Screw having roll-formed thread fully formed up to head thrust surface thereof

Claim 1

IN A HEADED SCREW HAVING ROLL-FORMED THREADS OF THE SAME HAND ON THE SHANK THEREOF AND BEGINNING AT THE LOWER END OF SAID SHANK, AND AN ENLARGED HEAD TERMINATING THE OPPOSITE END OF SAID SHANK AND HAVING AN UNDERFACE AND AN INDENTED PORTION ABOVE SAID UNDERFACE ADAPTED TO BE ENGAGED BY A TOOL FOR THE SCREW TO BE ROTATED AND ADVANCED AXIALLY OF SAID SHANK, THE IMPROVEMENT IN WHICH THE TOTAL UNDERFACE OF SAID HEAD COMPRISES A FRICTIONAL AREA, INCLUDING AN OUTER THRUST SURFACE IN A FLAT PLANE SUBSTANTIALLY NORMAL TO THE AXIS OF SAID SHANK AND AN ANNULAR CAVITY DISPOSED RADIALLY INWARDLY FROM SAID THRUST SURFACE, THE AREA OF SAID THRUST SURFACE BEING 70% TO 96% OF THAT PORTION OF SAID PLANE DIRECTLY UNDERLYING SAID UNDERFACE AND SAID ANNULAR CAVITY BEING POSITIONED ABOVE SAID PLANE AND ADJOINING THE JUNCTION OF SAID UNDERFACE AND SAID SHANK RADIALLY INWARDLY OF SAID ROLL-FORMED THREADS, WHEREBY SAID PLANE IS POSITIONED BELOW SAID JUNCTION AND DEFINES A SHANK LOWER PORTION DISPOSED BELOW SAID PLANE AND INCLUDING SAID LOWER END OF THE SCREW AND A SHANK UPPER PORTION DISPOSED ABOVE SAID PLANE, AND SAID ROLL-FORMED THREADS OF SAME HAND CONTINUE FROM SAID LOWER END OF THE SCREW UPWARDLY ON SAID SHANK LOWER PORTION AND INCLUDE AN UPPERMOST ROLLFORMED THREAD TERMINATING AT A THREAD-LIKE ROLL-FORMED STRUCTURE CARRIED BY SAID SHANK UPPER PORTION AND DISPOSED IN SAID ANNULAR CAVITY CLOSELY ADJACENT TO SAID JUNCTION, WHEREBY SAID ROLL-FORMED UPPERMOST THREAD OF THE ROLL-FORMED THREADS ON SAID SHANK LOWER PORTION IS AVAILABLE FOR THE SCREW TO ENGAGE FIRMLY EVEN A THIN WALL OBJECT AGAINST SAID THRUST AREA OF THE SCREW WHEN THE SCREW IS DRIVEN FOR THE PURPOSE BY MEANS OF A TOOL APPLIED TO THE INDENTED PORTION OF SAID SCREW HEAD.