Patent ID: 6035689
Filing Date: 2000-03-14
Classification: B21D

Abstract:
Process for forming an elongated unitary rivet button of selected longitudinal height from substantially-planar container closure sheet metal, for subsequent conversion into a unitary rivet for securing a convenience-feature on an external surface of a scored portion to be severed from such sheet metal by such opener, comprising(A) providing rigid flat-rolled sheet metal can stock of preselected thickness gauge, between opposed substantially-planar surfaces, for securing a convenience-feature opener by converting a unitary rivet button formed in such scored portion into a unitary rivet;(B) displacing sheet metal from such substantially-planar scored portion by forming a unitary annular bead, with sheet metal between an outer periphery ring and a concentric inner ring of such bead protruding from a substantially-planar surface of such scored portion,such annular bead being circular, in plan view, andsymmetrical with relation to a centrally-located axis which is perpendicularly-transverse to such sheet metal plane, withsuch annular bead circumscribing a substantially-planar center panel located radially inward of such concentric inner ring,such center panel having a geometric center which is coincident with intersection of such centrally-located axis for such annular bead, then(C) displacing sheet metal of such substantially-planar center panel and sheet metal of such protruding annular bead, so as to form a large-diameter protrusion in which such large diameter is centered on such centrally-located axis,such protrusion having an arch-shaped configuration in a cross-sectional plane which includes such centrally-located axis, with sheet metal, centrally-located of such arch-shaped protrusion, establishinga major portion of the desired longitudinal height for such unitary rivet button, at its closed end,such protrusion having an outer periphery established substantially by such outer ring of such annular bead of step (B), anda centrally-located compound-curvature portion substantially comprising sheet metal from such center panel of step (B); and, then,(D) forming such centrally-located sheet metal of such arch-shaped protrusion into a unitary rivet button having a compound-curvature closed end and a substantially cylindrical sidewall portion contiguous to its open end, with(i) forming of such rivet button being carried out so as to establish an average sheet metal thickness which is substantially uniform in such compound-curvature portion at such closed end and in such substantially cylindrical portion contiguous to its open end, bylimiting decrease in sheet metal thickness of such centrally-located sheet metal, during such rivet button fabrication, to about 1.5% to about 17.5% of sheet metal thickness of such centrally-location portion, and(ii) returning remaining sheet metal from such peripheral portion arch-shaped protrusion to such substantially-planar scored sheet metal which is to be severed.