Permanently set bridge plug

Claim 1

IN A WELL TOOL HAVING A BODY, SLIP AND EXPANDER MEANS ON SAID BODY OPERABLE IN RESPONSE TO LONGITUDINALLY DIRECTED SETTING FORCES APPLIED THERETO FOR ANCHORING THE TOOL IN A WELL CONDUIT, SAID SLIP MEANS BEING MOVABLE OUTWARDLY OF SAID BODY, AND A PACKING MEANS ON SAID BODY EXPANDABLE IN RESPONSE TO SAID SETTING FORCES FOR PACKING OFF THE WELL CONDUIT, THE IMPROVEMENT COMPRISING, IN COMBINATION, ANNULAR RESTRAINING MEANS ENCIRCLING AND ENGAGING SAID SLIP MEANS, SAID RESTRAINING MEANS BEING CONSTRUCTED OF A DUCTILE, STRETCHABLE MATERIAL WITH A PREDETERMINED YIELD STRENGTH SUCH THAT THE OPERATION OF SAID SLIP AND EXPANDER MEANS CAN BE DELAYED UNTIL SAID PACKING MEANS CAN BE SUBSTANTIALLY EXPANDED AND, AFTER YIELDING, SAID RESTRAINING MEANS CAN FUNCTION TO CONTROL OUTWARD MOVEMENT OF SAID SLIP MEANS.