Today in 1939, US Patent 2183505 A was issued, an invention of Gerald D. Peet, for his “Keg.” There’s no Abstract, although in the description it includes this summary:

My present invention is concerned with transportation beer kegs or barrels, and more especially with such kegs as are intended not only to serve as dispensing containers but also to cool and maintain the brew cool within the interior thereof by the circulation of cooling fluid therethrough.