 He would later establish a separate company, Bert E. Mills Corporation, and, in 1946, help to develop the first vending machines to sell hot coffee.In 1907, Herbert S. Mills collaborated with Charles Fey, the inventor of the slot machine, to produce the Mills "Liberty Bell".In 1926, the company had moved to a plant of , comprising a factory and administrative building, at 4100 Fullerton Avenue in the northwest of Chicago.