GB2161571A - Pierce nut, panel assembly and attachment method - Google Patents

Abstract

A polygonal pierce nut (20) which may be automatically flush mounted on a panel (P) in a die fixture wherein the nut has a groove (36) surrounding the self-piercing pilot (26), the groove having an inclined outer side wall (42) formed on flange portions (32) at the corners of the nut, there being channels (46) between the flange portions (32). The die fixture includes a die button (54) having a clinching lip (64) which deforms the panel (P) into the re-entrant groove (36) in a two-stage continuous deformation in which first the panel is deformed around the inclined outer side walls (42) of the groove (36) to trap the panel (P) and the panel (P) is then deformed against the groove bottom wall (40) to engage substantially the entire groove bottom wall with the pierced panel edge engaging the groove inner wall (38). The main portion of the panel abuts against the flange portion faces (34) which are generally parallel to but spaced below the piercing face (28) of the pilot (26) with portions deformed into the nut channels (46). <IMAGE>

Description

SPECIFICATION Pierce nut, panel assembly and method The present invention relates to self-piercing, flush mountabie nuts which may be automatically attached to a panel in a die set or fixture, the method of attaching such a self-piercing nut, and the resultant nut and panel assembly.

Pierce nuts have been commercially successful, particularly in the automotive industry, wherein the pierce nuts are automatically installed by a die fixture generally located in a large die press such as is utilized to form metal panels. Pierce nuts are fed to the die fixture in bulk or in a continuous strip and a pierce nut is installed in the panel with each stroke of the die press as disclosed in United States Patent Specifications Nos. 3,108,368 and 3,969,808.

Commercial pierce and clinch nuts are generally formed from a rolled metal section, which may be T-shaped, as shown in United States Patent Specification No. 3,152,628, or the pierce nut may include flanges on opposed sides of the pilot and re-entrant grooves in the flanges, forming a flush-mounted assembly as disclosed in United States Patent Specifications Nos. 3,469,613 and 3,648,747. The prior art also discloses various embodiments of die formed or cold headed pierce and clinch nuts, such as disclosed in United States Patent Specifications Nos. 3,282,515, 3,736,969, 3,878,599 and 4,389,766. However pierce nuts formed by cold heading have not heretofor been commercially successful in the automotive industry because of the cost of forming such pierce nuts and the problems associated with the installation of such nuts.It will be noted that pierce nuts formed by cold heading generally include a central pilot having a pierce face, a circular groove which surrounds the pilot and a flange portion which surrounds the groove. The panel portion adjacent the pierced panel edge is deformed into the groove to form a mechanical interlock. Such installations are generally press sensitive, wherein an over-hit of the installation die fixture may deform the nut, particularly the flange portions, and an under-hit may result in poor retention. Various attempts have been made to solve these problems, including a complex configured groove as disclosed in United States Patent Specifications Nos.

3,878,599 and 4,389,766, in the latter of which the flange portion is intentionally deformed. These attempts to solve the problems associated with cold headed pierce nuts have not been commercially successful to date.

More recently, a simplified square pierce nut was introduced having a frusto-conical pilot and triangular flange portions located at the four corners of the nut, separated by channels coincident with the bottom of the groove which surrounds the pilot. Such a pierce nut is installed by a die set including a head having a reciprocal plunger, which drives the pierce nut through a nose member of the head into the panel to pierce the panel, and an opposed die button which deforms the panel into the nut grooves to secure the nut on the panel. This nut is alsp very press sensitive. In a die over-hit, the unsupported flanges are deformed outwardly, jamming the nut in the head. In an under-hit, the panel is not deformed beneath the frusto-conical pilot, resulting in insufficient retention for commercial applications, with the result that the nut pulls out of the panel when stressed.

The pierce nut, panel assembly and method of this invention seek to eliminate the problems associated with the die formed or cold headed pierce nuts described above, as will now be described.

The preferred pierce nut utilized in the method of this invention forming the nut and panel assembly may be cold headed or die formed and is relatively simple, making the pierce nut less expensive than the cold headed pierce nuts described in the above referenced United States patents. The pierce nut is polygonal preferably having four or more sides.

According to the present invention then, a pierce nut for attachment to a panel comprises a central pilot having an annular piercing face, a bore extending through the pilot generally perpendicular to the piercing face, a grooving surrounding the pilot having inner and outer side walls and a bottom wall, flange portions located at the corners of the polygonal pierce nut on opposed sides of the pilot, each of the flange portions having a panel supporting face generally parallel to and spaced below the plane of the pilot piercing face, and the inner walls of the flange portions adjacent said pilot together defining the groove outer side wall and being inwardly inclined from the groove bottom wall toward the pilot piercing face to define a re-entrant groove having a restricted opening at said panel supporting faces.

In the preferred embodiment of the pierce nut, the groove includes radial channels spaced from the corners of the polygonal nut having a bottom wall coincident with the bottom wall of the groove and separating the flange portions located at the nut corners. In the most preferred embodiment, the outer groove wall of the nut includs relieved portions extending into the flange portions.

Also according to the present invention, a pierce nut and panel assembly comprises a nut, as described above including the radial channels, and a pierced panel, to which the nut is secured, having a main portion bottomed on the panel supporting faces of the nut-flange portions, its top surface generally flush with the pilot piercing face and including portions deformed into the nut radial channels, the panel having secondary portions deformed around the inner walls of the flange portions adjacent the pilot so as to be in close engagement with the groove outer wall, and the panel having a third portion adjacent the pierced edge of the panel deformed and thinned against the groove bottom wall to engage substantially the entire groove bottom wall beneath the inclined outer groove wall with the pierced panel edge engaging the groove inner wall, the secondary and third panel portions forming a mechanical interlock in the pierce nut groove.

Furthermore, according to the present invention, a method of attaching a pierce nut as described above to a panel comprises locating the nut opposite a panel with the pilot piercing face facing the panel, driving the pierce nut into piercing engagement with the panel, piercing a slug from the panel with the piercing face and forming a pierced panel edge, deforming a portion of the panel adjacent the pierced panel edge into the nut groove around the inclined groove outer wall, entrapping the panel portion in the nut groove, deforming the panel portion against the groove bottom wall, thinning and deforming the panel portion into engagement with the groove inner side wall and the inclined outer groove wall, locking the panel portion in the nut groove with the panel adjacent the panel portion bottomed on the panel supporting faces of the flange portions, and supporting the outer surface of the nut as the panel portion is deformed against the nut groove bottom wall, preventing deformation of the flange portions.

Moreover, a preferred method of attaching a pierce nut as described above to a die fixture which includes a die button having a generally flat end face, a central bore and a projecting lip surrounding the bore having generally the same configuration as the nut groove and adapted to be received in the nut groove, a nose member having a generally flat end face, a polygonal bore through the end face having an internal surface configured to closely receive the polygonal nut and a plurality of channels in the end face spaced from the nut corners when the nut is located in the bore, and a plunger telescopically received and reciprocal in the nose member bore, comprises locating a panel adjacent the die button end face in generally parallel relation thereto, and locating the nut in the nose member bore with the pilot piercing face opposite the panel, the plunger being located opposite the nut and generally coaxial aligned with the die button bore, moving the plunger relative to the nose member to engage the nut, driving the nut into engagement with the panel to install the nut on the panel in a single continuous motion, the pilot piercing a slug from the panel and forming a pierced panel edge and said one panel slug received in said die button bore, the die button lip deforming a portion of the panel adjacent the pierced panel edge into the nut groove around the inclined outer groove side wall, entrapping the panel portion in the groove, beneath the die button lip, the die button lip then deformingt the panel portion agaist the groove bottom wall, deforming and thinning the panel portion beneath the inclined outer groove wall, locking the panel portion in the nut groove with the panel adjacent the panel portions bottomed on the panel supporting faces of the flange portions, and the outer wall of the flange portions being resiliently biased against the internal surface of the nose member bore at the corners of the nut as the panel portion is deformed against the nut groove bottom wall, thereby preventing deformation of the flange portions, and the nose member channels receiving fragments of the nut, preventing jamming of the nose member bore.

As mentioned above, the pierce nuts may be delivered to the nose member bore in bulk or strip form, wherein the pierce nuts may be interconnected by frangible connector means as described in United States Patent Specification No. 3,845,860.

The pierce nut located in the nose member bore opposite the die button is then installed by moving the plunger relative to the nose member and die button to engage the nut, driving the nut into piercing engagement with the panel and installing the nut on the panel in a single continuous motion. The die fixture is generally located in a large die press and a pierce nut is installed in a panel with each stroke of the press.

The nut pilot then pierces a slug from the panel which forms a pierced panel edge and the panel slug is received in the die button bore and discharged from the die fixture. The die button lip then deforms a portion of the panel adjacent the pierced panel edge into the nut groove around the inclined outer groove wall, entrapping the panel portion in the nut groove beneath the die button lip. The die button lip then deforms the panel portion against the groove bottom wall, thinning the panel and deforming the panel portion beneath the inclined outer groove wall and preferably against the inner groove wall and pilot, locking the panel portion in the nut groove with the main panel portion bottomed on the panel supporting face or faces of the flange portions.

As described, the polygonal bore of the nose member closely receives the polygonal nut at the corner portions of the nut and the flange portions are resiliently biased against the polygonal bore of the nose member as the panel portion is deformed against the nut groove bottom wall preventing deformation of the flange portions or jamming of the nut in the nose member bore. The channels through the end face of the nose member may also receive nut fragments formed when the press is recycled with a nut already installed in the panel, which may occur inadvertently or during start-up of the press. In such a double hit situation, the flange portions "explode" radially outwardly, normally damaging or jamming the head.In the preferred embodiment of the nose member and method of this invention, the nose member firmly supports the nut flange portions during installation and the nut fragments are harmlessly guided out of the head through the channels in the nose member.

As described, the preferred embodiment of the pierce nut includes radial channels extending through the flange portions and relieved portions in the outer groove walls extending into the flange portions. In the method of installing the preferred embodiment of the pierce nut, the main portion of the panel is bottomed on the panel supporting faces of the flange portions and deformed into the nut channels, providing anti-rotation means. The relieved portions, which may be concave semi-circular grooves in the outer groove walls, cooperate with the nose member bore to prevent deformation of the flange portions.

The panel portion deformed in the bottom of the nut groove is deformed into the relieved portions, particularly in an over-hit condition, avoiding deformation of the flange portions of the nut.

The nut and panel assembly and method of this invention is thus less sensitive to press settings. The two-stage method of deforming the panel portion into the nut groove ensures that the panel portion is first entrapped in the groove by deforming the panel around the inclined outer groove side wall, beneath the die button lip. As described, the entrapped panel portion is then deformed and thinned against the groove bottom wall to engage the groove outer side wall, substantially the entire groove bottom wall and the pierced panel edge is preferably deformed to engage the groove inner side wall or pilot. The groove inclined outer side wall is particularly important to the installation method of this invention.In an under-hit condition, where the panel portion may not be deformed sufficiently for the pierced panel edge to firmly engage the pilot portion, the retention remains sufficient for commercial purposes because the panel portion is deformed beneath the inclined groove outer wall during the initial deformation of the panel portion. Further, in an over-hit condition, the flange portions are not deformed because the flange portions are retained against deformation by the configured bore of the nose member and the panel is deformed into the relieved portions in the groove outer wall.

The nut, panel assembly and method of this invention thus provide important advantages over the prior art. The die formed or cold headed pierce nut is less expensive to produce than the complex groove configurations disclosed in the patented prior art. Further, the method of this invention assures sufficient retention for commercial applications in an under-hit die condition and the installation head is not jammed or damaged in an over-hit condition.

The invention will now be further described by way of example with reference to the accompanying drawing, in which: Figure 1 is a perspective view from above of one embodiment of the pierce nut of the present invention; Figure 2 is a plan view of the pierce nut shown in Fig. 1; Figure 3 is a cross sectional side view of the pierce nut shown in Fig. 2, taken along the line 3-3 of that Figure; Figure 4 is a perspective view from above of a second embodiment of the pierce nut of this invention; Figure 5 is a plan view of the pierce nut shown in Fig. 4; Figure 6 is a cross-sectional side view of the pierce nut shown in Fig. 5, taken along the line 6-6 of that Figure; Figure 7 is a perspective view from above of a die button suitable for installation of the pierce nut shown in Figs. 1 to 3;; Figure 8 is a bottom view of the pierce nut shown in Figs. 1 to 3 in an installation die fixture ready for installation; Figure 9 is a cross-sectional side view of the installation die fixture and pierce nut shown in Fig. 8, taken along the line 9-9 of that Figure, including a panel and the die button shown in Fig. 7; Figure 10 is a partial cross-sectional side view similar to Fig. 9 but taken along the line 9-10 of Fig. 8; Figure 11 is a perspective view from above of a die button suitable for installation of the pierce nut shown in Figs. 4 to 6; Figure 12 is a bottom view of the pierce nut shown in Figs. 4 to 6 in an installation die fixture ready for installation; Figure 13 is a cross-sectional side view of the installation die fixture shown in Fig. 12, taken along the line 1 3-1 3 of that Figure, with a panel and the die button shown in Fig.

11; Figure 14 is a bottom view of the nut and panel assembly shown in Figs. 9 and 10; and Figure 15 is a bottom view of the nut and panel assembly shown in Fig. 1 3.

Figs. 1 to 3 illustrate one preferred embodiment of the pierce nut of this invention. The disclosed pierce nut 20 is polygonal having four side walls 22 joined by truncated corner portions 24. The pierce nut includes a central pilot 26 having a flat annular piercing face 28 surrounding a threaded bore 30. The disclosed embodiment includes flange portions 32 located at the corner portions of the nut, each having a panel supporting face 34 parallel to but spaced below the plane of the piercing face 28 of the pilot 26, as best shown in Fig. 3.

A groove 36 surrounds the pilot portion which includes a cylindrical, continuous inner side wall 38, which defined the exterior wall of the pilot, a bottom wall 40 and a discontinuous inclined outer side wall, which is defined by the inner side walls 42 of the flange portions 32 adjacent the pilot 26. In the embodiment of the pierce nut shown in Figs.

1 to 3, the outer side walls 42 of the groove include relieved portions 44 in the form of concave semi-circular grooves opposite the pilot portion 26 at the corners of the nut. The pierce nut also includes radial channels 46 through the flange portions 32, separating the flange portions and including a bottom wall coincident with the bottom wall 40 of the groove. It will also be noted that the side walls 48 of the channels are relatively inclined to improve the retention of the nut on the panel as described more fully hereinbelow.

Finally, the end of the nut opposite the pilot is truncated, as shown at 50, to reduce the weight of the pierce nut.

The alternative embodiment of the pierce nut 1 20 shown in Figs. 4 to 6 includes six side walls 1 22 joined by corners 124. The pilot 126 includes an annular piercing face 1 28 surrounding a threaded bore 1 30. The disclosed embodiment of the pierce nut includes six flange portions 1 32 located at each corner of the hexagonal pierce nut 1 20 and each flange portion includes a panel supporting face 1 34 parallel to but spaced below the plane of the piercing face 1 28 as best shown in Fig. 6.

The pierce nut 1 20 includes a groove 1 36 which surrounds the pilot 1 26 having a cylindrical, continuous inner side wall 1 38 defined by the exterior wall of the pilot 126, a bottom wall 140 and discontinuous inclined outer side wall defined by the inner side walls 142 of the flange portions 1 32 adjacent the pilot.

The embodiment of the pierce nut shown in Figs. 4 to 6 also includes a plurality of radial channels 146 spaced equidistant between the corners 1 24 of the nut each having a bottom wall coincident with the bottom wall 140 of the nut groove 136. The channels 146 extend through the flange portions 1 32 and include side walls 148 perpendicular to the bottom wall 140 of the groove. The bottom of the nut opposite the pilot 1 26 may be truncated as shown at 1 50 to reduce the weight of the nut.

As described above, the pierce nut of this invention is preferably polygonal, however, the preferred number of sides will depend upon the particular application. Where the flange portions are spaced by a substantial distance, the outer side walls of the groove preferably include relieved areas such as shown at 44 in Figs. 1 to 3. The nut bore may be threaded, as shown, or the bore may be unthreaded for use with a self-tapping screw or bolt. In the disclosed embodiments, the inner side wall of the groove is preferably cylindrical and perpendicular to the bottom wall of the groove, as shown at 38 in Figs 1 to 3 and 138 in Figs. 4 to 6, to avoid deformation of the pilot and thread distortion during the installation of the pierce nut.However, it is possible in certain applications to use an inclined inner wall, such that both side walls of the groove converge towards piercing face of the pilot. The pierce nut is preferably formed of a metal, such as steel, which is not subject to distortion during the installation of the nut. It is possible however to utilize the pierce nut of this invention as a pierce and clinch nut, wherein the pilot is deformed during the installation process to increase the retention of the nut on the panel.

A die set or fixture suitable for installing the pierce nut shown in Figs. 1 to 3 by the method of this invention is shown in Figs. 7 to 10. The die fixture includes a die button 54, a nose member 56 and a plunger 58 as shown in Fig. 1 0. The die button has a generally flat end face 60, a central bore 62 and an annular clinching lip 64 projecting from the end face 60. As best shown in Fig.

7, the clinching lip 64 is configured to be telescopically received in the groove 36 of the pierce nut. Thus, the internal bore 62 is cylindrical to be closely received around the cylindrical surface 38 of the pilot and the outer wall 66 is generally square with truncated corners 68. Further, the outer wall 66 of the clinching lip is inclined outwardly from the top surface to avoid severing of the panel, improve the retention and avoid sticking of the clinching lip in the nut groove.

The nose member 56 includes a square central bore or nut passage 70 which closely receives the side walls 22 of the pierce nut 20 as best shown in Figs. 8 and 10. A plurality of channels 72 are provided through the flat end face 74 of the nose member. The channels 72 are defined in the axes of the nose member perpendicular to the rectangular bore or channel 70 and spaced equidistant from the corners of the nut passage, as shown in Fig. 8. Further, the width of the channels 72 are greater than the maximum dimension of the flange portions 32 of the pierce nut to receive flange portion fragments in a recycle of the die fixture as described herein. The plunger 58 may be square and is telescopically received in the nose member channel 70 as also described hereinbelow.

As described above, the die fixture utilized in the installation of the pierce nut of this invention is normally attached in a large die press. In such an arrangement, the die button 54 will be secured to one platen of the press and the nose member 56 and plunger 58 will be secured in the opposed platen of the die press. The die press may be utilized to simultaneously form the panel into a contoured configuration, wherein a plurality of pierce nuts may be installed in the panel with each stroke of the die press. The die press normally generates several tons of pressure and it is therefore difficult to control precisely the nut installation pressure of the die fixture. The nose member 56 is only partially shown because the installation head, which includes the nose member 56 and plunger 58 may be otherwise conventional.The installation head normally includes a feed mechanism which feeds pierce nuts into the nut passage 70, beneath the plunger 58 and a linkage assembly, as described in the above referenced United States Patent Specifications.

Having described the preferred embodiments of the pierce nut of this invention and one preferred embodiment of the die fixture, it is now possible to describe the preferred method of installing a pierce nut on a panel.

It will be understood that the components of the die fixture may be attached to either die shoe or platen of a die press. In the disclosed method of assembly, the die button 54 is illustrated as it would be attached to the lower die shoe. It will be understood, however, that the positioning of the components of the die fixture may be reversed in an up-pierce arrangement. The terms used herein, such as upper, lower, bottom, and so forth are therefore relative terms. The disclosed die button 54 is generally cylindrical including a keyway 76 for accurate location of the die button relative to the nose member and the pierce nut ready for installation. The die button also includes a counterbore 78 (Figs. 9 and 10) coaxially aligned with and communicating with said bore 62 to enable the panel slug to be discharged without binding.

Referring to Figs. 8 to 10, the method of this invention includes first locating the panel P above the flat end face 60 of the die button 54 in generally parallel relation thereto and with the clinching lip 64 aligned with the groove 36 of the pierce nut 20 as shown in Figs. 9 and 1 0. A pierce nut 20 is then located in the bore or nut channel 70 of the nose member beneath the plunger 58 as shown in Fig. 10. The plunger is not shown in Fig. 9 to enable the location of the channels 72 to be seen through the end of the nose member and the length of the channels relative to the thickness of the nut 20 to be appreciated.As described in the above referenced United States Patent Specifications the pierce nuts are normally received through a transverse channel in the installation head, not shown, transferred to the nose member channel 70 by a feed pawl and located and supported at the intersection of the channels beneath the plunger 58. The die press is then closed, biasing the flat end surface 74 of the nose member against the panel P and the plunger moves downwardly in the nose member passage 70, driving the nut 20 against the panel P, piercing the panel P as shown in Fig. 9. The panel P is pierced between the upper inner edge of the die button lip 80 and the outer edge 82 (Fig. 1) of the pilot forming a panel slug S of the same general configuration as the nut pilot.In the disclosed embodiment, the panel slug S is circular, unless the pilot is simultaneously clinched, and the slug S is received in the bore 62 of the die button and discharged through the counterbore 78.

As described above, the panel portion adjacent the pierced panel edge is then deformed into the nut grooves in a continuous two-stage deformation. The panel portion is first deformed around the outer inclined side wall 42 of the nut groove 36 beneath the die button lip 64, trapping the panel portion in the grooves for final installation. Continued movement of the pierce nut 20 under the plunger 58 moves the die button lip 64 further into the nut groove and the panel portion is then deformed and thinned against the bottom of the groove, deforming the panel portion radially outwardly beneath the inclined outer groove wall, to firmly engage the outer groove wall, and radially inwardly to engage the inner groove wall 38, forming a mechanical interlock between the panel portion and the nut groove without slitting the panel.

As will now be understood, and as shown in Fig. 14, the panel P following installation includes a main panel portion 84 (Fig. 9) bottomed on the panel supporting faces 32 of the nut flange portions, a second portion 86 (Fig. 10) which extends from the main panel portion into the nut grooves against and beneath the inclined outer groove side walls 42 and a third panel portion 88 deformed and thinned against the bottom of the groove to engage substantially the entire groove bottom wall, the inclined outer wall and preferably against the groove inner wall 38. The mechanical interlock thus includes a leg portion 86 and a foot portion 88 which securely retains the panel in the groove. Further, as shown in Fig. 14, portions 90 of the main panel portion are deformed into the nut channels providing anti-rotation means and preventing distortion of the nut flanges, as described hereinbelow.

During the final installation of the nut on the panel, wherein the panel portion is deformed and thinned against the bottom groove wall, the nut corner portions 24 are fully supported in the nut passage 70 as shown in Figs. 8 and 1 0. The flange portions 32 are resiliently biased outwardly against the configured nut channel 70 without deformation of the flange portions as the panel portion is deformed in the bottom of the nut groove.

The panel may also be deformed into the relieved portions 44 in the inclined outer side wall 42 of the nut groove, relieving the pressure on the flange portions. Deformation of the nut flanges reduces the retention strength of the nut on the panel and may cause binding of the nut in the nose member. The method of this invention is thus less sensitive to the die setting. In an over-hit condition, wherein the die button lip 64 overtravels into the nut grooves, the pressure is relieved in the nut channels 46 and the relieved portions 44 and the nut flanges are not deformed, as described.In an underhit condition, wherein the die button lip does not travel into the nut grooves sufficiently to deform the panel portion against the bottom of the groove to fully engage the inner groove wall, the installation is sufficient for commercial purposes because the panel is deformed beneath the inclined outer wall of the groove during the initial deformation of the panel portion and against the bottom of the groove to deform the panel against the inclined outer groove wall. This is an important feature of the pierce nut, panel assembly and method of this invention. Further, the channels 72 in the end of the nose member are adapted to receive nut fragments in a double hit condition wherein the die press is recycled with a nut already installed in the panel.When the die press is recycled, the flange portions are sheared from the nut already installed in the panel and the remainder of the nut including the pilot portion is pushed through the panel. The second nut is then installed in the place of the first nut. The sheared flanged portions are received in the channels 72 in the nose member and directed out of the die fixture without damaging the nose member. The method of this invention therefore combines the advantages of a fully supported nut, preventing deformation of the flanged portions, while avoiding damage to the nose member by providing means to accommodate a double hit situation.

Figs. 11 to 1 3 illustrate a second embodiment of the die fixture which may be utilized to install the pierce nut 1 20 shown in Figs. 4 to 6. The die fixture includes a die button 154, a nose member 1 56 and a reciprocal plunger 1 58. The die button 1 54 includes a flat end face 160, a central bore 1 62 and a projecting clinching lip 1 64 which surrounds the bore 1 62. In the disclosed embodiment, the clinching lip 1 64 is generally circular to be received in the circular nut groove 136, preferably having an inclined outer wall 1 66 which prevents slitting or tearing of the panel and sticking of the clinching lip in the nut groove.

The nose member 1 56 includes a hexago nal bore or nut passage 1 70 which closely receives the outer side walls 1 22 of the hexagonal pierce nut 1 20 and fully supports the pierce nut at the corners 1 24 as shown in Figs. 1 2 and 13. As described abdve, the nose member also preferably includes a plurality of radial channels 1 72 through the flat end face 1 74 of the nose member which receives nut fragments when the die press is recycled with a nut already installed in the panel.The disclosed die button 1 54 is generally cylindrical and includes a keyway 1 76 for accurately locating the die button and a counterbore 1 78 which receives and discharges the panel slugs.

The method of installing the pierce nut 1 20 on a panel P is substantially the same as described hereinabove. The panel P is located on the die button 1 54 generally parallel to the flat end face 1 60. A pierce nut 1 20 is then located in the nut passage 170 of the nose member 1 56 with the piercing face 128 of the pilot 1 26 facing the panel. The nose member 1 56 and plunger 1 58 are then moved relative to the die button 154, as described above. The plunger 1 58 then engages the pierce nut to drive the pierce nut 1 20 into piercing engagement with the panel P.The panel is then pierced between the inner piercing edge 1 80 of the die button lip 164 and the outer edge 182 of the nut pilot 1 26. The panel slug S is then received in the central bore 1 62 of the die button and the panel slug S is discharged through counterbore 178.

The panel portion adjacent the pierced panel edge is then deformed into the pierced nut groove 1 36 in a continuous two-stage deformation. First, the panel portion is deformed around the groove outer side wall 142 into the nut groove beneath the clinching lip 1 64 to trap the panel metal in the groove.

Second, the panel portion is deformed and thinned against the bottom wall of the groove by the clinching lip 1 64 to deform the panel portion radially outwardly against the inclined outer groove wall 142 and radially inwardly against the inner side groove wall 1 38 forming a mechanical interlock between the panel portion and the nut groove, as described above. As best shown in Fig. 13, the inclined outer surface 1 66 of the die button lip directs the panel radially outwardly to firmly seat the panel beneath the inclined outer groove wall.

As described above, the resultant nut and panel assembly includes a main panel portion 184, which is bottomed on the panel supporting faces 1 34 of the flange portions 132, a second panel portion or leg portion 186 which extends from the main panel portion into the nut groove 1 36 and a third panel portion or foot 1 88 which is deformed to engage substantially the entire groove bottom wall 140, beneath the inclined outer groove wall 142 and preferably against the inner groove wall 1 38. Further, as shown in Fig.

15, the main panel portion includes portions 1 90 which are deformed into the radial channels 146 in the pierce nut which extend through the flange portions 1 32. In Fig. 13, the plunger 1 58 is shown partially retracted to illustrate the location and function of the channels 172 in the nose member 156. As described above, the channels 1 72 receive the flange portion fragments in the event that the die press is recycled with a pierce nut already installed in the panel. The method of installation may be otherwise the same as described in relation to the installation of the pierce nut shown in Figs. 1 to 3.

It will bellunderstood that modifications may be made to the disclosed pierce nuts, panel assemblies and method of this invention within the scope of the appended claims. For example, the flange portions may, in certain applications, be continuous around the pilot where relieved portions are provided at the corners. Further, the pierce nut, which is preferably cold headed or die formed, may have any number of sides, wherein the corner portions are preferably supported in the nose member as described. It is, however, possible to support alternate corner portions in the nose member where the pierce nut has a greater number of sides and relieved portions are provided in the outer side groove wall to avoid deformation of the flange portions during assembly.

Claims (22)

1. A polygonal pierce nut for attachment to a panel, comprising a central pilot having an annular piercing face, a bore extending through the pilot generally perpendicular to the piercing face, a groove surrounding the pilot having inner and outer side walls and a bottom wall, flange portions located at the corners of the polygonal pierce nut on opposed sides of the pilot, each of the flange portions having a panel supporting face generally parallel to and spaced below the plane of the pilot piercing face, and the inner walls of the flange portions adjacent said pilot together defining the groove outer side wall and being inwardly inclined from the groove bottom wall toward the pilot piercing face to define a reentrant groove having a restricted opening at said panel supporting faces.

2. A pierce nut as claimed in claim 1 having radial channels extending through the flange portions with bottom walls coincident with the bottom wall of the groove, spaced from the nut corners and separating the flange portions.

3. A pierce nut as claimed in claim 1 or 2, wherein the groove inner side wall is cylindrical, continuous and generally perpendicular to the groove bottom wall.

4. A pierce nut as claimed in claim 1, 2 or 3 wherein the groove outer side wall includes relieved portions extending into the flange portions at the corners of the nut.

5. A pierce nut as claimed in claim 4 wherein the relieved portions are concave and semicircular.

6. A pierce nut as claimed in any one of claims 1 to 5 having a polygonal outer surface including generally flat outer side walls and a plurality of corner portions joining the flat walls.

7. A pierce nut as claimed in claim 2 and 6 wherein the radial channels have relatively inclined walls at the nut outer side walls.

8. A pierce nut as claimed in any one of claims 1 to 7 wherein the bore extending through the pilot is threaded.

9. A pierce nut and panel assembly, comprising a nut according to claim 2 or any claim appendent thereto and a pierced panel to which the nut is secured having a main portion bottomed on the panel supporting faces of the nut-flange portions, its top surface generally flush with the pilot piercing face and including portions deformed into the nut radial channels, the panel having secondary portions deformed around the inner walls of the flange portions adjacent the pilot so as to be in close engagement with the groove outer wall, and the panel having a third portion adjacent the pierced edge of the panel deformed and thinned against the groove bottom wall to engage substantially the entire groove bottom wall beneath the inclined outer groove wall with the pierced panel edge engaging the groove inner wall, the secondary and third panel portions forming a mechanical interlock in the pierce nut groove.

1 0. A pierce nut and panel assembly as claimed in claim 9, wherein the pilot is cylindrical and groove inner wall is generally perpendicular to the groove bottom wall.

11. A pierce nut and panel assembly as claimed in claim 9 or 10 wherein the pierce nut has at least six sides including a flange portion located at each corner of the polygonal nut.

1 2. A pierce nut and panel assembly as claimed in claim 9, 10 or 11 when appended to claims 4 or 5 wherein the second panel portion is deformed into said relieved portions.

1 3. A method of attaching a pierce nut according to any one of claims 1 to 1 2 comprising locating the nut opposite a panel with the pilot piercing face facing the panel, driving the pierce nut into piercing engagement with the panel, piercing a slug from the panel with the piercing face and forming a pierced panel edge, deforming a portion of the panel adjacent the pierced panel edge into the nut groove around the inclined groove outer wall, entrapping the panel portion in the nut groove, deforming the panel portion against the groove bottom wall, thinning and deforming the panel portion into engagement with the groove inner side wall and the inclined outer groove wall, locking the panel portion in the nut groove with the panel adjacent the panel portion bottomed on the panel supporting faces of the flange portions, and supporting the outer surface of the nut as the panel portion is deformed against the nut groove bottom wall, preventing deformation of the flange portions.

14. A method of attaching a pierce nut according to any one of claims 1 to 11, which includes a die button having a generally flat end face, a central bore and a projecting lip surrounding the bore having generally the same configuration as the nut groove and adapted to be received in the nut groove, a nose member having a generally flat end face, a polygonal bore through the end face having an internal surface configured to closely receive the polygonal nut and a plurality of channels in the end face spaced from the nut corners when the nut is located in the bore, and a plunger telescopically received and reciprocal in the nose member bore; the method comprising locating a panel adjacent the die button end face in generally parallel relation thereto, and locating the nut in the nose member bore with the pilot piercing face opposite the panel, the plunger being located opposite the nut and generally coaxially aligned with the die button bore, moving the plunger relative to the nose member to engage the nut, driving the nut into engagement with the panel to install the nut on the panel in a single continuous motion, the pilot piercing a slug from the panel and forming a pierced panel edge and said panel slug received in said die button bore, the die button lip deforming a portion of the panel adjacent the pierced panel edge into the nut groove around the inclined outer groove side wall, entrapping the panel portion in the groove, beneath the die button lip, the die button lip then deforming the panel portion against the groove bottom wall, deforming and thinning the panel portion beneath the inclined outer groove wall, locking the panel portion in the nut groove with the panel adjacent the panel portions bottomed on the panel supporting faces of the flange portions, and the outer wall of the flange portions being resiliently biased against the internal surface of the nose member bore at the corners of the nut as the panel portion is deformed against the nut groove bottom wall, thereby preventing deformation of the flange portions, and the nose member channels receiving fragments of the nut, preventing jamming of the nose member bore.

15. A method as claimed in claim 14, when utilising a nut according to claim 2 or any claim appendent hereto, wherein the panel is also deformed into the radial channels of the nut.

16. A method as claimed in claim 13 or 14 when appendant to claim 4 or 5, wherein the panel portion is deformed into outer side wall relieved portions in co-operation with the internal surface of the nose member bore to prevent deformation of the nut flange portions.

1 7. A method as claimed in claim 14, 1 5 or 1 6 wherein the panel portion is deformed into engagement with the groove inner side wall as the panel portion is deformed beneath the inclined groove outer wall into engagement with the groove outer side wall adjacent the bottom wall.

18. A method as claimed in any one of claim 14 to 17, wherein the portion is thinned and deformed into engagement with the groove inner side wall.

1 9. Pierce nuts, for attachment to a panel, substantially as herein described by way of examples with reference to and as illustrated in the accompanying drawings.

20. A pierce nut and panel assemblies substantially as herein described with reference to and as illustrated in Figs. 9 10 and 1 2 to 1 5 of the accompanying drawings.

21. Methods of attaching a pierce nut to a panel substantially as herein described with reference to the accompanying drawings.

22. Pierce nut and panel assemblies when produced by the methods of any one of claims 12 to 17 and 20.