Abstract:
Light fixtures for illuminating spaces that use light emitting diode-based light sources and that incorporate chip on board technology that enables the light emitting diode to be mounted directly on a portion of the light fixture. In some embodiments, the light fixture includes a reflector assembly onto which the light emitting diode is directly mounted. In other embodiments, the reflector assembly includes an aperture that receives a board having chip on board technology onto which the light emitting diode is directly mounted. In some embodiments, the light fixture also includes a diffuser for diffusing the light emanating from the light emitting diodes.

Description:
FIELD OF THE INVENTION 
     The invention generally relates to light fixtures that use light emitting diodes and that incorporate chip-on-board technology to enable the light emitting diodes to be mounted directly on a portion of the fixture. 
     BACKGROUND OF THE INVENTION 
     Various types of light fixtures are known. Traditional light fixtures presently used in a typical office environment comprise a troffer with at least one fluorescent lamp and a lens having prismatic elements for distributing the light. Typical light fixtures may also use parabolic reflectors to provide a desired light distribution. The fluorescent lamp has long been the light source of choice among lighting designers in many commercial applications, particularly for indoor office lighting. A description of such a fluorescent light fixture may be found in U.S. Pat. Nos. 7,229,192 and 7,261,435, the entire contents of both of which are hereby incorporated by reference. 
     For many years the most common fluorescent lamps for use in indoor lighting have been the linear T5 (⅝ inch diameter), T8 (1 inch diameter), and the T12 (1½ inch diameter). Such bulbs are inefficient and have a relatively short lamp life. Thus, efforts have been made to identify suitable alternative illumination sources for indoor office lighting applications. Light emitting diodes (“LEDs”) have been identified as one alternative to traditional fluorescent bulbs. 
     An LED typically includes a diode mounted onto a die or chip, where the diode is surrounded by an encapsulant. The die is connected to a power source, which, in turn, transmits power to the diode. An LED used for lighting or illumination converts electrical energy to light in a manner that results in very little radiant energy outside the visible spectrum. Thus, LEDs are extremely efficient, and their efficiency is rapidly improving. For example, the lumen output obtained by 20 LEDs may soon be obtained by 10 LEDs. 
     Conventional light fixtures that use LEDs as the light source utilize a separate printed circuit board (“PCB”) that is pre-populated with LEDs wired to the PCB. During assembly of the light fixture, the PCB (with LEDs mounted thereon) is then fastened to the light fixture housing using either multiple screws or other suitable fasteners. This process requires that PCBs be ordered in advance and inventoried prior to assembly, which increases the length of the production cycle for each finished light fixture. 
     Moreover, the use of a separate circuit board that then must be attached to a portion of the light fixture also increases product assembly time and decreases thermal conductivity between the LEDs and the light fixture housing. Because there is decreased thermal contact between the LEDs and the housing of the light fixture, the use of intermediate conductive materials is often required. All of this leads to increased expense and decreased efficiency. 
     Thus, there is a need for a light fixture that utilizes LEDs as the light source and that is configured so that the LEDs are able to be directly mounted to a portion of the housing of the light fixture. 
     SUMMARY OF THE INVENTION 
     In certain embodiments there is provided a light fixture that incorporates chip-on-board (“COB”) technology whereby at least one LED is mounted directly to a fixture component, such as, but not limited to, the reflector. In other embodiments, at least one LED is mounted to a separate board that is coupled to the fixture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure including the best mode of practicing the appended claims and directed to one of ordinary skill in the art is set forth more particularly in the remainder of the specification. The specification makes reference to the following appended figures, in which use of like reference numerals in different features is intended to illustrate like or analogous components. 
         FIG. 1  is a partially exploded bottom perspective view of a light fixture according to one embodiment of the present invention. 
         FIG. 2  is a partially exploded bottom perspective view of a light fixture according to another embodiment of the present invention. 
         FIG. 3  is partially cut-away, partially exploded bottom perspective view of the light fixture of  FIG. 2 . 
         FIG. 4  is a partially exploded bottom perspective view of a light fixture according to another embodiment of the present invention. 
         FIG. 5  is a partially cut-away, partially exploded bottom perspective view of the light fixture of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a light fixture  10  according to one embodiment of the invention. Light fixture  10  comprises a housing  12 , at least one reflector assembly  14 , and at least one diffuser  18 .  FIG. 1  illustrates a two-cell light fixture  10  having a first cell  11  and a second cell  13 , but one of skill in the art would understand that light fixture  10  alternatively could have only one cell or more than two cells. The various embodiments of this invention will be described generally in relation to a single cell of the illustrated two-cell light fixture. 
     As shown in  FIG. 1 , reflector assembly  14  includes a bottom portion  24 . Individual LEDs  22  are mounted directly on an underside portion  24  of reflector assembly  14  using what is known in the art as chip on board (“COB”) technology, or direct chip attachment. Specifically, the LEDs are soldered or otherwise affixed to the underside portion  24  and copper traces are printed directly on the underside portion  24  of reflector assembly  14  to electrically interconnect the LEDs. Such direct attachment to the fixture streamlines the manufacturing process by avoiding the need to first mount the LEDs on a PCB and then subsequently attach the PCB to the fixture. Moreover, direct attachment of the LEDs to the metal reflector provides a direct path for dissipation of heat generated by the LEDs (and thus improves the transfer of heat from the LEDs) and obviates the need for an intermediate conductive material. 
     The plurality of individual LEDs  22  serve as a light source for illuminating an area. The LEDs  22  may be single-die or multi-die light emitting diodes, DC or AC, or may be organic light emitting diodes (“O-LEDS”). The LEDs  22  may be white or may include color or multicolor LEDs  22 , or may include a variety of different colors of LEDs  22 . In some embodiments, LEDs  22  are blue. LEDs  22  may include lenses that surround the LEDs to direct the emitted light. In some embodiments, a phosphor-infused silicon compound (or any suitable polymer infused with phosphor) may be deposited over at least some of the LEDs (more particularly, the lenses covering the LEDs) to alter the color of their emitted light as desired. 
       FIGS. 3-4  illustrate an alternative embodiment of a light fixture  10 . Except where indicated, the light fixture of  FIGS. 3-4  is identical to that shown in  FIG. 1  and thus  FIGS. 3-4  use the same reference numbers to refer to the same structures. The fixture of  FIGS. 3-4  differs from that of  FIG. 1  in that the LEDs are not mounted directly to the underside portion  24  of the reflector assembly  14 . Rather, the LEDs are first mounted directly to a board  26 , but in the same manner described above. An aperture  20  is provided through the reflector assembly  14  that is shaped and sized to receive board  26 . Specifically, board  26  is positioned between the back of the housing  12  (not shown) and the reflector assembly  14  so that the LEDs  22  align with the aperture  20  in the reflector assembly  14 . Board  26  is mounted to the reflective assembly  14  using any suitable mechanical means. When the board  26  is so positioned relative to the reflector assembly  14 , light from the LEDs is emitted from the fixture the same way light is emitted from the fixture of  FIG. 1 . In some embodiments, board  26  is comprised of metal or any other suitable thermally conductive material and can be formed of the same material and/or is the same color as the reflector assembly  14 . 
       FIG. 4  illustrates a partial cut-away view of light fixture  10  with board  26  assembled therein. The board  26  may be of any size and shape and is not limited to the relatively narrow boards shown in  FIG. 4 . Rather, it may be desirable to use a board with wider or longer dimensions to enhance heat dissipation. Moreover, a separate board need not be provided for each cell in the fixture. Rather, as shown in  FIG. 5 , sets  31  and  33  of LEDs  22  may be mounted on a single board  26  that can be positioned relative to the reflector assemblies  14  so that each set  31 ,  33  of LEDs  22  aligns with a cell aperture  20 . Again, use of a single, larger board may be desirable to improve the heat transfer properties of the fixture. 
     People of skill in the art would easily appreciate that other configurations than those illustrated in the Figures may be employed. By way only of example, as one alternative to the light fixture illustrated in  FIGS. 3-4 , instead of being mounted on a separate board, the LEDs  22  may be attached directly to the underside of the back of the housing  12  so that light from the LEDs  22  is emitted through the aperture  20  in the reflector assembly  14 . As another non-limiting embodiment, the board  26  itself may form the back of the housing  12 . As yet another non-limiting embodiment, the board  26  may be affixed above the back of the housing  12  and apertures  20  may be provided in both the housing  12  and the reflector assembly  14  so that the LEDs  22  align with the apertures in the reflector assembly  14  and the housing  12 . 
     While the plurality of LEDs  22  are shown in the embodiments as extending in two substantially parallel rows, one of skill in the art will recognize that the LEDs may be positioned in any suitable configuration on a reflector assembly  14  or board  26 . 
     Using a portion of the light fixture  10  as the carrier for the COB technology allows for fast programmable application of the LEDs onto the light fixture  10  without manual labor and without the possibility of programming errors. Using a light fixture  10  having COB technology is particularly well suited for an automated high speed production process where the quantity and characteristics of the LEDs used as the light source may be programmed into the light fixture  10  as the fixture  10  is being built and assembled. 
     In the various embodiments, light emanating from the LEDs  22  is diffused by diffuser  18  that is positioned between the LEDs  22  and the area to be illuminated. Diffuser  18  may have any shape including curved, rectilinear, parabolic, or any other appropriate shape to diffuse light emitted from the LEDs  22  to provide an aesthetically pleasing appearance. Diffuser  18  may be formed of plastic or any other suitable material that allows a sufficient amount of light to pass through the diffuser. Diffuser  18  is connected to reflector assembly by any appropriate mechanical or chemical means. In some embodiments, as shown in the Figures, diffuser  18  has arms  32 ,  34  that snap-fit over the edges of the reflector assembly. In other embodiments, diffuser  18  may be attached to the reflector assembly using mechanical fasteners. 
     The foregoing is provided for purposes of illustration and disclosure of embodiments of the invention. It will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.