Abstract:
An outdoor lighting fixture is disclosed including a first housing containing the fixture ballast or power supply, a second housing enclosing a lamp. Each of the housings is sealed. A support stem joins the two housings and defines a thermal air gap between the two. The only conductive thermal path between the two housings is through the stem and the fasteners engaging the stem and the two housings. In one embodiment, a plurality of tubular spacers are located on elongated screw fasteners define the size of air gap. In another embodiment a single fastener includes washers defining the air gap size. In that embodiment, the fastener may be hollow and acts as a conduit for the electrical leads for the fixture. In another embodiment one closure for a housing includes fins for cooling the fixture.

Description:
BACKGROUND OF THE INVENTION 
   Throughout lighting industry and particularly, outdoor lighting such as walkway, flood and spot light applications, it is the desire of manufacturers and of the purchasers and the public that the lighting be reliable with lowest operating cost while meeting safe lighting requirements, require little or no maintenance and have long life. Weather, vandalism, and other factors can adversely affect the life of such fixtures and particularly their lamps and internal power supplies, such as ballasts or transformers. 
   The heat generated in the fixture itself in both the power supply which may be a transformer operating from typical 115-volt lines to serve low voltage lamps and the lamps themselves generate substantial heat. Heat generated by the fixture itself is a major factor in determining the operating life of the power supply or transformer and the lamp. A notable exception is solar powered lighting, however such systems rarely provide enough light for most applications where safety and reliability are controlling criteria. 
   The most common solution to the minimization of thermal damage to the key components, the power supply and the lamps in outdoor walkway and other architectural lighting is to provide large thermal conductive bodies such as aluminum housings which act as heat sinks and which sometimes have integral fins to aid in radiating the heat into the surrounding air. Fins, though effective, often detract from the ornamental appearance of the fixture. 
   An ideal shape for such outdoor walkway and other architectural applications is a cylindrical body, preferably with the power supply toward one end and the lamp assembly at the opposite end. That has given rise to fixtures with a fin section between the two heat sources with the expectation that it will serve to dissipate heat from both sections of the fixture while accepting the appearance of the fins. Examples of various finned fixtures are well known in the art. 
   BRIEF DESCRIPTION OF THE INVENTION 
   Faced with the present state of the art, one object of this invention is to provide walkway or other architectural lighting fixture with improved thermal energy removal. 
   Another object of this invention is to provide a lighting fixture with enhanced power supply and lamp life. 
   Still another object of this invention is to provide a lighting fixture in which the features responsible for enhanced thermal energy removal are virtually hidden from view. 
   Another object of the invention is to provide an attractive lighting fixture, which has enhanced protection from vandalism damage. 
   These objectives are achieved by a lighting fixture which includes a power supply housing, lamp and lamp housing or housings, a stem for mounting the fixture of metal having good thermal radiation properties assembled into an elongated structure. Internal, substantially concealed fastener or fasteners attach the housings to form one structure with a minimally visible thermal isolation air gap. 
   Some of the fasteners define one or more air gaps, which are located between the heat generating elements of the fixture, particularly the lamp and the power supply located in their respective housings. 
   The support stem for the fixture has substantial mass to radiate heat and to provide a rugged structural mount while conducting heat to whatever support to which it is attached. 
   Only one or two small fasteners such as setscrews, concealed at the bottom of the fixture provide access to the interior of the fixture in the event that access to the fixture is required. 
   In one embodiment, a single fastener joins the power supply housing to the stem and to the lamp and socket housing and constitutes the only thermal conduction path between the housings. 
   In other embodiments a plurality of internal fasteners joining the housings and the stem secure the entire assembly together while defining one or more air gaps and constitute the only thermal conduction path between the power supply housing, the stem and the lamp housing. 
   Another feature of the invention is a relatively massive swivel stem pivotally secured to the stem to provide a further thermal conduction path while conducting power leads to the stem and to the fixture providing angular adjustment of the orientation of the fixture. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     This invention may be more clearly understood from the following detailed description and by reference to the drawing in which: 
       FIG. 1  is a perspective view of a lighting fixture in accordance with this invention; 
       FIG. 2  is a side elevational view of the lighting fixture of  FIG. 1 ; 
       FIG. 3  is an electronic block diagram of the fixture of  FIG. 1 ; 
       FIG. 4  is an exploded view of the fixture of  FIG. 1 ; 
       FIG. 5  is a side elevational view of the fixture of  FIG. 1  with portions broken away to show internal features thereof; 
       FIG. 6  is a front elevational view of the fixture of  FIG. 1 ; 
       FIG. 7  is a side elevational view of a first alternate embodiment of this invention; 
       FIG. 8  is a longitudinal sectional view of the first alternative embodiment of  FIG. 7  taken along line  8 - 8  of  FIG. 7 ; 
       FIG. 9  is a side elevational view of a second alternative embodiment of this invention employing fins for additional radiation cooling; 
       FIG. 10  is a partly exploded side view of the finned fixture of  FIG. 9 ; 
       FIG. 11  is a further exploded view of the embodiment of  FIG. 9 ; 
       FIG. 12  is a front elevational view of the finned section of the fixture of  FIG. 7 ; and 
       FIG. 13  is a front elevational view of the shroud or lens holder of the embodiment of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A first embodiment of this invention may be seen in  FIGS. 1 through 6  with the external features appearing in  FIGS. 1 ,  2  and  6  and the internal components in  FIGS. 3 and 4  and of a lighting fixture, generally designated  10 . The fixture  10  from the exterior comprises a power supply housing  12 , a supporting stem  14  and a lamp and socket housing  16 . The outer end of the housing  16  includes a shroud  18  as protection for the lens  20  of the fixture  10  which appears in  FIGS. 1 and 6 . Each of the foregoing defines an attractive, generally cylindrical body  22  with the stem  14  extending downward to constitute a support for the fixture  10 . A swivel stem  24  is located at the bottom of the stem  14  and is pivotable over an angle in the order of 60 or so degrees for adjusting the direction of the light beam emitted from the fixture  10  while supplying its operating power. 
   The support stem  14  and the swivel stem  24  include internal openings, unshown in  FIG. 1  for the passage of power leads  26 P from an external power line, unshown, to the interior of the fixture  10  where mating internal openings in the stem  14  and the power supply housing  12  provide external power to the power supply  28  of  FIGS. 3 and 4  to the fixture. 
   From the standpoint of a casual observer, the fixture  10  appears to be a virtually continuous cylindrical structure, with a base provided by the stem  14  and the swivel stem  24 . Hardly noticeable is an air gap  32  which is in the order of less than ¼ inch in width extending around the body  22  adjacent to the stem where it matches the contour of the housings  12  and  16 . The internal (radial) surfaces defining the air gap  32 , preferably have the same color treatment as the body  22  as a whole, e.g. black finish, and become virtually invisible. 
   The air gap  32 , as described in more detail below, in combination with the body fasteners  46 F and spacer tubes of  FIG. 4  are instrumental in providing enhanced thermal protection for the internal electrical components of the fixture, namely the lamp  30 , its socket  32  and the power supply transformer or ballast  28  of  FIGS. 3 and 4 . Socket  32  is mentioned since they are commonly the first to suffer from heat damage in a fixture of any type. 
   Reference is now made to  FIG. 3 , which is a block diagram of the electronic elements of each of the embodiments of this invention. In  FIG. 3 , three incoming leads  26 , one black, one white, both power leads and one green which is the grounding lead for the fixture  10  constitute the input to the power supply  28 , identified in  FIG. 3  as the ballast, the socket  34  for the lamp  36 , shown in dashed lines within its reflector  38 . In accordance with this invention, the power supply  28  and the lamp  36  are virtually entirely thermally isolated from each other. 
   For a greater understanding of the invention, reference is now made to  FIG. 4 , which is an exploded view of the lighting fixture of  FIG. 1  showing not only the housings  12  and  16 , the stem  14  and the swivel stem  24  but also showing the sealed internal power supply  28  which may be a transformer or ballast. A typical such power supply is a VS 39 watt 120 volt electronic ballast such as a Model MC39-1-F-1200 Ballast of the Hatch Transformer, Inc. when using a 39 watt PAR lamp or a 39 watt TC lamp. The ballast  28  has three input leads  26 , white, black and green (ground) and two output leads to the lamp socket  34 . 
   All of these leads extend out of the power supply (ballast) housing  12  through the housing  12  internal cover plate  40  and a lead tube  42 , to the socket housing  44 . The socket housing  44  is hollow and the lamp leads  26 L pass directly through housing  44  and are secured and electrically connected to respective terminals of socket  34 . Power leads  26 P extend part way through housing  44  and exit through its sidewall through port  44 P, through the mating port (unshown) of stem  14  and end port or slot of the swivel stem  24  to exit for connection to the local  120   v  power line when all is assembled and installed. 
   A plurality of fasteners  46 F such as machine screws, extend through matching openings in cover plate  40 , partially through the socket housing  44  and are secured in place by matching nuts  46 N. Tubes  48  slide over respective fasteners  46  F and are of sufficient length to space the housing  12  and its cover plate  40  by ⅛ to ¼ in. from the near edge of socket housing  44  and stem  14 , thereby creating air gap  32  of  FIGS. 1 and 2 . Each of the openings in the cover plate  40 , and the housing  44  are sealed with silicone sealant or the like against any moisture. The cover plate  40  is threaded into matching threads in housing  12  and locked with a virtually hidden set screw SS on the underside of the fixture for security. 
   Key to this invention is the fact that the fasteners  46 F and tubes  48  are the only thermal conductive path between the ballast  28 , its housing  12  and the lamp  36  and its housing  16 . The entire body assembly  22 , the stem  14  and the swivel stem  24  constitute a thermal radiating body with an air gap  32  isolating the thermal conduction path between the two heat generating elements, the ballast  28  and the lamp  36  so neither can effectively transfer heat energy to the other. 
   FIRST ALTERNATE EMBODIMENT 
   Reference is now made to  FIGS. 7 and 8  for a basic version of this invention which not only serves to illustrate this invention but incorporates additional features serving to reduce the number of parts but provides equal or superior thermal isolation of the ballast and the lamp from each other and facilitates sealing the fixture and the process of wiring the fixture. 
   The fixture of  FIGS. 7 and 8 , generally designated  110  comprises a power supply housing  112  with its threaded end closure  113  secured with a locking set screw SS, a stem  114 , with its swivel stem  124 , a lamp housing  116  and a shroud or lens protector  118  making up the major components viewable from the exterior. These structural components bear corresponding reference numerals similar to the embodiment of  FIGS. 1-6  but in the one hundred series of numerals. Additional components visible in  FIGS. 7 and 8  from the exterior are two spacers, one of which,  142  appearing in both  FIGS. 7 and 8  and spacer  140  appearing only in  FIG. 8 . These spacers  140  and  142  are actually metal washers. Spacer  140  which separates the ballast housing  112  from the stem  114  and spacer  142  which separates the stem  114  from the lamp housing  116 . These spacers  140  and  142  define three adjoining air gaps  132 ,  134  and  136 , appearing in  FIG. 8  between the stem  114  and the two heat generating housings  112  and  116 . The three air gaps effectively separate the two heat generation components, namely the power supply  28  in housing  112  and the lamp  136  in housing  116 . The only thermal conductive path between the two housings  112  and  116  is through the spacers  140  and  142  and the fastener  146  that extends from housing  112  through the stem  114  to housing  118 . The fastener  146  passing through a close fitting bore in stem  114  is in direct thermal contact with the stem  114  for heat transfer by conduction out of the fixture  110 . 
   As shown in  FIG. 8 , the fastener  146 F is shown as hollow with a bore of sufficient size to allow the passage of the five wires, normally plastic insulated copper. The lamp leads  126 L pass entirely through the fastener  146  to the socket  134  while the power leads  126 P exit the fastener  146  through a hole in its sidewall shown in dashed lines to enter a mating bore in the stem  114  to exit the fixture  110  through a similar bore or slot in the swivel stem  124  to outside power. 
   The only thermal conductive path between the housing  112  and  116  is via the single fastener  146  and the spacers  140  and  142  which are in intimate contact with the stem  114  which is a readily available heat sink and thermal conductor to the support for the fixture. 
   This embodiment has minimum openings to the housings  112  and  116  that require sealing as compared with many exterior fixtures for enhanced protection from moisture intrusion. 
   When the fastener  146  is hollow as shown in the cutaway section of  FIG. 8  and includes a sidewall smooth edged hole H, the power leads  126 P exit the fixture through that hole H and matching holes in the stem  114  and a matching slot in the swivel stem  124  to the external power source. Wiring paths are indicated in  FIG. 5  partially in solid lines and when hidden by dashed lines. 
   In accordance with this invention feature, all wiring within the fixture  110  passes through a single sealed passage in the stem  114  in the thermal dissipation path of the fixture and which may serve to provide cooling of the leads  126 P and  126 L, as well. 
   SECOND ALTERNATE EMBODIMENT 
   For high intensity lighting applications, for example, 150 watt, maximum which may utilize T6 CDM Type MH lamps. Fixtures incorporating the thermal dissipation features of the foregoing embodiments are modified in accordance with the second alternate embodiment which is shown in  FIGS. 9 through 12 . 
   The same components used in the embodiment of  FIGS. 1-5  are used herein and bear the same reference numerals. The descriptions above for those figures will apply to this second alternate embodiment. 
   The fixture, generally designated  210  includes the power supply housing  212 , the stem  214 , the lamp housing  216  and the swivel stem  224 . The diameter of the fixture  210  may be larger than the previous embodiments, e.g., approximately 5 in. in diameter as compared with 2½ inch diameter for lower wattage fixtures. 
   The notable difference in this embodiment is the presence of a finned section  260  including a number of integral cooling fins  262  and a threaded end closure section  264  of  FIG. 11  which seals the inner end of the lamp housing  216 . The opposite or outer end of the lamp housing  216  is closed by a threaded lens mounting ring  268 . A central core section  270  of the finned section  260  may be seen between the fins  262  along its central diameter. The central core  270  includes a through-hole  272 , appearing in  FIG. 12  allowing for the passage of leads  26 L and  126 L of the earlier figures to reach the lamp socket  34  as in the earlier embodiments. 
   The finned section  260  provides a heat radiating section in the fixture, aesthetically integrated into the fixture  210  as a whole and provides the further functions of sealing the fixture, conduction of electrical leads  26 P and  26 L and mounting the lamp housing  216  to the stem  214 . 
   General 
   Lamp fixtures in accordance with this invention, in general, are manufactured from machined or cast aluminum and have a durable exterior coating, O rings and silicone sealant in accordance with sound manufacturing standards as defined, particularly by the Underwriters Laboratories, Inc. They employ aluminum reflectors for the lamps and flat tempered or borosilicate glass lens secured in place by silicone sealant. 
   The preferred lamps, depending upon the wattage requirements are as follows: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Fixture Rating 
               Lamp Type 
               Ballast Type 
             
             
                 
             
           
           
             
               150 Max 
               T6 CDM MH 
               MC 150-1-F-120U 
             
             
               100 Max 
               PAR 38 CDM MH 
               M10012-27CK-5EU 
             
             
                70 MAX 
               T6 CDM MH 
               MC 70-1-F-120U 
             
             
                39 MAX 
               PAR20 MH 
               M39120CK-6EUN-F 
             
             
                20 MAX 
               TM CDM 
               RMH-20-E-LF 
             
             
                 
             
           
        
       
     
   
   Suppliers of the foregoing lamps and ballasts are well known in the lighting field. 
   Pre-production lighting fixtures incorporating the principles of this invention have met all of the standards of the Underwriters Laboratories, Inc. Standard 1598 for luminere including the temperature rise requirements and Canadian CSA standards C22.2 No. 250.0 and the Canadian specific standards. 
   The versatility of fixtures incorporating this invention to accommodate the broad range of power ratings is believed to be owed, at least in part, to the thermal dissipation capabilities afforded by this invention. 
   The foregoing embodiments and the descriptions are representative of the preferred embodiments of this invention and are not to be considered as limiting. Rather, the invention must be determined by reference to the following claims, as stated below and given the protection afforded by the Doctrine of Equivalents.