US 3882756 A
A fastener primarily intended for fastening a heavier gauge structural member to one or more members of lighter gauge. The fastener comprises a relatively small pilot point by virtue of which the fastener is self piercing with respect to the lighter gauge member or members to which the heavier gauge member will be fastened, an intermediate transition section immediately following the pilot point so as to stretch-extrude the initial hole to proper size, and a deep threaded body portion to anchor itself within the extruded hole. Preferably the working transition section is also threaded so as to lead the main body portion of the fastener into the pilot hole as enlarged by extrusion. The contour of the working transition section is such as to blend gradually into the larger main body portion of the fastener from the relatively small, self piercing pilot point.
Description (OCR text may contain errors)
United States Patent Sauer et al.
1451 May 13,1975
[ SELF PIERCING STRUCTURAL FASTENER HAVING A WORKING TRANSITION Primary Examinen-Edward C. Allen SECTION Attorney, Agent, or F irmMelville, Strasser, Foster &
Hoffman  Inventors: Gilbert F. Sauer, Franklin; Donald M. Taylor, Ross, both of Ohio  Assignee: Armco Steel Corporation,  ABSTRACT Mlddletown Ohm A fastener primarily intended for fastening a heavier  Fil d; M 3, 1973 gauge structural member to one or more members of lighter gauge. The fastener comprises a relatively [211 App]' 356934 small pilot point by virtue of which the fastener is self Related US. A li ti D t piercing with respect to the lighter gauge member or  Continuation of Ser. No. [71,255, Aug. I2, 1971, members to which the heavier gauge member will be abandoned fastened, an mtermediate transition section immediately following the pilot point so as to stretch-extrude 52 U.S. Cl 85/41; 85/46 the initial hole to Proper Size, and a p threaded 51 1m. (:1. F16b 25/00 body Portion anchor itself Within the extruded hole-  Field of Search 85/41, 46, 47 Preferably the Working transition Section is also threaded so as to lead the main body portion of the  References Cited fastener into the pilot hole as enlarged by extrusion.
UNITED STATES PATENTS The contour of the working transition section is such as to blend gradually into the larger main body portion gzffg 85/41 of the fastener from the relatively small, self piercing 3:094:895 6/l963 Broberg 85/47 plot FOREIGN PATENTS OR APPLICATIONS 2 Claims, 1 Drawing Figure 1,150,769 4/l969 United Kingdom 85/46 7 C /6c 47 E fie /6 F a /6b L 1 SELF PIERCING STRUCTURAL FASTENER HAVING A WORKING TRANSITION SECTION CROSS REFERENCE TO RELATED APPLICATIONS AND INVENTIONS This is a Continuation application of the copending application Ser. No. 171,255, filed Aug. 12, 1971, and now abandoned, in the name of the same inventors and entitled SELF PIERCING STRUCTURAL FAS- TENER HAVING A WORKING TRANSITION SEC- TION.
BACKGROUND OF THE INVENTION 1. Field of the Invention The self piercing fastener of this invention is particularly suited for connecting heavier structural members to lighter gauge members or panels. A supplementary nut may or may not be used. The fastener is completely self locating into a hole extruded in the lighter gauge panel in the region of the pierced hole initiated by the pilot point. This presents an optimum condition for building connections.
2. Description of the Prior Art Although no formal search of the patent art has been made in connection with the invention herein shown, described and claimed, much of this art is known and has been reviewed. It would appear that the following United States patents are of interest. Johnson, U.S. Pat. No. 3,238,836; Hanneman U.S. Pat. No. 3,125,923; Kahn U.S. Pat. No. 3,177,755; Rogers U.S. Pat. No. 413,968; Smith U.S. Pat. No. 3,357,295; Barth U.S. Pat. No. 2,703,419; Hafertep U.S. Pat. No. 1,114,135; Haynes U.S. Pat. No. 2,388,482; Dewar U.S. Pat. No. 2,479,730; Broberg U.S. Pat. No. 3,094,895; Hanneman U.S. Pat. No. 3,288,015; Lovisek U.S. Pat. No. 3,286,579; and Lindstrom U.S. Pat. No. 3,094,893; Canadian Pat. No. 696,358 (Grossberndt) is also of interest. 1
In general the known prior art fasteners rely on the removal of metal to enable the fastener to assume its final position. This requires an expenditure of effort to produce the pressures required in order to effect the connection and much time is consumed. Objects which are achieved by the fastener of the instant invention, therefore, are the speedy installation of the fastener with a reduction in the pressure required to effect the connection. These results are made possible largely because the initial, pierced hole is enlarged by extrusion without the removal of additional metal.
SUMMARY OF THE INVENTION The fastener of this invention utilizes a pilot point the diameter of which is quite small in relationship to the diameter of the fastener body. This small pilot point removes a minimum of metal. The initial hole so produced is one enlarged by extrusion a stretching of the metal. The fastener may be modified by arranging the threads of the fastener body so as to achieve the maximum differential between the major and minor diameters thereof. In some instances it may be desirable to employ a nut in which case the nut is provided with a special mating thread; such a nut is usually employed only where maximum design requirements must be met. In most cases the relatively deep threads of the main body portion of the fastener, cooperating with the hole as enlarged by the extrusion function of the transition section, are sufficient to effect the fastening desired. The heavy gauge member will be provided with a preformed clearance hole of sufficient diameter to permit the threaded fastener body to pass therethrough into the hole extruded in the lighter gauge metal by the working transition section of the fastener. This working transition section may also be threaded, even deep threaded. In this case the major and minor diameters of the threaded working transition section will taper from adjacent the pilot drill point to the threaded fastener body, both of these diameters blending respectively with the major and minor diameters of such main fastener body.
BRIEF DESCRIPTION OF THE DRAWINGS The drawing comprises a single FIGURE showing the fastener of this invention in position to fasten a heavier gauge member to two lighter gauge members; parts of the FIGURE are shown in section and others are diagrammatically illustrated by dotted lines.
DESCRIPTION OF THE PREFERRED EMBODIMENT The fastener of this invention is generally indicated at 10. It comprises a washer head 11, a threaded fastener body 12, a working transition section 13 and a drill point 14. The fastener is shown as holding a heavy gauge structural member 15 to two lighter gauge panels 16a and 16b. The nominal or major diameter of the fastener is indicated at 17 and the minor or root diameter of such fastener is indicated at 18. The pitch dimension is indicated at 19. The hole extruded in the light gauge panel is indicated at 20 and the clearance hole provided in the heavy gauge structural member is indicated at 21.
The diameter of the drill point 14 is relatively small and should not exceed about one-half the nominal or major diameter 17 of the fastener body 12. The minor or root diameter 18 of the fastener body 12 should be approximately 1% times the diameter of the drill point 14. Thus the minor or root diameter 18 of the fastener body 12 should be about 66% or about two-thirds of the major diameter 17. The pitch dimension 19 of the fastener body 12 should be sufficient to cooperatively receive the total thickness of the light gauge panel or panels into which the fastener is threaded, such total thickness including the extruded portion 160, whereby the extruded material will be in intimate contact with the root diameter 18 of the fastener body 12. As can be seen in the Figure the extruded portion strengthens the lighter gauge panel or panels in the region of the hole 20 thereby increasing the resistance to the fastener pulling out. The length of the transition section should not be less than the diameter of the drill point to provide a desirable entry angle therebetween for extruding the light gauge material. In those instances wherein the working transition section 13 of the fastener 10 is threaded, as is depicted in the drawing, the major and minor diameters of the threads of such transition section should,taper so as, moving from the drill point 14 to the fastener body 12, to blend with the major and minor diameters l7 and 18 of such fastener body respectively. Portions of the tapered major and minor diameters of the working transition section 13 are indicated at 13a and 13b respectively.
From what has been said it will be observed that the fastener of this invention is designed with a relatively small pilot point and a transition section which extrudes a proper sized hole so as to lead the main body of the fastener into the pilot hole with minimum pressure. The body of the fastener may be deep threaded as illustrated to such extent that the relationship of the major diameter and minor diameter will in fact produce sufficient interference so that, within certain design load limit conditions, a nut is not required. If conditions so dictate, however, a nut having threads to mate with those of the body of the fastener may be employed.
The transition section, made up of the tapered threads 13a and tapered body 13b, working in the small pilot hole pierced by the pilot drill, extrudes a hole of sufficient size to receive the threaded body portion 12 of the fastener. Although such extrusion could be accomplished by the body portion 13b alone, thus eliminating the tapered threads 13a, it has been determined that best results are achieved when both of the tapered sections 13a and 13b are employed.
The precise configuration of the drill point 14 illustrated is not critical except that it should fall within the limits indicated above. And it may be possible that the transition section could be some sort of metal removing section, such as a reamer, although it has been found much more preferable to remove as little material as possible in the transition from initial pierce to that hole size which will cooperatively receive the threaded body portion 12 of the fastener. Thus, for example, other known fasteners are generally smaller and employed either to fasten light gauge materials to heavy gauge materials or to fasten light gauge materials to light gauge materials; such other fasteners, therefore, re move so much of the metal as to permit the fastener to pass through the hole with little interruption. Use of a nut is usually mandatory in those cases. This is not the kind of action and relationship sought by practicing this invention in its preferred form.
In summary, the self piercing structural fastener incorporating the working transition section of this invention removes a minimum amount of metal and to this end the diameter of the pilot point is small in relationship to the nominal diameter of the fastener body. The hole so initially pierced is then enlarged by the working transition section which stretch-extrudes the metal in the region of the pierced hole. The threads of the fastener body 12 should have a maximum differential between the major and minor diameters thereof. A nut, especially threaded to mate with the threads of the fastener body 12, may be employed in extreme conditions.
By enlarging the initially pierced hole without removing metal the pressure required to effect the connection of the heavy gauge metal to the light gauge panel is reduced. Speedy installation is effected. In the preferred form of the invention, as illustrated, wherein the working transition section is itself threaded, with the tapers shown and described, best results are achieved when these threads are relatively deep and inclined. This affords maximum extrusion to the hole, the fastener body is thereby pulled into the hole with minimum pressure, and the hole as so extruded, considering also the direction of extrusion, gives the optimum in thread engagement when the fastener body 12 enters the extruded hole.
It will be apparent to those skilled in the art that modifications may be made in this invention without departing from the scope and spirit thereof. Although the invention has been described and illustrated in terms of certain structural elements, these are not to constitute a limitation on the claims except insofar as they are specifically set forth in them.
The embodiments of the invention in which an exclusive property or priviledge is claimed are defined as follows:
l. A self piercing structural fastener, for fastening relatively heavy gauge material to relatively light gauge material, comprising a threaded main body having constant major and root diameters of the thread of said threaded main body, said root diameter being about two-thirds of said major diameter, a drill point for initially piercing the light gauge material and the diameter of which drill point does not exceed approximately one-half the said major diameter of the said threaded main body, a tapered and threaded working transition section extending between said drill point and said main body, the length of said transition being at least the dimension of the said drill point diameter, the major and root diameters of the thread of said tapered and threaded transition section increasing gradually and uniformly from the said drill point diameter throughout the said transition section so as to blend respectively with the major and root diameters of said threaded main body, the said root diameter of said threaded main body being approximately one and onethird times the said diameter of said drill point, whereby said light gauge material is stretch-extruded as said transition section passes through the hole initially pierced by said drill point, and the pitch dimension of said threaded main body being sufficient to cooperatively receive the total thickness of said light gauge material as stretch-extruded by said transition section, whereby said stretch-extruded light gauge material will be in intimate contact with the said root diameter of said main body, and whereby said fastener may be passed through a preformed hole in said heavy gauge material of greater diameter than the major diameter of said main body and into the hole initially pierced in said light gauge material so that said main body may thread its way into said initially pierced hole as stretchextruded by said transition section speedily and with a minimum of pressure while achieving good holding power.
2. The fastener of claim 1 wherein said main body is surmounted by an integral one-piece washer head.
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