Abstract:
A light fixture having a light source, first and second heat sinks with corresponding first and second thermal interfaces having complementary curved surfaces, and a linkage having cams, and springs to create contact pressure between the thermal interfaces when the light fixture is in an operation mode and to permit movement between the thermal interfaces when the light fixture is in an adjustment mode. When the light fixture is in operation mode, the first and second heat sinks work in combination to provide a highly effective heat dissipation system. When the light fixture is in adjustment mode, the separation created permits the light source to move along an adjustment path to change the angular direction of the light emitted and to rotate about a rotational axis, providing a full range of directional lighting orientations.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention pertains to the field of light fixtures, and, in particular to adjustable light fixtures. 
       BACKGROUND OF THE INVENTION 
       [0002]    Recessed lighting is very popular in residential and commercial buildings given its unobtrusive and aesthetically pleasing appearance. Recessed lighting removes from view all electric hardware and wiring, placing everything behind a wall or ceiling. However, recessed light fixtures, specifically those with an LED light source, generate heat when the light source is illuminated. This heat can become substantial and can cause certain components of the light fixture to fail or can cause even more significant emergencies, such as fires. 
         [0003]    As such, there is a need in the art for effective heat dissipation systems for light fixtures employing LED light sources. It is further desirable for the light fixture to provide adjustable orientations of the light source to direct the light emanating from the light fixture. Optimally, this can be accomplished by providing angular adjustment in combination with rotation about an axis, permitting a full range of angled directional lighting about a rotational axis. 
         [0004]    It is therefore desired to provide a light fixture that combines a heat dissipation system with a full range of angular and rotational orientation options for the light emission direction, especially for a recessed light fixture employing one or more LEDs as a light source. Because heat dissipation systems can be large and somewhat unwieldy, there is a need in the art for an effective system that can be used in a recessed light fixture while retaining the desired flexibility of light emission orientations. 
       SUMMARY OF THE INVENTION 
       [0005]    Accordingly, it is an object of the present invention to provide a highly effective heat dissipation system in combination with the art&#39;s need for re-orientation of the light source to allow directional lighting. It is a further object of the present invention to provide a manner of locking the light fixture&#39;s heat dissipation system while in an operation mode to optimize the system&#39;s effectiveness. 
         [0006]    These and other objectives are achieved by providing a light fixture having a light source, first and second heat sinks with corresponding first and second thermal interfaces having complementary surfaces, and means to create contact pressure between the thermal interfaces when the light fixture is in an operation mode and to permit movement between the thermal interfaces when the light fixture is in an adjustment mode. When the light fixture is in operation mode, the first and second heat sinks work in combination to provide a highly effective heat dissipation system. When the light fixture is in adjustment mode, the separation created permits the light source to move along an adjustment path to change the angular direction of the light emitted and to rotate about a rotational axis, providing a full range of directional lighting orientations. 
         [0007]    The present invention accomplishes its objectives by providing a light fixture comprising a light source, first and second heat sinks, the light source being mounted to the first heat sink and the first heat sink being operable to conduct heat generated by the light source during operation. The light fixture has both an operation mode and an adjustment mode, In the operation mode, the first heat sink is fixed relative to the second heat sink and a first thermal interface of the first heat sink is pressed into contact with a second thermal interface of the second heat sink in a contact area such that the second heat sink operates to conduct heat from the first heat sink through the contact area and dissipate the heat into an ambient environment. In the adjustable mode, the first heat sink is movable relative to the second heat sink to a plurality of operation positions to allow adjustment of the light source&#39;s position relative to the second heat sink. The light fixture is operational in either the operation mode or the adjustment mode and in any of the plurality of operation positions. 
         [0008]    In some embodiments, the light fixture also comprises a means to generate contact pressure between the first and second thermal interfaces while the light fixture is in operation mode. 
         [0009]    In certain embodiments, the first thermal interface is displaced from the second thermal interface while the light fixture is in adjustment mode. 
         [0010]    In some embodiments, the contact area of the first and second thermal interfaces of the first and second heat sinks is at least about 100 cm. 
         [0011]    In certain embodiments, the first heat sink is continuously movable relative to the second heat sink along an adjustment path when the light fixture is in adjustment mode, and the light fixture is operable to be in either the operation mode or the adjustment mode at any position along the path. 
         [0012]    In some embodiments, the adjustment path is curved, and the first and second thermal interfaces have complementary curved surfaces. In certain embodiments, the first thermal interface has a convex curved surface and the second thermal interface has a concave curved surface, or vice versa. 
         [0013]    In some embodiments, the first thermal interface is in the form of a partially cylindrical convex surface, the second thermal interface is in the form of a partially cylindrical concave surface complementary to the first thermal interface, and the arc length of the second thermal interface is substantially greater than the arc length of the first thermal interface. 
         [0014]    In certain embodiments, the light fixture also comprises a means for changing the mode of the light fixture between operation and adjustment modes. The mode changing means may also be operable to maintain the light fixture in operation mode. 
         [0015]    In some embodiments, the mode changing means can comprise a first guide fixed relative to the second heat sink and a first cam connected to the first heat sink. While in operation mode, the first cam bears on the first guide, thereby pressing the first thermal interface against the second thermal interface. While in adjustment mode, the first cam releases the first thermal interface from the second thermal interface. 
         [0016]    In certain embodiments, the first cam of the mode changing means is connected to the first heat sink through an elastic means. When in operation mode, the elastic means would be deformed; when in adjustment mode, the elastic means would be at rest. 
         [0017]    In some embodiments, the first cam of the mode changing means has a flat surface that, when the light fixture is in operation mode, bears on the guide to maintain the light fixture in operation mode. 
         [0018]    In certain embodiments, the mode changing means also comprises a second guide fixed relative to the second heat sink and first and second pairs of cams connected to the first heat sink through the elastic means, with the first and second pairs of cams deposed on opposed sides of the first thermal interface. When in operation mode, the first and second pairs of cams bear on the first and second guides, respectively, and press the first thermal interface against the second thermal interface. When in adjustment mode, the first and second pairs of cams release the first thermal interface from the second thermal interface. 
         [0019]    In some embodiments, the mode changing means also comprises a linkage connected to the first and second pairs of cams. In certain embodiments, the linkage comprises a handle adapted to articulate the linkage to change the light fixture between operation and adjustment modes, with the handle accessible by the user through an aperture of the light fixture. 
         [0020]    In some embodiments, the light fixture also comprises an illumination aperture that permits light emanating from the light source to pass through. The illumination aperture has an aperture plane, and as the light fixture slides along the adjustment path, the optical axis of the light source will pass through the aperture plane at different angles. 
         [0021]    In certain embodiments, the light fixture further comprises a support, and the second heat sink can rotate relative to the support and the first heat sink is supported by the second heat sink. 
         [0022]    Other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings and accompanying detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a perspective view of one embodiment of an adjustable light fixture constructed in accordance with the invention, showing the light source in a first rotational orientation; 
           [0024]      FIG. 2  is a perspective view of the light fixture of  FIG. 1 , showing the light source in a second rotational orientation; 
           [0025]      FIG. 3  is an elevation view in cross-section of the heat dissipation system of the light fixture of  FIG. 1 , showing the light source in a zero (0) degree tilt orientation and the modality changing linkage in the locked position; 
           [0026]      FIG. 4  is an elevation view in cross-section of the heat dissipation system of the light fixture of  FIG. 1 , showing the light source in a zero (0) degree tilt orientation and the modality changing linkage in the unlocked position; 
           [0027]      FIG. 5  is a perspective view in cross-section of the heat dissipation system of the light fixture of  FIG. 1 , showing the light source in a tilted orientation and the modality changing linkage in the locked position; 
           [0028]      FIG. 6  is a perspective view of an assembly of the light source and first heat sink of the light fixture of  FIG. 1 , showing the modality changing linkage in the unlocked position; 
           [0029]      FIG. 7  is a perspective view of the assembly of the light source and first heat sink of the light fixture of  FIG. 1 , showing the modality changing linkage in the locked position; 
           [0030]      FIG. 8  is an elevation view in cross section of the light fixture of  FIG. 1  showing the light fixture in the adjustment mode, with the modality changing linkage in the unlocked position and a gap between the thermal interface of the first heat sink and the thermal interface of the second heat sink; and 
           [0031]      FIG. 9  is an elevation view in cross section of the light fixture of  FIG. 1  showing the light fixture in the operation mode, with the modality changing linkage in the locked position and the thermal interface of the first heat sink in contact with the thermal interface of the second heat sink. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Referring to  FIGS. 1-9 , an embodiment of a light fixture  10  constructed in accordance with the invention preferably has a support frame  12  providing a support for affixing the light fixture to an external support structure, such as a ceiling or wall structure (not shown). The light fixture  10  also has a light source  14 , such as a Light-Emitting Diode (LED), or another suitable light source, for emitting light through an aperture  30  of the light fixture  10 . The light fixture  10  is adapted to permit tilting and rotation of the light source  14  relative to the support  12  to allow aiming of the light beam emitted from the light fixture. 
         [0033]    The light fixture  10  has a heat dissipation system comprising several heat sinks, preferably comprised of thermally conductive material such as aluminum (or another suitable material), which cooperate to dissipate heat generated by the light source, while allowing for adjustment of tilt and rotation positions of the light source. The heat dissipation system includes a first heat sink  16  fixedly connected to the light source  14 , which is operable to conduct heat away from the light source  14  during operation of the light fixture  10 . The first heat sink  16  has a base  18  which is thermally coupled to the light source  14  (and/or a mount for the light source), and has a thermal interface  20 , which is opposite the base  18 . For example, in the case of a Light-Emitting Diode (LED) light source, where one or a plurality of LEDs are mounted to a substrate such as a printed circuit board (PCB) or the like, the base  18  of the first heat sink  16  can be connected to a side of the substrate opposite the LEDs and the thermal interface is disposed on a side of the first heat sink  16  opposite the base  18  such that the first heat sink is operable to conduct heat from the light source  14  to the thermal interface  20  through a body of the heat sink. 
         [0034]    The light fixture  10  includes a second heat sink  22  preferably having heat dissipating fins  24  disposed on an exterior surface thereof and having a thermal interface  26  on an interior thereof adapted to engage and thermally couple with the thermal interface  20  of the first heat sink  16 . 
         [0035]    The second heat sink  22  is preferably rotatably mounted to the support  12 , for rotation about a rotation axis which is preferably aligned (co-linear) with a center axis  28  of the light fixture passing through a center  31  of the aperture  30  of the light fixture  10  perpendicular to a plane of the aperture. Preferably, the second heat sink  22  is operable to rotate more than 360 degrees about the rotation axis, but the light fixture  10  includes an over-rotation stop to prevent rotation greater than a predetermined amount, for example more than 365 degrees. Further, the light fixture  10  preferably includes a rotation lock to selectively permit and prevent rotation of the second heat sink, which lock is accessible through the aperture. 
         [0036]    The first heat sink  16  and light source  14  are preferably mounted to and supported by the second heat sink  22  such that rotation of the second heat sink  22  about the rotation axis results in rotation of the first heat sink  16  and light source  14 . This rotation allows for rotational aiming of the optical axis of the light source about the rotation axis. 
         [0037]    The light fixture  10  has an operation mode wherein the tilt position of the light source  14  and first heat sink  16  are fixed relative to the second heat sink  22 . To permit tilt aiming of the light source  14 , the light fixture  10  also has an adjustable mode wherein the position of the light source  14  and first heat sink  16  are movable relative to the second heat sink  22  to allow tilt adjustment of the position of the light source  14  and the optical axis relative to the center axis  28  of the light fixture  10 . 
         [0038]    In the operation mode, the thermal interface  20  of the first heat sink  16  is pressed into contact with the thermal interface  26  of the second heat sink  22  substantially throughout a contact area (preferably at least about 100 cm 2 ), to thermally couple the first and second thermal interfaces over the contact area, whereby the second heat sink  22  is operable to remove heat directly from the first heat sink  16  by thermal conduction through the contact area to dissipate the heat into an ambient environment  60  through the fins  24 . 
         [0039]    Preferably, the first heat sink  16  and light source  14  are fixed relative to the second heat sink  22  in the operation mode, but can rotate about the rotation axis relative to the frame  12 , along with the second heat sink  22 . In the adjustable mode, the light source  14  and first heat sink  16  are movable relative to the second heat sink  22  to allow for adjusting the position of the light source  14  relative to the second heat sink  22  (i.e., tilt). In the adjustable mode, the thermal interface  20  of the first heat sink  16  is displaced (e.g., spaced) from the thermal interface  26  of the second heat sink  22 , and the position of the first heat sink  16  and light source  14  is adjustable relative to the second heat sink  22  to a plurality of operation positions along an adjustment path (or preferably continuously to any position along the path). The light fixture  10  can be, alternately, in either the operation (fixed) mode or adjustable mode in any of the operation positions along the adjustment path. 
         [0040]    Preferably, the adjustment path follows a curve lying on a plane parallel to the center axis  28  of the light fixture and concave toward the plane of the aperture  30  such that, during movement of the first heat sink  16  and light source  14  along the adjustment path, the optical axis of the light source  14  pivots (tilts) relative to the center axis  28  of the light fixture. Preferably, in a first operation position along the path, the optical axis is co-linear with the center axis  28  (See  FIG. 3 ), and in all other operation positions, the optical axis is angularly displaced from, but intersects the center axis  28  at the center  31  of the aperture  30  (See  FIG. 5 ). 
         [0041]    The adjustable mode allows the light fixture  10  to change from, for example, a down-light orientation wherein the light emitted from the light fixture is directed straight through (perpendicular) to an aperture plane of the light fixture (e.g., at zero (0) degree tilt;  FIG. 3 ), to a wall-wash orientation wherein the light is emitted through the aperture at an acute angle (θ) relative to the aperture plane (e.g., up to forty (40) degrees tilt, or more;  FIG. 5 ). Preferably, the first operator position (zero (0) degree tilt) is a limit position at one end of the adjustment path so that the light fixture can be easily and reliably placed in the zero (0) degree tilt position. 
         [0042]    To accommodate the curved adjustment path, the thermal interfaces  20 ,  26  of the first and second heat sinks  16 ,  22  have complementary curved surfaces. Preferably, the thermal interface  20  of the first heat sink  16  is in the form of a partially cylindrical convex surface having a radius of curvature equal to that of the curved adjustment path, and the thermal interface  26  of the second heat sink  22  is in the form of a complementary, partially cylindrical concave surface. However, preferably, an arc length of the thermal interface  26  of the second heat sink  22  (as measured along the adjustment path) is substantially longer than an arc length of the thermal interface  20  of the first heat sink  16 . For example, the arc length of the thermal interface  26  of the second heat sink  22  may be 2 to 10 times greater than that of the first thermal interface  20  to allow the first heat sink  16  to thermally couple with the second heat sink  22  in at least two non-overlapping positions along the adjustment path. 
         [0043]    The light fixture  10  preferably has a linkage mechanism  32  connected to the first heat sink  16  to change the modality of the light fixture  10  between the operation mode and the adjustment mode. The linkage  32  includes, on each of two opposed lateral sides  34 ,  36  of the first heat sink  16 , a first link  38  connected to the first heat sink  16  by one or more resiliently deformable members, such as a plurality of springs  40 ,  42 , adapted to bias the thermal interface  20  of the first heat sink  16  against the thermal interface  26  of the second heat sink  22  in the operation mode. 
         [0044]    On each lateral side  34 ,  36 , the linkage  32  also includes second and third links  44 ,  46  pivotally connected to the first link  38 , preferably at first and second ends thereof, respectively. The second and third links  44 ,  46  are connected together by a pin  64  (see  FIG. 7 ) on one of the second and third links which is received in a complementary slot  45  in the other link. Each lateral side  34 ,  36  also includes first and second cams  48 ,  50  integrally formed with, or fixed relative to, the second and third links  44 ,  46 , respectively. Preferably, the cams  48 ,  50  rotate about points where the associated second and third links  44 ,  46  pivot relative to the first link  38 . The cams  48 ,  50  are operable to bear on one of two parallel guide rails  52  on either lateral side of the first heat sink, which guide rails are preferably integrally formed with (or fixed relative to) the second heat sink  22 . Preferably, the guide rails  52  are curved, forming the aforementioned curved adjustment path. 
         [0045]    Preferably, the second links  44  of each side of the linkage  32  are interconnected by a handle  54  which is accessible by a user through the aperture  30  of the light fixture  10  so that a user can adjust and fix the position of the light source  14  using one hand, after the light fixture  10  is installed. 
         [0046]    To place the light fixture  10  in the operation mode, the linkage  32  is moved to a locked position ( FIG. 9 ), for example by urging the handle  54  toward the second heat sink  22 , causing the cams  48 ,  50  to rotate and bear on the associated guide rail  52  and the thermal interface  20  of the first heat sink  16  to move toward and press against the thermal interface  26  of the second heat sink  22  (via the first link  38  and the resiliently deformable members  42 ,  44 ) forming a direct thermal connection between the first and second heat sinks  16 ,  22 . Preferably, the linkage  32  remains in the locked position and maintains the light fixture  10  in the operation mode unless urged out of the locked position. For example, each cam  48 ,  50  can include a flat surface  56 ,  58  which is tangential to and bears on the guide rail  52  in the operation mode to maintain the light fixture  10  in the operation mode. Preferably, the resiliently deformable members  42 ,  44  provide for relatively constant contact pressure between the two thermal interfaces  20 ,  26  among the various operation positions along the adjustment path, which contact pressure maintains the light fixture in the operation mode. 
         [0047]    To place the light fixture  10  in the adjustable position, the linkage  32  is moved to an unlocked position ( FIG. 8 ), for example by moving the handle  54  away from the second heat sink  22 , causing the cams  48 ,  50  to rotate and allowing the first link  38  and thermal interface  20  of the first heat sink  16  to release and move away from the thermal interface  26  of the second heat sink  22  such that the thermal interface  20  of the first heat sink  16  is displaced from the thermal interface  26  of the second heat sink  22 , creating a gap  62 . 
         [0048]    It should be understood, of course, that the specific form of the invention herein illustrated and described is intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.