Method of attaching a fastening element to a panel

Abstract

The method of attaching a fastening element to a metal panel within a panel opening using a die member having an annular concave die cavity. The fastening element includes a tubular riveting portion and a radial flange portion and a fastening portion. The internal and external surfaces of the tubular riveting portion are relatively uniformly inclined toward the radial flange portion such that the thickness of the tubular riveting portion at the free end is less than the thickness adjacent the radial flange portion. In the preferred embodiment, the internal surface of the tubular riveting portion is cylindrical and the external surface is slightly conical tapering inwardly toward the free end to reduce the force required to radially deform the free end of the tubular portion radially outwardly. Further the outer surface of the radial flange portion is generally polygonal having arcuately radially inwardly concave side surfaces spaced by relative thin convex arcuate edge surfaces reducing the force required to drive the flange portion into the panel during final installation of the fastening element. The method of this invention includes driving the free end of the tubular barrel portion through an opening in the panel into the die member, thereby deforming the free end of the barrel portion radially outwardly and deforming the radial flange portion into the panel.

Description

FIELD OF THE INVENTIONThe present invention relates to an improved self-riveting or self-attaching fastening element, preferably a self-riveting male fastening element such as a stud, bolt or the like, which is permanently attached to a panel in an opening in the panel. More specifically, the present invention relates to a self-riveting fastening element having a tubular riveting portion which is received through an opening in the panel into a concave annular die cavity to permanently rivet the fastening element to the panel.BACKGROUND OF THE INVENTIONSelf-riveting male fastening elements of the type disclosed herein were first developed by Profit Verbindungstechnik GmbH & Co. KG of Germany, a company related to the assignee of the present application, as disclosed in U.S. Pat. No. 5,092,724. The fastening element includes a tubular or annular piercing and riveting portion or barrel portion which in the preferred embodiment pierced an opening in the panel which is then received thro...

AI Technical Summary

Benefits of technology

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. In the most preferred embodiment of the self-riveting fastening element of this invention, the internal surface of the tubular riveting portion is cylindrical and parallel to the longitudinal axis of the tubular riveting portion and the external surface is sonically tapered toward the free end of the riveting portion. Most preferably, the free end of the tubular riveting portion includes an outer arcuate surface which smoothly blends into the conical external surface providing a smooth transition from the arcuate outer surface into the conical external surface. The cone angle of the external surface is between about one and five degrees or most preferably between two and three degrees. As described more fully below, this relatively simple modification of the tubular riveting portion results in a significant reduction in the force required to deform the free end of the tubular riveting portion radially outwardly of greater than ten percent. The reduction is force required is achieved without significantly reducing the strength of the deformed hook-shaped free end of the tubular riveting portion.

The force required to drive the radial flange portion of the self-riveting fastening of this invention into the panel is reduced by providing a plurality of arcuate radially inwardly concave surfaces on the radially outer or exterior surface of the radial flange portion. This modification reduces the area of the radial flange portion driven into the panel adjacent the opening and further increases the torque required to turn the self-riveting fastening element relative to the panel following installation. Torque resistance is also an important feature of a self-riveting fastening element of the type described herein because the fastening element is utilized to attach a second element to the fastening element and panel assembly. For example, the self-riveting male fastening element of this invention may include an integral threaded bolt portion which extends from the panel. The bolt is then used to attach an automotive component, for example, to the fastening element and panel assembly which is secured in place by a conventional nut. During the engagement of the nut, however, the bolt may be subject to twisting forces, particularly where the nut is cross-threaded or a thread forming nut or bolt is used and a torque wrench is used. The fastening portion may therefore be subject to substantial tensional loads and must be able to withstand turning of the fastening element relative to the panel following installation. In the most preferred embodiment of the self-riveting fastening element, the radial flange portion is generally polygonal having, for example, six or eight sides. The radially inwardly concave surfaces are defined in the side surfaces of the polygonal radial flange portion located between the points or edges. In the most preferred embodiment, the "edges" of the polygonal radial flange portion include a thin convex arcuate surface and the radially inwardly concave surfaces are located between the thin convex arcuate surfaces of the edges. The radially inwardly concave surfaces between the concave arcuate surfaces most preferably have a relatively large radius. The radius of curvature of the concave arcuate surfaces is defined such that the arc is spaced from the external surface of the tubular riveting portion. In the most preferred embodiment, the radius of the arcuate radially inwardly concave surface is greater than the radius of the external surface of the tubular riveting portion.

Problems solved by technology

This modification reduces the area of the radial flange portion driven into the panel adjacent the opening and further increases the torque required to turn the self-riveting fastening element relative to the panel following installation.

During the engagement of the nut, however, the bolt may be subject to twisting forces, particularly where the nut is cross-threaded or a thread forming nut or bolt is used and a torque wrench is used.

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