Patent Publication Number: US-9416951-B1

Title: Compact indirect lighting system with improved thermal performance

Description:
A portion of the disclosure 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 disclosure, 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 
     This application claims benefit of the following patent application(s) which is/are hereby incorporated by reference: None 
     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 and optical lens devices for distributing light from a light source to a specified area. More particularly, this invention pertains to an indirect area lighting system having improved thermal performance. 
     Conventional lighting systems typically offer optical efficiencies of between 50 to 80%. In other words, only 50 to 80% of the light being emitted from the light source would exit the lighting system. Higher efficiency indirect lighting systems typically result in reduced “lit appearance” uniformity. To combat this problem, conventional volume lighting systems typically include a combination of indirect and direct lighting. However, direct lighting allows the viewer of the lighting system to directly see the light source which is generally undesirable as the brightness of the direct lighting can be distracting. 
     Lighting fixtures and systems typically must include some means for dissipating heat that is generated by the light source and related components. Conventional solutions for the thermal dissipation of heat from indirect lighting systems include heat spreaders located generally on the front of the lighting system facing the viewer. A direct view of the heat spreader may produce an undesirable aesthetic appearance for the lighting system. 
     What is needed, then, are indirect lighting systems using components and methods providing improved thermal performance. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention generally relates to a compact indirect lighting system with improved thermal performance. 
     One aspect of the present invention is a lighting apparatus including a light source. The light source emits light toward a primary optical surface. The primary optical surface is configured to receive and redirect light emitted by the light source. A secondary optical surface is configured to receive redirected light from the primary optical surface and further redirect the light in a primary emission direction. The lighting apparatus can include a central opening extending through the apparatus. The central opening can define a convective path through the apparatus. 
     In some embodiments, a thermally conductive cover can be placed over the central opening such that the thermally conductive cover is positioned in the convective path. The thermally conductive cover can include at least one through-hole overlapping the central opening such that air in the convective path can pass through the thermally conductive cover. Such a configuration can help improve the thermal performance of the lighting apparatus. In some embodiments, the thermally conductive cover can be a heat spreader having one or more through-holes. The through-holes can be substantially aligned with the convective path such that air can flow through the heat spreader. 
     In some embodiments, the apparatus includes a lens body, the primary and secondary optical surfaces being located on the lens body. The lighting apparatus can be manufactured by revolving a uniform cross-section, or the uniform cross-section can be extruded to form an elongated apparatus. In some embodiments, the primary and secondary optical surfaces can be substantially symmetric about the central opening. 
     One object of the present invention is to provide an efficient indirect lighting system. 
     Another object of the present invention is to provide a lighting system with improved thermal performance. 
     Another object of the present invention is to provide a lighting system with a desirable aesthetic appearance. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a lighting apparatus according to the present invention. 
         FIG. 2  is a perspective cross-sectional view of the lighting apparatus of  FIG. 1 . 
         FIG. 3  is a detailed cross-sectional view of a heat spreader insert of the lighting apparatus of  FIG. 1 . 
         FIG. 4  is a front elevation cross-sectional view of the lighting apparatus of  FIG. 1 . 
         FIG. 5  is a bottom perspective view of the lighting apparatus of  FIG. 1 . 
         FIG. 6  is a perspective exploded view of the lighting apparatus of  FIG. 1 . 
         FIG. 7  is a detailed perspective view of the heat spreader of the lighting apparatus of  FIG. 1 . 
         FIG. 8  is a perspective view of another embodiment of a lighting apparatus according to the present invention. 
         FIG. 9  is a perspective cross-sectional view of the lighting apparatus of  FIG. 8 . 
         FIG. 10  is a front elevation cross-sectional view of the lighting apparatus of  FIG. 9 . 
         FIG. 11  is a front elevation cross-sectional view of a third embodiment of a lighting apparatus of the present invention. 
     
    
    
     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. 
     A perspective view of a first embodiment of a lighting apparatus  10  according to aspects of the present invention is shown in  FIG. 1 . A perspective cross-sectional view of the lighting apparatus  10  of  FIG. 1  is shown in  FIG. 2 . The lighting apparatus  10  can include a lens body  12  having multiple optical surfaces and a light source  14 . A primary optical surface  16  can be located on the lens body  12 , and configured to receive and subsequently redirect light emitted from the light source  14 . A secondary optical surface  18  can also be located on the lens body  12 . The secondary optical surface  18  can be configured to receive redirected light from the primary optical surface  16 . The secondary optical surface can then further redirect the light in a primary emission direction  20 . In some embodiments, secondary optical surface can have a first portion  18   a  and a second portion  18   b . In some embodiments, the first and second portions  18   a  and  18   b  can be substantially planar. In other embodiments, one or more of the first and second portions  18   a  and  18   b  can be curved or rounded. 
     The lighting apparatus  10  can include a central opening  22 . In the embodiment of  FIG. 1 , the central opening  22  is defined in and extends through the lens body  12 . The central opening  22  can define a convective path  24  through the apparatus  10 . The convective path  24  can allow air to flow through the apparatus  10 , which can help increase thermal convection between the apparatus  10  and the ambient air. In some embodiments, the central opening  22  can be defined in a portion of the primary optical surface  16 , the secondary optical surface  18 , or both. 
     In some embodiments, as shown in  FIG. 2 , the lighting apparatus  10  can further include a thermally conductive cover  26 . The thermally conductive cover  26  can include at least through-hole  32  overlapping the central opening  22 . The thermally conductive cover  26  can be made of a material with a generally high thermal conductivity, including but not limited to, aluminum alloys, copper, diamond, steel, carbon, graphite, or other composite materials. The thermally conductive cover  26  in some embodiments may be formed of a material having a thermal conductivity of at least 25 watts per meter kelvin. In other embodiments, the thermally conductive cover  26  may be formed of a material having a thermal conductivity of at least 100 watts per meter kelvin. In some embodiments, the thermally conductive cover can be a thermally conductive sheet, a heat sink, or a heat spreader. The thermally conductive cover  26  will hereinafter be referred to as a heat spreader. 
     The heat spreader  26  can be in physical contact with the light source  14 . In other embodiments, the heat spreader  26  can be in physical contact with the lens body  12 , including either the primary optical surface  16  or the secondary optical surface  18 , or both. In still other embodiments, the heat spreader  26  can be in physical contact with both the light source  14  and the lens body  12 . The heat spreader  26  having enhanced thermal conductive properties can help heat generated by the light source  14  and retained by the lighting apparatus  10  to dissipate to the heat spreader  26  through conduction. The heat spreader  26  can help produce an increased temperature differential with the ambient air such that air readily moves along the convective path. The heat spreader  26  can then transfer the heat to the ambient air through both convection and radiation. As such, the thermal performance of the lighting apparatus  10  over an extended period of time can be enhanced by the use of the thermally conductive heat spreader  26 . 
     A detailed view of the heat spreader  26  can be seen in  FIG. 3 . The heat spreader  26  can cover or be located over the central opening  22 , such that the heat spreader  26  is positioned directly in the convective path  24 . The heat spreader  26  in some embodiments can include an insert  28  that extends into the central opening  22 , and a flange  30  that can connect to the lighting apparatus  10 . In  FIG. 3 , the flange  30  is in contact with both the light source  14  and the lens body  12 . 
     The heat spreader  26  can include at least one through-hole  32 . The through-hole  32  can be substantially aligned with the convective path  24 , such that air moving along the convective path  24  passes through the heat spreader  26 , thereby increasing thermal convection between the heat spreader  26  and the ambient air. In some embodiments, the heat spreader  26  can include a plurality of through-holes  32  to help increase the amount of surface area on the heat spreader  26  that is in contact with the ambient air as well as the air passing through the heat spreader  26  along the convective path  24 . Such a configuration can help increase thermal convection and radiation between the heat spreader  26  and the ambient air such that the thermal performance of the lighting apparatus can be further enhanced. 
     Referring now to  FIG. 4 , in some embodiments the lighting apparatus can include a central axis  34 . The central axis  34  can generally define a rotational axis of symmetry for the apparatus  10 . In some embodiments, the primary optical surface  16 , the secondary optical surface  18 , or both, can be radially symmetric about the central axis  34 , as shown in  FIG. 4 . In some embodiments, the central opening  22  can be located on the central axis  34 , and the primary optical surface  16  and the secondary optical surface  18  can be offset from the central axis  34 , thus allowing air to flow through the central opening  22  and through the apparatus  10 . In some embodiments, the primary optical surface  16 , the secondary optical surface  18 , or both, can be substantially symmetric about both the central axis  34  and the central opening  22 . 
     In some embodiments, the primary optical surface  16  can be shaped as an off-axis parabola, or a portion of a parabola that does not include the vertex of the parabola. The first portion  18   a  of the secondary optical surface  18  can form an angle  48  with the second portion  18   b  of the secondary optical surface  18  between about 20 degrees and about 70 degrees. In other embodiments, the angle  48  formed between the first portion  18   a  and the second portion  18   b  can be between about 35 degrees and about 55 degrees. In other embodiments, the angle formed between the first portion  18   a  and the second portion  18   b  can be about 45 degrees. Such an embodiment can show about a 93 percent optical efficiency without having a “lit-appearance” uniformity penalty. 
     In some embodiments, as shown in  FIG. 4 , the light source  14  can include two or more light emitting diodes, the light emitting diodes also being offset and positioned substantially symmetrically about the central axis  34 . In some embodiments the two or more light emitting diodes  14  can also be positioned substantially symmetrically about the central opening  22 . The heat spreader  26  in some embodiments can be aligned coaxially with the central axis  34  of the lighting apparatus  10 . As such, air passing through the heat spreader  26  can flow along the convective path  24  in a direction substantially parallel to the central axis  34 . 
     As can be seen in  FIG. 4 , light  36  can be emitted from the light source  14  and be directed towards the primary optical surface  16 . The primary optical surface  16  can then redirect the light  36  towards the second optical surface  18 . The second optical surface  18  can then further redirect the light in a primary emission direction  20 . The primary emission direction  20  denotes the general direction in which light  36  is redirected by the secondary optical surface  18 , when the light  36  is observed collectively. It is not a requirement that all individual rays of light  36  be redirected by the second optical surface  18  in a collimated fashion such that all the light is redirected in a substantially parallel orientation or uniform direction. However, in some embodiments, the primary and secondary optical surfaces  16  and  18  can be configured such that the light  36  can be redirected by the second optical surface  18  in a collimated or substantially parallel fashion. 
     In some embodiments, once the light  36  has been redirected by the second optical surface  18 , the light  36  then exits or is emitted from the lighting apparatus  10 . In other embodiments, the lighting apparatus  10  can further include a third optical surface  38 . The third optical surface  38  can be oriented substantially transverse to the primary emission direction  20 . The third optical surface  38  can be configured to receive redirected light  36  from the secondary optical surface  18 . The third optical surface  38  can then further redirect the light  36  in a secondary emission direction  40 . The secondary emission direction  40  can be designed for depending on the desired distribution of the lighting apparatus  10 . The angle or orientation of the third optical surface  38  can be varied in order to produce a distribution of light in a desired secondary emission direction  40 . The third optical surface  38  in some embodiments can be angled or configured to increase the beam angle of the light  36  being emitted from the lighting apparatus  10 . Increasing the beam angle of the light distribution can allow a larger area to be lit by the lighting apparatus  10 . In other embodiments, the third optical surface  38  can be configured to produce an asymmetric light distribution, or a geometrically patterned light distribution. 
     In some embodiments, as shown in  FIG. 4 , the lighting apparatus  10  can further include an optical window  42 . The optical window  42  can be configured such that substantially all light  36  being emitted by the lighting apparatus  10  passes through the optical window  42 . The optical window  42  can include diffusers, micro lenses, micro prisms, Fresnel patterns, kinoforms, or other surface characteristics. The optical window  42  can help scatter or disperse the light  36  exiting the lighting apparatus  10  in order to produce a unique or different lit appearance. 
     In the embodiments shown in  FIG. 1-4 , the lighting apparatus  10  includes a lens body  12 . The primary and secondary optical surfaces  16 ,  18  may be located on or be a part of the lens body  12 . As such, light  36  being emitted by the light source  14  travels through the lens body  12  until it exits the lighting apparatus  10 . In other embodiments, the primary and secondary optical surfaces can be two separate structures that define an open space in which light travels before exiting the lighting apparatus  10 . 
     In either embodiment, the primary optical surface  16  can be specularly reflective. The primary optical surface  16  can be a total internal reflective surface, or the primary optical surface  16  can have a mirror finish such that all light directed at the primary optical surface  36  is reflected towards the secondary optical surface  18 . The secondary optical surface  18  in some embodiments can also be specularly reflective. The secondary optical surface  18  can also be a total internal reflective surface, or have a mirror finish such that light directed at the secondary optical surface  18  is reflected by the secondary optical surface  18  out of the lighting apparatus  10 . 
     In some embodiments, as shown in  FIG. 11 , the secondary optical surface  18  can be a refractive surface such that light  36  being redirected towards the secondary optical surface  18  is not reflected, but passes through the secondary optical surface  18 , the light  36  being bent as it passes through the secondary optical surface  18  such that the secondary optical surface  18  redirects the light  36  in a primary emission direction  20 . In the embodiment of  FIG. 11 , the secondary optical surface  18  includes multiple concave lenses which can bend and redirect the light  36  in the primary emission direction  20 . 
       FIG. 4  shows a cross-section view of the embodiment of  FIG. 1 . In  FIG. 1 , this cross-section is revolved to produce the lighting apparatus  10 . However, in some embodiments, this cross-section can be extruded to form a linear or elongated lighting apparatus. The apparatus can include a midline or central plane  44 . The central opening  22  can be located on a midline or central plane  44  and extend through the apparatus  10 . The primary optical surface  16  can be substantially symmetric about the midline or central plane  44 , and therefore symmetric about the central opening  22 . In some embodiments, the secondary optical surface  18  can also be substantially symmetric about the midline or central plane  44  and the central opening  22 . 
     Because an extruded lighting apparatus  10  could have significant length, some embodiments may include multiple central openings  22  to increase the thermal performance along the entire length of the apparatus. The central openings  22  could define one or more convection paths  24  through the lighting apparatus  10 . In those embodiments with multiple central openings, the apparatus can further include multiple thermally conductive covers or heat spreaders  26 , with a heat spreader  26  covering each central opening  22  and placed in a convective air path  24 . 
     In some embodiments, the primary optical surface  16  can be one integral surface, as seen in the revolved embodiment of  FIG. 1 . In other elongated embodiments having the cross-section shown in  FIG. 4 , the primary optical surface  16  further includes a first primary optical surface  16   a  and a second primary optical surface  16   b . The central opening  22  and the convective path  24  can be defined between the first and second primary optical surfaces  16   a  and  16   b . In some embodiments, the first and second primary optical surfaces  16   a  and  16   b  can be substantially symmetric about the central opening  22 . The first and primary optical surfaces  16   a  and  16   b  can be connected by one or more connection pieces spanning across the central opening  22 . In such embodiments, the secondary optical surface  18  can also include two separate pieces in a similar arrangement as the first and second primary optical surfaces  16   a  and  16   b    
     As can be seen in  FIG. 5 , in some embodiments of the lighting apparatus  10 , the primary optical surface  16  can be oriented to obstruct a direct view of the light source  14  when the apparatus  10  is viewed from along the primary emission direction  24 . As such, the apparatus  10  can be an indirect lighting system, such that an observer does not look directly at the light source. Looking directly at a light source  14  can be bright and painful for the eyes of the observer, which can be undesirable. Having the primary optical surface  16  obstruct a direct view of the light source  14  can allow the lighting apparatus  10  to emit a desired amount of light without potentially hurting the observer&#39;s eyes. 
     For the orientation of the lighting apparatus  10  as shown in  FIG. 4 , the configuration of the light source  14 , primary optical surface  16 , and secondary optical surface  18  allow the lighting apparatus  10  to be an indirect lighting system having the light source  14  located on a side of the lighting apparatus generally opposite the primary emission direction  20 . As such, the heat spreader  26 , which can help dissipate heat from the light source  14 , can also be located on a side of the lighting apparatus  10  generally opposite the primary emission direction  20 . 
     In many conventional indirect lighting systems, the light source is located in a side of the lighting apparatus generally facing the primary emission direction. The light source emits light generally away from the primary emission direction, and a reflector then redirects the light in the primary emission direction. Heat management systems connected to the light source in these conventional systems are then necessarily located on a side of the lighting apparatus generally facing the primary emission direction. In such a system, when an observer views the apparatus from the primary emission direction, the heat spreader is readily visible, which can produce an aesthetically undesirable appearance. Having the heat spreader  26  on a side of the lighting apparatus  10  generally opposite the primary emission direction  20 , as shown in  FIG. 4 , can help produce a more desirable aesthetic appearance for the lighting apparatus  10 . 
     The primary optical surface  16  in some embodiments can be configured such that all light  36  from the light source  14  is redirected by the primary optical surface  16  towards the secondary optical surface  18 . For such embodiments, no light  36  from the light source  14  is emitted from the lighting apparatus  10  without first being redirected by the primary optical surface  16 . Accordingly, an observer can be prevented from viewing any direct light  36  from the light source  14  when the apparatus  10  is viewed from any direction. 
     An exploded view of the lighting apparatus of  FIG. 1  is shown in  FIG. 6 . The lens body  12  can be one continuous revolved piece. The heat spreader  26  can then be positioned or inserted to cover the central opening  22  such that the one or more through-holes  32  are aligned with the convective path  24 . The heat spreader insert  28  can be inserted into the central opening  22 , such that the heat spreader flange  30  contacts the lens body  12 . In some embodiments, the light source  14  can be connected directly to the heat spreader  26 . The heat spreader and light source  14  can be manufactured as one insert that can then be connected to the lens body  12 . In some embodiments, the lens body  12  can include a circumferential channel  46  surrounding the central opening  22 . When the heat spreader  26  is placed in position to cover the central opening  22 , the light source  14  can be configured or positioned on the heat spreader  26  to rest in the circumferential channel  46 . The light source  14  placed within the circumferential channel  46  can help ensure that the light emitted from the light source  14  passes directly into the lens body  12 . 
     A detailed view of an embodiment of the heat spreader  26  can be seen in  FIG. 7 . In some embodiments, the light source can include multiple light emitting diodes  14  (LEDs). The LEDs in some embodiments can be positioned substantially symmetrically about the central opening  22 . In  FIG. 7 , showing a heat spreader  26  for a revolved embodiment, the LEDs  14  can be radially or rotationally symmetric about the central opening. In an extruded embodiment, the light source  14  can include two rows of LEDs positioned symmetrically about the central opening  22 . Symmetrically positioned LEDs  14  can help produce a uniform or consistent light distribution profile from the lighting apparatus  10 . Having multiple LEDs  14  can help increase the overall amount of light being emitted by the lighting apparatus  10 , or can increase the intensity of the light distribution. 
     A second embodiment of a lighting apparatus  10  of the present invention is shown in  FIG. 8 . The apparatus  10  again includes a light source  14 , a primary optical surface  16 , and a secondary optical surface  18 . However, the embodiment of  FIG. 8  does not include a lens body  12 . The optical surfaces  16  and  18  are spaced apart such that light emitted by the light source  14  passes through air as it is being redirected by the primary and secondary optical surfaces  16  and  18 . As such, air can be circulated between the primary and secondary optical surfaces  16  and  18 , as well as around the light source  14 , to provide improved thermal performance. 
     A cross-section view of the embodiment of  FIG. 8  is shown in  FIG. 9 . The interior convective path  50  is shown between the primary optical surface  16  and the secondary optical surface  18  such that air can pass over both surfaces. Additionally, air can flow around the light source  14 . As such, the primary optical surface  16 , the secondary optical surface  18 , and the light source  14  can allow heat transfer to the ambient air through convection as well as radiation, thereby helping to improve the thermal performance of the lighting apparatus  10 . 
     A front elevation cross-sectional view of the embodiment seen in  FIG. 8  is shown in  FIG. 10 . The primary optical surface  16  can again be an off axis parabola in some embodiments. The secondary optical surface can have a first portion  18   a  and a second portion  18   b . The first portion  18   a  in  FIG. 10  can be slightly rounded. However, the slightly rounded first portion  18   a  can still generally form an angle  48  with the second portion  18   b  similar to the angle described for  FIG. 4 . As such, the second embodiment can achieve the same optical efficiency. 
     The primary optical surface  16  can be configured to receive light from the light source  14  and redirect it towards the secondary optical surface  18 . The secondary optical surface  18  subsequently redirects the light in a primary emission direction  20  out of the lighting apparatus  10 . The primary optical surface  16  can be positioned to obstruct a direct view of the light source  14  when the lighting apparatus is viewed from the primary emission direction  20 . The light source  14  can also emit light in a generally conical pattern in some embodiments such that all light from the light source  14  is reflected by the primary optical surface  16 . As such, no direct light is seen by an observer when viewing the lighting apparatus from any direction. In some embodiments, the primary and secondary optical surfaces  16  and  18  can be substantially rotationally symmetric about a central axis  24 . 
     Thus, although there have been described particular embodiments of the present invention of a new and useful Compact Indirect Lighting System with Improved Thermal Performance 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.