EP0303107A2 - Antiglare device - Google Patents

Abstract

The antiglare means for a workplace (2), illuminated by a window (3), in a closed room (1) is provided by a slatted blind (4) comprising mirror-coated slats (5) having an upward concave curvature and which rise towards the room (1). A retroreflecting foil (6) is bonded to each slat bottom in order also to block out, in the case of relatively large distances between the slats, light rays from the ground and those which have been reflected from the slat below and to give a bright, optically pleasing impression from the workplace (2). <IMAGE>

Description

The invention relates to an anti-glare 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 a predetermined room height, the direction from the outside being different most of the light incident opening through the anti-glare device reaches an angular range substantially above the horizontal.

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), although higher luminances are to be expected from certain directions (e.g. towards the sun or against a white wall) 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 in the room, so that artificial lighting is often necessary even during the day.

Good anti-glare devices are characterized in that, on the one hand, they are below a critical angle, in all According to 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 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 an anti-glare 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 achieved in that the anti-glare device consists of a retractable slat blind, the slats of which are concavely curved in cross-section over their entire length and at least partially mirrored, and in that the upper inner longitudinal edge of each slat facing the room is in the operating position is in height in the area of the upper outer longitudinal edge facing away from the room, parallel to it, or higher than this, and that the undersides of the slats are retroreflective at least in an area on the room side.

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, lamellae are understood to mean the actual thin, elongated, leaf-shaped lamellae, 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 lamellar 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. Enter and blind between the slats without reflection between those areas of the room that are usually used as workplaces.

Due to the feature according to the invention that the upper inner longitudinal edge of each lamella 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, a suitable choice of the lamella spacing means that between the lamellae 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 increased, for example (ie the direct light rays enter the room less steeply downwards) by reducing the lamella spacing. However, a reduction in the louvre spacing also presents problems: inevitable multiple reflections between two louvres, each preferably mirrored above and below, reduce the total amount of light entering through the 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 are also generally reflective below, if there is a relatively large slat spacing, there is a risk of glare from light rays that come from the ground outdoors (for example in the case of snow) through one-time reflection on the underside of the slat to the work place to be dimmed 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. The retroreflective areas provided according to the invention ("retroreflective" is understood to mean a surface which preferably reflects back in the direction of incidence, while "mirrored" means a normal directional reflection according to the known law of reflection)) areas on the underside of the slats also allow compliance with the dimming condition, but additionally indicate the advantage that diffuse light falling on the room is not swallowed, but is scattered back into the room, slightly scattered. 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 proportion of light rays that are reflected after the reflection 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 it 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 tangent 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 slat 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 the top, which allow an enlarged slat spacing, it is advantageously possible to look out (downwards) through the glare protection if one approaches 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 geometrical relationships in the anti-glare device according to FIGS. 5 and 6.

1 shows a work station 2 arranged in a partial area of the 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 which is essentially 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 no anti-glare protection is required, the blind can be pulled up into the position labeled 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 space 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 straight line g rising up 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, almost complete masking 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.

In order to optimize the luminous efficacy, the lamella in area A is slightly raised in relation to the ellipse (dashed line) according to a polynomial of the form ax ^b + c, the coefficients a, c and the exponent b being 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 (12)

1.Dazzle 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 workstation, reduces the luminance of the light entry opening which can be perceived from below a predetermined room height, with the light entry opening coming from different directions from the outside striking light through the anti-glare device largely reaches an angular range substantially above the horizontal, characterized in that the anti-glare device consists of a slatted blind (4) which can be pulled open, the slats (5) of which are concavely curved in cross section over their entire length and at least are partially mirrored that the upper inner longitudinal edge (5a) of each lamella (5) facing the space (1) in the operating position has a height in the region of the upper outer longitudinal edge (5b) facing away from it, parallel to it, or higher than this lies and that the undersides of the slats (5) are retroreflective at least in an area on the room side. 2. Anti-glare device according to claim 1, characterized in that the retroreflective area (6) each on the underside of the lamella (5) from the lower inner longitudinal edge (5a) to the area of the lowest point (P) of the lamella (5) extends. 3. Anti-glare device according to claim 1 or 2, characterized in that a retroreflective film (6) is glued to the undersides of the slats (5). 4. Anti-glare device according to one of claims 1 to 3, characterized in that the slats (5) are mirrored except for the retroreflective areas. 5. Anti-glare device according to one of claims 1 to 4, characterized in that the slats are suspended in an immovable, fixed position, which they occupy when the slatted blind is lowered. 6. Anti-glare device according to one of claims 1 to 5, characterized in that the two upper longitudinal edges (5a, 5b) of a lamella (5) containing plane (ε) with over 10 °, preferably with about 20 °, to the room (1 ) increases. 7. Anti-glare device according to one of claims 1-6, characterized in that at least part of the slats (5) - seen in cross section - is essentially elliptically profiled, with a focal point (F₁) of the ellipse part in each case in the region of the outer longitudinal edge (5b ) of the overlying lamella, preferably on this longitudinal edge (5b) and the second focal point (F₂) in the region of the inner longitudinal edge (5a) of the overlying lamella. 8. Anti-glare device according to claim 7, characterized in that the main axis (g) of the ellipse part to the room to be dimmed (1) towards the horizontal (x) increases with an angle of rise (β). 9. Anti-glare device according to claim 7 or claim 8, characterized in that each lamella (5) extends so far to the interior (1) that a horizontal plane containing the inner upper longitudinal edge (5a) of a lamella (5) just a tangential plane forms the underside of the overlying lamella (5). 10. Anti-glare device according to one of claims 7-9, characterized in that at least part of the elliptically profiled slats in the area between the outer longitudinal edge (5b) and the deepest point (P) of the slat (5) lying area is slightly raised compared to the elliptical cross-sectional shape . 11. Anti-glare device according to one of claims 1-10, characterized in that the radiation critical angle to the horizontal, below which hardly diffuses light from the anti-glare shield (4) into the room (1) for different at diffuse radiation on the outside of the anti-glare shield (4) Height ranges of the slatted blind (4) is different. 12. Anti-glare device according to claim 11, characterized in that the slatted blind (4) is divided into at least two superimposed areas (4a, 4b) with different slat positions and / or shapes, the radiation cut-off angle (α) is different.

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