GB1198276A - Improvements in or relating to Power Tools Incorporating Planetary Friction Gears - Google Patents

Abstract

1,198,276. Friction gearing; change speed gearing. ROBERT BOSCH G.m.b.H. 4 Oct., 1967 [5 Oct., 1966], No. 45169/67. Headings F2D and F2Q. [Also in Division B3] A planetary friction gear in a power tool comprises an input sun gear 11 (Fig. 1a) having two frusto-conical or arcuately sectioned friction surfaces with their larger diameter ends adjacent one another, the friction surfaces engaging respective sets of ball planets 18 in a common output planet carrier 16, and an internal ring gear formed of two rings 19, 20 connected together against relative rotation and urged together by adjustably preloaded Belleville springs 123 (Fig. 3) or a helical compression spring 23b (Fig. 1a to maintain the frictional grip of the gears. The drive slips at an adjustable predetermined torque loading. The train of Fig. 1a, or a modified form (Fig. 1, not shown) is used in a portable grinder (see Division B3), the rings 19, 20 being held stationary. In a two-speed drill (Fig. 3) the sun gear 111 is integral with the motor shaft 104 and the planet carrier 117 has a toothed gear extension 116 meshing a gear 141 on the tool spindle 112. The ring gears 119, 120 are connected by pins 130 to an axially slidable sleeve 129 moved by a rod 133 having a hand knob 133a and a spring detent 135 to locate it in one or other of two positions. In its right hand position (Fig. 3) the sleeve 129 and gears 119, 120 are held stationary by engaging lugs 137, 138 for reduced drive, and in its left hand position recesses 140 of the sleeve 129 engage dogs 139 of the carrier 117 to look up the planetary train for direct drive to the gear 116.