Patent Publication Number: US-7911357-B2

Title: Tricolor signal housing

Description:
BACKGROUND 
     The present exemplary embodiments relate to signal housings. They find particular application in conjunction with housing multiple LED groups within an automotive, railway, vehicular, waterway, illumination, and/or pedestrian signal. One particular application for such a signal is to substitute three separate and distinct LED groups each in its own housing into a single integrated tri-color signal within one housing. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications. 
     Automotive, railway, vehicular, waterway, illumination, and/or pedestrian signals are employed to regulate motorists and pedestrians via various commands. These commands are provided by various illuminated elements with particular colors and/or shapes that are each associated with an instruction. Elements are conventionally illuminated via incandescent bulbs which use heat caused by an electrical current to emit light. When electrical current passes through a filament (e.g., tungsten), it causes the filament to heat to the point that it glows and gives off light. Such illumination can be covered with a colored lens and/or template to provide a meaningful instruction that can be viewed in a variety of external lighting conditions. 
     The filament is a resistive element in the incandescent bulb circuit. The amount of current drawn by the filament is proportional to its impedance. This impedance value increases as the temperature of the filament increases. Thus, a conventional lamp has a larger initial current draw which drops in proportion to the increase in the filament impedance. This variation in current draw is known and a predetermined range can be utilized to monitor the lamp operation. As such, a lamp failure condition can be identified based on the amount of current drawn by the filament. In one example, the filament fails (e.g., breaks) causing the impedance approaches an infinite value and the current value decreases to almost zero. If the current drawn is outside of the predetermined range, a responsive action can be initiated by a current monitor or other control system. 
     Unlike incandescent-based signals, LED-based signals consist of an array of LED elements, which draw much less power. LED-based signals have numerous advantages over incandescent signals, such as greater energy efficiency and a longer lifetime between replacements than conventional signals. However, there are some drawbacks related to current LED signal designs. Three LED signals are generally employed to replace conventional incandescent signals on a one-to-one basis. In addition, current multiple color LED signals are susceptible to color mixing failure due to poor insulation design. 
     What are needed are systems and methods to provide multi-color signal designs with a single integrated signal that is consolidated into one housing. 
     BRIEF DESCRIPTION 
     In one aspect, a traffic signal housing includes a bottom housing element that has a radius and a power circuit that is connected to an external source via one or more pluggable connectors through the bottom housing element. Three distinct arrays of LEDs provide a tri-color signal, wherein each array is powered by the power circuit. A distribution cover is coupled to the bottom housing element to enclose the power circuit and the LED arrays. 
     In another aspect, a tricolor LED signal housing includes a bottom housing element that has a radius to accommodate one or more traffic signal circuit components on a front side. A plurality of pluggable connectors are permanently built in a back side of the bottom housing element, wherein each pluggable connector accommodates a wire. A power supply PCB includes a plurality of pluggable connectors that are mounted to thereon, wherein each pluggable connector provides direct electrical connectivity from the wire to the power supply PCB. A lighting circuit includes three distinct groups of LEDs in a single array, each group having a disparate color wherein current is drawn by each LED group from the power supply PCB. 
     In yet another aspect, a method is employed to combine three distinct arrays of LEDs into a single housing. A bottom housing element is assembled to a power/control circuit on a first side, wherein the bottom housing element includes a plurality of pluggable connectors on a second side of the bottom housing element, each pluggable connector accommodates a wire. The power/control circuit is mounted to the bottom housing in a fool-proof manner through the alignment of the pluggable connectors. A single LED PCB, that includes three distinct LED arrays, is connected to the power/control circuit. A distribution cover is coupled to the bottom housing element to enclose the power control circuit and the LED PCB. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a detailed exploded view of a tricolor signal housing, in accordance with an aspect of the subject invention. 
         FIG. 2  illustrates an isometric exploded view of a tricolor signal housing, in accordance with an aspect of the subject invention. 
         FIG. 3  illustrates a front isometric view of a tricolor signal housing, in accordance with an aspect of the subject invention. 
         FIG. 4  illustrates a rear isometric view of a tricolor signal housing, in accordance with an aspect of the subject invention. 
     
    
    
     DETAILED DESCRIPTION 
     In describing the various embodiments of the lighting system, like elements of each embodiment are described through the use of the same or similar reference numbers. 
       FIG. 1  illustrates a detailed exploded view of a tricolor signal housing  100 . The tricolor signal housing  100  includes a bottom housing element  102  that is designed to accommodate one or more traffic signal circuits to facilitate power delivery and control to a plurality of illumination elements contained therein. In one approach, the tricolor signal housing  100  is utilized to accommodate an LED traffic signal that includes a plurality of LED groups wherein each LED group is a disparate color. In this manner, a traffic signal can provide necessary disparate light output to provide appropriate traffic (e.g., pedestrian vehicular transit rail, etc.) control. 
     The bottom housing element  102  includes a plurality of pluggable connectors  104  to facilitate the connection of a plurality of wires to one or more circuits contained inside the tricolor signal housing  100 . In one approach, the bottom housing element  102  facilitates electrical connection of wires that deliver power to a plurality of pluggable connectors  108  that are operably connected to a power/control PCB circuit  106  via the pluggable connectors  104 . 
     In one approach, the bottom housing element  102  has a flat bottom and a flared side wall that extends around the circumference of the circular shaped bottom housing element. The side wall profile can include one of a parabolic, an orthogonal, or other shape as desired. Moreover, the diameter and shape of the bottom of the bottom housing element  102  can vary based on the PCB size, LED array size, mask size, lens size, or size of a distribution cover, for example. It is to be appreciated that that size and/or shape of the bottom housing element can vary based on various size or design requirements. 
     A plurality of dummy loads  110  can be coupled to the power/control PCB circuit  106  to draw additional current into the traffic signal power circuitry. Such additional current draw accommodates legacy control systems which are configured based on such current consumption. Each dummy load  110  includes a body  112  and a pair of terminals  114  to facilitate electrical connection to the power/control PCB circuit  106 . A molded dummy load cover  116  can provide a seal over the dummy load terminals  114  to inhibit accidental short-circuits between the electrical connections associated therewith. In addition, the molded dummy load cover  116  can expose the dummy load body  112  to heat dissipation via ambient air. 
     The power/control PCB circuit  106  is electrically coupled to an LED PCB  118  which is utilized to hold a plurality of LEDs thereon. A mask  120  blocks some of the phantom reflection from the LEDs on the LED PCB  118  via a plurality of individual apertures that correlate one-to-one to the number of LEDs mounted on the LED PCB  118 . A lens  122  receives light directed from the LEDs on the LED PCB  118  in order to direct and collimate the light into one or more desired directions. A distribution cover  124  receives light output from the lens  122  to provide a homogenous light distribution to emulate conventional incandescent signal lamps and further reduce the phantom reflections from the signal. In this manner, an LED signal can be substituted for an incandescent signal to provide a lower cost, substantially the same light output. 
     Generally, retrofitting conventional incandescent traffic signals requires a one-to-one substitution wherein an LED array and corresponding lens and distribution cover are utilized to replace an incandescent lamp for each disparate lamp color. In one example, a conventional traffic signal is comprised of three incandescent lamps that are colored red, yellow and green. A conventional retrofit would replace each incandescent lamp with the appropriate corresponding colored LED array that would be contained in three disparate housings, one for each incandescent signal lamp. In order to provide a more seamless and cost effective solution, all three colors (red, yellow and green) can be utilized with a single LED signal under one housing. This tricolor LED signal contains an LED array that has three disparate groups of LEDs that correspond to the three colors being replaced (e.g., red, yellow, green). 
     In order to facilitate a single LED array which outputs three disparate colors, the power/control PCB contains three disparate power supply units and three disparate monitoring circuits that correspond to each of the three colors utilized on the LED PCB  118 . The power supply unit for each color each utilize an optional dummy load (e.g., resistive element) to increase the current draw of each LED group to emulate the current draw of a conventional incandescent lamp. In order to provide power to each of the power supply units, a pair of wires is utilized to connect the input of the power supply unit to a line voltage. 
     Additionally, each corresponding dummy load  110  is coupled to the appropriate power supply via a wire pair. Accordingly, in order to accommodate a tricolor signal, a total of six wires is required to provide connectivity to line voltage to each of the three power supply. The bottom housing element  102  includes twelve pluggable connectors  104  wherein the wires can be inserted to electrically connect to twelve pluggable connectors  108  that are mounted on the PCB supply/control circuit. In one approach, the pluggable connectors  104  are permanently built in the back of the housing to create a seal that is water and dust resistant. Moreover, the pluggable connectors  104  simplify assembly of the traffic signal housing  100  when in production. 
     A conductive plate  132  can be placed between the bottom housing element  102  and the dummy loads  110  to provide a mounting surface thereon. The conductive plate  132  can be utilized to dissipate heat generated by each of the dummy loads  1   10 . In one example, the conductive plate  132  is made of aluminum. However substantially any conductive material can be employed. The conductive plate  132  can be mounted to the rear side of the bottom housing element  102  via a plurality of fasteners, such as screws for example. The dummy loads  110  can also all be mounted to the conductive plate  132  via fasteners. 
     The dummy load cover  116  is mounted to the conductive plate via one or more fasteners (e.g., screws) to cover the terminals at either end of each of the dummy loads  110 . The dummy load bodies  112  are passed through the apertures and thereby are exposed to the ambient air to provide additional heat dissipation for the dummy loads  110 . Accordingly, the combination of the conductive plate  132  and the exposed dummy load cover  116  provides ample cooling for the dummy loads  110 . In this manner, an efficient and simplistic design is utilized to facilitate simple assembly for production of the tricolor signal and corresponding traffic signal housing  100  and further to facilitate straight forward replacement of components when a maintenance issue arises. In one example, the dummy load cover  116  is made of a non-conductive material such as plastic or a similar material. 
     In one approach, the wires  126 ,  128 , and  130  that deliver power to the tricolor traffic signal  100  can be color coded to avoid erroneous assembly. In one example, a pair of power input wires corresponds to the LED color of each of the LED groups such that a pair of red wires, a pair of yellow wires and a pair of green wires are employed to inform a user (e.g., assembler, maintenance personnel) immediately of which wires provide power to the corresponding light output. 
     Moreover, each wire can employ a strain relief component  134 that mitigates strain placed on the wire pairs  126 ,  128 ,  130  when in operation. Such strain relief components  134  can substantially extend the life time of the wires  126 ,  128 ,  130  as used in the field. The strain reliefs can mitigate mechanical wear and tear to the electrical connections. Moreover, to facilitate ease of production assembly and replacement in the field, each pluggable connector cavity can be identified via identification engraved in the bottom housing element  102  that states what color each of the pluggable connectors  104  are connected therewith. 
       FIG. 2  illustrates an isometric exploded view of the traffic signal housing  100 . The LED tricolor power signal  100  can be employed to provide control in a wide variety of applications such as a rail wayside signal, a traffic signal, a rail searchlight, and/or one or more transit applications, for example. The LED tricolor signal  100  can include a plurality of benefits over conventional means such as high insulation between power circuits for each LED array, a light output detection, a single input connector (e.g., 12-pin) to provide seamless connection to conventional systems, an optional dummy load, a dummy load detection and a design that meets one or more industry standards, such as a safety integrity level  4 . 
     The LED tricolor signal  100  can be employed to replace three conventional signal heads into a one integrated signal under one housing while maintaining safety and reliability requirements. Three colors can be utilized on a single LED board driven by three disparate power supplies to insure appropriate light output uniformity, fail safe and high insulation between all different colors. In this manner, failure from mechanical vibration is mitigated and cost associated with conventional three head systems is eliminated. 
     Utilizing the tricolor power signal  100 , LED lights for railway signs can be more robust than conventional systems. Moreover, a safer electronic base is employed that is capable of turning off a defective light under a wide variety potential electronic circuit degradation conditions. To provide power to three LED arrays on a single head, three power supplies are employed. Such design can minimize space requirements since only a single head is required. The tricolor power signal  100  can also provide uniformed light intensity and beam angle while eliminating color mixing failure. 
     The tricolor power signal  100  includes a power supply unit (PSU)  106 , an LED light source array  118  and a monitoring circuit. In one embodiment, the PSU  106  is representative of a plurality (e.g., three) power supplies wherein each one drives a particular disparate LED array. The LED array  118  is similarly representative of one or more sets of LEDs that can correlate to the plurality of power supplies represented by the PSU  106 . 
     In one embodiment, the LED array  118  includes a pattern of four columns (one group of four LEDs connected in parallel) by twenty two rows (twenty two groups connected in series) for the Red LEDs, four by thirty-three for the Yellow LEDs and six by fifteen for the Green and White LEDs. In case of an LED failure in a group over the course of operation, the current is redistributed to the other LEDs of the same group and the signal maintains its light output. 
     Although one embodiment of the LED array  118  is described herein, it is to be appreciated that substantially any number of LEDs, with various colors in disparate configurations can be employed. In one approach, almost four hundred LEDs are arranged and placed on an LED board. However, the circuits described herein can be arranged in substantially any manner utilizing any number or type of components (e.g., surface mount, through-hole, etc.). 
       FIG. 3  illustrates a front isometric view of the traffic signal housing  100  which includes a distribution cover  124 , the LED array  118 , the mask  120  and the lens  122 . As shown, the distribution cover  124  is coupled to the bottom housing element  102  to provide a sealed unit to prevent any water or dust from entering the inside of the traffic signal housing  100 . As depicted four through ways are utilized with the distribution cover  124  to accommodate a number of screws that are fastened via the rear of the bottom housing element. The wires  126 , 128 , 130  are also depicted in disparate colors in association with an aspect of the subject invention. 
       FIG. 4  illustrates a rear isometric view of the traffic signal housing  100 . As shown, the dummy load cover  116  is fastened to the rear of the bottom housing element via four screws through the conductive plate  132 . The dummy load bodies  112  are exposed to the ambient air wherein the dummy load terminals  114  are covered via the dummy load cover  116 . 
     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.