Patent ID: 8347986

Claim:
A roller cone drill bit operable to form a wellbore extending through a downhole formation comprising: a bit body having at least one support arm extending therefrom; a respective cone assembly rotatably mounted on a journal extending from each support arm; a respective lubricant container disposed in each of the at least one support arms; a lubricant passageway disposed in each of the at least one support arms to communicate lubricant between the respective lubricant container and at least one bearing surface associated with rotation of the respective cone assembly mounted on each of the at least one support arms; at least one opening formed in exterior portions of the lubricant container to accommodate communication of lubricant with the lubricant passageway; the lubricant container having a first end exposed to downhole well fluid pressure while drilling the wellbore; a pressure release mechanism disposed within the first end of the lubricant container; the pressure release mechanism operable to release lubricant from the first opening in the lubricant container when lubricant pressure within the lubricant container exceeds pressure of downhole well fluids proximate to the first opening of the lubricant container by a selected amount; the pressure release mechanism including a piston disposed within the first end of the lubricant container; the piston having a first, closed position blocking release of lubricant through first opening in the lubricant container; the piston having a second, open position operable to allow release of lubricant through the first opening in the lubricant container; and a biasing mechanism disposed within the lubricant container to maintain the pressure relief mechanism in its first, closed position until lubricant pressure in the lubricant container exceeds downhole well fluid pressure adjacent to the first end of the lubricant container by the selected amount.