Patent Publication Number: US-8988635-B2

Title: Lighting system for transparent liquid crystal display

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Application No. 61/546,809, filed on Oct. 13, 2011 and incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments generally relate to a lighting system for a transparent liquid crystal display (LCD). 
     BACKGROUND OF THE ART 
     Display cases are used in a number of different retail establishments for illustrating the products that are available for sale. In some instances these display cases may be coolers or freezers which are placed in grocery stores, convenience stores, gas stations, restaurants, or other retail establishments. In other instances these display cases may be non-refrigerated transparent containers used in a jewelry or watch store, bakery, deli, antique shop, sporting goods store, electronics store, or other retail establishments. While the design and appearance of the product itself does provide some point-of-sale (POS) advertising, it has been found that additional advertising at the POS can increase the awareness of a product and in turn create additional sales. 
     Most retail establishments already contain some POS advertising, and depending on the type of establishment the proprietor may want to limit the amount of ‘clutter’ in the retail area—resulting in a very limited space for additional POS advertising. It has now become desirable to utilize the transparent glass that is typically placed in display cases with additional POS advertising. Most notably, it has been considered that transparent LCDs may be positioned along with the transparent glass and could display additional advertising materials while still allowing a patron to view the products inside the display case. 
     SUMMARY OF THE EXEMPLARY EMBODIMENTS 
     An exemplary embodiment provides mullion light assemblies adjacent to each vertical edge of the transparent LCD. Each mullion light assembly preferably contains a center channel which allows cooling air to pass through the channel. LED mounting substrates along with a plurality of LEDs are positioned along the length of the center channel sidewalls and are angled inwardly towards the rear of the display case. Preferably, the LEDs are in conductive thermal communication with the center channel sidewalls. In an exemplary embodiment, thermal fins are also placed in thermal communication with the center channel sidewalls. Electrical components, including the power modules for driving the LEDs may also be positioned within the mullions and may be placed in thermal communication with the center channel sidewalls and the optional thermal fins. 
     In an exemplary embodiment, an optional lens is positioned adjacent to the LEDs and is adapted to collimate the light exiting the LEDs and the lens. In further embodiments, each LED is positioned between a pair of vertical louvers so as to direct the light away from the LCD and towards the rear of the display case (or towards the goods within the display case). Alternatively, a flange may extend from the sidewall of the center channel and angle towards the rear of the case so as to direct the light away from the LCD and towards the rear of the display case (or towards the goods within the display case). 
     When used with a display case having a door, a sensor may be positioned so as to sense whether the door is open or closed. When open, the LEDs may be turned off so that a consumer is not exposed to high light levels. A temperature sensor may also be used to turn on/off the cooling fans when a maximum temperature has been reached. 
     The foregoing and other features and advantages of the present invention will be apparent from the following more detailed description of the particular embodiments, as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of an exemplary embodiment will be obtained from a reading of the following detailed description and the accompanying drawings wherein identical reference characters refer to identical parts and in which: 
         FIG. 1  is a perspective view of a pair of transparent LCDs for use within a display case. 
         FIG. 2  is a front elevation view of the display case from  FIG. 1  where the front glass and masking has been removed to show electrical components for operating the LCD and lighting assembly. 
         FIG. 3  is a top perspective view looking down the center mullion and showing an optional air flow embodiment. 
         FIG. 4  is a top perspective view of the center mullion where the fan has been removed. 
         FIG. 5  is a top perspective view of the center mullion showing the details of the mullion lighting assembly. 
         FIG. 6  is a perspective sectional view showing another optional air flow embodiment. 
         FIG. 7  is a top perspective view of another embodiment for the mullion lighting assembly. 
         FIG. 8  is a sectional view showing an exemplary embodiment of the optional lens and LEDs. 
         FIG. 9  is an optical ray trace of the LED and lens embodiment shown in  FIG. 8 . 
         FIG. 10  is a top plan view of a pair of opposing mullions, showing the approximate ray trace of the resulting light pattern. 
         FIG. 11  is an electrical schematic of an embodiment for operating the transparent LCD lighting system. 
         FIG. 12  is a flow chart for one embodiment of the software logic for operating the system shown in  FIG. 11 . 
         FIG. 13  is a flow chart for one embodiment of the software logic for operating the system shown in  FIG. 11 . 
         FIG. 14  is a perspective sectional view showing another optional air flow embodiment. 
         FIG. 15  is a detailed perspective sectional view showing detail A indicated in  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION 
     The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments of the invention are described herein with reference to illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIG. 1  is a perspective view of a pair of transparent LCDs for use within a display case. Protective glass  170  is preferably positioned in front of the LCDs and contains a masking portion  175  surrounding at least a portion of the perimeter of the protective glass  170 . It should be noted that only the front glass/LCD assemblies are shown in these figures, as the remaining details of the case are commonly known and do not depend upon the transparent LCDs and the exemplary lighting system. The embodiments of the lighting system described herein can be used with any number of display case designs, either temperature controlled or not, and with doors that open or glass that remains stationary. 
       FIG. 2  is a front elevation view of the front glass/LCD assemblies from  FIG. 1  where the front glass  170  and masking  175  has been removed to show electrical components  180  for operating the LCD  190  and lighting assembly. The electrical components  180  may include any or all of the following: timing and control board (TCON), video player, hard drive/storage, microprocessor/CPU, wireless receiver, cellular data receiver, and internet connectivity. At least some of the electrical components  180  are in electrical communication with the LCD  190 . Preferably, the power (for the LEDs and/or electrical components  180 ) and the video signals are supplied to the electrical components  180  through CAT 6 cabling. 
     Transparent LCD  190  has edge mullion  120  adjacent to a first side with center mullion  125  adjacent to the opposing side. Similarly, transparent LCD  191  has center mullion  125  adjacent to a first side with edge mullion  130  adjacent to the opposing side. Fans  100  are positioned adjacent to each of the mullions  120 ,  125 , and  130  and adapted to draw cooling air through the mullion. Although shown at the top of each mullion, fans  100  could also be placed at the bottom of the mullion or within the mullion. One or more fans could be used with each mullion. 
       FIG. 3  is a top perspective view looking down the center mullion  125  and showing an optional air flow embodiment. The center mullion  125  is comprised of a base mullion assembly  200  which is generally adjacent to the edge of the front glass/LCD assembly. A mullion lighting assembly  300  is preferably attached to the base mullion assembly  200 . In some embodiments, the base mullion assembly  200  is a common mullion assembly found in traditional display cases, such that the mullion lighting assembly  300  can be easily retrofit onto the existing base mullions found in cases that have already been built and possibly installed. 
     In this embodiment, fans  100  are positioned at the top and bottom of the mullion lighting assembly  300  so as to draw a path of cooling air through a center channel  310  running down the center of the mullion lighting assembly  300 . The fans  100  may draw cooling air from the top to the bottom or from the bottom to the top of the mullion lighting assembly  300 . Louvers  250  are positioned along the sides of the mullion lighting assembly  300  and are adapted to control the light emitted from the mullion lighting assembly  300 . 
       FIG. 4  is a top perspective view of the center mullion  125  where the fan  100  has been removed. The mullion lighting assembly  300  for the center mullion  125  generally contains a trapezoidal cross-section where a base portion contains a plurality of thermal fins  350  on the side facing the center channel  310  and setoff mounts  360  for electrical components  370  on the side opposing the center channel  310 . While this orientation is preferable, it is also contemplated to place the electrical components within the center channel  310  while placing the thermal fins  350  on the opposing side (or using no thermal fins  350  at all). 
     The legs of the trapezoidal mullion lighting assembly  300  are preferably angled relative to the base portion, and contain the LED assemblies  330 A and  330 B. As this LED assembly  300  is for the center mullion  125 , it contains a LED assembly  330 A (for the transparent LCD  191 ) and an opposing LED assembly  330 B (for the transparent LCD  190 ). For the edge mullions  120  and  130 , only one LED assembly is necessary, so they would not necessarily have the trapezoidal cross-section as shown here or the dual LED assemblies, although both could still be used. Preferably, the LED assemblies  330 A and  330 B are angled inwardly towards the center channel  310 . Although shown and described with a trapezoidal cross-section, a triangular cross-section is specifically contemplated as well and would be within the scope of the invention. 
     The LED assemblies  330 A and  330 B are preferably in conductive thermal communication with the sidewalls of the center channel  310 . In an exemplary embodiment, the LED assemblies  330 A and  330 B are also in conductive thermal communication with the thermal fins  350 . The louvers  250  are preferably positioned adjacent to the LED assemblies  330 A and  330 B. The electrical components  370  are preferably in conductive thermal communication with the sidewalls of the center channel  310 . In an exemplary embodiment, the electrical components  370  are also in conductive thermal communication with the thermal fins  350 . The electrical components  370  may include the power supplies for driving the LED assemblies  330 A and  330 B. The electrical components  370  may also include the power supplies for driving the transparent LCD and the electrical components  180 . 
       FIG. 5  is a top perspective view of the center mullion showing the details of the mullion lighting assembly  300 . An LED mounting substrate  337  contains a plurality of LEDs  336  and is positioned adjacent to the sidewalls of the center channel  310 . In some embodiments, the LED mounting substrate  337  is a PCB and in an exemplary embodiment the LED mounting substrate is a metal core PCB. Here, an optional lens  340  is positioned in front of the LED mounting substrate  337 . In this embodiment, the optional lens  340  contains a plurality of collimating elements  335 , where each collimating element  335  is centered above an LED  336 . 
     In this embodiment, the louvers  250  are positioned adjacent to the optional lens  340 , however, it should be noted that the louvers  250  are optional, as some embodiments may not require the louvers  250  if the lens  340  and the collimating elements  335  are properly designed. However, in this embodiment the louvers  250  are comprised of vertical louvers  225  and horizontal louvers  226  which are substantially perpendicular to the vertical louvers  225 . In some embodiments, only the vertical louvers  225  may be used. Here, a vertical louver  225  is positioned on each side of the LED  336  and collimating element  335  pair and arranged so as to direct the emitted light away from the LCD and towards the rear of the display case or towards the goods within the display case. In other words, each LED  336 /collimating element  336  is preferably positioned between a pair of vertical louvers  225  which prevents the majority of the emitted light from passing directly through the LCD (a phenomenon known as ‘headlighting’ which will be discussed further below.) The vertical louvers  225  are adapted to control the direction of the light in the horizontal plane. The horizontal louvers  226  may control the direction of the light in the vertical plane. 
     Also in this embodiment, the mullion lighting assembly  300  contains a tab  301  which overlaps an opposing tab on the base mullion  200 . Here, the mullion lighting assembly  300  can simply snap onto the base mullion  200 . Of course, many other variations for attaching the mullion lighting assembly  300  to the base mullion  200 , including but not limited to fasteners, clips, adhesive, or welding. 
     Although shown as a series of members which extend from the base of the mullion lighting assembly  300 , where the members are longest near the center of the channel  310  and become shorter as one moves from the center towards the lighting assemblies  330 A and  330 B, this orientation for the thermal fins  350  is not required. While this design provides an exemplary cooling performance, all that is required of the thermal fins  350  is to provide an increased surface area for the cooling air to extract heat from the thermal fins  350 . Preferably, the thermal fins  350  are comprised of a thermally conductive material. In an exemplary embodiment the thermal fins  350  would be metallic, preferably aluminum. 
       FIG. 6  is a perspective sectional view showing another optional air flow embodiment. In this embodiment, a dividing element  400  is positioned near the mid-point of the center channel  310 , dividing the center channel into a first portion with apertures  410  and a second portion with apertures  420 . A fan  100  is positioned at the exit of each portion. When the fan  100  is in operation, cooling air is drawn into the center channel  310  through apertures  410 / 420 , pulled through the center channel  310 , and exhausted at the exits near the fan  100 . Of course, the opposite flow would also be possible, where cooling air is drawn into the channel  310  at the fan  100  and then exhausted out of the apertures  410 / 420 . In this exemplary embodiment, a higher number of apertures are positioned near the dividing element  400  than near the fans  100 . The apertures  410 / 420  are preferably positioned near the top of the center channel  310  sidewalls. 
       FIG. 7  is a top perspective view of another embodiment for the mullion lighting assembly  500 . In this embodiment, the channel  310  contains a base portion having the thermal fins  350 , and side portions which angle inwardly towards the center of the channel  310 . The side portions contain the LED mounting substrate  337  with a plurality of LEDs  336 . This embodiment also contains the optional lens  340  where a collimating element  335  is positioned adjacent to each LED  336 . Notably in this embodiment, a flange  525  extends from the base portion of the mullion lighting assembly  500 , from an area adjacent to the bottom of LED mounting substrate  337 . The flange  525  angles towards the LEDs  336  as it extends away from the base portion. In other words, the flange  525  is positioned at an acute angle relative to the transparent LCD. 
       FIG. 8  is a sectional view showing an exemplary embodiment of the optional lens  340  and LEDs  336 . Each collimating element  335  is preferably positioned above the centerline of each LED  336 . Each collimating element  335  preferably contains a notch which is adjacent to each LED  336 . The notch may be defined as a top surface  347  which is substantially perpendicular to the center axis of the LED  336 , as well as at least two side surfaces  349  which are substantially perpendicular to the top surface  347 . Some embodiments of the optional lens  340  may contain four side surfaces  349  (as this view is a sectional view, these additional side surfaces are not shown). 
     This embodiment of the lens also includes a pair of angled reflecting surfaces  342  which begin near the LED mounting substrate and angle away from the center axis of the LED  336 . This embodiment of the lens also includes an arc  345  which is positioned above the LED  336  and is preferably centered about the central axis of the LED. In an exemplary embodiment, the angled reflecting surfaces  342  preferably operate via total internal reflection (TIR). Also in an exemplary embodiment, the surfaces  347 ,  349 , and  345  are preferably coated with an anti-reflective (AR) coating. 
       FIG. 9  is an optical ray trace of the LED and lens embodiment shown in  FIG. 8 . Ideally, the majority of the light which enters through the side surfaces  349  of the notch will reflect off surfaces  342  and exit the top surface of the lens. Also ideally, the majority of the light which enters the top surface  347  of the notch exits through the arc  345 . 
       FIG. 10  is a top plan view of a pair of opposing mullions, showing the approximate ray trace of the resulting light pattern from the embodiments described above. Here, either (1) the lens  340  only, (2) the vertical louvers  225  only, (3) the flange  525  only, (4) the vertical louvers  225  and the lens  340 , or (5) the flange  525  and the lens  340  direct the emitted light towards the rear of the case (away from the LCD/front glass assembly  810 ). The light rays  700  represent the resulting direction for the majority of the emitted light. The light ray  750  represents the maximum angle (θ 1 ) towards the LCD that the emitted light can poses without causes ‘headlighting.’ Here, light ray  815  indicates what would be known as headlighting, where a light ray exits the mullion lighting assembly and passes directly through the LCD/front glass  810  without reflecting off the interior of the display case or the goods within the display case. When headlighting occurs, an observer that is passing in front of the LCD may be able to observe the bright, point source of light from the LEDs. This is distracting to most observers and can be uncomfortable if very bright. Here, the angle (θ 2 ) at which the light ray  815  directly impacts the LCD is larger than the maximum angle (θ 1 ), such that headlighting occurs. It should be noted that while this phenomenon (as well as light ray  815 ) can be substantially eliminated by some of the embodiments described above, it is not a requirement of any embodiment of the invention to eliminate all headlighting. 
     In this particular embodiment, the front glass/LCD assembly  810  forms part of a door which can be opened/closed to provide access into the case by a consumer. A door sensor  800  is positioned such that an electrical signal can be generated which indicates whether the door is open or closed. 
       FIG. 11  is an electrical schematic of an embodiment for operating the transparent LCD lighting system. A microprocessor/CPU is placed in electrical communication with the door sensor and an optional temperature sensor. The microprocessor/CPU may comprise any one of the following: EPROM, EEPROM, microprocessor, RAM, CPU, or any form of software driver capable of reading electrical signals from the door sensor and optional temperature sensor and controlling the power sent to the LEDs and to the fans. The temperature sensor is preferably positioned somewhere within the mullion lighting assembly to determine temperatures either within the center channel  310 , at the LEDs  336 , or at the electrical components  370 . The microprocessor/CPU is also preferably in electrical communication with the fan power supply and LED power supply. 
       FIG. 12  is a flow chart for one embodiment of the software logic for operating the system shown in  FIG. 11 . To prevent the bright lights of the mullion lighting assemblies from impacting the sight of a consumer opening a display case, it may be desirable to turn off the LEDs when the door is opened. Also, to reduce the noise, it may be desirable to turn off the fans when the door is opened as well. For this method, the software continuously checks the door sensor to determine if the door has been opened. If not, power is sent to the LEDs and to the fan. Once the door is opened, no power is sent to the LEDs or the fan. The software would then return to check the door sensor to determine once it has closed. 
       FIG. 13  is a flow chart for one embodiment of the software logic for operating the system shown in  FIG. 11 . This embodiment provides an extension from the method shown in  FIG. 12  to account for a maximum temperature (Tmax) for the mullion lighting assembly. Again, when the door sensor determines that the door is open, no power is sent to the LEDs or fan. When the door sensor determines that the door is closed, the software moves to check the temperature sensor and compares the temperature measurement to Tmax. If the temperature is less than Tmax, then power is sent to the LEDs but not to the fan. If the temperature is greater than Tmax, then power is sent to the LEDs and to the fan. 
       FIG. 14  is a perspective sectional view showing another optional air flow embodiment. In this embodiment, a dividing element  400  is positioned near the mid-point of the center channel  310 , dividing the center channel into a first portion with apertures  410  and a second portion with apertures  420 . A fan  100  is positioned at the exit of each portion. When the fan  100  is in operation, cooling air is drawn into the center channel  310  through apertures  410 / 420 , pulled through the center channel  310 , and exhausted at the exits near the fan  100 . Of course, the opposite flow would also be possible, where cooling air is drawn into the channel  310  at the fan  100  and then exhausted out of the apertures  410 / 420 . In this exemplary embodiment, a higher number of apertures are positioned near the dividing element  400  than near the fans  100 . The apertures  410 / 420  are preferably positioned near the top of the center channel  310  sidewalls. 
     Notably in this embodiment, additional apertures are positioned on the sidewalls of the channel  310  which are adjacent to (and may be fastened to) the electrical components  370  so that an additional flow of cooling air can be used to cool the electrical components  370 . 
       FIG. 15  is a detailed perspective sectional view showing detail A indicated in  FIG. 14 . As shown, aperture  880  is positioned on the sidewall of the channel  310  to allow cooling air to flow along the electrical components  370 . Typically, the electrical components  370  contain printed circuit boards (PCBs)  881  and the embodiment shown allows cooling air to flow on both sides of the PCBs  881  (i.e. on the side facing the center channel  310  and on the side opposite the channel  310 ). Setoff mounts  360  may again be used to attach the PCBs  881  to the sidewalls of the channel  310  and preferably establish conductive thermal communication between the PCBs  881  and the sidewalls of the channel  310 . 
     Having shown and described a preferred embodiment of the invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention and still be within the scope of the claimed invention. Additionally, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims.