GB954885A - - Google Patents

Abstract

954,885. Percussive drills. DOWTY MINING EQUIPMENT Ltd. July 25, 1960 [May 11, 1959], No. 16085/59. Heading B4C. [Also in Division F1] In a pneumatic or hydraulic pressure reciproeating engine for supplying power to rock drills or hammers, a piston 3 slidable in a cylinder 2 has a piston-rod 4 extending through a sealed opening 5 in the cylinder for transmitting reciprocating energy, e.g. to the spring-loaded head 7 of a drill, and a sliding valve 14, 15, capable of oscillation with springs 21, 23 associated therewith, connects each end of the cylinder 2 alternately to fluid supply and return ports 24, 25 through fluid passages 28, 29 to cause reciprocation of the piston in accordance with oscillation of the valve, the piston being connected to the springs for transmitting reciprocating energy thereto to maintain the valve in oscillation whereby reciprocation of the piston is also maintained. As shown, the piston is formed with a recess 11 equal in diameter to the piston-rod diameter and sealingly engaging in the upper end of the cylinder 2 a projection 12 provided with a bore 13 forming the valve cylinder. Alternatively, the piston is provided with a hollow rod extending in a sealed manner in the casing 1 and connected to a valve cylinder. The valve rod 16 is formed with a head 19 and a shoulder 22 between which and a flange 18 in the piston bore the springs 21, 23 are compressed. In the position shown, the piston 3 is displaced slightly upwardly by a spring 8 acting on the drill head 7. To commence operation, pressure fluid is supplied through port 24 and passes through port 26 to piston 3 urging it downwardly. The piston will then start to oscillate at a frequency governed by the actual frequency of the valve and springs, reciprocating energy being transferred to the drill head 7 by impact. In a modification, inlet and return ports are provided respectively on the outside and between the lands 14, 15 of the valve and pressure fluid acts on the whole cross-section of the end of the piston opposed to the piston-rod.