Patent ID: 7032684

Claim:
A rock drill comprising a frame, a percussion device provided with a reciprocable percussion piston which moves along a longitudinal path; a shank arranged in the longitudinal path to be struck in its rear end by the percussion piston, a rotating device including a rotating bushing arranged around the shank for rotating the shank, and drilling components attached to a front end of the shank; at least one axial support piston arranged rearwardly of the shank; a source of pressure medium; a pressure channel for conducting pressure medium from the source and against a rearwardly facing side of the axial support piston to push the axial support piston in a forward axial direction; the pressure channel arranged to conduct the pressure medium for applying a force to the at least one axial support piston solely in a forward direction; the axial support piston being arranged to support the shank in the axial direction during drilling; and a pressure reducing device including a valve movable between different positions for effecting drilling and striking-off operations including, during striking-off a position for only partially reducing the pressure of the pressure medium applied from the source to the axial support piston when drilling components are struck off by the percussion piston, wherein the drilling equipment is supported by the axial support piston by a pressure which is lower when the drilling components are struck off than during a drilling operation.