WO2011064765A2

WO2011064765A2 - Light guiding venetian blinds with prism-shaped slat surfaces

Info

Publication number: WO2011064765A2
Application number: PCT/IB2010/055512
Authority: WO
Inventors: Helmut Koester
Original assignee: Helmut Koester
Priority date: 2009-11-30
Filing date: 2010-11-30
Publication date: 2011-06-03
Also published as: WO2011064765A3

Abstract

The invention is related to Venetian blinds which are installed behind glass windows and fagades comprising an upper blind portion and a lower blind portion. The slats are at least partly toothed at least at the upper side. The have at least partly reflective surfaces in the kind of prismatic reflectors for light guidance. The reflecting prisms are arranged parallel to the lateral edges in the longitudinal direction of the slats. The prisms are shaped with a longer side X₁ and a shorter side X₂ so that different angles α and β arise between the catheti and hypotenuses of the prisms and a prism side facing daylight incidence will result as primary reflector. The innovation is characterized in that the exterior glazings 32, 33 are used only in the upper blind portion of a window as a secondary reflector for light redirection 34, 35 and 50, 51 between the slats back into the interior space, and in the lower blind portion, the light redirection 22, 44, 48, 49 on the exterior glazings 23, 24 back into the interior space is screened off.

Description

Light Guiding Venetian Blinds With Prism-shaped Slat Surfaces

The present invention relates to inside Venetian blinds to be arranged behind glass windows and fagades as in accordance with the preamble of the main claim.

It has generally been known to reflect light via mirror geometries of a slat blind through a window glazing back to the outside into the exterior space in order to protect the interior space from overheating. It has also generally been known to produce blinds in two pieces wherein the upper blind portion is provided in an open version and the lower blind portion in a closed version. By the upper blind portion, the light is guided by reflection on the slat upper side into the interior, in the lower blind portion it is reflected by reflection of the closed blind to the outside.

The disadvantage of such blinds, however, is the necessity to provide different angles of the slats in the lower and the upper areas. The blinds are closed at their lower part and deprived of the visibility to the outside. The lower blind part, in addition, darkens the interior space considerably since the slats have to be turned to the closed state in order to reject the sun light and to evade reflections and glares of retro-reflected sun radiation on the interior side of the window glazing.

It has also been known to provide the slats on the upper side thereof in prism shape and to guide the light out via reflecting prisms. In US 6, 367,937 B2, a variety of prism structures have, for instance, been described. How to exactly shape these prisms and how to make the slats follow the altitude of the sun, has for instance been revealed in WO/2001/000958. In that case, the prisms are arranged so that a steep light deflection of the incident sun radiation to the outside is obtained. The advantage of the reflected light guidance is the freedom from glare. Sun radiation back-reflected into the glazing cannot glare because the reflection on the pane surfaces, as observed from the interior space, is not visible even in case of an open Venetian blind since the reflection is absorbed or diffusely reflected on the lower side of the upper slat. Now it is of course desirable to deflect the light in the upper window area more intensively, glare free into the room depth. It is, therefore, the aim of the present invention to develop a Venetian blind which, in the lower area, guides the incident sun light out without glare and, in the upper window area, guides the sun light out as well for the purpose of passive cooling; a small portion of the light radiation deflected at the upper slat surfaces, nonetheless, is to be deflected to the interior to the ceiling and into the room depth in order to save in artificial illumination. This task is to be solved by means of a toothed slat surface while it is not necessary, as is the case in common reflective slats, to arrange the individual slats within a blind at different tilt angles. It is, therefore, the task of the present invention to develop a transparent Venetian blind which, notwithstanding the even flat angles of incidence of all slats both in the upper and the lower blind portion, will fulfill the following different, partly contrasting, light- technological function: The blind should not, in the lower part in case of an open slat position, show any glare on the glass panes and should reflect, by retro-reflection, sun light or sun energy irradiation even in case of flat angles of incidence. The blind should in the upper portion, with the slat position open, deflect sun light or sun irradiation by deflection but, at the same time, should deflect a small portion of the sun light into the room depth and to the ceiling in order to save artificial light.

This task is fulfilled by the characterizing clause of main claim 1.

By means of the steep angles β of the shorter prism sides x, the sun light is mono- reflectively projected on the interior side of the outer glazing so that the secondary reflections of reflected radiation are deflected at the outer glazing between the slats into the interior room depth or to the interior room ceiling, and in this way will serve improved day light illumination in the depth of the interior room. At the same time, the blinds serve, however, also the shading and the passive cooling since, depending on the kind of glazing or the glass coating, at least a large part will be permitted to pass out through the glazing.

In the lower blind portion, the light reflected back by the slats into the fagade glazing is guided to the upper and the lower side of the adjacent slat and via one, or a plurality of, reflections is finally guided back into the outer space.

It is alone by the different angle dispositions of the primary mirrors of the prisms within a blind and the light guidance and light reflections effected thereby that completely contrary and advantageous light guiding effects and light actions are obtained in the interior room.

In the lower blind portion and in the upper blind portion, different optical systems are obtained with the same slat disposition and the same appearance of the blind. The optical effect of the slat surfaces acts together with the reflective properties of glass panes as an overall system. The desired effects and actions of an improved daylight il- lumination with simultaneous shading and passive cooling of an interior room are particularly obvious in case of sun protection panes which display increased reflection in the visible range of sun irradiation. The figures show further advantages of the invention. Figure 1 shows the cross section of a toothed prism-shaped embodiment of the slat upper side.

Figures 2 and 3 show the light incidence on the primary mirror and the light guidance of deflected light radiation.

Figure 4 shows the optical function of a two-part blind for room illumination. Figure 5 to Figure 8 show the mirror analysis on glass panes of radiation reflected on primary mirrors for individual beams.

Figures 5.1 and 5.2 show advantageous variants of the prisms.

Figure 9 to Figure 12 show secondary reflections of complete bundles of beams.

Figures 9.1 , 9.2, 9.3, 9.4 as well as Figures 1 1 .1 , 1 1.2, 1 1 .3, 1 1 .4 show an analysis of the reflected light.

Figure 1 shows a slat toothed on the concave upper side with the prisms 10 to 13 and further ones having angles a between the long cathetus Xi and the hypotenuse and the angles β at the short cathetus x₂ and the hypotenuse. In the following Figures the ray- tracings are following the law: angle of incidence equals angle of reflection.

The Figures 2 and 3 show the light incidence on the primary mirror. As the primary mirrors, those catheti x-i or x₂, respectively, are referred to which are hit by direct sun radiation and which reflect the radiation primarily mono-reflective, i.e. by one single reflection at an angle γ-ι or γ₂ back in the direction of the outer space. As secondary mir- rors, the outer panes are referred to, as far as they reflect the radiation deflected by the primary mirror back in the direction of the interior space.

In Figure 2, the long prism side x-i serves at a small angle a as primary mirror. In Figure 3, the short prism side x₂ serves at a large angle β a primary mirror. If sun radia- tion impinges on the long, flat disposed prism side x-i , the radiation is deflected steeper upwards at an angle γ₂, if sun radiation impinges on the short, more steeply disposed prism side x₂, and the radiation is deflected more flatly at an angle γ-ι .

Figure 4 shows the cross section of a window zone A and B with the requirements of the light deflection properties of a Venetian blind. Above a height of 1.70 m in section A, the light may be deflected, free from glare for the user of the interior room, to the ceiling or to the depth of the space. Below 1 .70 m in section B, the light should completely be deflected so that no light reflection into the interior space occurs at the panes since this would glare the user.

Figures 5 to 12 now show the secondary reflections on the glass panes of an outer glazing of the different prisms in co-operation between the slats and the glazing. It is the reflectory interaction between slat and glass pane which basically constitutes the idea of the invention. Embodiments according to Figure 5 and Figure 6 are preferably disposed in the lower window area of a fagade; embodiments according to Figure 7 and Figure 8 are preferably disposed in the upper window area.

In Figures 5 and 6, and 9 and 10, respectively, the prisms are shaped according to the teaching of Figure 2. The reflections 21 , 22 on panes 23, 24 are deflected either to the under side of an upper slat (Figure 5) or to the upper side of a lower slat (Figure 6). The reflection cannot, therefore, be seen from the interior room. The lower blind portion is glare-free.

In the Figures 7 and 8, and 1 1 and 12, respectively, the primary mirrors are disposed steeper as in accordance with the teaching of Figure 3 with the consequence that the deflected-out light radiation 30, 31 impinges on the window pane 32, 33 in a way so that the secondary reflections 34, 35 are deflected between the flatly disposed Venetian blind slats into the interior room thus effecting a daylight brightening. It is the aim of the present innovation to obtain in the lower window area γ₂ < Υι and in the upper win- dow area γ-ι< γ₂. In order to realize this aim, the construction rule of the present invention is: Lower window area: primary mirror x-i > x₂ for an angle α < β; upper window area: primary mirror x₂ < Xi for an angle β > a.

The teaching of the invention makes possible to produce a deflection Venetian blind having properties in favor of a glare-free sun protection in the lower visual range of a window. In the upper window area, it becomes possible to obtain, by flat light guidance back into the outer glazing, by secondary reflection an optimized daylight illumination in the depth of the room.

It is an advantage that all slats in the upper and in the lower part of the Venetian blind have identical tilt angles and thereby ensure a more homogeneous view from the inside and a good visibility through the blind. It is a further advantage that the slats in spite of identical tilt angles, nonetheless, fulfill various light-technical functions. It is another advantage, too, that the Venetian blind requires only one motor or a simple control while neither the upper nor the lower portion of the Venetian blind has to be controlled separately. An additional advantage is the possibility to employ identical slats from the same production line both in the upper and the lower blind. The fact that because of expansions of the guide cords, the tilt angle of the slats is mostly somewhat more flat at their lower portion is in this case irrelevant. The invention is not restricted to a uniform tilt angle in the upper and in the lower areas. In order to obtain special light guid- ance effects, the upper portion may be more open or more closed than the lower window area by using different tilt angles of the slats.

In Figures 9 to 12, complete bundles of beams 40 to 43 impinge through the outer glazing on the slats disposed in the interior and are tracked on the prisms and the glazing as to their reflection behavior. In this case, one portion of the radiation 44 to 47 transmits through the glazing to the outside. The portion of the radiation secondarily reflected in the glazing is reflected in the lower part of the window as shown in Figures 9 and 10 to an upper or a lower slat, and in the upper part of the window, in Figures 1 1 and 12, as a bundle of beams 50, 51 to the interior to obtain the desired optimization of daylight guidance into the interior and improved room illumination.

Figures 9.1 , 9.2, 9.3, 9.4 show an analysis of the single reflections. Figure 9.2 shows the solar irradiation onto the louvers. Figure 9.3 shows the first reflection by the cathetus Xi as explained in Figure 2. Figure 9.4 shows the reflection by the above lou- ver downwards into the fagade glazing. Some light is passing trough the glazing; some light is reflected back onto the lower louver. Figures 1 1 .1 , 1 1.2, 1 1 .3, 1 1.4 show an analysis of the reflections between slats in the upper portion of a blind in an inverse position of the slats. Figure 1 1 .2 shows the solar irradiation. Figure 1 1.3 shows the reflection by the cathetus x₂ of the prismatic structured mirror surface as demonstrated in Figure 1. Figure 1 1.4 and 1 1 .5 show the reflec- tion of light hitting the long cathetus x₂. This light will be reflected on the neighboring short cathetus x-i and from there back into the fagade glazing. Some of the light is passing the fagade glazing, some of the light is reflected back inside, partially onto the ceiling, partially onto the lower side of the upper slat. The upper slat will reflect the light unto the working plane.

A further variant of the innovation in Figure 5.1 provides that the tips of the prism 14, 15, 16 of Figure 1 and 17, 18 of Figure 2 be made flat so that the light radiation 19 impinging on flattened slat tips 15 is deflected to the interior. Such flattening may either be made only in the upper area of a window or on the slats of the lower blind portion. It is also possible to provide such flattening only in partial ranges of the slats, i.e. either near the slat edges oriented to the exterior space or those oriented to the interior room. The flattening may also be of different width and of different inclination.

Further embodiments of the invention may be taken from Figures 5 to 12, and particu- lar from Figures 5.1 and 5.2. In Figure 5.1 , the toothed, or prismatic-structured slat 80 is optically superimposed, in a partial area 81 by a flat reflector in which the prism tips 82 to 84 are flattened. By the flattening, light deflection to the interior space is obtained in the direction opposed to the reflection on the catheti of the prisms. Such flattening is advantageously provided when shaping the slats to a concave/convex form whereby, additionally, bulges come up caused by displacement of material. For reasons of a simplified representation, these bulges are not shown.

It is particularly advantageous to one-sidedly apply the flattenings in the lower blind portion in Figures 5, 6 and 9, 10 only on the slat half oriented towards the interior space. In this way, it is only for the flat winter sun of Figures 5 and 9 that energy and light guidance 60, 61 into the building is obtained as in the meaning of passive solar architecture. A slat cross section of Figures 5 to 12 is shown in detail in Figure 5.2. In Figures 7, 8 and 1 1 , 12, the low sun 70, 71 and the high sun 72, 73 is redirected towards the interior space by the same type of slats as in Figures 5, 6 and 9, 10. The slats in the upper blind portion are disposed in an inversed position. On the flattenings, the high sun and zenith light, too, is deflected into the room depth. Via the width of the flattening, the portion of the light redirected into the interior in relation to the reflection to the outside can be controlled by the width of the catheti.

It is the advantage of the present innovation that only by the inverse fitting position of the slats in the upper window area of an otherwise identically produced slat, the optical and thermal properties of the Venetian blind may be optimized so that the lower blind portion protects from glare while the upper blind portion serves for an improved glare- free day light yield.

The flattenings in the upper window area of the Venetian blinds, in particular, may be provided with additional line-shaped, for instance, v or u shaped, indents substantially extending at right angles to the line screen of the prismatic tooth formation. The light impinging into the indents will then be laterally deflected or reflected as well so that an improved bi-directional room illumination is obtained about the whole width of the interior space. To obtain this, the indent sides are shaped inclined as in a v-shaped indent.

Claims

Claim 1

Venetian blinds to be arranged behind glass windows and fagades comprising an upper blind portion and a lower blind portion and slats which are at least partly toothed at least at the upper side thereof and which have at least partly reflective surfaces in the kind of prismatic reflectors for light guidance, the reflecting prisms being arranged parallel to the lateral edges in the longitudinal direction of the slats, the prisms being shaped with a longer side x-i and a shorter side x₂ so that different angles a and β arise between the catheti and hypotenuses of the prisms and a prism side facing daylight incidence will result as primary reflector, characterized in

that the exterior glazings (32, 33) are used only in the upper blind portion (A) of a window as the secondary reflector for light redirection (34, 35 and 50, 51 ) be- tween the slats back into the interior space, and

in the lower blind portion (B), the light redirection (22, 44, 48, 49) on the exterior glazings (23, 24) back into the interior space is screened off.

Claim 2

Venetian blinds according to claim 1 , characterized in

that within a Venetian blind, the prisms in the upper blind portion are disposed towards daylight incidence with the short side (x₂) thereof, and in the lower blind portion are disposed towards daylight incidence with the long side (x-i) thereof, and

- that in the upper blind portion a short prism side x₂ and in the lower blind portion a long prism side (x-i) is used as primary reflector, and

that the primary daylight receiver faces of the prisms are disposed at steeper angles (β) in the upper blind portion and in more flat angles (a) in the lower blind portion, and that in the upper blind portion, the daylight and sun light reflected in the direction of the exterior space is deflected at a more flat angle (γ-ι) and in the lower blind portion is deflected at a steeper angle (γ₂). Claim 3

Venetian blinds according to claim 1 , characterized in that the slat tilt angles are selected smaller in the upper window area and larger in the lower window area.

Claim 4

Venetian blinds according to claim 1 , characterized in that in the upper blind portion (x-i < x₂) and in the lower blind portion (x₂ > x-i ) is provided.

Claim 5

Venetian blinds according to claim 1 , characterized in that the slat tilt angle is selected larger in the upper window area and smaller in the lower window area.

Claim 6

Venetian blinds according to one or a plurality of the foregoing claims, characterized in that the prisms are provided in partial areas of a slat cross section only.

Claim 7

Venetian blinds according to one or a plurality of the foregoing claims, characterized in that the angles a and/or β of the individual prisms vary within one slat. Claim 8

Venetian blinds according to one or a plurality of the foregoing claims, characterized in that the tips of the prisms (82-84) are flattened and that the flattening serves the light redirection into the interior space (19). Claim 9

Venetian blinds according to claim 8, characterized in that the flattenings in the upper Venetian blind portions are provided at least strip-shaped on the slat side facing the outer space and that the flattenings in the lower Venetian blind portion are provided at least strip-shaped on the slat side facing the interior space.

Claim 10

Venetian blinds according to claim 8 and 9 and a plurality of the foregoing claim, characterized in that the slats have on their upper sides line-shaped v or u shaped indents at right angles to the toothed structure.