GB1203249A - Improvements in and relating to starter switches for electric discharge lamps - Google Patents

Abstract

1,203,249. Thermal switches. BERLINER GLUHLAMPEN-WERK VEB. 18 Oct., 1967, No. 47384/67. Heading H1N. A glow-type starter switch for electric discharge lamps, more particularly fluorescent lamps, comprises a bi-metal electrode so arranged that the glow discharge on the bimetal electrode takes place mainly on the bimetal component with the lower coefficient of expansion and the bi-metal component with the higher coefficient of expansion is mainly heated by conduction from the component with the lower coefficient of expansion rather than directly by the glow discharge. Thus the bimetal electrode has an increased amount of heat at the moment of closing as a result of which the duration of the closed contact condition is extended. One or both of the bi-metal components may be covered with materials such that the bi-metal component with the higher coefficient of expansion exhibits the higher cathode drop. This bi-metal component may be covered with a layer which is non- gassing, electrically insulating and heat resistant, such as Al 2 O 3 or SiO 2 , by electrophoresis, by metallizing or other process. Alternatively this bi-metal component may be screened in its at-rest position by a covering which does not follow the deflection of the bi-metal such as nickel or ceramics. The bi-metal electrode may be in the form of a hairpin. The legs of the hairpin may be prestressed at normal temperature if the bi-metal is to operate at a higher than normal ambient temperature. The bimetal electrode may be straight and two may be provided to work together, or it may be in beta form. The electrodes may be welded to their current supply members.