| 摘要 |
A sealed rotary drill bit has a plurality of leg members, with each leg member having a projecting conical cutter receiving journal. A conical cutter has friction reducing bearings interior to the conical cutter for rotatably mounting the cutter on the respective journal. A sealing arrangement retains lubricant for the bearings. A circumferential porous gas restrictor is positioned concentric with and spaced outwardly from the sealing arrangement to form an annular gas chamber therebetween. Pressurized gas is carried by passageways into the annular gas chamber. The porous gas restrictor, which can be formed of metal particles bonded together, prevents drilling debris from getting past it, but the porosity of the restrictor allows pressurized gas to pass therethrough as a controlled dissipation and wash away drilling debris, thereby shielding the sealing arrangement from debris that might otherwise reach the sealing arrangement. The sealing arrangement can include an inner seal and an outer seal positioned concentric to each other with the circumferential seal gap therebetween filled with lubricant. |
