Abstract:
A self-contained LED lighting assembly for use in a refrigerated cabinet contains a plurality of LEDs mounted upon a substrate, each using a refractive lens designed to evenly disperse the light emitted from each LED into a flat, wide pattern suitable for lighting the contents of the cabinet. Heat is effectively removed from each LED and transported to an interior air space within the LED lighting assembly housing. The system is designed to replace current lighting systems and is sized fit within the space provided for current lighting systems, without the need for substantial modification, cutting, or removal of the current lighting systems. The assembly may be composed of individual LED lighting modules wired end-to-end to provide a desired length of strip lighting. Upon complete installation, the system provides the same or better lighting using only a fraction of the power required by the system replaced.

Description:
[0001]    This application claims priority from Provisional Application 61/107,203 filed Oct. 21, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a refrigerated cabinet lighting system and, more particularly, to a self-contained LED lighting assembly for use within a refrigerated cabinet. The system is designed to replace current lighting systems and is sized fit within the space provided for current lighting systems without the need for substantial modification, cutting, or removal. Upon complete installation, the system provides the same or better lighting using only a fraction of the power required by the system replaced. The system further provides for improved startup and switching capabilities, thereby facilitating zoned and motion-detection lighting schemes that further reduce electrical power consumption. 
         [0003]    Lighting systems for refrigerated cabinets have changed a great deal since the inception of the light bulb. Early systems used incandescent bulbs, which required vastly more energy and produced far greater heat. Still later systems used florescent tubes that provided additional light using far less power and producing far less heat output. For example, a typical florescent lighting system used inside refrigerated cabinets includes a five-foot long florescent tube consuming approximately 60 watts of power, whereas the prior incandescents used twice that amount. At least one of these tubes is generally placed inside the cabinet door frame between refrigerated doors. Typically, many stores have anywhere from 10-200 doors, thereby requiring from ten to two hundred 60 watt florescent tubes for lighting. Although these florescent tubes provide ample light and use far less electricity than incandescent bulbs, these florescent bulbs nevertheless consume a great deal of power, especially given the fact that they traditionally run 100% of the time the store is open to the public. 
         [0004]    By contrast, LED lighting systems traditionally use from one-fourth to one-tenth the electrical power required by florescent lighting. Early LED lighting systems, such as the system set forth in U.S. Pat. No. 7,121,675 to Ter-Hovhannisian, use LED lighting systems designed to replace previous generation refrigerated cabinet lighting systems. The Ter-Hovhannisian system presented many advantages over prior art florescent systems but required a complete replacement of the prior lighting system to be effective. In other words, Ter-Hovhannisian&#39;s system requires that the housing, bulb, ballast, power supply, etc. previously installed for the refrigerated cabinet be completely removed before Ter-Hovhannisian&#39;s system can be installed. Even after installation, Ter-Hovhannisian&#39;s lighting system suffered from additional problems. For example, the LED lights generally provided illumination in only a small directional beam directly in front of each LED, thereby leaving the side-to-side items largely unilluminated. 
         [0005]    Still other systems, such as U.S. Patent Application Pub. No. 2004/0012959 to Robertson et al., present an improved solution that nevertheless continues to suffer from directional illumination problems. The system set forth in Robertson et al. proposes to fill a florescent tube with a plurality of LEDs so that a direct fluorescent tube replacement will function with LEDs. The primary problem with this approach is that far more LEDs are required to provide sufficient illumination in a small omni-directional tube than would otherwise be required to provide uni-directional illumination in other devices. 
         [0006]    What is needed is an LED illumination system that overcomes the present limitations of the prior art by providing a direct replacement LED lighting assembly designed to fit within the confines of a standard five foot florescent tube space limitations. What is also needed is an LED lighting system that is self-contained, requiring no removal of the florescent lighting system&#39;s ballast, housing, and power supply. These items are now considered hazardous waste and disposal is very costly; therefore, leaving these items in place is a preferable solution to removal. And finally, what is also needed is an LED lighting system that uses a minimum amount of LEDs, yet provides light in a sufficiently wide dispersion pattern so as to evenly and completely light the contents of a refrigerated cabinet both front-to-back and side-to-side. 
         [0007]    Accordingly, an object of the present invention is to provide an LED lighting system for use in a refrigerated cabinet that may be installed directly within the space previously occupied by a standard florescent lighting tube. Another object of the present invention is to provide that LED lighting system using a small amount of LEDs evenly spaced and strategically utilized to provide lighting for the entire interior of a refrigerated cabinet. Still another object of the present invention is to provide a specially designed refractive lens that is placed directly over each LED to evenly and completely disburse all the light from the LED in an even pattern throughout the interior of the refrigerated cabinet. Other objects and benefits of the present invention will become apparent from the detailed description when taken in conjunction with the drawings provided. 
       SUMMARY OF THE INVENTION 
       [0008]    The foregoing objects have been achieved in the present invention, whereby the present invention overcomes the above-identified and other deficiencies in conventional LED lighting systems by providing a self-contained LED lighting system capable of being placed directly in the space previously occupied by florescent tubes within a refrigerated cabinet. The apparatus disclosed herein provides for direct replacement of florescent lighting and incandescent lighting by providing a correctly sized LED lighting assembly designed for direct installation in place of previous lighting systems. The apparatus provides numerous advantages over the prior art, including the fact that most of the components of current lighting systems can be left in place during installation. For example, all the components in a fluorescent lighting system except the bulb may remain in place, thereby avoiding the need for hazardous waste disposal generally required for disposal of the ballast. The system also provides a specially designed refractive lens that is customizable for various types of LEDs. When installed, the lens provides a wide pattern of light dispersion more suitable for lighting within a refrigerated cabinet. The lens also provides greater heat dispersion and removal by completely encapsulating each LED. 
         [0009]    The lighting apparatus is sized to fit in the space previously occupied by the bulb being replaced. No cutting of the previous housing, wiring etc. is requiring to install the lighting apparatus. When installed, the LED illumination system provides the same or greater light output as the bulb it replaces in a warm or acceptable white color, something that is only possible very recently due to upgrades in LED technology. The apparatus also provides the light using far less power than the bulb it replaces. Unlike prior art systems, the lighting apparatus is fully enclosed, with all components, including the power supply, housed within the apparatus. 
         [0010]    The invention comprises a plurality of LEDs carried on a rigid substrate. Underlying the substrate, a heat sink system is provided using a thin layer of metal on the bottom of the substrate. Immediately surrounding each of the plurality of LEDs is a plurality of metal-lined heat sink holes that are in metal to metal contact with the thin layer of metal on the bottom of the substrate. When the specially designed lens is placed over the LED, the outer circumference of the lens contacts the substrate to uniformly space the lenses above each LED for uniform illumination. The heat sink system operates to channel the heat produced by each LED downwards through each of the plurality of heat sink holes into the open channel provided below the rigid substrate. Heat is therefore absorbed in at least two ways: first, by air convection from the space surrounding the LED to the space below the LED; second, by metal-to-metal conduction from the metal line holes to the metal layer on the bottom of the rigid substrate. 
         [0011]    The invention also comprises a constant-current power supply rather than a mere constant-voltage or regulated power supply as seen in prior art systems. Constant-current power supplies better regulate power consumption and improve long-term reliability of the LEDs. The power supply is mounted directly below the rigid substrate and within a C-channel housing designed to carry the rigid substrate. As such, the C-channel, rigid substrate, LEDs, and lenses are all provided in an integrated and self-contained apparatus. 
         [0012]    The invention further comprises a specially designed lens directly over-laying each LED on the substrate. The lens is preferably clear and uncoated, generally a polycarbonate or other form of clear plastic. The lens is designed to evenly disburse light from each of the LEDs in a flat, wide pattern in front of and lateral to each LED. This allows the LED to deliver light evenly over a nearly 180° arch in front of each LED, rather than delivering nearly all of the light in a beam less than 90° wide directly in front of the LED as provided by prior art systems. The lens also contacts and encapsulates each LED to improve lighting dispersion and heat removal away from each LED and into the C-channel below. An embodiment of the lens is provided, wherein five individual lenses are formed by injection molding into a substantially flat and rigid assembly designed to fit directly over a similarly sized flat and rigid substrate. To support exact placement of each lens directly above each of the LEDs, a placement nipple is provided. The placement nipple is designed to protrude into direct fitting holes within each of the rigid substrates. And finally, the lens is specially designed to operate with a variety of LEDs based on size, color, temperature, power, and shape. In other words, each lens may be computer designed to optimize potential lighting patterns based upon the specific type of LED being used. 
         [0013]    In a highly advantageous aspect of the invention, a modular LED strip lighting assembly may be provided in standard lengths by simply changing the number of lighting modules included in the housing. The modular assembly includes a longitudinal housing with a plurality of LED lighting modules carried end-to-end along a length of said housing. A plurality of LEDs is carried by the lighting modules and a plurality of refractive lens carried by the housing covering the LEDs for dispersing a wide angle of light from each of the LEDs. A constant current control circuit is carried by at least one of the lighting modules for delivering a generally constant electrical current to the LEDs. Advantageously, the LED lighting modules include at least one master lighting module and at least one slave lighting module associated with the master module wherein the current control circuit is carried on the master lighting module and is electrically connected to the LEDs on the master and slave lighting modules. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    The construction designed to carry out the invention will hereinafter be described, together with other features thereof. 
           [0015]    The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown and wherein: 
           [0016]    The construction designed to carry out the invention will hereinafter be described, together with other features thereof. 
           [0017]    The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown and wherein: 
           [0018]      FIG. 1  is a perspective view of an LED illumination system installed within a refrigerated cabinet, according to a preferred embodiment of the invention. 
           [0019]      FIG. 2  is a perspective view of an LED lighting assembly, according to a preferred embodiment of the invention. 
           [0020]      FIG. 3A  is a perspective view of the various components of an LED lighting assembly broken down into individual pieces. 
           [0021]      FIG. 3B  is a perspective view of a portion of the main components of an LED lighting assembly broken down into individual pieces. 
           [0022]      FIG. 3C  is a perspective view of a portion of the main components of an LED lighting assembly fitted together. 
           [0023]      FIG. 4A  is a side view of a standard LED indicating a narrow dispersion pattern of light emitted. 
           [0024]      FIG. 4B  is a side view of the same LED with a specially designed refractive lens overlaying the LED to improve its light dispersion pattern. 
           [0025]      FIG. 5A  is a perspective view of a portion of a lens assembly indicating a specially designed lens and alignment nipple. 
           [0026]      FIG. 5B  is a bottom view of the same specially designed lens indicating the lens curvature. 
           [0027]      FIG. 5C  is a side view of the same specially designed lens further indicating the lens curvature. 
           [0028]      FIG. 6A  is a side view cut-away of a specially designed lens indicating the interior curvature and shape of the lens. 
           [0029]      FIG. 6B  is a top view of the same specially designed lens indicating the location of the individual curves within the lens. 
           [0030]      FIG. 6C  is a bottom view of the same specially designed lens further indicating the lens&#39; curvature. 
           [0031]      FIG. 7A  is a side view of an LED mounted on a rigid substrate over-laid by a specially designed lens. 
           [0032]      FIG. 7B  is a top view of the same LED mounted on a rigid substrate and over-laid by a specially designed lens, also indicating the LED power connections, heat sink holes, and location of the lens. 
           [0033]      FIG. 7C  is a bottom view of the same LED mounted on a rigid substrate, indicating the metal-lined underbody of the rigid substrate and the metal-lined holes surrounding the LED. 
           [0034]      FIG. 8A  is a side view cut-away of an LED mounted on a rigid substrate and over-laid by a specially designed lens along with a blowup indicating the LED in close perspective. 
           [0035]      FIG. 8B  is an enlarged blowup of an LED mounted on a rigid substrate, indicating the metal lined heat sink holes and the passage of heat there through. 
           [0036]      FIG. 9A  is a top view of a specially designed lens over-laying an LED mounted on a rigid substrate and having metal-lined heat sink holes appurtenant thereto. 
           [0037]      FIG. 9B  is a cut away perspective of the same specially designed lens over-laying an LED and heat sink holes. 
           [0038]      FIG. 10  is a graphic representation of the lighting intensity and dispersion pattern of light emitted from three common LEDs. 
           [0039]      FIG. 11  is a bottom plan view of a modular LED lighting assembly according to the invention. 
           [0040]      FIG. 12  is a top plan view of a modular LED lighting assembly according to the invention. 
           [0041]      FIG. 13  is a perspective view of a modular LED lighting assembly according to the invention. 
           [0042]      FIG. 14  is an end view of a modular LED lighting assembly according to the invention with an end plate removed. 
           [0043]      FIG. 15  is an in end view of a modular LED lighting assembly according to the invention with end plate installed. 
           [0044]      FIG. 16  is a schematic view of a master LED lighting module and current control circuit according to the invention. 
           [0045]      FIG. 17  is a schematic view of a slave LED lighting module according to the invention. 
           [0046]      FIG. 18  is an illumination and distance graphical drawing according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0047]    Referring now in more detail to the drawings, the invention will now be described in more detail. As can best be seen in  FIG. 1 , a LED lighting assembly, designated generally as A, is illustrated attached to the door of a refrigerated cabinet  10 . Refrigerated products are typically stored in the cabinet behind the glass display doors for display to customers. When a customer  12  approaches cabinet  10 , the contents  14  of cabinet  10  are illuminated by LED lighting assembly A. LED lighting assembly A is constructed and arranged for placement in the location where a florescent tube was formerly installed in florescent lighting assembly  18  of the cabinet. Assembly  18  is installed on door post  20  between each of the refrigerated cabinet doors  22  and is typically four feet from adjacent door posts. In the illustrated embodiment, light assembly A includes an elongated channel housing  16 , a LED lighting assembly  21  carried by the housing over an open top thereof having a substrate  34  with a plurality of individual LED units  24  which include a LED  36  and a lens  46  on lens cover plate  40 . Light is emitted from each of the individual LED units  24  carried upon the surface of the LED lighting assembly and refracted as indicated to provide an evenly disbursed and desirable light pattern for uniform illumination of the interior of refrigerated cabinet  10 . Typically, the door  22  of refrigerated cabinet  10  is lined with glass so that customers  12  can view the contents  14  of refrigerated cabinet  10  prior to opening the door  22 . A plurality of LED units  24  is generally necessary to provide sufficient lighting to uniformly illuminate the interior of refrigerated cabinet  10 . That plurality of LED units  24  is configured in the preferred embodiment of  FIG. 1  within C-channel housing  16 . 
         [0048]    Referring now to  FIG. 2 , a preferred embodiment of LED lighting assembly A is illustrated. Mounting bracket  26  is used to install the lighting assembly into the space formerly occupied by a florescent lighting bulb, such as that used on florescent lighting assembly  18  of  FIG. 1 . In the preferred embodiment of  FIG. 2 , fifteen individual LED units  24  are used to produce sufficient illumination to uniformly light the interior of a cabinet such as refrigerated cabinet  10 . Lens plate  40  includes a rigid substrate  28  mounted in C-channel housing  16 . 
         [0049]    If LED lighting assembly A is disassembled into its main component parts, as indicated by the embodiment of  FIG. 3A , one notes that the LEDs and lenses are preferably mounted in three sections of five each. Within C-channel housing  16 , three individual constant current supplies  32  are provided to power each section of five LEDs  36  mounted on the three rigid substrates  34 . C-channel housing  16  contains two grooves on each side of its outer most edge (as shown in  FIG. 3B ) for receiving each of the three rigid substrates  34 . When installed, the rigid substrates rest near the surface of C-channel housing  16 . The combination encloses current supplies  32  and conductors  38  within C-channel housing  16 . Power is provided to each of the three LED sections  34  by constant current power supplies  32 , which are wired together in parallel by conductors  38  beneath rigid substrates  34  and lens plates  40 . 
         [0050]    As shown in  FIG. 3B , rigid substrate  34  is designed to slide into lower groove  78  of C-channel housing  16 . Likewise, lens plate  40  is designed to slide into upper groove  80  so that it rests directly above and in contact with rigid substrate  34 . When installed, as indicated by  FIG. 3C , lens plate  40  rests directly upon rigid substrate  34 . The combination of rigid substrate  34  and mounting bracket  26  act together to enclose the air space within C-channel housing  16 . 
         [0051]    Once each of the rigid substrates  34  is installed in C-channel housing  16 , each of the three groups of lens plates  40  are affixed thereto directly above each of the three corresponding rigid substrates  34  according to placement and fitting of alignment nipples  42 . Both rigid substrates  34  and lens plates  40  are held in place by flexible compression of C-channel  16  within lower groove  78  and upper groove  80 , respectively. Each of the lens plates  40  are properly aligned by alignment nipples  42 , which project into alignment nipple receiving holes  44  found in equidistant locations along each of rigid substrates  34 . In other words, alignment is made possible by alignment nipples  42 , which project downward and into alignment nipple receiving holes  44  so that the respective lateral positions of rigid substrate  34  and lens plate  40  remain fixed. Once installed, each of the lenses  46  directly overlays LEDs  36  to provide for proper dispersion of the light emanating from LEDs  36  and to provide for proper removal of the heat generated by LEDs  36  as discussed with reference to  FIG. 7 . 
         [0052]    Referring now to  FIG. 4A , LED  36  is shown mounted upon rigid substrate  34 . Without lens  46  over-laying LED  36 , the dispersion of light from LED  36  generally ranges no greater than 90°, as indicated by angle  48 . One of the primary advantages of the invention is improved light dispersion provided by lens  46 . As shown in  FIG. 4A , the range of light dispersion normally provided by an unaided LED is very narrow, rarely greater than 90°. 
         [0053]    In addition, a thin metal layer  50  is provided upon the bottom of rigid substrate  34  for heat removal as discussed further with reference to  FIGS. 7 &amp; 8 . Metal layer  50  runs the length of the underside of rigid substrate  34 . When in use, LED  36  generates heat. That heat is channeled by lens  46  and heat sink holes  70 , as more fully discussed with reference to  FIG. 8B . 
         [0054]      FIG. 4B  indicates the improved light dispersion according to an embodiment of the invention using lens  46 . Light emanating from LED  36  is refracted using lens  46  to produce a much wider and nearly 180° angle  52 . This wider angle dispersion is possible because the specially designed lens  46  optimizes and refracts light emanating from LED  36  into a substantially flat and wide pattern more suitable for lighting the contents of a wider, flatter area such as the interior of a refrigerated cabinet  10 . Because the contents  14  of a refrigerated cabinet  10  typically rest both in front of and lateral to the light source on door post  20 , the light source must be able to project a wide angle pattern of light, such as angle  52 . In other words, narrow angle  48  would be unsatisfactory for lighting a refrigerated cabinet  10  because the light emitted would only manage to light the contents  14  directly in front of LED  36 . Other cabinet contents  14  that rest lateral to (on each side) LED  36  would receive little or no light from the uncorrected LED  36  shown in  FIG. 4A . By contrast, the specially designed lens  46  of  FIG. 4B  refracts the light emitted from LED  36  so that the light projected from the surface of lens  46  is uniform in a wide angle pattern sufficient to light all the contents  14  of refrigerated cabinet  10 . 
         [0055]      FIG. 5A  illustrates a side view of lens  46  according to an embodiment of the invention. The interior dome  54  that resides directly above the LED is specifically designed and matched to individual types of LEDs. Interior dome  54  works with exterior dome  56  in combination to provide the widest and most desirable dispersion of light capable of being produced with the chosen individual LED. In other words, interior dome  54  and exterior dome  56  are specially designed to optimize light dispersion given a particular LED&#39;s optical characteristics. In a preferred embodiment, domes  54  and  56  are specially shaped according to a particular LED&#39;s shape, color, lumen output, etc., using any of a number of commercially available software applications, such as Code V® or LightTools®. 
         [0056]    In accordance with the above, an all-refractive lens was designed for the refrigerator strip light application. The design achieves an efficiency of 90%, effectively illuminating a 60 inch tall by 28 inch wide product surface area from a range of 4 inches beyond the face of the lens. The design achieved plus or minus 25% luminance uniformity, in spite of the extreme aspect ratio presented by the product surface. The front face of the lens is a smooth, low-profile nearly spherical surface that can be easily cleaned. The lens uses clear PMMA (acrylic) material, and can be produced using compression molding techniques. 
         [0057]    In this way, lens  46  can also be specially designed to suit a particular application. For example, lens  46  could be adapted to provide lighting in a non-refrigerated environment where, heat output is less of a concern. In such a case, a more powerful LED could be used to provide greater light intensity and lens  46  could be shaped to project that light in any desired pattern, angle, or direction as needed. Overhead lighting in small or large rooms is one likely possibility because lens  46  could easily be adapted for wider or narrower angles as needed given ceiling height. The same is true for landscape lighting and many other applications, where the primary variable is the pattern of light needed. Given the invention&#39;s adaptability to many potential lighting patterns, lens  46  is easily shaped to provide the intensity and coverage of light needed. 
         [0058]      FIG. 5A  illustrates an embodiment adapted to a refrigerated application for several reasons. The lower-most portion of dome  54  contacts the rigid substrate at lower edge  58  so as to surround the LED, and provide a defined spacing between the lens and LED. In this way, lower edge  58  encapsulates the LED. Optical efficiency is optimized by forcing all of the light emitted from the LED to travel up from lower edge  54  through interior dome  58  out through exterior dome  56 . None of the light escapes, therefore, from between lower edge  54  and rigid substrate  34 . As discussed more fully with reference to  FIG. 8B , the heated air is then forced downward by the heat sink into the open cavity within C-channel housing  16 . 
         [0059]    As illustrated in  FIG. 5B , lower edge  58  is circular and designed to protrude slightly below lens plate  40  so as to allow lens plate  40  to rest upon the rigid substrate  34  without contacting the rigid substrate  34  in other locations.  FIG. 5B  further illustrates the interior dome  54  as it appears from a bottom view. 
         [0060]      FIG. 5C  illustrates a top prospective view of the lens, wherein exterior dome  56  is clearly visible as a hemispherical protrusion from lens plate  40 . The interior dome  54  is also visible with respect to the remainder of the lens. And, finally, the ring of lower edge  58  is also visible from the surface as indicated. 
         [0061]    Alignment nipple  42  is also indicated as it would appear on a preferred embodiment of the invention. Alignment nipple  42  protrudes downward with sufficient length to insert into a corresponding alignment receiving hole in rigid substrate  34 , whereby lens plate  40  is precisely placed to position each lens  46  directly above each LED. 
         [0062]      FIG. 6A  illustrates a side view cutaway of lens  46 . Interior dome  54  is shown as a substantially bell-shaped interior hollow space that resides directly above the LED. Exterior dome  56  is illustrated as a hemispherical protrusion directly above interior dome  54 . Each of these two domes work together to maximize the light dispersion from LED  36 . Again, lower edge  58  of lens  46  is also indicated. 
         [0063]      FIG. 6B  illustrates the same lens  46  from above. Downward projecting lines from  FIG. 6A , to  6 B, to  6 C, indicate the relative positions of each particular section of lens  46  as the lens is rotated from side view in  FIG. 6A , to top view in  6 B, to bottom view in  FIG. 6C . The circular rings of interior dome  54  remain visible through the surface of exterior dome  56  along with lower edge  58 . As the lens is rotated 180° and shown from a bottom view in  FIG. 6C , each of these circular rings remain visible. 
         [0064]    Referring now to  FIG. 7A , a side view cutaway of lens  46  mounted directly above LED  36  is illustrated, according to an embodiment of the invention. As shown, interior dome  54  resides directly above LED  36  so that a substantially bell-shaped interior portion is provided in the air space directly above LED  36 . As the light emanates from LED  36  and projects upwards into interior dome  54 , that light is refracted through a combination of interior dome  54  and exterior dome  56  to produce a very wide angle of light dispersion. 
         [0065]    Alignment nipple  42  is also indicated as it projects through alignment nipple receiving hole  44 . Each lens plate  40  includes two or more alignment nipples  42  that are inserted into alignment nipple receiving holes  44  to ensure proper alignment of each lens  46  directly above each LED  36 . 
         [0066]    When the lens plate  40  and rigid substrate  34  are rotated 90° to view both from above as indicated in  FIG. 7B , all of the components in this embodiment of the invention are visible. LED  36  is shown at the center of  FIG. 7B  as powered by positive conductor  68  and negative conductor  66 , which connect at connection points  64  and  62 , respectively. Both conductors are preferably stamped onto the surface of rigid substrate  34 . The LED housing  60  is now visible also. Lower edge  58  of lens  46  surrounds LED  36 , its housing  60 , and a plurality of heat sink holes  70 . If this same embodiment is rotated 180° so as to be viewed from its bottom as illustrated in  FIG. 7C , the only portions remaining visible are the thin metal assembly  50 , residing along the bottom of substrate  34 , the plurality of heat sink holes  70  surrounding LED  36 , and alignment nipple receiving holes  44 . 
         [0067]      FIG. 8A  continues this line of drawings with a side-view cutaway of lens  46  mounted above substrate  34 . Blowup  8 B is indicated in  FIG. 8B , to more fully illustrate heat sink holes  70  and their operation. As illustrated in  FIG. 8B , lower edge  58  of lens  46  contacts rigid substrate  34 , thereby surrounding the area in the immediate vicinity of LED  36  and the plurality of heat sink holes  70 . Moreover, LED  36  and heat sink holes  70  are fully encapsulated within a confined air space underneath bell-shaped interior dome  54 . In this way, the heat emanating from LED  36  is forced downward through the plurality of heat sink holes  70 . Heat transfer occurs through heat sink holes  70  in at least two ways. First, heat is conducted through the metal lining inside each of the plurality of heat sink holes  70 , because the metal lining inside each hole  70  is in metal-to-metal contact with the metal lining  50  on the bottom of rigid substrate  34 . Second, the air within the interior dome  54  is forced downward through convection and expansion of the air above LED  36 , because heat sink holes  70  provide the only means of escape for the heated air. In this way, heat generated by operation of LED  36  travels downward to heat sink  50 , where that heat dissipates along the length of heat sink  50 &#39;s surface into the open cavity within C-channel housing  16 . 
         [0068]    Referring now to  FIG. 9A , a top view perspective of a lens overlaying an LED is illustrated. As shown, lower edge  58  of lens  46  completely surrounds LED  36  and LED housing  60 , and contacts substrate  34  for defined spacing and uniform illumination ( FIGS. 8A ). If a portion of the lens covering is removed as shown in cutaway  FIG. 9B , the LED housing  60  and LED  36  are plainly visible along with the plurality of heat sink holes  70 . 
         [0069]      FIG. 10  is a graphical representation of the light emissions from three common types of LEDs. As indicated, the graph of  FIG. 10  contains outwardly projecting concentric rings, each of which indicates successive one foot distances away from the LED shown in the center. Each of those rings also illustrates a successive 200 lux increase in lighting intensity. And, finally, the rings also show directional orientation of the light emanating from the LED. In other words, the graphical shapes indicated provide a close approximation of the lighting pattern observed projecting outward from the LEDs in actual use with an embodiment of lens  46  over-laying each LED. 
         [0070]    A Cree XR-C LED is indicated in the diamond-shaped pattern, whereby the light projects in a substantially flat, wide pattern with a maximum of approximately 550 lux at a distance of 2½ feet from the Cree XR-C LED. The Rebel 50 LED shown in the square pattern has a very flat emanating light beam that maximizes at approximately 700 lux at approximately 3½ feet lateral to the LED, whereas only approximately 150 lux is observed directly in front of the Rebel 50 LED from less than a foot away. The Rebel 90 LED is similarly shown in a triangular pattern. The Rebel 90 LED is a recent creation that provides 90 lumens per watt, yet still provides an acceptably warm white color output. When an embodiment of the invention is applied, the Rebel 90 emits almost 1200 lux at nearly 6 feet lateral to the center of the LED and as much as 400 lux directly in front of the LED. One can see from these graphical representations that the preferred embodiment lens flattens and widens the angle of dispersion of each LED so as to provide a substantially uniform and desirable lighting pattern not only from front-to-back but also from side-to-side, thereby making the light pattern ideal for interior lighting of a refrigerated cabinet  10  as indicated in  FIG. 1 . Without application of lens  46 , each of the graphs in  FIG. 10  would show full intensity of light directly in front of each LED with virtually no intensity side-to-side. 
         [0071]    Referring now to  FIGS. 11 through 18 , an alternate embodiment of the invention is disclosed in a modular, low profile assembly. As can best be seen in  FIG. 11 , a modular LED lighting assembly, designated generally as B, is illustrated which is attached to the door of a refrigerated cabinet the same as the LED lighting assembly A. The LED lighting assembly B has many of essentially the same elements as found in lighting assembly A, and those elements will be given like reference numerals. The LED lighting assembly B has the advantages of a lower profile, low voltage, and a modular lighting assembly configuration. The low profile allows a greater perpendicular distance, P, between the light source and the product shelf and increase illumination of the food product in the refrigerated cabinet. The low voltage arrangement facilitates the low profile by removing the power supply from the lighting assembly, removes heat from the assembly, provides increased reliability, and results in Class 2 voltage classification for safety and UL certification. 
         [0072]    Referring to  FIG. 14 , it can be seen that housing  90  has a low profile defined by a depth of approximately 1.33 inches in the illustrated embodiment. The housing has a width of approximately 2.27 inches and a length of approximately 5.0 feet. The depth profile of housing  16  in  FIGS. 3B and 3C  is approximately 1.81 inches or about 0.50 inches deeper than the low profile housing. However, this amount is significant. Since food product is often placed close to the door and the light source the width of the illumination can be significantly reduced leaving a dark area between shelf illumination patterns. An additional, 0.50 inches in distance results in a wider illumination pattern to eliminate or reduce dark areas according to the invention. 
         [0073]    Advantageously, lighting assembly B is constructed from a plurality of lighting modules C either in the form of a master module or a slave module, as explained below. The modular lighting assembly construction allows the lighting system to be constructed in different lengths in a convenient and expeditious manner. In the illustrated embodiment, 15 LED light assemblies, each including a LED  36  and a lens  46 , are provided in a five-foot lighting assembly strip. As can best be seen in  FIG. 14 , low profile C-channel housing  90  includes a lower groove  78  and an upper groove  80 , respectively. Lens plates  40  are held in place by the upper grooves  80  and the LED substrates are held in place in lower groove  78 . The lens plates and LED substrates include alignment nipples  42  and holes  44 , respectively. A series of LEDs is arranged along the LED substrate  34  and a series of lenses  46  is arranged along the lens plate  40 . Except for the modular construction to be disclosed in more detail below, the lens plate  40 , the lenses  46  with exterior dome  56  and interior dome  54  are the same. The LED substrates  92  include master modules  94  and slave modules  96 . As can best be seen in  FIG. 14 , the master modules  94  have a current control circuit  98  printed on the bottom of the substrate. 
         [0074]    As can best be seen in  FIGS. 11-13 , illustrated modular lighting assembly B includes five LED lighting modules C. There are three master lighting modules  94  and two slave lighting modules  96  illustrated as a five foot lighting assembly. The modules are provided in one-foot lengths (11.4 inches). One slave assembly is associated and used with one master assembly due to the voltage drop across the modules based on the voltage required for each LED. For example, in the illustrated embodiment, each LED requires 3.5 volts or 21.5 volts for six lights in one master module and one slave module. Continuing the module in this manner in the illustrated embodiment allows use of a low voltage power supply  100  of 24 volts. 
         [0075]    Modular lighting assembly B, includes a first master lighting assembly  94   a,  a first slave lighting assembly  96   a,  a second master lighting assembly  94   b,  a second slave lighting assembly  96   b,  and a third master lighting assembly  94   c.  This results in a standard five-foot lighting assembly B. Low voltage source  100  is connected to the light control circuit  98  of each master lighting module  94 . Electrical conductors  102  and  104  connect the low voltage across the master and slave lighting modules, and conductors  106  and  108  connect the low voltage source to current control circuits  98 . In turn, the current from the control circuits is delivered to LEDs  36  on the lighting modules via current delivery circuits  110 . The current control and delivery circuits, and the conductors are preferably printed on the bottom substrate of the lighting modules and the associated master and slave modules are electrically wired together. 
         [0076]    Power input to master lighting module  94   a  is input to current control circuit  98  which delivers a constant current to the LEDs  36  of master and slave modules  94   a  and  96   a.  At the same time, power is applied to current control circuit  98  of master lighting modules  94   b  and  94   c  via conductors  102  and  104 . Master lighting module  94   b  delivers a constant current to the LEDs on master lighting module  94   b  and slave lighting module  96   b.  Master lighting module  94   c  only delivers current to the LEDs on master module  94   c.    
         [0077]    Referring to  FIGS. 17 and 18 , constant current control circuit  98 , and master lighting modules C,  94  will be described in more detail. Master lighting modules  94  includes a current control circuit  98  imprinted on the bottom thereof by standard printing circuit techniques. The heart of the current control circuit is a LED driver chip U 1  which converts the low voltage to a current source for LEDs  36 , and makes adjustments to the output to ensure the LED driver current is constant despite variables and supply and load. Any suitable driver chip may be utilized, such as a LM3402 driver chip available from National Semiconductor. A capacitor C 3  is connected across the power source to control the amount of power ripple that is induced to driver chip U 1 . A resistor R 1  is connected to the drive chip to control the amount of on time of the MOSFET switch internal to the driver chip. A bypass capacitor C 4  is connected to the drive chip as a bypass filter capacitor for the internal voltage regulation of driver chip U 1 . A diode D 6  provides a path for the current supply by an inductor L 1  when the MOSFET internal to the driver U 1  is off. A storage capacitor C 2  is used to dampen the output pulses to the LEDs  36  provided by inductor L 1 , and the inductor stores the current used to feed the string of LED lights  36 . A current control resistor R 2  determines the average current supplied to the string of LEDs  36  via the driver chip U 1  and inductor L 1  in accordance with its value. Finally, a diode D 4  protects the circuit from reverse polarity at the connection of power supply source  100 . Of course, other suitable constant current controllers may be used as within the purview of those skilled in the art. 
         [0078]    As can best be seen in  FIG. 18 , illustrates low profile lighting assembly B disposed in front of a shelf  114 , or other product containing structure, which has been found highly advantageous in providing uniform illumination of the product in front of the lighting assembly and behind the glass enclosure, particularly when the food is close to the LED light units  24  as in large walk-in coolers where product is pulled to the front of the cooler. Often, the product is placed at a perpendicular distance (D) of less than four inches, which reduces the illumination and darkens the cooler. Typically, the light assembly of the present invention provides a uniform illumination of the product at 14 inches on either side of the lighting assembly, i.e. a 28-inch total width (W) of uniform illumination. Preferably, the light assembly illuminates approximately one-half of the shelf width (14 inches) on either side of the center line of the light source. When the low profile lighting assembly B is used, the perpendicular distance may be effectively increased by approximately 0.50 inches spreading the illumination width if the produce is close. 
         [0079]    The all-refractive lens assembly of the refrigerator strip light has been found to provide an efficiency of 90%, effectively illuminating a 60 inch tall by 28 inch wide product surface area from a range of 4 inches beyond the face of the lens. The lens assembly achieves plus or minus 25% luminance uniformity, in spite of the extreme aspect ratio presented by the product surface. The front face of the lens is a smooth, low profile nearly spherical surface that can be easily cleaned. The lens uses clear PMMA (acrylic) material, and can be produced using compression molding techniques. 
         [0080]    The lighting system of the present invention is provided for use primarily within refrigerated cabinets such as that illustrated in  FIG. 1 . However, the lighting system described herein is suitable for a wide variety of other applications not listed herein. Although several embodiments have been described in some detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not limited to the embodiments provided herein. These illustrated examples are offered by way of illustration of the invention&#39;s versatility and not meant to limit the invention any way. The present invention may be embodied in other specific forms without departing from its spirit and essential characteristics. The described embodiments are to be considered in all respects only illustrative and not restrictive. The scope of the invention is, therefore, indicating by the appended claims, rather than by the foregoing description. All changes that come within a meaning and range of equivalency of the claims are embraced within their scope.