Patent Application
20050068630
The present invention relates to a sun protection device for transparent apertures in buildings against direct incident sunlight entering the interior of the building. The sun protection comprises at least one flat optical element consisting of an at least partially transparent material, is installable in the region of the building aperture, and has two flat element sides facing each other, of which one is designed non-structured and plane, and the other is provided with prismatic linearly extending structural elements running in parallel and recurring periodically in lateral direction.
Glazed surfaces are being increasingly employed in modern architecture. Fundamentally, this element of architectonic design has much to recommend it, on the one hand, because solar radiation/solar energy transmitted through the windows can effectively contribute to covering thermal energy needs during the heating period and, on the other hand, because light conditions are noticeably improved by daylight enhancing illumination.
Windows and sunlight-transmitting glazing can, however, also have undesirable effects. For example, intensive, direct incident sunlight can be glaring in the interior of rooms, in particular, at computer screen workplaces. Furthermore, on warm summer days, too great solar energy input can lead to uncomfortably high room temperatures.
Today, in particular, in commercial construction (administration and office buildings, . . . ), the energy primarily needed for cooling in summer often exceeds the energy needed for heating in the winter. Thus, there is a justified desire to avoid undesired solar energy input as far as possible in summer and, if there are computer screen workplaces located in the glazed room, to avoid glare.
In addition to the classical approaches, such as placing awnings or balconies before the window surfaces, mechanical shading, respectively sun protection systems with moveable parts, such as venetian blinds and sheer curtains, as well as technically complicated switchable optical layers—all these solutions have various drawbacks such as inflexible illumination of the interior of the room, too high costs or technically unsolvable for large window surfaces—light-guiding optical elements operating on the basis of optical refraction, reflection and/or interior total reflection are known and, thus, are elements for sun protection and glare protection and contribute to improving exploitation of daylight.
Such type optical elements are usually designed as transparent flat elements and are provided with prismatically designed structures on at least one of their surfaces. Depending on the angle of incidence, these structures transmit, deflect, scatter or reflect the incident light. If such type surface elements are installed in a stationary manner, as a result of the seasonally varying position of the sun, the direct sunlight is selectively reflected in certain periods, e.g. during the summer months. Whereas during the rest of the year, it can pass the light deflection system almost unhindered.
The applications of the light-deflecting prisms can be broadened in that the structured areas are installed in such a moveable manner that the alignment of the structure in relation to the light source can be selectively varied. DE 1 497 348, DE 31 38 262 A1, U.S. Pat. No. 4,773,733, DE 195 42 832 A1 or DE 197 00 111 A1 describe such systems in which structured lamellas or prism rods are borne in a rotatable manner about an essentially horizontal axis, due to which the light-guiding structures align selectively or guide according to the sun. However, the drawbacks associated with classical venetian blinds and sheer curtains regarding high purchase costs and susceptibility to mechanical failure also apply to these moveable systems.
In other systems, the light-guiding structure, respectively the optically effective structure, is applied in a flat stationary manner on a transparent pane, board or glazing. The structure that influences the path of the light can lie either on the side facing the light source (“exterior”) or on the side facing away from the light source (“interior”) of a transparent or translucent board or glazing. DE 831 449 or FR 2 463 254 describe such type systems with externally located reflecting, prismatic structures which fulfill the desired functions. Internally located prismatic systems are described in, e.g, DE 113 391, U.S. Pat. No. 2,812,691, U.S. Pat. No. 4,519,675, DE 35 17 610 A1, DE 195 38 651 A1 or DE 198 34 050 A1. Moreover, systems with structures on the interior as well as on the exterior are described in for example DE 1 50 365.
DE 26 15 379 A1, DE 32 27 118 C2 and U.S. Pat. No. 4,498,455 describe light-guiding systems in which the effect of a light-guiding prism system, respectively a prismatically arranged lamella system, is further improved in that one or a multiplicity of flanks of the respective prism structure, respectively the lamellas, are provided with a highly reflecting, absorbing or strongly scattering coating, thus for example are metal coated. Only the rotatably borne lamella systems, such as lamellas, prism rods, allow in certain positions partial direct vision through the glazing system between two adjacent lamellas/rods.
However, all the mentioned flatly installed systems have the drawback that, due to the structuring, direct vision through the flat systems is impossible. Flatly installed systems can, therefore, not be employed in façade areas in which direct visions is desired or even an absolute necessity.
Another system in which partial optical direct vision is given is composed of complementary structures which utilize that, when passing a thin, plane-parallel split, the beam is only minimally offset in parallel. Thus an element that fulfills a sun protection function due to total reflection at certain angles of incidence can be provided with direct visions properties in that a complementary structure is added to the element. Such type systems are known, for example, from DE 17 40553, DE 11 71 370, U.S. Pat. No. 2,976,759, U.S. Pat. No. 3,393,034, U.S. Pat. No. 4,148,563, U.S. Pat. No. 4,519,675, U.S. Pat. No. 5,880,886, DE 195 42 832 A1 and DE 196 22 670. However, those complementary structures, which are designed with slanted triangular prisms as the basic structure, have the disadvantage that there are no joining surfaces to which the structure and complementary structure could be tacked together respectively glued together. In the prior art structures, whose basic structure is always designed “rectangular”, as described in DE 17 40 553 and DE 196 22 670, the fronts can be utilized as gluing surfaces. DE 196 22 670, in particular, describes one possibility, respectively one method, how structure and complementary structure can be joined and connected.
Only U.S. Pat. No. 5,880,886 (Milner, 1994) describes assembled structures and complementary structures having a partial direct vision that are suited for flat application, i.a., in vertical glazing. Compared to a triangular prism in the assembled structures, the tip of the prism is “replaced” by a part of the surface, which is essentially aligned plane-parallel to the continuous “rear side” plane surface and allows partial direct vision. The direct vision region, respectively the part of the surface which allows in principle partial direct vision, is located at any rate on the “protruding side” of the structure. In contrast to this, the complementary structures mentioned in U.S. Pat. No. 5,880,886 do not possess any direct vision areas, but rather (partial) direct vision is solely achieved by the complementary property of the two utilized structures.
Due to their two-component design, the prior complementary structures with optical direct vision properties are complicated and consequently expensive to produce. Moreover, they all have light deflecting properties which are only able to deflect the incident sunlight into the interior of the room, preferably toward the ceiling area. There is no deviation to the outside, respectively by reflection to the outside does not occur or only to a limited extent.
The object of the present invention is to provide a sun protection device for transparent apertures in buildings against direct incident sunlight entering the interior of the building in a manner that ensures effective sun protection and at the same time possesses optical direct vision properties. The geometry and construction of the sun protection device should be as simple as possible in order to keep production costs low. Furthermore, the sun protection should contribute decisively to reducing incident light entering the interior of the building, in particular when the sun stands high, as occurs during the warm seasons.
The solution to the object of the present invention is set forth in claim 1. Advantageous features that further develop the inventive idea are the subject matter of the subclaims and the entire description, in particular, with reference to the preferred embodiments.
A key element of the present invention is that a sun protection device for transparent apertures in buildings against direct incident sunlight entering the interior of the building, comprising at least one optical flat element consisting of at least partially transparent material, is installable in the region of the building aperture, and has two flat element sides facing each other, of which one is designed non-structured and plane, and the other is provided with prismatic linearly extending structural elements running in parallel and recurring periodically in lateral direction, is designed in such a manner that the structured flat element side facing the non-structured, plane designed flat element side is provided with an at least largely coparallel surface, over which the individual structural elements project. The individual structural elements each have a triangular cross-section surface enclosed by a lateral edge, which coincides with the surface, and by two lateral flanks protruding above the surface. The individual structural elements, thus, represent three-dimensional prismatic bodies which are defined by the two unoccupied defining surfaces, which each are associated to the two lateral flanks protruding above the surface. In order to ensure the optical direct vision properties through the invented flat element, at least two adjacent structural elements are disposed separated laterally from each other by a flat section of the surface. By means of each of these flat sections, a practically unimpeded direct vision is ensured through the optical flat element consisting of transparent material. Moreover, one of the two lateral flanks and the surface form a 90°-α angle. Furthermore, the two lateral flanks form together an a +β angle and finally the other lateral flank and the surface form a 90°-β angle. In any event, a is not equal to β so that it is ensured that one lateral flank is always longer than the other. However, for reasons of effective light deflection it is particularly advantageous if the longer lateral flank is always disposed facing the incident sunlight.
The sun protection device designed according to the present invention, for which the terms light-deflection device or antiglare device are equally applicable, is based on creating optically effective surface structuring on an optical flat element consisting of a transparent material. The periodically recurring structural elements disposed on one surface of the flat element are separated in such a manner that in the event of oblique illumination, none of the single structural elements shades an adjacent structural element. Notably, if the structural elements were lined up in a row directly adjacent to each other, the shadows of the single structural elements would fall on the respective adjacent structural element, due to which the optical effect of the structural element would be lost at least in the shaded area. However, if the single structural elements are separated in such a manner that no, respectively only negligible, shading occurs between the single adjacent structural elements and, in addition, if the flat section which the spacing of the two directly adjacent structural elements rendered unoccupied remains unstructured and preferably remains plane, an optical situation of two exactly plane-parallel or practically plane-parallel panels is yielded in these flat sections—looking at the respective flat section and the, flat anyway, rear side of the flat element—thereby permitting unimpeded, in particular image-retaining direct vision.
Even in the embodiment variants of the invented sun protection device, in which the respective flat sections mutually laterally separating the two structural elements form a small angle with the plane rear side of the flat elements, the optical direct vision properties are still retained although the direct vision image is imaged slightly offset, which in some circumstances is tolerable and in some cases even desired.
Advantageously, the flat element is installed with its structured flat element side in the region of the building aperture in such a manner that the structured side of the flat element faces the incident sunlight. As will be shown in more detail, the flat element designed according to the present invention, however, is able to develop a desired antiglare effect, respectively protective effect, in inverse installation form, i.e. the structured side of the flat element faces the interior of the building.
Even if the main interest and field of application of such flat elements is the integration of the sun protection effect designed according to the present invention in vertically oriented building apertures, respectively by integrating the sun protection device in vertical window surfaces, their use in tilted building apertures, such as for example in roof areas or slanted façade flanks is fundamentally also possible and feasible.
The exact geometric design and arrangement of the lateral flanks, respectively the defining surfaces of the single structural elements depends fundamentally on the type and purpose of their use, i.e. depending on whether the flat elements are arranged in a vertical or oblique manner or whether the structured side of the flat element faces toward or away from the incident sunlight. Particular attention should be paid to the local lighting conditions given by the latitude as well as by the season-dependent orbit of the sun, respectively the angle of the position of the sun.
In view of the preceding individually to be considered conditions, the lateral flanks, respectively the defining surfaces of the single structural elements should preferably be oriented slanted toward each other and toward the incident sunlight in such a manner that the sunlight impinging on the individual structural elements from a certain angle is almost completely masked out, i.e. deflected to the outside by way of internal total reflection, respectively reflected into an external region facing away from the interior of the building. However, if the sunlight impinges on the corresponding structural elements from the other angles, the sunlight is guided or deflected into the interior. Consequently, the sun protection device according to the invented design, in which the structured side S faces the light source, is distinguished in its transmission properties by a characteristic disruption of the hemispherical optical transmission of direct incident sunlight on the structural elements. A detailed description is given, by way of example, in the following with reference to the drawings.
The present invention is made more apparent, by way of example in the following without the intention of limiting the scope or spirit of the overall inventive idea using preferred embodiments with reference to the accompanying drawings.
a,b show schematic sectional drawings to explain the structural elements designed according to the present invention (1a: prior art),
a shows the prior art situation in which a one-sided structured flat element F is irradiated by sunlight hν. The single structural elements SE bordering each other directly adjacent in a sawtooth-structured manner yield, in oblique radiation, to mutual self-shading (see hatching). However, in regions where self-shadowing occurs, the single structural elements lose their optical effect. In contrast to this,
In contrast to the arrangement of flat element F depicted in
To aid in understanding the optical effect of the sun protection device according to the invented design,
Furthermore, it is assumed that the flat element F is preferably integrated vertically in a building façade aperture and is oriented facing south. In the same manner, it is feasible to orient the flat element F in oblique positions as well as in positions aligned between southeast to southwest. Depending on the orientation and the manner of installment of the sun protection device, the geometric embodiments and the inclination of the defining surface A* and B* should be suited thereto. Notably, this is decisively determined by the so-called sun profile angle αP, corresponding to the angle between one flat normal relative to a vertical surface and the projection of the sun direction on that plane, which is tentered by the surface normals and a vertical straight line. Thus, for example, for a surface vertically aligned exactly in south direction, the sun profile angle αp assumes values between a minimum angle αpu and a maximum angle αpo, always depending on the geographical latitude and the ecliptic in the following manner:
αpu=90 °−Φ−δmax<αp<90°−Φ+δmax=αpo
In the above relationship Φ stands for the latitude and δmax=23.45° for the maximum declination respectively maximum ecliptic yielded by the inclination of the axis of the earth in relation to the orbit of the sun.
In order to determine the design of the structural elements SE, the aforementioned conditions need to be taken into consideration if direct incident sunlight is largely to be prevented from entering the interior of the room.
If the flat element F is to be installed vertically and preferably aligned exactly in south direction, the following design criteria can be determined regarding the design of each single structural element: if, according to
This case is given if the sunlight radiation assumes at least the smallest sun profile angle αpu1, given by the following relationship:
αpu1=90°−60 +arc sin[n sin(arc sin(1/n)−(90°−α))]
This case is depicted in
Furthermore, the shading effect due to back reflection is intensified if, in addition, a ray of light entering the flat element F through the top defining surface A* is then totally reflected at the directly adjacent defining surface B* in such a manner that the ray of light finally impinges on the rear flat element side E at an angle at which the total reflection also occurs. Such a case is given if the sun radiation assumes at least a lower sun profile angle of the following form:
αpu2=90°−α+arc sin[n sin(arc sin(1/n)+α+2β−0°)].
The upper limit of the masking out region is determined by a beam path which also enters the flat element F through the defining surface A* and impinges on the lower defining surface B* from the interior. However, if in contrast to the preceding case, total reflection no longer occurs at the defining surface B*, a considerable part of the sunlight radiation is transmitted through the flat element. The respective upper critical angle assumes the following form:
αpo=90°−α+arc sin[n sin(arc sin(α+β−arc sin(1/n))].
With the aid of the preceding three critical angles, respectively equations, the masking region of the sun protection device designed according to the invention can be individually adapted to different lighting situations by selecting the angles α and β and selecting the defining surfaces A* and B*.
Additional possible optimization is the selection of the structural height h of the single structural elements SE. If, for example, in the case of maximum partial direct vision, the flat element should mask out sunlight in the region between αpu2 and αpo, the minimum height h of the single structural elements SE is determined by the condition that self-shading still just occurs at the lower angle limit αpu2 of the masking out region, thus the following formula is given:
h≈P/[tan(α)+tan(αpu2)].
In this case, P stands for the period length of a structural element SE. This period length is yielded by the sum of the length of the lateral edge C and the clear span of the flat element D (see
A similar relationship can also be determined for the lower sun profile angle αpu1.
If the height h of the structural element SE is selected smaller, the direct vision region increases at the expense of the shading effect, respectively the masking effect. If the height h is selected higher, in some circumstances the masking effect improves further, but the direct vision diminishes accordingly.
The selection of a suited structure also depends (as the preceding equations indicate) on the refractive index of the material used. It is to be noted that the latitude in design/execution and the to-be-expected optical functionality and effect of the sun protection element is greater the greater the refractive index is. Usually, today materials with approximately 1.4<n<1.7 are available, with plastics with high refractive indices of n>1.55 being preferably suited for an invented sun protection element.
The preceding embodiments relate, as mentioned in the introduction, to a flat element whose structured flat element side S faces incident sunlight. If, however, the structured side of the flat element faces away from the light source, respectively from the incident sunlight, other critical angles are yielded, which however someone skilled in the art would derive on the bases of the preceding reflections.
With reference to the representation of
However, if it is desired that shading be only moderate and consequently room illumination with daylight greatly improved, the edges can be preferably rounded or one of the two oblique defining surfaces A* or B* can be curved or both can be curved.
Light deflection at cones or curved surfaces generally leads to the occurrence of a glossy vertical band in the transmission, i.e. the horizontal component of the beam direction is not altered by the deflection at the rounding but definitely the vertical component is, resulting in the mentioned effect of a bright essentially vertical stripe.
This effect can be both weakened or completely prevented in that the single structural elements are also not exactly plane in the direction of their translation axis, but rather have a slight waviness, respectively slight curvatures, along their translation axis. In this manner, the light of the glossy band is distributed on a larger angle region and the, in some circumstances, disturbing glare effect is reduced. The waviness of the structural elements along the translation axis preferably has a stochastic character, because otherwise oblique glossy bands or other bright visible structures may form.
The optical functionality of the single structural elements SE can be further improved in comparison to the ones described in the preceding by providing one or a multiplicity of defining surfaces or partial areas of the structural elements SE with an optically effective layer. Such a type optically effective layer can develop, for example, a reflecting scattering or absorbing effect. In order to produce such types of effective layers, the structured flat element side S undergoes PVD (physical vapor deposition) coating, e.g. vapor deposition or sputtering) or CVD (chemical vapor deposition) coating. In an especially preferred manner, such a type coating process can be conducted by way of oblique masking in such a manner that surfaces of parts, respectively of partial areas, of the structural elements SE are treated selectively, thereby utilizing that the particles of the deposition processes move in a preferred direction in the gas phase (e.g. the vapor particles in vapor deposition, the scattered particles in sputtering) and thus form shadows, i.e. regions with lower a deposition rate compared to the adjacent regions, during coating of the structured surfaces.
In order to further improve the optical direct vision properties of the flat element F described in the preceding, in particular, in the case of providing a dielectric boundary along, for example, the defining surface B*, a preferred embodiment according to
In the preferred embodiments shown in
However, it must be noted that, in combinations with complementary flat element structures, the original flat element F is the first optically effective element in the light path and, therefore, the first optically effective element for the incident light. In this manner, the effect of such a type system generally differs very strongly from an isolated antiglare device as described in the preceding. The consequence is that a complementary flat element system F/F′, in which the complementary flat element F′ lies closest to the light source, requires a special structural design. If the structural elements of the original flat element F are provided on the side facing away from the light source, adding a complementary flat element does not influence the essential optical effect of the original flat element.
In a preferred embodiment, one or both of the joined flat elements can be fabricated of a transparent, flexible material, for example, a type of flexible foil or thin board. Suited rolling processes in which the complementary structures are interconnected can be employed to produce such type flexible complementary flat elements.
To economize on material, reduce absorption effects and facilitate integration of the sun protection device, for example, in an composite insulation glass, as well as to ultimately considerably reduce costs, it is especially advantageous to miniaturize the light-guiding prismatically designed structural elements. Such a microstructured flat element can, for example, be applied onto the glass pane as backing in the form of a microstructured foil. It is also feasible to directly structure the surface of a pane, for example of a window pane. A further advantage of micro-structures is, in particular, that the human eye can, in some circumstances, not resolve them, thus a quasi-homogeneous appearance is created.
This quasi-homogeneous appearance is, in particular, of advantage if the sun protection element is not to be utilized on a south oriented, but rather on an otherwise orientated area or façade. In this case, a desired sun protection function dependent on the sun profile angle can be ensured if the extended structural elements SE no longer are orientated horizontally, as is the case when oriented southward, but rather are tilted. If the sun protection element has a quasi-homogeneous appearance, this necessary tilting does not architectonically or aesthetically limit the possible use of the element.
Gray-tone lithography is especially suited to produce such type microstructures. This process usually is confined to areas small than 10 cm2. However, prismatic structures can also be produced by means of material-removal processes or precision metal removing processing, for example, micro-milling or micro-blasting. Although large areas are processed with such a type process, the involved technical difficulties increase considerably for desired area sizes larger than 25 cm2. However, even today interference lithographic processes offer the possibility of structuring large areas of up to 2500 cm2 successfully in the desired homogeneous manner.
If a miniaturized structure in the form of a master structure is present, the latter can be applied to large areas by means of molding processes, thereby permitting replication of the microstructure. In this manner, surface structures can be transferred to or imprinted on various organic or inorganic materials, in molds or foils of any type or surface. Replication processes that should be mentioned in this context, are, for example, rolling imprinting processes, stamp imprinting processes and injection molding processes. With the preceding processes, it is, in particular, possible to produce the structured surface cost-effectively.
An especially preferred form of use of the invented sun protection device is integration in an insulation glass composite system. A flat element which is structured on the side facing the interior or a foil in general is applied onto the inner side of the outer pane (or in the case of triple glazing onto the inner side of the middle pane), whereas a flat element which is structured on the exterior is generally applied to the outer side of a pane which lies on the interior. Depending on the requirements, in individual cases, a third, fourth or a further layer, respectively pane, may be required in the insulation composite glass, respectively realized.
Finally FIGS. 9 to 11 show some transmission diagrams dependent on the lighting situation for the following concrete embodiments:
A vertically aligned sun protection device facing the light source and having the parameters α=48°, β=6°, h/P=0.5, n=1.59 (refractive index of the transparent material) possesses the property that only maximally up to 1.7% of the directed radiation, which enters solely from a profile angle range between 57° and 66°, is transmitted. In such a type structure, the direct vision part makes up approximately 39% of the overall area.
This type of structure, therefore, is suited as seasonal sun protection for south façades in geographic latitudes in which the highest summer sun positions are smaller than 67°, e.g. the geographical latitude of Freiburg i. Br., Germany (φ=48°). Thus, in a period from May 2nd to August 11th, up to more than 98% of the directed direct sun radiation is reflected or absorbed by the element. In the transition periods for instance from March 12th to May 1st and August 12th to September 30th, only maximally 40-50% of the direct radiation is transmitted through the element. At the same time, high transmission and, therefore, solar energy contribution to room heating is ensured during winter. Good illumination with daylight is given at all times in a rearward space by means of the high transmission at high incidence angles.
The next example, shown in
Finally
The flanks and edges are curved, respectively rounded, in such a manner that, unlike in the preceding cases in which a part of the incident radiation is precisely masked out, in each irradiation situation as well as in the incidence angle region in which principally a shading effect occurs, always one part of the incident light is scattered into the depth of the rearward space. The transmission level depends greatly on the type and extent of the curvatures and the waviness compared to a plane, sharp-edged structure.
Due to its specific masking angle region, the element on which
Reference Signs
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 61 938.3 | Dec 2001 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP02/13738 | 12/4/2002 | WO |
