PURPOSE: To improve control mode selectivity by allowing a display window on a control panel to indicate the light projected from a projector while allowing the projector to follow the main driving plate of the side link mechanism of a heater unit turning along a plurality of stages.

CONSTITUTION: When a switch knob 31 is set in the automatic position, the projecting part 25 of a projector L is in a bent mode V if a main driving plate 9 is in the same mode V, light passes through a light guide G, and the bent mode is indicated on a display window 30 on a control panel P. When the main driving plate 9 set in a bi-level mode B by a controller, the projector L travels to the same mode B via a cable C, light from the projecting part 25 is projected from the display part 30 of the control panel P through the light guide G, allowing the device in a bi-level mode to be indicated. In such a way, any mode is indicated while the projector L follows the motion of the main driving plate 9, so that said mode is automatically indicated, allowing mode selection to be facilitated.