US2763814A - Electronic fluorescent illuminating lamp - Google Patents

Description

Sept W, 1956 R. F. D. NAVARRE ALIAS MALHERBE 2,753,314

ELECTRONIC FLUORESCENT ILLUMINATING LAMP Filed April 17, 1953 2 Sheets-Sheet l m vfmiron ROGfR mmgm DES/Rf mvmzm MALHmBE avziw/M ATTORNEYS Sept, W. 1956 R. F. n. NAVARRE ALIAS MALHERBE fi fi ELECTRONIC FLUORESCENT ILLUMINATING LAMP Filed April 17, 1955 2 Sheets-Sheet 2 Rm mum m/mmmm mmm v$ii ATTORNEY United States Patent ELECTRONIC FLUORESCENT 'ILLUMINATING LAMP Roger Francois Dsir Navarre, alias Malherbe, Paris, France, assignor, by mesne assignments, to Sahel S. A., Tangier, Morocco Application April 17, 1953, Serial No. 1349, 536 Claims priority, application France April 22,1952 14- Claims. (Cl. 315-341) Fluorescent lamps or tubes operating by electronic discharge as used hitherto for illuminating purposes are provided with a gas filling and their supply with electric energy requires auxiliary regulating devices, chiefly transformers.

The present invention resorts to an electronic emission produced in a high vacuum and adapted to energize a fluorescent substance with a view to producing an intense source of light that may be used for illuminating purposes, and the operation of which does not require the action of any stabilizing means.

A lamp according to my invention includes chiefly a chamber bounded by a transparent wall or envelope and inside which is produced a high vacuum, said chamber enclosing an electron emitting cathode and an anode, while a fluorescent coat is provided in the path of the electrons emitted by the cathode, and thus the kinetic energy acquired by said electrons under the action of the difference in potential applied between the anode and the cathode is transformed into luminous energy at the moment of the impact of the electrons on the fluorescent coat, the current used having a value which is sufficiently high for producing the desired luminous power. Under such conditions, the intensity of the current passing through the lamp is limited by the space charge and it is possible to connect the lamp directly with the electric mains or the like supply of D. C. or A. C. electric energy without a transformer.

In the execution of the present invention, the chamber forming the body of the lamp may be constituted as a tube or bulb somewhat similar to standard incandescent lamp bulbs or tubes. The chamber may be bounded by a wall of suitable transparent material such as glass,

quarta or the like. The nature of said transparent material may be such that it allows all the visible'and invisible radiations produced inside the chamber to pass, or else .only a fraction of said radiations, which it may be desired amperes. The electronic stream produced may be of a continuous, alternating, or pulsating nature.

The fluorescent coat may be applied either on the anode which assumes then a suitable shape in order to provide the desired distribution of the luminous rays, or on the transparent wall of the transparent chamber or else both on the anode and on the wall of the chamber, or again on any other support, provided said coat is located in the path of the electrons in a manner such as to obtain a luminous efliciency that is a maximum.

In addition to the general arrangement .referrred to "Ice 'hereinabove, my invention provides the application to a lamp according to my invention, of certain means generally used for' electronic optics and which I have found to be particularly suitable'for the mass production of an electronic fluorescent illuminating lamp having a high luminescent cfiiciency; i

Generally speaking, I have found in the making of such a lamp that the spacing of the anode with reference to the cathode requires, if it is desired to obtain a substantial flux or current intensity without reaching prohibitively high voltages, the use of means capable of partly netitralizing the space charge.

On first consideration it may appear that such a means may consist in introducing a gas into the chamber. The ions formed by the electronic bombardment would neutralize then the negative charges in the vicinity of the cathode. However, such a method appears impracticable in the case of the present invention. The lamp being intended for direct connection without transformers with a supply mains operating under constant voltage and having consequently a low internal impedance, without any interemdiate stabilizing means being provided, the presence of gases in the chamber might lead to the jumping of arcs and consequently to the short-circuiting of the supply mains and to the destruction of the lamp.

Other means may include the insertion between the anode and the cathode of a grid maintained at a positive potential wtih reference to the cathode and the part played by which would consists in neutralizing the space charge at the cathode value. Theoretically, such an ar rangement appears as favorable but in practice, however, it is diflicult to produce because, if it is desired to have a substantial power on the anode by reason of the spacing between the latter and the cathode, and also by reason of the diffraction of the electrons by the elements in the biased grid, this would lead to the dissipation of a much larger energy by the field grid. In addition to the practical diificulties encountered in the removal of the energy dissipated by the grid, the total efliciency of such an arrangement would be poorand would lead to intolerable commercial results.

i in accordance with the present invention, I have conceived of the association with such a positively biased grid, of a second grid inserted between said positive grid and the cathode and maintained at the potential of the cathode or at a potential that is slightly negative with reference to the latter. This second grid allows obtaining an economical adjustment or modulation of the luminous flux, and chiefly it plays the part of focalizing means for the electronic beam whereby the latter may pass, without substantial losses, through the zone containing the grid that is positively biased.

I may still further improve this arrangement by giving the two above-mentioned grids substantially the same pitch and mounting them in a manner such that the bars or elements of the positive grid may lie in the electronic shadow of the elements of the grid assuming a negative or zero potential that is, in registration therewith. Under such conditions, the positive grid, which collects about 10% of the electronic fiux when no special care is exercised, collects only 3 to 5% thereof it the elements in the two grids are thus suitably aligned with reference toone another.

In certain special cases, and in particular whenever the positive grid lies at a potential that is higher than that of the anode, it may be of interest to insert a suppressor grid which prevents any secondary electrons from actually leaving the electrode from which they have been knocked ofii. :However, in most cases, it is possible to omit such a suppressor grid as the space charge between the electrodes is sufficient to prevent such a production of secondary electrons.

Generally speaking, it is possible to mount the cathode and the grid in the conventional manner according to which these different parts are arranged coaxially in cylindrical, prismatic or parallelopipedic formation. However, in the case where certain fluorescent substances are used, whose light outputs are exinguished when submitted to the action of infra-red rays, it is possible to avoid or to reduce such an action of the infra-red rays produced by the cathode which is generally heated to 600 C., by resorting, according to my invention, to flat structural parts.

By reason of the low voltages applied, it may be of interest for the fluorescent coating or screen to be perfectly conductive and to form the actual anode of the lamp. This may be obtained by depositing the fluorescent powder on the metallized or metal-sprayed inner surface of the chamber wall. According to the case, said metallization deposit may be opaque, reflecting, semi-transparent or transparentv In accordance with my invention, it may be of advantage, instead of resorting to such metallization, to use for the construction of the chamber, a glass that is conductive along its surface or throughout its mass.

Inthe case where the fluorescent screen is applied over an opaque or reflecting metal spray coat, I provide in the wall of the chamber a transparent gate or window that is located so as to allow the radiations to pass out of the lamp in the direction that is most suitable for their emission and for their utilization.

In the case of the application to the tube wall of a semi transparent or transparent metal spray, or else in the case of the use of a conductive glass for the wall of the lamp, the fluorescent screen or coating may in contradistinction occupy the whole surface of the chamber wall.

In order to cut out the unpleasant stroboscopic effect that is liable to appear when the lamp is used with an A C. source, by reason of the fact that only one half of a cycle is used, it may be of interest to use in the formation of the fluorescent screen a phosphor powder having a large persistence in the formation of the fluorescent screen. In this latter respect, it should be remembered that the more persistent a fluorescent substance is, the more easily it is saturated when submitted to the cathodic stream. It is also a well known fact that the persistence of the fluorescent substances is less in the case of the substances sensitive to the cathode stream than of those sensitive to the action of light and that certain substances producing ultra-violet rays have a better energy yield than substances producing visible rays.

Considering these facts, it may be of advantage, in accordance with an improved arrangement forming part of my invention, to resort to compound fluorescent screens including both substances reacting under the action of cathodic stream and further substances reacting under the action of light. Such screens may thus be obtained through the mixture of both kinds of substances or else by forming superposed layers of such different substances. Again, in accordance with a simpler embodiment, the anode may be coated with substances which will emit ultra-violet rays when submitted to a cathodic stream, while a transparent gate or window formed in the wall of the chamber is coated by substances that are sensitive to radiations in the vicinity of the visible spectrum and that transform the ultra-violet rays into visible light.

Further features and advantages of my invention will appear from the following description, reference being made to the accompanying drawings, the description and drawings being given by way of a mere exemplification and by no means in a limiting sense. In said drawings:

Fig. 1 is an axial vertical cross-section of a first embodiment of the lamp according to my invention.

Figs. 2 and 3 are diagrammatic cross-sections of two modifications thereof.

Figs. 4 and 5 are vertical. axial cross-sections of two" further embodiments of a lamp according to my inven-' tion.

In the example illustrated in Fig. l, 1 is a bulb of transparent material, at least in the part through which the luminous rays are to pass. 2 designates the electronemitting cathode that is indirectly heated and that extends substantially along the axis of the bulb 1 and is fed with electric current through the wires 3 and 4, 5 designates an anode assuming in the case illustrated in Fig. l. the shape of a helix arranged coaxially round the cathode 2. On the wall of the bulb 1 facing the electrodes is applied an inner fluorescent coat 6 of any suitable conventional composition.

As shown in Fig. 2, the cathode 2 in this embodiment, is arranged as above described along the axis of the bulb 1, while the anode 5 forms a semi-cylindrical part ar ranged substantially in coaxial relationship with reference to the bulb and to the cathode, said anode carrying in this case the fluorescent coat 6. The anode 5' may also assume a parabolic or the like suitable shape.

In the modification of Fig. 3, the fluorescent coat 6 is applied as in the case of Fig. l to the wall of the bulb 1 and two coaxial grids 7 and 8, constituted by helices, bars or a grating of suitable shape, are inserted at suitably calculated distances between the thermo-emitting cathode 2 and the fluorescent coat 6.

In the example illustrated in Fig. 4, the chamber 1 of the lamp is defined by a bulb of glass or the like transparent material, the shape of which is similar to that of a mushroom and the socket of which is provided with a fitting that is not illustrated and through which it may be mounted after the manner of the conventional incandescent bulbs. 2 designates again an electron emitting cathode of the indirectly heated type constituted for instance by a nickel tube of any suitable cross-section, that is coated with emissive substances and is arranged substantially along the axis of the bulb 1. The heating of said cathode is provided by a helically wound filament 9 of tungsten covered with alumina or the like insulating material and extending inside the cathode tube 2. The cathode 2 and the filament 9 are mounted in the two superposed mica washers 10 and 11 carried at the corresponding ends of the cathode by the socket 1a; said washers serve also as supports for the two grids 12 and 13 surrounding the cathode 2 and which will be described with further detail hereinafter.

The inner wall of the portion of the bulb 1 nearest the socket is covered by a metal layer 14 forming the anode and over which is applied a fluorescent coat 6. The wall of the part of the bulb that is opposed to the socket is, in the example illustrated, devoid of any coat and forms a transparent gate or large window which provides a free passage for the luminous rays emitted by the coat 6 in the direction that is best suited for the utilization of the lamp. 7

The grids 12 and 13 are constituted for instance by helices of circular or rectangular cross-section that are secured to the mica washers 10 and 11 by the longitudinal bars 15. The grid 12, located in the immediate proximity of the cathode 2, may be electrically connected with the latter. It is shown in Fig. 4 as brought by any suitable means such as a battery 16 to a negative voltage with reference to the cathode. The outer grid 13 may be connected electrically with the anode 14 or as shown in Fig. 4 may be brought in any suitable manner to a positive potential with reference to the cathode as by a battery 17. The anode battery is shown at 18. The convolutions of grid 13 have substantially the same pitch and are arranged with reference to those of the grid 12 in a manner such as to lie in the electronic shadow of the convolutions of grid 12, that is, in registration therewith.

As already mentioned hereinabove, the fluorescent coat 6, applied over the metal sprayed coat 14 forming the anode, may be constituted advantageously by a luminesof the latter.

cent substance adapted to emit ultra-violet rays under the action of the incident cathode stream, while-the wall of the bulb 1, opposite to the socket 1a, maybe coated with photo-luminescent substances adapted to transform such ultraviolet rays into visiblelight.

On the other hand, instead of producing the anode through spraying, it is possible to resort to a wall made of a conductive glass actually forming the anode. In this case, the fluorescent coat 6 may be applied over the entire internal surface of the bulb 1.

In the modification of Fig. 4 illustrated in Fig. 5, the anode 14 and the fluorescent coat '6 are applied as in the example of Fig. 4 to the :portion of the inner wall of the bulb 1 adjacent to the socket 1a, but the cathode 2 and the grids 12' and 13' are constituted by flat elements extending perpendicularly to the axis of the bulb l, .and substantially parallel to each other, the heating filament 9 being positioned in parallelism with the plane By reason of this arrangement, the infrared rays emitted by the-cathodeJZ are directed for the major part towards that part of "the'wall-of the bulb that is not coated with a fluorescent substance and they exert consequently no light-extinguishing effect -on the coat 6. The elements-of outer grid l3 are arranged in registration with the elements of grid 12,-as shown, and in the electronic shadow thereof, as in Fig. 4.

Obviously, my invention is not limited in its execution to the particular examples-illustrated and described and it may be executed in various other manners. In particnlar, the vacuum chamber may'assume a diflerent shape and ifor instance it maybe tubular. In this latter case, his possible tomount at one endof'the tube a system of electrodes having a flat structure similar to that of Fig. 5, while the fluorescent screen'may be carried in the t'ube'in any manner disclosed hereinaboveaccording to the result sought for.

What I claim is:

1. An electronic fluorescent illuminating lamp comprising a transparent evacuated bulb having a longitudinal axis of symmetry, an electron-emitting cathode and lanancde mounted inside said bulb, mounted symmetrically With reference to said'longitudinalaxis of symmetry, means for producing a flux of electrons between the cathode and the anode, and a coat of fluorescent material carriedinside the bulb in the path of the electron flux and adapted to transform the kinetic energy ofthe electrons flowing between the cathode and the anode and impinging on said coat into luminous energy, and two grids positioned between the cathode and anode at different distances therefrom and screening the cathode with reference to the anode, means for biasing the said grid that is nearest to the cathode to a potential that is at the utmost equal to that of the cathode, and means for biasing the second said grid to a positive potential with reference to the cathode, the two grids having substantially the pitch, and the elementary parts of said positively biased grid being located in the electronic shadow of the other said grid.

2. An electronic fluorescent illuminating lamp such as claimed in claim 1, in which the grids are arranged coaxially around the cathode.

3. An electronic fluorescent illuminating lamp such as claimed in claim 1, in which the cathode and the grids are cylindrical and are arranged coaxially.

1. An electronic fluorescent illuminating lamp such as claimed in claim l, in which the cathode and the grids are of right prismatic shape and are arranged coaxially.

5. An electronic fluorescent illuminating lamp such as claimed in claim 1, in which the cathode and the grids are constituted by superposed flat elements mounted substantially perpendicularly to said longitudinal axis.

6. An electronic fluorescent illuminating lamp compris ing a transparent evacuated bulb having a shape similar to that of a mushroom, the top wall of which includes a transparent gate, an electron-emitting cathode arranged substantially along'the axis of said bulb, ra metal-sprayed anode facing-the gate in the bulb wall and formed-on the inside of the bulb wall, means for producing a flux of electrons between the cathode and the anode, and a fluorescent coat applied on said metal-sprayed anode and adapted to transform the kinetic energy of the electrons impinging on the anode into luminous energy passing through the gate, and two grids screening the cathode with reference to the anode, means for biasing the grid-that is nearestto the cathode to a potential that is at the utmost equal to that of the cahode, and means for biasingthe second grid to a positive potential with reference to the cathode, the two grids assuming substantially the same pitch and the elementary parts of the positively biased grid being located in the electronic shadow of the other grid.

7. An electronic fluorescent illuminating lamp comprising a transparent evacuated bulb having a shape similar to that of a mushroom, the top wall of which includes a transparent gate, a cylindrical electron-emitting cathode arranged substantially along the axis of said bulb, a-metalsprayed anode facing the gate in the bulb wall and formed on the inside of the bulb wall, means for producing a flux of electrons between the cathode and the anode, and a fluorescent coat applied on said metal sprayed anode and adapted to transform the kinetic energy of the electrons impinging on the anode into luminous energy passing through the gate, and two cylindrical grids arranged coaxially round the cathode, means for biasing the grid that is nearest to the cathode to a potential that is at the utmost equal to that of the cathode, and means for biasing the second grid to a positive potential with reference to the cathode, the two grids assuming substantially the same pitch and the elementary parts of the positively biased grid being located in the electronic shadow of the other grid.

8. An electronic fluorescent illuminating lamp comprising a transparent evacuated bulb having a shape similar to that of a mushroom, the top wall of which includes a transparent gate, a flat electron-emitting cathodearranged substantiallyperpendicularly to the axis-of said bulb, a

metal-sprayed anode facing the gate in the bulb wall and formed on the inside of the bulb wall, means for producing a flux of electrons between the cathode'and the'anode, and a coat of fluorescent material applied on said metalsprayed anode and adapted to transform the kinetic energy of the electrons flowing betweenthe cathode and the anode and impinging on said coat into luminous energy, two flat grids superposed parallely to thecathode,

means for biasing the grid that is nearest to the cathode to a potential that is at the utmost equal to that of the cathode, and means for biasing the second grid to a positlve potential with reference to the cathode, the two grids assuming substantially the same pitch and the elementary parts of the positively biased grid being located in the electronic shadow of the other grid.

9. An electronic fluorescent illuminating lamp compris ing a transparent evacuated bulb, the wall of which is made of an electrical conducting glass and is adapted to form an anode, an electron-emitting cathode inside said bulb, means for producing a flux of electrons between the cathode and the anodic bulb wall, and a fluorescent coat applied on the anodic bulb wall and adapted to transform the kinetic energy of the electrons flowing between the cathode and the anode and impinging on said coat into luminous energy, and two grids screening the cathode with reference to the anode, means for biasing the grid that is nearest to the cathode to a potential that is at the utmost equal to that of the cathode and means for biasing the second grid to a positive potential with reference to the cathode, the two grids assuming substantially the same pitch, and the elementary parts of the positively biased grid being located in the electronic shadow of the other grid.

10. An electronic fluorescent illuminating lamp comprising a transparent evacuated bulb having a shape similar to that of a mushroom, the top wall of. which includes a transparent gate, an electron-emitting cathode arranged substantially along the axis of said bulb, a metal- -sprayed anode facing the gate in the bulb wall and formed on the inside of the bulb wall, means for producing a flux of electrons between the cathode and the anode, a fluorescent coat applied on said metal-sprayed anode and adapted to transform the kinetic energy of the electrons impinging on the anode into luminous energy in the form of ultra-violet rays, a further coat of fluorescent material covering the transparent gate and adapted to emit visible light under the action of the impact thereon of the ultraviolet rays produced by the anodic coat, and two grids screening the cathode with reference to the anode, means for biasing the grid that is nearest to the cathode to a potential that is at the utmost equal to that of the cathode and means for biasing the second grid to a positive po tential with reference to the cathode, the two grids as suming substantially the same pitch, and the elementary parts of the positively biased grid being located in the electronic shadow of the other grid.

11. In a high-vacuum fluorescent illuminating tube, a transparent evacuated envelope of substantially mushroom shape and having a longitudinal axis of symmetry and further having a socket portion and an illuminating face crown portion opposite said socket portion and corresponding to the crown portion of a mushroom, an elongated cathode mounted centrally in said tube, a first grid and a second grid mounted coaXially around said cathode in spaced relation to said cathode and to each other. a metal coating layer applied to the inner face of the socket portion of said envelope and constituting the anode of said tube, and a luminescent coating applied over said metal layer, said two grids having the same pitch and being mounted with the elements of the said grid more remote from the cathode being positioned in the electronic shadow of the elements of said grid nearer said cathode with reference to the stream of electrons from said cathode.

12. In a high-vacuum fluorescent illuminating tube, a transparent evacuated envelope of substantially mushroom shape and having a longitudinal axis of symmetry and further having a socket portion and an illuminating face crown portion opposite said socket portion and corresponding to the crown portion of a mushroom, an elongated cathode mounted centrally in said tube, a first grid and a second grid mounted coaxially around said cathode in spaced relation to said cathode and to each other, a metal coating layer applied to the inner face of the socket portion of said envelope and constituting the anode of said tube, and a luminescent coating applied over said metal layer, said two grids having the same pitch and being mounted with the elements of the said grid more remote from the cathode being positioned in the electronic shadow of the elements of said grid nearer said cathode with reference to the stream of electrons from said cathode, said cathode and said grids being mounted substantially parallel to and surrounding said longitudinal axis of symmetry of said tube.

13. in a high-vacuum fluorescent illuminating tube, a transparent evacuated envelope of substantially mushroom shape and having a longitudinal axis of symmetry and further having a socket portion and an illuminating face crown portion opposite said socket portion and corresponding to the crown portion of a mushroom, an elongated cathode mounted centrally in said tube, a first grid and a second grid mounted coaxially around said cathode in spaced relation to said cathode and to each other, a metal coating layer applied to the inner face of the socket portion of said envelope and constituting the anode of said tube, and a luminescent coating applied over said metal layer, said two grids having the same pitch and being mounted with the elements of the said grid more remote from the cathode being positioned in the electronic shadow of the elements of said grid nearer said cathode with reference to the stream of electrons from said cathode, said cathode and said grids being constituted of flat elements mounted perpendicularly to the longitudinal axis of symmetry of said tube.

14. A tube according to claim 13, said luminescent coating applied to said metal layer being adapted to emit ultra-violet radiation when excited by a stream of electrons from said cathode, and the inner face of the illuminating face crown portion of said tube being coated with a substance which gives out visible light under the impact of ultra-violet radiation.

References Cited in the file of this patent UNITED STATES PATENTS 1,650,921 Winkelmann Nov. 21, 1927 2,108,880 Braden Feb. 22, 1938 2,115,839 Briefer May 3, 1938 2,177,705 Friederich Oct. 31, 1939 2,222,668 Knoll Nov. 26, 1940 2,392,161 Leverance Jan. 1, 1946

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