US2689928A - Process for lighting ionic tubes, particularly tubes with auxiliary priming electrodes - Google Patents

Description

Sept. 21, 1954 P. M. G. TOULON 2,689,928 PROCESS FOR LIGHTING IONIC TUBES, PARTICULARLY TUBES WITH AUXILIARY PRIMING ELECTRODES Filed Feb. 16, 1950 5 Sheets-Sheet 1 6, 9 INVENTOR.

PER/PE M4? 700w A TTOR NE Y5 Sept. 21, 1954 OULON 2,689,928

P. M. G. T PROCESS FOR LIGHTING IONIC TUBES, PARTICULARLY TUBES WITH AUXILIARY PRIMING ELECTRODES Filed Feb. 16, 1950 5Sheets-Sheet 2 Z INVENTOR. flaws 1/6. -7b(/1.0/v

p 1954 P. M. G. TOULON 2,689,923

PROCESS FOR'LIGHTING IONIC TUBES. PARTICULARLY TUBES WITH AUXILIARY PRIMING ELECTRODES Filed Feb. 16, 1950 5 Sheets -Sheet :s

INVENTOR. flaw: M 6! 751/404 ATTORNEYS P. M. G. TOULON 2,689,928 PROCESS FOR LIGHTING IONIC TUBES, PARTICULARLY TUBES WITH AUXILIARY PRIMING ELECTRODES Filed Feb. 16, 1950 5 Sheets-Sheet 4 u .9 m Q Q u u w m m IIIIIIIIIIII I m m I I I I I I I I I I I I I I I I I NQIT I I I I I I I II II m m I I & m m I I I I I I I I I I I I I I II I I I I I I II- II I I I I I I .Q} I I I I I I I I I I I I I I I I I I n I \\II I I n I I m m\\ I I I m\\ I I I I I I I I m .I I I I I I I I I I I I I I I I I u n u m I I n I I Sept. 21, 1954 INVENTOR.

ATTORNEYS Patented Sept. 21, 1954 UNITED: STATES PATENT OFFICE PROCESS FOR LIGHTING IONIC TUBES, PARTICULARLY TUBES WITH AUXILIARY PRIMING ELECTRODES Application February 16, 1950, Serial No. 144,452

Claims priority, application France February 17, 1949 Iii Claims. 1:

The .presentiinvention relates generally to devices for initiating the arc in electronic gaseous conduction devices, and particularlyin gaseous conduction device: of'thetypes'which have control electrodes, and which rely for their operation upon electrical conductivity. ofgas or ionized vapor. Accordingly, the present invention finds particularapplicationlto sealed tubes containing mercury vapor andxvarified gas, such as helium, xenon, and the-like; in"which"initiation of thearc is: caused during: each period of an alternating current'by meanssof a priming electrode; One tube of'this' character, which isgenerally known initheart, is commonlydesignated by the name ignitron.-.

In orders'to'iaccomplish:initiationcf an arc in devices of the ignitron'. type, it is necessary to release in xthe ignitor elec'trodeof the ignitron, which corresponds. with". a: control: electrode, a fairly intense.- current,. having a magnitude'of about 5 amperes; atafairly-high'voltage; say about 30 volts; The duration. of the current whichiissapplied to. the ignitorrelectrodes may be relatively short, ofltheorder. of one-ten thousandth of a second orless. It is possible to obtain a flow of currentof the*charactervdescribed by discharging a fairly high capacity,- which is charged to a..voltage: of 100 .-vo1ts,- through a relatively low: resistance;

Formanyapplications of control electrode -controlled'gaseous conduction devices; and particularly 'forthecontrolled rectification of alternating current, for voltage and: current. regulation systems'inxgeneral, and forfrequency transformationsystems, it isressentialthat the timing of the application of current to the timing of firing electrodebe preciselywdefined, because-the operation of' 'such systems depends: fundamentally on therelative -phase of the firing voltage applied to the'control el'ectrodeand the-alternating volt-- age appliedbetween' the'anode andcathode' of the gaseous conduction device.

Onepresently'accepted. and normal technique for controlling'firingof gaseousconduction de- ViCGSaCOl'lSlSlJS ofthe employment ofauxiliary ionic tubes for this-purpose; For-"example, for thefiring oftignitron-s, it has become conven-' tional tozemploy'a thyratron conn'ecteduin series with :the ignitor electrode, maintainingthe-control-J electrode of the) thyratron normally below 2 firing voltage, and bringing the control voltage applied to the control electrode of the'thyratron up to a firing value at the instant when firing of the ignitronis desired. When the ignitron fires,

, the thyratron permits a fairly high current to pass to the ignitor electrode, this current'being limited only by such resistance as may be connected in series with the ignitor electrode. This current is suificient'to fire the ignitron, but once the ignitron has fired the total current flow therethrough is not subject to control. Accordingly, in order to control the average value of the'ignitron current, it is conventional to feed the control electrode ofthe'thyratron with pulses of voltage, which are de-phased in relationship to the alternating voltage'applied to the anode of the thyratron, thereby controlling the firing times of-the ignitron. It is conventional to'obtain a controlled de-phasing ofthe grid voltage of the thyratron by means of a saturable reactor and associated resistances, by means of phase controllable transformers, and by similar systems.

While the conventional procedures have proven satisfactory, in general, they present the disadvantage of being'inherently extremely complicated and expensive, since it is necessary to provide a largenumber of control'components which are heavy, delicate, fragile, and expensive in'first cost; and which are subject to considerable maintenance difficulties.

The present invention remedies the defect by furnishing means for firing gaseous conduction devices, and particularly'ignitrons, by means of extremely simple, sturdy and cheap control devices, which are easy to maintain and to regulate.

It is, accordingly, a broad object of the inven* tion to provide novel firing devices for gaseous conduction electronic tubes.

It is, accordingly, a broad object of the invention to provide novel firing devices for gaseous conduction electronic tubes.

It-is a further broad object of the invention to provide firing systems for gaseous conduction devices generally, which shall be simpler, more economical, sturdier, and easier to maintain and regulate, than has been the case in the prior art.

It isstill another object of the invention to provide novel firing systems for an ignitron, whichrely upon spark discharges in air.

Itis another object of the invention to provide a system for firing ignitrons by means of controlled spark discharges in air, wherein the spark discharge from a source of relatively low voltage high current is initiated in response to an auxiliary spark discharge produced in response to a relatively high voltage low current source.

It is still a further object of the invention to provide a polyphase system of frequency transformation, which may be employed particularly to reduce the frequency of welding current, while controlling the magnitude thereof.

It is still another object of the invention to provide a system for rectifying alternating current by means of gaseous discharge devices operating in air.

It is still a further object of the invention to provide a system for rectifying alternating current by means of a device which may be controlled by a control electrode, and which operates in air, as an ionic conduction device.

A further object of the invention resides in the provision of a system for frequency division of voltages provided by a. polyphase line, by selectively and in predetermined sequence ef fecting firing of gaseous conduction devices in series with each phase of the line.

The above and still further features, objects and advantages of the present invention will become apparent upon consideration of the following detailed description of various specific embodiments thereof, especially when taken in conjunction with the accompanying drawings wherein:

Figure 1 is a schematic circuit diagram of an ignitron rectifier having an igniting circuit arranged in accordance with the present invention;

Figure 2 is a circuit diagram of a modification of the system of Figure 1;

Figure 3 is a detailed drawing of electrode structure for use in the system of Figure 2 Figure 4 is a circuit diagram of a modification of the system of Figures 1 and 2, wherein the invention is applied to current rectification or frequency transformation, of voltages supplied by a polyphase line, and wherein control electrode controlled gaseous discharge devices are of the type which operate in air as a gaseous conduction medium;

Figure 4A is a detail view of one of the gaseous discharge devices shown in Fig. 4.

Figure 5 is a schematic circuit diagram of a welding system arranged to transform the frequency of a three phase line to single phase current of lower frequency than that provided by the line;

Figure 6 represents a wave form diagram illustrating the character of current flow in the system of Figure 5;

Figure 7 is a wave form diagram illustrating the character of current flow in the system of Figure 5 when employed for frequency division;

Figure 8 is a further wave form diagram representing current flow in the system of Figure 5, for one mode of operation thereof, and showing the order in which firing of the gaseous conduction devices of Figure 5 are required to take place in order to accomplish the wave form illustrated in the figure; and

Figure 9 is a modification of the wave form diagram of Figure 8 showing the timing pulses and wave form obtainable for a different order of frequency division.

Briefly described, and in accordance with the present invention, I utilize pulses of high voltage, but of small current, to effect priming of a spark gap, these pulses of voltage being obtained preferably by means of a circuit maker and breaker operating in conjunction with an induction coil. The sparks generated may then be distributed by means of a distributor of conventional character, which may be driven by means of a synchronous motor, synchronized with line voltage applied to the main gaseous conduction devices. The high priming voltage is utilized to effect ionization in a spark gap. Once ionization has been accomplished a heavy flow of current from a further circuit is caused to pass through the spark gap and to the control electrode of the gaseous conduction device to accomplish firing therein.

Referring now more particularly to the drawings, and having reference initially to Figure 1 thereof, reference numeral l identifies an ignitron tube which may be of conventional character per se, and which comprises an anode 2, a cathode 3 and an ignitor electrode 4. The ignitron I may be connected in series with an A.-C. line 5, one side of which is connected to the anode 2, and the other side of which is connected to the cathode 3 via a load 6 represented as a resistance.

Firing of the ignitron I is accomplished by applying relatively heavy currents to the ignitor electrode 4 at times during the A.-C. cycle of the voltage supplied by the line 5 when the anode 2 is positive. By controlling the firing times within the cycle the average value of the current flowing in the load 5 may be controlled.

Firing current for the ignitor electrode 4 may be generated as follows. A spark gap device is provided having two principal electrodes 1 and B and an auxiliary electrode 9, the electrodes being mutually adjacent, and operating in air. The principal electrode 1 may be connected to the ignitor electrode 4 via a protective resistance II), which serves to limit flow of current to the ignitor electrode 4. The principal electrode 8 may be connected in series with a protective resistance H, and secondary winding l2 of a transformer l3, to the cathode 3 of ignitron l. Connected across the secondary winding I! may be a condenser [4, which becomes charged in response to voltage supplied by the winding l2, and which discharges across the principal electrodes 1 and B and through the ignitor elec-- trode 4, when the gas existing in the gap between the principal electrodes 1 and 8 becomes ionized. Normally, the spacing between the principal electrodes 1 and 8 is insufficient to permit break-down or ionization of the gas contained therebetween in response to the voltage developed across the secondary winding l2 of transformer l3. Transformer I3 is energized by means of a primary winding l2 which is connected across the line 5, and is energized therefrom via a phase controlling condenser 15 and resistance 16, which are provided in association with the primary winding M in order to advance the phase of the current flowing in primary winding I4 relative to the voltage existing on the line 5.

Ionization of the air existing in the gap between the principal electrodes 1 and 8 is accomplished by applying to auxiliary electrode 9 a transient high voltage, preferably at low current. To this end, voltage is derived from the line 5 via a transformer l1, and is applied to a rectifier arrangement l8, which may be of the well known Rectox type, at the output of which is provided a filtering arrangement l 92 Across the inductance 20 of filter I 9* is" then= developed a DI-C. voltage of constant magnitude: Connected across the" inductance20 oracross the filter l9; and" in series with oneanother; area pair of breaker points'Z'I; which areadapted to open andclose in response toaro-tating cam-22, and the primarywinding 23 of an induction coil 24; supp-lied witha secondary winding-25f Accordingly; while the breaker'pointsare'closed, D.-C. current flows in the primary'winding'23. When the breakenpoints'fl open; this current' is suddenly interrupted, and in accordancewith well known laws of electricity a high transient voltage is generated in the'sec'o-ndarywinding 25; The secondary winding 25" isconnected at oneend tothe rotary'armdfi of a'distributorZT, and'at" its other end with'the principal electrode 8; One of the switch contacts 28 of the rotary distributor 2115 connected to the auxiliary "electrode 9' The'camlzfand the switch armiBare driven from a synchronousmotor 29; whichis energizedlfrom the line '5. The'timi'ng ofthe cam 22 is so arranged "that a breakof 'the' breaker points 2! occurs once during each cycle of the voltage supplied by thelin'eo5g and the structural arrangement may be such,- in accordance with principles wellknown in theart; that"the==precise point-in the period of the At-C. voltage sup"- plied by theline 5 at whiclrbreaking of the points 2| takes place may be determined by adjusting the phasing of the cam 22.

Accordingly, as the cam 22"rotates'the breaker points 2l' open and close, andlvoltage piulses'are applied between principal electrode 8 and-:auxiliary electrode 9, once duringfeach cycle, at times when the anode 2 is positively polarized. When asufiiciently high voltage is'impressed'fromv the secondary winding 25" between" principali electrode 8 andthe auxiliary electrode 9 adi'scharge occurs, which. ionizes thelair existing in the gap between the electrodes 7,1 8fan-dI9I When the air is ionized a relatively low. resistance. path between electrodes 1 and 8115 created, so that essentially ionization. of the air. is equivalent to closureiof a switch. across principal electrodes 7 land.8.

The condenser M, which at this instant is charged inlsuch sense that principal. electrode 8 is positive relative to cathode 3; discharges across the gap betweenelectrodese'l and Xiand from the ignitorl electrode 4 to the. cathode 3;. Discharge ofv the condenser i4 establishes a. sufliciently heavy flow of. current from ignitorw electrode il'to cathode 3-to establish an ionizedgaseous vapor within the ignitron I, andthelatter thenv fires, current fiowingciro-manodel to. cathode land through load 6-. Since the breaker points 2! ,may beconstrained to break onceduringneach cycle of the.A.-C. voltage supplied by. the line and ata predetermined point within'the. cycle, the operation of the system results-in successive-firings of the ignitron-I, and accordingly oflsucces sive pulses of unidirectional current fiow-infthe load 6. The magnitude: of this-current flo-w'may be readily controlled by controlling the: timing of the cam 22.

Referring now moreparticularly'to' Figure 2 of the accompanying drawings; there is illus trated a modification of the system of-Figurel, which involves primarily provision oia modified system for developing firing pulses for theignitor electrode l: In the system of Figurez the-vol-tage supplied by the line 5"is- *applied" directly to 6. the ignitor-electrode: 4 ihstead: ot 'via-v as transs former.-'

In the system of Eigure 2 there: are employed breaker: points: 2|, cam 22. for actuating: the breaker pointsalternately into opennand closed position, a synchronous motor? BL for driving the cam 22, and a distributor: 21, vall of which serve to energize the-"secondary winding; 25 0f an ins ductioncoil 2'4 periodically in synchronism. with the voltage suppliedby the line 5. The. primary winding 23 of' the inducti0n coil 24-ris supplied with DL-C'I currentfrom" a rectifier' and'filterrw; which may comprise, as'in the system of Figureil, a transformer l'i, rectifler'l 8; and filter l9; l The voltage generated across the secondary winding 25 is'applied' betweeman auxiliary electrodewfi and a principal electrode 8-,-: as in the system. of Figure 2. Accordinglyeach time a high voltage 'is generated in secondary winding 25 the gasexistfing in the gap electrodes li an'd '9 becomesionized. Ionizationof the gas" reduces the-total resistance between the electrodes ii and 9' to an 1 extremely low-value, from an extremely'high value, and is equivalent roughly to closure of a switch; A

circuit is thereby completed from the'positive terminal of 5 the source 30 through the primary winding 31 of transformerta, from-gap l to gap 8; through secondary winding 2'5of transformer 24-; and'back tothe negative terminal ofsource 301" There-is also thus completed acircuit'exstending from transformer 24 through. primary winding =3! and across the gap between electrodes T and 8: Thecondenser 29is normallycharged to a D.-C.' voltage; since the condenser 29' is normallychargedto the full voltage of the DI-C. source 30"while=the'gap between electrodes 1 and 8-is'deionized; Ionization of the gap results-then in discharge of the condenser z through 'the primary winding 3|" and through the gap; this dischargebeingof a transient nature,- since' once the condenserhascompletedits'discharge no fur theivoltage is available for-maintaining the spark across the electrodes land-8:

The transformers? may be. provided witha seoondary'winding 33, which is connected in series with an-R: E by-pass condenser=34 and"a tuning condenser 35; The-sudden-impact of current flow in the primary winding 3| results in high frequency-oscillations, if the valueof the condenser 29- and the design of the windings of the transformer 32'aresuitable, and the primary circuit" comprising primary winding 3i and condenser 29 maybe tuned to the'samefrequency as is the secondary circuit comprising winding 33', tuning condenser- 35 and by-passcondense-r 34. The high frequency oscillations result in the generation of an extremely high voltage across'the secondary winding 33, which, how'- ever; are prevented-from application to the ignitor' electrode 4- by theby-pass condenser 34. Essentially the high frequency voltage is applied thenacr'oss' a sparkgap consisting of electrodes 35 'and'36 which are connected across the condenser 352' The spark gap comprising electrodes 36 and 37 discharges; thus completing a circuit for currentfl'owing from the line 5 through protective resistance 23, secondary winding 33 of transformer 32electrodes'36 and 37 i'gnitor electrode 4'} cathode 3, load sand to the other side ofline 51' Figure 3" of the accompanying drawings illustrates in cross section a suitable arrangement forthe spark gap 1 device comprisingelectrodes I, 8 and 8-; whichis utilized in'thesystemiiof Eigure 2; It will: be: noted;that: the electrode fl-is a sharply pointed electrode co-acting with the electrode 8, which is provided at its face adjacent to the point 40 of electrode 9 with a slightly concave surface 4|. The electrodes 8 and 9 further are generally co-axial. Accordingly, upon application of an intense voltage between electrodes 8 and 9, a spark is generated between the point 4|] and the surface 4|, which effects intense ionization of the air existing in the vicinity thereof. The electrode 1 is in the form of an annulus, having a central aperture symmetrically placed with respect to the axis of the electrodes 8 and 9, and with the plane of the annulus perpendicular to the axis. Additionally, the aperture is arranged to overlap slightly the electrode 8 and is very closely spaced with respect thereto. As a consequence of the intense ionization of the air existing between electrode points 40 and 4|, and of the very slight distance which separates electrodes l2 and I3, the passage of current between electrodes I2 and I3 may be very readily effected, even in response to voltages of quite low value, say of the order of 100 volts.

While I have illustrated the present invention as applied to the firing of ignitron tubes, it will be clear that the principles of the invention may find much wider application, and particularly may be employed to effect firing of gaseous conduction electronic devices of various character, including those which utilize mercury cathodes, or are supplied with xenon vapor, or other gaseous media. In addition, the present invention may be extended to the priming of spark gaps operating in free air, as will become evident as the description proceeds, and may be applied not only to rectification of alternating currents, but also to systems for transforming the frequency of alternating currents.

The present invention further finds particular application to the production of a lower frequency current from a higher frequency current, provided by a three phase line, such lower frequency currents having particular application to the art of spot welding or other types of resistance welding with currents of high intensity.

It is well known that the supply of welding machines from a three phase network at commercial power frequencies presents difiiculty because of the unfavorable power factor introduced into the network by the character of the welding load, and further because of the dissymmetry of the load introduced into the network.

In accordance with the present invention, it is possible to produce a current of lower frequency from one of higher frequency, by abstracting energy equally from all the phases of a three phase network, while at the same time enabling ready control of the starting time and the welding time of the welding equipment. The necessary control is effected by controlling the distribution of firing sparks, in accordance with a proper sequence, to a plurality of gaseous conduction devices connected between the lines of a three phase line and a welding load.

Reference is now made to Figure 4 of the accompanying drawings wherein is illustrated a system for reducing the frequency of current flowing from a three phase line by means of equipment of the character hereinabove disclosed, or alternatively, for rectification of such current.

The system of Figure 4 utilizes, instead of ignitrons or the like, gaseous conduction devices which are capable of operating in free air, and

which do not require envelopes. When ignitrons are utilized in order to generate alternating currents, as is essential in the process of frequency transformation, it is essential to use a pair of back-to-back tubes, or tubes disposed in inverse parallel relation, in each one of the phases of a three phase line. By utilizing spark gap gaseous conduction devices of the type shown in Figure 4A; operating in free air, on the contrary, it is possible to take advantage of the fact that current may flow in the spark gaps in either direction, thereby reducing the total number of gaseous conduction devices which must be employed.

Referring now more particularly to Figures 4 and 4A of the accompanying drawings, the reference numeral identifies a cam, which actuates a pair of breaker points 5| and 52 in alternation, and each pair alternately into open and closed position. There is further provided a source of D.-C. voltage 53, connected in series with the primary winding 54 of a transformer 55. The breaker points 5| and 52 are connected in shunt with each other, and with the voltage source 53 and the primary winding 54 connected in series. Accordingly, whenever either one of the breaker points 5|, 52 is closed a D.-C. circuit is completed for the primary winding 54, and whenever either of the points is suddenly opened, when the other point is also open, an abrupt interruption of current flow in the primary winding 54 will take place. The net effect is, then, the generation in the secondary winding 56 of the transformer 55 of successive high voltage pulses oc curring six times for each rotation of the cam 50, these high voltage pulses being equally spaced in time, but being controllable in respect to phase by suitably adjusting the position of the cam 50, or of the breaker points 5|, 52 with respect to the cam 50.

One end of the secondary winding 56 is grounded and the other end is connected to the rotary arm 51 of a rotary switch 58 having six equally spaced stationary contacts 59.

The switch arm 51 and the cam 58 are driven in synchronism by means of a synchronous motor 60, so that the high voltage generated in a secondary winding 56 is distributed in succession among the stationary switch contacts 59454 inclusive, during rotation of the rotary arm 51.

The switch contacts 59 and 62 are connected together and to a first line 66; the switch contacts 6| and 63 are similarly connected together and to another line 61; the succeeding switch contacts 6| and 63 are similarly connected together to a line 61 and the stationary switch contacts 6| and B4 are similarly connected to a further line 68. Since the switch contacts 59, 50, 6|, 62, 63, 64 follow each other, in respect to time of contact with arm 51, it follows that the lines 66, 61 and 68 will be successively energized from the secondary winding 56, and that each one of the lines will be twice energized during each cycl of rotation of the cam 50, the rotary switch arm 51, and the drive motor 65.

The voltages applied to the line 66, 61 and 68 are applied respectively to priming voltage generators 69, 10, and 1| which may be specifically of the character of the priming voltage generators disclosed in Figures 1 and 2, and described in detail hereinbefore, and utilized in the embodiments of my invention illustrated in those figures for applying priming current to control electrode 4 0f ignitron Accordingly, at the output of the priming voltage generators 69, 10 and 1| will be 9 provided pulses of relatively high voltage and current intensity, for application to the gaseous conduction devices 12, 13 and HI-respectively. The latter are provided with priming electrodes I5, I6 and 11, which are broadly equivalent to the ignitor electrodes 4 of the ignitrons I. Whilein the case of ignitrons an electrode corresponding with an anode and a further electrode corresponding with a cathode are provided, in the case of the gaseous conduction devices utilized in the system of Figure 4, the anodes and cathodes are interchangeable, since gaseous conduction takes place by means of an are or spark discharge in air. The principal electrodes of each of the gaseous conduction devices 12, I3 and 14 are in the form of a central cylinder (78, i9, Eli!) surrounded by a further cylinder (BI, 82, 83) with a gap between the cylinders. A magnetic field (not illustrated) may be provided in a direction parallel to the cylinders, to effect rotation of the sparks generated between the principal electrodes. Each one of the outer cylinders 8|, 82, 83 is connected via a suitable choke 84, 85, 86, respectively to ground. Th inner cylinders I8, I9 and 80 respectively, are connected to the separate phases 81, 8t, 89, of a three phase power source 90, connected in Y, and with its neutral point connected to one end of a load 9| the other end of which is grounded.

If We assume now that priming sparks are applied to the priming electrodes 15, 16 and I! of gaseous conduction devices 12, I3 and 14, respectively, approximately at the initiation of a cycle of voltage in the corresponding phases '81, 88 and 89 of the three phase source 90, and while the voltages are positive going, the gaseous conduction devices l2, l3, '14 will pass positive current through the load GI and back to the neutral point of the three phase source 90 in pulses of half wave sine shape, mutually displaced by 120, as shown at lines Hit, ltl and m2 of Figure 6. On the other hand, if the priming takes place while the voltages are negative going the current'fiow in the load will be in the opposite direction, and similarly displaced by 120, as illustrated-at lines I03, m4, m5 of Figure 6. If, as in the system of Figure 4 the priming takes place on both negative and positively going voltages, in the separate phases of the three phase line, current flowing in the load 9| will be of alternating character, or will reverse in frequency. If, furthermore, the rate of rotation of the arm 5'! of the rotary switch and the rate of rotation of the cam 50 is not in synchronism with the alternating voltages supplied by the three phase line 90, there will .be generated in the load 9! a current thefrequency of which is dependent upon the speed of rotation of the cam 50 and of the arm 51, and in general a lesser frequency Will be so generated, various wave forms or frequencies being possible by suitable selection of the rates of rotation. At the same time the magnitudes of the current flowing may be controlled by adjusting the phasing of the priming voltages supplied to priming electrodes I5, 16, TI, respectively, by adjusting the phasing of the rotary switch arm 5'! and the cam 50. By disconnecting certain of the switch contacts-such as 62, 63, 64 or 59, 60, 61 the system may be utilized for rectification, and the rectified current may be caused to flow in either direction, depending upon which set of three contacts is. eliminated from the circuit.

A'set of gears with definite ratios (not shown) may be interposed between the cam 50 and the commutator, so that the wave form .may .be

changedsasrequired .bypermutation of the timing oflcircuit breaking with. respect ,to the contacts establishedby the commutator .arm. Another way of achieving. asimilar. result is ,bydisconnectingrthecontacts from their leads in permutations suchthat the proper, alternance. of. phase bediscontinued in agpredetermined fashion.

.The system .ofFigure .4. may. beduplicated utilizing ignitronsin placeof the. gaseous conduction.devices.l2,-l3, l4, whichoperate in air, and which are -inherently .;bi-.,directional. In such case, however, each. phase or. thelinemust be supplied With tWo back-to-baok. orinversely parallel connected'ignitronsas illustratedin Figure 5 of theaccompanying drawings. The mode of controllinglthe times ofenergization of theignitrons, however, maybe .entirely analogous with .that illustrated inv Figure 4 of the drawings.

.Thereis further.illustratedinFigure 5 of the drawings,-.a-.mode of connectionof a.plurali ty of ignitronswith a welding transformer I lllhaving aisecondary .winding I. I I and welding electrodes H2. This may be. accomplished .by connecting ignitronpairslw, H4, H5, H6, H1, H8 in inverseparallel relation between. each pair of lines of .the. threephase. source I.2.0,.'-and .by connecting eachpair of ignitron in series-with azseparate primingwvinding, ,as .121, I22, .I.Z3,.a1l..of which are wound on the same core I24, and all of which are-so wound as to provide additive currents in thesecondary windingIII. By controlling the cadence in [which the ignitrons are fired, as in the system. ofFiguredof the drawings, various Wave formsmay becaused .to appear inv the secondary winding III, and thefrequency of the current flowing in thewinding III vmaybereduced-with respect to the frequency present on the three phase. line I 20, in various ratios.

vReferring particularly to Figure 7 of the drawings there is illustrated at line A, a graph of the alternating voltage present in one phase of the three phase network. By sequentially transferring currentthrough the ignitrons in succession .in groups of two time adjacent phases of the three phase line, it is possible to obtain a frequency .in .thewelding load which is equal to three-fifths of the fundamental frequency of the three phase line, as at curve B.

Byenergizing the ignitrons inalternation in groupsof three successive phases, it is possible to obtaina waveform in accordance with curve C, which corresponds with a frequency equal to three-.sevenths of the fundamental frequency of the three phase line.

.By energizing .inalternation in-groups of four -successivephases of the three phase line, it is possible to. obtain a wave form corresponding with that illustrated at D of Figure 7, which corresponds to. a frequency equal to three-ninths, or one-third, of the fundamental frequency.

.By energizing in alternation in groups of five successive phases, it-is possible to obtain a wave form corresponding with E of Figure '7, which corresponds to three-elevenths of the fundamentalfrequency.

.Other possibilities will occur to those skilled in theart.

Reference .isnowmade to Figure 8 of themcompanying drawings, which provides a basis for furtherexplanation of the mode of energization oftheignitrons in order to providethe wave form illustrated at line B of Figure '7, the wave form being provided in Figure 8, at line B,;correspond- .ing with that shown inFigur 7, IineIB. The

pulses illustrated at lines I30, HI .and I32 have been numbered with the numerals corresponding with the ignitrons of Figure 5, so that considering Figure 8 as a timing diagram for firing the ignitrons of Figure by successive pulses, and reading from left to right, pulses must be applied to the ignitrons as numbered, to provide the output wave form shown at line B. It will be seen that the cycle of events involves twelve operations, after which the cycle repeats itself.

A similar diagram is shown in Figure 9 for generating the wave form shown at line C thereof, the timing pulses being shown related in time to the wave form diagram. The groups of ignitrons of Figure 5 may be designated as A, B and C, in the separate phases, and each of the ignitrons may be given a plus or minus designation, in accordance with the direction in which it passes current. Provided with this key, it will be evident that the pulses shown at line I40 represent those applied to ignitrons H3 and I I4, those shown at line l4! represent the pulses applied to ignitrons H5, H6, and those shown at line I42 correspond with the pulses applied to the ignitrons H1, H8. To determine to which of a pair of ignitrons the pulse is applied it is merely necessary to perceive whether a plus or minus indication is adjacent the pulse. The overall pulse generating requirement is indicated at line 23 or the diagram.

While I have not shown any specific distributing arrangement for distributing the pulses shown at line E of Figure 7, at line I33 of Figure 3, at line MB. of: Figure 9, such arrangements will be obvious to those skilled in the art, and the necessary techniques are those utilized commonly in distributing ignitron pulses to gasoline engine cylinders, at the present time.

While I have described and illustrated various specific embodiments of my invention, it will be clear that variations in detail and in general arrangement may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim and desire to secure by Letters Patent of the United States:

1. In combination, in a system for controlled firing of gaseous conduction electronic devices, a gaseous conduction electronic device having an anode, a cathode, and a control electrode, a spark generating device comprisingthree mutually adjacent electrodes in a gaseous atmosphere, means for establishing ionization in said gaseous atmosphere between two of said mutually adjacent electrodes, said last means comprising a source of relatively high transient voltage and relatively low current, means responsive to said ionization for establishing ionization current flow between one of said last mentioned two electrodes and the third of said three mutually adjacent electrodes, said last means comprising a source of relatively low voltage and relatively high current, and a circuit comprising said last mentioned two electrodes and said control electrode in series.

2. The combination in accordance with claim 1 wherein said gaseous conduction electronic device is a device having a liquid metallic cathode and wherein said control electrode is an ignitor electrode.

3. The combination in accordance with claim 1 wherein said gaseous conduction electronic device is an ignitron.

4. The combination in accordance with claim 1 wherein said gaseous conduction electronic device is a thyratron.

5. The combination in accordance with claim 1 wherein said gaseous conduction electronic device is a spark gap device.

6. The combination in accordance with claim 1 wherein said gaseous atmosphere is air.

7. In combination, in a system for controlled firing of gaseous conduction electronic devices, a plurality of aseous conduction electronic devices, each of said plurality of gaseous conduction electronic devices having an anode, a cathode and a control electrode, a source of firing voltage for said devices, a source of direct current, a circuit maker and breaker, an induction coil having a primary and a secondary winding, a circuit interconnecting said source of direct current, said circuit maker and breaker and said primary winding, means actuating said circuit maker and breaker periodically to initiate and terminate current flow in said primary winding, thereby to induce high voltage pulses in said secondary winding, a separate sparking device associated with each of said devices and comprising three spark electrodes mutually adjacent and separated relatively small gaps, a gaseous atmosphere in said gaps, means for connecting said secondary winding across two of said spark electrodes of one of said sparking devices, a source of relatively high current and low voltage, means for connecting said last mentioned source across one of said two spark electrodes and the remainone of said three spark electrodes of said one of said sparking devices, and a circuit connectin in series said last mentioned source and said one of said two spark electrodes and said remaining one of said three spark electrodes of said one of said sparking devices, and means connecting said secondary winding with said separate sparking devices periodically in a predetermined order.

8. The combination in accordance with claim '7 wherein said gaseous conduction electronic devices are devices having liquid metallic cathodes, and wherein said control electrodes are ignitor electrodes.

9. The combination in accordance with claim 7 wherein said gaseous conduction electrode is an ignitron.

10. The combination in accordance with claim '7 wherein said gaseous conduction electronic device is a spark gap device.

11. The combination in accordance with claim 7 wherein said gaseous conduction electronic device operates in air.

12. The combination in accordance with claim 7 wherein said gaseous atmosphere is air.

13. The combination in accordance with claim 7 wherein said source of relatively high current and low voltage comprising a charged condenser.

14. The combination in accordance with claim '7 wherein said source of relatively high current and low voltage comprises a source of alternating voltage of a predetermined frequency, and wherein a voltage of said predetermined frequency is applied between anode and cathode of each of said gaseous conduction electronic devices.

15. The combination in accordance with claim 1 wherein is further provided a source of alternating voltage, and means connecting said alternating voltage between said anode and said cathode, and wherein said source of relatively high transient voltage comprises a circuit having in series therewith a circuit maker and breaker, and wherein said circuit maker and breaker is operated in synchronism with said alternating current, and wherein said source of relatively low voltage and relatively high current further comprises said source of alternating voltage.

16. In combination with a source of polyphase A.-C. voltage, at least one gaseous conduction device connected in circuit with each phase of said source of polyphase voltage, each of said gaseous conduction devices comprising an anode, a cathode and a control electrode, means for firing said gaseous conduction devices in a predetermined sequence and each during a period of said A.-C. voltage, said means for firing each of said gaseous conduction devices comprising a separate main spark gap in air and having an auxiliary starting electrode, means for generating a high voltage on said auxiliary starting electrodes in sequence and transiently in response to each cycle of said A.-C. voltage to ionize said air, and means responsive to ionization of said air to transfer priming current across said main spark gap, said last means comprising said source of A.-C'. voltage, and means for transferring said priming current between said cathode and said control electrode.

17. The combination in accordance with claim 16 wherein said gaseous conduction devices each comprises a liquid cathode and wherein said control electrodes are igniter electrodes.

18. The combination in accordance with claim 16 wherein said gaseous conduction devices are sparking devices operative in air.

19. The combination in accordance with claim 16 wherein said at least one gaseous conduction device connected in circuit with each phase of said source of polyphase voltage comprises a pair of back-to-back connected gaseous conduction devices connected in circuit with each of said phases.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,550,203 Burstyne Aug. 18, 1925 1,738,464 Wade et al Dec. 3, 1929 2,074,930 Marx Mar. 23, 1937 2,110,700 Elder Mar. 8, 1938 2,231,674 Ludwig Feb. 11, 1941 2,263,307 Lord Nov. 18, 1941 2,298,210 Gulliksen Oct. 6, 1942 2,379,462 Spencer July 3, 1945 2,400,457 Haine May 14, 1946 2,402,608 Klemperer June 25, 1946 2,472,671 McNulty June 7, 1949 2,478,901 Edgerton Aug. 16, 1949 2,478,906 Edgerton Aug. 16, 1949

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