Today in 1973, US Patent 3758008 A was issued, an invention of Mack S. Johnston, for his “Tapping Assembly for Beer Kegs and the Like.” Here’s the Abstract:

A keg adapter for beer kegs and the like with gas and liquid passageways containing normally closed valves, which when opened permit compressed gas to be admitted to the keg and beer to be withdrawn therefrom, said valves being biased toward the closed position by actuators which contain permanent magnets. A tapper is connected to a source of compressed gas and to a beer faucet and contains a tap rod, which, when manually actuated, seals the tapper to the adapter and interconnects the gas source and the faucet with the interior of the keg.