Abstract:
A method of building and transferring a tread  12  or a tread belt reinforcing assembly  14  on a building drum  10  is disclosed. The steps include applying at least one uncured tread component  12, 14  onto a radially collapsible building drum  10 , inserting the at least one uncured tread component  12  and the radially collapsible building drum  10  into an open segmented mold  2  wherein a plurality of mold tread forming segments  4  are radially expanded; contracting the plurality of mold tread forming segments  4  pressing into the at least one uncured tread component  12, 14 ; collapsing the building drum  10 ; and removing the building drum  10  thereby transferring the at least one uncured tread component  12, 14  into the mold. The preferred building drum apparatus  10  has a portable radially expandable and axially rotatable support means  20 ; a drive means  30  for rotating the support means  20  about the axis, a plurality of arcuate or straight segments  22  slidably mounted over the support means, the plurality of arcuate or straight segments  22  forming an annular building surface  24 ; a means  40  for radially expanding and contracting the radially expandable and axially rotatable support means; a means for receiving and accepting the tread or tread belt assembly while mounted on the plurality of arcuate or straight segments  22  mounted onto the portable support means  20 , the receiving means  2  being a segmented mold  2  with radially movable tread forming segments  4.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a method and an apparatus for building and transferring a tread or a tread belt reinforcing structure on a building drum.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the manufacture of pneumatic tires elastomeric components, some of which are reinforced by cords of textile or wire, are formed as long strips. These strips are assembled together to form a carcass subassembly in a first stage of assembly. This carcass typically has one or more cord reinforced plies, a pair of bead cores and an air impervious liner. Additional strips of material such as apexes, shoulder gum strips and chippers and chaffers may also be used in this first stage of tire assembly.  
           [0003]    In a second stage the tread rubber and belt or breaker reinforcing structure is typically applied to the carcass after the carcass has been toroidally shaped on the tire building drum. The tread rubber can be of one homogeneous compound or more. Typically the tread is a sophisticated composite of many different rubber materials co-extruded to form a tread strip. The belt or breaker reinforcing layers generally include two layers or more of cross plies reinforced by equal but oppositely oriented cords of textiles, such as nylon or aramid or wire such as steel. Additionally, overlays or underlays of generally circumferentially oriented cords may be added as an additional layer.  
           [0004]    Tires typically have been built using this two-stage assembly. Once assembled this uncured assembly of the components is placed in a mold to be vulcanized to form a finished tire.  
           [0005]    High speed and efficient ways to manufacture tires require the processes to be reliable and fast. Accordingly, manufacturers of tires have experimented with and perfected many ways to improve on the basic two-stage assembly of tires.  
           [0006]    One method described in U.S. Pat. No. 3,865,670 taught the use of an expansible and contractible transfer ring for conveying a breaker tread assembly from a building drum in a tire building machine to a tire carcass mounted on a tire shaping machine.  
           [0007]    An improved but somewhat similar U.S. Pat. No. 3,888,720 also disclosed a separate tread breaker building drum designed to vary in size to accommodate different sizes of tires.  
           [0008]    Similarly, the Charles E. Todd U.S. Pat. No. 3,865,669 also disclosed an expansible and contractible transfer ring for conveying a breaker-tread assembly.  
           [0009]    Each of these prior art patents recognized that an assembly of a tread belt to a tire carcass can be accomplished off-line or separate from the carcass building machine. Once formed into a ring these tread breaker assemblies could be moved to encircle a tire carcass, the carcass inflated to contact the inner surface of the tread breaker assembly and then stitched together by a roller mechanism to form a green or uncured tire assembly to be placed into a mold.  
           [0010]    While these assembly techniques provided efficiencies in production, none really changed the method for actually forming a tire assembly.  
           [0011]    Conventional tire molds, whether two piece molds or segmented molds, form the tread surfaces by pressing groove forming ribs and sipe forming blades into the tread rubber as the tire is molded. As this is done the belt cords, particularly those directly under the groove-forming ribs deflect in small but noticeable undulations. These undulations create a variety of changes across the tread that actually can vary the surface or change the amount of tread rubber across the otherwise normal appearing tire. These non-uniformities can lead to mass imbalance issues, irregular wear and a variety of associated ride and handling performance issues. The goal in tire manufacturing is to minimize unpredictable non-uniformities in manufacturing while also building the tire in a very cost-efficient manner.  
           [0012]    The object of the present invention is to provide a method that minimizes or eliminates the influence of the tread forming mold surfaces as the tire is molded.  
           [0013]    A further object of the invention is to provide a more productive method of assembling the tread-belt or breaker reinforcing structure to the carcass.  
           [0014]    Another objective is to change the method of how the tread forming surfaces engage the tread rubber.  
           [0015]    Still another objective is to provide a novel apparatus for forming the tread-belt or breaker assembly and to employ that apparatus to a unique tire building system.  
         SUMMARY OF THE INVENTION  
         [0016]    A method of building and transferring a tread on a tread belt reinforcing assembly on a building drum is disclosed. The steps include applying at least one uncured tread component onto a radially collapsible building drum; inserting the at least one uncured tread component and the radially collapsible building drum into an open segmented mold wherein a plurality of tread forming segments are radially expanded; contracting the plurality of tread forming segments pressing into the at least one uncured tread component; collapsing the building drum; and removing the building drum thereby transferring the at least one uncured tread component into the mold.  
           [0017]    The method further includes inserting a tire carcass into the mold; closing the mold; expanding the carcass under pressure forcing the carcass into contact with the at least one uncured tread component forming a tire assembly; and curing the assembly.  
           [0018]    Preferably, the method provides the additional step of heating the at least one uncured tread component to a temperature above ambient most preferably at 110° C. or more, prior to closing the segments and wherein the at least one uncured tread component is warmed and softened as the segments press into the tread.  
           [0019]    The step of applying at least one uncured tread component also can include applying one or more cord reinforced belt, breaker, overlay or underlay layers onto the building drum prior to applying one or more layers or strips of uncured tread rubber to form a tread-belt reinforcing assembly.  
           [0020]    The apparatus for building and transferring a tread or tread belt reinforcing assembly has a radially expandable and axially rotatable support means; a drive means for rotating the support means about the axis; a plurality of arcuate or straight segments slidably mounted over the support means, the plurality of arcuate or straight segments forming an annular building surface; a transfer means for removing the plurality of arcuate or straight segments from the support means and wherein the transfer means provides radial support for the plurality of arcuate or straight segments when the support means is contracted.  
           [0021]    The apparatus further includes a means for radially expanding and contracting the radially expandable and axially rotatable support means.  
           [0022]    The preferred apparatus has a portable radially expandable and axially rotatable support means; a drive means for rotating the support means about the axis, a plurality of arcuate or straight segments slidably mounted over the support means, the plurality of arcuate or straight segments forming an annular building surface; a means for radially expanding and contracting the radially expandable and axially rotatable support means; a means for receiving and accepting the tread or tread belt assembly while mounted on the plurality of arcuate or straight segments mounted onto the portable support means, the receiving means being a segmented mold with radially movable tread forming segments.  
           [0023]    The preferred apparatus further has a plurality of arcuate or straight gap spanners interposed between an adjacent pair of arcuate or straight segments and wherein each pair of adjacent arcuate or straight segments has a gap of at least 0.050 in. (1.25 mm) in the radially expanded position, the gap spanners providing a radially outer surface which bridges between and overlaps pairs of adjacent segments. When radially contracted the arcuate or straight segments reduce the circumferential gap and thereby circumferentially reduce the length of the surface supporting the tread or tread belt reinforcing assembly, thereby releasing the tread or tread belt assembly.  
           [0024]    The arcuate or straight segments and the overlapping gap spanners when mounted on the support means and fully expanded provide a rigid internal surface that prevents the tread or tread belt assembly from locally distorting as the mold tread forming segments are closed. Once closed the tread rubber is pressed into the tread forming surface securing the tread or tread belt reinforcing assembly. Once secured the arcuate or straight segments of the support means are contracted releasing from the inner surface of the tread or tread belt assembly. After contracting, the entire portable support means with contracted arcuate or straight segments can be removed from the mold while the mold&#39;s tread forming segments are in a closed position holding the tread or tread belt assembly. Then the uncured carcass can be placed into the mold and the mold closed and the curing processes can be initiated.  
           [0025]    Definitions  
           [0026]    “Apex” means an elastomeric filler located radially above the bead and interposed between the plies and the ply turnup.  
           [0027]    “Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire.  
           [0028]    “Bead” means that part of the tire comprising an annular tensile member 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.  
           [0029]    “Breaker Structure” refers to at least two annular layers or plies of parallel reinforcement cords oppositely oriented having the same angle or about 5° less than the parallel reinforcing cords in carcass plies, generally about 20° to less than 50° with reference to the equatorial plan of the tire.  
           [0030]    “Belt Structure” 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.  
           [0031]    “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.  
           [0032]    “Casing” means the carcass, the belt reinforcement and other components of the tire excluding the tread.  
           [0033]    “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.  
           [0034]    “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.  
           [0035]    “Cord” means one of the reinforcement filaments, cables, or strands of which the plies in the tire are comprised.  
           [0036]    “Equatorial plane (EP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of its tread.  
           [0037]    “Innerliner or 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.  
           [0038]    “Overlay” means one or more layers of parallel cords underlying tread above the belt structure and having cord angles typically 0° to 15° with respect to the equatorial plane of the tire.  
           [0039]    “Ply” means a continuous layer of rubber-coated parallel cords.  
           [0040]    “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire.  
           [0041]    “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°-90° with respect to the equatorial plane of the tire.  
           [0042]    “Section height” means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.  
           [0043]    “Section width” means the maximum linear distance parallel to the axis of the tire and between the exterior of its sidewalls when and after it has been inflated at normal pressure for 24 hours, but unloaded, excluding elevations of the sidewalls due to labeling, decoration or protective bands.  
           [0044]    “Shoulder” means the upper portion of sidewall just below the tread edge.  
           [0045]    “Shoulder gum strip” means an elastomeric reinforcement located in the shoulder region of the carcass.  
           [0046]    “Sidewall” means that elastomeric portion of a tire between the tread and the bead.  
           [0047]    “Subassembly” means an unvulcanized assembly of laminated unreinforced tire components to which a cord reinforced ply or plies and other tire components can be added to form a casing.  
           [0048]    “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.  
           [0049]    “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.  
           [0050]    “Underlay” means one or more layers of parallel cords underlying the belt structure or at least one layer of the belt structure and having cord angles typically 0° to 15° with respect to the equatorial plane of the tire. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0051]    The invention will be described by way of example and with reference to the accompanying drawings in which:  
         [0052]    [0052]FIG. 1 is a perspective view of the tread or tread belt assembly building drum of the present invention;  
         [0053]    [0053]FIG. 2 is a cross-sectional view of the tread or tread belt assembly building drum of the present invention;  
         [0054]    [0054]FIG. 3 is a perspective view of the transfer means engaged in the support means of the building drum;  
         [0055]    [0055]FIG. 4 is a cross-sectional view of the apparatus taken from FIG. 3;  
         [0056]    [0056]FIG. 5 is a perspective view showing the transfer means with the support means attached thereto and separated from the building drum;  
         [0057]    [0057]FIG. 6 is a cross sectional view of the apparatus taken from FIG. 5;  
         [0058]    [0058]FIG. 7 is a cross-sectional view of the tread or tread belt assembly building drum attached to the drive means for rotating the drum and illustrating the means for radially expanding and contracting the support means as well as an overload clutch means;  
         [0059]    [0059]FIG. 8A is a cross-sectional view of the adjacent arcuate or straight segments with a gap spanner shown in the expanded fully open position;  
         [0060]    [0060]FIG. 8B is the same features illustrated in FIG. 8A but in the fully collapsed contracted position;  
         [0061]    [0061]FIG. 9 is a perspective view of the building drum assembly showing a tread belt assembly as applied to the support surface;  
         [0062]    [0062]FIG. 10 is a cross-sectional view of the tread or tread belt assembly mounted on the building drum and being placed into an opened mold;  
         [0063]    [0063]FIG. 11A is a cross-sectional view of the tread or tread belt assembly mounted on the building drum with the mold being closed onto the assembly;  
         [0064]    [0064]FIG. 11B is a cross-sectional view of the tread belt assembly in the mold with the building drum collapsed and being removed from the mold; and  
         [0065]    [0065]FIG. 12 is a cross-sectional view of the mold and tread or tread belt assembly being cured to a carcass assembly mounted on a collapsible building drum assembly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0066]    With reference to FIG. 1, a perspective view of the tread or tread belt assembly building drum of the present invention is illustrated. As shown, the building drum  10  has a radially expandable and contractible support means  20 . The support means  20  has a radially outer surface  24  for building a tread or tread belt reinforcing structure onto the surface  24 . The surface has a plurality of arcuate or straight segments  22  which are connected by gap spanner segments  21  around the peripheral surface of the tread building support means. The arcuate or straight segments  22  and gap spanner segments  21  are slidably attached onto the building drum support means  20 . Each arcuate segment  22  has a hole or opening  55  for accepting a plurality of pins located on a transfer means  50 . The pins  54  can be pressed into the openings  55  and provide a means  50  for transferring the arcuate or straight segments and gap spanner segments as an assembly onto and off the support means  20 .  
         [0067]    As used herein, each segment  22  and gap spanner segment  21  can have a flat or straight circumferentially or laterally extending surface or, alternatively, an arcuate surface. Hereinafter the segments will be generally referred to as arcuate while it is understood the surface may be straight in either the circumferential direction or the lateral direction.  
         [0068]    As illustrated, in FIG. 1 the transfer means  50  has an annular transfer ring  51  and a guide ring  52 . The guide ring  52  is slidably inserted over the pins  54  and the pins  54  are rigidly attached to the transfer ring  51  as shown. On the exterior surface of the transfer means  50  are shown three knobs  53 .  
         [0069]    With reference to FIG. 2, a cross sectional view of the building drum  10  is shown along with the transfer means  50 . The transfer means  50  is shown not engaged to the building drum  10  or to the arcuate or straight segments  22 . The combination of the arcuate or straight segments  22  and the gap spanner segments  21  form a subassembly commonly referred to as the deck. The term “deck” is commonly referred to with a similar meaning as that of the deck of a boat. It is an exterior surface upon which one can stand or build the tread assembly. For purposes of this invention the building surface  24  will commonly be referred to as the deck  24 . This deck  24  which is an assembly of the arcuate or straight segments  22  and the gap spanning segments  21  is slidably mounted over deck segment guides  116  and  117 . Once slid over these guides  116 ,  117  a detent assembly called a deck segment locking pin  115  engages and secures the deck  24  to the drum expansion segment  114  as illustrated. To remove the deck assembly  24  from the radially expandable and contractible tread building drum, the transfer means  50  is pushed into the holes  55  wherein the pins  54  engage the deck segment locking pins  115  thereby releasing them when the pins  54  are fully engaged. This is illustrated in FIGS. 3 and 4. Once engaged the transfer means  50  can be used to slidably remove the deck assembly  24  as shown in FIG. 5. The pins  54  provide radial support for the deck assembly  24  and hold the assembly  24  in the position as shown for removal. The perspective view of the removed deck assembly  24  provides a better illustration of the deck segment guides  116  and  117  and the drum expansion segment  114 . As shown, the arcuate or straight segments  22  have the deck segment locking pin  115  engaged by the pin  54 . A spring  129  is used in the contracted position when the pin  54  is inserted as shown in FIG. 6. Once the pin  54  is removed the spring  129  is free to release and allow the locking pin  115  to extend radially inwardly to accomplish the locking of the mechanism. This is as illustrated in the cross-sectional view of FIG. 6.  
         [0070]    In order for the tread belt building drum  10  to expand radially and contract radially and to provide a surface  24  upon which a tread belt assembly can be built, the building drum  10  must accept a drive means  30  that provides rotational movement of the entire building drum assembly  10  as shown in FIG. 7. The drive means  30  is connected to a motor (not illustrated) which can provide rotational movement of the tire building drum assembly  10 . The drive means  30  includes a drive spline  100  which is connected to a screw drive shaft  101  and which is embedded inside a drum quick-mount mounting cone  102  as illustrated. The quick-mount mounting cone  102  provides for rapid engagement and disengagement of the drum assembly  10 . The drum quick-mount mounting cone  102  has a key  104  with a key locating pin  103  as illustrated and a longitudinally extending keyway  105  as illustrated. A drum inboard housing  106  is illustrated on the left-hand side of FIG. 7 and a corresponding drum outboard housing  107  is on the right-hand side of FIG. 7. On the opposite side of the drive means  20  and the drum assembly  10  is an outboard support cone  108 . The outboard support cone  108  has a live center receptacle  109 . The live center permits easy rotation of the drum assembly  10  while the entire assembly is being rotated. Looking internally at the center of the mechanism or apparatus  10  there is a ball screw or acme threaded screw assembly  110 . As illustrated the threaded assembly  110  is comprised of two components, one having left-hand threads and an opposite side having right-hand threads. These two components are pinned together to provide simultaneous rotation of the mechanism. On the left-hand side is an inboard ball nut or acme nut  111  connected to one end of the threaded screw  110  and on the opposite or outboard side another ball nut or acme nut  112  is illustrated. A ball screw overload protection clutch mechanism is illustrated at  113 . This mechanism  113  provides capability of disengaging the shaft  110  and permitting the drum assembly  10  to collapse if the pressure is exceeded beyond the capability of the clutch  113 . This override clutch protection system  113  ensures that when the mold closes or pressure is applied to the radially outer surface of the deck  24 , the deck  24  can collapse as the clutch  113  disengages, permitting the entire unit or drum  10  to collapse slightly preventing any overload from damaging the internal workings of either the mold or the mechanism  10 . Radially directly inward of the deck  24  or its arcuate or straight segments  22  there is illustrated a drum expansion segment  114 . The drum expansion segments  114  are threadedly engaged by threaded fasteners  125  to an expanding segment base  123  as illustrated. They are also located by pins  122  as shown. Radially inward of the expanding segment base  114  is an outward outboard segment cone bushing  121  and an inboard segment cone bushing  120  which are threadedly attached using screws or threaded fasteners  126  as illustrated to the expanding segment base  123 . Radially inward of the inboard segment bushing  120  is the inboard expansion cone  118 . Similarly, on the outboard side the outboard segment cone bushing  121  is radially outward of an outboard expansion cone  119 . The bushings  120  and  121  are designed to slide along the cone surfaces of the inboard expansion cone  118  and outboard expansion cone  119 , respectively. As shown, the building drum  10  is in an expanded position such that the radially outer deck or building surface  24  is radially expanded. As the drive shaft  101  is spun or rotated inside the bearings  127 ,  128  the inboard ball nut  111  and outboard ball nut  112  push the expansion cones both inboard and outboard  118  and  119 , respectively, radially to the center plane of the building drum  10 . As these cones  118 ,  119  push to the center plane, the conical surface permits the expanding segment base  123  and its bushings  120  and  119  to slide along the conical surfaces and contract radially inwardly.  
         [0071]    With reference to FIG. 8A in the fully expanded position the arcuate or straight segments  22  are shown with a gap G between each segment in the fully radially expanded position. The gap G is preferably at least 0.050 in (1.25 mm) as measured between the adjacent segments. The gap spanning segment  21  is constrained in channels  25 . Each gap spanning segment  21  has lobes  26  that are captured within these channels  25 . They may be slid laterally to remove the segments  21 ,  22  but are constrained such that the arcuate or straight segments  22  can move circumferentially a certain extent until they engage the lobes  26  as illustrated. This permits a diametrical expansion of the assembly  10  by a few millimeters. The ends of the segments  22  have a chamfered surface  27  which provides a space for the gap spanning segment to occupy at the correct diameter for tread belt building. Upon contraction, as shown in FIG. 8B, the arcuate or straight segments close upon each other and the gap spanning segments  21  are moved within the channels  25  such that the lobes  26  contact the interior surface of the arcuate or straight segments as illustrated in FIG. 8B. When this occurs the gap G between the adjacent arcuate or straight segments  22  is closed permitting each of the segments  22  to contract radially inwardly. This feature enables one to build a tread or tread belt assembly in such a manner that the tread or tread belt assembly can easily be removed once assembled to the deck assembly  24 . This will be discussed later in detail.  
         [0072]    With reference to FIG. 9, the tread drum assembly  10  is shown wherein a typical tread belt reinforcing structure  14  is shown assembled to the exterior surface or peripheral surface of the deck  24 . As shown, a first belt layer  16  is illustrated lying adjacent to the surface  24 . At the lateral edges of the first belt layer  16  are two belt edge elastomeric strips  17 . Interposed in between the elastomeric strips  17  is a second belt layer  15  having cords oriented oppositely relative to the first belt layer  16 . Optionally, and as illustrated, an overlay  18  is shown. The overlay  18  is a circumferentially extended cord reinforced structure that overlays both the second belt layer  15  and the first belt layer  16  and the underlying gum strips  17 . Radially outward of the overlay  18  is an unvulcanized layer  12  of tread rubber. As illustrated the tread rubber  12  may be provided as strips of rubber wound and laid adjacently or can be provided as a single layer.  
         [0073]    With reference to FIG. 10, once the tread belt assembly  14  is applied onto the building surface  24 , the entire building drum assembly can be placed inside a mold  2 . In the illustrated embodiment, the tread assembly  14  is shown mounted on a building drum  10  that is in a radially expanded position and placed inside the open and expanded mold  2 . The mold  2  has tread forming segments  4  on each side, a bottom plate  6 , a pair of bead forming rings  11  and  9 , a top plate  8 , and a tread forming segment  5  attached to the top plate  8 . Once inserted inside the mold  2 , as shown in FIG. 11A, the mold  2  is closed and in the particular embodiment illustrated the mold segments contract against the tread belt assembly on the tread belt drum assembly  10 . In this methodology the tread rubber  12  is then forced into the tread forming grooves of the segments  4 . Once fully contracted the tread rubber  12  would adhere to the tread forming segments  4 . As illustrated it is preferred that the tread rubber  12  be warmed or applied to the building drum  10  hot, such that when the mold closed, the rubber is relatively softened so that it will easily accept, adapt and conform to the tread forming segments  4 . It is believed that the tread  12  should be warmed to a temperature of approximately 110° C., preferably between 90° C. and 110° C. Once the pressure is applied as shown, assuming the pressure does not exceed the desired limits, the entire tread belt assembly  14  will be adequately adhered to the internal surfaces of the tread forming segments  4 . While the mold  2  is still closed, it is desirable then to contract the tread belt drum assembly  10  into a radially contracted position. The tread belt  14  will remain in the tread forming segments  4 . Once fully retracted the drum  10  is freed from the tread belt assembly  14  and the top plate of the mold  8  can be removed along with the associated connected components as was illustrated in FIG. 10. Once the mold top plate  8  is removed, the tread drum assembly  10  can be removed from the mold  2 . Once removed the tread belt  14  is left in the mold  2  with the segments  4  closed and a tire building drum assembly  7  with a green carcass  72  already mounted to it can be placed into the mold  2 . As shown in FIG. 12 the carcass building drum assembly  7  has an axle  70  that is contoured and locked into the mold using locking detents  74 . Once closed a gaseous fluid or steam is introduced into the interior through the axle  70  and the internal pressure is applied to the carcass adhering it to the tread belt assembly at the interfacial surfaces. The tire is then cured in this self-locking mold  2  as illustrated in FIG. 12.  
         [0074]    When a mold  2  is first closed and the tread building drum assembly  10  is inside the mold, should the mold be misaligned or the tread rubber  12  not properly aligned for closing the segments  4 , then the clutch mechanism  113  will disengage allowing the entire assembly  10  to collapse, thereby preventing damage to the mold  2  as previously discussed.  
         [0075]    The present invention permits the assembly of the tread belt assembly  14  to be made on the building drum  10  and as illustrated and the building drum  10  being portably movable permits the entire assembly to be placed inside a mold whereby the tread belt assembly  14  can be transferred directly to the mold  2  prior to being applied to the carcass  72 . Then the tread building drum assembly  10  can be collapsed and removed from the mold  2  and the entire green carcass  72  on a building drum assembly  7  can be inserted into the mold  2 , locked into position, pressurized and cured to form a finished tire.  
         [0076]    This method for molding tires is described in a self-locking and copending patent application entitled “The Method For Curing Tires and a Self-Locking Tire Mold”, U.S. Pat. Ser. No. 10/417,849, filed on Apr. 17, 2003, which is incorporated herein by reference in its entirety. The core building drum assembly  7  for mounting the carcass directly onto is described in U.S. patent application Ser. No. 10/388,733, filed Mar. 14, 2003 and is entitled “Radially Expansible Tire Assembly Drum and Method for Forming Tires”, the contents of which are incorporated herein by reference in its entirety also.  
         [0077]    In an alternative method of practicing the invention, the tread  12  or tread belt assembly  14  can be applied to the deck  24  when the deck  24  is set at an outside diameter less than the diameter required to fit precisely in the closed mold position. Typically a small amount of at least 0.5 mm less than the desired finish diameter of the tread belt  14  is selected. In this method of assembly, once the tread  12  or tread belt assembly  14  is placed in the open mold  2  and after the mold  2  is closed and the mold segments  4  are contracted embedding into the tread rubber  12 , then the drive means  30  can be rotated, expanding the building drum  10  from the slightly smaller build diameter to the precise mold diameter required. This additional expansion firmly compresses the tread  12  or tread belt assembly  14  into the mold tread forming segments  4  and insures a slight tensioning of the tread  12  or tread belt assembly  14  into the mold tread forming segments  4  and insures a slight tensioning of the tread  12  or tread belt assembly  14 . Then the deck  24  can be retracted releasing it from the tread  12  or tread belt assembly  14  as previously discussed.