Today in 1975, US Patent 3913608 A was issued, an invention of Mack S. Johnston, for his “Keg Adapter Valve.” Here’s the Abstract:

A valve member containing controlled gas and liquid passageways for admitting gas into a keg and for dispensing liquid therefrom through a relatively small opening is mounted on the inside of the keg in alignment with said opening. A tapper connector member is mounted on the outside of the keg and is connected to and in operative relationship with the valve member.