| 摘要 |
A pneumatic down-the-hole drill having a frame (21 ), a pneumatic percussion piston (24) that moves in a reciprocating manner as pressurized air is fed into the DTH-drill and strikes a tool in the front end of the frame (21), mounted movably in the longitudinal direction of the frame (21 ), a feed channel for feeding compressed air to the DTH-drill, and shoulders in the frame (21 ) and in the percussion piston (24) for controlling compressed air to provide an impact movement. In the rear end of the frame (21 ) the DTH-drill comprises a combustion chamber (26) and an acceleration piston (25) which is arranged to push the percussion piston (24) during the impact movement for a portion of the percussion piston (24) travel, means for feeding combustion air and fuel into the combustion chamber (26), whereby the percussion piston (24) is arranged to push the acceleration piston (25) after the impact into the combustion chamber (26) and to compress the air in the combustion chamber (26) prior to feeding the fuel into the combustion chamber (26). |
