Fluid actuated retrievable well tool

Claim 1

IN A WELL TOOL ADAPTED TO BE LOWERED IN A WELL BORE ON A RUNNING-IN STRING: A BODY STRUCTURE HAVING A GENERALLY RADIAL CYLINDER THEREIN; A GRIPPING MEMBER MOVABLE IN SAID CYLINDER; MEANS FOR CONDUCTING FLUID UNDER PRESSURE TO SAID CYLINDER AND AGAINST SAID GRIPPING MEMBER TO SHIFT SAID GRIPPING MEMBER AGAINST THE WELL BORE TO ANCHOR SAID BODY STRUCTURE IN THE WELL BORE; MEANS IN SAID CONDUCTING MEANS THROUGH WHICH THE CONDUCTED FLUID MUST PASS IN EXPANDING SAID GRIPPING MEMBER FOR TRAPPING SAID FLUID UNDER PRESSURE IN SAID CYLINDER TO PREVENT RELEASE OF SAID GRIPPING MEMBER FROM THE WELL BORE; AND MEANS SEPARATE FROM SAID TRAPPING MEANS AND OPERABLE BY THE RUNNING-IN STRING FOR RELIEVING SAID FLUID UNDER PRESSURE TO RELEASE SAID GRIPPING MEMBER FROM THE WELL BORE.