Patent Publication Number: US-7708430-B2

Title: Reflector-baffle for luminaires

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation application of U.S. Ser. No. 11/346,515, filed Feb. 2, 2006, the contents of which are incorporated by reference herein in their entirety, which claims priority to U.S. provisional application 60/650,058 filed Feb. 4, 2005, the contents of which are also hereby incorporated herein by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   Directing light incident from a light fixture in a precise way while maintaining adequate shielding of the source presents a challenge. Louvers or baffles are typically used to direct light and to prevent direct viewing of the light source, for example, so a lamp is not in direct view of an observer&#39;s eyes. 
   As best seen in  FIGS. 1   a  and  2 , a traditional baffle consists of a series of parallel blades  1  placed under the light source  6  to obscure or prevent direct viewing of the light source  6  or to control brightness of the luminare  2 . Baffle blades  1  have traditionally been designed in one of two ways, flat or parabolic. 
   As shown in  FIG. 1A , a flat baffle blade  1  simply occludes, absorbs or disperses (see  FIG. 1   b ) the light  7  that would otherwise be directed in an undesirable direction such as into an observer&#39;s eyes  8 . 
   A parabolic baffle  9  has vertically orientated sides  10  designed to perform the dual function of shielding the light source  6  and reflecting the light  7  rather than absorbing the light  7  ( FIG. 1   c ). A variation of the parabolic design is the “para-wedge” which has vertically orientated “sides”  10  and  10   a  that are both parabolic and wedge shaped as shown in  FIG. 1   d.    
   Note: for purposes of this patent application, applicants note that “side” is defined herein as a surface with a substantially vertical orientation as opposed to a “top” which is defined herein as a surface having a substantially horizontal orientation. 
   Thus, the efficiency and effectiveness of the prior art baffle blades  1  depends upon the surface finish of the baffle blades  1  as well as its shape. For example, the flat baffle blade  1  is thinner than the parabolic baffle blade  9  so it allows more light to propagate through the aperture; however, since the parabolic blades  9  typically have a specular finish, light that hits the side  10  of the baffle blade is reflected rather than absorbed. 
   Additionally, parabolic baffle blades  9  are typically constructed such that the upper most part of the baffle blades  9  are either folded over or “hollowed out” due to fabrication or cost considerations. 
   Thus, it would be advantageous to make use of the light  7  which strikes the top horizontally orientated section of the baffle blades that is otherwise scattered randomly or simply absorbed. As described in detail below, by designing a baffle blade in which the top surface is considered and designed as a useful reflecting surface, more light can be redirected into a chosen direction rather than letting it be absorbed or scattered randomly. 
   SUMMARY OF THE INVENTION 
   An embodiment may comprise a baffle blade for a luminaire comprising a blade member. The blade member comprising a reflective top section; and at least one side of the blade member; wherein the reflective top section has a reflective surface that has a substantially horizontal orientation in the luminaire; and wherein the sides of the blade member have a substantially vertical orientation in the luminaire; and wherein the reflective top section is structured so that light is directed from the reflective top section to a predetermined location. 
   An embodiment may also comprise an article of manufacture comprising: a blade member comprising: a reflective top section; and at least one side of the blade member; wherein the reflective top section has a reflective surface that has a substantially horizontal orientation in relation to the at least one side; and wherein the reflective top section is structured so that light is directed from the reflective top section to a predetermined location. 
   An embodiment may also comprise a luminaire comprising: a reflector; and at least one baffle blade having a reflective top section; wherein the reflective top section is structured so that light is reflected from the reflective top section to the reflector in order to redirect light towards a predetermined direction and to increase light output of the luminaire in a specific direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike. 
       FIG. 1   a  is a prior art baffle which blocks the view of the light source by absorbing light. 
       FIG. 1   b  is a prior art baffle which blocks the view of the light source by dispersing light. 
       FIG. 1   c  is a prior art baffle which blocks the view of the light source by redirecting light. 
       FIG. 1   d  is a prior art baffle which has a wedge profile. 
       FIG. 2  is a prior art luminaire with a prior art baffle. 
       FIG. 3  is a perspective view of a luminiare with an exemplary embodiment of the baffle of the invention. 
       FIGS. 4   a - 4   d  show top, front, side and isometric views of an embodiment of the invention with an array of uniform baffle blades with reflective top sections. 
       FIGS. 5   a - 5   d  show top, front, side and isometric views of an embodiment of the invention with an array of uniform baffle blades with reflective top sections and an additional reflective strip under the light source. 
       FIGS. 6   a - 6   d  show top, front, side and isometric views of an embodiment of the invention with an array of variable width baffle blades (widest under the light source) with reflective top sections. 
       FIGS. 7   a - 7   d  show top, front, side and isometric views of an embodiment of the invention with an array of variable width baffle blades (widest under the light source) with reflective top sections and an additional reflective strip located under the light source. 
       FIGS. 8   a - 8   d  shows top, front, side and isometric views of an embodiment of the invention with an array of variable width baffle blades (narrowest under the light source) with reflective top sections. 
       FIG. 9  shows a section through a luminaire fitted with a flat/horizontal profile baffle of an embodiment. 
       FIG. 10  shows a section through a luminaire fitted with a elliptically shaped profile baffle of an embodiment. 
       FIG. 11  is a candlepower distribution curve (polar plot) of a prior art luminaire with a typical baffle. Most of the light is allowed to hit the floor between the shelving. 
       FIG. 11A  is a candlepower distribution curve (polar plot) of a prior art luminaire. 
       FIG. 12  is a candlepower “two-wing” distribution curve (polar plot) of a luminaire using an exemplary embodiment of the baffle of the invention. In this example the baffle blades are wider under the lamp to re-use the light that would otherwise be directed or “spilled” onto the floor and to redirect that light to the target surfaces (vertical shelving). The blades are narrower at the sides to allow direct light from the source to reach the vertical shelving. 
       FIG. 12A  shows  FIGS. 11 ,  12 , and  11 A overlaid and scaled using a source with the same lumen output for all three. 
       FIG. 13   a  is a luminaire of another embodiment of the invention wherein the baffle blades are narrower under the light source and wider to the sides. In this example it is desirable to allow direct light from the source to pass (toward nadir) and reflect light at the edges off of the top surfaces of the baffle in an upward direction. 
       FIG. 13   b  is a cross-sectional view of the luminaire in  FIG. 13   a.    
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following example is a luminaire used for lighting book stacks or aisles or other spaces which is enhanced by incorporating the baffle designs and baffle blade members of an embodiment of the invention. Additionally, custom or semi-custom applications are commonly ordered by customers such as lighting for specific merchant aisles. Thus, other configurations are also envisioned and intended to be covered by the attached claims. 
   Directing light from a luminaire in a precise way to evenly light a surface while maximizing candlepower presents a challenge as shown by the luminaire  2  of Prior Art  FIG. 11 . A good example is lighting book stacks or shelves  4  in libraries and media centers where the aisles are typically 32″, 42″, and 48″ wide and 84″ to 96″ high. This high and narrow space requires a specific photometric distribution to evenly illuminate the media or bookshelves from top to bottom while not wasting light by sending it incident onto the floor rather than to the book shelves  4 . Also, due to the geometry of the space, linear fluorescent luminaires are most often used to illuminate the vertical surfaces down the length of the aisles. 
   Additionally, The Illuminating Engineering Society of North America (IESNA) recommends a minimum illuminance level of 30 vertical foot-candles on a book stack at 30 inches above the finished floor  5 . Many existing luminaires used for this application employ high wattage fluorescent lamps or multiple lamps in cross-section (side-by-side) to achieve the recommended light level. The resulting connected power load (in watts) or lighting power density (“LPD”—in watts per square foot) does not comply with the applicable energy code requirements. 
   For example, ANSI/ASHRAE/IESNA have jointly published an “ASHRAE Energy Standard” which many local states have adopted or incorporated into their building codes. California has established a more stringent energy code known as “Title 24”. These standards specify the maximum allowable LPD for various areas within a building. The current ASHRAE LPD allowance for library stacks is 1.7 watts/sq.ft. The current California Title 24 LPD allowance for library stacks is 1.5 watts/sq.ft. 
   Working backwards, the maximum allowable wattage lamp to comply with these LPD allowances can be calculated. For example: a 36″ wide aisle with 12″ deep book stacks on either side of the aisle for a length of 4 feet represents a 20 square foot area. Based on the ASHRAE standard of 1.7 watts per square foot the maximum allowable connected load for a fixture used in this space must not exceed 34 watts (derived from 1.7 W/SqFt×20 SqFt). Based on California Title 24 the connected load cannot exceed 30 watts (1.5 W/SqFt×20 SqFt). 
   Thus, it would be advantageous to have a luminaire available, which would not only comply with the energy code requirements, but also provide the IESNA recommended light levels. In addition to meeting the energy and illuminance targets, it is desirable that luminaires be designed to minimize discomforting glare from normal viewing angles as well as be of minimal size. 
   As shown in Prior Art  FIG. 2 , stack light luminares  2  typically employ baffle blades  1  to reduce discomforting glare. The baffle blades  1  used in the  FIG. 2  luminaire consist of an array of uniform shaped baffle blades  1  located at the bottom aperture of the luminaire  2  to shield the lamp light source  6  and to reduce unwanted brightness when viewed from below, for example, when looking down the length of the aisle. As shown in  FIG. 1   d , in the prior art device, any upper edges  10   a  of the side  10  of baffle blade  1  located closest to the light source  6  are flattened edges (see  FIG. 1   d ) or are partially open or “hollowed out” (not shown) due to fabrication or cost considerations. Light which hits any upper edges  10   a  of the sides  10  of the baffle blades  1  is minimal because the area is small in size, and the light is either partially absorbed and/or partially scattered. Thus, this light incident upon the upper edges  10   a  of side  10  is not used effectively for lighting. 
   Therefore, what is desired is a luminaire with an improved and novel baffle that may light both vertical sides of a selected space such as an aisle or any narrow corridor (library stacks, archives, retail store aisles, etc.) evenly from top to bottom in an efficient manner. For example, it would be desirable for the efficiency gained to help a user meet the energy code requirements, and to meet the IESNA recommended light levels discussed above in detail. In order to accomplish this, the present invention “harvests” the light which hits the top sections of the baffles and uses this otherwise wasted light to augment the resultant light distribution and to increase output without requiring a larger, less efficient, bulb for example. Reusing this otherwise scattered or wasted light also helps minimize unwanted spill light incident upon the floor and helps minimize unwanted and discomforting glare while achieving high luminaire efficiency while minimizing mass. Additionally, beneficial considerations also include appearance and cost. 
   The present invention may meet the above needs in several ways. Additionally, the description below is not intended to be limited to only one specific embodiment. 
     FIG. 3  shows an example of an embodiment of a directional luminaire  19  which produces the resultant improved “directional” light distribution  12  as shown in  FIG. 12  by making use of a novel reflective top surface baffle blade concept. From the shape of the directional light distribution  12 , it can be understood that the vertically orientated surfaces of the shelves  4  are “directionally” illuminated evenly from near the floor to near the uppermost sections of the shelves  4 . As noted above, this directional light distribution  12 , is an improved design over typical prior art luminaire  2  design, because it maximizes light  11   a  directed to the vertical surfaces by not wasting useable light by use of novel baffles blades having reflective top surfaces, so that resultant light output can be maximized without resorting to use of more powerful light sources requiring more energy. 
   For example, it can be seen from the shape of the directional light distribution  12  in  FIG. 12 , in comparison to the prior art light distribution  3  in  FIG. 11 , that light that would otherwise be sent towards the floor is redirected to evenly illuminate the surfaces of the book shelf or shelves  4  in an aisle in a store for example from top to bottom. In this example, this directional control of the light distribution  12  is enabled in part by directional reflector  13  working in conjunction with the novel reflective top sections baffle blades  4  as shown in the embodiments of  FIGS. 9 and 10  by the path of propagating light rays  11   a ,  11   b , and  11   c . Specifically, as seen in  FIGS. 9 and 10 , the tops of the baffle blades comprise horizontally orientated reflective top sections  14   a  of the reflective baffle blades  14  which are designed to redirect light back to the directional reflector  13  or other device in order to redirect light  11   a  (see reflection points  11   b ) back into the resultant output beam  11   c  to light the target surfaces more evenly with improved and maximized output without necessitating use of a larger more energy inefficient bulb for example. Thus, it is possible to increase the resultant output candlepower by using novel baffle blade  4  having reflective top sections  14   a.    
   Six specific and representative embodiments will be discussed below in detail. However, this disclosure is not intended to be interpreted to be limited to only these specific examples as variations and equivalents thereof are envisioned and intended to be covered herein by the attached claims and would be apparent to those skilled in the art. 
   First as shown in  FIGS. 4   a - 4   d , an embodiment may comprise a reflective baffle blade  14  for use with a luminaire comprising a blade member having a uniform width and a reflective top section  14   a  which in this case is a horizontally orientated flat reflective surface  15  that is structured so that light is reflected in a desired direction as shown in  FIG. 4   c  for example. 
   Second, another embodiment is shown in  FIGS. 5   a - 5   d  wherein an additional reflective strip  16  is added to an array of reflective baffle blades  14 . These reflective baffle blades  14  are of the same shape and as the reflective baffle blades shown in  FIGS. 4   a - 4   d . This additional reflective strip  16  provides additional reflected light as shown in  FIG. 5   c  by reflection point  16   a  which is propagated to become a component of resultant output beam  11   c . In this embodiment the reflective strip  16  is located under the source, for example parallel to the light source, to minimize light directed downward. 
   Third, another embodiment is shown in  FIGS. 6   a - 6   d  wherein a variable width reflective baffle blade  17  for a luminaire comprises a blade member having a variable width as shown in  FIG. 6   a  and a reflective top section  17   a . The reflective top section  17   a  has a curved, elliptical, or custom shaped surface wherein the surface is structured so that light is reflected (see reflection points  17   b  to become part of resultant beam  17   c  as shown in  FIG. 6   c . In this embodiment, the variable width baffle blades  17  are widest under the light source to minimize light directed downward directly beneath the light source  6 . It is important to note that these blades may also be made of uniform width depending upon the required application. 
   Fourth, another embodiment of the invention is shown in  FIGS. 7   a - 7   d  which is the same as the embodiment discussed above in reference to  FIGS. 6   a - 6   d  except for an additional longitudinal reflective strip  16  that is arranged perpendicular to the variable width baffle blades  17 . The reflective top section  17   a  of the baffle blades  17 , and the reflective strip  16  are structured so that light is reflected to become part of resultant beam  17   c  as shown in  FIG. 7   c . In this embodiment, the reflective strip  16  is located under the light source  6  and the variable width baffle blades  17  are widest under the light source  6  to minimize light directed downward directly beneath the light source  6 . 
   Fifth, another embodiment of the invention is shown in  FIGS. 8   a - 8   d . In this embodiment the variable width baffle blades  17  are made narrow under the light source  6  to maximize light directed directly downward from the light source  6 . 
   Sixth, another embodiment of the invention is shown in  FIG. 13 . This is an example of an open top luminaire application. In this embodiment, the variable width baffle blades  17  are made narrow under the light source  6  to maximize light directed directly downward from the light source  6 . Therefore, this illustrates that a directional reflector  13  is not always required and thus is not essential to the novel concept or invention as a whole, but may be used depending upon the application requirements. This embodiment also allows control over light projected upward to light a ceiling for example. 
   Thus, as the embodiments above demonstrate, many configurations of the invention are possible depending upon the required application. Thus, it is not required herein to provide a design specification or an exhaustive list of all possible custom applications which could use the overall novel reflective baffle blades having reflective top sections of the present invention. However, a partial list includes illumination of book shelves or book stacks, aisles including aisles located in stores, and illumination of any opposing vertical surfaces in general. 
   It is also noted that the entire top surface of the variable width baffle blade may act as a useful reflector and not merely at the widest part. In contrast, most prior art luminaires of this type have a top surface that is not reflective and that is hollowed out. Thus, as discussed above, the top surface of the present embodiment baffle may have a specifically shaped contour and width which may be, but is no limited to an elliptical shape, and which becomes wider directly under the lamp to harvest and re-use the lamp energy that would otherwise go directly to the floor and put it back into the main beam which lights the vertical desired surface more evenly as shown in  FIG. 12 . Alternatively, the blades could become wider at the sides to allow more light directly to the floor, or may be an even width if so desired. 
   While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.