US1984426A - Gaseous electric discharge device - Google Patents

Description

Dec. 18, ,1934. M. PIRANI ET AL 1,984,426

GASEOUS ELECTRIC DISCHARGE DEVICE Original Filed June 9, 1930 INVENTORS ATTORNEY Patented Dec. 18, 1934 PATENT OFFICE GASEOUS ELECTRIC DISCHARGE DEVICE Marcello Pirani and Martin Reger, Berlin, Germany, assignors to General Electric Company, a corporation of New York Application June 9, 1930, Serial No. 459,868. Renewed April 5, 1934. In Germany July 10,

14 Claims.

The present invention relates to gaseous electric discharge devices generally and more particularly the invention relates to such devices in which a metal vapor is used as the entire gaseous content or as a. component of the gaseous content similar to those described in German application P. 60,764 VIII/2H2, filed July 12, 1929 and P. 60,944 VIII b/21f2, filed August 6, 1929.

It is well known that in such electric discharge devices the vapor of the metals used,'whi'ch may be mercury, sodium, potassium, cadmium, zinc, caesium or their alloys or mixtures thereof and particularly sodium or caesium, condenses very easily, lowering the vapor pressure, when the temperature of the container of the device is cooled by the outside temperature. Hence the operating characteristics of the device are dependent on or determined by the outside temperature since a change in metal vapor pressure changes the operating characteristics as pointed out in the applications referred to above. If the outside temperature drops to a very low degree the light column may be totally extinguished.

The object of this invention is to make such electric discharge devices operate independently of changes in the outside temperature by preventing condensation of the vapor present therein thus avoiding the use of an oiiset chamber and heating mechanism for supplying vapor to the tube.

The invention attains its object by maintaining the walls of the container of such device at a temperature at which harmful metal vapor condensation does not take place. This is accomplished by the use of sintered oxide electrodes similar to those disclosed in the application of Ewest and Pirani, Serial Number 377,044, instead of the usual metal electrodes, though it will be understood that any other suitable electrode may be used, said oxide electrodes permitting the use of high current densities in the discharge device thus increasing the heat of the discharge to maintain the walls of the container at a high temperature. The outside temperature may then vary over a comparatively wide range without aiiecting the operating characteristics of the device as metal vapor condensation is avoided in spite of the higher vapor pressure due to the high temperature of the container walls. Hitherto it was thought impossible to use oxide electrodes in conjunction with devices containing alkali metal vapors, such as sodium and caesium vapors, for it was thought that the oxide would be reduced to a metal by the alkali metal present in the device and would then vaporize more. easily than the oxide and not be as capable in maintaining the necessary high electron emission. We have proven by experiment, however, that such change in the oxide may take place in some types of electric discharge devices, but does not take place in the type disclosed in the drawing, these being positive column glow or are light sources.

In the drawing accompanying and forming part of this specification two embodiments of the invention are shown in which Fig. 1 is a side elevational view of the new and novel electric discharge device and Fig. 2 is an alternatii e embodiment of the new and novel electric discharge device.

Like numbers denote like parts in both views the device.

Referring to Fig. 1 the invention comprises a container 1 having sintered oxide electrodes 3, 3 sealed therein at both ends thereof, said electrodes 3, 3 having current leads 2, 2 connected thereto. Said container 1 has a gaseous atmosphere therein consisting of an easily condensible alkali metal vapor such as sodium or caesium vapor, or a mixture of such metal vapor with a discharge conducting gas or ,gases. As hereinbefore pointed out the use of "bxide electrodes in conjunction with such devices makes possible the 'use of higher current densities to obtain a greater discharge heat to maintain the container walls at a higher temperature than was possible hitherto with the use of metal electrodes and thus harmful condensation of the metal vapor is avoided at lower outside temperatures. If it is desired to operate the device in lower outside or surrounding temperatures than is possible even with the use of oxide electrodes, the container 1 may be made wholly or in part, as desired, of a heat absorbing glass such as Schott glass BG 9 and BG 10 which will absorb the ifra-red or heat rays emitted by the discharge in said container 1. Thus the gaseous discharge is maintained with the desired operating characteristics even at a lower outside temperature than is possible with the use of oxide electrodes alone, since the container walls due to the absorbing of the heat rays are maintained at a higher temperature. Heat absorbing glasses as a class are referred to in the International Critical Tables, Volume 2, pages 89 and 106, Volume 5, page 273 and the bulletin of the Bureau of Standards, Volume 14 and the BG 9 and BG. 10 glasses above referred to are listed in'Bulletin #4213 of the Jenaer Glaswerke Schott and Gen, the title of thehulletin being Jenaer Color and Filter Glass for Scientific and Technical Uses, published in April, 1929. BG 10 glass has the folowing composition:

If the device is to be operated in extremely low outside temperatures the container 1 may be double walled as shown in Fig. 2, either one or each of said walls being of heat absorbing glasses such as those described in connection with Fig. 1. The space between said walls may be evacuated or filled with a gas which absorbs the infrared rays, such gas may be, for example, nitrogen or argon and particularly carbon. dioxide or water vapor. It will be understood that the inner or outer walls of said double walled container 1 may be made of heat absorbing glass only in part if desired.

The important discovery set forth above that by virtue of the use of oxide electrodes in devices such as shown at 1, the tube can be run at higher current densities and the wall of the tube maintained at a temperature such that the metal vapor does not condense at the surrounding temperatures ordinarily metwith in practice results in a new tube of simple construction comprising a sealed container, having oxide electrodes which are non-sputtering and non-disintegrating in the presence of the rare, or common, gas. or metal vapor fillings of such tubes, used either alone or in combination, and thus the use of an offset chamber and the attendant vapor pressure regulating mechanism can be dispensed with, although it will be understood that in extreme cases such an arrangement can be used with our new oxide electrode lamp or the heat absorbing glass wall of BG 9 glass, or the double walled container construction may be used therewith, or said constructions may be used alone or in combination with each other to meet the particular needs of the service of the lamp, in the lighting field, or the industrial use of the lamp in photochemistry, where operations are carried on at normal or extreme high or low temperatures and constant operation of the lamp is required.

While we have described the container made of a glass having high absorption characteristics in the infra-red region of the spectrum only in conjunction with electric discharge devices having oxide electrodes and an alkali metal vapor gaseous atmosphere it will be understood that we contemplate using containers made of such glass for glass to prevent condensation of said metal vapor. 2. In an electric discharge device, a container,

I a filling of easily condensible alkali metal vapor bodies to maintain high current density in said' metal vapor, said container being of heat absorbing glass to prevent condensation of said metal vapor.

4. An electric discharge lamp comprising a container, electrodes sealed therein comprising a thermionic cathode, a gaseous atmosphere comprising metal vapor and a gas which is non-condensible at ordinary temperatures and a light transmitting heat retaining means supplemental to said container.

5. An electric discharge lamp comprising a container, electrodes sealed therein comprising a thermionic cathode, a gaseous atmosphere comprising metal vapor and a gas which is non-condensible at ordinary temperatures, said container being of heat absorbing glass to prevent condensation of said metal vapor.

6. An electric discharge lamp comprising a container, electrodes sealed therein comprising a thermionic cathode, a gaseous atmosphere comprising metal vapor said container being of heat absorbing glass to prevent condensation of said metal vapor.

7. In an electric discharge, positive column lamp device, a container, a filling of easily condensible alkali metal vapor, and homogeneous, oxidic electrodes therein, the electrodes being adapted to pass a current of high density through the metal vapor, and having high electron emissivity at the operating temperature of the lamp device, whereby condensation of the metal vapor is prevented when the lamp is exposed to low temperature atmospheres.

8. In an electric discharge lamp device, a container, a filling of easily condensible alkali metal vapor therein, electrodes for said container composed of sintered oxidic material, homogeneous throughout, and adapted to pass a current of high density through said metal vapor, whereby the electrodes become strongly electron emissive at the operating temperature of the lamp and compensate for heat losses to the surrounding at- -mosphere therefrom which tend to extinguish the discharge.

9. In a sell-heating gaseous discharge lamp device, a container with walls absorbent to infrared rays, a composite filling for said container comprising a rare gas and an easily condensible metallic vapor, in combination with homogeneous oxidic electrodes for said container adapted to pass a current of high density through the composite filling, whereby the metallic vapor component of the filling is maintained at its characteristic light radiating temperature when the lamp device is operating in low temperature atmospheres.

10. In a self-heating gaseous discharge lamp device, a double walled container comprising a discharge tube and a heat insulating chamber surrounding said tube and filled with an infra-red ray absorbent gas, an easily condensible metallic vapor filling for said discharge tube and oxidic electrodes adapted to pass a high density current of electricity through said filling, whereby the lamp device is maintained at a substantially uniform temperature under wide variations of temperature in the surrounding atmosphere.

ll. An electric discharge lamp comprising a container. electrodes sealed therein comprising a thermionic cathode, a gaseous atmosphere comprising alkali metal vapor and a gas which is non-condensible at ordinary temperatures and a light transmitting heat retaining means supple mental to said container.

12. An electric discharge lamp comprising a container, electrodes sealed therein comprising a thermionic cathode, a gaseous atmosphere comprising sodium vapor and a gas'which is non-condensible at ordinary temperatures and a light transmitting heat retaining means supplemental to said container.

13. In an electric discharge device a. ccntainer, electrodes sealed therein, at least one of which is a non-sputtering, non-disintegrating oxide electrode, a gaseous filling for said container'comprising a fixed gas'and a metal vapor and a light transmitting heat retaining means supplemental to said container.

14. In an electric discharge device a container, electrodes sealed therein, at least one of which is a non-sputtering, non-disintegrating oxide electrode, a gaseous filling for said container comprising a fixed gas and mercury and a light trans mitting heat retaining means supplemental to said container.

MARCELLO PIRANI. MARTIN REGER.

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