Abstract:
An improved method and apparatus permits the insertion and removal of an electronic monitoring device from a tire, while securing the electronic monitoring device to the tire so that stress, strain, impact, cyclic fatigue and vibration are minimized. After a rubber patch is vulcanized, the patch is permanently assembled to the innerliner of a vulcanized tire by affixing it to the tire innerliner. An electronic monitoring device, after having been encapsulated in a suitable rigid potting material to form a rigid tag, is fitted with a power source to form a tag assembly in a shape which allows for insertion into a cavity in the patch. The tag is carefully inserted into the cavity housing. The tag assembly is locked into place within the cavity using a suitable removable locking device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional application claiming priority from U.S. patent application Ser. No. 09/455,977 filed Dec. 6, 1999, which has issued as U.S. Pat. No. 6,386,251; which is a continuation of U.S. Pat. No. 6,030,478 (Ser. No. 09/021,518 filed Feb. 10, 1998); the disclosures of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   This invention pertains to an apparatus and a method of inserting and removing an active tag into a compartment which is permanently attached to a tire. More particularly, this invention sets forth a method and apparatus for inserting and removing an electronic device encapsulating in a rigid material, into a compartment of a vulcanized rubber patch which is permanently attached to a vulcanized tire. 
   2. Background Information 
   It is desirable to monitor engineering conditions of tires, such as wear, internal pressure and internal temperature in order to reduce tire costs and maximize vehicle efficiency. Of course, it is advantageous to perform such monitoring in large truck tires, which are expensive. 
   Prior art methods of monitoring large truck tires have included passive integrated circuits embedded in the body of the tire, or self-powered circuits which are positioned external to the tire. The passive integrated circuits rely on inductive magnetic coupling or capacitative coupling to energize the circuit, thus providing power to the circuit from a source remote from the tire. Self-powered circuits positioned external to the tire are exposed to damage from the environment such as weather, road hazards and even vandalism. 
   Recent engineering advances have permitted the installation of monitoring devices having active integrated circuits within tires. One such device is described in U.S. Pat. No. 5,562,787 to Koch et al. entitled “Method of Monitoring Conditions of Vehicle Tires”, incorporated herein by reference, and assigned to the assignee of the present invention. These devices include an active circuit powered by a dedicated long life, miniature battery and at least one sensor for detecting, optionally storing and transmitting real time engineering conditions within the tire. Such devices are capable of being programmed to remain in an active, but dormant condition, but will switch automatically to an “awakened” condition in response to an external signal or a condition which exceeds preset limits. 
   One of the problems faced with such active devices is that they are delicate electronic devices that must operate in the harsh environment of a tire. Thus it is important to secure these devices in the tires to minimize the effect of the harsh tire environment on them, while still permitting them to be exposed to this environment to allow accurate monitoring of the engineering conditions for the life of the tire. These active devices have previously been mounted in tires by first encapsulating the device or power-containing circuit in a material which forms a rigid or semi-rigid encasement about the device, thereby inhibiting straining of the device as a result of applied stresses during operation. Such materials have included non-foam compounds such as urethanes, epoxies, polyester-styrene resins, hard rubber compositions, and the like. The encapsulated device is then placed into a green rubber material which forms a housing or is placed in a green rubber pocket or pouch that becomes part of the tire. The encapsulated device is then permanently set within the rubber material during a subsequent vulcanizing operation. The encapsulated device, including the power source or battery, is then permanently assembled to the tire, so there is no way to replace the battery once it is discharged, nor is there a practical way to disassemble the encapsulated device to repair a failed component. 
   While the methods and apparatus of U.S. Pat. No. 5,562,787 provide an acceptable method of assembling an active chip into a tire cavity, an improved method and apparatus which permits assembly and disassembly of the encapsulated device and battery from the tire. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with the present invention, an improved method and apparatus for assembling and disassembling an active electronic monitoring device into a tire is disclosed. 
   The improved method and apparatus permits the insertion and removal of an electronic monitoring device from a tire, while securing the electronic monitoring device to the tire so that stress, strain, impact, cyclic fatigue and vibration are minimized. A rubber patch having a first side which includes a housing with a cavity having a preselected configuration and a second opposite side approximating the contour of an innerliner of a tire is prepared. Although the rubber patch may be assembled to the tire and vulcanized with the tire, it is much more practical to assemble the rubber patch to the tire after both the rubber patch and the tire have been vulcanized. After the rubber patch is vulcanized, the patch is permanently assembled to the innerliner of a vulcanized tire by affixing the second opposite side of the patch to the tire innerliner. The electronic monitoring device, after having been encapsulated in a suitable rigid potting material to form a rigid tag, is fitted with a power source to form a tag assembly in a shape which allows for insertion into the contour of the cavity housing which is carefully inserted into the cavity housing. The tag assembly is locked into place within the cavity using a suitable removable locking means. 
   An advantage of the present invention is that the tag assembly may be inserted into the tire after vulcanization of the tire and after the assembly of the patch to the tire. Because the tag assembly is locked into place using removable locking means, the tag assembly may be removed at any time during the life of the tire to replace the rigid tag or the power source. Thus, if a battery fails, it may be easily replaced so that the tag assembly can continue to operate. If the rigid tag fails because of a failure of any of the components comprising the tag, it can easily be removed or replaced. 
   Another advantage of the present invention is that is a tire is to be retreaded, the tag assembly may be removed from the tire during the vulcanizing operation and replaced after completion of the vulcanizing operation, so that the sensitive and delicate electronic circuitry of the rigid tag and the batter are not subjected to the harsh environment of the vulcanizing operation, which could destroy or adversely affect its life. 
   Since the tag assembly is removable for repair or replacement, a further advantage is that, in the event of a failure of the battery or any component of the rigid tag, it is not necessary to assemble a second patch assembly to the tire. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention itself, however, both as to its organization and its method of practice, together with further objects and advantages thereof, may best be understood by the following description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a cross-sectional view of the rubber patch of the present invention showing the housing and cavity for the tag assembly; 
       FIG. 2  is a cross-sectional view of the rubber patch of the present invention attached to the innerliner of a tire; 
       FIG. 3  is a cross-sectional view of the electronic monitoring device embedded in potting material; 
       FIG. 4  is a cross-sectional view of the mold used to embed the electronic monitoring device in the potting material; 
       FIG. 5  is a cross-sectional view showing a battery attached to the tag; forming a tag assembly; 
       FIG. 6  is a cross-sectional view of the tag assembly assembled inside the cavity of the tire patch, with a locking device holding the tag assembly in place, before crimping of the locking device; 
       FIG. 7  is a second embodiment of the present invention depicting a cross-sectional view of the tag assembly being locked inside the cavity of the tire patch with a threaded insert; 
       FIG. 8  is a third embodiment of the present invention showing a threaded tag assembly threaded into the cavity of the rubber patch housing; and 
       FIG. 9  is a fourth embodiment of the present invention, shown in perspective, showing a slot and tab arrangement for locking a tag assembly to a rubber patch housing. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described below with reference to the drawings. 
     FIG. 1  shows a rubber patch  10  of the present invention. The patch  10  has a first side  12  which includes a housing  14  with a cavity  16  of a preselected configuration. As shown in  FIG. 1 , the housing  14  has a cavity  16  which is cylindrical, although the cavity  16  may be of any convenient configuration, as will become apparent from the description which follows. The patch has a second opposite side  18  approximating the contour of an innerliner of a tire (not shown). In a preferred embodiment, the rubber patch is vulcanized and then assembled to the vulcanized tire. Although any method for assembling the vulcanized rubber patch to the vulcanized tire, one acceptable and preferred method is set forth in U.S. Pat. No. 5,971,046; the disclosures of which are incorporated herein by reference. In accordance with the referenced application, the patch may be a rubber selected from the group consisting of Ethylene Propylene Diene Monomer (EPDM) rubber, butyl rubber, natural rubber, neoprene and mixtures thereof. One preferred embodiment is a mixture of chlorobutyl rubber and natural rubber. Another preferred embodiment is a mixture of Styrene-Butadiene rubber (SBR) and natural rubber. Typically, patches made of these rubber compositions may be cured by heating to a temperature of about 150° C. and holding at this temperature for about 30 minutes. The time and temperature may be modified as necessary to achieve sufficient curing of the patch for further assembly. The second side of the patch  18  approximates the contour of an innerliner of a tire. The contour of the second side  18  preferably is radiused to have about the same radius as the tire to which it is assembled, the radius being larger for larger tires. For very large tires, such as for off-the-road tires, the radius may be eliminated altogether, so that there is no contour and the opposite side is flat, having no contour. 
   Affixed to the second side  18  of the vulcanized tire patch is a dual cure bonding layer  20 , which has a first side (not shown) and a second side  22 . This dual cure bonding layer may be assembled to the patch at any time following vulcanization of the patch and prior to assembly of the patch assembly to the tire innerliner. The dual cure bonding layer is permanently assembled to the patch to form patch assembly  60 . A non-curing cement (not shown) is applied to side  18  of the patch in order to hold the dual cure bonding layer  20  onto the patch. The non-curing cement and the dual cure bonding layer are products of Patch Rubber Company. The important feature of the dual cure bonding layer is that it can be chemically activated and cured, without the need for heating to an elevated temperature. The process is diffusion controlled, however, and some minimal heating will speed the curing process. The dual cure bonding layer may be any material which can be activated and cured to the vulcanized rubber of the tire innerliner and the vulcanized patch. Preferably, however, the dual cure bonding rubber is natural rubber. The dual cure bonding rubber, after application of the activating cement, may cure at room temperature over a period of seventy-two (72) hours. However, if more rapid curing is desired, this may be accomplished by heating to 45° C. for at least twenty-four hours. 
   Referring now to  FIG. 2 , patch assembly  60  is then assembled to the innerliner  75  of tire  71 . Activating cement is first applied to second side  22  of dual cure bonding layer  20 . The patch assembly is then stitched to the innerliner of the vulcanized tire and the patch assembly/tire assembly is allowed to cure for a sufficient time and temperature to form a strong bond between the tire and the patch assembly. The times and temperatures utilized for this curing may be basically the same times and temperatures as previously discussed. To ensure a strong bond, the patch assembly optionally may be clamped to the tire innerliner  75 , until the curing cycle is completed. 
   The electronic monitoring device is a circuit board which includes sensors and optionally, an antenna. The electronic monitoring device may include a power source or battery, although the battery may be attached to the electronic monitoring device at a later time. In the preferred embodiment, the battery is not included as part of the electronic monitoring device. The electronic monitoring device  34  is encapsulated in a potting material  40  which solidifies into a rigid material as shown in FIG.  3 . Referring to  FIGS. 3 and 4 , the electronic monitoring device  34  is placed within a mold  42  having a first half  52  and a second half  54 . The mold is then filled with the potting material  40  in fluid form, which fills the mold and flows around the electronic monitoring device and allowed to cure, resulting in a rigid tag. Any potting material having a Young&#39;s Modulus of at least 30,000 psi and which is capable of being molded around the electronic monitoring device without damaging any of the components of the device. Preferably, the potting material has a Young&#39;s Modulus of at least about 100,000 psi. Two preferred potting materials include epoxy and urethane. If desired, the curing of the potting material around the electronic device may be accelerated by preheating the mold to an elevated temperature which is above ambient, but below the temperature at which damage to the electronic monitoring device will occur. A preferred temperature is about 80° C. After the epoxy has been cured, the mold halves  52 ,  54  are separated, yielding a rigid, encapsulated tag  30 . In a preferred embodiment,  FIG. 5 , a battery  68  which provides power to the tag  30  is attached to the tag to form a tag assembly  70 . Although the battery is shown as held in position contacting the electronic monitoring device  34  by threading, any suitable means of attaching the battery to the circuit board so that the battery may be removed is acceptable. Alternate means of attaching the battery to the circuit board may include spring clips, lock pins or other hold down devices. 
   The tag assembly  70  may be of any configuration which allows it to fit within the contour of the cavity  16 , both of which are cylindrical in the embodiment shown in FIG.  1 . In the preferred embodiment, tag assembly  70  is assembled into the cavity  16  as shown in FIG.  6 . Since the rubber patch assembly can be attached to the tire using an air cure or low temperature cure, it is understood that the sequence of assembling the tag assembly into the rubber patch housing may be accomplished either before or after the rubber patch is attached to the tire innerliner. Tag assembly includes an optional antenna  72 . Housing  14  includes slots  74  to receive the antenna. After the tag assembly  70  is in place within the cavity, at least one lock pin  76  is inserted through a first aperture  78  in housing  80 . As shown in  FIG. 6 , lock pin  76  is positioned across at least a portion of the top of tag assembly  70 , preferably through a second aperture  82  on the opposite side of the housing. Alternatively, lock pin  76  could extend into the potting of tag assembly  70 . 
   The positioning of the lock pin is not critical, so long as lock pin  78  positively secures tag assembly  70  into position within cavity  16  and prevents tag assembly  70  from moving. After insertion through the housing  14 , the lock pin  76  is deformed so that it will not back out of the apertures. Tag assembly  70  may then be removed from the housing by simply drilling lock pin  76  out of aperture  78 . 
   Many different methods of positively locking the tag assembly can be accomplished. By way of illustration of equivalent locking techniques, instead of a locking pin, a self-tapping screw may be inserted through aperture  78  and screwed into position within the potting. 
   In a second embodiment of the present invention, illustrated in  FIG. 7 , tag assembly  70  has a profile corresponding to that of cavity  16 . Tag assembly is assembled into the bottom of cavity  16 . Housing  14  extends above tag assembly  70  after it has been assembled into cavity  16 . Insert  90 , also having a profile corresponding to cavity  16  is the inserted into the housing until the bottom  96  of insert  90  contacts the top of tag assembly  70 , thus securing it in place. Insert  90  is then locked in place. This may be accomplished by any convenient method, such as by extending a locking pin through insert  90  and deforming it, or by utilizing locking tabs to secure insert  90  to patch assembly  10 . However, in the preferred embodiment shown in  FIG. 7 , insert  90  includes external threads  94  which correspond to internal threads  92  formed in housing  14 . Insert  90  is screwed into housing  14  until the insert bottom  96  contacts the top of tag assembly  70 . Of course, regardless of the method used to secure tag assembly  70  in place in cavity  16 , tag assembly is readily removable for battery replacement or replacement of the entire assembly  70  by removing insert  90  from housing  14 . It is obvious that tag assembly  70  may be reinserted after accomplishing repair or replacement, or after retreading of the tire by simply replacing insert  90  over the reassembled tag assembly and locking insert  90  in place as discussed above. 
   In a third embodiment of the present invention,  FIG. 8 , a tag assembly of  110  including the components previously discussed, is formed with external threads  112  in the potting. Rubber patch assembly  120 , also similar to rubber patches previously discussed, includes internal threads  122  formed in housing  124  which mate with the external threads  112  of tag assembly. Tag assembly  110  is assembled into rubber patch assembly  120  by simply screwing tag assembly  110  into housing  124 . While this arrangement normally should be sufficient to lock tag assembly to rubber patch assembly, an optional locking pin or set screw may be added to the assembly to lock the internal and external threads in place and prevent tag assembly from backing out of the housing of rubber patch assembly  120 . 
   From the foregoing, other embodiments should be obvious. For example, a slot and spline arrangement not shown may be used to lock the tag assembly into the housing. Mating slots and splines are formed in the potting of the tag assembly and in the housing. After placing the tag assembly into the housing, an optional locking device as previously discussed may be used to prevent the tag assembly from backing out of the housing. 
   In yet another embodiment, depicted in  FIG. 9 , tag assembly  130  is formed with at least one tab  132 , while housing  142  of rubber patch  140  is formed with slots  144  corresponding to tabs on tag assembly  130 . At the bottom of the slots is a ring  146  having an internal diameter corresponding to the slot depth on the housing and extending from each slot at least partially around the housing bottom. Once tabs  132  of tag assembly  130  are mated with slots  144  of rubber patch and tag assembly  130  is inserted into housing  142 , tag assembly  130  is rotated sufficiently so that tabs  132  are rotated into ring  146  and no longer are aligned with slots  144 , locking the tag assembly to rubber patch  140 . An optional locking mechanism, such as discussed previously, may be added to lock tag assembly  130  to rubber patch  140  if there is a concern about rotation of tag assembly  130  with respect to rubber patch assembly. Another method of locking tag assembly  130  to rubber patch  140  is to insert a piece of material (not shown) into at least one slot  144 , for example by an interference fit between the slot and the material, so that in the event of rotation of the parts with respect to one another, even if the tabs  132  and slots become aligned, tabs  132  are prevented from moving axially in the slot. It is obvious that an equivalent structure can be achieved by reversing the arrangement of slots  144 , ring  146  and tabs  132  between tab assembly  130  and housing  142 . In this arrangement, at least one tab is formed in the housing and at least one slot corresponding to tabs is formed in tab assembly. 
   While in accordance with the patent statutes, the best mode and preferred embodiment has been set forth above, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.