Patent Publication Number: US-6698908-B2

Title: Lighting fixture optical assembly including relector/refractor and collar for enhanced directional illumination control

Description:
FIELD OF THE INVENTION 
     The present invention relates to lighting fixtures and luminaires, and more particularly to an improved optical assembly including a reflector/refractor device and a reflector collar for enhanced directional illumination control. 
     DESCRIPTION OF THE RELATED ART 
     Various arrangements are known for reflectors when used as lighting fixtures and luminaires. Some known reflectors are manufactured in metals such as aluminum and steel, or of a glass or plastic. These materials are then painted, plated, or chemically brightened to function as reflectors. Vacuum metallizing, vapor or chemical deposition can be used to place a thin metal layer onto the surface of the metal, plastic or glass to act as reflector. There are also prismatic internal reflection glass and plastic reflectors which use the index of refraction to control the reflectance of light and redirect it into a distribution of light. Some glass reflectors are known to use a metal cover spun around the exterior to eliminate uplight, radiated by the large rounded portion of their prism peaks and roots, and the cover is used as a means of glare control and to maintain a clean exterior internal reflection surface. However, this creates a very dark reflector exterior and a very bright aperture brightness, and when installed in a room this reflector produces very reduced uplight with no means of adjusting the glass reflectors&#39; reflected surface brightness to any other ambient lighting concerns or conditions. 
     Improvements over prior art arrangements have been provided by prismatic reflector/refractor, such as disclosed in the following United States patents. 
     U.S. Pat. No. 4,839,781 issued to Josh T. Barnes and Ronald J. Sitzema Jun. 13, 1989 and assigned to the present assignee, discloses a reflector/refractor device for use with a variety of lighting fixtures and light sources. The reflector/refractor device includes a body having a predetermined profile and defining a cavity with the body having an inside surface and an outside surface. An illuminating source for emitting light is disposed within the cavity substantially along a central vertical axis of the body. The body includes a series of sectional zones for reflecting and refracting light. The exterior surface of the device includes a plurality of substantially vertical prisms consisting of reflective elements, refractive elements and elements that may be either reflective or refractive depending on light center location. These reflective or refractive elements act in combination to selectively vary light distribution characteristics of vertical and lateral angles, and intensities, by vertical displacement of the illuminating lamp source. 
     U.S. Pat. No. 5,444,606 issued to Josh T. Barnes and Paul C. Belding Aug. 22, 1995 and assigned to the present assignee, discloses a combination of a prismatic reflector and a prismatic lens is provided for use with lighting fixtures. A reflector body has a substantially parabolic contour defining an interior cavity. The reflector body includes a plurality of prisms for receiving, transmitting and reflecting light. A lens body has a first mating surface engaging the reflector body, an opposed inverted conical surface, and a sloping sidewall extending between the mating surface and the opposed inverted conical surface. The mating surface of the lens body has a larger diameter than the opposed inverted conical surface. The opposed inverted conical surface includes a plurality of prisms for receiving and for redirecting light. 
     Prior art of collar attachment to polymeric prismatic reflectors has been generally limited to using a stamped aluminum rings as a simple retention device, and generally as a means of reflecting extraneous light away from the Nadir position of a photometric distribution. These designs concentrated on producing batwing distributions. 
     The original reflector collar designs were intended to produce only batwing distributions with spacing criteria of 1.6:1 to 2.0:1. While the original designs of the collar and polymeric reflector provided excellent overall efficiency and coefficient of utilization for room cavity designs, it meant that batwing distributions would often need to be spaced closer than their intended spacing to meet required footcandle levels and watt per square foot energy consumption legislation. A need for narrower spacing with higher footcandle levels below the luminaire was needed to reduce the number of luminaires consuming energy in the lighted space. This also meant increasing or achieving horizontal footcandle requirements at the floor and maintaining vertical footcandle levels on shelving or racks of warehouses and interior lighting of commercial stores. In essence this is a shift in design practice which was to cover large areas of open space with uniform illumination, to a concept of concentrating illumination and energy use in narrower patterns for specific lighting requirements and tasks. 
     A need exists for effective mechanism for providing enhanced directional illumination control for an improved optical assembly. It is desirable to provide such an improved optical assembly for concentrating illumination and energy use in narrower patterns for specific lighting requirements and tasks. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide an improved optical assembly including a reflector/refractor device and a collar for enhanced directional illumination control. Other important objects of the present invention are to provide such an improved optical assembly including a reflector/refractor device and a collar for enhanced directional illumination control substantially without negative effect; and that overcome many of the disadvantages of prior art arrangements. 
     In brief, an improved optical assembly including a reflector/refractor device and a reflector collar provided for enhanced directional illumination control. The reflector/refractor has a predefined shape and has a plurality of reflector/refractor prisms on an exterior body surface for reflecting and refracting light. A light source is disposed within the reflector/refractor substantially along a central vertical axis of the reflector/refractor. The reflector collar supports the reflector/refractor and attaches the reflector/refractor to a luminaire ballast. The reflector collar has a predetermined contour and a plurality of reflector impressions formed into the predetermined contour. The predetermined contour and the plurality of reflector impressions provide directional illumination control for the optical assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention together with the above and other objects and advantages may best be understood from the following detailed description of the preferred embodiments of the invention illustrated in the drawings, wherein: 
     FIGS. 1A and 1B are top and side elevational views illustrating a prismatic reflector/refractor device in accordance with the preferred embodiment; 
     FIG. 2 is a partially broken away view of an optical assembly including the prismatic reflector/refractor device of FIGS. 1A and 1B together with a collar for enhanced directional illumination control in accordance with the preferred embodiment; 
     FIG. 3 is a bottom elevational view of the collar of FIG. 2 in accordance with the preferred embodiment; 
     FIG. 4 is a side sectional view of the reflector collar for enhanced directional illumination control in accordance with the preferred embodiment taken along line A—A of FIG. 2; 
     FIG. 5 is a top elevational view of the collar of FIG. 2 in accordance with the preferred embodiment; 
     FIG. 6 is an enlarged fragmentary view of the collar of FIG. 2 illustrating multiple concave reflector impressions selectively formed into the reflector collar contour; 
     FIGS. 7A,  8 A and  9 A respectively illustrate light ray traces with the prior art prismatic reflector/refractor device of FIGS. 1A and 1B from the top, middle and bottom of a light source; 
     FIGS. 7B,  8 B and  9 B respectively illustrate light ray traces of the reflector collar in accordance with the preferred embodiment from the top, middle and bottom of a light source; 
     FIGS.  7 BB,  8 BB and  9 BB respectively illustrate light ray traces of an enlarged portion of the reflector collar in accordance with the preferred embodiment from the top, middle and bottom of a light source; and 
     FIGS. 7C,  8 C and  9 C respectively illustrate light ray traces of the optical assembly of FIG. 2 including the prismatic reflector/refractor device of FIGS. 1A and 1B together with the collar for enhanced directional illumination control in accordance with the preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with the invention, an improved optical assembly is provided by a clear prismatic reflector/refractor having its exterior surface substantially covered with multiple internal reflecting prisms in combination with a reflector collar of the preferred embodiment that is arranged to provide additional optical control. The reflector collar of the preferred embodiment is used for the attachment of a polymeric prismatic reflector/refractor to a luminaire ballast capsule and provides a means of narrowing the photometric distribution of the polymeric prismatic reflector/refractor. The narrowing of the distribution causes an increase to the efficiency in the 0-40 degree zonal lumens while maintaining the overall efficiency of the polymeric prismatic reflector through the use of the reflector collar predetermined contour and multiple small concave reflector impressions that are formed into the reflector collar. 
     Having reference now to the drawings, in FIGS. 1A and 1B, there is shown a prismatic reflector/refractor device generally designated as  100  in accordance with the preferred embodiment. The prismatic reflector/refractor  100  is formed of a substantially transparent light transmitting material, such as an acrylic or similar material. 
     Prismatic reflector/refractor  100  is specifically designed to provide a certain amount of additional light through its sidewall for adding additional illumination to the surround, increasing the uniformity in the surround, and for spreading the lamp image over a large area to reduce glare from a light source or lamp  110 . 
     The reflector/refractor  100  of the preferred embodiment has a plurality of vertical prisms  102  on an outside or exterior surface  104  extending between an upper flange, opening  106  and a lower flange, opening  108 . The prismatic reflector/refractor  100  advantageously is the type described in the above-identified U.S. Pat. Nos. 5,444,606 and 4,839,781. The subject matter of each of the above-identified U.S. Pat. Nos. 5,444,606 and 4,839,781 is incorporated herein by reference. 
     In accordance with features of the invention, a reflector collar  200  for enhanced directional illumination control of the preferred embodiment and reflector/refractor  100  are provided in combination to construct an optical assembly  202  of the preferred embodiment as illustrated in FIGS. 2-6 and FIGS. 7B,  8 B and  9 B. Reflector collar  200  is used for the attachment of a polymeric prismatic reflector/refractor  100  to a luminaire ballast capsule (not shown). The reflector collar  200  narrows the photometric distribution of the reflector/refractor  100  through the use of its shape and multiple small concave reflector impressions  220  that are embossed into the reflector collar  200 . Each of the multiple concave reflector impressions  220  is formed as a segment of a sphere at a predetermined depth and a prescribed spread of diffusion from the lamp source  110 . 
     In accordance with features of the invention, the reflector collar profile  210  includes the generally concave reflector impressions  220  facing the lamp center arranged at predetermined locations and at a predetermined density to create a controlled spreading of the reflected light away from the lamp  110  and the sidewall of the polymeric reflector/refractor  100 . The spreading of the reflected light from the reflector collar  200  is distributed to project the majority of the rays through the bottom opening  108  of the polymeric reflector/refractor  100 , thus increasing the intensity of the distribution and narrowing the distribution of the polymeric reflector. 
     Referring to FIGS. 2,  3 ,  4 ,  5 , and  6 , the polymeric prismatic reflector/refractor  100  rests on a lower portion  204  of the reflector collar  200  and held in position by a plurality of bendable tabs  206  cut from the reflector/collar contour and bent over an upper neck opening defined by flange  106  of the polymeric prismatic reflector/refractor  100  during assembly of the optical assembly  202 . Reflector collar  200  has a predetermined contour generally designated by the reference character  210  and is arranged for forming an extension of the interior contour of the polymeric prismatic reflector/refractor  100 . The reflector collar shape  210  is matched generally as continuation of the interior contour of the polymeric reflector/refractor  100  progressing from a lower edge  212  having a larger diameter than the top flange opening  106  of the polymeric reflector/refractor  100  and the predetermined shape  210  continues to a central opening  214  in the of the reflector collar  200  for receiving the lamp  110 . The reflector collar  200  supports the polymeric prismatic reflector  110  with the lower reflector collar edge  212  positioned approximately 1 inch or 2.56 cm. below the upper flange  106  of the polymeric prismatic reflector  110 . The down-light reflector collar  200  includes features  216  and a series of different patterns  218  cut into the collar for attachment to one of various commercially available ballasts or luminaire ballast capsules. 
     The down-light reflector collar  200  of the preferred embodiment is made from a highly reflective aluminum and preferably is bright dipped and anodized to maintain the high reflectance of the metal. When assembled in optical assembly  202 , the reflector collar  200  effectively narrows the overall distribution of the polymeric prismatic reflector/refractor  100 , increasing the 0-40 degree zonal efficiency of the photometric distribution while maintaining the overall efficiency of the polymeric prismatic reflector. The increase in efficiency of the 0-40 degree area will cause some reduction in the uplight values of the 90°-180° zonal efficiency. However, this reduction is controlled by the size of down-light reflector collar  200  and not intended to eliminate all of the uplight. The result leaves substantial illumination available for the use of this uplight illumination in areas where it may be advantagous to provide some uplight. This is especially important in high ceiling mounting heights to reduce some of the ceiling brightness while at the same time not creating a dark cavern effect ceiling in the room or lighting installation. 
     Referring to FIG. 2, the down-light reflector collar  200  is designed with the predetermined contour  210  to enhance the directional control of the polymeric reflector/refractor  100 . The overall contour  210  of the reflector collar  200  is defined or shaped from the intersection of a plurality of predetermined radii generally indicated by radii R 1 -R 6 , each having its center respectively indicated by P 1 -P 6  offset from the vertical axis V of the polymeric prismatic reflector lamp source  110 , and each rotated horizontally about the centerline of the vertical axis of the polymeric prismatic reflector/refractor  100  to generate the down-light reflector collar contour  210 . 
     In accordance with features of the invention, additional optical control of reflector collar  200  to narrow the distribution of the polymeric prismatic reflector/refractor  100  using either clear enveloped lamps or phosphor coated lamps  110  is simply and effectively achieved by the use of multiple concave reflector impressions  220  selectively formed into the contour  210  of the reflector collar  200 . These impressions  220  have been implemented with the shape of predetermined segments of a sphere, but it should be understood that impressions  220  are not limited to these shapes. The concave reflector impressions  220  creating overlapping reflected distributions of reflected illumination to fill in and smooth a bat-wing distribution photometric distribution produced by the polymeric prismatic reflector to create a bell curve distribution, filling in the 0-40 degree zonal efficiency of the photometric distribution. 
     The concave reflector impressions  220  are formed, for example, on a core of a hydroforming die by an EDM process leaving raised convex segments of a sphere on the core surface and these forms are pressed into the reflector contour at a predetermined size and depth. Each raised segment of a sphere standing above the reflector core form, produces an impression  220  of a concave reflector, and the core form of a hydroforming die is selectively covered with these raised segments of a sphere to produce multiple concave reflectors of defined shape and depth relative to the reflector collar contour which in turn provide the desired distribution with reflector collar  200 . Each embossed impression  220  is designed to increase the efficiency in the 0-40 degree zone of the photometric light distribution of the optical assembly with little loss in efficiency or optical control of the prismatic polymeric reflector/refractor  100 . 
     The primary shape  210  of the down-light reflector collar  200  includes, for example, six separate intersecting radii R 1 -R 6 , each having a position P 1  offset from the predetermined centerline axis of the HID source. Each position of these radii is rotated about the predetermined centerline axis of the HID source to form the base line contour  210  of the reflector collar  200 . Into five of the six radii segments a series of the small concave reflectors  220  are formed as negative segments of a sphere that are calculated for position and depth of spread to later be impressed into the contour  210  during the manufacturing process. Each series of these impressions  220  are designed as small concave reflectors in the final stage of the manufactured reflector collar  200  to redirect light from the lamp  110  in a direction passing close to the envelop of the lamp but not back through the arc tube of the HID lamp. Computerized raytracing advantageously is used to establish the spread of each spherical segment impression  220  and its respective location on the collar surface, as well as the pattern density of spherical segment impressions  220  on the contour of the reflector collar  200 . 
     As best seen in FIGS. 3 and 6, each impression  220  in the reflector collar contour  210  is comprised of a negative segment of a sphere but could be other calculated shapes. Each series of negative impressions  220  provides controlled spread of the light from the lamp  110  at predetermined intervals complementing the distribution from the primary polymeric prismatic reflector/refractor  100  into the 0-40 degree zonal lumen quadrant. The series of the small concave reflector impressions  220  are designed to provide gradually decreasing spread and intensity of the reflected illumination from the concave impressions  220  approaching the lower edge  212  with the lowest spread and intensity of the reflected illumination from the concave impressions  220  on the lower portion  204  that supports the polymeric prismatic reflector/refractor  100 . The series of the small concave reflector impressions  220  having radii, such as R 7  from a center point P 7  as shown in FIG. 6, that generally follow the reflector collar contour  210 . Each impression  220  is defined by a raised surface on the spinning chuck or on the surface of a hydroforming core. For example, each shape forming respective reflector impressions  220  is first machined into the surface of an EDM electrode and this electrode then is used to electrically machine and form each raised shape on a steel core. This raised shape is compressed into the wall thickness of the aluminum down-light collar contour  210  during the reflector collar forming process. Each of the negative impressions  220  is compressed into the aluminum collar curvature at predetermined intervals in the collar material, with each individual impression  220  having a predetermined prescribed depth and curvature. 
     FIGS. 7A,  8 A and  9 A respectively illustrate light ray traces with the prior art prismatic reflector/refractor device  100  and a prior art collar from the top, middle and bottom of the light source  110  for comparison with function of optical assembly  202  including the reflector collar  200  of the preferred embodiment as shown in FIGS. 7C,  8 C and  9 C. The rays are traced at the top, midpoint and bottom of the HID lamp  110  on several positions along the vertical axis of the polymeric reflector contour  100  to create a desired pattern of the distribution and can be used for determining the necessary number and arrangement of the impressions  220  the reflector collar  200 . For clarity the rays traces are not shown that pass through the area normally occupied by the lamp  110 . 
     FIGS. 7B,  8 B and  9 B respectively illustrate light ray traces of the reflector collar  200  in accordance with the preferred embodiment from the top, middle and bottom of the light source  110 . FIGS. 7B,  8 B and  9 B show the distribution of the rays as they are distributed through the lower opening  108  of the polymeric reflector, but without the detail of the polymeric reflector  110  for clarity. The light ray positions are again respectively shown starting at the top, midpoint and then the bottom of the HID arc tube  110  at a predetermined lamp center within the polymeric prismatic reflector. Note that the reflected path of the rays are directed away from the lamp envelope and toward the lower opening  108  of the polymeric reflector/refractor  100 . As shown in these ray traces of FIGS. 7B,  8 B and  9 B, the distribution of the reflector collar  200  is not parabolic in shape or distribution. The contributions to the lower 0-40 degree zonal efficiencies of a photometric distribution are selective. Reflector collar  200  provides maximum spread and intensity of the reflected illumination from the concave reflector impressions  220  near the upper opening  206  with gradually decreasing spread and intensity of the reflected illumination approaching the lower reflector collar portion  204  supporting the polymeric prismatic reflector/refractor  100 . 
     FIGS.  7 BB,  8 BB and  9 BB respectively illustrate light ray traces from an illustrated enlarged lower portion  204  of the reflector collar  200  in accordance with the preferred embodiment from the top, middle and bottom of the light source  110 . Multiple concave reflector impressions  220  are shown within the illustrated lower portion  204  of the reflector collar  200  that generally provide a lower spread and intensity of the reflected illumination from the reflector collar  200 . 
     FIGS. 7C,  8 C and  9 C respectively illustrate light ray traces of the optical assembly of FIG. 2 including the prismatic reflector/refractor device  100  together with the reflector collar  200  for enhanced directional illumination control in accordance with the preferred embodiment. The effective function of the reflector collar  200  may be appreciated from a comparison of the ray traces for the optical assembly  202  shown in FIGS. 7C,  8 C and  9 C with the ray traces for the prior art prismatic reflector/refractor device  100  shown in FIGS. 7A,  8 A and  9 A. 
     While the present invention has been described with reference to the details of the embodiments of the invention shown in the drawing, these details are not intended to limit the scope of the invention as claimed in the appended claims.