Patent Publication Number: US-2007122605-A1

Title: Apparatus and method of manufacturing reduced gauge tire ply

Description:
FIELD  
      This invention relates to pneumatic tires, and more particularly, the invention relates to ply constructions for tires.  
     BACKGROUND OF THE INVENTION  
      Modern passenger tires are typically constructed utilizing two or more layers of ply or a fabric woven from reinforcement filaments or cords. There has been an increasing trend among tire manufacturers to reduce tire weight without sacrificing structural integrity. One way to decrease weight in the tire is to eliminate ply where it is not needed. Typically, the area under the tread is one area where the ply can be reduced in thickness. Even a small decrease in the amount of materials needed to produce a tire can result in significantly decreased material expenses for a manufacturer engaged in high-volume tire production. There is a need for a tire having reduced weight that provides the desired performance characteristics and can be produced with fewer materials at a lower cost.  
     SUMMARY OF THE INVENTION  
      The present invention provides a method of making reinforced ply for a tire, the method comprising the steps of: calendering a base coat of rubber between a first and second calender rollers, calendering a skim layer of rubber between an assembly roller and a fourth calender roller, pressing a plurality of cords onto the skim layer of rubber forming a cord layer, and mating the base coat of rubber with the cord layer to form a layer of ply.  
      The invention provides in a second aspect a method of making ply comprising: extruding a plurality of cords through a cross-head extruder, wherein the cords are aligned in a die, and forming a base layer of rubber wherein the cords are impregnated within the base layer.  
      The invention provides in a second aspect a layer of ply comprising a layer of gum rubber and a plurality of cords partially embedded within the layer of rubber.  
      The invention will best be understood with reference to the following description of preferred embodiments taken in conjunction with the accompanying drawings.  
     DEFINITIONS  
      “Aspect Ratio” means the ratio of a tire&#39;s section height to its section width.  
      “Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire.  
      “Bead” or “Core” means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers.  
      “Belt Structure” or “Reinforcing Belts” means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17° to 27° with respect to the equatorial plane of the tire.  
      “Bias Ply Tire” means that the reinforcing cords in the carcass ply extend diagonally across the tire from bead-to-bead at about 25-65° angle with respect to the equatorial plane of the tire, the ply cords running at opposite angles in alternate layers  
      “Breakers” “Tire Breakers” means the same as belt or belt structure or reinforcement belts.  
      “Carcass” means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire.  
      “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction; it can also refer to the direction of the sets of adjacent circular curves whose radii define the axial curvature of the tread as viewed in cross section.  
      “Cord” means one of the reinforcement strands, including fibers, which are used to reinforce the plies.  
      “Inner Liner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.  
      “Inserts” means the reinforcement typically used to reinforce the sidewalls of runflat-type tires; it also refers to the elastomeric insert that underlies the tread.  
      “Ply” means a cord-reinforced layer of elastomer-coated, radially deployed or otherwise parallel cords.  
      “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire.  
      “Radial Ply Structure” means the one or more carcass plies or which at least one ply has reinforcing cords oriented at an angle of between 65° and 90° with respect to the equatorial plane of the tire.  
      “Radial Ply Tire” means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire.  
      “Sidewall” means a portion of a tire between the tread and the bead.  
      “Laminate structure” means an unvulcanized structure made of one or more layers of tire or elastomer components such as the innerliner, sidewalls, and optional ply layer. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      In the accompanying drawings:  
       FIGS. 1A and 1B  are a partial cross-sectional view of a first embodiment of a ply layer, and a first and second ply layer, respectively;  
       FIGS. 2A and 2B  are a partial cross-sectional view of a second embodiment of a ply layer, and a first and second ply layer, respectively.  
       FIGS. 3A, 3B ,  3 C,  3 D and  3 E are partial cross-sectional views of a third embodiment of a ply layer;  
       FIG. 4  is a side view of a calender system for forming ply;  
       FIG. 5  is a side view of a cross feed extruder system having a die as shown in  FIG. 5A  for forming ply as shown in  FIGS. 5B, 5C  and  5 D.  
       FIG. 6  is a side view of a second embodiment of a calender system for forming ply;  
       FIG. 7  is a side view of a second embodiment of a calender system for forming ply;  
       FIGS. 8-10  are front views of alternate dies for use in the calender systems of the inventions.  
       FIG. 11  is a cross-sectional view of a tire assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
      Any or all of the ply layers in a tire may be comprised of one or more layers of a reduced gauge ply having a reduced thickness on the order of about 30% to about 100% of the gauge thickness of a standard layer of ply. The ply configurations as described herein may be used in tire configurations such as, for example, passenger tires, truck tires, aircraft tires or off the road tires.  
      A standard layer of ply is defined herein as having a depth or gauge in the range of about 0.03 to about 0.06 inches, typically 0.045 inches. A standard layer of ply typically has a cord spacing in the range of about 18 to about 36 epi, generally about 28 epi, and with cord diameters in the range of about 0.020 to about 0.04 inches. The ply layers in a tire may have different thicknesses. Alternatively, one or more of the ply layers may have a reduced cord spacing on the order of about 30% to about 100% of the epi spacing of a standard layer of ply. Alternatively, any or all of the ply layers in a tire may be comprised of a reduced gauge ply having a reduced thickness on the order of about 30% to about 100% of the normal gauge thickness and a reduced cord spacing on the order of about 30% to about 100% of the epi spacing.  
      One example of a ply layer construction is shown in  FIGS. 1   a  and  1   b . The first layer and second layer of ply  10  may each have a gauge thickness in the range of about 30% to about 100% of standard ply gauge, and a cord spacing in the range of about 30% to about 100% the standard cord spacing. In one example, ply layers  10  may each comprise a gauge thickness of about 50% standard thickness and a reduced cord spacing of about 50% of the standard cord spacing. When layers  10  are combined together, the total thickness of both layers is about 100% of the standard thickness and a combined epi cord spacing of about 100% of the standard epi. However, ply layers  10  may each have different gauge thickness and cord spacing and when layered together, the combined total thickness may result in a nonstandard thickness and cord spacing.  
      As shown in  FIG. 1B , the cords of ply layers  10  may be oriented at the top edge of the ply so that the cord  12  is flush with the gum layer  14 . The cords of the first layer of ply  10  may be offset from the cords of the second layer of ply as shown in  FIG. 9B . For example, when the two layers of ply are assembled together, they may have the thickness and cord spacing of a typical layer of ply. In one example, the thickness of the ply layers is about 0.036 inches and the cord diameters are about 0.026 inches in diameter. The cord spacing of each layer is about 14 epi. When layered together as in  FIG. 1B , the full gauge thickness of the combined layers is about 0.072 inches and 28 EPI. The cords are staggered.  
      Alternatively as shown in  FIGS. 2A and 2B , ply layers  20  have the cords  22  impregnated about half way into the gum surface  24  of the ply. The layers  20  may be stacked on top of each other so that the gum or back edge  26  of the first ply layer mates with the upper surface  28  of the second ply layer as shown in  FIG. 2B . For example, if 0.026 in diameter cords are used in a 0.023 in thick gum base, this results in a 0.10 thickness “t” between the lower end of the cord to the end of the ply. In one example, the thickness of the ply layers  20  are about 0.023 inches and the cord diameters are about 0.026 inches in diameter. The cord spacing of each layer is about 14 epi. When layered together as in  FIG. 2B , the full gauge thickness of the combined layers is about 0.042 inches and 28 EPI. The cords are preferably staggered when the ply layers are assembled together.  
      Alternatively as shown in  FIGS. 3A-3D , ply layers  30  have the cords  32  impregnated about half way into the gum surface  34  of the ply, with a skim coat  36  of rubber layered over the cords. The layers  30  may be stacked on top of each other so that the gum or back edge of the first ply layer mates with the upper surface of the second ply layer as shown in  FIG. 3D . Ply layers  30  may be assembled such that the cords are abutted face to face wherein the cords of the upper layer are located between the cords of the lower layer, as shown in  FIG. 3B , C. The skim coat  36  forms a protective barrier over the cords  32 . The skim coat may comprise a thin layer of gum rubber, having a thickness typically in the range of about 0.003 to about 0.007. Preferably the cords are encapsulated between the gum rubber and the skim coat layer.  
      The ply layers as described above may be formed from a calender system  400  as shown in  FIG. 4 . Rubber is fed to the nip of first calender roll  402  and a second calender roll  404  to form the base gum layer  406  of the ply. Trim knife  408  is used to trim off excess rubber to form the desired width of the base gum layer  406 . Pull off roller  410  guides the base gum layer  406  and maintains the appropriate tension. The base gum layer  406  is fed to assembly roller  412  having a die  414  located in mating contact with the base gum layer  406 . A plurality of cords  415  are fed through the die inlet into engagement with the base gum layer mounted over the assembly roller  412 . The die  410  maintains the desired cord spacing. Examples of dies which may be used with the system  400  are shown in  FIGS. 8-10 , and are described in more detail in copending patent application Ser. No. 11/240,430 filed on Sep. 30, 2005, which is hereby incorporated by reference.  
      The cords upon exiting the die, are pressed into the top layer of the base ply by the pressure of the die against the assembly roller  412 . An optional skim coat of rubber  422  may be applied as a top layer over the cords. Rubber is fed between two rollers  418 , 420  having a desired clearance gap to form the desired gauge of the rubber skim coat. The skim coat  422  is applied over the cord/gum layer wherein stitcher roller  414  stitches the skim layer onto the cord/gum layer. Trim knife  424  trims the formed ply to the desired width.  
      The ply layers shown in  FIGS. 1-3  may also be formed from a cross-feed extruder system  500  shown in  FIG. 5 . As shown in  FIG. 5   a , a cross-feed extruder die  510  may be used having grooves  514  in the upper plate  512  of the die for receiving the cords therein. The grooves are spaced to match the desired cord epi spacing. The cords are pulled through the grooves  514  in the cross feed extruder die by pull-up roller  520 . The angle α of the pull up roller  520  is adjustable to pull cords more or less tightly against grooves  514  in die. The higher the angle, the more tightly the cords lie against grooved  514 . The angle α may be, for example, in the range of about 20-60 degrees. As the cords are pulled through the cross feed extruder, they are coated with rubber. The resulting ply  530  formed by the cross-head extruder has a base gum layer  532  with cords  534  impregnated into the base layer. A thin layer of rubber coats the cords. The ply layers  530  may be assembled top to bottom as shown in  FIG. 5   c  or wherein one of the ply layers is flipped over so that the cords are face to face as shown in  FIG. 5   d.    
      A second embodiment of a calendering system is shown in  FIG. 6 . Rubber is fed to the nip of a first calender roll  602  and second calender roll  604  to form the base gum layer  600  of the ply. Trim knife  608  is used to trim off excess rubber to form the desired width of the base gum layer  600 . For example, the base gum layer may be trimmed to a strip of about 3.7 inches wide, with a thickness of about 0.030 inches.  
      A bank of rubber is fed into nip of calender rollers  612  and  620 , in order to produce a thin skim coat  630  of rubber, which for example, may have a gauge of about 0.003 to about 0.005 inches. A plurality of cords are pressed into the skim coat  630  via a die  410  as described above, located in mating contact with the skim coat layer  630 . The die  410  is mounted adjacent the assembly roller  612  so that the cords are in mating engagement with the skim coat  630 . A plurality of cords are fed through the die inlet into engagement with the skim coat gum layer  630  mounted over the assembly roller  612 . The die maintains the desired cord spacing. The cords are pressed into the top layer of the base ply by the pressure of the die against the assembly roller  612 . The cords may be stitched into the skim coat by cord stitcher roller  632 . The base gum layer  600  is fed to the nip of assembly roller  612  for mating engagement with a skim coat cord impregnated layer  650  forming ply layer  655 . An optional secondary stitcher  660  may be used to eliminate any remaining trapped air. Trim knife  670  trims the ply layer  655  to the desired width before being pulled off the calender system by rollers  680 .  
      A third embodiment of a calender system  700  is shown in  FIG. 7 . Rubber is fed by an extruder or other means for processing rubber (not shown) to the nip of first calender roll  702  and a second calender roll  704  to form the base gum layer  706  of the ply. Trim knife  708  is used to trim off excess rubber to form the desired width of the base gum layer  706 . For example, the base gum layer may be trimmed to a strip of about 3.7 inches wide, with a thickness of about 0.030 inches. Base gum layer is then fed to assembly roller  710 . Cords fed into die  410  are pressed into the base gum layer on assembly roller  710 . The cord impregnated base gum layer  702  is fed to the nip of assembly roller  712  and roller  714  for mating engagement with a skim coat layer  716 , wherein the assembled components form a ply layer  720 . An optional secondary stitcher  760  may be used to eliminate any remaining trapped air. Trim knife  770  trims the ply layer  720  to the desired width before being pulled off the calender system by rollers  780 .  
     EXAMPLE 1  
      A cross-sectional view of a tire assembly  200  is shown in  FIG. 11 . Ply layer  210  is located radially outward of the inner liner  112 , and has a first end  212  located adjacent bead  114   b . The ply layer  210  extends up from the first end  212 , up the sidewall  104   b , under the tread  102 , down the other sidewall  104 a and extends down to the other bead  114   a . The ends  212 , 214  of ply layer  210  do not wrap around either bead. A second layer of sidewall ply  220   a,b  is located radially outward of the first layer of ply  210  in the sidewall and shoulder area. A first sidewall ply  220   a  has a first end  222  located under the inner tread belt  108  and extends down the sidewall  104   a , wraps around the bead  114   a  and apex  116   a , and has a turned up end  224  located on the interior of the tire assembly. A second sidewall ply  220   b  has a first end  226  located under the inner tread belt  108  and extends down the sidewall  104   b , wraps around the bead  114   b  and apex  116   b , and has a turned up end  228  located on the interior of the tire assembly. Thus the second layer of ply  220  does not extend under the crown portion of the tire. Each of the ply layers  210 , 220  has a reduced thickness of about 0.026 and a reduced cord spacing of about 18 epi. When assembled together, the total gauge thickness is about 0.052 inches with a cord spacing of 36 epi. Any of the ply configurations described in the preceding paragraphs would work with the tire configuration.  
      While the present invention has been described with respect to certain specific examples, it will be apparent that many modifications and variations are possible without departing from the scope of the following claims.