Patent Publication Number: US-2018036790-A1

Title: Punch rivet and also a method and apparatuses for attachment of individual components to one another of which at least one component is formed by a workpiece of composite material

Description:
This patent application is a divisional application of U.S. patent application Ser. No. 14/476,369, filed Sep. 3, 2014, which claims priority to German Patent Application No. 102013217632.5, filed on Sep. 4, 2013, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     The present invention relates to a method and apparatuses for fastening individual components to one another using a punch rivet of which at least one component is formed by a workpiece of composite material. 
     Punch rivets are known, they are usually used in order to secure two components in the form of sheet metal parts to one another. This is known as “Durchsetzfügen” in German and as “clinching” in English. For this purpose, a punch rivet has a flange of larger diameter, a rivet section of smaller diameter and a ring-like component contact surface at the side of the flange adjacent the rivet section and surrounding the rivet section. This surface is frequently a conical surface and is pressed during the pressing of the punch rivet into the two components into the surface of the upper sheet metal part, with the side of the flange remote from the rivet section being flush with the upper side of the upper sheet metal part. 
     The free end of the rivet section is formed by a conical surface which converges inwardly and in the direction of the flange. This leads to the rivet section being spread in trumpet-like manner during the pressing in of the punch rivet as a result of the forces acting on the conical surface and to the rivet section not piercing the second component. The components are held together as a result of the wedge action of the trumpet-like shape of the rivet section, which is filled with material of the components. 
     The object of the present invention is to provide a novel punch rivet which is suitable for the connection of at least two panel-like components to one another of which at least one component consists of a fiber or fabric reinforced plastic, with a high quality rivet joint being achievable which ensures a high strength connection of the components to one another without a pronounced danger existing that the punch rivets that are used can be torn out of one component or a plurality of components or that undesired fatigue effects occur in the course of time. 
     Frequently one is concerned with joining two or three components (or eventually even more components) to one another, with at least one component consisting of the said fiber or fabric reinforced plastic. It can for example consist of a component of such a composite material and a component of metal, or of two components of such a composite material, or of two components of a composite material of this kind and a component of metal, or of three components of the said composite material. 
     Hitherto only a few proposals have been made for the mechanical joining of components of the named composite material. Most of these are concerned with the embedding of fastening elements or reinforcement plates into individual components which can be secured together with customary fastening elements. This is, however, relatively complicated and expensive and disturbs the process sequence in the manufacture of the individual components. 
     U.S. Pat. No. 7,160,047 describes the attachment of fastener elements in the form of bolt elements or nut elements to a component. which consists of a composite material which is defined there as a brittle or resilient component which consists for example of a material having a hollow spaces or pores, such as for example plastics, wood, metal foams, metals which are filled with hollow bodies or plastics or another relatively soft material and which are optionally present in the form of a sandwich construction or as a composite material, for example in the form of a single ply or multi-ply structure with for example two sheet metal or plastic layers with a core of one of the above-named substances or materials. 
     The present invention is in particular concerned in contrast with workpieces which consists of a fiber or fabric reinforced plastic and in particular those with a duroplastic matrix material, with the invention have also being suitable for use with workpieces in the form of sheet metal parts. In contrast to the materials defined in U.S. Pat. No. 7,160,047 the present workpieces are relatively hard and thin so that other considerations have to be made for the processing of the materials in the sense of attachment of fastener elements. 
     With regard to the definition of composite materials which ca be used in the context of the present invention the following is explained: 
     Under the designation fiber or fabric reinforced plastic one understands composite materials with high strength fibers such as for example aramid fibers, carbon fibers or glass fibers which are either present as relatively short filling fibers or as long filaments, or in the form of a fabric manufactured from filaments, and embedded in the matrix material of plastic. Thermoplastic materials can admittedly be used as the plastic; however, duroplastic plastics are normally used for coachwork components. The corresponding components are generally present in panel form, as a rule with a three-dimensional shape. 
     In order to satisfy the above named object there is provided, in accordance with the invention, a punch rivet for the attachment of individual components to one another, of which at least one component is preferably formed by a workpiece of composite material, with the punch rivet having a flange of larger diameter, a rivet section of smaller diameter and a ring-like component contact surface at the side of the flange adjacent to the rivet section and surrounding the rivet section, wherein the rivet section has a ring surface at its free end for the piercing of the two workpieces, with the ring surface standing at least substantially perpendicular to the central longitudinal axis of the punch rivet and optionally having an inner concave ring surface which forms the transition from the end face of the punch rivet to the hollow inner space of the rivet section, with the punch rivet having a central passage which extends over the full length of the punch rivet. 
     In accordance with a special embodiment of the punch rivet, the punch rivet has an inwardly projecting ring shoulder in the region of the rivet section. 
     With a design of this kind one endeavors, in contrast to customary punch rivets, to fully pierce the components which lie on one another, so that a high quality rivet bead can be generated at the side of the lower component remote from the flange. For this purpose the punch rivet of the invention must be significantly longer than the total thickness of the stack of the components lying on one another, in contrast to known punch rivets which do not fully penetrate the stack. 
     Furthermore, the invention relates to the recognition that components of a fibre or fabric reinforced plastic, in particular one with a duroplastic matrix material, tends to crumble under the forces acting at the free end of the piercing section, which is exploited here in the sense that the handling of the piercing slug which arises is facilitated because it has a transverse dimension which corresponds approximately to the inner diameter of the rivet section. 
     The method of the invention for the attachment of individual components to one another using the above-named punch rivet in accordance with the invention includes the following steps:
     a) arrangement of the die button against one of the two components to be secured to one another, which are placed on one another, wherein the die button has a bore which is dimensioned to receive the rivet section,   b) carrying out a relative movement of the punch rivet with the free end of the rivet section to the fore towards the components arranged on one another and in the direction of the die button,   c) piercing of the components with the free end of the rivet section and introduction of the rivet section into the bore of the die button until the component contact surface comes into contact with the component adjacent to the flange,   d) using a plunger in order to dilate the punch rivet at least locally and   e) forming a rivet bead by reshaping the free end region of the rivet section in order to clamp the components between the flange and the rivet bead.   

     In this manner a high quality connection of the components to one another is first brought about. With the step of using a plunger in order to at least locally dilate the punch rivet a wholly new way is pursued of introducing a punch rivet and of at least preparing the beading over operation. The dilation of the punch rivet can be brought about by the axial movement of a plunger through the passage and coming from the flange side of the punch rivet, with the plunger being provided with a ring shoulder which brings about the dilation, which tapers in the direction of the free end adjacent the punch rivet and which has a maximum diameter which is larger than the smallest diameter of the passage. 
     Through the dilation of the flange rivet a partly loosened matrix material with the component around the pierced holes can be pressed together so that the punch rivet sits firmly in the punch holes. The undamaged material of the components radially outside of the pierced holes is hereby set under pressure and this particularly favorable for the fatigue characteristics. 
     The ring shoulder of the plunger which tapers in the direction of the free end of the plunger adjacent the punch rivet and which has a maximum diameter which is larger than the diameter of the passage, but smaller than the outer diameter of the rivet section, is preferably pressed into the passage of the punch rivet and brings about a dilation of the passage within the components. In this way the above-mentioned action is enhanced and the strength of the metallic punch rivet increases as a result of the deformation. 
     The method can be further developed in that the central passage has an inwardly directed projection at the region of the rivet section, with the ring shoulder of the plunger being introduced into the passage of the punch rivet until it enters into contact with the inwardly directed projection of the rivet section and presses the latter and the free end of the rivet section outwardly in order to form a rivet bead. 
     In this way not only is the desired dilation of the punch rivet brought about over its entire length, but rather the rivet bead is at least partly brought about by the corresponding deformation, and indeed while the components are being firmly pressed together in the axial direction of the punch rivet in the press or in the tool which is used. This likewise leads to a high quality rivet connection. 
     The use of a plunger which forms a part of a tool that is used is particularly favorable in that the plunger is reused. It is thus not to be compared with a mandrel which is used with blind rivets and which has to be present as a disposable part from each blind rivet and has to be broken each time in order to set the rivet bead. Furthermore, using the plunger there are no torn-off heads as was the mandrel of a blind rivet which could be lost and could cause damage. In other respects the plunger in accordance with the invention can also not be compared with the mandrel of a blind rivet because it operates with a compressive force and not with a tensile force as is the case with the mandrel of the blind rivet. 
     The above-named methods can be improved when the plunger has a guide region at the front end which is guided in the passage of the hollow rivet section. 
     Furthermore, it can be advantageous, when the central passage of the punch rivet has a larger diameter in the region of the flange in comparison to the hollow rivet section, with the diameter corresponding substantially to the diameter of the ring shoulder, whereby the flange of the punch rivet is essentially not dilated by the plunger. The dilation of the punch rivet is not required precisely at this point because the transition from the rivet section into the flange of the punch rivet mainly takes place via a fillet which itself serves for the compressive stress. 
     The plunger can moreover have a smaller diameter at the side of the ring shoulder remote from the punch rivet in order to minimize frictional forces within the passage and wear of the plunger. 
     The piercing slugs which are arisen from the components in the steps b) and c) are preferably dispensed off through the preferably divergent bore of the first die button together with the crumbled material which is produced by the action of the free end of the rivet section. 
     A further particularly favorable layout of the method is possible when the die button is provided with an end recess, which accommodates the flange of the punch rivet, arranged at a side of the components which are placed against one another, when the die button has a passage which starts from the center of the ring recess and is dimensioned to dispense the pierced slugs and when the rivet section of the punch rivet projects out of the end of the die button. The corresponding method includes the following steps:
         using a hold-down member on the other side of the components which are placed against one another,   piercing the components with the free end of the rivet section by a relative movement between the die button and the hold-down member until the rivet section is received in a passage of the hold-down member and the component contact surface comes into contact with the component adjacent to the flange and piercing slugs are generated from the components,   moving a plunger through the passage of the hold-down member and through the passage of the punch rivet, with the plunger having a front end region and a ring shoulder arranged behind the front end region, with the front end region of the plunger pressing the piercing slugs through the passage of the punch rivet and with the free end region of the rivet section which projects at the side of the components remote from the flange being shaped by the ring shoulder into a rivet bead.       

     Here also a dilation of the pierced rivet is effected and indeed in the simplest case only in the region of the free end of the rivet section which projects out of the components. This is also very advantageous since the components are pressed together during this formation of the rivet bead as a result of the tools that are used (press, robot or force-actuating tongs). 
     In this embodiment the passage of the rivet can also be dilated as explained above in conjunction with the movable plunger. 
     Moreover, the front end region of the plunger preferably has a smaller diameter than the internal diameter of the rivet section and is preferably rounded at the free end in order to hereby deform the pierced slugs in shell-like manner and reduce them in diameter, whereby they can be more easily pressed through the passage of the punch rivet and into the passage. 
     In the above-named method, which operates with a hold-down member which can be part of a setting head, the hold down member can be equipped with movable segments which in the closed position engage around the free end of the rivet section without clearance or with little clearance and can be moved apart from one another in order to permit the formation of the rivet bead. 
     In the previously described method a further method step can take place such that By using a second die button with a central post and a concavely rounded ring surface surrounding the central post, the end of the rivet section projecting out of the components can be beaded over or calibrated to form a rivet bead, with the central post of the die button preferably being of divergent form in the direction away from the flange. When one is not satisfied with the mechanical properties of the rivet bead formed by means of the plunger, or with its shaping, or wishes to improve it, then this can take place as explained directly above with the aid of a second die button which fully forms the rivet bead or corrects its shape, for example in the sense of the bead flushly contacts the direct adjacent component and does not have contact only over of a small area. 
     The invention is also concerned with apparatuses which are designed to carry out the method. Such advantageous apparatuses can be taken from the claims  16  to  26 . 
    
    
     
       Further developments of the invention will now be described in more detail with reference to practical embodiments and to the drawings in which are shown: 
         FIGS. 1A to 1C  a punch rivet in accordance with the invention and indeed in an end view ( FIG. 1A ) onto the rivet section of the punch rivet, in a partly sectioned side view ( FIG. 1B ) and in a perspective representation ( FIG. 1C ), 
         FIGS. 2A to 2C  representations of three phases of the attachment of a punch rivet in accordance with  FIGS. 1A to 1C  to two components to be secured to one another, with the  FIG. 2A  showing the starting position,  FIG. 2B  the processing of the elements in accordance with  FIG. 2A  and  FIG. 2C  the resulting first product, 
         FIGS. 3A to 3C  representations of further phases of the processing of the first product of  FIG. 2C , here shown again as  FIG. 3A , by means of the apparatus of  FIG. 3B  in order to generate a finished product in accordance with  FIG. 3C . 
         FIGS. 4A to 4C  a further punch rivet in accordance with the invention and indeed in an end view ( FIG. 4A ) on the rivet section of the punch rivet, and in a partially sectioned side view ( FIG. 4B ) and in a perspective representation ( FIG. 4C ), 
         FIGS. 5A to 5C  a series of drawings to explain the processing of the punch rivet in accordance with the invention and in accordance with  FIGS. 4A to 4C , with  FIG. 5A  showing the starting position,  FIG. 5B  showing the situation of after the closing of the tools that are used and  FIG. 5C  showing the finished component assembly, 
         FIGS. 6A to 6E  a series of drawings to explain an alternative processing of a punch rivet in accordance with the invention in accordance with  FIGS. 1A to 1C , with  FIG. 6A  showing the starting position,  FIG. 6B  showing the situation after the introduction of the components into the tools that are used,  FIG. 6C  showing the situation after the closing of the tools that are used,  FIG. 6D  showing the removal of the pierced slugs and  FIG. 6E  showing the finished component assembly and 
         FIG. 7  a hold-down member in accordance with the invention in a perspective representation. 
     
    
    
     Referring now to the  FIGS. 1A to 1C  a punch rivet  10  is shown there for the attachment of individual components  40 ,  42  to one another ( FIG. 2A ) of which at least one component  40  is formed by a workpiece of composite material. 
     The punch rivet  10  has a flange  12  of larger diameter D 1 , a rivet section  14  of smaller diameter D 2  and a ring-like component contact surface  18  at the side  16  of the flange adjacent to the rivet section  14  and surrounding the rivet section  14 . The rivet section  14  has at its free end  20  a ring surface  22  for the piercing of the two components  40 ,  32  that stands at least substantially perpendicular to the central longitudinal axis  24  of the punch rivet  10  and has an inner concave ring surface  26  which forms the transition from the end face  22  of the punch rivet  10  into the hollow internal space  28  of the rivet section. This concave ring surface  26  is not essential and it is also not essential for the ring surface  22  to stand strictly perpendicular to the central longitudinal axis  24 , it could form an enclosed angle of 80 to 100° with the longitudinal axis and could also be rounded. 
     The component contact surface  18  is shown here as a conical surface, this is however also not essential, this surface could also stand perpendicular to the longitudinal axis. Recesses  30  and noses  32  are located at the component contact surface  18  such as are known as features providing security against rotation for bolt elements. Such features  30  and  32  are not essential for a punch rivet  10  because for punch rivets security against rotation is not required. Nevertheless they help to achieve an intimate connection with the adjacent component. 
     The area of the component contact surface  18  is defined by the diameter of the flange  12  and this should be selected sufficiently large that the surface pressure is designed for the material having regard to the properties of the first component and the forces which originate in operation from the punch rivet or are transmitted by the punch rivet. The rivet section  14  has a right cylindrical hollow internal space  28  and a right cylindrical jacket surface. The length of the rivet section exceeds the total thickness of the components which are to be secured to one another by an amount which permits the formation of a rivet bead. 
     In this example, the punch rivet  10  is of hollow shape, i.e. such that a central passage corresponding to the hollow internal space  28  extends over the full length of the hollow rivet. 
     The reference numeral  34  points to a fillet, which forms the transition from the rivet section  14  into the sheet metal contact surface  18 . 
     The method for the attachment of individual components  40 ,  42  to one another using a punch rivet in order to form a first product will now be described with reference to  FIGS. 2A to 2C . In this example at least the upper component  49  is formed by a workpiece of composite material. The component  42  can be a sheet metal part or can be a further workpiece of composite material. It will be understood that in this application (including the patent claims) the term “composite material” is used in the sense of the above-quoted definition. It is also noted that the punch rivet can be so attached that the component contact surface  18  comes to lie, as shown here, on the upper component  40  or inverted, so that it contacts the sheet metal component  42 . Furthermore, the method is not restricted to the attachment of two components to one another. 
     In  FIG. 2A  the punch rivet  10  of  FIG. 1A  bis  1 C is arranged above the first component  40 , with the free end face  20  of the rivet section  14  being designed to pierce the two workpieces  40 ,  42 , and with the punch rivet further having a central passage which extends over the full length of the hollow rivet, the method includes the following steps:
     a) Arrangement of the die button  50  against one of the components which are to be secured to one another and which are placed on one another, with the die button having a bore  52  which is dimensioned to receive the rivet section  14 , i.e. has a diameter which corresponds to that of the rivet section or is fractionally larger than this.   b) Carrying out a relative movement of the punch rivet  10  in the arrow direction  54  by means of the piercing head  60  with the free end  20  of the rivet section to the fore against the components  40 ,  42  arranged on one another and in the direction of the die button  50 , For this purpose the piercing head has a recess  62  which receives the flange  12  of the punch rivet.   c) Piercing of the components  40 ,  42  with the free end  22  of the rivet section  14  and introduction of the rivet section into the bore  52  of the die button  50  until the component contact surface  18  comes into contact with the component  40  adjacent the flange  12 . At the same time the underside  64  of the piercing head comes into contact with the upper component  40 . On the piercing of the components a piercing slug (not shown here) arises from each component which falls through the bore  52  together with any crumbled material of the components  40 ,  42 .   d) Utilizing a plunger  66  in order to at least locally dilate the punch rivet  10 . In this connection it can be seen in  FIG. 2B  that the plunger  66  is guided in a bore  68  of the piercing head  60  for an axial movement in the arrow direction  54  relative to the piercing head  60  along the central longitudinal axis  24  of the punch rivet i.e. of the piercing or setting head. The dilation is evident from the reference numerals  72  in  FIG. 2C , above all through the transition  74  into the original internal diameter  36  of the rivet section  14  where this transition  74  here being formed by the ring shoulder  78  of the plunger  66  which comes to lie approximately at the level of the underside of the lower component  42  in  FIG. 2B . The ring shoulder  78  is formed by a tapering of the plunger in the direction towards the lower end so that the dilation of the hollow space  28  of the punch rivet  10  takes place progressively. The ring shoulder  78  has a maximum diameter which is larger than the smallest diameter of the passage  36  but is significantly smaller than the outer diameter of the rivet section  14  of the punch rivet  10 .
       The component assembly which has arisen from the previously described method is shown in  FIG. 2C . It can be designated as a first product which proceeds in the context of a two-path or two-stage method from the first stage. The second stage is shown in  FIGS. 3A to 3C , in this respect the drawing in accordance with  FIG. 3A  is identical with the drawing in accordance with  FIG. 2C  it was only repeated in order to simplify the representation.   In the second stage of the manufacturing process the first product is processed further to the finished product and indeed by the further step:   
       e) Forming a rivet bead  80  by shaping the free end region  15  of the rivet section  14  in order to clamp the components  40 ,  42  between the flange  12  and the rivet bead  80 . This takes place with the die button  90  of  FIG. 3B . This die button  90  is provided with a central post  92  and a concavely rounded ring surface  94  surrounding the central post  92  whereby the end of the rivet section  14  remote from the flange  12  which projects out of the components  40 ,  42  is beaded over to form a rivet bead  80 . The finished product can be seen in  FIG. 3C .   

     The attachment of the punch rivet by means of the piercing head  60  and the die button  50 , optionally while using the further die button  90 , has only been so portrayed above for the purpose of explaining the principles. 
     For the attachment of the punch rivet  10  it is normally introduced into a so-called setting or piercing head which is built into a press and which delivers punch rivets or fastener elements one after the other to a sequence of workpieces  40 ,  42 . In this connection a spring-loaded hold down member (likewise not shown but also well-known per se) is normally used which surrounds the punch rivet or the fastener element and which serves to press the workpiece, here the components  40 ,  42  against the end face of the die button  50  so that the workpiece  40 ,  42  can be held in its intended position and clamped together. The punch rivet  10  or the fastener element is normally moved in the direction towards the workpiece  40 ,  42  by means of a plunger (likewise not shown) of the piercing head  60  in the direction towards the workpiece  40 ,  42 , with the piercing head being so designed that a sequence of punch rivets  10  can be fed to the piercing head but only one punch rivet  10  is supplied to the respective workpiece, here consisting of the two components  40 ,  42 , and punched into the workpiece for each stroke of the press. 
     As explained above the die button  50 , is located beneath the workpiece  40 ,  42  and normally has a cylindrical shape which is let into a corresponding bore (not shown) of a receiving tool (likewise not shown). 
     As usual for the attachment of fastener elements, this discussion relates to a piercing head  60  which is arranged at the upper tool of a press or at an intermediate platen of the press, whereas the tool which receives the die button  50  is the intermediate platen of the press or the lower tool of the press respectively. An inverted arrangement would also be possible in which the setting head is arranged at the lower tool of the press or at an intermediate platen of the press and the free end  20  of the rivet section  14  is directed upwardly, whereas the die button  50 , which then faces downwardly, is then located at the intermediate platen or at the upper tool of the press respectively, an arrangement which will later be explained in more detail in connection with  FIG. 6B . 
     It is in no way essential to use a press for the attachment of the punch rivet to the workpiece. By way of example a robot, for example in accordance with the European patent 0 691 900 could be used, with the die button  50  and the piercing head then being carried by the robot. However, a percussion tool or another tool could also be used for the attachment of the punch rivet to the components, for example a tool in accordance with one of the following protective rights DE-PS 197 47 267, EP 0 890 397 or DE-PS 197 01 088. 
     It is indeed generally customary to attach fastener elements  10  to a workpiece with the central longitudinal axis  24  arranged vertically. However, an orientation of this kind is in no way essential. Instead of this the longitudinal axis  24  could have any desired orientation in space. Accordingly, when geometrical terms such as vertical or top or bottom or above and below are used in this application, then this is to be understood in such a way that the designations simply relate to the orientation of the corresponding figure and should in no way be restrictively construed. 
     Depending on the purpose the components in the form of a finished product in accordance with  FIG. 3C  are intended to satisfy, the manufacture in two passes in accordance with  FIGS. 2A to 2C , on the one hand, and  FIGS. 3A to 3C , on the other hand, and can also take place in different ways. The manufacture of the first product and of the finished product can also take place in different stages of one plant, for example in a progressive tool if smaller sheet metal parts are to be attached to composite components, above all when a plurality of operations are to be carried out and can be realized in a press. Alternatively, the first product can be manufactured in one plant and the final product in a second plant of the same factory; the two plants can be part of a transfer system; or the two plants can be located at different locations in the same factory or in different factories or in different areas of the same production hall. 
     Furthermore, the possibility exists of placing a further pre-holed component (not shown) in the second manufacturing stage in accordance with  FIGS. 3A to 3C  over the projecting rivet section against the underside of the second component  42  and this further component (which can also consist of plural components) can then be fixed to the two first named components  40  and  42  by the subsequently formed rivet bead  80 . 
     The method just explained above can also take place in such way that the piercing slugs  56  which arise are removed as indicated through the preferably diverging bore  52  of the first die button  50 . 
     It is particularly favorable when the central passage  36  extends over the entire length of the hollow rivet and has an inwardly directed projection  38  in the region of the rivet section  14  as is shown in  FIGS. 4A to 4C . These Figures show an alternative form of the punch rivet  10  which is provided with the same reference numerals as in  FIGS. 1A to 1C . It will be understand that parts which are provided with the same reference numerals have the same form or function as the previously described parts unless something is stated to the contrary, so that a renewed description of the parts, or of their function, is not required, but rather the previous description applies. This convention also applies for all parts described here and the further description will concentrate only on the differences. Here the only difference lies in the fact that the passage  36  of the punch rivet has an inwardly directed projection  38  in the region of the free end of the rivet section  14 . 
     With this design of the punch rivet  10  the method then proceeds as is shown in  FIGS. 5A to 5C . 
     There, after the piercing of the components  40 ,  42  by the free end  20  of the rivet section  14  the ring shoulder  78  is introduced into the passage  36  of the punch rivet  10  until it comes into contact with the inwardly directed projection  38  of the rivet section  14  and presses the latter and the free end region  15  of the rivet section outwardly, in order to form a rivet bead  80  in accordance with  FIG. 5C . With this the first product is finished and counts as a finished product, since this is a high quality rivet bead  80 . 
     If one wishes to have a better shaping of the rivet bead  80  then this can be achieved by using tools above all the die button  90  which are shown in  FIGS. 3A to 3C  and were described in conjunction with these Figures. Since then no large deformation of the rivet is necessary one can speak here of a calibration of the rivet bead. 
     An alternative process for the attachment of the punch rivet  10  in accordance with  FIGS. 1A to 1C  will now be explained with reference to  FIGS. 6A to 6E .  FIG. 6A  first shows the general geometrical arrangement of the parts with the punch rivet  10  beneath the component  40  with the flange at the bottom and the free end  20  of the rivet section  14  directly below the first component  40 . The component  42  is here arranged above the first component  40  which is however not essential. As can be seen from  FIG. 6B  in this embodiment a die button  100  is used having an end face recess  102  which receives the flange  12  of the punch rivet on the one side of the components  40 ,  42  which are placed on one another, in this case beneath the components  40 ,  42 . The die button  100  has a passage  104  which starts from the center of the ring recess  102  and is dimensioned to dispose of the piercing slugs  56  ( FIG. 6C ) and the rivet section  14  of the punch rivet  10  projects out of the end face  106  of the die button  100  with the method including the following steps:
         using a hold-down member  110  on the other side of the components  40 ,  42  which are placed against one another,   piercing the components  40 ,  42  with the free end  20  of the rivet section  14  by a relative movement in the direction of the arrow between the die button  100  and the hold-down member  110  until the rivet section  14  is received in a passage  112  of the hold-down member  110  and the component contact surface  18  comes into contact with the component  40  adjacent to the flange  12 , with piercing slugs  56  being generated from the components  40 ,  42 ,   moving a plunger  114  through the passage  112  of the hold-down member  110  and through the passage  36  of the punch rivet  10 , with the plunger  114  having a front end region  116  and a ring shoulder  118  arranged behind the front end region  116 , with the front end region  116  of the plunger pressing the piercing slugs  56  through the passage  36  of the punch rivet and the free end region  15  of the rivet section  14  which projects at the side of the components  40 ,  42  remote from the flange  12  being shaped by the ring shoulder  118  into a rivet bead  120 .       

     Various variants of the method explained above are possible. It is for example not essential that the passage  36  of the punch rivet  10  is dilated in the region of components  40 ,  42  by the plunger  114  or by its ring shoulder  118 , it will be sufficient if only the free end region  20  of the rivet section  14  which projects out of the components  40 ,  42  is reshaped to the rivet bead  120  by the ring shoulder  118 . 
     Furthermore, the possibility exists of reshaping or calibrating the rivet bead  120  by means of a die button  90  in accordance with  FIG. 3B . 
     The die button  100  in the illustration in accordance with  FIG. 6B  is actually only suitable for a lay-in process at which the punch rivets  10  are laid one after the other into the die button  100 . For an automated production the die button  100  can be replaced by a setting or piercing head which permits the automatic supply of punch rivets  10 . 
     Furthermore, the hold-down member  110  is shown in  FIG. 6B  as a solid component which is also basically possible. It is however better to use a construction of the hold-down member in accordance with  FIG. 7 . 
     The hold-down member in accordance with  FIG. 7  is equipped with movable segments  122 . The segments  122  are in the shown closed position in operation in which they surround the free end region  15  of the rivet section without clearance or with little clearance and can be moved apart from one another in order to permit the formation of the rivet bead  120 . Examples of die buttons with movable segments are known for the processing of punch rivets in which the sheet metal material is not pierced (see for example WO00/16928) and can be modified for the purpose of the present invention in order to realize the hold-down member  110  in accordance with the invention. 
     Furthermore the hold-down member  110  of  FIG. 7  can be part of a setting or piercing head. One advantage of a hold down member is that it serves to clamp the components  40 ,  42  together during the piercing operation, between itself and the die button (for example 100), and this is very important to achieve a clean piercing operation. 
     In all embodiments materials can be named as an example from the material of the punch rivets which, in the context of cold deformation, achieve the strength values of class  8  in accordance with the ISO standard or higher, for example a  3562  alloy in accordance with DIN 1654. Also aluminum alloys, in particular those of higher strength can be used for the punch rivets, for example AlMg5. Fastener elements of higher strength magnesium alloys, such as for example AM50, can also be considered. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  punch rivet 
           12  flange 
           14  rivet section 
           15  free end of rivet section 
           16  side of the flange adjacent the rivet section 
           18  component contact surface 
           20  End 
           22  ring surface 
           24  longitudinal axis 
           26  cocabe ring surface 
           28  hollow internal space of rivet section 
           30  recesses 
           32  nose 
           34  fillet radius 
           36  passage of the punch rivet 
           38  projection 
           40  component 
           42  component 
           50  die button 
           52  bore, 
           54  arrow direction 
           56  piercing slug 
           60  piercing head, 
           62  recess of the piercing head 
           64  underside 
           66  plunger 
           68  bore 
           69  guide region 
           72  dilated portion 
           74  transition 
           76  inner diameter 
           78  ring shoulder 
           80  rivet bead 
           90  die button 
           92  central post 
           94  concavcely rounded semi-toroidal ring surface 
           100  die button 
           102  recess 
           104  passage 
           106  end face 
           110  hold down member 
           112  passage 
           114  plunger 
           116  end region 
           118  ring shoulder 
           120  rivet bead 
           122  segments