GB596206A - Improvements in artificial arms - Google Patents

Abstract

596,206. Artificial arms. OTTERMAN, J. Sept. 28, 1945, No. 25208. [Class 81 (ii)] An artificial arm comprises an operating member actuable by a flexion cord and a selector mechanism for coupling the operating member separately and independently either to an elbow joint for flexing the arm or to a driving member for a hand or other appliance. As shown the forearm structure 20 and the appliance drive shaft 15 are carried by a cylinder 23 rotating in trunnion bearings 24 formed on a flanged cup 26 which swivels inside the arm bucket 11. A pulley member 44, 45 rotatably mounted centrally on the cylinder may be turned by a cord 14 and restored to home position by a spring 49. A spring- pressed pawl 70 mounted on the pulley normally engages a slot in the cylinder 23 so that the forearm is flexed on pulling the cord 14. Downward movement of a lever 16 actuates a sliding cam 68, Fig. 3, which disengages the pawl 70 from the cylinder, and locks the cylinder against rotation by engaging a bolt mounted on a trunnion, Fig. 4, in one of many holes formed in the cylinder. A spider 75 inside the cylinder carries two ratchet wheels 81, 82 each provided with a bevel wheel 79, 80 meshing with a bevel wheel 74<1> on the drive shaft. Mounted on either side of the pulley member are spring-pressed pawls 83, 84 which can cooperate with the ratchet wheels, and two rocker members 90 linked by a bridge 91 and a pin 92 which fits under the tail 93 of the pawl 70. A fixed cam 100 depresses the rocker and holds both pawls 83, 84 disengaged near the home position of the pulley. Again, when pawl 70 engages the cylinder the fingers 94 on the rocker disengage both pawls 83, 84 so that the shaft cannot be rotated. When pawl 70 is disengaged the rocker lifts clear. Tappets 85, 86 mounted at right angles on the pulley member then maintain one or other of the pawls disengaged so that rotation of the pulley rotates the shaft in one or other direction. A spring-pressed trip pawl 97 and star wheel 87 rotate the tappets and reverse the pawls in engagement at the start of each rotation of the pulley. The trip pawl may be lifted clear by twisting the knob 101. The swivelling cup 26 may be retained in selected positions by a spring-pressed ball and socket device 36 or by a lever and notch device, Fig. 9. The appliance fitted at. the wrist may be rotated by a sleeve tube surrounding the drive shaft 15 and fitted with a mutilated gear co-operating with pegs mounted on one or both of the trunnion bearings as the forearm is flexed, Fig. 10. The Provisional Specification describes a modification in which rotation of the elbow joint is achieved by simultaneously engaging both the ratchet pawls and thus preventing rotation of the shaft. Specifications 133,344, [Class 81 (ii)], 596,209 and 596,212 are referred to.