Abstract:
A lamp fixture for mounting a high intensity discharge (HID) lamp. The lamp fixture integrates components needed to operate the HID lamp, including a lamp socket and a ballast, into a compact assembly covered by an enclosure. The fixture facilitates dissipation of heat from the lamp and ballast through a base mounting so that thermal insulation of the ballast transformed is not required, thereby reducing the weight of the device. The fixture may further include a diffuser mounted to the enclosure to distribute light from the HID lamp in a uniform manner. The fixture is particularly useful for mounting HID lamps within illuminated signs.

Description:
[0001]     This application claims priority to U.S. Patent Application Ser. No. 60/559,118 (pending) filed Apr. 2, 2004, and incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to lighting systems, and more particularly to a high intensity discharge lighting system for use with illuminated signs.  
       BACKGROUND OF THE INVENTION  
       [0003]     Illuminated signs are widely used by businesses and other entities to indicate the location of a place of business or to display information to the public in a manner that may be readily seen at nighttime or during other periods of low light. While many forms of illuminated signs are known, one popular and economic method of providing an illuminated sign involves the use of high intensity discharge (HID) lamps in conjunction with transparent or translucent sign panels having visible indicia mounted or otherwise disposed on the surface of the panels. The HID lamp is positioned behind the sign panel and light is transmitted through the panel to illuminate the sign.  
         [0004]     HID lamps are known in the art and operate by creating an arc between metal electrodes to produce high levels of intense light from a relatively small source. HID lamps are relatively energy efficient and provide long service life. Similar to fluorescent lamps, HID lamps require a ballast to aid in starting and maintaining operation of the lit lamp. Because HID lamps require high-voltage electricity and emit heat and ultraviolet radiation, manufacture and use of HID illuminated signs are covered by various codes, such as the National Electric Code, and standards, such as those developed by organizations such as Underwriters Laboratories, Inc. (UL®).  
         [0005]     To fabricate an HID illuminated sign, a manufacturer typically obtains lamp components, such as HID lamp sockets and ballasts, and integrates the individual components into a sign support structure according to guidelines such as those established by the UL® standards. Accordingly, fabrication of each illuminated sign essentially involves assembling the HID lamp components from scratch, largely because the UL® requirements have made it difficult to integrate the components into a modular fixture which may be used for all sign configurations. In particular, integrating the components into a single fixture makes it difficult to dissipate heat generated by the HID lamp and the ballast in accordance with UL® standards. To better control the heat, transformers are often potted in an insulative material, such as asphalt, and therefore the assemblies are very heavy.  
         [0006]     One commercially available lighting fixture is a perimeter lighting system that is configured to be mounted within the interior of an illuminated sign at locations around the peripheral edge of the sign. Accordingly, one drawback of this lighting fixture is that the light is concentrated toward the outer periphery of the sign and therefore does not uniformly light interior portions of the sign. The fixture requires a lens to help direct light toward the center of the sign and is also relatively heavy and expensive. Other conventional HID luminaires are generally unacceptable for illuminating interiorly lit signs because such luminaires are configured to provide highly directional lighting, whereas the objective of illuminated signs is to provide as much light as possible in every direction  
         [0007]     A need therefore exists for a lightweight, economical fixture for mounting HID lamps which is convenient for use in illuminated signs.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a lamp fixture for mounting high intensity discharge, or HID, lamps. The lamp fixture integrates all of the components needed to start and maintain operation of the HID lamp, including a lamp socket and a ballast, into a single, compact assembly. In one embodiment, the lamp fixture includes a mounting base to which all of the components are secured, and a housing cover which may be secured to the base to enclose the fixture components. The mounting base includes mounting flanges which facilitate securing the lamp fixture to the framework of an illuminated sign.  
         [0009]     In another embodiment, the lamp fixture includes several heat shields secured to the mounting base to divide the lamp fixture into individual compartments for housing the lamp socket and the ballast. The ballast includes a conventional core and coil-type transformer and an oil-filled capacitor. The heat shields also separate the transformer from the capacitor. Advantageously, the heat shields prevent heat from the HID lamp from overheating the transformer.  
         [0010]     In another embodiment, the mounting base includes a heavy steel bottom plate for dissipating heat generated by the fixture. The transformer is mounted to the mounting base such that it is firmly in contact with the bottom plate to optimize conductive heat transfer from the transformer to the mounting base. The housing cover also includes louvered vents which cooperate with the mounting base and heat shields to manage the thermal characteristics of the lamp fixture, and to dissipate heat generated by the HID lamp and the transformer.  
         [0011]     In yet another embodiment, the lamp fixture includes a diffuser mounted to the housing cover, proximate the HID lamp. The diffuser helps to evenly distribute light from the HID lamp and, when used with an illuminated sign, helps to alleviate bright spots on the sign panels adjacent the HID lamp.  
         [0012]     In another embodiment, an outdoor, illuminated sign includes a sign support frame, at least one transparent or translucent sign panel mounted to the frame, at least one lamp fixture mounted to the sign frame, and an HID lamp installed in the lamp fixture.  
         [0013]     The features and objectives of the present invention will become more readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.  
         [0015]      FIG. 1  is a perspective view of an exemplary HID lamp fixture according to the present invention, with broken sections depicting detail of fixture components;  
         [0016]      FIG. 2A  is an exploded perspective view of the HID lamp fixture of  FIG. 1 ;  
         [0017]      FIG. 2B  is a top plan view of the mounting base of  FIG. 2A ;  
         [0018]      FIG. 2C  is a perspective view of a transformer bracket used with the mounting base of  FIG. 2A ;  
         [0019]      FIG. 3  depicts a front elevational view of a typical illuminated sign in which the lamp fixture of  FIG. 1  is used; and  
         [0020]      FIG. 4  is a side elevational view of the sign of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION  
       [0021]     Referring to  FIG. 1 , there is shown an exemplary high intensity discharge (HID) lamp fixture  10 , according to the present invention. The HID lamp fixture  10  includes a mounting base  12 , which supports various components of the lamp fixture  10 , as will be discussed more fully below. A housing cover  14  is secured to the mounting base  12  to enclose the lamp components. The lamp fixture  10  may further include an optional diffuser  16  which may be secured to the fixture  10 , generally atop the housing cover  14 .  
         [0022]     With continued reference to  FIG. 1 , and referring further to  FIGS. 2A, 2B  and  2 C, the mounting base  12  includes a bottom plate  20  upon which the lamp components are mounted. In one embodiment, the bottom plate  20  is stamped from sheet metal, however, it will be recognized that the bottom plate  20 , as well as the rest of mounting base  12 , may be formed from other materials and by other methods. Flanges  22   a ,  22   b  are provided at respective longitudinal ends  24   a ,  24   b  of the mounting base  12 . Slots  26  and/or apertures  28  are formed through the flanges  22   a ,  22   b  for receiving bolts or other fasteners to facilitate securing the mounting base  12  to a support surface. A pair of sidewalls  30   a ,  30   b  are formed along oppositely facing lateral side edges of the mounting base  12  and apertures  32  are formed therethrough for receiving fasteners  34 , which may used to secure the housing cover  14  to the mounting base  12 , as depicted in  FIG. 1 .  
         [0023]     The bottom plate  20  of the mounting base  12  is separated into individual compartments  36   a ,  36   b ,  36   c  by three upstanding heat shields  38 ,  40 ,  42  secured to the bottom plate  20 . In the exemplary embodiment shown, the heat shields  38 ,  40 ,  42  comprise generally rectangular steel plates having angled lower edges  38   a ,  40   a ,  42   a  for securing the heat shields  38 ,  40 ,  42  to the bottom plate  20  such as by spot welds  44  applied to the angled edges  38   a ,  40   a ,  42   a  and the bottom as shown most clearly in  FIG. 2B .  
         [0024]     A mounting shelf  50  is secured on one side of the first heat shield  38  and has an aperture  52  sized to receive a ceramic lamp socket  54  for mounting the HID lamp. The lamp fixture  10  further includes a ballast  56 , for starting and maintaining illumination of an HID lamp installed in the lamp socket  54 . The ballast  56  includes a conventional core and coil type transformer  58  secured to the bottom plate  20  between the first and second heat shields  38 ,  40 , and an oil-filled capacitor  60  secured to the base plate  20  between the second and third heat shields  40 ,  42 . To facilitate heat transfer from the transformer  58  to the bottom plate  20 , the transformer  58  is firmly seated against the bottom plate  20  by a pair of mounting brackets  62   a ,  62   b  secured to the bottom plate  20  and cooperating with corresponding brackets  64   a ,  64   b  attached to the transformer  58 .  
         [0025]     Transformer brackets  64   a ,  64   b  are shown more clearly in  FIG. 2C , and each comprises an elongate lower bracket portion  72  having downturned ends  73 . A plate-like upper bracket portion  74  extends upwardly from a side edge of the lower bracket portion  72 . A pair of spaced tabs  75  are formed on opposite sides of the top end of the upper bracket portion  74  to receive an end portion of the transformer  58  therebetween. Apertures  76  formed through the tabs  75  facilitate securing the brackets  64   a ,  64   b  to the transformer  58  with threaded fasteners. Additional apertures  78  formed through the lower bracket portion  72 , near the downturned ends  73 , are sized to receive threaded fasteners inserted therethrough to engage corresponding apertures  79  formed through mounting brackets  62   a ,  62   b  when transformer brackets  64   a ,  64   b  are arranged to straddle the mounting brackets  62   a ,  62   b . Advantageously, the threaded fasteners inserted through aligned apertures  78  and  79  may be adjusted to draw the transformer  58  firmly against the bottom plate  20  so that conductive heat transfer between the bottom plate  20  and the transformer  58  is maximized.  
         [0026]     The lamp socket  54 , the transformer  58  and the capacitor  60  are electrically coupled by appropriate wiring as known in the art. Advantageously, wire leads  66  from the lamp socket  54  are coupled to wires  68   a ,  68   b  from the transformer  58  and capacitor  60  of the ballast  56  by 1,000 volt-rated closed-end crimp connectors  70 . The lamp fixture  10  is provided with various wire leads for connecting the ballast  56  to 120, 208, 240, and 277 volt AC sources. When the housing cover  14  is secured to the mounting base  12 , as depicted in  FIG. 1 , the first, second and third heat shields  38 ,  40 ,  42  thermally insulate the lamp socket  54 , transformer  58  and capacitor  60 , and help to dissipate heat to the bottom plate  20 .  
         [0027]     With continued reference to  FIGS. 1 and 2 A, the housing cover  14  of the lamp fixture  10  will now be described. In the embodiment shown, the housing cover  14  is a generally box-shaped enclosure having an open end for receiving the components of the lamp fixture  10  therein when the housing cover  14  is fitted over the mounting base  12  as depicted in  FIG. 1 . The mounting cover  14  includes a top wall  80  positioned generally opposite the mounting base  12 , and a pair of confronting sidewalls  82   a ,  82   b  extending generally downward from opposite lateral side edges of the top wall  80 . The top wall  80  and first and second sidewalls  82   a ,  82   b  of the housing cover  14  have bent edge portions  84   a ,  84   b ,  84   c  provided on respective longitudinal ends  86   a ,  86   b  whereby first and second end plates.  88   a ,  88   b  may be secured to the top wall  80  and sidewalls  82   a ,  82   b , for example by spotwelding. Several apertures  90  are formed through the bottom ends  92   a ,  92   b  of the first and second sidewalls  82   a ,  82   b  to facilitate securing the housing cover  14  to the mounting base  12 , such as with screw fasteners  34 , as depicted in  FIG. 1 .  
         [0028]     The top wall  80  also includes an aperture  100  formed proximate the location of the lamp socket  54  so that when the housing cover  14  is fitted to the mounting base  12 , the end of the lamp socket  54  protrudes above the top wall  80  to facilitate installing an HID lamp within the lamp socket  54  while the remainder of the lamp socket  54  is recessed within the housing cover  14 . The recessed configuration of the lamp socket  54  gives the fixture  10  a low-profile that facilitates installation in tight spaces and makes retrofitting older sign units with the lamp fixture  10  easier. To facilitate heat dissipation, a plurality of louvered vents  102  are formed in the first and second sidewalls  82   a ,  82   b  and in the first end panel  88   a  of the housing cover  14 . The housing cover  14  may further include perforated knock-outs  104  formed in the top wall  80 , sidewalls  82   a ,  82   b  or end panels  88   a ,  88   b  to facilitate creating openings through which various electrical connections may be routed through the housing cover  14  to the components of the lamp fixture  10 .  
         [0029]     An access opening  108  is formed through the second end panel  88 b to provide user access to a compartment behind the third heat shield  42  so that wiring connections can be easily accomplished. The access opening  108  is covered by an access panel  109  removably secured to end plate  88 b by a fastener  34 , as depicted in  FIG. 1 . Top wall  80  also includes several small apertures  106  disposed generally around the lamp socket aperture  100  to facilitate mounting a diffuser  16  atop the housing cover  14 , as depicted in  FIG. 1 . In the embodiment shown, the hole pattern of the small apertures  106  is configured to correspond to holes formed through the diffuser  16  such that the diffuser  16  may be mounted atop the housing cover  14  in a desired orientation.  
         [0030]     As shown in  FIG. 1 , the lamp fixture  10  may further include a diffuser  16  which may be coupled adjacent the HID lamp socket  54  to facilitate evenly distributing light emitted from an HID lamp (not shown). In the exemplary embodiment shown, the diffuser  16  is a generally unshaped member having a bottom wall  120  and a pair of upstanding, confronting sidewalls  122 ,  124  extending generally upwardly from the bottom wall  120 . Apertures  126  formed through the sidewalls  122 ,  124  of the diffuser  16  help to diffuse light that is emitted from the lamp in a direction directly toward the surfaces of the sidewalls  122 ,  124 . When arranged in a sign structure with the sidewalls  122 ,  124  substantially parallel to the sign panels, the diffuser  16  provides a buffer between the bright light source of the lamp and the sign face. The open top  128  and side ends  130  of the diffuser  16  permit light to freely emanate from the HID lamp along directions parallel to the sidewalls  122 ,  124 . In one embodiment, the surfaces of the diffuser  16  are painted gloss white to increase the efficiency of light reflected from the sidewalls  122 ,  124  and bottom wall  120  and to reduce light absorption into the diffuser  16  itself. While the diffuser  16  is depicted having a plurality of circular apertures  126  in a closely spaced arrangement, it will be recognized that apertures in various other shapes, such as differently sized holes or slots, may be formed in various other patterns through the diffuser  16  to obtain various levels of light diffusion, as may be desired.  
         [0031]     Referring now to  FIGS. 3 and 4 , there is shown an exemplary illuminated sign  140  incorporating high intensity discharge lamps in lamp fixtures  10  as described above. The sign  140  comprises a sign support frame  142  to which a pair of spaced confronting sign panels  144  are mounted. The sign panels  144  are translucent or transparent to permit light emanating from a central portion of the sign  140  to be transmitted through the panels  144  and thereby illuminate the sign  140 . Various indicia  146  in the form of letters, number or symbols are disposed on the sign panels  144  as known in the art. The internal structure of the sign support frame  142  is depicted. Several HID lamp fixtures  10 , as described above, are secured to the sign support frame  142  at various spaced locations within the interior of the sign perimeter. For example, the fixtures  10  may be spaced and arranged within the frame  142  such that the lamp centers are located at 4-foot horizontal and vertical distances from one another. It will be recognized that various other arrangements for supporting and spacing the HID lamp fixtures  10  throughout the interior of the sign  140  are possible. Advantageously, the support base  12  of the lamp fixture  10  permits the lamp fixture  10  to be secured to the sign support  142  in a variety of ways such as by bolting, clamping, or otherwise fastening the support base  12  to the sign support frame  142 .  
         [0032]     The HID lamp fixture  10  of the present invention provides a compact, integral unit that facilitates mounting HID lamps within illuminated sign systems. Advantageously the mounting base  12 , in conjunction with the heat shields  38 ,  40 ,  42  and louvered vents  102  on the housing cover provides superior heat dissipation from the fixture  10 , while maintaining the temperature of the ballast  56  at appropriate levels so that thermal insulation of the ballast  56 , typically accomplished by insulative potting material, is not necessary. This results in a ballast  56  which is much more lightweight compared to conventional ballast configurations used in HID lighting applications. Accordingly, the lamp fixture  10  is lighter in weight than the assembled components typically used by sign manufacturers in a conventional HID illuminated signs.  
         [0033]     While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant&#39;s general inventive concept.