Patent ID: 8739895

Claim:
A machine tool for impacting a work piece comprises: a pneumatic percussion mechanism having a cup-shaped exciter cylinder with an inner chamber open in a direction of impact, the inner chamber being defined, at least partially, by a shell-type wall, the shell type-wall having at least one ventilation opening and a recess, the at least one ventilation opening spaced at a distance from the recess in the direction of impact; and a free piston movable in the inner chamber, the free piston including a sealing element located in the inner chamber and contacting an inner surface of the shell-type wall, the sealing element sealing off the at least one ventilation opening when the sealing element is oppositely situated from the at least one ventilation opening, the sealing element, when in the region of the recess, being separated at a distance from the shell-type wall when the sealing element is oppositely situated from the recess.