Abstract:
A bridge patch for use with a tire is provided. The bridge patch modifies the magnitude, orientation, or both of the mechanical forces, and particularly the stress-strain relationship, imparted by the inner liner of a tire in order to obtain the desired stress-strain relationship for operating an electromechanical transducer element attached to the bridge patch. The bridge patch includes at least one pad configured for attachment to the inner liner of the tire, and a bridge member attached to the pad and separated from contact with the tire. In certain embodiments, bridge patch includes a bridge member that is arch-shaped and is connected to two pads, one each located on the ends of the bridge member.

Description:
TECHNICAL FIELD OF THE INVENTION 
   The present invention relates generally to a bridge patch attached to the inner liner of a tire that carries an electrical circuit with an electromechanical transducer element. The bridge patch is configured to impart mechanical forces to the electromechanical transducer element in a predetermined fashion when the tire experiences deformation. 
   BACKGROUND 
   The incorporation of electrical circuits into tire assemblies allows for a variety of functions including pressure monitoring, temperature monitoring, and the tracking of identification data and other information. An electromechanical transducer element, such as a piezo element, can be used to power the electrical circuit. The electromechanical transducer element converts forces imparted thereon into electrical power for use in running the electrical circuit. 
   One way of imparting forces to the electromechanical transducer element resides in utilizing tire deformation during vehicle operation. Deformation in the tire may produce, for example, a strain field of up to 50,000 microstrain that can be converted into electrical energy. However, subjecting the electromechanical transducer element to this amount of strain may cause the element to break if, for instance, the optimum peak strain of the element is 3000 microstrain. Furthermore, deformations within a tire during operation are generally non-uniform in amount and direction, creating difficulties in properly orienting a transducer element to efficiently harness energy from the deformations. Accordingly, a device that carries the electromechanical transducer element and imparts mechanical forces in a predetermined way (i.e. a desired stress-strain relationship) to the electromechanical transducer element when the tire experiences deformation would be useful. 
   SUMMARY 
   Various features and advantages of the invention will be set forth in part in the following description, or may be obvious from the description. The present invention provides a bridge patch for supporting electronics, including an electromechanical transducer element, within a tire. In general, one or more pads are configured for attachment to, or integration with, the inner liner of a tire and provide support to a bridge member that is attached to the pad but separated from the inner liner. Various parameters in the construction of the bridge member and pads may be altered to impart a particular and desired stress-strain relationship to the electromechanical transducer element during tire operation. As such, the amount and direction of forces applied to the electromechanical transducer element are controlled in a manner that protects the element from excessive force while applying the amount necessary to power associated electronics. 
   The bridge patch of the present invention can have a variety of configurations. For instance, the bridge member may be either substantially straight or arch-shaped. When arch-shaped, the bridge member may be arranged so that it is either concave or convex with respect to the inner liner of the tire. One or more supporting rails may also be located on the bridge member for increasing the stiffness of the bridge member if desired. To reduce stress concentrations, one or more ends of the bridge member may be cylindrical in shape in order to form a larger surface area at the point connection to the pad. 
   For example, in one exemplary embodiment, the present invention provides a tire assembly that includes a tire having an inner liner. A first pad and a second pad are attached to the inner liner of the tire and are separated from one another by a predetermined distance. A bridge member is provided that has at least two ends. On end is attached to the first pad, the another end attached to the second pad. The bridge member is separated from contact with the tire. An electromechanical transducer element is attached to the bridge member and is configured for converting mechanical energy from the tire into electrical energy. As such, the bridge member is configured with the first and second pads so as to control the mechanical energy imparted to the electromechanical transducer element as a result of the deformation of the inner liner during operation of the tire. 
   In another exemplary embodiment, the present invention provides a bridge patch assembly for use with a tire having an inner liner. The assembly includes at least one pad configured for placement upon the inner liner of the tire. A bridge member is attached to the pad and configured to be separated from contact with the tire when the pad is attached to the tire. An electromechanical transducer element is located upon the bridge member and is configured for converting mechanical energy from deformation of the tire into electrical energy. The pad may consist of a single pad to which the bridge member is attached. Alternatively, three pads may be provided, including a first pad, a second pad, and a third pad. As such, the second pad is located substantially between the first pad and the third pad. The bridge member is attached to the first pad and the second pad; at least one connecting element is attached to the second pad and the bridge member so as to further constrain the movement of the bridge member during use of the bridge patch with the tire. 
   Alternatively, where a single pad is used, the patch may be attached to the inner liner of a tire so that a chamber is formed having an interior space defined by the bridge member, the single pad, and the inner liner of the tire. The interior space may be fluidly sealed from the remaining interior space of the tire or, an aperture may be created to provide fluid communication with the interior space so defined. The bridge member may be arched, substantially flat, or other shapes may be used. When arch-shaped, the bridge member may arch towards or away from the inner liner of the tire. To help reduce stress concentrations, the bridge member may include rolled or cylindrically-shaped ends where connected to the pad. One or more rails may be included with the bridge member to increase its stiffness. 
   The present invention also provides a method for obtaining a desired stress-strain relationship on an electromechanical transducer element. In one exemplary embodiment, a method of the present invention includes providing a tire having a pair of pads located on the inner liner of the tire, bridging the pads with a bridge member such that the bridge member is separated from contact with the inner liner of the tire, and attaching an electromechanical transducer element to the bridge member. An additional step of sizing the thickness of the bridge member in order to provide the desired stress-strain relationship on the electromechanical transducer element during tire operation may be included. Similarly, this method may include a step of sizing the width of the bridge member in order to provide the desired stress-strain relationship on the electromechanical transducer element during tire operation. A step of spacing the bridge member from the inner liner of the tire in order to provide the desired stress-strain relationship on the electromechanical transducer element during tire operation may also be added. Finally, a step may be included for selecting a material for the bridge member such that the material has a modulus of elasticity that contributes to creating the desired stress-strain relationship on the electromechanical transducer element during tire operation. 
   These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of an exemplary embodiment of a bridge patch taken along line  1 - 1  of  FIG. 2 . 
       FIG. 2  is a perspective view of a tire assembly incorporating the exemplary embodiment of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of an exemplary embodiment of a bridge patch with a pair of cylindrically-shaped ends. 
       FIG. 4  is a cross-sectional view of another exemplary embodiment of a bridge patch arching towards the tire surface. 
       FIG. 5  is a cross-sectional view of an exemplary embodiment of a bridge patch having a plurality of connecting elements and a third pad. 
       FIG. 6  is a cross-sectional view taken along line of  6 - 6  of  FIG. 7 . 
       FIG. 7  is a perspective view of an exemplary embodiment of a bridge patch without an arch shape. 
       FIG. 8  is a plan view of an exemplary embodiment of a bridge patch with arch-shaped pads. 
       FIG. 9  is a plan view of an exemplary embodiment of a bridge patch with a single pad. 
       FIG. 10  is a cross-sectional view taken along line  10 - 10  of  FIG. 9 . 
       FIG. 11  is a perspective view of an exemplary embodiment of a bridge patch with a single pad having a passageway defined therethrough. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations. 
     FIGS. 1 and 2  illustrate an exemplary embodiment of a bridge patch  12  of the present invention attached to inner liner  34  of a tire  14 .  FIG. 1  provides a cross-sectional view of patch  12  while  FIG. 2  shows a tire assembly  10  with bridge patch  12  attached to the inner liner  34  of tire  14 . Although shown attached opposite the crown of tire  14  with the length of the bridge member  22  oriented perpendicular to the axis of the tire  14 , bridge patch  12  may be located at a variety of other positions and orientations with respect to tire  14 . 
   Referring to  FIG. 1 , a pair of pads  16  and  18  are attached to the inner liner  34 , and an arch-shaped bridge member  22  is attached on either end to pads  16  and  18 . An electrical circuit  24  that includes an electromechanical transducer element  26 , such as a piezo element, is attached to the bridge member  22 . The bridge member  22  is thus suspended over and does not contact the inner liner  34 . As previously discussed, to correctly function, the electromechanical transducer element  26  may require a different stress-strain relationship from that imparted to the inner liner  34  during operation of tire  14 . The desired stress-strain relationship for transducer element  26  can be created through placement of transducer element  26  onto bridge patch  12 . More specifically, bridge patch  12  and pads  16  and  18  can be configured to convert the stress-strain relationship imparted by deformation of the inner liner  34  into the desired stress-strain relationship for the electromechanical transducer element  26 . 
   For example, as shown in the exemplary embodiment of  FIG. 1 , bridge member  22  is configured into an arch-shape between pads  16  and  18 . This configuration can be used to reduce the magnitude of the stress-strain relationship the electromechanical transducer element  26  would otherwise experience if it were attached directly to inner liner  34 . Additionally, the materials used in the construction of pads  16  and  18  can also allow for a reduction in the stress-strain experienced by transducer element  26  by operating to absorb or deflect part of the stress-strain that occurs during deformation of inner liner  34 . 
     FIGS. 1 and 2  are provided by way of example of the present invention. As will be discussed, bridge patch  12  may also be used to redirect the stress-strain relationship in order to accommodate a desired orientation of the stress-strain relationship on the electromechanical transducer element  26 . Further, the bridge patch  12  may be configured so that the magnitude and orientation of the stress-strain relationship is uniform across the entire bridge member  22 . Alternatively, the bridge patch  12  may be configured so that the magnitude and orientation of the stress-strain relationship is different at various locations on the bridge member  22 . 
   To so obtain the desired stress-strain relationship on the bridge member  22 , various elements of the construction of the bridge patch  12  can be altered to provide the desired result. For instance, the width, thickness, shape and/or modulus of elasticity of the bridge member  22  or pads  16  and  18  may be varied to obtain the desired stress-strain relationship for the electromechanical transducer element  26 . Additionally, the distance separating the inner liner  34  from the bridge member  22  may also be varied in order to help obtain the desired stress-strain relationship. Thus, using the teachings disclosed herein, one of ordinary skill in the art will understand that various parameters may be adjusted in order to transform the stress-strain relationship of the inner liner  34  into the desired stress-strain for bridge patch  12 . Various exemplary embodiments of the bridge patch  12  will now be discussed in greater detail. 
   For example, referring now to  FIG. 4 , bridge patch  12  may be alternatively configured so that bridge member  22  is arched in and towards inner liner  34 . The electromechanical transducer element  26  may be attached to either side of the bridge member  22  depending upon the stress-strain relationship desired during operation of tire  14 . 
   Alternatively, bridge patch  12  may be configured as shown in  FIG. 5 . Here, an additional pad  20  is attached to the inner liner  34  and is located between pads  16  and  18 . One or more connecting elements  28  may be attached to both pad  20  and bridge member  22 . The connecting elements  28  stiffen the bridge member  22  and help obtain the desired stress-strain relationship. 
   Although previously described as arch-shaped, bridge member  22  may also be configured to be substantially straight, as shown in  FIGS. 6 and 7 . Bridge member  22  may be provided with one or more supporting rails  32  in order to help stiffen bridge member  22  and subsequently produce the desired stress-strain relationship. Supporting rails  32  may be provided in any number, thickness, cross-sectional shape, or size in order to achieve a desired stiffness of bridge member  22 . 
   In this exemplary embodiment, as is true with all exemplary embodiments of the present invention, pads  16  and  18  may be configured in order to help obtain the desired stress-strain relationship. For instance, the thickness, shape, or materials of construction selected for pads  16  and  18  can be varied in order to help obtain the desired stress-strain relationship on bridge member  22 .  FIG. 8 , for example, shows a configuration where the pads  16  and  18  are arch-shaped, instead of being simply rectangular as shown in other exemplary embodiments. 
   Although described as incorporating a plurality of pads  16  and  18 , bridge patch  12  can be configured so that only a single pad  16  is present.  FIG. 9  shows one such exemplary embodiment where the perimeter of bridge member  22  is attached to a single pad  16 . This arrangement of bridge patch  12  causes tire  14 , pad  16 , and bridge member  22  to define an interior space  36  as shown in  FIG. 10 . Interior space  36  may be fluidly sealed from the rest of the air in tire  14  when tire  14  is mounted onto a wheel. The difference in air pressure between interior space  36  and the rest of the air in tire  14  could be used to help impart a desired stress-strain relationship on bridge member  22  that is subsequently transferred to the electromechanical transducer element  26 . Alternatively, as shown in  FIG. 11 , an aperture  38  may be defined through pad  16  in order to equalize the air pressure between interior space  36  and the rest of the air in tire  14 . 
   The construction of pads  16  and  18 , shown throughout the exemplary embodiments in the figures provided herein, can be provided as separate parts that are attached to the inner liner  34 . Alternatively, pads  16  and  18  may be molded onto the inner liner  34  during the building process of the tire  14 . Pads  16  and  18 , along with bridge member  22 , may be made of a variety of different materials. For example, pads  16  and  18  may be made of rubber while bridge member  22  may be made of steel, polymers, fiberglass, or a composite structure. Preferably, bridge member  22  is made of a material that is capable of experiencing repeated deformations without fatigue failure. Pads  16 ,  18  may be anchored to inner liner  34  in such a manner so as to pre-stress electromechanical transducer element  26  in either compression or tension should such a condition benefit the performance of electromechanical transducer element  26 . 
   Electrical circuit  24 , which includes electromechanical transducer element  26 , can be attached to bridge member  22  in any manner commonly known in the art. By way of example only, an adhesive may be used to attach electrical circuit  24 . Electromechanical transducer element  26  may be incorporated into the electrical circuit  24 , or may alternatively be attached to bridge member  22  separate from electrical circuit  24 . Although shown in  FIG. 1  as being attached to the side of bridge member  22  that is opposite inner liner  34 , it should be understood that electromechanical transducer element  26  may be attached to either side of bridge member  22 . 
   Additionally, bridge patch  12  may be designed so as to reduce or eliminate a possible stress concentration located at the point of attachment between the bridge member  22  and pads  16  and  18 .  FIG. 3  shows bridge member  22  with a pair of cylindrically shaped ends  30  and  31  that are attached to pads  16  and  18 . The enlarged surface area of cylindrically-shaped ends  30  and  31  helps to distribute stress located at the point of attachment between bridge member  22  and pads  16  and  18  so that a stress concentration at this location is either reduced or eliminated. Cylindrically shaped ends  30  and  31  may be formed into bridge member  22  in a variety of manners. For instance, if bridge member  22  is made of a metal, the ends may be simply rolled into a cylindrical shape in order to form cylindrically-shaped ends  30  and  31 . If bridge member  22  is made of a stiff polymer, bridge member  22  may be molded with cylinders on each end or alternatively, could have cylinders adhered onto each end in order to form the cylindrically shaped ends  30 ,  31 . As necessary, this stress-reducing feature may be used with any of the exemplary embodiments described herein. 
   It should be understood that the present invention includes various modifications that can be made to the exemplary embodiments of the tire assembly  10  and bridge patch  12  as described herein that come within the scope of the appended claims and their equivalents.