GB433374A - Improvements relating to pneumatic percussive tools - Google Patents

Abstract

433,374. Percussive tools. CLIMAX ROCK - DRILL & ENGINEERING WORKS, Ltd., 4, Broad Street Place, Blomfield Street, London, and ST. STEPHENS, R. DE H., Homefield, Camborne, Cornwall. Feb. 8, 1934, No. 4248. [Class 124] [See also Group XXVI] A differential sleeve valve with an external shoulder is arranged to the rear of and co-axially with the cylinder. Its ends and interior are open to the rear of the cylinder the fluid supply to which and an auxiliary exhaust therefrom being controlled by the forward enlarged end of the valve. The fluid-supply to the forward end of the cylinder and an auxiliary therefrom are controlled by a recess around the rear end of the valve. Fluid from the cylinder acts on the shoulder to throw the valve forward, and compression reverses it. A valve to blow out the debris is provided. The distributing valve shoulder 26 constantly communicates with the exhaust through a passage 34, and is put into communication with the cylinder through a passage 30 which is opened by the main piston prior to the opening of the main exhaust port 32. The forward side of the shoulder 24 communicates with the exhaust through a passage 36, and a second passage 34 communicates with the exhaust upon movement of the valve. Excess pressure on the area 26 over the rearwardly-acting difference in pressure on the two ends of the valve effects the forward movement. Fluid is supplied to the rear cylinder end through passages 42, 18 over the end of the valve, and to the forward cylinder end through passages 40, 50 controlled by the valve recess between the shoulders 44, 52 which also controls an auxiliary exhaust from the forward cylinder end through a passage 54. During the back stroke of the piston, after the closure of the port 32, an auxiliary exhaust takes place over the shoulder 26 of the valve until the port 30 is passed. The resulting compression reverses the valve which is temporarily locked in its end positions. A small leak port 56 supplies pressure fluid to the rear of the cylinder to ensure starting. A ha,nd-controlled rotary valve 62 may be used to blow out the debris. This closes the apertures 34 to atmosphere and puts them into communication with the main exhaust port 32 which is also closed. A supplementary exhaust 72 is provided for the back of the cylinder. In consequence, the valve is held forwardly and the piston rearwardly to ensure the passage of air to the front of the cylinder.