Illumination – Light source and modifier – Louvered or grid type modifier
Reexamination Certificate
1999-05-17
2001-04-24
Husar, Stephen (Department: 2875)
Illumination
Light source and modifier
Louvered or grid type modifier
C362S342000
Reexamination Certificate
active
06220729
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a luminaire comprising:
concave, elongated reflectors which are arranged so as to be essentially opposite and parallel to each other, and which reflectors limit, with a longitudinal edge, a luminous window;
means for accommodating an elongated electric lamp between the reflectors;
a plurality of flat, light-scattering lamellae between the reflectors, transverse to the reflectors and transverse to the luminous window, which lamellae have an inner edge and a concave outer edge in the luminous window.
Such a luminaire is known from U.S. Pat. No. 5,758,954.
In the known luminaire, the inner edge of the lamellae is straight, so that, near the reflectors, the lamellae exhibit a greater height dimension, i.e. a larger distance from the inner edge to the outer edge, than centrally between the reflectors.
The reflectors do not only focus the light generated by a lamp accommodated in the luminaire but also screen the lamp in a direction transverse to the lamp, and in directions surrounding said direction, so that the lamp can only be observed through the longitudinal edges of the reflectors, see
FIG. 2
a
, outside a selected angle &agr; made with a plane Q. In the longitudinal direction of the lamp, and in directions surrounding said direction, the lamellae have a screening effect, so that, also in the longitudinal direction of the lamp, the lamp can only be observed outside an angle made with plane Q. In this manner, the reflectors and the lamellae preclude glare if the luminaire is observed at relatively large angles with the normal to plane Q. This screening effect is also necessary to prevent disturbing reflections, for example at display screens. Screening is efficient if there is a screening effect both in directions around the longitudinal direction of the lamp and in a direction transverse to the lamp at a substantially equal angle &agr;.
The above-mentioned document explains that for efficient screening, the lamellae must have a concave outer edge. In conventional lamellae, which do not only have a straight inner edge, but also a straight outer edge, screening in the longitudinal direction of the lamp is greater than in directions surrounding the longitudinal direction. If the screening effect in the longitudinal direction of the lamp is chosen to be equal to that in a direction transverse to the lamp, then the screening effect in directions around the longitudinal direction is too small and the standard for screening is not met in all directions. If this is precluded, for example by arranging the lamellae with a smaller interspace, then the screening effect in the central part of the lamellae is excessive, leading to a loss of light caused by additional reflections at the lamellae. This can be attributed to the fact that reflections are always accompanied by absorption.
The lamellae of the known luminaire may alternatively be three-dimensional bodies, for example folded from aluminium strip, which flare out from the outer edge to the inner edges. The inner edges of the lamellae may also be concave in order to preclude that, after reflection at the surfaces of the lamellae facing the lamp, bright images of the lamp are formed on the reflectors, which can be observed as disturbing bright spots from the angle &agr; screened by the reflectors.
It is a drawback of the known luminaire having flat lamellae, that the lamellae cause undesirable reflections and unnecessary loss of light.
In DE-U-7613194 a description is given of a luminaire in which the flat lamellae have a largely convex outer edge and a largely concave inner edge. The known, above-described drawback of lamellae having a straight outer edge, i.e. inefficient or insufficient screening, applies to a greater extent to these lamellae.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a luminaire in which undesirable reflections at the lamellae are reduced.
This object is achieved, in accordance with the invention, in that the inner edge of the lamellae is convex.
This measure has various consequences.
As a result of the convex shape of the inner edge of the lamellae, the lamellae are less voluminous than they would be if they had a straight inner edge. As a result, fewer light rays are intercepted on their way to the reflectors and fewer reflections, which lead to a loss of light due to absorption, occur. The convex shape of the inner edge has no consequences for the screening of the lamp in its longitudinal direction and in directions surrounding the longitudinal direction, because for screening, apart from the entire outer edge of the lamellae, only the center of the inner edge is important.
Due to the thickness of lamellae, light which, in the case of lamellae having a straight inner edge, falls on the lamellae close to the reflectors, is cast onto the reflectors, which reflect the light in such a way that it leaves the luminaire and lands within the angle &agr; screened by the reflectors. In accordance with the opening paragraph of the above-cited document, this is precluded by providing the lamellae with an inner edge which is concave in shape. These reflections are particularly disturbing in known lamellae which have a three-dimensional shape and which, as described above, have a greater thickness dimension near the inner edge than near the outer edge, particularly if the lamellae are made of a reflecting or semi-mat material. The occurrence of disturbing light within the angle &agr; screened by the reflectors, which has already been reduced by using flat lamellae, is further suppressed by the measure in accordance with the invention.
In the case of these solid lamellae, the smaller volume of the lamellae with a convex inner edge also leads to a smaller material content. This is an important aspect regarding the cost price of the luminaire. If the lamellae are manufactured by cutting, for example punching, them from strip material, then the convex inner edge of the lamellae causes the amount of waste material to be reduced.
In a favorable embodiment, the inner edge and the outer edge of the lamellae are essentially parallel. In this case, there is no waste material and the formation of the outer edge of a first lamella results in the formation of the inner edge of a second lamella. However, while maintaining a proper screening of the lamp to be accommodated in the luminaire, the convexity given to the inner edge may exceed the concavity given to the outer edge. In this case, the lamellae become narrower in the direction from the center to the reflectors. The inner edge narrows towards the outer edge. These lamellae, which are even less voluminous, have the advantage that they cause even fewer interceptions and hence fewer reflections.
The lamellae may be made, for example, of a metal and may, or may not, be painted white or another color. They may be provided, for example, with decorative perforations. Unpainted lamellae may be mat or semi-mat. The lamellae may alternatively be made of a translucent synthetic resin which passes light in a scattering manner or of a non-translucent synthetic resin which may or may not be colored. If highly reflective flat lamellae were to be used, then they would show mirror images of the accommodated lamp and, since they are flat and do not deflect incident light, they would still cast concentrated light in the screened angle, which might cause glare.
Particularly near the inner edge, the flat, scattering lamellae of luminaires may still exhibit a relatively high brightness. In a particular embodiment of the luminaire in accordance with the invention, the lamellae have profiled surfaces. For example, they may comprise folds with an amplitude which extend along the outer edge. As a result, an observer sees alternate zones of relatively high and relatively low brightness on the surface of the lamellae, where light is deflected, respectively, towards and away from an observer, so that the lamellae as a whole have an average brightness which is lower than the brightness of unfolded lamellae.
In a modification of thi
Halajian Dicran
Husar Stephen
U.S. Philips Corporation
LandOfFree
Luminaire does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Luminaire, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Luminaire will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2473724