Abstract:
A recessed lighting fixture includes a lamp housing and a separate compact junction box, which contains a power supply that drives the lamp and serves in part to divide the interior cavity of the junction box into two separate wiring compartments. The junction box has two end walls spaced along an axis and a releasably secured, sleeve-like cover (side wall) surrounding and closing the cavity. The cover can be moved axially in either direction relative to the end walls to open the wiring compartments. The junction box and the lamp housing are mechanically connected only by a flexible conduit and a flexible tether, which prevents undue strain on the electrical connections between the joined components. The lighting fixture is particularly suitable for retrofit installations, especially where small-aperture downlights are desired.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from provisional application Ser. No. 61/483,912, filed May 9, 2011, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to lighting fixtures and junction boxes, and to recessed lighting fixture assemblies in which the associated junction box is connected to the lamp housing by a flexible conduit. 
       BACKGROUND OF THE INVENTION 
       [0003]    Certification standards of Underwriters Laboratories Inc. (UL) require that a recessed lighting fixture be designed and constructed to allow room-side access to the junction box where the branch circuit connections to the lighting fixture are made as well as access to any associated electrical component (transformer, ballast, driver, etc.). Access must be through an opening not less than six inches across. UL standards also require that the junction box be integral to the lighting fixture or securely fastened to its enclosure or frame. If the junction box is attached by a flexible conduit, it must have “additional means of securement.” 
         [0004]    Many recessed lighting fixtures have their associated junction boxes and other components (transformer, ballast, driver, etc.) disposed laterally of the housing that contains the lamp assembly. In a traditional arrangement for lighting fixtures having an aperture of six inches or larger, the lamp housing, the junction box and other components are supported on a common pan or frame, which is secured to the adjacent building structure (joists, ceiling grid, etc.). A releasable connection between the lamp housing and the pan or frame allows the lamp housing to be dislodged and withdrawn from the ceiling opening to permit access to the nearby junction box and other components. In another common arrangement, often used in retrofit applications or other situations where the entire lighting fixture is to be supported only by an existing ceiling, the junction box and other components are supported on a laterally extending strut or arm attached to the lamp housing, usually forming a generally L-shaped unit. The lighting fixture is installed from below the ceiling through a ceiling opening that closely surrounds the lower end of the lamp housing when fully seated. The lighting fixture is removable through the same opening for servicing and access to the junction box. The size of the ceiling opening dictates the maximum size of the junction box and any other lighting fixture component, which must fit through the opening during installation and also during removal for servicing. 
         [0005]    Many L-shaped retrofit assemblies can be somewhat difficult to install and remove, especially in situations where joist spacing is tight or where obstructions such as joist blocking, ductwork or piping are located close to the lighting fixture installation hole. Further, the small installation holes (e.g., 2⅞ inch or smaller) required for small aperture lamp housings make junction box miniaturization challenging, especially where the junction box must house a transformer, driver or other component. When above-ceiling access is available from the room through a properly sized auxiliary opening, a standard junction box can be used. Otherwise the usual solution is to mount the transformer or driver in an accessible remote location, which requires additional labor and materials. 
       SUMMARY OF THE INVENTION 
       [0006]    One aspect of the invention concerns a compactly packaged junction box assembly for electrically powering a load. Such an assembly comprises a housing enclosing a cavity; a power supply within the cavity having an input side for receiving power from a source and an output side for delivering power to a load; and a chassis within the cavity supporting the power supply and substantially dividing the cavity into first and second wiring compartments. The power supply is situated in an aperture in the chassis with the input side facing the first compartment and the output side facing the second compartment. 
         [0007]    In this assembly, the power supply preferably occupies a portion of each wiring compartment and is supported on a mounting flange at one edge of the aperture. The overall shape of the housing preferably is cylindrical. Openings in the housing&#39;s end walls communicate with the two wiring compartments to enable wiring to both sides of the power supply. 
         [0008]    Another aspect of the invention concerns an arrangement of junction box features that facilitate access to its interior. The arrangement includes an axially extending support in the junction box cavity carrying two axially spaced end walls, and a releasably secured side wall surrounding and closing the cavity between the end walls. When released, the side wall is movable axially in either direction relative to the end walls to open and permit access to the cavity. 
         [0009]    This arrangement preferably includes a resiliently biased retractable stop near each end wall that engages and releasably secures the side wall in a closed position surrounding the cavity. Each retractable stop, which may be a portion of a spring clip, preferably engages a respective end of the side wall when in its closed position. The overall shape of the junction box preferably is cylindrical. Openings in the end walls communicate with the cavity. 
         [0010]    The invention also concerns a lighting fixture assembly that includes a junction box or junction box assembly as described above flexibly attached to a lamp housing containing a lamp assembly. A flexible conduit interconnects the junction box and the lamp housing with wiring therein for supplying power to the lamp assembly. A flexible tether, which preferably runs through the flexible conduit, has one end anchored to the lamp housing and the other end anchored to the junction box. The length of the tether prevents undue strain on the wiring and its connections, and preferably prevents undue strain on the flexible conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Preferred embodiments of the disclosed invention, including the best mode for carrying out the invention, are described in detail below, purely by way of example, with reference to the accompanying drawing, in which: 
           [0012]      FIG. 1  is a side elevational view of the recessed lighting fixture of the invention installed in and above a ceiling; 
           [0013]      FIG. 2  is a perspective view of the lighting fixture of  FIG. 1 , with some parts removed for clarity and with top housing  18  and cylindrical cover  72  shown as transparent to reveal inner details; 
           [0014]      FIG. 3  is an enlarged perspective view of the lamp housing portion of the lighting fixture of  FIG. 1 , with top housing  18  shown as transparent; 
           [0015]      FIG. 3A  is an exploded perspective view of the upper portion of the lamp housing of  FIG. 3 , showing an alternative wiring arrangement; 
           [0016]      FIG. 4  is an exploded perspective view of the lamp housing of  FIG. 3 ; 
           [0017]      FIG. 4A  is a partial perspective view of the lamp housing of  FIG. 3 , shown in a disassembled state; 
           [0018]      FIG. 5  is an enlarged perspective view of the junction box portion of the lighting fixture of  FIG. 1  shown in a partially open condition, the cylindrical cover  72  shown as transparent; 
           [0019]      FIG. 6  is a top perspective view of the chassis of the junction box of  FIG. 5 ; 
           [0020]      FIG. 7  is a bottom perspective view of the junction box chassis of  FIG. 6 ; 
           [0021]      FIG. 8  is a top perspective of the junction box of  FIG. 5  without the cylindrical cover; 
           [0022]      FIG. 9  is a top perspective view of the junction box of  FIG. 8  taken from the opposite side; 
           [0023]      FIG. 10  is a bottom perspective view of the junction box of  FIG. 8 ; 
           [0024]      FIG. 11  is a bottom perspective view of the junction box of  FIG. 10  taken from the opposite side; 
           [0025]      FIG. 12  is a side elevational view of the junction box of  FIG. 8  showing wiring in both compartments thereof; 
           [0026]      FIG. 13  is a perspective view of the junction box of  FIG. 12  showing wiring in the input (supply) compartment thereof; and 
           [0027]      FIG. 14  is a perspective view of the junction box of  FIG. 12  showing wiring in the output compartment thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Referring to  FIGS. 1-5 , a lighting fixture according to the invention comprises a lamp housing  10 , a junction box assembly  40  and a flexible metal conduit  30  interconnecting the lamp housing and the junction box and protecting wiring within. Lamp housing  10  comprises a metallic tubular lower body  12 , a finned metallic upper housing  16  and a metallic, generally square two-part top housing  18  (shown as transparent in  FIGS. 2 ,  3  and  4 ). Lower body  12  houses a removable reflector  13  having a bottom annular trim flange  14 ; and it has two tangential, oppositely directed retention springs  15  that removably secure the lamp housing  10  in a properly sized installation hole H in ceiling C, with trim flange  14  bearing against the lower surface of the ceiling. Junction box  40  simply rests on the ceiling near the lamp housing. 
         [0029]    Three screws  22  securely fasten the three-sided, U-shaped bottom half  20  of top housing  18  to fins of upper housing  16 . The inverted box-shaped top half  24  of top housing  18  fits over and is secured to the upstanding sides of bottom half  20  by two screws  26 . One end of conduit  30  is received in an aperture  28  in one side of top half  24  and is retained therein by a suitable wire-protecting metallic connector  32 , such as the flanged connector disclosed in U.S. Pat. No. 4,880,387 (incorporated herein by reference). The same or a similar connector  34  secures the other end of conduit  30  to an end of junction box  40 . The conductivity afforded by these connectors enables metallic conduit  30  to provide an electrical grounding path from lamp housing  10  to junction box  40 , which is grounded as described below. 
         [0030]    A lamp assembly  19  is mounted to the bottom of upper housing  16  so as to be disposed within lower body  12  when the lower body is joined to the upper housing. Light generated by the lamp assembly is dispersed and/or focused by reflector  13 , while heat generated by the lamp assembly is dissipated by the finned heat sink of upper housing  16 . As used herein, “lamp assembly” means a light source of any type powered by electricity, such as an incandescent lamp (e.g., conventional tungsten filament or halogen), a compact fluorescent lamp, an LED light engine, etc. In the illustrated preferred embodiment, the lamp assembly is an LED light engine, such as a high output XSM LED module manufactured by Xicato (http://www.xicato.com/products.php). As shown in  FIGS. 4 and 4A , upper housing  16  is joined to lower body  12 , preferably by means of external threads  27  on the mounting ring of lamp assembly  19 , those threads mating with internal threads  29  at the upper end of lower body  12 . The inherent adjustability of this threaded connection accommodates small variations in the length of reflector  13 , which may be due to manufacturing tolerances, allowing for accurate close positioning of the small upper-end aperture of reflector  13  relative to lamp assembly  19  for proper optical performance. A nylon-tipped set screw  17  prevents relative rotation of the threaded parts after adjustment. 
         [0031]    Insulated conductors W in protective flexible conduit  30  emerge in top housing  18 , extend through upper housing  16  and are connected to lamp assembly  19 . Preferably, as seen in  FIG. 3A , conductors W terminate in top housing  18  in a first connector half  21 , which mates with a second connector half  23  wired via conductors  25  to lamp assembly  19 . Such a connector arrangement facilitates removal and replacement of lamp assembly  19 . Alternatively, twist-on connectors can be used in top housing  18  to connect conductors W to conductors  25 . 
         [0032]    Conductors W emerge from the other end of conduit  30  in junction box  40 , where they are connected to a power supply  42  as more fully described below. Also within conduit  30  is a flexible tether  36  that emerges in top housing  18  where it is secured by a crimped eye-lug  37  riveted at  38  to the top half  24  of that housing. The other end of tether  36  emerges from conduit  30  in junction box  40  where it is secured to junction box chassis  44  by a crimped eye-lug  46  and a screw  47 . The length of tether  36  is selected such that it functions as a strain relief cable to prevent undue strain on the conductors W and their connections, and preferably to prevent undue tensile loading on flexible conduit  30 . Tether  36  preferably is conductive and preferably is made of braided galvanized or stainless steel. If metallic, tether  36  provides an electrical grounding bond between lamp housing  10  and junction box  40 . The preferred path of tether  36  is through flexible conduit  30  as illustrated, but the tether instead could run externally of the conduit, optionally loosely tied to the conduit by tape, nylon ties or other means. 
         [0033]    Referring to  FIGS. 5-14 , chassis  44  closely surrounds power supply  42 , which is mounted in a generally rectangular central aperture  45  in the base of chassis  44 . A broad longitudinal mounting flange  48  protruding from one longer side of aperture  45  has two mounting slots  50  near its distal edge. Two additional mounting slots  52  are formed in the base of chassis  44  near the proximal end of flange  48 . As seen in  FIGS. 5 ,  8  and  12 - 14 , two mounting straps  54  pass through slots  50 ,  52  and surround power supply  42  to firmly secure it in position against flange  48 . For the sake of simplicity, mounting straps  54  are omitted from  FIGS. 9-11 . Nylon cable ties may be used as mounting the straps; however, any suitable mounting hardware could be used depending on the configuration of the power supply and/or any mounting tabs it may have. 
         [0034]    Axially spaced circular end plates  60 ,  62  are riveted at  63  to apertured tabs  56 ,  58 , respectively, at the ends of chassis  44 . Each end plate has a peripheral notch  64  that accommodates a resilient spring clip  66 , which is riveted at  67  to a narrow longitudinal flange  68  protruding from one edge of chassis  44 . Each of the two spring clips  66  has a shoulder  70  that engages an end of sleeve-like cylindrical cover  72  (see  FIGS. 1 and 2 ), the two shoulders acting as opposing stops to trap the cover in a closed position closely surrounding chassis  44  and end plates  60 ,  62 . Inward finger pressure on either spring clip  66  allows its shoulder  70  to clear the end of cover  72 , which can then be slid open axially past the depressed spring clip as shown in  FIG. 5  and completely removed, if desired. 
         [0035]    Any other suitable arrangement could be used instead of the illustrated spring clips to releasably maintain the cover  72  in a closed position. Such devices could be mounted on chassis  44 , on one or both end plates  60 ,  62  or on the cover  72  itself. By way of example only, each end plate  60 ,  62  could carry a linearly or pivotally retractable member (spring-loaded or otherwise), which when extended acts as a stop against an end of the cover  72  to keep it closed. Alternatively, one or more screws could secure the cover to chassis flange  68  or to an adjacent tab carried by an end plate. Furthermore, while a right circular cylinder is the preferred shape of the junction box, the shape of the end plates and the matching cross-section of the cylindrical cover could vary somewhat as long as the described functionality is not impaired. In order to facilitate below-ceiling installation and removal of the lighting fixture assembly as described below, the maximum width of the junction box  40  should be no greater than the maximum width of the lamp housing  10  (excluding retention springs  15 ). 
         [0036]    Chassis  44  divides the interior of the junction box into two compartments  80 ,  90  in which wiring for different voltages is separately maintained. In the preferred embodiment, power supply  42  is a step-down transformer (driver) that converts line (supply) voltage fed to input compartment  80  to a lower voltage for powering the LED light engine of lamp assembly  19  from output compartment  90 . Thus, the input leads  82  of power supply  42  are disposed in input compartment  80  (shown with plug-in connectors in  FIGS. 12 and 13 ), while the lower voltage output and control leads  92  are disposed in output compartment  90  (shown with twist-on connectors in  FIGS. 12 and 14 ). As used herein, the term “power supply” broadly means any device that converts, conditions or otherwise modifies or adapts supplied electrical power for a specific load or application. 
         [0037]    End plate  60  has an opening  74  through which line voltage and ground conductors (not shown) are fed to input compartment  80 , which also houses a ground wire (see  FIGS. 12 and 13 ) secured to chassis  44  by a screw  77  (see  FIG. 11 ). Through branch wiring can be accommodated via opening  74  by using an appropriate duplex connector. End plate  62  has an opening that supports a conventional, outwardly projecting thermal protector  76 , which is connected to wiring in input compartment  80  (see  FIGS. 12 and 13 ). End plate  62  also has an opening  78  in which an end of conduit  30  is received and is secured by connector  34  (see  FIG. 5 ). Conductors W in conduit  30  thus communicate with lower voltage output compartment  90 , where they are connected to driver output leads  92  (see  FIGS. 12 and 14 ). An opening in end plate  60  adjacent output compartment  90  is closed by a knockout  79 , which can be removed for the separate entry of low voltage control wiring, such as for a lamp dimming control. 
         [0038]    Installation of the lighting fixture assembly is straightforward. Cover  72  is released and slid open over conduit  30  in the direction of lamp housing  10  to expose input compartment  80 . Supply wiring above the ceiling is pulled through the fixture installation hole H, passed through and clamped in opening  74  (using an appropriate connector) and connected to input leads  82  and the fixture ground wire. Cover  72  is then slid closed and latched. Junction box  40  is then passed upward through the installation hole H followed by flexible conduit  30 . Junction box  40  simply rests on the upper surface of the ceiling. With retention springs  15  squeezed around lower body  12 , the lamp housing  10  is pushed upwardly into the installation hole until the springs pop out above the ceiling, locking the fixture in place. A slight clockwise twist of the reflector  13  seats it firmly against the ceiling. The fixture can be removed from the ceiling easily by first twisting the reflector  13  slightly counterclockwise while applying slight downward pressure. Once the retention springs  15  are accessible, they are squeezed together and the lamp housing is pulled down out of the installation hole, followed by flexible conduit  30  and junction box  40 . 
         [0039]    While a preferred embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims. While the lighting fixture of the invention has been described as well-suited for a retrofit, ceiling-supported installation, the lamp housing and junction box components could also be removably mounted on a joist-supported pan or frame above a ceiling. Furthermore, the advantage of compactness realized by the described junction box configuration would make it suitable for use in other applications or situations as long as applicable electrical code requirement are observed.