Figure 5.10. Willison Coupler.
When a railroad car must be moved from one place to another, it must be coupled with other cars in a
train, the coupling must be maintained until the car reaches its destination, and then the coupler must be
unlocked to disconnect the car from the other cars. Since 1933, freight cars in the United States have been
equipped with the E coupler that performs these three functions. It automatically couples and locks, but it must
be uncoupled manually. For a safe, efficient operation the coupler height must be properly set and the knuckle
play must not be excessive.
Couplers on most foreign equipment are either the hook-and-link or the Willison. Requiring manual
coupling and uncoupling, the hook-and-link has a link that is placed over a hook on another car's coupler; a
lever then tightens the connection until all slack is taken up. Buffers on either side of the coupler absorb jolts
and shocks and prevent cars from running together. The Willison coupler is like the E coupler in that it couples
automatically but it, too, is used with buffers on the ends of the car. It has a transition device--a hook-and-link--
that makes it possible to connect the car it is installed on with a car equipped with-the hook-and-link coupler.