US2007929A - Electric radiation device - Google Patents

Description

July 9, 1935.

C. H. BRASELTON `ELECTRIC RADIATION DEVICE Filed Aug. 19, 1930 Patented July 9, 1935 UNITED STATES PATENT OFFICE ELECTRIC RADIATION DEVICE poration of Delaware Application August `19,

6 Claims.

This invention relates to an improved type of electric radiation device based on the type of radiator which utilizes a highly activated conducting layer of ionizable gases in conjunction with a metallic conductor, both metal and gas forming a combined source of radiated energy.`

Among the objects of the present inventionis to provide a radiation device which utilizes an improved means for making conductive the gases intermediate adjacent conducting terminals.

Another object of the invention is to provide a combined gas discharge and metal-gas conductor radiator which utilizes a minimum area of activating range on the metal conductor, thus simplifying the operative and structural features of the device.

Still another object of the invention is to provide an electric radiation device in which may be utilized second class conductors of the type which .when heated emit radiant energy selectively, such, for example, as light energy.

Further objects such as may relate to methods of manufacture and details of construction, as well as to the underlying theories involved, will appear on consideration of the following specification and of the accompanying drawing, in which:

Fig. 1 is a view in elevation of a radiator embodying features which may be preferred;

Fig. 2 is a view of a modification showing modified electric discharge electrodes;

Fig. 3 is an enlargement of a detail of the ionizing element of the device; and

Fig. 4 is a View of a third modification of the radiator.

In my Various co-pending applications, particularly application Serial No. 459,048, filed June 3rd, 1930, I have described a type of device for securing radiant energy -of varied frequencies which combines with a metallic conductor an ionized layer of gases adjacent thereto, which layer is conductive to an electric current, and in conjunction with the metal conductor provides dual sources of radiation.

1n accordance with said applications, a filament of appropriate resistance, such, for example, as 150 ohms, is coated with various alkaline earth metal oxides such as the oxides of barium, strontium, calcium or other materials which have been found to emit electrons densely when heated. The base filament is tungsten or tantalum wirejalthough other metal conductors may be used. 'It is not necessary ordinarily that the base material be highly refractory, as the operating temperatures may be relatively low, in many cases not being above that of low.redheat.

The filament is preferably coiled and coated with materials as above` mentioned, which may be initially in the proportions of grams of barium carbonate, 40 grams of calcium carbon- 1930, Serial No. 476,343

ate, 8 grams of barium nitrate with a binder of suflicient nitrocellulose dissolved in amyl acetate to hold the coating on the wire, and the filament is then mounted on a stem support and --sealed in the bulb of the envelope.

The exhaust pump is then connected to the bulb and an oven lowered thereupon to raise the temperature of the bulb and contents to about 400 C., or to as high a temperature as the envelope will stand without softening. Simultaneously electric current is passed through the filament which is heated to red heat of approximately 600 Cl. The heat and exhausting process is continued until there is no fluorescence when the high tension current is directed against the wall of the bulb, or in other words, until there is practically no more gas inside of the bulb. A vacuum of about one-half of a micron is an approximate limiting value.

The current is then increased through the filament so that the'temperature thereof is slowly raised until it is about 800 degrees, or a bright red color, the exhaust operation being continued until the newly emitted gases are removed. The oven is then raised from the bulb and the filament heated to about l200 C., the pumping being continued until a high vacuum of one-half micron is again obtained.

The pump is then shut off, the current turned off, and about one-half mm. of neon gas admitted to the bulb. The filament current is then turned on and gradually increased until a diffused glow completely fills the bulb. When the discharge is uniform throughout the' bulb, which usually takes less than ten minutes to occur, the so-called activating process for the filament coating is completed. Should white discharge spots appear on the filament or support rods, it is an indication that the gases or vapors within the bulb have not been completely removed, and the bulb is again exhausted and the whole process of activation repeated. When the activating process is nally complete, the filament temperature is raised for a short interval to about 1400" C., and the pumping operation is again resumed to remove any undesirable gases which may have been thrown off during the activation process.

The filament circuit is then disconnected and -the pump turned off and the appropriate amount of gas admitted to the bulb. In one form of my invention I utilize neon and argon gases in the relative amounts of 50 mm. of neon gas, and 150 mm. of argon. Other monatomic gases such as krypton, helium, or metal vapors such as those of mercury, csium, and rubidium may also be used. The bulb is then sealed off and a small quantity of magnesium flashed to absorb additional impurities, thus completing the process.

I have further developed and described in my zo-pending applications a type of radiator which includes the basic principles hereinabove described but combines therewith parallel gas discharge electrodes, so that there are three separate sources of radiation instead of two, these including the metal conductor itself, the activated atmosphere of gases immediately surrounding the metal conductor, and the gas discharge between electrodes connected in parallel with the metal conductor, this gas discharge being sustained by,

energy derived from the activated atmosphere surrounding the metal conductor.

In accordance with the present invention, which constitutes an improvement of the three source electric radiator above mentioned, I integrate the various radiation sources forming a unified and combined energy source of increased eiliciency and utility.

Referring to Fig. 1, there is disclosed an envelope IIl which may be of transparent material such as lglass to permit visibility of the operation of the internal elements of the device, this envelope being closed except for an initial base opening II, to which is sealed the stem or support I2, this stern protruding inwardly within the envelope. Mounted on said support are three standards I3, I4, and I5, the standards I3 and I4 being extensions of the lead-in wires I5 and I6, and the latter adapted to be connected to an appropriate external electrical power source. To the upper terminals of the standards I3 and I4 is secured by appropriate means, such as by welding, the conductor I'I which may be of tungsten, tantalum, or similar refractory metals, and which is coiled to a diameter approximating three or four thousandths of an inch in order to secure suillcient resistance to the filament, and for other purposes as will be hereinafter described.

A small section I8 of the coiled conductor I1 is coated with a material which when heated emits electrons in profusion, this material taking the form of various oxides of the type of strontium, barium, calcium and the like, as hereinabove ref erred to in connection with my co-pending applications. The approximate midpoint of the conductor I'I is attached to the standard I5 in order to receive support therefrom.

Also attached to the standards I3 and I4 so as to include the conductor II as an axis are tubular members I9 and 20, each of these members having closed ends 2| and 22 which are attached as by welding to the standards I3 and I4 and which in addition have open ends with the edges 23 and 24 flared and turned backwardly, these edges 23 and 24 being opposite each other so that a cylindrical gap is formed between these edges. The members I9 and 20 may be of refractory material such as tungsten, or they may be of a conductor of the type which when heated emits radiation selectively. VSuch materials, particularly in the visible energy range, are the oxides of magnesium, thorium, cerium, yttrium, and other metals of the rare earth group, and also various combinations of these and other oxides, such as the combination of the oxides used in the Nernst gl'ower and the Welsbach mantle. These selective radiators may be used alone or in mixed combinations with a refractory metallic conductor, or a metal conductor may be imbedded within the selective radiator material to increase the conductivity thereof.

The various elements as described as mounted upon the standards I3, I4, and I 5 are in the completed device immersed within the envelope III in an atmosphere of gases which preferably should be inert, these gases, as hereinabove mentioned, taking the form of argon, neon, helium, krypton,

ately adjacent thereto, and with appropriate pressure conditions, as for example, 200 mm. of mercury, combined with appropriate voltage conditions which function to bring about a proper heating of the electron emitting coating and the requisite potential drop through the gases, a

highly activated layer of conducting gases forms in proximity to the conductor. .t the same time a potential is inserted intermediate the electrodes 23 and 24 through the intermediate gases.

Ordinarily, and without other external influences, the potential drop is insufficient between these electrodes to cause an electric discharge to take place. However, because of the formation of the activated gaseous layer adjacent to this region the conductivity of the intermediate gas layer is increased by ionization and convection to a point where a discharge readily forms between these electrodes at 'the normal operating potential of the device. This discharge functions as a source of radiation which is additive to that derived from the luminous gas sheath I8 about the conductor Il, as well as that from the bare portions of the conductor I I which are not shielded by the tubular members I9 and 2U. Where visible radiation is desired gases are selected which when the three sources of radiation are combined will tend to produce a color of light desired. By modifying the proportions of metal vapor such as caesium or mercury and other gases it is possible to secure a large variety of visible colors, as well as radiation of the ranges above and below the visible range.

Where the tubular members I9 and 20 are conductors of low resistances the radiation properties thereof and of the electrodes 23 and 24 are of relatively small importance. However, the radiation of these elements may be heightened by increasing the resistance over the mixture of materials therewith which have low conductivity, or by cutting down the metallic cross-section where metals are used. In Fig. 2, for example, I have shown a modified construction in which the electrodes-30 and 3I are in the shape of rings, the ring portions being in the shape of bands curving slightly away from each other. 'I'hese rings are mounted on standards 32 and 33 and connected to lead-in wires 34 and 35 which are electricall connected to the main lead-in wires I5 and I6.' It is apparent that by this construction the mass of the gas discharge electrodes is very considerably diminished and that by varying the crosssectionalv mass of the electrodes the resistance thereof can be modified so that in operation these electrodes may be heated and thereby add to the radiation of the device as a whole.

In Fig. 4 a further modification of the invention is illustrated which takes the form of a device having a support I2 on which are standards 40, 4I, 42, and 43. Intermediate the standards 40 and 43 is interposed a coiled tungsten conductor 44 having an electron emitting coating 45 which extends throughout the length of the coiled tungsten. Secured to standard 4I is a tubular member 46 having a :dared electrode 41 which is secured about .the `conductor 44 so that the conducto'r forms the axis thereof. A similar tubular element 48 with a flared electrode 49 is mounted on the standard 42 so that the electrodes of the two elements 46 and 46 are opposite to each other. 'Ihe elements 46 and 48 should preferably be perforated at 5B so as to permit emanation of the radiation from the activated gas layer and the heated conductor 44. In this manner may be obtained the maximum utilization ofthe radiation from the device.

Various specic substances have been mentioned which constitute the materials of the conductor, the coating, and the electrodes, as well as surrounding gases. .f It is also obvious that the energy emanation from the device may be modified by the type of envelope i0 which may be made of materials having selective permeability for different wave lengths of radiant energy. For lighting purposes ordinary glass is satisfactory. but for ultra-violet rays substances such as quartz or certain silicates should be utilized. I have mentioned the desirability of a coating over the conductor, and this under ordinary circumstances is desirable, such as where the tungsten is used as a metal conductor.

I do'not desire to limit myself moreover to a coated conductor, inasmuch as I have found that certain other metals and substances, such as tantalum, have la higher electron emissivity for a given temperature than tungsten and that where gas pressures and voltages are properly selected in conjunction with a conductor having the req`ulsite tendency o! emission, an operative device may be obtained without coating the conductor with special electron emitting substances. Also. instead of placing the coating material externally of the coil, the same may be applied within the coil in the shape of a rod or pencil or as a plastic core material which is subsequently hardened by baking. Accordingly, in the claims hereto appended, the term coating is intended to cover both inner and outer applications of the coating material.

The gases employed have been referred to as monatomic and as readily ionizable, or as vapors of metals. other gases than those mentioned, such as nitrogen, may be employed, providing appropriate controlling factors are introduced. A fundamental requirement appears to be in connection with these gases that the breakdown potential of the same along the axis of the conductor be less than the potential necessary to raise the temperature of the electron emitting material or coating to its operative temperature of electron emission.

Various modifications of this invention may occur to those skilled in the art, and accordingly, I do not desire to be limited to the modifications as described, except insofar as limitations are imposed by the claims hereto appended.

Having thus described my invention. what I desire to claim is:

1. In an electric radiator the combination of an envelope. a support mounted therein, a plurality of standards mounted on said support, a single continuous, high resistance conductor positioned between two of said standards. said conductor being in the shape of a closely wound coil, a coating of electron emitting material containing alkaline earth metal oxides on said conductor adjacent the mid-point thereof, two conducting electrodes forming closed loops about the conductor mounted on either of said standards, said electrodes being positioned opposite each other adjacent said coating, means for electrically connecting said ele'ctrodes to points adjacent the terminals of said conductor, and an atmosphere of ionizable gases within said envelope.

2. In an electric radiator the combination of an envelope, a support mounted therein, a single, continuous conductor withinthe envelope, standards supporting said conductor upon said support, a coating of electron emitting material upon a section of said conductor, tubular electrodes surrounding said conductor and having proximity to each other adjacent the coated area of the conductor, said electrodes having curved faces, means for electrically connecting each of said electrodes to one end of said conductor, and an inert gas including argon and neon within said envelope. Y

3. In an electric radiator the combination of an envelope and means within said envelope for securing a dual electric gas discharge, said means comprising a single, continuous and straight conduetor, a coating thereon of. electron emitting material, a plurality of annular electrodes surrounding said conductor adjacent said coating, an ionizable gas within said envelope, and means for supporting said electrodes and conductor within the envelope.

4. In an electric radiator the combination of -an envelope, a support mounted therein, a single,

continuous conductor within the envelope, stand- Iards supporting said conductor upon said support, a coating of electron emitting material upon a section of said conductor, tubular electrodes surrounding said conductor and having proximity to each other adjacent the coated area of the l conductor, means for electrically connecting each of said electrodes to one end of said conductor, andan inert gas including argon, neon, and a metallic vapor within said envelope.

5. In an electric radiator the combination of an envelope, and means within said envelope for securing a dual electric gas discharge, said means comprising a conductor having a portion adapted, when heated, to emit electrons in profusion` a plurality of electrodes surrounding said conductor adjacent said coating, means for creating a potential difference between said electrodes greater than the potential diilerence across the electron emitting portion of said conductor, an ionizable gas within said envelope, and means for supporting said electrodes and conductor within the envelope.

6. An electric radiator comprising in combination an envelope, a support mounted therein, a plurality of standards mounted on said supports,

an ionizable gas within said envelope, two elecstraight coil of wire connected between said standards and passing through said electrodes and a coating of electron emitting material containing alkaline earth metal oxides on said wires.

CHESTER H. BRASELTON.

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