US1980032A - Self-starting enclosed arc lamp - Google Patents

Description

Nov. 6, 1934. c. H. BRASELTON SELF STARTING ENCLOSED ARC LAMP Filed Oct. 21, 1930 2 Sheets-Sheet 1 IN VEN TOR Y- 1934- c. H BRASELTON 1,980,032

SELF STARTING ENCLOSED ARC LAMP Filed Oct. 21, 1930 2 Sheets-Sheet 2 INVENTOR Patented Nov. 6, 1934 1,980,032 SELF-STARTING ENCLOSED ARC LAMP Chester H. Braselton, New York, N. Y., assignmto Sirian Lamp Company, Newark, N. J a corporation of Delaware Application October 21,

'10 Claims.

This invention relates to arc lamps, and particularly to that type of arc lamps in which the arc is self-starting and sustaining and is permanently enclosed within the container.

Among the principal objects of the present invention is to'provide'an arc lamp of the permanently enclosed type in which the arc will form at ordinary house voltages on the closure of the electric switch connecting the lamp to the power circuit. Another object of the invention is to provide a self -starting arc lamp which may be continuously operated in an enclosed container without the necessity of replenishing the gaseous atmosphere in which the arc operates.

Another object of the invention is to provide an arc lamp in which illumination is derived not only from the arc itself, but from the electrodes defining the arc.

Still another object is to provide an arc lamp in which a variety of various gases and electrodes may be used for obtainingvarious types of radiation either for purposes of illumination or for Figs. 4 and 5 are views of modifications of the preferred disclosure.

A'type of lamp or energy radiator has been developed in.which a coil of tungsten wire is .coated with anelectron emitting material, such as alkaline oxides, and electric current passed through this tungsten coil while immersed in a static atmosphere of inert 'monatomicgases, such as those of neon, argon, krypton; nitrogen and the like. Under such circumstances a halo or layer of activated gases forms about the tungsten coil and serves as a source of energy radiation.

In thepresent invention I'utilize the invention above described to the extent of obtaining thereby an active gaseous atmosphere, but I employ this atmosphere for purposes of maintaining an arc discharge between separated electrodes.

Referring to the drawings, I have shown in Fig. 1 a container 10, which may :be of transparent material, such as glass, particularly where the radiator is intended for use as a source for illumination. To'the base of this container is sealed 55 an inner support or stem 11, arising from which are three standards 12, 13' and 14; The standards 12 and 13 each arise to the central point in the container, forming sections 15 and 16, each of which may preferably be enclosed in an insu-.

lating coating or'in tubes 17 of glass, for the 1930, Serial No. 490,123

of approximately one-sixteenth (1 5) of an inch,

andthe diameter of the coil may vary from four hundredths (.04) to eight-hundredths (.08) of an inch, or may be larger, dependent upon the size of the lamp and the uses to be made of the same. Sections 24 and 25 of the coils 20 and 21 are coated with electron emitting material. These sections are spaced away from the ends 22 and 23 of the coils, these ends and portion of the coils adjacent thereto being free of any coating material. The coating substance forming coated sections 24 and 25 consist of alkaline oxides, such as the oxides of barium, strontium, calcium, and the like, these substances, when heated, emitting electrons in considerable profusion. In the radiator hereinabove referred to, a method'of forming and applying a coating to a. base metal, such as tungsten or tantalum, is used. In the present instance, while utilizing the principles of said method, I modify it as follows. The tungsten wire, which is preferably coiled as stated, is coated with a paste externally, or the paste may be applied internally ofthe coil so as to be in contact with themeta-l thereof. This paste includes, for example, in an intimate mixture, barium carbonate, calcium carbonate and barium nitrate in'the relatve proportions of 40 grams of barium carbonate, 40 grams of carbonate calcium, and 8 grams of barium nitrate with a binder of sumcient nitrocellulose dissolved in amyl acetate to make a coating which adheres to the wires. The coated coils are then mounted on their standards and fixed to the stem support and the whole sealed inthe bulb of the container. An oven is then lowered over the bulb and the bulb heated to as high a temperature as the envelope will stand without softening, the temperature generally being in excess at 400 C. Simultaneously, a connection is made to the exhaust pump and as gases are admitted to the walls of the container and to the various elements within the container, the same is removed by the pump. When the emanation of gases ceases, as indicated by the drop in pressure, to a point in the neighborhood of 9. micron, the -oven is removed and the container and its contents heated by means of a high tension electro-magnetic coil heater. This liberates additional gases which are removed by the pump. When the gas process is completed the coating of the tungsten coil is in proper condition for use in a lamp.

It has been found advantageous, as a means of eliminating gases from the voltage container, to admit neon gas in small amounts, subsequently heating the container and removing the neon and other gases liberated. A test of proper gas conditions within the bulb is obtained by the use of a high tension discharge, the inner bulb atmosphere being bluish when any foreign gases are still present within the container.

Mounted on the standard 14 of the support 11 is a small capsule or box 26 having an aperture Z'Itherein and containingsmall masses of the meta1 calcium, caesium chloride, and in some cases a mixture of cerium metals,.such as is obtained from monazite sand and known under the trade name of Misch-Metal. This last substance has not been found necessary in the preparation of the atmosphere of the radiator, although in some instances it improves the operation. Chemically pure inert gases are used in the bulb. Before the bulb is removed from the pump these inert gases are inserted therein. For this purpose neon gas to the amount of 50 mm. of mercury is found to be satisfactory, although the amount is not critical, amounts as low as 25 mm. giving good results. Various other gases may be added in relatively small amounts, such as argon, but neon has been found to be the most useful because of its relatively high conductivity to electricity.

By means of the high tension electro-magnetic heating device, the metal and compounds contained in the capsule 26 are nowvaporized, the caesium chloride disintegrating to liberate chlorine, and the calcium combining with .the chloride to form calcium chloride. As the caesium in the form of a vapor mixes with the neon, it thus forms an atmosphere of neon and caesium immersing and surrounding the tungsten coils 20 and 21 and their coatings 24 and 25. The caesium vapor also condenses on the electrodes 22 and 23, since the tungsten of the electrodes is electronegative to caesium.

In operation, it is necessary only to apply an ordinary potential, such as is available in residences and oflices, to the standards 12 and 13 01' the radiator. A potential of 110 volts of alternating current is usually available, and when this voltage is applied to the lamp a discharge forms between the ends 22 and 23 of the coil, the caesium coating on the electrodes functioningto lower the breakdown potential of the gases between the electrodes. This, of course, is fol1owed.by a heating up of the tungsten wires 20 and 21, and the coatings 24 and 25 become electron-emittin and ionize the atmosphere, and in this way serve to maintain a gaseous discharge intermediate the ends of the coils 20 and 21.

It has been found that the electrical capacity of this circuit and of the electrodes is suificient to maintain the arc discharge without any electrode' disintegration, and further, that no chemical reactions take place where the gas removing treatment of the process has been carried out so as to prevent any secondary chemical combinaaifects the operation of the device.

The color ,of the arc discharge is a brilliant white, this arising from the arc and from the incandescent electrodes which are luminous for a short distance from the ends 22 and 23 of the electrodes. Should the arc tend to travel alon the wire coil, the presence of the tungsten'rods 18 and 19 serve to provide additional electrodes of substantial mass which will maintain the arc without any further movement toward the nickel supports, thus safe-guarding the effective operation of the lamp.

In Fig. 4 I have shown a modification of the invention which consists in the identical elements of Fig. 1 with the exception that placed in electrical series with the tungsten coil circuit is a length of iron wire 30 which is supported between a short piece of tungsten 31 welded to the nickel standard 15 and to the lead-in wire 32, the outer end of which is adapted to make connection to the power circuit. The iron wire 30 consequently is series with the lead-in wire 32, tungsten rod 31, the coils 20 and 21, standard 16, and lead-in wire 13.

The iron wire coil 30 is so dimensioned that drop across the arc, is equal to the most eifective operating potential. Also, the resistance of the iron wire is such as to bring it within the temperature range ordinarily below 500 C. in which there is no large increase of resistance for change of voltage, in this way acting as a ballast and tending to maintain a uniform voltage across the electrode to the arc.

In Fig. 5 an additional modification of the invention is shown in which the coils 20 and 21 terminate in tungsten cylinders or tubes, thus forming the electrode points between which the discharge forms, while the- coils 20 and 21 make up the necessary potential drop from the supporting standards .to the electrode cylinders 40 and 41. In this modification, therefore, there is provided a larger mass than would be available if the resistance wire were alone used.

The coating substance forming sections 24 and 25 may be applied externally or internally of the coil. I have found also that the alkaline oxides may be mixed with a conductor to form a homogeneous body. For example, thorium oxide, together with thorium, may be mixed with tungsten bycombining thorium nitrate with tungstic acid and this mixture placed in the form of a filament. The presence of the thorium compound or the element bothtends to increase the electron emissivity of the conductor, thereby accomplishing the purpose of-the coating as herein above described.

I have found also that the emissivity of the conductor may be increased by including within the container a vapor of calcium or caesium. These vapors may be introduced by heating solid pellets of the metal in the container after it is otherwise completed, by means of electro-magnetic induction.

Various alternative arrangements of the lamp structure may be made which should be mentioned. For instance, instead of the electrode coil 21 I may employ a single straight rod or wire bearing the coating 25. Also, the coating 25 may not necessarily be applied externally or internally as a coating but may be in the shape of a triangular rod having contact against the coil at two or three points. By this means a minimum amount of ionization may be produced which is desirable under certain uses. Other rod shapes may be employed which will permit variation in the amount of ionization. I have also indicated the standards 15 and 16 as insulated, but it is obvious that such insulation may be extended through the base portion of the standards 12 and 13 and that this insulation may be any dielectric or non-conducting substance, including glass or quartz.

A feature of the lamp as described is the fact thatthe ionization produced on the coated electrodes tends to restrain vaporization of the tungsten material of the electrodes and thus prevent blackening of the container surface. This is of considerable importance where the radiator is used for illuminating purposes.

Modifications other than as hereinabove described may, of course, be made by those skilled in the art to which this invention pertains, and.

' phere of caesium vaporin said envelope.

2. In an electric radiating device the combination of an envelope, supports therein, a plurality of standards mounted on said supports, coils of refractory wire mounted on two of said standards, the end of each of said coils being adjacent an end of the other coil, a coating of electron emit ting material on said coils on areas spaced from said adjacent ends, said adjacent ends being bare when the device is in operation, and an atmose phere of caesium and neon gases within said envelope.

3. In an electric radiatingdevice the combination of an envelope, supports therein, a plurality of standards mountedon said supports, coils of refractory wire mounted on two of said standards, the end of each of said coils being adjacent an end of the other coil, a coating of electron emitting material on said coils on areas spaced from said adjacent ends, said adjacent ends being bare when the device is in operation, and an atmosphere of caesium and neon gases within said envelope, said mixed gases preferably exceeding a pressure of 10 mm. ofmercury.

4. In an electric radiating device the combination of an envelope, a support therein, a plurality of standards mounted on said'support, a coil of refractory wire mounted on said standards having adjacent ends separated from each other, the

. distance of separation of said coils being approximately one-sixteenth 6) of an inch, a coating of electron emitting material comprising oxides of the alkaline earth metals on said coils at points other than the ends thereof, a coating of caesium on said coil ends, and an atmosphere of gases within said envelope including an inert gas and eluding an inert gas and caesium vapor.

6. In an arc discharge lamp which is adapted to function at normal commercial voltages the combination of an envelope, a support therein, tubular refractory metal coils mounted on said support with ends adjacent but separated from each other, the distance of separation of said coils being approximately one-sixteenth (1 g)- of aninch, a coating comprising an'alkaline oxide only on portions of said coils removed from the ends thereof, a coating of caesium on the coil ends, and an atmosphere of gases including an inert gas and caesium vapor within said envelope.

'7. In an arc discharge lamp which is adapted to function at normal commercial voltages the combination of an envelope, a support therein, tubular refractory metal coils mounted on said support with ends adjacent but separated from each other, a coating comprising an alkaline oxide only on portions of said coils removed from. the endsthereof, a coating of caesium on the coil ends, and an atmosphere of gases including an in-- ert gas and caesium vaporwithin said envelope, and means for maintaining the voltage drop between the coils when in operation at a predetere mined value.

8. In an arc discharge lamp which is adapted to function "at normal commercial voltages the combination of an envelope, a supporttherein, tubular refractory metal coils mounted on said support with ends adjacent but separated from each other, a coating comprising an alkaline oxide on portions of said coils removed from the. ends thereof, a coating of caesium on the coil ends, and an atmosphere of gases including an inert gas and caesium vapor within saidenvelope, and means for maintaining the voltage drop between the coils when in operation at a predetermined value, said means including a length of iron wire.

thereof, a coating of caesium on the coil ends, and

an atmosphere of gases including an inert gas and caesium vapor within said envelope, and means for maintaining the voltage drop between the 1 coils when in operation at a predetermined value, said means including a length of iron wire, the resistance of which is such that when electric current passes through said wire and between said coils the temperature of the iron wire does not exceed approximately 500 C.

10. In an arc discharge lamp which is adapted to function at normal commercial voltages the combination of an envelope, a support therein, tubular refractory metal coils mounted on said support with ends adjacent but separated from each other, a coating comprising an alkaline oxide only on portions of said coils removed from the ends thereof, a coating of caesium on the coil ends, 'and an atmosphere of inert gases includs 1 ing an inert gas and caesium vapor within said envelope, and means for maintaining the voltage drop between the coils when in operation at a predetermined value, said means consisting of a material, the specific resistivity of which below a.

temperature near 500 C. increases relatively slowly, and above a temperature near 500 C. increasesrelatively rapidly.

CHESTER H. BRASELTON.

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