Percussion boring device and method for reversing a percussion boring device

A percussion boring device comprising:

• a casing;
• a guide tube fixed to the casing;
• an impact piston configured to be actuated in a reciprocating manner within the casing;
• a control bushing axially displaceable on the guide tube to (i) a first switching position to actuate the percussion boring device in a first movement direction in which the impact piston strikes a front impact surface, and to (ii) a second switching position to actuate the percussion boring device in a second movement direction in which the impact piston to strike a rear impact surface, wherein the impact piston is also axially displaceable on the control bushing;
• a control line operatively coupled to the control bushing, and a control valve;
• a control pressure source, in fluid communication with the control valve, operative to generate a high fluid pressure for axially displacing the control bushing to the first switching position for movement of the percussion boring device in the first movement direction, the high fluid pressure generated by the control pressure source being higher than an operating pressure for actuating the impact piston in the reciprocating manner in the first movement direction and the second movement direction;
• and
• wherein the control valve in a first position is operative to apply a pressure lower than the operating pressure to the control bushing to place the control bushing in the second switching position for movement of the percussion boring device in the second movement direction, and
• wherein the control valve in a second position is operative to apply the high fluid pressure from the control pressure source to place the control bushing in the first switching position for movement of the percussion boring device in the first movement direction.

A method for operating a percussion boring device including an impact piston in a forward movement direction and a reverse movement direction, the forward movement direction configured to strike a front impact surface to actuate the percussion boring device and the reverse movement direction configured to strike a rear impact surface to actuate the percussion boring device, and a control bushing axially displaceable on a guide tube for switching a movement direction of the impact piston, responsive to movement of the control bushing, comprising:

• applying an operating pressure to the impact piston to actuate the impact piston in a reciprocating manner within a casing in one of the forward movement direction and the reverse movement direction;
• applying, by a control pressure source operatively coupled with the control bushing, one of a first fluid pressure and a second fluid pressure for axially displacing the control bushing on the guide tube and bringing the control bushing into one of (i) a first switching position in which the impact piston strikes the front impact surface to actuate the percussion boring device in the forward movement direction by application of the first fluid pressure and (ii) a second switching position in which the impact piston strikes the rear impact surface to actuate the percussion boring device in the reverse movement direction by application of the second fluid pressure, wherein application of the first fluid pressure is selected via a control valve with a selectable position configured to cause a fluid pressure in a control pressure line to be increased above the operating pressure to cause the operating pressure to displace the control bushing to the first switching position to actuate the percussion boring device in the forward movement direction;
• wherein the second fluid pressure is lower than an operating pressure for moving the impact piston in the forward movement direction and the second movement direction.