GB190626388A - Improvements relating to Rock Drills and other Percussive Tools. - Google Patents

Abstract

26,388. Rayner, G. H., and Walton, C. Nov. 21. Rock drills.-A valve for rock drills and other percussive tools whether simple high-pressure or compound working, of the type which is held in position by the difference in areas exposed to fluid of two connected parts of the valve, is formed with a middle collar which has a larger area exposed to fluid than the end pistons. In the first case, Fig. 1, air or steam enters by the central port, locks the valve in its forward position on account of the difference of areas g, i, and passes down the port b to drive out the piston, exhaust passing through port c, spaces o, m, and port x, and also through passage e, groove k, and space m. When the auxiliary passage d is uncovered, fluid passes to the front of the piston h, drives back the valve and leaks through a groove l of smaller area than passage d to the exhaust port x. The valve is held in this position by the difference of areas i, h.- When the passage e is uncovered in the back stroke of the piston, the valve is driven forward, fluid leaking through groove k. In the latter case, Fig. 2, an extra collar r is used, and the exhaust port is moved. When the piston in its back stroke uncovers the passage d, the valve is driven to the left, closes the exhaust port, and opens the space u to the inlet port a. The valve is held in this position by pressure acting on the difference of the two centre areas. The two ends of the cylinder are.thus in communication through passages b, m, o, c, and the piston having a larger rear end is driven forward. A groove s connects the inlet a with the space o, to compensate for leakage through wear of parts. The piston-rod may be arranged at the other end of the piston, the area exposed to high pressure being made smaller than that exposed to expansive pressure, so as to effect the blow by high pressure.