Patent Publication Number: US-8979601-B2

Title: Electric connecting terminal as well as method and device for producing an electric connecting terminal

Description:
Electric connecting terminal and also method and device for producing an electric connecting terminal 
     The invention relates to an electric connecting terminal with a serration arrangement having a gradient-shaped sharpness profile. Further, the invention relates to a production method for such an electric connecting terminal. 
     Electrical conductors are frequently terminated at their free ends with connection pieces which permit contacting of the conductor with corresponding contact partners. For this, inter alia connecting terminals are used which permit solder-free connection to the conductor structure. These terminals, which are also known as crimp connection terminals, are typically manufactured from a metal sheet by means of a punching process. In such case, a conductor-side section of the connecting terminal has at least one tab which is bent around the conductor and then is crimped therewith for the purposes of mechanical and/or electrical connection. In the case of electrical conductor structures which are coated with an insulating layer, such as a thin enamel layer or a parasitic oxide layer, the disturbing insulating layer has to be removed or broken through in order to produce sufficient electrical contact between the connecting terminal and conductor structure. Connecting terminals in which the surface which contacts the conductor has special sharp-edged serration structures are used for this. Upon crimping of the connecting terminal, the parasitic insulating layer is broken through by the serration structures cutting into the metallic conductor. By means of appropriate crimping, good extension and associated galling of the materials involved is permitted, which in turn achieves good electrical contacting. The transition resistances prove to be stable long-term over the lifetime, in particular for aluminium conductors and hard copper conductors with small cross-sections. 
     The use of sharp-edged serrations however also leads to undesirable mechanical weakening of the relevant conductor, since the conductor cross-section is reduced at the relevant points by the serration structures cutting in. This effect proves particularly harmful in the case of conductors made from brittle materials, such as aluminium. Further, the use of such a connecting terminal may also be unfavourable in the case of conductors which are constructed from a plurality of thin strands. In this case, the sharp-edged serrations can effect severing of individual conductor strands. 
     A conventional connecting terminal is typically produced by means of a punching process, the serrations in a subsequent “ploughing” process being produced outside the punch. In this process, a plurality of knife-like “ploughing” structures arranged next to one another are drawn across the conductor contact surface of the connecting terminal transversely to the direction of insertion of the cable, in order to produce groove-like structures with symmetrical heapings of material. 
     Departing from this prior art, it is an object of the invention to provide an electric connecting terminal which permits both sufficient electrical connection and sufficient mechanical connection between the connecting terminal and conductor, and in addition is inexpensive to produce. This object is achieved by an electric connecting terminal according to Claim  1  and also by a production method for an electric connecting terminal according to Claim  3 . Further, the object is achieved by a device according to Claim  8 . Further advantageous embodiments of the invention are set forth in the dependent claims. 
     According to the invention, an electric connecting terminal for connecting to an electrical conductor structure is provided which comprises a serration arrangement, comprising a plurality of serration structures, for cutting into the electrical conductor structure in a conductor-side section. The serration arrangement in this case has a gradient-shaped sharpness profile formed by heapings of material produced in an embossing process. The gradient-shaped profile of the serration arrangement means that a conductor structure in the conductor-side region of the clamping connection is cut into only slightly, in order to prevent mechanical weakening of the conductor structure in this region. On the other hand, the conductor structure in the contact-side region of the clamping connection is cut into more deeply, in order to ensure sufficient electrical contact. This is advantageous in particular in the case of aluminium wires, enameled wires or wires made from hard alloys. Further, the connecting terminal according to the invention can also be used for electrical lines with small or very small cross-sections. The connecting terminal can be produced particularly beneficially due to the use of the embossing process. 
     In one embodiment, provision is made for the serration structures to have asymmetrical heapings of material which were produced by a lateral flow of material during the embossing process. Such heapings of material form sharp-edged structures, which simplifies penetration into hard conductor materials. Owing to the lateral flow of material brought about by the embossing process, the heapings of material come out at varying heights. This achieves a beneficial profile for the crimped connection with a conductor structure. 
     According to the invention, further, a method for producing an electric connecting terminal is provided in which a serration arrangement, comprising a plurality of serration structures, for cutting into an electrical conductor structure is produced in a conductor-side section of the electric connecting terminal. In this case, the serration arrangement is produced in an embossing process with a gradient-shaped sharpness profile. Owing to the use of an embossing process, heapings of material which can be used as sharp-edged structures for cutting into corresponding conductor structures can be produced particularly easily. The sharpness of the serration structures which increases in a gradient shape permits an improved connection between the terminal and the conductor structure, since the serration structures can cut in more easily and more deeply in the end section of the conductor structure than in a front conductor section. 
     In one embodiment, provision is made for asymmetrical heapings of material to be produced on the individual serration structures in the embossing process, which heapings of material form the gradient-shaped sharpness profile of the serration arrangement. With the aid of asymmetrical heapings of material, particularly sharp edges can be formed, which facilitates cutting into corresponding conductor structures. 
     In a further embodiment, provision is made for the embossing process to take place with the aid of an embossing means comprising a plurality of asymmetrical embossing structures, which means brings about a lateral flow of material in the direction of insertion of the conductor which produces the asymmetrical heapings of material of the serration structures ( 131 ,  132 ,  133 ,  134 ,  135 ,  136 ,  137 ,  138 ) in the conductor-side section of the connecting terminal. The desired gradient profile of the serrations can thereby be achieved in a particularly simple manner. 
     A further embodiment provides for the electric connecting terminal ( 100 ) to be cut out from a metal sheet ( 101 ) in a punching process, 
     the embossing process being integrated in the punching process. The production of the connecting terminal can thereby be considerably simplified. 
     In a further embodiment, provision is made for a further embossing process to be carried out in which at least a part of the serration structures is cut into by means of sharp-edged knife structures in order to produce additional sharp ridges on the serration structures. Due to the splitting-up of the serration structures and the accompanying formation of sharp-edged ridges, additional relative deformations are more easily achieved upon crimping, which increases the contact stability. 
     According to the invention, a device for producing an electric connecting terminal is provided which comprises a punching means and a punching base. Further, the device comprises an embossing means, with the aid of which a serration arrangement, comprising a plurality of serration structures, with a gradient-shaped sharpness profile are produced in a conductor-side section of the electric connecting terminal. Serration structures can be produced in the connecting terminal very simply with the aid of the embossing means. 
     In one embodiment, provision is made for the embossing means to comprise a plurality of serration-shaped embossing structures with asymmetrical flanks. Serration structures with asymmetrical heapings of material can be produced with the aid of such embossing structures. 
     A further embodiment provides for the embossing structures to be shark-fin-shaped or sawtooth-shaped. These embossing structures are particularly well suited for producing asymmetrical heapings of material. Further, a lateral flow of material in the workpiece can be brought about particularly simply therewith, by which flow a gradient-shaped sharpness profile of the serration arrangement is formed. 
     In a further embodiment, the conductor-side flanks of the embossing structures are formed substantially perpendicularly. This means on one hand that the lateral flow of material induced by the embossing operation takes place particularly effectively in the desired direction. On the other hand, particularly sharp-edged heapings of material may form on perpendicular flanks, which in turn improves the properties of perforation of the relevant serrations into the conductor material. 
     Finally, in a further embodiment, provision is made for the embossing means to be integrated within the punching means. The integration of the embossing die in the punching die simplifies the production operation, since the punching process and the embossing process can be carried out jointly or shortly one after another. 
    
    
     
       The invention will be explained below with reference to drawings. Therein: 
         FIG. 1  shows a perspective view of a device according to the invention with a metal sheet arranged between the punching die and the punching base; 
         FIG. 2  shows the finished punched component with serration structures produced in an embossing process; 
         FIG. 3  shows a device according to the invention for producing a connecting terminal, comprising a punching means and an embossing means with a metal sheet arranged between the die and the punching base; 
         FIG. 4  shows the device of  FIG. 3  during a punching operation; 
         FIG. 5  shows the device of  FIGS. 3 and 4  with a finished punched component; 
         FIG. 6  shows the device of  FIGS. 3 to 5  during an embossing operation in which the serration structures are produced on the component; 
         FIG. 7  shows the device of  FIGS. 3 to 6  with the finished component; 
         FIG. 8  shows an embossing means with a plurality of shark-fin-shaped serration structures; 
         FIG. 9  shows the embossing means of  FIG. 8  during the embossing operation; 
         FIG. 10  shows the finished component with a number of serration structures produced by the embossing operation; 
         FIG. 11  shows the electric connecting terminal of  FIG. 10  upon cutting into an electrical conductor structure; 
         FIG. 12  shows a variation of the embossing method according to the invention for producing mirror-symmetrically arranged serration structures; 
         FIG. 13  shows a further variation of the embossing method according to the invention for producing mirror-symmetrically arranged serration structures and a flat middle region; and 
         FIG. 14  shows a further embossing process, in which additional sharp ridges are produced on the serration structures by means of a second embossing die comprising a plurality of knife structures. 
     
    
    
     The production method for the connecting terminal according to the invention is explained in  FIGS. 1 and 2  below. For this,  FIG. 1  shows the starting situation for the combined punching and embossing process. Therein, a metal sheet  101  which serves as a blank is arranged between a punching die  210  which serves as a punching means and a die plate  220  which serves as a cutting base. The shape of the component to be produced is formed as a negative impression  211  in the punching die  210 . The cutting base  220 , in contrast, has the positive form of the component which is to be produced, so that the metal sheet  101  upon lowering of the punching die  210  is cut out along the cutting edges, which are complementary to each other, of the negative impression  211  formed in the punching die  210  and of the cutting base  220 . 
     According to the invention, the device  200  shown in  FIG. 1  further has an embossing means  230 . The embossing means  230  may, as is the case here, be formed as an embossing die integrated within the punching die  210 , which embossing die engages in an opening region  213  of the punching means  210 . The embossing die  230  in this case comprises a plurality of embossing structures  231  which are in the form of serrations arranged in a groove shape. This is merely indicated in  FIG. 1 . 
     Owing to the integration of the embossing die  230  in the punching die  210 , the embossing of the desired serration structures can take place immediately after the connecting terminal  100  has been cut out from the metal sheet  101  which serves as a blank. The embossing process can in principle also take place before the punching process. 
     Depending on the application, it may be advantageous to form the embossing die  230  as an embossing means which is spatially arranged separately from the punching means  210 . In this case, which is not shown here, the blank  101  is transferred, after the punching, from the punching means  210  into the embossing means  230 , or vice versa. 
       FIG. 2  shows the finished cut-out connecting terminal  100  which is equipped with the desired serration arrangement  130 . The connecting terminal  100  in the present example comprises a conductor-side section  110  and a contact-side conductor section  120 , which in the present example of embodiment is formed as a pole shoe. The two sections  110 ,  120  are connected together via a common bridge section. 
     The conductor-side section  110  has the desired serration arrangement  130 , which according to the invention is constructed from groove-shaped serration structures running next to one another. The serration structures in this case extend transversely to the direction of insertion of the conductor  501 , which extends parallel to the axis of symmetry of the connecting terminal  100 . Although the serration structures  131  to  139  shown here extend substantially across the entire breadth of the conductor-side section  110  of the connecting terminals  100 , serration structures which merely extend over part of the breadth of the section  110  are also possible, depending on the application. Further, also a plurality of serration arrangements may be arranged next to one another on the conductor-side section  110 . 
     The punching process and the embossing process for a simple connecting terminal  100  were explained with reference to  FIGS. 1 and 2 . Depending on the application, the form of the connecting terminal and of the individual sections may vary. If the production of connecting terminals takes place in a mass production process, as is usually the case, it is not individual pieces of metal sheet but strip-shaped metal sheets which are used as blanks. The punching then takes place in a continuous process, the cut-out workpieces being connected together by means of thinner bridges for better handling. In the punching process, the conductor-side section  110  may already also be pre-bent in order to facilitate further steps, in particular the crimping. The punching die  210  and the cutting base  220  may be correspondingly preformed for this purpose. Depending on the respective application, a negative punching means may also be used, the punching die having the shape of the component to be produced and the cutting base serving as negative impression. Further, the punching means may also be in roller form, the punching die and cutting base being arranged on two contra-rotating rollers. This permits a continuous punching or embossing process. 
     In  FIGS. 3 to 5 , the punching operation and the embossing operation are illustrated in a diagrammatically simplified cross-sectional view. Therein,  FIG. 3  shows the starting situation, in which the sheet metal piece  101  which serves as a blank is arranged between an upper tool part which serves as a punching die  210  with an integrated embossing die  230  and a lower tool part  220  which serves as a cutting base. In the present example of embodiment, the embossing die  230  comprises a plurality of serration-shaped embossing structures  231 , which are merely indicated here for clarity. The embossing structures  231  which extend in a groove-shape have according to the invention sawtooth-shaped cross-sectional profiles with asymmetrical flanks, the left flanks in each case extending substantially perpendicularly at least over a partial region. In the following method step, the desired component is cut out from the metal sheet  101  and then the desired serration structures are embossed into the conductor contact surface  102  of the metal sheet  101 . As is illustrated in  FIG. 4  by means of arrows, the punching die  210  is moved in the direction of the die plate  220  for this purpose. This transfers the contour of the die plate  220  into the metal sheet. Owing to the complementary formation of the die  210  and of the cutting base  220 , the lateral parts  211  of the die  210  which serve as punch knives slide along the outer periphery of the cutting base  220  and carry the excess metal sheet  103  with them. 
     Once the punching process has taken place, the punching die  210  is guided upwards ( FIG. 5 ) and then the embossing process is carried out. In so doing, the embossing die  230  is lowered onto the blank  101  such that the embossing structures during the embossing operation are pressed into the contact surface  102  of the punched connecting terminal  100 . Due to the asymmetrical construction of the serration-shaped embossing structures  231 , the two flanks having different angles of inclination, the material of the machined workpiece  101  is displaced to different extents by the two flanks. As shown in  FIG. 6 , the flatter right flank of the teeth pushes the material effectively to the right, whereas the preferably perpendicular left flank of the teeth does not cause any substantial displacement of material in the workpiece. Due to the flow of material  104  in the direction of insertion of the conductor  501  which is yielded effectively therefrom, material is pressed effectively against the steep left flank of the embossing structures and raised up on this flank. The heaping of material thus produced forms a sharp-edged ridge, the height or sharpness of which increases from left to right owing to the flow of material  104 , represented by means of an arrow, in the workpiece  100 . 
     Once the embossing has taken place, the embossing die  230  is raised again in order to release the finished component  100 . As shown in  FIG. 7 , the component  100  now has the desired teeth  130  with sharper-edged serration structures increasing in a gradient shape from left to right. 
     The physical form of the embossing structures may vary according to the application. Thus for example embossing means with shark-fin-shaped embossing structures can also be used.  FIG. 8  shows a cross-section through such an embossing means  230  as part of the die  210 . As is shown here, the shark-fin-shaped embossing structures  231  to  239  also preferably have a substantially perpendicular left flank. The right flank of the embossing structures  231  to  239 , on the other hand, is formed with the typical S-shaped contour. Owing to its larger displacement volume, the use of shark-fin-shaped embossing structures means that a greater flow of material can be induced in the workpiece than is the case with the aid of the wedge-shaped embossing structures shown in  FIGS. 3 to 5 . This opens up the possibility of adapting the flow of material to the respective application by varying the flank profile. 
     As is shown in  FIG. 9 , a flow of material which is directed towards the right is brought about upon pressing the embossing structures  231  to  239  into the workpiece  100 . This causes the material to be raised up on the steep flanks of the teeth in the interstitial spaces. Due to the flow of material, indicated by means of the arrow  104 , in the workpiece  100 , once the embossing process has ended, there is more material on the right side than on the left side of the workpiece  100 , which means that the heapings of material on the right side are higher than on the left side. 
     As shown in  FIG. 10 , the higher heapings of material of the right side also bring about a more acute or sharper profile of the relevant serration structures, since the material rises higher here. Thus the sharpness of the serration structures  131  to  138  which is achieved, and hence the sharpness profile of the serration arrangement  130 , increases from left to right in a gradient shape. Upon the crimping of a connecting terminal  100  which is configured in this manner with a conductor structure, the serration structures  131 ,  132 ,  133 ,  134  on the conductor input side therefore penetrate only relatively slightly into the conductor core, so that the conductor structure at this point is not excessively mechanically weakened. The serration structures  131  to  134  on the conductor input side therefore contribute primarily to the mechanical fastening of the conductor structure within the connecting terminal  100 , and less to the production of a sufficient electrical contact between the connecting terminal  100  and conductor structure  500 . On the other hand, the contact-side serration structures  135  to  138 , owing to the relatively higher heapings of material and the associated sharper-edged ridges, penetrate further into the conductor structure  500 , which means that a particularly good electrical connection between the connecting terminal  100  and the conductor structure  500  can be achieved. 
     In order to make clear the mode of operation of the special connecting terminal  100 ,  FIG. 11  shows the serration arrangement  130  engaged with an electrical conductor structure  500 . In this case, the original path of the conductor structure  500  is indicated by means of the broken line. As is shown here, the depth of penetration of the serration structures  131  to  138  into the relevant conductor structure  500 , increases from left to right owing to the different heights of the heapings of material. In this case, dependent on the material properties of the conductor structure, more or less large amounts of conductor material may flow into the gaps in the serration structures  131  to  138  upon crimping the terminal. Particularly in the case of soft materials, virtually complete filling of the gaps may take place. 
     Depending on the application, a plurality of serration arrangements may also be produced. Inter alia, the serration structures of two serration arrangements may be arranged mirror-symmetrically to each other.  FIG. 12  shows an embossing operation in which two serration arrangements which are mirror-symmetrical to each other are produced. On the other hand, in the example of embodiment of  FIG. 13  additionally a flat region between the serration arrangements which are arranged mirror-symmetrically to each other is produced by means of a correspondingly formed embossing die  230 . 
     Since as many sharp-edged structures as possible are advantageous for producing a good electrical contact between the connecting terminal and conductor structure, the number of sharp-edged ridges can be increased by splitting up individual serration structures. This can be done for example by a second embossing operation in which an embossing die  240  equipped with a plurality of sharp, wedge-shaped blades  241 ,  242 ,  243 ,  244 ,  245 ,  246 ,  247 ,  248  is pressed into the previously produced serrations  131 ,  132 ,  133 ,  134 ,  135 ,  136 ,  137 ,  138 . Such a situation is shown in  FIG. 14 . 
     The embossing according to the invention of the serration structures is achieved by a special formation of the embossing die  230  in the punching tool  200 . One important prerequisite for the desired heapings of material is constituted on one hand by a sufficiently large displacement of material by the embossing/embossing removal operation (summarily), which brings about a flow of material transversely to the serration structures. On the other hand, it is advantageous if the serration structures, at least on one side, have very largely perpendicular flanks against which the transversely-flowing material can rise up. Asymmetrical ridges which are increasingly sharper in a gradient shape can be obtained particularly well on the perpendicular flanks with periodic sawtooth-like or shark-fin-like formations of the flanks of the embossing die. These are to be arranged in the crimp in particular in regions of the greatest compression. 
     The embodiments disclosed in the preceding description in conjunction with the figures are merely examples of embodiment of the invention. In this case, depending on the application, all the features disclosed in this connection, both individually and in combination with each other, may be relevant for realising the invention. Also, the invention is not intended to be restricted merely to the embodiments shown here. Rather, it is within the spirit of the invention to vary the number, the arrangement and the dimensions of the individual serration structures in order to permit an electrical and/or mechanical connection between the connecting terminal and conductor structure which is optimised for the requirements of the respective application.