I've seen almost identical machines in the late 1970's at the Firestone plant in Los Angeles. They mix the rubber compounds after they come out of the "Banburys" that do the initial mixing. The drums contain cold water run through them. After the worker peels up the rubber from the drum, he will put the batch in the top, where it will be squashed & blended. The friction & compression would heat the rubber up to smoking hot. There have been several guys pulled into the machine over the years. The overhead bars are for an emergency stop to shut off the machine.