GB607001A - Improvements in artificial limbs - Google Patents

Abstract

607,001. Artificial limb drive mechanism. MOLLER, A. A., and HOBBS, E. W. Jan. 23, 1946, No. 2228. [Class 81(ii)] An artificial limb comprises an electric motor to eftect relative movement between parts of the limb, a motor starting switch and an automatic device to stop the motor when relative movement is obstructed. As shown the forearm unit 11 is carried by a cylinder 16 mounted in trunnion bearings 17 formed on a swivelling cup at the base of a bucket 10 for the stump. The cylinder houses a motor 18, which drives the pinion 33 through a worm reduction gearing 26, 27, 29, 30 and a " torque switch" 34, and a reversing motor starter 60. A sleeve 45 mounted on a trunnion to slide about a stop on rotation by the lever 14 carries a cam 50, a toothed part-circular rack 44, and a member 57. In one position, Fig. 6 (not shown), the member 57 thrusts aside the clutch 55, and the cam retracts the bolt 42, Fig. 5, which locks the cylinder in the trunnion, so that rolling of the pinion 33 on the rack 44 flexes the arm. Movement of the sleeve displaces the cam 50 allowing the spring pressed bolt 42 to lock, retracts the member 57 and allows pinion 33 to mesh with spring pressed clutch member 55 to drive the shaft 54, by means of dogs 58, 99. The shaft 54 drives, e.g. a hand or other appliance. When flexion or rotation is obstructed the spring blade 35 of switch 34 twists so that contact 36 touches one of contacts 38 to energize the electromagnet 65, and attract the armature 66, an insulating stud 80 on which opens the contacts 68, 168 and stops the motor. The reversing starter 60 carries two slip rings 72, 73 having single axial contacts 75, 76 disposed at opposite ends of a diameter and connected to the supply leads. Each pull on the cord 15 and pawl 64 rotates the star-wheel 62 and the switch through 90 degrees which gives a start, stop, reverse, stop cycle by successive contacts with contacts 77, 78 which connect with the motor brushes 23. Studs 81 on one end of the switch co-operate with a projection 82 to release the contact breaking armature 66 on operation of the switch. A main switch 79 and dry battery are provided in the bucket 10. A rod 83 pivoted to a trunnion at 84 carries a compressed spring 86 which bears against a bracket 85 on the forearm structure to balance its weight. In a wrist attachment modification, Figs. 8 and 9 (not shown), the sliding sleeve selector mechanism does not appear. The Provisional Specification describes the use of an overload relay for stopping the motor, a modified reversing switch having a contact slide, and flexion of the arm by a cord. Specifications 596,206, 596,209 and 596,212 are referred to.