Today in 1959, US Patent 2877790 A was issued, an invention of Emil Clemens Horst, for his “Self-Closing Valve for Tap Bushings of Kegs.” There’s no Abstract, although in the description it includes this summary:

The present invention relates to self-closing valves, and more particularly to valves used with tap bushings of beverage kegs for sealing off the interior of the kegs except during such time that said kegs are on tap for dispensing the contents therefrom.