Abstract:
A removable spindle for use in a thermal transfer printer houses dual RFID reader antennas that are used to read an RFID tag attached to the core of the print media. The information provided by the RFID tag enables the printer to self-calibrate based on the type of media loaded. The antenna design eliminates “null” areas at which the tag cannot be read, and enables the tag to be read around and across the entire length of the printer spindle. The design also allows the media holder to be easily removed from the printer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Not applicable. 
       FIELD OF THE INVENTION 
       [0002]    The field of the present invention is printer systems, and more particularly antenna systems for use in a auto-configurable printer. 
       BACKGROUND 
       [0003]    The set up and calibration of thermal transfer printers can be both cumbersome and expensive. In most thermal transfer printers, full calibration requires feeding several feet of label stock and ribbon material. This calibration process must be performed each time a different type of media is loaded into the printer. The set up and calibration process can be avoided if the printer can discern what type of media is loaded. 
         [0004]    To simplify printer set-up, various methods have been used to identify the media loaded into a thermal transfer printer, including touch cell memory components and barcodes. In these applications, a code or memory component including media identification data is coupled to the media provided in the printer. The data is read when the media is positioned in the printer, and the printer is configured for the appropriate media. 
         [0005]    One method that is particularly well-suited for identifying media in a thermal transfer printer is radiofrequency identification or RFID technology. Unlike barcode or touch cell memory applications, RFID does not require either a line of sight or a direct connection to the identifying code or memory component to acquire data about the media loaded into the printer. 
         [0006]    Antenna systems used in these types of printers for reading the data from the RFID tags, however, typically comprise a single horizontal coil or loop antenna housed in the media spindle of the printer. When the RFID transponder travels around the circumference of such an antenna, there are null areas at which the RFID reader cannot download information from the RFID transponder associated with the tag. These null areas occur when the RFID tags are perpendicular to the plane of the antenna, and, although the width of the null areas can be varied, they can never be eliminated. These nulls create problems if the printer attempts to gather information from the RFID transponder while the transponder is located in a null. This problem is particularly troublesome when the media is initially loaded into the printer, and when it is important to verify the type of media inserted into the printer. 
         [0007]    The present invention addresses these problems. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect, the present invention provides an antenna system for use in a printer system. In this antenna configuration, two coil or loop antennas are located in a media spindle of a printer. A controller in the printer switches the RFID reader between two antennas when it fails to receive a signal from the antenna that is being polled. When the RFID transponder is located in a null area for one antenna, for example, the reader will switch to the opposing antenna, which will be in an optimum orientation relative to the transponder. Whenever the RFID transponder is located in a null of one reader antenna, the opposing antenna will always be in an optimum orientation. The control system therefore compensates for nulls and allows the reader to successfully download information from and upload information to the transponder in any position along or around the circumference of the printer media spindle. 
         [0009]    The antenna system of the present invention, moreover, is easily positioned in and removed from the printer. In one embodiment, the media spindle utilizes spring-loaded contact pins which are mounted on printed circuit boards coupled to the antennas in the antenna system. These circuit boards are connected to the antenna circuit boards via coaxial cable, and the resulting antenna assembly is located within the media holder housing. 
         [0010]    When the media holder assembly is installed into the printer housing, the spring pins or contacts can make electrical connection with corresponding round, flat button contacts in the receptacle for the media holder in the printer housing, with the loading of the springs inside the media holder contact pins providing consistent electrical contact. To ensure long life for the spring contact pins, and to prevent forces acting on the pins in directions other than that of spring actuation, the media holder housing is designed to fit very closely into the receptacles in the printer housing. The close fit prevents lateral movement of the contact pins along the surface of the contact buttons. Furthermore, the spring contact pins are located below flush in the media holder housing. Therefore, when the media holder is not installed into the printer, the pins are protected from damage by the media holder housing. 
         [0011]    In another aspect of the invention, a printer is provided with an RF transceiver and an antenna assembly sized and dimensioned to be received in the interior of a core of a roll of media including at least one RFID tag. The antenna assembly comprises a first antenna and a second antenna, and the first antenna is positioned with respect to the second antenna to allow the RF transceiver to acquire data from the RFID tag from the other of the first and second antennas when a selected one of the first and second antennas is in a null area for data communications from the RFID tag. A controller is connected to the RF transceiver, and is programmed to switch between the first and second antennas to avoid the null area. 
         [0012]    In yet another aspect of the invention, a printer includes a housing, a printer circuit, and a removable spindle. The housing includes a receptacle, and the printer circuit is positioned in the housing, and includes an RF transceiver coupled to the receptacle through a switch. The removable spindle includes an antenna assembly comprising a first and a second antenna to provide a communication link to the RF transceiver, and an antenna connector that is receivable in the receptacle for connection to the printer circuit. The printer circuit further includes a controller for selectively coupling the RF transceiver to one of the first and second antennas to allow the printer circuit to communicate to an RFID tag on a roll of media provided on the removable spindle. 
         [0013]    In still another aspect of the invention, a spindle for retaining a roll of media in a printer is provided. The spindle includes a first and a second planar antenna, in which the second planar antenna is positioned with respect to the first planar antenna to provide communications to an RF transceiver in the printer when the first planar antenna is in a null area. 
         [0014]    These and other aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of a printer constructed in accordance with the present invention; 
           [0016]      FIG. 2  is an exploded view of the printer housing base of the printer of  FIG. 1  and an associated media holder assembly; 
           [0017]      FIG. 3  is an exploded view of the media holder assembly of  FIG. 2 , illustrating a media base and antenna assembly; 
           [0018]      FIG. 4  is a perspective view of the antenna assembly of  FIG. 3 ; 
           [0019]      FIG. 5  is a bottom view of the media base of  FIG. 3 , illustrating a plug for coupling the media assembly to the printer housing; 
           [0020]      FIG. 6  is a partial view of the printer housing base of  FIG. 2 , illustrating a receptacle for mating with the plug of  FIG. 5 ; 
           [0021]      FIG. 7  is a cutaway side view of the plug of  FIG. 5  as received in the receptacle of  FIG. 6 ; 
           [0022]      FIG. 8  is a cutaway view of a roll of media receiving an antenna assembly; 
           [0023]      FIG. 9  is a block diagram of a control system for a printer constructed in accordance with the invention; 
           [0024]      FIG. 10  is a top view of a printed circuit board illustrating the traces that form each of the loop media antennas; and 
           [0025]      FIG. 11  is a top view of a printed circuit board illustrating traces that form a ribbon antenna that can be used in the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Referring now to the figures and more particularly to  FIG. 1 , a printer  10  including a printer housing  11  having a printer housing base  12  is shown. Referring now also to  FIG. 2 , the printer housing base  12  is sized and dimensioned to receive a print head (not shown) and associated circuitry for printing information, such as text, on a media provided in a media holder assembly  14 . 
         [0027]    Referring still to  FIG. 2 , the printer housing base  12  includes media holder receptacles  32  which are formed as depressions in on opposing sides of the printer housing base  12 , and which are sized and dimensioned to receive a media holder plug  27  provided in the media holder assembly  14 . The interconnection between the plug  27  and receptacle  32  provides an electrical connection between the media holder assembly  14  and printer housing  12  as described more fully below. 
         [0028]    Referring now to  FIG. 3 , an exploded view of the media holder assembly  14  is shown. The media holder assembly  14  includes a media holder base  30 , which includes media holder plugs  27  extending from opposing sides. The media holder base  30  is sized and dimensioned to receive an antenna assembly  22  which, referring now also to  FIG. 4 , includes a first antenna  21  and a second antenna  23  which, as shown here, can be substantially planar in construction. Referring now also to  FIG. 10 , each of the antennas  21  and  23  is preferably constructed on a printed circuit board that includes a trace  52  that extends around the perimeter of the printed circuit board, forming a loop. As shown, the antennas  21  and  23  are substantially orthogonal to one another, that is, the antennas are positioned substantially 90 degrees apart. However, the antenna assembly  22  can include two or more antennas that are positioned with respect to one another to allow the antennas to be electrically switched to compensate for nulls encountered by any one of the antennas in the antenna assembly  22 , as described below. The antennas, therefore, can be varied in number and provided at different angles, depending on the width of the null area, and other factors. 
         [0029]    Referring still to  FIGS. 3 and 10 , each of the antennas  21  and  23  further includes a printed circuit board  24  mounted to the antenna printed circuit board, and that includes contact pins  26  that are connected to the loop  52  of the corresponding antenna  21  or  23 . A coaxial cable  28  connects the antenna printed circuit board  21  or  23  to the contact pins  26 . The contact pins  26  are preferably spring-loaded contacts, which provide a good electrical connection to receptacle  32 , as discussed below. Although pins are described here, the antenna connector can also be sockets or other types of connectors. 
         [0030]    Referring now to  FIG. 5 , the media holder plugs  27  formed in the media holder base  30  include depressions provided in a bottom surface of the plugs  27 . The depressions  27  are sized and dimensioned to receive the contact pins  26 . As received in the plug  27 , the contact pins  26  rest in the depression  29  formed in the bottom surface of the plug  27 , and do not protrude from the media holder  14 . The depression  29  therefore protects the contact pins  26  from being bent in directions other than that of spring actuation, preventing bending, tearing, shearing, or other damage to the contact pins  26 . 
         [0031]    Referring now also to  FIG. 6 , as discussed above, the printer housing  12  includes a media holder receptacle  32  that houses electrical connectors for interconnection with the plug  27 . As shown here, the connectors can be button contacts  34 , which are round and flat and therefore provide a consistent electrical connection between the contact pins  26  and the button contacts  34 , particularly where the contact pins  26  are spring-loaded contacts. Depending on the construction of the contact pins  26 , however, various types of connectors can be provided in the receptacle  32 , including pins, sockets, or other connectors. Furthermore, the orientation of the plug  27  and receptacle  32  can be reversed, and various other modifications made to the interconnection between the media holder base  30  and housing  12 . 
         [0032]    Referring now also to  FIG. 7 , a cutaway view of the media holder  14  as received in the printer housing  12  is shown, illustrating particularly the interconnection between the receptacle  32  and plug  27 . As shown here, the plug  27  is received in the receptacle  32  in a tight, interference fit. When the plug  27  is inserted into the receptacle  32 , the contacts pins  26  are aligned with and rest on the button contacts or pads  34 . As described above, the contact pins  26  are preferably spring loaded and therefore provides a good electrical connection to the button contacts or pads  34 . The contact pins  26  are connected directly to the spring contact PC board  24  which, as described above, is connected to an antenna  21  or  23 . A coaxial cable  36  connects the button contacts  34  to internal printer circuitry, described below with reference to  FIG. 9 . 
         [0033]    Referring now to  FIG. 9 , a block diagram of a printer circuit for use in a printer employing the present invention is shown. The printer includes a printer control circuit  40  which, as described above, can control communications between RFID tags as provided on a roll of media and on a ribbon inserted into the printer. The printer control circuit  40  includes a microprocessor  42  or other controller element, an RF transceiver  44  for communicating with RFID tags and transponders, and one or more RF switches  46  and  48 , for switching between antennas. The printer control circuit  40  can also control a print head (not shown) to drive the print head to print on the printer media, although a separate circuit can also be provided for this function. 
         [0034]    Referring still to  FIG. 9 , in operation, the control circuit  40  is programmed to select between antennas  21  and  23  through RF switch  48  based on whether data can be received from the selected antenna. The output of the media antenna is fed through switch  48  to an RF transceiver  44  which provides information acquired from the RFID tags or transponders associated with the media antennas  21  and  23  to the microprocessor  42 . Referring now to  FIG. 8 , the cutaway side view of the media roll as positioned on the antenna assembly  22  is shown. To provide data to the printer, an RFID transponder  18  is coupled to the interior of a media core  16  associated with the media. The transponder  18  includes a memory component which stores data indicating the type of media that is provided on the core  16 . This information can include, for example label material type, height and width of printable area, label color, correlating acceptable ribbons, etc. 
         [0035]    Referring again to  FIG. 9 , optionally, a second antenna  50  can be provided to read from and write to an RFID tag or transponder associated with the ribbon inserted into the printer prior to a printing process. The ribbon antenna  50  is connected to the microprocessor  42  selectively through the RF switch  46  which, as shown, is also controlled by the microprocessor  42  to select input from one of the media antennas  21  or  23  or the ribbon antenna  50 . Referring now also to  FIG. 11 , the ribbon antenna  50  is provided on a circuit board, which includes a trace  54  in the form of a loop or coil. 
         [0036]    Referring now to  FIG. 8 , in operation, a roll of printer media  17  is positioned on the media holder assembly  14 . The roll of media  17  includes a media core  16  to which an RFID tag or transponder  18  is coupled. The RFID transponder  18  stores data about the type of media that is being positioned in the printer  10 . The roll of media  17  is positioned over the spindle or antenna assembly  22 , such that the antennas  21  and  23  are substantially centered in the media core  16 . When the media  17  is properly positioned, the media holder assembly  14  is plugged into the receptacles  32  in the printer housing  12 , providing a connection between the contact pins  26  and contact buttons  34 , as shown in  FIG. 7 . 
         [0037]    Referring again to  FIG. 8  and also to  FIG. 9 , null areas, where a corresponding antenna cannot access an RFID tag  18 , are located directly above the wires or traces that form the coil antennas  21  and  23  on the printed circuit boards that form antennas  21  and  23 , and can prevent the printer circuit  40  from reading the data from the RFID transponder  18  when the transponder  18  is located at a null, which can be particularly troublesome when the media is initially loaded into the printer. To allow the RFID transponder  18  to be read irrespective of its position, the printer control circuit  40 , and particularly microprocessor  42 , selectively activates the RF transceiver  44  to acquire data from the RF tag  18 , and activates switch  48  to query the RFID tag  18  via either antenna  21  or antenna  23 . The microprocessor switches antennas if it cannot read data from the RFID tag  18  using the connected antenna  21  or  23 , which provides an indication that the RFID tag  18  is in a null area. As described above, the microprocessor  42  can also selectively switch antenna  50  into the print control circuit  40  to read data associated with an RFID tag associated with the ribbon, which can then be used to determine operating characteristics for the printer, or to assure a match between the print media and ribbon. 
         [0038]    It should be understood that the methods and apparatuses described above are only exemplary and do not limit the scope of the invention, and that various modifications could be made by those skilled in the art that would fall under the scope of the invention. For example, although specific types of connectors are described above for coupling the antenna system to the printer, it will be apparent that various other types of known plug and receptacle elements can be used, and various types of electrical contacts can also be used. Additionally, although the invention is described above as including two antennas that are substantially orthogonal, it will be apparent that more than two antennas could be used. Furthermore, these antennas could be arranged with respect to one another in a number of ways to allow for reading of data when the RFID tag is in a null area associated with any one antenna. Additionally, although the invention is described above specifically with reference to a thermal transfer printer, the present invention can be used in various types of printers and other types of equipment where rolls are used in conjunction with RFID transponders or tags.