Abstract: A fluid pressure compensator for a lubrication system in a rotary drill bit includes a diaphragm (44) with an enlarged thickness central portion (62) having a generally hemispherically shaped deformation (72) at its center to form a minimal thickness thereat progressively increasing to the enlarged thickness. A self sealing puncture (74) is provided at the center of the diaphragm (44) to relieve excess pressure differentials in the lubrication system internally of the drill bit and excess pressure differentials in the drilling fluid externally of the drill bit. The diaphragm (44) has an enlarged protuberance (64) about its outer periphery which is secured in sealing relation within a groove formed by sealing surfaces (66, 68, 70) on a leg (10) of the rotary bit and associated securing cap (46). A protective cup (42) supports the diaphragm (44) in an extended position and has dimples (58) for supporting the diaphragm (46) on the bottom (40) of the lubricant reservoir (49).

Abstract: A seal assembly for a roller cutter bit mounted in an annular cavity between a roller cutter and a journal. A mechanical spring on the roller cutter urges in an axial direction sealing faces on respective rigid seals into sealing engagement with each other against the bias of an opposed to elastomeric seal. Even upon permanent or compression set of elastomeric seal, the sealing force is maintained by the mechanical seal against the sealing faces on the rigid annular rings.

Abstract: A rotary drill bit comprising a bit body having at least one depending leg at its lower end having a generally cylindrical bearing journal, a roller cutter of generally conical shape having a recess therein receiving the journal a bearing system for rotatably mounting the roller cutter on the journal, and a lubrication system for providing lubricant to the bearing system comprising a reservoir of lubricant, passaging in the bit body for fluid communication between the reservoir and the bearing system, and a seal member between the roller cutter and the journal blocking flow of lubricant out of the bit body. The seal member is of annular shape and is held in a seal cavity between the roller cutter or the journal, with an annular engagement face thereof in sealing, sliding frictional engagement with one of the bearing members.

Abstract: A seal assembly for a rotary drill bit of the type comprising a bearing journal constituting a first bearing member, and roller cutter having a blind end bore therein, constituting a second bearing member, receiving the journal and an annular recess at the open end of the bore, the annular recess and journal defining an annular cavity in the bit. The seal assembly is positioned in the cavity for holding lubricant in the bit and comprises a ring of relatively rigid material movable with respect to the journal and the roller cutter in the longitudinal axial direction thereof and having a sealing face. An elastomeric seal member sealingly engages the movable ring and one of the bearing members and biases the ring to a position in which the sealing face of the ring is in sealing engagement.

Abstract: A dynamic seal is disclosed for sealing between a rotating cutter and a drill bit journal in an underground formation drilling bit, which seal utilizes a static elastomeric seal ring abutting a metal seal ring having a dynamic sealing face.