Today in 1971, US Patent 3608790 A was issued, an invention of Mack S. Johnston, for his “Tapping Device For Beer Kegs and the Like.” There’s no Abstract, although in the description it includes this summary:

The present invention relates to a new improved tapping device for drawing fluids such as beer from containers such as beer kegs or barrels using a gas to drive the fluid from the container. Particularly, the present invention relates to a new improved tapping device usable with conventional beer kegs of the type having a 1% inch tapping opening and comprising a novel keg adapter for sealing and the keg opening, a unique coupler reliably attachable to the adapter at the dispensing establishment for dispensing beer, a new siphon tube configuration for the keg adapter whereby the keg may be substantially completely drained of beer notwithstanding its employment in high-pressure systems, and a novel beer shutoff valve for the coupler whereby flow of beer from the keg to the faucet can be shutoff at the keg.