US2479173A - Circuit and starter for electric discharge devices - Google Patents

Description

Aug. 16, 1949. LEMMERS CIRCUIT AND STARTER FOR- ELECTRIC DISCHARGE DEVICES Filed July 26, 1944 I nvem'lor z Eugene Lemmer's,

llghting up all the Patented Aug. 16 1949 crncun:

AND STARTER Foa. sLEc'rum DISCHARGE DEVICES Eugene Lemmers, Cleveland Heights, Ohio, as.

signer to General ration at Ncw'flork Electric Company, a some Application July 26, lsieflsenai No. 5:46.621

This invention relates "to'the starting control of electric discharge devices, andis very useful for fluorescent tubes of positive column discharge type, as well as for varlous other discharge devices. The invention is especially adaptable for starting discharge devices quickly, without the delay usually entailed by preheating their cathodes. It lends itself with peculiar advantage to the conversion of hot-starting" or cathode-preheating systems to virtually instantaneous cold starting, without cathode preheat.

As is well known, the voltage required to start a discharge through gas or vapor is considerably higher than that required to maintain it after it has started. Even this operating voltage is often different from ordinary lighting supply circuit voltages. Accordingly, atransi-ormer'is generally interposed between the supply circuit and the discharge circuits oi. an installation, to give the required voltage; In any case, current limiting chokes or ballasts (usually having inductance) are commonly included in the discharge circuits.

Most fluorescent lamps of positive column low pressure discharge type are at present hot-starting', with flow of heating current through their cathodes to preheat them before discharge'ls initiated. For this purpose, a starting circuit with an automatic switch therein is connected across thedischarge circuit, in parallel with the dis charge gap of the lamp and through heating means embodied in the cathodes. The automatic switch passes current through the cathode-heating means long enough to bring the cathode(s) of a lamp up to an adequate emissive temperature, the starting circuit, givand then suddenly opens ing rise to a high voltage kick between the electrodes (due to the inductance in the discharge circuit, and much higher than the operating voltage of that circuit) which generally 's'ufllces to initiate the discharge.

The time requiredto preheat the cathodes to the operating temperature of adequate thermionic emission is appreciable, so that at best an undesirable brief intervalelapses between the closing of the wall switch or other manual switch controlling afi installation and the actual lighting up of'the lamps. Moreover, the action of startersin common use is olten irregular, so that the lapse of time between closing the control switch and lamps may often amount to a quarter of a minute, more or less. These drawbacks have heretofore been unavoidable in practice, because starting oi lamps co'ldf' without cathode preheat, resulted in rapid distintegration of the cathodes and blackening'of the lamps.

1 Glaim. (Cl- 315- 439) 2 Recently, cathodes-havebeen evolved which stand cold starting so 'much better that it would 7 seem feasible to do away with hot starting and with starting switches, so that fluorescent lamps would light instantly (or practically so) when the controllingswitch is closed, just like incandescent lamps. For this purpose, a leakage-reactancc transformer interposed between the-lighting supply circuit and the dischargecircults may be provided, to give high open-circuit voltage for initiating discharge, followed by suitably lower voltage for ordinary operation.

While this arrangement is generally successful and satisfactory, it has the disadvantage or requiring larger and more expensive transformers than those now inuse tor hot-starting installations. Moreover, it makes the advantages of quick cold-startingunavailable to present users of fluorescent lampswithout expensive alterations of their installations, requiring new auiiiliarlcs which under existing circumstances may not be available for sometime to come. v

To meet the problems thus presented'l have devised starting systems or arrangements which afford quick or virtually instantaneous starting combinedwith the advantage of utilizing present inexpensive types of equipment and systems of wiring unaltered, whether for'new installations or in existing installations. This I accomplish with novelswitch arrangements actuatedon the plezo electric principle, and virtually instantaneous in their action, or practically so. Such a switch can be adapted to most or all of the known starting systems; and in the case of existing hotstarting installations, it can be substituted for present delayed action starters with no more trouble than is involved in replacing the present starters when worn out. While piezoeelectri'c operation is especially suited for operation of discharge dcvices on A. Q, it-can also be adapted to devices operated onD'. Cfby including in series with it a buzzer orother means for producing suitably rapid intermittent current and voltage impulses.

Various other features and advantages of the invention will appear from the description of species and forms oiembodlment, and iromfthe drawings.

In the drawings, Figs. 1, 2f ,3, and s are dia rams pressure positive column fluorescent lamp exem- 3 plified in U. S. Patents Nos. 2,294,203 to Peters, 2,330,161 to Townsend, and 2,306,925 to Aicher, heretofore ordinarily started hot after a period of cathode preheat. As shown in Fig. 1, the tubular radiation-transmitting envelope of the device I has spaced-apart activated thermionic cathodes 2, 2 in its ends. These electrodes 2, 2 may be of the usual coiled or coiled-coil tungsten filament type, coated or charged with activating oxides such as a mixture including barium and strontium oxides. The envelope may contain a low-pressure,

. or flexes in opposite directions alternately.

atmosphere of starting gas, such as argon ata pressure of 2 to 4 mm. of mercury, or other inert Amode of operation of the system shown in Fig. 1 is that when the switch I is closed to turn rare gas(es) at a corresponding pressure, and

also a vaporizable and ionizable working substance or metal such as mercury, of which a surplus supply (exceeding what will vaporize during operation of the device) is indicated by a mercury droplet 3: inside the envelope. An internal coating of fluorescent material or phosphor 4 on the envelope walls isalso indicated.

The discharge device is shown connected across a discharge circuit 5 including the inductive (ballastfi, which also serves as a starting inductance, and the make-and-break wall or other manual switch 'l. For energizing it, the discharge circuit 5 is shown connected across the secondary of an autotransformer 8 whose primary connection is across a voltage source such as an ordinary 60 cycle A. C. lighting circuit of some 110 to 120 volts, for example. To illustrate usual conditions of operation, two similar discharge devices I, l are shown connected across the transformer secondary in parallel lead and lag circuits 5, 5, one of which includes a condenser 9. The transformer 8 is of course chosen to give or assure the desired voltage across each of the discharge circuits 5, 5, which for an ordinary 40 watt fluorescent lamp may be of the order of 220 volts R. M. S. on open circuit, more or less. Once the discharge has started, the voltage across each device I is regulated or reduced by its ballast 6 to a favorable value for the operation of the device I, which may be the closed circuit voltage on which the device would be operated in present hot-starting practice.

For the purposes of my invention, a starting circuit I is shown connected across the discharge circuit (or across each of the circuits 5, 5) through or at the cathodes 2, 2 of the corre sponding discharge device I, as is usual in present hot-starting practice; and in this starting circuit is interposed an interrupting switch II that is piezo-electrically operated or actuated, by means of any suitable crystal member I2, such .as piezo-electric Rochelle salt, for example. As

shown, the crystal member I2 is connected in the starting circuit Ill (and thus across the di"- charge circuit 5) very much like a condenser, in shunt with the switch II. lamp I in the lag circuit 5, a condenser I3, suitably of about 1 mfd. capacity for a iii-watt lamp I, may be connected in circuit II) in series with the switch II. The crystal member I2 may consist of one single crystal with metallic foil affixed and electrically connected to its opposite faces and to the lead wires of the starting circuit III; or it may consist of two superposed crystals with foil cemented between their adjacent faces and other foils ailixed to their opposite, remote faces, one lead wire being then connected to the intermediate foil, and the other to both the outer foils. A rectangular crystal member I2 may be sunported at one end and may carry a motion-multiplyihg arm I4 attached to its other end, with In the case of the.

:heavier current on the lamps I, I, A. C. voltage is applied in each first voltage impulse inthe proper direction, the

crystal member I'2 flexes or twists to the right in Fig. 1, the switch II automatically closes, and a flows in the circuit I0 via the switch II. On the ensuing reverse voltage impulse, the crystal member I2 flexes or twists to the left in Fig. 1, and thus allows or compels the switch II to open. This action may be repeated during several A. C. voltage cycles in the discharge circuit 5, until on one of the opening movements of switch contact IS the resulting voltage kick between the electrodes 2, 2 is in such phase relation to the discharge circuit voltage between these electrodes and of such magnitude that the discharge starts. The action is so rapid, however, that to the eye, and for practical purposes, the lamp I' startsinstantaneously when the switch 1 is closed. Once started, the discharge shorts the starting circuit In, including both the switch II and the crystal I2, so that further operation of the switch II during the running of the lamp I does not occur, or has no material efiect.

The eifect of the capacitor I3 in the circuit III of the lag-circuit lamp I is to improve the starting action, making it possible to start on lower voltages in the lag discharge circuit 5, and with fewer operations of the switch II for each start. For example, with a condenser I3 of .1 mfd.

capacity, a 10-watt fluorescent lamp will start of the switch II the voltage in circuits 5, ID has reversed, the condenser'potential then adds to the supply potential in the circuits '5, I5 as the energy stored in the condenser is dumped through the lamp I. Studies of the starting action show that if a condenser I3 of 1 mfd.

capacity is charged to about 900 to 1000 volts D. C., a discharge in lamp I starts on .a single make by switch II; while if this same condenser I3 is charged to only about volts D. 0., some six successive make and. break cycles by switch -I I (each with. the condenser so charged) must occur before the discharge starts.

The capacity of the condenser I3 is not very critical: e. g., a 40-watt fluorescent lamp starts as well with a 3 or 4 mfd. condenser as with a 1 mfd. condenser, or somewhat better; and, on the other hand, a condenser of less than 1 mfd. is also more or less helpful. A condenser of such small capacity as mfd. requires some 20 makes-andbreaks for a start if charged each time to about 170 volts.

The system shown in Fig. 2 differs from that in Fig. 1 in that the movable contact I6 of switch II is carried by the crystal I2 or its motionmultiplying arm I4, instead of being resiliently flexed by the arm, and in having a glow-discharge device or glow-lamp I! connected in series with the crystal member I2 across the switch II. Before the discharge in lamp I starts, the full open-circuit voltage in the lag circuit 5 is applied across the glow device I! and suifices to break it down and maintain a discharge through it, so that A. C. voltage is applied to crystal member I2, and switch II operates as above described. While lamp I is in operation, however, the voltage across circuit In is so reduced that glow device II ceases to pass current and drops out, thus opening circuit I so that A. C. voltage is no'longer applied to crystal member I2, current flow through it ceases, and switch I I does not operate.

Figs. 3 and 4 illustrate the application of the invention to a discharge device I such as a coldstarting low pressure positive column fluorescent lamp, exemplified in U. S. Patents Nos. 2,146,579 to Inman and 2,306,925 to Aicher. The system shown in Fig. 3 differs from that in Fig. 1 in that the starting circuit III with its switch II and crystal member I2 is connected directly across discharge circuit 5 between ballast 6 and discharge lamp I, instead of through the cathode coils 2, 2; or, in other words, circuit In is connected across the cathodes 2, 2 partly through the discharge circuit leads. As shown in Fig. 3, a capacitor or condenser I9 of moderate capacity is inter osed in circuit 5 between ballast 6 and circuit I0. 7

In the system shown in Fig. 4, the starting circuit I0 is connected across discharge circuit 5 in advance of ballast 6, but includes a coil in inductive relation to ballast 6, or, in other words, the secondary of a transformer or induction coil having the coil of ballast 6 as its primary. A resistance 2I is shown connected in circuit I0 in series with switch II, crystal member I2, and coil 20, for regulating and controlling the voltage and current in circuit In.

In Figs. 2, 3, and 4, various parts and features are marked with the same reference characters as their homologues in preceding figures, in order to dispense with repetitive description.

What I claim as new and desire to secur by Letters Patent of the United States is:

In combination with a gaseous electric discharge device having a starting circuit in parallel therewith and an inductive member in series therewith operable upon making and breaking of the starting circuit to induce a relatively high voltage across the device for starting it, a starting switch having its contacts connected in said starting circuit to make and break the circuit, and a piezo-electrie crystal electrically connected in said starting circuit to be distorted upon application of potential thereto and physically arranged to actuate said switch contacts upon distortion thereof, and a capacitor in series with said switch.

EUGENE LEMMERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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