Improvements relating to glow discharge thermal switches and operating circuits for electric discharge lamps employing same

摘要

663,608. Thermal switches. BRITISH THOMSON-HOUSTON CO. Ltd., WALKER, C. H., and LARGE, F. E. April 8, 1949. [April 8, 1948] No. 9383/50. Divided out of 663,530. Class 38 (v). [Also in Group XXXV] A glow discharge switch for starting and operating a discharge lamp comprises a fixed contact 4 normally engaging a contact 7 on one end of a U-shaped bimetal strip 1. The latter is arranged to be heated, so as to open contacts 4, 7 and strike the lamp, by the discharge between the strip and an auxiliary electrode 3, connected to the supply side of the ballast impedance (not shown), as in Specification 663,530. The contacts 4, 7 are then maintained open by the discharge until the supply is switched off. In order to ensure that the lamp is rapidly relit in the event of momentary interruptions in the supply, as in connection with traction systems, a second auxiliary electrode 17 is connected to contact 4, so that should the lamp discharge cease and the supply is reconnected, the full operating voltage causes a discharge between electrode 17 and strip 1. This deflects strip 1 even more so that electrodes 3, 17 are engaged by contacts 7, 18 on the strip. The lamp heating circuit is thus made over contacts 7, 17 and the glow discharge short-circuited by contacts 3, 18. The strip 1 recools and when contacts 7, 17 open the lamp restrikes, the strip being kept deflected by the glow discharge between it and the electrode 3 as before.