GB946678A - Improvements in or relating to rock drilling and like boring apparatus - Google Patents

Abstract

946,678. Percussive drills. HALIFAX TOOL CO. Ltd. June 29, 1961 [July 7, 1960], No. 23814/60. Heading B4C. [Also in Division E1] A " down the hole " percussive pneumatic drill has conduit means to supply flushing liquid or gas into the bore hole independently of the compressed air for operating the drill. The drill comprises a cylinder 1, a bit 4, a piston 6, and a distributer valve 7 controlling ports 9, 10 for supplying air below the piston and ports 11 for supplying air above the piston. The cylinder is slidable on a shock absorber piston 13 having ports 15 for the supply of air to a check valve 17 immediately above the valve 7. The piston 13 is connected to the drill string 19 which is formed by tubes according to Specification 946,679 and is connected to a rotation motor at the earth's surface. The piston has a plunger 30 which projects into a bore 34 of the valve chest 8 of the valve 7 when the drill is reciprocating against the earth, the plunger and bore forming a bypass valve which is the subject of Specification 946,677. The drill string has a central conduit for the passage of the flushing fluid and connected by a coupler 44 to a tube 42 which discharges fluid into a central bore 51 of the bit having outlets 52. The operating air for the drill passes through the string in the annulus about the central conduit to the interior of the piston 13. Air passes down through the ports 15 and valve 17 to the valve 7. The valve 7 supplies air above the piston 6 through ports 11 when the valve is raised due to air pressure below it, and supplies air below the piston 6 through ports 9, 10, ducts 23, 24 and ports 25 when in its lowest position. Towards the ends of the downward and upward strokes of the piston 6 air is exhausted through ports 12, space 35, channels 36, and the bore 51 in the bit. When the bit is moved out of contact with the earth the plunger 30 withdraws from the bore 34 and most of the air passes to above the piston 6 to hold it down and stop reciprocation whilst the rest of the air flows through the ports 10 and ducts 24 to the bit. The drill is suitable for sub aqueous drilling. Specifications 714,663, 844,607 and 844,608 also are referred to.