Improvements in or relating to protective arrangements for electric discharge tubes

摘要

554,515. Electric supply for discharge lamps. PHILIPS LAMPS, Ltd. (Naamlooze Vennootschap Philips' Gloeilampenfabrieken). Feb. 6, 1942, No. 1620. [Class 38 (iv)] To prevent repeated attempts at starting or restarting a discharge lamp (and thereby to avoid damage to the ballast chokes &c.) the lamp is disconnected altogether, when the heating of the choke or other accessory apparatus becomes excessive, by the action of a thermal switch which directs a current through the pre-heating circuit sufficient to blow a fuse therein or to disrupt a filament. In the form shown in Fig. 1, where the normal pre-heating circuit is through a starting thermal glow switch 9 unsuccessful starting of the lamp heats the choke 6 and finally closes the thermal switch 13 to short-circuit a portion of the choke and put an excessive current through the filament 3 and the fuse 10 enclosed therewith. The arrangement may also take account of the direct-current component taken by the lamp, when the filaments become dissimilar, for example, in Fig. 3 the thermal switch 40 acts on repeated mis-firing, whereas switch 41 acts with excessive direct-current component, each of the switches effecting a connection, as before, to blow the fuse 37.