Today in 1988, US Patent 4728010 A was issued, an invention of Mack S. Johnston, for his “Keg Tapper.” Here’s the Abstract:

A keg tapper for use with a keg having a neck with a closure valve carried therein and a flange with a tapered edge on the neck. An arrangement for attaching the tapper at the flanged neck so that completion of the attachment opens the inner valve of the keg closure. A plunger carried in the keg tapper with an arrangement for moving the plunger axially within the tapper body to engage the keg closure and open the outer valve. A keg tapper which can be utilized in the tavern configuration and in the picnic configuration.