Patent Abstract:
A tire building drum and a method of building a tire carcass is disclosed. The tire building drum has a center section comprised of a plurality of segments that are radially and axially movable. The building drum further comprises shoulder sections that are axially movable. The shoulder sections include radially expandable bead locks. The method employs the steps of applying one or more carcass layers, locking the bead locks and moving the center section radially outwardly while moving the bead locks axially inwardly.

Full Description:
FIELD OF THE INVENTION 
   The invention relates to a tire building drum, more particularly to a tire building drum having a high central crown region. 
   BACKGROUND OF THE INVENTION 
   The manufacture of tires typically involves a tire building drum wherein numerous tire components are applied to the drum in sequence, forming a cylindrical shaped tire carcass. This stage of the tire building process is commonly referred to as the “first stage” of the tire building process. The tire carcass is then typically removed from the tire building drum and sent to a second stage, expandable tire shaping drum where the carcass is expanded into a toroidal shape for receipt of the remaining components of the tire such as the belt package and a rubber tread. The completed toroidally shape unvulcanized tire carcass or green tire is then removed from the second stage drum and subsequently molded and vulcanized into a finished tire. 
   The prior art process thus requires two tire building drums and the transfer of the carcass from one drum to the other. Further, a problem often arises in precisely locating and anchoring the tire beads on the unvulcanized tire carcass, especially during the transportation of the tire beads from the first stage drum to the second stage drum. Variations in bead positioning can result in ply distortion in the tire. 
   Tire manufacturers have recently begun moving towards the utilization of a single tire building drum, for both the first and second stage tire building. This requires that the tire building drum be capable of axial expansion and contraction as well as radial expansion/contraction. Further, it is important to maintain a positive bead lock during the entire tire building process, including the tire shaping, so that the ply cord length is maintained, resulting in good tire uniformity. Due to the fact that the tire building drum axially and radially expands, it is important that both sides of the tire building drum move in synchronization. If one side of the drum is out of synchronization with the other side of the drum, problems in tire uniformity can occur. It is additionally desired to support the apex and bead assembly in a vertical manner while avoiding unwanted displacements of the tire components, particularly the ply. 
   SUMMARY OF THE INVENTION 
   The invention provides in a first aspect a tire building drum comprising a rotatable drum having a center section and a first and second shoulder section, wherein each of said shoulder sections is independently movable in the radial direction and the axial direction; said center section being radially expandable, said center section further comprising a first half and a second half, wherein the first half and the second half are axially movable with respect to each other so that the center section has an adjustable width. 
   The invention provides in a second aspect a tire building drum comprising: a rotatable drum having a center section and a first and second shoulder section, wherein each of said shoulder sections is independently movable in the radial direction; said center section having a plurality of radially expandable and axially movable segments. 
   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: 
       FIGS. 1A and 1B  are perspective side views of a tire building drum shown in the start position and the high crown (radially expanded) position; 
       FIG. 2  is a cross-sectional view of the tire building drum shown in the start position; 
       FIG. 3  is a cross-sectional view of the tire building drum shown in the bead lock position; 
       FIG. 4  is a cross-sectional view of the tire building drum in the expanded high crown condition; 
       FIG. 5  is a cross sectional view of the tire building drum showing the stop pin locked in the outside position; 
       FIG. 6  is an end view of the tire building drum taken in the direction  6 - 6  of  FIG. 5  showing the lock ring in the locked position; 
       FIG. 7  is a cross sectional view of the tire building drum showing the stop pin unlocked; 
       FIG. 8  is an end view of the tire building drum taken in the direction  8 - 8  of  FIG. 7  showing the lock ring in the unlocked position; 
       FIG. 9  is a cross sectional view of the tire building drum showing the stop pin locked in the inside position preventing shoulder axial movement; 
       FIG. 10  is an end view of the tire building drum taken in the direction  10 - 10  of  FIG. 9  showing the lock ring locking the stop pins in the inside position; 
       FIG. 11  is a cross sectional view of the tire building drum shown in the drum shaping position; 
       FIG. 12  is a perspective view of a synchronization mechanism for the tire building drum; 
       FIGS. 13A and 13B  are cross sectional views of the tire building drum showing the center synchronization member and the center segment in the collapsed position and in the radially expanded position, respectively; 
       FIGS. 14A and 14B  are top, side views of the center segments shown in the axially collapsed position and the axially expanded position, respectively; 
       FIGS. 15 and 16  are cutaway perspective views of the tire building drum with the center segments removed, and showing the center synchronization mechanism and the lifter arms in the retracted and the radially outer position, respectively. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIGS. 1 through 5 , an exemplary tire building drum  5  of the present invention is illustrated. As shown more particularly in  FIGS. 1A and 1B , 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 center section is further divided into a right hand side and a left hand side, which are both axially and radially movable, as described in more detail, below. Adjacent the center section  20  are first and second bead locking mechanisms  25 , which are also radially movable as shown in  FIG. 1B . Adjacent the bead locking mechanisms are first and second shoulder segments  29 . Both the bead locking mechanisms and the shoulder segments are axially movable. Thus, both the left hand side and the right hand side of the drum are axially movable. These components are described in more detail, below. 
   Center Section 
   The center section  20  of the tire building drum further comprises a plurality of center segments  22  located about the outer circumference of the drum. Each of the center segments are split into a left hand side  22   a  and a right hand side  22   b , as shown in  FIG. 14 . Each side  22   a ,  22   b  has one or more finger-like projections  24  which are slidably received in one or more opposed recesses  26  in an interdigitated or interlocked manner. The center segments  22  can thus axially expand or contract as the fingers slide within the recesses. 
   The center section  20  may also radially expand as shown in  FIGS. 1   b  and  4 . The center section  20  can radially expand in the range of about 20 to about 50 mm. As each center segment  22  radially expands, the gap between center segments increases. Provided within each center segment half  22   a,b  is a radially oriented piston chamber  28 . Received in each chamber  28  is an elbow-shaped linkage  30  connected to an actuator  32 , such as a piston  33 . A control system (not shown) actuates the pistons  33 , causing linkage  30  to slide from the retracted position shown in  FIG. 3  to the actuated position shown in  FIG. 4 . When the linkages  30  are actuated, the linkages push the center segments radially outward into the high crown position as shown in  FIG. 4 . 
   In order to ensure that the left hand side and right hand side of the center segments  22  move together in synchronization, a center synchronization mechanism  50  is provided, and is shown in  FIG. 12 . The center mechanism  50  includes two outer rings  52  joined together by a first and second linkage mechanism  54 . The rings  52  are rotatably mounted in the tire building drum within the center segments  22 . The linkage mechanisms  54  function to keep the outer rings  52  rotating in synchronization together. When linkages  30  are actuated to push the center section into the high crown position, the linkages  30  push up a plurality of lifter rods  35  through slots  37 . The lifter rods  35  are connected to a plurality of support arms  39  which are connected to the outer rings  52 . When the lifter rods  35  are actuated into their radially outer position, the support arms  39  are likewise actuated into their radially outer position, causing both of the center rings  52  to rotate. The connecting linkage  54  between the center rings  52  keeps the rings rotating in synchronization so that the left hand side and the right hand side of the center segments  22   a,b  move together when actuated in the radial direction. See  FIGS. 13   a  and  13   b  and  FIGS. 15-16 . 
   The first and second linkage mechanisms  54  also allow the outer rings  52  to axially expand and contract. The linkages of the linkage mechanism  54  can fold up as shown in  FIG. 9 , enabling the center section of the tire building drum to have an axially smaller dimension. The linkages  54  may also outwardly expand, enabling the center section of the tire building drum to have an axially wider position.  FIG. 4  illustrates the linkages in a partially expanded condition. 
   The exterior surface of the center section is covered by a sleeve  60  mounted thereon. Each end  62  of the sleeve  60  are secured in sleeve clamps  70  located adjacent the center section segments. The sleeve clamps  70  move axially inward during the center radial expansion into the high crown position, retarding motion of the center sleeve. This feature prevents the tire components from moving since the underlying sleeve does not move, resulting in better tire uniformity. The sleeve clamps  70  are actuated by pistons  72  controlled by the tire drum control (not shown). When the center section of the tire building drum is expanded radially outward into the high crown position, the sleeve clamp pistons  72  are actuated, resulting in the sleeve clamps  70  sliding axially into a recess  74  located between the bead lock mechanism and the center segments. This motion is coordinated in order to retard motion of the sleeve. Thus, the axial tension of the sleeve is maintained due to the actuation of the bead locks, as well as the ply and other tire components. However, the circumferential tension in the sleeve is higher over the high crown section. When the drum screws axially together during the shaping of the tire, the sleeve is no longer axially tensioned, and buckles up over the center section as shown in  FIG. 11 . 
   Bead Lock Mechanism 
   Adjacent the center section  20  are first and second annular bead locking mechanisms  25 .  FIG. 2  illustrates the bead locking mechanisms  25  in the retracted position, while  FIG. 3  illustrates the bead locking mechanisms  25  in the radially expanded or bead clamp position. The drum control system (not shown) actuates the bead lock pistons  27  into engagement with rocker arm  29  which engages an end of the bead lock mechanism, pushing the bead lock mechanism radially outward into the bead clamp position. 
   The bead lock mechanisms are also independently axially movable, as described below. Further, the amount of axial movement of the bead lock mechanisms may be adjusted by the positioning of stop pin  85  shown in  FIGS. 5 and 6 . 
   Shoulder Section and Shoulder Clamp Lock 
   The right and left hand shoulder section  29  of the tire building drum  5  is defined as the drum components located axially outward of the centerline of the center section, inclusive of the sleeve clamps and the bead lock mechanisms. The left and right hand shoulder sections of the tire building drum are axially slidable on bearing sleeves. The shoulder sections  29  are actuated by drive pins  125  mounted on nuts  130 , which ride along 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. 
   When the center section  20  of the tire building drum  5  moves into the high crown position as shown in  FIG. 4 , the bead lock mechanisms  25  and the sleeve clamp mechanism  70  are further actuated axially inward by pistons  72 , 73  so that sleeve clamp is received in recess  74 . The bead lock mechanisms and the sleeve clamps are actuated axially inward about the same axial distance as the radial distance traveled by the center segments  22  into the high crown position. The axial actuation of the bead lock mechanisms and sleeve clamps preferably occurs simultaneously with the movement of the center segments into the high crown position. 
   Because both shoulder sections  29  can move axially, it is important to secure the shoulder sections in place after the center section  25  of the tire drum has moved into the high crown position. In order to secure each shoulder section, a rotatable lock ring  80  mounted in each section of the shoulder section, locks one or more stop pins  85  in its outer position. When the stop pin is in its outer position, the shoulder section can move axially. See  FIGS. 5 and 6 . One or more actuators such as an air piston  92  actuate the rotatable lock ring  80 . When the shoulder section is actuated to its axially inner position, stop pin  85  is also actuated or locked in its inner position as shown in  FIGS. 9 and 10 . Lock ring is rotated over the retracted stop pin openings, preventing the stop pin from moving. Since the stop pin cannot move, the shoulder sections which are engaged by the stop pin, are prevented from axially moving as well. 
   Drive Shaft 
   A central drive shaft  120  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 . 
   Turn Up Bladders 
   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. 
   Method of Operation 
   The sequence of building an exemplary tire utilizing the tire drum of the present invention is explained below. The tire building can be fully automated or may require an operator to manually cut and splice the components as they are applied to the tire building drum  5 . The components listed below can be varied for a particular tire construction. Some tires have more components than others. For example, some tires of the tube type may not require a liner. 
   First, the drum is set to the start position, as shown in  FIGS. 1   a  and  1   b . In the start position, the center section and shoulder sections are in their radially innermost positions, and the drum width is set to the start position. The start position width may very depending on the tire being manufactured. Next, the tire building components such as the tire liner, shoulder gum strips, chafers, sidewalls, optional run flat inserts, and ply are applied to the drum in successive order. 
   Each of the components described above requires, if applied separately, a rotation of the building drum  5  to form the component into a cylindrical shape. Alternatively, these components may be fed to the tire building drum  5  as one or more subassemblies. In either case, the ends of the components or subassemblies must be spliced together. 
   Next, the bead cores are positioned axially at a predetermined axial location generally above or slightly inward of the chafers but over the toe guard strip if used. Then, an apex filler strip would be placed with an end onto bead core and extending axially inwardly relative to the bead cores. Alternatively, the use of a preassembled bead-apex subassembly can be used. It is important to note that the tire building drum of the present invention can utilize beads of different diameters for the same tire. 
   The bead-apex subassembly is then pivoted into axially alignment with the axis of the tire building drum  5 . Similarly, the bead loaders are positioned into axial alignment with the tire building drum  5 . Once aligned, the bead loaders move axially inwardly over the bead core to position the bead-apex subassemblies  2  precisely onto the cylindrically-shaped carcass  10  over the bead lock mechanism of the tire building drum. The bead loader then releases the bead apex subassembly on the drum  5  while the drum bead lock mechanism radially expands, locking the bead cores into position. The bead lock mechanisms are actuated by the bead lock pistons  27 , which contact rocker arm  29 , pushing the bead lock mechanism radially outward into engagement with the bead or bead apex subassembly. 
   Next, the center of the drum expands into the high crown position as the shoulder segments move axially inward. The drum control system (not shown) actuates pistons  33 , causing the linkages  30  to slide from the retracted position shown in  FIG. 3  to the actuated position shown in  FIG. 4 . When the linkages  30  are actuated, the linkages push the center segments radially outward into the high crown position as shown in  FIG. 4 . When linkages  30  are actuated to push the center section into the high crown position, the linkages  30  push up a plurality of lifter rods  35  through slots  37 . The lifter rods  35  are connected to a plurality of support arms  39  which are connected to the outer rings  52 . When the lifter rods  35  are actuated into their radially outer position, the support arms  39  are likewise actuated into their radially outer position, causing both of the center rings  52  to rotate in the same direction. The connecting linkage  54  between the center rings  52  keeps the rings rotating in synchronization so that the left hand side and the right hand side of the center segments move together when actuated in the radial direction. See  FIGS. 11   a  and  11   b  and  FIGS. 13-14 . 
   When the center of the drum expands into high crown position, the right and left hand shoulder sections move axially inwards until the sleeve clamps abut the crown pistons  28 . Then the shoulder sections are locked into place when lock ring rotated by air pistons, entrapping the lock pins in their innermost position, preventing the shoulder sections from axially moving. 
   Next, the ply turnup ends can be folded over by actuating the inflatable turnup bladders at each inboard and outboard end of the building drum  5 . The turnup bladders roll the carcass ply turnups and the sidewalls, if they have been previously attached, over onto the central support segments and carcass ply. As noted, the center segments radially typically expand approximately 30 millimeters above the initial start position. However, the amount of radial expansion may vary depending upon the tire size. It is desired to have a range of expansion from about 20 mm to about 50 mm. This permits the triangular shaped apex to be folded over at the tip or radial extremes, however, maintaining its vertical position or almost vertical position relative to the thickest or base portions of the apex nearest the bead cores  12 . This greatly facilitates the construction of the carcass ply and ensures that the apexes are not overly distorted during the building process as is commonly done in the prior art method of assembling tire carcasses. 
   Once the tire turnup ends are folded over, the sidewalls can then either be applied or if previously applied, the entire assembly can then be stitched using roller mechanisms (not shown). The stitching procedure ensures that entrapped air is pushed outwardly of the carcass and that the components are firmly adhered to the adjacent underlying tire carcass components. 
   Once the stitching has been accomplished, the tire building drum axially contracts. The building drum  5  between the beads is charged with air or other fluid medium which passes through the central segment support mechanism and the radially expanded center segments to toroidally shape the tire carcass as illustrated in  FIG. 11 . When this is accomplished, the radially outer tip of the apex strip is moved back to its almost vertical position and the tire has been built in such a fashion that the carcass, particularly at the bead core area is not overly stressed. This high crown building drum  5 , using the center segments, ensures that the carcass has at least partially vertically extending ply portions prior to the ends being turned up. This more closely assimilates the finished tire shape. Additionally, the movement radially outward of the central segments is about equal to the axial movement of the locked bead core on each side. This ensures that the amount of axial tension is controlled to the tire carcass each and every time it is toroidally inflated, greatly improving the reliability of the finished product. 
   Next, the tire building drum is further moved axially inward, and the tread belt and reinforcing structure is applied to the carcass and then stitched. Next the shoulder clamp is actuated to the unlocked position, and the shoulder sections and the center section are moved radially inward to the start position of the drum. The green tire is then removed. 
   While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

Technology Classification (CPC): 1