Abstract:
An attachment between a monitoring device and an innerliner of a tire includes the use of an epoxy adhesive that bonds the monitoring device directly to the inner surface of the innerliner of the tire. The innerliner is first roughened in a manner that provides a roughened portion of the innerliner without removing the entire thickness of the innerliner. The entire thickness of the innerliner is not removed because the innerliner is preferably more than {fraction (1/16)} of an inch thick. The thickness of the innerliner allows the rigid cured epoxy to bond the monitoring device to the inner surface of the innerliner while allowing the innerliner to flex with the tire so as to not break the seal between the rigid epoxy and the innerliner. The monitoring device is preferably located at a low flex area of the tire to help avoid the problem of the innerliner flexing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional application of currently pending U.S. patent application Ser. No. 09/206,042 titled Method of Attaching Sensitive Electronic Equipment to the Inner Surface of a Tire; the disclosures of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates generally to pneumatic tires and devices that are adhered to pneumatic tires to monitor the conditions of the tires. More particularly, the present invention is related to the connection of the monitoring device to the tire. Specifically, the present invention relates to the method of attaching and the attachment of a monitoring device to the inner surface of a pneumatic tire using a surface preparation and an adhesive.  
           [0004]    2. Background Information  
           [0005]    It is desired in the art to monitor the conditions of tires while they are installed and in use on a particular vehicle. It is particularly desirable to measure tire wear, internal temperature, and internal pressure. Other desirable measurements may be the number of tire rotations that have occurred in given time. These measurements are preferably capable of being taken while the tire is in use without having to remove the tire from the vehicle or otherwise interrupt the use of the vehicle to take the measurements. It is particularly desirable to monitor the conditions and statistics on large off-the-road truck tires because the off-the-road tires are expensive and subject to harsher conditions than typical passenger car tires. The off-the-road tires on large trucks and other vehicles also must be regularly maintained to maximize vehicle efficiency. It is also desirable to monitor the tires of certain on road trucks and buses.  
           [0006]    Numerous types of such monitoring devices are known in the art. One type of known monitoring device uses a passive integrated circuit embedded within the body of the tire that is activated by a radio frequency transmission that energizes the circuit by inductive magnetic coupling. Other prior art devices used for monitoring tire conditions include self-powered circuits that are positioned external of the tire, such as at the valve stem. Other active, self-powered programmable electronic devices are disclosed in U.S. Pat. Nos. 5,500,065, 5,573,610, 5,562,787, and 5,573,611 which are assigned to the assignee of the present application.  
           [0007]    One problem common to each of these monitoring devices is the problem of attaching the monitoring device to the tire. The attachment problem is difficult when the monitoring device is attached to the inside surface of the tire, the outside surface of the tire, or imbedded within the body of the tire. The attachment problem is difficult because the forces on the electronic device are significant and numerous. Tires not only are subjected to rotational forces when the vehicle is moving but also are subjected to various impact forces when the tire contacts bumps or surface irregularities. The attachment of the monitoring device to the tire must be strong enough and secure enough to maintain the position of the monitoring device with respect to the tire while experiencing all of these forces while also protecting the monitoring device from damage resulting from these forces.  
           [0008]    Another problem with the attachment of a monitoring device to a tire is that the tire must be balanced about its rotational axis to efficiently perform. The monitoring device itself already adds weight to the tire that may require the tire to be counterbalanced. It is thus desired to minimize the weight of the attachment so that additional counterbalancing weights do not have to be added to the tire. It is thus desired to provide an attachment that is strong and secure while being small and lightweight.  
           [0009]    Another problem experienced with attaching a monitoring device to a pneumatic tire is that the surface where the monitoring device is being anchored is often not stable. Tires are designed to flex and stretch to accommodate various pressures and forces. The attachment of the monitoring device to the tire must accommodate the movement and stretching of the tire surface where the monitoring device is connected. Such accommodation must last throughout the life of the tire and function at a wide range of temperatures and pressures. In the patents listed above, the monitoring devices are held in a pocket that is formed with a piece of material connected to the innerliner of the tire. Although these pockets function for their intended purposes, the construction of the pockets increases the counterbalancing problem and increase the complexity of the assembly steps.  
           [0010]    A further problem experienced in connecting a monitoring device to a pneumatic tire is that tires are manufactured on automated assembly lines. The attachment method must be able to be relatively easily engineered into the existing automated tire assembly lines to be useful. As such, the method of attaching the monitoring device to the pneumatic tire should minimize any manual steps or steps that require precise component manipulation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0011]    In view of the foregoing, it is an objective of the present invention to provide an attachment that may be used to connect a monitoring device to the inner surface of a pneumatic tire that overcomes each of the problems experienced in the art.  
           [0012]    Another objective of the present invention is to provide an attachment that maintains the connection between the monitoring device and the tire when the tire experiences predictable rotational and shock forces.  
           [0013]    Still another objective of the present invention is to provide an attachment for connecting a monitoring device to a pneumatic tire that is lightweight so that the tire does not have to be excessively counterbalanced.  
           [0014]    Yet another objective of the present invention is to provide an attachment for connecting a monitoring device to the interior of a pneumatic tire that accommodates the stretching and movement of the inner surface of the pneumatic tire.  
           [0015]    A further objective of the present invention is to provide a method for attaching a monitoring device to the interior surface of a pneumatic tire that is easy to perform and may be performed by automated machinery in a tire manufacturing line.  
           [0016]    A further objective of the present invention is to provide a method for attaching a monitoring device to the inner surface of a pneumatic tire that may be used at a variety of locations inside the pneumatic tire.  
           [0017]    A further objective of the present invention is to provide a method for attaching a monitoring device to the inner surface of a pneumatic tire that does not require additional structural elements to be inserted into the tire or attached to the tire to secure the monitoring device.  
           [0018]    An additional objective of the present invention is to provide an attachment and method for attaching a monitoring device to the interior surface of a pneumatic tire that is of simple construction, that achieves the stated objectives in a simple, effective, and inexpensive manner, that solves the problems, and that satisfies the needs existing in the art.  
           [0019]    These and other objectives and advantages of the present invention are achieved by an attachment that includes an adhesive characterized by high viscosity at room temperature and capable of curing at 100° C. and lower, the adhesive adhering a monitoring device to the innerliner of a pneumatic article where the innerliner is at least 0.06 inch thick.  
           [0020]    Other objectives of the present invention are achieved by a method for adhering a monitoring device to a tire including the steps of selecting a portion of the innerliner of the tire where the monitoring device will be connected; roughening the selected portion of the innerliner; applying an adhesive to at least one of the monitoring device and roughened portion; placing a monitoring device on the roughened portion of the innerliner; and curing the adhesive. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0021]    The preferred embodiment of the invention, illustrative of the best mode in which Applicants contemplated applying the principles of the invention, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims.  
         [0022]    [0022]FIG. 1 is a sectional view of a pneumatic tire with a monitoring device attached to the innerliner of the pneumatic tire by the method of the present invention;  
         [0023]    [0023]FIG. 2 is a perspective view of a monitoring device attached to the innerliner of the pneumatic tire by the method of the present invention;  
         [0024]    [0024]FIG. 3 is a perspective view of the monitoring device lifted away from the innerliner to show the treatment of the innerliner and the monitoring device according to the concepts of the present invention;  
         [0025]    [0025]FIG. 4 is a plan view of an unencapsulated monitoring device; and  
         [0026]    [0026]FIG. 5 is an enlarged sectional view similar to FIG. 1 showing an encapsulated monitoring device attached to the innerliner of a pneumatic tire. 
     
    
       [0027]    Similar numbers refer to similar elements throughout the specification.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    A pneumatic article in the nature of a vehicle tire is depicted in the drawings and is indicated generally by the numeral  10 . Tire  10  is of known construction and includes a pair of sidewalls  12  which extend outwardly from a pair of bead rings  14 . A tread package  16  is located at the outer ends of sidewalls  12 . Tire  10  further includes a plurality of cords or belts  18  that provide structural strength to tire  10 . Tire  10  is supported on a rim  20  in a manner that provides an inner chamber  22  between tire  10  and rim  20 . Inner chamber  22  is filled with pressurized air when tire  10  is in use to allow tire  10  to support the weight of the vehicle on which tire  10  is used. The pressurized air in chamber  22  is maintained in tire  10  by an innerliner  24  that is substantially impervious to air. Innerliner  24  is of known construction and includes not only butyl rubber but also chloro-butyl rubber, bromo-butyl rubber, and combinations thereof with up to less than 50% natural rubber. It is known in the tire building art that it is difficult to bond to innerliner  24 .  
         [0029]    The body of tire  10  is formed from a flexible and somewhat compliant rubber that flexes and stretches when tire  10  is in use. The movement of tire  10  is also transferred to innerliner  24  complicating the problem of bonding an article to the inner surface  26  of innerliner  24 . The structure of tire  10  results in areas of tire  10  that flex more than other areas of tire  10 . The areas that flex the least are the areas closest to rim  20 . These areas are the low flex areas  28  that extend approximately 25% up sidewalls  12  and in some tire  10  configurations extends up to 50% of the height of sidewall  12 . In most tire  10  configurations, low flex area  28  is 25% of the height of sidewalls  12 .  
         [0030]    It is also known in the art that innerliner  24  is formed in different thicknesses for different tires  10 . The thickest innerliners  24  are used on off-the-road tires that are used with large vehicles. The thickness of off-the-road innerliners  24  are typically greater than at least 0.06 inch and are frequently greater than ¼ of an inch. Many truck and bus radial tires have innerliners greater than at least 0.06 inch whereas most passenger tires have an innerliner  24  that is less than 0.06 inch thick.  
         [0031]    An objective of the present invention is to provide an attachment  30  that may be used to connect a monitoring device  32  to innerliner  24  of tire  10  in a manner that securely holds monitoring device  32  in position when tire  10  is used throughout the life of tire  10 . Monitoring device  32  may be any of a variety of monitoring devices known in the art. In the embodiment of the invention depicted in the drawings, monitoring device  32  is an active electronic monitoring device that includes a microprocessor  34 , a pressure sensor  36 , and a battery  38  such as shown and described in U.S. Pat. Nos. 5,562,787, 5,573,611, 5,500,065, and 5,573,610, the contents of which are incorporated herein by reference. Each of these elements may be supported on a board or substrate  40  and connected to an antenna  42 . It is desired in the art to encapsulate monitoring device  32  in a structurally stable housing  44  that may be a substantially rigid epoxy. Monitoring device  32  includes a bottom surface  46  that is used to bond monitoring device  32  to inner surface  26  of innerliner  24 .  
         [0032]    In accordance with another objective of the present invention, the method of attaching monitoring device  32  to innerliner  24  includes the following steps. A location on innerliner  24  in low flex area  28  is first selected to connect monitoring device  32 . The selected location is first roughened to provide a roughened surface  50  that will accept the adhesive used in the present invention. This roughening may be performed by a buffing tool such as a tungsten carbide tool, sand blasting or by a variety of other known tools. Inner surface  26  of innerliner  24  is roughened by removing about 1 mil of material but preferably about 2 mils to remove the cure skin of innerliner  24  that is formed when tire  10  is cured. Roughened area  50  is then cleaned with an innerliner cleaner or a rubber cleaner such as cleaner fluid order no. 16-480 supplied by Patch Rubber Company a division of Myers Industries, Akron, Ohio. The cleaner may also be any degreasing solvent such as a 1, 1,2-trichloroethylene or heptane.  
         [0033]    Roughened area  50  is then primed with a positive chlorine compound such as any chlorinated primer. A 3% trichlorotriazinetrione solution in butyl acetate is preferred.  
         [0034]    Generally, any conventional rubber primer known to the art and to the literature can be utilized. Heretofore, typically chlorine or chlorine-containing compounds have been utilized to prime rubber. That is, a halogen or preferably a chlorine donor compound is utilized. A preferred rubber primer of the present invention is trichlorotriazinetrione which can be applied to the rubber as by brushing, spraying, etc., desirably in a multiplicity of coats. For example, a 3 percent trichlorotriazinetione solution in butyl acetate can be applied in a plurality of coatings such as three, allowing several minutes, e.g., 5 minutes drying time between coatings. Immediately after application of the last coating, its surface can be wiped off with RYMPLECLOTH® to remove by-products such as oils which migrate to the surface. The rubber surface can then be allowed to dry at ambient temperature for about 10 to 15 minutes.  
         [0035]    Other rubber primers include the various N-halohydantoins, the various N-haloamides, the various N-haloimides, and combinations thereof. Examples of various desirable N-halohydantoins include 1,3-dichloro-5, 5-dimethyl hydantoin; 1,3-dibromo-5,5-dimethyl hydantoin; 1,3-dichloro-5-methyl-5-isobutyl hydantoin; and 1,3-dichloro-5-methyl-5-hexyl hydantoin. Examples of N-haloamides include N-bromoacetamide and tetrachloroglycoluril. Examples of N-haloimides include N-bromosuccinimide and the various chloro substituted s-triazinetriones, commonly known as mono-, di-, and trichloroisocyanuric acid. The various mono-, di-, or tri-chloroisocyanuric acids, or combinations thereof are a preferred rubber primer with trichloroisocyanuric acid being especially preferred. A three percent by weight trichloroisocyanuric acid solution in butyl acetate is available from Lord Corporation as Chemlok 7707.  
         [0036]    The various N-halohydantoins, N-haloamides, and N-haloimide rubber primers usually exist in solid form. They are readily soluble in polar solvent such as acetone and can be applied in liquid form. Application of these rubber primers generally occur at ambient temperatures. Application can be in any conventional manner as through brushing, spraying, and the like. A typical amount of the N-halohydantoins, N-haloamides, and N-haloimide primer in the solvent, for example, ethyl acetate or acetone, is generally from about 0.1 to about 10 percent by weight based upon the total weight of said rubber primer and solvent, and preferably is from about 0.5 percent to about 5 percent. Of course, higher or lower concentrations can be utilized. This solvent system has been found to dry within a matter of minutes so that the adhesive can be applied shortly thereafter. It is thought that the rubber primer adds halogen groups, for example, chlorine to the cured rubber bead which activates the surface thereof, allowing the adhesive to adhere strongly to the cured rubber surface. Still additional rubber primers include various acetamides such as chloroacetamide, bromoacetamide, iodoacetamide, and the like. The thickness of the rubber primer layer can vary greatly and often is thin since it reacts with the rubber.  
         [0037]    The primer  48  is allowed to dry thoroughly on area  50  before monitoring device  32  is bonded to innerliner  24 . Bottom surface  46  of monitoring device  32  is then degreased using acetone on a purified cheesecloth such as RYMPLECLOTH® brand, sold by American Fiber and Finishing, Inc. of Westford, Mass., and may also be textured to increase its surface area and ability to bond.  
         [0038]    Monitoring device  32  is then bonded to area  50  using a suitable adhesive  52 . A preferred adhesive  52  is an epoxy adhesive such as the FUSOR® 310B/320 adhesive that is available from Lord Corporation of Cary, N.C. Adhesive  52  is generally characterized as having a high viscosity at room temperature and capable of curing at temperatures of 100° C. or lower. Adhesive  52  generally consists of essentially epoxy and amine having a ratio of 2.5 parts epoxy to one part amine curative. Adhesive  52  may be spread on bottom surface  46  and area  50 . Monitoring device  32  is then placed on area  50  with sufficient pressure to squeeze excess adhesive  52  out from under monitoring device  32 . The excess adhesive  52  is removed and monitoring device is held in place by a suitable device such as a clamp or a piece of tape (not shown). Monitoring device  32  is held in place and adhesive  52  is allowed to cure for  16  to 24 hours. When a faster cure is desired, heat can be applied to decrease the cure period. Adhesive  52  is substantially rigid when it cures.  
         [0039]    Rigid cured adhesives are not generally compatible with areas of tire  10  that move and flex when tire  10  is used. The above adhesive attachment system functions best when innerliner  24  is thick enough to allow inner surface  26  thereof to form a rigid bond with adhesive  52 . Innerliners  24  on off-the-road tires  10  and on many truck and bus tires are typically thick enough to allow attachment  30  to properly function. The rigid bond is not disturbed or broken when tire  10  and innerliner  24  flex as a result of forces on tire  10  because of the thickness of innerliner  24 . As can be perhaps best seen in FIG. 5, a significant portion  54  of innerliner  24  remains intact between roughened portion  50  and the body of tired  10 . Innerliner portion  54  flexes with tire  10  and functions as a buffer that accommodates the flexing and movement of tire  10  without breaking the bond between adhesive  52  and innerliner  24 . This accommodation is possible because innerliner  24  is thick in off-the-road and on certain truck and bus tires  10 . When the thickness of portion  54  of innerliner  24  is decreased, the flex and movement of the body of tire  10  have a better chance of breaking the rigid adhesive  52  that connects monitoring device  32  to innerliner  24 . When attachment  30  of the present invention is used on innerliner  24  of an off-the-road or truck and bus tires, innerliner portion  54  flexes enough throughout the life of tire  10  to prevent the bond between adhesive  52  and innerliner  24  from breaking throughout the life of tire  10 .  
         [0040]    Attachment  30  may also be used to connect monitoring device  32  to a different location on tire  10  such as the top surface  60  of tire  10  as depicted in the dashed lines shown in FIG. 1. A monitoring device  32  may be attached to top surface  60  when the configuration of tire  10  results in top portion  60  having low flex properties.  
         [0041]    Attachment  30  thus achieves the objectives of the present invention by providing a lightweight attachment that securely attaches monitoring device  32  to innerliner  24  throughout the life of tire  10 . Tire  10  thus does not have to be excessively counterbalanced because attachment  30  is lightweight. Attachment  30  may also be easily created by automated equipment on an existing automated tire manufacturing line because attachment  30  does not require additional structural elements to be added to tire  10  or monitoring device  32  such as the flaps of the prior art that cover monitoring device  32  to hold monitoring device  32  in a pocket. Likewise, attachment  30  further does not require monitoring device  32  to be embedded within the body of tire  10 .  
         [0042]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0043]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.