US2351270A - Electric discharge device and method of operation - Google Patents

Description

Patented' June 13, 1944 snnc'rnrc DISCHARGE nnvrcn AND METHOD or orsna'rron Eugene Lemmers, signer to General tion of New York Elec Cleveland Heights, Ohio, astric Company, a corpora- Application August 1, 1941, Serial No. 405,060

'9 Claims.

This invention relates to electric discharge devices and their operation, and involves novelty in the control of electric discharges. One advantage that can be obtained through the invention is the elimination of troublesome accessories, in-

cluding starting and current-limiting means like ballasts,'thermal cut-out switches, etc. Another advantage is improvement of the voltage-current characteristics of electric discharge devices, es-' 'pecially discharge devices containing gas or vapor, even to the extent of enabling such devices to start and operate with a positive overall voltage-current characteristic, and without resort to specially high voltage for starting. The invention is applicable to discharge devices of suitable types already known, without necessity for any radical modification, and without need for elaborate or expensive accessories-though its range of useful capabilities can be considerably increased by the use of special features and arrangements that are referred to hereinafter. The invention may be applied to discharge devices producing useful'radiatlons for various purposes, such as germicidal tubes or lamps, and lamps used industrially for irradiating or treating many substances and products, and for fluorescent lighting. I have hereinafter explained the invention with particular reference to a device suitable for use as a fluorescent lamp.

Very generally, electric discharge through gases and vapors display a negative resistance or voltage-current characteristic. Such characteristics are due to positive ions in the discharge atmos phere, which area necessary accompaniment and.

factor of the discharge, and which act to augment it in a cumulative manner: i. e., ions once produced result in the production of more ions, which produce still more ions, etc., etc. Once the discharge is started, therefore, it automatically increases and "runs aware-unless the current is limited by means of a ballast resistor, or the like, ,in series with the discharge.

In the operation of one-way discharge devices on pulsating or alternating current, the discharge atmosphere is ionized or kept ionized by the pemosphere, and so discharge recurs, intermittently, on each voltage impulse in the proper direction. If, on the other hand, both electrodes of a discharge device are emissive, the discharge takesplace in opposite directions alternately. In

' either case, it is the persistence of ionization in the discharge atmosphere from one voltage impulse to the next that enables the ionization and the dischaige to build up cumulatively from impulse to impulse until (in the absence of extrinsic control over the current) the discharge reaches run-away proportions, l I

In accordance with my invention, such persistence of ionization isprevented; and if necessary, each period of discharge is additionally limited in duration so that any real runaway in a single discharge period is impossible.- For this purpose, 'an'intermittent discharge is initiated and reinitiated at such periods in the series of voltage impulses or of A. C. cycles that the duration of the discharge each time is too short for the current to attain-an excessive value before the discharge is terminated by fall of the discharge voltage; while the outage interval from the resulting termination of the discharge to the initiation of the next succeeding discharge permits substantial deionization of the discharge atmosphere. If the duration of a discharge-voltage impulse or cycle is sufficiently brief, an outage interval that assures adequate or substantial de-.

ionization before the next such impulse may afford all the control necessary. The explanation of why runaway does not occur in such cases riodically recurring pulses or waves 'of the discharge voltage and the consequent emission of electrons from a charge device. During zero or reverse-voltage periods of the voltage cycle,'the emission of electrons and the discharge itself cease, and the discharge atmosphere starts to deionize: but the voltage impulses and the resulting emissions of electrons succeed one another before there is time for total decay of ionization in the discharge atcathode electrode of the dis-r seems to be that during the part of each cycle when the discharge is going on, ions are not formed fast enough, and the envelope walls have not time to trap enough of them to come to.

equilibrium; while by the next ignition, the ions have decayed away: hence each firing or discharge is essentially just like the one directly' before it. In other words, the intermittent main discharges remain-isolated, as well as the auxiliary ionizing discharges that initiate them.

For GO-cycle A. C. current, it is found satisfactory in practice to fire or initiate one-way disharge on one peak of each cycle, which may be either the positive or the negative voltage peak: e. g., the discharge may be initiated somewhat before the voltage reaches its maximum positive value or crest, or at any time thereafter while its positive-value suffices for a'discharge across the discharge gap. This may be called quartercycle operation, since the discharge endures only about one-fourth of each sine-wave period, while the remaining three-quarters is available for deionization of the discharge.'atmosphere, Apparently the deionization time is something like $60 second. at any rate, such quarter-cycle opera-- tion does give a positive over-all characteristic to the discharge. For A. C. current approximating 25=cycle frequency, more or less, two-way discharge likewiseshows a positivecharacteristic when suitably initiated on each peak (positive f and negativ'ei-of each cycle, since such half-' cycle operation afiords substantially the same. length of time for deionizationas does quartercycle operation on60-cycle A. C.

I have found that control of. ionization and discharge as aboveindlcated can be etlecied very simply and directly through the agency-oi an auxiliary ionization. of thedischarge atmosphere: i. e., theatmosphere is specially ionized during uch of themain voltage impulses or A. C. halfwaves that the main discharge thus initiated or ignited and the ionization of the atmosphere that enables it to take place both die out. each time, before the next succeeding'ionization. Besides this choice of periods in the series of main Voltage impulses or half-waves which allow ionization to decay, the particular points of the impulses or half-waves where ionization iseflected may be chosen according to the.duration and; wattage that are desired for the main discharge, as well as to allow it to die out, each time, too soon for the main discharge current to becomeexcessive. An ionizing voltage or discharge for these purposesgranr similar to Figs. 1 and 3 showing a single discharge device and its connections, suitable for halt-cycle operation like the 0 devices in Fig.3.

Figs. 6 and 7 are diagrams illustrating simplifled electrical supply systems for discharge devices like that in Fig. 1 and Fig. 8 is a similar diagram showing as somewhat different discharge device, as well; as a modified systemof electrical connections.

Figs. 9, 10, 11 and 12 are diagrams illustrating discharge devices sim'ilarto that of Fig. 1 with ancillary ionizing arrangementsand including electrical supply connections; Fig. 13 is a similar diagram showing modifications in the discharge device, as well as in the electrical system; and Fig. 14' is a similar diagram showing further modification of the device and of the electrical system. r

Fig. 1 illustrates the application of my invention to a well-known simple type of one-way electric discharge device that comprises a vitreous tubular envelope ll having at one end anode disc l5 connected .to alead I'G-sealed through the end of the envelope, and having at its other end .a cathode H which may be of filamentary thermion'ic type ;(such as a coiled coil of tungsten may be provided in various ways, a few of which I have illustrated and explained hereinafter.

Such an auxiliary ionizing discharge may preferably Be A. C. Iorjthe sake or simplicity oi -the power supply, if for no other reason. As the voltage for this auxiliary discharge need on-its peaks only just above or a. little above the ionizing potential of the discharge atmosphere, and as the current required in it is butsmall, its

control as against running away presents np serious problem: the fact that it need only fire for an instant on the peaks of the auxiliary voltage cycle tends to give it an overall positive characteristic oi ltsown; and any extrinsic control needed is aljiorded by the means ordinarily employed to deivoltage naturally .employed for the main discharge. Control of the timing of the main discharge with respect to the main voltage cycle may be effected either by adjusting the peak value of the auxiliary voltage, or by adjusting the f phase relation metween the'mainkand auxiliary. voltage cycles. The frequencies of these main and auxiliary pulsating or A. C. voltage cycles will, in practice, bear a simple arithmetical relation to one another, if they are not actually' the same; and they will usually be approximately in phase, even when subject to slight adjustment of their phase relationior purposes 0! timing.

Various other features and advantages oimy invention will become apparent from thetollowing description of species and forms offgmbodiment, and from the drawing. In the drawing, Fig. l is a diagrammatic illustration of a simple form of electric discharge d6? vice adaptable for the purposes 01 my invention,

,and of suitable electrical connections therefor;

Fig. 2 is a voltage diagram illustrating the operation of the system shown in Fig. 1; Fig. 3 is a diagram similar to' Fig. 1 showing two such d'is-' charge devices reversely' connected, rectifier V and strontium oxides), and isshown co between leads l8, l8 sealed through the end of wire activated with the usual mixture of arium ected the envelope. Provision fo'rpassing pulsating or A. 0. current through the cathode coil I! may be made by connecting its leads l8, l8 across the secondary of a transformer 20whose primary is connected by leads 2|, 2| across any suitable auxiliary power source. p. The anode lead l6 and one of the cathode leads l8 are shown connected to a -main power circuit 22 from any suitable pulsating' or A. C. power source P. The envelope, I4

a drop 23 inside the envelope l4, an an internal -rive the low auxiliary voltage from the higher may contain a low-pressure atmosphere of gas or vapor, or both, such as argon and mercury; or, preferably, the gas may consist of neon with a small admixture ot.argon--e. g., about 0.5% or 5%. A surplus supply of mercury is indicated by coating of fluorescent materialor phosphor 25 on the envelope walls is also indicated. i

The pulsating or A. 0. main voltage from source l? should be suiiicient, at or near its peak value, to sustain a discharge between theelectrodes l5, ll, though not high enough to start one across so long a gap. The pulsating or A. C. auxiliary voltage irom source 17 should not only be sufllcient to heat the'cathode l'l toelectron-emissivejemperature, but also highenough, at or near its peak value, to ionize the atmosphere in the device, thus -producing an ionizing discharge along the oathode II between its leads l8, I8 which results in or, in other-words. fires the main discharge. The

exact .time or 'stage ofits voltage cycle at which the main discharge thusfires may be varied'and controlled either by varyingthe phase relation between the 1 main and auxiliary voltages, or by varying th range and peak value of the auxiliary voltage wave, so as to change the point or stage in the auxiliary voltage cycle at which it reaches ionizing value, or both. Variation of the auxiliary voltage is perhaps the easier method; but variation'oi the phase relation affords -a greater range or control. The range of phase adjustment ordinarily required is relatively small, so that the twovoltage cycles may always be approximately in phase withone another.

point of. main discharge ignition and of its duration in each voltage cycle may be helpi l not Adjustment of the ascna'ro one lead It connected to the main A. C. power cironly to insure against runaway of the discharge, but as a means of adjusting the lumen output rating of a given fluorescent lamp. Furthermore, the luminous emciency may be increased by reducing the wattage of the device, in this manner.

below that resulting from the earliest ignition consistent with a positive characteristic.

Assuming that the sources P and p both furnish 60-cycle A. 0., the main discharge between electrodes l5 and I! will preferably be fired by the auxiliary discharge somewhat ahead of the crest of the main voltage peak of a half-cycle, and will persist till about the end of this half-cycle. This is indicated in Fig. 2 for the half-cycle I by the ordinate F1 intersecting the main and auxiliary voltage curves V and v, and by the shaded area to the right of this ordinate under the curve V.

As her shown, the auxiliary and main voltage cycles are exactly in phase, and both discharges fire the instant the auxiliary voltage reaches-the ionizing potential of the'discharge atmosphere, ahead of the crests of both voltage peaks. According to this diagram, in other words, the auxiliary voltage reaches and exceeds the ionizing potential E at the crests of its own'peaks. Dying out when the main voltage falls to zero at the end of. this half-cycle, at the point 0, the main discharge remains out during next halfcycle II because there'is no emissive cathode to support discharge in the reverse direction. During nearly or about half of the ensuing half-cycle III, the main discharge is still out, because the ionization from the previous discharges has decayed; but at the ordinate F2, somewhat ahead of the crest of this half-cycle III, the auxiliary discharge will again ionize the atmospher in the device, and the main -discharge will again fire exactly as in the first instance-as indicated by the shaded area to the right of F2. This quarter cycle or quarter-wave operation continues ining anode 30 is connected by a lead 3| to the definitely, as long as suitable pulsating or A. C. voltages are supplied from p and P gested by the ordinate-F3. ,r Fig. 3 shows a pair of one-way discharge devices such as hereinbefore described reversely arranged and connected, rectifier fashion, so asto give approximate half-cycle operation as illustrated in Fig. 4. Fig, 4 also diilers from Fig. 2. in. show-; ing the auxiliary voltage cycle as leading the main voltage cycle and firing on its own wave crests, instead of being in exact phase withth'e main voltage cycle and firing ahead A of its own wave crests. According to Fig. 4, in other words, the auxiliary voltage only just reaches the ionizing potential Ed the discharge atmosphere at the crests of its own peaks. In Figs. 3 and 4, various as is s scult 22, so that each of these electrodes I1 functions altemately'as cathode and as anode for the alternate main voltage half-waveaand also provides the auxiliary ioniiing discharge for these half-waves. Accordingly, the same reference numerals are applied to various corresponding parts and features in Figs. 1, 3 and 5, as a means of dispensing with repetitive description. So closely,.indeed, does this single Fig. 5 device correspond to the double Fig. 3 arrangement that its operation on 25-cycle A. C. is essentially represented by the same Fig. 4 diagram.

It is convenient, of course, that the main and auxiliary voltage and current sourcesPfp should be identical-4. e., that the auxiliary voltage should be derived from the main voltage. Such a simplification is' illustra 6, where the cathode l7 main power circuit 22 in parallel with. the electrodes l5, IT by leads 21a, Zia and an interposed resistor 26, and in another form ln Fig. 7, where the primary of the transformer 20 is connected by leads 2"), 2lb across the main power circuit 22 in parallel with the electrodes l5, H. A further variation is illustrated in Fig. 8, where the cathode I To is shown as of indirectly heated type, comprising. a heatin coil 21 connected between the leads, I80, I80 and surrounded by an electron-emissive cylinder 28 coated with activating material 29. Here the auxiliary ionizing discharge takes place between the activated cathode surface 29 and a separate auxiliary anode 30, while the coil 27 is only a heater-the voltage through which preferably is not high enough to ionize; As here shown, the cathode cylinder and one of the heating coil leads l8care connected together and to one. end of the secondary of the transformer 200; the other lead me is connected to the midpoint of this secondary; and the auxiliary ionizother end of said secondary. Accordingly, the

. produce the auxiliary discharge.

parts :and features essentially correspondingto those in Figs. 1 and 2 are marked with similar reference characters, thus dispensing with remately the-last l0% of petitive descriptions. The principal point to be 6 observed is that one of the discharge devices .shown in Fig. 3 fires on the positive half-cycles,

while the other fires on the negative half-cycles. Accordingly, the powerfactor is very much better for this combination than for a single device op- 6 crating as illustrated in Figs. 1 and 2.

Half-cycle operation with its greatly improved power-factor can be obtained not only with two one-way discharge devices operatedvon -cyc1e A. C. as explained above in connection with Figs.

, The essentials for quarter-cycle operation on 60- cycle vA. C. as described above are, of course, that the device should be able to conduct in but one direction, so as to fire only on alternate halfcycles; that the main. discharge gapand voltage should be such that the device cannot fire on the firing half-cycles until ignited by the auxiliary ionizing discharge; and that this ignition be timed and limited (in either of the ways ,hereinbefore indicated) to occur some time during approxithe firing half-cycles. Even When the auxiliary and main discharges are energized from a com 6, 7 and 8, the phase relation between the auxiliary and main voltages canbe adjusted to time the ignition of the main discharge by various well-known means of displacing the derived auxiliary voltage out of phase with the main voltage,

such as saturating transformers, chokes, or capacitors, for example.

A discharge device such as shown in Figs. 3, 6, and 7 may be built with an envelope tube M of 1 inch internal diameter 6 inches long;- with an anode plate I5 of sheet molybdenum inch in diameter; with a cathode l1 consisting of. an-

ordinary l5-watt fluorescent lamp cathode; and

1 in having cathodes 11 at both ends, each with with a filling of argon at an absolutepressure of ted in one form in Fig, is connected across the on source P,-as in Figs."

4 mm. of mercury, plus a mercury droplet 23 ample to assure a surplus during operation. On Gil-cycle A. C.,' such a device operates satisfactorily (without ballast) under a voltage of approximately 10 volts (root mean square) across the cathode circuit Hand of 30 .volts' (root mean square) across the main power circuit 22, with a main discharge current of approximately 0.4 ampere. The R. M. S. voltages here stated correspond, of course, to substantially higher actual voltages at the peaks of the A. C. sine waves, as represented in Figs. 2 and 4. The main discharge current is very sensitive to small voltage changes. either in the main power circuit 22, or in the auxiliary circuit l8.

Besides the available voltage in the main power I circuit 22, the practicable length of such a discharge device is limited by the distance to which ionization from the glow discharge at the cathode I! will spread in the envelope tube It. For a 1- inch tube charged with argon, the length limit is about 8 inches to nearly 12 inches; but it in creases as the diameter of the tube M is increased, and is also greatly influenced by the composition of the atmosphere in the envelope H: e. g., ionization extends much further in an atmosphere of neon with a small admixture of argon than in neon alone.

However, such limitations on tube length can in practice be overcome by means of ancillary ionizers at suitable intervals in the length of the tube, so that the zone of influence from one overlaps that of the next one; and the tube length can be as great as permitted by the available supply' voltage. This is illustrated in Figs. 9-14, which show a few of the many possible arrangements and circuits.

Fig. 9 shows a one-way discharge device like that of Fig. 1 provided with an intermediate auxiliary anode 35 located within the ionizing range of the cathode I1, and close enough to the main anode Hi to bring the latter within ionizing range of the discharge between the electrodes 11 and 35. The electrode 35 is connected to the cathode side of the main power circuit 22 through the secondary of a leakage reactance transformer 36 whose primary is connected across the circuit 22. The transformer 36 is so selected that the voltage between cathode I! and electrode 35 is sufficient to produce discharge across this gap when the atmosphere is ionized by the discharge along cathode l1; whereupon the ionization extends to the right-hand end of the tube and the discharge jumps to the main anode l5-thus short-circuiting and extinguishing or reducing to insignificant proportions the discharge between electrodes l1 and 35, owing to the resistance of the secondary of the transformer 36 in series with the electrode gap "-35.

This Fig. 9 arrangement is peculiarly flexible because of thepractically unlimited choice of starting voltage across the gap |135 that is afforded through the selectionof the transformer 36: i. e., this starting volta'ge may, if desired, exceed the voltage of the source P by a wide margin. For example, a Fig. 9 tube of 1 inch internal diameter 54 inches long may be operated without ballast on a voltage of 160 volts across the electrode gap I|-i5, using avoltage of 300 volts across the electrode gap |'I-35 for starting.

The discharge device shown in Fig. 10 has an ancillary anode 35c located within the ionizing range of the auxiliary discharge at the cathode l1, and connected through a resistance 31 to the anode side of the main power circuit 22. Thus the full value of the main voltage from source P is felt between the electrodes l1 and 35a until the gas is ionized by the discharge at the cathode l1, whereupon the device breaks down first to the ancillary anode 35c and then to the main anode I5, this discharge short-circuiting and thus extinguishing or reducing to insignificant proportions that between electrodes l1 and 35s, owing to the resistance 31.

The discharge device shown in Fig. 11 involves a cumulative reduplication of the Fig. 10 arrangement: 1. e., the discharge between electrodes 11 and 35e jumps first to another ancillary anode 35f and then to the main anode l5, successively short-circuiting and reducing or extinguishing the discharges between electrodes l1 and 35e, 35f, owing to the resistances 31 and 31f.

The discharge device shown in Fig. 12 has two ancillary electrodes 359. and 38'connected through resistances 31g and 39 to the opposite sides of the main power circuit 22. The full value of th main voltage from source P is felt between electrodes 35g and 38 until ionization of the atmosphere by the discharge at the cathode ll. Thereupon discharge occurs across the electrodes 35g and 38, then jumps to the electrodes l1 and I5, short-circuiting and reducing the discharge between 35g and 38, owing to resistances 31g and 39.

Fig. 13 shows a device which combines essential features of Figs. 6, 8 and 10 in a simplified form. Its cathode l'lh is of indirectly heated type like that in Fig. 8, with its coil 21h (which merely heats, without having any ionizing discharge along it) connected in a circuit 21h across the main power circuit 22, and its cathode tube 28h grounded to one of .the coil leads lBh. It has an auxiliary ionizing anode 30h connected to the anode side of the main power circuit 22 through a lead including a resistance 3lh such that the voltage of discharge across the electrodes llh, 30h is just about sufiicient to ionize the discharge atmosphere at or near the crest of its peak. 'Its ancilliary ionizing anode 35h and its connections may be essentially like the parts designated by the same reference numerals in Fig. 10. In order to dispense with repetitive description, corresponding parts and features in Figs. 6, 8, 10 and 13 are marked with the same reference numerals-a distinctive letter being added where such distinction appears necessary.

The device shown in Fig. 14 resembles that of Fig. 13, but differs as regards the cathode of I11 and the auxiliary electrode 301: i. e.,- the cathode H7 is shown ofthe cold-starting activated coil type, like that of an ordinary fluorescent lamp. andthe auxiliary anode 30a is located close to it and connectedto the anode side of the circuit through a resistance 3 la'. Thus the full value of the main voltage from source P is initially felt between the electrodes I17 and 3M, and suflices for cold-cathode initiation of discharge between them. Once this discharge isstarted, its voltage is reduced to substantially the ionizing potential of the atmosphere by the resistance 3M, and it continues as an auxiliary ionizing discharge like that in the Fig. 1 and other devices, igniting the main discharge at the proper points on the firing half-waves. If the desired length of the device requires, the ancillary electrode 357 with its resistance connection 317' may be provided, operating just likethe corresponding parts in Figs. 10. 11 and 13. To dispense with repetitive description, corresponding parts and features in Figs. 10, 11.13 and 14 are marked with the same refer- 2,351,270 ence numerals, distinctive letters being added where distinction seems necessary.- ,7 K

'What I claim as new and desire to secure by Letters Patent or the United States is:

1. A method of producing and controlling intermittent electric discharge through an ionizable atmosphere; which method comprises applying across a .main discharge gap between electrodes in said atmosphere amain pulsating voltage of peak value suflicient to sustain discharge to allow the ionization accompanying each main discharge pulse ignited as aforesaid to die out be- 1 tore ignition or the next succeeding main disacross said gap, but insuflflcient to initiate such discharge; intermittentlyfapplying across a gap between electrodes in said atmosphere an ionizing potential suflicient to initiate a discharge thereacross, which ionizes said atmosphere andthus ignites a main discharge pulse under said main pulsatingvoltage; and timing the .intermittent application of said ionizing potential to allow the ionization accompanying each main discharge pulse ignited as aforesaidto die out be- 'fore ignition of the next succeeding main discharge pulse.

2. A method of producing and controlling intermittent electric discharge through an ionizable atmosphere; which method comprises applying across a main discharge gap between electrodes in said atmosphere a'main pulsating voltage of peak value-sufficient to sustain discharge across said gap, but insufficient to initiate such discharge; intermittently applying across a substantially shorter gap' between electrodes in said atmosphere an ionizing potential sufllclent' to charge pulse.

5. A method of "producing andcontrolling intermittent electric discharge through an ionizable atmosphere; which method comprises applying across a gap between main one-way discharge electrodes in said atmosphere a 60-cycle voltage peak value sufllcient to sustain discharge across said gap, but insuflicient to initiate such discharge; intermittentlyapplying across an auxiliary gap between electrodes in said atmosphere,

near the peaks of said 60-cycle voltage in the direction of discharge permitted by said one-way discharge electrodes, an ionizing potential sufficient to initiate a discharge across said auxiliary gap which ionizes said atmosphere and ,thus ignites a main discharge pulse between said oneway discharge electrodes; and timing the intermittent applicationoi said ionizing potential to allow-the ionization accompanyingeach main discharge pulse ignited aspaforesaidto die out a before ignition oi the next succeeding main disinitiate a discharge across said shorter gap, which ionizes said atmosphere and thus ignites a main discharge pulse under said main pulsating voltage; and timing the intermittentapplication of said ionizing potential to allow the ionization accharge pulse.

6. A method of producing and controlling intermittent electric discharge through an ionizable atmosphere; which method comprises applying across a gap between main two-way discharge electrodes in said atmosphere a voltage of frequency approximating 25 cycles and of peak value suflicient to sustain discharge across said gap, but insufllcient to'initiate such discharge; intermittently applying across an auxiliary gap between electrodes in said atmosphere, near the peaks of said voltage in both directions, an ionizcompanying each main discharge pulse ignited as ing potential sutficiimt to initiate a discharge across said auxiliary gap which ionizes said atmosphere and thus ignites a main discharge pulse between said main discharge electrodes; and

timing the lnterinittentv application of said ionizing potential to allow the ionization accompanying each main discharge pulse ignited as aforesaid to' die out before ignition of the next suc-- 'ceeding main discharge pulse.

7'. In combination, anelectric discharge device comprising an envelope containing an ionizable atmosphere, and electrodes therein; means for applying between electrodes aforesaid a main initiate a discharge across said shorter, gap, i

which ionizes safdatmosphere and thus ignites a main discharge pulse under said main A. 0. voltage; and timing the cycles of said A.,C. ionizing potential to allow the ionization accompanying each main discharge pulseignited as aforesaid to die out before ignition of the next succeeding main discharge pulse.

4. A method of producing and controlling intermittent electric discharge through an ionizable atmosphere; which method comprises applying across a main'discharge gap between electrodes in. said atmosphere a main'pulsating voltage of peak-"value sumcient to sustain discharge across said gap, but insuflicient to initiate such dis .chargezr-intermittently applying across a substantia shorter gap between electrodes in said atmosphere a substantially lower potential pulsating voltage approximately in phase with the pulsations of the first-mentioned voltage, and reaching the ionizing potential of the atmosphere only on its peaks, which thus ionize said atmosphere and ignite main discharge pulses under said main pulsatingyoltage; and timing the intermittent application of said ionizing potential pulsating voltage of' peak value sufficient to sustain discharge across their gap, but insuflicient toinitiate such discharge; and. means for intermittently applying between electrodes aforesaid an ionizing potential suflicient to initiate a discharge thereacross, which ionizes said atmosphere and thus ignites a main discharge pulse under said main pulsating voltage, the intermittent application of ionizing potential being timed to allow the ionization accompanying each main discharge pulse ignited as aforesaid --to die out before ignition of the 'next succeeding main discharge pulse. i 1

8. In combination, an electric discharge device comprising an envelope containing an ionizable atmosphere,-and electrodes therein afiording a 'main discharge gap and a, substantially shorter auxiliary discharge gap; means for applying across-said main discharge gap am'ain pulsating voltage of peak value sufficient/to sustain discharge across said gap, but insuflicient to initiate such discharge; and means for intermittently applying across said auxiliary discharge gapan ionizing potential sufiicient to initiate a discharge thereacross, which ionizes said atmosphere and thus ignites a main discharge pulse across said main discharge gap, the, intermittent application of ionizing potential being timed to allow the ionization accompanying each main discharge pulse ignited as aforesaid to die out before ignition of the next succeeding main'discharge pulse.

9. In combination, an electric discharge device comprising an envelope containing an ionizable atmosphere, and electrodes therein aifording a one-way main discharge gap and a substantially shorter auxiliary discharge gap; means for applying across said one-way discharge gap a main A. C. voltage of peak value suiflcient to sustain discharge across said gap. but insuiiicient to initiate such discharge; and means for applying gap which ionizes said atmosphere and thus il nites a main'discharge pulse across said one-way gap, the cycles of said A. C. ionizing potential being timed to allow the ionization accompanying: each main discharge pulse ignited as aforesaid: to die out before ignition of the next succeeding;

main discharge pulse.

EUGENE LEW

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