operational air line can be rotatably connected to a rotary valve that supplies the control chamber with operational air or vents air from the chamber application_number US 9401306 A description the ram boring device shown in to fig1 includes a casing 1 having an interior for accommodation of a stop ring 2 with axis parallel vent channels 3 a control pipe 4 immovably supported in the casing 1 and supplied with operational air via a torsion resistant hose the front end of the control pipe 4 projects into a chamber 7 which is part of a percussion piston 8 and provided with control openings 6 an axially movable control sleeve 10 which is movably supported on the control pipe portion 11 of greater diameter is disposed between the control pipe 4 and the outer jacket 9 of the percussion piston chamber 7 an outer collar 12 is located at the front end surface of the control pipe 4 or control pipe portion 11 of greater diameter and covers the front face of the control sleeve 10 and is flush with the control sleeve 10 fig2 a furthermore control openings 13 are arranged in the front section 11 of the control pipe 4 of greater diameter and are covered by the control sleeve 10 during forward operation of the ram boring device as illustrated in fig2 3 an inner collar 14 used to guide the control sleeve 10 on the outer pipe 15 surrounding the control pipe 4 is disposed in the rear section of the control sleeve 10 a control chamber 16 in which a connecting channel.