Patent GB-661131-A (GB)
Title: Improvements in or relating to prosthetic devices
IPC: A61F2/68
Filed: 1949-06-27
Abstract: 661,131. Artificial legs, HENSCHKE, U. K., and MAUCH, H. A. June 27, 1949 [July 9, 1948], No. 16978/49. Class 81 (ii). An automatically and voluntarily controlled artificial leg comprises knee locking means allowing the leg to either yield freely or gradually under the weight of the wearer's body a control element positioned by forces such as gravity, &c. and forces produced by the leg movements being incorporated in said means for controlling a shiftable element which locks the knee before the beginning of the stance phase and unlocks it before the beginning of the swing phase of each stride. As shown, Fig. 1, the thigh 10 of an artificial leg is journalled by a pin 12 to a shank 11, a U-shaped bracket 13 supporting a cross pin 15 on which is journalled the lower end of an hydraulic cylinder 16. Two straps 17 are secured on opposite ends of the pins, 12, 15, whilst journalled on a cross pin 20 parallel with the pin 12 is a piston shaft 21 slidable through the cylinder 16 and formed at its lower end with a piston, 40, Fig. 3. A piston 25 surrounding the shaft 21 is biased downwardly by a spring 26 against a fixed snap ring 27 thereby compressing the oil within the lower part of the cylinder. Within the shaft 21 is a rod 28 formed at its lower end with a piston 47 having a blind bore 49. Ports 46 are provided within the piston bore 43 corresponding to holes 50 in the bore 49. Also a port 51 in the bore 49 connects with the underside of the piston 40 by the groove 44 and opening 45 the passage 45, 44, 51, 50, 46 providing a leakage path for the fluid when the check valve 54 is closed this leakage path allowing the knee to yield gradually when the knee lock is in operation. The alignment of port 51 and groove 44 is adjusted by longitudinal movement of the rod 28 controlled by the conical screw 33 whilst rotative movement of the rod 28 by strings attached to the lever 36 causes the ports 50 to be put in or out of registry with the openings 46. The control element for the locking means is a pendulous element 58 suspended at the point 57 within the bore 49 by a universal knuckle joint whilst the shiftable element is a check valve 54 loosely supported by screws 53 attached to the bottom flange 52 of the piston 47. In operation bending movement of the knee causes downward movement of the piston 40 with corresponding upward fluid flow whilst during straightening of the leg the piston moves upwards the fluid flow being downwards. Upon the amputee carrying his good leg forward prior to taking a step with the artificial leg the check valve 54 is down and the element 58 well over the surface 56 since the shank is rearwardly inclined and the element is weighted at 59 to ensure a naturally rearwardly inclined position. Although the knee is bending the knee lock yields freely since the valve 54 is jammed open by the element 58. As the stump of the leg is decelerated in its forward motion preparatory to taking the step the shank is swung forward causing the fluid in the cylinder 16 to flow downwards via ports 46, 50, thereby opening the valve 54 and causing the element 58 to rotate as the cylindrical inside shape of the bore 49 causes the fluid to rotate about the cylinder axis forming an eddy. The centrifugal forces on 58 press it against the wall of the bore 49 so that if during its forward movement the shank is interrupted for instance by stumbling the valve 54 is free to close thereby locking the knee. When in continuation of the normal step the foot is set upon the floor prior to transferring body weight to it the knee may be biased in a bending direction but downward movement of the piston 40 and subsequent closure of the valve 54 locks the knee the element 58 still rotating due to its inertia. In a modification the control element is a circular disc actuated by hydraulic and magnetic forces.