Abstract:
Gas cylinder and RFID (radio frequency identification) transponder assemblies and related methods are disclosed that utilize fixed orientations for RFID transponders to overcome problems existing with previous solutions. The disclosed embodiments provide an advantageous solution for utilizing metal plates, such as metal identification plates, to house RFID transponders and to fix the orientation of the RFID transponders to overcame the adverse effects of metal structures distorting the magnetic fields associated with gas cylinders. This fixed orientation combined with a transponder embodying a copper wire antenna wound around a longitudinal axis of a ferrite core and the use of PSK (phase shift keying) modulation allows for adequate reader performance despite the presence of interfering metal structures such as a metal plate used to house an RFID transponder.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to miniature electronic devices and more particularly to miniature transponder devices suitable for assets management and other purposes. 
       BACKGROUND 
       [0002]    Prior RFID (radio frequency identification) tags exist that are used to help track various products. RFID tags are typically an assembly including an RFID transponder coupled into a protective housing, and the assembly can then be used for assets management, container safety inspection purposes, fraud prevention, ownership identification or other purposes. One application for such RFID tags, for example, is the use of RFID tags to help track hazardous products, such as liquid propane gas (LPG) stored in metal containers or cylinders. 
         [0003]      FIG. 1A  (Prior Art) is a diagram of an embodiment  100  including a container or cylinder  102 . The container  102  can be, for example, a metal cylinder holding LPG (liquid propane gas) or other hazardous or non-hazardous material. The gas cylinder  102  includes a metal valve flange  108  welded into a central opening at the top of the cylinder  102 . As described in more detail below, the metal valve flange  108  can be configured to provide a primary valve opening into which a valve can be inserted and coupled. For example, the opening can be threaded to allow a primary valve to be attached by screwing the valve into place. As also described further below, a second opening can also be provided in the metal valve flange into which a second valve can be inserted and coupled. For example, the second opening can also be threaded and provide a secondary access port into which an emergency pressure relief valve can screwed into place. Such a relief valve is a mandatory regulatory requirement in some geographic regions for certain containers, such as metal cylinders holding LPG in Brazil In addition, as depicted, one or more metal stay plates  106  can also be connected to the gas containing portion of the cylinder  102  and to a metal ring  110 . The metal ring  110  can be used, for example, to protect valves coupled to a metal valve flange  108 , and the metal ring  110  can be used for picking up or moving the cylinder  102 . 
         [0004]      FIG. 1B  (Prior Art) is a diagram for a metal valve flange  108  for the metal cylinder  102  of  FIG. 1A  (Prior Art). The metal valve flange  108  includes a primary valve opening  114  and a secondary valve opening  112 . The primary valve opening  114  is configured to receive a valve, such as a brass valve, which can be screwed into place. The secondary port opening  112  is also configured to receive a valve, such as a brass pressure relief valve, which can also be screwed into place. 
         [0005]    Many gas containers or cylinders, such as those represented in  FIGS. 1A-1B , are already in commercial use, and do not have RFID tags or RFID transponders for security and tracking purposes. Further, existing containers or cylinders are being re-used so that many non-tagged containers and cylinders are still being used and will likely continue to be used. As part of the re-use process, a metal identification plate is often used to label or re-label the container/cylinder after mandatory periodic requalification, overhaul and/or retesting of the cylinder has been performed. 
         [0006]      FIG. 2A  (Prior Art) is a diagram for a metal plate  200 , such as a C-shaped metal plate, that can be used to provide labeling information for a cylinder  102  that has been re-qualified. The metal plate  200 , for example, can include company information, tare weight of the container, data pertinent to the requalification process performed, date of next inspection and/or any other desired information required by the regulating agency. 
         [0007]      FIG. 2B  (Prior Art) is a diagram for a metal plate  200  that has been coupled to a valve flange  108 , for example, by welding the metal plate  200  to the valve flange  108 . As in  FIG. 1B  (Prior Art), the valve flange  108  can include a primary valve opening  114  and a secondary relief valve port  112 , if desired. 
         [0008]    As stated above, many gas containers or cylinders, such as those represented in  FIGS. 1A-1B , are already in commercial use, and do not have RFID tags or RFID transponders for safety, security and tracking purposes. Determining an effective and secure method for including RFID transponders on these gas cylinders is a difficult problem facing many countries that rely heavily on gas cylinders for energy needs. Further, one problem associated with placing RFID transponders on prior art gas cylinders is that metal structures, such as metal stay plates and protective rings, interfere with RFID communications. 
       SUMMARY OF THE INVENTION 
       [0009]    Gas cylinder and RFID (radio frequency identification) transponder assemblies and related methods are disclosed that utilize fixed orientations for RFID transponders to overcome problems existing with previous solutions. The disclosed embodiments provide an advantageous solution for utilizing metal plates, such as metal identification plates, to house RFID transponders and to fix the orientation of the RFID transponders to overcome the adverse effects of metal structures distorting the magnetic fields associated with gas cylinders. This fixed orientation combined with a transponder embodying a copper wire antenna wound around a longitudinal axis of a ferrite core and the use of PSK (phase shift keying) modulation allows for adequate reader performance despite the presence of interfering metal structures such as a metal plate used to house an RFID transponder. Other features and variations can be implemented, if desired, and related systems and methods can be utilized as well. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    It is noted that the appended drawings illustrate only exemplary embodiments of the invention and are, therefore, not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0011]      FIG. 1A  (Prior Art) is a diagram for a gas container having a metal valve flange, such as a metal cylinder holding liquid propane gas (LPG). 
           [0012]      FIG. 1B  (Prior Art) is a diagram for a metal valve flange for the cylinder of  FIG. 1A  (Prior Art). 
           [0013]      FIG. 2A  (Prior Art) is a diagram of a C-shaped metal plate that is used for identification and labeling of containers such as the container of  FIG. 1A  (Prior Art). 
           [0014]      FIG. 2B  (Prior Art) is a diagram of the C-shaped metal plate of  FIG. 2A  (Prior Art) welded to the metal valve flange of  FIG. 1B  (Prior Art). 
           [0015]      FIG. 3A  is a top-view diagram of a C-shaped metal plate having a recess formed in its bottom surface for housing a transponder and fixing its orientation. 
           [0016]      FIG. 3B  is a bottom-view diagram for a C-shaped metal plate having a recess formed in its bottom surface for housing a transponder and fixing its orientation. 
           [0017]      FIG. 3C  is a top-view diagram for the C-shaped metal plate of  FIGS. 3A-3B  that has been affixed to the metal valve flange of a gas cylinder. 
           [0018]      FIG. 4  is a diagram for the fixed orientation of the transponder with respect to the center axis for the primary opening in the metal valve flange. 
           [0019]      FIG. 5A  is a diagram for an alternative embodiment using a metal plate that is fixed, for example, to a protective metal stay plate for the gas cylinder. 
           [0020]      FIG. 5B  is a bottom-view diagram for a metal plate having a recess formed in its bottom surface for housing a transponder and fixing its orientation. 
           [0021]      FIG. 5C  is a top-view diagram for a metal plate having a recess formed in its bottom surface for housing a transponder and fixing its orientation. 
           [0022]      FIG. 6A  is a diagram for a nozzle reader assembly that can be used to read the transponders described herein. 
           [0023]      FIG. 6B  is a diagram for a hand held reader that can be used to read the transponders described herein. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Assemblies and related systems and methods for fixed orientation of RFID (radio frequency identification) transponders with respect to gas cylinders are disclosed that overcome problems existing with previous solutions. In particular, the disclosed embodiments provide an advantageous solution for utilizing metal plates, such as metal identification plates, to house RFID transponders having elongated ferrite core antennas and to fix their orientation with respect to the gas cylinder. The disclosed embodiments and fixed orientation allow for adequate performance where it would be assumed that metal structures would render reader communication inoperable. Other features and variations can be implemented, if desired, and related systems and methods can be utilized as well. 
         [0025]    The embodiments will now be described in more detail with respect to  FIGS. 3A-C ,  FIG. 4 ,  FIGS. 5A-5C  and  FIG. 6 . According to the embodiments described herein, RFID transponders having an antenna wire wrapped around a ferrite core are oriented in particular ways to improve the overall performance of the system and to overcome interference caused by metal structures. Further, if desired, the RFID transponders can use PSK (phase shift keying) modulation to improve communication with readers where metal plates are used to house the RFID transponders or where other metal structures may interfere with communications between the RFID reader and transponder. It is further noted that the RFID transponders described herein are particularly useful for controlling and monitoring the distribution and use of hazardous materials in objects or containers, as well as the safety of the containers themselves. 
         [0026]      FIG. 3A  is a top-view diagram  300  for a metal plate  306 , such as a C-shaped metal plate, that has been configured to include a recess or indentation  304 . Recess  304  is configured to provide space to house a transponder  302  once the metal plate  306  is coupled to a gas cylinder, such as on top of a valve flange. Further, the recess or indentation  304  is formed within the bottom surface of the metal plate  306  and is oriented so as fix the orientation of the RFID transponder with respect to the valve flange. This fixed orientation improves performance of the RFID transponder  302  with respect to an RFID reader, which will typically be placed over or near the valve flange for the gas cylinder. This desired orientation for the RFID transponder is described in further detail below with respect to  FIG. 4  and  FIG. 5A . It is noted that the metal plate  306  can be other shapes, as desired, and that the C-shape depicted is just one example shape. It is further noted that the bottom surface of the metal plate can be slightly conical in shape so as to fit along the curved top surface of a valve flange, which is typically curved to match the shape of a gas cylinder to which it is welded. 
         [0027]    It is further noted that the transponder  302  has a ferrite core antenna made of copper wire (e.g., 5-15 microns thickness) that is wound around an elongated ferrite core and connected to an RFID integrated circuit. Further, the transponder  302  can be encapsulated in glass for additional protection against outside elements over a long time periods. Alternatively, the transponder  302  can be used without protective glass encapsulation. The transponder  302  is preferably a miniaturized transponder having a size of about 100 cubic millimeters (mm) or less and having dimensions of about 10-14 mm or less in length (L) and about 2-3 mm or less in diameter (D). Example miniaturized transponders are described, for example, in U.S. Pat. No. 5,281,855, U.S. Pat. No. 5,572,410, U.S. Pat. No. 5,084,699, U.S. Pat. No. 7,176,846, U.S. Pat. No. 7,825,869, and U.S. Pat. No. 7,855,649, each of which is hereby incorporated by reference in its entirety. 
         [0028]      FIG. 3B  is a bottom-view diagram  350  for the metal plate  306  that has been configured to include a recess or indentation  304 . As stated above, the recess or indentation  304  is configured to fix the orientation of the RFID transponder  302  and to provide space to house the transponder  302  once the metal plate  306  is coupled to a container. Thus, the recess or indentation  304  is preferably slightly bigger than the transponder  302  so as to house the transponder  302  while still fixing its orientation. 
         [0029]      FIG. 3C  is a top-view diagram  370  for a metal plate  306  that has been coupled to a valve flange  108 , for example, by welding the metal plate  306  to the valve flange  108 . The transponder  302  (not seen) is positioned underneath the metal plate  306  within the recess or indentation  304 . As described above, the valve flange can include a primary valve opening  114  and a secondary relief valve port  112 , if desired. It is noted that techniques other than welding could also be used to fix the metal plate  306  to the valve flange  108 . For example, a glue or an epoxy material could be used to couple the metal plate  306  to the valve flange  108 . 
         [0030]      FIG. 4  provides a diagram  400  for the fixed orientation of the transponder  302  with respect to the primary valve opening  114  of the valve flange  108 . The “X” marks the center axis  412  of this valve flange  108  and its primary valve opening  114 . While the metal plate  306  that covers the transponder  302  would be expected to interfere with the transponder  302  so that detection using a RFID reader would be very difficult if not impossible, it has been found that orienting the transponder as shown in  FIG. 4  allows for acceptable reader performance despite the metal plate  306  covering the transponder  302 . In particular, as depicted, the transponder  302  has a ferrite core antenna  402  that is elongated in shape, and the direction of this elongation, as represented by arrow  404 , is oriented with respect to the center axis  412  of the primary valve opening  412  such that the angle of deviation is less then or equal to 40 degrees. In other words, the elongated ferrite core antenna  402  within the recess  304  has a fixed orientation such that a line passing through a center of the elongated ferrite core antenna  402 , as represented by arrow  404 , is less than or equal to 40 degrees offset from a line  406  passing through a center axis  412  of the valve flange and the RFID transponder  402 . When this orientation is maintained by the recess or indentation  304  for the metal plate  306 , reception of the communications by the transponder  302  to a reader are adequate, even though the plate  306  is metal and would be expected to interfere too much with the transponder  302  for operable communications. 
         [0031]    Looking in more detail to  FIG. 4 , the desired fixed orientation of the transponder  302  will be further explained. The dotted line  406  represents a line extending through the transponder  302  and the center axis  412  of the primary opening  414  in the plane of the valve flange  108 . The dotted line  408  represents a line perpendicular to the dotted line  406 . The arrow  404  represents a line passing through the elongated ferrite core antenna  402  when the transponder  302  is fixed in place by the metal plate  306 . The arrow  404  can also be considered to represent the elongated direction of the recess or indentation  304  that houses the transponder  302 , as it will determine the orientation of the transponder  302  once the assembly is completed. The lines  410  and  412  represent potential deviations or offsets in the direction to which the arrow  404  points (i.e., direction of elongated core) from the line  406 . It is desired that the deviations  420  and  424  from the line  406  be equal to or less than 40 degrees, and preferably be equal to or less than 15%. As such, it is desirable for the angles represented by  422  and  426  to be equal to or greater than 50 degrees, and preferably be equal to or greater than 75%. This fixed orientation of the ferrite core  402  with respect to the center axis  412  of the main valve opening  114  allows for adequate reception by an RFID reader of communications from the RFID transponder  302 , where one would expect signals to have been blocked by the metal plate  306 . 
         [0032]    This communications between the RFID transponder  302  and an RFID reader is further improved by the use of PSK modulation by the RFID transponder. For example, the metal plate  304  can interfere with the RFID communications. Further, when a metal ring, such as ring  110 , is used to protect valves with respect to a gas cylinder  102 , the metal ring  110  can also interfere with RF signals being communicated to and from an RFID transponder  302 . It is found that it is preferable to utilize PSK (phase shift keying) modulation for the RF signals being used to communicate information to and/or from the RFID transponder  302 . For example, when PSK modulation is used by the RFID transponder  302 , increased communication range is achieved with respect to a reader that is reading information from the RFID transponder  302 , as compared to implementations where FSK (frequency shift keying) modulation or ASK (amplitude shift keying) modulation is being used. As such, using PSK modulation with respect to the RFID transponder  302  is preferable in these embodiments where a metal plate  304  is used to house the RFID transponder  302  and to fix its orientation with respect to the gas cylinder  102 . Still further, it is noted that the RFID transponder  302  can be configured to use frequencies equal to or less than 200 kHz in communicating with an external reader to further improve performance. 
         [0033]      FIG. 5A  is a diagram for an alternative embodiment  500  where a transponder under a protective metal plate  502  is coupled in a different manner to the gas cylinder  102 , such as to a stay plate  504  that is coupled to the gas cylinder  102  and to a protective ring  505 . For this alternative embodiment  500 , the RFID transponder is still oriented within a particular offset range with respect to the center axis of the valve flange  108 . As depicted, this center axis is represented by dotted line  506 . Dotted line  508  represents a line that is perpendicular to the dotted line  506 . As described above, the transponder included under the protective plate  502  includes an elongated ferrite core antenna, such as thee elongated ferrite core antenna  402  in  FIG. 4 . This elongated ferrite core antenna is aligned with the center axis  506  or offset from this line within a particular range to provide for adequate reader performance. In particular, similar to  FIG. 4 , the deviation or offset lines  510  and  512  are equal to or less than 40 degrees from the center axis  506 , as represented by arrows  522 ,  526 ,  528  and  530 . In such an embodiment, the angles represented by  520 ,  524 ,  532  and  534  are equal to or greater than 50 degrees. Preferably, the angles of deviation or offset represented by arrows  522 ,  526 ,  528  and  530  are equal to or less than 15 degrees to provide improved reader performance. In such a further embodiment, the angles represented by  520 ,  524 ,  532  and  534  are equal to or greater than 75 degrees. It is noted that this fixed orientation is determined such that a line passing through a center of the elongated ferrite core antenna (e.g., line  510  or  512  when offset or deviated from line  506 ) is less than or equal to 40 degrees offset from a line  506  passing vertically through a center axis of the central opening of the gas cylinder they are considered to be in the same plane. 
         [0034]      FIG. 5B  is a bottom-view diagram for a metal plate  502  having a recess or indentation  552  formed in its bottom surface for housing a transponder  302 . When the metal plate  502  is affixed to a portion of the container, such as the stay plate  504 , the orientation of the transponder  302  is then fixed with respect to the center axis  506  of the primary valve opening. The metal plate  502  can be coupled to the stay plate  504 , for example, by welding the metal plate  502  to the stay plate  504 . Other techniques could also be used to fix the metal plate  502  to the stay plate  504 , such a glue or an epoxy. As depicted, the metal plate  502  is a four-sided metal plate. However, as described above, other shapes could also be used, if desired, and the metal plate can be configured to have a bottom surface that conforms or matches the shape of the surface to which the metal plate is being attached. 
         [0035]      FIG. 5C  is a top-view diagram for the metal plate  502  having a recess or indentation  552  formed in its bottom surface for housing the transponder  302  and for fixing its orientation. As indicated with the dotted lines, transponder  302  sits under the metal plate  502  and within the recess or indentation  552 . 
         [0036]    It is noted that other metal protection mechanisms welded or otherwise affixed to the gas cylinder  102  can be used to provide for valve assembly protection and a carrying facility. For example, the metal protection mechanism can be a metal carrying handle welded to the gas cylinder  102 . The metal protection mechanism can also be a metal ring and one or more metal stay plates welded together and to the gas cylinder  102 , as shown in  FIG. 5A . The metal plate  502 , which houses the transponder  302 , can be welded or other affixed to these metal protection mechanisms or other structures, as desired, depending upon how the gas cylinder is implemented. 
         [0037]      FIG. 6A  is a diagram for a nozzle reader assembly  600 . The nozzle reader assembly  600  includes an antenna portion  608 , a nozzle connector portion  606 , and a hose  604 . The nozzle reader assembly  600  can be used to read the transponder  302  on the cylinder  102  during refueling. 
         [0038]      FIG. 6B  is a diagram for a hand held reader  602 . The hand held reader  602  can be positioned over the valve flange  108  and can then be used to read the transponder  302  on the container or cylinder  102 . 
         [0039]    It is noted that other reader configurations could also be used, if desired. For example, a horizontal panel reader could be used to read the transponder  302  on the gas cylinder  102 . In operation, the horizontal panel reader could be placed above the valve assembly, as well as above any protective carrying ring coupled to the gas cylinder. Further, a conveyor belt can be used to move a plurality of gas cylinders under the horizontal panel reader to allow for more efficient reading of transponders on a large number of gas cylinders. 
         [0040]    Further modifications and alternative embodiments of this invention will be apparent to those skilled in the art in view of this description. It will be recognized, therefore, that the present invention is not limited by these example arrangements. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It is to be understood that the forms of the invention herein shown and described are to be taken as the presently preferred embodiments. Various changes may be made in the implementations and architectures. For example, equivalent elements may be substituted for those illustrated and described herein, and certain features of the invention may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the invention.