| 摘要 |
PCT No. PCT/AU93/00135 Sec. 371 Date Dec. 16, 1994 Sec. 102(e) Date Dec. 16, 1994 PCT Filed Mar. 31, 1993 PCT Pub. No. WO93/20322 PCT Pub. Date Oct. 14, 1993.A drill stem arrangement and method in which the motor for providing the hammer action is in the drill stem near to the drill bit. The motor is driven by pressurised liquid and a proportion of the liquid is used for flushing drill cuttings and cooling the drill bit. |
