GB592140A - Improvements in control apparatus for electric luminous discharge tubes - Google Patents

Abstract

592,140. Control systems for discharge lamps. HEAYBERD, F. C., KRIMHOLTZ, J., and HEAYBERD & CO., Ltd., F. C. May 22, 1945, No. 12735. [Classes 38 (ii) and 38 (iv)] Fluorescent and other discharge tubes having filamentary electrodes are started by a switch in the preheating circuit which comprises a bimetal element permanently short circuiting a low-resistance auxiliary winding on the ironcored, air-gapped, current-limiting choke coil. Figs. 1 and 2 show a single-turn winding 5 embedded in a side cheek of an insulating former of thermo-setting plastic material, which former carries the choke winding. The ends of the winding 5 are permanently connected to the ends of a bifurcated bimetal element 6 carrying a contact co-operating with a contact member 8 to constitute a normally closed switch interconnecting the filamentary electrodes. To assist in maintaining this switch open whilst the discharge tube is running the bimetallic element may'be arranged in the vicinity of the gap in the choke core so as to be heated additionally by eddy currents. As shown, the bimetallic element is supported by being moulded at 3c into. the side cheek, which is extended to carry terminals providing convenient connections for the supply circuit and circuit elements, including voltage-accommodating tappings of the choke. The contact elements of the switch may be removable and adjustable so that the preheating time of each of a set of lamps may be made different from the rest to cause ignition in sequence.