Sheet metal expansion anchor adapted to clamp the screw upon insertion thereof

Claim 1

AN EXPANSION FASTENER FOR SCREWS, COMPRISING, A ONE-PIECE LENGTH OF SHEET METAL HAVING AN ENLARGED CENTRAL PORTION AND FIRST AND SECOND ARMS EXTENDING IN SIDE-BYSIDE PARALLELISM FROM RESPECTIVELY OPPOSITE EDGES OF SAID PORTION, SAID ARMS BEING ARCUATE IN TRANSVERSE SECTION TO CONJOINTLY DEFINE A TUBULAR PASSAGEWAY FOR A SCREW, SAID PASSAGEWAY HAVING A CENTRAL LONGITUDINAL AXIS, THE SIDE EDGES OF SAID ARMS BEING FLANGED OUTWARDLY SUBSTANTIALLY RADIALLY OF SAID AXIS AND HAVING PENETRATING POINTS SPACED UNIFORMLY THEREALONG, THE DISTAL ENDS OF SAID ARMS CONVERGING TOGETHER TO FORM POINTS OF CONTACT WITH A SCREW, FOR SEPARATING SAID ARMS, THERE BEING AN I-SHAPED OPENING IN SAID PORTION, CENTRALLY THEREOF, WITH ITS AXIS OF SYMMETRY NORMAL TO SAID LONGITUDINAL AXIS, SAID PORTION BEING FOLDED ALONG A LINE OFFSET FROM AND PARALLEL WITH SAID AXIS OF SYMMETRY TO POSITION IN LONGITUDINALLY OFFSET RELATION, CORRESPONDING CONTIGUOUS PENETRATING POINTS OF THE RESPECTIVE ARMS, SAID OPENING DEFINING A PAIR OF OPPOSITELY-DISPOSED, SPACED, UPSTANDING LUGS EXTENDING FROM THE ENDS OF SAID ARMS AND CONVERGING AT THEIR TOP ENDS TO FORM SCREW-ENGAGING POINTS, THE DIAMETER OF SAID TUBULAR PASSAGEWAY BEING SUBSTANTIALLY GREATER THAN THE DISTANCE BETWEEN SAID LUGS AND SAID DISTAL ENDS, SAID ARMS EXPANDING ABOUT A TRANSVERSE AXIS BELOW AND ADJACENT SAID POINTS, IN RESPONSE TO PASSAGE OF A SCREW BETWEEN THE DISTAL ENDS OF SAID ARMS, WHEREBY SAID SCREW-ENGAGING POINTS OF SAID LUGS ARE URGED TOGETHER.