Importance

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Abstract

A rolling cutter drill bit comprises a main body and three depending legs, each leg having a cantilevered bearing spindle on which a rolling cutter is rotatably mounted. Bearings located between the cutter and spindle include a radial bearing, and a thrust bearing configured to carry onward thrust loads from the cutter onto the spindle. A bearing seal defines an enclosed region between the cutter and the spindle in which the bearings are located, and a pressure balanced lubricant delivery system within the spindle delivers lubricant to the bearings. The lubricant delivery system includes a non-return valve to allow lubricant to flow into the area of the enclosed region containing the thrust bearing and the area is bounded by a tortuous flow path which allows a more restricted flow of lubricant out of the thrust bearing area and into another area of the enclosed region, without pressurizing the bearing seal. The non-return valve may be replaced by a flexible barrier ring in the tortuous path which deflects to allow a greater flow of lubricant into the thrust bearing area.

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First Claim