Screw fasteners and terminal boards incorporating the same

Claim 1

A SCREW FASTENER OF THE SELF-THREADING TYPE COMPRISING AN ELONGATED SHANK, AN ENLARGED HEAD TERMINATING THE REAR END OF SAID SHANK, A FIRST THREAD CARRIED BY THE FRONT PORTION OF SAID SHANK AND INCLUDING A NUMBER OF HELICAL TURNS AND HAVING A FIRST FIXED PITCH, AND A SECOND THREAD CARRIED BY THE REAR PORTION OF SAID SHANK AND INCLUDING A NUMBER OF HELICAL TURNS AND HAVING A SECOND FIXED PITCH, THE FRONTMOST TURN OF SAID FIRST THREAD TERMINATING ADJACENT TO THE FRONT END OF SAID SHANK AND THE REARMOST TURN OF SAID SECOND THREAD TERMINATING ADJACENT TO THE REAR END OF SAID SHANK, THE REARMOST TURN OF SAID FIRST THREAD AND THE FRONTMOST TURN OF SAID SECOND THREAD BOTH TERMINATING ADJACENT TO THE BOUNDARY BETWEEN THE FRONT AND REAR PORTIONS OF SAID SHANK AND CLOSELY ADJACENT TO AND IN ALIGNMENT WITH EACH OTHER SO THAT SAID FIRST AND SECOND THREADS CONSTITUTE CONTINUATIONS OF EACH OTHER ALONG SAID SHANK, SAID FIRST AND SECOND THREADS HAVING SUBSTANTIALLY THE SAME MAJOR DIAMETER AND HAVING SUBSTANTIALLY THE SAME MINOR DIAMETER AND SAID FIRST AND SECOND PITCHES BEING SUBSTANTIALLY DIFFERENT FROM EACH OTHER, THE ROOTS OF THE TURNS OF SAID FIRST THREAD HAVING A GREAT AMOUNT OF TRUNCATION AND THE ROOTS OF THE TURNS OF SAID SECOND THREAD HAVING A SMALL AMOUNT OF TRUNCATION, WHEREBY IN THE FORWARD DRIVING MOVEMENT OF SAID FASTENER INTO A SET POSITION WITH RESPECT TO AN ASSOCIATED WORKPIECE SAID FIRST THREAD FORMS A CORRESPONDING FIRST THREADED STRUCTURE IN THE WORKPIECE PILOT HOLE AND THEN SAID SECOND THREAD BREAKS-UP THE FIRST THREADED STRUCTURE MENTIONED AND FORMS A CORRESPONDING SECOND THREADED STRUCTURE IN THE WORKPIECE PILOT HOLE, AND WHEREBY IN INITIAL RETROGRADE MOVEMENT OF SAID FASTENER FROM ITS SET POSITION INTO A PARTIALLY WITHDRAWN POSITION WITH RESPECT TO THE WORKPIECE SAID SECOND THREAD ROTATES READILY IN THE SECOND THREADED STRUCTURE MENTIONED AND IN FURTHER RETROGRADE MOVEMENT OF SAID FASTENER BEYOND ITS PARTIALLY WITHDRAWN POSITION WITH RESPECT TO THE WORKPIECE SAID FIRST THREAD BINDS IN THE SECOND THREADED STRUCTURE MENTIONED, THEREBY EFFECTIVELY TO SECURE SAID FASTENER TO THE WORKPIECE AND TO ESTABLISH A LIMITED RANGE OF SUBSEQUENT READY MOVEMENTS OF SAID FASTENER BETWEEN ITS SET POSITION AND ITS PARTIALLY WITHDRAWN POSITION.