US009186224B2
`
`(12) United States Patent
`US 9,186,224 B2
`(10) Patent No.:
`(45) Date of Patent: McCloskey et al.
`Nov. 17, 2015
`
`(54) FATIGUE TESTING SYSTEM FOR
`PROSTHETIC DEVICES
`
`(72)
`
`(71) Applicant: Biomedical Device Consultants and
`Laboratories of Colorado, LLC, Wheat
`Ridge, CO (US)
`Inventors: Benjamin McCloskey, Evergreen, CO
`(US); Craig Weinberg, Denver, CO
`(US); Steven Weinberg, League City,
`TX (US)
`(73) Assignee: BIOMEDICAL DEVICE
`CONSULTANTS & LABORATORIES
`
`( * ) Notice:
`
`LLC, Wheat Ridge, CO (US)
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl.No.: 14/523,104
`
`(22)
`
`(65)
`
`Filed:
`
`Oct. 24, 2014
`
`Prior Publication Data
`
`Feb. 12,2015
`US 2015/0040644 A1
`Related US. Application Data
`
`(63) Continuation of application No. 14/137,313, filed on
`Dec. 20, 2013, which is a continuation of application
`No. 12/718,316, filed on Mar. 5, 2010, now Pat. No.
`8,627,708.
`
`(60) Provisional application No. 61/158,185, filed on Mar.
`6, 2009.
`
`(51)
`
`Int. Cl.
`A613 19/00
`G01N 3/32
`
`(2006.01)
`(2006.01)
`(Continued)
`
`(52) US. Cl.
`CPC ............... A613 19/46 (2013.01); A61F 2/2472
`(2013.01); G01M 99/007 (2013.01); G01N3/32
`(2013.01);
`
`(Continued)
`
`(58) Field of Classification Search
`CPC ............ G01N 3/32; G01N 2203/0089; G01N
`2203/0246; G01N 2203/0204; G01N
`2203/0476; A61B 19/46; A61F 2/2472;
`G01M 99/007
`
`USPC .............................................................. 73/37
`
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,911,735 A
`4,381,663 A
`
`10/1975 Di Crispino
`5/ 1983 Swanson
`
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`
`CA
`JP
`
`2438336
`08086728 A2
`
`2/2002
`4/1996
`
`(Continued)
`OTHER PUBLICATIONS
`
`International Search Report and Written Opinion, Application No.
`PCT/US2010/061740, Sep. 9, 2011, 9 pages.
`
`(Continued)
`
`Primary Examiner 7 Lisa Caputo
`Assistant Examiner 7 Philip Cotey
`(74) Attorney, Agent, or Firm 7 Dorsey and Whitney LLP
`
`(57)
`
`ABSTRACT
`
`A fatigue testing system provides simultaneous cycle testing
`for a plurality of prosthetic devices under simulated physi-
`ological loading conditions. A plurality of sample holders
`containing test samples of prosthetic devices is positioned
`between a distribution chamber and a return fluid chamber to
`
`form an integrated test chamber. A reciprocating linear drive
`motor operates a rolling bellows diaphragm to cyclically
`pressurize fluid within the test chamber and drive the pres-
`surized fluid through the prosthetic devices being tested. The
`test chamber defines a return flow conduit in fluid communi-
`
`cation with each ofthe sample holders, the return fluid cham-
`ber, and the distribution chamber. Compliance chambers and
`throttle valves associated with each of the sample holders
`regulate the pressure gradient and back pressure across the
`prosthetic devices being tested.
`
`7 Claims, 9 Drawing Sheets
`
` 131
`1 NR SOURCE
`
`
`
`PRESSURE
`
`REGULATOR
`
`1M5 :
`
`
`
`
`AMPLlFlER s
`
`CONTROL
`svsrsm
`
`
`
`
`
`
`
`
`
`
`
`PAGE 1 OF 20
`
`WATERS TECHNOLOGIES CORPORATION
`
`EXHIBIT 1001
`
`WATERS TECHNOLOGIES CORPORATION
`EXHIBIT 1001
`
`PAGE 1 OF 20
`
`

`

`US 9,186,224 B2
`
`Page 2
`
`8,034,608 B2
`8,196,478 B2
`8,318,414 B2
`8,584,538 B2
`8,627,708 B2
`2002/0116054 A1*
`2003/0066338 A1
`2003/0110830 A1
`2003/0125804 A1*
`2003/0199083 A1
`2004/0016301 A1 *
`2007/0185534 A1
`2009/0132043 A1
`2010/0225478 A1
`2011/0066237 A1
`2011/0146385 A1
`2011/0259439 A1
`2014/0109651 A1
`2015/0040644 A1 *
`
`10/2011 Dancu
`6/2012 Lorenz et al.
`11/2012 Dancu et a1.
`11/2013 VlcCloskey et al.
`1/2014 VlcCloskey et al.
`8/2002 Lundell et a1.
`................. 623/21
`4/2003 Vlichalsky et a1.
`6/2003 Dehdashtian et a1.
`7/2003 Kruse et a1.
`.................... 623/21
`10/2003 Vilendrer et a1.
`1/2004 Vloreno et a1.
`.................. 73/849
`8/2007 Conti et a1.
`5/2009 George et a1.
`9/2010 VIcCloskey et a1.
`3/2011 Vlatheny
`6/2011 Weinberg et a1.
`10/2011 \Ieerincx
`4/2014 VIcCloskey et a1.
`2/2015 VIcCloskey et a1.
`
`.............. 73/37
`
`
`
`FOREIGN PATEI\T DOCUMENTS
`
`""""""
`
`73/37
`
`WO
`WO
`
`W02010/102185 A3
`W02010/024669 A2
`
`9/2010
`3/2010
`
`~~~~~~~~~ 73/168
`
`OTHER PUBLICATIONS
`
`Supplementary European Search Report, Application No. EP
`107493769, Jan. 8, 2015, 8 pages.
`Examination Report, Canadian Intellectual Property Office, Appli-
`cation No. 2,754,257, Nov. 25, 2014, 3 pages.
`
`* cited by examiner
`
`(51)
`
`Int. Cl.
`G01M 99/00
`A61F 2/24
`
`(2011.01)
`(2006.01)
`
`(52) us. Cl.
`CPC G01N 2203/0089 (2013.01); G01N 2203/0204
`(2013.01); G01N2203/0246 (2013.01); G01N
`2203/0476 (2013.01)
`
`(56)
`
`References Cited
`
`US. PATENT DOCUMENTS
`
`........... 73/37
`
`>>>>>>>>>>>
`
`A>i<
`
`4,450,710
`4,546,642
`4,682,491
`4,972,721
`5,176,153
`5,272,909
`5,406,857
`5,528,944
`5,531,094
`5,670,708
`5,792,603
`6,062,075
`6,810,751
`6,881,224
`7,254,988
`7,348,175
`7,363,821
`7,472,604
`7,587,949
`7,621,192
`
`5/1984
`10/1985
`7/1987
`11/1990
`1/1993
`12/1993
`4/1995
`6/1996
`7/1996
`9/1997
`8/1998
`5/2000
`11/2004
`4/2005
`8/2007
`3/2008
`4/2008
`1/2009
`9/2009
`11/2009
`
`Nettekoven
`Swanson
`Pickard ..................
`Conti
`Eberhardt
`Nguyen et al.
`Eberhardt et al.
`Hoyt et al.
`More et al.
`Vilendrer ...............
`Dunkelman et al.
`Ritz et al.
`...............
`Moreno et al.
`Kruse et al.
`Keeble
`Vilendrer et al.
`Black et al.
`Moore et al.
`Dingmann et al.
`Conti et al.
`
`PAGE 2 OF 20
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`PAGE 2 OF 20
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`

`

`U.S. Patent
`
`NOV.17,2015
`
`Sheet 1 of 9
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`US 9,186,224 B2
`
`131
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`NRSOURCE
`
`PRESSURE
`REGULATOR
`
`
`
`AMPUHER&
`CONTROL
`SYSTEM
`
`COMPUTER
`
`371
`
`100
`
`PAGE 3 OF 20
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`PAGE 3 OF 20
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`

`

`US. Patent
`
`Nov. 17, 2015
`
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`US. Patent
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`Nov. 17, 2015
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`U.S. Patent
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`NOV. 17, 2015
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`PAGE 6 OF 20
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`PAGE 6 OF 20
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`Nov. 17, 2015
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`Nov. 17, 2015
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`Nov. 17, 2015
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`PAGE 9 OF 20
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`PAGE 9 OF 20
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`

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`US. Patent
`
`Nov. 17, 2015
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`US 9,186,224 132
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`U.S. Patent
`
`NOV. 17, 2015
`
`Sheet 9 of 9
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`186,224 B2
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`PAGE 11 OF 20
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`

`

`US 9,186,224 B2
`
`2
`
`1
`FATIGUE TESTING SYSTEM FOR
`PROSTHETIC DEVICES
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`other prosthetic technology, at accelerated frequency over
`time to determine the efficacy, resiliency, and wear of the
`devices.
`
`Fatigue testing is accomplished by first deploying the pros-
`thetic 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 physi-
`ological appropriate conditions which may include: pressure,
`temperature, flow rate, and cycle times.
`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
`
`20
`
`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
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`provide a motive force to drive the working fluid through its
`cycles within the test chamber, including the sample holders.
`Testing and test conditions are controlled by a control
`computer that permits both input oftest conditions and moni-
`tors 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
`system in which the computer monitors and actively controls
`testing parameters to ensure that the test conditions remain
`within the pre-set condition parameters.
`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 sinusoi-
`dal or non-sinusoidal pressure and/or flow waveforms across
`the prosthetic devices. Pressure waveforms may also be
`applied that produce a pre-defined pressure gradient over time
`to a prosthetic device being tested.
`In one exemplary implementation, a device for simulta-
`neous cyclic testing of a plurality of prosthetic devices is
`composed of a test chamber, a drive motor and a fluid dis-
`placement member. The test chamber is pres surizable 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 aper-
`ture in a lower face 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 ofthe fluid distribution chamber. The mani-
`
`fold of the return chamber defines a plurality of ports config-
`ured 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 dis-
`tribution chamber to the fluid return chamber. The test cham-
`
`ber 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, acycli-
`cally, or a combination of both. The fluid displacement mem-
`ber 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 chamber. In this manner, cyclic and acyclic
`fluid pressures may be maintained throughout the test cham-
`ber.
`
`This application is a continuation of US. application Ser.
`No. 14/137,313 filed 20 Dec. 2013 entitled “Fatigue testing
`system for prosthetic devices,” which is a continuation ofUS.
`application Ser. No. 12/718,316 filed 5 Mar. 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 Mar. 2009
`entitled “Apparatus and method for fatigue testing of pros-
`thetic valves,” which are hereby incorporated herein by ref-
`erence in their entirety.
`
`10
`
`15
`
`TECHNICAL FIELD
`
`The technology described herein relates to systems and
`methods for fatigue testing of prosthetic devices, in particu-
`lar, but not limited to, prosthetic vascular and heart valves,
`under simulated physiological loading conditions and high-
`cycle applications.
`
`BACKGROUND
`
`Prior prosthetic valve testing apparatus and methods typi-
`cally use a traditional rotary motor coupled with mechanisms
`to produce regular sinusoidal time varying pressure field con-
`ditions. To accurately simulate physiologic conditions and/or
`produce a more desirable test condition, especially at accel-
`erated testing speeds, a non-sinusoidal time dependent pres-
`sure field may be desired. This is not easily accomplished
`with a mechanistic approach. Furthermore, current systems
`employ a flexible metallic bellows or conventional piston and
`cylinder as drive members to provide the pressure actuation.
`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 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 appli-
`cations.
`
`The information included in this Background section ofthe
`specification, including any references cited herein and any
`description or discussion thereof, is included for technical
`reference purposes only and is not to be regarded subject
`matter by which the scope of the invention is to be bound.
`
`SUMMARY
`
`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, atrial septal defect technolo-
`gies, 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
`
`PAGE 12 OF 20
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`PAGE 12 OF 20
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`

`

`US 9,186,224 B2
`
`3
`In another exemplary implementation, a device for accel-
`erated 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 5
`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 cham-
`ber to the fluid return chamber. The excess volume area is in
`
`10
`
`fluid communication with the fluid return chamber and pro-
`vides a volume for storing a volume of a test system fluid
`when the test system fluid is under compression.
`In a further exemplary implementation, a method is pre-
`sented for operating an accelerated cyclic test system for
`evaluating a valved prosthetic device. Avolume oftest 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.
`This Summary is provided to introduce a selection of con-
`cepts 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 sub-
`ject matter, nor is it intended 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.
`
`15
`
`20
`
`25
`
`30
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`35
`
`FIG. 1 is a combined isometric view and schematic dia-
`
`4
`
`FIG. 9 is a schematic diagram of an exemplary computer
`system for controlling a fatigue testing system.
`
`DETAILED DESCRIPTION
`
`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 gra-
`dients 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 ab solute pres sure and/or differential pres sure and
`flow conditions necessary to cycle test prosthetic devices
`mounted in the test chamber. The flexible rolling diaphragm
`thrusts toward the lower section ofthe 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 move-
`able 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.
`Plural sample holder tubes are coupled in parallel across
`the test chamber which has plural fluid distribution channels
`in communication with each ofthe sample holders. The lower
`distribution chamber of the test chamber has a single fluid
`reservoir in fluid flow communication with each of the plu-
`rality 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 ofthe 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 ofthe 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.
`
`These components operate together to provide a differen-
`tial pressure and flow conditions necessary to cycle the pros-
`thetic device. The internal conditions, which may include,
`among other things, temperature, differential pressure, and
`system pressure, are electrically communicated to monitor-
`ing 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.
`
`One exemplary implementation of a fatigue testing system
`100 for any of a variety of prosthetic devices is depicted in
`FIGS. 1 through 5B. The fatigue testing system 100 may be
`understood as having two primary components, a test cham-
`ber 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 housing 157 while the test
`
`40
`
`45
`
`gram of an exemplary implementation of a fatigue testing
`system and a corresponding control system.
`FIG. 2A is a front elevation view of the fatigue testing
`system of FIG. 1.
`FIG. 2B is an enlarged view ofthe motor support in the area
`surrounded by the circle labeled 2B in FIG. 2A.
`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.
`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.
`FIG. 4B is an isometric view in cross section of a portion of 50
`the fatigue testing system if FIG. 1 detailing a flexible rolling
`diaphragm pump connected to a linear piston drive system in
`an upstroke position.
`FIG. 5A is an isometric view in cross section of a portion of
`the test chamber of the fatigue testing system detailing an 55
`isolation valve in an open position.
`FIG. 5B 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.
`FIG. 6 is a schematic diagram in cross section of an alter-
`native implementation of a test chamber for use in a fatigue
`testing system.
`FIG. 7 is a graph depicting three exemplary pressure con-
`trol waves for generation by test control software to provide
`pressure across a sample device being tested.
`FIG. 8 is a schematic diagram of a software and hardware
`implementation for controlling a fatigue testing system.
`
`60
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`65
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`US 9,186,224 B2
`
`5
`chamber 106 is supported on a base plate 111 forming a top
`surface ofthe 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 con-
`sistent operating conditions across each of the multiple
`sample chambers of the fatigue testing system 100 as further
`described below.
`
`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 1 04 and is centered underneath the test cham-
`
`ber 106. The lower end ofthe drive motor 105 is supported by
`a spring 103 that interfaces with a horizontal foot 10411 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 10411 of the motor stabilizer 104
`where it is secured on the underside ofthe 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 ofthe linear motor 105 to support the weight of
`the thrust rod 108 of the linear drive motor 105 when the
`
`linear drive motor 1 05 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 caus-
`ing an extremely large pressure gradient across test samples
`in the test chamber 106, which could damage the test samples.
`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 ofthe upper
`end of the thrust rod 108 for alignment and mechanical con-
`nection 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 alter-
`nate functionality than the linear drive motor 105 of desired
`for a particular prosthetic device. The number of cycles com-
`pleted during a test session may be monitored by a cycle
`counter (not shown) that monitors the motion ofthe thrust rod
`1 08 ofthe linear motor 1 05, which may be aflixed to the motor
`support plate 109.
`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
`supported by a pair of alignment mounts 155 that are fixed to
`and extend upward from the motor support plate 109. The
`alignment collar 107 ensures that the cylinder 113 and the
`drive motor 105 maintain axial alignment.
`A central aperture in the bottom of the cylinder 113
`receives the upper shaft extension 112. This aperture in the
`bottom wall of cylinder 113 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
`
`10
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`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`6
`displacement within the cylinder 1 13 as the linear drive motor
`105 drives the upper shaft extension 112 up and down.
`The fluid drive member can be sized based on the volumet-
`
`ric requirements of the test chamber 106 or test samples.
`Depending on the volume displacement required for a par-
`ticular application, the cylinder 113 and corresponding piston
`114 may be swapped out for sizes of larger or smaller diam-
`eter. 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 pres sure differentials, within the test chamber 106
`depending upon the type of sample being tested or the par-
`ticular testing protocol being implemented.
`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, corre-
`sponding 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 frus-
`tum-shaped aperture and, in some embodiments, might even
`be cylindrical to accommodate a larger cylinder 113 of a
`common diameter.
`
`In one implementation, the fluid drive member has a flex-
`ible diaphragm drive 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, poly-
`meric or synthetic based material. The flexible diaphragm
`115 is highly compliant with low resistance to axial deforma-
`tion 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
`
`ofthe piston 114. The outer diameter ofthe sidewalls 11411 of
`the piston 114 is slightly smaller than the inner diameter ofthe
`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 11411 of the piston 114 are posi-
`tioned within the sidewalls ofthe 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.
`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 11511 ofthe 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 flex-
`ible 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 influ-
`ence ofthe piston 114.
`
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`PAGE 14 OF 20
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`US 9,186,224 B2
`
`7
`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 cav-
`ity of the cup-shaped diaphragm 115. This flange surface
`11511 is sandwiched between the flange surface 11311 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 11511 of the diaphragm 115.
`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 func-
`tionality within the linkage components below the test cham-
`ber 106. For the sake of clarity, the plenum 118 shown in FIG.
`3 depicts only a single sidewall port 143 that, in this embodi-
`ment, 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 4B). If not in use for a particular test configu-
`ration, 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 ofthe 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.
`As previously 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 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 seal