US2066599A - Ankle joint for artificial limbs - Google Patents

Description

s. A. WlLLETT 2,066,599 JOINT FOR ARTIFICIAL LIMBS Patented Jan. 5, I937 UNITED STATES,

2,066,599 ANKLE JOINT FOR ARTIFICIAL LIlVIBS Samuel A. Willett, Paducah, Ky., assignor. of

one-half to Birmingham Artificial Limb Company, Birmingham, Ala., a corporation of Alabama Application July 18, 1935, Serial No. 32,003

14 Claims.

My invention relates to certain new and useful improvements in an ankle joint for artificial limbs, my object being to provide a joint in which the articulated joint elements are held in engagement by an elastic body of substantial mass which is brought under initial compression by the manner of assembling the ankle element and which permits both vertical play and limited universal angular play between the shin member and the foot piece.

My invention contemplates the provision of a substantially cylindrical or barrel shaped resilient body to occupy the axis of the ankle joint and v I be interposed between the interlocked metallic joint members and a limb element in such manner as to form a resilient support for the shin piece which provides both for vertical and angular play of the foot, 'the elastic body being so 4 L shaped and held under compression between seats on the shin and foot pieces as to exert a resilient effect that cooperates with the standard elastic foot pads in restoring and maintaining the normal relationship between foot and shin piece when the limb is at rest. More particularly, my invention contemplates the provision'o-f an elongated barrel shaped solid cushion member, which has approximately a one inch diameter at the center so as, to provide a substantial mass of elastic material in the middle portion of the ankle joint, the tapering of this body'toward the ends being desirable to provide for the requisite universal play at the ankle joint Without undue pressure on the body at any point i. that will allow the foot piece to rock from side to '35 side at any angle with sufiicientfreedom for comfort. l

My invention further contemplates interposing such an axial cushion body as is described in the m preceding paragraph between a saddle extending 40 transversely across the ankle joint and attached preferably to the shin piece, a U-bolt being mounted astride this saddle and connected tothe foot in the longitudinal center plane, this U-bolt acting both to mechanically couple the foot and shin piece and compress the cushion body in such manner and position as to allowthe desired limited universal motion for the foot.

My invention further contemplates as an added feature of importance that the axial cushion body as it becomes compressed as the weight comes on the ankle joint will cause a sufficient separation of the coupled metallic joint elements so that the Wearers Weight will floaton the cushion 5 member and in reality there is no appreciable frictional engagement between the metallic elements in the normal play of the foot.

Myinventio-n, which I have shown only in its preferred embodiment but which may be variously modified Without departing from its novel principles of construction, will be best understood by reference to the accompanying drawing, in which: i

Fig. 1 is a vertical central longitudinal section through the foot and shin piece assembled by 10 my improved ankle joint.

Fig. 2 is a transverse section through the foot showing the saddle in side elevation with its studs broken away.

Fig. 3 is a detail cross section of the seat por- 15 tion in'the foot piece for the elastic body shown in dottedlines.

Fig. 4 is a detail view of the axial cushion body. Similar reference numerals refer to similar parts throughout the drawing. 20

In the preferred embodiment of my invention illustrated, I show conventionally a shin piece 5 having its ankle portion ii of usual contour and adapted to be received in the top recess 1 in the foot 8 and there to rest in the usual manner upon 25 the instep cushion 9 and the heel bumper Hi, the latter being reduced in size and seated in a vertical recess II in theheel. In the foot piece I provide a straight'transverse bearing seat l2 ex- 7 tending entirely across the foot piece and struck 0 on an are substantially coaxial with the transverse axis of the ankle joint In the longitudinal central plane of the foot, on each side of this bearing I2, I provide openings through which the threaded shanks of U-bolt it are adapted to be passed downwardly and forwardly through the foot so that the U-bolt lies in a vertical central longitudinal plane through the foot.

The threaded ends of the U-bolt project into the bottom recess M in the foot and receive metal 40 lock washers l5 and nuts it by which the U-bolt is tightened up to couple the foot and shin pieces.

I mount transversely across the underface of the ankle portion 5 of theshin piece an arcuate shaped saddle plate H, the exterior contour of which conforms substantially to the inner arc .of the bend in the U-bolt l3 and this saddle piece is provided at its center on top with spaced raised elements l8 which form a seat to receive the U-bolt l3 on top so as to prevent transverse displacement between the saddle and the U-bolt, these elements it being flared apart as they approach the side edges of the saddle so as to ofier no resistance to a limited universal angular play of the U-bolt l3 as it responds to the play of the foot.

This saddle l1 carries on each side of the bolt seat elements I 8, I8 a vertical attachment stud 19, these studs lying in a transverse axial plane and extending upwardly through the solid lower end 6 of the shin piece into the recess therein where they are passed through lock washers 20 and made fast by the nuts 2|.

The ankle element 6 is formed with a seat that extends transversely across the ankle joint and conforms to the shape of the saddle elements I! and i8, being additionally recessed to receive the U-bolt l3 with a loose fit that provides clearance for both vertical and angular play for the U- bolt l3 relative to the saddle.

The most important feature of my invention consists in the elastic or resilient body 23 that is interposed axially of the ankle joint between the seat l2 in the foot and the saddle I! on the shin. This body has preferably a barrel-like shape and I have obtained excellent results with a body composed of best grade elastic rubber and having a diameter of one inch at its center tapering to 'V ths of an inch at each end. While it is not essential, it is preferable that the element be reduced in diameter toward the ends as thereby to free the joint better for the limited universal play of the foot that is so essential for full walking freedom. This axial elastic body 23 is set into the foot seat l2 with the saddle piece I! resting on it and the U-bolt l3 astride it and the saddle. The parts as shown thus assembled in Fig. l and to set up the joint, the nuts 2| are tightened fully to lock the saddle in position on the shin piece and the nuts l6 are tightened to draw the U-bolt I3 against the saddle and the saddle against the elastic body 23 so as to put it under the desired initial pressure between the seat l2 and the saddle.

It is desirable to bring this elastic body 23 under substantial initial compression, this being determined empirically according to the comfort of the individual wearer. With the ankle joint thus assembled, it will be apparent that the foot and shin are interlocked by the direct engagement between the metallic elements l3 and I1 and so held that when the wearers weight comes on the joint the shin piece will float on the interposed elastic body 23. The shin piece is designed so that the U-bolt I3 is held by the interposed body 23 in contact with the saddle I! while provision is made in the ankle portion of the shin for the U-bolt to have a limited vertical play requisite for the floating support of the shin and also angular play relative to the saddle to allow the foot free motion about the center of the ankle joint as an axis. It will be apparent when the full weight of the wearer comes upon the elastic body 23 its further compression will ease the engagement between the U-bolt and the saddle and will thus leave the foot piece freer to float, but the space in which the U-bolt l3 works does not permit it to move vertically far enough away from the saddle to produce objectionable noise in the joint. Preferably, the elastic body 23 extends substantially the full width of the ankle element 6, thus providing an ample elastic support both at the center and at the sides of the foot.

It will be noted that the compression on this elastic member is greatest at the center and least at its ends. This tends to free the foot piece better for limited universal angular play without imposing undue compression on any part of the elastic body 23 which would tend to rapidly destroy its resiliency.

In my ankle joint the heavy duty imposed when the weight of the wearer on the heel and toe of the foot is taken by the engagement between the metallic coupling elements with the resilient body 23 at rest except for its initial compression but when the direct load comes on the ankle joint the weight of the wearer shifts onto the resilient body and the metallic elements are freed, leaving the foot free for its limited universal play. While it is preferable that the metallic elements be respectively connected as shown to the foot and shin piece such connection is obviously reversible without material change in function.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In an artificial limb, an ankle joint comprising a shin member, a foot member, a body of resilient material occupying the axis of the ankle joint and extending transversely across same, a metallic saddle fitted lengthwise on said body and secured to one of said members, and a U-bolt astride said saddle and body and connected to the other member free for articulation relative to said saddle and the member to which the saddle is secured.

2. An artificial limb according to claim 1, in which the saddle is substantially coextensive with the axis of the ankle joint and is mounted free for angular play on said resilient body.

3. An artificial limb according to claim 1, in which the saddle is arcuate and said resilient body is rounded to fit the saddle and elongated to extend approximately across the ankle joint.

4. An artificial limb according to claim 1, in which the resilient body is elongated and tapered toward its ends and extends axially of the ankle joint under initial compression between said saddle and the diametrically opposed limb member.

5. In an artificial limb, the combination with a shin piece and a foot, of two metallic elements to couple said shin and foot at the ankle joint free to articulate, means to cause said elements to engage and take the full leverage thrust applied at the ankle joint from weight of the wearer on the toe of the artificial foot, and an elastic element interposed in the ankle joint in position to hold said metallic elements normally engaged and adapted to yield and free said elements so as to form an elastic support for the load applied vertically on the joint.

6. An artificial limb according to claim 5, in combination with an elastic instep bumper interposed between the toe and the ankle joint to form a resilient fulcrum for yieldingly supporting the load on the toe portion when said metallic elements are engaged.

7. An ankle joint construction for artificial limbs, comprising a U-bolt, a saddle adapted to fit into the bight of said bolt free to articulate and having means to anchor it to a limb member, and a rubber cushion adapted to be received between the saddle and the limb member to which the U-bolt is attached.

8. An ankle bolt construction for artificial limbs, comprising a U-bolt, a saddle adapted to fit into the bight of said bolt free to articulate and having means to anchor it to a limb member, and a rubber cylinder adapted to fit between the legs of the U-bolt against concave seatsin said saddle and the opposed limb member.

9. An artificial limb comprising shin and foot members, metallic elements which are interlocked at the ankle joint to couple said members free for relative vertical and angular play, and a resilient member interposed axially of the ankle joint in position yieldably to hold said elements engaged and, as it becomes compressed under downward pressure at the joint, to free said metallic elements by relative movements in a vertical plane from engagement and become the sole support at the joint axis for the wearers weight.

10. An artificial limb comprising shin and foot members, metallic elements which are engaged to couple said members for relative vertical and angular p1ay, and a resilient member mounted under initial compression along the joint axis in position normally to hold said elements engaged and adapted to yield under the wearers weight to free said metallic elements for relative vertical displacement, thereby to support the wearers weight transmitted through the ankle joint on to said resilient member and leave the shin member riding said resilient member free for limited universal angular play thereon.

11. An artificial limb according to claim 1-0, in which the yielding member at the ankle joint is elongated to extend substantially across the joint and is reduced in thickness toward its ends.

12. An artificial limb comprising shin and foot 7 members, metallic elements which are engaged to couple said members for relative vertical and angular play, and a resilient member interposed axially of the joint in position as it yields under pressure at the joint to free said metallic elements to separate vertically and thereby transmit the wearers weight through the ankle joint onto said resilient member, said member being elongated and disposed substantially coextensive with the axis of the ankle joint.

13. An ankle joint construction for artificial limbs, which comprises in combination with shin and foot members. a U-bolt connected to one member over a concave seat therein extending transversely of the joint, a rubber cylinder in said seat, a saddle engaging the cylinder opposite to said seat and connected to the other member, said saddle being held against the bight of said U-bolt by the elastic resistance of said cylinder when the foot is at rest and being free to move relative to said U-bolt as said cylinder yields responsive to the weight of the wearer on said joint.

14. In an ankle joint for the foot and shin members of an artificial limb, metallic elements secured to said members and adapted to interlock them free for articulation and relative vertical movement between said members, a transversely elongated elastic body mounted under compression in the ankle joint and adapted yieldingly to resist vertical displacement and angular play between foot and shin, and an elastic bumper interposed between the foot and shin members on the toe side of said compression member and adapted to supply the yielding support when the metallic elements interlock to resist the leverage applied by the weight of the wearer on the toe of the foot,

SAMUEL A. WILLE'IT.

Images