Abstract:
A lighting fixture comprising an optimized linear module lighting device and a plurality of parabolic fins. The optimized linear module lighting device comprises a substrate comprising at least first, second, and third portions. The optimized linear module lighting device further comprises a plurality of light-emitting elements. A first set of the light-emitting elements are disposed on the first portion of the substrate; a second set of the light-emitting elements are disposed on the second portion of the substrate; and a third set of the light-emitting elements are disposed on the third portion of the substrate. The second set of light-emitting elements is disposed above at least one of the parabolic fins and is less dense than the first and third sets of light-emitting elements.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/803,485, entitled “LED Lighting Device Having Optimized LED Placement for Parabolic Fixtures” and filed Mar. 20, 2013, the contents of which application are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to lighting technology and, more specifically, to optimizing the placement of LEDs in LED tubes; LED linear modules, strips, films, and panels; or other sources of lighting to increase total efficacy for mounting in existing parabolic troffer fixtures, for retrofit kits, or for new parabolic troffer fixtures. 
       BACKGROUND OF THE INVENTION 
       [0003]    Parabolic fixtures are often referred to as fluorescent troffers. As used herein, the term, “parabolic fixture,” is used to describe a fixture that was initially designed to hold fluorescent tubes or fixtures that have a plurality of openings with reflective or non-reflective parabolic fins that frame the openings. Troffer-style fixtures are often used in commercial office and industrial spaces throughout the world. Troffers to date incorporate linear fluorescent light bulbs that span the length of the troffer. Troffers are often mounted to or suspended from ceilings, such as being held by a “T-grid.” Often the troffer may be recessed into the ceiling, with the back side of the troffer, referred to as the troffer pan, protruding into the plenum area above the ceiling a distance of up to six inches or more. 
         [0004]    Exemplary conventional parabolic fixtures are illustrated in  FIGS. 1 through 6 .  FIG. 1  illustrates a parabolic fixture  100  having nine openings  110  separated by parabolic fins  115 A,  115 B,  115 C, and  115 D. Mounted in the parabolic fixture  100  are three LED tubes  120 A,  120 B, and  120 C, each respectively comprising a plurality of LEDs  125 A,  125 B, and  125 C. The dimensions of the parabolic fixture  100  are 2 ft. by 2 ft. (600 mm by 600 mm). 
         [0005]      FIG. 2  illustrates a parabolic fixture  200  having 12 openings  210  separated by parabolic fins  215 . Mounted in the parabolic fixture  200  are three LED tubes  220 A,  220 B, and  220 C, each respectively comprising a plurality of LEDs  225 A,  225 B, and  225 C. The dimensions of the parabolic fixture  200  are 2 ft. by 2 ft. (600 mm by 600 mm). 
         [0006]      FIG. 3  illustrates a parabolic fixture  300  having 16 openings  310  separated by parabolic fins  315 . Mounted in the parabolic fixture  300  are four LED tubes  320 A,  320 B,  320 C, and  320 D, each respectively comprising a plurality of LEDs  325 A,  325 B,  325 C, and  325 D. The dimensions of the parabolic fixture  300  are 2 ft. by 2 ft. (600 mm by 600 mm). 
         [0007]      FIG. 4  illustrates a parabolic fixture  400  having 12 openings  410  separated by parabolic fins  415 . Mounted in the parabolic fixture  400  are two LED tubes  420 A and  420 B, each respectively comprising a plurality of LEDs  425 A and  425 B. The dimensions of the parabolic fixture  400  are 2 ft. by 4 ft. (600 mm by 1200 mm). 
         [0008]      FIG. 5  illustrates a parabolic fixture  500  having 18 openings  510  separated by parabolic fins  515 . Mounted in the parabolic fixture  500  are three LED tubes  520 A and  520 B, each respectively comprising a plurality of LEDs  525 A,  525 B, and  525 C. The dimensions of the parabolic fixture  500  are 2 ft. by 4 ft. (600 mm by 1200 mm). 
         [0009]      FIG. 6  illustrates a parabolic fixture  600  having 24 openings  610  separated by parabolic fins  615 . Mounted in the parabolic fixture  600  are four LED tubes  620 A,  620 B,  620 C, and  620 D, each respectively comprising a plurality of LEDs  625 A,  625 B,  625 C, and  625 D. The dimensions of the parabolic fixture  600  are 2 ft. by 4 ft. (600 mm by 1200 mm). 
       SUMMARY OF THE INVENTION 
       [0010]    In accordance with an aspect of the present invention, there is provided an optimized linear module lighting device. The optimized linear module lighting device comprises a substrate comprising at least first, second, and third portions. The optimized linear module lighting device further comprises a plurality of light-emitting elements. A first set of the light-emitting elements is disposed on the first portion of the substrate; a second set of the light-emitting elements is disposed on the second portion of the substrate; and a third set of the light-emitting elements is disposed on the third portion of the substrate. The second set of light-emitting elements is less dense than the first and second sets of light-emitting elements. 
         [0011]    In accordance with another aspect of the present invention, there is provided an optimized LED strip, film or panel device. The optimized LED strip, film or panel device comprises a substrate comprising at least first, second, and third portions. The optimized LED strip, film or panel device further comprises a plurality of light-emitting diodes (LEDs). A first set of the LEDs is disposed on the first portion of the substrate; a second set of the LEDs is disposed on the second portion of the substrate; and a third set of the LEDs is disposed on the third portion of the substrate. The second set of LEDs is less dense than the first and second sets of LEDs. In an exemplary embodiment, the substrate of the optimized LED strip, film or panel device comprises a further portion in which no LEDs are disposed. Such portion corresponds to a fin of a troffer in which the optimized LED strip, film or panel device is configured to be mounted. 
         [0012]    In accordance with another aspect of the present invention, there is provided a lighting fixture comprising an optimized linear module lighting device and a plurality of parabolic fins. The optimized linear module lighting device comprises a substrate comprising at least first, second, and third portions. The optimized linear module lighting device further comprises a plurality of light-emitting elements. A first set of the light-emitting elements is disposed on the first portion of the substrate; a second set of the light-emitting elements is disposed on the second portion of the substrate; and a third set of the light-emitting elements is disposed on the third portion of the substrate. The second set of light-emitting elements is disposed above at least one of the parabolic fins and is less dense than the first and third sets of light-emitting elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    For the purpose of illustration, there are shown in the drawings certain embodiments of the present invention. In the drawings, like numerals indicate like elements throughout. It should be understood that the invention is not limited to the precise arrangements, dimensions, and instruments shown. In the drawings: 
           [0014]      FIGS. 1-6  illustrate conventional parabolic fixtures in which conventional LED tubes are mounted. 
           [0015]      FIG. 7A  illustrates a side, cross-sectional view of a conventional fixture in which a conventional LED tube is mounted. 
           [0016]      FIG. 7B  illustrates a plan view of the LED tube of  FIG. 7A . 
           [0017]      FIG. 8A  illustrates a side, cross-sectional view of a fixture in which an LED tube is mounted, the LED tube comprising a plurality of LEDs disposed in an arrangement optimized for lighting efficacy, in accordance with an exemplary embodiment of the present invention. 
           [0018]      FIG. 8B  illustrates a plan view of the LED tube of  FIG. 8A , in accordance with an exemplary embodiment of the present invention. 
           [0019]      FIG. 9  illustrates a plan view of a fixture in which a plurality of light panels is disposed, in accordance with an exemplary embodiment of the present invention. 
           [0020]      FIG. 10  illustrates a plan view of a fixture in which a plurality of single high output LEDs or densely clustered LED is disposed, in accordance with an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Reference to the drawings illustrating various views of exemplary embodiments of the present invention is now made. In the drawings and the description of the drawings herein, certain terminology is used for convenience only and is not to be taken as limiting the embodiments of the present invention. Furthermore, in the drawings and the description below, like numerals indicate like elements throughout. 
         [0022]    Efficacy is the total fixture efficiency to deliver the most light to desired areas. In a conventional parabolic fixture, such as any of fixtures  100  through  600 , the parabolic fins  115  through  615  are typically wider on the side of the fixture  100 - 600  mounted to a ceiling (the top ceiling side) than on the other side of the fixture  100 - 600 . Thus, the parabolic fins  115  through  615  are tapered, and the ceiling side of the fins  115  through  615  block the light emitted by the LEDs  125  through  625  of the LED tubes  120  through  620 . An exemplary region of the LEDs  125 A,  125 B, and  125 C of the LED tubes  120 A,  120 B, and  125 C blocked by the fin  115 B is indicated in  FIG. 1  as region  130 . It is to be understood that a similar region of the LEDs  125 A,  125 B, and  125 C of the LED tubes  120 A,  120 B, and  125 C is also blocked by the fin  115 A and that similar regions of the LEDs  225 ,  325 ,  425 ,  525 , and  625  of respective LED tubes  220 ,  320 ,  420 ,  520 , and  620  are blocked by the horizontal fins  215 ,  315 ,  415 ,  515 , and  615  of the fixtures  200 ,  300 ,  400 ,  500 , and  600 . 
         [0023]    Referring now to  FIG. 7A , there is illustrated a side view of a cross section of a conventional fixture  700  in which a conventional LED tube  720 A comprising a plurality of LEDs  725 A is mounted in a conventional arrangement. Illustrated are three openings  710 A through  710 C in the fixture  700  separated by parabolic fins  715 A and  715 B. As seen from the cross section, the fins  715 A and  715 B are wider at the side nearest to the LED tube  720 A compared to the side furthest from the LED tube  720 A.  FIG. 7A  illustrates a region  730 A of the LEDs  725 A located above the fin  715 A and a region  730 B of the LEDs  725 A located above the fin  715 B. 
         [0024]    Illustrated in  FIG. 7B  is a plan view of the LED tube  720 A as seen from the illumination area below the conventional fixture  700 . The LED tube  720 A includes LEDs  725 A mounted on all portions thereof, including portions  721 A. 1 ,  721 A. 2 ,  722 A. 1 ,  722 A. 2 , and  722 A. 3  illustrated in  FIG. 7B . Portions  721 A. 2  and  721 A. 2  of the LED tube  720 A illustrated in  FIG. 7A  correspond to regions  730 A and  730 B illustrated in  FIG. 7A . 
         [0025]    Referring to  FIGS. 7A and 7B  together, because light  716 A and  716 B emitted by the LEDs  725 A in the portions  721 A. 1  and  721 A. 2  is reflected by upper surfaces  717 A and  717 B of respective fins  715 A and  715 B, the efficacy of the fixture  700  is negatively affected. Thus, the placement of the LEDs  725 A on the LED tube  720 A is not optimized. 
         [0026]    Illustrated in  FIG. 8A  is a side view of a cross section of a fixture, generally designated as  800 , in which linear module lighting device  820 A, specifically an LED tube  820 A, is mounted therein, in accordance with an exemplary embodiment of the present invention.  FIG. 8B  illustrates a plan view of the LED tube  820 A as seen from the illumination area below the fixture  800 . The fixture  800  may be a new fixture or a retrofitted fixture. 
         [0027]    Referring to  FIGS. 8A and 8B  together, the fixture  800  further comprises three openings  810 A,  810 B, and  810 C separated by parabolic fins  815 A and  815 B. As seen from the cross section, the fins  815 A and  815 B are wider at the side nearest to the LED tube  820 A compared to the side furthest from the LED tube  820 A.  FIG. 8A  illustrates a region  830 A of the LED tube  820 A located above the fin  815 A and a region  830 B of the LED tube  820 A located above the fin  815 B. 
         [0028]    The LED tube  820 A comprises a plurality of LEDs  825 A disposed on a substrate  805 . The LEDs  825 A are disposed in the portions  822 A. 1 ,  822 A. 2 , and  822 A. 3  of the substrate  805  of the LED tube  820 A corresponding to the openings  810 A,  810 B, and  810 C, respectively. No LEDs  825 A are disposed in the portions  821 A. 1  and  821 A. 2  of the LED tube  820 A corresponding to the upper surfaces  817 A and  817 B of the fins  815 A and  815 B, whereas there are four LEDs in each of the portions  721 A. 1  and  721 A. 2  of the LED tube  720 A. Thus, light  816 A and  816 B emitted by the LEDs  825 A is not reflected (or minimally reflected) back toward the LED tube  820 A. By reducing the number of LEDs  825 A, changing the spacing of the LEDs  825 A, or eliminating them altogether (as illustrated in  FIG. 8B ) directly above the parabolic fins  815 A and  815 B in the portions  821 A. 1  and  821 A. 2 , the efficacy of the LED tube  820 A in the fixture  800  is increased over the LED tube  720 A in the fixture  700 . 
         [0029]    It is to be understood in other exemplary embodiments of the optimized LED tube  820 A that there may be one, two, or three LEDs  825 A remaining in each of the portions  821 A. 1  and  821 A. 2  depending on output requirements of the LED tube  820 A. In each optimized case, the portions  821 A. 1  and  821 A. 2  have fewer LEDs  825 A, or more specifically a lower LED density, than the other areas  822 A. 1 ,  822 A. 2 , and  822 A. 3 . This approach to placing the LEDs  825 A applies for single or triple rows of diodes (or any number of rows of diodes) in addition to the double rows shown in  FIG. 8B . 
         [0030]    In exemplary embodiments of the fixture  800 , the fins  815 A,  815 B each have a width of ¾ in. or 1 in., i.e., the upper surface  817 A,  817 B of either fin  815 A,  815 B has a width of either ¾ in. or 1 in. In such embodiments, the width of each of the portions  821 A. 1  and  821 A. 2  is, respectively ¾ in. or 1 in. Thus, the ratio of the width of each of the portions  821 A. 1  and  821 A. 2  to the width of the upper surface  817 A,  817 B of either fin  815 A,  815 B is 1:1. Such ratio may vary between 1:1 and 2:1, depending on the beam angle of the LED used, for example. For example, in another exemplary embodiment the width of each of the portions  821 A. 1  and  821 A. 2  is 1.5 in., and the width of the upper surface  817 A,  817 B of either fin  815 A,  815 B is 1 in. In yet another exemplary embodiment the width of each of the portions  821 A. 1  and  821 A. 2  is 2 in., and the width of the upper surface  817 A,  817 B of either fin  815 A,  815 B is 1 in. 
         [0031]    It is to be understood that different fixtures may have fins having upper surfaces having widths other than ¾ in. or 1 in. In such embodiments, the ratio of the width of each of the portions  821 A. 1  and  821 A. 2  to the width of the upper surface of the fins in such fixtures still may be anywhere from 1:1 to 2:1. Further, it is to be understood that not all fixtures have fins having upper surfaces that have uniform widths. Some fixtures have a combination of upper widths of fins. Thus, the width of each of the portions  821 A. 1  and  821 A. 2  may differ as the width of the upper surface of the corresponding fin differs from that of other fins in the fixture. The ratio of each portion  821 A. 1 ,  821 A. 2  to the width of the upper surface of the corresponding fin, however, is still between 1:1 and 2:1 depending on the beam angle of the LED used, for example. 
         [0032]    The decrease in wasted light resulting from reducing or omitting LEDs in one portion  821 A. 1 , for example, is marginal relative to the total light output from the fixture  800 , but the decrease in wasted light is compounded by the number and type of fins in the fixture  800 , above which corresponding portions of LED tubes have reduced numbers of LEDs or no LEDs, in accordance with exemplary embodiments of the present invention. Current LED manufacturers provide a uniform distribution of diodes across an LED tube or retrofit light panel. By placing the diodes in a non-uniform position to account for the parabolic fins  815 A and  815 B, the LED fixture  800  retrofitted with LED tubes  820 A requires less wattage to deliver the same useable amount of light or may use the same amount of electricity to deliver an increased level of useable light. 
         [0033]    The optimized LED placement for parabolic fixtures described herein is applicable beyond LED tubes to include insert light panels that mount to the underside of a fixture housing. Illustrated in  FIG. 9  is a plan view of a fixture  900 , in accordance with an exemplary embodiment of the present invention. The fixture  900  comprises a plurality of light panels  920 A-I disposed in openings  910 A-I between fins  915 . The size and placement of the light panels  920 A-I are optimized for openings  910 A-I of the fixture  900 . The gaps between adjacent light panels  920 A-I may be sized using the techniques described above for LED tube  820 A. 
         [0034]      FIG. 10  illustrates a plan view, as seen from the illumination area below, of a fixture  1000  comprising single high output LEDs or densely clustered LEDs  1020 A-I disposed in respective openings  1010 A-I, in accordance with an exemplary embodiment of the present invention. The high output LEDs or densely clustered LEDs  1020 A-I are spaced between the parabolic fins of the fixture. 
         [0035]    It is to be understood that the LED tube  820 A, the light panels  920 A-I, and the high output LEDs or densely clustered LEDs  1020 A-I may be used with many different size fixtures, such a 2 ft. by 2 ft. troffer, such as illustrated in  FIGS. 1-3 , in a 2 ft. by 4 ft. troffer, such as illustrated in  FIGS. 4-6 , or any other suitably dimensioned troffers. 
         [0036]    It is to be understood that the exemplary embodiments of the present invention described herein are not limited to using LED tubes, light panels, high output LEDs, or densely clustered LEDs. Other exemplary embodiments of the present invention comprising linear lighting modules using any known light-emitting elements, laminated film applications or other substrates such as diodes on printed circuit boards, metal core boards, FR4 boards, metal strips, or diodes directly applied to heat sinks, with placement of light-emitting elements optimized as described above, are contemplated. Exemplary substrates and LED lighting devices that may benefit from optimized LED placement using the techniques described above are described in further detail in U.S. application Ser. No. 13/188,029 of Szoradi et al., filed Jul. 21, 2011 and entitled, “Light Engine Device with Direct to Linear System Driver,” the contents of which are incorporated herein by reference in their entirety. 
         [0037]    These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it is to be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It is to be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention.