US3112893A - Reflector - Google Patents

Description

1963 w. F. CROSBY ETAL 3,112,893

REFLECTOR.

Filed Aug. 11, 1961 INVENTORS h/uunn EC/eosBY mm 0/)RYL 0. JqLL/vA/v United States Patent 3,Til2,$93 REFLECTUR William F. Eroshy, New Berliord, Mesa, and Daryl D. Sullivan, Corning, FLY, assignors to Corning Glass Works, (learning, N.Y., a corporation of New York Filed Aug. ll, N61, fler. No. 13%,663 Claims. (ill. 24ll-ltl3) This invention relates to optical reflectors and more particularly to a novel reflector which is mountable in and conformable to the general shapes of presently existing luminaire housings of varying designs but which exhibits optical advantages characteristic of reflectors having circular cross sections.

Presently existing luminaire housings exist in a variety of shapes dictated by such considerations as appearance, available space and the amount of light which is to be emitted in any given direction. One disadvantage encountered in luminaires having non-spherical reflectors is the fact that light traveling from the reflector to any point on the refractor does not impinge on the refractor at the same angle as light rays traveling from the light center directly to the same point. Consequently, it is diflicult to design refractors which, when used in conjunction with non-spherical reflectors, will transmit both direct rays and reflected rays in the directions necessary to given desired patterns of illumination. This difficulty is encountered to a much lesser degree in luminaires employing reflectors which are circular in cross section, since such reflectors redirect light rays such that their components in the planes of the circular sections are coincident with those of rays traveling directly from the light center to the same points on the refractor.

Accordingly, it is an object of this invention to provide a reflector which can be conveniently substituted for the reflectors in presently existing luminaires and which exhibits the above-mentioned characteristics generally found only in reflectors having circular cross sections.

This and other obiects which will be apparent from the following description are accomplished by the provision of a reflector having a stepped reflecting surface which comprises a plurality of surfaces of revolution about a common directrix, said surfaces intersecting at least one plane perpendicular to the directrix so as to form circles of differing radii about the point of intersection of the plane and the directrix.

The construction and functioning of the reflector of this invention can be understood by a reference to the accompanying drawing representing one embodiment suitable for inclusion in a generally ovate luminaire, wherein:

FIGURE 1 is a plan view looking into the reflector of this invention,

FIGURE 2 is a view taken on line 2-2 of FIGURE 1,

FIGURE 3 is a view taken on line 3-3 of FIGURE 1, and

FIGURE 4 is a typical sectional View of the reflector taken as indicated by line i -4 of FIGURE 2.

As previously pointed out, the reflecting surface of the reflector of this invention comprises a plurality of surfaces of revolution. A typical arrangement is illustrated in the drawing in the form of reflector it) having a generally ovate shape, as indicated by oval reflector rim ll, and having a reflecting surface 12 which is generally ovate in shape but which is made up of re ecting steps, such as 13, which are in the form of surfaces of revolution with a common directrix passing through light center 14 perpendicular to the plane of the paper in FIGURES 1 and 4 and indicated by broken line 16 in FIGURES 2 and 3.

It is a characteristic of a surface of revolution that its intersection with planes perpendicular to its directrix are in the form of arcs of circles having their centers at the hllzfiflfi PatentecliDec. 3, i965 "ice intersections of the directrix with the respective planes. A typical curve 15 formed by the intersection of surface 12 of reflector lit with the plane perpendicular to the directrix of its stepped surfaces is indicated in FZGURE 4 and is representative of the intersection of any such plane with the reflector surface. As can be seen, this intersection is in the form of a number of arcs of concentric circles having their center on directrix 16. These arcs are connected by lines such as 17, which preferably lie in a radial direction with respect to the center of curvature of the arcs so that substantially no light is reflected therefrom. That is, the surfaces, such as 18, which form the loci of lines 17 and which connect the circular steps 13, lie in planes which pass through and include directrix 16. It is to be understood that any plane perpendicular to directrix 16 will intersect surface 12 to form a curve generally similar to curve 15.

Since any plane perpendicular to directrix it? will intersect the reflector in a series of circles, and since, as can be seen from the drawings, all light emitted from light center 14 and impinging on reflector surface 12 falls upon the steps 13 which consist of the loci of these circles, it follows that all such light will fail upon some such imaginary circular intersection. Any light ray falling upon any such imaginary circular intersection may be considered as having two components, one in the plane of the intersection and the other in a direction perpendicular to this plane and parallel to the directrix. According to well-known optical laws, the component in the plane will be reflected from the circular intersection back in the same path which it followed in reaching the circular intersection and through the point forming the intersection of the directrix with the plane of the circular intersection. Since the only other component lies parallel to the directriX, it is seen that the path of the actual reflected ray will dififer from this reflected component only by the addition of a component parallel tot he directrix. That is, the actual reflected ray will also pass through some point along the directrix. Thus all rays emitted from light center 14 and impinging on the surface of reflector it) will be directed back through directrix 16.

All rays emitted from light center 14 and reflected through directrix 16 fall either on the reflector or on the refractor. If a ray falls on the reflector, it will once again be redirected through the directrix and so repeatedly until it finally emerges from the reflector to impinge on the refractor. This means that all rays impinging on the refractor will come from the direction of some point on the directrix. That is, all rays impinging on any given point on the refractor lie in a plane passing through that point and including directrix lie and hence have the same components in a plane which passes through that point on the refractor and is perpendicular to the directrix.

Thus, if, for example, reflector ltl is included in a street lighting lurninaire, directrix 16 might be oriented vertically, and all rays falling on any point on the refractor would have the same components in the horizontal direction. Consequently, the problem of redirecting in horizontal directions the light emitted from the luminaire is simplified, since the refractor will bend through the same angle in the horizontal plane and emit in the same horizontal direction both reflected rays and those passing directly from the light center to the refractor. Such luminaires are of particular value where accurate horizontal light distribution is necessary, as, for example, in fourway luminaires for lighting street intersections and for directing beams of light down both streets in each direction.

Although the reflector of this invention has been illustrated in an embodiment suitable for inclusion in an ovate luminaire housing, it should be understood that the various surfaces of revolution comprising the reflecting surfaces thereof may be formed with varying radii to give any desired overall confl uration to the reflector while retaining its characteristic optical circularity.

What is claimed is:

1. A reflector having a concave reflecting surface with an edge defining an opening for the emission of light from said reflector, said reflecting surface comprising a plurality of surfaces of revolution about a common directrix passing through said opening, said surfaces of revolution intersecting at least one plane perpendicular to said directrix so as to form a plurality of arcs of circles having differing radii and having a common center at the intersection of said directrix with said plane perpendicular thereto, said arcs forming together a generally non-circular configuration.

2. A reflector according to claim 1 wherein said reflecting surfaces are connected by surfaces lying in planes which include said directrix.

3. In a concave reflector of generally ovate form having an edge defining an opening for the emission of light from said reflector, the improvement which comprises forming the inner surface of said reflector as a series of surfaces of revolution about a common directrix passing through said opening, at least two of said surfaces of revolution intersecting a plane perpendicular to said directrix to form circles of differing radii and having a common center at the intersection of said directrix and said plane perpendicular thereto, said arcs forming together a generally non-circular configuration.

4. A reflector according to claim 3 in which said sur- '4 faces of revolution are connected by surfaces lying in planes which include said directrix.

5. The combination with the light source of a reflector having a concave reflecting surface with an edge defining an opening for the emission of light from said reflector, said reflector having a continuous inner surface comprising a plurality of steps, each of said steps comprising a surface of revolution and a plane surface, each of said surfaces of revolution having a common directrix passing through said light source and said opening and each of said plane surfaces being in a plane which passes through and includes said directrix, said steps being formed such that the said surface of revolution of each step connects with the said plane surface of another step, said surfaces of revolution intersecting at least one plane perpendicular to said directrix so as to form a plurality of arcs of circles having differing radii and a common center at the intersection of said directrix and said plane perpendicular thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,189,621 Post et al. July 4, 1916 1,814,326 Melton July 14, 1931 2,196,548 Cohu Apr. 9, 1940 FOREIGN PATENTS 475,410 Great Britain Nov. 16, 1937 533,135 Belgium Nov. 30, 1954

Claims (1)

1. A REFLECTOR HAVING A CONCAVE REFLECTING SURFACE WITH AN EDGE DEFINING AN OPENING FOR THE EMISSION OF LIGHT FROM SAID REFLECTOR, SAID REFLECTING SURFACE COMPRISING A PLURALITY OF SURFACES OF REVOLUTION ABOUT A COMMON DIRECTRIX PASSING THROUGH SAID OPENING, SAID SURFACES OF REVOLUTION INTERSECTING AT LEAST ONE PLANE PERPENDICULAR TO SAID DIRECTRIX SO AS TO FORM A PLURALITY OF ARCS OF CIRCLES HAVING DIFFERING RADII AND HAVING A COMMON CENTER AT THE INTERSECTION OF SAID DIRECTRIX WITH SAID PLANE PERPENDICULAR THERETO, SAID ARCS FORMING TOGETHER A GENERALLY NON-CIRCULAR CONFIGURATION.

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