| 摘要 |
<p>A rotary roller reamer (10) for a borehole has several rollers (11). Each roller (11) rotates about a fixed spindle (13) held at its ends in wedge blocks (14). The spindle (13) has two central passages (19), one at each end. At one end, passage (19) contains a freely slidable piston (21), which is subject to external pressure via a breather aperture (22). The other end passage (19) is blocked by a pressure plug (27) which, when removed, permits injection of grease through passages which include the bearing surfaces of the roller (11) and spindle (13). External pressure is applied to the grease through piston (21), so that there is little or no pressure differential to otherwise force mud into the bearing.</p> |
