Patent Publication Number: US-2007121329-A1

Title: Airfield edge-light utilizing a side-emitting light source

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation of U.S. application Ser. No. 10/931,192 filed on Aug. 31, 2004.  
      The present system is related to U.S. patent application Ser. No. 10/096,440 by Hansler et al. entitled “Elevated Airfield Runway and Taxiway Edge-Lights utilizing Light Emitting Diodes” filed on Mar. 12, 2002 and which claims priority from U.S. Provisional Patent Application Ser. No. 60/278,766, filed on Mar. 26, 2001, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      This invention is related to airfield lighting (e.g. runway, taxiway and obstruction), and more particularly, to a side-emitting lighting system utilizing a side-emitting Light Emitting Diode (LED).  
      Airport edge lighting has been in existence for many years utilizing incandescent lighting technology. Conventional designs that utilize incandescent lights have higher power requirements, lower efficiency, and low lamp life which needs frequent, costly relamping by maintenance professionals.  
      Some airfield-lighting manufacturers are using more efficient devices such as LEDs where the LEDs are arranged in multiple rings shining outward. Optics of some sort are then used to concentrate the light in the vertical and horizontal directions to meet Federal Aviation Administration (FAA) specifications.  
      Recently, implementations utilizing top emitting LEDs have been introduced which require additional light directing components as well as costly reflection and/or refraction techniques in order to comply with current FAA specifications and predetermined criterion.  
      What is needed is an airfield edge-lighting system that can utilize as few as one LED in a more efficient manner more efficiently while meeting the required FAA standards.  
     SUMMARY OF THE INVENTION  
      The present invention, in accord with an aspect disclosed herein, comprises a runway, taxiway or obstruction lighting system. The lighting system includes a housing and a light assembly in communication with the housing. The light assembly includes a base with a top surface and a bottom surface whereby the bottom surface of the base is in communication with the housing, a side-emitting light emitting diode positioned on the top surface of the base, and a cover suitably capable of transmitting light, the cover disposed around the side-emitting light emitting diode and in communication with the housing.  
      An aspect of the present system includes an electrical circuit for operatively controlling an intensity of the light emitting diode in accordance with a predetermined criteria (e.g. FAA requirements). The electrical circuit may also suitably allow for retrofitting the present light assembly into an existing incandescent lighting system.  
      In one embodiment, a single side-emitting light emitting diode (LED) is provided and suitably adapted to emit light according to a predetermined criterion. Additionally, the side-emitting LED may be suitably adapted to emit light approximately 0 to 6 degrees from a horizontal plane parallel with a mounting surface. As well, the system may be configured such that the light is dispersed from the side-emitting LED in a 360-degree pattern.  
      An alternative embodiment of the present invention employs multiple side emitting LED&#39;s to realize the higher photometric requirements for obstruction lights.  
      Further embodiments include a base configured to function as a heat-sink. Yet another embodiment has a heating element disposed within the cover and in close communication with the light assembly. The heating element may be configured with a thermostat for controlling the heating element.  
      Other embodiments include a cover that is cylindrical in shape. Also, the cover may be tinted or colored (e.g. blue for taxiway edge lighting applications). Further, the cover may include a lens for refracting light emitted from the LED in accordance with a predetermined criterion.  
      Still more embodiments may include an extension connected to the housing for elevating the light assembly above a mounting surface, whereby the light assembly and the extension are in a substantially vertical alignment. As well, the extension may include a frangible portion that fractures according to predetermined criterion.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  illustrates an elevated edge-light system, according to a disclosed embodiment;  
       FIG. 2  illustrates an elevated edge-light system, according to an alternate disclosed embodiment; and  
       FIG. 3  is a detailed drawing of an elevated edge-light system in accordance with an aspect of the present invention.  
       FIG. 4  is a perspective view of a elevated edge-light system using a side emitting light with a heater in accordance with an aspect of the present invention.  
       FIG. 5  illustrates an elevated edge-light system employing three side emitting light sources in accordance with an aspect of the present invention.  
       FIG. 6  illustrates an inset edge light system in accordance to an aspect of the present invention.  
       FIG. 7  is a circuit diagram of a heater circuit in accordance with an aspect of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The following includes examples of various embodiments and/or forms of components that fall within the scope of the present system that may be used for implementation. Of course, the examples are not intended to be limiting and other embodiments may be implemented without departing from the spirit and scope of the invention.  
      The Federal Aviation Administration (FAA) standards provide guidelines for the manufacture and implementation of airfield edge-lighting systems. Specifically, the FAA standards provide guidelines for the intensity and directional projection of light used in airfield lighting applications. The content and guidelines of the FAA specifications, including but not limited to Advisory Circular (AC) 150/5345-43E dated Oct. 19, 1995 and Advisory Circular 150/5345-46B dated Sep. 1, 1998 are hereby incorporated into this specification by reference in its entirety.  
      The present innovation is generally directed toward an LED lighting assembly. More specifically, one embodiment of the present innovation is directed toward a lighting assembly utilizing a side-emitting light source (e.g. side-emitting light emitting diode (LED)) for use in airport and airfield edge and obstruction lighting applications. For example, aspects of the present invention include a lighting assembly utilizing a side-emitting light source that is compliant with one or more of FAA specifications for L-810 Obstruction Light (AC 150/5345-43E and the FAA LED Engineering Brief document 2004), L-852T LED Taxiway Edge Light (AC 150/5345-46B and FAA LED Engineering Brief document 2004), and L-851T LED Elevated Taxiway Edge Light (AC 150/5345-46B and FAA “LED Engineering Brief document 2004”).  
      The FAA standards stipulate that a taxiway edge lighting apparatus must meet certain photometric criterion. For example, the current FAA specification mandates that the light intensity projected from the lighting element must be at least 2.0 candela (a unit of luminous intensity) between 0 and 6 degrees from the horizontal axis (the horizontal axis being perpendicular to the longitudinal axis of a mounting rod), and a minimum of 0.2 candela between the remaining angle of 6 and 90 degrees from the horizontal axis.  
      One embodiment of the disclosed lighting system is in accordance with the current FAA requirements for taxiway edge lighting. It will be appreciated that the present system may be suitably configured to accommodate alternate and/or future predetermined criteria (e.g. intensity, angle of projection) and/or specifications.  
      Referring now to  FIG. 1 , there is illustrated an elevated edge-light system  100 , according to a disclosed embodiment. Generally, the system  100  comprises a light assembly  105  elevated above the surface of the ground  110 . The light system  100  includes a light assembly  105 , a housing  115  that may be secured at its base to a support structure  120  (e.g., an aluminum pipe extension). As shown, the support structure  120  may include a frangible portion  130  in accordance with a predetermined criterion.  
      As illustrated in  FIG. 1 , a source of power may be suitably provided from power elements located inside a power box  125 . Additionally, circuitry  135  may be provided in order to enable the operation of the present system  100  to comply with predetermined criterion. In operation, the output of the electrical circuit element  135  may be operatively configured to supply the required power to light assembly  105 . In operation, power from the output of the electrical circuit  135  may be carried across one or more wires (not shown) to light assembly  105  to illuminate a light source  140 .  
      Although the disclosed embodiment of  FIG. 1  illustrates the power box  125  and circuitry  135  located within housing  115 , a skilled artisan will appreciate that the components may be disposed in any location without departing from the operation and scope of the present innovation. For example, the power box  125  and circuitry  135  may be located in alternate locations such as within support structure  120 , remotely in-ground  110  or the like without departing from the spirit and scope of the present innovation.  
      Preferably, light assembly  105  includes a single side emitting LED  140  as a light source, a mounting base  145  to support the side emitting LED  140  and a cover  150  for transmitting the light from the side-emitting LED. To comply with FAA regulations, the single side emitting LED  140  has a minimum light output of approximately 20-30 lumens.  
      An advantage of using an LED as opposed to an incandescent bulb is that an LED has a much longer life cycle. A typical LED has a life of 56,000 hours when operated at high intensity, and 150,000 hours (the equivalent of 34 years when operated 12 hours a day) when operated at medium intensity.  
      It will be appreciated that the mounting base  145  may be suitably configured to function as a heat sink (e.g., ¾ inch aluminum) such that heat is transferred from the LED assembly  140  to the housing  115  and other attached structures to prolong the operating life of the LED assembly  140 .  
      It will be appreciated that the mounting base or heat sink  145  may be suitably attached to the housing  115  by conventional means while utilizing a thermal grease or comparable material between the mounting base  145  and the housing  115  to facilitate heat transfer from the LED assembly  140  to the housing  115 , and also between the LED assembly  140  and the mounting base  145  for the same purpose.  
      It will be appreciated that the single side-emitting diode  140  of the embodiment may be any side-emitting light source known in the art. For example, a Luxeon™ Star or provided by Lumileds Lighting, LLC, 370 West Trimble Road, San Jose, Calif., 95131 may be utilized in accordance with the disclosed embodiments. Preferably, the LED has a minimum light output of 20-30 lumens.  
      The side-emitting LED  140  may be suitably configured to emit light in a 360 degree pattern. For example, the side emitting LED  140  may be suitably configured to emit light corresponding to an angle A 0 to 6 degrees above a horizontal plane B perpendicular with the optical axis C. It will be appreciated that the angle A may be adjusted in accordance with any desired lighting effect. It will be appreciated, that any desired beam pattern may be achieved by utilizing any number of optical techniques. For example, optical manipulating techniques such as depressions and/or apex angles may disposed within the cover  150  in order to refract and/or reflect the light to correspond to any desired beam pattern or predetermined criterion or standard. As well, alternate side-emitting light sources  140  may be configured to alter the beam pattern in accordance with desired criterion. Additionally, in accordance with a predetermined criterion, the light intensity from 6 degrees from horizontal to the optical axis C may be arranged to be 0.2 candela.  
      Although the embodiment utilizes a glass cover  150 , it will be appreciated that other translucent materials capable of transmitting light known in the art may be used without departing from the present lighting system  100 . For example, the cover  150  may be constructed of materials including, but not limited to, plastic, composites or the like.  
      In accordance with an aspect of the present invention, cover  150  is manufactured to have the highest transmissivity when used with a monochromatic LED light source. The color of the material (e.g., glass) is tuned to the wavelength of the LED light source to obtain the maximum light output. For example a blue cover and a LED for a taxiway light, a red cover and red LED for an obstruction light.  
      The support structure  120  may suitably secure to the mounting base  115  to provide a stable support for the light assembly  105  during harsh weather conditions or other conditions impacting operation and/or orientation of the lighting system  100 . The support structure  120  may suitably elevate light assembly  105  above the surface of the ground  110  wherein the light assembly  105 , support structure  120 , and power box  125  are in a substantially vertical alignment. Although the embodiment shown is vertically orientated, an artisan will appreciate that other alternate configurations, such as a flush fixture, of the present system may be utilized without departing from the scope of the present system.  
      An adjustment means (not shown) may be provided at the junction of the base of the housing  115  and the support structure  120  so that the longitudinal axis C (i.e., the optical axis) of the light assembly  105  may be adjusted to be maintained in a substantially vertical orientation. It will be appreciated that any adjustment means known in the art may be used without departing from the scope of the present lighting system  100 .  
      As shown, the support structure  120  may suitably include a frangible section  130  which may function as an easy breakaway of the light assembly  105  and upper end of the support structure  120  if, for example, an aircraft, maintenance vehicle, or other forces exert a predetermined pressure on the frangible section  130  sufficient to cause breaking thereof.  
      It will be appreciated that any breakaway technique known in the art may be used to accomplish the frangible characteristics. For example, the frangible section  130  may comprise a groove scored into the support structure  120 , which groove is designed with a sufficient length, depth, and orientation in the support structure  120  to facilitate separation of the light assembly  105  and upper end of the support structure  120  from the power box  125  at or near the surface of the ground  110 . For example, where a threaded pipe extension is utilized as the support structure  120 , the frangible section  130  may be a groove scored into the pipe surface, which pipe is a single piece of pipe extending from the light assembly  105  to the power box  125 .  
      Alternatively, the frangible section  130  may also suitably comprise a compressed powderized metal coupler (not shown) designed to separate under predetermined stress parameters utilized in accordance with the particular application. In any case, the function of the frangible connection  130  may be suitably configured to facilitate a breakaway function under stressed conditions to protect the lighting system  100  and the aircraft or other vehicle that may impact the lighting system  100  from damage.  
      The power box  125  may suitably and operatively couple power from a power feed (not shown) extending, for example, through an in-ground conduit (not shown) to one or more of the lighting systems  100 . In the embodiment, the power box  125  may suitably include an electrical circuit element  135  configured to control the photometric characteristics of the light source  140  in accordance with a predetermined criteria (e.g. FAA standards).  
      Additionally, the electrical circuit element  135  may be designed to enable the retrofit of lighting system  100  into a conventional or standard incandescent lighting system. In other words, circuitry  135  may be provided to enable a variety of light sources  140  (e.g. side-emitting light emitting diode) to provide light intensity in accordance with a predetermined criteria (e.g. FAA specifications).  
      It will be appreciated that the support structure  120  to elevate the light assembly  105  above the ground as illustrated is optional. For example, the light assembly  105  may be suitably operable such that the base  145  of the light assembly  105  may be situated on or close to the ground surface  110 . Alternatively, the light assembly  105  can be positioned in the ground such that only the cover  150  sufficiently protrudes to provide the required output light in accordance with desired criterion.  
      Referring now to  FIG. 2 , there is illustrated a lighting system  200  in accordance with an alternate embodiment. As shown, lighting assembly  205  may optionally include a heating element  210  to provide heat to a light source chamber  215 . As illustrated, light source chamber  215  is the space formed around a light source  225  (e.g. LED) and defined by an inner wall of the cover  220  and mounting base  230 .  
      It will be appreciated that the heating element  210  may be any component known in the art capable of heating the light source chamber  215 . In operation, the heating element  210  raises the temperature of the light source chamber  215  in order to control the weather effects on the cover  220 . For example, by heating the light source chamber  215 , the higher temperature may suitably reduce icing, fogging and snow accumulation on top surface of the cover  220 . As earlier discussed with reference to  FIG. 1 , it will be appreciated that the mounting base  230  may suitably function as a heat sink, alone, or in conjunction with housing  235  in order to protect the longevity of the light source  225 .  
      Referring now to  FIG. 3 , there is are illustrated exploded view drawings of an elevated edge-light system  300  in accordance with an aspect of the present invention. The power supply and electronic circuitry for system  300  are displayed within circle  304 . A plug  318  is used to couple system  300  to an external electric power source. Wires  328  conduct the power from plug  318  to the electronic circuitry shown in circle  304 .  
       FIG. 3B  shows a mounting assembly  330  in accordance with an aspect of the present invention. The mounting assembly comprises a heat sink  306 . At the top of the assembly  330  is a side emitting LED  308 . The bottom of assembly  332  is adapted to mount on top  332  of housing  302 . Heating element  310  is mounted around mounting assembly  330 . Wires  320  and  322  are connected to wires  324  and  326  to provide power to heating element  310  and side emitting LED  308  respectively.  
       FIG. 3C  shows a cutaway view of a cover  312  in accordance with an aspect of the present invention. Cover  312  is suitably adapted to mount on housing  302  and cover mounting assembly  330 . Cover  312  has a convex surface  314  that is used to disperse light from side emitting LED  308  corresponding to a desired angle. For example side-emitting LED  308  may be suitably configured to emit light in a 360 degree pattern along a horizontal axis. Convex surface  314  adjusts the light along the horizontal axis to achieve a desired lighting effect. It will be appreciated, that any desired beam pattern may be achieved by utilizing any number of optical techniques. For example, optical manipulating techniques such as depressions and/or apex angles may disposed within the cover  312  in order to refract and/or reflect the light to correspond to any desired beam pattern or predetermined criterion or standard. Cover  312 , is comprises of a translucent material capable of transmitting light. In accordance with an aspect of the present invention, cover  312  is manufactured to have the highest transmissivity when used with a monochromatic LED light source. The color of the material (e.g., glass) is tuned to the wavelength of side emitting LED light  308  to obtain the maximum light output. A second convex surface  316  adjusts light along the vertical axis.  
       FIG. 4  is a detailed view of a mounting unit  400  for a side emitting light with a heater in accordance with an aspect of the present invention. As shown, the mounting unit  400  has a heater support insulator  402  mounted on top of heat sink  308 . Insulating paper  404  is between mounting unit  400  and heating element.  
       FIG. 5  illustrates an elevated edge-light system  500  employing three side emitting light sources in accordance with an aspect of the present invention. The additional light sources can provide additional light intensity such as is required under FAA guidelines for obstruction lights.  
       FIG. 5A  is a side view of the system  500  and  FIG. 5B  is a cutaway top view of the system along lines A-A of  FIG. 5A . System  500  comprises a housing  502  that contains an LED electronics module  504 . LED electronics module  504  is used for supplying the power to side emitting LED&#39;s  508 ,  510 ,  512 . The power from the LED electronics module  504  can be varied control the intensity of side emitting LED&#39;s  508 ,  510 ,  512 . The wavelength of LEDs  508 ,  510 ,  512  is selected to produce a desired output color. LED mounting/heatsink sub assembly  506  is mounted on top of housing  502  and is used for mounting side emitting LED&#39;s  508 ,  510  and  512 . Cover  514 , an airfield lighting dome, is mounted on top of housing  502  and help in place by screws  516 . The color of cover  514  is suitably adapted to match the wavelength of LEDs  508 ,  510  and  512 . Cover  514  has a convex surface  518  for directing light in a direction along a substantially horizontal direction from the sides of side emitting LED&#39;s  508 ,  510 ,  512 . Another convex surface  520  allows light from the top or side of LED&#39;s  508 ,  510 ,  512  to go in a substantially vertical direction to comply with FAA regulations.  
      As can be seen from  FIG. 5B , side emitting LED&#39;s  508 ,  510 ,  512  are positioned so that at least two of LED&#39;s  508 ,  510 ,  512  are visible along a horizontal plane. As shown, the LED&#39;s  508 ,  510 ,  512  are spaced apart by 120 degrees from a central point  522  and are equidistantly spaced from each other. However, any arrangement that allows at least two of LED&#39;s  508 ,  510 ,  512  to be visible from any angle when viewed from the ground or in the air above the ground.  
       FIG. 6  illustrates an inset edge light system  600  designed to be installed in pavement in accordance to an aspect of the present invention. An inner bottom cover  602  has an opening  603  for wires  605  to be coupled to plug  604  for supplying power to the LED control electronics  606 . LED control electronics  606  comprises electronic circuitry for controlling the current and intensity of side emitting LED  608 . Side emitting LED  608  can be any side emitting diode such as a Luxeon LXHL-FB1C or LXHL-FB5C having the desired optical characteristics, e.g., color, intensity. A glass or acrylic dome  610  of constant thickness covers the side emitting diode. Dome  610  is clear since system  600  is designed to be installed in the pavement, thus no visual guidance is given when the light fixture is off. Furthermore, the slope of dome  610  typically ranges from 0 to 20 degrees to comply with FAA regulations and dome  610  is designed to bend the light from side emitting LED  608  at the proper angles, typically 0 to 6 degrees to comply with FAA requirements. Side emitting LED  608  is mounted on prism clamp and LED heatsink  616 . Prism clamp and LED heatsink  616  is preferably machined to hold dome  610  in place. Top cover  614  secures dome  610  to the surface of prism clamp and LED heatsink  616 , and secures prism clamp and LED heatsink  616  to bottom cover  602 . Sealing gasket  612  sealingly engages dome  610  with top cover  614  and prevents external contaminants, such as rain, ice or snow, from getting inside system  600 .  
      Dome  610  is configured to bend the light from side emitting diode  608  at the desired angles. For example, by making the slope of dome  610  approximately 20 degrees and using a 5W, the results illustrated in Table 1 are obtained.  
                           TABLE 1                                   Degrees vertical   Candela                          0   3.1           1   3.4           2   3.9           3   4.5           4   5.0           5   5.6           6   4.8           7   4.3           8   3.8                      
 
      Thus, as can be seen from table 1, the light from side emitting LED  608  is focused at angles of 0 to 8 degrees and complies with FAA requirements for an L-852T in-pavement light, which is 2 candelas from 0 to 6 degrees, and 0.2 candela at all other angles. Because side emitting LED  608  is much shorter than a standard incandescent bulb with similar intensity, the height of dome  610  is lower than for an incandescent bulb. For example, the distance from the top of dome  610  to the top of top cover  614  can be as small as a quarter inch.  
       FIG. 7  is a circuit diagram of a heater circuit  700  in accordance with an aspect of the present invention. This heater circuit can be employed with lighting systems using a side emitting LED such as heater elements  210  ( FIG. 2 )  310  ( FIG. 3 ). Because LED&#39;s are more efficient in generating photons than an incandescent light, they generate much less heat. Heating the lighting system may be desirable to prevent the accumulation of snow and ice in cold environments.  
      A constant current source  702  supplies current I to circuit  720 . The constant current source can be suitably adapted to supply a constant current at varying levels. For airfield edge lighting circuits, currents varying between 2.8A and 6.6A are common. The current I flows into current transformer  704 . Current transformer  704  has a primary coil  706  and a secondary coil  708 . The ratio of primary coil  706  to secondary coil  708  is selected to obtain the desired constant current in secondary circuit  722 . For example, if the ratio of the primary coil to the secondary coil is 1:1, then the current in circuit  722  will be substantially the same as the current in circuit  720 . Plug  710  couples circuit  722  to the secondary coil  708  of current transformer  704 .  
      In accordance with an aspect of the present invention, circuit  722  is a circuit comprising a LED with associated electronics  712  in series with a heater element  714 . The electronics portion of the LED with associated electronics  712  comprises a power supply that supplies power to the LED based on the current flowing through circuit  722 . Thermostat  716  is in parallel with heater element  714 . Because a constant current is flowing through circuit  722 , the sum of the currents through heater element  714  and thermostat  716  will be constant. When heating is desired, thermostat  716  will provide more resistance, or it can act as an open circuit, to force more current through heater element  714 . When heating is not desired, thermostat  716  provides less resistance, or it can act as a short circuit, so that less current will flow through heater element  714 . Because circuit  722  is essentially a series circuit comprising LED with associated electronics  712  in series with the combination of heating element  714  and thermostat  716  with a constant current source, the operation of heating element  714  does not effect the operation or intensity of light from the LED because a constant current flows through the LED power supply. Circuit  720  can also have additional current transformers  718  allowing additional lighting systems (not shown) to be connected.  
      While the present system has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants 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. Therefore, the system, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s general inventive concept as defined by the appended claims.