binary 1 (L=1)), CTP (and hence the signal MCP for the case when the signal L is a binary 0 (L=0)), and MCP for the case when L=1. As illustrated in FIG. 3, the signals CK, CH, and CL are square wave signals, the signal CL having half the frequency of the signal CH, which in this case has one quarter the frequency of the signal CK. For example, as indicated above the signals CK, CH, and CL can have frequencies of 2.56 MHz, 640 kHz, and 320 kHz respectively. Also as indicated above, the control pulse signal CTP is a PWM signal having negative-going pulses with the same frequency, 640 kHz, as the signal CH. As shown in FIG. 3, the pulses of the signal CTP have a falling edge which has a fixed timing centered relative to a binary 0 part of the signal CH, and a rising edge which is indicated by a double-headed arrow as occurring at a variable time depending on the PWM for controlling the output voltage of the power converter.
When the signal L is a binary zero (L=0), the AND gate 44 is inhibited so that the pulse mask signal PM is also a binary zero, and the output signal MCP is the same as the signal CTP as shown in FIG. 3. In this case the signal MCP supplied to the power converter as the signal CP is exactly the same as in the prior art. The power converter of FIG. 1 then operates entirely as described in U.S. Pat. No. 5,103,387, at an operating or switching frequency of 640 kHz. Thus a control circuit of the line interface circuit can provide the signal L=0 for operating the power converter as in the prior art to provide the desired high power levels for high voltage signalling such as ringing on the subscriber line.
When the signal L=1, the AND gate 44 is enabled, so that the pulse mask signal PM is the same as the signal CL. Via the OR gate 46, the binary 1 periods of this pulse mask signal inhibit alternate negative-going pulses of the signal CTP to produce the masked control pulse signal MCP. In consequence, it can be seen that the signal MCP in this case has a halved frequency of 320 kHz, and half the duty cycle of the signal CTP. Thus the control circuit of the line interface circuit can provide the signal L=1 for operating the power converter at the halved switching frequency, and hence with about half the switching losses, to provide the lower power levels for the more prolonged operating situations such as message waiting and d.c. feed as discussed above.
The halved duty cycle of the masked control pulse signal MCP is particularly advantageous in view of the nature of the power converter. The power converter has a so-called flyback or buck-boost architecture, in which energy stored in the inductor constituted by the primary winding of the transformer 10 is entirely transferred to the output in every switching cycle of the converter. In this circuit the current through the primary winding of the transformer rises linearly with time for as long as the controlled path of the FET 14 is conductive. Maintaining the same duty cycle at the halved operating frequency of 320 kHz as at the previous operating frequency of 640 kHz would undesirably result in increased peak currents in the primary winding circuit, and is not necessary because the extra power that this would generate is not required for the lower-power halved operating frequency. Halving the duty cycle in this case avoids any increase in peak currents, and is consistent with the lower power output required from the power converter at the lower operating frequency.
Thus it can be appreciated that in accordance with this embodiment of the invention, the power converter can have either of two operating modes, determined by the additional signal L. With L=0, the power converter operates at a switching frequency of 640 kHz for delivering high power levels to the load. With L=1, the power converter operates at the halved switching frequency of 320 kHz, switching losses are thereby approximately halved, and the duty cycle is halved so that there is no increase in peak currents. The PWM 42 continues to operate at the higher frequency of 640 kHz, but half of its output pulses in the signal CTP are masked. This provides a lower power output at greater efficiency, which is desirable for the prolonged operating situations such as message waiting and d.c. feed to the subscriber line as discussed above.
It should be appreciated that the power converter continues to operate as a fixed frequency, variable pulse width or duty cycle power converter (as distinct from variable frequency power converters), but the arrangement provides a selection of two different fixed frequencies for the power converter. As these fixed frequencies are harmonically related, narrow band filtering continues to be sufficient to remove unwanted switching energy. In addition, it will be noted that both frequencies are above the critical range of 4 kHz to 270 kHz for low spectral energy transmitted to the subscriber line, so that there is no need for complex filtering, which would increase costs and space requirements, in this frequency range.
FIG. 4 illustrates in a block diagram a known arrangement of a two-wire telephone subscriber line interface circuit, which is typically part of the telephone C.O., including a power converter or controlled voltage generator (CVG) 50 as described above. The line interface circuit also comprises a line driver circuit 52, a switching circuit 54 and a sensing circuit 56 via which outputs of the line driver circuit 10 are coupled to the tip wire T and the ring wire R of a two-wire telephone subscriber line 58, and the control circuit 60. Reference is directed to U.S. Pat. No. 5,323,461 already referred to for a complete description of the arrangement and operation of FIG. 4, which is only briefly described below.
The sensing circuit 56 provides on paths represented by a line 62 to the control circuit 60 signals representing currents on the line 58. The control circuit 60 monitors these currents and provides control signals for the power converter 50 and the switching circuit 54 via control paths 64 and 66 respectively. The power converter 50 is connected via a battery voltage line BV (typically -48 volts) and a battery return line BR (ground or zero volts) to the C.O. battery represented at 12 in FIG. 1. The power converter 50 produces at its output as described above a voltage CV which is controlled by the control circuit 60 via the control paths 64, via which the control circuit provides the signal MCP as described above.
The battery voltage line BV and the controlled voltage line CV are connected to the switching circuit 54, which under the control of the control circuit 60 selectively connects either of these to a driver voltage line DV which constitutes a supply voltage line for the line driver circuit 52. The tip and ring drive outputs of the line driver circuit 52, lines TD and RD respectively, are also connected to the switching circuit 54 which can connect them selectively, again under the control of the control circuit 60, to tip voltage and ring voltage lines TV and RV respectively, which in turn are coupled to the tip and ring wires T and R respectively via the sensing circuit 56 in known manner. The switching circuit 54 can also selectively connect, under the control of the control circuit 60, the controlled voltage line CV to one or both of the lines TV and RV to supply high voltage signalling to the line 58 as described above. The battery return line BR is optionally also connected to the switching circuit 54.
In operation, the control circuit 60 can control the switching circuit 54 to connect the line CV to the line TV and/or the line RV for high voltage signalling on the line 58, and to connect the line BV to the line DV to power the driver circuit 52 from the C.O. battery. The control circuit in this mode can produce either the signal L=0 for high power delivery such as for ringing signals, or the signal L=1 for low power delivery such as for a message waiting signal. Alternatively, the control circuit 60 can control the switching circuit 54 to connect the line CV to the line DV to power the driver circuit 52 from the power converter, and to connect the lines TD and RD to the lines TV and RV respectively for d.c. feed to the line 58. In this mode the control circuit 60 produces the signal L=1 for low power operation of the power converter 50.
Although the embodiment of the invention as described above is particularly convenient, especially in that it requires only the addition of the gates 44 and 46 and an extra stage of frequency division in the divider 40, together with the binary control signal L, the invention is not limited to this. Other switching frequencies, optionally with other than 2:1 frequency and/or duty cycle ratios, may be used, and with appropriate filtering the frequencies could be within the critical frequency range from 4 kHz to 270 kHz. Other arrangements can also be provided for producing the lower frequency pulse signal for controlling the power converter and determining its switching frequency. In addition, other control arrangements may be provided for selecting different switching frequencies for the power converter, and a selection from more than two such frequencies may be provided to facilitate operation at various different maximum power levels.
It is also noted that, although the above description largely relates high voltage signalling to high power levels and lower voltages to lower power levels, this need not be the case. For example, for message waiting signalling the power converter is required to provide high voltages and relatively low power, so that in this high voltage signalling state the power converter can be operated in its low frequency and low power mode as described above.
Thus although a particular embodiment of the invention has been described in detail, it should be appreciated that these and numerous other modifications, variations, and adaptations may be made without departing from the scope of the invention as defined in the claims. | A power converter forming part of a telephone subscriber line interface circuit selectively generates a ringing signal waveform, for supply to the line, or a supply voltage for a driver circuit for providing loop current on the line. First and second fixed frequency PWM signals are used to control the power converter, and hence the voltage which it generates, for the ringing signal waveform and the supply voltage respectively. The first PWM signal enables the power converter to provide a high power level needed for ringing signals. The second PWM signal has a lower frequency, and hence results in lower switching losses and power dissipation, and a lower duty cycle, suitable for the lower power level needed for the supply voltage, and is conveniently produced by masking pulses of the first PWM signal. The frequency of the second PWM signal is greater than 270 kHz, to avoid transmitting spectral energy to the line below this frequency. |
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to purine 4'-thioarabinonucleosides.
2. Related Art
The only purine 4'-thioarabinonucleoside reported heretofore is 9-(4-thio-β-D-arabinofuranosyl)adenine disclosed in J. Org. Chem., 33(1), pp. 189-192, 1968. However, that journal does not describe the biological activities of this compound.
Thus, it can be seen that purine 4'-thioarabino -nucleosides have scarcely been studied thus far. Therefore, it was considered that purine 4'-thioarabinonucleosides having biological activities superior to those possessed by previously known 4'-thioarabinonucleoside might be discovered.
SUMMARY OF THE INVENTION
Under the aforementioned circumstances, we conducted careful research to achieve the above object and found that a variety of purine 4'-thioarabinonucleosides can be easily obtained in a reduced number of reaction steps by the use of the novel synthesis method we developed, and that the resultant compounds have antiviral activities. The present invention was achieved based on these findings.
Accordingly, an object of the present invention is to provide a novel class of purine 4'-thioarabinonucleosides and a method for synthesizing these compounds.
In one aspect of the present invention, there is provided purine 4'-thioarabinonucleoside represented by the following formula I!: ##STR2## wherein B represents a purine base other than adenine.
In another aspect of the present invention, there is provided a method for preparing purine 4'-thioarabinonucleoside of formula I! comprising steps 1 through 4 described below.
Step 1:
In step 1, a sulfonyl group is introduced to each of the 2- and 5- positions of a compound of formula II!, after which the compound is reacted with a sulfide to obtain a compound represented by formula III!: ##STR3## wherein R 1 represents an alkyl group and R 2 represents a protective group for a hydroxyl group.
Step 2:
The furanose ring of the compound represented by formula III! is hydrolyzed and then reduced to obtain a compound represented by formula IV!: ##STR4## wherein R 1 and R 2 have the same meanings as defined above. Step 3:
The compound of formula IV!, while the hydroxyl groups at the 2- and 5- positions of the compound are protected, is reacted with an oxidizing agent to form a sulfoxide. The sulfoxide is converted into a compound of formula V! through Pummerer rearrangement: ##STR5## wherein Ac represents an acetyl group and each of R 2 and R 3 represents a protective group for a hydroxyl group.
Step 4:
The compound of formula V! is subjected to a glycosylation reaction so as to introduce a purine base represented by B to the 1- position of the saccharide moiety, after which the protective groups for the hydroxyl groups in the saccharide moiety are eliminated to obtain a compound of formula II!: ##STR6## wherein Ac, R 2 , R 3 , and B have the same meanings as defined above.
In still another aspect of the present invention, there is provided a pharmaceutical composition comprising purine 4'-thioarabinonucleoside represented by the above-described formula I! as an active ingredient.
The other objects, features, and advantages of the present invention will become apparent from the following description.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention will next be described in detail.
(1) Compounds
The compounds of the present invention are represented by formula I! described above. Purine bases represented by B in the formula encompass, in addition to well-known bases of nucleic acid such as guanine and hypoxanthine excepting adenine, azapurine derivatives (8-azapurine, 2-azapurine, etc.) and deazapurine derivatives (3-deazapurine, 7-deazapurine, etc.). B may have one or a plurality of substituents (such as lower (C1-C5) alkyl, halogen, amino, alkoxy, etc.) as a result of introduction of these substituents to one or more arbitrary positions of the above-mentioned bases including adenine. Specific examples of bases having such substituents include, but are not limited to, 2-aminopurine, 2,6-diaminopurine, 6-chloropurine, 6-chloro-2-aminopurine, 6-methoxypurine, 6-methoxy-2-aminopurine, and 6-cyclopropylmethylamino-2-aminopurine.
The compounds of the present invention may take the forms of salts, hydrates, or solvates. Examples of the salts include acid addition salts formed in combination with inorganic acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc.) or organic acids (fumaric acid, tartaric acid, succinic acid, etc.).
The hydrates and solvates may be those in which 0.1-3.0 molecules of water or a solvent is added to 1 molecule of the compound of the present invention or a salt thereof. Also, the compounds of the present invention encompass a variety of isomers such as α-anomers, β-anomers, and tautomers.
Particularly preferred are 9-glycosylated compounds of the β-anomer type. Specific examples of preferred compounds of the present invention include the following:
9-(4-thio-β-D-arabinofuranosyl)guanine
9-(4-thio-β-D-arabinofuranosyl)hypoxanthine
9-(4-thio-β-D-arabinofuranosyl)-2-aminopurine
9-(4-thio-β-D-arabinofuranosyl)-2,6-diaminopurine
9-(4-thio-β-D-arabinofuranosyl)-6-chloropurine
9-(4-thio-β-D-arabinofuranosyl)-6-chloro-2-aminopurine,
and
9-(4-thio-β-D-arabinofuranosyl)-6-methoxy-2-aminopurine.
(2) Process of Manufacture
The compounds of the present invention are synthesized through the following 4 steps.
Step 1:
In Step 1 of the method of the present invention, a sulfonyl group is introduced to each of the 2- and 5- positions of a compound of formula II!, after which the compound is reacted with a sulfide to obtain a compound represented by formula III!: ##STR7## wherein R 1 represents an alkyl group and R 2 represents a protective group for a hydroxyl group.
The starting material used in the method of the present invention is a xylose derivative (hereinafter may be referred to as the starting compound) represented by formula II!.
Examples of the alkyl group represented by R 1 include C1-C3 lower alkyl groups such as methyl and ethyl, and substituted or unsubstituted benzyl groups such as benzyl and methoxy benzyl.
The protective group for the hydroxyl group represented by R 2 is not particularly limited so long as it is selected from those which are generally used. Specific examples of the protective group include alkyl groups, silyl groups, and acyl groups. More specifically, alkyl groups which may be used for the purpose of protection include those listed for R 1 . Examples of silyl groups include t-butyldimethylsilyl, t-butyldiphenylsilyl, etc., and examples of acyl groups include acetyl, benzoyl, pivaloyl, etc.
The starting compound of the method of the present invention may be prepared using a well-known method such as the one described in Tetrahedron, 37, pp. 2379-2382 (1981), the content of which is incorporated herein by reference.
Examples of the sulfonyl group which is introduced into the hydroxyl groups at the 2- and 5- positions of the compound of formula II! include mesyl and tosyl.
A mesylation reaction and tosylation reaction may be performed using conventional methods. For example, mesylation reaction may be performed as follows. One mole of a starting compound is reacted with 2-10 mols, preferably 2-4 mols, of mesyl halide (e.g., mesyl chloride) at 0-100° C. for 0.5-5 hours while stirring in the presence of a base such as triethylamine in an organic solvent such as methylene chloride, acetonitrile, dimethylformamide, or pyridine (when pyridine is used as the organic solvent, a base such as triethylamine is not necessarily used). The reaction is preferably performed in an atmosphere of an inert gas such as argon or nitrogen.
Subsequently, the thus-obtained compound is reacted with a sulfide to afford a compound of formula III!.
The sulfide used in this reaction is not particularly limited as long as it is a metal sulfide (preferably, alkali metal sulfide) such as sodium sulfide, potassium sulfide, etc.
The reaction may be performed by reacting 1 mol of a starting compound with 1-20 mols of a sulfide at a temperature between room temperature and 150° C. for 0.5-5hours while stirring in an organic solvent such as dimethylformamide, dimethylsulfoxide, etc. When necessary, the reaction may be performed in an atmosphere of an inert gas such as argon or nitrogen.
The thus-produced compound of formula III! may be separated and purified using conventional means for the separation and purification of protected saccharides. For example, the mixture may be partitioned using ethyl acetate and water, after which silica gel column chromatography may be performed using an organic solvent mixture for elution such as n-hexane-ethyl acetate, thereby separating and purifying the formula III! compound.
Step 2:
In Step 2 of the method of the present invention, the furanose ring of the compound represented by formula III! is hydrolyzed and then reduced to obtain a compound represented by formula IV!: ##STR8## wherein R 1 and R 2 have the same meanings as defined above.
The method of hydrolysis is not particularly limited so long as the furanose ring of the compound of formula III! can be hydrolyzed by the method. Methods using acid catalysts are particularly preferred.
Examples of acid catalysts include inorganic acids such as hydrochloric acid, sulfuric acid, etc. and organic acids such as acetic acid and trifluoroacetic acid.
The hydrolysis reaction may be performed in a water-soluble ether-derived solvent such as tetrahydrofuran, dioxane, etc. in the presence of any one of the above-mentioned acid catalysts between room temperature and 100° C. for 0.5-5 hours while stirring.
When the thus-obtained compound is subjected to a reduction reaction, a compound of formula IV! is obtained.
Examples of reducing agents include tetrahydroborates such as sodium tetrahydroborate (sodium borohydride), potassium tetrahydroborate, etc.
The reduction reaction may be performed by reacting 1 mol of a compound of formula III! with 0.2-10 mols of a reducing agent in an alcoholic solvent such as methanol at a temperature between -80 and 100° C. for 0.5-3 hours while stirring.
The thus-obtained formula IV! compound may be separated and purified using conventional means for the separation and purification of protected saccharides. For example, neutralization of the reaction mixture at the completion of reaction, evaporation of the organic solvent, extraction using chloroform, and silica gel column chromatography may serially be performed so as to obtain the target compound as a separated and purified product.
Step 3:
In Step 3 of the method of the present invention, the compound of formula IV! is reacted with an oxidizing agent while protecting the hydroxyl groups at the 2- and 5- positions of the compound to form a sulfoxide. Subsequently, the sulfoxide is converted into a compound of formula V! through Pummerer rearrangement. ##STR9## wherein Ac represents an acetyl group and each of R 2 and R 3 represents a protective group for a hydroxyl group.
Examples of the protective groups represented by R 3 and introduced to the 2- and 5- positions of the compound of formula IV! include lower alkyl groups such as methyl and ethyl; substituted or unsubstituted benzyl groups such as benzyl and dimethoxybenzyl; silyl groups such as t-butyldimethylsilyl and t-butyldiphenylsilyl; and acyl groups such as acetyl, benzoyl, and pivaloyl.
Protective groups may be introduced by routine methods. For example, protective groups may be introduced by reacting 1 mol of a compound of formula IV! with 2-10 mols, preferably 3-8 mols, of an alkylating agent such as benzyl chloride, benzyl bromide, or p-methoxybenzyl chloride in a single organic solvent such as dimethylformamide, dimethylsulfoxide, etc. or in a solvent mixture such as tetrahydrofuran-dimethylsulfoxide in the presence of a base such as sodium hydride in an atmosphere of an inert gas such as argon, nitrogen, etc. at 0-50° C. overnight while stirring.
Examples of the oxidizing agent used in the oxidizing reaction include m-chloroperbenzoic acid and sodium metaperiodate.
The oxidizing reaction may be performed by reacting 1 mol of a compound of formula IV! in which the hydroxyl groups at the 2- and 5- positions are protected with 0.2-5 mols of an oxidizing agent (such as m-chloroperbenzoic acid, sodium metaperiodate, etc.) in an organic solvent such as methylene chloride or alcohol (e.g., methanol) in a stream of an inert gas such as argon or nitrogen, if necessary, at a temperature between -100 and 0° C. for 10 minutes to 2 hours.
When the thus-obtained sulfoxide is subjected to a Pummerer rearrangement reaction, a compound of formula V! is obtained.
The Pummerer rearrangement reaction may be performed by a conventional method. For example, the sulfoxide is stirred for 1-5 hours between 60° C. and the refluxing temperature in an acid anhydride such as acetic anhydride.
The thus-obtained formula V! compound may be separated and purified using conventional separation and purification techniques. For example, neutralization, evaporation of the organic solvent, extraction from the aqueous layer using chloroform, and silica gel column chromatography may sequentially be performed so as to obtain the formula V! compound as a separated and purified product.
If a purification step is required to be performed before oxidation reaction, the mixture may be partitioned using ethyl acetate and water, after which silica gel column chromatography may be performed using an organic solvent mixture for elution such as n-hexane-ethyl acetate, thereby separating and purifying the formula V! compound.
Step 4:
In Step 4 of the method of the present invention, the compound of formula V! is subjected to a glycosylation reaction so as to introduce a base represented by B to the 1- position of the saccharide moiety, after which the protective groups for the hydroxyl groups in the saccharide moiety are eliminated to obtain a compound of formula I!. ##STR10## wherein Ac, R 2 , R 3 , and B have the same meanings as defined hereinbefore.
Specific examples of Lewis acids used in the glycosylation reaction include, but are not limited to, trimethylsilyl trifluoromethane sulfonate, tin tetrachloride, titanium tetrachloride, zinc chloride, zinc iodide, and boron trifluoride.
The glycosylation reaction may be performed by reacting 1 mol of a compound of formula IV! with 1-10 mols of a base of nucleic acid and 0.1-10 mols of any one of the aforementioned Lewis acids in an organic solvent such as methylene chloride, chloroform, dichloroethane, acetonitrile, or dimethylformamide in a stream of an inert gas such as argon or nitrogen at a temperature between -50 and 100° C. for 1-3 hours. If a silylated base of nucleic acid is used, 7-glycosylated compounds can be synthesized with priority.
Subsequently, when the protective group for the hydroxyl group in the saccharide moiety is eliminated, a compound of formula I! is obtained.
The elimination of the groups protecting the hydroxyl groups may be suitably performed by hydrolysis, catalytic hydrogenation, or any other conventional process in accordance with the protective groups used. For example, when the protective groups are benzyl groups or benzyl-derived groups, they are eliminated through reaction with boron trichloride for between 10 minutes and 6 hours at a temperature between -100 and 50° C. in methylene chloride in a stream of an inert gas such as argon or nitrogen.
The thus-obtained compound I! may be separated and purified by a suitable combination of conventional separation and purification methods (recrystallization, a variety of column chromatography procedures, etc.) for nucleosides.
(3) Use
Since the compounds of the present invention exhibit excellent antiviral activities, pharmaceutical compositions containing the compounds as active ingredients are useful for the prevention or the treatment of subjects who have been infected with a virus or who run the risk of infection with a virus.
Examples of target viruses include herpes simplex virus type 1 (hereinafter referred to as HSV-1), herpes simplex virus type 2 (hereinafter referred to as HSV-2), human cytomegalovirus (hereinafter referred to as HCMV), and varicella zoster virus (hereinafter referred to as VZV), all of which belong to the herpes virus family.
The dosage of the compound of formula I!, an active ingredient of the pharmaceutical composition of the present invention, varies depending on the patient's age and body weight, identity of disease, severity of disease, tolerance to the drug, manner of administration, etc. Therefore, the dose is determined considering these factors as a whole so as to be suited to the patient. Generally, the dose is between 0.001 and 1,000 mg/kg body weight, and preferably between 0.1 and 100 mg/kg body weight, per day, and is administered at a single treatment or in plural doses.
The manner of administration is not limited, and may be peroral, parenteral, enteral, or topical administration.
When pharmaceutical compositions containing the compound of the present invention are formulated, it is a general practice to incorporate ordinarily employed carriers, vehicles, and other additives. Carriers may be either solid or liquid. Examples of solid carriers include lactose, kaolin, sucrose, crystalline cellulose, cornstarch, talc, agar, pectin, stearic acid, magnesium stearate, lecithin, and sodium chloride; and examples of liquid carriers include glycerol, peanut oil, polyvinyl pyrrolidone, olive oil, ethanol, benzyl alcohol, propylene glycol, and water.
The compositions may take arbitrary forms. For example, if a solid carrier is used, tablets, powders, granules, capsules, suppositories, lozenges, etc. may be formed, and if a liquid carrier is used, syrups, emulsions, soft gelatin capsules, creams, gels, pastes, sprays, injections, etc. may be formed.
The compounds of the present invention are expected to be developed and used as medicinal agents due to their remarkable antiviral activities. Moreover, the method of the present invention is particularly useful for the manufacture of purine 4'-thioarabinonucleoside because firstly it employs an inexpensive substance as a starting material, secondly it requires a reduced number of steps, and thirdly its procedure is simple and easy.
EXAMPLES:
The present invention will next be described by way of example. However, the invention should not be construed as being limited by any of the examples.
Example 1:
Synthesis of Ia-α!9-(4-thio-α-D-arabinofuranosyl)-2,6-diaminopurine and Ia-β!9-(4-thio-β-D-arabinofuranosyl)-2,6-diaminopurine (in formula I!, B=2,6-diaminopurine):
1) Synthesis of 2,5-anhydro-3-O-benzyl-1-O-methyl-2-thio-β-D-arabinofuranose (formula III!, R 1 =Me, R 2 =Bn)
While cooling on ice, methanesulfonyl chloride (6.33 ml) was added to 80 ml of pyridine in which 3-O-benzyl-1-O-methyl-β-D-xylofuranose (6.93 g, formula II!, R 1 =Me, R 2 =Bn) had been dissolved. The mixture was stirred for 1 hour at room temperature under a flow of argon. Reaction was stopped by adding ice-water, after which the solvent was evaporated. The residue was partitioned using ethyl acetate-water, and the organic layer was dried. The solvent was evaporated, and the residue was dissolved in dimethylformamide (DMF, 100 ml). Sodium sulfide (9.84 g) was added, and the mixture was stirred for 1 hour at 100° C. under a flow of argon. The solvent was evaporated, and the residue was partitioned using ethyl acetate-water. The organic layer was washed using water and then dried. The solvent was evaporated and the residue was purified by silica gel column chromatography. The fraction eluted with 5-10% ethyl acetate-n-hexane was collected and concentrated to obtain 5.05 g of the target compound (yield 73%).
1 H--NMR (CDCl 3 ) δ 7.36-7.29 (5H, m), 4.89 (1H, s), 4.62 (1H, d, J=11.7 Hz), 4.52-4.48 (2 H, m), 4.37-4.36 (1H, m), 3.34 (4H, s), 3. 04 (1H, dd, J=10.3, 2.0 Hz), 2.77 (1H, dd, J=10.3, 1.5 Hz)
2) Synthesis of 2,5-anhydro-3-O-benzyl-1-O-methyl-2- thio-α-D-arabinofuranose (formula III!, R 1 =Me, R 2 =Bn)
The procedure of 1) was repeated using 3-O-benzyl-1-O-methyl-α-D-xylofuranose (6.13 g, formula II!, R 1 =Me, R 2 =Bn) instead of 3-O-benzyl-1-O-methyl-β-D-xylofuranose , thereby obtaining 4.75 g of the target compound (yield 42%).
1 H--NMR (CDCl 3 ) δ7.39-7.30 (5H, m), 5.13 (1H, d, J=2.4 Hz), 4.66 (1H, d, J=11.7 Hz), 4.5 3 (1H, d), 4.36-4.35 (1H, brm), 4.29 (1H, t, J=2.4 Hz), 3.51 (1H, t, J=2.4 Hz), 3.47 (3H, s), 3.04 (1H, dd, J=10.5, 2.2 Hz), 2.95 (1H, dd, J=10.5, 1.2 Hz)
3) Synthesis of 3-O-benzyl-1-deoxy-4-thio-D- arabinofuranose (formula IV ! , R 2 =Bn)
2,5-Anhydro-3-O-benzyl-1-O-methyl-2-thio-D- arabinofuranose (9.50 g, α:β=1:1) was dissolved in tetrahydrofuran (THF, 200 ml). To the solution was added 4N--HCl (100 ml), and the mixture was stirred for 1 hour at room temperature. The reaction mixture was neutralized using solid sodium hydrogencarbonate. Insoluble matter was removed by filtration, after which THF was evaporated under reduced pressure. Extraction was performed three times using chloroform, and the organic layer was dried. The solvent was evaporated, and the residue was dissolved in methanol (150 ml). While cooling on ice, a methanol solution containing 1.43 g of sodium borohydride was added dropwise. After completion of addition, the mixture was stirred for 45 minutes while being cooled on ice. The reaction mixture was neutralized using acetic acid, after which the solvent was evaporated and the residue was partitioned using chloroform-water. The aqueous layer was extracted twice using chloroform, and the organic layer was dried. The solvent was evaporated, and the residue was subjected to silica gel column chromatography. The fraction eluted with 33-50% ethyl acetate-n-hexane was collected and concentrated to obtain 8.18 g of 3-O-benzyl-1-deoxy -4-thio-D-arabinofuranose (yield: 90%).
1 H--NMR (CDCl 3 --D 2 O) δ7.38-7.27 (5H, m) , 4.6 4 (2H, s) , 4.38 (1H, dt, J=2.9, 4.4 Hz), 3.96 (1H, t, J=2.9 Hz), 3.78 (1H, dd, J=2.9, 11.7 Hz), 3.66 (1H, dd, J=3.9, 11.7 Hz), 3.60 (1H, dt, J=2.9, 3.9 Hz), 3.21 (1H, dd, J=4.4, 11. 2 Hz), 2.90 (1H, dd, J=2.9, 11.2 Hz)
4) Synthesis of 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose (formula V!, R 2 =R 3 =Bn)
3-O-Benzyl-1-deoxy-4-thio-D-arabinofuranose (5.0 g, 20.8 mmol) was dissolved in dimethylformamide (100 ml). To the solution was added 60% sodium hydride (4.16 g, 104 mmol) under a flow of argon, and the mixture was stirred for 1 hour at 0° C. After the one hour of stirring, benzyl chloride (16.8 ml, 146 mmol) in dimethylformamide (52 ml) was added dropwise. The resultant mixture was stirred overnight at room temperature and subsequently poured into ice-water so as to stop the reaction.
The mixture was partitioned using ethyl acetate. The organic layer was washed with saturated brine and then dried over sodium sulfate. The solution was concentrated and purified by silica gel column chromatography (AcOEt: Hex =1:6), thereby obtaining 5.54 g of 1-O-deoxy-2,3,5-tri-O -benzyl-4-thio-D-arabinofuranose (yield: 63.3%).
Elementary analysis: for C 26 H 28 O 3 S
Calculated C: 74.25, H: 6.71
Found C: 74.28, H: 6.82
1 H-NMR (CDCl 3 ) δ7.35-7.25 (15H, m) , 4.90 (1H m), 4.72-4.45 (6H, m), 4.11 (1H, m), 3. 69 (1H, dd, J=7.3, 8.8 Hz), 3.56 (1H, ddd, J=3.4, 6.4, 7.3 Hz), 3.50 (1H, dd, J=6.4, 8.8 H z), 3.08 (1H, dd, J=4.9, 11.2 Hz), 2.90 (1H, dd, J=4.4, 11.2 Hz)
The resultant tribenzyl derivative (2.88 g, 6.85 mmol) was dissolved in distilled methylene chloride (40 ml). To the solution was added dropwise 80% m-chloroperbenzoic acid (1.48 g, 6.85 mmol) dissolved in distilled methylene chloride (40 ml) while maintaining the temperature at -78° C. under a flow of argon. The mixture was stirred for 30 minutes, and then the reaction was stopped using a saturated aqueous sodium hydrogen carbonate solution.
Subsequently, the mixture was extracted with methylene chloride, and the organic layer was washed once with a 10% sodium thiosulfate solution, twice with a saturated aqueous sodium hydrogen carbonate solution, and then once with saturated brine, followed by drying over sodium sulfate. The solution was concentrated to quantitatively obtain a sulfoxide.
To the resultant sulfoxide (6.85 mmol) was added acetic anhydride (34.2 ml), and the mixture was heated while stirring for 3 hours at 100° C. The mixture was allowed to cool, brought to dryness under reduced pressure, and purified by silica gel column chromatography (AcOEt:Hex=1:10), thereby obtaining 1.79 of 1-O-acetyl-2,3,5-tri-O -benzyl-4-thio-D-arabinofuranose (yield: 56.5%).
Elementary analysis: for C 28 H 30 O 4 S.0.75H 2 O
Calculated C: 70.63, H: 6.67
Found C: 70.37, H: 6.24
1 H--NMR (CDCl 3 ) δ 7.35-7.24 (15H, m), 6.07 (1H, d, J=3.9 Hz), 5.98 (1H, d, J=2.9 Hz), 4. 83-4.48 (6H, m), 4.26 (1H, dd, J=2.9, 4.9Hz), 4.18 (1 H, dd, J=3.9, 8.8 Hz), 4.12 (1 H, dd, J =6.8, 8.8 Hz), 4.03 (1H, dd, J=4.9, 6.4 Hz), 3.76 (1H, m), 3.73-3.44 (2H, m), 3.40 (1H, m), 2.04 (3H, s)
5) Synthesis of Ia-α!9-(4-thio-α-D-arabinofuranosyl) -2,6-diaminopurine and Iaβ!9-(4-thio-β-D-arabinofuranosyl) -2,6-diaminopurine (in formula I!, B=2,6-diaminopurine)
1-O-Acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose (800 mg, 1.67 mmol) was dissolved in distilled acetonitrile (7 ml). 2,6-Diaminopurine (452 mg) and molecular sieve 4A (897 mg) were added thereto. To the resultant mixture was added dropwise trimethylsilyl triflate (0.75 ml) at room temperature, and the mixture was stirred for 1 hour. Subsequently, a saturated aqueous sodium hydrogen carbonate solution was added, followed by stirring for 30 minutes to stop the reaction. The mixture was extracted with methylene chloride, and the organic layer was washed with a saturated aqueous sodium hydrogen carbonate solution, followed by drying over sodium sulfate. The residue was concentrated and purified by silica gel column chromatography (5% MeOH in CHCl 3 ). The resultant purified product (378 mg, 0.70 mmol) was dissolved in distilled methylene chloride (5 ml). 1.0 M Boron trichloride (4.2 ml) was added dropwise at -78° C. and the mixture was stirred for 1 hour. The mixture was further allowed to react for 2 hours at -20° C. The reaction was stopped using a saturated aqueous sodium hydrogen carbonate solution (1.05 g). The mixture was separated using methylene chloride, after which the aqueous layer was concentrated and desalted by silica gel column chromatography (CHCl 3 :MeOH=5:1). Subsequently, the title compound was obtained via reverse phase HPLC.
Ia-α! Melting point: 241-247 C. (H 2 O)
UV λ max (H 2 O) 281 nm (ε10300)
UV λ max (H 2 O) 259 nm (ε9000)
Elementary analysis for C 10 H 14 N 6 O 3 S.1H 2 O
Calculated C: 37.97, H: 5.10, N: 26.57
Found C: 37.90, H: 5.12, N: 26.39
1 H--NMR (DMSOd 6 ) δ8.00 (1H, s), 6.67 (2H, b r, D 2 O exchangeable), 5.78 (2H, br, D 2 O exchangeable), 5.75 (1H, br, D 2 O exchangeable ),5.58 (1 H, br, D 2 O exchangeable), 5.56 (1H, d, J=7.3 Hz), 4.90 (1H, br, D 2 exchangeable), 4.45 (1H, t, J=7.3 Hz), 3.86 (1H, dt, J=1.0, 11.0 Hz), 3.70 (1H, t, J=7.8 Hz), 3.6 3 (1H, m), 3.45 (1H, dt, J=8.1, 11.0 Hz)
Ia-β! Melting point: 292-295° C. (H 2 O)
UV λ max (H 2 O) 282 nm (ε0400)
UV λ max (H 2 O) 258 nm (ε8900)
Elementary analysis for C 1 H 14 N 6 O 3 S.0.75H 2 O
Calculated C: 38.52, H: 5.01, N: 26.95
Found C: 38.82, H: 4.97, N: 26.89
1 H--NMR (DMSOd 6 ) δ7.93 (1H, s), 6.67 (2H, b r, D 2 O exchangeable), 5.93 (1H, d, J=5.4 Hz) 5.74 (1H, d, J=4.9 Hz, D 2 O exchangeable), 5. 51 (1H, d, J=4.9 Hz, D 2 O exchangeable), 5.1 9 (1H, br, D 2 O exchangeable), 4.12 (1H, dt, J=5.9, 6.8 Hz), 4.04 (1H, dt, J=5.4, 6.8 Hz), 3.83 (1H, dd, J=4.9, 10.7 Hz), 3.68 (1H, dd, J=6.8, 10.7 Hz), 3.22 (1H, ddd, J=4.9, 5.9, 6.8 Hz,)
Example 2:
Synthesis of Ib-β!9-(4-thio-δ-D-arabinofuranosyl)guanine (in formula I!, B=guanine):
The procedure of Example 1-5) was repeated using 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose and guanine, thereby obtaining the title compound. The target compound was also able to be obtained by treating the compound prepared in Example 1 with deaminase.
Ib-β! Melting point: 260-264° C. (H 2 O)
UV λ max (H 2 O) 273 nm (ε9900)
UV λ max (H 2 O) 256 nm (ε13200)
Elementary analysis for C 10 H 13 N 5 O 4 S.1H 2 O
Calculated C: 37.85, H: 4.76, N: 22.07
Found C: 37.84, H: 4.76, N: 21.71
1 H--NMR (DMSOd 6 ) δ10.56 (1H, br), 7.92 (1H, s), 6.44 (2H, br, D 2 O exchangeable), 5.86 (1H, d, J=5.4 Hz), 5.71 (1H, d, J=5.4 Hz, D 2 O exchangeable), 5.49 (1H, d, J=4.9 Hz, D 2 O exchangeable), 5.14 (1H, t, J=5.4 Hz, D 2 O echangeable), 4.07 (1H, dd, J=5.4, 11.0 Hz), 4.03 (1H, dd, J=6.6, 11.0 Hz) 3.83 (1H, dt, J =5.4, 5.9 Hz), 3.67 (1H, dt, J=5.4, 5.9 Hz), 3.21 (1H, dt, J=5.4, 6.6 Hz)
Example 3:
Synthesis of Ic-α!9-(4-thio-α-D-arabinofuranosyl)adenine and Ic-β!9-(4-thio-β-D-arabinofuranosyl)adenine (in formula I!, B=adenine):
The procedure of Example 1-5) was repeated using 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose and adenine, thereby obtaining the title compound.
Ic-α! Melting point: 250° C. (H 2 O)
UV λ max (H 2 O) 261 nm (ε13600)
Elementary analysis for C 10 H 13 N 5 O 3 S 1
Calculated C: 42.40, H: 4.63, N: 24.72
Found C: 42.32, H: 4.60, N: 24.44
1 H--NMR (DMSOd 6 ) δ8.41 (1H, s), 8.15 (1H, s) 7.24 (2H, br, D 2 O exchangeable), 5.79 (1H, d, J=4.9 Hz, D 2 O exchangeable), 5.73 (1H, d, J=7.3 Hz), 5.61 (1H, d, J=4.4 Hz, D 2 O exchangeale), 4.93 (1H, t, J=4.6 Hz, D 2 O exchangeable), 4.56 (1H, dt, J=4.4, 7.3 Hz), 3.89 (1H, dt, J=3.9, 10.7 Hz), 3.75 (1H, dt, J=4. 4, 7.8 Hz), 3.66 (1H, ddd, J=3.9, 7.8, 8.1 Hz), 3.50 (1H, dt, J=8.1, 10.7 Hz)
Ic-β! Melting point: 138-140° C. (H 2 O)
UV λ max (H 2 O) 261 nm (ε11800)
Elementary analysis for C 10 H 13 N 5 O 3 S 1 .2H 2 O
Calculated C: 37.61, H: 5.37, N: 21.93
Found C: 37.66, H: 5.37, N: 21.93
1 H--NMR (DMSOd 6 ) δ8.36 (1H, s), 8.13 (1H, s), 7.22 (2H, br, D 2 O exchangeable), 6.05 (1H, d, J=5.4 Hz), 5.72 (1H, br, D 2 O exchangeable ), 5.51 (1H, d, J=2.9 Hz, D 2 O exchangeable), 5.19 (1H, br, D 2 O exchangeable), 4.18-4.1 1 (2H, m), 3.87 (1H, dd, J=3.9, 11.2 Hz), 3.7 8 (1H, dd, J=6.6, 11.2 Hz), 3.25 (1H, ddd, J=3.9, 5.9, 6.6 Hz)
Example 4:
Synthesis of Id-α!9-(4-thio-a-D-arabinofuranosyl)-2-aminopurine and Id-β!9-(4-thio-p-D-arabinofuranosyl)-2-aminopurine (in formula I!, B=2-aminopurine):
The procedure of Example 1-5) was repeated using 1-O-acetyl-2,3,5-tri-0-benzyl-4-thio-D-arabinofuranose and 2-aminopurine, thereby obtaining the title compound.
Id-α!
1 H--NMR (DMSOd 6 ) δ8.56 (1H, s), 8.37 (1H, s), 6.54 (1H, s), 5.81 (1H, d, J=5.9 Hz), 5.65 (1H, d, J=7.3 Hz), 5.62 (1H, d, J=4.9 Hz), 4.93 (1H, t, J=5.1 Hz), 4.47 (1H, dt, J=7.3 Hz), 3. 89 (1H, dt, J=3.4, 11.2 Hz), 3.72 (1H, dt, J=8.1 Hz), 3.64 (1H, dt, J=3.4, 8.1, 8.3 Hz), 3. 43 (1H, dt, J=8.3, 11.2 Hz)
Id-β!
1 H--NMR (DMSOd 6 ) δ8.56 (1H, s), 8.29 (1H, s), 6.51 (2H, s), 6.00 (1H, d, J=4.9 Hz), 5.74 (1H, d, J=4.9 Hz), 5.50 (1H, d, J=4.4 Hz), 5.16 (1H, t, J=4.9 Hz), 4.10 (1H, dt, J=4.9, 5.9 H z), 3.92 (1H, dt, J=3.4, 11.2 Hz), 3.75 (1H, dt, J=5.9, 8.3 Hz), 3.70 (1H, dt, J=7.8, 8.3, 11.2 Hz), 3.51 (1H, dt, J=7.8, 11.2 Hz)
Example 5:
Synthesis of Ie-α!7-(4-thio-α-D-arabinofuranosyl)adenine and Ie-β!7-(4-thio-β-D-arabinofuranosyl)adenine (in formula I!, B=adenine):
The procedure of Example 1-5) was repeated using 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose and silylated adenine (prepared via subjecting adenine and a catalytic amount of ammonium sulfate to refluxing in hexamethyldisilazane overnight), thereby obtaining the title compound.
Ie-α! Melting point: 247-249° C. (H 2 O)
UV λ max (H 2 O) 275 nm (ε9000)
UV λ max (H 2 O) 251 nm (sh, ε6000)
Elementary analysis for C 10 H 13 N 5 O 3 S 1 .0.55H 2 O
Calculated C: 40.96, H: 4.85, N: 23.88
Found C: 41.27, H: 5.22, N: 23.99
1 H--NMR (DMSOd 6 ) δ8.62 (1H, s), 8.22 (1H, s), 6.96 (2H, br, D 2 O exchangeable), 6.01 (1H, br, D 2 O exchangeable), 5.93 (1H, d, J=7.3 H z), 5.63 (1H, d, J=4.4 Hz, D 2 O exchangeable), 5.03 (1H, t, J=5.1 Hz, D 2 O exchangeable), 4. 16 (1H, dt, J=7.3, 8.3 Hz), 3.91 (1H, ddd, J=3.4, 5.1, 10.7 H z), 3.80 (1H, t, J=8.3 Hz), 3. 63 (1H, ddd, J=3.4, 7.8, 8.3 Hz), 3.53 (1H, d dd, J=5.1, 7.8, 10.7 Hz)
Ie-β! Melting point: 163-167° C. (H 2 O)
UV λ max (H 2 O) 273 nm (ε8900)
UV λ max (H 2 O) 249 nm (sh, ε6000)
Elementary analysis for C 10 H 13 N 5 O 3 S 1 .0.75H 2 O
Calculated C: 40.47, H: 4.92, N: 23.59
Found C: 40.83, H: 4.87, N: 23.64
1 H--NMR (DMSOd 6 ) δ68.89 (1H, s), 8.15 (1H, s) 6.80 (2H, br, D 2 O exchangeable), 6.08 (1H d, J=5.9 Hz), 5.78 (1H, d, J=5.9 Hz, D 2 O exchangeable), 5.46 (1H, d, J=5.9 Hz, D 2 O exchangeable), 5.33 (1H, t, J=4.6 Hz, D 2 O exchangeable), 4.14-4.10 (1H, m), 3.87-3.83 (1H, m), 3.81-3.79 (2H, m), 3.16 (1H, ddd, J=4.4, 7.8, 8.3 Hz)
Example 6:
Synthesis of If-α!7-(4-thio-α-D-arabinofuranosyl)-2,6-diaminopurine and If-β!7-(4-thio-β-D-arabinofuranosyl)-2,6-diaminopurine (in formula I!, B=2,6-diaminopurine):
The procedure of Example 1-5) was repeated using 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose and silylated 2,6-diaminopurine (prepared via subjecting 2,6-diaminopurine and a catalytic amount of ammonium sulfate to refluxing in hexamethyldisilazane overnight), thereby obtaining the title compound.
If-α!
1 H--NMR (DMSOd 6 ) δ8.21 (1H, s), 6.49 (2H, s), 5.97 (1H, bs), 5.76 (1H, d, J=7.8 Hz), 5.62 (1H, bs), 5.59 (2H, s), 5.02 (1H, bs), 4.12 (1H, dt, J=8.3 Hz), 3.89 (1H, m), 3.58-3.49 (2H, m), 3.46 (1H, dt)
If-β!
1 H--NMR (DMSOd 6 ) δ8.51 (1H, s), 6.30 (2H, s), 5.95 (1H, d, J=5.4 Hz), 5.44 (2H, s), 4.08 (1 H, dd, J=5.4 Hz), 3.86 (1H, dd, J=8.3 Hz),3. 78-3.72 (2H, dd×2, J=3.4, 4.9, 11.2 Hz),3. 13 (1H, dt, J=3.4, 4.9, 8.3 Hz)
Example 7:
Synthesis of Ig-α!7-(4-thio-α-D-arabinofuranosyl)-2-aminopurine and Ig-β!7-(4-thio-β-D-arabinofuranosyl)-2-aminopurine (in formula I!, B=2-aminopurine):
The procedure of Example 1-5) was repeated using 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose and silylated 2-aminopurine (prepared via subjecting 2-aminopurine and a catalytic amount of ammonium sulfate to refluxing in hexamethyldisilazane overnight), thereby obtaining the title compound.
Ig-α!
1 H--NMR (DMSOd 6 ) δ8.79 (1H, s), 8.42 (1H, s), 6.28 (2H, s), 5.93 (1H, bs), 5.70 (1H, d, J=7. 3 Hz), 5.65 (1H, bs), 4.99 (1H, bs), 4.23 (1H, dt, J=7.3, 7.8 Hz), 3.91 (1H, dt, J=3.4, 11. 2 Hz), 3.70 (1H, dt, J=7.8, 8.3 Hz), 3.66 (1H, m, J=3.4, 7.8, 8.3 Hz), 3.51 (1H, dt, J=7.8, 11.2 Hz)
Ig-β!
1 H--NMR (DMSOd 6 ) δ8.76 (1H, s), 8.59 (1H, s), 6.14 (1H, s), 6.00 (1H, d, J=5.9 Hz), 5.69 (1H, d, J=5.4 Hz),5.45 (1H, d, J=5.4 Hz),5.26 (1H, t, J=4.9 Hz), 4.09 (1H, m), 3.93 (1H, m, J=5.9 Hz), 3.81 (1H, m, J=4.4 Hz), 3.77 (1H, m), 3.24 (1H, m)
Formulation Example 1: Tablets
______________________________________Compound of the invention 30.0 mgMicrocrystalline cellulose 25.0 mgLactose 39.5 mgStarch 40.0 mgTalc 5.0 mgMagnesium stearate 0.5 mg______________________________________
Using the above components, tablets were prepared via a routine method.
Formulation Example 2: Capsules
______________________________________Compound of the invention 30.0 mgLactose 40.0 mgStarch 15.0 mgTalc 5.0 mg______________________________________
Using the above components, capsules were prepared via a routine method.
Formulation Example 3: Injection preparation
______________________________________Compound of the invention 30.0 mgGlucose 100.0 mg______________________________________
The above components were dissolved in purified water for injection preparations, thereby obtaining an injection liquid.
Test Examples
Test Method
(1) Anti-HSV-1 Activity and Anti-HSV-2 Activity
1. Human fibroblasts derived from fetal lungs were subjected to subculturing in Eagle MEM supplemented with 10% semi-fetal calf serum (Mitsubishi Chemical Corporation) at a 1:2-4 split every 4 days.
2. A suspension of cells obtained by splitting their parent cells (1:2) was seeded in a 12-well multi-plate (2 ml/well), followed by culturing for 4-5 days at 37° C. in a CO 2 -incubator.
3. The culture liquid was discarded, and Hanks' MEM (250 μl) containing 50-150 PFU of VR-3 strain of HSV-1 or MS strain of HSV-2 was inoculated, and the virus was allowed to be adsorbed for 30 minutes at 37° C. Thereafter, the viral liquid was discarded.
4. A 2.5% serum-added Eagle MEM containing a test compound and 0.8% methylcellulose was added and the resultant mixture was incubated in a CO 2 -incubator for 2-3 days at 37° C. Generally, a test compound is diluted in serial 1/2 log 10 , and the maximal concentration is 10 μg/ml.
5. The culture liquid was discarded, and the cells were stained with a 0.5% crystal violet solution. Under a stereoscopic light microscope, the number of plaques in each well was counted. Using the equation below, the plaque formation inhibitory ratio (percent inhibition) was obtained.
Percent Inhibition=(1 -N.sub.1 /N.sub.2)×100
wherein N 1 represents the number of plaques in wells containing the test compound and N 2 represents the number of plaques containing in the control well (which contains no test compound).
6. The plaque formation inhibitory ratio was plotted on a graph with respect to the concentration of the test compound (logarithmic representation). From this doseplaque inhibition curve, the concentration of the test compound exhibiting 50% inhibition was obtained (ED 50 ).
(2) Anti-Varicella Zoster Virus (VZV) Activity
1. Human fibroblasts derived from fetal lungs were subjected to subculturing in Eagle MEM supplemented with 10% semi-fetal calf serum (Mitsubishi Chemical Corporation) at a 1:2-4 split every 4 days.
2. A suspension of cells obtained by splitting their parent cells (1:2) was seeded in a 12-well multi-plate (2 ml/well), followed by culturing for 4-5 days at 37° C. in a CO 2 -incubator.
3. The culture liquid was discarded, and 750 μl of a 5% serum-added Eagle MEM containing 50-100 PFU of Oka strain of VZV was inoculated, and the virus was allowed to be adsorbed for 1 hour at 37° C.
4. Without removing the virus, 750 μl of Hanks' MEM containing the test compound was added, and the resultant mixture was incubated in a CO 2 -incubator at 37° C. Generally, a test compound is diluted in serial 1/2 log 10 , and the maximal concentration is 10 μg/ml.
5. After culturing for 4-5 days, the culture liquid was discarded, and the cells were stained with a 0.5% crystal violet solution. Under a stereoscopic light microscope, the number of plaques in each well was counted. Using the equation used in (1) above, the plaque formation inhibitory ratio was obtained.
6. The plaque formation inhibitory ratio was plotted on a graph with respect to the concentration of the test compound (logarithmic representation). From this doseplaque inhibition curve, the concentration of the test compound exhibiting 50% inhibition was obtained (ED 50 ).
(3) Anti-Human Cytomegalovirus Activity
1. Human fibroblasts derived from fetal lungs were subjected to subculturing in Eagle MEM supplemented with 10% semi-fetal calf serum (Mitsubishi Chemical Corporation) at a 1:2-4 split every 4 days.
2. A suspension of cells obtained by splitting their parent cells (1:2) was seeded in a 12-well multi-plate (2 ml/well), followed by culturing for 4 days at 37° C. in a CO 2 -incubator.
3. The culture liquid was discarded, and 750 μl of a 5% serum-added Eagle MEM containing 50-100 PFU of AD-169 strain of HCMV was inoculated, and the virus was allowed to be adsorbed for 1 hour at 37° C.
4. Without removing the virus, 750 μl of Hanks' MEM containing the test compound was added, and the resultant mixture was incubated in a CO 2 -incubator at 37° C. for 4 days. Generally, a test compound is diluted in serial 1/2 log 10 , and the maximal concentration is 10 μg/ml.
5. The medium was changed to a fresh 2.5% serum-added Eagle MEM containing 0.8% methylcellulose and the test compound having the same concentration, followed by culturing further for 4-5 days.
6. The culture liquid was discarded, and the cells were stained with May-Gruenwald's-Giemsa (×10). Under a stereoscopic light microscope, the number of plaques in each well was counted. Using the equation used in (1) above, the plaque formation inhibitory ratio was obtained.
7. The plaque formation inhibitory ratio was plotted on a graph with respect to the concentration of the test compound (logarithmic representation). From this doseplaque inhibition curve, the concentration of the test compound exhibiting 50% inhibition was obtained (ED 50 ).
The results of these tests are shown in Table 1 below.
TABLE 1______________________________________Compound ED.sub.50 (μg/ml)No. HSV-1 HSV-2 VZV HCMV______________________________________Ia-β 0.52 0.40 0.11 0.022Ib-β 0.49 0.59 0.11 0.011______________________________________ | The present invention provides a novel purine 4'-thioarabinonucleoside represented by the following formula 1!: ##STR1## wherein B represents a purine base other than adenine. Also disclosed are a method for preparing the purine 4'-thioarabinonucleoside and pharmaceutical compositions containing the purine 4'-thioarabinonucleoside. |
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to brake elements and more particularly to a method of removing a brake lining therefrom.
2. Description of the Related Art
As the number of vehicles on our highways continues to grow, so will the demand for replacement auto parts including brake shoes used with drum brakes and brake pads used with disc brakes. Brake shoes and pads are well known and have a base plate with a lining rivetted or otherwise bonded thereto. The lining progressively wears down until such time as the brake shoes and pads have to be replaced. The auto industry has for years recycled brake shoes and pads by replacing the old linings with new ones. However, the process to remove these linings has been uneconomical, time consuming and awkward.
It is an object of the present invention to provide a novel device for removing the lining from brake elements.
SUMMARY OF THE INVENTION
Briefly stated, the invention involves a device for removing the lining from a brake element, comprising:
frame means,
fixture means supported by the frame means for locating a brake element, the brake element having an inner concave surface and an outer convex surface, the fixture means having a first surface to engage the inner concave surface;
clamping means for removably clamping the brake element to the fixture means;
the fixture means further comprising a plurality of rivet extraction means, each of the rivet extraction means being arranged to align with a corresponding rivet in the brake element,
the fixture means further comprising a second surface,
cam means providing a cam surface adjacent the second surface, the rivet extraction means being arranged to engage the cam means at the second surface.
In another aspect of the present invention, there is provided a technique for processing a brake element, comprising the steps of:
providing a frame,
supporting a fixture by the frame for locating a brake element, the brake element having an inner concave surface and an outer convex surface,
providing the fixture with a first surface to engage the inner concave surface;
removably clamping the brake element to the fixture;
providing in the fixture a plurality of rivet extraction elements, and arranging the extraction elements to align with a corresponding rivet in the brake element,
providing the fixture with a second surface,
providing a cam element with a cam surface adjacent the second surface, and arranging the rivet extraction elements to engage the cam means at the second surface, thereby to extract the rivets from the brake element.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention will now be described, by way of example only, with reference to the appended drawings in which:
FIG. 1b is an exploded perspective view of a brake element;
FIG. 1 is a fragmentary perspective view of a brake element processing device;
FIG. 1ais a front view of the device illustrated in FIG. 1;
FIG. 2 is an enlarged fragmentary perspective view of a portion of the device illustrated in FIG. 1;
FIG. 2a is an enlarged front view of a portion of the device illustrated in FIG. 1;
FIG. 3 is a rear fragmentary view of the device illustrated in FIG. 1;
FIG. 4 is a fragmentary part-schematic view taken on line 4--4 of FIG. 1;
FIG. 5 is a fragmentary sectional view of a portion of the device illustrated in FIG. 1;
FIG. 6 is a fragmentary perspective view of another portion of the device illustrated in FIG. 1;
FIG. 7 is a fragmentary side view of yet another portion of the device illustrated in FIG.1;
FIG. 7a is a schematic view of the portion illustrated in FIG. 7;
FIG. 8 is a fragmentary sectional view of yet another portion of the device illustrated in FIG. 1; and
FIG. 9 is a view taken on arrow 9 of FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before discussing the preferred embodiment, it would be useful to describe the typical brake element, such as a brake shoe 10 as illustrated in FIG. 1b, As can be seen, the brake shoe 10 has a central web portion 12 and two outer rivet-containing shoe portions 14, 16 each on a corresponding side of the web portion 12, along with an inner concave surface 18 and an outer convex surface 20. A brake lining 22 is attached to the shoe portions 14, 16 by way of rivets 24. The pattern of the rivets of course will vary with the type of brake shoe and the manufacturer thereof.
Referring to the figures, there is provided a device 30 for removing the brake lining from a brake element, such as a brake shoe 10. The device 30 has a frame means in the form of a frame assembly shown generally at 32. A fixture means 34 is supported by the frame means and is provided to locate a brake shoe 10. Clamping means in the form of three hydraulic rams 36 are provided for removably clamping the brake shoe 10 to the fixture means. The rams are arranged at the two, twelve and ten o'clock positions in order to engage the end regions and the central region of the brake shoe.
Referring to FIG. 5, the fixture means is in the form of an arcuate fixture member, as part of a cylindrical fixture assembly 38 with a pair of cylindrical portions 38a, 38b joined by a pair of blocks shown at 38e in FIG. 5 thereby to form a gap between the portions to accommodate the central web portion 12 of the brake shoe.
One of the blocks 38e is also equipped with a shoe ejection mechanism 41 having a ejection block 41a joined to a piston 41b itself slidably mounted in a passage 41c in the block 38e. A spring biases the piston downwardly and the lower end of the piston is pivoted to a link 41d which in turn is pivoted to a yoke 41e thereby to provide a free end that is downwardly movable to displace the block upwardly to eject the brake shoe. If desired, the shoe ejection mechanism may be automated by way of a solenoid shown in phantom at 41f in place of line 41e.
Referring to FIG. 1a, each portion 38a, 38b of the fixture assembly 38 has a rectangular cross section and with a first surface 38c to engage the inner concave surface 18 of the brake lining and a second surface 38d. Located on opposite sides of the fixture assembly are reject chutes 39 to transfer the remains of the removed lining away from the remaining brake shoe.
A cam means in the form of a cam assembly 40 is provided inside the fixture member and has a cam surface 42 adjacent the second surface 38d. The cam assembly 40 is fixed to a shaft 44 which is arranged to rotate about a central first axis corresponding to the central axis of the arcuate member and is operable in a plane perpendicular with the first axis. Referring to FIGS. 7 7a, the cam assembly 40 further includes first and second cam members 46, 48 spaced by a spacer member 50, which is aligned with the web portion 12 and wherein the first and second cam members 46, 48 are aligned with a respective one of the outer shoe portions 14, 16 of the brake shoe. Referring to FIG. 7, each cam member has a pair of cam elements 46a, 46b, 48a, 48b. Each cam elements is aligned with one row of rivets and are spaced by a spacer portion 46c, 48c. It will be seen that the cam elements are offset or staggered for each cam member so that the pins driven for example by cam element 48b are displaced first, followed by the pins driven by cam element 48a, followed thereafter the pins driven by cam elements 46b and 46a respectively.
The fixture means further includes a plurality of rivet extraction means shown generally at 52 in FIG. 2a each of the rivet extraction means 52 being arranged to align with a corresponding rivet in the brake shoe 10. In this embodiment, the fixture member has a number of passages 54 and each rivet extraction means 52 includes a sleeve 56 removably mounted in the passage 54 and an extraction pin 58 slidably mounted in the sleeve 56. Each passage 54 is arranged so that the pin 58 travels along an axis perpendicular to and passing through the axis of the shaft 44.
Each pin 58 has a relatively thick trunk section 59 and a head portion 60 extending beyond the second surface 38b for engagement with the cam surface of the corresponding cam member. Guide means in the form of a guide flange 62 is mounted on the outer surface of each spacer portion for engaging the head portions 60 thereby to maintain the head portion 60 in engagement with the cam surface 42 to retract the pin 58 during a predetermined range of return travel of the first cam member 46.
Referring to FIG. 6, each ram 36 of the clamping means is provided with an anvil 36a with a number of passages 36b along its periphery. The dimensions of the anvil and the passages are arranged so that the anvil may be engaged with the entire width of the brake shoe while not interfering with the rivet extraction pins 58.
Referring to FIG. 4, the frame assembly includes a back plate 32a and a pair of rear supports 32b, all of which are secured to a base plate 32c by way of threaded fasteners. The shaft is supported on the back plate by way of a bearing unit 44a and a lock nut 44b. The cam assembly is keyed to the shaft by the key shown at 44c and the dimensional tolerances between the shaft and the cam assembly are sufficiently close to ensure a force fit therebetween. The shaft is further formed with a thickened midsection 44e and a flange 44f, the latter of which works with the lock nut to hold the shaft in position relative to the back plate.
The end of the shaft 44 adjacent the cam assembly is supported by the fixture member 38 with a bushing element therebetween at 44d. The bushing is held within a cross member 45, itself secured to the periphery of the fixture member 38, thereby allowing the shaft to rotate relative to the stationary fixture assembly, itself secured to the base plate. The shaft extends through the back plate and terminates at a pinion element 70. Aligned with the pinion element 70 is a vertically oriented rack element 72 supported by a linear bearing assembly 74. Driving the rack element is a hydraulic ram 76. The rack element is movable downwardly toward and through a passage 32e formed in the base plate 32c to allow the full length of the rack element to be used to drive the pinion. The hydraulic ram 76, along with the rams 36 driving the anvils are controlled by a hydraulic valve unit 78 which is fed by a hydraulic pump reservoir unit 80.
The valve assembly 78 is joined with the ram 76 by way of line 78a and with the rams 36 by way of lines 78b, 78c and 78d. In turn, the return lines 80a, 80b, 80c and 80d join the rams 76 and 36 with the reservoir 80 to complete the hydraulic circuit.
Referring to FIGS. 1a and 2, each ram 36 is mounted on the back plate 32a by way of a brace 35, itself held against the back plate by removable fasteners. If desired, the brace may be made adjustable by way of adjustment slots 35a, thereby permitting the anvils to be aligned with the new rivet pattern of a different brake shoe. The brace 35 includes a back plate 35b and a pair of outwardly extending support webs 35c. Extending between and joined to the webs 35c is a support plate 35d with a passage therethrough to receive the piston of each hydraulic ram 36. The hydraulic ram 36 has a base block 36a which is also fixed to the support plate.
Each anvil is provided with a positioning arm 36d which extends past a contact switch 37. The positioning arm ends with a jog 36e which is arranged to engage the contact arm 37a of the contact switch to register the extension of the ram to a position with the anvil firmly on the brake shoe. The brace further incudes a cross member 35e secured to the support webs 35c and carries both the contact switch 37 and a pair of positioning wheels 37b to guide the positioning arm. The contact switch is well known and has a wheel 37c mounted on its remote end to engage the job. Referring to FIG. 1, the middle ram is further provided with a protective shield 43 which is mounted on a pair of lateral extensions 36f of the positioning arm 36d.
Referring to FIG. 4, a controller 82 is also provided for monitoring the functioning of the device 10. The controller has a programmer controller unit such as that sold under the tradename OMRON. A number of contact switches, such as that shown at 37, are provided at 84 to monitor the arrival of the three anvils to their position on the upper surface of the brake shoe. A contact switch is also provided to monitor the arrival of the rack element to a fully extended position corresponding to the arrival of the cam assembly to a full displacement position. Finally, either one of a pair of activation buttons 86 may be depressed to activate the device.
The controller 82 conveys signals to valve the valve assembly, that is to the valve units controlling rams 36 and 76, by way of paths 82a to 82d. In addition, the controller receives signals from contact switches 37 by way of paths 83a to 83d and from the activation switches by way of a pair of paths, one of which is shown at 83e.
The device 10 may be operated in the following manner. First, a brake shoe is installed on the fixture assembly. One of the activation buttons may then be depressed causing the controller to open the valves controlling the supply of hydraulic fluid to the three rams 36, thereby causing the anvils to be displaced to a position against the outer convex surface of the brake lining. As each anvil reaches its appropriate destination, a respective contact element registers the arrival with the controller. When all three switches register arrival, the controller opens the valves controlling the supply of hydraulic fluid to the ram 76 causing the downward travel of the rack element and the resultant rotation of the pinion, in turn causing the corresponding rotation of the cam assembly in a counter-clockwise rotation as viewed in FIG. 1a.
Due to the relative offset of the cam elements, the cam element 48b first engages the pins near the two o'clock position of the brake shoe as viewed from FIG. 1a. As the cam element 48b progresses, so does the cam surface progressively upwardly causing each successive pin element in its path to be displaced upwardly. As a result, the pin is pressed against a corresponding rivet and under the action of the anvils, forces the rivet through the lining. As the cam element 48b progresses the cam element 48a follows at the two o'clock position and so on until all four cam elements have upwardly displaced all of the pins resulting in the extraction of all rivets holding the lining to the shoe.
the contact switch 84 registers the arrival of the cam assembly to its full rotation position and a signal is conveyed to that effect to the controller. As a result, the controller opens the valves causing the cam assembly to be returned to its ready position and the anvils to be returned to their ready position, leaving the lining, possibly in pieces, loose on top of the shoe. The lining may then be ejected along either reject chute 39. The operation to return the cam assembly to its ready position is governed by a timer 86 by way of path 86a.
Periodically, the force of the anvil against the shoe causes the shoe to jam into the fixture. In this case, the ejection device may be activated by downwardly depressing the link 41d of the ejection mechanism causing the block to be upwardly displaced forcing the web upwardly out of the fixture.
Due to the rugged environment of the device, periodically, an ejector pin will be broken or become worn. The device is arranged to permit the pins to be removed, simply by pulling the pin out of the sleeve from the top of the fixture assembly, without the need for further disassembly. Similarly, the sleeves are force fit into the passages and can be replaced by simply tapping them out.
Periodically, a brake shoe may be positioned improperly on the fixture assembly, causing the rivets of the brake shoe to be mismatched with the corresponding pins. As a result, some of the pins may in fact be aligned with the base of the shoe rather than a pin. To detect the presence of an improperly positioned brake shoe, a pressure sensor 88 is provided on the hydraulic line supplying the hydraulic ram 76 to sense a sudden increase in supply pressure as would occur if a pin were pressed against the steel base rather than the rivet. The sensor conveys a reset signal to controller 82 via path 88a in the presence of this sudden increase in supply pressure. For example, a normal hydraulic pressure needed to force a rivet from the shoe might be about 2500 psi. A misaligned pin might cause for example pressures as high as 2800 psi or higher until pin failure. Therefore, the sensor should detect pressures exceeding normal operating pressures, such as say 2600 pounds, while taking into account normal variations in rivet strength.
Referring to FIGS. 1 and 1a, the device may be incorporated into an assembly line by providing conveyors for both the shoes and the lining. For example, a conveyor 90 may if desired be located beneath the device to collect lining fragments from the fixture assembly. In this case, the device would be provided with passages 92 in the downward trajectory of the lining fragments from the fixture assembly in place of the reject chutes, along with a collection hopper to gather the fragments for delivery to the conveyor. | Disclosed herein is a device for processing a brake element having a frame supporting a fixture for locating a brake element. The brake element has an inner concave surface and an outer convex surface. The fixture has a first surface to engage the inner concave surface. A clamp arrangement removably clamps the brake element to the fixture which has a plurality of rivet extraction elements, each being arranged to align with a corresponding rivet in the brake element. The fixture has a second surface and a cam element is provided with a cam surface adjacent to the second surface and the rivet extraction elements are arranged to engage the cam means at the second surface. |
TECHNICAL FIELD
This invention relates to wafer holding and support fixtures having low effective thermal mass and a method for making such fixtures.
BACKGROUND OF THE INVENTION
Rapid thermal processing equipment has found prior application in the manufacture of electronic integrated circuits in processing not involving a chemical reaction such as thermal annealing in Rapid Thermal Annealing (RTA) apparatus manufactured by such companies as Varian Associates, Inc., A.G. Associates and Eaton Corporation. The semi-conductor wafers are treated in an RTA from room temperatures to about 400° to 1400° C. in periods of time on the order of a few seconds. The ability of such RTA systems to rapidly heat and cool a wafer from room temperature to such high temperatures in periods of up to 10 seconds make them attractive for use in chemical reaction processes such as epitaxial film, amorphous silicon or polycrystalline silicon deposition. Such processes are referred to as Rapid Thermal processing (RTP) systems. Examples of such RTP systems currently being sold for chemical reaction purposes are manufactured by ASM Epi and AG Associates.
The wafer holding fixtures and other components of RTA equipment have in the past been comprised of quartz which results in inherent problems with its use. Quartz is inadequate in RTP systems because of the effect the process reaction environment has on quartz and the thermal incompatibility with materials that are deposited on quartz surfaces. There is a need for wafer holding fixtures for use in RTP systems consisting of materials other than quartz.
U.S. Pat. No. 4,481,406 discloses that wafer support structures formed of non-conductive refractive materials such as a ceramic material are useful in RTP equipment. Wafer holders of, for example, silicon carbide chemical vapor deposited on graphite provide the necessary compatibility with process environment and resists the thermal shock of rapid temperature fluctuations from room temperature to 1400° C. In a typical chemical vapor deposition (CVD) process, the graphite or other substrate to be coated is heated in a suitable reactor and then a silicon-containing gaseous reactant mixture is introduced to the reactor. The gaseous reactant mixture reacts at the surface of the substrate to form a coherent and adherent layer of the desired coating. By varying the gaseous reactant mixture and other CVD process parameters, various types of deposit coatings can be produced. The disadvantage of using a CVD coated substrate is that the thermal mass of all of these prior art support structures is high relative to that of the wafer so that they do not undergo the rapid temperature changes that are needed in RTA and RTP systems. This makes such applications for such CVD coated substrates unattractive.
U.S. Pat. No. 4,417,347 discloses the use of metal membranes of tantalum and molybdenum having the necessary low thermal mass to facilitate the rapid heating and cooling for RTA systems. However, such materials are not useful in RTP systems because of the reaction between the metals and the silicon which form metal silicides in the epi process. Such reactions create unacceptable problems of particulates in the epi system and contamination of the wafers being processed.
SUMMARY OF THE INVENTION
In contrast, the fixtures of the present invention overcome the disadvantages of the prior art wafer holders presently being used in RTA and RTP systems. The wafer holders of this invention are not reactive with the process environment and have a thermal mass more comparable to that of the wafers they support. This results in an order of magnitude difference in the thermal response time of the RTP systems which use the holders of this invention when compared to the CVD coated substrate holders or supports of the prior art.
The fixture comprises a planar surface containing a recess to receive the wafer with the planar surface consisting essentially of chemical vapor deposited (CVD) silicon carbide. In one embodiment of the present invention, a sidewall is connected to the planar surface and has a height greater than the depth of the recess. The sidewall may extend either above or below the planar surface. The sidewall may be perpendicular to the planar surface or form either an acute or obtuse angle thereform. Its particular configuration will depend on the particular RTA or RTP in which it is placed. To provide for added stability, a peripheral annular section or annulus is attached to the sidewall. To provide for additional structural rigidity if required for a given application, the annulus comprises silicon carbide deposited onto graphite. In those cases where such rigidity is not required, the graphite can be removed as set forth below to leave the annulus hollow. If the graphite is allowed to remain in the annulus, it is essential that the annulus be sufficiently remote from the recess as allowed by the reaction chamber design and by the thin cross-section of the silicon carbide planar surface or membrane between the annulus and the wafer. This means that the semiconductor wafer being processed is isolated from any significant thermal mass of the holder and will provide the necessary rapid thermal response of the wafer.
The method for making the fixture comprises shaping a block of graphite or other suitable substrate material into the desired configuration for the particular RTA or RTP application. The minimum shaping requires that the substrate includes a planar surface containing the recess. Means for masking are provided for those regions of the substrate which are not to receive a CVD coating of silicon carbide, i.e. those regions in which the substrate is to be removed. Such masking means are provided at least in those regions on the backside of the fixture adjacent to the wafer recess. The substrate is then chemical vapor deposited with silicon carbide in a manner, for example, as that set forth in U.S. Pat. No. 4,772,498, issued 20 Sept. 1988. The silicon-containing gas used to form the silicon carbide coating can be selected from-the group consisting of silicon tetrachloride, silane, chlorosilane, trichlorosilane, methyl trichlorosilane and dimethyl dichlorosilane. If silicon tetrachloride, silane, dichlorosilane or trichlorosilane is used, it is necessary to supply a source of carbon to produce silicon carbide. The source of carbon can be any hydrocarbon, preferably low molecular weight aliphatic hydrocarbons such as paraffins, alkenes and alkynes having 1 to 6 carbon atoms, and aromatics and other hydrocarbons having 1 to 6 carbon atoms which do not contain oxygen, particularly suitable examples include, methane, ethane, propane, butane, methylene, ethylene, propylene, butylene, acetylene, and benzene.
The substrate is removed in the region immediately adjacent to the wafer recess, which region has not been coated with silicon carbide. This can be done by machining, grit-blasting, drilling, dissolving or burning. Japanese Kokai Pat. No. 62-124909, published 6 June 1987, describes various methods for removing substrate material in the method of making ceramic reaction tubes used in the semiconductor manufacture in which the substrate is first chemically vapor deposited with silicon carbide and the substrate is then removed by combustion or dissolution with a suitable acid or solvent.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, the accompanying drawings are provided in which:
FIG. 1 is a perspective view of one embodiment of the wafer holding fixture of the present invention having a solid recess;
FIG. 2 is a cross-sectional view of the fixture taken through 2--2:
FIG. 3 is a cross-sectional view of another embodiment of the fixture having an annular section;
FIG. 4 is a cross-sectional view of the FIG. 3 placed within a typical RTP unit;
FIG. 5 is a perspective view of still another embodiment of the fixture of the present invention having a recess with an opening therethrough with a cut-away section showing the annulus;
FIG. 6 is a cross-sectional view of the substrate which has been shaped into the configuration that is used to form the fixture of FIGURE 5; and
FIG. 7 is a cross-sectional view of one of the two masks used to form the fixture of FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGS. 1 and 2, wafer holder 1 consisting of CVD silicon carbide has upper planar surface 2 and sidewall 3 each having a thickness in the range of about 0.015 to about 0.025 inches. Planar surface 2 has solid recess 4 having a depth substantially the same as the thickness of holder 1 and has inner rim 6 and outer rim 7.
FIG. 3 illustrates another embodiment of the present invention in which holder 10 has upper planar surface 12, sidewall 13 and hollow annular section or annulus 14. Planar surface 12 has inner rim 15, outer rim 16 and solid recess 17 having outer edge 19 separated from inner rim 15 of planar surface 12 by the thickness of the CVD SiC. The width of hollow annulus 14, from inner sidewall 20 to sidewall 13, is less than 50% of the distance from inner rim 15 to outer rim 16 of planar surface 12 so that annulus 14 is sufficient distal to outer edge 19 of recess 17 to allow for the necessary rapid response time for the thermal change of the wafer and holder 10 in the RTA or RTP systems.
FIG. 4 illustrates holder 1 positioned within typical RTP system 21 comprising top and bottom closures 22 and 24 and external sources not shown, so that sidewall 3 of holder 1 matches sidewall 25 of system 21. It is apparent that the exact design of holder 1 will depend on the configuration of the particular RTP or RTA system selected.
FIG. 5 illustrates still another ambodiment of this invention in which holder 30 comprises planar surface 32 having inner rim 33 and outer rim 34, vertical sidewall 35, open, annular recess 36 having outer edge 37 and upper inner edge 38 and lower inner edge 39. The thickness of sidewall 40 formed between inner edge 33 and outer edge 37 and the thickness of sidewall 41 formed between upper inner edge 38 and lower inner edge 39 is equivalent to the depth of the CVD deposition of silicon carbide. The cut-away view shows annulus 42 comprising silicon carbide coated inner vertical wall 44 and lower surface 45 on graphite core 46. The width of annulus 42 from coated sidewall 35 to inner wall 44 is approximately 1/3 the width of planar surface 32 from inner rim 33 and outer rim 34 so that annulus 42 is sufficient remote from recess 36 to result in the optimum thermal response for wafers on annular recess 36.
The wafer holder comprising simply a planar surface with a recess, which is not shown, has the fastest rapid response time of the fixtures of the present invention. However, an external positioning fixture is required to mount such a holder in an RTP. Holder 30 shown in FIG. 5 is the type of fixture having a very fast response time, as well as having the stability and rigidity without requiring an external positioning fixture. The disadvantage of holder 30 is that there is less control of the temperature of the exposed lower portion of the wafer mounted in annular recess 36 than in holders in which the recess is solid such as in holder 10 shown in FIG. 3.
FIGS. 6 and 7 illustrate the components used to make holder 30. Disk 50 comprising a suitable substrate material 51, e.g. graphite, has upper planar surface 52, outer sidewall 53 and lower planar surface 54. The first step of the method is to shape disk 50 into the desired configuration of holder 30 by machining upper planar surface 52 to form upper recess 55 in the center of disk 50 equidistant from its periphery. Upper recess 55 is machined to form lower recess 56. The next step is to flip disk 50 over and to machine lower planar surface 54 to form lower cylindrical space 57 having sidewall 58 and lower surface 59. Mask 60 having larger diameter surface 61 and smaller diameter 63 as shown in FIG. 7 is designed to mask lower surface 59 during the CVD coating step of the method of this invention while permitting coating of sidewall 58. It is critical that larger diameter surface 61 of mask 60 is smooth and has substantially the same diameter as the diameter of cylindrical space 57 so that larger diameter surface 61 forms a close fit with sidewall 58 at juncture 64 and with lower surface 59. The dimensions and the surface finish of smaller diameter surface 63 are not critical except that its diameter is significantly less than the diameter of larger diameter surface 61. Another mask not shown is of similar size and shape as mask except that the larger diameter surface of this mask is substantially the same as the diameter of lower recess 56 so as to form a close fit within wall 69 of lower recess 56 at juncture 71 and with lower surface 70 to mask lower surface 70 during the CVD coating while permitting coating of walls 69 and 72 of recesses 56 and 55, respectively.
In order to provide the necessary CVD coating, disk 50 and the mask not shown together with mask 60 mounted as set forth above are placed in any suitable CVD reactor. One example of such a reactor is described and illustrated in Ser. No. 933,077, filed 20 Nov. 1986 now U.S. Pat. No. 4,772,498, issued 20 Sept. 1988. A uniform thickness of silicon carbide is chemically vapor deposited onto upper planar surface 52, outer sidewall 53, lower planar surface 54, sidewall 58, annular surface 65, and walls 69 and 72 as well as the exposed surfaces of the mask not shown and mask 60, i.e. smaller diameter surfaces not shown and 63 and sloping sidewall not shown and 62, to a depth equal to the desired thickness of holder 1. The substrate is withdrawn from the CVD reactor and the masks are removed from recess 55 and cylindrical space 57. At least a substantial portion of the graphite of uncoated inner surface 70 and lower surface 59 and adjacent to inner sidewall 58 are removed by machining. For example, SiC coated disk 50 is bored from the center of inner surface 70 out to wall 69 by a vertical milling machine. Then a diamond grinding wheel is used to grind smooth the surface of the silicon carbide coating adjacent juncture 69. Coated disk 50 is flipped over and the graphite above uncoated surface 59 is milled to within a fraction of an inch of the silicon coating on upper planar surface 52 and annular surface 65 and the remaining fraction of an inch of graphite is grit blasted away to result in support 30 shown in FIG. 5. Graphite core 46 at this stage in the process contains coated sidewall, coated inner surface 45 and partially coated region between coated sidewall 53 and at least partially coated inner wall 45. Support 30 is then placed into the reactor to coat an additional fraction of an inch of silicon carbide over the exposed graphite surface of inner surface 70. After the second CVD coating, inner wall 45 is slightly tapered due to the combined effects of the second coating and the lower gas diffusion on the inner surface closer to the backside of upper planar surface 52. The fact that the SiC coating on inner wall 45 is tapered inward because the fabrication process is not critical to the ultimate function of holder 30.
In the embodiment shown in FIG. 30, the graphite core is removed by drilling a series of holes in inner wall 45 and support 30 is then placed in a furnace and heated to about 1200° C. to burn out the graphite that remains in graphite core 46. If it is believed necessary, the fixture can be returned to the CVD reactor to coat over any of the holes.
The example below illustrates the foregoing process of preparing the fixtures of the present invention.
EXAMPLES
Example 1
Two of the three components composed of SiC6 graphite supplied by Toyo Tanso Ltd. were fabricated into the shapes corresponding to FIGURES 6 and 7. The third component, not shown, had substantially the same shape as that of mask 60 shown in FIG. 7. The component of disk 50 shown in FIG. 6 had an outside diameter of about 6 inches and was about 0.5 inches thick. The thickness of sidewall 58 was approximately 0.25 inches, and the depth of recess 68 and of recess 55 were each 0.025 inches. The three graphite components were subsequently purified at 2,000° C. with chlorine gas in a high temperature purification reactor. The three components were assembled with the mask of FIG. 7 and the mask not shown were located in lower cylindrical space 57 and lower recess 56, respectively of the component of FIG. 5, as set forth above. The assembly was then placed into a CVD reactor and 0.020 to 0.025 inches of SiC was deposited onto its exposed surfaces by the pyrolysis of methyl trichlorosilane at 1250°-1300° C.
Subsequent to the CVD deposition step, the upper mask (not shown) was removed by making a single point diamond cut at juncture 71. Lower mask 60 was easily removed as there was substantially no coating at juncture 64 between sidewall 58 and inner surface 59 because of diffusion limitations during the deposition process. A hole was machined through the central region of disk 50 of substantially the same diameter as the diameter of recess 56. The coated disk 50 was flipped over and the uncoated graphite was machined to within 1/16 inch from the SiC on the backsides of upper planar surface 52 and annular surface 65. The remaining graphite was grit-blasted away backside of disk 40 which left a holder having sidewall, upper planar surface and recess containing a substantially silicon carbide of 0.025 inch, with an open central region, and a region of residual graphite which was not removed, which forms annulus 46. This structure was then placed back into the CVD reactor and the exposed graphite surface of inner sidewall of annulus 46 was coated with an additional 0.007 inch of SiC. The resulting holder 30 illustrated in FIG. 5 was removed from the reactor.
Holder 30 has been calculated to have a heat capacity of about 25 calories/° C. This is a reduction of over seventy-five per cent in heat capacity from a holder prepared by silicon carbide coating the graphite substrate, which was calculated to have a heat capacity of about 113 calories/degree C. Therefore, the heat-up rate of the support of the present invention in a uniform heat flux will be over four times that of prior art CVD coated graphite supports.
Example 2
Two components composed of SiC6 graphite supplied by Toyo Tanso, Ltd. were fabricated into a substrate component and a mask used in the preparation of holder 1 illustrated in FIGS. 1 and 2. The two graphite components were subsequently purified at about 2000° C. with chlorine gas in a high temperature purification reactor system. The two components were then assembled with the substrate component oriented with its recess upward, resting into the recess of the mask to prevent coating of the backside of the substrate component. The assembly was placed into a CVD reactor and 0.020-0.025 inches of SiC was deposited onto its exposed surfaces by the pyrolysis of methyl trichlorosilane at 1250°-1300° C. to form upper planar surface 2, sidewall 3, and solid recess 4 of holder 1.
Subsequent to the deposition step, the mask was removed from the substrate component by making a single point diamond cut at the juncture between the mask and the substrate component. The majority of the graphite was machined from the interior of this component from the masked, uncoated backside. A diamond grinder was used to smooth the exposed edge of the silicon carbide at such a juncture, and then the remaining graphite was removed by grit blasting.
The resulting holder 1 has been calculated to have a heat capacity of only about 10 calories/degree C., which is a reduction of over an order of magnitude from the calculated 113 calories/degree C. for the SiC coated graphite substrate. Therefore the heat-up rate of the support of the present invention in a uniform heat flux will be over ten times that of prior art CVD coated graphite supports.
Example 3
An alumina substrate is prepared in the form of a disk substantially in the shape of FIG. 1 having a recess in its upper planar surface and a thickness substantially the same as the desired thickness of the sidewall of the wafer support. The alumina is coated on all surfaces with a slurry of graphite powder in water and the powder is allowed to dry. The substrate is placed on a flat, circular graphite plate having a somewhat larger diameter than the disk which serves to mask the backside of the support from deposition of SiC. The substrate on the plate is then placed into a CVD reactor and is coated with a uniform coating of SiC having a thickness of about 20 thousandth of an inch. After the deposition, a single point diamond cut is made at the juncture of the substrate with the graphite plate in order to remove the substrate from the plate. The substrate of alumina coated with graphite powder has a higher coefficient of thermal expansion than the silicon carbide and will have shrunken away from the coating on cooling from deposition temperatures. The graphite powder coating will assist in preventing adhesion of the SiC coating to the substrate and the substrate can easily be removed from the silicon carbide part. The lower edge where the single point cut is made is smoothed with a diamond grinding step and lightly grit blasted on the lower surface. This will remove and residual graphite powder. Should an open recess area be provided as in FIG. 5 to further reduce the thermal mass in the vicinity of the wafer, the opening can be diamond machined or ground into the final part. | A semiconductor wafer holding and support fixture having a low effective thermal mass comprises a planar surface having a recess for a wafer and consisting essentially of chemical vapor deposited silicon carbide. The wafer holder is specifically designed to isolate the wafer from regions of significant thermal mass of the holder. The wafer holder is particularly adapted for accomplishing chemical reactions in rapid thermal processing equipment in the fabrication of electronic integrated circuits. The method for making such an article comprises shaping a substrate, e.g. Graphite, to provide a planar surface having a recess installing means for masking any regions of the substrate where silicon carbide is not desired, chemically vapor depositing a conformal outer coating of silicon carbide onto the substrate, removing the means for masking and removing the graphite by machining, drilling, grit-blasting, dissolving and/or burning. |
CLAIM FOR PRIORITY
[0001] This application is a national stage of PCT/DE03/01407, published in the German language on Nov. 20, 2003, which claims the benefit of priority to German Application No. DE 102 20 337.7, filed on May 7, 2002.
TECHNICAL FIELD OF THE INVENTION
[0002] The invention relates to a method for operating an internal combustion engine equipped with a three-way catalytic converter.
BACKGROUND OF THE INVENTION
[0003] Conventional methods, such as those disclosed in DE 195 11 548 A1, DE 198 01 815 A1 or DE 199 53 601 A1, with the last-mentioned document also disclosing evaluation of a catalytic converter as regards ageing by evaluating the air mass value of the combustion air that is sucked in by the internal combustion engine.
[0004] In the case of internal combustion engines, emitted exhaust gases can be given an aftertreatment in the exhaust gas duct by using a three-way catalytic converter that oxidizes or reduces harmful substances of the exhaust gas to innocuous compounds. However, it is also known that such internal combustion engines equipped with a three-way catalytic converter for achieving a high degree of efficiency must be supplied with an average stoichiometric air/fuel mixture; in such a lambda regulation, the oxygen contents of the exhaust gas is measured by means of so-called lambda probes and the air/fuel mixture is regulated to an average value close to lambda=1 because three-way catalytic converters only function in a tight range around lambda 1 as requested. This range is also designated as the catalytic converter window.
[0005] In order to increase the degree of efficiency of a three-way catalytic converter, the air/fuel mixture is designed in such a way that in the forced activation acting on the lambda regulation as anticipatory control around the stoichiometric set value, default values are set alternately with an over-stoichiometric and under-stoichiometric mixture in cycles. Because of the forced activation, the default value for the lambda value in rich phases is lower than the stoichiometric set value and in lean phases is greater than the set value.
[0006] Alternately, supplying oxygen to and extracting oxygen from the three-way catalytic converter results in suitable oxygen ratios for the oxidation and reduction phases.
[0007] Because the reducing or oxidizing effect of a three-way catalytic converter decreases tremendously in the case of values set below or above a set value for the stoichiometric mixture, care must be taken that in the forced activation within the average time, an air/fuel mixture is always used in the catalytic converter window.
[0008] Therefore, in the prior art in lean and rich phases of the forced activation, a default value deviating by the same amount from the stoichiometric set value is set in each case and the phases are equal in length. Lambda deviations from the default value possibly determined by interference are balanced out by a lambda regulator.
SUMMARY OF THE INVENTION
[0009] The invention relates to a method for operating an internal combustion engine equipped with a three-way catalytic converter in the case of which a lambda value of the air/fuel mixture, with which the internal combustion engine is supplied, is set below and above a stoichiometric set value in a cyclically alternating manner during a forced activation, whereby the lambda value in rich phases is less than the stoichiometric set value and in lean phases is according to the stoichiometric set value, in the case of which during the forced activation, the rich phases and the lean phases are matched to one another according to a specified criterion.
[0010] The invention discloses a method of the above-mentioned type in such a way that the forced activation brings about a higher degree of efficiency of a three-way catalytic converter.
[0011] The invention discloses a generic method in that for the criterion according to which the phases are matched, the air mass is used that is supplied to the internal combustion engine as combustion air in rich and lean phases.
[0012] The invention is based on the knowledge that it is important for the efficiency of a three-way catalytic converter to remove again during the rich phase the amount of oxygen stored in a lean phase. Because the amount of oxygen by means of which a three-way catalytic converter is filled in the lean phase and which is removed in the subsequent rich phase depends on the amount of air that is fed into the internal combustion engine as combustion air, the basic approach according to the invention directly depends on the actual parameters influencing the filling and removal process. In addition, influences that have an air mass flow that change during the filling and emptying process, no longer have an interfering effect because they are taken into consideration when determining the criterion. Therefore, the invention replaces the previously time-based forced activation in the linear lambda regulation with an air mass flow-based forced activation and as a result again achieves a high degree of efficiency of the three-way catalytic converter because the catalytic converter window is set in a more stable manner.
[0013] The invention has the further advantage that in rich and lean phases, deviations from the stoichiometric set value can be selected freely and in particular can differ.
[0014] Therefore, if the load or the rotational speed of an internal combustion engine changes, the air mass supplied within a unit of time also changes and therefore also the amount of oxygen fed into or extracted from a three-way catalytic converter within a unit of time. Whereas a purely time-based forced activation has to correct resulting errors via a guide regulator also to be provided for the lambda regulation, the air mass flow-based forced activation automatically takes care of a corresponding balancing, since the lean or rich phases are shortened or lengthened in a corresponding way. As a result, the method according to the invention makes the lambda regulation more precise because an error is not only eliminated afterwards, but avoided from the start.
[0015] Of importance for the air mass flow-based forced activation is the fact that in lean and rich phases, the same amount of oxygen is fed into or removed from the catalytic converter. In principle, a set amount can then be specified for this. Alternatively, this set amount can be managed dynamically, i.e. a rich phase or a lean phase are ended if they are matched to the immediately preceding lean and rich phase according to the criterion.
[0016] In the case of the air mass flow-based forced activation, the air mass is used as a criterion for the oxygen mass relevant to a filling or removal process of a three-way catalytic converter. In a preferred further development, a direct volume for the oxygen mass that is emitted in the lean and rich phases in the exhaust gas by the internal combustion engine can be used as the criterion. For this purpose, the oxygen load during the lean phase can be calculated as follows by summation or integration of the air mass flow:
MO2 = 0.23 · ∫ i = 0 i = TM ( 1 - 1 LAM ) · M L . ⅆ t .
[0017] This formula gives the oxygen mass MO2 as a function of the absolute lambda value LAM, the flow of the air mass ML and time TM that it takes a lean phase. If instead of the absolute lambda value LAM, the deviation DLAM from a set value 1 assumed for the catalytic converter window is used, the formula is as follows:
MO2 = 0.23 · ∫ i = 0 i = TM ( 1 - 1 DLAM ) · M L . ⅆ t .
[0018] Therefore, the deviation is the difference between the default value of the forced activation and the stoichiometric set value that is adhered to on average. The above-mentioned relationship also applies to the rich phase in which oxygen is extracted, however DLAM is then negative.
[0019] As can be seen, the concept according to the invention avoids a further error which inherently underlies the purely time-based basic approach: it assumes that the oxygen mass supplied to the lean operating phases is the same as that removed in the rich phases from the catalytic converter. However, this is not the case because also in the case of deviations from the same amount, DLAM of the fraction of the integral between brackets is smaller for lean operating phases than for rich operating phases.
[0020] The forced activation according to the invention is not based on this assumption and instead balances the rich and lean phases—and does this independently of the selection for DLAM and of the air mass flow. The integrated air mass, the average air mass or also the oxygen mass calculated according to the above-mentioned formula can be, for example, the criterion for the oxygen mass. Here the accuracy requirement and the costs can be balanced.
[0021] A particularly accurate regulation of forced activation and at the same time relatively low costs can be achieved at the same time if, as criterion, an integral is used over the air mass supplied during the rich or lean phase. In addition, the amount by which the default value in rich phases is set below the stoichiometric set value is selected so that it is equal to the amount by which the default value in lean phases is set above the stoichiometric set value. However, this does not have to be the case. The integral can be executed easily and automatically takes different values in the rich and lean phases into consideration.
[0022] When adapting a controller to an internal combustion engine type, different parameters are usually set, i.e. applied. Therefore, the oxygen mass can be set in the case of the air mass flow-based forced activation. However, in order to be able to achieve the highest possible parallelism to previous forced activation systems, it is advantageous to apply a time duration as before. For this application, preference should be given to a further development of the invention in the case of which in each cycle the rich or the lean phase is executed for a specific time thus determining the air mass, and during the subsequent lean or rich phase, the air mass is integrated and the phase ends if the air masses are the same.
[0023] Therefore, the time provided together with the previous forced activation concepts no longer gives both the duration of the lean phase and the rich phase, but only defines (indirectly) the oxygen mass that is relevant to the lean or rich phase. The directly subsequent rich or lean phase is then regulated on the basis of the oxygen mass supplied or extracted in the specified time.
[0024] Therefore, a first phase (it can be both a lean and a rich phase) that is executed for a specific time is defined, and which in terms of value, defines the criterion for the composition of the second subsequent phase (in the same way as the rich or lean phase) via the relevant amount of oxygen or the air mass.
[0025] The parallelism to the values used in conventional forced activation concepts can be increased further if at the start of a first phase (for example, a rich phase), the current air mass flow from which the internal combustion engine receives its combustion air is determined and a time is established for which the first phase has to last for this period in the case of this air mass flow in order to achieve a predetermined oxygen mass. Therefore, in the forced activation, the first phase is then carried out precisely for this time and indeed independently from how the air mass flow changes. However, the air mass or the oxygen mass during the first phase is detected. The second phase is developed in such a way that the same air mass or oxygen mass is obtained.
[0026] This embodiment of the method provides an air mass or the oxygen mass as the target value, but which is made available in the form of a time for the default value of the first phase whereby the highest possible parallelism to previous forced activation concepts applies with regard to the application of parameters.
[0027] The basic approach according to the invention, as is also expressed in this further development, makes it possible to precisely match the amounts of oxygen removed or fed into the three-way catalytic converter to each another, i.e. the following equation applies:
∫ i = 0 i = TM ( 1 - 1 DLAM ) · ML ⅆ t = ∫ i = 0 i = TF ( 1 - 1 DLAM ) · M * L ⅆ t
[0028] The basic approach according to the invention makes it possible that a uniformity is achieved by the specific composition of the lean phase duration TM as well as the rich phase duration TF. Then, as has already been mentioned, it is also taken into account that in lean phases the difference DLAM between the default value and the stoichiometric average is positive, but is negative in rich phases in the case of which the expression between brackets in lean phases is less than in rich phases. Over and above that, the default value can now be selected freely in the lean or rich phases and DLAM in particular need no longer be equal to the amount for the two phases.
[0029] The concept according to the invention can be used to particular advantage in the case of multi-cylinder internal combustion engines with two independent cylinder groups that can be supplied with an air/fuel mixture. In order to prevent the independent lambda-regulated cylinder groups drifting apart, it is worthwhile in the case of the concept according to the invention for there to be a forced synchronization between the two groups, for which reason in a preferred further development of the invention care is taken that on ending each second phase (lean or rich phase) of a cylinder group, the corresponding phase of the other cylinder groups also ends automatically or that a predetermined phase shift is adhered to.
[0030] Therefore, in the case of a multi-cylinder internal combustion engine with two independent cylinder groups which can be supplied with an air/fuel mixture, a method is preferred which determines a criterion for a cylinder group and is used by default. Therefore, with regard to the forced activation a cylinder group is operated as a master group and the other one follows as a so-called slave group. Therefore, the default by the master group can take place in many different ways as has already been mentioned above. However, it is of considerable importance that at specific times a forced synchronization takes place. For this, an air mass set value, a set value for the average air mass, a set value for the oxygen mass, etc. can be specified.
[0031] In a further development that is very easy to execute as far as control is concerned, in which the application for a multi-cylinder internal combustion engine is linked to a further development that can be applied by a period of time, there is provision, in the rich or lean phase for a cylinder group to be determined as the criterion and used as default. Therefore, a rich phase of a cylinder group is carried out time-regulated and at the same time the supplied air and oxygen mass is detected. The rich phase of the other cylinder group is then developed according to this air mass or oxygen mass value. Likewise, the lean phases of both cylinder groups; in this case care must be taken that the deviation from the stoichiometric set value in rich phases is not less than in the lean phases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The invention is explained in greater detail on the basis of the accompanying drawings. They are as follows:
[0033] FIG. 1 time sequences of the lambda change and the air mass in the case of an air mass-based forced activation.
[0034] FIG. 2 a flow diagram for carrying out an air mass-based forced activation.
[0035] FIG. 3 a further embodiment of a method for the air mass-based forced activation in the case of which a time value for the application on an internal combustion engine type can be set.
[0036] FIG. 4 time sequences of the lambda change and the air mass in the case of an air mass-based forced activation for an internal combustion engine with two cylinder groups which can be supplied independently with an air/fuel mixture.
DETAILED DESCRIPTION OF THE INVENTION
[0037] For an internal combustion engine in the case of which a three-way catalytic converter is arranged in the exhaust gas duct and runs under a linear lambda regulation, in a forced activation a default value is set around a stoichiometric lambda set value as the anticipatory control for the lambda regulation. In this case, a shift of the mixture alternately to the lean and the rich is given.
[0038] In the lean shift, the three-way catalytic converter, that has oxygen storage properties, is filled with oxygen whereas it is emptied again in the rich shift. This filling and emptying process depends on the difference between the default value and the stoichiometric set value in the phases, i.e. on the amplitude of the forced activation as well as the duration of the shift.
[0039] The amount of oxygen by means of which the three-way catalytic converter is filled and extracted depends on the amount of air that is fed into the internal combustion engine during combustion. The oxygen mass fed into a lean phase takes place according to the following equation:
MO2 = 0.23 · ∫ i = 0 i = TM ( 1 - 1 LAM ) · M L . ⅆ t .
in which case ML represents the air mass and DLAM the lambda change, i.e. the amplitude of the forced activation. This equation is also designated as the oxygen mass integral.
[0040] In order to now ensure that the filled or emptied amount of oxygen in lean and rich phases of the forced activation is equal, the integral is calculated in each case. In this case, the lean phase is executed in such a way that a specific oxygen mass value MO2 is set. The directly subsequent rich phase is also developed in such a way that precisely this oxygen mass value MO2 is achieved.
[0041] FIG. 1 shows a lambda curve 1 as a time sequence in which case the lambda change DLAM is plotted over time t. The lambda change DLAM is then possibly approximated to a quadrilateral function during the operation of an internal combustion engine so that in the half cycles 3 and 4 , a constant lambda change DLAM is given in each case.
[0042] Therefore, the transitions between the half cycles 3 and 4 correspond to a linear change, the slope of which is selected in such a way that in this case there is no loss of comfort during the operation of an internal combustion engine.
[0043] The lambda value DLAM in each half cycle 3 and 4 is used to calculate the oxygen mass by means of the above-mentioned integral. Therefore, the lean phase duration TM is the time between two zero passages of the lambda curve 1 . As a result, an oxygen mass curve 2 drawn in on FIG. 1 in which the air mass ML is recorded over time t is obtained. As can be seen, the oxygen mass integral curve 2 also runs cyclically and is synchronous to the lambda curve 1 . At the end of the lean phase duration TM the oxygen mass integral curve 2 has a local minimum.
[0044] The end of a lean phase and thereby the end of a half cycle 3 is determined on the basis of the oxygen mass integral curve 2 . If the value of the oxygen mass integral is lower than a value MO2, a switching point 5 is determined in the case of which the lean phase ends, i.e. the lambda change DLAM that was constant up to now then changes to zero with the above-mentioned slope and then changes to the opposite value for the lean phase. For the zero passages the lean phase duration TM then ends and the rich phase duration TF then follows. From this zero passage, the value of the oxygen mass integral again increases. If it reaches zero then an additional switching point 6 is achieved for which the end of the rich phase duration begins and the lambda change DLAM is again set to the value for the next lean phase with the above-mentioned slope.
[0045] As can clearly be seen from the lambda curve 1 in FIG. 1 , this concept results in the fact that the default value in the forced activation is selected and that there are different durations for the lean and rich phases. They are in each case developed until exactly the same value MO2 is achieved so that a continuous supply in the average stoichiometric mixture is ensured.
[0046] This method for the forced activation is shown diagrammatically in FIG. 2 which assumes that a rich phase was used as the start. First of all, in a step S 1 the internal combustion engine is operated with a slightly rich mixture, i.e. the lambda value LAM is lowered; this can be seen diagrammatically in step S 1 by a minus sign.
[0047] Subsequently, the oxygen mass integral is calculated in a step S 2 . This can be the above-mentioned integral. However, if the lambda value can be kept constant it need not be taken into consideration and an integral or sum formation via the air mass flow alone is sufficient.
[0048] Subsequently, a test is performed in a step S 3 to determine whether or not the achieved sum is above a value MO2. Should this not be the case (“N”-branch) it would be necessary to return to step S 2 , i.e. the rich phase is continued.
[0049] However, if the value MO2 is achieved on the other hand (“J”-branch), the default value is now raised in a step S 4 which brings about a leaner mixture, i.e. a lean lambda value LAM is specified. In step S 4 this can be seen by means of a plus sign.
[0050] During the resulting lean phase, the oxygen mass integral is again determined on the one hand or the air mass is summed up or integrated. This takes place in a step S 5 .
[0051] Subsequently, step S 6 requests whether or not this summation again reached the value MO2. If this is not the case (“N”-branch) the lean phase is continued, i.e. step S 5 is once again carried out. However, if on the other hand the oxygen mass value MO2 is achieved (“J”-branch) it would be necessary to return to before step S 1 , i.e. a rich phase once again follows.
[0052] Therefore, in terms of the concept shown diagrammatically in FIG. 2 , the lean phases and the rich phases are matched to a same value MO2 in each case. It will be possible to select this value depending on the properties of the three-way catalytic converter and can particularly also be increased or decreased for diagnostic purposes deviating from normal operation for the short-term, for example, in order to check the behavior of the three-way catalytic converter.
[0053] FIG. 3 diagrammatically shows an alternative embodiment of the method. In this case, in a step S 7 a cycle period T is first of all initialized, i.e. set to zero. Subsequently in a step S 8 a rich phase to reduce the lambda value LAM is carried out. In step S 9 , an oxygen mass integral calculation or the summation or integration of the air mass then follows in the same way as in step S 2 .
[0054] Next in a step. S 10 , the cycle time T is raised, i.e. increased by one time increment. A request in a step S 11 checks whether or not the current cycle time t exceeds a threshold value SW. If this is not the case (“N”-branch) the rich phase is continued, i.e. step S 9 is continued. If, on the other hand, the cycle duration has exceeded a predetermined threshold value SW2 (“J-branch”), the value of the sum or the integral is stored in a step S 12 via the air mass as an oxygen mass value MO2. It then serves to regulate the subsequent lean phase. Subsequently, the steps S 13 , S 14 and S 15 that conform to the steps S 4 to S 6 are carried out.
[0055] The air mass-based criterion for matching the rich and the lean phases in the forced activation can also for example be used for internal combustion engines that have several two cylinder groups—the air/fuel mixture of which can be set independently from one another. This is usually the case for internal combustion engines with several cylinder supports, for example, in the case of V6 or V8 configurations.
[0056] FIG. 4 shows lambda curves 1 a and 1 b as well as the oxygen mass integral curves 2 a and 2 b for a forced activation in the case of such systems.
[0057] There is also provision in this case, at certain times, for forced synchronizations between the two cylinder groups to be carried out so that there is no drifting apart of the two groups with regard to the forced activation. Such a drifting apart would be supported by numerical inaccuracies. The lambda curves 1 a and 1 b shown in FIG. 4 provide a forced synchronization at the end of the lean phase of a bank of cylinders.
[0058] In the case of the forced activation, a bank of cylinders is operated as a so-called master, i.e. it supplies the default values with regard to the air mass-based balancing criterion to the other bank that runs as a slave. The lambda curve of the master-operated bank is provided with a reference symbol 1 a in FIG. 4 and is also drawn in with a thicker line intensity in the same way as the associated oxygen mass integral curve 2 a.
[0059] The half cycles 3 a and 4 a of the lean or rich phases of the cylinder bank operated as master correspond to those of FIG. 1 so that these descriptions can be referred to concerning this matter.
[0060] If a switching point 5 a is reached, the end of the half cycle 3 a is implemented and a half cycle 4 a follows, the end of which is initiated in the switching point 6 . The half cycles 3 b and 4 b of the cylinder group operated as slave orientate themselves to the oxygen mass values MO2 that were reached default-specifically in the case of switching points 5 a or 6 . As can be seen from the oxygen mass integral curve 2 b for the slave cylinder bank that is operated with a push-pull operation to the master cylinder group in the forced activation, the switching point 5 b is reached in time after the switching point, i.e. the half cycle 3 b takes longer than the half cycle 3 a . The reason for this being the value of the expression in brackets which depends on the indicator DLAM in the above-mentioned oxygen mass integral, shifts in equal amounts DLAM in rich and lean phases.
[0061] Therefore, for this reason the half cycle 4 a is also longer than the half cycle 4 b . In the oxygen mass integral curve 2 b it stands out that during the half cycle 4 b , there is no integration. This is due to the fact that on reaching the switching point 6 that is defined by the oxygen mass integral curve 2 a for the master cylinder group there is a forced synchronization of the half cycles 4 a and 3 b , so that it is ensured that the push-pull operation or the specified phase shift between the forced activation of the master cylinder group and the slave cylinder group is retained. However, for the case that a cylinder group can be switched off, the integration should be carried on so that the slave support can then be used as the master bank for the short term.
[0062] The additional lambda curve 1 a and 1 b as well as the oxygen mass integral curve 2 a and 2 b clearly shows the influence of the oxygen mass integral on the duration of the rich and lean phases and with that also the period of the forced activation. There, the oxygen mass integral curve 2 a and 2 b proceeds with a clearly lower slope, i.e. the internal combustion engine clearly sucks in a smaller air mass flow than before. Therefore, the half cycles 4 b and 3 a are extended accordingly.
[0063] Balancing by means of an air mass-based criterion not only brings about that lean and rich phases in each case are the same under the degree of efficiency viewpoints, but an optimum oxygen mass that is fed into or extracted from the three-way catalytic converter can also be set. | The invention relates to a method for operating an internal combustion engine that is equipped with a three-way catalytic converter. According to the inventive method, a lambda value of the air/fuel mixture, with which the internal combustion engine is supplied, is set below and above a set value in a cyclically alternating manner during a forced activation whereby the lambda value in rich phases is less than the set value and in lean phases, is greater than the set value. During the forced activation, the rich phases and the lean phases are matched to one another according to a specified criterion. The invention provides that the amount, by which the lambda value in rich phases is set below the set value, is selected so that it is equal to the amount, by which the lambda value in lean phases is set above the set value. When determining the criterion, an air mass is used that is supplied to the internal combustion engine during the rich and lean phases. |
GOVERNMENT CONTRACT
[0001] The Government of the United States of America has certain rights in this invention pursuant to Contract No. DE-FC26-97FT34139 awarded by the U.S. Department of Energy.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to pressurized fuel cell generators, and more particularly relates to an energy dissipater which reduces unwanted heat build-up in the combustion zone of the generator during shut-down of the generator.
[0004] 2. Background Information
[0005] Conventional solid oxide electrolyte fuel cell (SOFC) generators typically include tubular fuel cells arranged in a grouping of rectangular arrays. Each fuel cell has an upper open end and a lower closed end, with its open end extending into a combustion zone. A typical tubular fuel cell has a cylindrical inner air electrode, a layer of electrolyte material covering most of the outer surface of the inner air electrode, and a cylindrical fuel electrode covering most of the outer surface of the electrolyte material. An interconnect material extending along the length of the fuel cell covers the circumferential segment of the outer surface of the air electrode which is not covered by the electrolyte material. An electrically conductive strip covers the outer surface of the interconnect material, and allows electrical connections to be made to an adjacent fuel cell or bus bar. The air electrode may comprise a porous lanthanum-containing material such as lanthanum manganite, while the fuel electrode may comprise a porous nickel-zirconia cermet. The electrolyte, which is positioned between the air and fuel electrodes, typically comprises yttria stabilized zirconia. The interconnect material may comprise lanthanum chromite, while the conductive strip may comprise nickel-zirconia cermet. Examples of such SOFCs are disclosed in U.S. Pat. No. 4,395,468 (Isenberg), U.S. Pat. No. 4,431,715 (Isenberg) and U.S. Pat. No. 4,490,444 (Isenberg). More advanced pressurized SOFC generators are disclosed in U.S. Pat. No. 5,573,867 (Zafred et al.).
[0006] During operation of the fuel cell generator, air is provided to an inside air electrode of each tubular cell, and hydrogen-rich fuel is supplied to an outside fuel electrode surface. The fuel and oxidant are utilized electrochemically to produce electrical energy. The depleted air, comprising about 16 percent oxygen, exits the open end of the cell, and the spent fuel of low hydrogen concentration is eventually discharged into a combustion area surrounding the cell open ends.
[0007] During normal run conditions, the fuel gas entering the SOFC combustion zone has a low concentration of hydrogen due to the fuel being consumed within the cell stack. In addition, a relatively large amount of oxygen depleted air exits the cells, keeping the air/fuel ratio well beyond stoichiometric in the combustion plenum. This helps to keep the combustion zone temperature at approximately 950° C., well within the allowable range for the cells. In addition, the high volumetric flow of air out of each cell may be sufficient to protect the air electrode and open end from any risk of hydrogen reduction.
[0008] However, during certain generator stop conditions with the stack in an open circuit condition, that is, loss of grid connection, the air supply may be reduced to a maximum of about 10 percent or less of the normal airflow. The fuel flow to the generator is replaced with a reducing purge flow which serves to protect the fuel electrode from oxidation. This purge flow may cause any stored fuel within the generator to be pushed into the combustion zone where it burns with the available air. There are two primary concerns with this situation. First, the air/fuel ratio is closer to stoichiometric and will result in more combustion and a hotter combustion zone temperature. Second, the reduced air flow leaving each cell may not be sufficient to completely protect the open ends of the cells from hydrogen reduction. Either of these problems have the potential for causing damage to the fuel cells.
[0009] Several alternatives have been proposed in the past in an attempt to lessen the severity of this condition. The auxiliary airflow could be increased, thereby reducing the combustion zone temperature, as well as providing added protection for the open ends. This would require larger, more expensive blowers, as well as an uninterruptable power supply large enough to handle their power requirements. The cell open ends presently extend a short distance beyond the upper open end support board, which forms the floor of the combustion zone. Extending the open ends further may move the ends away from the board and reduce the risk of hydrogen reduction, provided that the low airflow still provides air to the board surface so that combustion occurs there and not at the open cell end. However, this approach has the drawback of exposing more of the cell surface area to the flame temperature. Conversely, reducing the cell extension will protect more of the cell surface from the flame, but possibly expose the open ends to more unburned hydrogen. Yet another solution may be to coat the open ends with a material that will prevent reduction of the exposed air electrode.
[0010] U.S. Pat. No. 5,023,150 (Takabayashi) taught a fuel cell power generator wherein a resistor is connected by a switching circuit across positive and negative terminals when the generator is shut down. Takabayashi involves clamping a fixed load across the generator terminals. The size of the load is not changed. The load is switched on or off based on the stack voltage. If this is done very rapidly, it has the appearance of controlling the current by changing the effective resistance of the load, without actually changing that resistance. Nonetheless, the actual load resistance remains the same. This type of control is often called time proportioning, because a fixed load is connected across the supply for a portion of the cycle, and disconnected for its balance. Since the Takabayashi invention uses semiconductor switches, it becomes expensive, or unfeasible, when the current is high.
[0011] In U.S. Pat. No. 6,025,083, Veyo et al. attempted to solve the above-described problems for non-pressurized SOFC generators by utilizing a fuel dissipater concept, consisting of a fixed resistive load that is switched across the cell stack terminals upon transition to normal or emergency shutdown. The load draws current, which electrochemically consumes the fuel flushed by a nitrogen/hydrogen purge gas mixture used in such situations, thus reducing the combustion zone temperatures and protecting the cells. As the fuel inventory is depleted by the load, the stack voltage drops in response to reduced H 2 and CO concentrations and, at some point, a minimum allowable terminal voltage, is reached. The limiting voltage is equal to the nickel oxidation potential at the operating temperature, plus some margin. When this is reached, a voltage sensing circuit disconnects the load by actuating a shunt trip breaker. The voltage sensing and switching circuit can be powered by the stack voltage, making the fuel dissipater “passive” (self-contained). Other dissipater designs may incorporate sensing circuits which are powered by external sources.
[0012] The previously described Veyo et al. fuel dissipater design involved a constant resistance value with only two switching functions: on and off. That design consisted of a resistive load bank (in practice, two electric immersion heaters connected in parallel) and a voltage sensing and switching circuit. The heaters were mounted in the steam supply system water tank and were expected to draw about 7 amps/cell. The voltage sensor was an alarm module which actuated a shunt trip breaker when the nickel oxidation voltage (0.62 V nominal) plus a margin (0.05 V) was reached. The electronics were powered by the stack cell terminal voltage using a voltage divider circuit. The expected duration of the dissipation current was about two minutes, until the load was disconnected by the sensed low stack voltage. This worked well for atmospheric pressure SOFC generators, but many recent designs for SOFC generators including hybrid soft/micro-turbine generators, require high pressure operation for greater efficiency. In Veyo, et al., the size of the load was constant and resistance could not be changed in response to a sudden voltage change making it not flexible in changing voltage situations.
[0013] However, for an SOFC generator operating at higher pressures (that is, greater than one atmosphere), the conditions and requirements for a fuel dissipater are significantly different. First, the volume of the fuel inventory to be dissipated is significantly higher. In the atmospheric unit, only fuel in open volume is considered. A significant quantity of fuel contained within the porosity of the cell stack insulation boards, usually alumina, is not included, since flow from the porous insulation board to the stack is assumed to be by diffusion only and, therefore, occurs at a slow rate and is considered to be insignificant. However, during shutdown in a pressurized unit, the generator is placed on open circuit and the containment is depressurized. Fuel stored within the board porosity will flow out of the boards due to the depressurization. As a result, the volume of fuel in the boards (approximately 94% porous) must be included in the stored fuel inventory. Second, the fuel flow rate in the pressurized design is controlled primarily by the depressurization rate and is much larger than for the atmospheric design. For representative pressurized generator designs, the nominal cell current can be as high as about 80 amps/cell at 85% fuel consumption, compared to 7 amps/cell for a comparable atmospheric design. For a three-resistor unit, currents in the range of 240 amps may be required by a pressurized design, versus 21 amps for an atmospheric design. Third, the fuel flow rate to the cells is not well known due to various factors which can affect the depress urization rate and the fuel composition.
[0014] In the atmospheric generator, the fuel flow rate will be set by the nitrogen/hydrogen mix purge flow rate, which is controlled accurately by orifices in the gas supply line. Also, fuel bypass of the cell stack is not likely to occur at one atmosphere, so that all fuel flow into the stack is assumed to reach the cells without bypassing. In the pressurized design, the fuel flow rate will depend on the exhaust flow rate, the total mass of gas in the test vessel (a function of the temperature gradients inside the test vessel), and the purge flow rates. The fuel purge gas flow rate may be small compared to the fuel flow from depressurization. The exhaust flow may be controlled by a fixed flow resistance (such as, a valve) in the exhaust line. The flow will vary as the system depressurizes, from higher flow at the beginning of the depressurization to lower flow at the end of the depressurization. Furthermore, the hydrogen and carbon monoxide content of the fuel will decline as the fuel is used. The net result is that the fuel consumption at the cells could be significantly higher or lower than the predicted value, depending on how these various factors deviate from the calculated values, making the expected for flow rate and cell voltage difficult to estimate.
[0015] As can be seen, a pressurized SOFC generator poses a substantially greater number of difficulties and imponderables during shutdown, to the extent that it is a completely different generator than an atmospheric generator. What is now needed is an advanced energy dissipater design for the new SOFC generators which will operate in a pressurized environment and which can meet changing voltage situations.
[0016] The present invention has been developed in view of the foregoing and to address other deficiencies of the prior art.
SUMMARY OF THE INVENTION
[0017] It is a main object of this invention to provide an improved fuel dissipater that will be effective when used in a pressurized SOFC generator and which can meet changing voltage situations. These and other objects are accomplished by providing a fuel cell generator characterized by and comprising: solid oxide electrolyte fuel cell stacks acting on pressurized hydrogen and carbon monoxide-containing fuel and pressurized oxygen-containing oxidant to provide electrical energy, in which the stacks have positive and negative terminals; a stack energy dissipater which operates on amplitude proportioning of a resistive load, comprising an electrical resistance load, said load comprising an array of at least two cooled, electrically connected resistors controlled by a voltage-sensitive multi-settable point relay, where individual switching contactors allowing for variable resistance loads are disposed between the array and a circuit breaker; where the circuit breaker is in electrical contact with the positive terminal and each of the resistors in the array is in contact with the negative terminal, so that the energy dissipater can draw current, in order to consume hydrogen and carbon monoxide-containing fuel stored within the generator during a transient operation. When a wide range of current is desired, at least three resistors arranged in parallel/series combination is highly preferred. The use of at least three resistors provides the most flexible system. A very useful array contains from three to about seven resistors and FIG. 3 illustrates use of four resistors (resistance elements). The current is dissipated as heat, and the problems associated with the oxidation of hydrogen-rich fuel in the combustion zone of the fuel cell generator are reduced or eliminated.
[0018] The invention also includes a method of dissipating energy during shutdown of a fuel cell generator characterized by and comprising: converting pressurized hydrogen and carbon monoxide-containing fuel and pressurized oxygen-containing oxidant to electrical energy in a fuel cell generator; shutting down the fuel cell generator; and drawing current from the fuel cell generator after the generator shuts down thereby to consume at least a portion of the hydrogen and carbon monoxide-containing fuel remaining in the generator and to convert the fuel to oxidized products, thereby to substantially prevent overheating of the generator, wherein the fuel cell generator contains solid oxide electrolyte fuel cell stacks having positive and negative terminals, where a stack energy dissipater which operates on amplitude proportioning of a resistance load is effective to draw current from the fuel cell generator after shutdown by means of an array of at least two electrical resistors providing a load which is electrically connected to the negative terminal at two or more locations, where the electrical resistors are also electrically connected through individual switching contactors and an associated voltage sensitive multi-settable point relay to a circuit breaker, which circuit breaker is electrically connected to the positive terminal at two or more locations, and where the fuel and the oxidant are pressurized to over 151.6 kPa. The term “kPa” here means k pascals absolute pressure. In all instances, the term “amplitude proportioning of a resistance load” means that the resistance of the load is changed by switching resistors into and out of the circuit, in response to changing fuel cell stack voltage, requiring use of at least 2 resistors. However, as mentioned previously, use of at least 3 resistors provides the most flexible system when a wide range of current is desired.
[0019] Thus, this invention requires a network of resistors which may be switched into and out of the circuit to maintain the stack voltage between minimum and maximum limits, where resistors are individually switched at different voltage levels. The switching of resistors into and out of the circuit in response to changing voltage constitutes control of the stack voltage ad current of amplitude modulation of the resistance. After the fuel is oxidized, the energy dissipater is passively and automatically disconnected. The term “pressurized”, as used herein, means operating at a pressure over 1.5 atmospheres (151.6 kPa or 22 psia).
[0020] Operation of the “stack energy dissipater” or SED is especially important when depressurizing pressurized hybrid for cell/micro-turbine generator systems. In pressurized systems the quantity of fuel which must be consumed is much greater than in unpressurized systems, and the release rate (and, therefore, the current required to dissipate the fuel) can be much higher. In order to reduce the pressure in the generator, the mass of gas must be reduced by flowing out through the cell stack exhaust. Typically the depressurization rate is very high at the beginning of a shutdown transient and becomes less as the pressure becomes lower. Thus, the flow rate of the fuel vented from the stack is much higher at the beginning of a depressurization transient than it is at the end. It is necessary to draw high current to dissipate the high fuel flow rate early in the depressurization, but this same high current may damage the cell stack later in the depressurization when the flow rate of fuel being vented is lower. Further, the release rate may be difficult to control, or predict, and it may strongly depend on the operating conditions of the generator immediately before depressurization. The depressurization rate may be much higher and the quantity of fuel to be dissipated much larger if the transition to shutdown occurs when the generator is colder, such as during heatup and loading, than if the transition occurs during steady state operation. The fuel composition (and therefore the heating value) will be different if transition to shutdown occurs while the generator is being loaded, than it would be if the transition was from steady state operation. Similarly, the depressurization rate may be much higher if the air flow into the generator is lower, such as during an emergency shutdown situation where the air supply may be bottled air at a rounded flow rate, as opposed to a normal shutdown where the air supply is the gas turbine compressor and the air flow rate is high. The same “stack energy dissipater” or SED may be required to handle all of these various conditions without damaging the cells, and so it is essential for pressurized systems to operate the stack energy dissipator on amplitude proportioning of a resistance load.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention is further illustrated by the following non-limiting drawings, in which
[0022] [0022]FIG. 1 is a schematic plan view of a SOFC generator stack showing the arrangement of multiple tubular fuel cells within the generator.
[0023] [0023]FIG. 2 is a perspective view of an individual tubular fuel cell having an open top end which extends into the combustion zone of a fuel cell generator.
[0024] [0024]FIG. 3 is a schematic diagram of a fuel cell generator energy dissipater in accordance with one embodiment of the present invention, and
[0025] [0025]FIG. 4 shows the expected Nernst potential for different fuel consumption at expected shutdown conditions.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] [0026]FIG. 1 is a schematic top view of a conventional SOFC generator stack 10 showing the arrangement of multiple tubular solid oxide fuel cells (SOFCs) 12 into a plurality of fuel cell bundle rows 12 ′ within the generator. Positive and negative electrical connection buses 21 and 22 are shown electrically connected to the bundle rows 12 ′, which provide electrical energy. Insulation 11 , usually in the form of low-density porous alumina insulation boards, surrounds the SOFCs 12 .
[0027] [0027]FIG. 2 is a perspective view of an individual tubular fuel cell 12 having a bottom end 13 and a top end 14 which extends into a combustion zone 15 of the fuel cell generator. The inner layer of the fuel cell 12 comprises a porous air electrode 16 , while the outer layer of the fuel cell comprises a porous fuel electrode 17 . During normal operation of the fuel cell, oxygen-containing oxidant gas, such as air, A I is introduced into the fuel cell 12 by a tube 18 . After the air or other oxygen-containing gas is injected by the tube 18 into the fuel cell 12 , it is exhausted A E through the open upper end 14 of the fuel cell. During electrical power generation operations, the air exiting the fuel cell 12 has a reduced oxygen content due to its consumption within the cell. Hydrogen-containing fuel F I , typically in the form of reformed natural gas or the like, flows along the exterior of the fuel cell 12 in contact with the porous fuel electrode 17 . During electrical power generation operations, most of the hydrogen in the fuel is consumed in a known manner to produce electrical energy. In the pressurized SOFC generator of this invention, A I and F I will be introduced at a pressure greater than 1.5 atmospheres (151.6 kPa) and up to about 10 atmospheres (1013 kPa).
[0028] During shutdown of the generator, the hydrogen and carbon monoxide fuel is no longer consumed and the fuel F E passing into the combustion zone 15 is rich in hydrogen and carbon monoxide. At the same time, the oxygen-containing gas AE injected into the fuel cell 12 is no longer depleted, and oxygen-rich gas exhausts through the open end 14 of the fuel cell into the combustion zone 15 . Thus, during a generator shutdown, the introduction of additional hydrogen, carbon monoxide and oxygen into the combustion zone 15 causes more combustion and higher temperatures within the combustion zone. In this invention, the chemical energy of the hydrogen and carbon monoxide containing fuel remaining within the fuel cell stacks and porous insulation surrounding the stacks is converted to electrical energy and dissipated as heat in the array of resistors outside the generator, instead of by burning with oxidant in the generator.
[0029] In accordance with the present invention, increased temperatures in the combustion zone 15 are reduced or eliminated by drawing current from the fuel cell 12 during shutdown of the generator. As used herein, the term “shutdown” means the opening of the electrical load circuit consisting of the SOFC dc output and any electrical loading device such as a DC/AC inverter system. The energy dissipater of the present invention includes at least two air-cooled electrical resistors, which dissipate electrical energy from the fuel cells in the form of heat. The electrical resistors may be of any suitable size and resistance. For example, four electrical resistance heaters of around 9 ohms resistance each encased in a stainless steel bar weighing approximately 600 pounds will suffice for a 300 kW pressurized SOFC stack design. These parameters may be altered, depending on the particular stack design with which this device will be employed. Preferably at least one resistor ( 55 ) may be switched by relays to be in series with the other resistors, as shown in FIG. 3. Thus, if there are three resistors, two would preferably be as parallel and a third resistor can be switched into that circuit in series allowing greater variation of resistance used.
[0030] During normal operation of the pressurized fuel cell generator, the operating temperature in the combustion zone is usually from about 850° C. to about 1000° C. However, during shutdown without fuel dissipation, the temperature in the combustion zone may increase by 250° C. or more by burning the fuel. In accordance with the present invention, the buildup of heat in the combustion zone upon shutdown of the generator is substantially prevented. If the same amount of heat energy is distributed uniformly over the total mass of the cell stack by electrochemical utilization of the fuel, the resulting temperature increase would be about 9° C. Since the cells are 50% efficient, half the energy will be dissipated in the resistors of the system energy dissipator and half will heat the cells so that the resulting stack rise will be about 4° C. Thus, the temperature in the combustion zone does not increase by more than about 4° C. after the pressurized generator shuts down.
[0031] [0031]FIG. 3 is a schematic diagram of a fuel cell generator stack energy dissipater (SED) 20 in accordance with an embodiment of the present invention. Relay contacts are shown with the relay coils de-energized. The energy dissipater 20 is connected across electrical conductors connected to the main positive and negative terminals 21 and 22 of the fuel cell generator. The major components of the energy dissipater include a voltage sensitive, multi-settable point sensor relay 23 that takes its power from the power bus being sensed, or from an external source; resistors, or resistance elements, which must be at least two, preferably at least three, and can be, as shown in this embodiment four elements, 28 , 53 , 54 , and 55 , to serve as an electrical load on the cell stack; relays 32 , 36 , 60 , and 61 and contractors 26 , 57 , 58 , and 59 to switch the load into and out of the circuit; and a shunt trip circuit breaker 24 , having at least two major connections to the positive terminal 21 (to electrical conductors connected to the terminal). The connections are shown as 50 , 51 and 52 in FIG. 3. The circuit breaker 24 is effective to disconnect the at least two preferably three resisting elements (load) from the power bus 21 and 22 when a specified appropriate minimum low voltage level is detected. Four separate resisting elements 28 , 53 , 54 and 55 , preferably in parallel and series combination as shown, are shown in FIG. 3, all being cooled by an air or water stream 56 passing, for example, through a conduit. Natural convection or radiation cooling could or the resistors could also be used, or the resistors could be sealed and placed in a water-cooled environment, or the resistors could heat a metal mass. The resisting elements (or resistors) have at least two major connections to the negative terminal 22 (to electrical conductors connected to the terminal). The connections are shown as 50 ′, 51 ′ and 52 ′ in FIG. 3. Contactors 26 , 57 , 58 and 59 , each associated with a resisting element, close the dissipater circuit when coils C 1 through C 4 are energized. Two three-pole relays 60 and 61 are used to enable and disable the SED remotely. Relay 32 is used to disable the SED when the minimum allowable stack voltage is sensed.
[0032] Referring again to FIG. 3, the load, which can range from two to about seven resistors, in this embodiment, as shown, consists of four separate air cooled resistors 28 , 53 , 54 and 55 , as described previously (and not necessarily equal resistances), connected in a series/parallel configuration. Commercial immersion heaters of the appropriate rating or radiant heaters could also be used, as required by the application. Each resistor is connected in series with a contactor (one of 26 , 57 , 58 and 59 ) and with the four pool shunt trip breaker 24 . The contactors 26 , 57 , 58 , and 59 switch the resistors in and out of the load circuit. They are actuated by coils C 4 , C 3 , C 2 and C 1 . Three of the four contactor coils C 1 , C 3 , and C 4 are energized or de-energized by a quad setpoint voltage sensor module 23 . The fourth contactor C 2 is energized immediately upon initiation of the trip signal. After timer relay 36 closes, C 2 remains connected across the generator terminals until the SED is disengaged by opening the shunt trip breaker 24 . Relays 60 and 61 situated between the quad setpoint relay 23 and coils C 1 through C 4 are used to activate or de-activate the circuits to the coils C 1 through C 4 . During normal operation of the SOFC generator, relays 60 and 61 are energized by a voltage signal from the SOFC control system. This opens the contacts in 60 and 61 , deactivating the SED by de-energizing the coils C 1 through C 4 and their associated contactors 26 , 57 , 58 , and 59 . When the SED is needed, the SOFC control system removes the energizing voltage from relays 60 and 61 , closing the contacts in relays 60 and 61 and completing the circuit between 23 and coils C 1 through C 4 .
[0033] Relay 32 is part of the disconnect circuit. Its coil is energized by the fourth contact of the quad setpoint relay 23 . When the stack voltage drops to the minimum permissible voltage, contact 5-10 of 23 opens, de-energizing 32 and causing contact 7-1 of 32 to change state to 7-4. This de-energizes C 2 , opening contactor 58 and disconnecting resistor 54 . At the same time, the change of state of relay 32 from 7-1 to 7-4 completes a circuit which activates the trip coil of shunt trip breaker 24 , disconnecting the load resistors from the cell stack until such time as an operator manually resets the breaker 24 . A set of auxiliary contacts 38 remove any sustained voltage from being impressed across the low energy shunt trip coil in breaker 24 . The auxiliary contacts 38 open when the shunt trip coil trips the circuit breaker 24 open. This ends the sequence. Before restart, the circuit breaker 24 must be manually reset. A circuit breaker status indicator 33 may optionally be used to indicate whether the circuit breaker 24 is tripped.
[0034] A timing relay 36 is provided between relay 32 and shunt trip breaker 24 to prevent premature disconnection should the stack voltage drop momentarily below the minimum voltage when the SED is first engaged. When the SED is first engaged, the contacts within the timer will be open, blocking the shunt trip signal to circuit breaker 24 . After a predetermined time, the timer will change state, closing the contacts and enabling activation of the shunt trip circuit in 24. In the interim, the quad setpoint relay 23 , by energizing and de-energizing relay 32 , can connect and disconnect series resistors 54 and 55 permitting the SED to unload (open circuit) the generator on low voltage and reload the generator if the voltage recovers. If the voltage increases to higher levels, the other relays and resistors will respond to control the voltage accordingly.
[0035] The quad setpoint module senses four separate, programmable voltage setpoints, each associated with one of four contacts 2-7, 3-8, 4-9, and 5-10 in the module 23 . The contacts in the module 23 change state (de-energize) when the voltage drops below their respective setpoints. Should the voltage rise above the setpoint, the contacts change state (energize) and close again. The device permits individual switchung of the contactors 26 , 57 , 58 and 59 , and places the corresponding resistors across the cell terminals. The net result is that when the voltage rises, more of the parallel resistor legs are switched in, and current flow increases. When the voltage drops, one or more of the resistors 28 , 53 , 54 and 55 , which may have different resistance values, is switched out, causing current flow and fuel consumption to decrease. If the reduced fuel consumption results in reestablishing the stack voltage, one or more of the resistors may be switched back into the circuit. The objective is to maintain the stack voltage between predetermined levels until the residual fuel is spent and the generator can no longer support the terminal voltage. At the predetermined low voltage level, the dissipater will permanently open the circuit to prevent the cells from operating at the nickel oxidation potential. Final lockout of the dissipater is accomplished through the lowest module setpoint contact 5-10, where the closure of the low voltage channel results in the permanent trip of the shunt trip breaker 24 . A manual reset of the shunt trip/breaker 24 is required to rearm the dissipater.
[0036] In a quad setpoint system, the setpoint module controls three resistor legs and one shunt trip breaker. Any number of resistor kegs is possible, depending on the needs of the application. In the example of FIG. 3, the relays can vary the load to effect any of four configurations in response to the stack voltage: three parallel resistors (stack voltage >12.4V, contacts 2-7, 3-8, and 4-9 closed in 23, contact 5-10 open), two parallel resistors (12.1V<stack voltage<12.4V, contacts 4-9 and 5-10 open, all other contacts closed in 23), one resistor (11.8V<stack voltage<12.1V, contact 3-8 closed, all other contacts open in 23), and in two series resistors (1.5V<stack voltage<11.8V, all contacts open in 23). Resistor 55 is the series resistor, which is always wired in series with contactor 58 and resistor 54 . For the parallel resistance combinations resistor 55 is shorted by closing contact 59 , effectively removing resistor 55 from the load.
[0037] Note that contact 5-10 of 23 is a fail closed contact ad opens when energized. Closing this contact energizes the shunt trip circuit breaker, which opens the circuit between the SED and the generator terminals, thus disconnecting the SED. The shunt trip breaker must be reset manually to rearm the SED.
[0038] Note also that the voltages given in the embodiment of FIG. 3 are appropriate for a small generator stack of 48 cells. For larger stacks, the voltage setpoints for each contact will be higher and the voltage divider resistances (10K-ohms in FIG. 3) required to scale the stack voltage to the 0-10V input range of the multi-setpoint module will be different.
[0039] Because of the ability to adjust the resistance in response to change in the stack voltage (either up or down), this system has advantages when the flow conditions are not well known, or when flow oscillations or fuel composition changes might occur. If the system is engaged and the fuel flow rate is lower than expected, or if the H2+CO composition is not as high as expected, the module will adjust the total load to compensate. Conversely, there is much greater design latitude to compensate for uncertainties in the fuel flow analyses. By selecting a total resistance that provides for higher than expected currents, the dissipater can be configured to allow for higher than expected fuel flow. This allows for the fluid system design to be less complex, since flow conditions do not need to be as precisely known to protect the cells. In the design of this invention, as shown in FIG. 3, the quad setpoint sensing module combines the functions if several devices to achieve the desired results: stack voltage sensing, voltage setpoint adjustment, and relay contacts to actuate the cells of the switching contactors. These functions could reside in separate devices, if desired. Also shown is a separate battery power supply 62 to provide power to the setpoint module in the event of a primary power supply failure. As an alternative, the module could be powered by an uninterruptable power supply (UPS) if the generator control system is so equipped. Also shown is a 24VDC control system to enable the SED through relays 60 and 61 . The control system could be configured using alternate standard voltage services (for example, 120 VAC), instead of 24 VDC.
[0040] The multi-setpoint stack energy dissipator of this invention allows the current to the reduced in response to the changing fuel flow rate (or fuel composition), without going to zero. A single resistor system would either not dissipate enough fuel at the start of the transient (resulting in high combustion zone temperatures), or would draw too much current later in the transient (resulting in damage to the cells from high fuel utilization). By varying the size of the load resistance over a very wide range of high current, the multi-setpoint dissipater keeps the cell stack combustion zone temperature within reasonable limits, but does not endanger the cells due to high fuel utilization (total depletion of the available fuel).
[0041] While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives could be developed in light of the overall teaching of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the claims appended and any and all equivalents thereof. | An apparatus and method are disclosed for eliminating the chemical energy of fuel remaining in a pressurized fuel cell generator ( 10) when the electrical power output of the fuel cell generator is terminated during transient operation, such as a shutdown; where, two electrically resistive elements (two of 28, 53, 54, 55) at least one of which is connected in parallel, in association with contactors ( 26, 57, 58, 59), a multi-point settable sensor relay ( 23) and a circuit breaker ( 24), are automatically connected across the fuel cell generator terminals ( 21, 22) at two or more contact points, in order to draw current, thereby depleting the fuel inventory in the generator. |
BACKGROUND OF THE INVENTION
The cams with which the present invention is principally concerned have long been well known in configuration, per se, and have become identified generically by the term "gerotor". They are characterized by internal or external contours which, unlike the teeth of conventional gears, are lobed and exhibit continuous curvature rather than discontinuous or irregular shapings. When such contouring is exactly in accordance with theory, mated inner and outer cams, or one such cam cooperating with a circular array of rollers in place of the other, lend themselves to highly-efficient cooperations wherein all lobes and/or rollers are constantly in working meshed contact while one is orbited within the other. For the latter purpose, the outer one of the two cams, or cam and array of rollers, normally has a number of lobes or rollers which exceeds by one the number of the other. Examples of constructions in which such units are advantageously used in such devices as pumps, hydraulic motors and speed changing transmissions may be found in U.S. Pat. No. 3,574,489 -- Pierrat and in copending application Ser. No. 530,224, filed Dec. 6, 1974, for "Mechanical Drives" -- Pierrat. Contouring of the cams is so critical, and has been so difficult to achieve with the requisite precision, that early versions were matched as sets which were worn to about the right shapings by running-in which burnished their surfaces to an acceptable operating fit. Subsequent versions, precise enough to allow for interchangeability, have since become commercially available, but are evidently difficult to produce because their cost is very high. The manufacturing technique which suggests itself is that of guiding a circular milling cutter of the like around the periphery which is to be shaped into the lobes, under the direction of a contour guide or in accordance with a computed program to which either or both of the cutter and cam blank are slaved as to relative motion. However, the sizes and lobe numbers of such cams may vary widely, and the contouring guides or programs must be of equal variety and based upon complex calculations and/or empirically-derived data. Special-purpose cutting machinery capable of performing such needed contouring tend to be expensive and to call for uncommon operating skills.
Our improved and unusual approach to realizing the critically-contoured lobed cams, with great precision and ease and economy, requires neither contour guides nor programmed computer-controlled automatic cutting machines; instead, it uniquely recognizes and takes into account a distinctive combination of synchronized reverse-direction rotary and orbital motions and develops these by way of a novel and uncomplicated fixture in which the needed special relative motions between a cutter and cam blank are automatically and accurately generated and are readily changeable to meet varied contouring specifications.
SUMMARY
A preferred arrangement for machining "gerotor" lobed cams in accordance with the present teachings comprises a rigid platen held in non-turning relation to a base by way of mutually-perpendicular slides forming an X--Y suspension which nevertheless allows the platen to move laterally. Atop the platen is secured a first rotary table capable of mounting a cam blank and rotating it about a first axis normal to the platen at a relatively slow angular rate governed by a gear train and electric drive motor which are also carried by the platen. Dependent from the underside of the same platen is a second rotary table which turns an adjustable-eccentricity crank arm in a suitable bearing fixed with the base, the axis of rotation of the second rotary table also being normal to the platen and the rotation thereof being mechanically synchronized with that of the first table by gearing with the same electric drive motor, although the latter gearing turns the second table at a relatively rapid rate and in a direction opposite to that of the first table. The vertical cutting tool of a circular milling machine, upon which the base of the aforesaid assembly is mounted, is brought into lateral material-removal relationship with the cam blank as the drive motor rotates the two tables, with the result that the desired number and contouring of lobes is occasioned in accordance with preselected settings of the eccentricity and of gear ratios determined by one gear in the train serving the first table. The arc circumscribed by the cutting edges of the cutting tool is the same as that of rollers or cooperating cam surfaces with which the cam is to be used. Synchronism between the angular rotations of the two tables, as selected by said one gear, is such that the second table turns once for each angular excursion of the first table which is equal to the intended spacing between adjacent lobes of the finished cam.
Accordingly, it is one of the objects of the present invention to provide for unique and advantageous fashioning of gerotor cams by way of combined synchronized rotation and opposite-direction circular orbiting of a cam blank while continuous-curvature lobe surfaces are shaped by a cutter having a configuration matched with that of rollers or other surfaces with which the cam is to be used and operated at a relatively fixed position.
Another object is to provide novel and improved apparatus for relatively low-cost and versatile precision machining of gerotor cams in a variety of sizes and with different numbers of continuous-curvature lobe surfaces, by way of fixturing in which a cam blank is automatically oriented for proper removal of material in a conventional type of cutting machine, the fixturing being powered and synchronized to effect simultaneous orbiting of the cam blank in one direction and rotation in the other.
BRIEF DESCRIPTION OF THE DRAWINGS
Although the aspects and features of this invention which are considered to be novel and unobvious are expressed in the appended, claims, further details as to preferred practices and as to the further objects and features thereof may be most readily comprehended through reference to the following description of preferred embodiments taken in connection with the accompanying drawings, wherein:
FIG. 1 presents a plan view of two companion sun-and-planet sets of rollers and lobed cams for use in a speed-reducing mechanical drive, the cam elements being of configuration with which this invention is concerned;
FIG. 2 is a plan view of one of the lobed cams of FIG. 1, in association with a tool used in its cutting and with designations of orbiting and rotational movements involved in its cutting;
FIG. 3A represents an enlarged and partly-broken-away fragment of a cam like that of FIG. 2 at a time during machining when its eccentricity is at one extreme;
FIG. 3B is an illustration like that of FIG. 3A but for the condition when eccentricity is at the opposite extreme;
FIG. 4 provides a front view of portions of a cam-cutting fixture mounted upon the bed of a milling machine and cooperating with a cutting tool of the same machine;
FIG. 5 supplies a front view of an electric motor and synchronizing gear drive for the fixture of FIG. 4;
FIG. 6 illustrates the drive of FIG. 5 in an alternate position and with a different gear substituted for control of the number of cam lobes to be produced; and
FIG. 7 is a top view of the arrangement of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The paired sets of cams, 8 and 9, and cooperating rollers, 10 and 11, which appear in FIG. 1 are of configuration and arrangement suitable for exploitation in a speed-reducing mechanical drive which has been known heretofore and which requires precisely-contoured continuous-curvature lobed cams in a variety of sizes and with different numbers of lobes for different speed changes. Lobed cams 8 and 9 each function there as a "planet gear" and have their epitrochoid-curvature external lobes in cooperative "meshed" engagements with the rollers, 10 and 11, respectively, pinned to the disks 10a and 11a to form external "sun gears" within which the inner planet cams may orbit. In accordance with established practice, each of the planet cams 8 and 9 has one less convex lobe or "tooth" than there are rollers functioning after the manner of "teeth" on the sun disk encircling it, the cam 8 having eleven lobes for the surrounding twelve rollers 10 and the cam 9 having twenty-three lobes for the surrounding twenty-four rollers 11. The two planet cams 9 and 8 are intended to be integral or otherwise locked angularly together face to face, with their centers 12 and 12' lying along a common eccentric axis of a circular eccentric shoulder of an input shaft (not shown), the cams being rotatable together about that eccentric shoulder. Centers 13 and 13' of the sun disks 10a and 11a coincide with the central axis of the same input shaft. When one of the sun disks, such as 11a, is angularly restrained, the other will turn and provide a significantly-reduced speed of rotational output in relation to that of the input shaft. Rotation of the input shaft, and its eccentric shoulder, causes cam 9 to orbit within the circular array of rollers 11 of the fixed sun disk 11a, that orbiting yielding a reverse-direction rotation of cam 9 about its center 12' with a speed reduction determined by its number of lobes; simultaneously, cam 8 angularly locked with cam 9 must undergo a like rotation, and, in so doing, orbits within the circular array of rollers 10 and thereby forces sun disk 10a to rotate at a yet further reduced speed as dictated by the number of lobes on cam 8. The total speed change effected by this combination is determined by the relationship (N 1 ) (N 2 +1)/N 1 -N 2 , where N 1 is the number of lobes of cam 9 and N 2 is the number of lobes of cam 8.
If cams 8 and 9 have their lobes shaped properly, all of the cooperating rollers 10 and 11 will at all times be in mating contacts therewith and nearly half of the rollers and lobes will be operative to share the load being transmitted; noise and backlash are advantageously minimized in such an arrangement, and outstanding torque-transmitting capabilities are promoted. Cylindrical rollers, and their circular equi-angularly spaced arrays on disks, can be realized readily enough using known manufacturing techniques. However, the contouring of the cam lobes poses problems as noted hereinbefore, and which are perhaps better appreciated in relation to the operating requirements stated with reference to the arrangement of FIG. 1. Such problems are obviously posed also by alternative constructions wherein pins are substituted for the rollers, and wherein internally-lobed cams cooperate with externally-lobed cams or rollers or pins.
FIG. 2 illustrates our approach to the forming of a lobed cam such as the cam 9 of FIG. 1. There, dashed linework 14 represents the original circular outline of a blank from which the cam is machined, its center being designated 14'. A cutting tool 15, such as a conventional fluted milling cutter, is rotated about an axis 15' normal to the blank in position to engage its periphery, and, simultaneously, the blank is orbited such that its center 14' moves along a relatively small circular path or orbit, designated by dashed linework 16, in one angular direction, 17, at a relatively rapid rate, while the blank is also being turned about its center 14' in an opposite angular direction, 18, at a slower rate. Unless the said angular directions are opposite, the resulting lobes will not have the correct gerotor curvatures and the cams will not be suitable for the applications described. In FIGS. 3A and 3B, wherein the same reference characters are used to designate the same or functionally-corresponding parts and relationships as in FIG. 2, a portion of a cam such as cam 9 is shown at extremes of its material-removal engagements with cutter 15. The maximum radial span, 19a, from the center 14' of cam 9 to the outer tip of a convex lobe, occurs when that center is on the point of orbit 16 laterally most removed from the cutter (FIG. 3A), and the minimum radial span, 19b, from the center 14' of cam 9 to the innermost part or bottom of a concave lobe, occurs when that center is on the diametrically-opposite point of orbit 16, laterally closest to the cutter (FIG. 3B). The common maximum depth, or height, 20 (FIG. 3A), of all the lobes corresponds to the diameter of orbit 16. Cutter 15, when of the rotary type illustrated, is preferably turned about its fixed-position axis 15' in a direction, such as 21, which allows it to bite into advancing material of the cam blank. At the same time that the cam blank is orbited in one direction, so that it will advance toward and retreat from the cutter sinusoidally at a given periodicity, it is also turned at a uniform rate and a slower periodicity in the opposite angular direction, and the number of full orbits for each full turn is preselected to equal the full number of continuous-curvature lobes desired. The diameter of cutter 15 is preferably the same as that of the rollers with which the cam is to cooperate, such as rollers 11 in the case of cam 9. Although a milling-type cutter 15 is preferred, a single-bladed cutter or abrasive cutter may also be revolved about axis 15' in its place, or alternatively, another form of cutter may be drawn or reciprocated at the desired site or rotated about an axis normal to axis 15', for example, with like material-removal effects.
The machining apparatus illustrated in FIG. 4 includes a unique fixture, 22 (FIGS. 4 and 7) which develops the movements of a cam blank needed to realize the desired gerotor-lobe curvatures and which can be accommodated readily by a generally-conventional milling machine having a mounting bed 23 and a vertical spindle 24 for rotation of a fluted cutting tool 15a about a vertical axis 15a'. Fixture 22 includes a sturdy baseplate 25, which may be secured to the machine mounting bed 23, and an intermediate rigid plate 26 suspended in vertically-spaced relation to that baseplate, and a rigid top mounting platen 27 suspended in vertically-spaced relation to the intermediate plate. Atop the mounting platen 27 there is fixed a first rotary table 28, which is of a known construction including a table 28a supported in bearings for rotation about a vertical axis 14a' and having a laterally-extending input shaft 28b which turns worm gearing to rotate table 28a about its axis 14a'. Dependent from the underside of the same mounting platen 27 is a second rotary table 29 which is like the first, but inverted, and includes a table 29a supported in bearings for rotation about a vertical axis and has a laterally-extending shaft 29b which turns worm gearing to rotate table 29a about its axis. Intermediate plate 26 is suitably cut away (not visible in the drawings) to accommodate the presence of the second rotary table 29 and to allow it to cooperate with a bearing 30 in baseplate 25 which is disposed eccentrically in relation to the axis of the table 29a. Both of the tables 28a and 29a have customary provisions for releasably clamping items to their exposed table surfaces; in the case of the first table 28a, such a clamping is effected at 28c to hold a cam blank 9' in place coaxially with axis 14a', and, in the case of the inverted second table 29a, such a clamping is effected at 29c to hold a shaft 31 in the baseplate bearing 30 in eccentric relation to the vertical axis of the lower rotary table 29a. Cam blank 9' represents the item to which lobe contouring is imparted by the cutter 15a, and the eccentricity of the axis 31a of shaft 31, which functions as a crankshaft, determines the circular orbit referred to earlier herein.
When input shaft 29b to lower rotary table 29 is turned, the eccentricity to which shaft 31 has been set in its relation to the axis of rotated table 29a will tend to cause mounting platen 27 to describe a circular movement, or orbit. However, the needed circular orbiting of platen 27 must occur without any accompanying rotation, for purposes of the intended lobe contouring. Such orbiting, without attendant rotation, is guided by an X--Y suspension which enables platen 27 to slide laterally in each of two mutually-perpendicular directions, as needed to accommodate the circular orbiting motion imparted by the crankshaft 31. That X--Y suspension includes two spaced parallel cylindrical slide shafts, 32, 33 (FIGS. 4 and 7), affixed to sides of intermediate plate 26, and two further spaced parallel cylindrical slide shafts, 34, 35, affixed to opposite sides of that same plate 26. Free ends of those slide shafts are mated with suitably-aligned low-friction bushings held by support blocks. Bushings 32a, 32b, 33a and 33b, are fixed to the underside of mounting platen 27 by way of support blocks such as 32c, and 32d, for example, so that the platen may slide on shafts 32 and 33 in directions shown at 36. In turn, bushings 34a, 34b, 35a and 35b are fixed atop baseplate 25 by way of support blocks 34c, 34d, 35c and 35d, to allow the aforesaid combination of the mounting platen 27 and its sliding support upon intermediate plate 26 to slide, in turn, in directions shown at 37, normal to directions 36 (FIG. 7).
Such rotary motion as does occur atop mounting platen 27 is that which is prescribed by upper rotary table 28a as it is driven by its input shaft 28b, and that motion occurs relatively rapidly and in precise synchronism with the orbiting motion prescribed by lower rotary table 29a as it turns crankshaft 31 in response to drive by its input shaft 29b. Moreover, as has already been said, the upper table is rotated in a direction, such as that of arrow 18', which is opposite to the angular direction which the mounting platen 27 is orbited. These synchronized angular motions are preferably derived from a common source, which in the case of fixture 22 is the angular motive output from a bevel gear 38 driven by the shaft of an electric motor 39 supported by and movable with mounting platen 27 (FIGS. 5, 6 and 7). That bevel engages another, 40, which turns input shaft 29b of the lower rotary table at a relatively high speed. Within gear box housing 41, the high-speed rotation of shaft 29b is geared down to two related lower speeds of two spaced externally-disposed like pinion gears 42 and 43, the rotational speed of one conveniently being made twice that of the other, and both being in the same angular direction. Either of pinions 42 and 43 may be selected to drive the input shaft 28b of upper rotary table 28 by way of its attached spur gear 44, and, in each instance, such drive is achieved through a train of gears 45, 46 and 47 mounted on a pivot arm 48 which may be pivoted about the axis 28c of spur gear 44 and shaft 28b. Pivot arm 48 may be locked in either of two position, via a fastener 49 (FIGS. 5 and 6); in one such position, represented in FIGS. 5 and 7, gear 47 meshes with pinion 42 to drive the rotary table 28 at one predetermined speed, and, in the other position, illustrated in FIG. 6, the same gear 47 instead meshes with pinion 43 to drive the rotary table 28 at a second predetermined speed, in the same direction. Advantageously, one of the gears in the train between the shafts of pinions 42 and 43 and input shaft 28b of rotary table 28 is made interchangeable with other gears, as a means for conveniently determining and setting the number of cam lobes to be cut. As shown, gear 47 is disposed to serve that function; it is releasably keyed to the same shaft as gear 46, and is at an accessible site for substitution of another gear with a different number of teeth, and may be pivoted into appropriate engagement with either pinion 42 or 43 by simple fastening of pivot arm 48 at angular positions wherein different diameters of gear 47 are allowed for and wherein minimum backlash or looseness can occur.
In operation, a cam blank 9' is fastened atop upper rotary table 28 with its intended center coincident with the axis of rotation 14a' of that table, and an appropriate gear 47 is put into place, with its number of teeth being selected to dictate that table 28 will rotate one full turn each time the lower rotary table 29 is rotated oppositely a full number of turns equal to the full number of lobes desired on the finished gerotor-contoured cam (i.e., once for each eight orbits, in the case of the eight-lobed cam 9' illustrated in FIG. 7). In addition, the eccentricity of the axis 31a of crankshaft 31 in relation to the vertical axis of rotation of lower table 29 is set at a desired value, equal to one-half the depth of lobes to be produced (i.e., the diameter of the resulting circular orbiting being equal to the intended depth of the lobes). Under common powering from electric motor 39, the cam blank is then caused to orbit relatively rapidly in one angular direction while being rotated slowly in the opposite direction, the X--Y suspension allowing the orbiting movements while preventing all rotation other than that controlled by the upper rotary table. Milling cutter 15a is rotated via its spindle 24, in a direction which allows it to bite into advancing material of the cam blank. Spindle 24 is conventionally movable to bring the edges of cutter 15a to precisely the intended distance from the central axis 14a' of upper table 28 which will yield a lobed cam of the desired maximum diameter.
More than a single cam blank may be contoured at one time, as by stacking them for the cutting. Also, one cam blank may have two different sets of lobes contoured upon it, with a first contouring being performed to about half its depth and the second contouring being performed upon the remainder after the blank has been turned over. It is not necessary that full-depth contouring of the lobes be achieved at once, and, instead it may be preferred to remove relatively small amounts of material during successive full rotations of the cam blank until the full contouring is realized. Backlash problems are avoided if the operations are continued without reversals.
The supporting machine may be of a construction and orientation other than that of the vertical milling machine illustrated, and the fixture may then be oriented appropriately for that setting. Other such machines include a horizontal miller, jig bore, cylindrical or surface grinder, equipped with contoured or formed tools. The tool diameter in the case of a vertical miller is the same as that of rollers to be used with the cam, and the grinding wheel of a jig bore would have that tool diameter also, whereas the rotary milling cutter of a horizontal miller or the grinding wheel of a cylindrical or surface grinder would be ground to a radius equal to the radius of the rollers to be used. Eccentricity settings for the orbiting may be carefully controlled by use of a known type of micrometer-feed boring head utilized for the purpose of holding the shaft 31 in eccentric relation to the axis of rotation of the bottom rotary table. The X--Y suspension may of course assume forms other than that illustrated, and drives and associated gearing may likewise be expressed in different ways with comparable results. Accordingly, it should be understood that the specific practices and preferred embodiments herein referred to have been offered by way of disclosure rather than limitation, and that various modifications, additions and substitutions may be effected by those skilled in the art without departure from these teachings; it is therefore aimed in the appended claims to embrace all such variations as fall within the true spirit and scope of this invention. | Continuous-curvature lobed cams, such as are variously used after the manner of gearing in orbital-drive mechanical transmissions, hydraulic motors and the like, are formed with the precise and continuous distinctive contouring which is essential to their successful operation by way of a simple and inexpensive cutting tool rotated about a fixed axis in a conventional machine while the cam blank with which it is in a material-removing engagement is both rotated relatively slowly in one angular direction and orbited relatively rapidly and synchronously along a circular path in the opposite angular direction. Synchronism between the slow rotary and rapid orbital motions is achieved in a machine-mounted fixture through geared drive of two rotary tables from a common motive source on the same movable platen which mounts the two rotary tables. One of the rotary tables orbits the platen along an adjustable-eccentricity path relative to the supporting machine bed, as accommodated by an X-Y mount, and the number of cam lobes to be fashioned is determined by introducing an appropriate gear in an adjustable gear train between the motive source and the other rotary table which rotates the cam blank. |
FIELD OF THE INVENTION
The present invention relates to internal combustion engines, and more particularly to systems and methods for protecting an intake manifold during reverse engine rotation.
BACKGROUND OF THE INVENTION
An internal combustion engine generally operates in four modes; an intake mode, a compression mode, a combustion mode and an exhaust mode. During reverse rotation of an engine, the engine cycle executes in a reverse order whereby the compression mode is followed by the intake mode. For example, when an engine that is stopped begins to start again, the engine may have a cylinder that was in a compression mode at the moment of stopping. Compression pressure in the cylinder may push a piston in reverse toward bottom dead center (BDC). When engine speed increases, a cylinder with injected fuel may experience ignition and the reverse rotation may be accelerated.
Conventional engines will rarely rotate in reverse for long periods of time. Torque control systems are capable of limiting the duration of the reverse rotation. However, the problem arises more frequently in hybrid electric propulsion systems. An external force (such as an electric motor) can rotate the internal combustion engine in reverse for longer durations at higher speeds. Conventional torque control systems are not able to control torque under these conditions.
If reverse rotation occurs, engine components such as the intake manifold can be damaged. Reverse rotation may cause a compressed air/fuel mixture to flow back into the intake manifold during the intake stroke through an open intake valve. Pressure in the intake manifold increases. If further reverse rotation occurs, pressure may increase further and cause damage to the intake manifold.
In addition to damage to the intake manifold, reverse rotation of the engine may cause further problems such as excess bearing wear and damage to gaskets, hoses and sensors connected to the intake manifold.
SUMMARY OF THE INVENTION
A method of protecting an intake manifold of an engine of a hybrid propulsion system including an electric motor comprises detecting a reverse rotation of an engine. A fuel injector of the engine that is rotating in reverse is commanded to cease operation. A spark plug of the engine that is rotating in reverse is commanded to cease operation. The ceasing of reverse rotation of the engine is then confirmed.
In another feature, the method comprises notifying a diagnostic module of the reverse rotation.
In another feature, an electric motor is commanded to cease operation after detecting reverse rotation is performed, wherein commanding the electric motor to cease operation further comprises commanding the electric motor to begin forward rotation.
In another feature, the method comprises commanding the fuel injector to re-enable and commanding the spark plug to re-enable after confirming of the ceasing of reverse rotation of the engine is performed.
In other features, detecting reverse rotation comprises comparing an actual cam sensor signal to an expected cam sensor signal. Wherein the expected cam sensor signal is determined based on the actual cam sensor signal and a crankshaft sensor signal.
In other features, the expected cam sensor signal is set to a previously stored actual cam sensor signal, and wherein detecting reverse rotation further comprises comparing a state of the actual cam sensor signal to a state of the expected cam sensor signal while the engine is operating in at least one of a first region and a second region and when a camshaft and crankshaft are synchronized.
In still other features, the expected cam sensor signal is set to an expected reverse cam sensor signal, and wherein detecting reverse rotation further comprises comparing an edge of the actual cam sensor signal to an edge of the expected cam sensor signal for a selected crank angle region relative to top dead center of a specified cylinder when a camshaft and crankshaft are not synchronized.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a schematic illustration of a hybrid propulsion system including the intake manifold protection system according to the present invention;
FIG. 2 is a flowchart illustrating the steps for identifying reverse rotation of an engine of the propulsion system; and
FIG. 3 is a flowchart illustrating the intake manifold protection method according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify the same elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
Referring now to FIG. 1 , an engine propulsion system 10 includes an engine 12 that combusts an air and fuel mixture to produce drive torque. Air is drawn into an intake manifold 14 through a throttle 16 . The throttle 16 is electronically controlled to regulate mass air flow into the intake manifold 14 . Air within the intake manifold 14 is distributed into cylinders 18 . Although four cylinders 18 are illustrated, it can be appreciated that the engine propulsion system of the present invention can be implemented in engines having a plurality of cylinders including, but not limited to, 2, 3, 5, 6, 8, 10, 12 and 16 cylinders.
A fuel injector 20 injects fuel that is combined with the air as it is drawn into the cylinder 18 through an intake port. An intake valve 22 selectively opens and closes to enable the air/fuel mixture to enter the cylinder 18 . The intake valve position is regulated by an intake camshaft 24 . A piston (not shown) compresses the air/fuel mixture within the cylinder 18 . A spark plug 26 initiates combustion of the air/fuel mixture, driving the piston in the cylinder 18 . The piston drives a crankshaft 28 to produce drive torque.
Combustion exhaust within the cylinder 18 is forced out through an exhaust manifold 30 when an exhaust valve 32 is in an open position. The exhaust valve position is regulated by an exhaust camshaft 34 . The exhaust is treated in an exhaust system (not shown). Although single intake and exhaust valves 22 , 32 are illustrated, it can be appreciated that the engine 12 can include multiple intake and exhaust valves 22 , 32 per cylinder 18 . An electric motor 36 provides an alternate source of power needed to rotate the crankshaft 28 of the engine 12 . A control module 38 senses inputs from the engine system and responds by controlling the aforementioned components of the propulsion system 10 .
Control module 38 can determine when the engine 12 is operating in reverse rotation by evaluating a pulse train signal generated by a cam sensor 40 and a pulse train generated by a crankshaft sensor 41 . Referring now to FIGS. 1 and 2 , the flow of control executed by the control module 38 according to the present invention will be described in more detail. In order to detect reverse rotation of an engine 12 , control first determines an engine position that indicates whether the camshaft 24 and crankshaft 28 are synchronized. For purposes of clarity, the following discussion relates to the intake camshaft 24 (hereinafter referred to as camshaft 24 ). As can be appreciated, a similar approach can also be applied to the exhaust camshaft 34 .
In step 100 , the sensors sense the position of the camshaft 24 and the crankshaft 28 . The. position of the camshaft 24 is determined relative to the position of the crankshaft 28 . The camshaft and the crankshaft are synchronized if their states match a preselected pattern, and the engine has sustained it's own forward rotation as measured by crankshaft speed. If the camshaft 24 and crankshaft 28 are synchronized in step 110 , a state of the camshaft signal is evaluated in step 120 for a selectable region defined by a first and a second angle of the camshaft 24 . The state of the signal can be either high or low. In step 120 , if an actual cam signal state matches a cam signal state previously sensed at the selectable region, the engine 12 is rotating in a forward direction at step 130 . Otherwise if an actual cam signal state does not match a cam signal state previously sensed at the selectable region, the engine 12 is rotating in a reverse direction at step 140 .
Referring back to step 110 , otherwise, if the camshaft 24 and crankshaft 28 are not synchronized, in steps 150 and 160 an edge of the camshaft sensor signal is evaluated at a region defined by a first and a second angle of the crankshaft position referenced relative to top dead center of a cylinder 18 . The reference cylinder 18 can be selectable. The signal edge can be either low to high or high to low. In step 150 , if an actual camshaft signal edge matches an expected reverse camshaft signal edge for that region, the engine 12 is rotating in a reverse direction at step 140 . Otherwise, in step 160 , if an actual camshaft signal edge matches an expected forward camshaft signal edge for that region, the engine is rotating in a forward direction at step 130 . Otherwise, the rotation of the engine 12 is indeterminate at step 170 . The expected forward camshaft signal edge and the expected reversed camshaft signal edge can be selectable according to an angle of the camshaft.
Referring now to FIGS. 1 and 3 , once control determines the engine 12 is rotating in reverse, subsequent actions are taken to protect the intake manifold 14 . FIG. 3 is a flowchart illustrating the steps taken by the control module 38 . In step 200 , control commands the electric motor 36 to stop reverse rotation. In step 210 , control disables fuel by commanding the fuel injector 20 to cease operation. In step 220 , control disables spark by commanding the spark plug 26 to cease firing. The actions of steps 210 and 220 are likely to occur at the same time. In step 230 , control will notify an on-board diagnostic module of the reverse rotation condition. The diagnostic module can set a diagnostic code and perform any diagnostic functions if the diagnostic module determines to do so. Once reverse rotation has stopped 240 , control re-enables fuel in step 250 by commanding the fuel injector 20 to inject fuel, re-enables spark in 260 by commanding the spark plug 26 to initiate combustion, and exits the loop.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims. | A method of protecting an intake manifold of an engine of a hybrid propulsion system including an electric motor comprises detecting a reverse rotation of an engine. A fuel injector of the engine that is rotating in reverse is commanded to cease operation. A spark plug of the engine that is rotating in reverse is commanded to cease operation. The ceasing of reverse rotation of the engine is then confirmed. |
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional application No. 61/215,584, filed May 7, 2009, the entire contents of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to a cutting apparatus. More particularly, but not by way of limitation, the present invention relates to a method and apparatus for removing a fitting from a pipe.
[0004] 2. Brief Description of the Related Art
[0005] A number of prior art devices have been suggested for removing a fitting from a pipe. However, these devices suffer from a number of limitations and deficiencies. One such device is disclosed in U.S. Pat. No. 6,929,430, issued to Dever. Dever discloses a water closet flange removal tool that includes an axial shaft, a cylindrical guide body attached to a lower end of the shaft, and a cylindrical wall cutter mounted above the guide body and on the axial shaft. The Dever tool uses a single component wherein the cylindrical guide body is intended to guide the cylindrical wall cutter along the interior surface of the pipe to thereby position the cylindrical wall cutter along the outside of the pipe to remove the fitting.
[0006] However, the Dever tool suffers from a number of problems with the design and operation thereof. For example, the diameter of the cylindrical guide body is fixed such that it can only be used with a pipe having a specific diameter. The cylindrical guide body cannot be adjusted to fit properly in a number of different pipes having different diameters. Using the Dever tool to remove a fitting from a pipe having an inside diameter that varies because of, for example, differences in manufacturing tolerances, wear and tear associated with normal use, or the like, would limit the accuracy or reliability of the Dever tool. For example, if the Dever tool were to be used to remove the fitting from a pipe wherein the interior dimension of the pipe had been expanded through normal wear and tear and differing manufacturing tolerances, the cylindrical guide body would not form a secure fit within the interior pipe wall and there may be sufficient room within the pipe for the cylindrical guide body to move laterally with respect to the central axis of the pipe. As would be understood, in this situation, the excess movement of the cylindrical guide body within the interior of the pipe would result in the cylindrical wall cutter being misaligned with the central axis of the pipe. In such a case, the cylindrical wall cutter would likely contact the pipe, thereby destroying or otherwise damaging the pipe.
[0007] In addition, the Dever tool could not be used with a pipe that has an interior dimension smaller than specified due to, for example, different manufacturing tolerances and/or obstructions within the pipe. In such a situation where the interior dimension of the pipe is less than that of the outer dimension of the cylindrical guide body, Devers cylindrical guide body would be too large to be inserted into the pipe and thereby could not be used at all.
[0008] Another limitation of the Dever tool is the cylindrical guide body and cylindrical wall cutter being axially attached to a single rod. As would be understood in the art, an individual using the Dever tool with, for example, a drill, wherein the individual did not maintain substantially perfect alignment of the rod axis with the central axis of the pipe could thereby twist and alter the angle where the cylindrical wall cutter contacts the pipe and/or the fitting. In this instance, the cylindrical wall cutter could likely contact the pipe in addition to the fitting, thereby causing damage to the pipe. That is, an individual using the Dever tool would be required to maintain almost perfect alignment throughout the operation of the system to prevent damage to the pipe. In the instant described above wherein the interior dimension of the pipe was enlarged such that the cylindrical guide body did not maintain a consistent fit, the individual using the Dever tool could more likely misalign the single rod with the central axis of the pipe and thereby damage or destroy the pipe.
[0009] Yet another limitation of the Dever tool is presented wherein the interior of the pipe is blocked or configured such that the cylindrical guide body could not be extended downward therein for the length necessary for the cylindrical wall cutter to remove the exterior fitting. That is, because the Dever tool relies on the cylindrical wall cutter and the cylindrical guide body to be fixed on the axial rod, in an instance where the interior of the pipe is obstructed or is configured, for example, with an elbow positioned near the entrance to the pipe, the user would not be able to extend the cylindrical guide body into the pipe a sufficient length for the cylindrical wall cutter to remove the fitting.
[0010] Thus, the Dever system suffers from a number of limitations wherein it could not be used for certain configurations of a pipe and/or it could not be used in a situation in which the interior dimension of the pipe was larger than the exterior diameter of the cylindrical guide body.
[0011] To this end, a need exists for an improved apparatus and method for removing a fitting from a pipe with minimal or no damage to the pipe. It is to such an apparatus and method that the present invention is directed.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0012] FIG. 1 is a sectional view of a fitting removal apparatus with a guide assembly positioned inside a pipe and a cutter assembly shown in a pre-cutting position.
[0013] FIG. 2 is an elevational view of the fitting removal apparatus of the present invention.
[0014] FIG. 3 is a sectional view taken along line 3 - 3 of FIG. 2 .
[0015] FIG. 4 is a sectional view taken along line 4 - 4 of FIG. 2 .
[0016] FIG. 5 is a sectional view of the fitting removal apparatus illustrating the cutter assembly having cut through a fitting.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0017] Referring now to the drawings, and in particular to FIGS. 1-2 , shown therein and designated by reference, numeral 10 is a fitting removal apparatus 10 constructed in accordance with the present invention. Broadly, the apparatus 10 includes a cutter assembly 12 and a guide assembly 14 . The guide assembly 14 includes a guide member 16 and a support assembly 18 for supporting the guide member 16 . The cutter assembly 12 includes a rotary hole saw 20 , a mandrel 22 , and a guide rod 24 .
[0018] In FIG. 1 , the apparatus 10 is shown with the guide assembly 14 positioned inside a pipe 26 having a fitting 28 attached thereto. The cutter assembly 12 is shown in a pre-cutting position. In general, the guide member 16 is secured inside the pipe 26 via the support assembly 18 such that the guide member 16 is securely positioned in a coaxial relationship with a central axis of the pipe 26 . The guide rod 24 of the cutter assembly 12 is then partially inserted into the guide member 16 wherein a rotational force is then applied to the cutter assembly 12 via, for example, a drill (not shown). The guide rod 24 is then further inserted into the guide member 16 such that the cutter assembly 12 is thereby lowered onto the pipe 26 having the fitting 28 attached thereto. The guide member 16 being securely positioned in coaxial relationship with the pipe 26 maintains substantial alignment of the central axis of the pipe 26 with the central axis of the guide rod 24 of the cutter assembly 12 . Thus, the central axis of cutter assembly 12 is substantially aligned with the central axis of the pipe 26 , via the guide member 16 and the support assembly 18 , permitting the cutter assembly 12 to be lowered about the pipe 26 in an aligned manner. Further, the rotary hole saw 20 is sized to have an interior diameter 30 which substantially corresponds to an outer diameter 31 of the pipe 26 . Therefore, when the cutter assembly 12 is lowered about the pipe 26 , rotary hole saw 20 thereby removes the fitting 28 without contacting or otherwise damaging the pipe 26 . Once the apparatus 10 has been used to remove the fitting 28 from the pipe 26 , the guide assembly 14 can then be removed and the pipe 26 can then be reused, or a new fitting can be attached thereto without requiring replacement or repair of the pipe 26 .
[0019] Referring now to FIG. 3 , shown therein in more detail is a sectional view of a preferred embodiment of the guide assembly 14 constructed in accordance with the present invention. The guide assembly 14 includes the guide member 16 and the support assembly 18 discussed above. The guide member 16 is embodied as a circular tube or pipe having an axial opening therein so as to define a guide passage 32 having a central axis. The guide member 16 can be constructed of a rigid material such as, for example, steel, iron, or the like. The guide passage 32 slidingly receives the guide rod 24 of the cutter assembly 12 . Further, as will be described in more detail below, the guide member 16 includes a plurality of threads 34 extending along at least a portion of the exterior surface which permit the guide member 16 to be secured to, and adjusted relative to the support assembly 18 .
[0020] The support assembly 18 includes a top member 36 , a bottom member 38 , and an expandable gripping member 40 . The support assembly 18 secures the guide member 16 within at least a portion of the pipe 26 such that the central axis of the guide passage 32 is in a coaxial relationship with the central axis of the pipe 26 . The guide member 16 is adjustable by a user of the apparatus 10 to change the outside diameter of the gripping member 40 wherein the guide assembly 14 is thereby securable inside the pipe 26 . In particular, the guide assembly 14 is constructed such that, in a relaxed state, the gripping member 40 has a diameter smaller than the diameter when the member 40 is in a compressed state, or otherwise acted upon by the top member 36 and the bottom member 38 , and caused to expand.
[0021] One such example of a support assembly can be found in U.S. Pat. No. 4,493,344, issued to Mathison, the entire contents of which are herein incorporated by reference. However, other embodiments of a support assembly would become apparent to one having ordinary skill in the art.
[0022] The bottom member 38 is affixed to, or otherwise positioned on the guide member 16 such that the bottom member 38 is stationary, i.e., the bottom member 38 is not adjustable or otherwise movable in relation to the guide member 16 . The gripping member 40 is positioned on top of the bottom member 38 and the top member 36 is positioned on top of the gripping member 40 . The guide assembly 14 further includes a top fastener 42 adapted to adjust the pressure on the top member 36 , i.e., apply an axial force to the top member 36 to move the top member 36 towards the bottom member 38 . As should be understood, as the top member 36 is moved towards the bottom member 38 , the gripping member 40 is compressed which causes the member 40 to expand. As the gripping member 40 expands, its outside diameter increases which then causes it to contact the interior surface of the pipe 26 . Increased pressure applied to the gripping member 40 by the top member 36 provides added radial force on the gripping member 40 so as to secure the gripping member 40 against the interior surface of the pipe 26 . Thus, the support assembly 18 securely supports the guide member 16 within at least a portion of the pipe 26 while maintaining axial alignment of the central axis of the guide passage 32 with the central axis of the pipe 26 .
[0023] The top member 36 includes a top angled face 44 and the bottom member 38 includes a bottom angled face 46 , which cooperate to act on or otherwise apply pressure to the gripping member 40 thereby compressing the gripping member 40 . As the gripping member 40 is compressed, or otherwise acted upon, it is thereby forced outward causing the gripping member 40 to expand in a radial direction. It should be understood that, although shown as angled faces, the top angled face 44 and the bottom angled face 46 can be configured in any number of shapes and/or configurations to thereby perform similar functions without departing from the scope and intent of the present invention. Examples of such alternative configurations include a stepped face, rounded face, and the like.
[0024] Referring again to FIG. 3 , the bottom member 38 is fastened to or otherwise affixed to the guide member 16 via a bottom fastener 48 which permits adjustment of the bottom member 38 along the axial direction of the guide member 16 . For example, as discussed above, the guide member 16 includes a plurality of threads 34 along at least a portion of its exterior length. The bottom member 38 is affixed to the guide member 16 using the bottom fastener 48 wherein the bottom fastener 48 includes a plurality of threads adapted to cooperate with the plurality of threads 34 to thereby secure the bottom member 38 to the guide member 16 . As would be understood in the art, when the bottom fastener 48 is affixed to the guide member 16 via the plurality of threads 34 , the bottom member 38 would then be stationarily affixed to the guide member 16 when in use, for example, when the guide assembly 14 is affixed inside the pipe 26 . However, when not in use, the bottom member 38 may be adjustable along the axial direction of the guide member 16 . That is, the bottom member 38 may be rotated around the guide member 16 via the plurality of threads to raise or lower the bottom member 38 along the axial length of the guide member 16 . As would be further appreciated in the art, adjustment of the bottom member 38 would be accomplished prior to operational use of the apparatus 10 (i.e., before the guide assembly 14 is inserted into the pipe 26 ). The bottom member 38 could be adjusted along the axial length of the guide member 16 prior to use wherein the user of the apparatus 10 ensures that the guide assembly 14 is configured to fit within the pipe 26 .
[0025] The top member 36 is positioned on the guide member 16 to secure the gripping member 40 between the bottom member 38 and the top member 36 . The top member 36 includes a central passage 50 for receiving the guide member 16 . The top member 36 is secured to the guide member 16 using the top fastener 42 . The top fastener 42 can be embodied as a nut or other fastening device known in the art. However, the top fastener 42 can be embodied as other fasteners which achieve similar functionality. For example, the top fastener 42 can be embodied as a wing-nut, a spring loaded tensioning device, a quick release device, and the like. The top fastener 42 can be embodied as a variety of mechanisms which operate on the top member 36 to apply force thereon to move the top member 36 towards bottom member 38 or release force from the top member 36 , thereby releasing pressure on the gripping member 40 .
[0026] Alternatively, the top member 36 may be affixed to the guide member 16 in a manner similar to which the bottom member 38 is affixed to the guide member 16 (i.e., using a fastener similar to the bottom fastener 48 ). In this embodiment, the top member 36 includes a fastener with a plurality of threads whereby a user can manually rotate the top member 36 along the thread 28 of the guide member 16 to adjust the position of the top member 36 relative to the bottom member 38 . For example, the top member 36 can include holes, wings, or other configurations whereby the user of the apparatus 10 can rotate the top member 36 to move the top member 36 towards or away from bottom member 38 .
[0027] The gripping member 40 can be constructed using any malleable material capable of expanding in a radial direction when a compressive force is applied thereto, and retracting when the force is released. Examples of such materials include rubber or other polymeric materials which are known in the art. The gripping member 40 permits use of the guide assembly 14 in the pipe 26 when the interior dimension of the pipe 26 varies outside of predefined parameters. That is, the gripping member 40 permits use of the apparatus 10 in the pipe 26 when the interior dimension of the pipe 26 varies because of, for example, differences in manufacturing tolerances, normal wear and tear associated with use, and the like. A user of the apparatus 10 can adjust the top member 36 to apply pressure to the gripping member 40 to cause the member 40 to expand radially and conform to the contour of the interior of the pipe 26 . Similarly, in the case where the interior dimension of the pipe 26 is smaller than anticipated, the user could manually restrict the gripping member 40 to ensure that the guide assembly 14 is positionable within the pipe 26 .
[0028] In use, the guide assembly 14 is positioned and secured inside the pipe 26 , as shown in FIGS. 1 and 5 . Initially, the distance between the top member 36 and the bottom member 38 would be such that little or no pressure is applied to the gripping member 40 . That is, the guide assembly 14 is configured such that the outside diameter of the gripping member 40 is at its smallest to allow the guide assembly 14 to be positioned inside the pipe 26 . The user then adjusts the top member 36 , in the manner described above, along the axial length of guide member 16 (e.g., towards the bottom member 38 ). As the top member 36 is adjusted towards the bottom member 38 , the top member 36 and the bottom member 38 apply pressure to the gripping member 40 . As the pressure applied to the gripping member 40 increases, the member 40 expands outwardly (radially) so as to contact the interior walls of the pipe 26 and secure the guide assembly 14 inside the pipe 26 .
[0029] Referring now to FIG. 4 , shown therein is a sectional view of the cutter assembly 12 constructed in accordance with the present invention. The cutter assembly 12 includes the rotary hole saw 20 and the guide rod 24 . Guide rod 24 can be embodied as a solid rod constructed using metal, steel, or other rigid material known in the art. The guide rod 24 is sized and shaped to be slidingly and rotatably received in the guide passage 32 . The rotary hole saw 20 has a cylindrical wall 52 defining an open end and having a plurality of cutting teeth 54 on the open end. The cylindrical wall 52 can optionally include one or more relief ports 56 which operate to dissipate heat or otherwise reduce the heat of the cutter assembly 12 when in use. Additionally, the relief port 56 can be used to eject or otherwise remove debris generated when the apparatus 10 is in use.
[0030] The Cutter assembly 12 further includes the mandrel 22 to which the guide rod 24 is connected. The guide rod 24 can be either permanently affixed to mandrel 22 , or can be detachable. The mandrel 22 has a shank 58 for attachment to a rotary device such as a drill.
[0031] The rotary hole saw 20 has an interior diameter 30 which substantially corresponds to the outer diameter 31 of the pipe 26 such that the interior diameter 30 is substantially sized so as to remove the fitting 28 without contacting or damaging the outside of the pipe 26 .
[0032] Referring now to FIGS. 1 and 5 , shown therein is the apparatus 10 as it would be used in operation. As shown in FIG. 1 , the guide assembly 14 has been secured inside the pipe 26 such that the guide member 16 , including the guide passage 32 , is securely fixed in a coaxial relationship with the central axis of the pipe 26 , and the guide passage 32 of the guide member 16 is substantially parallel to the central axis of the pipe 26 . As was discussed above, the guide assembly 14 is secured inside the pipe 26 using, for example, the top fastener 42 to apply a force to the top member 36 so as to apply pressure to the gripping member 40 , causing the gripping member 40 to expand and thereby engage the inside wall of the pipe 26 . With the guide assembly 14 secured inside the pipe 26 , the guide rod 24 of the cutter assembly 12 is then inserted at least partially inside the guide passage 32 of the guide assembly 14 . With the guide rod 24 inserted into at least a portion of the guide passage 32 , rotational force can be applied to the cutter assembly 12 , and the guide rod 24 can be further inserted into the guide passage 32 so as to cause the cutting teeth 54 to engage the fitting 28 . The cutter assembly 12 is lowered until the cutting teeth pass through the fitting 28 , as shown in FIG. 5 .
[0033] From the above description it is clear that the present invention is well adapted to carry out the disclosed aspects, and to attain the advantages mentioned herein as well as those inherent in the invention. While presently preferred implementations of the invention have been described for purposes of disclosure, it will be understood that numerous changes may be made which readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed. | An apparatus and method for removing a fitting from a pipe having a central axis. The apparatus includes a guide member which defines a guide passage and a means for supporting the guide member within at least a portion of the pipe with the longitudinal axis of the guide passage in a coaxial relationship with the central axis of the pipe. The apparatus also includes a rotary hole saw having a cylindrical wall provided with a plurality of cutting teeth on an open end thereof and a central axis of rotation. The cylindrical wall defines a cylindrical chamber. A guide rod is connected to the rotary hole saw such that the guide rod extends through the cylindrical chamber of the hole saw and beyond the open end thereof in coaxial alignment with the central axis of rotation. The guide rod is slidingly receivable in the guide passage of the guide member. |
TECHNICAL FIELD OF THE INVENTION
This invention relates to micromechanical devices and more particularly to support structures integral to such devices.
BACKGROUND OF THE INVENTION
One type of light deflecting spatial light modulator (SLM) is the digital micromirror device (DMD). DMDs are available in several different forms including flexure beam, cantilever beam, and both conventional and hidden hinge torsion beam designs. Each type of DMD includes an array of small mirrors which move out of a resting position, e.g. rotate or deflect, in response to an electrostatic field produced by an electrical signal, typically called an address signal. The resting position of the mirror is typically parallel to the surface of the device. Light is reflected from the surface of the mirror and as the mirror is moved, the direction of the reflected light is changed. The resting position of the mirror is determined by a beam or spring, often called a hinge, which supports the mirror and which stores energy during mirror movement. This stored energy tends to return the mirror to the resting position when the address voltage is removed or reduced.
Deformable micromirror devices are also referred to as DMDs. The difference between digital micromirror devices and deformable micromirror devices is that digital micromirror devices are operated in a bistable mode, as taught in U.S. Pat. No. 5,061,049, issued Oct. 29, 1991, and entitled "Spatial Light Modulator and Method". Digital operation of the micromirror devices includes the application of a bias voltage that ensures that the mirrors have a maximum rotation in either the "on" or "off" direction regardless of the magnitude of the address voltage. The mirror deflection of deformable micromirror devices is an analog function of the voltage applied to the device. The structure of digital micromirror devices and deformable micromirror devices is very similar, and in some cases identical. The disclosed invention may be used in conjunction with either digital, or deformable micromirror devices.
DMDs are typically used in a dark field projection arrangement and can be used, for example, in HDTV applications where a large array of pixels is necessary for the desired image resolution. In addition to the high resolution capabilities of the DMD, another feature that is very useful in video display applications is the speed at which the mirror can be controlled, or the response time of the device. The short response time allows the present generation of DMDs to be toggled on and off up to 180 thousand times each second. Each deflection cycle stores energy in the DMD beam or spring and mechanically stresses the device structure.
DMDs are part of a larger group of devices known as micromechanical devices. Micromechanical devices include some accelerometers, flow sensors, electrical motors, and flow control devices. These devices are often fabricated by processes known as micromachining. Micromachining involves the removal of unwanted material from either the substrate on which the device is being fabricated, or from one or more layers of material that is deposited during the fabrication of the device. The material is typically removed to allow some part of the completed device to move. For example, material must be removed from a motor to allow a rotor to spin around a stationary shaft. In the case of a DMD, material must be removed from below the DMD mirror to allow the mirror to deflect or rotate.
Sometimes an entire layer, called a sacrificial layer, is used during the fabrication process. For example, DMDs are typically fabricated by depositing a sacrificial layer over the circuitry required to deflect the mirror. Mirrors and their hinges are then built on this spacer layer by depositing and patterning one or more metal layers. The metal layers are typically aluminum or an aluminum alloy and are patterned to define a mirror connected to at least one hinge cap by a hinge. In early forms of DMDs, the sacrificial layer was removed from beneath the mirrors and hinges, leaving a portion of the sacrificial layer to support the hinge caps. The mirrors were suspended by the hinges above the wells formed by removing the sacrificial material.
Recent DMD designs include a hole, or via, formed in the sacrificial layer at the location of each hinge cap prior to depositing the hinge metal. When the hinge metal is deposited on the sacrificial layer, it is also deposited on the walls of the via, creating a topless hollow post structure known as a "spacervia." After the mirrors, hinges and hinge caps are patterned, all of the sacrificial layer is removed leaving only the spacervia to support the hinge caps away from the device substrate. Other types of DMDs, such as the so called "Hidden Hinge" torsion beam device as taught by U.S. Pat. No. 5,083,857, issued Jan. 28, 1992 and entitled "Multi-Level Deformable Mirror Device", use two or more sacrificial layers. The hidden hinge torsion beam DMD uses one set of spacervias to support the hinges above the device substrate and a second set of spacervias to support the mirror above the hinges.
The electrostatic forces used to deflect the mirrors generate mechanical stresses in the supporting hinge and spacervia structures. These stresses can lead to a failure in the supporting structure, ruining the device. There is a need in the art for an improved support structure for DMDs and other micromechanical devices.
SUMMARY OF THE INVENTION
The present invention provides a structure and process for an improved support post structure, called a support pillar. The support pillar may be used in a micromechanical device, particularly a digital micromirror device (DMD). The support pillar is fabricated by depositing a layer of pillar material on a substrate, patterning the pillar material to define the shape of the support pillar, and depositing a metal layer over the remaining pillar material, thereby enclosing the pillar material in a metal sheath. A spacer material may be deposited around the support pillars to provide a planar surface level with the tops of the support pillars on which to fabricate additional structures.
The support pillar may be used to support the hinges and mirrors of any type of digital micromirror device including the conventional torsion beam DMD and the hidden hinge DMD. Hidden hinge DMDs may be fabricated using the support pillar to support either the hinges, the address electrodes, or the mirror, or any combination thereof.
The disclosed support pillar and method of fabricating the same have several advantages over existing designs including improved support structure strength.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a perspective view of a portion of a typical hidden hinge torsion beam DMD array of the prior art.
FIG. 2 is an exploded perspective view of a hidden hinge torsion beam DMD element of the prior art.
FIG. 3A is a cross-sectional view of metal being sputtered onto a substrate and a layer of sacrificial material.
FIG. 3B is a cross-sectional view of the substrate of FIG. 3A after metal has been sputtered onto it.
FIG. 3C is a cross-sectional view of the substrate of FIG. 3A after metal has been sputtered onto it and the sacrificial material removed.
FIG. 4A through 4Q are cross-sectional views taken along the hinge axis of one element of a DMD array showing various stages in the fabrication of a DMD element having support posts according to one embodiment of the present invention.
FIG. 5 is a cross-sectional view showing the metal step coverage of the hinge support pillar of FIG. 4C.
FIG. 6 is a perspective view of a portion of a typical torsion beam DMD having improved support posts according to one embodiment of this invention.
DETAILED DESCRIPTION
A new fabrication process is needed to yield sufficiently strong and reliable support structures which may be used in DMDs and other types of micromechanical devices. To avoid confusion between existing support structures and the improved structure taught herein, support structures of the prior art will be referred to as "spacervias," while the improved structures taught herein will be referred to as "support pillars." Although the specific embodiments shown in this disclosure will show only DMD structures, the methods and structures taught are applicable to many other micromechanical devices.
FIG. 1 shows a perspective view of a portion of a hidden hinge torsion beam DMD array 100 of the prior art. Hidden hinge devices rely on two levels of spacervias to hold a mirror 102 away from a substrate 104. The first spacervia level includes a hinge support spacervia 106, and an address electrode support spacervia 108. The hinge support spacervia 106 supports one end of a torsion hinge 110 away from the device substrate 104. The torsion hinge 110 attaches to the top of the hinge support spacervia 106 via a thick metal hinge cap 111. The metal hinge cap 111 strengthens the connection between the thin metal torsion hinge 110 and the hinge support spacervia 106 by ensuring adequate metal to metal contact between the hinge metal and the spacervia metal. On each hinge cap 111, is a landing site 112 which stops the rotation of either of two adjacent mirrors 102 when the mirrors 102 are rotated towards the landing site 112. The address support spacervia 108 is used to hold an address electrode 114 away from substrate 104. The address support spacervias 108 and the hinge support spacervias 106 are typically the same height.
The second spacervia level includes a mirror support spacervia 116 which holds the mirror 102 above the torsion hinges 110. The mirror support spacervia 116 is fabricated on a thickened portion of the torsion hinge 110 called a hinge yoke 118. Like the hinge cap 111, the hinge yoke 118 strengthens the connection between the thin metal torsion hinge 110 and the mirror support spacervia 116 by ensuring adequate metal to metal contact between the torsion hinge 110 and the mirror support spacervia 116. The height of the mirror support spacervia 116 may be varied to control the maximum angular rotation of the mirror 102.
FIG. 2 is an exploded view of a single hidden hinge torsion beam DMD element. In addition to the structures discussed in regard to FIG. 1, FIG. 2 shows a metal bias/reset bus 200 and metal pads 202 which are deposited on the surface of the substrate 104. The metal bias/reset bus 200 supports the hinge support spacervias 106 and the metal pads 202 support the address electrode support spacervias 108. The metal pads 202 are connected, through vias 204 in a protective oxide layer 203, to the addressing circuitry built into the surface of the substrate 104 and serve to electrically connect the address electrode support spacervias 108 to the addressing circuitry. The bias/reset bus 200 and the metal pads 202 are typically fabricated as part of the third device metalization layer or M3. The first two metal layers, M1 and M2, are used to interconnect the address circuitry on the substrate.
Referring back to FIG. 1, each mirror 102 and its address electrodes 114 form the two plates of an air gap capacitor. If a sufficient voltage bias is applied between the address electrode 114 and its associated mirror 102, the resulting electrostatic force will cause the mirror 102 to deflect towards the address electrode 114 thereby twisting the torsion hinge 110. If the applied voltage is sufficiently large, the mirror 102 will deflect until the mirror tip 103 touches the associated landing site 112 on the hinge cap 111, stopping the mirror rotation. If the hinge cap 111 did not contact the mirror tip 103 and stop the rotation of the mirror 102, the mirror 102 would touch the address electrode 114 and short circuit the bias voltage. Because there is one address electrode 114 on each side of the hinge axis in each element, the mirror 102 may be rotated in either direction, allowing the mirror 102 to assume one of two fully deflected states.
When the bias voltage is removed from the mirror 102 and address electrodes 114, the energy stored by the deformation of the torsion hinge 110 will tend to return the mirror 102 to the undetected or neutral state. However, short-range attractive forces between the mirror 102 and the landing site 112 often cause the mirror 102 to stick to the landing site 112. When this occurs, a technique known as resonant reset may be used to free the stuck mirrors 102. The resonant reset technique uses a voltage pulse, or series of pulses, to store mechanical energy in the mirror 102. Typically resonant reset is a series of five -24 volt pulses applied to the mirror 102 at the resonant frequency of the mirror 102, approximately 5 MHz. Each pulse creates a very strong attraction between the mirror 102 and the address electrode 114. Because the mirror tip 103 is held in place by the landing site 112, the center of the mirror 102 bends towards the substrate 104 and the upper surface of the mirror 102 becomes concave. When the pulse is removed, the attraction ceases and the mirror 102 springs upward, becoming convex. Subsequent pulses increase the mirror deformation thereby storing additional energy. By the time the final reset pulse is removed, the energy stored in the mirror 102 is sufficient to spring the mirror 102 away from the landing site 112, allowing the energy stored in the torsion hinge 110 to return the mirror 102 to the neutral position.
The electrostatic forces responsible for deforming the mirror 102 and the torsion hinges 110 also torque and flex the spacervias 106, 108, 116 which support portions of the device. The stresses involved can cause the spacervias 106, 108, 116 of prior art DMDs to break, destroying the device. These failures usually occur via two failure modes. The first failure mode occurs when a spacervia 106, 108, 116 breaks at or near the point of attachment of the hinge cap 111, address electrode 114, or mirror 102, that is supported by the top of the spacervia. The second primary failure mode occurs when a spacervia 106, 116, or 108 breaks at or near the point of attachment to the bias/reset bus 200 or hinge yoke 118 beneath the spacervia 106, 108, 116. Failures of the spacervias 106, 108, 116 have been attributed to the poor metal coverage on the spacervia walls, or step coverage, obtained through the present fabrication processes. Usually the metal is too thin either at the base or near the top of the spacervia.
The address electrode support spacervias 108, the hinge support spacervias 106, and the mirror support spacervias 116 of the prior art are typically made by lining a hole, or via, in a sacrificial material with sputtered metal. When the sacrificial material is removed, the liner remains forming a spacervia. FIG. 3A depicts metal particles 300 being sputtered towards a substrate 302 that is partially covered by sacrificial material 304. During the sputtering process, the metal 300 approaches the surface from all directions. Therefore, metal may reach a flat horizonal surface 320 from a 180° arc, as shown by region 306.
Point 308 at the base of the wall structure 310 is shaded by the wall structure 310 and can only receive metal arriving at point 308 from a 90° arc, as shown by region 312. Because point 308 can only receive metal from half the are that a planar surface receives metal from, only about half as much metal will be deposited at point 308 compared to a planar area with no shading. The shading problem is even greater for the via 314. Metal must approach the bottom comers of the via 314 almost vertically as shown by region 316. Because more metal can reach the top portion of the walls compared to the bottom portion, an overhang will develop. The overhang further restricts metal from reaching the bottom of the wall, resulting in poor metal coverage of the lower portions of the wall.
FIG. 3B shows a metal layer 318 which has been sputtered onto the substrate 302 and spacer 304 of FIG. 3A. Metal layer 318 is thinner on the sides of a wall structure 310 than on a flat horizontal surface 320. The metal layer 318 is especially thin on the bottom portion of the via 314. A thin area also develops immediately below the top of the via 314. This thin area is caused by overhang 322 which develops at the top of the via 314 as the metal layer 318 is being sputtered. FIG. 3C shows the substrate 302 and metal layer 318 after the sacrificial material 304 has been removed. This leaves a spacervia 324 that was formed in the via 314 through the sacrificial material 304. The thin, weak areas of the metal layer 318 near both the top and bottom of the spacervia 324 are prone to failure when the spacervia 324 is stressed.
The higher the aspect ratio (i.e. ratio of the via height to via width), the worse the step coverage near the bottom of the via is likely to be. When fabricating a spacervia 324, a thick metal layer must be deposited to ensure that adequate metal reaches the lower walls of the via 314. Unfortunately, the metal thickness cannot be arbitrarily increased. As the metal is deposited, the overhang 322 grows faster than the thickness of the metal on the lower portions of the walls and will eventually seal off the via preventing any additional metal from entering the via 314. Other constraints also limit the amount of metal that may be deposited into the via 314 during the typical DMD fabrication steps. For example, during the fabrication of a typical hidden hinge DMD of the prior art, the mirror support spacervia 116 and the mirror 102 are formed during the same metal deposition step. Depositing too much metal will thicken the mirror 102 which reduces the mirror specularity and requires a higher resonant reset frequency. Reset efficiency drops off markedly with increasing reset frequency, because of frequency dependent damping effects. Also, increasing the mirror thickness lengthens the response time of the mirror 102 by increasing the mirror moment of inertia.
There are at least three improvements to spacervias 324 that may increase their strength. First, the size of a spacervia 324 could be enlarged to allow better metal coverage of the sides of the spacervia 324. However, because the mirror support spacervia 116 has an open top which reduces the active area of the DMD mirror 102, enlarging the mirror support spacervia 116 results in an unacceptable loss in mirror active area. Enlarged address support spacervias 108 also reduce the usable size of address electrodes 114, thereby reducing the electrostatic force generated between the address electrode 114 and the mirror 102. A second approach involves changing the profile of the spacervia 324 to avoid reentrant spacervia contours. Reentrant contours occur when the via 314 used to form the spacervia 324 widens after entering the sacrificial material in which the via 314 is formed. A spacervia with a reentrant contour is similar to the overhang discussed above. The overhang causes the reentrant contour spacervia to have poor metal step coverage near the top of the spacervia 324 and may allow the hinge cap 111 or mirror 102 to break away from the spacervia 324. Another solution is to grow an oxide liner on the inside of the spacervia 324 after the metal is deposited. The oxide liner is grown on the inside of the spacervia 324 at the base of the spacervia 324 to give it increased mechanical strength where the metal thickness is insufficient. Although these improvements increase the strength of spacervias 324, they have not yet yielded a sufficiently strong, reliable spacervia 324 for DMDs.
A new architecture and process has been invented to address the mechanical weaknesses of the spacervia 324 design. It replaces the photoresist vias of the prior designs with photoresist pillars. Because the pillars are relatively far apart, the base of the pillars is not shaded to the extent that the base of a via is shaded during the sputtering process. The step coverage of a pillar is much better than the step coverage of a hole or trench having the same aspect ratio. Therefore, a support pillar with the disclosed architecture has much better strength than a spacervia 324 of the prior art.
FIGS. 4A through 4Q show a cross-sectional view of a DMD element 401, according to one embodiment of the present invention, during the various stages of its fabrication. The cross-sectional views are taken along the hinge axis as shown by 206 in FIG. 2. FIG. 4A shows a substrate wafer 400, typically silicon, on which addressing circuitry and the first two metalization layers previously have been fabricated. The second metal layer is covered with a protective oxide layer 403. Vias 204, shown in FIG. 2, are opened in the oxide layer 403 to allow the metal pads 202 to contact the addressing circuitry fabricated on the substrate 400. Although not shown in FIG. 4A, a thin metal layer is typically deposited over the protective oxide layer 403. This thin metal layer, which is typically tungsten or aluminum, establishes electrical contact with the addressing circuitry on the substrate 400 and may act as an etch stop during subsequent etch steps.
A first layer of pillar material 402, typically a positive organic photoresist layer approximately 1.0 μm thick, is applied to the substrate 400. The layer of pillar material 402 is patterned and developed to leave portions of pillar material 404, as shown in FIG. 4B, which will form an integral part of the hinge support pillars. Portions of the layer of pillar material 402 also will form address electrode support pillars. However the address electrode support pillars are not shown in the cross section of FIGS. 4A-4Q. After the portions of pillar material 404 have been formed, they may be deep UV hardened to a temperature of approximately 220 ° C. to prevent them from melting or bubbling during the remaining processing steps.
Other materials may be used instead of photoresist for the layer of pillar material 402. Alternate materials are typically dielectrics such as polysilicon, oxide, nitride, or oxynitride. When a dielectric is used, the thin metal layer deposited over the protective oxide layer 403, and into the vias 204, may be used as an etch stop, facilitating complete removal of the pillar material 402 from the vias 204. Although other materials may be used for the pillar material layer 402, photoresist is preferred because most alternate materials require separate patterning and etching steps. For example, a 1 μm thick silicon dioxide layer may be grown on the substrate wafer 400 and covered with a layer of photoresist. The photoresist is patterned and developed to protect only the portions of the silicon dioxide layer that are to form the support pillars. The silicon dioxide layer is then etched leaving only the desired portions of pillar material 404.
After patterning the layer of pillar material 402, the substrate 400 and the remaining portions of pillar material 404 are covered with a layer of metal 406, as shown in FIG. 4C. The metal layer, typically aluminum or an aluminum alloy, which forms the third metalization layer, M3, is typically sputtered onto the protective oxide layer 403 and the remaining pillar material 404 to a thickness of 4000 Angstroms. The M3 metalization layer is patterned to form the bias/reset bus 200 and metal pads 202 that were shown in FIG. 2. Because the sectional views in FIGS. 4A-4Q are taken along the hinge axis, the bias/reset bus appears as a continuous layer and the results of patterning the M3 layer are not shown. The completed hinge support pillar 408 is comprised of the remaining portions of pillar material 404 and a sheath of the M3 metal layer 406 which forms the bias/reset bus.
FIG. 5 is a cross-sectional view of one portion of a partially fabricated DMD 500 following the deposition of the M3 metal layer 406 showing the step coverage of a metalized hinge support pillar 408 from FIG. 4C. The portion of pillar material 404 is encased in a metal sheath which is thinner on the sides than on the top. As discussed above in regard to FIG. 3, the reduction in metal on the sidewalls compared to metal on the top is due to the partial shading of the pillar material 404. Although the sidewalls receive less metal than the top of the pillar material 404, the other remaining portions of pillar material 404 are spaced far enough apart to allow the sidewall to receive metal from a wider arc, region 312 of FIG. 3A, than the spacervias of the prior art. Therefore, the sidewalls receive more metal, and more uniform coverage than the prior art spacervias. The improved metal coverage, combined with the composite nature of the metalized support pillar 408 results in a much stronger support pillar that does not exhibit a tendency to break away from either the hinge cap or the substrate.
Referring to FIG. 4D, a first spacer layer, called the hinge spacer layer 410, is spun onto the substrate over the hinge support pillars 408. The hinge spacer layer 410 is typically a 1.0 μm thick layer of positive photoresist. As shown in FIG. 4D, the hinge spacer layer 410 will have a bump 412 above each pillar 408. The bumps 412 are caused by the process of spinning on the photoresist and are not desirable. If less photoresist is used to form hinge spacer layer 410, the bumps could be avoided but there may be significant undulations in the surface of the photoresist caused by the `shadow` of the pillar 408 as the photoresist flows around the pillar 408. The viscosity of the photoresist, which is a function of temperature, the spin-rate of the substrate wafer 400, and the thickness of the spacer layer 410 all affect the surface of the finished layer. Under some conditions, it may be advantageous to deposit multiple thin layers rather than one thick layer. The ideal spacer layer 410 is perfectly planar and extends from the substrate wafer 400 to the top of the pillar 408, leaving a perfectly planar surface on which to continue fabricating the device.
The bumps 412 formed above each pillar 408 are removed by an oxygen plasma etch to provide access to the pillars 408 and to planarize the surface of the spacer layer 410. Planarization of the hinge spacer layer 410 is important in order to ensure consistent hinge strength and integrity. Also, any non-planar features of the spacer layer 410 and the tops of the pillars 408 will be replicated by the fabrication process and affect subsequent layers. The hinge spacer layer 410 is typically deep UV hardened to a temperature of approximately 200° C. to prevent flow and bubbling during subsequent processing steps.
The hinge layer 418, as shown in FIG. 4F, is typically formed by the sputter deposition of a thin aluminum alloy onto hinge spacer layer 410. The hinge layer 418 is typically 600 Angstroms thick and consists of 0.2% Ti, 1% Si, 98.8% Al. According to the buried hinge fabrication process, as taught by U.S. Pat. No. 5,061,049, an oxide layer is deposited, typically by plasma deposition, over the hinge layer 418 and patterned in the shape of the torsion hinges to form oxide etch stops 420.
A second level of pillars is built over the hinge metal layer 418 to form the mirror support pillar. The mirror support pillar is fabricated by the same process used to fabricate the hinge and address electrode support pillars. A second layer of pillar material is deposited on the substrate wafer, and patterned to leave portions of pillar material 422 as shown in FIG. 4G. The second layer of pillar material is typically a 2.2 μm thick layer of photoresist which is deep UV hardened to 180° C. to prevent flow and bubbling during subsequent processing steps. No degradation of the hinge spacer layer 410 or the hinge support pillars 404 occurs because the first two layers of photoresist were hardened to a higher temperature (200° and 220° C.).
Next, as shown in FIG. 4H, a thick layer of electrode metal 424 is deposited over the first hinge metal layer 418 and the pillar material 422. The electrode metal layer 424 is typically 3750 Angstroms thick and is sputter deposited to form the mirror support pillar, hinge cap, and address electrodes. As the electrodes are being deposited, the pillar material 422 is encapsulated by the electrode metal forming the mirror support pillar 426 comprised of the pillar material 422 and a sheath of electrode metal 424. After the electrode metal 424 is deposited, an oxide layer is deposited and patterned as shown in FIG. 4I to form a mirror support pillar etch stop 428, a hinge cap etch stop 430, and an address electrode etch stop (not shown). The mirror support pillar etch stop 428 is patterned to protect both the mirror support pillar and the hinge yoke from the subsequent etch step.
After patterning the etch stops, the electrode metal layer 424 and the hinge metal layer 418 are both etched, leaving only the portions of the metal layers protected by the etch stops as shown in FIG. 4J. The etch stops 420, 428, 430 are then stripped off as shown in FIG. 4K. A second photoresist spacer layer, called the mirror spacer layer 432 is then spun onto the water, see FIG. 4L, and etched back to provide access to the tops of the mirror support pillar 426 and to planarize the second spacer layer as shown in FIG. 4M.
A mirror metal layer 438 is deposited onto the second spacer layer 432 and the top of the support pillar 426. Typically the mirror metal layer is sputter deposited 4250 Angstroms thick. Another oxide layer is plasma-deposited and patterned to form a mirror etch stop 440 as shown in FIG. 4O. The mirror metal layer 438 is then plasma etched to form the mirror 442, as shown in FIG. 4P.
Wafer level processing is now complete. The device must still be undercut by removing the remaining mirror spacer 432 and hinge spacer layers 410 and stripping the mirror oxide etch stop 440 from the mirror 442. Because the mirrors 442 are very fragile after the mirror spacer layer 432 is removed, the devices are typically sawn apart before undercutting the devices. However, this constraint is not a result of the disclosed process but rather a limitation due to existing methods of wafer separation. When wafer separation processes that do not create damaging debris or require damaging cleanup steps become available, the process steps may be reordered to allow the devices to be completed before the wafer is separated.
The mirror etch stop 440 is left in place during wafer separation to protect the mirror surface. The wafers are coated with PMMA, sawn into chip arrays and pulse spin-cleaned with chlorobenzene. After wafer separation, the chips are placed in a plasma etching chamber where mirror etch stop 440 and both spacer layers 432 and 410 are completely removed leaving air gaps 444 and 446 under the hinges and mirrors as shown in FIG. 4Q. It is possible to leave portions of the spacer layers 432 and 410 as long as there is a sufficient air gap to allow the hinge to deform and the mirror to deflect.
Because the thermal coefficient of expansion of the encapsulated pillar material nearly matches the thermal coefficient of expansion of the aluminum pillar sheath, the encapsulated material may be left inside the support pillars. If the difference between the thermal coefficient of expansion of the encapsulated material and the thermal coefficient of expansion of the aluminum pillar sheath is too great, the support pillar may break when exposed to high or low temperatures. To prevent damage to the support pillar caused by a mismatch in thermal expansion coefficients, a hole could be patterned in either the electrode or hinge metal layers to allow the encapsulated material to be removed by plasma etching.
Although a process of fabricating support pillars has been taught thus far only in terms of the hidden hinge DMD, many other devices could make use of the process. A conventional torsion beam DMD 600, shown in FIG. 6, consists of a mirror 604 supported by two torsion hinges 606 over address electrodes 608 fabricated on a semiconductor substrate 610. The disclosed process could be used to form the hinge support pillars 602 which support the hinges 606 away from the substrate 610. Other micromechanical devices such as accelerometers, flow sensors, temperature sensors, and motors could also use the disclosed process. The disclosed process advantageously provides support pillars that are stronger than the spacervias of the prior art.
Thus, although there has been described to this point a particular embodiment for a support pillar and process, it is not intended that such specific references be considered as limitations upon the scope of this invention except insofar as set forth in the following claims. Furthermore, having described the invention in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art, it is intended to cover all such modifications as fall within the scope of the appended claims. | A support pillar 426 for use with a micromechanical device, particularly a digital micromirror device, comprising a pillar material 422 supported by a substrate 400 and covered with a metal layer 406. The support pillar 426 is fabricated by depositing a layer of pillar material on a substrate 400, patterning the pillar layer to define a support pillar 426, and depositing a metal layer 406 over the support pillar 426 enclosing the support pillar. A planar surface even with the top of the pillar may be created by applying a spacer layer 432 over the pillars 426. After applying the spacer layer 432, the spacer layer 432 is etched to expose the tops of the pillars. |
TECHNICAL FIELD OF THE INVENTION
The present invention concerns an illuminating instrument, in other words an instrument which is intended to be controlled by an operator and to produce lights which vary or fluctuate. Such an instrument allows the composition of light divisions which can then be played repeatedly by interpreters or expositors, in the same manner as a pianist executes a musical piece which has been composed beforehand. The instrument can also be played automatically, by programmed control, in the same manner as a mechanical piano or a street organ.
To comprehend the invention, it is useful to consider a parallel between the domain of music and that of light and color.
In the musical domain, obviously after the basic components of rhythm or dynamics and the association of sounds, there exist only two fundamental parameters, the frequency and the intensity of any one sound. These parameters and components together define a "plan" in which a sound may be defined by one point. However, it is difficult to obtain pure sounds and, in practice, instruments have been developed which each give associations of sounds characteristic of very individualized musical concordances. One single piece of music gives very different effects on different instruments.
In the domain of lights, the fundamental parameters which are at the disposal of the user are more numerous since they are three in number: they define a "space" in which a "light" is defined by a point (this space is known as the "Munsell color system"). Of course, secondary parameters analogous to those of the musical domain are also present in the domain of lights: association of lights (spectrum), dynamic characteristics (growth and decline).
This analogy between music and "lights" however is not so simple as has been indicated and it is intended solely for understanding of the diversity of the possible commands in a light instrument, a diversity which is a great deal more extensive than in the musical domain.
Just the same as an apparatus capable only of emitting sounds is not a musical instrument (it is the respect for certain conditions which gives its musical character to a sequence of sounds), an apparatus capable of emitting lights is not necessarily a light instrument. In fact, it is the condition of the selection of the lights and their variations which make that instrument a light instrument and a genuine instrument allowing artistic expression.
It is possible to consider that a television monitor is a light instrument of the bidimensional type, to the extent that the images formed satisfy the conditions of selection. When a television monitor reproduces an image filmed directly with the aid of a camera, it does not constitute a true light instrument since it is occupied solely with restitution of a scene of which the camera avails itself in its totality. On the other hand, when the camera is used to display a synthesized image, the assembly comprising the monitor and the means which have been used to create this synthesized image constitute a light instrument.
It is known that the synthesis of television images is a considerable practice requiring considerable technical skill, given the very large number of points to be defined in one single image. This work becomes inordinate when a truly animated or enhanced program must be realized because it requires several tens of images per second. It is therefore obvious that the operator of such a system cannot "play" the instrument in real time since months of work are required for creation of a short sequence of a few seconds. The route of television synthesis of images then does not permit the realization of a light instrument which can be played in real time.
The known instruments to give a play of light often call attention less to the artistic domain than to that of advertising.
PRIOR TECHNOLOGY
Apparatuses are already known which comprise light source which are not very extended, are in pinpoints or are linear. The most current are those constituted by gas discharge signs. These signs sometimes coprise several complicated motifs, sometimes placed before a color background which may be uniform or may not. These devices do not constitute true light instruments because they are fixed: the various linear elements function in an all or nothing manner, and the only parameters at the disposal of an operator are the time periods for illumination and extinction of each element. This restriction of the parameters over which an operator has disposal gives this type of apparatus its mechanical and repetitive character which rapidly bores and turns away the observers. It is only when an assembly is formed of numerous separate independent signs that one can generally recognize a certain artistic flavor (as the view of a downtown area at night, from aboard an aircraft at low altitude).
Apparatuses having extended light sources are also known, comprising for instance a focusing screen with a large surface behind which is placed a source which is of large dimensions (constituted for instance of series of rectilinear discharge tubes placed side by side). A colored composition is displayed on this focusing screen. The entirety constitutes a work in light, but this is not a light instrument, because the sole possibility of control by the operator, aside from an optional overall regulation of the intensity, is a change of the composition, as though one is changing a slide transparency or a negative.
Great Britain Pat. No. 849 680 describes an apparatus intended to give polychromatic effects and having a wrinkled or crimped reflecting surface and sources placed in front of this surface. It does not concern transparent or translucent composition, in other words it does not concern working by transmission, nor does it concern sources placed behind the composition.
French patent application No. 2 529 065 concerns a decorative assembly in which an opaque picture element is illuminated from a source in front of it.
French patent application No. 2 136 917 concerns a process of enhancement or animation according to which the light is projected on a surface from the front. This surface is neither translucent nor transparent.
DESCRIPTION OF THE INVENTION
The invention is based upon the determination of conditions which allow the realization of a true light instrument which can be controlled by an operator, a composer, or interpreter or expositor. It also concerns a process for the creation of light scores by enhancement of a light structure, and an instrument allowing the composition and interpretation of such scores.
The principal conditions which must be satisfied in a light instrument are the following.
First of all, the instrument must form a bidimensional or tridimensional light structure which is static. This structure must include at least two extended sources having different effective zones. (The bidimensional or tridimensional region wherein the illumination varies when the light intensity and/or the light spectrum of the extended source varies is called "effective zone".) Preferably, the structure also includes at least one overall extended source, in other words an extended source of which the effective zone covers over a large part of or the entire structure. According to the invention, the extended sources which are used present progressive variations, independent and controlled relative to their light intensity and/or their light spectrum.
The apparatus is of great interest when as many as four sources are being used, and the number of sources being used is preferably equal to eight.
The sources are preferably of at least two different colors. It is also particularly advantageous that the order of at least one extended source be able to vary or fluctuate, in other words that the light source have a light spectrum which varies or fluctuates in the course of time, independently from its fluctuation or variation in intensity or in conjunction with its intensity variation or fluctuation.
Preferably, the sum of the effective zones of the sources covers the entire or almost the entire visible support structure. It is advantageous that an extended source have at least one effective zone which covers the greatest portion of the visible support structure. This source or these sources are called "background" sources hereinafter in the present specification, as opposed to the "partial" sources which each have a relatively reduced effective zone, for example less than one fourth of the visible structure.
The effective zones of the extended source are preferably overlapping. Thus, it is advantageous that the effective zones of the partial sources cover over those of the background sources. However it is also advantageous that the effective zones of certain partial sources which are adjacent to each other be overlapping. This characteristic is important because it allows one single element of the instrument to present different colors according to the ratios or relations of intensities or the spectra of the different light sources.
The extended light sources must present variations of intensity in a wide range, which preferably may extend as far as the complete extinction of the source, and also, the sources preferably present variations of light spectra. These variations of intensity and/or of spectrum of the extended light sources advantageously have time constants on the order of one second to several tens of seconds. Of course, this condition is included in general and overall terms, but does not exclude either local or temporal different conditions, such as a constant maintenance or a very rapid variation of light source. If the intensity of a source is held at a constant level, then a part of the structure becomes fixed, and this must be avoided unless this fixed aspect is actually the intended objective which is sought. A rapid variation or fluctuation constitutes an assault when it is repeated too often. On the other hand, a rapid variation or fluctuation of one single source or of a small number of sources, in an occasional manner, accentuates the composition and gives an interesting effect.
The process satisfying the aforementioned conditions allows the composition and interpretation of true scores of light, in which the operator at any moment controls the variations of intensity and optionally of color of the various light sources. It is preferable that this control be assured by control of the type of variation and the velocity of variation of the intensity of each source or of each group of sources, when the number of sources is sufficiently large.
Since the controls of variation or fluctuation of intensity and color of the light sources can be assured by purely static means, for instance electronic circuits, the instrument can itself be entirely static, without any movable part other than those parts controlled by the operator in order to introduce the commands.
More precisely, the invention concerns a process for the enhancement of a light structure comprising a composition having extended surfaces and several light sources, comprising the realization of a composition in transparent or translucent form, the arrangement of the light sources on the side of the composition opposite that of the observer, the light sources being made up of extended sources, each having an effective zone within the composition, or groups of such extended sources, and the progressive variation, independent and controlled, of the intensity of each of the extended sources and each group of extended sources.
The process advantageously comprises the use of light sources on the one hand in the form of partial sources or groups of partial sources, each having an effective zone which covers only a small part of the composition, and on the other hand in the form of at least one background source having an effective zone, the sum of the effective zones of the background sources of one single color being equal to the entirety or almost the entirety of the composition. The background light sources are to be of different colors.
The invention also concerns a light instrument of the type which forms a light structure which comprises a composition having extended surfaces and a plurality of light sources, the composition being transparent or translucent, the light sources being placed on the side of the composition which is opposite and facing that of the observer, wherein the light sources are extended sources, each having an effective zone, the instrument besides that including devices which are intended to cause variation of fluctuation of the light intensity of certain light sources or certain groups of sources at least. It is advantageous that the instrument comprise at least one extended background light source having one effective zone, the sum of the effective zones of the background sources covering over practically the entirety or almost the entire light structure.
It is advantageous that the instrument comprise at least one device which is intended to cause variation of the color of the light from at least one extended light source. The extended source having a color which varies can be made up of at least two elementary sources having different light spectra, and the device which is intended to cause the variation or fluctuation of the color is made up of a device intended to cause the variation or fluctuation of the relations of the light intensities of the elementary sources.
An extended background light source is preferably formed of a plurality of partial sources of which the variations of intensity are controlled simultaneously by one single control device.
It is advantageous that the devices intended to cause the variation of fluctuation of the light intensity of each source or of each group of sources comprise a computer and a data entry device. In one embodiment, the data entry device is a data acquisition device having a plurality of command channels for direction and variation of speed. In another embodiment, the data entry device is a data display reader device to read data which has been progammed in the memory beforehand.
In one embodiment, the light structure of the instrument is bidimensional, and the instrument comprises a support frame, a diffusion plate placed before the frame and together constituting a composition, a plurality of elementary light sources supported by the frame, color filters placed between at least some of the sources and the diffusion plate, and a command device to control the variation or fluctuation of the light intensity of each elementary source.
In another embodiment, the light structure of the instrument is tridimensional, and the instrument includes a support frame, a plurality of extended sources each comprising at least one elementary source and an extended source which is illuminated at least in part by at least one elementary source, with the extended sources being mounted in several different planes, and a command device to control the variation or fluctuation of intensity of each source.
In this last embodiment, the extended illuminated surfaces which are illuminated by the elementary light sources and which can have any shape or form, such as flat, cylindrical, conical, hemispherical or corrugated, can be sources operating by transmission or by reflection.
BRIEF DESCRIPTION OF THE DRAWING
Other characteristics and advantages of the invention will be understood more clearly from the following description, in reference to the attached drawing, wherein:
FIG. 1 shows a transverse cross section of a part of a bidimensional light structure according to one embodiment of the invention; and
FIG. 2 is a diagram of the command or control apparatus of the light sources of the structure of FIG. 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The apparatus shown partially in FIG. 1 forms the light structure of a light instrument according to the invention. This apparatus comprises a rear plate 10 intended to constitute a frame or support for the other elements of the structure. This plate can be of any sufficiently rigid material and it is preferably opaque. A diffusion plate 12 is mounted at some distance from plate 10, in front of it, by devices which are not shown but are of any suitable type.
A plurality of extended light sources are formed by the apparatus. Each extended light source comprises one or more light elementary sources, a surface limiting and defining the effective zone of the source, and optionally a deflector limiting the field of the light source or its effective zone.
More precisely, FIG. 1 shows five partial extended light sources and one background extended source. These sources are formed by elementary light sources 21, 22, 24, 26 and 25, by deflectors 14, 16, 18 and 20 and by extended surfaces which in this case are constituted of colored filters applied against the diffusion plate and carrying references 27, 28, 30, 32 and 33. For an observer placed at some distance on the other side of the diffusion plate, the spots of color corresponding to the filters appear to be juxtaposed and are sometimes partially overlapping.
Deflector 18 carries an elementary light source formed by a light 34 which is nearer the diffusion plate than the other sources and which has an effective zone which is much more extended since it in fact covers over all of the effective zones of the other extended sources. This is a "background extended light source" or a background source, contrary to the other extended sources which are called "partial" sources because they have only limited effective zones.
One embodiment is to be considered. Filter 30 may be a yellow filter and light source 24 a blue light: the effective zone of light 30 will appear to an observer to be yellow or green, according to its intensity. On the other hand, however, if light 34 illuminates this same filter 30 with a red light, this effective zone will then appear to be orange or red, according to the intensity of the light. Therefore it is possible to obtain different colors by means of one single placement of the elements of the light structure, by application of different and separate commands to the various elementary sources.
The partial extended source comprising filter 32, deflectors 14 and 16 and elementary source 26 comprises two different lights placed behind one single filter. The two lights can be controlled in such a manner that the relation of their intensities varies. If the two lights emit light beams of different colors, the visible color of the effective zone of this light will vary for the observer.
Although it has been indicated that the effective zones of the extended sources were defined by the filters, said filters are not indispensable. In fact, if the elementary light sources are themselves colored, the effective zones will be colored. The colors of the different zones can be clearly separated, as shown by reference 36, in other words they can be without any overlap. However they can also be overlapped, as shown by reference 38, where the colors of the two zones appear to the observer to be merged together.
The most significant possibility allowed by the invention is the variation or fluctuation of the light intensity of each source, preferably relatively slow, with time constants on the order of a few seconds to some tens of seconds. Therefore it is necessary according to the invention that this intensity be able to be controlled according to the invention. This characteristic is obtained with an apparatus as shown in FIG. 2.
The apparatus shown in FIG. 2 provides for regulation of the intensities of several elementary light sources, independently from each other, by use of data indicating on the one hand the type of variation of intensity and on the other hand the speed of said variation. In practice, the data introduced for each elementary light source are on the one hand the change or lack of change of the direction of variation and on the other hand an elementary pitch of elementary variation of the intensity in a very short period, preferably shorter than the twenty-fifth of a second. A constant intensity is obtained by constant change of the direction of variation, or by use of anullment of the pitch.
FIG. 2 shows two devices for data entry, on the one hand a joy stick 40 for data entry and on the other hand a computer 42. The joystick determines the proper elementary light source by its azimuth, the amplitude of the pitch by the amplitude of its displacement in relation to the central position, and the direction by the depression or lack of depression of the joystick in its support. Of course, the joystick at any certain moment gives only the data concerning one simple elementary light source. It is therefore necessary that suitable devices retain the value of the pitch of each source until the subsequent command or until a threshold value is reached. Of course, these data can be furnished by a computer 42 which in the traditional manner comprises a central processor 44, a main or RAM memory 46 and passive or ROM memory 48, a keyboard 50 and a screen 52.
The signals from the joystick or the computer cannot be used directly by the lights, and they in fact constitute command signals only. Each light source 54 is therefore associated with a transmission channel comprising, starting from an input-output circuit 56 having data lines and address lines, a register 58 (which may be of the 74LS273 type), a digital-analog converter 60 (for instance of the DAC0800 type), and an amplification stage 62 comprising an operational amplifier 64 (which may be of the LM741 type) and a power transistor 66 (for instance of the TIP120 type) suitably connected to an input furnishing the energy required for the light sources 54.
Before being able to compose a light score, the user must realize the light structure, in other word first execute an operation of plastic art: positioning of the lights and the deflectors which define the effective zones, selection and arrangements of the filters which in and of themselves already form a colored composition but which have the drawback of being static. The invention then allows the enhancement of this composition, by action taken on the intensities and their contrasts, and by accentuation or reduction of the color contrasts.
Although an embodiment of the bidimensional type has been described, the invention also concerns tridimensional structures. In this case, a plurality of extended light sources are placed in close proximity with each other. These sources can give or not give variations of color but will always allow variations of fluctuations of intensities. The extended light sources can be of any form. Interesting results have been obtained with elementary light sources placed in colored translucent wrappers, with hollow open cylinders at one end and having an elementary light source which is not directly visible, and with rippled forms giving effects of cast shadows.
In the case of a tridimensional structure, the composition is advantageously one single uncolored diffusion plate which allows the differences of depth of the various sources to be distinguished from each other.
One advantage of the invention is that the light instrument can be purely static and have no movable part, except for the data entry device. However, some particular effects can be obtained by coupling the instrument with dynamic elements, for instance a motor which moves a movable member. Thus, a motor can be used for control of an obturator or a revolving polarizer intended to cause the variation or fluctuation of the intensity of a light source of which the intensity cannot be directly modulated (for instance a gas discharge tube). However, these are only optional elements, as are also any plurality of pinpoints or linear light sources, in other words non-extended light sources, added to the instrument.
POSSIBILITIES OF INDUSTRIAL EXPLOITATION
The instruments according to the invention are suitable either in the form of instruments allowing for artistic expression, or as decorative elements controlled by computer and participating in the enhancement or animation of public places. | Animation of lighting structures. Method and instrument implementing a plurality of extensive sources of lights having intensities which vary independently in the course of time and optionally a colored spectrum which also varies. The variations of the different sources which are either localized or global are controlled in real time by an operator or may be programmed. The controlled parameters are preferably the direction and the speed of the intensity variation. Application to the making of instruments for the creation and interpretation of light scores. |
This application is a division, of application Ser. No. 07/412,162, filed 09/25/1989, now U.S. Pat. No. 5,004,117 granted Apr. 12, 1991.
BACKGROUND OF THE INVENTION
Field of The Invention
The present invention relates generally to a cap for protecting the cylinder valve of a gas cylinder. More particularly, the invention concerns a safety cap and the method of making the same for use in connection with portable gas cylinders which positively protects the cylinder valve against damage and, at the same time, permits ready access thereto.
DISCUSSION OF THE INVENTION
Gas cylinders typically comprise strong steel vessels of cylindrical shape in which gases are stored under high pressure. Provided at one end of the gas cylinder is a necked down portion having a cylinder valve including a valve outlet fitting to which a pressure regulator or the like can be connected. A hand-wheel for operating the valve is typically permanently attached to the valve stem.
Threads on the necked down portion of the cylinder provide a means whereby a heavy steel cap is screwed over the valve to protect it from injury during shipment. If the cylinder valve should ever be broken off, the very high pressure of the gas in the cylinder, upon escaping tends to give the cylinder rocket propulsion. Because of this danger, it is essential that the cap be in place during shipment and handling of the gas cylinder.
In the past, the cylinder cap has traditionally been made in a generally cylindrical configuration closed at its upper end by a heavy dome shaped wall and open at its lower end for threaded interconnection with the necked down portion of the gas cylinder. Typically, vertically extending, slot-like openings are provided in the wall of the cap to permit release of gas. To gain access to the cylinder valve it is necessary to remove the cylinder cap. This is highly undesirable because removal of the cap exposes the cylinder valve to damage and the resultant possibility of a catastrophic accident Additionally, the configuration of the prior art cylinder cap makes handling of the cylinder difficult since no safe gripping surface is provided on the cap.
The device of the present invention uniquely overcomes the drawbacks of the prior art cylinder caps by providing a cylinder cap of a novel configuration which permits ready access to the cylinder valve and also provides a built-in hand grip that makes handling of the gas cylinder considerably easier and safer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a safety cylinder cap for use with gas cylinders to protect the cylinder valve, in which the cap need not be removed from the gas cylinder to gain access to the cylinder valve.
Another object of the invention is to provide a cylinder cap of the aforementioned character which includes a conveniently located gripping member for use in transporting the gas cylinder.
Another object of the invention is to provide a safety cylinder cap which is configured to protect the cylinder valve should the gas cylinder fall over or be dropped during transport.
Still another object of the invention is to provide a method for making a safety cylinder cap of the character described in which the apertured, a bell-shaped body of the cap is formed from a single sheet of planar material.
Yet another object of the invention is to provide a method described in the preceding paragraph which enables the cylinder cap to be expeditiously manufactured at low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a generally front perspective view of the safety cap of the present invention shown connected with a gas cylinder of the character used to contain compressed gas.
FIG. 2 is a generally rear perspective view of the safety cap.
FIG. 3 is a greatly enlarged fragmentary cross sectional view taken along lines 3--3 of FIG. 1.
FIG. 4 is a side elevational, diagrammatic view of the safety cap partly in cross section to illustrate the configuration of the gripping portion of the device.
FIG. 5 is a fragmentary view taken along lines 5--5 of FIG. 4.
FIG. 6 is a side elevational view of the starting, planar workpiece used in the method of fabricating the safety cap of the present invention.
FIG. 7 is a side elevational view illustrating the accomplishment of the first step of the method of the invention.
FIG. 8 is a cross sectional side elevational view illustrating the second step of the method of the invention.
FIG. 9 is a cross sectional side elevational view illustrating the third step of the method of forming the safety cap of the present invention.
FIG. 10 is a side elevational cross sectional view illustrating the fourth step of the method of the invention.
FIG. 11 is a side elevational cross sectional view illustrating the fifth step of the method of the invention.
FIG. 12 is a side elevational cross sectional view illustrating the sixth, step of the method of the invention.
FIG. 13 is a side elevational cross sectional view illustrating the seventh step of the method of the invention.
FIG. 14 is a side elevational cross sectional view illustrating the eighth step of the method of the invention.
FIG. 15 is a side elevational cross sectional view illustrating the ninth step of the method of the invention.
FIG. 16 is a rear elevational view of the partially formed safety cap of the invention illustrating the tenth step of the method of the invention.
FIG. 17 is a front elevational view of the partially fabricated safety cap illustrating the eleventh step of the method of the invention.
FIG. 18 is a side elevational view of the safety cap of the invention illustrating the twelfth step of the method of the invention.
FIG. 19 is a side elevational cross sectional view of the safety cap of the invention illustrating the thirteenth of the method of the invention.
FIG. 20 is a view taken along lines 20--20 and partly broken away to better illustrate the configuration of the finished form of the safety cap of the invention and to illustrate the fourteenth step of the method of the invention.
DESCRIPTION OF THE INVENTION
Referring to the drawings and particularly to FIGS. 1 and 2, the safety cylinder cap of the present invention is there illustrated and generally designated by the numeral 12. The safety cap 12 is shown in threaded interconnection with a gas cylinder 14 of standard construction. In the embodiment of the invention shown in FIGS. 1 and 2, the safety cap comprises a generally bell-shaped body 16 including a first end portion 18 having a first opening 20 of a first size. Safety cap 12 also includes a generally cylindrically shaped, second end portion 22 which is of a second size smaller than the size of opening 20. End portion 20 includes an internal wall 24 which is threaded for interconnection with the threads 26 provided on gas cylinder 14.
As best seen by referring to FIG. 2, adjustment means, generally designated by the numeral 28, are provided for adjusting the size of the second opening 30 of the device. A curved side wall 32 interconnects first and, second end portions 18 and 22 and is provided with a first aperture 34 (FIG. 2) and a second oppositely disposed larger aperture 36 (FIG. 1). Provided proximate the upper margin of aperture 36 is a grip, or finger engaging means for engagement with the fingers of a person lifting the safety cap and the safety cap interconnected with the gas cylinder 14. In the present embodiment of the invention, the finger engaging means is provided in the form of an elongated plastic gripping member 38 having a longitudinally extending slot 39 which defines a pair of spaced apart walls 38a and 38b. Slot 39 is of a width to closely receive the edge of the curved side walls 32 disposed proximate the upper portion of aperture 36.
As best seen by referring to FIG. 3, the upper margin of wall 32 is provided with peripherally extending, rounded bead portion 40. Provided proximate the edge 36a of aperture 36 is a pair of spaced apart, inwardly protruding protuberances 42 which are closely received within a pair of apertures 44 formed in the rear wall 38b of gripping member 38 (FIG. 2). Protuberances 42, in cooperation with apertures 44, securely lock the plastic hand grip member 38 in position over the edge portion 36a of wall 32 defined by the upper extremity by aperture 36. As indicated in FIG. 4, the lower edges of gripping member 38 are rounded to provide comfortable gripping of the safety cap in the manner shown in FIG. 4.
Turning now to FIGS. 2 and 5, the lower cylindrically shaped portion 22 of the device of the invention is provided with a vertically extending slit 46. Connected to cylindrical portion 22 on opposite sides of slit 46 is a pair of outwardly extending apertured ears 48. Apertures 48a in ears 48 closely receive a connector means, or bolt 50 having a head portion 52 adapted to engage the outer face of one ear 48 and a threaded shank portion 52a. Shank portion 52a receives a nut 53 which is in engagement with the outer face of the other ear 48. Ears 48, along with bolt 50 and nut 53, comprise portions of the adjustment means of the embodiment of the invention shown in the drawings. By tightening nut 53 on bolt 50, it is apparent that the width of slot 46 can be slightly narrowed thereby decreasing the size of the second opening 30 in the safety cap. As previously mentioned the adjustment means of the invention permits fine adjustments to be made to the size of the second opening so that the device can be properly threadably interconnected with the threads 26 provided on the gas cylinder. When necessary the adjustment means can also be used to lock the cap in place on the cylinder.
In using the device of the present invention, the lower, or second portion of the device, is threadably interconnected with the threads 26 provided on the gas cylinder. The device is then turned so that aperture 36 is positioned opposite the cylinder valve provided on the gas cylinder. If necessary, nut 53 can be tightened on bolt 50 to lock the cap securely in this position. With the cap thusly oriented, the cylinder valve of the gas cylinder is readily accessible without the necessity of removing the safety cap from the gas cylinder.
A unique feature of the device of the present invention resides in the fast that the entire device, save for the adjustment means, can be constructed from a single sheet of planar starting material identified in FIG. 6 by the numeral 56. The various steps in the method of making the safety cap of the invention are illustrated in FIGS. 6 through 20 and will be described in the paragraphs which follow.
Starting with the planar sheet 56, the first step in the method of the invention is to draw the starting material into a cup shaped body 58 of the character shown in FIG. 7. Cup shaped body 58 has an open first end 58a and a second end 58b closed by a top wall 58c. A side wall 60 interconnects first and second ends 58a and 58b.
By a second drawing step a flange 62 is then formed about the open end of the cup shaped body. Following the second draw the flanged, cup-shaped configuration is then restruck to flatten the flange into the configuration identified in FIG. 9 by the numeral 62a. This done, the flange 62a is trimmed in the manner shown in FIG. 10 to form a foreshortened flange 62b. The annular shaped material trimmed from the configuration, designated in FIG. 10 by the numeral 63, is discarded. Following the trim step the lower margin of the cup shaped member is curled to form a peripherally extending rounded bead 64.
The semi-finished product, shown in FIG. 11, is then subjected to a third drawing step wherein the upper portion 60a is roughly formed into a general cylindrical shape and the lower portion 60b is roughly formed into a general bell-shaped configuration. Upon completion of the third draw, a fourth draw is undertaken during which the configuration shown in FIG. 12 is drawn to the configuration shown in FIG. 13. In this step portion 60a is formed into a generally cylindrical shaped portion 66 which is foreshortened and has a diameter less than the diameter of the upper portion 60a. At the same time that portion 66 is being formed, portion 60b is refined into a more elongated bell-shaped portion 68 having an opening 69 which is coaxially aligned with portion 66. At the completion of the fourth drawing step to form the configuration shown in FIG. 13, it is apparent that the interim product has taken on the general exterior shape of the finished device of the invention.
Following the fourth drawing step, as described in the preceding paragraph, the configuration shown in FIG. 13 is placed within an appropriate piercing mechanism so that the central portion 70 of the upper wall 71 of the configuration shown in FIG. 13 is cut away to define a generally circular opening 72 of a predetermined internal diameter. Following the piercing step, is a deburring step which results in the reforming of upper portion 66 into a cylindrical section 74 of the character shown in FIG. 15. The internal diameter of cylindrical section 74 is slightly greater than the diameter of aperture 72 formed in the piercing step.
The interim configuration shown in FIG. 15 is next subjected to a piercing step wherein a slot 76 is formed in cylindrical section 74 and at the same time an aperture 78 is formed in wall 68. As indicated in FIG. 16, slot 76 extends throughout the length of cylindrical section 74 and joins aperture 78 Following the first side piercing step just described, the opposite side of the interim work piece is pierced to form a second aperture 80 which is of a considerably larger size than aperture 78. A comparison of the configuration of the interim article, shown in FIG. 17, with the general configuration of the finished article, shown in FIG. 1, reveals that the basic internal and external configuration of the device of the apparatus has thus been formed from the single planar sheet of material 56 through a series of sequential forming, piercing and deburring steps.
The next step in the method of the present invention involves the interconnection of the outwardly extending ears 48 to cylindrical section 74 on either side of slot 76. Ears 48 are affixed to the cylindrical section 74 by any suitable means such as spot welding. Following affixing of ears 48, which form a part of the adjustment means of the invention, the inner surface of cylindrical section 34 is threaded to form internal threads 84 of the character shown in FIG. 19. Following the threading step, the previously identified protruderences 42 are formed proximate the edge of aperture 80 and the finger engaging means, or elongated member 38, is snapped into position over the edge 36a of the aperture 80 (FIG. 19).
As a final step bolt 50 is inserted through the apertures 48a formed in the outwardingly extending ears, and nut 3 is threaded onto the threaded shank of the connector, or bolt 0. Comparing the finished article shown in FIG. 20 with the device of the invention shown in FIG. 1, it is to understood that the cylindrical portion 74 corresponds with upper portion 2; the internal opening 69 corresponds with opening 20; bell-shaped side wall 68 corresponds with wall 32; aperture 34 corresponds with aperture 78; and aperture 36 corresponds with aperture 80.
It is readily apparent the method of the invention, as described in the proceeding paragraphs, permits the cylinder cap of the invention to be produced more expeditiously and considerably less expensively than the prior art cylinder caps generally in use.
Having now described the invention in detail in accordance with the requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims. | A cylinder cap and method of making the same for use with gas cylinders of standard construction to protect the cylinder valve from damage should the cylinder be knocked over or dropped. The cylinder cap is uniquely formed to allow convenient access to the cylinder valve without having to remove the cap from the cylinder. A gripping member is provided in the cylinder valve access aperture of the bell-shaped cap for use in safely transporting the gas cylinder. In accordance with the method of the invention, the apertured, bell-shaped body of the cap is formed from a single sheet of planar material by means of a series of drawing and piercing steps. |
This application is a division of application Ser. No. 07/362,350 filed on Jun. 6, 1989, now abandoned.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having electrode regions of high concentration and a method of manufacturing the same.
2. Description of the Background Art
FIG. 1 is a sectional view showing a conventional semiconductor device of isolated type composite element structure. As shown in FIG. 1, an insulated gate field-effect transistor 10A and a junction bipolar transistor 10B are formed in an upper layer part of an n - -type polysilicon substrate 1 to be insulated/isolated by insulating films 2. N + -type layers 3 of prescribed thickness are formed on the insulating films 2, and n - -type layers 4 are formed on the n + -type layers 3.
In an element forming region (hereinafter referred to as "island") provided with the field-effect transistor 10A, a p-type well region 5 is formed in an upper layer part of the n - -type layer 4, while n + -type source regions 6 are selectively formed on the surface part of the p-type well region 5.
Polysilicon gates 8 are formed on surface parts of the p-type well region 5 held between the surfaces of the n - -type layer 4 and the source regions 6 through a gate oxide film 7. Drain electrodes 9 are formed on the surface of the n + -type layer 3, and a source electrode 11 is formed over a part of the surface of the n + -type source regions 6 and a part of the surface of the p-type well region 5 held between the n + -type source regions 6, while gate electrodes 12 are formed on the polysilicon gates 8. The electrodes 9, 11 and 12 are insulated from each other by passivation films 18.
In another island provided with the bipolar transistor 10B on the other hand, a p-type base region 13 is formed in an upper layer part of the n - -type layer 4. An n + -type emitter region 14 is formed in a part of the surface of the p-type base region 13. An emitter electrode 15 is formed on the n + -type emitter region 14 and a base electrode 16 is formed on the p-type base region 13, while a collector electrode 17 is formed on the n + -type layer 3. The electrodes 15 to 17 are insulated from each other by passivation films 18.
FIGS. 2A to 2G are sectional views showing a method of forming the islands in the semiconductor device shown in FIG. 1. This method will now be described with reference to these figures.
A resist film 22 is formed on the surface of a monocrystal n - -type substrate 21 as shown in FIG. 2A, and patterned as shown in FIG. 2B. The patterned resist film 22 serves as a mask to etch the n - -type substrate 21, thereby to define V-shaped cavities 23 as shown in FIG. 2C. An interval l between each pair of adjacent cavities 23 defines the width of each island.
Then, an n-type impurity such as phosphorus is diffused on the surface of the n - -type substrate 2 including the cavities 23, to form an n + -type layer 3. Pretreatment (removal of a phosphorus glass layer etc. formed on the n + -type layer 3) is performed through hydrofluoric acid system chemicals, and thereafter an insulating film 2 such as a thermal oxidation film is formed on the n + -type layer 3, as shown in FIG. 2D.
An n - -type polysilicon layer 24 is formed on the insulating film 3 through epitaxial growth technique, as shown in FIG. 2E. Then, the rear surface of the n - -type substrate 21 is polished, to expose the insulating film 2 and the n + -type layer 3 on the rear surface of the n - -type substrate 21, as shown in FIG. 2F.
Then, the n - -type substrate 21 is so turned over as to complete a plurality of islands 25, in which the n - -type polysilicon layer 24 corresponds to the n - -type polysilicon substrate shown in FIG. 1 and the remaining n - -type substrate 21 corresponds to the n - -type layers 4 shown in FIG. 1 while the respective islands 25 are insulated by the insulating films 2, as shown in FIG. 2G. The field-effect transistor 10A and the bipolar transistor 10B are manufactured in the respective islands 25 thus obtained.
The n + -type layers 3, which are brought into ohmic contact with the drain electrodes 9 and the collector electrode 17, respectively, must be increased in thickness as well as in concentration in order to minimize ON resistance and drain-to-source forward voltage in the field-effect transistor 10A and to minimize collector-to-emitter saturation voltage in the bipolar transistor 10B.
However, it is extremely difficult to form thick n + -type layers 3 of high concentration by an impurity diffusion method, since the processing takes too much time to degrade workability and since the value of concentration which can be realized through diffusion is limited to about 10 18 to 10 19 cm -3 .
SUMMARY OF THE INVENTION
In the first aspect of the present invention, a semiconductor device comprises a semiconductor substrate, at least one active region formed on the semiconductor substrate, and an electrode region formed in the active region, the electrode region comprising a polycrystalline semiconductor layer containing an impurity of a prescribed conductivity type in high concentration and a diffusion layer of the prescribed conductivity type formed in a periphery of the polycrystalline semiconductor layer.
In the second aspect of the present invention, a method of manufacturing a semiconductor device comprises the steps of preparing a semiconductor substrate, forming an active region on the semiconductor substrate, forming a polycrystalline semiconductor layer containing a prescribed conductivity type impurity in high concentration in the active region, and diffusing the prescribed conductivity type impurity from the polycrystalline semiconductor layer serving as a diffusion source to form a diffusion layer in a periphery of the polycrystalline semiconductor layer, the diffusion layer together with the polycrystalline semiconductor layer defining an electrode region.
According to the present invention, an electrode region is defined by a polycrystalline semiconductor layer, which is formed in an active region and contains a prescribed conductivity type impurity in high concentration, and a diffusion layer which can be formed by diffusion from the polycrystalline semiconductor layer by using the polycrystalline semiconductor layer as a diffusion source, whereby the electrode region can be formed in high workability, high concentration and wide thickness.
Accordingly, an object of the present invention is to provide a semiconductor device having an electrode region of high concentration in desired thickness, and a method of manufacturing the same.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a conventional semiconductor device of isolated type composite element structure;
FIGS. 2A to 2G are sectional views showing a method of manufacturing the semiconductor device shown in FIG. 1;
FIG. 3 is a sectional view showing an embodiment of a semiconductor device of isolated type composite element structure according to the present invention;
FIGS. 4A to 4G are sectional views showing a method of manufacturing the semiconductor device shown in FIG. 3; and
FIGS. 5A to 5D are sectional views showing a method of manufacturing a field-effect transistor and a bipolar transistor
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 3 is a sectional view showing a semiconductor device of isolated type composite element structure according to an embodiment of the present invention. As shown in FIG. 3, this semiconductor device of the embodiment is provided with polysilicon layers 30a containing an n-type impurity in high concentration and n + -type diffusion layers 30b obtained by impurity diffusion from the polysilicon layers 30a serving as diffusion sources, in place of the n + -type layers 3 formed on the insulating films 2 in prescribed thickness in the conventional device shown in FIG. 1. Other structure of this embodiment is identical to that shown in FIG. 1, and hence redundant description about that will be omitted.
FIGS. 4A to 4G are sectional views showing a method of forming islands in the semiconductor device shown in FIG. 3. This method will now be described below with reference to these figures.
A resist film 22 is formed on the surface of a monocrystal n - -type substrate 21 as shown in FIG. 4A, and patterned as shown in FIG. 4B. The patterned resist film 22 serves as a mask to etch the n - -type substrate 21, thereby to define V-shaped cavities 23 as shown in FIG. 4C. An interval l between each pair of adjacent cavities 23 define the width of each island.
Then, polysilicon layer 30a containing an n-type impurity in high concentration is formed on the surface of the n - -type substrate 21 including the cavities 23 in thickness of tens of microns. Thereafter the substrate 21 is continuously introduced into an insulating film forming furnace, thereby to form an insulating film 2 on the polysilicon layer 30a in thickness of several microns. At the same time, an n + -type diffusion layer 30b is formed in a portion of the n - -type substrate 21 on the periphery of the polysilicon layer 30a by thermal diffusion of the impurity contained in the polysilicon layer 30a, as shown in FIG. 4D.
An n - -type polysilicon layer 24 is formed on the insulating film 2 by epitaxial growth technique, as shown in FIG. 4E. Then, the rear surface of the n - -type substrate 21 is polished to expose the insulating film 2, the polysilicon layer 30a and the n + -type diffusion layer 30b on the rear surface of the n - -type substrate 21, as shown in FIG. 4F.
The n - -type substrate 21 is so turned over as to complete a plurality of islands 25, in which the n - -type polysilicon layer 24 corresponds to the n - -type polysilicon substrate 1 shown in FIG. 3 and the remaining n - -type substrate 21 corresponds to the n - -type layers 4 shown in FIG. 3 while the respective islands 25 are insulated by the insulating films 2.
A field-effect transistor 10A and a bipolar transistor 10B are manufactured in the islands 25 thus obtained, through the following steps: FIGS. 5A to 5D are sectional views showing a method of manufacturing the field-effect transistor 10A and the bipolar transistor 10B. This manufacturing method will now be described below with reference to these figures.
First, the n - -type polysilicon substrate 1 is pretreated with hydrofluoric acid system chemicals. Then, an oxide film 31 is formed on the surface of the n - -type polysilicon substrate by thermal oxidation or the like, and the oxide film 31 is selectively patterned by photolithography to define windows 31a. Then, an impurity is diffused from the windows 31a of the oxide film 31, to form a p-type well region 5 in an upper layer part of an n - -type layer 4 in an island 25a and a p-type base region 13 in an upper layer part of an n - -type layer 4 in an island 25b, as shown in FIG. 5A.
Then, the oxide film 31 is removed from the island 25a and a thin oxide film 32 is formed on the surface of the n - -type epitaxial substrate 1 by thermal oxidation or the like. A polysilicon layer 33 is formed on the oxide film 32. The oxide film 32 is coalesced with the oxide film 31 on the island 25b, to be slightly increased in thickness. Then, the polysilicon layer 33 and the oxide film 32 are selectively etched to define windows 33a. An n-type impurity is diffused from the windows 33a of the polysilicon layer 33 to form n + -type source regions 6 and an n + -type emitter region 14 in upper layer parts of the p-type well region 5 and the p-type base region 13, respectively, as shown in FIG. 5B. If the field-effect transistor 10A is of a double diffusion type, a p-type impurity may be diffused from the windows 33a before formation of the n + -type source regions 6.
Thereafter the polysilicon layer 33 is selectively etched to form polysilicon gates 8 on the island 25a, as shown in FIG. 5C. Then, an oxide film is formed over the entire surface of the n - -type epitaxial substrate 1 and selectively etched, thereby to form passivation films 18 in the islands 25a and 25b, as shown in FIG. 5D.
Thereafter a conductive layer is formed on the n - -type epitaxial substrate 1 including the passivation films 18 and selectively etched, thereby to define drain electrodes 9, a source electrode 11 and gate electrodes 12 in the island 25a and an emitter electrode 15, a base electrode 16 and a collector electrode 17 in the island 25b, as shown in FIG. 3. Thus, the field-effect transistor 10A is formed in the island 25a and the bipolar transistor 10B is formed in the island 25b.
In the aforementioned embodiment, the n + -type regions for serving as electrode regions in the islands 25 are formed by the polysilicon layers 30a doped with an n-type impurity in high concentration and the n + -type diffusion layers 30b obtained by diffusion of the impurity from the polysilicon layers 30a. Impurity concentration of the polysilicon layers 30a can be easily and correctly increased to about 10 19 to 10 20 cm -3 . N + -type layers of 20 μm in thickness can be formed in a short time of about 20 minutes by means of formation of the polysilicon layers 30a although about four hours have been required in the conventional impurity diffusion method. Therefore, the film thickness can be increased in a short time. Thus, n + -type layers of high concentration can be formed in the islands 25 in desired thickness with good workability.
When the field-effect transistor 10A is manufactured in the island 25, ON resistance and drain-to-source forward voltage can be minimized by bringing the polysilicon layer 30a and the diffusion layer 30b into ohmic contact with the drain electrodes 9, while collector-to-emitter saturation voltage can be minimized when the bipolar transistor 10B is manufactured in the island 25, by bringing the polysilicon layer 30a and the diffusion layer 30b into ohmic contact with the collector electrode 17.
Further, the n + -type diffusion layers 30b are simultaneously formed with the insulating films 2, whereby the manufacturing steps are not increased as compared with the prior art.
Although the above embodiment has been described with reference to a semiconductor device of isolated type composite element structure, the present invention is also applicable to all types of semiconductor devices which require an electrode region of high concentration in desired thickness in active regions of semiconductor elements. | An electrode region, which is formed in an active region in a semiconductor element forming region isolated by dielectric isolation, for example, comprises a polycrystalline semiconductor layer containing a predetermined conductivity type impurity in high concentration and a diffusion layer of the sam conductivity type formed in a periphery of the polycrystalline semiconductor layer. The polycrystalline semiconductor layer can be easily and correctly increased in impurity concentration and increased in high workability in thickness. Thus the semiconductor device having an electrode region of high concentration in desired thickness can be implemented. |
BACKGROUND OF THE INVENTION
1. Field of the Invention
In recent years, aluminum alloy structures that have resistance against high pressures have been widely used in various applications including heat exchangers for natural gases. To meet such demands, it has been necessary to increase the strength of the exchangers against high pressure encountered. The present invention relates to a manufacturing method which helps increase the strength of joint portions by improving a solidified structure at brazed joint portions formed by brazing aluminum alloy structures.
2. Background of the Prior Art
To date, brazing materials used for brazing aluminum alloy structures are generally composed of an Al-Si type alloy when it is to be brazed with flux, or is composed of an Al-Si-Mg type alloy when it is to be brazed without flux. However, the joint formed by using such brazing materials provides a solidified structure which includes a eutectic structure, and is brittle. In particular, when a brazing material of the Al-Si-Mg type is used or when the base metal contains magnesium, the brazed joint further loses the strength.
Study has so far been conducted extensively to reinforce the brazed joints. In the case of a plate-fin type heat exchanger, for example, limitations are imposed on the size of the brazed portions of fins though it may vary depending upon the shape of protuberance of fins, amount of brazing material supplied, properties of the brazing material, and the like. In treating the plate-fin type heat exchangers, furthermore, a method has been proposed to increase the strength against the pressure relying upon the aging and hardening of a base metal of the Al-Mg-Si type by using a heat-treated aluminum alloy as a fin material, effecting a solution heat treatment thereof after the brazing, and thereafter effecting hardening and tempering. According to this method, however, the base metal is limited to a heat-treated aluminum alloy (Japanese Patent Publication No. 11948/1982).
SUMMARY OF THE INVENTION
Unlike the above-mentioned methods, an object of the present invention is to provide a manufacturing method which increases the strength of the solidified structure of the brazed joint portions formed by brazing aluminum alloy structures with flux or without flux, based on an idea that with the high-pressure plate-fin type heat exchanger which requires large strength in the joints, it is essential to increase the strength of the structure of brazed joints of fins.
The inventors have investigated the joint structure from various viewpoints, and have found that silicon is crystallized in the form of needles, magnesium is segregated conspicuously, and magnesium is bonded to aluminum, silicon and iron to form compounds that are hard and brittle. A pressure was applied into the heat exchanger to break the brazed portions of fins by tensile or shearing force. Observation of the broken surfaces through a scanning electron microscope revealed the formation of the above-mentioned compounds in large amounts.
Based upon the above results, the inventors have conducted extensive tests to improve the structure in an attempt to strengthen such brittle solidified structures, and have discovered an improved method which helps obtain the superior results as described below.
The current invention resides in a method of producing aluminum alloy structures characterized in that an aluminum alloy structure is heated at a temperature of 500° to 570° C. for at least one hour, said aluminum alloy structure being obtained by the combination of brazing sheets formed by cladding both surfaces of a core member with a brazing material and a fin member made of an aluminum alloy which has not been treated with heat.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a micrograph with a magnification of 400 times showing needle-like silicon crystals in the eutectic structure in a joint when the method of the present invention is not put into practice;
FIG. 2 is a micrograph with a magnification of 400 times showing granulated silicon crystals in a joint when the method of the present invention is put into practice;
FIG. 3 is a photograph with a magnification of 250 times of an EPMA characteristic X-ray image showing a metal structure in which magnesium is segregated in a joint when the method of the present invention is not put into practice;
FIG. 4 is a photograph with a magnification of 250 times of an EPMA characteristic X-ray image showing a metal structure in which magnesium is dispersed in a joint when the method of the present invention is put into practice;
FIG. 5 is a perspective view of a plate-fin type heat exchanger that was put to the burst test; and
FIG. 6 is a front view showing a portion of FIG. 5 on an enlarged scale.
______________________________________1 - brazing sheets 2 - fins3 - brazing material 4 - spacer bars5 - test paths 6 - dummy paths7 - core members______________________________________
DESCRIPTION OF THE INVENTION
Based upon a standpoint that a brazed joint portion resembles a cast structure that has been melted, cooled and solidified, the inventors have achieved the method of the present invention. The inventors have investigated the structure obtained when a joined portion of a brazing member JIS-BA 4004 and a base member JIS-A 3004 is subjected to homogenization (heat treatment at a temperature of 500° to 570° C. for at least one hour) or not subjected to such a treatment, and have observed changes as illustrated in FIGS. 1 to 4.
That is, needle-like crystals of silicon in the eutectic structure shown in FIG. 1 prior to the homogenization are granulated as shown in FIG. 2 through the homogenization effected at 540° C. for four hours. Magnesium in the eutectic structure shown in FIG. 3 prior to the homogenization is transformed into a solid solution with other elements as shown in FIG. 4 through the homogenization effected at 540° C. for four hours. It is further observed that compounds containing magnesium are scattered. The above-mentioned transformations help increase the toughness of the joint structure and increase the strength of the whole joint against breaking by tensile force or shearing force such as through applied internal pressure.
It was confirmed that the above transformation can also be obtained in the same way as described above even when the homogenization is effected after the joint has been brazed but while the joint is being cooled, or even when the homogenization is effected after the joint which has been brazed is cooled near to room temperature and is heated again under appropriate conditions. This invention can be further understood by reference to the examples set forth below.
EXAMPLES
Heat exchangers of the plate-fin structure shown in FIG. 5 were produced by flux brazing or fluxless brazing in accordance with the method of the present invention. High pressure was applied thereinto to carry out bursting test. In FIG. 5, reference numeral 1 denotes brazing sheets, 2 denotes fins, 3 denotes a brazing material, 4 denotes spacer bars, and 5 denotes test paths. As for the flux brazing, a brazing material JIS-BA 4047 was used in combination with various aluminum alloy fin materials which had not been treated with heat. As for the fluxless brazing, a brazing material JIS-BA 4004 was used in combination with various aluminum alloy fin materials which had not been treated with heat.
The test results were as shown in Table 1. When the method of the present invention was put into practice, the ultimate strength at the brazed joints of fins was increased by 45% to 114% compared with the case when the method of the present invention was not put into practice. Owing to this improvement, there were obtained brazed joints of fins of a strength higher than the ultimate strength of fins.
TABLE 1__________________________________________________________________________ Pressure forBrazingBrazing Base metal Heat-treating burst Brokenmethodmaterial (fin material) condition test sample portion Remarks__________________________________________________________________________Flux 4047 1100 none 320 kg/cm.sup.2 (G) fins joint strengthBrazing not confirmed 500° C. × 1 Hr 326 " joint strength not confirmed 570° C. × 24 Hr 319 " joint strength not confirmed 3003 none 362 fins 500° C. × 1 Hr 383 " joint strength not confirmed 570° C. × 24 Hr 370 " joint strength not confirmed 3004 none 355 joints 500° C. × 1 Hr 508 fins joint strength not confirmed 570° C. × 24 Hr 515 " joint strength not confirmed 5005 none 267 joints 500° C. × 1 Hr 416 " 570° C. × 24 Hr 430 "Fluxless4004 1100 none 292 kg/cm.sup.2 (G) jointsBrazing 500° C. × 1 Hr 320 fins joint strength not confirmed 570° C. × 24 Hr 325 " joint strength not confirmed 3003 none 314 joints 500° C. × 1 Hr 383 fins joint strength not confirmed 570° C. × 24 Hr 381 " joint strength not confirmed 3004 none 344 joints 500° C. × 1 Hr 500 " 570° C. × 24 Hr 528 fins joint strength not confirmed 5005 none 190 joints 500° C. × 1 Hr 399 " 570° C. × 24 Hr 407 "__________________________________________________________________________
As demonstrated above, the present invention offers many effects as described below.
That is, even in the case of large structures in which the brazing is effected under severe conditions and brazed joints of sufficiently large size are not obtained, the method of the present invention makes it possible to increase the strength of joints to meet the purposes. Further, it has been considered that sufficiently strong brazed joints are not obtained with the materials which contain magnesium. By adopting the method of the present invention, however, the strength of brazed joints can be increased to meet the purposes.
With the brazing materials of the Al-Si-Mg type, furthermore, the joints tended to become brittle since magnesium is left in the brazed joints. By adopting the method of the present invention, however, the strength of the joints can be increased to meet the purposes.
According to the present invention, it is possible to produce a heat exchanger made of an aluminum alloy of the plate-fin structure that can withstand the internal pressure of as great as 500 kg/cm 2 (G), for the first time, relying upon the fluxless brazing method using a brazing material of the Al-Si-Mg type.
ng a brazing material of the Al-Si-Mg type. | A brazing method is disclosed which provides superior strength in the brazed joint formed. The brazed structure is subjected to a heat treatment after brazing, which improves the strength of the joint even if Magnesium compounds are employed. |
FIELD OF THE INVENTION
The present invention relates to “active implantable medical devices” as defined by the Jun. 20, 1990 Directive 90/385/CEE of the Council of the European Communities.
BACKGROUND OF THE INVENTION
The invention more particularly concerns the family of apparatuses that deliver to the core pulses of high energy (i.e., pulses notably exceeding the energy provided for simple stimulation) to try to put an end to a tachyarrhythmia. These devices are called “implantable defibrillators” or “implantable cardiovertors,” it being understood that the invention also covers implantable defibrillators/cardiovertors or defibrillators/cardiovertors/stimulators.
“Implantable defibrillator” or “implantable cardiovertor” devices have two principal parts—a pulse generator, and a probe or a system of probes. The pulse generator monitors cardiac activity and generates high energy pulses when the heart presents a ventricular arrhythmia that is deemed susceptible to being treated. When the high energy is comprised between approximately 0.1 and 10 J, the therapy is referred to as “cardioversion” and the electric shock is called “cardioversion shock.” When the high energy is greater than approximately than 10 J, the therapy is called defibrillation and the electric shock is called “defibrillation shock.” The pulse generator is connected to one or more probes comprising electrodes whose role is to distribute this energy to the core in a suitable way.
The present invention relates to the particular case where the generator is connected to a “mono-body” probe, that is a single probe carrying the various electrodes making it possible to deliver shocks of defibrillation or cardioversion. The shock electrodes appear as windings of wire supported by a distal tubular extremity of the probe and are intended to come into contact with cardiac tissues at the place where the cardioversion or defibrillation energy must be applied. The windings are connected to a conducting wire traversing the length of the probe.
Mono-body probes generally comprise two shock electrodes: a first electrode, known as “supraventricular,” which will be positioned in the high vena cava to apply the shock to the atrium; and a second electrode, a ventricular one, which will be located more closely to the distal extremity of the probe.
The mono-body probes are generally of the “isodiameter” type, i.e., they have the same diameter over the entire length of the distal part intended to be implanted in the venous network. This facilitates implantation, as well as any later explantation. This means that the external surface of the windings forming the shock electrodes is flush with the external surface of the probe, so as not to present any change in diameter along the implanted length of the probe.
The manufacturing of these mono-body probes is relatively delicate, taking into account the presence of the windings, the requirements for continuity of probe diameter, and the need for carrying the electric connection inside the body of the probe with the electrical conductor allowing delivery of the shock energy.
The technique employed until now to manufacture these probes consists of taking a plurality of tubular sections of encasable sheath, one after another, setting up the windings, and electrically connecting them progressively to their internal conductor at the various sections of the tube of the probe. This structure, which makes it possible to answer the specific constraints associated with manufacturing these probes, has, however, the disadvantage of creating zones and/or electric weaknesses at the places where the various sections are connected, in particular short-circuits on the high voltage conductor supplying the shock energy. However, in practice, it has been noted that the ruptures of the insulated tube support often occur at the places of the connections between the various sections of sheath, because of the zones of weakness locally created at the place of these connections. Moreover, this structure of encased sections implies a relatively complex and long manufacturing process, in particular because of the need for sticking the successive sections together. U.S. Pat. No. 6,374,142 and PCT Application No. WO-A-02/087689 describe such mono-body isodiameter probes produced starting from encased successive sections of sheath.
OBJECTS AND SUMMARY OF THE INVENTION
One of the goals of the present invention is to cure the above-described disadvantages by proposing another structure for the distal part of a mono-body defibrillation probe—a structure that does not present a zone of weakness in the vicinity of the windings and can be manufactured simply and quickly.
The probe of the invention is a mono-body defibrillation probe of the known type described above, i.e., with a probe body that includes at its distal extremity an insulated sheath core of a tubular flexible material, supporting at its periphery at least one winding of wire forming a shock electrode for application of a defibrillation or cardioversion energy, this winding being electrically connected to an electrical conductor extending longitudinally in an internal lumen inside the sheath core.
In a manner characteristic of the invention, the sheath core extends axially without solution of continuity (i.e., without interruption) in the area(s) supporting the winding(s).
Very advantageously, the sheath core locally comprises a crossing cavity located in the vicinity of at least one of the winding ends. It is envisaged moreover that an insert of conducting material, of a size homologous with the aforesaid cavity, is placed therein, with this insert being electrically connected, on the interior side, with the electrical conductor and, on the external side, with the corresponding extremity of the winding.
In particular, the sheath core can comprise a cavity in the vicinity of each extremity of the winding, and it then comprises also a crossing longitudinal slit connecting the two cavities and radially extending from the external surface of the sheath core to the internal lumen thereof, so as to allow, by elastic strain of the material of the sheath core on both sides of the slit, the introduction into the cavities and the internal lumen of the unit formed by the final extremity of the electrical conductor provided beforehand with the two inserts to which it was mechanically and electrically connected.
In one embodiment of the invention, it is envisaged to have junction ring for mechanical and electric connection of the insert to the winding, this ring being a cylindrical ring of conducting material, with an internal surface able to cooperate with a part turned towards the outside of the insert, and an external surface comprising a connection part able to cooperate with a part turned towards the interior of the extremity of the winding. This ring can in particular comprise, in the area of internal surface able to cooperate with the insert, an assembly part capable of allowing mechanical and electric solidarization from the ring to the insert. The assembly part is preferably a part comprising a crossing opening able to allow solidarization of the ring to the insert by welding from the outside. Moreover, the diameter of the assembly part is greater than the diameter of the connection part, the difference of the diameters being approximately equal to double the thickness of the winding, so that the external surface of the ring is approximately level with the external surface of the winding.
Preferably, the probe is provided with an external envelope made of a flexible insulated material sheathing the sheath core along its length, except for the area of the winding, with the diameter of the external envelope being approximately equal to the diameter of winding. In this case, the ring can also comprise, at the opposite side of the connection part, a shafting part receiving the extremity of the external envelope adjacent to the winding. For the assembly, the insert can comprise, on the interior side, a sleeve, axially oriented, for crimping the insert to the electrical wire. Preferably both the space included between the radial walls of the slit and the internal volume of the lumen in the area of the slit are provided with an electrically insulated sealing material, such as polymeric resin that is hardenable, e.g., an adhesive silicone.
BRIEF DESCRIPTION OF THE DRAWINGS
Further benefits, features, and characteristics of the present invention will become apparent to a person of ordinary skill in the art in view of the following detailed description of a preferred embodiment of the invention, made with reference to the annexed drawings, in which like reference characters refer to like elements, and in which:
FIG. 1 is an overall view of a mono-body defibrillation probe according to the present invention;
FIG. 2 is an enlarged perspective view, of the proximal extremity of the tubular sheath, at the place where the sheath terminates to widen and be divided into a plurality of conductors connected to a connector;
FIG. 3 is a perspective view showing the sheath core and the elements that will be there inserted to later allow connection to the defibrillation winding; and
FIG. 4 is a detailed cross-section of the part of the probe at the place of the defibrillation winding, showing the various internal elements and the way that the electric connection with the winding is carried out.
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1 , reference 10 indicates generally a mono-body probe of which the distal extremity 12 is intended to be introduced by the venous network into the two atrial and ventricular cavities, so as to detect there cardiac activity and apply as needed a defibrillation or cardioversion shock. The probe is provided at its proximal extremity 14 with various elements for connection to an appropriate generator, e.g., a generator of the Defender or Alto or Ovatio type manufactured by the assignee hereof, ELA Medical, Montrouge, France.
Probe 10 carries a first shock electrode 16 , intended to be placed in the right ventricle and constituting, e.g., the negative terminal for application of the potential voltage of defibrillation or cardioversion. This ventricular shock electrode 16 is connected by a connection conductor 18 on a connection terminal 20 to the generator, advantageously a terminal of the DF-1 standard type.
Probe 10 also carries at its distal part 12 a second shock electrode 22 , which is known as a “supra-ventricular” an electrode, intended to be positioned in the high vena cava for application of a shock to the atrium. This supra-ventricular shock electrode 22 is connected by connection conductor 24 on connection terminal 26 to the generator, preferably also with a DF-1 standard connector.
Probe 10 is also equipped with an extremity electrode 28 , which is a detection/stimulation electrode intended to be positioned at the bottom of the right ventricular cavity. This electrode 28 is connected by a conductor 30 on a connection terminal 32 to the pacemaker, advantageously with an IS-1 connector standard.
As shown in FIG. 4 , conductor 30 is a hollow conductor, e.g., a conductor internally wound, having in its center a lumen 34 that allows introduction of a stylet for the guidance of distal extremity 12 by a physician into the venous network at the time of implantation of the probe 10 .
Referring again to FIG. 1 , the defibrillation potential can be applied between the supra-ventricular shock electrode 22 and the generator case, or between the ventricular shock electrode 16 and the generator case, or between electrodes 16 and 22 , in a bipolar mode.
The configuration just described (i.e., two defibrillation electrodes and one stimulation electrode) is, however, not restrictive, and the invention is also applicable to the case of a probe equipped with only one defibrillation electrode winding, or not including a distal stimulation electrode, or including two stimulation electrodes (for a stimulation in bipolar mode, in particular), etc.
FIGS. 2 and 4 more precisely show the configuration of three conductors 18 , 24 , and 30 in the distal tubular extremity 12 of the probe 10 . These conductors are placed in respective lumens of a tubular sheath core 36 made out of a flexible insulated material such as a silicone. The conductors 18 and 24 , which must transmit the defibrillation or cardioversion energy, are micro-cables having their own insulators, respectively 38 and 40, e.g., in ETFE. The silicone material constituting the sheath core 36 presents excellent properties of fatigue strength. Regardless, it would be difficult to make the sheath core 36 penetrate in the venous network just as it is, and for this reason the sheath core is wrapped outside by a sheath 42 made out of a material with low coefficient of friction, e.g., polyurethane.
The present invention relates more particularly to the way in which the probe 10 is constructed/assembled in the vicinity of the shock electrode windings 16 and 22 . FIGS. 3 and 4 illustrate a preferred structure for the ventricular shock electrode winding 16 . Because this structure is the same supraventricular shock electrode winding 22 , the structure for that winding will not be further described in detail.
In a way characteristic of the invention, the sheath core 36 is a solid tube, without solution of continuity over the entire length of the distal part 12 , in particular in the area of the windings 16 and 22 . This is due to a particular structure of the electric connection system between the winding and its corresponding conductor located inside the sheath core 36 .
Thus, as illustrated in FIGS. 3 and 4 , conductor 18 , intended to feed the winding 16 , is equipped with two metal parts 46 , 46 ′ which function as inserts, solidarized mechanically, and electrically connected, with the conductor 18 by setting of (sliding) sleeves 48 , 48 ′ over a stripped length emerging from insulator 38 .
It is indeed desirable to have an electric connection of conductor 18 with the two ends of winding 16 , in order to produce the most homogeneous possible electric field between these two ends at the time of application of the defibrillation or cardioversion energy. If the winding is fed by its two ends, the current density will be better distributed, thus avoiding the risk of burning the surrounding tissues. For a defibrillation shock that can require application of energy of up to 40 joules, the peak voltage can reach 750 V. For this voltage, the homogeneity of the electric field at the time of the shock is a significant constraint to take into account when designing the probe.
As illustrated in FIG. 3 , the sheath core 36 comprises two cavities 50 , 50 ′, which extend from the external surface of the sheath core to the lumen 44 ( FIG. 4 ) receiving conductor 18 . These two cavities 50 , 50 ′ are joined together by a longitudinal slit 52 ( FIG. 3 ), which extends along the sheath core 36 and radially from the external surface of the sheath core to the lumen 44 ( FIG. 4 ) receiving conductor 18 . The interior dimensions of these cavities 50 , 50 ′ are homologous with the external dimensions of inserts 46 , 46 ′, so that the inserts can be entirely placed into the cavities, with their upper surface 54 ( FIG. 4 ) being level with the upper surface 56 of the sheath core 36 . On the interior side, the lower face 58 of insert 46 preferably rests on the surface 60 of the lumen 44 .
The electric and mechanical connection of inserts 46 , 46 ′, and thus of conductor 18 , with winding 16 , is carried out via junction rings 62 , 62 ′. The junction ring 62 presents a central part 64 , from which interior surface 66 comes in contact with the upper surface 54 of insert 46 . The external surface 68 of the central part 64 has a diameter roughly equal to the external diameter of winding 16 and the external diameter of the polyurethane sheath 42 ; based on that, the external surface 70 of the sheath is level with the external surface 68 of the ring, thus ensuring the required isodiameter configuration. On the side that is farthest from the winding 16 , ring 62 comprises a part of lesser diameter 72 intended to fix with force (friction force fit) in the interior extremity of the external sheath 42 . On the side that is closest to the winding, the ring 62 comprises a part of lesser diameter 74 intended to fix with force in the interior extremity of winding 16 .
To ensure the electric and mechanical solidarization of insert 46 to the connection ring of 62 (and thus winding 16 ), the central part 64 of the ring is equipped with an opening 76 , making it possible to carry out from the outside welding point 78 (like that illustrated on the right FIG. 4 ), preferably a laser welding point.
Lastly, under winding 16 , the remaining space around conductor 18 and around the various contiguous elements is filled with an electrically insulated sealing material, e.g., a setting polymeric resin, such as a resin silicone.
One now will describe the manner of carrying out such a probe structure with a mechanical continuity of the sheath core 36 in the area supporting the electrode.
First of all, the sheath core 36 is prepared with its external sheath 42 only in the proximal area of the probe, i.e., on the left part of FIG. 4 . This external sheath thus stops in the vicinity of cavity 50 on the proximal end of the probe 16 , i.e., toward the left in FIGS. 3 and 4 . Separately (e.g., on another preparation setup) insulator 38 of conductor 18 is stripped on its distal side over an adaptable length, to crimp there two contact blocks 46 , 46 ′ at a desired distance, by means of sleeves 48 , 48 ′. The unit obtained is illustrated partly on the top portion of FIG. 3 . Conductor 18 is then threaded by its proximal extremity (i.e., the one opposed to the contact blocks 46 , 46 ′) into lumen 44 via opening 50 of the sheath core 36 , while letting exceed on the distal side the free part with the inserts 46 , 46 ′. The set formed by this length of wire with the inserts 46 , 46 ′ is then completely introduced inside the sheath core 36 , by placing two inserts 46 , 46 ′ in the two homologous cavities 50 , 50 ′, with the part of conductor 18 connecting these two inserts being introduced by elastic deformation of sheath core material on both sides of slit 52 . Once the unit is thus introduced, sleeves 48 , 48 ′ and conductor 18 find their place inside lumen 44 and the two lips of slit 52 can thus regain their initial shape. The unit is maintained tightly in place with a local injection, via slit 52 , of a resin silicone mass (reference number 80 on FIG. 4 ), which thus comes to fill lumen 44 at the place of slit 52 and cavities 50 , 50 ′, with a tight obturation of lumen 44 on both sides of the unit thus made up.
The following stages consist of, successively:
1. slipping on the ring 62 , 2. fixing the ring 62 in the part of external sheath 42 located on the proximal side of the probe (on the left on FIG. 4 ); 3. slipping on the winding 16 ; 4. fixing the proximal extremity of the winding on the ring 62 ; 5. slipping on the ring 62 ′; 6. fixing the ring 62 on the distal extremity of the winding 16 ; 7. slipping the sheath 42 ′ on the distal side of the probe; and 8. fixing on the ring 62 ′.
The unit is thus mechanically assembled. The operation is repeated identically for the other winding. Laser welding points 78 make it possible to perform the electric and mechanical connection of the rings 62 , 62 ′ on the one hand to the ends of winding 16 (in zone 74 ), and on the other hand to the respective inserts 46 , 46 ′.
One skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation. | A probe including at its distal extremity a tubular flexible sheath core supporting at least a winding forming a shock electrode and connected to a electrical conductor of connection extending in a internal lumen of the sheath core. The sheath core extends axially without a solution of continuity in the area supporting the winding. In particular, the sheath core comprises cavities to receive and hold conducting inserts, of homologous size with cavities formed locally close to the ends of the winding, the insert being connected to the interior side to the electrical conductor, and on the external side to the corresponding extremity of winding. A longitudinal slit connects the two cavities and allows, by elastic deformation of the sheath core, the introduction into the cavities and in the internal lumen of the unit formed by the final extremity of the electrical conductor beforehand equipped with its two inserts. |
RELATED APPLICATIONS
This patent application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/373,143, filed Apr. 17, 2002, the entire contents of which are hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a container which provides for incremental withdrawal of tubular plastic. More particularly, the present invention is directed to such a container which incorporates in or on the container housing and/or the enclosed tubular plastic a composition having malodor-counteractant activity.
2. Description of the Related Art
Many items in life are associated with smells generally found to be unpleasant to the olfactory sense (“malodor”). The fact is that the disposal of these items in everyday life can be a hassle. For example, babies generate a significant number of feces/urine-laden diapers which due to the smell require frequent trips to the outside garbage can. Likewise, certain foods, like meats and fish, generate smells within a few days of being placed into a kitchen trash receptacle often requiring the emptying of the kitchen trash receptacle long before it is filled with trash. Similarly, pets such as cats generate considerable amounts of excrement-laden litter that often require more frequent trips to the outside garbage receptacle than would otherwise be necessary.
Malodors are frequently comprised of amines, thiols, sulfides, short chain aliphatic and olefinic acids, aldehydes and esters. For example, indole, skatole, and methanethiol are found in toilet odors, perpidine and morpholine in urine, and pyridine and triethyl amine in garbage odors, such as fish.
Most trash receptacles are fitted with a lid designed to contain odors when the lid is closed. However, most lids are not designed to be perfectly air-tight in respect of their receptacles, or after repeated use become less-than air tight, permitting malodor to emanate from the receptacles even when they are closed. Even with the most air-tight containers, upon opening the container, the noxious odors escape into the area giving an extremely unpleasant sensation to the person attempting to add more trash to the receptacle. Location of the receptacles in a remote location is inconvenient and generally unsatisfactory.
Another problem with trash receptacles is that they tend to retain noxious odors even after the trash is ultimately removed. After a period of time a thorough and complete cleaning of such receptacles is necessary.
Several approaches have been used to counteract malodors. The simplest of these techniques involves inhibition of the formation of the malodor itself, by for example exposing the otherwise odorous material to antimicrobials and enzyme inhibitors. A more common technique, however, is masking which is performed by superimposing a stronger pleasant odor over a malodor. Suppression of malodor may also be effectuated by exposing an odorous material to a compound that causes a negative deviation of Raoult's law. In another technique, cross-adaptation, the sensation of the malodor is impaired by blocking malodor olfactory receptors. Malodor may also be eliminated by exposing the malodor to a compound that either reacts with the malodor components to form non-odorous products, or that absorbs or adsorbs, as for example in a molecular porous or cage-like structure, the malodor.
Numerous compounds, which range from non-descript plant extracts to single and multiple chemical entities, have been touted to reduce the sensory perception of malodors. For example, U.S. Pat. No. 3,077,457 to Kulka discloses fumaric acid esters as malodor counteractants, while U.S. Pat. No. 4,187,251 to Kulka discloses esters of alpha-, beta-unsaturated monocarboxylic acids as malodor counteractants. U.S. Pat. No. 3,923,005 to Fry et al. discloses the use of chlorophyll to remove the smell from used cat litter, while U.S. Pat. No. 4,989,727 discloses a malodor counteractant consisting of deodorizing ingredients extracted from plants and is said to be useful for a wide variety of smells, including sulfur and nitrogen compound odors. Other compounds disclosed to be useful as malodor counteractants include water-soluble organic polymers having an average molecular weight of at least 100,000 (U.S. Pat. No. 4,909,986 to Kobayashi et al.), a mixture of an acid anhydride with a copper compound (U.S. Pat. No. 4,959,207 to Calhoun), a,Ω-alkanedicarboxylic acids and moncarboxylic acid esters of oligoglycerols (U.S. Pat. No. 5,718,887 to Wolf et al.—useful in reducing body odor), betacyclodextrin (U.S. Pat. No. 5,534,165 to Pilosof et al.), and undecylenic acid and its derivatives. U.S. Pat. Nos. 4,009,253, 4,187,251, 4,310,512, 4,622,221 to Schleppnik disclose the use of 4-cyclohexyl-4-methyl-2-pentanone, alkyl cyclohexyl alkyl ketones, acetic and propionic acids, and cyclohexyl alkyl ketones, respectively, as malodor counteractants. WO 02/051788A1 (PCT/CH01/0076) discloses certain aromatic unsaturated carboxylic esters wherein the unsaturation is conjugated to both the aromatic ring and the carbonyl group portion of the carboxylic ester to be useful in the a malodor counteractants.
A particularly difficult trash to retain for ultimate disposal is diapers. Diapers are typically stored and accumulated in a container. The cumulative odor of diapers being stored within the container frequently reaches such an offensive level that the diapers must be disposed of before the container is full. The latter leads to a large use of container liners such as bags, and excessive emptying operations. Excessive emptying operation can be of particular concern as one hesitates to leave the infant unattended or to carry the infant and the soiled diapers to a remote location. A further problem associated with such containers is that the containers themselves over time tend to retain the malodor even when no diapers are present in the containers. Therefore a thorough and complete cleaning of such containers is often necessary to reduce the lingering odor. Further, as many diaper disposal receptacles are not child-proof, toddlers playing around the container may inadvertently open the container to allow odors to escape or the child may reach in to touch solid diapers.
Numerous receptacles have been proposed for temporarily holding diaper waste. These receptacles typically employ one of several approaches to reduce the emanation of malodor from the receptacle, which may be characterized as the use of making agents, odor sorbent material, inner lids or seals, air locks or sealed packaging.
The scented diaper pail has been commercially available for many years. Scent is added to the diaper pail in the hope of hiding the smell of the malodor by producing a smell that masks the malodor to the olfactory senses. The problem with such pails is that the masking smell itself can often become irritating to the consumer, as well as the fact that most scented diaper pails loose their masking effect after a period of time.
An odor sorbent effect relies on chemical absorption or adsorption or of accumulated odors or chemical association between the malodor and the sorbent material. An example of such approach is set forth in U.S. Pat. No. 5,174,462 to Hames which uses an activated charcoal adsorber mounted in a perforated holder beneath the container lid to adsorb malodors while the lid is closed. U.S. Pat. No. 2,411,430 to Hodson shows a diaper container including an odor absorbing material attached to a lid portion of the container. In U.S. Pat. Nos. 5,022,553 and 5,158,199 to Pontius, there is disclosed a diaper container for temporarily storing soiled diapers prior to final disposal that employs a liner comprising a pad of non-woven synthetic fibers impregnated with an odor absorbing material, such as activated carbon. U.S. Pat. No. 5,147,055 discloses a container that includes an outer lid and an interior flap carrying an activated charcoal filter to retain and absorb the odors within the container.
Receptacles employing inner lids or seals typically position the inner lid or seal between the conventional container pail and an outer lid in order to reduce leakage of odors when the outer lid is closed and/or to minimize the time during which the user is exposed to malodors accumulated in the pail while adding more waste. For example, U.S. Pat. No. 4,427,110 to Shaw Jr. includes a canister and seal insert having a plurality of slits intersecting centrically to provide flexible, sliced pie-shaped sectors adapted to be flexed downward into the canister base. The top has a handle with a deodorizer and has a frusto-conical plunger adapted to flex the sectors of insert downward so as to permit a soiled diaper to be deposited trough the sectors into the canister.
The air lock approach includes a lid that covers a first chamber, a transfer mechanism, and a second chamber for finally receiving the waste. After depositing waste into the first chamber, the user closes the lid and then actuates a transfer mechanism to transfer the waste material from the first chamber to the second chamber. For example, U.S. Pat. Nos. 5,535,913 and 5,655,680 to Asbach et al. describe a diaper pail with a constrictor located under the lid. Operation of the pail involves opening the lid, depositing the waste into the holding chamber, and closing the lid. The constrictor is then opened allowing the waste to fall from the holding chamber into the storage chamber. Finally, the constrictor is closed to prepare the pail for the next deposit of waste. Therefore, malodors from the second chamber are never directly exposed to the outside environment. Other examples of this approach are disclosed in U.S. Pat. No. 1,226,634 to Briese, U.S. Pat. No. 1,239,427 to Bunnel & Gates, and U.S. Pat. No. 1,265,148 to Warren.
The sealed packaging approach requires a mechanism for sealing a waste in a liner bag attached to the disposal receptacle. An example of such device is the Turn N Seal Diaper Pail sold by Safety 1.sup.st (which also incorporates an inner lid). The pail has a mechanism for twisting closed the neck of a plastic liner bag used to hold the soiled diapers. U.S. Pat. No. 5,125,526 to Sumanis discloses a garbage pail in which the bag is secured to a rotatably mounted holder inside the pail, the top of the bag fastened in place so that rotation of the holder opens and closes the neck of the bag by twisting it. U.S. Pat. Nos. 6,370,847 and 6,516,588 to Jensen et al. which discloses a disposal system employing heat-sealing members moved between an open position and a closed/sealed position by either twisting an inner lid, closing the lid, or moving an activation arm. The sealing member thermally-fuse the tubing to form a sealed package containing the diaper. Individual sealed packaging may also be employed, as for example shown in U.S. Pat. Nos. 4,869,049 and 5,590,512 to Richards et al., U.S. Pat. Nos. 5,813,200 and 6,170,240 to Jacoby et al., U.S. Pat. No. 6,128,890 to Firth, U.S. patent application Ser. No. 10/138,058 (Pub. No. US2002/0162304A1, published Nov. 7, 2002) in which a container has an inner storage chamber accessed via a closable lid and an intermediate tubular core. In the Richards' individual packaging receptacle embodiment a replaceable cassette houses flexible tubing surrounding a core. While not limited thereby, an example of a representative cassette is shown in U.S. Pat. No. 4,934,529 to Richards et al. As would be understood by one of ordinary skill in the art, other cassette constructs, such as shown in U.S. Pat. No. 3,536,192 to Couper, may be employed. The flexible tubing is dispensed from the cassette. The length of flexible tubing is stored along side the core with a closed end disposed at the lower end of the core. After a diaper is deposited into the tube, the core is rotated, which twists the flexible tube to create a seal above the diaper. To dispose the next diaper the user opens the lid and inserts the diaper. The previous seal is pushed downward, and a new seal is formed by twisting the tube above the newly deposited diaper. Thus the device stores the diapers in a series of individually wrapped packages in the storage chamber, each package being separated from adjacent packages by twists in the tube.
While trash retention receptacles of the past that are conventionally stored within buildings, such as diaper retention receptacles, have employed numerous methods for reducing malodor emanating therefrom, prior art trash retention receptacles have not been found effective enough to please many users of the receptacles. Furthermore many proposed receptacles have been found not to be economically practical. For example, while certain receptacles employing masking agents or odor sorbents are initially quite efficacious in malodor counteractant activity, such agents and odor sorbents typically fail after periods of time due to exposure to the ambient environment. Replacement of the masking agent or odor sorbent is typically difficult, and the need for replacement occurs in an un-anticipatable manner and without warning. Receptacles that do not employ masking agents or odor sorbents typically do not provide malodor abatement for significant periods of time, particularly as air locks and inner lids tend either fail ab initio or over time to effectuate a hermetic seal, and the materials comprising the devices which employ air locks, inner lids, and/or package sealing mechanisms alone often become contaminated with malodors themselves.
There is a need for an improved apparatus for temporarily storing waste before ultimate disposal, in particular waste such as diapers contaminated with fecal material and urine. Preferably such devices would provide malodor abatement using masking agents and/or sorbents in a manner such that the activity of the masking agents and/or sorbents is not quickly degraded by ambient conditions. Furthermore, preferred devices would provide for periodic replacement of the sorbents and/or masking agents used in the device without an unanticipated recognition of the need to replace the same, and without unanticipated failure. Lastly, a preferred device should be designed to efficiently mitigate malodor without adding great expense.
SUMMARY OF THE INVENTION
The present invention overcomes many of the problems associated with prior art temporary waste storage receptacles by providing enhanced malodor mitigation by way of incorporating malodor counteractants into or on a replaceable cassette that houses tubular flexible plastic for use in sealed packaging and individual sealed packaging apparatuses. Such construct may provide significantly enhanced protection against the emission of malodors from the waste receptacle, and overcomes the problem of determining when the malodor counteractant needs to be replaced by associating an amount of malodor counteractant sufficient to counteract malodor release with the amount of tubing enclosed within the cassette. That is, new malodor counteractant is added to the temporary waste storage receptacle each time the cassette is replaced, i.e. when the tubing runs out. In particular there is provided an improved cassette for storing flexible tubing packed therein in layered form, wherein the improvement comprises a malodor counteractant incorporated into or on said cassette.
In one embodiment there is provided a container holding a supply of plastic, tubular stock for the incremental withdrawal of portions thereof, said container comprising a malodor counteractant which is preferably selected from the group consisting of a malodor adsorbing compound, a malodor absorbing compound, a masking agent, an cage compound (a compound that holds a malodorous compound or element within a molecular cage of the compound). The malodor counteractant may be microencapsulated.
In another embodiment, there is provided a cassette for use in dispensing flexible tubing packed therein in layered form, the cassette comprising a rigid body formed by a central tubular core open at top and bottom, a surrounding casing wall positioned to provide a space between said tubular core and said casing wall and a base wall joining a lower end of said surrounding casing wall to the lower end of said tubular core, a length of flexible tubing packed profusely in a tightly layered mass in said space to constitute a pack surrounding said tubular core, and a cap placed over a portion of said pack, said cassette comprising a malodor counteractant. Again the malodor counteractant may be selected from the group consisting of a malodor adsorbing compound, a malodor absorbing compound, a masking agent, a cage compound. The cap of such cassette may be adjoined to said central tubular core or to said casing wall, or less preferably to the base. The malodor counteractant may be found in or on said central tubular core, surrounding casing wall, the base wall, the cap, the flexible tubing, or the space between said tubular core and surrounding casing wall. The malodor counteractant may also be placed in a layer deposited on a feature of the cassette selected from the group consisting of: the central tubular core, the casing wall, the base wall, the cap, the flexible tubing, the space between the tubular core and surrounding casing wall. In one embodiment the malodor counteractant is microencapsulated.
In yet another embodiment there is provided a cassette for use in dispensing flexible tubing packed therein in layered form, the cassette comprising a rigid body formed by a central tubular core open at top and bottom, a surrounding casing wall positioned to provide a space between the tubular core and the casing wall and a base wall joining a lower end of the surrounding casing wall to the lower end of the tubular core, a length of flexible tubing packed profusely in a tightly layered mass in the space to constitute a pack surrounding the tubular core, a cap placed over a portion of the pack, and a layer on the surface of the cassette comprising an encapsulated malodor counteractant.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and advantages thereof will be more readily apparent by reference to the detailed description of the preferred embodiments when considered in connection with the accompanying figures, wherein:
FIG. 1A is a first embodiment cassette for storing tubular flexible plastic having a gasket containing one or more malodor counteractants.
FIG. 1B is a second embodiment cassette for storing tubular flexible plastic having a gasket containing one or more malodor counteractants in microencapsulations.
FIG. 2 is a cross-sectional view of an exemplary individual sealed packing device of the prior art.
DETAILED DESCRIPTION OF THE INVENTION
There is provided in one embodiment of the present invention malodor counteractant stored in or on the material comprising the tubular flexible plastic storage cassette. The material for example may be stored in or on the casing wall of the cassette, any annular cap that may exist on the cassette, on or in the tubular flexible plastic stored in the cassette, or in or on the tubular core. As would be understood by one of ordinary skill in the art, whether deposition of the malodor counteractant is preferably made within the material comprising the cassette, or on such material, may depend on the ability of the malodor counteractant to effectuate its activity when incorporated into the material comprising the cassette and its ability to withstand the molding temperatures.
In another embodiment of the present invention, the malodor counteract is stored in a gasket or layer attached to the cassette housing, preferably on a top or bottom portion of the cassette. The gasket or layer should be composed of a material that easily adsorbs or absorbs the malodor counteractant, or which easily incorporates the malodor counteractant, and which allows substantial release of the malodor counteractant over time.
In yet another embodiment of the present invention, the malodor counteractant is housed in a slow-release film, and the encapsulated malodor counteractant is applied to a portion of the cassette. The film may react with ambient conditions (such as moisture in the air) to provide for slow release of the malodor counteractant. In another preferred embodiment the encapsulation is of the type that will break when friction is encountered. In such embodiment, it is preferred that the encapsulated malodor counteractant be placed in a position of the cassette which will be exposed to friction when the cassette is turned in operation of the sealed packaging and individual sealed packaging apparatus, for example the bottom portion of the cassette. Thus as the cassette is turned a portion of the encapsulates will break releasing a fresh quantity of malodor counteractant.
Slow release films of the malodor counteractants and microencapsulation of the malodor counteractants may be produced by any of the methods known to those of ordinary skill in the art. For example, U.S. Pat. No. 3,655,129 to Seiner discloses various coatable films which have entrapped within their polymeric matrix minute droplets of a liquid non-solvent, such droplets which may comprise fragrances and deodorants. U.S. Pat. No. 4,898,633 to Doree et al. discloses articles comprising a thermoplastic substrate bearing rupturable microcapsules in a binder on at least one surface thereof. U.S. Pat. No. 4,254,179 teaches a method for impregnating a porous foam product with a fragrance which is released over an extended period of time. The encapsulated particles of fragrance are preferably frangible so that the external forces break the capsules to release the fragrance. Many other processes exist for manufacturing microcapsules including those described in U.S. Pat. Nos. 3,516,846, 3,516,941, 3,778,383, 4,087,376, 4,089,802, 4,100,103, and 4,251,386 as well as British Patent Specification Nos. 1,156,725, 2,041,319 and 2,048,206. As would be understood by one of ordinary skill in the art, the most advantageous technique to produce the microencapsulated malodor counteractant would depend on the chemical characteristics of the particular malodor counteractant selected for encapsulation.
In yet another embodiment, the malodor counteractant is stored in a dispensing housing through which the tubular flexible plastic courses, such that a measured amount of malodor counteractant is released each time a measured amount of tubular flexible plastic is dispensed from the cassette. The malodor counteractant may be released onto the tubular flexible plastic, or may be released into the ambient environment.
According to yet another embodiment of the invention, the malodor counteractant is incorporated into or on the tubular flexible plastic stored in the cassette itself. Packages formed using the tubular flexible plastic stored in the cassette in many cases provide unexpectedly good malodor reduction capacity when compared to packages comprising the same tubular flexible plastic which is not dispensed from the cassette. The latter may be due to the fact that the malodor counteractants are not exposed to the ambient environment as long as their non-housed counterparts, thus they are not exposed as long to components of the ambient environment (such as moisture) which may diminish the activity of the malodor counteractant. Furthermore, the latter may be due to fact that enclosure of the counteractant-treated tubular flexible plastic in a relatively sealed environment reduces the rate at which volatile malodor counteractants volatilize into the atmosphere.
Individual packaging may be performed by incorporating twists in the flexible tubular plastic above and below a waste quantum, or by sealing above and below the waste quantum by other methods such as by thermo-sealing, or by incorporating mechanical methods of attachment, such as hook and loop technology, at points along the tubular flexible plastic to allow for sealing at such points.
The optimal malodor counteractant for any particular cassette will vary according to the materials that are to be stored in the temporary waste storage receptacle as well as the material into which the counteractant is placed or attached to. Examples of malodor counteractants that could be employed in the cassette include fumaric acid esters as disclosed, for example, in U.S. Pat. No. 3,077,457 to Kulka, alpha-, beta-unsaturated monocarboxylic acids, as disclosed, for example, in U.S. Pat. No. 4,187,251 to Kulka, chlorophyll, a mixture of an acid anhydride with a copper compound as disclosed, for example, in U.S. Pat. No. 4,959,207 to Calhoun, a,Ω-alkanedicarboxylic acids and moncarboxylic acid esters of oligoglycerols as disclosed, for example, in U.S. Pat. No. 5,718,887 to Wolf et al., beta-cyclodextrin as disclosed, for example, in U.S. Pat. No. 5,534,165 to Pilosof et al., aromatic unsaturated carboxylic esters wherein the unsaturation is conjugated to both the aromatic ring and the carbonyl group portion of the carboxylic ester as disclosed, for example, in WO 02/051788A1 (PCT/CH01/0076), a composition of fragrance materials as set forth, for example, in European Patent Application No. 0-404470, undecylenic acid and its derivatives, 4-cyclohexyl-4-methyl-2-pentanone, alkyl cyclohexyl alkyl ketones, acetic and propionic acids, and cyclohexyl alkyl ketones, as disclosed, for example in U.S. Pat. Nos. 4,009,253, 4,187,251, 4,310,512, and 4,622,221 to Schleppnik.
Now turning to the figures, there is seen in FIG. 1A a cassette embodiment of the present invention, cassette [ 40 ], for dispensing flexible tubular plastic which may find employment in a individual seal packaging system of the type described by Richards et al. Flexible tubular plastic [ 44 ] is stored between tubular core [ 46 ], casing wall [ 42 ] and cassette bottom [ 52 ]. Tubing [ 44 ] is dispensed through gap [ 50 ] to produce dispensed tubing [ 58 ] which exists the cassette [ 38 ] through opening [ 60 ]. Cassette [ 40 ] of such embodiment includes an annular cap [ 48 ] which acts as a retaining cover to help retain tubing [ 44 ]. Annular cap [ 48 ] is shown in FIG. 1A to be attached to casing wall [ 42 ]. Annular cap [ 48 ] may be affixed to the body of the cassette by detent means [ 56 ]. Cassette [ 38 ] in such embodiment includes a gasket or layer [ 54 ] which comprises in or on the gasket/layer malodor counteractant.
Now turning to FIG. 1B , there is shown another cassette embodiment of the present invention, cassette [ 64 ] which may also be used for dispensing flexible tubular plastic and which may find employment in a individual seal packaging system of the type described by Richards et al. As in the cassette [ 40 ] embodiment of FIG. 1A , flexible tubular plastic [ 44 ] is stored between tubular core [ 46 ], casing wall [ 42 ], and bottom [ 52 ]. Tubing [ 44 ] is likewise dispensed through gap [ 50 ] to produce dispensed tubing [ 58 ] which exists the cassette [ 64 ] through opening [ 60 ]. Cassette [ 64 ] of such embodiment, however, includes an annular cap [ 48 ], which acts as a retaining cover to help retain tubing [ 44 ], but which is attached to tubular core [ 46 ]. Annular cap [ 48 ] is affixed to the tubular core [ 46 ] by detent means [ 56 ]. Cassette [ 64 ] in such embodiment includes a gasket or layer [ 54 ] which comprises in or on the gasket/layer malodor counteractant that is microencapsulated [ 62 ] allowing for controlled release of the malodor counteractant.
FIG. 2 illustrates an exemplary embodiment of an individual sealed packing system of the prior art [ 10 ] in which cassettes of the present invention may be employed. The device [ 10 ] comprises a substantially cylindrical container [ 12 ] having a removable cover [ 14 ] at the top of the cylindrical container [ 12 ] and an access door [ 18 ] at the bottom of the cylindrical container [ 12 ]. The removable cover [ 14 ] has an opening covered by a hinged lid [ 20 ]. A ring-shaped flange [ 22 ] is located inside the cylindrical container [ 12 ], and a tubular core [ 24 ] rests on the flange [ 22 ]. Continuous length flexible tubing [ 26 ] is stored within the tubular core [ 24 ]. A twist rim [ 28 ] is rotatably coupled to the tubular core [ 24 ]. Rotating the twist rim [ 28 ] twists the flexible tubing [ 26 ].
A plurality of retention springs [ 30 ] are attached to the flange [ 22 ]. The retention springs [ 30 ] hold a waste package [ 32 ] within the flexible tubing [ 26 ] stationary while the twist rim [ 28 ] rotates to twist the flexible tubing [ 26 ] and seal the end of the waste package [ 32 ]. An aperture in the twist rim [ 28 ] preferably contains a clear plastic panel. In one preferred embodiment of the present invention, the twist rim [ 28 ] incorporates a cutting device [ 36 ] to sever the flexible tubing [ 26 ] when the cylindrical container [ 12 ] is filled.
The cover [ 14 ] is removably attached to the cylindrical container [ 12 ]. When the cover [ 14 ] is removed, an end of the flexible tubing [ 26 ] can be removed from the roll of flexible tubing [ 26 ] contained within the tubular core [ 24 ] and knotted. This knot of flexible tubing [ 26 ] is then placed into the cylindrical container [ 12 ] through the flange [ 22 ] toward the bottom of the cylindrical container [ 12 ] and forms a bag for storing waste packages [ 32 ]. Waste packages [ 32 ] are placed into the bag formed by flexible tubing [ 26 ], and the flexible tubing [ 26 ], together with the waste package [ 32 ], is held stationary by the plurality of retention springs [ 30 ] inside of the cylindrical container [ 12 ] coupled to the flange [ 22 ].
Throughout this specification, the word “comprise” or variations such as “comprises” or “comprising” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
STATEMENT REGARDING PREFERRED EMBODIMENTS
While the invention has been described with respect to preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications can be made to the invention without departing from the spirit or scope of the invention as defined by the appended claims. All documents cited herein are incorporated in their entirety herein. | A container holding a supply of plastic, tubular stock for the incremental withdrawal of portions thereof, said container comprising a malodor counteractant. |
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 11/323,031 entitled “Thermoset Nanocomposite Particles, Processing For Their Production, And Their Use In Oil And Natural Gas Drilling Applications”, filed Dec. 30, 2005, which claims priority to U.S. Provisional Application No. 60/640,965 filed Dec. 30, 2004. This application is also a continuation-in-part of U.S. patent application Ser. No. 11/451,697 entitled “Thermoset Particles With Enhanced Crosslinking, Processing For Their Production, And Their Use In Oil And Natural Gas Drilling Applications”, filed Jun. 13, 2006. The contents of prior application Ser. Nos. 11/323,031, 11/451,697 and 60/640,965 are fully incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for the fracture stimulation of a subterranean formation having a wellbore by using impact-modified ultralightweight thermoset polymer nanocomposite particles as proppants. Without reducing the generality of the invention, in its currently preferred embodiments, the thermoset polymer matrix of said particles comprises a terpolymer of styrene, ethyvinylbenzene and divinylbenzene; carbon black is used as the nano filler, suspension polymerization in the rapid rate polymerization mode is performed to prepare said particles, and post-polymerization heat treatment is performed in an unreactive gas environment to further advance the curing of the thermoset polymer matrix. One main benefit of the incorporation of impact modifier(s) is to enable the use of larger quantities of crosslinker, nano filler, or combinations thereof, in the formulation from which the particles are prepared; thus achieving higher maximum use temperatures, higher fracture conductivities throughout the use temperature range, or combinations thereof, without inducing brittleness in the particles. The fracture stimulation method of the invention can be implemented by placing said particles in the fracture either as a packed mass or as a partial monolayer. Without reducing the generality of the invention, said particles are placed as a partial monolayer in its preferred embodiments.
BACKGROUND
1. Introduction
[0003] U.S. Pat. No. 6,248,838, “Chain entanglement crosslinked proppants and related uses”; the background section of U.S. patent application Ser. No. 11/323,031 entitled “Thermoset nanocomposite particles, processing for their production, and their use in oil and natural gas drilling applications”; and the background section of U.S. patent application Ser. No. 11/451,697 entitled “Thermoset particles with enhanced crosslinking, processing for their production, and their use in oil and natural gas drilling applications”, provide background information related to the present invention and are fully incorporated herein by reference. The background discussion below is intended to supplement the background discussions in these three prior filings, and focuses entirely on impact modification.
[0004] Impact modification has only been given limited and cursory consideration in prior art on fracture stimulation. U.S. Patent Application No. 20040043906 cited impact modifiers among the types of additives that can be incorporated into polymeric proppants in order to control their mechanical properties. U.S. Patent Application No. 20060078682 disclosed particles for use as proppants, where the particles comprise a substrate comprising an inorganic material, and an organic coating (disposed upon the substrate) which may optionally contain impact modifiers intended mainly to impart elastic properties to the organic coating. U.S. Pat. Nos. 5,597,784 and 6,372,678, and U.S. patent application Nos. 20050194141 and 20070036977, disclosed fracture stimulation technologies utilizing coated proppants comprising more than one coating layer, where a “reinforcing agent” may be interspersed at the boundary between different layers of the coating, and impact modifiers may serve as reinforcing agents.
[0005] Applicant has, however, found no prior art in the patent literature, and no publications in the general scientific literature, that disclose a method for the fracture stimulation of a subterranean formation having a wellbore by using impact-modified ultralightweight thermoset polymer nanocomposite particles as proppants. The discussion below is hence intended to be mainly of a pedagogical nature, by providing background information that will help those in the field understand the invention better by familiarizing them with key information related to impact modification. Since the preferred embodiments of the invention involve the use of thermoset nanocomposite particles having styrenic polymer matrices, this description of information related to impact modification will be done in the context of the impact modification of styrenic polymers.
2. Types of Impact-Modified Styrenic Polymers
[0006] High-impact polystyrene (HIPS) is the most commonly used impact-modified styrenic polymer. Copolymers of styrene with other suitable vinylic monomers (such as other styrenic monomers, acrylic monomers, nitrile monomers, monomers containing ion exchange capable functional groups, etc.) have also been toughened. Crosslinked versions of many of these styrenic polymers, with divinylbenzene being the most commonly used crosslinking agent, have also been toughened. Macroporous styrenic beads of various compositions (sometimes crosslinked with divinylbenzene) have also been toughened. See Conway et al. (1997) for the toughening of porous aminated crosslinked poly(vinylbenzyl chloride—divinylbenzene) beads. See Coelho et al. (2000) and World Patent No. WO9607675 for the toughening of copolymers that have been crosslinked with divinylbenzene. U.S. Pat. No. 5,847,054 teaches a method for the preparation of crosslinked styrenic polymer particles containing an impact modifier, for use as additives intended to increase the “dullness” (reduce the glossiness, make more matte) and/or enhance the impact strengths of thermoplastic and thermoset polymers when incorporated into them. U.S. application No. 20050154083 teaches styrenic particle compositions (possibly crosslinked to a slight extent by using a small amount of a comonomer such as divinylbenzene, and possibly also containing an impact modifier) encapsulating high aspect ratio particles; and intended to be used as pigments which, when incorporated into any of a very wide variety of matrix polymers, will impart attractive optical properties to those matrix polymers.
[0007] Syndiotactic polystyrene (a highly crystalline form of polystyrene that has especially high stiffness and heat resistance, but that is even more brittle than ordinary general-purpose polystyrene) has also been toughened (U.S. Pat. No. 5,352,727 and U.S. Pat. No. 5,436,397) by incorporating impact modifiers.
[0008] Styrenic polymers containing fillers of a wide variety of types (ranging from nanoparticles to macroscopic fibers) have also been toughened. The fillers in these polymers provide functions such as reinforcement, densification and/or magnetism (as in World Patent No. WO9607675 which teaches a method for producing toughened crosslinked copolymer beads that may contain solid magnetic particles). There is some evidence that improved dispersion of solid particulate fillers can be obtained if a dispersing agent that reacts to form covalent bonds with (and thus becomes grafted onto) the matrix polymer is used.
[0009] Thermoplastic polymer blends with improved impact resistance have been obtained by mixing toughened styrenic polymers with other thermoplastic polymers of interest by techniques such as melt blending.
[0010] Toughened styrenic polymers have also been incorporated as additives in other polymers to impart some special properties to the host polymer.
[0011] While impact-modified styrenic polymers have been used in many industrial applications, applicant does not believe that these applications include the use of impact-modified styrenic polymers as proppants in the fracture stimulation of a subterranean formation having a wellbore.
[0012] Nor is applicant aware of any patented or reported methods for the fracture stimulation of a subterranean formation having a wellbore by using impact-modified ultralightweight thermoset polymer nanocomposite particles based on any other type of polymeric matrix material as proppants.
[0013] 3. Improvements Resulting from Impact Modification
[0014] Rubber modification is the most common method for the impact modification of styrenic polymers. It has provided up to several times higher notched Izod impact strength and much higher ductility (as quantified by the ultimate tensile elongation); without large losses in the stiffness (elastic moduli), strength, gloss, or heat distortion temperature. Increasing effectiveness of impact modification in improving the mechanical properties has been shown to correlate with increasing energy dissipation by the deformation of the rubbery phase (as quantified by its “tan 6” peak) during dynamic mechanical analysis under cyclic deformation.
[0015] See Turley and Keskkula (1980), Choi et al. (2000), Coelho et al. (2000), Aiamsen et al. (2003), Qiao-long et al. (2005), Rivera et al. (2006), U.S. Pat. No. 5,352,727, U.S. Pat. No. 5,436,397 and European Patent No. EP0475461 for some examples of the effects of rubber modification on the mechanical properties. Toyoshima et al. (1997) provide an example of the optimization of the balance between the impact strength and gloss by means of the choice of impact modifier. U.S. Pat. No. 5,475,053 teaches impact-resistant thermoplastic (including HIPS) molding compositions having a matte surface. Cho et al. (1997) show that the environmental stress cracking resistance in the simultaneous presence of a hostile chemical environment along with a mechanical load can also be improved by rubber modification.
4. Rubbers Used as Impact Modifiers for Styrenic Polymers
[0016] Many types of rubbers can be and have been used as tougheners for styrenic polymers, with varying levels of effectiveness in improving the properties, practicality of manufacturing, and economic viability in terms of the balance between improved properties and increased cost.
[0017] Polybutadiene (dissolved in the reactive monomer mixture after being placed there in a solid particulate form) is the rubbery phase that is most often incorporated as a toughener into polystyrene in order to manufacture HIPS.
[0018] Hydroxyl-terminated polybutadiene liquid rubbers have also been used. Their liquid state allows their easy incorporation (with grafting) into polystyrene, with a controlled particle size, during polymerization. See Coelho et al. (2000) for this approach.
[0019] The effects of using polybutadienes of different chain microstructure (different cis-1,4, trans-1,4, and vinyl-1,2 isomer contents) have also been investigated. For example, it has been shown by Rivera et al. (2006) that some polybutadiene microstructures provide noticeably more favorable balances between impact modification and the other mechanical properties.
[0020] Natural rubber, poly(alkyl acrylate) rubbers, partially or completely hydrogenated diene rubbers, and olefinic rubbers, are some other examples of rubbers that have been used as impact modifiers. For example, see Aiamsen et al. (2003) for the use of radiation-crosslinked natural rubber, Qiao-long et al. (2005) for the use of nanosilica-containing poly(butadiene styrene) rubber, European Patent No. EP0475461 for the use of a selectively partially hydrogenated polybutadiene, and U.S. Pat. No. 5,847,054 for the use of olefinic rubbers.
[0021] It is also worth noting that some of the terms that may be used for the different types of rubbers overlap. Sometimes, they may refer to the same type of molecular structure obtained in different ways. For example, a completely hydrogenated polybutadiene or a completely hydrogenated polyisoprene has the same general type of molecular structure as a polyolefin. Both are fully saturated aliphatic hydrocarbons. The difference is that one is obtained by polymerizing butadiene or isoprene and hydrogenating the resulting polymer; while the other is obtained directly by reacting olefinic monomers such as ethylene, propylene and/or 1-butene.
[0022] Various block copolymers (such as styrene-butadiene or styrene-isoprene diblock and styrene-butadiene-styrene or styrene-isoprene-styrene triblock copolymers and their partially hydrogenated versions) have been used either as impact modifiers on their own or as compatibilizers between polystyrene and an impact modifier such as polybutadiene. For some examples, see Conway et al. (1997), Cho et al. (1997), Toyoshima et al. (1997) and Aiamsen et al. (2003). A method using block copolymers as impact modifiers incorporated into crosslinked styrenic polymer particles is taught in U.S. Pat. No. 5,847,054. Impact-modified syndiotactic polystyrene compositions containing block copolymers are taught by U.S. Pat. No. 5,352,727 and U.S. Pat. No. 5,436,397; while U.S. Pat. No. 5,380,798, U.S. Pat. No. 5,475,053 and World Patent No. WO9607675 teach some other examples of the use of block copolymers as impact modifiers for styrenic polymers.
[0023] The rubbers used in the impact modification of styrenic polymers include both thermoset elastomers and thermoplastic elastomers. Thermoset elastomers (usually more simply referred to as “rubbers”), such as crosslinked polybutadiene and crosslinked polyisoprene, have a covalently crosslinked three-dimensional network structure, but possess a low glass transition temperature [below “room temperature” (25° C.)]. Thermoplastic elastomers, such as styrene-butadiene diblock copolymers and styrene-butadiene-styrene triblock copolymers, contain soft domains that are “physically crosslinked” by hard domains, while they lack a covalently crosslinked three-dimensional network structure. Both thermoset elastomers and thermoplastic elastomers are used simultaneously in some formulations for the impact modification of styrenic polymers. An example is the use of a crosslinked polybutadiene as the main component of the impact modifier, along with some thermoplastic styrene-butadiene diblock copolymer that serves mainly as a compatibilizer between the styrenic phase domains and the polybutadiene phase domains.
[0024] If there is a significant reactivity difference between the styrenic monomer(s) and the other type(s) of monomer(s) present in a reactive mixture, then there is a tendency towards the formation of a heterogeneous morphology [with domains rich in the styrenic polymer and domains rich in the product(s) of the polymerization of the other type(s) of monomer(s)] even when the reaction is started with a mixture of monomers rather than incorporating the non-styrenic component in an oligomeric or polymeric form. See, for example, Lu and Larock (2006). This article also illustrates the utilization of a renewable resource (corn oil) as a source of monomers for use in the preparation of polymer composites. The growing use of renewable resources as feedstocks will be discussed further in the next paragraph.
[0025] A background paper on biopolymers, published by the U. S. Congress, Office of Technology Assessment (September 1993), suggested that the use of biologically derived polymers could emerge as an important component of a new paradigm of sustainable economic systems that rely on renewable sources of energy and materials. This concept has, indeed, gained increasing acceptance in the years that followed the publication of the background paper. The utilization of monomers obtained from biological starting materials (such as amino acids, nucleotides, sugars, phenols, natural fats, oils, and fatty acids) in the chemical synthesis of polymers is an important component of this paradigm of sustainable development. This is an area of intense research and development activity because of the global drive to reduce the dependence of the world economy on petrochemical feedstocks. Such renewable feedstocks can be obtained from a wide variety of microorganism-based, plant-based, or animal-based resources. The utilization of monomers, oligomers and polymers obtained from renewable resources as components of polymer composites is, therefore, anticipated to continue to increase in the future. Among renewable feedstocks for the synthesis of polymeric products, natural fats and oils extracted from some common types of plants [such as soybean, sunflower, canola, castor, olive, peanut, cashew nut, pumpkin seed, rapeseed, corn, rice, sesame, cottonseed, palm, coconut, safflower, linseed (also known as flaxseed), hemp, castor bean, tall oil, and similar natural fats and oils; and especially soybean, sunflower, canola and linseed oils] appear to be very promising as potential sources of inexpensive monomers. Some animal-based natural fats and oils, such as fish oil, lard, neatsfoot oil and tallow oil, may also hold promise as potential sources of inexpensive monomers. U.S. patent application No. 20050154221 teaches integrated chemical processes for the industrial utilization of seed oil feedstock compositions. An article by Pillai (2000) discusses the wealth of high value polymers that can be produced by using constituents extracted from cashew nut shell liquid. Belcher et al. (2002) show that the blending of functionalized soybean oil with petrochemical-based resins can increase the toughness of a petroleum-based thermoset resin without compromising stiffness, while also improving its environmental friendliness.
5. Methods for Manufacturing Impact-Modified Styrenic Polymers
[0026] In toughening styrenic polymers by incorporating polybutadiene, the most common preparation method is bulk-suspension copolymerization. In applying this method, a prepolymer is first prepared by using bulk polymerization. The preparation of HIPS in the form of beads (or pellets) is then completed via suspension polymerization. It is, however, also possible to use bulk polymerization by itself, or (as taught, for example, in U.S. Pat. No. 4,730,027) suspension polymerization by itself from the beginning to the end to prepare HIPS.
[0027] Batch polymerization is most commonly used, but methods (such as the one taught in U.S. patent application No. 20030083450) are available for continuous polymerization.
[0028] When suspension polymerization is used (either by itself or after bulk polymerization), substantially spherical polymer beads of a wide variety of desired diameters can be produced by varying the process parameters (and especially the stirring rate).
[0029] The details of the formulation and processing conditions play crucial roles in determining the extent of grafting, as well as the size distribution and morphology of the rubbery domains. For example, the stirring (shear) rate is a process variable that has been used to control the dispersed rubbery domain size. Faster stirring normally results in smaller rubbery domain sizes. The effects of processing conditions on the morphologies of heterophasic polymeric materials (including toughened polymers and toughened polymeric composites) have been discussed by Bicerano (2002) in terms of the interplay between thermodynamic and kinetic factors.
[0030] One usually obtains thermoplastic pellets of HIPS with most of the approaches that are practiced since there is no crosslinker in the typical HIPS formulation. These thermoplastic HIPS pellets can then be melted for processing via techniques such as molding or extrusion into fabricated articles of desired shapes and sizes.
6. Optimum Incorporation of Impact Modifiers in Styrenic Polymers
[0031] There is an optimum incorporated rubber particle size. This size depends upon various factors. It typically ranges from 1 to 3 microns in diameter. See Toyoshima et al. (1997), Bicerano (2002) and Aiamsen et al. (2003) for discussions of the effects of rubber particle size.
[0032] The use of 5% to 15% by weight of polybutadiene (with 7% by weight being viewed as an optimum value by some experts) is the most common approach. However, the rubbery phase volume fraction in HIPS is typically much higher than the weight fraction of the rubber since the rubbery phase domains also normally contain a lot of occluded polystyrene. For further discussions of the optimum rubber weight fraction and/or rubbery phase volume fraction, see Turley and Keskkula (1980), Cho et al. (1997), Choi et al. (2000) and Aiamsen et al. (2003).
[0033] In general, much better impact modification is obtained if the rubbery material becomes covalently bonded to (grafted onto) the styrenic polymer chains during preparation rather than just being physically blended into the polymer. See Cho et al. (1997), Choi et al. (2000), Qiao-long et al. (2005) and Rivera et al. (2006) for examples of this effect. This is why suspension polymerization techniques, which lead to the grafting of an impact modifier containing one or more reactive functionalities onto the matrix polymer, are normally preferred to approaches such as the melt blending of a rubber into polystyrene.
[0034] A reactive impact modifier can be incorporated into the formulation as a monomer, as an oligomer, or as a polymer. The use of a reactive oligomer or polymer as the impact modifier can cause the mixing of the impact modifier into the formulation to become more difficult than the use of a monomeric impact modifier of similar chemical structure, especially if the reactive oligomer or polymer is a solid. However, once a reactive oligomer or polymer impact modifier is mixed adequately with the other components of the formulation, this approach may offer the advantage of the more facile attainment of a heterophasic morphology where the impact modifier is present in phase-separated domains that provide an optimum toughening effect with the least possible reductions of other important properties such as stiffness (modulus) and strength.
SUMMARY OF THE INVENTION
1. Introduction
[0035] The present invention relates to a method for the fracture stimulation of a subterranean formation having a wellbore by using impact-modified ultralightweight thermoset polymer nanocomposite particles as proppants.
[0036] The main ingredients of the particles are the thermoset polymer matrix (Section 2), the nanofiller which provides reinforcement (Section 3), and the impact modifier (Section 4).
[0037] Additional formulation ingredient(s) may also be used during the preparation of the particles; such as, but not limited to, initiators, catalysts, inhibitors, dispersants, stabilizers, rheology modifiers, buffers, antioxidants, defoamers, plasticizers, pigments, flame retardants, smoke retardants, or mixtures thereof. Some of these additional ingredient(s) may also become either partially or completely incorporated into the particles.
[0038] The particles are manufactured by suspension polymerization (Section 5) and postcured by heat treatment (Section 6) before being used in fracture stimulation (Section 7).
2. Matrix Polymer
[0039] Any rigid thermoset polymer may be used as the matrix polymer. Rigid thermoset polymers are, in general, amorphous polymers where covalent crosslinks provide a three-dimensional network. However, unlike thermoset elastomers (often referred to as “rubbers”) which also possess a three-dimensional network of covalent crosslinks, the rigid thermosets are, by definition, “stiff”. In other words, they have high elastic moduli at “room temperature” (25° C.), and often up to much higher temperatures, because their combinations of chain segment stiffness and crosslink density result in a high glass transition temperature.
[0040] For the purposes of this disclosure, a rigid thermoset polymer is defined as a thermoset polymer whose glass transition temperature, as measured by differential scanning calorimetry at a heating rate of 10° C./minute, equals or exceeds 45° C. The gradual softening of an amorphous polymer with increasing temperature accelerates as the temperature approaches the glass transition temperature. As discussed by Bicerano (2002), the rapid decline of the stiffness of an amorphous polymer (as quantified by its elastic moduli) with a further increase in temperature normally begins at roughly 20° C. below its glass transition temperature. Consequently, at 25° C., an amorphous polymer whose glass transition temperature equals or exceeds 45° C. will be below the temperature range at which its elastic moduli begin a rapid decline with a further increase in temperature, so that it will be rigid.
[0041] Some examples of rigid thermoset polymers that can be used as matrix materials in the nanocomposite particles utilized as proppants in implementing the fracture stimulation method of the invention will be provided below. It is to be understood that these examples are provided without reducing the generality of the invention, to facilitate the teaching of the invention.
[0042] Commonly used rigid thermoset polymers include, but are not limited to, crosslinked epoxies, epoxy vinyl esters, polyesters, phenolics, melamine-based resins, polyurethanes, and polyureas. Rigid thermoset polymers that are used less often because of their high cost despite their exceptional performance include, but are not limited to, crosslinked polyimides. For use in proppant particles suitable for different embodiments of the fracture stimulation method of the invention, these various types of polymers can be prepared by starting from their monomers, from oligomers that are often referred to as “prepolymers”, or from combinations thereof.
[0043] Many additional types of rigid thermoset polymers can also be used. Such polymers include, but are not limited to, various families of crosslinked copolymers prepared most often by the polymerization of vinylic monomers, of vinylidene monomers, or of mixtures thereof.
[0044] The “vinyl fragment” is commonly defined as the CH 2 =CH— fragment. So a “vinylic monomer” is a monomer of the general structure CH 2 =CHR where R can be any one of a vast variety of molecular fragments or atoms (other than hydrogen). When a vinylic monomer CH 2 =CHR reacts, it is incorporated into the polymer as the —CH 2 -CHR— repeat unit. Among rigid thermosets built from vinylic monomers, the crosslinked styrenics and crosslinked acrylics are especially familiar to workers in the field. Some other familiar types of vinylic monomers (among others) include the olefins, vinyl alcohols, vinyl esters, and vinyl halides.
[0045] The “vinylidene fragment” is commonly defined as the CH 2 =CR″-fragment. So a “vinylidene monomer” is a monomer of the general structure CH 2 =CR′R″ where R′ and R″ can each be any one of a vast variety of molecular fragments or atoms (other than hydrogen). When a vinylidene monomer CH 2 =CR′R″ reacts, it is incorporated into a polymer as the —CH 2 -CR′R″— repeat unit. Among rigid thermosets built from vinylidene polymers, the crosslinked alkyl acrylics [such as crosslinked poly(methyl methacrylate)] are especially familiar to workers in the field. However, vinylidene monomers similar to each type of vinyl monomer (such as the styrenics, acrylates, olefins, vinyl alcohols, vinyl esters and vinyl halides, among others) can be prepared. One example of particular interest in the context of styrenic monomers is alpha-methyl styrene, a vinylidene-type monomer that differs from styrene (a vinyl-type monomer) by having a methyl (—CH 3 ) group serving as the R″ fragment replacing the hydrogen atom attached to the alpha-carbon.
[0046] Thermosets based on vinylic monomers, vinylidene monomers, or mixtures thereof, are typically prepared by the reaction of a mixture containing one or more non-crosslinking (difunctional) monomer(s) and one or more crosslinking (three or higher functional) monomer(s).
[0047] The following are some specific but non-limiting examples of crosslinking monomers that can be used: Divinylbenzene, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, trimethylolpropane dimethacrylate, trimethylolpropane diacrylate, pentaerythritol tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, pentaerythritol diacrylate, bisphenol-A diglycidyl methacrylate, ethyleneglycol dimethacrylate, ethyleneglycol diacrylate, diethyleneglycol dimethacrylate, diethyleneglycol diacrylate, triethyleneglycol dimethacrylate, and triethyleneglycol diacrylate, a bis(methacrylamide) having the formula:
[0000]
[0000] a bis(acrylamide) having the formula:
[0000]
[0000] a polyolefin having the formula CH 2 =CH-(CH 2 ) x -CH=CH 2 (wherein x ranges from 0 to 100, inclusive), a polyethyleneglycol dimethylacrylate having the formula:
[0000]
[0000] a polyethyleneglycol diacrylate having the formula:
[0000]
[0000] a molecule or a macromolecule containing at least three isocyanate (—N=C=O) groups, a molecule or a macromolecule containing at least three alcohol (—OH) groups, a molecule or a macromolecule containing at least three reactive amine functionalities where a primary amine (—NH 2 ) contributes two to the total number of reactive functionalities while a secondary amine (—NHR—, where R can be any aliphatic or aromatic organic fragment) contributes one to the total number of reactive functionalities; and a molecule or a macromolecule where the total number of reactive functionalities arising from any combination of isocyanate (—N=C=O), alcohol (—OH), primary amine (—NH 2 ) and secondary amine (—NHR—, where R can be any aliphatic or aromatic organic fragment) adds up to at least three, 1,4-divinyloxybutane, divinylsulfone, diallyl phthalate, diallyl acrylamide, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate or mixtures thereof.
[0048] The following are some specific but non-limiting examples of non-crosslinking monomers that can be used: Styrenic monomers, styrene, methylstyrene, ethylstyrene (ethylvinylbenzene), chlorostyrene, chloromethylstyrene, styrenesulfonic acid, t-butoxystyrene, t-butylstyrene, pentylstyrene, alpha-methylstyrene, alpha-methyl-p-pentylstyrene; acrylic and methacrylic monomers, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, diethylene glycol acrylate, diethylene glycol methacrylate, glycerol monoacrylate, glycerol monomethacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, butanediol monoacrylate, butanediol monomethacrylate; unsaturated carboxylic acid monomers, acrylic acid, methacrylic acid; alkyl vinyl ether monomers, methyl vinyl ether, ethyl vinyl ether; vinyl ester monomers, vinyl acetate, vinyl propionate, vinyl butyrate; N-alkyl substituted acrylamides and methacrylamides, N-methylacrylamide, N-methylmethacrylamide, N-ethyl acrylamide, N-ethyl methacrylamide;
[0049] nitrile monomers, acrylonitrile, methacrylonitrile; olefinic monomers, ethylene (H 2 C=CH 2 ) and the alpha-olefins (H 2 C=CHR) where R is any saturated hydrocarbon fragment; vinylic alcohols, vinyl alcohol; vinyl halides, vinyl chloride; vinylidene halides, vinylidene chloride, or mixtures thereof.
3. Nanofiller
[0050] By definition, a nano filler possesses at least one principal axis dimension whose length is less than 0.5 microns (500 nanometers). Some nanofillers possess only one principal axis dimension whose length is less than 0.5 microns. Other nanofillers possess two principal axis dimensions whose lengths are less than 0.5 microns. Yet other nanofillers possess all three principal axis dimensions whose lengths are less than 0.5 microns. Any reinforcing material possessing one nanoscale dimension, two nanoscale dimensions, or three nanoscale dimensions, can be used as the nanofiller. Any mixture of two or more different types of such reinforcing materials can also be used as the nano filler. The nano filler is present in an amount ranging from 0.001 to 60 percent of the total particle by volume.
[0051] Without reducing the generality of the invention, to facilitate the teaching of the invention, we note that nanoscale carbon black, fumed silica, fumed alumina, carbon nanotubes, carbon nanofibers, cellulosic nanofibers, natural and synthetic nanoclays, very finely divided grades of fly ash, the polyhedral oligomeric silsesquioxanes; and clusters of different types of metals, metal alloys, and metal oxides, are some examples of nano fillers that can be incorporated into the nanocomposite particles used as proppants in implementing the fracture stimulation method of the invention. Since the development of nano fillers is an area that is at the frontiers of materials research and development, the future emergence of yet additional types of nano fillers that are not currently known may also be readily anticipated.
4. Impact Modifier
[0052] Thermoset nanocomposite particles possessing greater resistance to heat distortion, greater stiffness, greater environmental resistance, or combinations thereof, can be produced by incorporating larger percentages of crosslinker, nano filler, or combinations thereof, into the formulation. However, increasing the percentages of crosslinker, nanofiller, or combinations thereof, can sometimes result in the embrittlement of the particles. Embrittlement is undesirable for the use of the particles as proppants since it can cause the generation of fines when a closure stress is applied, thus causing a reduction in the flow of liquids or gases through the fracture.
[0053] The impact modifier enables the use of larger quantities of crosslinker, nano filler, or combinations thereof, in the formulation from which the particles are prepared; to achieve higher maximum use temperatures, higher fracture conductivities throughout the use temperature range, or combinations thereof, without inducing brittleness in the particles. Any mixture of two or more different types of impact modifiers may also be used as the impact modifier.
[0054] The impact modifier is present in an amount ranging from 0.1 to 65 weight percent in the mixture of the impact modifier, plus the monomer, oligomer, or combinations thereof that react to form the matrix polymer. It comprises at least one of a monomer, an oligomer or a polymer; obtained or derived from a petrochemical feedstock, a renewable feedstock, or a combination thereof. Some examples will now be provided without reducing the generality of the invention.
[0055] The impact modifier may comprise at least one of a monomer, oligomer or polymer selected from the group consisting of polybutadiene (including its solid and liquid forms, and any of its variants comprising different cis-1,4, trans-1,4, and vinyl-1,2 isomer contents), natural rubber, synthetic polyisoprene, polychloroprene, nitrile rubbers, other diene rubbers, partially or completely hydrogenated versions of any of the diene rubbers, acrylic rubbers, olefinic rubbers, epichlorohydrin rubbers, fluorocarbon rubbers, fluorosilicon rubbers, block and/or graft copolymers prepared from formulations comprising styrenic monomers and diene monomers, partially or completely hydrogenated versions of block and/or graft copolymers prepared from formulations comprising styrenic monomers and diene monomers, silicone rubbers, rubbers containing aliphatic or partially aromatic polyether chain segments, rubbers containing aliphatic or partially aromatic polyester chain segments, rubbers containing aliphatic or partially aromatic polyurethane chain segments, rubbers containing aliphatic or partially aromatic polyurea chain segments, rubbers containing aliphatic or partially aromatic polyamide chain segments, ionomer resins which may be partially or wholly be neutralized with counterions; other rubbery homopolymers, copolymers containing random, block, graft, star, or core-shell morphologies, and mixtures thereof; and the monomeric or oligomeric precursors of any of the cited types of rubbery polymers.
[0056] The impact modifier may, additionally or simultaneously or alternatively, comprise at least one of a monomer, oligomer or polymer obtained or derived from renewable resources selected from the group consisting of soybean, sunflower, canola, castor, olive, peanut, cashew nut, pumpkin seed, rapeseed, corn, rice, sesame, cottonseed, palm, coconut, safflower, linseed, hemp, castor bean, tall oil, fish oil, lard, neatsfoot oil, tallow oil, and similar natural fats and oils.
[0057] Some illustrative examples will now be provided without reducing the generality of the invention. The impact modifier may be polybutadiene. It may be polybutadiene plus a styrene-butadiene diblock copolymer. It may contain an aliphatic polyester component synthesized by using monomers obtained from soybean oil in addition to containing a polybutadiene component. It may consist entirely of an aliphatic polyester that has been synthesized by using monomers obtained from petrochemical feedstocks or from soybean oil. With any of these examples, and the many other embodiments that can be readily imagined by workers skilled in the art, the impact modifier may be added into the formulation as an oligomer, as a polymer, or as a monomer which will react with the other components of the reactive mixture during the manufacture of the particles. It may also be added as any suitable combination of monomers, oligomers and/or polymers.
5. Suspension Polymerization
[0058] Any method for the fabrication of thermoset polymer nanocomposite particles known to those skilled in the art may be used to prepare the particles which are utilized as proppants in implementing the fracture stimulation method of the invention.
[0059] Without reducing the generality of the invention, it is especially practical to use methods that can produce the particles directly in the desired (usually substantially spherical) shape during polymerization from the starting monomers. A substantially spherical particle is defined as a particle having a roundness of at least 0.7 and a sphericity of at least 0.7, as measured by the use of a Krumbien/Sloss chart using the experimental procedure recommended in International Standard ISO 13503-2, “Petroleum and natural gas industries—Completion fluids and materials -Part 2: Measurement of properties of proppants used in hydraulic fracturing and gravel-packing operations” (first edition, 2006), Section 7, for the purposes of this disclosure.
[0060] Without reducing the generality of the invention, it is especially useful to produce the substantially spherical particles discussed in the paragraph above with an average diameter that ranges from 0.1 mm to 4 mm for use in fracture stimulation applications.
[0061] Without reducing the generality of the invention, suspension (droplet) polymerization, where the polymer precursor mixture is dispersed in a suitable liquid medium prior to being polymerized, is currently the most powerful manufacturing method available for accomplishing this objective. In pursuing this approach, it is especially important for the nanofiller particles to be well-dispersed within the liquid medium so that they can become intimately incorporated into the thermoset nanocomposite particles that will be formed upon polymerization.
6. Heat Treatment
[0062] If a suitable post-polymerization process step is applied to the thermoset polymer nanocomposite particles, in many cases the curing reaction will be driven further towards completion so that the maximum possible temperature at which the fracture stimulation method of the invention can be applied by using these particles will increase.
[0063] In some instances, there may also be further benefits of a post-polymerization process step. One such possible additional benefit is an enhancement in the flow of the gases, fluids, or mixtures thereof, produced by the subterranean formation towards the wellbore even at temperatures that are far below the maximum possible application temperature of the fracture stimulation method. Another such possible additional benefit is an increase of such magnitude in the resistance of the particles to aggressive environments as to enhance significantly the potential range of applications of the fracture stimulation method utilizing the particles.
[0064] Processes that may be used to enhance the degree of curing of a thermoset polymer include, but are not limited to, heat treatment (which may be combined with stirring, flow and/or sonication to enhance its effectiveness), electron beam irradiation, and ultraviolet irradiation.
[0065] Without reducing the generality of the invention, we focused mainly on the use of heat treatment as a post-polymerization process step during the manufacturing of the particles. Such heat treatment can be performed in many types of media; including a vacuum, a non-oxidizing gas, a mixture of non-oxidizing gases, a liquid, or a mixture of liquids.
[0066] It is possible, in some instances, to postcure the “as polymerized” particles adequately as a result of the elevated temperature of a downhole environment of a hydrocarbon reservoir during the application of the fracture stimulation method of the invention. However, since it does not allow nearly the same level of consistency and control of particle quality, this “in situ” approach to heat treatment is generally less preferred than the application of heat treatment as a manufacturing process step before using the particles in fracture stimulation.
7. Fracture Stimulation
[0067] The fracture stimulation method of the invention is implemented by using stiff, strong, tough, heat resistant, and environmentally resistant ultralightweight thermoset polymer nanocomposite particles. Such particles may be placed either as a proppant partial monolayer or as a conventional proppant pack (packed mass) in implementations of the invention.
[0068] The optimum mode of particle placement is determined by the details of the specific fracture that needs to be propped. In practice, the use of ultralightweight particles as proppant particles in implementing the fracture stimulation method of the invention provides its greatest advantages in situations where a proppant partial monolayer is the optimum mode of placement. Furthermore, the development of the fracture stimulation method of the invention has resulted in partial monolayers becoming the optimum proppant placement method in many situations where the use of partial monolayers was either impossible or impractical with previous technologies.
[0069] In any case, the method for fracture stimulation comprises (a) forming a slurry comprising a fluid and a proppant, (b) injecting this slurry into the wellbore at sufficiently high rates and pressures such that the formation fails and fractures to accept the slurry, and (c) thus emplacing the proppant in the formation so that it can prop open the fracture network (thereby allowing produced gases, fluids, or mixtures thereof, to flow towards the wellbore).
[0070] The most commonly used measure of proppant performance is the conductivity of liquids and/or gases (depending on the type of hydrocarbon reservoir) through packings of the particles. A minimum liquid conductivity of 100 mDft is often considered as a practical threshold for considering a packing to be useful in propping a fracture that possesses a given closure stress at a given temperature. In order for a fracture stimulation method to have significant practical utility, a static conductivity of at least 100 mDft must be retained for at least 200 hours at a temperature greater than 80° F. It is a common practice in the industry to use the simulated environment of a hydrocarbon reservoir in evaluating the conductivities of packings of particles. The API RP 61 method, described by a publication of the American Petroleum Institute titled “Recommended Practices for Evaluating Short Term Proppant Pack Conductivity” (first edition, Oct. 1, 1989), is currently the commonly accepted testing standard for conductivity testing in the simulated environment of a hydrocarbon reservoir. As of the date of this filing, however, work is underway to develop alternative testing standards, such as International Standard ISO 13503-5, “Petroleum and natural gas industries—Completion fluids and materials—Part 5: Procedures for measuring the long-term conductivity of proppants” (final draft, 2006).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] Details will now be provided on the currently preferred embodiments of the invention. These details will be provided without reducing the generality of the invention. Persons skilled in the art can readily imagine many additional embodiments that fall within the full scope of the invention as taught in the SUMMARY OF THE INVENTION section.
[0072] The fracture stimulation method of the invention is preferably implemented by placing the ultralightweight thermoset polymer nanocomposite particles in the fracture as a partial monolayer. We have found, under standard laboratory test conditions, that the use of particles of narrow size distribution such as 14/16 U.S. mesh size ((diameters in the range of 1.19 to 1.41 millimeters) is more effective than the use of broad particle size distributions. We have also found, under standard laboratory test conditions, that 0.02 lb/ft 2 is an especially preferred level of coverage of the fracture area with a partial mono layer of thermoset nanocomposite particles of sufficient stiffness and strength that possess an absolute density of 1.054. However, real-life downhole conditions in an oilfield may differ significantly from those used under laboratory test conditions. Consequently, in the practical application of the fracture stimulation method of the invention, the use of other particle size distributions, other coverage levels, or combinations thereof, may be more appropriate, depending on the conditions prevailing in the specific downhole environment where the fracture stimulation method of the invention will be applied.
[0073] The thermoset polymer matrix consists of a terpolymer of styrene (S), ethyvinylbenzene (EVB) and divinylbenzene (DVB). The current preference for the use of such terpolymers instead of copolymers of S and DVB is a result of economic considerations related to monomer costs. DVB, which functions as a crosslinker, is present in an amount ranging from 3% to 35% by weight of the reactive monomer mixture of the preferred embodiments.
[0074] Carbon black, possessing a length that is less than 0.5 microns in at least one principal axis direction, is used as the nanofiller at an amount ranging from 0.1% to 15% of the total particle by volume.
[0075] An impact modifier that has one or more reactive functionalities capable of causing the impact modifier to become grafted onto the thermoset polymer matrix is preferred. The impact modifier is incorporated in an amount ranging from 3 to 35 percent by weight in the mixture of the impact modifier, plus the S, EVB and DVB monomers that react to form the matrix polymer. A polymer additive grade of polybutadiene, sold as a solid, is dissolved in the organic phase of the suspension used in the suspension polymerization process, and becomes grafted onto the thermoset polymer matrix as a rubbery phase when polymerization forms the S-EVB-DVB terpolymer matrix. A block copolymer may also be used in some embodiments, usually mainly serving as a compatibilizer between the styrenic matrix and the polybutadiene-rich rubbery domains but sometimes also providing additional impact modification of its own.
[0076] Suspension polymerization in its “rapid rate polymerization” mode is performed to prepare the particles. The most important additional formulation ingredient (besides the reactive monomers and the impact modifier) that is used during polymerization is the initiator. The initiator may consist of one type molecule or a mixture of two or more types of molecules that have the ability to function as initiators. We have found with experience that the “dual initiator” approach, involving the use of two initiators which begin to manifest significant activity at different temperatures, often provides the best results.
[0077] Additional formulation ingredients, such as catalysts, inhibitors, dispersants, stabilizers, rheology modifiers, buffers, antioxidants, defoamers, plasticizers, pigments, flame retardants, smoke retardants, or mixtures thereof, may also be used when needed. Some of the additional formulation ingredient(s) may become either partially or completely incorporated into the particles in some embodiments of the invention.
[0078] The suspension polymerization conditions are selected such that the particles to be used in the fracture stimulation method of the invention are selectively manufactured to have the vast majority of them fall within the 14/40 U.S. mesh size range (diameters in the range of 0.42 to 1.41 millimeters). The particles are sometimes separated into fractions having narrower diameter ranges for use in an optimal manner in proppant partial mono layers.
[0079] Post-polymerization heat treatment in an unreactive gas environment is performed as a manufacturing process step to further advance the curing of the thermoset polymer matrix. This approach works especially well (without adverse effects such as degradation that could occur if an oxidative gaseous environment such as air were used and/or swelling that could occur if a liquid environment were used) in enhancing the curing of the particles. The particles undergo a total exposure to temperatures in the range of 150° C. to 200° C. for a duration of 10 minutes to 90 minutes, inclusive, in an unreactive gas environment. The specific selection of an optimum temperature and duration of heat treatment within these ranges depends on the formulation from which the particles were prepared. Nitrogen is used as the unreactive gas environment.
EXAMPLES
[0080] Some theoretical examples of preferred embodiments of the fracture stimulation method of the invention will now be given, without reducing the generality of the invention, to provide a better understanding of some of the ways in which the invention may be practiced. Workers skilled in the art can readily imagine many other embodiments of the invention with the benefit of this disclosure. Some comparative examples will also be given of embodiments that do not meet a key requirement of the invention and hence are not expected to perform adequately.
Example 1
[0081] The fracture stimulation method of the invention is applied in a situation where it will provide the maximum possible benefit as compared with prior fracture stimulation methods. The downhole environment is one where the use of a proppant partial monolayer would be very effective in the extraction of hydrocarbons from a reservoir but has not been practical previously because of the unavailability of proppant particles of near neutral buoyancy in water along with sufficient stiffness, strength and environmental resistance. The ultralightweight thermoset polymer nanocomposite particles used in implementing the fracture stimulation method of the invention overcome this difficulty. Detailed consideration of the downhole environment results in the determination that 14/16 U.S. mesh size particles would be optimal. Particles in this size range are placed into the fracture as a partial monolayer by using slickwater as the carrier fluid.
[0082] The thermoset polymer matrix of the nanocomposite particles used in this example consists of a terpolymer of styrene (S), ethyvinylbenzene (EVB) and divinylbenzene (DVB). The quantities of these three monomers in the reactive monomer mixture are 68.73% S, 11.27% EVB and 20% DVB by weight. However, the complete polymer also contains 10% of an “impact modifier” grade of polybutadiene by weight in the mixture of the total amount of impact modifier and styrenic monomers. Relative to this total amount, the quantities of the main ingredients of the polymer are 61.86% S, 10.14% EVB, 18% DVB and 10% polybutadiene. In addition, the particle contains 1% by volume of carbon black as a nanofiller. The particles are prepared by rapid rate suspension polymerization. They are then postcured in a nitrogen environment for 20 minutes at a temperature of 185° C.
Example 2
[0083] The same types of particles are used as in Example 1. However, detailed consideration of the downhole environment shows that an the use of the full available 14/40 U.S. mesh size range of the particles will be optimal. Particles in this size range are placed into the fracture by using slickwater as the carrier fluid.
Example 3
[0084] It is determined, by detailed consideration of the downhole environment, that the use of particles in the 16/30 U.S. mesh size and the transport of these particles into the fracture by using slickwater as the carrier fluid will be optimal.
[0085] It is also determined that, since this particular hydrocarbon reservoir is deeper than the one considered in Example 1, the proppant pack will need to be able to withstand both a significantly higher closure stress and a significantly higher temperature than in Example 1. These factors result in the need to use thermoset polymer nanocomposite particles prepared from a formulation containing both a larger amount of crosslinker and a larger amount of nanofiller. The use of a larger total amount of impact modifier, including a compatibilizer, overcomes the increased tendency towards embrittlement resulting from the use of larger quantities of crosslinker and nanofiller. The post-polymerization heat treatment is also applied in a more vigorous manner in order to approach full cure with the formulation used in these particles.
[0086] More specifically, the quantities of the three monomers in the reactive monomer mixture are 53.09% S, 16.91% EVB and 30% DVB by weight. However, the complete polymer also contains 10% of an “impact modifier” grade of polybutadiene plus 3% of a styrene-butadiene diblock copolymer by weight in the mixture of the total amount of impact modifier and the styrenic monomers. The total of the two components of the impact modifier thus amounts to 13% of the total amount of impact modifier and styrenic monomers. Relative to this total amount, the quantities of the main ingredients of the polymer are 46.19% S, 14.71% EVB, 26.10% DVB, 10% polybutadiene, and 3% styrene-butadiene diblock copolymer. In addition, the particle contains 1.5% by volume of carbon black as a nanofiller. The particles are prepared by rapid rate suspension polymerization. They are then postcured in a nitrogen environment for 30 minutes at a temperature of 195° C.
Comparative Example 1
[0087] As in Example 1, except that an impact modifier is not included. The particles are stiff and strong, but brittle. Their brittleness causes them to be inadequate for use in a proppant pack in the implementation of the fracture stimulation method of the invention.
Comparative Example 2
[0088] As in Example 3, except that an impact modifier is not included. The particles are stiff and strong, but brittle. Their brittleness causes them to be inadequate for use in a proppant pack in the implementation of the fracture stimulation method of the invention.
[0089] Finally, it will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims. | A method for fracture stimulation of a subterranean formation includes providing a thermoset polymer nanocomposite particle precursor composition comprising a polymer precursor mixture, dispersed within a liquid medium, containing at least one of an initiator; at least one of a monomer, an oligomer or combinations thereof, said monomer and oligomer having three or more reactive functionalities capable of creating crosslinks between polymer chains; at least one of an impact modifier; and nanofiller particles substantially dispersed within the liquid medium; subjecting the nanocomposite particle precursor composition to suspension polymerizing conditions; subjecting the resulting nanocomposite particles to heat treatment; forming a slurry comprising a fluid and a proppant that includes the heat-treated nanocomposite particles; injecting the slurry into a wellbore; and emplacing the proppant within a fracture network in the formation. |
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to DE 10 2010 041 383.6 filed Sep. 24, 2010 and to DE 10 2011 009 303.6 filed Jan. 24, 2011, the entire contents of each of which are herein incorporated fully by reference.
FIGURE SELECTED FOR PUBLICATION
FIG. 3
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to passive valve for multi-valve devices for sealing a container or a line as well as a multi-valve device for a contamination-free connection of two drums or two lines, in particular having partial valves rotatable about a single axis. More particularly, the present invention provides a passive valve designed to be free of bearing supports protruding positively out of the passive valve.
2. Description of the Related Art
Generic multi-valve devices are employed in the field of contamination-free docking systems for methods and systems for sensitive and/or toxic solids, primarily in the pharmaceutical industry. A double valve technology for use on rigid drums and a flexible half closure for another application to flexible drums have become established as technologies for docking a drum onto a process unit or docking a line onto a drum or docking line onto another line or undocking them therefrom. These drums are also subsumed under the term “container” in this patent application.
Known double-valve or half-valve systems consist of two half valves. Each half valve tightly closes a drum. After docking and the associated operation of connecting to a second half valve, both half valves can then be rotated about a common axis for the transfer of product from a first drum into a second drum. The known systems also typically consist of an active half valve, usually mounted permanently on installations, and a passive half valve, usually mounted on mobile drums. The active half valve can be controlled for rotation while the second half valve is entrained.
One disadvantage of the known double-valve systems is that direct docking of mobile drums with their respective passive half valves onto one another is impossible because in this case there is no control of the rotation. A complex docking mechanism consisting of two active valves mounted back-to-back is necessary in such known systems to be able to implement this, which is encountered frequently.
According to an alternative apparatus known in the art for docking two passive half valves, for example, according to EP 1 947 039 A1, passive half valves are docked by means of a drive ring arranged between the passive half valves and are then opened. Docking of drums onto one another while maintaining zone separation in the docked state of the drums is impossible with such an existing apparatus. The zone separation would be necessary in the case of discharge from an insulated container, for example, or in factories in which the material is conveyed by means of gravity through various floors, for example, where the floors are each assigned to different spatial zones. Zone separation in this sense means that a partition, for example, a ceiling passage, is completely closed between two different zones even when drums and/or process units are not docked there, and thus the zone separation is further ensured.
Further, the drive ring according to EP 1 947 039 A1, the contents of which are incorporated herein by reference, forms an interspace between the passive valves between the zones and is a weak point from the standpoint of freedom from contamination. The interspace may become contaminated and/or may itself contaminate the surroundings as soon as a passive valve is removed. Furthermore, because of the known force induction technology, a half valve made entirely of plastic cannot be implemented for such drive rings having a drive fin. The high required torque, which is input via the drive fin, would deform the half shafts of the passive valves. These half shafts are required as bearing supports after a very short period of time and would thus make them unusable.
However, the demand for half valves made entirely of plastic persists for applications in which the weight of the respective half valve plays a major role and/or in which plastic half valves on plastic containers are even being considered for disposable use. The problems of known multi-valve devices explained above form the basis of the present invention with the goal of overcoming their disadvantages.
These problems are at least partially solved by a passive valve for multi-valve devices for sealing a container or a line as well as a multi-valve device for a contamination-free connection of two drums or two lines, in particular having partial valves rotatable about a single axis, or a passive valve designed to be free of bearing supports protruding positively out of the passive valve.
ASPECTS AND SUMMARY OF THE INVENTION
The present invention relates to a passive valve for multi-valve devices for sealing a container or a line. According to one aspect of the invention, the passive valve is free of bearing supports which protrude in a positive sense out of the passive valve. The present invention also relates to a multi-valve device for contamination-free connection of two containers or two lines with partial valves that can be rotated about a single axis. According to this aspect of the invention, at least three partial valves, which are arranged essentially parallel to one another and can be put under tension so they can be sealed with respect to their surroundings, can be rotated about the single shared axis. Such passive valves also permit an embodiment without a true active valve but instead with a tool that can be inserted between the passive valves.
The present invention is based on the idea of implementing a docking mechanism consisting of three one-third valves or even multiple partial valves, which can be rotated about a single shared axis, instead of implementing a docking mechanism consisting of only two half valves. The third and/or partial valves lie in flat contact with one another, so that no interspaces remain unfilled and can become contaminated or cause contamination themselves. The present invention now presents the use mentioned first in the field of double valves, also known as half valves, depending on the point of view, and opens up previously impossible application areas with a new technology step.
The passive valve for multi-valve devices according to the invention is suitable for sealing a container or a line. The passive valve is arranged in a housing so that it is rotatable about an axis and the housing is in turn tightly connected to the container or the pipe. Corresponding openings in the container or line may also be designed in the housing. In a closed position, the container or the line is sealed around the complete circumference by means of the passive valve. In an open position, the passive valve allows the fluid medium to flow in at least one direction of flow.
According to the invention, the passive valve is designed to be free of bearing supports protruding in a positive sense out of the passive valve. The inventive passive valve does not have any partial shaft journals, such as those which would be necessary with known multi-valve devices. A rotatable receptacle in the housing is proposed, allowing use of other materials, in particular plastic, for the passive valve. Less expensive passive valves have thus been proposed here. The passive valves may be used in conventional dual valve devices and in novel triple valve devices such as those which are also the subject matter of the present patent application.
According to an advantageous embodiment of the passive valve, at least two opposing bearing grooves along the axis are embodied as semicircular curves around the axis. The bearing grooves are recessed in the passive valve in a negative sense.
According to another advantageous embodiment of the passive valve, a longitudinal groove extends along the axis and beyond an interfacial surface of the passive valve that can be turned away from the container or the line. A tool which transfers the rotational motion of the passive valve can be inserted into the longitudinal groove in such a way that conforms to the contour.
According to yet another advantageous embodiment of the passive valve, a countersunk region extending as far as a sealing face which terminates the interfacial surface on the outside radially is arranged centrally in an interfacial area that can be turned away from the container or the line, so that a cavity is formed between the passive valve and another valve. Such a cavity is formed not because of the tool to be inserted but instead is formed between the passive valves which nevertheless seal one another directly with sealing surfaces which run almost completely around the periphery.
In the case of multi-valve devices such as those according to the present invention, a passive partial valve or the passive valve, which corresponds in principle to conventional half valves, is mounted on the drum, the container, the line and/or the process unit.
In one of the inventive multi-valve devices having three valves according to the invention, the interfacial surface of the respective partial valve designed as a passive valve, said interfacial surface being directed outward away from the drum and/or process unit does not extend up to a plane in which the axis is situated, in deviation from known half valves. The respective interfacial surface is set back a few millimeters in parallel with the axis in comparison with a plane aligned perpendicular to the direction of flow. The passive partial valves are referred to below as first and third partial valves.
The first and third partial valves are advantageously each a plate construction having a nominal diameter, which does not extend beyond the nominal diameter comprising a plate support. Each partial valve has a plate that corresponds to a cross section of a pipe to be sealed. In comparison with the conventional half valves according to advantageous embodiments of the invention, the plates of the plate construction do not have a shaft, a shaft journal or pin. The manufacture of the partial valves designed as passive valves can in the meantime be implemented much less expensively than is the case with known passive valves.
According to still another advantageous embodiment of the invention, an additional second partial valve, which is designed as a completely self-sealing active valve that appears to be almost completely traditional, forms part of a drive unit for the entire multi-valve configuration. The respective passive partial valves described above can be docked on the second partial valve from both sides. After docking, all the partial valves may be rotated about the shared axis.
Three or more third valves or partial valves rotating about one axis require bearings for all valves, which must be coordinated very precisely with one another in order to allow a joint rotation. In the docked state, this second partial valve can then maintain the zone separation described in the introduction because of its inherent imperviousness, whereas the drums move in different zones. In the docked position, a transfer of granular product material in the direction of flow, for example, can be implemented, while completely maintaining this zone separation and with no risk of contamination at all, because after the partial valves are closed, the first and/or third partial valves can be undocked from the second partial valve without exposing a contaminated surface. The induction of force to open and close the partial valves always takes place via solid plate surfaces, which readily allows a use of plastics for the first and third partial valves.
Another aspect of the passive valves according to the invention is the secured locking of these valves in the undocked state, so that uncontrolled opening can be prevented reliably. With known systems, this is implemented with metallic locking pins. In order to implement this aspect as simply as possible without using these metallic pins, the present invention provides for a passive housing of the respective passive valve to be designed as a two-component injection molded plastic part, which holds the valve plate in position in the undocked state, as is done with a collet, for example. The core of the passive housing, which is made of a solid plastic and resembles a spreading mandrel, is completely sheathed with an elastomer and thus constitutes a finished sealing housing.
In the docking process, in locking the advantageously designed passive housing to an active housing, the respective passive housing is spread by a conical mating contour in the second partial valve. When the passive housing is spread apart, this exposes the passive partial valve for switching from the closed position to the open position. The required opening torque can therefore be reduced significantly in comparison with conventional valves. The spreading mandrel principle requires an accurate matching of locking force to the undocked partial valves and unlocking force in the docking process in order to ensure reliable functioning.
The three-valve system allows additional interesting applications. For example, only one drum or one process unit can be easily docked, opened and emptied on one side of the second partial valve without product contamination of the outwardly directed surface of the passive valve on the drum or the process unit. Likewise, the active second partial valve may be designed as a washing valve, in which case the second partial valve has integrated washing nozzles, which allow cleaning of third valves in the docked opened state.
In this washing process, either two docked drums or two process units may also be washed together with one another, or just one docked drum or one process unit may be washed if a washing adapter is docked, e.g., as a drain container instead of the third partial valve.
Advantages of the inventive multi-valve device thus include, the possibility of docking drums/process units with only passive partial valves each, while completely retaining the zone separation, as well as the availability of passive partial valves made entirely of plastic due to optimal torque input and the spreading mandrel locking principle. These advantages permit a connection between flexible disposable drums and rigid stainless steel components and a connecting element is created. For the first time, a multi-valve device having passive valves that can be manufactured inexpensively allows docking of mobile drums or lines onto one another, such that the robustness of the valve technology offers advantages with regard to stability. Nevertheless, a passive valve according to the invention may even be considered to be a disposable component because of the simple design and being made entirely of plastic. As a result, highly flexible applications with the option of opening and emptying of a drum/process unit which is merely docked or unit, while retaining the freedom from contamination of the drum/process valve have been developed.
The above and other aspects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
A further understanding of the present invention can be obtained by reference to a preferred embodiment set forth in the illustrations of the accompanying drawings. Although the illustrated preferred embodiment is merely exemplary of methods, structures and compositions for carrying out the present invention, both the organization and method of the invention, in general, together with further objectives and advantages thereof, may be more easily understood by reference to the drawings and the following description. The drawings are not intended to limit the scope of this invention, which is set forth with particularity in the claims as appended or as subsequently amended, but merely to clarify and exemplify the invention.
For a more complete understanding of the present invention, reference is now made to the following drawings in which:
FIG. 1 shows a perspective view of a multi-valve device according to one exemplary embodiment of the present invention with the device in a closed position;
FIG. 2 shows another perspective view of the multi-valve device shown in FIG. 1 but with the device in an open position;
FIG. 3 shows a perspective exploded view of the multi-valve device shown in FIG. 1 ;
FIG. 4 shows an axial section through the multi-valve device in the closed position as shown in FIG. 1 along an axis about which the partial valves can be rotated jointly;
FIG. 5 shows an axial section through the multi-valve device in the open position as shown in FIG. 2 along an axis about which the partial valves can be rotated jointly;
FIG. 6 shows an axial section through the multi-valve device in the closed position as shown in FIG. 1 along a line perpendicular to the axis;
FIG. 7 shows an axial section through the multi-valve device in the open position as shown in FIG. 2 ;
FIG. 8 shows a perspective view of a passive partial valve with a passive housing of the multi-valve device in the open position as shown in FIG. 2 in an exploded diagram without any other partial valves; and
FIG. 9 shows an exploded view of a double-valve device with inventive passive valves similar to the multi-valve device shown in FIG. 3 .
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As required, a detailed illustrative embodiment of the present invention is disclosed herein. However, techniques, systems, compositions and operating structures in accordance with the present invention may be embodied in a wide variety of sizes, shapes, forms and modes, some of which may be quite different from those in the disclosed embodiment. Consequently, the specific structural and functional details disclosed herein are merely representative, yet in that regard, they are deemed to afford the best embodiment for purposes of disclosure and to provide a basis for the claims herein which define the scope of the present invention.
Reference will now be made in detail to several embodiments of the invention that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. For the sake of a better overview, not all reference numerals have been entered into all figures. The drawings are in simplified form and are not to precise scale.
FIGS. 1 through 8 show an exemplary embodiment of an inventive multi-valve device for a contamination-free connection of two drums or two lines. FIG. 8 only shows a passive valve with a passive housing while additional components of the multi-valve device are not shown in FIG. 8 .
FIGS. 1 and 2 show the multi-valve device according to the present invention in different positions. FIG. 1 shows a closed position and FIG. 2 shows an open position. For switching between the closed position and the open position, partial valves 10 , 20 , 30 can be rotated about a single axis A. The axis A is perpendicular to a direction of flow D in which material can be directed from the first drum and/or the first line into the second drum and/or the second line through the multi-valve device when the partial valves 10 , 20 , 30 are rotated into the open position.
The partial valves 10 , 20 , 30 are each arranged in a housing 14 , 24 , 34 so that they are sealed with respect to one another with the interfacial surfaces 15 , 25 , 35 facing one another in a docked position. FIGS. 1 and 2 show such a docked position in a perspective view in which the interfacial surfaces 15 , 25 , 35 have been brought into contact. In contrast with that, FIG. 3 shows an exploded view of the multi-valve device according to the invention in which the partial valves 10 , 20 , 30 are not in contact at their interfacial surfaces 15 , 25 , 35 but instead are arranged at a distance from one another and above one another in the direction of flow D. This is how a position shortly before reaching the docked position may appear.
In the exemplary embodiment of the invention shown here in FIGS. 1 and 2 , three partial valves of the multi-valve device can be brought into contact with one another; these may also be referred to as one-third valves. Of the partial valves 10 , 20 , 30 , a first partial valve 10 and a third partial valve 30 function as passive valves, while a second partial valve 20 functions as an active valve because the second partial valve 20 can be pivoted about the axis A, driven by a drive and rotatably mounted in an active housing 24 . In the docked position, at least one of the passive valves is entrained by the active valve in switching from the closed position to the open position or vice versa. The multi-valve device functions even when only the active valve is docked on a single passive valve, for example, in a cleaning operation. Thus, the second passive valve is needed only in regulating operation when two drums or lines are joined to one another, each being closed with a passive valve.
As seen more clearly in FIGS. 4-7 , the active second partial valve 20 has opposing pins 22 , which are opposite one another as seen along the axis A and are outside of a valve plate, while also being mounted to rotate about the axis A in the active housing 24 . Furthermore, the second partial valve 20 has elevations 21 along the axis A and opposite it in the area of the valve plate, intended for cooperating with interfacial surfaces 15 , 35 of the first and second partial valves 10 , 30 because the passive parts because the passive partial valves 10 , 30 have corresponding recesses 11 , 31 . Such surface topographies of the interfacial surfaces 15 , 25 , 35 ensure that the partial valves 10 , 20 , 30 are centered with one another in docking and also ensure the centered position in each of the aforementioned positions of the multi-valve device.
The active plate 20 is hemmed by the active housing in the closed position, tilted to a sealing strip 26 . Thusly, every interfacial surface 12 , 25 , 35 is hemmed by the sealing strip 26 . The sealing strip 26 seals the interfacial surfaces 15 , 25 , 35 in each of the positions relative to one another against the material. Furthermore, the sealing strip 26 is advantageously strippable against the respective passive housing 14 , 24 , while the partial valves 10 , 20 , 30 are reaching the closed position. In the closed position the sealing strip 26 is in a compacted state between the second partial valve 20 and the active housing 24 .
The active housing 24 has cams arranged opposite the axis A so that they can be swiveled toward the passive housing 14 , 34 of the first and third partial valves 10 , 30 in the docked position in order to apply tension to the housings 14 , 24 , 35 in the docked position. The cams engage in a peripheral groove in the respective passive housing 14 , 34 .
The design of the passive housing 14 , 34 and one of the passive valves 10 , 30 can be seen in FIG. 8 . The passive housing 14 , 34 consists of a jacket 141 , which can be spread on one side and faces the active valve 20 with a receiving section 143 facing away from the respective drum and facing the active valve 20 along the direction of flow D. Slots 146 which are open at one end and are aligned along the direction of flow D are arranged in the receiving section 143 so that they pass through the jacket 141 from the outside to the inside.
A ring 142 which protrudes beyond the jacket 141 in the direction of flow D facing the active valve is accommodated in the receiving section 143 , so that a sealing face is formed between the housings 14 , 24 , 34 and also between the jacket 141 and the passive valves 10 , 30 . The ring 142 has an inside surface 145 facing the first and/or third partial valves 10 , 30 with which it is sealed against the first and/or third partial valves 10 , 30 .
The ring 142 serves not only to form a seal but also serves to secure the passive valve 10 , 30 in the closed position. The ring 142 is put under tension toward the outside by the first and/or third partial valves 10 , 30 when the partial valve 10 , 30 is in the closed position. The ring 142 relaxes toward the inside due to its flexibility as soon as the partial valves 10 , 30 are placed in the open position. A surface contour of the ring 142 can advantageously secure the partial valve in this way if the first or third partial valve 10 , 30 can be pivoted out of the closed position only by overcoming a resistance. Following the ring 142 toward the outside, the receiving section 143 can also be spread outward.
The passive housing 14 , 34 also has bearing shells 144 , the curvature of which is formed coaxially to be both hollow cylindrical and semicylindrical with the axis A. The bearing shells 144 are opposite one another along the axis A and are accommodated in the jacket 141 as well as in the ring 142 .
The active second partial valve 20 is arranged to be rotatable about the axis A by means of its pins 22 and is in contact with the passive partial valves 10 , 30 at its interfacial surfaces 15 , so that the partial valves can be entrained by the active partial valve 20 when switching from the closed position to the open position. The passive partial valves 10 , 30 remain in position at least due to the bearing shells 144 , such that the bearing shells 144 protrude into the passive partial valves 10 , 30 and also into the second partial valve 20 in the open position (cf. FIG. 5 ). The active housing 24 also supports the pins 22 following the axis A in addition to the bearing in the bearing shells 144 and can also be rotated in connection to the bearing shells 144 .
Only the passive housings 14 , 34 , the sealing strip 26 and the contact surfaces 17 of the first and third partial 10 , 30 facing away from the interfacial surfaces 15 , 35 are in contact with the material in the various positions of the multi-valve device.
FIG. 9 shows an exemplary embodiment of a passive valve 300 according to the present invention. The passive valve 300 may be regarded as an alternative to the first and third partial valves 10 , 30 of FIGS. 1 through 8 . Instead of the second partial valve 20 , now a tool 200 is arranged along the axis A which can be inserted into a longitudinal grooves 315 in the passive valve 300 . The longitudinal groove 315 runs along the axis A.
The tool 200 extends as an elongated component between two operating levers 240 which are rigidly connected to one another and are intended for gripping the housing 340 of the passive valve 300 with round fittings 242 which are provided instead of an active housing. The tool 200 can be rotated about the axis A by means of the operating lever 240 and a securing device and thereby entrains the passive valve 300 when the fittings 242 are positioned according to a safety specification. For this purpose, the tool 240 has a contour whose surfaces are in contact with interfacial surfaces 350 , which are congruent in at least some section in the longitudinal grooves 320 of the passive valves 300 .
Half-round bearing grooves 320 are formed in the passive valve 300 opposite one another around the axis A and along the axis A, a bearing shell 344 of the housing 320 engaging in these grooves. The bearing shells 344 in this way support the passive valve 300 , so that it can be rotated about the axis A in the housing 340 , such that according to an advantageous embodiment, twisting is blocked until the fittings 242 have been positioned.
The interfacial surfaces 350 of the passive valves have a countersunk region 330 on the inside radially extending to a sealing surface 360 running peripherally on the outside radially. Thus the adjacent surfaces have been reduced to regions that are essential for the sealing effect. Only these regions must remain free of foreign substances to prevent them from separating.
LIST OF REFERENCE NUMERALS
10 First partial valve
11 Recess
14 Passive housing
15 Interfacial surface
17 Contact surface
20 Second partial valve
21 Elevation
22 Pin
24 Active housing
25 Interfacial surface
26 Sealing strip
30 Third partial valve
31 Recess
34 Passive housing
35 Interfacial surface
141 Jacket
142 Ring
143 Receiving section
144 Bearing shell
145 Inside surface
146 Slot
200 Tool
240 Lever
242 Fitting
300 Passive valve
315 Longitudinal groove
320 Bearing groove
330 Countersunk region
340 Housing
344 Bearing shell
350 Interfacial surface
360 Sealing surface
A Axis
D Direction of flow
N Nominal diameter.
Having described at least one of the preferred embodiments of the present invention with reference to the accompanying drawings, it is to be understood that such embodiments are merely exemplary and that the invention is not limited to those precise embodiments, and that various changes, modifications, and adaptations may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. The scope of the invention, therefore, shall be defined solely by the following claims. Further, it will be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and the principles of the invention. It should be appreciated that the present invention is capable of being embodied in other forms without departing from its essential characteristics. | The invention relates to a passive valve for multi-valve devices for sealing a container or a line. According to one aspect of the invention, the passive valve is free of bearing supports which protrude in a positive sense out of the passive valve. The invention also relates to a multi-valve device for contamination-free connection of two containers or two lines with partial valves that can be rotated about a single axis. According to this aspect of the invention, at least three partial valves, which are arranged essentially parallel to one another and can be put under tension so they can be sealed with respect to their surroundings, can be rotated about the single shared axis. |
REFERENCE TO APPLICATION
The present application is a continuation-in-part of U.S. patent application Ser. No. 11/717,411 entitled “Semi-Rigid Flexible Duct”, filed Mar. 13, 2007 now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 11/389,623, entitled “Flexible Semi-Rigid Clothes Dryer Duct”, filed Mar. 24, 2006 now abandoned, the contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to ducts, particularly semi-rigid flexible ducts.
BACKGROUND OF THE INVENTION
Ducts are used for different purposes, including for the conveyance of air, such as in ventilation, heating and cooling systems, or for conveying away exhaust gas from clothes dryers or other similar machines, as well as for carrying electrical cables and wiring, or other utilities.
When used for air conditioning or ventilation systems, such as within suspended ceilings, particularly in industrial and office premises, the ducts are circular and must be supported, as they have little self-support.
A further, very well known use of ducts is an exhaust vent for clothes dryers, in which the duct is fabricated of a resilient wire helix covered with vinyl or aluminum tubing. Both type of ducts lack structural integrity, while the vinyl-covered duct is not flame resistant. The lack of structural integrity of these ducts typically results in sagging and crinking thereof, causing the duct, over time, to become lined with lint from the clothes dried in the dryer, posing a fire hazard. In the United States alone, thousands of fires associated with clothes dryers occur, causing deaths and injuries and millions of dollars in damages. It is generally recommended by clothes dryer manufacturers not to use vinyl ducts such as these for dryer exhaust transition ducts.
Representative of the prior art in ventilation systems is U.S. Pat. No. 5,281,187 to Whitney, for a “Unitary Vent and Duct Assembly” which discloses a “semi-rigid flexible duct” for a ventilation system installed with a suspended ceiling structure. The duct taught in this patent is actually a solid aluminum tube which is corrugated or “accordion-folded” so that it can be compressed or compacted for storage or shipping. The corrugated aluminum tube duct taught therein, is meant to be coupled to a duct assembly of which it is an integral part, which is intended only for installation within a framed section of a suspended or dropped ceiling. However, once such a tube has been compressed and then re-extended for installation, it is unlikely to maintain its rigidity, depending on the thickness of the aluminum. A tube of this type maintains its rigidity by virtue of its being fabricated of solid metal, is heavy and expensive and can be unwieldy to install. The corrugated aluminum, when extended after compression, has significant ridges and other obtrusive topographical features along its interior due to the corrugations, which cause frictional resistance to the air flow within, a further disadvantage.
Corrugated aluminum is also employed for the exhaust vent of clothes dryers, as, for example, in U.S. Pat. Nos. 5,121,948, 5,133,579, and 5,145,217, which solve the above-described problem of insufficient rigidity, but by using totally rigid segments. Even though the aluminum tubing itself is clearly fire resistant, the ridges and other internal topographical features similar to those mentioned hereinabove with respect to the Whitney patent, also cause frictional resistance to the air flow within, permitting accumulation of lint, which, as stated hereinabove, presents a fire hazard.
U.S. Pat. No. 5,526,849, included herein by reference, to Gray for a “Flexible Duct” discloses a duct and a method for manufacture thereof. The duct disclosed therein is formed of plastic tapes wound on a rotating mandrel with a wire resilient helix and a yarn helix therebetween. The duct so produced, while flame resistant, has rigidity limited to that provided by the wire helix. The additional yarn helix complicates the manufacturing process and adds to the internal topographical features of the duct, increasing friction and the possibility of lint accumulation therein, as described above.
The shape of ducts also has significance. Relatively heavy, rectangular metal ducts, formed of heavy gauge sheet metal, are often used for heating and cooling systems in industrial and office premises. A rectangular cross-sectional shape is desired due to the possibility of placing the duct against a support surface, and thereby utilizing available space more efficiently than a circular duct. These ducts are limited, however, in length, due to their relatively heavy weight and rigidity, as well as to transportation considerations. Accordingly, several lengths of these ducts may need to be joined together on site in order to provide adequate lengths of duct. It will be appreciated that they also require sufficiently strong hangers and other mechanical supports to be provided so as to provide adequate support. Furthermore, specially made corner portions must be provided to take account of bends.
A further consideration that must be taken into account when installing exhaust ducts for directing exhaust gases from machines, is the fact that the exhaust vents (or in the case of air conditioning units, the cool air supply vents) often have a square or rectangular shape, requiring somewhat unorthodox adaptive connections to conventional round ducts.
During manufacturing of conventional round ducts, a problem has been encountered with wrapping of semi-rigid materials, such as thin aluminum sheet, about a rotating mandrel. While the semi-rigid materials provide flexibility to the resulting duct produced in this fashion, the manufacturing process is complicated due to the fact that semi-rigid materials may tear under the tension applied during the wrapping procedure. The solution to this problem, until now, has been to avoid the use of thin aluminum sheets in constructing semi-rigid ducts, and to rely on heavier, more rigid materials, which do not lend themselves to flexibility, and are unwieldy to install, as mentioned above in relation to U.S. Pat. No. 5,281,187 to Whitney.
Therefore, it would be desirable to overcome the above-mentioned disadvantages associated with the prior art of semi-rigid flexible ducts.
SUMMARY OF THE INVENTION
The present invention seeks to provide a semi-rigid, multi-purpose flexible duct that is fire resistant and that is lighter in weight and less expensive than those used in the prior art, while maintaining rigidity and structural integrity, even after having been compressed to a compacted configuration for shipping and storage and then re-extended for installation. Further, the duct has minimal internal topographical features or structure, even when re-extended after having been compressed to a compacted configuration for shipping and storage.
A further aim of the present invention is to provide a semi-rigid, multi-purpose flexible duct having a cross-sectional configuration which may be round, square or rectangular according to need, and which may be used for such diverse uses as gas transport, for example in air conditioning systems or as a gas dryer duct; and the enclosure of utility pipes and cables in an isolated and low-fire-hazard environment.
The present invention further seeks to provide a method for manufacturing such a duct that is simple, fast, and efficient.
In a preferred embodiment there is provided a duct, which includes a pair of coaxial sleeves including an inner sleeve and an outer sleeve, each constituting a thin aluminum sheet used as the construction material for the duct, provided as an aluminum foil ribbon with sufficient thickness to provide flexibility and withstand the tension developed during the wrapping procedure about a rotating mandrel.
There is thus provided, a semi-rigid, flexible duct, which, in accordance with the present invention, may be used for gas transport, such as in cooling or heating systems or for machine exhausts, including but not limited to clothes dryers. It may further be used for enclosing utility lines, such as water, gas, electricity, and telecommunications, particularly when the duct is employed in its rectangular configuration. The duct of the present invention, when formed so as to have a rectangular cross-section, may easily be disposed between two leaves of a hollow wall construction, beneath a suspended wooden or other floor, and within a suspended ceiling, so as to provide an efficient, lightweight yet secure, and easily installable manner of passing utility lines behind, beneath or below building elements.
In a preferred embodiment there is provided a semi-rigid duct, comprising a pair of aluminum foil ribbons wrapped to form a pair of coaxial sleeves, having an inner sleeve and an outer sleeve disposed parallel to and about the inner sleeve, and a resilient helical element disposed between them;
wherein each of the inner sleeve and the outer sleeve have metallic properties;
wherein the helical element imparts helical corrugations to the inner sleeve and the outer sleeve, such that the duct is axially extendible between a compacted configuration suitable for storage and for shipping and an extended configuration; and wherein the inner sleeve and the outer sleeve are of a predetermined thickness rendering the duct substantially rigid when in the extended configuration, and enabling the duct to maintain its substantial rigidity upon extension from the compacted configuration.
An advantage of the above-mentioned embodiment of the present invention is that due to its rigidity and structural integrity, there is a reduction in the tendency of the duct to accumulate lint, thereby reducing fire hazards.
A further advantage of the above-mentioned embodiment of the invention is that unlike the prior art flexible ducts, such as mentioned in U.S. Pat. No. 5,526,849 (see Background), the elimination of a plastic layer from the duct construction further reduces fire hazards.
In the preferred embodiment, the thickness of the inner sleeve and of the outer sleeve is in the range of 24 to 35 microns.
In a preferred method of manufacturing a semi-rigid flexible duct, the method comprises the steps of
a) providing a mandrel of preselected diameter for fabricating a duct therearound;
b) providing a first continuous aluminum ribbon of predetermined thickness to form a first continuous tape;
c) providing a second continuous aluminum ribbon of predetermined thickness to form a second continuous tape;
d) wrapping the first continuous tape with a predetermined overlap around the mandrel to form an inner sleeve;
e) winding a wire around the inner sleeve; and
f) wrapping the second continuous tape with a predetermined overlap around the inner sleeve and the wire winding to form an outer sleeve disposed parallel to and about the inner sleeve, thereby to form a duct.
In another preferred embodiment there is provided a duct which incorporates the use of plastic layers, and includes a pair of coaxial sleeves, including an inner sleeve and an outer sleeve disposed parallel to and about the inner sleeve, and a resilient helical element disposed between them;
wherein each of the inner sleeve and the outer sleeve includes a first layer having metallic properties and one or both of which further include a second, plastic layer bonded to the first layer having metallic properties;
wherein the helical element imparts helical corrugations to the inner sleeve and the outer sleeve, such that the duct is axially extendible between a compacted configuration suitable for storage and for shipping and an extended configuration;
and wherein all the layers of both the inner sleeve and the outer sleeve are of a thickness predetermined to together render the duct substantially rigid when in the extended configuration and to together enable the duct to maintain its substantial rigidity upon extension from the compacted configuration.
When a predetermined length of the duct is in the extended configuration and is disposed horizontally and supported at a first end thereof, the duct is fabricated to bend under the influence of gravitational force such that a second unsupported end thereof is lower than the first supported end by no more than a predetermined percentage of the predetermined length. Further, when a predetermined length of the duct is in the extended configuration and is disposed horizontally and supported at both ends thereof, the duct is fabricated to bend under the influence of gravitational force such that the central portion thereof is also lower than the level of the supported ends by no more than a predetermined percentage of the predetermined length, which, for a 2 meter length of a duct with a diameter of approximately 10 centimeters, will be less than 1 centimeter for an extended duct that was not compacted and less than 5 centimeters for a duct that was extended from the compacted configuration. Additionally, when the duct is in the extended configuration after having been compressed to the compacted configuration, the inward-facing surface of the first layer having metallic properties of the inner sleeve is substantially smooth and featureless except for the helical corrugations.
Further, both the inner sleeve and the outer sleeve include a first layer having metallic properties and a second, plastic layer, forming thereby, respectively, an inner two-layer laminate and an outer two-layer laminate, which are fabricated of fire-resistant and puncture-resistant materials. In all of the two-layer laminates, the layers are bonded together with a fire-retardant adhesive and the inner two-layer laminate is also bonded to the outer two-layer laminate with a fire-retardant adhesive.
Additionally, the first layers having metallic properties of the inner two-layer laminate and the outer two-layer laminate are fabricated of aluminum ribbon of predetermined thicknesses and the second, plastic layers of the inner two-layer laminate and the outer two-layer laminate are fabricated of polyester ribbon of predetermined thicknesses, respectively bonded together to form thereby, respectively, an inner two-layer laminated tape of predetermined thickness and an outer two-layer laminated tape of predetermined thickness, and wherein the inner two-layer laminate is an inner helical wrapping with a predetermined overlap of the inner two-layer laminated tape and the outer two-layer laminate is an outer helical wrapping with a predetermined overlap of the outer two-layer laminated tape.
Further, in the inner sleeve, the second plastic layer is disposed parallel to and about the first layer having metallic properties and in the outer sleeve, the first layer having metallic properties is disposed parallel to and about the second plastic layer. The first layer having metallic properties of the inner two-layer laminate is fabricated of aluminum ribbon of a thickness in the range 6 to 12 microns, and the first layer having metallic properties of the outer two-layer laminate is fabricated of aluminum ribbon of a thickness in the range 24 to 35 microns. The second plastic layers of both the outer and inner two-layer laminates are fabricated of polyester ribbon of a thickness in the range 10 to 14 microns.
Additionally, the resilient helical element is fabricated of a metal having spring-like resilience, such as, a wound galvanized wire of a diameter in the range 0.9 to 1.3 millimeters.
Further, in accordance with a preferred embodiment of the invention, the resilient helical element is aligned with the inner wound wrapping so that the wound galvanized wire is approximately centered over the overlap of the inner helical wrapping of the inner two-layer laminated tape and the outer helical wrapping of the outer two-layer laminated tape is aligned with the resilient helical element so that the overlap of the outer helical wrapping of the outer two-layer laminated tape is approximately centered over the spaces between the wires of the wound galvanized wire of the resilient helical element.
In accordance with a further embodiment of the invention, the duct also includes an insulating sheath fabricated of fiberglass, disposed parallel to and about the outer sleeve, and an enclosing jacket disposed parallel thereto and thereabout. The enclosing jacket is a multi-layer jacket including a tubular, plastic inner wrapping and a two-layer laminate outer wrapping, including a plastic inner layer and an outer layer having metallic properties, bonded together with a fire-retardant adhesive, disposed parallel and about the tubular, plastic inner wrapping and bonded thereto with a fire-retardant adhesive. The plastic inner wrapping is fabricated of polyester ribbon of predetermined thickness, and the plastic inner layer of the two-layer laminate outer wrapping is fabricated of polyester ribbon of predetermined thickness and the outer layer having metallic properties of the two-layer laminate outer wrapping is fabricated of aluminum ribbon of predetermined thickness. The insulating sheath is fabricated of fiberglass of a thickness in the range 25 to 60 millimeters. The plastic inner wrapping is fabricated of polyester ribbon of a thickness in the range 10 to 14 microns. The plastic inner layer of the two-layer laminate outer wrapping is fabricated of polyester ribbon of a thickness in the range 10 to 14 microns, and the outer layer having metallic properties of the two-layer laminate outer wrapping is fabricated of aluminum ribbon of a thickness in the range 6 to 9 microns.
The duct may serve as a gas transport duct or as a duct for enclosing utility supply lines, and has a cross-sectional configuration which may be circular or polygonal, such as square or rectangular.
There is further provided, in accordance with the present invention, a method for manufacturing a semi-rigid, flexible duct which includes the steps of
a) providing a mandrel of preselected diameter for fabricating a duct therearound;
b) combining a first aluminum continuous ribbon of predetermined thickness with a first polyester continuous ribbon of predetermined thickness to form a first two-layer laminated continuous tape;
c) combining a second aluminum continuous ribbon of predetermined thickness with a second polyester continuous ribbon of predetermined thickness to form a second two-layer laminated continuous tape;
d) wrapping the first two-layer laminated continuous tape with a predetermined overlap around the mandrel with the first aluminum ribbon facing inward toward the mandrel and the first polyester ribbon facing outward with respect to the mandrel to form an inner two-layer sleeve;
e) winding a wire around the inner two-layer sleeve; and
f) wrapping the second two-layer laminated continuous tape with a predetermined overlap around the inner two-layer sleeve and the galvanized wire winding with the second polyester ribbon facing inward toward the mandrel and the second aluminum ribbon facing outward with respect to the mandrel to form an outer two-layer sleeve disposed parallel to and about the inner two-layer sleeve, thereby to form a duct.
Additionally, the step b) of combining a first aluminum ribbon includes the sub-step of applying a fire-retardant adhesive between the first aluminum ribbon and the first polyester ribbon to bond them together; and the step c) of combining a second aluminum ribbon includes the sub-step of applying a fire-retardant adhesive between the second aluminum ribbon and the second polyester ribbon to bond them together. Further, the step of b) combining a first aluminum ribbon further includes the sub-step of coating the polyester face of the first two-layer laminated continuous tape with a fire-retardant adhesive; the step c) of combining a second aluminum ribbon further includes the sub-step of coating the polyester face of the second two-layer laminated continuous tape with a fire-retardant adhesive; and in the step d) of wrapping the second two-layer laminated continuous tape, the outer two-layer sleeve is bonded to the inner two-layer sleeve with the galvanized wire winding therebetween.
Additionally in accordance with the method of the present invention, the step e) of winding a wire includes the sub-step of aligning the wound wire with the overlap of the first two-layer laminated continuous tape so that the wound wire is approximately centered over the overlap of the first two-layer laminated continuous tape, and the step f) of wrapping the second two-layer laminated continuous tape includes the sub-step of aligning the second two-layer laminated continuous tape so that the overlap thereof is approximately centered over the spaces between the windings of wire.
Further in accordance with the method of the present invention, the steps d), e), and f) of wrapping the first two-layer laminated continuous tape, winding the galvanized wire, and wrapping the second two-layer laminated continuous tape are performed by rotating the mandrel as the first two-layer laminated continuous tape, the galvanized wire, and the second two-layer laminated continuous tape are respectively deposited thereupon; and the steps d), e), and f) of wrapping the first two-layer laminated continuous tape, winding the galvanized wire, and wrapping the second two-layer laminated continuous tape are performed continuously and simultaneously with predetermined phase differences, with respect to the rotation of the mandrel, therebetween. Namely, the steps d) and e) of wrapping the first two-layer laminated continuous tape and winding the galvanized wire are performed continuously and simultaneously with a phase difference of 360 degrees, with respect to the rotation of the mandrel, therebetween; and the steps e) and f) of winding the galvanized wire and wrapping the second two-layer laminated continuous tape are performed continuously and simultaneously with a phase difference of 120 degrees, with respect to the rotation of the mandrel, therebetween.
In accordance with an additional embodiment of the present invention, the method further includes, after the step f) of wrapping the second two-layer laminated continuous tape, the steps of:
g) sheathing the outer two-layer sleeve with a fiberglass insulating sheath of a thickness in the range 25 to 60 millimeters, disposed parallel thereto and thereabout; and
h) enveloping the insulating sheath with an enclosing jacket.
Additionally, the step h) of enveloping includes the following sub-steps:
1) providing a mandrel of preselected diameter for fabricating the enclosing jacket therearound;
2) combining a polyester continuous ribbon of predetermined thickness with an aluminum continuous ribbon of predetermined thickness to form a two-layer laminated continuous tape;
3) wrapping a polyester continuous ribbon of predetermined thickness around the mandrel to form an inner plastic sleeve; and
3) wrapping a polyester continuous ribbon of predetermined thickness around the mandrel to form an inner plastic sleeve; and
4) wrapping the two-layer laminated continuous tape around the inner plastic sleeve with the polyester ribbon facing inward toward the mandrel and the aluminum ribbon facing outward with respect to the mandrel to form an outer two-layer sleeve disposed parallel to and about the inner plastic sleeve.
The sub-step 2) of combining includes the sub-sub-step of applying a fire-retardant adhesive between the polyester ribbon and the aluminum ribbon to bond them together, and the sub-step 3) of wrapping a polyester ribbon includes the sub-sub-step of coating the outer face of the inner plastic sleeve with a fire-retardant adhesive to bond it to the two-layer laminated tape.
Additionally, the sub-steps 3) and 4) of wrapping a polyester ribbon and wrapping the two-layer laminated tape are performed by rotating the mandrel as the polyester ribbon and the two-layer laminated tape are respectively deposited thereupon. Further, the sub-steps 3) and 4) of wrapping a polyester ribbon and wrapping the two-layer laminated tape are performed continuously and simultaneously with a predetermined phase difference, namely, of 360 degrees, with respect to the rotation of the mandrel, therebetween.
In accordance with a preferred embodiment of the present invention, the method further includes in step f) of winding, the additional step of imparting to at least a portion of the duct, a polygonal cross-sectional configuration, such as square or rectangular.
Thus, the present invention advantageously provides a semi-rigid, multi-purpose flexible duct that is fire resistant and that is lighter in weight and less expensive than those used in the prior art.
Further advantages of the invention will become apparent from the following drawings and description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which:
FIG. 1 is a side view of a portion of a duct having a circular cross-sectional configuration, constructed and operative in accordance with the embodiments of the present invention;
FIG. 2 shows a cross sectional view of a portion of a duct constructed and operated in accordance with a first embodiment of the present invention;
FIG. 3 shows a top view of a mandrel construction used in manufacturing the duct of FIG. 1 ;
FIG. 4 shows a front view of the mandrel of FIG. 3 , being fed by wire and aluminum foil tape used in the manufacturing process;
FIG. 5 shows a perspective view of the mandrel of FIG. 3 during the manufacturing process;
FIG. 6 shows a wire-feed system for tension control of the wire fed to the mandrel;
FIG. 7 shows an aluminum tape-feed system for tension control of the tape fed to the mandrel;
FIG. 8 is a schematic, dimensionally exaggerated cross-sectional view of a second embodiment of the duct of FIG. 1 ;
FIG. 9 is a schematic oblique view of a segment of a duct that has been compressed;
FIG. 10 is a schematic oblique view of a duct similar to that shown in FIG. 1 , further including an insulating sheath, constructed and operative in accordance with a further embodiment of the present invention;
FIG. 11 is a schematic, dimensionally exaggerated cross-sectional view of the duct of FIG. 10 ;
FIG. 12 is a schematic view of a duct, constructed and operative in accordance with an embodiment of the present invention, which is installed as an exhaust transition duct of a clothes dryer;
FIG. 13 is a schematic axial view of a duct such as that of FIG. 1 being fabricated according to the method of the present invention;
FIG. 14 is an enlarged detailed, schematic, dimensionally exaggerated, cross-sectional view of a portion of the wall of a duct such as that of FIG. 1 ;
FIG. 15 is a schematic axial view of an enclosing jacket such as that of FIG. 11 being fabricated according to the method of the present invention;
FIG. 16 is a schematic representation of the vertical sag of the unsupported center of a segment of duct such as that of FIG. 1 supported at its ends;
FIG. 17 is a schematic representation of the vertical displacement from the horizontal of the unsupported end of a segment of duct such as that of FIG. 1 supported at its other end;
FIG. 18 is a schematic representation of the fabrication of an insulated duct such as that of FIG. 11 ;
FIG. 19A is a side view of a portion of a duct having a square cross-sectional configuration, constructed and operative in accordance with a further embodiment of the present invention;
FIG. 19B is a schematic dimensionally exaggerated cross-sectional view of the duct of FIG. 19A ;
FIG. 20A is a schematic oblique view of a duct similar to that shown in FIG. 19A , but having an insulating sheath, constructed and operative in accordance with yet a further embodiment of the present invention;
FIG. 20B is a schematic dimensionally exaggerated cross-sectional view of the duct of FIG. 20A ;
FIG. 21A is a pictorial representation of a square section gas transport duct;
FIG. 21B is a pictorial representation of a rectangular section utility line duct;
FIG. 21C is a pictorial representation of a compound duct;
FIG. 22 is a schematic representation of the fabrication of the insulated polygonal duct illustrated in FIGS. 20A and 20B ;
FIG. 23A is a schematic diagram of apparatus for imparting a selected polygonal cross-sectional configuration to a circular duct;
FIG. 23B is an enlarged schematic representation of the apparatus identified as B in FIG. 23A ; and
FIG. 23C is an end view of the apparatus illustrated in FIG. 23B .
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, there are shown, in FIG. 1 , a side view of a segment of a duct, referred to generally as 30 , constructed and operative in accordance with the embodiments of the present invention, and a schematic axial cross-sectional view of a first embodiment thereof in FIG. 2 . As shown in the cross-sectional view of FIG. 2 , duct 30 is of a two-layer cylindrical construction having an axis 32 and corrugations 34 , and may be used for gas transport or for enclosing utility lines.
In accordance with the present invention, the specific description below of cylindrical duct 30 applies equally to non-cylindrical ducts, such as non-insulated square duct 100 (FIGS. 19 A- 19 B) and insulated square duct 110 ( FIGS. 20A-20B ), as well as variations thereof, all as described hereinbelow.
By way of clarification, the term “helical,” and variations thereof, derives from the description of the manufacture of the ducts of the invention, and relates to the act of winding various elements in a spiral or helix. In the embodiments of the invention in which the duct remains cylindrical, the helical windings clearly remain helical. In those polygonal embodiments of the invention however, the windings, while not being strictly helical, retain a general square-helical arrangement, and may be referred to as such, although mainly they are referred to merely as “windings” or “wound.”
Referring now to FIG. 2 , duct 30 has inner and outer sleeves, referenced 35 and 37 , respectively, which are coaxial, each preferably being formed of a wound helical wrapping of a single-layer aluminum ribbon provided as a tape, 36 a and 36 b , bonded together with adhesive layers 38 a and 38 b , each layer of adhesive on a ribbon layer, respectively. Coaxially wound around inner sleeve 35 is a wound helical wire 40 , preferably galvanized wire, disposed between inner sleeve 35 and outer sleeve 37 encapsulated between two layers of adhesive, 38 a , 38 b , thereby bonding layers 35 and 37 to helical wire 40 and to each other. Aluminum ribbon 36 b is helically wound around a mandrel 42 (see FIG. 3 , discussed hereinbelow), to form inner sleeve 35 .
Referring now to FIG. 3 , the construction of mandrel 42 is shown, comprising a plurality of rollers 44 . Rollers 44 are all individually rotatable, and each is mounted on a fixed plate 43 at an angle 46 with respect to the plate 43 . Each individual roller 44 has formed therein a set of grooves 48 for accepting the wire 40 ( FIG. 1 ) which forms the basis for the spiral format of the flexible duct 30 . These grooves 48 are precision-shaped and are precision-spaced apart in order to accept the predetermined flow of wire 40 , and this flow is established by the angle 46 of the roller. Typically the angle 46 is adjusted to establish the correct flow of both wire and ribbon. The wire 40 is fed from a spool onto the mandrel 42 , and the mandrel 42 is designed such that each individual roller 44 is mounted thereon at a particular angle 46 , to provide a flow effect which enables the tape 36 ( FIG. 4 ) to be fed onto the mandrel 42 and to be taken off in a helical form. Thus, the wire feed becomes a spiral form for the length of the duct 30 being drawn off the mandrel 42 in an automatic fashion.
Referring now to FIGS. 4-5 , there are shown, respectively, a front view and perspective view of mandrel 42 in the midst of the process of fabricating a duct 30 . The size of the duct 30 being fabricated is determined by mandrel 42 which is rotated about its longitudinal axis 56 . Inner single-layer aluminum tape 36 b is helically wound with a predetermined overlap 33 around mandrel 42 as it turns to produce the single-layer inner sleeve 35 of duct 30 as a first step in forming duct 30 . Galvanized wire 40 is helically wound around the single-layer inner sleeve 35 of duct 30 as mandrel 42 turns with the single-layer inner sleeve 35 formed thereupon. Outer single-layer aluminum tape 36 b is helically wound with a predetermined overlap 31 around the inner sleeve 35 of duct 30 with galvanized wire 40 wound thereabout as mandrel 42 turns with the single-layer inner sleeve 35 and the wire 40 wound thereupon to produce the single-layer outer sleeve 37 of duct 30 .
Referring now to FIG. 6 , a wire-feed system 50 for tension control of the wire 40 fed to the mandrel 42 is shown. The tensioning of the wire 40 is provided by equipment placed on the automatic wire-feed system 50 which incorporates a load cell 52 that controls an electronic brake 54 which controls the flow of wire 40 onto the mandrel 42 , supplied by the wire feed supply spool 56 . The equipment for tensioning also includes a plurality of tension pulleys 58 .
Referring now to FIG. 7 , there is shown an aluminum tape-feed system 60 for tension control of the tape 36 fed to the mandrel 42 . A load cell 65 and electronic brake 63 , are provided to control rotation of the spool 68 of aluminum tape 36 , thereby providing it with tension. With the correct control of the spool 68 rotation, to provide a constant tape tension, a proper feed and feed rate are achieved for automatically winding the tape 36 onto the mandrel 42 which is rotated at a sufficient speed to provide an automatic flow for efficient production of the flexible duct 30 . A glue applicator 66 is mounted on the system 60 as well for applying glue to the aluminum tape 36 so the two layers of tape 36 will bond to the wire 40 and to each other, when creating the duct 30 .
The tension of the two aluminum ribbons 36 a , 36 b must be identical and constant at all times, otherwise the ribbon will tear. Also, the tension of the wire 40 must be constant and equal to the tension of the two aluminum ribbons 36 a , 36 b . The tension typically required for fabricating a duct 30 ranges between 65 kgf-70 kgf. The rollers 44 of the mandrel 42 are mounted to plate 43 , and are designed so as to provide a flexible spring-like action which absorbs any irregularities in the tension settings or any irregularities associated with the tape and wire materials being used.
Referring now to FIG. 8 there is shown a schematic, dimensionally exaggerated cross-sectional view of a second embodiment of the duct 30 of FIG. 1 . Duct 30 has inner and outer sleeves, referenced 35 and 37 , respectively, which are coaxial and are of a laminate construction, each preferably being formed of a wound helical wrapping of a two-layer laminated tape formed of two layers of ribbon, 36 b , 39 b , and 36 a , 39 a , respectively, bonded together with adhesive layers 62 , 64 . Inner sleeve 35 has an internal layer of aluminum ribbon 36 b and an external layer of polyester ribbon 39 b bonded together with adhesive layer 62 to form a two-layer laminated tape which is helically wound around a mandrel ( 42 , see FIG. 13 , discussed hereinbelow) to form inner sleeve 35 . Coaxially wound around inner sleeve 35 is a wound helical wire 40 , preferably of galvanized wire, disposed between inner sleeve 35 and outer sleeve 37 encapsulated within adhesive layer 38 . Outer sleeve 37 is fabricated in a manner similar to inner sleeve 35 , but wherein, the helically wound two-layer laminated tape has an internal layer of polyester ribbon 39 a and an external layer of aluminum ribbon 36 a , bonded together with adhesive layer 64 . The wound galvanized wire 40 imparts corresponding corrugations 34 to duct 30 , as can be seen in FIG. 1 .
Polyester ribbon layers 39 b and 39 a are both heat resistant and fire retardant and further are made thick enough to contribute to the rigidity and structural integrity of duct 30 together with aluminum ribbon layers 36 b and 36 a , which, being metallic, are fireproof as well. The adhesive employed in adhesive layers 62 , 38 , and 64 is also heat resistant and fire retardant. It should be noted that polyester ribbon layers 39 b and 39 a are also puncture resistant, which is a further advantage of the duct 30 of the present invention.
Duct 30 is manufactured fully extended by a continuous process, further described hereinbelow, and is then cut to a desired length. The corrugations 34 imparted thereto by wound helical wire 40 allow duct 30 to be axially compressed into a compact configuration convenient for storage or shipping. When duct 30 is compressed, as shown in FIG. 3 , aluminum layers 36 b and 36 a and polyester layers 39 b and 39 a naturally fold between the ridges (referenced 34 in FIG. 1 ) created by wound helical wire 40 . For example, a 2.4 meter length of 10 centimeter diameter duct fabricated in accordance with the present invention can be compressed to a length of approximately 15 centimeters, which is comparable to the compression of simple prior art ducts described hereinabove that do not have the advantages and improvements of the present invention.
A particular advantage of the unique, multilayered construction of the present invention is that duct 30 maintains its rigidity and structural integrity and functions like a totally rigid duct even after having been compressed to its compact configuration and re-extended to its original length.
Referring now to FIG. 9 , there is shown a compressed segment of the duct 30 . The ability to compress the duct after it has been manufactured is advantageous for purposes of storing and shipping. Furthermore, the duct 30 retains its shape after compression so once it is extended it returns to its original duct shape, retaining its substantial rigidity.
Referring now to FIG. 10 , there is shown a schematic oblique view of a segment of a duct, referred to generally as 75 . A schematic axial cross-sectional view of duct 75 is shown in FIG. 11 .
Referring now to FIG. 11 , duct 75 is similar to that shown in FIG. 1 , but also includes an insulating layer 70 disposed parallel to and about outer sleeve 37 constructed and operative in accordance with a further preferred embodiment of the present invention. Additionally, insulating layer 70 has an enclosing jacket serving as a vapor barrier, referred to generally as 72 , and disposed thereabout. Insulating layer 70 is typically fabricated of fiberglass, which provides the desired insulation and is fire resistant. Enclosing jacket 72 is formed of an inner helical winding of polyester ribbon 39 , bonded with a layer of heat and fire retardant adhesive 38 and an outer helical winding of a two-layer laminated tape having an inner layer of polyester ribbon 39 and an outer layer of aluminum ribbon 36 bonded together by a heat resistant and fire retardant adhesive 38 .
In a preferred embodiment of the present invention, insulating layer 70 and enclosing jacket 72 of duct 75 have the following dimensions. Depending on the application, insulating layer 70 typically may be either 25 or 50 millimeters in thickness. The wrapping of polyester ribbon 39 is 12 microns thick. The two-layer laminated tape of the outer helical winding has an inner polyester ribbon layer 39 that is 12 microns thick and an outer aluminum ribbon layer 36 that is 7 microns thick, so that, with the adhesive 38 , outer helical winding has a thickness of 21 microns. It should be noted that the above-mentioned dimensions are typical and are exemplary of a preferred embodiment of the present invention, and that the present invention is not limited thereto.
Enclosing jacket 72 is manufactured by a continuous process, similar to that used for manufacturing duct 30 , and is then cut to a desired length. Duct 75 is assembled from an insulating layer 70 cut to the desired length and an enclosing jacket 72 cut to the desired length, which are drawn onto a segment of uninsulated duct, similar to duct 30 , cut to the desired length.
Referring now to FIG. 12 , there is shown a schematic view of a duct 30 , constructed and operative in accordance with an embodiment of the present invention, installed as an exhaust transition duct of a clothes dryer 78 . Duct 30 is connected to dryer exhaust port 80 and has a vertical segment 82 and two right angle bends 84 connecting it to an outside exhaust port 86 , thereby allowing it to vent the exhaust gases of clothes dryer 78 . The features of the present invention discussed hereinabove, notably the rigidity and structural integrity and the reduced tendency to accumulate lint are particularly advantageous in applications such as this.
The advantageous properties of the duct of the present invention result both from its unique construction described hereinabove and from the method of manufacture thereof.
Referring now to FIG. 13 , there is shown a schematic axial view of a duct, referred to generally as 30 , in accordance with the present invention being fabricated according to the method of the present invention. The size of the duct 30 being fabricated is determined by mandrel 42 which is rotated about its longitudinal axis 56 . Inner two-layer laminate tape 35 is helically wound with a predetermined overlap 88 ( FIG. 14 ) around mandrel 42 as it turns to produce the two-layer inner sleeve of duct 30 as a first step in forming duct 30 . Galvanized wire 40 is helically wound around the two-layer inner sleeve of duct 30 as mandrel 42 turns with the two-layer inner sleeve formed thereupon. Outer two-layer laminate tape 37 is helically wound with a predetermined overlap 90 ( FIG. 14 ) around the two-layer inner sleeve of duct 30 with galvanized wire 40 wound thereabout as mandrel 42 turns with the two-layer inner sleeve and the wire wound thereupon to produce the two-layer outer sleeve of duct 30 .
Referring now to FIG. 14 , there is shown an enlarged detailed schematic cross-sectional view of a portion of the wall of a duct, referred to generally as 30 , constructed in accordance with the present invention, being fabricated according to the method of the present invention. Inner two-layer laminate tape, referred to generally as 35 , is formed by combining an aluminum ribbon 36 b with a polyester ribbon 39 b by applying a fire-retardant adhesive 62 therebetween to bond them together. Similarly, outer two-layer laminate tape, referred to generally as 37 , is formed by combining a polyester ribbon 39 a with an aluminum ribbon 36 a by applying a fire-retardant adhesive 64 therebetween to bond them together. It should be noted that inner two-layer laminate tape 35 and outer two-layer laminate tape 37 are both prepared prior to their being helically wound around mandrel 42 ( FIG. 13 ) to fabricate duct 30 , and that inner two-layer laminate tape 35 is wrapped around the mandrel 42 with the aluminum ribbon 36 b side inward toward the mandrel 42 and outer two-layer laminate tape 37 is wrapped around the mandrel 42 with the polyester ribbon 39 a side inward toward the mandrel 42 . It should further be noted that inner two-layer laminate tape 35 and outer two-layer laminate tape 37 are each respectively helically wound with a predetermined partial overlap, 88 and 90 respectively, so that successive wrappings produce continuous inner and outer two-layer sleeves. Additionally, it should be noted that the wires of wire winding 40 are aligned approximately centered above the overlap 88 in inner two-layer laminate tape 35 , and the overlap 90 in outer two-layer laminate tape 37 is aligned approximately centered above the spaces between the wires of wire winding 40 , which has been found to enhance the strength and rigidity of duct 30 . Prior to inner two-layer laminate tape 35 and outer two-layer laminate tape 37 being helically wound around the mandrel to fabricate duct 30 , the outer, polyester ribbon 39 b side of inner two-layer laminate tape 35 and the inner, polyester ribbon 39 a side of outer two-layer laminate tape 37 are coated with a fire-retardant adhesive, such as with a rolling adhesive applicator 66 ( FIG. 7 ), thereby allowing them to be bonded together with an adhesive layer 38 which also encapsulates galvanized wire winding 40 therebetween, when all are wound around mandrel 42 ( FIG. 13 ) so as to fabricate duct 30 .
Returning now to FIG. 13 , it can be seen that both inner two-layer laminate tape 35 and outer two-layer laminate tape 37 , as well as galvanized wire 40 , are all continuously and simultaneously wrapped and wound, respectively, around mandrel 42 as it rotates. The wrappings and the winding, while occurring simultaneously, are performed with predetermined phase differences, with respect to the rotation of mandrel 42 , between them. Thus, duct 30 is fabricated in one continuous operation. In an exemplary preferred embodiment of the present invention, the phase difference between the wrapping of inner two-layer laminate tape 35 and the winding of galvanized wire 40 is 360 degrees or one complete rotation of mandrel 42 , and the phase difference between the winding of galvanized wire 40 and the wrapping of outer two-layer laminate tape 37 is 120 degrees or one third of a complete rotation of mandrel 42 about axis 56 .
For the insulated duct 75 of FIGS. 10 and 11 , enclosing jacket 72 is fabricated by a process analogous to that used to fabricate duct 30 described hereinabove.
Referring now to FIG. 15 , there is shown a schematic axial view of an enclosing jacket, referred to generally as 72 , in accordance with the present invention being fabricated according to the method of the present invention. A two-layer laminate tape 92 with an inner polyester ribbon layer and an outer aluminum ribbon layer bonded with a fire-retardant adhesive is formed. A continuous inner plastic sleeve 92 a is produced by helically winding a polyester ribbon 39 around a rotating mandrel 42 of the desired diameter, and a continuous outer two-layer sleeve 92 b is produced by helically winding the two-layer laminate tape 92 around the inner plastic sleeve 92 a as the mandrel rotates, with a fire-retardant adhesive layer applied therebetween. Further as described hereinabove, enclosing jacket 72 is produced in one continuous operation, with continuous inner plastic sleeve 92 a and outer two-layer sleeve 92 b both wrapped around mandrel 42 continuously and simultaneously, with only a specific phase difference, with respect to the rotation of mandrel 42 , between them. In a preferred embodiment of the present invention, the phase difference between the wrapping of the inner plastic sleeve 92 a and that of the outer two-layer sleeve 92 b is 360 degrees or one complete rotation of mandrel 42 about axis 94 . In additional embodiments of the present invention, an additional tape of open-mesh laid fiberglass scrim may be wrapped between polyester ribbon 39 and two-layer laminate tape 92 in enclosing jacket 72 (not shown).
To produce insulated duct 75 ( FIGS. 10 and 11 ), a piece of continuously produced uninsulated duct 30 ( FIG. 13 ) is cut to the desired length, and a piece of continuously produced enclosing jacket 72 ( FIG. 11 ) is cut to the desired length. As shown schematically in FIG. 18 , the desired length piece of enclosing jacket 72 , together with an insulating fiberglass sheath 70 of the desired length and suitable inner and outer diameters, are drawn over the desired length piece of uninsulated duct 30 to produce the insulated duct 75 shown in FIGS. 10 and 11 .
Referring now to FIG. 16 , there is shown, schematically, the vertical sag c of the unsupported center 101 of a horizontal segment of duct 200 spanning between two supports 215 a distance L apart. For example, for a length of duct that has been returned to its extended configuration after having been compressed, a 1.5 meter horizontal span of 10 centimeter diameter duct with no support in its center will substantially maintain its rigid shape and sag in the unsupported center by no more than 1 centimeter, while a similar 2 meter horizontal span of 10 centimeter diameter duct will sag in the unsupported center by no more than 5 centimeters. For a length of duct 30 that has not been compressed, a 1.5 meter horizontal span of 10 centimeter diameter duct that has no support in its center will maintain its rigid shape with negligible sag, while a 2 meter horizontal span of 10 centimeter diameter duct will sag in the unsupported center by no more than 1 centimeter.
Referring now to FIG. 17 , there is shown, schematically, the vertical displacement y from the horizontal of one unsupported end 96 of a horizontal segment of duct 97 of length L, as a result of bending due to gravity, when the other end 98 has support 99 . Similarly, a vertically deployed segment of the duct of the present invention will maintain its rigidity, and not sag or collapse, even when returned to its extended configuration after having been compressed. As will be clear to those familiar with the art, these features represent a major improvement over the prior art, including solid aluminum corrugated tubes such as those employed in the invention of the Whitney patent (U.S. Pat. No. 5,281,187) discussed hereinabove.
Another advantage of the unique multilayered construction of the present invention is that when it is fully extended after compression, the inward-facing surface of the aluminum layer 36 b of the inner sleeve 35 is substantially smooth and featureless except for the helical corrugations imparted by wire winding 40 . This reduces frictional resistance to air flow within the duct, and, for clothes dryer exhaust transition ducts, significantly impedes the accumulation of lint inside the duct, thereby greatly reducing the fire hazard cited hereinabove with respect to the prior art.
Referring again to FIG. 8 , in a preferred embodiment of the present invention in a typical product of the invention, duct 30 may have the following exemplary dimensions. The two-layer laminated tape of inner sleeve 35 has an inner aluminum ribbon layer 36 b that is 7 microns thick and a polyester ribbon layer 39 b that is 12 microns thick, so that, with the adhesive 62 , inner sleeve 35 has a thickness of 21 microns. The wire helix 40 is a 0.9 mm diameter galvanized wire. The two-layer laminated tape of outer sleeve 37 has an outer aluminum ribbon layer 36 a that is 25 microns thick and a polyester ribbon layer 39 a that is 12 microns thick, so that, with the adhesive 280 , outer sleeve 37 has a thickness of 39 microns. The use of the thinner (7 microns) aluminum ribbon layer 36 b in inner sleeve 35 contributes to the above-mentioned smoothness of with the adhesive 280 , outer sleeve 37 has a thickness of 39 microns. The use of the thinner (7 microns) aluminum ribbon layer 36 b in inner sleeve 35 contributes to the above-mentioned smoothness of the inner surface of duct 30 . It should be noted that the above-mentioned dimensions are typical and are exemplary of a preferred embodiment of the present invention, and that the present invention is not limited thereto. It should further be noted that, with suitable dimensions for the other layers of the duct of the present invention, either polyester layer 39 b of inner sleeve 35 or polyester layer 39 a of outer sleeve 37 may be omitted without loss of the improvements in rigidity of the present invention, albeit at a cost of additional thickness of aluminum, resulting in additional weight and expense. As such, either of these alternative configurations should be considered as being included in the present invention, as well as alternative dimensions of the layers that can still provide the desired performance of duct 30 . Similarly, metallic layers or plastic layers fabricated of materials having properties comparable to those of the aluminum and polyester layers described hereinabove should also be considered as being included in the present invention.
Referring now to FIG. 18 , there is shown is a schematic representation of the fabrication of an insulated duct, fabricated from the three following layers which have been described hereinabove: 1. Internal layer of duct 30 ; 2. intermediate layer which is insulating layer 70 , and 3. Outer layer which is enclosing jacket 72 .
Referring now to FIGS. 19A-21C , there are provided ducts which are generally similar to those shown and described above in conjunction with FIGS. 1 , 8 - 17 , and which have similar characteristics of strength, durability, puncture resistance and fire resistance, and thus are not specifically described again herein, save with reference to the differences between the ducts previously illustrated and those described hereinbelow.
Referring now initially to FIGS. 19A-19B , duct 100 is a non-insulated polygonal duct, generally similar to that shown and described hereinabove in conjunction with FIGS. 1 and 8 . Typically, it may be a square section duct used for gas transport, such as for ventilation, cooling, and heating systems, or for an exhaust system, as illustrated in FIG. 21A at 120 .
Referring now to FIGS. 20A-20B , duct 110 is an insulated polygonal duct, generally similar to that shown and described hereinabove in conjunction with FIGS. 10-11 . Typically, and as seen in FIG. 21B , it may be a rectangular section duct 120 ′, used for utility lines 122 , such as electricity communications, gas, or water.
Referring now to FIG. 21C there is seen a portion of a compound duct 125 which has both a cylindrical portion, referenced 30 ′, substantially as shown and described above in conjunction with FIGS. 1 , 8 - 9 ; and a square or rectangular portion, referenced 100 ′, substantially as shown and described above in conjunction with FIGS. 19A-19B . The two differently shaped portions are connected via a transition portion 122 . Typically, compound duct 125 is primarily cylindrical, and has a rectangular end portion so as to facilitate connection of the duct to the outlet ports of different types of gas emitting machines, wherein the outlet ports are square or rectangular. Use of the illustrated duct clearly avoids the necessity of unorthodox and sometimes unsafe connections, in order to connect a square or rectangular machine outlet to a cylindrical duct. The compound duct 125 may be formed as described below in conjunction with FIGS. 23A-23C , or by any other suitable method.
Referring now to FIGS. 22-23C , the polygonal ducts of the present embodiment may be manufactured in substantially the same manner as shown and described hereinabove in conjunction with FIGS. 13 , 14 , and 18 , as may be observed from the first three steps of the flow chart of FIG. 22 , which are identical to those described hereinabove in conjunction with FIG. 18 . In the present embodiment however, the cylindrical duct which results from the hitherto described method of manufacture, is converted, either wholly or partially, into a polygonal duct, preferably square or rectangular, as shown at 100 ′ in FIG. 22 .
Referring now to FIGS. 23A-23C , conversion of a length of cylindrical duct 30 may be achieved by mounting a length thereof onto an expanding metal profile 126 , having an external shape adapted to expand to the shape and size desired. Once the duct 30 is mounted onto profile 126 , the profile is operated as known in the art, so as to expand against the interior surface of the round duct, thereby to deform it into a predetermined shape. As seen in the drawings, it may also be desired to complement the outward deformation forces applied from the interior of the duct by the expanding metal profile 126 , by external deformation forces, such as may be provided by trolley 128 . Trolley 128 comprises a chassis 130 , onto which are mounted a plurality of cylindrical wheels 132 which, as seen in FIG. 23C , define, together with wheels 132 , internal right-angled profiles 134 . As trolley 128 travels along the profile 126 and then engages duct 30 , the duct is stretched both from the interior by profile 126 , and is also squeezed between the profile 126 and the inward-facing right-angled profiles of trolley 128 , thereby to impart to the duct a desired polygonal shape. In the present example, this shape is rectangular, but this is by way of example only, as it could be any desired shape, whether rectangular, or any other type of polygon. In accordance with an alternative embodiment of the invention, there may be provided an additional trolley in order to properly form the bottom corners of the polygonal duct.
Clearly, also in accordance with the present invention, and referring also to FIG. 21C , in the event that a cylindrical duct is to remain cylindrical but with a square or rectangular end only, such as for connection purposes to the outlet of a gas emitting machine, this will be done by mounting only that portion of the duct desired to be transformed, onto the expanding profile, thereby to obtain a rectangular or square portion, referenced 100 ′ in FIG. 21C .
It will further be appreciated by persons skilled in the art that the scope of the present invention is not limited by what has been specifically shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is defined solely by the claims, which follow. | A semi-rigid, flexible duct including a pair of coaxial sleeves, namely an inner sleeve and an outer sleeve disposed parallel to and about the inner sleeve and a resilient wound element disposed between the sleeves. Each of the inner sleeve and the outer sleeve constitutes an aluminum foil ribbon. The wound element imparts corrugations to the two sleeves, such that the duct is extendible between a compacted configuration suitable for storage and for shipping and an extended configuration suitable for installation in a gas transport arrangement. Both the inner sleeve and the outer sleeve are of a predetermined thickness rendering the duct substantially rigid when in an extended configuration and enabling the duct to maintain its substantial rigidity upon extension from a compacted configuration. Optionally, at least one of the sleeves further includes a second, plastic layer bonded to the aluminum foil ribbon layer. |