Abstract:
A radio frequency identification device is enclosed in an enclosure suitable for harsh environments, and is resistant to physical, chemical, temperature, and electro-magnetic abuse. The enclosure includes a shell member configured to deflect direct blows to the transponder and can be shaped to fit various types of surfaces to which it can be affixed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/985,916, entitled “RFID Transponder Enclosure for Harsh Environments,” and filed Nov. 6, 2007. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of radio frequency identification (RFID), and in particular to RFID devices for harsh environments. 
     BACKGROUND ART 
     Industrial equipment, such as that used in the oil industry to transfer fluids and gases, has rigorous materials, inspection and use requirements where the accurate and rapid identification of the equipment is necessary. The equipment referenced is typically subjected to extremely harsh and abusive use. Industry attempts to affix devices containing RFID transponders, generally referred to RFID tags, to equipment such as this has typically met with failure due to the tag being damaged, lost or destroyed. 
     SUMMARY OF INVENTION 
     In one embodiment, an RFID tag comprises a mounting member, comprising a shell member, an extension positioned with the shell member and configured for attachment to a correspondingly configured surface, a elastomeric member, positioned in the shell member, and an RFID electronics assembly, positioned interior to the elastomeric member. 
     In another embodiment, a method of enclosing an RFID electronics assembly in an RFID tag comprises embedding the RFID electronics assembly in an elastomeric member, forming an impact-resistant shell in the RFID tag, and bonding the elastomeric member to the shell. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of apparatus and methods consistent with the present invention and, together with the detailed description, serve to explain advantages and principles consistent with the invention. In the drawings, 
         FIG. 1  is a top view illustrating a mounting member of an RFID tag according to one embodiment; 
         FIG. 2  is a side view illustrating the mounting member of the RFID tag of  FIG. 1 , after formation of a shell member in the mounting member; 
         FIG. 3  is a perspective view illustrating a separately formed shell member according to another embodiment; 
         FIG. 4  is a top view illustrating an elastomeric member according to one embodiment; 
         FIG. 5  is a side view illustrating the elastomeric member of  FIG. 4 ; 
         FIG. 6  is an axial view illustrating an object with the RFID tag of  FIG. 2  attached to the object; 
         FIG. 7  is a perspective view illustrating an RFID electronics assembly and packing member according to one embodiment; 
         FIG. 8  is a perspective view illustrating the RFID tag mounting member of  FIG. 2  and the elastomeric member of  FIGS. 4 and 5 ; 
         FIG. 9   a  is an end view illustrating an elastomeric member of another embodiment; 
         FIG. 9   b  is a top view illustrating the elastomeric member of  FIG. 9   a.    
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Various embodiments of an RFID tag are packaged in such a manner suitable for harsh environments. The embodiments are extremely durable and resistant to physical, chemical, temperature and electro-magnetic abuse. In addition, the various embodiments can be produced economically and can be used for a wide range of harsh RFID placement environments. 
     In one embodiment, an RFID electronics assembly with a dipole winding is placed inside an impermeable housing within a protective and chemically resistant packaging which in turn is placed under a protective hard outer shell. The outer shell is shaped to deflect direct blows and may have extensions to it which may be shaped to fit various surfaces, be they flat, curved or contoured. The extensions also enable the item to be welded, bolted, glued or otherwise affixed to a parent component or to a part which in turn may be affixed to a parent component. 
     Turning to  FIG. 1 , a mounting member  100  of one embodiment is illustrated in top view. The mounting member  100  is shown prior to formation of a shell for holding the RFID electronics assembly, and can be manufactured as a straight flat band, then shaped to fit the desired configuration for mounting. An opening  110  is formed in the mounting member  100 . 
     Then in  FIG. 2 , the mounting member  100  is illustrated in side view, after formation of the shell member  210  and curving the mounting member  100  to match the curvature of an object to which the mounting member  100  is to be attached (not shown in  FIG. 2 ), typically referred to as a parent component. Extension arms  220  provide for attachment of the mounting member to the parent component. 
     In one embodiment, the mounting member  100  is a steel band, but the mounting member  100  can be any type of material appropriate for the mounting to the parent component. In most oilfield equipment, for example, this will be a type of stainless steel, however it may be MONEL® metal, aluminum, titanium, polyetheretherketone (PEEK) plastic, or any other material appropriate for the intended application. 
     The mounting member  100  can be welded, glued, bolted or otherwise affixed to the parent component. In some embodiments, an attachment portion, such as a slot, hole, or tab, can be formed in the ends of the extension arms  220 , allowing for attachment of a band or other attachment member to the mounting member to surround the parent component, holding the mounting member in place. 
     Although the shell member  210  is illustrated and described above as integral with the remainder of the mounting member  100 , the shell member  210  can be manufactured as a separate piece and attached to the mounting member  100  as desired.  FIG. 3  is a perspective view of a separate shell member  300  that is designed to be inserted through the opening  110  of the mounting member  100 , instead of being integral with it. The shell member  300  typically has an opening  310 , which functions as the opening  110  does in the integrally formed shell member  210 . 
     Turning now to  FIG. 4 , an elastomeric member  500  according to one embodiment is illustrated in top view. A raised portion  530  protrudes from the upper surface  510  of the elastomeric member  500 , to engage with the opening  110  in the shell member  210  of the mounting member  100 , as described below. The raised portion  530  can be formed in the upper surface  510  directly, or by pressure when the elastomeric member  500  is positioned in the shell member  210 . In  FIG. 5 , the elastomeric member  500  is illustrated in end view, allowing the cavity  520  that is shown in phantom in  FIG. 4  to be seen. The cavity  520  can be formed by molding, grinding, drilling, or any other desired technique for forming a cavity in the elastomeric member  500 . The cavity  520  is sized to allow the insertion of the RFID electronics assembly. 
     In one embodiment, the elastomeric member  500  is made out of PEEK thermoplastic. PEEK is used because it is highly resistant to chemicals, has high strength, absorbs impacts well, has a high melting point and maintains a low brittleness at temperatures below that of liquid nitrogen. Pigment can be added to the elastomeric material for UV resistance if desired. Other materials can be used instead of PEEK thermoplastic, depending on the environmental and operational characteristics of the application. For example, acrylonitrile butadiene styrene (ABS) or other molded plastic could be used under some environmental and operational conditions. 
       FIG. 6  is an axial view illustrating a mounting member  100  together with an elastomeric member  500  as in  FIGS. 4 and 5 , forming an RFID tag that is attached to a parent component  600 . One skilled in the art will recognize that the shapes of the mounting member  100  and elastomeric member  500  are by way of example and illustrative only, and any desired shape can be used to match the shape of the parent object  600 . 
     The elastomeric member  500  holds an RFID electronics assembly  710  within a packing member forming an impermeable, typically spherically ended, cylinder made of high purity industrial grade glass  700 , as shown in  FIG. 7 . For some applications, an optimal frequency for the RFID electronics assembly  710  is 125 KHz-135 KHz, but in other applications a different frequency range may be optimal. In some applications, a high frequency RFID electronics assembly  710  can be used. The packing member  700  is inserted into the cavity  520  in the elastomeric member  500  to minimize stress on the glass. The cylindrical shape of the packing member of  FIG. 7  is illustrative and by way of example only, and other shapes can be used depending on the environmental conditions of the intended use. In some embodiments, the packing member  700  is bonded to the elastomeric member  500  to hold it in place using an epoxy. In such embodiments, the epoxy bonding the packing member  700  to the elastomeric member  500  has properties that are appropriate for the expansion coefficients of the material and the temperatures and chemicals to which the RFID tag may be exposed. 
     As described above, the lobe  530  of the elastomeric member  500  containing the RFID electronics assembly can be designed to protrude up into the opening  110  of the shell member  210  so that if the elastomeric member  500  debonds from the shell member  510 , the elastomeric member  500  will continue to be effectively retained under the shell member  210  by the lobe or raised section  530 . 
     In some embodiments, such as illustrated in  FIG. 8 , the window or opening  110  of the shell member  210  is designed and manufactured such that the internal edges  810  adjacent the opening  110  of the shell member  210  form an oblique angle relative to the elastomeric member  500 , allowing for the bonding material of the elastomeric member  500  to have a stronger bond to the shell member  210 . In one embodiment, the bonding material is an epoxy. In another embodiment, the bonding material is the same material as the elastomeric member  500  itself, such as would occur if the elastomeric material is insert molded onto the shell member  210  during manufacture. 
     In one embodiment, the RFID electronics assembly  710  is packed within the packing member  700  in a silicon or other similar gel material to absorb vibration and avoid crystallization at sustained high temperatures. Other types of materials can be used, so long as they reduce vibration transmission to the RFID electronics assembly or avoid crystallization at sustained high temperatures. One such material is a silica gel that allows operation of the RFID tag at sustained temperatures over 160° C. The specific temperature range is illustrative only, and use of materials that would allow operation of the RFID tags at other sustained temperature ranges is contemplated. The RFID electronics assembly  710  typically has wire bondings that are appropriate for the sustained high and low temperatures that they will encounter in some applications and carries an identifier in such a manner that the identity of the RFID tag will not be lost during sustained high temperature exposure. In some embodiments, the RFID electronics assembly  710  is designed such that it will continue to perform well in high magnetic fields and not be destroyed by rapid and strong magnetic fluctuations nearby. Preferably, the winding of the RFID antennae is placed around a dipole such that the signal will be optimized within the shape of the shell member  210 . 
     The shell member  210  as illustrated in the figures has a convex configuration containing the elastomeric member  500  containing the RFID electronics module. The convex configuration is designed to provide a curved surface that would deflect blows or forces occurring across an axis parallel to the curved surface. The shell member  210  is designed to be strong enough and the angles of the convex curve are configured so as to transfer the energy of most anticipated direct blows through to the parent part  600 , rather than allowing significant deformation of the RFID electronics assembly  710 , causing failure of the RFID tag. 
     The curved shell member  210  as illustrated in the figures is open ended and open topped via a small window, the opening  110 . The RFID electronics assembly is situated with the shell member in such a position that the RFID dipole antennae is parallel to the axis of the shell member  210 , optimizing the electromagnetic field of the assembly and the performance of the antennae. The open ends of the convex curve of the shell member  210  allow the electronic field to complete itself around the dipole curve. These features allow optimum readability of the RFID tag, but are not all necessary for an RFID tag to work. For example, a closed ended curved shell portion could be used to provide impact protection along other axes, such as a hemispherical shell. In such a configuration, additional windows optionally may be formed in the protective shell member  210  for optimal field strength. 
     In one embodiment, the RFID electronics assembly  710  uses EPROMs to hold the tag identity. In other embodiments, laser etched circuits can be used to configure the tag identity, allowing use of the RFID electronics assembly  710  in environmental conditions where EPROMs are unsatisfactory. 
       FIGS. 9   a - 9   b  illustrate an elastomeric member  900  according to another embodiment. In this embodiment, instead of a monolithic elastomeric member in elastomeric member  500 , the elastomeric member is composed of multiple parts that mate with each other to form the elastomeric member  900 . As shown in  FIG. 9   a , the elastomeric member  900  has two portions  910  and  920 . The relative shapes of the portions  910  and  920  are illustrative and by way of example only and any desired pair of shapes can be used. For example, in one embodiment, portion  910  can be a flat plate and portion  920  can be a covering for the plate  910 , forming a cavity between the portions  910  and  920 . 
     In some embodiments, as illustrated in  FIG. 9   a - 9   b , one or more clips  930  can be used to hold the packing member  700  to one of the portions  910  or  920 , holding the packing member  700  in the elastomeric member  900 . The shape of the depicted clip is illustrative only and any desired shape of clip can be used. The clip can be formed integrally with one of the portions  910  or  920 , as shown in  FIGS. 9   a - 9   b  or can be formed separately and attached to one of the portions  910  or  920  before use. 
     Alternatively, the packing member can be allowed to move in the elastomeric member  500  or  900  by “floating” it in a cushioning gel, protecting the packing member  700  from vibrations and other physical forces with the gel, without rigidly bonding or holding the packing member  700  in place. 
     In some embodiments, pressure exterior to the elastomeric member  500  or  900  is equalized with pressure in the cavity or space interior to the elastomeric member  500  or  900 , to help avoid damage to the packing member  700 . This is typically done by forming a passageway from the interior of the elastomeric member  500  or  900  to an exterior surface, such as the passageway  940  of  FIG. 9   b , but any technique for equalizing interior and exterior pressure can be used. The placement, size, and shape of the passageway  940  is by way of example and illustrative only and any convenient passageway configuration and location can be used. 
     While certain exemplary embodiments have been described in details and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not devised without departing from the basic scope thereof, which is determined by the claims that follow.