Today in 1946, US Patent 2393518 A was issued, an invention of Stephen T. Clarke, for his “Fermentation Of Beer.” There’s no Abstract, but the description explains that the “object of the invention is to provide’a process and apparatus of the top fermentation type which will produce a very full drinking beer of high stability and character.” It continues:

The whole process of fermentation is carried out under pressure in a single enclosed vessel having at the top thereof a detachable cone or dome provided with an outlet pipe of small diameter terminating in a device such as a nipple for controlling the pressure. The outlet of the pipe is at or near the top of an enclosed yeast-back provided with a cock or valve which normally is open to the atmosphere to relieve pressure in the yeast-back. The yeast-back is also provided with a draining tube for returning the yeast drainings to the fermenting vessel.