Abstract:
A luminaire comprising a housing, plurality of reflectors, lamps and electrically connected lamp sockets. The luminaire has at least two asymmetrical reflectors that are symmetrically opposed to each other and ideally has at least one symmetrical reflector located between the asymmetrical reflectors.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to luminaires and more particularly to luminaires using reflectors to provide widespread lighting footprint. 
   BACKGROUND OF THE INVENTION 
   A commonly used type of luminaire for illuminating large work areas is a reflective, fluorescent luminaire. These luminaires are typically either recessed into the ceiling or are mounted on the ceiling within a housing that contains the reflector(s) and lamps. Common applications include lighting for offices, workspaces or large retail areas. 
   Existing fluorescent luminaires typically include a number of fluorescent lamps disposed within a housing and have reflectors placed above the lamps. Often louvers are placed below the luminaire to prevent scattering of the light and to focus the light onto the horizontal surface below. As the fluorescent tubes are usually long and narrow, these luminaires also tend to be long and narrow. The industry standard fluorescent luminaire has eighteen cells formed by the louvers and uses three thirty-two Watt lamps. Most of the assemblies and reflectors are symmetrical. A drawback associated with such symmetrical luminaires is that the reflector is not particularly efficient because of internal reflections, the resulting light distribution pattern has low vertical foot-candles and the light pattern emitted is not optimized for any particular application. 
   In many lighting applications, the design goal is to provide a widespread light distribution pattern throughout the entire 180 degree area beneath the luminaire along with the greatest efficiency possible. The widespread light pattern increases the footprint over which light is projected and also results in increased vertical foot candles. As opposed to measuring just the light intensity on the horizontal area beneath the luminaire, vertical foot candles measures the amount of light intensity on a vertical surface below the luminaire. Increased vertical foot candles can be desirable for applications that require light to be spread over a vertical surface such as a display rack, rather than being focused down onto the top of a horizontal surface such as a desk. Also, the greater the efficiency of the luminaire the more light there is that is available for the widespread footprint, thereby resulting in increased light intensity throughout the footprint. Greater efficiency also permits the use of smaller wattage, energy saving lamps in the luminaire. To achieve these goals, some other luminaires have used asymmetrical reflectors and asymmetrical lamp placements, however, most of these are for applications in which the luminaires are used to direct light only onto a specific area. These approaches have been used in a variety of luminaires, including those by Krogsrud in U.S. Pat. No. 4,683,526, by Grierson in U.S. Pat. No. 5,727,870 and by Shemitz in U.S. Pub. No. US2002/0003699. In each of these examples the luminaire provides increased wide angle lighting and vertical foot candles in a particular region below the luminaire, however, such increases are made at the expense of the lighting directly below the luminaire. 
   Another approach is to use an adjustable reflector to permit lighting the desired area regardless of the specific application. This however, results in a less stable luminaire that requires adjustment and costs more to manufacture because of the added complexity of having moving parts. Further, the efficiency of such luminaires is greatly reduced either because they use materials that are flexible that are not the best possible reflectors or they use more solid reflector elements that are moved around but have spacing between the elements. An example of the flexible approach is shown by Waldmann in U.S. Pat. No. 6,244,729. An example of the movable elements approach can be seen by Littman in U.S. Pat. Nos. 5,564,815 and 5,803,585. 
   Thus, there is a substantial need for a luminaire that can provide wide angle lighting and significant vertical foot candles without requiring adjustment during installation or based upon subsequent applications. 
   SUMMARY OF THE INVENTION 
   The present invention provides a luminaire comprising: a housing; a plurality of reflectors disposed within said housing, wherein at least two of said reflectors are asymmetrical reflectors that are symmetrically opposed from each other; lamps disposed beneath each of said reflectors; and lamp sockets disposed within the reflector areas being sized to receive the base of said lamps, said lamp sockets being electrically connected to a power source and having an electrical contact and being electrically connectable to the bases of said lamps. Each of the asymmetrical reflectors has a generally parabolic shape. 
   Preferably, the portion of the asymmetrical reflector located centrally above the lamp has a peak shape, and the portion of the asymmetrical reflector located toward the inner side of the peak shape portion is a narrower parabolic shape than the portion of the asymmetrical reflector located toward the outer side of the peak shape portion. 
   The present invention is a luminaire which overcomes wide angle lighting drawbacks associated with the currently existing luminaires. More specifically, the luminaire comprises a housing in which multiple lamps are each disposed within their own reflectors and the reflectors have at least a pair of asymmetric reflectors that are disposed symmetrically relative to each other. This permits the middle lamps and reflectors, if used, to provide a standard light distribution pattern, while the outer asymmetric pairs are used to provide a wider angle of illumination and increased vertical foot candles. 
   In the preferred embodiment, the luminaire has three lamps and reflectors, including one symmetrical reflector in the center and two asymmetrical reflectors on the sides. The center lamp and reflector provides a standard light distribution pattern that is focused on the horizontal space below the luminaire, while the two side lamps and reflectors are principally responsible for providing the increased wide angle illumination and vertical. 
   The preferred embodiment of the luminaire disclosed herein has resulted in an eighty-five percent efficiency rating which makes the luminaire eligible for many available energy rebate programs. Further, the luminaire provides fifty percent greater vertical foot candles than the industry standard for luminaires having eighteen cells and using three thirty-two Watt lamps. 
   It would also be possible to use arrangements in which no symmetrical reflectors were used, but only pairs of asymmetrical reflectors disposed symmetrically relative to each other, so two, three, four or more pairs of lamps and reflectors could provide wider luminaires if required for an application. 
   Likewise, it would also be possible to use an arrangement where multiple lamps and symmetrical reflectors were used in the middle of the luminaire with the asymmetrical reflectors and lamp pairs being used toward the outside of the luminaire for similar mixed light distribution patterns. 
   By virtue of the foregoing, there is thus provided a luminaire that provides increased vertical foot candles and a widespread light distribution pattern. Additionally, the design of the reflectors provides a high efficiency as the result of the minimized internal reflections, thereby providing greater illumination and permitting the use of lower wattage lamps, thereby reducing usage of electricity while preserving usable light output. Further, the luminaire permits use of a single luminaire type for varying applications without requiring reflector adjustments. 
   These and other objects and advantages of the present invention shall become apparent from the accompanying drawings and the detailed description thereof 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention. 
       FIG. 1  is a side perspective of the luminaire in accordance with the principles of the present invention. 
       FIG. 2  is a detailed side perspective of the symmetrical center reflector of the luminaire. 
       FIG. 3  is a detailed side perspective of the asymmetrical side reflectors of the luminaire. 
       FIG. 4  is a diagram showing the candela distribution for the preferred embodiment of the luminaire. 
       FIG. 5  is a bottom perspective view of a portion of the luminaire. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The luminaire  10 , as depicted in  FIGS. 1 and 5 , comprises a housing  12  in which three reflectors  14  are disposed, including a center reflector  15  and side reflectors  16 . While it would be possible to form the reflectors together in a single piece, it is more convenient to form them as separate reflectors. The reflectors  14  are then joined using braces  18  with any common bonding means such as adhesives, screws or locking tabs. The outer edges  19   a  and  19   b  of the side reflectors  16  are then joined to the edge of the housing  12 . Within each reflector  14  volume is a lamp  20  having a base at each opposed end  21 , and which is held in place at the ends  21  via a set of commonly used fluorescent tube sockets  22 . The sockets are electrically connected to a power source, and have an electric contact for electrically connecting to the base of the lamps. Louvers  24 , as depicted in  FIG. 5 , can also be attached to the luminaire  10  to provide additional direction for the light. 
     FIG. 1  also depicts the placement of the lamps  20  within the reflectors  14 . In the preferred embodiment, each of the reflectors  14  is about 7.3 inches wide and 3.8 inches high. The center of each lamp  20  is placed about  1 . 2  inches below the top of the reflectors  14 , and in line with the bottom edge of the upper portion of the reflector. The center of the lamp  20  in the center reflector  15  is centered about 3.65 inches from each outer edge of the center reflector  15  and the lamps  20  of the side reflectors  16  are biased toward the center of the luminaire  10 , the center of such lamps  20  being about 3.1 inches from the inner edge of the side reflectors  16  and about 4.2 inches from the outer edges  19   a  and  19   b  of the side reflectors  16 . Accordingly, the lamps  20  of the side reflectors  16  are each located about 6.8 inches apart from the lamp  20  of the center reflector  15 . The lamps are preferably fluorescent tubes having a length substantially longer than the width of the reflectors. 
   The upper portions of the reflectors are shown in more detail in  FIGS. 2 and 3 . The center reflector  15  is symmetrical and the two side reflectors  16  are asymmetrical. From the edge  30   a  to edge  30   b  the preferred reflector embodiment is about 3.75 inches wide. From the center point  31  of the center reflector  15 , a V shaped peak  32  having an exterior angle of 110 degrees, and preferably not less than 110 degrees, with the point disposed downward extends in each direction for 0.372 inches. The subsequent segments  33   a – 33   d  are formed at interior angles  34   a – 34   d  with the preceding segments, starting from the end of the peak  32 , of 145 degrees, 154 degrees, 164 degrees and 167 degrees, and have respective lengths of 0.357 inches, 0.444 inches, 0.516 inches and 0.232 inches. The reflector  15  terminates from the end of segment  33   d  at an exterior angle of 125 degree with a length of 0.312 inches, thereby forming edges  30   a  and  30   b . The asymmetrical reflectors  16  have a length measured from the outer edge of edge  40   a  to edge  40   b  of about 4.5 inches. The side reflectors also each start with a V shaped peak  42  having an exterior angle of 110 degrees formed with two segments of 0.372 inches. From the end of the exterior peak segment  42   a , subsequent reflector segments  43   a – 43   g  are formed at interior angles  44   a – 44   g  with the preceding segment, starting from the peak segment end  42   a , of 145 degrees, 163 degrees, 174 degrees, 176 degrees, 176 degrees, 177 degrees and 176 degrees and having respective lengths of 0.58 inches, 0.37 inches, 0.379 inches, 0.379 inches, 0.379 inches, 0.379 inches and 0.191 inches. The reflector terminates from the end of segment  43   g  at an exterior angle of 147 degrees with a length of 0.312 inches, thereby forming the outer edges. The other symmetrical side of the reflector is formed with segments  45   a – 45   c  at interior angles  46   a – 46   c  to the preceding segments, starting from the interior end of the peak segment  42   b , of 145 degrees, 128 degrees and 154 degrees, and having respective lengths of 0.372 inches, 0.444 inches and 0.452 inches. The reflector terminates from the end of segment  45   c  at an exterior angle of 103 degrees with a length of 0.312 inches, thereby forming the inner edges. 
   The resulting luminaire  10  provides wide angle light distribution as shown in the candela distribution chart depicted in  FIG. 4 . 
   While the present invention has been illustrated by description of an embodiment which has been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages will readily appear to those skilled in the art. Thus, the invention in its broadest aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from the details without departing from the spirit or scope of applicant&#39;s general inventive concept.