GB1264915A - - Google Patents

Abstract

1,264,915. Impelling tools. MISSION MFG. CO. 9 July, 1969 [29 July, 1968], No. 34671/69. Heading B4C. [Also in Division E1] A "down-the-hole" drill comprising a casing 8, an attachment 16 for connection to a support column (not shown) supplying working fluid to the drill, an anvil 44 carrying a bit 53, a hammerpiston 7 reciprocable in the casing, and passages leading the fluid to the working fluid chambers 19, 20, has part 74 of the passages formed in the structural part of the casing. The casing comprises a barrel having ends 9, 10 connected by a reduced portion 11, and half shells 12, 13 welded together and to the ends, the passages being formed between flats 75 on the portion. In a modification the passages are shorter, are formed' by grooves in the portion and are arranged with additional passages so that leakage between high pressure and exhaust passages is prevented. Fluid'supplied to the-drill when the bit is resting on the hole bottom causes the piston to vibrate. When the parts of the drill are positioned as shown the fluid passes through the passages 33, 66, ports 70, 71, parts 74, openings 73 and passages 85 to the chamber 19 to drive the piston downwardly whilst the chamber 20 is exhausted through ducts 56, 57. When the piston is-in its lowest position the nozzles 35, 58, are respectively, clear of, and within the duct 61 through the piston so that the chamber 19 is exhausted and the piston is driven upwardly by fluid from. the passages- 74 supplied to the chamber 20 through openings- 72 and passages 86. When fluid is supplied to the drill with the anvil suspended by its head 47, fluid from the passage- 74' passes through; openings 73 and combines with flow through a choke 62 to pass through the ducts 61, 56, 57 to clear the borehole.