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Self-attaching female fasteners and method of forming female fastener elementsRelated Patent Categories: Expanded, Threaded, Driven, Headed, Tool-deformed, Or Locked-threaded Fastener, Internally Threaded Fastener Element, E.g., Nut, Etc., MultipartSelf-attaching female fasteners and method of forming female fastener elements description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060099048, Self-attaching female fasteners and method of forming female fastener elements. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 60/420,518 filed Oct. 23, 2002. FIELD OF THE INVENTION [0002] This invention relates to a self-attaching female fastener and method of manufacturing or forming self-attaching female fastener elements, including pierce, clinch and weld nuts, wherein the body portion is generally rectangular and the pilot portion may be any shape including generally circular or cylindrical, wherein the body portion is formed by rolling and the pilot portion is formed by cold heading or in a progressive die. BACKGROUND OF THE INVENTION [0003] The predecessor in interest of the assignee of this Application invented and developed the first self-piercing female fastener, now commonly referred to as a pierce nut as shown, for example, in U.S. Pat. No. 2,707,322. The pierce nut disclosed in this patent has been commercially successful, particularly for mass production applications for attachment of one component to a second component by the automotive and appliance industries. In a typical application, the pierce nut is installed in a metal panel by an installation head, which is commonly installed in the upper die shoe or platen of a die press, and a die member or die button is installed in the lower die shoe or die platen. The pierce nuts are fed to the installation head, which includes a reciprocating plunger, and a pierce nut is installed by the plunger with each stroke of the die press. The panel to which the pierce nut is installed may be simultaneously formed by the die press. Of course, numerous improvements have been made to the pierce nut disclosed in the above-referenced patent, including improved retention, by providing dovetail-shaped grooves on opposed sides of the pilot portion as described, for example, in U.S. Pat. No. 3,648,747, also assigned to the predecessor in interest of the assignee of the present application. Finally, in many mass production applications, it is preferable to assemble the pierce nuts in a continuous frangible strip, as disclosed in U.S. Pat. No. 3,845,860, which is also assigned to the predecessor in interest of the assignee of the present Application. [0004] The pierce nuts disclosed in the above-referenced U.S. patents are formed by rolling the desired cross-sectional configuration of the pierce nut, generally starting with round wire, as known by those skilled in this art. The round wire is then rolled by flattening opposed sides of the wire and the wire is then continuously rolled into the desired cross-section of the pierce nut, wherein the pierce nut section includes a rectangular central projecting pilot portion and flange portions on opposed sides of the pilot portion. In the Hi-Stress.TM. pierce nut, available from the assignee of this Application, grooves are rolled into the flange portion on opposed sides of the pilot portion preferably having at least one inclined groove wall, referred to as a "re-entrance" groove, which improves retention of the fastener on the panel following installation. The rectangular pilot portion of the pierce nut strip is then pierced, forming the pierce nut bore, and the section is then cut to length between the pierce bores and the bore may be tapped, if desired. [0005] As will be understood by those skilled in this art and shown in the above-referenced U.S. patents, the pierce nuts formed by the rolling method described above are rectangular and include a rectangular pilot portion. However, in certain applications, it is desirable to have a pierce nut of the type described above, wherein the pilot portion is not rectangular, but is generally cylindrical for example. It has not been possible, however, to form a pierce nut having a generally cylindrical pilot portion by conventional rolling processes. It is an object of this invention to combine the advantages of a high speed rolling process with conventional cold header or progressive die techniques to form a pierce nut of the type described above having a pilot portion which is not rectangular and preferably generally cylindrical in shape. SUMMARY OF THE INVENTION [0006] As set forth above, the present invention relates to a self-attaching fastener and a method of forming self-attaching female elements, which combines the advantages of commercial high speed rolling processes and self-attaching fasteners having a generally circular or cylindrical pilot portion formed by cold heading or progressive die techniques. As used herein, the term "cold heading" includes any method of forming in a die or die press, including forming in a progressive die. The self-attaching female fastener elements formed by the method of this invention may include a central pilot portion having any convenient shape which may be formed by cold heading techniques, including cylindrical or generally cylindrical pilot portions and female fastener elements formed by this method may be utilized either as a pierce or clinch nut, depending upon the application for the female fastener element. [0007] The method of forming self-attaching female fastener elements of this invention includes forming a body portion of the female fastener element by rolling a continuous metal wire or strip including flange portions on opposed sides of the strip having a cross section of the flange portions of the self-attaching female fastener elements to be formed and a body or midportion between the flange portions. In one preferred embodiment, the flange portions project from the midportion, each having a top or bearing face spaced above the plane of the midportion, and the midportion may have opposed planar faces between the flange portions. The method of this invention then includes cutting the strip into discrete segments of equal length, each having a length equal to a desired length of the self-attaching female fastener elements, including end faces where the strip has been cut. The piercing operation may be performed either following cutting of the strip into discrete segments or more preferably prior to the cutting step, providing greater control of the location of the opening through the midportion of the female fastener elements. [0008] The method of this invention further includes separately forming the pilot portion of the self-attaching female fastener elements by cold heading and inserting the pilot portion into the openings formed in the midportion of the body portion, wherein the pilot portion includes an end face spaced above the plane of the midportion. Where the self-attaching female fastener elements are to be utilized as a pierce nut, the end face of the pilot portion is preferably spaced above the panel supporting faces of the flange portions. The pilot portion is preferably formed by cold heading and may therefore take any desired shape for the application of the female fastener element, including generally cylindrical. [0009] The pilot portion may also be formed from a metal which is harder than the metal strip forming the body portion. This is a particular advantage where the self-attaching fastener element is utilized as a pierce nut providing improved strength for the pilot portion which pierces the metal panel and a softer metal for the body portion which supports the panel. Where the fastener is utilized as a clinch nut, the pilot may be formed of a softer metal, such as aluminum. [0010] In one preferred embodiment of the method of forming self-attaching female fastener elements of this invention, the pilot portion is generally cylindrical, but includes radial portions or splines which form an interference fit with the opening through the midportion of the body portion, thereby preventing rotation of the pilot portion relative to the body portion. In the disclosed embodiment, the pilot portion is generally cylindrical and includes radial splines, each having a cylindrical outer surface, having a major diameter greater than the opening through the midportion of the body portion, providing an interference fit and preventing rotation of the pilot portion relative to the body portion. In this embodiment, the splines continue above the plane of the midportion of the body portion, providing additional torque resistance when the pierce nut is installed in a panel. [0011] In the disclosed embodiment of the method of forming self-attaching female fastener elements of this invention, the opening formed through the midportion of the body portion includes a counterbore opening through the backface of the body portion and the separately formed pilot portion includes a radial flange portion which is received in the counterbore, preventing pull-through of the pilot portion following installation. The method of forming self-attaching female fasteners of this invention thereby provides the advantages of a rolled section formed by a high speed rolling mill with the advantages of a self-attaching female fastener element formed by cold heading techniques. [0012] As will be understood from the above description of the method of forming a female fastener of this invention, the self-attaching female fastener of this invention includes a generally rectangular body portion preferably formed by rolling techniques as described above including flange portions on opposed sides of the body portion and a midportion between the flange portions having an opening therethrough and a separately formed, generally cylindrical pilot portion having an axial length greater than the midportion and a major diameter greater than the opening through the midportion of the body portion press fit through the opening having an end face spaced above a plane of the mid portion. As set forth above, the pilot portion may be formed of a metal harder than the body portion, particularly when the female fastener is utilized as a self-piercing fastener element. In a preferred embodiment, the pilot portion includes a plurality of spaced radial splines having a major diameter greater than an internal diameter of the opening through the midportion and the midportion is deformed radially inwardly between the spaced radial splines. In a preferred embodiment, the spaced radial splines include a generally cylindrical outer surface having an outer diameter greater than the internal diameter of the opening through the midportion and relatively inclined side walls. That is, at least one of the side walls is inclined toward the opposed side wall forming an opening between the side walls having a width less than the inner surfaces between the spaced radial splines. In a preferred embodiment, both side walls are inclined toward the opposed side wall providing optimum torque resistance to rotation of the pilot portion relative to the body portion. Other advantages and meritorious features of the self-attaching fastener and method of forming self-attaching female fastener elements will be more fully understood from the following description of the preferred embodiments, the appended claims, and the drawings, a brief description of which follows. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 illustrates schematically a method of forming the body portion of one embodiment of a self-attaching female fastener element; [0014] FIG. 2 is a cross-section of FIG. 1 in the direction of view arrows 2-2; [0015] FIG. 3 is a cross-section of FIG. 1 in the direction of view arrows 3-3; [0016] FIG. 4 is a perspective view of one embodiment of a separately formed pilot portion; [0017] FIG. 5 is a partially cross-sectioned side view illustrating a method of installing the pilot portion shown in FIG. 4 in the body portion illustrated in FIG. 3; [0018] FIG. 6 is a top perspective view of a self-attaching female fastener element of this invention formed by the method of this invention; [0019] FIG. 7 is a bottom view of the self-attaching female fastener element shown in FIG. 6; Continue reading about Self-attaching female fasteners and method of forming female fastener elements... 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