Today in 1870, US Patent 103498 A was issued, an invention of Charles Pohlmanx, for his “Improved Apparatus For Preserving Beer.” There’s no Abstract, though it’s described this way in the application:

The nature of my invention consists in an elastic bag, formed in a shape to accommodate itself to the inside of a barrel, to which it is applied, in such a manner that, when the bag is filled with air, and supplied with air under pressure, the bag will gradually expand, and exert a pressure upon the liquid in the cask in which it is placed.