US2135691A - Gaseous electric discharge device - Google Patents

Description

GASEOUS ELECTRIC DISCHARGE DEVICE Filed Dec. 2, 1936 INVENTORS Hans AlcerHwum Marcello Pirani A ORNEY ?aten ted Nov. 8, ii T33 UNH'ED STATES rATENT OFFICE GASEOUS ELECTRIC DISCHARGE DEVICE Application In December 2, 1936, Serial No. 113,919 Germany December 6, 1935 3 Claims. (01. 176-124) from diflerent parts thereof and which is useful in the advertising and illumination fields. Still furtherobjects 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. gaseous electric discharge device having a oigasestherein, which gases have dif-- ferent' ionizing potentials, emits diflerent colored lighti'fromidiflerent'parfs thereof when the de- "vicej is op'erated ondirect current since the gas having-aa-lower ionizing potential travels toward the cathode-and the" gas having the higher ionizingpotent ial travelstoward the anode under the influence of the direct current discharge. This .25 separation .of the gases is known in the art as electrophoresis. and 'in pronounced cases in dischargedevic'esa-having an elongated tubular con- I tainerthe tube has-the appearance of two linear luminescent' columns of different color, for example, when a mixture of'neon and argon is used inthe tube? the device appears red at one end thereof and blue-violetv at the other end thereof.

When suehdevices are operated on symmetrical alternating current this phenomena does not take place because the tendency of the gases to separate during one half cycle is overcome by the reversal of current flow in the next half cycle. It is,

of course, possible to cause the separation of the gases in an alternating current device by super- 40 imposing a direct current on the alternating current, but such an apparatus is expensive and complicated.

' The present invention attains its objects by transforming in the lamp itself a symmetrical alternating current supplied to the discharge device into. an unsymmetrical alternating current to a degree that separation of the constituents of the gas mixture takes place with the efiect described above. The transforming of the symmetrical alternating current supplied to the tube into unsymmetrical alternating current can be accomplished in many difierent ways, for example,

when thermionic electrodes are used the electrode at one end of the tubular container has a difierent electron emissive capacity than that of the electrode at the other end of the tube; or when cold electrodes are used one electrode isactivated and the other is not, or when cold electrodes of equal size are used in each end of the tube the tube is connected across a high voltage 5 transformer which has an operating voltage slightly greater than the starting voltage of the tube and a particularly sensitive part of the tube is grounded. The sensitive part of the tube is discovered by groping either with the bare hand or with a grounded band. The assymmetry of the alternating current is equivalent to the super-' imposing of a direct current on the alternating current applied to the tube and has a like efiect, that is, it causes the separation of the constituents of the gas mixture so that one end of the tube emits a light typical of the gas collected thereat and the other end of the tube emits light typical of the different gas collected thereat.

It is 'sufilcient for the purpose of the invention if the separation of the gases in the tube proceeds only to that point whereat the gas having the lower ionizing potential is moved out of one part of the tube. Since the gas having the higher ionizing potential is excited to luminescence by the discharge only in that, part of the tube containing very little of the gas having the lower ionizing potential the tube then emits difierent colored light from different parts thereof.

Preferably the tubular container of the device is many times greater in length than in'diameter and the diameter itself is preferably small. The thermal diffusion of the gases in the tube, which tends to overcome'the separation of the gases under the influence of the unsymmetrical alternating current, is thus minimized. Preferably the percentage of gas having the lower ionizing potential, for example, argon in an argon helium mixture, or mercury in a neon mercury mixture, is such that it is just sufiicient to emit light. We have observed that the smaller the amount of the component having the lower ionizing potential the faster is the separation of the gases in the tube.

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 one embodiment of the invention, and

Fig. 2 is a similar view of another embodiment 50 of the invention.

Referring to Fig. 1 of the drawing the gaseous electric discharge device comprises a tubular container I having electrodes 2 and 3 sealed therein at the ends thereof and having a gaseous atmos- 55 phere therein. Said electrodes 2 and I are electron emitting when heated to an elevated temperature by the eifects of the discharge incidentthereat and consist oi a pellet of electron emitting material, such as barium oxide, having a illament of high melting point material, such as tungsten, wrapped around said pellet. The electrodes I and s are selected so as to have different electron emissive capacity. The gaseous atmosphere consists of a mixture of helium at a pressure of approximately 8.7 mm. and argon at a pressure of approximately 0.3 mm. The tubular container I is about 7 mm. in diameter and the electrodes 2, 3 are separated a distance of about 300 mm. When the lamp described above is connected to a source of symmetrical alternating current a visible separation of the gas mixture takes place immediately after the discharge has started and the maximum separation of the constituents takes place in approximately 30 seconds.

The discharge in the end of the tube whereat the less emissive electrode is mounted appears yellow-rose in color and the discharge at the opposite end of the tube appears blue-violet in color. A tube having this appearance is, of course, useful for advertising purposes.

When cold electrodes 5 and 6 are used a sensitive part of the container i is connected to ground by band I, as shown in Fig. 2 of the drawing, and as disclosed above.

When the gaseous atmosphere comprises a metal vapor and a fixed gas, such as a mixture 01' neon and mercury vapor, a similar separation takes place, the blue colored light from the mercury vapor being present at the electrode having the smaller cathode drop and the red neon light appearing at the electrode with the larger cathode drop. In this case it is advantageous to place the source of the mercury vapor at that end of the tube to which the vapor travels during the operation of the tube. 'This is accomplished in many diiferent ways, for example, an oifset chamber mounted at the desired part of the tube is particularly eflective. Preferably, however, the quantity of vaporizable mercury in the tube is suchthat it is completely vaporized during the operation thereof.

When desired, a light approximating white light can be obtained from a device similar to the device described above when the container I is filled with mercury vapor and contains neon at a pressure of approximately 2 mm. Inthis case the tube is preferably surrounded by a light diflusing jacket which mixes the red and the blue light emitted from different parts of the tube. In this case the container'i is preferably of U-shape or is coiled helically. When desired, sodium is introduced into the tubular lamp container oi the .above embodiment and the light from the sodium is visible at the cathode having the smallest drop, the blue light of the mercury is visible' in the center portion of the tube and a red luminescent neon light is visible adjacent the other electrode.

While we 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 arsenal those museum artwithoutdeparting from emits light diiierent in color than the emitted by any of the gases in the tube, desired, a yellow fluorescent material, zinc silicate, is applied to that part ofthe' "the container surrounding the luminous mercury the broad spirit and scope of the invention, for

column of a device containing neon and mercury 10 each of said gases having a diiferent ionising N potential said electrodes being cold electrodes, the voltage of said current source being slightly higher than the starting voltage of said device. a sensitive part of said device being grounded to transform the symmetrical alternating current as into unsymmetrical alternating current in said device to cause said device to emit diiferent colored light from different parts thereof.

v 2. In combination a current source of symmetrical alternating current, a gaseous electric discharge device connected across the terminals of said source, said device comprising an elongated tubular container. electrodes sealed therein at the ends thereof, a mixture of gases therein. each of said gases having a diiierent ionising potential said electrodes being cold electrodu, the voltage of said current source being slightly higher than the starting voltage of said device, a sensitive part of said device being grounded to transform the symmetrical alternating current into unsymmetrical alternating current in said device to cause the discharge in said device to emit diiierent colored light from different parts thereof and a luminescent material capable of light emission under irradiation by said discharge mounted in light receiving relation to said discharge.

3. In combination a current source of symmetrical alternating current, a gaseous electric discharge device connected across the terminals of said source, said device comprising an elon' gated tubular container, electrodes sealed therein at the ends thereof, a mixture of argon and metcury vapor therein, each of said gases having a diiferent ionizing potential said electrodes being cold electrodes, the voltage of said current source being slightly higher than the starting voltage of said device, a sensitive part of said device being grounded to transform the symmetrical alternating current into unsymmetrical alternating current in said device to cause the discharge in said device to emit diflerent colored light from different parts thereof and a luminescent material capable of light emission under irradiation by said discharge mounted in light receiving relation to said discharge.

HANS AL'I'ER'I'HUH..

MARCEIID PIRANI.

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