Patent GB-840617-A (GB)
Title: Improvements relating to resilient joints for artificial limbs
IPC: A61F2/60
Filed: 1958-10-15
Abstract: 840,617. Artificial limbs. LEICESTER, T. E. Oct. 15, 1958. [Oct. 24, 1957], No. 32921/58. Class 81 (2). A self-locking joint, in particular a knee or ankle joint, for artificial limbs comprises a ball housing attached to one limb section which articulates with a ring attached to the other limb section, a resilient ball held within the ring by the housing and a curved device between the ball and ring adapted to lock them to each other whenever the wearer puts weight on the limb. As shown in Figs. 1, 6, 9, applied to a knee joint, the housing is formed of two symmetrical portions 11, 12 bolted together at 13 and having an attachment plate 14 mounted on an artificial thigh 15, each portion having a side opening 16 which receives an internally-ridged check plate 17, guide fins 20 on the plates 17 engaging in grooves (not shown) in the housing to allow axial but not rotary movement. The plates 17 are moved inwardly to grip the ball 23 by adjusting screws 22 passing through cover plates 21 secured to the housing. Ring portions 28, 29 of channel section are mounted, for rotational movement only, with a washer 25A optionally interposed, in an annular groove 25, 26 in the housing 11, 12. A block 31 connecting the ring portion 29 to an attachment plate 32 on the shin protrudes through a cut-away portion 27, Figs. 1 and 6, of the annular groove 25, 26 and may have tough rubber buffers 34 bonded to it to ease the jar should the wearer overflex the joint. The lower ring portion 29 has within its channel an integral circuate web 35, Fig. 9, terminating at each end in a curved cantilever 39 to which is pivoted a bell-crank 40. Flanking the web 35 are two pairs of arcuate claw levers 37 pivoted to the ring portion 29 at 38 and carrying metal treads 45 which, when the levers are in their outermost position, lie below the web 35. In use, the plates 17 are adjusted so that the ball 23 is laterally compressed and presses slightly on the web 35 at the bottom and on the channel edges 36, Fig. 6, at the top, leaving a slight clearance between the ring portions 28 and 29 which are rotatable in the groove 25, 26. When weight is put on the leg, the base is compressed, moving the ring portion 29 towards the ring portion 28 so that one arm 41 of the bell-crank 40 engages in a notch 42, Fig. 1, in the upper portion and rotates the crank until the other arm 43 engages under a bridge 44, Fig. 9, connecting each pair of claw levers 37 and forces the levers into gripping engagement with the ball 23. This locking occurs when weight is applied irrespective of the angle between the upper and lower limb sections. The bell-cranks may be replaced by rollers secured to the levers and bearing directly on the upper ring portion and the housing-ring may be attached to the shin and thigh respectively. In another embodiment, Fig. 12, halves 45A of the housing are bolted to the thigh 46 and receive a check plates 48 similar to the plates 17 and adjusted similarly by cover-plates 49 to grip a resilient ball 50. Flanges 51 on the housing members 45A form an annular seating for a ring 54, washers 52 being held in place by the ball 50. The ring 54 comprises two parallel annular plates 57 joined by a web 58 and an attachment block 55 with a toothed member 57 mounted on its upper surface. Between the ring 54 and the ball 50 is a claw ring 59 and inwardly projecting teeth 60 firmly gripping the ball 50. In use, the housing and the ring 54 are capable of relative pivotal movement until weight is put on the limb when the ball 50 is slightly compressed and teeth 61 in the outside of the ring 59 lock in the toothed member 56.