| 摘要 |
An apparatus comprising a downhole tool having a body defining an outer surface, a plurality of standoffs distributed about the outer surface, and a hydraulic circuit operatively coupled to the standoffs. The hydraulic circuit includes a plurality of hydraulically actuated pistons, each of which is operatively coupled to a respective one of the standoffs to extend and retract the respective standoff. The pistons are hydraulically coupled and sized to extend or retract the respective standoffs at substantially the same rate in response to a hydraulic control signal.
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