| 摘要 |
PCT No. PCT/EP88/00085 Sec. 371 Date Oct. 24, 1988 Sec. 102(e) Date Oct. 24, 1988 PCT Filed Feb. 5, 1988 PCT Pub. No. WO88/06673 PCT Pub. Date Sep. 7, 1988.A drilling device for drilling a borehole and comprising a drilling tool, a drill pipe extending into the borehole for conducting a flow of liquid thereinto for generating an oscillating percussion force applied to the drilling tool, a longitudinally movable impulse tube located below a lower end of the drill tube, a throttle located between a lower mouth of the drill tube and an upper mouth of the impulse tube for controlling a ration of flow portion of the liquid outside and inside the impulse tube in accordance with longitudinal position thereof, and a spring-loaded thrust valve for controlling the flow of liquid inside the tube. |
