Today in 1879, US Patent 212898 A was issued, an invention of William F. Class, for his “Improvement in Apparatus for Supplying Beer-Barrels.” There’s no Abstract, although in the description it includes this summary:

The nature of my improvement consists of a semi-spherical chamber made of india-rubber or other suitable elastic material and connected at the base with a frame or stand having an outlet and an inlet valve-opening. within the chamber is a spiral spring extending from By means of said spring the chamber is expanded after being compressed. The said valve-opening admits the air, and the valve closes on compressing the chamber to force the air out through the induction opening into the barrel, keg, etc.