GB1187585A - New or improved Tool for Driving Fasteners and the like with Impact and/or Rotary Motion - Google Patents

Abstract

1,187,585. Impact screwdrivers. G.K.N. SCREWS & FASTENERS Ltd. 5 July, 1967 [17 Aug., 1966], No. 36765/66. Heading B3N. [Also in Division B4] A screw driver comprises a shaft 20 rotatable by a motor 12 through an overload clutch, and a hammer 25 for producing hammer blows to the shaft, driven by a pneumatic piston 22 whose air supply is controlled by a valve 29, on or in the tool body, which valve is actuated to cause operation of the hammer when a predetermined force exerted on the tool body is reached or exceeded. Motor 12 may be electric, or hydraulic but preferably comprises an air motor, and drives a sleeve 19 through bevel gears 16, 17 and a hollow shaft 18 to which the sleeve is splined. Sleeve 19 has a splined extension which co-operates with a toothed ring 21e abutting a thrust bearing 21d on the extension. A second ring 21a is driven by the extension through balls 21b, and this ring has dog teeth which co-operate with dog teeth on a further ring 21 splined to shaft 20. A rod 30 for actuating valve 29 is carried by a nose 32, urged to the left as shown by a spring 34. In operation, when the bit B is applied to the work, the tool parts move to the left relative to the bit and nose 32. Spring 34 is compressed, rod 30 actuates valve 29, which admits pressurized air into a chamber 27. Piston 22 is normally held against a seat 36, by air which is allowed to flow through a passage 38. However, when the pressure in chamber 27 overcomes the pressure in chamber 40, piston 22 is rapidly accelerated, and overcomes spring 51 so that an impact is delivered to shaft 20 and bit B. This enables a fastener, i.e. a self-tapping screw, to pierce a workpiece, whereupon a trigger 15 is actuated to rotate motor 12, and thus cause the screw to be screwed into the workpiece. A number of successive impacts may be produced by applying a sufficient force to the body of the tool to compress spring 34.