US2413127A - Colored light signal - Google Patents

Description

Dec. 24, 1946. w WELLS 2,413,127

COLORED LIGHT S IGNAL Filed May 18, 1945 the roundel, but a small Patented Dec. 24, 1946 COLORED LIGHT SIGNAL Wesley B. Wells, Wilkinsburg, Pa., assignor to The Union Switch & Pa., a corporation Signal Company, Swissvale, of Pennsylvania Application May 18, 1945, Serial No. 594,399

7 Claims. I

My invention relates to light signals, and particularly to light signals of the searchllght type which are capable of selectively projecting a plurality of beams of light of dilferent colors from a single light source.

One well-known form of signal of the type described is shown and described in an application for Letters Patent of the United States, Serial No. 548,108, filed by me on August 4, 1944, and comprises a light unit for concentrating the light rays from an associated source at a focal point, a lens unit having a focal point which coincides with the focal point of the light unit for converting the light rays from the light source into a beam of substantially parallel rays, and a plurality of color filters which are selectively interposed into the light beam adjacent the common focal point of the light and lens units to impart to the beam the desired color. Heretofore, the color filters have usually comprised a flat glass roundel about one inch in diameter, and with the roundels constructed in this manner, external light rays entering the signal through the lens unit are caused to pass through the focal point of the lens unit whereupon they strike the side of the roundel nearest the lens unit. The greater portion of each of these rays will pass through percentage of each ray is reflected by the surface of the roundel. Some of the reflected rays are reflected in such directions that they will not reenter the signal beam, but other ones of these rays will leave the signal through the lens unit in a beam which may be parallel to the signal axis. That is to say, ex-

ternal light entering the signal will be partially reflected by the roundels, and will leave the signal in the form of a beam which may be parallel to the axis of the signal beam and which covers the central portion of the lens over an area. equal to approximately half of the lens area. Under the conditions most frequently encountered in practice, the intensity of the reflected light is insufllcient to produce any material effect upon the signal indication. However, under certain adverse conditions such as in the early morning or in the late afternoon when the sun is near the horizon and the signal is so located that the sun can shine directly into the lens unit, the intensity of the reflected beam may become sufficiently great to fade out the signal indication, destroying its true color and materially shortening the range of the signal. The indication produced by such reflected light is generally referred to as a phantom indication, and the principal object of my invention is to provide a novel construction of ro-undel which will prevent phantom indications in signals of the type described.

According to my invention, I construct the roundel with such a shape that any external light rays entering the signal through the lens unit will, if reflected only once by the rounds], be reflected in such directions that they will not reenter the lens unit, and, if reflected more than once by the roundel, will be so weakened that if they do reenter the signal beam through the lens unit, they will have substantially no efl'ect on the color or range of the normal signal indication. In the preferred form of my invention, the roundels are made conical in shape, but it should be understood at the outset that I do not wish to limit myself to this particular shape.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall describe one form of light signal embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a. view partly in side elevation, and partly in vertical section, showing one form of light signal embodying my invention.

Referring to the drawing, the light signal in the form here shown is of a well-known type in widespread commercial use, and comprises alight unit A, an operating mechanism B and .a lens unit C. The light unit A and operating mechanism B are disposed within a suitable housing I, while the lens unit C is secured in place in front of an opening 2 provided in the forward wall la of the housing I.

The lens unit 0 is of well-known construction and comprises a doublet made up of two spaced lenses 4 and 5 mounted in the outer and inner ends, respectively, of a tubular casing 6 commonly referred to as a lens barrel. The two lenses 4 and 5 are of plano-convex type, and are both clear or colorless. "Secured to the outer end of the lens barrel directly above the outer lens 5 is a hood I which performs the usual function of shielding the lens 5 from the direct rays of the sun.

The light unit A comprises an electric lamp 10 having a concentrated filament II, and an elliptical reflector I? which concentrates the rays of light from the filament H at a focal point 13 which coincides exactly with the focal point of the lens unit C.

The operating mechanism B is similar to that disclosed and claimed in Letters Patent of the United States No. 2,172,724, granted to myself and another on September 12, 1939, for Light signals, and comprises a top plate l5 having secured thereto a polarized electroresponsive motor means (not shown) for operating between an intermediate and two extreme positions a spectacle arm I 5 which projects upwardly through an opening in the top plate into an auxiliary housing I! which is secured to the upper side of the top plate. The spectacle arm is provided at its upper end with three angularly spaced color filters which align respectively with two glass windows I8 and i9 according as the spectacle arm occupies its one extreme position, its other extreme position or an intermediate position midway between its two extreme positions. Only the color filter which is normally colored red is shown in the drawing, but spectacle arms of the type described are well known and it is therefore deemed to be unnecessary to show this spectacle arm in detail herein.

The operating mechanism also comprises suitable contact mechanism not shown, operated by the motor means for controlling similar signals, relays or other apparatus forming part of a complete signal system.

The operating mechanism is removably secured within the casing I, and is so positioned with respect to the casing that the light rays emitted by the light unit A will pass through the windows l8 and IS on opposite sides of the common focal point of the light and lens units, in the manner indicated by the dot and dash lines 2i. It will be apparent, therefore, that the signal will display an indication the color of which will depend upon the color of the particular filter which is in alignment with the windows.

As shown, the window [8 is flat, while the window I9 is convex.

As was pointed out hereinbefore, the purpose of my present invention is to prevent light rays which may enter the signal from outside the signal through the lens unit C from being reflected by the roundel back into the signal beam in a manner which will cause a phantom indication, and according to my present invention I accomplish this result by so shaping the roundels that external light, if directly reflected by the surface of the roundel nearest the lens unit, will be reflected in such directions that it will not reenter the lens unit, and if reflected more than once by the surface of the roundel, will be so weakened in intensity that it will have no appreciable effect on the light beam.

In the preferred shape shown, the roundel 2B is conical and is disposed with its apex facing the light unit in such a position that its apex coincides with the axis of the signal beam. The roundel must have a sufficient diameter and must be located sufficiently close to the common focal point of the light and lens units to completely intercept the beam from the light unit. Furthermore, in order to prevent external light rays from being directly reflected into the lens unit, the ele ments of the cone must have such a slope that no light rays entering the signal through the lens unit will strike any element of the cone at right angles.

With the roundels constructed as just described, their effect on external light rays entering the signal through the lens unit can best be illustrated by tracing th paths of a number of typical rays. The paths of these rays prior to striking the roundels are indicated by full lines, while the paths of these rays after reaching the roundel are indicated by long dash lines or short dash lines according as the light passes through the roundel or is reflected by it. As shown, the paths of eight typical rays, designated 22 to 28, inclusive, which enter the signal through the top half of the lens unit and parallel to the signal axis are illustrated, It will be noted that these rays upon striking the signal lens 5 are concentrated by the lenses of the lens unit at the common focal point of the light and lens units, and after passing through this focal point, these rays diverge and strike the surface of the roundel nearest the focal point. The greater portions of these rays pass through the roundel, but a small percentage of each ray is reflected by the surface of the roundel. Any light which passes through the roundel will have the same color as the light entering the signal beam from the light source and will not therefore have any tendency to produce a phantom indication. It will be noted that those portions of the rays which are reflected directly by the roundel such as those indicated by the long dash lines 22, 23 and 24 are reflected in such directions that they do not reenter the lens unit. A portion of the ray 29 which strikes the apex of the cone may theoretically reflect back upon itself so that it will leave the signal by the same path which it entered the signal, but the amount of this reflected light is too small to cause any appreciable phantom indication. The rays 21 and 28 shown striking the nearest side of the roundel will be partially reflected to the opposite side of the cone where the majority of the reflected light will pass through the cone and a small portion will be reflected out through the lenses as shown by the long dash lines 21 and 28. After leaving the signal, these rays which are very weak due to being doubly reflected, are disposed at an angle to the signal axis and consequently have very little or no eiTect on the normal beam from the signal.

It should be particularly pointed out that while as shown in the drawing the conical roundel is disposed with its apex facing the light source and with its base facing the lens unit. the only reason for disposing the roundel in this manner is because of space considerations in the particular signal illustrated. With other well-known forms of similar signals where clearances will permit, the roundel may be reversed in position so that the apex faces the lens unit and the base faces the light unit with equally good results.

One advantage of a, light signal embodying my invention is that it completely eliminates phan tom indication under the most adverse conditions encountered in practice.

Although I have herein shown and described only one form of light signal embodying my invention, it i understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a light signal comprising a light unit for concentrating the rays of light from a light source at a focal point which coincides with the focal point of a lens unit which converts the light rays into a signal beam of substantially parallel rays and means for interposing in the signal beam adjacent the focal point a colored roundel to impart a distinctive color to the signal beam, the improvement which consists in providing said roundel with substantially a conical shape to prevent it from directly reflecting back into the lens unit light rays which initially enter the signal through the lens unit.

2. In a light signal comprising a light unit for concentrating the rays of light from a. light source at a focal point which coincides with the focal point of a lens unit which converts the light rays into a signal beam of substantially parallel rays and means for interposing in the signal beam adjacent the focal point a colored roundel to impart a distinctive color to the signal beam, the improvement which consists in providing said roundel with substantially a conical shape to cause it to divert from the signal beam substantially all light rays striking it from a source outside of the signal.

3. A light signal comprising a light unit for concentrating the rays of light from a light source at a focal point, a lens unit having a focal point which coincides with the focal point of the light unit for converting the light rays from the light source into a beam of substantially parallel rays, and a color filter interposed in said beam adjacent said focal point to impart to the beam 9. distinctive color, said filter being in the form of a cone the elements of which are inclined to the axis of the signal beam at such an angle that substantially all rays entering the signal through the lens unit and striking the surface of the cone will be reflected in directions which will prevent them from reentering the lens unit.

4. A light signal comprising a light unit for concentrating the rays of light from a light source at a focal point, a lens unit having a focal point which coincides with the focal point of the light unit for converting the light rays from the light source into a beam of substantially parallel rays, and a, color filter interposed in said beam adjacent said focal point to impart to the beam a distinctive color, said filter being in the form of a cone the elements of which are inclined to the axis of the signal beam at such an angle that any rays entering the signal through the lens unit and directly reflected by the cone will be reflected in directions which will prevent them from re- 5 entering the lens unit.

5. A light signal comprising a light unit for concentrating the rays of light from a light source at a focal point, a lens unit having a focal point which coincides with the focal point of the 10 light unit for converting the light rays from the light source into a beam of substantially parallel rays, and a color filter in the form of a cone disposed in said beam adjacent said focal point with its axis coinciding with the beam axis.

6. A light signal comprising a light unit for concentrating the rays of light from a light source at a focal point, a, len unit having a focal point which coincides with the focal point of the light unit for converting the light rays from the z light source into a beam of substantially parallel rays, and a color filter in the form of a cone disposed in said beam adjacent said focal point with its axis coinciding with the beam axis and with its apex closest to the light source.

7. A light signal comprising a light unit for concentrating the rays of light from a light source at a focal point, a lens unit having a focal point which coincides with the focal point of the light unit for converting the light rays from the light source into a beam of substantially parallel rays, and a color filter interposed in said beam adjacent said focal point to impart to the beam a distinctive color, said filter being in the form of a cone the elements of which are inclined to the axis of the signal beam at such an angle that no external light rays entering the signal through the lens unit will strike any element of the cone at right angles.

WESLEY B. WELLS.

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