US Patent 7431078 Using pipe shrinkage upon expansion to actuate a downhole tool

A downhole tool with a mandrel that is expanded downhole is further actuated due to relative longitudinal movement between the mandrel and a member that accommodates radial expansion without undergoing as much shrinkage as the expanded mandrel or any shrinkage at all. In a packer application, the packer can be set in open hole or cased hole and the relative longitudinal movement that results from mandrel expansion leaves a residual longitudinal compressive force on the sealing element and a tensile reaction force on the underlying mandrel.