US2906924A

US2906924A - High-frequency spark device

Info

Publication number: US2906924A
Application number: US771116A
Authority: US
Inventors: Frungel Frank
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-11-02
Filing date: 1958-10-31
Publication date: 1959-09-29
Anticipated expiration: 1976-09-29

Description

Sept. 29, 1959 F. FRUNGEL 'HIGH-FREQUENCY SPARK DEVICE 4 Sheets-Sheet 1 Filed OCT.. 31, 1958 u mw. vm mm Nm.

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Abri..

Sept. 29, 1959 F. FRUNGx-:L

HIGH-FREQUENCY SPARK DEVICE 4 Sheets-Sheet 2 Filed Oct. 51, 1958 Sept. 29, 1959 F. FRUNGEL 2,906,924

HIGH-FREQUENCY SPARK DEVICE Filed Oct. .'51, 1958 4 Sheets-Sheet 5 ,d WWA- Sept. 29, 1959 F. FRUNGEL HIGH-FREQUENCY SPARK DEVICE 4 Sheets-Sheet 4 Filed 001'.. 3l, 1958 United States Patent Oil-ice 2,906,924 Patented Sept. 29, 1959 HIGH-FREQUENCY SPARK DEVICE Frank Fringel, Hamburg-Rissen, Germany Application October 31, 1958, Serial No. 771,116

Claims priority, application Germany November 2, 1957 8 Claims. (Cl. 315-163) The present invention refers to high-frequency spark devices, and more particularly to such devices of this nature which are intended to produce an extremely high number of consecutive bright flashes of extremely brief duration, the pulse frequency of these flashes being either freely selectable or controlled from the outside. Se-

quences of spark dashes of the type mentioned above areV useful for the exposure of cinematographic lms, the length of the picture series being comparatively very great, or also for so-called impulse telephony.

Whenever the individual phases of rapidly changing phenomena are to be photographed cinematographically, then usually high frequency cameras are used. Cameras of this type make it possible to produce during very brief time periods a very great number of consecutive individual pictures or frames, approximately 3,000 to 25,000 frames per second. It is apparent that in such a procedure extremely high standards must be applied to the means of illumination. In some respects the prevailing requirements are met by known types of spark gap chambers. Such spark-gap chambers yfurnish very bright and also sufficiently brief flashes which is of great importance for the quality of the picture because the sharpness of the picture increases with the briefness of the light flash used for the exposure. ln addition to the above mentioned requirements of brightness and briefness the light flashes must meet still other conditions. The brightness must remain uniform throughout, and the time intervals between the individual flashes must be very constant, yet the number of consecutive ilashes during a unit of time must be as great as possible. If for instance a 16 mm. film of a length amounting to 120 meters, a length that can be accommodated in regular high-frequency cameras, is to be exposed over its entire length, then a series of flashes in the amount of about 15,000 is required. It has been found that it is quite diicult to meet all of these above conditions as far as the construction of the spark-gap chambers and also of the control devices is concerned. In order to overcome the above implied difficulties it has been proposed to arrange a plurality of spark-gaps in parallel with each other and to ignite them in consecutive order. Such an arrangement has been disclosed by Cranz-Schardien. While such an arrangement yields comparatively satisfactory results in many respects the disadvantages thereof are apparent. To mention only the most striking disadvantages, a uniform and constant brightness of the flashes cannot be obtained with a plurality of separate spark-gap chambers because a plurality thereof cannot be produced so that all of the chambers are identical in their performance. For similar reasons it is hardly possible to obtain a regular and constant spacing between the individual flashes.

It is therefore a main object of the present invention to eliminate all the disadvantages typical of the known spark-gap devices and to provide a high-frequency spark device which operates with only one single light sparkgap, which is capable of furnishing ashes of sufficient 2 brightness and briefness, and of doing this for a comparatively long period of time as a sequence of flashes of high pulse frequency.

Other objects and advantages of the present invention will become apparent from the following specification.

With above objects in mind a preferred embodiment of the invention provides in a high-frequency spark device a quenched-spark-gap chamber means filled with gas, preferably with pure hydrogen, and equipped with a series of mutually spaced spark electrodes, for instance 2() electrodes; a light-spark-gap chamber means filled with gas including a rare gas, preferably a mixture of hydrogen and argon, and equipped with spark-gap means connected in series with said quenched-spark-gap chamber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; and impulse transformer means in circuit-with said spark-gap chamber means and with said capacitive storage means for controlling the spark-discharges in said series-connected spark-gap chamber means.

It should be noted that the control of the sequence o spark discharges is, in general, made dependent upon the standard perforation of the cinematographic films, or upon the operation of the photographic shutter by means of magnetic or optical pick-up devices. Moreover, in the case of comparatively short series of ashes, the control may be exercised by means of electronic delay lines or by means of dropping weights operating contacts during the drop and thus determining time intervals with high precision. Finally, the control of the spark device may be performed by coupling it with the shutter of a drum type camera in such a manner that for every rotational cycle of the drum exactly one such series of flashes is released whereby a full use of the available length of lm is insured without the danger of pictures overlapping each other.

A high-frequency spark device according to the invention mainly comprises, for reasons of practical construction, preferably three main components or units: the spark-gap light source, the power supply unit, and the control device.

The novel features `which are considered as characteristic for the invention are set forth in particular in the ,appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figure l is a schematic diagram of the light source unit;

Figures 2a and 2b illustrate in the form of a schematic diagram a power supply and control arrangement; and

Figure 3 illustrates as a schematic diagram in greater detail a modified embodiment of a power supply and control device.

Referring now to Figure l, a high frequency flash lamp according to the invention mainly comprises two separate spark-gap chambers, which may be each an assembly of a cylindrical body with end pieces or may be integral vessels which are sealed by application of heat like bulbs. The chamber 1 constitutes the lightspark-gap chamber and serves for the emission o f light. It is filled with a rare gas or a mixture of gas, preferably a mixture of hydrogen and argon, while the unit 2 is a quenched-spark-gap chamber, preferably of Ythe type having a great number of individual electrodes, 20 for instance, and is lled with substantially pure hydrogen. The electrodes 3 of the unit 2 are made of .pure ,electrolytic copper with .the ,purpose ,of providing hydrogen and argon.

for good cooling. The two spark-gap chambers are connected in series with each other and are connected with a condenser battery C1 to CS, the condensers of which may be put to operation selectivelyby means of the individual switches S1 to S5 so that the available capacity in the operation of the device can be adjusted to particular requirements regarding the characteristics of the desired ashes and to the ash frequency. The condensers C1 to C5 are preferably made by coiling a material known by the name Styroex, the coiled layers being firmly pressed one upon the other and surrounded with a conductive cylindrical member which is capable of compensating for the self-inductivity of the coil and may be used directly as a terminal for connecting the condenser in the circuit. Both spark-gap units 1 and 2 are controlled by means of a common igniting or impulse transformer 4 which however may also be sub- 'divided into two separate transformers, and which is supplied with energy from the control device described further below. The transformer 4 supplies from its secondary winding which is sub-divided energy to the spark-gap arrangement 2 via a plurality of condensers C6 to C9 connected to selected interspaced electrodes 3. At the same time the transformer 4 feeds via the condenser C10 a special igniting electrode S of the spark-gap chamber 1 with steep impulses the energy peak whereof should be at least about 200 kw. If the device is to be operated at very low spark frequencies then the quenchedspark-gap chamber 2 can be short-circuited by means of a switch S6 whereby simultaneously only the condenser C9 remains connected with the electrode 5 in the lightspark-gap chamber 1. In this case only the one end portion 4 of the impulse transformer 4 remains operative and the operation of the device may be carried out in the same manner as ordinary single spark devices or stroboscopes are operated because in-the case of pulse frequencies below 1,000 c.p.s. the time required for deionization characteristic of the spark-gap chamber 1 is by itself suflicient for insuring a satisfactory performance.

In the quenched-spark-gap chamber 2 the individual velectrode discs 3, which as stated above have excellent Acooling capacity, are spaced extremely closely to each other so that, since this unit is lled with hydrogen, a gas of high thermal conductivity, the time for deionization amounts only to usec. Using this type of a quenched-spark-gap chamber pulse frequencies of up to about 200,000 flashes per second can be obtained.

It is to be noted that here the rst time it is proposed to provide a quenched-spark-gap chamber which is controlled in its performance by suitable control means.

It is advisable that the type of gas filling, gas pressure in the light-spark-gap chamber 1 as well as the spacing of the electrodes therein are chosen in such a manner that it is possible one-half or even more of the entire energy put through this chamber is consumed therein. However, in the quenched-spark-gap chamber 2 only just so much energy turnover should take place that the full blocking potential is maintained.

In operation, the cooperative action of the two sparkgap chambers is the following: due to the difference between the characteristics of the gas fillings therein, the quenched-spark-gap arrangement 2 assumes immediately after the sparkover a condition in which conductivity between the spark electrodes is entirely eliminated because of the very brief time required for deionizing the varea so that any flow of energy is discontinued, however -at the same time, the light-spark-gap chamber 1 will still contain ionized gas because of the greater time required for deionization of the gas mixture containing In particular, as the impulse transformer is energized and ignition effected both spark-gap chambers are abruptly ionized, the faster acting hydrogen is rendered conductive by freeing electrons more .rapidly than the rather sluggish light emitting rare gas in the light-spark-gap chamber 1, so that the internal resistance existing in the quenched-spark-gap chamber 2 collapses extremely rapidly whereafter the entire available energy concentrates in the light-spark-gap chamber 1. In consideration of the acoustic phenomena connected with spark discharges and in view of the high current peaks ranging up to more than 5,000 amperes, it is advisable to use chambers of substantially cylindrical or similar symmetrical form and assembled from a cylinder made of hard glass or quartz and suitable end pieces, so that this assembly is capable of resisting the veryV strong detonation-like sound waves emanating from the spark, while integral vessels sealed otf by fusion easily suffer damage under such circumstances. However, this does not mean that the latter type of chambers could not be used.

The parallel-combination of a condenser C10 with a resistor R1 serves to separate the general circuit arrangement from the igniting electrode 5 so as to prevent the strong discharge currents immediately following the ignition from discharging at least partly into the impulse transformer 4 which would be highly undesirable. The circuit shown by Figure l also contains auxiliary terminals 6 which may be used for connecting to this circuit variable condensers in addition to the shown condensers of the circuit, in order to deal with extremely high pulse frequencies or with extremely bright single ashes. The entire spark lamp arrangement comprising the two series-connected spark-gap chambers 1 and 2 and the other components shown in Figure l there may be connected with a power unit furnishing high voltage and with a control unit by means of a plug connection 7 having a plurality of bushings and which therefore is capable of being connected with a connecting cable leading to the other units. tically any length because the actual length of the cable is not critical provided that the input arrangement leading to the transformer 4 as well as the output arrangement at the other end of the cable is accurately adjusted to the impact wave resistance of the cable.

Figures 2n and 2b illustrate, taken together, the combination of a high-frequency power supply unit and a control unit. The circuits of Figures 2a and 2b are to be regarded as being inter-connected by connecting the terminals a, b, c, d, e and f of Figure 2b with terminals p, q, r, s, t, and u of Figure 2a in the following manner: a--p, b-q, c-r, d-t, f-u, or, faculative, e-p instead of a-p.

Referring now specifically to Figure 2a, the most important component of the control unit is the tube T1 which is a hydrogen filled thyratron of conventional type, which however in contrast to its usual arrangement, is here connected with a grid choke L1 connected in parallel with an attenuating resistor R2 which has a resistance equal to about four times the value of a periodic limiting resistance of the choke L1. The control grid of the tube T1 which is ordinarily kept at a negativepotential is therefore caused by abrupt impulses to change to a positive condition. However, the resonant frequency of the series combination of the choke L1 and the capacity of the grid of the thyratron T1 is so dimensioned that after a brief interval, within 1-10 frsec., for instance 4 lisce. already a strong negative impulse follows on account of the passing of the wave curve through zero, within the inductance, whereby the grid potential is pushed to a value of approximately -500 volts. Hereby the plasma existing between cathode and grid of T1 which was formed by the preceding positive impulse, is extinguished or eliminated electrostatically. Surprisingly it has been found that by this arrangement and operation the peak frequency by a hydrogen filled thyratron can be increased to about tenfold value of the peak frequencies ordinarily assigned to tubes of this type. In order to limit the current in the anode circuit of the hydrogen thyratron T1 a very smallinductance member 12 is connected in said anode Such cables may have prae-` circuit where it `has Aonly .the ,function vof :a safety deyice. The group of condensers C11 and C12 which can be put into circuit in a selectable manner, are to be of ythe frequency responsive type and discharge after `the ignition of the thyratron T1 across the impulse transformyer 8 which has a tap from where a connection leads to the cable connecting this unit with the vimpulse transformer 4 of the device illustrated VbyFigure l. The tap of transformer S is so positioned and selected with re- .spect to impedance conditions, 'which can be checked by taking an oscillograph observation, so that no reflections zappear at the cable connection .and that an accurate adjustment of all of the components to each other is insured. This is of great importance because any impulse -reection returning from the spark-gap units and reaching Vthe anode of the'thyratron T1 might cause this to ignite again whereby the safe-guarding effect of the choke L1 regarding the grid would be voided. To the contrary, Vthe arrangement must be provided, as shown, in such a ymanner that the adjustment of the components to each other insures that every discharge impulse of the condensers C11 and C12 is absorbed by the impedance of the cable right at the tap of the transformer 8 which :most advantageously contributes as an additional factor `to causing a prompt extinction of the spark. lt should be noted that under certain circumstances, at a spark impulse frequency of e.g., 100,600V pulses per second at medium discharge energy of only V3/100 joule stored in the condensers C11 and C12, a power supply Vof 1 kw. may be required.

The other components of the control unit, not described in detail, are more or less conventional and do not form a part of this invention. The control grid of the thyratron T1 is triggered by means of a cathode follower arrangement comprising the cathode resistor R3 of a duo-triode T2 via the condenser C13 by means of the required steep impulses. The size of the condenser C13 must be chosen in relation to the choke coil L1 and the resistor R3 in such a manner that a noticeable, but not undesirably great additional attenuation through resistor R3 vis applied to the choke L1. For the desired formation of the impulse peak it is important in this arrangement that resistor R3 and condenser C13 as well as the choke L1 jointly constitute a series resonance tuned circuit which effectively insures the steepness of the rise of the pulse. A transformer 1t) which is attenuated by resistor 4 for avoiding oscillations the coupling relation between the two tube systems is insured. The second grid of the tube T2 is controlled by a multi-vibrator stage comprising the tube T3, in such a manner that the arrangement as shown has a frequency range from l0 to 50,000 impulses per second. In all those cases in which not a fixed frequency is to be used which can be adjusted by means of the selector switches S7 and ySS and by means of the variable resistor R5, but in which a frequency is imposed from the outside, for instance by synchronization with the perforations of a synchronized strip of film so that each individual spark flash serves to eX- pose one frame or the lm, a tube T4 is connected in advance of the rest of the whole circuit. Thistube T4 ampliiies the weak signals received at the input terminals near the condenser C14 from some outside pick up device and serves to distort the signals on account of the specific characteristic of its circuit having no bias voltage'applied to the grid, in such a manner that only the negative impulses are transmitted while all positive pulses are caused to take their way via the resistor R6 and the grid to the cathode. ln this manner duplications of flashes in the case of low pick-up frequencies are prevented. The received impulses are then transmitted via the condenser C15 and undergo an amplitude limitation in the rectifier 9 where also their polarity is delinitely xed so that only suitable impulses are transmitted as outside control signals to the rest of the circuit, the selector switches S7 and S8 being positioned in alignment 436 with the stationary contacts to the far right thereof, as iindicated by dotted lines 2a.

Figure 2b is intended to illustrate the essential components of the power supply unit for the high-frequency control device illustrated by Figure 2a. It should be noted, that for practical reasons it would be unwise to to design this power supply unit so large that a continuous service in the magnitude of 1 kw. could be obtained there.- from because such a continuous service would be detrimental for the hydrogen-thyratron T 1, besides it is not possible to accommodate in a high-frequency camera film strips or" so great a length that a continuous service `could be taken into consideration. Therefore, assuming a reasonable duration of a series of igniting pulses for the hydrogen-thyratron T1, the condenser lC16 in the power supply unit should be chosen which .is just large enough, e.g. for storing energy in the amount of 500 watt seconds, that it is capable to furnish through a sufficient long period of time, e.g. one-quarter to one-half of a second, l kw. to the tube T1. vThe condenser C16 is immediately recharged by the rectifier 11 via the charging resistor R7 which is attenuated by the condenser C17 and bridged by the relay coil 12, which operates a switch contact whereby a recharging current supplied across the resistor R7 is switched olf if, e.g., a short circuit load should develop. This might occur through unintentional ignition of the thyratron T 1 due to some trouble or fault in the circuit or through an unduly long duration of a series of spark flashes of high pulse frequency. As soon as the elay l2 again closes its switch contact the condenser C16 is again fully charged. If meanwhile the reasons for the unintended ignition of the thyratron has disappeared then the continued operation of the circuit is thus made possible, otherwise the relay 12 would again operate to disconnect the circuit by opening of its switch contact. By subjecting in this manner a current-responsive relay to the anode current of a thyratron in such a manner that the relay ascertains a mean value of the current in an integrating manner over a constant period of time which corresponds to the thermal load carrying capacity of the thyratron, it becomes possible to operate a thyratron reliably in the range of pulse frequencies which otherwise could not be handled by conventional equipment.

In accordance with the invention it is however also possible to operate the tube T3 in Figure 2a'with a basically fixed characteristic frequency and to. provide for a frequency modulation in a manner known per se by varying the grid bias potential of one or both control grids of this tube. This can be done by .impressing upon this tube 'a modulating potential which may come from a low -frequency amplifier and correspond to frequencies of speech or music, said modulating potential being converted into an impulse spacing modulation. In suchV a case and under such conditions the entire high-frequency spark device could be used as a telephony transmitter for impulse telephony with visible or invisible light rays. In the case of telephony the power supply unit must be con structed so as to be able to furnish more energy because spoken sentences or the like would entail longer periods of continuous 'operation than the unwinding of a lm strip for which the whole apparatus is ordinarily designed.

In the case of telephony just discussed, the relay 12 would have to be controlled by the input of speech in such a manner that the circuit is operating by current supply and by transmitting tiashes of light, only when a modulation signal is being transmitted while during intervals of silence the circuit remains without current supply.

Figure 3 illustrates a modified example of a 'power supply and control unit according to the invention. The important component of this high-frequency power supply unit is the condenser battery C18. This battery of condensers is charged by means of a group of tubes T5 to T10 connected to and supplied by a .high voltage transformer 13 which can be operated in different steps or stages controlled by selector switches shown, kso that the condensers can be charged to different predetermined potentials. The condenserrbattery C18 thus distributes among the condensers thereof the possibly arising high peaks of energy requirements so that the first peaks will be prevented from appearing in the supplying outside power lines. This is of particular importance because usually at the same time when a series of sparks is Vstarted an additional heavy load is imposed on the power 'supply line, for instance due to the start of the very powerful camera motors. However, as soon as the camera motors have picked-up to run at their regular speed and therefore do not require a particularly high current supply, then it is again permissible to demand a larger energy supply from the power lines. It can be seen ltherefore that the condenser battery C18 serves to buffer a sudden high load on the power lines during those periods during which other devices which cooperate with the device according to the invention consume a large tamount of current. It is, however, also possible to op- 'erate with a comparatively small rectifier and to feed a 'lwhole series of flashes solely from the condenser battery C18, particularly if only comparatively very short lengths of tilm strips are being used. It has been found 'in practical experiments that for instance 500 spark flashes can be energized without any diiculty out of such a condenser battery at a voltage of 9 kv. if the condenser has a capacity of the magnitude of 100 uf.

In operation, it is important to provide the charging circuit for the condenser battery C18 with a relay 14 which is shown as being inserted in the feed line to the center portion of the transformer 13. The purpose of the relay 14 is to disconnect the circuit from the power vline in coordination with or corresponding to the thermal `load capacity of the spark light chamber means so that a 'destruction of these means through two long series of 'spark ashes at the highest energy consumption is pre- "vented. Therefore the relay 14 is so constructed that it is characterized by the same thermal lag and the same rate of cooling as the light-spark-gap chamber 1 and 'the quenched-spark-gap chamber 2. If for instance these chambers have been heated up to 200 C. and if further heating is not permissible, then the relay 14 should have reached substantially the same temperature and the switch contact of the relay should be set so that at this tempera- 'ure the relay is energized or the switch contact thereof is moved to open position. After a brief interval for lcooling off during which for instance the temperature may 'drop 20 C., it might be permissible to let another spark series of only 10% of the duration of the first series fol- 'low. In that case the relay 14 would again permit the production of such a brief series of sparks and then it vwould again disconnect. However after a longer period of time permitting greater cooling, the relay also would have cooled off sufficiently to permit again the production of a full length series of sparks. It may be mentioned that the relay 14 may be constructed in such a manner that the strong current which iiows to the transformer '13 passes a current transformer the low resistance secondary whereof is connected to a thermoresponsive rod serving as load resistor and which is surrounded by conventional insulating material as for instance rock wool, aluminum foil, ground asbestos or ground tire clay in such a manner that its thermal lag corresponds to the A thermal characteristics of the spark-gap chamber means. A further refinement of the circuit which serves to insure most eiiiciently a faultless operation of the high- :frequency spark device according to the invention, is the arrangement of the tube T11 together with its pertaining ccircuit components. This tube has the following task: ordinarily any condenser is charged via a charging resistor. When such a condenser is discharged, e.g. periodically with 1000 discharges per second, then of course the Ytime constant determined by the relation between the chargingresistor and the condenser, will be fixed at approximately j76,000 of a second. Then one can be sure -that no undesired intermediate dischargesV can occur due Ato excessive potentials. However if a very large range of frequencies of pulses is to be taken into consideration, as for instance in a device according to the invention amounting to a range from l0 to 50,000 pulses per second, then it is impossible to predetermine which frequency of pulses or discharges will be used in one or the other case. Therefore, in the present application one fixed charging resistor would be impractical. Therefore, as is shown in Figure 3, a plurality of resistors R8, R9 and R10 are provided which are all controlled by a selector switch S9 so that the selected one will determine the time constant of the discharge. As can be seen, it is also possible to provide as an auxiliary element a quenching choke 15 which insures a very slow rise of current irnmediately after the dischargel of the particular condenser and thereby also insures the elimination of the ionization in the spark-gap chambers. Still all these arrangements would not suice for preventing that between two consecutive spark flashes, e.g. at a pulse frequency of 30 kilocycles still an undesired spurious discharge takes place. Such spurious undesired flashes are very detrimental, particularly in the case of producing films which are later to be reproduced or projected as a slow motion picture because then every irregular exposure or spark picture would immediately be recognized as a fault of the lm. For this reason the tube T11 is arranged in the circuit of Figure 3, i.e., in the high-frequency power supply unit so as to be connected in the connection used for charging the condensers C1 to C5 shown in Figure 1. The tube T11 is provided with a grid bias circuit comprising the condenser C20, resistor R11 and a rectifier 20 operating across the resistor R12. The tube T11 is a thyratron filled with mercury vapor or advantageously rather with hydrogen, and is triggered from an impulse transformer 16 via the condenser C19, the transformer 16 being supplied by the connection 17 which is shielded and leads via the bushing 18 of the plug connection 19 to the high frequency control device illustrated by Figure 2a. The following is attained by this arrangement: every time the spark-gap chamber 1 is ignited, also the hydrogen-thyratron T11 is made conductive. Actually this does not occur exactly simultaneously but due to the time lag caused in the transformer 16 the ignition of the thyratron T11 occurs a brief time later. In the meantime however the spark-gap chamber 1 has produced a discharge, and the pertaining condenser is now, since the tube T11 is again conductive, recharged, but the tube T11 comes again non-conductive at the moment when the potential difference between the anode and cathode, in the case of a hydrogen-thyratron drops below 500 volts so that the condensers shown in Figure 1 are completely disconnected from the charging condenser battery C18. The same charging and discharging performance occurs again in the predetermined manner only when the thyratron T11 is ignited again.

It should be noted particularly that in this manner a very dangerous trouble that may occur in the spark devise is safely eliminated. Should it occur that in the spark-gap chamber circuit of Figure l only one condenser or no condenser at all is put into circuit then the discharge of the condenser battery C18 would, when the seriesconnected spark-gap chamber means 1 and 2 are ignited, take the form of a gigantic arc which would pass entirely through the said chambers and if it would not destroy the same but only generate a bright arc light effect on the illuminated object, the entire photographic program would be seriously affected and a possibly otherwise valuable film would be spoiled. Such an arc-like discharge is safely prevented by the arrangement of the tube T11 in the circuit because this tube becomes conductive for a very brief period only through the ignition thereof which follows immediately after a spark discharge in the sparkgap chambers. It is clear that an arc discharge across the spark-gap chambers would not furnish an impulse through the transformer 16 so that in this case the tube T11 would not be ignited. In practice the provision of the tube T11 has resulted in the great advantage that the frequency range has been extended at least experimentally to series of 150,000 spark ashes per second.

It should be noted also 4that by means of relay switch 21 the whole device can be switched into a condition of non-operability. The relay switch 21 can be made to operate by means of a switch contact S shown at the plug connector 19, so that whenever the plug is pulled out of its counterpart member no high voltage is applied to the bushing which is supposed to carry the high voltage, to the contrary, the whole device is discharged across suitable discharge resistors. It is highly advisable to provide powerful devices of this type with such additional high voltage safety devices because otherwise substantial danger of accidents would prevail.

f It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of spark devices differing from the types described above.

While the invention has been illustrated and described as embodied in high-frequency spark devices, it is not intended to be limited to the details shown, since various Vmodifications `and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and,therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a high-frequency spark device, in combination, a quenched-spark-gap chamber means filled with gas and equipped with a series of mutually spaced spark electrodes; a light-spark-gap chamber means lled with gas including a rare gas and equipped with spark-gap means connected in series with said quenched-spark-gap chamber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; and impulse transformer means in circuit with said spark-gap chamber means and with said capacitive storage means for controlling the spark-discharges in said series-connected spark-gap chamber means.

2. A high-frequency spark device as claimed in claim l, wherein said quenched-spark-gap chamber means is filled with substantially pure hydrogen gas, and said lightspark-gap chamber means is lled with a mixture of hydrogen and argon gas.

3. In a high-frequency spark device, in combination, a quenched-spark-gap chamber means filled with gas and equipped with a series of mutually spaced spark electrodes; a light-spark-gap chamber means filled with gas including a rare gas and equipped with spark-gap means connected in series with said quenched-spark-gap charnber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; impulse transformer means in circuit with said spark-gap chamber means and with said capacitive storage means for controlling the spark-discharges in said series-connected spark-gap chamber means; and a charging control device including hydrogen-filled high-speed triode means, in circuit with said capacitive storage means and with said impulse transformer means, for being ignited by a positive igniting impulse applied simultaneously with a spark-discharge in said series-connected spark-gap chamber means and capable of applying, after being ignited, a charge potential to said capacitive. storage means, timing means being connected with said triade means in such a manner that the latter becomes conducf tive and permits the re-charging of said capacitive storage means only after the ionization of the gas in said spark-gap chamber means, substantially coincident with said spark discharge, has subsided, whereby said capacitive storage means are disconnected from said seriesconnected spark-gap chamber means after every discharge therein.

4. In a high-frequency spark device, in combination, a quenched-spark-gap chamber means lled with gas and equipped with a series of mutually spaced spark electrodes; a light-spark gap chamber means filled with gas including a rare gas and equipped with spark-gap means connected in series with said quenched-spark-gap chamber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; impulse transformer means in circuit with said spark-gap chamber means and with said capacitive storage means for controlling the spark-discharges in said series-connected spark-gap chamber means; a charging control device including hydrogen-filled high-speed triode means, in circuit with said capacitive storage means and with said impulse transformer means, for being ignited by a positive igniting impulse applied simultaneously with a spark-discharge in said series-connected spark-gap chamber means and capable of applying, after being ignited, a charge potential to said capacitive storage means, timing means being connected with said triode means in such a manner that the latter becomes conductive and permits the re-charging of said capacitive storage means only after the ionization of the gas in said spark-gap chamber means, substantially coincident with said spark discharge, has subsided, whereby said capacitive storage means are disconnected from said seriesconnected spark-gap chamber means after every discharge therein; and attenuated quenching choke means, connected in circuit with the control grid of said triode means, for combining its inductive reactance with the capacitive reactance of said control grid so as to respond to said positive igniting impulse by a negative counterimpulse acting on said control grid and following said igniting impulse after a predetermined brief time interval so as to eliminate the plasma between the cathode and said control grid of said triode means.

5. In a high-frequency spark device, in combination, a quenched-spark-gap chamber means filled with gas and equipped with a series of mutually spaced spark electrodes; a light-spark gas chamber means filled with gas including a rare gas and equipped with spark-gap means connected in series with said quenched-spark-gap chamber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; impulse transformer means in circuit with said spark-gap chamber means and with said capacitive storage means for controlling the spark-discharges in said series-connected spark-gap chamber means; a charging control device including hydrogen-filled high-speed triode means, in circuit with said capacitive storage means and with said impulse transformer means, for being ignited by a positive igniting impulse applied simultaneously with a spark-discharge in said series-connected spark-gap chamber means and capable of applying, after being ignited, a charge potential to said capacitive storage means, timing means being connected with said triode means in such a manner that the latter becomes conductive and permits the re-charging of said capacitive `storage means only after the ionization of the gas in said spark-gap chamber means, vsubstantially coincident with said spark discharge, has subsided, whereby said capacitive storage means are disconnected from said series-co-nnected sparkgap chamber means after every discharge therein; attenuated quenching choke means, connected in circuit with the control'grid of said triode means, for combining its inductive reactance with the capacitive reactance of said control grid so as to respond to said positive igniting impulse by a negative counter-impulse acting on said control grid and following said igniting impulse after a predetermined brief time interval so as to eliminate the plas- Vma between the cathode and said control grid of said triode means; high-power cathode-follower type amplifier tube means, connected in circuit with said control grid of said triode means, for triggering the latter; coupling condenser means inserted between the cathode of said amplifier tube means and said control grid; and cathode resistor means connected to said cathode of said amplifier tube means in such a manner that said cathode resistor means together with said coupling condenser means conitributes to attenuate said triode means.

6. In ahigh-frequency spark device as claimed in claim '5, input means connected in circuit with said cathodefollower type amplier tube means for starting and stopping the operation of the latter depending upon input sigrials from outside control sources.

7. In a high-frequency spark device, in combination, a quenched-spark-gap chamber means filled with gas and equipped with a series of mutually spaced spark electrodes; a light-spark-gap chamber means filled with gas including a rare gas and equipped with spark-gap means connected in series with said quenched-spark-gap charnber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; impulse transformer means in circuit with said spark-gap chamber means and with said capacitive storage means `for controlling the spark-discharges in said series-connected spark-gap chamber means; and power input means `for supplying the spark device with operating power, said power input means including thermo-responsive switch means capable of acting as a coulomb counter and adjusted to the thermal load capacity of said spark-gap chamber means, for interrupting the power input when a Apredetermined amount of spark discharge energy has been including a rare gas and equipped with spark-gap means connected in series with said quenched-spark-gap charnber means; capacitive storage means in circuit with said series-connected spark-gap chamber means for feeding impulses to said series-connected spark-gap chamber means; impulse transformer means in circuit with said spark-gap chamber means and with said capacitive storage means for controlling the spark-discharges in said series-connected spark-gap chamber means; a charging control device including hydrogen-filled high-speed triode means, in circuit with said capacitive storage means and with said impulse transformer means, for being ignited by a positive igniting impulse applied simultaneously with a spark-discharge in said series-connected spark-gap chamber means and capable of applying, after being ignited, a

Vcharge potential to said capacitive storage means, timing means being connected with said triode means in such a manner that the latter becomes conductive and permits the recharging of said capacitive storage means only after the ionization of the gas in said spark-gap chamber means, substantially coincident with said spark discharge, has subsided, whereby said capacitive storage means are disconnected from said series-connected spark-gap chamber means after every discharge therein; and power input means for supplying the spark device with operating power, said power input means including thermo-responsive switch means capable of acting as a coulomb counter and adjusted to the thermal load capacity of said sparkgap chamber means, for interrupting the power input when a predetermined amount of spark discharge energy has been consumed by spark discharges in said spark-gap chamber means, and a chargeable condenser means connected with said triode means for supplying by its discharge said triode means with energy, said chargeable condenser means including timing means adjusted to a discharge time corresponding to adjustment of said thermo-responsive switch means.

References Cited in the le of this patent UNITED STATES PATENTS i 2,442,189 Bellinger May 25, 1948 2,478,907, Edgerton Aug. 16, 1949 2,700,120 Germeshausen Jan. 18, 1955 2,763,812 McKinney et al Sept. 18, 1956 2,793,323 Miller May 21, 1957