Patent Publication Number: US-2019184656-A1

Title: Strip lamination method and apparatus

Description:
FIELD OF THE INVENTION 
     The invention relates generally to rubber processing, and more particularly to a method and apparatus for making a strip of rubber. 
     BACKGROUND OF THE INVENTION 
     The invention describes a method and apparatus necessary to make a strip of rubber material useful for tire building. Typical prior art methods of making a rubberized strip generally utilize expensive equipment such as gear pumps and extruders. Extruders are typically very high pressure and require large amounts of horsepower in order to form a small strip. Extruders are expensive, and if not used properly, may overheat or overwork the rubber. Thus, an apparatus and method of efficiently producing a rubber strip is desired. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, an apparatus for forming a strip of rubber is described. The apparatus comprises a support frame; a first and second roller mounted on the support frame, wherein the first and second rollers are spaced apart from each other; and an application roller located adjacent a head, and a channel formed between the head and the outer surface of the application roller and the inner surface of the head; wherein said channel has an inlet and an outlet, wherein the inlet is located near the second roller, and the outlet is located adjacent a die. 
     A method of forming a rubber strip comprising the steps of providing a support frame with a first and second roller mounted thereon, wherein the first and second rollers are spaced apart from each other; threading a rubber stock about the first and second roller, and then through a channel formed between a head and a rotating application roller, and then through an outlet die. 
     Definitions 
     “Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100 percent for expression as a percentage. 
     “Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire. 
     “Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire. 
     “Chafer” is a narrow strip of material placed around the outside of a tire bead to protect the cord plies from wearing and cutting against the rim and distribute the flexing above the rim. 
     “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction. 
     “Equatorial Centerplane (CP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of the tread. 
     “Footprint” means the contact patch or area of contact created by the tire tread with a flat surface as the tire rotates or rolls. 
     “Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle. 
     “Lateral” means an axial direction. 
     “Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane. 
     “Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges. 
     “Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is a front perspective view of a strip forming apparatus of the present invention; 
         FIG. 2  is a closeup view of the strip forming apparatus of  FIG. 1  shown with only half of the application roller for clarity; 
         FIG. 3  is a front view of the applicator wheel of  FIG. 2 ; 
         FIG. 4  is a front perspective view of the strip forming apparatus illustrating the path of the rubber. 
         FIGS. 5 and 6  are a side views of a second embodiment of a milltruder head and the application roller from different angles; 
         FIG. 7  is a bottom view of the milltruder head of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a strip forming apparatus  100  is shown. The strip forming apparatus  100  includes a mounting frame  110  that is rectangular in shape, with a significantly longer vertical length than width. The mounting frame  110  has an upper end  112  that is pivotally mounted to a servomechanism  120 . The servomechanism  120  functions to traverse the mounting frame forward and aft. The mounting frame  110  hangs vertically on the servomechanism allowing the stitching pressure to be adjusted by the traverse position. The angle α that the strip forming apparatus makes with the vertical direction may be adjusted by a servo mechanism  118 . In order to adjust the stitching pressure, the angle α of the strip forming apparatus is varied. Variation of the angle changes the stitching pressure. Very low stitching pressure can be achieved which is required for small rubber strips. The stitching pressure can be adjusted by the traverse position of the strip forming apparatus in relation to a tire building drum, as described in more detail below. 
     As shown in  FIG. 1 , the mounting frame  110  has a length L and a width W, wherein the length L is aligned with the vertical direction. The length/width ratio is greater than 10. The mounting frame  110  has a plurality (at least two) of spaced apart preheat rollers  130 ,  140 ,  150 ,  160 ,  170  that are positionally fixed and rotatably mounted on the frame. The preheat rollers  130 - 170  are preferably aligned in the vertical direction so that the centers of each roller are preferably in a straight line. Each roller is spaced apart from an adjacent roller in the range of 1-5 inches. The rollers are not calendaring the rubber, as they are spaced apart. Calendering involves forming a shape between two rollers. 
     Each preheat roller has internal heaters (not shown). Preferably, each preheat roller is heated to a different temperature than the other preheat rollers. Preferably, the preheat rollers are progressively heated to a higher temperature so that the first preheat roller  130  is the coolest roller, while the second preheat roller  140  is heated to a higher temperature than the first preheat roller  130 . The third preheat roller  150  is heated to a higher temperature than the second preheat roller  140 , and the fourth preheat roller  160  is heated to a higher temperature than the third preheat roller  150 . Likewise, the fifth preheat roller  170  is heated to a higher temperature than the fourth preheat roller  160 . In summary, the preheat rollers are preferably maintained at progressively higher temperatures, increasing in temperature in the incremental range of about 5-20 degrees per roller with decreasing height of the mounting frame, so that the first or highest roller  130  is the coolest and the lowest roller is the hottest. 
     It is also preferred that the preheat rollers progressively increase in rotational speed from the highest vertical roller  130  to the lowest vertical roller  170 , so that the lowest vertical roller  170  is the fastest. 
     The rubber strip path is wound around the preheat rollers as shown in  FIG. 4 . As the rubber strip is wound around the preheat rollers, the increase in roller speed and temperature results in the strip being stretched and thinned to a strip having the desired width and thickness. In a first example, the series of vertically oriented preheat rollers process rubber stock having a 4-inch width, ¼ inch thickness into a 3-inch wide, ⅛-inch strip of rubber. However, the rubber stock could be any size. The strip formed from the strip forming apparatus may be as narrow as ⅛ inch and wider, and is not limited in size. Typically, the strips are in the range of 0.3 to 2 inches for tire building applications. 
       FIG. 2  illustrates the path of the rubber strip after exiting the series of vertically oriented preheat rollers  130 - 170 . The rubber strip is fed into the opening  210  of a feedbox of a milltruder  200 . The milltruder includes a milltruder head  220  and an application forming roller  230 . A channel  240  is formed between the milltruder head  220  and the forming roller  230 .  FIG. 2  only illustrates half of the forming roller  230  for clarity, while  FIG. 3  illustrates the entire forming roller  230 . The channel  240  preferably decreases in area from the inlet to the outlet adjacent a die  250 . The rubber is fed into the opening of the channel into engagement with the rotating forming roller and the lower end  222  of the head  220 . Preferably, the milltruder head  220  is heated. 
       FIG. 3  illustrates the application forming roller  230 . The application forming roller  230  is comprised of a first conical half  232  and a second conical half  234  separated by a central band  236 . The conical halves  232 , 234  are arranged so that the largest diameter is adjacent the band  236 , while the smallest diameter is axially outward of the band  236 . The application roller  230  may additionally optionally comprise a plurality of grooves or serrations  238 . The grooves or serrations  238  will increase pressure in die area which will increase output. The application roller  230  may optionally comprise a radial groove  260 . The radial groove  260  is used to increase the quality of the edge of the strip. Once rubber fills the groove  260 , it will flow the full 360 degrees back to the head. This action will pull any flash away from the rubber strip being applied to a tire building drum leading to a higher quality product. 
     As the application roller  230  rotates, it pulls rubber between the roller  230  and the milltruder head  220 . As the rubber moves toward a die  250 , the rubber is compressed and mixed both circumferentially and axially in the channel  240  between the milltruder head  220  and application forming roller  230 . The axial mixing/movement is also increased due to the conical shape of the application roller. Since the outer diameter of the roller has a higher surface speed than the smaller diameter of the cone, rubber will tend to migrate to the surfaces with higher surface velocities, ie towards the band  236 , generating additional mixing and pressure at the die opening. If more work or heat is required to process the rubber, the die  250  can be moved out to allow rubber to form a band around the application roller similar to a mill. This will allow multiple “passes” of rubber between milltruder head and roller, thus increasing work input. 
     The strip forming apparatus  100  may apply a strip of rubber onto a drum  300  or onto a carcass under construction. The application pressure may be adjusted by adjusting the angle α that the apparatus forms with the vertical direction. 
     An alternate embodiment of a milltruder head  400  is shown in  FIGS. 5-7 . As shown in  FIG. 7 , the milltruder head  400  has a lower surface  410  having a curved surface. The lower surface  410  has a hole  424  for receiving a pin  426  therein. The pin  426  preferably has a beveled upper surface that protrudes from the lower surface  410  of the head. The pin functions to direct the flow of rubber towards a V shaped groove  420  located on the lower surface. The V shaped groove has a narrow portion of the V terminating in a die outlet  430 . The die outlet  430  is positioned adjacent the band  236 . 
     The advantages of the system are: Significant reductions in capital costs of a system vs extrusion. Significantly lower horsepower required (lower energy costs). Since the size of the system is small, multiple strips can be applied to the building drum simultaneously. This reduces capital cost and increases output because fewer drums and less conveying of building drums is required. Since the entire assembly is hanging vertically, stitching application pressures can be more easily achieved vs present extrusion technology. This leads to reduced trapped air and a higher quality product. Being able to control this stitching pressure also allows for reinforcement to be applied directly to the building drum without pre-calendering, further reducing complexity and costs. 
     Variations in the present invention 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.