`
`TITLE
`
`Fatigue testing system for prosthetic devices
`
`INVENTORS
`
`Benjamin McCloskey of Evergreen, Colorado
`
`Craig Weinberg of Denver, Colorado
`
`Steven Weinberg of League City, Texas
`
`CROSS REFERENCE TO RELATED APPLICATIONS
`
`[0001]
`
`This application is a continuation of US. application no. 14/137,313 filed 20
`
`December 2013 entitled “Fatigue testing system for prosthetic devices,” which is a
`
`continuation of U.S. application no. 12/718,316 filed 5 March 2010 entitled “Fatigue testing
`
`system for prosthetic devices," which claims the benefit of priority pursuant to 35 U.S.C.
`
`§ 119(e) of US. provisional application no. 61/158,185 filed 6 March 2009 entitled
`
`“Apparatus and method for fatigue testing of prosthetic valves,” which are hereby
`
`incorporated herein by reference in their entirety.
`
`TECHNICAL FIELD
`
`[0002]
`
`The technology described herein relates to systems and methods for fatigue
`
`testing of prosthetic devices, in particular, but not limited to, prosthetic vascular and heart
`
`valves, under simulated physiological loading conditions and high-cycle applications.
`
`BACKGROUND
`
`[0003]
`
`Prior prosthetic valve testing apparatus and methods typically use a traditional
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`rotary motor coupled with mechanisms to produce regular sinusoidal time varying pressure
`
`field conditions. To accurately simulate physiologic conditions and/or produce a more
`
`desirable test condition, especially at accelerated testing speeds, a non-sinusoidal time
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`dependent pressure field may be desired. This is not easily accomplished with a
`
`mechanistic approach. Furthermore, current systems employ a flexible metallic bellows or
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`conventional piston and cylinder as drive members to provide the pressure actuation.
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`Flexible metallic bellows are not ideal because they require high forces to operate and
`
`resonate at 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
`
`employed in these systems are subjected to fiction and thus have severely limited life in high
`
`cycle applications.
`
`[0004]
`
`The information included in this Background section of the specification, including
`
`any references cited herein and any description or discussion thereof, is included for
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`technical reference purposes only and is not to be regarded subject matter by which the
`
`scope of the invention is to be bound.
`
`4830-0530-7168‘d
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`PAGE 1 OF 34
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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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`PAGE 1 OF 34
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`
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`Attorney Docket No. P201384.US.05
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`SUMMARY
`
`[0005]
`
`A design for a fatigue testing system for cyclic, long-term testing of various types
`
`of prosthetic devices (e.g., cardiac valves, vascular valves, stents, atrail septal defect
`
`technologies, vascular linings, and others) is designed to impart a repeating loading
`
`condition for the test samples during a test run. However, the system is also designed to be
`
`variable in its abilities so it can accurately test multiple technologies. Thus, the system may
`
`be variably configured depending upon the device being tested to impart a particular loading
`
`profile to repeatedly expose the prosthetic device being tested to desired physiological
`
`loading conditions during a testing run. The purpose is to simulate typical or specific
`
`physiologic loading conditions on a vascular or heart prosthetic valve, or other prosthetic
`
`technology, at accelerated frequency over time to determine the efficacy, resiliency, and
`wear of the devices.
`
`[0006]
`
`Fatigue testing is accomplished by first deploying the prosthetic device in an
`
`appropriately sized sample holder, e.g., a rigid or flexible tube, canister, housing or other
`
`appropriate structure for holding the device being tested. The sample holder is then placed
`
`between two halves of a test chamber that together form a reservoir for a working fluid. The
`
`test chamber is in turn mounted to a drive system. The sample holder and valve being
`
`tested are then subjected to physiological appropriate conditions which may include:
`
`pressure, temperature, flow rate, and cycle times.
`
`[0007]
`
`An implementation of a drive system for the fatigue testing system may include a
`
`linear actuator or magnetic-based drive motor coupled to a flexible rolling diaphragm. The
`
`drive system is coupled to a lower opening in the test chamber and is in fluid communication
`
`with the fluid reservoir in the test chamber. The flexible rolling diaphragm (or “rolling bellow”)
`
`is reciprocally moveable to pressurize and depressurize fluid and interacts with the lower
`
`section of the fluid reservoir to provide a motive force to drive the working fluid through its
`
`cycles within the test chamber, including the sample holders.
`
`[0008]
`
`Testing and test conditions are controlled by a control computer that permits both
`
`input of test conditions and monitors feedback of the test conditions during a testing run.
`
`Computer system control may be either an open loop control that requires user intervention
`
`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.
`
`[0009]
`
`The fatigue tester is capable of simulating physiologic conditions on prosthetic
`
`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 across the prosthetic devices.
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`Pressure waveforms may also be applied that produce a pre-defined pressure gradient over
`
`time to a prosthetic device being tested.
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`PAGE 2 OF 34
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`
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`Attorney Docket No. P201384.US.05
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`[0010]
`
`In one exemplary implementation, a device for simultaneous cyclic testing of a
`
`plurality of prosthetic devices is composed of a test chamber, a drive motor and a fluid
`
`displacement member. The test chamber is pressurizable and has a fluid distribution
`
`chamber with a first manifold defining a plurality of ports configured to receive and fluidicly
`
`couple with a first end of each of a respective plurality of sample holders. The fluid
`
`distribution chamber also defines an aperture in a lowerface in fluid communication with a
`
`pressure source. The test chamber also has a fluid return chamber with a second manifold
`
`disposed opposite and spaced apart from the first manifold of the fluid distribution chamber.
`
`The manifold of the return chamber defines a plurality of ports configured to receive and
`
`fluidicly couple with a second end of each of the respective plurality of sample holders. A
`
`fluid return conduit both structurally and fluidily connects the fluid distribution chamber to the
`
`fluid return chamber. The test chamber also has a compliance chamber which provides a
`
`volume for holding a gas or an elastic material that compresses under a pressure placed
`
`upon fluid in the test chamber and allows fluid in the test chamber to occupy a portion of the
`
`volume. The drive motor is configured to operate cyclically, acyclically, or a combination of
`
`both. The fluid displacement member is connected with and driven by the drive motor to
`
`provide the pressure source that increases and decreases a pressure on fluid in the test
`
`In this manner, cyclic and acyclic fluid pressures may be maintained throughout
`chamber.
`the test chamber.
`
`[0011]
`
`In another exemplary implementation, a device for accelerated cyclic testing of a
`
`valved prosthetic device includes a pressurizable test chamber. The pressurizable test
`
`chamber contains test system fluid and is further composed of a fluid distribution chamber, a
`
`fluid return chamber, a fluid return conduit, and an excess volume area. The fluid
`
`distribution chamber is positioned on a first side of the valved prosthetic device and is in fluid
`
`communication with a pressure source. The fluid return chamber is positioned on a second
`
`side of the valved prosthetic device. The fluid return conduit is both structurally and fluidily
`connects the fluid distribution chamber to the fluid return chamber. The excess volume area
`
`is in fluid communication with the fluid return chamber and provides a volume for storing a
`
`volume of a test system fluid when the test system fluid is under compression.
`
`[0012]
`
`In a further exemplary implementation, a method is presented for operating an
`
`accelerated cyclic test system for evaluating a valved prosthetic device. A volume of test
`
`system fluid is stored in an excess volume area during a system driving stroke that opens
`
`the valved prosthetic device. The stored volume of test system fluid is then released during
`
`a return stroke that closes the valved prosthetic device.
`
`[0013]
`
`This Summary is provided to introduce a selection of concepts in a simplified form
`
`that are further described below in the Detailed Description. This Summary is not intended
`
`to identify key features or essential features of the claimed subject matter, nor is it intended
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`3
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`PAGE 3 OF 34
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`PAGE 3 OF 34
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`
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`Attorney Docket No. P201384.US.05
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`to be used to limit the scope of the claimed subject matter. A more extensive presentation of
`
`features, details, utilities, and advantages of the present invention is provided in the following
`
`written description of various embodiments of the invention, illustrated in the accompanying
`
`drawings, and defined in the appended claims.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0014]
`
`FIG. 1 is a combined isometric view and schematic diagram of an exemplary
`
`implementation of a fatigue testing system and a corresponding control system.
`
`[0015]
`
`FIG. 2A is a front elevation view of the fatigue testing system of FIG. 1.
`
`FIG. 28 is an enlarged view of the motor support in the area surrounded by the
`[0016]
`circle labeled 2B in FIG. 2A.
`
`[0017]
`
`FIG. 3 is a partial cross sectional view of a test chamber of the fatigue testing
`
`system taken along line 3-3 of FIG. 1.
`
`[0018]
`
`FIG. 4A is an isometric view in cross section of a portion of the fatigue testing
`
`system if FIG.
`
`1 detailing a flexible rolling diaphragm pump connected to a linear piston drive
`
`system in a down stroke position.
`
`[0019]
`
`FIG. 4B is an isometric view in cross section of a portion of the fatigue testing
`
`system if FIG.
`
`1 detailing a flexible rolling diaphragm pump connected to a linear piston drive
`
`system in an upstroke position.
`
`[0020]
`
`FIG. 5A is an isometric view in cross section of a portion of the test chamber of
`
`the fatigue testing system detailing an isolation valve in an open position.
`
`[0021]
`
`FIG. SB is an isometric view in cross section of a portion of the test Chamber of
`
`the fatigue testing system detailing the isolation valve in a closed position.
`
`[0022]
`
`FIG. 6 is a schematic diagram in cross section of an alternative implementation of
`
`a test chamberfor use in a fatigue testing system.
`
`[0023]
`
`FIG. 7 is a graph depicting three exemplary pressure control waves for
`
`generation by test control software to provide pressure across a sample device being tested.
`
`[0024]
`
`FIG. 8 is a schematic diagram of a software and hardware implementation for
`
`controlling a fatigue testing system.
`
`[0025]
`
`FIG. 9 is a schematic diagram of an exemplary computer system for controlling a
`
`fatigue testing system.
`
`DETAILED DESCRIPTION
`
`[0026]
`
`The system of the present invention generally includes a linear actuator or
`
`magnetic based drive coupled to a flexible rolling bellows diaphragm to provide variable
`
`pressure gradients across test samples mounted in a test chamber housing a fluid reservoir.
`
`These components operate together to act as a fluid pump and, when combined with a fluid
`
`control system, provide the absolute pressure and/or differential pressure and flow
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`4830-0530-7168\1
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`
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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
`
`flexible rolling diaphragm thrusts toward the lower section of the test chamber to provide a
`
`motive force to drive the working fluid through cycles within the test chamber. The flexible
`
`diaphragm is coupled to a lower opening in the test chamber and is reciprocally moveable to
`
`pressurize and depressurize fluid within the lower section of the main housing. The flexible
`
`rolling bellows diaphragm drive system has a very low inertia as compared to other drive
`
`systems, e.g., a metal bellows or a standard piston-in-cylinder drive. The flexible diaphragm
`
`is highly compliant with low resistance to axial deformation across its entire axial range of
`motion.
`
`[0027]
`
`Plural sample holder tubes are coupled in parallel across the test chamber which
`
`has plural fluid distribution channels in communication with each of the sample holders. The
`
`lower distribution chamber of the test chamber has a single fluid reservoir in fluid flow
`
`communication with each of the plurality of sample holders. The distribution chamber
`
`includes a manifold with a plurality of fluid outlet ports, and each fluid outlet port
`
`communicates with an inflow opening of a test holder. The upper return chamber of the test
`
`chamber includes a similar manifold with a plurality of fluid inflow ports and compliance
`
`chambers. Each fluid inflow port communicates with an outflow opening of a respective
`
`sample holder. A central return flow channel is provided between the return chamber and
`
`the distribution chamber of the test chamber reservoir to provide a return flow of the working
`
`fluid from the outflow section of the sample holders. A throttle control and a check valve are
`
`disposed at the inflow and outflow ends of the central return flow channel, respectively, to
`
`regulate fluid flow during testing. The throttle control serves to partially regulate the pressure
`
`across the prosthetic devices being tested as well as the return flow of the working fluid in
`the fluid test chamber.
`
`[0028]
`
`These components operate together to provide a differential pressure and flow
`
`conditions necessary to cycle the prosthetic device. The internal conditions, which may
`
`include, among other things, temperature, differential pressure, and system pressure, are
`
`electrically communicated to monitoring and controlling software on a test system computer.
`
`The motion of the fluid pump and therefore the system dynamics are controlled via test
`
`system control software. The pressure field resulting from the pump motion is easily
`
`controlled and can be set as a simple sine wave or as any complex user created waveform.
`
`[0029]
`
`One exemplary implementation of a fatigue testing system 100 for any of a
`
`variety of prosthetic devices is depicted in FIGS.
`
`1 through 58. The fatigue testing
`
`system 100 may be understood as having two primary components, a test chamber 106 and
`
`a drive motor 105. The fatigue testing system 100 may be both partially mounted upon and
`
`housed within a base housing 157 formed and supported by a number of frame
`
`members 102.
`
`In the implementation shown, the drive motor 105 is housed within the base
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`Attorney Docket No. P201384.US.05
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`housing 157 while the test chamber 106 is supported on a base plate 111 forming a top
`
`surface of the base housing 157. The base housing 157 may be open on its sides or
`
`enclosed with removable panels as desired. A number of leveling feet 101 may be attached
`
`to the bottom of the base housing 157 to provide for leveling of the fatigue testing
`
`system 100 and thereby assist in creating consistent operating conditions across each of the
`
`multiple sample chambers of the fatigue testing system 100 as further described below.
`
`[0030]
`
`In the embodiment shown in FIGS. 1 and 2A with greater detail shown in FIG. 2B,
`
`the drive motor 105 may be a 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
`
`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
`
`lower shaft extension 156 is attached to and extends downwardly from a thrust rod 108 of
`
`the linear drive motor 105, through the spring 103, and through a bearing-lined aperture in
`the foot 104a of the motor stabilizer 104 where it is secured on the underside of the
`
`foot 104a as shown in FIG. ZB. 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
`
`support the weight of the thrust rod 108 of the linear drive motor 105 when the linear drive
`
`motor 105 is in an unpowered state. Further, in the event of a power failure during
`
`operation, the spring 103 prevents the thrust rod 108 from dropping quickly and causing an
`
`extremely large pressure gradient across test samples in the test chamber 106, which could
`
`damage the test samples.
`
`[0031]
`
`The upper end of the linear drive motor 105 is fixed to a motor support plate 109
`
`that is in turn supported by several frame members 102 of the base housing 157. An
`
`aperture in the motor support plate 109 provides for passage of the upper end of the thrust
`
`rod 108 for alignment and mechanical connection with components interfacing with the test
`
`chamber 106.
`
`It should be noted that while a linear drive motor 105 is depicted in the
`
`figures, other types of motors, for example, a regular DC motor or a voice coil, may be used
`
`to offer alternate functionality than the linear drive motor 105 of desired for a particular
`
`prosthetic device. The number of cycles completed during a test session may be monitored
`
`by a cycle counter (not shown) that monitors the motion of the thrust rod 108 of the linear
`
`motor 105, which may be affixed to the motor support plate 109.
`
`[0032]
`
`Several linkage components are provided between the drive motor 105 and the
`
`test chamber 106 as shown to best advantage in FIGS. 2A and 3. These components
`
`together form the drive member for creating a driving pressure on fluid in the system. An
`
`upper shaft extension 112 is fixed to and extends from an upper end of the thrust rod 108
`
`and further extends axially within a cylinder 113. The cylinder 113 is supported about the
`
`upper shaft extension 112 within an alignment collar 107. The alignment collar 107 is further
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`Attorney Docket No. P201384.US.05
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`supported by a pair of alignment mounts 155 that are fixed to and extend upward from the
`
`motor support plate 109. The alignment oollar 107 ensures that the cylinder 113 and the
`
`drive motor 105 maintain axial alignment.
`
`[0033]
`
`A central aperture in the bottom of the cylinder 113 receives the upper shaft
`
`extension 112. This aperture in the bottom wall of cylinder 1 13 is lined with a bearing 162 to
`
`provide a low friction interface between the cylinder 113 and the upper shaft extension 112
`
`as the upper shaft extension 112 moves within the cylinder 113 as further described below.
`
`A piston 114 in the shape of an inverted cylindrical cup may be mounted to the top of the
`
`upper shaft extension 112 for axial displacement within the cylinder 113 as the linear drive
`
`motor 105 drives the upper shaft extension 112 up and down.
`
`[0034]
`
`The fluid drive member can be sized based on the volumetric requirements of the
`
`test chamber 106 or test samples. Depending on the volume displacement required for a
`
`particular application, the cylinder 113 and corresponding piston 114 may be swapped out
`
`for sizes of larger or smaller diameter. The cylinder 113 and corresponding piston 114 may
`
`thus be provided in a variety of diameters in order to provide different volume displacements
`
`for a given stroke, and thereby pressure differentials, within the test chamber 106 depending
`
`upon the type of sample being tested or the particular testing protocol being implemented.
`
`[0035]
`
`The top edge of the cylinder 113 extends radially to form a flange 113a that
`
`interfaces with a bottom surface of a drive adapter 117. The drive adapter 117 may also be
`
`provided in a variety of alternative different sizes to interface with different types of
`
`cylinders 113 of various diameters. Thus, corresponding drive adapters 117 and alignment
`
`collars 107 are similarly swapped for adjustment to the size of the cylinder 113. For
`
`example, as shown in FIG. 3, the aperture in the drive adapter 117 is shaped as a frustum
`
`with a wider upper mouth toward the test chamber 106 and walls that then taper to a smaller
`
`opening at the interface with the top of the cylinder 113.
`
`In another embodiment with a
`
`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 accommodate a larger cylinder 113 of a common
`diameter.
`
`[0036]
`
`In one implementation, the fluid drive member has a flexible diaphragm drive
`
`system as illustrated in FIGS. 3, 4A, and 4B. The diaphragm 115 may be a cap-like or cup-
`
`|ike member constructed of a non-reactive and flexible thin rubber, polymeric or synthetic
`
`based material. The flexible diaphragm 115 is highly compliant with low resistance to axial
`
`deformation across its entire axial range of motion within the cylinder 113 and the aperture in
`
`the drive adapter 117. However, alternative configurations of the diaphragm 115 may be
`
`employed so long as the configuration is capable of low friction and low resistance to
`
`deformation under the influence of the piston 114. The outer diameter of the sidewalls 1143
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`Attorney Docket No. P201384.US.05
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`of the piston 114 is slightly smaller than the inner diameter of the cylinder 113 to provide a
`
`uniform gap therebetween. The gap is designed to be large enough to allow the sidewall of
`
`the diaphragm 115 to fold in half against itself, i.e., evert, within this gap when the
`
`sidewalls 114a of the piston 114 are positioned within the sidewalls of the cylinder 113.
`
`It
`
`may thus be noted that in operation flexible diaphragm 115 will operate as a rolling bellows
`when the linear drive motor 105 is actuated.
`
`[0037]
`
`Many advantages of a low friction flexible diaphragm 115 as opposed to a rigid
`
`metallic bellows or traditional piston and cylinder drive may be appreciated. The lateral
`
`surfaces of the diaphragm 115 evert between the sidewalls 115a of the piston 115 and the
`
`sidewalls of the cylinder 113 as the piston 114 reciprocates within the cylinder 113 and drive
`
`adapter 117. However, this eversion occurs with very low friction and low heat generation,
`
`and exerts very little resistance to piston 114 movement. As such, the drive motor can
`
`operate with a low driving force for either small or large displacements requiring low current
`
`draw and thus low energy expenditure. The flexible diaphragm 115 is highly compliant with
`
`low resistance to axial deformation across its entire axial range of motion. Alternative
`
`configurations of the diaphragm 115 may also be employed so long as the configuration is
`
`capable of very low fiction and very low resistance to deformation under the influence of the
`
`piston 114.
`
`[0038]
`
`The cup-shaped flexible diaphragm 115 is mounted on top of the piston 114. The
`
`end wall of the diaphragm 115 is held against the top of the piston 114 by a rigid,
`
`disk-shaped cap 116, which is fastened to the upper shaft extension 112 via fastener 158
`
`(e,g., a set screw threaded within the upper extension shaft 112). A flange surface 115a
`
`extends radially outward and circumferentially around the opening to the cavity of the
`
`cup-shaped diaphragm 115. This flange surface 115a is sandwiched between the flange
`
`surface 113a of the cylinder 113 and the bottom surface of the drive adapter 117 to maintain
`
`a pressure seal between the test chamber 106 and the drive components.
`
`In view of FIG. 3,
`
`the tapering of the frustum-shaped wall 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]
`
`A top surface of the drive adapter 117 is fastened to a plenum 118 that defines a
`
`center cylindrical aperture aligned coaxially with the aperture of the drive adapter 117 and
`
`the cavity defined by the cylinder 113. As shown in FIGS. 4A and 4B, a plurality of ports
`
`may be defined within the sidewall of the plenum 118 to provide fluid fill, drainage, or other
`
`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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`Attorney Docket No. P201384.US.05
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`embodiment, is used as a fluid inflow port. However, additional ports may be defined within
`
`the plenum 118 if desirable (see, e.g., FIGS. 4A and 48).
`
`If not in use for a particular test
`
`configuration, the sidewall ports 143 in the plenum 118 may be plugged. The plenum 118
`
`may be of constant diameter to interface with an aperture in the base plate 111 of the base
`
`housing 157. For this reason it can now be understood why in some embodiments the
`
`opening in the top surface of the drive adapter 117 may be of a larger diameter than the
`
`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]
`
`As previously indicated, the test chamber 106 sits atop 0f 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
`
`distribution chamber 126 is supported by the gate guide plate 120. The gate guide
`
`plate 120, the distribution chamber 126, and the base plate 111 may all be fastened together
`
`via bolts (not shown) extending upward from the underside of the base plate 111. A pair of
`
`gate seals 160 may be positioned between the gate guide plate 120 and the distribution
`
`chamber 126. The gate seals 160 may be a set of stacked O-rings surrounding the central
`
`apertures in the gate guide plate 120 and the distribution chamber 126. The gate seals 160
`
`may be 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]
`
`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
`
`advantage in FIGS. 5A and 5B, may be positioned within the channel in the gate guide
`
`plate 120. The gate valve 119 is shown in a radially withdrawn, open position in FIG. 5A,
`
`such that there is an open passage between the center apertures defined within the gate
`
`plate 120 and the distribution chamber 126.
`
`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. SB, the gate valve 119 is pushed radially
`
`inward such that the flat plate forming the gate valve 119 extends completely across the
`
`center apertures and is sealed between the gate seals 160 to fluidically separate the gate
`
`guide plate 120 and the linkage elements below it from the rest of the test chamber 106
`
`above it. Closure of the gate valve 119 thus allows for easy maintenance of the drive
`
`motor 105 or the piston driver 114 (e.g., replacement of the flexible bellows diaphragm 115)
`
`without having to drain the test chamber 106.
`
`[0043]
`
`As previously noted, the distribution chamber 126 is positioned on top of the gate
`
`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 embedded within 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.
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`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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`implemented ifdesired. 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-way valve 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 formed as 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 recesses in 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 hold it 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 may be 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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`Attorney Docket No. P201384.US.05
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`[0047]
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`A return 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 return chamber 136 is mounted on top ofthe return chamber manifold 154 in a
`[0048]
`similar manner as the distribution chamber 126 is mounted to 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 for