The fifth wheel is a kind of traction parts used to pull semi-trailer. The traction vehicle equipped with this traction link is also known as saddle tractor. The fifth wheel is mainly composed of seat cover plate, saddle base and locking mechanism, seat plate, separation connection mechanism and support. There is a saddle base on both sides below the seat cover plate pressed by steel plate, which is connected with the seat cover plate with a pin shaft. The saddle base can rotate back and forth with the pin shaft as the center. The bottom surface of the saddle base is connected with the pulled tractor by screws. Under the seat cover plate, a tightening mechanism composed of horseshoe iron, inclined iron, hook tongue, adjusting disc, cross bar, pull rod and spring is set. The horseshoe iron is fixed on the seat cover plate, the pull rod, corss bar and incluned iron are connected through pin shaft. The pull rod is connected with the rib plate under the seat cover plate by spring. The two tails of the saddle shaped seat cover plate are large arcs, and there is a butterfly shaped concave surface in the middle, which divides the whole plane into five parts of similar size.
The fifth wheel can not only bear part of the vertical mass of the semi-trailer, but also play the role of towing the semi-trailer. At the same time, it is the steering mechanism of the semi-trailer. The shape of both sides of the seat cover plate is a streamline shape with wide middle and narrow sides. Under the seat cover plate is welded with a well shaped reinforcing rib, and a set of lubrication pipeline is also set under the seat cover plate.