| 摘要 |
A downhole tool (110) comprises a body (112) defining a chamber, with a piston (124, 126) axially movable in the chamber in a first direction from a first position in response to an applied pressure force. The tool further comprises a member (116) movable in an opposite second direction, and a ratchet assembly (120) between the piston and the member permitting movement of the piston in said first direction without corresponding movement of the member, and coupling the piston to the member when the piston is moved in said second direction. The tool also comprises means (134) for biassing the piston in said second direction towards said first position, whereby movement of the piston in the first direction may be translated to corresponding movement of the member in the second direction. <IMAGE> |
