US 1897587 A
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Feb. 14, 1933.
Filed July 22, 1931 INVENTOR Z'ZZa/zQQZZO' dQouvn/o BY Maya/[ ATTORNEY Patented Feb. 14, 1933 UNITED STATES PATENT OFFICE ELECTRIC COMPANY, A CORPORATION OF NEW YORK GASEOUS ELECTRIC DISCHARGE DEVICE Application fled July 22, 1931, Serial No.
The present invention relates to gaseous electric dischargedevices generally and more particularly the invention relates to such devices in which the gaseous atmosphere consists wholly or in art of a metal vapor similar to the device disclosed in co-pendmg application, Serial Number 459,868, filed June 9, 1930, being the invention of Marcello Pirani and Martin Roger.
As pointed out in the specification of the application referred to above the metal vapor present in the container of the devrce condenses readily when the walls of the container are cooled by the outside temperature which changes the operating characterist cs of the device. The object of the present invention is to prevent the condensation of the metal vapor present in gaseous electric discharge devices.
The invention attains itsobject by coating the walls of the container of the electric discharge device with a material which transmits all the visible light radiations emitted by said device, but which absorbs all the infra-red or heat rays emitted by said device. Gold or silver are suitable materials for this purpose and are applied to the container in a very thin film, or a dustlike coating, or deposit by methods well known in the arts, such as by chemical deposition, or cathode sputtering. I have found that a film of gold due to its slightly yellowish green tinge is most suitable for a device having sodium vapor therein and silver due to its weak blue tinge is most suitable for a device having a filling of cadmium, or mercury va- In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in sectional side elevation.
Referring to the drawing the gaseous electric discharge device comprises a glass container 7, having electrodes 5 and 6 sealed therein and a gaseous atmosphere therein, said gaseous atmosphere consists either of a metal vapor such as mercury, sodium, potassium cadmium, zinc, or calcium, or of a mixture of a metal vapor with a discharge conducting gas. Electrodes 5 and 6 are of the 552,458, and in Germany August 21, 1880.
electron emittin sintered, mixed metal and oxide type, whic glow during the operation of the device and which permit the use of a high current density .to heat the container 7. Glass container 7 is made of the usual glasses well known in the art, such as lead glass, lime lass, soda glass. Said container 7 is coate externally with an extremely thin film, or dustlike covering, or deposit 8 of metal such as gold, or silver which absorbs the infra-red, or heat rays emitted by the gaseous electric discharge device, but which transmits the visible light radiations emanating from said device as is well known in the arts. Such a coating of silver also transmits the ultra-violet radiations emanating from an electric discharge device filled with mercury vapor or other gaseous filling rich in such radiations and having a container which is transparent to ultra-violet radiations such as a quartz container; Havin this construction the container 7 of the device is maintained at a high temperature so that the metal vapor present in the gaseous atmosphere does not condense. If desired only those arts of the container which are heated but slightly by the gaseous discharge durin the operation of the device may be covere with the gold or silver coating.
It will be understood of course that where an alkali metal vapor, such as sodium, is used in the aseous atmosphere of the device container 7 should be made of a glass resistant to the effects of such metal vapor, such as, the glass disclosed in co-pending application Serial Number 470,436, filed July 24, 1930, being the invention of George Gaidies and Marcello Pirani.
While I have shown and described a particular embodiment of my invention it will be understood that various substitutions, modifications, and changes may be made in the form and details thereof without departure from the broad spirit and scope of the invention, for example, the container 7 may be a double walled container similar to that described in the co-pending application" referred to hereinbefore, any suitable type of electrodes may be used and any of the well known methods of applying the heat absorbing metal to the lass container ma he used such as those emp oyed in the manu acture of fractionating mirrors.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. In an electric discharge device, a container, a filling of discharge supporting eas- 11y condensible metal vapor therein, electrodes sealed therein, and a transparent noble metal coating on said container.
2. In an electric discharge device, a container, a fillin of discharge supporting easily condensib e metal vapor such as sodium vapor therein, electrodes sealed therein, and a transparent coating of gold on said container.
3. In an electric discharge device, a container, a filling of discharge supporting easily condensible metal vapor such as cadmium Vapor therein, electrodes sealed therein, and a transparent coating of silver on said container.
4. In an electric discharge device, a container, a filling of discharge supporting easily condensible metal Vapor therein, electrodes sealed therein, andan exterior coating of noble metal on said container.
In witness whereof, I have hereunto set my hand this 10th day of July, 1931.