Abstract:
An LED light fixture has an extruded base housing element defining an opening which is removably bridged by a metal heat sink to which is mounted at least one LED. A plastic cover lens has deflectable legs with axial concave elements which engage with outwardly facing convex elements on cover mount members which protrude from the heat sink on either side of the LED. The LED power supply may be supported in a compartment above the heat sink. The cover lens has a wrap-around connection to the heat sink cover mount members which is tolerant of variation in heat sink extrusion dimensions, and which is insensitive to variations in main housing element dimensions. Alternative trim elements and cover lenses allow field configuration of the fixture to various applications.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to light fixtures in general, and more particularly to light fixtures involving light emitting diodes (LEDs). 
     LED light sources offer significant advantages over incandescent lights in terms of energy efficiency and useful lifetime. The LEDs can be provided in continuous strips of diodes which enable mounting within compact light fixtures which may be utilized in a wide range of applications. LED performance is temperature dependent, and can suffer at elevated temperatures. LED light fixtures thus often make use of passive heat sinks to dissipate the heat generated internally. Because the strip of individual LEDs which serves as the LED fixture&#39;s light source is comprised of multiple point sources, the fixture is commonly provided with an extruded plastic diffuser or cover lens which attaches to an extruded aluminum housing which holds the LED strip. Sometimes the housing itself acts as the heat sink for the LEDs. 
     Retention of the cover lens in place on the fixture is an important aspect of an LED light fixture. If the cover lens is too loose, it runs the risk of separating from the light fixture, often located overhead. If it is too tight, it can be difficult to remove for servicing. Many LED fixtures with extruded housings attach the cover lens by disposing outwardly extending portions of deflectable legs of the cover lens within inwardly facing slots or grooves of the main housing. However, with the typical tolerances of extrusion manufacture, if this connection is not tight enough, the cover lenses can fall off the fixtures. Moreover, because forces are applied to the housing itself when the cover lens is removed or reinstalled during service, this lateral movement on the main housing risks cracking in the drywall within which a fixture is mounted, especially where the fixture is mudded in place. 
     Furthermore, light fixtures can be mounted in many fashions, flush to the surface of a wall ceiling or floor, in hung ceilings or drywall ceilings, suspended, mounted to project from a wall or ceiling, for downlighting, uplighting, or wash lighting, and in other fashions. Minimizing the number of distinct parts to accommodate all these options is an important objective. In addition, construction projects are often subject to change, and pose a logistical challenge to fixture suppliers to provide light fixtures of the right type and size to suit the needs of the moment. 
     What is needed is an LED light fixture that securely retains its cover lens while permitting convenient servicing with little risk of cracking drywall installations, and which has wide variability of installation mode with a minimum of parts. 
     SUMMARY OF THE INVENTION 
     The LED light fixture of the present invention provides a heat sink which bridges an opening in a base housing element and which is removably fastened to the housing element to control the spacing of the base housing element&#39;s side members. A plastic cover lens has deflectable legs with axial concave elements which engage with outwardly facing convex elements on cover mount members which protrude from the heat sink on either side of the LED strips. The LED power supply may be supported in a compartment above the heat sink. The cover lens thus has a wrap-around connection to the heat sink cover mount members which is tolerant of some variation in heat sink extrusion dimensions, and which is totally insensitive to variations in main housing element dimensions. The main housing element accepts various trim pieces, and the heat sink accepts a variety of lenses and lens covers which are interchangeable in the field, even after the main housing element has already been installed. End caps are provided which allow finished fixtures of any desired length to be readily formed in the field by cutting to length the base housing element and cover lenses. 
     It is an object of the present invention to provide an LED light fixture having cover lenses which are securely attached yet readily removed as needed. 
     It is another object of the present invention to provide an LED light fixture which can be readily configured in the field for different lighting applications. 
     Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an end view of an LED light fixture of this invention. 
         FIG. 2  is an end view of a heat sink of the fixture of  FIG. 1 , with LEDs mounted thereto, and various lens options over the LEDs. 
         FIG. 3  is an end view of a flush cover lens for use in an LED fixture of this invention. 
         FIG. 4  is an end view of a drop cover lens for use in an LED fixture of this invention. 
         FIG. 5  is an end view of a flanged trim piece for use in an LED fixture of this invention. 
         FIG. 6  is an end view of a mud-in trim piece for use in an LED fixture of this invention. 
         FIG. 7  is a fragmentary cross-sectional view of an LED fixture of this invention installed in a drywall opening. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring more particularly to  FIGS. 1-7 , wherein like numbers refer to similar parts, an LED light fixture  20  is shown in  FIG. 1 . The fixture  20  employs a modular construction which allows it to be readily configured in the field for many alternative applications with a few alternative components. All the configurations begin with an extruded aluminum base housing element  22 . The base housing element  22  is of constant cross section and may be extruded to any desired length, and is readily cut down to size in the field to match the exact dimensions of the site where it is being installed. The base housing element  22  may be, for example, about 3 and ⅝ inches wide, and about 3 and ⅞ inches tall. 
     The base housing element has a first side member  24  which is joined to a second side member  26  by a top member  28 . A first connecting flange  30  extends inwardly from the first side member  24 , and a second connecting flange  32  extends inwardly from the second side member  26  towards the first connecting flange. The connecting flanges may be positioned about 2 and ⅜ inches from the top of the base housing element. A first opening  34  is defined between the interior margins  36  of the connecting flanges. As shown in  FIG. 2 , a heat sink  38  is formed as another extruded aluminum part with constant cross section. The heat sink  38  has a mounting segment  40  extending horizontally and an array of parallel heat radiating fins  42  that extend upwardly in the direction of the top member  28 . 
     Each connecting flange  30 ,  32  has a downwardly opening slot  44  spaced outwardly from a flange interior margin  36 . One of the heat sink fins  42  is received within each of these slots  44 , as shown in  FIG. 1 . The heat sink  38  is then releasably secured to the base housing element  22  by fasteners  46 , as shown in  FIG. 7 , which extend through the heat sink and engage within downwardly facing fastener slots  48  formed in the connecting flanges  30 ,  32 . It will be observed that the base housing element extrusion  22 , because of its larger size, is prone to dimensional variation as a consequence of the manufacturing process. In particular, the side members  24 ,  26 , which extend a significant distance from their point of connection at the top member  28 , are prone to being more or less close together at their most remote ends. The compact and smaller size of the heat sink  38  means that its side to side dimensions are better controlled. Hence, the heat sink  38 , when inserted across the first opening  34  effectively controls the spacing between the first side member  24  and the second side member  26  of the base housing element  22 . 
     With the heat sink  38  fastened in place, an interior compartment  50  is defined within the base housing element  22  between the top member  28  and the heat sink which extends for the length of the fixture  20  and which provides a volume within which to receive one or more LED power supplies  52 . The power supply  52  will usually be connected to a source of mains power (not shown), and will include an AC to DC converter so as to provide direct current power to the LEDs  54  which are the light sources of the fixture  20 . An electrical cable  123  connects the power supply to the LEDs  54 , as shown in  FIG. 1 . The cable  123  may pass through a hole drilled in the heat sink  38 . The power supply  52  may be provided with sidewardly projecting flanges  55  which overlie the fins  42  of the heat sink  38 . Fasteners  57  extend through the flanges  55  into a groove between two fins of the heat sink  38 . A flexible cable lanyard  59  is preferably secured to the assembly of the power supply  52  and the heat sink  38 . The lanyard  59  serves to retain the assembly of the power supply and the heat sink associated with the housing, to retain overhead control of the assembly, prevent it falling free of the housing when the fasteners that hold it in place are removed to permit servicing of the fixture. 
     As shown in  FIG. 2 , the LEDs  54  are preferably provided as a strip  56  of many axially aligned LEDs affixed to an axially extending substrate which is glued to the mounting segment  40  of the heat sink  38  facing downwardly. The heat sink  38  has a first cover mount member  58  and a second cover mount member  60  which extend downwardly from the mounting segment on either side of the LED strip  56 . Multiple LED strips  56  may be provided, each in a channel  62  separated from the others by intermediate walls  64 . As shown in  FIGS. 2 and 7 , each cover mount member  58 ,  60  has a downwardly extending leg  66  and a foot  68  which extends sidewardly from the leg, such that the feet project away from one another. Each foot has a sidewardly protruding convex element  69 , preferably a portion of a cylinder, for example about 270 degrees of a narrow cylinder. 
     The cover mount members  58 ,  60  engage with a plastic cover lens  70  to retain it securely but releasably to the heat sink  38 . The cover lens  70  has a lens element  72  which allows light from the LEDs to escape the fixture. The cover lens  70  may be transparent, frosted, or colored and may serve to diffuse the light of the individual LEDs. The cover lens  70  protects the LEDs from dust and environmental material, and also serves a decorative purpose as it is the appearance feature of the fixture which is chiefly visible, in particular when the LEDs are not illuminated. The cover lens  70  controls the characteristics of the light which is shed by the fixture. It may be extruded from a plastic resin which is an acrylic blend. For example, DR101, a flexible clear acrylic, may be blended with V045, an optically clear acrylic, to yield a flexible part resistant to breaking as it is bent, yet which is clear and energy efficient in transmitting emitted light, and resistant to deterioration when exposed to ultraviolet light. DR101 is a transparent high impact and heat resistant Poly(Methyl Methacrylate) Acrylic. V045 is a thermoplastic acrylic resin. 
     The fixture  20  may accommodate cover lenses of various sizes to achieve a desired surface treatment of the fixture. The shallowest cover lens  70 , shown in  FIG. 1 , is a regress cover lens, in which the lens element  72  is recessed within the fixture. A deeper cover lens is the flush cover lens  74 , shown in  FIGS. 3 and 7 , which has a flush finish, and an even deeper cover lens is the drop cover lens  76  shown in  FIG. 4 , which projects below the base housing element. 
     Because the light fixture can be as much as eight feet long, or even longer, it is important that the cover lens  70  is securely retained within the fixture, lest it fall from an overhead position. At the same time, it should be readily removed for servicing the fixture without disturbing the installation of the fixture  20 , particularly in applications where it is mudded into drywall or tile, where inordinate stress on the housing might crack or disturb the surrounding drywall or tile. The mechanism for retaining the cover lens to the heat sink is a resilient engagement between the flexible cover lens  70  and the rigid cover mount members  58 . All the cover lens embodiments  70 ,  74 ,  76  have similar attachment mechanisms although they may vary in proportions. 
     As shown in  FIG. 7 , the flush cover lens  74  has two arms  78  which extend upwardly from and are joined by the lens element  72 . It will be observed that the corners where the arms  78  join the lens element  72  preferably are advantageously free of reinforcing structural elements or outwardly projecting flanges that would cast a shadow within the lens or otherwise detract from an even illumination of the lens element  72 . Each arm  78  has a connecting member  80  which engages one of the heat sink cover mount members  58 ,  60 . The connecting member  80  may be comprised of a first flange  82  which extends inwardly from the cover arm  78  joined to an inlet ramp  84  which extends inwardly and back towards the lens element  72 , and a concave element  86  joined to the inlet ramp which opens sidewardly towards the convex element  69  of the heat sink foot  68 . The concave element  86  may preferably define a segment of a cylinder, for example somewhat less than 180 degrees, for example preferably between 102 to about 132 degrees, and most preferably about 122 degrees, that mates with the cylindrical convex portion  69  of the cover mounting foot  68 . Thus the cover lens  74  is pressed into place so that the inlet ramps  84  engage the rigid cover mount members  58 ,  60  on the heat sink, thereby deflecting the arms  78  outwardly, until the concave elements  86  of the connecting members  80  snap into place on the convex elements  69  of the cover mount members. This sideward deflection of the arms securely retains the cover lens  74  to the heat sink. Yet, the cover lens  74  is readily removed for servicing of the fixture  20 , by engaging an axial end of the cover lens  74  and pulling it downwardly. 
     Thus the heat sink cover mount members  58 ,  60  are positioned between the cover lens connecting members  80 , so the resilient cover lens arms  78  releasably urge the cover lens connecting members against the heat sink cover mount members, to engage the cover lens concave elements  86  against the heat sink foot convex elements  69 . This arrangement on the one hand has the wide length of the entire cover lens to flex, while on the other hand, is tolerant of slight variations in dimension of the heat sink  38  or the cover lens while still forming a secure connection. Moreover, the arrangement provides for significant deflection of the arms  78  and an interference or engagement between the connecting member and the cover mount member engagement of, for example, 0.080 inches. This arrangement allows the cover lens to remain securely affixed despite some variation in size of either the cover lens or the heat sink. 
     In addition to the cover lens  74 , the light of the LEDs may be conditioned by auxiliary lenses  88 , shown in  FIG. 2 . The auxiliary lenses  88  attach to the heat sink over individual LED strips within a particular channel  62  and may be clear, frosted, half-frosted, with a gel color, or other treatment to produce the desired lighting effect. Types of auxiliary lenses include a thin diffusing lens  90  and a collimating lens  92  which tightens the light beam from the LED strip. The auxiliary lenses  88  each have side ribs  94  with sidewardly disposed grooves or recesses  96  which engage with mating side ribs  98  which run the length of the channels  62  along the intermediate walls  64 . Different types of auxiliary lenses  88  may be positioned over each channel or some or all channels may be left without any auxiliary lens. The auxiliary lenses  88  may be used in conjunction with one of the cover lenses  70 ,  74 ,  76 , or they may be used without a cover lens. Fixtures with auxiliary lenses may be used for general illumination, wall grazing, wall washing, and high ceiling downlighting or combinations of these applications. 
     The different cover lenses may be used in different situations or when different effects are desired. For example the regress cover lens  70  may be used when extra glare control is needed, or simply for its distinctive appearance. The flush cover lens  74  gives a flush appearance to the fixture and works well for general illumination and wall washing. The drop cover lens  76  may be used in T-grid applications, as the lens protrudes from the fixture to more nearly match the surround ceiling tiles. The drop cover lens  76  may also be used simply for its distinctive appearance. It should be noted that the fixture may also be deployed with no cover lens whatsoever. 
     The fixture is provided with alternative trim elements which finish the appearance of the fixture on either side of the cover lens. For various appearances and applications, a customer may select a flush trim element  100 , shown in  FIG. 1 ; a flanged trim element  102 , shown in  FIGS. 5 and 7 ; or a mud-in trim element  104 , shown in  FIG. 6 . Each trim element  100 ,  102 ,  104  is an extruded aluminum part of constant cross section, generally in the shape of an L, which has an inside member  106  which extends parallel to the side members  24 ,  26  of the base housing element, and an outside member  108  which extends outwardly from the inside member. 
     The flush trim element  100  may be used for applications where the fixture does not need to overlap the surrounding surface, for example a wooden surface or a tile surface. In tile applications the fixture can be grouted in with the tile. As shown in  FIG. 1 , the lower ends of the base housing element  22  side members  24 ,  26  have downwardly facing trim slots  110  which receive a narrow positioning rib  112  which extends from the outside member  108  of the trim element  100 . The inside member  106  of the trim element extends between the base housing element side member and the heat sink  38 , and has a narrow mounting rib  114  which extends towards the heat sink. The innermost end of the inside member  106  of the trim element  100  is received within a mounting slot  116  which is formed in the underside of the connecting flange  30  of the base housing element  22 . The mounting slot  116  is parallel to the slot  44  and is spaced from it by a land  118 . The trim element  100  is removably secured to the base housing element  22  by screw fasteners  120  which engage the trim element mounting rib  114  against the land  118 . The fasteners  120  extend into the same slot  48  which receives the fasteners  46  which secure the heat sink to the base housing element flange. The trim element fasteners  120  and the heat sink fasteners  46  are thus offset axially from one another, and the fasteners for each may be spaced about 2 feet apart. It will be noted that although a pair of trim elements  100  is required to finish the opening of the base housing element  22 , the same trim element may be used as both a left hand and a right hand finish piece by rotating a trim element about a vertical axis. 
     The flanged trim element  102 , shown in  FIGS. 5 and 7 , may be used for applications where the fixture requires a flanged trim which extends outwardly to overlap the neighboring surface, for example when the neighboring surface is drywall, or where it is desired too cover a cut opening in wood or tile. The outside member  122  of the flanged trim element  102  extends outwardly beyond the side member of the base housing element. 
     The mud-in trim element  104 , shown in  FIG. 6 , has a wide but thin outside member  124  which projects beyond the side member of the base housing element and will be employed in drywall installations where the outside member  124  is covered with joint compound or drywall mud to provide a seamless connection between the drywall and the fixture. 
     As shown in  FIG. 7 , a cavity  126  is defined on the interior of each base housing element side member  24 ,  26 , running parallel to the side member and extending between an upper slot  127  and a lower slot  129 . The cavity  126  receives an optional installation aid  128  which may be used in installing assemblies of multiple fixtures  20  in tight situations. Although each fixture  20  will be supported independently, as described below, it is desirable that multiple fixtures when installed end to end be, as much as possible, flush with one another to present an uninterrupted appearance. The flush appearance may be facilitated by narrow connecting pins or rods  130  which extend through semi-cylindrical slots  132  at the lower ends of the side members  24 ,  26 , positioned above and connecting with the trim slots  110 . However, it will be observed that in a constricted installation, for example at the last fixture in a long row of fixtures in a recessed installation, there is not room to preassemble the two side by side pins and the fixture. The installation aid  128  is a narrow plate which is installed within the cavity  126  prior to inserting the fixture  20  next to an already installed fixture. The installation aid can then be gripped from beneath the two adjoining fixtures and extracted from the recess to bridge the gap between the two fixtures and urged into the neighboring cavity to hold the fixtures aligned while the rods  130  are also partially extended from one fixture to the neighboring one. 
     The base housing element  22  may be provided with corner and median screw bosses  131 , as shown in  FIG. 7 , to receive screws  134  which mount end caps  136  to give a finished end to the fixture. The end caps  136  may be provided in various sizes to neatly finish the ends of the fixture depending on which trim element is used. For example the end cap used with the flanged trim elements may have narrow projections matching the projections of the flanged trim element outside members  122 . End caps will be omitted where two fixtures are joined end to end. 
     The fixture  20  may be mounted through various conventional mounting mechanisms. As shown in  FIG. 7 , for a recessed installation, for example within a drywall ceiling, conventional galvanized steel hangers  138  may be provided in the ceiling construction, and provided with the shanks of bolt fasteners  139  extending downwardly through spaced top openings  140  in the top member  28  of the base housing element  22 . Nuts  142  are attached from the interior of the base housing element  22  which secure it to the hanger  138 . Although not illustrated, spaced cables may be secured to the top member  28  of the base housing element with interior grippers, to allow the fixture  20  to be suspended from an overhead attachment of the cables. Similarly, the base housing element  22  may be provided with conventional wall mounting hardware such as a galvanized hanger screwed or welded to the side member of the base housing element, which attaches with screws to a bracket which is mounted to a wall. 
     Although in the recessed installation regions above the fixture are not required to be illuminated, when the fixture  20  is suspended or mounted to a wall, it may be desirable to direct light upwardly as well as downwardly. The base housing element  22  is configured to accept LED strips and cover lenses to direct light in both directions, as shown in  FIG. 1 , where an optional top-mounted installation of an LED strip  56  and a collimating lens  92  is shown. The top member  28  of the base housing element  22  has two cover mount members  144  similar to the cover mount members  58 ,  60  on the heat sink. The upper cover mount members  144  have sidewardly facing convex elements which mate with the concave elements  86  of the cover lens connecting members. Thus any of the cover lenses  70 ,  74 ,  76  can be engaged with the cover mount members  144  to overlie LEDs mounted to the top member  28 . 
     It should be noted that while the top and bottom or directions relative to the base housing element are mentioned, the fixture may be installed in various orientations depending on the conditions of the installation. For example, the fixture may be given a recessed installation in a ceiling, in which case it will direct light downwardly, but the same fixture may be given a recessed installation in a floor to direct the light upwardly, or it may be recessed in a vertical wall to direct light sidewardly. Where the fixture is recessed, the portion above the top member  28  may be left unfinished. Alternatively, in a suspended or wall mounted installation, it may be desired to finish the upper surface of the fixture. This may be done with an extruded aluminum lid which has a horizontal surface which extends between the first and second base housing element side members  24 ,  26 . 
     The modular fixture  20  thus makes it possible for a customer to change the installation approach or application for the fixture in the field. If a customer finds that a fixture must be used in a different way than originally anticipated at the time of placing the order, the manufacturer may be able to ship only a different trim piece, lens, or cover lens, rather than an entirely different fixture. 
     It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.