Lighting Fitting

Abstract

A lighting fitting for an electric luminous source having a molded part of transparent material surrounding the luminous source. The molded part is open on the top and at the bottom and has a first lower system of outer prisms and a second upper system of two outer prisms, all of them located in planes normal to the symmetry axis of the luminous source. A top part offers the luminous source a concave reflecting surface. The assembly is arranged so that a part of the luminous rays emerge directly through the lower opening of the molded part, another part is refracted by the first system of prisms, another part undergoes a total reflection in the second system of prisms, emerging out of the first prism of this second system in a diver form and of the second prism in a convergent form without hitting the lower located prisms, and part of the light rays is reflected downwards and outwards by the upper reflecting surface. The molded part may comprise another system of inner prisms disposed in planes which pass through the symmetry axis and direct the light rays in an asymmetric form relative to the ground's plane.

Description

This invention is closely related to the U.S. Pat. 3,348,037 which was issued on Oct. 17, 1967 to the applicant.

The present invention relates to a lighting fitting for deriving the highest output ratio of the flux produced by a light source, in order to obtain a polar curve of light distribution of a wide shape, and, therefore, capable of producing a strong and uniform illumination of any space.

The present invention consists in a lighting fitting which includes a support or holder for an electric light source, a moulded piece of transparent material surrounding the light source focus and formed by two systems of prisms situated in planes normal with respect to the axis of symmetry of the light source, the lower system, consisting of small prisms arranged to function by refraction, and the upper system, consisting of two larger prisms arranged to function by total internal reflection, the fitting being provided on top with a reflecting member that receives the upper part of the light flux not intercepted by the prisms and directs it downwards in such a way that the reflected light rays cross each other without falling on the prismatic piece below.

In one form of the invention, the total light flux produced by an electric bulb, which may be either an incandescent, mercury or a high-pressure sodium lamp, is divided into five zones, viz a low one for direct illumination, a low-middle one which collects the light flux by means of system of refracting prisms, a low-intermediate one in which the light flux passes through a total internal reflection prism, emerging in a diverging manner, the upper intermediate one in which the light flux passes through a total internal reflection prism emerging in a converging manner, and an uppermost zone in which the light flux is reflected by a polished reflecting surface. In each case, the light flux coming from the lamp is refracted or reflected, respectively, with a minimum of losses, so that the reflected light flux in the upper zone does not hit the prismatic part, and the flux passing through said prismatic part does so only once, i.e., without hitting the diverse prisms.

In the accompanying drawings:

FIG. 1 represents a light fitting, showing a sectional view of its right half, according to the present invention,

FIG. 2 shows an alternative fitting for use with a mercury fluorescent lamp bulb,

FIG. 3 shows the same fitting with a sectional view through its right-hand half, and an outside view of its left-hand half,

FIG. 4 shows the central part of the fitting and part of its rim seen from the bottom upwards on the section line A-A' of FIG. 3, in the case of a symmetrical type fitting, and

FIG. 5, shows, on a different scale, the central part of the fitting, as seen from section B-B' in FIG. 3 in the case of an asymmetrical-type fitting.

In carrying the invention into effect according to one convenient mode by way of example, FIG. 1 shows a lighting fitting which includes a lamp bulb 1', a holding block 2' with different types of prisms 3', 4', and 5', and a reflecting surface 6'.

In FIG. 1 the light ray paths through each of a number of different zones are clearly to be seen. Thus, the light rays between R.sub.1 and R.sub.2 belong to a direct illumination zone; the light rays between S.sub.1 and S.sub.2 belong to a zone in which the refracted light rays pass through an assembly of the small prisms 3'; the light rays between T.sub.1 and T.sub.2 belong to a zone in which the diverging light rays emerge from the prisms 4' after having undergone a total internal reflection within the prism; the light rays between U.sub.1 and U.sub.2 belong to a zone in which the converging light rays emerge from the prisms 5' after having undergone a total internal reflection within the prism; and the light rays between V.sub.1 and V.sub.2 belong to a zone in which they converge after being reflected by the reflecting surface 6'.

The holding block for the prisms surrounds the lamp bulb 1' and receives a great share of the light flux. It is open as at its lower part and at its top, its inner space is concave shaped and in its center coincides approximately with that of the light bulb. Its inner and lower part 7 has a circular arc section, the center of which coincides with that of the lamp bulb 1' and in its inner and upper part 8 its section is straight but slightly inclined outwards from the vertical, to permit easy withdrawal from a mould after its formation by an injection moulding process from a transparent plastics material. The small refracting prisms, as indicated at 3', possess outer upper conical surfaces of straight generatrix, coaxial with the lamp's axis of symmetry, and the surfaces of their lower outer part are conical and coaxial with the bulb's axis of symmetry and of straight generatrix whose inclination is such that they may be readily removed after formation in a mould.

The lower prism 4' of the two large prisms which work by total internal reflection, and whose axes are coaxial with the lamp's axis of symmetry, possesses a conical outer and upper surface of straight generatrix whose inclination is such that it will permit its removal from a mould, and on its outer and lower side the prism is so shaped with straight and curved lines as to cause the light rays to diverge when emerging. The large top prism 5' presents a section which on its outer top side is made up by a logarithmic spiral curve line, and on its outer and lower side it is limited by curved and straight lines in such a way that the light rays converge when emerging, their paths crossing each other without hitting the prism situated next below.

The reflecting surface 6' has a concave or toroidal shape with a protruding center. Its profile is made up of circular arcs joining other arcs, their centers being situated on the lower side, whereby the arcs nearer the axis of symmetry and the rim of the fitting have a smaller radius, and the arcs of the intermediate zone between the rim and the center have a larger radius, so that the light rays which pass nearer the axis of symmetry are reflected back downwards without interfering with the lower prismatic part, while the light rays which are further away from the axis of symmetry are reflected in that part of the reflecting surface whose curve is more pronounced, in a near vertical direction, thus crossing the light rays whose paths lie before them.

FIG. 2, which shows an arrangement which includes a mercury fluorescent bulb 1, in which the prisms block 2 presents on its outer side a profile similar to that shown in FIG. 1 which corresponds to the incandescent lamp's profile, but the two upper prisms 5 and 4 have smaller dimensions and the number of lower lying prisms 3 is reduced, while inside them there are provided several vertical prisms 27 which extend through both ends 33 and 34, which detail in its sectional view is to be seen in FIG. 5. The purpose of these prisms is to distribute the light flux in a horizontal plane to be explained later. It goes without saying that if the prisms 27 are not present, as is the case in FIG. 1, the distribution of the light flux will be symmetrical. The reason for the dimensions of the upper prisms 5 and 4 being smaller, is to alter the portion of the light flux received by the horizontal prisms corresponding to the angle .delta..sub.2 with respect to the light flux received by the reflector which corresponds to the angle .delta..sub.3. It must be remembered that in the present case of the mercury fluorescent bulb, the light flux is emitted through the total surface of the bulb to provide a flux which is rather more diffuse than directional, and since the prisms block is situated near the bulb, the light flux cannot be directed as if it were from an incandescent lamp. On the other hand, if it is a reflector of rather greater dimensions compared to those of the bulb and farther away from same, the reflected flux is more directional than the flux emitted through the prisms block. Therefore, in the case of the mercury fluorescent bulb, in order to obtain a suitable polar curve the light flux portion received by the reflector must be increased, consequently decreasing the flux received by the block of prisms.

In FIG. 3 there is shown a type of lantern based on the above-described principles. It consists of an annular piece 9 that is fitted to a mast 10 and serves to support a lampholder 26 and having moreover, ventilation holes 11, curved slots 12 and some holes 13 through which rods 14 are screwed and secured by their ends joining the part 9 to the upper cap 15 and being fixed by lock nuts 16, 17.

The rods 14 may be two, three or four in number and between each two rods there will be two, three or four sectors 18 which altogether make up a transparent surface in the shape of a frustrum cone open at the top and resting on the lower slots 12. The sectors 18 are composed of transparent plastic and are held at the top by the slots 19 in extensions 20 of a triangular piece 21, which embraces the rods 14 which pass through them through enlarged openings 22. Helicoidal compression springs 23 surround the rods 14 and are situated between the extensions 20 and the reflecting surface beside a cap 15. In turn, the extensions 20 have some edges 24 to which are screwed at one end pieces 25 which are screwed at the other end to the upper edge of the block of prisms 2, constituting a support for said prisms. In this way, to dismount the sectors 18, to take out the block 2, or to remove the lamp 1, it suffices to press the triangular piece 21 upwards, whereby the sectors 18 can be removed from their slots. It should be noted that the apparatus has good ventilation, the air being able to circulate through the chimney draught on entering through the openings 13 and leave through the gap between the edge of the sectors 18 and the edge of the upper cap 15.

This type of lantern, instead of being mounted on the mast 10, could be hung up by its top by simply adding an auxiliary piece. When a high pressure sodium lamp is being used the apparatus must be arranged for fitting the lamp with the cap at the top.

In FIG. 4, (corresponding to the case of FIG. 1) there is shown the symmetrical form of revolution around the axis of the lamp both of the block of prisms 2 and of the reflecting surface 6, the whole combination being viewed from the bottom.

In this case of FIG. 1, the polar curves of light distribution are the same in all the meridian planes that pass through the axis of the fitting, i.e., they are of the type of symmetrical horizontal illumination, which is the suitable one for streets with open places, squares, parks, etc. On the other hand, in the case of FIG. 2, different types of asymmetrical horizontal illumination, suitable for main roads or streets with more or less traffic, may be obtained in the following manner.

In FIG. 5, there is shown on a larger scale, for the case of an asymmetric type fitting such as that of FIG. 2, the block of prisms seen through the section B B' of FIG. 3, with an indication of the path of the rays through the interior prisms which constitute an addition in this case to the block of prisms 2--symmetric of FIG. 1--to make them asymmetrical. Such prisms 27 are positioned on planes passing through the vertical axis of symmetry of the apparatus, all situated along the inside of the block of prisms 2 of FIG. 2, and extended by the ends 33 and 34, their object being to cause the rays coming from the light focus to undergo a first refraction that guides them in their horizontal projection towards a dominant direction, which, in this case, coincides with the axis CC' of FIG. 5. One must bear in mind that we are concerned here with the light flux caught by the prisms 27 in the zone .delta..sub.2 and zones .delta..sub.4 and .delta..sub.5 of various dimensions, but part of the light flux from the lamp corresponding to zone (.delta..sub.1 -.delta..sub.5) is direct, and the part (.delta..sub.3 -.delta..sub.4) is reflected by the surface 6, these light fluxes being uniformly distributed.

There is, consequently, a greater concentration of light flux in the direction CC' of FIG. 5, and a lesser concentration in the direction PP', normal to CC', whereby the polar distribution curve in the horizontal plane corresponds to the type known as axially asymmetrical. The prisms 27 are small, although in the drawing they are shown a little larger (one of the latter being equal to four of the former) and have a radial face 28, i.e., a face that lies in a plane which runs through the vertical axis of symmetry of the apparatus, while the other face 29 lies also in a vertical plane at the angles .alpha..sub.1, .alpha..sub.2, .alpha..sub.3 that are constant for determined groups of prisms, with the corresponding radial planes. These prisms may be inclined at the various angles .alpha..sub.1, .alpha..sub.2, .alpha..sub.3 corresponding to the deviations Y.sub.1 =10.degree., Y.sub.2 =20.degree., Y.sub.3 =30.degree., of the light rays, i.e., Y.sub.2 =2Y.sub.1, Y.sub.3 =3Y.sub.1, as is necessary for the right superposition of the light fluxes. In the case of FIG. 5, which we take as an example, the prisms in the upper right hand quadrant (angle .beta..sub.2) follow each other in the order: .alpha..sub.1, .alpha..sub.2, .alpha..sub.3, .alpha..sub.3, .alpha..sub.3, .alpha..sub.2, .alpha..sub.2, .alpha..sub.1, .alpha..sub.1, in order to obtain an axial asymmetrical diagram, the arrangements of the prisms being symmetrical with regard to CC' axis and to an axis PP' normal to CC', or, that is to say, that the angles .beta..sub.1, .beta..sub.2, .beta..sub.3, .beta..sub.4, which comprise the groups of prisms of equal distribution, are all 90.degree.. Also, in the case of FIG. 5, if starting from a point D, we draw some segment between the radii 31, 32, parallel to the faces 29, the geometrical figure 30 obtained will have the shape of several portions DH, HI, IE, EF, FG of a logarithmic spiral joined together, the angles .alpha..sub.1, .alpha..sub.2, .alpha..sub.3 formed by the segments with the radii 31, 32 being constant. From the shape of the geometrical figure 30 one is able to predict the degree of asymmetry obtained in the polar horizontal distribution curve.

Various forms of asymmetry can be obtained, and, consequently, various polar horizontal curves, by varying the distribution of the prisms in the different combinations embraced by the angles .beta.. Thus, we may make the angles .beta..sub.1, .beta..sub.2 smaller than 90.degree., and consequently .beta..sub.3, .beta..sub.4 greater, in order to obtain curves with one single axis of symmetry, i.e., PP'.

In this case, the prisms comprised by the angles .beta..sub.1 and .beta..sub.2 follow each other from point D on in the following order: .alpha..sub.1, .alpha..sub.2, .alpha..sub.3, .alpha..sub.3, .alpha..sub.2, .alpha..sub.2, .alpha..sub.1, .alpha..sub.0, (this one without prisms). and the prisms comprised by the angles .beta..sub.1, .beta..sub.4 from the point diametrically opposite D on will follow each other in the order: .alpha..sub.1, .alpha..sub.2, .alpha..sub.3, .alpha..sub.3, .alpha..sub.3, .alpha..sub.3, .alpha..sub.2, .alpha..sub.2, .alpha..sub.1, .alpha..sub.1. By this means we shall obtain a polar curve of the type called nonaxially asymmetrical.

Claims

I claim:

1. A lighting fitting comprising a support for an electric light source, a transparent moulded piece surrounding said light source having a lower and an upper system of prisms situated in planes normal with respect to the axis of symmetry of said light source, said moulded piece being open at its top and bottom and situated coaxially with said light source, said lower system comprising small prisms arranged to function by refraction, and said upper system comprising two larger prisms arranged to function by total internal reflection, a reflecting member at the top of said fitting that receives the upper part of the light flux not intercepted by said prisms directing it downwardly so that the reflected light rays cross each other without falling on said prisms below, said moulded piece being concave in its inner and lower part and slightly conical in its inner and upper part, said small prisms having conical outer and upper surfaces of a straight generatrix coaxial with said source's axis of symmetry and conical outer and lower surfaces coaxial with said source's axis of symmetry, and said larger prisms having an upper and outer surface of conical shape coaxial with said source's axis of symmetry and a conical outer lower surface coaxial with said source's axis of symmetry having a mixed generatrix of straight lines and curves so that the rays totally reflected on the outside upper surface come out in divergent manner for the large lower prism and cross each other for the large upper prism so that the rays from the upper prism do not touch the prism below it.

2. A light fitting as claimed in claim 1 wherein said reflecting member has a profile made up of circular arcs joined together with their centers lying in the lower part of the fitting, said circular arcs adjacent the rim and adjacent the center of said fitting having a radius smaller than the intermediate arcs, said reflecting member having a concave surface with a protruding center part and a curvature increasing towards the rim so that the rays nearest said source's axis of symmetry emerge with an inclination outside said moulded piece and the rays from said source which travel farther away from said moulded piece and are not collected by said prisms are reflected by said reflecting member downwardly in a near vertical direction and cross the former rays.

3. A light fitting as claimed in claim 1, wherein said moulded piece and said reflecting member have surfaces of revolution around said source's axis of symmetry to give a polar horizontal symmetrical light distribution curve.

4. A lighting fitting comprising a support for an electric light source, a transparent moulded piece surrounding said light source having a lower and an upper system of prisms situated in planes normal with respect to the axis of symmetry of said light source, said moulded piece being open at its top and bottom and situated coaxially with said light source, said lower system comprising small prisms arranged to function by refraction, and said upper system comprising two larger prisms arranged to function by total internal reflection, a reflecting member at the top of said fitting that receives the upper part of the light flux not intercepted by said prisms directing it downwardly so that the reflected light rays cross each other without falling on said prisms below, said moulded piece comprising at its inner surface a second system of small prisms formed by a plurality of groups of prisms, said last-named prisms comprising a first face situated on a plane that passes through the axis of symmetry of said light source and a second face situated on a plane parallel to said axis of symmetry, said prisms being identical within the same group but differing from group to group so that the deviation angles of the refracted rays for the several groups of prisms are in the ratio of 1:2:3, said different groups of prisms being arranged to obtain a polar curve of horizontal distribution of the light in the desired asymmetrical form.

5. A lighting fitting comprising a support for an electric light source, a transparent moulded piece surrounding said light source having a lower and an upper system of prisms situated in planes normal with respect to the axis of symmetry of said light source, said moulded piece being open at its top and bottom and situated coaxially with said light source, said lower system comprising small prisms arranged to function by refraction, and said upper system comprising two larger prisms arranged to function by total internal reflection, a reflecting member at the top of said fitting that receives the upper part of the light flux not intercepted by said prisms directing it downwardly so that the reflected light rays cross each other without falling on said prisms below, an element upon which is mounted said support, rods attached to said element supporting said reflecting member, said element having ventilation holes and a slot on the lower part thereof, sectors in the form of a truncated cone of transparent plastic material fitted to said holes and slot, a triangular piece holding said sectors at the top, said triangular piece having extensions on the edge of which are fixed said sectors, said edge serving as a fixing point for certain pieces that support said moulded piece and said rods through openings in an extension of said triangle, spring means whereby said triangle can be moved against the influence of said spring means along a portion of said rods for easy mounting and dismounting of said sectors, said light source and said moulded piece, said spring means normally urging said triangle to a fixed position in which said moulded piece and said sectors are held in position.