Abstract:
Apparatus and method for forming a clinched joint between at least two panels with a rivet or slug by driving the rivet or slug into the at least two panels thereby outwardly deforming at least the inner end of the slug or rivet. Rings or components forming parts of the joint can be secured to the panels wherein the rings or components are acting as the dies for forming the joint.

Description:
This application is a continuation of application Ser. No. 08/244,041, filed May 20, 1994 now abandoned, which is the national stage of PCT/AU92/00631, filed Nov. 11, 1992. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to improved panel clinching methods. The term &#34;clinching&#34; is also known as &#34;press joining&#34; or &#34;integral fastening&#34;. 
     2. Prior Art 
     Spot welding is the most commonly used technique for joining vehicle body components in the automotive industries. As the strength of each spot weld cannot be guaranteed, eg. due to the inclusion of rubbish between the components, or poor weld penetration, designers must increase the number of welds to ensure adequate joint strength. 
     Spot welding has not yet been developed as an accurate, reliable method for joining galvanized steel or aluminum components. 
     With galvanized steel, welding action destroys the galvanized about the weld site, making it liable to corrosion. 
     Aluminum has great potential in the automobile field due to its light weight, but the lack of a suitable spot welding method is one reason which has minimized its application. 
     One alternative to spot welding is the use of self-piercing rivets, and a method of, and apparatus for, the fastening of metal panels with self-piercing rivets is disclosed in U.S. Pat. No. 4,615,475 (Fuhrmeister) (International Publication Number WO 84/04710). 
     A further alternative method is metal clinching, where two sheets of metal are deformed into a locking engagement using a punch-and-die combination. Examples of metal clinching methods are disclosed in: 
     1. DE 4009813 (Fraunhoffer-Ges Ford Ange); 
     2. DE 1452820 (Philips Patentverwaltung GmbH); 
     3. DE 3726392 (Kuka Schweissanlage); 
     4. EP 330061 (Eckold W. &amp; Co GmbH); 
     5. EP 215449 (Rapp E.); 
     6. GB 2244946 (Fairacre Limited); 
     7. GB 2123734 (BTM Corporation); 
     8. U.S. Pat. No. 3,919,955 (Du Vernay); and 
     9. U.S. Pat. No. 387,599 (Ladouceur et al). 
     While these methods enable metal sheets to be joined together, they have relatively low shear and axial load strengths, and the joints do not have an outer face substantially flush with the surrounding sheet metal (and are therefore not applicable in exposed areas, eg. within an engine compartment). 
     SUMMARY OF THE PRESENT INVENTION 
     It is an object of the present invention to provide a panel clinching method where the shear strengths of the clinching joint are increased. 
     It is a preferred object to provide a method where the axial load strength of the clinched joint is increased. 
     It is a further preferred object to provide a method where the outer face of the joint may be substantially flush with the surrounding sheet metal. 
     It is a still further preferred object to provide a method where ancillary components may be supported by or from the clinched joint. 
     It is a still further preferred object to provide a method where the clinched joint may be &#34;capped&#34; to constrain any stress lines in the metal panels in the region of the joint. 
     Other preferred objects will become apparent from the following description. 
     In one aspect, the present invention resides in a panel clinching method wherein: 
     a hollow rivet or full tubular slug is driven or inserted into a clinched joint and at least the inner end of the shank of the rivet or slug is outwardly-deformed within the joint. 
     The term &#34;outwardly-deformed&#34; shall be used to include deformation of all or part of the shank or stem of the rivet or slug in at least one direction lateral (or transverse) to the longitudinal axis of the shank or stem. 
     In a single stage method, the rivet or slug may be inserted into the joint as the joint is formed, the rivet or slug cooperating with the punch to deform the panels into the supporting die. In a two-stage process, the rivet or slug cooperating with the metal panels into the die, and a sleeve external to the punch then deforms the rivet or slug within the joint. 
     The bore of the rivet or slug may be threaded, serrated or otherwise profiled to engage and support an anchor, e.g., a wiring loom support, a trim cover panel fastener or the like. A plastic insert may be fitted to the rivet or slug to provide a flush outer face. 
     Preferably, the panels are pre-clamped to the die before the punch drives the rivet or slug into the panels to form the clinched joint; or before the clinched joint is formed and the rivet or slug inserted into the joint. 
     In a second aspect, the present invention resides in a panel clinching method where a solid or semi-tubular rivet or slug is driven or inserted into a clinched joint and at least the inner end of the shank of the rivet or slug is outwardly-deformed within the joint. 
     In a single stage process, the rivet or slug is interposed between the punch and the outer panel (to be joined) and the rivet or slug is used to deform the metal panels into the die as the clinched joint is formed. 
     In a two-staged process, a conventional button-type clinched joint is formed and then the rivet or slug is pressed into the joint by the punch. 
     Preferably, the panels are pre-clamped to the die before the clinched joint is formed. 
     In a third aspect, the present invention resides in a panel clinching method where a ring, or a body or component having a tapered bore or recess, is supported by a die and at least one panel is deformed into the ring or the bore or recess to form a clinched joint therewith. 
     Preferably, the panels are deformed behind the ring or into engagement with inwardly-divergent walls in the recess. 
     In a fourth aspect, the method of the third aspect is used in combination with the hollow rivet or tubular slug of the first aspect, or the solid or semi-tubular rivet or slug of the second aspect. 
     In a fifth aspect, the present invention resides in a clinched joint for panels formed by the method of any one of the first to fourth aspects. 
     While the invention is particularly suitable for joining sheet metal panels, it is also suitable for polymeric materials (eg. polyethylene, polyurethane, polypropylene, nylon) where one or more metal panels are substituted by panels of polymeric material. For example, the methods are suitable for joining, e.g. an aluminium sheet to a polypropylene sheet, where the polymeric sheet may be locally preheated e.g. by the supporting die) to assist in the &#34;flow&#34; of the polymeric material as the joint is formed. The rings or components may also be formed of polymeric material and be clinched to metal and/or polymeric material sheets. 
     The shanks of the rivets or slugs may be provided with external splines, grooves, teeth or other protrusions or recesses to provide additional grip between the rivets or slugs and the panels in the clinched joint. 
     Adhesives can be applied, eg. to the shanks of the rivets or slugs to assist bonding of the rivets or slugs to the panels. Adhesives may also be provided within the bore of the tubular or semi-tubular rivets or slugs to be extruded into the clinched joint, as the rivets or slugs are deformed, to assist the bonding of the rivets or slugs to the panels. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional side view of a hollow rivet or tubular slug suitable for clinching two panels of metal together; 
     FIGS. 2 to 5 are sectional side views of the steps in a two-stage process of forming a clinched joint of a first embodiment; 
     FIG. 6 is a sectional side view of the clinched joint of the first embodiment; 
     FIG. 7 is a sectional side view of a modified tubular rivet or slug; 
     FIGS. 8 to 11 are sectional side views of the steps in a single-stage process of forming a clinched joint of a second embodiment; 
     FIG. 12 is a sectional side view of the clinched joint of the second embodiment; 
     FIG. 13 is a sectional side view of a solid rivet or slug; 
     FIGS. 14 and 15 are sectional side views of the steps of forming a clinched joint of a third embodiment; 
     FIG. 16 is a sectional side view of the clinched joint of the third embodiment; 
     FIG. 17 is a sectional side view of a semi-tubular rivet or slug; 
     FIGS. 18 to 22 are sectional side views of the steps of forming a clinched joint of the fourth embodiment; 
     FIG. 23 is a sectional side view of the clinched joint of the fourth embodiment; 
     FIGS. 24a, 24b, and 24c are top plan, sectional and bottom plan views, respectively, of a ring; 
     FIG. 25 is a sectional view of the clinched joint of the fifth embodiment; 
     FIG. 26 is a similar view of a modified form of the clinched joint of FIG. 25; 
     FIGS. 27a, 27b, and 27c are top plan, sectional and bottom plan views, respectively, of a component; 
     FIG. 28 is a sectional side view of a clinched joint of a sixth embodiment; 
     FIG. 29 is a similar view of a modified form of the clinched joint of FIG. 28; 
     FIGS. 30a, 30b, and 30c are top plan, sectional and bottom plan views, respectively, of a second component; 
     FIG. 31 is a sectional side view of a clinched joint of a seventh embodiment; and 
     FIG. 32 is a sectional side view showing the clinched joint of FIG. 31 where the component is supported in a die. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 to 6, the tubular rivet 10 of FIG. 1 is driven into the metal panels to form the clinched joint 11 of FIG. 6. 
     The metal panels 12, 13 to be joined together are supported on the die assembly 14 of a clinching or tools, the die assembly having expandable and contractable collets 16 associated with a collet holder 17 and anvil 18 arranged to allow the joint 11 to be released when formed. 
     The clinching tool 15 has a pre-clamping head 19 which clamps the metal panels 12, 13 to the die assembly and has internal (spring-loaded) balls 19A to locate and centralise the rivet 10. A punch 20 is slidably journalled in a sleeve 21 slidably journalled in the pre-clamping head 19, and the punch 20 and sleeve 21 are connected to respective hydraulic rams (not shown). 
     The operation of the clinching tool 15 will now be described. 
     After the metal panels 12, 13 are clamped to the die assembly 14 by the pre-clamping head 19, the punch 20 is driven through the rivet 10 into engagement with the upper panel 12, with the sleeve 21 engaging the rivet 10. The punch 20 and rivet 10 are advanced to deform the metal panels 12, 13 into the die assembly 14 (see FIG. 4). The sleeve 21 is then advanced to cause the inner end of the rivet 10 to be outwardly-deformed (see FIGS. 5 and 6). 
     The anvil 18 can be spring-loaded or forcibly raised as a post-forming operation against the punch 20 to assist in deforming the rivet or slug. 
     The insertion and deformation of the rivet assists in locking the metal panels 12, 13 together, with increase in the shear and axial separation strengths (i.e.) in the direction of arrows A and B, respectively). 
     The bore 22 of the rivet 10 may be threaded to receive a fastener or plug to support, e.g. an electrical wiring loom or a plastic insert to form a flush cover for the clinched joint 11. 
     Referring now to FIGS. 7 to 12, a modified tubular rivet 110 has a tapered end 123 to its inner bore 22. 
     In this one-stage method, the sleeve 21 is eliminated and the punch 120 is slidably journalled in the pre-clamping head 119. The metal sheets 112, 113 are supported by the die assembly 114 and clamped thereto by the clamping head 119. The punch 120 engages the rivet 110 (see FIG. 9) and drives the rivet 110 into the metal panels 112, 113 which are deformed into the die assembly 114 (see FIG. 10). The punch 120 is further advanced (see FIG. 11) to deform the inner end of the rivet 110 to form the clinched joint 111 (see FIG. 12). 
     To increase the strength of the clinched joints 11, 111, a solid or semi-tubular rivet or slug may be used. 
     Referring now to FIGS. 13 to 16, a solid slug 210 (FIG. 13) has a concave recess 222 at its lower end and is used to form the clinched joint 211 of FIG. 16. 
     The metal sheets 212, 213 are clamped to the die assembly 214 by the clamping head 219 (see FIG. 14). The punch 220 is advanced to drive the slug 210 (as an extension of the punch 220) into the metal panels 212, 213 to deform the panels into the die assembly 214 to form the clinched joint 211. It will be noted that the head of the slug 210 is flush with the outer face of panel 212 and such a joint is suitable where aesthetic appeal is required, e.g. on a visible surface of a vehicle body. 
     The semi-tubular slug 310 (see FIG. 17) has a tapered end 323 to its bore 322. 
     In the two-stage process shown in FIGS. 18 to 23, the metal panels 312, 313 are pre-clamped to the die assembly 314 by the clamping head 319 and the punch 320 is advanced (see FIG. 19) to form a conventional button-type clinched joint 311A (see FIG. 20). The punch 320 is retracted and a semi-tubular slug 310 is placed in the clinching tool. 
     The pre-clamping head 319 clamps the panels (see FIG. 21) and the punch 320 is advanced to drive the slug 310 into the clinched joint 311A to deform the slug 310 to form the clinched joint 311 (see FIG. 23). 
     Referring now to FIGS. 24 and 25, the rivets or slugs (10, 110, 210, 310) may be substituted by a (metal or plastic) ring 410 which engages the lower panel 413 to lock the clinched joint 411, the panels 412, 413 being deformed into the divergently tapered bore 422 of the ring 410. The ring 410 is supported by a die assembly (not shown) as the punch (not shown) deforms the panels 412, 413, the ring 410 acting as the die body. 
     As shown in FIG. 26, straps or clips 424 may be formed integrally with the ring 410, e.g. to secure wiring to a vehicle body. If requested, the ring 410 can be combined with the method of FIGS. 17 to 23, where a solid or semi-tubular slug is pressed into the clinched joint 411 to form a flush surface with panel 412. 
     A component 510 (see FIGS. 27 to 29), with a tapered recess or bore 522, and a screw-threaded hole 525 (as part of a sub-assembly--not shown) can also be employed as the die for the clinched joint 511 and provide a mount for the sub-assembly secured to the panels 512, 513. 
     As shown in FIG. 29, a solid slug 210 can be pressed into the clinched joint 511. (The slug 210 may be screw-threaded and have a slot, Philips-head slot or an Allen-head recess to enable the slug 210 to be removed later if required for disassembly of the joint 511.) 
     FIGS. 30 to 32 show the attachment of a second component 610, with a bore 622 and a plain spigot (FIG. 30) or screw-threaded end spigot 626 (FIG. 31), secured to the clinch-joint 611. (The spigot may also be profiled, e.g. engageable in a catch or lock means.) 
     FIG. 32 shows the component 610 supported by a die assembly 614 during the clinching step. 
     In the methods shown in FIGS. 24 to 26; 27 to 29; and 30 to 32, two panels 412, 413; 512, 513; 612, 613 are shown secured in the ring 410, and components 510, 610. The methods are also applicable to securing a single panel to the ring 410 on components 510, 610. 
     In addition, in all of the methods, one or bath panels may be a polymeric sheet (e.g. polypropylene). It is preferred that the inner sheet (e.g. 13, 113) being the polymeric sheet and the die assembly may be heated at the location of the clinched joint to assist &#34;flow&#34; of the polymeric material. 
     For improved recycling, it is preferred that the rivets 10, 110; slugs 210, 310; ring 410; or components 510, 610 be of the same type of material as the panels as this will obviate the need for disassembly of the joints. 
     As an indication of the advantage of methods of the present invention, the use of an 8 mm solid rivet or slug in conjunction with a clinched joint increase the shear strength of a sheet metal joint by 50%, and the strength in both the shear and axial separation directions can be maintained within controlled limits, unlike spot welds. This means the number of clinched joints can be much less than the number of spot welds, and the joints-can also support sub-assemblies. 
     Various changes and modifications may be made to the embodiments described and illustrated without departing from the scope of the present invention defined in the appended claims.