Patent GB-750371-A (GB)
Title: Improvements in artificial limbs
IPC: A61F2/58
Filed: 1953-12-15
Abstract: 750,371. Artificial arms. BLATCHFORD & SONS, Ltd., C. A., and BLATCHFORD, B. G. Dec. 14, 1954 [Dec. 15, 1953], No. 34880/53. Class 81(2). An artificial elbow joint having a forearm which moves in unison with a quadrant fixed on the elbow shaft and mounted in an upper arm bucket, the quadrant having a number of slots which may be engaged by a locking latch, in which a selector is operated by a pull cord such that of successive pulls on the cord, one pull causes the selector to engage and move release means for disengaging the latch from the quadrant, the latch being held disengaged by a catch member, and the selector disengaging from the release means on release of the pull cord ready for the next pull, which pull causes the selector to move the catch member so that the latch engages the quadrant. The slotted quadrant 6 and forearm side steels 5 are fixed to the elbow shaft 4 mounted in the upper arm bucket 1. Mechanism for moving and locking the latch 7 is mounted on a frame 3 attached in the upper arm bucket 1. The latch 7 is at the free end of a latch arm 7a which is rockable on a fixed shaft 7b with a first rocker arm 9. A tension spring 12 connects the first rocker arm 9 with a second rocker arm 13 which is pivoted on a fixed bolt 13b on which a catch arm 11 is also pivotally mounted. The tension spring 12 tends to draw the first and second rocker arms 9, 13 closer together. To disengage the latch 7 from a slot 6a in the quadrant 6, a pull is exerted on an operating cord 14d which is attached to a link 14 which is secured to the second rocker arm 13 and projects outside the upper arm bucket 1. Such a pull moves the second rocker arm 13 and a selector dog 15 upwardly about the bolt 13b. The selector dog 15 is mounted on a pivot 15a on the second rocker arm 13 and normally moves with the rocker arm 13 from which it can be displaced against a spring. As the selector dog 15 moves about the bolt 13b, a jaw 16 formed in it engages a release pin 10 on the first rocker arm 9. The release pin is forced along an edge 11a of the catch member 11 until it enters a detent 11b in the catch member 11. At the same time the rocker arm 9 is pivoted about the shaft 7b and the latch 7 and latch arm 7a move away from the quadrant 6. On release of the operating cord 14 the second rocker arm 13 and selector dog 15 move to their starting position. The forearm is then free to be adjusted to a new position while the latch 7 is held disengaged by the engagement of the release pin 10 in the detent 11b. To cause the latch 7 to again engage a slot 6a, the operating cord 14d is again pulled. The jaw 16 moves upwardly about the bolt 13b and engages a pin 11c on the catch member 11. Continued movement of the selector dog 15 pivots the catch member 11 on the bolt 13b against a spring 11d until the release pin 10 is clear of the detent 11b. The first rocker arm 9 can then pivot under the action of the tension spring 12 so that the latch 7 re-engages a slot 6a. The latch 7 moves in a slot 8a in a stainless steel plate 8. To reduce noise in operation of the mechanism, the selector dog 15 and catch arm 11 are made of fibrous sheet material and buffers 13c, 17 are provided on the frame 3 and selector dog 15 respectively and at the top of latch slot 8a. The latch 7 and the slotted part of the quadrant 6 are made of steel.