Abstract:
A host article and electronic tag assembly includes an article portion of rubber-based material composition. The electronic device and antenna attach to or are embedded within the article portion. The antenna is constructed to be flexible and at least partially composed of a flexible conductive material such as conductive rubber. The flexible antenna conductive material is selected to provide material composition properties substantially equivalent to the rubber-based article portion, whereby rendering the antenna mechanically compatible for incorporation into the article portion. A change in compression within the rubber-based article portion changes compression forces exerted from the article portion on the antenna arms which, in turn, results in a detectable change in signal strength from the tag. The antenna may further be configured and positioned within the article portion to change transmission characteristics responsive to a change of air pressure in an ambient adjacent air mass within the article, and thereby function as an air pressure sensor.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to electronic tags and, more specifically, to RFID electronic tags incorporated into a finished product such as a tire. 
       BACKGROUND OF THE INVENTION 
       [0002]    RFID electronic tags are incorporated into a variety of finished articles or products such as tires. Such tags include an electronic device for storing data such as a product identification number. The data stored within tag memory is transmitted upon receipt of an interrogation signal from the tag to a remote reader during the product life cycle to provide useful information concerning the product. 
       SUMMARY OF THE INVENTION 
       [0003]    In an aspect of the invention, a product and electronic tag assembly are provided including a rubber-based article portion. The electronic device and antenna attach to or embed withinthe article portion. The antenna is constructed to be flexible and at least partially composed of a flexible conductive material such as conductive rubber. The flexible antenna conductive material is selected to provide material composition properties substantially equivalent to the article portion, whereby rendering the antenna transparent and mechanically compatible for incorporation into the article portion. 
         [0004]    According to another aspect, the flexible antenna is of a dipole configuration including first and second antenna arms composed of conductive rubber and connected to respective contacts of the electronic device. The flexible antenna arms and the electronic device may be wholly or partially embedded within the article portion or attached thereto. 
         [0005]    In yet a further aspect, the electronic device includes a circuit module and a separator component composed of non-conductive material encasing the circuit module and separating the antenna arms. The antenna arms are secured to the article portion whereby at least a surface portion of the antenna arms faces outwardly and exposed from the article portion in an exposed relationship to an ambient adjacent air mass such as, but not limited to, the air within a tire cavity. The antenna arms may thus be configured and positioned to change transmission characteristics responsive to a change in pressure exerted on the antenna arms by surround article portion material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention will be described by way of example and with reference to the accompanying drawings in which: 
           [0007]      FIG. 1  is a perspective view of a RFID tag representative of the prior art; 
           [0008]      FIG. 2  is a perspective view of a RFID tag electronic device pursuant to the invention; 
           [0009]      FIG. 3A  is a longitudinal sectional view of an RFID tag embodied pursuant to the invention with the intermediary non-conductive separator component removed for the purpose of illustration; 
           [0010]      FIG. 3B  is a longitudinal sectional view of the RFID tag with the separator component in place; 
           [0011]      FIG. 5  is a perspective view of an alternatively configured electronic device in which the integrated circuit chip and contact array comprising the electronic device is not encased within a casing; 
           [0012]      FIG. 6  is a longitudinal sectional view of the alternative tag configuration showing encasement of inward ends of the antenna arms by a separator component. 
           [0013]      FIG. 7  is a block level diagram of the procedure for configuring and utilizing the tag as a pressure sensor device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring first to  FIG. 1 , a conventional RFID tag  10  is shown to include a substrate  12  supporting an IC (integrated circuit) package  13  having edge contact arrays  16 ,  18 . A pair of rigid metallic conductive coiled antenna arms  20 ,  22  are electrically coupled to respective contact arrays  16 ,  18  of the IC package  14 . The IC package includes an IC chip (not shown) of conventional construction for performing data memory and data transmitting functions. The contacts  16 ,  18  are generally of serpentine configuration extending from the IC chip and bending downward to remote ends supported by the substrate  12 . It is to those ends that the coil antenna arms  20 ,  22  are coupled by soldering or other known techniques. 
         [0015]    The dipole antenna constituted by the coils  20 , 22  communicate data from the IC package  14  to an external reader. The tag  10  may be incorporated into sundry articles or products by embedding the tag  10  within the article or affixing the tag to the article by adhesive or other known techniques. Coupling the tag  10  with an article or product allows information such as product identification data stored within the IC package to be accessed throughout the life cycle of the product. 
         [0016]    In some end use applications, the product is subjected to rigorous stresses and strains during normal use. Such forces may cause the antenna arms  20 ,  22  to separate from the CI contacts  16 ,  18  and cause a malfunction. Moreover, the material composition of the metallic coil antenna arms  20 ,  22 , the substrate  12 , and the IC package  14  may be dissimilar to the material composition of the host article into which the tag is incorporated. In such an event, the tag is considered “non-transparent” and bonding the tag to a portion of the article or product may become problematic. Failure of the bond may cause the entire tag to become separated from the article or product during use. 
         [0017]      FIG. 2  shows one IC package  24  configured pursuant to the invention. The package includes an outer casing  26  enclosing an IC chip (not shown) from which arrays of contact arms  28 ,  30  extend in coplanar linear form. The arrays of contacts  28 ,  30  extend through opposite sides of the casing  26  as shown. Each of the contact arms  28 ,  30  are elongate and are preferably, although not necessarily, of a straight, non-serpentine configuration, unlike the contacts  16 ,  18  of the device  14  shown in  FIG. 1 . As used herein, “electronic device” is used interchangeably with “IC package” and refers to the IC circuitry and contacts used in the performance of tag functions such as identification data storage and transmission. The electronic device may include an outer casing  26  as shown in  FIG. 2  or may be configured without a casing as shown in  FIG. 4  as will be explained. 
         [0018]    With reference to  FIG. 3A , the subject tag  32  is shown. IC package or device  24  is positioned in line with a pair of antenna arms  34 ,  36 . The antenna arms  34 .  36  are composed of a conductive rubber compound or matrix from commercially available solid or liquid conductive rubber products such as, but not limited to, Zoflex (manufactured and sold by XILOR Inc., and located in Knoxville, Tennessee. The antenna arms  34 ,  36  are connected to the RFID electronics at respective arrays of contacts.  28 ,  30 . Connection is established by encasing the contacts  28 ,  30  within inward ends  38 ,  40  of the arms  34 ,  36 , respectively. The arms  34 ,  36  are of flexible conductive rubber construction having a thickness or width D at inward ends  38 ,  40  sufficient to encase the contacts  28 ,  30  and to overlap respective opposite ends of the electronic device or IC package  24 . That is, the depth, width D, is wider than the IC package  24  whereby allowing the antenna arm inward ends  38 ,  40  to extend over opposite sides and edges of the IC package  24  as seen from  FIG. 3A . 
         [0019]      FIG. 3B  shows the placement of a separator component  42  about the IC package  24 . The component  42  encases the IC package  24  and is composed of non-conductive material such as a non-conductive rubber. The component  42  thus electrically separates the antenna arms  34 ,  36  and further serves to protect the IC package  24 . Preferably, although not necessarily, ends  44 ,  46  of the separator component  42  will overlap the ends  38 ,  40  of the arms  34 ,  36 , thus creating a complete rubber-based casing of the entire tag assembly. That is, the entire tag  32  is sheathed in a rubber base that will be transparent when embedded into an article or product such as a tire that is composed primarily of rubber. The RFID tag  32  thereby lends itself to a low cost method of production such as an extrusion process in which the conductive arm  34 , IC device  24 , non-conductive separator component  42 , and conductive arm  36  are sequentially extruded into a finished tag. The resultant tag will be flexible and bond better and more easily into a rubber product such as a tire. Moreover, because the components are of rubber materials, the tag is more non-obtrusive within a tire portion such as a wall, making the bonding of the tag to the tire stronger and less prone to failure. The risk of tag separation from the tire is thereby minimized. 
         [0020]      FIGS. 3A and 3B  show a tag embodiment in which the electronics is encased.  FIGS. 4 and 5  show an alternative tag embodiment  48  that eliminates the encasement package of the electronics and affixes flexible conductive rubber-based antenna arms  56 ,  58  directly to edge contacts  52 ,  54  of an integrated circuit  50 . The IC  50  has arrays of contacts  52 ,  54  along opposite edges. The antenna arms  56 ,  58  composed as described above from flexible conductive rubber. Inward ends  60 ,  62  of the arms  56 ,  58  affix over the edges of the IC and thereby establish electrical contact. The diameter or thickness of the arms  56 ,  58  is greater than the thickness of the IC  50 . A separator  64 , as shown by  FIG. 5 , encases the IC  50  and is dimensioned to overlap the inward ends  60 ,  62  of the arms  56 ,  58 . The separator component  64  is formed of non-conductive material such as rubber. The resulting tag shown in  FIG. 5  is thus completely encased by a material (rubber) compatible with and transparent to the material of a host rubber article such as a tire. The IC  50  is further protected by the flexible external sheath created by the arms  56 ,  58  and the separator component  64 . 
         [0021]    The tag  48  can be inserted in its entirety within a wall of an article or product such as a tire sidewall. The RFID tag becomes transparent when embedded into the tires because tires are likewise composed primarily of rubber having generally the same mechanical and material properties as the tag antenna arms  56 ,  58 . As a result, performance of the tire is not degraded by the presence of the tag  48  and a bonding of the tag within a tire sidewall is less likely to fail over time from tire use. Compatibility is used herein to mean materials having like mechanical and material properties. Compatibility between the tag  48  composition and that of the host tire product portion into which the tag is embedded thus creates a desired transparency between the tag and the tire. 
         [0022]    The tag  48  may be completely embedded within a wall of the tire; partially embedded; or externally affixed by adhesive or other means. When completely embedded, the flexibility of the tag will complement the flexibility the surrounding tire wall (i.e. become transparent). If partially embedded, a portion of the tag  48  will remain exposed. If affixed by adhesive, the tag  48  will be exposed to the ambient air cavity. It is commonplace to internally mount an RFID to either a tire sidewall defining the tire cavity or to an underside of the tire tread tire portion defining the cavity. So positioned, the tag  48  is proximate to the tire cavity that becomes pressurized when the tire is mounted to a wheel. 
         [0023]    It is contemplated that the tag, whether in the configuration  32  or  48 , when mounted to tire, will function to transmit product identification data, when subjected to an interrogation signal, to a remote reader by means of the dipole antenna arms  34 ,  36  ( FIGS. 3A ,  3 B) or  56 ,  68  ( FIGS. 4 ,  5 ). The use of the RFID tag may be extended if desired for deployment as a low cost, durable and passive (requiring no internal power source) pressure sensor for detecting air pressure within an adjacent pressurized ambient air mass. In a tire, the tag can serve as a pressure sensor for measuring the air pressure within a tire cavity. For use as a pressure sensor in a tire, the tag antenna arms are composed of a flexible, electrically conductive, and pressure sensitive material such as conductive polymers or a pressure sensitive polymer. Such a material is commercially available from XILOR, Inc. The signal strength returned from the RFID tag when it is interrogated will vary based on the surrounding pressure brought to bear on the tag antenna arms because the impedance of the rubber changes with pressure. 
         [0024]    If the RFID tag and its antenna arms are completely embedded within a rubber composed wall of an article or product, the RFID tag by varying signal strength will indicated changes of pressure within that wall bearing upon the tag. In the case of measuring tire cavity air pressure, the tag may be embedded within a wall of the tire defining the tire cavity. Changes in air pressure within the cavity will change compression forces within the tire walls defining the tire and will thereby vary the compressive forces bearing on the antenna arms. The change in compression forces on the tag antenna arms will be reflected in a variance in signal strength, whereby serving to communicate tire cavity air pressure. 
         [0025]    The RFID tag may also be partially embedded within the tire wall such that a portion or the entirety of the antenna arms remain exposed to the ambient air mass within the tire cavity. In this system, changes in tire cavity air pressure will directly impact against the tag antenna arms and change impedance of the rubber therein. The change in signal strength can be detected by an external reader and calculations made to determine the air pressure within the cavity that correlates with the impedance values within the antenna arm rubber. Likewise, the tag may be mounted against the tire sidewall by adhesive agents or the like, and a similar procedure used to measure the signal variation resulting from pressure changes against the tag antenna arms. 
         [0026]    In the aforementioned pressure sensor applications, as seen from the block diagram of  FIG. 6 , it is necessary to first study and calculate the conductive rubber within the antenna arms and how the impedance will vary according to pressure on the arms. Once such a study and calculations are completed, pressure sensor application of the tag within a product and article can be made. An interrogation of the tag from an external signal will result in data transmission from the tag to a reader. The transmission signal can then be analyzed and, from its strength, the impedance of the antenna arms deduced. From the impedance value thus calculated, the pressure against the antenna arms may be determined and a conclusion of air pressure within the tire cavity necessary to produce such a pressure on the arms can be calculated. 
         [0027]    With specific reference to  FIG. 6 , the procedure for implementing a pressure sensor tag application is as follows calculate impedance of tag rubber antenna arms; calculate changes in antenna arm impedance resulting from changes in pressure exerted on antenna arms; determine changes in tag transmission signal strength from changes in antenna arm impedance; ilncorporate tag into rubber-based tire wall defining pressurized tire cavity; Interrogate tag to initiate return data signal; measure strength of return data signal; calculate impedance of antenna arms required to result in measured data signal strength; determine pressure exerted on antenna arms required to result in calculated antenna arm impedance; calculate air pressure within the tire cavity required to generate pressure exerted on antenna arms. 
         [0028]    Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.