US 2367444 A
Description (OCR text may contain errors)
Jan. 1 6, 19450 O sT SIGNAL LIGHT Filed April 5, 1941 Patented Jan. 16, 1945 SIGNAL LIGHT Orville Siam, Chicago, Ill., assignor to Stam-O- Lite, Inc., Chicago, Ill., a corporation Illinois Application April'5, 1941, Serial No. 387,040
3 Claims. (Cl. 177-329) This invention relates to light-controlling devices and more particularly to means for substantially eliminating so-called phantom light from traflic signals, such signals, for instance, as are commonly used at street intersections and railroad crossings. When the invention is used in connection with such signal lights, the brii-,
liance of the signal when the light is on is not materially reduced and, when the light is ofl," light rays from outside sources are not reflected from the signal to produce so-called phantom" light.
It is an object of the invention to provide an electric bulb in combination with a suitable traffic signal reflector and lens wherein the bulb is so constructed and related to the reflector as to absorb incoming rays when the light is on.
It is also an object to providea bulb which will be cheap to manufacture and can be installed in the ordinary manner in the usual trafllc lights and will not easily get out of order.
In the present invention the bulb is provided with certain predetermined light-absorbing areas and these areas are so positioned on the bulb, and so related to each other and to the reflector, that suflicient illumination is provided for the usual trafiic signals when the signal is on and, when the signal is o a suillcient number of the incoming light rays from an extraneous source will be absorbed by the light-absorbing areas on the bulb so that there will be substantially no disturbing "phantom light reflected from the device.
In the embodiment shown and described herein, the light-absorbing areas are an integral part of the bulb. However, it will he understood that they may be any suitable coverings or coatings on or in the bulb, or the required portion of the glass itself may be made light-absorbing, the important consideration being that the light-intercepting or shading areas shall be light-absorbing to a suflicient extent to perform the desired functions.
In' ordinary trafllc lights a comparatively large bulb is ordinarily used and a large-diameter substantially annular filament usually forms the light source. This filament is in a transverse plane substantially in the focal region of the reflector, and the large filament diameter provides a source of illumination around, but spaced 9. considerable distance from, the axis of the bulb and reflector. Therefore, any one point in the filament has a comparatively wide angle of illumination on the reflector oven when portions of the bulb are shaded. In view of this characteristic, it is possible to provide certain light-absorbing areas on the bulb without materially decreasing the eflective illumination of the signal light as a whole. Also, if these light-absorbing areas are so positioned on the bulb that they intercept substantially all of the incoming light rays which otherwise would cause phantom light, then. due to the fact that the phantom" light is eliminated, a h'gher wattage bulb may be used if desired and a very brilliant signal-light may be obtained with no disturbing phantom" light when the signal is ofi."
When light is projected into the usual trafllc signal from an extraneous source such as from a brilliant sun or from sunlight reflected from white clouds, the light rays pass through the lens and strike the reflector and are then usually reflected transversely to some point on the opposite side of the reflector and then outwardly through the lens to cause a brilliant phantom light. Many accidents are caused by this phaniom" light, as it is often impossible to be sure whether the light is ofl or on." ractically all extraneous light rays which enter through the lens and which produce phantom" light are reflected transversely across the reflector and usually through the bulb before being directed outwardly.
The present invention, therefore, is constructed and arranged to intercept the stray rays within the signal device and to absorb these rays so that they do not pass outwardly through the lens in sufficient quantities to cause any disturbing amount of phantom light.
Further objects will be apparent from the specification and the appended claims.
In the drawing:
Fig. 1 is a vertical sectional view through the usual trafllc signal and illustrates one embodiment of the invention.
Fig. 2 is an enlarged elevation of the bulb illustrated in Fig. 1.
Fig. 3 is an end view of the bulb shown in Fig. 2.
Referring to the drawing in detail, the embodiment illustrated comprises a signal light having the usual reflector I, socket 2, and lens 3. A bulb 4 is provided with the usual base 5 and may be supported in the socket 2 in the usual manner.
The bulb is provided with a comparatively wide light-absorbing area or band 6 extending a material distance from the base 4 toward the filament l, and the outer edge of this area is preferably serrated or provided with spaced projecting areas 8 extending therefrom toward the front or the bulb. The light-absorbing area 6 extends to a comparatively large-diameter portion of the bulb so that the extraneous rays entering the front end of the bulb substantially parallel to the axis thereof, and a major portion of the extraneous rays entering at an angle to the axis will be absorbed thereby, as will be described later.
Closely adjacent the largest diameter of the bulb are a plurality of comparatively narrow zigzag or sinuous light-absorbing areas; in the present embodiment two areas 9 and Ill are shown.
These areas are preferably positioned closely adjacent but on opposite sides of the plane of the filament, substantially as shown, and the forward end of the bulb is provided with a comparatively wide light-absorbing annular area ll having its inner edge serrated or provided with projections I2 similar to the projections 8 previously described with relation to the area 6. The annular band I l is arranged to provide a circular clear glass portion I3 of the bulb at the front end thereof, preferably concentric with the axis, and this circular portion is preferably materially larger than the diameter of the filament I of the bulb, as shown in Fig. 3, and preferably slightly smaller than the largest diameter of the band 6. It will be apparent that with this arrangement any direct extraneous rays entering through the clear glass portion l3 parallel to the axis of the bulb will be absorbedand will not cause phantom light by being reflected outwardly from the back portion of the reflector. Furthermore, substantially all extraneous rays entering through the clear space l3 at an angle to the bulb axis will be absorbed either by the band 6 or the zigzag bands 9 and Ill, and any stray rays which might reach the reflector will be so scattered or so few in number that they will not cause disturbing phantom light.
It has been found that, with a bulb of the character described used in combination with the reflector I and lens 3, the outgoing rays, when the light is on, are not sufficiently interfered with to materially reduce the illumination of the signal. Also, the shaded or light-absorbing areas of the bulb absorb a sufficiently large number of the incoming rays from an extraneous source when the light is off, so that phantom light is eliminated. The incoming rays are obstructed and absorbed as they are reflected transversely within the signal light. They, therefore, cannot be transmitted outwardly through the lens in any material number.
When the usual signal is on, rays normally striking the rear portion of the reflector closely adjacent the bulb are not particularly effective and, therefore, the light-absorbing portion 6 may be provided without materially decreasing the illumination. However, this area does intercept all incoming rays which otherwise would be transmitted through that portion of the bulb to the opposite side of the reflector and then outwardly to cause phantom light. Similarly, the area covered by the wide light-absorbing band H is not particularly effective for signal illumination even when made of clear glass, and therefore this area is also covered and the inner edge of this area is substantially in alignment with the outer edge of the reflector and the adjacent edge of the filament 'l as illustrated by the dotted line H.
As previously stated, any extraneous rays entering the bulb through the clear glass circular area I3 at the front thereof will be absorbed by striking one of the light-absorbing areas of the bulb and reflected incoming rays such as shown by the dot and dash lines 15 will also be absorbed by one of the areas.
The intermediate'zigzag bands 9 and 10 are also so related to the filament and reflector and to the other areas of the bulb that substantially all incoming rays from any angle which otherwise would go through the central portion of the bulb and be reflected from the side of the reflector will be either absorbed while passing through the bulb or after being reflected from the reflector I.
The contours of the various parts of the zi zag bands are so related that the peaks and valleys of each band on opposite sides of the bulb at diametrically opposed points in the same plane are in opposed relation. Due to this relationship and to the general relationship of all of the bands to each other, only an ineffective number of the incoming reflected rays may again be reflected outwardly.
It is intended, of course, that the invention should not be limited to the specific embodiment I or embodiments disclosed herein, since modifications may be made, and it is contemplated, therefore, by the appended claims to cover any such modifications as fall within the true spirit and scope of this invention.
Having thus described this invention, what is claimed and desired to be secured by Letters Patent is:
. 1. A signal light of the character described comprising a concave reflector having a focal region, a bulb having a light source substantially in said focal region, and a series of light-absorbing annular shields on the surface of said bulb substantially in axial alignment with said light source and said reflector, said shields being in spaced end-to-end relationship to provide lightturning areas therebetween, with a plurality of said shields on opposite sides of the approximate focal .plane of said reflector, the shields adjacent said plane being of comparatively narrow substantially zigzag formation with the peaks and valleys directed substantially parallel with said axis, the peaks on one side of said axis being substantially diametrically opposite the corresponding valley on the other side.
2. In a signal light, the combination with the usual concave reflector and lens and an electric bulb in said reflector having a comparatively large-diameter light source adjacent the focal region and substantially in the focal plane of said reflector, of an annular light-absorbing shield on the bulb surface at the rear of said light source and of sufficient diameter to shield a material portion of said reflector around and adjacent the axis thereof, an annular shield on said bulb surface in front of said light source and positioned to intercept substantially all extraneous rays from a comparatively wide annular area of said lens immediately adjacent said reflector, and a plurality of annular light-absorbing shields on said bulb surface between said rear and front shields and spaced therefrom and from each other, said bands having irregular edge contours so that portions of a band on one side of said bulb are out of diametrically opposed alignment with any portion of the same band on the opposite side.
3. A bulb for a signal light of the character described, aid bulb having a sealed envelope with the usual large-diameter light source therein, material portions of the area of the envelope of said bulb being substantially light-absorbing, said portions being distributed in annular bands in spaced axial alignment around said light source positioned to prevent light emission from said bulb except through comparatively narrow annular portions adjacent a transverse plane through said light source and through a lighttransmitting area at 'the front end of the bulb, said last area being of materially smaller diameter than aid annular light-transmitting areas.
CERTIFICATE OF CORRECTION. Patent No. 2,567,1M. January 16, 19L L onvnm sun.
It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 51;, for "oven" read --even--; page 2, second column, line 50,
claim 1, for "turning" re "transmitting"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 8th day of May, A. 'D.- 1915.
. Leslie Frazer (Seal) Acting 'Commissi oner of Patents.