Self-riveting fastening element

DETAILED DESCRIPTION As described above, the improved self-riveting fastening element of this invention is designed for permanent attachment to a metal panel or plate within a panel opening by a die member having an annular concave die cavity.
The self-riveting fastening element includes a tubular riveting portion having generally cylindrical internal and external surfaces and a free end.
The self-riveting fastening element further includes a radial flange portion integral with the tubular riveting portion opposite the free end having a diameter greater than the tubular barrel portion and adapted to be driven into the panel as the tubular riveting portion is driven through the panel opening into the annular die cavity.
Where the self-riveting fastening element is a male fastening element, the radial flange portion forms part of a body portion of the fastening element, which bridges the tubular riveting portion and closes the end of the tubular barrel portion opposite the free end and a male fastening portion such as a stud or bolt is integral with the flange or body portion opposite the tubular riveting portion and preferably coaxially aligned with the tubular riveting portion.
An annular drive surface is thus defined around the male fastening portion.
Where the self-riveting fastening element is installed in a preformed opening, as will be required for installation in heavier gauge panels, the tubular riveting portion is first aligned with the panel opening, then driven through the panel opening by a plunger into an annular concave die cavity of a die member.
The die member then deforms the free end of the tubular riveting portion radially outwardly preferably in a hook or U-shape and the radial flange portion is simultaneously driven into the panel entrapping the panel metal between the radially deformed hook-shaped riveting portion and the flange portion, forming a secured fastening element and panel assembly.
The force required to deform the free end of the tubular riveting portion in the concave die cavity is significantly reduced by reducing the thickness of the tubular riveting portion adjacent the free end, wherein the internal and external surfaces of the generally cylindrical tubular barrel portion are slightly inclined toward the radial flange portion, such that the thickness of the tubular riveting portion uniformly increases from the free end toward the radial flange portion