| 摘要 |
PURPOSE:To make it possible to stably show a disired temperature control effect while simplifying the construction and surely preventing excessive temperature rise by controlling power supply to a heating member through a switching element changing according to a quantity of heat. CONSTITUTION:While a vacuum evaporation heater 4 is not conducted, the tip 7a of a bimetall 7 is contacted with the surface of the heater 4 electrically conductively. And when a switch 6 is closed to supply power, the heater 4 is conducted through the bimetal 7 for heating a fluorescent lamp 1. When the temperature of the heater exceeds a prescribed value, the bimetal 7 is transformed for separating its tip projection 7a from the surface of the heater 4 while the conduction to the heater 4 is stopped. Thereby, the bimetal 7 is cooled for conducting again the heater 4. By repeating said operation the temperature of the heater 4 and the internal temperature of a fluorescent lamp 1 are maintained within a proper range for obtaining a stable optical output while preventing an accident due to excessive rise of temperature of the heater 4. |
