GB190815790A - Improvements in and relating to Fluid Operated Percussive Tools. - Google Patents

Abstract

15,790. Johnston, A. G. Kent-. July 24. Rock drills.-Relates to a percussive tool having two pistons, one of which d acts as the percussive means and strikes the second piston q, which has a stem u attached to the tool through the medium of a ratchet or like device. After a blow, pressure fluid enters through the port k to return the piston q, and a spiral groove 3 and pin z cause a slight rotation. When the piston q has returned and rotated a small distance, a passage v registers with a groove w and pressure fluid flows through the passage and groove to return the hammer piston d. If the tool jambs, the piston q is prevented from returning, and, as the passage v and groove w do not then register, no fluid passes through them and reciprocation is stopped. In the position shown, pressure fluid enters the rear cylinder space through passages t, l to move the hammer piston forward, the exhaust passing through ports m, x. The piston q is thus struck and moves forward and rotates. A port o is uncovered and pressure fluid enters to act on the valve piston h and move the valve to the right, opening the passage k to the supply pipe s and opening the rear cylinder space and valve piston chamber b to exhaust through passages n, x. A port p is opened during the return stroke to reverse the valve, and the entering fluid cushions the piston and moves it on its forward stroke again. The valve is locked in either position by the entering fluid acting on the end ; the tool may thus be used in any position. The rotation of the stem u acts through the ratchet device to rotate the tool in one direction. The cylinder a is preferably in two parts and has an extension r connected to suitable feed-mechanism.