Joint movement limiting arrangement for prosthetic legs

[57] ABSTRACT

A stop arrangement for a joint of an artificial leg is described which normally limits pivotal movement of a leg portion connected to the joint to a predetermined extent commensurate with stable walking on the leg. The arrangement includes a stop in the joint which prevents over travel of the leg portion connected to the joint and buckling of the leg under the amputee. The stop mechanism is selectively releasable to permit full pivotal movement of the joint as required for sitting, or the like and, if desired, may be locked in the released position.

Claims, 8 Drawing Figures

<img file="US3663967A_D0001.tif" />

Patented May 23, 1972

3,663,967

Sheets-Sheet 1

<img file="US3663967A_D0002.tif" />

Patented May 23, 1972

3,663,967

Sheets-Sheet 2

<img file="US3663967A_D0003.tif" />

3,663,967

JOINT MOVEMENT LIMITING ARRANGEMENT FOR PROSTHETIC LEGS

BACKGROUND OF THE INVENTION

In the field of prosthetics, various artificial legs have been devised to enable the amputee to resume walking. In the case of an amputee having a leg removed above the knee or hip joint, a suitable artificial leg requires mechanical counterparts of the missing joints in order that leg movement may be effected. Heretofore, artificial legs for replacing legs removed above the hip joint have included a pivot joint connecting the thigh portion to a bucket adapted to be strapped about the waist and receive the remaining portion of the trunk of the amputee. The joint typically includes a stop to prevent excessive rearward movement of the leg, while forward movement is resiliently constrained by a stiff resilient strap connected between the bucket and the shank or lower portion of the leg. The strap is such as to resiliently retain the leg in vertical position with the joint engaging the stop. The leg may be thrust forward, by appropriate movement of the wearer, against the restoring force of the strap to a forward position in engagement with the ground surface. The restoring force then facilitates return of the leg to vertical position in the completion of a step. However, extreme care must be taken that the leg is not thrust too far forward beyond a dead center position wherein the leg will continue to pivot forward rather than be returned rearward and thus buckle beneath the wearer. Although disadvantageous in walking, this movement beyond dead center position permits the leg to assume a horizontal position to enable the wearer to sit. Existing knee joints employed in artificial legs are basically similar to the above described conventional hip joints insofar as they limit movement in one direction, while permitting constrained movement in the opposite direction. However, with a knee joint the directions are reversed, forward movement being limited and constrained, rearward movement being permitted. Under some circumstances rearward movement of the knee joint may be excessive and cause buckling of the leg under the wearer.

SUMMARY OF THE INVENTION

The basic object of the present invention is to provide selectively releasable stop means in a joint for an artificial leg for limiting the intended constrained movement of a leg portion connected to the joint to a non-excessive amount during walking to prevent inadvertent buckling of the leg under the wearer. Upon release of the stop means by the wearer, the joint if freed for conventional full movement to enable the wearer to assume a sitting position. The joint includes a first mounting means for connection to the bucket, in the case of a hip joint, or to the thigh portion of the leg in the case of a knee joint. A second mounting means is adapted for securance to a lower portion of the leg, and the two securing means are hingedly secured together for pivotal movement with respect to one another. In accordance with the particularly salient aspects of the invention, a stop lug is rigidly secured to one of the mounting means, and a stop block is carried by the other. The stop block is selectively movable between a normal position engageable with the stop lug to prevent excessive pivotal movement of the joint, and a release position non-engageable with the lug to permit conventional full pivotal movement of the joint. Thus, pivotal movement of the joint is limited to prevent buckling of the leg while free pivotal movement may be provided as required to permit sitting, etc. A lock is provided for locking the stop block in the release position whenever desired, such as when a joint actuation or control mechanism is utilized with the leg.

An artificial leg in accordance with the invention may be arranged to include a stopped hip joint in combination with a conventional knee joint, a stopped knee joint alone in instances where the wearer has a thigh stump, or a stopped hip joint and a stopped knee joint. In the latter case, the leg may be arranged to facilitate simultaneous release of the stops of both joints under the control of a single release actuator. The leg may be arranged to permit adjustment of the length of the pivotal leg portion connected to each joint, as well as variation in the extent of limited pivotal movement thereof to accom5 modate the needs of the individual wearer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view with portions broken-away of j₀ an artificial leg in accordance with the present invention, the leg including a stopped hip joint and conventional knee joint and being depicted in standing position.

FIG. 2 is a view similar to FIG. 1, but depicting the leg in stopped forward position in the taking of a step.

FIG. 3 is a view similar to FIGS. 1 and 2, but depicting the leg in stop released forward position assumed in sitting, or the like.

FIG. 4 is an exploded perspective view of the stopped hip joint arrangement of the leg.

FIG. 5 is a front elevational view with portions broken-away of the joint arrangement.

FIG. 6 is a sectional view taken at line 6—6 of FIG. 5.

FIG.· 7 is a partial perspective view of the stop block plunger pin depicting a bayonet lock arrangement by which the stop 25 block may be selectively locked in a release position.

FIG. 8 is a perspective view of a modified form of joint in accordance with the present invention arranged for use with existing artificial legs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, FIGS. 1-3 in particular, there is shown an artificial leg 11 for an amputee having the leg removed at or above the hip joint. As is conventional, the 35 leg includes a bucket 12 which may be strapped about the waist of the wearer and is adapted to receive the portion of the trunk remaining after the amputation is performed. A thigh portion 13 is hingedly secured to a small leg portion depending from the bucket by means of a mechanical articulated hip 40 joint 14. The thigh portion includes a cover 16 or hard plastic, or the like.

In accordance with standard practice, the joint 14 is arranged to limit pivotal movement of the thigh portion 13 in the rearward direction to a substantially vertical position, as 45 shown in FIG. 1, and to permit constrained pivotal movement in the forward direction to enable the leg to assume a walking position, as shown in FIG. 2, or a sitting position, as shown in FIG. 3. In this regard, a stiffly resilient strap 17 of hard rubber or the like is secured between a point on the bucket rearward ³® of the joint 14 and a point adjacent the lower end of the cover 16. Thus, the strap resiliently constrains the forward pivotal movement of the thigh portion 13, and when same is thrust forward, as shown in FIG. 2, the strap tends to return the thigh portion rearward to vertical position as shown in FIG. 1. However, when the thigh portion is thrust too far forward, it exceeds a dead center position and the strap pulls the thigh portion forward and upward. This is necessary in order that the thigh portion may assume the horizontal sitting position de6q picted in FIG. 3.

The leg illustrated in FIGS. 1-3 is also provided with a conventional lower leg or shank portion 18 pivotally connected to the thigh portion 16 by means of a conventional knee joint 19, of, for example, the constant friction counterweighted variety. 65 Such a joint limits forward pivotal movement of the lower leg portion to a substantially vertical position and permits constrained rearward movement thereof. As in the case of the hip joint, the knee joint has a dead center position beyond which movement of the lower leg portion will continue rearwardly.

It will be appreciated that although the over movement of both the hip and knee joints is required to permit sitting, it is undesirable in walking. In accordance with the present invention, an articulated joint arrangement is provided which facilitates selective prevention of the pivotal movement of one 75 of the leg portions with respect to another beyond the dead

3,663,967 center position during walking, and release of the joint to permit conventional full pivotal movement for sitting. More particularly, with regard to the hip joint 14, and referring to FIGS. 4-7, it is to be noted that same includes a first mounting means in the form of a plate 21 secured to the bucket 12, as by means of screws 22. A second mounting means in the form of a Lishaped yoke 23 is pivotally connected to the plate, and a shaft 24 is secured to the web of the yoke to depend therefrom interiorly of the cover 16 and define the core of thigh portion 13. Shaft 24 is adjustable in length to accommodate the needs of the individual wearer. In this regard, the shaft is preferably comprised of telescoping inner and outer sections 20 and 25 which may be locked together by set screws as shown.

The lower end of shaft 24 is provided with an outwardly flared annular flange 26 to facilitate securance to a disc member 27 of the conventional knee joint 19. Pivotal connection of the yoke to the plate is preferably facilitated by means of a sleeve or collar 28 fixedly secured to the plate and fitted with ball bearings 29 in its opposite ends. A headed pivot pin 31 extends through the parallel spaced sides or legs of the yoke, the bearings 29, and sleeve 28 to receive a cap screw 32 and thus complete the pivotal connection.

The previously mentioned selective limiting and release of pivotal movement in a first direction is preferably facilitated by means of a stop lug 33 which projects outwardly from sleeve 28 and terminates in a face 30 which is engageable with a selectively movable stop block 34 carried by the yoke 23. The yoke has a V-shaped rear end portion 36 between the parallel spaced sides thereof, and the upper face of the end portion engages the plate 21 to limit rearward pivotal movement to a position wherein the thigh portion 13 is substantially vertical. The block 34 then includes a V-shaped end 37 conformed to the end portion 36 of the yoke. A headed bushing 38 is threadably received in and extends through one of the sides of the yoke to project interiorly therefrom, and a headed plunger pin 39 extends through an aperture in the opposite side of the yoke and is received in the bushing. The pin also extends through the lock 34 and a rectangular collar 41 on the opposite side of the block from the bushing. The collar is fixedly secured to the pin 39 as by means of a set screw 42 and is of a length to extend between the block and side of the yoke when the block is in a first position engageable with the lug 33. In this regard, it is to be noted that a cushioning washer 40 is provided on pin 39 between block 41 and the side of the yoke. A spring 43 is coaxially disposed on the pin 39 with one end engaging one of the sides of the yoke concentrically with the bushing 38 and the other end engaging the block. The spring is in compression and thus resiliently urges the block away from the bushing to a position determined by the collar 41 engaging the opposite side of the yoke, as shown in full line in FIG. 5. As previously noted, the block is engageable with the lug in this position. The headed end of the plunger pin is also extended from the side of the yoke. Upon forward pivoting of the yoke when the thigh portion 13 is thrust outward as shown in FIG. 2, the block hence engages the lug, as shown in phantom line in FIG. 6, to prevent excessive pivotal movement of the thigh portion beyond dead center position. When it is desired to sit and full pivotal movement is required, the plunger pin 39 is depressed to a second position depicted in phantom lines in FIG. 5 to in turn translate the block out of engagement with the lug. The yoke is thus free to pivot to the extent required. Once the yoke has pivoted the edge of block 34 past face 30 of lug 33, the side of the lug maintains the block in the released position so that it is unnecessary for the user to hold it in such position against the pressure of spring 43. When the wearer stands and the yoke pivots rearward, the spring 43 urges the block and plunger pin to their normal position once the edge of the block passes by the face 30 and stopped forward pivotal movement is restored.

In some instances, it is desirable that the leg joint be freely pivotal without interference by the stop block even when the wearer is standing. For example, if the leg includes a joint control or actuation mechanism the wearer may wish to override the pivot limiting stop means. As an important feature of the invention, means are provided for selectively locking the stop block in the second position and out of the way of travel of the stop lug. With reference to FIG. 7, bushing 38 includes a longitudinally extending slot 44 which terminates at its inner end in a transverse slot 46. A pin 47 radially projects from plunger pin 39 to normally ride within slot 44. Upon actuation of the plunger pin to translate block 33 to its second, releasing position, pin 47 becomes located at the inner end of slot 44 adjacent slot 46. Rotation of plunger pin 39 in the direction of arrow 48 in FIG. 7 will thus cause pin 47 to enter slot 46, thereby locking pin 39 in its plunged position and block 33 in the release position. The head 49 of plunger pin 41 includes a diametrically extending projecting rib 51 to facilitate gripping of the head to cause the pin rotation whenever it is desired to so lock the block in the release position.

Referring now to FIG. 8, there is shown a modified form of the joint which is arranged for use with a wooden leg. The modified joint 14' is generally similar to that previously described except that the yoke 23' includes a pair of parallel spaced straps 51 depending from the opposite sides thereof. The straps are provided with vertically spaced apertures 52 for receiving screws to be threaded into a wooden thigh portion inserted therebetween. The provision of more than one set of apertures in the straps permits adjustment of the length of a leg to accommodate the needs of an individual wearer.

While the locking arrangement of the invention has been described in connection with the hip joint of an artificial leg, it will be appreciated that it could also be utilized in a knee joint. Moreover, hydraulic or other control means may be used to effect movement of the stop means between the pivot releasing and limiting positions, such as when it is desired to actuate the stop means from a location remote from the joint in which it is incorporated.