EP0303107B1 - Antiglare device - Google Patents

Description

The invention relates to a glare protection device for a light entry opening leading into a room, in particular for a window, which at least for partial areas of the room, for example the workplace, reduces the luminance of the light entry opening which is perceptible from below a predetermined room height, the glare protection device consisting of a retractable louvre blind , whose lamellae are concavely curved in cross-section over their entire length and where the upper inner longitudinal edge of each lamella facing the room in the operating position is located in the area of the upper outer longitudinal edge facing away from the room, parallel to it, or higher than this (see DE-A-2 830 745).

The high window luminance, or the resulting glare, which is particularly disturbing at the workplace, particularly when using screens, stems on the one hand from the high celestial luminance, which can also occur when the sun is hidden, and on the other hand from reflections of the sky radiation, of course also directly Sunlight counts, on other buildings or on snow-covered ground, for example. In any case, the light that strikes a window opening in practice is diffuse (i.e. it strikes from all possible directions), with higher luminances from certain directions (e.g. the sun or that facing a white wall) clearly being expected than from others.

Drawn curtains and usual slat blinds with closed slats bring a satisfactory reduction in window luminance; however, this only at the expense of a substantial reduction in the amount of light entering the room, so that artificial lighting is often necessary during the day.

Good anti-glare devices are characterized in that, on the one hand, they are below a critical angle, in general the horizontal, allow only a little light to enter the room and thus prevent glare, for example at the workplace (dimming condition), but on the other hand let as much light through as possible in order to get by without artificial lighting during the day. For example, a prismatic acrylic glass structured similar to a Fresnel lens is known, which is fixedly mounted behind a window glass pane. The main disadvantage of such a glare protection device is that it cannot simply be removed when it is not needed, for example when it is already dark outside. A view to the outside is never possible. In addition, cleaning the actual window glass is difficult. Another known glare shield has practically the same disadvantages, which consists of physical lamellar profiles made of aluminum, on which the incident light is specifically reflected. The slat profiles can be pulled open. Due to their great thickness, namely half of the free space between the slats, you still have a package when pushed together which takes up half the window height and which is completely opaque when opened.

The object of the invention is to provide an improved anti-glare device of the type mentioned at the outset which, provided the anti-glare conditions are met for certain room areas, brings a large amount of light into the room overall and which, if no anti-glare protection is required, can be quickly and easily brought into a position, in which it releases at least a large part of the light entry opening. Furthermore, the glare protection in the operating position should create a bright, visually appealing impression from the room, in particular also from the dimmed room area (workplace).

According to the invention this is solved by the features of claim 1.

As with the previously generally swiveling blackout blinds, the blinds according to the invention can be raised and lowered quickly and easily as required, for example using elevator cords. In the context of the present invention, slats are understood to mean the actual thin, elongated, sheet-shaped slats, the upper and lower sides of which are essentially equidistant and have the same profile. With such slats, the slat package that is raised is only relatively small and can disappear in a conventional blind box.

It is already known to mirror slats. however, these lamella arrangements do not serve as glare protection, but rather to bring parallel sun rays striking far back into rooms from a relatively narrowly limited angular range. For this purpose, the slats are inwardly sloping towards the room and have the relatively large slat spacing in the lowered state in the case of pivotable normal slatted blinds. Such lamella arrangements are not suitable as glare protection, since they are only designed for a relatively narrowly limited angle of incidence, namely that of the direct sun rays.

Slightly flatter rays of light can e.g. B. enter without reflection between the slats and dazzle those lower areas that are usually used as workplaces. US-A-2 209 355 and FR-A-25 74 469 also show mirrored, concave lamellae. Because of the large slat spacing and the likewise reflecting underside of the slats, light rays can also enter the room downwards directly or after reflection on the underside of the slats and lead to glare, which is to be avoided by an anti-glare device of the type according to the invention.

Due to the feature of the invention that the upper inner longitudinal edge of each slat facing the room is higher in height in the region of the upper outer longitudinal edge facing away from it, parallel to it, or higher than this, through a suitable choice of the slat distance, one achieves that between the slats without reflection In any case, light entering the room enters approximately horizontally or diagonally upwards and thus does not lead to glare in the room in the case of conventional windows. The direct beam of light entering at the deepest angle downwards through the glare shield extends generally tangentially to the underside of a slat, which is curved upwards and outwards, and enters the room past the inner upper edge of the slat below. Such a light beam defines a critical angle to the horizontal at which no direct (without reflection on the glare protection) from the outside enters through the light entry opening and the glare protection. This critical angle can be z. B. increase (ie the direct light rays enter the room less steeply downwards) by reducing the lamella spacing. However, a reduction in the lamella spacing also presents problems: due to inevitable multiple reflections between two each, preferably above and below mirrored slats reduce the total amount of light entering through glare protection. In addition, with a reduced slat spacing, more slats are required, which on the one hand increases the costs and on the other hand leads to undesirably high slat packs when the slat blind is opened.

In the case of the slats, which generally also reflect below, if there is a relatively large slat distance, there is a risk of glare from light rays that come from the ground outdoors (e.g. in the case of snow) due to one-time reflection on the underside of the slat on those to be dimmed Get to work. In order to avoid this, it is in principle possible to blacken the underside of the slats in a manner known per se. However, this is necessarily associated with a greater loss of light. In addition, such a "blackened" glare protection would appear dark from the workplace, which is just as undesirable as the swallowing of other room light by such blackened slat undersides.

In the embodiment of FIG. 3.1, DE-A-2830745 shows slats lying one above the other with reflecting upper sides and black undersides, the slats rising towards the room. The purpose of this lamella arrangement is to direct sunlight onto a heat receiver arranged in front of the facade. Part of the sunlight also reaches the black underside of the slats and is absorbed there. A targeted redirection of light into the room, as is typical for generic anti-glare devices, does not take place. In the other exemplary embodiments, the black slat side lies at the top for the purpose of generating heat energy, so that practically no light is reflected from the slats into the room at all.

The retroreflective areas provided according to the invention ("retroreflective" is understood to mean a surface that preferably reflects back in the direction of incidence, while "mirrored" means a normal directional reflection according to the known reflection law), areas on the underside of the lamellae also allow compliance with the dimming condition but additionally the advantage that diffuse light from the room is not swallowed, but is scattered back into the room in a slightly scattered manner. At the same time, the retroreflective underside of the slats creates a non-dazzling, yet bright, visually appealing impression from the workplace. As already mentioned, retroreflective surfaces preferably reflect the incident light beam back in this direction of incidence, ie this back reflection is not completely exact. Rather, the reflected light is reflected back with a scattering angle of typically a few degrees around the direction of incidence. This means that there can be no glare from the glare protection due to any light sources in the room. Unlike with blackened slat undersides, retroreflective slat undersides also bring one between the Slats present scattered light in the room, which represents a gain in the total amount of light brought into the room. Retroreflective layers can be sprayed on, for example, or can be stuck on as foils, as are already used for traffic signs. For dimming ground radiation, it is generally sufficient if the retroreflective area extends on the underside of the slat from the lower inner longitudinal edge to the area of the lowest point of the slat. For manufacturing reasons, however, it can be advantageous if the retroreflective area extends over the entire underside of the slats.

Despite the fulfillment of the anti-glare conditions, the amount of light entering through the anti-glare protection of the light which is diffusely incident from the outside should be reduced as little as possible, that is to say only one should enter the room as few reflections as possible. This can be achieved at least for the sky radiation coming essentially from above, according to a preferred feature of the invention, in that at least some of the slats - viewed in cross section - are essentially elliptically profiled, with a focal point of the ellipse part in each case in the region of the outer longitudinal edge of the slat lying above, preferably lies on this longitudinal edge and the second focal point lies in the region of the inner longitudinal edge of the slat lying above. Light rays occurring through the outer focal point or in the space underneath on the upper side of a lamella enter the room after only a single reflection through the second focal point or below, while observing the dimming conditions, except for the portion of the light rays that after reflection on the Top of a slat still get to the underside of the slat above. If the second focal point lies exactly on the inner longitudinal edge, this last-mentioned proportion of the light rays is very low. If the second focal point is in the area of the inner longitudinal edge, but does not coincide with it, some light rays may emerge after reflection on the top of the slat and subsequent second reflection on the underside of the slat above, from the glare protection to the work place to be dimmed. In order to avoid this, the underside of the slats can be blackened at the appropriate points or, which is considerably more favorable in terms of light output and visual impression of the glare protection, can be designed to be retroreflective.

A preferred embodiment, in which the main axis of the ellipse part rises towards the area to be dimmed with respect to the horizontal with an angle of rise, allows larger lamella spacings. By extending the upwardly curved slats towards the room, with a horizontal plane containing the inner upper longitudinal edge of a slat just forming a tangential plane to the underside of the slat above it, it can be achieved in a simple manner that direct light rays are only an angle above the horizontal through the Can glare through.

A further preferred feature of the invention, namely that at least some of the elliptically profiled slats in the area lying between the outer longitudinal edge and the deepest point of the slat is slightly raised compared to the elliptical cross-sectional shape, the light yield, that is to say the total amount of light passing through, can be optimized by one takes into account that the incident radiation in general mostly comes from above. The optimal extent of the above-mentioned increase can be determined, for example, by calculation, the coefficients and exponents of a polynomial approach being optimized for the lamella shape in this area.

According to a preferred embodiment of the invention it is therefore provided that the plane containing the two upper longitudinal edges of a lamella rises towards the room by more than 10 °, preferably by approximately 20 °.

Such a lamella arrangement advantageously allows larger lamella spacings and higher luminous efficacy with the same critical angle for directly entering light rays. It is clear that the glare, in turn, obstructs the view from the workplace to the outside by the glare protection or is not possible at all. In the case of the last-mentioned preferred arrangement with slats placed inwards at an angle, which allow an enlarged slat distance, it is advantageously possible to look out (downwards) through the glare protection when approaching the light entry opening.

In order to have optimal glare protection even in the case of large window areas, a preferred feature of the invention provides that the radiation critical angle to the horizontal, below which hardly any light from the glare shield enters the room in the case of diffuse irradiation onto the outside of the glare shield, differs for different height ranges of the slatted blind is. This can be achieved by means of a slatted blind with at least two superimposed areas which have different slat positions and / or shapes.

The invention is explained in more detail below with reference to exemplary embodiments by the drawing.

1 shows a room with a workplace to be protected from glare through a window, one of many possible arrangements of the anti-glare device according to the invention being shown schematically, FIG. 2 a schematic representation of an embodiment of the anti-glare device according to the invention, FIG. 3 one schematic cross section through two lamellae of a further exemplary embodiment, FIG. 4 shows the fade-out behavior achieved with an anti-glare device equipped with lamellae of FIG. 3 (transmission with diffuse radiation as a function of the entry angle into space measured horizontally), FIG. 5 shows the same representation 3 for another exemplary embodiment, FIG. 6 the associated blanking behavior and FIG. 7 the geometric relationships in the anti-glare device according to FIGS. 5 and 6.

1 shows a work station 2 arranged in a partial area of room 1. Diffuse light enters the room 1 from outside via a light entry opening designed as a window 3. The glare protection 4 arranged inside the window 3 prevents the luminance of the window which can be perceived from the workplace from being too high and thus causing glare. The anti-glare area 4a directs light which is diffusely incident from the outside into an angular area substantially above the horizontal limit beam h, while the lower anti-glare area even allows essentially light beams to enter which are above the lower limit beam angle α. A typical light beam path is designated by l.

According to the invention, the glare protection consists of a Fig. 2 slat blind 4 shown in more detail, the slats 5 are concavely curved over their entire length upwards and are at least partially mirrored. In addition, the inner longitudinal edge 5a facing the space 1 is of the same height (see FIGS. 2 and 3) or higher (see FIGS. 5 and 7) than the outer longitudinal edge 5b. If glare protection is not necessary, the blind can be raised to the position designated 4 'in FIG. 2.

In Fig. 3 two slats 5 of an embodiment are shown schematically in cross section. In the specific case at hand, the slat width is 80 mm and the slat distance is 11 mm. The outer longitudinal edge 5b is the same height as the inner longitudinal edge 5a. The deepest below the horizontal without reflection direct light beam l₁ includes only a small negative angle β with the horizontal X. The slats are - seen in cross section - parts of ellipses of the focal points F₁, F₂ on the longitudinal edges 5a, b of the respective slats above. This means that almost all the rays hitting the top of the slat from the outside enter room 1 with only one reflection, while maintaining the dimming conditions.

The masking behavior of an anti-glare device with lamellae 5, as shown in FIG. 3, is shown in FIG. 4 as a function of the angle of entry into the room, with diffuse illumination from the outside being present. There is practically no radiation below the horizontal (y = 0). If the underside of the slats is mirror-finished, the values indicated by bare crosses result. By gluing a retroreflective sheeting 6 onto the underside of the slats (only shown for the upper slat in FIG. 3), the luminance can be reduced even further in directions below the horizontal (see circled crosses in FIG. 4) without the To change the amount of light in the upper range (positive y) significantly.

In the embodiment according to FIGS. 5, 6 and 7, the slats 5 are also elliptically curved, but the focal points F 1, F 2 lie on a line g rising upwards at β = 20 ° and which contains the two upper longitudinal edges 5a, 5b of a slat Level ε also rises towards room 1. The deepest directly entering the room 1 light beam is designated l₁ and is horizontal.

The lamella spacing d is considerably larger than in the exemplary embodiment according to FIG. 3 or 4, which saves material and causes smaller lamella packs when being opened. In addition, with the slats according to Fig. 5 or 7 you can look down into the open when approaching the blind.

The inner focal point F₂ is not entirely at the inner longitudinal edge 5a of the overlying longitudinal edge 5a but still further above (Fig. 7). The result of this is that, for example, focal rays, such as l₂, do not emerge after reflection, but instead reach the underside of the lamella above and from there to the workplace to be dimmed. This applies if the undersides of the slats are mirrored and is shown in FIG. 6 (mere crosses) in the fact that the transmission is also quite significant in directions below the horizontal (negative y). This is remedied by a retroreflective layer or film 6, which, as is shown for a lamella 5 in FIG. 5, is arranged on all undersides of the lamella. Without significantly changing the conditions for positive y, an almost complete blanking for angles below the horizontal is achieved (circled crosses are values with retroreflective values Layer). The retroreflective sheeting 6 extends to the lowest point P of a lamella 5.

leicht angehoben, wobei die Koeffizienten a, c und der Exponent b auf einem Computer rechnerisch optimiert werden.In order to optimize the light output, the lamella in area A is opposite the ellipse (dashed) according to a polynomial of the shape ${\text{ax}}^{\text{b}}\text{+ c}$

slightly raised, whereby the coefficients a, c and the exponent b are mathematically optimized on a computer.

In principle, the slats could be pivoted to change the light distribution like conventional blackout slats. However, this is certainly at the expense of light output and other optical properties. The slats therefore preferably always maintain one and the same optimized position. However, by partially opening the slatted blind, the fade-out behavior can be changed in a simple manner and, for example, the time of day and weather conditions can be adapted.

Claims (10)

1. An anti-glare arrangement for a light admission opening which leads into a room, in particular for a window, which at least for parts of the room, for example the place of work, reduces the brightness of the light admission opening, which is perceptible from below a predetermined level in the room, wherein the anti-glare arrangement comprises a slat-type venetian blind (4) which can be pulled up and the slats (5) of which are curved concavely upwardly in cross-section over their entire length, and wherein the upper inner longitudinal edge (5a) of each slat (5), which edge is towards the room (1), is disposed in the operative position in terms of height in the region of the upper outer longitudinal edge (5b) which is away from the room (1) and which is parallel to the inner edge, or is higher than said outer longitudinal edge, characterised in that the slats (5) are mirrored at least on their top sides, that the undersides of the slats (5) are retro-reflecting at least in a region which is towards the room, and that the spacing and the position of the slats is so selected that the light which is incident on the light admission opening from different directions from the exterior passes through the anti-glare arrangement for the most part into an angular region which lies substantially above the horizontal.
2. An anti-glare arrangement according to claim 1 characterised in that a retro-reflecting foil (6) is stuck on to the bottom sides of the slats (5).
3. An anti-glare arrangement according to claim 1 or claim 2 characterised in that the slats (5) are mirrored except for the retro-reflecting regions.
4. An anti-glare arrangement according to one of claims 1 to 3 characterised in that the slats are suspended in a non-pivotable fixed position which they assume when the slat venetian blind is let down, wherein the plane (ε) containing the two upper longitudinal edges (5a, 5b) of a slat (5) rises towards the room (1) preferably at over 10°, in particular at about 20°.
5. An anti-glare arrangement according to claim 4 characterised in that the retro-reflecting region (6) extends in each case at the underside of the slat (5) from the lower inner longitudinal edge which is towards the room and which adjoins the underside, to the region of the lowest point (P) of the slat (5).
6. An anti-glare arrangement according to one of claims 1 to 5 characterised in that at least a part of the slats (5) as viewed in cross-section is of a substantially elliptical profile, wherein a focal point (F₁) of the elliptical part is disposed in each case in the region of the outer longitudinal edge (5b) of the slat disposed thereabove, preferably on said longitudinal edge (5b), and the second focal point (F₂) lies in the region of the inner longitudinal edge (5a) of the slat disposed thereabove.
7. An anti-glare arrangement according to claim 6 characterised in that the major axis (g) of the elliptical part rises at an upward angle (β) relative to the horizontal (x) towards the room (1) in which the level of glare is to be reduced.
8. An anti-glare arrangement according to claim 7 or claim 8 characterised in that each slat (5) extends towards the room (1) to such an extent that a horizontal plane containing the inner upper longitudinal edge (5a) of a slat (5) just forms a tangential plane to the bottom side of the slat (5) disposed thereabove.
9. An anti-glare arrangement according to claim 4 and one of claims 6 to 8 characterised in that at least a part of the elliptically profiled slats is slightly raised relative to the elliptical cross-sectional shape in the region between the outer longitudinal edge (5b) and the lowest point (P) of the slat (5).
10. An anti-glare arrangement according to one of claims 1 to 9 characterised in that the slat-type venetian blind (4) is divided into at least two superposed regions (4a, 4b) with different slat positions and/or shapes, the radiation critical angles (α) of which are different.

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