| 摘要 |
The invention relates to a hydraulic rotary-percussive hammer drill (1) comprising a body (2) containing an alternating impact piston (4) which slides due to the effect of a main hydraulic feed circuit (22), said main circuit also being intended to cause an essentially annular stop piston (5) to slide in a cavity (3) of the body. The aforementioned stop piston comprises (i) a front face which is in contact with a shank (7) and which is intended to position said shank at a pre-determined distance from the impact piston and (ii) a rear face opposite a rear wall of the cavity. The invention is characterised in that, when the main circuit is stopped, an external hydraulic feed circuit (23) can introduce a pressurised fluid between the rear face of the stop piston and the rear wall of the cavity, such as to maintain a space between same. The inventive hammer drill is suitable for drilling installations.
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