Knuckle coupler

The Janney Coupler is a semi-automatic railway coupler. The earliest commercially successful version of the knuckle coupler, it was patented by Eli H. Janney in 1873 (U.S. Patent 138,405).

In the United Kingdom, where it is fitted to some rolling stock, mostly for passenger trains, it is also known as a Buckeye Coupler, possibly originating from the coupler's manufacture as early as 1890 by the Buckeye Steel Castings firm in Columbus, Ohio.

The AAR/APTA Type E, Type F, and Type H tightlock couplers are all compatible knuckle couplers, but are employed on specific rail car types (general freight, tank cars, rotary hoppers, passenger, etc.).

Early knuckle couplers using a variety of proprietary head designs, but all using the most up to date MCB contour when cast, were the MCB, Janney (later version), Tower, Sharon, Climax, Gould, Burns, Miller, and as many as 100 others.

Prior to the formation of the AAR (Association of American Railroads) these were known as MCB Couplers (Master Car Builders Association). After 1910 the MCB reconstituted itself into the AAR.

In 1913 the American Steel Foundries (ASF) had developed the new Type "D" coupler that was accepted as the standard coupler for the United States, and no new equipment could be built using any other coupler. This standard design ended the market for couplers with a proprietary head design, which were common in the MCB days, to all but those exported from the US to other countries not governed by the AAR standards.

The Alliance coupler, named after the ASF-owned foundry in Alliance, Ohio, was developed as a lighter build than the AAR Type "D" coupler, and was marketed by the Amsted Corporation, the parent corporation of ASF, as the "Standard Coupler for the World". It was and is still the most used knuckle coupler in the world. The modern Alliance coupler still uses the modern AAR-10 and/or -10A contour, as well as others, but cannot be used in the US on an "interchanging" railway.

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Wikipedia