Hydraulically operated mandrels

摘要

Expandable tubular mandrels have lengthwise sections the upper ends of which are joined by a head. Hydraulically operated piston-cylinder units within the mandrel are spaced apart lengthwise of the sections and connected to the mandrel in a manner such that the axis of each unit extends lengthwise of the mandrel and expanding and contracting forces are applied to the mandrel sections when the units are operated to vary their overall length, to effect mandrel expansion when their overall lengths are changed in one direction and mandrel retraction when changed in the opposite direction.