WO1987005680A1

WO1987005680A1 - Luminaire

Info

Publication number: WO1987005680A1
Application number: PCT/DK1987/000028
Authority: WO
Inventors: Christian Bartenbach
Original assignee: Solar Armaturproduktion A/S
Priority date: 1986-03-14
Filing date: 1987-03-13
Publication date: 1987-09-24
Also published as: ATA67186A; AT385343B; EP0259470A1

Abstract

Luminaire with an essentially rotationally symmetrical reflector. The reflector comprises an ellipsoidal section (1), in the first focus (F1) of which the light bulb (3) is situated, and which section extends until a plane (5) normal to the major axis (4) and through the second focus (F2). From this section (1) essentially all light rays emanate as basic radiation. With the object to limit the angular range of the radiation from the major axis (4) under maintaining a high light output, a glare protective section (2) is arranged at the region of said normal plane (5), which glare protective section extends divergent from said plane relative to the major axis (4). By varying the axes ratio (a:b) of the ellipsoidal section (1), and by differently formed glare protective sections (2), the distribution pattern of the light output may be varied over a wide range.

Description

L UM I NA I RE-

This invention concerns a luminaire with -an at least partly essen¬ tially rotationally symmetrical reflector in one piece or split into va¬ rious pieces, said reflector comprising an ellipsoidal section, the ge¬ neratrix of which is a part of an ellipse and with the light emitting part of a lamp being arranged in the region at one focus of the ellipse, and wherein the ellipsoidal section of the reflector extends until a plane extending normal to the major axis of the ellipse in the region at the second focus of the ellipsoid.

Socalled spherical luminaires are known, in which the generatrix of the ellipsoidal section is essentially half of an ellipse, and where¬ in this section is continued by a spherical reflector with an exit open¬ ing. Such spherical luminaires are especially used for the illumination of predetermined areas where the surroundings should remain dark, and are generally satisfactory for this purpose. Such spherical luminaires are, because of their light emitting characteristics, not so well suited for a wide illumination of a room. Further, such spherical luminaires have the drawback that the radiation emitted from the point-shaped light source (e.g. a halogen incandescent lamp) is reflected by the spherical reflector back onto the light source, thereby causing a further heating of the already thermally strained high-power light source. This effect is enhanced because of the rather enclosed design of these luminaires.

Further a rotationally symmetrical reflector is known, of which the- generatrix is part of an ellipse, wherein the reflector extends un- til a normal plane through the second focus of the generating ellipse. From a luminaήre equipped with only such a reflector, light rays are e- mitted at angles up to 90° from the major axis. This very wide light di¬ stribution is only slightly variable by varying the axes ratio of the generating -ellipse- and will in an -case- produce a strong-glare, and is therefore not suitable for illumination of rooms.

It is the object of the invention to provide a luminaire of the above described general kind, suited for halogen incandescent lamps or halogen metal vapour lamps, wherein the thermal strain of the lamp, in spite of a compact construction, should be kept modest, and which lumi- naire can provide a high light output with a luminance distribution within a certain angular region from the longitudinal axis of the lamp. Further, the light distribution of the luminaire according to the inven¬ tion should be variable over a wide range by fundamentally unchanged ba- sic construction by the use of different reflector parts.

This is obtained according to the invention by the luminaire of the above described general kind being provided with a glare protective section, continuing the ellipsoidal section, and initially divergent re- lative to the lamp main axis at the region by said transverse plane.

Contrary to the luminaires known in the art, wherein also those parts of the r-eflector which surround the lamp are tailored to the par¬ ticular glarefree illumination desired, in order to obtain a high lumi¬ nous efficiency, whereby the possibilities for variation by further screening sections is very limited, the invention makes it possible, through the use of an ellipsoidal section extending until the normal plane through the second focus, to produce a socalled basic radiation with a non-specific angular distribution, and then to restrict this ra¬ diation to a particular angular region by the use of a screening section extending from the ellipsoidal section and initially divergent relative to the major axis. Hereby a luminaire system is provided, wherein the luminance distribution is variable over a wide range with the same basic construction.

The luminous distribution of the radiation emanating from the el- lipsoidal section of the reflector, i.e. the socalled basic radiation, will, by the use of lamps with small dimensions (approximately point like), depend essentially exclusively upon the ratio between the axes of the ellipsoidal reflector. This basic radiation is composed from a por¬ tion of direct radiation emanating from the ellipsoidal reflector sec- tion with no reflections within a relatively narrow angular region, and a reflected radiation portion emanating from the ellipsoidal section of the reflector after only one reflection, crossing the second focus of the ellipsoid and emanating within a wide angular region.

This-. angular region extends cut to an angle of approximately 90° from the major axis of the lamp defined by the ellipsoidal section, as the second focus is located in essentially the same transverse plane perpendicular to the major axis as the end of the ellipsoidal section. In total approximately all of the light emitted from the lamp, re¬ spectively the luminous parts hereof, will exit the ellipsoidal section, although the light rays emitted from the lamp do not return to the lamp and thus cause no excessive heating hereof. Since the luminous parts of the lamp have finite dimensions, and because of manufacturing tolerances in the reflector, the reflected light rays within the basic radiation will exit the ellipsoidal section within a region around the second fo¬ cus. This, though, causes no fundamental change of the radiation charac¬ teristics of the luminaire, and in the following a perfect radiation pattern is therefore assumed. The glare protection section provided according to the invention, extending from the ellipsoidal section, and diverging from the ellipsoi¬ dal section relative to the major axis in the area of the transverse plane crossing the second focus of the ellipse, ensures that the basic radiation is screened, i.e. the angular region measured from the longi- tudinal axis of the lamp, within which the radiation will emanate from the luminaire, is limited by reflection without significant loss of light. The divergent start of the glare protective section ensures that no light rays within the basic radiation will be reflected backwards into the ellipsoidal section, where they could cause a reduced light output from the luminaire and cause a thermal strain of the lamp.

The screening of the direct radiation portion presents no diffi¬ culties, since the screening requirements for the narrow direct radia¬ tion portion by the fulfilment of certain glare protection conditions, concerning the widespread reflected radiation portion of the basic ra- diation, largely will be met. By a predetermined length (measured in the direction of the longitudinal axis of the lamp) of the glare protective section, and possibly by using an aperture in the region by the trans¬ verse plane through the second focus of the ellipse, any glare restric¬ tion condition for the directly radiated portion can be satisfied even by an extreme, almost spherical, form of the ellipsoidal reflector sec¬ tion.

By the preferably essentially rotationally symmetrical form of the glare protective reflector section relative to the major axis of the el¬ lipsoidal section a particularly simple-attachment of the_glare protec- tive section to the ellipsoidal section is possible.

To prevent the emanation from the luminaire of light rays, in par¬ ticular from that portion of the basic radiation, which is termed re¬ flected radiation, at larger angles than the predetermined limiting angle from the longitudinal axis, (i.e. a certain glare condition), the generatrix of the rotationally symmetrical glare protective section of the reflector is according to a preferred embodiment of the invention a part of a parabola, the focus of which is located in the region at the second focus of the ellipse, and the axis of which comprises an angle from the major axis, or it is essentially a -contour, having one point common with the said parabola located in that focal plane of the pa¬ rabola which is normal to the major axis, and having in any point of the contour a tangential inclination relative to the major axis, which is greater than or equal to the inclination of said parabola part in that point of the parabola which is located on the same normal to the major axis as the point on the contour. Hereby any focal ray, i.e. any light ray within the reflected radiation portion, reflected in the glare pro¬ tective section will, in case of the parabola, exit parallel to the axis of the parabola. The angle comprised by the parabola axis relative to the major axis thus defines the limiting angle, above which no light rays can exit from the luminaire. It is, of course, understood that points on the contour and points on the parabola are described macrosco- pically. The reflector surface microstructure (roughness etc.) is not part of the consideration described.

In case the contour is curved as described, the inclination of the contour in the point located in the focal plane of the parabola perpen¬ dicular to the major axis defines the limiting angle. In case the tan¬ gential inclination of the contour, as also described, is greater than that of the parabola, the glare condition will be satisfied by reflec¬ tion anywhere in the glare protective section, since light rays reflect¬ ed within the glare protective section will exit with a narrow angle from the major axis, as would be the case with the corresponding inner imiting parabola. Obviously, the glare protective section must have a certain length in the direction of the longitudinal lamp axis (i.e. the exit end must be at a given distance from the ellipsoidal section) to prevent light rays of the widespread reflected radiation portion of the basic radia¬ tion from exiting above the required limiting angle from the major, axis, and directly out of the luminaire (i.e. with no reflections in the glare protective section). This condition is easily met.

On the other hand, a too great length of the glare protective sec¬ tion would cause reflected light beams to be reflected one or several times before exiting the luminaire, which is undesirable because of the associated loss of light.

To prevent that, it is according to a preferred further embodiment of the invention provided that the straight line, connecting an end point of the glare protective section adjacent the ellipsoidal section, and another end point of the glare protective section located oppositely relative to the major- axis, and distally from the ellipsoidal section, will comprise an angle with the major axis,, which is larger than or equal to that of the axis of the parabola, corresponding to the limiting 5 parabola for defining the limiting angle. Hereby any focal ray reflected within the glare protective section will exit the luminaire with no further reflections.

The maximum light output will be achieved by a preferred embodi¬ ment, wherein the axis of the parabola is situated at an angle from the

1.0 major axis, which is smaller than or equal to that of the straight con¬ necting line through the second focus of the ellipsoidal section of the reflector, and through that end point of the parabola, respectively the contour, defining the glare protective section, which is situated di¬ stally from the ellipsoidal section. Hereby all light rays within the

15 reflected radiation portion of the basic radiation that already meet the glare condition (i.e. their angle from the major axis is smaller than that of the parabola axis) will exit the luminaire without reflections in the glare protective section. By a such short glare protective sec¬ tion care must be taken to ensure sufficient screening of the direct ra-

20 diation portion.

The properties of the basic radiation can be modified by modifying the axes ratio of the ellipsoidal section.

The radiation properties of the luminaire may though primarily and with unchanged basic construction be modified by the forming of the

25 glare protective section. It is here advantageous, when the reflector comprises at least two essentially rotationally symmetrical reflector parts, that are disconnectably connected, each of two reflector parts having at least one annular rim preferably located in a plane normal to the major axis, by which the reflector-parts may be interconnected. A

30 such embodiment facilitates the luminaire assembly in the housing and the change of light bulbs by a not easily accessibly mounted luminaire.

As the manufacture of hollow bodies that are internally reflective is complicated it is advantageous that a reflector part, constituting part of the ellipsoidal section, has the form of a half ellipsoid,

35 whereto at least one further reflector part is attachable, and that the remaining part of the reflector of the ellipsoidal section, and the part of the reflector forming the glare protective section, is formed in one piece. Of course, the reflector could alternatively comprise reflector parts divided along the longitudinal lamp direction-, whereby also the manufacture of hollow bodies is avoided.

An asymmetrical radiation distribution relative to the longitudi¬ nal lamp axis can be provided according to a preferred embodiment of the invention by providing the part of the reflector forming the glare pro¬ tective section with a recess within the glare protective section, and preferably arranging it rotatable relative to the ellipsoidal section. Hereby it is for example possible to illuminate a wall or parts hereof by luminaires arranged at the ceiling. In the following the invention will be explained by embodiments shown in the drawings, it being understood that these embodiments are examples not intended to limit the invention.

Figure 1 shows the optical geometry of an embodiment by a schema- tical central longitudinal sectional view through the reflector, figure 2 shows a reflector with the same ellipsoidal section as in figure 1, but with a narrower glare protective section, figure 3 shows a section through a further embodiment of the lumi¬ naire according to the invention, figure 4 shows a compact embodiment in a central longitudinal sec¬ tion, and figure 5 shows an embodiment for wall illumination.

- - The luminaire shown in figure 1 comprises essentially a rotation- ally symmetrical reflector with an ellipsoidal section 1 with a major axis 4 and. a thereto attached glare protective section 2, and a halogen incandescent bulb 3, the luminous portion of which is situated in the region at the first focus F, of the ellipsoidal section 1. For matters of simplicity attachment fittings are not shown in figure 1. Reference may be had to figures 3 to 5.

The ellipsoidal section 1 extends until the plane 5 normal to the major axis 4 through the second focus F₂ of the ellipse. The ellipsoidal section 1 produces a basic radiation, the direct radiation portion of which emanates from the luminaire under a small angle α_D (basic ray 1,). The glare protective section 2, which starts divergent relative to the major axis in the region at the normal plane 5, and which in this embodiment is also rotationally symmetrical, will not reflect any light rays back into the rotationally elliptical or ellipsoidal section 1. That would, besides loss of light, cause thermal, strain of the lamp 3.

The most important purpose of the glare.protective section 2 is to prevent emanation of light rays above a certain limiting angle a (in fi¬ gure 1 = 45°) from the major axis 4 (the longitudinal lamp axis). It must therefore reflect light rays 1« emanating from the ellipsoidal sec¬ tion 1 under angles up to approximately 90° from the major axis corre¬ spondingly, i.e. so that no rays emanate with larger angles from the ma¬ jor axis than the predefined limiting angle a.

A parabola p with a parabola axis 6 inclined by the angle a and with a focus F located at the second focus F« of the ellipsoidal sec¬ tion as generatrix of the glare protective section will just meet this condition that all light rays of the basic radiation exiting through F₂ will exit the lamp with the angle defined by the parabola axis 6. A curve or contour k, diverging more than the limiting parabola p, used as generatrix for the glare protective section, will reflect all focal rays crossing F₂ (e.g. 1₂) within an angle limited by the range of the angle α. The glare condition is thus met.

Since the straight line g conneting P, and P₂ is situated with just the angle α from the major axis 4, all light rays reflected within the glare protective section 2 exit the luminaire after just one reflec¬ tion.

The ellipse ratio (major axis a relative to minor axis b) defines the distribution of the basic radiation, which is further influenced by the glare protective section 2. Greater axes ratios a:b cause a narrower basic radiation.

The luminaire shown in figure 1 produces a rotationally symmetri¬ cal luminance distribution pattern, which is widespread, though within the limiting angle α equal to 45°.

By a.different glare protective section 2 a substantially narrower luminance distribution (limiting angle a equal to 30°) may be produced by the same ellipsoidal section 1 as in figure 1. A such glare protec¬ tive section 2 is shown in figure 2. The generatrix of this glare pro¬ tective section 2 is close to a part of a parabola with the parabola a- xis 6 and the focus F„ = F<,.

P 2 Apart from halogen incandescent lamps 4 (figure 1) also halogen metal vapour lamps 3' may be used, which will then be arranged in the luminaire as shown in figure 3. The bulb fixtures 7 are located outside the reflector in a lamp housing 8, carrying the reflector by fixtures 9, 10, and mounted to a ceiling panel 11.

The lamp bulb 3' traverses the ellipsoidal section of the reflec¬ tor. The luminous part of the light bulb 3' is located in the region at the first focus F,. The glare protective section 2 is here frusto-coni- cal.

The reflector comprises three disconnectably connected reflector parts la, lb, and 2a interconnected by bolts 13, guided in bushings 12. Annular rims 14, 15, and 16 permit a simple and secure connection of the reflector parts la, lb, and 2a. In the region at the normal plane through F₂ a UV-filter glas 17 is arranged. At this same place, but also at other places, infrared fil¬ ters or pure glasses may be arranged (not shown).

The embodiment shown in figure 4 with a halogen incandescent lamp is particularly compact. The surfaces of the glare protective section 2 are displaced inwardly relative to the opening of the ellipsoidal sec¬ tion la, lb. Hereby only a fraction of the direct radiation portion from the lamp 3 is lost. In return a simpler construction is obtained ful¬ filling the same glare condition. A glas plate 17' may be arranged in the region at F_2< Alternatively to the rotationally symmetrical glare protective sections also glare protective sections with recesses 18 are useful for particular purposes, such as the embodiment shown in figure 5, which is designed for wall illumination. The reflector part 2a of the glare pro¬ tective section is here rotatable (around the major axis 4) relative to the rest of the luminaire, so that the illumination may be directed to different walls by turning as wished.

For construction-al reasons it may be advantageous to arrange an essentially cylindrical spacer section (not shown) between the ellipsoi¬ dal section and the glare protective section. The reflectors shown may comprise pressed, eloxed and with magne¬ sium slightly alloyed aluminium. Obviously, the invention does not de¬ pend upon the particular choice of material in the reflector.

Claims

1. Luminaire with a reflector in one part or divided into several parts, and at least partly essentially rotationally symmetrical, with an ellipsoidal section, the generatrix of which is a part of an ellipse, wherein the luminous portion of a lamp is located in the region at the first focus of-the ellipse, and wherein the ellipsoidal section of the reflector extends to a plane normal to the major ellipse axis through the second focus of the ellipse, characterized in that an essentially rotationally symmetrical glare protective section (2), extends from the ellipsoidal section (1) and initially divergent relative to the major axis (4) in the region at the said normal plane (5).

2. Luminaire according to claim 1, characterized by the generatrix of the rotationally symmetrical glare protective section (2) of the re¬ flector being a part of a parabola (p), the focus F of which is situat¬ ed in the region (2) at the second focus (F₂) of the ellipse, and of which the parabola axis (6) is situated at an angle (α) from said major axis (4), or by the generatrix being essentially a contour (k), having with the parabola (p) one point (P,) in common located at that focal plane (5) of the parabola (p) which is perpendicular to the major axis (4), and of which the tangent inclination relative to the major axis (4) in any point of the contour is greater than or equal to the inclination of-said parabola part (p) in a point of the parabola located at the same normal plane to the major axis (4) as the respective point on the con¬ tour.

3. Luminaire according to claim 2, characterized in that the straight line (g) connecting a first end.point (P,) of the_^glare protec- tive section (2) adjacent the ellipsoidal section (1), and a second end point (P₂) located oppositely relative to the major axis (4) and at the end distally from the ellipsoidal section (1), exhibits an angle from the major axis (4), which is greater than or equal to that of the para¬ bola axis (6).

4. Luminaire according to claim 2, characterized by the parabola axis (6) exhibiting an angle from the major axis (4), which is smaller than or equal to that of the straight line through the second focus (F₂) of the ellipsoidal section (1) of the reflector, and through the end point (P₂) of that part of the parabola (p)., respectively the contour (k), that generates the glare protective section (2).

5 5. Luminaire according to any of the claims 1 to 4, characterized by the reflector comprising at least two disconnectably interconnected essentially rotationally symmetrical reflector parts (la, lb, 2a), and in that two reflector parts (la, lb) each have at least one annular rim (14, 15) preferably located in a plane normal to the major axis, by 10 which the reflector parts (la, lb) may be interconnected.

6. Luminaire according to any of the claims 1-5, characterized by the part of the reflector section (la), forming the ellipsoidal section (1), having essentially the form of a half-ellipsoid, whereto at least

15 one further reflector part (lb, 2a) may be connected.

7. Luminaire according to claim 6, characterized by the remaining reflector part of the ellipsoidal section and the reflector part forming the glare protective section being constructed in one piece.

20

8. Luminaire according to any of the claims 1-6, characterized by the reflector part forming the glare protective section (2) being a se¬ parate constructive element (2a).

• 25 9. Luminaire according to any of the claims 1-8, characterized by at least the reflector part (2a) forming the glare protective section (2) in the area of this glare protective section (2) having a recess (18) and preferably being arranged rotatable onto a reflector part (lb) of the ellipsoidal section. -

30

10. Luminaire according to any of the claims 1-9, characterized by being provided with a filter (17) and/or a transparent plate (17') pre¬ ferably disconnectably connected to the reflector and preferably arrang¬ ed in the region at the focal plane through the second focus (F₂) of the

35 ellipsoidal section (1) of the reflector.