Patent ID: 7874382

Claim:
A ram boring device, comprising: a casing, a percussion piston disposed inside the casing and constructed for back and forth movement; a control pipe immovable in an axial direction and having at least one control opening, said control pipe being configured as a rotary valve for rotation between a first position and a second position, a control sleeve disposed in surrounding relationship to the control pipe between the control pipe and the percussion piston, said control sleeve being constructed to define a control chamber with the control pipe, and a substantially torsion-resistant operational-air line rotatably coupled to the control pipe for supply of operational air to the control chamber to axially move the control sleeve from a forward position to a backward position, when the control pipe is turned to the first position, wherein the control chamber is vented, when the control pipe is rotated to the second position to thereby allow movement of the control sleeve from the backward position to the rearward position.