GB191201461A - Improvements in Hammer Rock Drills and in Percussive Hammers and similar Tools. - Google Patents

Abstract

1461. Daw, A. W., and Daw, Z. W. Jan. 18. Percussive drills. - Relates to hammer rock drills, percussive hammers and similar tools, in which a rifled or feathered part 27 formed on the piston-rod of such drill or tool engages a correspondingly grooved sleeve 25, and means are provided for transmitting the movement of the sleeve in one direction to the bit or tool, and consists in making this sleeve to constitute an extension of the cylinder 2 of the drill, the front part of the piston proper 4 passing into and engaging the bore of the extension on the forward stroke of the piston. In one arrangement, a feathered or rifled bar 19 projects into the rear of the piston, the motion of the sleeve 25 in one direction being transmitted to the chuck 31 by means similar to those described in Specification 15,511/10, namely a spring- pressed sleeve 28 having ratchet teeth 29 which engage with similar teeth on the chuck. In a modification, the rifled bar 19 is mounted so that it may rotate, in one direction only, in the cylinder head. The feathers on the pistonrod are in this case straight, and the sleeve 31 forms an integral part of sleeve 25, sleeve 28 being dispensed with. Pressure fluid for effecting the return stroke of the piston may be led from the valve-chest by a passage 13 to an annular recess 13<a> at the forward end of the cylinder 2, through ports 25<b> in the rear end of the extension 25, and through grooves between the feathers 27 to the front end of the piston; or the passage 13 may lead direct to the front end of the extension 25.