US2892076A - Lighting fittings - Google Patents

Description

Jam; 23, 1959 K. Moos LIGHTING FITTINGS Filed Aug. 28. 1957 IINVENTOR [Kaspar/yaw United States Patent LIGHTING FITTINGS V Kaspar Moos, Lucerne, Switzerland Application August 28, 1957, Serial No. 680,781

Claims. (Cl. 240-45 This invention relates to lighting fittings, particularly for illumination of streets, of the type comprising light sources mounted within hollow reflectors.

The most important requirement of such lighting fit tings, particularly when they are used for street illumination, is a uniform distribution with minimum losses of the light rays of the source of light impinging on the reflector surfaces, for illuminating the largest possible street surface. j

It is of great economical importance to meet this requirement as entirely as possible, since it is essential for traflic security. When designing an illuminating system for a street, it is important that the desired intensity of illumination may be obtained with the smallest possible number of lighting fittings and that the used fittings are economical. It is further essential how the light rays reflected on the street are distributed, i.e. whether the rays uniformly illuminate the street, or whether a succession of alternate lighter and darker areas are formed.

On the one hand, the number of light fittings should be as small as possible, while on the other hand, these fittings must illuminate the greatest possible surface area of the street. The reflected light'rays .mus't comprise a great angle of radiation, while the light rays emitted by the light source directly towards the street form a small angle of radiation only, in order to avoid blinding, in other words, the light source must be screened as far as possible for the eyes of the persons using the street. Further, in light fittings having several light sources, it is reguired that when one of the sources fails, the whole Width of the street remains illuminated.

To accomplish the above mentioned requirements great difficulties are encountered, and in an eflort to avoid the same, light fittings having composite reflectors and several light sources have already been proposed but have not fully satisfied.

According to the present invention, in a lighting fitting having a plurality of light sources associated with hollow reflectors, each reflector surface is formed by one half-of an ellipsoid divided by a plane of section through the longest and the shortest axes thereof, at least two reflectors being joined together with their longitudinal axes in alignment, the vertex sections of the adjacent ends of the two reflectors being cut away and a light source being disposed at or in proximity to each of the parallel half axes of the reflectors.

The accompanying drawings show several embodiments of a lighting fitting according to the invention.

Fig. 1 is an axial section of a lighting fitting having two reflectors.

Fig. 2 is a view from below of a lighting fitting according to'Fig. 1.

Fig. 3 is an axial section of a lighting fitting having three reflectors.

Fig. 4 is a view from below of the lighting fitting according to Fig. 3.

Fig. 5 shows a modified arrangement of a lighting fitting having three sections.

Fig. 6 illustrates the paths of the light rays emitted by a lighting fitting having two reflector The fitting according to Figs. 1 and 2. comprises two hollow reflectors 11 and 12 which are elliptical when viewed in plan.

An end portion of each reflector is cut away and the two reflectors are secured together along a junction line 1 to form a lighting fitting. The reflecting surfaces of the hollow reflectors 11 and 12 are each formed by one half of an ellipsoid which has been divided by a sectional plane through the longest and the shortest axes of the ellipsoid. In the lighting fitting formed by the hollow reflectors 11 and 12 the half axes a and b of the semiellipsoidal reflector surfaces are vertically directed in parallel relationship, while the longest axes c and d are in alignment with each other. Each reflector surface is associated with a light source A or B, respectively, which sources are disposed on the same level in the half axes of the reflectors 11 and 12, respectively. For reasons of manufacturing it may be advantageous to omit the upper curved surface portion of the reflectors; thus the corresponding upper portion of the lighting fitting according to Figs. 1 and Z is flat.

In the example according to Figs. 3 and 4 the lighting fitting comprises two ellipsoidal outer or end reflectors 11 and 12 of which the two vertex portions facing each other are cut off, and an ellipsoidal intermediate reflector 13 having both vertex portions cut oif. The three reflectors are joined together along the lines 1. The reflecting surface of the intermediate reflector 13 also has the shape of one half of an ellipsoid which is divided by a sectional plane through the longest and the shortest axes. The longest axes of the three reflecting surfaces of the lighting fitting according to Figs. 3 and 4 are in alignment, while the three half axes are vertically directed. In each of the hollow reflecting surfaces 11, 12 and 13, a light source A, B and C, respectively, is mounted in the half axis of the corresponding reflector and at the same level. The light source C of the intermediate refiector is tube-shaped; if desired also the light sources A and B could be tube-shaped. Such light sources obviously could also be used in the two-part lighting fitting of Figs. 1 and 2. The upper portion of the three reflectors of the lighting fitting shown in Figs. 3 and 4 is also formed by a flat surface.

The three hollow reflectors can be removably attached to each other as shown in Fig. 5 by means of straps 14, or screws or the like to form a three-part lighting fitting. In this manner any desired number of sections can be attached to each other. a

In the example according to Fig. 5 reflecting partition walls 111 and 121 are provided having the shape of the vertex portions which had been cut off from the hollow reflectors 11" and 12, and which can be inserted to complete the reflecting surfaces 11 and 12 in the lighting fitting. This possibility also exists in lighting fittings in which the reflector surfaces are permanently fixed to each other or are integrally formed.

The path of the light rays in a lighting fitting formed of two hollow reflectors is illustrated in Fig. 6. The rays of the light source B of the reflector 12 are shown in full pinging the reflecting surfaces from the light sources A and B, respectively, at these points is described. The

The paths of the light rays emitted by the source A are designated by A and those emitted by the source B with B. The rays impinging at the point 110 are additionally designated by 110 and in analogous manner the rays impinging at the point 120 are designated by 120. In this manner the self-radiation of a reflector, i.e. the rays emitted by its own source of light as well as the rays emitted by the other source of light are visibly illustrated. The rays of the light source B are supposed to be divided by the ray B 110 in two beams, one beam being designated by p and the other beam by a. It is visible from the drawing that the light beam [3 results in the self-radiation of the reflector 12 while the beam or is radiating into the reflector 11 and is again reflected by this latter. The ray B 110 is the first ray of the light source B which is impinging on the reflector 11 at the jointing line 1. It is clearly seen from the drawing that the two reflectors 11 and 12 are joined in such a manner or, in other words, that the distance between the two light sources A and B with respect to their level and the reflecting surfaces is so chosen that the limit ray B 110 impinging on the reflecting surface of the reflector 11 at the jointing line 1 of the beam or is reflected to a further point 112 situated on the equator of this reflecting surface with respect to its longitudinal axis. This ray is further reflected to a point 110 and from there to the point 113 and is finally leaving the reflector 11. The path of the limit ray B 114 forms a mirror image with respect to the equator of the reflector 11 and deviates from this course only at the point 113; the ray B 110 leaving the reflector 11 is still to be considered as a limit ray. All other rays of the beam or which enter into the reflector 11 under a more obtuse angle than the limit ray B 110 leave this reflector between the finally reflected portion B 110 of this ray and the light source A.

When now the light ray A 110 is considered, i.e. a ray of the own radiation of the reflector 11 emitted by the light source A which also is reflected at the point 116, it is clear that the own radiation of one reflector and the rays emitted by the light source of the other reflector and entering into the first reflector spatially complete each other.

This feature of the lighting fitting according to the invention becomes more evident by the light rays of the self-radiation of the reflector 12. It is seen that the upwardly directed rays of the beam after reflection, illuminate a street surface below the light source B and that the illuminated surface, according to the paths of the rays of this beam the angle of which increases with respect to the vertical, the illuminated area increases, while from a certain angle of inclination of these rays, the downwardly reflected rays progressively converge more and more towards the street surface, until finally the reflected rays of the beam [5' impinge on the street surface together with the self radiation of the reflector 11.

It can be seen that the self radiation of each reflector illuminates a determined surface area situated below the respective reflector but a portion of the light beam [3 of one reflector impinges on the surface portion which is illuminated by the self radiation of the second reflector. On the other hand, the surface portion illuminated in this manner is additionally illuminated by the rays of the beam or of one reflector, which rays are reflected by the second reflector.

The path of the rays of a lighting fitting according to the invention makes possible the disposition of the fitting with its longitudinal axes extending transversely to the street so as to enable the illumination of the entire width of the street from one of the longitudinal sides thereof. In this manner, a uniformly illuminated surface of high light intensity extending longitudinally of the street on both sides of a lighting fitting is obtained, which surface is of comparatively great extent as compared with that obtained by conventional lighting fittings, so that for an 4 equal or a higher degree of illumination a smaller number of fittings according to the invention may be used.

It is apparent from the drawing that the direct light rays from the source of light are impinging on the street surface under relatively steep angles so that a lighting fitting according to the invention is almost entirely exempt of blinding effect.

The cooperation of at least two reflectors of the described type prevents the uni-lateral emerging of light from the lighting fitting towards a single side of the street also then, when one of the light sources does not operate. The path of the light rays of one reflector results in a completion and amplification of the action of the light rays of the other reflector. This feature particularly is of essential importance when different sources of light such as for example a mercury high pressure lamp and a sodium vapour lamp are combined with the reflectors of the lighting fitting. The purpose of such arrangements is to improve the colour of the emitted light in order to improve the conditions of sight, particularly during fog. It is clear that the degree of the obtained success is decisively influenced by the effective degree of mixture of the combined light and it is evident that this degree of mixture is extraordinarily high with the lighting fitting according to the invention. The formation of shadow effects of different colour on the street surface is thereby prevented.

In the examples of the invention having more than two reflectors the path of rays remains in principle the same and allows various possibilities of combination, for example of the intensity of illumination, of mixture, of colour, and others. Any desired particular effects can be obtained by the shape of the ellipsoids according to which the reflecting surfaces are formed. It has been found that an ellipsoid according to the following formula gives the best results:

in which 1 2 181 cm.

The flattening of the top of the reflector surfaces does not have any influence on the illuminating efiect of the lighting fitting and particularly on the width of radiation.

It is to be mentioned, and it is clear from the form of the reflecting surfaces and from the paths of the rays that the fact that, in the described lighting fitting the source of light has spatial dimensions and is not a true point has been taken into consideration.

I claim:

1. A lighting fitting, particularly for street illumination, comprising at least two reflector surfaces having a common light exit plane, a light source associated with each reflector surface, each reflector surface being formed at least adjacent to the light exit plane as an ellipsoid divided by said plane through the longest and the shortest axes thereof, the reflectors being joined together with their longitudinal axes in alignment, the vertex sections of the adjacent ends of the two joined reflectors being cut away, and the light sources being disposed with their center on the half axes of the reflectors.

2. A lighting fitting according to claim 1, wherein the distance between two light sources, their level on the half axes, and the shape of the semi-ellipsoids are so determined, that a light ray of the light source of one reflector impinging on the other reflector in immediate proximity to the joining line of the two reflectors is re flected towards a point of this latter reflector which is situated on the equator of the reflecting surface with respect to the longitudinal axis thereof.

3. A lighting fitting according to claim 2, wherein the hollow reflectors are detachably secured to each other.

4. A lighting fitting comprising three reflecting surfaces, each reflector surface being formed by one half of an ellipsoid divided by a plane of section through the longest and the shortest axes thereof, the three reflector 5. A lighting fitting according to claim 4, wherein two 0 6 reflecting partition walls having the shape of the two vertex portions cut away from said two end reflector surfaces are fixed to said intermediate reflector surface at the two ends thereof joining the end reflector surfaces.

References Cited in the file of this patent UNITED STATES PATENTS Wheeler Sept. 27, 1881 Sanford July 12, 1910

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