Abstract:
A vehicle coupling for producing a mechanical connection between a first and a second vehicle including a coupling body ( 1 ) in which at least one structural area ( 2 ) of the coupling body ( 1 ) is made of a metallic foam ( 3 ).

Description:
BACKGROUND 
     The invention relates to a vehicle coupling for establishing a mechanical connection between a first and a second vehicle, wherein the vehicle coupling includes a coupling body. 
     The coupling body and the components which cooperate with same are usually produced by in a casting process, using cast steel or spheroidal graphite iron, or also by welding sheet metal parts. The resulting robust design is necessary under the expected high operating forces in order to avoid deformations and ensure maximum wear protection. However, these designs used heretofore have the disadvantage that the nominal weight of the vehicle coupling is very high, which in turn disadvantageously affects the curb weight of the vehicle, resulting in a correspondingly lower available payload for a specified maximum allowable total weight. A further disadvantage of cast components lies in the risk of formation of inclusions and shrink holes, particularly in regions where localized aggregations of metal are necessary. 
     Consequently, the object of the invention is to provide a vehicle coupling having a nominal weight that is much lower than known vehicle couplings. 
     SUMMARY 
     The object is achieved according to the invention by using a vehicle coupling in which at least one structural area of the coupling body is made of a metal foam. The essential advantage of the metal foam lies in the very high strength, with a unit weight that is much lower than steel. 
     The metal foam is produced from a blowing agent and a metal powder which is added thereto, the metal powder usually being composed of aluminum or steel. After the blowing agent and metal powder are combined and mixed, a first shaping process is carried out, followed by foaming. The foam structure results in an extremely low bulk density with only slightly reduced strength of the metal foam. 
     The coupling body preferably includes a coupling plate of a fifth wheel coupling. Alternatively, the coupling body may be formed from a coupling jaw of a trailer or pin coupling. 
     It has proven to be advantageous when the metal foam has a complete or partial coating. The vehicle coupling or the correspondingly designed areas made of metal foam have a comparatively rough surface, which may be smoothed by a coating. In addition, the coating may increase corrosion resistance. The coating may be formed from a filling lacquer, for example. 
     The coating may also be provided by extrusion coating or foam enclosure with a plastic. This coating may be applied to all or part of the vehicle coupling. 
     In particular, individual components may be fully encapsulated by the coating. 
     The structural area is advantageously formed in a sandwich design. The sandwich design is a design in which multiple layers having different characteristics are embedded in a material. As a construction method, the sandwich design refers to a form of lightweight construction in which the components are made of force-absorbing cover layers which are spaced apart by means of a relatively soft, usually lightweight, core material. These parts are very resistant to bending and buckling while having a low weight. The core material transmits shear forces which occur, and supports the cover layers. 
     In the sandwich design the metal foam forms the core, which is joined to at least one cover layer made of steel and/or plastic and/or aluminum. At locations where a closed-pore surface is required, for example to achieve low coefficients of friction, customary sheet steel or optionally also a plastic layer should be used. 
     As an alternative or in addition to the sandwich design, the structural area advantageously includes a support element made of metal foam which is provided on the coupling body. A “support element” is understood to mean a rib structure which reinforces the coupling plate or coupling jaw. For a fifth wheel coupling, this rib structure is situated on the underside of the coupling plate, and for a coupling jaw, on the exterior of the conically expanded insertion opening. 
     The support element is advantageously connected to the coupling body by means of an adhesive layer. The adhesive layer may be provided using a plastic compound which preferably is fiber-reinforced. 
     Thermoplastics or duroplastics are suitable materials for the plastic compound. A thermoplastic plastic deforms when heated, and maintains its shape upon cooling. The most well-known thermoplastics are polypropylene, polyethylene, polyester, polyvinyl chloride, and polyamide. Duroplastics, also referred to as duromers, are plastics which can no longer be deformed after hardening. Duroplastics are hard, glass-like polymeric materials which are fixedly crosslinked in three dimensions via primary chemical bonds. The crosslinking is achieved during mixing of precursors having branching sites, and is activated either chemically at room temperature, using catalysts, or thermally at high temperatures. 
     A plastic foam in particular may also be used as a plastic compound. Likewise, use of a metal foam is particularly well suited for producing an adhesive layer. 
     Further possibilities for connecting the support element to the coupling body are thermal joining, or a screw or rivet connection. 
     Due to the high flexural strength, according to one preferred embodiment the metal foam is situated in a section of the coupling body located in the force flow. 
     The metal foam is advantageously provided with a bearing point and/or fastening hole. The bearing points are provided on a fifth wheel coupling at oppositely situated lateral positions for supporting the coupling plate on bearing blocks located therebeneath. The fastening holes may be designed as a threaded insert part, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For better understanding, the invention is explained in greater detail below with reference to five figures, which show the following: 
         FIG. 1 : shows a partial view of the bottom of a coupling plate of a fifth wheel coupling; 
         FIG. 2 : shows a cross section along section line A-A in  FIG. 1 , according to a first embodiment having a support element glued to the coupling plate; 
         FIG. 3 : shows a cross section along section line A-A in  FIG. 1 , according to a second embodiment having a support element provided with a foam enclosure; 
         FIG. 4 : shows a cross section along section line A-A in  FIG. 1 , according to a third embodiment having a coupling plate with a sandwich design; and 
         FIG. 5 : shows a cross section along section line A-A in  FIG. 1 , according to a fourth embodiment having a support element which is screwed to the coupling plate. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a bottom view of a coupling plate  4  of a fifth wheel coupling, for which the invention is explained as a representative for all coupling bodies  1 . 
     On its rear side  15  the coupling plate  4  has an insertion opening  16  in which a king pin of a trailer (not shown) may be inserted into the fifth wheel coupling in a customary manner. The insertion opening  16  is delimited on both sides by a coupling horn  17 , only the right coupling horn  17 , viewed in the direction of travel, being visible in the illustration of  FIG. 1 . 
     In driving mode, the underside of the trailer (also not shown) is supported on the bearing region  18  (see  FIG. 2 ) of the coupling plate  4 . Thus, in this bearing region  18  considerable forces are introduced into the coupling plate  4 . So that the entire coupling plate  4  does not have to be provided with a great material thickness and a correspondingly high weight, a structural area  2  in the form of a support element  10  made of metal foam  3 , which projects downward with respect to the coupling plate  4 , is situated on the underside  19  (see  FIG. 2 ) of the coupling plate  4 . One of the two mirror-symmetrical bearing points  13  which supports the coupling plate  4  on bearing blocks (not illustrated) is shown on the support element  10  made of metal foam  3 . 
     The support element  10  includes a base plate  10   a  which extends essentially horizontally, and on which vertical wall sections  10   b  are provided. 
     As shown in  FIG. 2 , the support element  10  is glued beneath the coupling plate  4  by means of an adhesive layer  11 . The adhesive layer  11  is essentially limited to the contact area of the support element  10  with respect to the coupling plate  4 . The metal foam  3  of the support element  10  allows a fastening hole  14 , for example, to be introduced in a particularly easy manner. Additional units or also components of the closure mechanics may then be screwed into this fastening hole and to the coupling body  1 . 
       FIG. 3  shows another embodiment in which the support element  10  next to the adhesive layer  11  is provided with a coating  5 . The coating  5  is applied as a foam enclosure  6 , and almost completely encloses the support element  10 . The foam enclosure  6  is omitted in only one area around the fastening hole  14 , so that at that location the metal foam  3  forms an externally accessible surface. This surface made of metal foam  3  allows higher surface pressures for the components which are to be screwed on at the fastening hole  14 . 
       FIG. 4  illustrates another embodiment having a coupling plate  4  in a sandwich design  7 . The top side  20  of the coupling plate  4  has a sheet metal plate as an upper cover layer  9   a  to ensure a resistant bearing region  18  having a low coefficient of friction. A trailer plate (not shown) which is supported thereon is thus able to slide on the bearing region  18  with low wear. 
     The metal foam  3  has been introduced directly beneath the upper cover layer  9   a  as the core  8  of the sandwich design, and after hardening forms a positive-fit connection with the cover layer  9   a . The sandwich design  7  also has a lower cover layer  9   b , which likewise adheres directly to the metal foam  3 . The lower cover layer  9   b  may in particular be a plastic layer. 
     The lower cover layer  9   b  is joined to the additional support element  10  made of metal foam  3  by means of an adhesive layer  11 . In this embodiment as well, a completely cast-in or foamed attachment of the support element  10  is possible. 
       FIG. 5  shows an alternative attachment of the support element  10  to the coupling plate  4  by means of multiple connecting elements, for which screws  12  are illustrated by way of example. These connecting elements pass through the coupling plate  4  in the vertical direction, and are fixedly held to the underside  19  by means of a nut. In this embodiment an adhesive layer  11  may be dispensed with entirely. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               1  Coupling body 
               2  Structural area 
               3  Metal foam 
               4  Coupling plate 
               5  Coating 
               6  Foam enclosure 
               7  Sandwich design 
               8  Core 
               9   a  Upper cover layer 
               9   b  Lower cover layer 
               10  Support element 
               10   a  Base plate 
               10   b  Vertical wall section 
               11  Adhesive layer 
               12  Screw 
               13  Bearing point 
               14  Fastening hole 
               15  Rear side 
               16  Insertion opening 
               17  Coupling horn 
               18  Bearing region 
               19  Underside 
               20  Top side