Abstract:
Apparatus for mounting an electronic tag within a tire includes a patch having a first side for mounted location against an inner liner of the tire, a second opposite side, and a socket member extending into the second side. A housing is provided having an internal tag receiving chamber defined by sidewalls and an elongate assembly bolt extends through the housing passageway and into the patch socket member to attach the housing to the patch. A remote end of the assembly bolt protrudes through the patch and carries a temperature sensor that engages the tire inner liner and transmits temperature data to electronic data transmission means within the housing. A lower portion of the housing sidewall is adapted to angle inward toward the lower housing end and a pressure measuring device is mounted within the angled sidewall portion. The housing comprises a cup and a top member, the top member covering the cap and including a dependent skirt portion engaging the patch second surface along a lower edge to seat the housing upon the patch. The cup and top components are preferably formed of a rubber matrix.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to pressure and temperature measurements of a tire and, more specifically, to apparatus for measuring off-the-road tire temperatures and pressures for diagnosing any impending failure thereof. 
   BACKGROUND OF THE INVENTION 
   In order to transport bulk materials, such as coal, iron ore, and other minerals, the mining and other industry uses Off-The-Road (OTR) vehicles that may weigh up to 670 tons when fully loaded. As a result, extremely high internal stresses are imposed on the tires of such vehicles in the course of their daily use. Such internal stresses are proportional to the speed at which the vehicle is driven and excessive speed can result in a destruction of the vehicle tires. Consequently, the speed of an OTR vehicle is controlled on the basis of the operator&#39;s perception of the condition of the tires at any given time. Accurate information regarding the tires, particularly its pressure and temperature, is therefore essential in order to assist the operator and avoid damage to an OTR vehicle&#39;s tires. It is, therefore, advantageous to provide a tag for measuring OTR vehicle tire pressure and temperature and communicating such information to the operator. 
   Because of the extremely rigorous operational and environmental conditions in which OTR vehicle&#39;s operate, a suitable tag must, in addition to being accurate, be durable and of high structural and operational integrity. In the environment in which the OTR vehicles operate, it is not uncommon for foreign material to invade the tire air cavity. Such material along with anti-corrosive liquid can be abrasive and cause damage to the tag transmitters and contaminate the electronics, leading to premature failure of the tag. 
   Various attempts have been made to monitor the tire condition in an OTR vehicle and to provide operators with timely information concerning such conditions. For example, U.S. Pat. No. 6,255,940, incorporated herein by reference, teaches apparatus for monitoring tire condition and includes a tag housing and a patch having a first side for mounting against the inner liner of the tire and a second, arcutately-shaped side and an internally threaded socket member. A threaded steel assembly bolt is made to extend from a side of the tag housing and into the threaded socket of the patch. The tag housing includes means for measuring temperature within the tire cavity through measurement of the temperature of the steel assembly bolt. Additionally, pressure is measured by the tag and the temperature and pressure data are transmitted to an external processor and display. 
   While the apparatus in the aforesaid patent works well and represents an advancement over prior art, the industry remains in need of apparatus for a tire monitoring system of still greater durability and resistance to damage from environmental contaminants. Moreover, still greater accuracy than that achieved heretofore in the measurement of temperature and pressure conditions within an OTR tire is desired. Deducing the temperature of the tire cavity through measurement of the apparatus bolt, as taught in the prior art, is inherently less than precise. 
   SUMMARY OF THE INVENTION 
   The present invention addresses the needs of the industry by the provision of apparatus for mounting an electronic tag within a tire. The apparatus includes a patch having a first side for mounted location against an inner liner of the tire, a second opposite side, and a socket member extending into the second side. A housing is provided having an internal tag receiving chamber defined by sidewalls and an elongate assembly bolt formed of thermally non-conductive material extends through the housing passageway and into the patch socket member to attach the housing to the patch. A remote end of the assembly bolt protrudes through the patch and carries a temperature sensor that engages the tire inner liner and relays temperature data to the tag electronics within the housing for transmission to an external reader. A lower portion of the housing sidewall is adapted to angle inward toward the lower housing end and a pressure measuring device is mounted within the angled sidewall portion. The housing comprises a cup and a top member, the top member covering the cap and including a dependent skirt portion engaging the patch second surface along a lower edge to seat the housing upon the patch. The cup and top components are preferably formed of a material impervious to structural degradation over time and the penetration of contaminants or ambient fluids into the housing chamber. 
   Descriptions 
   “Bead” generally means an annularly shaped member located within either of the inner radial end portions of a tire. 
   “Bead Portion” generally means either of the opposed radial inner end portions of the carcass of a tire including a bead, the portion of a ply which is looped about the bead, and the rubber material surrounding the bead and ply portion. 
   “Carcass” generally means the tire structure including the beads and ply, but excluding the belt structure, undertread over the ply and the tread. 
   “Equitorial Plane” means the imaginary plane extending perpendicular to the axis of rotation of the tire and passing through the center of the tread; or the plane containing the circumferential centerline of the tread. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described by way of example and with reference to the accompanying drawings in which: 
       FIG. 1  is a partial, one-half, cross-sectional view of a pneumatic tire having mounted therein an electronic tire tag according to the invention; 
       FIG. 2  is an enlarged transverse cross-sectional view of the details of the tag of  FIG. 1 , showing the encapsulating and mounting structures thereof; 
       FIG. 3  is top plan view of the apparatus in the assembled condition; 
       FIG. 4  is a transverse sectional view through the assembled apparatus taken along the line  4 — 4  of  FIG. 3 ; and 
       FIG. 5  is a bottom plan view of the cup component of the housing assembly. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows half of a partial transverse cross-sectional view of a typical pneumatic tire  10  for an OTR vehicle, mounted on a wheel rim  12  thereof. Since the tire  10  is generally toroidally-shaped and symmetrically arranged with respect to an imaginary equatorial plane  14 , the transverse cross-section of the other partial half of the tire  10  includes like or corresponding parts, and it should be understood that the explanation applies to the other half of the tire  10  as well. 
   The tire  10  has a cavity  16  for receiving pressurized air when the tire  10  is mounted on the wheel rim  12 . The tire  10  generally comprises a central tread  17  having opposite sides generally indicated by the numeral  18 . In addition, the tire  10  includes a plurality of radially-extending belts  20  and  22  that are centrally disposed radially-inward of the tread  17 . The belts  20 ,  22  have opposite side edges  23 ,  24 , respectively. A carcass  25  is included opposite sidewalls  27  which merge with radially extend inward from opposite tread sides  18  to form therewith opposite shoulder portions generally indicated by numeral  28 . The carcass includes opposite bead portions  29  at the radial inner ends thereof. Each of the bead portions  29  includes an annularly-shaped bead  29   a  therein for urging the bead portions  29  into abutment with the wheel rim  12 . Moreover, the carcass  25  includes one or more plies  30  radially disposed inwardly of the belts  20 ,  22 . The ply  30  radially extends between and is looped about the opposed beads  29   a . Adjoining the carcass  25  is a radially extending innerliner  35  disposed inward of the ply  30 . While the tire  10  is a radial tire, the subject invention can be utilized in biased tires as well. 
   According to the invention, an electronic tire tag  40  ( FIGS. 1 and 2 ) is preferably fixedly secured to the inner liner  35  of the tire  10  at an area thereof located substantially directly radially inward of a side edge  23  of the belt  20  that is closest to the innerliner  35  of the tire  10  and adjacent to a shoulder portion  28  of the tire  10 . Other locations of the tag are also possible in accordance with the invention. Since the tag  40  is preferentially located adjacent an area of the innerliner  35  where the tire  10  is thickest and least able to dissipate heat, the temperature measurements taken at this location are the most closely related to determining whether or not an internal breakdown of the tire  10  is imminent. The breakdown is typically due to internal stresses causing delaminations of the belts  20 ,  22 , ply  30  and surrounding vulcanized rubber material  36  at the shoulder portions  28  of the tire  10 . 
   The electronic tag  40  ( FIGS. 1 and 2 ) generally comprises a micro-controller  42  and a temperature sensing device  44  electrically connected thereto by conductor  46  for sampling the temperature of the innerliner  35  of the tire  10 . Further, the tag  40  generally includes pressure sensing structure  48  electrically connected to the micro-controller  42  for sampling the air pressure within the tire  10 . The tag  40  further includes a pair of printed circuit boards  50  electrically connected to the microcontroller  42 . The boards  50  include a transmitter (not shown) for transmitting relevant information concerning the respective samplings taken by the temperature and pressure sensing devices  44  and  48 . 
   A tag electronically functional and suitable for use in conjunction with the subject invention is as shown in U.S. Pat. No. 6,225,940B, incorporated by reference herein. The tag  40  preferably includes a battery  51  that is conventionally electrically connected to the micro-controller  42  for energization thereof. The pressure sensing device  48  is of a type commercially available. By way of example, without intending to limit the invention, a pressure sensor suitable for use is sold by Measurement Specialties, Inc., 1871 N. Capitol Avenue, San Jose, Calif. 95132 and is commercially designated as Part No. 85-100A-OP. The transmitter structure on boards  50  preferably includes an antenna (not shown). 
   The tag further includes structure for connecting the tag  40  to the tire  10 . The connecting structure preferably includes a bolt  62  and a threaded portion  64  thereof extending from the tag  40 . A central axial passageway  66  extends through the bolt  62  from a remote tapered tip  67  to an internal bolt end  68 . The tag  40  is preferably entirely encapsulated in an encapsulation material such as a potting epoxy or a mixture of epoxy and glass beads coated with urethane. 
   The encapsulated tag ( FIG. 2 ) is preferably not directly connected to the innerliner  35  of the tire  10 . Rather, a vulcanized rubber patch  70 , having embedded therein an internally threaded nut  71 , is affixed to the innerliner  35  of the tire  10 . In one embodiment, the patch  70  has a lens-shaped transverse cross-section, defined by a substantially flat side  72  having a generally circular perimeter connectable to the innerliner  35 . Patch  70  further includes an arcuate shaped inner side  73  disposed on the opposite side of the patch. The arcuate patch side  73  includes a medial portion  74  of substantially planar configuration. Side  72  of the patch  70  is dimensioned for disposition in abutment with the substantially arcuate shaped area of the innerliner  35 . Side  73  of the patch  70  faces the interior of the tire  10 . The encapsulated tag  40  has a substantially rectangularly shaped transverse cross-section and generally mounts against the substantially straight side  74 . The encapsulated tag  40  is connected to the patch  70  by threadably connecting the bolt  62  into the nut  71  of the patch  70 . 
   With reference to  FIGS. 1 ,  2 ,  3 , and  4 , the tag  40  includes a housing shell assembly generally indicated by numeral  80 . The assembly  80  comprises a top cover member  82  and a bottom cup member  84 . Preferably, members  82 ,  84  are molded separately by conventional means and constructed of a rubber matrix such as butyl rubber. It is common for foreign material and anti-corrosive liquid to invade a tire cavity. Heretofore, such material would migrate into the housing of a conventionally configured tag. Once within the housing, the material would contact transmitters or other electronic components and cause damage and premature failure. The rubber composition used in the creation of members  82 ,  84  is resilient and less prone to abrasion and cracking, thus making the assembly  80  less susceptible to liquid penetration. 
   The top cover member  82  is substantially cylindrical and comprises dependent peripheral side walls  86  merging into a top, generally planar, top surface  88 . The cup member  84  comprises upstanding peripheral sidewalls  90  and lower sidewall portions  92  that cant inwardly toward a central aperture  94  through a lower end of the cup member  84 . Thus, the upper portion of the cup member  84  is substantially cylindrical while the lower portion of cup member  84  is of a generally inverted conical configuration. The sidewalls  90  and lower sidewall portions  92  define an internal upwardly open central chamber  96 . Formed to extend into the chamber  96  from the sidewalls  90  are molded shoulders  98 . Shoulders  98  serve to support and register the circuit board  50  within the cup chamber  96 . The cover member  82  and the cup member  84  are circular in cross-section with the cover member closely fitting over the cup member as seen best from FIG.  2 . In the assembled condition, the sidewalls  86  of the cover member  82  are disposed to the outside and closely adjacent the sidewalls  90  of the cup member  84 , with the top surface  88  of the cover member  82  enclosing the open side of the internal chamber  96 . 
   With reference to  FIGS. 2 and 5 , a generally circular socket or well  100  is formed within the canted inward sidewall portions  92  of the cup member  84  dimensioned for close receipt of the pressure sensing device  48 . The socket  100  is defined by inwardly extending molded perimeter flange  102  and socket floor  103 . At least one, and preferably multiple vent apertures  104  are formed to extend through the socket floor  103 . The pressure sensor  48  is seated within the well  100  and is sealed from the environment of the tire to eliminate the chance of contamination from anti-corrosive liquid in the tire cavity. The pressure sensor  48  is mounted within the well  100  such that it is preferably, but not necessarily, against the socket floor  103  and generally flush with the outside of the cup member sidewall portion  92 . The vent aperture(s)  104  extend through the socket floor  103  and are relatively small in diameter, for example on the order of 0.05 inch. The apertures  104  allow for accurate pressure sensing by the pressure sensor  48 . 
   The temperature sensor  44  is seated within the axial passageway  66  of the bolt  62  at the bolt tip  67 . Without limiting intention, a temperature sensor suitable for incorporation into the subject embodiment is sold by Dallas Semiconductor Corp., 4401 South Beltwood Parkway, Dallas, Tex. 75244 under the part No. DS18820X. The sensor  44  is connected to the electronics on board  50  by means of the conductor  46  extending upwardly through the passageway  66  and exiting from the inward bolt end  68 . The bolt  62  is preferably a ½ inch diameter hollow bolt formed of a relatively thermally non-conductive material such as Torlon or nylon. The bolt threaded portion  64  passes through the cup member hole  94  and threadedly engages the nut  71  entrapped within the patch  70 . Nut  71  is likewise formed preferably of a relatively thermally non-conductive material such as Torlon or nylon. The thin layer of material in patch  70  beneath the nut  71  is removed to expose an underside of the nut. The bolt portion  64  is of sufficient length to protrude through the nut  71  and exit the underside  72  of the patch  70  in order to allow the tip  67  of the bolt to contact the innerliner  35  of the tire. The bolt  62  is screwed down until it touches or penetrates the innerliner  35  of the tire. The temperature sensor  44 , disposed within the tip, likewise physically contacts the tire inner liner. Such contact between the temperature sensor  44  and the tire innerliner  35  greatly increases the validity of the temperature reading. Alternative systems for measuring the temperature of the tire do so in an analogous manner by measuring the air cavity temperature. Such a reading may be significantly different than the actual tire temperature obtained through the practice of the subject invention. The bolt  62 , it will be appreciated, thereby achieves the dual purposes of mechanically connecting the housing cup member  84  to the patch  70  and carrying the temperature sensor into direct contacting engagement with the tire innerliner  35  for accurate temperature measurement. 
   As described above, the cover member  82  and the cup member  84  are separately molded from a rubber based material such as nitrol rubber. After curing, the holes  104  for the pressure sensor  48  and the through hole  94  may be punched in the cup member  84  at the locations indicated. Alternatively, the holes  104  and  94  may be molded in directly with the manufacture of cup member  84 . The cup member  84  may then be used as a potting shell in which the electronic components are placed. Specifically, printed circuit board  50  and the electronic components carried thereon are inserted within chamber  96  and placed upon the molded shoulders  98 . The pressure sensor  48  is positioned within the socket  100  with electrical connection established between the sensor  48  and the transmitter on board  50 . The bolt  62  is likewise located within the chamber  96  with the bolt threaded portion or shaft  64  extending through the housing hole  94  and the patch in the manner described previously. A potting epoxy is then poured into the cup member  84  over the electronic components to secure and protect them. 
   After the epoxy has cured, a fast-dry rubber cement is added to the outside of the cup member sidewalls  90  and the inside of the top shell sidewalls  86 . These surfaces may be molded with a textured finish to increase the adhesion with the rubber cement. Once the cement has dried, a rubber gum strip is wrapped once around the bottom cup member  84  and the top cover member  82  and the two halves are then stitched together to further increase the bond therebetween. 
   The resultant housing  80 , thusly formed and assembled, represents an enclosure relatively impervious to penetrating outside contaminants. The rubber composed top and bottom components  82 ,  84  can flex with the operation of the OTR vehicle tire without cracking. The electronics contained within the housing  80  are thereby protected. From  FIGS. 2 and 4 , it will further be appreciated that the placement of the pressure sensor  48  within the canted sidewall portions  92  of the cup member  84  creates an air gap between the sensor  48  and the top surface  74  of the patch  70  post assembly. The air gap so created is exposed to the tire cavity and, through vent apertures  104 , allows the pressure sensor to accurately read the cavity air pressure. The bolt shaft portion  64 , carrying temperature sensor  44  within tip  67 , is in direct contact with the tire liner. Accurate and direct temperature data is thereby facilitated and may be conveyed to the transmitter within the tag shell and transmitted to an external reader. It will also be noted that the bolt  62  and patch nut  71  are formed thermally isolates the temperature sensor  48  and minimizes heat loss from the region of the tire engaged by the sensor  48 . Accuracy in the temperature reading is enhanced thereby. 
   As seen from  FIGS. 1 and 2 , the lower portion of the cover member sidewalls  86  creates a peripheral skirt surrounding the lower portion of the tag housing  80 . The presence of the skirt serves to further protect the pressure sensor  48  mounted within sidewall portion  92 . Finally, the subject housing  80  provides with a minimal number of relatively inexpensive to manufacture and assembly components, a method for mounting an electronic tag within an OTR vehicle tire that is durable, resistant to contaminant infiltration, and functionally advantageous in obtaining accurate temperature and pressure data from the tire. 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.