| 摘要 |
PCT No. PCT/FI92/00085 Sec. 371 Date Sep. 24, 1993 Sec. 102(e) Date Sep. 24, 1993 PCT Filed Mar. 25, 1992 PCT Pub. No. WO92/16718 PCT Pub. Date Oct. 1, 1992.An apparatus comprising a rotatable tool having a drill head and a method for regulating the penetration of the apparatus in rock or soil are disclosed. In particular, the apparatus and method of the invention are designed to prevent damage to drill bits mounted on the drill head when any one of the drill bits encounters an excessive opposing force as, for example, would result if the drill bits impacted a rock when drilling in soil. The apparatus includes mechanism for detecting the excessive force acting on one or more drill bits and automatically restricts the driving force which moves the tool forward. |
