| 摘要 |
A rotary steerable tool for use in a downhole drilling apparatus for adjusting the direction of drilling. The tool comprises a tubular outer housing (18 Fig 1B) and a row of steering pushers 24 slidably mounted to the housing for movement between an extended position, in which the steering pusher engages a wall of a borehole, and a withdrawn position. A tubular sleeve (4 Fib 1A) is mounted inside the housing to transmit rotary drive to a drilling bit. A pressure chamber 22 defined between the sleeve and the housing communicates with the steering pushers to move the steeling pushers to the extended position. A piston 56 is slidably mounted in the sleeve and is moved by means of changes in drilling fluid pressure between a first axial position, in which the interior of the sleeve communicates directly with the pressure chamber for directional drilling, and a second axial position, in which the interior of the sleeve does not communicate directly with the pressure chamber for straight drilling. The piston or sleeve may have a guide track 64 and guide follower means 66 for retaining the piston in the first or second axial positions and the piston may be biased towards a third axial position by a biasing means 74. Also disclosed is a clutch mechanism coupling the housing to the sleeve and an indicator means for indicating the relative position of the housing to the sleeve. |
