Abstract:
A troffer-style luminaire includes first and second side ends and a top end extending between the side ends. The side and top ends define an interior region. Light emitting diodes (“LEDs”) are coupled along interior surfaces of the side ends, within the interior region. At least some of the LEDs are coupled to the interior surfaces by being wedged between members protruding into the interior region from the interior or other surfaces. In addition, or in the alternative, one or more spring clips can apply a force that holds the LEDs against the interior surfaces. A reflector extends between the LEDs and the top member and reflects light from the LEDs towards a bottom end of the frame. The light emitted by the LEDs is directed to the reflector and then indirectly emitted through the bottom end, into a desired environment.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to troffer-style luminaires (“troffers”) and more particularly, to a troffer that uses indirect light from light emitting diodes to output light with low glare and good cutoff. 
       BACKGROUND 
       [0002]    A luminaire is a system for producing, controlling, and/or distributing light for illumination. For example, a luminaire can include a system that outputs or distributes light into an environment, thereby allowing certain items in that environment to be visible. Luminaires are often referred to as “light fixtures”. 
         [0003]    A troffer is a light fixture that includes a relatively shallow, inverted trough-shaped housing (or “trough”) within which at least one light source is disposed. The trough includes a substantially closed top end and a bottom end with an opening through which light from the light source is emitted. Generally, the trough is either suspended from a ceiling or other surface or installed in an opening therein. For example, the trough can be recessed within the ceiling, with the bottom end of the trough being flush with the ceiling. Traditional troffers include fluorescent light sources, with one or more fluorescent lamps extending across a length of each troffer. 
         [0004]    Increasingly, lighting manufacturers are being driven to replace fluorescent lamp fixtures with light emitting diode (“LED”) fixtures because LEDs tend to have better longevity than fluorescent lamps. Existing LED troffers include multiple LEDs spaced along the length of a top, interior surface of the troffer, with each LED pointing downward, into the environment to be illuminated. Because the LEDs are separate, bright light sources that emit light directly into the environment, the existing LED troffers generally emit light with bright and dark spaced spots onto a surface and poor cutoff. In particular, light emitted by the existing LED troffers tends to result in a substantial amount of glare because the shallow troughs of the LED troffers do not allow the LEDs to be recessed deep enough to achieve good cutoff. Accordingly, a need currently exists in the art for an improved LED troffer with reduced glare, improved cutoff, and more consistent light output. 
       SUMMARY 
       [0005]    The invention provides a troffer that uses indirect light from LEDs to output light with low or no glare and good cutoff. The troffer includes a frame having first and second side ends. A top end of the frame can include top edges of the side ends. The top end also may include one or more top members and/or reflectors extending between the side ends. The frame also can include one or more bottom members extending across at least a portion of a bottom end of the frame. The ends of the frame define an interior region within the frame. 
         [0006]    A first plurality of LEDs are coupled along an interior surface of the first side end, within the interior region. The troffer may or may not also include a second plurality of LEDs coupled along an interior surface of the second side end, within the interior region. For example, a troffer that only includes the first plurality of LEDs may emit light in a substantially asymmetric distribution, and a troffer that includes both the first and second pluralities of LEDs may emit light in a substantially symmetric distribution. 
         [0007]    At least some of the LEDs can be coupled to their respective interior surface by being wedged between first and second members protruding into the interior region from the interior surface or another surface. In addition, or in the alternative, one or more spring clips can apply a force that presses the LEDs to the interior surfaces. For example, each spring clip can be at least partially disposed around one of the protruding members, with an end of the spring clip pressing an end of a substrate associated with the LEDs against the interior surface. As described in more detail below, pressing the substrates to the interior surfaces allows for transfer of thermal energy from the LEDs to the interior surfaces. 
         [0008]    A reflector extends between the LEDs and the top end of the frame and reflects light from the LEDs towards a bottom end of the frame. The reflected, indirect light from the LEDs is emitted through the bottom end, into a desired environment. For example, the reflector can include a single arc-shaped member that extends between the side ends and reflects light from the first plurality of LEDs. Alternatively, the reflector can include two arc-shaped members that extend between the side ends. Each arc-shaped member can be associated with one of the first and second pluralities of LEDs and can reflect light generated therefrom. Because the light generated by the LEDs is indirectly emitted into the environment, via the reflector, the light emitted by the troffer has reduced glare and better cut-off compared to traditional LED troffers that directly emit light from shallowly-recessed LEDs. In certain exemplary embodiments, the bottom members, if any, block light from traveling directly from the LEDs to the environment, providing additional protection from glare as well as enhanced cut-off. 
         [0009]    These and other aspects, features and embodiments of the invention will become apparent to a person of ordinary skill in the art upon consideration of the following detailed description of illustrated embodiments exemplifying the best mode for carrying out the invention as presently perceived. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description, in conjunction with the accompanying figures briefly described as follows. 
           [0011]      FIG. 1  is a perspective bottom view of a troffer, in accordance with certain exemplary embodiments. 
           [0012]      FIG. 2  is an exploded view of the troffer of  FIG. 1 , in accordance with certain exemplary embodiments. 
           [0013]      FIG. 3  is a partial perspective view of an interior region of the troffer of  FIG. 1 , in accordance with certain exemplary embodiments. 
           [0014]      FIG. 4  is a partially exploded side view of the troffer of  FIG. 1 , in accordance with certain exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0015]    The following description of exemplary embodiments refers to the attached drawings, in which like numerals indicate like elements throughout the figures.  FIGS. 1-4  illustrate a troffer  100 , according to certain exemplary embodiments. With reference to  FIGS. 1-4 , the troffer  100  includes a frame  105  having a first side end  105   a , a second side end  105   b , and a top end  105   c  extending between the first side end  105   a  and the second side end  105   b . Third and fourth side ends  105   e  and  105   f  extend between the side ends  105   a  and  105   b , on opposite sides of the frame  105 . In certain exemplary embodiments, each side end  105   a - b  and  105   e - f  extends from the top end  105   c  at a substantially orthogonal angle. 
         [0016]    In certain exemplary embodiments, the troffer  100  also includes a pair of bottom members  105   d  extending towards one another, between the first and second side ends  105   a  and  105   b . Each bottom member  105   d  extends from a respective one of the side ends  105   a  and  105   b . In certain exemplary embodiments, each bottom member  105   d  extends from its respective side end  105   a ,  105   b  at a substantially orthogonal angle. An aperture  106  extends between the bottom members  105   d , substantially along an axis thereof. 
         [0017]    In certain exemplary embodiments, each bottom member  105   d  is integrally formed with its respective side end  105   a ,  105   b , and the top end  105   c  is integrally formed with at least one of the side ends  105   a - b  and  105   e - f . For example, the members  105   d  and/or top end  105   c  can be formed with one or more of the side ends  105   a - b  and  105   e - f  via molding, casting, extrusion, or die-based material processing. Alternatively, at least one of the bottom members  105   d , the top member  105   c , and/or the side ends  105   a - b  and  105   e - f  can include a separate component that is separately coupled to at least one of the other components via solder, braze, welds, glue, plug-and-socket connections, epoxy, rivets, clamps, fasteners, or other fastening means. Although the exemplary embodiment is depicted in the figures as having a substantially rectangular-shaped geometry, alternative embodiments of the frame  105  have any of a number of different shapes, including, without limitation, a square shape and a frusto-conical shape. For example, in certain exemplary embodiments, one or more of the side ends  105   a - b  and  105   e - f  can be angled outward or inward relative to the top end  105   c . In addition, the frame  105  may not include a top member  105   c  in certain alternative exemplary embodiments. In such embodiments, top edges of the side ends  105   a - b  and  105   e - f  can define a top end of the frame  105 . 
         [0018]    The frame  105  also is capable of being configured in a number of different sizes. In certain exemplary embodiments, the frame  105  is two feet wide by two feet long. In other exemplary embodiments, the frame  105  is two feet wide by four feet long. A person of ordinary skill in the art having the benefit of the present invention will recognize that these sizes are merely exemplary and the frame  105  can have any other size in alternative exemplary embodiments. The frame  105  is configured to be suspended from, or recessed within, a ceiling or other surface (not shown). 
         [0019]    The side ends  105   a - b  and  105   e - f  together with the top end  105   c  and the bottom members  105   d  define an interior region  107 . As best seen in  FIG. 4 , each side end  105   a ,  105   b  includes a heat sink member  110  that has an interior side  110   a  within the interior region  107  and an exterior side  110   b  disposed opposite the interior side  110   a , outside of the interior region  107 . The interior side  110   a  includes a top platform  108  and a bottom platform  109 . Each of the platforms  108  and  109  includes an elongated member that extends substantially perpendicularly or angularly from the interior side  110   a , into the interior region  107 . Each of the platforms  108  extends longitudinally along the length of its respective side end  105   a ,  105   b . The top platform  108  engages and at least partially supports a reflector  150 , as described below. Each bottom platform  109  and a ridge  111  extending angularly from an interior side  105   d  a of the bottom platform&#39;s corresponding bottom member  105   d  support a substrate  120  for one or more LEDs  115 , as described below. 
         [0020]    The substrates  120  and LEDs  115  are thermally coupled to the interior sides  110   a , along longitudinal axes thereof. More specifically the substrates  120  and LEDs  115  on each interior side  110   a  are disposed substantially along a longitudinal axis of the interior side&#39;s corresponding side end  105   a ,  105   b . In certain exemplary embodiments, some or all of the LEDs  115  on each side  110   a  are mounted nearly end to end on a common substrate  120 , substantially in the form of a “strip.” Alternatively, groups of one or more of the LEDs  115  can be mounted to their own substrates  120 . In certain alternative exemplary embodiments, the troffer  100  can include LEDs  115  disposed only on one of the interior sides  110   a.  In such embodiments, the troffer  100  can emit light in a substantially asymmetric distribution. 
         [0021]    Each substrate  120  includes one or more sheets of ceramic, metal, laminate, circuit board, mylar, or another material. Each LED  115  includes a chip of semi-conductive material that is treated to create a positive-negative (“p-n”) junction. When the LEDs  115  are electrically coupled to a power source, such as a driver  125 , current flows from the positive side to the negative side of each junction, causing charge carriers to release energy in the form of incoherent light. 
         [0022]    The wavelength or color of the emitted light depends on the materials used to make each LED  115 . For example, a blue or ultraviolet LED typically includes gallium nitride (“GaN”) or indium gallium nitride (“InGaN”), a red LED typically includes aluminum gallium arsenide (“AlGaAs”), and a green LED typically includes aluminum gallium phosphide (“AlGaP”). Each of the LEDs  115  is capable of being configured to produce the same or a distinct color of light. In certain exemplary embodiments, the LEDs  115  include one or more white LEDs and one or more non-white LEDs, such as red, yellow, amber, green, or blue LEDs, for adjusting the color temperature output of the light emitted from the troffer  100 . A yellow or multi-chromatic phosphor may coat or otherwise be used in a blue or ultraviolet LED to create blue and red-shifted light that essentially matches blackbody radiation. The emitted light approximates or emulates “white,” incandescent light to a human observer. In certain exemplary embodiments, the emitted light includes substantially white light that seems slightly blue, green, red, yellow, orange, or some other color or tint. In certain exemplary embodiments, the light emitted from the LEDs  115  has a color temperature between 2500 and 5000 degrees Kelvin. 
         [0023]    In certain exemplary embodiments, an optically transmissive or clear material (not shown) encapsulates at least some of the LEDs  115 , either individually or collectively. This encapsulating material provides environmental protection while transmitting light from the LEDs  115 . For example, the encapsulating material can include a conformal coating, a silicone gel, a cured/curable polymer, an adhesive, or some other material known to a person of ordinary skill in the art having the benefit of the present disclosure. In certain exemplary embodiments, phosphors are coated onto or dispersed in the encapsulating material for creating white light. In certain exemplary embodiments, the white light has a color temperature between 2500 and 5000 degrees Kelvin. 
         [0024]    Although illustrated in the figures as being arranged in a substantially rectangular-shaped geometry, a person of ordinary skill in the art having the benefit of the present disclosure will recognize that the LEDs  115  can be arranged in any geometry. For example, in certain alternative exemplary embodiments, the LEDs  115  are configured in circular or square-shaped geometries. The LEDs  115  are coupled to the substrate(s)  120  by one or more solder joints, plugs, screws, glue, epoxy or bonding lines, and/or other means for mounting an electrical/optical device on a surface. Similarly, each substrate  120  is typically coupled to one of the interior sides  110   a  by one or more solder joints, plugs, screws, glue, epoxy or bonding lines, and/or other means for mounting an electrical/optical device on a surface. In certain exemplary embodiments, each substrate  120  is coupled to its corresponding interior side  110   a  by a two-part arctic silver epoxy. 
         [0025]    In addition, or in the alternative, one or more spring clips  145  applies pressure to at least a portion of each substrate  120  to couple the substrate(s)  120  to the interior sides  110   a . Each spring clip  145  is disposed at least partially around one of the bottom platforms  109 , with an end  145   a  of each spring clip  145  engaging a first end  120   a  of each substrate(s)  120 . Each spring clip  145  applies pressure for holding the substrate  120  up against the interior side  110   a . A second, opposite end  120   b  of each substrate  120  rests on at least a portion of the ridge  111  proximate the side  110   a . The ridge  111  and spring clip  145  essentially wedge the substrate  120  against the side  110   a . In certain exemplary embodiments, the substrate  120  is coupled to the side  110   a  by placing the bottom end  120   b  between the ridge  111  and the side  110   a , placing the top end  120   a  flush against the side  110   a , and engaging each spring clip  145  to the bottom platform  109  so that the end  145   a  of the spring clip  145  engages the top end  120   a . In certain alternative exemplary embodiments, the troffer  100  does not include the ridge  111 , and each substrate  120  rests on the interior side  105   d  a of its corresponding bottom member  105   d.    
         [0026]    The LEDs  115  are electrically connected to the driver  125 , which supplies electrical power to, and controls operation of, the LEDs  115 . For example, one or more wires (not shown) couple opposite ends of each substrate  120  to the driver  125 , thereby completing one or more circuits between the driver  125 , substrate(s)  120 , and LEDs  115 . In certain exemplary embodiments, the driver  125  is configured to separately control one or more portions of the LEDs  125  to adjust light color and/or intensity. Although illustrated in the figures as being disposed within the interior region  107 , substantially along a center of the top member  105   c , the driver  125  can be located substantially anywhere else in or remote from the troffer  100 , in certain alternative exemplary embodiments. 
         [0027]    As a byproduct of converting electricity into light, LEDs  115  generate a substantial amount of heat that raises the operating temperature of the LEDs  115  if allowed to accumulate. This heat can result in efficiency degradation and premature failure of the LEDs  115 . Each heat sink member  110  is configured to manage heat output by the LEDs  115 . In particular, each heat sink member  110  is configured to conduct heat away from the LEDs  115  by increasing the amount of surface area thermally coupled to the LEDs  115 . Each heat sink member  110  is composed of any material configured to conduct and/or convect heat, such as die cast or extruded metal. 
         [0028]    As set forth above, the interior side  110   a  of each heat sink member  110  includes a surface to which the LEDs  115  and substrates  120  are thermally coupled. At least one fin  160  extends from the exterior side  110   b  of each heat sink member  110 , away from the interior region  107 . Each fin  160  includes an elongated member that extends longitudinally at least partially along its respective side end  105   a ,  105   b . In certain exemplary embodiments, multiple fins  160  extend substantially perpendicular from and longitudinally along, and are spaced laterally apart along, the respective side ends  105   a  and  105   b , between the top end  105   c  and a corresponding one of the bottom members  105   d . Although illustrated in the figures as having a substantially rectangular-shaped geometry, each fin  160  is capable of having any of a number of different shapes and configurations. For example, each fin  160  can include a solid or non-solid member having a substantially rectilinear, rounded, or other shape. 
         [0029]    Each heat sink member  110  is configured to dissipate heat from the LEDs  115  thermally coupled thereto along a heat-transfer path that extends from the LEDs  115 , through the substrate  120 , and to the fins  160  via the respective end  105   a ,  105   b  associated with the substrate  120 . The fins  160  receive the conducted heat and transfer the conducted heat to the surrounding environment (typically air in the ceiling) via convection. In certain exemplary embodiments, heat from the LEDs  115  and substrate  120  is transferred along a path from the LEDs  115  to the substrate  120 , from the substrate  120  to the side  110   a , from the side  110   a  through the respective side end  105   a ,  105   b  to the first end  160   a  of one or more of the fins  160 , from each first end  160   a  to a second end  160   b  of the corresponding fin  160 , and from each second end  160   b  to the surrounding environment. Heat also can be transferred by convection directly from the side  110   b  and/or the fins  160  to one or more gaps between the fins  160 . 
         [0030]    As best viewed in  FIG. 2 , the reflector  150  includes a member with two substantially arc-shaped segments  151   a  and  151   b  that converge along a line extending from the center of side end  105   e  to the center of side send  105   f . Each segment  151  includes a first end  152  that engages a top surface  108   a  of a respective one of the top platforms  108 , and a second end  153  that converges with the second end  153  of the other segment  151 . The top platforms  108  support at least a portion of the weight of the reflector  150 . In certain exemplary embodiments, the first end  152  extends angularly from a main body portion  154  of each segment  151 , so that the first end  152  is substantially flush with the top platform  108 . Alternatively, the first end  152  extends along the main body portion  154  without the first end  152  being flush with the top platform  108 . Each main body portion  154  is substantially convex, extending upward from the first end  152 , towards the top member  105   c , and downward from an apex  155  (of the main body portion  154 ) proximate the top member  105   c , towards the second end  153 . 
         [0031]    Each segment  151  includes a reflective surface formed on one or both sides, or coupled thereto, for reflecting light generated by the LEDs  115  located proximate the first end  152  of the segment  151 . In particular, segment  151   a  reflects light generated by the LEDs  115  coupled to the first side end  105   a , and segment  151   b  reflects light generated by the LEDs  115  coupled to the second side end  105   b . Alternatively, segment  151   a  can reflect light generated by the LEDs  115  coupled to the second side end  105   b , and segment  151   b  can reflect light generated by the LEDs  115  coupled to the first side end  105   a . The reflected light travels downward from the reflector  150 , between the bottom members  105   d . Thus, the troffer  100  indirectly emits light generated by the LEDs  115  into an environment beneath the troffer  100 . Because the light generated by the LEDs  115  is indirectly emitted into the environment, via the reflector  150 , the light emitted by the troffer  100  has reduced glare and better cut-off compared to traditional LED troffers that directly emit light from shallowly-recessed LEDs. In certain exemplary embodiments, the bottom members  105   d  block light from traveling directly from the LEDs  115  to the environment, providing additional protection from glare as well as enhanced cut-off. In certain alternative exemplary embodiments, one or both of the side ends  105   a  and  105   b , and/or the LEDs  115  coupled thereto, can be angled relative to the top end  105   c  to help enhance cut-off. 
         [0032]    In certain exemplary embodiments, a lens  170  extends between the bottom members  105   d , filling at least a portion of the aperture  106 . The lens  170  includes an optically transmissive or clear, refractive or non-refractive material (not shown) that provides environmental protection for the LEDs  115  and other internal components of the troffer  100  while also transmitting light from the LEDs  115  into the environment. The lens  170  may not be included in certain alternative exemplary embodiments. 
         [0033]    Although specific embodiments of the invention have been described above in detail, the description is merely for purposes of illustration. It should be appreciated, therefore, that many aspects of the invention were described above by way of example only and are not intended as required or essential elements of the invention unless explicitly stated otherwise. Various modifications of, and equivalent steps corresponding to, the disclosed aspects of the exemplary embodiments, in addition to those described above, can be made by a person of ordinary skill in the art, having the benefit of this disclosure, without departing from the spirit and scope of the invention defined in the following claims, the scope of which is to be accorded the broadest interpretation so as to encompass such modifications and equivalent structures.