Today in 1970, US Patent 3498313 A was issued, an invention of Daniel E. Belich, for his “Beer Keg Tap.” Here’s the Abstract:

This application discloses a tap in which the portion of the tap from the head to the bottom of the keg may remain in place during merchandising. The user needs only a small coaxial outlet unit attached to tap beer and gas pressure lines. The outlet unit is small and easily cleaned, and represents only a modest investment for the tavern keeper. The portion of the device which is retained in the barrel contains valving arrangements which prevent the escape of beer or gas pressure from a partially used keg when the outlet is withdrawn, and provide improved Valve arrangements which rely on elastic valve members for admission of air under pressure.