Patent Publication Number: US-10777914-B2

Title: Earthing pin for a motor vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/EP2018/055227, filed Mar. 2, 2018, which claims priority under 35 U.S.C. § 119 from German Patent Application No. 10 2017 204 197.8, filed Mar. 14, 2017, the entire disclosures of which are herein expressly incorporated by reference. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a grounding pin for connecting a vehicle body to a pole of a vehicle battery, a grounding pin connection with such a grounding pin, and a motor vehicle with such a grounding pin or grounding pin connection. 
       FIG. 1  shows a known grounding pin  1  for connecting a vehicle body to a minus pole of a vehicle battery. The grounding pin  1  has a pin plate  2  from which a pin shaft  3  protrudes, the pin shaft being provided with an external thread. A cable lug of a line leading to the vehicle battery can be fastened to the grounding pin  1 . More precisely, the cable lug is mounted on the grounding pin  1  such that the pin shaft  3  extends through the opening of the cable lug and is then screwed tight by means of a nut on the pin shaft  3  on the grounding pin  1 . One end of the cable lug opposite the line is provided with an angle section, which encloses the pin plate  2  so that the cable lug can only be oriented in one of the four predetermined positions, each set off from the others by 90°. When attaching the grounding line one must pay attention that a particular orientation of the cable lug is required, or else the cable guidance of the grounding line is not optimal or not possible as intended. This particular orientation may vary according to the vehicle model. Due to the variable orientation possibility, however, a wrong orientation or wrong installation is possible, which might then become evident during the laying of the line, for example, but unnecessary work time is squandered. 
     One problem which the present invention proposes to solve is to provide a grounding pin for connecting a vehicle body to a pole of a vehicle battery, which heightens the installation safety. 
     According to one exemplary embodiment of the invention, a grounding pin is provided for connecting a vehicle body to a pole of a vehicle battery, comprising a pin plate and a pin shaft which protrudes from the pin plate and is provided with an external thread and the longitudinal axis of which forms a center line of the grounding pin, wherein the pin plate has a single or two installation securing faces which point radially outward and which are each parallel to a face which passes through the center line, wherein a minimum distance between a circumferential face of the pin plate and the center line lies in the range of the installation securing face/faces, and wherein the pin plate is provided with a connection face which points away from the pin shaft and is matched to the vehicle body for welding purposes. Because the installation securing face creates a region forming the circumferential region with the smallest distance in relation to the overall circumferential face, a cable lug can only be mounted in a predefined orientation on the grounding pin, which creates installation safety. 
     According to a further exemplary embodiment of the invention, the circumferential face of the pin plate is round outside of the installation securing face/faces. 
     According to a further exemplary embodiment of the invention, contact wedge elements are provided around the pin shaft, each of them having an edge which starts at the radially outward pointing face of the pin shaft and extends at a slant away from the pin shaft and toward the pin plate. Thanks to these contact wedge elements, the junction resistance between the cable lug and the grounding pin is decreased. 
     According to a further exemplary embodiment of the invention, the pin plate on the side facing toward the pin shaft has two parallel faces, of which an outer face surrounds an inner face as a ring and the inner face is situated closer to the pin shaft along the center line than the outer face. 
     According to a further exemplary embodiment of the invention, the pin shaft is provided with an external thread, especially an M8 thread or larger. It has been found that a thread of size M8 is best suited for the function of a grounding pin in motor vehicles. 
     According to a further exemplary embodiment of the invention, the connection face is provided with welding elevations, especially welding elevations that are suitable for a hump welding. 
     According to a further exemplary embodiment of the invention, the installation securing face extends in a straight line and entirely through the pin plate. This installation securing face extending entirely through the pin plate is easy and thus cost-effective to produce. 
     According to a further exemplary embodiment of the invention, the installation securing face is the surface of a groove, so that on either side of the installation securing face there are situated side flanks of the groove. 
     Furthermore, the present invention provides a grounding pin connection with a grounding pin according to one of the preceding exemplary embodiments and a cable lug, which can be fastened on one end of a cable and has an angle section at its end opposite the cable, which lies against the installation securing face. 
     Moreover, the present invention provides a motor vehicle with such a grounding pin or such a grounding pin connection. 
     In the following, a preferred exemplary embodiment of the present invention shall be described, making reference to the accompanying drawings. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a three-dimensional representation of a grounding pin of the prior art; 
         FIG. 2  is a three-dimensional representation of a grounding pin according to a first exemplary embodiment of the invention; 
         FIG. 3  is a three-dimensional representation of a grounding pin connection with a grounding pin and a cable lug according to a first exemplary embodiment of the invention; 
         FIG. 4  is a three-dimensional representation of a grounding pin according to a second exemplary embodiment of the invention; and 
         FIG. 5  is a three-dimensional representation of a grounding pin connection with a grounding pin and a cable lug according to a second exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 2  is a three-dimensional representation of a grounding pin  10  according to a first exemplary embodiment of the invention. The grounding pin  10  comprises a pin plate  11  and a pin shaft  12  protruding from the latter. The pin shaft  12  is provided with an external thread. A longitudinal axis or a center line of the pin shaft  12  forms a center line  13  of the grounding pin  10 . The pin plate  11  in the exemplary embodiment shown has a single installation securing face  14 . The installation securing face  14  is a flat surface extending parallel to a plane passing through the center line  13 . It is also possible to provide two such installation securing faces  14 , which are preferably situated directly adjacent to each other. Except for the installation securing faces  14 , the pin plate  11  has a round circumference. The installation securing face  14  extends entirely through the pin plate  11 , parallel to a plane drawn through the center line and at a distance from the latter. The side of the pin plate  11  facing toward the pin shaft  12  has two parallel faces, which run substantially perpendicular to the center line  13 , one outer face  15  surrounding an inner face  16  as a ring. The inner face  16 , in regard to the center line  13 , lies closer to the pin shaft  12  than the outer face  15 . In the connection area between the pin shaft  12  and the pin plate  11 , contact teeth  17  are provided (only some of them being provided with reference numbers). The contact teeth  17  are arranged in a row around the end of the pin shaft  12  at the pin plate side. An edge of each contact tooth  17  starting from the radially outward pointing side of the pin shaft  12  extends in a straight line away from the pin shaft  12  and toward the pin plate  11 , so that this edge is oriented for example at 45° with respect to the center line  13 . Starting from this edge, the contact tooth  17  broadens out in wedge fashion toward the pin plate  11 . The distance (measured along a normal of the installation securing face  14  passing through the center line  13 ) between the installation securing face  14  and the center line  13  is shorter than the distance between the rest of the circumferential face, outside the installation securing face(s)  14 , and the center line  13 . 
     The grounding pin  10  is preferably made of steel and is put into the described shape in particular by pressing. The installation securing face  14  may be formed already by the pressing process, although it is preferably formed after the pressing by milling or cutting. The external thread of the pin shaft  12  is formed on the pin shaft  12  after the pressing process. 
       FIG. 3  is a three-dimensional representation of a grounding pin connection with the grounding pin  10  of  FIG. 2  and a cable lug  18 . The side of the pin plate  11  facing away from the pin shaft  12  is fashioned as a connection face  19 . This connection face  19  is adapted to being welded to a vehicle body. More precisely, a plurality of welding elevations  20  are provided for this purpose, which taper in the form of elevations in the direction away from the connection face  19 . For the welding on of the grounding pin  10 , an electrode of a welding apparatus is placed against the locations of the welding elevations  20 , but on the opposite side to the connection face  19 , and the grounding pin  10  is energized with current. The current flowing through the welding elevations  20  causes the welding elevations  20  to melt at least partly, so that the connection face  19  is fastened to the vehicle body. 
     The cable lug  18  has a cuff  21 , in which one end of the grounding line leading to a vehicle battery (more precisely, to a minus pole of the vehicle battery) can be fixedly clamped. From the cuff  21  there extends a fastening section  22  of the cable lug  18 , having a continuous opening. In the fastened state, the pin shaft  12  extends through the continuous opening and the fastening section  22  is screwed fast by a nut screwed onto the external thread of the pin shaft  12 , whereupon the contact teeth  17  are pressed into the material of the cable lug  18  and thus ensure a better contact. For an installation-safe fastening of the cable lug  18  on the grounding pin  10 , the installation securing face  14  is provided. At the end of the cable lug  18  situated opposite the cuff  21 , the cable lug  18  is provided with an angle section  23 . More precisely, the angle section  23  and the fastening section  22  form substantially a 90° angle, with the angle section extending in the direction away from the pin shaft  12 . In the mounted state of the cable lug  18 , the angle section  23  lies against the installation securing face  14 . Since the installation securing face  14  is situated closer to the center line  13  than the rest of the circumferential face of the pin plate  11 , due to the interaction between angle section  23  and installation securing face  14  the cable lug  18  can only be secured in this position which is predetermined due to the orientation of the installation securing face  14  during automated welding. Neither is a twisting of the mounted cable lug  18  possible any longer (except for a certain tolerance) after the angle section  23  lies against the installation securing face  14 . 
       FIG. 4  is a three-dimensional representation of a grounding pin  100  according to a second exemplary embodiment of the invention.  FIG. 5  is a three-dimensional representation of a grounding pin connection with the grounding pin  100  and a cable lug  118 . In order to avoid repetition, for this second exemplary embodiment only differences from the first exemplary embodiment will be described and except for these differences reference is made to the description of the first exemplary embodiment. 
     The pin plate  111  of the second exemplary embodiment differs from the pin plate  11  of the first exemplary embodiment only in that the installation securing face  114  does not extend entirely through the pin plate  111 , but instead is a surface of a groove  124 . That is, on either side of the installation securing face  114  there are provided side flanks of the groove  124  at a 90° angle. The statements regarding the minimal distance of the installation securing face  114 , however, still hold, as in the first exemplary embodiment. The angle section  123  differs from the angle section  23  of the cable lug  118  in that it is narrower, so that it fits into the groove  124 . The dimension of the angle section  123  in a direction parallel to the installation securing face  114  basically corresponds to the dimension of the installation securing face  114  in the same direction. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.