Today in 1988, US Patent EP 0142966 B1 was issued, an invention of Roger John Hyde, for his “Valved Closure for Kegs or Casks.” There’s no Abstract, although in the description it includes this summary:

This invention relates to valved closures for pressure vessels, such as kegs or casks for beverages dispensed through the valved closure by pressure gas admitted to the keg or cask through the closure.