Blind rivet assembly

Claim 1

A blind rivet assembly comprising: a shell having an elongate shank, a head at one end, and a bore throughout the head and shank; a shell bore having a radially enlarged counterbore at a head end thereof and an annular locking shoulder facing towards the head end at a junction of the counterbore and a remainder of the bore; a shell shank having a weakened zone which extends longitudinally of the shank from a position spaced from the tail end of the shank towards the head end thereof; a stem extending through the bore of the shell and having an elongate pulling portion which projects from the head end of the shell, and an elongate plugging portion connected to the pulling portion by a breakneck and disposed substantially within the shell shank bore, the plugging portion being formed with a radially enlarged stem head at the end thereof remote from the breakneck, and disposed beyond the tail end of the shank, the plugging portion having a diameter greater than a diameter of the pulling portion; a cylindrical skirt surrounding a portion of said plugging portion adjacent said breakneck and forming an extension of said plugging portion, said skirt having an annular face facing said pulling portion and being separated from said plugging portion by a cleavage having a diameter substantially the same as said pulling portion; and an annular enlarged diameter bead defined on said pulling portion adjacent said breakneck, said bead having a tapered side and a diameter smaller than that of said skirt and greater than that of said cleavage; whereby, when the assembly is inserted through aligned apertures in workpieces to be thereby riveted together so that at least part of the shell shank zone projects beyond the workpiece on the blind side thereof, and the pulling portion of the stem is pulled with the increasing tension with respect to the shell by a pulling tool, compression exerted by the stem head on the shell shank tail end causes radial enlargement of at least part of the weakened zone of the shell shank to form a blind head, while the plugging portion moves through the shell bore towards the head end thereof and thereafter the shell shank tail end deforms to allow the entry of the stem head thereinto, and thereafter the skirt is deformable into locking engagement with the annular locking shoulder of the shell counterbore by a projecting rim of the tool, and the stem is fracturable at the breakneck to leave the plugging portion plugging the shell bore, whereby said annular bead guides said projecting rim into alignment with said skirt face.