Patent Publication Number: US-6905227-B2

Title: Light emitting diode retrofit module for traffic signal lights

Description:
This application claims the benefit of U.S. Provisional Application No. 60/408,260, filed Sep. 4, 2002, and entitled Light-Emitting Diode (LED) Retrofit Module For Traffic Signal Lights. 

   FIELD OF THE INVENTION 
   The present invention relates to Light-Emitting Diode (LED) lamps for traffic signal lamps, and more particularly to an improved retrofit LED lamp module and method for replacing conventional light bulbs in traffic signal lamps with the improved retrofit LED lamp module, including 12 and 8 inch round traffic signal lamps, pedestrian signs, hand signs, arrow signs and signs with messages. 
   BACKGROUND OF THE INVENTION 
   Light emitting diode (LED) lamps have been developed to replace conventional incandescent or fluorescent lamps for reducing electrical and maintenance costs, and for increasing reliability. LED lamps consume less electrical energy than conventional lamps while exhibiting much longer lifetimes. Such LED lamps typically include a power supply and a plurality of LEDs mounted on a flat or curved surface. 
   One growing use of LED lamps is the replacement of incandescent light bulbs in traffic signal lamps. A common conventional traffic signal lamp is illustrated in  FIGS. 1A and 1B , and includes a housing  1 , a front door plate  2 , a lens  3 , a reflector  4  and an incandescent light bulb  5 . Retainers  6  affix the lens  3  to the front door plate  2 , which opens via hinges  7  to allow access to the interior of the housing  1 . Light bulb  5  screws into threaded electrical socket  8 , which is electrically attached to a terminal strip  9 , which in turn receives its power from the traffic signal controller. 
   It is known to replace the incandescent light bulb  5  with an LED lamp, along with the lens  3  since the lens may be designed specifically for the output of an incandescent light bulb. In a conventional traffic signal lamp retrofit procedure, the lens  3 , light bulb  5 , reflector  4  and socket  8  are all removed, and an LED lamp module  10  is installed onto the front door plate  2  to replace lens  3 , as illustrated in FIG.  2 . Wires  11  from the LED lamp module are connected to the terminal strip  9 . The lamp module  10  includes up to several hundred LEDs all mounted on a flat printed circuit board and are evenly distributed across the lens area. 
   The above mentioned retrofit method has several drawbacks. First, it is time consuming and labor intensive to remove the reflector and socket, and access the terminal strip with new wiring. Because traffic is usually blocked in order to access traffic lights, time is of the essence. Second, in order to safely disconnect the socket connector wires from the terminal strip, and connect new wires from the LED lamp module to the terminal strip, the power to the traffic signal must be temporarily turned off, which disrupts traffic flow through the intersection. Finally, once the retrofit is complete, it is not possible to put the original incandescent lamp back in the traffic signal lamp, for example, in case a spare LED lamp module is not available. 
   U.S. Pat. No. 6,268,801, which is incorporated herein by reference, discloses a method and apparatus for retrofitting traffic signal lamps with LED modules, without having to remove the reflector  4  and socket connector  8 , and without having to access the terminal strip with new wiring. The LED module disclosed in this patent includes a plurality of light emitting diodes evenly distributed on a flat PC board, a power supply electrically connected to the plurality of light emitting diodes, and wires extending from the power supply that terminate in a threaded electrical connector compatible with the socket connector  8 . The method of retrofitting the traffic signal lamp includes removing the lens from the front door plate, removing the threaded light bulb from the socket connector, affixing the LED lamp module to the front door plate, and connecting the threaded electrical connector of the LED lamp module to the socket connector. This retrofit procedure is simple, takes very little time and labor, and can be safely performed without turning power off to the traffic signal lamp. Typical traffic signal lamps have lenses that are 8 or 12 inches in diameter. As long as the outer rim of LED lamp module has a similar shape and diameter as the outer rim of lens, then the same retainers that secured the lens in place onto the front door plate can be used to secure the LED lamp module in place. Thus, the LED lamp module preferably has a flange that is shaped and sized to match the outer rim of the lens that it replaces. 
   It is also well known in the art to make LED lamps by mounting a plurality of outwardly facing LEDs to a spherical lamp head, which terminates with a threaded electrical connector. Such an LED lamp simulates the light distribution of a standard light bulb, except the light is generated by the outwardly facing LEDs instead of an internal filament. This LED lamp can be easily substituted for a conventional traffic light bulb, but the intensity from such a lamp can be problematic. Not only is it difficult to mount enough LEDs on the spherical lamp head to produce the desired luminosity, but light emanating therefrom must still reflect off of the reflector, which can be optically lossy and degrade over time. The traffic light lens may also have to be replaced to produce the desired illumination pattern. 
   Recently, more efficient and higher power LEDs have been developed that reduce the number of LEDs which are necessary to meet signal lamp output intensity requirements (e.g. can be as few as 2 for some applications). For example, Dialight Corporation (of Farmingdale, N.J.) markets an LED module  12  (shown in  FIG. 3 ) containing only 18 high power LEDs  14 , which provide as much light output as a conventional 80-300 LED array on a 12 inch diameter circuit board. To provide an aesthetically acceptable appearance, the Dialight LED module has all 18 LEDs  14  mounted together in a concentrated small cluster on the rear wall  15  of the module&#39;s housing  13 . A planar Fresnel lens  16  and curved outer lens  17  are both mounted to the flange  18  that engages with the front door plate of the traffic signal lamp housing. The Fresnel lens  16  collimates the diverging light output to evenly illuminate the outer lens  17 . Wires  19  extend from the LED module for connection to the traffic signal lamp&#39;s terminal strip. 
   In order to fully illuminate the Fresnel/outer lenses  16 / 17 , the LEDs  14  must be placed a minimum distance D 1  behind the Fresnel lens. For a 12 inch diameter module, even with the LEDs placed at the very rear of the module, the distance D 2  between the front surface of the flange  18  and the rear wall  15  still exceeds approximately 109 mm (D 2  for 8 inch diameter module exceeds approximately 102 mm). Moreover, since there is no room behind the LEDs for the module&#39;s power supply  20 , the housing sidewall must extend laterally far enough to accommodate the module&#39;s power supply  20  so that it does not block the light emitted by the LEDs from reaching the lenses  16 / 17 . Since most conventional 12 inch diameter traffic signal lamps have a depth of approximately 112 mm ±2 mm (measured from the back surface of the door plate  2  to the bottom of reflector  4  or to the socket connector  8  should it protrude up from the reflector bottom) and most conventional 8 inch diameter traffic signal lamps have a depth of approximately 80 mm ±2 mm, and a spherical or parabolic shape that is narrower than the profile of the Dialight lamps, the depth and shape of these lamps simply prevents it from fitting inside conventional traffic lamp reflectors. Thus, the installation of the Dialight lamp is cumbersome and time consuming because it requires removal of the existing traffic signal lamp reflector, electrical socket, and electrical connection to the terminal strip. 
   There is a need for a high power LED lamp module that fits inside a conventional traffic signal lamp reflector, and which facilitates a fast and simple retrofit thereof without having to turn off power thereto. 
   SUMMARY OF THE INVENTION 
   The present invention solves the aforementioned problems by providing an LED lamp module that conveniently installs into conventional traffic signal lamps without having to remove the reflector and electrical socket connector therein. 
   The LED lamp module of the present invention includes a housing, a plurality of LEDs, a power supply, wires, a Fresnel lens, and an outer lens. The housing includes a rear wall portion, a side wall portion extending from the rear wall portion, a flange extending from the side wall portion and having a front surface that defines a flange plane, and a spacer ring portion extending from the flange by a height H and terminating with an open end. The plurality of LEDs are disposed inside the housing for producing diverging light. The power supply is disposed in the housing between the plurality of LEDs and the rear wall portion, and are electrically connected to the plurality of light emitting diodes. The wires are connected to the power supply and extend from the housing and terminate in a threaded electrical connector. The Fresnel lens extends across the open end for collimating the diverging light from the LEDs. The outer lens disposed over the Fresnel lens for receiving the collimated light, wherein the Fresnel lens is disposed a first distance from the light emitting diodes so that the collimated light just fills and illuminates the entire outer lens. 
   In another aspect of the present invention, the LED lamp module includes a housing, a plurality of LEDs, a power supply, wires, a Fresnel lens, and an outer lens. The housing includes a rear wall portion, a side wall portion extending from the rear wall portion, a flange extending from the side wall portion and having a front surface that defines a flange plane, and a spacer ring portion extending from the flange by a height H and terminating with an open end. The plurality of LEDs are disposed inside the housing for producing diverging light. The power supply is disposed in the housing and electrically connected to the plurality of light emitting diodes. The wires are connected to the power supply and extend from the housing and terminate in a threaded electrical connector. The Fresnel lens is curved and extends across the open end for collimating the diverging light from the LEDs. The outer lens is planar and is disposed over the Fresnel lens for receiving the collimated light. The Fresnel lens is disposed a first distance from the light emitting diodes so that the collimated light just fills and illuminates the entire outer lens. 
   In yet one more aspect of the present invention, the LED lamp module includes a housing, a plurality of LEDs, a power supply, wires, a Fresnel lens, and an outer lens. The housing includes a rear wall portion, a side wall portion extending from the rear wall portion, a flange extending from the side wall portion and having a front surface that defines a flange plane, and a spacer ring portion extending from the flange by a height H and terminating with an open end. The plurality of LEDs are disposed inside the housing for producing diverging light. The power supply is disposed in the housing between the LEDs and the rear wall portion, and is electrically connected to the plurality of light emitting diodes. The wires are connected to the power supply and extend from the housing and terminate in a threaded electrical connector. The Fresnel lens is curved and extends across the open end for collimating the diverging light from the LEDs. The outer lens is planer and is disposed over the Fresnel lens for receiving the collimated light. The Fresnel lens is disposed a first distance from the light emitting diodes so that the collimated light just fills and illuminates the entire outer lens. The outer lens has a diameter of about 8 or 12 inches, wherein the spacer ring portion height H is selected such that the flange plane is separated from the rear wall portion by a second distance that does not exceed about 70 mm if the outer lens diameter is about 8 inches and about 100 mm if the outer lens diameter is about 12 inches. 
   Other objects and features of the present invention will become apparent by a review of the specification, claims and appended figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a side cross-sectional view of a conventional traffic signal lamp. 
       FIG. 1B  is a back view of the front door from a conventional traffic signal lamp. 
       FIG. 2  is a side cross-sectional view of a conventional traffic signal lamp containing a conventional LED lamp module. 
       FIG. 3  is a side cross-sectional view of a conventional high power LED lamp module. 
       FIG. 4  is a side cross-sectional view of the high power LED lamp module of the present invention. 
       FIG. 5  is a side cross-sectional view of a traffic signal lamp retro-fitted with the high power LED lamp module of the present invention. 
       FIG. 6  is a partial side view of the high power LED lamp module of the present invention, with a removable electrical connector disposed along its electrical wires. 
       FIG. 7  is a partial side view of the high power LED lamp module of the present invention, with a removable electrical connector disposed at the housing rear wall. 
       FIG. 8  is a partial side view of the high power LED lamp module of the present invention, where the threaded electrical connector includes a pronged plug and a threaded adapter. 
       FIG. 9  is a side cross-sectional view of a traffic signal lamp retro-fitted with the high power LED lamp module of the present invention, where the Fresnel lens is curved and the outer lens is flat. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is an LED lamp module utilizing high power LEDs that is ideal for installation in conventional traffic signal lamps. 
   A high power LED lamp module  30  according to the present invention is illustrated in  FIG. 4 , and includes a housing  32 , a plurality of high power LEDs  34  disposed in the housing  32 , a power supply  36  disposed in the housing and behind the LEDs  34  for supplying electrical power thereto, and electrical wires  38  that are connected to the power supply  36  at one end and terminate in a threaded electrical connector  40  at the other end. The housing includes a rear wall portion  42  on which the power supply  36  and LEDs  34  are mounted, a sidewall portion  44 , a flange  46  extending out from the sidewall portion  44 , and a spacer ring portion  48  extending from the flange  46  by a predetermined height H and terminating in an open end  47 . A Fresnel lens  50  and outer lens  52  are mounted over the spacer ring portion open end  47 . The housing sidewall portion  44  has a rounded (spherical) or parabolic shape similar to that of conventional traffic signal lamp reflectors. 
   The Fresnel lens  50  is separated from the high power LEDs  34  by a distance D 3  such that the diverging light from the LEDs  34  is collimated by the Fresnel lens  50  and just fills and illuminates the entire outer lens  52 . For a 12 inch diameter module  30 , the distance D 4  between the front surface of flange  46  (which defines a flange plane FP) and the rear wall portion  42  can be as low as about 80 mm, which is significantly less than distance D 2  (˜109 mm) shown in  FIG. 3 , primarily because of the height H of spacer ring portion  48  which positions Fresnel/outer lenses  50 / 52  further away from the LEDs  34 . Likewise, for an 8 inch diameter module  30 , the distance D 4  can be as low as about 58 mm. The reduced distance D 4  provides sufficient space inside the housing to position the power supply  36  behind the LEDs  34  where it cannot block any light. The reduced distance D 4 , coupled with the rounded or parabolic shape of sidewall portion  44 , allows the module  30  to be mounted in a standard traffic signal lamp without removing its reflector, its threaded electrical socket connector, and the electrical connection to the terminal strip, while still providing plenty of space for the electrical connection therebetween using connector  40 . It has been found that the module  30 , with its electrical connector  40 , can be reliably retrofitted into most 12 inch diameter conventional traffic signal lamps so long as distance D 4  does not exceed about 100 mm, and into most 8 inch diameter conventional traffic signal lamps so long as distance D 4  does not exceed about 70 mm. 
   The retro-fitted traffic signal lamp according to the present invention is illustrated in  FIG. 5 , and includes a signal lamp housing  54 , a front door plate  56 , a reflector  58  and a threaded socket connector  60 . Retainers  62  mount the front surface of flange  46  of the LED lamp module  30  against the front door plate  56 , which opens via hinges to allow access to the interior of the signal lamp housing  54 . The threaded electrical connector  40  screws into socket connector  60 . Wires  64  connect socket connector  60  to a terminal strip  66 , which receives its power from the traffic signal controller. The spacer ring portion  48  of housing  32  extends through front door plate  56 , with the height H selected to maintain the proper distance D 3  between the LEDs  34  and the Fresnel lens  50  for proper illumination of the outer lens  52 . 
   In order to retrofit the conventional traffic signal lamp of  FIG. 1  with the LED lamp module  60  as shown in  FIG. 4 , the front door plate  56  is rotated open to expose the inside of traffic signal lamp housing  54 . Retainers  62  are loosened, and lens  3  is removed. Flange  46 , which preferably has the same outer circumference and shape as the lens  3 , is affixed to the front door plate  56  by the retainers  62 . The incandescent light bulb  5  is unscrewed out of the existing socket connector  60 , and threaded electrical connector  40  is screwed into socket connector  60 . Then, the front door plate  56  is closed. 
   For many traffic signal lamp applications, a non-symmetrical radiation pattern therefrom may be desired. For example, if the traffic signal lamp is located over a roadway, the majority of the light output should be directed straight out of the lamp, and/or slightly downward, toward the traffic. Thus, the positioning of the LED&#39;s, and/or the lenses  50 / 52  used therewith, can produce an asymmetrical lamp output. If this is the case, then the lamp housing  32  and/or the lenses  50 / 52  can be rotated before the retainers  62  are tightened, to produce the desired non-symmetrical radiation output pattern. 
   This retrofit procedure is simple, takes very little time and labor, and can be safely performed without turning power off to the traffic signal lamp. Typical traffic signal lamps have lenses that are 8 or 12 inches in diameter. As long as the flange  46  of LED lamp module  30  has a comparable shape and diameter as the outer rim of lens  3 , then the same retainers  62  that secured the lens  3  in place on the front door plate  56  can be used to secure the LED lamp module  30  in place. It is possible to re-use the lens  3  removed from the front door plate as the outer lens  52  of the lamp module  30 . A spacer can be used around flange  46  to match the flange size with that required by retainers  62 . 
     FIGS. 6-8  show alternate embodiments of the LED lamp module  30  of the present invention.  FIG. 6  illustrates a removable electrical connector  68  on wires  64  to facilitate screwing in threaded connector  40  into socket connector  60 .  FIG. 7  illustrates a removable connector  70  mounted to the LED module housing  32  that connects to wires  64 .  FIG. 8  illustrates that the threaded connector  40  comprises a pronged plug  72  and a threaded adapter  74 . The threaded adapter  74  screws into the socket connector  60 , and the pronged plug  72  plugs into the adapter  74 . 
     FIG. 9  illustrates another alternate embodiment of the LED lamp module  30 , which is shown mounted in a standard traffic signal lamp with a reflector  58  having more of a parabolic shape. With this embodiment, the Fresnel lens  50  is curved (concave) and the outer lens  52  is flat, which reduces the minimum distance D 3  between the LEDs  34  and the Fresnel lens  50  necessary to just fill and illuminate the entire outer lens  52  with the light from the LEDs  34 . By reducing distance D 3  with a curved Fresnel lens, there is more room for the power supply, and/or the distance D 4  between the flange plane FP (defined by the front surface of flange  46 ) and the rear wall  42  can be reduced as well. The housing  32  divides the lamp module  30  into two compartments: an LED compartment  76  (containing the LEDs  34 ) and a power supply compartment  78  (containing the power supply  36 ). The sidewall portion  44  of the LED lamp module  30  conforms with the parabolic shape of the reflector  58 . 
   The present invention allows for the retrofit of a conventional traffic signal lamp (with the lamp module  30  of the present invention) in less than 5 minutes, as compared to installation times exceeding 20 minutes where the reflector and socket connectors must be removed. The advantages of the present invention include: 1) using more efficient and fewer high power LEDs, 2) reducing installation times (which saves installation costs and reduces traffic interruption), and 3) eliminating the need for removal and disposal of reflectors and socket connectors from traffic signal lamps. 
   It is to be understood that the present invention is not limited to the embodiment(s) described above and illustrated herein, but encompasses any and all variations falling within the scope of the appended claims. For example, part or all of the reflector  26  could be removed during the retrofitting process, so long as the socket electrical connector stays intact, to benefit from the threaded electrical connector  40 . In fact, the reflector  26  and the socket electrical connector could be removed entirely, and the module  30  directly hardwired to the terminal strip  66 . Further, the method of the present invention applies to any lamp that utilized a conventional threaded light bulb with a lens mounted thereover. One in the art will appreciate that the collimated light exiting the Fresnel lens is not perfectly collimated light, but rather is simply less divergent than the light entering the Fresnel lens. Lastly, while  FIGS. 4 and 9  show one of the Fresnel and outer lenses  50 / 52  as being planar with the other as being curved, it is possible that both lenses are planar, or both lenses are curved.