| 摘要 |
PURPOSE:To eliminate the occurrence of discharge spot and to prevent the disconnection of filament, by encapsulating a light emission tube, starting heat-responsive element and a heating filament contained in a container into an outer tube together with gas. CONSTITUTION:A light emission tube 10, bimetal switch 4 and a heating filament 5 are contained in an outer tube 7 for high pressure sodium lamp, while gas having pressure lower than 100 Torr is encapsulated for the purpose to suppress the surge voltage due to the operation of the bimetal switch 4. The filament 5 is enclosed by a container 27 made of glass while having the thermal conductivity then faced against the bimetal switch 4. Consequently the surge voltage produced instantaneously with the opening of the bimetal switch 4 is prevented from discharging not between the contacts 22, 23 but between the filament 5 and the contact 23 thereby the disconnection of the filament 5 can be effectively prevented. |
