GB647262A - Improvements in or relating to transportable electric lighting units - Google Patents

Abstract

647,262. Supply systems for space discharge lamps; converting. OLDHAM & SON, Ltd., and AKROYD, H. Aug. 27, 1947, No. 23767. [Classes 38 (ii) and 38 (iv)] [Also in Group XI] A fluorescent discharge lamp L1 is supplied from a low-voltage D.C. source such as an accumulator 8 (see also Group XI) through a vibratory make-and-break device 1-6 included in the primary circuit 11 of a step-up transformer 12, the secondary winding 13 of which gives a high open circuit voltage to strike the lamp, a normal operating voltage whilst the lamp is running and, if required, a reduced voltage for pre-heating the lamp electrodes 15, by providing the transformer with a high reactance or including resistance in the transformer. windings or circuit. Preferably the primary winding has a centre tapping connected to one pole of the battery and the two ends are connected alternately to the other pole of the battery by the vibrator. Alternatively when two lamps are provided the primary windings of the respective transformers may be energized alternately by the vibrator to avoid flicker. A voltage regulator, such as a barreter 10, is included in the primary circuit to reduce the effect of changes in the battery voltage and which is short-circuited by contacts 19 when a push switch 18 is operated to connect through its contacts 17 the electrode heaters 15 either to the transformer secondary 13 or direct to the battery during starting. The barreter may be included in the primary circuit of each transformer. The vibrator comprises a resilient contact-carrying reed 1 adapted to vibrate between and contact alternately fixed contacts 6 by arranging for the coil of the driving magnet 4 to be short-circuited when contact 5 makes with left-hand contact 6. Additional contacts 5a, 6a may be provided for additional lamps. Quench circuits 7 bridge the contact gaps. A condenser 20 is connected across the secondary winding 13 to improve the waveform.