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US 5,520,255 AGranted
Modulated bias unit for rotary drilling
AssigneeCamco Drilling Group Limited
InventorsJohn D. Barr, Richard E. Thorp, Robert A. Russell
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AssigneeCamco Drilling Group Limited
InventorsJohn D. Barr, Richard E. Thorp, Robert A. Russell
Estimating the term…
A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled. A selector control valve modulates the fluid pressure supplied to each actuator in synchronism with rotation of the drill bit so that, as the drill bit rotates, each movable thrust member is displaced outwardly at the same selected rotational position so as to bias the drill bit laterally and thus control the direction of drilling. The control valve is a disc valve comprising two relatively rotating elements having contiguous surfaces formed of polycrystalline diamond. The elements are maintained in coaxial relation by a polycrystalline diamond bearing pin which extends axially from one element and engages in a central axial bearing aperture in the other element.
A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprising at least one hydraulic actuator having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled, a selector control valve which modulates fluid pressure supplied to the actuator in synchronism with rotation of the drill bit, and in selected phase relation thereto so that, as the drill bit rotates, the movable thrust member is displaced outwardly at the same selected rotational position so as to bias the drill bit laterally and thus control the direction of drilling, the control valve being a disc valve comprising two relatively rotating elements having contiguous surfaces formed of polycrystalline diamond, and the rotating elements being maintained in coaxial relation by a bearing pin of superhard material which extends axially from one disc and engages in a central axial bearing aperture in the other disc.
Dependencies are inferred from the claim text.