JP6694342B2 - Bent piece and rubber mold - Google Patents

Description

  Embodiments of the present invention relate to a vent piece and a rubber molding die.

  A mold used for molding a rubber product such as a tire (that is, a rubber molding mold) is provided with a vent hole as an exhaust hole for exhausting air inside the mold. For example, in a tire vulcanization molding die, a large number of vent holes are formed in order to exhaust air existing between the unvulcanized tire and the die.

  A rubber material flows into these vent holes during molding to form whisker-shaped protrusions called spews, so that a separate removing step is required. Therefore, various proposals have been made to prevent the rubber material from flowing in while allowing the exhaust from the vent hole.

  For example, in Patent Document 1, as a vent piece to be attached to a belt hole, a vent hole is provided from one end of a vent piece body, a recess communicating with the vent hole is provided from the other end, and the recess is made of a metal sintered body. It is disclosed to use a porous body having a porous body. This document discloses that the vent hole forms a vent spew, and therefore the length of the vent hole is set to be short.

JP, 2007-062235, A

  In the technique disclosed in Patent Document 1 described above, in order to make the vent spew inconspicuous, it is conceivable to reduce the diameter of the ventilation hole, but if it is simply reduced, exhaust from the ventilation hole will be insufficient. For example, when the ventilation hole communicates with only one void formed between the granular materials of the porous sintered body, it is communicated with other voids inside the porous sintered body, but Once the void is filled with rubber material, it can no longer be evacuated. On the other hand, if the diameter of the vent hole is increased to enhance the exhaust effect, the vent spew becomes thicker and the appearance is impaired.

  The embodiment of the present invention aims at providing a vent piece which can make exhaust nature and appearance both compatible.

  A vent piece according to an embodiment of the present invention is a vent piece that is attached to a vent hole of a rubber molding die, and has a cylindrical peripheral wall portion that fits into the vent hole and an end wall that closes one end of the peripheral wall portion. A casing having a portion, and an aggregate of granular materials loaded in the casing, the end wall portion is provided with a vent hole for communicating the aggregate with the outside of the casing, The pores are formed in a long hole shape extending over a plurality of voids formed between the granular materials of the aggregate.

  In the rubber molding die according to the embodiment of the present invention, the vent piece is attached to the vent hole.

  According to this embodiment, it is possible to improve the exhaust performance from the vent hole while suppressing the deterioration of the appearance.

It is sectional drawing of the rubber molding die which concerns on one Embodiment. It is a principal part expanded sectional view of the rubber molding die which shows the state which attached the vent piece to the vent hole. (A) is a plan view of the vent piece, (B) is a sectional view taken along the line XX, and (C) is an enlarged plan view of the periphery of the vent hole.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a rubber molding die 10 according to an embodiment. The mold 10 is a mold for vulcanizing and molding a pneumatic tire, that is, a tire vulcanizing and molding mold. The mold 10 forms an annular tread mold part 12 for molding a tire tread part, a pair of upper and lower side mold parts 14, 14 for molding a sidewall part of a tire, and a bead part of a tire. And a pair of upper and lower bead rings 16, 16 for forming a cavity 18 which is a molding space for a pneumatic tire.

  The tread molding surface, which is the inner peripheral surface of the tread mold portion 12, is provided with a ridge 20 for forming a groove in the tread portion, and an area defined by these ridges 20 is a rib or block in the tread portion. It is a concave portion 22 for forming the land portion.

  The inner surface 24 of the mold including the tread molding surface is provided with a vent hole 26 for venting air, which communicates with the outside of the mold 10. The vent hole 26 is provided in each recess 22. The vent holes 26 are provided not only on the inner peripheral surface of the tread mold portion 12 but also on the sidewall molding surface of the side mold portion 14.

  As shown in FIG. 2, a vent piece 30 is attached to the vent hole 26. The vent piece 30 includes a casing 32 that fits into the vent hole 26, and an aggregate 36 of the granular material 34 that is loaded into the casing 32.

  The casing 32 has a cylindrical peripheral wall portion 38 that fits inside the vent hole 26, and an end wall portion 40 that closes one end of the peripheral wall portion 38. In this example, the casing 32 also includes an end wall portion 42 that closes the other end of the peripheral wall portion 38. The casing 32 can be formed of a metal such as iron (eg, steel) or aluminum, for example. The peripheral wall portion 38 has a cylindrical shape, preferably a cylindrical shape. The end wall 40 is a lid that closes one axial end surface of the peripheral wall 38, and is provided integrally with the peripheral wall 38. The end wall 42 is a lid that closes the other axial end surface of the peripheral wall 38.

  The aggregate 36 is filled inside the casing 32, and therefore has a columnar shape, preferably a columnar shape, corresponding to the inner surface shape of the peripheral wall portion 38. Since the aggregate 36 is an aggregate of a large number of particles 34, it is a porous body having voids between the particles 34 and the voids communicate with each other. Therefore, the assembly 36 has a large number of vertical holes extending in the axial direction (height direction) and allows air to pass therethrough. As the aggregate 36, those in which the respective granular materials 34 are not bonded may be used, but it is preferable to use those in which the entire granular materials 34 are bonded to each other so as to be integrated. For example, as the aggregate 36, it is preferable to use a sintered body of the granular material 34 (a porous sintered body).

  As a material of the granular material 34, a metal such as iron (for example, steel) or aluminum is preferable. The shape of the granular material 34 is preferably a sphere, and more preferably a sphere having a uniform diameter with no variation in particle size. The particle size of the granular material 34 is preferably 0.2 to 1.0 mm, and thereby the effect of suppressing clogging due to the inflow of the rubber material can be enhanced while ensuring air permeability.

  Here, for the particle size of the granules 34, an image is obtained by microscopic observation, and the diameter (the length at the maximum transfer portion) of 10 randomly selected granules is measured using this image. This is the average particle diameter obtained as the arithmetic mean thereof.

  When a sintered body of the granular material 34 is used as the aggregate 36, its manufacturing method is not particularly limited, and it can be manufactured by an ordinary sintering method or a sintering method using a 3D laser printer. Examples of the usual sintering method include a method of molding with a mold and sintering by heating while applying pressure. As a sintering method using a 3D laser printer, for example, a powder sintering additive manufacturing method or the like can be used.

  As shown in FIG. 3, a ventilation hole 44 is provided in the upper end wall 40 of the casing 32. The ventilation hole 44 connects the assembly 36 housed inside the casing 32 and the outside of the casing 32, and is provided so as to penetrate the end wall 40.

  The ventilation hole 44 is formed in a long hole shape extending across a plurality of voids 46 formed between the granular materials 34 of the assembly 36. Specifically, as shown in FIGS. 3A and 3C, voids 46 are formed between the plurality of granular materials 34 on the axial end surface of the assembly 36. A plurality of the voids 46 are formed when viewed from the axial end surface of the assembly 36. The ventilation hole 44 is formed in a long hole shape (that is, a slit shape) having an elongated opening that extends so as to straddle the plurality of voids 46 (that is, to pass over the plurality of voids 46). Therefore, the plurality of voids 46 on the end surface of the assembly 36 are in direct communication with the outside (that is, the cavity 18) via the ventilation holes 44. In this example, the ventilation hole 44 is formed so as to straddle the four voids 46, as shown in FIG.

  The width W of the ventilation hole 44 is preferably smaller than the particle diameter of the granular material 34 of the aggregate 36. For example, the width W of the ventilation hole 44 can be set to, for example, 0.1 mm or more and less than the particle size of the granular material 34. The length L1 of the ventilation hole 44 is not particularly limited as long as it is longer than the width W of the ventilation hole 44 and spans the plurality of voids 46 as described above, and is, for example, 0.5 to 3. It may be set within the range of 0.0 mm.

  As shown in FIG. 3A, in this example, two ventilation holes 44 are provided in the end wall 40. That is, the two ventilation holes 44, 44 having a long hole shape are provided in parallel with each other. It should be noted that only one vent hole 44 may be provided in the end wall 40, or three or more vent holes 44 may be provided. From the viewpoint of improving air permeability, it is preferable to provide two or more air holes 44 in the end wall 40.

  As shown in FIG. 3 (B), the lower end wall 42 of the casing 32 is provided with a ventilation hole 48 in the same shape as the upper end wall 40. The assembly 36 and the outside of the casing 32 are communicated with each other via the.

  The outer diameter D of the vent piece 30 is not particularly limited, and may be 2.0 to 5.0 mm or 2.0 to 3.5 mm, for example. The height (axial length) L is not particularly limited and may be, for example, 5 to 20 mm or 10 to 15 mm.

  As shown in FIG. 2, the vent piece 30 is fitted and fixed in the vent hole 26. The vent piece 30 is attached so that the end wall 40 at the one end faces the cavity 18 of the mold 10, and is exposed on the molding surface of the mold 10. Therefore, the surface of the end wall 40 constitutes a part of the molding surface.

  Specifically, the vent hole 26 is provided with a mounting hole portion 28 into which the vent piece 30 is mounted. The mounting hole portion 28 is a hole having a cylindrical surface opening to the inner surface 24 of the mold at the end portion of the vent hole 26 on the inner surface 24 side of the mold, and the step portion 28A is provided to the main body flow path portion of the vent hole 26. It has a shape that is spread out. The mounting hole portion 28 is formed in a size corresponding to the outer diameter D and the height L of the vent piece 30, and in this example, when the vent piece 30 is press-fitted into the vent hole 26, the vent piece 30 is tightly fitted. As described above, the inner diameter of the mounting hole portion 28 is set to be slightly smaller than the outer diameter of the vent piece 30.

  When manufacturing a pneumatic tire using the above-described mold 10, an unvulcanized tire (green tire) is set in the mold 10 and the mold is closed, and then a bladder (not shown) arranged inside is set. The unvulcanized tire is vulcanized and molded by inflating and pressing the unvulcanized tire against the inner surface 24 of the mold and keeping it in a heated state. At that time, in this embodiment, the air accumulated between the unvulcanized tire and the inner surface 24 of the mold passes through the vent holes 44 of the end wall 40 and the assembly 36 in the vent piece 30, and the end wall 42. The air is discharged from the vent hole 26 to the outside through the vent hole 48 of the. The rubber material penetrates the air holes 44 of the end wall 40, but is prevented from entering the inside by the aggregate 36 of the particles 34. Therefore, it is possible to suppress the inflow of the rubber material into the vent hole 26 while enabling the exhaust from the vent hole 26, and the spew removing step is also unnecessary.

  According to the present embodiment, since the ventilation hole 44 of the casing 32 facing the cavity 18 is formed in the shape of an elongated hole that straddles the plurality of voids 46 in the assembly 36 inside thereof, the following operational effects are achieved. It That is, since the ventilation hole 44 is formed so as to straddle a plurality of voids 46, even if one of the voids 46 is clogged by the rubber material that has entered the ventilation hole 44, the exhaust air is exhausted through the other voids 46. Therefore, the exhaust performance can be improved. In addition, by making the ventilation holes 44 elongated, the vent spews formed by the ventilation holes 44 can be made inconspicuous and the deterioration of the appearance can be suppressed while improving the exhaust performance. be able to. In particular, by setting the width W of the ventilation hole 44 to be smaller than the particle diameter of the granular material 34, the vent spew can be made more inconspicuous and the deterioration of the appearance can be suppressed.

  Further, since the vent piece 30 is composed of the casing 32 that fits into the vent hole 26 and the aggregate 36 of the granular material 34 that is loaded into the casing 32, the vent piece 30 is excellent in workability, and the vent hole 26 of the mold 10 is excellent. Easy to attach to. Further, by using the sintered body of the granular material 34 as the aggregate 36, the mounting in the casing 32 is easy. When such a sintered body is used, the lower end wall 42 of the casing 32 is unnecessary, that is, the casing has the end wall only on one end side and the end portion on the other end side. You may use the thing without a wall. Further, even when the end wall 42 is provided, it is not necessary to provide the long vent hole 44 like the end wall 40 on the one end side as the vent hole 48, and the vent hole 48 is formed in a general round hole shape. May be.

  According to this embodiment, since the aggregate 36 of the granular materials 34 is provided in the vent piece 30, it is possible to suppress the inflow of the rubber material while allowing the air to pass therethrough. Further, the air layer existing inside the aggregate 36 makes it easy to ensure heat retention and maintain the vulcanization promoting effect.

  Although the tire vulcanization molding die has been described in the above embodiment, it can be used for a die for molding various rubber products such as a vibration-proof rubber member.

  Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention.

10 ... Mold, 12 ... Tread mold part, 14 ... Side mold part, 18 ... Cavity, 24 ... Mold inner surface, 26 ... Vent hole, 30 ... Vent piece, 32 ... Casing, 34 ... Granular material, 36 ... Aggregate , 38 ... peripheral wall portion, 40 ... end wall, 44 ... vent hole, 46 ... void

Claims (4)

A vent piece attached to the vent hole of a rubber molding die,
A casing having a cylindrical peripheral wall portion that fits into the vent hole and an end wall portion that closes one end of the peripheral wall portion; and an aggregate of granular materials loaded in the casing,
The end wall portion is provided with a ventilation hole that communicates the assembly with the outside of the casing, and the ventilation hole extends over a plurality of voids formed between the granular materials of the assembly. Vent piece formed in a hole shape.   The vent piece according to claim 1, wherein a width of the vent hole is smaller than a particle diameter of the granular material.   The vent piece according to claim 1, wherein the aggregate is a sintered body of the granular material.   A rubber molding die in which the vent piece according to any one of claims 1 to 3 is attached to a vent hole.

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