| 摘要 |
<p>1534445 Boring earth DRESSER INDUSTRIES INC 25 Feb 1976 [27 Feb 1975] 07465/76 Heading E1F In a roller-cutter drill bit 10, each cutter 14 is mounted on a spindle 13 by a bearing system including roller bearings 16 running in a raceway groove in the cutter 14, a seal 20 being provided between the cutter 14 and spindle 13. As described the bearing system includes roller bearing 16, ball bearing 17, friction bearing 18 and thrust button 19. In a first embodiment, as shown, the flushing fluid is air which is circulated through passages 27, 22, 26 to cool the spindle 13 and bearing system, the air being prevented from entering the bearing system by seal 24. In a second embodiment (not shown) which uses liquid as the flushing fluid, the bearing is supplied with lubricant from a reservoir whose pressure is equalised with the hydrostatic pressure in the borehole by means of a flexible diaphragm.</p> |
