The common form of non-automatic coupler, used in Great Britain for goods wagons, consists of a chain and hook; the chain hangs loosely from a slot in the draw-bar, which terminates in a hook, and coupling is effected by slipping the =chain of one vehicle over the hook of the next.
Another form of coupler, which used to be universal in the United States, though it has now been almost entirely superseded by the automatic coupler, was the " link and pin," which differed fundamentally from the couplers commonly used in Europe, in the fact that it was a buffer as well as a coupler, no :side buffers being fitted.
The essential change from the link and pin to the automatic coupler is in the outboard end or head of the draw-bar.
This form of automatic coupler has now gained practically universal acceptance in the United States.
This body pursued the subject with more or less diligence, and in 1884 laid down the principle that the automatic coupler should be one acting in a vertical plane - that is, the engaging faces should be free to move up and down within a considerable range, in order to provide for the differences in the height of cars.
In 1887 a committee reported that the coupler question was the " knottiest mechanical problem that had ever been presented to the railroad," and over 4000 attempted solutions were on record in the United States Patent Office.
The method of constructing the working faces of this coupler is shown in fig.