Patent Description:
It has been known from <CIT> and <CIT> to form slats in fold-shape while the folds are worked-in either by embossing only into the upper side, or the slats are shaped out, at least partly, in large folds. It is of disadvantage that these slats are rigid and can no longer be wound on a coil for further processing. The folds will either deform or the slats will twist without springing back to their straight original position. Wound-up slats, in particular, might crease, i.e. they might for instance deform plastically so that the light guiding properties might be impaired. Louvers in <FIG> in <CIT> with prisms on their upper and their lower side with very small prisms as explained in connection with <FIG> cannot be produced. The slat material will only form out without sharp edges. In case of a softer base material like pure aluminium the base material will be cut into small strips by the edges of the prism shaped tools. Trying to find a compromise in the hardness of the material one faces the problem that the louvers will never spring back into their original position after bending.

From patent documents <CIT>, <CIT>, it has been known to produce Venetian blinds from slats with prism contours which include partly a first portion oriented to a sun light irradiation side, and a second portion oriented towards the interior space. The Venetian blinds slats are provided, at least partly with longitudinal grooves having prism-shaped reflective surfaces. The sun side Ks of the prismatic mirrors is oriented towards the sun irradiation and a shadow side K to the interior space. The Venetian blinds slats are arched out concavely/convexly. In particular, document <CIT> discloses a light guiding slat for a sun protection system, wherein the light guiding slat is made of a band material, has an elongated form with a longitudinal direction, a cross section and an elevation height setting and is provided for the formation of a Fresnel reflector for light guidance with a plurality of folds, wherein the folds are substantially made by folding and/or bending of the band material, wherein at least two neighbouring fold sides are folded relative to each other and a fold edge extends between these fold sides in longitudinal direction of the light guiding slat, wherein the light guiding slat has a width, wherein the total shape of the light guiding slat, wherein the light guiding slat has a width, wherein the total shape of the light guiding slat is concavely or convexly arched in cross direction, wherein the light guiding slat has a total height which is composed of the height through the concave/convex arching of the total form and of the height of the folds, wherein the height of the folds results, depending on the shape of the slat, from the distance of parallel straight lines or parallel curves passing through the tips of the folds.

In <CIT>, in Fig. 17a, a light deflection of an edged horizontally disposed slat is shown, as a problem, which back-reflects, and focuses, the incident light into the irradiation cross section while not defining the slat contour to obtain focussing and glare freedom in an outer glazing. Neither are the slats, as would be common, curve-shaped in cross section but rather s-shaped or edged, and are not, therefore, suited to be processed on existing Venetian blinds automats for the production of concave-convexly shaped slats.

A general objective for light-directing Venetian blinds systems consists in that in case of a possibly open Venetian blind, i.e. most possible flat slat angle of incidence, the direct sun be deflected and, at the same time, as a consequence of the flat slat position, a very good view-through is obtained and, additionally, make furthermore possible an increased diffuse light entry for improved interior space daylight illumination. The Venetian blinds systems and the slat mirrors should, moreover, be glare-free for the user of the interior space.

In order to reach this goal, the prior art has developed slat contours with Fresnel optics. In <CIT>, slats are shown having a structural mirror upper side and a smooth or a stepped slat under side. In <FIG> and <FIG>, the slats are shown for different angles of incidence. From the reflection, it becomes apparent that this constitutes Fresnel optics having a focus in the area of the front sun longitudinal edge of the slat positioned towards irradiation incidence. In order to avoid glare in the glass panes, the focus is disposed, in <CIT>, so that a critical angle αs (<FIG>) is not exceeded. To this end, the slats follow the angular height of the sun.

The disadvantage of the Fresnel structure according to <FIG> and <FIG> of <CIT> consists in that the slats have to be disposed in a tilted position at an angle of incidence of <NUM>° already which causes that the view-through between the slate and the light entry is reduced. A further disadvantage is that at an angle of incidence of > <NUM>° in <FIG> even in a tilted slat position already a second reflection on the under side of the slats will occur. An additional disadvantage is seen in that, as a consequence of the concentrated impact of reflected radiation, the under sides might flash up which leads to extreme glare.

In <FIG> and <FIG> of <CIT>, light guiding slats are shown having prisms which a cathetus inclination of <NUM>°/<NUM>° relative to the hypotenuse, wherein the flat-pitched longer <NUM>° catheti are oriented to the incidence of the sun and the <NUM>° catheti are oriented towards the interior space (see also <FIG>). In case of a horizontal slat position, these prism-structured slats will not yield mono-reflectivity before an angle of incidence γ > <NUM>° is reached. The maximum height of the sun on the <NUM>th degree of latitude is <NUM>°. According to the present state of the art, pendulum reflections will come up between the slats in the case of horizontal slat position, notwithstanding the prism structuring, which produce avoidable heating up. Good high-purity aluminium reflectors having anodized surfaces will reach <NUM>% total reflection, <NUM>% of the radiation will be absorbed. When pendulum reflection occurs between the slats, the absorption of the inciding light rays will increase after <NUM> reflections already to about <NUM>%, in case of <NUM> reflections to more than <NUM>%. In case of an irradiation of <NUM>/watts/m<NUM>, this will correspond to a heat absorption of <NUM> watts/m<NUM>. To avoid such high energy absorption in the case of open slat position and summery high sun incidence, is the aim of the present innovation as demonstrated in <FIG>.

<FIG> shows an enlarged representation of the slats of <FIG> and <FIG> of <CIT>. In <FIG>and <FIG>. as well as in the further figures, the radiation patterns on the slats according to <FIG> are shown. <FIG> shows the radiation incidence onto a horizontally arranged slat at an angle γ = <NUM>° and a desired view-through D between the slats of D/a ~ <NUM>%. In <FIG>, the back-reflection from <FIG> into the outer space is shown. A focus F is obtained in the outer space. In <FIG>, a sun incidence γ = <NUM>° is shown. In <FIG>, the back-reflection is deflected to the under side of the upper slat. From this slat under side, the light is back-reflected, in the case of a mirror coating of the under side according to <FIG>, to the bottom plane in the outer space. Therefore, at the summery angle of incidence γ = <NUM>° already, two reflections are required to deflect the sun with the Venetian blinds opened. <FIG> show a light incidence γ = <NUM>° onto the slat of <FIG>. In <FIG>, the light deflection to the under side of the upper slat, in <FIG> the back-reflection onto the underside of the lower slat, and in <FIG> the back reflection into the outer space is shown. In the present case, therefore, at least <NUM> reflections are required to deflect the sun. Counterproductive overheating of the window area should, therefore, be expected.

Fold-shaped slats as shown in <FIG> of ED<CIT> cannot with a view to the large steps be coiled up without deforming the folds and bending the slats.

In <FIG> and <FIG> of <CIT>, slats having extremely different cross-sectional thicknesses are shown. The disadvantage of such slats is that they cannot be produced from a ready-manufactured surface-treated band material but rather only as extruded slats with the disadvantage of subsequent surface treatment. A further disadvantage is that the ready and extruded slats cannot be wound up on coils and be stored at the premises of the subsequent processing plant. The slats can only be further processed when cut in a costly way to pieces of desired lengths. In this case, too, particularly in connection with <FIG>, glare might come up on the under side of the slats. Further disadvantage is that the louvers in case of bending in their length will stay deformed.

The object of the invention is to indicate a folded slat that can be coiled in order to facilitate transport and flexibility of subsequent processing.

The object of the invention is solved by the features of claim <NUM>.

The radius of <NUM> might be required for particularly sensitive slats having a low flow limit, for instance those made of soft highly reflective aluminium. A typical radius of a coil has a maximum of <NUM> so that a slat suited for such bending radius can at least be coiled, in a thin layer, onto such a coil to be transported or stored. Typically, however, the coiling core of such coils has a substantially smaller diameter so that it is preferred that the slat having a radius of <NUM>, particularly preferred of <NUM> or <NUM>, may be coiled up. A coil may then be covered with a lot of slat material up to a non-critical maximum diameter. If a slat is wound onto a too-low coiling radius, it will deform which means that after decoiling, bending of the slat remains and/or the slat crumples, for instance at the sides of the folds. Since many materials show a small plastic hysteresis at elastic deformation, an unavoidable small plastic deformation may remain even in case of a permissible coiling radius. In particular, no crumpling will occur. Slats to be coiled up having such plastic deformations fall within the scope of the invention as defined in claim <NUM> as well, which is meant by the wording "without any substantial plastic deformation" in claim <NUM>. The same applies for plastic deformations by creeping behaviour of materials over a long period of time. The bending radius without any substantial plastic deformation depends on the material strength, the modulus of elasticity and the total height of the light guiding slat in the radial direction of the bend. Thicker slats are stressed already at less bending, i.e. at larger bending radii so that they may more easily be plastically deformed. The total height of the slat may in this way adjusted to the bending radius to be reached and to the flow limit to render them better coilable. The total height is composed of the height through the concave/convex arching of the total form and of the height of the folds. The height of the folds results, depending on the shape of the slat, from the distance of parallel straight lines or parallel curves passing through the tips of the folds. The thickness of the band material will not substantially change by deforming it into fold shape so that on the upper side and on the under side of the light guiding slat the same contour can be seen.

A reflector in the meaning of the present application need not have the optimum reflection like a mirror. By horizontal slat position, a concave, convex or plane slat is to be understood the end points of which are substantially on a horizontal.

The folds are substantially produced, according to the invention, by folding and/or bending the band material.

As typical embodiments, slats or slat geometries or a sun protection system is suggested which fulfils at least one, or a combination, of the following requirements or includes the following features:
The cross section of the light guiding slat, in cross direction, a plurality of, or all, fold edges on the upper side and a plurality of, or all, fold edges on the under side are disposed each on one of two assumed parallel straight lines or parallel curves, two parallel lines and/or two parallel curves are each spaced from each other at a distance of less than <NUM>, preferably of less than <NUM>. This leads to a smaller thickness of the slat which is in many cases well suited for coiling up.

The light guiding slat is made of a band material having a base material thickness of <NUM> to <NUM>, preferably a base material thickness of <NUM> to <NUM>.

<FIG> shows the perspective of the micro folding of a typical slat having a width of <NUM>, in multiple enlargement. This slat corresponds to the contour of <FIG>.

While the slats become stiffer by micro folding, an absolutely desired effect though, they do not deform when they are wound onto a large core. By using a hard-base material having an elastic limit R > <NUM> N/mm<NUM>, preferably R > <NUM> N/mm<NUM>, the slat remains flexible. Although the band will be strained by the fold formation and material thickness change will occur, the slat may receive a ready surface prior to the forming-in. Varnishes even anodized surfaces and PVD layers will undergo micro folding without being destroyed.

A further advantage of micro folding is the slenderness and the little total height h of the slats and hence an improved view-through D. In view of the thin base material, glares will no longer occur on the slat edges either.

Another advantage is the possibility of use for processing an annealed soft band material that can easily be moulded and will obtain its final hardness by straining caused by micro deformation. Within one pass in the roller or embossing tool, a material strain of about <NUM>% takes place, which leads to an extreme hardness. Caused by the micro folding, the softer base material will first start flowing during one single pass in the tool whereby easy deformability and after the glow a great final hardness will be obtained. Particularly advantageously, soft annealed base materials are used which will obtain in the final hardening an elastic limit of > <NUM> up to <NUM> N/mm<NUM>, even <NUM> up to <NUM> N/mm<NUM>, and hence elastic properties with sufficient resetting ability.

The advantage of the invention can also be seen in the ease of fabrication of the slat contours from very thin band material of metallic material such as aluminium, high-quality steel, brass or from plastic materials or plastic foils and the further processing off the coil as in the case of common Venetian blinds.

Of preference is elastic material of minimum material thickness. This will be assured by using band material having a thickness of < <NUM>, preferably <NUM> to <NUM>, and a fold height of d < <NUM>, preferably d < <NUM>. Folds having small dimensions as compared to the dimensions of the slat are preferably provided for the slat.

In one embodiment, folds, or sun sides βn are shaped so that the primary reflection for angles of incidence < angle αS of the shadow line S constitutes the only reflection while up to an angle of incidence γ = <NUM>° no pendulum reflections between the slats will occur. With a view to the given objectives and for any optional distance of the slats from one another, the correct mirror prism or fold contour may be found, particularly for a horizontal slat position in order to simultaneously realize a largest possible view-through D and, in spite of shadowing, high daylight entry. By the folding of the under sides, moreover, de-glaring can be obtained in that the under sides are only partly visible in view of the foldings and reflected radiation is primarily guided into the upper sides of the lower slats and therefrom back to the outer space from which the sun irradiation emanates <FIG>).

The sun sides Ks have preferably, in case of a horizontal slat position relative to the horizontal, an angle β<NUM> in an irradiation area E and a larger angle β<NUM> towards the interior space I. Valid is β<NUM> < β<NUM>. The light guiding slats have a width b und a distance a relative to each other so that between the light guiding slats a horizontal view-through D results. Between an upper slat edge in irradiation area E and a lower slat edge towards the interior space I, a shadow line S at an angle αs relative to the vertical V is formed.

The angle of shadow line αs relative to the glazing plane may be obtained from a connecting line between the edge of an upper slat facing the sun irradiation side and the edge of the lower slat facing the interior space.

In an embodiment of the light guiding slat, the complete upper side of the light guiding slat is covered by folds. In this way, the upper side is used at optimum for light directing.

The total shape of the light guiding slat is concavely or convexly arched in cross direction, and the arching height of the concave or convex arc is less than <NUM>/<NUM> and more than <NUM>/<NUM>, preferably <NUM>/<NUM> of o slat width.

In a further embodiment of the light guiding slat, its upper side and/or its under side has, at least partly, a metallic glaze wherein at least one of the fold edges of the folds or between two folds deglazing is provided by means of a varnish cover, in particular also portions of a sun side and/or shadow side of one of these folds, wherein these parts are adjacent, particularly to the fold edge.

In a further embodiment of the invention, a light guiding slat is suggested where at least part of the fold contours, particularly all fold contours, are symmetrically formed in a cross section in cross direction of the light guiding slat about a middle axis (y) so that the contour of the light guiding slat in the cross section, at least partly and particularly completely, is composed of two mirror-inverted slat cross sectional parts (<NUM>, <NUM>).

In a further development, a plurality of shadow sides (K), particularly all shadow sides (K), are formed by reflection at a mirror plane at least approximately proceeding in elevation height setting of the light guiding slat and through the centre of the light guiding slat in cross direction, at least partly mirror-inverted to sun sides (Ks). Properties of the slat are, therefore, contained in two opposite irradiation directions. The shadow sides (K), sections of a fragmented shadow side parabolic groove in the kind of a Fresnel reflector and the sun sides (Ks) preferably form sections of a fragmented sun side parabolic groove in the kind of a Fresnel reflector, wherein the shadow side parabolic groove and the sun side parabolic groove intersperse each other section-wisely. This makes two focussing systems possible on the same upper side of a slat. The shadow side parabolic groove, a shadow side focussing zone (F<NUM>) and the sun side parabolic groove have a sun side focussing zone (F<NUM>) each disposed, at least approximately, in an assumed plane each, which for the shadow side parabolic groove extends from the sun longitudinal edge and for the sun side parabolic groove from the shadow longitudinal edge in elevation height setting each, wherein a parabola axis (x<NUM>) of the shadow side parabolic groove extends, at least approximately, through the sun longitudinal edge of the light guiding slat and the shadow side focussing zone (F<NUM>), and a parabola axis (x<NUM>) of the sun side parabolic groove extends, at least approximately, through the shadow longitudinal edge of the light guiding slat and the sun side focussing zone (F<NUM>). This orientation of the parabolic grooves is particularly advantageous in connection with the light directing properties of the slats. The light directing properties of the light guiding slats remain after a rotation of the light guiding slat about <NUM>° about an axis in its elevation height setting preferably the same, at least approximately. The slat can, therefore, be further processed without any regard to the direction of the installation.

A further aspect of the invention relates to a sun protection system with a slat according to one of the aforementioned embodiments. In one embodiment of the sun protection system, the distance between the light guiding slats is about the same as the distance between a focussing zone and that of one of the longitudinal edges of the light guiding slat. The position of the focussing zone results from the irradiation in the direction of the shadow line. Light from the lower slat will not, in view of the concentration in the focussing zone, fall onto the under side of the following upper slat if a steeper irradiation direction than the direction of the shadow line causes that die focussing zone moves away from the slat. In this way, one single reflection is sufficient to guide inciding sun light away from the sun protection system and from an interior space to be protected. In case of a more flat irradiation, the focussing zone may move to the under side of the upper slat so that sun radiation reflected on the lower slat into the focusing zone is further reflected, in a section reflection on the under side of the upper slat, into an outer space on an irradiation side of the sun protection system. In order to obtain the effects referred to, a Fresnel reflector may be provided on the upper side of the slats with a suitable alignment which effects the positioning referred to. of the focussing zone. If between the outer space and the sun protection system a glazing is arranged, no reflection will, preferably at least approximately, occur on the glazing visible from the interior space to be protected. This may be obtained by a suitable provision of the under side of the upper slat and a suitable design of the Fresnel reflector.

A further aspect of the invention relates to methods for the manufacture of the light guiding slats. In one embodiment of the method for the manufacture it is suggested to produce the variants of geometry of an upper side of the light guiding slat as defined in the claims and/or the specification by embossing the slat upper sides, particularly by roller stamping moulds, wherein the under side is not embossed and preferably remains smooth, to which end the under side may be treated on a non-embossing roller. Embossing may require a greater material thickness than the folded variants and/or a soft starting material. Slats produced in that way may be employed in a sun protection system as defined in the claims and/or the specification or may be used for a sun protection system according to the application claims. The method for the manufacture may be used for the production of all embodiments of light guiding slats and particularly for the production of the geometries of light guiding slats as described in the specification and/or the claims, wherein the process feature possibly suggested for one embodiment or geometry, i.e. that folds have to be made in the upper side by bending, folding or tilting, and/or that the band material after remoulding has a substantially uniform thickness, need not necessarily be applied. However, a concave/convex total shape of the light guiding slat might for instance be produced by bending, embossing, particularly roll-embossing, during the folding.

In a further aspect of the invention, the use of light guiding slats is suggested. By the use of light guiding slats of identical type in various areas of a sun protection system with different functions, advantages in connection with the costs and higher quality safety in the production of the sun protection system will result.

The figures show exemplary embodiments of the present invention. The figures show.

In <FIG> the construction specifications for a horizontal operation position of the curves are defined. In the present case, the ratio of slat distance a to slat width b is a/b ~ <NUM>. However, this ratio may optionally e selected. For an optional ratio a/b, the inclination β of the sun-irradiated fold sides Ks. in the area of the slat edges to the horizontal will be explained in the following.

Valid for the horizontal position is α'S = <NUM>° - αS. αS is the inclination of the shadow line S relative to the vertical V or the vertical glazing of a façade to which a sun protection system has been applied in which the slats are arranged. For the inclinations β of the sun sides Ks in the area of the slat edges relative to the internal space I; the following standard is valid <MAT> <MAT>.

β<NUM> is the angle of incidence of the sun side Ks relative to the irradiation side near the irradiation area E. β<NUM> is the angle of incidence of the sun side K near the interior space I. βn are the angles of incidence of any optional sun sides Ks within the slat cross section. βm is the angle of incidence in the centre of the slat. The fold sides Ks may be disposed before other reflectors of different optics (see <FIG>) or after them (see <FIG>). Reflectors of different optics, for instance light guidance elements with opposed light guidance (<FIG>), may be arranged within the slat cross section as well. However, curtains having slats are also conceivable which do not have an angle β<NUM> in the irradiation area nor an angle β<NUM> towards the interior space because it is primarily the plurality of the fold angles βn between β<NUM> and β<NUM> which counts. Preferably, the fold angles βn are between β<NUM> and β<NUM>.

In <FIG>, the sun sides Ks are positioned in a continuous rhythm in a steeper position between β<NUM> and β<NUM>. As an angular rhythm, the following may for instance be valid <MAT>.

n is the number of folds between the folds in the irradiation area E and the interior space I behind the façade. The positioning of the folds is realized on a concave/convexly curved contour. The concave/convex arching is determined according to the requirements of stiffness/moment of resistance of the slat prior to starting the construction by the height h and amounts in the present case for instance to h ~ <NUM>/<NUM> to <NUM>/<NUM> of the slat width b. The slats may concavely be arched downward or convexly upward. The folds are preferably shaped as micro folds having edge lengths of from < <NUM> to <NUM> and smaller edge lengths or also larger edge lengths. As explained in <FIG>, this may either refer to a plurality of parallel folds or to only a few, for instance <NUM> or <NUM>, folds in case of very narrow slats having a width of from <NUM> to <NUM>.

The formation of angles β<NUM> = αS/<NUM> and β<NUM> = αS need not be precise. Alone by manufacturing tolerances, small different angles might be obtained. Deviations of ± <NUM>° do in fact ameliorate effectiveness and functionality of mirror systems - even minimum glares might come up in case of back reflection in the outer glazing. Minimum roundings off will come up in the production of the tips of the folds. The point of the present innovation is to find out the desired values for the tool manufacture. With a view to tolerances, focussing zones might also come up as shown, as an example in <FIG> and other figures. Sun incidence of > <NUM>° may be reflected at an angle < αs in the glazing and might lead to minimum glare in it. In countries having low sun altitudes, this would be insignificant. It is recommended to realize a glare freedom of minimum <NUM>° angle of incidence. With a view to the reflection on the outer glazing, sun incidence of > <NUM>° can substantially be neglected. For the angles β<NUM> and β<NUM> defined in the present case, however, the construction is glare-free for all angles up to a light incidence of <NUM>°.

Of no problem for avoiding any glare is β<NUM> < αS.

If the ratio of a to be changes, the rule <MAT> may continue to be used.

As an alternative to the continuous increase of the angles β<NUM> relative to β<NUM>, an irregular increase/decrease may be selected as shown in the second portion of <FIG>. In this case, the angles βn of the sun-irradiated fold side Ks and the angle of the shadowed fold side K in partial zone (<NUM>) to the irradiation cross section were determined as βn <NUM>°, in partial zone (<NUM>) to the interior space as <NUM>° each. Of advantage is a right angle between K and Ks so that in case of double reflections between K and Ks back reflection in the elevation angle of sun irradiation is obtained.

The shaping of the slats is not only restricted to the concave/convex arching. The slat may additionally also be edged so that in the cross section slat parts will result by which an irregular adjustment to the required angle Ks occurs (<FIG>). Not only the slat itself may be arched concave/convexly, so may the edges of the folds as well. Particularly in case of larger folds, it is recommended to arch the fold sides concavely.

In <FIG>, β<NUM> = <NUM>° and β<NUM> = <NUM>°. These data on the angles may be particularly advantageous for the ratio a/b ~ <NUM>. The optical effects of the slat constructions can be taken, as examples, based on the ray tracing in <FIG>. The light radiation back-directed into the glazing V and reflected to the interior space impinges exclusively onto the under side of the upper slat without falling into the observer's eye in the interior space or causing any glare.

<FIG> shows the sun irradiation parallel to the shadow line αs = <NUM>°. In case of light incidence parallel to the shadow line, no glare will occur by the back-reflection reflected by glazing V. All reflections in the glass will exclusively impinge upon the under side of the upper slat since no ray > αs will be reflected.

<FIG> shows the ray tracing for high summer sun at an angle of <NUM>°. No reflected ray exceeds angle αS. In this way again it is ensured that the reflections will impinge solely upon the under side of the upper slat while no glares will occur.

In addition to the process for determining the fold shaping in relation to the arching and the distance of the slats from one another, a further process for determining the formation of the angles β is suggested in <FIG>:
A parabola axis x is put into shadow line S. Focus F is put onto the under side of an open slat in the irradiation area E and may with a view to the tolerances referred to in the beginning form a focussing zone which is shown, as an example, as a dotted circular surface. The focussing zone is preferably as small as possible, which becomes possible by a most precise generation of the geometry of the slat and/or by using thinnest band material. A parabola point PP is put into the starting point of a lower slat in a sun protection system having a plurality of slats arranged in parallel relative to each other and one above the other on the sun irradiation side E. The tangent inclination β<NUM> is αS/<NUM>. The zero point of the parabola has the tangent inclination αs. The parabola P with the parabola axis X in the inclination angle αs of the shadow line S is fragmented and the individual fragments are shifted in parallel up to the desired slat contour. All fold sides Ks should depending on the production quality be in most exact alignment with a point of impact T.

Even if the sun side Ks of the first fold in angle β<NUM> or the last fold in angle β<NUM> do not exist since the slat includes further functional portions (see <FIG> or <FIG>), the construction according to the invention at angle βn with parabola axis X in coincidence with shadow line S remains, nonetheless, valid.

In <FIG>, the slat of <FIG> is shown having partly flattened fold or prism tips in a partial zone (<NUM>) oriented toward the interior space I. By the flattening, a superposition of the fold structure by a second light guiding system occurs by which the radiation impinging onto the flattening is deflected into an opposite direction, i.e. towards the inside. In the lower window area of a window between the interior space I and a sun protection system with the slats, the flattening is advantageously directed toward the interior space I, in the upper window area or the sky light area of the window, however, towards the irradiation area so that in the sky light area steeply inciding radiation can be deflected into the room depth. The light deflection at the flattened fold tips in the lower window area is shown by the inciding ray bundle <NUM> and the deflected ray bundle <NUM>. In the sky light area, the same slat type from <FIG> is installed rotated about <NUM>° about a vertical axis.

In order to explain the advantage of the present invention under energetic points of view as compared to the prior art, diagrams are shown in <FIG>. On the abscissa, the sun incidence angles are shown with relation to the vertical. On the ordinate the total energy transmission g or the proportionate absorption in % is depicted. The following characteristics are shown:
Characteristic <NUM> shows the total energy transmission g of a light guiding slat in combination with a single-pane glazing with <NUM> % total reflection of the anodized aluminium surface as in accordance with the state of the art of <FIG>, <FIG>. Characteristic <NUM> shows the total energy transmission g of an innovative light guiding slat according to <FIG>, <FIG>. The dashed area between line <NUM> and line <NUM> shows the reduced total energy transmission g or the significantly improved reduction of the energy input in view of the optimized innovative shaping of the slats which effects a smaller summery heating up because of the mono-reflectivity or effects that the pendulum reflections between the slats are avoided.

The absorption on the slat according to <FIG> is shown by dashed line <NUM>; the absorption on the slat of the invention of <FIG> is shown by line <NUM>. The marked area between line <NUM> and <NUM> in <FIG> shows the increased absorption in view of the multi-reflectivity of the prior art and the significantly improved sun and heat protection of the slat of the invention in case of summery angles of incidence of a sun incidence starting from <NUM>°.

Line <NUM> shows the direct transmission between the slats in case of horizontal slat position. It is identical for both slats since the identical ratio of slat width b to slat distance a and the horizontal slat position was selected.

<FIG> shows the variant of a folded slat having a convex slat upper side and a concave slat under side. In this case, the construction rules are valid as for instance explained in connection with <FIG> in that the convex upper side of the Fresnel mirror is either shaped in or bossed in. Here, a ray bundle <NUM> is shown at an angle γ = <NUM>° - αS = α'S and the primary reflections <NUM>. The optical behaviour of the slat corresponds to that of the concave/convex slat of <FIG>, <FIG>. The catheti of the fold Ks ideally intersect again a point of impact T<NUM> by which a further construction principle of the slats is described.

The construction methods referred to above are defined on the base of a horizontal operational position of the slats. The embodiments of the slats are not, however, restricted to a horizontal operational position of the curtain. To be able to look from the work place at the window to a street at a lower level, a slat tipping angle of <NUM>° to <NUM>° to the outside might be considered as an optimum. In this case, the same construction methods might be applied to a tilted slat. Because of the horizontal plane disposed obliquely relative to the surface of the slat, a deviating geometry of the slat upper side will result with substantially the same effect. The folds are arranged twisted relative to the slats for horizontal standard alignment and have different side lengths. The innovation is not, therefore, restricted to the horizontal position of the slats although this position is shown as particularly advantageous.

<FIG>, on the other side, shows the total energy transmission g in % of the slat system/Venetian blinds as a function of the angle of incidence of the sun behind a one-pane glazing. Curve <NUM> (<NUM>) of the slat of <FIG> is considered the state of the art. Curve <NUM> shows the optimized slat of <FIG> and <FIG>. The hatched area <NUM> shows the reduced g value while the edge conditions are the same. The g value of the slat of <FIG> is dashed in curve <NUM> (see also <NUM> in <FIG>). This shows clearly the optimization process of the constructions. The improved g values between the slats according to <FIG> and <FIG>, as compared to the state of the art of <FIG>, result from reduced secondary reflections between the folds or the primary sides and from less reflections onto the under sides of the upper slats (ping-pong effect), particularly in case of flatter angles of incidence.

<FIG> shows a detail of the fold of the slat section of the slat of <FIG> and <FIG>. Here, it is demonstrated that the individual folds become larger towards the edges and smaller towards the centre. The sun sides Ks <NUM> to <NUM> become smaller from the edges toward the centre as well.

<FIG> shows a slat which follows the construction method of <FIG> which, however, has an advantage over the slats of <FIG>, <FIG>, <FIG>. The latter have an unsymmetrical slat cross section. In practice and in view of the similarity of the slat halves, the natural eye cannot recognize which slat edge is to be oriented to the outside and which slat edge to the inside. In practice, it might happen that the slats are incorrectly fitted in a sun protection system fitted. To avoid such fitting-in error in the curtain, the slat of <FIG> is suggested which is characterized by a symmetrical construction of the two slat halves <NUM> and <NUM>, wherein the slat halves are reflected on symmetry axis y. Such symmetrical contour also simplifies the rolling process and avoids the undesired "Camber effect", i.e. a side distortion of the slats. The reflected fold or prism flanks to the fold flanks which, as shadow sides K of the folds are in the shadow on the slat half oriented to the direction of the irradiation side, are now, as sun sides K of the folds on the slat half <NUM> on the other side in cross direction of the slat exposed to the sun and follow as to their inclination angles also in symmetry the logic of the fragmented parabola.

According to <FIG>, the construction is performed following the following rule: The construction of parabola P<NUM> is reflected at the central axis y. Parabola P<NUM> results to which belongs a focussing zone F<NUM> at the final point of the upper slat toward the interior space. In this way, the shadow sides K have the geometry of a spatially displaced fragmented parabola P<NUM>.

As the starting material of the slats described with reference to the figures, a flat band may be used having a thickness of from <NUM> to <NUM> which, advantageously, is already provided with a ready metallised or good reflective surface. A typical total thickness d of slats up to a width of <NUM> measured from fold tip to fold tip amounts to about <NUM> to <NUM>, preferably <NUM> to <NUM> where the total thickness d is constant over the complete cross section. This makes it possible to wind the band after shaping-in again on a coil and to later reshape it concave/convex in a roll gap.

The idea underlying the invention consists in shaping the thickness d so small that the folds do not deform when being wound on a coil. While the slats become stiffer through such folding which is considered a well desired effect, they do retain their flexibility without buckling. In this way, the bands may be further processed off the coil as semi-finished products by traditional venetian blinds automats and manufactured to ready venetian blinds curtains. To this end, the concave/convex roller sets available in production machines and dies with hole and cutting shears may be adapted to the total thickness d. In order not to damage the fold tips it is conceivable to use rubber or plastic rollers.

An advantageous method for producing the innovative slats consists in guiding a flat band between a pair of rolls having a structured top roll and a structured bottom roll and to shape the flat band between the rolls to the desired micro or fold structure. Top and bottom roll have a uniform prismatic lacing with a concave-convex contour.

In a further operational step, the fold-structured flat band may be arched or reshaped to a concave/convex shape by which an angular displacement βn of the already pre-formed terminal angles β<NUM> and β<NUM> takes place. Via the segment height h of the slats, the angle β<NUM> and β<NUM> may be adjusted.

From the point of view of the production process, too, it is of advantage to shape the individual folds symmetrically as shown in <FIG> or in connection with the slat halves in <FIG> to avoid axial forces in the rolls. When symmetrically formed, exclusively vertical compressive forces will occur between the pair of rolls so that axial strain of the roller bearings, on one hand, and the risk of an oblique or uneven strain entry in the slat, on the other. with the consequence of the exit of twisted and/or obliquely folded slat will be reduced.

It is, however, extremely difficult to shape the slats, in a second procedural step, to the desired concave/convex form since in the roller tool, the slats are in contact with the rolls only via the tips of the individual folds. This might cause the slats to "swim" in the tool. The folded band might run out of track. It is, however, conceivable to enter into this roller tool in addition to the concave/convex form, the form of the folds so that the pre-formed band will stick in a large area to the band. The concave/convex shape of the tools may consider that after deforming the slat may elastically spring back into its final form.

A further production process provides, therefore, that in a first procedural step the slats are shaped to a concave/convex form and in a second procedure step to the microstructure.

In <FIG>, the slats of <FIG> are formed in a further procedural step butterfly-shaped, or double concave/convex, with two adjacent arcs. These slats are mainly used in the sky light area of windows to deflect steeply inciding light <NUM> to the depth of the interior space. This refers also for flatter angles of sun incidence, as shown in <FIG>. Completely contrary to the lower window area where de-glaring of the panes and slat surfaces is desired, the light above eye level is back reflected in such a flat manner into outer glazing <NUM> by the special fold shape that the reflection in pane <NUM> may be deflected between the slats into the depth of the interior space. To realizes such effects, a slat is used which in comparison with the slat of <FIG> with concave under side is rotated about <NUM>° upwards and then tipped in the centre.

<FIG> shows a slat of <FIG>, however, with a changed folding (<NUM>) <NUM> in the slat centre. The folding has very flat angles of the shaded fold side K so that the inciding sun is deflected in the slat centre into the interior space I. The sun side Ks follows the angular course βn of <FIG>. <FIG> shows an enlargement of the folding of the middle portion (<NUM>) <NUM>. In the present case, there results a fold angle of about <NUM>°. <FIG> shows the light distribution towards the interior and toward the outside (E) on façade level <NUM>.

In <FIG>, the second portion (<NUM>) of a slat disposed towards the interior space I of <FIG> with light deflection to the interior space ceiling is shown. At a light irradiation at the angle αs in parallel to the shadow line, a focussing zone F is formed in the area of the interior space edge of the upper slat. This slat is primarily used in the lower window area. By the steep light re-direction to the interior space ceiling, glare of the user of the interior space is avoided.

<FIG> shows the light distribution for an angle of incidence of the sun according to <FIG> on façade level <NUM>.

<FIG> shows the particular light deflection of portion (<NUM>) <NUM>. The sun-irradiated fold sides <NUM>, <NUM> und further ones show a very flat angle. The shadowed fold side follows the Fresnel optics of the sun-irradiated fold sides on the irradiation side of the curtain. The fold angle α amounts to between <NUM>° and <NUM>°, in the present case to <NUM>° and effects a light deflection outside of the focussing zone.

<FIG> shows the slat of <FIG> rotated about <NUM>° about a vertical axis. The arrangement of portion (<NUM>) <NUM> toward the irradiation side is selected in the upper window area of a curtain in order to re-direct horizontal radiation in flat angles into the interior space. The light distribution on façade level <NUM> is shown in <FIG>.

The advantage of a provision of portions (<NUM>) with opposed light guidance consists also in that one single slat type will make possible, without any tool change and only by slat rotation about <NUM>°, a user-adapted glare-free light guidance, or, light deflection, in the lower and the upper window area in favour of space depth illumination and saving an otherwise common electric illumination.

<FIG> show the light re-direction on the folded slat under sides. In <FIG>, a ray bundle <NUM> impinges from the upper side of a lower slat to the under side of an upper slat. This ray bundle results from an angle of sun incidence > αs at horizontal slat position, for instance the slat of <FIG>.

<FIG> show the light re-direction at or between the folds. Most of the rays <NUM> in <FIG> are re-directed to the upper side of the lower slat and therefrom directed to the sky. Only a very small proportion <NUM> will meet the observer's eye in the interior space.

Claim 1:
Light guiding slat for a sun protection system, wherein the light guiding slat is made of a band material, has an elongated form with a longitudinal direction, a cross direction and an elevation height setting and is provided for the formation of a Fresnel reflector for light guidance with a plurality of folds,
wherein the folds are substantially made by folding and/or bending of the band material,
wherein at least two neighbouring fold sides (Ks, K) are folded relative to each other and a fold edge extends between these fold sides (Ks, K) in longitudinal direction of the light guiding slat,
wherein the light guiding slat has a width (b),
wherein the total shape of the light guiding slat is concavely or convexly arched in cross direction, and the arching height of the concave or convex arc is less than <NUM>/<NUM> of the slat width (b),
wherein the light guiding slat has a total height (W) which is composed of the height through the concave/convex arching of the total form and of the height of the folds,
wherein the height of the folds results, depending on the shape of the slat, from the distance of parallel straight lines or parallel curves passing through the tips of the folds,
wherein the band material is of a hard base material having an elastic limit of more than <NUM> N/mm<NUM>, wherein the band material has a thickness of less than <NUM>,
and wherein the height of the folds is less than <NUM>,
such that the light guiding slat has a total height (W) which is so small that the light guiding slat has a form to be coilable with a coiling radius of <NUM> or less without any substantial plastic deformation.