JPS63151408A - Bladder for vulcanizing and molding tire - Google Patents

Abstract

PURPOSE:To permit better deflating effect to be exhibited by a method in which the width of the main part of bent groove is made smaller and the depth thereof is made greater toward the corresponding part of tire shoulder from the clamp part. CONSTITUTION:A bladder B for vulcanizing and molding tire is formed of a rubber, and vent groove 4 is formed on the outer surface of the cylindrical body 1 from the clamp part 2 to the corresponding part 3 of tire shoulder. In the groove 4, the width of the main part 4m is made gradually smaller as it goes toward the part 3 from the clamp part 2, and the depth thereof is made deeper as it goes toward the part 3 from the part 2. In the tip part 4t of the groove 4, the width and depth are made smaller as it goes toward the tip. During the expansion in vulcanization and molding, the cross sectional shape of the groove 4 can be kept almost constant in the longitudinal direction from the part 2 to the part 3, permitting better deflating effect to be exhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a bladder attached to a tire vulcanization molding apparatus.

[Prior art]

In a tire vulcanization molding apparatus, a rubber balloon-shaped bladder is provided inside a mold to inflate and press the inner surface of an unvulcanized tire using air pressure. A vent groove for air release is provided on the outer surface of the cylindrical body of the bladder, so that the bladder and the inner surface of the unvulcanized tire can be brought into good contact.

As shown in FIG. 4, the main portion 14m of the vent groove 14 provided in the conventional bladder, excluding the tip 14t, has the same width and depth as the lengthwise direction. When such a bladder is inflated, the shape of the vent groove 14 does not maintain a uniform groove shape in the longitudinal direction, and the width becomes wider and the depth becomes shallower as it goes from the clamp part to the corresponding part of the tire shoulder part. It was becoming like that. In particular, near the corresponding part of the tire shoulder, the cross-sectional shape before inflation was as shown in Figure 5A, but due to stretching, it became wider and shallower as shown in Figure 5B, reducing the air venting effect. There was a problem with this.

Further, there is no problem when the bladder is new, but as the rubber becomes fatigued, the edge portion 14e of the vent groove 14 becomes a sharp protrusion. Therefore, this edge portion 14e
When inflated, it would bite into the inner liner inside the tire, causing damage to the carcass cord due to heat.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned conventional problems, to make the shape of the vent groove uniform in the longitudinal direction when the bladder is inflated, and to exhibit a good air venting effect. It is an object of the present invention to provide a bladder for tire vulcanization molding that can be used.

[Structure of the invention]

To achieve the above object, the present invention provides a bladder in which a vent groove is provided on the outer peripheral surface of a cylindrical body, in which the width of the main part of the vent groove is narrowed from the clamp part toward the corresponding part of the tire shoulder part, and The groove main portion is characterized by increasing in depth from the clamp portion toward the corresponding portion of the tire shoulder portion.

Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings.

FIG. 1 shows a tire vulcanization molding pladder according to an embodiment of the present invention. This bladder B is molded from rubber, and has clamp parts 2, 2 formed at both ends of its cylindrical body 1 to be gripped by a vulcanization molding apparatus. Further, a plurality of vent grooves 4 are formed on the outer surface of the cylindrical body 1, extending from the clamp portion 2 to the corresponding portion 3 of the tire shoulder portion.

The vent groove 4 is formed such that the groove width at the main part 4m becomes narrower as it goes from the clamp part 2 to the corresponding part 3 of the tire shoulder part, whereas the groove depth is narrower from the clamp part 2 to the tire shoulder part It is formed so that it becomes deeper toward the corresponding portion 3 of the section. Further, the tip end portion 4t of the vent groove 4 is formed such that both groove width and depth become smaller toward the tip end.

Further, in the present invention, it is preferable that the edge portion 4e of the vent groove 4 has an arcuate curved surface as shown in FIG.

According to the above-described bladder B according to the present invention, when inflated during tire vulcanization molding, the cross-sectional shape of the vent groove 4 has a constant pattern in the longitudinal direction from the clamp portion 2 to the corresponding portion 3 of the tire shoulder portion. maintained. Therefore, this vent groove 4 can exhibit a good air venting effect.

Furthermore, if the edge portion 4e of the vent groove 4 is formed into a curved surface as shown in Fig. 3, even when the rubber becomes fatigued, the edge portion 4e will not dig into the inner liner, and the carcass cord will be heated. There is no possibility of damage caused by Accordingly, the inner liner can be made thinner.

〔Effect of the invention〕

As described above, in the bladder of the present invention, the width of the main part of the vent groove is narrowed from the clamp part to the corresponding part of the tire shoulder part, and the depth of the main part of the vent groove is narrowed from the clamp part to the corresponding part of the tire shoulder part. Since the vent groove is made larger toward the corresponding portion, the shape of the vent groove when the bladder is inflated can be uniform in the longitudinal direction, and an extremely good air venting effect can be achieved.

In addition, if the edge of the vent groove is formed into a curved surface,
Even if the rubber becomes fatigued, the edge portion will not dig into the inner liner during tire molding, so the carcass cord will not be damaged by heat, unlike conventional bladders. This also allows the inner liner of the tire to be made thinner.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a bladder according to an embodiment of the present invention, FIG. 2 is a perspective view of a vent groove provided in the same bladder, FIG. 3 is a sectional view of a vent groove according to another embodiment, and FIG. The figure is a perspective view of a vent groove provided in a conventional bladder, Figure 5A is a sectional view of the vent groove of a conventional bladder before inflation, and Figure 5B is a vent groove when a conventional bladder is inflated. Cross-sectional view of the groove, No. 6
The figure is a sectional view of a vent groove that is deformed when a conventional bladder rubber becomes fatigued. B... Bladder 11... Cylindrical body, 2... Clamp part, 3... Corresponding part of tire shoulder part, 4
...Vent groove, 4m...The main part (of the vent groove).

Claims (2)

[Claims] (1) In a bladder in which a vent groove is provided on the outer peripheral surface of the cylindrical body, the width of the main portion of the vent groove is made narrower from the clamp portion toward the corresponding portion of the tire shoulder portion, and the depth of the main portion of the vent groove is reduced. A bladder for tire vulcanization molding, characterized in that the bladder is deepened from the clamp part to the corresponding part of the tire shoulder part. (2) The tire molding bladder according to claim 1, wherein the edge portion of the vent groove is formed into a curved surface.