Pneumatic hammer

PCT No. PCT/EP92/02434 Sec. 371 Date Jun. 22, 1993 Sec. 102(e) Date Jun. 22, 1993 PCT Filed Oct. 23, 1992 PCT Pub. No. WO93/08363 PCT Pub. Date Apr. 29, 1993.A pneumatic hammer is provided with an adjusting piston (37) dependent on the supply pressure, which adjusts the stroke length of the working piston (16). Thereby, the same pneumatic hammer may be operated both at low and high supply pressures. With high supply pressures, either the early ending of the acceleration phase or the early start of the compression phase or the shortening of the working cylinder shortens the stroke length. Thereby, the pneumatic hammer performs impacts with a substantially constant single-impact energy, regardless of the supply pressure. High supply pressures increase the impact frequency. This results in a considerably improved efficiency at a high drill capacity, a reduced wear and a reduced risk of ruptures of the components of the hammer.