Today in 1995, US Patent 0472298 B1 was issued, an invention of Yutaka Fujimoto, Takaaki Furuhashi, Katsuoki Kawanishi, and Ryo Sakazume, assigned to Sapporo Breweries Limited, for their “Keg For Draft Beer.” There’s no Abstract, although in the description it includes this summary:

A keg for a liquid to facilitate cooling of the liquid retained in the keg and to keep the temperature of the cooled liquid in the keg, comprising:
   a keg body for retaining the liquid therein and having an upper face (3), a lower face (5), a side face (4) and a mouth piece (2) for providing the liquid into the keg body and ejecting the liquid therefrom, said keg body being formed of a keg inner cylinder (1) for constituting a container for the liquid and a keg outer cylinder (6), said keg inner and outer cylinders being laminated together to form a space and air being removed from the space to form a vacuum adiabatic layer (VL) therebetween; characterized in that the keg outer cylinder (6) substantially covers the keg inner cylinder (1) except one of the upper and lower fades (3, 5) of the keg body, and in that a cooling face (Cz) is formed on said one of the upper and lower faces (3, 5) of the keg body where the inner cylinder (1) is not covered so that the liquid inside the inner cylinder (1) can be cooled through the cooling face and the temperature of the liquid inside the inner cylinder is kept by the adiabatic layer defined between the inner and outer cylinders.