US 2135480 A
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REFLECT ING GLOW LAMP Filed Aug. 26, 1936 Iwvewiiw Cam 61,- by
Patented Nov. 8, 1938 UNITED STATES BEFLECTING GLOW LAMP Clarence Birdseye, Gloucester, Mass., assignor, by mesne assignments, to Birdseye Electric Company, a corporation of Delaware Application August 26, 1936, Serial No. 97,912
This invention relates to gaseous discharge lamps of the tubular type and comprises an improved lamp having a reflecting surface incorporated in such a manner therein that the light 5 from the lamp is concentrated and directed in a beam of controlled direction rather than being uniformly emitted from all sides of the tube as heretofore.
More specifically my invention concerns ways and means of accomplishing this result in a relatively exact manner, since a generally satisfactory result will not be obtained, for example, by the simple expedient of making one half of the conventional cylindrical tube into a suitable reflecting surface. A reflecting gaseous discharge lamp of this simple design, while definitely superior to the same lamp without the reflecting surface, in thematter of directing and concentrating the light. will have a very wide cut-off .20 angle, much greater than 180, becauseof the high degree of luminosity of the curved transmitting area of the tube. This effect produced by the glowing tube surface, which appears to act as the light source, and which, because it stands out in a curved surface in front of the reflecting area, actually sends rays back behind the plane delineating the reflecting area. Thus in the case of a cylindrical tube made into a reflecting surface over half its area bounded by a plane passing through the axis of the cylinder, the cutofl angle, instead of being 180, actually is very much'greater, and this makes control of the rays from such a simple reflecting gaseous discharge lamp extremely difiicult.
In order to avoid this effect of an extremely wide angle of cut-off and almost uncontrolled direction of the rays from such a reflecting gaseous discharge lamp, it is proposed to impart to it three novel characteristics, viz.(1) make more'than one-half of the surface area of the tube into the reflector (so that more than half of the cross section of the tube perpendicular to the axis constitutes the reflecting surface), (2) flatten the transmitting surface, so that it does not appear to stand out in front of the reflecting area, and (3) shape the tube so that it is no longer a cylinder, not only flattening the transmitting area, but also deepening the trough, the surface of which is the reflecting area. Any one of these characteristics alone will aid in reducing the angle of cut-off and will make possible better control of the light 'rays, and a complete solution of the difliculty is readily possible by employing two or more of these characteristics in combination.
A gaseous discharge lamp of this character may be constructed to transmit substantially all its light within the confines of a definite beam of the desired shape and direction, and thus be utilized as a more efficient source of illumination than the gaseous discharge lamps heretofore available. Moreover, a lamp of this characteristic has a wide field of application not satisfactorily filled in the past. For example such a lamp may be used in front of a show window without upsetting the desired color effect within the display area.
Since the light rays emitted by a gaseous dis-.
charge lamp are usually of pronounced color, such rays are most undesirable for illuminating colored articles and great care must be taken not to allow rays from the lamp to fall upon goods being displayed. Green rays, for example, are effective to turn yellow goods to a mustard color, or orange goods to a brownish color. In using a gaseous discharge lamp constructed in accordance with the present invention, however, it is possible to direct all the rays of the lamp outwardly and. thus keep the show window space clear of the undesirable rays.
While my invention may be applied to lamps having a gas-filled tube of circular cross section, in the preferred embodiment of my invention I propose to carry the invention further and utilize it in lamps having a tube of non-circular cross section, for example, in tubes having a longitudinally flattened transmitting face, and reflecting walls comprising the body of the tube and terminating at its transmitting face. The body of the tube may be of any desired cross-sectional shape suitable to contain the column of ionized gas, or its walls may be shaped to reflect the light emitted from the gas column outwardly through the transmitting face of the tube. For example, I have shown herein a tube having a flattened transmitting face and a trough-shaped body portion provided with a reflecting coating. Preferably, and as herein shown, the reflecting surface may comprise more than half of the peripheral area of the tube. In accordance with my invention, the reflecting surface is incorporated in the lamp itself as an applied metal coating, or part of the tube may be of white opalescent glass and so act as a reflector. The transmitting surface on the other hand, may be of clear glass or frosted or otherwise treated in accordance with the requirements of the service to be supplied.
The lamp of my invention may be employed for advertising purposes and the tube bent into any desired configuration with its transmitting face directed as desired. For illuminating puris employed a tube of circular cross section,
Fig. 2 is a corresponding view in cross section on enlarged scale,
Figs. 3 and 5 are views in elevation of lamps in I which are employed tubes of non-symmetrical cross section,
Figs. 4 and 6 are corresponding views in cross section on enlarged scale,
Fig. '7 is a view in elevation of a lamp having a tube of flat spiral form.
The gaseous discharge glow lamps herein illus-- trated may contain neon gas, argon, carbon dioxide, mercury or sodium vapor, or any other gaseous medium suitable for the maintenance of a.
gaseous discharge between suitable electrodes within appropriate pressure ranges, or this gaseous discharge may be excited by any other suitable means' such as a high frequency electromagnetic field set up by an oscillating vacuum tube or a spark coil, etc. Electrodes are used with high voltage alternating current but are unnecessary with the high frequency field set up by such means as the oscillating vacuum tube and spark coil, for example.
The lamps shown in the drawing are represented more or less conventionally. In Figs. 1' and 2 the tube III of the lamp is circular in cross section and provided with an exterior coating ll of metallic silver constituting a reflecting surface extending circumferentially approximately and covering the tube Hi from end to end. The tube is provided with end caps and electrodes which are represented conventionally. In this lamp light is transmitted through the clear portion of the tube in a beam directed forwardly and this beam is reinforced by reflected light which is confined against spreading by the reflecting coating II. It will be seen therefore that the lamp provides a wide band of diffused light whose marginal portions emanate from the forward uncoated portion of the tube III, the light band being intensified in a central zone by light reflected from the coating II.
The tube of the lamp shown in Figs. 3 and 4 is not symmetrical in cross section and comprises a trough-shaped portion 12 which is provided face.
with an exterior coating ll of metallic silver and a flattened transmitting face I! which may be clear or frosted as desired. In this lamp the amount of diffused light transmitted is reduced as compared to the lamp of Figs. 1 and 2 by the flattening of the face l3. The arrangement I centrated beam of substantially parallel rays.
The lamp of Figs. 5 and 6 is also non-symmetrical in cross section comprising a tube hava ing an outwardly convex transmitting portion l5 and a concave rear wall l6 externally provlded with a coating ll of metallic silver. This lamp is effective for emitting a wide band of diffused light supplemented by a divergent band of light reflected by the coating II.
The lamp of Fig. 7 comprises a tube having a portion l9 trough-shaped in cross section and a flattened transmitting face Ill. The troughshaped portion is provided with a coating 20 of metallic silver and the tube as a whole is given a spiral form so that it constitutes a unit of substantially circular outline acting to transmit a relatively small amount of diffused light transversely and a relatively large amount of reflected light in a direction perpendicular to its general plane.
Various other applications of the invention will be apparent to those skilled in the art and changes in design, construction and arrangement are contemplated to meet different service demands. While metallic silver has been referred to as the material of the reflecting coating of the lamps; any material suitable to provide an eflicient reflecting surface may be employed within the scope of the invention.
Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is,
1.,A gaseous discharge lamp comprising a gas fllled tube having a longitudinal convex trans- CLARENCE BIRDSEYE.