Patent Publication Number: US-7910943-B2

Title: Light emitting diode fixture and heat sink

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     FIELD OF THE INVENTION 
     This invention is directed generally to light emitting diode fixtures, and more particularly, to heat sinks providing for compact light emitting diode fixtures. 
     BACKGROUND OF THE INVENTION 
     Generating visible light with traditional light sources, such as incandescent or fluorescent light sources, is inefficient because thermal energy is also produced as a by product of the process. The wasted thermal energy is generally directed away from the light source in the direction of the radiant beam of light. Fixtures, such as light shades or reflectors, or even the target illuminated by the light source, receive the wasted thermal energy, and consequently, rise in temperature. In some instances, the rise in temperature can reduce the useful life of a product. Further, the arrangement of traditional light sources are limited to designs that can withstand the waste thermal energy. 
     In contrast to traditional light sources, solid state lighting, such as a light emitting diode (“LED”), is more efficient at generating visible light than many traditional light sources. Although LEDs do not generally radiate heat in the direction of the beam of light produced, implementation of LEDs for many traditional light source applications has been hindered by the amount of heat build-up within the electronic circuits of the LEDs. Heat build-up reduces LED light output, shortens lifespan and can eventually cause LEDs to fail. 
     Accordingly, heat sinks have been used to dissipate heat away from LEDs; however, in the past, LEDs have been thermally coupled to heat sinks with adhesive tapes. The use of adhesive tape introduces several problems, such as the labor and time intensive process of providing tape for each individual LED. Further, adhesive tapes are susceptible to being displaced during the assembly process, resulting in less than optimal heat dissipation. 
     SUMMARY 
     The present invention concerns a fixture for multiple LEDs and provides a compact light fixture that is significantly smaller in size in comparison to traditional light fixtures while having a greater light producing capability. Further, the fixture is designed to accommodate compact arrangements of LEDs that provide greater luminescence and the ability to control lighting effects in a compact design not previously available with traditional light sources. 
     In one embodiment, a device for dissipating heat from light emitting diodes can include a heat sink with a plurality of protrusions, a control board coupled to the heat sink and a plurality of light emitting diode light engines mounted to the control board. The individual heat sink protrusions of the plurality of heat sink protrusions can align with individual light engines of the plurality of light engines and the control board can secure the light engines against the heat sink protrusions. Also, the control board can couple to the heat sink with a securing member and the light engines can extend from the control board a uniform distance. 
     In another embodiment, the plurality of light engines can produce red, green and blue light. Additionally, at least one individual light engine can produce red, green and blue light. Still further the control board can provide a plurality of apertures for receiving a light engine lens housing and the light engines can operate less than or equal to a die junction temperature of 125° C. 
     Also in accordance with the inventive aspects, a light fixture is provided. The light fixture can include a housing providing a heat sink, where the heat sink can provide a plurality of protrusions. A control board coupled to the heat sink can also be included, where the control board provide an aperture to receive a lens housing and an aperture to receive a coupling member to secure the control board to the heat sink. Still further, a plurality of light emitting diode light engines can be mounted to the control board where the individual heat sink protrusions of the plurality of heat sink protrusions can align with individual light engines of the plurality of light engines. 
     In another embodiment, the plurality of light engines can produce red, green and blue light. Additionally, at least one individual light engine can produce red, green and blue light. Also, the light engines can extend from the control board a uniform distance. 
     A method of manufacturing a light emitting diode housing is also provided in accordance with the inventive arrangements. The method can include the steps of providing a housing with a heat sink having a plurality of heat sink protrusions, providing a control board with a plurality of light engines and assembling the housing with the control board arranged such that the individual light engines of the plurality of light engines align with the individual heat sink protrusions of the plurality of heat sink protrusions. The method can also include the steps of securing the control board to the heat sink with a securing member, applying a thermal interface material between the light engine and the heat sink protrusion and wiring the control board to receive signals from a control console. 
     These and other aspects and features of the invention will become apparent upon review of the enclosed drawings and detailed description below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There are shown in the drawings embodiments which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a perspective view of one embodiment of a light emitting diode fixture in accordance with the inventive arrangements; 
         FIG. 2  is an exploded view of the embodiment of  FIG. 1 ; 
         FIG. 3  is a top plan view of the control board of the embodiment of  FIG. 1 ; 
         FIG. 4   a  a circuit diagram of one embodiment of the control board of  FIG. 3 ; 
         FIG. 4   b  is one embodiment of the wiring of the embodiment of  FIG. 1 ; 
         FIG. 4   c  is one embodiment of the wiring for multiple fixtures of  FIG. 1 ; and 
         FIG. 5  is another perspective view of the embodiment of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention is directed to a light emitting diode fixture with a housing  100  for light emitting diodes and provides a compact light fixture that efficiently dissipates heat created during operation. The housing  100  may have numerous configurations and applications, such as a spotlight or floodlight used for utility reasons or for lighting effects during entertainment. 
     Referring to  FIGS. 1 and 2 , an embodiment of a housing  100  is shown. The housing  100  can include a body  105 , an inner transparent plate  110 , an outer transparent plate  115 , a brace  120 , a visor  125 , a base  130 , a movable connector  135  and conduit fittings  140 , although it will be understood that the invention is not limited in this regard as the invention can include any or all of these components. The base  130  can be attached to a wall or other support structure and wiring for electricity and communications can be fed through conduit fittings  140  or scored knockout structures (not shown) on the base  130 . The base  130  can be connected to the housing  105  with movable connector  135 , which can pivot and/or rotate for adjustment of the direction of the light produced. Additionally, it should be noted that the housing  105  can be directly attached to a support structure, such as a wall. 
     Referring to  FIGS. 2 and 3 , a control board  145  is also provided for mounting a plurality of light engines  150  and light, engine lens housings  155  holding lenses  156  over the light engines  150 . As used herein, a light engine  150  is an any optical system that can collect light from a lamp, such as light emitting diode, and deliver the light to a target, which can be used by the target or can be reformatted, such as improving spatial, angular kind/or spectral uniformities of the light. Additionally, the light engines  150  can feature one or more LEDs, which can all be a single color or can be various colors. For instance, and individual light engine  150  can include one or more red LEDs, one or more green LEDs and one or more blue LEDs such that the light engine  150  can be produce red, green or blue light or any combination thereof. The light engine  150  can be any suitable light engine, such as the Lamina BL-4000 produced by Lamina Ceramics of Westampton, N.J. 
     The light engine lens housings  155  can be any suitable structure for holding lenses  156  over the light engines  150 . The lenses  156  can be changed to provide various desired lighting effects. Further, the light engine lens housings  155  can snap fit into apertures  170  for easy installation and removal. Notably, the lenses  156  and the light engine housings  155  can be individually removed for each individual light engine  150  and can also be removed and inserted without removing the control board  145 . 
     The control board  145  can include suitable logic circuitry for providing electrical control over the individual light engines  150  mounted on control board  145 . Additionally, the control board  145  can contain suitable etching and wiring for control of the light engines  150 , such as the exemplary circuit diagram shown in  FIG. 4   a . As shown in  FIGS. 4   a  and  4   b , the control board  145  can be wired through the conduit fittings  140  and can be in communication with a control console (not shown) operating in compliance with the DMX512, DMX512/1990 or DMX512-A protocols, or any extensions thereof. These protocols can specify the transmission voltages, the data rate, the format of the data content, the type of cable and the type of connector to be used. 
     With such a system, the level of light provided by the light engines  150  can be controllable from light levels from 0 to 100 percent into 256 steps. In operation, the control console can send levels to the light engines as a sequence of numbers, including a reset or break signal, a start code, and a sequence of numbers to control light properties, such the intensity. Additionally, multiple housings  100  can be wired to one control console in a daisy chain configuration, as shown in  FIG. 4   c.    
     Referring to  FIGS. 2 ,  3  and  5 , the light engines  150  are spatially arranged on the control board  145  such that the light engines  150  align with protrusions  160  of heat sink  165 . The light engines  150  are aligned for direct contact with heat sink protrusions  160  and to ensure that individual light engines  145  are centered on the individual heat sink protrusions  160 . The heat sink  165  and the heat sink protrusions can be made of any suitable material, such as black anodized, aluminum extrusions or any other suitable materials. 
     Such an aligned direct contact arrangement ensures the junction temperature, T junction ) which is the temperature where the light is generated, does not exceed the limits of the light engine  150  or adversely affect the quality of the light produced by the light engine  150 . The T junction  is dependent upon the thermal resistance of the light engine  150 , the heat sink protrusion  160  and any medium between the light engine  150  and the heat sink protrusion  160 , as shown by the following equation, T junction =RΘ total ·Power+T ambient +T guard band . The thermal resistance is calculated by dividing the difference in temperature between two points on a body by the energy that flows between two points per unit time and can be expressed by the following equation 
                 R   ⁢           ⁢   Θ     =     L     K   ·   A         ,         
where RΘ=Thermal Resistance; L=Thickness; A=Cross-sectional area; and K=Value of thermal conductivity. Thermal resistance can also be expressed by the following equation
 
                 R   ⁢           ⁢   Θ     =       Δ   ⁢           ⁢   T     Q       ,         
where; ΔT=Change in temperature to area of interest; and Q=Heat flux.
 
     Further, the T junction  is dependent upon the thermal resistance values for each element in the thermal path, the overall thermal resistance can be expressed by the following equation, RΘ total =Σ i+1   n RΘ i  or RΘ total =RΘ j−p +RΘ p−h +RΘ h−a , where RΘ j−p =Resistance of the Light Engine; RΘ p−h =Resistance of the Thermal Interface Material; and RΘ h−a =Resistance of the Heat Sink. Thus, the light engine  150  performance is dependent upon the thermal resistance of each element in the thermal path. 
     The combination of the control board  145  with the plurality of light engines  150  spatially arranged to align with the heat sink protrusions  160  ensures that thermal resistance is minimized in multiple manners. For instance, the light engines  150  are centered on the heat sink protrusions  160  to ensure maximum surface area contact, in contrast to an individually placed light engine and heat sink that may be misaligned. Additionally, the plurality of light engines  150  and the plurality of heat sink protrusions  160  can be arranged in arrays or some other arrangement as needed. 
     Further, mounting the light engines  150  to the control board  145  ensures that the light engines extend a uniform distance from the control board in the direction of the heat sink protrusions  160 . Additionally, the heat sink protrusions  160  can extend from the heat sink  165  a uniform distances such that the control board  145  and light engines  150  lay flat on the heat sink protrusions  160 . Such dimensions of the housing  100 , the control board  145  and the heat sink protrusions provides direct contact between the light engines  150  and the heat sink protrusions  160 . To further ensure the direct contact, a securing member  175 , such as a screw, can be used to securely couple the control board  145  to the heat sink  165  through aperture  185  and to threaded receiving structures  180 . Securing the control board  145  to the heat sink  165  provides another advantage that the light engines  150  will not be displaced from the heat sink protrusions  160  even if the housing  100  is accidentally dropped or receives a physical blow. 
     Additionally, thermal interface materials can be applied to the light engine  150  and/or the heat sink protrusion  160  to fill any gaps from irregularities in the interface between the light engine  150  and the heat sink protrusion  160 . Thermal interface materials include greases, such as silicone based grease with ZnO, Al 2 O 3 , AlN, BN or other metal particles, gels, such as silicon or olefin materials including Al, Al 2 O 3 , Ag. Other suitable interface materials can also be used. 
     In operation, heat sink protrusions  160  dissipate heat produced by the light engines  150  to ensure that the junction temperature does not exceed 115° C. for optimal operating efficiency. Even when operating the light engines  150  to produce a maximum light intensity, the heat sink protrusions  160  ensure that the junction temperature does not exceed 125° C., which is the maximum temperature beyond which the light engine may fail. 
     It will be appreciated that, although terms such as upper, lower, front, and back have been included in this description, these are merely used to aid in the description of the features. Although the device  10  has a preferred orientation in use, it will function if installed in an orientation different from the illustrated embodiment. In such a case, parts described herein as being upper or lower will be reversed or altered, and the invention is not intended to be limited in this regard. 
     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention. All publications and patents mentioned herein are incorporated by reference in their entirety, including all figures, graphs, equations, illustrations, and drawings to describe and disclose specific information for which the reference was cited.