| 摘要 |
PROBLEM TO BE SOLVED: To ensure that a starter becomes permanently inoperative in the event of the failure of a light emitting tube by connecting a discharge gap means in parallel with a starter which is connected in parallel with the tube and in series with a first, normally closed heat-reacting switch and a current fuse. SOLUTION: A series circuit of a starter 2 comprising a series circuit of a glow starter 2a and a heating resistor 2b, a first, normally closed heat-reacting switch 3, and a current fuse element 4 is connected in parallel with light emitting tube 1. If the tube 1 cannot be started to operate, the glow starter 2a is heated by application of voltage and is normally closed to stop pulse voltages. Further, at or above a heat-resisting temperature, a hole opens in a bulb, and the switch 3 is opened so that no pulse voltages are produced again. If a rare gas for starting the tube 1 leaks out of an outer tube 9 because of a decrease in airtightness of the sealed part of the tube 1, etc., a discharge occurs at startup between the electrodes 5a, 5b of a discharge gap 5 connected in parallel with the starter 2. Therefore, the fuse element 4 is melted by the short-circuit current of a ballast 10. |
