Abstract:
A waterproof illumination device for simulating the lighting effect of neon lighting with the additional feature of being unaffected by water submersion. The device comprises a plurality of space point light sources secured within a waveguide that is waterproofed by sealing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. utility patent application Ser. No. 09/982,705 filed Oct. 18, 2001, now U.S. Pat. No. 6,592,238 entitled Illuminating Device for Simulating Neon Lighting, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to waterproof illumination devices using optical waveguide and, more particularly, to lighting devices for the simulation of neon lighting using optical waveguides and high intensity low voltage light sources, ideally adapted for use within an aqueous environment unsuitable for normal neon lighting devices 
     Neon lighting which is produced by the electrical stimulation of the electrons in the low pressure neon gas filled glass tube has been a main stay in advertising and for outlining channel letters and building structures for many years. A characteristic of neon lighting is that the tubing encompassing the gas has an even glow over its entire length irrespective of the viewing angle. This characteristic makes neon lighting adaptable for many advertising applications including script writing and designs because the glass tubing can be fabricated into curved and twisted configurations simulating script writing and intricate designs. The even glow of neon lighting being typically devoid of hot spots allows for advertising without visual and unsightly distractions. Thus, any illumination device that is developed to duplicate the effects of neon lighting must also have even light distribution over its length and about its circumference. Equally important, such lighting devices must have a brightness that is at least comparable to neon lighting. Further, since neon lighting is a well established industry, a competitive lighting device must be light in weight and have superior “handleability” characteristics in order to make inroads into the neon lighting market. 
     Neon lighting is recognized as being fragile in nature. Because of the fragility and heavy weight primarily due to its supporting infrastructure, neon lighting is expensive to package and ship. Moreover, it is extremely awkward to initially handle, install, and/or replace. Any lighting device that can provide those previously enumerated positive characteristics of neon lighting while minimizing its size, weight, and handleability shortcomings will provide for a significant advance in the lighting technology. Traditional neon is particularly not suited for use within an aqueous environment. If moisture penetrates the structure of a traditional neon lighting, it will impair the contact points of the electrical accessories and will result in electrical shortage and damages. Waterproofing neon lighting devices to prevent such problems typically require encapsulating the entire neon lighting device in a waterproof envelope, such as an acrylic. This adds considerable bulk to the neon device and increases the manufacturing expense. 
     U.S. Pat. No. 4,891,896 issued on Jan. 9, 1990 to Boren and assigned to the Gulf Development Company is an example of many attempts to duplicate neon lighting. Like this attempt, most prior art neon simulations have resulted in structures difficult to fabricate and providing a little in the way of weight and handling benefits. The Boren patent exemplifies this by providing a plastic panel with essentially bas-relief lettering. The material comprising the lettering is transparent and coated with a translucent material. The surrounding material is opaque. When the panel is back lit, the lettering tends to glow with a neon-like intensity. 
     It is therefore a paramount object of the present invention is to provide for an energy efficient, virtually unbreakable alternative to neon lighting capable of being submerged in an aqueous environment. 
     Additional objects of the invention will become readily apparent and addressed through a reading of the discussion below and appended drawings. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention is an illumination device for simulating the lighting effect of neon lighting that is unaffected by water submersion. The device comprises a plurality of spaced point light sources secured within a waveguide and housing waterproofed by sealing. In a preferred embodiment, the device is a profiled and sealed rod with an enclosed lighting source of a string of point light sources spaced a distance apart sufficient to permit the mapping of the light emitted by each point light source into the rod. The point lighting sources and electrical leads connected to the lighting sources are encased in a waterproof sealing or potting compound essentially transparent to the light emitted by the light sources. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevated perspective view of an illumination device of the present invention; 
     FIG. 2 is a perspective similar to that of FIG. 1 with a portion broken away to show the interior; 
     FIG. 3 is an expanded side view of the illumination device as shown in FIG. 1; 
     FIG. 3A is an enlarged wall segment of the illumination device shown in FIG. 3; 
     FIG. 3B is an enlarged wall segment like that shown in FIG. 3A with a variation in its structure; 
     FIGS. 4-6 are respective front, side, and top elevation views of the diodes connected to an electrical board as used in the present invention; 
     FIGS. 7A and 7B show, respectively, a graph illustrating the light distribution characteristics of a single point light source and a schematic of the device used to measure the same; 
     FIGS. 7C and 7D show, respectively, a graph illustrating the light distribution characteristics of a single point light source mounted within a device constructed in accordance with the present invention and a schematic of the device used to measure the same; and 
     FIGS. 7E and 7F show, respectively, a Mercator-like top projection and a side schematic of the illuminated lateral surface of the waveguide with overlapping individual light distribution patterns. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     To provide the desired result, i.e., an illumination device that is an effective simulator of neon lighting, it is important that the proper materials be selected for the component parts and those parts appropriately and geometrically positioned so that the resulting illumination device has an essentially uniform light intensity distribution pattern over the entire surface with the maximum obtainable brightness. To accomplish this, it is necessary to use a high intensity but dimensionally small light source together with an element that acts both as an optical waveguide and light scattering member, but permits light to exit laterally out of its surface (a “leaky waveguide”). By placing the light source contiguous such a leaky waveguide in a specific manner so as to cause the waveguide to uniformly glow over its lateral surface while maximizing the amount of light exiting the surface, applicants are able to obtain an illumination device that rivals or surpasses the uniform glow of neon tubing. There are many light sources which have a high light intensity output similar or equal to neon, but most are dimensionally too big to be practical, are fragile, or consume too much energy. It has been further observed that the best light source would likely have a small diameter that provided a uniform light output over an extended length. However, such a light source has not yet been developed to the technological state providing the intensity needed. Thus, applicants have determined that the best available light source for the purpose here intended is a string or strings of contiguously mounted, essentially point light sources such as spaced apart high intensity LEDs. 
     The ultimate objective of the illumination device of the present invention is to simulate an illuminated neon tube that glows with the proper intensity and uniformity over its length. Thus, applicants have determined that it is important that the leaky waveguide (used to simulate the neon tube) be comprised of a profiled rod of material having sufficient diffusivity that collectively with the other components of the invention visually eliminates any recognizable individual light distribution light pattern that originates from a respective LED or other light source. As stated above, the profiled waveguide preferentially scatters light along its length, but ultimately allows light to exit through its lateral surfaces. 
     Such a waveguide provides a visible elongated or oval-like light pattern for each LED, brightest at the center and diminishing continuously out from the center along the major and minor axis of the pattern. By spacing the LEDs a certain distance apart and each LED an appropriate distance from the exposed and lateral far side of the leaky waveguide, the light intensity distribution patterns on the surface of far side of the leaky waveguide are caused to overlap to such an extent that the variations in the patterns are evened out. This causes the collective light pattern on the lateral surface to appear to an observer to have an uniform intensity along the length of the waveguide. Other components of the illumination device of the present invention including, for example, the shape of the light sources may assist in establishing the required brightness and uniformity. 
     Structurally, the preferred embodiment of the present invention is portrayed in FIGS. 1-3 and shown generally as character numeral  10 . The device  10  may be considered as having two major body components. The first component is a waveguide  12  having an exposed curved lateral surface  13  serving as the light emitting surface and a hidden lateral surface  15  (best seen in FIG. 3) that serves as the light receiving surface. Waveguide  12  is the aforementioned leaky waveguide and surface  13  serves as the counterpart to the neon tube. That is, the light laterally entering the waveguide from a light source juxtaposed to the surface  15  is preferentially scattered so as to exit with a broad elongated light intensity distribution pattern out of surface  13 . Visually, the waveguide  12 , when not illuminated internally, has a milky appearance due to the uniform scattering of ambient light that enters the waveguide and that ultimately exits the lateral surface thereof. 
     Applicants have found that acrylic material appropriately treated to scatter light and to have high impact resistant to be the preferred material for use in forming the waveguide components of the present invention. When shaped into the profiled rods, the rods take on the desired leaky waveguide characteristics. Moreover, such material is easily molded or extruded into rods having the desired shape for whatever illumination application may be desired, is extremely light in weight, and withstands rough shipping and handling. While acrylic material having the desired characteristics is commonly available, it can be obtained, for example, from AtoHass, Philadelphia, Pa. under order number DR66080. When shaped into a rod, such acrylic material is observed to have the leaky waveguide characteristics desired. Other materials such as such as beaded blasted acrylic or polycarbonate provided with the desired preferential light scattering characteristics may be used as well for other applications. 
     The second component of the present invention is a housing  14  positioned adjacent the a lateral light receiving surface  15  of the waveguide  12 . The housing  14  comprises a pair of side walls  20 ,  22  abutting and downwardly extending from the lateral light emitting surface  13  and defining an open ended channel  18  that extends substantially the length of waveguide  12 . The housing  14  generally functions to house the light source and electrical accessories and to collect light not emitted directly into surface  15  and redirect it to the waveguide. In other words, the housing  14  further serves to increase the light collection efficiency by directing by reflection the light incident upon the internal surfaces of the housing  14  into the waveguide  12  and assist in the scattering of the light. From a viewer&#39;s perspective, it is desirable that the visual appearance of the housing  14  not be obtrusive with respect to the glowing surface  13  of the waveguide  12 ; thus, it is preferred that the outside surface  13  of the housing  14  be light absorbing and thus visually dark to an observer. Again, it is preferred that the housing  14  also be made from an impact resistant acrylic material with the outer surface walls  20 ,  22  having an outer regions formed from a dark pigmented, thus light absorbing, acrylic while the inner regions are made from a white pigmented, thus light reflecting, acrylic. The two regions are best viewed in FIG. 3A show an enlarged segment of wall  20  in which the outer region  20   a  is the dark acrylic and the inner region  20   b  is the white acrylic. Such acrylic materials preferably are the same as used for the waveguide. While the waveguide  12  and housing  14  may be separately formed and then appropriately joined, it is preferred that the components be molded or extruded as a unit in long sections with the channel  18  already formed. The individual sections can be easily shaped into the desired configurations with the channel  18  actually aiding in the bending of the housing  14 . 
     An alternate wall structure is shown in FIG. 3B in which the wall  20 ′ has three components, an outer dark region  20   c , and intermediate light reflecting  20   d , and a transparent wall  20   e . The outer and intermediate regions  20   c  and  20   d  could be dark and white coatings painted on the wall  20  which itself may be comprised of a transparent acrylic material. 
     Although the above discussion sets forth a preferred construction of the housing, it should be understood that in some applications the reflecting and absorption characteristics may be provided by light reflecting and absorption paint or tape. Additionally, there may be little concern about the visibility of the housing  14 . In such instances it may not be necessary to provide the light reflecting and/or absorption characteristics to the outer surface of the side walls  20 ,  22 . 
     It is important that the potting compound  30  (shown in FIG. 3) used to fill channel  18  have the desired light transmitting characteristics and be effective in maintaining the positioning of both the LEDs  24  and the board  26 , and protecting the LEDs  24  from water penetration. Moreover, as the illumination device  10  of the present invention has application in a submerged environment, the potting compound  30  provides the necessary waterproofing to the LEDs  24  and associated electrical member connections. Further, it is preferable that the potting compound  30  harden into an impact resistant material having an index of refraction essentially matching that of the housing  24   a  of the LEDs  24  to minimize Fresnel losses at the interface there between. The potting compound  30  further adds strength to the structure by filling in the channel  18  and assists in reducing hot spots from forming on the lateral surface  13 . As is also seen in FIG. 3, the bottom surface  36  of the device  10  may be covered with a light reflecting surface  32  which may be, for example, a white potting compound and this optionally covered with a light absorbing material  34 . 
     The intensity of the point light sources preferably used by the present invention are typically sufficient to provide the requisite brightness. It bears repeating that the quintessentially feature of the present invention, however, is the careful spreading or distribution of the individual light patterns of the point light sources such that the light patterns are preferentially expanded along the light emitting surface and form an oval-like light intensity pattern. Equally important is that the minor axis of the oval-like light intensity pattern extends substantially the entire circumferential width of the curved light emitting surface. The preferential spreading of each of the light intensity patterns along the waveguide also permits the overlapping of the individual light patterns. This in turn enables the present invention to provide an observed uniform collective light pattern along and over the entire light emitting surface. 
     There are various parameters that have an impact on both the brightness and uniformity of the light intensity pattern emitted by the surface  13  of the waveguide  12 . Among the most important are the scattering characteristics of the waveguide material, the spacing “l” between LEDs  24  as shown in FIG. 2, the lensing effect of the LED housing  24   a , the shape and structure of the housing  14 , and the distance “d” (shown in FIG. 3) from the apex of the LED housing  24   a  along a line perpendicular to the axis of the waveguide  12  to the apex point  12   a  on the lateral surface  13 . To promote uniformity of the light intensity distribution pattern on the surface  13  of the waveguide  12 , a line of LEDs  24  must be positioned a predetermined distance “d” from apex point  12   a  of the waveguide. This string of LEDs  24  are electrically connected to and spaced along an elongated circuit board  26  within the housing  14 . Positioning the LEDs  24  too close to the surface will cause a “hot spot”, i.e., a region of higher light intensity to locally appear on the surface  12   a  of the waveguide and spoil the quality of the uniform glow. Placing in too far from surface  12   a  will clearly and undesirably diminish the overall light intensity emanating from the waveguide  12  and may also prevent the minor axis of the oval-like pattern from extending over the circumferential width of the light emitting surface. As an example only, it has been determined that when the curved surface has a radius of curvature of about ⅜ inch and a circumferential width of about 19 mm, the device  10  (shown in FIG. 3) has a height “h” of about 25 mm and a width “w” of about 9.5 mm, and the LEDs have a candle power of about 280 mcd and are spaced apart about 12 mm, the distance “d” should be about 17.75 to 17.80 mm. 
     To better understand the principal under which the present invention operates, reference is now made to FIGS. 7A-7F. A single LED or point light source provides a narrow light intensity pattern  54  as graphically portrayed by FIG.  7 A. Such a graph can be generated by using a photocell type of device  50  portrayed in FIG.  7 B and progressively measuring the light intensity at various angles from the center line  51 . This light pattern  54  should be contrasted to the one in FIG. 7C in which the pattern  56  is considerably broader with a concomitant reduction in the intensity along the center line  51 . FIG. 7C represents the broad pattern emitted by the lateral surface  13  of the waveguide  12  constructed in accordance with the present invention. 
     As stated above, it is important that the distance “d” and the LED spaced apart distance “l” be such that the oval-like intensity patterns of the individual LEDs overlap as portrayed in the schematic representation of FIG.  7 E and the projection depicted in FIG. 7F schematically represents a plurality of LEDs  24  providing an broadened overlapping elliptical-like light intensity patterns  31  on the lateral surface  13  of the waveguide  12 . FIG. 7D is top view using a Mercator-like projection of the light pattern areas  24  on the lateral surface.  13 . The minor axis of the light intensity patterns  31  are represented by arrow  33 . As stated above, for any given dimension of the waveguide and spacing of the point light sources, it is important that the distance “d” be appropriately set so distance so that the minor axis of the light intensity distribution pattern extends substantially the entire circumferential width of the curved lateral light emitting surface  13 . For purposes of this disclosure the light intensity distribution pattern can be defined as the visible area of the light pattern extending out from the center region of the area that is visible discernible by an observer. 
     To further assist in the preferential diffusion and scattering of the light intensity pattern, applicant has further determined that the use of oval shaped LEDs  24  as shown in FIG. 6 are helpful. The best effect is obtained when the oval shaped LEDs  24  are positioned so that the major axis of the ellipse traced by the oval seen in top elevation view is directed along the long axis of the waveguide  12 . 
     From the discussion above, it may now be appreciated that the illumination device of the present invention is rugged and resists breakage that normally would be expected for neon lighting counterparts in shipping and handling and is capable of being completely submerged in water and the like without any additional structural requirement. The illumination sources, preferably solid state lighting devices such as LEDs, uses far less electrical energy and remains relative cool to the touch. This allows the illumination device of the present invention to be used in places where the heat generated by neon lighting precludes its use, including locations requiring liquid submersion. Moreover, the light weight of the illumination device facilitates mounting on support structures that could not support the relative heavy weight of neon lighting and its required accessories. Finally, the illumination device is flexible in its use, allowing a tremendous variety of lighting techniques very difficult to obtain in neon lighting without substantial expense. Other advantages and uses of the present invention will be clearly obvious to those skilled in the art upon a reading of the disclosure herein and are intended to be covered by the scope of the claims set forth below.