| 摘要 |
This invention relates to a rotary drill bit having a body with leg members, where each of the leg members has a projecting conical cutter receiving journal. A conical cutter having an axially extending recess open at one end has friction reducing bearings interior to the conical cutter for rotatably mounting the cutter on the journal. A plurality of lubricant carrying conduits interior to the leg members extending into the bearings provides lubricant for the bearings. This invention provides an improved sealing arrangement for preventing an excessive loss of lubricant from the bearings. The conical cutter is adapted with seal receiving grooves at its open end of the recess to receive two seals, with a circumferential seal gap located between the seals. The outer seal is less rigid than the inner seal and when the circumferential seal gap is supplied with lubricant it bleeds past the outer seal to wash away drilling debris. Lubricant can be supplied to the circumferential seal gap by lubricant carrying conduits which carry lubricant from the bearings and/or separate reservoirs, or the inner seal could be a hydrodynamic seal which permits migration of some of the lubricant from the bearings into the circumferential seal gap but prevents contaminates and lubricant from the circumferential seal gap from traveling past the hydrodynamic seal back into the bearings. |
