PURPOSE: To heat a pressure belt while exerting a high heat quantity for the downward pressure area by mixing steam in a gaseous pressure medium, e.g. air, before the pressure chamber and exerting the pressure on the back of the pressure belt in the area of the pressure chamber by using the steam-air mixture.

CONSTITUTION: The air is mixed with steam generated by an evaporator 10 before a pressure chamber 5. Then, the steam-air mixture is sent into the pressure chamber 5, and exerted on the back of a steal-made pressure belt 2 that moves in the direction of the arrow 3 for heating. In other words, a part of the steam in the steam-air mixture precipitates on the belt 2 as condensed droplets, releasing heat of condensation as an intensive heat quantity not only to the belt 2 but also to the workpiece 4 to be machined by the belt 2. Incidentally, the steam-air mixture is designed to enter the chamber 5 through a path extending in the vertical direction, pass through the path 12 and flow out of the chamber 5. In Figure, 1 is a press, 6 a pressure plate, 9 a transporting device, and 7 a sealing strip.