US1903493A - Gas discharge light - Google Patents

Description

April 11, 1933. Q L, BECK AL 1,903,493

GAS DISCHARGE LIGHT Filed NOV. 50, 1929 FIGJ;

I v Elvwwtozs Leo L. Bqgk v Aubrey E. Nob/e.

$33 f-hel r 5 MW 2: W

Patented Apr. 11, 1933 UNITED STATES PATENT OFFICE LEO L. BECK, F WESTFIELD, NEW JERSEY, AND AUBREY E. NOBLE, OF LYN BROOK, NEW

YORK, ASSIGNOBS, BY KESNE ASSIGNMENTS, TO GENERAL TUBE LIGHTS CORPORA- 'IION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE GAS DISCHARGE LIGHT Application filed November 80, 1929. Serial No. 410,679.

The present invention relates to gaseous discharge devices of the type in which the discharge of electricit through rare gases causes the emission 0 light, more particularly a device in which the discharge of electricity through the gas or gas mixture causes the emission of white light.

The term white light as used herein has a specific meaning and relates to a light, which when subjected to spectrum analysis, has a composition approaching that of sunli ht.

The invention thus provides a new and improved white light by means of WhlCll the color of objects viewed thereby appears to be much the same as the color of the same objects when viewed by sunlight.

The invention furthermore provides a luminous tube device containing a lar e proportion of helium which nevertheess is adapted to emit a white light and 1s also adapted to possess a lon life notwithstanding the tendency of hellum to be absorbed by electrode action and other phenomena. The invention furthermore provides a new and improved luminous tube device containing a mixture of helium and neon in combination with electrodes or an electrode stabilized by a new and improved method, the mixture of helium and neon being so proportioned and the balance of these proportions being so maintained by the cooperative action of the cathode or electrodes with the gas mixture that a long life white light is obtained having a well proportioned and rich spectrum and being thereby well adapted for general illumination and photographic purposes.

The invention furthermore comprises a luminous tube device which although comprising a large proportion of a very active gas such as helium, is nevertheless adapted to have a long life notwithstanding the fact that the helium may be employed at relatively low and optimum pressures and that the energy efficienc of the li ht is consequently high, that 1s, the-\cand e power per unit of electrical energy consumed is relatively high.

When helium is employed as the path of a gaseous discharge in a tube provided with electrodes, the disappearance of the helium is ordinarily very rapid owing to its action upon the cathode. The life of the device can be increased by employing helium at relatlvely high pressures, as for example to mlllimeters of mercury, but the increase of life secured thereby is not sufficient to meet the demands of a long life commercial luminous tube device and furthermore the potential drop in the gas column is so hi h as to materially lower the efiiciency of t edevice as a light producer. On the other hand, when helium is employed at more eific1ent pressures such as in theneighborhood of 3 to 5 millimeters of mercury, the life of the device is ordinarily very short and may be as low as 30 to 50 hours.

According to the present invention helium at its mosteflicient pressure range such as for example 3 to 5 millimeters of mercury is blended with a relatively small proportion of neon, as for example from one-tenth of one per cent to three per cent and the mixture is employed as a rarified gaseous filling 1n an envelope containing discharge electrodes, one or both of which are stabilized by a new and improved method as will be hereinafter described and the gaseous filling is subjected to a discharge current whereby positive column light is emitted the light having the characteristics herein described.-

For example, a gaseous mixture composed of 97.75 per cent of helium and 2.25 per cent of neon at a total pressure of 3 to 5 millimeters of mercury may be placed in an elongated transparent envelope provided with electrodes as hereinafter described and subjected to a high potential alternating cur rent having for example characteristics such as 15,000 volts and milliamperes. Such a device will operate at high luminous eificiency and will emit a white light having a rich and well proportioned spectrum and will possess an effective life of more than 2,000 hours such as 3,000 hours or more as compared with a life of to hours with ordinary electrodes and 300 to 400 hours with electrodes provided with a metal of the alkali group such as caesium, potassium or sodium.

While the use of a mixture of helium and neon carefully proportioned in the manner described has been found to emit light of the desired character,'when subjected to an electric discharge, such a mixture would be ordinarily unfitted for use inasmuch as the rapid disappearance of helium particularly at the low pressures such as 3 to 5 millimeters hereinabove mentioned, would result in commercial failure on account of the short life of the device. By employing electrodes or a cathode suitably stabilized in combination with a helium neon mixture at pressures such as 3 to 5 millimeters and by employing the helium and the neon in correct proportions, the present invention provides a device which possesses first, relatively high efiiciency, that is to say, a relatively small consumptlon of electrical energy and a relatively high light emission as compared with a similar gaseous mixture and operating at higher pressures, secondly, a white light with a rich and well proportioned spectrum and well adapted for illumination and photographic purposes, thirdly a long life notwithstanding the low pressures and consequently the relatively small amount of gas present.

The invention furthermore provides, in combination, a cathode or electrodes so stabilized and adapted to co-act with the gaseous filling that not only is long life attained but also the proper balance between the proportion of neon and helium is maintained.

The proportion of neon is very small with reference to that of helium and although the helium tends to be absorbed much more rapidly than neon, the latter gas would ordinarily tend to disappear rapidly on account of .its very small proportion with a consequent destruction of the proper quality of light. However, by a suitable correlation of the electrode material with the gaseous mixture as herein described, the desired uniformity of the ratio of the gaseous components is maintained.

According to the present invention the electrodes are provided with suitable oxides. The oxides as such may be employed or may be generated in situ as by the decomposition of compounds which upon heating yield the oxides. Oxides of the electro-positive elements may be used as for example, the oxides of the alkaline earth metals and, in some cases the oxides of rare earth metals. The oxides employed are deposited or coated on the cathodes or electrodes in such a manner as to provide permanent adherent coating.

What areherein termed the suboxides are particularly desirable. These may be generated in situ by coating a refractory metallic electrode with a peroxide and decomposing the peroxide by means of heat in the presence of a refractory metal such as iron, nickel, copper and the like. For example, an iron electrode may be coated with barium peroxide and then subjected to heat to bring about decomposition or reduction in order to form an active coatingwhich will possess stabilized properties in combination with the gaseous mixture as hereinabove set forth. The term active coating has herein the arbitrary meaning that it relates to an oxide or material formed therefrom which as part of a discharge electrode possesses such properties as enable it to act in conjunction with the gaseous filling to produce the characteristics de scribed such as long life, high efficiency and permanency of the gaseous mixture and of the quality of light emitted therefrom.

The invention will be described in more detail by reference to the accompanying drawing which illustrates one embodiment of the apparatus of the invention and means for the practice of the process thereof. It is intended and will be understood that such specific embodiment is merely illustrative.

Figure 1 represents a tube provided with electrodes of the character described and further adapted to be operated by a high potential low current discharge, such as 12,000 volts and 25 milliamperes.

Figure 2 represents a refractory metallic electrode provided on the inside thereof with a suitable oxide coating.

- The discharge tube 1 may have any desired form such as the U shape shown and is provided at'each end with portions containing discharge electrodes 3 which in the event that alternating current is employed, may be, as shown, identical in form and structure. The electrodes are connected by lead wires 4 and 5 to the secondary 6 of a' transformer the primary 7 of which is connected to a source of current such as the generator 8. The tube 1 contains a gaseous filling comprising a mixture of helium and neon at a total gaseous pressure adapted to operateat a high luminous efficiency such pressure being in the neighborhood of 3 to 5 millimeters of mercury as measured in the usual way, such as 4 millimeters. The proportionof neon in the aseous mixture may be from one-tenth '0 one per cent to ten percent or more and is preferably in the neighborhood of 2.25 per cent of neon and 97.75 per cent of helium. A mixture in the proportion specified is adapted upon operation of the tube to emit what is defined herein as a white light. To repeat this definition, a white light as used herein, is one whichhas a spectrum which is so proportioned as to resemble the composition of sunlight and which enables objects to be recorded by the eye or by a camera in such a Way that the proportions of the various colors in the object viewed are not distorted.

Figure 2 shows an enlarged view partly in section of one of the electrodes. The nickel electrode 2 is provided upon the inside thereof with a coating 10 which is durable and permanent and comprises. the thermolyzed decomposition products of barium peroxide in contact with the nickel electrode. The coating consists of what is termed for the purposes of the present application, a suboxide of barium.

In operation, a small current and a high voltage are impressed upon the gaseous column as for example, 15,000 volts and milliamperes and the combination of stabilized electrodes with the gaseous mixture at a carefully chosen pressure and containing carefully adjusted proportions of components results in the production of a white light which operates at a high luminous efiiciency and possesses a remarkably long life.

Not only long life of the gaseous filling as a whole but long life of light of the desired 1 quality is a desideratum, that is throughout the life of the device it is important to preserve the proper balance between the small proportion of neon and large proportion of helium. The neon should be kept within a suitable range such as, for example, from 0.1 to 3 per cent. The necessity of maintaining a proper balance of gas ratios is appreciated when it is noted that if the proportion of neon falls substantially below 0.1 per cent, the color emitted is largely that of helium and if the proportion of neon goes much above 3 per cent the neon color becomes too prominent, while in the range of 0.1 er cent to 3.0 per cent, the color attained is a lend or combination of the helium and neon spectra of such a character that the resulting light is very valuable as a substitute for sunlight.

The display of merchandise such as clothin for example, calls for a light that will re ect colors without distortion. The present invention provides such a light and possesses marked advantages as compared with incandescent lights.

The advantages of the invention'have been set forth in some detail and the preferred embodiments have been described. It is to be understood, however, that various changes may be made without departing from the invention or sacrificing any of the advantages enumerated, or any other advantageous results which may be attained by an application of the principles and facts set forth.

What we claim is 1. A cold cathode gaseous discharge lumi nous tube device comprising in combination an envelope, an anode and a cathode therein, a helium-neon gaseous mixture adapted to emit positive column white light containing neon in the proportion of 0.1 to 3 per ceng, the said cathode comprising an active on e.

2. A cold cathode gaseous discharge luminous tube device comprising in combination an envelope, an anode and a cathode therein,

adapted to emit positive column white light, the said cathode comprising a suboxide.

3. A cold cathode gaseous discharge luminous tube device comprising in combination an envelope, an anode and a cathode there- 1n, a helium neon gaseous mixture adapted to emit positive column white light containmg neon in the proportion of 0.1 to 3 per cent, the said cathode comprising the thermolyzed decomposition products of a metallic oxide. 1

4. A cold cathode gaseous discharge luminous tube device comprising in combination an envelope, an anode and a cathode therein, a helium neon gaseous mixture adapted'to emit positive column white light containing neon in the pro ortion of 0.1 to 3 per cent, the, said cath e comprising barium suboxide and the device having a life in excess of 2,000 lamp hours.

In testimony whereof we aflix our signatures.

LEO L. BECK. AUBREY E. NOBLE.

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