US2118981A - Electric discharge tube - Google Patents

Description

y 1938. H. M. MUNCHERYAN 2,118,981

ELECTRIC DISCHARGE TUBE Filed July 3, 1936 INVENTOR.

Hrand j?urzclzer an ATTORNEY Patented May 31, 1938 Fro ELECTRIC DISCHARGE TUBE Hrand M. Muncheryan, Los Angeles, Calif.

Application July 3, 1936, Serial No. 88319 9 Claims.

My invention relates to electric discharge tubes adapted for illumination, rectification, and voltage regulation which can be mounted and operated in an ordinary incandescent lamp socket.

It is a purpose of my invention to provide a tube of this character which is capable of being started and operated at voltages" corresponding to the low operating voltages of incandescent lamps.

A further purpose of my invention is the provision of an electric discharge tube which, with no increase in current consumption and at low operating temperatures, produces illumination of considerably greater intensity than is possible with incandescent lamps, and of the same radiant character as incandescent lamps.

It is also a purpose of my invention to provide an electric discharge tube embodying electrodes having electron-emitting chemicals which, during operation of the tube, partially decompose and produce a gaseous medium having that characteristic of producing radiant light of great intensity and daylight in color, when ionized.

I will describe only one form of electric discharge tube embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing:

Fig. 1 is a view showing in longitudinal section one form of electric discharge tube embodying my invention.

Fig. 2 is a similar view taken at right angles to Fig. 1.

Fig. 3 is a transverse sectional view taken on the line 33 of Fig. 1.

Fig. 4 is a view showing in detail perspective the electro-conducting elements of the tube.

Referring now to the drawing, the tube includes a transparent envelope l5 which is generally similar to an incandescent lamp bulb. The envelope is provided with a central glass stem l6 through which pass leads I! and Ill. The envelope is mounted in a standard base which in-- cludes a threaded metal cup l9 filled with a body of insulation 20, the lead I! passing through the insulation and electrically connected to the .cup in any convenient manner, as at 2|. The cup has an open bottom closed by an insulating cap 22 and secured to this capby a tubular rivet 23 is a metal contact disk 24. A lead 25 is secured to and extends inwardly from the disk for connection to one terminal of a choke coil 26 situated within the body 20. The other terminal of the coil is connected to the lead l8.

From the glass stem I6 a tube 21 passes outwardly of the envelope for exhausting the envelope of air and refilling it with the required gases. This tube has an opening 28 leading to? the interior of the envelope, and its free end is sealed ofi after the pumping process. Integral with the inner end of the stem I6 is a bowlshaped glass support 29 enclosing two electrodes 30 preferably, although not necessarily, of substantially semi-circular form with their flat sides confronting. These electrodes are electrically separated one from the other by a septum 3| of insulating material which is preferably transparent, such as mica.

The septum is of a width slightly less than the internal diameter of the envelope, and of such a length as to terminate short of the rounded end of the envelope. It is supported in fixed position by a pair of electro-conducting elements 32 and 33, in the form of metal strips arranged centrally at opposite sides of the septum with one of their ends extending between the electrodes 30 and spot-welded thereto so as to be electrically connected therewith. The other ends of the strips are bent in opposite directions around the free end of the septum and spaced from each other as shown.

The element strips are provided with integral and lateral extensions 32 and 33, respectively, bent and extended through slots 34 in the septum 3|, so that the free ends of the extensions of one strip are disposed at the opposite side of the septum from that of the respective strip, and in spaced relation to the other strip. Also, the extensions of one strip are staggered with relation to those of the other strip to provide intervening electric discharge gaps. It will be understood that the gap between the terminals of the strips which are bent around the end of the septum also constitute an electrical discharge p- Thus it is now apparent that the two electro-conducting elements 32 and 33 are electrically connected to the respective electrodes 30 and electrically disconnected from each other, with discharge gaps along the length thereof and at the free terminals thereof. Further, the association of the strips and extensions with the electrodes and septum, is such that the septum is securely held in fixed position within the envelope.

At the center of each electrode 30 is a receptacle 35 perforated or porous and of inverted cup form. This receptacle is secured in the electrode by screw-threading, indicated at 36, or in any other suitable manner, and it contains a composition 31 constituting a source of carbon dioxide, as will be presently described. To the electrodes 30 are connected the leads I! and I8, respectively, so that the receptacles and the compositions therein constitute parts of the electrodes.

In practice, the envelope is adapted to be filled with a mixture of neon, argon and carbon dioxide, or any of the other inert rare gases in combination with carbon dioxide. This mixture is contained in the envelope at a pressure of between 7 and 16 millimeters of mercury pressure, with a preferred pressure of 9 millimeters. Preferably, the gases are employed in the ratio of 60% neon, 10% argon, and 30% carbon dioxide.

The electrodes 30 are made of any suitable refractory metal such as copper, iron, or nickel, preferably copper; The copper is coated with any suitable electron-emitting substance such as a mixture of thorium and zirconium compounds. I have found that to thorium oxide and 10% to 25% zirconium oxide gives very satisfactory results.

The receptacle 35 may be made of perforated metal or carbon. In either event the composition 31 constituting the source of carbon dioxide preferably comprises barium carbide 20% to 30%, magnesium carbonate 50% to 60%, and lanthanum carbonate 20% to 30%, all mixed with a binder of equal parts of sodium silicate and zir conium hydride.

carbonates are desirable because during the operation of the tube the salt dissociates into the element radical and carbonate radical. The carbonate radical still further dissociates into carbon dioxide and the remaining oxygen combining with the element radical forms an oxide of that element. As the amount of carbon dioxide gas in the envelope decreases by use, the carbonate salts thereby compensate, for this decrease by producing carbon dioxide gas. carbon dioxide is constantly fed into the path of the discharge where it is utilized together with other gaseous matters in the production of light in the envelope.

Barium carbide further decomposes into barium and carbide radical which reacts with the oxygen given off by carbonate radicals of magnesium and lanthanum, and produces more carbon dioxide, which is essentially utilized in the production of a luminous column of light between the electrodes. Zirconium hydride acts as dissociator of barium carbide into barium and carbon, and also acts as a catalyst in the formation of carbon dioxide of this free carbon and the excess oxygen liberated by the carbonate radicals.

Further, zirconium has the property of absorba ing a large quantity of carbon dioxide gas during processing of the tube, as well as when the tube is inactive. In the latter case, the absorption property of zirconium is utilized to reduce the number of carbon dioxide molecules in the envelope and thereby facilitate ionization of the inert gases when restarting the tube, thus rendering the carbon dioxide as emitted from the composition more easily ionizable.

The electro-conducting elements 32 and 33 and their extensions are made of any metal having that property of emitting electrons when a potential is applied thereto while coated with an alkali earth metal. Cadmium, antimony and aluminum are metals possessing this electron-emitting property, and preferably I employ aluminum. In the drawing, 39 indicates the coating of an alkali earth metal such as magnesium oxide or barium As this cycle goes on,.

oxide, either of which are goodelectron-emitting materials.

In operation of the tube, a potential applied to the electrodes momentarily establishes a starting path for the discharge having a rising voltage characteristic. This starting path includes the coated elements 32 and 33 and their extensions,

the extensions and the free ends of the elements functioning as auxiliary electrodes, With alternating current applied to the tube, first the extensions of one element and then the other operferred to the gaseous path between the electrodes,

and the function of the strips and extensions ceases almost entirely. With transfer of current to the gaseous medium a running path from one electrode around the septum to the other electrode is established having a falling voltage characteristic. Once this running path is completed the positive luminous column is completed within the envelope.

By virtue of the many auxiliaryelectrodes thus provided, and the large volume of electrons emitted from the elements 32 and 33 and their coatings 39, starting and further ionization of the inert gaseous filling in the envelope is rapidly effected to reduce the starting period and the period of prolongation of the luminous column.

Carbon dioxide has been selected as constituting a part of the gaseous filling because it possesses that property when ionized of producing, for all practical purposes, white light or daylight, and, hence, a light which is radiant and of great intensity. However, carbon dioxide is ionizable only at relatively high voltages, and hence, if used alone in a tube, the tube could not be operated on volt current in place of an incandescent lamp. Therefore, to effect ionization of carbon dioxide without increasing the potential applied, it is mixed with one or more inert gases which are ionizable at relatively low voltages.

Thus, through initial ionization of the inert gases ionization of carbon dioxide is eflected without increasing the voltage beyond that necessary to ionize the inert gases.

My reason for selecting carbon dioxide is not because it is the only chemical that possesses that property of producing radiant light of great luminosity when ionized, but because it is the cheapest of known chemicals possessing this property. Other related chemicals and anthraquinone and its related group may be employed.

By reason of the auxiliary electrodes as described above and the choke coil 26,sputtering due to abnormal current density or fluctuations at the electrodes during any interval of current alternation, is eliminated.

I claim:

1. An electric discharge tube, comprising; an

envelope containing a gaseous filling; a pair of electrodes mounted side by side within the envelope; a septum of insulating material extending between the electrodes; and electro-conducting elements secured to the electrodes and embracing the septum for holding the latter in fixed position within the envelope.

2. An electric discharge tube, comprising; an envelope containing a gaseous filling; a pair of electrodes mounted side by side within the envelope; a septum of insulating material extending between the electrodes; and at least a pair of electro-conducting elements on opposite sides of the septum secured to the electrodes and each element having parts extending through the septum and'spaced from the parts of the other element to form intervening gaps.

3. An electrode for discharge tubes, comprising; a body of refractory metal coated with an electron-emitting substance; a porous receptacle of electro-conducting material; and a composition in said receptacle comprising barium carbide, magnesium carbonate and lanthanum carbonate.

4. An electrode for discharge tubes, comprising; a body of refractory metal coated with an electron-emitting substance; a porous receptacle of electro-conducting material; a composition in said receptacle comprising barium carbide, magnesium carbonate and lanthanum carbonate; and a binder comprising zirconium hydride and an equal amount of sodium silicate.

5. An electrode for discharge tubes, comprising; a body of refractory metal coated with an electron-emitting substance; a porous receptacle of electro-conducting material; and a composition in said receptacle comprising 20% to 30% barium carbide, 50% to 60% magnesium carbonate, and 20% to 30% lanthanum carbonate.

6. In an electric discharge tube, a pair of electrodes; a septum of insulating material between the electrodes; elements on opposite sides of the septum electrically connected to the electrodes and electrically disconnected from each other, each of said elements being constructed of aluminum coated with magnesium oxide.

7. In an electric discharge tube; a septum of insulating material having slots therein; and a pair of electro-conducting elements at opposite sides of the septum having lateral extensions, the extensions of one element being extended through certain of the slots and the extensions of the other element being extended through the remaining slots and spaced from the extensions of the first element to provide intervening gaps.

8. An electric discharge tube, comprising; an envelope containing an inert gas; a pair of electrodes side by side within the envelope adjacent one end thereof; each comprising a cupped body of a refractory metal coated with an electronemitti'ng substance, and a porous receptacle fixed centrally within the body and containing carbonates for producing carbon dioxide gas in the envelope; a slotted septum of insulating material having one end between the electrode bodies and the other end spaced from the other end of the envelope; a pair of electro-conducting strips at opposite sides of the septum having one of their ends secured to the electrode bodies and the other of their ends extended around the free end of the septum; angular extensions on said strips projecting through the slots of the septum and coacting with each other and the strips to secure the septum in fixed position within the tube and to form gaps between the strips and extensions; and a coating of electro-emitting material on the strips and extensions.

9. An electric discharge tube, comprising; an envelope containing an inert gas; a pair of electrodes side by side within the envelope adjacent one end thereof; each comprising a cupped body of a refractory metal coated with an electronemitting substance, and a porous receptacle fixed centrally within the body and containing carbonates for producing carbon dioxide gas in the envelope; a slotted septum of insulating material having one end between the electrode bodies and the other end spaced from the other end of the envelope; a pair of electro-conducting strips at opposite sides of the septum having one of their ends secured to the electrode bodies and the other of their ends extended around the free end of the septum; and extensions on said strips projecting through the slots of the septum and coacting with each other and the strips to secure the septum in fixed position within the tube and to form gaps between the strips and extensions.

HRAND M. MUNCHERYAN.

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