Patent Publication Number: US-8984780-B2

Title: Edge-lit light engine module for signs and sign

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of the invention relates to signage generally, and more particularly to certain new and useful advances in the application of energy-efficient light emitting diodes (LEDs) to signs and displays. 
     2. Description of Related Art 
     Various configurations exist for illuminating a sign or a display. For example, front-lit signs are illuminated using one or more light sources that are exterior to the sign. Back-lit signs are illuminated using one or more light sources, most commonly fluorescent bulbs, which emit light by ionizing mercury vapor. The ionized mercury vapor emits ultraviolet light. The ultraviolet light impinges a phosphor coated on the inside of the fluorescent bulb, causing the phosphor to fluoresce, giving off light. Non-electrical signs are illuminated using a radioluminescent material such as tritium. Some signs form graphics and/or words out of a tube that is filled with a gas, such as neon, argon or krypton. The gas emits light when electrical energy passes from an electrode at one end of the tube through the gas to an electrode at the other end of the tube. 
     More recently, edge-lit signs have been developed. These illuminate flat, thin sign faces by inputting light from multiple edges of the sign face. One or more LEDs can be used as light sources, but due to heat and physical design constraints, but those used tend to be low-power LEDs. Moreover, such LEDs typically have a fixed geometry that is sized for a specific sign face size or application. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure describes embodiments of a module that can be used to illuminate a sign or a display and a sign using such a module. The module includes a base member, two opposing side members coupled to the base member forming a channel therebetween and a light engine configured to fit within the channel that includes at least one light source. The channel is configured to receive a partial edge of the planar sign. The opposing side members have at least one attachment element capable of connecting the module to the partial edge of the planar sign. The light source may include at least one light emitting diode (LED). The attachment element aligns the light engine at a predetermined position relative to the partial edge of the planar sign. The planar sign includes a light guide. The attachment element, such as through holes, tabs, or locating fingers, aligns the light engine at a predetermined distance from the light guide, which provides close tolerance matching between the light engine and the light guide. Examples of the attachment elements include a tab, a through hole, and a locating finger. 
     In another embodiment, a sign is provided. The sign includes a planar sign face, a light guide coupled to the planar sign face and a housing. The housing includes a channel to receive a partial edge of the planar sign face and a light engine configured to fit within the channel and having at least one light source. At least one attachment element connects the housing to the partial edge of the planar sign face, at a predetermined position relative to the top edge of the light guide, facilitating internal reflection of the light source within the planar sign face. The position may be a predetermined distance between the at least one light source and the top edge of the light guide. The light guide is only attached to a partial edge of the planar sign face. 
     In yet another embodiment, a sign is provided. The sign includes a planar sign face having a first, set of through holes formed there through, a light guide with at least one edge coupled to the planar sign face, and a housing. The housing includes two opposing side members having a second set of through holes, a base member coupled with the two opposing side members forming a channel therebetween where the channel is dimensioned to receive a partial edge of the planar sign face and a light engine configured to fit within the channel which has at least one light emitting diode (LED). The first and second set of through holes are aligned such that the at least one LED is disposed at a predetermined position from the top edge of the light guide to facilitate internal reflection of light emitted from the LED within the planar sign face. The predetermined position may be the distance between the at least one LED and the top edge of the light guide. 
     Other features and advantages of the disclosure will become apparent by reference to the following description taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Reference is now made briefly to the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of an embodiment of a kit comprising an edge-lit light engine module and a display; 
         FIG. 2  is a perspective view of the kit of  FIG. 1  in an assembled state; 
         FIG. 3  is a perspective view an embodiment of the housing of  FIG. 1 ; 
         FIG. 4  is a plan view of the light engine of  FIG. 1 , with LEDs removed to show circuit traces; 
         FIG. 5  is another plan view of the light engine of  FIG. 1 , with a plurality of LEDs installed; 
         FIG. 6  is a side view of the edge-lit light engine module of  FIG. 1 ; and 
         FIG. 7  is a side view of the kit of  FIGS. 1 and 2  in an assembled state. 
     
    
    
     Like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the embodiments consistent with the invention, examples of which are illustrated, in the accompanying drawings. In describing particular features of different embodiments of the present invention, number references will be utilized in relation to the figures accompanying the specification. Similar or identical references in different figures may be utilized to indicate similar or identical components among different embodiments of the invention. 
     The subject matter of the invention relates to a sign face is plastic or other clear or filled polymer material that can transmit and internally reflect light. The sign face surface has a coating or features that permits light to exit with a desired intensity, pattern or location. Additionally, the sign body may contain a structure embedded therein to reflect light within the sign body and/or to permit light to exit the sign surface and/or the embedded structure. The sign face may be planar. An edge-lit light engine module couples with the sign face. The light engine module comprises At least one light source or a linear array of light sources mounted on a circuit board substrate. This substrate is mounted within a housing, formed of a heat-conductive material that serves as a heat sink and protective enclosure. The enclosure captures at least a partial edge of the sign face, and serves to overlap and reflect the light source/sign interlace at a specific position to facilitate internal light reflection. This overlap position may vary depending on the wattage of light sources used, the type of material that comprises the sign face, etc. The housing includes an attachment element or fastener such as a through hole, a tab, or locating finger used to mount, attach, or position the sign face. These attachment element(s) are dimensioned to provide close tolerance matching such that the edge of the sign face or the light guide attached to or within the sign face is precisely located with respect to the light engine within the housing. However, the housing can be coupled with the sign face using other types of fastening techniques, such as bonding, gluing and/or fixturing. 
     Advantageously and in contrast to prior approaches, the housing need not encompass an entire side or large area of the sign face, but rather mounts or attaches to only a partial edge of the sign face, using a tab or other attachment mechanism. The edge lit modular configuration of this housing and light engine combination permits fixed, specifically located and controlled light entry into the sign face. Moreover, this modular configuration ensures consistent fitting or light source placement with respect to the light source/sign interface. The physical size and dimensions of the light engine module are typically smaller than the physical size and dimensions of the sign face to which it is coupled. 
     Other advantages over prior approaches include that the housing and light engine substrate interface serve as a heat sink, permitting the use of high output LEDs. This heat dissipation, which is improved relative to prior approaches, ensures a full service life. The light engine module can be scaled and configured for application on circular sign face disks, rectangular disks or irregular shapes. Material thickness may vary as required. The module locating fasteners serve to carry the load of the larger, heavier sign face and can be used as mounting provisions. The edge-lit light engine module is remotely powered resulting in compact size and a visually appealing installation. The edge lit housing assembly is versatile, and can be a stand-alone product. Moreover, a single standard size unit may be used to illuminate a variety of sizes or diameters of signs. 
       FIG. 1  is an exploded perspective view of an embodiment of a kit  10  comprising light engine module  100  and a sign face  200 .  FIG. 2  is a perspective view of the kit  10  of  FIG. 1  in an assembled state.  FIG. 3  is a perspective view an embodiment of the housing  110  of  FIG. 1   
     Referring to  FIGS. 1 ,  2  and  3 , the light engine module  100  comprises a housing  110  and a light engine  150 . The light engine module  100  can be manufactured and sold as a stand-alone unit or manufactured and sold with the sign face  200 . In either case, the light engine module  100  houses the light engine  150  and aligns the light engine  150  at a predetermined position with and/or spacing from a portion of the partial edge of the planar sign or the top edge of light guide  210 . The predetermined position facilitates an optimal transfer of light from the light engine  150  to the sign face  200 . The light guide is a clear, translucent or partially filled acrylic, polycarbonate or glass material through which light is distributed and subsequently extracted from. The predetermined position may be a specific distance between the top edge of light guide  210  and the light engine  150 . The light engine module  100  also supports the sign face  200  via one or more fasteners  117 . The fasteners can be, for e.g., pins, rivets or bolts that fit in one or more aligned attachment element such as through holes  114 ,  203 . Through holes  114  are formed in the housing  110 . Through holes  203  are formed in the tab  204  of the sign face  200 . Additionally, the housing  110  of the light engine module  100  draws heat from the light engine  150  and dissipates the heat into the surrounding environment. 
     As shown in  FIG. 2 , the housing  110  of the light engine module  100  has a predetermined thickness  118 , length  119  and width  120 . The housing  110  is formed of an opaque material having a high thermal conductivity. Examples of such materials include, but are not limited to aluminum alloys, copper, and composite materials. As shown in  FIG. 1 , one or more side members  111  of the housing  110  overlap the partial edge of the sign face  200  or tab  204  of the sign face  200  containing a light guide  210 . This overlap causes light from the light engine  150  entering the tab  204  to be reflected and/or diffused throughout the entire sign face  200 . Without this overlap, a significant portion of light from the light engine  150  would immediately escape the tab  204 . The one or more side members  111  have smooth outer surfaces, but can include textured or finned outer surfaces to improve transfer of heat from the light engine  150  to the environment. The components of the housing  110 , e.g., base member  116  and one or more side members  111 , can be integrally formed or alternatively formed as individual components and pieced together. 
     As shown in  FIGS. 1 and 2 , the housing  110  comprises a base member  116  that is coupled with at least one side member  111 . Two side members  111  are used for two-sided signs, and are positioned to form a channel  113  therebetween. The channel  113  is configured or dimensioned to receive (or slide over) the light engine  150  and a portion of the sign face  200 , such as the light guide  210 , partial edge of the sign or tab  204 . At least the interior surfaces of the side members  111  of the channel  113  can be highly polished and/or lined with an optically reflective material to facilitate transfer of light from the light engine  150  to the sign face  200 . In one embodiment, the portion of the sign face  200  that fits within the channel  113  of the housing  110  of the light engine module  100  is a tab  204  containing a light guide  210 . The tab  204  containing a light guide  210  is coupled to the sign face  200  or integrally formed. Each side member  111  has a leading edge  112 . Either or both of the leading edges  112  are straight or formed in an aesthetically pleasing shape. The side members  111  are dimensioned to cover the light engine  150  and to overlap the tab  204  or light guide  210  of the sign face  200 . This arrangement facilitates an efficient transfer of light from the light engine  150  to the edge  201  of the tab  204  or light guide  210  of the sign face  200 . 
     As shown in  FIGS. 4 and 5 , the light engine  150  comprises a substrate  151  on which one or more series or parallel circuits are formed. These circuits, which may use either constant current or constant voltage, power one or more light sources  152 . The light sources  152  are high-power light emitting diodes (LEDs). High-power LEDS may be used, for example, LEDs configured to use about 500 milliwatts to about 10 watts or more in a single package. The light sources  152  may be flat LED packages, with or without lenses or covers. If light sources  152  equipped with lenses or covers are used, such lenses or covers may fit within one or more receptacles formed in the tab  204 . A thermal interface material may be disposed between a surface of the substrate  151  and an interior surface of the base member  116  of the housing  110  of the light engine module  100 . 
     As shown in  FIG. 3 , a hole  121  is formed in the base member  116  of the housing  110 . A first tube  115  is aligned with the hole  121  and coupled with the base member  116 . A second tube  153  is coupled with the substrate  151  of the light engine  150 , as shown in  FIGS. 1 and 2 , for example. The second tube  153  has a smaller diameter than the first tube  115 , and fits within the first tube  115  when the light engine  150  is positioned in the housing  110 . The second tube  153  contains one or more electrical leads that supply power to the one or mom circuits that are formed on the substrate  151 . One or more through holes  122  can be formed in the base member  116  to align with through holes  156  ( FIGS. 3 and 4 ) in the substrate  151  of the light engine  150 . 
     The sign face  200  may be formed of any material that can contain and reflect light from within it. Examples of materials that can be used to form the sign face  200  include, but are not limited to: acrylic, polycarbonate, glass, quartz crystal, vinyl (PVC), clear aerylonitrile butadiene styrene (ABS) and polyethylene terephthalate (PET) [make sure these are spelled out somewhere]. The sign face  200  has any desired 2D or 3D shape, and is configured or viewing from either one side or two sides. When configured for one-sided viewing, the sign face  200  has a reflective material or treatment applied to at least its back surface and/or edge  205 . When configured for two-sided viewing, the sign face  200  has a reflective material or treatment  302  applied to its edge  205  ( FIG. 1 ). In either case, the reflective material or treatment  302  functions to prevent light emitted into the interior of the sign face  200  from escaping from the back surface and/or edge  205 . For example, the edge  205  and/or back surface of the sign face  200  may be highly polished. As another example, optically reflective tape may be applied to the edge  205  of the sign face  200  or to a surface of an edgeband  300 . As another example, a surface of the edgeband  300  may be highly polished and/or have an optically reflective finish. 
     The sign face  200  has at least one tab  204  containing a light guide  210  formed along an edge  201  thereof. Unlike the edge(s)  205  of the sign face  200 , the edge  201  of the tab  204  does not have an optically reflective material  302  applied to it. Instead, the edge  201  of the tab  204  is configured to receive light emitted from the light engine module  100 . At least the tab  204  of the sign face  200  has a predetermined thickness  206 , length  207 , and width  208 , which generally match the corresponding thickness  118 , length  119  and width  120  of the light engine module  100 . The corners  209  of the tab  204  may be shaped or otherwise designed to scatter and diffuse light emitted from the light engine module  100 . One or more through holes  203  are formed in the tab  204  at positions that correspond to the positions of through holes  114  formed in the housing  110  of the light engine module  100 . Although round through holes  203  and  114  are illustratively shown, the through holes  203  and  114  may have any suitable cross-sectional shape. Like the through holes  114  formed in the housing  110  of the light engine module  100 , the through holes  203  are positioned to be between the light engine  150 , and the edge  201  of the tab  204 , and the body of the sign face  200 . As noted above, the edge  201  of the tab  204  can have one or more receptacles formed therein into which the one or more light sources  152  fit. 
     The thickness  118 , length  119  and width  120  of the light engine module  100 , the housing  110 , the light engine  150  and/or the tab  204  will vary depending on a number of factors, such as the number of lumens per square foot to be reflected through one or both surfaces  202  of the sign face  200 , the dimensions of the sign face  200 , the wattage, type and/or configuration of the light sources)  152 , etc. Typically, each side member  111  has a length greater than its width, and a thickness that, is less than its width. In one embodiment, the light engine module  100  is configured to produce about 250 lumens to about 500 lumens per square foot of the sign face  200 . This exemplary output range is anticipated to increase over time. 
       FIG. 4  is a plan view of the light engine  150  of  FIG. 1 , with LEDs removed to show the circuit traces  156 .  FIG. 5  is another plan view of the light engine  150  of  FIG. 1 , with a plurality of LEDs  152  installed. Referring to  FIGS. 4 and 5 , the linear substrate  151  comprises a central power connection located in the second tube  153 . Two series circuits  154  and  155  are disposed on either side of the central power connection located in the second tube  153 . A plurality of light sources  152  are coupled with the series circuits  154  and  155 . 
       FIG. 6  is a side view of the edge-lit light engine module  100  of  FIG. 1 .  FIG. 7  is a side view of the kit  10  of  FIGS. 1 and 2  in an assembled state.  FIG. 6  shows the channel  113  empty, and the light engine  150  fitted against the base member  116 , as previously described. The light engine  150  includes the substrate  151  and the light source(s)  152 ,  FIG. 7  shows the channel  113  fitted around the partial edge or tab  204  of the sign face  200  (not shown in FIG.  6 / 7 ) so that the edge  201  of the tab  204  contacts the light source  152  without stressing it. This is merely one embodiment of the invention. For example, there may also be a gap between the partial edge of the sign face  200  and the light source(s)  152 . As mentioned above, the edge  201  of the tab  204  may have one or more receptacles (not shown) formed therein to receive the light source lens or housing. 
     As shown in  FIGS. 6 and 7 , the light engine module  100  may further comprise a seal  160  that makes the light engine module  100  weatherproof. The seal  160  is a clear potting material, sealant or gasket that encapsulates the light engine  150  within the housing  110 . If a gasket is used, it may be equipped with holes that correspond to the location(s) of the light source(s)  152  so that contact between the light source(s), and/or their lenses or housings, and the edge  201  of the tab  204  can be achieved. The channel  113  can be configured so that the clear material that forms the seal  160  flows up and around the edge of the tab  204 . 
     Referring to FIGS.  1 , 2 ,  3 ,  4  and  5 , an edge-lit light engine module  100  may be assembled using the following steps, in any suitable order and/or in parallel, unless otherwise noted. The housing  110  is formed of a material having a high thermal conductivity. A portion of an inner surface of one or both side members  111  is configured to be optically reflective. The through hole(s)  114  are marked and/or bored. Optionally, the power conduit hole  121  is formed through the base member  116 , and the tube  115  is aligned with the power conduit hole  121  and coupled with the base member  116 . The power leads of the light engine  150  are fitted through the power conduit hole  121 . A thermal interface material is applied to an inner surface of the base member  116  and/or to a back surface of the substrate  151  of the light engine  150 . The light engine  150  is positioned adjacent the inner surface of the base member  116  and fasteners, bolts, rivets, screws, etc., are fitted through the through holes  156  in the substrate  151  and the aligned through holes  122  in the base member to secure the light engine  150  in place and ensure a good thermal bond between the base member  116 , the substrate  151  and/or the thermal interface material. A weatherproofing gasket may be added. 
     An illuminated sign is assembled using the following steps, in any suitable order, unless otherwise noted. A sign face  200  is cut or molded in a desired shape and may have a tab  204 . An assembled edge-lit light engine module is positioned to cover, or enclose, the tab  204 . If the through holes  114  and  203  have already been formed, they are aligned and secured with fasteners  117 . Otherwise, the through holes  114  and  203  are formed using a computer numerical control (CNC) machine equipped with computer assisted design (CAD) or other software that specifies the location and positioning of the through holes  114  and  203 . Then the fasteners  117  are fitted into the aligned through holes  114  and  203  to secure the edge-lit light engine module  100  to the sign face  200 . In this manner, the light engine  150  is precisely aligned and positioned relative to the edge  201  of the tab  204  of the sign face  200 , for example at a predetermined distance. 
     In operation, current from a power source (not shown) flows through the power leads to the series circuits  154  and  155 , and from, the series circuits  154 ,  155  to the light, sources  152 , which illuminate and emit light. This emitted light is transferred across the substrate/sign interface and into the thickness of the material that forms the sign face  200 . Thereafter, the light is internally reflected so that it traverses and illuminates the sign face  200  to a desired intensity (lumens per square foot, or equivalent). 
     As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
     Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. Other embodiments will occur to those skilled in the art and are within the scope of the following claims.