GB2161386A - Artificial leg joint - Google Patents

Abstract

An artificial leg joint is provided having a first part (2) connectible to an upper leg stump or thigh, a second part (3) connectible to an artificial leg, which first and second parts (2, 3) are pivotally interconnected for movement of the second part (3) between a straight leg position substantially in line with the first part (2) and a bent leg position at least substantially at right angles to the first part (2). The joint (1) includes selectively actuable rotary lock means (4) connected between the first and second parts (2, 3) and means (5) for actuating the lock means (4) in response to differences in load exerted on the leg joint corresponding to different operative postural positions taken up by a wearer of an artificial leg fitted with the joint, so that with the leg joint operatively connecting an artificial leg to an upper leg stump or thigh, lifting the artificial leg out of contact with the ground or like frees the joint lock means allowing the leg to be pivoted freely at the joint into the straight leg position for walking or kicking and back towards the bent leg position to a limited angular extent but then engages the joint lock means (4) to prevent further pivotal movement of the leg at the joint towards the bent leg position, lightly loading the artificial leg against the ground or like surface, frees the joint lock means (4) allowing the leg to be pivoted freely at the joint in either direction between the straight and bent leg positions to permit the wearer sitting down, and heavily loading the artificial leg against the ground or like surface, such as when the wearer is walking or standing, engages the joint lock means (4) at any position of the leg between the straight and bent leg positions to prevent pivotal movement of the leg at the joint towards the bent leg position while still allowing pivotal movement of the leg at the joint towards the straight leg position. <IMAGE>

Description

SPECIFICATION Artificial leg joint This invention relates to an artificial leg joint.

Conventional artificial leg joints usually have a ball member connectible to an upper leg stump or a thigh and a complimentary socket member including a friction band connectible to the artificial leg. Such artificial leg joints have the drawbacks of being relatively large and cumbersome, relatively quick wearing resulting in a short operative life and do not enable the wearer to kick a ball with the artificial leg freely pivotable at the joint.

There is thus a need for a generally improved artificial leg joint which reduces the foregoing drawbacks associated with conventional artificial leg joints.

According to the present invention there is provided an artificial leg joint having a first part connectible to an upper leg stump or thigh, a second part connectible to an artificial leg, which first and second parts are pivotally interconnected for movement of the second part between a straight leg position substantially in line with the first part and a bent leg position at least substantially at right angles to the first part, selectively actuable rotary lock means connected between the first and second parts, and means for actuating the lock means in response to differences in load exerted on the leg joint corresponding to different operative postural positions taken up by a wearer of an artificial leg fitted with the joint, so that with the leg joint operatively connecting an artificial leg to an upper leg stump or thigh, lifting the artificial leg up out of contact with the ground or like so freese the joint lock means allowing the leg to be pivoted freely at the joint into the straight leg position for walking or kicking and back towards the bent leg position to a limited angular extent but then engages the joint leg means to prevent further pivotal movement of the leg at the joint towards the bent leg position, lightly loading the artificial leg against the ground or like surface, freese the joint lock means allowing the leg to be pivoted freely at the joint in either direction between the straight and bent leg positions to permit the wearer sitting down, and heavily loading the artificial leg against the ground or like surface, such as when the wearer is walking or standing, engages the joint lock means at any position of the leg between the straight and bent leg positions to prevent pivotal movement of the leg at the joint towards the bent leg position while still allowing pivotal movement of the leg at the joint towards the straight leg position.

Advantageously the first part includes a stirrup member having two spaced apart arms fixed at one end to and extending substantially perpendicularly from a base substantially parallel to one another, and a plate-like flap member substantially Tshaped in plan pivotally connected at or adjacent the free end of its stem to the free ends of the arms to overlie the stirrup member so that the stem of the flap member overlies or covers the opening between the arms and the cross pieces of the flap member overlies or covers the base of the stirrup member, the ends of the cross piece extending in the direction of the base beyond the positions at which the arms extend from the base, with the flap member being pivotally displaceable about its pivotal connection towards and away from the stirrup member between a first end position in which the cross piece is furthest still away from the stirrup member base, a second end position in which the cross piece is closest to the stirrup member base against the return action of the resilient biass means and an intermediate position between the first and second end positions, and with the flap member being securable to an upper leg stump or thigh or a wearer to extend substantially at right angles to the longitudinal axis thereof with the stirrup member depending from the flap member and with the pivotally connected free end of the stirrup member stem directed forwardly of the wearer.

Preferably the second part includes an elongated housing portion having a substantially planar base portion connectible at one end to an artificial leg to extend axially therefrom which base portion has two spaced arms fixed at one end to and extending substantially perpendicularly from the base portion, substantially parallel to one another, which arms and base portion are dimensioned such that the arms fit slidably between the first part stirrup member arms and are pivotally connected thereto by a pivot shaft fixedly connectible to the stirrup member arms to extend therebetween substantially parallel to the flap member pivot axis and intermediate the stirrup member free arm ends and the ends of the stirrup member arms connected to the base portion, with the housing portion being freely pivotally mounted on the pivot shaft which extends through complementary apertures provided through the housing portion arms, so that the housing portion base portion in the straight leg position of the joint depends from the stirrup member on the side thereof opposite to the flap member and substantially perpendicularly to the flap member in the first end position, and with the housing portion base portion directed forwardly by the wearer.

Conveniently the rotary lock means includes a cylindrically bored cylindrical housing member and, rotationally housed in said housing member bore, a generally cylindrical cam member with a generally circular periphery and an annular generally cylindrical lock member, with the annular lock member pivotally interconnecting the housing member and cam member relative to one another about a rotary pivot axis formed by the longitudinal axis of the cylindrical bore, wherein the annular lock member is housed in the housing member bore with the outer periphery of the lock member in rotary slidable contact with the inner periphery of the housing member bore so that the housing member is rotatable about the lock member, which lock member has at least three bearing members movably housed in apertures opening radially through the inner and outer peripheries of the lock member at peripherally spaced locations therearound, and the cam member has a generally circular periphery with, spaced around the cam member periphery, at least three substantially planar or dished cam faces, which cam member is housed in the lock member in peripheral slidable contact with the inner periphery of the lock member with the bearing members in contact with the respective cam faces, and means being provided, on or engageable with the lock member whereby the lock member can be rotatably displaced to a limited extent between two operative positions to rotate the annular lock member in either direction to a limited extent about the rotary pivot axis relative to the housing and cam members, so that with the lock member in one of the two operative positions, the housing member may rotate relative to the cam member about the lock member in either direction, and with the lock member in the other of the two opposite positions, the lock member is rotatively displaced relative to the cam and housing members causing the bearing members to be displaced by the lock member along and up their respective cam faces, towards and into wedged locking engagement between the inner periphery of the housing member cylindrical bore and the respective cam faces to stop rotary movement of the housing member relative to the cam member in the direction of said other operative position but not in the opposite direction towards said one operative position.

Preferably the housing member containing the cam member, annular lock member and bearing members is located between the second part housing portion arms with the pivot shaft extending through a corresponding bore extending through the cam member coaxially with said rotary pivot axis, and with the cam member being fixedly connected to said pivot shaft to prevent rotation relative thereto.

Advantageously the housing member is located in a cylindrical band with the interposition between the band and housing member of a friction lining, there being a radial projection from the outer surface of the band locatable in a corresponding recess in the second part housing portion base portion, with the interposition of resilient cushioning means between the projection and recess, to connect the housing member via the friction lining and cylindrical band to the second part housing portion for pivotal movement with the second part housing portion about the pivot shaft fixed to the first part when the second part is pivotally displaced between the straight and bent leg positions, and the degree of friction exerted by the friction lining between the housing member and cylindrical band being selected to provide for slip between the housing member and the cylindrical band if excessible pivotal force is applied to the first or second parts of the joint from the straight to the bent leg positions when the rotary lock means is engaged.

Conveniently the degree of friction selected is adjustable by peripherally dividing the band at one point in the direction of the rotational axis thereof so that the peripheral length of the band can be altered by adjustment means to cause the band to grip more or less on the friction lining and hence the friction lining to grip more or less on the housing member.

Preferably the lock means includes a first cover plate fixedly attachable to the cam member so that the first cover plate and cam member are rotationally fixed relative to one another and so that the housing member cylindrical bore is closed at one end by the cover plate and at the other end by a second cover plate to retain the cam member and lock member in the cylindrical bore between the first and second cover plates which are centrally bored to fit over the pivot shaft, and with the first cover plate being pivotally connectible to the pivot shaft to prevent rotation relative thereto.

Preferably the means whereby the lock member can be rotatably displaced is a projection on one side of the lock member and extending in a direction parallel to the rotary pivot axis, engageable in and projecting through a corresponding slot provided in the cover plate, which projection and slot are dimensioned such that the projection can be displaced in the slot to a limited extent between the said two operative positions to rotate the lock member in either direction to a limited extent about the rotary pivot axis relative to the first cover plate and cam member.

Conveniently each bearing member is resiliently biassed by at least one spring housed in a corresponding recess in the lock member of the trailing side of the bearing member with respect to the other operative position and communicating with the associated bearing member aperture.

Preferably the bearing members are ball or roller shaped.

Advantageously the first cover plate is attached to the cam member by at least two screws or rivets passing through the first cover plate and engaging in threaded bores in the cam member.

Preferably the means for actuating the lock means includes an axially bored cam plate arranged on the pivot shaft adjacent the first cover plate to which it is attached by four spaced apart post members projecting from the first cover plate through corresponding elongated apertures provided in the cam plate, which elongated apertures are dimensioned to allow the camp plate limited angular movement about the pivot shaft with respect to the first cover plate, there being a corresponding slot provided through the cam plate to receive the lock member projection.

Preferably the means for actuating the lock means includes an axially bored cam bush rotatably mounted on the pivot shaft adjacent the cam plate, which cam bush is fixedly attached to the adjacent second part housing portion arm to pivot with the latter about the pivot shaft,a cam surface being provided on the cam plate about the end of the bore therethrough adjoining the cam bush.

Advantageously the means for actuating the lock member includes three elongated links located between the cam plate and said adjacent second part housing portion arm, of which the first link is piv otally mounted at one end on the first post member end projecting through the cam plate and has an elongated slot at its other end for receiving the end of the lock member projection projecting through and from the cam plate, the first link having a cam follower surface for engagement with the cam surface provided on a cam plate and being resiliently connected to the second post member end projecting through the cam plate by a first spring connected between the first link other end and the second post member end.

Conveniently the second link is pivotally mounted at one end on the third post member end projecting through the cam plate and has an elongated slot intermediate its ends engageable on a fifth post member provided on and projecting from the cam plate towards the adjacent second part housing arm, the second link having a cam follower surface for engagement with the cam surface provided on the cam bush.

Preferably the third link is pivotally connected at one end to the other end of the second link, and resiliently connected to the fourth post member end projecting through the cam plate by a second spring connected between the fourth post member end and a point on the third link intermediate its ends, with the other end of the third link having an elongated slot pivotally engageable with the cross piece of flap member, so that with the leg joint operatively connecting an artificial leg to an upper leg stump or thigh, lifting the artificial leg up out of contact with the ground or like surface pivots the flap member into its first end position, lightly loading the artificial leg against the ground or like surface, pivots the flap member into the intermediate position, and heavily loading the artificial leg against the ground or like surface pivots the flap member into the second end position against the return action of the resilient bias means located between the flap member and the first part stirrup member and operative to urge the flap member from the second end position towards the intermediate position.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a perspective view from the front of an assembled artificial leg joint according to one embodiment of the invention, Figure 2 is a side elevational view of the leg joint of Fig 1, Figure 3 is an end elevational view from the rear of the leg joint of Fig 1, Figure 4 is an exploded perspective view of the leg joint of Fig 1, Figure 5 is a perspective view of rotary lock means and rotary lock actuating means of the embodiments of the embodiments of Fig 1, Figure 6 is an exploded perspective view of Fig 5, Figure 7 is a diagrammatic detail end view showing a flap member of the embodiment of Fig 1 in a first end position and a projection of the rotary lock means in one operative position, Figure 8 is a view similar to that of Fig 7 showing the flap member in the first end position and the rotary lock means projection in the other operative position, Figure 9 is a view similar to that of Figs 7 and 8 but showing the flap member in an intermediate position and the rotary lock means projection in said one operative position, and Figure 10 is a view similar to that of Figs 7, 8 and 9 but showing the flap member in a second end position and the rotary lock means projection in said other operative position.

An artificial leg joint of the invention, generally indicated at 1 in the accompanying drawings, basically includes a first part 2, a second part 3, a selectively actuable rotary lock means 4 and means S for actuating the lock means 4. The first part 2 is connectible to an upper leg stump or thigh, the second part 3 is connectible to an artificial leg such as by means of a spigot 6, and the first and second parts 2 and 3 are pivotally interconnected by a pivot shaft 7 for movement of the second part 3 between a straight leg position substantially in line with the first part 2 as shown in Figs 1, 2 and 3, and a bent leg position (not illustrated) at least substantially at right angles to the first part 2, and preferably approximately 135 to the straight leg position.

The rotary lock means 4 is connected between the first and second parts 2 and 3 via the pivot shaft 7 in a manner which will be subsequently described, and the means 5 are operable to actuate the lock means 4 in response to differences in load exerted on the leg joint 1 corresponding to different operative postural positions taken up by a wearer of an artificial leg fitted with the joint.Thus the means 5, with the leg joint 1 operatively connecting an artificial leg to an upper leg stump or thigh and with the artificial leg lifted up out of contact with the ground or like surface operates to free the joint lock means 4 allowing the leg to be pivoted freely at the joint 1 into the straight leg position as shown in Fig 1 for walking and back towards the bent leg position to a limited angular extent, preferably of the order of 15 , but then engages the joint lock means 4 to prevent further pivotal movement of the leg at the joint 1 towards the bent leg position. Thus the leg may be kicked forward in the air about the joint 1 for walking and used for kicking a wall.Initial contact with the wall will deflect the leg backwardly towards the bent position to the limited extent allowed, preferably no more than 15Q, whereupon the rotary lock means 4 will actuate and prevent the leg being returned further towards the bent leg position.

Lightly loading the artificial leg against the ground or like surface, causes the actuating means 5 to free the joint lock means 4 allowing the leg to be pivoted freely at the joint 1 in either direction between the straight and bent leg position to permit the wearer sitting down. Heavily loading the artificial leg against the ground or like surface, such as when the wearer is walking or standing, causes the actuating means 5 to engage the joint lock means 4 at any position of the leg between the straight and bent leg positions to prevent pivotal movement of the leg of the joint 1 towards the bent leg position whilst still allowing pivotal movement of the leg at the joint 1 towards the straight leg position.Looking at Fig 2 of the drawings, in the bent leg position the second part 3 is caused to adopt a position substantially at right angles to that shown, pivoted rearwardly about the pivot axis of the pivot shaft 7 towards the right of the Figure.

The first part 2 of the leg joint 1 includes a stirrup member 8 best seen in Fig 4, having two spaced apart arms 9 fixed at one end to and extending substantially perpendicularly from a base 10 and a plate-like flap member 11 substantiallyTshaped in plan. The flap member 11 is pivotally connected at or adjacent the free end of its stem 12 to the free ends of the arms 9 by means of a shaft 13. The shaft 13 extends between and is fixedly connected to the free ends of the arms 9 and freely passes through corresponding apertures 14 provided through spaced apart ear portions 15 depending from the free end of the stem 12 of the flap member 11 as shown in Fig 4 so that the ear portions 15 fit between the spaced apart arms 9 of the stirrup member 8.

In this way the flap member 11 overlies the stirrup member 8 as shown in Figs 1 to 4 so that the stem 12 overlies or covers the opening between the arms 9 and the cross piece 16 of the flap member 11 overlies or covers the base 10 of the stirrup member 8. The ends 16a of the cross piece 16 extend in the direction of the base 10 beyond the positions at which the arms 9 extend from the base 10 in the manner of lateral projection for cooperation with resilient bias means in the form of springs 17 in a manner which will be hereinafter described.

The flap member 11 is pivotally displaceable about its pivotal connection at the shaft 13 towards and away from the stirrup member 8 between a first end position A as shown in Figs 7 and 8 in which the cross piece 16 is furthest away from the stirrup member base 10, a second end position C shown in Fig 10 in which the cross piece 16 is closest to the stirrup member base 10 against the return action of the resilient bias means springs 17, and an intermediate position B as shown in Fig 9 between the first and second end positions A and C.

The flap member 11 is securable to an upper leg stump or thigh of a wearer in any convenient manner to extend substantially at right angles to the longitudinal axis thereof with the stirrup member 8 depending from the flap member 11 in the position shown in Figs 1 to 4 and with the pivotally connected free end of the stirrup member stem 12 directed forwardly of the wearer as shown in Figs 1 and 4.

The second part 3 includes an elongated housing portion 18 having a substantially planar base portion 19 connectible at one end to an artificial leg via the spigot 6. As shown in Fig 4 of the spigot 6 is secured to two spaced apart arms 20 provided on the base portion 19, for example by means of screws 20a. The arms 20 are fixed at one end 2 and extend substantially perpendicularly from the base portion 19, substantially parallel to one another. The dimensions and location of the arms 20 and base portion 19 are such that the arms 20 fit slidably between the first part stirrup member arms 9 and are pivotally connected thereto by the pivot shaft 7. The pivot shaft 7 is fixedly connected to the stirrup member arms 9, in any convenient manner such as by means of a key way 7a engaging with a corresponding projection 21 on the aperture through the stirrup member arm 9 as shown in Figure 4.The other arm 9 may be provided with an elongated slot like aperture 22 for receiving a correspondingly shaped end 7b fixedly to locate the shaft 7 across the arms 9 of the stirrup member 10 to extend therebetween substantially parallel to the pivot axis of the flap member 11. The shaft 7 may be removably attached to the stirrup member arms 9 by means of a washer 23 and screw 24.

Thus the arms 20 of the second part housing portion 18 are located on the shaft 7 intermediate the stirrup member free arm ends and the ends connected to the base portion 10 so that the housing portion 18 is freely pivotally mounted on the pivot shaft 7. In the straight leg position of the joint, for example as shown in Fig 1, the housing portion base portion 19 depends from the stirrup member 8 on the side thereof opposite to the flap member 11 and substantially perpendicular to the flap member in the first end position A. The housing portion base portion 19 is, in use of the joint, directed forwardly of the wearer. Of course the form of the stirrup member 8 and housing portion 18 is such that the joint cannot pivot beyond the straight leg position but can only pivot from the straight leg position towards the bent leg position and vice versa.

The rotary lock means 4 carried on the pivot shaft 7 between the arms 20 of the housing portior 18 includes a cylindrically bored cylindrical housing member 25 as shown particularly in Figs 4 and 6, and, rotationally housed in the housing member bore, a generally cylindrical cam member 26 with ; generally circular periphery and an annular generally cylindrical lock member 27. The lock member 27 pivotally interconnects the housing member 25 and cam member 26 for rotary pivotal movement of the housing member 25 and cam member 26 relative to one another about a rotary pivot axis formed by the longitudinal axis of the cylindrical bore 25a through the housing member 25. The loc member 27 is housed in the housing member bore 25a with the outer periphery of the lock member 27 in rotary slidable contact with the inner periphery of the housing member bore 25a, as shown in Fig 6, so that the housing member 25 is rotatable about the lock member 27. Also as shown in Fig 6 the lock member 27 has at least three bearing members 28, preferably in the form of roller, movably housed in apertures 29 opening radially through the inner and outer peripheries of the loci member 27 at peripherally locations therearound.

The cam member 26 has a generally circular periphery with, spaced around the cam member pe periphery, at least three substantially planar or dished cam faces 30.

The cam member 26 is housed in the lock member 27 in peripheral slidable contact with the inner periphery of the lock member 27 and with the bearing members 28 in contact with the respective cam faces 30. Means are provided, in the form of a projection or tab 31 on the lock member 27 whereby the lock member 27 can be rotatably displaced to a limited extent between two operative positions X and Y as shown in Figs 7 to 10 to rotate the lock member 27 in either direction to a limited extent about the rotary pivot axis relative to the housing member 25 and cam member 26. Thus with the lock member 27 in one operative position X the housing member 25 may rotate relative to the cam 26 about the lock member 27 in either direction about the pivot axis.With the lock member 27 in the other operative position Y the lock member 27 along and up their respective cam faces 30 towards and into wedged locking engagement between the inner periphery of the housing member cylindrical bore 25a and the respective cam faces 30 to stop rotary movement of the housing member 25 relative to the cam member 26 in the direction of the other operative position Y but not in the opposite direction towards the one operative position X.

As shown in Figs 4 and 6 the housing member 25 containing the cam member 26, annular lock member 27 and bearing members 28 is located between the second part housing portion arms 20 with the pivot shaft 7 extending through a corresponding bore 26a which extends through the cam member 26 coaxially with the rotary pivot axis. The ca member 26 is fixedly connected to the pivot shaft to prevent rotation relative thereto. This conveniently is by means of a further key projection 32 provided in the cam member bore 26a and engaging in the key way 7a in by pivot shaft 7.

The housing member 25 is located in a cylindrical band 33 as shown in Figures 4 and 5 with the interposition between the band 33 and housing member 25 of a friction lining 34. The band 33 has a radial projection 35 from the outer surface thereof locatable in a corresponding recess 36 in the second part housing portion base portion 19 with the interposition of resilient cushioning means 37 in the form of a rubber ring, between the projection 35 and recess 36. The projection 35 and recess 36 thus connect the housing member 25 via the friction lining 34 and band 33 to the second part housing portion 18 about the pivot shaft 7 fixed to the first part 2 when the second part 3 is pivotally displaced between the straight and bent leg positions.The degree of friction exerted by the friction lining 34 between the housing member 25 and band 33 if excessive pivotal force is applied to the first or second parts of the joint from the bank leg positions when the rotary lock means 4 is engaged.

The degree of friction can be adjustably selected by peripherally dividing the band 33 at one point in the direction of the rotational axis thereof to leave a gap in the band periphery. Flanges 38 are provided one on each of the outer edges of the gap in the band periphery for movement towards and away from one another by means of screws 38a to alter the peripheral length of the band 33 t cause the band to grip more or less on the friction lining 34 and hence cause the friction lining 34 to grip more or less on the housing member 25.

The rotary lock means 4 also includes a first cover plate 29 fixedly attachable to the cam member 26 such as by screws 39a as shown in Fig 6, so that the first cover plate 39 and cam member 26 are rotationally fixed relative to one another and so that the housing member cylindrical bore 25a is closed at one end by the first cover plate 39. At the other end bore 29a is closed by a second cover plate 40 to retain the cam member 26 and lock member 27 in the cover plates 39 and 40 centrally bored to fit over the print shaft 7.

Means 7 are provided whereby the lock member 27 can be rotatably displaced. Such means includes the projection or tab 31 which extends from one side of the lock member 27 in a direction parallel to the rotary pivot axis and engages in and projects through a corresponding slot 41 provided in the first cover plate 39. The projection 31 and slot 41 are dimensioned to permit displacement of the projection 31 in the slot 41 between the said two operative positions X and Y to rotate the lock member 27 in either direction to a limited extent about the rotary pivot axis relative to the first cover plate 39 and cam member 26. Additionally in the rotary lock means 4 each bearing member 28 is resiliently biassed by a spring 28a housed in the respective bearing member aperture 29 on the trailing side of the bearing member with respect to the other position Y.Alternatively the spring 28a to communicate with the associated bearing member aperture 26. Alternatively the bearing members 29 may be ball rather than roller in form.

Additionally the rotary lock actuating means 5 includes an axially bored cam plate 42 arranged on the pivot shaft 7 adjacent the first cover plate 29 to which it is attached by four spaced apart post members 43 to 46 projecting from the first cover plate 39 through corresponding elongated apertures 46 provided in the cam plate 42. The elongated apertures 47 are provided through the cam plate 42 to receive the lock member projection 31.

The rotary lock actuating means 5 also includes an axially bored cam bush 49 rotatably mounted on the pivot shaft 7 adjacent the cam plate 42. The cam bush 49 is fixedly attached to the adjacent second part housing portion arm 20, for example by being a press fit in the aperture therein for the pivot shaft 7, to pivot with the arm 20 about the pivot shaft 7. A similar distance piece bush 50 without a cam surface is provided at the other end of the shaft 7 against the other arm 20 of the housing portion 18, as can be seen in Fig 5. A cam surface 51 is provided on the cam bush 49 on a side thereof adjacent to a further cam surface 52 are provided on the cam plate 42. Cam surfaces 51 and 52 are provided about the end of the bore through the cam plate and cam bush receiving the pivot shaft 7.

Also forming part of the rotary lock actuating means 5 are three elongated links 53 to 55 located between the cam plate 42 and the adjacent second part housing portion arm 20. The first link 53 is pivotally mounted at one end on the end of the first post member 43 projecting through the cam plate 42 and has an elongated slot 53a at or adjacent its other end for receiving the end of the lock member projection 31 projecting through and from the cam plate 42. This first link 53 has a cam follower surface 53b on its innermost side for engagement with the cam surface 52 on the cam plate 42. The first link 53 is resiliently connected to the end of the second post member 44 projecting through the cam plate 42 by a first spring 56 connected between the end of the first link 53 adjacent the slot 53a and the end of the second post member 44.

The second link 54 is pivotally mounted at one end on the end of the third post member 45 projecting through the cam plate 42. The second link 54 has an elongated slot 54a intermediate its ends engageable on a fifth post member 57 provided on and projecting from the cam plate 42 towards the adjacent second part housing portion arm 20. This second link 54 also has a cam follower surface 54b for engagement with the cam surface 51 on the cam bush 49.

The third link 55 is pivotally connected at one end by means of a pivot connection 58 to the end of the second link 54 remote from the end thereof carried on the third post member 45. The third link 55 is resiliently connected to the end of the fourth post member 46 projecting through the one of the cam plate slots 47 by a second spring 59 connected between the fourth post member 46 and a point on the third link 55 intermediate its ends. The end of the third link 55 remote from the pivotal connection 58 has an elongated slot 55a pivotally engaged with the flap member cross piece 16 in any convenient manner such as by means of a right angle bracket piece 60 to which it is pivotally connected as shown in Figs 4 and 7 to 10.

Thus with the leg joint 1 operatively connecting an artificial leg to an upper leg stump or thigh, lifting the artificial leg up so that the foot portion thereof comes out of contact with the ground or like surface, causes the flap member 11 to pivot about its shaft 13 into the first end position A as shown in Fig 7. Such pivotal movement of the flap member 11 is occassioned by the fact that it is connected directly to the upper leg stump or thigh whereas the second part of the joint 3 is connected directly to the artificial leg and to the stirrup member 8. Thus the weight of the leg hanging freely in air pulls the housing portion 18 and attached stirrup member 8 away from the flap member 11 thus pivoting the latter about its pivot shaft 13 into the first end position A.

Thus as shown in Fig 7 with the flap member 11 in the end position A the third link 55 pulls the second link 54 upwardly rotating the cam plate 42 anticlockwise via the fifth post member 57 and slot 54a. This brings the nose of the cam surface 52 on cam plate 42 into contact with the nose of the cam follower surface 54b on the second link 54. In this position the artificial leg can be swung forwardly from the bent leg position towards the straight leg position about the joint 1 with the leg in the air. In this position there is no weight or load on the artificial leg. However once the leg reaches the straight leg position of the joint return movement towards the bent leg position, with the leg in the air, is only possible for a limited angular movement, preferably about 15 from the straight leg position.This enables an artificial leg fitted with the leg joint 1 of the invention to be used for kicking a ball in air as immediately after contact has been established between the artificial leg 4 and the ball return movement of the artificial leg about the leg joint 1 is prevented after an initial travel of about 15 by the rotary lock means actuating to lock the joint against further return movement towards the bent leg position.

This is achieved, as shown in Fig 8, by initial return movement of the leg and hence of the housing portion 18 about the pivot shaft 7 with the flap member 11 in the first end position A causing the cam plate 42 to rotate further in the anti-clockwise direction under the action of the second spring 59 turning the cam plate 42 to the full extent permitted by the shaft 55a in the third link 55. In this position the first link 53 displaces the projection 31 and attached cam member 26 into the locked engagement operative position Y from the unlocked operative position X shown in Fig 7. This displacement of the projection 31 in its slot 41 into the engagement position Y of the rotary lock means 4 only occurs if the cam follower surface 54b on the second link 54 comes off the nose of the cam surface 51 of the cam bush 49 and settles on the root thereof as can be seen in Fig 8.Thus in effect in the Fig 8 position the rotary lock means engages when the leg returns from the straight leg position towards the bent leg position through approximately 15 because the shaft 7 and hence the cam bush 49 rotates sufficiently from the cam surface 51 to rotate past the cam follower surface 54 on the second link 54 thereby allowing the second spring 59 to displace the second link 54 thereby allowing the second spring 59 to displace the second link 54 radially inwardly towards the pivot axis of the shaft 7 thereby rotating the cam plate 42 anticlockwise by means of the fifth post member 57 attached to the cam plate 42 and entrained by the second link 54.

This is of great advantage to a wearer of an artificial leg fitted with the leg joint 1 of the invention as it enables the wearer to take part in athletic activity without fear of the artificial leg joint collapsing under him when a ball is kicked as is the problem with conventional leg joints. Of course this engagement of the rotary lock means after a limited return movement of the artificial leg in the air is of great advantage when walking normally and encountering an obstruction with the artificial leg in the air. The leg joint 1 of the invention pre vents the artificial leg returning to the bent leg po sition in such an encounter which is not the case with conventional leg joints and this affords a con siderable safety improvement.The degree of free return movement permitted with the leg joint 1 and artificial leg in the air and the flap member 11 in the first end position A can be determined to be more or less than 15 depending upon the position of the cam bush 49 on the housing member arm 20 and the dimensions of the cam surface on the cam bush 49. Additionally the friction lining 34 en ables the artificial leg to be returned towards the bent leg position even with the rotary lock means 4 in the locked position as shown in Fig 8 if the arti ficial leg encounters a return loading greater than that permitted by the friction lining 34 and this avoids damage to the wearer and/or to the rotary lock means 4.

Lightly loading the artificial leg fitted to the leg joint 1 of the invention against the ground or like surface frees the rotary lock means 4 allowing the leg to be pivoted freely at the joint in either direc tion between the straight and bent leg positions to permit the wearer to sit down. This is done as can be seen from Fig 9 by reason of the flap member 11 being depressed slightly into the intermediate position B about its pivot shaft 13. In this position B the flap member cross piece ends 16a rest lightly ,against the top ends 61a of bolts 61 slidably mounted on projecting portions 10a provided on or connected to the arms 9 of the stirrup member 8 in lateral extension of the base 10.These bolts 61 are loaded by the springs 17 acting between the ends 61a and in the intermediate position B of the flap member 11 as shown in Fig 9 no force is exerted by the flap member 11 on the bolt ends 61a. In this position the third link 55 holds the second link 54 in a position against the return action of the sec ond spring 59 where the cam plate 42 is rotated clockwise part way to the median position of its permitted movement. At this point the nose on the cam surface 52 of the cam plate 42 engages the cam follower surface 53b on the first link lifting the first link 53 radially away from the pivot axis through the pivot shaft 7 and hence displacing the projection 31 and attached lock member 27 into the disengaged unlocked operative position X as shown in Fig 9.The rotary lock means will remain in the unlocked condition and the projection 31 in position X permitting rotary movement of the housing member 18 and attached artificial leg about the pivot shaft 7 in either direction between the straight and bent leg positions as long as the flap member 11 is held in the intermediate position B B by light load applied to the foot of the artificial leg commensurate with the foot being rested lightly on the ground. In this position the wearer of an artificial leg and leg joint 1 of the invention is able to sit with the artificial leg joint freely mova ble.

When the artificial leg attached to the leg joint 1 of the invention is heavily loaded by the wearer against the ground or like surface, such as when the wearer is walking or standing, the rotary lock means 4 is engaged at any position of the leg between the straight and bent leg positions to prevent pivotal movement of the leg at the joint towards the bent leg position but while still allowing pivotal movement of the leg of the joint 1 towards the straight leg position. This is achieved, as can be seen from Fig 10, by the weight applied to the flap member 11 with the foot portion of the artificial leg on the ground displacing the flap member 11 against the return action of the spring 17 of the bolt 61, into the second end position C.This causes the cam plate 42 to rotate about the pivot shaft 7 in a clockwise direction by the fifth post member 57 being displaced in a clockwise direction by the second link 54 which is in turn displaced radially away from the pivot axis through the pivot shaft 7 by the third link 55 being displaced downwardly by the flap member 11. In this position the second link cam follower surface 54 is held clear of the cam surface 51 on the cam bush 49 and the first spring 56 pulls the projection 31 into the engaged locked position Y of the rotary lock means 4 at any angular position of the artificial leg and housing member 18 of the joint 1 between the straight and bent leg positions provided the flap member 11 is held in the second end position C by continuing pressure of the wearer thereon thus loading the foot portion of the artificial leg heavily against the ground.

As can be seen from Fig 5 the assembly of the links is such that the second link 54 first on the cam plate 42 on its first post member 57 and is retained thereon in any convenient manner such as by locking side clips or split pins. The third link 55 is connected to the second link 54 externally thereof with respect to the cam plate 42 by means of the pivotal connection 58 which likewise is provided with a locking side clip or split pin. The first link 53 likewise is held on its respective post members by locking side clips or split pins. The amount of travel permitted for the flap member 11 about its pivot shaft 13 towards and away from the stirrup member 8 is controlled by means of a stud 62 projecting downwardly from the cross member 16 through a hole in the stirrup member base 10 for engagement by a lock nut 62a on the undersurface of the stirrup member. This lock nut 62a can be rotated up or down the screw threaded end of the stud 62 to vary the degree of pivotal movement permitted to the flap member 11. A resilient washer may be located between the nut 62a and the stirrup member 8 to prevent rattle.

Advantageously the first link 53 is made sufficiently resilient to enable its cam follower surface 53b to jump the nose of the cam surface 52 when the projection 31 cannot be moved, for example when the lock means 4 is held in the engaged position Y by external forces. Such resilience may be obtained by moulding the link 53 from nylon or like plastics material or by the provision of a further biassing spring on the link 53. The resilience avoids damage to the joint in such circumstances.

Claims (18)

1. An artificial leg joint having a first part con nectible to an upper leg stump or thigh, a second part connectible to an artificial leg, which first and second parts are pivotally interconnected for movement of the second part between a straight leg position substantially in line with the first part and a bent leg position at least substantially at right angles to the first part, selectively actuable rotary lock means connected between the first and second parts, and means for actuating the lock means in response to differences in load exerted on the leg joint corresponding to different operative postural positions taken up by a wearer of an artificial leg fitted with the joint, so that with the leg joint operatively connecting an artificial leg to an upper leg stump or thigh, lifting the artificial leg up out of contact with the ground or like frees the joint lock means allowing the leg to be pivoted freely at the joint into the straight leg position for walking or kicking and back towards the bent leg position to a limited angular extent but then engages the joint lock means to prevent further pivotal movement of the leg at the joint towards the bent leg position, lightly loading the artificial leg against the ground or like surface frees the joint lock means allowing the leg to be pivoted freely at the joint in either direction between the straight and bent leg positions to permit the wearer sitting down, and heavily loading the artificial leg against the ground or like surface, such as when the wearer is walking or standing, engages the joint lock means at any position of the leg between the straight and bent leg positions to prevent pivotal movement of the leg at the joint towards the bent leg position while still allowing pivotal movement of the leg at the joint towards the straight leg position.

2. An artificial leg joint according to claim 1, wherein the first part includes a stirrup member having two spaced apart arms fixed at one end to and extending substantially perpendicularly from a base substantially parallel to one another, and a plate-like flap member substantially T-shaped in plan pivotally connected at or adjacent the free end of its stem to the free ends of the arms to overlie the stirrup member so that the stem of the flap member overlies or covers the opening between the arms and the cross pieces of the flap member overlies or covers the base of the stirrup member, the ends of the cross piece extending in the direction of the base beyond the positions at which the arms extend from the base, with the flap member being pivotally displaceable about its pivotal connection towards and away from the stirrup member between a first end position in which the cross piece is furthest still away from the stirrup member base, a second end position in which the cross piece is closest to the stirrup member base against the return action of the resilient biass means and an intermediate position between the first and second end positions, and with the flap member being securable to an upper leg stump or thigh or a wearer to extend substantially at right angles to the longitudinal axis thereof with the stirrup member depending from the flap member and with the pivotally connected free end of the stirrup member stem directed forwardly of the wearer.

3. An artificial leg joint according to claim 2, wherein the second part includes an elongated housing portion having a substantially planar base portion connectible at one end to an artificial leg to extend axially therefrom, which base portion has two spaced arms fixed at one end to and extending substantially perpendicularly from the base portion, substantially parallel to one another, which arms and base portion are dimensioned such that the arms fit slidably between the first part stirrup member arms and are pivotally connected thereto by a pivot shaft fixedly connectible to the stirrup member arms to extend therebetween substantially parallel to the flap member pivot axis and intermediate the stirrup member free arm ends and the ends of the stirrup member arms connected to the base portion, with the housing portion being freely pivotally mounted on the pivot shaft which extends through complementary apertures provided through the housing portion arms, so that the housing portion base portion in the straight leg position of the joint depends from the stirrup member on the side thereof opposite to the flap member and substantially perpendicularly to the flap member in the first end position, and with the housing portion base portion directed forwardly of the wearer.

4. An artificial leg joint according to claim 3, wherein the rotary lock means includes a cylindrically bored cylindrical housing member and, rotationally housed in said housing member bore a generally cylindrical cam member with a generally circular periphery and an annular generally cylindrical lock member. with the annular lock member pivotally interconnecting the housing member and cam member for rotary pivotal movement of the housing member and cam member relative to one another about a rotary pivot axis formed by the longitudinal axis of the cylindrical bore, wherein the annular lock member is housed in the housing member bore with the outer periphery of the lock member in rotary slidable contact with the inner periphery of the housing member bore so that the housing member is rotatable about the lock member, which lock member has at least three bearing members movably housed in apertures opening radially through the inner and outer peripheries of the lock member at peripherally spaced locations therearound, and the cam member has a generally circular periphery with, spaced around the cam member periphery, at least three substantially planar or dished cam faces, which cam member is housed in the lock member in peripheral slidable contact with the inner periphery of the lock member with the bearing members in contact with the respective cam faces, and means being provided, on or engageable with the lock member whereby the lock member can be rotatably displaced to a limited extent between two operative positions to rotate the annular lock member in either direction to a limited extent about the rotary pivot axis relative to the housing and cam members, so that with the lock member in one of the two operative positions, the housing member may rotate relative to the cam member about the lock member in either direction, and with the lock member in the other of the two opposite positions, the lock member is rotatively displaced relative to the cam and housing members causing the bearing members to be displaced by the lock member along and up their respective cam faces, towards and into wedged locking engagement between the inner periphery of the housing member cylindrical bore and the respective cam faces to stop rotary movement of the housing member relative to the cam member in the direction of said other operative position but not in the opposite direction towards said one operative position.

5. An artifical leg joint according to claim 4, wherein the housing member containing the cam member, annular lock member and bearing members is located between the second part housing portion arms with the pivot shaft extending through a corresponding bore extending through the cam member coaxially with said rotary pivot axis, and with the cam member being fixedly connected to said pivot shaft to prevent rotation relative thereto.

6. An artificial leg joint according to claim 5, wherein the housing member is located in a cylindrical band with the interposition between the band and housing member of a friction lining, there being a radial projection from the outer surface of the band locatable in a corresponding recess in the second part housing portion base portion, with the interposition of resilient cushioning means between the projection and recess, to connect the housing member via the friction lining and cylindrical band to the second part housing portion for pivotal movement with the second part housing portion about the pivot shaft fixed to the first part when the second part is pivotally displaced between the straight and bent led positions, and the degree of friction exerted by the friction lining between the housing member and cylindrical band being selected to provide for slip between the housing member and the cylindrical band if excessible pivotal force is applied to the first or second parts of the joint from the straight to the bent leg positions when the rotary lock means is engaged.

7. An artificial leg joint according to claim 6 wherein the degree of friction selected is adjustable by peripherally dividing the band at one point in the direction of the rotational axis thereof so that the peripheral length of the band can be altered by adjustment means to cause the band to grip more or less on the friction lining and hence the friction lining to grip more or less on the housing member.

8. An artificial leg joint according to claim 7, wherein the lock means includes a first cover plate fixedly attachable to the cam member so that the first cover plate and cam member are rotationally fixed relative to one another and so that the housing member cylindrical bore is closed at one end by the cover plate and at the other end by a second cover plate to retain the cam member and lock member in the cylindrical bore between the first and second cover plates which are centrally bored to fit over the pivot shaft, and with the first cover plate being pivotally connectible to the pivot shaft to prevent rotation relative thereto.

9. An artificial leg joint according to claim 8, wherein the means whereby the lock member can be rotatably displaced is a projection on one side of the lock member and extending in a direction parallel to the rotary pivot axis, engageable in and projecting through a corresponding slot provided in the cover plate, which projection and slot are dimensioned such that the projection can be displaced in the slot to a limited extent between the said two operative positions to rotate the lock member in either direction to a limited extent about the rotary pivot axis relative to the first cover plate and cam member.

10. An artificial leg joing according to claim 9, wherein each bearing member is resiliently biassed by at least one spring housed in a corresponding recess in the lock member of the trailing side of the bearing member with respect to the other operative position and communicating with the associated bearing member aperture.

11. An artificial leg joint according to claim 10, wherein the bearing members are ball or roller shaped.

12. An artificial leg joint according to claim 11, the first cover plate is attached to the cam member by at least two screws or rivets passing through the first cover plate and engaging in threaded bores in the cam member.

13. An artificial leg joint according to claim 12, wherein the means for actuating the lock means includes an axially bored cam plate arranged on the pivot shaft adjacent the first cover plate to which it is attached by four spaced apart post members projecting from the first cover plate through corresponding elongated apertures provided in the cam plate, which elongated apertures are dimensioned to allow the cam plate limited angular movement about the pivot shaft with respect to the first cover plate, there being a corresponding slot provided through the cam plate to receive the lock member projection.

14. An artificial leg joint according to claim 13, wherein the means for actuating the lock means includes an axially bored cam bush rotatably mounted on the pivot shaft adjacent the cam plate, which cam bush is fixedly attached to the adjacent second part housing portion arm to pivot with the latter about the pivot shaft, a cam surface being provided on the cam plate about the end of the bore therethrough adjoining the cam bush.

15. An artificial leg joint according to claim 14, wherein the means for actuating the lock member includes three elongated links located between the cam plate and said adjacent second part housing portion arm, of which the first link is pivotally mounted at one end of the first post member end projecting through the cam plate and has an elongated slot at its other end for receiving the end of the lock member projection projecting through and from the cam plate, the first link having a cam follower surface for engagement with the cam sur face provided on a cam plate and being resiliently connected to the second post member end projecting through the cam plate by a first spring connected between the first link other end and the second post member end.

16. An artificial leg joint according to Claim 15, wherein 1 the second link is pivotally mounted at one end on thethird post member end projecting through the cam plate and has an elongated slot intermediate its ends engageable on a fifth post member provided on and projecting from the cam plate towards the adjacent second part housing arm, the second link having a cam follower surface for engagement with the cam surface provided of the cam bush.

17. An artificial leg joint according to claim 16, wherein to the the third link is pivotally connected at one other end of the second link, and resiliently connected to the fourth post member end projecting through the cam plate by a second spring connected between the fourth post member end and a point on the third link intermediate its ends, with the other end of the third line having an elongated slot pivotally engageable with the cross piece of flap member, so that with the leg joint operatively connecting an artificial leg to an upper leg stump or thigh, lifting the artificial leg up out of contact with the ground or like surface pivots the flap member into its first end position, lightly loading the artificial leg against the ground or like surface, pivots the flap member into the intermediate position, and heavily loading the artificial leg against the ground or like surface pivots the flap member into the second end position against the return action of the resilient bias means located between the flap member and the first means stirrup member and operative to urge the flap member from the second end position towards the intermediate position.

18. An artificial leg joint substantially as hereinbefore described with reference to the accompanying drawings.