Patent Publication Number: US-8540535-B2

Title: Cable lug with shell-shaped part and fastening device

Description:
The invention relates to a system for fastening a round conductor to a connection element with a fastening device. The invention also relates to a method for fastening a round conductor to a connection element with a fastening device. 
     The connection of round conductors to connection elements, which in practice are often formed flat, is as a rule difficult. On the one hand a reliable electrical contact of the round cable with the connection element must be ensured, and on the other hand this electrical contact must also be guaranteed if for example vibrations or impacts act on the connection element. 
     This object is achieved according to the invention by a system for fastening a round conductor to a connection element, comprising a connection element that has at one end an at least partially shell-shaped part, a round conductor closed by a contact element, the contact element being adapted for contacting the connection element, and a fastening device that is adapted to fasten an end region of the round conductor, lying in front of the contact element, in the region of the shell-shaped part of the connection element to the said connection element by frictional force (force-fit). 
     This object is furthermore achieved by a method for fastening a round conductor closed with a contact element to a connection element, wherein the contact element is adapted to contact the connection element and the connection element comprises at one end an at least partially shell-shaped part, by means of a fastening device, comprising positioning an end region of the round conductor, lying in front of the contact element, in the shell-shaped part of the connection element and fastening the end region of the round conductor by frictional force (force-fit) to the connection element in the region of the shell-shaped part of the connection element by means of a fastening device. 
     The at least partially shell-shaped part is designed so that a suitably corresponding part of an end region of the round conductor lying in front of the contact element can be accommodated when the end region of the round conductor is positioned in the at least partially shell-shaped part of the connection element. The connection element may for example be designed in one piece. The connection element may for example form a cable lug for accommodating the round cable. 
     The fastening device is adapted so as to fasten the end region of the round conductor lying in front of the contact element in the region of the shell-shaped part of the connection element to the connection element by frictional force (force-fit). For example, an underneath side of the round conductor in the end region is connected to the shell-shaped part of the connection element by frictional force (force-fit) by means of the fastening device. The fastening device can for example be formed so as to be reversible, in other words the fastening can be released and then be used as a fastening device again, or the fastening device can also be designed to be irreversible, in other words after fastening has been effected the friction type (force-fit) fastening remains in place. 
     Due to the frictional type (force-fit) fastening of the end region of the round conductor to the connection element in the region of the shell-shaped part of the connection element, on the one hand a secure fastening of the round conductor to the connection element is achieved, and on the other hand the contact element is brought into a predefined position in relation to the connection element and is held in this predefined position by the frictional type (force-fit) fastening. A simple electrical contact of the contact element with the connection element can thus take place. 
     The connection element may for example be a connection element for a motor vehicle electrical circuit, in which a round conductor is to be connected to the electrical circuit via the connection element. The connection element may for example be formed substantially flat except for the shell-shaped part. The cross-section of the shell-shaped part of the connection element may for example be configured substantially C-shaped, U-shaped or V-shaped. 
     The connection element may for example consist of aluminium or of copper or of some other conducting material, for example an alloy. The round cable may for example consist of aluminium or of copper or of some other conducting material, for example an alloy. 
     For example the round cable may be a copper round cable, the contact element may be formed from aluminium or from copper, and the connection element may be formed from copper or aluminium. Furthermore, the contact element may additionally be joined to the connection element by adhesive bonding (material bond). The adhesive bonding (material bond) can be produced for example between a contact element formed from aluminium and a connection element formed from copper, or between a contact element formed from copper and a connection element formed from aluminium. Thus, a copper/aluminium connection can be produced between the contact element and the connection element. The contact element and the connection element may however also be formed from the same material, for example copper or aluminium. 
     The fastening device may be any suitable fastening device for the afore-described frictional type (force-fit) connection with the connection element in the shell-shaped part. 
     According to an advantageous embodiment it is proposed that the fastening device at least partially surrounds the round conductor in the end region. 
     The fastening device may for example be positioned at least partly around the end region of the round conductor and an underneath side of the shell-shaped part of the connection element, so that the end region of the round conductor and the underneath side of the shell-shaped part of the connection element is at least partially surrounded by the fastening device, whereby the fastening device exerts a force on the round conductor in the end region so that the round conductor in the end region is pressed into the shell-shaped part of the connection element. 
     The fastening device may for example also be formed together with the shell-shaped part of the connection element, for example by a fastening segment that together with the shell-shaped part at least partially surrounds the end region of the round conductor and produces the frictional type (force-fit) connection. The fastening segment may for this purpose be joined to the shell-shaped part, for example by snap-in engagement, by adhesive bonding (material bond), or by another suitable connection. 
     For example, the fastening device may be shaped to be substantially annular, the annular fastening device being positioned for example at least partially around the end region of the round conductor and an underneath side of the shell-shaped part of the connection element, whereby the annular fastening device exerts a force on the round conductor in the end region so that the round conductor in the end region is pressed into the shell-shaped part of the connection element. 
     The fastening device may for example be a ring, which can be formed for example in one piece, two pieces or a plurality of pieces. The one-piece ring may for example be formed as a closed ring, which for example by pressing or by a spring metal exerts the force for the frictional type (force-fit) fastening. The one-piece ring may however also be formed so it can be closed on one side, in which for example snap-in elements can be provided for the snap-in engagement of this closable side. The two-piece or multipiece ring may also embrace snap-in elements for the snap-in engagement of the individual parts of the ring. 
     In addition the annular fastening device may for example be formed together with the shell-shaped part of the connection element, wherein for example a shell-shaped ring segment together with the shell-shaped part surrounds the end region of the round conductor and produces the frictional type (force-fit) fastening. 
     The term ring is not restricted in that only circular rings are to be understood by this term, but also other, substantially annular configurations are understood by the term ring. 
     According to an advantageous embodiment it is proposed that the contact element is formed as a flat part and that the connection element in the region of the contact area be formed as a flat part. 
     According to an advantageous embodiment it is proposed that the shell-shaped part is formed in such a way as to fix the round conductor in the transverse direction. 
     The connection element can for example in a transition region between the shell-shaped part and the contact area for the contact element have a step or edge or wall, which delimits the shell-shaped part in the transverse direction of the round cable inserted into the shell-shaped part. The end of the end region of the round cable can thus be fixed in the transverse direction by means of this step or edge or wall, when the round cable in the end region is inserted into the shell-shaped part. 
     According to an advantageous embodiment it is proposed that the round conductor in the end region has an insulation. The round conductor can also have an insulation in the other regions that are not associated with the end region. 
     According to an advantageous embodiment it is proposed that the insulation of the round conductor is stripped in a region in which the round conductor, in the case where the conductor is fastened by the fastening device, abuts against the shell-shaped part of the connection element. Thus for example edge regions of the shell-shaped part adjoin the remaining insulation in the end region of the round conductor. In this way for example a flush transition from the insulation in the end region of the round conductor to the shell-shaped part can be achieved. For example, the underneath side of the shell-shaped part can be configured so that the underneath side and the remaining insulation in the end region of the round conductor have a substantially circular cross-section. Thus, the round conductor with the stripped region in the end region can be inserted into the shell-shaped part and can then be fastened in a frictional manner (force-fit) by the fastening device to the connection element. 
     According to an advantageous embodiment it is proposed that the contact element is configured so that it abuts against a contact area of the connection element lying behind the shell-shaped part of the connection element, when the fastening device fastens in a frictional manner (force-fit) the end region of the round conductor. 
     The contact element and the round conductor closed with the contact element may for example be configured so that the contact element is pressed against the contact area when the fastening device fastens in a frictional manner (force-fit) the end region of the round conductor in the region of the shell-shaped part of the connection element to the said connection element. Thus, a particularly reliable electrical connection of the contact element with the connection element can be achieved. The contact area can for example be formed flat, as can the underneath side of the contact element, which during the fastening is pressed by the fastening device against the contact area. 
     The fastening device can thus ensure, due to the frictional type (force-fit) fastening, on the one hand a reliable fastening of the round conductor in the end region to the connection element, wherein at the same time an electrical contact of the round conductor with the contact element is achieved by pressing the contact element against the contact area. The contact element is for example securely connected to the end-side cable of the round conductor, so that a predefined position of the contact element is ensured when the round conductor in the end region is fastened in a frictional manner (force-fit) to the connection element by the fastening device. 
     According to an advantageous embodiment it is proposed that an insulation surrounds the contact element, the end region of the round cable and the connection element in the region of the contact area and the shell-shaped part of the connection element. 
     For example, this insulation can be a sprayed-on insulation, but can also be a shrink hose or another suitable insulation. 
     For example the insulation can be applied before the fastening device is applied and fastened. 
     For this purpose the shrink hose can for example, as already explained, be slipped over the contact element, the end region of the round cable and the connection element in the region of the contact area and of the shell-shaped part of the connection element, and then shrunk. Thus, the shrink hose can provide an insulation in the region of the contact area and the shell-shaped part of the connection element and also provide an insulation of the contact element of the round cable. 
     For example, the insulation can also be sprayed over the contact element, the end region of the round cable and the connection element in the region of the contact area and of the shell-shaped part of the connection element. 
     According to an advantageous embodiment it is proposed that the shell-shaped part of the connection element ends flat. 
     This flat shaped end of the shell-shaped part may for example be advantageous when using a shrink hose, since damage to the shrink hose is avoided. The flat end can for example also be realised by a bevelled end. 
     According to an advantageous embodiment it is proposed that the fastening device is a two-part fastening clip, in which the two parts are designed so as to engage by snap-in engagement with one another and in the snap-in engagement at least partially surround the end region of the round conductor and an underneath side of the shell-shaped part of the connection element, and in this way press the round conductor into the shell-shaped part. 
     For example, the two parts can in the snap-in engagement form a substantially annular fastening clip, which surrounds the end region of the round conductor and the underneath side of the shell-shaped part of the connection element and thus provides for the frictional type (force-fit) fastening. The two parts of the fastening clip may for example be formed of plastic material, but can however also be formed of metal or a metal alloy. The snap-in engagement can be achieved by suitable snap-in elements, which are arranged on the first and/or second part of the fastening clip. These snap-in elements can for example form snap-in hooks or extensions that actively engage with the respective snap-in hooks. Other suitable snap-in elements can however also be used. According to an advantageous embodiment it is proposed that the first part of the fastening clip includes a region in which the first part is configured in such a way as to at least partially embrace, during snap-in engagement, the end region of the round conductor on the side of the round conductor opposite the connection element. For example this region can be C-shaped or U-shaped or V-shaped, or can also have another shape that at least partially corresponds to that of the end region of the round conductor. 
     According to an advantageous embodiment the second part of the fastening clip comprises a region in which the second part is configured so that, during snap-in engagement, it at least partially embraces the underneath side of the shell-shaped part of the connection element. This region of the second part of the fastening clip can for example be U-shaped or also C-shaped or V-shaped, or can have another shape corresponding at least partially to the end region of the round conductor. 
     Thus, for example, the first part of the fastening clip can be slipped from above onto the end region of the round conductor, while the second part of the fastening clip can be slipped from below onto the underneath side of the shell-shaped part of the connection element, so that the first part and the second part of the fastening clip engage by snap-in engagement with one another and thereby form a snap-in-engaged fastening clip that embraces the end region of the round conductor and the shell-shaped part of the connection element. The snap-in-engaged fastening clip is in this connection designed so as to exert a pressure on the end region of the round conductor in the direction of the shell-shaped part of the connection element. 
     According to an advantageous embodiment it is proposed that the second part of the fastening clip comprises a positioning element that cooperates with a complementary positioning element on the underneath side of the shell-shaped part of the connection element, so as to position the second part of the fastening clip. 
     For example, this positioning element of the second part can be formed as a pin, and the complementary position element on the underneath side of the shell-shaped part can be a corresponding positioning hole. If therefore the second part is slipped onto the underneath side of the shell-shaped part so that the pin is engaged in the hole of the underneath side, then a rotation of the snap-in-engaged fastening clip can thereby be prevented. The pin can also be formed on the underneath side of the shell-shaped part, in which case the complementary hole is then correspondingly formed in the second part of the fastening clip. Other suitable positioning elements can however also be used. 
     According to an advantageous embodiment it is proposed that the first part of the fastening clip comprises two snap-in elements arranged respectively at one end of the first part, and that the second part of the fastening clip comprises two snap-in elements arranged respectively at one end of the second part, and these snap-in elements are configured in such a way that the first part and the second part of the fastening clip can engage with one another by snap-in engagement on both sides. 
     For example, a snap-in element of one part of the fastening clip can form a snap-in lug, and a complementary snap-in element of the other part of the fastening clip can form a snap-in hook. Other snap-in elements can however also be used. 
     Thus, the first part of the fastening clip can be engaged by snap-in engagement with the second part of the fastening clip via the snap-in elements on both sides, whereby the snap-in-engaged fastening clip presses the round conductor in the end region into the part of the connection element. 
     According to an advantageous embodiment it is proposed that the fastening clip comprises a hinge, which movably connects one end of the first part and one end of the second part of the fastening clip to one another, wherein the first part and the second part respectively comprise a snap-in element, which is arranged on an end of the respective part lying opposite the hinge, and these snap-in elements are configured so that the first part and the second part of the fastening clip can engage by snap-in engagement with one another on one side. 
     This hinge can for example be formed by a film hinge. Thus, for example, the snap-in engagement of the fastening clip can take place by swivelling the first part with the aid of the hinge and snap-in engagement via the snap-in elements. 
     According to an advantageous embodiment it is proposed that the first part and the second part of the fastening clip are respectively shell-shaped, wherein the shell-shaped second part is configured so as to grip over two end regions of the shell-shaped first part and become locked in these two end regions. 
     For example, the internal radius of the shell-shaped second part in the contact region with the first part, i.e. the two end regions of the first part, can be slightly less than the external radius of the first part in these two end regions. The shell-shaped second part can have a certain flexibility, so that the second part expands slightly when slipped over the first part and a particularly secure snap-in engagement with the first part can thereby be achieved. The shell-shaped first part can comprise respectively a snap-in element in each of the two end regions, while the shell-shaped second part comprises on the inside in its two end regions, these end regions being able to be slipped over the corresponding end regions of the shell-shaped first part, respectively a snap-in element complementary to the respective snap-in elements of the shell-shaped first part. The shell-shaped part of the first part and of the second part of the fastening clip respectively can for example be C-shaped, V-shaped, U-shaped or can form another suitable, at least substantially shell-shaped part. 
     Thus, first of all the first part of the fastening clip can for example be slipped from above onto the end region of the round conductor, followed by the second part of the fastening clip that can be slipped from below over the underneath side of the shell-shaped part, so that the second part of the fastening clip embraces the two end regions of the shell-shaped first part and is securely engaged by snap-in engagement in these regions by the respective snap-in elements. The frictional type (force-fit) fastening of the end region of the round conductor to the shell-shaped part of the connection element is achieved in this way. 
     According to an advantageous embodiment it is proposed that the fastening device is a compressed metal ring, which embraces the end region of the round conductor and an underneath side of the shell-shaped part of the connection element. 
     The metal ring is for example slipped onto the round cable and at the same time over the shell-shaped part, so that the slipped-on metal ring embraces the end region of the round cable and the underneath side of the shell-shaped part of the connection element. The metal ring is then compressed, so that the compressed metal ring in the end region of the round cable presses into the shell-shaped part of the connection element. The metal may for example be steel or another metal or an alloy. The compressed metal ring may for example be formed in one part. 
     According to an advantageous embodiment it is proposed that the fastening device is a spring metal ring, which embraces the end region of the round conductor and an underneath side of the shell-shaped part of the connection element. 
     The spring metal ring is for example slipped onto the round cable and over the shell-shaped part, whereby the slipped-on spring steel ring presses the end region of the round cable into the shell-shaped part of the connection element. The spring metal ring may be formed in one piece. The spring metal of the spring metal ring may for example also be an alloy. 
     According to an advantageous embodiment it is proposed that the fastening device comprises a crimping element that clamps around the end region of the round conductor and an underneath side of the shell-shaped part of the connection element. 
     For example, the crimping element can also be slipped onto the round cable and at the same time over the shell-shaped part of the connection element, so that the slipped-on crimping element embraces the end region of the round cable and the underneath side of the shell-shaped part of the connection element. The crimping element is then crimped, so that the crimped crimping element presses the end region of the round cable into the shell-shaped part of the connection element. The frictional type (force-fit) fastening of the end region of the round cable in the shell-shaped part of the connection element is thus achieved by the crimping of the crimping element. 
     According to an advantageous embodiment it is proposed that the crimping element is a metal band. 
     This metal band may for example be an individual isocrimp formed as metal. 
     According to an advantageous embodiment it is proposed that the crimping element is formed as an O-shaped crimp, a wire crimp or an overlapping crimp. 
     For example, the wire crimp can be formed of metal, wherein for example an inwardly oriented wire claw is present at each end of the wire crimp, which on crimping produces a claw-like engagement with the insulation of the connection cable in this region. For example, this wire crimp is slipped over the round cable and the underneath side of the shell-shaped part of the connection elements in such a way that the two wire crimps are disposed on the upper side of the round cable, i.e. on the side of the round cable facing away from the shell-shaped part. Thus, the two wire crimps engage like claws for example at the top in the insulation of the connection cable, while simultaneously the lower end region of the round cable is pressed into the shell-shaped part of the connection element. 
     According to an advantageous embodiment it is proposed that the fastening device comprises a clip that is substantially U-, V- or C-shaped in cross-section, which includes a fastening element at each end, wherein each of the fastening elements is configured so as to embrace, at least partially for a two-sided fastening, an underneath side of the shell-shaped part of the connection element from respectively one side. 
     The fastening elements of the clip may for example be snap-in elements, and the underneath side of the shell-shaped part of the connection element can have snap-in elements that are complementary to these snap-in elements. For example, the fastening elements of the clip can form snap-in hooks, and the complementary snap-in elements on the underneath side of the shell-shaped part can form receivers for engaged snap-in hooks. However, other snap-in elements and complementary snap-in elements can also be used. 
     The clip can thus be slipped from above onto the end region of the round conductor, until the fastening elements at least partially embrace the underneath side of the shell-shaped part and there form a snap-in engagement with the underneath side of the shell-shaped part of the connection element. For example, the round conductor in the end region can be stripped in the contact area for the shell-shaped part of the connection element, so that the remaining insulation in the end region of the round conductor is sealed flush with the shell-shaped part of the connection element. The clip can be produced for example from plastic or a metal or from a metal alloy. 
     The clip can for example correspond to the shell-shaped ring segment described hereinbefore. 
     According to an advantageous embodiment it is proposed that the fastening device has a metal shell element that is substantially U-, V- or C-shaped in cross-section, which has at both ends respectively an edge region that is complementary to a respective edge region of the shell-shaped part of the connection element, and wherein the metal shell element is engaged by adhesive bonding (material bond) to the respective edge region of the shell-shaped part of the connection element in such a way that the metal shell element and the shell-shaped part form a one-piece ring embracing the end region of the round conductor. 
     The metal shell element is for this purpose placed for example on the two oppositely facing edge regions of the shell-shaped part so that the metal shell element and the shell-shaped part form a ring surrounding the end region of the round conductor. The metal shell element can thus correspond to the afore-described shell-shaped ring segment. 
     Following this, a first force is for example exerted on the metal shell element in the direction of the shell-shaped part, while for example at the same time the underneath side of the shell-shaped part is supported, or a force substantially opposite to the first force is exerted on the underneath side of the shell-shaped part. Due to the exerted force or forces, the round conductor in the end region is forced into the shell-shaped part of the connection element. 
     At the same time each of the two edge regions of the metal shell element, which abut against the respective edge region of the shell-shaped part, are engaged by adhesive bonding (material bond). This can take place for example by welding, soldering, bonding or a similarly suitable method for adhesive bonding (material bond). The now single-piece ring, comprising the metal shell element and the shell-shaped part of the connection element, exerts the cohesive fastening force. 
     According to an advantageous embodiment it is proposed that the fastening device is a ring that can be closed on one side by a closure device, which is adapted so as to embrace, in the closed state, the end region on the round conductor and an underneath side of the shell- shaped part of the connection element. 
     The ring closable on one side can for example form a ring having a substantially U-shaped cross-section, which is separated at a point in the cross-section and has there at each end a closure means for the one-sided closure of the ring. These closure means may for example form snap-in closure means. In order to fasten the ring closable on one side this ring is for example slipped in the open state onto the round cable and at the same time over the shell-shaped part, so that the slipped-on ring embraces the end region of the round cable and the underneath side of the shell-shaped part of the connection element. The ring is then closed by the closure means, so that the closed ring presses the end region of the round cable into the shell-shaped part of the connection element. For this purpose the ring is for example pressed together with a certain force, against the resistance of the ring, until the closure means closes the ring on one side and produces the frictional type (force-fit) fastening. 
     The ring may be formed for example of plastic or of metal or a metal alloy. The ring closable on one side may be formed in one piece. 
     The aforementioned exemplary embodiments can, so far as is technically feasible, be combined in all variants with one another, and in particular individual features of different embodiments can also be combined together with one another. 
     The object and the method are described in more detail hereinafter with the aid of figures illustrating exemplary embodiments. 
    
    
     
       In the Figures: 
         FIG. 1  shows an exemplary system according to a first embodiment; 
         FIG. 2   a  shows an exemplary connection element according to a first embodiment; 
         FIG. 2   b  shows an exemplary connection element according to a second embodiment; 
         FIG. 2   c  shows an exemplary connection element according to a third embodiment; 
         FIG. 2   d  shows a cross-section of an exemplary shell-shaped part according to a first embodiment; 
         FIG. 2   e  shows a cross-section of an exemplary shell-shaped part according to a second embodiment; 
         FIG. 2   f  shows a cross-section of an exemplary shell-shaped part according to a third embodiment; 
         FIG. 3   a  shows an exemplary system according to a second embodiment in a first representation; 
         FIG. 3   b  shows an exemplary system according to a second embodiment in a second representation; 
         FIG. 3   c  shows an exemplary system according to a third embodiment; 
         FIG. 4   a  shows an exemplary system according to a fourth embodiment; 
         FIG. 4   b  shows an exemplary system according to a fifth embodiment; 
         FIG. 5   a  shows an exemplary system according to a sixth embodiment; 
         FIG. 5   b  shows an exemplary system according to a seventh embodiment; 
         FIG. 6   a  shows an exemplary system according to an eighth embodiment; 
         FIG. 6   b  shows an exemplary system according to a ninth embodiment; 
         FIG. 6   c  shows an exemplary system according to a tenth embodiment; 
         FIG. 7  shows an exemplary system according to an eleventh embodiment; 
         FIG. 8   a  shows an exemplary system according to a twelfth embodiment in a first representation; and 
         FIG. 8   b  shows an exemplary system according to a twelfth embodiment in a second representation. 
     
    
    
     An exemplary system for fastening a round conductor  200  to a connection element  100  is shown in  FIG. 1 . The round conductor  200  is closed with a contact element  210 . Furthermore the round conductor  200  can have an optional insulation  230 . The contact element  210  is adapted so as to be electrically connected to the connection element  100 . 
     The connection element  100  comprises an at least partially shell-shaped part  110 . This at least partially shell-shaped part  110  is configured in such a way that a suitably corresponding part of an end region  220  of the round conductor  200 , lying in front of the contact element  210 , can be accommodated when the end region  220  of the round conductor  200  is positioned in the at least partially shell-shaped part  110  of the connection element  100 . The connection element  100  may consist for example of aluminium or of copper, or of another conducting material, for example an alloy. The connection element  100  may be formed in one piece. The connection element  100  may for example form a cable lug for receiving the round cable  200 . 
     In addition the system comprises a fastening device (not shown in  FIG. 1 ), which is adapted to fasten in a frictional manner (force-fit) the end region  220  of the round conductor  200 , lying in front of the contact element  210 , in the region of the shell-shaped part  110  of the connection element  100  to the connection element  100 . This frictional type (force-fit) fastening is represented in  FIG. 1  for example by the arrow  300 . In the system illustrated by way of example in  FIG. 1 , the underneath side of the round conductor  200  is joined in a frictional manner (force-fit) in the end region  220  to the shell-shaped part  110  of the connection element  100 . The shell-shaped part  110  of the connection element  100  can be shaped corresponding to the roundness of the round conductor  200  in the end region  220 . 
     By means of the frictional type (force-fit) fastening of the end region  220  of the round conductor  200  to the connection element  100  in the region of the shell-shaped part  110  of the connection element  100 , on the one hand a secure fastening of the round conductor  200  to the connection element  100  is achieved, and on the other hand the contact element  210  is brought into a predefined position in relation to the connection element  100  and is held in this predefined position by the frictional type (force-fit) fastening. A simple electrical contact of the contact element  210  with the connection element  100  can thus take place. 
     For example, the contact element  210  can be configured so that the contact element  210  abuts a contact area  120  of the connection element  120  lying behind the shell-shaped part  110  of the connection element  100 , when the fastening device fastens the end region  220  of the round conductor  200  in a frictional manner (force-fit). The contact element  210  and the round conductor  200  closed with the contact element  210  may for example be configured in such a way that the contact element  210  is pressed onto the contact area  120  when the fastening device fastens in a frictional manner (force-fit) the end region  220  of the round conductor  200  in the region of the shell-shaped part  110  of the connection element  100 , to the connection element  100 . A particularly secure electrical connection of the contact element  210  with the connection element  100  can thus be achieved. The contact area  120  can for example be formed flat, as can the underneath side of the contact element  220 . In addition the connection element  100  can for example be formed substantially flat except for the shell-shaped part  110 . For example, the contact element  210  can be formed as a flat part, and the connection element  100  in the region of the contact area  120  can be formed as a flat part. 
     The connection element  100  can for example have a step  105 , or edge  105 , or end wall  105 , in a transition region between the shell-shaped part  110  and the contact area  120  for the contact element  210 , which delimits the shell-shaped part  110  in the transverse direction of the round cable  200  laid in the shell-shaped part. The end of the end region  220  of the round cable  200  can thus be fixed in the transverse direction by this step  105  or edge  105  or end wall  105 , when the round cable  200  in the end region  220  is inserted into the shell-shaped parts. 
     The connection element  100  may for example be a connection element for a vehicle electrical circuit, in which a round conductor  200  is to be connected to the electrical circuit via the connection element  100 . 
     The fastening device may be any suitable fastening device for the aforedescribed frictional type (force-fit) connection. For this purpose various exemplary possible realisations are illustrated hereinafter, which however are not to be understood as restrictive. 
       FIG. 2   a  shows an exemplary connection element  100  according to a first embodiment, which is based on the connection element  100  previously illustrated in  FIG. 1 . The exemplary connection element illustrated in  FIG. 2   a  has at the end of the shell-shaped part  110  a bevelled mouth portion  115 , which adjoins the two edge regions  150 ,  160  of the shell-shaped part  110 . This bevelled mouth portion  115  may for example be advantageous when using a shrink hose casing. 
       FIG. 2   b  shows an exemplary connection element  100 ′ according to a second embodiment. In the connection element  100 ′ the underneath side  130  of the shell-shaped part is bounded respectively by a bead  131 ,  132 . The beads  131 ,  132  may for example be advantageous for positioning the fastening device. 
     Furthermore the exemplary connection element  100 ′ can also comprise an optional positioning element  140 , which in  FIG. 2  is formed as a recess  140 , for example a hole. 
       FIG. 2   c  shows an exemplary connection element  100 ″ according to a third embodiment. This connection element  100 ″ has a flat end portion  115 ′ of the shell-shaped part  110 . This flat end portion  115  may for example be advantageous when using a shrink hose. 
       FIG. 2   d  shows a cross-section of an exemplary shell-shaped part  110  according to a first embodiment. The cross-section of this shell-shaped part  110  is essentially C-shaped. The C shell-shaped part  110  terminates on both sides with the respective edge region  150 ,  160 , which lie opposite one another. 
       FIG. 2   e  shows a cross-section of an exemplary shell-shaped part  110  according to a second embodiment. The cross-section of this shell-shaped part  110  is substantially U-shaped. 
       FIG. 2   f  shows a cross-section of an exemplary shell-shaped part  110  according to a third embodiment. The cross-section of this shell-shaped part  110  is essentially V-shaped. 
     The illustrated cross-sections should be understood only as examples. Thus, for example, the opening angles of the shapes can differ. For example, the C-shaped configurations also include closed shell-shaped parts, in which the shell-shaped part is more than 180° in cross-section, or open shell-shaped parts, in which the shell-shaped part is less than 180° in cross-section. This applies appropriately also to the other illustrated cross-sections. The aforementioned explanations regarding the exemplary cross-sections refer not only to the configuration of the shell-shaped part  110 ,  100 ′,  100 ″, but can also be applied to other features in the description, such as for example parts of the fastening device. 
       FIG. 3   a  shows an exemplary system according to a second embodiment in a first representation, which is explained in conjunction with the second representation of the second embodiment illustrated in  FIG. 3   b.    
     The fastening device  400  in this second embodiment is a fastening clip  400  comprising two parts  410 ,  420 , wherein the two parts  410 ,  420  are adapted so as to engage by snap-in engagement with one another, and during the snap-in engagement to embrace at least partially the end region  220  of the round conductor  200  and an underneath side  130  of the shell-shaped part  110  of the connection element  100 ′, and thereby press the round conductor  200  in the end region  220  in the region of the shell-shaped part  110  into the connection element  100 ′. 
     The first part  410  of the fastening clip  400  comprises a region  415 , in which the first part  410  is configured so as to at least partially surround by snap-in engagement the end region  220  of the round conductor  200  on the side of the round conductor  200  opposite the connection element  100 , as is illustrated by way of example in  FIG. 3   b . The first part  410  of the fastening clip  400  may for example be C-shaped, as illustrated in  FIGS. 3   a  and  3   b , or also U-shaped or V-shaped, or have another shape corresponding at least partially to the end region  220  of the round conductor  200 . 
     The second part  420  of the fastening clip  400  comprises a region  425 , in which the second part  420  is configured so as to at least partially embrace by snap-in engagement the underneath side  130  of the shell-shaped part  110  of the connection element  100 . The second part  420  of the fastening clip  400  may for example be U-shaped, as illustrated in  FIGS. 3   a  and  3   b , or also C-shaped or V-shaped, or may have another shape corresponding at least partially to the end region  220  of the round conductor  200 . 
     In addition the connection element  100 ′ may include the previously described beads  131 ,  132 , which are arranged so that the second part  420  of the fastening clip  400  is positioned on both sides by means of the beads  131 ,  132 . A sideways slipping of the fastening clip  400  can be avoided in this way. 
     Furthermore the connection element  100 ′ may comprise the aforedescribed positioning element  140 , which in this example is a hole  140 . The second part  420  of the fastening clip  400  comprises a positioning element  424  complementary to the positioning element  140 , which may for example be a pin  424 . The pin  424  is arranged in such a way in the region  425  of the second part  420  that the pin  425 , when this region  425  of the second part  420  at least partially embraces the underneath side  130  of the shell-shaped part  110 , is inserted in the hole  140  and thereby prevents a rotation of the fastening clip. 
     The first part  410  of the fastening clip  400  comprises two snap-in elements  411 ,  412  arranged respectively at one end of the first part  410 , and the second part  420  of the fastening clip comprises two snap-in elements  421 ,  422  arranged respectively at one end of the second part  420 , and these snap-in elements  411 ,  412 ,  421 ,  422  are configured so that the first part  410  and the second part  420  of the fastening clip  400  can engage by snap-in engagement with one another on both sides. 
     For example, a snap-in element  421  of a part  420  of the fastening clip  400  can form a snap-in hook  421 , and the complementary snap-in element  411  of the other part  410  can form a snap-in hook receiver  411 , as illustrated by way of example in  FIG. 3   a . Other snap-in elements may however also be formed. 
     Thus, the first part  410  of the fastening clip  400  can be engaged by snap-in engagement on both sides with the second part  420  of the fastening clip over the snap-in elements  411 ,  412 ,  421 ,  422  on both sides, whereby the snap-in engaged fastening clip  400  presses the round conductor  200  in the end region  220  into the shell-shaped part  110  of the connection element  100 ′. 
     For example, the fastening clip  400  according to the second exemplary embodiment can also comprise a hinge (not shown), which movably connects one end of the first part  410  and one end of the second part  420  of the fastening clip to one another. For example the snap-in elements  411  and  421  can be replaced by this hinge, which may for example be a film hinge. The first part  410  and the second part  420  comprise respectively a snap-in element  412 ,  422 , which are arranged on an end of the respective part  410 ,  420  lying opposite the hinge, these snap-in elements  412 ,  422  being configured so that the first part  410  and the second part  420  of the fastening clip  400  can engage in by snap-in engagement with one another on one side. Thus, for example, the snap-in engagement of the fastening clip  400  can take place by rotating the first part  410  with the aid of the hinge and snap-in engagement by means of the snap-in elements  412 ,  422 . 
     The fastening clip, i.e. in this embodiment the first part  410  and the second part  420 , may for example be formed of plastic, but may also for example be formed of metal or a metal alloy. 
       FIG. 3   c  shows an exemplary system according to a third embodiment, which again comprises a fastening clip  400 ′ with a first part  410 ′ and a second part  420 ′, wherein the first part  410 ′ and the second part  420 ′ of the fastening clip  400 ′ are in each case shell-shaped, and the shell-shaped second part  420 ′ is configured so as to grip by snap-in engagement over two end regions  416 ,  417  of the shell-shaped first part  410 ′. 
     For example the internal radius of the shell-shaped second part  420 ′ in the contact region with the first part  410 ′, i.e. the oppositely facing end regions  416 ,  417  of the first part  410 ′, may be somewhat smaller than the external radius of the first part  410 ′ in the end regions  416 ,  417 , wherein the material of the second part  420 ′ has a flexibility such that the second part  420 ′ can expand so as to be slipped over the first part  410 ′. 
     In addition the middle region  414  of the second part  410 ′ lying between the two end regions  416 ,  417  can have a larger external radius, so that a step  418 ,  419  is formed between the middle region  414  and the respective end regions  416 ,  417 , which step separates the middle region  414  from the end regions  416 ,  417  and serves as a boundary for an edge region  428 ,  429  of the respective end of the second part  420 ′ of the fastening clip, so that the second part  420 ′ when slipped onto the first part  410 ′ abuts with the respective end region  428 ,  429  against the respective step  418 , 419  and is positioned. These steps  418 ,  419  may for example also be formed by a bead. 
     Furthermore the first part may comprise snap-in elements  411 ′,  412 ′, which can engage by snap-in engagement with complementary snap-in elements  421 ′,  422 ′ of the second part  420 ′ when the second part  420 ′ of the fastening clip  400 ′ is slipped over the first part  410 ′ of the fastening clip  400 . The snap-in elements  411 ′,  412 ′ of the first part  410 ′ may for example form snap-in hook recesses  411 ′,  412 ′, and the snap-in elements  421 ′,  422 ′ of the second part  420 ′ may form snap-in hooks  421 ′,  422 ′, or vice versa. 
       FIG. 4   a  shows an exemplary system according to a fourth embodiment, in which the fastening device is a spring metal ring  510 , which embraces the end region  220  of the round conductor and the underneath side  130  of the connection element  100 ″. The spring metal ring  510  is for example slipped onto the round cable  200  and over the shell-shaped part  110 , whereby the slipped-on spring steel ring presses the end region  220  of the round cable  200  into the shell-shaped part  110  of the connection element  110 ″. The spring metal ring  510  can be formed in one piece. 
     For example, the insulation  230  of the round conductor  200  is stripped in a region in which the round conductor  200  abuts against the shell-shaped part  110  of the connection element  100 ″ in the case where fastening is effected by the spring metal ring, as is illustrated by way of example in  FIG. 4   a . Thus, for example, the edge areas  150 ,  160  of the shell-shaped part adjoin the remaining insulation  230  in the end region  220  of the round conductor  200 . For example the underneath side  130  of the shell-shaped part can be configured so that the underneath side  130  and the remaining insulation  230  in the end region  220  of the round conductor  200  are substantially circular in cross-section. The spring metal ring can thus abut uniformly against the underneath side  130  and the remaining insulation  230  in the end region of the round conductor  200 . The spring metal ring may for example be a spring steel ring, and the spring metal may also be an alloy. 
       FIG. 4   b  shows an exemplary system according to a fifth embodiment, in which the fastening device is a pressed metal ring  520  that surrounds the end region  220  of the round conductor and the underneath side  130  of the connection element  110 ′. The metal ring  520  is for example slipped onto the round cable  200  and over the shell-shaped part  110 , so that the slipped-on metal ring  520  embraces the end region  220  of the round cable  200  and the underneath side  130  of the shell-shaped part  110  of the connection element  100 ′. The metal ring  520  is then pressed, so that the pressed metal ring forces the end region  220  of the round cable into the shell-shaped part  110  of the connection element  110 ′. The metal may for example be steel or another metal or an alloy. The pressed metal ring  520  may be formed in one piece. 
       FIG. 5   a  shows an exemplary system according to a sixth embodiment. In this sixth embodiment, as also in the seventh embodiment illustrated in  FIG. 5   b , a crimping element  610 ,  620  is used as fastening device, wherein the crimping element  610 ,  620  is slipped onto the round cable  200  and over the shell-shaped part  110 , so that the slipped-on crimping element  610 ,  620  embraces the end region  220  of the round cable  200  and the underneath side  130  of the shell-shaped part  110  of the connection element  100 ′. The crimping element  610 ,  620  is then crimped, so that the crimped crimping element  610 ,  620  forces the end region  220  of the round cable  200  into the shell-shaped part  110  of the connection element  110 ′. 
     As is illustrated by way of example in  FIG. 5   a , the crimping element  610  may be a metal band  610 , for example an individual isocrimp formed as metal. As is illustrated by way of example in  FIG. 5   b , the crimping element  620  may also be a wire crimp  620  formed of metal, which for example comprises at each end at least one wire claw  621 ,  622  for the claw-type engagement with the insulation  230  of the connection cable  200 . 
     An O-crimp or an overlapping crimp may for example also be used as crimping element  610 ,  620 . 
       FIG. 6   a  shows an exemplary system according to an eighth embodiment, wherein the fastening device  410  is the spring metal ring  510  of  FIG. 4   a . The pressed metal ring  520  of  FIG. 4   b  may however also be used. Accordingly one of the various connection elements  100 ,  100 ′ and  100 ″ may be used. 
     Before the respective metal ring  510  is slipped over the round cable  200  and the shell-shaped part  110 , an insulation  650  may for example be applied over the contact element  210 , the end region  220  of the round cable  200 , and the connection element  100 ″ in the region of the contact area  120  and of the shell-shaped part  110  of the connection element  100 . Thus, the insulation  650  embraces the contact element  210 , the end region  220  of the round cable  200  and the connection element  100 ″ in the region of the contact area  120  and of the shell-shaped part  110  of the connection element  100 ″ and provides an insulation there. 
     For example, the insulation can be sprayed on, or can also be a shrink hose that is slipped on, or some other suitable insulation. 
     The slipped on spring metal ring  510  or pressed metal ring  520  respectively presses the end region  220  of the round cable  200  embracing the insulation  650  into the shell-shaped part  110  of the connection element  100 ″. 
       FIG. 6   b  shows an exemplary system according to a ninth embodiment, in which the fastening device  660  is a ring  660  closable on one side. 
     This ring  660  is adapted so as to embrace the end region  220  of the round conductor  200  and the underneath side  130  of the shell-shaped part  110  of the connection element  100 ″ in the closed state, as illustrated in  FIG. 6   b . The ring  660  closable on one side may for example be a ring  660  that is substantially O-shaped in cross-section, which is separated in cross-section at a point  665 , and there comprises at each end a closure means  661 ,  662  for the one-sided closure of the ring  660 . These closure means  661 ,  662  may for example form snap-in elements  661 ,  662 , as illustrated in  FIG. 6   b . In order to fasten the ring  660  closable on one side, this ring  660  is slipped, for example in the open state, onto the round cable  200  and over the shell-shaped part  110 , so that the slipped-on ring  620  embraces the end region  220  of the round cable  200  and the underneath side  130  of the shell-shaped part  110  of the connection element  110 ″. The ring  660  is then closed by the closure means  661 ,  662 , so that the closed ring  660  presses the end region  220  of the round cable  200  into the shell-shaped part  110  of the connection element  110 ′. For this purpose the ring  660  is for example pressed together with a specific force, against the resistance of the ring, until the closure means  661 ,  662  close the ring on one side. 
       FIG. 6   c  shows an exemplary system according to a tenth embodiment, which shows the closable ring  660  known from  FIG. 6   b  in combination with an applied insulation. The insulation  650  can, as previously explained with regard to the eigth embodiment, be applied over the contact element  210 , the end region  220  of the round cable  200 , and the connection element  100 ″ in the region of the contact area  120  and of the shell-shaped part  110  of the connection element  100 ″, before the closable ring  660  is slipped on. 
       FIG. 7  shows an exemplary system according to an eleventh embodiment, in which the fastening device comprises a metal shell element  710  with a U-, V- or C-shaped cross-section, which at both open ends comprises respectively an edge region that is complementary to a respective edge region  150 ,  160  of the shell-shaped part  110  of the connection element  100 , and wherein the metal shell element  710  is connected by adhesive bonding (material bond)  750  to the respective edge region of the shell-shaped part of the connection element so that the metal shell element  710  and the shell-shaped part  110  form a one-piece ring embracing the end region  220  of the round conductor  200 . 
     The metal shell element  710  is for this purpose placed for example on the two oppositely facing edge regions  150 ,  160  of the shell-shaped part  110  so that the metal shell element  710  and the shell-shaped part  110  form a ring embracing the end region  220  of the round conductor  200 . A first force  760  is then for example exerted on the metal shell element  710  in the direction of the shell-shaped part  110 , while at the same time the underneath side  130  of the shell-shaped part  110  is supported or a force  770  acting substantially opposite to the first force  760  is exerted on the underneath side  130  of the shell-shaped part  110 , as is illustrated for example in  FIG. 7 . Due to the exerted force or forces, the round conductor  200  in the end region  220  is pressed into the shell-shaped part  110 . At the same time each of the two edge regions of the metal shell elements  760 , which abut against the respective edge region  150 ,  160  of the shell-shaped part, are joined to one another by adhesive bonding (material bond). This may be carried out for example by welding, soldering, bonding or by another suitable means. The now one-piece ring, comprising the metal shell element  710  and the shell-shaped part  110  of the connection element  100 , exerts the frictional fastening force (force-fit). 
       FIG. 8   a  shows an exemplary system according to a twelfth embodiment in a first representation, which is explained in conjunction with the second representation of the twelfth embodiment illustrated in  FIG. 8   b.    
     The fastening device forms a clip  810  that is substantially C-shaped in cross-section, which includes at each end a fastening element  811 ,  812 , wherein each of the fastening elements  811 ,  812  is configured so as to embrace, at least partially for a two-sided fastening, the underneath side  130  of the shell-shaped part  110  of the connection element  100 ′″ from respectively one side. This embracing of the underneath side  130  of the shell-shaped part  110  by the fastening elements  811 ,  812  is shown by way of example in  FIG. 8   b . The clip  810  may also have another shape, for example may be substantially U-shaped or V-shaped in cross-section. 
     The fastening elements  811 ,  812  of the clip  810  may for example be snap-in elements  811 ,  812 , and the underneath side  130  of the shell-shaped part  110  of the connection element  100 ′″ can have snap-in elements  181 ,  182  complementary to these snap-in elements  811 ,  812 . For example, the fastening elements  811 ,  812  of the clip  810  can form snap-in hooks  811 ,  812 , and the complementary snap-in elements  181 ,  182  on the underneath side  130  of the shell-shaped part  110  can form indented snap-in hook receivers  181 ,  182 . Other snap-in elements and complementary snap-in elements may also be used. 
     The clip  810  that is substantially U- or V- or C-shaped in cross-section may have a shape such that the clip  810  fastened on the shell-shaped part  110  by the fastening elements  811 ,  812  forms a two-piece ring embracing the end region  220  of the round conductor  200 , which presses the round conductor  200  in the end region  220  into the shell-shaped part  110  and provides the frictional (force-fit) engagement. The clip  810  can thus form a clip-engaged ring  810 . The clip  810  may be formed of a suitable metal or also of plastic. 
     The connection element  100 ′″ may be based on any of the previously described connection elements  100 ,  100 ′,  100 ″. 
     The previously mentioned embodiments can, so far as is technically feasible, be combined in all possible variants with one another, and in particular also individual features of different embodiments can be combined with one another.