GB113207A - Improvements in the Wrist and Elbow Joints of Artificial Arms. - Google Patents

Abstract

113,207. Wilson, W. J., and Markham, F. A. Feb. 26, 1917. Limbs, artificial.-The forearm is raised relatively to the upper arm by means of a cord controlled by the wearer's body movements; this action also causes the elbow joint, and with it the complete forearm, to swicel about the lower end of the upper arm. Simultaneously, the wrist swivels relatively to the lower end of the forearm, and the hand as a whole turns about a hinge joint in the wrist. The operating-cord h, Fig. 2, passes over pulleys j mounted in the upper arm f above and below the swivel joint g, f<1>, the pulleys being normally at an angle on opposite sides of the joint, as indicated in the sectional view, Fig. 4, and the end of the cord is anchored at the ring i to the forearm. Thus when the cord is tensioned, the forearm is raised about the elbow pivot e, and the whole of the parts rotate about the swivel joint g. The initial stress upon the cords rocks a detent lever v, to which the anchoring ring i is attached, so as to withdraw a spring detent v<3> from one of a series of holes w in the elbow joint, the detent re-engaging as the tension ceases. The swivel joint may be locked by a manually operated bolt x in the elbow part of the upper arm, adapted to enter one of a number of holes in the upper arm above the swivel joint. The above-mentioned movements produce a tension in a cord k, anchored in the upper arm at k<1>, and passing over pulleys l, k<3> and down the outer side of the forearm, to a swivel joint b<1>, c<1>, Fig. 8, immediately above the wrist, the cord producing a rotation by means of pulleys m, m<1> as in the case of the upper-arm swivel joint. Finally, the cord passes over a pulley k<4>, mounted upon the hinge-pin a<1> of the wristjoint proper, causing the hand a to turn as a whole inwards simultaneously with the swivelling, and is ultimately secured to and operates a lever mechanism n for moving the fingers of the hand, in opposition to a spring t, which is described in Specification 112,539. The swivel plates f, f<1> and b<1>, c<1> have slots n, Fig. 4, to permit passage of the operating-cords, are provided with ball bearings, and are restored to normal position by springs p coiled around segmental rods q carried by one plate over similarly shaped recesses admitting the projection of apertured lugs s upon the opposite plate so as to work over the segmental rods. The springs bear at one end against the lugs and at the other against the securing-plates r of the rods. The wrist swivel-joint may have a loch similar to that provided for the elbow swivel.