US Patent 7624797 Downhole tool operated by shape memory material

The invention features the use of a shape memory material in a downhole application to provide an energy source for at least in part setting the tool. In a specific application the springs that set slips for a liner hanger are made from the shape memory material and easily pre-compressed below the transition temperature when the material has low modulus of elasticity. The tool is run into position where a heat source such as well fluids or a heater can bring the springs above the transition temperature to store a force. The tool is then independently released to allow the stored force to set the tool.