Patent Publication Number: US-8985816-B2

Title: Light fixture with central lighting housing and peripheral cooling housing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a nonprovisional of U.S. Provisional Patent Application No. 61/654,761, filed Jun. 1, 2012, and titled Light Fixture with Central Lighting Housing and Peripheral Cooling Housing, which is herein entirely incorporated by reference. 
     BACKGROUND 
     The present invention relates to light fixture cooling features, and particularly, to providing a light fixture with internal and external surfaces and cooling paths to facilitate cooling. 
     Managing the temperature of light sources in a light fixture is generally important to performance and longevity. This is particularly true with newer highly efficient lighting technology, for example, light sources such as LEDs or laser diodes. LEDs are generally selected to maximize the light output for a given power consumption at a reasonable cost. Because LED light sources operate at a much lower temperature than typical incandescent light sources, less energy is wasted in the form of heat production. However, LEDs tend to be more sensitive to operating temperature and lower operating temperatures also provide a much smaller temperature difference between the LED and the ambient environment, thus requiring greater attention to thermal management to transfer and dissipate any excess heat generated by the LED driver and emitter so that the design operating temperature for the components are not exceeded. 
     As temperatures rise, the efficacy of the LED is reduced, reducing the light output, and reducing the lifespan of the LED. LED lighting fixtures generally include both LED drivers and LED emitters. To facilitate dissipation of heat, convection, conduction, and radiation are available modes of heat transfer. For LED light fixtures, dissipation of heat by conduction is often provided by one or more LED packages being mounted on a heat sink The heatsink is generally integral with or thermally coupled with the light housing, which often includes external cooling fins to further facilitate the dissipation of heat from the light fixture by convection and radiation. 
     For example, one prior art design seeking to address these concerns provides fins between a central light housing and an outer rim that are thin in width and height, and thus provide vary little surface area to transfer heat from the light to the channel of air passing through the light fixture. Additionally, no structure limits visibility vertically through the cooling channels or redirects airflow horizontally across further surfaces of such a light fixture mounted to a ceiling or similar overhanging structure. 
     Another prior art design seeking to address these concerns provides a very narrow set of vertical airflow channels around the periphery of the central light housing, the channels formed by an outer ring and vertical cooling fins, and the vertical cooling fins extend radially inwardly above and toward the center of the central light housing. Thus, in the case of mounting the light fixture against a ceiling, any airflow extending upwardly through the very narrow airflow channels flows outwardly between the ceiling and top of the light fixture, and thus will not benefit provide from further heat exchange if the air flow had included flow across the radially inwardly extending fins on the top side of the central light housing. 
     Therefore, it is desirable to provide a lighting fixture design that maximizes cooling by thermal convection for the light emitter and driver in a central light package housing, shields the cooling features and through the fixture view from as many viewing angles as practical, and redirects vertical airflow to a radially outwardly direction and across further cooling structure when mounted against a ceiling. 
     SUMMARY 
     The present invention may comprise one or more of the features recited in the attached claims, and/or one or more of the following features and combinations thereof. An illustrative light fixture includes a cylindrical lighting package housing surrounded peripherally by a cooling housing providing airflow cooling channels. The airflow cooling channels are defined in the space between the circumference of the cylindrical lighting package housing and a rim around the periphery of the light fixture. The cooling housing provides wide and long openings for cool air to rise vertically from below the light fixture into the airflow channels defined in part by cooling fins and a horizontally arranged radial ring supporting the cooling fins. The airflow continues through radial exit channels, providing radially outward flow below a ceiling the fixture is mounted on. The arrangement of the radial ring fin support between the vertical cooling fins also eliminates or minimizes the view through the airflow channels and to the ceiling. 
     An illustrative embodiment of the light fixture includes a light package housing including emitters; an illumination side of the light package housing, the emitters projecting light from the illumination side; a top side of the light package housing, located opposite the illumination side; and a cooling housing extending peripherally around an outer circumference of the light package housing, the cooling housing including a plurality of cooling fins, a rim, and a radial ring fin support. The rim can couple the cooling fins around an outer circumference of the cooling housing, the plurality of cooling fins can span radially between the outer circumference of the light package housing, and the radial ring fin support can radially spans a portion of adjacent vertical fins between the rim and the outer circumference of the light package. 
     The radial ring fin support can form an annulus extending from the rim and inwardly toward the outer circumference of the light package housing such that a vertical cooling channel remains between the radial ring fin support, the outer circumference of the light package housing, and adjacent ones of the plurality of cooling fins. The radial ring fin support can span a substantial portion of the vertical openings between the rim, the outer circumference of the light package housing, and adjacent ones of the plurality of cooling fins. The bottom side of the radial ring fin support can redirect radially inwardly at least a substantial portion of the vertical cooling channel path extending upwardly from a bottom side of the support and between adjacent ones of the plurality of cooling fins. 
     The top side of the light package housing can include a flat portion for mounting the light fixture to a ceiling. The top side of the radial ring fin support, ceiling, and adjacent ones of the plurality of cooling fins can form cooling paths extending radially outward from an upper portion of the outer circumference of the light package housing. The light package housing can be about cylindrical. 
     The light package housing can further include at least one emitter driver and the cooling housing surrounds the outer circumference of the portion of the light package housing containing the at least one emitter driver. The cooling housing can surround the outer circumference of the portion of the light package housing containing the emitters. 
     The rim can spans vertically from the illumination side to the top side. The plurality of cooling fins can each include a top edge adjacent the outer circumference of the lighting package housing that is about coplanar with the top surface of the lighting package housing. 
     Another illustrative embodiment of a light fixture, includes a light package housing including emitters; an illumination side of the light package housing, the emitters projecting light from the illumination side; a top side of the light package housing, located opposite the illumination side; a cooling housing extending peripherally around an outer circumference of the light package housing, the cooling housing including a plurality of cooling fins, a rim, and a radial ring fin support; and a plurality of vertical cooling channels defined between the rim, outer circumference of the light package housing, and adjacent ones of the plurality of cooling fins. The rim can couple the cooling fins around an outer circumference of the cooling housing; the plurality of cooling fins can span radially between the outer circumference of the light package housing; and the radial ring fin support can radially span a portion of adjacent vertical fins between the rim and the outer circumference of the light package, a bottom side of the radial ring fin support redirects radially inwardly, toward the light package housing, each of the plurality of vertical cooling channels. 
     Yet another illustrative light fixture, includes a light package housing including emitters; an illumination side of the light package housing, the emitters projecting light from the illumination side; a top side of the light package housing, located opposite the illumination side; a cooling housing extending peripherally around an outer circumference of the light package housing, the cooling housing including a plurality of cooling fins, a rim, and a radial ring fin support; and a plurality of vertical cooling channels defined between the rim, outer circumference of the light package housing, and adjacent ones of the plurality of cooling fins. The rim can couple the cooling fins around an outer circumference of the cooling housing; the plurality of cooling fins can span radially between the outer circumference of the light package housing; and the radial ring fin support can forms an annulus extending from the rim and inwardly toward, but not touching, the outer circumference of the light package housing, and a bottom side of the radial ring fin support redirects radially inwardly, toward the light package housing, each of the plurality of vertical cooling channels. 
     Additional features of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description particularly refers to the accompanying figures in which: 
         FIG. 1  is a side view of an illustrative lighting fixture according to the present invention mounted on a ceiling; 
         FIG. 2  is a top view of the lighting fixture of  FIG. 1 ; 
         FIG. 3  is a bottom view of the lighting fixture of  FIG. 1 ; 
         FIG. 4  is a bottom side perspective section view of the lighting fixture of  FIG. 1 , taken along sections line  4 - 4  shown in  FIG. 2 ; 
         FIG. 5  is a top perspective section view of the lighting fixture of  FIG. 1 , taken along section line  5 - 5  shown in  FIG. 1 ; 
         FIG. 6  is a top perspective section view of the lighting fixture of  FIG. 1 , taken along section line  6 - 6  shown in  FIG. 1 ; and 
         FIG. 7  is a bottom side perspective exploded view of the lighting fixture of  FIG. 1 ; 
     
    
    
     DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     For the purposes of promoting and understanding the principals of the invention, reference will now be made to one or more illustrative embodiments illustrated in the drawings and specific language will be used to describe the same. 
     Referring to  FIGS. 1-4 , a first illustrative embodiment of a light fixture  30  according to the present invention is illustrated. The light fixture  30  includes a light source  32 , including an emitter  34  ( FIG. 2 ; as used herein, “emitter” refers to a single emitter or an array of emitters) and a driver  36  ( FIGS. 4-5 ; as used herein, “driver” refers to a single driver or an array of drivers), contained within a central, cylindrical light package housing  50 . The light fixture  30  also includes a cooling housing  60  encircling an outer circumference  52  of the light package housing  50 . 
     The light source  32  may be, but is not limited to, an LED emitter  34  and associated driver  36 , as are typically used in the commercial lighting industry. For example, the associated driver  36  converts AC power to appropriate DC power and may also include additional LED power and control features. 
     The light package housing  50  and cooling housing  60  can be formed from, for example, die cast aluminum or an aluminum alloy. The housings  50  and  60  may be separately formed, integrally formed, or a portion of housing  50  may be integrally formed with housing  60 , or vice-versa. The emitter  34  can be thermally coupled and mounted to the light package housing  50 , which is thermally coupled to the cooling housing  60 . For example, as shown in  FIG. 7 , the emitters  34  can be coupled with annular heat transfer surface  53 , which are thermally coupled and/or integrally formed with vertical cooling fins  74  (discussed below). 
     As it typical of commercial lighting fixtures, the light package housing  50  may also include components that enclose the emitter  34  within light package housing  50 , for example, including a light reflector  54  and lens or other cover  56  adjacent a bottom, illumination side  58 . The light package housing  50  further houses and may enclose the driver  36 , for example, adjacent a top side  59 , opposite the illumination side  58 . The top side  59  can be coupled to a ceiling  100  or other mounting, structural, or non-structural member. 
     Referring to  FIGS. 1-4 , the cooling housing  70  defines a rim  72  around on outer circumference and a plurality of cooling fins  74  coupled between the outer circumference  52  of the light package housing  50  and the rim  72 . The cooling housing  70  also defines a shroud  76  on the illumination side  58 , and a radial ring fin support  78  nearer the top side  59 . From the illumination side  58 , the shroud  76  defines windows exposing openings  77  between adjacent cooling fins  74  and extending radially between the rim  72  and the outer circumference  52  of the light package housing  50  ( FIGS. 3 and 4 ). From the top side  59 , openings  79  are defined between adjacent cooling fins  74  and extend radially between the radial ring fin support  78  and the outer circumference  52  of the light package housing  50  ( FIGS. 2 and 4 ). 
     The plurality of fins  74  are in thermal conductivity with the emitters  34  and dissipate heat from the emitters to the surrounding environment. More specifically, referring to  FIG. 4 , the first airflow cooling channels  92  are defined through openings  77  by the space between the rim  72 , the outer circumference  52  of the light package housing  50 , and each adjacent fin  74 . The cooling channels  92  extend vertically from the bottom side  58  at openings  77 , upwardly toward and along the bottom side of radial ring fin support  78 , through openings  79  on the top side  79 , and radially outward toward rim  72  and between fins  74  and along a top side of the radial ring fin support  78 , as indicated by second airflow cooling channels  94  in  FIGS. 2 and 4 . 
     Advantageously, the above described and illustrated structure provides a path for cool air to flow upwardly into through openings  77 , for heat from the light fixture  30  to be transferred into the airflow from the fins  74 , radial ring fin support  74 , and outer circumference  52  of the light package housing, and for the heated air to exit through openings  79  and flow away from the light fixture  30 . Optionally, the cooling fins  74  can be parallel, and/or evenly spaced, as shown in  FIGS. 1-3 . The first and second airflow cooling channels  92  and  94  span around the circumference of the light fixture  30  between the rim  72  and outer circumference  52  of the light package housing  50 , except where interrupted by shroud  76  between adjacent openings  77  ( FIG. 3 ). 
     Advantageously, radial ring fin support  78  provides support to the fins  74  and more surface area for convective and radiant heat transfer to the surrounding air than the fins  74  and outer circumference  52  of the light package housing  50  alone provide. Also advantageously, stylistic aspects of the rim  72 , shroud  76 , and the radial ring fin support  78  and their relative arrangement provide a more aesthetically appealing appearance of the light fixture  30 , limiting the spiny look typical of LED lighting fixtures covered with cooling fins, while also retaining the needed cooling surface area, cooling air paths, and arrangement of the cooling fins  74  projecting beyond the outer circumference of the light package housing  50 . For example, in addition to any functionality provided, the rims  72 , shroud  76 , and radial ring fin support  78  also aesthetically conceal portions of the light fixture  30 , and eliminate or substantially limit the vertical see through of the ceiling  100  from the illumination side  58 . As shown in  FIG. 3 , only a narrow band  102  of the ceiling  100  is visible through the windows  77  and radially inside of the radial ring fin support  78 . Adding further aesthetic appeal, the illumination side of the cooling housing  60  can slope upwardly between the outer circumference  52  of the light package housing  50  and rim  72 , and the top side of the cooling housing  60  can slope downwardly between the outer circumference of the light package housing and rim. 
     While the invention has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as illustrative and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit and scope of the invention as defined in the claims and summary are desired to be protected.