Patent GB-1386942-A (GB)
Title: Artificial limbs
IPC: A61F2/00
Filed: 1973-01-19
Abstract: 1386942 Artificial limb joint HUGH STEEPER (ROEHAMPTON) Ltd 19 Jan 1973 2840/73 Heading A5R Artificial Arm: An artificial arm comprises a pair of rigid tubular members 10, 12, Fig. 2, pivotally connected at adjacent ends to form an elbow joint, in which one of the members 10 is provided near the pivotal connection with a hollow spring biased movable locking member 16 having a nose portion 20 adapted to engage and hold fast a toothed portion 22 provided on and rigid with the member 12, the locking member 16 having an operating cord 28, an axially-immovable rotatable cylindrical pawl 30 within the hollow member 16 and having a ring of axially-projecting teeth 31, 33 at each end, the teeth 31, 33 being bevelled, a pair of inwardly projecting pins 35, 37 in the hollow member 16 arranged to strike the teeth 31, 33 when the pawl 30 is moved in opposite directions by the spring 18 and the chord 28 respectively, the pin 35 engaging grooves 41 of differing depth as the pawl 30 is rotated by the pins 35, 37, so that when the chord 28 is pulled once the pawl 30 releases the locking member 16 so that it engages the toothed portion 22 and, on being pulled a second time, frees the locking member 16 from the toothed portion 22 so that the two limb members 10, 12 can pivot relative to each other. The limb members 10, 12 are made of light aluminium alloy. An artificial hand 36 is removably carried by the end of the member 12 and operated by a cord 38 attached to a movable part of the hand. The limb members 10, 12 and the pivotal connection are covered by a removable sleeve (40), Fig. 1, (not shown) of foamed synthetic plastics material, which sleeve (40) resembles an arm and is covered by a flesh coloured stocking. A pair of freely rotatable wheels 42, made of a low friction material such as nylon, facilitates pivotal movement of the arms 10, 12 when they are covered by the sleeve (40). A post 44 projects outwardly from the member 12 and carries the cord 38 so that it may be pulled without tearing the sleeve (40). The upper end of the member 10 is attached to a shoulder piece (46). In order to prevent the toothed portion 22 from biting into the sleeve (40), a flexible shield 48 of synthetic plastics material extends between the adjacent ends of the members 10, 12. The shield 48 has a slot (50), Fig. 3, (not shown) in its lower end, for the passage of the member 12. A pivot pin 14 passes through holes in a forked end (34) of the member 10 so that the toothed portion 22 forms part of the pivotal connection and the nose portion 20 is allowed to move through an axial opening in the lower part of the member 10 to engage the toothed portion 22. A stop member 32 is fitted on the toothed portion 22 and abuts an opposing surface on the member 10 to prevent backward swinging of the member 12. The artificial joint can, alternatively, be used as a knee joint by forming the members 10, 12 of appropriate length and attaching an artificial foot 52 to the member 12. Operation: when the cord 28 pulls the locking member 16 upwards, the pin 37 strikes the bevelled surface of one of the lower teeth 33, thereby rotating the pawl 30 until the pin slips into one of the grooves 43 between the teeth 33. When the cord 28 is released, the spring 18 urges the locking member 16 downwardly so that the pin 35 strikes the bevelled surface of one of the upper teeth 31 which are circumferentially displaced relatively to the teeth 33. The pawl 30 rotates until the pin 35 slips into one of the grooves 41. Thus, each time the cord 28 is pulled and released, the. pawl 30 rotates and the pin 35 is transferred to an adjacent groove 41. Since adjacent grooves 41 have different depths, the first pull on the cord 28 causes the nose portion 20 to say, engage a notch 26, while the second pull causes the nose portion to be supported clear of the notches 26 so that the members 10, 12 can pivot relative to each other.