| 摘要 |
An elongated body, capable of serving as a length of drill string, has two major portions with each portion providing an end for connection to the drill string with drilling fluid channels extending from end to end. One portion extends into the other and is hinged therein for deflection of the center lines of opposite ends. A piston in the body responds to drilling fluid flow to actuate the deflection of a few degrees. A turret carried by the body has a cam and groove relationship with the structure carried by the piston such that it turns one increment each time the piston makes a round trip of axial excursions. On alternate round trips of excursions, the piston is stopped short of the movement needed to deflect the body and instead holds the body straight until the fluid flow is reduced to begin another piston excursion. An internal valve is operated by the piston to cause a pressure rise in the drilling fluid stream when the piston moves enough to deflect the body. The fluid pressure change is detectable at the surface to indicate to the driller that the deflected state then exists.
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