GB190713267A - Improvements in Fluid Pressure Percussive Rock Drills - Google Patents

Abstract

13,267. Macfarlane, D. L., Mahaffey, E. B., Neal, C. L., and Jenks, E. W. June 7. Rock drills.-A rock drill of the type having an enlarged hollow head or expansion chamber 21 at one end, and a forward end reduced to pass through the chamber 7 to strike the tool, has the ports leading to the annular space 27 some distance from the end, so that part of the rear stroke is effected by cushioned air. The air or steam is admitted through a three-way valve 31, which may be turned by a handle to allow air to pass either through the port 32 into the cylinder, or through both ports 32, 33. The port 33 is connected by a passage 16 and chamber 17 with the hollow piston-rod 41 of a feed - bar, from which the fluid may be exhausted by allowing the groove in the valve connected to atmosphere to engage with the port 33. Fluid passes into the chamber 27, and in the position shown passes through ports 23 in an annular groove in the piston into the interior of the piston, which is driven out. When the ports 23 reach the chamber 9, fluid is exhausted from behind the piston, which is returned until the port 32 is uncovered, by the fluid compressed by the shoulder 26 in the forward stroke. The exhaust may pass through the tube 10, which may be plugged when not required, or through holes 13 in the bush 12 to blow out grit and chips ; the bush is shrunk into its place. In a modified form the valve may turn in the cylinder head.