Today in 1899, US Patent 639761 A was issued, an invention of Frederick Orth and Frederick Schimper, for their “Underback.” There’s no Abstract, although in the description it includes these claims:

This invention relates to an improved construction of the underback, a vessel into which the unfermented beer flows from the hop-back to be conveyed by the pump to the surface cooler. Heretofore this underback was made in the form of a small open vessel which required constant watching and attendance to prevent an overflow and to regulate the ratio between inflow and outflow. If in spite of precautions an overflow would take place, the employees would be apt to become scalded, and the shutting of the cooks would be accompanied with considerable difficulty. By our construction all the above objections are overcome, and after the cooks have been opened and the pump started the beer will be delivered without liability of running over and without requiring any attention whatever.