Abstract:
A solid state replacement light module for a high intensity discharge light fixture. The module is comprised of an elongated generally planar body having a first side including a plurality of light emitting diodes and a second side including a plurality of heat dissipating fins. The second side further includes an electronic module. The body also includes a hinge mechanism suitable for attachment to the light fixture.

Description:
BACKGROUND 
     Exterior lighting is used to illuminate roadways, parking lots, yards, sidewalks, public meeting areas, signs, work sites, and buildings, to name a few examples. Traditionally, such lighting systems used high-intensity discharge (HID) lamps, often high pressure sodium (HPS) lamps. The move towards improved energy efficiency has brought to the forefront light emitting diode (LED) technology as an alternative to HID lighting in commercial and municipal applications. LED lighting has the potential to provide improved energy efficiency and improved light output in outdoor applications. 
     The Cobra Head type light fixture is perhaps the most commonly found style of roadway fixture. It would be advantageous to convert existing Cobra Head style HID lamps to LED light sources without having to discard the entire fixture assembly. There is therefore a need for an improved LED retrofit solution for outdoor applications that does not require replacement of the existing fixture. 
     With reference to  FIG. 1 , a typical roadway lighting fixture is depicted. The Cobra Head lighting fixture  1  comprises a housing  3  having a central longitudinal axis “L”. The housing  3  includes a center section  5  arranged about the center longitudinal axis “L” of the housing  3  and running substantially along one half the length of the longitudinal axis of the housing  3 . The center section  5  defines a forward compartment enclosing an HID lamp  7  and a reflector  9 . The compartment is accessed via a door (not shown) hinged to a bottom surface of the fixture to provide access to the compartment from below. Typically, the door includes an opening receiving a lens through which light generated by the HID lamp  7  exits the fixture  1 . A rear section  11  of the housing  3  defines a rearward compartment housing a power supply  13  such as a ballast. The rear compartment also receives post  15 . A second door (not shown) is provided to cover the power supply  13  and provide independent access thereto. Alternatively, a single door is provided which is hingedly connected to the fixture  1  and provides access to center section  5  and rearward section  11  when opened. 
     According to one available LED retrofit system a replacement LED light source can be installed as follows. First, the door of an existing roadway illuminaire is opened, the existing HID lamp, reflector and lens are removed and recycled. Optionally, the existing ballast and other electrical components can be similarly removed. An LED light engine is then installed into the opening in the door from which the lens was removed. A safety cable is installed between the LED light engine and a main body of the fixture. Power leads are attached between the LED light engine and the power leads of the light fixture. Thereafter, the fixture door is closed and latched to achieve final installation of the LED luminaire. Although functional, this design can suffer from thermal management issues. 
     The present disclosure is directed to an improved simple and economic LED module for replacement of an HID lamp in an outdoor fixture. 
     BRIEF DESCRIPTION 
     According to a first embodiment, a solid state replacement light module for a high intensity discharge light fixture is provided. The module is comprised of an elongated general planar body. The body has a first side including a plurality of light emitting diodes and a second side including an electronics module. The body further includes a means for rotatable attachment to the light fixture. 
     According to a second embodiment, a method of retrofitting a roadway lamp fixture is described. The method comprises providing an LED inclusive door which is cooperatively shaped and sized relative to an opening in the lamp fixture. The LED inclusive door includes a first side with a plurality of light emitting diodes and a second side including an electronics module. An existing door is removed from the fixture at its hinged connection to the fixture and the LED inclusive door is installed to the fixture at the hinged connection. The electronics module is connected to the fixture power lines. 
     According to a third embodiment, a method of retrofitting a roadway lamp fixture is provided. The method comprises removing existing roadway lamp, fixture door, removing a lamp and electronics suitable for driving the lamp from the fixture. Further steps include installing electronics suitable for driving a plurality of light emitting diodes, connecting the electronics to a power line within the fixture and installing a door including a plurality of light emitting diodes which is sized substantially the same as the removed existing door. An electrical connection between the electronics suitable for driving the light emitting diodes and the plurality of light emitting diodes is also established. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a perspective view of a prior art Cobra Head roadway fixture; 
         FIG. 2  is a perspective view of a Cobra Head roadway fixture including an LED replacement module; 
         FIG. 3  is a perspective view of the LED replacement module; 
         FIG. 4  is a bottom view of the module of  FIG. 3 ; 
         FIG. 5  is a side view of the module of  FIG. 3 ; 
         FIG. 6  is a top view of the module of  FIG. 3 ; 
         FIG. 7  is a bottom view of the module of  FIG. 4  with optical elements  48  and  52  removed; and 
         FIG. 8  is a side elevation view of the fixture of  FIG. 2  with the module door open. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a convenient and economical device for the replacement of an HID light source in a light fixture. The disclosure finds particular relevance to roadway fixtures, such as the commonly employed Cobra Head style. Of course, although reference is made herein to the Cobra Head style of fixtures, the LED lighting module described is amenable to other similar types of lighting fixtures. 
     Referring to  FIG. 2 , a light fixture  20  including the subject replacement LED light source is depicted. More particularly, a standard roadway light fixture  20  including a main housing  22  has been modified to include an LED lighting module  24 . In this regard, the perimeter of the LED lighting module  24  is shaped cooperatively to base opening  26  of the main housing  22 . 
     Referring now to  FIGS. 3-7 , the present disclosure provides a light engine module  24  including a plurality of LEDs  28  disposed on a printed circuit board  30 . The LEDs can emit in combination at least 1500 lumens. Printed circuit boards  30  are mounted to and in thermal communication with elongated and substantially planar body  32 . Body  32  is provided with a plurality of hollow bosses  35  which receive screws (not shown) that facilitate mounting printed circuit board(s)  30  to body  32 . In this manner, through holes between outboard side  37  of body  32  and inboard side  39  can be avoided. Preferably, body  32  is comprised of a cast metal having a high thermal conductivity to facilitate heat dissipation via spreading throughout the entire roadway lighting fixture  20 . A plurality of heat dissipating fins  34  are also provided to enhance heat dissipation by increasing surface area. 
     Electronics modules  36  are provided to facilitate the conversion of alternating current to DC current for powering of the LEDs  28 . The light engine module  24  is provided with a pair of tabs  40  which facilitate the attachment to a hinge element on the existing main fixture housing  22 . Moreover, cooperative tabs or a recess on the main fixture housing  22  can receive tabs  40  and be joined together via a post pin or other element. 
     A clip element  44  may be provided at end  46  of the light engine module  26  to permit selective rotatable mating to light fixture  20  and retain the module in a closed position. Alternatively, if the original HID fixture includes a clip on the main housing  22 , it is envisioned that original clip can be utilized to retain the replacement LED module  24 . 
     Alternative means for joining the light engine module  24  to fixture main housing  22  can include a spring, strap, hinge, hook or other mechanical joinder which allows sufficient rotation to open the LED lighting module. 
     An optic  48  is provided on the outboard side  37  of body  32 . Optic  48  overlays the LEDs  28  and facilitates transmission of a desired light pattern. Optical elements  52  are additional reflectors that direct light outwardly at a relativity higher orientation to direct light between adjacent poles. If poles are relatively close, the additional light elements  52  may be unnecessary. Nonetheless it is considered advantageous to provide multiple LED arrays having different focal points to provide light on different targets. 
     Referring now to  FIG. 8 , by removing the forward compartment door, the rearward compartment door and the internal HID components and attaching the LED lighting module to the hinge elements used in association with the rearward component door, the bottom section of the lighting fixture  20  is replaced in its entirety with an LED light module  24 . This solution is similarly employed when the entire base of the HID light fixture is closed by a single door providing access to the HID lamp and the ballast components. 
     Advantageously, the present retrofit solution creates a light fixture having excellent heat sinking for LED generated heat as LED lighting module  24  is a large mass body which is in thermal communication with main fixture housing  22 . The present LED replacement module can be a complete retrofit module to convert a traditional roadway light fixture from an HID light source to an LED light source by removing the electrics door, the optical door, and associated brackets and replacing them with a complete LED module that fits the existing housing as an integral replacement door. The assembly can be in the form of combined optical door/power door to be separated into two distinct assemblies. 
     The assembly enables easy field conversion of HID roadway fixtures to LED. By integrating, the LED optical system and power electronics into a single retrofit door assembly, the conversion to LED would be quick, low cost and have good thermal performance. 
     The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.