| 摘要 |
A seal assembly (46) for a rotary drill bit (10) having a pressure balanced lubrication system is mounted in a pocket (48) between a journal (16) and a roller cutter (18). The seal assembly (46) has a pair of rigid seal rings (50, 52) in sliding sealing contact with each other and a pair of elastomeric seal rings (54, 56) in side by side relation sealing against the inner peripheral surfaces (62, 64) of the rigid seal rings (50, 52) for continuously urging the sealing faces (58, 60) of the rigid seal rings (50, 52) into sliding sealing contact. The pressure balanced lubrication system has a pressure compensating diaphragm (38) and lubricant passages (40, 42, 44) extending directly from the lubricant reservoir (35) to the lubricant chamber (48A) in the pocket (48) for minimizing fluid pressure differentials between the lubricant chamber (48A) and the drilling fluid chamber (48B). Drilling fluid in the drilling fluid chamber (48B) acts against the rear faces (63, 65) of the metal seal rings (50, 52) to hold the sealing faces (58, 60) in sliding sealing contact.
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