Today in 1969, US Patent 3436319 A was issued, an invention of Louis Anton Freiherr Von Horst and Maximilian Kellner, for their “Thin Layer Steam Distillation of Hop Oil Extract.” There’s no Abstract, but it’s described as relating “to a process of producing essential oil of hop preparations, and more particularly to a continuous process of producing such oil of hop, and to products obtained thereby,” with something approximating an abstract:

Improved process of recovering oil of hop from a solvent extract of hops by steam distillation in a novel manner, namely by passing the hop extract downwardly in a thin layer along an externally heated surface counter currently to the upwardly flowing steam in an oxygen-free atmosphere. This process has the advantage of completely recovering the oil of hop from the steam distillate and simultaneously producing a residual hop extract containing other components of said extract in substantially unaltered form. If the temperature of the starting solvent extract of hops is between about 80 C. and about 135 C., partial isomerization of the humulones to the isohumulones which are important brewing additives, takes place.