Patent GB-720152-A (GB)
Title: Improvements in and relating to artificial legs
IPC: A61F2/60
Filed: 1952-06-18
Abstract: 720,152. Artificial limbs. REGNELL, C. E. June 18, 1952 [July 2, 1951], No. 15379/52. Class 81 (2). An artificial leg comprises a thigh portion to which a lower limb portion is pivoted by a knee joint and a foot portion which is linked to the lower limb portion in the interior of which a hydraulic knee joint locking device is provided which is actuated by a thrust acting on the foot portion to lock the knee joint at the instant thrust is applied irrespective of the angular position of the lower limb portion with respect to the thigh portion and by release of the thrust to allow pivotal movement between the thigh portion and the lower limb portion, the foot portion being axially slidable relative to the lower limb portion and transmitting said thrust to the locking device irrespective of whether it is applied under the toe or heel part of the foot portion. The knee joint locking device H contained within the lower limb portion 3 comprises two cylinders 5a, 5b between which is a valve housing 8. The cylinders 5a, 5b contain a liquid such as oil. Pistons 6a, 6b, which reciprocate within the cylinders 5a, 5b respectively, are mounted on a common rod 9 which projects through a cover 10 to the top cylinder 5a and is connected with the knee-joint shaft 2 by a link 11 fixed to the shaft 2 and pivoted to the rod 9. The lower cylinder 5b is connected by a stem 12 with a bolt 13 (Fig. 9) fixed across the lower end of the lower limb 3. The bolt 13 forms part of an attachment 14 constituting the end of the lower limb 3. An intermediate member 16 between the lower limb 3 and the foot 4 carries a socket 16a which projects through an opening in the attachment 14 and is provided with oval holes 16c for the passage of the bolt 13. The intermediate member 16 pivots on a bolt 15 relative to the foot 4 against a spring 4a and is provided with a stop 4b and pads 4c. A stud 18 (Fig. 11) rigidly secured to the intermediate member 16 is pivotally connected with a movement transfer rod 20, the uppermost end of which is linked with a lever connected with an actuating member 22 (Fig. 12) for a primary control valve 25 in the valve housing 8. A Bowden cable 1b or other suitable means similarly connects a manually operable member 1a with a secondary valve (not shown) contained in the housing 8. Any thrust applied to the foot portion 4 e.g. when transferring the weight of the body to the artificial limb, moves the intermediate member 16 nearer to the attachment 14 by approximately .02 inch and is transferred by the rod 20 to rotate the primary valve actuating member 22 which releases the stem of the valve 25 so that it is closed by the action of a spring 25d. Liquid is then prevented from flowing between the cylinders 5a, 5b of the locking device H so that the knee-joint is locked. On removing the thrust applied to the foot 4 the valve actuating member 22 is rotated in the opposite direction so that it engages a notch 25f on the'stem of the valve 25 thus opening the valve so that liquid can flow between the cylinders 5a, 5b and the knee-joint is free to bend. The wearer of the artificial leg can free the knee-joint when locked, when a thrust is still being applied to the foot 4, by actuating the member 1a which causes the rotation of a secondary valve actuating member (not shown) which is rotated to move the secondary valve stem by engaging a notch therein in a similar manner to the operation of the primary valve. A passage between the cylinders 5a, 5b through which liquid flows when the secondary valve is opened contains an adjustable needle valve which allows only a gradual bending of the knee-joint. The spaces above the piston 6a in the upper cylinder 5a and below the piston 6b in the lower cylinder 5b are also filled with liquid, the two spaces being interconnected through the piston rod 9 which is hollow and is provided with an opening 9b into the upper cylinder 5a and has an open end in the lower cylinder 5b. Packing 7 around each piston 6a, 6b is so arranged that during use liquid tends to flow into the spaces between the pistons 8a, 6b and the valve housing 8. Liquid may be added to the cylinders 5a, 5b through a stoppered opening 9c in the piston rod 9.