Abstract: A hammer mechanism is disclosed, which incorporates a hammer piston driven by a driving piston via a pressure-gas cushion in a working chamber. The hammer piston controls the transference of flushing gas from the working chamber to the tool during normal operation and has an extreme position in which the hammer piston does not interfere with the transference of flushing gas.

Abstract: A method for damping the movement of the hammer piston of a hammer mechanism and for catching the hammer piston in a forward end position when the drill tool is situated outside the operating range of the hammer piston is disclosed. During the return stroke of the hammer piston gas is driven from one chamber to another chamber through a slot. When the hammer piston exceeds its normal range of operation gas is driven through the slot in the other direction and also through a channel in the machine housing so that a weaker damping is obtained than during the return stroke. A hammer mechanism to be operated according to the above method is also disclosed.