| 摘要 |
<p>An apparatus for overdrilling a buried line includes a rotatably driven thrust linkage and/or traction linkage, and has a forward end which is connected to a ring-shaped to hollow cylindrical overdrilling head which embraces the line. The overdrilling head is provided interiorly with a centering protrusion for spontaneous centering of the overdrilling head in concert with the line.</p> |
