US2182778A - Gaseous electric discharge device - Google Patents

Description

Dec. H. ALTERTHUM AL 2,182,778

GASEOUS ELECTRIC DISCHARGE DEVICE Filed Aug. 17, 1938 INVENTORS Hans Alterthu m Avved, Lompe Kurt Wieeanol.

ORNEY Patented Dec. 12, 1939 UNITED STATES 2,182,778 GASEOUS ELECTRIC DISCHARGE DEVICE Hans Alterthum,

Lompe, Berlin,

Neuendorf, near Berlin, Germany,

Berlin-Wilmersdorf, and Kurt Wiegand, lichen-1 Arved assignors to General Electric Company, a corporation of New York Application August 1'1, 1938,

In Germany September 10,

3 Claims.

The present invention relates to gaseous electric discharge devices of the positive column type, and particularly to devices of this type containing mercury vapor.

A particular object of the invention is to produce a gaseous discharge device having a positive volt-ampere characteristic, whereby it may be operated on a. constant potential system without ballast. Other objects and advantages of the invention will appear from the following detailed specification or from an inspection of the accompanying drawing.

The invention consists in the new and novel structure hereinafter set forth and claimed.

Mercury vapor discharge devices of the low pressure positive column type as heretofore constructed ordinarily contain, in addition to the mercury vapor, a gas such as neon or argon, or mixtures thereof, at a pressure of at least 2 mm. of mercury. Such tubes may have either cold electrodes of the sheet metal type or activated thermionic cathodes, dependent upon the amperage for which they are designed, and ordinarily have a diameter of from 10 to 60 mm. All of these tubes of the prior art need for their operation a series impedance which must limit the tube current and must consume the difierence between the reignition voltage and the burning voltage. Without this series resistance, the tube current would increase indefinitely because, with increase of the current strength, the tube voltage drops and therefore a higher voltage is not necessary to obtain a larger current as is the case for instance with metallic current conductors. If one plots the current dependent on the voltage, then such tubes, as is well known, have a falling characteristic, while metallic current conductors have a ris ng characteristic.

We have now discovered that the necessity of such a series impedance is eliminated with a novel lamp structure of our invention. Thus we have found that by making the tube relatively lar e, the volt-ampere characteristic of mercury of low pressure mercury discharge tubes is rising or positive with current strengths of to 300 m. a., provided a' definite gas filling is contained within the device.

According to the invention, an electric mercury low pressure tube provided with oxide electrodes, at an inside diameter of the tube amounting to at least 30mm. and at a current load of NO .to 300 m. a., is provided with a filling of neon which is under a pressure of less than 2 mm. mercury column, The volt-ampere characteristic of such a tube is rising, and indeed the more Serial No. 225,396

strongly rising the longer the tube is. Such a tube, like an ordinary incandescent lamp, can therefore be operated without a series resistance. This novel positive volt-ampere characteristic is due to the fact that the voltage gradient in the 5 mercury neon mixture, i. e. the electric field strength measured in the positive column, increases with a rising current strength so markedly that it more than'ofisets the voltage drop of the oxide electrodes, which of course still 10 decreases with a rising current strength. With the use of argon of equal pressure, or of neon of higher pressure, or with the use of smaller tube diameters with a desired gas filling, the characteristic on the other hand is not rising with an 16 equal current load.

With tubes constructed and operated according to the invention, it has also been found to be advantageous if a small amount of argomfis added to the neon ground filling of less than 2 mm. 20 pressure, for facilitating the first ignition or also the reignition. By means of experiments it was found that the amount of the added argon should, as much as possible, not amount to 2% of the amount of neon, and expediently to about 0.2% 25 of the amount of neon.

For the purpose of illustrating the invention we have shown a preferred embodiment thereof in the accompanying drawing.

As shown in this drawing a mercury low pres- 30 sure tube according to the invention consists for example of a tube 34 mm. in diameter in which two oxide electrodes 2 and 3 are supported at a distance of 1 meter from each other. These electrodes, as illustrated, are of a type intended to be 35 heated by the discharge, but where desired, other types of electrodes are used. The tube I is filled with neon at a mercury column pressure of 1.5 mm., to which 0.2% of argon is added. The tube is also provided with a small amount of mer- 40 cury to provide the desired vapor.

When such a tube is operated with a potential such that a current of 100 to 300 m. a. is passed therethrough the device operates stably without a ballast impedance, despite reasonable fluctua- 45 tions in the voltage of the source, due to the novel positive volt-ampere characteristic which is inherent in this device within this current range. Hence this device is not only highly efllcient, due to the avoidance of the energy loss 50 which would otherwise be sustained in the series ballast, but also requires less investment, and also eliminates the problem of suitably disposing of the stabilizing impedance.

Tubes according to the invention are provided. 5

where desired, with an outer or preferably an inner coating of fluorescent substances, or can also consist of a fluorescing glass, whereby the light output of the device is increased and the color thereof changed in a manner well known in the art.

While we have described our invention by reference to a particular embodiment thereof, it is to be understood that various omissions, substitutions and changes, within the scope of the appended claims, may be made therein without departing from the spirit of the invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, an electric gaseous discharge device having a positive volt-ampere characteristic comprising a sealed tubular container at least 'n1m. in diameter, electrodes within said container and spaced to permit a positive column discharge therebetween, mercury within said container and a filling of gas consisting of at least 98% neon at a pressure of less than 2 mm. within said container, and means to supply a current of from 100 to 300 milliamperes to said device, whereby said device operates stably with a positive volt-ampere characteristic.

2. In combination, an electric gaseous discharge device having a positive volt-ampere characteristic comprising a sealed tubular container at least 30 mm. in diameter, electrodes within said container and spaced to permit a positive column discharge therebetween, mercury within said container and a filling of gas consisting of at least 98% neon with argon constituting the balance at a pressure of less than 2 mm. within said container, and means to supply a current of from 100 to 300 milliamperes to said device, whereby said device operates stably with a positive volt-ampere characteristic.

3. In combination, an electric gaseous discharge device having a positive volt-ampere characteristic comprising a sealed tubular container at least 30 mm, in diameter, electrodes within said container and spaced to permit a positive column discharge therebetween, mercury within said container and a filling of gas consisting of neon containing 0.2% argon at a pressure of less than 2 mm. within said container, and means to supply a current or from 100 to 300 milliamperes to said device, whereby said device operates stably with a positive volt-ampere characteristic.

HANS AL'I'ER'I'HUM. ARVED LOMPE. KURT WIEGAND.

Images