Abstract:
A power and communication system is provided for a product information display system associated with a product display or storage establishment having multiple product display or storage areas. A plurality of electronic display tags are mounted adjacent the product display or storage areas. An electrical power system supplies a/c. power to the display tags. A main power distribution loop is connected to the power supply and is magnetically coupled to multiple branch power distribution loops which extend along selected groups of display tags for supplying power to those display tags.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 08/116,468 filed Sep. 3, 1993 now U.S. Pat. No. 5,537,126. 
    
    
     This applicatin is a continuation of application Ser. No. 08/309,934 filed Sep. 21, 1994 now abandoned. 
     1. Field of the Invention 
     This invention relates generally to electronic display tag systems for use in product display or storage establishments and, more particularly, to a power and control signal distribution arrangement for such display tag systems. 
     2. Background of the Invention 
     Both wired and wireless electronic shelf tag systems have been proposed heretofore, as in U.S. Pat. Nos. 5,198,644; 5,172,314; 5,111,196; 5,019,811; 4,937,586; 4,821,291; 4,603,495; 4,525,713; 4,521,677; and 4,500,880. The wired systems have the advantage of not requiring batteries or photovoltaic power sources in the tags. A disadvantage of the wired systems, however, is the need to install thousands of feet of wire. A typical grocery store may use 20,000 tags, and a wired tag system typically uses an average of three feet of wire per tag. Thus a total of 60,000 feet of wire may be required in a single store. 
     In addition to the installation problem, wired systems require numerous connections between the wires and the display tags, between the wires on the shelves and wires on the gondolas on which the shelves are usually mounted, and between the wires on adjacent gondolas. These numerous connections complicate the re-location of gondolas, or the re-location of shelves within a gondola. In addition, the contacts used to make the connections must either be made of expensive corrosion-resistant material, such as gold-plated contacts, or else replaced from time to time as corrosion occurs. 
     Another problem with wired display tag systems is electrostatic discharge, which can occur if a shopper gets too close to an inadequately protected wire or connector contact. Such discharges can damage the expensive electronic equipment included in the tag system, and can cause even greater losses by shutting down the display system. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide an improved electronic display tag wiring system which avoids the need for electrical contacts in the numerous connections among the various components of the system. A related object is to provide an improved electronic display tag system which does not require batteries or photovoltaic sources in the tags. 
     It is another important object of this invention to provide such an improved electronic display tag wiring system which facilitates the installation of the thousands of feet of wire required in such a system. In this connection, a related object of the invention is to provide such an improved system which also facilitates relocation of gondolas or of the shelves within a gondola. 
     A further object of this invention is to provide an improved electronic display tag wiring system which significantly reduces the cost of installing and maintaining the system. 
     Yet another object of this invention is to provide such an improved electronic display tag wiring system which virtually eliminates any risk of losses due to electrostatic discharges. 
     A still further object of this invention is to provide an improved electronic display tag wiring system which greatly reduces the need for periodic replacement of corroded parts. 
     In accordance with the present invention, the foregoing objectives are realized by providing a power and communication system for electronic display tags which includes a plurality of such tags mounted adjacent to the multiple product display or storage areas, an electrical power supply for supplying a-c. power to the display tags, a source of control signals for the display tags, multiple branch distribution loops each of which extends along a selected group of the display tags for supplying power and control signals to the display tags, and a main distribution loop connected to the power supply and control signal source and magnetically coupled to the branch loops for supplying power and control signals to the branch loops. 
     In a preferred embodiment of the invention, the branch distribution loops, at least portions of the main distribution loop, and magnetic cores for forming the magnetic couplings are all prefabricated as modular units which can be easily and quickly installed and assembled on site in the product display or storage establishment, and which can also be easily disconnected and re-connected whenever it is desired to rearrange any portion of the display or storage system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of a typical layout of part of a retail store equipped with a product information display system embodying the present invention; 
     FIG. 2 is an enlarged view of a portion of FIG. 1; 
     FIG. 3 is an enlarged section taken generally along line  3 — 3  in FIG. 2; 
     FIG. 4 is an enlarged plan view of the end portion of the module mounted on the top of one of the gondolas illustrated in FIGS. 1 and 2; 
     FIG. 5 is an enlarged end elevation of one of the gondolas illustrated in FIGS. 1 and 2; 
     FIG. 6 is an enlarged side elevation of one of the two vertical wiring modules included in each gondola, as illustrated in FIG. 5; 
     FIG. 7 is a section taken generally along line  7 — 7  in FIG. 6; 
     FIG. 8 is a section taken generally along line  8 — 8  in FIG. 6; 
     FIG. 9 is a further enlarged end elevation of the top portion of the gondola illustrated in FIG. 5, with the end wall of the gondola broken away to show the internal structure; 
     FIG. 9 a  is a schematic illustration of a portion of the main distribution loop in the system of FIGS. 1-8; 
     FIG. 10 is an enlarged and exploded view of the junction box mounted on the top of the end portion of the gondola illustrated in FIG. 9; 
     FIG. 11 is a side elevation of the exploded junction box of FIG. 10; 
     FIG. 12 is a diagrammatic exploded side elevation of the various wiring and coupling modules included in the power and communication system illustrated in FIGS. 1 and 2; 
     FIG. 13 is an enlarged vertical section through one of the shelf rails in the system of FIGS. 1 and 2; 
     FIG. 14 is a side elevation of the rail of FIG. 13 with the wiring installed thereon; 
     FIG. 15 is a vertical section through one of the shelves in the system of FIGS. 1 and 2, and illustrating the electrical wiring arrangement at the rear of the shelf; 
     FIG. 16 is an enlarged side elevation of one of the wiring elements illustrated in FIG. 15; 
     FIG. 17 is an end elevation of the wiring element of FIG. 16; 
     FIG. 18 is an enlarged end elevation of one of the shelves in the system of FIG. 1.; 
     FIG. 19 is an exploded perspective view of one of the magnetic core units used to form the magnetic coupling between the wiring on one of the shelves and one of the vertical wiring modules; 
     FIG. 20 is a top plan view of the magnetic core module illustrated in FIG. 19; 
     FIG. 21 is a side plan view of the module illustrated in FIG. 20; and 
     FIG. 22 is an end elevation of the module of FIGS. 20 and 21, after the module has been closed around the two pairs of connectors that complete a magnetic coupling. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     Turning now to the drawings, FIG. 1 depicts part of a retail store including a product information display system arranged according to a preferred embodiment of the present invention. The system includes a plurality of display tags  10  disposed along the front rails  11  of the store&#39;s multiple display shelves  12 . The prices, descriptions and/or special information for all the products are displayed on the front edges of the shelves  12 , near the respective products. Typically, there is a one-to-one correspondence between each display tag  10  and a particular item of merchandise. Although certain applications may require a display tag  10  to display product-related information regarding multiple products, e.g., the respective products above and below the display tag  10 , preferably each display tag  10  displays information for only one product. 
     The information to be displayed at each display tag  10  is provided by a system controller  13 . The system controller  13  communicates with the display tags  10  through a gondola-mounted area controller  14  which services a large number of display tags  10  in a prescribed area. Each area controller  14  is contained in an enclosed housing which is mounted on one of the gondolas  15  on which the shelves are mounted. The system controller  13  regularly communicates with the display tags  10  for monitoring and reporting display tag failures to the system user and for identifying service inquiries and updating the display information, e.g., with price changes. 
     Each area controller  14  supplies both power and control signals to its display tags via a single main distribution loop and numerous branch distribution loops. The area controller  14  also monitors the display tags and receives signals generated by the tags, such as service requests and acknowledgement signals. A single area controller can usually service at least 1000 display tags. Although the gondolas  15  in FIGS. 1 and 2 are illustrated with only three shelves on each side, a gondola typically has about twelve shelves (six on each side), with an average of about six tags per shelf, or 72 tags per gondola. Thus, a single area controller can service  12  to  15  gondolas. 
     The main distribution loop connected to each area controller  14  is formed by a series arrangement of two standard modules  22  and  23  (see FIG.  12 ). The first module  22  will be referred to herein as the “transfer module,” and is simply a pair of parallel wires  24  and  25  encased in a dielectric strip  26  that can be easily attached to the top of a gondola  15 . The dielectric surrounding each wire preferably has a thickness of about 0.015 to 0.020 inch to protect the system from electrostatic discharges. If desired, the flat side of the strip  26  may be coated with an adhesive  26   a , protected until installation by a releasable backing, to facilitate application of the strip to the gondola. The dielectric strip  26  containing the two wires  24 ,  25  can be manufactured in large quantities at a low cost by a conventional extrusion process. The distance between the wires  24 ,  25  is preferably minimized to reduce inductance. For example, when the wire is 18 AWG multi-strand wire, the center-to-center spacing of the wires may be 0.125 inch. As illustrated in FIG. 4, the mounting strip  26  is removed from a 2 to 3-inch length of both wires at both ends, and a quick connect  27  is crimped onto each exposed wire end. 
     The second module  23  used to form the main distribution loop will be referred to herein as the “coupling module,” and extends vertically along one end of each side of the gondola. Each coupling module  23  is a pair of parallel conductors  30  and  31  joined at the lower end to form a U-shaped segment of the main distribution loop. A single module  23  is used to distribute power and control signals to all the shelves on one side of a gondola. As in the case of the transfer module  22 , the conductors  30 ,  31  in the coupling module  23  are encased in a dielectric strip  32  which covers the outside surface of each conductor  30 ,  31  with a dielectric thickness of at least 0.015 to 0.020 inch to protect the system from electrostatic discharges. 
     To facilitate installation of the coupling module  23  in the 0.25-inch gap that normally exists behind the shelves on a gondola (see FIG.  5 ), the conductors  30 ,  31  are preferably in the form of thin flat strips of copper, e.g., 0.110 inch by 0.018 inch. These strips are contained in channels of a dielectric strip  32  having a total thickness of 0.0446 inch, and are held in place by a thin insulating plastic sheet  33  (FIG. 7) that is thermally bonded to the dielectric strip  32 . A conductive cross bar  34  connects the two conductors  30 ,  31  at the lower end of the strip  32 . At the upper end, the two conductors terminate in a configuration that mates with the quick connects  27  on the ends of the transfer module  22 , so that the two modules  22  and  23  can be easily and quickly snapped together. 
     In order to facilitate coupling of the conductors  30  and  31  to the branch distribution loops on the shelf rails, rectangular holes  35  are formed in the central web of the dielectric strip  32 , at regular intervals along the length of the strip. As will be described in detail below, these holes  35  are used to receive a snap-on magnetic core module that couples the main and branch distribution loops. The center-to-center spacing of the holes  35  along the length of the strip is preferably the same as that of the shelf-mounting holes  36  in the shelf-support column  37  on the gondola (FIG.  9 ), so that a hole  35  will always be located close to the rear edge of a shelf, regardless of where the shelf is mounted on the gondola. The coupling modules  23  may be prefabricated in different lengths to match the dimensions of gondolas of varying heights. 
     To facilitate alignment of the transfer and coupling modules  22  and  23  at the top of each gondola, and to enclose the connections between these two modules, the junction box  40  shown in FIGS. 9-12 is preferably used. This junction box  42  also aligns the holes  35  in the coupling module  23  with the shelf-mounting holes  36  in the gondola. This junction box  40  is formed in two parts  41  and  42 , joined by a series of snap locks formed by depending clips  43  on the upper part  41  and mating holes  44  in the lower part  42 . The upper ends of the coupling modules  23  are aligned by a pair of plugs  45  which fit through a corresponding pair of holes  46  in a pair of opposed vertical walls  47  and  48  of the junction box. The prongs on the inner ends of the plugs  45  fit into corresponding holes  49  (FIG. 10) near the upper ends of the coupling modules  23 , thereby fixing the positions of the upper ends of the coupling modules both horizontally and vertically. 
     The transfer module  22  on the top of the gondola is registered in a pair of notches  50  formed in the lower ends of a pair of guide legs  51  depending from opposite sides of the upper part  41  of the junction box. This registration ensures that the quick connects  27  on the end of the transfer module  22  will be conveniently located with respect to the upper ends of the conductors  30  and  31  in the coupling module  23 . 
     To position the junction box  40  itself, the lower part  42  has a depending alignment leg  52  which fits into the interior of the shelf-support column  37  of the gondola. The open top of this steel column  37  is normally closed with a plastic cap, which can be simply removed and replaced with the lower part  42  of the junction box. Thus the junction box  40  will always be precisely positioned with respect to the ends of the gondola shelves, whose positions are fixed by the steel column  37 . 
     Each shelf  12  has its own branch distribution loop, mounted on the rear side of an extruded plastic rail  60  that snaps onto the front of a standard shelf. FIGS. 13 and 14 illustrate a preferred arrangement for mounting the display tags  10  on a conventional shelf  12  which includes a depending rail  61  (FIG. 18) formed as an integral part of the shelf. The auxiliary rail  60  is snapped into the shelf rail  61  and extends continuously along the full length of a shelf  12  for receiving both the display tags  10  and the branch loop. 
     The auxiliary rail  60  is designed so that the display tags  10  and a conductor  62  that forms the branch loop may be snapped into place on the rail. The insulated conductor  62  is mounted in two channels  63  and  64  formed near the top and bottom of the rear wall of the rail  60 . The tags  10  are received in a channel  65  formed in the front side of the rail  60 . The tags are recessed inside, and held in place by, a pair of flanges  66  and  67  so that the tags do not protrude from the rail. A curved rib  65   a  extends across a major portion of the space behind the upper flange  66  so as to form a spring element that can be deflected by pressing a tag upwardly behind the flange  66 ; the rib  65   a  then exerts a biasing pressure on the inserted tag to hold it in place on the rail  60 . A hollow core  68  on the rear side of the rail  60  snaps into the open recess formed on the front of a standard shelf rail  61  to hold the rail  60  in place on the shelf rail  61 . 
     When a display tag  10  is attached to the rail  60 , a pick-up coil on the tag is in close proximity to the two parallel runs of the conductor  62  on the rear side of the rail  60 . Thus, the pick-up coil is electromagnetically coupled to both segments of the conductor  62 . The conductor  62  is snapped into the top channel  63  of the rail  60 , spans the length of the store shelf  12 , and then loops to the bottom channel  64  of the rail  60  and spans the length of the shelf rail again. Alternate phasing of vertically adjacent shelves minimizes cross talk between adjacent conductors along the shelves and avoids any significant radiation of signals from the entire system or susceptibility from other sources. 
     At the rail end adjacent the vertical coupling module  23 , the conductor  62  is extended to form a U-shaped segment  70  that can be magnetically coupled to the module  23 . As can be seen in FIGS. 14-17, the portion of the U-shaped extension  70  adjacent the end of the rail  60  is simply a side-by-side extension of the two runs of wire  62  mounted on the rail. This portion of the extension  70  is long enough to traverse the underside of the shelf, from the front edge to the rear edge, and may be provided with an adhesive coating on one side to facilitate attachment thereof to the underside of a shelf. At the lower end of the rear edge of the shelf, the two ends of the wire  62  are joined to two legs of a U-shaped flat conductor  71  enclosed in a thin, flat dielectric case  72 . This flat conductor  71  is similar to the flat copper conductors  30 ,  31  in the coupling module  23 , and the closed end portion  73  of the encased U-shaped conductor  71  has exactly the same width and thickness as the coupling module  23 . It also has a rectangular hole  74 , between the legs of the U, of exactly the same dimensions as the holes  35  in the coupling module  23 . Accordion folds  75  are preferably formed near the open end of the U to permit the length of the U to be varied slightly to accommodate small variations in the distance between the rear edge of the shelf and the nearest hole  35  in the coupling module  23 . 
     To form a magnetic coupling between the branch and main distribution loops, the flat U-shaped portion  71  of the branch loop extension  70  is placed flat against the coupling module  23  with the rectangular holes  74 ,  35  in the two flat elements in exact register with each other. A two-piece magnetic core  80  is then clamped against opposite sides of the two flat elements, and fastened together by a hinged dielectric casing  81  attached to the two parts of the core. One part of the magnetic core  80  is an E-shaped piece  82  in which the middle arm  83  of the E is dimensioned to fit into and extend through the registered rectangular holes in the two flat elements  73  and  23 . The other two arms  84  and  85  of the E extend along the outside edges of the two flat elements. 
     The second part of the magnetic core  80  is a straight piece  86  which closes the open side of the E when the two pieces  82  and  86  are brought together. The resulting core completely surrounds the two conductors in both flat elements  73  and  23 , as can be seen in FIG. 22, and also fills the common central opening formed by the registered holes  74 ,  35  between the two pairs of conductors. Thus, current flow in either loop  70  or  23  will induce a corresponding current flow in the other loop through the magnetic coupling. The energy transfer through the magnetic coupling is highly efficient, e.g., as high as 95%. 
     To hold the two pieces of the magnetic core together, with the two flat elements  73  and  23  sandwiched between the core pieces  82  and  86 , the hinged dielectric case  81  for the core pieces includes a latch that snaps closed as the two core pieces are brought into engagement with each other. Specifically, a channel  87  with an inturned lip  88  formed on one free end of the housing flexes outwardly as it is forced past an angled lip  89  on the other free end of the housing. When the edges of the two lips  88  and  89  clear each other, the outer lip  88  snaps into the groove formed by the inner angled lip  89 . This snap-action latch enables an installer to quickly and easily assemble the magnetic couplings that join the numerous branch loops to the various coupling modules  23  in the main loop. If the shelves are re-arranged at a later time, the core module can be easily unlatched, re-located, and re-latched. The two core pieces  82  and  86  are preferably pre-attached to their hinged case  81  by adhesive bonding so that the two core pieces and their case can be handled as a single part during assembly and dis-assembly of the magnetic coupling. 
     The modular construction of this invention permits large display tag systems to be assembled from only a few different types of prefabricated modules. The principal modules are the transfer module and the coupling module that make up the main distribution loop, the rail module that includes a branch distribution loop, and the magnetic core module. The junction box is not part of the electrical system but is another repetitive module that facilitates assembly of the electrical modules. Mass production of this relatively small number of modules reduces the overall cost of the display tag system, and significantly shortens the time required for installation. Moreover, the resulting system is highly reliable and relatively maintenance-free because of the small number of electrical contacts subject to corrosion. The system is also largely immune from damage from electrostatic discharges because all vulnerable portions of the system are enclosed in protective casings. Finally, this system provides virtually unlimited flexibility for the owner to re-locate any desired section of the display or storage facility with only minimal additional work to disconnect and re-connect the display system.