EP0601389B1 - Lamp with a light influencing cover glass - Google Patents

Abstract

A lamp (1) is specified having a luminous means (2) which has an elongate light-generating device (3), a reflector (5) having an exit opening (6), and a light-influencing cover glass (7) which is arranged in front of the exit opening (6) of the reflector (5). With a lamp of this kind it should be possible to achieve a uniform brightness in the room (space) to be illuminated despite the elongate extension of the light-generating device (3). For this purpose the cover glass (7) is constructed as a pane and has on its side facing the reflector (5) structured elements (8) which project in the direction of the reflector (5). <IMAGE>

Description

The invention relates to a lamp with a lamp that has an elongated light generating device, a reflector that has an outlet opening, and a light-influencing cover, which is arranged in front of the outlet opening of the reflector, is designed as a disc and on its side facing the reflector in the direction has structural elements projecting onto the reflector.

Luminaires of this type can be used to illuminate or illuminate a room with artificial light. With room lighting of this type, illuminants have been developed in recent years which ensure a high luminous efficacy despite relatively low electrical outputs. With an electrical power consumption of just 70 watts, a normal living or working space can be sufficiently illuminated. For example, high-pressure mercury vapor lamps or other halogen or halide lamps are used for this purpose.

Such illuminants are very bright. This brightness is generated, for example, by an arc and concentrates on a small area, which, however, is not punctiform, but elongated, that is to say it has a greater extent in one direction than in other directions. Such illuminants usually have to be installed horizontally, which is partly due to thermal reasons. The elongated extension cannot therefore be made to disappear by another arrangement of the illuminant. The elongated extension of the illuminant, even if it is only very small, leads to an uneven light distribution in the room, which is undesirable in many cases.

The light distribution can be influenced by the shape of the reflector. In many cases it is possible to distribute the light in the desired manner using a free-form reflector. Such free-form reflectors are very complex to construct. Their area of application is usually limited to a specific lamp. As a simplification, it has been proposed (DE 37 40 901 A1) to give the reflector a reflective surface which is composed of different sections. In connection with projection systems, further reflectors have been proposed (DE 30 27 774 C2, DE 30 27 719 A1), which achieve a homogenization of the projected light by dividing the reflection surface into several ring-shaped areas that lie on different contours. However, the manufacture of such reflectors is relatively complex.

It is also known to matt the reflectors without the cover, which results in better light scattering. However, this only blurs the sharp contour of the lamp, but the illumination can not even in the desired degree. In addition, there is an increased proportion of scattered light which is lacking in the useful luminous flux, so that the advantage achieved, namely being able to ensure adequate lighting with low electrical powers, is partially lost again.

Another lamp is known from FR 2 623 597. This lamp has a pyramid or a cone as a cover, which covers the outlet opening of the reflector with its base. A lamp is arranged in the reflector so that its longitudinal extension is substantially perpendicular to the base. With this arrangement, a relatively bright and thus far visible light should be able to be generated.

US-A-2 732 488 shows a lamp with a reflector in which a light source assumed to be punctiform is arranged. The outlet opening of the reflector is covered by a diffusing screen which has structural elements projecting towards the reflector on its side facing the reflector. These are designed as rays that go radially outward from the center of the cover and have several sections with different flank inclinations. In the vicinity of the center, these structural elements are triangular in cross-section, while they have a rounded shape in the area of the edge.

A lamp according to the preamble of claim 1 is known from DE-U-90 12 286. There, the illuminant with the elongated light generating device is arranged in the middle and surrounded in a ring by another illuminant. Separate reflectors are provided for both lamps. Both reflectors are covered by a common cover facing towards has projecting structural elements on the reflectors. The purpose of this lamp is to create a lamp that enables better illumination of the near and far areas while saving energy.

DE-A-27 48 981 shows a lighting device for vehicles in which a reflector is covered by a lens which consists of two layers molded from plastic.

The invention has for its object to be able to generate a relatively uniform illumination even with a non-point light generator.

This object is achieved in a luminaire of the type mentioned at the outset in that the structural elements are in the form of tetrahedra which point with a point to the center, one side being arranged parallel to the plane of the pane.

In other words, these sides of all tetrahedra lie in one plane. This plane is perpendicular to the main axis of the reflector. By designing the structural elements as tetrahedra, not only does a wedge project in the direction of the reflector. This wedge also has a decreasing height towards the center, which results in a double triangular effect and thus a corresponding refraction and reflection of the light rays, which contributes to the desired uniformity of brightness. The structural elements have interfaces to the air or to the medium filling the space between the cover and the reflector, so that when the light rays enter the structural elements, the light rays are refracted. A further refraction occurs when it emerges from the pane. Depending on the angle of incidence, some of the radiation does not enter the window, but is reflected back to the reflector, from where it hits the window at a different angle. Through a skilful selection of the structural elements, that is, through an arrangement of the interfaces that control the reflection and transmission behavior of the pane in such a way that incident light can only pass through at certain angles, a very uniform light distribution in the room and thus a uniform brightness can now be achieved Ensure the area to be illuminated.

It is preferred that the structural elements are arranged periodically in a circular manner around a center of the disk, all the structural elements colliding with two adjacent structural elements without a gap and the structural elements being arranged point-symmetrically around the center of the disk. This arrangement has the advantage that the disc can be used without paying attention to the orientation of the lamp. This considerably simplifies the assembly and maintenance of such a lamp. The structural elements cover the surface of the pane, which faces the outlet opening of the reflector, in such a way that there are no gaps between adjacent structural elements, through which light rays could pass through the pane without interruption. At least on a circular ring, a structure of the disk on the side facing the reflector is thus specified, which makes it possible to design the light distribution by repeatedly refracting and reflecting the light rays in such a way that the desired uniform light distribution is produced on the other side of the disk.

A surface opposite the tip is preferably designed as an isosceles triangle. Regardless of the direction from which the light rays fall on the tetrahedron, the tetrahedra pose the same. This also helps to even out the brightness.

It is preferred that the surface is formed as an uneven triangle, the leg lying in the plane of the disc is longer than the other two legs of equal length. This limits the steepness of the sides of the tetrahedron so that the desired refraction of the incident light rays is generated.

It is particularly preferred here that the triangle has two equal angles in the range from 20 ° to 40 °. With such an inclination, it is ensured that the light incident from the reflector is partially refracted and partially reflected back into the reflector, from where it is again reflected back onto the pane.

n eine ganze Zahl und r der Abstand der Fläche vom Mittelpunkt, ausgedrückt in Millimetern, ist. Mit dieser Maßnahme läßt sich die Höhe der einzelnen Tetraeder unterhalb eines vorbestimmten Maximalwerts halten. Je größer der Radius der Scheibe wird, desto mehr Tetraeder werden verwendet. Die Zahl der Tetraeder sollte allerdings in einem bestimmten, durch den obigen Ausdruck definierten Bereich bleiben, um die gewünschte Brechungswirkung sicherstellen zu können.A number n of tetrahedra is preferably provided, wherein $$\text{0.35 xr ≤ n ≤ 0.85 xr,}$$

n is an integer and r is the distance of the surface from the center, expressed in millimeters. With this measure, the height of the individual tetrahedra can be kept below a predetermined maximum value. The larger the radius of the disk, the more tetrahedra are used. However, the number of tetrahedra should remain in a certain range defined by the above expression in order to ensure the desired refractive effect.

A flat surface is preferably provided between the tips of the tetrahedra. This simplifies production. The structure in the area of the center would otherwise be too fine. The flat surface, in which no light rays are refracted by tetrahedra or other structural elements, is arranged at a position where practically no parasitic light rays can escape.

The flat surface is preferably at least approximately circular, the circle having a radius which is 10% or less of the distance of the surface from the center. The flat surface is therefore relatively small. On the other hand, this ensures that the structure of the tetrahedra does not become too fine up to the boundary of this circle.

The side of the disk facing away from the reflector is preferably flat. Light rays that cross the pane vertically due to the refraction that occurs when they enter, emerge unbroken from the pane. Rays of light that have an inclination are here again Broken. In addition to these optical effects, the flatness of this exit side of the pane has the advantage that the appearance of the pane affects the design options when furnishing a room to be illuminated less.

The disk advantageously has a thickness that is greater than the greatest height of the structural elements. On the one hand, this gives the required strength of the disc. On the other hand, this results in optimal conditions for the refraction of the light rays and thus for the uniformity of the brightness.

The disk and the structural elements are particularly advantageously formed in one piece. This means that there is no renewed refraction at the transition from the structural elements to the pane. In addition, such a monolithically designed object can be manufactured relatively easily, for example by casting, without further processing steps being necessary, such as assembling the structural elements and the pane.

The disc is advantageously designed as a UV filter. In addition to the function of homogenizing the light, it also has a protective function.

Fig. 1

einen Querschnitt durch eine Leuchte,

Fig. 2

eine perspektivische Darstellung einer Scheibe und

Fig. 3

eine Draufsicht auf die Scheibe.

The invention is described below with reference to a preferred embodiment in conjunction with the drawing. Show here:

Fig. 1

a cross section through a lamp,

Fig. 2

a perspective view of a disc and

Fig. 3

a top view of the disc.

A lamp 1 has a lamp 2. The illuminant 2 has a light generating device 3, which is shown in the present case as a filament and which has a certain extent in the longitudinal direction. The expansion in the longitudinal direction is exaggerated for reasons of clarity. The illuminant is suspended in a suspension 4 within a reflector 5. The reflector 5 has a cross-sectional shape which corresponds to a conic section, as is generally known. The reflector 5 has an outlet opening 6, which is covered by a disc 7. The disk 7 is provided on its side facing the reflector 5 with a large number of structural elements in the form of tetrahedra 8. The tetrahedra 8 have tips 9 which point to the center 10 of the disk 7. The tetrahedra 8 are arranged in a circle around the center 10 and in such a way that the bases 11 of all tetrahedra lie in a common plane. This plane is parallel to the plane of the disk, ie perpendicular to the main axis 12 of the reflector 5. The remaining three sides 13, 14, 15 of the tetrahedron 8 project in the direction of the reflector 5. The surface 15 of the reflector, which faces away from the center 10, ie the tip of the tetrahedron 8, forms an isosceles but non-equilateral triangle. The two same angles a, b have a size of about 30 ° in the present case. Regardless of the side from which light occurs on the tetrahedron 8, this light is refracted in the same way. However, not all light is refracted at the chosen angle. Rather, some of the light is reflected back to the reflector 5, from where it is sent again to the disk 7 until it occurs on the tetrahedron 8 at an angle that allows the light to enter the disk 7.

The formation of the structural elements as a tetrahedron 8 not only results in an inclination which corresponds to the side lines of the surface 15, but the sides 13, 14 are also inclined inwards, i.e. the height of the structural elements decreases with decreasing radius.

The tips 9 of the tetrahedra 8 are not guided to the center 10. Here the structure would become so fine that it would be difficult to manufacture. The tips 9 of the tetrahedra 8 therefore leave a flat surface 16 around the center 10, which is essentially in the form of a circle, the radius of this circle being 10% or less of the distance of the surface 15 from the center 10. The flat surface 16 is so small that no significant amounts of light can pass through it and contribute to an uneven brightness in the room under the lamp 1.

The disc 7 is formed in one piece with the tetrahedra 8, i.e. the disc 7 and the tetrahedron 8 together form a monolithic block made of a translucent material. However, this material has the additional property that it serves as a UV filter, so that a lamp 2 can easily be used, in whose emission spectrum a certain UV component is present. High-pressure mercury lamps can also be used.

The disc 7 is flat on its underside 17.

wobei r in Millimetern eingesetzt wird und n natürlich eine ganze Zahl bildet. In vielen Fällen ist es vorteilhaft, wenn n eine durch 2 oder durch 4 teilbare Zahl ist.In the present case, 36 tetrahedra 8 are shown. The number of tetrahedra depends on the radius of the disk. The larger the radius of the disk, the greater the number of tetrahedra, whereby the number n can be estimated using the following formula: $$\text{0.35 xr ≤ n ≤ 0 85 xr}$$

where r is entered in millimeters and n is of course an integer. In many cases it is advantageous if n is a number divisible by 2 or by 4.

The tetrahedra 8 are arranged rotationally symmetrically around the center 10, i.e. they form a structure that recurs periodically around the center 10 in the direction of rotation. It is therefore irrelevant in which orientation the pane 7 and the reflector 5 are assembled.

The greatest height of the tetrahedron 8, i.e. the height of the surface 15 is smaller than the thickness of the disc 7 without tetrahedron 8. On the one hand, this leads to a certain mechanical stability of the disc 7. On the other hand, a refractive behavior is achieved that the emerging light is very even.

Claims (12)

1. Lamp having a means of illumination (2), which comprises an elongated light producing device (3), a reflector (5), which comprises an exit opening (6), and a covering (7) affecting the light, which is arranged in front of the exit opening (6) of the reflector (5), is constructed as a disk (7) and on its side facing the reflector (5) comprises structural elements (8) projecting towards the reflector (5), characterised in that the structural elements are constructed as tetrahedra (8) having one vertex (9) pointing towards the centre (10), one side (11) being arranged parallel to the plane of the disk (7).
2. Lamp according to Claim 1, characterised in that the structural elements (8) are arranged periodically repeating in essentially circular manner about a central point (10) of the disk, all the structural elements (8) abuting without a gap in each case on two neighbouring structural elements and the structural elements being arranged with radial symmetry about the centre (10) of the disk (7).
3. Lamp according to Claim 1 or 2, characterised in that a surface (15) opposite the vertex (9) is constructed as an equilateral triangle.
4. Lamp according to Claim 3, characterised in that the surface (15) is constructed as a non-equilateral triangle, the side of which located in the plane of the disk (7) being longer than the two other sides of equal length.
5. Lamp according to Claim 3 or 4, characterised in that the triangle has two equal angles (a, b) in the range from 20° to 40°.
6. Lamp according to one of the Claims 1 to 5, characterised in that a number n of tetrahedra (8) is provided such that $$\text{0.35 x r ≤ n ≤ 0.85 x r}$$

   

   n being a whole number and r the distance of the surface (15) from the centre (10).
7. Lamp according to one of the Claims 1 to 6, characterised in that a planar surface (16) is provided between the vertices (9) of the tetrahedra (8).
8. Lamp according to Claim 7, characterised in that the planar surface (16) is constructed in at least approximately circular manner, the circle having a radius which amounts to 10% or less of the distance of the surface (15) from the centre (10).
9. Lamp according to one of the Claims 1 to 8, characterised in that the side (17) of the disk (7) facing away from the reflector (5) is planar.
10. Lamp according to one of the Claims 1 to 9, characterised in that the disk (7) has a thickness which is greater than the greatest height of the structural elements (8).
11. Lamp according to one of the Claims 1 to 10, characterised in that the disk (7) and the structural elements (8) are constructed in one piece.
12. Lamp according to one of the Claims 1 to 11, characterised in that the disk (7) is constructed as a UV filter.

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