Today in 1966, US Patent 3244326 A was issued, an invention of Glen C. Bull Jr., for his “Apparatus For Dispensing Fluid Material.” There’s no Abstract, although in the description it includes this summary:

The present invention comprises, in brief, maintaining a substantially constant desired pressure on a body of beer within a spigotted container of draught beer by incrementally admitting gas under pressure from a reservoir into an expansible bag within the container, to preserve the effervescence of the beer and to discharge desired quantities of beer when the spigot is opened.

The primary object of this invention is, therefore, to effectively, economically, and safely store, transport, and incrementally dispense beer at a nearly constant pressure from a packaged unit.

Another object of this invention is to provide for the u safe, convenient, and economical handling, storing,l preserving, transporting, and/or dispensing of any liquid which requires a continuous surface pressure, or freedom from contamination by air or other similar infuences, or a covering membrane which will effectively follow the liquid surface as the liquid is dispensed, or any combination of these requirements, at a pressure which remains nearly constant as the liquid is dispensed.