| 摘要 |
PCT No. PCT/GB90/00892 Sec. 371 Date Jan. 23, 1991 Sec. 102(e) Date Jan. 23, 1991 PCT Filed Jun. 8, 1990 PCT Pub. No. WO90/15221 PCT Pub. Date Dec. 13, 1990.A moling system comprises a mole (10) having a head (26) with a slant face at the leading end of a string of hollow rods (20). The rods are rotatable by a rig (12). The mole is an impact mole fed by air passed through the rods. While the mole rotates it travels approximately straight, but nonrotating it travels according to the direction of the slant face (28). The mole contains a radio sonde having one coil lying lengthwise and one transverse to the lengthwise direction of the mole. A receiver (22) is traversed across the ground to locate the radio sonde and display roll angle. The mole is stopped from rotating at the correct position when steering is required and powered without rotating to change course. An impact activated switch in the mole switches off the battery supply while the impact mechanism is activated. |
