| 摘要 |
<p>A drill string anchor (1) for use in a well bore, the anchor having a body (11), a through bore (12) and a plurality of anchor assemblies (13), each assembly comprising an anchor member (20), a piston (2) supported within a body and a biassing means (3). The piston is radially movable in response to fluid pressure in the through bore between a first retracted position and a second extended position in which the piston drives the anchor member into contact with the wall of the well bore. The biassing means acts to provide a force biassing the piston towards the first retracted position.</p> |
