One sided fastener device

Claim 1

A blind fastener assembly for clamping a plurality of complementary plate-like workpieces together with access from only one side thereof, comprising a threaded fastener member with a radially enlarged driving head including rotation inducing surfaces, a sleeve member comprising a tubular body with a head provided with means to resist rotation when said sleeve is mounted in a complementary workpiece at an outer end thereof and a gradually tapered portion at its distal end, the tapered portion of said sleeve comprising two frustoconical sections of different and successively greater angles of taper from the body to the distal extremity of said sleeve, the body of the sleeve member being generally cylindrical of a predetermined diameter substantially equal to the diameter of apertures formed in the complementary workpieces, the threaded fastener member extending through the sleeve so that the distal end of the fastener projects beyond the distal end of the sleeve, the tapered portion including rib means formed thereon and extending generally longitudinally thereof to the free extremity of the sleeve, an expansion member including an internally threaded first end portion threadingly engaging the distal end of the fastener and a workpiece clamping second end portion, said second end portion being generally tubular with an outer diameter substantially equal to the predetermined diameter of the sleeve body and an inner diameter greater than the diameter at the free extremity of the tapered section but less than the diameter at the juncture of the two frustoconical sections, generally longitudinally extending slot means extending through the second end portion toward the first end portion, the slot means forming a pair of wing-like tubular segments adapted to be deflected radially outwardly as the expansion member is pulled upwardly over the tapered section of the sleeve as a result of rotation of the screw relative to the expansion member, the slot and rib means coacting to prevent relative rotation between the expansion member and sleeve member, the uppermost edge of each wing-like tubular segment being convex toward the head of the sleeve thereby lying in a plane inclined downwardly toward the slot when the expansion member is in an unexpanded condition but adapted to lie in a plane substantially perpendicular to the axis of the fastener assembly when expanded to clamp the bottommost plate with line contact.