GB652807A - Improvements in or relating to apparatus for providing fluorescent lighting in vehicles - Google Patents

Abstract

652,807. Supply systems for space discharge lamps. DAVIS, B. A., and WRIGHT, W. J. July 29, 1948, No. 20271. [Class 38 (iv)] A system for supplying a plurality of discharge tubes from a low-voltage source particularly for the internal illumination of vehicles includes means for supplying current from the source to the tube heaters, means for creating a voltage surge to strike the tubes and means for opening the heating circuit to each tube in sequence, thereby starting each lamp in sequence. In the arrangement shown, the low voltage supply which may comprise the vehicle battery feeds a rotary transformer RT, the output current of which, to preheat the tubes electrodes, is taken via a polarity change-over switch RS (combined with the input " On/Off " switch), a choke Ch to provide the usual voltage surge, through the filamentary electrodes of the lamps T1, T2, T3, series-connected by contacts 10, 11, 12 of relays R1, R2, R3, and ballast resistances 13, 14. The coils of relays R2 and R3 and the heaters of thermal switches Thl, Th2 and Th3 are energized from the source over contacts of the relays. Switch Th2 closes to short-circuit part of the resistive ballast, and with a timedelay switch Th1 closes to energize relay R1, whereupon contact 10 opens to interrupt the heating current and cause the choke to strike tube T1; contact 10c maintains the relay energized and contact 10a opens to de-energize relay R2 whereupon contact 11 opens to again interrupt the heating current, now passing through the discharge space of tube T1, and start tube T2 ; contacts 11a, 11b interrupt the heating current to switch Th1 and contact 11c de-energizes relay R3, whereupon contact 12 opens to start tube T3; contact 12c interrupts heating current to switch Th2 and thereby remove the short-circuit from portion 13 of the ballast resistance and contacts 12a, 12b interrupt heating current to switch Th3 provided for overload protection whereby the switch Th3 operates to blow fuse X and interrupt the coil circuit of relay R. The ballast resistance may be included in the low-voltage circuit (Fig. 2, not shown), and the relay contacts may be manually operated. In another arrangement (Fig. 3, not shown), the relay coils provide the voltage surges which are introduced into the heating circuit, through resistances by a thermal switch. Two relays are shown controlling three tubes, the second relay being provided with delayed opening contacts for the third tube.