IE47845B1 - Lockable hinge joint for limb supports and other orthopaedic appliances - Google Patents

Description

The present invention relates to a locable joint which is particularly, but not exclusively useful as a knee joint of an orthpaedic leg support.

A leg brace includes thigh supports (steels) to either side of the thigh and shank steels to either side of the lower part of the leg, the thigh and shank steels on each side of the leg being connected by a pivot joint at knee level. The pivot joint on one or both sides of the knee is arranged to be locked when the patient is standing or walking but has to be releasable to allow the knee to flex when the patient is sitting. The release mechanism may be operated by a ring catch or drop lock which is a sliding ring on the thigh steel which may be lowered into engagement with the pivot joint to lock it and which is lifted to release the joint. Another kind of lock known as a bar lock or french lock involves a hinged release member pivoted to the thigh steel and operated by lifting an extension bar attached to the release member. Where bar locks are used, the pivot joints on both sides of the knee are normally lockable and the release members on opposite sides of the knee are interconnected by means of a bar extending around the back of the knee. A further kind of release mechanism employs a hinged release member having an extension bar to which a lifting cable may be fixed. The patient's disability may often affect parts of his body other than his legs, and the arthcpaedie fitter has to select from the j;ange of available release mechanisms one which is within - 3 the patient's capacity to operate.

Known types of release mechanism and in particular the ring catch and bar lock mechanisms operate on different principles and require differently shaped hinge members. The fact that different kinds of release mechanism require the differently shaped hinge members and different ancillary parts decreases the length of production runs and increases the number of parts required to be stocked by a limb fitting centre, both of which are factors tending to increase the cost of orthopaedic limb supports. It is an object of the invention to provide a release mechanism in which the same hinge members may be used in association with different release mechanisms and in particular in association with a release operating analogously to a ring catch by upward finger pressure from the rear of the release member and also in association with a bar lock or cable release, the only modification required being to the release member.

Manually operated ring catches are not normally spring loaded into the locked position and suffer from the disadvantage that they may accidentally be shaken out of engagement while the patient is walking. The joint of the invention may be released by upward finger pressure like a manual ring catch but the release member is spring loaded into the locked position. A further disadvantage of currently available ring catches is that although they may have little play when new, significant play is liable to develop as a result of wear, but such a tendency is not significantly exhibited by the hinge joint of the invention.

Broadly stated the invention provides a releasably lockable joint for an orthpaedic limb support or for an artificial limb, which joint comprises first and second members pivoted 4784S - 4 together at their ends for relative flexing movement and having stop faces which abut when the joint is straight to prevent movement beyond the straight position, the pivoted end of the first member having an arcuate portion which terminates in a recess or shoulder and the second member having a channel which is in register with the base of said recess or shoulder when the joint is straight and which extends generally radially away from the recess or shoulder with respect to the pivot axis, a detent slidable in the channel being resiliently biassed into a position in which it engages said recess or shoulder and being retractable into the channel by operation of a release lever pivoted at one end to one longitudinal edge of the second member and extending transversely of the second member so that its other end projects beyond the other longitudinal edge of the second member with a pivotal connection to the detent at an intermediate position along the length of the release lever, the detent being supported or supportable in a retracted position by said arcuate portion when the joint is flexed and being urged into engagement with said recess or shoulder when the joint is straightened to lock the joint in the straight position.

The lockable joint may additionally comprise a releasable catch for locking the detent in the retracted position.

Such a catch may comprise an auxiliary channel in the second member opening into the detent channel, a ball catch in the auxiliary channel resiliently biassed to project therefrom and a recess in the detent positioned to be engaged by the ball of the ball catch when the detent is retracted. The detent is preferably wedge shaped, with its rear face which engages an upwardly directed locking face of the recess or shoulder in the first member inclined at a small acute angle 47846 - 5 typically of the order of 10 degrees with respect to the other face thereof, the locking face of the recess or shoulder being directed parallel to the inclined face of the detent when the joint is straight so that when the detent is slid into engagement with the shoulder or recess, its inclined face is wedged against the lock face which wedging action minimises play in the pivot. A further factor tending to minimise play is that the interengaging faces of the detent and the shoulder or recess may be directed at approximately a right angle to the stop faces when the joint is in the straight position and the interengaging faces and the stop faces are a quarter circle removed from one another with respect to the pivot axis and so exert a wedging action taking up any play in the pivot.

The release may comprise a lever extending transversely of the second member and pivoted at an edge thereof, the lever being connected by means of a pivot pin to the detent and extending from the opposite edge. The lever is preferably in the form of an external ring fitted to the second member with its front edge pivotally received in a recess in the front edge of the second member and the internal surface of its rear edge normally spaced from the rear edge of the second member, an upward movement of the rear edge of the ring retracting the detent into the channel. The rear portion of the ring may be further provided with a socket for receiving an extension lever which forms part of a bar lock or cable lift.

Preferably the joint is manufactured as a sub-assembly separate from the steels of the limb support into which it is to be incorporated. The outer ends of the first and second members are preferably formed with an internal axial channel 8 43 - 6 dimensioned to receive the end of the respective steel which is then screwed or riveted in place. The end of the member may have its sides split longitudinally so that the fixing screws can be passed through each side of the member and through the steel to force the sides together and clamp the steel rigidly therebetween.

Various embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which similar parts are denoted by similar numerals and: Figure 1 is a side view of a manually lockable joint for an orthopaedic limb support with the second member shown partly in section, the joint being in the straight position? Figure 2 is a side view of the joint shown in Figure 1 in a flexed position; Figure 3 is a side view of a joint similar to that shown in Figures 1 and 2 but arranged for automatic locking; Figures 4(1), 4(11) and 4(111) show a first member and the end portion of steel and respectively illustrate a partially broken away side view, a rear view and a section along the line A-A of Figure 4(1) looking in the direction of the arrows; Figures 5(1), 5(11) and 5(111) are similar to Figures 4(1) to 4(111) but illustrate a different method of attachment of the steel to the first member? Figures 6(1) and 6(111) are side views of two different forms of pivoting ring catch fitted to the second member; Figures 6(11) and 6 (Ila) are side views of the first and second members arranged to be operated by a bar lock and in the straight and in a flexed position respectively; - 7 Figure 6(IV) is a side view of a second member arranged to be operated by means of a cable lift.

Referring to Figure 1, a first member 10 having a head in the form of an eye-bolt is pivoted to a second member 11 also having an eye-bolt head by means of a pivot bush (not shown) which passes through the eyes of the bolt heads and is held in place by a locking screw 12 (Figure 6). The front portions of the end edges of the members 10 and 11 are formed with respectively transversely extending stop faces 13 and 14 which when the joint is straight abut toprevent further angular movement of the members. It will be noted that in the straight position the axis of the member 11 is parallel to and offset forwardly of the axis of the member 10. The eye-bolt portion of the member 10 is formed with a zone 15 of reduced thickness bounded by an arcuate peripheral edge 16 terminating in a shoulder defined by a face 17 directed inwardly parallel to the longitudinal direction of the member 10 and a face 18 which is a transverse continuation of the stop face 13. It will be noted that the stop face 13 is formed on a portion of the member 10 which is of full thickness and it may be made of ample area and is well spaced from the pivot so that the unit load thereon is low and the rate of wear is minimised. The head of the member 11 is split to provide a pair of transversely spaced leaves between which the zone 15 of the member 10 is pivotally received. A rectangular channel 19 in the member 11 is aligned with its longitudinal direction at a small acute angle (typically about 10 degrees) to the axis of the member 11 and with its lower portion positioned to be in register with the shoulder defined by faces 17 and 18 of the member 10 when the joint is straight. A detent 20 slideable in the channel 19 is urged into engagement with the shoulder by means of a spring 21. It will be noted that the rear face of the detent is inclined at a small acute angle (typically about 10 degrees) with respect to the longitudinal direction 19 and is parallel to the lock face 17 on the member 10 when the joint is in the straight position, both faces being parallel to the axis of the member 10. The detent 20 is dimensioned to engage the lock face 17 with its end clear of the bottom face 18. It exerts a wedging action on the lock face 17 when the joint is locked so that there is minimal play. In a typical joint the detent and lock face engage over a distance of 3 mm. or more and when the joint is new there is a distance of 1.5 mm. or more between the end face of the detent and the bottom face 18 of the shoulder for wear take-up. The joint has the advantage that wear of the detent and lock face does not give rise to play but instead the wear is automatically taken up by engagement of the wedge with the lock face 17 at a detent position closer to the bottom face 18 of the shoulder than it occupied when the joint was new.

Figures 1 and 2 illustrate a joint which is arranged to be held unlocked until deliberately set to lock. An auxiliary bore 22 extends into the channel 19 from the front face of member 11 and has a catch formed by a ball 23 and spring 24 which as shown in Figure 2 urges the ball 23 into engagement with a rebate 25 in the front face of the detent 20 to hold the detent in a retracted position.

An actuating ring 26 is fitted over the member 11 with its front portion pivotally received in a recess 27 in the front edge of the member 11 and is connected at an intermediate position to the detent 20 by means of a pivot pin 28. In the locked position shown in Figure 1 the actuating ring is urged downwardly by means of the detent spring 21 but its rear face - 9 4784S may be lifted as shown in Figure 2 to retract the detent 20 into the channel 19 and compress the spring 21.

In use as a knee joint of an orthopaedic leg brace, the joint is locked when the patient is standing or walking. When he or she wishes to sit down, the rear end of the actuating ring is lifted to retract the detent out of engagement with the lock face 17 and into the channel 19 where it is held in a retracted position by engagement of the ball catch 23, 24 with the rebate 25. When the patient stands up and the joint is straightened, the rear end of the actuating ring is depressed to disengage the ball catch and allow the detent to snap downwardly into engagement with the lock face 17 to lock the joint against flexing.

The arrangement shown in Figure 3 is generally similar to that shown in Figures 1 and 2 except that the ball 23 and ball spring 24 have been omitted. When the actuating ring 26 has been operated to retract the detent the joint may be flexed as shown in Figure 3. On release of the actuating ring the detent is supported in a partially retracted position by the arcuate peripheral edge 16 and the members 10 and 11 may be straightened. As soon as the members 10 and 11 reach the straight position the detent 20 automatically snaps into engagement with the lock face 17 to lock the joint against flexing.

As stated above, it is preferred to manufacture the joint as a separate sub-assembly to be fitted into the limb brace or artificial limb.

One way of fitting the steels (which may be formed from steel or Dural) into the hinge is shown in Figures 4(1) to 4(111) and involves forming an internal axial channel in split ends of the first and second members and clamping the steel in position by means of countersunk fixing screws - 10 passing through the steel and through each of the split portions 29 and 30 of the member. This arrangement has the advantage that separate castings are not required to produce left and right handed versions of the joint. A more conventional way of fitting the steels is shown in Figures 5(I) to 5(III) in which an end of a steel having milled side edges is a push-fit in a C-shaped channel formed in the end of the member and is secured thereto by countersunk fixing screws.

Figures 6(1) and 6(111) show two different shapes of hinged ring catch 26 fitted to the member (II), lifting the rear face causing the joint to unlock. In Figure 6(1) finger pressure is applied to the back of the actuating ring 26 and in Figure 6 (II) finger pressure is applied to a rear side portion thereof. Figures 6(11) and 6 (Ila) show the actuating ring 26 fitted with an extension bar and arranged to operate as a bar lock. Figure 6 (IV) shows the member 26 having an extension 32 whose distal· end is formed with an eye for fixing the cable of a cable lift system.

It will be understood that the invention described above is not restricted to the details of the preferred forms described by way of example above which may be modified without departure from the scope of the invention, as defined in the appended claims.

Claims (9)

1. A releasably lockable joint for an orthopaedic limb support or for an artificial limb, which joint comprises first and second members pivoted together at their ends for relative flexing movement and having stop faces which abut when the joint is straight to prevent movement beyond the straight position, the pivoted end of the first member having an arcuate portion which terminates in a recess or shoulder and the second member having a channel which is in register with the base of said recess or shoulder when the joint is straight and which extends generally radially away from the recess or shoulder with respect to the pivot axis, a detent slidable in the channel being resiliently biassed into a position in which it engages said recess or shoulder and being retractable into the channel by operation of a release lever pivoted at one end to one longitudinal edge of the second member and extending transversely of the second member so that its other end projects beyond the other longitudinal edge of the second member with a pivotal connection to the detent at an intermediate position along the length of the release lever, the detent being supported or supportable in a retracted position by said arcuate portion when the joint is flexed and being urged into engagement with said recess or shoulder when the joint is straightened to lock the joint in the straight position.

2. A joint according to Claim 1, further comprising a releasable catch for locking the detent in the retracted position.

3. A joint according to Claim 2 wherein the releasable catch comprises an auxiliary channel in the second member opening into the detent channel a ball catch in the auxiliary channel resiliently biassed to project therefrom, and a recess - 12 in the detent positioned to be engaged by the ball of the ball catch when the detent is retracted.

4. A joint according to any preceding claim wherein the detent is wedge shaped and its rear face is inclined at a small acute angle with respect to the front face and engages an upwardly directed locking face of the recess or shoulder in the first member, said locking face of the recess or shoulder being directed parallel to the inclined face of the detent when the joint is straight so that when the detent is slid into engagement with the shoulder or recess its inclined face is wedged against the lock face to minimise play.

5. A joint according to any preceding claim wherein the interengaging faces of the detent and the shoulder or recess are directed at approximately a right angle to the stop faces when the joint is in the straight position.

6. A joint according to any preceding Claim wherein the lever is in the form of an external ring fitted to the second member with its front edge pivotally received in a recess in the front edge of the second member and the internal surface of its rear edge normally spaced from the rear edge of the second member, an upward movement of the rear edge of the ring retracting the detent into the channel.

7. A joint according to Claim 6 wherein the rear portion of the ring is provided with a socket for receiving an extension lever which forms part of a bar lock or cable lift device.

8. A releasably lockable joint for an orthopaedic limb support or for an artificial limb, substantially as hereinbefore described with reference to, or as illustrated in Figures 1 and 2 of the accompanying drawings. - 13

9. A releasably lockable joint for an orthopaedic limb support or for an artificial limb substantially as hereinbefore described with reference to or as illustrated in Figure 3 of the accompanying drawings.