| 摘要 |
A "hole bottom" hammer drill comprising a tubular body (1) supplied with compressed air, a drill bit (3) and a percussion piston (38) caused to move in an inner cylinder (7) by a mechanism distributing compressed air alternately below and above the piston. The hammer drill includes a device (29) for injecting gas oil into the chamber (71) above the piston (38) and a mechanism (34, 35) for triggering the injection during the upward stroke of the piston (38); the additional compression effects the combustion of the air-gas oil mixture, thus projecting the piston (38) towards the drill bit (3).
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