GB1252512A - - Google Patents

Abstract

1,252,512. Percussive tools. GARDNERDENVER CO. 20 March, 1969 [26 Sept., 1968], No. 14833/69. Heading B4C. [Also in Divisions E1-E2] A down-the-hole percussion drill comprising a hammer piston 21 which delivers blows to the shank 32 of a bit 30, has a multipassage tube 72 extending from a discharge bore 76 to a pressure fluid inlet 44; the tube 72 has a conduit 98 to conduct fluid to a drive-chamber 26 for lifting the hammer piston between strokes, passages 81, Fig. 3, having ports 84, 86 to exhaust motive fluid from drive chambers 24, 26 and a conduit 92 to by-pass fluid from the inlet to flushing ports 88, 90. The drill is attached to the lower end of a rotatable drill pipe 12 through which pressurized fluid (air) is supplied. The tube 72 has a partition 82, containing the conduits 92, 98 and defining the passages 81. In operation, air from the inlet enters the chamber 24 through conduits 60 and 114 to drive the hammer piston downwards. Air from the chamber 26 is thereby displaced into a space 104 and through a port 110 in the conduit 98 and passes out through a port 102 into a chamber 100 to depress a valve member 66 which closes the conduit 114. As the descending hammer piston uncovers the ports 84 the air in the chamber 24 is exhausted to the exterior. Air then passes from the inlet and the conduit 60 to the chamber 100 and down the conduit 98 into the chamber 26 to lift the hammer piston for the next stroke. The air in the chamber 26 is exhausted to the exterior as the rising hammer piston uncovers the ports 86. The by-pass conduit 92 may contain a constricting plug 94 having a suitable diameter bore 96. When the drill is lifted from the hole bottom, the bit and hammer piston fall until lugs 34 engage a seating 36 so that the port 110 is covered by the part 120 of the shank, and a port 112 is uncovered, thus preventing reciprocation of the hammer piston and ensuring that all the air passes to the flushing ports.