| 摘要 |
PURPOSE:To surely prevent burning of a ballast by connecting in parallel a safety device comprising a series circuit of a usually-open type thermal action switch and a heating filament to a luminescent tube. CONSTITUTION:A safety device comprising a series circuit of a usually-open type thermal action switch 20 and a heating filament 21 is connected in parallel to a luminescent tube 3 which is accommodated in an outer tube 1 whose inside is evacuated, and the filament 21 is brought into contact with a stem 15 of the outer tube or closely arranged near the stem 15. If the luminescent tube leaked during lighting, the same voltage as lamp voltage is applied to the switch 20 and glow discharge is taken place and the switch is closed. Current flows to the filament to heat it and a hole is produced on the wall of the outer tube or the stem by this heat, and a large amount of air is introduced inside the outer tube. Thereby, the luminescent tube is turned off and burning of a ballast is prevented. |
