US2216237A

US2216237A - Source of ultra violet light

Info

Publication number: US2216237A
Application number: US691396A
Authority: US
Inventors: Hannum John Andrew
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1933-09-28
Filing date: 1933-09-28
Publication date: 1940-10-01
Anticipated expiration: 1957-10-01

Description

06L 1, 1940. J. HANNUM 2,216,237

SOURCE 0! ULTRA VIOLET LIGHT Original Filed Sept. 28, 1933 in its spectrum.

Patented on. l, 1940 PATENT OFFICE SOURCE OF ULTRA VIOLET LIGHT John Andrew Hannum, Cleveland Heights, Ohio,

alaignor to General Electric Company, a corporation of New York Application September 28, 1933, Serial No. 691,396 Renewed May 13, 1938 4 Claims.

Ultra violet light has become of such importance and is used for so many commercial purposes that it is highly desirable to be able to produce it at a nominal cost, and at the same time with a high intensity. At the present time, among its commercial uses may be listed the irradiation oi milk, cereal foods and tobacco. A rather popular use which has recently come into prominence is the use of ultra violet light to produce artificial sunburn on the human body.

This form of light radiation which is just short of the visible spectrum at the short wavelength end is at present produced in several ways. The two best known methods are the use of the carbon arc; and a mercury arc in a quartz container.

There are two essentials demanded of ultra violet light: First, it must come from a powerful source; second, from an efilcient source. Two things are meant by the term efilcient source. First, there must be a maximum of output for a given amount of electrical energy supplied; second, this output must be as free from any light other than ultra. violet as possible. In short, the object is to produce as much ultra violet with as little input as possible.

The present lamps have several objections from the standpoint of both the quantity of rays or light emitted, as well as the efiiciency of the lamp used to emit this light. The average ultra violet light source emits in addition to ultra violet, light in the visible spectrum and radiation in the infra red.

The element indium is the most outstanding of all metals in regard to the number of lines emitted It has a far greater number of lines in the ultra violet as compared with the rest of the spectrum than has any other element. Not only is the profusion of lines greater in the ultra violet spectrum, but the intensity of these lines is to a marked degree greater than similar lines of any other element. Thus, it will be seen that by making use of a source of ultra violet light comprising essentially luminous indium as a source it will be far superior to any known means of producing this light. My invention, by using metallic indium, results in a light source which is both eillcient and capable of producing an intense light.

I use a container the walls of which will pass ultra violet light and which may be evacuated or filled with an inert gas. Electrodes protrude into this container as a. means of bringing the electrical energy required therein. Also in this container is a quantity of'indium either in the elementary state oras an alloy, amalgam or salt.

illustrates the preferred embodiment thereof.

In accomplishing these objects it is to be understood that I am not limiting myself to the specific disclosures shown in the drawing and hereinafter 1 described.

Referring now to the drawing:

Figure l is a front elevation of my improved source of light.

Figure 2 is a sectional view as indicated by the 20 line 2--2 on Figure -1.

Figure 3 is an elevation of an end portion of a lamp using my preferred form of cooling fins.

Figure 4 is a section through this portion of the tube as indicated by the line 4-4 on Figure 3.

Figure 5 is a side elevation of a modified form of tube which allows the cooling of the auxiliar tubes containing the electrode leads.

In Figure 1 l0 indicates the main body tube of the lamp and l i the auxiliary tubes through 30 which the electrodes are conducted to the main tube. The electrode leads i2, preferably made of tungsten, may be connected to any suitable source of electrical energy. The tubes comprising the lamp shell are preferably made of transparent quartz.

In bringing the electrodes into the lamp it is of course necessary to have an effective seal in order that the hermetical seal of the entire device may be maintained. Thus in Figure 2 the electrode 40 lead l2 enters a cup or funnel-shaped portion iii of auxiliary tube H and then passes through the tube proper past the constriction it into the body tube ID. The funnel-shaped portion i3 contains therein a seal of silver chloride l5 which 46 not only firmly holds the electrode lead but seals the tube against ingress of air.

This silver chloride is poured into the funnel in a molten state and upon hardening effects the It may happen that when this 50 required seal. silver chloride is poured into the funnel a small amount of it will descend into the tube H and even flow across the horizontal portion as far as the constriction I4 before solidifying. No attempt is made to form a tight seal between the container at the constriction and the electrode lead contained in the tube. The constriction merely serves the purpose of causing the metallic silver chloride to be in effect dammed up and prevent it from passing the construction. The constriction also prevents any molten indium which may descend into the tube l6 from passing the constriction. Thus at no time can the silver chloride or the indium come in contact either with the other.

The active agent of my invention is the indium which becomes luminous due to electrical excitation and furnishes the principal source of the ultra violet light emitted through the walls of the quartz container. This indium may be in the form of a pure element or as a salt, amalgam or alloy. Thus in the bottom portion of the arcuate body tube i0 is deposited a quantity of indium 2U Electrode leads l 2 have projecting tips 2|, extend ing slightly into the body tube 40. I

The body tube I b is predominantly arcuate with the exception of the tube bottom 40 between the junctions of the auxiliary tubes with the main tube. This upwardly curved portion provides pockets H where the electrode leads enter the body tube for a purpose which will be hereinafter described.

One form of using indium in this lamp is as an amalgam of mercury containing indium. Indium in any form is deposited in the tube 10 through the upwardly projecting tube 22 before this tube is sealed. In the case of a mercury amalgam it is desirable to place the amalgam in the tube through a funnel sufliciently long to reach the bottom of the body tube to prevent the tendency of the amalgam to gather on the sides of the quartz or other material comprising the tube. The actual electrodes in the lamp are the indium which is deposited in the pools 4i formed where the auxiliary tube containing the electrode lead enters the main body tube. When the tube is in operation the indium which may have been solid becomes liquid and is retained in contact with the electrode leads it? by the sides of the pool 4!.

When the lamp is finally assembled it becomes necessary to either evacuate the interior or perhaps fill it with an inert gas to allow the arc to function. This evacuation takes place through the projecting tube 22 which may thereafter be sealed to retain the vacuum within the tube. As heretofore mentioned, the molten indium has a tendency to adhere to the sides of the lamp tube and short circuit the electrodes. One method of preventing this consists of exposing the inside of the tube and the indium to a dilute solution of hydrochloric or other acid, principally to clean the oxides from the indium. As the tube is heated as hot as possible during evacuation the dissolved oxides volatilize oil and are removed from the lamp interior.

Upon the complete evacuation or if desired the addition of an inert gas the projecting tube 22 is sealed as a final step in providing an hermetically sealed quartz container for the electrodes and the indium.

If it is desired to cool a portion of the electrode encasing tubes this may be done with a form of tube as will now be described. Referring to Figure 5, tube ll descends to form a horizontal portion 25, then is extended upwardly to form a U- shaped portion 26, and then another horizontal portion 2?, after which the electrode is conducted to the body tube ill. The upwardly facing U- shaped portion comprising parts H, 25, and 26 may be inserted in a tank 30, which contains a suitable cooling fluid to surround part oi the tube.

It is usually necessary to provide a means of cooling 9, portion of the indium vapor in order to condense it. A cooling means such as indicated in Figures 3 and 4 is preferred. Around the ends of the body tube Hi, as shown in Figure 4, are wrapped strips of metal I! which are bolted together with bolt 8i and nut 52. The strips ID are allowed to project beyond the bolt in the form of parallel strips 53. These strips may be pulled apart as indicated by 55 to increase the area through which they may radiate heat from the body tube II.

To start the lamp it is necessary to heat the quartz container to a temperature to melt the indium therein. The tube is then rocked until the molten indium forms a connection between the electrodes which have been previously connected to a suitable source of electrical energy. This energy may be either alternating or direct current. When the molten indium flows away from one of the electrodes the circuit is broken and a portion of this indium vaporizes and continues to carry the electric energy from one electrode to another.

When the indium vaporizes it becomes luminous through electrical excitation and gives of! the desired ultra violet light.

It will be seen from my disclosure that I have provided an eillclent source of ultra violet light at a nominal cost. I provide an electric are which uses for its chief light source indium made luminous through electrical excitation. This indium because of the remarkable intensity of its spectrum lines and because of the profusion of these lines in the range of ultra violet light, is an admirable source of such light; both because of its intensity and because of its efllciency for a given electrical input.

Having described my invention, I claim:

1. A source of ultra violet light comprising a crescent shaped container with its bottom portion arched upwardly adjacent the midsection, a hollow tube portion on each side of the midsection and leading downwardly therefrom and reversed upon itself to lead upwardly and terminating in an upwardly opening cup portion, an electrode lead in each tube extending from said cup portion to the region where the respective tubes join the container, sealing material in said cup portions surrounding said electrode leads and a quantity of indium in said container to facilitate passage oi. an electric potential from one lead to the other.

2. A source of ultra violet light comprising an elongated container, a hollow tube portion on each side of the midsection and leading downwardly therefrom and reversed upon itself to lead upwardly and terminating in an upwardly opening cup portion, an electrode lead in each tube extending from said cup portion to the region where the respective tubes join the container, sealing material in said cup portions surrounding said electrode leads and a quantity of indium in said container to facilitate passage of an electric potential from one lead to the other,

3. A gaseous discharge device comprising a crescent shaped container with its bottom portion arched upwardly adjacent the midsection, a hollow tube portion on each side of the midsection and leading downwardly therefrom and reversed upon itself to lead upwardly and terminating in an upwardly opening cup portion, an electrode lead in each tube extending from said cup portion to the region where the respective tubes join the container, sealing material in said cup portions surrounding said electrode leads and a quantity of vaporimble metal in said container to facilitate passage of an electric potential from one lead to the other.

4. A gaseous discharge device comprising an elongated container, a hollow tube portion on each side 0! the mldsection and leading downwardly therefrom and reversed upon itself to lead upwardly and terminating in an upwardly openin: cup portion, an electrode lead in each tube extending from said cup portion to the region where the respective tubes join the container, sealing material in said cup portions surrounding said electrode leads and a quantity of vaporizable metal in said container to facilitate passage of an electric potential from one lead to the other.

JOHN A. HANNUM.