Rotary-percussive hydraulic perforator provided with a stop piston and a braking chamber

A rotary-percussive hydraulic perforator comprising:

• a body;
• a shank mounted in the body and intended to be coupled to at least one drill bar equipped with a tool;
• a striking piston slidably mounted inside the body according to a striking axis and configured to strike the shank, the striking piston including a braking surface which extends transversely to the striking axis;
• a braking chamber configured to hydraulically brake the striking piston when the striking piston exceeds a predetermined striking position, the braking chamber being configured to be partially closed by the braking surface of the striking piston when the striking piston exceeds the predetermined striking position;
• a stop piston which is tubular and which is slidably mounted inside the body along an axis of displacement substantially parallel to the striking axis, the stop piston being configured to apply a pushing force on the shank, the stop piston comprising a bearing surface configured to abut against a stop surface provided on the body, so as to limit a stroke of displacement of the stop piston towards the shank;
• a main hydraulic supply circuit configured to control an alternating sliding of the striking piston according to the striking axis, the main hydraulic supply circuit including a high-pressure fluid supply conduit and a low-pressure fluid return conduit, wherein the body and the striking piston delimit at least partially a first control chamber permanently connected to the high-pressure fluid supply conduit and a second control chamber which is antagonistic to the first control chamber;
• a control distributor configured to fluidly connect the second control chamber alternately to the high-pressure fluid supply conduit and to the low-pressure fluid return conduit so as to control striking and return strokes of the striking piston;
• wherein the braking chamber extends from a bottom surface of the first control chamber and towards the shank;
• and
• wherein the rotary-percussive hydraulic perforator is configured such that the bearing surface and the stop surface are axially spaced apart from each other by a predetermined spacing distance simultaneously when:
• the shank bears on the stop piston and is in contact with the striking piston, and
• the braking surface of the striking piston is located at an inlet edge of the braking chamber.