| 摘要 |
<p>A hydraulic percussion drill (12) includes a piston hammer (50) disposed in a cylinder (14) for reciprocating movement in response to pressure fluid acting continuously on one transverse face (62) of the piston hammer (50) and in response to valving (104) of pressure fluid alternately to an opposed piston face (54) of the piston hammer (50) by a tubular sleeve valve (28) disposed around the piston hammer (50).</p> |
