| 摘要 |
A percussion drilling apparatus having an outer casing, a fluted inner sleeve affixed to the outer casing, a hammer piston having a longitudinal opening therethrough adapted to fit around extensions of a cyclic valve positioned at the top of the inner casing, and a foot valve mounted atop a drilling bit at the bottom of the apparatus. An air channel positioned between the inner sleeve and outer casing is adapted to cooperate with channels on a reciprocating hammer piston to alternately drive the hammer piston up and down.
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