Blind rivet

Claim 1

A blind rivet type fastening device comprising: a thermo plastic hollow rivet and an integrally formed plastic setting mandrel made of the same material as the hollow rivet, said hollow rivet having an unbroken, continuous wall, hollow tubular cylindrical shank having a set head at one end of the tubular shank, said setting mandrel having a cylindrical draw shank telescopically received within said tubular rivet shank and being spaced from the tubular rivet shank by a cylindrical gap, and an enlarged mandrel head having a diameter larger than the internal diameter of the tubular rivet shank, said mandrel head extending axially beyond said tubular shank; a first frangible break joint extending radially inwardly from the end of the tubular shank towards the draw shank, bridging said space by a bead portion which establishes a readially inwardly tapered end of a blind bore establishing said cylindrical gap, said first joint and bead portion being an integral connection between the tubular shank and the draw shank of the mandrel; a second frangible break joint axially beyond said tubular shank and located between said draw shank and said mandrel head whereby axial force exerted on the mandrel draw shank to pull the mandrel head into the tubular shank will first break the first break joint by shear forces without imposing fracturing stress on the second break joint to permit axial movement of the mandrel and pull the mandrel head into the tubular shank to form the tubular shank into a closure head having outwardly bulging contour corresponding to the contour of the mandrel head whereby said bead portion being a thickened end of the shank grips around and hugs the mandrel head; and further axial force will break the second break joint to disconnect the draw shank from the mandrel head and permit withdrawal of the draw shank from the tubular rivet shank to leave the hollow tubular rivet shank unoccupied between its set head and said enlarged mandrel head.