Abstract:
There is provided an LED light fixture including a housing adapted to be mounted a predetermined height above a surface. The housing includes at least one LED emitter situated so as to emit light toward the surface below the housing. A first lens plate is provided and is removably attached to the housing. The first lens plate has a first opening therein and a first lens having a first angle of light dispersion is received in the opening. The opening of the first lens plate is aligned with the LED emitter so that the first lens controls the footprint of the pattern of light from the LED emitter which impinges upon the surface.

Description:
RELATION TO PRIOR APPLICATION 
       [0001]    This is a U.S. non-provisional application relating to and claiming the benefit of U.S. Provisional Patent Application Ser. No. 61/512,453 filed Jul. 28, 2011. 
     
    
     BACKGROUND 
       [0002]    Light emitting diode (LED) lighting systems are becoming more and more popular because of their efficiency and lifespan advantages over more traditional lighting systems such as incandescent, fluorescent and HID lighting systems. An LED light source is easier to control as it is directional. Instead of emitting three hundred sixty degrees as all previous light sources, LEDs emit light in one direction in patterns of ninety to one hundred forty-five degrees. However, all lights including LEDs have undesirable excessive amounts of waste light in certain situations. Waste light is light dispensed where it is not needed or is usable. This is the case with all lights when mounted high as with bay lights. Bay lights disperse some of their light at side angles at heights where it is not usable. It would be advantageous to have a method of controlling light which is normally emitted to the fixtures&#39; sides and redirect it downward, thus minimizing this loss of light and energy. For example, with a twenty-five foot average ceiling height, four hundred watt metal halide fixtures spaced every thirty feet from one another are usually all that is necessary for proper lighting. If the ceiling height is forty-eight feet, usually it requires a six hundred watt or one thousand watt replacement, or a dual head four hundred watt system to replace the individual four hundred watt fixtures so as to obtain the same light to illuminate the same area due to the “waste light” loss. In most cases, fixtures must be set closer to one another for the same reason to create the needed light level. 
         [0003]    With existing lighting marketed for years, such as incandescent, quartz, fluorescent and HID (sodium, mercury, metal halide), optimal control could only be adjusted by utilizing a means of reflectors as all the previous light systems emit light within a three hundred sixty degree circumference and the shape of the bulbs and tubes does not lend to accurate light dispersion. Thus, various fixtures at varying power levels were required for different light heights and distribution coverages. With the more controllable LED technology, newly introduced to commercial lighting, it is possible to provide more accurate light dispersion. 
         [0004]    As LEDs are directional (not three hundred sixty degrees), it is possible to develop the LEDs/LED arrays with lensing molded to the LED emitter itself and, in some cases, small lenses or reflectors can be mounted to the LED board. This is somewhat of a step forward. With these methods, light dispersion is much more controllable, however, it produces the same restriction as earlier reflector systems with previous lights as, once the lens or reflector is mounted to the LED, it is now limited to a certain angle of light output and height. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with one form of this invention there is provided an LED light fixture including a housing adapted to be mounted at predetermined heights above a surface. The housing includes at least one LED emitter. The LED emitter is situated so as to emit light toward the surface. A first lens plate is provided and is removably attached to the housing. There is at least one opening in the first lens plate. A first lens is received in the opening. The opening of the first lens plate is aligned with the LED emitter whereby the first lens controls the angle of light dispersion of the light from the LED emitter and the footprint of the pattern of light which impinges on the surface. Preferably the housing includes a plurality of LED emitters and the lens plate includes a plurality of openings and lenses. 
         [0006]    Preferably, a second lens plate is included having a second lens with a different angle of light dispersion from the first lens. The first lens plate is replaced by the second lens plate when the housing is mounted at a height above the surface which is different from the first predetermined height. 
         [0007]    In accordance with another form of this invention there is provided a method for providing a substantially uniform light pattern from a light fixture having at least one LED emitter for various mounting heights of the fixture. The light fixture further includes a housing and a first lens plate. The first lens plate has at least one opening and a first lens having a first angle of light dispersion is received in the opening. The first lens is adjacent to the LED emitter. The method includes mounting the fixture at a first distance above a surface; energizing the LED emitter wherein light is emitted through the first lens and forms a light pattern on the surface having a predetermined footprint; removing the first lens plate from the light fixture; and replacing the first lens plate with a second lens plate. The second lens plate has at least one opening therein and a second lens having a second angle of light dispersion is received in the opening. The second lens is adjacent to the emitter. The method further includes mounting the fixture at a second predetermined distance above the surface; and energizing the LED emitter wherein light is emitted through the second lens and forms a light pattern on the surface having a footprint substantially equal to the first predetermined footprint. 
         [0008]    In yet another form of this invention there is provided an LED lighting system including a light fixture with a housing. The housing includes an emitter plate having at least one LED emitter mounted thereon. A first lens plate having at least one opening therein is provided. A first lens having a first angle of light dispersion is mounted in the opening in the first lens plate. A second lens plate having at least one opening therein is also provided. A second lens having a second angle of light dispersion is mounted in the opening in the second lens plate. The light fixture is mountable at various heights above a surface. The first lens plate is attached to the housing for a first predetermined height above the surface. The first lens is located adjacent to the LED emitter wherein a light pattern having a predetermined footprint is formed on the surface. The second lens plate is attached to the housing for the second predetermined height above the surface. The second lens is located adjacent to the LED emitter wherein a light pattern having substantially the same predetermined footprint is formed on the surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The subject matter which is regarded as the invention is set forth in the claims. The invention, however, may be better understood in reference to the accompanying drawings in which: 
           [0010]      FIG. 1  is a partially exploded perspective view showing one embodiment of the subject invention. 
           [0011]      FIG. 2  is an inverted partial perspective view showing a portion of the embodiment of  FIG. 1  in more detail. 
           [0012]      FIG. 3  is a side elevational view of several lenses which may be used with the lens plate of the embodiment of  FIG. 1 . 
           [0013]      FIG. 4  is a side elevational view of a portion of the embodiment of  FIG. 1 . 
           [0014]      FIG. 5  is a schematic illustration showing the relationship between the angle of light dispersion of various lenses and various fixture heights above a surface. 
           [0015]      FIG. 6  illustrates the overlap of the light patterns on a surface using four fixtures. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    This invention enables the control of light patterns using a single light fixture for many applications and for various heights. The fixture includes a removable lens plate which is populated with individual optic or dome lenses which are mounted in line with LED emitters which in turn are mounted on an emitter plate located within the light fixture. The invention enables the lens plate to incorporate multiple lenses, all with the same angle of light dispersion, to accurately control the exact light coverage or footprint as well as the intensity of the light in a specific area at a given height. An identical lens plate can also be utilized with dome type lenses to disperse the light further to the sides which is particularly useful in a low ceiling application since the light intensity is not as critical directly below the fixture in a low mounting position. The lens plate can also be populated with a mix of various lenses, including a mix of optic lenses and dome lenses for other custom applications. This allows for a single fixture to be utilized in a wide array of lighting circumstances. Appropriate optical lenses are commercially available from LED World. Appropriate dome lenses are commercially available from Ximenwerun Technology Corp. 
         [0017]    The lens plate not only allows for a multitude of applications of a single fixture, it also allows for the same fixture to be relocated in various areas at various heights simply by exchanging the lens plate alone without a substantial change in the lighting pattern or light intensity. For example, at a thirty foot height, a ninety-five watt LED bay fixture having sixty degree light dispersion individual optic lenses within a lens plate can replace a four hundred watt metal halide fixture. At a twenty foot height, the LED fixture may best be suited with individual ninety degree light dispersion optic lenses to optimize the light output. Finally at twelve to fifteen foot heights, one could use dome lenses within the lens plate of the LED fixture. In addition, at twelve to fifteen foot heights, a combination of one hundred twenty degree light dispersion optic lenses, mixed with dome lenses, may be the optimal choice to acquire the desired light coverage. Most any degree and spread of light combination or degree of coverage can be achieved easily, with very little time and effort, simply by replacing the lens plate, using any number of individual optic or dome lenses, or any combination thereof, within the lens plate to precisely control the light emission in any area and in any situation by using a single fixture. 
         [0018]    Referring now more particularly to  FIG. 1 , there is provided LED light fixture  10  having a housing  12 . Housing  12  includes main housing  13 , mounting plate  14 , and emitter plate  16 . Mounting plate  14  is attached to main housing  13  which attaches to a ceiling (not shown). A plurality of LED emitters  18  and associated heat sinks  34  are mounted on emitter plate  16 . In the embodiment of  FIG. 1 , there are six LED emitters. There is a plurality of holes  20  in main housing  13  used for mounting the lower fixture to main housing  13 . Holes  25  are for attaching lens plate  24  to emitter plate  16  through holes via spacers  28  using spacer screws  22 . The mounting screws pass through holes in both the emitter plate  16  and mounting plate  14 . Thus, the mounting plate  14  and emitter plate  16  are secured to the main housing  13 . Lens plate  24  is removably attached to emitter plate  16  by screws  26 . A plurality of stand-off spacers  28  maintains a predetermined distance between lens plate  24  and emitter plate  16 . Lens plate  24  includes six openings  30  therein. Each opening receives lens  32 . Stand-off spacer  28  also maintains a predetermined distance between LED emitter  18 , mounted on heat sink  33 , and optic lens  32 . Preferably this spacing between LED emitter  18 , mounted on heat sink  33 , and lens  32  is five millimeters for optic lenses. Preferably, for a dome type lens such as dome lens  34  shown in  FIG. 4 , the LED emitter  18  penetrates to the inside of the dome. Dome lens  34  surrounds LED emitter  18 . As can be seen in  FIG. 2 , a shim  36  may be provided and located between the top of spacer  28  and emitter plate  16  to increase the distance between the LED emitter  18  and lens  32  so as to change the angle of light even further. In the preferred embodiment, emitter  18  is attached to heat sink  33  which, in turn, is attached to emitter plate  16 . Emitter  18  may also be attached to a circuit board (not shown). The combination of emitter  16  and heat sink  33  is often referred to as an LED module. 
         [0019]    As previously indicated, lenses having various angles of light dispersion may be used with lens plate  24  depending on the height that the fixture is placed above the surface, such as the ground or the floor of a building. For example, lens  32  may be hollow dome lens  34  which has a light dispersion of more than one hundred eighty degrees and in addition, the inside of the lens is frosted so as to evenly diffuse the light. This hollow dome lens is particularly adapted for use at lower levels. In addition as shown in  FIG. 4 , by using a hollow dome lens which has been internally frosted, a limited amount of light disperses upwardly towards the ceiling which eliminates the cave effect. 
         [0020]    Lens  32  may be any of a number of lenses having various light dispersions such as lens  34 ,  37 ,  38  and  40  shown in  FIG. 3 . Lens  37 , which is a solid optical lens, has a light dispersion of ninety degrees and is ideal for heights above the surface of fifteen to twenty feet. Lens  38  is also a solid optical lens and has light dispersion of sixty degrees which makes it ideal for ceiling heights of eighteen feet to thirty-five feet. Lens  40  is also a solid optical lens and has a forty-five degree light dispersion and is ideal for ceiling heights of thirty to fifty feet. The difference in the light dispersion is accomplished by using lenses with different radii of curvature, as well as shim  36 . 
         [0021]    Individual lenses may be replaced on the lens plate  24  to achieve optimum lighting for the surface, such as the floor. However, it is preferred that a lens plate having lenses with the same light dispersion be replaced with a lens plate having lenses with different light dispersions when it is desired to mount the fixture  10  at a different height above a surface. By using removable screws  26 , the replacement of a lens plate is made easy. Thus, by merely replacing a lens plate, the fixture may be used at different heights to provide the same lighting footprint for a given area of a surface such as a floor. This is best illustrated in reference to  FIG. 5 . 
         [0022]      FIG. 5  shows fixture  10  which is mounted at various levels above surface  42 , which in this embodiment is a floor. Also in this embodiment, fixture  10  is mounted to a ceiling. 
         [0023]      FIG. 5  shows five angles of light dispersion,  44 ,  46 ,  48 ,  50  and  52 , each representing a lens plate having lenses with a particular light dispersion. Line  44  illustrates use of a lens, such as dome lens  34 , having a light dispersion of more than one hundred eighty degrees mounted twelve feet above the floor  42 ( a ). Line  46  illustrates use of lens  37  having a light dispersion of ninety degrees with an elevation of fifteen feet above the floor. Line  48  represents use of a lens having a seventy degree light dispersion with the fixture being twenty feet above the floor. Line  50  represents a thirty-four degree light dispersion with the fixture mounted forty feet above the floor. Line  52  represents use of a lens having a twenty-two degree light dispersion where the fixture is mounted sixty feet above the floor. All of these lenses and fixture mounting heights provide a fifteen foot footprint of light on the floor. While there is some loss of light intensity at higher levels, the loss is not significant with this method. 
         [0024]      FIG. 6  illustrates the overlap of floor lighting when using four ceiling mounted fixtures  10  located twenty feet apart. Other lighting fixtures in addition to indoor bay lights may be used, such as street lights. A preferred method for providing a substantially uniform lighting pattern from a light fixture for various mounting heights is set forth below. 
         [0025]    The fixture is first mounted a predetermined distance above a surface. The LED emitters are energized so that light is emitted through lenses in the first lens plate and forms a lighted pattern on the surface having a predetermined footprint. The first lens plate is removed from the light fixture and replaced with a second lens plate. The second lens plate is substantially the same as the first plate except that it is populated with lenses having a different angle of light dispersion from the lenses of the first lens plate. The fixture is then mounted a second distance above the surface. The LED emitters are energized so that the light is emitted through the second lens plate and forms a lighted pattern on the surface having a footprint which is substantially equal to the first predetermined footprint. 
         [0026]    While the invention has been described in terms of the above embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.