US2007925A - Diffused discharge lamp - Google Patents

Description

July 9, 1935.

C. H. BRASELTON DIFFUSED DISCHARGE LAMP Filed Oct. 9, 1930 I INVENTOR .vices andparticularly to such devices in which u Patented July 9, 1935 UNITED STATES- PATENT OFFICE 4 DIFFUSED DISCHARGE l' Chester `l-Lraselton, New York, N. Y., assignor to Sirian -LampCompany, Newark, N. J., a corporation oLDelawarcf One. 'of the objects of the` in`vention is to pro--I 5. duce yan electric discharge device yin which the.

dischargeis distributed Luniformly over considerable area. f

Another objectof the potential difference between adjacent parts of the device so as to form an arc between them.

Other objects of the invention and objects relating to the construction and assembly 'of the various parts will be vevident as thedescription of the invention proceeds.

One embodiment ofthe invention has been il'-l lustrated in the accompanying drawing in which:

Fig. 1 isv a perspective view of my improved lamp; and

Fig. 2'is an enlarged longitudinal sectional view of a portion of thev electron emitting element.

In my application entitled Electrical discharge device filed June 3, 1930, Serial No. 459,048, I describe a discharge device in which a coil of Illamentary resistance wire is coated with an electron emitting material and when energized in an atmosphere of ionizable gas under suitable pressure a discharge takes place longitudinally of the coil which surrounds the coil like a halo producing an intense illumination. The present invention contemplates the use of such coils closely positioned in parallel relation and connected electrically in series in such a.l way that potential difference between adjacent points on any parts of the coils is substantially thesame. Such a device may be constructed in the following manner:

An envelope Ill of glass or any other desired transparent material may be sealed upon the usual press I I forsupporting the elements of the device. A pair of electron emitting elements I2 and I3 maybe mounted at one end upon the support rods I4 and I5 which are sealed in the press Illand at the other end upon the support rods I6 and I1 which are also sealedin theA press. A11 `of `the support rods may extend upwardly within the bulb and may be so positioned that the elements I2 and I3 will extendin parallel relation and close to one another. A short connector I8 maybe welded vto the twosupport rods I5 and` I6 to electricallyy connect them together and a pair of leading-in wires I9 and 20 may be connected respectively` to the support rods- Il and I-1. The electron emitting elements I2 and I3 may each comprise a coil 2I (see Fig. 2) of resistance agire such as tungsten, molybdenum. tantalum,

1930,` serial Nc. 481,395 (ci. 17651) or nichrorne, which may .have a relatively small 'diameter soas` tobe stiff enough to support itself and may be coated'with electron emitting material 22 which may be any ofthe well-known materials used for that purpose such"as the oxides of the alkali earthl metals or mixtures of suchn oxidesI and Ithe mixture may preferably contain thel invention is to 'increase a material having selective radiation such as the oxides of yttrium, cerium, and calcium to increasethe radiation therefrom. The latter oxl0 ide may be preferred because 'it is electron emitting at temperatures which are notimpractical. The electron emitting material may be applied to the coil in any desired manner as by; a brush andthe outer, surface of the coil may be coated, 15 as indicated, or leach individual turn may be coated.

'With the elements mounted upon the press II and the press sealed in the Venvelope I0, as indicated, the envelope may be connected to a vac- 20 uum pump in the usual manner and an oven placed over it to raise'the temperature to between 350 to 400 C. or to as high a temperature as the glass will stand without softening The iilament current is simultaneously turned on and the 25 Atemperature of the filament raised to about 600 C. orto adull red heat. This drives out cervtainiof the gases from the filament and other parts of the lamp and when there is no more gas present as is evidenced by the lack of iiuores- 30 cenfce when high tension current is directed against the walls of the bulb and a high vacuum of preferably .5 micron is obtained current may be increased through the filament and the temperature thereof slowly raised until about 800 C. 35 is reached'with a bright red color. This drives out the binder in the electron emitting material andl other occluded gases that may be present. When no more gas is found inthe bulb the oven may be raised and the filament heated to ap 40 proximately 1200 C. the pump being connected all this time to maintain the high vacuum. and draw the gases out of ,the bulb. Whenthe high vacuum is again obtained the lpump may be shut off and the filament current 45 Iturned olf and a slight amount' of inert gas, such as neon. at about 1/2 pressure may be admitted to the bulb 'and they filament current turned on again and gradually increased. Spots of 1ocalized discharge will 'then `appear having a' red- 50 Vdishpcolor and will gradually spread until a diffused glow completely fills the bulb. This process appears to activate the electron emitting coating and.may;be maintained until the discharge throughdut the entire bulb which 554 usually takes less than ten minutes. During this time the current on the filament should not be raised too high so that the coating will not be destroyed or thrown oilfrom the filament. If white discharge spots appearon the lament or support rod it is an indication that there are more gases or vapors in thebulb and the bulb should preferably be again exhausted and the whole process of activation repeated.

When the activation is completed the filament temperature may be raised for a moment to about 1400 C. and the vacuum pump may again be connected and the gas pumped out to remove any undesirable gases which may have been thrown oii during the activation process.A When the high Vacuum is again obtained the filament circuit may be disconnected, the pump turned oif, and about 50 mm. of neon gas admitted to they bulb followed by about mm. of argon.

If desired the bulb may then be sealed off and flashed with magnesium to clean up the gases within the bulb. Magnesium may be introduced into the bulb by placing -a small amount in a container 23 which may be attached by means of a connector 24 to one of the support rods, as the rod I4. When the container is heated by external bombardment the magnesium flashes.

When the device is connected to a power circuit current enters the lead-in wire I 9 and passes up through the support rod I4, through the electron emitting element I2, the support rod I6, the connector I8, the support rod I5, the electron emitting element I3, the support rod I1, and passes out through the lead-in wire 20. This energizes the electron emitting elements I2 .and I3 and it will be noted that inasmuch as they are the same resistance each, any point on one will have a. difference of potential from a corresponding point on the other. of approximately half the potential across the lead-in Wires I9 and 20 and thus a uniform difference in potential exists throughout the length of the elements.

When the coils are raised to the proper temperature thereis apparently anv electron emission from the electron emitting coating which ionizes the gas in the immediate vicinity of the coils. The ionized region in the vicinity of each of the coils appears to provide a conducting path along the coil which supports the discharge therealong. ,-Inasmuch however as there is a difference in potential between adjacent points on the two coils there will also be a discharge across the gap between the coils and thus the illumination of the device is greatly increased.

While I have described the use of neon and argon gas within the bulb other inert gases may be used but I prefer the monatomic gases suchA `23 adjacent the magnesium and when the magnesium is flashed it will combine with the salt liberating the `free metal which then condenses on the inner Walls of the bulb to be evaporatedagain when the bulb is heated in use.

While certain specific pressures of the gas have been mentioned these may be varied as greater,

pressures tend to conne the discharge closer around the filament and lower pressures appear to permit it to increase in diameter.

While a certain specific type of an electron -emitting element has been illustrated and described other such elements may be used. For instance, the coil, instead of Ahaving a solid coating on the outer surface thereof, may have the surface partially coated or each individual turn may be coated with the material, or the coil may be wound around a core of electron emitting material, or the filament wire itself may have the electron emitting material incorporated in it such as thoriated tungsten wire which may be made by treating tungstic acid and thorium nitrate, or other constructions. may be used, the essential feature being that sufficient resistance is provided for the particular voltage and current desired and that electron emitting material is in contact with at least a portion of the conducting element.-

Many modifications of the invention may be resorted to without departing from the spirit thereof, and I do not therefore desire to limit myself to what has been shown and described except as such limitations occur in the appended claims.

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

1. In an electric discharge device a pair of substantially parallel electron emitting elements with one end of one element electrically connected to the opposite end of the other element, means to connect the other ends of both ele'- ments to opposite sides of a source `of potential, andan inert ionizable gas surrounding said elements and having such a pressure that theA ionization thereof is conned to the region of said elements when said elements are energized whereby in operationa uniform overlapping of the discharge from the -two elementsoccurs, the breakdown potential of said gas per unit length along the element being less when energized by ionization from said element than the potential drop along the conductor necessary to raise the same to electron emitting temperature, and said electron emitting elements having an emissivity when heated in excess of that from thorium oxide. 2. In an electric discharge device a pair of substantially parallel, spaced apart, electron emitting elements with one end of one element connected electrically to the opposite end of the other element, means toconnect the other ends of both elements to opposite sides of a source of potential.

. and an ionizable gas having a pressure in the neighborhood of 200 mm. of mercury surrounding said elements whereby in operation a uniform overlapping of the discharge from the two elements occurs, the breakdown potential of said gas per unit length along the element being less when energized by ionization from said element than the potential drop along the conductor necessary to raise the same to electron emitting temperature, and said electron emitting elements having an emissivity when heated in excess of that from thorium oxide.

3. In an electric discharge device a pair of substantiallyparallel, spaced apart, electron'emitting elements with one end of one element elec- -trically connected to the opposite end of the other element, means to connect the other ends of both elements to opposite sides of a source of potential, and a mixture of neon and argon gas surrounding said elements and having a pressure Aof substantially 2,00 mm. of mercury whereby in operation a uniform overlapping of the discharge from the two elements-occurs, and said electron ting elements with one end of one element electrically connected to the opposite end of the other element so that the elements are connected together in series, each of said elements comprising a fllaxnentary resistance wire and electron emit-y ting material in contact with said wire, and an- ,f ionizable gas surrounding said elements and having a pressure sufcient to'conne the ionization thereof to the region of said elements when said elements are energized whereby in operation a uniform overlapping of the discharge from the two elements occurs, the breakdown potential of said gas per unit length along the element being less when energized by ionization from said ele-' ment than-the potential drop along the conductor necessary to raise the same to electron emitting temperatureand-said electron emitting elements spaced apart, with the end of one conductor connected electrically to the opposite end of the other conductor, .means to connect the otherv ends of both conductors to opposite sides of a source of potential, electron emitting material in contact with one of saidconductors, and an ionizable gas surrounding said conductors and having a pressure of substantially 200 mm. of mercury whereby in operation auniform overlapping of the'discharge from the two elements occurs, the breakdown potential of said gas per unit length along `the element being less when energized by' ionization from said element than the potential drop along the conductorl necessary to raisel the` same to electron emitting temperature, and said electron emitting elements having an emisslvity when heated in excess of that from thorium oxide.

6. In an electric discharge device a coil of fllamentary resistance wire, a second coil of filamentaryv resistance wire spaced from said irst coil, but substantially parallel therewith, means to connect one end of said iirst coil to the opposite end of said second coil, means to connect the other ends of both coils to opposite sides of Aa source of potential, electron emitting material in surface contact with one of said coils, and an ionizable gas having a pressure of substantially 200 mm. or mercury surrounding said coils whereby in operation a uniform overlapping of thev discharge from the two elements occurs, the breakdown potential of said gas .per unit length along theelement being less when energized by ionization from said element than the potential drop along the conductor necessaryto raise the same to electron emitting temperature, and said electron emitting elements having an emissivity when heated in excess of that from thorium oxide.

` 7. In an electric discharge device a pair of coils of iilamentary wire spaced apart but substantially parallel with each other, acoating of electron emitting material on each of said coils, said coilsvhaving the end of one electrically connected to the'opposite end of the other, means to connectthe other ends of both coils to opposite sides of a source of potential, and amixture of neon and argon gas surrounding said coils at a pressure of substantially 200 mm. of mercury whereby in operation a uniform overlapping of the discharge from the two elements occurs, and said Yelectron emitting elements having an emissivity when heated in 'excess of that from thorium oxide. V

CHESTER BRASELTON.

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