Abstract:
A puck light fixture has a puck shaped housing, the interior divided by a partition into a circular central compartment encompassed by an outer compartment. Air conduits closed to the housing interior admit flow of ambient air between top and bottom openings in the housing. The air conduits are in heat exchanging relationship with the partition for dissipating heat generated by a lamp in the central compartment and thereby lowering the operating temperature of electrical wiring and connectors in the outer compartment so as to allow use of lower rated wiring for on site hard wiring of the puck fixture.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally to the field of electric light fixtures and more particularly concerns an improved puck type light fixture. 
     2. State of the Prior Art 
     So-called puck lights are relatively small light fixtures with a flat circular disk shape reminiscent of a hockey puck. Puck lights are primarily intended for installation in or on wood shelving and cabinets, although they can also be mounted on other surfaces. 
     Existing puck lights tend to operate at relatively high temperatures because the small enclosures, a few inches in diameter, do not readily dissipate heat from the high intensity halogen or other compact light sources used. Internal temperatures may reach 200 to 250° Centigrade, and electrical codes require use of special high temperature wire connected in the puck light. Such high temperature wires are a specialty item and not usually kept on hand by electrical contractors who install such fixtures. Consequently, puck light manufacturers pre-wire their puck lights with a fixed length of connecting wire which extends from the puck light housing and terminates in a pre installed electrical connector. 
     UL (Underwriters Laboratories), which certifies such puck light fixtures, does not permit the wiring to be cut if the fixture is sold with a connector in order to remove the connector in order to extend the wiring. Puck lights are often installed in groups where they are most conveniently wired in daisy chain arrangements. However, the factory provided wiring tends to be relatively short, e.g. four inches in length between the puck light housing and the factory installed connector, which sets a maximum spacing between adjacent puck lights of eight inches using the existing wiring. It is desirable to have greater latitude in the spacing of daisy chained puck lights. 
     Furthermore, UL requires that the puck light fixture allow access to the lamp element in the fixture for relamping without exposing an end user to the electrical wiring in the fixture. Existing puck lights comply with this requirement by providing a removable glass cover held over the lamp element by a spring-loaded retainer, or the like, but do not provide for access to the wiring of the puck light. 
     For the forgoing reasons, existing puck lights are not installed by “hardwiring” i.e. by leading conventional electrical wiring into the puck light housing and making an interior electrical connection therein for supplying power to the lamp socket of the fixture. Because existing puck lights are sold with factory prewired external power connectors they are known as “portable” fixtures and fall under a different provision of the UL Combined Standards than hard wired luminaires. 
     A need exists for puck type light fixtures which can be hard-wired in the field using conventional electric power cables without the limitations imposed by factory installed high temperature wiring and connectors. 
     SUMMARY OF THE INVENTION 
     The invention provides a puck light having a puck housing including a housing top and a housing bottom, an outer wall between the top and the bottom, a generally annular partition between the top and the bottom dividing the housing into a central compartment and an outer compartment substantially closed to each other, a terminal block in the outer compartment, a lamp socket in the central compartment electrically connected to the terminal block for powering a lamp supported in the central compartment above a light aperture in the housing bottom, air passages through the partition between exterior vent openings in the top and the bottom of the housing, the passages being closed to each compartment such that ambient air may flow through the housing in the air passages in heat exchanging relationship with the partition for reducing heat flow across the partition from the central compartment thereby to maintain relatively low operating temperatures in the outer compartment. Preferably, the lamp socket is in heat sinking contact with the partition such that heat from the socket is dissipated by conduction through the partition and transfer to the flow of ambient air. The terminal block may be held in the outer compartment in a press fit between the outer wall and the partition. 
     In the presently preferred embodiment of the invention the partition has concentric inner walls connected to each other by spaced apart radial fins or spokes for defining the air passages between the inner walls and between the fins or spokes. The concentric inner walls form an arc of circle and the arc is closed by a socket mounting wall with socket retainers for holding the lamp socket in thermal contact with the mounting wall. The puck housing including the housing top, the outer wall, the inner walls and the radial fins may be all formed as a single unit of heat conductive material, e.g. cast aluminum, and the housing bottom may include a cover plate between the partition and the outer wall for closing the outer compartment, and a lens holder defining the light aperture of the central compartment. The lens holder may be hinged or removable for allowing access to the lamp socket in the central compartment for relamping of the puck fixture. The cover plate may be removable for access to the terminal connection block for hard wiring of the puck fixture in the field. The puck housing has at least one knock-out opening in one or both of the housing top and the outer wall for introducing external electrical wiring into said the compartment for connection to the terminal block. 
     A domed light reflector may be removably fitted in the central compartment between the housing top and the lamp socket for reflecting light emitted by a lamp installed in the lamp socket toward the light aperture. A center fastener may secure the reflector to the housing top. 
     In the presently preferred embodiment the cover plate is fastened to the outer wall and the housing top with removable fasteners such as threaded screws and the lens holder is hinged to the cover plate for movement between a closed condition for holding a lens under a lamp in the lamp socket and light reflector and an open position admitting access for installation or replacement of a lamp in the lamp socket. In this preferred embodiment the vent openings of the air passages in the housing bottom are disposed along an arc between the cover plate and the lens holder. 
     The annular partition also serves as a light baffle against diffusion of light from the lamp in the central compartment into the air passages or into the outer compartment. 
     The puck housing may be further ventilated with one or more center slots in the housing top for venting the central compartment, with the light reflector providing a light baffle covering the lamp to keep against diffusion of light through such center slots. The puck light may be still further ventilated with one or more outer slots in the housing top for venting the outer compartment. 
     Holes are provided through the housing top in the outer compartment for passing mounting fasteners for fastening the puck housing to an overlying mounting surface such as a wooden shelf or the like. 
     More generally, the puck fixture of this invention comprises a puck housing defining a circular central compartment encompassed by an outer compartment between a housing top and a housing bottom, a partition separating the central compartment from the outer compartment and air passages between said housing top and said housing bottom and closed to each said compartment for placing a flow of external ambient air in heat exchanging relationship with said partition thereby to dissipate heat produced by a lamp in said central compartment and thus reduce the temperature in said outer compartment during operation of the puck fixture. 
     The puck light of this invention may also be understood as comprising a puck housing with a circular central compartment encircled by an outer compartment and spaced therefrom by an annular gap open at a housing top and a housing bottom, fins or spokes across the annular gap interconnecting the central compartment and the outer compartment such that ambient air flowing through the gap between the top and bottom of the housing passes in heat exchanging contact with the fins or spokes thereby to carry away heat generated by operation of a lamp in the central compartment and flowing through the spokes towards the outer compartment, thereby to maintain a lower operating temperature in the outer compartment of the puck light. In this embodiment the central compartment is enclosed by a circular first inner wall, the outer compartment extends radially between a second inner wall and an outer circular wall, and the gap and the spokes extend between the first inner wall and the second inner wall. A lamp socket may be housed in the central compartment in heat exchanging contact with the first inner wall such that heat from the socket flowing through the first inner wall is conducted onto the spokes and there transferred to ambient air flowing through the gap prior to reaching the outer compartment. 
     These and other improvements, features and advantages of the present invention will be better understood from the following detailed description of the preferred embodiment taken with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side bottom view of a puck type lighting fixture according to this invention; 
         FIG. 2  is a top side perspective view of the puck light of  FIG. 1 ; 
         FIG. 3  is a side view of the puck light of  FIG. 1 ; 
         FIG. 4  is a plan view of the bottom of the puck light of  FIG. 1 ; 
         FIG. 4A  is a bottom plan view of the open and empty one piece puck housing; 
         FIG. 4B  is a top plan view of the top side of the puck housing; 
         FIG. 5  is a perspective view showing the puck light of  FIG. 1  with its bottom cover plate removed to expose the interior of the puck light housing; 
         FIG. 6  is an exploded bottom-side perspective view of the puck light of  FIG. 1 ; 
         FIG. 7  is an exploded top-side perspective view of the of the puck light of  FIG. 1 ; 
         FIG. 8  is an exploded side view of the of the puck light of  FIG. 1 ; 
         FIG. 9  is a cross-section taken along the line B-B in  FIG. 4 ; 
         FIG. 10  is a cross-sectional view taken along line A-A in  FIG. 3 ; and 
         FIG. 11  is a perspective view showing typical hard wiring of the puck light of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the accompanying drawings, in which like elements are designated by like numerals,  FIGS. 1 ,  2  and  3  depict a puck style light fixture generally designated by numeral  10  according to this invention. Puck light  10  may be either surface mounted or recess mounted to the underside of a shelf or the bottom of a wall hung cabinet with its top side  14  supported against an overlying mounting surface, in the case of a surface mount, or recessed in a hole cut in the mounting surface in the case of a recess mounting. 
     Puck light  10  has a puck housing  12  with a housing top  14 , a housing bottom  16  and a circular outer wall  18  between the housing bottom  16  and the housing top  14 . The housing bottom  16  includes a cover plate  20  with a circular outer edge  20   a  and an arcuate inner edge  20   b . The housing bottom  16  also includes an annular lens holder  22  adapted to hold any of different interchangeable lenses, light filters or baffles, such as the honeycomb light baffle  24  illustrated in  FIG. 4 . The lens holder  22  is hinged to the cover plate  20  at  22   a  in a manner which will be described below. The cover plate  20  is fastened to the housing  12  of puck light  10  by a pair of threaded fasteners  26 . 
       FIG. 5  shows the puck light  10  with cover plate  20  and lens holder  22  removed to expose the interior of the fixture housing  12 . A partition generally designated by numeral  28  divides the interior of the housing  12  into a generally circular central compartment  34  encompassed by a generally annular outer compartment  36 . In an assembled condition of the puck light  10  the two compartments are essentially closed to flow of air between each other. Partition  28  includes two concentric circularly curved inner walls, including a first inner wall  28   a  and a second inner wall  28   b  radially located between the first inner wall  28   a  and outer wall  18 . Partition  28  further includes a number of circumferentially spaced apart radial fins or spokes  30 . Inner walls  28   a,b  and fins  30  together define a number of air passages  30  arranged in an arc between the central and outer compartments  34 ,  36 . Each of the air passages  30  extends through the thickness of housing  12  between corresponding bottom vent openings  32   a  in the housing bottom  16  and opposite top vent openings  32   b  in housing top  14 , as best understood by reference to the cross section in  FIG. 10 . 
     The first and second inner walls  28   a ,  28   b  together define a partition arc circumferentially extending approximately ¾ of a circle. This arc is closed by a mounting wall  38  extending between the opposite ends of the arc, to complete the partition  28 . A lamp socket  40  is mounted to the mounting wall  38  and held in heat exchanging contact with the mounting wall by socket tabs  42  contained in a socket retaining structure  122  integrally formed on the housing top  14  and the center facing side of mounting wall  38 . Retaining structure  122  may consist of four posts in a configuration adapted to receive and hold the socket  40  between them. Mounting of socket  40  in the puck housing  12  merely involves pressing the socket  40  into the retaining structure  122 . The lamp socket  40  has a pair of socket pins  44  each of which fits into a corresponding pin slot  46  in mounting wall  38 . As a result lamp socket  40  is housed in the central compartment  34  with its flat bottom  40   a  held in thermal contact with the center facing side of mounting wall  38  and with socket pins  44  extending into the outer compartment  36  through pin slots  46 . Lamp socket  42  is selected for accepting and powering a desired light source, such as a halogen lamp  50  or an LED element, in central compartment  34  of the puck light  10 . 
     A terminal connector block  52  is contained in the outer compartment  36  between the outer side of mounting wall  38  and the outer wall  18 . The terminal block  52  contains a first set of terminals for attaching the electrical conductor wires of a power cable and a second set of terminals for connecting internal insulated wire conductors between terminal block  52  and socket pins  44  in the outer compartment  36 , for providing electrical power from the power cable through the internal wires to the lamp socket  40 . These internal wires are entirely contained in the outer compartment  36  between the terminal block  52  and pins  44 . The radial width of outer compartment  36  is such as to receive terminal block  52  in a press-fit to hold block  52  against significant radial displacement, and ridges  68  are formed on outer wall  18  for also holding terminal block  52  against excessive circumferential along outer compartment  36 . 
     Puck light  10  is further provided with a light reflector  54  which includes a reflector bowl  54   a  and a radially extending reflector tab  54   b  as well as center hole  54   c . Reflector  54  is fastened by screw fastener  116  through center hole  54   c  and threaded into a center hole  114  provided in the housing top  14 . The diameter of reflector bowl  54  is such as to make a close fit with the diameter of the first inner wall  28   a , with a reflector rim  54   d  resting upon a supporting ledge  28   c  of the first inner wall  28   a . When reflector  54  is so installed the reflector tab  54   b  overlies and covers lamp socket  40  as best seen in  FIGS. 5 and 9 . The reflector  54  has a cutout  56 , shown in  FIG. 7 , which allows the pins  44  and the base of lamp bulb  50  to pass through the reflector bowl for installation in lamp socket  40 . 
     In the exploded views of  FIGS. 6 ,  7  and  8  the reflector  54  is shown between socket  40  and the puck light housing  12  for convenience and clarity of illustration. However, in the assembled condition of the puck light  10  seen in  FIG. 5  the lamp socket  40  lies between reflector tab  54   b  and housing top  14 , the lamp bulb  50  is contained in reflector bowl  54   a , and the terminal block  52  is contained in outer compartment  36  between the housing top and the reflector tab  54   b.    
     A pair of threaded fasteners  26  pass through corresponding holes  20   c  in cover plate  20  and thread into corresponding internally threaded bosses  62  extending from the housing top for holding the cover plate  20  closed against outer wall  18 , and with the inner rim  20   b  of the cover plate lying against the top edge of the second inner wall  28   b , thereby covering and closing the outer compartment  36 . From the foregoing it will be seen that outer compartment  36  is essentially walled-off and closed from the center compartment  34  by the partition  28 , and is also covered and closed independently of the center compartment  34 . 
     Each of center and outer compartments  34 ,  36  is provided with its own top ventilation openings formed through housing top  14 , which in the described embodiment take the form of arcuate ventilation slots  64  in central compartment  34  and arcuate ventilation slots  66  in outer compartment  36 , as best seen in  FIGS. 4A and 4B . 
       FIG. 10  shows in cross-section how each of the air passages  32  extend fully through puck housing  12  between bottom vent openings  34   a  and top vent openings  34   b  respectively, and that air passages  32  are closed to both the center compartment  34  as well as outer compartment  36 . The cross-section of  FIG. 10  also shows how the outer wall  18 , inner walls  28   a  and  28   b  and mounting wall  38 , as well as radial fins  30  are all formed integrally with puck housing  12 , as by casting of a material chosen for heat conductivity, such as aluminum. 
     In operation of the puck light  10 , the bulb  50  or other light source in center compartment  34  generates not only light but also a considerable amount of heat which, for one thing, heats the lamp socket  40  to an elevated temperature. The lamp socket  20  is, however, in thermal contact with mounting wall  34  which conducts heat away from the socket  40  and towards portion of partition  28  with air passages  32 , where the heat is distributed among first inner wall  28   a , second inner wall  28   b  and radial fins  30 . These structures present a relatively large combined surface area distributed among air passages  32  and in heat exchanging contact with ambient air external to puck light  10  flowing through passages  32 . Ambient air heated by the operating puck light  10  will tend to rise by convection into lower vent openings  34   a  and exhaust through top vent openings  34   b , as suggested by the arrows in  FIG. 10 . 
     The lens holder  22  has a hinge tab  70  which reaches under cover plate  20  at  22   a  and hooks under the curled inner edge of the cover plate  20 . Diametrically opposite to hinge tab  70  is a latch  72  which fits into an axial slot  74  defined in first inner wall  28   a  where it makes snap spring engagement with a raised catch  76  formed on the center facing side of the second inner wall  28   b , as best seen in the cross-section of  FIG. 9 . Latch  72  is released by pressing radially inwardly latch end  72   a  so as to disengage the latch from catch  76 , thereby allowing the lens holder  22  to swing about the captive end of hinge tab  70  from the normal, closed position shown in  FIGS. 1 through 3  to an open position which allows access to the lamp  50  for relamping of the puck light  10  if needed. It will be appreciated that opening of the lens holder  22  does not expose any of the internal wiring of the puck light  10  during the relamping process, thereby permitting safe relamping by an end user without intervention by a licensed electrician. 
     The puck light  10  is provided with multiple knockout openings  80 , including two generally opposed openings in outer wall  18  and two additional knockouts  80  in housing top  14 . This permits a choice of wire access during installation of the fixture. If access is inconvenient through the top  14  of the fixture, electrical wiring can be introduced into the outer compartment  36  through one or both of the knockouts  80  in outer wall  18 . If on the other hand access is convenient through the top  14 , one of the knockouts  80  in housing top  14  may be selected for introducing a power cable into the outer compartment  36 . 
     Raised spacers or stand-offs  82  are provided on the exterior of housing top  14  for the purpose of maintaining an exhaust and ventilation space between the puck light  10  and an overlying mounting surface to which the puck light is fastened, for example in the case where the puck light is surface mounted to the underside of a shelf. 
     Surface mounting of puck light  10  is accomplished by use of conventional mounting screws such as wood screws, passing through three mounting screw holes  84  in the housing top. The screw holes  84  also pass through stand offs  82  to ensure that the ventilation spacing is maintained between the puck light top  14  and the overlying mounting surface. 
       FIG. 11  illustrates how the puck light  10  is hardwired in the field using conventional electrical power cable C. The end  102  of cable C is introduced into outer compartment  36  through an open knockout  80  which in this example is located on outer wall  18 . Cable C contains three insulated electrical wires, including a red colored positive conductor  104 , a white colored neutral conductor  106 , and a green colored ground conductor  108 . The ground wire  108  is electrically connected to the puck light housing  12  by means of one of two grounding screws  110  engaged in corresponding internally threaded bosses  112  formed integrally with the puck light housing  12  as by the aforementioned metal casting of the same. 
     Terminal block  52  includes a terminal strip  52   a  and an insulating cover  52   b  which is removed during hardwiring as shown in  FIG. 11 . Terminal strip  52   a  is connected by internal insulated electrical wires  112  to the pins  44  of lamp socket  40 . Positive and neutral wires  104 ,  106  respectively are connected to the appropriate terminals of terminal strip  52   a  so as to electrically connect each of these wires to a corresponding one of internal wires  112  and thereby supply electrical power to lamp  50  in socket  40 . Once the wiring is completed as shown in the  FIG. 11  the cover  52   b  is replaced over terminal strip  52   a  and the assembled terminal connector block  52  is returned to outer compartment  36  as shown in previous drawings, with the various wires bent and folded as needed to fit in compartment  36 . Puck light  10  is then closed by assembling cover plate  20  to the bottom side of the puck light housing and fastening the cover plate with fasteners  26  as previously explained. 
     A chain of such puck lights  10  can be hardwired in the field with any desired spacing between adjacent puck lights  10  in the chain by interconnecting adjacent pairs of puck lights with interconnect lengths of conventional conductor such as 18-3SJT electrical cable. The interconnect hard wire connection is made using a second one of the knockouts  80 , using the second ground screw  110  for the interconnect ground wire, and connecting the positive and neutral conductors of the interconnect to corresponding terminals at the opposite end of the terminal block  52  so as to transmit electrical power from the first puck light to a second puck light in a daisy chain installation. 
     Puck light  10  can be mounted in two ways: it can be surface mounted such that the housing top  14  is against a mounting surface, for example where the puck light is fastened to the underside of a shelf, or the puck light can be recess mounted in a hole cut in a mounting surface such that the puck housing  12  is recessed in the supporting structure with the housing bottom i.e. the cover plate  20  generally flush with the outer surface of the mounting structure, e.g. the puck light recessed in a hole cut in a false bottom of a cabinet with the cover plate flush with the bottom surface of the cabinet. In such case a false bottom is usually provided inside the cabinet to make a closed wiring space in the bottom of the cabinet through which an electrical power cable can reach the top of the puck light and be hardwired through the knockouts  80  in the housing top  14  of the puck light  10 . 
     Another feature of the puck light  10  of this invention is a optional field installable trim ring  120  which can be mounted in an interference fit between cover plate  20  and the edge of the outer wall  18  and is secured once fasteners  26  are installed for holding the cover plate in place on the puck light  10 . The trim ring  120  has an enlarged outside diameter greater than the diameter of outside wall  18  so as to cover and hide the edge of the mounting hole in which the recessed puck light is installed, for a more aesthetically pleasing and better finished installation. For purposes of recess mounting the puck light  10  can be fitted with a pair of retaining spring clips  128  which slide into clip receptacles  130  integrally formed with puck housing  12  as seen in  FIGS. 4B ,  7  and  10 . When installed clips  128  are pressed against the outer wall  18  by the rim of the mounting hole and maintain an outward spring force to hold the puck light  10  in its recess hole. 
     While a particular embodiment of the invention has been described and illustrated for purposes of clarity and explanation, it must be understood that many changes, substitutions and modifications to the described embodiment will be apparent to those having only ordinary skill in the art without thereby departing from the scope of the invention which is defined by the following claims: