Patent Publication Number: US-9835322-B1

Title: Flow through extended surface troffer system

Description:
A portion of the invention of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the reproduction of the patent document or the patent invention, as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     REFERENCE TO SEQUENCE LISTING OR COMPUTER PROGRAM LISTING APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to lighting systems. There are a variety of lighting systems and particularly troffer lighting systems which can be used to illuminate open spaces. Light emitting diodes (LEDs) are becoming increasingly popular as a lighting source because they are energy efficient, durable, and long-lasting. However, light sources, including LEDs, tend to generate a substantial amount of heat as they are being operated. If heat produced by the light source is not dissipated from the lighting system, then the lighting system can become increasingly hot, which can have negative effects for the overall functionality and efficiency of the lighting system, and can be potentially hazardous to the end user. 
     More particularly, this invention pertains to a lighting system with improved heat dissipation. In some conventional solutions, a printed circuit board for one or more light sources can be directly attached to a light fixture troffer or housing in an effort to increase conduction, convection, and radiation between the light source and the surroundings. Direct attachment of the printed circuit board to the troffer or housing limits the design to direct lighting systems. Such lighting systems can be undesirable as they can produce glare and shadows to observers. 
     In other embodiments, heat sinks have been used to dissipate heat away from light sources. The printed circuit board can be attached directly to a heat sink. Heat sinks, while effective, can add to the cost of the overall lighting system. Additionally, in indirect lighting systems, heat sinks are necessarily directly seen by an observer, and may not be aesthetically pleasing when incorporated into such lighting systems. 
     What is needed, then, are improvements to lighting systems with heat dissipation systems. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the present invention is a lighting apparatus including a printed circuit board having a first side and a second side. A first light source can be mounted on the first side of the printed circuit board and a second light source can be mounted on the second side of the printed circuit board. A first optical member can be positioned to receive and redirect light from the first light source. A second optical member can be positioned to receive and redirect light from the second light source. At least one vent aperture can be defined in the printed circuit board, the vent aperture located between the first and second optical members. The vent aperture in the printed circuit board can help allow air to pass between the two optical members. 
     In some embodiments, the lighting apparatus may additionally include a housing at least partially surrounding the printed circuit board, the first and second light sources, and the first and second optical members. The housing can include a housing vent. The housing vent and the aperture in the printed circuit board define a first convective path between the first and second optical members. The first convective path can help increase convection between the printed circuit board and the ambient as well as between the first and second optical members and the ambient. 
     In another aspect, the present invention is a lighting apparatus including a printed circuit board and a first light source mounted on the printed circuit board. A first optical member can be positioned to receive and redirect light projected from the first light source, the first optical member having a first back side facing away from the first light source. The apparatus can include a first thermally conductive sheet thermally coupled to the printed circuit board and extending over the first back side of the first optical member. As such, the thermally conductive sheet can act as an extended heat transfer surface that can help increase heat dissipation away from the printed circuit board and the first light source via increased conduction, convection, and radiation from the thermally conductive sheet. 
     Yet another aspect of the present invention is a lighting apparatus including a printed circuit board. A first light source and a second light source can be mounted to the printed circuit board. A first optical member can be positioned to receive and redirect light from the first light source, the first optical member having a first back side facing away from the first light source. A second optical member can be positioned to receive and redirect light from the second light source, the second optical member having a second back side facing away from the second light source. A first thermally conductive sheet can be thermally coupled to the printed circuit board and disposed on the first back side of the first optical member. A second thermally conductive sheet can be thermally coupled to the printed circuit board and disposed on the second back side of the second optical member. A vent aperture can be defined in the printed circuit board between the first and second thermally conductive sheets. As such, the thermally conductive sheets can help increase heat dissipation away from the printed circuit board. Additionally, the vent aperture can allow air to circulate between the thermally conductive sheets, thereby helping increase convection between the thermally conductive sheets and the ambient. 
     Numerous other objects, advantages and features of the present invention will be readily apparent to those of skill in the art upon a review of the following drawings and description of a preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a top perspective view of an embodiment of a lighting apparatus of the present invention 
         FIG. 2  is a perspective partial cross-sectional view of the lighting apparatus of  FIG. 1 . 
         FIG. 3  is a detailed cross sectional view of the lighting apparatus of  FIG. 1   
         FIG. 4  is a plan view of an embodiment of a thermally conductive sheet of the lighting apparatus of  FIG. 1 . 
         FIG. 5  is a partial exploded view of the lighting apparatus of  FIG. 1 . 
         FIG. 6  is a bottom perspective view of the lighting apparatus of  FIG. 1 . 
         FIG. 7  is a cross section view of the lighting apparatus of  FIG. 1  further including a light source driver enclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that is embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention. 
     To facilitate the understanding of the embodiments described herein, a number of terms are defined below. The terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a,” “an,” and “the” are not intended to refer to only a singular entity, but rather include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as set forth in the claims. 
     As described herein, an upright position is considered to be the position of apparatus components while in proper operation or in a natural resting position as described herein. Vertical, horizontal, above, below, side, top, bottom and other orientation terms are described with respect to this upright position during operation unless otherwise specified. The term “when” is used to specify orientation for relative positions of components, not as a temporal limitation of the claims or apparatus described and claimed herein unless otherwise specified. The term “lateral” denotes a side to side direction when facing the “front” of an object. 
     The phrase “in one embodiment,” as used herein does not necessarily refer to the same embodiment, although it may. Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. 
     This written description uses examples to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
     It will be understood that the particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention may be employed in various embodiments without departing from the scope of the invention. Those of ordinary skill in the art will recognize numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims. 
     All of the apparatuses and/or methods disclosed and claimed herein may be made and/or executed without undue experimentation in light of the present invention. While the apparatuses and methods of this invention have been described in terms of the embodiments included herein, it will be apparent to those of ordinary skill in the art that variations may be applied to the apparatuses and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit, and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention as defined by the appended claims. 
     A top perspective view of an embodiment of a lighting apparatus  10  of the present invention is shown in  FIG. 1 . The lighting apparatus  10  can include a housing  12  and a light source driver  14  connected to the housing  12 . The housing  12  can contain a recess that can receive the various components of the lighting apparatus  10 . The light source driver  14  can provide power to the apparatus  10  during use. 
     A perspective partial cross-sectional view of the lighting apparatus  10  of  FIG. 1  is shown in  FIG. 2 . The apparatus  10  can include a printed circuit board  18 . A first light source  20  and a second light source  22  can be mounted to the printed circuit board  18 . In some embodiments, the printed circuit board  18  can have a first side  24  and a second side  26 . The first light source  20  can be mounted to the first side  24  of the printed circuit board  18 . The second light source  22  can be mounted to the second side  26  of the printed circuit board  18 . The light source driver  14  shown in  FIG. 1  can be electrically connected to the printed circuit board  18  such that power can be supplied to the light sources  20  and  22  from the light source driver  14  via the printed circuit board  18 . 
     A first optical member  28  can be positioned to receive and redirect light from the first light source  20 , and a second optical member  30  can be positioned to receive and redirect light from the second light source  22 . In some embodiments, the first and second optical members  28  and  30  can have reflective surfaces  32   a  and  32   b . In some embodiments, reflective surfaces  32   a  and  32   b  can be specular reflective surfaces. In other embodiments, reflective surfaces  32   a  and  32   b  can be total internal reflective surfaces. The reflective surfaces  32   a  and  32   b  can redirect light from the light sources  20  and  22  in a downward direction in  FIG. 2  out of the lighting apparatus  10 . 
     In some embodiments, the lighting apparatus  10  can include at least one vent aperture  34  extending through the printed circuit board  18 . The vent aperture  34  can be positioned or located on the printed circuit board  18  between the first and second optical members  28  and  30  such that air can pass through the vent aperture  34  and between the optical members  28  and  30 . The vent aperture  34  being located between the first and second optical members  28  and  30  is defined as the vent aperture  34  being located at a horizontal or vertical position that is between the horizontal or vertical positions of the first and second optical members  28  and  30  respectively. Thus, the aperture can be positioned slightly below, above, to the left, or to the right of the optical members  28  and  30 , as shown in  FIG. 2 , and still be located between the optical members  28  and  30 , such that air can pass through the aperture  34  and between the optical members  28  and  30 . 
     In some embodiments, the housing  12  can at least partially surround the printed circuit board  18 , the first and second light sources  20  and  22 , and the first and second optical members  28  and  30 . The housing  12  can include at least one housing vent  40 . In some embodiments, a first housing vent  40  can be located or positioned adjacent or proximate to the first optical member  28 , and a second housing vent  42  can be located or positioned adjacent or proximate to the second optical member  30 . In some embodiments, a first row of housing vents  44  can be located adjacent the first optical member  28 , and a second row of housing vents  46  can be located adjacent the second optical member  30 . 
     Referring now to  FIG. 3 , the at least one housing vent  40  and the vent aperture  34  in the printed circuit board  18  can define a convective path  48  through the apparatus  10  between the first and second optical members  28  and  30 . In those embodiments with a first and second housing vent  40  and  42  positioned adjacent the first and second optical members  28  and  30  respectively, the vent aperture  34  and the first housing vent  40  can define a first convective path  48 . The vent aperture  34  and the second housing vent  42  define a second convective path  50 . The first convective path  48  can then be positioned adjacent the first optical member  28  and the second convective path  50  can then be positioned adjacent the second optical member  30 . Therefore, during use, air can pass through the aperture  34  in the printed circuit board  18  and adjacent to both the first and second optical members  28  and  30 , which can help increase convection between the printed circuit board  18  and an exterior  52  of the apparatus  10 , and between the first and second optical members  28  and  30  and an exterior  52  of the apparatus  10 . 
     In some embodiments, the vent aperture  34  can be located centrally on the printed circuit board  18 , such that the aperture  34  can be substantially equidistant from the first and second optical members  28  and  30 . Such positioning of the vent aperture  34  can help equally distribute air to both sides of the lighting apparatus  10 . 
     Referring again to  FIG. 2 , in some embodiments, the first optical member  28  can have a first back side  36 , and the second optical member  30  can have a second back side  38 . The first back side  36  can face away from the first light source  20  and be positioned generally opposite the reflective surface  32   a  on the first optical member  28 . The second back side  38  can face away from the second light source  22  and be positioned generally opposite the reflective surface  32   b  on the second optical member  30 . 
     The apparatus  10  can include a first thermally conductive sheet  54  disposed on the first back side  36  of the first optical member  28 . A second thermally conductive sheet  56  can be disposed on the second back side  38  of the second optical member  30 . The first and second thermally conductive sheets  54  and  56  can be thermally coupled to the printed circuit board  18  and extend over or across the first and second back sides  36  and  38  respectively of the first and second optical members  28  and  30 . In some embodiments, the first and second thermally conductive sheets  54  and  56  can additionally be thermally coupled to the first and second light sources  20  and  22  respectively. 
     As the apparatus  10  is being used, the first and second light sources  20  and  22  can produce a substantial amount of heat. Because the light sources  20  and  22  are mounted to the printed circuit board  18 , heat from the light sources  20  and  22  can be dissipated to the printed circuit board  18 . The first and second thermally conductive sheets  54  and  56  can then be thermally coupled to the printed circuit board  18  to dissipate heat away from the light sources  20  and  22  via the printed circuit board  18 . 
     The thermally conductive sheets  54  and  56  can be formed of any suitable material that can be configured to act as a passive heat exchanger. These materials can include, but are not limited to, aluminum alloys such as 1050A, 6061, or 6063, copper, diamond, or composite materials such as copper tungsten pseudoalloy, silicon carbide in aluminum matrix (AlSiC), diamond in copper-silver alloy matrix (Dymalloy), beryllium oxide in beryllium matrix, or any other suitable materials known in the art. In some embodiments, the first and second thermally conductive sheets  54  and  56  are made from graphite. In some embodiments, the thermally conductive sheets  54  and  56  can have a thermal conductivity greater than about 100 W/mK. In other embodiments, the thermally conductive sheets  54  and  56  can have a thermal conductivity greater than about 200 W/mK. A higher thermal conductivity can help increase the amount of heat that is dissipated away from the printed circuit board  18  and the light sources  20  and  22  through conduction with the thermally conductive sheets  54  and  56 . 
     The first and second thermally conductive sheets  54  and  56  extend across the first and second back sides  36  and  38  of the first and second optical members  28  and  30  respectively to provide extended thermally conductive surfaces which can also help increase dissipation of heat from the light sources  20  and  22  through convection and radiation to the exterior or ambient  52  of the apparatus  10 . 
     Referring again to  FIG. 3 , in those embodiments including thermally conductive sheets  54  and  56 , the vent aperture  34  can additionally be located between the first and second thermally conductive sheets  54  and  56 . As such, the first convective path  48  can be defined through the aperture  34  in the printed circuit board  18  and the first housing vent  40  such that air can flow over the first thermally conductive sheet  54 . Similarly, the second convective path  50  can be defined through the vent aperture  34  and the second housing vent  42  such that air can flow across the second thermally conductive sheet  56 . During operation of the lighting apparatus  10 , heat from the light sources  20  and  22  being dissipated to the thermally conductive sheets  54  and  56  can cause the thermally conductive sheets to become hot. Thus, the air immediately around the thermally conductive sheets  54  and  56  can heat up due to convection from the thermally conductive sheets to the air. The warmer air can have relatively lower air pressure. The warm, low pressure air can help encourage air flow along the first and second convective paths  48  and  50  across the thermally conductive sheets  54  and  56 , as cooler, high pressure air can move into the space occupied by the warmer air, thereby producing air flow. 
     Thus the thermally conductive sheets  54  and  56  can help increase conduction of heat away from the printed circuit board  18  and the light sources  20  and  22 , and can also help increase air flow over the thermally conductive sheets  54  and  56 . Increased air flow can help increase convection from the thermally conductive sheets  54  and  56  to the ambient or exterior  52  of the apparatus  10 . An increase in heat dissipation from the lighting apparatus  10  to the ambient or exterior  52  of the apparatus  10  can help lower the overall temperature of the lighting apparatus  10 , which can help increase the efficiency and longevity of the apparatus  10 , and can also help reduce the potential for fire hazards. 
     As can be seen from  FIG. 3 , the lighting apparatus  10  can emit light in a primary emission direction  58 . In some embodiments, light sources  20  and  22  can be configured to project light initially in a direction opposite the primary emission direction  58  such that the light is then reflected by the first and second optical members  28  and  30  in the primary emission direction. Additionally, some light can be reflected by the first or second optical members  28  and  30 , and subsequently reflect by the housing  12 , and emitted in the primary emission direction  58 . As such, the lighting apparatus  10  can be an indirect lighting system. 
     The printed circuit board  18  in some embodiments can be positioned to at least partially obstruct a direct view of the light sources  20  and  22  from the primary emission direction  58 . As such, the printed circuit board  18  can help reduce glare to an observer of the apparatus  10 . Glare from a lighting apparatus can hurt an observer&#39;s eyes and can be undesirable. In some embodiments, the printed circuit board  18 , in combination with the housing  12 , can obstruct a direct view of the light sources  20  and  22  when the lighting apparatus  20  is viewed from any angle. 
     In some embodiments, the printed circuit board  18  can be positioned to at least partially obstruct a direct view of the thermally conductive sheets  54  and  56  when the apparatus  10  is viewed from the primary emission direction  58 . One problem with many conventional indirect lighting systems is that a heat sink must be attached directly to a printed circuit board. Because the lighting system is indirect, a heat sink would typically face or be viewable by an observer. The heat sink may not be aesthetically pleasing to an observer. In the apparatus shown in  FIG. 3 , the thermal management system is predominantly hidden from the observer, which can help produce a more aesthetically pleasing appearance to the observer, as shown in  FIG. 6 . 
     A flat plan view of a thermally conductive sheet  54  used in the lighting apparatus of  FIG. 1  is shown in  FIG. 4 . The thermally conductive sheet  54  can include a longitudinal portion  60 . The thermally conductive sheet  54  can also include a plurality of strips  62  extending from the longitudinal portion  60 . The thermally conductive sheet  54  in some embodiments can be made from a flexible material such that the strips  62  can be bent as needed and adhered to an optical member. 
     A partial exploded view of the lighting apparatus  10  of  FIG. 1  is shown in  FIG. 5 . The longitudinal portions  60  of the first and second thermally conductive sheets  54  and  56  can be mated or adhered to the printed circuit board  18 . Bottom sides  64  of the first and second optical members  28  and  30  can then be placed on top of the longitudinal portions  60  of the first and second thermally conductive sheets  54  and  56  respectively. The plurality of strips  62  on each of the first and second thermally conductive sheets  54  and  56  can be wrapped around the bottom sides  64  of the first and second optical members  28  and  30  respectively. The plurality of strips  62  on each of the first and second thermally conductive sheets  54  and  56  can then be disposed or adhered to the first and second back sides  36  and  38  of the first and second optical members  28  and  30  respectively. Connection rods  66  can then be used to connect the printed circuit board  18  to the housing, as shown in  FIG. 3 , thereby fixing the optical members  28  and  30  and the thermally conductive sheets  54  and  56  in position on the apparatus  10 . 
     The first and second optical members  28  and  30  in some embodiments can be two separate pieces. In other embodiments, as shown in  FIG. 5 , the first and second optical members  28  and  30  can be integrally formed as one piece. The two optical members  54  and  56  can be attached by multiple connection pieces  68 . The connection pieces  68  can define one or more through-holes  70  between the first and second optical members  28  and  30 . The plurality of strips  62  on each of the thermally conductive sheets  54  and  56  can then be bent around the bottom sides  64  of the optical members  28  and  30 , and received through the through-holes  70 . Some embodiments can also include a plurality of vent apertures  34  in the printed circuit board  18 , as shown in  FIG. 6 , and each through-hole  70  between the first and second optical members  28  and  30  can be positioned over a corresponding vent aperture  34 , such that air passing through an aperture  34  can also pass through the through-hole. 
     Referring again to  FIG. 5 , in some embodiments, the lighting apparatus  10  can further include a first plurality of light sources  72  located on the first side  24  of the printed circuit board  18 , and a second plurality of light sources  74  located on the second side  26  of the printed circuit board. The first plurality of light sources  72  can be positioned to project light towards the first optical member  28 . The second plurality of light sources  74  can be positioned to project light towards the second optical member  30 . Having multiple light sources on each side of the printed circuit board  18  can help increase the light output to the desired space to be illuminated. 
     A cross sectional view of an embodiment of a lighting apparatus  10  is shown in  FIG. 7  having a light source driver enclosure  76 . The enclosure  76  defines a space about the light source driver  14 . The light source driver  14  can be placed on the housing  12  such that the light source driver  14  partially covers the first and second rows of housing vents  44  and  46  in the housing  12 . As such, the light source driver  14  can be positioned adjacent the first and second convective paths  48  and  50  as the first and second convective paths  48  and  50  pass through the first and second rows of housing vents  44  and  46  respectively. As air passes through the vent aperture  34  in the printed circuit board  18 , along the first and second convective paths  48  and  50 , and through the first and second rows of housing vents  44  and  46 , the air passes over the light source driver  14  which can additionally help cool the light source driver  14 . The housing  12  can also include a first row of secondary housing vents  78  and second row of secondary housing vents  80 . The first convective path  48  can extend out of the first row of housing vents  44  and through the first row of secondary housing vents  78  such that air along the first convective path  48  can be exhausted through the bottom of the lighting apparatus  10 . Similarly, the second convective path  50  can extend out of the second row of housing vents  46  and through the second row of secondary housing vents  80  such that air along the second convective path  50  can be exhausted through the bottom of the lighting apparatus  10 . 
     Thus, although there have been described particular embodiments of the present invention of a new and useful Flow Through Extended Surface Troffer System it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.