Valveless down-the-hole drill
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United States of America Patent
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-
Dec 13, 1988
Grant Date -
N/A
app pub date -
Jan 25, 1988
filing date -
Jan 26, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A valveless down-the-hole hammer drill is actuated by fluid such as compressed air. The drill includes a piston disposed within a chamber defined within an outer wear sleeve, an air diverter at one end and a suspendably mounted drill bit at the other end, wherein the piston has a slidable contact surface with the chamber towards each end of the piston, such that the piston is slidably reciprocable within the chamber. Porting and exhaust arrangements alternately supply and exhaust live pressure fluid to either end surface of the piston to reciprocate it and cause it to repeatedly strike the drill bit. An intermediate compression chamber is defined between the two sliding contact surfaces of the piston between the piston and the outer wear sleeve. Air trapped in the intermediate chamber is compressed so as to apply a retarding force on the piston towards the end of the return stroke, and to provide additional impetus to the piston on the commencement of the drive stroke. Sealing arrangements to reduce air leakage past working clearance gaps are also disclosed.
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