| 摘要 |
A down-hole hammer includes a two-piece drill bit retained in a casing having an interior surface with a plurality of longitudinal grooves formed therein. The drill bit comprises a bit shank and a bit head mounted on the bit shank. The bit shank and the casing are rotationally connected by a number of pins received in the grooves. A symmetrical free piston divides the casing into an upper working chamber and a lower working chamber. The piston slides on an air control assembly including a ported tube extending axially from said air supply to an axial bore in the shank of the bit to guide exhaust air through discharge ports at the cutting face of the bit, the bit reciprocating on the end of the tube. The upper and lower check valves in the air control assembly and openable by supply pressure against a spring bias in response to working fluid supply pressure. 8a, * 13 9 a 1 11 22a, 21o- 12 5a 3 5a 2 b |
