US1971907A - Gaseous discharge device - Google Patents

Description

Au 28-, 1934. c G FOUN 1,971,907

GASEOUS D ISCH ARGE DEVI CE Original Filed July 2, 1928 Inventor-z Clifton G.F'o u rid.

I ZZA/ HisAttorneg.

Patented Aug. 28, 1934 T OFFICE GASEOUS DISCHARGE DEVICE Clifton G.

New York Found, Schenectady, to General Electric Company,

N. Y., asslgnor a corporation of Application July 2, 1928, Serial No. 289,696

.. Renewed. October 26, 1933 5 Claims. (01. 176-122) The present invention relates to electrical discharges in gases, and in particular comprises new gaseous glow devices adapted for operation with alternating current.

It is the object of my invention to provide a convenient form of thermionic arc device for illumination or other purpose, which will be operable with alternating current at ordinary distribution potentials.

Prior to my invention electric discharge devices having a positive column of high luminosity have been constructed for operation with alternating current by providing two anodes together with a single cooperating cathode. Such devices required a threewire supply circuit, and in some cases are subject to arcing between the anodes.

In accordance with my invention I have provided gaseous discharge devices, which operate with a long positive column discharge,- and having electrodes at opposite ends which function reversibly as cathode and anode will respect to one another.

In thermionic gaseous devices having an elonated envelope in. which the distance between the electrode is long relative to the distance of the electrodes from the walls, the walls of the envelope appear to have a grid-like effect in resisting the starting of a discharge. Apparently the walls become negatively charged will not start through the gas between the electrodes until enough positive ions have been formed by a high voltage impulse to discharge the nega-' tive charge on the walls. I have discovered that in such an elongated envelope under suitable conditions successive electric discharges can be operated in opposite directions without requiring the continuous operation of a-high voltage ionizing means -oran operating voltage which is appreciably higher than a continuous or direct current discharge would require in an envelope of the same size and shape.

Apparently under suitable conditions of gas pressure and the geometrical relation of the electrodes to one another and to the envelope, the' time required for a complete diffusion and discharge of the positive ions is greater than the time d ring which, in an alternating current cycle, the impressed voltage is too low to support a discharge.

My invention will be pointed out with greater particularity in the appended claims and will be more fully understood by reference to the ac- 'companying drawing as explained by the following description.

In the drawing Fig. 1 is a perspective view of a and a discharge" gaseous glow lamp embodying my invention, part of the envelope being removed; Fig. 2 is a. longi-- tudinal section of an electrode and adjacent parts; and Fig. 3 is a diagram of anelectrical circuit suitable for operating my improved lamp.

Referring to Fig. 1, the lamp illustrated comprises an elongated tubular envelope 1, vconstituted of glass, quartz, or other suitable transparent material, and having at opposite ends reentrant stems 2, 3, through which pass respectively current conductors 4, 5 and 6, 7.

Upon these respective pairs of conductors are mounted the electrodes 8, 9 each of which function alternately as cathode and anode. The structure of these electrodes is shown in detail in Fig. 2. As these electrodes operate each alternately as anode and cathode they may be similar or identical in structure. The electrodes illustrated comprise a'hollow body or cylinder 10, which is heated by radiation or conduction or both from a heater 11 which is located within the cylinder 10, the electric circuit being constituted by the conductor 5 connected to one of the terminals of the heater 11, the cylinder 10, which is welded or otherwise joined to the oppo- 30 site terminal of the heater, and the conductor 5, to which the cylinder 10 is in turn joined. The cylinder 10 which may consist of a foundation metal such as nickel, iron or platinum, is coated with thermionically active material, such as an alkaline earth oxide. For example, it may be coated with a layer of barium carbonate preferably admixed with a cellulose compound binder, the carbonate later being decomposed by heating the foundation metal to a temperature of about 1300 C. in a maintained vacuum. The heater 11 consists of a suitable refractory metal .such as tungsten or molybdenum. Surrounding the cylinder 10 is a shield 12, which preferably is connected to the conductor 5, and serves both to conserve the heat required for maintaining the cathode-at an operating temperature and to reduce deposition of evaporated cathode material on the wall of the envelope.

Thermionic electrodes, such as herein described, having a broad emitting surface are superior to ordinary filamentary cathodes for gaseous glow devices and will be briefly referred to as broad cathodes. The surface area and electron emissivity of such a broad thermionic cathode should be chosen to give a total electron emission which is capable of supporting the luminous discharge without causing thefall of potential at the cathode to rise above the value at which the electric disintegration becomes ap- 'ducing gas or vapor,'such illustrative example, a

- lower voltage.

preciable. If the high then the effect of positive ion bombardment on the cathode is negligible and the lamps have a long life.

After the electrodes have been formed and degassed and the vitreous envelope has been baked and evacuated of gas, a luminosity-proasneon, helium or mercury vapor is admitted. For example, neon at a pressure of about 1.5 to 3 millimeters of mercury may be employed.

As shown in Fig. 3, the terminals of the electrodes 8, 9 may be connected to an auto-transformer 14 which is connected to a supply circuit 15. The wiresi, 5 and 6, '1 are connected respectively by the conductors 16, 1'7 and 18, 19 to the sections 20 and 21 of the transformer secondary for the supply'of electrode heating current. In order to start the lamp into operation a high potential impulse is impressed upon it by any suitable means examples of which are well known.

For illustrative purposes, a starting device has been shown comprising a mercury switch 22 which is connected to an intermediate point of the transformer 14 through a resistance 23 and an end terminal by the conductor 24 in circuit with a magnet 25. When the supply circuit 15 is energized the magnet 25 lifts its. armature 26, thereby interrupting the flow of current in'the switch circuit and impressing the resulting high voltage impulse on the lamp terminals. These terminals when up to temperature are emitting electrons and ready to start into operation a thermionic discharge when the high voltage discharge is impressed upon them.-

'A discharge, when once started, will continue to operate at ordinary lighting circuit voltage, that is, the voltage of to 220 volts. As an lamp having a tubular envelope about 40 inches long (about one meter) and 1 inches (about 4 c. m.) in diameter provided with broad thermionic electrodesat opposite ends, and containing neon. gas at a pressure of two millimeters of mercury may be operated steadily to produce a luminous discharge with alternating, sixty "cycle current of about one ampere and an impressed voltage of about 220 volts. A shorter lamp can be operated with a Such a discharge willhave an over-all luminous efficiency of about 10 lumens per watt. A preponderate proportion of the voltage consumed in such a lamp is consumed in the gaseous discharge and only a small proportion at the electrodes.

electron emission is sufficiently cooperating electrodes, each comprising sealed envelope containing a What I claim as new and desire to secure by Letters Patent of the United States is:

1. An alternating current arc lamp comprising a sealed envelope, a luminosity-producing gas therein, and cooperating electrodes spaced apart a distance which is long relative to their size and comprising hollow metal bodies, electric resistance heaters within said hollow bodies, leadingconductcrs therefor sealed into said envelope, and a material coating said hollow bodies having a higher electron emissivity than said bodies, each of said hollow metal bodies having a surface area such that the anode drop in said lamp is substantially zero.

2. An alternating current positivecolumn arc lamp comprising an elongated tubular sealed envelope, a luminosity producing g'as therein, and cooperating electrodes located at opposite ends of said envelope and serving alternately as anode and cathode, a coating of ,material of high electron emissivity on each of said electrodes, each of said electrodes having ,a surface area such thatthe anode drop in said lamp is substantially zero.

3. An alternating current positive column are lamp comprising an elongated tubular sealed entherein, and a metallic body, a coating of high electron emissivity on said body and a tubular metallic; shieldextending about said body and connected thereto, located at opposite ends of said envelope and serving alternately as anode and cathode, each of said electrodes having a surface of such area that the anode drop in said lamp is substantially zero.

4. An alternating current lamp comprising. a sealed envelope containing a luminosity-producing gas, cooperating electrodes therein which serve alternately as anode and cathode, each of said electrodes having a surface of high electron emissivity, and means to heat each of said electrodes, the surface area af eacli of said electrodes being such that the anode drop in said lamp is substantially zero.

5. An alternating current iamp comprising a luminosity-producing gas and cooperating thermionic electronemitting electrodes which serve alternately as anode and cathode, the surface area of each of said electrodes being such that the anode drop in said lamp is substantially zero.

velope, a luminosity producing gas CLIFTON G. FOUND

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