Patent Publication Number: US-2021187887-A1

Title: Tire building drum and method of building a tire

Description:
FIELD OF THE INVENTION 
     The invention relates to a tire drum, and a method of building a tire. 
     BACKGROUND OF THE INVENTION 
     Current tire building drums typically are cylindrical surfaces useful for the application of various tire components such as plies.  FIG. 8  illustrates the conventional tire building process, wherein a tire building drum capable of crowning is used. As shown  FIG. 8 b   , the beads are locked, the drum is expanded radially outward, and the apex is applied so that the tip is located radially outward of the bead. As shown in  FIG. 8 c   , the ply is then turned up around the bead and apex, and then additional components such as a down ply, a second apex and/or chafer is then applied ( FIG. 8 d   ). As shown in  FIG. 8 e   , the entire assembly is then turned down (rotated clockwise) on a different station. After application of several tire components of varying thicknesses to the drum, this may result in an uneven surface. The uneven surface may produce undesired results, such as wrinkling of the tire components during the build process. 
     Thus, an improved tire building drum and method of making a tire is desired which eliminates the wrinkling of tire components. 
     Definitions 
     For ease of understanding this disclosure, the following items are defined: 
     “Apex” means an elastomeric filler located radially above the bead and interposed between the plies and the ply turn-up. 
     “Axial” and “axially” means the lines or directions that are parallel or aligned with the longitudinal axis of rotation of the tire building drum. 
     “Bead” means that part of the tire comprising an annular tensile member commonly referred to as a “bead core” wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim. 
     “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. 
     “Carcass” means an unvulcanized 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. 
     “Casing” means the tire carcass and associated tire components excluding the tread. 
     “Chafers” refers to narrow strips of material placed around the outside of the bead to protect cord plies from the rim, distribute flexing above the rim, and to seal the tire. 
     “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction. 
     “Cord” means one of the reinforcement strands of which the plies in the tire are comprised. 
     “Equatorial Plane (EP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of its tread. 
     “Innerliner” 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. 
     “Insert” means an elastomeric member used as a stiffening member usually located in the sidewall region of the tire. 
     “Ply” means a continuous layer of rubber-coated parallel cords. 
     “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire building drum. 
     “Radial Ply Tire” means a belted or circumferentially restricted pneumatic tire in which at least one layer of ply has the ply cords extend from bead to bead at cord angles between 65° and 90° with respect to the equatorial plane of the tire. 
     “Shoulder” means the upper portion of sidewall just below the tread edge. 
     “Sidewall” means that portion of a tire between the tread and the bead. 
     “Tread” means a rubber component which when bonded to a tire carcass includes that portion of the tire that come into contact with the road when the tire is normally inflated and under normal load. 
     “Tread Width” means the arc length of the tread surface in the axial direction, that is, in a plane parallel to 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 view of a tire building drum of the present invention; 
         FIG. 2  is a perspective view of a tire building drum of the present invention; 
         FIG. 3A  is a side cross-sectional view of a tire building drum of the present invention, while  FIG. 3B  is a close up view of detail B of  FIG. 3A ; 
         FIG. 4  is a side cross-sectional view of a tire building drum of the present invention shown with tire building components thereon; 
         FIG. 5  is a close up view of one end of the tire building drum of  FIG. 4  illustrating the placement of the bead, apex, ply and down ply; 
         FIG. 6 a    is a perspective view of the left hand side center sleeve component, while  FIG. 6 b    is a top view of the left hand side center sleeve component; 
         FIG. 7  is a side view of the sleeve component; 
         FIGS. 8A-8E  illustrate a method of forming a tire; and 
         FIGS. 9A-9F  illustrate a method of forming a tire using the tire building drum of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 through 2 , an exemplary tire building drum  5  of the present invention is illustrated. The tire building drum  5  of the present invention solves the problem of an uneven application surface during the tire building stage caused by the application of various tire components. The uneven surface may result in the wrinkling of tire components due to the uneven surface. The tire building drum  5  solves this problem by providing sloped segments which create a pocket for the varying thicknesses of the tire components to create an even or “flat” surface for the application of the down ply. The sloped segments are described in more detail, below. 
     The tire building drum  5  of the present invention is a full stage drum that can articulate from a fully collapsed position (not shown) to a radially expanded and axially contracted position. As shown more particularly in  FIG. 1 , the tire building drum  5  has a left hand side  7  and a right hand side  9  joined together by a center section  20 . 
     The tire building drum includes a central drive shaft  120  that is provided for rotational movement of the tire building drum  5  about its longitudinal axis. The central shaft  120  is connected to a drive means (not shown). Provided within the central drive shaft  120  is a central screw  121 . The central screw  121  is supported at each end by bearings  123 . The threads on one side of the central screw  121  are left handed and on the opposite side are right handed. On the left hand side is an inboard nut  125  connected to the one end of the threaded screw  121  and similarly on the opposite right hand side is an outboard ball nut  125  connected to the central screw  121 . 
     The left shoulder section  7  and right hand shoulder section  9  of the tire building drum are each axially slidable on respective bearing sleeves  8 , 10 . The shoulder sections  7 , 9  are actuated by the central drive screw  121 . Rotation of the central drive screw  121  moves the drive pins  125  mounted on nuts  130 , which ride along the central drive screw  121 . When the central screw is rotated, the nuts  130  move axially inward/outward, causing the drive pins  125  and each shoulder section to move axially inward/outward in corresponding fashion. In addition, the drive pins are also in mechanical cooperation with the split center segments, causing the split center segments  22   a,b  to axially extend or contract. 
     The center section  20  of the tire building drum as shown in  FIGS. 3A and 4 , further comprises a plurality of sloped segments  22   a  on the left side of the center section and a plurality of sloped segments  22   b  located on the right side of the drum. The sloped segments  22   a , 22   b  each have an angled outer surface  29   a , 29   b  located at the center section shoulders. The angled outer surface  29   a , 29   b  is angled at an angle α in the range of about 15 to about 45 degrees, more preferably in the range of about 15-30 degrees.  FIGS. 3 a  and 3 b    illustrate the application of a tire bead B and an apex A. The angled outer surfaces create a pocket for the apex, ply and inner liner components so that a flat application surface is created for the application of a down ply. This solves the problem of the down ply wrinkling, or the problem of too much material such as the toeguard between the ply and down ply ending. 
     As shown in  FIG. 6 a   , the left hand side center segment  22   a  has one or more finger like projections  24   a , with recesses  26   a . As shown in  FIG. 6 b   , the right hand center segment  22   a  has three finger-like projections  24   b  with recesses  26   b  between the finger like projections  24   b . The finger projections  24   b  of the right hand center segments are slidably received in the opposed elongate slots  26   b  of the left hand center segments so that the finger projections cooperate with the opposing slots in an interdigitated or interlocked manner. Likewise, the three finger like projections  24   b  are slidably received in three opposed elongate slots  26   a . The center segments  22   a,b  thus cooperate with each other to allow the center section  20  to axially expand or contract due to the opposing fingers sliding within the opposing aligned recesses. 
     The center section  20  may also radially expand as shown in  FIGS. 3-5 . The center section  20  can radially expand in the range of about 20 to about 50 mm. As each center segment  22   a,b  radially expands, the gap between the center segments increases. As best shown in  FIG. 5 , provided within each center segment half  22   a,b  is a radially oriented piston chamber  28 . Received in each chamber  28  is a linkage  30  connected to a common actuator (not shown), such as a piston. When the linkages  30  are actuated, the linkages push the center segments  22   a , 22   b  radially outward into the high crown position as shown in  FIG. 5 . 
     Adjacent the center section  20  are first and second bead locking mechanisms  25   a,b , which are also radially expandable for engagement into the beads. With the drum of the present invention, the bead locking mechanism is independent of the drum crowning. After the carcass is made and the beads are locked, then the drum is crowned to reveal the specialized pocket for the apex to hide in, thereby allowing a flat surface for the down ply. 
     An upper bladder  150  extends axially outward from the bead lock mechanism  25  to the respective ends of the tire building drum. The upper bladder  150  extends over a lower bladder  152 , which is mounted in the shoulder area of the drum and extends axially outward to the respective ends of the tire building drum. The upper and lower bladders function as turnup bladders which are used to inflate and, thereby, make the turn-up ends of the ply wrap about the apex and bead cores. 
       FIGS. 9 a - f    illustrated the new and improved tire building process using the drum of the present invention. The drum of the present invention eliminates the need for the extra step of turning down the entire assembly on a different station. The drum of the present invention produces a simplified turn down with no wrinkling of tire components. As shown in  FIG. 9 a   , the beads are applied to the tire building drum surface. As shown in  FIG. 9 b   , the center section of the drum is crowned using a much lower radial expansion (1.3 inches) the radial expansion of a high crown drum. (2 inches or more). Next, the apex or bead and apex combination is applied to each sloped shoulder  29  of the drum of the present invention as shown in  FIG. 9 b   . Next as shown in  FIG. 9 c   , the ply is turned up over the bead and apex as shown, forming a flat surface to apply the additional tire components such as a down ply and a second apex. As shown in  FIG. 9 d   , a down ply that has been stretched is then applied, an optional second apex and/or chafer may additionally be applied. AS shown in  FIG. 9 e   , the bead lock is released and a chafer is applied under the bead. As shown in  FIG. 9 f   , the bead is locked and the chafer is turnup up over the bead. 
     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.