GB1042349A - Improved hydraulic piston-actuating apparatus - Google Patents

Abstract

1,042,349. Percussive tools. THOR POWER TOOL CO. July 23, 1963 [July 31, 1962,] No. 29096/63. Heading B4C. An hydraulically-actuated percussive tool, such as a rock drill, comprises a piston 23 reciprocable in a cylinder 25 between first and second terminal positions and having small and large operative areas 59, 60 respectively, the smaller area being permanently acted upon by fluid pressure so as to urge the piston toward the first terminal position, and a valve 39 for intermittently placing the larger area in communication with the pressure source so as to urge the piston toward the second terminal position against the action of the biasing pressure. The cylinder is mounted in a housing 21 including ports 49, 51 and 52 connected to the pressure fluid and ports 44, 45 and 46 connected to the return back to the supply reservoir. The valve spool is slidable in a cylinder 38 mounted in a housing 22 and is normally biased to the position shown by pressure fluid acting on the end 40 of the spool via port 50 and passage 52. In operation, when a control valve is actuated, pressure fluid is fed, via the port 49, to act on the small area 59 defined by a land 56 on the piston. The piston then moves to the right, causing the fluid in front of the larger area 60 defined by a land 57, to be forced back to the reservoir via ports 66, 68, annular passage 69, ports 70 and 45. When the land 56 passes a port 71, the pressure fluid flows via ports 72, 73, into a chamber 40 so as to act on the large end 41 of the spool valve moving it to the right and thereby causing a land 74 thereon to cut-off the return flow. Pressure fluid is now able to flow via ports 51, 78 anular chambers 77, 69, ports 68, 66, to act on the large area 60 of the hammer piston to thereby drive it on its working stroke. Pressurized fluid for clearing the tool bit is fed via a pipe 32 and port 33. The tool is also rotated by means of an independent hydraulic mounted on the housing 21.