| 摘要 |
Drill cuttings in the borehole are prevented from entering the area between the bearing pin and the cone cutter of a rotary rock bit by a cone mouth air screen. The cone cutter includes an internal cavity and a cone mouth positioned over the bearing pin. Bearings are located within the internal cavity between the bearing pin and the cone cutter. A passage extends through the bit body and the bearing pin for conducting a gaseous drilling fluid to the internal cavity for cooling the bearings. A screen means is positioned in the cone mouth between the cone cutter and the bearing pin for preventing solids in the borehole from entering the internal cavity and for allowing the circulating gaseous drilling fluid to pass from the internal cavity into the borehole.
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