Patent GB-640948-A (GB)
Title: Improvements in or relating to glow discharge thermal switches and circuits incorporating such switches
Inventor: BALAAM NORMAN BENJAMIN
IPC: H05B41/08
Filed: 1947-09-23
Abstract: 640,948. Control systems for space discharge lamps. CROMPTON PARKINSON, Ltd. Sept. 23; 1947, No. 25845. [Class 38 (iv)] [Also in Group XXXVII] A glow discharge switch 1 for starting two discharge lamps 6, 7 connected either in series or parallel and energized by A.C. or D.C., comprises bimetallic electrodes 2, 4 co-operating respectively with fixed electrodes 3, 5. In a parallel arrangement for an A.C. supply (Fig. 1, not shown), the pairs of electrodes 2, 3 and 4, 5 are connected across the lamps 6, 7 which are connected to the supply respectively through an inductance and an inductance and capacitance in series, whereby the lamps are started in the usual manner. In a similar arrangement utilizing D.C. each lamp is connected to the supply through a resistance 8. If the bimetal electrodes 2, 4 are connected to the - ve pole as in Fig. 2, they will be heated directly by the glow discharge and quickly close their circuits to start the lamps, whereas by connecting them to the +ve pole (Fig. 3, not shown) they will be indirectly heated and take longer to respond. Alternatively, one bimetal electrode may be connected to the - ve pole and the other to the +ve pole so that one lamp starts before the other (Fig. 4, not shown). In a series arrangement, Fig. 5, the bimetal electrodes 2, 4 are connected to an A.C. supply and heated directly by the glow discharge, or alternatively they may be indirectly heated by connecting instead the fixed electrodes 3, 5 to the supply (Fig. 6, not shown). The electrodes are so shaped and disposed that one bimetal electrode makes contact before, and preferably breaks contact after, the other bimetal electrode. Fig. 7 shows a similar arrangement for a D.C. supply; the rigid electrode 5 connected to the - ve pole is enveloped by the glow discharge and heats, and is engaged by, its bimetal electrode 4 whereby the electrodes 2, 4 and 5 are enveloped by the discharge and the electrodes 2, 3 engage and a heating .current passes through the lamp filaments. Preferably, the electrodes are so arranged that on cooling the bimetal 2 which closed last, opensits contact first. In an identical circuit arrangement (Fig. 8, not shown), the electrode 5 is situated instead between the bimetals 2, 4 which are thereby both indirectly heated, bimetal 2 preferably being heated more strongly so as to close its circuit first. On cooling, the bimetals break contact in turn. In a further arrangement similar to Fig. 7, the bimetals 2, 4 are instead positioned outside the fixed electrodes 3, 5 and connected to the supply whereby the bimetal connected to the - ve pole is directly heated (Fig. 9, not shown). In Fig. 10, which shows an arrangement for starting a single D.C. lamp 15, the bimetal electrodes 16, 17 are permanently connected respectively to the rigid electrodes 19, 18. On closing the supply circuit the - ve bimetal 17 engages the electrode 19 and the lamp filaments 15<SP>1</SP>, 15<SP>2</SP> are heated, the bimetal then cools and starts the lamp in the usual way. With this arrangement the polarity of the switch is immaterial.