Today in 1975, US Patent 3905522 A was issued, an invention of Mack S. Johnston, assigned to Draft Systems, for his “Keg Tapping Device.” Here’s the Abstract:

In one form hereof, there is disclosed a keg adapter having a siphon body formed of bar stock receivable through the opening of a keg from without the keg. The siphon body has liquid and gas passages extending longitudinally of the keg adapter terminating at their upper ends in a pair of bores disposed eccentrically of the central axis of the keg adapter. In another form, there is disclosed a keg adapter having a siphon body formed primarily of tubular stock with tubular members receivable through the opening of a keg from without the keg. The tubular members per se comprise liquid and gas passages terminating at their upper ends in a pair of openings disposed eccentrically of the central axis of the keg adapter and opening through a flange member formed of bar stock. A coupler unit, having a pair of depending probes, is engageable with either form of the keg adapter with the probes being receivable in the bore holes or tubes as applicable to form a continuation of the liquid and gas passages. A sleeve is provided in the liquid passage of both adapters for opening a normally closed liquid valve therein. A gas valve is axially spaced from the liquid valve and in both forms includes a gas check valve comprising a flexible envelope having a slit and which envelope lies in communication with the gas passage. In the one form, the gas valve also includes a spring-biased valve plate mounting an O-ring sealing about the walls of the gas passage. The tips of the probes on the coupler unit in the one form depress the associated valve members to open the valves and permit ingress of gas through the coupler unit and keg adapter into the keg and egress of liquid from the keg through the keg adapter and coupler unit. In the other form, the tip of the liquid probe on the coupler depresses the sleeve to open the liquid valve whereby air flows through the coupler into the keg past the check valve of the adapter and beer flows outwardly from the keg through the adapter and coupler.