GB190808930A - Improvements in Electrically Driven Percussive Tools, specially applicable for Rock Drilling or Stoping. - Google Patents

Abstract

8930. Knight, J. April 24. Rock drills.-An electrically-driven rock drill of the type in which a piston or hammer is reciprocated electro-magnetically, comprises an outer casing 1 containing a rotatable sleeve 2, within which a cylinder 5 carrying the impact piece 6 can slide but not rotate. A bobbin 27 carrying one or two solenoids 28 is fitted in the cylinder 5 and contains an armature or hammer 30. The circuits through the coil or coils 28 are suitably arranged to produce reciprocation of the hammer 30 at any desired speed. The sleeve 2 is fitted with a handle 8 by which it can be rotated through say half a revolution for the purpose of turning the drill, and the movement of the handle 8 operates one or more plungers 10 in cylinders 11, through one or more cranks 9. The air thus compressed is delivered down a passage 12 and through holes 26 in a ring 20 to a space 13 behind the cylinder 5, which is thus given a resilient pneumatic feed. The impact piece 6 and the tool 7 are preferably axially perforated for the purpose of leading air to the nose of the tool. The casing 1 is mounted in a grip sleeve 32 supported from the usual post. Cocks or relief valves 33 are fitted on the ends of the cylinders 11, by the opening of which the cylinder 5 may be quickly returned to its inner position.