Earth boring bit and lubricator/compensator therefor

A well drilling bit comprising:

• a bit body including a centralized portion and a plurality of radially and circumferentially spaced legs depending longitudinally from the centralized portion;
• a respective cutter body rotatably mounted on the free end of each leg with bearing means cooperative between each leg and the respective cutter body;
• wherein the bit body has a respective lubricant passage therethrough communicating with each bearing and with a generally upwardly opening lubricant reservoir recess in the bit body distal the respective bearing;
• and
• a respective lubricating mechanism in each lubricant reservoir recess, each lubricating mechanism comprising
• an elastomeric compensator diaphragm extending generally laterally across the respective recess and dividing the recess into a lower zone communicating with the respective lubricant passage and otherwise closed, and an upper zone including an open mouth of the recess, the diaphragm including an annular, peripheral, radially outwardly projecting flange having at least one annular, axially acting, compression spring therein and elastomeric material at least partially covering the spring;
• a cap disposed above the diaphragm in the recess for releasably retaining the diaphragm in the recess with the spring at least slightly deflected, and defining a vent communicating the upper zone with the exterior of the bit body;
• first seal means cooperative between an underside of the flange and a generally upwardly facing shoulder in the recess, sealing the diaphragm to the bit body in a generally axial direction with respect to the recess;
• and second seal means cooperative between an upper side of the flange and a lower, axially facing end surface of the cap, sealing the diaphragm to the cap in a generally axial direction with respect to the recess.