Abstract:
A trailer coupling for motor vehicles has a bar, a ball provided on the bar, the bar being automatically adjustable between an idle position and an operating position, and an adjusting drive including an electric motor which automatically adjust the bar between the idle position and the operating position.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a trailer coupling for motor vehicles with a bar on which a ball is located in the usual manner. 
     As long as trailer couplings are not used the ball-bar protruding beyond the rear bumber disturbs. For solving this problem trailer couplings are known whose ball-bar may be disassembled. It has been found that the disadvantage of the known trailer couplings is that the disassembly of the ball-bar is physically very demanding. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the object of the invention to put forward a trailer coupling which does not have this disadvantage. 
     The object is solved by the features of patent claim  1 . 
     Further advantageous formations of the invention are described in the dependent claims  2  to  8 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in more detail by way of a preferred embodiment form with reference to the drawings, wherein further advantageous details can be deduced from the drawings. The same parts with regard to their function are provided with the same reference numerals. 
     The drawings show individually: 
     FIG. 1 an elevation of the trailer coupling according to the invention, with an axial adjustment into the idle position, 
     FIG. 2 a lateral view of the trailer coupling according to the invention and according to FIG. 1, 
     FIG. 3 a lateral view of a ball-bar according to FIG. 1, 
     FIG. 4 an elevation of a sleeve for receiving the ball-bar according to FIG. 3, 
     FIG. 5 a lateral view of the sleeve according to FIG. 4, 
     FIG. 6 a view according to arrow A in FIG. 5, 
     FIG. 7 a lateral view of an alternative embodiment form with a pivotable ball-bar, 
     FIG. 8 a section according to line B—B of FIG. 7, through the drive of the ball-bar, 
     FIG. 9 a lateral view of a further embodiment form with a laterally pivotable coupling bar, and 
     FIG. 10 a plan view of the embodiment form according to FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1 the adjustable trailer coupling is indicated at  1 . It consists essentially of an axially adjustable bar  2  whose outer end carries a ball  3  as well as a guiding sleeve  4 , a motor with planet gears  6 , a spur gear  7  and an adjusting spindle  8 . 
     The guiding sleeve  4  on both sides carries in each case an assembly flange  9  in which there are incorporated threaded bores  10 . The whole trailer coupling  1  is assembled onto a vehicle in that by way of screws it is fastened onto a suitable bracket of the vehicle. With this screws engage into the threaded bores  10 . 
     The bar  2  is accomodated by the guiding sleeve  4 . For this purpose the bar  2  comprises a rear guiding surface  11  and a front guiding surface  12  which via a cone  13  blend into a somewhat slimmer bar  2 . 
     Furthermore in the guiding sleeve  4  an annular inner cone  14  is fastened. Finally in the guiding sleeve  4  there are formed guiding slots  15 . 
     On the bar  2  in the rear region there is fastened a pin-like connecting rod  16  which engages into the guiding slot  15 . Furthermore in the bar  2  there is incorporated a pocket hole with an inner thread  17 . 
     The adjusting spindle  8  is screwed into the mentioned inner thread  7  and is rotated by an electrical motor via the spur gear  7  as well as the planet gear  6 . The individual gearwheels of the gear  7  are mounted between lateral plates  19  and  20 . The housing of the planet gear  6  and the guiding sleeve  4  are rigidly connected to the plate  20 . The adjusting spindle  8  is likewise rotatably mounted in the plates  19  and  20  so that it can be rotated by the electrical motor  5  as desired. 
     If the motor  5  is driven in the corresponding direction, then the adjusting spindle  8  also rotates. At the same time the bar  2  which is arranged as a nut on the adjusting spindle  8  and is secured against rotation by the connecting member  16  is pushed outwards. With this axial movement the bar  2  is guided in the guiding sleeve  4  by the guiding surfaces  11  and  12 . The bar reaches its end position when the outer cone  13  sits rigidly in the annular inner cone  14 . 
     As long as the guiding slots  15  run in the axial direction, the bar  2  maintains its radial position. After roughly half the adjusting distance the guiding slots  15  blend into a spiral-shaped course. This results in the fact that the bar  2  on extending then correspondingly turns so that the ball  3  in the operating position points vertically upwards. The operating position is shown in FIGS. 1 and 2 by dashed lines. 
     For a better understanding the essential parts are again individually shown in FIGS. 3 to  6 . 
     An alternative embodiment form of a trailer coupling is shown in FIG.  7 . With this embodiment form the bar  2  is not axially displaced, but is pivoted about an axis  24 . 
     For an easier understanding only the bar  2  with its pivoting drive  21  is shown, wherein known additional drive parts such as a gear motor, are not shown. 
     FIG. 7 shows a pivoting drive  21  with which the bar  2  can be pivoted upwardly about approximately 90° . 
     The drive however can in a slightly modified form serve for passing through other pivoting angles. 
     With a correspondingly modified installation location, and an adapted bar  42  for this, a modified pivoting drive  41  may also be applied for a horizontal pivoting of the bar  42 . Such a pivoting drive  41  is shown in the FIGS. 9 and 10. 
     With the embodiment shown in FIG. 7 the bar  2  however is pivoted vertically upwards. For this purpose it is pivotably mounted between two plates  22  and  23  about the axis  24  on the pintail  25 . 
     Furthermore the bar  2  comprises a limb  26  whose function can be seen from FIG.  8 . 
     In FIG. 8 a section corresponding to the marking effected in FIG. 7 is shown. In the region of the limb  26  the bar  2  is thus provided with a slot  27 . Furthermore perpendicular to the plane of the slot there is provided a bearing bore  28  for the pintail  25 , a bearing bore  29  for a pinion shaft  31  as well as a bore with an inner thread  30  for a blocking cone  32 . 
     As mentioned the pintail  25  is rotatably mounted between two plates  22  and  23 . In the region of the slot  27  of the bar  2 , the pintail  25  comprises a toothing  33 . A gearwheel  34  engages into this toothing  33 , the gearwheel being mounted on the pinion shaft  31 . With the gearwheel  34  there meshes a further gearwheel  35  which is connected to a shaft  36  in a rotatably rigid manner. 
     On the shaft  36  on both sides of the gearwheel  35  there is each mounted a blocking cone  32  in a rotatably rigid but axially displaceable manner. This blocking cone  32  comprises an outer thread  37  which engages into the inner thread  30 . For the blocking cone  32  a locking opening  38  is provided in the plates  22  and  23 . 
     In the position shown in FIG. 8 the blocking cone  32  should be retracted in the usual manner into the locking opening  28 . For a better recognition it is shown in a position in which the bar  2  may be pivoted. 
     The ends of the pinion shaft  31  are guided in arc-shaped slots  39  of the plates  22  and  23 . The remaining bores of the plate  22  shown in FIG. 7 serve for its fastening onto the vehicle or serve the fastening of a further gear with a suitable electrical drive or the connection by way of distance bolts. 
     The position of the bar  2  represented in FIG. 7 with dashed lines corresponds to its operating position. For pivoting the bar  2  then, a gearwheel  40  rigidly connected to the pintail  25  is driven. Since firstly the blocking cone  32  is retracted into the locking opening  38  of the plate  23 , the bar  2  can still not be pivoted about the axis  24 . Instead of this via the toothing  33  and via the gearwheel  34  the gearwheel  35  is rotated. Since this gearwheel is rigidly connected to the shaft  36 , the shaft  36  drives the blocking cone  32 . Since the outer thread  37  of the blocking cone is engaged with the inner thread  30 , at the same time the blocking cone  32  moves axially inwards until it is completely extended out of the locking opening  38 . As soon as the blocking cone  32  comes to bear on the gearwheel  35 , the gearwheel  35  and the gearwheel  34  which is engaged with it are blocked. By way of this the pintail  25  drives the blocked gearwheel  34  and the pinion shaft  31 , so that the pinion shaft  31  is pivoted about the axis  24 . At the same time the pinion shaft  31  which is mounted in the bearing bore  29  of the bar  2  then drives this bar so that the bar  2  is pivoted. This pivoting movement finishes as soon as the pinion shaft  31  reaches the end of the slot  39 . 
     For the purpose of clarity it must be mentioned that in FIG. 8 the left blocking cone is not shown. 
     For the electrical drive it is provided for this to be switched off as soon as the laod exceeds a previously set limiting value. In this way damages are avoided, in the case that on moving the bar  2  foreign bodies should inhibit the further operation. So that the adjustment cannot be initiated during the journey of the vehicle it is furthermore provided for the trailer coupling to only be able to be operated outside the compartment of the vehicle. It is particularly advantageous when the operating means, for example a switch, is arranged in the boot of the vehicle. 
     In this manner there is created a vehicle coupling which is easily and comfortably brought into a position in which it no longer disturbs.