Abstract:
The present invention provides a method of making a tire bead ( 16 ) with a tape ( 10 ) composed of two parallel wires ( 12   a   , 12   b ) having a coating ( 28 ) of resilient elastomeric material and connected by a web ( 14 ). The tire bead ( 16 ) can be built by winding the tape ( 10 ) in side by side relation and in successive superposed layers of predetermined widths and with convolutions spanning superposed layers to provide the tire bead ( 16 ) of predetermined cross-sectional area.

Description:
TECHNICAL FIELD 
     The present invention generally relates to wire fabrics and structures. More particularly, this invention relates to tire beads and their methods of manufacturing. 
     BACKGROUND OF THE INVENTION 
     A tire bead is that part of a tire which anchors the tire onto a wheel&#39;s rim. It is essentially an annular tensile member or inextensible hoop. Every tire has two such beads which are located within the rubber which makes up the inner-most circumference on each side of the tire. 
     In the usual procedure for manufacturing tire beads, the ends of individual wires, the exteriors of which are often rubber coated, are fed into a tire bead making machine. Machines of this type are old and well known in the tire building art. 
     Typical machines of this type are disclosed in U.S. Pat. Nos. 1,913,336, 2,902,083 and 5,385,621. These machines comprise a rotating drum about which the wire is wrapped a predetermined number of turns, dependent upon the strength and/or cross-sectional area of the tire bead desired. Standard equipment on such machines includes the means for automatically introducing the leading end of the wire into a gripper on the drum, intermittently operated means for rotating the drum, a stacking device which moves the incoming wire so as to control and build-up the cross-sectional shape of the resulting tire bead, and a knife to sever the incoming wire at the end of each building cycle. During the pause in the rotation of the drum, the finished tire bead is ejected laterally from the drum. 
     One deficiency of conventional tire bead making machines is their relatively slow operating speeds and consequently the amount of time required to fabricate a tire bead. To overcome this deficiency, various methods have been attempted to feed such tire bead machines a strap comprised of four parallel wires held together by a coating of rubber or other elastomeric material. A rectangular cross-sectional shaped tire bead formed using a standard style strap is shown in FIG.  1 . 
     However, because such straps are not pliable, their use has been seen to severely limit the range of cross-sectional shapes of the tire beads which can be built-up by using them. For example, a conventional hex cross-sectional shaped tire bead, see FIG. 2, which is commonly used in the tire industry, cannot be built up using the types of straps shown in FIG.  1 . Also, by increasing the number of wires forming each bead, the strength of the bead is reduced. 
     Another deficiency of conventional tire bead making machines is the problem associated with how to deal with the cut ends of the resulting tire bead. The springback nature of the wire ends can result in their coming loose and causing wire misalignments which can result in an unacceptable number of manufacturing interruptions in order to restring and realign the wires. 
     Thus, despite the prior art, there still exists a need for more efficient tire bead manufacturing processes. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a more efficient tire bead manufacturing process as defined in one or more of the appended claims and as such, having the capability of accomplishing one or more of the following subsidiary objects. 
     An object of the present invention is to provide a method of constructing a tire bead with a strap containing two parallel wires enmeshed in an elastomeric material. 
     Still another object of the present invention is provide a new and improved type of tire bead formed of the strap of two parallel wires. 
     Other objects and advantages of this invention will become readily apparent as the invention is better understood by reference to the accompanying drawings and the detailed description that follows. 
     SUMMARY OF THE INVENTION 
     The present invention is generally directed to satisfying the needs set forth above and the problems identified with prior tire bead manufacturing processes. Prior problems, associated with low operating efficiencies for tire bead machines are resolved by the present invention. 
     In accordance with one preferred embodiment of the present invention, the foregoing need can be satisfied by providing a method of making a tire bead characterized by the steps of forming a tape composed of a plurality of parallel wires coated with a resilient elastomeric material, the elastomeric material connecting adjoining parallel wires by a web formed between the wires, the web being of a predetermined size so as to yield the tape sufficiently pliable so as to allow the tape to be positioned to build up a tire bead having the same cross-sectional areas that can be built using individual wires, and forming a tire bead by winding such a tape a predetermined number of superimposed convolutions. 
     In another preferred embodiment, the present invention is seen to take the form of the above described method wherein the winding of the tape proceeds with the convolutions of the tape being laid in side by side relation and in successive superposed layers of predetermined widths to provide a tire bead of predetermined cross-sectional area. 
     In another preferred embodiment, the present invention is seen to take the form of a tire bead formed by any of the above described methods. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The structure, operation, and advantages of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is the cross-sectional view of a conventional tire bead fabricated by layering four straps, each of which consists of six parallel wires enmeshed in a rubber coating; 
     FIG. 2 is a cross-sectional view of a conventional hex cross-sectional shaped tire bead; 
     FIG. 3 is a side view of a tire bead manufacturing process according to the present invention; 
     FIG. 4 is a cross-sectional view of a tire bead tape according to the present invention; and 
     FIG. 5 is a cross-sectional view of a hex tire bead made from a tape according to the present invention. 
    
    
     DEFINITIONS 
     “Bead” or “Bead Core” generally means that part of the tire comprising an annular tensile member of radially inner beads that are associated with holding the tire to the rim; the beads being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein are shown preferred embodiments of the present invention and wherein like reference numerals designate like elements throughout, there is shown in FIG. 3 a side view of a tire bead manufacturing process according to the present invention. 
     This embodiment is seen to comprise the steps of providing a tape  10 , as shown in FIG. 4, composed of a plurality of parallel wires  12   a , 12   b  coated with a resilient elastomeric material. The elastomeric material connects the adjoining parallel wires by a web  14  formed between the wires. The web  14  is of a predetermined size so as to yield the tape sufficiently pliable to allow the tape to be bent to build up the same cross-sectional areas that can be built up using individual wires. Tire beads  16  are formed by winding the tape  10  a predetermined number of superposed turns around the drum  18  of the tire bead machine  20 . 
     The tire bead manufacturing process of FIG. 3 is seen to comprise a plurality of large creels  22  which supply individual wires  12   a , 12   b . These creels are arranged side-by-side so that only one shows in FIG.  3 . The individual wires  12   a , 12   b  are drawn from the creels  22  and passed into a spacing device  24 , such as a grooved guide roller, which serves to bring the wires into parallel alignment in a single horizontal plane, this being the basis for the eventual tape which these wires will comprise. The wires are next drawn through a tubing machine  26  where a coating  28  of elastomeric material, as shown in FIG. 4, is forced around and between the separate wires  12   a , 12   b  to coat the wires while forming a web  14  of predetermined size between the adjoining wires. A set of dies and inserts for the tubing machine&#39;s extruder are used to create the web&#39;s precise dimensions. The tubing machine is of any standard make and does not make up a part of the present invention. 
     See FIG. 4 for a cross-sectional view of the resulting tape  10  after it has passed through a cooling section  27  which is used set the elastomeric material. The tape  10  has a coating  28  about the wires  12   a , 12   b  and a web  14  interconnecting the coated wires  12   a , 12   b . The web  14  has a thickness “t” and a width “w” which depends on the specific application. While tape  10  as shown, can be formed with two parallel wires, it is also within the terms of the present invention to form the tape of more wires, such as  6  or  8 , embedded in elastomeric material and then slice the tape into a plurality of tapes of two wires embedded in rubber having a web therebetween. 
     In order to permit continuous operation of this process, a festooning storage device  30  is placed after the cooling section  27 . The tape from the festooning device  30  is wound upon the drum  18  of the tire bead making machine  20 . The tire bead making machine  20  has all the standard equipment usually included on such machines, including the mechanical components  32  for automatically introducing the leading end of the tape  10  into a gripper (not shown) on the drum  18 , and for intermittently rotating the drum. A stacking device  34  of conventional design moves the incoming tape  10  so as to control and build-up the cross-sectional shape of the resulting tire bead. A knife  36  severs the incoming tape at the end of each building cycle. During the pause in the rotation of the drum  18 , the finished tire bead  16  is ejected laterally from the drum. 
     Table I below shows preferred parameters for the webs  14  formed when various sizes of round steel wires are used in manufacturing the tapes  10  from which the tire beads are formed: 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 Wire 
                   
                 Coating 
                 Web 
                 Web 
               
               
                 Diameter 
                 Elastomeric 
                 Thickness 
                 Thickness 
                 Width 
               
               
                 (in) 
                 Material 
                 (in) 
                 (in) 
                 (in) 
               
               
                   
               
             
             
               
                 0.050 
                 Rubber 
                 0.005 
                 0.020-0.025 
                 0.010 
               
               
                 0.072 
                 Rubber 
                 0.005 
                 0.025-0.030 
                 0.010 
               
               
                   
               
             
          
         
       
     
     Using such web sizes, it has been found that the resulting tapes  10  can be positioned at between 135 to 150 degree angles with respect to the majority of tape layers applied to a cylindrical drum in order to allow the tapes to be optimally configured to make the full range of cross-sectional shapes used in various tire bead configurations. For example, FIG. 5 shows a cross-sectional view of a hexagonal shaped tire bead  16  formed by using a tape  10  having two parallel wires  12   a , 12   b  embedded in an elastomeric coating. In this example, a tape  10  is wound about a drum  18  so as to form twelve convolutions  10   a , 10   b , . . .  10 L of the single tape about the drum  18 . These convolutions typically are wound side to side within layers which are build up around the drum to yield the desired cross-sectional shape such as is the hexagonal shaped tire bead  16 . 
     Typically, the tape  10  is wound in a groove  40  formed in the outer circumference of drum  18 . First the tape is wound onto the drum  18  at one end of the groove followed by an adjacent winding convolution  10   b . Then, the stacking device positions the next convolution  10   c  above and slightly to the right of convolution  10   b  so that the left side of the web rests above the web section of convolution  10   b . After convolution  10   d  is applied in the manner just described, the convolution  10   e  is applied so that one wire is adjacent the second layer and the second wire of convolution  10   e  begins the third layer. After convolutions  10   f  and  10   g  are applied, the convolution  10   h  is applied to end the third layer and begin the fourth layer. The construction process continues to form the bead shown in FIG.  5 . The ability of the tape  10  with the double wires to straddle two layers provides the flexibility for forming a bead having any desired shape including but not limited to a triangular, pentagonal or hexagonal shape. The outside convolutions  10   c , 10   h  in the second, third and fourth layers have half convolutions oriented so that a line a—a between the centers of the convolution&#39;s parallel wires is at an angle α with respect to comparable line b—b between the centers of the adjoining convolutions in the same layer. While a might be sixty degree for a hexagonal shaped bead, any other angle can be used depending on the final bead shape. 
     While the invention has been described in combination with embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing teachings. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.