Abstract:
A method may include the steps of: (a) providing a tire mold; (b) providing an extruder operatively connected to a head with a die assembly; (c) inserting at least a first compound into the first extruder; (d) forming an extrudate from the die assembly; (e) applying the extrudate directly from the die assembly into the tire mold to form a tire tread component; and, (f) controlling movement of the tire mold to correspond to the extrudate delivery.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    A. Field of Invention 
         [0002]    This invention pertains to the art of methods and apparatuses regarding the manufacture of tires, and more particularly to methods and apparatuses regarding the application of tire tread components directly from an extruder/gear pump into a tire mold. 
         [0003]    B. Description of the Related Art 
         [0004]    Conventionally, tires are made by first assembling a tire carcass on a flat drum. The drum is then expanded to place the carcass into the required toroidal shape. Separately, a tread is formed, typically using an extruder, and a belt package is made. The belt package is placed over the carcass and the tread is subsequently placed over the belt package. This creates an unvulcanized or “green” tire. The green tire is then placed into a tire mold where internal pressure is used to push the green tire against the mold, forcing the tread into the specific mold pattern. After sufficient time and temperature within the mold, the green tire becomes vulcanized, or cured. While such conventional tire making processes work well for their intended purposes, they have disadvantages. 
         [0005]    One disadvantage is related to the well known fact that tires are generally assembled from many separate components. In order to maintain high quality for tires, each of these components must be precisely located and accurately shaped within the completed tire. Maintaining the required shapes and obtaining sufficient accuracy in the positions of the components is extremely difficult in practice because of the readily deformable nature of the unvulcanized material that is used and because of the conventional gross changes in shape which are impressed on the tire during assembly. What is needed, then, is an improved way to position tire components to minimize these disadvantages. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one embodiment of this invention, a method comprises the steps of: providing a tire mold; providing a first extruder operatively connected to a head with a die assembly; inserting at least a first compound into the first extruder; forming a first extrudate from the die assembly; applying the first extrudate directly from the die assembly into the tire mold to form a tire tread component; and, controlling movement of the tire mold to correspond to the first extrudate delivery. 
         [0007]    According to another embodiment of this invention, the step of controlling movement of the tire mold to correspond to the first extrudate delivery, comprises the step of rotating the tire mold corresponding to the first extrudate delivery. 
         [0008]    According to another embodiment of this invention, a tire tread component is formed in one revolution of the tire mold. 
         [0009]    According to another embodiment of this invention, a tire tread component is formed with more than one revolution of the tire mold. 
         [0010]    According to another embodiment of this invention, the extrudate is spread onto the tire mold with a spread surface. 
         [0011]    According to yet another embodiment of this invention, an assembly comprises: a tire mold; a first extruder operatively connected to a head with a die assembly, the head positioned juxtaposed to the first tire mold so that a first extrudate from the head is directly applied into the tire mold to form a tire tread component; a rotation device for use in rotating the first tire mold; and, a control system for use in controlling rotation of the tire mold to correspond to the first extrudate delivery. 
         [0012]    According to another embodiment of this invention, the extruder comprises a gear pump. 
         [0013]    According to another embodiment of this invention, the extruder comprises an extrudate size adjustment mechanism that can be used to adjust the size of an opening through which the extrudate exits the head. 
         [0014]    According to another embodiment of this invention, the assembly also comprises a nozzle connected to the head for use in applying the first extrudate at a width less than the tread width. 
         [0015]    One advantage of this invention is that a tire tread can be applied directly to a tire mold eliminating the need to expand or stretch the tread into the mold. 
         [0016]    Another advantage of this invention, in one embodiment, is that by adjusting the size of the extrudate opening, the head can be used to apply multiple tread components to multiple tire molds. 
         [0017]    Another advantage of this invention, in another embodiment, is that extrudate can be directly applied to a tire mold as a laminate that is gradually built up, layer upon layer or layer beside layer until the tire component is fully applied to the tire mold. 
         [0018]    Still another advantage of this invention, according to another embodiment, is that a precise amount of extrudate can be delivered using a gear pump at a predetermined speed that corresponds to the rotational speed of the tire mold. 
         [0019]    Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention may take physical form in certain parts and arrangement of parts, embodiments of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein: 
           [0021]      FIG. 1  is a schematic representation of an extruder assembly, according to one embodiment of this invention, applying a tread compound directly to a tire mold. 
           [0022]      FIG. 2  is cross-sectional view of a tire mold. 
           [0023]      FIG. 3  is a schematic representation of one embodiment rotation device for use in rotating a tire mold. 
           [0024]      FIG. 4  is a schematic representation of another embodiment rotation device for use in rotating a tire mold. 
           [0025]      FIG. 5  is a schematic representation similar to that shown in  FIG. 1  but including a gear pump. 
           [0026]      FIG. 6  is a schematic representation of an extrudate size adjustment mechanism. 
           [0027]      FIG. 7  is a perspective view of a nozzle attached to an extruder assembly head. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the invention only and not for purposes of limiting the same,  FIG. 1  shows an extruder assembly  10  applying an extrudate  12  directly to a tire mold  100 . By “directly” it is meant that the extrudate moves non-stop, without being stored, out of the extruder assembly  10  and into the tire mold  100 . More specifically, the extruder assembly  10  shown is applying a tread extrudate  12  directly against or into the tread forming portion  102  of the mold  100 . A tire is thus being built from the outside in to form a very low tension tire. By placing the tread extrudate  12  directly into the mold  100  no expansion or stretching of the tread extrudate  12  is required. The resulting tire thus has very good uniformity. 
         [0029]    With continuing reference to  FIG. 1 , the extruder assembly  10  may include a housing  14  supported on a base  16 . Within the housing  16  a screw  20  may be used to masticate and move a compound  22 , which may be an elastomeric compound such as rubber. The compound  22  may be fed into a feed chute  24  by which it contacts the screw  20  and is thereby moved as the screw  20  rotates. The compotmd may then enter and flow through a flow channel  52  formed in a head  30  and then through a die assembly  50  to create the extrudate  12 . It should be noted that this invention will work with any type of extruder assembly that delivers the extrudate  12  directly into the tire mold  100 . In another embodiment, two or more extruder assemblies can be used. It is well known, for example, to use duplex or triplex extruders that feed the same head  30 . This provides a convenient way to extrude multiple compounds into a single extrudate  12 , such as a tread extrudate comprising a tread base fonned of one compound and a tread cap fonned of another compound. 
         [0030]    With reference now to  FIGS. 1-4 , this invention will work well with any type of tire mold chosen with sound engineering judgment. In one embodiment, shown, the tire mold  100  is a segmented tire mold having multiple radially movable tread forming segments  104  that when closed form an annular tread ring  110  having a tread ring width W 1 . The tread ring  110  provides the tread forming portion  102  of the tire mold  100 . The operation of a segmented mold as well as other types of molds is well known and thus will not be described in detail. It should be noted that this invention will work well with any orientation of the tire mold  100  including but not limited to placing the mold  100  so that the central axis  108  is substantially parallel to a ground surface, as shown in  FIG. 1  or placing the mold  100  so that the central axis  108  is substantially perpendicular to a ground surface, as shown in  FIGS. 3-4 . 
         [0031]    With continuing reference to  FIGS. 1-4 , a rotation device  120  of any type chosen with sound engineering judgment may be used to rotate the tire mold  100  and/or the tread ring  110  for purposes to be discussed further below. In one embodiment, shown in  FIG. 3 , the rotation device  120  comprises a hub  122  having multiple arms  124 . The hub  122  may be positioned near the central axis  108  of the tire mold  100 . The radial distal ends of the alms  124  may have gripping portions  126  that are secured to the radially outer surface of the tire mold  100 . To rotate the mold  100 , it is only necessary to attach the rotation device  120  to the tire mold  100  and then rotate the hub  122  in any manner chosen with sound engineering judgment. In another embodiment, shown in  FIG. 4 , the rotation device  120  comprises a gear ring  128  formed on or placed on the radially outer surface of the tire mold  100 . Only a segment of the gear ring  128  is shown in  FIG. 4  but it is to be understood that the gear ring  128  may extend substantially around the periphery of the tire mold  100 . A pinion gear  130  having gear teeth that engage the gear teeth on the gear ring  128 , can be rotated in any manner chosen with sound engineering judgment to thereby rotate the tire mold  100 . It is to be understood that the rotation devices  120  shown in  FIGS. 3 and 4  are illustrative only and that numerous other devices and methods of rotating the tire mold  100  are possible with this invention. 
         [0032]    With reference now to  FIG. 5 , in yet another embodiment, the extruder assembly  10  includes an integrated gear ptump  40 . The gear pump  40  may be positioned as shown between the end of the screw  20  and the head  30 . The gear pump  40  delivers a precise amount of extrudate  12  at a predetermined speed as required. The specific gear pump used can be of any type chosen with sound engineeringjudgment. The gear pump may be, for example, the gear pump described in U.S. Pat. No. 7,040,870 titled GEAR PUMP WITH GEARS HAVING CURVED TEETH AND METHOD OF FEEDING ELASTOMERIC MATERIAL, which is incorporated herein by reference. In another embodiment, the extruder assembly  10  comprises a gear pump that is connected directly to the screw. An example of this type of arrangement is described in Publication No. US 2005/0220919 titled EXTRUDER/GEAR PUMP ASSEMBLY which is incorporated herein by reference. 
         [0033]    With reference now to  FIGS. 1 ,  5  and  6 , in another embodiment the head  30  may include an extrudate size adjustment mechanism  31  that can be used to adjust the size of the opening through which the extrudate  12  exits the head  30 . To adjust the thickness of the extrudate  12  between a minimum of zero and a maximum of T 2 , the adjustment mechanism  31  may include a thickness plate  58  positioned in the flow channel  52  that may be adjusted in an upward direction D 1  and in a downward direction D 2 . To adjust the width of the extrudate  12  between a minimum of zero and a maximum of W 2 , the adjustment mechanism  31  may include a pair of width plates  60 ,  60  positioned in the flow channel  52  that may be adjusted in an inward D 3  and an outward direction D 4 . The thickness plate  58  and the width plates  60 ,  60  can be position adjusted in any manner chosen with sound engineering judgment such as a mechanical adjustment mechanism. For the embodiment shown, electric motors  62 ,  62  can be used to adjust the positions of the plates  58 ,  60 ,  60 . In one embodiment, each width plate  60 ,  60  can use an individual motor  62 . In another embodiment, the width plates  60 ,  60  can be mechanically linked so that only one motor  60  is required to simultaneously move both plates  60 ,  60 . By using the adjustment mechanism  31  to adjust the size of the opening through which the extrudate  12  exits, the head  30  may provide various sized extrudates for any desired purpose such as for molds having different sized tread forming regions. 
         [0034]    With reference now to  FIGS. 1 and 7 , in another embodiment a nozzle  200  may be attached to the head  30 . The nozzle  200  can be of any size and shape chosen with sound engineering judgment and may have a nozzle flow channel that at one end commtnicates with the flow channel  52  formed in the head  30  and at the opposite end has a nozzle opening  208  where the extrudate  12  can be directly applied to the tire mold  100 . The nozzle flow channel can be of any size and shape chosen with sound engineering judgment. In one embodiment, the nozzle flow channel may taper from a substantially circular cross section to a tongue shaped nozzle opening  208 . Such a tapered nozzle flow channel provides low pressure, low swell and uniform flow characteristics for the extrudate  12 . The nozzle  200  may comprise a spread surface near to the nozzle opening  208  which will be described further below. 
         [0035]    With continuing reference to  FIGS. 1 and 7 , in another embodiment the nozzle  200  may be position adjusted with respect to the head  30  to permit added flexibility in applying the extrudate  12  to the tire mold  100 . In a specific embodiment, the head  30  may have a fixed head portion  32  and a rotating head portion  34 . The rotating head portion  34  may rotate about a rotation axis along an arc of, for one non-limiting example, 270 degrees to provide easy access to the tire mold  100 . It is to be Lmderstood that an arc of 270 degrees is illustrative only. The nozzle  200  may be attached to the rotating head portion  34  in any manner chosen with sound engineering judgment. It is also contemplated to rotatably connect the nozzle  200  directly to the head  30  without the use of a rotating head portion. 
         [0036]    With reference now to  FIG. 7 , in another embodiment a roller shoe, not shown but resembling a wheel, may be positioned near the nozzle opening  208 . A position cylinder (not shown) may be used to adjust the position of the roller shoe. The cylinder may be pneumatic, hydraulic or of any other type chosen with sound engineering judgment. The outer surface of the roller shoe may be used as a spread surface as will be described further below. The outer surface, in one embodiment, may have a urethane coating for prevent the roller shoe from sticking to the extrudate  12 . In another embodiment, a friction shoe  250  may be positioned near the nozzle opening  208 , as shown in  FIG. 7 . The friction shoe  250 , in one embodiment, may “float” in that the friction shoe  250  may be movable independent of the nozzle  200 . In one specific embodiment, a cylinder (not shown but it may be similar to the position cylinder described above) may be used to permit the friction shoe  250  to rest against the extrudate  12  as it is being applied to the tire mold  100  independent of the nozzle  200  position. In another embodiment, a heating mechanism (not shown) may be used to heat the friction shoe  250  to aid in the placement of the extrudate  12 . The heating mechanism may be electric, hot water or of any other type chosen with sound engineering judgment. The friction shoe  250 , which can have any usable shape, has an outer surface  254  which may be used as a spread surface  256  as will be described further below. In yet another embodiment, both a roller shoe and a friction shoe  250  may be used together. In one embodiment, the shoes can be independently controlled and in another they can be moved together. It is to be understood that the positioning, including relative positioning, of the shoes can be any chosen with sound engineering judgment may be used. 
         [0037]    With reference now to  FIGS. 1 ,  5  and  7 , a control system  500  may be used to control the operation of the extruder assembly  10 , the rotation device  120 , the nozzle  200  position, the position and temperature of the shoes etc. The control system  500  can be of any type chosen with sound engineering Judgment and may, for example, comprise a microcomputer. 
         [0038]    With reference now to  FIGS. 1 and 2 , in operation, a tire mold  100  which may have a tread ring  110  with a ring width W 1  matching the tire to be made is chosen and positioned in proper alignment with respect to the rotation device  120 . A compound  22  is then inserted into the extruder assembly  10  which is operated. The control system  500  is used to cause the output of the extruder assembly  10  to correspond with the rotation of the tire mold  100 . For the arrangement shown in  FIG. 1 , in one embodiment, the width and thickness of the extrudate  12  is appropriate to match in one revolution of the tire mold  100 , the tire component being applied to the tire mold  100 . If the tire component is a tread, for example, the extrudate  12  may include all the rubber used to form the tread and may have a width that matches the width of the tread portion of the tire mold  100 , such as the tread ring  110 . More specifically a first edge of the extrudate  12  exiting the die assembly  50  is applied to a location on the tire mold  100 . The extrudate  12  is then wrapped continuously to the tire mold  100  as the tire mold  100  or tread ring  110  is rotated one revolution. The extrudate  12  is then terminated to defme an extrudate strip defining a second edge for the extrudate  12 . The second edge of the extrudate  12  is then applied substantially to the same location on the tire mold  100  to form the tire tread component. In another embodiment, the width and/or thickness of the extrudate  12  may be less than required to form the tire component in one revolution of the tire mold  100 . In this case, two or more revolutions of the tire mold  100  may be required to complete the application of the tire component to the tire mold  100  and the extrudate  12  may be considered a laminate that is gradually built up, layer upon layer and/or layer beside layer, until the tire component is fully applied to the tire mold  100 . The use of layers in this manner greatly reduces the well known difficulties in splicing together opposite ends of a single component strip. For the arrangement shown in  FIG. 5 , the operation is similar to that described above regarding  FIG. 1  except that the gear pump  40  is used to more precisely deliver an amount of extrudate  12  at a predetermined speed as required. For the arrangement shown in  FIG. 6 , the operation is similar to that described above regarding  FIGS. 1 and 5  except that the size of the opening through which the extrudate  12  exits the head  30  may be adjusted prior to the formation of the extrudate  12 . 
         [0039]    For the arrangements shown in  FIG. 7 , the overall operation is similar to that described above regarding  FIGS. 1 and 2 . However, while it is contemplated to use the nozzle  200  to provide the extrudate  12  with a width and thickness to match in one revolution of the tire mold  100  the tire component being applied to the tire mold  100 , the nozzle  200  is especially useful in applying a laminate that is gradually built up, layer upon layer and/or layer beside layer, until the tire component is fully applied to the tire mold  100  as described above. In another embodiment, the nozzle spread surface can be used to spread the extrudate  12  onto the surface of the tire mold  100  (or to the surface of a previously applied layer of extrudate  12 ) similar to the manner in which a butter knife is used to spread butter onto a piece of bread (though the viscosity of the extrudate may be considerably greater than that of butter). This spreading of the extrudate  12  helps eliminate any air pockets that may otherwise form under the extrudate  12  as it is applied. The roller shoe and friction shoe  250  may provide their own spread surfaces which can be used in addition to or as an alternate to the nozzle spread surface. Advantages to the use of the roller shoe include the ease in rolling over splices and lower drag. Advantages to the use of the heated friction shoe  250  include permitting the nozzle  200  to remain at optimum extrusion temperatures with a relatively shorter length and better spreading characteristics (due to the relatively higher temperature of the spread surface  256 ). When both shoes are used together, the advantages of each can be combined. 
         [0040]    Various embodiments have been described, hereinabove. It will be apparent to those skilled in the art that the above methods and apparatuses may incorporate changes and modifications without departing from the general scope of this invention. It is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.