US2298239A - Light source - Google Patents

Description

1942- .1. R. STIRNKORB LIGHT SOURCE Filed July 22, 1940 1NVENTOR.

cfohw 1B Sr/R/wrams.

ATTORNEYS.

Patented Oct. 6, 1942 EEEQE.

LIGHT SOURCE John R. Stirnkorb, Cincinnati, Ohio, assignor to Science Laboratories, Inc., Norwood, Ohio, a

corporation of Ohio Application July 22, 1940, Serial No. 346,819

1 Claim.

My invention relates to light sources of elongated shape and employing an arc struck between interspaced electrodes in an ionized atmosphere. Long, tube-like lamps of the class referred to have hitherto been developed for many purposes including, but without limitation, the production of ultra-violet radiation for therapeutic, bactericidal or activation work; and fluorescent type tubes are now coming into increasing use for illumination, wherein ultra-Violet radiation generated by an arc impinges upon a coating of fluorescent substances on the inside of the envelope and produces visible light.

My invention relates primarily to the solution of a problem which becomes most pronounced in long tube-like light sources, used in a horizontal position, and in which the atmosphere is a relatively high pressure atmosphere. The are discharges in lamps become relatively thick and relatively cooler as the pressure of the ionized atmosphere is lowered, tending ultimately toward a glow discharge. In high pressure lamps, however, the arc becomes thin and intense and de velops comparatively great heat. When such lamps are used horizontally, there tends. to be a bowing of the are which in extreme instances may permit the arc to touch the sides of the envelope. Under these circumstances, the life of the light source is imperiled because the envelope may melt. It is an object of my invention to overcome these disadvantages, to provide means for keeping, particularly, a thin and intense arc away from the nvelope, and to prolong the life and safety of use of the light source.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these speci Fig. 3 is a transverse sectional view taken along I the lines 33 of Fig. 1.

Fig. 4 is a partial longitudinal section of a light source showing a modified form of my arc centering means.

Fig. 5 is a transverse sectional view related to Fig. 4 and showing a face View of the centering means.

Fig. 6 is a partial longitudinal section illustrating both another type of arc centering means and. a mode of mounting it in a lamp structure.

Fig. 7 is a view, with parts in section of yet another embodiment of theinvention.

I shall not herein describe with particularity the various forms of light source construction to which may invention may be applied. The effectiveness and utility of the invention is not dependent upon the nature of the electrodes, the nature of the starting means embodied in connection with the light source, or the manner in which ionization is started in the atmosphere. For a complete description of one form of structure to which the present invention is well adapted, I refer to my copending application entitled Light sources, Serial No. 345,807, filed July 16, 1940.

In connection with the problem to the solu-' tion of which my invention is addressed, I have discovered that a thin, intense arc may be prevented from bowing to the extent ofv striking the envelope, even where the envelope .is very long and thin, if the arc is centered in the envelope at one or more places between the electrodes.

1 have further discovered that the arc may be so centered by placing in the envelope one or more are centering devices comprising walls having central perforations. The number and spacing of arc centering means between the electrodes in any given lamp may be varied in accordance both with the length of the lamp and with the diameter of its envelope; but I have discovered that if the arc is centered at frequent enough intervals, the amount of bowing of the are between the points at which it is centered can be controlled in such a way as to make sure that the arc will not come into contact with the envelope under any conditions of use. I have further discovered the surprising fact that the arc will seek a central perforation in a baffle or arc centering means in preference to any outlying passageway which there may be.

Referring to Fig. 1, l indicates the envelope of a light source having bases 2 and 4 at either end. Electrode means, comprising wires 5 and 6 or 7 and 8, as the case may be, pass through presses in the ends of the envelope and are connected respectively with contact prongs 9 and It Or I I and tion, depending upon the use to which th light source is to be put. The envelope may carry on its inside a coating of fluorescent substance.

In Fig. 1 for centering the arc, I provide midway between the arc electrodes 5, 6 and 1, 8, a baflle means l having a central perforation I6. This baffle means may be a disc of any material substantially shaped to fit the interior of the tube l and, in this embodiment fusible to the glass or capable of adhering to fused glass. During the assembly of the light source, while the disc I5 is held in position, the tube l is fused to the disc at intervals as shown at I! by local application of a fusing flame.

The disc or bafile may be made of a wide variety of substances. Ordinary glass, Pyrex glass, or any of the special glasses may be employed; but I have also used such materials as ceramics, quartz, carbon, mica and metals. Due to the intense heat of the are a relatively high melting point material is desirable. However, it is not necessary that the bafile be entirely unaffected by the heat of the arc. A perforated glass disc, for example, may tend to bead about the edges of the perforation and gradually the perforation may tend to become somewhat enlarged. However this action occurs so slowly as compared with the normal length of life of the light source as to make the use of glass substances quite feasible.

I have encountered no difficulties of mechanical character in connection with the use of baffle means. Where the baflie is to be interfused with the envelope or where the glass of the envelope is to be softened and pressed about the edges of the baffle member so as to hold it, I may do this entirely around the circumference of the tube; but I have not found it necessary. Sufficient shaping or interfusion to hold the baffle is all that is required, and I find that if interspaces, as indicated at I 8 in Fig. 3, exist between the periphery of the disc and the internal circumference of the envelope, these interspaces have no effect on the operation of the baffle. This is for the reason indicated above, namely, that the arc seeks the central perforation and passes therethrough in preference to any outlying channels of communication.

This fact among others makes possible the use of baflie means such as illustrated in Figs. 4 and 5. Here I have shown a metallic disc or washer l9 centrally perforated at 20, and about its periphery provided with feet 2|, alternate ones of which are bent in opposite directions. These feet engage the interior of the tube and the fit may be snug enough to make it unnecessary otherwise to retain the position of the baflie. The bending of the feet in opposite directions provides a relatively broad peripheral bearing for the baffle and prevents displacement of the bafiie by tilting.

In no instance have I encountered any difficulty arising from the heating of the baffle by the arc and differential rates of contraction and expansion of the envelope and the baffle. This is true not only of the non-metallic and/or refractory materials which I may employ, but it is true also in the case of metal. While undoubtedly heat is transmitted to the envelope'by the baffle, the rate of conduction of heat away from the joint by the envelope and the rate of loss of heat to th surrounding air seems sufficient to prevent any difficulty in actual practice.

Another mode of aflixing a baffle or are centering means is shown in Fig. 6. Here the envelope 22 has been peripherally bowed as at 23 to provide a groove on the inside of the envelope. Relatively thin and bendable or resilient baffle means 24, perforated as at 25, may be bowed to permit its insertion in the tube and allowed to spring outwardly in the internal groove 23 much as a crystal is installed in a watch.

In Fig. 2 I have shown the use of a plurality of interspaced baflle means 26, 21 and 28 in a light source embodying a tube 29 which is relatively very long and thin. It will easily be within the skill of the worker in the art to determine the number of bafiles or are centering devices he will need; but it may be noted that the length of the arc is not the only criterion. The relative diameter of the tube or envelope must be considered and also the nature of the arc itself as determined by the nature and pressure of the atmosphere as well as the degree of bowing of the are encountered in view of these factors.

In Fig. '7 I have shown yet another structure for the purpose wherein the envelope 26 is provided internally with one or a plurality of baflle members having tubular bodies 21', and end flanges 28, shaped to conform generally to the interior of the envelope. Where the tube-like bafiies are short in length, they may be made of opaque substance, for example ceramics, or metal. But a single, long tubular means may be employed to keep the arc away from the envelope. Where this is done, the tubular means must, of course, be transparent or translucent, and in ultraviolet devices, should be pervious at least to the desired wave lengths of the ultraviolet spectrum. Also, by reason of its close proximity to the intense are, it should be heat resistant. Thus quartz, or heat resistant glass should be used. In the use of such tubes within an envelope, however, considerable savings may be made over the manufacture of the whole lamp of quartz or heat resistant glass. The tube may be coated on its outside surface with fluorescent substances, and may be so coated before the tube is placed in the envelope.

The tube or tubes are preferably anchored to the envelope as at 29 to prevent displacement.

It will be within the skill of the worker in the art moreover to apply my teachings to light sources of different character than the specific ones here illustrated. Modifications may be made in my invention without departing from the spirit of it.

Having thus described my invention what I claim as new and desire to secure by Letters Patent, is:

In a light source, an envelope, arc electrodes in an ionizable atmosphere therein, and at least one means in said envelope intermediate said electrodes for centering said arc, said means comprising a perforated disc extending substantially across the breadth of said envelope, said disc being a disc of metal, the edge of said disc being formed into divided tongues, and said tongues alternately being angularly bent, some in one direction and some in another so as to engage the inner surface of said envelope and form a bearing therein at interspaced points to preclude the tilting of said disc, the fit of the tongued disc in said envelope being sufficiently snug to minimize movement of said disc longitudinally of said envelope.

JOHN R. STIRNKORB,

Images