Abstract:
An adapter for a trailer socket of a trailer coupling for coupling a trailer, wherein the adapter comprises a base body and a primary contact arrangement mounted thereon and comprising a plurality of primary contacts corresponding to a European or German standard, in particular seven primary contacts according to DIN 1724 or thirteen primary contacts according to ISO 11446, for establishing an electric connection to corresponding socket contacts of the trailer socket. The adapter comprises a secondary contact arrangement mounted on the base body with secondary contacts according to a US American standard, so that a trailer plug corresponding to the US American standard can be electrically connected to the secondary contact arrangement for the power supply of a trailer, the secondary contact arrangement and the primary contact arrangement being connected to one another via an electric connection arrangement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to DE 102012013653.6, filed Jul. 10, 2012. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an adapter for a trailer socket of a trailer coupling for coupling a trailer, wherein the adapter comprises a base body and a primary contact arrangement mounted thereon and comprising a plurality of primary contacts corresponding to a European or German standard, in particular seven primary contacts according to DIN 1724 or thirteen primary contacts according to ISO 11446, for establishing an electric connection to corresponding socket contacts of the trailer socket. 
     The trailer socket may for example be a 13-pin trailer socket according to ISO 11446 or a 7-pin trailer socket according to DIN 1724. The provision of an adapter designed for example for connecting a 13-pin trailer plug according to ISO 11446 to a 7-pin trailer socket according to DIN 1724 is known. The known adapter allows for standardised wiring at low cost. However, apart from these typical DIN-to-DIN adapters or DIN-to-ISO adapters, no other socket adapters are available. As a rule, country-specific sockets or socket wiring have to be provided, which is complicated and expensive. 
     SUMMARY OF THE INVENTION 
     The present invention is therefore based on the problem of providing an alternative adapter for a trailer socket in order to expand the range of application for a standard trailer socket according to DIN 1724 or ISO 11446. 
     To solve this problem, it is provided in an adapter of the type referred to above that the adapter comprises a secondary contact arrangement mounted on the base body with secondary contacts according to a US American standard, so that a trailer plug corresponding to the US American standard can be electrically connected to the secondary contact arrangement for the power supply of a trailer, the secondary contact arrangement and the primary contact arrangement being connected to one another via an electric connection arrangement. 
     A trailer coupling developed for the European market and having corresponding wiring, for example, can now be used on the US American market as well without requiring complex conversion measures, adaptations or specific trailer sockets. 
     The pin assignment of a 13-pin socket according to DIN ISO 11446 may for example be as follows: 
     Contact  1 : Direction indicator left 
     Contact  2 : Rear fog light 
     Contact  3 : Earth for circuits  1 - 8   
     Contact  4 : Direction indicator right 
     Contact  5 : Rear light, contour light, number plate light right 
     Contact  6 : Brake lights 
     Contact  7 : Rear light, contour light, number plate light left 
     Contact  8 : Reversing light 
     Contact  9 : Power supply (permanent plus) 
     Contact  10 : Charging line for trailer battery, power supply, ignition switch-controlled 
     Contact  11 : Earth for circuit via contact  10   
     Contact  12 : Trailer identifier 
     Contact  13 : Earth for circuit  9   
     The pin assignment of the 7-pin socket according to DIN 1724, ISO 1724 and ISO 1185 is as follows: 
     Contact  1 : Direction indicator left 
     Contact  2 : Rear fog light 
     Contact  3 : Earth for circuits  1 - 7   
     Contact  4 : Direction indicator right 
     Contact  5 : Rear light, contour light, number plate light right 
     Contact  6 : Brake lights 
     Contact  7 : Rear light, contout light, number plate light left 
     It can for example be seen that contacts  1  to  7  are identical for ISO 11446 and DIN 1724, while the 13-pin socket is provided with additional contacts, for example for a permanent plus circuit of the trailer. Contact  12  of a trailer socket according to ISO 11446 is basically provided for a trailer identification. This, however, is rarely the case in practical applications. 
     At this point, further aspect of the invention becomes relevant, according to which an electric connection set is provided for a trailer coupling for operation with the adapter according to the invention, the connection set comprising a trailer socket with a 13-pin contact arrangement according to ISO 11446 and contact  12  of the trailer socket being for example configured for the selection of an electric brake of the trailer. Unless needed for other purposes, other contacts but contact  12  would obviously be suitable as well. Contact  10  is for example suitable for this purpose, if the trailer does not require a charging line. 
     The adapter expediently comprises at least one secondary contact for transmitting a signal for the selection of an electric brake of the trailer. This secondary contact is electrically connected to a primary contact which matches the contact, for example contact  12 , provided for the selection of an electric brake of the trailer. 
     Both the primary contacts and the secondary contacts may for example have plug-in projections or sockets or both, depending on the requirements of the standard, the socket into which the adapter is inserted or the plug which is inserted into the adapter. In a primary side designed according to ISO 11446, for example, the primary contacts are represented by plug-in projections. If, on the other hand, the primary side is to meet the requirements of DIN 1724, the contacts  2 ,  5 ,  7  are for example designed as female contacts or sockets. 
     The secondary contacts are preferably designed as sockets. 
     The secondary contact arrangement expediently comprises seven electric contacts. The secondary side of the adapter is expediently constructed in accordance with a mechanical and electric design which the US manufacturer Pollack produces in great numbers. The secondary side of the adapter therefore for example corresponds to a Pollack socket type. This being so, the term “standard” should also be understood to mean that the US plug or the secondary side respectively corresponds to a standard commonly observed in the market. 
     An advantageous aspect of the invention provides that the secondary contact arrangement comprises at least one brake light/direction indicator contact provided for the selection of a combined brake light/direction indicator of the trailer. This is because in the USA the brake light commonly acts as direction indicator as well. The brake light/direction indicator contact (of the secondary side) is electrically connected to a brake light primary contact for the selection of a brake light and to an indicator primary contact of the primary contact arrangement for the selection of a left- or right-hand direction indicator in such a way that that a current is applied to the secondary-side brake light/direction indicator contact if a current is applied to the brake light primary contact or the direction indicator primary contact. If therefore the primary contact for brake lights or the primary contact for direction indicators is supplied with power, the output-side secondary contact—the secondary brake light/direction indicator contact - has power as well. It is obviously expedient if a combined secondary brake light/direction indicator contact is provided both for the right-hand and for the left-hand side of the trailer, i.e. for the right-hand and the left-hand combined brake light/direction indicator. 
     A feedback between the primary contacts for brake lights and direction indicators via the secondary brake light/direction indicator contact is expediently avoided by means of the following measures. It is expediently provided that at least one electric diode element is provided between the brake light primary contact and the brake light/direction indicator contact or between the direction indicator primary contact and the brake light/direction indicator contact, the diode element being electrically conductive in a direction from the brake light primary contact or the direction indicator primary contact to the brake light/direction indicator contact and non-conducting in the opposite direction. The diode element may for example comprise a blocking diode, a transistor or the like. 
     Other electric measures, for example complex electronic simulation or decoupling measures, may of course also be provided in the adapter. Galvanic isolation is also possible, for example by separating the primary-side circuit from the secondary-side circuit galvanivally using a transformer in order to avoid the feedback referred to above. 
     The base body is expediently provided with a thread for tightening into a mating thread of the trailer socket. The primary side of the base body is expediently designed to be standardised, i.e. it has the mechanical properties of a typical trailer plug according to ISO 11446 or DIN 1724 for example. A screw thread can also be designed in the manner of a bayonet. 
     A cover retaining projection for holding a cover of the trailer socket in an open position is expediently provided on the base body. This cover retaining projection expediently also serves as an anti-rotation device, so that the adapter, which is a quasi-plug on its primary side, cannot be inadvertently unscrewed from the trailer socket. 
     The cover retaining projection expediently has an external contour which fits into an internal contour of the cover of the trailer socket, for example positively, or at least positively in some sections. 
     The secondary side of the adapter is expediently closable, for example by means of a cover. The cover is preferably designed as a hinged cover, i.e. being preferably mounted pivotable on the base body. 
     The base body is expediently represented by a housing of the adapter. The base body may of course a single-piece or a multi-piece component. It is also possible for the respective contact arrangements to be designed as contact inserts which can be inserted into a corresponding recess of the base body or the base housing of the adapter. 
     One primary contact of the adapter is expediently provided for the selection of an electric brake of the trailer and connected to a corresponding secondary contact. This primary contact may for example be contact  12 . Other contacts can obviously be assigned accordingly. 
     A further circuit variant can provide that separate primary rear light contacts are present for a right-hand and a left-hand rear light of the trailer on the primary side, i.e. in the primary contact arrangement, while a single secondary rear light contact is provided in the secondary contact arrangement and is in this case advantageously connected electrically to both of the separate primary rear light contacts. Here, too, a diode circuit may be provided, preventing for example a flow of current from one primary rear light contact to the other primary rear light contact via the secondary rear light contact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are explained below with reference to the drawing, of which: 
         FIG. 1  is an oblique perspective view of an adapter according to the invention from its secondary side, 
         FIG. 2  is an oblique perspective view of the adapter according to  FIG. 1  from its primary side, 
         FIG. 3  is a front view of a primary contact arrangement of the adapter according to  FIG. 2 , 
         FIG. 4  is an oblique side view of the adapter according to  FIGS. 1-3  from below, 
         FIG. 5  is a circuit diagram and an electric connection arrangement of the adapter according to the preceding figures, and 
         FIG. 6  shows a trailer coupling with a trailer socket into which the adapter according to  FIGS. 1-5  can be inserted. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A coupling arrangement  90  as shown in  FIG. 6  comprises a trailer coupling  91  with a coupling arm  92  on which a coupling part, for example a spherical head  93 , is mounted. 
     The trailer coupling  91  is designed to be releasable, i.e. the coupling arm  92  can for example be mounted on, for example plugged onto, a holder  94  or removed again from this holder  94 . 
     This is of course irrelevant in the present context; the invention can obviously be used in a trailer coupling which can be pivoted between a position of use and a position of non-use, for example, or in a trailer coupling which is permanently mounted on the towing vehicle. 
     The holder  94  is for example mounted on a crossmember Q of a motor vehicle K. As a rule, the holder  94  is concealed behind a rear valance or a bumper of the motor vehicle K, which is not shown, however. 
     In a socket holder  95 , which may for example be stationary or movable, a trailer socket  96  having a contact arrangement  100  with socket contacts  101 - 113  is located. The contact arrangement  100  is located in a housing  97  of the trailer socket  96  and expediently closable by a cover  98 , which is, however, not necessary. The cover  98  is in the known manner pivotably mounted on the housing  97  by way of a pivot bearing  99  and can be moved between a closed position as shown in the drawing and an open position in which the socket contacts  101 - 113  are accessible. 
     The socket contacts  101 - 113  are for example designed as receptacles. The pin assignment of the socket contacts  101 - 113  follows the arrangement for contacts  1 - 9 ,  13  according to ISO 11446 as explained above. Contact(s)  2  and/or  10  and/or  11  may be unassigned, for example. 
     A plug according to a US standard, for example a so-called Pollack plug, cannot be directly connected to the trailer socket  96 . For the brake lights and the right-hand and left-hand direction indicators, for example, the separate socket contacts  106 ,  104  and  101  are provided, while in the US standard the left-hand direction indicator also serves as the left-hand brake light of the trailer and the right-hand direction indicator serves as the right-hand brake light of the trailer in a manner of speaking. In addition, the US plug does not match the European trailer socket  96  in mechanical terms. This is where the invention becomes relevant. 
     To connect for example a so-called Pollack plug according to a US standard or a typical US convention to the trailer socket  96 , the adapter  20  having a primary side P and a secondary side S is provided. The primary side P corresponds to ISO 11446, i.e. the primary contacts  1 - 13  of a primary contact arrangement  15  have a typical electric assignment according to ISO 11446 and a mechanical arrangement corresponding to standard. The primary contacts  1 - 13  are for example designed as plug-in projections  22 . 
     The plug-in projections  22  are for example arranged in a recess  23  of a housing  21  of the adapter  20 . The housing  21  forms a base body  24  of the adapter  20 . The primary contacts  1 - 13  are for example arranged on a contact insert  25  located in the interior of the housing  21 . The primary contacts  1 - 13  or the plug-in projections  22  are surrounded by a circumferential wall  26  of the housing  21 . On the outside of the circumferential wall  26 , a thread  27  is provided, which can be screwed into a female thread of the trailer socket  96  which is not visible in the drawing. 
     On the circumferential wall  26 , there is further provided a cover retaining projection  28  which projects radially outwards beyond the circumferential wall  26 . The cover retaining projection  28  holds the cover  98  of the trailer socket  96  open. It further forms an anti-rotation device to secure the adapter  20  screwed into the female thread of the trailer socket  96  against rotation when the cover retaining projection  28  is in engagement with the cover  98 . 
     The cover retaining projection  28  comprises a plate  29  the external contour  30  of which corresponds to an internal contour of the cover  98 . The external contour  30  fits into the internal contour of the cover  98  at least substantially positively. A foot part  31  extends between the plate  29  and the circumferential wall  26 . 
     Between the section of the circumferential wall  26  where cover retaining projection  28  is located and a free end face region of the circumferential wall  26 , a flanged projection  33  extends; this forms a stop body while the thread  27  is tightened into the trailer socket  96 . 
     The primary contacts  1 - 13  have the following pin assignment: 
       1  Direction indicator left 
     
       2 
     
       3  Earth for pins  1 - 8   
       4  Direction indicator right 
       6  Brake light left and right 
       7  Rear light left and right 
       8  Reversing light 
       9  Permanent plus K130 
     
       10 
     
     
       11 
     
       12  Electric brake 
       13  Earth for contact  9   
     On the secondary side S, secondary contacts  51 - 57  of a secondary contact arrangement  50  are provided. 
     The secondary contacts  51 - 57  are designed as contact tabs which fit into corresponding sockets on a diagrammatically represented so-called Pollack plug S. The Pollack plug S supplies via a connecting line V electric components of a trailer A of which only the plug S is shown, for example brake lights/direction indicators, an electric brake etc. 
     The central secondary contact  57  comprises two opposite contact tabs  59  which enclose an interior where a corresponding plug-in projection of the Pollack plug can be inserted. In principle, the secondary contact  57  is therefore designed as a socket. 
     The secondary contacts are arranged in a recess  60  of the housing  21  to protect them from the environment. The recess  60  is bounded by the circumferential wall  26 . 
     At this point, it should be noted that the circumferential wall  26  is substantially cylindrical, but this is not essential. The circumferential wall  26  may further be stepped, i.e. have different sections  35 ,  36  and  37  with different diameters in the longitudinal direction  34  of the adapter  20 . The section  35  may for example represent the circumferential wall around the recess  23 , while the section  36  represents a central section with the cover retaining projection  28  and has a smaller diameter than the front section  35 . The section  37  represents the circumferential wall around the recess  60  on the secondary side S. 
     It is, however, advantageous if an external contour of the adapter  20  approximately corresponds to an external contour of the of the trailer socket  96 , so that the adapter  20  mounted on the trailer socket  96  together with the trailer socket  96  forms a single unit in a manner of speaking and is as compact as possible. 
     The secondary contacts  51 - 57  are for example arranged on a contact insert  67  which is installed into the housing  21 . It is, however, also possible for the primary contacts  1 - 13  and/or the secondary contacts  51 - 57  to be held by the housing  21  directly, for example by injection-moulding the housing material around them. 
     A flange plate  61  is provided on the section  37 , i.e. on the secondary side S. The secondary side S is further provided with a cover  62  for closing the secondary contact arrangement  50 . 
     The cover  62  is easily gripped by a handle  63  which projects from a base body of the cover  62 . 
     The cover  62  is pivotably mounted on the flange plate  61  by means of a pivot bearing  64 . The cover  62  could of course alternatively be pivoted at another point of the housing  21 . It is expediently provided that the cover  62  completely closes the recess  60  and expediently encompasses or covers the outside of the section  37  of the circumferential wall  26  which encloses the recess  60  as well. The circumferential wall  26  therefore engages with a recess  65  on the cover  62  when the latter is closed. 
     In the primary contacts  1 - 13 , i.e. on the primary side P, a coding  38  is provided, for example a projection which engages with a corresponding coding not shown in the drawing which is provided in the trailer socket  96 , so that the adapter  20  can only be inserted into the trailer socket in the correct angular position. Expediently, a coding  66 , for example a recess suitable for engagement with a corresponding mating coding on the US trailer plug not shown in the drawing, is provided on the secondary side S, i.e. in the secondary contacts  51 - 57 . 
     The flange plate  61  in a manner of speaking forms a front stop for the US plug. It is advantageously provided that the mechanical components on the secondary side S cover the mechanical components of the adapter  20  which lie behind when the adapter  20  is mounted on the trailer socket  96 . The flange plate  61  for example projects beyond the outer circumference of the circumferential wall  26  to the same extent as the cover retaining projection  28 . 
     At this point, it should be noted that it is of course not absolutely necessary to provide a projection on the adapter  20  in order to hold the cover  98  of the trailer socket  96  open, but the plate  29  could for example be mounted directly on a housing having a larger circumference, in which case the foot part  31  would not be required, for example. 
     The secondary contacts  51 - 56  have the following pin assignment: 
       51  Direction indicator left and brake left 
       52  Earth 
       53  Electric brake 
       54  Direction indicator right and brake right 
       55  Permanent plus K130 
       56  Rear light left and right 
       57  Reversing light 
     The socket contacts of the trailer socket  96  are wired as follows: 
     Socket contact  101 : Direction indicator left 
     Socket contact  102 : Rear fog light (optional) 
     Socket contact  103 : Earth for contacts  1 - 8   
     Socket contact  104 : Direction indicator right 
     Socket contact  105 : Rear light right 
     Socket contact  106 : Brake lights left and right 
     Socket contact  107 : Rear light left 
     Socket contact  108 : Reversing light 
     Socket contact  109 : Power supply (permanent plus) or terminal  30   
     Socket contact  110 : Charging line for trailer battery, power supply, ignition switch-controlled (optional) 
     Socket contact  111 : Earth for circuit via contact  10   
     Socket contact  112 : Electric brake 
     Socket contact  113 : Earth for circuit via contact  9   
     In the trailer socket  96 , a signal for the actuation of an electric brake of the trailer is therefore applied to the socket contact  112 . This is because in the USA an electric brake is provided from a specified trailer weight onwards. If the trailer socket  96  is used without the adapter  20  and if for example a trailer with a plug contact assignment according to a European standard is used, this does not cause any damage as a rule, because the socket contact  112  is usually not used. 
     An innovative circuit diagram for connecting the primary contacts  1 - 13  to the secondary contacts  51 - 57  is shown in  FIG. 5 . An electric connection arrangement  70  comprises electric lines L 1 , L 3 -L 9 , L 12  and L 13  which are connected to the primary contacts  1 ,  3 - 9 ,  12  and  13 . 
     The line L 9  connects the primary contact  9  directly to the secondary contact  55 , which means that permanent plus is switched through in a manner of speaking. The primary contact  8  is likewise directly connected to a secondary contact, this being to the secondary contact  57  for the reversing light of the trailer via the line L 8 . 
     Finally, the primary contact  12  assigned to the electric brake is likewise directly connected to a secondary contact, this being the secondary contact  53 , via the line L 12 . 
     As US wiring provides only a single power supply for the right-hand and the left-hand rear lights, the two lines L 5 -L 7  are connected to one another, leading as line S 6  to the corresponding secondary contact  56  for the rear light of the trailer. 
     Each of the primary contacts  3  and  13  is assigned to a chassis earth and can be connected to corresponding socket contacts  103  and  113  of the trailer socket  96 . On the secondary side, only a single chassis earth is provided in the adapter  20 , this being at the secondary contact  52 . In accordance with this, the two lines L 3  and L 13  are electrically connected to one another and routed as line S 2  to the secondary contact  52 . 
     As a US trailer only has a combined brake light/direction indicator, which is permanently supplied with power in the braking process and with pulsed power when indicating a change in direction, corresponding secondary contacts  51 ,  54  are provided for the left-hand and the right-hand brake light/direction indicator; these represent brake light/direction indicator contacts in a manner of speaking. The secondary contacts  51 ,  54  are however not directly connected to the associated primary contacts  1  and  6  or  4  and  6  respectively, but via a diode circuit comprising diode elements  71 - 74 , such as blocking diodes, transistors or the like. 
     The diode circuit with the diode elements  71 - 74  is preferably arranged on a printed circuit board  75 , but so-called floating wiring can of course be used as an alternative. It is for example also possible for the printed circuit board  75  to be integrated with, for example, the contact insert  25  or the contact insert  67  with the secondary contacts  51 - 57 , or for the contact inserts  25  and/or  67  to form supports for electronic components such as the diode elements  71 - 74 . 
     This printed circuit board  75  or another electronic component may, for example, also support a simulation circuit  76  which may e.g. comprise a storage capacitor, transistors or the like for simulating at least one function on the secondary side S of the adapter  20  towards the primary side P. The simulation circuit  76  may for example simulate flashing pulses at the direction indicator primary contacts  1  and  4  even if there is a steady current applied on the secondary side to the secondary contacts  51  and  54  when a steady current is delivered by the brake light primary contact  6 . It is for example possible for the simulation circuit  76  to check whether a current pulse is coming via the lines L 1  or L 4  while the secondary side circuit is at the same time permanently closed via the lines S 1  or S 4  (in the case of the brake light) or is in any case closed during the primary side current pulses (in the case of the direction indicator); on the primary side, it would simulate that at the lines S 1  or S 4  the circuit is closed via the trailer direction indicators during the current pulses. 
     The lines L 1  and L 6  are connected via diode elements  71  and  73  to a line S 1  which is in turn connected to the secondary contact  51 . 
     The lines L 4  and L 6 , which are connected to the primary contacts  4  and  6 , are connected to the secondary contact  54  via diode elements  72  and  74  which are connected to a line S 4  on the output side. 
     The secondary contacts  51  and  54  therefore are brake light/direction indicator contacts for example.