US2075641A

US2075641A - Gaseous electric discharge device

Info

Publication number: US2075641A
Application number: US91195A
Authority: US
Inventors: Eduard G Dorgelo
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1935-07-08
Filing date: 1936-07-17
Publication date: 1937-03-30
Anticipated expiration: 1954-03-30
Also published as: FR807735A; NL47695C

Description

GASEOUS ELECTRIC DISCHARGEDEVICE Filed July 17, 1956 Amen 70m:

l'aumfo 6: [701M510 AT ORNEY Patented Mar. 30, 1931 PATENT OFFICE 2,075,641 GASEQUS ELECTRIC DISCHARGE DEVICE Eduard G. Dorgelo, Eindhoven, Netherlands, assignor to General Electric Company, a'corporationot New York Application July 17, 1936, Serial No. 91,195

In Germany July 8, 1935 1 Claim.

The present invention relates to gaseous electric discharge devices generally and more particularly the invention relates to such devices having a tubular container and a gaseous atmosphere therein consisting of or comprisinga metal vapor.

In the operation of devices of this type deposits of condensed vapor frequently accumulate in the regions of the container between each electrode and the end of the tube adjacent thereto since these parts of the container are heated less by the discharge than the parts of the container surrounding the discharge path between the electrodes and consequently are at a lower 15 temperature during the operation of the device. This disadvantage is very noticeablein devices having a quantity of dimcultly vaporizable metal therein, that is a metal the vapor pressure of which is less than 1 mm. at a temperature of 200 0., such as sodium, cadmium, magnesium,

for maximum efliciency; while the actual temperatures of their envelope or bulb walls range from about 220 C. or less to about 275 C. or more. The boiling point of sodium being about 877 C., the sodium vapor in the commercial lamp bulb is continually condensing on its inner surface and vaporizing again, with a tendency to accumulate and remain in any region or area that is relatively cool, because of the slower vaporization from the cooler region. This means that the sodium vapor pressure in the envelope will tend to fall below that corresponding to the general lamp temperature, and to approach that corresponding to the lowest temperature envelope part which is detrimental to the light output and efiiciency of the device. When the structure of'the device is such that parts of the con- 40 tainer are at a lower temperature than other container parts during'the operation of the device increasing the temperature of the whole container until the lowest temperature container part is at such temperature that an effective practicable since the energy expended in heating the higher temperature parts-of the container to a still higher temperature is wasted and further the container may be weakened or strongly attacked by the metal vapor at the higher temperature parts thereof.

The above disadvantage can be avoided by closing of! the part of the tube behind the electrodes from the other tube parts. This necessi- 55 tates the mounting of a septum in the container zinc, or the like. Commercial sodium vapor lamps aim at operating temperatures around 250 C.

vapor pressureis present in the device is imwhich increases the manufacturing cost oi the device. The problem can be solved by mounting the electrodes close to the ends of the container whereat the current leads are sealed.

. In this last structure the conducting seals are at an elevated temperature during the operation of the device and are apt to become gas pervious to terminate the useful life of the device.

The object of the present invention is to provide a gaseous electric discharge device of the above type which is simple in structure, is inexpensively manufactured and which has a long operating life. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in .the art from the following particular description.

xenon, is introduced into the lamp and is at a pressure of 2 mm. when cold, that is, at room temperature. During the operation of the de-' vice the metal vapor which penetrates into the space behind the main discharge supporting electrode is ionized and the ionized vapor is attracted back to the cathode that is in the direction of the discharge path between the main discharge supporting electrodes. The auxiliary discharge thus creates a cataphoresis action which counteracts the diffusion of the vapor particles toward the cooler ends of the container. The temperature of the seal at the end of the container can be lower than that temperature at which the seal becomes gas pervious without causing deposits of condensed sodium to form on said seal parts. The pressure of the fixed gas in the container must be appreciable, that is, 2 mm. or more, or else the cataphoresis action is not effective since the rate of diffusion of the metal is. too rapid at lower fixed gaspressure. In order to obtain a cataphoresis action sufiicient to overcome the difiusion of the vaporous particles into the cooler end portions of the container the discharge current of the auxiliary should be at least 3% of the main discharge current. The auxiliary electrode is connected to the current lead of the main electrode other than the main electrode to which said auxiliary electrode is adjacent by a resistance which regulates the auxiliary discharge current. This connection is either in the container, external thereto but mounted thereon, or may be remote from the container.

In the drawing accompanying and forming part of this specification a gaseous electric discharge lamp embodying the present invention and a circuit therefor is shown schematically.

Referring to the drawing the gaseous electric discharge lamp comprises a U-shaped container I having main

discharge supporting electrodes

2 and 3 sealed therein. Said

electrodes

2 and 3 are electron. emitting when heated-and consist of filaments of high melting point material, such as tungsten, which are coiled helically and which are provided with an electron emitting material, such as an alkaline earth oxide. The current leads for said

electrodes

2 and 3 are sealed into the

pinch parts

4 and 5, respectively of the container I. The external parts 6 and I of the current leads of the electrode tube are connected to the secondary coil 3 of the transformer 9, the primary coil ll of which is connected across the terminal I9 and I! of the alternating." current source II. The external parts I2 and I3 of the current leads for the electrode 3 are connected to the-secondary coil I4 of the transformer IS the primary coil I 6 of which is likewise connected toward the terminals I9 and I! of the alternating current source II. The electrode 2 is connected by lead Ii to the terminal I! of said current source II through the external resistance I8 and the electrode 3 is connected by current lead I2 to the terminal I8 of said source II. The

electrodes

2 and 3 are heated to an electron emitting discharge supporting temperature by said transformers 9 and I5 respectively. When desired said

electrodes

2 and 3 are heated to this temperature by the discharge incident thereat in which case the transformers 9 and I5 are omitted, when desired.

10 Auxiliary electrodes 20 and 2I are mounted between said

electrodes

2 and 3 and the

pinch parts

4 and 5 respectively of the container I. Said electrodes 20 and 2I consist of a cylindrical shell of high melting point metal such as molyb- 45 denum, and are supported in said container I by current leads fused into said

pinch parts

4 and 5 respectively. The auxiliary electrode 20 is connected through the resistance 22 to the current lead I2 of the main electrode 3 and the auxiliary 50 electrode 2I is connected through the resistance 23 to the current lead 6 of the main electrode 2. Said

resistances

22 and 23 have a value of several thousand ohms, when desired. The container I has therein a rare, starting gas, such as 55 neon, at a pressure of approximately 10 mm. at room temperature and a quantity of dimcul'tly vaporizable material, such as sodium, the vapor of which is light emitting during operation of the device. During the operation of the device 0 a positive column discharge occurs between the

main electrodes

2 and 3 which act alternately as cathode and anode. Since the auxiliary electrode 20 is connected to the main electrode 3 through the resistance 22 a voltage diiierence exists be- 5 tween "said electrodes and an auxiliary discharge takes place therebetwecn, the electrode 20 serving only as anodefor said auxiliary discharge. The

electrodes

2 and 20 act asa single phase rectifier, a discharge occurring therebetwecn 7 only when the auxiliary electrode 20 is positive .with respect to the main electrode 2. Secondly the auxiliary discharge current, which is, preferably, about 5% of the maindischarge current flows only in one direction, that is, in the direction of the main discharge path between said

electrodes

2 and 3. The auxiliary discharge between said

electrodes

2 and 20 ionizes the sodium atoms which enter the space between said

electrodes

2 and 20 from the part of the container I surrounding the main discharge path between the

electrodes

2 and 3. The sodium ions are attracted to the cathode of the auxiliary discharge, that is, to the main electrode 2, and the sodium vapor is thus prevented from reaching the pinch part 4. As the auxiliary discharge current flows only during that half cycle in which the auxiliary electrode 2 is negative with respect to the other main electrode 3 the cataphoresis action resulting from the. auxiliary discharge opposes the cataphoresis action caused by the main discharge. The cataphoresis action caused by-the main discharge causes a movement of the sodium ion to the main electrode 2 when said electrode 2 is acting as a cathode. The advantageous eflect exerted by the auxiliary discharge is enhanced by the relatively large gap between the auxiliary electrode and the main electrode which gap is greater than the diameter of the container I.

The auxiliary discharge between the main electrode 3 and the auxiliary electrode 2I has the same effect on the vapor ions and the sodium atoms are thus prevented from reaching the pinch part 5.

Gaseous electric discharge lamps having the structure described above are inexpensively manufactured, are eflicient in operation and have a long operating life since the seal at the end thereof is at a lower temperature than would be the case were the

main electrodes

2 and 3 mounted closely adjacent thereto and at the same time deposits of condensed sodium vapor are prevented from forming in the ends of the container behind the

main electrodes

2 and 3 and the sodium vapor is thus maintained in a vaporous condition in the main discharge path between said

electrodes

2 and 3 during the operation of the device.

While I have shown and described and have pointed out in the annexed claim 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, is:-

A gaseous electric discharge device comprising a tubular container, electrodes sealedthereln at the ends thereof, a gaseous atmosphere therein at a pressure greater than 2 mm. at room temperature and a vaporizable material therein, one of said electrodes being an auxiliary electrode and two of said electrodes being main discharge supporting electrodes, said auxiliary electrode being mounted adjacent one of said main discharge supporting electrodes and being interposed between said main electrode and the adjacent end of the container, the distance between said main electrode and said auxiliary electrode being greater than the diameter of said container, said auxiliary electrode being connected through a resistance to the main electrode other than that to which said auxiliary electrode is adjacent.

EDUARD G. DORGELO.