US2007942A - Quartz tube lamp - Google Patents

Description

R SELT QUARTZ TUBE LAMP Filed Oct. 21, 1930 INVENTOR Patented July 9, 1935 2,007,942

UNITED STATES PATENT OFFICE QUARTZ TUBE LAIMP Chester H. Braselton, New York, N. Y., assignor to Sirian Lamp Company, Newark, N. J a corporation of Delaware Application October 21, 1930, Serial No. 490,125

2 Claims. (Cl. 176-1) This invention relates to an improved form I! of the standard I3 is a coil of tungsten wire of lamp or electric radiator in which energy emisl8, which has a diameter of approximately .08". sion from a solid emitter is combined with radi- This wire, for a portion of its length, has a coatation from a gas surrounding the emitter. ing I9 of electron emitting material. This mate- One of the objects of. the present invention is rial is applied to the conductor in the following 5 to provide a lamp of the above mentioned type in manner, as described in the co-pending applicawhich the gas discharge adjacent the conductor tion hereinabove mentioned. is confined by means of a transparent solid sub- In accordance with said application, a filament stance. Another object of the invention is to proof appropriate resistance, such, for example, as

10 videashield for electronic emission in agas which 150 ohms, is placed in heating relationship with 10 resists high temperatures and electrical conducvarious alkaline earth metal oxides, such as the tivity at said high temperatures. oxides of barium, strontium, calcium or other Another object of the invention is to modify materials which have been found to emit electhe type of emission of the combination solid and trons densely when heated. The base filament is gaseous conductor by the utilization of a shield tungsten or tantalum wire, although other metal 15 of special material, conductors may be used. It is not necessary, or-

Further objects relating to general improvedinarily, that the base material be highly refracments in this type of radiator and improvements tory, as the operating temperatures may be relain various details and specific features of the intively low, in many cases not being above that of vention, together with improvements in the low red heat. 20 -method of manufacture of the same will become The filament is preferably coiled and the oxides apparent on consideration of the following speeither applied as a paste to the exterior of the cification and of the accompanying drawing, in coil, or as a core or rod to the coil interior. The whi h oxide material initially may be in the propor- Fig. 1 is a view in elevation of a modification of tions of 40 grams of barium carbonate, 40 grams 25 the invention, which may be preferred; and Of calcium carbonate, 8 grams of barium nitrate Fig. 2 is a detail showing an enlargement of a with a binder of sufficient nitrocellulose dissolved portion of the conductor emitter. in amyl acetate to hold the coating on the wire.

In my co-pending application, Serial No. The filament is then mounted 'on a stem sup- 459,048, filed June 3, 1930, I have described a type port and sealed in the bulb of the envelope. 3 of lamp or energy emitter in which a conductor is The exhaust pump is then connected to the coated with a substance which emits electrons bulb and an oven lowered thereupon to raise the profusely when heated. This coated conductor is temperature of the bulb and contents to about immersed in an inert gas, such as argon, neon, 400 C., or to as high a temperature as the enor mixtures of the same, and with or without the velope will stand without softening. Simultane- 35 addition of various metallic vapors, such as that ously, electric current is passed through the filaof caesium, and the whole placed in a container. ment, which is heated to red heat of approx- When the coating is heated by means of the conimately 600 C. The heat and exhausting procductor, an; ionized vapor of gases forms about ess is continued until there is no fluorescence the conductor, which, together with the heated when the high tension current is directed against 4 conductor, is a source of visible and invisible rathe wall of the bulb, or in other words, until there diation. is practically no more gas inside of the bulb. A

The type of lamp hereinabove mentioned and vacuum of about one-half of a micron is an apdisclosed in said co-pending application, is utilized proximate limiting value.

in the present invention. I enclose in an enve- The current is then increased through the fila- 45 lope I0, which may be of glass or other transment so that the temperature thereof is slowly parent material, a support II, which is also of raised until it is about 800 degrees, or a bright glass, and it is sealed to the container. Mounted red color, the exhaust operation being continued on the support II are standards l2, l3 and I4, of until the newly emitted gases are removed. The

suitable metal, such as nickel. These standards oven is then raised from the bulb and the file- 50 extend through the stem or support H to points ment heated to about 1200 C;, the pumping being external to the bulb so that appropriate electric continued until a high vacuum of one-half mipotential may be applied thereto. The standard cron is again obtained.

I! has an L-shaped bend l5, and connected be- The pump is then shut off and the current tween the end It of this bend and the upper end tuned ofl, thus completing the process. Where 55 a more complete amalgamation of the coating is desired, about one-half mm. of neon gas is admitted to the bulb. The filament current is then turned on and gradually increased until a difl'used glow completely fills the bulb. When the discharge is uniform throughout the bulb, the filament current is turned ofl and the pump applied to remove the neon gas. The filament temperature is then raised for a short interval to about 1400" 0., with the pump operating to remove any undesirable gases which may have been thrown off during the activation process. Should white discharge spots appear on the filament or support rods, it is an indication that the gases or vapors within the bulb have not been completely removed, and the bulb is again exhausted and the whole process of activation repeated.

With the actuation process satisfactorily completed, the filament circuit is disconnected and the pump turned off and the appropriate amount of gas admitted to the bulb. In one form of my invention I utilize neon and argon gases in the relative amounts of 50 mm. of neon gas, and

mm. of argon. Other monatomic gases, such as krypton and helium or metal vapors such as those of mercury, caesium and rubidium may also be used. The bulb is then sealed oil" and a small quantity of magnesium flashed to absorb additionaly impurities, thus completing the process. Chemically pure gases are desirable.

The standard [4 is extended parallel to the conductor l8 and has welded thereto supporting cross bars 20 and 2| which terminate in coils 22 and 23, these latter serving to support a tube of quartz 2|. The tube 24 encloses the coated sections of the conductor l8.

Surrounding the standard I2 is a tube 25 of glass or similar insulating material, which serves to prevent short-circuiting between this standard and the associated standard I! and conductor l8.

When appropriate inert gases are included within the container In, such, for example, as the combination of neon and argon in the proportions of 50 mm. 01 neon and 150 mm. of argon, together with a small percentage of the vapors of caesium or mercury, and an electric tension applied to the standards I2 and I3 through the external lead-in wires, the conductor l8 becomes heated together with its coating l9, and a layer of ionized gases forms adjacent the coated conductor. This ionized layer is within the quartz tube. The purpose of tile quartz tubing is now apparent in that it serves to confine the activated gaseous layer adjacent the conductor. An active gaseous emanation of this type tends to spread out and become diffused, so that the luminosity and energy per unit volume is materially diminished. The quartz tube confines emanation by reason of its physical dimensions and because its resistance to electric current flow is not affected by the electronic and ionic bombardment, and hence, it is not disintegrated by the high temperatures, nor does it become conductive. Moreover, because of its transparency, where the device is intended for visible radiation, radiation is not prevented.

It is important that the inner diameter of the quartz tube be appropriately determined so as not to cause deposition of particles of the conductor or its coating. This seems to be in part a function of the temperature of the quartz tubing, and it is preferable that the mass of the tube should not be too large per unit length so as to exercise too great a lagging effect on the temperature conditions within the bulb Ill. Quartz has been mentioned as a satisfactory material for this purpose, although various other material having equivalent properties may also be used. A visible radiation requires that the tubing 2 be transparent to light, but the radiator is, of course, usable for other purposes, such as the securing of infra-red or ultra-violet radiation, in which case it is not requisite that the tubing be transparent to visible radiation.

As suggested above, the light is intended for use as a radiator, and there is no intent to confine the radiation to the visible range, although the modification as shown depends primarily for visible radiation in conjunction with a quartz tubing.

A light emission secured by this device, in conjunction with the quartz tubing, is very bright and brilliant. The light energy primarily is derived from the conductor and coating and the layer or ionized gases adjacent the tube within the tubing. However, a portion of the energy radiation comes from the tube itself, and by suitable dimensioning of the tube, more or less of the radiation may be concentrated in the quartz tube itself.

The filament has been described as coated with a coating material IQ, for the purpose of augmenting the electron emission of the conductor and thereby to cause ionization of the adjacent gases. However, instead of the coating, the material of the coating may be mixed in with the conductor material so that a homogeneous mixture exists without any external coating, and will function in a manner similar to the coated conductor. For example, I may employ thoriated tungsten; that is, tungsten which includes a mixture of tungsten, thorium or thorium oxide, obtained by chemically combining thorium nitrate with tungstic acid. The presence of the thorium oxide throughout the tungsten mass of the conductor brings about the increase of ionization desirable for this type of lamp.

Mention should be made also of the desirability of including a small amount of calcium with the caesium vapor introduced by means of pellets of metals which are subsequently vaporized by electro-magnetic means. The presence of the calcium with the caesium vapor, either as such, or as a deposit on the conductor, tends to increase the emciency of the lamp.

The various elements of the lamp as hereinabove mentioned define an operative construction. However, certain structural modifications may be made which adapt the lamp for specific uses or increase its operativeness under certain conditions. For instance, due to electrical surge effects or high temperatures, arising from other causes, the tungsten coil adjacent its point of connection with the supports may tend to fracture. To overcome this difliculty the wire at this point may be made thicker, or an additional alternative conducting path may be provided, as shown in Fig. 2.

This conductor may terminate in a coil 26 surrounding the primary coil and thus supply an enlarged conducting path for excess current, and in this way prevent fracture. Various other means for preventing fracture may be utilized.

The use of a coiled wire has been detailed in connection with this lamp. I have found also, however, that a straight coated wire will accomplish the same results and is preferable in certain arrangements. I have also found that where a limited amount of coating material is desirable, it mav be applied in the form of an elongated core having an angular cross-section, such as that of a triangle. This form, for instance, gives contact at two or possibly three points on the interior of the coil, providing a much lesser amount of ionized material than if the whole interior'were coated with the same.

Note should be made that both the standards l3 and M may be encased in an insulator tube, such as a glass tube 25, as applied to the standard l2. Other insulating materials, such as coated compounds, maybe applied to the standards instead of the glass tubes. A further feature of the invention to which attention should be directed is that the ionization of the coating tends to prevent vaporization of the tungsten, and hence the lamp may be operated at higher temperatures without blackening the interior of the bulb. This is very advantageous for lamps intended primarily for illumination.

Attention should be directed to the fact that the halo or layer of active gases may be varied in thickness by variation in the pressure of the gas. A low pressure tends to difiuse and enlarge the halo, while a high pressure tends to confine the halo to the immediate surface of the electron emitting substance. Consequently, in the commercial design of radiating devices, such as the type described, there should be a correlation between the diameter of the interior of the quartz tube and the pressure of the gas so that there will not be a sufficient diffusion of the ionized gas layer beyond the diameter of the tube, as this may result possibly in decrease in efficiency and also in discoloration of the tube interior. This application is a modification of the invention shown in my co-pending application Serial No. 478,050, filed August 27th, 1930.

Various structural details have been shown in this modification of the invention. These, of course, may be varied without departing from the scope of the invention as defined in the claims hereto appended.

I claim as my invention:

1. An energy radiating device comprising a container, a support therein, a single conductor within said container and mounted on said support, means to electrically connect both ends of said conductor to points outside of said container, an electron emitting coating having an electron emissivity equal to that of the alkaline earth metal oxides on said conductor, and a tube of quartz surrounding a coated portion of said conductor and mounted on said support, and an atmosphere of ionizable gas within said container, said gas having a breakdown potential per unit length less than that of the unit length of conductor necessary to raise the coating thereon to electron emitting temperature.

2. An energy radiating device comprising a container, a support mounted therein, a single conductor mounted on said support, means to connect both ends of said single conductor to points outside of said container, a coating of electron emitting material having an electron emissivity equal to that of the alkaline earth metal oxides on said conductor, a tube of transparent and heat resistant solid material enclosing the coated portion of said conductor and mounted on said support, and an ionizable gas within the container, said gas having a breakdown potential per unit length less than that of the unit length of conductor necessary to raise the coating thereon to electron emitting temperature.

CHESTER H. BRASELTON.

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