Abstract:
A backlit sign with an LED module, with a housing that includes a top wall having a first length, a bottom wall having a second length, and a pair of opposing sidewalls each having a third length, wherein at least a portion of one of the sidewalls is translucent. One or more LED modules are mounted to the top wall and include a plurality of LEDs for producing light. The first, second and third lengths are selected to maximize illumination of the sidewalls by the produced light, and to minimize a width and weight of the sign. A mirror can be used to increase the reflectivity of the bottom wall.

Description:
This application is a continuation in part application of U.S. application Ser. No. 10/452,672, filed May 30, 2003, now U.S. Pat. No. 6,761,471 which claims the benefit of U.S. Provisional Application No. 60/417,211, filed Oct. 8, 2002. 

   FIELD OF THE INVENTION 
   The present invention relates to light emitting diode (LED) modules, and more particularly to an LED module for commercial and street name signs presently illuminated with fluorescent tube lighting. 
   BACKGROUND OF THE INVENTION 
   Light emitting diodes (LEDs) have been widely used in many applications to replace conventional incandescent lamps, fluorescent lamps, neon tube lamps and fiber optic lights. LEDs consume much less electrical power, are far more reliable, and exhibit much longer lifetimes, than their conventional counterparts. As a result, LEDs have been configured to replace conventional light sources for many applications. For example, LED lamps have been developed to replace screw-in incandescent light bulbs for traffic signals (as shown in U.S. Pat. No. 6,036,336), and exit signs (as shown in U.S. Pat. Nos. 5,416,679, 5,459,955, 5,526,236, 5,688,042, 5,949,347). In each case, the LEDs are mounted onto a lamp housing having a conventional threaded electrical connector that engages with the threaded socket connector in the traffic signal lamp or exit sign. Thus, retrofitting the traffic signal and exit signs simply involves unscrewing the conventional lamp and screwing in the LED lamp. 
   Retrofitting with LED lamps the vast numbers of backlit commercial and street name signs, which utilize fluorescent lighting, is more problematic. These signs typically include a housing containing one or more fluorescent tube lamps, and one or more translucent face plates (sidewalls) that are back-illuminated by the fluorescent lamp(s) (i.e. to form characters, designs, symbols, etc.).  FIGS. 1A and 1B  illustrate a conventional backlit street name sign, which includes a housing  1 , a pair of fluorescent tube lamps  2  and a pair of opposing translucent face plates  3  that indicate a street name. Each of the fluorescent tube lamps  2  are connected to and suspended by a pair of electrical connectors  4 , which are well known in the art. The face plates  3  are angled slightly downwardly for better viewing from below.  FIGS. 2A and 2B  illustrate a convention backlit commercial sign, where there is only a single translucent face plate  3  (which is not angled downwardly), and three fluorescent tube lamps  2  for illumination. 
   Replacing the short-lifespan fluorescent tube lamps in conventional backlit commercial and street name signs can be difficult, because such signs are typically elevated and inaccessible, disposed over roadways, and/or hard to open. What is worse is that there is no standard size for such signs, for the fluorescent tube lamps  2  used therein, and for the spacing between the electrical connectors  4 . Thus, designing an LED lamp retrofit that fits a wide variety of such signs, that evenly and sufficiently illuminates such signs, and that is easy to install without the need for special tools, has been difficult. Adding to that difficulty is the fact that many such signs are suspended in a way that the sign rocks, vibrates and shakes in the wind. 
   There is a need for a versatile LED lamp design for retrofitting conventional backlit commercial and street name signs that is easy to install and fits in a variety of sign sizes and configurations. There is also a need for a backlit sign design that minimizes size and weight, while maximizing even illumination. 
   SUMMARY OF THE INVENTION 
   The present invention solves the aforementioned problems by providing an LED lamp design and method for conveniently retrofitting conventional backlit signs. The present invention also provides a new or retrofitted sign design that minimize the sign size and weight, while maximizing its illumination. 
   The present invention is a sign that includes a housing having a top wall having a first length, a bottom wall having a second length, and a pair of opposing sidewalls each having a third length, wherein at least a portion of one of the sidewalls is translucent, and a first LED module mounted to the top wall and including a plurality of LEDs for producing light, wherein the first, second and third lengths are selected to maximize illumination of the sidewalls by the produced light, and to minimize a width and weight of the sign. 
   Other objects and features of the present invention will become apparent by a review of the specification, claims and appended figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a partially broken away side view of a conventional backlit street name sign. 
       FIG. 1B  is a side cross-section view of the conventional backlit street name sign taken along line  1 B- 1 B in  FIG. 1A . 
       FIG. 2A  is a partially broken away side view of a conventional backlit commercial sign. 
       FIG. 2B  is a side cross-section view of the conventional backlit commercial sign taken along line  2 B- 2 B in  FIG. 2A . 
       FIG. 3A  is a side view of the LED module of the present invention. 
       FIG. 3B  is an end cross-section view of the LED array of the present invention, taken along line  3 B- 3 B in  FIG. 3A . 
       FIG. 4  is a side view of the mounting mechanism of the present invention. 
       FIG. 5A  is a side view of a conventional backlit sign retrofitted with the LED modules of the present invention. 
       FIG. 5B  is an end cross-sectional view of a conventional backlit sign retrofitted with the LED modules of the present invention. 
       FIG. 6A  is an end cross-sectional view of the LED array of the present invention, with parallel mounting surfaces. 
       FIG. 6B  is an end cross-sectional view of a conventional backlit sign retrofitted with the LED array shown in  FIG. 6A . 
       FIG. 7A  is an end cross-sectional view of a conventional backlit sign retrofitted with an alternate embodiment of the LED module of the present invention. 
       FIG. 7B  is an end cross-sectional view of the alternate embodiment of the LED module of the present invention. 
       FIG. 8A  is an end cross-sectional view of a conventional backlit sign retrofitted with a plurality of the LED module shown in  FIG. 7B . 
       FIG. 8B  is a side cross-sectional view of a conventional backlit sign retrofitted with a plurality of the LED module shown in  FIG. 7B . 
       FIG. 9  is an end cross-sectional view of the backlit LED module sign of the present invention. 
       FIG. 10  is an end cross-sectional view of another alternate embodiment of the LED module of the present invention. 
       FIG. 11  is an end cross-sectional view of another embodiment of the backlit LED module sign of the present invention. 
       FIG. 12  is an end cross-sectional view of yet another embodiment of the backlit LED module sign of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is an LED module that mounts in conventional backlit commercial and street name signs. The LED module  10  is illustrated in  FIGS. 3A and 3B , and includes one or more LED arrays  12 , a pair of side support arms  14 , a pair of mounting mechanisms  16 , and a power supply  18 . 
   Each LED array  12  includes a support member  20  (which can act as a heat sink) having one or more mounting surfaces  22  on which a plurality of outward facing light emitting diodes (LEDs)  24  are mounted. If the LED module  10  is for use with a double sided sign (one having two opposing translucent plates), then the support member  20  preferably includes two mounting surfaces  22  on opposing sides of the support member  20 , as shown in  FIG. 3B . If the sign also has downwardly angled translucent plates (e.g. see  FIG. 1B , where plates are not parallel to each other), then the mounting surfaces  22  can be downwardly angled (as shown in  FIG. 3B , where surfaces  22  generally face in opposite directions but are not parallel to each other) so that LEDs  24  mounted thereon are directly facing the angled translucent plates (i.e. each mounting surface is parallel to the translucent plate it faces). The LEDs can be mounted on the mounting surfaces in any appropriate configuration, such as the linear configuration illustrated in  FIG. 3A  (i.e. a linear array of LEDs), where the LEDs provide a high output intensity and a wide viewing angle. 
   The support arms  14  are attached to and support the ends of the support members  20 , as shown in  FIG. 3A . Support arms  14  can be made of any rigid material, and preferably include electrical connections, wiring or conductive material or components to convey electrical power from the power supply  18  to the LEDs  24 . The size of the LED module  10 , as well as the number of LED arrays  12  and the number of LEDs  24  in each array, are selected to fit and properly illuminate the sign to be retrofitted. 
   The mounting mechanism  16  is best shown in  FIG. 4 , and includes a mounting member  28  either rigidly connected to or integrally formed as part of one of the support arms  14 , a pair of scissor arms  30 , a pair of adjustment screws  32 , and a tightening screw  34 . The scissor arms  30  are preferably S-shaped, and each includes an upper portion  30   a , a mid-portion  30   b , a lower mid portion  30   c , and a lower portion  30   d . The scissor arm mid portions  30   b  are rotatably connected together by a bolt  36  that extends through a vertical slot  38  formed in the mounting member  28 . For each scissor arm  30 , a bolt  40  extends from its lower mid-portion  30   c  and through a horizontal slot  42  formed in the mounting member  28 . Each of the adjustment screws  32  is threaded through the lower portion  30   d  of one of the scissor arms  30 , and terminates in an engagement surface  33 . In the preferred embodiment, each adjustment screw  32  includes an engagement block of material  44  conducive to forming a friction fit (e.g. compressible or course materials, etc), with the engagement surface  33  at the end of the engagement block  44 . The tightening screw  34  is threaded through one of the scissor arm upper portions  30   a , and is rotatably engaged with the other scissor arm upper portion  30   a . Each of the screws  32 / 34  includes a conventional adjustment end (Phillips, flat blade, Allen key, etc.) for rotation thereof, thus allowing the LED module  10  to be installed with no special tools (i.e. nothing more than just a screw driver or Allen key). 
   To retrofit a conventional backlit sign, its housing is opened and the fluorescent tube lamps therein are removed. The adjustment screws  32  of the LED module(s) to be inserted inside the sign are adjusted so that the engagement surfaces  33  for each pair of adjustment screws  32  are separated slightly less than the interior depth of the sign&#39;s housing at its base. After the LED module is placed inside the sign housing, each of the mounting mechanisms are operated by rotating its tightening screw  34  to separate the scissor arm upper portions  30   a  from each other, which also separates the lower portions  30   d  from each other as well, thus driving the engagement surfaces  33  away from each other and against the sign&#39;s sidewalls to form a secure friction fit therebetween. As the tightening screw  34  is adjusted, the bolts  36 / 40  slide in slots  38 / 42  to accommodate the movement of the scissor arms  30 , while minimizing the vertical movement of the mounting member  28  during installation. Bolts  36 / 40  secure the scissor arms to the mounting member  28 , to ensure support arm  14  cannot move relative to the sign&#39;s housing once installation is complete. The minimum sign depth compatible with the mounting mechanism is dictated mainly by the sizes of the mounting member  28  and scissor arms  30 , and the maximum sign depth compatible with the mounting mechanism  16  is dictated mainly by the length of the adjustment screws  32  (i.e. how far the engagement surfaces  33  can be separated). Thus, a single sized mounting mechanism  16  can be compatible with a very large range of sign depths. Shorter or longer adjustment screws  32  can be swapped in/out of scissor arms  30  to vary the range of compatible sign depths even further. 
   Once the LED module is affixed to the sign housing using the mounting mechanism, the power supply  18  is electrically connected to the sign&#39;s electrical supply. This can be done by hard wiring the power supply  18  to the sign&#39;s electrical supply wiring. If space is needed, the sign&#39;s conventional fluorescent tube lamp electrical connector  4  may be removed from the sign. Alternately, the power supply  18  can include a power cord that terminates in an electrical connector that is compatible with and connects to the electrical connector  4  already present in the sign, negating the need for any hardwiring. 
     FIGS. 5A and 5B  illustrate the LED module of the present invention mounted inside a conventional backlit sign. Two LED modules  10  are placed end to end inside the sign housing  1 , although any number and orientation of LED modules  10  can be used depending upon the sign&#39;s dimensions and lighting requirements. The pair of LED modules  10  can share a single power supply  18 , or each include a dedicated power supply  18  as shown in  FIG. 5A . Conventional street name signs typically have a height of about 18 inches, a depth of 6 to 12 inches (typically larger at the top of the sign), and a length of about 4 to 10 feet. Thus, the LED modules  10  of the present invention used to retrofit existing street name signs preferably have a length of 1 to 3 feet, and a height of about 15 inches. The number of LED modules  10  and their dimensions should be such that light from the LEDs brightly and evenly illuminates the entire face plate(s)  3 . 
     FIGS. 6A and 6B  illustrate the LED module of the present invention mounted inside a commercial double sided backlit sign, where the opposing face plates  3  are parallel to each other. In such a case, the LED array support members  20  each include two mounting surfaces  22  on opposing sides of the support member that are parallel to each other, so the LEDs  24  mounted thereon directly face the opposing translucent face plates  3 . Typical backlit commercial signs are 1 to 10 feet in height and length, and 4-12 inches in depth. 
     FIGS. 7A and 7B  illustrate an alternate embodiment of the LED module  10 , where the LEDs  24  are mounted to a base plate  46  (which can act as a heat sink), and an optical lens  48  is disposed over the LEDs  24 . This embodiment of LED module  10  is installed along one or more of the sign&#39;s interior housing walls, as shown in  FIG. 7A . The lens  48  disperses the light from the LEDs to evenly illuminate the sign&#39;s translucent face plate(s)  3 . Depending on the sign&#39;s size and illumination requirements, several LED modules of this type can be installed inside the sign housing, for example along two or more housing sides, as illustrated in  FIGS. 8A and 8B . This embodiment is ideal for signs that are subjected to excessive movement or vibrations, as it eliminates the need for long support arms extending from the periphery of the sign&#39;s housing. 
   There are numerous advantages of the present invention. The LED modules of the present invention can be easily and quickly installed into conventional backlit signs, often requiring nothing more than just a screw driver. A single LED module is compatible with a very wide range of sign depths. The installed LED modules will not become loose within the sign housing over time, even with sign movement or vibration. 
     FIG. 9  illustrates an alternate embodiment of a new or retrofitted sign, where the housing  50  has dimensions selected to minimize the sign size and weight, while maximizing its illumination. Specifically, the housing includes top and bottom walls  52 / 54 , and sidewalls (faceplates)  56 , where housing as an upper width A (i.e. top wall  52  has length A), a height B (i.e. sidewalls  56  have a length B), and a lower width C (i.e. bottom wall  54  has length C), selected to maximize the illumination of sidewalls  56 , while also minimizing size (mainly width) and weight. Ideally, a single LED module  10  is attached to the top wall  52  to illuminate the sign. For example, upper width A can vary between 1-12 inches, height B can vary between 12 and 120 inches, and lower width C can vary between 0 and 6 inches. 
     FIG. 10  illustrates an alternate embodiment of the LED module  10 , which includes a sidewall  58  extending up from the base plate and including a notch  60 . The lens  62  includes a flange  64  that engages with notch  60 . This configuration provides for easier manufacture, and possible replacement of lens  62 . 
     FIG. 11  illustrates an alternate embodiment of a new or retrofitted sign, where the top wall  52  includes two surfaces  52   a / 52   b  that are angled toward each other (not parallel) such that each surface  52   a / 52   b  faces toward one of the sidewalls  56  more than the other sidewall  56 . A pair of LED modules  10  are mounted on the top wall  52 , one on each of the surfaces  52   a / 52   b . Each LED module  10  is oriented to direct a majority of the light generated therefrom onto the opposing sidewall  56 .  FIG. 12  illustrates a further enhancement of even illumination, by using a mirror  66  mounted on bottom wall  54  to redirect light back toward the sidewalls  56 . 
   It is to be understood that the present invention is not limited to the embodiment(s) described above and illustrated herein, but encompasses any and all variations falling within the scope of the appended claims. For example, support member  20  could be two separate support members mounted back to back, or a composite structure that includes one or more PC boards mounted together or to a rigid material. Bolts  36 / 40  can be any rigid member (e.g. pins, rivets, etc.) that can slidably attach the scissor arms  30  to the mounting member  28  via slots  38 / 42 . Only some (or even none) of the scissor arm lower portions may include the adjustment screws  32 , in which case some (or even all) of the engagement surfaces may be on or attached to the scissor arm lower portions themselves (e.g. its outer side surface). Bolts  40  could extend from portions of scissor arms  30  above mid-portion  30   b  (and bolt  36 ), instead of below mid-portion  30   b  as shown in  FIG. 4 , if raising or lowering the height of the engagement surfaces relative to the mounting member  28  is not problematic. The power supply  18  could be incorporated inside the support member  20 , so that each LED array  12  has its own power supply  18 . The number of LED arrays  12  for each module  10 , and the number and orientation of modules  10  in each sign, can vary to meet the lighting requirements of the sign. Lastly, for the purposes of this disclosure, references to a translucent face plate (sidewall) includes face plates (sidewalls) having portions that transmit light, with or without any diffusion, with or without any color filtering, and with or without opaque portions that form designs or characters.