JP2017035841A - Tire vulcanization mold and tire vulcanization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of preventing spews from being formed on a surface of a tire after being vulcanized so that a trimming step after vulcanization can be omitted even in a case of using a mold having a vent hole.SOLUTION: Provided is a tire vulcanization mold in which a plurality of vent holes, each having one end being opened to a molding surface and other end being opened to outside, are formed. A narrow part with a smaller sectional area than other part of the vent hole is provided at an end part of the vent hole on the molding surface side and a wall surface of the vent hole is formed in a tapered shape such that a sectional area of the vent hole becomes gradually larger toward the outside, so that rubber flown into the vent hole in a closed state is cut in the narrow part in an open state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire vulcanizing mold used in a vulcanizing process of a pneumatic tire and a tire vulcanizing apparatus including the tire vulcanizing mold.

  Generally, a pneumatic tire is manufactured through a vulcanization process in which a raw cover is vulcanized using a tire vulcanization mold (hereinafter, also simply referred to as “mold”). In the vulcanization process, the mold on which the raw cover is set is closed and heated and pressurized while the raw cover is in contact with the molding surface of the mold. At this time, the mold is placed between the molding surface and the raw cover. If air remains, a so-called bear dent may occur on the tire surface after vulcanization, which may impair the commercial value of the tire.

  Therefore, conventionally, in order to prevent the occurrence of this bear, as shown in FIG. 4, a number of vent holes 2 penetrating the mold from the molding surface 14 of the mold 1 toward the mold exterior 15 are provided. Air is discharged from the vent hole (Patent Document 1).

  However, if the rubber of the raw cover T flows into the vent hole 2 after the air is exhausted, protrusions called spewes are formed on the surface of the tread of the tire after vulcanization and the commercial value is lowered. The process of trimming the spew is performed after the sulfur process.

JP 2014-113742 A

  However, in the above trimming process, the spew is cut along the tread surface of the tire and the spew is cut, so there is a possibility that the tread surface is scratched and cannot be shipped as a product. Further, the time and labor spent in the trimming process lead to an increase in tire costs.

  Therefore, the present invention can prevent spew formation on the surface of the tire after vulcanization even if a mold provided with a vent hole is used, and eliminates the need for a trimming step after vulcanization. It is an object to provide a technology that can be used.

  The inventor has intensively studied and found that the above-described problems can be solved by the invention described below, and has completed the present invention.

The invention described in claim 1
A tire vulcanization mold in which a plurality of vent holes having one end opened on the molding surface and the other end opened to the outside are formed,
A narrowed portion having a smaller cross-sectional area than the other part of the vent hole is provided at the end of the vent hole on the molding surface side,
The wall surface of the vent hole is formed in a tapered shape so that the sectional area of the vent hole gradually increases toward the outside.
A tire vulcanization mold characterized in that rubber flowing into the vent hole when closed is cut at the narrowed portion when opened.

The invention according to claim 2
2. The tire vulcanization mold according to claim 1, wherein a depth of the narrowed portion from the molding surface is 0.5 mm or less.

The invention according to claim 3
A tire vulcanizing apparatus in which the tire vulcanizing mold according to claim 1 or 2 is accommodated in a container,
The container is formed with a space communicating with the outer end of the vent hole,
The tire vulcanizing apparatus is provided with a suction device for sucking rubber in the vent hole into the space by decompressing the space formed in the container.

  According to the present invention, spew formation on the surface of a tire after vulcanization can be prevented even when a mold provided with a vent hole is used, and a trimming step after vulcanization is unnecessary. Technology that can be provided.

It is sectional drawing which shows typically the vent hole vicinity of the metal mold | die for tire vulcanization | cure which concerns on one embodiment of this invention. FIG. 2 is a cross-sectional view schematically illustrating a state in which rubber of a raw cover flows into a vent hole in the tire vulcanization mold in FIG. 1. It is sectional drawing which shows typically the left half of the tire vulcanizer provided with the suction device. It is sectional drawing which shows typically the vent hole vicinity of the conventional vulcanization die for tires.

  Hereinafter, the present invention will be described based on embodiments.

1. FIG. 1 is a cross-sectional view schematically showing the vicinity of a vent hole of a tire vulcanization mold according to the present embodiment, and FIG. 2 shows a vent in the tire vulcanization mold of FIG. It is sectional drawing which shows typically the state in which the rubber | gum of the raw cover flowed into the hole.

  As shown in FIG. 1, a tire vulcanization mold 1 according to the present embodiment has a vent hole 2 having one end opened on the molding surface 14 and the other end opened on the mold exterior 15 as in the conventional case. When the mold 1 is closed, air between the raw cover T and the molding surface 14 is discharged from the vent hole 2 to the mold exterior 15. Although not shown, a plurality of vent holes 2 are formed in one mold 1.

  However, the tire vulcanizing mold 1 according to the present embodiment is provided with a narrowed portion 21 having a smaller cross-sectional area than the other portions of the vent hole 2 at the end of the vent hole 2 on the molding surface 14 side. At the same time, the conventional tire vulcanization is such that the wall surface 22 of the vent hole 2 on the mold outer side 15 is tapered so that the cross-sectional area of the vent hole 2 gradually increases toward the mold outer side 15. It is different from the mold.

  That is, in the conventional tire vulcanizing mold 1, as shown in FIG. 4, the cylindrical vent hole 2 is formed perpendicular to the molding surface 14, so that the mold 1 is opened after vulcanization. In doing so, the rubber flowing into the vent hole 2 escapes from the vent hole 2 and is formed on the surface of the tire as a spew.

  In contrast, in the present embodiment, as shown in FIG. 2, a narrowed portion 21 is provided at the end of the vent hole 2 on the molding surface 14 side, and the wall surface 22 of the vent hole 2 is a mold. Since it is formed in a tapered shape that spreads toward the outside 15, the rubber that has flowed into the vent hole 2 when the mold is opened after vulcanization is small without forming spew on the surface of the tire. It is cut at the narrowed portion 21 having a cross-sectional area.

  For this reason, according to the present embodiment, the trimming process after the vulcanization process can be eliminated, and problems such as generation of scratches on the tread surface and an increase in manufacturing process costs that have occurred in the trimming process occur. Nothing will happen.

  In addition, it is preferable that the depth D from the molding surface 14 of the constriction part 21 is 0.5 mm or less. If the depth D exceeds 0.5 mm, the rubber G cut at the narrowed portion 21 may remain on the tire surface while having a length that can be regarded as spew.

  Moreover, it is preferable that the diameter of the constriction part 21 is (phi) 1.0-1.5mm. Thereby, the rubber G flowing into the vent hole 2 can be appropriately cut at the narrowed portion 21.

  Note that “the wall surface of the vent hole is formed in a tapered shape” is not necessarily limited to the case where the entire wall surface of the vent hole is formed in a tapered shape, and the position where the rubber flows is formed in a tapered shape. What is necessary is just to have a part which is not formed in a taper shape like FIG. 1, FIG.

2. Tire Vulcanizing Device When the tire vulcanizing mold 1 according to the above-described embodiment is used, the cut rubber G remains in the vent hole 2 as shown in FIG. In the next and subsequent vulcanization processes, it becomes difficult to efficiently exhaust the air between the molding surface 14 and the green cover T, and a new problem arises that bears are generated in the vulcanized tire. Sometimes.

  For this reason, when using the tire vulcanizing mold according to the above-described embodiment, it is preferable to use a tire vulcanizing apparatus including a suction device that sucks and removes rubber remaining in the vent hole.

  FIG. 3 is a cross-sectional view schematically showing a tire vulcanizing apparatus equipped with such a suction device. The tire vulcanizing apparatus 3 includes a container 4 that accommodates the mold 1 described above. In the figure, 52 is a packing and 53 is a filter.

  In the tire vulcanizing device 3, a space 51 is formed in the container 4 so as to communicate with the end of the vent hole 2 on the mold exterior 15 side, and the container 4 serves as a suction device that sucks the rubber in the vent hole 2. Pressure reducing means (not shown) for reducing the pressure of the space 51 is provided. Since the pressure reducing means depressurizes the space 51, the rubber remaining in the vent hole 2 is sucked and collected in the space 51, so that the vent hole 2 is not clogged with the rubber remaining in the vent hole 2. The air between the molding surface 14 and the raw cover T can be discharged efficiently.

  Hereinafter, the present invention will be described more specifically with reference to examples.

1. Test Method Among the segments divided into nine in the circumferential direction, one segment is provided with a vent hole having the structure shown in FIG. 1, and the other segment is provided with the conventional vent hole shown in FIG. Using a tire vulcanization mold, tires having a tire size of 195 / 65R15 were continuously vulcanized 10 times.

  Further, as a tire vulcanizing apparatus that accommodates the above-described tire vulcanizing mold, a tire vulcanizing apparatus provided with a suction device that sucks rubber by reducing the pressure in the vent hole as shown in FIG. 3 was used.

2. Evaluation (1) Evaluation Method Each tire after vulcanization was visually observed to examine the presence or absence of spew formation on the tread surface and the occurrence of bears.

(2) Evaluation Results In the vulcanized tire, spews were formed corresponding to all the vent holes in the portion that was in contact with the segment provided with the conventional vent holes shown in FIG. On the other hand, spew was not formed in the portion where the segment provided with the vent hole shown in FIG. 1 was in contact.

  From this, as shown in FIG. 1, the narrowed portion is formed at the end of the vent hole on the molding surface side, and the wall surface of the vent hole is formed into a taper shape extending toward the outside of the mold, thereby vulcanizing. It was confirmed that spew formation can be prevented on the surface of the subsequent tire.

  Further, since the suction device for sucking the rubber in the vent hole is provided, in the segment provided with the vent hole having the structure as shown in FIG. 1, the molding surface is similar to the segment provided with the conventional vent hole. The generation of bear due to the air remaining between the cover and the raw cover was not confirmed.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Tire vulcanizing die 2 Vent hole 3 Tire vulcanizing device 4 Container 14 Molding surface 15 Mold exterior 21 Narrow portion 22 Vent hole wall surface 51 Space 52 Packing 53 Filter D Narrow portion depth G Rubber T Raw cover

Claims (3)

A tire vulcanization mold in which a plurality of vent holes having one end opened on the molding surface and the other end opened to the outside are formed,
A narrowed portion having a smaller cross-sectional area than the other part of the vent hole is provided at the end of the vent hole on the molding surface side,
The wall surface of the vent hole is formed in a tapered shape so that the sectional area of the vent hole gradually increases toward the outside.
A tire vulcanization mold characterized in that rubber flowing into the vent hole in a closed state is cut at the narrowed portion in an open state.   The tire vulcanization mold according to claim 1, wherein a depth of the narrowed portion from the molding surface is 0.5 mm or less. A tire vulcanizing apparatus in which the tire vulcanizing mold according to claim 1 or 2 is accommodated in a container,
The container is formed with a space communicating with the outer end of the vent hole,
A tire vulcanizing apparatus, wherein a suction device is provided for sucking rubber in the vent hole into the space by decompressing the space formed in the container.

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