Patent Publication Number: US-2023140396-A1

Title: A prosthesis coupling, a socket coupling, a rotary connector core and a compliant mounting element

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to a rotatable and removable wrist connection for a prosthetic hand of the type commonly referred to as a Quick Wrist Disconnect (QWD). 
     BACKGROUND 
     Prosthetic limbs are typically attached to a user&#39;s stump via a socket which conforms to the shape of the stump. A connector may be provided to allow the prosthesis to be attached and detached from the stump. In the case of a wrist it is desirable for the prosthetic limb to be both rotatably coupled and easily connected to and removed from a stump. Additionally, for an automated hand, signals need to be conveyed through the connector to the hand. 
     In the 1970&#39;s Otto Bock developed a rotatable and removeable prosthetic connector, as described in U.S. Pat. No. 3,900,900, that has become the industry standard and is commonly referred to as a Quick Wrist Disconnect (QWD) connector. A prothesis coupling component is secured to the prosthetic limb and a socket coupling component is secured to a socket secured to a patient&#39;s stump. The prothesis coupling and socket coupling may be engaged by being pushed together such that they are then axially locked together. The prosthesis can then be rotationally positioned by the user via a detent mechanism in the coupling until the prosthesis is rotated through about 330 degrees to allow release. 
     By virtue of the rotational positioning and the release mechanism actuation requiring the same action by the user, the standard QWD may suffer from accidental release, potentially exposing a user to risk or damaging an expensive prosthetic limb. The standard QWD may suffer from accidental release, potentially exposing a user to risk or damaging an expensive prosthetic limb. Further, the push locking arrangement may not move the movable snap ring of the socket coupling sufficiently to ensure that the prosthesis coupling and socket coupling are locked together, again potentially exposing a user to risk or damaging an expensive prosthetic limb. 
     For an automated hand a rotary connector core is rigidly mounted to the socket coupling and this may be subject to damage as the rotary connector core is inserted into a rotary connector housing of a prosthesis socket before mechanical coupling occurs. The connection between a rotary connector core and a socket coupling may also not be waterproof which may allow water to enter and interfere with signals or damage electrical or electronic components. Further, rotary connector cores are typically molded which is complex and expensive and does not easily allow variation. 
     SUMMARY 
     In a prosthetic QWD connector it is desirable for any new QWD design to be backwards compatible with the industry standard QWD connector. This creates challenges due to features of the existing QWD design, the need for a rotatable coupling and the very limited available space. The prosthetic QWD connector disclosed herein can have any of the following and/or other advantages. 
     The present disclosure provides examples of prosthetic QWD connectors that are compact, have lower risk of accidental release, provide positive locking and allow easy release whilst providing backwards compatibility with the industry standard QWD connector. 
     The present disclosure also provides examples of prosthetic QWD connectors including a compliantly mounted rotary connector core capable of allowing movement of the rotary connector core with respect to the socket coupling, thus allowing certain forces during coupling to be absorbed without damaging the rotary connector core whilst also providing a waterproof seal between a socket coupling. 
     The examples above can provide a QWD connector that is backwards compatible with standard QWD connectors whilst offering one or more of the advantages outlined above. 
     In some configurations, a prosthesis coupling can be configured to rotatably and releasably engage with a race of a socket coupling and comprise: a first sleeve including a first annular ball race section; a second sleeve having a second annular ball race section; and bearings provided within a race formed by the first ball race section and the second ball race section, wherein the first and second sleeves may be relatively moved such that: in a first configuration, in which the first ball race section and the second ball race section are brought together, the bearings are constrained to an outer annular zone, preventing removal of the prosthesis coupling when engaged with a socket coupling; and in a second configuration, in which the first ball race section and the second ball race section are moved apart, the bearings may move to an inner annular zone, allowing removal of the connector from a socket. 
     In some configurations, the prothesis coupling can be configured to rotatably and releasably engage with a race of a socket coupling and comprise: a body having an annular section; a first annular ball race section provided on the annular section; a second annular ball race section movable between first and second positions on the annular section: bearings provided within a race formed by the first ball race section and the second ball race section; and a release actuator movable in a first direction with respect to the body to move the second annular ball race section between: a first configuration in which the first ball race section and the second ball race section are brought together such that the bearings are constrained to an outer annular zone, preventing removal of the connector when engaged with a socket coupling; and a second configuration in which the first ball race section and the second ball race section are moved apart such that the bearings may move to an inner annular zone, allowing removal of the prosthesis coupling from a socket coupling. 
     In some configurations a socket coupling can include a socket body for receiving a wrist coupling having a rotary connector core extending from the socket body wherein the rotary connector core is compliantly mounted to the socket body. 
     In some configurations a rotary connector core can include a compliant mounting element. 
     In some configurations a compliant mounting element can be configured to engage with a socket coupling and a rotary connector core so as to allow movement between the socket coupling and rotary connector core about the compliant mounting element. 
     In some configurations a rotary connector core can comprise a plurality of stacked sections consist of alternating conductive sections and insulating sections tensioned together to maintain a cylindrical form by a tensioning element between the top and bottom of the stack. 
     In some configurations a socket body can include a compliant mounting element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure are described with reference to the drawings of certain embodiments, which are intended to schematically illustrate certain embodiments and not to limit the disclosure. 
         FIG.  1    shows an exploded view of the components of a first example prosthesis coupling. 
         FIG.  2    shows a top perspective view of an assembled prosthesis coupling of the components shown in  FIG.  1   . 
         FIG.  3    shows a cross-sectional view of the prosthesis coupling of  FIG.  2   . 
         FIG.  4    shows a cross-sectional view of a socket coupling for receiving the prosthesis coupling of  FIGS.  1  to  3   . 
         FIG.  5    shows a partial section of  FIGS.  1  to  4    illustrating locking of the prosthesis coupling to a socket coupling. 
         FIG.  6    shows a partial section of  FIGS.  1  to  4    illustrating unlocking of the prosthesis coupling from a socket coupling. 
         FIG.  7    shows an exploded view of the components of a second example prosthesis coupling. 
         FIG.  8    shows a top perspective view of the prosthesis coupling of  FIG.  7    assembled from the components shown in  FIG.  7   . 
         FIG.  9    shows a cross-sectional view of the prosthesis coupling of  FIGS.  7  and  8   . 
         FIG.  10    shows the prosthesis coupling of  FIGS.  7  to  9    in an unlocked configuration. 
         FIG.  11    shows the prosthesis coupling of  FIGS.  7  to  9    in a locked configuration. 
         FIG.  12    illustrates unlocking of the prosthesis coupling of  FIGS.  7  to  11    from a socket coupling. 
         FIG.  13   a    shows a cutaway perspective view of the outer sleeve of the prosthesis coupling of  FIGS.  7  to  12   . 
         FIG.  13   b    shows a perspective view of the inner sleeve of the prosthesis coupling of  FIGS.  7  to  12   . 
         FIG.  14    shows a perspective view of the locking ring of the prosthesis coupling of  FIGS.  7  to  12   . 
         FIGS.  15   a  to  15   c    show a modified form of the second example prosthesis coupling including a biasing mechanism between the inner and outer sleeves. 
         FIG.  16    shows an example rotary connector core compliantly mounted to a socket coupling. 
         FIG.  17    shows a perspective view of the rotary connector of  FIG.  16    attached to a compliant mounting element. 
         FIG.  18    shows a rotary connector housing. 
         FIG.  19    shows an exploded view of the rotary connector core of  FIG.  16   . 
         FIGS.  20   a  and  20   b    show an example connection between a rotary connector core and a socket coupling. 
     
    
    
     DETAILED DESCRIPTION 
     Although certain embodiments and examples are described below, those of skill in the art will appreciate that the disclosure extends beyond the specifically disclosed embodiments and/or uses and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the disclosure herein disclosed should not be limited by any particular embodiments described below. In the examples below ball bearings are employed but it will be appreciated that non-spherical bearings, such as roller bearings could be employed. 
     Example Prosthesis Coupling 
     The present disclosure provides examples of a prothesis coupling for rotatable and releasable connection to a socket connector.  FIGS.  1  to  3    show a first example prosthesis coupling  1  having an axis  2 . An interface plate  3  allows attachment to a prosthetic limb. A button  4  locates within apertures  5  and is movable laterally with respect to the axis  2 . Button  4  is secured to ramp plate  6  by screws  7 . When button  4  is depressed ramp plate  6  moves inwards, moving ramps  8  towards ramp surfaces  9  of annular inner sleeve  10 . 
     A castellated ring  11  and wave spring  12  are provided about main body annular sleeve  13 . Annular sleeve  13  provides an annular body for mounting the snap rings and detent as described below. Snap ring retainer  15  is mounted to main sleeve body  13  to retain static snap ring  17  in place. Detent ring  18  is mounted on main sleeve body  13  so as to define two annular regions in which dynamic snap ring  20  may be positioned about sleeve body  13 , as will be described below. Inner sleeve  10  may act on pins  16 , located in apertures  22  of main sleeve body  13 , to move dynamic snap ring  20  from an upper to a lower position. 
     The snap rings  17  and  20  provide ball race sections defining a ball race constraining the longitudinal movement of bearings  19  in the direction of axis  2 . Bearing cage  21  retains the bearings radially within it. 
       FIG.  3    shows a cross-sectional view of an assembled prosthesis coupling  1  as shown in  FIGS.  1  and  2    (engaged with a socket coupling) with a standard QWD socket coupling shown alone below in  FIG.  4   . When the prosthesis coupling  1  and socket coupling  23  are locked together ball bearings  19  run in track  24  of socket coupling  23  and rotary connector core  25  couples with rotary connector housing  26  to allow electrical signals to pass from socket coupling  23  to prothesis coupling  1 . Bosses  27  assist in locking the dynamic snap ring  20  in its locked position as will be described below. 
     Prior to attachment of a prosthesis coupling to a socket coupling the dynamic snap ring is in the position  20 ′ shown in  FIG.  6   , below detent ring  18 , which allows the ball bearings to move inwardly to pass the race  24  of a socket coupling. As prosthesis coupling  1  is urged towards socket coupling  23  bosses  27  force dynamic snap ring  20  up from position  20 ′, within a first annular recess below detent  18 , over detent ring  18 , to position  20  within a second annular recess below detent  18 . As the dynamic snap ring  20  moves to this upper position the distance between the dynamic snap ring  20  and the static snap ring  17  decreases and the ball bearings  19  are forced outwards into race  24  of socket coupling  23  so as to retain the prosthesis coupling to the socket coupling, due to the constrained positions of the ball bearings, whilst allowing relative rotation. 
     Referring now to  FIG.  6    disengagement of prosthesis coupling  1  from socket coupling  23  will be described. A release actuator is provided by button  4 , ramp plate  6  and inner sleeve  10 . Push button  4  may be recessed within interface plate  3  to avoid accidental actuation. When push button  4  is depressed ramp plate  6  is moved inwards, lateral to axis  2 , against ramp surface  9  of inner sleeve  10 . This forces inner sleeve  10  down, forcing pins  16  down, which in turn forces dynamic snap ring  20  down over detent  18  to position  20 ′. With dynamic snap ring  20  in position  20 ′ the ball bearings may move inwardly to positions  19 ′, which allows the ball bearings to move out of race  24 , thus allowing the prosthesis coupling  1  to be removed from socket coupling  23 . The bosses  27  do not prevent the dynamic slip ring  20  moving down as the prosthesis coupling moves up as inner sleeve body  10  is forced down. 
     It will be appreciated that other actuation mechanisms may be employed where a release element is moved relative to the prosthesis coupling to effect release. Instead of being pushed in, ramp plate  6  could be rotated about axis  2  via a lever projecting outward from ramp plate  6 . In this arrangement one of ramps  8  would be oppositely inclined to that shown, as would a corresponding ramp surface  9 . In another example a cam may be rotated by a lever in a plane through axis  2  with the cam acting upon inner sleeve  10  to move it downwards to effect release. 
     Referring now to  FIGS.  7  to  12    a second example prosthesis coupling will be described. Prosthesis coupling  100  includes an interface plate  101  having a pair of push buttons  102  on either side having ramps  103  at their distal ends. The push buttons  102  are slidably mounted with respect to the interface plate  101  and biased outwardly by springs  104 . Ramps  105  are secured to lifters  106  which can lift locking ring  107  when the push buttons  102  are depressed. Wave spring  109  and castellated ring  110  are provided below interface plate  101 . Main compression spring  111  is provided about barrel  112  to bias the outer sleeve  114  downwards. Lock ring compressing spring  113  is positioned to bias locking ring  107  downwards. 
     In this example an outer sleeve  114  is rotatably engaged about an inner sleeve  115  with ball race sections  116  and  117  of each sleeve forming a ball race. In this example the spacing between ball race sections  116  and  117  is adjusted by relative axial displacement between the inner and outer sleeves. This axial displacement could be achieved by pure axial displacement or with rotation, as described in the example below. In this example a number of ramps  118  are provided on inner sleeve  115  which engage with projections  119  of outer sleeve  114 . It will be appreciated that instead of this construction inter-engaging threads (or partial threads) could be provided on the inner and outer sleeves. 
     A bushing  120  and threaded ring  121  are provided about outer sleeve  114 . Ball bearings  122  are retained within a region defined by the axial separation of race sections  116  and  117  and the bearing cage  123 . When outer sleeve  114  is rotated anti-clockwise projections  119  may ride up ramp  118  to create a large axial spacing  124 ′ between race sections  116  and  117  (see  FIG.  10   ) allowing bearings  122  to move inwardly into an inner annular zone and allow the prosthesis coupling to be connected to or disconnected from a socket coupling. When outer sleeve  114  is rotated clockwise projections  119  may ride down ramp  118  to create a smaller axial spacing  124  between race sections  116  and  117  (see  FIG.  11   ) forcing ball bearings  122  to move outwardly to an outer annular zone such as to retain the prosthesis coupling to a socket coupling. It will be appreciated that the directions of relative rotation would be opposite if the ramp sections were oppositely inclined. The relative axial displacement between the race sections  116  and  117  thus allows two configurations: a first configuration in which the first ball race section  116  and the second ball race  117  section are brought together such that the bearings are constrained to an outer annular zone, preventing removal of the connector when engaged with a socket coupling; and a second configuration in which the first ball race section  116  and the second ball race section  117  are moved apart such that the bearings may move to an inner annular zone, allowing removal of the prosthesis coupling from a socket coupling. 
     To prevent accidental release relative rotation between sleeves  114  and  115  to separate the race sections  116  and  117  (i.e. from the configuration shown in  FIG.  11    to the configuration shown in  FIG.  10   ) may require a release of a locking mechanism. The locking mechanism could consist of one or more pins passing through apertures in the inner and outer sleeves in the configuration shown in  FIG.  11   , which may be removed to allow rotation to the configuration shown in  FIG.  10   . Such pins may be of any desired cross-section or shape and simply need to engage apertures in the sleeves to prevent rotation. Alternatively, a locking mechanism may require rotation of an element relative to the interface plate  101  to allow relative rotation between sleeves (a detent mechanism may also be included to avoid unintentional rotation of such a locking mechanism). Below an example locking mechanism employing a locking ring is described. 
     When the inner and outer sleeves have the configuration shown in  FIG.  11    projections  108  of locking ring  107  engage in slots  120  in outer sleeve  114  and notches  121  in inner sleeve  115  (best shown in  FIGS.  13   a    to  14 ) which prevent relative rotation between the sleeves when projections  108  are engaged, thus preventing separation of race sections  116  and  117  to permit release of the prosthesis coupling from the socket coupling. As illustrated in  FIG.  12   , when buttons  102  are pressed inwards ramps  103  act against ramps  105  to lift locking ring  107  via lifters  106  to remove projections  108  from slots  120  in outer sleeve  114  and notches  121  in inner sleeve  115  to permit relative rotation of the sleeves. Thus, upon depression of the buttons a prosthesis coupling may be rotated relative to a socket coupling (by about 45 degrees in this case) to allow release of the prosthesis coupling from the socket coupling. 
     If the prosthesis coupling of the second example is not correctly operated there is a risk that the first ball race section  116  and the second ball race  117  section may remain together when the prosthesis coupling is removed from a socket coupling such that the bearings are constrained to an outer annular zone, preventing future engagement with a socket coupling. With reference to  FIGS.  15   a  to  15   c    a biasing means, in the form of a helical torsion spring  125 , is provided to causes relative rotation between the inner sleeve  115  and outer sleeve  114  to urge them towards the second configuration (race sections  116  and  117  moved apart), when the locking mechanism does not prevent relative rotation. In this way when the prothesis coupling is removed from a socket coupling the ball race may easily return to the second configuration, allowing attachment to a socket coupling. 
     It will be appreciated that a range of biasing means may be employed including extension, compression or torsional biasing elements and a helical torsion spring is given by way of non-limiting example. 
     Referring to the example of  FIGS.  15   a  to  15   c    a helical torsion spring  125  is provided within inner sleeve  115 . A first leg of helical torsion spring  125  engages with an aperture in inner sleeve  115 . A second leg  127  of helical torsion spring  125  passes through a slot  128  in inner sleeve  115  and engages with an aperture in outer race  114 . The configuration is such that the helical torsion spring  125  rotates the inner sleeve  115  with respect to the outer sleeve  114  towards the second configuration, when the locking mechanism does not prevent relative rotation. In this way race sections  116  and  117  may easily return to the second configuration when removed from a socket coupling to allow easy future engagement with a socket coupling. 
     Referring to  FIGS.  16  to  19    examples of a compliant mount, rotary connector and socket coupling will be described. As shown in the exploded view of a rotary connector core in  FIG.  19    the rotary connector core  200  can be formed by alternately stacking conductive rings  201  and insulating rings  202 . Electrical connectors  203  pass through the insulating rings  202  and are electrically connected to one or more conductive ring  201  as required. A tension screw  204  screws into tension nut  205  to retain the stack together to form a core. Lock ring  206  and base  207  lock together to secure the core to a compliant mounting element  208 . Plug nut  209  is secured to the end of tension nut  205 . 
     The assembled rotary connector core  200  with a compliant mounting element  208  is shown in  FIG.  17   . The rotary connector core  200  engages with the bore  211  of a rotary connector housing  210  of a prosthesis coupling. 
     Referring to  FIG.  16    a rotary connector core  200  is shown mounted to a socket coupling  218  by a compliant mounting element  208 . A recess  220  formed in compliant mounting element  208  engages with flange  219  of socket coupling  218  to provide a compliant mounting arrangement of the rotary connector core  200  relative to socket coupling  218 . This allows a degree of movement of the rotary connector core  200  relative to socket coupling  218  during coupling to avoid damage to the rotary connector core  200 . 
     The rotary connector core  200  is designed to preferentially flex and/or deform at the compliant mounting element  208  which may suitably be formed of a material having a DMTA damping factor of between 0.05 to 0.8, preferably between 0.05 to 0.5, over a temperature range of −20° C. to 100° C. The material preferably has a resilience of between 20% to 60% and a Shore A hardness of between 10 to 90 (more preferably a Shore A hardness of between 30 to 60) or alternatively a Shore D hardness of between 40 to 90. The compliant mounting element preferably provides impact absorption for forces applied to the connector core in a direction normal to the central axis such that the connector core may deviate by at least 5 degrees (preferably 10 degrees and more preferably 15 degrees) relative to the central axis due to elastic deformation of the mounting block. A force of between 2.5 and 20 Newtons applied laterally or normal to the tip of the connector core preferably results in angular rotation with respect to the central axis of at least 3 degrees, preferably at least 5 degrees, due to elastic deformation of the mounting block. The mounting block may be formed of elastomers, rubber, silicone, compressible polymers or thermoplastics materials. Preferably the material is a thermoset elastomer (either hydrocarbon, fluorocarbon or silica-based), a thermoplastic elastomer, a thermoset rubber, an inherently soft thermoplastic. It may also be an alloy or blend or a foamed composition of any of the above polymers. 
     The compliant mounting arrangement may allow non-destructive movement of the rotary core with respect to the socket coupling without causing damage to the rotary connector core  200 . In one example the compliant mounting element  208  may allow the rotary connector core  200  to non-destructively deflect by more than 15 degrees with respect to the socket coupling. Advantageously in this example the compliant mounting element  208  may also provide a waterproof seal between the rotary connector core and the socket body. The seal is preferably waterproof to any one of the standards, IPx5, IPx6, IPx6K, IPx7 or IPx8. 
     Referring to  FIGS.  20   a  and  20   b    a further example of a compliant mount, rotary connector core and socket coupling will be described. A first part  230  includes a rotary connector core  231  secured to a compliant mount  232  and a mounting ring  233  secured to the compliant mount  232 . The compliant mount has the properties of the compliant mount described above. The mounting ring has a number of projections  234  dimensioned to fit within notches  237  in the complementary mounting ring  236  of socket  235 . This allows first part  230  to be engaged with socket coupling  235  from its distal end simply by inserting it so that projections  234  are aligned with notches  237  and then pushing and rotating the first part with respect to the socket coupling  235  in twist-lock fashion to secure the mounting rings together. 
     It will be appreciated that the compliant mount could be secured to the socket coupling with mounting rings provided at the interface between the rotary connector core  231  and the compliant mount  232 . It will also be appreciated that the mounting rings may employ a variety of interengagement techniques, such as a screw thread, bayonet fitting, push fit etc. 
     In other examples compliance may be provided within the rotary connector core itself. For example a compliant material could be provided between base  207  and lock ring  206 . In other examples compliance may be provided within socket coupling  218 , for example by providing a compliant material between the socket coupling  218  and a rigid surface to which a rotary connector core is mounted. 
     It should be emphasized that many variations and modifications may be made to the embodiments described herein, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims. Further, nothing in the foregoing disclosure is intended to imply that any particular component, characteristic or process step is necessary or essential.