VERTICAL TYPE CONTINUOUS HEAT TREATMENT FURNACE

PURPOSE:To stably control the material tension in a furnace to low tension with the need for just a low level of the speed control for an intermediate let-off machine without requiring a tension detector of high accuracy by providing a free loop of the material to the inlet side of the furnace body and executing the in-furnace tension control of a weight balance type. CONSTITUTION:The free loop 12 of the material 1 is provided between the intermediate let-off machine 4 and the furnace body 5. The loop 12 lets off the material 1 successively from the let-off machine 4 in such a manner that the position on the bottom surface of the loop 12 is held constant in order to balance the weight with the material 1 in the furnace with guide rolls 6 as a fulcrum. A simple sensor such as photosensor is simply required to detect the position of the bottom surface of the loop 12. A motor 10 of the let-off machine 4 is controlled to be accelerated and decelerated by receiving the signal of the sensor. The material 1 is passed at a specified speed in this state by speed reference rolls 8 in the furnace body 5, by which the material is heat- treated. The material is then coiled by a coiler 9.