| 摘要 |
An apparatus (10) for keeping a down hole drilling tool vertically uses a pendulum (36). The pendulum (36) controls flow from outlets (34) of drilling fluid chambers (30), providing drilling fluid to centralizer (24) activating pistons (26) acting upon centralizer blades (24). When the outer housing (12) deviates from a vertical orientation, the pendulum (36) swings by force of gravity to assume an angularly offset pivotal position. This adjusts the hydraulic pressure in one or two of the outlets (34) for one or two of the drilling fluid chambers (30) resulting in a change in the hydraulic force acting upon one or two of the pistons (26) causing one of the centralizers (24) to change their position to urge the outer housing (12) back toward the vertical position until the pendulum (36) again assumes the concentric pivotal position and the balanced pressure equilibrium in the drilling fluid chambers (30) is restored.
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