US2007933A - Lamp construction - Google Patents

Description

C. H. BRASELTON July 9, 1935.

LAMP CONSTRUCTION Filed Dec. 4, 1931 2 Sheets-Sheet l July 9, 1935. c. H. BRASELTON 2,007,933

LAMP CONSTRUCTION Filed Dec. 4, 1951 2 Sheets-Sheet 2 INVENTOR Patented Jul, 9,1935

LAMP CONSTRUCTION Chester H. Braselton, New York, N. Y., assignor to Sirian Lamp Company, Newark, N. J., a corporation of Delaware Application December 4, 1931, Serial No. 578,939

6 Claims. (01. 176-1) This invention relates to improvements in energy emitting devices and apparatus, and particularly to the type of energy emitter which utilizes, in conjunction with a first-class solid conductor,

a gaseous conducting film or layer.

This application is a continuation in part of my co-pending application Serial No. 490,583, filed October 23rd, 1930.

One of the principal objects of the invention is to provide an enlarged current carrying capacity for a conductor which is adapted to carry an electric current, as well as maintain a layer of conducting gases adjacent the tube. Another object of the invention is to provide an auxiliary conductor adjacent the ends of a primary conductor which will tend to prevent fracture or breakage of the primary conductor due to excessive current flow.

Still another object of the invention is to provide an auxiliary conductor which also functions to support a primary conductor as well as a coat ing placed around said primary conductor. Another object is to provide an auxiliary conductor which may be easily afixed to the primary conductor without interfering with the positioning or operation of the primary conductor.

Another object of the invention is to provide means for increasing the life of a coiled conductor having a coating thereon which terminates at a point displaced from the support to which the coil is attached. An additional object of the invention is to provide an auxiliary supporting conductor at the end of primary conductor which, while intended primarily to operate as the terminal of a gas discharge, nevertheless will not interfere with the normal action of the primary conductor where there is no gaseous discharge present.

Various other objects of the invention, such as relate to details of manufacture, processes and various broader conceptions, will become apparent on consideration of the following description and the accompanying drawings, in which Fig.1 is a View in elevation, partly in section, illustrating the application of the invention to a lamp having a two-sectioned filament;

Fig. 2 is a detail of the connection as made to the filament;

Fig. 3 is a modification of the showing of Fig. 2; and

Figs. 4 to 15 inclusive are additional modifications of the invention of Fig. 2.

In my co-pending application, Serial No. $59,048, filed June 3, 1930, I have described a form .of lamp or energy emitter which employs a conductor coated with electron emitting material and immersed in an atmosphere of inert ionizable gases, such as argon, neon, nitrogen, krypton and xenon. When the electron emitting coating is .heated by the passage of an electric current 5 through the conductor, the adjacent gases are ionized and form a conducting layer for an electric current in parallel with the metallic conductor. Where the gases are such as to be luminous when heated, the gas layer may serve as a 10 source of illumination in addition to the heated conductor or coating therefor.

In accordance with said specification, a lamp of the above mentioned type is constructed by coating 9. length of coiled tungsten wire of ap- 15 propriate resistance and length with various electron emitting oxides, such as those of barium, strontium or calcium, mounting the filament so coated on appropriate supports within a gas type container or bulb and treating the above eleg0 ments to remove occluded gases and appropriately solidify the coating. These latter operations are carried on by drawing a vacuum in the bulb and passing electric current through the filament to raise the temperature of the filament and its 25 coating to about 600 C. while the exterior of the bulb is being heated by an oven of about 300 or 400 C., or as high as the bulb substance will permit.

After a vacuum of about one-half micron has 30 been obtained, the filament temperature is stepped up to about 800 C. and the liberated gases again withdrawn. The oven may then be removed and a filament subjected to a third heating at about 1200 C., at which temperature the 35 residual gases are again drawn ofi. The appropriate gases are then conducted into the bulb and at the proper. pressures, sealed therein. Any of the gases above mentioned, or mixtures thereof, or mixtures of the various metal vapors, such as those of mercury, caesium, rubidium and the like may be used. The pressures also may be varied within wide limits, pressures from 20 mm. of mercury up to 400 mm. having been found to be satisfactory. The lamp is now ready for use. Ordinary commercial voltages, as 110 volts, may be employed for the lamp, but in such cases the resistance should be such as to prevent leakage or abnormal gas discharges. It has been found desirable, in some instances, to divide the filament into sections, each of which requires a working voltage between 20 and 40, this tending to improve the efliciency of the lamp operation. Alternatively, a group of low voltage lamps may be connected in series.

A usual method of utilizing a filament of a lamp, such as hereinabove described, is to weld the ends of a single coil of wire of uniform crosssection to nickel supports of enlarged cross-section, the turns of the coil along its length being coated by electron emitting material up to points adjacent the contact points. This leaves a short length of uncoated filament between the end of the coating and the support. When such a lamp is in operation, therefore, the uncoated sections of the ends of the filament carry not only the current passing through the metal of the turns of the coil, but also the current which leaks through the heated coating and the gas discharge current surrounding the coating. The uncoated end sections of the filament are therefore overloaded if the coated filament is operating at its normal current carrying capacity, and is moreover not able to take care of excess currents due to surges and the like. Consequently, these uncoated sections fuse or break because of the heat and make the lamp inoperative within a relatively short interval of time.

Referring now to Fig. 1 of the drawings, 1 have illustrated a bulb or container I0 having a stem II sealed therein, and on which are mounted three standards I2, I3 and I4, of nickel or other metal which is suificiently refractory for lamp use. To the top I5 of the standard I3 is attached a cross bar I6 having depending ends I! and I8. The standard I2 has an offset section I9, and similarly the standard I4 has an offset section 20, and intermediate the section I9 and the depending end ll of the cross bar I6, and also between the standard section 20 and the depending end I8 of the cross bar I6, are interposed coiled filaments 2I and 22. These filaments may he of tungsten, molybdenum or other refractory wire of uniform cross section, and the ends are attached, as by spot-welding, to the supports. A coating of electron emitting material 23 is applied to both filaments.

To each end of both of these filaments is also applied a coil of bare tungsten wire 24 of relatively few turns, one end of which is welded or otherwise attached to the adjacent support, and the other end of which is free. This coil extends only a short distance along the length of the primary conductors 2I or 22, and is external to the coating 23 which it may or may not touch. These coils 24 form, in effect, electrodes or terminals for gas discharge passing intermediate the ends of the primary conductor. When the coating 23 is heated by the passage of an electric current through the primary conductors 2I and 22, the inert gases in the bulb III which are closely adjacent the coating 23, become activated by electron emission, and therefore electrically conducting, and a layer of current carrying gases thereupon forms with the secondary coils 24, serving as terminals or electrodes therefor.

The secondary coils 24 do not necessarily contact with the primary conductor or the coating thereon, although, because of its relatively small conductivity, it is not important, whether or not the coating be touched. For many uses it is preferable that there be no metallic contact between primary and secondary coils except at the common end unless the cross-sectional area of the combined conductor is such as not to cause undue cooling at this point. By providing the excess current carrying capacity at the ends of the filaments, over-heating, due to the gas discharge current, is prevented, and consequently fusing, due to excess heat, is obviated.

Fig. 2 shows in detail the type of end connection-of the primary and secondary coils 2| and 24 with the intermediate coating 23. It should be pointed out in this connection that it lsnot necessary that the coating be intermediate the two coils, as I have found that the gas discharge forms as readily or more satisfactorily when the coating is within the primary coil 2|, either applied as a coating or as a solid core contacting with and heated by the primary coil.

Various modifications have been illustrated of the invention. In Fig. 3, I have illustrated a modification in which a coating 25 is made to include the secondary coil 24, as well as the primary coil 2|. This structure enhances rigidity of the end structure, and hence holds the coating material in place at the high potential ends of the filament where excess heating takes place.

Fig. 4 illustrates a modification in which there is no coating material applied, the coating substance being impregnated in the material of the primary coil 26 or secondary coil 21, or both coils. For example, a pressed filament of tungsten and calcium oxide with the tungsten preferably in excess of would serve as a satisfactory ionizing element when immersed in an inert gas of appropriate pressures.

The modification of Fig. 5 differs from that of Fig. 2 in that the secondary coil 28 has a diameter approximately similar to that of the primary coil 29, the secondary coil being wound so that its turns are interposed between adjacent turns of the primary coils. A coating 30 of electron emitting material is applied over both coils, as shown clearly in the figure.

In Figs. 6 and 7, I have illustrated a primary coil 2I and 33, and a solid electrode 33 and 34 inserted in the open ends of the coil, the outer end of the electrode being welded or otherwise fixed to the standard. In the case of Fig. 6 the electrode has a flat terminal 35 and is of uniform cross section, while in Fig. 7 the electrode at its inner end 36 is tapering in formation. In the case of Fig. 6 the gas discharge is to the thickened electrode section as well as to the bare end of the primary conductor. In Fig. 7 there is no coating shown, the substance of the conductor being of electron emitting material or the other variables of the lamp being such as to cause the formation of a layer of conducting gases about the solid turns of the conductor. In this case the tapered end of the electrode avoids contact of the same with the turns of the coil, and thus prevents undue cooling which would merely prevent the formation of a gas layer about the cooled turns and hence defeat the purpose of the electrode in serving as an auxiliary conductor for the gas discharge current.

Figs. 8 and 9 illustrate a modification wherein there is a core of electron emitting material hav-- ing a cross section of such formation as differs from that of the coil in which it is placed. Fig. 9 illustrates the cross section being triangular, there being three points of contact along the axis of the coil. By this means the amount of ionization is limited and excessive gas discharge current is prevented. This construction is, of course, used in connection with the secondary coil which functions as with other modifications to carry a portion of the total current of the conducting elements.

Fig. 10 illustrates a modification in which the cross sectional area of the conductor 38 is dimi:.=-- ished as one moves from the attached end of the coil. The substance of the coil material, as suggested hereinabove in connection with Figs, 4 and 7, may have incorporated therewith electron emitting material, such as oxide of calcium, or as previously stated, the gases and the pressures v thereof, as well as the voltages, may be'such as to cause an appreciable gas discharge when using ordinary conductors, such as tungsten. In this embodiment of the invention the increase in diameter as the end of the coil is approached should be not too large as to cause cooling with attendant distruction of the layer of conducting gases.

The modification shown in Fig. 11 substitutes for the metal wire secondary conductor, a mixture of tungsten powder and lithium oxide. This mixture is formed by mixing the tungsten powder with a solution of lithium nitrate, heating the same slightly, thus reducing the nitrate to lithium oxide. This mixture is a good conductor, and when heated, emits light selectively so that it is useful for emitters employed for lamps. The tungsten-lithium oxide coating is applied over the joint connecting the nickel rod support and the end of the tungsten coil, as shown clearly in Fig. 11. Other refractory conducting coatings may also be used.

Fig. 12 illustrates still another modification and in which is utilized. a plurality of concen trio enclosing stub coils to, M, ii and 43, the length of successive coils diminishing toward the exterior diameter. Variation in length is for the purpose of varying the current carrying capacity'of the total conducting area. This change in capacity should be gradual instead of abrupt in order to prevent too rapid cooling of the electrodes.

Figs. 13, 14 and 15 illustrate modifications which are a part of my copending application hereinabove referred to. In Fig. 13 the electrode takes the form of a dished terminal 44, the gas discharge terminating on the edge of the dish. In Fig. 14 the primary conductor extends through an aperture 45 formed in the base of the secondary electrode or terminal, which is also dished, or concave in formation, but also having a fiat lateral edge 16. The modification of Fig. 15 illustrates an attachment of the primary conductor to an excessively large support terminal it which also serves as an electrode for the gas discharge current.

In all of the modifications hereinabove mentioned it may be observed that an enlargement of the normal current carrying capacity is achieved. Also, in general, the construction is such as to prevent undue cooling of the conductors atthe point where both become effective, since if the primary conductor is cooled at the point where the secondary conductor is active, the gaseous discharge fails to form at that point and the end of the discharge is shifted inwardly beyond the end of the auxiliary conductor. This, of course, will defeat the purpose of the auxiliary conductor inasmuch as there will be insumcient current carrying capacity beyond the end of the secondary conductor.

It has also been hereinabove mentioned that while it is not essential, it is desirable that there be electrical separation between the primary and secondary conductor except at the point of support. This is not necessary, however, where the cross sectional area of the combined conductors is graded, so as to have an increasing cross section approaching the support points. The cooling effect, due to the increase in cross section, should be such as to not prevent the formation of the conducting gaseous layer, while at the same a;

jWhile I have described a terminal connecting,

means as applicable to a type of lamp of radiating. device in which a gas discharge current is formed [adjacent a conductor, it is obvious that the-de- Zvlce may be utilized where a second class con- .ductor' is twisted about a primary metal conductor, the second .class conductor, when heated, passing current of added amounts which must be removed }by the terminal connections. In this case the secondary terminals should be wound about and contact with the coating material as, for example, as illustrated in Figs. 3 and 5, so that when the coating becomes conductive, the ex cess current may be heated thereby.

Various other modifications of the invention other than hereinabove described may be made by those skilled in this particular field of invention, and I do not desire, therefore, to be limited except insofar as appropriate limits are imposed by the claims hereto appended.

I claim as my invention:

1. In an electric emitting device the combination of a container, a support therein, a plurality of standards mounted on said support, a coiled filamentary conductor constituting the sole source of the discharge of the device mounted between two of saidstandards, an electron emitting material having an emissivity in excess of thorium oxide in contact with said coiled filament, an ionizable gas immersing said filament, and. a secondaryconducting element enclosing an end of said filament and attached to the standard to which the filament is attached.

2. In an electric emitting device the combination of a container, a support therein, a plurality of standards mounted on said support, a coiled filamentary tungsten conductor constituting the sole source of the discharge of the device mounted between two of said standards, an electron emitting material including one of the alkaline metal oxides in contact with said coiled filament, an ionizable gas immersing said filament, and a secondary conducting element enclosing an end of said filament and attached to the standard to which the filament is attached, said gas including neon.

3. In an electric emitting device the combination of a container, a support therein, a plurality of standards mounted on said support, a. primary coil of wire constituting the sole source of the discharge of the device interposed between two of said standards, electron emitting material having an emissivity in excess of thorium oxide placed in contact with said wire, an atmosphere of ionizable gases surrounding said wire and electron emitting material, said gas forming a conducting layer about said coated wire when the wire is heated by the passage of an electric current therethrough, and auxiliary conducting means adjacent the end portions only of said wire, said means comprising a secondary coil of wire, one end of which is free and the other end of which is attached to the standard to which the end of the primary coil is attached.

4. In an electron emitting device the combination of a container, a support therein, a plurality of standards mounted on said support, a filament constituting the sole source of the discharge of the device connected between two of said standards, electron emitting material-having emissivity in excess of thorium oxide adjacent said filament, an ionizable gas immersing said filament, and a plurality of auxiliary conductors attached to the standards to which the ends of the filament are attached, the other ends of the conductors being free and terminating at diiferent points along the length of the filament.

5. In an electron emitting device the combination or a. container, 9, support therein, a plurality of standards mounted on said support, a coiled filament constituting the sole source oi the discharge of the device connected between two of said standards, said filament adapted when heated to emit electrons with a density approximately equal to that 01 barium oxide, an ionizable gas surrounding said filament, and a second coil of conducting material 01' relatively short length positioned adjacent an end of said filament and attached to the standard to which the filament is attached, said auxiliary coil being concentric with and approximately of the same diameter as said first mentioned coil.

6. In an energy emitting device the combination or a container, a support therein, a plurality of standards mounted on said support, a coil of ,of relatively short length enclosing the ends of said filament, one end of said auxiliary coils being attached to the adjacent standard to which the adjacent end of the filament is attached.

CHESTER H. BRASELTON.

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