Patent Publication Number: US-9885209-B2

Title: Light-control assembly

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 13/589,835 filed Aug. 20, 2012 which is U.S. Pat. No. 8,893,434, which is a continuation-in-part of U.S. patent application Ser. No. 12/903,904 filed Oct. 13, 2010, now U.S. Pat. No. 8,245,444, and Ser. No. 10/600,261 filed Jun. 20, 2003, now U.S. Pat. No. 7,281,353. The entire disclosures of the foregoing patent applications are hereby incorporated by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure pertains to architectural structures designed to pass light and, more particularly, to transparent/translucent panel systems for controlling the level of light admitted through horizontal and sloped glazing, skylights, roofs, walls, and other architectural structures designed to pass light and to readily constructed light-control assemblies designed for reliable light-blocking that are particularly effective in dynamic control of daylighting and shading. In the light-control assemblies elongated light control members such as opaque or translucent slats or other light-blocking members are rotated up to 360° by applying rotary force to the light-blocking members to achieve black-out or near black-out conditions. The assemblies achieve unusually effective light-blocking through the use of beams having circular bores with laterally compliant and other light-blocking members. 
     BACKGROUND 
     The U.S. Department of Energy as well as sustainable construction organizations and the like are pressing for the installation of dynamic daylighting and shading systems to improve energy efficiency in buildings. Innovations are sorely needed to meet this need. 
     Various types of transparent and translucent glazing systems are available for the construction of horizontal, vertical and sloped glazing in skylights, roofs, walls, and other architectural structures designed to pass light for daylighting interiors or other purposes. When using such glazing systems, it is therefore desirable, in accord with sustainable construction criteria, to optimize the system&#39;s shading coefficient to reduce solar heat gain on hot summer days and during peak sunlight hours year round, while providing maximum light and solar heating on cold winter days and when it is otherwise needed or desired. It is also often desirable to control glare and direct sunlight in order to ensure the comfort of those who occupy the space exposed to the glazing system. If architects and space planners can be freed from the constraints of current light transmission control in horizontal, vertical and sloped glazing in skylights, roofs, walls, and other architectural structures, they will be able to maximize interior daylight without the burden of unmanaged heat gain or discomforting glare more effectively address these shading requirements and meet sustainable construction criteria. Furthermore, these considerations apply as well to shading of open unglazed areas. 
     Indeed, if the level of light entering overhead large glazed as well as unglazed areas can be simply, efficiently, effectively and uniformly controlled with little or no light leakage between, e.g., multiple adjacent light-controlling members, it will provide architects and space planners with important new tools. They will be able to maximize energy efficiency with aesthetic and sustainable designs to a degree not previously possible. And, sun tracking control shading systems can dynamically rotate light-blocking members up to 360° to efficiently shade small or large glazed and open, unglazed areas to provide the desired uniform light level inside the space thereunder would be particularly desirable. 
     The known approaches to controlling the amount of light admitted through glazing systems—particularly on a large scale and in overhead, horizontal and sloped glazing applications—are limited and are generally unreliable, noisy and often difficult and expensive to construct, assemble on-site, maintain and service. Also, existing approaches suffer from non-uniform and excessive light leakage between adjacent light-controlling members which appears as an aesthetically undesirable series of often irregular bright lines. Additionally, although it is often desirable to retrofit light-controlling systems to already constructed glazing systems, this is not easily accomplished with current light-controlling systems. There is therefore substantial need for an economic and readily constructed and retrofitted light-controlling system that may be used for shading glazed areas of all sizes, including very large glazed areas. There is also substantial need for such light-controlling systems that can be easily assembled, maintained and serviced, in which the light is uniformly distributed across the glazed area, and in which light leakage is de minimis or eliminated or, where present, is kept to narrow and regular lines. 
     Prior approaches to controlling the level of light passing into architectural structures have included louver blind assemblies using pivoting flexible light-controlling members operable behind a window or sandwiched inside a chamber formed by a double-glazed window unit. Such louver blinds require substantial support of the flexible members which, additionally, must be controlled from both their distal and their proximal ends. Furthermore, louver blinds are difficult and expensive to assemble, apply, operate, maintain and replace, and cannot be readily adapted for use in non-vertical applications or in applications in which it is either desirable or necessary to control the flexible members from only one end. Louver blinds are particularly problematic when it comes to applications in which the installation requiring light-control or shading is very long, e.g., 10 ft., 20 ft., 40 ft., 60 ft. or more. In addition, dynamic control of louver blinds in large overhead shading applications is complicated, expensive, difficult to install and maintain, and often simply impractical. Furthermore, rotating louver blinds require that rotary force be applied to the top edge of the blinds. This is because louver blinds are flexible and rely on the force of gravity to hang vertically in the proper desired position and therefore cannot be rotated from their base. Thus, louver blinds cannot be used in generally horizontal overhead glazing application or in sloped applications, where rotation must be controlled from the base or proximal end and the force of gravity on non-vertical louver blinds would create untold complications and very non-uniform shading. 
     Other approaches to controlling the level of light passing through architectural structures have used motorized shades or drapery. These approaches are also problematic, particularly in the applications noted above where the glazing is large and would require very long shades or blinds, e.g., on the order of 10 ft., 20 ft., 40 ft., 60 ft. or more, since such large shades would be heavy, difficult to manipulate and maintain, and expensive. The mechanics of controlling and manipulating motorized shades or drapery of any size is quite complicated and therefore motorized shades and drapery are expensive and difficult to maintain. Also, it is not possible to achieve uniform light distribution across a wide glazed space with motorized shades or drapery. 
     U.S. Pat. Nos. 7,281,353; 6,499,255; and 6,978,578 provide other more recent approaches to addressing the challenge of providing dynamic daylighting and shading systems on a large scale and in overhead, horizontal and sloped glazing applications. These patents utilize a plurality of rotatably-mounted light-blocking tubular members having at least one portion that is substantially opaque and means for rotating the light-blocking members to block out varying amounts of radiation by varying the area of the opaque portions presented to the incoming light. In the systems described in the above three patents, the light-blocking members are combined in a series of adjacent segregated elongated tubular cells or mounted for rotation in individual or paired cross-members positioned between light transmitting panels. As an alternative to tubular members, a generally rigid opaque member may be used if fitted with rings spaced along this member. Indeed, even the tubular members may be fitted with such rings in order to facilitate tubular member rotation and to improve performance. Attachment of the rings requires notching of the generally rigid opaque member and can be difficult and time-consuming for both generally flat and tubular members. Also, the rings, which unfortunately may interfere with light-blocking, must nevertheless be wide enough to accommodate longitudinal movement due to thermal expansion and contraction. Determining the width and location of the rings and ring-receiving notches is complex and, indeed, may require architectural approval before being implemented in custom applications, often making the use of such rings inconvenient and expensive. 
     In the system of the &#39;578 patent, the centers of rotation of the light-blocking members do not remain in place as the light-blocking members are rotated resulting in increased torque and load on the motor and varying horizontal positioning of the light-controlling members. Since the light-blocking members often do not run true because they are inadequately restrained and therefore bend and snake about as they rotate, they produce uneven and continuously varying spacing between adjacent members with uneven light distribution and an unacceptable appearance of disarray of the light-blocking members. When these light-blocking members are used in vertically oriented applications, they can disengage from lower-cross-members and run far more untrue with even greater increases in the torque/motor load and irregular lateral movement. When they are used in applications calling for an inclined orientation, the light-blocking members tend to disengage from the lower cross members and rotate in an uncontrolled manner, rubbing against one another, resulting in increased friction and torque and producing problematic noise. Finally, in tests simulating the application of snow and wind loads, excessive friction is produced between the light-blocking members and the cross-members which could cause early failure. 
     The paired upper and lower cross members of the &#39;353 patent solve the above problems. Also, when this system is in the fully closed position, there may be more light leakage than often desired. 
     While the designs provided by the above three patents represent important advances in the art, they have another drawback. For these designs, the light-blocking components of adjacent tubular members cannot come sufficiently close to each other when the systems are in their fully closed configuration due to intervening structural features. Therefore total blackout or near total blackout light blocking cannot be achieved. 
     We provide a significantly improved design in one of our two patent applications, U.S. patent application Ser. No. 12/903,904 filed Oct. 13, 2010. In the &#39;904 application, a beam with adjacent bores separated by web portions is described. Bearing members comprising an annular ring are dimensioned to fit within the bores and are provided with a flange extending radially outwardly from the rings. The bearings are mounted to the beam with the flanges in an offset fashion. A first bearing member is mounted in a first bore with its flange adjacent to a first beam face, its ring extending into the bore and a next bearing member mounted in a next adjacent bore with its flange adjacent the opposite beam face and its ring extending into the bore. This bearing structure and disposition makes it possible to bring the edges of adjacent light-controlling members close together when the members are closed making them more effective in light-blocking than has heretofore been thought possible. 
     However, in various applications, including where the web portions in the beam of the &#39;904 application between the bores are increased in width for structural or other reasons, it is desirable to provide alternative embodiments to achieve total or near total blackout where the adjacent edges of the light-blocking members are able to span the increased width webs between adjacent bores. 
     The present system provides a transparent/translucent panel unit in which the transmission of light across the system can be adjusted from almost full transparency or translucency to near total opacity. 
     SUMMARY 
     It is an objective to provide light-control assemblies in which the transmission of light can be adjusted from almost full transparency or passage of light to total black-out or near total black-out. 
     It is another objective to provide light-control assemblies that is reliable, quiet in operation, and readily constructed, maintained and serviced. 
     It is yet another objective to provide light-control assemblies that may be readily assembled on-site and that can be used in both new construction and retrofit applications. 
     It is still a further objective to provide a light-control assembly that accommodates thermal expansion and contraction of the components of the assembly, including the light-controlling members, when the assembly is subjected to wide-ranging temperature changes at the site of installation so that, e.g., slats in the assembly can move longitudinally within bearing members free from limitations imposed by rings and notches as the slats lengthen or shorten due to temperature swings. 
     Still another objective is to provide light-control assemblies that may be readily used with horizontal, vertical and sloped glazing in skylights, roofs, walls and other glazed and open unglazed architectural structures designed to pass light for daylighting interiors or other purposes. 
     Another objective is to provide light-control assemblies that can be readily serviced on-site. 
     Yet another objective is to provide light-control assemblies that can be spaced along any desired length of adjoining very long light-blocking members to accommodate rotation of the light-blocking members up to 360° by applying a rotary force about their longitudinal axes at only one end of the light-blocking members. 
     A still further objective is to provide light-control assemblies that can simply and efficiently be used with photovoltaic members. 
     Another objective is to provide light-control assemblies that can be made of modular components so larger assemblies can be economically and readily constructed and used in dynamic control of daylighting and shading in applications of varying widths. 
     A still further objective is to provide light-control assemblies that can accommodate radius bends in light-blocking members and that will continue to operate reliably in such installations. 
     It is still another objective to provide light-control assemblies with light-controlling members that may be free of notching and/or rings or other material removal and can be easily and simply slid into position. 
     It is a further objective to provide efficient, economic means for supporting and maintaining light-controlling members in panel units having spaced flat panels or sheets in ways not heretofore thought possible. 
     These and other objectives will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, objects and advantages of embodiments may be best understood by reference to the following description, taken in conjunction with the following drawings, in which like reference numerals identify like elements in the several figures, and in which: 
         FIG. 1  is an elevational view of a portion of a prior art panel in accordance with the teaching of U.S. Pat. No. 6,499,255; 
         FIG. 2  is a front elevation view of a panel unit in accordance with present embodiments, attached to adjacent panel units which are shown in partial view; 
         FIG. 2A  is a partial enlarged view of the spacer rails of  FIG. 2 ; 
         FIG. 2B  is an elevational view of an alternate panel joining arrangement in accordance with the present embodiments; 
         FIG. 3  is an enlarged partial front elevation view of one panel joining flange which may be used with the present embodiments; 
         FIG. 4  is a front elevation view of adjacent panel units angled with respect to each other to form a roof ridge; 
         FIG. 5  is a partial enlarged view of a portion of the structure illustrated in  FIG. 4 ; 
         FIG. 6  is a plan view, of a portion of the structure illustrated in  FIG. 4 ; 
         FIG. 7  is a perspective view of a honeycomb polycarbonate translucent panel which may be used in constructing a panel unit in accordance with the present embodiments; 
         FIG. 8  is a diagrammatic perspective view of a series of abutting light-controlling members; 
         FIG. 9  is a series of alternative designs of light-controlling members which may be used in present embodiments; 
         FIG. 9A  is an enlarged partial view of a pair of particular light controlling members in abutting position; 
         FIG. 9B  is a partial view of a light-controlling member comprising a flat opaque member with a series of rings spaced along its length; 
         FIG. 9C  is an alternate embodiment of a light-controlling member structure of  FIG. 9  in which an opaque member is assembled into opposing slots of a hemispherical tube light-controlling member and then a second hemispherical tube is assembled to the first tube to form a complete tubular configuration; 
         FIGS. 10A-10C  are diagrammatic representations of two light-controlling members in three difference relative positions, showing the passage of varying amounts of light; 
         FIG. 11A  is a partial enlarged perspective view of a scalloped carrier member for supporting adjacent light-controlling members and  FIG. 11B  is a similar partial perspective view showing a pair of juxtaposed scalloped carrier members; 
         FIGS. 12A and 12B  are front elevation views of, respectively, a series of adjacent light-controlling members of a single panel unit with top and bottom scalloped carrier members spaced therefrom and with the top and bottom scalloped members affixed together and holding the light-controlling members in place; 
         FIG. 13  is an exaggerated diagrammatic representation taken in elevation view of a single light-controlling member resting in a scallop in a carrier member; 
         FIGS. 14A-14C  are, respectively, a top plan view of a single panel unit, an end view thereof, and a cross-section thereof; 
         FIG. 15  is a representation of three alternative means for transmitting motion across adjacent light-controlling members; 
         FIG. 16  is comprises end views of means for transmitting motion across adjacent light-controlling members; and 
         FIGS. 17A and 17B  comprise alternative embodiments in which a metal screen and insulating materials are located within the panel system. 
         FIG. 18  is a perspective view of an embodiment of a light-control assembly in accordance with an embodiment including a single beam and two pairs of retainers; 
         FIG. 18A  is a partial view of a web portion between adjacent bores in the beam of the light-control assembly of  FIG. 18 ; 
         FIG. 19A  includes top and bottom perspective views of an exemplary flanged bearing member that may be used in a light-control assembly embodiment; 
         FIG. 19B  includes top, elevation and bottom views of the bearing member of  FIG. 19A ; 
         FIG. 19C  is a view of a bearing member as in  FIGS. 19A and 19B  with the addition of a slot in the side of the bearing member; 
         FIG. 19D  is an elevation view of yet another alternative bearing member design; 
         FIG. 20A  includes an end elevation view of a hemispherical light-controlling member and an end elevation view of the hemispherical light-controlling member mounted in the bearing member of  FIG. 19D ; 
         FIG. 20B  includes an end elevation view of a tubular light-controlling member, a front elevation view of yet another bearing member design and an end elevation view of the tubular light-controlling member mounted in this bearing member; 
         FIG. 20C  is an end elevation view of a light-control slat with longitudinally disposed slots mounted onto tab members; 
         FIG. 20D  is an end elevation view of yet another light-controlling member mounted in a bearing member circular bore; 
         FIG. 20E  is an end elevation view of another light-controlling member, mounted in the bearing depicted in  FIGS. 19A and 19B ; 
         FIG. 20F  is an end elevation view of another light-controlling member, mounted in another fashion in the bearing depicted in  FIGS. 19A and 19B ; 
         FIG. 21A  is an exploded view of the light-control assembly of  FIG. 18  including an optional reinforcing U-channel; 
         FIG. 21B  is an enlarged partial perspective view showing corresponding ends of two light-control assembly beams as the beams are interlocked; 
         FIG. 21C  is a partial elevation view of corresponding interlocking ends of two beams of the light-control assembly of  FIGS. 18 and 21A ; 
         FIG. 22A  is a partial perspective view of portions of two adjacent scallops of a retainer of the light-control assembly of  FIGS. 18 and 21A ; 
         FIG. 22B  includes partial perspective views of the back side of two portions of the retainers of  FIGS. 18 and 21A  showing corresponding locking pins and locking cavities; 
         FIG. 22C  is a partial elevation view of the mechanism by which the locking pins and locking cavities of  FIG. 22B  mate; 
         FIG. 23A  is a perspective view of a light-controlling member which may be used; 
         FIG. 23B  is a partial front elevation view of a portion of the light-control assembly of  FIG. 18  in which light-controlling members depicted in  FIG. 23A  are mounted in place in the assembly and rotated to a fully closed position; 
         FIG. 23C  is partial front elevation view of two light-controlling members as depicted in  FIG. 23A  highlighting the close-fitting relationship of the member edges when the light-controlling members are in the fully closed position; 
         FIG. 23D  is a perspective view of an alternative embodiment of the light-controlling member of  FIG. 23A  in which elastomeric materials is provided along the edges of the light-controlling member; 
         FIG. 23E  is a top partial view of two adjacent light-controlling members as depicted in  FIG. 23D  in the fully closed position, with the top of the light-controlling assembly removed to facilitate the depiction; 
         FIG. 23F  is partial front elevation view of two light-controlling members as depicted in  FIG. 23D  highlighting the close-fitting relationship of the member edges in the fully closed position; 
         FIG. 24  is a diagrammatic representation of two light-controlling members fitted with reflective surfaces to maximize light transmission when the light-controlling members are in the open position; 
         FIG. 25  is a perspective view of a drive mechanism that may be used to rotate adjacent light-controlling members; 
         FIG. 26  is a diagrammatic representation of an installation including drive gears, light-controlling members in open and closed positions, light-controlling assemblies and associated side framing; 
         FIG. 26A  is a partial end view taken along line  26 A of  FIG. 26  of a light-control assembly beam mounted in a side beam; 
         FIGS. 27A-27F  are diagrammatic representations of applications of light-control assembly embodiments mounted respectively between top and bottom glazing, below a top glazing, below a skylight, vertically, in inclined applications; and in curved applications; 
         FIG. 28  depicts a series of alternative light-blocking member configurations; and 
         FIG. 29  depicts micro-prismatic toothing on the surface of a light-blocking member; 
         FIG. 30  is a front elevation view of an alternative beam embodiment and  FIG. 30A  is side elevation view thereof; 
         FIG. 30B  illustrates a flat beam embodiment in the form of opposed scalloped carriage members; 
         FIG. 31  is a front elevation view of an alternative retainer embodiment intended to be used with the beam of  FIGS. 30 and 30A  and  FIG. 31A  is a side elevation view thereof; 
         FIG. 32  is a front elevation view of an alternative bearing member design intended to be used with the beam of  FIGS. 30 and 30A  and  FIG. 32A  is a side elevation view thereof; 
         FIG. 33  is a front elevation view of an alternative light control assembly containing the beam, retainer and bearing members of  FIGS. 30-32  and  FIG. 33A  is a cut-away view of the assembly of  FIG. 33  taken along lines  33 A- 33 A in  FIG. 32 ; 
         FIG. 34  is a partial perspective view of an alternative beam design designed to capture bearing members within off-set bore grooves; 
         FIGS. 35A-35C  are cross-sectional views of light blocking members in the form of slats with compliant lateral segments; 
         FIGS. 36A-36D  are cross-sectional views of alternative slat embodiments with laterally compliant edges comprising flat-resilient gaskets, hook shaped gaskets, and beads of resilient material. 
         FIGS. 37A-37C  are cross-sectional views of still further slat embodiments in which compliant lateral segments are provided with flexible links; 
         FIG. 38  is another slat design in which the lateral segments are triangular and are split at their apices; 
         FIG. 39A  is a cross-sectional view of a slat with flexible members attached to lateral segments by flexible arms; 
         FIGS. 39B and 39C  are, respectively, cross-sectional diagrammatic views of two adjacent slats in accordance with  FIG. 39A  mounted on a beam, as seen in cross-sectional elevation and plan views; 
         FIGS. 39D and 39E  are top-plan partial views of slats with notches along their lateral edges; 
         FIG. 39F  is a partial top-plan partial view of a pair of slats in which rectangular notches are shown juxtaposed next to beam webs; 
         FIGS. 40A and 40B  are cross-sectional views of hemispherical light-blocking members having flexible outer lips to provide lateral compliance; 
         FIG. 41  is a cross-sectional view of a tubular light-blocking member with diametrically opposed flexible lips to provide lateral compliance; and 
         FIGS. 42A-42C  are views of flexible support members having apertures containing rings for receiving light-control members. 
     
    
    
     DETAILED DESCRIPTION 
     Turning first to  FIG. 1 , an elevational view of a transparent or translucent panel  10  in accordance with the teaching of prior U.S. Pat. No. 6,499,255 is shown. Panel  10  includes a series of half-cylinder louvers  12  rotatably mounted in a series of adjacent, segregated cells  16  separated by walls  17 . Louvers  12  each have an opaque top surface  18 . Thus, in the illustrated embodiment where the louvers are in the fully closed position, light rays  20  strike opaque surfaces  18 , which block light transmission through the louvers. Unfortunately, the transparent or translucent material in the walls  17  between adjacent cells remains unblocked, which means that light rays  22  will penetrate the panel through these walls. Thus, even with all of the louvers in the fully closed position, the panels of the &#39;255 patent admit light: in one commercial embodiment of this invention, the panels have been found to admit a minimum of about 6% light transmission. Also, the panel of the &#39;255 consists of one integral, hollow core, multi-cell panel with inserted radiation-blocking members in the cells, which means that serviceability and maintenance options are limited. 
     The panel systems of the present invention are referred to as being transparent/translucent. It is intended to mean by this that the panel systems range from transparent (transmitting light rays so that objects on one side may be distinctly seen from the other side) through translucent (letting light pass but diffusing it so that objects on one side cannot be clearly distinguished from the other side). Also, the panel systems may be tinted. Typical tinting colors include white, bronze, green, blue, and gray, although other colors may be used. Further, the panels may have a matte finish. Finally, combinations of different top and bottom panels may be used, such as clear/clear, white/clear, clear/white, bronze/clear, green/clear, green/white, bronze/white, white/white, etc. 
     Also, when reference to “light” is made in the description of the present invention, it should be construed to include the spectral range of visible light as well as electromagnetic radiation below and/or above that spectral range. 
     Turning now to  FIG. 2 , a panel system unit  30  in accordance with the invention is shown consisting of two generally flat transparent/translucent panels, including an interior panel  32  and an exterior panel  34 . Panels  32  and  34  are generally parallel and are separated a distance “x” by elongated spacer rails  36  with top and bottom ledges  37  which extend along the lateral edges  38 ,  40 ,  42  and  44  of the interior and exterior panels. This spacing may be of any desired size, since the spacing of the panels can be adjusted to accommodate whatever diameter is chosen. While panels  32  and  34  may be of any desired width, currently preferred widths are 24, 48 and 60 inches. Also, while the panels may also be any desired length, it is currently intended that panels about 2 feet to 60 feet in length will be used. 
     The lateral edges of the panels may be provided with respective panel joining flanges  46 ,  48 ,  50  and  52  for conveniently assembling the panels together. In one such panel-joining arrangement, the flanges each have a smooth outer face  54  and an inner face  56  with tooth-like detents  58   a - 58   c  ( FIG. 3 ), whose function will be explained below. A similar joining flange structure is described, for example, in U.S. Pat. No. Re. 36,976, the contents of which are incorporated herein by reference. Also, panels with different panel joining flange designs and other panel-joining arrangements may be used. 
     As seen best in  FIG. 2A , spacer rails  36 , in turn, each have an outer bracket  60  shaped as shown, to provide a middle attachment section  61  and offset ends  62  and  64 . The brackets are attached to the outer surface of each of the spacer rails by conventional means, with attachment section  61  centered along the rails, thereby defining top and bottom channels  66  and  68  between the outer surface of the spacer rails and the inner surface of the bracket. The channels are dimensioned to accept flanges  48 - 52  in a tightly fitting manner to firmly and sealingly join the panels under an elastic deformation of the detents. Thus, when the panels are pressed home to assemble the panel system unit with the inner surfaces of panels  32  and  34  abutting ledges  37 , there is resistance to removal of either of the panels from these channels. If and when a repair is needed, it is necessary only to release one corner of the panel flange with an appropriate tool, and then continue to zip it along the length of the panel to release the entire panel. The panel can be reinstalled after the repair is completed by again pressing the panels home to seat the panel flanges in the channels. 
     An alternate panel-joining arrangement is depicted in  FIG. 2B . In this embodiment, internal and external panels  32   a  and  34   b  may be any appropriate sheet material. The sheets are held together in this embodiment by retainers  36   a  which extend along the opposite lateral edges of the sheets. Retainers  36   a  include two channels  39  and  41  in which the lateral edges of the sheets snugly rest and a spacer  51  carrying the flanges at the desired sheet spacing of the panel system. The retainers preferably are made of aluminum or of another metal which either inherently resists corrosion or is treated to resist corrosion. 
     Any number of fully assembled panel units  30  can be joined to adjacent panel units to achieve the panel system width called for in a particular application. Adjoining panel units may be fixed to each other using a clamping system  70 . This clamping system includes a bottom member  72  with a base  74  and elongated bottom pedestals  76  and  77  along each lateral edge of the base. An upstanding bracket  78  along the center of the base with a series of screw thread-receiving apertures  80  along its length. Clamping system  70  also includes a top member  82  with an upstanding reinforcing strip  84  along its center and a series of screw-receiving apertures  86  running along the strip. Along each lateral edge of the top portion, a pair of elongated top pedestals  88  and  90  are provided with apertures for receiving resilient sealing gaskets  92 . 
     In order to join the adjacent lateral edges of the panel units, the clamping members are positioned as illustrated, with elongated bottom pedestals  76  and  77  abutting the exposed surface of the interior panels and sealing gaskets  92  of top pedestals  88  and  90  abutting the top surface of the exterior panels. A series of screws  94  spaced, for example, at intervals of about 8-16 inches, are passed through the apertures  86  and into the thread-receiving apertures  80 , and screwed home to lock the clamping member together and seal the connection from outside elements. 
       FIGS. 4 and 5  illustrate an alternate application of the invention where adjacent panel units are angled with respect to each other to form a roof ridge. In this embodiment, a modified clamping system design  70 ′ is used. This modified clamping system generally corresponds to clamping system  70  except that base  74 ′ and top member  82 ′ are angled to produce the desired ridge slope. 
     A series of four panel units assembled to produce a panel system for use in a skylight is illustrated in  FIG. 6 . In this fully assembled system, the four panel units  30   a ,  30   b ,  30   c , and  30   d  are each individually assembled and joined to adjacent panel units as illustrated in  FIG. 2  and described above. 
     The use of removably mounted interior and exterior panels facilitates easy replacement of damaged panels without exposing the interior of the enclosed structure. Adding or replacing a double-layer on other glazing system, in contrast, would be significantly more difficult and expensive, and could produce damage requiring repairs that interrupt the function of the architectural structure in which the panel system is mounted. 
     Thus, assuming for purposes of illustration that exterior panel of panel unit  30   b  has to be removed to remedy a problem within the panel unit. This can be accomplished by inserting an appropriate tool at point A to remove the leading corner of the panel flange from its corresponding channel and then continue to zip it along the length of the panel to release the entire panel. This is repeated at point B whereupon the entire panel is removed, the problem is remedied and the exterior panel re-installed by positioning the flanges adjacent the channels and pressing the exterior panel home as describe earlier. It should be noted that this entire repair operation can be accomplished without disturbing the interior panel of the panel unit. Also, either of the sheets of the alternative panel-joining arrangement of  FIG. 2B  may be removed in a similar fashion by slipping the appropriate channel from the edge of the sheet which is to be removed and reattaching the channel when the repair is completed. 
     A wide variety of different types of panels made of various transparent and translucent materials may be used, including, but not limited to, plastics (including, but not limited to, polycarbonates and acrylics), fiberglass, perforated metal fabric, or glass. It is preferred, however, that the panels have at least the appropriate light transmitting properties and a minimum resistance to impact of about 10 ft/lb. Also, a UV-resistant architectural face can be co-extruded with the panel to minimize the need for periodic resurfacing. 
     In one preferred embodiment, a Pentaglas® honeycomb polycarbonate translucent panel available from CPI International Inc. (Lake Forest, Ill.) will be used. These polycarbonate panels are described in U.S. Pat. No. 5,895,701, which is incorporated herein by reference, have an integral extruded honeycomb structural core consisting of small honeycomb cells approximately 0.16 inch by 0.16 inch which provides internal flexibility to absorb expansion and minimize stress and resists impact buckling. The resulting design offers smaller spans between rib supports, resulting in stronger durability, as well as superior light quality, visual appeal, higher insulation and excellent UV resistance. The internal flexibility of the panels absorbs thermal expansion through the panel in all directions (on the x, y, and z axes). This minimizes stress in all directions and preserves dimensional stability. The panels also have a high impact absorbing and load bearing property, a good ratio of weight to strength, and UV protection on both sides of the panel. The superior light diffusion capabilities ensure excellent quality of natural light. The panels are environmentally friendly, non-toxic, and made of 100% recyclable material. 
     A series of elongated rotatably mounted light-controlling members  100  corresponding in length to the length of the panel units are disposed between panels  32  and  34 , as represented in a diagrammatic perspective fashion in  FIG. 8 . As described below, the light-controlling members may be of a variety of different structures. In a preferred embodiment, the light-controlling members will have a circular outer rotation surface (e.g., an elongated tube or a series of outer annular members disposed along the light-controlling members generally perpendicularly to the longitudinal axes of the light-controlling members) extending at least about 180° around their circumference. In the illustrated embodiment, the light-controlling members abut each other (tolerance about 1-3 mm) to maximize the light blocking capability of the system. This is a preferred embodiment of the invention. However, in alternative embodiments, the light-controlling members may be spaced from each other permitting some light to pass between adjacent light-controlling members, so long as the circular engagement surfaces of adjacent light-controlling members remain in contact. 
     A series of alternative designs of the light-controlling members  100  are illustrated in cross-section in  FIG. 9 . For example, a light-controlling member  100   a  may be used, comprising a generally elongated transparent or translucent tube  102  having a diameter “B”. A generally planar light-blocking or opaque member  104  is positioned in the tube across its diameter by co-extruding the outside tubular wall and the light-blocking or opaque member or by inserting the light-blocking or opaque member in a preformed tube. 
     The light-blocking or opaque member need not be flat but may, for example, be wider than the allowed space and inserted in a “bowed” or other configuration. In the illustrated embodiment, tube  102  may be replaced by a series of annular members or rings  103  spaced along an opaque member  105  ( FIG. 9B ). In this embodiment, the opaque member should be sufficiently rigid so that applying rotary movement to the opaque member at any point along its length will cause the entire light-blocking or opaque member to rotate about its longitudinal axis without causing the opaque member to twist substantially out of its initial configuration. 
     The light-blocking members may be opaque or they may be translucent or tinted to a level which produces the desired degree of light-blocking. Also, the light-blocking members may be segmented into light-blocking or opaque portions and transparent/translucent portions. For example, in a 40-foot panel unit with corresponding 40-foot light-controlling members, the first 10 feet of one or more of each of the light-blocking members may be opaque, the next 5 feet transparent/translucent, and the last 25 feet opaque. Such a segmented arrangement might be used where it is desired to maintain a lighted area at all times. 
     Light-controlling member  100   b  is generally of the same design as light-controlling member  100   a  including a tube  106 , except that longitudinal sills  108  project radially from the outer surface of the tube. When the tubes are positioned so that the sills abut at least partially as the tubes rotate ( FIG. 9A ), the range of motion of the tubes is limited by the abutting sills to 180°. Also, the sills may be either opaque themselves (as shown) or coated with a light-blocking or opaque material. This provides enhanced light blocking when the sills approach and reach an abutting position since light between the tubes is blocked by the sills. Furthermore, the use of light-blocking or opaque sills in this fashion makes it possible to increase the spacing between the adjacent tubes without sacrificing light blocking between the tubes, so long as the sills are also widened to insure that they extend into the space between the adjacent tubes. Of course, tubes with light-blocking or opaque sills as described above may also be arranged so that the sills do not actually touch as the tubes rotate, which will permit some light to pass between the sills when the light-controlling members are in the closed position. Lastly, the tubes may be provided with only one light-blocking or opaque sill each or with more than two sills at varying locations about the circumference of the tubes. 
     Light-controlling member  100   c  comprises a tube  110  with opaque-coated outer sills  112  and a pair of opposing slots  114  and  116  formed at the inside diameter of the tube to receive an opaque member  118  which is assembled into the tube after it is formed. In all cases, the opaque member is rendered opaque by known techniques, such as painting, by coating with an opaque film, by applying an opaque plastic layer by co-extrusion, etc. Also, fire resistant materials such as metal slots may be used as the opaque member to improve the fire resistance of the panel system. Additionally, different colors and designs may be applied to the opaque members to increase the visual interest of the panel system as the opaque members move into the closed position. Indeed, the opposite sides of individual opaque members may be differently colored or bear different designs to produce different visual effects by rotating the light-controlling members 180° from one fully closed position to the other. 
     Another light-controlling member design is designated  100   d . This tube has a generally hemispherical cross-section and preferably its circumference extends to 180°. Although an opaque surface may be coextruded across the diameter of the tube (not shown), in the illustrated embodiment the tube  120  includes a pair of opposing slots  122  and  124  at the inside diameter of the tube to receive an opaque member  126  which is assembled into the tube after it is formed. When this structure is used, a series of annular members or rings may be disposed along the length of the light-controlling member to permit complete rotation of the light-controlling member. In another alternative embodiment, once the opaque member is assembled into opposing slots  122  and  124 , another tube  125  with a generally hemispherical cross-section and lands  128  may be assembled to tube  120  (e.g., by creating an adhesive bond or a clip-on type connection at the lands) to produce a complete 360° tubular configuration as seen in  FIG. 9C . 
     Light-controlling member  100   e  comprises an opaque member  132  with a supporting wall  130 , together forming an elongated light-controlling member with a “T” shaped cross-section, as shown. The reinforcing rib  7  adds rigidity to the opaque member and also helps position the opaque member within a series of rings  128  which are spaced along the light-controlling member. In a less preferred embodiment of the invention, the reinforcing rib may be eliminated. Light-controlling member  100   f , in turn, includes a series of annular members of rings  136  and an opaque member  138  with generally perpendicular supporting walls  140  and  142  which extend along the length of the tube and abut the rings at their apex  143 . Other tube configurations are illustrated in U.S. Pat. No. 6,499,255, and are incorporated herein by reference. 
       FIGS. 10A-10C  are diagrammatic representations of two light-controlling members  100   d  in three different positions. In  FIG. 10A , the two light-controlling members are in the “fully closed” position, with the opaque members  126  of the tubes  120  adjacent each other and fully blocking incoming light  144 . This figure should be contrasted with the depiction of the prior art system of U.S. Pat. No. 6,499,255 in which in the fully closed position depicted, light rays  22  penetrate the panel through the walls  17  between the cells  16 . In  FIG. 10B , tubes  120  have been rotated 90° so that the maximum amount of light  144  may pass by the tubes. Finally, in an intermediate position of the tubes as shown in  FIG. 10C , only a portion of the light will pass. 
     In each of the embodiments of this invention, the opaque members may be replaced with light-blocking members which are not opaque but rather are semi-opaque so that a limited amount of light will pass in the fully closed position, as may be required or desired in certain applications. Also, the opaque or semi-opaque members may include photovoltaic solar cells to generate electricity, preferably in conjunction with means for maximizing the photovoltaic output by rotating the light-controlling members with movement of the sun across the sky to insure that the photovoltaic solar cells continuously receive the maximum possible sunlight exposure. Finally, where the sole objective is to generate electricity, the opaque members may be replaced with transparent or translucent photovoltaic solar cells. 
     We turn now to  FIGS. 11A, 11B, 12A and 12B . These figures illustrate scalloped carriage members  150  each comprising a generally horizontal base  152 , and a series of hemispherical cut-outs or “scallops”  154  in their top surface. Scallops  154  are intended to receive the light-controlling members and are therefore slightly greater in diameter than the light-controlling members. Thus, as illustrated in  FIG. 13 , the area of contact between the outer surface C of the tube  102  and the inner surface of a scallop  154  is minimized, thereby minimizing the friction between the two, as the light-controlling member is rotated. 
     In the fully assembled panel, support of the light-controlling members may be provided by a series of carriage members spaced along the panel for supporting and horizontally positioning the light-controlling members adjacent each other. The scalloped carriage members may be used singly or in pairs, clamped together using a clamping spring  150 , as depicted in  FIG. 12B . When the carriage members are used with light controlling members with sills, as in  100   c  of  FIG. 9 , the sills should be cut away to provide clearance for the carriage members. Furthermore, since the use of sills permits increased spacing between adjacent light-controlling members, the spacing between the scallops can be increased, permitting a concomitant increase in the surface area of the abutting surfaces  151  and  153  ( FIG. 12A ) of the carriage members and the option of placing connecting members (e.g., hook and loop (Velcro®) connectors, self-tapping screws, snap fasteners, etc.) at those abutting surfaces to help lock the carriage members together. 
     The carriage members preferably will be made of a low friction material such as a low friction engineered plastic like polycarbonate or a low friction metal like aluminum, and the scallops and/or the portions of the light-controlling members riding in the scallops may be coated with a slippery coating such as Teflon. Also, when a hemispherical light-controlling member is used (e.g.,  100   d ), rings may be disposed on the light-controlling member at the point of contact with the scallops to extend the range of rotation. When hemispherical light-controlling members with sills are used, the sills may be cut away to permit annular members to be disposed on the light-controlling member at the point of contact with the scallops. 
     A fully assembled panel system  160  is shown in  FIGS. 14A, 14B, and 14C  (respectively, top plan, side elevation and cross-sectional views), with a series of scalloped carrier members  150 A,  150 B and  150 C spaced within a panel unit comprising interior panel  162 , exterior panel  164 , and a series of light-controlling members  166  within the panel system resting on the scalloped carrier members which support the light-controlling members. 
     Turning now to  FIG. 15 , three alternative means for transmitting motion across adjacent light-controlling members are illustrated. In the first motion-transmitting arrangement, an annular endcap  170  is attached to one end of a light-controlling member  172  and the endcap is provided with a band  174  of a high coefficient of friction material, such as rubber or polyurethane, so that circular motion imparted to one light-controlling member in the series of adjacent members will impart motion to the remaining members due to the frictional linkage achieved by the high coefficient of friction material positioned in alignment on adjacent members. One or more bands  174  may also be applied along the light-controlling members when they are tubular, either in lieu of the band on endcap  170  or in addition to it. Also, it is preferred that the bands be clear or translucent, particularly when they are disposed along the light-controlling members. Additionally, where the light-controlling members have sills, as discussed above, the sills will be cut away to provide clearance for the rings. 
     In the second motion-transmitting arrangement, one or more notched bands  176  are positioned along a light-controlling member  178  and aligned so that the intermeshed bands of adjacent light-controlling members transmit motion imparted to one member across the series of intermeshed members. Such intermeshing bands may also be used on an endcap as described above and further use of clear or translucent intermeshing bands is preferred. Also, as in the prior embodiment, where the light-controlling members have sills as discussed above, the sills will be cut away to provide clearance for the rings. 
     In the third motion-transmitting arrangement, the outer surface  182  of each of light-transmitting members  180  is provided (as by extruding) with a cogwheel cross-section, as shown, including a series of teeth  184  extending along their length so that the adjacent light-transmitting members intermesh to transmit motion imparted to one member (as by a drive motor (not shown)) across the series of intermeshed members. An opaque member  188  is preferably positioned within the cogwheel cross-section between a diametrically opposing pair of teeth  184   a  and  184   b  so that the opaque member extends into the teeth and is supported along its lateral edges within the opposing teeth. This embodiment has some significant advantages. First, the intermeshing teeth provide a wide tolerance as to fit between adjacent light-controlling members and tolerance to dirt or other extraneous matter which may find its way into the area. Second, since the opaque member extends into the teeth and is supported along its lateral edges within the opposing teeth in the closed position, the opaque members of adjacent light-controlling members will overlap, blocking the passage of light between adjacent light-controlling members. 
     End views of the light-transmitting members resting within a series of three panel systems,  186 ,  188  and  190  as described above are illustrated in  FIG. 16 . In panel system  188 , however, a small gear  192  is located between the adjacent spaced light-controlling members to enable the light-controlling members to rotate in the same direction as the adjacent notched bands intermesh with the wheels. 
     The above and other methods may be used for rotating adjacent light-controlling members where rotary motion is imparted to one or more (but not all) of the adjacent light-controlling members either manually or by motorized means, as represented diagrammatically by feature M in  FIG. 12A . Any of the mechanisms described in U.S. Pat. No. 6,499,255, for example, may be used for imparting such rotary motion. 
     Turning now to  FIGS. 17A and 17B , a further embodiment of the present invention is disclosed in which space  200  is provided above the plane of the adjacent light-controlling members in the panel unit. Thus, for example, in  FIG. 17A , a panel joining system  202  much like that of panel joining system  36  in  FIG. 2  is shown, except that this panel-joining system  202  has an elongated upstanding bracket  204  and is used in conjunction with elongated spacer rails  208 , shown in side view at the right of the figure. A different enlarged panel-joining system  210  is used in the embodiment of  FIG. 17B  with different panels, and the panels are held together by a different attachment mechanism. In both cases, enlarged clamps  209  are used to joint adjacent panel units. 
     In both the embodiments of  FIGS. 17A and 17B , a series of “I” beams  208  are positioned at intervals between the lateral edges of the interior and exterior panels to create an air space  210  between the panels. In  FIG. 17A , a panel of a non-combustible generally light-transmitting material, such as a metal screen  212 , is positioned above the light-controlling members and held tautly in position. In  FIG. 17B , a series of “I” beams  208  are positioned at intervals between the lateral edges of the interior and exterior panels to create an air space  210  between the panels. In  FIG. 17A , a layer of light transmitting fire-resistant insulating material, such as loose glass fibers  214 , is disposed immediately above the screen in air space  210  to add thermal insulation and to enhance the fire resistance of the panel system. The screen and insulating material prevent or delay the passage of burning particles through the panel system, in accordance with the requirements of ASTM E-108 Class A Fire Rating Requirements. The resulting panel system thus provides the light transmission and control characteristics of the other embodiments of the invention as well as improved fire resistance. 
     Turning now to  FIG. 18 , a light-control assembly  310  is illustrated. Assembly  310  includes first and second opposed faces  314  and  316  first and second ends  315  and  317 , and a series of adjacent circular bores  318  extending between the opposed faces of the assembly and exemplary bearing members  330  shown mounted in two adjacent bores  318   a  and  318   b . Bores  318  are formed in the beam  370  ( FIG. 21A ) of the assembly which will be described below. The longitudinal axes  322  of the bores preferably will be generally parallel to each other although they need not be generally parallel in all embodiments. 
     Adjacent circular bores  318  are separated by a web portion  320  ( FIGS. 18 and 18A ) of beam  370  ( FIG. 21A ) defined by the lateral spacing of the bores. Web portion  320  will be shaped as indicated in  FIG. 18A  with its thinnest dimension “A” at the point where the diameters of the adjacent bores that define the web are co-linear. 
     In some embodiments it is preferred that web portion  320  be as thin as possible in order to optimize the light-blocking performance of the light-control assembly by minimizing the distance between the adjacent edges of the light-controlling members when they are in the closed position, as will be described in more detail below in connection with  FIGS. 23C and 23F . Of course, web portion  320  must not be so thin as to adversely affect the structural integrity of the beam. 
     While it is preferred in some embodiments described herein that web portion  320  be as thin as possible in order to optimize the light-blocking performance by minimizing the distance between the adjacent edges of the light-controlling members when they are in the closed position, other embodiments described herein will accommodate thicker web portions. 
     The optimal web thickness A or A′ at the point where the diameters of the adjacent bores that define the web are co-linear ( FIGS. 18A and 18B ) will depend on the material out of which beam  370  is made as well as the thickness of the beam between its opposed faces and other structural features of the beam and other structural components of the light-control assembly. In one embodiment, where the beam is made out of polycarbonate, the bores are about 45 mm in diameter and the thickness between the opposed faces of the beam is about 16 mm, the web can be as thin as about 1 mm. in thickness at dimension A. Such a thin web is desirable in some embodiments. In other embodiments however web thickness A′ will be greater (preferably at least 2 mm for structural or other reasons. 
     Embodiments of light-control assembly  10  include bearing members  330  as shown in  FIG. 18  and as illustrated in enlarged form in  FIGS. 19 and 19B . In this embodiment, bearing members  330  each include an annular ring  332  dimensioned to fit rotatably within bores  318  and a retention flange  334  extending radially outwardly from the rings. The width of flange  334  may be less than or equal to the thickness A of web portion  320  between the bores to preclude interference between the flange and light-blocking members mounted in bearings in the adjacent bores. 
     In embodiments in which web thickness A′ is large enough to accommodate adjacent bearing flanges (i.e., the flanges are not offset), the total width of the flanges of adjacent bearings may be less than or equal to the thickness A′ of web portion  320  between the bores to preclude interference between the flanges of the adjacent bearings. 
     Bearing members  330  have at least two diametrically opposed notches  336   a  and  336   b . Notches  336   a  and  336   b  have opposed notch bottoms  338   a  and  338   b  spaced a predetermined distance apart “B”. In the embodiment of these figures, notches  336   a  and  336   b  extend through the rings and into the flanges leaving web portions of the flange  340   a  and  340   b  below the bottom of each of the notches. In this illustrated embodiment bearing members  330  also include an optional second pair of diametrically opposed notches  336   c  and  336   d  equally spaced from notches  336   a  and  336   b  to help maintain the circularity of the bearing members when they are made by a plastic injection molding process. 
     The bearing members in this embodiment also include pairs of guide and retention tabs  342   a  and  342   b  located on opposite edges of the notches. Tabs  342   a  and  342   b  project from the inner surface  344  of the ring to define a “V” shaped receiving cavity that opens towards the center of the bearing member. 
     Notches  336   a  and  336   b  (optionally including retention tabs  342   a  and  342   a ) are designed to receive light-blocking members in the form, for example, of slats  450 , which are described below in connection with the description of  FIGS. 23A-23E and 18-32  and which themselves act as opaque reflecting, spectral controlling or translucent barriers. Notches  336   a  and  336   b , of course, can receive other types of light-blocking members that act as opaque, translucent, reflecting or spectral controlling barriers including without limitation flat light-blocking members, light-blocking members  600   a - 600   k  of  FIG. 28 , tubular designs light-blocking members  6008 - 600   o  of  FIG. 28  and the tubular hemispherical light-controlling members fitted with opaque or translucent barriers, as described below. The shapes shown in  600   m - 600   o  of  FIG. 28  employ the principle of retro-reflection as disclosed in US 2006/028845A1, the pertinent disclosure of which is incorporated by reference. Finally, as illustrated in  FIG. 29 , micro-prismatic toothing  602  may be provided on the surface  604  of a light-blocking member to achieve retro-reflection either alone or on a geometric retro-reflective surface as in  FIG. 28 . Such micro-prismatic toothing will help avoid overheating and glare. Also, the micro-structured mirroring may be rolled onto an aluminum substrate, and then glossed, anodized and formed into a desired geometrical shape. 
       FIG. 2C  illustrates an alternative bearing member structure  333  having a relief slot  335  that passes through the annular ring and retention flanges of the bearing member. This slot facilitates mounting of bearing members structured in this way since the bearing member can be pressed together to close the slot when the rings are inserted in the bores. After insertion, the bearing members will be released so that they can spring back to their original configuration ensuring rotatable mounting in the bores. Such slotted bearing members not only facilitate assembly into the bores but also are forgiving of tolerance variations and thermal expansion/contraction of other components in the light-control assembly. 
       FIG. 19D  depicts yet another bearing member design  350  in which retention flange  334 , as well as the optional guide and retention tabs are not used and notches  352   a ,  52   b ,  352   c  and  352   d  extend through the rings  354  but not into retention flanges  356  thereby establishing a smaller predetermined distance B1 between notch bottoms  352   a  and  352   b  which is smaller than distance “B”. Additionally, the web portions of the flange below the bottom of each of the notches in this embodiment are thicker than web portions  340   a  and  340   b  since the notches do not extend into the flanges. 
       FIG. 20A  illustrates a hemispherical tubular light-controlling member  360  which may be used with, e.g., any of bearing members  330 ,  333  or  350 . Light-controlling member  360  includes a clear tubular hemispherical portion  362  and a generally flat opaque or translucent barrier component  364 . The opaque or translucent barrier component includes ledges  365  which extend beyond the outer surface of the tubular hemispherical portion. These ledges are dimensioned to rest in notches  352   a  and  352   b  of bearing member  350 A as shown (or in the corresponding notches of bearing members  330  or  333 ) while the tubular hemispherical portion preferably fits within the inner wall  366  of ring  354  of the bearing member (or the corresponding inner walls of the rings of bearing members  330  or  333 ). 
       FIG. 20B  illustrates an alternative arrangement where a hemispherical tubular light-controlling member  360 ′ is mounted in a bearing member  331 . This hemispherical member includes a generally flat opaque or translucent barrier component  364 ′ and optional supporting members  365 . Bearing member  331  has inwardly diametrically directed locking tab members  373  which retain the hemispherical member in place in the bearings. 
     Bearing  331  may also be employed as illustrated in  FIG. 20C  with a light-controlling member in the form of a slat  1120  which has longitudinally disposed elongated slots  1122  at each of its lateral edges which may be mounted onto tab members  73  as shown in this figure. 
       FIG. 20D  illustrates a 360° tubular light-controlling member  367  including a clear tubular component  368  and a generally flat opaque or translucent barrier component  369  which is mounted across the diameter of the tubular member. The alternative light-blocking members of  FIG. 28  may also be used in lieu of component  369 . Also, the micro-prismatic toothing of  FIG. 29  may be employed. A bearing member that may be used with this configuration may comprise, e.g., the structure of bearing members  330 ,  333  or  350 , but preferably will not have either notches or tabs. For example, bearing member  355  having ring  357  and flange  359  may be used. In this embodiment, the tubular light-controlling member preferably will fit snuggly against the inner wall  361  of the ring of bearing member  355  which itself will be rotatably mounted in bore  318 . 
     When reference is made to a feature as being opaque or translucent it is intended to mean that the feature ranges from translucent (letting some light pass but diffusing it so that objects on one side cannot be clearly distinguished from objects on the other side) to opaque (letting no appreciable amount of light pass). When reference is made to “light”, this term should be construed to include the spectral range of visible light (with or without the electromagnetic radiation with wavelengths below and above that of the visible light). When reference is made to a light-controlling member as being “spectral controlling” it is intended to mean that one or more selected portions of the spectrum are allowed to pass or are blocked, e.g., that a UV, IR or other wavelength range is allowed to pass or is blocked. When reference to a light-controlling member as being “reflecting” or “reflective” it is intended to mean that some or all of the incident light (including e.g., a selected wavelength range) is bent or sent back from a blocking surface of the light-controlling member. 
     Any light-blocking components used in the described embodiments, such as the opaque or translucent or spectral controlling barrier components  364 ,  369  or  600   a - 600   o , may be tinted to a level that produces the desired degree of light-blocking. Also, the light-blocking components may be segmented into light-blocking or opaque portions and transparent/translucent portions. For example, in 40-foot light-controlling members, the first 10 feet of one or more of each of the light-blocking components may be opaque, the next 5 feet transparent/translucent, and the last 25 feet opaque. Such a segmented arrangement might be used where it is desired to maintain a light-admitting area at all times. Also, translucent portions may be tinted. Typical tinting colors include white, bronze, green, blue and gray; although other colors may be used. Finally, light-controlling members may have one face (e.g., face  465  of light control member  450  or one face of flat portions  364  or  369 ) and a different treatment on the other face (e.g., face  467  of light control member  450  or the opposite face of flat portions  364  or  369 ). For example, one face may have a reflective surface and the other may have a diffusing surface so that the light-controlling member may be rotated into a first position in which it reflects incoming light away from the covered space and a second position in which the non-reflective surface diffuses the incoming light that strikes it. 
     The barrier components may include photovoltaic solar cells along their surface to generate electricity, preferably in conjunction with means for maximizing the photovoltaic output by rotating the light-controlling members to track the movement of the sun across the sky, ensuring that the photovoltaic solar cells continuously receive the maximum possible sunlight exposure. This combination provides in a single assembly both effective dynamic control of daylighting and shading and efficient electricity generation. 
       FIG. 20E  illustrates yet another light-controlling member  451  comprising a pair of perpendicular cross pieces  453  and  455  which preferably are coextruded. Cross piece  453  is opaque in this embodiment, although it may, of course, have a different surface treatment, as discussed above. Additionally, feet  457  are formed at the opposite ends of the cross pieces are generally perpendicular to the cross pieces. Preferably, opaque cross piece  453  passes through clear feet to maximize light-blocking Feet  457 , which will rest against the inner wall  374  of bearing member  355  to retain light-controlling member  151  in place, may be curved to follow the curvature of the inner surface of the bearing member and preferably will be clear as shown. As a result, opaque cross piece  453  is positioned and held in place across the diameter of the bearing member and presents minimal light-blocking when light-controlling member  451  is in the fully open position. 
       FIG. 20F  illustrates yet another light-controlling member design. This design includes cross pieces  459  and  461  which generally correspond to cross pieces  453  and  455  of  FIG. 20C . In this embodiment, however, there are no feet. Rather, the ends  463  of the cross pieces fit in opposed notch bottoms  336 A- 336 D and in guide and retention tabs  342 A and  342 B of bearing member  330 . It should be noted that in the embodiments of  FIGS. 20C and 20D  both bearing members  330  and  355  include retention flanges, but these have been removed for purposes of illustration. Other bearing designs (e.g. bearing members  330 ,  333 ,  350  or  355 ) may be used with this light-controlling member design. 
     Turning now to  FIG. 21A , an exploded view of light-control assembly  312  is shown, including a beam  370  at the center of the assembly having bores  318  in which the bearing members rotate. Since beam  370  in this embodiment is made by plastic injection molding for purposes of minimizing friction, weight and material usage, the beam is molded with rings  372  defining bores  318  along their inner surface  374 . Adjacent rings  372  intersect on their periphery and are joined along lateral conjunction segments  376 . Preferably, the beam will be made of a clear or translucent material like polycarbonate to help camouflage the light-control assembly. However, the beam may also be made by known techniques using aluminum, steel or other appropriate materials. 
     At least one and preferably three or more rollers or roller assemblies may be mounted on the beam about the periphery of the bores to contact the outer circular surface of the bearing members. This will help reduce friction and wear particularly in heavy usage applications, where the light-controlling members are heavy, or where it is necessary or desirable to minimize the number of light-control assemblies. Furthermore, where such rollers or roller assemblies are used they may be spaced from the front and back faces of the beam and/or undercut to create a gap for retaining the bearing members in lieu of or in addition to retainers  410  or  610  which are discussed below. 
     The injection molded beam illustrated in  FIG. 21A  also includes top and bottom strips  378  and  380 , front and rear faces  314  and  316 , and a series of repeating top and bottom support ribs  382   a - 382   c  defining cavities  383   a - 383   c , as illustrated. The combination of the laterally conjoined rings, top and bottom strips, support ribs and cavities together make the beam lightweight yet give it sufficient rigidity to resist bending forces to ensure reliable operation of the light-control assembly. 
     The beam of  FIG. 21A  preferably is designed for modular applications where a series of beams having, for example, six bores that are approximately 45 mm in diameter can be easily and reliably interconnected to produce a longer composite light-controlling assembly of a desired width comprising a multiple of the width of a single light-control assembly. For example, such a modular assembly nominally 600 mm in width could be constructed and used in applications where the light-controlling members are any desired length from, e.g., up 15 meter or more. 
     Thus, the first end  384  of the illustrated beam  370  includes top and bottom trapezoidal projections  386   a  and  386   b  that fit into trapezoidal cavities  402   a  and  402   b . Trapezoidal projection  386   a  and corresponding trapezoidal cavity  102   a  are shown in the partial enlarged views of  FIGS. 21B and 21C . In  FIG. 21C  it is seen that trapezoidal projection  386   a  includes a base surface  388  protruding beyond a generally flat face  390  of beam end  384 . Trapezoidal cavity  402   a  is dimensioned to receive trapezoidal projection  386   a , so that face  388  of the trapezoidal projection is adjacent to flat bottom surface  104  of the trapezoidal cavity. Also, beam end  400  includes a flat face  404  dimensioned to abut flat face  390  of beam end  384  where the trapezoidal projection slides into the trapezoidal cavity as shown in  FIG. 21C . 
     Additionally, flexible locking clips  392  ( FIG. 21A ) project from the flat surface  390  of first end  384 . These clips are designed to flex inwardly as adjacent beams are moved into alignment and then to lock in place when the adjacent beams are fully laterally aligned. 
     The trapezoidal projections are aligned and moved into their corresponding trapezoidal cavities as illustrated in  FIG. 21B . When corresponding front and back faces  314  and  316  of the beams are aligned, clips  392  will snap into place locking the adjacent beams together. Thus, any number of beams may be locked together in this way to modularly produce an overall light-control assembly of the desired width. 
     Once the desired number of beams is assembled along with the other components of the light-controlling assembly an optional reinforcement member may be applied across the top and/or the bottom edges of the assembly. For example, a metal U-channel  411  ( FIG. 21A ) may be used for this purpose. Such a reinforcement member may also be used to attach the light-control assembly to existing structure under or over glazing or opened unglazed areas using appropriate profiling members. Finally, appropriate holes may be located in the reinforcement member in alignment with bores  421  in the beam and corresponding holes  423  in retainers  410  (see below) and appropriate fasteners (not shown) may be used to insure reliable attachment. 
     Light-control assembly  310 , in the illustrated embodiment, also includes at least a single retainer  410  and preferably pairs of front and back retainers  410  which are designed to be oriented as shown and attached to either one or both of the front and back faces  314  and  316  of the beams to retain the bearing members. The bearing members are thus coupled to the beam by trapping the retention flanges of the bearing members between the faces of the beam and the back surfaces  416  of the retainers. (The top front retainer was removed from  FIG. 21A  to facilitate viewing of the overall assembly.) Retainers  410 , in the illustrated embodiment, have a scalloped edge with a series of semi-circular openings  412  each having an inner surface  414  of a diameter corresponding to that of bores  318 . As in the case of the beams, the retainers preferably will be made of a transparent or translucent material like polycarbonate to help camouflage the light-control assembly, but can be made of any desired material. 
     As best seen in  FIG. 22A , the back sides  422  of the retainers include a ridge  424  with inner surface  414  corresponding to the inner surface  319  ( FIG. 18 ) of bores  318  and an undercut  426  behind the ridge creating a back face  428  and an annular cavity  431  dimensioned to receive and trap flange  434  of the bearing members without impeding rotation of the bearing members. Thus, the flanges of the bearing members are captured in the curved undercuts  426  of retainers  410 . Alternatively, such undercuts may be formed in the face of the beam about the circumference of bores  318  to serve the same function as retainer undercuts  426  which may instead have a flat inner surface  414  in such an arrangement. In yet another alternative, both the surface of the beam and the inner surface of the retainer may be undercut so that these undercuts can cooperate in capturing the flanges of the bearing members in place in the light control assembly. 
     Additionally, as best seen in  FIG. 22B  tabs  420   a ,  420   b  and  420   c  project generally perpendicularly from the retainer back surfaces  416  and are positioned and dimensioned to fit in cavities  383   a ,  383   b  and  383   c  of the beam to ensure proper positioning of the retainers on the beams. 
     Finally, retainers  410  include alternating locking pins  430  and locking cavities  432  which are disposed on the backside of the retainers so that when retainers are positioned on opposite sides of the beam, the locking pins and locking cavities are aligned and paired up so that they can interconnect. These locking pins and locking cavities are illustrated in an enlarged form in  FIG. 22B . A pair of fully interlocked pins and cavities is illustrated in the cross-sectional view of  FIG. 22C . 
     Locking pins  430  include ribs  434   a - 434   d  which project in diametrically opposite directions and have outer edges that are dimensioned to rest securely within locking cavity  432 . Additionally, bottom rib  434   d  includes a nose portion  436  having a ramp surface  438  and a locking face  440 . Locking cavities  132  also include a tubular portion with longitudinal slits  442  defining a top flexible tubular portion  446 . 
     Thus, when retainers  410  are properly positioned on faces  314  or  316  of the beam with ribs  120 A- 120 C aligned with cavities  383   a - 383   c  and locking pins  430  aligned within locking cavities  432 , the retainers are pressed together until they rest against the opposite faces of the beam. Nose portion  436  is positioned and dimensioned so that as it moves into cavity  432  the top flexible tubular portion  446  flexes upwardly as the nose portion flexes downwardly until the nose portion hooks onto a latch bar  447  whereupon the locking pins lock in the cavities affixing the retainers onto the front and back of the beam. Additionally, when multiple beams are joined together, the retainers will be offset as shown in  FIG. 21A  to cover the seams between adjacent interlocked beams and enhance the security of the attachment. 
     However, before the assembly of the retainers onto the beams is completed, a first bearing member  330  is mounted in a first bore such as bore  318   a  of  FIG. 18  with its flange  334  adjacent the first beam face  314  and its ring extending into the bore. The next bearing member is mounted in the next adjacent bore such as bore  318   b  of  FIG. 18  with its flange adjacent the second beam face  316  and its ring extending into the bore. The bearing members are mounted in each successive bore in this alternating fashion, so that looking at one of the faces of the beam, the flanges are at the front of every other bore. Looking at the opposite face of the beam, the flanges will be in the remaining alternate bores. This insures that the flanges in adjacent bores will not interfere with each other. In one alternative embodiment the retainers may be secured to the beams with screws or other fasteners that pass through holes  423  in the retainers and into bores  421  in the beam which are aligned with the holes. 
     In other embodiments in which laterally compliant light-blocking members as described below are used, web thickness A′ may be large enough to accommodate adjacent bearing flanges (i.e., the flanges are not offset) so long as the total width of the flanges of adjacent bearings are less than or equal to the thickness A′ of web portion  320  between the bores to preclude interference between the flanges of the adjacent bearings. Thus, a first bearing member  330  may be mounted in a bore such as bore  318   a  of  FIG. 18  with its flange  334  adjacent one of the beam faces, i.e., adjacent first beam face  314  with its ring extending into the bore. The next bearing member may then be mounted in the next adjacent bore such as bore  318   b  of  FIG. 18  with its flange also adjacent the same face, i.e., first beam face  314  with its ring extending into the bore (although it may be mounted with its flange adjacent the second beam face if a second retainer is used). The remaining bearing members will be mounted in the remaining bores in this fashion. 
       FIGS. 30-33  illustrate alternative light control assembly embodiments. These include generally flat alternate beam embodiments  600  of  FIGS. 30 and 30A  having a series of circular bores  602  which pass through the central section of the beam  603  and define web portions  604  between the bores. Top and bottom ribs  606  and  608  are located at the top and bottom of the central section of the beam. The flat beam embodiment may be in the form of opposed scalloped carriage members  607 A and  607 B which may be clamped together or otherwise held in place, as illustrated in  FIG. 30B . The beam of course may also be a unitary member. 
       FIGS. 31 and 31A  depict an alternative U-shaped retainer design  610 . Retainer  610  as best viewed from its end  612  includes a front leg  614  and a back leg  616  defining an opening  618  between the two legs. A channel  620  is formed at the top of opening  618  to receive top rib  606  of beam  600 . Retainer  610  also includes scalloped edge  621  with circular openings  622  corresponding in diameter to the diameter of bores  602 . As in the case of retainer  410 , retainer  610  is undercut at  624  to receive bearing member  626  as will be explained below. 
     Bearing member  626  comprises a flat annular ring  628  with pairs of diametrically opposed notches  630  having opposed notch bottoms  632  generally corresponding to notches  336   a - 336   d  and notch bottoms  338   a - 338   d  of bearing members  330 . Bearing member  626  also includes a circular outer edge  634  as depicted in  FIG. 32A . 
     A fully assembled alternate light control assembly  700  is shown in  FIGS. 33 and 33A . This assembly is constructed by aligning bearing members  626   a  and  626   b  with adjacent bores  602  with each adjacent bearing member offset with respect to its adjacent bearing member(s), i.e., on opposite sides of the beam. The rings preferably overlap the web portions between adjacent bores. With the bearing members positioned in this way retainers  610  are pressed down upon the top and bottom ribs of beam  600  to generally spread the legs of the retainer until the ribs come to rest in channels  620  whereupon the legs of the retainer snap back in place, locking retainers to the top and bottom ribs of the beam and thereby capturing the offset-positioned bearing members in assembly  700 . As can be seen in  FIG. 33 , the outer edges of the bearing members are captured within undercuts  324  ( FIG. 31 ) in retainers  610 . In a yet further alternative embodiment, such undercuts may be provided along the outer edge of bores  602  in lieu of or in addition to undercuts  624  of the retainers to perform the same retention function. 
     Turning now to  FIG. 34 , an alternate beam design  702  is shown with bores  704   a  and  704   b . These bores have respective inner surfaces  706   a  and  706   b  with circular grooves  708   a  and  708   b  that are shown offset with respect to each other but need not be offset. This beam will thus accept and retain, e.g., bearing members  330 ,  333 ,  350 ,  355 , and  626 . In the case of all but bearing member  333 , the bearing members will be forced into the bore grooves. Slot  335  in bearing member  333  is therefore preferred in the sense that relief slot  35  makes it easier to squeeze this bearing member together before insertion released so that when it is released flanges  334  will rest in the appropriate grooves to complete the assembly. Similar relief slots or other relief means may be provided in any bearing member intended to be mounted in bores  704   a  and  704   b . Additionally, it is noted that when using a beam design like that of beam  702 , the bearing member flanges may be shifted from the outer ring edges to intermediate locations along the outer surfaces of the annular rings of the bearing members to engage grooves  706   a  and  706   b.    
     In another embodiment, as illustrated in  FIGS. 42A-42C , the beam and paired carriage members may be replaced by at least one flexible support member  1200  (three are shown) comprising general parallel top and bottom members  1202  and  1204  joined by upstanding dividers  1206  which form a series of apertures  1208 . A series of rings  1210  are positioned in the apertures. Finally, as shown in  FIG. 42C , light-controlling members such as slats  1102  can be mounted within the rings as depicted in this figure. Also, while apertures are preferably rectangular as shown, they may be any shape that permits rings  1210  to be reliably fixed in place. 
     Light-controlling members such as slats  450  of  FIGS. 23A and 23B  may be mounted in the bearing members and other supporting structures described above. Slats  450 , in the illustrated embodiment, are plastic extruded to form top and bottom walls  452  and  454 . Walls  452  and  454  are each made up of a central segment  456  and lateral segments  458  which define lateral cavities  457  and walled central cavity  459 . The slats may be opaque or translucent. An air space  460  is maintained between the top and bottom walls by forming ribs  462  which, in the illustrated embodiment, are disposed perpendicularly at the lateral edges of central segment  456 . Slat  450  also has a front face  465  and a back face  467 . Also, in the illustrated embodiment, holes  464  are formed in the central segment adjacent the drive end  466  of the slats to facilitate locking the slats to a drive mechanism  550  as shown in  FIG. 25 , as discussed below. This segmented configuration gives the slats important rigidity characteristics while maintaining light weight and producing minimal interference with light transmission when the assembly is in a fully open position. 
       FIG. 23C  is a representation of two slats  450  resting within slots  36   a  and  36   b  of bearing member  30 . In this representation retention flange  334  of the left bearing member will rest against back face  316  of beam  370  while retention flange of the right retention flange  334  of the right bearing member will rest against front face  314  of beam  370 . Since the retention flanges of the bearing members are offset in this fashion they do not interfere with each other and thereby make it possible to bring corresponding edges  470  of the two slats far closer together than has been conceived of or implemented in any prior art light-control device. 
     In an alternate embodiment, slats  474  of  FIG. 23D  are made laterally compliant by providing them with deformable top and bottom edges  480  and  482  as illustrated in this Figure. These deformable top and bottom edges may be formed by extruding deformable edge shapes, co-extruding flexible edges or otherwise attaching deformable strips  484  to top and bottom edges  480  and  482 . Thus, when these slats are in a fully closed position corresponding generally to that depicted in the partial overhead view of  FIG. 23E , the deformable/flexible edges will be compressed along web portion  320  of each of the beams leaving virtually all of the remaining space between adjacent slats closed off by the deformable edges beyond the web portions, as illustrated.  FIG. 23F  is a diagrammatic representation corresponding generally to  FIG. 23D  which highlights the contact between deformable edges  480  and  482  of slats  474  where the retention flanges of the bearing members are offset on opposite sides of the beam. If the edge shapes are sufficiently deformable, an enlarged web thickness A′ may be used and the flanges of adjacent bearings need not be offset so long as the total width of the flanges of adjacent bearings is less than or equal to the thickness A′ of web portion  320  between the bores to preclude interference between the flanges of the adjacent bearings. 
     Light-controlling members as illustrated in  FIGS. 23A-23E  (and  FIGS. 35A-39B and 40A-41  as described below) may be mounted in the bearing members. The light-controlling members may be extruded plastic. For example, light-controlling members in the form of slats  450  may be plastic extruded to form top and bottom walls  452  and  454 . Walls  452  and  454  are each made up of a central segment  456  and lateral segments  458  which define lateral cavities  457  and a walled central cavity  459 . The slats may be opaque or translucent. The spacing between top and bottom walls  452  and  454  is maintained by ribs  462  which, in the illustrated embodiment, are disposed perpendicularly to top and bottom faces  465  and  469  of central segment  456 . Also, holes  464  may be formed in the central segment adjacent the drive end  466  of the slats to facilitate locking the slats to a drive mechanism such as mechanism  550  shown in  FIG. 25  and as discussed below. This segmented configuration gives the slats important rigidity characteristics deriving from the central and lateral segments while maintaining light weight and producing minimal interference with light transmission when the assembly is in a fully open position. 
     The illustrated configuration of slats  150  and  151 , as well as the slats of  FIGS. 35A-39B , gives them desirable longitudinal, torsional, and deflection rigidity. The term “torsional rigidity” is intended to refer to the ability of the slats to resist deformation when forces are applied to rotate them within the light-control assembly. “Longitudinal rigidity” is intended to refer to the ability of the slats to withstand deformation or deflection when a force is applied generally along the longitudinal axis of the slats such as when the slats are slid into the light-control assembly, as will be described in more detail below. “Deflection rigidity” is intended to refer to the ability of the slats to withstand bowing under the force of gravity or other forces which act generally perpendicularly to the longitudinal axis of the slats. 
     The top and bottom walls of slat  450  join together to form laterally spaced top and bottom edges  468  and  470 . In the illustrated embodiment, these edges are dimensioned to fit into the opposed slots  336   a  and  336   b  of bearing members  330  although they may, of course, be used with other bearing member designs or even mounted without bearings. Thus, when the mounted slats are rotated into the closed configuration illustrated in  FIG. 23B  light will be able to pass only in the gap  472  between the adjacent slats. 
     The various slats described herein may include photovoltaic solar cells to general electricity, preferably in conjunction with means for maximizing the photovoltaic output by rotating the light-controlling members with movement of the sun across the sky to insure that the photovoltaic solar cells continuously receive the maximum possible sunlight exposure while providing daylighting into the space below. 
       FIG. 24  illustrates another important feature with respect to slat design  486  in which, for purposes of illustration, triangular top and bottom segments  487  with opposite beveled faces  490  and  492  are emphasized. Angles “C” and “D” of triangular top and bottom segments  487  preferably should be greater than 45 degrees. Slats  486  may be fit within bearing members in the same fashion as slats  450  and  474 , described above. In accordance with the teaching above, segments  490 ,  491  and  492  (and preferably the corresponding segments on the opposite face of the slat) will be opaque, translucent, spectral controlling or reflective. Thus, when slat  486  is in the fully open position illustrated in this figure and segment  490  has a reflective surface most of the incoming light hitting that surface will be reflected into the area below shown diagrammatically as an enclosed area  496 . When segment  490  is, e.g., white opaque, an estimated 60% of the incoming light hitting that surface will be reflected into the area below. Finally, when segment  490  is translucent an estimated 30% of the incoming light hitting that surface will be reflected into the area below. This is depicted diagrammatically in  FIG. 24  which shows light rays  494   a  and  494   b  striking surfaces  490  and  492  of adjacent open slats and being directed downwardly to the area below the slats. Of course, when the slats are rotated 90 degrees to their closed position, they will block, reflect, etc. some or all of the incoming light, as described earlier. 
     Finally, it is noted with respect to slats  486  that the light-reflective surfaces of segments  490 ,  491  and/or  492  may be micro-prismatic reflective surfaces. Total light enhancement can be achieved by positioning such micro optical prisms to tunnel additional light into the interior space below the light-controlling members. 
     Turning now to  FIG. 35A , a laterally compliant light-blocking member in the form of slat  800  is shown. This slat includes a walled central cavity  802  corresponding generally to walled central cavity  459  of slat  450  ( FIG. 23A ). Central cavity  802  comprises side ribs  804  and  806  which are joined to the top and bottom faces  808  and  810  of the central cavity. 
     Slat  800  also includes laterally compliant lateral segments  812  and  814  which are generally triangular in shape. These lateral segments include first legs  816  and  817  which extend from ribs  804  and  806  respectively forming resilient joints  807  and  809 . 
     Each of first legs  816  and  817  of the lateral segments curves back upon itself to form respective preferably rounded apices  818  and  820  and second legs  822  and  824  which are directed toward side ribs  804  and  806 . Unlike first legs  816  and  817 , however, second legs  822  and  824  are not attached to the ribs, but rather stop short of the ribs as shown at free ends  826  and  828 . Preferably, free ends  826  and  828  of second legs  822  and  824  curve inwardly to form radii  830 . 
     Thus, when slat  800  is mounted to beam  70  and the slats are rotated into their fully closed position, apices  818  and  820  of adjacent slats will intersect causing first legs  816  and  817  to comply or flex inwardly about resilient joints  807  and  809  producing a like compression at web portions  320  (whether of smaller thickness A or larger thickness A′), as illustrated for slats  174  in  FIGS. 23D and 23E . As also shown in  FIGS. 23D and 23E , virtually all of the remaining space between adjacent slats will be closed off at intersecting apices  518  and  520  of adjacent slats to produce a black-out or near black-out condition along nearly the entire length of the slats. 
     Turning now  FIG. 35B , a similar slat design  832  is shown. Slat  832  thus corresponds to slat  800  of  FIG. 35A  except that strengthening ribs  840  and  842  extend between legs  816 / 822  and  817 / 824  to increase the rigidity of lateral segments  812  and  814 , causing the lateral compliance of the slat to be focused on flexure about joints  807  and  809  where the slats encounter the web portions of the beams in which the slats are mounted. Thus, when slats  832  are in the fully closed position, the second legs will be bent about joints  807  and  809  at web portions  320  while beyond the web portions their apices  818  and  822  will be closely abutting. 
       FIG. 35C  illustrates yet another laterally compliant slat  844 . The structure of this slat corresponds to slat  800  through apices  818  and  820 . However, in this design second legs  845  and  846  which correspond generally to second legs  822  and  824  of slat  800  are shortened and so have free ends  848  and  850  spaced from third legs  852  and  854  which extend from top and bottom faces  808  and  810  toward second legs  845  and  846  and are generally coplanar with these second legs. Legs  845 / 852  and  846 / 854  have respective free ends which preferably curve inwardly to form corresponding radii as shown. Thus, when the slats comply laterally at web portions  320  of the beams in which they are mounted and along the intersecting apices of adjacent slats, the radii will meet and bypass each other where the side segments be compressed beyond the point of intersection of the radii. 
       FIG. 36A  shows another slat embodiment  870  in which the lateral segments are closed triangles. The structure of this slat thus corresponds generally to slat  800 . Here, however, the second legs are attached to side ribs  804  and  806  adjacent to the point at which they are in turn attached to top and bottom faces  808  and  810  thus forming rigid triangular lateral segments  878  and  880 . Additionally, outwardly directed generally flat resilient gaskets  886  and  888  project from the apices  882  and  884  of the lateral segments. Gaskets  886  and  888  may be made of any suitable resilient material such as rubber or an appropriate flexible plastic. These gaskets may be coextruded with the rest of the slats using conventional techniques either along the apices  882  and  884  or along an outside surface  890  of either of the first or second legs of each of the lateral segments. The gaskets may also be glued in place using conventional techniques. 
     Gaskets  886  and  888  preferably will be opaque or near-opaque. Since the gaskets are resilient they will bend out of the way when slats  870  are inserted into the beams facilitating assembly of the system. And, when the slats are rotated into a fully closed or near-fully closed position, the gaskets will closely abut except at web portions  320  to achieve a black-out or near black-out condition along nearly the entirety of the closed slats. Also, since the gaskets are resilient, the slats may be rotated past the point of intersection so that the gaskets flex past each other. 
       FIG. 36B  illustrates a slat design  892  that corresponds to slat  870  of  FIG. 36A  except that cavities  894  and  896  are formed in apices  898  and  900 . In the illustrated embodiment cavities  894  and  896  are circular but they may be of other shapes. Resilient gaskets  902  and  903  having an enlarged base position are press fit or otherwise attached to cavities  904  and  905 . Gaskets  902  and  903  will operate like gaskets  886  and  838  of  FIG. 36A . 
       FIG. 36C  illustrates yet another slat design  910  which corresponds generally to slat  870  of  FIG. 36A  except that beads  912  and  913  of resilient material providing lateral compliance are located along apices  914  and  916  of the slat. Beads  912  and  913  may be made of foam rubber, or other suitable opaque or near opaque resilient material. Resilient beads  912  and  913  may be attached by any appropriate means including co-extrusion, RF gluing or through the use of appropriate adhesives. 
     Turning now to  FIG. 36D , another slat design  920  corresponding generally to the slat design of  FIG. 36A  is illustrated which differs in that gaskets  922  and  924  are radiused inwardly to produce a hook-like shape as shown presenting curved outer surfaces  926  and  928  and respective upwardly and downwardly directed cavities. These curved outer surfaces facilitate lateral compliance and will hook together where the slats are fully closed to achieve enhanced light-blocking Since they are resilient, they also may bypass as the slats are rotated beyond the fully closed position. 
       FIG. 37A  illustrates yet another slat design  930 . In this design, the lateral segments are closed triangles  932  and  934  as in the embodiments of  FIGS. 36A-36D . However, here walled central cavity  936  is designed to supply the desired lateral compliance. Central cavity thus includes side ribs  938  and  940  and top and bottom faces  942  and  944 . The top and bottom faces, however, are interrupted at their midpoints  946  and  948  a central flexible link  950 . The flexible link enables the slats to flex inwardly at web portions  320  while achieving a black-out or near black-out condition along the rest of the abutting slats when they are in a closed position. 
       FIG. 37B  shows a further slat embodiment  960 . In this embodiment, walled central cavity  962  is a closed rectangle and lateral segments  963  and  965  are generally in a triangular arrowhead shape. The lateral segments have opposite apices  964  and  966  at their lateral edges and are designed to flex inwardly to give the slat the required lateral compliance. Thus, first and second pairs of legs  967 / 968  and  969 / 970  are attached to the opposed lateral segments  972  of the walled central cavity by flexible links  974 / 976 . 
       FIG. 37C  illustrates a slat  982  that is similar to slat  960  of  FIG. 37B  except that the lateral segments  984  and  986  of slat  982  have flexible links  988  and  990  formed by cut-outs  989  and  991  at the top of each of lateral segments. In an alternate embodiment the flexible links may be offset by placing the cutouts on opposite sides of the lateral segments. 
     Turning now to  FIG. 38 , a slat design  992  is shown in which the lateral segments  994  are provided with laterally extending pairs of legs  996  which establish elongated open cavities  998  split at their apices  1000 . The lateral segments are also preferably provided with reinforcement legs  1002  as shown. The legs are able to laterally conform by flexing out of the way when the slats are inserted into the beams and to return to their initial configuration beyond web portions  320  between the bores to achieve black-out or near black-out along the slats beyond the web portions when the slats are closed. 
       FIG. 39A  depicts yet another laterally compliance slat design  1100 . This slat design includes a walled central cavity  1102 , and lateral segments  1104  and  1106  which are trapezoidal in shape. The lateral compliance of the slats is achieved by flexible members  1108  which are attached to the lateral segments by flexible arms  1110 . The flexible members may be any desirable shape. In this embodiment they each include a base  1112  and a curved portion  1114  extending from the base to leave a space  1116  at its distal end. This design therefore allows for flexure both at the flexible arms  1110  and at the point of attachment of the flexible members  1114  to base  1118 . 
       FIG. 39B  shows a pair of adjacent slats  1102  mounted in bearings beam  1104 . As can be seen in this figure, the flexible members are shaped and dimensioned to rest within the diametrically opposed notches  36 A and  36 B of the bearings. 
       FIG. 39C  is a top diagrammatic representation of slats  1102  in a fully closed position. As can be seen in this figure, the slats are closely abutting along  1107  and only slightly spaced at area  1106  where they pass around the web between the adjacent slats. 
     Additionally, it is noted that the slats may be notched where they pass across the webs in the bearing members. This is shown in  FIGS. 39D and 39E . For example, in  FIG. 41D  slat  1102  has a pair of rectangular notches  1114  along its opposite lateral edges. These notches are formed to fit about the bearings to which the slats are mounted to improve light blocking. In  FIG. 41E , corresponding notches cut-outs  1116  are trapezoidal in shape. In both cases, these notches permit the slats to product even closer to total black-out when they are in their closed position by reducing area  1106  of  FIG. 1C   39 C. 
       FIG. 39F  is a top plan view of a pair of slats  1102  in which rectangular notches  1114  are shown juxtaposed next to webs  1115  in beam  1117 . As can be seen in these figures, the notches are slightly larger than the width of the webs. As a result, friction between the edges of the slats and the webs is greatly reduced if not entirely eliminated. Second, this spacing will accommodate lateral expansion of the slats under normal operating conditions. Finally, the small rectangular gaps formed by the notches in the slats may be seen from a distance but due to their regular repeating geometrical shape, will be aesthetically desirable. 
       FIGS. 40A and 41B  illustrate hemispherical light-blocking member  1010  and  1012  generally in accord with the cylindrical embodiments of  FIGS. 20A-20E  having a light-blocking component  1012 . In  FIG. 40A  the hemispherical member is provided with flexible downwardly curving lips  1014  (which curve away from the outer hemispherical surface) and in  FIG. 40B  the hemispherical light-blocking member is provided with flexible upwardly curving lips  1016  (which curve toward the outer hemispherical surface). In both cases, the lips will laterally conform when the light-blocking members are inserted into the beams and return to their uncompressed configuration beyond web portions  320  between the bores to achieve black-out or near black-out along the slats beyond the web portions when the slats are closed. 
     Next,  FIG. 41  illustrates a tubular light-blocking member  1020  which includes diametrically opposed generally flat flexible lips  1022  which extend outwardly from the outside surface of the tubular member, opposite the edges of their central light-blocking component  1024 . These flexible lips will laterally conform when the light-blocking members are inserted into the beams and return to their uncompressed configuration beyond web portions  320  between the bores to achieve black-out or near black-out along the slats beyond the web portions when the slats are closed. 
     The various resilient features of  FIGS. 35A-41  comprise resilient means that achieve compliance or flexibility along the edges of the light-blocking means. 
     A drive mechanism  500  that may be used is illustrated in  FIG. 25 . The drive mechanism includes a gear box  502  having a shaft  504  with a mounting comb  506  having tines  508  positioned and dimensioned to fit within lateral cavities  357  of slat  350  and a central member  310  dimensioned and positioned to fit within the central cavity  459  of slat  450 . The mounting comb thus retains the slat on the drive mechanism. Central member  510  may also have a projection (not shown) that fits in hole  464  of the slat to lock the slat onto the comb. 
     Worm gear  512  (mounted onto shaft  504  of the mounting combs) meshes with an internal worm (not shown) having a circular axial cavity  516  with a key  518 . Thus a rotation shaft  22  with a corresponding slat to receive key  218  is designed to be passed through cavities  216  of drive mechanisms  200  associated with each of a series of slats in a modular light-control assembly. As a result, rotation of the shaft will produce corresponding and coordinated rotation of all of the slats associated with drive mechanisms attached to the shaft. 
     This is illustrated in  FIG. 26  which shows, at the top of the figure, a series of 12 slats  450  in the closed position above a series of 12 slats in the open position at the bottom of the figure. The slats are supported in a light-control assembly  310  which is shown at the left of the figure, rotated 90 degrees to better view of the light-control assembly. In fact, a series of such light-control assemblies will be spaced along these slats at appropriate distances to ensure that the slats are maintained properly in position. The light control assemblies can be mounted in side beam  526  as shown in  FIG. 26A . It should also be noted that each light-control assembly  310  in this figure comprises two beams, each having six circular bores  318  joined at their corresponding trapezoidal projections and trapezoidal cavities, as discussed earlier. 
     Looking to the right of  FIG. 26 , a series of 24 drive mechanisms  500  are shown each with mounting combs  506 . While the mounting combs are shown removed from the slats for purposes of illustration, in operation the mounting combs, of course, will be positioned in the ends of the slats, as described earlier. Finally, shaft  522  passes through keyed circular openings  518  in each of the drive mechanisms. Thus, a motor  524  attached to the shaft can be used to simultaneously rotate all of the slats. Finally, connectors  528  may be used to create as wide assembly as needed by connecting a series of shafts  522 . For example, in one modular single motor design, an assembly of 40′ wide×40′ long can be constructed with up to 240 slats operated by a single motor. 
     Light-control assembly  310  may be used in a variety of different applications. For example, it may be mounted between clear or translucent panels  550  and  552  as in the embodiment of  FIG. 27A . Alternatively, the light-control assembly may be mounted under a clear or translucent sheet  554  as shown in  FIG. 27B  (or it may be mounted over a clear or translucent sheet). Additionally, the light-control assembly may be mounted under a skylight  556  as shown diagrammatically in  FIG. 27C . Alternatively, a light-control assembly may be disposed vertically as shown in  FIG. 27D  or at inclined angle as shown in  FIG. 27E . In yet other embodiments, the light-control assembly may be used in curved applications, as depicted in  FIG. 27F . Although the depictions of  FIGS. 27D-27F  are comprised only light-controlling members  450  and supporting light-control assemblies  310 , they may be used with any appropriate light-controlling members and they may be disposed under, over or adjacent to clear or transparent sheets or between pairs of clear or transparent sheets. Finally, the light-control assembly may be used without clear or translucent sheets or panels to shade open unglazed areas. 
     Panels and sheets  550 ,  552 ,  554  and skylight  556  may be made of various transparent and translucent materials, including, but not limited to, plastics (including, e.g., polycarbonates and acrylics), fiberglass, perforated metal fabric, or glass. In one preferred embodiment, a Pentaglas™ honeycomb polycarbonate translucent panel available from CPI Daylighting Inc. (Lake Forest, Ill.) will be used in these applications. These polycarbonate panels, which are described in U.S. Pat. No. 5,895,701 (incorporated herein by reference), have an integral extruded honeycomb structural core consisting of small honeycomb cells approximately 0.16 inch by 0.16 inch which provides internal flexibility to absorb expansion and minimize stress and resists impact buckling. The resulting design offers smaller spans between rib supports, resulting in stronger durability, as well as superior light quality, visual appeal, higher insulation and excellent UV resistance. The internal flexibility of the panels absorbs thermal expansion through the panel in all directions (on the x, y, and z axes). This minimizes stress in all directions and preserves dimensional stability. The panels also have a high impact absorbing and load bearing property, a good ratio of weight to strength, and UV protection on both sides of the panel. The superior light diffusion capabilities ensure excellent quality of natural light. The panels are environmentally friendly, non-toxic, and made of 100% recyclable material. 
     Also, the light-control assembly may be provided with automatic sun tracking, with appropriate embedded programming that senses the daylight outside and manages the level of light and solar heat gain inside based on the level of sunlight outside. This will enable users to control natural daylight and comfort levels in any space—whether covered by glazing or not—all day long, and all year long, simply by setting desired light levels. 
     The beam, retainers, and light-controlling members may be made of any desirable material. In one preferred embodiment, these components may be injection molded from polycarbonate resins or acetyl. Preferably at least the bearing members and more preferably all of the components of the light-control assembly will be molded from polytetrafluoroethylene-infused polycarbonate resins. Also, although in the illustrated preferred embodiment the beam, bearing members, retainers, and slats are injection molded, one or more of these components may be made in other ways and may be made of other materials, as appropriate. For example, beam  370  may be made of punched aluminum. 
     A light-control assembly generally as in  FIG. 18  may be assembled as follows: 
     1. A beam  370  is provided and a series of bearing members, such as bearing members  330 , mounted in the bores of the support member with the retention flanges of the bearing members adjacent a face of the beam. 
     2. Retainers  410  are positioned on opposite faces  314  and  316  of the beam so the tabs  420   a ,  420   b  and  420   c  of the retainers fit in cavities  383   a ,  383   b  and  383   c  of the beams and locking pins  430  are pressed home in locking cavities  432 . The retainers are thus locked to the beam with the retention flanges of the bearing members trapped between the back face  429  of the retainer on the opposite faces of the beam. 
     3. Optionally, the desired number of light-control assemblies  310  are interconnected by aligning trapezoidal projections  386   a  and  386   b  at one end of the beam of each assembly with trapezoidal cavities  402   a  and  402   b  at the other end of the adjacent beam whereupon the projections are slid into the cavities until the adjacent beams lock together, as described earlier, to form an enlarged modular radiation control assembly of the desired length. Also, where two or more beams are laterally connected to form an enlarged assembly, multiple pairs of retainers preferably will be applied offset with regard to the seam between the adjacent interlocked beams to further reinforce the assembly. 
     4. A series of radiation control assemblies are then positioned longitudinally under, above, between or adjacent the glazing that is to be treated by the light-control assembly with the bores of the radiation-control assemblies aligned. The radiation control assemblies are mounted in place by appropriate means such as by using side beams  526  ( FIG. 26A ). For modular “cassette” design a mounting jam can be used. 
     5. Next, light-controlling members such as slats  450  or  474  of the appropriate length are slid into place in the laterally aligned bores of the bearing members so that they are supported within the successive light-controlling assemblies. In the case of slats  450  and bearing members  330 , the slats will be slid into diametrically opposed notches  336   a  and  336   b  so that the opposite top and bottom edges  468  and  470  of the slats rest in opposed notch bottoms  338   a  and  338   b . The longitudinal rigidity of the slats ensures that they can be slid into place in the successive bearing members without buckling. The torsional rigidity of the slats ensures that the slats can be rotated from one end with twisting out of shape. Finally, the deflection rigidity ensures that, one in position, the slats will not sag. Furthermore, it is noted that the overall assembly is thus readily assembled on-site and that can be used in both new construction and retrofit applications. It also ably accommodates thermal expansion and contraction of the components of the assembly, including the light-controlling members, when the assembly is subjected to wide-ranging temperature changes at the site of installation. The slats can move longitudinally within the bearing members free from the limitations imposed by rings and notches as they lengthen or shorten due to temperature swings. 
     6. Then, the slats are aligned and appropriate drive means attached to the control ends of the slats. “Aligned” in this context means that the slats will be parallel to each other when in the fully opened position and co-planer when in the fully closed position. 
     7. The resulting light-control assembly is now ready to provide light-blocking from almost full transparency to total black-out or near total black-out at a level of reliability which has heretobefore not been possible. 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments and does not pose a limitation on the scope of the embodiments unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the embodiments. 
     Preferred embodiments are described herein, including the best mode known to the inventors for carrying them out. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the embodiments to be practiced otherwise than as specifically described herein. Accordingly, embodiments include all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed embodiments unless otherwise indicated herein or otherwise clearly contradicted by context.