| 摘要 |
PURPOSE:To reduce the starting voltage of a metal vapor electric-discharge lamp while maintaining the heat insulating effect of the end of the emission tube during the lighting of the lamp by positioning heat-shielding bodies, which are movable due to the deformation of a heat-responsive member, in such a manner that they are apart from the outer surface of the end of the emission tube during the non-lighting and that they come close to said outer surface during the lighting. CONSTITUTION:At the starting of a metal vapor electric-discharge lamp, in a starting unit 21, a bimetal switch is opened due to the heat of a tungsten filament, a kick voltage is added to the secondary voltage of a ballast so as to produce a high-voltage pulse, and thus produced high-voltage pulse is applied to electrodes 15a and 15b. Here, since the high-voltage pulse is applied to a near-by conductor 18 as well, a large electric-potential gradient is generated between the near-by conductor 18 and the base-side electrode 15b, and the starting of the lamp is facilitated. Heat-shielding bodies 17a and 17b, differently from the conventional ones, are positioned apart from the outer surface of the end 22 of an emission tube. Since they are not located near the electrode part as mentioned above, the intensity of an electric field produced between the electrode 15b and the near-by conductor 18 is not reduced by the heat-shielding body 17a or 17b. As a result, a sufficiently low starting voltage can be realized. |
