Cover for luminaires (lighting fittings, light fixtures)

The invention relates to a cover for lights, which have on their side facing the lamp of the lamp in rows and rows arranged pyramidal profiles, which are formed as a truncated pyramid with the base surface parallel upper boundary surface. Covers of this type are known from US-PS 3,351,753 and GB-PS-1 365 507. Through these covers a light control is to be achieved, is limited in the angle of the light beams to reduce the glare. In GB-PS-1 365 507, for this purpose, the upper boundary surfaces of the truncated pyramids are coated with an opaque material, while in US Pat. No. 3,351,753, the side surfaces of the truncated pyramids and the spaces between the truncated pyramids are provided with an opaque material.

A cover, in which serve for directing light pyramids, which follow each other in rows and rows and on the lamp side of the lamp facing side of the cover, is known from US-PS-3,258,590. Although the light control by such a profiling is not unfavorable in itself, it can be favorable Ausblendwinkel achieve, so adhere to this known construction two not inconsiderable disadvantages. The one disadvantage lies in the production, it is very difficult to manufacture inexpensively and efficiently such profiles with sharp pyramids as standard. The other disadvantage is photometric type. Due to the high surface portion of the inclined pyramid side surfaces a considerable part of the right angles falling on the cover light rays is reflected and hidden with the result that a cover of the known type has only a poor optical efficiency.

Although a suitable light control is achieved by these known covers, but due to the opaque areas of the cover, which is a considerable. Part of the entire surface of the cover, the efficiency of the luminaire is significantly reduced. Based on the known covers, the invention aims to provide a cover that can be produced both rationally and in series and which has a high optical efficiency.

According to the invention, this is achieved with a cover of the type mentioned above in that the cover entirely consists of crystal clear material. The invention is based on the recognition that with such a cover, a light steering can be achieved with a limitation of the angle of reflection, the efficiency over the conventional covers is substantially increased.

Embodiments of the invention illustrate the drawings. Show it:

1 is an oblique view of a cover of a first embodiment:

2 is an oblique view of a cover of a second embodiment:

FIG. 3 shows a truncated pyramid in an enlarged scale compared to FIGS. 1 and 2;

Fig. 4 shows schematically a light in an oblique view seen from below, here in the central region at an assumed point the light rays emerging at the Ausblendwinkel τ are illustrated by a conical surface.

The Fig. 1 and Fig. 2 show obliquely a luminaire cover 1 made of crystal-clear material, specifically from the side facing the lamp. This cover 1 has on the side facing the lamp of the lamp in rows and rows arranged profiling in the form of truncated pyramids with relatively steep edges or side surfaces eighth Follow in the embodiment of FIG. 1 Such truncated pyramids 3 of the same dimensions in rows and rows directly on top of each other, so are in the embodiment of FIG. 2 in rows and rows such truncated pyramids 3 arranged like a checkerboard, ie, between two successive truncated truncated 3, a profiling is recessed, the recessed surface corresponds to the base surface of a truncated pyramid 3 in terms of their length and width. The truncated pyramids preferably have a square base surface.

FIG. 3 shows in a relation to Figs. 1 and FIG. 2 is an enlarged cross-sectional view of such a truncated pyramid 3. Here are the essential sizes of the truncated pyramid indicated: height of the truncated pyramid - h; Side length d, measured at half height h of the truncated pyramid 3; Angle of incidence - α; Angle of refraction - ß \ inclination angle of the side surfaces 8 of the truncated pyramid relative to the base surface 6 - u; Skip angle - τ (usually between 60 and 70 '); Refractive index n = sin α / sin β.

At the base surface 6 of the truncated pyramid 3 connects to a plane-parallel section 5, which does not affect the beam path, and which is formed by the fact that the V-shaped cuts to form these truncated pyramids can not be pulled through to the full extent of the base plane of the cover.

Starting from a masking angle of 60-70 'and conventional glass-clear plastics for such covers, as they are available, for example, under the trade name acrylic glass, resulting in consideration of the inventive measure a cover with dense on the lamp side

AT 403 403 Β

Occupation of such truncated pyramids, as Figs. 1 and 2 illustrate.

Fig. 4 shows schematically a lamp with a cover of the type according to the invention seen obliquely from below. On the outside, this cover is smooth. At a point P assumed here in the middle, the light rays emerging under the masking angle τ delimit a conical mantle 4. The ratios shown here with respect to the point P also apply to all other points of this luminous cover.

To limit the Ausblendwinkels τ to a maximum value of T_Max these truncated pyramids 3 are so dimensioned that the ratio of d / h is equal to or less than d / h t tan (arc sin (sin (rmax) / n)). The angle of inclination u of the side surface 8 with respect to the base surface 6 is equal to or less than u £ 90 * 1/2 (arc sin (1 / n) - arc sin (sin (rmax) / n)) or greater than u> 2. arc sin (1 / n).

For example, in the case of a cover material with a value of n = 1.55 and a masking angle of 70 ', this means that the ratio d / h is £ 0.76 and that the angle of inclination ul is between 80.5 × and 88.5 × , If a Ausblendwinkel be achieved by 60 ', the ratio d / h must be £ 0.67 and the inclination angle u. between 80.5 'and 86.9' lie. The light that strikes the sloping surfaces is then refracted or reflected to match the selected rejection angle limit. Was here a range of approx. 60 - 70 ', it is quite conceivable, also from other Ausfallwinkelbegrenzungen go out.

Thanks to the measure according to the invention, it is possible to produce covers for luminaires which have a high optical efficiency despite the limitation of the drop angle of the light beams.