Patent Application
20130108475
The description herein relates to a pump apparatus driven by a plurality of actuators acting on a resilient chamber such as the type of tubing often used in healthcare environments or flexible rubber or plastic tubing of the type often used in industrial environments. By compressing, or pinching, the resilient chamber in a pattern, material may be urged from one end of the chamber to another. In certain examples, the flow can be reversed by reversing the pattern. In certain examples the flow can be increased or decreased by varying the speed of the pattern or the stroke of the actuators.
Smart material actuators which use a material that will expand or contract in connection with the application of an electric potential may be used in such pumps. Where the necessary level of compression, or pinching, is within the range of the expansion range of the smart material device, such actuators may be of a design in which the smart material device acts directly upon the chamber. Where additional stroke length is required, mechanically amplified smart material actuators may be utilized, including mechanically amplified smart material actuators such as those described herein and in the incorporated references. Use of smart material actuators in certain examples of the pumps described herein can have the benefit of low power usage, fast operation, and improved controllability.
Actuator-driven pumps, including certain of the examples described herein, can be suitable in a variety of applications, including without limitation, medical applications in which it is desirable to be able to easily replace the resilient chamber with a new chamber between uses without the need to sterilize a previously used chamber. Pumps according to the examples described herein can also be useful in applications that require more precise flow control, reversibility, or low power consumption.
This application hereby incorporates by reference U.S. applications Ser. No. 11/156,408 (Apparatus and Process for Optimizing Work from a Smart Material Actuator Product), Ser. No. 13/203,737 (Mountable Arm Smart Material Actuator and Energy Harvesting Apparatus), Ser. No. 13/203,729 (Small Scale Smart Material Actuator and Energy Harvesting Apparatus, Ser. No. 13/203,743 (Smart Material Actuator Adapted for Resonant Operation); International Publications WO2012/118548 (High Speed Smart Material Actuator with Second Stage), WO 2012/079012 (Multiple Arm Smart Material Actuator with Second Stage), WO 2011/103328 (Smart Material Actuator with Enclosed Compensator); and U.S. Pat. Nos. 6,717,332 6,717,332 (Apparatus Having A Support Structure And Actuator); 6,548,938 (Apparatus Having A Pair Of Opposing Surfaces Driven By A Piezoelectric Actuator); U.S. Pat. No. 6,737,788 (Apparatus Having A Pair Of Opposing Surfaces Driven By A Piezoelectric Actuator); U.S. Pat. No. 6,836,056 (Linear Motor Having Piezo Actuators); U.S. Pat. No. 6,879,087 (Apparatus For Moving A Pair Of Opposing Surfaces In Response To An Electrical Activation); U.S. Pat. No. 6,759,790 (Apparatus For Moving Folded-Back Arms Having A Pair Of Opposing Surfaces In Response To An Electrical Activation); U.S. Pat. No. 7,132,781 (Temperature Compensating Insert For A Mechanically Leveraged Smart Material Actuator); U.S. Pat. No. 7,126,259 (Integral Thermal Compensation For An Electro-Mechanical Actuator); U.S. Pat. No. 6,870,305 (Apparatus For Moving A Pair Of Opposing Surfaces In Response To An Electrical Activation); U.S. Pat. No. 6,975,061(Apparatus For Moving A Pair Of Opposing Surfaces In Response To An Electrical Activation); U.S. Pat. No. 7,368,856 (Apparatus And Process For Optimizing Work From A Smart Material Actuator Product); and U.S. Pat. No. 6,924,586 (Uni-Body Piezoelectric Motor).
Other features will become apparent from the attached drawings, which illustrate certain examples of the apparatus of this invention, wherein
While the following describes certain examples of apparatuses according to the inventions set forth in the claims, it is to be understood that this description is to be considered only as illustrative of the principles and is not to be limitative of the inventions set forth in the claims as numerous other variations, all within the scope of the claims, will readily occur to others in light of this description.
Herein, the term “adapted” shall mean sized, shaped, configured, dimensioned, oriented and arranged as appropriate.
As discussed herein, the term “smart material” refers to piezoelectric materials that change their shape upon application of an appropriate electrical potential, also including versions of such materials sometimes created by doping known piezoelectric materials to change their electrical or mechanical properties. A “smart material device” is a device comprising smart material that is adapted for a particular application. One example of a smart material device is a multilayer piezoelectric stack comprising sections of smart material, each having an opposing positive electrode and negative electrode such that the sections of the stack are electrically joined. Upon application of a suitable electric potential, the smart material sections expand. Alternatively, upon compression of the piezoelectric stack an electric potential is created between the electrodes. By stacking multiple layers together, the expansion and electrical harvesting characteristics are added together. An example of such a multilayer piezoelectric stack is a co-fired, multilayer ceramic piezoelectric stack. Such piezoelectric stacks may be formed by printing electrodes on either end of a ceramic piezoelectric material. The layers are then stacked and fired together to create a unitary structure. Such stacks are available from a number of suppliers, including NEC. Such stacks are convenient for use in actuators having various dimensions, including very small actuators on the order of two millimeters in length, 0.5 millimeters to one millimeters in thickness and one millimeters in width. As will be understood by those of skill in the art, this is only one example and many different stack sizes can be formed using different numbers of layers, and different layer thicknesses, thereby providing for actuators suitable for a wide variety of applications.
Another type of multilayer piezoelectric stack is a stack 100 formed of sections of a single-crystal piezo material. Single crystal piezo materials can be created in a variety of configurations and are considered by some to be more efficient than co-fired ceramic materials. As such, less material may be used to generate effects comparable to larger co-fired stacks. Piezoelectric stacks formed of single-crystal piezoelectric materials may conveniently be used in even smaller embodiments of actuators, including sizes, for example, of one millimeters in length (the lengthwise axis being the axis along which the crystal predominantly expands upon application of an electric current to the crystal), and 0.3 millimeters square. Once again, it will be clear to those of ordinary skill in the art that many different sizes, including both larger and smaller sizes, may be created using such stacks. It will also be clear that different varieties of smart material devices may be preferred in different applications depending on factors including cost, durability, availability, expansion potential, and electrical efficiency. Therefore, the examples described herein are not intended to be limited by a particular type or size of smart material device, except to the extent such limitation is expressly stated.
Actuator-driven pumps, including those described herein, comprise a plurality of actuators adapted to act on a resilient chamber and a controller adapted to activate such actuators according to one or more patterns. Referring to
Resilient chamber 110 is thus arranged in a position in which it can be acted upon by smart material actuators 120, 120′, and 120″ such that activation of smart material actuators 120, 120′, and 120″ will cause each to compress resilient chamber 110 in different locations. The compression may be such that resilient chamber 110 is compressed to a depth that may conveniently range from of one third of the diameter of the chamber, to a depth sufficient to substantially close or seal the chamber so that liquid may not pass through it. As is shown, the actuators may conveniently be arranged in a series such that the distance along the resilient chamber between each actuator is substantially the same, however, pumps according to this description also include pumps having distances between actuators that are not essentially the same.
By activating and deactivating smart material actuators 120, 120′, and 120″ according to a pattern, material (such as a gas or a liquid), can be urged from first inlet end 108 toward outlet end 112, or vice versa. It will be understood that inlet end 108 and outlet end 112 are locations on resilient chamber 110, which may be of any length and need not include separations at inlet end 108 or outlet end 112. It will be further understood that in examples in which pump 100 can operate in either direction, the terms “inlet” and “outlet” are used for convenience to illustrate operation in one direction and are not intended to imply operation in the other direction is not possible.
Smart material actuators 120, 120′, and 120″ are operably connected to controller 180. As illustrated, such connection may conveniently be electrical in nature such that controller 180 supplies the necessary electrical current to effect the required activation and deactivation of smart material actuators 120, 120′, and 120″. The power for such activation may conveniently come from a power source 187. It will be understood however, that other configurations are possible, including configurations in which smart material actuators 120, 120′, and 120″ are separately connected to a power source and controller 180 provides a digital signal to trigger the necessary activations and deactivations.
Controller 180 may conveniently comprise electrical circuitry for activating and deactivating smart material actuators 120, 120′, and 120″, that circuitry conveniently including a logic unit, a timing unit 186, and a flow adjustment unit 189. The logic unit is represented in
The flexibility of controller 180 can be enhanced in certain applications, by placing a flow rate sensor 114 in operable connection with resilient chamber 110 and controller 180. As illustrated, flow rate sensor 114 is proximate to outlet end 112, but the examples described herein are not intended to be limited to such placement as other placements (including before inlet end 108 or at an upstream or downstream location remote from pump 100) are also feasible depending on the application. Processor 185 may then be programmed to selectively increase or decrease the flow rate of actuator-driven pump 100 in response to signals from flow rate sensor 114 to ensure a consistent flow or flow pattern is maintained. In this way processor 185 may adjust the operation of smart-material actuators 120, 120′, 120″ automatically based on the rate of material flow received from flow rate sensor 114, or in response to a signal from another device such as general purpose computer (not illustrated) that provides signals through flow adjustment unit 189 or directly to processor 185. Accordingly, flow direct and/or flow rate may be adjusted manually (in examples in which flow adjustment unit 185 is a manual switch), manually based on a flow rate feedback (where flow adjustment unit 185 is adapted to allow a user to set a flow rate and flow rate sensor 114 provides a signal indicating the rate of flow), automatically (in which case the flow adjustment unit 189 or processor 185 receives signals from an external device to increase or decrease speed), or automatically based on flow rate feedback (in which case flow adjustment unit 189 or processor 185 receives signals to increase or decrease flow rate and flow rate sensor 114 provides a signal indicating the rate of flow). Schematically shown controller 180 is intended to represent all of these possible variants.
Flow rate increases may be achieved by speeding up the activation pattern, including by decreasing the interval between activation of smart material actuators 120, 120′, and 120″ and flow rate decreases may be achieved by slowing down the activation pattern including by increasing the interval. Alternatively, flow rate can be selectively increased by causing controller 180 to increase the stroke length of smart material actuators 120, 120′, and 120″ thereby achieving a greater degree of compression of resilient chamber 110, or flow rate can be selectively decreased by causing controller 180 to decrease the stroke length. Likewise, flow reversal may be achieved by causing controller 180 to reverse the pattern.
A method of pumping a material utilizing an actuator-driven pump is also disclosed. As has been indicated, flow of actuator-driven pump 100 may be achieved by processor 185 causing smart material actuators 120, 120′, 120″ to activate in a predetermined sequence adapted to urge a material through resilient chamber 110. In the case of a pump comprising inlet smart material actuator 120, central smart material actuator 120′, and outlet smart material actuator 120″ the predetermined sequence may conveniently proceed as follows:
As used in table 1, “Open” refers to a state in which a smart-material actuator is either not compressing resilient chamber 110 or is compressing it to a substantially lesser degree, and “Activated” refers to a state in which a smart material actuator is compressing resilient chamber 110 either completely or to a substantially greater degree. In such a progression, during time period 1, material enters the area of resilient chamber 110 between inlet smart material actuator 120 and central smart material actuator 120″. During time period 2, Inlet smart material actuator 120 activates, thereby resisting backflow and creating an initial pumping force. During time period 3, outlet smart material actuator 120″ opens and central smart material actuator 120′ activates, thereby urging the material through resilient chamber 110. During time period 4, which is optional, outlet smart material actuator 120″ activates, thereby resisting backflow. After time period 4, the cycle repeats, beginning with time period 1. It will be apparent to those of ordinary skill in the art that, during the progression, smart material actuators 120, 120′, 120″ never come into direct physical contact with the material flowing through said tube. As such, it is feasible for resilient chamber 110 to be a replaceable tube (such as are commonly used in medical applications) having a substantially sterile interior surface. Such a configuration can be desirable in certain healthcare applications as it allows avoiding contamination by enabling replacement of resilient chamber 110 (in this case tubing) between uses without requiring sterilization of the remainder of the apparatus. It is also possible for resilient chamber 110 to be a body vessel such as an artery, vein, blood vessel, or other vessel capable of conveying a bodily fluid of a human or animal, either inside or outside the body. In such applications, actuator-driven pumps of the kind described herein could be used to improve circulation and for other medical applications involving pumping of a bodily fluid. For non-medical applications, including industrial applications, resilient chamber 110 could be any type of tube or chamber capable of conveying the material to be pumped including, without limitation, plastic or rubber tubes. The material used is largely a matter of choice depending on the desired application, provided that it is capable of conveying the material to be pumped and is resilient enough to undergo repeated compression and decompression by the pump actuators as necessary for the application.
Timer 186 enables processor 185 to cause said smart material actuators 120, 120′, 120″ to activate at predetermined intervals according to such a progression, thereby causing material to be pumped. Such activations may conveniently repeat at rates between 40 Hz and 100 Hz or, depending of the stroke length of smart material actuators 120, 120′, 120″, the interior volume of resilient chamber 110, and the nature of the material to be pumped, at any other desirable rate adapted to produce the desired flow. Substantially upon adjustment of said flow control unit 189, said processor 185 will cause flow to increase or decrease by increasing or decreasing the rate. Said processor 185 may also, in conjunction with or independent of a rate increase, increase the stroke of smart material actuators 120, 120′, 120″, thereby also increasing the pumping force or flow rate. Decreasing the stroke of smart material actuators 120, 120′, 120″, would have a similar, but opposite effect of decreasing the pumping force. The combination of rate and stroke needed to obtain a given flow will vary depending on the back pressure, viscosity of the fluid, resilience of resilient chamber 110, and similar factors. The greater the viscosity of the material and/or back pressure, the greater the need for a full compression of resilient chamber 110 and a slower rate of flow. The lower the viscosity and/or back pressure, the less the need for full compression, and the higher tolerance for a faster rate. The sequence can be adjusted via electronic control to reverse the direction of flow by reversing the pattern as well. Actuator-driven pump 100 therefore operates in both directions and can proportionally control flow and pressure.
A method of pumping a material utilizing an actuator-driven pump having four or more smart material actuators is also disclosed. As has been indicated, flow of actuator-driven pump 200 may be achieved by processor 285 causing smart material actuators 120, 120′, 120″, 120′″ to activate in a predetermined sequence adapted to urge a material through resilient chamber 110. In the case of a pump comprising inlet smart material actuator 120, first central smart material actuator 120′, second central smart material actuator 120″ and outlet smart material actuator 120′″ the predetermined sequence may conveniently proceed as follows:
In such a progression, during time period 1, liquid enters the area of resilient chamber 110 between inlet smart material actuator 120 and outlet smart material actuator 120′″. During time period 2, inlet smart material actuator 120 activates, thereby resisting backflow and creating an initial pumping force. During time period 3, first central smart material actuator 120′ closes, thereby creating a further pumping force. During time period 4, second central smart material actuator 120″ closes, creating further pumping force, and outlet smart material actuator 120′″ opens allowing the pressurized material to escape. During time period 5, which should be considered optional, outlet smart material actuator 120′″ activates, thereby resisting backflow. After time period 5, the cycle repeats, beginning with time period 1.
It will be apparent to those of ordinary skill in the art in light of the foregoing description that pumps according actuator-driven pumps can also be formed with more than four actuators. Each new actuator creates an additional time period before the final time period. During that extra time period, the additional actuator will activate, ultimately leading to the opening of the final actuator. In this fashion, pumps with any number of actuators may be created. It will also be apparent in light of this description that, as additional actuators are added, it is not necessary, and indeed is not desirable, for all preceding actuators to be closed at the same time. Instead, using the four actuator progression described above as an example, once first central smart material actuator 120′ closes in time period 3, inlet smart material actuator 120 could open. Then, in time period 4, first central smart material actuator 120′ could open substantially upon second central smart material actuator 120″ closing. Using this sequence, time period 5 could be skipped, and the progression would return to time period 1 after time period 4. The following table illustrates this progression.
It will also be understood that the time periods discussed herein are intervals and not instants. Accordingly, depending on the back pressure, flow and fluid characteristics of the material to be pumped, during a given period, processor 185, 285 may cause one actuator to activate fully before the preceding actuator begins to open, or the preceding actuator may begin to open while the subsequent actuator is in the process of closing. Other variations are possible, and are within the scope of the present invention, and will be readily understood by those of ordinary skill in the art in light of the foregoing description.
The pumps described herein may be created with any actuator adapted to compress a resilient chamber that is capable of operating at the required frequency. In particular, electro-magnetic, pneumatic and direct action piezoelectric actuators may be used. One particularly suitable type of actuator for use in the pumps described herein, however, is a mechanically amplified smart material actuator, such as those illustrated in
Mechanical webs 140 may also be formed of a variety of materials including stainless steel, steel, invar, aluminum, carbon fiber and others. Mechanical webs 140 comprise inner resilient members 142 connected to movable supporting member 130 and outer resilient members 144 connected to actuating arms 150, and 151. Whereas actuating arm 151 is adapted to be connected to a pump base (such as bases 105 and 205 illustrated in
As has been described, smart material device 125 is affixed between first mounting surface 129 and second mounting surface 148. Application of an electrical potential by a controller (such as controllers 180 and 280 illustrated in
As is illustrated in
As with the previously described example, compensator 227 has a first mounting surface 229 and movable supporting member 230 has a second mounting surface 248 that is opposed and substantially parallel to first mounting surface 229, with smart material device 225 positioned in between. In very small applications, smart material device can formed of a single crystal or layers of crystal as has been described.
Similarly, mechanical webs 240 comprise inner resilient members 242 connected to movable supporting member 230 and outer resilient members 244 connected to actuating arms 250, and 251. Whereas actuating arm 251 is adapted to be connected to a pump base (such as bases 105 and 205 illustrated in
As has been described, smart material device 225 is affixed between first mounting surface 229 and second mounting surface 248. Application of an electrical potential by a controller (such as controllers 180 and 280 illustrated in
Other smart material actuator designs may also be used with the pumps described herein. One such design, illustrated in
Actuating arms 350 comprise a first actuating arm end 352 in operable connection with one outer resilient member 344 and an opposed second actuating arm end 354. Second stage 370 comprises at least one second stage resilient member 372 having a first second stage resilient member end 371 attached to said second actuating arm end 354 and a second second stage resilient member end 373 attached to a second stage mounting block 374.
Second stage mounting block 374 can be adapted to be in operable connection with a resilient chamber such as resilient chamber 110 illustrated in
As will be understood by those of ordinary skill in the art, in such applications, smart material actuator 320 can be mounted to a pump base (not illustrated) by mechanically connecting compensator 327 to the base (not illustrated) such that second stage mounting block 374 is in operable connection with a resilient chamber such as resilient chamber 110 illustrated in
Actuating arms 450 comprise a first actuating arm end 452 in operable connection with one outer resilient member 444 and an opposed second actuating arm end 454. Second stage 470 comprises four second stage resilient members 472, each having a first second stage resilient member end 471 attached to second actuating arm end 454 and a second second stage resilient member end 473 attached to a second stage mounting block 474.
As described in connection with smart material actuator 420, second stage mounting block 473 can be adapted to be in operable connection with a resilient chamber such as resilient chamber 110 illustrated in
Smart material actuator 420 can be mounted to a pump base (not illustrated) by mechanically connecting compensator 427 to the base (not illustrated) such that second stage mounting block 474 is in operable connection with a resilient chamber such as resilient chamber 110 illustrated in
Additional suitable smart material actuator examples, including examples having enclosed compensators, more than two actuating arms, and being capable of operation at high speeds or in a resonant condition are described in the incorporated references.
As will be readily recognized by those of ordinary skill in the art, pumps as described herein may be manufactured in a variety of sizes adapted to the needs of differing applications. Larger chambers and more viscous materials shall respond to larger and/or more powerful actuators to obtain a given flow rate. Larger resilient chambers will also require actuators with a larger stroke length to obtain the desired compression.
Other variations and embodiments of the pumps and actuators described herein will be apparent to those of ordinary skill in the art in light of this specification, all of which are within the scope of the present invention as claimed. In addition, while the scale used in the figures is illustrative of the principles of the components described herein, it will be apparent to those of skill in the art that different dimensions (including without limitation smart material device sizes, actuating arm lengths, mechanical web dimensions, and distances between actuating arms and compensators) will be applicable in different applications. Accordingly nothing in the foregoing description is intended to imply that the claimed invention is to be limited to the examples described or illustrated herein.
This application claims priority from U.S. provisional patent application Ser. No. 61/551,530 filed Oct. 26, 2011, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61551530 | Oct 2011 | US |
