Abstract:
A prosthetic attachment locking assembly includes a distal adaptor fittable in the bottom of a socket for a residual limb stump and has an upper surface configured to accept an end of a stump liner. The internal surface of the socket merges smoothly with the upper surface of the distal adaptor. The distal adaptor has a pin bore through which a lock pin of the stump liner may extend, and a lower surface having a plurality of projections. A lock body of a prosthetic attachment lock has a pinion gear engagable with the lock pin to lock the lock pin, and an upper surface matably engagable with the projections such that the lock body and the distal adaptor may be connected via the projections and the upper surface of the lock body. The pinion gear is mounted to a centering axle. A one-way clutch for the pinion gear incorporates a sleeve non-rotatably mounting the centering axle such that the centering axle does not bind when it is pressed to move longitudinally. The centering axle is thus movable against a biasing force of a spring to disengage the gear from the lock pin.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is directed to a prosthetic attachment locking assembly which locks a residual limb stump to a prosthetic limb. More particularly, it relates to a prosthetic attachment lock incorporated into such an assembly.  
           [0003]    2. Description of the Related Art  
           [0004]    A prosthetic limb is conventionally secured to an amputee&#39;s residual limb stump by securing the prosthetic limb within a rigid socket part. This may commonly be done by shaping the socket such that it can form an air tight seal with the stump. In this case, a one way valve may be provided in the socket to permit air to be expelled from the socket as the stump is introduced, and the socket is held onto the stump by the resulting suction. While this is a comfortable form of suspension, an air leak due to stump shrinkage for example, can cause loss of suspension.  
           [0005]    It is also known to secure the prosthetic limb to the stump by a lock pin. In this technique, the amputee first dons a sock-like sock liner formed of an elastomer with an optional fabric cover. The bottom end of the liner is formed of a rigid material such as urethane, and the lock pin extends from this rigid bottom. Such stump liners are well known, such as that manufactured and sold by The Ohio Willow Wood Company under the name Alpha Locking Liner. The pin is extended through the wall of the socket and a distal adapter mounted within or outside of the socket, and can be locked onto a prosthetic attachment lock mounted to the prosthetic limb to secure the prosthesis, optionally in conjunction with a suspension sleeve. Examples of a conventional locking assembly of this type are found in U.S. Pat. Nos. 5,507,837 and 5,888,234.  
           [0006]    While conventional prosthetic attachment locking assemblies generally work well, they have a number of shortcomings. Amongst these is a tendency for the end of the lock pin to catch on a seam between the interior surface of the socket and the lip formed at the edge of the distal adapter when a distal adapter is fitted within the bottom of the socket. Another shortcoming is that the prosthetic attachment lock may also need to mate with the distal adapter through the intermediary of the bottom wall of the socket, which reduces the stability and structural rigidity of the joint. It is also necessary to use different distal adapters for test sockets which are made of a thermoplastic material, and definitive sockets which are made of a fiber reinforced laminate, and so it is necessary to use two kits for each prosthesis, which increases the final cost.  
           [0007]    A further shortcoming of the conventional prosthetic attachment locks lies in the manner of releasing the lock pin from the locking device. Conventionally, the pin has a longitudinal series of rack-like serrations and extends through a pin bore of the lock body. The teeth of a pinion gear in the lock body extend into the pin bore to engage the teeth of the lock pin therein. The pinion gear is mounted for one way rotation to permit entry of the lock pin into the pin bore but lock the lock pin against removal. The lock pin can be released only by moving the pinion gear in a direction parallel to its rotational axis until it disengages from the lock pin, e.g., via a manual release button.  
           [0008]    A problem with this conventional design is that the one way clutch incorporates the shaft onto which the pinion gear is mounted. Therefore, the force from the lock pin which has been tightened onto the gear is directly transferred to the gear shaft, which causes the shaft to bind and makes it difficult to manually push the manual release button sufficiently to release the lock pin.  
         SUMMARY OF THE INVENTION  
         [0009]    It is therefore an object of the invention to overcome the aforementioned shortcomings of the conventional design.  
           [0010]    It is a further object of the invention to provide a prosthetic attachment lock in which the pinion gear is more easily released from the lock pin while a load is being applied to the gear via the lock pin.  
           [0011]    It is a further object of the invention to provide a more stable and rigid joint for the prosthetic attachment locking assembly.  
           [0012]    It is a further object of the invention to provide a single prosthetic attachment lock which can be used with either a thermoplastic or thermoset socket and which can be reused.  
           [0013]    It is a further object of the invention to provide a prosthetic leg with a better fit, better suspension and less noise by combining the reliability of a pin suspension with the comfort and performance of a suction suspension.  
           [0014]    According to a feature of the invention, the above and other objects are achieved by a prosthetic attachment lock comprising a lock body having a pin bore into which a lock pin may be inserted, and a locking device in the lock body. The locking device includes a centering axle rotatably mounted in the lock body, a pinion gear mounted to the centering axle, a sleeve non-rotatably mounting the centering axle for longitudinal movement, and a one way clutch connected between the lock body and the sleeve.  
           [0015]    A spring is engaged to bias the centering axle relative to the sleeve along the longitudinal axis of the centering axle such that the pinion gear engages the lock pin to lock the lock pin. The centering axle is movable against the biasing force of the spring to disengage the gear from the lock pin.  
           [0016]    According to another feature of the invention, the above and other objects are achieved by a prosthetic attachment lock including a lock body having a pin bore into which a lock pin may be inserted, and a locking device in the lock body and having a gear engagable with the lock pin to lock the lock pin in the pin bore, disengaging means for permitting the gear to disengage from the lock pin, and means independent of the disengaging means for permitting only one way rotation of the gear.  
           [0017]    According to yet another feature of the invention, the above and other objects are achieved by a prosthetic attachment locking assembly comprising a distal adaptor fittable in the bottom of a socket for a residual limb stump and having an upper surface configured to accept an end of a stump liner, the distal adaptor having a pin bore through which a lock pin of the stump liner may extend, and a lower surface having a plurality of projections. A lock body has an element engagable with the lock pin to lock the lock pin and an upper surface matably engagable with the projections such that the lock body and the distal adaptor may be connected via the projections and the upper surface of the lock body.  
           [0018]    According to yet another feature of the invention, the above and other objects are achieved by a prosthetic attachment locking assembly comprising a rigid socket into which a residual stump having a stump liner with a lock pin may be introduced, and a distal adaptor fittable in the bottom of the socket and having an upper surface configured to accept the end of a stump liner. The internal surface of the socket merges smoothly with the upper surface of the distal adaptor.  
           [0019]    According to yet another feature of the invention, the above and other objects are achieved by a prosthetic attachment locking assembly comprising a rigid socket into which a residual stump having a stump liner with a lock pin may be introduced, a prosthetic attachment lock, a distal adaptor fittable in the bottom of the socket and having an upper surface configured to accept the end of a stump liner and a lower surface having a plurality of projections extending through the wall of the rigid socket such that the distal adaptor may be fixed to the prosthetic attachment lock via the projections.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0021]    [0021]FIG. 1 is an exploded view of a prosthetic attachment locking assembly according to the invention;  
         [0022]    [0022]FIGS. 2A, 2B and  2 C are respectively top, sectional and bottom views of a distal adapter according to the invention, in which the sectional view of FIG. 2B is taken along line B-B of FIG. 2A;  
         [0023]    [0023]FIG. 3A and 3B are respectively top and sectional views of a prosthetic attachment lock according to the invention, in which the sectional view of FIG. 3B is taken along line III-III of FIG. 1; and  
         [0024]    [0024]FIG. 4 is a detail showing a locking device according to the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    A preferred embodiment according to the invention is illustrated with reference to the attached non-limiting figures in which the same reference numerals are used to refer to the same or similar parts throughout the various views.  
         [0026]    Referring first to FIG. 1, a prosthetic attachment locking assembly is composed of a distal adapter  10  and a prosthetic attachment lock  20 . The distal adapter  10 , shown in greater detail in FIGS.  2 A- 2 C, is preferably formed of machined aluminum although other rigid materials having the requisite characteristics may be used. It is generally formed as a roughly cylindrically body having a part-spherical concave upper surface  22  and a generally planar lower surface  24 . A central pin bore  26  extends through the body of the distal adapter  10  from the upper surface  22  to the lower surface  24 . The upper part of the pin bore  26  is in the form of a conical outward taper  26   a  which merges with the upper surface  22 , while the lower end of the pin bore  26  is extended downwardly by an annular rim  26   b.    
         [0027]    A number (four in this embodiment) of projections  24   a  extend integrally downward from the bottom surface  24 , adjacent the periphery of the bottom surface and by the same distance as the rim  26   b . The projections  24   a  form flat bottom surfaces into which threaded screw holes  24   b  are bored.  
         [0028]    An air expulsion hole  27  extends through the body of the distal adapter from the top surface  22  to the bottom surface  24 .  
         [0029]    A series of annular grooves  29  in the peripheral cylindrical surface of the distal adapter can hold sealing rings such as O-rings  29   a , for the purpose described below.  
         [0030]    In the state illustrated in the figures, the distal adapter  10  is sealingly fitted into the bottom of a rigid socket  40 . The sealing at the periphery of the distal adaptor  10  is assured by the sealing rings  29   a . The socket may generally be of a conventional design except as noted below, and may be formed of a thermoplastic material or a carbon fiber laminate, although it may instead be formed of other materials which can satisfy the functional requirements of a prosthetic socket. Generally speaking, the socket  40  has an internal surface  42  whose shape can cooperate with a residual limb stump so that the stump can comfortably fit within the socket and form an air tight seal.  
         [0031]    The distal adapter  10  may be fitted within the bottom of the socket  40  in a variety of ways, including press fitting the distal adaptor into the already formed socket, or by the socket being molded or laid up (laminated) around the distal adapter  10 . In any case, the internal configuration of the inner surface  42  of the socket wall should be such that it forms a smooth or seamless transition to the edge of the top surface  22  of the distal adapter so that the end of the lock pin  60  of the prosthetic attachment locking assembly will not catch on a lip, and can smoothly be guided to the top surface  22  and the pin bore  26 . This seamless merging can be accomplished by providing that the inner surface  42  of the wall of the socket, in its portion  44  located at and immediately above the edge of the top wall  22  of the distal adapter  10 , has substantially the same radius and center as the part-spherical top surface  22 . The radius of the top surface  22  is preferably 0.3 to 5 inches, more preferably 1.5 to 2 inches, and the outside diameter of the distal adapter  10  is preferably 1 to 3 inches.  
         [0032]    As best seen in FIG. 1, the rim  26   b  and the projections  24   a  extend through the wall  20  of the bottom of the socket  40  and provide flat external surfaces coplanar with the bottom exterior surface  46  of this bottom wall. The projections  24   a  therefore provide surfaces integral with the distal adapter for secure and stable attachment of the prosthetic attachment lock  20 , and the rim  26   b  provides a seal against air leakage from the joint between the air expulsion hole  27  and a colinear air hole  48  in the bottom of the socket  40 .  
         [0033]    The prosthetic attachment lock  20  has a lock body  20 A which may be in the form of a flat disk with a generally rectangular shape (although in the illustrated embodiment the lock body is not precisely rectangular). It may be made of machined aluminum or another rigid material which is adaptable to the same purpose. The lock body  20 A may have planar upper and lower surfaces  20 Aa and  20 Ab, and a pin bore  28  extending therethrough from the upper surface  20 Aa to the lower surface  20 Ab. Through holes  30  are also provided at positions which may be aligned with the threaded screw holes  24   b  in the projections  24   a  of the distal adapter  10 . It is therefore possible to securely fix the lock body  20 A to the distal adapter by screws or bolts which can pass through the holes  30  and be threaded into the screw holes  24   b , thereby clamping the lock body  20 A between the prosthetic limb  50  and the socket  40  and securely joining the socket  40  to the prosthetic limb.  
         [0034]    The lock body  20 A also has an air valve hole  32  which can hold a one way air valve  32   c , e.g., an elastomeric “duck bill,” and which has outlet  32   a  or  32   b . The air valve hole is a aligned with, and communicates with, the air expulsion holes  27  and  48  for expelling to the outside the air which is displaced by the insertion of the residual stump into the socket. The one way valve  32   c  closes to maintain the suction once the stump is inserted.  
         [0035]    Although the one way valve  32   c  is shown in its preferred location in the prosthetic attachment lock  20 , it can be located in another part of the prosthetic attachment lock. Also, a muffler (not shown) made of micro-cellular foam or another suitable material may be provided at one of the outlets  32   a  or  32   b . A filter (not shown) may be positioned at the valve so as to keep contaminants from the socket from reaching the valve.  
         [0036]    The lock pin  60  may be mounted, e.g., by molding or screwing, to a rigid urethane body  62  secured or formed at the lower end of the stump liner  64 . The body  62  has a dome-like lower surface which can mate with the upper surface  22  of the distal adapter  10 . The lock pin has a series of tooth-like serrations and may be conventional, except that it further includes an annular sealing element  66  formed of rubber or some other elastomeric material and shaped to form an air tight seal with the conical taper  26   a  of the distal adapter when the lock pin  60  is locked into the prosthetic attachment lock.  
         [0037]    Referring particularly to FIGS. 3B and 4, a cylindrical bore  36  for housing the locking device is formed in the lock body  20 A and extends from one of the side surfaces into the lock body such that it intersects the pin bore  28 . It is extended by a smaller diameter centering the hole  38  which cooperates with the locking device as set forth below.  
         [0038]    The locking device  80 , which is best seen in FIG. 4, has a centering axle  82  which is extended by a pin  84  which is guided for longitudinal and rotational motion by the centering bore  38  of the lock body  20 A acting as a bearing for the pin  84 . A locking gear  86  is fixedly mounted on the centering axle and can be located within the bore  36  such that its teeth extend into the pin bore  28  and mesh with the serrations of the lock pin  60  when the lock pin  60  extends into the pin bore  28 . As a result, movement of the lock pin  60  into the pin bore  28  will cause rotation of the locking gear  86  and the centering axle  82 , but removal of the lock pin  60  is prevented by the one-way clutch (described below) which prevents opposite rotation of the locking gear  86 . The above described locking device is conventional, except for the features of the one-way clutch set forth below.  
         [0039]    The centering axle  82  is slidably mounted for movement along its length within the bore of a load bearing sleeve  88 , which bore forms a linear bearing for the centering axle  82 . However, rotation between the centering axle  82  and the sleeve  88  is prevented by a dowel  90  which extends through a bore in a flange  92  of the sleeve  88 , and also extends through an elongated slot  94  of the centering axle  82 .  
         [0040]    The load bearing sleeve  88  cooperates with an outer sleeve  96  and clutch elements  98  of a one-way rotation clutch. A conventional clutch usable for this purpose may be the Stock Drive Products roller clutch model S99NH3MURC1012. The outer sleeve  96  of the clutch may be fixed by press fitting within the bore  36 . On the other hand, the load bearing sleeve  88  is permitted by the one-way clutch to rotate in one direction within the bore  36 . In turn,  5  the centering axle  82  and the locking gear  86  rotate with the sleeve  88  due to the dowel  90  extending through the slot  94 . The length of the slot  94  is such as to permit the centering axle to move longitudinally within the sleeve  88  until the gear  86  disengages from a lock pin  60  in the pin bore  28 .  
         [0041]    A push button  100  is attached to an end of the centering axle and extends out of the lock body  20 A. A spring  102  engaged between the push button  100  and the flange  92  of the sleeve  88  biases the locking gear  86  into the position shown in FIG. 3B in which it extends into the pin bore  28  so as to be able to engage and lock the lock pin  60  held therein. One can manually rotate the gear  86  by turning the push button  100 . One can also manually inwardly push on the push button, against the biasing force of the spring, for causing the centering axle and the locking gear  86  to slide in the direction of the arrow A in FIG. 3B until the locking gear  86  exits from the pin bore  28 . The locking gear  86  then disengages from the lock pin  60  which can be removed from the lock body  20 A without impediment.  
         [0042]    In this embodiment, the linear bearing support of the centering axle  82  within the bore of the sleeve  88  comprises an example of disengaging means for permitting the gear to disengage from said lock pin. The one-way clutch  96 - 98  held in place by sleeve  88  and retaining ring  89  comprises an example of means for permitting only one way rotation of the gear  86 . This one-way clutch is independent of the disengaging means since clutch elements do not engage with the centering axle  82  or the inner bore of the sleeve  88 .  
         [0043]    During socket fabrication, the distal adapter is typically attached to a model of the user&#39;s stump. For a thermoplastic socket, the thermoplastic is formed over the distal adapter  10  and the model of the stump. The thermoplastic on the distal end of the socket is then removed or reshaped until the projections  24   a  are exposed so that the prosthetic attachment lock  20  and the prosthetic limb  50  can be attached. When making a fiber reinforced laminated socket, the reinforcing fiber is positioned across the sides of the socket and across the bottom surface  24  of the distal adaptor  10  between the projections  24   a . A flat laminating plate is then attached to the projections  24   a , and the laminating resin is formed over the model of the stump and the distal adaptor. The flat laminating plate is then removed, leaving a flat surface for attaching the prosthetic attachment lock  20  and the prosthetic limb  50 .  
         [0044]    In use, the amputee applies the stump liner to the residual limb stump such that the lock pin  60  is located at the end of the stump. The user then steps into, or pulls on, the socket  40 . As the user does so, the end of the lock pin, which may initially bear against the inner surface  42 , smoothly moves from engagement with the inner surface  42  of the socket to engagement with the part-spherical top surface  22  of the distal adapter due to the surface radius at  44 . The part-spherical surface  22  then guides the lock pin  60  toward the pin bore  26 . Eventually, the lock pin fits into, and extends through, the pin bore  26  of the distal adapter and through the pin bore  28  of the lock body  20 A. As this occurs, the lock gear  86  rotates to permit the lock pin  60  to pass through the pin bore  28 , but the one-way clutch prevents its removal. Simultaneously, an air tight seal is formed between the residual stump and the inner surface  42  of the socket, causing air to be expelled through the air holes  27  and  48 , and through the one way valve  32   c . The one way valve, moreover, prevents air return so as to assure a suction lock.  
         [0045]    The user can then rotate the button  100  so as to rotate the gear  86 , thereby further and securely locking the lock pin  60  in the pin bore  28 . A slot at the end of the push button will accept a coin or the head of a screwdriver to assist in locking down the lock pin. This presses the body  62  onto the upper surface  22  and compresses the seal material  66  to prevent air leakage past the pin bore  26 . It also creates an upward reaction load on the lock pin  60 , which is transferred to the one-way clutch.  
         [0046]    When it is desired to remove the stump from the prosthesis, the user pushes the button  100  in the direction A. Since the turning load applied onto the gear  86  by the reaction load on the lock pin  60  is resisted by a one-way clutch which is defined between the sleeves  88  and  96 , and which is not incorporated into the centering axle  82 , the centering axle  82  can readily move independent of this load and can easily slide in response to the pressure on the button  100  to release the lock pin  60 .  
         [0047]    Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. For example, the distal adaptor  10  and the prosthetic attachment lock could be combined in a single unit. It is therefore to be understood that the invention may be practiced otherwise than as specifically described herein.