Patent ID: 7878263

Claim:
A pressure-fluid-operated percussion device comprising a frame allowing a tool to be arranged within the frame and movable in its longitudinal direction, means for feeding pressure liquid to the percussion device and for returning pressure liquid to a pressure liquid tank, and means for producing a stress pulse in the tool by utilizing pressure of the pressure liquid, wherein the percussion device comprises a working pressure chamber filled with pressure liquid and, between the working pressure chamber and the tool, a transmission piston which is movably arranged in the longitudinal direction of the frame and which is in contact with the tool at least during stress pulse generation, and a charging pressure chamber on the side of the transmission piston facing the tool so that the transmission piston is provided with a pressure surface facing the working pressure chamber and on the side of the charging pressure chamber a pressure surface facing the tool, wherein the means for producing a stress pulse comprise a pressure liquid source connected with the working pressure chamber in order to maintain pressure in the working pressure chamber, and means for intermittently feeding, to the charging pressure chamber, pressure liquid whose pressure enables the transmission piston to be pushed towards the working pressure chamber, against the pressure of the pressure liquid in the working pressure chamber and into a predetermined backward position of the transmission piston such that pressure liquid is discharged from the working pressure chamber, and, when the transmission piston is in said position and substantially in contact with the tool, for alternately allowing pressure liquid to be discharged rapidly from the charging pressure chamber so that a force produced by the pressure of the pressurized pressure liquid in the working pressure chamber and flowing thereto from the pressure liquid source pushes the transmission piston in the direction of the tool, compressing the tool in its longitudinal direction and thus generating a stress pulse in the tool while maintaining the piston in contact with the tool during compression of the tool, wherein the means for feeding pressurized pressure liquid to the working pressure chamber are arranged to feed the pressure liquid such that the pressure in the working pressure chamber remains substantially constant during operation of the percussion device.