Attorney Docket No. P201384.US.05
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`TITLE
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`Fatigue testing system for prosthetic devices
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`INVENTORS
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`Benjamin McCloskey of Evergreen, Colorado
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`Craig Weinberg of Denver, Colorado
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`Steven Weinberg of League City, Texas
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`CROSS REFERENCE TO RELATED APPLICATIONS
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`[0001]
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`This application is a continuation of U.S. application no. 14/137,313 filed 20
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`December 2013 entitled “Fatigue testing system for prosthetic devices,” which is a
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`continuation of U.S. application no. 12/718,316 filed 5 March 2010 entitled “Fatigue testing
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`system for prosthetic devices,” which claims the benefit of priority pursuant to 35 U.S.C.
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`§ 119(e) of U.S. provisional application no. 61/158,185 filed 6 March 2009 entitled
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`“Apparatus and methodfor fatigue testing of prosthetic valves,” which are hereby
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`incorporated herein by referencein their entirety.
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`TECHNICAL FIELD
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`[0002]
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`The technology described herein relates to systems and methodsfor fatigue
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`testing of prosthetic devices, in particular, but not limited to, prosthetic vascular and heart
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`valves, under simulated physiological loading conditions and high-cycle applications.
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`BACKGROUND
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`[0003]
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`Prior prosthetic valve testing apparatus and methods typically use a traditional
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`rotary motor coupled with mechanismsto produce regular sinusoidal time varying pressure
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`field conditions. To accurately simulate physiologic conditions and/or produce a more
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`desirable test condition, especially at accelerated testing speeds, a non-sinusoidal time
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`dependentpressurefield may be desired. This is not easily accomplished with a
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`mechanistic approach. Furthermore, current systems employa flexible metallic bellows or
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`conventional piston and cylinder as drive membersto provide the pressure actuation.
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`Flexible metallic bellows are not ideal because they require high forces to operate and
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`resonateat frequency, necessitating the use of larger driving systems and limiting the
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`available test speeds. Piston and cylinder arrangements are not ideal because the seals
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`employed in these systems are subjected to fiction and thus have severely limited life in high
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`cycle applications.
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`[0004]
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`The information included in this Background section of the specification, including
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`any references cited herein and any description or discussion thereof, is included for
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`technical reference purposesonly and is not to be regarded subject matter by which the
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`scopeof the invention is to be bound.
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`WATERS TECHNOLOGIES CORPORATION
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`EXHIBIT 1002
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`WATERS TECHNOLOGIES CORPORATION
`EXHIBIT 1002
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`Attorney Docket No. P201384.US.05
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`SUMMARY
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`[0005]
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`A design for a fatigue testing system for cyclic, long-term testing of various types
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`of prosthetic devices (e.g., cardiac valves, vascular valves, stents, atrail septal defect
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`technologies, vascular linings, and others) is designed to impart a repeating loading
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`condition for the test samples during a test run. However, the system is also designed to be
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`variable in its abilities so it can accurately test multiple technologies. Thus, the system may
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`be variably configured depending upon the device being tested to impart a particular loading
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`profile to repeatedly expose the prosthetic device being tested to desired physiological
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`loading conditions during a testing run. The purposeis to simulate typical or specific
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`physiologic loading conditions on a vascular or heart prosthetic valve, or other prosthetic
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`technology, at accelerated frequency over time to determine the efficacy, resiliency, and
`wear of the devices.
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`[0006]
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`Fatigue testing is accomplished byfirst deploying the prosthetic device in an
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`appropriately sized sample holder, e.g., a rigid or flexible tube, canister, housing or other
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`appropriate structure for holding the device being tested. The sample holder is then placed
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`between two halves of a test chamber that together form a reservoir for a working fluid. The
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`test chamber is in turn mounted to a drive system. The sample holder and valve being
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`tested are then subjected to physiological appropriate conditions which mayinclude:
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`pressure, temperature, flow rate, and cycle times.
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`[0007]
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`An implementation of a drive system for the fatigue testing system mayinclude a
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`linear actuator or magnetic-based drive motor coupled to a flexible rolling diaphragm. The
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`drive system is coupled to a lower opening in the test chamber and is in fluid communication
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`with the fluid reservoir in the test chamber. The flexible rolling diaphragm (or “rolling bellow”)
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`is reciprocally moveable to pressurize and depressurize fluid and interacts with the lower
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`section of the fluid reservoir to provide a motive force to drive the working fluid through its
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`cycles within the test chamber, including the sample holders.
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`[0008]
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`Testing and test conditions are controlled by a control computer that permits both
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`input of test conditions and monitors feedbackof the test conditions during a testing run.
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`Computer system control may be either an open loop control that requires user intervention
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`in the event a condition falls outside pre-set condition parameters or a closed loop control
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`system in which the computer monitors and actively controls testing parameters to ensure
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`that the test conditions remain within the pre-set condition parameters.
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`[0009]
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`The fatigue tester is capable of simulating physiologic conditions on prosthetic
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`devices at an accelerated rate. The fatigue tester may also be configured to create either
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`sinusoidal or non-sinusoidal pressure and/or flow waveforms acrossthe prosthetic devices.
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`Pressure waveforms may also be applied that produce a pre-defined pressure gradient over
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`time to a prosthetic device being tested.
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`plurality of prosthetic devices is composedof a test chamber, a drive motor andafluid
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`[0010]
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`In one exemplary implementation, a device for simultaneous cyclic testing of a
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`Attorney Docket No. P201384.US.05
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`displacement member. The test chamber is pressurizable and has a fluid distribution
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`chamber with a first manifold defining a plurality of ports configured to receive and fluidicly
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`couple with a first end of each of a respective plurality of sample holders. The fluid
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`distribution chamber also defines an aperture in a lower facein fluid communication with a
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`pressure source. The test chamber also hasa fluid return chamber with a second manifold
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`disposed opposite and spaced apart from the first manifold of the fluid distribution chamber.
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`The manifold of the return chamber defines a plurality of ports configured to receive and
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`fluidicly couple with a second end of each of the respective plurality of sample holders. A
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`fluid return conduit both structurally and fluidily connects the fluid distribution chamber to the
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`fluid return chamber. The test chamber also has a compliance chamber which provides a
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`volume for holding a gas or an elastic material that compresses under a pressure placed
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`upon fluid in the test chamber and allowsfluid in the test chamber to occupya portion of the
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`volume. The drive motor is configured to operate cyclically, acyclically, or a combination of
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`both. The fluid displacement member is connected with and driven by the drive motor to
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`provide the pressure source that increases and decreases a pressure on fluid in the test
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`In this manner, cyclic and acyclic fluid pressures may be maintained throughout
`chamber.
`the test chamber.
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`[0011]
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`In another exemplary implementation, a device for accelerated cyclic testing of a
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`valved prosthetic device includes a pressurizable test chamber. The pressurizable test
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`chamber contains test system fluid and is further composed ofa fluid distribution chamber, a
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`fluid return chamber,a fluid return conduit, and an excess volume area. The fluid
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`distribution chamber is positioned on a first side of the valved prosthetic device andis in fluid
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`communication with a pressure source. The fluid return chamber is positioned on a second
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`side of the valved prosthetic device. The fluid return conduit is both structurally and fluidily
`connectsthe fluid distribution chamber to the fluid return chamber. The excess volume area
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`is in fluid communication with the fluid return chamber and provides a volume for storing a
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`volume of a test system fluid when the test system fluid is under compression.
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`[0012]
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`In a further exemplary implementation, a method is presented for operating an
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`accelerated cyclic test system for evaluating a valved prosthetic device. A volume oftest
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`system fluid is stored in an excess volume area during a system driving stroke that opens
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`the valved prosthetic device. The stored volume of test system fluid is then released during
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`a return stroke that closes the valved prosthetic device.
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`[0013]
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`This Summaryis provided to introduce a selection of concepts in a simplified form
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`that are further described below in the Detailed Description. This Summaryis not intended
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`to identify key features or essential features of the claimed subject matter, nor is it intended
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`Attorney Docket No. P201384.US.05
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`to be usedto limit the scope of the claimed subject matter. A more extensive presentation of
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`features, details, utilities, and advantagesof the present invention is providedin the following
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`written description of various embodiments of the invention, illustrated in the accompanying
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`drawings, and defined in the appendedclaims.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`[0014]
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`FIG. 1 is a combined isometric view and schematic diagram of an exemplary
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`implementation of a fatigue testing system and a corresponding control system.
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`[0015]
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`FIG. 2Ais a front elevation view of the fatigue testing system of FIG. 1.
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`FIG. 2B is an enlarged view of the motor support in the area surroundedby the
`[0016]
`circle labeled 2B in FIG. 2A.
`
`[0017]
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`FIG. 3 is a partial cross sectional view of a test chamber of the fatigue testing
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`system taken alongline 3-3 of FIG. 1.
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`[0018]
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`FIG. 4A is an isometric view in cross section of a portion of the fatigue testing
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`system if FIG.
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`1 detailing a flexible rolling diaphragm pump connected to a linear piston drive
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`system in a down stroke position.
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`[0019]
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`FIG. 4B is an isometric view in cross section of a portion of the fatigue testing
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`system if FIG.
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`1 detailing a flexible rolling diaphragm pump connected to a linear piston drive
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`system in an upstroke position.
`
`[0020]
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`FIG. 5A is an isometric view in cross section of a portion of the test chamber of
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`the fatigue testing system detailing an isolation valve in an open position.
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`[0021]
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`FIG. 5B is an isometric view in cross section of a portion of the test chamber of
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`the fatigue testing system detailing the isolation valve in a closed position.
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`[0022]
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`FIG. 6 is a schematic diagram in cross section of an alternative implementation of
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`a test chamber for use in a fatigue testing system.
`
`[0023]
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`FIG. 7 is a graph depicting three exemplary pressure control waves for
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`generation by test control software to provide pressure across a sample device being tested.
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`[0024]
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`FIG. 8 is a schematic diagram of a software and hardware implementation for
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`controlling a fatigue testing system.
`
`[0025]
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`FIG. 9 is a schematic diagram of an exemplary computer system for controlling a
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`fatigue testing system.
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`DETAILED DESCRIPTION
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`[0026]
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`The system of the present invention generally includes a linear actuator or
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`magnetic based drive coupled to a flexible rolling bellows diaphragm to provide variable
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`pressure gradients across test samples mounted in a test chamber housing a fluid reservoir.
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`These components operate together to act as a fluid pump and, when combined with a fluid
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`control system, provide the absolute pressure and/or differential pressure and flow
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`Attorney Docket No. P201384.US.05
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`conditions necessary to cycle test prosthetic devices mounted in the test chamber. The
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`flexible rolling diaphragm thrusts toward the lower section of the test chamber to provide a
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`motive force to drive the working fluid through cycles within the test chamber. The flexible
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`diaphragm is coupled to a lower opening in the test chamber andis reciprocally moveable to
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`pressurize and depressurize fluid within the lower section of the main housing. The flexible
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`rolling bellows diaphragm drive system has a very low inertia as compared to other drive
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`systems, e.g., a metal bellows or a standard piston-in-cylinder drive. The flexible diaphragm
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`is highly compliant with low resistance to axial deformation acrossits entire axial range of
`motion.
`
`[0027]
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`Plural sample holder tubes are coupled in parallel across the test chamber which
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`hasplural fluid distribution channels in communication with each of the sample holders. The
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`lower distribution chamber of the test chamber hasa single fluid reservoir in fluid flow
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`communication with eachofthe plurality of sample holders. The distribution chamber
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`includes a manifold with a plurality of fluid outlet ports, and each fluid outlet port
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`communicates with an inflow opening of a test holder. The upper return chamber of the test
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`chamber includes a similar manifold with a plurality of fluid inflow ports and compliance
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`chambers. Eachfluid inflow port communicates with an outflow opening of a respective
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`sample holder. A central return flow channel is provided between the return chamber and
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`the distribution chamber of the test chamber reservoir to provide a return flow of the working
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`fluid from the outflow section of the sample holders. A throttle control and a check valve are
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`disposed at the inflow and outflow ends of the central return flow channel, respectively, to
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`regulate fluid flow during testing. The throttle control serves to partially regulate the pressure
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`across the prosthetic devices being tested as well as the return flow of the working fluid in
`the fluid test chamber.
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`[0028]
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`These components operate together to provide a differential pressure and flow
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`conditions necessary to cycle the prosthetic device. The internal conditions, which may
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`include, among other things, temperature, differential pressure, and system pressure, are
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`electrically communicated to monitoring and controlling software on a test system computer.
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`The motion of the fluid pump and therefore the system dynamics are controlled via test
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`system control software. The pressurefield resulting from the pump motion is easily
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`controlled and can be set as a simple sine wave or as any complex user created waveform.
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`[0029]
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`One exemplary implementation of a fatigue testing system 100 for any of a
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`variety of prosthetic devices is depicted in FIGS. 1 through 5B. The fatigue testing
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`system 100 may be understood as having two primary components, a test chamber 106 and
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`a drive motor 105. The fatigue testing system 100 maybe both partially mounted upon and
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`housed within a base housing 157 formed and supported by a number of frame
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`members 102.
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`In the implementation shown, the drive motor 105 is housed within the base
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`housing 157 while the test chamber 106 is supported on a baseplate 111 forming a top
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`surface of the base housing 157. The base housing 157 may be open on its sides or
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`enclosed with removable panels as desired. A number of leveling feet 101 may be attached
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`to the bottom of the base housing 157 to provide for leveling of the fatigue testing
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`system 100 and therebyassist in creating consistent operating conditions across each of the
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`multiple sample chambersofthe fatigue testing system 100 as further described below.
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`[0030]
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`In the embodiment shown in FIGS. 1 and 2A with greater detail shown in FIG. 2B,
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`the drive motor 105 may bea linear motor. The linear drive motor 105 is mounted vertically
`on a motor stabilizer 104 and is centered underneath the test chamber 106. The lower end
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`of the drive motor 105 is supported by a spring 103 that interfaces with a horizontal
`foot 104a of the motor stabilizer 104 that extends underneath the linear drive motor 105. A
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`lower shaft extension 156 is attached to and extends downwardly from a thrust rod 108 of
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`the linear drive motor 105, through the spring 103, and through a bearing-lined aperture in
`the foot 104a of the motor stabilizer 104 whereit is secured on the underside of the
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`foot 104a as shown in FIG. 2B. The spring 103 is mounted concentrically about the lower
`shaft extension 156 and abuts the lower end of the thrust rod 108 of the linear motor 105 to
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`support the weight of the thrust rod 108 of the linear drive motor 105 when the linear drive
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`motor 105 is in an unpoweredstate. Further, in the event of a power failure during
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`operation, the spring 103 prevents the thrust rod 108 from dropping quickly and causing an
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`extremely large pressure gradient across test samplesin the test chamber 106, which could
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`damage the test samples.
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`[0031]
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`The upper endof the linear drive motor 105 is fixed to a motor support plate 109
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`that is in turn supported by several frame members 102 of the base housing 157. An
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`aperture in the motor support plate 109 provides for passage of the upper end of the thrust
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`rod 108 for alignment and mechanical connection with components interfacing with the test
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`chamber 106.
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`It should be noted that while a linear drive motor 105 is depicted in the
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`figures, other types of motors, for example, a regular DC motor or a voice coil, may be used
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`to offer alternate functionality than the linear drive motor 105 of desired for a particular
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`prosthetic device. The number of cycles completed during a test session may be monitored
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`by a cycle counter (not shown) that monitors the motion of the thrust rod 108 of the linear
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`motor 105, which may be affixed to the motor support plate 109.
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`[0032]
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`Several linkage components are provided between the drive motor 105 and the
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`test chamber 106 as shownto best advantage in FIGS. 2A and 3. These components
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`together form the drive member for creating a driving pressure on fluid in the system. An
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`upper shaft extension 112 is fixed to and extends from an upper endof the thrust rod 108
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`and further extends axially within a cylinder 113. The cylinder 113 is supported about the
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`upper shaft extension 112 within an alignment collar 107. The alignment collar 107 is further
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`supported by a pair of alignment mounts 155 that are fixed to and extend upward from the
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`motor support plate 109. The alignment collar 107 ensures that the cylinder 113 and the
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`drive motor 105 maintain axial alignment.
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`[0033]
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`A central aperture in the bottom of the cylinder 113 receives the upper shaft
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`extension 112. This aperture in the bottom wall of cylinder 113 is lined with a bearing 162 to
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`provide a lowfriction interface between the cylinder 113 and the upper shaft extension 112
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`as the upper shaft extension 112 moveswithin the cylinder 113 as further described below.
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`A piston 114 in the shape of an inverted cylindrical cup may be mounted to the top of the
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`upper shaft extension 112 for axial displacement within the cylinder 113 as the linear drive
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`motor 105 drives the upper shaft extension 112 up and down.
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`[0034]
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`The fluid drive member can be sized based on the volumetric requirements of the
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`test chamber 106 or test samples. Depending on the volume displacement required for a
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`particular application, the cylinder 113 and corresponding piston 114 may be swapped out
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`for sizes of larger or smaller diameter. The cylinder 113 and corresponding piston 114 may
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`thus be provided in a variety of diameters in order to provide different volume displacements
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`for a given stroke, and thereby pressure differentials, within the test chamber 106 depending
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`upon the type of sample being tested or the particular testing protocol being implemented.
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`[0035]
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`The top edge of the cylinder 113 extends radially to form a flange 113a that
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`interfaces with a bottom surface of a drive adapter 117. The drive adapter 117 may also be
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`provided in a variety of alternative different sizes to interface with different types of
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`cylinders 113 of various diameters. Thus, corresponding drive adapters 117 and alignment
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`collars 107 are similarly swapped for adjustment to the size of the cylinder 113. For
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`example, as shown in FIG. 3, the aperture in the drive adapter 117 is shaped as a frustum
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`with a wider upper mouth toward the test chamber 106 and walls that then taper to a smaller
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`opening at the interface with the top of the cylinder 113.
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`In another embodiment with a
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`larger diameter cylinder 113, the drive adapter 117 may have a larger diameter lower
`
`opening defining more sharply angled sidewalls of the frustum-shaped aperture and, in some
`
`embodiments, might even be cylindrical to accommodatea larger cylinder 113 of a common
`diameter.
`
`[0036]
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`In one implementation, the fluid drive member hasa flexible diaphragm drive
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`system as illustrated in FIGS. 3, 4A, and 4B. The diaphragm 115 may be a cap-like or cup-
`
`like member constructed of a non-reactive and flexible thin rubber, polymeric or synthetic
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`based material. The flexible diaphragm 115 is highly compliant with low resistance to axial
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`deformation acrossits entire axial range of motion within the cylinder 113 and the aperture in
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`the drive adapter 117. However, alternative configurations of the diaphragm 115 may be
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`employed so long as the configuration is capable of low friction and low resistance to
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`deformation under the influence of the piston 114. The outer diameter of the sidewalls 114a
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`of the piston 114 is slightly smaller than the inner diameter of the cylinder 113 to provide a
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`uniform gap therebetween. The gap is designed to be large enough to allow the sidewall of
`
`the diaphragm 115 to fold in half againstitself, i.e., evert, within this gap when the
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`sidewalls 114a of the piston 114 are positioned within the sidewalls of the cylinder 113.
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`It
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`may thus be noted thatin operation flexible diaphragm 115 will operate asarolling bellows
`when the linear drive motor 105 is actuated.
`
`
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`[0037] Many advantagesofa lowfriction flexible diaphragm 115 as opposedtoarigid
`
`metallic bellows ortraditional piston and cylinder drive may be appreciated. The lateral
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`surfaces of the diaphragm 115 evert between the sidewalls 115a of the piston 115 and the
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`sidewalls of the cylinder 113 as the piston 114 reciprocates within the cylinder 113 and drive
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`adapter 117. However, this eversion occurs with very low friction and low heat generation,
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`and exerts very little resistance to piston 114 movement. As such, the drive motor can
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`operate with a low driving force for either small or large displacements requiring low current
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`draw and thus low energy expenditure. The flexible diaphragm 115 is highly compliant with
`
`low resistance to axial deformation acrossits entire axial range of motion. Alternative
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`configurations of the diaphragm 115 may also be employed so long as the configuration is
`
`capable of very lowfiction and very low resistance to deformation under the influence of the
`
`piston 114.
`
`[0038]
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`The cup-shaped flexible diaphragm 115 is mounted on top of the piston 114. The
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`end wall of the diaphragm 115 is held against the top of the piston 114 bya rigid,
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`disk-shaped cap 116, which is fastened to the upper shaft extension 112 via fastener 158
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`(e,g., a set screw threaded within the upper extension shaft 112). A flange surface 115a
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`extends radially outward and circumferentially around the opening to the cavity of the
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`cup-shaped diaphragm 115. This flange surface 115a is sandwiched between the flange
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`surface 113a of the cylinder 113 and the bottom surface of the drive adapter 117 to maintain
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`a pressure seal between the test chamber 106 and the drive components.
`
`In view of FIG. 3,
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`the tapering of the frustum-shapedwall defining the aperture in the drive adapter 117 to an
`
`opening of comparable diameter to the diameter of the sidewalls forming the cylinder 113
`
`becomes apparent, i.e,., the need for corresponding surfaces between the flange of the
`
`cylinder 113 and the bottom surface of the drive adapter 117 to retain the flange
`
`surface 115a of the diaphragm 115.
`
`[0039]
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`A top surface of the drive adapter 117 is fastened to a plenum 118 that defines a
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`center cylindrical aperture aligned coaxially with the aperture of the drive adapter 117 and
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`the cavity defined by the cylinder 113. As shown in FIGS. 4A and 4B, a plurality of ports
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`may be defined within the sidewall of the plenum 118 to provide fluidfill, drainage, or other
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`functionality within the linkage components below the test chamber 106. For the sake of
`
`clarity, the plenum 118 shown in FIG. 3 depicts only a single sidewall port 143 that, in this
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`embodiment, is used asa fluid inflow port. However, additional ports may be defined within
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`the plenum 118 if desirable (see, e.g., FIGS. 4A and 4B).
`
`If not in use for a particular test
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`configuration, the sidewall ports 143 in the plenum 118 may be plugged. The plenum 118
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`may be of constant diameter to interface with an aperture in the base plate 111 of the base
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`housing 157. For this reason it can now be understood why in some embodiments the
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`opening in the top surface of the drive adapter 117 may be of a larger diameter than the
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`opening in the bottom surface of the drive adapter 117 as the drive adapter 117 mates with a
`
`constant diameter plenum 118 in contrast to a variable diameter cylinder 113.
`
`[0040]
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`Aspreviously indicated, the test chamber 106 sits atop of the base plate 111 on
`
`the base housing 157. The foundation of the test chamber 106 may in some embodiments
`
`include a gate guide plate 120 that also defines a central aperture that is coextensive in
`
`diameter with and concentrically aligned with the aperture in the base plate 111. A
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`distribution chamber 126 is supported by the gate guide plate 120. The gate guide
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`plate 120, the distribution chamber 126, and the base plate 111 mayall be fastened together
`
`via bolts (not shown) extending upward from the underside of the base plate 111. A pair of
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`gate seals 160 may be positioned between the gate guide plate 120 and the distribution
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`chamber 126. The gate seals 160 may bea set of stacked O-rings surrounding the central
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`aperturesin the gate guide plate 120 and the distribution chamber 126. The gate seals 160
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`maybe slightly recessed within corresponding annular grooves formed in a bottom surface
`
`of the distribution chamber 126 and a top surface of the gate guide plate 120.
`
`[0041]
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`A shallow flat channel 159 of a width at least slightly greater than the diameter of
`
`the gate seals 160 may be formed to extend radially from the center aperture within the top
`
`surface of the gate guide plate 120. A flat rectangular knife or gate valve 119, shown to best
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`advantage in FIGS. 5A and 5B, maybe positioned within the channel in the gate guide
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`plate 120. The gate valve 119 is shownin a radially withdrawn, open position in FIG. 5A,
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`such that there is an open passage between the center apertures defined within the gate
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`plate 120 and the distribution chamber 126.
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`In this position, the gate seals 160 press
`
`against each other to create a fluid tight seal about the central apertures.
`
`[0042]
`
`In a closed state as depicted in FIG. 5B, the gate valve 119 is pushed radially
`
`inward such that the flat plate forming the gate valve 119 extends completely across the
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`center apertures and is sealed between the gate seals 160 to fluidically separate the gate
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`guide plate 120 and the linkage elements belowit from the rest of the test chamber 106
`
`aboveit. Closure of the gate valve 119 thus allows for easy maintenanceof the drive
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`motor 105 or the piston driver 114 (e.g., replacementof the flexible bellows diaphragm 115)
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`without having to drain the test chamber 106.
`
`[0043]
`
`Aspreviously noted, the distribution chamber 126 is positioned on top of the gate
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`guide plate 120. The distribution chamber 126 defines a much wider but shallow cavity with
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`Attorney Docket No. P201384.US.05
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`an interior bottom wall that slants radially inward until it reaches a common diameter with the
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`aperture of the gate plate 120.
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`In this embodiment, one or more resistive heaters 130 may
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`be embeddedwithin the bulk of the distribution chamber 126 underneath the fluid cavity
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`defined by distribution chamber 126.
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`In one embodiment a separate heater 138 may be
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`located immediately beneath each sample holder 129 (as further described below) to aid in
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`the uniformity of heat distribution within the fluid in the test chamber 106.
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`[0044]
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`A distribution chamber manifold 153 is mounted to a top surface of the
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`distribution chamber 126, for example, by bolting the two surfaces together about the
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`perimeter. The distribution chamber manifold 153 may form a conical diverter surface 122
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`that extends downward into the cavity of the distribution chamber 126. A center bore 164
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`extends through the distribution chamber manifold 153, including through the diverter 122.
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`This center bore forms part of a return flow path 128 as further described below. The
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`distribution chamber manifold 153 may further define a plurality of bores 166 spaced about
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`the perimeter of the distribution chamber manifold 153.
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`In the embodiment shown in FIGS. 1
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`through 3, eight perimeter bores 166 are defined at a uniform radial distance from the center
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`and are equiangularly spaced apart. However, in alternative embodiments, there may be
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`greater or fewer perimeter bores 166 and different or non-uniform spacing may be
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`implementedif desired. A sample inlet tube 147 forming the bottom half of a sample
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`holder 129 is connected within and seals against each of the perimeter bores 166 of the
`distribution chamber manifold 153.
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`[0045]
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`Similarly, a lower conduit wall 124(2) of a telescoping center conduit 124 mounts
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`within and seals against the center bore 164 in the distribution chamber manifold 153. A
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`one-wayvalve 127 or similar check valve is positioned within the center bore 164 of the
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`distribution chamber manifold 153 below the lower conduit wall 124(2) of the center
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`conduit 124. The second half of the center conduit 124 is formedas a cylindrical upper
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`conduit wall 124(1) with an inner diameter substantially the same as an outer diameter of the
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`lower conduit wall 124(2) such that the center conduit 124 can be expanded or contracted in
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`length. One or more center seals 161, for example, in the form of O-rings mounted within
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`annular recessesin the outer surface of the lower conduit wall 121(2) provide a fluid tight
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`seal interface with the interior surface of the upper conduit wall 124(1).
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`[0046]
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`Each of the sample holders 129 is also composed of a sample outlet tube 148
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`that sits atop a respective sample inlet tube 147. The actual test sample 130 (e.g., a
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`prosthetic device) may be sandwiched between the sample inlet tube 147 and sample outlet
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`tube 148 to holdit in place within the test chamber 106.
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`In other embodiments (not shown)
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`each of the sample holders 129 maybe an integral unit with a test sample 130 mounted
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`within by any of a variety of means that may be specific to the nature of the particular test
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`sample 130.
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`4830-0530-7168\L
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`Attorney Docket No. P201384.US.05
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`[0047]
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`Areturn chamber manifold 154 is positioned atop each of the sample outlet
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`tubes 148 and the upper conduit wall 124(1) of the center conduit 124. The return chamber
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`manifold 154 defines corresponding perimeter bores 167 for mating with each of the sample
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`outlet tubes 148 and a center aperture 165 for mating with the upper conduit wall 124(1) of
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`the center conduit 124. Each of the interfaces between the sample outlet tubes 148 and the
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`center conduit 124 with the return chamber manifold 154 is configured to provide a fluid tight
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`seal between the components.
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`A returm chamber 136 is mounted on top of the return chamber manifold 154 ina
`[0048]
`similar manner as the distribution chamber 126 is mountedto the distribution chamber
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`manifold 153. The return chamber 136 defines one or more compliance chambers 135
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`which, in the embodiment of FIGS. 1-3, are composed of cavities associated respectively
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`with each of the sample holders 129. As used herein, “compliance” refers to the ability of the
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`cavities forming the compliance chambers 135 to absorb some of the pressure placed upon
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`the fluid in the