Hydraulic rotary-percussive hammer drill provided with a stop piston

A hydraulic rotary-percussive hammer drill, comprising:

• a body;
• a shank intended to be coupled to at least one drill bar equipped with a tool;
• a striking piston slidably mounted inside the body along a striking axis and configured to hit the shank;
• a stop piston which is slidably mounted in a cavity of the body according to an axis of displacement substantially parallel to the striking axis, the stop piston including a front face facing the shank and configured to position the shank in a predetermined balanced position with respect to the striking piston, and a rear face opposite to the front face and located opposite a rear wall of the cavity;
• and
• a high-pressure fluid feed-in conduit and a low-pressure fluid return conduit;
• the body and the stop piston delimiting at least partially a first control chamber permanently connected to the high-pressure fluid feed-in conduit and configured to urge the stop piston forwards, the hydraulic rotary-percussive hammer drill further comprising a connecting channel configured to fluidly connect the first control chamber to the low-pressure fluid return conduit when the rear face of the stop piston is located at a distance from the rear wall of the cavity which is larger than a predetermined value,
• wherein the body and the stop piston further delimiting at least partially a second control chamber configured to urge the stop piston forwards, and wherein the hydraulic rotary-percussive hammer drill comprises a fluidic communication channel which opens into the second control chamber and which is configured to supply the second control chamber with high-pressure fluid, the fluidic communication channel being provided with a calibrated orifice.