Abstract:
A lighting fixture including a light-emitting arrangement having first and second ends. The light-emitting arrangement includes (a) at least one LED at the first end and (b) a heat sink connected to the at least one LED and having a length extending therefrom toward the second end. There are LED power circuitry components spaced from the light-emitting arrangement and positioned adjacent the second end of the light-emitting arrangement. The fixture includes an elongate tubular channel formed along the length of the heat sink and having wiring therein from the power-circuitry components to the LED(s).

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation of patent application Ser. No. 13/101,711, filed May 5, 2011, the entirety of the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to lighting fixtures and, more particularly, to fixtures using LEDs. 
       BACKGROUND OF THE INVENTION 
       [0003]    In recent years, the use of light-emitting diodes (LEDs) for various common lighting purposes has increased, and this trend has accelerated as advances have been made in LEDs and in LED-array bearing devices. Indeed, lighting applications which have been served by fixtures using high-intensity discharge (HID) lamps and other light sources are now increasingly beginning to be served by LEDs. Such lighting applications include many types of outdoor and indoor lighting, including roadway lighting, parking-lot lighting, factory lighting and recessed lighting. Creative work continues in the field of LED-lighting development, and also in the field of using LEDs for light fixtures in various applications, which increasingly extends to interior lighting, including high-ceiling surface lighting. It is the latter field to which this invention relates. 
         [0004]    Lighting fixtures using LEDs as light source for various applications present particularly challenging problems in fixture development. Heat dissipation is one of the major problems that needs to be solved in LED light fixture. 
         [0005]    Lighting-fixture adaptability is also an important goal for LED light that are often presented and mounted in different areas with broad spectrum of lighting requirements and with varying mounting ways. 
         [0006]    In short, there is a significant need in the lighting industry for improved lighting fixtures using LEDs—fixtures that are adaptable for a wide variety of mountings and situations, and that satisfy the problems associated with heat dissipation. 
       OBJECTS OF THE INVENTION 
       [0007]    It is an object of the invention to provide an improved lighting fixture that overcomes some of the problems and shortcomings of the prior art, including those referred to above. 
         [0008]    Another object of the invention is to provide an improved lighting fixture that is readily adaptable for a variety of mounting positions and situations. 
         [0009]    Another object of the invention is to provide an improved LED-lighting fixture an excellent heat dissipation. 
         [0010]    Still another object of the invention is to provide a ceiling fixture mounting assembly configured for easy and convenient installation and performance of routine maintenance of the fixture. 
         [0011]    How these and other objects are accomplished will become apparent from the following descriptions and the drawings. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention is an improvement in LED lighting fixtures. The inventive lighting fixture includes a housing having an inner surface and open first and second ends formed by closed-perimeter first and second edges, respectively, and defining an elongate top-to-bottom open space. The first end forms a light opening. A light-emitting arrangement is positioned in the open space. The arrangement includes (a) at least one light emitter positioned for directing light toward the light opening and (b) a heat sink connected to the light emitter(s). The heat sink preferably has a plurality of heat-dissipation surfaces extending away from the light opening. The heat sink is configured and positioned in the open space to facilitate fluid-flow therealong and through the open space. 
         [0013]    It is highly preferred that the heat sink is so positioned and arranged in the open space to permit constant air circulation through the heat sink More specifically, cool air from outside the fixture enters the open space through the light opening. When the cool air is heated while flowing through the heat sink, it turns into hot air which raises up through the open top. The rising hot air removes heat from the heat sink and creates a vacuum which draws fresh cool air from outside the fixture into the light opening for flow through the heat sink. Such air circulation can occur indoor and outdoor. 
         [0014]    The housing is configured to have substantially congruent cross-sections along substantially its entire length. In some embodiments, the housing is a cylindrical structure which, when hung vertically, has substantially vertical wall surrounding the open space. In some embodiments, the housing has a right cylindrical shape which has a surface generated by a straight line moving substantially parallel to the centerline along a full annular path, regardless of its shape. A preferred right cylindrical shape is generated by a substantially circular path of line movement, and most preferably is a surface which is coaxial with the centerline. 
         [0015]    The open space has a centerline and the heat-dissipating surfaces are fins extending away from the centerline. The fins may extend radially away from the centerline. In some embodiments, the fins extend away from the centerline to terminate in distal edges spaced from the inner surface of the housing. 
         [0016]    In some other embodiments, the fins extend away from the centerline to terminate in distal edges at the inner surface of the housing. In such embodiments, the light-emitting arrangement is substantially stabilized on the centerline. In some of such embodiments, there is only a set of fins of greater cross-dimension positioning their distal edges at the inner surface of the housing to hold the light-emitting assembly substantially on the centerline. Such set of fins with greater cross-dimension divide the open space into separate chimneys. 
         [0017]    In some alternative embodiments, a centerer holds the light-emitting arrangement substantially on the centerline, thereby facilitating fluid-flow along the heat sink and through the open space. In such embodiments, the light-emitting arrangement is substantially free of contact with the inner surface of housing. The centerer is disposed between the light-emitting arrangement and the housing. 
         [0018]    The centerer may include at least one bracket that is secured to the light-emitting arrangement. Such bracket preferably has a mounting portion secured to the light-emitting arrangement and at least one leg portion extending from the mounting portion to a free end at the inner surface of the housing. The centerer may further include a bumper secured to the free end of each leg portion. The bumper is preferably made of a polymeric or other suitable material reducing rattling sound in the fixture. 
         [0019]    In preferred embodiments, the at least one light emitter includes an LED. The light emitter may be an LED-array module. The heat sink preferably includes a module-supporting portion with the LED-array module secured thereagainst and the heat-dissipation surface(s) extending from the module-supporting portion. 
         [0020]    It is preferred that the LED-array module is recessed from the light opening. An inner wall preferably extends concentrically with the housing inner surface from the LED-array module to the light opening to form with the housing a venting gap permitting fluid-flow therethrough. The fixture preferably includes an end-portion secured to the inner wall interior and defining the light opening. 
         [0021]    The LEDs are preferably mounted on a mounting board in a known manner. The mounting board preferably is a circuit board of a type known in the art, including those manufactured by Philips, Cree, Bridgelux, etc. The circuit board is preferably secured against the heat sink for dissipating heat produced by LEDs during operation. An LED emitter may be in a form of an “LED package,”—a term known in the industry, or any other form providing LED-emitted light. Some examples of LED packages have one or multiple number of light-emitting diodes on a base. Such multiple diodes may emit light with the same wave length which produce a common-color light. Alternatively, multiple diodes may emit light of different waive lengths thus different colors which may me blended to achieve a desired-color light. Persons skilled in the art would appreciate a broad variety of available LED emitters. 
         [0022]    Term “centerline,” as used with reference to the open space, means a line that indicates a center of at least one lateral dimension. For example, the fixture may have the open space and/or the light opening which are symmetrical along only one of its lateral dimension. In such example, the centerline will be along the axis of such symmetry. Alternatively, the housing may define an open space and/or a light opening having asymmetrical shape. In such case, the centerline will be situated along approximate center of such shape; and the emitter that is off-centerline is preferably in a farthest available position from such approximate center. The term “centerline” is in no way limiting the configuration of the housing or the light opening to any particular shape. 
         [0023]    Each LED emitter defines an emitter axis. In preferred embodiments, the light-emitting arrangement includes a lens for each emitter at least one of which is off-centerline in a first lateral direction and has its associated lens configured for distribution of the emitter light in off-axial direction across the open space and passing through the opening at the end-portion that is off-centerline in the opposite lateral direction. Such off-axial light distribution widens the illumination angle from the fixture while having no more than minimal light directed onto the end-portion. 
         [0024]    It is preferred that the mounting board is substantially planar. The mounting board preferably has a peripheral region surrounding a non-peripheral region. In such embodiments, the emitter(s) with the lens(es) configured for off-axial light distribution is/are on the peripheral region and at least one other emitter is on the non-peripheral region. The emitter on the non-peripheral region may have its associated lens configured for axial light distribution from the emitter with no more than minimal light directed onto the end-portion. The peripheral region preferably has a shape concentric with the opening. 
         [0025]    It should also be understood that some embodiments of the present invention, which have fewer LEDs for a lower light output, may include only emitters with lenses configured for off-axial light distribution. 
         [0026]    The off-axial light distribution, which allows a great widening of an angle at which LED-emitted light exits the fixture, is achieved with LED lenses specifically designed for directing mostly all of light from a selected emitter off-axially. In an example of such lens, the lens surfaces provides a total internal reflection (TIR) allowing a minimal loss of light. An example of the lenses that may be used to achieve such wide light distribution are described in U.S. patent application Ser. No. 12/173,721 filed on Jul. 15, 2008, the entire contents of which are incorporated herein by reference. 
         [0027]    Preferred embodiments of the inventive lighting fixture include an enclosure forming a substantially closed chamber. 
         [0028]    The enclosure may be positioned within the open space. It is highly preferred that such enclosure have a cross dimension which is smaller than the cross dimension of the open space therealong, thereby allowing fluid-flow within the open space and past the enclosure. 
         [0029]    The enclosure within the open space may be positioned at the open second end of the housing. Such enclosure preferably has a cover which includes outwardly-extending mounting portions securing the enclosure to the housing while maintaining an open gap for fluid-flow thereabout to and from the open space. It is preferred that the light-emitting arrangement be secured with respect to the enclosure. 
         [0030]    An LED driver is preferably within the chamber and electrically connected to the LED(s). 
         [0031]    Depending on the fixture positioning and mounting configuration, the enclosure may be positioned substantially in the middle of the fixture. In such embodiments, two light-emitting arrangements may be positioned at both first and second open ends of the housing forming two respective light openings. Both light-emitting arrangements are preferably electrically connected to LED-driver(s) within the enclosure. Such fixture provides in two opposite directions such as light up and down. 
         [0032]    The heat sink is preferably secured with respect to the enclosure. Such embodiments preferably include a connector securing the heat sink in spaced relation with respect to the enclosure. 
         [0033]    For a given longitudinal housing dimension, the connector has a length chosen according to the longitudinal dimension of the heat sink that is required to accommodate necessary heat dissipation. This allows light-output adjustment of the lighting fixture without varying the longitudinal housing dimension. 
         [0034]    For example, some fixture applications may have less-lighting requirement achievable with fewer LEDs. Low number of LEDs may produce a lower heat load such that a shorter heat sink may be sufficient and more economical. However, while only a few LEDs may be sufficient to satisfy lighting requirements, it may still be desirable to have the same overall look and dimensioning as those of fixtures with a greater number of LEDs and a longer heat sink. 
         [0035]    It is preferred that the enclosure be preferably spaced away from the LED(s). The heat sink preferably forms a closed through channel providing a wire passage from the LED driver(s) to the LED(s). The heat sink may include a stem with the heat-dissipation surfaces extending therefrom. The heat-sink stem preferably includes the channel passing wires therethrough. The heat-sink stem preferably extends along the centerline. The heat-dissipation surfaces are preferably continuous-wall fins extending away from the stem. 
         [0036]    The inventive light fixture may be adapted for several mounting ways. One such way is mounting to a vertical wall with a side arm or bracket. Another way is a pendant suspension from an overhead surface or structure utilizing a cable. Such pendant mounting allows for straight vertical suspension from inclined overhead surfaces or structures. And yet another mounting way is direct mounting of the fixture to an overhead structure or surface. 
         [0037]    Another aspect of this invention is an assembly for mounting a fixture to an overhead surface. The inventive mounting arrangement significantly simplifies installation of the fixture in a suspended orientation with respect to a ceiling or other overhead structure. The inventive mounting arrangement permits such installation be performed by one person alone. 
         [0038]    This is a great improvement to prior mounting arrangements which required at least two people for an installation of a single fixture. Such prior arrangements included several upwardly-positioned fasteners which needed to be tightened in a small space between a top of the fixture and the overhead surface. This required one person holding the fixture and at least one other person tightening the fasteners by using special tools which permit limited substantially-horizontal rotation for tightening vertically-oriented screws. Moreover, this very tedious and time-consuming operation has to be performed at great heights. 
         [0039]    The inventive assembly includes a top member adapted for mounting with respect to the overhead surface. It is preferred that the top member include a substantially vertical wall defining a mounting way receiving a fastener therein. 
         [0040]    The mounting way preferably has an open lower end an upward way-portion extending from the open lower end. A lateral way-portion extends laterally from the upward way-portion and terminates at a closed end. 
         [0041]    The fastener includes a fastener head on a shaft extending substantially horizontally from the fixture. The substantially-horizontal orientation of the fastener facilitates its tightening in small spaces between the fixture top and the overhead surface. The fastener preferably has a tapered threaded shank and a slotted head having a cruciform into which a screwdriver with a cruciform point fits. Such fastener is known as Philips™ screw. 
         [0042]    The fixture is mounted to the overhead surface or structure by mounting the top member with respect to the overhead structure. The fixture is positioned to align the fastener with the open end of the mounting way and then lifted to slide the fastener up the upward way-portion and continue sliding the fastener laterally along the lateral way-portion to the closed end thereof. Once the fastener is at the closed end, the fastener is tightened toward the fixture for firm and secure engagement therebetween. 
         [0043]    The closed end of the mounting way is sized larger than a vertical cross-dimension of the lateral way-portion and smaller than the fastener head. When the fastener is tightened, the closed end receives the fastener head which is larger than the vertical cross-dimension of the lateral way-portion. The fastener head of the tightened fastener is, therefore, stopped from sliding back along the lateral way-portion, thereby holding the top member in fixed position against the fixture. To remove the fixture, the fastener just needs to be loosened enough to remove the fastener head from the closed end to slide the fastener shank back laterally through the mounting way and down and out the open end. 
         [0044]    The fixture includes a substantially-horizontal top surface and a mounting wall extending upwardly from the top surface. The fastener extends substantially horizontally from the upwardly-extending mounting wall. The top-member vertical wall has a lower end which is positioned at the fixture top surface. 
         [0045]    The inventive mounting assembly further includes a resilient member between the fixture top surface and the top-member lower end. The fastener and the lateral way-portion are each positioned at substantially equal distances from the fixture top surface and the top-member lower end, respectively. During installation, the resilient member is compressed to permit sliding of the fastener along the lateral way-portion. When released, the resilient member forces the fastener shaft against an upper edge of the lateral way-portion. 
         [0046]    The top member includes a topwall configured for mounting to the overhead surface and a surrounding sidewall extending downwardly from the topwall. The surrounding sidewall includes an outward flange at the fixture to surface. The surrounding sidewall includes the vertical wall defining the mounting way. 
         [0047]    The resilient member is preferably a gasket positioned between the top-member outward flange and the fixture top surface. 
         [0048]    The mounting wall further preferably includes a securing slot extending between an open edge and a closed slot-end spaced laterally away from the fastener. 
         [0049]    The top member includes a securing protrusion extending inwardly from the sidewall inner surface. The securing protrusion is positioned such that it is engaged by the securing slot of the mounting wall when the fastener is slid to the closed end of the mounting way. 
         [0050]    In some preferred embodiments, the fixture includes at least a pair of spaced securing slots. And the top member includes a pair of spaced securing protrusions extending inwardly from the sidewall of the top member. Each securing protrusion is positioned to be engaged by the corresponding one of the securing slots. 
         [0051]    The mounting wall preferably includes a foot portion affixed to the fixture top surface and an upright portion. The fastener extends from the upright portion. The fixture preferably includes a pair of free-standing spaced apart upward securing walls each spaced from the mounting wall. Each securing wall includes a foot portion affixed to the fixture top surface and an upright slotted portion which includes the securing slot. 
         [0052]    Therefore, to mount the fixture to the overhead surface or structure, the fixture is positioned to align the fastener with the open end of the mounting way and then lifted to slide the fastener up the upward way-portion. The resilient member is compressed to permit sliding of the fastener along the lateral way-portion to the closed end thereof. While rotating the fixture to slide the fastener along the mounting way, simultaneously the securing slots rotate with the fixture and engage the securing protrusions of the top member. The mounting is completed by releasing the resilient member to force the fastener shaft against the edge of the closed end and tightening the fastener in the closed end such that the fastener head is recessed with respect to the lateral way-portion preventing any sliding back. 
         [0053]    For most heat dissipation, it is preferred that substantially all parts of the fixture are made of aluminum. The top member bears the entire weight of the fixture and, therefore, is required to have greater strength. The top member is preferably made of steel that allows top-member wall be relatively thin while providing necessary strength. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0054]      FIG. 1  is a top perspective view of a lighting fixture in accordance with this invention. 
           [0055]      FIG. 2  is a bottom perspective view of the lighting fixture of  FIG. 1 . 
           [0056]      FIG. 3  is a top plan view of the inventive lighting fixture. 
           [0057]      FIG. 4  is a bottom plan view of the inventive lighting fixture. 
           [0058]      FIG. 5  is a cross-sectional view of the lighting fixture, as indicated in  FIG. 3 . 
           [0059]      FIG. 6  is another cross-sectional view of the lighting fixture, as indicated in  FIG. 3 . 
           [0060]      FIG. 7  is a perspective view of a light-emitting assembly. 
           [0061]      FIG. 8  is a perspective view of the light-emitting assembly secured with respect to a chamber enclosure and having an inner wall secured to the assembly. 
           [0062]      FIG. 9  is a fragmentary perspective view showing connection between the light-emitting arrangement and a chamber enclosure. 
           [0063]      FIGS. 10 and 11  are fragmentary perspective views of the lighting fixture showing an inventive mounting arrangement with the fastener being sled along the mounting way. 
           [0064]      FIG. 12  is a fragmentary perspective view showing the fastener extending from a mounting wall on a top surface of the fixture. 
           [0065]      FIG. 13  is a fragmentary perspective view showing the top surface of the fixture with the mounting wall and a pair of securing walls extending therefrom. 
           [0066]      FIG. 14  is a perspective view of an interior of a top member with a resilient gasket secured thereto. 
           [0067]      FIG. 15  is a fragmentary perspective view of the lighting fixture showing an inventive mounting arrangement prior to fastener entering a mounting way. 
           [0068]      FIG. 16  is a schematic side view of an LED module having distribution of light in off-axial and axial direction with respect to each emitter axis by corresponding LED lenses. 
           [0069]      FIG. 17  is a top plan view of an embodiment with fin edges at the inner surface of the housing. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0070]      FIGS. 1-15  illustrate preferred embodiments of the inventive lighting fixture  10  which includes a housing  20  having an inner surface  23 , an open first end  21  and an open second end  22  each formed by a closed-perimeter first and second edges  210  and  220 , respectively. As best seen in  FIGS. 4 and 6 , housing  20  defines an end-to-end or top-to-bottom open space  12 . The open space of the preferred embodiment shown in the figures has an elongate configuration. As seen in FIGS.  2  and  4 - 6 , first end  21  forms a light opening  13 . A light-emitting arrangement  30  is positioned within open space  12 . Arrangement  30  includes (a) at least one light emitter  31  positioned for directing light toward light opening  13  and (b) a heat sink  40  connected to light emitters  31 .  FIGS. 7 and 8  best show heat sink  40  having a plurality of heat-dissipation surfaces  41  which extend away from light opening  13 . As seen in  FIGS. 3-6 , heat sink  40  is configured and positioned in open space  12  to facilitate fluid-flow therealong and through open space  12 .  FIG. 5  illustrates circulation of air  2  through open space  12  and along heat sink  40 . 
         [0071]    Housing  20  illustrated in  FIGS. 1-6  is a cylindrical structure which, when hung vertically, has substantially vertical wall  25  surrounding open space  12 . Edge  21  is shown as having edge  210  curled inwardly for finished appearance. 
         [0072]    Open space  12  has a centerline  14  (shown in  FIG. 5 ) and heat-dissipating surfaces  41  are fins  410  extending away from centerline  14 .  FIGS. 3 ,  4 ,  7  and  8  show fins  410  extending radially away from centerline  14 . In an embodiment illustrated in  FIGS. 3-6 , fins  410  extend away from centerline  14  to terminate in distal edges  43  spaced from inner surface  23  of housing  20 . 
         [0073]      FIG. 17  shows an embodiment of lighting fixture  10  including heat sink  40 C which has fins  410  extending away from centerline  14  to terminate in distal edges  43  at inner surface  23  of housing  20 . It is seen in  FIG. 17  that light-emitting arrangement  30  is substantially stabilized on centerline  14 . 
         [0074]      FIGS. 3 ,  5 ,  6  and  8  show a centerer  50  which holds light-emitting arrangement  30  substantially on centerline  14 . Such centering of light-emitting arrangement  30  facilitates fluid-flow along heat sink  40  and through open space  12 .  FIGS. 5 and 6  show light-emitting arrangement  30  substantially free of contact with inner surface  23  of housing  20 . It is further seen in  FIGS. 3 ,  5  and  6  that centerer  50  is disposed between light-emitting arrangement  30  and housing  20 . 
         [0075]    Centerer  50 , as best seen in  FIGS. 3 and 8 , includes brackets  51  each secured with respect to light-emitting arrangement  30 . Each bracket  51  has a mounting portion  52  secured at light-emitting arrangement  30  and at least one leg portion  53  extending from mounting portion  52  to a free end  54  at inner surface  23  of housing  20 . It is further seen in  FIGS. 3 ,  5 ,  6  and  8  that centerer  50  includes a bumper  55  secured to free end  54  of each leg portion  53 . 
         [0076]      FIG. 7  illustrates that light emitter  31  includes an LED  32 .  FIGS. 4 and 7  further show that light emitter  31  is an LED-array module  33 . It is best seen in  FIGS. 5-7  that heat sink  40  includes a module-supporting portion  44  with LED-array module  33  secured against such portion  44 . Heat-dissipation surface(s)  41  extend from module-supporting portion  44 . 
         [0077]    In fixture  10 , as illustrated in  FIGS. 2 ,  5 ,  6 ,  8  and  15 , LED-array module  33  is recessed from light opening  13 .  FIGS. 5 and 6  show an inner wall  15  extending concentrically with housing inner surface  23  from LED-array module  33  to light opening  13 .  FIGS. 5 and 6  further show that inner wall  15  forms with housing  20  a venting gap  16  permitting fluid-flow therethrough. As best seen in  FIGS. 5 and 6 , fixture  10  further includes an end-portion  17  secured within interior of inner wall  15  and surrounding light opening  13 . 
         [0078]      FIG. 7  illustrates that LEDs  32  are mounted on a mounting board  34  which is a circuit board of a type known in the art. Mounting board  34  is secured against heat sink  40  for dissipating heat produced by LEDs  32  during operation. 
         [0079]      FIG. 16  shows emitter axis  35  for each LED emitter  32 .  FIG. 16  further schematically illustrates light-emitting arrangement as including a lens  36  for each LED emitter  32 . One emitter  31  is off-centerline in a first lateral direction and has its associated lens  36 A configured for distribution of the emitter light  37 A in off-axial direction across the lateral dimension of the space between LED emitter  32  and light opening  13  and passing through opening  13  at end-portion  17  that is off-centerline in the opposite lateral direction. Such off-axial light distribution widens the illumination angle  38  from fixture  10  while having no more than minimal light directed onto end-portion  17 . 
         [0080]      FIGS. 5 ,  6  and  8  show lighting fixture  10  including an enclosure  60  forming a substantially closed chamber  61 . As best seen in  FIGS. 5 and 6 , enclosure  60  is positioned within open space  12  and has a cross dimension  62  which is smaller than corresponding cross dimension  120  of open space  12 . Such dimensioning allows fluid-flow within open space  12  and past enclosure  60 . 
         [0081]    An LED driver  11  is preferably within chamber  61  and electrically connected to LEDs  32 . 
         [0082]      FIGS. 5 and 6  illustrate enclosure  60  at open second end  22  of housing  20 . Enclosure  60  has a cover  63  (best seen in  FIGS. 1 ,  3  and  6 ). Cover  63  includes outwardly-extending mounting portions  64  which secure enclosure  60  to housing  20  while maintaining an open gap  18  for fluid-flow about cover  63  to and from open space  12 . 
         [0083]    As seen in  FIGS. 5 ,  6  and  8 , light-emitting arrangement  30  is secured with respect to enclosure  60 .  FIGS. 5 and 6  best show that heat sink  40  is secured with respect to enclosure  60  and that a connector  19  secures heat sink  40  in spaced relation with respect to enclosure  60 . 
         [0084]      FIGS. 7 and 8  illustrate heat sink  40 A and  40 B having different longitudinal dimension  45  (shown in  FIG. 6 ) that selected to accommodate necessary heat dissipation for a different number of LEDs.  FIG. 7  shows light-emitting arrangement  30 A which includes LED-array module  33 A with fewer LEDs than LED-array module  33 B shown in  FIG. 4  and, therefore, heat sink  40 A with longitudinal dimension  45  shorter than that of heat sink  40 B shown in  FIGS. 5 ,  6  and  8 . 
         [0085]    To accommodate a constant overall look and dimensioning of fixture  10  regardless of the number of LEDs and the dimensions of heat sink  40 , connector  19  for light-emitting arrangement  30 A has a length  190  chosen according to the longitudinal dimension  45  of heat sink  40 A and which is longer than for connector  19  for light-emitting arrangement  30 B with a greater number of LEDs  32  and longer heat sink  40 B. This allows light-output adjustment of lighting fixture  10  without varying the longitudinal dimension of housing  20 . 
         [0086]    As seen in  FIGS. 5 ,  6  and  9 , enclosure  60  is spaced away from the LEDs  32 .  FIGS. 5 and 6  show heat sink  40  forming a closed through channel  46  providing a wire passage from LED drivers  11  to LEDs  32 . Heat sink  40  includes a stem  47  with heat-dissipation surfaces  41  extending from stem  47 . It is seen in  FIGS. 5 and 6  that heat-sink stem  47  includes channel  46  passing wires  39  therethrough. As further seen in  FIGS. 5 and 6 , heat-sink stem  47  extends along centerline  14 . Heat-dissipation surfaces  41  show in  FIGS. 5-8  are continuous-wall fins  410  extending away from stem  47 . 
         [0087]      FIGS. 10-15  illustrate an assembly for mounting fixture  10  to an overhead surface  1 . The assembly includes a top member  70  adapted for mounting with respect to overhead surface  1 . As seen in  FIGS. 1 ,  3 ,  5 ,  6 ,  14  and  17 , the top member includes a topwall  71  and a surrounding substantially vertical sidewall  73  which extends downwardly from topwall  71  and defines a mounting way  80  receiving a fastener  81  therein. 
         [0088]    Mounting way  80 , which is best seen in  FIGS. 1 ,  10 ,  11 ,  14  and  15 , has an open lower end  82  and an upward way-portion  83  extending from open lower end  82 . A lateral way-portion  84  extends laterally from upward way-portion  83  and terminates at a closed end  85 . 
         [0089]    Fastener  81 , which is best seen in  FIGS. 12 ,  13  and  15 , includes a fastener head  811  on a shaft  812  extending substantially horizontally from fixture  10 . It is further seen in these FIGURES that fastener  81  has a tapered threaded shank.  FIGS. 10 and 11  further show that fastener head  811  is a slotted head having a cruciform into which a screwdriver with a cruciform point fits. Such fastener is known as Philips™ screw. 
         [0090]    Fixture  10  is mounted to overhead surface  1  by mounting top member  70  with respect to overhead surface  1 . Topwall  71  of top member  70  defines key-hole shaped apertures  72  dimensioned to accept screws secured to overhead surface  1 . Therefore, top member  70  is mounted to overhead surface  1  with screws tightened through smaller part of key-hole apertures. Such mounting provides for easy removal of top member to overhead surface  1  by simply loosening the screws and twisting top member  70  to release the screws through the larger part of key-hole shaped apertures  72 . Top member  70  can be easily re-attached to overhead surface  1  by lifting top member  70  to insert the screws into larger parts of each aperture  72 , then twisting top member  70  to position each crew at the smaller end of each corresponding key-hole shaped aperture  72 , thus have top member preliminary supported on screw heads, and securing top member  70  to overhead surface  1  by tightening the screws. Such operation can be clearly performed by one person alone which makes the fixture installation faster and less expensive. 
         [0091]    Once top member  70  is secured to overhead surface  1 , fixture  10  is positioned to align fastener  81  with open end  82  of mounting way  80 . Fixture  10  is then lifted to slide fastener  81  up through upward way-portion  83  and continue laterally along lateral way-portion  84  to closed end  85 . With fastener  81  at closed end  85 , fastener  81  is tightened for firm and secure engagement between top member  70  and fixture  10 . 
         [0092]    As seen in  FIGS. 10 ,  11 ,  14  and  15 , closed end  85  of mounting way  80  is sized larger than a vertical cross-dimension of lateral way-portion  84  and smaller than fastener head  811 . When fastener  81  is tightened, fastener head  811  is received in closed end  85  which is larger than the vertical cross-dimension of lateral way-portion  84 . Fastener head  811  of tightened fastener  81  is, therefore, stopped from sliding back along lateral way-portion  84 , thereby holding fixture  10  in fixed position against top member  70 . To remove fixture  10 , one person alone can loosen fastener  81  just enough to remove fastener head  81  from closed end  85  to slide fastener shaft  812  back laterally through mounting way  80  and down and out through open end  82 . 
         [0093]      FIGS. 12 ,  13  and  15  best illustrate that fixture  10  includes a substantially-horizontal top surface  65  and a mounting wall  66  extending upwardly from top surface  65 . These FIGURES illustrate top surface  65  as an exterior surface of cover  63  of enclosure  60 . Fastener  81  extends substantially horizontally from upwardly-extending mounting wall  66 . 
         [0094]    Vertical sidewall  73  of top member  70  has a lower end  74  which is positioned at top surface  65 . Surrounding sidewall  73  further includes an outward flange  76  at top surface  65 . 
         [0095]    The mounting assembly further includes a gasket  75  between fixture top surface  65  and lower end  74 . Gasket  75  is positioned between top-member outward flange  76  and top surface  65  of fixture  10 . 
         [0096]    Fastener  81  and lateral way-portion  84  are each positioned at substantially equal distances from top surface  65  and lower end  74 , respectively. During installation, gasket  75  is compressed to permit sliding of fastener  81  along lateral way-portion  84 . When released, gasket  75  forces fastener shaft  812  against an edge of lateral way-portion  84 . 
         [0097]    Mounting wall  66  further includes a securing slot  67  extending between an open edge  670  and a closed slot-end  671  spaced laterally away from fastener  81 . 
         [0098]      FIG. 14  shows that top member  70  includes a securing protrusion  77  extending inwardly from the inner surface of sidewall  73 . Securing protrusion  77  is positioned to be engaged by securing slot  67  of mounting wall  66  when fastener  81  is slid to closed end  85  of mounting way  80 . 
         [0099]      FIGS. 13 and 14  show that fixture  10  includes three spaced securing slots  67 . And, top member  70  includes three substantially-equally spaced protrusions  77  in the form of pins extending inwardly through sidewall  73 . Each securing protrusion  77  is positioned to be engaged by corresponding one of securing slots  67 . 
         [0100]    As best seed in  FIGS. 12 and 13 , mounting wall  66  includes a foot portion  660  affixed to top surface  65  and an upright portion  661  extending from foot portion  660 . Fastener  81  extends from upright portion  661 .  FIG. 13  illustrates that fixture  10  includes a pair of free-standing spaced-apart upward securing walls  68  each spaced from mounting wall  66 . Each securing wall  68  includes a foot portion  680  affixed to top surface  65  and an upright slotted portion  681  which includes securing slot  67 . 
         [0101]    Therefore, to mount fixture  10  to overhead surface  1 , fixture  10  is positioned at top member  70  secured to overhead surface  1 . Fastener  81  is aligned with open end  82  of mounting way  80 . Fixture  10  is then lifted to slide fastener  81  up along upward way-portion  83 . Resilient gasket  75  is compressed to permit sliding of fastener  81  along lateral way-portion  84  to closed end  85  thereof. While rotating fixture  10  to slide fastener  81  along mounting way  80 , securing slots  67  rotate with fixture  10  and engage securing protrusions  77  of top member  70 . The mounting is completed by releasing resilient member  75  to force fastener shaft  812  against the edge of closed end  85  and tightening fastener  81  such that fastener head  811  is recessed with respect to lateral way-portion  84  preventing any sliding back. 
         [0102]    A seen in  FIGS. 1 ,  10 ,  11  and  15 , top member  70  forms an enclosure for electrical leads  69  extending from chamber  61 . Topwall  71  of top member  70  further defines an aperture  710  for passing a security cable therethrough. 
         [0103]    While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.