Patent ID: 7484570

Claim:
Percussion device including a machine housing, a forwards and backwards movable percussion piston in the machine housing, and a reciprocatingly movable tubular valve body inside the machine housing, said percussion piston being arranged to subject a tool to impact, and said percussion piston including a first and a second driving surface arranged to be pressurized in order to drive the percussion piston forwards and backwards, said valve body including a first end surface and a second end surface, wherein pressurizing the first end surface tends to drive the valve body in a first direction and pressurizing the second end surface tends to drive the valve body in a second direction, whereby the valve body is arranged, over a channel arranged in the machine housing, to connect at least the second of the driving surfaces alternately to a pressure source or to low pressure, wherein an inner room in the tubular valve body is continuously connected to the low pressure over at least one opening through an envelope surface of the valve body.