[1]United States Patent Office 3,253@631 3,253 ,631 COL D-FORMED SELF-PIERCING INUT Ilans E. Reusser, Clevelind, Ohio, assignor to P-.epublic Steei ' Corporation, Cleveland, Olflo, a corporation oY New Jersey 5 Filed June 17, 1963, Ser. No. 288,300 3 Claims. (Cl. 151-41.73) This invention relates to self-piercin.- and clincwng nuts of the type adapted to be mounted upon and - through 10 a sheet metal panel and the method of securing such nuts to the panel. In recent years, self-pierein- and clinchin,@ nuts have beco me quite popular in the automotive and appliance indu stries where there is a larce demand for positive apd 15 effici ent means for makin- screw fastenings to relatively thin sbeet metal components, with access often available only to the attachin- side. T'he present invention resides in an improved selfpier cin.- and clinching nut which is attached to a metal 20 pane l in a one-stroke operation, ivherein the nutpierces a roun d openin.a through the metal panel while a cooperat- . in.- pierein.- die on the underside of the panel concurrently clinches the nut in place by displacin.- a port-Ion of the pane l metal into a specially contoured undercut recess 25 form ed in the nut. Selfpiercin.- and clinchin.- nuts adapted to be mounted upo n a metal panel in a oiae-strole operation have been avail able for some time; however, the nut of this - al)plication provides improvements not heretofore avaff @@le in 30 this field. In the past, it has been found that the most practical mea ns for insuring a positive clinching of the nut and prev enting axial moveme-@it was to utilize a nut in the form of a square or rectangular blank, as such -a nut 35 mou nted through a hole of correspondin.- shape naturally prov ided the maximum security against rotary displacement of the clinched nut. However, such means usually requ ired compl@icated tooling for assembling the nut due to the requirement of exact rotary orientation between the 40 recta n.-ular or polygonal nut and the correspondin.- or mati n@ ed-.es of the openin.- of the piercing die. Such a piercing die, requirin.- a far -reater degree of accuracy, is much more costly to produce than a piercing die whic h is entirely circular in form, as in the present 45 inve ntion. In many o'l the prior devices where the pier cin-. section of the nut is rectangular, the nut is usua lly clinched to the panel alon.a only two sides of the pier cing s-,ction, in contrast with the instant arran,@ement whic h provides an uninterrupted circular clinchin, to in- 50 sure an inherently more positive and fluid-ti.aht connection. The present construction precludes the necessity of - providin.- for rotary orientation between the ntit and pi,- rcing die, it bein.@ necessary only to insure axial ali.-r@- ,ment. To prevent the possibility of rotar-y displ@acement 5 0- of the nut subsequent to attachment to the panel, lockin.@ means are provided integral with the contoured undercut recess fornied in the nut. Many of the present self-piercing and clinching nuts Tely upon deformation of a portion of the nut subsequent 6 0 to piercin-. through the sheet, for the necessary clincbin.- action. In the subject invention, ho,,vever, there is no deformation of the nut durin.- its application to a metal panel. The -present nut includes a centralpiercing portion which 65 projects beyond the plane of the outer bearin-. rim by an amount which is no @reater than the thickness of any panel upon which the nut is to be applied. As a result of this construction, it will be seen that a flushmounted 70 asse@xnbly is prbvided wherein the central pierein.- portion of the nut never projects out beyond the outer surface of nted May 31, 1966 2 the panel to which it is applied. This flush mounting eliminates the requirement for additional embossment of the panel beyond the - periphery of the nut, a step required to otset protruding portions of the nut in so many of the known self-piereingand clinching nut assemblies. In addition, sharp piercing edges are provided on both the nut and cEe to insure a true shearing action when the nut is applied to the panel in order to prevent pinchipg and tearing of the panel materi@al, a condition prevalent with many of the - present self-piercing nuts and a cause of rapid deterioration of the pierein,o die. A further improvement resides in the ability to utilize panel material havin.- a wide range of thickness -and still achieve a flush -mounting without the necessity of changin.- the piercing die as the panel thickness is varied. There is no undesirable variation in the d!,formation and flow of the panel material during clinching with the result that a superior dearee of clinch retention stren.-th is obtained when even theminimum accep'@ab@le thickness of panel material is used. This clinch retention stren.-th increases as the panel thickness increases and with the present nut, the ratio between the minimui-@i and maximum acceptable panel thickn--ss is greater than 2-1. Prior known forms of flush mounting selfpiercin-, and clinchin.- nuts have been found to have several limitations, 'Such as: a narrower applicable ran.-e of panel thickness; fragile, piercin- die extp-nsions for extruding panel rnaterial that bind during the assembly operation; and die stakiiig or other deformation to portions of the nlit which is of greater hardness than the panel material; with resultant extrerne wear and binding of the piercing die durin.assembly. e nut blan of the present invention is readi adaptable to high production fabrication by common multistage ax-lal-pressure coldforming methods. The circular undercut recess portion of the nut for receiving the panel durin.- clinching is fordied in the sequence of these methods by upsetting the extended piercing portion of the nut radially and outwardly under axial pressure. By utili7in.- selected material, adequate work-hardness is imparted to 'Lhe nut blank by these methods to prevent it from b,- ing defor-med during the piercing and clinching operation. Althou,-h a cdnventional hexagonal perimeter nut form is preferable for high-speed thread tappin-. methods, the outer shape of the nut tylank has no significance With Tespect to the instant basic invention, said ghape often beir.-, govemed by other considerations such as the type of autornatic feeding apparatus being used and its specific mearis for gripping and centering the nut externally. Accordingly, one of the @objects @of the present invention is to provide a self-piercing and clinch-in,- nut adapted to be mounted upon a metal panel in a one-stroke punching operation. Another object of this invention is to ptovide a selfPiercing and clinching nut which ivill present a flush or non-protruding surface on the face of a metal panel when mounted therethrough. A fu@rther object of the invention is to provide a selfipiercing and clinching nut wwch, during assembly upon a metal panel, causes an improved flow of the adjacent panel material to brinabout a niore thorough locking between the two members. Still another object of the invention is to provide -a self-picireing and clinchin- nut having an outwarcffy projecting piercing edge and a recess therebeneath in-eluding locking means to prevent axial d-isplacement betnveen the nut and panel, A further object of the invention is to lyrovide a simple and efficient method of securing a self-.pietcing and clinlhing nut to a metal panel by a one-step punchinoperation wherein the nut is flush mounted relati-ve to' the Vlane of the panel.
[2]3,253,631 .3 W,ith these and other @objects in view which will more readily appear as the nature of the invention is bettet understood, the invention consists in the novel @construction, combinat-ion, iaild arrangement of parts, hereinafte't more fully described, illu trated, and claimed. 5 A ptefer@red and practical embodiment of the inven, t.ion is @shown in the a-ccompanying dra)@ing, in which: FIGURE I is a ve@rtical sect@ion th-rough a nut -con. structed according to the present invention. FIGURE 2 is a bottom plan view of the nut illust-rat- 10 ing the radial locking ribs. FIGURE 3 is a side elevation, partly in section, ghowing the nut of the invention being mounted through a metal panel by means of apunch and,die. FIGURE 4 is a side elevation partly in section similar 15 to FIGURE 3 and illustrating the mounting of the nut of the invention through a metal panel of greatet thickness. Sim!ilar reference characters desig@nate corresponding parts throughout the several figures of the drawing. 20 Referring now to the drawing, the self-piercing @and clinching nut comptises a nut blank de-signated - generally as I which is preferably cold-formed. The blank is @provided with an axial bore 2 having suitable t-hreads 3 formed therein for receiving an apptopriate screw-type 25 fastener element (not shown). The rea-r or top face 4 of the nut is of conventional construction, while the opposite front or attaching face 5 is particularly adapted fOT mountin-, upon the face of a sheet metal panel 6; Prefera@bly, the outer - perimeter 30 of the nut blank is of hexagonal shape as illustrated in FIGURE 2; however, the sha-pe of the perimeter has no bearing upon thepresent invention. The attac@hing face 5 is provided with an extended circular piercing Tim 7 @conce@ntric with the bore 2 and 35 in)-mediately adjacent thereto. The face 8 of the piercing rim 7 extends outwardly a critical distance beyond the plane iof the front bea-ring surface 9 of the - attaching face. Concentric with the piercing rim 7 is a - eircul@ar locking recess 10 formed in the -attacbing face 5 and 40 extending from the outer perimeter of the rim 7 to the inner edge of the bearing sur-face 9. It will be noted that the recess 10 extends TadiaRy inwardly beneath the outermost piercing edge 11 (>f the rim 7 to provide an undercut portion 12 defining the limits jof the neck 45 porti-on of the piercing rim 7. As previously mentioned, the plane of the face 8 projects outwardly f@rom the plane of surface 9 a distance which is less than the thickness of the thinhest sheet panel to be used. This insures that the bearing surface 9 50 will engage the upper surface 6 of the p,anel before t@he piercing edge 11 inimerges f -rom the underside of the pane,l. ]3y this means, several advantages are - achieved, namely: better flow of the panel metal; a cleaner edge on the hole; less distort-ion of the panel; and a - resultant 55 flush-mounted,n@ut. A plurality of radially extending locking ribs 13 are formed in the base of the locking (recess 10. These ribs 13 extend angularly from the inner circumference of the'bearing surface 9 to a point;short of the undercut 60 portion 12. . As shown in FIGURE 2, the ribs 13 each include a flat downwardly p-rojecting top su-rface 14, and a pair of diverging side walls 15 directed outwardly to the base of the recess 10. A plurality of depressions forming lock- 65 ing areas 16 are thus olbtainedbetween each pair of rib:s 13. Said areas 16 prefeTably ooeupy more spate than the volume of the ribs themselves as clearly - indicated in FIGURE 2. 4 fastening element. The self-piercing and clinching nut is picked up by a punch 19 having a pilot member 20,which is inserted in the axial bore 2 of the nut. As downward pressure is applied by the punch 19, it wiU be seen that the nut IL wiU bear upon the top surface of the panel 6, which is supported by the fixed piercing di6 17. As will be noted, the piercing die 17 is provided with an upwardly extending raised rim 21 adjacent the central aperture IS thereof. The inner diameter of said aperture, and thus also, said raised riin, is slightly larger than the outer diameter of the piercing edge 11 of the nut, so that when the punch 19 forces the riut blank down against the panel 6, it will be seenthat the edge 11 of the piercing rim 7 will cut through the panel 6 thereby knocking the resultant slug 22 therefrom through the aperture 18 in the piercing die. Again, it is pointed out that the bearing surface 9 of the nut engaged the upper surface of the sheet before the edge 11 had pierced the sheet. Continued pressure upon the nut 1 causes the raised rim 21 to force th6 sheet metal surrounding the hole in the panel up into the locking recess 10. As the bearing surface 9 of the nut retains the metal anel upon p the lower surface 23 of the piercing die 17, the raisbd rim 21 causes the sheet panel to fiow not only into the locking areas 16 between the locking ribs 13, but also to fiow laterally into the undercut portion 12 of the recess. In other words, the ribbed area of the locking recess 10 serves as a coining die with enough squeezing action to cause inward fiow of the metal and reduction of the diameter of the pierced panel -opening. ' It will be understood that the punch 19 is illustrated in more or less its simplest form. It could take on many forms, including a punch provided with retaining fingers for the nut as in an automatic machine. Thus, it will be seen that the foregoing reduction is used to retain the nut by clinching the metal into the neck portion. Due to the undercut nature of the neck portion, which receives fiowed metal displaced inwardly due to the presence of the ribs 13, the nut is retained against axial movement, while the metal forced into the locking areas 16 prevents any rotary movement of the nut. I
