Fasteners

Claim 1

A FASTENER FOR EXERTING AN ASSEMBLING FORCE ON A WORKPIECE MEMBER COMPRISING, IN COMBINATION, A PIN HAVING A LONGITUDINAL AXIS AND EXTERIOR CIRCUMFERENTIAL THREADS; A COLLAR MEMBER COMPRISING A TUBULAR PORTION WITH AN AXIS AND AN AXIAL INTERNALLY THREADED PIN-RECEIVING HOLE THERETHROUGH, SAID COLLAR MEMBER HAVING A BEARING SECTION AND A WRENCH-ENGAGING SECTION, A BEARING SURFACE ON SAID BEARING SECTION LYING SUBSTANTIALLY NORMAL TO THE COLLAR AXIS AND SURROUNDING SAID AXIS, WRENCH-ENGAGING SURFACES ADJACENT TO THE WRENCH-ENGAGING SECTION, AND A CIRCUMFERENTIAL GROOVE LOCATED BETWEEN SAID SECTIONS, SAID GROOVE PROVIDING A REDUCED CROSS-SECTION HAVING THE MINIMUM SHEAR STRENGTH OF SAID COLLAR WHEREBY THE WRENCHENGAGING SECTION WILL SHEAR AT A PREDETERMINED TORQUE; AND A SUBSTANTIALLY INCOMPRESSIBLE WASHER HAVING A SUBSTANTIALLY FLAT SIDE LYING SUBSTANTIALLY NORMAL TO SAID BEARING SURFACE, SAID WASHER HAVING A HOLE THERETHROUGH THROUGH WHICH THE PIN CAN EXTEND AND SUPPORT THE WASHER BETWEEN THE COLLAR MEMBER AND THE WORKPIECE MEMBER, AND A LAYER OF A SUBSTANTIALLY DRY LUBRICANT ON AND ADHERENT TO SAID FLAT SIDE, WHEREBY WHEN THE THREADED PORTION OF THE PIN PROTRUDES FROM THE WORKPIECE AND THE WASHER, THE COLLAR MEMBER CAN BE THREADED ONTO THE PIN AND TIGHTENED DOWN AGAINST THE WASHER, THE LUBRICANT COMPRISING A LAYER BETWEEN THE WASHER AND THE MEMBER AGAINST WHICH THE WASHER IS HELD SO THAT WHEN THE COLLAR IS TURNED BY A FORCE EXERTED ON THE WRENCH-ENGAGING SURFACES AND IS THEREBY ROTATED RELATIVE TO THE PIN, EXERTION OF TORQUE CAUSES THE SECTION OF THE COLLAR MEMBER BEARING THE WRENCH-ENGAGING SURFACES TO SHEAR OFF, LEAVING THE REMAINDER OF THE COLLAR MEMBER ON THE PIN, THE LUBRICANT LAYER SERVING TO MAINTAIN THE COEFFICIENT OF FRICTION UNIFORM BETWEEN THE LUBRICATED SIDE OF THE WASHER AND THE MEMBER IN CONTACT WITH SAID SIDE, THE LUBRICANT LAYER BEING OF SUBSTANTIALLY FILM THICKNESS, AND EXISTING ONLY ON AN EXTERIOR SURFACE OF THE WASHER.