GB796975A - Improvements in or relating to impact-wrenches - Google Patents

Abstract

796,975. Screwing-up nuts &c. ARO EQUIPMENT CORPORATION. March 28, 1956 [Dec. 5, 1955], No. 9676/56. Class 83 (3). In a portable nut-runner which delivers hammer-blows, a driver 28 is splined to a shaft 50 driven by a pneumatic-motor 49, and has a lug 30 engaging between cam-surfaces 26 on a hammer 22. The latter is located on a central pin 36 by an elongated slot 34, and in the radially-outward position of Fig. 5, engages a lug 16 on an anvil 14 shaped at 20 to fit a socket-wrench. The parts rotate anti-clockwise as shown in Fig. 5, to run a nut &c. on a bolt, and when the resistance to rotation increases, the cam-surfaces 26, 31 force the hammer 22 radially inwards, against centrifugal-force, so that lug 22<SP>1</SP> rides over the lug 16 and allows anvil 14 and the wrench to remain stationary. After passing over the lug 16, the hammer 22 is free to move outwards by centrifugal-force (Fig. 7, dotted lines), so that it is in position to deliver a hammer-blow to lug 16 at the end of the revolution, after which it rides over lug 16 again. The relative angles of surfaces 26, 31, 24 and slot 34 are such that the hammer is decelerated when moving inwards and accelerated when moving outwards to increase the force of the blows. The hammer and the cam-surfaces &c. are symmetrical so that the wrench may deliver hammer-blows to loosen a nut &c., on reverse rotation, after which continuous rotation unscrews the nut.