US2118452A - Electric lamp - Google Patents

Description

May 24, 1938. C. J LE BEL 2,118,452

ELECTRIC LAMP Original Filed Aug. 14, 1929 INVENTQOR CLARENCE J 5551. Br Q Arrow/5r Patented May 24, 1938 PATENT OFFICE- ELECTRIC LAMP Clarence J.

Le Bel, New York, N. Y., assignor to Raytheon Manufacturing Company, Newton,

Masa, a corporation of Delaware Original application August 14, 1929, Serial No. 385,707. Divided and this application January 28, 1935, Serial No. 3,689

5 Claims.

This invention relates to electric lamps and particularly to a lamp which will radiate a substantial portion of its energy in a predetermined portion of the spectrum. The lamp of this invention is characterized by an extraordinary high output of energy lying in the ultra-violet portion of the spectrum.

A lamp of this character has great utility in many fields. Thus for sterilizing and antiseptic purposes, such a lamp is very eiiicient. Furthermore, many chemical reactions, especially obscure organic reactions such as are involved in the tanning of leather, treating of foods and the like, are greatly accelerated by ultra-violet light. For purposes such as these it has been found that only a comparatively narrow portion of the spectrum in the ultra-violet region is useful, and any of the radiant energy outside of this spectrum is therefore wasted. While devices such as mercury arcs in quartz containers are generators of substantially powerful ultra-violet rays, their radiant energy is nevertheless distributed over a considerable spectrum in this region with a resultant loss of efiiciency.

An object of this invention is to devise a lamp in which radiant energy in a certain portion of the ultra-violet spectrum is generated in a much more efficient manner than has previously been the case. A further object is to devise a lamp which will be simple and cheap.

I have discovered that a metal vaporasuch as mercury, and an inert gas, such as argon or neon, at certain pressures when carrying a discharge, exhibit a remarkable phenomenon. Under operating conditions the pressure of either one of the rare gases may be between 1 and 8 mm. while the pressure of the mercury must be between 1 and 8 microns. The pressure of the rare gas is not very critical, and may be varied over substantially wide limits. It is, however, necessary to maintain the mercury pressure within critical limits. This may be done by either having the necessary amount of cooling surface in the tube or by artificially cooling the tube so that the desired pressure is maintained.

Sodium or other easily vaporizable metals may also be used instead of mercury, while a comparatively inert gas like nitrogen may be used instead of neon. In general the gas should have a high ionization potential.

When a lamp with such a mixture of gas is energized so that the gas therein becomes ionized, I have discovered that as much as 65% of the total radiant energy is emitted in the form of ultra-violet light having a wave length'in the case of mercury of about 2537 Angstrom units. By varying the pressure of the mercury within narrow limits, this percentage may be reduced somewhat as the energy goes into other wave lengths. v Apparently some obscure resonance phenomenon is involved in which rare gas particles freely interact with mercury particles to transfer substantially all energy to the latter, and cause it to emit as described. It is possible that some unstable compound of mercury and rare gas is formed which emits its characteristic radiation. The radiation emitted will in general be one of the prominent lines of the substance having the lower ionization potential, in this instance mercury.

By varying the mercury pressure over the wider limits, as from 1 to 20 microns, it is possible to ionize both the gas and the vapor, and change the color of the resulting light. In fact it is possible to go from the pure color of the gas to the pure color of mercury through the combination of the two colors by properly adjusting the mercury vapor pressure. In this latter case, however, the lamp does not emit as great a portion of its energy in the narrow region of the ultra-violet spectrum as is true when the mercury pressure is maintained within smaller limits.

Referring to the drawing, the figure shows an induction lamp drawn to full size.

In the figure is shown in true form, at substantially full size, an electrodeless induction lamp comprising a tubular portion Hi and bulb H2. Either or both may be made of material transparent to the ultra-violet rays generated. A coil H3 energized by a suitable source of high frequency, such as an oscillator H4, encircles bulb H2 and energizes the lamp.

After the tube has thus been constructed, it is treated in the customary manner to remove all occluded gases, and exhausted to a high vacuum. A small drop of mercury vapor, indicated by M, may be introduced within the container. In addition, a quantity of argon or neon may be introduced so that at the operating temperature of the tube, the pressure will preferably be within the limits previously specified. When the tube is first started, much of the discharge is carried by the rare gas. The discharge, however, warms the mercury so that its pressure becomes sufllcient for it to partake of the discharge. Within a very short space of time the lamp begins to function as a generator of ultra-violet rays.

For example, in a lamp embodying my invention and containing neon at about 4 mm. and mercury at about 2 microns, a discharge resulted in a very powerful emission of ultra-violet in a region of the spectrum below 2900 Angstrom units. A major portion of this energy was concentrated in the 2537 line. During the operation of this lamp, the current and pressure within the lamp could be adjusted so that practically the greatest portion of the energy was concentrated in the 2537 line.

This application is a division of my co-pending application, Serial No. 385,707 filed August 14, 1929.

What is claimed is:

1. As a new and improved article of manufacture, a container, an induction coil passing around a major portion of the wall of said container, a medium located within said container and adapted to become excited into luminescence by the passage of an alternating current through said induction coil, so as to produce an arc of predetermined dimensions within said container, a minor portion of the wall of said container being sufficiently spaced from said arc so that the temperature of said spaced part of the wall remains sufficiently low to prevent the pressure within said container from exceeding a predetermined. limit.

2. As a new and improved article of manufacture, a container having therein a gas and mercury, said container having a spherical portion of relatively large volume, and a coil substantially surrounding said spherical portion so that said spherical portion is directly with the field of said coil, said spherical portion having an integral extension which is beyond the field of said coil and which has a smaller volume than said spherical portion.

3. As a new and improved article of manufacture, a container having a gas and a vaporizable material located therein, a coil surrounding the major portion of said container, said coil being adapted, when 'the same is energized by the passage of an electric current through the same, to vaporize said material and to cause said gas and said vaporized material to emit light, said container having a minor portion oi. the wall thereof spaced from the zone of direct luminescence.

4. As a new and improved article of manufacture, a container having a gas and a vaporizable material located therein, a coil surrounding the major portion of said container, said coil being adapted, when the same is energized by the passage of an electric current through the same, to vaporize said material and to cause saidgas and said vaporized material to emit light, said container having a condensing chamber integral therewith and sharply defined from that portion of the container which is surrounded by said coil, said condensing chamber being beyond the zone of direct luminescence.

5. A method of producing light which consists in exciting into luminescence a gas which is located within an enclosed chamber and also exciting into luminescence a vapor which is located within said enclosed chamber, so as to produce a definite zone of direct luminescence, and allowing a part of said container which is beyond said zone to remain relatively cool in order to form a condensing chamber for said vapor, the volume of said condensing chamber being smaller than the volume of said zone, said gas and vapor being excited into luminescence by an electro-magnetic field which is produced external to said container.

CLARENCE J. LE BEL.

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