VENETIAN BLIND-TYPE SUN PROTECTION DEVICE

Abstract: A sun protection device of the Venetian blind type, comprising a number of spaced apart slats, of which slats the respective longitudinal axes are located substantially in one plane and extend substantially parallel to each other and which slats are of reflective design at least at their top surface, the top surface of each of the slats being of retroreflective design, so that, for any angle of incidence, light incident on that surface is reflected back in the direction of incidence.

Description: Title: Venetian blind-type sun protection device This invention relates to a sun protection device of the Venetian blind type, comprising a number of spaced apart slats, of which slats the respective longitudinal axes are located substantially in one plane and extend substantially parallel to each other, and which slats are provided with a top surface and a bottom surface and are of reflective design at least at their top surface. Such a sun protection device is known from EP 0 303 107. In the sun protection device known from this publication, the slats are concavely curved in upward direction. The top surface of each of the slats is designed as a mirror. What is achieved with such a construction is that a considerable part of incident solar radiation is reflected, so that undesired heat concentration at the sun protection device is prevented. A disadvantage of the known construction, however, is that it may entail nuisance to those living in the neighborhood due to the uncontrollable reflection from the mirror surfaces of the slats. The system may also entail a drawback for the users of the sun protection device, in that its use in a window may involve the slat-reflected light being in turn reflected from the pane in the window, which light, thus reflected twice, may have a disturbing effect in the space screened by the sun protection device. Depending on the angular adjustment of the slats, light reflected directly from the top surface may also be highly objectionable in the inner space. Due to these phenomena, it is not properly possi le to adjust the slats to any random angle. TO 2 574469 describes a sun protection device similar to EP 0 303 107, in which the top surface of the slats is designed as a flat or convex mirror surface. This sun protection device has the same disadvantages as the sun protection device according to EP 0 303 107. Further, US 5 204 777 discloses a sun protection device according to the preamble of claim 1, in which the slats, at the top surface thereof, consist of mirror facets extending in longitudinal direction, with adjacent mirror faces of adjacent mirror facets including an angle of approximately 90° and having a stepped configuration viewed in cross section of the slat. With such a construction, light incident on the top surface is reflected back in a plane through the longitudinal axis of the mirror facet and the direction of incidence, regardless of the adjustment angle of the slats. A disadvantage of this construction is that though the incident light is reflected back in one longitudinal plane defined by the longitudinal axis and the direction of incidence, the direction in which this light exits in this plane, leaving aside the direction of the normal, deviates from the direction in which the light enters. Only when the direction of incidence in the longitudinal plane formed by the direction of incidence and the longitudinal axis corresponds with the normal to the local slat surface is the direction of incidence equal to the direction of exit. As a consequence, in the construction according to US 5 204 777 too, the light reflected back can also entail a nuisance to those living in the neighborhood. DE 197 00 111 describes a similar sun protection device to US 5 204 777, in which the mirror elements extending in the longitudinal direction, in cross section of the slat, have a sawtooth configuration. In this sun protection device too, light incident at an angle with respect to a normal plane extending in transverse direction of the slat exits mirrorwise with respect to the transverse normal plane. In this sun protection device too, the direction in which the light exits in the longitudinal plane defined by the longitudinal axis and the direction of incidence, leaving aside the direction of the normal, deviates from the direction in which the light enters. The light reflected back can therefore entail a nuisance to those living in the neighborhood in a similar manner as in US 5 204 777. The invention contemplates a sun protection device of the type mentioned in the preamble, in which, while maintaining the advantages, the disadvantages mentioned are avoided. The stated object is achieved, according to the invention, with a sun protection device according to claim 1. What is achieved because the top surface of each of the slats is of retroreflective design, such that, for every angle of incidence, light incident on the top surface is reflected back in the direction of incidence, is that incident light, regardless of the direction of incidence, is reflected back to the source, so that any nuisance to the environment is avoided- In this sun protection device, the direction in which the light enters the longitudinal plane defined by the longitudinal axis and the direction of incidence is equal to the direction in which the light exits in the plane, also when it deviates from the perpendicular direction. The slats can have an upright, horizontal or oblique orientation, but preferably have their longitudinal axes extend virtually horizontally. The plane in which the longitudinal axes of the slats are located can be at least partly curved, such as, for instance, a tunnel-shaped plane having a U-shaped cross section. The plane in which the longitudinal axes are located, however, can also be substantially flat, for instance vertical, horizontal or oblique. Preferably, the slats have their longitudinal axes located in a substantially vertical plane. By the use according to the invention of slats having a retroreflective top surface, by which incident light is reflected back to the source, the heat load by solar irradiation is reduced to a still greater extent than in slats having a mirror surface. Also when the slats are only partly opened, a large part of the "upper hemispheric" incident light (sun, blue sky, luminqus clouds) is reflected directly in the direction of incidence. As a consequence, fewer multiple reflections are obtained, which could otherwise give rise to heat generation. The sun protection device according to the invention enables a relatively strong daylight entrance in a non-disturbing manner. The light is transmitted in a selective and metered manne_r. This proceeds inter alia as follows. A large portion of the lower hemispheric light of relatively low luminance, coining from the ground outside, is transmitted directly. This is diffuse light, which, via the sun protection device, ends up especially on the ceiling of a space screened by the sun protection device, adjacent a window in front of which the sun protection device is placed. A part of the light reflected by the slats in the direction of incidence will reflect from the window glass and pass between the slats in the direction of the ceiling. The higher the sun is in the sky, the steeper the direction of the reflected radiation, and the closer to the window the ceiling is lighted. Diffuse light coming from the blue sky or from a cloudy sky is reflected in a similar manner to the sunlight. Such light ends up at approximately the same place as the transmitted ground light. In a suitable embodiment of the sun protection device according to the invention, the top surface of the slats is of retroreflective design through a layer or coating applied thereto, which contains transparent glass or plastic beads. Such retroreflective material is, for instance, the material ScotchJite High Intensity Grade carried by the firm 3M. In another suitable embodiment of the sun protection device according to the invention, the top surface of the slats is of retroreflective design by a layer or coating applied thereto which contains total-reflection prisms. Such retroreflective material is, for instance, the material Scotchlite Diamond Grade VIP carried by the firm 3M. Preferably, in the above embodiments of the sun protection device according to the invention, the layer or coating is in the form of a self- adhesive film or self-adhesive tape. It is to be noted that the use of retroreflective material on slats of a sun protection device is known per se from the above-mentioned European patent 0 303 107. In the sun protection device known from that publication, the underside of the slats is retroreflective. The purpose of that is to screen the workplace from possibly blinding radiation coming from the ground outside the building, without having to take recourse to blackening the underside of the slats. A relatively strong daylight entrance, as described hereinabove for the sun protection device according to the invention, is not possible with slats having retroreflective undersides. In yet another embodiment of the sun protection device according to the invention, there are provided means for modifying the setting angle of each of the slats. Modifying the setting angle can contribute to an optimum screening. Preferably, the setting means are adapted for progressively modifying the setting angle of each of the slates in upward direction. This makes it possible to further optimize screening and light entrance. Suitably, further, the adjusting means can be computer-controlled means which are adapted for automatically controlling the setting angle of each of the slats based on a function of time and/or of the measured luminance. The sun protection device according to the invention with the retroreflective top surfaces of the slats can suitably form part of a sun protection system for an (accommodation) space in a building, in which one or more sun protection devices according to the invention are arranged in a window or windows of the space in question and wherein there is provided an array of directed or d rectable reflectors mounted on or near the ceiling of the space on the side of the sun protection device(s) to direct light transmitted by the sun protection device(s) to the location of the array of reflectors, to a place in the space which it is desired to light additionally. With such a directed reflective optical system, a metered quantity of the "directed sunlight" can be sent to a site of choice, for instance a workplace or to a wall which it is desired to illuminate additionally. The preferred site for such a directed reflective optical system is close to the window in front of which the sun protection device according to the invention is located, since at that point virtually throughout the year, a reasonable amount of light becomes available. The optical system can be integrated with the artificial lighting in the space in question, including a control system for metering the necessary amount of supplemental artificial light. The invention is elucidated with reference to the drawing, in which the single figure is a schematic representation of a sun protection device according to the invention included in a sun protection system. In the figure, a sun protection device 1 of the Venetian blind type is represented in cross section. The sun protection device 1 comprises a number of elongate slats 2. The longitudinal axes of the spaced apart slats 2 extend in horizontal direction, are parallel to each other and are located in a vertical plane. The sun protection device 1 comprises the conventional means (not shown) for varying the setting angle of the slats 2. Preferably, there are provided means for changing the setting angle of the slats progressively in upward direction. Thus, optimum screening and optimum entrance of light can be achieved. The sun protection device 1 is arranged along a pane 3 of a window in a space to be screened. Light from the free space outside the building, in which the space to be screened is present, falls onto the top surface (window side) of the slats 2. According to the invention, those slats 2, at least on the top surface or window side, are retroreflective in that those slats 2 on that side consist of retroreflective material. That material can be provided on the slats 2 as a layer. Preferably, such a layer is in the form of a self-adhesive film or a self-adhesive band or tape. Retroreflective material is material that reflects incident light, regardless of the angle of incidence, for the most part back to the light source. Such material can be a material based on transparent glass or plastic beads, for instance as marketed by 3M under the name of Scotchlite High Intensity Grade. Such material can also be a material based on total- reflection prisms, for instance as marketed by 3M under the name of Scotchlite Diamond Grade VIP. Such genuine retroreflective material, when applied to the top surface of the slats 2, has the advantage that the surroundings are not hindered by reflected light from, for instance, the sun, since the sunlight is exclusively reflected back in the direction of the sun. By retroreflection to the source itself, the heat load by solar radiation is reduced. Also when the slats 2 are partly opened, a large part of the "upper hemispheric" incident light (sun, blue sky or luminous clouds) is reflected in the plane of the direction of incidence or in the direction of incidence itself. The sun protection device according to the invention affords the possibility of a relatively strong daylight admission in a non-disturbing manner. The light is transmitted in a selective and metered manner. This proceeds in different ways, as follows. A large part of the low-luminance lower hemispheric light coming from the ground 4 of the space outside the space to be screened is transmitted directly by the sun protection device 1, in that it can pass between the slats 2, as indicated by arrows 5 and 6 enclosing an angle γ. The luminance of ground or lawn can actually be more than 5,000 cd m 2 . The transmitted light is diffuse light ending up substantially on the ceiling 7 in the vicinity of the window 3. Direct solar radiation is reflected by the slats 2 in the direction of the sun, as indicated by the double-headed arrow 8. A part of the reflected light will in turn be reflected from the window 3 in the direction of the ceiling 7. This is indicated by the arrow 9. This directed component of the direct solar radiation reflected from the pane glass towards the ceiling can account for 5 to 8% of the total solar radiation. The higher the sun is in the sky, the steeper the angle at which this directed component enters the space to be screened and the closer to the window 3 the ceiling 7 is illuminated thereby. The light travels as a homogeneous parallel beam and thus causes a homogeneous luminance of the ceiling 7 over the entire irradiated surface. This makes it possible to use an additional optical system, consisting of a series of reflectors 10 mounted on the ceiling 7 adjacent the window 3. By means of this additional system on the ceiling 7, a metered amount of the "directed sunlight" can be sent either to a workplace or deeper into the space to be screened, or to a wall which it is desired to illuminate additionally. Those skilled in the art will know how to design the reflectors and will be familiar with means to make such reflectors movable and adjustable. The additional optical system can, if desired, be integrated with the artificial lighting of the space to be screened and be coupled with a control system to meter the needed amount of supplemental artificial light- Diffuse light coming from the blue or cloudy sky (having a luminance of sometimes more than 10,000 cd m 2 ) is reflected, for each small area of the sky, in the same way as the sunlight, albeit that, obviously, a smaller amount of light is involved. For a small part, this diffuse light, after retro-reflection from the slats 2, is likewise reflected by the window 3 and, after passing between the slats 2, reaches approximately the same position on the ceiling as the "transmitted ground light". Investigation has revealed that if the sky is cloudy, this "reflected sky light" still amounts to about 50% of the "transmitted ground light". It may therefore be acceptable in some cases to use the sun protection according to the invention on the northern or western side of a building as well, for instance there where the luminance of the sky is too high for proper use of displays. It is noted that the retroreflective surface on the slats can be alternated with a non-retroreflective or less strongly retroreflective surface, so that a pattern, such as a logo, can be formed. Such a pattern can be visible at night when, for instance, lights of oncoming traffic shine upon the sun protection. A pattern may also be formed by setting the slats of some sun protection devices of a building in a non-reflecting position, by means of a control, while other sun protection devices are set in a reflecting position, for instance by angular displacement and or raising or lowering the slats. It is noted that the invention is not limited to the exemplary embodiments described here, but that many variants are possible. Such variants will be clear to those skilled in the art and are understood to fall within the scope of the invention as set forth in the following claims.

Claims: Claims 1. A sun protection device of the Venetian blind type, comprising a number of spaced apart slats, of which slats the respective longitudinal axes are located substantially in one plane and extend substantially parallel to each other and which slats axe provided with a top surface and a bottom surface and are of reflective design at least at their top surface, characterized in that the top surface of each of the slats is of retroreflective design, so that light incident on that surface, regardless of the angle of incidence, is for the most part reflected back in the direction of ncidence. 2. A sun protection device according to claim 1, characterized in that the respective longitudinal axes of the slats are located substantially in a vertical plane and extend virtually horizontally and substantially parallel to each other. 3. A sun protection device according to claim 1 or 2, characterized in that the top surface of the slats is of retroreflective design through a layer or coating applied thereto, which contains transparent glass or plastic beads. 4. A sun protection device according to claim 1 or 2, characterized in that the top surface of the slats is of retroreflective design through a layer or coating applied thereto, which contains total-reflection prisms. 5. A sun protection device according to claim 3 or 4, characterized in that the layer or coating is in the form of a self-adhesive film or self- adhesive tape. 6. A sun protection device according to any one of claims 1-5, characterized in that the sun protection device comprises means for modifying the setting angle of each of the slats. 7. A sun protection device according to claim 6, characterized in that the adjusting means axe arranged for modifying the setting angle of each of the slats progressively in vertical direction. 8. A sun protection device according to any one of claims 6-7, characterized in that the adjusting means axe computer-controlled means which are arranged for automatically controlling the setting angle of each of the slats as a function of the time and/or the measured luminance. 9. A sun protection system for an (accommodation) space in a building, characterized by one or more sun protection devices according to any one of claims 1-8, which sun protection devioe(s) is or are arranged along a window in a window frame or window frames of the space in question and by an array of directed or directable reflectors mounted on or near the ceiling of the space on the side of the sun protection device(s) for directing light reflected by the sun protection device(s) via the window to the place of the array of reflectors, to a place in said space which it is desired to illuminate additionally.

Inventors: TAEYMANS FRANCISCUS ALPHONSUS, TAEYMANS, FRANCISCUS, ALPHONSUS, MARIA
Applicants: ETAP NV, TAEYMANS FRANCISCUS ALPHONSUS, ETAP N.V., TAEYMANS, FRANCISCUS, ALPHONSUS, MARIA
Application year: 2000
Main classification: E06B9
IPC codes: E06B9