GB1301470A - - Google Patents

Abstract

1301470 Rotary percussive drills IMPEX-ESSEN GmbH 20 Aug 1970 [23 Sept 1969 40182/70 Heading B3C [Also in Division B4] An electrically operated rotary-percussive drill includes a tool holder 2 rotatable by an electric motor 5<SP>1</SP> through a gear unit provided with coupling means 3, and a striker 23 arranged to beat on a tool 24 in the holder 2, the gear unit providing for two speeds of tool rotation and the coupling means 3 having a neutral, non-driving position. A pinion 5 formed on the motor output shaft 5 drives an outer member 6<SP>1</SP> of a safety release clutch 6, a clutch hub 6<SP>IV</SP> being mounted on an intermediate shaft 4. A gear-wheel 8 is secured to the member 6<SP>1</SP> for rotation therewith and a further gearwheel 7 is mounted on the shaft 4, these wheels meshing with respective gear-wheels 10, 9 freely rotatable on the coupling shaft 3. Clutch elements 10<SP>1</SP>, 9<SP>1</SP> are selectively co-operable with the gear-wheels 10, 9 and clutch rims 12, 11 of the shaft 3 on sliding the shaft 3 against a spring 14 by means 27 a cam 17, the shaft 3 being thus rotatable at either of the speeds defined by the respective gear ratios. A pinion 3<SP>IV</SP> of the shaft co-operates with a gear-wheel 2<SP>1</SP> integral with the tool holder 2 to rotate the tool 24, the striker 23 being driven through an intermediate air cushion 22 by electrically operated piston/ cylinder means 19-21 to effect the percussive action of the tool. The cam 17 may be manually adjusted by means of a knob (16), Fig. 3 (not shown), between the driving and neutral positions, which positions are defined by a spring- loaded detent pin (18). A safety clutch 6 may be included only in the slower speed/higher torque transmission chain of the gear unit, or a clutch may be provided in each transmission chain (not shown). Also, the clutches 91, 10<SP>1</SP> may be omitted, the gear-wheels 9, 10, fixed to the shaft 3 being movable into respective engagement with the gear-wheels 7, 8.