Percussion device

A percussion device having a frame, to which a tool is mountable movable in its longitudinal direction relative to the frame of the percussion device, the percussion device containing a work chamber having a transmission piston mounted movable in the axial direction of the tool to compress the tool suddenly in its longitudinal direction by the pressure of the pressure fluid acting on the transmission piston to generate a longitudinal stress pulse to the tool, which propagates through the tool to a material being crushed, inlet and outlet channels for conducting the pressure fluid to the percussion device and away from it and a control valve that has a movably mounted switch member with one a first channel so that the switch member supplies pressure fluid alternately from the inlet channel to the work chamber to act on the transmission piston, whereby the transmission piston moves in relation to the frame of the percussion device toward the tool and, correspondingly, to discharge the pressure fluid that acted on the transmission piston from the percussion device, whereby during its return movement the transmission piston moves in relation to the frame of the percussion device back to its initial position, wherein

• a first control channel leads to a side of the transmission piston or a part connected to and moving along with the transmission piston,
• the switch member of the control valve has at one a second channel that connects the pressure fluid that acted on the transmission piston to flow during the return movement of the transmission piston through the control valve to the first control channel, and
• the transmission piston or the part connected to and moving along with the transmission piston has a second control channel that, when the transmission piston has moved from its initial position toward the tool, connects the first control channel to the outlet channel of the pressure fluid so that after the stress pulse has formed, during the return movement of the transmission piston, the pressure fluid that acted on the transmission piston is allowed to flow through the first and second control channels to the outlet channel and that said connection closes when the transmission piston has returned to its initial position, whereby the pressure fluid that remains in the work chamber forms a damping pillow that stops the return movement of the transmission piston to its initial position.