VENT SLEEVE FOR TIRE VULCANIZATION MOLD AND TIRE VULCANIZATION MOLD

Abstract

Disclosed is the invention having an object to prevent vent spew from being cut and clogged in vent holes of an aluminum mold in vulcanization molding of a tire containing an inorganic compounding agent. The present invention relates to a mold for vulcanizing and molding a tire containing an inorganic compounding agent, in which the mold is made of aluminum, and an embedded vent sleeve is made of stainless or metal containing 15% by mass or more of chromium.

Claims

1. A mold for vulcanizing and molding a tire containing an inorganic compounding agent, wherein the mold is made of aluminum, and an embedded vent sleeve is made of stainless or metal containing 15% by mass or more of chromium.

2. The mold according to claim 1, wherein a roughness (Ra) of an inner surface of a ventilation portion of the vent sleeve is 0.5 or more and less than 5.0.

3. The mold according to claim 1, wherein an overall length (c) of the vent sleeve is 10 times or more of a diameter (a) of the ventilation portion.

4. The mold according to claim 2, wherein an overall length (c) of the vent sleeve is 10 times or more of a diameter (a) of the ventilation portion.

5. The mold according to claim 1, wherein an overall length (c) of the vent sleeve is 20 to 40 times a wall thickness ((ba)/2) of the vent sleeve.

6. The mold according to claim 2, wherein an overall length (c) of the vent sleeve is 20 to 40 times a wall thickness ((ba)/2) of the vent sleeve.

7. The mold according to claim 3, wherein an overall length (c) of the vent sleeve is 20 to 40 times a wall thickness ((ba)/2) of the vent sleeve.

8. The mold according to claim 1, wherein the vent sleeve is tapered toward an outer surface of the mold.

9. The mold according to claim 2, wherein the vent sleeve is tapered toward an outer surface of the mold.

10. The mold according to claim 3, wherein the vent sleeve is tapered toward an outer surface of the mold.

11. The mold according to claim 1, wherein the vent sleeve is a stepped vent sleeve having a large diameter portion.

12. The mold according to claim 2, wherein the vent sleeve is a stepped vent sleeve having a large diameter portion.

13. The mold according to claim 3, wherein the vent sleeve is a stepped vent sleeve having a large diameter portion.

14. The mold according to claim 11, wherein an actual contact surface length (e) of the large diameter portion of the vent sleeve with an inner surface of the mold is about 2 times or more of a vent sleeve outer diameter (b).

15. The mold according to claim 11, wherein an actual contact surface length (e) of the large diameter portion of the vent sleeve with an inner surface of the mold satisfies a20be (a ratio between an outer circumference and an inner circumference of the vent sleeve).

16. The mold according to claim 14, wherein an actual contact surface length (e) of the large diameter portion of the vent sleeve with an inner surface of the mold satisfies a20be (a ratio between an outer circumference and an inner circumference of the vent sleeve).

17. The mold according to claim 8, wherein the vent sleeve is a vent sleeve manufactured by drawing processing.

18. A cleaning agent for cleaning a mold having an inner surface made of aluminum, for vulcanizing and molding a tire containing an inorganic compounding agent, wherein the cleaning agent is resin-based beads.

19. The cleaning agent according to claim 18, wherein the cleaning agent is beads made of melamine-based resin or coated on a surface with melamine-based resin.

20. A cleaning method for a mold having an inner surface made of aluminum, for vulcanizing and molding a tire containing an inorganic compounding agent, wherein the cleaning agent according to claim 18 is used.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a perspective view of an upper part of a vent sleeve of an embodiment, used in a mold of the present invention; and

[0015] FIG. 2 is a perspective view of an upper part of a vent sleeve of another embodiment, used in the mold of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] According to the present invention, there is provided a mold for vulcanizing and molding a tire containing an inorganic compounding agent, wherein at least an inner surface of the mold is made of aluminum, and at least an inner surface of a ventilation portion of a vent sleeve embedded in the mold is made of stainless or metal containing 15% by mass or more of chromium.

[0017] The present invention solves the problem of the cut of vent spew and remaining of a green tire in a mold, which are specifically caused in manufacture of a tire containing an inorganic compounding agent, with a vulcanization molding mold made of aluminum and a vent sleeve made of steel or metal containing 15% by mass or more of chromium to be embedded in the mold.

[0018] In the present specification, the inorganic compounding agent refers to an inorganic substance such as silica, which is blended for the purpose of improving the performance of a tire.

[0019] Vulcanization Mold

[0020] The mold for vulcanizing and molding a tire containing an inorganic compounding agent of the present invention is an aluminum mold generally used in a vulcanization process for a tire. At least the inner surface of the mold may be made of aluminum, or the entire mold may be made of aluminum.

[0021] Vent Sleeve

[0022] The vent sleeve used in the mold of the present invention will be described with reference to FIG. 1. In FIG. 1, an upper surface of a vent sleeve (1) forms an inner surface which is continuous with the inner surface of the mold when the vent sleeve (1) is embedded in the mold. In a preferred embodiment, the vent sleeve has a tapered cylindrical shape to facilitate embedding into an inside of a vent provided on the mold wall. At the center of the vent sleeve, a ventilation portion (10) is provided to exhaust air from inside the mold. In a preferred embodiment, the mold inner surface side of the ventilation portion is tapered such that the inner diameter decreases toward the mold outer side to promote the exhaust.

[0023] The vent sleeve is made of stainless at least at the portion with which a green tire comes in contact, that is, the upper surface and the inner surface of the ventilation portion, in particular, is made of metal containing 15% by mass or more of chromium. The entire vent sleeve may be made of stainless or metal containing 15% by mass or more of chromium. The portion with which a green tire comes in contact is made of stainless or metal containing 15% by mass or more of chromium. Thus, when the vulcanized tire is removed from the mold, a vent spew of the tire hardened after entering the ventilation portion is taken out together with the tire without being cut. Therefore, such a situation that the vent spew remains in the ventilation portion to prevent exhaust in a vulcanization process for a subsequent tire from is hindered. The vent spew taken out integrally with the tire is trimmed from the surface of the tire in a post process.

[0024] An inner surface roughness (Ra) of the mold or the ventilation portion of the vent sleeve is preferably about 0.5 to about 5.0, more preferably about 0.5 to about 3.0, most preferably about 2.0. If the inner surface roughness (Ra) of the ventilation portion exceeds 5.0, the friction with the vent spew increases when the tire is taken out of the mold, so that there is a risk that the vent spew may be cut to be clogged in the ventilation portion. On the other hand, even if the inner surface roughness (Ra) is less than 0.5, the vulcanized rubber adheres to the inner surface easily and the friction becomes large, so that there is a risk that the vent spew may be cut to be clogged in the ventilation portion.

[0025] In another embodiment, the vent sleeve used in the mold of the present invention may be a stepped vent sleeve having a large diameter portion (11) as illustrated in FIG. 2. The vent sleeve of this embodiment is supported in contact with an inner surface of a hole formed in the vulcanization mold at the outer periphery of the large diameter portion. The area in contact with the vulcanization mold is smaller in the vent sleeve of this embodiment than that of the vent sleeve of the embodiment illustrated in FIG. 1, and hence the resistance at the time of press-fitting into the mold is reduced, and the processing becomes easy.

[0026] An inner diameter (a) of the ventilation portion of the vent sleeve is preferably 1 mm to 2 mm because this facilitates trimming of the vent spew. If the inner diameter of the ventilation portion is less than 1 mm, the vent spew will be too thin and trimming after the vulcanization process will be difficult, and if it exceeds 2 mm, the required time to complete a vulcanization process of a tire blank will be long, and the length of the vent spew will be long, so that there is a risk that the vent spew may be cut inside the ventilation portion when the tire is taken out of the mold to be clogged in the ventilation portion.

[0027] An overall length (c) of the vent sleeve is equal to or greater than the length of the vent spew to be generated. If the overall length of the vent sleeve is shorter than the length of the vent spew to be generated, the distal end of the vent spew will be located outside the vent sleeve, and at the position, the internal pressure holding of the vent spew by the inner surface of the vent sleeve is released, with the result that the diameter of vent spew expands. Also, the distal end of the vent spew which protrudes to the outside of the vent sleeve by the slight resistance difference of the inner surface of the vent spew and the internal pressure received from a bladder is deformed into a spiral and interlocked with the tire when the vulcanized tire is released from the mold. Consequently, the distal end of the vent spew cannot be traced back the inside of the vent sleeve, and the vent spew is cut. Further, in order to ensure the strength of the vent sleeve, the overall length (c) of the vent sleeve is preferably about 40 times or less of the thickness of the vent sleeve ((ba)/2), more preferably 30 times or less. If the overall length (c) of the vent sleeve exceeds 40 times the thickness of the vent sleeve ((ba)/2), buckling occurs when the vent sleeve is punched into the hole formed in the mold.

[0028] An actual contact surface length (e) with the die in the stepped vent sleeve is about 2 times or more, more preferably 3 times or more of a vent sleeve outer diameter (b). This stabilizes the embedding direction of the vent sleeve, a desired embedding angle can be obtained to reduce processing error, and transfer of a vent sleeve mark to the tire can be minimized.

[0029] Furthermore, in the stepped vent sleeve, the actual contact surface length (e) is set to satisfy the formula: a20be (the ratio between the outer circumference to the inner circumference of the vent sleeve), which is an empirically obtained, from the viewpoint of heat transfer from the vulcanization mold to the vent sleeve. As a result, it is possible to secure the amount of heat received to the vent spew and to suppress the lengthening of the vent spew. However, when the actual contact surface length (e) is increased, the resistance at the time of pressing-fitting the vent sleeve into the mold also increases. The vent sleeve is embedded in the mold by impact to the upper surface or application of pushing force, but if the resistance at the time of press-fitting is increased, the upper surface is deformed (local diameter expansion only in the vicinity of the upper surface). If the upper surface is deformed, it becomes difficult to embed the vent sleeve to a desired depth, and the quality of the mold is also degraded. Therefore, the actual contact surface length (e) is preferably 40% or less of the overall length (c) of the vent sleeve, preferably 15 times or less of the vent sleeve thickness ((ba)/2), more preferably less than 10 times of the vent sleeve thickness ((ba)/2).

[0030] As a stepped vent sleeve which satisfies these dimensional conditions, one which has a ratio of a=1.2, b=3.0, c=25, d=2.8, e=9.0 can be given, for example.

[0031] With the use of a stepped vent sleeve which satisfies such dimensional conditions, both of the problems of the applicability to the mold and cut of the vent spew are solved, and a short vent spew is generated, so that trimming of the vent spew from the tread surface of the tire after the vulcanization process is facilitated.

[0032] The vent sleeve used in the present invention is made of stainless steel, preferably austenitic stainless steel, or metal containing 15% by mass or more of chromium, and hence can be manufactured by drawing processing such as swaging processing or drawing processing. The vent sleeve manufactured by drawing processing is preferable in that processing marks extend in the axial direction of the vent sleeve, and hence the resistance at the time of tire release is small, and that the adhesion to rubber decreases as the content of chromium increases, so that the vent spew is less liable to cut.

[0033] The present invention also provides, in another aspect, a cleaning agent for a mold for vulcanizing and molding a tire containing an inorganic compounding agent.

[0034] In discussion of the problem of cut of the vent spew at the time of vulcanization molding of a green tire containing an inorganic compounding agent, the inventors of the present invention have found out a phenomenon that, even if the inside of the vulcanization molding mold is cleaned using glass beads, a part of the vulcanized rubber remains on the inner surface of the mold.

[0035] In order to solve this problem, as a result of testing of various cleaning agents by the inventors of the present invention, it has been found that by using resin beads instead of glass beads, the vulcanized rubber on the inner surface portion of the mold can be removed. As the resin beads, the whole bead may be made of resin, or the bead surface may be coated with resin, and it is preferable to use a bead made of melamine resin or a bead coated with melamine on its surface. With use of mixed beads with a particle size of 50 m to 700 m, more preferably 100 m to 500 m, a balance between removal of vulcanized rubber in every part and cleaning time can be balanced.

[0036] The present invention also provides a cleaning method for a mold having an inner surface made of aluminum, for vulcanizing and molding a tire containing an inorganic compounding agent, using this cleaning agent.

[0037] The vent sleeve of the present invention can be used as a vent piece of a vulcanization mold of a tire containing an inorganic compounding agent. In addition, the cleaning agent for the mold of the present invention can be used to clean the vulcanization mold of a tire containing an inorganic compounding agent.