Light transmitting building material and method for producing the same

Abstract

A light-transmitting structure for use as a building block or panel, and a related method of fabrication. The structure includes a composite of a primary building material and one or more light-transmitting elements. The primary building material may have structural and/or insulative characteristics. The light-transmitting elements extend from one surface of the primary building material to the other and preferably make up a small part of the bulk of the structure. One or more light-concentrating elements are positioned on one or both surfaces of the structure and are configured to concentrate incoming light rays to the light-transmitting elements. The light-transmitting elements may be optical fibers, optical film in a parallel or intersecting arrangements, or other suitable geometries. The light-concentrating elements may be spherical, aspherical, or other geometries suitable for enabling light transmission through the primary building material via the light-transmitting elements. The structure may be fabricated in a variety of ways. In one process, the light-transmitting and light-concentrating elements may be formed separately and joined together in an aligned manner. In another process, both elements may be formed at the same time, either using a preformed mold, extrusion or shaping and selectively curing portions of a fluid with optical characteristics. The panel may be used to introduce light and or heating sunshine through the structure with little impact on its structural and/or insulative characteristics.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to building structures. More particularly, the present invention relates to traditionally opaque building materials including, but not limited to, cement, concrete blocks, wood, fiber batting and solid, cellular and porous polymeric structural and cover materials. Still more particularly, the present invention relates to systems and methods for making such traditional building materials capable of light transmission.

2. Description of the Prior Art

Buildings within which people live, work and play must have certain physical characteristics to ensure structural integrity in a manner that preserves the condition of the building and the security and comfort of the people within. That is, buildings are built to remain in place for some period of time, and to be used as intended, under the particular environmental conditions to be expected where the building is located. Unfortunately, these desired characteristics of a building tend to produce a conflict in the selection of materials used to build the building.

The primary conflict in building material selection relates to the use of materials that can be divided into two general categories: opaque and light transmitting. Opaque materials are those that provide structural integrity and protection from the external environment. Opaque materials most commonly used to fabricate buildings include cement, concrete blocks, wood, fiber glass insulation and solid, cellular and porous polymeric structural and cover materials. Light transmitting materials, on the other hand, provide the building occupants with day lighting and optionally the ability to observe the environment beyond the building without direct exposure thereto. Light transmitting materials most commonly used in the fabrication of at least portions of a building, primarily the windows, include glass and polymeric materials.

The limitations associated with each type of material are as fundamental as their advantages. Building occupants cannot see through the opaque structural materials to the outside environment. The opaque materials do not let in sunlight. As a result, sunlight cannot heat the interior of the building and artificial lighting is required to light the interior of the building. On the other hand, a window does not have the insulative or structural characteristics associated with opaque materials. As a result, building heat loss tends to occur through its windows much more so than through its opaque walls.

Some attempts have been made or disclosed to address the limitations associated with opaque building materials. Published US patent application Pub. No. 2005/0183372 and PCT application no. WO 03/097954 describe a building block with light-transmitting fibers, apparently sold under the trade name Litracon™ offered by the Litracon Company of Hungary. The Litracon™ product is fabricated in blocks that may be placed together. The visual image is blurry through the blocks and light transmission appears to be diffuse when the sample shown on the company's website is viewed. This is due to the optical fibers' property of transmitting light entering from many angles causing mixing and blurring of all but the closest objects or shadows. Also, the optical fibers provide for some light transmission but the light transmission is limited to the percentage of optical fiber included in the material. This creates a large trade off between light transmission and maintenance of the physical properties of the building material. U.S. Pat. No. 4,796,404 describes a light-transmitting thermal barrier. The light is also diffused in this structure. Further, the structure requires a trade-off between thickness, which determines thermal insulation characteristics, and light transmission. Finally, the Cabot Corporation offers an aerogel powder used to fill the core of lighting panels to enhance thermal insulation. However, the powder scatters light such that the panel may not be used as a window and, again, there is a trade off between light transmission and thermal insulation characteristics. Also, none of the above solutions provide for the selective transmission of light based on incoming angle which can allow for heat gain in a building during the winter months while rejecting building heating light during the summer months, for example.

Therefore, what is needed is a building material having structural and/or insulative characteristics of interest in the fabrication of commercial and residential buildings while providing such a material with optimized light-transmitting characteristics. Also, what is needed is such a building material wherein light passing therethrough may be focused rather than diffused. Further, what is needed is such a light-transmitting material that enables relatively clear viewing from inside the building of features outside of the building. Still further needed is a building material that can selectively transmit a majority of sunlight during the heating season while limiting light transmission during the non-heating season.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide building materials having structural and/or insulative characteristics of interest in the fabrication of commercial and residential buildings, and further having light-transmitting characteristics. It is also an object of the present invention to provide such a building material that transmits a large percentage of the light striking the panel's outer surface, the percentage being largely independent of the panel's thickness. In one preferred embodiment the panel transmits most of the light striking the outer surface during winter months while rejecting most of the light during the summer months. It is a further object of the present invention to optionally provide such a light-transmitting material that enables relatively clear viewing from inside the building of features outside of the building. In this embodiment the angles of light transmitted are tightly controlled such that image transmission is possible.

These and other objects are achieved by the present invention, which is a combination of components including a primary structural and/or insulative material, one or more light-transmitting elements, and one or more light-concentrating elements. The invention is a building block or panel of selectable thickness formed primarily of the structural and/or insulative material. The structural material may be, for example, concrete. The insulative material may be, for example a polymeric foam. This insulative and/or structural material will henceforth be referred to as the primary building material. The light-transmitting element(s) extend completely through the thickness of the panel, from the panel's first lateral surface to its second lateral surface. The primary building material occupies all or substantially all of the space between the faces of the panel not otherwise occupied by the light-transmitting elements. The light-transmitting elements are optically transparent materials, preferably formed of glass or polymeric material. It is intended that the light-transmitting elements make up a relatively small portion of the overall cross-section of the panel. The light-concentrating elements are attached to one or both of the first and second lateral surfaces of the panel. They are configured and arranged such that a majority of light (either from a single angle or multiple angles) striking the lateral surface of the panel is concentrated into the light-transmitting elements. As a result, a majority of the light striking the panel made of substantially opaque building material passes through the light-transmitting elements from the one lateral surface through to the other. A substantial amount of light is transmitted into the interior of the building using a minimal amount of light-transmitting elements, thereby maximizing the amount of structural and/or insulative material of the panel.

In one embodiment of the invention, the light-concentrating elements concentrate light striking the first side of the panel oriented to face the exterior of the building from a selectable specific angle or set of angles such that the light transmitted from the second or interior-facing surface of the panel forms an image, as would be the case with a window. In a second embodiment of the invention, the light-concentrating elements concentrate light from the exterior through the light-transmitting elements from as wide a set of entrance angles as possible such that the panel transmits a maximum percentage of light across the interior-facing surface to the interior of the building to maximize lighting and/or heating within the building. In a third embodiment, the light-transmitting elements are shaped to allow light from the light-concentrating elements to enter them only from certain angles of the sun so as to selectively allow sunlight to cross the panel when desired, such as only during specific hours of the day or specific days of the year. Additionally, one or more methods of fabricating the panels of the present invention, including the use of commercially available materials and existing general fabrication techniques, are described herein.

These and other advantages and aspects of the panel and related method of fabrication of the present invention will become apparent upon review of the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of the light-transmitting panel of the present invention showing the interior-facing side of the panel to the left and the exterior-facing side of the panel with array of light-concentrating elements to the right.

FIG. 2 is a front view of the exterior-facing side of the panel of the present invention showing one embodiment of an array of light-concentrating elements.

FIG. 3 is a cross-sectional side view showing an individual light-concentrating element concentrating light through a light-transmitting element with the interior-facing side of the panel of the present invention to the left and the exterior-facing side of the panel to the right.

FIG. 4 is a front elevation view of a spherical lens as a light-concentrating element.

FIG. 5 is a cross-sectional side view of a set of cylindrical lenses as the light-concentrating elements.

FIG. 6 is a front elevation view of a panel of the present invention showing the light-transmitting elements as an array of fibers.

FIG. 7 is a front elevation view of a panel of the present invention showing the light-transmitting elements as a parallel array of optical films.

FIG. 8 is a front elevation view of a panel of the present invention showing the light-transmitting elements as a grid array of optical films.

FIG. 9 is a front elevation view of a close-packed array of spherical lenses showing the location of curved light guides arranged for transmitting sunlight through most of the day during winter months while rejecting most of the sunlight during summer months.

FIG. 10 is a cross-sectional side view of the close-packed array of spherical lenses of FIG. 9, showing a close-up of two lenses with associated light-transmitting elements.

FIG. 11 is a sun chart used for calculating the sun's path for the latitude coordinate indicated to enable selection of the positioning of the light-transmitting elements of the embodiment of the invention of FIGS. 9 and 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A building panel 10 of the present invention is shown in FIG. 1. The panel 10 includes a first surface 14 that will be referred to herein as an exterior-facing panel side 14 or simply exterior side 14. The panel 10 further includes a second surface 12 that will be referred to herein as an interior-facing panel side 12 or simply interior side 12. The panel is preferably fabricated with a uniform selectable thickness extending from the exterior side 14 to the interior side 12, although it is contemplated that the thickness may be varied if desired (as when the outside surface is made to resemble a house's siding). The panel 10 is effectively a three-dimensional structure having selectable dimensions establishing the area it covers. The coverage area may be rectangular, circular or other shape and the panel may be framed or not for installation. The interior side 12 and the exterior side 14 are referred to as such to provide proper orientation of the components of the panel 10 when the panel forms part of a building structure. Specifically, the interior side 12 is that side of the panel 10 which faces toward the interior of the building, while the exterior side 14 is that side of the panel 10, which faces the environment surrounding the building, of which the panel 10 forms a part.

With continuing reference to FIG. 1 and reference to FIG. 2, the panel 10 is fabricated of a combination of components, including a primary building material 16, one or more light-transmitting elements 18, and one or more light-concentrating elements 20. The primary building material 16 provides the structural integrity and/or any thermal insulation characteristics of the panel 10. It is to be noted that the primary building material 16 may be a primarily insulative material, with structural support provided to the panel 10 by some additional means. For example, both the interior side 12 and the exterior side 14 of the panel 10 may be formed of continuous sheets of transparent polymer, which are held together by the light transmitting-elements 18 to form a strong panel, even when the primary building material 16 is a non-structural material such as fiberglass insulation, or an insulative powder such as aerogel powder or perlite. The light-transmitting elements 18 extend completely through the thickness of the panel between the interior side 12 and the exterior side 14. The light-concentrating elements 20 are positioned on the exterior side 14 of the panel 10. However, it is contemplated that the present invention may be formed with the light-concentrating elements 20 on the interior side 12 instead of the exterior side 14, or on both the interior side 12 and the exterior side 14. The location of the light-concentrating elements 20 is dependent upon the particular light and/or heat transmission characteristics of interest for the panel 10.

The arrangement of the panel 10 of the present invention provides improved energy consumption characteristics of the building of which it forms a part. As previously noted, windows generally have lower insulative or R-value characteristics than walls and insulative materials. Windows therefore lose heat at a faster rate than do the walls when the exterior of the building is colder than the interior. However, the panel 10 effectively acts as a window in that it is configured to allow light transmission. It also has insulative characteristics approaching those of insulated walls and, in fact, may be a net heat gain as light permitted to pass therethrough can be used as a heat source at the building's interior. The panel 10 may be configured to transfer light from a specified entry angle (or angles) and concentrate it through the light-concentrating elements 20 to the light-transmitting elements 18 to produce on the interior side 12 of the panel 10 a discernible image representative of the image in existence at the exterior side 14 of the panel 10. That may be achieved by using lens-like optical geometries as the light-concentrating elements 20 on the exterior side 14 of the panel 10. Alternatively, the panel 10 may be configured to collect light from the outside of the building at multiple angles in order to maximize light and/or heat transfer, without regard to image quality. That may be achieved by using nonimaging optical geometries as the light-concentrating elements 20 on the exterior side 14 of the panel 10. It may also be achieved by using spherical lens arrays coupled to light guides that are curved such that as the sun's angle changes in the sky the light focused to the back side of the lens continues to enter the light guide as will be described herein with respect to FIGS. 9-11. As an example, the panel 10 may be used as a skylight or wall panel, configured to produce either or both of discernible images (without the inherent heat loss associated with conventional windows and skylights) and light/heat transfer improvement.

An effective aspect of the panel 10 of the present invention is the arrangement of the light-transmitting elements 18 with respect to the primary building material 16 for both imaging and light/heat transfer improvement. Specifically, each of the light-transmitting elements 18, which elements are preferably some form of light-transmitting fibers, are combined with the primary building material 16 such that they form a small percentage of the total volume of the panel 10. In that way, the structural and/or insulative characteristics of the panel 10 approach that of the particular material used as the primary building material 16. The addition of the light-concentrating elements 20 on the surface only of the panel 10 provides a far greater light-impacting surface than the ends of the individual fibers that are the light-transmitting elements 18, but without effect on the structural and insulative characteristics of the panel 10 as established primarily by the characteristics of the primary building material 16. That light hitting the light-concentrating elements 20 is then substantially captured, the extent of that capturing being dependent upon the number, type and location of the individual light-transmitting elements 18 and the light-concentrating elements 20.

One example of the panel 10 as an insulative panel appearing to be transparent at least from within the building includes an array of lenses as the light-concentrating elements 20 positioned on the exterior side 14 of the panel 10, each lens having a diameter about 10 times larger than the diameter of the individual fibers that are the light-transmitting elements 18. In this arrangement, there would be a one-to-one correspondence of lens to fiber. In that arrangement, the cross-sectional area of the fiber is only about 1/100 of the cross-sectional area of the lens. By close packing the lenses to cover substantially the entire exterior side 14 of the panel 10, the fibers would only consume about one percent of the total volume of the panel 10, leaving the remaining 99% of the panel 10 to be formed of the primary building material 16. As a result, the panel 10 is substantially the primary building material 16, for structural and/or insulative purposes, while at the same time most all of the light contacting the exterior side 1.4 of the panel 10 from a set of angles is transmitting through to the interior side 12 of the panel. If used primarily for insulative purposes, the panel 10 would have an R-value nearly the same as that of conventional insulative building materials, but without appearing to be opaque to the individual at the interior side 12 of the panel 10. The quality of the image observed by that individual is dependent upon the lens size selected, the observed image formed of pixels corresponding in size to the size of the lenses positioned on the exterior side 14 of the panel 10.

The application of the light-concentrating elements 20 to the exterior side 14 of the panel 10 resolves the problem associated with existing attempts to render structural and/or insulative materials transparent, at least to an extent. Specifically, the light-concentrating elements 20 enable a much higher light transmission capability than possible with the light-transmitting elements 18 alone. As an example, a building product formed substantially of structural or insulative material with one percent of light-transmitting fibers extending from one surface to the other will only transmit to one surface something less than one percent of the light contacting the other surface, assuming normal losses such as from surface reflection. If more light transmission is of interest, more light-transmitting fibers must be incorporated. However, if there is an interest in transmitting a substantial portion of the light, then a corresponding proportion of the building product would have to include the light-transmitting fibers, with a corresponding reduction in the amount of structural/insulative material making up the building product and related reduction in structural/insulative characteristics.

FIG. 3 provides a close-up view of the concentrating or focusing of light into an exemplar one of the light-transmitting elements 18 by an exemplar one of the light-concentrating elements 20. Initial light rays 22 contacting the light-concentrating element 20 from a source external to the building of which the panel 10 forms a part are focused into the light-transmitting element 18. Dependent upon the particular material selected to form the light-transmitting element 18, a substantial portion of concentrating light rays 24 pass therethrough and emerge at the interior side 12 of the panel 10 as a transmitted light ray composition 26 producing an image pixel corresponding in size to the size of the light-concentrating element 20. The size, shape, material selected and proximity of the light-concentrating element 20 determines the focal point 28 of the focused initial rays 22 and the percentage of light passing to the light-transmitting element 18.

Those skilled in the art will recognize the types of materials and shapes to select for the fabrication of the light-concentrating elements 20, and their placement with respect to the location of the light-transmitting elements 18 on the exterior side 14 of the panel 20. For example, one shape of the light-concentrating element 20 may be spherical, as shown in FIG. 4, or it may be cylindrical, as shown in FIG. 5. If formed as spheres, the light-concentrating element 20 may be used to focus the initial light rays 22 to a point, suitable for light-transmitting elements 18 that are individual fibers of circular cross-section. Alternatively the fibers can possess any cross-sectional shape such as those with an arch-like geometry to capture the sun's arch like track through the sky as the focused light forms a point that moves in an arch across the back surface of the corresponding lens element. If formed cylindrically, the light-concentrating element 20 may be used to focus the initial light rays 22 into a line rather than a point, suitable for light-transmitting elements 20 that are in a form other than individual fibers. The use of multiple optical elements directing light into a single light-transmitting element is also envisioned to aid in the formation of crisp images.

In the example embodiment of the panel 10 of the present invention as described above, the light-transmitting elements 18 have been described as light-transmitting fibers arranged within the primary building material 16. An example representation of the arrangement of such light-transmitting fibers, identified individually as fibers 30, is shown in FIG. 6. It can be seen that the example configuration includes the fibers 30 in an evenly spaced square pattern within the primary building material 16. Alternatively, the fibers 30 may be positioned within the primary building material 16 in a close-packed pattern or a randomized pattern, dependent upon the particular light-transmitting characteristic of interest. The number and size of the fibers 30 are also selectable as a function of the particular light-transmitting characteristic of interest. The fibers 30 may be used in combination with the light-concentrating elements 20 shaped as represented in FIG. 4.

A first alternative embodiment of the configuration of the light-transmitting elements 18 of the panel 10 of the present invention is shown in FIG. 7. In that configuration, the light-transmitting elements, identified as sheets 32, are formed planar films of light-transmitting material positioned in a uniform spacing through the thickness of the panel 10 and retained in position by the primary building material 16. The panel 10 is formed as a lamination of the primary building material 16 preferably alternating with the sheets 32. The sheets 32 may be uniformly spaced, as shown, or they may be staggered in alternative or randomized patterns, dependent upon the light-transmitting characteristic of interest. Additionally, one or more of the individual light-transmitting sheets 32 may be formed of uniform thickness from the exterior side 14 to the interior side 12 of the panel 10. Alternatively, the sheets 32 may be of varied thickness, with the sheet thickness substantially uniform through the primary building material 16, but having either or both ends thereof at the exterior side 14 and/or the interior side 12 of greater thickness. This alternative thickness arrangement allows for greater light-receiving or light-producing capability where the light enters or exits the sheets 32, but without increasing the overall volume of the light-transmitting elements within the primary building material 16. As a result, this particular arrangement aids in maintaining the structural and/or insulative characteristics of the panel 10 while enhancing light transmission. The sheets 32 may be used in combination with the light-concentrating elements 20 shaped as represented in FIG. 5.

A second alternative embodiment of the configuration of the light-transmitting elements 18 of the panel 10 of the present invention is shown in FIG. 8. In that configuration, the light-transmitting elements, identified as sheets 32, are formed planar films of light-transmitting material positioned in a grid pattern through the thickness of the panel 10 and retained in position by the primary building material 16. The sheets 32 may be uniformly spaced from one another by the primary building material 16 and crossed, as shown, or they may be staggered in alternative or randomized patterns, dependent upon the light-transmitting characteristic of interest. The space of the panel 10 between the interior side 12 and the exterior side 14 not occupied by the sheets 32 is occupied by the primary building material 16. Additionally, one or more of the individual light-transmitting sheets 32 may be formed of uniform thickness from the exterior side 14 to the interior side 12 of the panel 10. Alternatively, the sheets 32 may be of varied thickness, with the sheet thickness substantially uniform through the primary building material 16, but having either or both ends thereof at the exterior side 14 and/or the interior side 12 of greater thickness. This alternative thickness arrangement allows for greater light-receiving or light-producing capability where the light enters or exits the sheets 32, but without increasing the overall volume of the light-transmitting elements within the primary building material 16. As a result, this particular arrangement aids in maintaining the structural and/or insulative characteristics of the panel 10 while enhancing light transmission. The sheets 32 may be used in combination with the light-concentrating elements 20 shaped as represented in FIG. 5.

A third embodiment of the configuration of the light-transmitting elements 18 of the panel 10 of the present invention is shown in FIGS. 9 and 10. In that configuration the light-transmitting elements 18, extend through the primary building material 16 from the interior side 12 to the exterior side 14. However, rather than straight-line individual fibers or flat panels as shown in FIGS. 6-8, the light-transmitting elements 18 are arched or curved in cross-section as shown in FIG. 9. The extent of the curvature of each light-transmitting element 18 is dependent upon the desire to facilitate or block light transmission through the panel 10. The curvature may be simple or compound.

As an example, if there is an interest to aid in warming a building using the panel 10 during winter months and to minimize sunlight-generating heat during summer months, the light-transmitting elements 18 may be arranged as shown in FIG. 9 with respect to the sun's passage through the sky as represented in FIG. 11. This arrangement would focus and transmit more sunlight when the sun is low on the horizon (winter months) while focusing and transmitting less light when the sun is high (summer months). In general, the light-transmitting elements 18 may be arranged in the primary building material 16 and in relation to the light-concentrating elements 20 to maximize or minimize light transmission through the panel 10 as desired by conforming with the arch of the sun when and where desired. The light-transmitting elements 18 may be formed as individual shaped fibers or continuous sheet with a repeating arch-shaped curve throughout the sheet.

The embodiment of the present invention shown in FIG. 9 also shows the array of light-concentrating elements 20 in a close-packed arrangement. This arrangement may be preferably for the light-transmitting element 18 orientation shown in any of the figures. The close packing of the light-concentrating elements 20 minimizes dead spaces, which dead spaces reduce the ability to take maximum advantage of capturing light transmitted by the sun. The space between individual lens is packed with primary building material 16 which is essentially insulative material. That insulative material does not aid in concentrating light to the light-transmitting elements 18. Nevertheless, a trade-off may be made between transmission effectiveness and fabrication goals.

Any of the three alternative arrangements of the light-transmitting sheets 32 as shown in FIGS. 7-10 may have certain advantages over use of the light-transmitting fibers 30 of FIG. 6. Specifically, it may be easier, and therefore less expensive, to fabricate the sheets 32 rather than the fibers 30. Additionally, the sheets 32 enable the individual viewing the interior side 12 of the panel 10 to observe the transmitted image from multiple angles within the building. That is, unlike light emission from a point, light emission from a plane (the sheets 32) allows for an image to shift when viewed from multiple angled observances of the plane. Use of the sheets 32 in a grid pattern as shown in FIG. 8 increases the number of angles from which the panel 10 may be viewed and the observable representation of the image on the other side of the panel 10 maintained. Of course, the sheets 32 take up a greater portion of the overall volume of the panel 10 than do a corresponding number of fibers 30, such as, for example, when a like number of like-sized lenses are used as the light-concentrating elements 20. Further, as noted, the optional use of light-transmitting with curved arches 19 of the light-transmitting elements 18 of FIGS. 9 and 10 allows for the formation of panels that transmit light during selected times of the day and year to provide building heating during only the winter months, for example, or lighting at only specific times of the day.

The panel 10 of the present invention in the several embodiments shown and in other related embodiments may be fabricated in a variety of ways to produce the several arrangements and configurations of light-transmitting elements 18 as described herein. The panel 10 may be fabricated using a thermoplastic material to form the light-transmitting elements 18. The thermoplastic material may be extruded through a die or set of dies to create an array of cylinders, strands or fibers. The formed light-transmitting elements 18 may then be attached as an array of desired configuration to the inner wall of the component functioning as the exterior side 14 of the panel 10 to be formed. The primary building material 16 is then applied to the same inner wall of the exterior side 14 in a manner that substantially or completely fills the gaps between individual ones of the light-transmitting elements 18. The primary building material 16 may be any material suitable for filling the gap and performing as an insulative or structural material. For example, the filling material may be a foamable polymer. The light-concentrating elements 20 may then be applied to the outer wall of the exterior side 14 of the panel. The light-concentrating elements 20 may be molded in place on the exterior wall or they may be preformed and bonded to the exterior wall. For example, the material used to produce the light-concentrating elements 20 may be a polymer material capable of being injection molded or thermoform molded in situ. Generally stated, the panel 10 may include extruded light-transmitting elements 18 spaced from one another by a filler material as the primary building material 16, and injection-molded polymeric light-concentrating elements 20.

In regard to the panel 10 including one or more fibers 30 as represented in FIG. 6, there are several fabrication options. In a first fiber-based panel fabrication option, strands of optical fiber held on a spool may be pushed or pulled through a fluid, which fluid may be processed into a solid, such as an insulative foam solid that is represented as the primary building material 16. For example, the liquid may be polyurethane curable into a foamed solid. The fibers are positioned in the uncured fluid where desired prior to the curing step. Strands of fibers may be repeatedly positioned within the fluid to build up a grid with an appearance such as that shown in FIG. 6. The fluid may be cured after the fiber strands have been positioned where desired. The resultant foam/fiber strands composition may be cut or otherwise formed into panels of building material having a light-transmitting characteristic. The light-concentrating elements 20 may then be added to a side of the fabricated panel defined as the exterior side 14 in a concentrator adding process described herein. It is to be noted that the fiber strands may be extruded and positioned in the fluid rather than pulled or pushed from a spool. It is also to be noted that the fluid material may be more structural than insulative, such as a concrete fluid allowed to cure with the fiber strands in position where desired.

In a second fiber-based panel fabrication option, the fluid may be allowed to cure or otherwise harden but having channels established therein for subsequent placement of the light-transmitting elements 1.8. The fiber strands may then be drawn into the channels so formed. Alternatively, the channels may be filled with a liquid that will cure into an optical material, such as an optical epoxy. The cured optical epoxy has light-transmitting characteristics suitable for the intended purpose. In this fabrication option, the material used to. form the primary building material 16 may be poured or injected into a mold cavity of selectable dimensions and having surfaces treated with a release material. The mold cavity includes an array of pins extending through the thickness of the cavity and arrayed in a pattern of selectable configuration. The poured or injected material is allowed to cure, foam or otherwise harden and the resultant solid with channels in the shape of the pin array is removed. Alternatively, the primary building material 16 can be extruded with the air channels left open. The optical material is then inserted into the formed channels. This fabrication method enables use of relatively sophisticated fiber array geometries. Additionally, the light-concentrating elements 20 may be formed as part of the process, based on inserts placed in the mold. For example, the light-concentrating elements 20 may be formed as Winston cones. Further, this method of fabrication allows for fabrication of the light-transmitting elements 18 and the light-concentrating elements 20 at the same time, rather than fabrication of the panel and subsequent attachment of the light-concentrating elements 20 thereto.

In a third fiber-based panel fabrication option, the fibers and the structural material would be formed at the same time in a coextrusion process. That is, the material used to form the primary building material 16 would be forced in or through a mold or die along with the material forming the fiber strands oriented in a desired configuration. The coextruded composition is cut to desired thickness to produce individual panels in a continuous process. Optionally, a third material may be extruded to provide an interface with a low refractive index between the optical material of the light-transmitting elements 18 and the primary building material 16. This extrusion method may be well suited for high-volume automated manufacturing.

The fabrication of the fiber-based panels may require more complex operations than the fabrication of the sheet-based panel represented in FIG. 7. One method for fabricating the sheet-based panel involves unrolling optical film from a roll into a sheet of selectable dimensions. The sheet is coated or otherwise treated with the fluid material, which is then allowed to cure into solid form with the sheet adjacent thereto. The sheet and material may be positioned within a retainer, such as a trough or mold, with dimensions approximating the desired cross-sectional dimensions of the finished panel. The process of placing sheets and the fluid may be repeated until a satisfactory buildup of the composition is completed. Alternatively, the sheets and structural material may be coextruded in a manner similar to that described above for the third fiber-based panel fabrication option. In another alternative, the sheet of optical film and the primary building material 16 may be preformed sheets of appropriate thicknesses that are alternately stacked and then bonded to a preformed light concentrating array on one surface perpendicular to the stack, such as a lenticular array, and an optical film or sheet on the other side. The primary building material 16 may be a nonmetallic material such as a foamable urethane or a concrete. The finished lay up may form a single panel or may be cut into multiple panels. The light-concentrating elements 20 may then be applied to a selected surface of the formed panel.

The grid pattern of the sheet-based panel represented in FIG. 8 may be fabricated in a manner as described in the first fiber-based panel fabrication option, but with fibers of optical material replaced with the primary building material 16 coated in a liquid that will cure into the optically transparent grid pattern when sections of the primary building material 16 are placed together. Alternatively, the primary building material 16 and the light-transmitting elements 18 may be coextruded in an intersecting pattern. Alternatively, the light-transmitting elements 18 may alone be extruded and then the resultant grid can be filled with the primary building material 1 6m which may be an insulative powder.

The light-transmitting elements 18 as curved light guides represented in FIGS. 9 and 10 may be fabricated by coextrusion. They may also be extruded, molded or thermoformed, for example, and then spaced with sheets of the primary building material 16 or coated with a liquid that will cure to form the primary building material 16 with the light-transmitting elements 18 therein. The light-transmitting elements 18, may also be formed as a grid with fabrication methods as mentioned above.

As noted, the light-concentrating elements 20 provide an advantage of the present invention in maximizing light transmission while minimizing adverse effects on the structural or insulation characteristics of the panel 10. For that reason, it is desirable that they be applied to the exterior side 14 and configured in a way that focuses incoming light to the light-transmitting elements 18 as effectively as possible. Any geometry that funnels light from a larger area into a smaller area would be more useful than no funneling at all. However, favorable geometries include, but are not limited to, spherical, aspheric, and Winston cone, at least for the fiber-based panel. That is, geometries that focus the light to a point or reduced cross sectional area. For the film-based panel configuration, preferable geometries include, but are not limited to, ones that produce elongated ray patterns, such that they focus the light in a line rather than to a point. For the grid-based panel configuration, preferable geometries include, but are not limited to, ones that produce elongated ray patterns in two axes, conforming substantially to the pattern of the grid of light-transmitting elements. An example would be given by two lenticular arrays super-imposed upon each other at 90 degree angles. It should also be noted that the light-concentrating elements 20 may have a flat geometry and yet still act as light concentrators of the present in that they may have a gradient in their refractive indices such as is found in GRIN lenses.

The light-concentrating elements 20 may be produced in sheet form and formed directly on the exterior side 14 of the panel 10. Prior to applying the light-concentrating elements 20 to the exterior side 14, the light-concentrating elements 20 may be fabricated using existing lens array manufacturing techniques including, but not limited to, molding, extruding and embossing. The array of light-concentrating elements 20 may be formed directly on the exterior side 14, preferably by first preparing that surface of the panel 10 to ensure suitable bonding of the array to the panel 10. That bonding may be achieved by forming the array on the exterior side 14 or by adhering a preformed array to the exterior side 14. Alternatively, as described above, the array may be formed when forming the light-transmitting elements 18. That is, the light-transmitting elements 18 and the light-concentrating elements 20 are fabricated at the same time such that they are aligned and have the same fabrication characteristics. That may be done instead of fabricating each separately and then attaching the array aligned so that individual ones of the light-concentrating elements 20 are properly aligned with corresponding ones of the light-transmitting elements 18.

In another method of fabrication, the primary building material 16 is first formed, including with spaced channels where the light-transmitting elements 18 are to be positioned, as previously described. This method permits establishment of the positioning of the light-transmitting elements 18 and the desired shape of the array of light-concentrating elements 20, such as in the form of Winston cones. Material used to create the light-transmitting elements 18 and the light-concentrating elements 20, such as a curable fluid with optical properties when cured, is then directed into the established channels within the preformed primary building material 16 phase of the composite panel 10. A mold including cavities in the desired shape of the array is filled and then the fluid allowed to cure and solidify in the desired shape. The mold is then removed.

In another example of a method of fabricating the light-concentrating elements 20 to the exterior side 14, a curable fluid with optical characteristics when cured may be applied in fluid form to the exterior side 14 of the previously formed primary building material 16. The fluid may be a UV-curing ink or adhesive formulated to produce an optical polymer, preferably with a high refractive index. Light of an appropriate wavelength, dependent upon the fluid selected, may then be directed from the interior side 12 through either channels established in the primary building material 16, or through light-transmitting elements 18 within such channels, to the curable fluid residing on the exterior side 14. The light is preferably transmitting at one or more selected and controlled angles so that the fluid cures on the exterior side 14 in the desired shapes of lenses to establish the array of light-concentrating elements 20. The light is transmitted for a controlled period of time so that curing of the fluid stops when the individual lenses are of the desired size and shape. Any excess fluid on the surface of the exterior side 14 that is not the subject of light curing is then removed and the cured material remaining forms the lens array. Additional light curing may be done as then needed. The advantage of this method of fabrication is that the individual light-concentrating elements 20 are automatically aligned with respective ones of the light-transmitting elements 18.

The light-transmitting elements 18 and the light-concentrating elements 20 may be fabricated of any material that is transmissive of light in the visible and/or infrared range. The same material may be used for both, or different materials may be used. The light-concentrating elements 20 may be applied to either or both of the interior side 12 and the exterior side 14 of the panel 10. The material selected may be glass or polymeric. Suitable polymeric materials include, but are not limited to, thermoplastics such as polymethylmethacrylate, polycarbonate, polyvinyl chloride, polyvinyl dichloride, polyvinyl difluoride, polystyrene, polypropylene, and polyester; thermosets such as optical-grade polyurethanes, epoxies, and acrylics. Materials that are transmissive in the wavelength range of about 8-14 μm may be useful for the light-transmitting elements 18 and/or light-concentrating elements 20 when the light-concentrating elements 20 are located on the interior side 12 of the panel 10. For example, that arrangement may be of use when the intent of the panel 10 is to transmit radiant heat out of a building to cool it.

The choice of material as the primary building material 16 of the panel 10 is relatively broad. The choice is dependent upon the particular structural and/or insulative characteristics desired for the panel 10. In one application, for which the panel 10 is to be primarily an insulative component of a building, the primary building material 16 may be selected from, but not limited to, foam, glass fiber, polymer microfibers, perlite, and aerogel; provided the material selected does not remove significant light from the light-transmitting elements 18, through absorption or transmission, for example. In another application, for which the panel 10 is to be primarily a structural component of a building, the structural material 16 may be selected from, but not limited to, wood, concrete, and aluminum or other metallic material, provided the material selected does not remove significant light from the light-transmitting elements 18. Further, the primary building material 16 may be, or may be joined thermally to, a material that functions as a storage mass. That is, the panel 10 or an array of the panels 10 may be used to transmit light that produces heat which is conducted to the storage mass material. When the panel 10 no longer aids in generating heat in the building, the storage mass material may produce heat for the building. In this application of the invention, the panel 10 aids in supplying a heat sink.

In further consideration of the material selected as the primary building material 16, it is useful to evaluate the Refractive Index (RI) of the material. The RI of the material has an effect on the light-transmitting capability of the panel 10 when there is no air interface between the materials. Standard insulation materials do not transmit light without significant loss and scattering. If the primary building material 16 of the panel 10 is in direct physical contact with the light-transmitting elements 18, and the structural material 16 has a RI equal to or greater than that of the material of the light-transmitting elements 18, the majority of light desired to be transmitted through those elements will be scattered and/or absorbed by the primary building material 16. However, a material selected as the primary building material 16 having a RI lower than that of the material of the light-transmitting elements 18, then the light passing through the light-transmitting elements 18 will be reflected back and scattering and/or absorption by that phase of the panel 10 will not occur. Those skilled in the art will recognize that the greater the difference in RI between the selected material of the structural material 16 and the material of the light-transmitting elements 18, the greater the number of angles of light transmission will result. When the RI differential is understood, the particular geometry of the array of light-concentrating elements 20 may be established to focus light to the light-transmitting elements 18 at angles that will result in light transmission rather than scattering or absorption. Those skilled in the art will recognize that any number of array geometries may be created to work well with the particular materials selected for the structural material 16 and the light-transmitting elements 18.

Optical fibers may be treated or modified to increase the RI differential between the light-transmitting elements 18 and the primary building material 16. For example, a glass fiber or an acrylic fiber may be coated with a fluorine-containing polymer, such as polyvinyl difluoride (RI=1.42). Alternatively, air with a RI=1, or polyvinyl acetate with a RI=1.47, may be adjacent to the fiber, or sheet for the panel construction of FIGS. 7-10. Examples of air in contact with the light-transmitting elements 18 include the use of glass or polymer fiber insulation, a packing material such as perlite or aerogel, or foam delaminated or otherwise unattached to the surface of the light-transmitting elements 18, to give an effective RI value that is that of air. In addition, materials such as polyvinyl acetate or polyvinyl difluoride may be foamed adjacent to the light-transmitting elements 18 to make direct contact therewith, or the unfoamed versions may be coated as a thin coating on the outside of the light-transmitting elements 18, such as during a coextrusion fabrication process. When a coating or other treatment with relatively low RI value is directly contacted to the exterior surfaces of the light-transmitting elements 18, the primary building material 16 may be selected without regard to its particular RI value. That is, the selected coating, rather than the selected primary building material 16, causes the light reflection.

As expected for the function of the panel 10 of the present invention, there will be exposure to external elements, including sunlight itself, which may cause degradation of the materials chosen to fabricate it. For that reason, the materials may be treated to minimize ultraviolet degradation and oxidation. There exist standard commercially available antioxidants, such as hindered phenols, and UV absorbers, such as modified benzophenones that are available and can be added to the materials of construction. Similarly, additives and/or coatings may be employed in the formation of either or both of the light-concentrating elements 20 and the primary building material 16 to block UV light and/or infrared light to allow light transmission while avoiding transmission of damaging UV wavelengths and heating infrared wavelengths where lighting but not heating of the building is desired.

The panel 10 of the present invention may be used to save energy within a building by effectively drawing in the heat associated with sunlight without compromising insulative characteristics. The insulative properties of the panel 10 may be improved by increasing its thickness while still enabling light transmission through the light-transmitting elements 18. The use of the light-concentrating elements 20 increases the percentage of light transmitted across the panel 10 with minimal reduction in physical properties of the primary building material 16. In the configuration of the panel shown in FIG. 3, light passes mainly in one direction, from exterior to interior, so that individuals can see out of the building but others cannot see into the building. Further, the panel 10 of the present invention may be used any time there is an interest in bringing light across a thermal barrier. For example, it may be used as an improvement to a Trombe wall. It may be used to improve the characteristics of a conventional wall, such as by providing a better heat source as indicated herein. For example, the panel 10 may be affixed to a conventional wall structure, such as a concrete wall. The sun's light would pass through the panel 10 and heat the concrete. The concrete, in turn, may then be a thermal source for the building, and would retain heat without overheating the building. As air is exchanged within the building, the thermal mass of the concrete wall would heat that air. This arrangement may supplement or replace existing internal heating systems, dependent upon the amount of sunlight available. The use of a panel that selectively transmits light during the heating season while rejecting light during the warmer months of the year would be extremely useful for this application. The panel 10 of FIGS. 9-10 would be suitable for this purpose. A panel 10 of the present invention could also be used for solar hot water heating with the benefit of bringing the light into the insulated envelope of the building such that water can be directly heated without the need for antifreeze solutions and heat exchangers. Still further, one or more of the panels 10 may be configured with an external appearance recognized as a conventional building exterior appearance. To aid this appearance, the light concentrating sheet can be painted any color on its inner surface wherever the light-transmitting element 18 is not attached or the primary building material 16 can be colored any desired color.

The present invention is an apparatus to improve lighting and/or energy usage characteristics of a building. The present invention is also a method of fabricating the structure with such characteristics. While the present invention has been described with particular reference to certain embodiments of the panel 10, including the primary building material 16, the light-transmitting elements 18 and the light-concentrating elements 20, it is to be understood that it includes all reasonable equivalents thereof as defined by the following appended claims.

Claims

1. A light transmitting building panel comprising:

a. a first surface and a second surface, the first surface including thereon one or more light-concentrating elements arranged to concentrate light striking the first surface;

b. one or more light-transmitting elements arranged to receive concentrated light from the one or more light-concentrating elements, wherein each of the one or more light-concentrating elements extends from the first surface to the second surface; and

c. a primary building material extending between the first surface and the second surface, wherein the primary building material spaces individual ones of the one or more light-transmitting elements from one another, and wherein the primary building material does not transmit light as well as the one or more light-transmitting elements.

2. The light transmitting building panel as claimed in claim 1 wherein the light-concentrating elements are arranged as an array of lenses.

3. The light transmitting building panel as claimed in claim 1 wherein the light-transmitting elements are optical fibers.

4. The light transmitting building panel as claimed in claim 3 wherein the optical fibers have a cross section that is not round.

5. The light transmitting building panel as claimed in claim 1 wherein the light transmitting-elements are sheets of optical material.

6. The light transmitting building panel as claimed in claim 1 wherein the light-transmitting elements form an extended grid of optical material.

7. The light transmitting building panel as claimed in claim 1 wherein the primary building material is a thermal insulator.

8. The light transmitting building panel as claimed in claim 7 wherein the primary building material is a foam insulation.

9. The light transmitting building panel as claimed in claim 7 wherein the primary building material is an insulative powder wherein the insulative powder is retained in the panel between the first surface and the second surface, and wherein the second surface is formed of a light transmitting material.

10. The light transmitting building panel as claimed in claim 1 wherein the primary building material is a load bearing material.

11. A method for fabricating a light-transmitting panel having structural and/or insulative characteristics, the panel including a material used to form a primary building material with light-transmitting elements extending therethrough and light-concentrating elements on at least one surface thereof, the method comprising the steps of:

a. injecting the material used to form the primary building material into a mold cavity of selectable dimensions and including an array of pins extending through the thickness of the cavity and arrayed in a pattern of selectable configuration of the light-transmitting elements;

b. curing the material with channels in the shape of the pin array to form a panel;

c. removing the array of pins from the channels;

d. inserting a fluid having optical characteristics into the channels;

e. curing the fluid to form the light-transmitting elements; and

f. applying the light-concentrating elements to a surface of the panel

12. The method as claimed in claim 11 wherein the channels are in the form of individual ports.

13. A method for fabricating a light-transmitting panel having structural and/or insulative characteristics, the panel including a material used to form a primary building material with light-transmitting elements extending therethrough and light-concentrating elements on at least one surface thereof, the surfaces of the panel including an inner wall and an outer wall, the method comprising the steps of:

a. extruding a plurality of the light-transmitting elements in a grid array,

b. cutting the extruded light-transmitting element array to form a panel,

c. affixed to the inner wall of the one surface of the panel;

d. applying the material used to form the primary building material to fill the spaces within the light-transmitting element array; and

e. affixing a molded array of the light-concentrating elements to the outer wall of the surface of the panel.

14. The method as claimed in claim 13 wherein the light-concentrating elements are formed by polymer injection molding.

15. The method as claimed in claim 13 wherein the material used to form the primary building material is a foamable polymer insulative material.

16. The method as claimed in claim 13 wherein steps c and e are reversed.