US2001516A - Gaseous electric discharge device - Google Patents

Description

May 14, 1935. c. BOL

GASEOUS ELECTRIC DISCHARGE DEVICE Filed May 16, 1933 A A A A ATTORNEY Patented May 14, 1935 I I 2,001,516

UNITED sTATEs PATENT OFFICE GASEOUS ELECTRIC DISCHARGE DEVICE Cornelia Bol, Eindhoven, Netherlands, asslgnor to General Electric Company, a corporation of New York Application May 16, 1933, Serial No. 671,318 In the Netherlands June 30, 1932 7 Claims. (Cl. 173-122) The present invention relates to gaseous electainer. It is preferable that the greater part of tric discharge devices generally and more parthe length of said passage be located in the cooler ticularly the invention relates to improvements in stem parts of said container. .During the manusuch devices in which a condensable metal vapor facture of the device all parts of the container forms the gaseous filling or is a component of the thereof can be evacuated to the degree desired 5 gaseous filling, similar to the devices described because of the communicating passage. The in my co-pending application Serial No. 644,099, diameterof the long passage is preferably less filed November 23, 1932. than the length of the mean free path of the ion- In the co-pending application referred to above ized gas particles and a capillary tube is preferthe stem parts of the container of the gaseous able, so that the rate of flow of the vapor there- 10 electric discharge device are closed off from the through is reduced to a minimum. During the part of said container surrounding the discharge first few hours of operation of the device the few path. Undesired condensation of the metal vapor ionized metal particles that do penetrate into around the stern parts of the devices, which are the part of said passage located in the cooler 15. the coolest parts of the device, is thus avoided stem part of said container condense therein and and the vapor pressure of the condensable metal the deposits of condensed material on the walls of corresponds to the temperature of the container the passage close said passage so that the stem rather than to thatof the cooler stein parts of parts of said container are closed off from the said container. Where the walls of the conother parts of said container during the re- ..0 tainer are at a proper temperature the conmainder of the operating life of the device. densable vapor is maintained in vaporous condi- In the drawing accompanying and forming tion in-the discharge path during the operation part of this specification an embodiment of the of the device even though the stem parts of the invention is illustrated, in which container are at a lower temperature. When an Fig. l is a side elevational partly sectional view alkali metal, such as sodium, is used as the of an electric discharge device embodying one 25 source of the condensable vapor in such a device form of the present invention, and it is practical to make the parts of said container Fig. 2 is a detail sectional view of the stem part surrounding the discharge path of a glass resistof a gaseous electric discharge device embodying ant to the chemical effects of the metal vapor and another form of the invention.

the stem parts of a different glass having better Referring to Fig. ,l of the drawing the new and 30 sealing characteristics. than said resistance glass novel gaseo e e d sc e device Comprises since the stem parts are protected from the metal a light transmitting container I made of a glass vapor during the operation of the device. resistant to the chemical effects of the gaseous Although gaseous electric discharge devices of filling therein. Electrodes 4 and 5 are sealed the type described above are successful in operainto said container I and the electrode inleads tion some diiiiculty has been experienced in therefor are sealed into the pinch part 2 of the evacuating the containers thereof during the stem 3. Said stem 3 is, when desired, made of a manufacture of the devices. The object of the difierent glass than said container I and of a present invention is to provide a gaseous elecglass having better sealing characteristics than tric discharge device the gaseous atmosphere of said resistant glass. Said electrode 4 is the cathwhich consists wholly or in part of condensable ode, said cathode 4 consists of a metal filament, metal vapor in which evacuation of all parts of such as a tungsten filament, coated with an electhe container of the device is easily accomplished tron emitting ma u as barium Oxide, and during the manufacture of the device and in is electron emitting when heated. Said electrodes which the stem parts of said container are closed 5 are plate shaped anodes and are arranged on off from the other parts of said container during either side of said cathode 4. The part of said the operation of the device. Still further objects container I surrounding said electrodes 4 and 5 and advantages attaching to the device and to has a gaseous filling therein comprising a conits use and operation will be apparent to those densable gas, such as a mixture of neon at ap- 5 skilled in the art from the following particular proxima y 1 m Pressure d d or a description and from the appended claims. mixture of argon and sodium. The sodium which The above object is attained by providing a is solid at room temperature and from which the long, narrow communicating passage connecting sodium vapor is generated by the heat of the disthe part of said container surrounding the discharge between said electrodes 4 and 5 during the charge path and the stem parts of said conoperation of the device is located in that part of said container surrounding the discharge path between said electrodes 4 and 5.

'I'he part of said container I surrounding said stem 3 and said stem 3 are the coolest portions of said container I during the operation of the device. The septum 6 closes off the cooler stem parts 3 of the container I from the part of said container I surrounding the discharge path between said electrodes 4 and 5. Said septum 6 consists of a heat insulation material resistant to the chemical effects of the gaseous filling, such as mica, glass, or the like and is a circular disc the diameter thereof corresponding to or closely approaching that of the inner walls of that part of container I surrounding said stem 3. The current inleads for said electrodes 4 and 5 pass through said disc 6. Said disc 6 rests on top of the pinch part 2 of said stem 3 and is forced against the lower part of a circular indentation I in the walls of said container I. The space, if any, between the rim of said disc 5 and the inner wall of said container I is sealed by a body 3 of suitable sealing material, such as a mixture of talcum and water glass.

If the spaces above and below the septum i were completely divided during the manufacture of the device it would be difllcult to evacuate all parts of the container I through a single exhaust tip. For this reason the tube 9, made of insulation material, such as magnesium oxide, is provided to connect the spaces on both sides of said container I. The greater part of the length of said tube 9 is located in the space about said stem part 3 and part of the outer wall of said tube 9 is contiguous to the wall of said stem 3. The part of said septum Ii through which said tube 9 passes fits tightly around said tube 9 and a suitable soldering material, such as a mixture of talcum'in water glass, is used to hold said tube 9 against the wall of said stem 3. The tube 9 is thus held rigidly in position in said container I. The diameter of the passage in said tube 9 is approximately the same as the length of the mean free path of an ionized gas particle and said tube 9 is of the nature of a capillary tube. Though the length of tube 9 is optional depending on the type of container it is advantageous but not essential that the tube 9 have a length of at least 5 times the diameter of the passage therein and a greater length is advisable in many instances. I prefer a tube of 1 sq. mm. cross section and 2 cm. in length.

Having the above structure the spaces above and below the septum 6 can be evacuated through a single exhaust tip communicating with either one of said spaces which simplifies the manufacture of the device.

The device is started into operation by heating the cathode 4 to an electron emitting temperature. Voltage is then applied across the terminals of said electrodes 4 and 5 to start the discharge between said electrodes 4 and 5. At first this discharge is conducted between said electrodes 4 and 5 by the neon. The heat of the discharge vaporizes the sodium, which is solid at room temperature, and the light emitted by the device is rich in rays characteristic of the sodium vapor. The flow of sodium vapor through the passage in said tube 9 during the-operation of the device is reduced to a minimum due to the small diameter and long length of said passage. Part, or all of the metal vapor that does pass through said tube 9 condenses on the cooler lower wall thereof contiguous and adjacent to the stem 3. After the device has been operating a few hours deposits of this condensed material completely closes the narrow e in said tube 9 and the spaces above and below said septum 6 are completely divided. The advantages of this division of the space surrounding the discharge 5 path between the electrodes 4 and 5 from the space about the stem 3 have been pointed out above.

Another embodiment of the invention is illustrated in Fig. 2 of the drawing. This embodi- 10 ment is similar in all respects to the embodiment illustrated in Fig. 1 except that the septumlis a metal disc III made of nickel or chrome-steel, for example. Said disc I0 is slightly dished so that it is somewhatilexible to allow for the expansion and contraction of the walls of the container into which the rim parts of said disc are fused. A layer II of glass resistant to the chemical effects of the metal vapor in the part of the container surrounding the discharge path in the device is applied to the surface of said disc I0 facing the gaseous electric discharge path in the device to protect said disc I9 from the chemical effects of said metal vapor. Four round openings are provided in said disc III to accommodate insulating tubes I2 and I3 made of magnesium oxide, for example. Said tubes I2 and I3 are attached to said disc ID by flowing the glass of layer II into the openings between the sides of said tubes I2 and I3 and the sides of the openings in said disc I3 which also closes said openings in said disc III. The electrode inleads I4 are sealed into an inverted stem I 5 and are led through said tubes I2 and I3. Said tubes I2 fit tightly around the electrode inleads I4 therein. A slight play is present between the inner wall of the tube I3 and the inlead I4 in said tube I3. The lower end of said tube I3 terminates a distance fromthe stem I5 while the lower ends of said tubes I2 are fused into said stem I5. The passage in said tube I3 connects the spaces above and below the disc III so that both spaces are exhausted through a single exhaust tip during the manufacture of the device. During the first few hours of operation of the lamp device the passage I 3 is closed by deposits of condensed material therein as the lower part of said tube I3 is colder than the upper part thereof during the operation of the device. A complete separation of the space above and be 5 low the disc III is thus effected with the operating advantages heretofore pointed out.

Duringthe operation of the above described gaseous electric discharge lamp devices that part of the walls of the container I surrounding the discharge path is maintained at a temperature higher than the condensing temperature of the condensable gas by the high current density discharge between the electrodes made possible by the use of a thermionic cathode 4, or by reducing the rate of the radiation of heat from the walls of said container I to a minimum by an evacuated bulb enclosing the container or by a double walled, evacuated jacket, for example, or a combination of these methods is used, when desired.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States:- 15

5. An electric discharge device comprising a,

1. An electric discharge device comprising a container, electrodes sealed therein, a gaseous filling therein comprising a condensable gas, a stem fused to said container, a septum between the part of said container surrounding the discharge path between said electrodes and the stem part of said container, and a capilliary tube through said septum.

2. An electric discharge device comprising a container, electrodes sealed therein, a gaseous filling therein comprising a condensable gas, a stem fused to said container, a septum between the part of said container surrounding the discharge path between said electrodes and the stem part of said container, and a capillary tube through said septum, the greater part of said capillary tube being in the stem part of said container.

3. An electric discharge device comprising a container, electrodes sealed therein, a gaseous filling therein comprising a condensable gas, a stem fused to said container, a septum between the 'part of said container surrounding the discharge path between said electrodes and the stem part of said container, and a capillary tube through said septum, the greater part of said capillary tube being in the stem part of said container and contiguous to said stem.

4. An electric discharge device comprising a container, electrodes sealed therein, a gaseous filling therein comprising a condensable gas, a stem fused to said container, a septum between the part of said container surrounding the discharge path between said electrodes and the stem part of said container, said container and said septum being of a material resistant to the chemical effects of said gaseous filling, said stem being of a different material and a capillary tube through said septum.

container, electrodes and electrode leads sealed therein, a gaseous atmosphere therein, a stem fused to said container, a septum between the part of said container surrounding the discharge path between said electrodes and the stem part of said container, a tube of small diameter extending through said septum, said tube surrounding one of said electrode leads and having an inside diameter larger than the diameter of said lead.

6. An electric discharge device comprising a container, electrodes and electrode leads sealed therein, a gaseous atmosphere therein, a stem and having an inside diameter larger than the diameter of said lead.

7. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmosphere therein, a stem fused to said container, a septum between the part of said container surrounding the discharge path between said electrodes and the stem part of said container, a vaporizable material in the part of said container surrounding the discharge path between said electrodes and a communicating passage between the stem part of said container and the part thereof surrounding the discharge path, the cross-section of said passage being such that deposits of condensed metal vapor close said passage during the operation of the device.

CORNELIB B011.

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