Automatic Coupler

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Automatic Coupler


a device for automatically coupling railway rolling stock and for transmitting and cushioning the effect of longitudinal stresses generated as the train moves and stops, as well as in classification yard work. The device couples cars automatically when they come together in the yard and automatically resets the parts of the mechanism to the ready position for coupling after a train has been broken up; the automatic coupler can be set to act as a buffer when the cars are not required to couple upon coming together. Uncoupling is performed manually (but the worker does not have to get in between the cars).

Figure 1. SA-3 automatic coupler

Figure 1 shows an automatic coupler and its placement on the end of the car. The body (13) of the automatic coupler accommodates the parts of the coupling mechanism. The draft clip (6), with the aid of the bolted key (8), the thrust plate (7), the front stop (9), and back stop (1), transmits longitudinal tensile and compressive stresses from the body of the automatic coupler to the car undercarriage by means of the draft friction gear (5). The pendulum gears (11) and the centering beam (12) reset the deflected body of the automatic coupler to its central position. The uncoupling lever (3) held in place by the mounting bracket (2), the uncoupling lever holder (10), and the chain (14) are used to disengage the automatic coupler or to set the mechanism in the uncoupling position when buffering action is required; the support cleat (4) holds up the draft clip with the draft friction gear and thrust plate. The body of the automatic coupler features two lugs—a large one and a small one— with an opening between them. In coupling, the small lug of one coupling enters the opening on the other, while the locks in the body of the automatic coupler bear against each other and intrude into the pockets (13) of the coupler body, thus completing the coupling. Once coupled, the automatic coupler is prevented by the lock retainer from coming loose under way in response to jolts. The automatic coupler is disengaged by rotating the lock lifter pin of either of the mating couplers, to unlock first the respective lock retainer and then run the lock back. Ready for recoupling, the locks are run forward as the small lug is withdrawn from the opening, or the lock retainer is lifted without disengaging the automatic coupler (when dealing with an erroneous disengagement).

The strength of automatic coupler parts is slightly less than the strength of the car undercarriage, so that the undercarriage will not be damaged when subjected to appreciable longitudinal stresses.


Vagony: Konstruktsiia, teoriia i raschet. Edited by L. A. Shadur and I.I. Chelnokov. Moscow, 1965.
Kolomiichenko, V. V., and V. G. Golovanov. Avtostsepka podvizhnogo sostava. Moscow, 1967.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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