Wikipedia
Ringfeder
Ringfeder is the trading name of a German company based in Krefeld. The company manufactures automatic bolt coupling devices. While they are not the sole manufacturer of these devices, their name (pronounced ring-feader) has become the universal term. Ringfeder are part of the large Swedish company, VBG, also a manufacturer of automatic coupling devices. Another manufacturer is , a part of the large German company, Jost.