| 摘要 |
A subsurface well tool having a hydraulic piston and cylinder assembly actuator which is adapted to be connected to and controlled by a hydraulic control line extending to the well surface. The assembly has a cross-sectional area exposed to the hydraulic control fluid which increases in one direction of movement of the assembly and decreases in the opposite direction for reducing surface operating pressure problems. Preferably, one of the piston and cylinder includes a tapered surface, and includes a flexible seal between the piston and cylinder.
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