Abstract:
One or more embodiments of the present invention provide a method for forming a tread on a green carcass comprising the steps of providing a tire building drum having a carcass thereon, applying a strip of a base compound continuously over one half of the carcass forming a first layer of base compound from the centerline of the carcass to a first lateral edge, applying a first tread cap compound over the base compound, applying a strip of a base compound continuously over the second half of the carcass forming a second layer of base compound from the centerline of the carcass to a second lateral edge, forming a chimney along an edge of the first tread cap compound, and applying a first tread cap compound over the second layer of the base compound.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates in general to tire manufacturing, and more particularly to a method for forming tire components, particularly the tread. 
       BACKGROUND OF THE INVENTION 
       [0002]    Tire manufacturers have progressed to more complicated designs due to an advance in technology as well as a highly competitive industrial environment. In particular, tire designers seek to use multiple rubber compounds in a tire component such as the tread in order to meet customer demands Using multiple rubber compounds per tire component can result in a huge number of compounds needed to be on hand for the various tire lines of the manufacturer. For cost and efficiency reasons, tire manufacturers seek to limit the number of compounds available due to the extensive costs associated with each compound. Each compound typically requires the use of a banbury mixer, which involves expensive capital expenditures. Furthermore, banbury mixers have difficulty mixing up tough or stiff rubber compounds. The compounds generated from the banbury mixers are typically shipped to the tire building plants, thus requiring additional costs for transportation. The shelf life of the compounds is not finite, and if not used within a certain time period, is scrapped. 
         [0003]    Thus it is desired to have an improved method which provides independent flow of two or more compounds from a single application head. More particularly, it is desired to be able to make a custom tire tread directly on the tire building machine in an efficient manner, reducing the need for multiple stations. It is further desired to provide a method and apparatus for forming a tread on a tire building drum using a single station or reduced number of stations while reducing the cycle time. 
       Definitions 
       [0004]    “Aspect Ratio” means the ratio of a tire&#39;s section height to its section width. 
         [0005]    “Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire. 
         [0006]    “Bead” or “Bead 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. 
         [0007]    “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. 
         [0008]    “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. 
         [0009]    “Breakers” or “Tire Breakers” means the same as belt or belt structure or reinforcement belts. 
         [0010]    “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. 
         [0011]    “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. 
         [0012]    “Cord” means one of the reinforcement strands, including fibers, which are used to reinforce the plies. 
         [0013]    “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. 
         [0014]    “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. 
         [0015]    “Ply” means a cord-reinforced layer of elastomer-coated, radially deployed or otherwise parallel cords. 
         [0016]    “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire. 
         [0017]    “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. 
         [0018]    “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. 
         [0019]    “Sidewall” means a portion of a tire between the tread and the bead. 
         [0020]    “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 THE DRAWINGS 
         [0021]    The invention will be described by way of example and with reference to the accompanying drawings in which: 
           [0022]      FIG. 1  is a schematic of a compound switching apparatus. 
           [0023]      FIG. 2  is a close up cross-sectional view of the compound switching apparatus of  FIG. 1 . 
           [0024]      FIG. 3  is a cross-sectional view of the compound switching apparatus in use. 
           [0025]      FIGS. 4A-4D  illustrate a tread being built on a tire building drum. 
           [0026]      FIGS. 5A-5D  illustrate a second embodiment of a tread being built on a tire building drum. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1  illustrates a first embodiment of a compound switching apparatus  10  suitable for use for making rubber compositions for tires or tire components such as the tread. The compound switching apparatus  10  is not limited to tire applications and may be used for example, to make other rubber components not related to tires such as conveyors, hoses, belts, etc. The compound switching apparatus  10  is particularly suited for making a tread or small tire components having a varying composition, such as inserts, apexes and treads (including those for retreaded tires). The compound switching apparatus  10  may be provided directly at the tire or component building station for direct application of the rubber composition to a tire building drum or other component building apparatus. 
         [0028]    The compound switching apparatus  10  is mounted upon a support frame  15 . A translatable support bar  16  is mounted to the upper end of the support frame. Preferably, the compound switching apparatus  10  is mounted upon a translatable support bar  16 , that can translate fore and aft in relation to a tire building machine  18 . 
         [0029]    As shown in  FIG. 1 , the compound switching apparatus  10  includes a first extruder  30  and a second extruder  60 , preferably arranged side by side as shown. The first extruder  30  has an inlet  32  for receiving a first rubber composition A as described in more detail, below. The first extruder  30  is driven by motor  20 . The second extruder  60  has an inlet  62  for receiving a second rubber composition B as described in more detail, below. The second extruder  60  is driven by electrical motor  50 . The first or second extruder  30 , 60  may comprise any commercial extruder suitable for processing of rubber or elastomer compounds. The extruder may comprise a commercially available extruder commonly known by those skilled in the art as a pin type extruder, a twin screw or a single screw extruder, or a ring type of extruder. One commercially available extruder suitable for use is a multicut transfermix (MCT) extruder, sold by VMI Holland BV, The Netherlands. Preferably, the extruder has a length to diameter ratio (L/D) of about 5, but may range from about 3 to about 5. A ring type, pin type or MCT type of extruder is preferred, but is not limited to same. 
         [0030]    The first extruder inlet  32  receives a first compound A, examples of which are described in more detail, below. The first extruder  30  functions to warm up a first compound A to the temperature in the range of about 80° C. to about 150° C., preferably about 90° C. to about 120° C., and to masticate the rubber composition as needed. The output end  34  of the first extruder  30  is connected to an inlet end  43  of a first gear pump  42 . Compound A is thus first extruded by the first extruder  30  and then pumped by the first gear pump  42  into a nozzle  80 . The first gear pump  42  functions as a metering device and a pump and may have gears such as planetary gears, bevel gears or other gears. 
         [0031]    The second extruder inlet  62  receives a second compound B, examples of which are described in more detail, below. The second extruder  60  functions to warm up the second compound B to the temperature in the range of about 80° C. to about 150° C., preferably about 90° C. to about 120° C., and to masticate the rubber composition as needed. The output end  64  of the second extruder  60  is connected to an inlet end  45  of a second gear pump  44 . Compound B is thus extruded by the second extruder  60  and then pumped by the second gear pump  44 , which functions as a metering device and a pump and may have gears such as planetary gears, bevel gears or other gears. 
         [0032]    The first and second gear pumps  42 , 44  are housed in a single housing  40  and are placed in close proximity to each other so that the outlet channels  46 , 48  of the first and second gear pumps are also in close proximity, as shown in  FIG. 2 . The outlet channels  46 , 48  are fed into a nozzle assembly  80 . The nozzle assembly  80  includes a dual passageway nozzle outlet  85  mounted on a mounting flange  81 . The nozzle assembly  80  has two internal passageways  82 , 84  throughout shown in  FIG. 2 , that maintain separation of the rubber flow from each extruder  30 , 60  to the nozzle outlet  85 . Alternatively, the nozzle outlet  85  may have only a single flow passageway in fluid communication with internal passageways  82 , 84 . 
         [0033]    A rotatable stitcher roller  90  is mounted adjacent the nozzle outlet  85  of the nozzle assembly  80 . The stitcher roller  90  is pivotally mounted upon a support stand  92 . An actuator  94  connected to the stitcher roller  90  pivots or rotates the support stand  92  about its end  93  when actuated. 
         [0034]      FIG. 3  illustrates the compound switching apparatus  10  located adjacent a tire building drum.  FIG. 3  illustrates a first compound A being applied to the tire building drum. After compound A is applied, a second compound B can be applied to the tire building drum without the need for retracting the equipment or otherwise altering the equipment. 
       Method Steps for Forming a Dual Tread 
       [0035]    In a first embodiment, the following method steps are utilized in order to make a dual compound tread profile, wherein the steps described are for forming the tread directly onto a carcass mounted on a tire building drum. In this embodiment, the dual compound applicator apparatus  10  is translated on frame  15  by the translatable support bar  16  to move the nozzle  80  into engagement with the outer surface  19  of the tire building drum  18  as shown in  FIG. 3 . Next, a tread base compound is extruded through the second extruder  60  and second gear pump  44  located in the housing  40 , and out the passageway  82  of nozzle  80 . As the tire building drum is rotated, the tread base compound is applied directly onto the carcass mounted on the tire building drum via nozzle  80 . The tread base compound is applied in thin strips in a continuous manner Typically, the strips are wound onto the carcass in a helical manner. Preferably, the strip is in initiated at the carcass centerline and helically wrapped to a first lateral end of the tire carcass as shown in  FIG. 4A , forming a base layer  100 . Next, a first tread cap compound is extruded through the first extruder  30  and first gear pump and then out through the nozzle. The first tread cap compound is applied directly over the base tread compound forming a first tread cap layer  104  as the tire building drum is rotated, resulting in one half of the carcass having a base layer  100  and a first tread cap layer  104  layered radially outward and over the base layer  100  as shown in  FIG. 4B . 
         [0036]    Next, the base compound is applied over the carcass from the centerline to the second lateral end of the tire carcass forming a base layer  108  as shown in  FIG. 4C . A chimney  110  is formed from the base compound and is applied in the centerline area with multiple layers to build the chimney  110 . Next, the first tread compound is extruded through the first extruder and first gear pump and then applied over the base layer  108  from the chimney  110  to the outer lateral edge to form a tread cap layer  112 , as shown in  FIG. 4D . 
         [0000]    Method Steps for Forming a Multiple Compound Tread with Base 
         [0037]    In a second embodiment, the following method steps are utilized in order to make a dual compound tread profile, wherein the steps described are for forming the tread directly onto a carcass mounted on a tire building drum. In this embodiment, there are two dual compound applicator apparati  10  used to form the multi compound tread. The first dual compound applicator  10  is used to apply the base compound and first cap compound. A second dual compound applicator  10  is used to apply the second cap compound and third cap compound. The nozzle  80  of the first compound applicator  10  is translated on frame  15  by the translatable support bar  16  to move the nozzle  80  into engagement with the outer surface  19  of the tire building drum  18 . Next, a tread base compound is extruded through the second extruder  60  and second gear pump  44  located in the housing  40 , and out the passageway  82  of nozzle  80 . As the tire building drum is rotated, the tread base compound is applied directly onto the carcass mounted on the tire building drum via nozzle  80 . The tread base compound is applied in thin strips in a continuous manner so that the strips are wound onto the carcass in a helical manner. Preferably, the strip is in initiated at the carcass centerline and helically wrapped to a first lateral end of the tire carcass as shown in  FIG. 5A , forming a first half of a base layer  200 . Next, a first tread cap compound is extruded through the first extruder  30  and first gear pump and out through the nozzle. The first tread cap compound is applied directly over the base tread compound forming a first tread cap layer  204  as the tire building drum is rotated, resulting in one half of the carcass having a base layer  200  and a first tread cap layer  204  layered radially outward and over the base layer  100  as shown in  FIG. 5B . The first tread cap layer  204  may be alternated with a second tread cap layer  206  or a third tread cap layer  208  as shown in  FIG. 5C  or as desired. The second dual applicator is used to apply the second tread cap layer to the tread. 
         [0038]      FIG. 5D  illustrates yet another embodiment of the tread configuration. As shown, the base compound is applied over the carcass forming a base layer  208  as shown. A chimney  210  is formed from the base compound and is applied in the centerline area with multiple layers to build the chimney  210 . Next, a first tread compound is extruded through the first extruder and first gear pump and then applied over the base layer  208  from the chimney  210  to the outer lateral edge to form a first tread cap layer  206 . A second compound is applied over the first tread cap layer  206  forming a radially outer layer  204  on the left hand side of the tread. On the right hand side of the tread, the configuration is reversed, with the second compound forming radially inner layer  204  and the first compound forming radially outer layer  206 . 
         [0039]    Variations in the present inventions are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.