GB1344837A - Gas powered drive unit - Google Patents

Abstract

1344837 Pneumatic actuators UNITED STATES SURGICAL CORP 20 April 1971 [28 April 1970] 10239/71 Heading F1D [Also in Division A5] A pneumatic actuator 10 for operating a surgical skin stapling instrument comprises a piston 16 with an integral output shaft for actuating the stapler, the piston 16 being reciprocable in a casing member 20, and a spool 28 for controlling reciprocation of piston 16, the spool 28 being movable over a short distance in a plug 22 and having a seal 46 which normally closes gas inlet 46 under the bias of spring 30 urging the piston and spool rightwards, Fig.1. Spool 28 and piston 16 have O-rings 58, 62, 72 housed in annular seats 60, 64, 74, the depth of the seats being greater than the O-ring diameters. Communicating with seats 60, 64, 74 are bores 56, 66, 76 which, during piston reciprocation, transmit gas pressure to the inner side of O-rings 58, 62, 72 to urge them into tight sealing contact with plug 22 and casing member 20. In operation, a triggering means Fig.3 (not shown) moves shaft 14 in the direction 116 thus permitting gas pressure in inlet 42 to act on seal 46 to urge the spool 28 leftwards. Gas thus passes through bore 56, communicating with seat 60, and then through a restriction and threaded bore 48 to the right side of piston 16 which is thus moved to the left. Gas is fed to bores 66, 76 which communicate with seats 64, 74. The end of the movement to the left of piston 16 is damped by progressive throttling through co-operating chambers 82, 84 on the piston 16 and member 20. The return stroke is effected by spring 30 which causes piston 16 to thrust gas through a by-pass 68 in spool 28 to an annular chamber 70 communicating with an exhaust port 90.