| 摘要 |
A downhole tool (100) for generating pressure pulses in a drilling fluid comprising an elongate body (107, 127) and a plurality of blades (116) spaced around the body. The blades are each divided into an independent front section (116a) and rear section (116b), forming a set of front sections and a set of rear sections, at least one of the set of front sections and the set of rear sections being mounted for rotation and being angularly displaceable relative to each other between a first position in which the sections are aligned and a second position in which the rear sections obstruct fluid flow between the front sections to generate a pressure pulse. The tool includes a first set of driving blades in front of the blades (116) for generating a torque on the blade sections, the driving blades being curved in a first direction, and an escapement means (129) which is radially movable to permit stepwise rotation of the blade sections, and thus to move the blade sections between the first and second positions. The tool additionally comprises a set of stator blades (162) positioned in front of the set of front sections. The stator blades are curved in a second direction opposite to the first direction.
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