Luminaire

Details Luminaire Luminaire

2002-03-19

2003-05-27

Tso, Laura K. (Department: 2875)

Illumination

Light modifier

Reflector

C362S346000, C362S347000, C362S297000

Reexamination Certificate

active

06568835

ABSTRACT:

The invention relates to a luminaire comprising:
a concave reflector with an optical center on an optical main axis in an optical main plane;
a light emission window which includes an acute angle with the optical main axis and extends transversely to the optical main plane;
a reflective screen which extends along the optical main axis of the reflector up to the light emission window, and extends transversely to the optical main plane;
a side panel at a first side of the main plane, contiguous to the screen, which reaches into the light emission window and bounds the reflector;
means for accommodating an electric lamp with a light source, which light source is situated around the optical center,
which reflector comprises elongated facets which extend along the screen.
Such a luminaire is disclosed in WO 98/45 643 (PHN 16295).
The known luminaire is intended to be used for the illumination of sites, for example sports fields, or to illuminate the road surface in a road tunnel, in which cases the light emission window is arranged horizontally, or it may also be used to illuminate facades, in which case the light emission window is arranged vertically.
The known luminaire comprises a reflector with a central row of facets, which is intersected by the optical main plane, which is a plane of symmetry in this luminaire, and, on each side thereof, one row of facets arranged at an angle therewith and bounded by a relevant side panel. The luminaire can suitably be used to accommodate a lamp having an elongated light source extending transversely to the plane of symmetry.
The known luminaire provides a light beam which, if the light emission window is horizontally arranged, is symmetrical in horizontal planes and asymmetrical in vertical planes. The reflective screen which, in this case, is in an oblique position facing downwards thus precludes that light is emitted at a large angle with the vertical. It is thus precluded that an observer looking at the luminaire from a distance is blinded if he looks against the light beam. As a result, the luminaire can very suitably be used to illuminate road tunnels, in which case the luminaire is mounted in the center of the ceiling of the tunnel and emits light against the direction of the traffic. Said luminaire thus illuminates both the road surface and the walls of the tunnel. To provide uniform illumination, a plurality of similar luminaires are mounted at a comparatively small distance from each other.
The illumination of a road surface by means of a light beam emitted against the direction of the traffic is very effective. In this case, light reflected by the road surface travels substantially upward towards the road user, enabling said road user to see the road surface. As regards the commonly used roadway lighting, the luminaires emit light, from a mast, in a downward direction on either side of the mast, half of the light being emitted on the side of the mast facing away from the road user. Said light is partly diffusely scattered by the road surface and partly reflected in a direction away from the road user so that it remains partly unobserved by the user. If the road surface is reflective, as in the case of, for example, a smooth bitumen surface, but particularly when the road surface is wet, the specular reflection by the road surface is greater and diffuse scattering is smaller. In this case the road surface is very dark. Also the light generated by the road user's own vehicle is specularly reflected away from the road user.
In the case of light traveling in the direction of the road user, however, much light is reflected towards the road user in the case of a specular, for example wet, road surface, resulting in good visibility of the road surface.
A drawback of the known luminaire resides in that if said luminaire is to be used as a road surface lighting, against the direction of the traffic, it must be mounted centrally above the section of the road where the traffic flow is unidirectional, as a result of which portals must be provided above the road, causing the application of the luminaire to be expensive. Another drawback resides in that the substantial amount of light that is incident on a tunnel wall if the luminaire is used for illuminating a tunnel, will be incident on the side of the road for oncoming traffic if said luminaire is used as a roadway lighting. Apart from the fact that this light cannot effectively be used for the intended purpose, it is undesirable because it is emitted in the direction of flow of the oncoming traffic.
It is an object of the invention to provide a luminaire of the type described in the opening paragraph, which can suitably be provided at a side of a roadway so as to uniformly illuminate a side of a road against the direction of flow of the traffic on said side of the road.
In accordance with the invention, this object is achieved in that the reflector is provided with:
a first reflector portion with facets, which extends, on the first side of the main plane, from the side panel to at least close to the main plane, and defines the main axis and the optical center,
a second reflector portion with facets, which extends opposite the side panel between the screen and the light emission window, on a second side of the main plane, which second reflector portion has a side axis which extends essentially through the optical center and is tilted essentially in the optical center with respect to the main axis
towards the light emission window so as to include an acute angle &agr; with the main axis upon projection in the main plane, and
towards the side panel to include an acute angle &bgr; with the main plane; and
a third concave reflector portion interconnecting the first reflector portion and the second reflector portion.
In operation, the luminaire in accordance with the invention provides a light beam that is asymmetrical both in vertical and horizontal planes. If the luminaire is mounted to a mast beside a side of the road for traffic traveling in one direction, the light emission window being in a substantially horizontal position facing downward, and the screen facing the oncoming traffic, said screen provides natural shielding against light radiation, i.e. light emitted directly to the exterior by the lamp as well as light emitted after reflection, in horizontal directions and downward directions including a small angle, generally up to 10°, with the horizontal, as a result of which dazzling is precluded. Also the reflector itself and the side panel, which include larger angles with the main plane than the downward angle wherein the screen is active, contribute to this shielding effect. The screen generally includes an angle with the light emission window ranging between approximately 20 and approximately 25°.
The first reflector portion forms a main light beam that is latitudinally incident on one side of the road at a comparatively large distance from the luminaire and narrows in the direction of the luminaire, and that will predominantly illuminate the part of the side of the road situated on the side where the luminaire is arranged.
The second reflector portion provides a side beam which, near the mast, latitudinally illuminates a side of the road and, up to a larger distance from the mast, the opposite side of the roadway. The third reflector portion provides a light beam that completes the illumination by the first and the second beam. In addition, there is the light that is emitted directly, without previous reflection, by the lamp accommodated, and the light that is reflected by the screen and the side panel.
By virtue of the asymmetry of the luminaire in accordance with the invention, the luminaire can suitably be used to illuminate a side of the road for traffic that keeps to the left, the luminaire being mounted to a mast provided at the median strip of the road, and hence also to illuminate a side of the road for traffic that keeps to the right if the mast is arranged at the roadside, however, a mirror-inverted embodiment of said luminaire is necessary to illuminate, from the m

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