GB1331506A - Rotary-percussion drills - Google Patents

Abstract

1331506 Portable drills ROBERT BOSCH GmbH 13 Nov 1970 [14 Nov 1969] 54077/70 Heading B3C [Also in Division B4] A drill comprises a motor for rotating a working spindle via a variable speed gear, a disengageable percussion mechanism which, when in operation, applies axial blows to the working spindle, and one manual adjusting member provided for changing the speed of rotation of the spindle and for engaging or disengaging the percussion mechanism. In the drill of Fig. 1, the output shaft 10 of an electric motor drives gear 11, 12 via an intermediate shaft (not shown). An axially movable shaft 15, having a gear 23 meshing with a gear 24 secured on the working spindle 6, may be keyed to either of the gears 11, 12 via a pin 14a in dependence on the axial position of the shaft 15, so that the working spindle may rotate at a higher or a lower speed. A spring 20 urges the shaft frowardly so that its forward end abuts a cam surface 50 integral with an adjusting sleeve 5. A cam or the rear surface of the sleeve coacts with a cam 37 on the forward surface of a member 36 fixed to the drill housing, and these cams are such that rotation of the sleeve 5 will cause bearing 42 and a toothed member 40 to move axially relative to ratchet-like teeth 38 on the member 36. The axial position of the bearing 42 defines the rearmost position of teeth 39 of the member 40, when the drill is presented to a work surface and is moved rearwardly against action of springs 43. The cams are such that, in operation, the drill will perform rotary percussive drilling or rotary drilling only at the higher and lower speeds. In the drill of Figs. 3 and 4 the motor rotates working spindle 127 through an arrangement similar to that of Fig. 1 excepting that axial movement of the shaft 111 is achieved by a movement of a crank pin 144 (Fig. 4) about the axis of a pin 143 attached to a gear-wheel 142 which is rotatable through two revolutions for each revolution of gear-wheel 140. The gearwheel 140 is rotated by a knob 141 and is held in each of four positions by a ball 142 engaging in an appropriate recess on a plate 141. A substantially rectangular cross sectioned pin 139 secured to the gear-wheel 140 is arranged so that when rotated and located either of two positions, teeth 130 will mesh with teeth 131 to provide percussion. In one of these two positions the shaft 111 will be rotated at a higher speed and in the other of these two positions it will rotate at a lower speed. In the other two positions of the pin 139 the drill will perform pure rotary drilling at a higher and a lower speed. In an alternative embodiment (Fig. 6, not shown) the crank pin is secured to the cross-sectioned pin.