Method for Manufacturing Tires

Abstract

A method for building a tire on a toroidal core, to include carcass plies with a high tensile resistance and bead portions with an improved rigidity, wherein the carcass plies (4, 10) are formed by continuously applying carcass cords (3, 9) onto an outer surface of the core over entire periphery thereof. An inner carcass ply (4) is formed by feeding the carcass cord (3) in a meridian direction of the core (1), and folding back the carcass cord (3) at each side portion of the core. Each radially inner peripheral portion (7) of the inner carcass ply (9) is turned-up radially outwards about a bead core (6). A skim rubber (8) is subsequently applying onto an outer surface of the inner carcass ply (9), which has been formed with the turned-up portions (7a). An outer carcass ply (10) is formed by feeding a carcass cord (4) in the meridian direction of the core (1) and folding back the carcass cord (4) at each side portion of the core (1), and applied onto an outer surface of the skim rubber (8).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) through 1(d) are schematic perspective views showing the steps in the method according to one embodiment of the present invention;

FIG. 2 is a schematic developed plan view showing one example of the inner carcass ply;

FIGS. 3( a) and 3(b) are schematic developed plan views showing further examples of the inner carcass ply;

FIGS. 4( a) and 4(b) are schematic sectional views showing the manner of turning-up the inner carcass ply;

FIG. 5 is a schematic perspective view showing the turned-up portion of the carcass ply;

FIG. 6 is a schematic sectional view showing one example of arrangement of the reinforcement rubbers; and

FIG. 7 is a schematic perspective view showing the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention is shown in FIG. 1 in which a rigid core 1 of substantially toroidal shape has an outer surface previously applied with an inner liner 2 of a predetermined thickness. The inner liner 2 may be formed, for example, by a spiral or helical winding of the ribbon-like rubber strip and lamination of the strip winding layers. As shown in FIG. 1(a), at least one carcass cord 3 comprised of an organic fiber material is applied onto the outer surface of the inner liner 2, from one side portion of the core 1 to the other side portion, so as to linearly extend in the meridian direction. At each side portion of the core 1, the carcass cord 3 is folded back in a U-shaped manner, while causing an indexing movement of the core 1 in a predetermined direction, over a predetermined angular range. These operations are repeated over an entire circumference of the core 1, so as to form an inner carcass ply 4, which is continuous in a zigzag manner, as shown in the developed view in FIG. 2.

In this instance, it is preferred to use a carcass cord 3 which has been subjected to a dipping process for improving the adhesion to the rubber. The above-mentioned application of the carcass cord 3 may be performed by using an apparatus disclosed in Japanese Patent Application Laid-open Publication Nos. JP 2000-52448A and JP 2002-127268A. The apparatus disclosed in the former patent document includes a swinging feed mechanism for causing a reciprocating movement, in the meridian direction of the core 1, of the cord passage provided at the tip end of an arm, a pin for winding and supporting the carcass cord 3 at a folding back position in the reciprocating movement of the cord passage, and a pressure mechanism including a pressure member that is movable toward and away from the pins, for urging the wound portion of the carcass cord 3 against the core 1. The pressure mechanism follows the indexing movement of the core 1 to undergo a swinging movement in the indexing direction, and is returned to its initial position after the pin has been separated from the core.

The apparatus disclosed in the latter patent document serves to ensure that the folded back portions of the carcass cord is more positively applied to the core 1, and thus includes a pin for winding and supporting the carcass cord 3 at the folding back portion in the reciprocating movement of the cord passage, and a pressure mechanism that is movable toward and away from the pins, for urging the wound portion of the carcass cord 3 against the core 1. The pressure mechanism is comprised of a pressure block that follows the indexing movement of the core 1 to move in the indexing direction, as well as a movement suppression block that is movable by an amount corresponding to two pitches of the indexing movement of the core 1 while urging the wound portion of the carcass cord 3 against the core 1, the carcass cord having been already applied to the outer peripheral surface of the core 1.

The inner carcass ply 4 is formed as shown in the developed view of FIG. 2, though it may be alternatively formed so that two or three carcass cords 3 are overlapped with each other at the folding back positions 5, as shown in the schematic developed plan view of FIGS. 3(a) or 3(b), or four or more carcass cords are overlapped with each other in the similar manner.

After the inner carcass ply 4 has been formed, as shown in FIG. 1(b), annular bead cores 6 held by a bead setter or the like are positioned relative to predetermined locations in the side portions of the core 1. Subsequently, as shown in FIG. 1(c), the inner peripheral portions 7 of the carcass ply 4, which are to be situated on the radially inner side of the bead cores 6, are turned-up radially outwards about the bead cores 6 so as to form turned-up portions 7a.

In this instance, the turning-up of the inner peripheral portions 7 in the inner carcass ply may be performed, for example, by a radial expansion deformation of bladders arranged in the inner peripheral portion of the core 1, or by successive operation of a mechanical expansion/contraction means, which is arranged in a predetermined storage position of the core 1, so that it is successively moved axially outwards and radially outwards. The turning-up of the inner peripheral portions 7 may be performed so that, as shown in a schematic sectional view in FIG. 4(a), the turned-up edge E of the carcass ply 4 is spaced from the main body portion of the carcass ply 4 or, as shown in FIG. 4(b), the turned-up edge E is alternatively in contact with the main body portion of the carcass ply 4.

In any of these cases, there may be arranged bead reinforcement rubbers, such as bead fillers having a thickness that is gradually reduced radially outwards, on the outer peripheral side of the bead core 6 and between the main body portion and the turned-up portion of the carcass ply 4.

FIG. 5 is a perspective view showing the turned-up portion 7a of the carcass ply 4 such as that shown in FIG. 3(a). This turned-up portion 7a includes carcass cords 3 which are crossed at their folding back portions so as to restrain each other, thereby further improving the withdrawal resistance of the carcass ply 4.

Subsequently, as shown in FIG l(d), a skim rubber 8 comprised of a ribbon-like rubber strip is wound spirally or helically on the outer surface of the inner carcass ply 4, and an outer carcass ply 10 is applied onto the outer surface side of the skim rubber 8. The outer carcass ply 10 may be formed in the same manner as the inner carcass ply 4, by applying a carcass cord 9 so as to extend in the meridian direction and folding back the carcass cord 9 at each side portion of the core 1. In this instance, the skim rubber 8 serves to prevent mutual contact of the inner carcass ply 4 and the outer carcass ply 10 with each other, thereby eliminating the risk of premature wear or fracture of the ply cords.

It is needless to mention that the formation of the outer carcass ply 10 also may be such as that shown in FIG. 2 or FIG. 3(a) or 3(b). However, it is preferred that the outer carcass ply has an inner peripheral edge that is positioned, as shown by imaginary lines in FIGS. 4(a) and 4(b), at a location corresponding to any region in the turned-up portion 7a of the inner carcass ply 4.

When the inner and outer carcass plies 4, 10 are formed in the manner explained above, if the tire to be built is a run-flat tire, reinforcement rubbers of crescent-shaped cross-section may be arranged in each side portions of the core 1, at a location between the inner liner 2 and the inner carcass ply 4 and/or a location between the inner and outer carcass plies 4, 10. Such reinforcement rubber may be formed by winding and laminating a ribbon-like rubber strip in desired regions, to have a desired cross-sectional shape.

In this instance, when reinforcement rubbers are interposed between the inner and outer carcass plies 4, 10, the reinforcement rubbers effectively contribute, at least in their regions, to provide an improved adhesion between these carcass plies through vulcanization. Thus, it is preferred to remove the skim rubber 8 from the region of the reinforcement rubbers, in view of avoiding increase in the weight and production cost of the tires.

FIG. 6 is a schematic sectional view showing an arrangement which includes the reinforcement rubbers at both locations. Reference numeral 11 denotes an inner side reinforcement rubber that is interposed between, and adhered to the inner liner 2 and the inner carcass ply 4, and reference numeral 12 denotes an outer side reinforcement rubber that is interposed between, and adhered to the inner carcass ply 4 and the outer carcass ply 10.

After the formation of the inner and outer carcass plies 4, 10 has been completed in the manner explained above, further tire constitutive members, such as belt layers, tread rubber, sidewall rubbers, rubber chafers, etc., which are not shown in the drawings, are formed and/or arranged on the outer side of the carcass plies 4, 10, so as to complete building of a desired green tire.

Claims

1. A method for manufacturing tires, wherein at least one carcass ply is formed by continuously applying a carcass cord onto an outer surface of a substantially toroidal core, over an entire periphery thereof, and various tire constitutive members are applied onto an outer surface of the carcass ply, so as to build a green tire, said method comprising: forming an inner carcass ply by feeding a carcass cord in a meridian direction of the core, and folding back the carcass cord at each side portion of the core;turning-up each radially inner peripheral portion of the inner carcass ply radially outwards about a bead;subsequently applying a skim rubber onto an outer surface of the inner carcass ply, which has been formed with the turned-up portions;forming an outer carcass ply by feeding a carcass cord in the meridian direction of the core, and folding back the carcass cord at each side portion of the core; andapplying the outer carcass ply onto an outer surface of the skim rubber.

2. The method for manufacturing tires according to claim 1, further comprising arranging said outer carcass ply so that radially inner peripheral edges thereof are overlapped with the respective turned-up portions of the inner carcass ply.

3. The method for manufacturing tires according to claim l, further comprising arranging said skim rubber over an entire region where said outer carcass ply is overlapped with the turned-up portions of the inner carcass ply.

4. The method for manufacturing tires according to claim 1, further comprising applying a reinforcement rubber onto an inner surface of the inner carcass ply at side regions of the core, said reinforcement rubber having a crescent-like cross-section.

5. The method for manufacturing tires according to claim 1, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

6. The method for manufacturing tires according to claim 2, further comprising arranging said skim rubber over an entire region where said outer carcass ply is overlapped with the turned-up portions of the inner carcass ply.

7. The method for manufacturing tires according to claim 2, further comprising applying a reinforcement rubber onto an inner surface of the inner carcass ply at side regions of the core, said reinforcement rubber having a crescent-like cross-section.

8. The method for manufacturing tires according to claim 3, further comprising applying a reinforcement rubber onto an inner surface of the inner carcass ply at side regions of the core, said reinforcement rubber having a crescent-like cross-section.

9. The method for manufacturing tires according to claim 6, further comprising applying a reinforcement rubber onto an inner surface of the inner carcass ply at side regions of the core, said reinforcement rubber having a crescent-like cross-section.

10. The method for manufacturing tires according to claim 2, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

11. The method for manufacturing tires according to claim 3, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

12. The method for manufacturing tires according to claim 4, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

13. The method for manufacturing tires according to claim 6, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

14. The method for manufacturing tires according to claim 7, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

15. The method for manufacturing tires according to claim 8, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.

16. The method for manufacturing tires according to claim 9, further comprising applying a reinforcement rubber between the inner carcass ply and the outer carcass ply at side regions of the core, in place of said skim rubber, said reinforcement rubber having a crescent-like cross-section.