Abstract:
A tire building core assembly is provided including a segmented toroidal core formed by a plurality of core segments configured in a closely adjacent array defining an outer tire-building toroidal surface. The tire building surface is configured having tire tread and sidewall build locations. Adjacent core segments provide adjacent and opposed annularly directed peripheral edge surfaces, opposed edge surfaces having interlocking elements that selectively engage to operatively deter relative radial movement between the adjacent core segments. The interlocking elements selectively disengage to operatively facilitate a disassembly of the segmented toroidal core.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to a tire building core for use in the construction of an uncured tire and, more specifically, to a core assembly used in tire build construction and curing cycles. 
     BACKGROUND OF THE INVENTION 
     Historically, the pneumatic tire has been fabricated as a laminate structure of generally toroidal shape having beads, a tread, belt reinforcement, and a carcass. The tire is made of rubber, fabric, and steel. The manufacturing technologies employed for the most part involved assembling the many tire components from flat strips or sheets of material. Each component is placed on a building drum and cut to length such that the ends of the component meet or overlap creating a splice. 
     In the first stage of assembly the prior art carcass will normally include one or more plies, and a pair of sidewalls, a pair of apexes, an innerliner (for a tubeless tire), a pair of chafers and perhaps a pair of gum shoulder strips. Annular bead cores can be added during this first stage of tire building and the plies can be turned around the bead cores to form the ply turnups. Additional components may be used or even replace some of those mentioned above. 
     This intermediate article of manufacture would be cylindrically formed at this point in the first stage of assembly. The cylindrical carcass is then expanded into a toroidal shape after completion of the first stage of tire building. Reinforcing belts and the tread are added to this intermediate article during a second stage of tire manufacture, which can occur using the same building drum or work station. 
     This form of manufacturing a tire from flat components that are then formed toroidally limits the ability of the tire to be produced in a most uniform fashion. As a result, an improved method and apparatus has been proposed, the method involving building a tire sequentially on a core or toroidal body. The core or toroidal body rotates about its axis as tire components are applied layer by layer to the outer core surface. When the tire build procedure is completed on the core, the green tire will have a shape and dimension only slightly smaller than the finished tire. The aforementioned variances resulting from conventional drum expansion are thus eliminated. Building a tire on a core to a final tire shape, dimension, and uniformity therefore allows for improved quality control of the finished product. 
     Once component by component tire build is accomplished on the core, the green tire must be subjected to heat during a curing cycle. The tire and core may be as a unit subjected to heat within a curing cycle whereby the green tire is cured. It is important to maintain structural integrity of the annular tire building surface throughout the tire curing cycle and readily facilitate a subsequent separation of the core from the cured tire. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, a tire building core assembly is provided including a segmented toroidal core formed by a plurality of core segments configured in a closely adjacent array defining an outer tire-building toroidal surface. The tire building surface is configured having tire tread and sidewall build locations. Adjacent core segments provide adjacent and opposed annularly directed peripheral edge surfaces, opposed edge surfaces having interlocking elements that selectively engage to operatively deter relative radial movement between the adjacent core segments. The interlocking elements selectively disengage to operatively facilitate a disassembly of the segmented toroidal core. 
     In another aspect, the interlocking elements are configured as a projection and a detent positioned and shaped for mating engagement. The projection may include an elongate bar having a leading portion extending from one of the adjacent core segment edge surfaces and the detent may constitute an elongate groove having a sectional configuration complementing the leading portion of the elongate bar. 
     The projection leading portion may, pursuant to another aspect, be defined by a plurality of adjoining inwardly angled planar surfaces and the elongate groove defined by adjoining complementarily inwardly angled planar sidewall surfaces. 
     As a further aspect, the elongate bar and the elongate groove may be positioned on a radially outward crown region of a respective core segment edge surface and may be dimensioned to span the width of the respective crown region. 
     Definitions 
     “Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% 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. 
     “Camber angle” means the angular tilt of the front wheels of a vehicle. Outwards at the top from perpendicular is positive camber; inwards at the top is negative camber. 
     “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 of the tire tread with a flat surface at zero speed and under normal load and pressure. 
     “Groove” means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions. The “groove width” is equal to tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. Grooves may be of varying depths in a tire. The depth of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. If such narrow or wide grooves are substantially reduced depth as compared to wide circumferential grooves which the interconnect, they are regarded as forming “tie bars” tending to maintain a rib-like character in tread region involved. 
     “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. 
     “Non-directional tread” means a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern has a preferred direction of travel requiring specific wheel positioning. 
     “Outboard side” means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle. 
     “Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire. 
     “Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves. 
     “Sipe” means small slots molded into the tread elements of the tire that subdivide the tread surface and improve traction, sipes are generally narrow in width and close in the tires footprint as opposed to grooves that remain open in the tire&#39;s footprint. 
     “Slip angle” means the angle of deviation between the plane of rotation and the direction of travel of a tire. 
     “Tread element” or “traction element” means a rib or a block element defined by having a shape adjacent grooves. 
     “Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread. 
    
    
     
       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 an annular tire building core assembly. 
         FIG. 2  is an enlarged front perspective view of a large core segment. 
         FIG. 3  is an enlarged rear perspective view of the large core segment of  FIG. 2 . 
         FIG. 4  is an enlarged front perspective view of a key core segment. 
         FIG. 5  is a rear perspective view of the key core segment of  FIG. 4 . 
         FIG. 6  is a side elevation view of an assembled core shown partially in section for illustration. 
         FIG. 7  is a side elevation view of the core of  FIG. 6  shown in partial section with a large segment disassembled from the core for illustration. 
         FIG. 8  is an enlarged sectional view of the designated portion of the core identified in  FIG. 7 . 
         FIG. 9A  is an enlarged sectional view of the designated mating insert portion of the core identified in  FIG. 8 . 
         FIG. 9B  is a sectional view of separated mating insert portions shown in  FIG. 9A . 
         FIG. 10  is a top perspective view of an insert from a large core segment. 
         FIG. 11  is a top plan view thereof. 
         FIG. 12  is a side elevation view thereof. 
         FIG. 13  is an enlarged section view of a connector screw used in affixing the insert. 
         FIG. 14  is a top perspective view of an insert from a key core segment. 
         FIG. 15  is a top plan view thereof. 
         FIG. 16  is a side elevation view thereof. 
         FIG. 17  is an enlarged section view of a connector screw used in affixing the key segment insert. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIGS. 1 and 2 , a tire building core assembly  10  is shown in the assembled configuration. The core assembly  10  includes an axial through bore  12  and is configured into a toroidal form substantially near the final shape and dimension of a tire. The core assembly  10  allows for a more accurate placement of tire components in the building of an uncured tire because the tire is built to near final shape. The core assembly  10  receives an elongate spindle assembly (not shown) through the axial throughbore  12 . The core assembly and spindle configuration are disclosed in copending U.S. patent application Ser. No. 11/292,991 published Jun. 7, 2007, incorporated herein by reference. The core assembly  10  is constructed from alternate key shell segments  16  and large shell segments  18  that together form a toroidal body having a toroidal tire build surface  14 . In general, the tire components are assembled to an outer toroidal surface  14  to form an uncured tire. The core assembly, including an uncured tire carried upon surface  14  may then be loaded into a mold for curing. During curing, the core assembly  10  provides additional curing heat through heating elements (explained following) located on the inside surface of core segments  16 ,  18 . The core assembly  10  is removed from the cured tire by moving each core segment  16 ,  18  inward into the throughbore  12  and then axially removing each segment in a sequential disassembly procedure. The segments are removed from the cured tire, starting with the wedge shaped key segments  16 . Once the key segments are pulled in radially, they may be removed axially from the tire followed by like removal of the large segments  18 . 
     Referring to  FIGS. 2 ,  3  and  7 , the core segments  18 , referred herein as the (relatively) large segments, are seen to be configured generally as a hollow wedge-shaped shell body  20 . The larger core segments  18  each have a narrower radially inward side and flare outwardly to a wider radially outward side. The shell body  20  defines tire sidewall-forming regions  21  and a radial outer tread-forming region  23  shaped and dimensioned to allow the build of a tire(s) thereon to a final dimension and configuration. The shell body  20  connects at the bottom with a connector block  22  by means of assembly screws  24 . The connector block  22  has a pair of electrical connector receiving sockets  26  and an alignment throughbore  28  for interfacing with a spindle unit (not shown). The shell body  20  defines an outward surface  30  consisting of spaced apart sidewall regions  21  transitioning into a tread region  23 , the regions  21 ,  23  being shaped in accordance with the tire to be built. A heating element  32  may be affixed to an inward surface of the shell body  20  that is serviced electrically through the electrical connectors  26  to heat the shell body  20  during a cure cycle. Wiring  34  is provided to supply power to the heating element  32 . 
     A pair of generally inverted-U shaped edge surfaces  38  border each side of the generally wedge shaped shell body  20  and face annularly outward. Each edge surface  38  includes side surfaces  37 ,  38  that transition into a radially outward crown region  36  of the edge surface  38 . An elongate interlocking insert element  40  is affixed to the crown region  36  of the edge surfaces  38 . The insert element  40  is attached to the shell body  20  by appropriate means such as screws  42  as shown. Extending axially along the insert element  40  is an elongate detent channel or groove  44  as shown in detail in  FIGS. 9A and 9B . The channel  44  faces outwardly within the edge surface crown region  36 . The insert element  40  mounts within a recess of edge surface region  36  such that edges  43  of the insert element  40  transition smoothly with the edge surface crown region  36 . 
     With reference to  FIGS. 4 ,  5 ,  7 , and  8 , the key segments  16  are alternately disposed with the large segments  18  to form the annular tire build surface  14 . The segments each are configured to provide a generally hollow shell body  46  that connects at a radially inward end to a connector block  48  by appropriate means such as screws  50 . Sockets  52  and an axial bore  54  extend through the block  48  in a manner similar with the block  22  explained previously. The wedge shaped shell body  46  provides an outer tire build surface  56 . 
     A pair of generally inverted-U shaped edge surfaces  57  border each side of the generally wedge shaped shell body  46  and face annularly outward. Each edge surface  57  includes side surfaces  58 A, B that transition into a radially outward crown region  60  of the edge surface  57 . An elongate interlocking insert element  62  is affixed to the crown region  60  of the edge surfaces  57 . The insert element  62  attaches to the shell body  46  by appropriate means such as screws  64  as shown. Extending axially along the insert element  62  and projecting outwardly is an elongate bar or rib  66  as shown in detail in  FIGS. 9A and 9B . The rib or bar  66  faces outwardly from the edge surface crown region  60 . The insert element  62  mounts within a recess of edge surface crown region  60  such that edges  63  of the insert element  62  transition smoothly with the edge surface crown region  60 . 
     As best seen from  FIGS. 6 ,  7 ,  8 ,  9 A,  9 B, and  10 - 17 , the core assembly  10  is configured in an assembled state as a toroidal form by circumferentially adjacent and alternating key segments  16  and larger shell segments  18 . Each segment is generally hollow and the respective edge surfaces  57 ,  38  of the adjacent segments  16 ,  18  within the assembled core are in closely spaced opposition. In the assembled condition, adjacent segments  16 ,  18  are so aligned that the insert element bars  66  of the key segments  16  enter into engagement with the insert element grooves  44  of the large segments  18 . The engaging pairs of insert elements  66 ,  44  are along the surface to surface radial intersection of the segments  16 ,  18 , as will be appreciated from  FIG. 6 . Moreover, the engaging pairs of insert elements  55 ,  44  are positioned along the radial outward periphery of the toroidal core  10  as shown in  FIGS. 6 and 7 . The peripheral location of the mating insert elements  55 ,  44  serve to deter radial relevant movement between respectively engaged core segments  16 ,  18  during the tire build and tire cure procedures, holding the core  10  in its intended form that closely duplicates that of the desired finished tire. 
     As will be appreciated from  FIGS. 7 ,  8 ,  9 A,  9 B, and  10 - 17 , the mating bar or rib  66  of the key segments  16  and the grooves or channels  44  of the large segments  18  have a complementary sectional profile such that a close surface to surface relationship is established when the bars  66  are situated within the channels  44 . The bar  66  in the configuration shown includes sides  70  A,B that converge at respective angles θ,Φ to a planar forward nose surface  71 . The channel  44  in the configuration shown is formed by complementary sides  68 A,  68 B that likewise converge at respective angles θ,Φ to a planar internal channel floor surface. The angles θ,Φ may be the same, however it is preferred that the angles differentiate within ranges of 95 to 135 degrees, and 120 to 170 degrees, respective. Extending in opposition at a sharper angle θ, surfaces  68 A and  70 A are aligned to resist radial movement of the core segments  16 ,  18  along the line of segment to segment abutment. The shallower angle Φ in opposed surfaces  68 B,  70 B facilitate ready separation of the core segments at the conclusion of a tire build and curing cycle. 
     From the foregoing, it will be understood that, during the cure cycle, large pressures are placed on the tire as a mold is closed and the tread and sidewalls are formed about the core assembly  10 . Additional pressure is created as the metal core assembly  10  is heated to cure temperature and the rubber cures and swells in the enclosed space defined by the mold. 
     Such pressures may act to cause deflections in the tire building core segments  16 ,  18 , particularly in the tread area. The segments  16 ,  18 , as shown and described, are formed into alternately shaped key and large segments to allow the disassembly and removal of the core  10  from the cured tire. Because the segments  16 ,  18  are shaped differently, they deflect differently under the influence of the curing pressure. Specifically, the large segments  18  deflect into contact with the key segments  16 . When the deflection is sufficient, the edge of the large segment  18  deforms radially outward on the ramp formed by the key segment contact. Conversely, the same contact forces the edge of the key segment  16  radially inward. Such deflections will tend to produce an edge or discontinuity, otherwise referred to as “step-offs” that is formed into the inside of the tire. 
     Eliminating the subject “step-offs” is accomplished by the addition of hardened inserts, composed preferably but not necessarily of hardened steel, to the edges of the segments  16 ,  18 . Specifically, the crown edge regions  36 ,  60  of the segments. The insert elements or bodies  40 ,  66  represent mating teeth that engage under pressure and prevent the relative deflection between the segments  16 ,  18 . Pairs of aligned segment inserts  40 ,  66  engage when the edges of the segments are forced together and the engagement prevents sliding of one segment against the other. The insert bar or rib depth and angles θ,Φ are effective in not preventing the segments  16 ,  18  from being disassembled once the tire has been cured. When disassembly of the core assembly from the tire is required, the key segments  16  are sequentially moved inward and out of the tire, followed by the large segments  18 . With the locking inserts  40 ,  66  engaged, disassembly of the core assembly  10  is initiated by a small radially outward movement of approximately one millimeter of the two large segments  18  immediately on opposite sides of the key segment prior to removal of the key segment. Such initial movement releases the key segment for disassembly. Once the key segment is removed, the large segments on either side may be moved back to their neutral positions to await their disassembly and removal from the tire. 
     While the channel and bar insert engagement is shown to place the channel within the key segment insert, and the bar within the large segment insert, such need not necessarily be the case. The bar and channel locking inserts may be switched. Other tooth and detent groove, or other locking insert element configurations may also be employed without departing from the invention. 
     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.