Patent GB-633546-A (GB)
Title: Improvements in or relating to mechanical artificial hands
IPC: A61F2/54
Filed: 1946-12-13
Abstract: 633,546. Artificial hands. SIMPSON, J. H., and HANGER & CO., Ltd., J. E. Dec. 13, 1946, No. 3193. [Class 81(ii)] Operating means for an artificial hand of the kind hereinafter described are provided whereby when the fingers are stopped from moving forward by the object to be gripped, but at the same time, a pawl is not fully and firmly engaged by a tooth of a rack, further relative movement of the rack with respect to the fingeroperating mechanism against an increasing force is provided, thereby to allow the pawl to engage the next tooth of the rack and to increase the grip exerted by the fingers. The said operating means is preferably contained within the hand which (Fig. 4) comprises a slide 214 carrying a pivoted yoke 225, in turn carrying pivoted members 223 connected by rods 221 attached to the fingers at 222. The lower joints of the fingers are attached to the upper by rods 233, the rod pivots being mounted eccentrically of the joint pivots so so that as the lower parts of the fingers are bent relatively to the palm, the upper parts are also bent relatively to the lower. The arrangement of yokes 223, 225 is such that when one or more fingers engage a part of the object to be gripped, the other fingers continue to close until they engage another part of the object or are fully closed. The slide 214 is movable against a spring 227 by a chain, &c., 230 passing round a drum 229 actuated by a lever 232 to the end of which is attached the operating cord 238. A rack 215 formed on one side of the slide is engaged by spring-urged pawl 216 releaseable by a lever 219 actuated by cord 239. The yoke 225 (Fig. 8) is carried by an arbor 226 on the slide, a rubber, &c., block 244 being provided to enable a rack tooth to be firmly and fully engaged by the pawl. Operating means for the hand (Fig. 1) comprises shoulder harness, the release thong 50 being connected by hook 48b to cord 239, and the finger closing cable 47 by hook 48a to cord 238; the cable 47 is actuated by an upward movement of the right shoulder transmitting a pull through cable 46 and mechanism contained in casing 43 held to the body by belt 42 and prevented from rising by link 44. The casing (Fig. 2) houses a sprocket wheel 52 fast on shaft 53 on which a quadrant casing 54 is freely pivoted, the quadrant being normally urged to its lowest position by spring 58. Cable 46 is continued as a chain 56 which runs in a channel in the quadrant, over sprocket 52, and is continued as cable 47. A lifting of the shoulder therefore pulls the latter cable. If now the belt 42 is tensed by the wearer's abdomen muscles, the pawl 73 to which it is connected is caused to engage the ratchet teeth of sprocket wheel 52, so that the shoulder can be lowered without the finger grip loosening, the quadrant dropping. Another shoulder lift is then possible, the sprocket being further rotated under the action of pawl 61. To unloosen the grip, pawl 73 is disengaged, and the quadrant drops, the toe 66 of lever 62 striking the bottom of the casing causing pawl 61 to disengage. A simpler form of harness is shown whereby shoulder movement is directly transmitted to hook 48b by Bowden cable. The hand attachment sheath may include a universal or rotable joint, and magnets may be provided in the finger tips. The thumb may be provided with flexing mechanism similar to that of the fingers. Sprocket wheel 51 may be replaced by two or more gears interconnected through a clutch mechanism whereby two or more ratios between the thumb and shoulder movement are provided. Parts of the body other than the shoulder may be used to provide for the finger movement. Cineplastic means to operate the hand, and preferably the release mechanism thereof may be used.