| 摘要 |
<p>The tool, for example an underreamer for descaling a casing (46), has an upper body (10) telescoped within a lower body (12) on which are pivoted operating arms (22). The arms (22) are deployed from a retracted to an extended position by the hydraulic pressure of drilling mud pumped through a through-bore (18) against a shoulder (26) causing the upper body (10) to move within the lower body (12), which movement pivots the arm (22) via camming surfaces (28,29). In the fully extended position, an outer surface (44) of the arm (22) acts as a locating pad, and the arm is mechanically locked by mating surfaces (34,36).</p> |
