"LOCKABLE PIVOTAL CONNECTION DEVICE"
This invention relates to a lockable pivotal connection device particularly, but not exclusively, suitable for use as a joint in an artificial limb such as an artificial leg and concerns an artificial limb having such a device.
There is a need for a relatively compact lockable pivotal connection device particularly for use with artificial limbs to replace limbs amputated close to the original joint.
According to the present invention there is provided a lockable pivotal connection device, including a cylindrically bored housing member, and rotationally housed in said housing member bore, a cam member with a generally circular periphery and an annular lock member, with the annular lock member pivotallyinterconnecting 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 adjacent 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, concave or convex cam faces, which cam member is housed in the lock member with the outer periphery of the cam member adjacent the inner periphery of the lock member and 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 at least two positions to rotate the annular lock member in either
direction to a limited extent about the rotary pivot axiu relative to the houning and cam members, so that with the lock member in one of said at least two 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 said at least two 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 position but not in the opposite direction towards said one position. Advantageously the outer periphery of the lock member is in rotary slidable contact with the inner periphery of the housing member bore and/or the outerperiphery of the cam member is in slidable contact with the inner periphery of the lock member.
Preferably the device includes a base member to which the cam member is fixedly attached, the annular lock member is in the form of a ring and the cam member is in the form of a disc or plate. Conveniently the device includes a cover plate fixedly attachable to the cam member plate and to the base member so that the cover plate, cam member plate and base member are rotationally fixed relative to one another and so that the housing member cylindrical bore is closed at least partially at one end by the base member and at the other end by the cover plate to retain the cam member plate and lock member ring in the cylindrical bore between the cover plate and base member.
Conveniently 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 a corresponding slot provided either in the cover plate or in the base member, which projection and slot are dimensioned such that the projection can be displaced
in the slot to a limited extent between the said at least two positions to rotate the lock member in either direction to a limited extent about the rotary pivot axis relative to the cover plate and cam member plate. Alternatively the means whereby the lock member ring can be rotatably displaced is a groove in, lever or cam on, at least one side of the lock ring member or a radial cutout in the housing member.
Advantageously the lock member is rotatably displaceable to a limited extent between three positions, namely a median position corresponding to said one position, a first end position, corresponding to said other position, on one side of the median position and a second end position on the other side of the median position, so that with the lock member in the second end position, the lock member is displaced relative to the cam and housing members in the opposite direction to that in the first end position causing the bearing members to be displaced by the lock member along and up their respective cam faces, in the opposite direction to that in the first end position, 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 the second end position but not in the opposite direction of the first end position. Preferably the bearing members are resiliently biassed in the direction of said other or first end positions and/or said second end position. Conveniently the bearing members are resiliently biassed towards the cam faces and away from the inner periphery of the housing member cylindrical bore.
Advantageously each bearing member is resiliently biassed by at least one spring housed in a corresponding recess in the lock member on the trailing side of the bearing member with respect to the other or first end position and communicating with the associated bearing member aperture. Conveniently two such springs are provided for each bearing member located one on each side of the bearing member with respect to the first and second end positions. Preferably the bearing members are ball or roller shaped.
Conveniently the cover plate is attached to the cam member plate and base member by at least two screws passing through the cover plate and cam member plate and engaging in threaded bores in the base plate.
Advantageously the housing member is cylindrical in shape with the bore opening uninterruptedly through one end of the housing member and opening via a reduced diameter aperture through the other end of the housing member. Suitably the ether end of the housing may be formed separate from the housing member but fixedly attachable thereto to rotate therewith. Conveniently the annular lock member has the shape of a ring carrying three or more bearing members in the foim of rollers.
Preferably the cam member is substantially cylindrical in form with a reduced diameter end portion one end of which, when the cam member and lock member are housed in the housing member bore, projects out of the housing member reduced diameter end aperture which provides a bearing for the reduced diameter end portion.
The cam member reduced diameter end portion may be rotatably secured in the housing member aperture by a circlip engaged around the reduced dismster end portion on the outer side of the housing member end wall with respect to the cam member. Additionally the device may include an axially bored cover plate fixedly attachable to the substantially cylindrical cam member at the endthereof remote from the reduced diameter end portion, to abut the housing member end through uihich the bore opens uninterruptedly, to close the latter.
Advantageously the rotary moυsrr.ent can be applied to the outer periphery of the housing member .
Conveniently rotary movement may be applied to the substantially cylindrical cam member via a shaft keyed to the cam member which is mountes on the shaft.
The invention also contemplates the provision of an artificial limb including at least one lockable pivotal connection device as aforesaid, as a joint.
Conveniently the limb includes mechanical, electrical, pneumatic or hydraulic means τor displacing the projection, and hence the lock member between the first, second and median positions.
Advantageously the artificial limb is in the form of a leg.
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 side view taken on the line A-A in Figure 3 of the lockable pivotal connection device according to a first embodiment of the invention,
Figure 2 in a view from above of the device of Figure 1
Figure 3 is a cross-sectional view of Figure 1 taken on the line B-3,
Figure A is an exploded perspective view of a slightly modified version of the device of Figures 1 to 3,
Figure 5 is an exploded side view of a lockable pivotal connecting device according to a further embodiment of the present invention,
Figure 6 is a plan view taken on the line F-F of Figure 5,
Figure 7 is a plan view taken on the line G-G of Figure
5, and
Figure 8 is an exploded perspective view of the device of Figures 5 to 7.
A lockable pivotal connection device according to a first embodiment of the invention as shown in Figures 1 to 3 and the modified version of Figure 4 of the accompanying drawings, includes a base member 1, a housing member
2, an annular lock member in the form of a ring 4 and a cam member in the form of a plate 7. The base member 1 and housing member
2 at least partially overlap and are pivotally interconnected at the overlapping region via the lock member ring 4 and cam member plate 7 which are housed in a cylindrical bore 3 in the housing member 2. The members 1 and 2 are rotatively pivotal relative to one another about a rotary pivot axis formed by the longitudinal axis of the cylindrical bore 3.
The annular lock member ring 4 is made of any convenient material such as bronze or brass and housed in the cylindrical bore 3 with the outer periphery 4a of the ring 4 adjacent to and preferably in rotary slidable contact with the inner periphery of the cylindrical bore 3 so that the housing member 2 is rotatable about the ring 4. This ring 4 has at least three bearing members 5, conveniently in the form of balls as illustrated, movably housed in apertures 6 opening radially through the inner and outer peripheries of the ring 4 at peripherally spaced locations therearound. Of course, if desired, more than three bearing members 5 may be provided.
The cam member plate 7 has a generally circular periphery with, spaced around the plate periphery, at least three substantially planar, concave or convex cam faces 8. As illustrated the faces 8 are planar. Of course the same number of cam faces 8 should be provided as are bearing members 5 for cooperation therewith.
The cam plate 7 is housed in the lock ring 4 with the outer periphery of the cam plate 7 adjacent to and preferably in peripheral slidable contact with the inner periphery 4b of the ring 4 and with the bearing members 5 in contact with the respective cam faces 8
as shown in Figure 1 of the drawings.
A cover plate 9 is fixedly attachable to the cam plate 7 and to the base member 1 in any convenient manner such as by two screws 10, so that the cover plate 9, cam plate 7 and base member 1 are rotationally fixed relative to one another and so that the housing member cylindrical bore 3 is closed at least partially at one end by the base member 1 and at the other end by the cover plate 9 to retain the cam plate 7 and lock ring 4 in the cylindrical bore 3 between the cover plate 9 and base member 1 as shown in Figures 1 to 3.
Means are provided for rotatably displacing the lock member ring 4. In this embodiment the means is a projection 11 provided on one side of the lock ring 4 to extend in a direction parallel to the rotary pivot axis of the device and engage in a corresponding slot 12 provided in the cover plate 9. Alternatively although not shown, the projection 11 may be replaced by a groove in, lever or cam on at least one side of the lock ring 4 or a radial cutout in the housing member 2. The projection 11 and slot 12 are dimensioned such that the projection can be displaced in the recess to a limited extent between a median position M, a first end position E1 on one side of the median position M and a second end position E2 on the other side of the median position M to rotate, fche ring 4 in either direction to a limited extent about the rotary pivot axis relative to the cover plate 9, cam plate 7 and bass member 1, as indicated diagrammatically in Figure 1.
Thus to operate the device of the present invention, particularly the device of the embodiment of Figures 1 to 4, the projection 11 can be displaced in the slot 12 In any convenient Manner such as by mechanical, electrical, pneumatic or hydraulic means,
not shown, so that with the projection 11 and ring 4 in the median position M the housing member 2 may rotate or be rotated relative to the base member 1 about the ring 4 in either direction D1 or D2 as shown in Figure 1. On displacing the projection 11, and thus the ring 4, into the first end position E1 the ring 4 is displaced relative to the cam plate 7 causing the bearing members 5 to be displaced by the ring 4 along and up their respective cam faces 8 towards and into wedged locking engagement between the inner periphery of the housing member cylindrical bore 3 and the respective cam faces 8 to stop rotary movement of the housing member 2 relative to the base member 1 in the direction D1 but not in the opposite direction D2. Similarly displacing the projection 11, and thereby the ring 4, into the second end position E2 displaces the ring 4 relative to the cam plate 7 in the opposite direction to that in the first end position E1 causing the bearing members 5 to be displaced by the ring 4 along and up their respective cam faces 8, in the opposite direction to that in the first end position E1, towards and into wedged locking engagement between the inner periphery of the housing member cylindrical bore 3 and the respective cam faces 8 to stop rotary movement of the housing member 2 relative to the base member 1 in the direction D2 but not in the opposite direction D1.
Thus in this way the device may be operated to allow the members 1 and 2 to rotate in either a clockwise or anti-clockwise direction or to prevent rotation between the members 1 and 2 in a clockwise or anti-clockwise direction as required. This is particularly desirable when the device is used as a joint in an artificial limb, such as an artificial leg, and it can be locked and unlocked simply by moving the projection 11 in any convenient manner by mechanical, electrical, pneumatic or hydraulic devicesuhich may be, in turn, activated by a sensor or sensors. As can readily be understood the energy required to actuate the device by moving the projection 11 is relatively small as indeed the locking force is not provided by the actuating force. The locking force, once the device is actuated, is provided by, in effect, a wedging action of the bearing members 5 in to
a tapering opening defined by the inner periphery of the cylindrical bore 3 in the housing member 2 and the associated cam face 8. In effect movement of the lock ring 4 towards the end positions E1 or E2 moves the bearing members 5 from the median position M in which they have sufficient clearance between the cam face 8 and inner periphery of the cylindrical bore 3 of the housing member 2 not to impede rotation of the housing member
2 about the ring 4, into a position where they are forced into the tapering opening or gap between the inner periphery of the bore 3 and the associated cam face 8 so as to jam or wedge by friction between the inner periphery of the bore 3 and the cam face 8 and thus lock the housing member 2 against rotation in the direction which tends to force the bearing members 5 further into the tapering opening or gap between the inner periphery of the bore 3 and the cam face 8. Of course movement of the housing member 2 in the opposite direction will not be impeded as this will tend to displace the bearing members 5 back out of the tapering opening or gap between the inner periphery of the bore 3 and the cam face 8 and thus out of wedging contact therewith.
Alternatively, although not illustrated, the projection 11 and slot 12 may be dimensioned such that the projection can be displaced in the slot to a limited extent between one position corresponding to the median position M and another position corresponding to, for example, the first end position E1. In this way a device may be produced wheh can be locked against rotary movement of the housing member 2 relative to the base member 1 in one direction only, such as in the direction D1 but not D2. Of course the device could be made so that the projection 11 is moveable between the one or median position M and another or second end position E2 to stop movement in the direction D2 but not D1. One way of providing this limited operation would be to put a stop, removable or fixed, on the device of Figures 1 to 4 in any convenient manner to prevent the projection 11 being moved other than between the median position M and one only of the end positions E1 or E2. Indeed the means for moving the projection 11 may be made operable so as to be capable of moving the
projection 11 between the median position M and only one of the end positions E1, E2.
In the embodiment of Figures 1 to 4 the bearing members 5 may be loosely housed in the apertures 6 in the ring 4 as shown in Figures 1 to 3 or may be resiliently biassed so as normally to urge the lock ring 4 towards the median position M of the projection 11 as shown in Figure 4. Additionally the bearing members 5 may be resiliently biassed towards the cam faces 8 and away from the inner periphery of the housing member cylindrical bore 3. As illustrated in Figure 4 the bearing members 5 are each provided with two biassing coil springs 13 housed in corresponding recesses 14 in the ring 4 and communicating with and one on either side of the associated bearing member aperture 6. If desired only one such spring 14 can be provided and one such recess 14 located on one side of the associated berring member 5 in the peripheral direction of the ring 4. Such one spring 14 is located on the trailing side of the bearing member 5 with respect to the other position of the projection 11 so as to urge the bearing member in the direction of the other position of the projection 11 towards the tapering opening or gap between the inner periphery of the bore 3 and cam face 8. This alternative is for use when the device is capable of restricting rotary movement in one direction only by having a lock ring 4 moveable only between said one and other positions. Alternatively the resilient bias may be provided by a pad or pads of elastic material instead of springs. In the embodiment of Figures 1 to 4 the cover plate 9 is attached to the cam plate 7 and base member 1 by at least two screws 10 passing
through the plates 7 and 9 and engaging in threaded bores 15 provided in the base plate 1. Moreover the slot 12 for the projection 11 is provided in this cover plate 9.
The embodiment of the invention illustrated in Figures 5 to 8 is basically similar to that of Figures 1 to 4 and like parts will not be redescribed in detail. However in the embodiment of Figures 5 to 8 the housing member 2 is cylindrical in shape with the bore 3 opening uninterruptedly through one end IB of the housing member 2 and opening via a reduced diameter aperture 17 through the other end 18 of the housing member 2. As illustrated in Figure 9 the end 18 may be formed separate from the remainder of the member 2 and fixedly attached thereto for rotation therewith such as by peripheral tabs 18a engaging in corresponding recesses 2b in the adjacent end face of the member 2. The lock member also is in the form of a ring 4 carrying at least three and preferably six bearing members in the form of rollers 5 with locating springs 13 housed in apertures 6.
The cam member 7 is substantially cylindrical in form having six cam faces 8, preferably planar, peripherally spaced therearound as illustrated In Figures 5 and 7. As shown in Figure 9 these faces 8 may be of reduced length relative to the rotational axis through the member 7 to provide an improved free running surface for the member 7 in the member 4. This cam member 7 is axially bored at 19 for mounting on a shaft, not shown, to which the cam member 7 may be connected via a key In keyway 20. A reduced diameter end portion 21 is provided on the cam member 7 so that one end of the portion 21 , when the cam member 7 and lock member 4 are housed in the bore 3, projects out of the housing member aperture 17 which provides a bearing for the portion 21. The portion 21 is secured in the the housing member aperture 17 by a clrclip 22 fitted in a corresponding groove 23 around
the portion 21 on the outer side of the wall 18 with respect to the cam member 7.
In the embodiment of Figures 5 to 8 the slot 12, in which the projection 11 is engaged, is provided through the cover plate 9 as shown in Figures 7 and 9. Also in this embodiment the cover plate 9 is axially bored to correspond to the diameter of the bore 19 and fixedly attached, in any convenient manner, to the cam member 7 at the end thereof remote from the portion 21 to abut the housing member end 16 to close the bore 3 with the cam member 7 and lock member 4 therein.
Rotary movement can be applied to the outer periphery of the housing member 2. To this end the member 2 may be force fitted or clamped into or on to a part connectible for example to an artificial limb component such as that attached to the stump of the amputated limb. Similarly rotary movement may be applied to the cam member 7 via the shaft keyed thereto at 20.
For artificial limb use, with the housing member 2 secured to the artificial limb component attachable to the stump of the amputated limb, the member 7 can be secured to the artificial limb itself via the shaft on which the member 7 is mounted.
In Figure 8 the lock ring 4 and cam member 7 have been shown slightly displaced angularly with respect of Figures 7 to 7, for convenience.
The small size of the device of the invention allows its thickness to be kept to a minimum and thus allows it to be fitted beside or below the stump of an amputated limb. This makes the device particularly useful as a joint where the space between the stump of the amputated limb and the joint of the artificial liπb is limited.