GB1342745A - - Google Patents

Abstract

1342745 Drilling machines ROBERT BOSCH GmbH 16 Dec 1970 [22 Dec 1969] 59615/70 Heading B3C [Also in Divisions B4 and F2] A drill including a hammer 18 for applying impacts to a tool holder 7<SP>1</SP>, the hammer being axially reciprocated by an electric motor via gear-wheels 10 and 12 and air cushions 21 produced between the hammer and an axially movable cylinder 16, comprises means for enabling or disabling rotation of a member 34 having internal longitudinal splines which engage with longitudinal external splines on the holder 7<SP>1</SP>. The means includes a gear-wheel 23 fast with gear-wheel 12 and meshing with gear teeth 24 on an annular drive body 25 which includes longitudinal bores 52 equally spaced circumferentially and each accommodating a compression spring 55 and balls 54 which are engageable in recesses 53 in annular members 27, 28 which form a bearing for the drive body. The under surface of the member 28 forms one part of a dog clutch. The other part 39 of the dog clutch is formed on the upper surface of an annular member 37 which is non-rotatable, but axially movable, relative to a shaft 31 carrying at its upper end a pinion 32 which engages with gearteeth 33 on the member 34. A sleeve 42 mounted on the member 37 has a projection 43 extending into a key way 44 in housing 9 and a coarse external thread which meshes with a coarse internal thread 46 on a switch member 47. In operation with the switch member moved in one direction to a position in which the dog clutch is engaged, the drill has a rotary/percussion operation and any overloading of the drill is relieved by the balls being cammed out of their recesses to permit the body 25 to rotate relative to the members 27, 28. Movement of the switch member in the opposite direction will cause sleeve 42 and thus member 37 to move axially relative to the shaft 31 so as to disengage the dog clutch, thus conditioning the drill for percussion only. The drill which has a handle (2) (Fig. 1, not shown) may be provided with a second handle 8. In alternative arrangements the hand grip portion (58) is rotatable relative to the portion (57), and the flange (59) is coupled by meshing gears or a pin-and-slot connection to the switch member so that the switch member can be moved upon rotation of the hand grip. The hand grip portion may be axially aligned with the switch member. Reference has been directed by the Comptroller to Specifrcation 1,206,853.