Today in 1969, US Patent 3422448 A was issued, an invention of Mack S. Johnston, for his “Tapping Device for Beer Kegs and the Like.” There’s no Abstract, but here’s his introduction in the description:

The present invention relates to a new improved tapping device for drawing fluid such as beer from containers such as beer kegs or barrels, using a gas to drive the fluid from the container. In particular, the invention relates to a new improved tapping device usable with conventional beer kegs and comprising a sub-unit, called a keg adapter, which constantly seals the keg, and a subunit, called a coupler, which is attached to the beer dispensing apparatus in a restaurant or tavern and is readily connected to the keg adapter so that the tapping device is automatically in operating condition.