(19)
(11)EP 3 045 301 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
04.11.2020 Bulletin 2020/45

(21)Application number: 14852011.7

(22)Date of filing:  16.09.2014
(51)International Patent Classification (IPC): 
B29D 30/12(2006.01)
B29C 35/02(2006.01)
B29C 33/02(2006.01)
(86)International application number:
PCT/JP2014/074439
(87)International publication number:
WO 2015/053050 (16.04.2015 Gazette  2015/15)

(54)

RIGID CORE FOR TIRE FORMING, AND TIRE MANUFACTURING METHOD USING SAME

STEIFER KERN ZUR REIFENHERSTELLUNG UND REIFENHERSTELLUNGSVERFAHREN DAMIT

NOYAU RIGIDE POUR LA FORMATION DE PNEU ET PROCÉDÉ DE FABRICATION DE PNEU L'UTILISANT


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 10.10.2013 JP 2013213137

(43)Date of publication of application:
20.07.2016 Bulletin 2016/29

(73)Proprietor: Sumitomo Rubber Industries, Ltd.
Kobe-shi, Hyogo 651-0072 (JP)

(72)Inventor:
  • SUGIYAMA, Naoki
    Hyogo 651-0072 (JP)

(74)Representative: Manitz Finsterwald Patent- und Rechtsanwaltspartnerschaft mbB 
Martin-Greif-Strasse 1
80336 München
80336 München (DE)


(56)References cited: : 
WO-A1-2013/001964
JP-A- 2013 146 905
JP-A- 2006 224 377
JP-A- 2013 184 368
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Technical field



    [0001] The present invention relates to a rigid core for forming a tire capable of preventing the occurrence of membrane-like mold flash caused by rubber bitten between core segments, and a tire manufacturing method using the same.

    Background art



    [0002] Recently, in order to improve the accuracy of forming a tire, a method for forming a tire by the use of a rigid core (hereinafter sometimes referred to as core method) has been proposed (see Patent Documents 1 and 2, for example).
    The rigid core has a core main body having a outer shape according with a shape of the inner surface of a vulcanized tire. A raw tire is formed by sequentially applying tire components onto the core main body. And the raw tire is, together with the rigid core, put into a vulcanizing mold to be sandwiched between the core main body as the inner die and the vulcanizing mold as the outer die, and the raw tire is vulcanization molded.

    [0003] A rigid core for forming a pneumatic tire according to the preamble of claim 1 is known from document JP 2006 224377 A.

    [0004]  As shown in Figure 8 (A), the core main body (a) is composed of a plurality of core segments (c) which are divided in the circumferential direction. Thus, after the tire is vulcanized, the core main body (a) is disassembled and removed. Each of the core segments (c) has mating faces (cs) in both end surfaces in the circumferential direction.
    The mating faces (cs) of each core segment (c) are butted to circumferentially adjacent mating faces, and thereby the core main body (a) is formed in an annular shape.

    [0005] Here, the temperature of the core main body (a) is changed from normal temperature (about 15 to 50 degrees C) during forming the raw tire to high temperature (100 degrees C or more) during vulcanization. Accordingly, as enlargedly shown in Figure 8 (B), the core main body (a) at the normal temperature is provided between the mating faces (cs, cs) with a gap (d) of about 0.2 mm, for example. As a result, in the thermal expansion state during vulcanization, the mating faces (cs) substantially contact with each other.

    [0006] In the core method, the vulcanizing mold is closed and the internal pressure is added before the core main body (a) expands thermally. Therefore, an phenomenon that part of the rubber (g) of the raw tire T penetrates into the gap (d), so-called rubber bite phenomenon, occurs.
    As shown enlargedly in Figure 8 (C), by the decrease in the gap (d) due to the thermal expansion, the rubber (g) penetrating into the gap (d) is extend as a thin membrane-like mold flash g1 and adhered to the mating faces (cs). As a result, at each time the tire is vulcanization molded, it is necessary to remove the membrane-like mold flash g1 from the mating faces (cs) of the disassembled core segments (c). Therefore, there is a problem such that the production efficiency of the tire is reduced.

    Prior art documents


    Patent documents



    [0007] 

    Patent Document 1: JP 2011-161896

    Patent Document 2: JP 2011-167979


    Summary of the invention


    Problems to be solves by the invention



    [0008] The present invention is intended to provide a rigid core for forming a tire and a tire manufacturing method using the same, in which essentially by providing in each mating face with a border recess extending along the outer peripheral edge, the bitten rubber can be prevented from adhering to the mating face as a membrane-like mold flash, and the tire manufacturing efficiency can be improved.

    Means for solving the problems



    [0009] According to claim 1, the present invention relates to a rigid core for forming a tire which is a rigid core for vulcanization molding a raw tire which comprises an annular core main body provided in an outer surface thereof with a tire molding surface for forming a raw tire and
    which is put into a vulcanizing mold together with the raw tire so as to mold the raw tire between the vulcanizing mold and the core main body,
    the core main body comprises a plurality of core segments which are divided in a circumferential direction,
    each of the core segments has both circumferential end surfaces as mating faces, and the mating faces adjacent to each other in the circumferential direction are butted to each other so as to form the core main body, and
    characterized in that
    each of the mating faces is provided with a border recess extending along an outer peripheral edge of the mating face and formed by cutting away a corner between the tire molding surface and the mating face.

    [0010] In the rigid core for forming a tire according to the present invention, the border recess has a wall surface parallel with the tire molding surface and a bottom surface parallel with the mating face.

    [0011] In the rigid core for forming a tire according to the present invention, the border recess has a border width w of 0.5 to 3.0 mm from the outer peripheral edge, and a depth D of 0.1 to 0.5 mm from the mating face.

    [0012] As defined in claim 2, the present invention also relates to a method for manufacturing a tire comprising a vulcanizing step for vulcanization molding the raw tire using the rigid core according to claim, and the vulcanizing step is characterized in that a rib-like portion protruding from the inner surface of the tire is formed by rubber of the raw tire flowing into the border recess.

    Effect of the invention



    [0013] In the present inventions, as described above, the mating faces of the core segments are provided with the border recesses extending along the outer peripheral edges of the mating faces by cutting away the corners between the tire molding surfaces and the mating faces.

    [0014] Meanwhile, when the mold is closed and in the initial stage of the vulcanization molding, a phenomenon that rubber is bitten between the adjacent core segments occurs.
    However, the bitten rubber is located in the border recess, and does not penetrate into the gap between the mating faces. Therefore, if the gap between the mating faces are closed thereafter by the thermal expansion of the core main body, the bitten rubber stays in the border recess and is vulcanized as rib-like protruding portions integrated with the inner surface of the tire.
    Thus, the bitten rubber can be prevented from being stretched into a thin film and adhering to the mating faces, therefore, the operation to remove it is not required, and it is possible to improve the production efficiency of tires.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0015] 

    [Figure 1]
    a cross-sectional view showing a vulcanization step using a rigid core according to the invention.

    [Figure 2]
    a perspective view of a core main body.

    [Figure 3]
    a side view for explaining a method for disassembling the core main body.

    [Figure 4]

    1. (A) is a side view of the core segment showing the border recesses of the mating faces.
    2. (B) is a front view of the core segment in which the mating face is viewed from the front.

    [Figure 5] a partial perspective view of the core segment showing the border recess of the mating face.

    [Figure 6] (A), (B) are partial sectional views for explaining the effect of the border recesses.

    [Figure 7] (A), (B) are a front view and a side view showing an example of the core segment.

    [Figure 8]

    (A) is a side view of a core main body,

    (B), (C) are partial cross-sectional views of mating faces for explaining the problems thereof.


    Mode for carrying out the invention



    [0016] Hereinafter, an embodiment of the present invention will be described in detail.
    A tire manufacturing method according to the present invention using a rigid core 1 comprises a raw tire forming step (not shown) and a vulcanization step (shown in Figure 1).

    [0017]  As shown in Figure 1, the rigid core 1 comprises an annular core main body 2 provided in the outer surface with a tire molding surface 2s.
    The tire molding surface 2s is formed in a substantially same shape as the inner surface of the finished tire after vulcanization.
    In the raw tire forming step, well known tire components, a carcass ply, a belt ply, a sidewall rubber, a tread rubber and the like are applied onto the tire molding surface 2s in succession. Thus, the raw tire T having a substantially same shape as the finished tire, is formed on the tire molding surface 2s.

    [0018] In the vulcanization step, the raw tire T is put into a vulcanizing mold B together with the core main body 2.
    Thereby, the raw tire T is vulcanized between the core main body 2 as an inner die and the vulcanizing mold B as an outer die.

    [0019] The rigid core 1 is composed of the annular core main body 2 and a cylindrical core 3 inserted into the center hole 2H thereof. Except for the core main body 2, conventional well-known structures may be employed in the rigid core according to the present invention. In this specification, therefore, only the core main body 2 is described hereinafter.

    [0020]  The core main body 2 in this example is hollow and having a cavity 4 therein which extends continuously in the circumferential direction.
    In the cavity 4 of the core main body 2, heating means (not shown) for heating the inside of the raw tire T such as electric heater is disposed.

    [0021] As shown in Figures 2, 3, the core main body 2 is formed from a plurality of core segments 5 which are divided in the circumferential direction.
    Each of the core segments 5 has mating faces 6 in both end surfaces in the circumferential direction.
    By butting the mating faces 6, 6 of the respective core segments 5 with each other in the circumferential direction, the core main body 2 is formed in an annular shape.

    [0022] In this example, the core segments 5 are constituted by first, second core segments 5A, 5B arranged alternately in the circumferential direction.
    In the first core segment 5A, the mating faces 6 on both sides in the circumferential direction are inclined to such direction that the circumferential width decreases toward the radially inside.
    On the other hand, in the second core segment 5B, the mating faces 6 on both sides are in the circumferential direction are inclined to such direction that the circumferential width increases toward the radially inside.
    Thereby, the core main body 2 is disassembled by firstly moving the second core segments 5B radially inward.
    After vulcanization molding, each core segment 5A, 5B is sequentially removed from the bead hole of the finished tire. The core 3 prevents the core segments 5 from moving radially inwardly and connects the core segments 5 integrally.

    [0023] In Figures 4 (A), (B), the first core segment 5A is shown as a representative.
    As shown in Figures 4 (A), (B), in each of the mating faces 6, a border recess 10 extending along an outer peripheral edge 6E of the mating face 6, is formed by cutting away a corner portion Q between the mating face 6 and the tire molding surface 2S.
    The above-mentioned outer peripheral edge 6E means a ridge line at which the mating faces 6 and the tire molding surface 2s virtually intersect.
    The border recess 10 is not need to be formed over the entire periphery of the mating face 6 as far as it is formed in a range where the tire molding surface 2S is formed.
    It is desirable that the border recesses 10 are also provided on the second core segments 5B not only the first core segments 5A.

    [0024] As shown in Fig. 5, the border recess 10 is formed in a stepped shape comprising a wall surface 10a parallel with the tire molding surface 2s and a bottom surface 10b parallel with the mating face 6.
    when formed in such stepped shape, in the rubber receiving space 11 formed by the opposite border recesses 10, 10 as shown in Figure 6, it is possible to ensure a large storage volume V of the rubber (g) for the opening width 11w, and
    it is possible to enhance the effect of suppressing the occurrence of the after-mentioned mold flash.

    [0025] when closing the mold or in the initial stage of the vulcanization molding, a phenomenon that rubber is bitten between the adjacent core segments 5, 5 occurs as shown in Figure 6 (A).
    However, the rubber (g) bitten at this time is located within the rubber receiving space 11, and does not penetrate into the gap d between the mating faces 6, 6.
    Therefore, even if the gap (d) between the mating faces 6, 6 is closed as shown in Figure 6 (B) due to the subsequent thermal expansion of the core main body 2, the bitten rubber (g) stays within the rubber receiving space 11 and is vulcanized as a rib-like protruding portion 12 integrated with the inner surface of the tire.
    Thus, the bitten rubber (g) can be prevented from being stretched into a thin film and adhering to the mating faces 6, therefore, it is possible to eliminate the operation to remove it.

    [0026] As described above, the rib-like protruding portions 12 are formed on the tire inner surface, therefore, travelling performance of the tire and the external appearance quality of the tire are not deteriorated.

    [0027] As shown in Figure 4, the border width W of the border recess 10 from the outer peripheral edge 6E is 0.5 to 3.0 mm, preferably 1.0 to 3.0 mm.
    The depth D of the border recess 10 from the mating face 6 is 0.1 to 0.5 mm.
    If the depth D is less than 0.1 mm, or, the border width w is less than 0.5 mm, then the receiving volume V of the rubber receiving space 11 is reduced, and it becomes difficult to fully exert the effect to suppress the occurrence of membrane-like mold flash.
    If the depth D exceeds 0.5 mm, the opening width 11W itself is increased and the amount of the bitten rubber g increases. Thus, there is a possibility that the effect to suppress the occurrence of the membrane-like mold flash is rather deteriorated.
    During vulcanization, the rubber (g) flows into the rubber receiving space 11 due to the internal pressure even after the gap (d) is closed.
    Therefore, if the border width w exceeds 3.0 mm, the protruding portion 12 becomes high, and increases in the contact area with the border recesses 10.
    Thus, the adhesion between the rubber (g) and the border recess 10 becomes strong, and a part of the protruding portion 12 is torn off from the tire when removing the core segments 5 from the finished tire.
    As a result, the torn protruding portion 12 is remained in the tire, and thereby the internal appearance is deteriorated. Therefore, the work to remove the torn protruding portion 12 is needed.

    [0028] In the core main body 2, the above-mentioned cavity 4 can be formed as being closed within each core segment 5 as shown in Figures 7 (A), (B), without extending continuously in the circumferential direction. That is, in each core segment 5, the cavity 4 is not opened in the mating faces 6.
    In this case, a heated fluid such as steam can be used as the heating means. By flowing the heated fluid into the cavity 4, the inside of the raw tire T is heated through the core main body 2.

    [0029] while detailed description has been made of an especially preferable embodiment of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiment.

    working Examples



    [0030] In order to confirm the effects of the present inventions, the core main bodies for forming a pneumatic tire of size 195/65R15, were experimentally manufactured based on the specifications shown in Table 1.
    And, pneumatic tires formed by using the core main bodies were evaluated with respect to the occurrence of membrane-like mold flash and the production efficiency of tires.

    [0031] They had substantially same specifications except for those listed in Table 1.
    The core main body was made of aluminum (coefficient of thermal expansion = 23.1 x 10^-6 / degree) and divided into ten core segments.
    The raw tire was formed when the core main body was at normal temperature (20 degrees C), and the core main body was heated to a high temperature of 150 degrees C in the vulcanizing mold.
    The gap (d) between the mating faces in the normal temperature state was 0.2 mm.
    In each of the border recesses, the wall surface was parallel with the tire molding surface and the bottom surface was parallel with the mating face.

    [0032] 
    1. (1) Occurrence of membrane-like mold flash:
      After vulcanization molding, the presence or absence of membrane-like mold flash adhering to the mating faces was visually observed.
      And it was evaluated by the number of occurrence of the membrane-like mold flash when one hundred tires were vulcanization molded. The smaller number is better.
    2. (2) Tire production efficiency:
      The sum of the working hours to remove the membrane-like mold flash and the working hours to remove torn protruding portions remaining in the inside of the tire, was evaluated by an index based on Comparative example 1 being 100.


    [0033] The smaller number is better because the working time can be shortened.
    [Table 1]
     comparative exampleworking example 1working example 2working example 3working example 4working example 5working example 6working example 7working example 8working example 9
    border recess none  
    border width W (mm) -- 0.5 1.0 2.0 3.0 3.5 2.0
    depth D (mm) -- 0.3 0.05 0.1 0.5 0.6
    Occurrence of membrane- like mold flash 100 95 3 0 0 0 0 0 0 13
    Tire production efficiency 100 95 3 0 0 22 58 0 0 0


    [0034] As shown in Table 1, it was confirmed that, in the rigid cores as working examples,
    the membrane-like mold flash did not occur, and the working time to assemble and disassemble the core main body can be shortened.

    Description of the signs



    [0035] 
    1
    rigid core
    2
    core main body
    2S
    tire molding surface
    5
    core segment
    6
    mating face
    6E
    outer peripheral edge
    10
    border recess
    10a
    wall surface
    10b
    bottom surface
    B
    vulcanizing mold
    Q
    corner
    T
    raw tire



    Claims

    1. A rigid core (1) for forming a tire which is a rigid core (1) for vulcanization molding a raw tire (T), comprising an annular core main body (2) provided in an outer surface thereof with a tire molding surface (2S) for forming a raw tire (T), and being put into a vulcanizing mold (B) together with the raw tire (T) so as to mold the raw tire (T) between the vulcanizing mold (B) and the core main body (2),
    the core main body (2) comprises a plurality of core segments (5) which are divided in a circumferential direction,
    each of the core segments (5) has both circumferential end surfaces as mating faces (6), and the mating faces (6) adjacent to each other in the circumferential direction are butted to each other so as to form the core main body (2), and
    each of the mating faces (6) is provided with a border recess (10) extending along an outer peripheral edge (6E) of the mating face (6) and formed by cutting away a corner between the tire molding surface (2S) and the mating face (6),
    characterized in that
    the border recess (10) has a wall surface (10a) parallel with the tire molding surface (2S) and a bottom surface (10b) parallel with the mating face (6) and
    the border recess (10) has a border width (w) of 0.5 to 3.0 mm from the outer peripheral edge (6E), and a depth (D) of 0.1 to 0.5 mm from the mating face (6).
     
    2. A method for manufacturing a tire comprising a vulcanizing step for vulcanization molding a raw tire (T) using the rigid core (1) according to claim 1, and
    the vulcanizing step is characterized in that a rib-like portion protruding from the inner surface of the tire is formed by rubber of the raw tire flowing into the border recess.
     


    Ansprüche

    1. Starrer Kern (1) zum Bilden eines Reifens, der

    ein starrer Kern (1) zum Vulkanisationsformen eines Rohreifens (T) ist, der einen ringförmigen Kernhauptkörper (2) umfasst, der in seiner Außenfläche mit einer Reifenformgebungsfläche (2S) zum Bilden eines Rohreifens (T) versehen ist und der zusammen mit dem Rohreifen (T) in eine Vulkanisierform (B) gelegt wird, um den Rohreifen (T) zwischen der Vulkanisierform (B) und dem Kernhauptkörper (2) zu formen,

    wobei der Kernhauptkörper (2) eine Vielzahl von Kernsegmenten (5) umfasst, die in einer Umfangsrichtung abgeteilt sind,

    eine jedes der Kernsegmente (5) beide Umfangsendflächen als Passflächen (6) aufweist und die in Umfangsrichtung zueinander benachbarten Passflächen (6) stumpf aneinanderstoßen, so dass sie den Kernhauptkörper (2) bilden, und

    eine jede der Passflächen (6) mit einer Randausnehmung (10) versehen ist, die sich entlang einer äußeren Umfangskante (6E) der Passfläche (6) erstreckt und durch Wegschneiden einer Ecke zwischen der Reifenformgebungsfläche (2S) und der Passfläche (6) gebildet ist,

    dadurch gekennzeichnet, dass

    die Randausnehmung (10) eine Wandfläche (10a) parallel zu der Reifenformgebungsfläche (2S) und eine Bodenfläche (10b) parallel zu der Passfläche (6) aufweist und

    die Randausnehmung (10) eine Randbreite (W) von 0,5 bis 3,0 mm von der äußeren Umfangskante (6E) und eine Tiefe (D) von 0,1 bis 0,5 mm von der Passfläche (6) aufweist.


     
    2. Verfahren zum Herstellen eines Reifens, umfassend einen Vulkanisationsschritt zum Vulkanisationsformen eines Rohreifens (T) unter Verwendung des starren Kerns (1) nach Anspruch 1, und
    wobei der Vulkanisationsschritt dadurch gekennzeichnet ist, dass ein rippenartiger Abschnitt, der von der inneren Oberfläche des Reifens vorsteht, durch Kautschuk des Rohreifens gebildet wird, der in die Randausnehmung fließt.
     


    Revendications

    1. Noyau rigide (1) pour former un pneumatique, qui est un noyau rigide (1) pour le moulage par vulcanisation d'un pneumatique brut (T), comprenant un corps principal de noyau (2) annulaire doté dans une surface extérieure de celui-ci d'une surface de moulage de pneumatique (2s) pour former un pneumatique brut (T), et étant placé dans un moule de vulcanisation (B) conjointement avec le pneumatique brut (T) de manière à mouler le pneumatique brut (T) entre le moule de vulcanisation (B) et le corps principal de noyau (2),
    le corps principal de noyau (2) comprend une pluralité de segments de noyau (5) qui sont divisés dans une direction circonférentielle,
    chacun des segments de noyau (5) a les deux surfaces d'extrémité circonférentielles en tant que faces appariées (6), et les faces appariées (6) adjacentes les unes aux autres dans la direction circonférentielle sont en butée les unes contre les autres de manière à former le corps principal de noyau (2), et
    chacune des faces appariées (6) est pourvue d'un évidement de bordure (10) s'étendant le long d'un bord périphérique extérieur (6E) de la face appariées (6) et formé en enlevant par découpe un coin entre la surface de moulage du pneumatique (2S) et la face appariée (6),
    caractérisé en ce que
    l'évidement de bordure (10) présente une surface de paroi (10a) parallèle à la surface de moulage de pneumatique (2S) et une surface de fond (10b) parallèle à la face appariée (6) et
    l'évidement de bordure (10) présente une largeur de bordure (w) de 0,5 à 3,0 mm depuis le bord périphérique extérieur (6E) et une profondeur (D) de 0,1 à 0,5 mm depuis la face appariée (6).
     
    2. Procédé de fabrication d'un pneumatique comprenant
    une étape de vulcanisation pour le moulage par vulcanisation d'un pneumatique brut (T) en utilisant le noyau rigide (1) selon la revendication 1, et
    l'étape de vulcanisation est caractérisée en ce qu'une partie en forme de nervure en projection depuis la surface intérieure du pneumatique est formée par le caoutchouc du pneumatique brut s'écoulant jusque dans l'évidement de bordure.
     




    Drawing


























    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description