Matrix lamp bank display and light filtering assembly
TECHNICAL FIELD 
     This disclosure relates to illuminated matrix lamp bank display sin which selected lamps illuminate a desired configuration of letters or other images. It pertains a specific light filtering system that makes it possible to present colored displays, while using a common white light source. 
     BACKGROUND OF THE INVENTION 
     Matrix lamp bank displays are widely used for promotional and informational purposes along roads, inside and outside of buildings, and in sports facilities. They can display written announcements, information, and graphic images. Both the written and graphic presentations can be either static or moving. 
     Like television, the first matrix lamp bank displays exhibited black and white presentations achieved by simply turning white incandescent lamps on or off at selected locations or &#34;pixels&#34; about the matrix. While these lamp bank displays are still widely used, there is a growing desire to present colored images, paralleling the widespread adoption of color in television motion pictures, printing and other forms of visual and graphic art. 
     One way to achieve a color matrix lamp bank display is to utilize cathode ray tubes capable of projecting multiple colors in various shades of grey. Such matrix displays are used for &#34;instant replay&#34; video presentations, typically in large sports facilities. Their utilization is limited by the extreme cost of such an installation. 
     A less-expensive form of matrix color display can be achieved by grouping multiple light sources adjacent to one another to present the primary colors (typically 4 - white, red, blue and green). The group of lamps is then activated in the same manner as the individual lamps in a simple black and white matrix, selecting the primary colors desired for the color presentation of each grouped area. At the present, this has been accomplished by using colored light sources, selecting lamps of the color or combination of colors required at each group of lamps. Any cover or lens over these lamps has been of a common tint, typically clear so as to avoid any modification of the lamp color when viewed from the exterior of the display. 
     Colored incandescent lamp bulbs are substantially more expensive to install and maintain, when compared to the installation and upkeep of matrix lamp bank displays using white lamps. Maintenance of a color lamp bank display requires an inventory of four different lamps. The installation or replacement lamps risks the possibility that a lamp of the wrong color will be placed within a group. To resolve these difficulties, and to reduce the initial and continuing costs relating to a color matrix lamp bank display, the present invention was developed, using a common white lamp as a light source and interchangeable light filtering assemblies placed forward of each lamp. This not only allows for use of inexpensive lamps, it also permits replacement of all lamps from a single lamp inventory. It allows for greater light balance between the selected colors by incorporating such balance into the lens design, thereby eliminating light variations in color and intensity due to lamp construction and age. 
     Another object of this invention is to provide a covering lens system that permits access to each lamp from the front of the display, making lamp replacement much easier than in earlier installations where lamp access was only available from the rear. The light filtering assemblies are designed to accommodate wide temperature fluctuations that typically occur in the environment of matrix lamp bank displays, and particularly to accommodate the generation of heat by lamp energization. 
     The above objects have been accomplished by two different embodiments of the invention, which are disclosed in detail. One larger embodiment, adapted specifically for exterior display installations, utilizes a separable lens and supporting frame. The second embodiment, designed for smaller indoor installations, utilizes a lens and frame which are integrally molded. In both embodiments, the lens is positioned along an inclined plane that minimizes reflective glare from sunlight or adjacent ceiling light sources. In both embodiments there is provision for ventilation of the lens to permit heat to escape from about the light source located behind it. Both embodiments permit removal and installation of individual light filtering assemblies for initial manufacturing purposes, as well as field repairs and lamp replacement. These features will be more evident from the detailed disclosure that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of the invention are illustrated in the accompanying drawings, in which: 
     FIG. 1 is a fragmentary front view of a matrix lamp bank display utilizing a first embodiment of the invention; 
     FIG. 2 is an enlarged fragmentary horizontal sectional view taken along line 2--2 in FIG. 1; 
     FIG. 3 is a front view of the light filtering assembly shown in FIG. 1; 
     FIG. 4 is a top view; 
     FIG. 5 is a side view; 
     FIG. 6 is a bottom view; 
     FIG. 7 is a fragmentary front view of a reflector sheet utilized in a matrix lamp bank display according to a second embodiment of the invention; 
     FIG. 8 is an enlarged fragmentary vertical sectional view taken through the second embodiment; 
     FIG. 9 is a front view of the light filtering assembly used in the second embodiment; 
     FIG. 10 is a top view; 
     FIG. 11 is a bottom view; 
     FIG. 12 is a rear view; and 
     FIG. 13 is a side view. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following disclosure of the invention is submitted in compliance with the constitutional purpose of the Patent Laws &#34;to promote the progress of science and useful arts&#34; (Article 1, Section 8). 
     FIGS. 1-6 show a first embodiment of this invention, designed for larger exterior installations, while FIGS. 7-13 show details of a second embodiment designed for smaller interior installations. As an example, the lamps of the first embodiment might be located on 3 inch centers, while the lamps of the second embodiment might be located on centers spaced apart by 3/4 of an inch. 
     The relational positions of the components described in this disclosure will be identified as seen by the viewer of the matrix lamp bank display. Thus, the light will be described as being projected &#34;forwardly&#34; from the light sources. The surfaces facing the viewer will be termed as &#34;front&#34; or &#34;forward,&#34; while those facing oppositely will be termed as &#34;rear&#34; or &#34;back.&#34; Since lamp bank matrixes are arranged in upright configurations, the top, bottom and side elements of the components will be described in their usual operational relationships on the display as viewed. 
     Referring to FIGS. 1 and 2, the matrix lamp bank display is presented by an upright planar array of light sources, shown as reflector lamps 10. The lamps 10 are directed parallel to one another in a common forward direction. They are arranged within an upright rectangular two dimensional matrix in horizontal rows and vertical columns. A desired two dimensional pattern of lighted or unlighted lamps 10 can be presented to a viewer by properly selecting the lamps or groups of lamps required for the pattern. In most instances, the individual lamp 10 will either be activated or not activated. It is possible to utilize varying &#34;shades of grey&#34; or intensity levels in the selected lamps that are activated, but this is essentially practical today only with respect to single color displays. Where multicolor displays are achieved by use of group lamps, the complexities of balancing colors at various intensity levels is highly difficult and not economical. It is further complicated by differences in lighted intensity that occur with lamp age. 
     A corresponding array of individually removable light filtering assemblies are located immediately forward of the lamps 10. Each includes a lens 13 and a supporting frame 17. The frames 17 are removably attached across the front of a matrix framework 12 that also supports the lamp sockets 11 and associated electrical and electronic components for the lamps. 
     For general reference, the matrix framework is shown as a series of upright extrusions 60, each having a front wall 61 that is punched with a circular aperture to provide access to a lamp 10 supported on a rear lamp pan 62. The front wall 61 is partially overlapped along each side to present vertical mounting grooves 63 facing transversely inward. These grooves releasably receive complementary flanges at the sides of each lens frame 17, as will be detailed below. 
     Each lens 13 is a planar solid lens covering the lamp 10 located behind it. Each lens has a front surface 14 which, when mounted on the lamp bank display, is individually inclined forwardly and upwardly from the planar array of lamps 10. The inclination of the lenses 13 minimizes sun glare in exterior installations, as well as glare created by ceiling lights in indoor installations. 
     Individual opaque frames 17 are structurally provided between each lens 13 and the array of lamps 10 for removably holding each lens 13 in a location forward of at least one lamp 10 in the array. The lens 13 and frame 17 are movable as a unit to install or replace the lamp 10 located behind it. Providing front access to the lamps 10 facilitates maintenance of the lamp bank display, since it permits visual inspection of unlighted lamps and minimizes the amount of apparatus that must be manipulated in order to change the lamps. This is to be contrasted with most prior lamp bank displays, which required lamp replacement to be accomplished from the rear of the display. 
     Each frame 17 includes a pair of parallel side walls 18, a top wall 19 and a bottom wall 20. The walls 18, 19 and 20 are perpendicularly joined at their respective ends to form an open rectangular enclosure extending from a common planar rear edge 21 to a common planar front edge 22 inclined angularly in a forwardly and upwardly direction relative to the rear edge 21. 
     The top wall 19 is provided with a series of ventilation apertures for permitting air heated by a lamp 10 to pass upwardly behind the lens 13 and exit through the top wall 19 as the heated air rises. These apertures include slots 23 extending to the front edge 22 of the frame 17 and slots 24 extending to its rear edge 21. Ventilation across each lens 13 is also facilitated by slots 25 formed through the bottom wall 20, which permit air to enter the enclosure directly behind the lens 13 for circulation purposes. 
     Each lens 13 is preferably translucent and tinted. The tint of a particular lens will depend on the lighted color desired in its location about the matrix. In a single color display, the tint of each lens 13 will be identical about the entire array of lamps 10. In a multicolor display, the lamps can be arranged behind groups of lenses 13 presenting three or four primary colors. In a specific example, the lenses 13 are arranged in rectangular groups of four, with the individual lenses in each group being tinted red, blue, green and clear. For a more pleasing color balance in the lighted display, the &#34;clear&#34; lenses 13 are actually tinted a light blue. 
     While the above description has been directed to the first embodiment of the invention, as illustrated in FIGS. 1-6, it is equally applicable to the second embodiment shown in FIGS. 7-13. This will be evident from the specific discussion of the features in the second embodiment. 
     In the first embodiment of the invention, color balancing is achieved by varying the thickness of the majority of the lens area. As shown in FIGS. 2 and 3, each lens 13 includes a central area 15 of protruding thickness extending substantially across its width and height, but terminating short of its peripheral edges. In this lens configurations, the central area is circular in shape. Since the thickness of the lens material determines its color density for light transmission purposes, the balance between differing colors can be achieved by varying the thickness of this central area 15. As one example, the thickness of area 15 in a four color display was less for the blue lenses 13 than for the green, red or clear (light blue) lenses. The specific thickness needed for proper color balance among each set of lenses must be determined by experimental tests utilizing the lamps 10 included in the lamp bank display. 
     The central area 15 is presented across the back surface of each lens 13, assuring a uniform planar appearance across their front surfaces 14. Proper positioning of each lens is assured by a chamfered corner 50 and complementary non-symmetrical corner configuration 51 on the receiving frame 17. 
     The individual lenses 13 are held within the surrounding frames 17 by a plurality of peripheral tabs 16 that fit within complimentary slots 29 formed adjacent to the front edge 22 of the enclosure presented by the walls 18, 19 and 20. 
     The matrix lamp bank display also includes horizontal weather shields 28 overlying the top walls 19 of the frame 17 in each horizontal row across the lamp bank display. The horizontal weather shields 28 are fixed across the front surfaces of upright extrusions 60 by screws or other suitable permanent fasteners. They structurally support the assembled frames 17, which freely rest on the weather shields 28 along each horizontal row in the completed matrix. The weather shields 28 prevent rain from entering through the slots 23 and 24 in the frame top wall 19. They also overlap the front of each lens 13 to assist in shading the lens front surface 14 from the sun or ceiling light sources. 
     Each frame 17 is held within the matrix framework 12 by means of co-planar flanges protruding oppositely outward adjacent the rear edge 21 of the frame. The flanges 27 are loosely received within complimentary mounting grooves 63 at the sides of extrusions 60 in the framework 12 to accommodate thermal expansion or contraction of the light filtering assembly. The slots 24 formed across the top wall 19 of frame 17 interrupt its rear edge 21 and permit the side walls 18 to be squeezed toward one another at rear edge 21 to facilitate entry of flanges 27 into the receiving slots that support frame 17 within framework 12. 
     The essential structural difference between the embodiment of this disclosure shown in FIGS. 1-6 and that shown in FIGS. 7-13 is that the second embodiment utilizes a lens that is integrally molded with its supporting frame. In this embodiment, the material within the lens and frame are therefore of the same tint, while the frame 17 of the first embodiment is preferably opaque. Both embodiments utilize a rectangular lens configuration, which permits the assembled lenses to substantially cover the front area of the assembled matrix lamp bank display. The rectangular lens shape also tends to visually enlarge the lighted area presented by the individual lamps, which are typically of a circular shape. 
     In the second embodiment, lens 30 and side walls 31 are integral. They retain the general shape described with regard to the embodiment in FIGS. 1-6. The lens 30 is surrounded by side walls 31, a top wall 32, and a bottom wall 33. The walls 31, 32, and 33 extend between a rear edge 34 and a front edge 35 that is coplanar with the front surface 36 of lens 30. Ventilating slots 37 are formed through the top wall 32. Each slot 37 interrupts the rear edge 34 across the top wall 32. The bottom wall 33 is recessed slightly to permit entry of air under the ends 30. The utilitarian aspects of these components are identical to those previously discussed with regard to the first embodiment. 
     In the smaller form of the invention, since space between adjacent light filtering assemblies is at a premium, attachment to the supporting structure is achieved by using rearwardly protruding posts 38 and 39. Posts 38 and 39 are located at diagonally opposite corners of the assembly as extensions of the walls that surround lens 30. It is preferable that there be at least two protruding posts 38 and 39 at opposite sides of the enclosure presented by walls 31, 32 and 33. A slot 40 is also formed through side wall 31 adjacent to the post 38 for permitting the post 38 to be deflected from its normal position as an extension of the walls 31 and 32 that intersect at the corner in which post 38 is formed. The outer ends of each post 38 and 39 are notched to interengage behind a wall surface to which the assembly is secured. 
     FIGS. 7 and 8 show one form of a matrix lamp bank display in which the second embodiment of the lens and frame can be effectively utilized. The assembly is built about a molded reflector plate 41 presenting a series of multi-faceted reflector recesses having central apertures for receiving small lamps 42. Each lamp 42 is mounted to a supporting printed circuit board 43 by means of individual sockets 45. The reflector plate 41 is fixed across the front of the printed circuit board 43 by screws 46 that engage rearwardly protruding bosses molded about the rear surface of the reflector plate 41 (FIG. 8). Reflector plate 41 is provided with complementary apertures 44 arranged about each reflector section to releasably receive the posts 38 and 39 of the individual light filtering assemblies mounted about the matrix lamp bank display. 
     Both embodiments of the invention readily lend themselves to multicolored lamp bank displays where differing colors are desired within adjacent lamp positions. Both provide maximum colored lens areas about a rectangular matrix lamp bank display, taking advantage of the corner areas surrounding individual lamps, as well as the areas immediately forward of them. Both embodiments facilitate thermal expansion by providing relatively flexible mounting between the lens and the supporting framework, and both facilitate ventilation of the lenses. Finally, both embodiments permit front access to the lamps for initial installation and replacement purposes. 
     In compliance with the statue, the invention has been described in language more or less specific as to structural features. It is to be understood, however, that the invention is not limited to the specific features shown, since the means and construction herein disclosed comprise a preferred form of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims, appropriately interpreted in accordance with the doctrine of equivalents.