GB191030032A - Improvements in Power Operated Percussive Tools. - Google Patents

Abstract

30,032. Haddan, H. J., [McKiernanterry Drill Co.]. Dec. 24. Percussive drills. -In rock drills, mining - machines, &c. in which a piston is reciprocated by an elastic fluid, a cushioning-piston, secured to a longitudinally - fixed bar, works in a cylinder in or carried by the percussion piston, and a passage is provided in the bar and a check valve in the cushioning - piston so that motive fluid flows into this cylinder during the forward stroke and is entrapped therein to cushion the return stroke and to increase the power of the next forward stroke. In one form of apparatus a piston 31 is driven forwards by air admitted through a port 29 and compressed by a second piston 26 driven by a motor 28, some air flowing through passages in the rifle bar 35 and a piston 20 carried thereby to a space 40, a check valve in the piston 20 preventing its return. During the stroke, air flows past a check valve 43 to the space below the piston 31, and this air returns the piston 31 when the piston 26 returns, the air in the space 40 then being compressed to cushion the piston 31 and increase the power of the next forward stroke. Valves 30, 44 control the air pressure. The rifle bar 35 is held against rotation, the ratchet-wheel reciprocating with the piston 31 and being engaged by pawls 38 in a frictionallyheld block 39 to rotate the piston 31. The block 39 yields under excessive strain to prevent breakage. In assembling, the piston 20 may be placed loosely in its cylinder, the air which passes below it in operation fixing it automatically on the conical end of the bar 35 In another form of apparatus, the rifle bar is rotatably carried by the rear cylinder head and carries a ratchet-wheel adapted to be engaged by pawls to cause intermittent rotation of the drill.