GB852752A - Improvements in motor driven rotary percussion apparatus - Google Patents

Abstract

852,752. Screwing-up and unscrewing screws &c. BOSCH G.m.b.H., R. Dec. 10, 1957 [Jan. 8, 1957], No. 38303/57. Class 83 (3). [Also in Group XXIV] An impact-wrench or screwdriver comprises a rotary-hammer 19 driven from a motor 2, 3 by a shaft 17, an anvil 18 connected to a socketwrench &c (not shown), interengaging-claws 23, 24, on the hammer and anvil, and a frictionclutch 50, 51, in the drive between the motor and shaft 17, the hammer lagging behind the shaft upon increase in torque-demand and moving away from the anvil; against the influence of a spring 35 under compression, to disengage the claws 23, 24, and a rotary-blow being struck by the claw 24 upon return of the hammer by spring 35. A ball 30 in a pocket 31 in the hammer and in a V-shaped slot 29 in the shaft 17, drivingly connects the hammer and the shaft, which bears at one end in the anvil and at the other in a gear 16 freely rotatable on the shaft and driven from the squirrel-cage electric motor by gears 13-15. The hub 45 of gear 16, forming the driving element of the friction clutch, has three equallyspaced axial grooves 55 receiving keys 54 on clutch-plates 51 stacked alternately with clutchplates 50, each of which has three outwardlydirected keys 52 engaging axial grooves 56 in the base 44 of the clutch-housing 32, which is keyed to shaft 17. The spring 35 loads the clutch through a ball-race 34 and a pair of pins 38, and acts on the hammer, camming the ball 30 to the apex of the groove 29. Displacement of the anvil, against the pressure of a spring 25, carries the claw 23 into the path of the rotating-claw 24 during operation of the tool. An increase in torque-demand reduces the speed of the anvil-and-hammer, thus causing the ball 30 to travel along the groove 29 from the apical position depicted, and disengagement of the claws. The spring 35 then returns the hammer, accelerating it until the ball resumes the apical position, and a rotaryblow is struck when the claw 24 again contacts claw 23.