Tool driving or impacting – Drive controlled by relative axial movement of tool – Drive motor controlled
Patent
1988-01-25
1988-12-13
Yost, Frank T.
Tool driving or impacting
Drive controlled by relative axial movement of tool
Drive motor controlled
173 73, 173119, 173139, B23Q 5033
Patent
active
047903902
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.
REFERENCES:
patent: 2859733 (1958-11-01), Bassinger
patent: 3958645 (1976-05-01), Curington
patent: 4030554 (1977-06-01), Kammerer, Jr. et al.
patent: 4084646 (1978-04-01), Kurt
Minroc Technical Promotions Ltd.
Wolfe James L.
Yost Frank T.
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