Importance

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Abstract

A roller cutter drill bit detachably secured to a drill string for delivering drilling fluid under pressure to the bit, comprising a plurality of bearing journals at its lower end and passaging extending down in the bit body to each of the journals for flow of the drilling fluid from the drill string to the journals. The bit further comprises a plurality of roller cutters, each having a bore adapted to receive a respective journal, and bearings in the annular cavity between each roller cutter and the respective journal for rotatably mounting the roller cutter on the journal. The drilling fluid when supplied in sufficient quantity flowing through the passaging, past the bearing means and exiting the bit in the bore via the bearing cavity for cooling and cleaning the bearings, but when supplied in insufficient quantity boring cuttings being allowed to enter the bearing cavity and fouling the bearings. In accordance with this invention, the bit is provided with a flush-out port in flow communication with the passaging to the journals for enabling fluid under pressure from a second source other than the drill string to be selectively delivered to the bearings for flushing the bearing cavity when the bit is outside the bore. A plug closes the flush-out port when the bit is not being flushed.

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First Claim