Dual-diaphragm lubricant compensator for earth-boring bits

摘要

An earth-boring bit has a bit body and at least one saddle member secured to the bit body to receive and support each of a pair of ends of a journal member. A cutter is mounted for rotation on the journal member and a bearing is defined between the cutter and journal member. A lubricant reservoir is formed in the journal member to receive a quantity of lubricant and is in fluid communication with the bearing. A seal means is provided between the cutter and journal member to retain lubricant in the bearing. A hydrostatic-pressure compensator is disposed in the lubricant reservoir in communication with hydrostatic-pressure in the borehole in which the bit operates. The hydrostatic-pressure compensator responses to hydrostatic-pressure to equalize a pressure differential across the seal means. An internal-pressure compensator is disposed in the lubricant reservoir and is responsive to the internal pressure of the lubricant to prevent the lubricant from being extruded past the seal means.