US2509005A - Flashtube triggering circuits - Google Patents

Description

y 3, 1950 H. w. LORD 2,509,005

FLASHTUBE TRIGGERING CIRCUITS Filed Oct. 17, 1949 2 Sheets-Sheet l I8 SATURABLE.

l7 6 LrLfL 5 4 28 J 29 a 27 O 57 2! 20 a Lrui A.C.

SOURCE Inventor: Harold W. Lord,

H is Attorney.

2 Sheets-Sheet 2 Filed 001;. 17, 1949 Fig.5. 56

WSATURABL;

Fig.4.

SATURABLE Inventor Haw-old W. Lord, by 49$ 4. 7'

H is Attorney.

Patented May 23, 1950 UNITED STATES PATENT OFFICE FIIA'SHTUBE TRIGGERING CIRCUITS Haroid W. Lord, Schenectady, N. Y., assignor-to Generalv Electric Company, a corporation of New York My invention relates to fiashtube' triggering circuits and-is-a continuation in part-of my copending application; SerialNumber 703,059; filed October 12, 1-946} now-aba-ndoned.-

Discharge devices=of thecold cathode-gasor mercury vapor type comonly known-inthe art as flashtubes have come into generaluse'particularly in photographic and: stroboscopic alpplicationsmainlybecause'of 'their ability. to emit high intensity illumination and to reach full intensity almostinstantaneously. usually desirable that the-device furnishilluinination only during very -shor-t increments oitime and to furnish sucha flash at any chosen instant and at any chosenrepetition rate.

Such a-device'usuallycomprises an-anode and cathode asthe main electrodes within a gastight glass enclosure in which-a smallquantity of gas or mercury in liquidfor vapor form-isplaced. A- metallic triggeringelectrode, commonly arranged in contact withthat portion of theouter surface of the glassenclosu-re nearthe cold cathode, may a-lsdbe-provided; Electrical discharge does not occur whennormal anode-to-cathode voltage is" applied, since'ionization remains sufliciently low to prevent' breakdown through the enclosed gas. However; ionizationtmay be increased sufficiently to cause discharge by sharply increasing the voltage-gradient in-the gas or a portion thereof. Sucha; voltage gradient increase causes increased ionizationsince displacement current or condenser charging current-in the dielectric consisting of the enclosed.- gas results; which current causes aditional ionization. This maybe accomplished 'by applying avoltage pulse between anode and cathode, or between triggering electrode and cathode. 'lhe required amplitude of the voltage pulse is less if a-triggering electrode is employed;

Such discharge continues as long as the anodeto-cathode voltageexceedsacritical value below which current flow stops. Thus a source of anode-to-cathode voltage capable of supplying energy and of'sharply: dropping load characteristic must be provided if fiashes of-short duration are desired. Further; a large triggering voltage must besuppliedat theinstant illumination is desired.-

Where a plurality of flashtubes are to be simultaneously dischargedit is desirable that the triggering current should notbeincreased beyond a magnitude which relativelyz small circuit making and breaking contacts, such as shutter contacts on a camera, may safely handlewith out additional rela'ying components.- At-'- the Also, it is same time, it is desirable toemploy a relatively simple controlcircuit as for single flashtube operation without employing duplicate triggering or relay circuits for the additional fiashtubes.

It is an object of my invention to provide a new and improved circuit which supplies reliable and adequate triggering voltage andadequate energy to the main discharge.

It is another object ofmy invention to-provide a new and improved circuit for a cold cathodegas or mercury vapor luminescent discharge device which is simple and compact and supplies all requirements of-the device.

It is another obj ect' of my inventionto provide an improved triggering circuit for multiple flashtube operation.

lt is a further object-of myinvention to providea fiashtube circuit arrangement for triggering of one or more slave flashtubes inresponse to the triggering of a first fiashtube.

Aecordingto my invention, I- employ in a-circult for producing light by adirect current discharge through one or more flashtubes, a saturable' core inductance-device connected inseries 5 between the direct current source and the flashpended claims.

tube load, together with" a; switching arrangementfor suddenl impressing a part or allof the voltage of thesource across the inductance device. Due to the initially high permeability of the inductance devicecore, very littlecurrent fiowsthrough the inductance device after the voltage is impressed untilthe core saturates, thus terminating the voltage pulse. This voltage pulseisemployedto trigger one or more flashtubes, the: inductancedevice being so designeddrawings inwhich Fig. 1 represents a'fiashtubetriggering and supply c-ircuitembodying my invention, and Figs. 2-. 3, and-a5 are modiiicm tions.

Referring now to Fig. 1, a triggering anden' erizingcircuit is shown which may be energized from-an A; C. source through the primary of transformer The usual switch 2 is provided in the primar circuit of t iSfOlZ'liSl" i 1201' energization or deenergization o the circuit. A voltage doubler rectifying circuit. supp-lied by the secondary 3 or" transformer 5, consists in part of condenser rectifier d, isolating resistor E, and condenser 53 connected in series across secondary 3='i with the rectifier E5 allowing current flow in the same direction as the order in which the elements are enumerated. Another rectifier 9 is connected across the serially connected secondary 3-& and condenser {or current flow through rectifier Q from terminal of secondary 3& towards the junction between condenser 5 and rectifier 6.

When energized, terminal 3 becomes positive with respect to terminal during one-half of each cycle of A. C. voltage. During this time rectifier 9 becomes conductive and charges condenser 5 and rectifier 5 remains nonconductive. During the next half cycle terminal t becomes positive with respect to terminal 3 and rectifier 6 becomes conductive and essentially double the voltage of secondary 35 is impressed across the resistance 7? condenser ii in series. Thus, condenser 53 becomes charged to a voltage double the maximum instantaneous voltage of secondary 3- 3 ii an A. C. voltage is on transformer l for a time not less than a minimum time dependent upon the values resistance l and condenser 8.

The voltage of condenser S is made available across a series circuit consisting of primary it of a saturable core transformer ll, condenser i i shunted by resistance l5, and a normally open switching device such as the normally nonconducting gaseous discharge tube it connected across condenser 8 with the cathode H of tube Ill connected to the negatively charged plate of condenser 23. Anode i2 of tube Iii is connected to one terminal of condenser l4. Control grid !3 of tube ill is held at zero normal bias voltage by resistor 59 connected from cathode H to grid 13. Resistor it is also part of a circuit consisting of condenser 29, isolating resistor 2|, and rectifier 22 connected in series across portion 23 of secondary 3- 1 of transformer l. Rectifier 22 is connected to allow current flow when ter minal 3 is positive with respect to terminal 4 of secondary S- l, thereby allowing condenser 28 to become charged to the maximum instantaneous voltage of coil 23 with its positive terminal connected to the junction of grid :13 and resistor l9. Condenser 2B and resistor 19 in series are shunted by a discharge keying device 24, the purpose of which will be explained. The cathode heater of tube It) may be supplied from the secondary coil 25 of transformer I.

A space discharge tube 26, such as is commonly known in the art as a flashtube, having a cold cathode 2i, anode 28 and triggering electrode 29 is employed as the controlled source of illumination. The voltage of condenser 8 is made available to tube 26 by connecting cathode El to one side of condenser 8 and anode 28 to the other side of condenser 3, the latter connection being made through the secondary winding 58 of transformer H. The trigger electrode 29 is connected to anode 28 through a resistance 39. Resistor 38 is employed to prevent sustained arcing between cathode and trigger electrode over the exterior surface of the tube, if such arc is initiated by any cause.

When the circuit is energized and key 2 1 is left open, tube l0 and tube 26 are both nonconducting. Condenser 8 is charged to a voltage equal to twice the maximum instantaneous voltage of secondary coil 34 of transformer i, as previously described. Condenser 20 is charged to a voltage equal to the maximum instantaneous voltage of secondary coil 23 of transformer i with the plate connected to grid 13 positively charged. Grid i3 is at a negative potential with respect to cathode ll of tube Ill as caused by voltage drop in resistor l9 while condenser 26 is being charged and arrives at zero potential when condenser 23 is fully charged. Tube I0 is of a type which requires a positive grid voltage to initiate a discharge through it. It has preferably a voltage rating in excess of the desired voltage charge on condenser 8, thereby preventing the possibility of loss of grid control at zero bias.

The anode to cathode Voltage on tube it is normally the full voltage of condenser 53 since no current is flowing in primary l8 of transformer ii and condenser i4 is uncharged. The anode to cathode voltage of tube 26 is also equal to the full voltage of condenser 8 since there is neither induced voltage in nor current through secondary it of transformer l1. Further, electrode is at anode potential since there is no current in resistor 38.

Actuation of key 24 drives grid it of tube l'l positively to a voltage equal to that of condenser 25 and initiates a discharge from cathode ii to anode i2. Resistor 2| prevents shorting of secondary 23 of transformer I while key 24 is depressed. It may be preferable to employ a low EC time constant in the circuit consisting of condenser 28 and resistor 19 in series to insure return of grid i3 to control status immediately after tube ill again becomes nonconducting. It is apparent that grid I3 may be controlled by other means such as an amplifier or electronic switching means without departing from the principles of my invention.

When tube it becomes conductive, a voltage appears across primary 16 of transformer ii to an amount les than condenser 3 voltage by the cathode-anode voltage of tube it) necessary to sustain tube current flow. Current then builds up in primary H3 and condenser l4 charges up. When insufficient voltage remains across tube iii to sustain current flow through it tube returns to a nonconducting status, causing current flow through it and through the primary iii to cease. Condenser M then returns to normal zero charge by discharging through the shunting resistor 15. Therefore, condenser l4 shunted by resistor constitutes automatic resetting means responsive to integrated current flow for causing the S WitCh" ing device [H to return to its normally open circuit condition.

When a D. C. voltage is suddenly applied across primary l6 as by causing tube ID to become conductive, a similar voltage appears across secondary ES whose magnitude bears the same ratio to the primary voltage as the turn ratio of transformer El. This secondary voltage adds to the voltage of condenser 8 to cause a sudden increase of voltage gradient within tube 26, thereby cans ing tube 2 5 to become conductive.

When tube 28 become conductive, the voltage across tube 26 suddenly decreases to a value just sufficient to maintain discharge through it. Thus the voltage across secondary I8 must necessarily change in direction and amount at the instant tube 28 becomes conductive. This voltage change may be considered as an induced voltage in secondary l8 caused by the initiation of current flow through it as required by tube 26. As the current flow to tube 25 increases, an induced voltage remains to an extentdependent upon the rate of chan e of .flux linkingsecondary l8, which in turn is complexly dependent upon current and the instantaneous reluctance of the magnetic circuit linking secondary I8. When tube 26 becomes fully conductive the magnetic circuit of transformer i1 is saturated as stated previously, the induced voltage of secondary I8 is consequently decreased to a small value, and secondary [8 may then be considered as a saturated reactor essentially decoupled from primary l6 and of relatively low inductance value. Energy is, therefore, supplied to tube 26 from condenser E at a voltage somewhat less than the decreasing voltage of condenser 8. Discharge of condenser 3 decrease its voltage and when this voltage becomes insufiicient to sustain discharge through tube 26, tube 26 again becomes nonconducting. Isolating resistor l prevents undue current flow in secondary 3-4 while tube H] and tube 23 are conductive.

The inductive efiect of secondary I8 may tend to prolong the discharge time of tube 26 since a current decrease through it in the range of current values below saturation current induces a voltage in secondary I8 by self induction of additive polarity with respect to the voltage of condenser 8. This may be compensated by using a smaller capacity for condenser 8 which will cause a more rapid decrease in voltage across condenser 8 when tube 26 is conducting. However, a higher voltage charge on condenser 8 should then be employed if the total energyavailable for illumination is to be the same.

The sequence described above may be repeated at any repetition rate which will allow sufficient time for recovery of proper charges on condensers 3 and 26 before the next discharge sequence occurs.

As shown in Fig. 2 a modification of a flashtube triggering circuit embodying my invention is employed to trigger a second or slav flashtube from the operation of a first or master flashtube. Accordingly, circuit terminals 3! and 32 are connected to the positive and negative terminals, respectively, of a direct current voltage source to appropriately charge a condenser 33 A resistor 34 is preferably connected in series between the condenser 33 and the voltage source to regulate the condenser charging rate as desired. A saturable core transformer 35, arranged similarly to the transformer I! in Fig. 1, has its common connection for one end of the primary winding 33 and one end of the secondary winding 3'! connected to the positively charged plate of the condenser 33. A gaseous discharge device or fiashtube 38 designed to emit light upon the passage of a substantial current between .its anode 39 and cathode at is connected in circuit with its anode connected to the other ,endof the primary winding .36 and its cathode connected to the negative- 1y charged plate of condenser 33. The fiashtube 38 has a triggering electrode 4| and is preferably of a type arranged to be triggered by a relatively low power pulse applied between its triggering electrode 4i and cathode 53 so that no gaseous discharge tube need be employed in its triggering circuit. A satisfactory voltage source for the triggering pulse may be suitably provided by connecting voltage divider resistors 42 and A3 in series across the plates of the condenser 33. The primary winding of a triggering transformer 44 is connected to the negative plate of the .con-

denser 33 and to the common connection of the voltage divider resistors 42 and 43 through a triggering condenser 45, and the secondary -wind-. ing of the triggering transformer 44 is connected between the triggering electrode 4,! and the oath-.- ode of the flashtube. The triggering impulse is provided by closing a switch 45 which is shunted across the voltage divider resistor 43, thereby impressing the full voltage of the condenser 33 across the series connected triggering condenser and primary winding of the triggering transformer 44. The resultant surge of voltage across the transformer primary is suitably multiplied in its secondary winding by the transformer turns ratio to breakdown the fiashtube .38 and initiate current flow between its main electrodes. The switch l'ii may be, for example, the contacts on the shutter mechanism of a camera, when the apparatus is employed in photographic applications.

Upon triggering of the master fiashtube 38 its anode-to-cathode voltage is reduced from substantially the full voltage of the condenser 33 to a value just sufficient to maintain discharge, thus suddenly impressing the greater part .of the voltage of condenser 33 across the primary winding 36 of the saturable core transformer 35. Accordingly, as described in the operation of the saturable core transformer I] of Fig. l, a trig.- gering voltage pulse appears across the secondary winding 3". of the transformer l1 whose :magnitude bears the same ratio to the primary voltage as the turns ratio of the transformer. A second or slave fiashtube 4! is connected to the energizing circuit with its cathode 48 connected to the negative plate of thecondenser 33 and its anode 43 connected to the end of the secondary winding 41. As previously described with respect to Fig. l the triggering electrode 58 of the slave fiashtube .41 is connected to the anode .49 through a series resistor 5|, the resistor serving to prevent the possibility of sustained arcing be tween the cathode and triggering electrode. After the core of the transformer 36 saturates, the primary and secondar windings present a relatively small impedance to current flow therethrough so that a large conductive current flows through flashtubes 38 and 417 from the charged condenser 33. Since it is desired that :both flash.- tubes carry a substantial portion of the discharged current, no current limiting .orresetting circuit elements corresponding to the condenser l4 and. the resistor 55 in Fig. 1 are employed in series with the master flashtube ,33. Flashtubes 3? and 43 may have the same operating charace teristics, in which case it is expedient that the primary and secondary windings of the transformer 36 have the same resistance, thus assuring an equal division of current throu h the fiashtubes. The division of the current between the fiashtubes may be adjusted in anyothermanner as desired by an well-know-n means.

Since the triggering excitation for the slave fiashtube i? is derived from the discharge =circuit of the master flashtube 38, no additional load is placed on the master flashtube triggering cir cuit, and accordingly more than one slave flashtube may be readily employed. In view of the low triggering energy required for simuitaneously flashing a plurality of fiashtubes, long operating life can be obtained from relatively light switch contacts, such as may be conveniently employed in a camera shutter mechanism.

In the modification of my invention illustrated by Fig. 3 a saturable reactor is employed for 7 triggering a plurality of flashtubes, the flashtu-bes suitably being of the type having a cathode and anode as the main electrodes, and a triggering electrode designed to render the tube conductive when a voltage impulse is applied between the triggering electrode and one of the main electrodes. As shown in the figure, terminals 52 and 53 of the charging circuit are connected respectively to the negative and positive terminals of a D.-C. voltage source, and a condenser 54, shown with its positively charged plate grounded, is connected to the terminals. A master fiashtube 55 has its main electrodes connected across the condenser 54 with the winding of a saturable reactor 55 connected in series between the flashtube cathode and negatively charged plate of condenser 54. The reactor may suitably comprise a substantially closed thinly-laminated ferromagnetic core with a coil consisting of a few turns of heavy copper wire or ribbon, the reactor being arranged to saturate within a few microseconds after a direct current voltage is impressed across it. A second or slave fiashtube i is connected with its main electrodes paralleling the corresponding electrodes of the master fiashtube 55.

A suitable triggering circuit 58 for initiating the discharge in the master fiashtube 55, similar to that provided in the embodiment of my invention illustrated by Fig. 2, is employed.

When the flashtube 55 begins to conduct, substantially all of the voltage of the condenser 54 is impressed across the terminals of the saturable reactor 55. In view of the relatively steep wave front of the voltage thus impressed, the sudden drop of voltage across the main electrodes of the master flashtube 55 is readily utilized in triggering the slave fiashtube 51. Accordingly, a triggering condenser 59 and the primary winding of a triggerin transformer 60 are connected in series across the slave fiasht'ube cathode and anode terminals. The condenser and transformer winding act as a differentiating circuit, and the steep wave front of the voltage drop acros the flashtube 55 appears as a sharply peaked voltage impulse across the primary winding of the triggering transformer 60. Accordingly, a corresponding voltage pulse appears across the secondary of the trigger transformer, multiplied by the turns ratio thereof. Since the trigger transformer secondary winding is connected between the trigger electrode and anode of the slave flashtube 51, a discharge is thus initiated between its main electrodes in response to the discharge between the main electrodes of the master flashtube 55.

Inasmuch as the core of the saturable reactor 56 saturates after the flow of current through its winding, the voltage drops sharply a few microseconds after the voltage of condenser 54 is impressed across it. Accordingly, as described previously, with respect to Fig. 2, a large discharge current from the condenser 54 flows through the saturable reactor 53 and is divided between the master and slave flashtubes 55 and 5'! respectively, rendering both luminescent.

As in the embodiment described in Fig. 2, it is obvious that, without departing from the spirit of my invention, more than one slave tube may be utilized. In a physical arrangement of the slave tube 51 with respect to the master tube 55, it is desirable, of course, that the circuit connections between the slave tube triggering transformer 65 and the slave tube 5'! be relatively short, although the other conductors may be of the triggering pulse.

a substantial length without impairing the operation of the slave circuit. It is to be noted that no secondary winding on the saturable reactor 51 is utilized as in the saturable core inductance devices employed in the embodiment shown in Figs. 1 and 2.

Referring to Fig. 4, a flashtube energizing and triggering circuit 51 is provided for a master flashtube 52 similar to the master fiashtube cir cuit shown in Fig. 2, but the discharge energy for a slave flashtube 63 is provided by a separate D.-C. voltage source; A slave tube triggering condenser 64 and a triggering transformer 55 are connected in series between the anode and cathode of the master flashtube 82 for triggering the slave fiashtube 63 in a manner previously described. One satisfactory physical arrangement of the slave tube triggering components is suggested by Fig. l in that the triggering condenser 54 may be physically positioned near the master fiashtube assembly so that the relatively long leads from the other plate of the triggering condenser and the anode of the master fiashtube 62 need have no potential between them except These leads preferably an tend as a coaxial cable to the primary winding terminals of the slave tube triggering transformer 65. A separate energizing circuit 66 for the slave fiashtube 63 eliminates the need for conductors other than for triggering between master and slave fiashtubes. A surge-limiting resistor 5? is shown in dotted outline between the cable conductors near the master fiashtube unit junction and may be used to prevent dangerously high potentials at the cable terminals when the slave unit is disconnected.

In the modification of my invention shown in Fig. 5, a flashtuoe is triggered in response to a relatively weak signal, such as provided by the operation of a photo tube. Again input termi nals 63 and 69 of the flashtube energizing circuit are arranged to be connected to the negative and positive terminals, respectively, of a direct current voltage source. A condenser it is connected across the input terminals so that it may be suitably charged to provide a discharge current between the main electrodes of a flashtube H. A saturable reactor 72 is connected in series between the negatively charged plate of the condenser l0 and the cathode of the fiasl1- tube H, and the discharge circuit is completed by connecting the positively charged plate of the condenser it to the fiashtube anode.

A gaseous discharge device 13, such as a thyratron which may be triggered by a sufficiently positive signal applied to its grid or control electrode, is connected in parallel with the fiashtube ll, through a current limiting and resetting circuit comprising a condenser 14 shunted by a resistor 15. Substantially the full voltage of the condenser lfi is impressed across the saturable reactor 12 when the thyratron I3 is rendered conductive, and a differentiating circuit comprising a condenser 15 and the primary winding of a triggering transformer ll, is connected in the manner previously described with respect to Fig. 3, to provide a positive triggering impulse in the secondary winding of the triggering transformer T1. Since the secondary winding is connected between the triggering electrode and anode of the flashtube H, the flashtube is rendered conductive upon the firing of the thyratron 13.

To provide a control voltage for triggering the thyratron l3, 9. pair of voltage divider resistors 18 and 19 are connected in series across the con- '9 'd'enser 10. -Aiphoto'tubeiilfl is employed as 1 acircuit closing means and is connected in series with a "dropping resistor 81 havinga very'high ohmic value, the iphototube anddroppingresistor being shunted around-the voltage divider resistor 19 to place a potential across the phototube. The phototube cathode is coupled to the grid of the thyratron 13 through a condenser 82 which transmits a positive triggering pulse to the grid when the phototube is suddenly rendered conductive'and its cathodethereby made more positive. Conventional-negative bias is provided for thethyratron 13 by a grid-biasingreSiStr 83 connected between-the thyratron grid and the oathode of the flashtube 1|,anda resistor 8 connectedbetween the thyratron'cathode and flashtube anode. This modification of my invention as shown in Fig. 5, has a special utility as an independent slave flashtube unit in that the photo- .tube .80 may be arranged to conduct in response tothe-light flash-from airemote master fiashtube.

'In-each-of the modifications described, I have utilized the peculiar non-linearcharacteristic of asaturable reactor so that a high impedance is presented to'asteep wave front of a suddenly impressed voltage for providing a triggering pulse and a relatively low reactor impedance is presented after saturation of the core to permit a substantial discharge current through the series circuit. It will be understood that numerous modifications vmay'besmade by those skilled in the art without actuallydeparting from the invention. .I, therefore, aim in the appended claims to cover all such equivalent variations as come within the .true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent is:

-1. In combination, a condenser, means for charging said condenser, a space discharge tube possessing an anode, cathode and triggering electrode, nieansincluding an impedance connecting said triggering electro'de'to said anode, a Winding possessing a saturable .core, means connecting said discharge tube from cathode to anode across said condenser in series with said winding, and ineansfor inducing a voltagepulse in said winding in additive polarity with respect to the charge on said condenser for triggering said discharge tube.

2. In combination, a condenser, means for charging said condenser, a space discharge tube possessing electrodes including an anode and a cathode, a winding possessing a saturable core, means connecting said discharge tube from cathode toano'de across saidcondenser in serieswith said winding, means'for inducing a voltage 'pul'sein said winding in additive polarity with respect'tothecharge on said condenser for triggerings'aid dischargetube.

3. In "combination, a condenser, means for charging saidcondenser, a saturable core transformer possessing 19, primary and a secondary winding, first circuit means including a switch adapted to cause a short current pulse through the primary of said transformer upon actuation of said switch, a space discharge tube possessing electrcdesdncluding an anodeand acathodasecond circuit means adapted to connect said discharge tube across said condenser and the secondary winding of said transformer in series thereby utilizing the transient voltage in said secondary winding caused by a short current pulse in said primary to trigger said space discharge tube andeallowingsdischarge of said condenser through said discharge tube.

'10 4. In combination, D.-C. energy storing means, means for supplying energy intermittently to said storing means, a saturable core transformer having at least two windings, normally open switching means, circuit means connecting one winding of said transformer and said switching means in series across said energy storing means, means for actuating said switchin means to closed condition, automatic resetting means responsive to integrated current-flow through said switching means for returning said switching means to normal open condition, a cold cathode space discharge tube possessing electrodes includinga cathode and an anode, and means connecting a second winding of said transformer and said space discharge tube in series across said energy storing means.

5.111 combination, an electrical condenser, means for intermittently charging said condenser, a saturable core transformer possessing at least two windings, a thermionic gaseous discharge tube possessing a cathode, anode, and control grid, means oonnectingsaid condenser, a windingof'said transformer and said gaseous discharge tube in series relationship, means controlling'the grid of said-gaseous discharge tube,

automatic resetting means responsive to the integrated current flow through said gaseous discharge tube for causing said tube to-become nonconducting, acold cathode space discharge tube possessing electrodes including a cathode 1 and an anode, and means connecting a second Winding of said transformer and said cold cathodedischarge tube in series acrosssaid-condenser.

6. An energizing-circuit fora flashtube comprising a- D.-C. voltage source connected-tosustain a flow of current through the fiashtube, a saturable core transformer having its secondary series connected in thecircuit between the flashtube and said source, and meansto apply a voltage impulse to the primary of said transformer of proper polarity to induce a voltage in the secondary having a polarityadditive to that of said source.

7. An energizing circuit for a, flashtube comprising acapacitor-connected between the oathode and anode of the flashtube, a saturable core transformer having its secondary series connected in the circuit between the flashtube and said capacitor, means for charging said capacitor to a -D.-C. voltage sufiicient to sustainbut notto initiate current through the fiashtube, and means toapply a Voltage impulse to the primary of said transformer of proper polarity to induce a voltagein the secondaryhaving a polarity additive to that of the capacitor voltage.

-8. An energizing circuit for a flashtube comprising a capacitor, circuit means for connecting said capacitor between the cathode and anode of the flashtube, a saturable core transformer having its-secondary series connected in the circuit between the fiashtube and said capacitor, means-for charging said capacitor to a D.-C. voltage sufiicient to sustain but not to initiate current through the 'flashtube, and switching means adapted upon actuation to suddenlyconnect the primary of said transformer across said capacitor, the relative polarities of the transformer primary and secondary being such that upon actuation of theswitchingmeansa voltage is induced in the secondary having a polarity additive to that of thecapacitor voltage.

9. An energizing circuit fora :flashtube comprising a capacitor connected between the oathode fiand anode of the flashtubaa saturable core transformer having its secondary series connected in the circuit between the fiashtube anode and said capacitor, means for charging said capacitor to a D.-C. voltage sufiicient to sustain but not to initiate current through the flashtube, and switching means adapted upon actuation to suddenly connect the primary of said transformer across said capacitor, the relative polarities of the transformer primary and secondary being such that upon actuation of the switching means a voltage is induced in the secondary having a polarity additive to that of the capacitor voltage.

10. An energizing circuit for a fiashtube comprising a capacitor connected between the oathode and anode of the fiashtube, a saturable core transformer having its secondary series connected in the circuit between the fiashtube and said capacitor, means for charging said capacitor to a D.-C. voltage sufiicient to sustain but not to initiate current through the flashtube, a normally non-conducting grid-controlled discharge tube connected in series with the primary of said transformer across said capacitor, and means to apply a triggering voltage to the grid of said discharge tube to make such tube conductive, the relative polarities of the transformer primary and secondary being such that upon the discharge tube becoming conductive a voltage is induced in the secondary having a polarity additive to that of the capacitor voltage.

11. In a fiashtube energizing circuit, apparatus for producing a triggering impulse comprising a first capacitor, means for charging said first capacitor, a transformer, a second capacitor, a normally non-conductive grid-controlled discharge tube, said first capacitor, the primary of said transformer, said second capacitor, and said discharge tube being series connected in a closed circuit loop, a resistor connected in parallel with said second capacitor, and means to apply a triggering voltage to the grid of said discharge tube to make such tube conductive.

12. An energizing circuit for a flashtube comprising a first capacitor connected between the cathode and anode of the flashtube, a saturable core transformer having its secondary series connected in the circuit between the fiashtube and said capacitor, means for charging said first capacitor to a D.-C. voltage sufficient to sustain but not to initiate current through the fiashtube, a second capacitor, a normally non-conductive grid-controlled discharge tube, said second capacitor and the primary of said transformer being connected in series in the order named between the anode of said discharge tube and one plate of said first capacitor, the other plate of said first capacitor being connected to the cathode of said discharge tube, a resistor connected in parallel with said second capacitor, and means to apply a triggering voltage to the grid of said discharge tube to make such tube conductive, the relative polarities of the transformer primary and secondary being such that upon the discharge tube becoming conductive a voltage is induced in the secondary having a polarity additive to that of the first capacitor voltage.

13. In combination, a flashtube having a cathode, anode, and triggering electrode, a resistor connecting the fiashtube anode and triggering electrode, a first capacitor having one of its plates connected to the fiashtube cathode, a saturable core transformer having its secondary connected between the other plate of said first capacitor and the fiashtube anode, means for charging said first capacitor to a D.-C. voltage sufficient to sustain but not to initiate current through the flashtube, a second capacitor, a normally nonconductive grid-controlled discharge tube, said second capacitor and the primary of said transformer being connected in series in the order named between the anode of said discharge tube and one plate of said first capacitor, the other plate of said first capacitor being connected to the cathode of said discharge tube, a first resistor connected in parallel with said second capacitor, a second resistor connecting the grid and cathode of said discharge tube, a source of negative voltage relative to the discharge tube cathode, a third capacitor connected between said source of negative voltage and the discharge tube grid, and switching means adapted upon actuation to suddenly short out the negative voltage applied to said third capacitor, So that the grid of the discharge tube is driven positive and the tube becomes conductive, the relative polarities of the transformer primary and secondary being such that upon the discharge tube becoming conductive a voltage is induced in the secondary having a polarity additive to that of the first capacitor voltage.

14. in combination, a fiashtube having a cathode, anode, and triggering electrode, a resistor connecting the fiashtube anode and triggering electrode, a first capacitor having its first plate connected to the fiashtube cathode, a saturable core transformer having its secondary connected between the second plate of said first capacitor and the fiashtube anode, a first voltage source connected to charge the first capacitor with its first plate positive relative to its second plate, secon capacitor, a normally non-conductive controlled discharge tube, said second capacitor and the primary of said transformer being connected in series in the order named between the anode of said discharge tube and the first plate of the first capacitor, the cathode of said discharge tube being connected to the second plate of the first capacitor, a first resistor connected in parallel with said second capacitor, a second resistor connecting the grid and cathode of said discharge tube, a second voltage source adapted to supply a voltage negative with respect to the cathode of said discharge tube, a third resistor and a third capacitor connected in series in the order named between the second voltage source and the grid of said discharge tube, and switchng means adapted upon actuation to suddenly establish a short circuit connection between the plate of the third capacitor connected to the third resistor and the cathode of the discharge tube, so that the grid of the discharge tube is driven positive and the tube becomes conductive, the relative polarities of the transformer primary and secondary being such that upon the discharge tube becoming conductive a voltage is induced in the secondary having a polarity additive to that of the first capacitor voltage.

15. An electric circuit comprising a saturable core inductance device and a switch connected in series, means for applying a voltage across said series-connected inductance device and switch in order to impress an impulse voltage across said inductance device when said switch is closed, a gaseous discharge device having electrodes including a pair of main electrodes, means for applying a voltage between said pair of main electrodes, and means responsive to said impulse voltage for rendering said discharge device conductive.

16. An electric circuit comprising a saturable core inductance device and a first gaseous discharge device connected in series, means for applying a unidirectional voltage across said seriesconnected inductance device and first discharge device, means for rendering said first discharge device conductive to impress an impulse voltage across said inductance device, a second gaseous discharge device having a pair of main electrodes, means for applying a unidirectional voltage across said pair of main electrodes, and means responsive to said impulse voltage to render said discharge device conductive.

17. An electric circuit comprising a saturable core inductance device, a first gaseous discharge device, an energy storage means, circuit means for connecting said inductance device and said first discharge device in series across said energy storage means, means for charging said energy storage means to a D.-C. voltage sufficient to sustain but not to initiate current through said first discharge device, means for rendering said fi st discharge device conductive to apply an impulse voltage across said inductance device, a second gaseous discharge device having a pair of main electrodes, means for applying a voltage across said pair of main electrodes, and means responsive to said impulse voltage for rendering said second discharge device conductive.

18. In a fiashtube circuit, a triggering circuit comprising a saturable core inductance device and a switch connected in series, means for applying a unidirectional voltage across said seriesconnec ted inductance device and said switch in order to impress an impulse voltage across said inductance device upon the closing of said switch, and means responsive to said impulse voltage for rendering said flashtube conductive.

19. An energizing circuit for a plurality of gaseous discharge devices each having a pair of main electrodes which comprises a saturable core inductance device, a circuit means for connecting said inductance device and the main electrode of one of said gaseous discharge devices in series, means for applying a unidirectional voltage across said series-connected inductance device and first discharge device, means for rendering said one of said discharge devices conductive to apply an impulse voltage across said inductance device, and means responsive to said impulse voltage for rendering another of said discharge devices conductive when its main electrodes are connected to a voltage source.

An energizing circuit for a flashtube comprising a capacitor, a saturable core inductance device connecting one terminal of said capacitor to the a of said fiashtube, a gaseous discharge device, said discharge device being connected to said capacitor through said inductance device, means to trigger said discharge device to cause a pulse of voltage in said inductance device, said flashtuce being arranged for triggering in response to such voltage pulses, said inductance device core being saturated by the induction current of said fiashtube and discharge device whereby substantially the full voltage of said capacitor is applied to said fiashtube to maintain conduction therein.

21. In combination, an energy storage means, means for charging said storage means, a saturaile core inductance device, a gaseous discharge device, circuit means for connecting said inductance device and said first discharge device in series across said energy storage means, means for rendering said first discharge device conductive to impress an impulse voltage across said inductance device, a second gaseous discharge device connected across said energy storage means in series with said inductance device, and means responsive to said impulse voltage for rendering said second discharge device conductive.

22. In combination, a plurality of gaseous discharge devices, a direct current voltage source connected to said discharge devices, a saturable core inductance device connected in series between said discharge devices and said voltage source, means for rendering one or said discharge devices conductive to suddenly apply a voltage cross said inductance device, and means responsive to said sudden voltage application to initiate current flow through another of said discharge devices, at least one of said discharge devices being arranged to emit light upon the passage of current therethrough.

23. An energizing circuit for a plurality of gaseous discharge devices comprising an energy storage means, means for charging said storage means, a saturable core inductance device, means for connecting said inductance device and one of said discharge devices in series across said energy storage means, means for rendering said one of said discharge devices conductive to switch an impulse voltage across said inductance device, means for connecting said inductance device and another of said discharge devices in series across said energy storage means, and means responsive to said impulse voltage for rendering said another of said discharge devices conductive, at least one of said discharge devices being arranged to emit light upon the passage of current therethrough.

24. A flashtube energizing circuit comprising a first gaseous discharge device, a capacitor, means for charging said capacitor, said capacitor being connected to sustain a flow current through said first discharge device when sai-c device is rendered conductive, a saturable core inductance device serially connected between said first discharge device and said capacitor, means for triggering said first discharge device for suddenly impressing at least part of the voltage of said source across said inductance device, and means responsive to said impressing of said voltage to trigger a second gaseous discharge device, at least one of said discharge devices being arranged to emit light upon the passage of current therethrough.

25. An energizing circuit for a fiashtube comprising a unidirectional voltage source connected to sustain a flow of current through the fiashtube, a saturable core inductance device serially connected between said fiashtube and said source, a gaseous discharge device, said discharge device being connected to said voltage source through said inductance device, means for rendering said discharge device conductive to establish a sudden change of voltage across said inductance device before saturation thereof, means for rendering said fiashtube conductive in response to said sudden change of voltage, said inductance device being saturated, by the conduction current of said fiashtube and said discharge device therethrough whereby substantially the full voltage of said source is applied to said discharge device and said flashtube.

26. An energizing circuit for a plurality of fiashtubes comprising a unidirectional voltage source connected to sustain a fiow of current through said fiashtubes, a saturable core transformer having its primary winding serially connected in circuit between a first or said plurality of fiashtubes and said source and having its secondary winding serially'connected in circuit be tween a second of said fiashtubes and said source,

means for rendering said first of said flashtubes conductive to thereby apply a voltage impulse to the primary winding of said transformer of proper plurality to induce a voltage in the secondary winding having a polarity additive to said source.

27. An energizing circuit for a plurality of fiashtubes comprising a condenser, means for charging said condenser to a voltage sufficient to sustain a fiow of current through said fiashtubes, a saturable core transformer having its primary winding serially connected in circuit between a first of said flashtubes and said source and a secondary winding serially connected circuit between a second of said flashtubes and said source, and means for rendering said first of said fiashtubes conductive to thereby apply a voltage impulse to the primary winding of said transformer of proper polarity to induce a voltage in the secondary winding having a polarity additive to said source.

28. In combination, an energy storing means, means for supplying energy to said storing means, a saturable core transformer having at least two windings, a first gaseous discharge device, circuit means connecting one winding of said transformer and said first gaseous discharge device in series across said energy storing means, a second gaseous discharge device, circuit means connecting a second winding of said transformer and said second discharge device in series across said energy storing means, and means for rendering said fi t gaseous discharge device conductive to thereby apply a voltage impulse to the primary winding of said transformer of proper polarity to induce a voltage in the secondary winding havin a polarity additive to said source.

29. In a flashtube energizing circuit, apparatus for producing a triggering impulse in the secondary winding of a triggering transformer comprising a first capacitor, means for charging said first capacitor, a saturable reactor, a normally non-conductive grid-controlled discharge device, said first capacitor, said reactor, and said discharge device being serially connected in a closed circuit loop, means for applying a triggering voltage to the grid of said discharge device to render said discharge device conductive, and a differentiating circuit comprising a serially connected second capacitor and the primary winding of said triggering transformer connected in parallel with said discharge device.

30. An energizing circuit for a plurality of fiashtubes comprising an energy storage means connected to sustain a flow of current through said flashtubes, means for charging said storage means, a saturable reactor serially connected between said fiashtubes and said storage means, means for rendering one of said fiashtubes conductive to cause a sudden change of voltage across said reactor before saturation thereof, means for rendering another of said fiashtubes conductive in response to said sudden change of voltage, said inductance device core being saturated by conduction of current of said flashtubes whereby substantially the full voltage of said source is applied to said flashtubes to cause said fiashtubes to become luminescent by the passage of current therethrough.

31. An energizing circuit for a plurality of gaseous discharge devices comprising a unidirectional voltage source connected to sustain a flow of current through said fiashtubes, a saturable core inductance device serially connected between said gaseous discharge devices and said source, means for rendering one of said discharge devices conductive to establish a sudden change of voltage across said inductance device before saturation thereof, and triggering means for rendering another of said discharge devices conductive in response to said sudden change of voltage, said triggering means comprising a capacitor and a transformer having two windings, said capacitor and one of said windings being connected in series across said one of said discharge devices, and the other of said windings being connected between a control electrode and main electrode of said another of said discharge devices, said inductance device being saturated by the conduction current of said fiashtubes whereby substantially the full voltage of said source is applied to said discharge devices.

32. An energizing circuit for a plurality of fiashtubes comprising a first capacitor, means for charging said first capacitor, a saturable core reactor, circuit means for connecting said reactor and one of said plurality of fiashtubes in series across said first capacitor, means for rendering said one flashtube conductive to impress an impulse voltage across said reactor, and triggering means responsive to said impulse voltage for rendering another of said flashtubes conductive, said triggering means comprising a second capacitor, a transformer, circuit means for connecting said second capacitor and the primary winding of said transformer across said one flashtube, and circuit means connecting the secondary winding of said transformer to said another of said fiashtubes.

33. An energizing circuit for a plurality of fiashtubes each having a pair of main electrodes and a triggering electrode, which comprises a first capacitor, means for charging said first capacitor, a saturable reactor, circuit means for connecting the main electrodes of at least one of said plurality of fiashtubes across said first capacitor through said reactor, means for triggering said one fiashtube to thereby impress an impulse voltage across said reactor, and triggering means responsive to said impulse voltage for rendering another of said fiashtubes conductive, said triggering means comprising a second capacitor, a transformer having a primary and secondary winding, circuit means for connecting said second capacitor and the primary winding of said transformer across said one flashtube, and circuit means connecting the secondary winding of said transformer between one of the main electrodes and the triggering electrode of said another of said flashtubes.

34. An energizing circuit for a plurality of flashtubes comprising a first capacitor, means for charging said first capacitor, a saturable core reactor, circuit means for connecting each of said plurality of flashtubes across said first capacitor in series with said reactor, means for rendering said one of said plurality of fiashtubes conductive to impress an impulse voltage across said reactor device, and triggering means responsive to said impulse voltage connected to render another of said flashtubes conductive, said triggering means comprising a second capacitor and a transformer with circuit means for connecting said second capacitor and a winding of said transformer across said one fiashtube.

HAROLD W. LORD.

No references cited.

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