GB2350419A

GB2350419A - Anti-dazzle slat for light fittings

Info

Publication number: GB2350419A
Application number: GB0009016A
Authority: GB
Inventors: Janusz Teklak
Original assignee: Siteco Beleuchtungstechnik GmbH
Current assignee: Osram SBT GmbH
Priority date: 1999-04-13
Filing date: 2000-04-12
Publication date: 2000-11-29
Anticipated expiration: 2020-04-12
Also published as: AT500187A1; DE19916601C2; AT500187B1; GB0009016D0; DE19916601A1; GB2350419B

Abstract

A slat 1 for light fittings comprises two side walls 2,3 spaced apart at the top and a roof surface 5 with concave and reflective portions wherein at least one of the side walls projects above roof surface 5 and has light absorbing material on the side 11,13 facing surface 5. Alternatively side walls 2,3 can be substantially flush with the roof surface (5, figure 3). The reflective surface may be provided by an attachment fixed to the roof between sidewalls 2,3. Concave surface 5 may be an ellipse, a hyperbola, parabola or consist of straight segments 7a, 7b, 9 in an approximately concave arrangement. Slat 1 may have a V-shape and may be fitted between sidewalls (22, figure 2) of a light fitting's grid (20), with reflective roof surface 5 facing the lamp (24) so that light is emitted with a predetermined boundary angle.

Description

2350419 PATENTS ACT 1977 Agents Ref: P14270GB-CAH/SJP/mrn 01PROVEMENTS IN

OR RELATING TO LIGHT FITTINGS THE INVENTION RELATES to a slat for a slatted grid according to the preamble of claim 1, and an associated grid and an associated light fitting.

A grid slat according to the preamble of claim I is known from German Utility Model G 8106 507.8, which propoes to provide the top of the grid slats with a specular-reflecting covering with lateral edge portions inclined in a plane transversely of the lamp axis. The covering formed in this way is received between the side walls of the slat, which project partially over it. More recent standards, particularly in the Anglo-Saxon countries, now specify not just longitudinal and transverse anti-dazzle, but also anti-dazzle effects in any arbitrary direction. It has been found that grids with grid slats of the type referred to in the preamble, which provide quite satisfactory anti-dazzle in the longitudinal and transverse direction in accordance with the less stringent standards, do not guarantee adequate anti-dazzle for C-planes at an angle to the lamp axis. Grids with a high efficiency due to a specular roof surface, in particular, often have problems in this respect.

It is the object of the invention to provide a grid slat and a grid of the type referred to in the preamble wherein the anti-dazzle effect is equally satisfactory in the C-90/270 plane (longitudinal direction), CO/180 plane 2 (transverse direction) and C-planes at an angle to the lamp axis. The invention is also to provide a light fitting having a better anti-dazzle effect.

According to the invention, this is achieved with a grid slat according to claims 1, 4 or 7, or a grid having slats of this kind. Advantageous embodiments of the invention are indicated in the subclaims.

The invention is based on the surprising discovery that the unsatisfactory anti-dazzle effect in C-planes at an angle to the lamp axis is due to reflections at the inner surfaces of the side walls which project upwards on both sides of the concave roof surface. Accordingly, the invention proposes to prevent or suppress these reflections. Three possible options are proposed for this purpose according to the invention.

According to a first solution which is the subject matter of claim 1, the disturbing reflection is prevented by the fact that the inner surface of the side walls is made light-absorbent. In departure from the traditional method of production in which one side of a reflecting element, such as a grid slat, is always constructed with unitary properties, it is proposed according to the invention that the top of the slat should have two lightabsorbent zones, namely the inner surfaces of the side walls, and a lightreflecting zone, namely the roof surface. The first solution of the invention is particularly advantageous for metal slats made from sheet metal, because the corresponding slats can be made by simply bending a metal sheet which has been appropriately cut to size and coloured. In particular, it is possible 3 to use as starting material a metal sheet which is reflecting on one side and light-absorbent on the other side.

According to a second solution, which is the subject matter of claim 4, reflection at the inner surfaces of the side walls is obviated by simply eliminating the projecting zones of these side walls. This can be done, on the one hand, by making the entire top as an attachment which is fitted over, for example, a V-shaped basic slat part, or by stamping out or cutting the side walls in the appropriate manner during the actual production, so that they are substantially flush with the reflecting roof surface.

According to a third solution proposed by the invention, the roof surface can also be made concave in a direction parallel and/or at an angle to the lamp axis so that light non-nally incident on the inner surfaces of the side walls of the slat is deflected by the roof reflector in zones of the light fitting in which the light is either absorbed or reflected with an admissible light exit angle in relation to the light exit aperture. A concave construction of this kind in a number of directions can be achieved, for example, by an appropriately shaped insert fitted between the side walls of the slat.

Overall, the invention uses surprisingly simple means to provide an important advance in the configuration of the light emission characteristic. It has been found particularly that light fittings with a large number of reflector slats, e.g. more than 10, have particular advantage from the invention. According to the invention, small zones having a high lighting density, which are permissible according to the current standards, but which nevertheless have a di!';turbing effect in individual cases, can be avoided.

4 According to a preferred embodiment, the roof surface in a crosssection perpendicular to the lamp axis is, at least in portions, constructed in accordance with a conic section, such as an ellipse, hyperbola or parabola, the parabola being preferred. Instead of an exact curve, an approximation to such a conic section can be provided, for example by straight segments, and this facilitates production.

Other features and advantages of the invention will be apparent from the following description of exemplified embodiments of the invention with reference to the accompanying drawings.

Fig. I shows one exemplified embodiment of a slat for a slatted grid according to the invention.

Fig. 2 illustrates the principle of anti-dazzle in C-planes at an angle to the lamp axis.

Fig. 3 shows a second embodiment of the invention.

Fig. I shows a slatted grid slat I having a V-shaped basic structure comprising two side walls 2 and 3 extending in the direction of the width. A reflecting roof surface 5 formed concavely in a cross-section perpendicularly to the direction of the thickness is provided at the top of the slat between the side walls 2 and 3 and comprises two oblique substantially straight portions 7a and 7b at the sides and a substantially horizontal portion 9 between the two portions 7a and 7b. The insides I I and 13 of the side walls 2 and 3 project beyond the roof reflector 5 in the region of the bevelled surfaces 7a and 7b and of the central horizontal portion 9.

The principle of anti-dazzle in C-planes obliquely to the lamp axis through a slat of this kind is illustrated in Fig. 2. Fig. 2 is a diagrammatic cross-section of a specular grid through a plane perpendicular to the lamp axis. In Fig. 2 the grid has the general reference 20. Reference 22 denotes the side walls of the grid and reference 24 a lamp. The slat has the general reference 1 as in Fig. 1.

The effect of the inclined portions 7a and 7b of the slat 1 is that the light incident thereon is reflected more intensively towards the centre of the grid and no light is reflected by the roof reflector 5 in angular zones having the reference 0 adjoining the top edge of the slat, so that the total effect is that the rays of light reflected at the roofs surface 5 are reflected, after again being reflected at the side walls 22, with a smaller angle to the vertical to the light exit aperture of the grid 20 than would be the case with a flat roof surface. Although the required anti-dazzle effect can often be improved in this way, it is achieved either incompletely or not at all in some cases.

To obtain or to improve the anti-dazzle effect in a C-plane at an angle to the lamp axis, the insides 11 and 13 of the two side walls 2 and 3 are constructed to be light-absorbent, at least in the zones in which they project beyond the roof surface 5. As a rule, these zones are coloured black. A light-absorbent construction of this kind can be achieved by applying a light-absorbent plastic film, by painting with a black paint, or in some other suitable manner.

6 Fig. 3 shows a second exemplified embodiment of the invention, wherein like references denote like elements with reference to Fig. 1, In this exemplified embodiment, the inner surfaces 11 and 13 of the side walls 2 and 3 projecting above the roof reflector are eliminated. Consequently, the disturbing reflections are also eliminated at these portions, such reflections resulting, in the prior art, in an unsatisfactory anti-dazzle effect in directions at an angle to the lamp axis.

The features of the invention disclosed in the preceding description, the claims and the drawings may be essential both individually and in any arbitrary combination for an embodiment of the invention in its various forms.

List of references 1 Grid slat 2 Side wall 3 Side wall Roof reflector 7a, 7b Oblique portions of the roof reflector 9 Horizontal central portion of the roof reflector 11 Inner surface of side wall 13 Inner surface of side wall Grid 22 Side wall of grid 24 Lamp 0 Angle zene 7 In the present specification "comprise" means "includes or consists of'and "comprisinj means "including or consisting of'.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof

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Claims

1. A slat for use in a grid of a light fitting with two side walls (2, 3) spaced apart at least at the top and a roof surface (5) which is situated between the side walls, is concave at least in portions, and at least partially reflecting, characterised in that a side wall projects above the roof surface (5) at least on one side of the roof surface (5) and on its side (11, 13) facing the roof surface (5) is constructed to be lightabsorbent at least in the zone projecting above the roof surface (5).

2. A slat according to claim 1, characterised in that the side walls (2, 3) project on both sides of the roof surface and the roof surface (5) extends substantially below the level of the top edge of the side walls.

3. A slat according to claim 1 or 2, characterised in that a projecting side wall (2, 3) is constructed with a light-absorbent coating on the side (11, 13) facing the roof sui face (5).

4. A slat for use in a grid of a light fitting with two side walls (2, 3) spaced apart at least at the top and a roof surface (5) which is situated between the side walls, is concave at least in portions and at least partially reflecting, characterised in that the side walls (2, 3) of the slat are substantially flush with the roof surface (5) at the top edge.

5. A slat according to claim 4, characterised by an attachment which comprises the reflecting roof surface (5) and the side walls of which form a part of the side walls of the slat.

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6. A slat according to any one of claims 1 to 5, characterised by an insert between the side walls of the slat which has the reflecting roof surface (5).

7. A slat for use in a grid of a light fitting, particularly according to any one of claims 1 to 6, with two side walls (2, 3) spaced apart at least at the top and a roof surface (5) which is situated between the side walls, is concave at least in portions and at least partially reflecting, characterised in that the roof surface (5) is concave at least in portions in a direction parallel and/or at an angle to the direction of the thickness of the slat.

8. A grid for a light fitting with side walls (22) for transverse antidazzle, said side walls defining a light exit aperture between them, and slats (1) according to any one of claims 1 to 7 disposed between the side walls, their reflecting roof surface (5) being turned away from the light exit aperture.

9. A light fitting with a lamp (24) and a grid (20) according to claim 8, characterised in that the lamp is so disposed relative to the grid slats (1) that none of the light incident from the lamp (24) on to the roof surface (5) is reflected in a plane perpendicular or at an angle to the lamp axis into a defined angular zone (p) adjoining the top edge of the slats, so that the light of the lamp (24) reflected from the roof surface (5) is delivered by the light fitting with a predetermined boundary angle.

10. A slat for use in a grid of a light fitting, substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

11. A slat for use in a grid of a light fitting, substantially as herein described with reference to and as shown in Figure 3 of the accompanying drawings.

12. A grid for a light fitting substantially as herein described with reference to the accompanying drawings.

13. A light fitting substantially as herein described with reference to the accompanying drawings.

14. Any novel feature or combination of features disclosed herein.