Abstract:
A method of accent lighting and an accent light including an LED and a light guide with polished proximal and distal ends. The LED is optically coupled to the proximal end and the distal end reflects the LED light back into the guide. Additionally, the distal end may include a reflective coating and the guide may be acrylic. Moreover, the guide may be supported by a vinyl support glued to the guide whereby the light output about doubles. Also, a longitudinal etch on the acrylic guide may make the light output about consistent along the guide.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to accent lighting, and more particularly to low light output accent lighting  
       BACKGROUND OF THE INVENTION  
       [0002]     Many consumers prefer to decorate their belongings with accent lights. Recently, for example, accent lights for automobiles, RV&#39;s and other vehicles have become popular. For another example, consumers frequently purchase hot tubs, saunas, and other leisure goods decorated with accent lights. Additionally, after market accent lights may be purchased by the consumer to decorate belongings which they already own, such as decks, patios, dock systems and so on. Likewise, low intensity lights (similar to accent lights) are preferred for location finding (e.g. in darkened theaters, outdoor areas at night, or pathways) and other general marking applications.  
         [0003]     Incandescent lights generally suffer from a number of disadvantages, which make them unsuitable for use as accent lights. First, they tend to be unreliable and prone to damage resulting in light failure, particularly from vibration, shock and corrosion. Moreover, an incandescent light consumes a relatively large amount of power, most of which is lost as sensible heat, not emitted as visible light, resulting in low efficiencies. Additionally, incandescent lights can cast a harsh light from a concentrated point source which further makes them unsuitable for use as accent lights in low ambient light conditions.  
         [0004]     Neon tube lights have also been employed as accent lights. But neon accent lights also suffer from disadvantages similar to those of incandescent lights. Neon lights are fragile and require excessive power in comparison to solid state LED lighting. Neon lights are also generally too bright for use as accent lights, particularly in low ambient light conditions. Thus, a need exists for accent lights which are highly reliable, damage resistant, and consume very little power (thereby creating little sensible heat) yet which still provide a diffuse, low intensity light, useful in low ambient light conditions.  
       SUMMARY OF THE INVENTION  
       [0005]     A method of accent lighting and an accent light is provided by the present invention.  
         [0006]     In particular the present invention includes a glow tube accent light which has an end-lit acrylic light guide acting as both a light diffuser and emitter. Since the light guide of the present invention possesses high light transmission efficiency, the glow tube may require only a single LED which is optically coupled to one end of the light guide to provide adequate accent illumination. To enhance the efficiency of the light guide, the end opposite the LED may be made optically reflective with a white coating. Thus, the opposite end reflects emitted light from the LED back into the light guide.  
         [0007]     Further efficiency enhancements may be included in the glow tubes of the present invention. For instance, the ends of the light guide may be smoothed to a mirror finish by clean flame polishing. Additionally, the light guide may be adhered to the light guide track housing. The adhesive creates a light seal which results in the light from the LED impinging on the track side of the light guide to be reflected to the front of the light guide. Thus, the light seal significantly increases the light output of the glow tube. Moreover, to enhance the consistency of the light output along the length of the light guide, longitudinal etches may be added to the light guide to more evenly distribute the light emission along the light guide. Accordingly, the LED illuminates the glow tube to a level and consistency suitable for viewing in low ambient light environments.  
         [0008]     In a first embodiment, the accent light includes an LED and a light guide with proximal and distal ends. The LED is optically coupled to the proximal end and the distal end reflects the LED light back into the guide. Additionally, the distal end may include a reflective coating and the guide may be acrylic. Moreover, the guide may be supported by a vinyl housing adhered to the light guide whereby the light output of the glow tube in the viewing direction is increased significantly relative to an isolated light guide. Also, a longitudinal etch on the acrylic guide may make the light output reasonably consistent along the guide. Thus, the present invention provides accent lights which diffuse and output a high percentage of the source light emitted by the LED.  
         [0009]     In another embodiment, a method of enhancing the light output from an accent light is provided. The method includes optically coupling a light emitting diode to a proximal end of a light guide and reflecting light from a distal end of the guide back into the guide. Additionally, the method may include coating the distal end with a white reflective material. Moreover, the light guide may be an acrylic tube. A support channel may also be provided for the acrylic tube and the two adhered together. Adding a support channel and adhering the channel to the acrylic tube significantly increases the light output of the accent light. Furthermore, a longitudinal etch may be made on the acrylic tube to make the diffuse light output along the length of the acrylic tube of a relatively uniform consistency. Thus, the present invention provides a method of enhancing the light output of an accent light to utilize a high percentage of the light emitted by the LED.  
         [0010]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0012]      FIG. 1  is a perspective view of a recreational vehicle which includes accent lights in accordance with the present invention.  
         [0013]      FIG. 2  is a perspective view of an accent light in accordance with a preferred embodiment of the present invention.  
         [0014]      FIG. 3  is a cross sectional view of an accent light in accordance with a preferred embodiment of the present invention.  
         [0015]      FIG. 4  is a flowchart of a method in accordance with a preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0016]     The following description of the embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0017]     As seen in  FIG. 1 , consumers frequently decorate their consumer products by adding accent lights to the product and its environs. In the exemplary scene shown in  FIG. 1 , a recreational vehicle  10  represents a typical consumer good which may be decorated with accent lights. Accent lights  12  are shown along the top edge of the recreational vehicle  10 . As well, accent lights  14  may be included within the cabin of the recreational vehicle  10 . A battery powered accent light  16  may also be set on (or affixed to) structures  18  near the recreational vehicle  10 . Additionally, a low intensity location marking light  19  may be provided on the edge of a step  21  leading into the recreational vehicle  10 . Being exposed to the weather, the accent lights  12  and  16  and the marking light  19  are waterproof and weatherproof, though the accent lights provided by the present invention need not be waterproof or weatherproof.  
         [0018]     Of course the recreational vehicle  10  also has conventional lights  20 . However, conventional lights  20  generally create intense, harsh light which is generally unsuitable for use when the recreational vehicle is parked in a campground. Thus, at night, when others nearby may be sleeping, the user may turn off the conventional lights  20  and turn on the accent lights  12 ,  14 , and  16 . Thus, the bright and harsh conventional light is replaced by low intensity diffuse light from the accent lights. Conventional incandescent lighting also consumes far more energy than solid-state diffuse lighting, usually requiring the periodic running of a generator, or of the RV engine for a time to recharge the electrical system. Diffuse LED accent lights, operating at a nominal 0.3 watts apiece, compared with the typical 7 to 12 watts of an incandescent, require less energy and can operate for a proportionally longer period on an equivalent amount of stored energy.  
         [0019]     Turning now to  FIG. 2 , a glow tube in accordance with a preferred embodiment of the present invention is shown. The glow tube  110  includes a support channel  112 , a transparent or translucent light guide  114 , and two end housings  116  and  118 . The support channel  112  encloses the light guide  114  on all but the side(s) through which the user wishes light to escape from the glow tube  110 . Also, the support channel  112  protects and supports the light guide in a recess diminished to hold the light guide  114 . The support channel  112  may be made of polypropylene or vinyl, white being one particular reflective color for the support, to enhance light reflection. The end housings  116  and  118 , when adhered to the support channel may clamp the assembly together and provide access for power leads (not shown), as well as containing the LED and associated lighting circuitry. Additionally, the end housings  116  and  118  may provide integral screw mounting attachment points to attach the glow tube  110  to various suitable structures or surfaces.  
         [0020]     Turning now to  FIG. 3 , the accent light  110  is shown in cross section. In particular, the light guide  114  may be generally bar, or rod, shaped and includes a proximal end  120  and a distal end  122 . Both ends may be polished to a mirror finish  124  of approximately 0.05 to 0.5 micron average surface roughness. In close proximity to, or abutting, the proximal end  120 , an LED  126  with associated circuitry on a small printed circuit board (not shown) is held in place by the end housing  116  and is optically coupled to the proximal end  120 . Additionally, potting resin  128  seals the LED  126  and associated circuitry against the environment and provides strain relief for a pair of electrical leads  130  which route power to the LED  126  and associated circuitry. Moreover, an electrical bridge and filter (not shown) may be provided either internally, or externally, to the glow tube to condition the electrical power for the LED  126 , thereby eliminating sensible flickering and power supply polarity issues. In a preferred embodiment, the LED  126  is a 5 millimeter, through hole, narrow cone (approximately 20 degrees) LED. In another embodiment, the resin potting material seals any electronics internal to the glow tube  110  and is an electronic/electrical grade epoxy resin having a minimum cured hardness, Shore D of at least 65.  
         [0021]     In contrast to the proximal end  120 , and at the distal end  122 , the end housing  118 , identical to the end housing  116 , encloses a reflector  132  in place against the distal end  122 . The reflector  122  may be a separate component or may be a coating applied to the distal end  122 . In certain embodiments, the reflector  132  may be a coating of reflective silvered or white ink applied to the distal end  122 . By eliminating light leakage from the non illuminated distal end  122 , and reflecting potential leakage light back into the light guide, the reflector  132  improves the efficiency of the light guide  114 . Herein, efficiency refers to the percentage of light emitted from the LED which escapes from the glow tube in the desired direction(s). In the alternative, end housing  118  may hold a second LED in close proximity to the distal end  122 , in an identical manner as proximal end  120 , instead of the reflector  132 .  
         [0022]     Additionally,  FIG. 3  shows a support channel  112  which may generally surround the light guide  114  on three sides, thereby allowing the light to escape from the light guide  114  along the remaining open side. Though, alternative embodiments may provide additional open sides from which light may escape. A sealant layer of adhesive  134  affixes the light guide  114  to the support channel  112 . Additionally, by eliminating a path of light leakage from the light guide  114 , the glue  134  serves as a “light seal” which tightly seals, surrounds and reflects light toward the open side, enhancing the efficiency of the light guide  114 . The adhesive may be a polyurethane sealant or a general purpose silicon sealant. It has been found that the resulting adhesive light seal increases the effective light output of the light guide  114  through the remaining open side by approximately 30% and improves the uniformity of light distribution.  
         [0023]     In another embodiment, the light guide  114  may be an acrylic rod. Moreover, a large number of fine longitudinal grooves, or etchings,  136  may be etched into the surface of the light guide  114 . It has been found that the longitudinal etchings, as opposed to a ‘frosting’ or fine pitting of the surface, provide light concentrating deformities which promote diffuse illumination throughout the length of the light guide  114 , without ‘shading’ of areas progressively distant from the illumination source. In another embodiment, the longitudinal etchings  136  run the length of the light guide  114 , are approximately 0.05 millimeters deep, and are approximately 0.05 millimeters wide. In addition, the etchings  136  may be on the surface of the light guide  114  which is exposed by the opening in the support channel  112  or may cover the entire circumferential surface of the light guide  114 . Supporting the unsuitability of a frosted, or fine pitted, surface, it has been found that eliminating, or avoiding, radial imperfections  138  and randomly orientated imperfections (e.g. sand blasting scratches and pits) further enhances the consistency of the light output by the light guide  114 . In accordance with the present embodiment, a glow tube  114  is provided which has a light output which varies less than about 30% along the length of a light guide  114  of approximately 0.3 m in length.  
         [0024]     Turning now to  FIG. 4 , a method of fabricating a glow tube in accordance with the principles of the present invention is shown. The method  200  includes forming a light guide of the desired size. In particular, a 12.8 millimeter acrylic rod may be cut to preferred lengths of about 6 inches, about 12 inches, about 18 inches, and about 24 inches. Extra length may be included to accommodate attachment of the end caps. See step  202 .  
         [0025]     In step  204  longitudinal etches are added to the sides of the light guide. The un-etched sides may be polished to eliminate radial and randomly orientated imperfections to further improve the light guide&#39;s efficiency. Meanwhile in step  206  the ends of the light guide may be polished to a mirror finish. In particular clean flame polishing may be employed to flow the acrylic surfaces thereby eliminating surface irregularities. A reflective coating may then be added to the distal end of the light guide. See step  208 .  
         [0026]     In step  210  the assembly of the electronic components may begin with mounting the LED and other internal circuit components on a PCB (printed circuit board). In the meantime the end housings may be assembled or fabricated as in steps  212  and  214  along with assembling the PCB in one of the end housings. As well, the support channel, or guide, may be formed as in step  216 .  
         [0027]     Adhesive may then be applied to the support channel or the light guide and the channel and the guide assembled. See steps  218  and  220 . Also, in step  222  the resin may be potted and applied to the LED (and other internal electronics). The end housings may then be affixed to the support channel as in step  220 . Appropriate quality control and performance tests may then be conducted on the glow tube. See step  224 .  
         [0028]     As those skilled in the art will recognize, the present invention provides a solid state accent light suitable for a variety of applications. In particular, the glow tubes provided by the present invention are durable and resistant to vibration and shock. It is estimated that glow tubes in accordance with the present invention may have average lifetimes of 100,000 hours or better. Additionally, the present invention provides glow tubes which are relatively insensitive to significant temperature variations.  
         [0029]     Also, the present invention provides LED end-lit glow tubes which require very little power relative to comparable incandescent lights, thereby being well suited for use with battery, or other limited stored energy power supplies. Accordingly, the glow tubes also produce little sensible heat. Additionally, the glow tubes of the present invention may be provided in any color for which an LED may be found. For instance, the present invention provides for red, green, blue, white, and amber glow tubes, thereby allowing wide consumer choice in color schemes. Furthermore, because of the high efficiency provided by the present invention, the light emitted from the glow tube may be intense enough so that operation of the glow tube (including its color) may be visually confirmed even in day time ambient light.  
         [0030]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.