US2349012A - Means for producing high frequency oscillations in illuminating electronic dischargelamp devices - Google Patents

Description

c. CSPAETH MEANS FOR PRODUCING HIGH FREQUENCY OSCILLATIONS IN ILLUMINATING ELECTRONIC DISCHARGE LAMP DEVICES Filed June 24, 1941 2 Sheets-Sheet 1 Tim- W 25 Y a ELK "as avg s2 IN V EN TOR.

C. SPAETH May 16, 1944.

v 2,349,012 MEANS FOR PRODUCING HIGH FREQUENCY OSCILLATIONS IN ILLUMINATING ELECTRONIC DISCHARGE LAMP DEVICES Eiled June 24, 1941 2 Sheets-Sheet 2 IN VEN TOR.

assesses May is, raceattach MEANS F 3 PRODUCING HIGH FREQUENCY OSCILLATIQNS IN 'HiLUIiIINATING ELEC- TRUNEC DISOHARGELAIVW DEVICES Charles Spaeth, Mamaroneck, N. Y. Application June 24, 1941, Serial No. 399,450

(01. sis-5246) A r 9 Claims.

This application is a continuation in part as to all common subject matter of my copending application Ser. No. 383,098 filed March 13, 1941 and relating to, Method of producing and transmitting high frequency oscillations.

The presentinvntion relates to improvements in electronic discharge devices of the high vacuum and/or gas-vapor filled type and to methods of producing low-medium, high and ultra-high frequency oscillations, by means of electronic dischar e devices herein disclosed which are suitable for radio, television, wired radio frequency transmission and other related fields.

In one aspect the invention relates to improvements in electronic discharge devices, particularly to devices used for purposes of illumination of the type involving the excitation of luminesduction tubes on low frequencies, around 60 cycles per second alternating current. At higher frequencies the rising and falling current flowing through the tube approaches values .closer together and forms a curve similar to curve 2, indicating a smaller area and also a shorter portion of the dynamic negative or falling characteristics, requiring consequently a smaller ballasting device to maintain the gaseous discharge. The curve 2 applies for operation of a gaseous electronic discharge tube with an alternating current of about 1000 cycles per second. If the frequency of the cent, fluorescent and phosphorescent materials by means of electronic or other discharges produced by new and improved types of oscillating and radiating units as disclosed in my copending application Ser. No. 383,098 filed March 13, 1941.-

Thepresent invention in one aspect alsoineludes fluorescent tubes or lamps or other electronic discharge devices used in the illuminating field embodying high frequency producing means for the purpose of increasing the luminous .eiflciency and to reduce the necessity of ballasting or stabilizing such gaseous discharge devices due to their inherent negative volt-ampere character- -istics. Fluorescent tubes, lamps or other light producing electronic discharge lamp devices of the gaseous-vapor filled type will produce visible light radiations of increased luminous efliciency and increased life as compared to present light producing electronic discharge lamps or tubes if energized with high frequency currents. K

The increase in luminous efliciency of gaseous conduction tubes of the electronic discharge type is partly due to the fact that the rising and falling current, if plotted in a voltage versus current diagram, describes a loop area for both periods of the supplied alternating current flowing through the lamp similar to the hysteresis curve in the magnetisation of iron, representing a loss of alternating current approaches radio frequency, the rising and falling current flowing through the tube during one cycle approaches values very close together and the curve resembles the line 3, which represents a pure ohmic resistance. If the frequency of the supplied alternating current energizing the fluorescent gaseous conduction tube is sufficiently high, current will flow mostly on the outside of the ionized positive gas-vapor column due to the skin efiect, the column representing a current carrying conductor. Because the outside of the ionized positive gas-vapor column in a long fluorescent tube of the conventional structure is next to the fluorescent coating material which is attached to the inside walls of the tube, a very intense ionization of the gas-vapor particles, due to the skin-eflect, takes place in the gas-vapor layer touching the fluorescent coating material, thus assuring a maximum energy transfer from the shortwave ultraviolet radiation into the longer wave visible light radiation. Since the ionization density is higher in the gasfllm next to the tubes walls and lower in the center or the core of the positive discharge column. due to the skin-effect, less absorption of shortwave ultraenergy. Since the static volt-ampere characteristic of a gaseous discharge is of the negative or falling type a large part of the as hysteresis cycle is of the fallingportion as indicated by the curve l in Fig. 20, therefore requiring-a considerable ballasting or stabilizing means in order to maintain the gaseous discharge besides the fact that the area of the gas hysteresis cycle is comsiderable, representing a loss of energy. These conditions apply for operation of gaseous conviolet radiation from the core reaching the fluorescent material on the tube walls takes place (by travelling through the gas-vapor atmosphere) thus contributing to an increase in luminous erficiency of the tube.

Light radiating units of the fluorescent tube or lamp type constructed in accordance with the preferred embodiments of this invention have certain important and new advantages in use as compared with fluorescent tubes or lamps of the usual type. Briefly, these advantages are:

'-1. Increased radiation efflcient in lumens per watt in the visible region of the lightand ultraviolet light spectrum.

2. Better lumen maintenance during the useful life or the lamp due to less sputtering and evaporation of the electrodernaterlal and blackening oi the tube or bulb.

approaching radio-frequencies.

3. Easy starting of the gaseous electronic discharge tube or lamp on low voltage circuits of the conventional 120 volt line voltage type, due to the high frequency oscillations produced within the tube or lamp.

4. Reduction of ballasting devices, necessary in the usual type of gaseous discharge devices, due to their inherent negative volt-ampere characteristics. By interposin into the discharge path of a gaseous electronic discharge device, taking place between two or more electrodes within a tube or bulb, means such as one or more diaphragms having one or more perforations or plates acting as capacity electrodes similar to a condenser, enough positive resistance is introduced into the circuit, containing the negative resistance of the gaseous discharge, to cause stabilization of the device and to reduce the usual necessary ballasting devices. This makes it possible to operate such devices embodying the new means to be operated directly from the usual current supply lines with very little ballasting means well known in the art to operate tubes of the usual type. By energizing electronic discharge tubes or lamps of the'fluorescent type, producing visible light radiations, or

other light producing gaseous discharge devices with high frequency currents instead of the usual conventional 60 cycles per second alternating current, above mentioned advantages are obtained. A greater energy and frequency conversionlfrom electrical energy into shortwave ultraviolet rad ation and into longer wave visible light radiation by means of the fluorescent, phosphorescent or luminescent materials takes place, resulting in a gain of 20% or more in. luminous efficiency (lumens per watt), if a given fluorescent tube or lamp is operated, for example, at 500 cycles per second, instead of at a frequency of 60 cycles per second of alternating current or with direct current.

Increasing the frequency of the current ener gizing the electronic discharge device causes an increase in luminous efliciency as the frequency becomes greater and values of luminous efficiencies much greater than the above mentioned increase of 20% are very easily obtainable if the frequency of the current flowing through the fluorescent tube or lamp is raised to frequencies Advantage of these facts is taken by making the fluorescent tubes or lamps self-generating high frequency current oscillators or rapid current interrupt'ers 'tudes (even complete extinction of the current between the cycles, if desired) and large power or frequency multipliers while acting at the same time as a light radiating device for illumination purposes.

Interposing into the path of the electronic discharge, taking place between one or more electrodes, means such as one or more diaphragms having one or more'perforations or plates acting as capacity electrodes and as a condenser simultaneously, the electronic discharge device may be made a source of self-generating high frequency oscillations. If the tube or electronic device is made self-rectifying at the same time. frequency are obtainable besides the fact that frequencies from several hundred cycles per second up to several thousand megacycles per second are easily obtainable. (1 megacycle=one million cycles per second.) Several thousand watts of high frequency energy of the order of several thousand megacycles are easily obtainable in the form of peaked pulses or of the sinusoidal or other shaped half wave or full wave current types.

The presence of a resonant circuit, consisting of a condenser and an inductance, permits also the easy starting of gaseous discharge devices, because high transient voltages are produced in the resonant circuit which easily ionize the gasvapor mixtures within the tube or lamp.

The voltage across a condenser, being charged, is under certain conditions in connection with an inductance very high compared against the value gas column'of the gaseous discharge tube of the.

conventional fluorescent tube having, for example in the 40 watt size a tube length of 48 inches, a tube diameter of about 1.5 inches and a useful life of about 2000 hours.

Operation of fluorescent gaseous discharge tubes or lamps with high frequency currents reduces also the sputtering of the electrodes, either of the oxide coated hot cathode type or of the thermionic type, thus reducing the deposition of electrode material on the fluorescent coating material (attached. to the tube walls) and keeping the tube walls from blackening to a considerable degree with the result of a better and higher lumen-maintenance rate during the useful life of the illuminating tube.

By placing the perforated capacity electrode or electrodes near the electron emitting hot cathodes and/or anodes within the tube, the evaporated and sputtered electrode and oxide coating materials are prevented from reaching the tube walls and are deposited on or near the capacity electrodes, which due to their perforations act simultaneously as a current-interrupter for the ionized gas column as previously disclosed.

,The result is that the evaporated and sputtered materials are kept from reaching the fluorescent coating material, attached to the tube walls, and prevents the fluorescent coating material from poisonng which greatly reduces the conversion efliciency of shortwave ultraviolet radiation into the longer wave visible light radiation. Fluorescent materials or so-called phosphors used in the manufacture of flouorescent lamps, such as calcium tungstate, magnesium tungstate, cadmium silicate and others are very sensitive to certain impurities and lose their high conversion efllaesaoio devices in suitably connected antenna circuits or wire transmission circuitspulsating or alternating high frequency currents of large power and of low-medium-high and ultra high frequencies. By interposing into the electronic discharge path capacitive and/or inductive means,- high-frequency oscillations and frequency multiplications ="are obtained.

These and other features of the invention will be best understood from the following description of certain preferred means and embodiments thereof, selected for purposes of illustration and shown in the accompanying drawings and in which,

.Figure 1 illustrates an electronic discharge device producing high-frequencyoscillations and frequency multiplication at the same time,

Figure 2 discloses in diagrammatic form the conversion of the supplied alternating current into pulsating or alternating current of higher frequency by frequency multiplication showing the wave shape before and after conversion.

Fig. 3 shows an electronic discharge device acting as a high-frequency current oscillator or high frequency interrupter producing frequency mul- 'tiplication simultaneously.

Fig. 4 illustrates a visible light radiation producing electronic discharge tube of the'fluorescent lamp type actingas a high frequency current interrupter or oscillator at the same'time.

Fig. 5 shows a modified electronic discharge tube producing visible light radiations and high frequency oscillations simultaneously.

Fig. 5A shows an enlarged-diagrammatic view of the combination condenser-electrodes acting simultaneously as a resonant circuit for frequency multiplication and as electrodes for the electronic or gaseous discharge.

Fig. 6 illustrates a modified electronic discharge tube acting as a high-frequency current interrupter and a visible light producing lamp device simultaneously.

Fig. 7 illustrates a light producing electronic discharge lamp oscillator acting as a frequency multiplier simultaneously for the purpose of increasing the luminous efllciency by energizing and ionizing the gaseous and fluorescent means of the lamp with high frequency currents.

Fig. .8 discloses a gaseous electronic discharge device capable of generating high frequency oscillations and light radiations of increased luminous efliciency. Fig. 8A showsa modified structure of the lamp device shown in Figure 8.

Fig. 9 shows an electronic device of the illuminating fluorescent tube type producing current interruptions of a high-frequency in order to raise j the luminous eiliciency.

.Fig. 10 illustrates in graphic form in a current versus time diagram the shape and form of the high-frequency current-interruptions produced by the devices shown in Figs. 8 and 9.

Fig. 11 discloses in a current-time diagram, the shape and form of the high-frequency oscillashown in Figs. 1 to 9.

Figure 12 illustrates the gaseous hysteresis cycles taking place in a gaseous conducting electronic discharge tube if energized with alternating currents.

Referring now to Fig. 1-, an electronic discharge deviceproducing high frequency oscillations and frequency multiplication at the same time is shown in diagrammatic form. A suitable source I of electric current, preferably an alternating current of low-medium or high-frequency is connected to the primary coil 2 ,which is inductively coupled to the coil 3, both coils representing a transformer. In case of low frequency alternating current, a transformer using an iron core is used while at high-frequencies, the iron core may be dispensed with. Low frequency refers to frequencies from 16 to 60 cycles per second. The alternating current source may in certain instances be replaced by a direct current source of a suitable potential if desired.

The ends of the secondary coil 3 of the transformer are connected to the two electrodes 5 and 5A of the electronic discharge device 4. The

- electronic discharge device 4 consist of a bulb or tube having two electrodes 5 and 5A placed and separated from each other at a suitable distance,

The electrodes may be of the cold or hot cathode type if a gaseous atmosphere is used within the bulb, as for example argon gas at a suitable pressure. The area of the electrodes in this case should be small as comparedto the area of the two metal-plate electrodes I and 8 in order to insure point to plate rectification of the supplied current. However thermionic electrodes either of the filament type, straight wire, coiled wire or coiled coil type may be used, employing tungsten-wire of the thoriated'type or other refractory metals, such as tantalum, molybdenum etc. Oxide coated electrodes or cathodes heated to the proper temperature in order to produce an electron emission using oxides such as barium oxides, strontium oxide, calcium oxide, thorium oxide or other suitable oxide mixtures or carbides or mixtures of bothmay be used.

If thermionic electrodes or oxide coated electrodes are used a separate source of electric current is required in order to heat the thermionic electrodes or the oxide coated cathodes to the proper temperature, the electric source for heating is indicated by the number 6 in the diagram.

Interposed between the two electrodes 5 and 5A are two metalplates I and 8, spaced very closely to each other and acting as a condenser. The spacing 9 between thesetwo metal plates should be less than the mean free path of the gas molecules at a given gas pressure in order to prevent ionization by collision of the gaseous atmosphere between the plates I and 8. This enables the two plates to act asa condenser and the shape of the plates should be such that they fit closely to the tube walls in order to prevent the gaseous discharge to leak around. Interposed between these two plates is, if desired, a plate 0 of mica to act as a dielectric for the condenser and also to prevent a discharge between the plates, a quartz crystal plate may also be used instead of a micaplate and by choosing the proper thickness of the quartz plate, it may cause the condenser and a connected circuit consisting of an inductance and capacity to oscillate at a certain frequency. The two condenser electrodes I and 8 are connected to the two antenna dipoles l0 and II or to a resonant circuit l2, comprise ing an inductance and a capacity, which may be coupled to any other circuit desired. The bulb or tube 4 is either highly evacuated or 'gasfllled and may have any suitable gas pressure from a fraction of a micron (one micron equals one thousandth of a millimeter) up-to atmosphere pressure or even above. The preferred gases used in a gasfllled bulb are inert gases, such as helium, argon, neon, krypton and xenon; metallic vapors such as those of mercury or sodium or other suitable metals may also be used. A globule H of mercury or a mercury alloy or ofsomeother metal may be located within said bulb 4. Of .course mixtures of above mentioned gases with or without metallic vapors may also be used within the bulb.

In operation of the electronic discharge device an electric current of a suitable frequency and of a suitable potential is applied between the electrodes 5 and 5A, after a suitable heating current has been passed through the electrodes 5 and IA, bringing the electrodes up to a temperature "to produce electron emission.

The supplied impressed low-medium or highfrequency voltage charges the condenser electrodes l and 8 by means of the electron streams and the ionized gas (being highly conductive) and/or metal vapor according to the polarity of the electrodes 5 and 5A acting as anodes and cathodes during a given cycle. While the charg-' ing takes place the two metal condenser plates '1 and 8 and the two antenna dipoles l and II will be caused to oscillate at their, own natural frequency, both representing a resonamt circuit comprising an inductance and capacity, thus causing the dipoles to radiate electromagnetic waves. 'When the charging voltage drops to zero,

the charged condenser plates will discharge through theionized gas, backover theelectron emitting electrodes ii and A and cause the resonant circuit again to oscillate and radiate.

' If therefore the supplied alternating current or voltage-and-frequency is very high it will cause the two condenser plates to be rapidly charged and discharged at the opposite potentials and consequently cause the antenna dipoles II and H to radiate a large-amount of energy at a very high frequency or at a very short wavelength, since the time constant for charging and discharging such a smallcondenser is extremely condenser plates I and 8, if desired, and as indi-' cated by the dotted lines in the circuit diagram to be used as a tank circuit for further frequency multiplication and to reduce harmonics.

Although the preferred shape of the supplied alternating current energizingthe electronic device is a sinusoidal shape, other shaped currents may be used, as for example triangular current shaped or rectangular current pulses. Squareor l0 rectangular current pulses are very suitable for energizing an dectronic discharge device in order topr'oduce frequency multiplication.

If therefore the electronic discharge device shown in Fig. 1' consists of a highly evacuated 5 bulb 4 instead of a gas filled bulb, rectangular or square current pulses for charging and discharging the two condenser plates 1 and 0 are obtained by impressing between the two thermionic filamentary electrodes 5 and 5A a sinusoidal alternating current having a peak voltage voltage to the voltage, producing the saturation current of the thermionic electrodes operating at a given temperature within an evacuated bulb very large, very steep sides of thesquare or rectangular current pulses are obtained, thus obtaining very short time intervals in which the voltage reaches the cut off point of saturation, thus permitting to obtain frequency multiplication ratios with suitable resonant circuits up to several millions. Fig. 2 shows a diagram in which the supplied impressed alternating current or voltage and the obtained current or voltage of multiplied frequencymre plotted as functions of time. The curve l3 represents the supplied altematinglow-medium or highfrequency 46 voltage or current.

The line I! represents the saturation current of the tube electrodes due to electron emission, indicating a conversion from a sinusoidal waveform into a square or trapezoid or rectangular wave or current form, suitable to excite and enshort. Since, the condenser charging frequency is relatively high and has been predeterminedby the frequency of the supplied impressed oscillator high frequency current, coupled to the coil 2 is a high frequency oscillator source l in this case, a large amount of energy will bestored in the condenser plate I 811d 8 although the capacity of the plates maybe small. For example, if the capacity of the plates I and 8 be 50 micromicro farads and the voltage of the charged condenser 4000 volts and the charging frequency 10 million cycles per second, about 2000 watts of energy willbe available for radiation at an extremely short wave length, since the discharge and charge time constant T=RC for 63% values islextremely short. R represents theresistance ergize by impulse excitation coupled resonant ing sinusoidal wave form is superimposed upon 05 at its d'pposite ends two electrodes ll of the type and C the capacity T represents the time. The

fact that the ionized gas-metalvapor ;medium has a' falling or negative volt-ampere characteristic, accelerates the time constant T since the internal ohmic resistance of such an ionized gas-metal vapor atmosphere is extremely small and has a variable-*value also simultaneously.

A'resonant circuit l2 comprising an inductance and a capacity may be connected to the two used in the device shown in Fig. 1, both being heated to electron emission temperatures by the electric current sources It. The tube is filled with a suitable monatomic gas or a mixture of gasesat a suitable gas pressure as previously 78 bore or perforation 2|: and 22, the two metal,

disclosed and the bulb or tube also contains if desired a globule of mercury, mercury alloy or. sodium. Interposed between said electrodes are ,two metal plates l9 and 20, each having a'small plates are spaced at such distance from each other, which is less than the mean free path of the gas molecules at a given gas pressure, so as to prevent ionization by collision of the gas molecules in the space between the plates l9 and 203. This enables the two plates to act as a contwo plate electrodes as and 2t are.also connected through the resistors 26 and 27 to the resistance IA which is connected in parallel to the electric source of current I thus permitting any potential desired to be applied to these plate electrodes, any static charges are also permitted to flow ofi through this means; if,..desired these resistors may be omitted. i

A source I of electric current of any suitable potential, either direct current or alternating current is connected across the tube it to the two electrodes H in order to energize the discharge device. The tube l6 may also be highly evacuated and be operated as a device being dependent on the pureelectron emission from the thermionic electrodes il instead of a gaseous discharge as above mentioned in connection with a gasfilled tube or bulb.

In operation of the device, a suitable. current, either direct or alternating current from the source II, will flow through one part of the resistance lA acting as a stabilizing means and through the tube it, by means of the electrodes ll emitting electrons and the ionized gas, through the perforations 2|-22 of'the condenser electrodes l9 and 23 thus establishing a closed circuit. Since the two plates Ill-20 acquire at the same time opposite charges, a plasma film of ionized gas forms in and around the perforations and increasing in size until the current is interrupted. At this time the two plates l9 and 20 act as a condenser, no discharge taking place between them due to their close spacing, which is less than the mean free path of the gas molecules at the gas pressure prevailing in the tube, and become charged therefore.

These charges will flow off through the resistors .26 and 2'! and permit the ionized discharge ,to pass again through the perforations and also close the current circuit through the tube. These current interruptions take place, according to the diameter of the perforations, gas pressure, capacity value of the condenser-plates l9-20, very rapidly and may cover a range from several hundred per second up to'several million per second and more. The voltage fluctuations between the plates 19 and 20 and acting as interrupter and condenser simultaneously are transferred to the tank circuit 25 and the antenna dipoles 23 and 24. It therefore the LC values of the tank circuit 25 are small, the resonant frequency produced in the circuit may be of increased frequency compared against the interrupter frequency. Frequency multiplication to the extent that the dipoles 23 and24 will radiate high frequency fields of the order corresponding to wavelengths of several centimeters and of large power is obtained.

As previously mentioned the operation of the device is not limited to gaseous discharges, but is also operative if a high vacuum exists within the. tube it. In this case pure electron emission from charge device to be used for illuminating purposes embodying means so as to produce current interruptions or high frequency oscillations within said lamp for the purpose to increase the luminous efliciency of said lamp. A tubular bulb or tube 23 contains at the opposite ends of'the tube two electrodes 29 similar to the ones shown in Fig. 1. Said filamentary electrodes are preferably made of highly refractory metals, such as tungsten for example and are also preferably coated with oxides of the alkali metals or rare earth metals, as for example Darius-strontiumcalcium oxides or oxides of thorium-zirconium etc. rhenium, zirconium or of other metals may also be'used or mixtures of oxides with carbides may be used. If very concentrated filamentary electungstate-etc.' The fluorescent coating 28A as in-' dicated by the dotted line in Fig. 4 is preferably on the inside of the tube. A globule of mercury 35 or mercury alloy or any other suitable metal vapor at the operating temperatureof the lamp is also provided for.

A gaseous atmosphere of a suitable pressure using monatomic gases such as argon, neon etc. is provided within the tube, although in certain instances no gaseousatmosphere is required, since the filamentary electrodes provide enough heat radiation to vaporize the mercury globule 35 and provide enough metallic vapor for the operation of the tube, thereby providing, the necessary source of ultraviolet radiation to excite the fluorescent coating material 28A by means of the ionized mercury vapor.

Interposed between the electron emitting electrodes which may be of any well known design. are the two condenser plate electrodes 34. and 33 having one or more perforations'near the centre of said plates, which fitclosely to the tube walls denser and acting as a tank circuit for frequency multiplication.

In operation of the tube, thesource of electric Carbides of metals, such as tantalum;

bilizing choke coil 3| produces a glow or are discharge between the filamentary electrodes 29 which ionizes the gaseous atmosphere and the mercury vapor between them, producing ultra- I as similarly as disclosed in the operation of the device shown in Figs. 3 or 1. The frequency of interruptions may vary from several hundred cycles per sec. up to hundred-thousand cycles per second or morefthus causing an increase in the luminous efllciency of the illuminating tube or lamp as compared against operation of the tube at theiconventional 60 cycles per second alternating current. A 40 watt fluorescent tube operated at about 500 cycles per second gives about a gainof 20%,in luminous efllciency (lumens per watt) against 50 to 60 cycles per second operation, with a corresponding increase in luminous efiiciency at'higher frequencies. The switch 36 is used for starting the tube and permits heating the electrodes up to electron emission temperature before the discharge starts, thus increasing ,the life of the electrodes. The condenser 31 in parallel to the switch reduces arcing and acts also to a certain degree as a by-pass condenser for the high frequency currents, being in shunt circuit to the tube.

Although the preferred location of the two plate electrodes 33-34 is about halfway between the twoend electrodes 29, any other locations may be chosen by moving said plate electrodes to either end of the tube to any desired location. Theplate electrodes 33 and 34 may be made of any suitable refractory material, preferably metals of high melting point and of low vapor-pressure, such as tungsten, tantalum, molybdenum etc.

Fig. 5 illustrates a modified structure of an electronic discharge device for illuminating purposes of the fluorescent tube type employing means to act as a light source and high frequency current oscillator simultaneously for the purpose to increase the luminous efllciency of the lamp. A tube 4| of a suitable length and diameter, for example having a diameter of about 2 inches and a length of about 48 inches contains at the opposite ends of the tube two electrodes 39 similar a to the ones disclosed in Fig. 4 or any other type of electrodes well known in the art of high vacuum or electronic discharge devices. The tube 4| is also provided-with a coating 40 of a fluorescent compound similar to the ones previously mentioned and indicated by a dotted line 40. A globule of mercury 43 is also provided for within the bulb. The fluorescent coating 40 may be either on the outside or on the inside of the tube, preferably on the inside.

A suitable gaseous .atmowhere of a suitable pressure is also provided for within the tube. Interposed between the electron emitting electrodes are two metalplates 42 and 43 having between them a mica plate or a quartz plate 45. The two metalplates 42 and 43 having between them, as mentioned before,'a mica or quartz plate represent therefore a condenser of a certain capacity and are of such shape and size so as to fit closely to the tube walls of the tube 4|, thereby preventing any discharge to leak by and dividing the tube into two separate chambers.

, current 39 of suitable potential through the stainductance and a condenser are connected to the two condenserplate electrodes 42 and 43. The

inductance of the resonaiit circuit 41. is preferably coupled to the inductance .46, which in series with the condenser 44, represents a shunt reso- 'nant circuit across the tube electrodes 33.

A switch 45 isconnected in parallel to the condenser 44 for the purpose of preheating the electrodes 39 to a temperature sufficient to produce electron emission before the, gaseous discharge takes place; and as soon as the gaseous atmosphere is ionized and started the discharge, the switch is opened leaving it to the discharge to keep the electrodes 39 'at'a electron-emitting temperature. A source 38 of electric current either direct current or alternating current of a suitable potential is connected across the tube electrodes 39. Very little ballasting is required; such as resistors or choke coils in the supply line of the electric current, since the two plates 42 and 43 act as a condenser, which in connection with the resonant circuit .41 represents a positive resistance to counteract the negative resistance of the gaseous electronic discharge, whichhas a falling volt-ampere characteristic. I

In operationof the tube or device, being energized from the electric source 35, a discharge takes place from one of the electrodes 39 through the ionized gas and/or metal vapor to the plate electrode 42, through the resonant circuit 41 t r the plate electrode 43 iiito the ionized gas to the electrode 39 at the other end of the tube. The two condenser-plate-electrodes- 42-43 become alternately charged to opposite potentials and discharged-if the energizingcurrent has a certain frequency, causing the resonant-circuit 41 to oscillate at its own natural frequency which is of a higher value, than the supply frequency.

The current changes in the circuit 41 are transferred by induction by means of the coil 46 to the shunt circuit 46 and 44 and are re-introduced again into the electronic discharge tube until steady operating conditions have been reached, very large voltage and current amplitudes may be obtained by means of this feed back circuit,'

favorable to excitation and ionization of the 'permit current flow at high frequencies, since a capacitive reactance of a condenser has a posi- A tank or resonant circuit 41 comprising an ture of the condenser plate electrodes 42 and 43 having special means attached thereto in,order to reduce the electrode voltage drop. The two metalplates 42 and 43 being spaced and having interposed between them a sheet of mica or a by'the properties of the 55 may be omitted or. vice versa.

I sesame quartz-crystal-plate it have attached to each plate an electrode member MB and MB of any suitable shape. These two electrode members may also be provided for with an oxide coating of high electron emission properties and in operation of the tube the discharge will maintain these two electrodes MB and MB at a temperature sufficient to produce electron emission, in the preferred type they consist of two small tungsten coils of a suitable coil diameter and pitch using a wire size small enough to heat up under the influence oi the discharge.

The two metal plates "t2 and it may a1so,have

an electron emitting coating MA and sea as previously stated, as for example, a barium azide coating and if desired the two coil electrode members MB and MB may be omitted in this case. The resonant circuit consists of an inductancedl and a condenser MA and is connected to the metal plate electrodes either as a parallel resonant or a series resonant circuit. For direct ourlil ' current is limited to a certain value and is in- ,terrupted periodically, producing current pulses rent operation of the tube a parallel circuit as shown in Fig. 5 is preferred in order to enable the direct current to flow through the inductance ll and keep the discharge going. For alternating current operation the capacitive reactance of the condenser MA is low enough to keep the discharge going in connection with the inductive reactance of the coil M in case of a series circuit connection.

, An electronic discharge device of the fluorescent ,type. used for illuminating purposes and acting as an electric current interrupter of a high-frequency simultaneously to raise the luminous efficiency, is shown in Fig. 6. The tube 5b is provided with a fluorescent coating 49 and a suitable gaseous atmosphere of proper pressure and has two electrodes M at the opposite ends of the tube. A globule 52 of mercury is also contained within the tube. Interposedbetween the two electrodes 5| is a plate or diaphragm 53 having a small perforation 54 in the centre of the plate. Said plate may be made of any suitable material, such as mica, porcelain, carbon, metal,

etc., preferably a metal plate of a highly refractory nature is desired. A source 51 of electric current of a suitable potential is connected through the wires 51A and 513 over a small inductance 55 to the two electrodes 5|, across the tube. A condenser 58 in connection with the inductance 55 acts asa shunt resonant circuit across the tube 50. In operation of the tube, being energized either from D. C.-or A. C. current of proper voltage, a discharge is producedvbetween the two electrodes 5|, which pass through the small perforation 54. The shape of the plate is such so as to fit closely to the tube walls.

An ionized plasma or gas film forms in the perforation 54 due to charges acquired by the plate 53 and causes the' diameter or the thickness of the plasma to increase or decrease and close and open the perforation for the electric dis charge current flowing through, thus causing electric current interruptions at a very high rate.

The resonant circuit consisting of condenser 56 and inductance 55 will also be utilized for the production of oscillations by being connected in shunt circuit to the tube 5|], acting as a tank circuit. 1

However it is understood that for the production of the interruptions this resonant.circuit is not necessary, that is to say only a very small inductance 55 is required while the condenser 1 Since the perforation 54 is small it has 'suflicient resistance to act as a stabilizing means for the electric charge and will permit the rise of the current flow only to a certain value, when it starts to break the current, consequently a very small inductance is required having an inductance value insumcient to stabilize the discharge if the dia:

phragm he were omitted.

' Fig. 10 shows in a diagram the current flow-v as shown in the graph or diagram. thus preventing excessive current-valiies to flow through the tube. The time constant of the circuit, the ionization and tie-ionization time, gas pressure, size of the perforation and the thickness of the diaphragm 53 are factors determining the interrupter frequency oi the current flowing through the tube.

The lamp structure shown in Fig. '1 consists of a bulb 58 having light transmitting properties adapted to be provided with a screw base or'its equivalent, so that it may be used in an ordinary lamp socket having the usual line voltage of about 120 volts. The inside wall of this bulb.

preferably being an oversized bulb to obtain a large surface area for the fluorescent or phosphorescent coating material s9 is coated with the usual fluorescent compounds as previously disclosed, colors or a white light approximating daylight. Although the actual wattage in the lamp consumed may be such that a smaller bulb would give, sufiicient wattage dissipation per square inch of bulb area, an oversized bulb is preferred to give increased coating surface area for the fluorescent or phosphorescent material and to keep the fluorescent coating sufficiently cool which is necessary for efflcient light radiation and conversion from. the ultraviolet into the visible light. The'bulb 58 contains a gaseous atmosphere of gases as previously mentioned at a. suitable pressure and a globule of mercury 68 oran alloy of mercury. Supported in the press 54, of a stem, by lead-in wires 89 and 10 are a pair of electron emitting electrodes of any well known typeypreferably a pair'ofoxide coated electrodes 63 and 64 consisting of coils of wire such as tungsten, having a fine wire coiling on x the tungsten wire core and an oxide coating thereon. The two electrodes 63 and 64 are connected to a source 61 of electric curent of a suitable potential through the lead wires 69 and 10. Interposed between the suitably spaced electrodes 63 and 64 are two metal plates BI and 62.

which are slightly separated by a sheet 60 of mica or a quartz plate acting as adielectricfor the two plates acting as a condenser. The two plates and the mica sheet are supported by the support wires 1| and 12 in the press of the stem. Connected to the two metal plates 6| and 62 by the two lead wires El and I2, is a resonant circuit consisting of an inductance 66 and a condenser 65 acting as a tank circuit for the production of high frequency oscillations and frequency multiplication. In certain instances this tank circuit may be omitted and the condenser plates 6| and 62 have sufficient capacity to act as a ballasting device and as a condenser, becoming suitably selected to produce diflerent,

oi the electric current source.

' charged and discharged at a great rate, produce current interruptions oi the electronic discharge and thus increase the luminous efllciency' oi. the lamp. It the dielectric used for the condenser plates 6i and 62 is a quartz plate or crystal of suitable ons. use is made of the piezoelectric properties oi such crystals causing said quartz plate to oscillate at its own natural frequency; producing oscillations of very constant frequency.

The modified structure oi Fig.5A

may be used in the lamp of Fig. 'l in place oi the plate-electrodes Stand '2 shown, if desired. In operation of the lamp the source. 61 of electric current I produces an ionization oi the gaseous atmosphere and mercury vapor surrounding the electrodes j364 and-the plate electrodes 88-42, causing a glow and/or arc discharge, said luminous glow producing ultraviolet radiation and excitation of I the fluorescent coating compound. The condenser plate electrodes Si and 62 being interposed into the discharge path of the two electrodes 63 and 54, resist the ion and electron flow between these'electrodes and act as a stabilizer, thus permitting the use of this lamp to be operatedwithout any further external ballasting device. The resonant circuit comprising the inductance 68 and condenser 65 connected to the plate-electrodes will be energized by the discharge andcause the current flowing through the tube to vary alternately at a regular rate. I If surrounding gaseous atmosphere is absorbed and converted into luminous radiation of the gaseousmetal vapor medium, which extends in the form oi' a luminous glow all over the bulb. Rectification between the electrodes is of course also obtained if the electrodes 63 and 80 are of the heated electron emitting type and the plate electrodes "-4! oi the cold electrode type, instead in the case of point to plate rectification in which case all electrodes may be cold electrodes;

' Fullwave rectification oi the supplied alternating current is obtained in the lamp shown in Fig. 7 and utilized tor the purpose or frequency multiplication as previously disclosed. i

The inductance 56 will permit for direct cur-Q; rent operation current flow through the lamp and cause operatingconditions as previously disclosed. As soon as the D. C. voltage is applied to the electrodes .3 and N the condenser plates "-82 and the condenser I will become charged and causethe voltage across these plates to in- .crease to twice the value oi the supplied line voltage. Ionization takes place in the gaseous medium around these condenserplates and causes discharging and lie-energizing oi the con densers with consequent current pulsations and interruptions oi a given frequency, determined by the time constants of the circuit.

It, is also suflicient to state here that the dimensions oi the two plate electrodes" and 02 76 radiating high frequency fields which due to the high conductivity of the should be such that a discharge either in the form of a glow or arc cannot take place directly 7 between the two electrodes '3 and 84, while othera wise a glow discharge between the'two charged 5 condenser plates ti and .62 through the outside surfaces facing the electrodes "-64 (no discharge being possible between the inside of the plates due to the mica sheet) should be permitted in order to discharge or de-energize the circuit consisting of the condenser plates "-42, condenser 65 and inductance 66. I

The proper spacing of the electrodes 63- from the plates 6 l-62 anda suitable gas pressure within the bulb will permit such operating conditions. Referring now to Fig. 8 a'modifled structure 0! the lamp disclosed in Fig. 7 is shown. A bulb ll I of glass or other material having light transmitting properties and a gaseous atmosphere of a suitable pressure is provided for. A quantity 0! mercury 14 or alloy is also contained within the bulb ii. The bulb II is covered either on the outside or inside with a fluorescent material hav. ing a certain coating density of fluorescent material per unit surface area of the bulb, the material being any one of the large group 01 compounds known to become fluorescent or'phoaphorescent under theinfluence of a electronic discharge or a ultraviolet radiation. A tubular stem ll supports by means of lead-wires the electrodes II and it, which may be of anywell known type, cold electrodes, hot-cathodes, direct and indirect heater type or'oi the type previously disclosed. The two electrodes 75 and 16 are connected as through the lead wires 15A and 16A to an electric source of current 19 of a suitable potential. Interposed between the two electrodes is a cylin drical cup-shaped member H which has a peroration 18 of a suitable size facing the two electrodes.' Said member ll may be provided for on the inside and outside with a barium oxide or azide compoundgin order to produce a negative glow discharge for starting of the lamp. The cup-shaped control member .ll is supported by a tight-fitting glass or isolantite insulating sleeve "A attached to the stem 13, thus shielding the electrode I6 completely from the rest 01 the bulb space, except through the perforation II. The

- member I1 is connected through a lead-wire and 5 a condenser 8| to one side of the electric source 19 at a point 8|.

In operation 01 the lamp the electric source or current 19 will produce between the two electrodes 15' and l8, which are suitably spaced, an

a plasma film 0r ionic sheath surrounding the perforation It a periodic constriction and expansion of the electronic discharge, thus causing current pulsations or interruptions of a high-lre- The cup-shaped control member ll hasfa relatively large surface area against either of the two electrodes is and 1e andproduces rectification or theelectric current, in case of A. C. current, be-

tween the electrode 16' and the member 11 in the form of a glow discharge, thus'charging the condenser it with pulsating direct current and discha sins through the gaseous atmosphere by means of the metal member 11 to either oi the electronic, glow or are discharge causing through ascents electrodes B oralt at a great rate set by the time-constant of the condenser to and the resistance of the discharge path through they gasvapor atmosphere. The control member "ii therefore receives periodic potential pulses, thus causing the plasma, film or ionic sheet, surrounding the aperture "it, to vary in size and thus cause modulation, pulsations or interruptions in the main discharge taking place between the elec trodes it and it accordingly, as previously dis closed. The condenser 8t may in certain instances be omitted and the member ll be leit open or neutral without any wire connections to any of the electrodes or to the circuit. Suificient charges acquired by the member ill! will produce a varying plasma film around and in the perforation it to producecurrent interruptions of a high-frequency as disclosed in Fig. 6.

Since both electrodes i5 and it are of the hot cathode electron emitting type they will act as anodes and cathodes alternatingly on A. C. current and permit rectification of the A. C. current relative to member "ii for charging the condenser to, which discharges consequently through the tube. As previously mentioned, the proper spacing between the electrodes, the proper size of the perforation it in the member ii, a suitable gas or vapor pressure, the capacity of the condenser 3t are the factors determining the generated frequency. The electric source it may beeither direct-current or alternating current of a suit-' able potential. The frequency generated within the lamp may vary from a few hundred cycles per second up to several hundred thousand per second or more.

8A discloses a modified structure to be used in a fluorescent lamp device as shown in Fig. 1 All parts of the electrodes and the circuit are shown for the purposes of simplicity without the bulb and are identified by the same numbers used in Fig. 14.

The electrode 16 in order to facilitate easy starting of the lamp on low voltage circuits consists of a tungsten wire coil being connected through the lead-wires 15A and B6B over a switch 832 and a small ballasting device 83 to a electric source 19 of a suitable potential.

If the switch 82 is closed an electric current flows through the electrode c011 l6 heating it to a temperature suillcient to produce electron emission and ionization oi the gas-vapor atmosphere within the bulb and as soon as this point has been reached the switch may be opened causing the electric source F9 to maintain a discharge between the electrodes ?5 and it. A rectification action takes place between the electrode it and the cup shaped electrode member it thus charging the condenser til with a direct current potential. The periodic interruption of the current flowing through the lamp is accomplished by the use of the condenser 80 and resistor 83 combination in the circuit containing the member ll, having one or more perforations I8. The condenser tll acquires a charge from the electric current source 79 through the resistance 83 as previously mentioned. Initially thevoltage across the condenser is zero, but as time goes on, the voltage across the condenser increases until at the endof RXC'microseconds, it has a value of about 63 per cent of the full line voltage value.

The charged condenser alternately discharges through the lamp, rechargesfrom the line volt age, redischarges into the lamp and so on-at a 'terruption of the current flowing between the main electrodes lb and it at the same rate.

Fig. 9 illustrates an electronic discharge tube used as a illuminating lamp of the fluorescent tube type embodying means to produce current interruptions or high frequency oscillations within said tube iorthe purpose to increase the luminous emciency. A tube 8t oiiight transmitting material is provided with a gaseous atmosphere of a suit-able pressure and contains a globule so of mercury. A coating oi fluorescent or phosphorescent material either on the inside or outside of the tube or embedded in the glass or other light transmitting material of the tube or is also provided for. Two electron emitting electrodes of the type previously described are at the opposite ends of the tube as indicated by the numbers tea and MB. One of the electrodes 35A is connected through an inductance 93 to one side of the electric source of current 9i while the other electrode 863 is connected through a resistance to the other side of the electric current source 9! of a suitable potential. A resistance 92 is connected across the current source St. A switch ti, having a condenser fit across it, is also provided for preheating the electrodes for starting purposes. member 88 having one-or more perforations t7 acting as a control electrode member is placed near or around the electron emitting electrode tthend is connected by a wire and a variable contact member to the resistance t2. Using the condenser til and resistance 95 combination in connection with the perforated control -member to, periodic interruptions of the electric current flowing through the gas and/or vaporfllled tube is accomplished. When the voltage of the source ti is connected to the tube by means of a switch, the electric source being assumed in this particular case to be direct current, the condenser 96 charges from the source iii through the resistance 95.

Initially the voltage across the condenser is zero, but as time goes on the voltage-across the condenser increases until after the time-interval of R times C microseconds, a value of 63% of the full line voltage is reached (R=resistance, C=capacity). This increasing condenser voltage is impressed across the inductance and the cathode-anode circuit of the tube, which'is prohibited from passing current by the 'direct bias voltage impressed to the control member 88 of the tube. This bias voltage, obtained by the resistor 92 across the direct current line 9! and acting as a pon'tiometer or voltage divider has such a value that it allows conduction through the tube when the condenser voltage has increased to a value less than the supply line voltage ti. The tube conducts at this moment and the condenser 95 starts to discharge sending a pulse of current through the inductance 93 and the tube 84. Because the resistance of the inductance and the, tube is less than the charging resistor 95, the condenser loses its charge through the tube much faster than it gains from the source 9i and consequently the voltage across the condenser decreases more or less rapidly to a value sufficiently low to stop the discharge in the tube. 'It, is necessary however to have the tube continue to be conducting at this time or the condenser would st'art recharging from the source 9| immediately again and the tube would be conducting again before cleionization had occurred or before the control member 88 had regained yutrol.

A cup shaped control,

The inductance 93 maintains the discharge for a brief time after the voltage value of extinction is reached. As soon as the discharge finally. stops, the condenser requires'time for recharging to the conduction or ignition point', thus obtaining enough time for deionization. Therefore the tube isv non-conducting until the condenser has been charged to a value which is below the line voltage at which the control member permits normal conduction to start.

The condenser jtherefore charges from the source 9| and discharges through the tube, re-

I chargesfrom the source again and'redischarges I through the tube at a great rate per second.

Instead of'employing a control member 88 en closing the electrode 86A completely as shown in the upper half of the Fig. 9, a perforated fiat disc diaphragm or control member 89 as shown in the lower half of the Fig. 9 may be used' to produce currer, interruptions in the tube. The

broken lines in the middle of the tube indicate a composite drawing illustrating another way and means of producing interruptions. In this particular case a perforated disc or plate acting as a control member is placed relatively close to one of the electrodes 86A and 863 or each of the electrodes may have a perforated plate. placed ahead of them. No connections to any part of the circuit are required and the actions taking place are similar to the ones disclosed in Fig. 6. By placing the perforated plate control-members 89 having one or more perforations 90 close to the electrodes 86Aand 863, these plate members will also act as shields and'prevent depositingof evaporated and sputtered electrode material on'the fluorescent coating material 85 in the positive column part of the tube 84 while all the sputtered electrode material will be held back behind the plate members in the space surrounding the electrodes. Better lumen maintenance is thus maintained throughout the life of the tube, besides the fact that the plate memtions in describing the various circuits covers the plates acting as a condenser and electrodes for the electronic discharge at the same time, an inductance connected to said condenser electrodes thereby constituting a resonant circuit, a source of electric current energizing said electronic device and charging and discharging said condenser electrodes bymeans of the electronic discharge from said thermionic electrodes and causing said condenser electrodes and said resonant circuit, to produce high frequency oscillations in said circuit.

2. In an oscillator, a bulb containing a gaseous atmosphere, thermionic electrodes for passing a discharge through said gas, a plurality of closely spaced metal plate members interposed between said thermionic electrodes acting 'as condenser and electrodes simultaneously, said condenser plates having small perforations, a source of electric current causing an electronic discharge between said thermionic electrodes, said periorated condenser plates periodically interrupting the electronic discharge flowing through said perforations of the condenser plates, thus causing-said condenser plates to charge and discharge through a resonant circuit connected to said condenser plates, thereby producing high frequency oscillations.

3. A light radiating electronic discharge oscillator, comprising a light transmitting gas-filled tube, luminescent material associated with said tube, thermionic electrodes spaced opposite within said tube, closely spaced perforated metal plates interposed between said electrodes actin as condenser electrodes, a source of electric current causing an electronic discharge between said thermionic electrodes, said perforated condenser electrodes periodically interrupting the electronic discharge, thus causing said condenser electrodes to charge and discharge through the tube by means of a resonant circuit connected to said condenser plate electrodes, thus energizing and ionizing the gas and the luminescent material range from about 100 cycles per second or more up to ultra high frequencies, since considerable increases iniuminous eillciency tor fluorescent tubes and lamps are obtained at a frequency of several hundred cycles per second already.'

It will be apparent to those skilled in the art that the features of this invention may be embodied in other physical structures without departure therefrom. I do not, therefore, desire to be strictly limited to this disclosure, which is provided for the purpose of illustrating and describing the invention, but rather to the scope of the claims granted.

What I claim is:

l. A high frequency oscillator comprising an electronic discharge device and a resonant circuit, said electronic discharge device consisting of-a tube having thermionic electrodes spaced opposite each other and having interposed between said thermionic electrodes spaced metal with high frequency currents thereby causinl said tube to radiate light of. increased luminous eiliciency. I

4. A light radiating electronic discharge oscillator, comprising a light transmitting gas-filled tube, a coating of luminescent material attached to said tube, spaced thermionic electrodes within said tube, spaced metal plates interposed between .'said electrodes, a resonant circuit connected to said metal plates, a source of electric current energizing said tube and charging and discharging said metal plates by means of the electronic discharge from said thermionic electrodes, thereby converting the current flowing through said tube into high frequency currents and causing the gaseous atmosphere and the luminescent coating to radiate light of increased emciency.

5. A light radiating electronic discharge oscil- -lator, comprising a light transmitting gas-vapor filled tube. a coating or fluorescent material as-- sociated with said tube, spaced thermionic electrodes within said tube, a perforated plate member interposed between said thermionic electrodes, a source of electric current producing anelectronic discharge between said electrodes, said pertorated plate member periodically interrupting the discharge current at a high-frequency thereby energizing the gas-vapor atmosphere and the fluorescent material with high-frequency currents and thuscausing light radiations of increased efliciency from said electronic discharge oscillator tube.

6. A light radiating electronic discharge lamp oscillator device, comprising a gas-filled bulb, a metallic vapor also within said bulb, a fluorescent material associated with said bulb, spaced thermionic electrodes within said bulb, a perforated member interposed between said electrodes, a source of electric current producing a electronic discharge between said electrodes, said perforated member being connected to a point of denser connected across said electrodes, said perforated member and condenser causing the electronic discharge to be converted into high frequency current pulsations thereby producing light radiations of increased luminous efiiciency from said lamp oscillator device.

7. A light radiating lamp oscillator, comprising a gas-vapor filled tube, a fluorescent material associated with said tube, spaced electrodes for passing a discharge through said atmosphere within said tube, a perforated electrode interposed between said electrodes, a resonant circuit comprising a condenser and an inductance connected to said perforated electrode and said other electrodes, a source of electric current energising said tube, said perforated electrode producing high frequency pulses or current interruptions within saidtube and its associated resonant circuit, thereby producing a high frequency'pul'se radiation or increased luminous efllciencftrom said lamp oscillator.

8. A radiating electronic oscillator comprising suitable potential of the electric circuit, a con-.

a gas-vapor filled tube, spaced electrodes within said tube, perforated members interposed between said electrodes, a resonant circuit com-.

, through said gas-vapor atmosphere, a perforated member interposed between said electrodes a resonant circuit comprising a condenser and an inductance connected across said electrodes, a source of electric current energising said tube, said perforated member producing periodic current interruptions or pulses of high voltage and large current amplitudes and of a very short time duration at a high rate of repetition, thereby producing high frequency oscillations and/or pulsations within said tube and its associated resonant circuit thus causing-said lamp oscillator to produce intense electromagnetic radiations of increased emclency.

CHARLES SPAETH.

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