I believe I have more on the topic buried somewhere. Randy Hees of the Nevada RR Museum in Boulder City knows a lot, IIRC. Also they must have info at the Carson City Nev RR Museum, too. I can't find anything in my Carbuilder's Dictionaries as I believe they predate Sams adoption by railroads, and I found nothing on a quick scan of Jack White's freight book--though I may have missed it.
The basic premise is a heavy link that sits in the drawhead and drops "automatically" (quotes intentional) when a drawbar enters.
Here are two images to start you out, found searching google books, the first an opinion piece from Ry Conductor of 1894 and the other an ad from Ry & Loco Engineering of 1896:
Dave Eggleston
Seattle, WA