Patent GB-1069018-A (GB)
Title: Tool for piercing and screwing self-tapping screws into a workpiece
Inventor: TURNBULL JOHN HILTON
IPC: B25B21/02
Filed: 1965-09-10
Abstract: 1,069,018. Screwdrivers; perforating. G.K.N. SCREWS & FASTENERS Ltd. Sept. 10, 1965 No. 38712/65. Addition to 1,056,699. Headings B3N and B3W. [Also in Division F2] A power-operated screwdriver for applying self-tapping screws to a workpiece by impacting the screw to pierce the workpiece, and then screwing it into the workpiece, comprises a screwdriver bit 351, Fig. 1, rotatably and slidably mounted in the screwdriver body 300, an electric motor 302 for rotating the bit. and a screwdriver bit impact member 313 operated by the motor. A rubber sleeve 318 is bonded to part 319 in the driver body, and also to a sleeve 316 carried on a shaft 317, and the latter has a screwed portion 320 which cooperates with a two-part nut (324) mounted on an end wall 321 of body 300. The nut comprises a pair of levers 322, Figs. 2 and 3 (not shown), pivoted at (323), and connected by a spring-urged toggle (325). The nut is normally closed on to the screwed portion 320, but the toggle can be broken to disengage the nut by a lever 332 actuated by a trigger 335. A rotatable sleeve 342 is splined to member 313 and has a collar 346 secured thereto, the collar being secured to a sleeve 347. The latter is connected to a ring 350 mounted on bit 351 through balls and grooves 349, 348, and the ring 350, and a ring 352 splined to the bit 351 constitute a slipping toothed clutch. In operation, the motor 302 is switched on with nut (324) closed, bit 313 is rotated through gears 308-312 and is moved axially to the right, Fig. 1 (not shown), due to the threaded engagement of portion 320 with the nut. Rubber sleeve 318 is distorted to thus store up energy and shaft 317 continues to move until it actuates a microswitch 337 to stop the motor. The screw is held against the work, trigger 335 is pressed to release nut (324), and sleeve 318 moves member 313 axially, to impact the screw. Switch 337 is actuated to start motor 302 and the screw pierces the work and is screwed home. In a modification, Figs. 4, 5 (not shown), the energy storage device is a fly-wheel (23), and the impact member (56) is actuated by a dog (24) on the fly-wheel. Electric motor (11) drives bit (49) through gears (12-14), (40), (41), (44-46) and clutch (51), (52). A sleeve (17) is rotatably and slidably mounted on shaft (15), and a friction disc (21) on the sleeve co-operates with a boss (22) on gear (14), to form a clutch. Fly-wheel (23) is screwed on to sleeve (17), and a pivoted spring-urged brake (25) presses lightly on the fly-wheel. In operation, motor (11) is rotated and sleeve (17) is moved to engage clutch (21), (22) by a lever (29) which is held in place by a trigger (35), and is thus rotated. Fly-wheel (23) is moved to the right, Fig. 4 (not shown), due to its screwed engagement with sleeve (17), trigger (35) is actuated to release arm (34), and sleeve (17) is moved to the right by spring (33), Fig. 4 (not shown). Clutch (21), (22) is disengaged and a dog (38) on sleeve (17) engages a fixed dog (39), to thus bring sleeve (17) to rest. The fly-wheel continues to rotate at high speed, and due to its threaded engagement with sleeve (17), moves to the left, Fig. 4 (not shown), whereupon dog (24) delivers an impact to member (56).