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  Trailer Coupling (truck)




In mechanical engineering a coupling counts as a detatchable connection. Of course it must be perfectly fitting to the trailer. In the case of the pin-coupling, it may only have a maximum of 1 millimeter play. To enable the process of coupling by a single person, the technology should also function automatically. This has the additional advantage of accident prevention, and in the meantime it is a legal requirement.

The hand-lever is important for the connection as well as the disconnection. Should the trailer be separated from the towing vehicle, this must be carried out, seen from the right, in a clockwise direction. Then, depending on the model, it stays where it is or, before re-coupling, must be pushed a little further.

The shooting bolt of the automatic coupling has, there where it is taken up by the drawbar eye, a slightly spherical shape. Thereby, the the differing heights between the vehicle and the trailer are compensated. In certain construction vehicles and, e.g., for military use, there is the additional possibility of twisting it about the transverse axis.

The trailer hitch, called the Rockinger 'trailer-hitch', must be relatively free of play, otherwise it can cause jerking movements in the entire tractor-trailer unit. Regardless of the axis about which this type of trailer is twisted, it must automatically return to its central position without the use of any force at all.

Once the trailer been has positioned with its towing-eye central to the coupling-jaw, it can give a certain amount of guidance in the automatic coupling process. Hereby, there is, in each of the above mentioned axial directions, a certain amount of torque required, with which this coupling-jaw must be held in the center position.

If the towing-eye is successfully positioned, a barrier is released, which causes the coupling-pin to snap downwards, thus placing the spherical part of the pin exactly in the center of the coupling-eye. It must however, be brought into the correct position before the hitching actually takes place. This is achieved either by unhitching, or it occurs through pressing, e.g., into a second notch position.

The closed coupling always has two safety pins. One can tell if they are engaged by the position of the hand lever. The end of one of the pins (red button in figure 1) is visible from the outside. If it is correctly engaged, it lies flush or sticks out a little. Here it can also be checked.

Nowadays, it's possible to do a lot from the drivers compartment. The coupling can be opened or closed pneumatically and a remote indication, either mechanically or electrically is possible. Of course, all this is also available as an electric system. 11/10




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