Abstract:
A patch and method for mounting an electronic monitoring device to the innerliner of a pneumatic tire is provided wherein the monitoring device is potted directly to an attachment patch. A frame is built on an attachment patch and the electronic monitoring device is disposed inside the frame. An encapsulation material is poured into the frame and cured to encapsulate the monitoring device directly against the patch. The patch may then be connected to the innerliner of a pneumatic tire.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional of U.S. application Ser. No. 09/539,856 filed Mar. 31, 2000; the disclosures of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention generally relates to a patch for mounting an electronic monitoring device to the inside surface of a pneumatic tire. More particularly, the present invention relates to a patch having an electronic monitoring device encapsulated directly to the patch so that it may be mounted to a tire with the patch.  
           [0004]    2. Background Information  
           [0005]    Monitoring the internal conditions of a pneumatic tire while the tire is in use on a vehicle is becoming increasingly desired in the art. One problem with this technology is protecting the relatively sensitive electronic monitoring device in the relatively harsh environment inside a tire. Another problem in the art is that the inner surface of a tire does not have surfaces where monitoring devices may be easily mounted in a secure manner.  
           [0006]    Protecting monitoring devices against harsh tire conditions has been accomplished in the past by encapsulating the monitoring device in an encapsulation or potting material. The potting material is poured over the monitoring device and fills the voids around the elements of the monitoring device. The material hardens and forms a protective block having a high modulus of elasticity around the elements of the monitoring device. The monitoring device is protected in this manner from the flexing and shock forces experienced in a pneumatic tire.  
           [0007]    Rubber patches are also known in the art to mount monitoring devices to the inner surface of a tire. The potted monitoring device has been connected to the patch with adhesive and the patch was then adhered to the innerliner of the tire. Other methods of mounting monitoring devices inside tires include forming a pocket in the tire and placing the monitoring device in the pocket. Other methods have placed a rubber patch over the top of the monitoring device to hold the monitoring device against the tire sidewall.  
           [0008]    One problem with these mounting solutions is the relatively high number of steps required to mount the monitoring device to the tire. Another problem is the number of times the monitoring device must be handled prior to mounting inside the tire. More importantly, the users of the monitoring devices desire stronger connections between the monitoring device and the tire.  
           [0009]    Another problem in the art occurs when the antenna is mounted in a different substraight than the monitoring device. In these situations, a connection must be formed between the monitoring device and the antenna. An example of this situation is shown in patent application Ser. No. 09/301,781 filed Apr. 29, 1999, which is owned by the Assignee of the present application. In this situation, a pair of connectors are used to form the direct physical connection between the antenna and the monitoring device. The problem that has occurred is that the adhesive used to bond the monitoring device to the patch is forced around the connectors sometimes flowing into the connectors. The art desires a solution to this problem by providing a method of connecting the encapsulated monitoring device to a patch while not fouling the connectors.  
         SUMMARY OF THE INVENTION  
         [0010]    In view of the foregoing, the present invention provides a mounted electronic monitoring device ready for mounting to the inside of the tire. The invention solves the problems in the art by directly potting the monitoring device to a rubber attachment patch to form an assembly.  
           [0011]    The assembly of the present invention includes a rubber patch having a first surface and a second surface. An electronic monitoring device is positioned adjacent the first surface of the patch with an encapsulation material surrounding at least a portion of the electronic monitoring device. The encapsulation material bonds with the patch to connect the encapsulated monitoring device to the patch.  
           [0012]    Another aspect of the invention preferably provides placing the connecting elements used to electrically connect the monitoring device to an antenna embedded within the patch in a location where the connecting elements are surrounded by the encapsulation material.  
           [0013]    Another aspect of the invention provides a method for creating the assembly wherein the number of handling steps and fabricating steps are minimized.  
           [0014]    The method of the present invention includes the steps of providing a patch having a first surface and a second surface, providing an electronic monitoring device adjacent the first surface of the patch, and encapsulating the electronic monitoring device directly to the first surface of the patch.  
           [0015]    An advantage of the invention is that the patch provides a secure mounting platform for the monitoring device that can be readily attached to the innerliner of a pneumatic tire.  
           [0016]    Another advantage of the invention is that the connection between the encapsulated monitoring device and the attachment patch does not rely on the strength of an adhesive to connect two separately formed elements.  
           [0017]    Another advantage of the invention is that the assembly protects the connections between the antenna and the monitoring device.  
           [0018]    Another advantage of the invention is that the connections between the monitoring device and the antenna do not become fouled by adhesive because the antenna and monitoring device are connected before the encapsulation material is poured into the mold.  
           [0019]    The foregoing advantages, construction, and operation of the present invention will become more readily apparent from the following description and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    The preferred embodiments of the invention, illustrative of the best mode in which applicant contemplated applying the principles of the invention, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended Claims.  
         [0021]    [0021]FIG. 1 is a sectional view of a pneumatic tire with an encapsulated monitoring device mounted to the innerliner of the tire with an attachment patch;  
         [0022]    [0022]FIG. 2 is a perspective view of the attachment patch with a potting frame assembled and placed on the upper surface of the attachment patch to surround the connectors for the antenna;  
         [0023]    [0023]FIG. 3 is a top plan view of FIG. 2;  
         [0024]    [0024]FIG. 4 is a sectional side view of the attachment patch and the potting frame with the electronic monitoring device positioned within the potting frame and the potting material being poured into the potting frame;  
         [0025]    [0025]FIG. 4A is a view similar to FIG. 4 showing an alternative embodiment of the invention where the potting frame is held against the attachment patch with pressure;  
         [0026]    [0026]FIG. 5 is a view similar to FIG. 4 showing the potting frame substantially filled with the potting material; and  
         [0027]    [0027]FIG. 6 is a view similar to FIG. 4 showing one embodiment of the final product.  
         [0028]    Similar numbers refer to similar parts throughout the specification. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    An assembly used to mount an electronic monitoring device to the inside surface of a pneumatic tire is indicated generally by the numeral  10  in the drawings. Assembly  10  preferably mounts the electronic monitoring device to the innerliner  12  of a pneumatic tire  14  so that the electronic monitoring device may monitor at least one engineering condition of tire  14 .  
         [0030]    Assembly  10  generally includes an attachment patch  20  and an encapsulated monitoring device  22 . Attachment patch  20  is used to connect encapsulated monitoring device  22  to innerliner  12  so that the monitoring device may perform its measurements. Attachment patch  20  includes a first side  24  configured to receive encapsulated monitoring device  22  and a second side  26  configured to attach to tire  14 . Attachment patch  20  is preferably fabricated from rubber. The rubber material is preferably vulcanized at a pre-selected temperature and a time sufficient to vulcanize the patch. The patch may be fabricated from 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 bromobutyl rubber. Another embodiment is a mixture of Styrene-Butadiene rubber (SBR) natural rubber. Typically, patches made from these rubber compositions may be cured by heating to a temperature of about 150 degrees Celsius and holding this temperature for about thirty minutes. The time and temperature may be modified as necessary to achieve sufficient curing of the patch for further manufacturing steps. The present invention also contemplates that patch  20  may be fabricated from a variety of other rubber mixtures known in the art. In addition to rubbers, patch  20  may be fabricated from other materials that may be adhered to tire  14  and accept encapsulated monitoring device  22  as described below. Thermoplastic Elastomers, Thermoplastic Urethanes or Thermoplastic Olefins may also be used to form attachment patch  20 .  
         [0031]    In one embodiment of the present invention, patch  20  carries an antenna  30  used to send and receive signals from encapsulating monitoring device  22 . Antenna  30  includes connecting elements  32  that protrude outwardly from the outer perimeter of patch  20 . Connecting elements  32  may be the male or female portion of a pin and socket-type connector. Connecting elements  32  are used to allow a monitoring package  34  to be plugged into antenna  30  after antenna  30  is cured into to patch  20 . Antenna  30  may be connected to patch  20  in a variety of other ways other than being cured into patch  20 . For instance, antenna  30  may be mounted on an outer surface of patch  20 . Monitoring package  34  may include the various sensors, controllers, memory devices, and power supplies necessary to perform the monitoring, transmitting, and receiving functions desired in the art. Monitoring package  34  must be connected to antenna  30  so that it may communicate with a data gathering device position outside of tire  14 . Monitoring package  34  also includes connecting elements  36  that are configured to mate with connecting elements  32  to form a direct electrical connection between monitoring package  34  and antenna  30 .  
         [0032]    In accordance with one of the objectives of the present invention, monitoring package  34  is encapsulated with an encapsulation material  40  directly to attachment patch  20  such that encapsulation material  40  is chemically and/or physically bonded to attachment patch  20 . In one embodiment of the invention, a frame  42  is fabricated and attached to first side  24  of attachment patch  20  by an adhesive  44  by applying adhesive  44  around frame  42  and ensuring a continuous bead of adhesive  44  around the perimeter. In one embodiment, a copper faced board having a thickness of 0.0345 inches is used to fabricate frame  42  by soldering the ends of four pieces together to form frame  42 . Another preferred material for forming frame  42  is glass-filled epoxy. In other embodiments, substantially any material may be used for frame  42  that will not interfere with a radio frequency signal if frame  42  remains connected to encapsulated monitoring device  22  as depicted in FIG. 5 and will not melt at the relatively high encapsulation or potting temperature. This temperature is typically 95-125 degrees Celsius.  
         [0033]    In another embodiment of the invention, frame  42  is held against first side  24  of attachment patch  20  by applying pressure as indicated by the numeral  46  against frame  42 . Pressure  46  maintains the correct position of frame  42  and prevents encapsulation material  40  from leaking out from between frame  42  and attachment patch  20 .  
         [0034]    Frame  42  is positioned on attachment patch  20  such that connecting elements  32  are disposed within frame  42 . The position of connecting elements  32  with respect to frame  42  is referred to as the connection location. It is an important aspect of the present invention to provide strength around the connection location so that the connections between monitoring package  34  and antenna  30  do not become loose with extended use of patch  10 .  
         [0035]    Depending on the material used to fabricate frame  42 , frame  42  may need to be sandblasted and degreased with solvent to clean the surface prior to performing the encapsulation steps of the present invention. For instance, the copper-faced board discussed above is preferably sandblasted and solvent washed to clean the surface. In addition, first side  24  of attachment patch  20  is preferably cleaned and primed with a 3% 1, 3, 5- T ri c hloro-s- t riazine t rione (Trichloroisocyanuric acid) (TCTT) solutions in butyl actetate. Side  24  was then wiped with a piece of Rymplecloth to remove the excess solvent and surface dirt. Patch  20  was then allowed to dry thoroughly. Adhesive  44  used around frame  42  is preferably FUSOR®D 320 (five parts by weight)/ 310  B (two parts by weight). FUSOR® is available from Lord Corporation. Adhesive  44  is then cured in an oven at 80 degrees Celsius for thirty minutes.  
         [0036]    Various other types of adhesives, frame materials, and surface preparations may be used without departing from the scope of the present invention. The specific materials and times described above are merely for the purpose of providing an exemplary embodiment of the invention and the best mode now known for performing the invention.  
         [0037]    Monitoring package  34  is then positioned within frame  42  so that it is suspended within frame  42  adjacent first side  24 . A chimney  48  may be attached to a sensor (such as a pressure sensor or a temperature sensor) on monitoring package  34  so that it may communicate with the atmosphere surrounding encapsulated monitoring device  22  after encapsulation material  40  is cured. Chimney  48  provides an air passage  50  to monitoring package  34 .  
         [0038]    After monitoring package  34  is positioned adjacent first side  24  and within frame  42 , encapsulation material  40  is introduced inside frame  42  to substantially surround monitoring package  34  and to fill substantially all voids around monitoring package  34  as depicted in FIG. 5. In the preferred embodiment of the present invention, encapsulation material  40  is a formulation including 100 gm STYCAST® 2651; 7 gm Catalyst 9; and 3 drops defoamer  88 . In another embodiment of the invention, encapsulation material  40  is a formulation including 110 gm STYCAST® 2651; 10 gm Phenyl Gycidyl Ether; 9.4 gm Catalyst 9; and 6 drops of defoamer  88 . These materials were mixed together at room temperature until thoroughly mixed. The formulation was degassed until foaming subsided. The formulation was then poured into frame  42  and allowed to cure in an oven at 55 degrees Celsius for thirty minutes. It was then post-cured at 80 degrees Celsius for thirty minutes. This process results in a strong encapsulated monitoring device  22  directly bonded to attachment patch  20 . Frame  42  may be left in position as depicted in FIG. 5 or removed as depicted in FIG. 6.  
         [0039]    Various other encapsulation materials  40  will also function with the present invention. For instance, a variety of epoxies and urethanes that are pourable and cure to a rigid tough material having a high modulus of elasticity may be used. It is desired that encapsulation material  40  having a Young&#39;s modulus of at least 30,000 psi and which is capable of being molded around electronic monitoring package  34 . Preferably, encapsulation material  40  will have a Young&#39;s modulus at least 100,000 psi.  
         [0040]    STYCAST®2651 is the preferred encapsulation material. Alternatively, high melting point polyurethanes and/or polyureas may be utilized. The polyurethanes are derived from polysiocyanates which generally have the formula R(NO) n  where n is an integer of 2, 3 or 4 with approximately 2 being preferred. The “n” may, however, vary and often is not an integer because combinations of various polysiocyanates can be utilized. R is an aliphatic having from about 2 to about 20 carbon atoms or preferably an aromatic including an alkyl substituted aromatic having from about 6 to about 20 carbon atoms with from about 6 to about 15 carbon atoms being desired, or combinations thereof. Examples of suitable polysiocyanates include 1,6-diisocyanto hexane; 2,2,4- and/or 2,4,4-trimethylhexamethylene diisocyanate; p- and m-tetramethyl xylene diisocyanate; dicyclohexylmethane-4,4′-diisocyanate (Hydrogenated MDI); 4,4-methylene diphenyl isocyanate (MDI); p- and m-phenylene diisocyanate; 2,4-and/or 2,6-toluene diisocyanate (TDI); durene-1,4-diisocyanate; isophorone diisocyanate and isopropylene bis-(p-phenyl isocyanate). TDI is desirably utilized. The various diphenylmethane diisocyanates (MDI) and mixtures of MDI with polymeric MDI having an average isocyanate functionality of from about 2 to about 3.2 are preferred.  
         [0041]    The preparation of the polyurethanes and/or polyureas are well known to the art and to the literature. For example, a short chain oligomer or polymer derived from polyester or polyether polyols generally having a molecular weight of from about 55 to about 1,000 and preferably from about 6 to about 200 are reacted with the above-noted diisocyanates to form a urethane prepolymer. Similarly, a short chain diamine can be utilized and reacted with the above-noted diisocyanates to form a urea prepolymer. Aromatic diisocyanates are generally utilized to yield high melting point urethane or urea prepolymers which also generally have a high modulus of elasticity. The resulting prepolymer is subsequently reacted with diols, diamine, diacids, or amino alcohols, and the like to cure the same and form a polyurethane or polyurea. Alternatively, the polyurethanes and/or polyureas are formed by reacting an existing prepolymer with the above-noted curing or chain extending agents.  
         [0042]    The equivalent ratio of isocyanate groups (NCO) reacted with the hydroxyl groups (OH) or amine groups (NH 2 ) of the short chain compound is generally from about 0.90 to about 1.10, desirably from about 0.95 to about 1.05, and preferably from about 0.98 to about 1.02.  
         [0043]    In general, thermoset epoxy resins are preferred. The epoxy resin or polymer is generally formed by the reaction of bisphenol A and epichlorohydrin. The preparation of epoxy resins is well known to the literature and to the art. Generally, epichlorohydrin is reacted with a variety of hydroxy, carboxy, or amino compounds to form monomers with two or more epoxied groups, and these monomers are then used in the reaction with bisphenol A. Examples of such compounds are the diglycidyl derivative of cyclohexane-1,2-dicarboxylic acid, the triglycidyl derivates of p-aminophenol and cyanuric acid, and the polyglycidyl derivative of phenolic prepolymers. Epoxidized diolefins can also be employed. Various co-reactants can be utilized to cure epoxy resins either through the epoxied or hydroxyl groups. Polyamines such as primary or secondary amines are a common curing agent such as aliphatic amines having a total of from about 2 to about 18 carbon atoms and desirably from about 4 to about 8 carbon atoms. Suitable compounds include diethylene triamine, triethylene tetraamine, tetraethylene pentaamine, 4,4′-diaminodiphenylmethane, and polyaminoamides. A combination of diethylene triamine and tetraethylene pentaamine is often desired. Aromatic amines can also be utilized such as those having a total of from 6 to 20 carbon atoms such as meta or paraphenylene diamine and the like. Other curing agents including polythiols, dicyandiamide (cyanoguanidine), diisocyanates, and phenolic prepolymers. Curing of epoxy resins can also be achieved by ring opening polymerization of the epoxied groups using either Lewis acids or Lewis bases.  
         [0044]    Accordingly, the improved attachment patch for mounting an electronic monitoring device to the inside of a pneumatic tire apparatus is simplified, provides an effective, safe, inexpensive, and efficient device which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior devices, and solves problems and obtains new results in the art.  
         [0045]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding; but 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.  
         [0046]    Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described.  
         [0047]    Having now described the features, discoveries, and principles of the invention, the manner in which the attachment patch for mounting an electronic monitoring device to the inside of a pneumatic tire is constructed and used, the characteristics of the construction, and the advantageous new and useful results obtained; the new and useful structures, devices, elements, arrangements, parts, and combinations are set forth in the appended claims.