Today in 1873, US Patent 141944 A was issued, an invention of John W. Moose, for his “Improvement in Apparatus For Preserving Beer on Draft.” There’s no Abstract, although in the description it includes these claims:

This invention relates to means for introducing air into casks to take the place of the liquid drawn out; and it consists in the combination, with a flexible bag or air holder, of a valve and bellows mechanism of a novel construction, as will be hereinafter more fully described. It further consists in the employment of a perforated tube for withdrawing the air from the flexible bag.