| 摘要 |
<p>An apparatus for tunnelling through soil, of the type in which a conical cutting head is rotatably mounted coaxially on a cylindrical housing and a toothed cutter bar is mounted radially on the cutting head adjacent an aperture in the cutting head. A flood door is mounted on the cutting head and is movable to open or close the aperture. Preferably a pair of doors are individually operable to converge or diverge in varying the size of the aperture. The cutter bar may be movable radially outward beyond the circumference of the cutting head to describe an arcuate path eccentric to the face of the cutting head.</p> |
