A touching plate of the emergency mechanism, which is located near the front panel of a casing, is rotatably pivoted, an arm is protruded from the touching plate so that it is opposite to a lever protruded from the end of a slide bar, a nozzle having a prescribed length, which is located near the thin rod contact face of the touching plate, is protruded concentrically to a through-hole integrally from the inner face of the front panel, the thin rod passed through the through-hole is guided by the nozzle so that the tip of the thin rod is brought into contact with the thin rod contact face of the touching plate. In this way, by pushing in the touching plate about the pivoting shaft, the slide bar is slid through the arm and lever, thereby slightly moving the tray forward.