US2144400A - Reflecting electric lamp - Google Patents

Description

3 c. BIRDSEYE 2,144,400

' REFLECTING ELECTRIC LAMP Filed Dec. 28, 1935 6 iwkzfiazt L9 attorneys Patented 17, 1 939 UNITED STATES PATENT OFFICE nnmcrmc Emo'rmc LAMP Clarence Birdseye, Gloucester, Mesa, assignor, by 'mesne assignments, to Birdseye Electric Company, Dover, DeL, a corporation of Delaware Application December 28, 1935, Serial No. 56,502

8Claims.

For example, in stage-lighting where colored effacts are desired, this is often accomplished by 15 piacingstandard lamp bulbs behind suitable color screens, usually made of gelatine. The color of the light shining on the stage may be changed by the operator of a key-board, each key controlling a single lamp or a series of a given color. In 20 la ge installations many lamps, each with its screen and external reflector, are employed. Gelatine screens are relatively cheap, but their life is short and the labor .cost of replacing them perhaps Once a week is high. Permanent color' 25 screens of glass are heavy and expensive, and must be replaced frequently because of breakage. Color screens produced by coating the bulb surface are often inefiicient transmitters. of light, and they temperature of such coatings during the periods of use isv high enough to cause rapid destruction of most colors and binders. Bulbs made entirely of colored glass are satisfactory within limits for the purpose, except fortheir first cost, which is generally very high, since the 35 colored glass is a relatively expensive material.

I have found that I can reduce the cost and upkeep of such an installation for producing colored light eilects, and at the same time eliminate the need of external reflectors, thus further re- 40 ducing cost and the space required for the installation, and secure these desirable results with an appreciable increase in lighting efficiency. This I achieve by employing a composite bulb having part of its surface made into a highly efflcient reflector, and preferably of such shape and disposition relative to'the light source within the bulb that all reflected rays pass directly out of the lamp through the transmitting area of the bulb, after not more than a single reflection, and

50 by using in combination with such a reflecting portion of the bulb a transmitting portion which is made of colored glass, or in some other way is different in chemical composition and in light transmitting properties from the rest of the bulb.

55 Thus the transmitting portion 01 the bulb becomes in effect a window withcertain characteristics that are different from the rest of the bulb, and may be of colored glass for the specific case discussed above, but also may be any other glass or material having specific optical proper- 5 ties different from those of the rest of the bulb, and which will in part determine the wave length of the transmitted light.

Such a window of selected glass may be sealed or fused into a bulb in a symmetrical position in its bulbous portion on a line with the main axis or with the axis of the reflecting portion of the bulb. Its size, in this position, may approximate the maximum diameter of the bulb, although it need not necessarily be hemispherical in shape, since a flatter curve would be equally satisfactory and would require less of the selected or colored glass. The rest of the bulb may preferably be silvered over either the inside or outside surface of plain glass, so that all of the light from the source would either be transmitted through the colored window directly as direct light, or after a single reflection from the silvered surface. If the colored window in a bulb of this shape were of smaller size than the maximum diameter of the bulb, and if the're'st of the bulb were silvered, or otherwise made into a highly efiicient reflecting surface, it is obvious that some of the reflected light would be trapped within the silvered surface, and would be reflected several times before leaving the bulb. This would result in a measurable decrease in lighting-efficiency, 'and'colored windows smaller'tha'n the maximum diameter of the bulb would be employed only when the sillciency was of secondary importance and when the cut-off angle was the determining consideration. I

Symmetrical lamps of other shapes than the standard shape may be readily constructed in this way, but in all such cases the diameter of the 49 I window is preferably that of the maximum bulb diameter in order to obtain highest efflciency; and

in general, substantially the rest of the bulb may be utilized as an eflicient reflector. The reflector, besides directing most of the light from the source through the window, also serves to hood the light source and thereby mask the uncolored parts of the bulb.

A window of dissimilar material may alternatively be located in the side walls of a bulb, 50 although a less efficient result will be secured because of trapped rays and multiple reflection, unless either the window covers approximately half the area of a bulb symmetrical about its main axis, or unless an asymmetrical bulb is used which has been designed to have such shape and provided with a reflecting surface such that all of the light leaves the bulb through the window either as direct light or after a single reflection. Such a bulb with a colored window occupying a part of the side wall. and with a,

sloping neck reflector, and with the rest of the bulb surface serving as a reflector to reflect light directly out through the colored window is an efflcient lamp for stage lighting effects.

In this same manner a quartz window may be sealed into a glass bulb for transmitting ultraviolet light rays, for example. In general I wish to include within the scope of this invention all lamp bulbs having windows of different transmitting properties than the rest of the bulb, and used with reflecting surfaces integral with the bulb to reflect light out through the window.

It may be desired in some cases to produce a diffuser! light from such window-bulbs and this may be obtained by frosting the transmitting portion of the bulb, or by frosting the glass under the reflecting deposit, or in some other way producing a diffusing reflecting surface, as ex-,

plained in the co-pending application Serial No.. 47,581.

These and other features of the invention will be best understood and appreciated from the following description'of two preferred embodiments thereof selected for purposes of illustration and shown in the accompanying drawing, in which,

Fig. l is a view in elevation, partly in section, of a lamp of symmetrical shape, and

Fig. 2 is a similar viewof a lamp shaped to direct a beam at right angles to its major axis.

The lamp shown in Fig. 1 has a composite bulb in which is included a cylindrical neck portion ill, a flaring or conical portion II and a curved or rounded end portion l2. The neck and body portions l0 and It may comprise any glass commonly used in commercial bulbs while the end portion I2 is herein shown as being red glass fused into the body of the bulb.

The lamp includes the usual metallic base It and mount l I through which project lead-in wires I! for a coiled coil filament l6. A desirable type of filament is that disclosed in. the pending application of Charles Spaeth, Ser. No. 15,605, consisting in a wire helix having a core of tungsten orthe like therein and being wound with its core in a secondary helix. As herein shown the filament is arranged in substantially V-shaped design disposed transversely to the major axis of the bulb.

The bulb is provided upon a predetermined portion of its surface with an interior reflecting coating I1 and for this purpose metallic silver may be satisfactorily employed. In the illustrated lamp the'reflecting coating ll extends from the line of maximum bulb diameter to aline in the neck of the bulb and it is supplemented by a reflecting disk l8 surrounding and insulated from the lead-in wires just beyond the inner end of the mount M.

In the lamp of Fig. 1 the light rays emanating from the filament it pass either directly out through the red glass end portion l2 or they are reflected by the coating I! or the disk It and pass out as reflected light through the portion l2. The coating l1, further, acts to hood the light of the lamp in all directions except where it is wanted, with the result that substantially all the light energy of the lamp is conmaximum diameter, a window of colored glass 'auacoo 1 servedanddirectedinto asingle rcstrictedbeam of red light.

The lamp of Fig. 2 is similar in constmction to that already described but of somewhat different shape. Its composite bulb has a cylindrical neck 20 and conical portion 2i disposed with its-axis at right angles to the axis of the I neck, and both made of clear glass of any commercial type. The bowl portion 2| may be circular or oval in cross section (in a plane perpendicular to the plane of the paper) and a curved or rounded face 22 of red glass is fused, as before, into the body of the bulb.

The lamp is provided with the usual base 23, and sealed-in mount 24 from which project lead-in and supporting wires 25. In this case the coiled coil filament 26 is supported in a plane substantially perpendicular. to the axis of the portion 2| instead of perpendicular to the principal axis of the lamp.

The inner end of the neck 20 and the entire inner surface of the bowl portion 2i are provided with a coating of metallic silver 21 or other eflicient reflecting material and this is supplemented by a reflecting disk 28 surrounding the lead-in wires and supporting wires 25 and so disposed as to constitute in effect a continuation of the surface of the bowl portions 2|. On account of the particular shape of the reflecting surface, which, as shown may be substantially parabolic, all rays emanating from the filament are collected into a single concentrated beam and directed outwardly through the red glass portion 22 of the bulb.

While I have illustrated only lamps having red glass window portions it will be understood that I contemplate the employment of any desired material in this portion of the lamp. For example, difierent' colors may be secured by introducing metallic or metalloid ingredients into theglass composition, or quartz or other light filtering material may be used. These may require other adjustments in the base materials forming the glass in order to equalize the coemcient of expansion of the fused portions of the bulb.

. It will be seen that by the present invention I provide a compact and eiflcient unit which may be installed in smallspace or manipulated conveniently by the user and which is useful in a broad field of lighting, therapeutic treatment and radiant energy application of all. sorts.

The lamp of Fig. 1 is the subject matter of my divisional application Serial No. 242,615, filed November 26, 1938, which contains also generic claims.

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

1. An electric lamp comprising a clear glass bulb having a neck, a parabolic portion disposed with its axis at right angles to the axis of said neck and having a metallic reflecting coating thereon, a flattened outwardly convex portion of colored glass fused into the dissimilar glass of the bulb as an integral part'thereof and located opposite to said parabolic portion, a support projecting out of the neck, and a filament located thereby substantially at the focus of the reflecting surface.

2. An electric lamp comprising a clear glass bulb having a neck merging into a substantially conical portion disposed with its axis at right angles to the neck and having a metallic reflecting surface extending substantially to its line of fused into the dissimilar glass of said conical portion and presenting an outwardly convex curved transmitting portion of a diameter equal to the maximum diameter of the bulb, and a filament supported in a plane at substantially right angles to the axis of the conical portion of the bulb.

3. An electric incandescent lamp comprising a bulb having a neck merging into an enlarged substantially parabolic portion disposed with its axis at an angle to the neck and flaring to a line of maximum diameter located in a plane beyond the neck, the interior walls of said parabolic portion having a metallic reflecting coating thereon, a substantially circular window of material havingdifierent optical properties from the glass of the bulb closing the larger end of said parabolic portion, a coiled tungsten filament supported in the neck of the bulb and centered in said parabolic portion, and a neck reflector disposed substantially in the general contour of the bulb.

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