Title:
Electrically powered hydraulic actuating system
Kind Code:
A1


Abstract:
An electrically powered hydraulic actuating system is disclosed. The system includes a pump that has a plurality of electro-magnetically actuated pumping chambers. The plurality of electro-magnetically actuated pumping chambers have a common inlet situated to supply the plurality of electro-magnetically actuated pumping chambers with low-pressure fluid. The plurality of electro-magnetically actuated pumping chambers also have a common outlet situated to receive fluid pressurized by the plurality of electro-magnetically actuated pumping chambers.



Inventors:
Hyde, Richard Mark (Naperville, IL, US)
Nelson, Bryan Edward (Lacon, IL, US)
Application Number:
11/984380
Publication Date:
05/21/2009
Filing Date:
11/16/2007
Assignee:
Caterpillar Inc.
Primary Class:
International Classes:
F04B17/03
View Patent Images:
Related US Applications:
20100097040ELECTRONIC CONTROL FOR A HYDRAULICALLY DRIVEN AUXILIARY POWER SOURCEApril, 2010Boisvert et al.
20090110563POWER RECOVERY SYSTEMApril, 2009Takita et al.
20090148310WORKING FLUID COOLING CONTROL SYSTEM FOR CONSTRUCTION MACHINEJune, 2009Satake
20060013698Locomotive air compressor system with enhanced protection against leakage causative of backflow of pressurized air from a reservoirJanuary, 2006Pervaiz et al.
20060034708Linear pump cooling systemFebruary, 2006Thomas et al.
20060171824Compressor connecting rod bearing designAugust, 2006Nieter et al.
20080199337ADMINISTRATION SET WITH TWO KEYSAugust, 2008Barak
20070194637Rotor assembly with balancing memberAugust, 2007Childe et al.
20070086905Brushless motor and fluid pump having the sameApril, 2007Nagata et al.
20060013711Hermetic compresssorJanuary, 2006Kakiuchi
20080260541Induction Motor ControlOctober, 2008Lifson et al.



Primary Examiner:
BERTHEAUD, PETER JOHN
Attorney, Agent or Firm:
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P. (WASHINGTON, DC, US)
Claims:
What is claimed is:

1. A pump, comprising: a plurality of electro-magnetically actuated pumping chambers; a common inlet situated to supply the plurality of electro-magnetically actuated pumping chambers with low-pressure fluid; and a common outlet situated to receive fluid pressurized by the plurality of electro-magnetically actuated pumping chambers.

2. The pump of claim 1, further including a piston disposed within each of the plurality of electro-magnetically actuated pumping chambers and magnetically urged in alternating directions to pressurize fluid.

3. The pump of claim 2, wherein: the piston includes a magnetic element; and the hydraulic pump includes a plurality of conductive coils substantially encompassing each of the plurality of pumping chambers, wherein each of the plurality of conductive coils are configured to receive an electrical current and generate a force that urges the magnetic element in a direction corresponding to a direction of the electrical current through the conductive coil.

4. The pump of claim 1, further including a piston disposed within each of the plurality of pumping chambers and magnetically urged in a first direction to pressurize fluid, and spring biased in a second direction.

5. The pump of claim 1, wherein each of the plurality of pumping chambers are actuated individually based on a demand.

6. A machine, comprising: a power source; at least one linkage member; at least one hydraulic actuator located remote from the power source and configured to move the at least one linkage member; and at least one hydraulic pump located proximal to the at least one hydraulic actuator, wherein the at least one hydraulic pump is electrically driven by the power source and configured to power the at least one hydraulic actuator.

7. The machine of claim 6, wherein: the at least one linkage member includes a plurality of the linkage members; the at least one hydraulic actuator includes a plurality of the hydraulic actuators located remote from the power source and configured to move the plurality of the linkage members; and the at least one hydraulic pump includes a plurality of hydraulic pumps located proximal the plurality of the hydraulic actuators, wherein the plurality of the hydraulic pumps are electrically driven by the power source and configured to power the plurality of the hydraulic actuators.

8. The machine of claim 7, wherein: the plurality of hydraulic actuators are paired with the plurality of linkage members to separately move the plurality of linkage members; and each of the plurality of hydraulic pumps is associated in a closed loop configuration with a different pairing of the plurality of hydraulic actuators and the plurality of linkage members.

9. The machine of claim 8, wherein each of the plurality of hydraulic pumps is sized for a particular pairing of the plurality of hydraulic actuators and the plurality of linkage members.

10. The machine of claim 6, wherein at least one of the plurality of hydraulic pumps is single acting and spring biased.

11. The machine of claim 7, wherein at least one of the plurality of hydraulic pumps is double acting.

12. The machine of claim 7, wherein each of the plurality of hydraulic pumps is a rail pump.

13. The machine of claim 7, wherein at least one of the plurality of hydraulic pumps is comprised of: at least two inlets; at least two outlets; and at least two check valves configured to allow a flow of fluid between the plurality of hydraulic actuators and the plurality of hydraulic pumps.

14. The machine of claim 6, wherein the at least one hydraulic pump includes: a piston configured to be affected by a magnetic force; a conductive coil substantially encompassing the piston, wherein the conductive coil is configured to receive an electrical current and generate a force that urges the piston in a direction corresponding to a direction of the electrical current through the conductive coil.

15. A method, comprising: producing electrical power at a first location; directing the electrical power to pressurize fluid at a second location, remote from first location; and directing pressurized fluid at the second location to move a work tool at the second location.

16. The method of claim 15, further including directing the electrical power from the first location to a plurality of locations remote from the first location to pressurize fluid at the plurality of locations; and directing the pressurized fluid at the plurality of locations to move the work tool at the plurality of locations.

17. The method of claim 16, wherein the fluid pressurized at the plurality of locations has a different characteristic at each of the plurality of locations.

18. The method of claim 17, wherein the characteristic includes a flow rate.

19. The method of claim 17, wherein the characteristic includes a pressure.

20. The method of claim 16, wherein pressurizing fluid at the plurality of locations includes generating a variable magnetic field.

Description:

TECHNICAL FIELD

The present disclosure relates generally to a hydraulic actuating system, and more particularly, to an electrically powered hydraulic actuating system.

BACKGROUND

Machines such as, for example, dozers, loaders, excavators, motor graders, and other types of machinery use one or more hydraulic actuators to accomplish a variety of tasks. These hydraulic actuators are fluidly connected to pumps that provide a flow of pressurized fluid to the actuators in order to do work. Current pumping systems commonly employ mechanical means to urge fluid to the actuators. These mechanical means tend to make the pumping systems large, expensive, and inefficient. In addition, the many moving parts associated with mechanical pumping systems often lead to high maintenance costs and the potential for early pumping system failure. Furthermore, since mechanical pumping systems require a direct mechanical connection to a power source, remote location of mechanical pumping systems can be difficult.

One method of countering the negative aspects of mechanical pumping systems is set forth in U.S. Pat. No. 6,468,057 (the '057 patent) issued to Beck on Oct. 22, 2002. The '057 patent describes a pump having a pumping chamber and a magnetic piston located therein. In addition, the '057 patent discloses a power source connected to an electromagnetic drive system associated with the magnetic piston. The electromagnetic drive system is used to move the magnetic piston throughout the pumping chamber. The movement of the magnetic piston in the pumping chamber pressurizes fluid and urges it in a desired direction. This process is completed without the pumping system being mechanically connected to a power source.

Although the electromagnetic pump described in the '057 patent may overcome some of the drawbacks of mechanically powered pumping systems, the pump in the '057 patent may be inefficient for varying flow rate and/or pressure demand situations. That is, the pump in the '057 patent may not have the ability to fluidly connect to multiple actuators with varying flow rate and/or pressure demands. Furthermore, the electromagnetic pump described in the '057 patent may also have limited applicability in high flow situations due to the pump's size. In order to accommodate large flow rates, the pump in '057 patent may need to be scaled up, resulting in high manufacturing costs and difficulty in remote placement.

The disclosed system is directed to overcoming one or more of the problems set forth above.

SUMMARY

In one aspect, the present disclosure is directed to a pump. The pump includes a plurality of electro-magnetically actuated pumping chambers, a common inlet situated to supply the plurality of electro-magnetically actuated pumping chambers with low-pressure fluid, and a common outlet situated to receive fluid pressurized by the plurality of electro-magnetically actuated pumping chambers.

In another aspect, the present disclosure is directed to a method of operating a machine. The method may include producing power at a first location, and directing the power to pressurize fluid at a second location, remote from first location. The method may also includes directing pressurized fluid at the second location to move a work tool at the second location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary disclosed machine;

FIG. 2 is a schematic illustration of an exemplary disclosed hydraulic circuit that may be used with the machine of FIG. 1;

FIG. 3 is a cross-sectional illustration of an exemplary disclosed pump that may be used in conjunction with the hydraulic circuit of FIG. 2; and

FIG. 4 is a schematic illustration of another exemplary disclosed pump that may be used in conjunction with the hydraulic circuit of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 100. Machine 100 may be a fixed or mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, machine 100 may be an earth moving machine such as an excavator, a dozer, a loader, a backhoe, a motor grader, or any other earth moving machine. Machine 100 may include a linkage system 101, a work tool 102 attachable to linkage system 101, and an operator interface 106 used to control motion of linkage system 101.

Linkage system 101 may include any structural unit that supports movement of machine 100 and/or work tool 102. Linkage system 101 may include, for example, a stationary base frame (not shown), a boom 109, and a stick 110. Boom 109 may be pivotally connected to the frame, while stick 110 may be pivotally connected to boom 109 at a joint 111. Work tool 102 may pivotally connect to stick 110 at a joint 112. It is contemplated that linkage system 101 may include an alternative configuration and/or a different number of linkage members than what is depicted in FIG. 1, if desired.

Numerous different work tools 102 may be attachable to stick 110 and controllable via operator interface 106. Work tool 102 may include any device used to perform a particular task such as, for example, a bucket, a fork arrangement, a blade, a shovel, a ripper, a dump bed, a broom, a snow blower, a propelling device, a cutting device, a grasping device, or any other task-performing device known in the art. Work tool 102 may be configured to pivot, rotate, slide, swing, lift, or move relative to machine 100 in any manner known in the art.

Operator interface 106 may be configured to receive input from a machine operator indicative of a desired work tool movement. Specifically, operator interface 106 may include an operator interface device 113 and an electronic control module 114. In one embodiment, operator interface device 113 may be a multi-axis joystick located to one side of an operator station. Operator interface device 113 may be a proportional-type controller configured to position and/or orient work tool 102 by producing and sending an interface device position signal to electronic control module 114. The interface device position signal sent from operator interface device 113 to electronic control module 114 may be indicative of a desired movement of work tool 102. It is contemplated that additional and/or different operator interface devices may be included within operator interface 106 such as, for example, wheels, knobs, push-pull devices, switches, pedals, and other operator interface devices known in the art.

Electronic control module 114 may include all the components required to perform the required system controls such as, for example, a memory, a secondary storage device, and a processor, such as a central processing unit. One skilled in the art will appreciate that electronic control module 114 can contain additional or different components. Associated with electronic control module 114 may be various other known circuits such as, for example, power supply circuitry, signal conditioning circuitry, and solenoid driver circuitry, among others.

Machine 100 may also include a plurality of hydraulic circuits 130, 140, 150 interconnecting linkage system 101 and controlled by electronic control module 114. Electronic control module 114 may communicate with hydraulic circuits 130, 140, 150 via control communication lines (not shown), and may be used to regulate operation of hydraulic circuits 130, 140, 150 in response to an operator input received via operator interface device 113.

As illustrated in FIG. 2, hydraulic circuits 130, 140, 150 may each have a plurality of fluid components that cooperate together to move linkage system 101 and/or work tool 102. Furthermore, while FIG. 1 depicts three hydraulic circuits 130, 140, 150, for the purposes of simplicity, FIG. 2 only depicts one that may be representative of any or all of hydraulic circuits 130, 140, 150.

Each of hydraulic circuits 130, 140, 150 may include an electromagnetic pump 201 drivingly coupled to a hydraulic actuator 202, and a tank 203 configured to hold a supply of low-pressure fluid. Electromagnetic pump 201 may be a rail pump. Furthermore, the fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, an engine fuel, or any other fluid known in the art. Electromagnetic pump 201 may draw fluid from tank 203, and hydraulic actuator 202 may return fluid to tank 203. It is also contemplated that each hydraulic circuit 130, 140, 150 may alternatively be connected to separate fluid tanks, if desired.

Hydraulic actuator 202 may include a tube 204 and a piston assembly 205. Piston assembly 205 may be disposed within tube 204 to form a first pumping chamber 206 and a second pumping chamber 207. First and second pumping chambers 206, 207 may be selectively supplied with pressurized fluid from electromagnetic pump 201, and selectively drained of the fluid to cause piston assembly 205 to displace within tube 204. This displacement may change an effective length of hydraulic actuator 202, thereby moving linkage system 101 and/or work tool 102.

Piston assembly 205 may include a piston 208 axially aligned with and disposed within tube 204. Piston assembly 205 may further include a piston rod 209 connectable to the frame of machine 100, boom 109, stick 110, and/or work tool 102 (disclosed to FIG. 1). Piston 208 may include a first hydraulic surface 210, and a second hydraulic surface 211 opposite first hydraulic surface 210. An imbalance of force caused by fluid pressure on first and second hydraulic surfaces 210, 211 may result in movement of piston assembly 205 within tube 204. For example, a force on first hydraulic surface 210 being greater than a force on second hydraulic surface 211 may cause piston assembly 205 to increase the effective length of hydraulic actuator 202. Similarly, when a force on second hydraulic surface 211 is greater than a force on first hydraulic surface 210, piston assembly 205 may retract within tube 204, thereby decreasing the effective length of hydraulic actuator 202. A flow rate of the fluid into and out of first and second pumping chambers 206, 207 may relate to a velocity of the change in effective length of hydraulic actuator 202. Furthermore, a pressure of the fluid in contact with first and second hydraulic surfaces 210, 211 may relate to an actuation force of hydraulic actuator 202. A sealing member (not shown), such as an o-ring, may be connected to piston 208 to restrict a flow of fluid between an internal wall of tube 204 and an outer cylindrical surface of piston 208. In another exemplary embodiment, actuator 202 may be a hydraulic motor (not shown).

A drain passageway 212 may be used to relieve fluid from hydraulic actuator 202 to tank 203 by way of a valve 213. Although disclosed as a single valve mechanism, the described functions of valve 213 may, alternatively, be accomplished by multiple separate or cooperating valve mechanism if desired. Fluid may be drawn from tank 203 and supplied to electromagnetic pump 201 via a fluid passageway 214. Electromagnetic pump 201 may pressurize the fluid, and direct the pressurized fuel to hydraulic actuator 202 through a fluid passageway 215 and valve 213.

Electromagnetic pump 201 may include a housing 216 that at least partially defines a first pumping chamber 217 and a second pumping chamber 218. Electromagnetic pump 201 may also include a piston 219 configured to be affected by magnetic forces. In one embodiment, piston 219 may be made of magnetic material. In another embodiment, piston 219 may be a ferromagnetic material such as, for example, iron nickel, and/or cobalt. Piston 219 may be disposed within housing 216 between first and second pumping chamber 217, 218.

Electromagnetic pump 201 may include a first inlet 220 and a second inlet 221 fluidly connecting first and second pumping chambers 217, 218 to fluid passageway 214 in parallel. A first inlet check valve 223 may be disposed between tank 203 and first pumping chamber 217, and may be configured to allow a unidirectional flow of low-pressure fluid from tank 203 to first pumping chamber 217. A second inlet check valve 224 may be disposed between tank 203 and second pumping chamber 218, and may be configured to allow a unidirectional flow of low-pressure fluid from tank 203 to second pumping chamber 218.

Electromagnetic pump 201 may also include a first outlet 225 and a second outlet 227 fluidly connecting first and second pumping chambers 217, 218 to fluid passageway 215 in parallel. A first outlet check valve 226 may be disposed between first pumping chamber 217 and valve 213, and may be configured to allow a unidirectional flow of fluid from first pumping chamber 217 to hydraulic actuator 202 via valve 213. A second outlet check valve 228 may be disposed between second pumping chamber 218 and valve 213, and may be configured to allow a unidirectional flow of fluid from second pumping chamber 218 to hydraulic actuator 202 via valve 213.

Electromagnetic pump 201 may have a conductive material 229 encompassing and/or forming a point of contact with first and second pumping chambers 217, 218. In one embodiment, conductive material 229 may be wound around first and second pumping chambers 217, 218 as a continuous coil. In another embodiment, conductive coil 229 may form two non-connected portions, with a first portion wrapped around first pumping chamber 217, and a second portion wrapped around second pumping chamber 218.

Conductive material 229 may be any type of material that allows electrical current to pass through it such as, for example, copper or aluminum. Conductive material 229 may be electrically connected (not shown) to electronic control module 114 and/or a power source 107 (shown in FIG. 1). Conductive material 229 may be configured to receive electrical current from power source 107. In one embodiment, power source 107 may be the primary mover of machine 100.

The electrical current supplied from power source 107 may be used to create a variable magnetic force (i.e., variable magnetic field) that urges piston 219 in a direction corresponding to the direction of the electrical current in conductive material 229. If the conducting material is formed into two non-connecting portions, power source 107 may connect to each of the two portions individually. The two connections may allow for power source 107 to supply electrical current to conductive material 229 at different levels and/or in different directions.

The cyclical movements of piston 219 may force high-pressure fluid to hydraulic actuator 202 via fluid passage way 215 and valve 213, causing piston assembly 205 to either increase or decrease the effective stroke length of hydraulic actuator 202. The change in effective length of hydraulic actuator 202 may be dependent upon the amount and direction of electrical current supplied to conductive material 229 from power source 107, as well as the position of valve 213. A sealing member (not shown) such as, for example, an o-ring, may be connected to piston 219 to restrict a flow of fluid between an internal wall of housing 216 and an outer cylindrical surface of the piston 219.

Control signals generated by electronic control module 114, and directed to hydraulic circuits 130, 140, 150 via communication line (not shown), may determine when and how much electrical current, as well as the direction of electrical current supplied to conductive material 229. For example, an operator may move operator interface device 113 to indicate a desired movement of linkage system 101. In response, electronic control module 114 may receive and/or generate communication signals indicative of the operator desired movement. The signals received and/or generated by electronic control module 114 may be used to determine the amount, as well as the direction of electrical current supplied to conductive material 229 in order to accomplish the desired movement of linkage system 101.

An alternative embodiment of electromagnetic pump 201 is depicted in FIG. 3. In this embodiment, electromagnetic pump 300 may only be electro-magnetically urged in a first direction. Specifically, electromagnetic pump 201 may include a return spring 301 that returns piston 219 in a second direction, opposite of the first direction. Because electromagnetic pump 300 is only electro-magnetically urged in a single direction, electromagnetic pump 300 only includes a single inlet and outlet.

Spring 301 may be a coil spring, a helical spring, a conical spring, or any other type of spring known in the art. Furthermore, spring 301 may be a tension spring, or a compression spring. Spring 301 may be made of any material that can be elastically formed to store and use mechanical energy. For example, spring 301 may be made out of spring steel, an elastomeric material, or any other type of material known in the art.

In an alternative embodiment illustrated in FIG. 4, machine 100 may include a single pump 400 having a plurality of electromagnetic pumping chambers 401, 402, 403 that may be used in place of multiple separate electromagnetic pumps 201 (disclosed in FIG. 1 and FIG. 2). Although FIG. 4 discloses three pumping chambers within a common housing 404, any number of pumping chambers may be used.

Housing 404 may include a common inlet 405 being connected to fluid passageway 214, and a common outlet 406 being connected to fluid passageway 215 (illustrated in FIG. 2). The plurality of pumping chambers 401, 402, 403 may have individual inlets, outlets, and check valves that allow the flow of fluid between pumping chambers 401, 402, 403, and inlet 405 and outlet 406. The individual inlets, outlets, and check valves of FIG. 4 may be at similar locations and perform similar tasks as the inlets, outlets, and check valves disclosed in FIG. 2. Each of pumping chambers 401, 402, 403 may be substantially similar to electromagnetic pump 201. Furthermore, the movement of piston 219 may cause high-pressure fluid to travel from pumping chambers 401, 402, 403 to one or more hydraulic actuators 202.

Pumping chambers 401, 402, 403 may be any combination of electromagnetic pump 201, electromagnetic pump 300, and/or any type of pump known in the art. For example, in one embodiment, pumping chamber 401 may be electromagnetic pump 201, with pumping chambers 402, 403 being electromagnetic pump 300 (disclosed in FIG. 3). In another embodiment, pumping chambers 401, 402, 403 may all be composed of electromagnetic pump 300.

The pumps described herein may be paired in a closed-loop configuration with specific actuators. This closed-loop pairing may include pumps that are individually sized to meet the demands of the specific actuator with which the pump is paired. The sizing may be determined by the desired pump and actuator characteristics such as, for example, flow rate and/or pressure.

Furthermore, for electromagnetic pump 400 (disclosed in FIG. 4), pumping chambers 401, 402, 403 may be actuated individually and/or at different rates depending on the desired flow rate output. For example, in one embodiment, a small desired flow rate (associated with work tool 102 moving a small load) may result in power source 107 supplying electrical current to only the conductive material encompassing pumping chamber 401. If the desired flow rate increases (associated with work tool 102 moving a large load), power source 107 may then supply electrical current to conductive material encompassing additional pumping chambers 402, and/or 403. Furthermore, the electrical current supplied to pumping chambers 401, 402, 403 may at different times, in different directions, and/or in different amounts.

INDUSTRIAL APPLICABILITY

The disclosed system may be applicable to any machine where it is desirable to minimize cost of hydraulic circuits, and allow for remote placement of hydraulic circuits. Furthermore, the disclosed system may be applicable to any machine requiring flow rates of pressurized fluid and/or having multiple actuators demanding different flow rates. The disclosed system may minimize cost and size, while improving response and efficiency by allowing for fewer parts in creation of the disclosed system. The disclosed system may be more efficient and responsive since the individual pumps can be sized with an actuator depending upon the desired task. Furthermore, the disclosed system may allow for remote placement since it may be powered electrically instead of mechanically. The operation of hydraulic circuits 130, 140, 150, as illustrated in FIG. 1 and FIG. 2, will now be explained.

During operation of machine 100, an operator may manipulate interface device 113 to indicate a desired movement of machine 100. Throughout this manipulation process, electronic control module 114 may receive the desired movement indications, generate corresponding signals indicative of desired flow rates of fluid, and supply the signals to power source 107, and hydraulic circuits 130, 140, 150 accordingly.

In response to operator input to either extend or retract piston assembly 205, fluid may be pressurized by electromagnetic pump 201, and selectively directed to hydraulic actuator 202 through fluid passage way 215. Electronic control module 114 may move valve 213 to a flow-passing position, thereby allowing pressurized fluid to the appropriate one of first and second pumping chambers 206, 207. Substantially simultaneously, valve 213 may allow the draining of the appropriate one of the first and second pumping chambers 206, 207 to tank 203, thereby creating a force imbalance on piston 208 that causes piston assembly 205 to move.

For example, if an extension of at least one of hydraulic circuits 130, 140, 150 is requested, valve 213 may be moved to the position that allows pressurized fluid to flow from electromagnetic pump 201 to first pumping chamber 206. Substantially simultaneous with the directing of pressurized fluid to first pumping chamber 206, valve 213 may allow fluid from second pumping chamber 207 to drain to tank 203. If retraction of at least one of hydraulic circuits 130, 140, 150 is requested, valve 213 may be moved to the position that allows pressurized fluid to flow from electromagnetic pump 201 to second pumping chamber 207. Substantially simultaneous to the directing of pressurized fluid to second pumping chamber 207, valve 213 may allow fluid from first pumping chamber 206 to drain to tank 203.

Power source 107 may supply electrical current to conductive material 229 to create an electromagnetic force that urges piston 219 in a desired direction with a desired velocity and force. The movement of piston 219 may urge the fluid in a desired direction, thereby efficiently accomplishing the desired movements of machine 100. The amount and direction of electrical current supplied to conductive material 229 may be dependent upon the desired movement of machine 100.

The disclosed system may efficiently handle varying flow rate and/or pressure demand situations since the plurality of rail chambers (FIG. 4) may fluidly connect to multiple actuators with varying flow rate and/or pressure demands.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed hydraulic system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed hydraulic system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.





 
Previous Patent: Oil pump resonator

Next Patent: Microfluidic Device