GB1007431A - Improvements in and relating to artificial limbs - Google Patents

Abstract

1,007,431. Artificial legs. J. L. COOK. Jan. 15, 1962 [Oct. 13, 1960], No. 35166/60. Heading A5R. An artificial leg has upper and lower leg portions pivotally interconnected at the knee joint and means associated with the knee joint to straighten the leg after a predetermined bent position has been reached, the means being rendered inoperative by pivotal movement of the foot relative to the lower leg portion. The knee joint comprises a pivot 12, the pins 37 of which are splined to the shin portion 11 and to a set of parallel interconnected arms 30 for pivotal movement therewith. A second set of arms 31 is pivotal on the pivot 12 and normally moves with the set of arms 30, the two arms 31 having spring-urged detents 49 which engage ratchets 50 on the two outer arms 30. A third set of arms 28 is pivotal about the pivot 12, the arms being interconnected by a transverse rod 40, which is interconnected by a spring 41 with a transverse rod 36 interconnecting the arms 30. Chains 27 extend from the arms 28 over wheels 51, carried by the arms 31, to a pair of crank levers 22, 23 pivoted to the leg at 26 and connected by a rod 21 to the heel behind a needle or ball bearing 14 interconnecting the shin and foot portions. As the wearer steps forward with the other leg, the foot portion 13 pivots about the bearing 14 relative to the shin to cause the rod 21 to move so that the chains 27 are loosened. As weight is transferred to the other leg and the foot portion 13 leaves the ground, the knee joint is free to bend so that the arms 28 and 31 move towards a cross bar 53 in the thigh portion 10. The arms 31 carry levers 48 which, as bending of the knee continues and the leg is swung forwardly, abut the cross bar 53 and are turned to push arms 28 forwardly away from arms 31 sufficiently for the spring 41 to be moved over its dead centre position. The spring then pulls the arms 28 and 30 towards one another so that firstly the arms 28 abut a second cross bar 54 in the thigh portion and thereafter the leg is straightened as the foot approaches the ground forwardly of the wearer. As the foot is placed on the ground, it pivots to its original position so that the rod 21 causes tightening of the chains 27 which pulls the arms 28 and 31 back to their original position. When the wearer desires to sit, the chains are loosened by raising the foot, the knee joint is bent to operate the parts as for walking but, as the foot carries the weight of the wearer, the spring 41 does not bring about straightening of the leg. As bending of the knee continues, the cross bar 54 in the thigh portion pushes the arms 28 and 31 rearwardly until the detents 49 ride rearwardly over the ratchet 50 and the spring 41 is moved rearwardly over its dead centre position so that it acts to hold the leg in a sitting position. In rising, a stop 56 in the thigh returns the parts to their original positions.