JP2019018492A - Tire molding die - Google Patents

Abstract

To provide a tire molding die capable of maintaining a good appearance quality as well as a good initial performance of the tire without making a spew protrude from a tread surface of the tire and without requiring a trimming operation.SOLUTION: In a tire molding die having a concave part 8 for forming a land part 20r of a tire tread on a die surface of a partial die 5 and formed with a vent hole 9 drilled in a bottom surface 8s of the concave part 8 and communicating with the outside, a buried hole 9b is formed to a predetermined depth from the bottom surface 8s of the concave part 8 of the vent hole 9, there is provided a cylindrical body 10 which passes through a shaft hole 11 having a diameter smaller than that of the vent hole 9 as a central axis. A base end side embedded part 10b is buried in an embedding hole 9b and the cylindrical body 10 is implanted in the bottom surface 8s of the concave part 8. The cylindrical body 10 has a slit 12 which communicates the shaft hole 11 and an outer circumferential space of the cylindrical body 10 in at least a distal end side part 10a.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a tire mold for vulcanizing a tire.

A tire molding die for molding a tire having a tread surface of a block pattern is formed with a plurality of recesses defined by protrusions that form land portions of the tire tread on the mold surface.
During the vulcanization molding, when the mold surface is pressed against the unvulcanized rubber of the raw tire, if unvulcanized rubber flows into the recess of the mold surface, air or air is generated between the inner surface of the recess and the unvulcanized rubber. Gas is confined, and gas accumulation is likely to occur particularly at the corners of the recesses, and depressions (bears) due to the gas accumulation are formed on the surface of the molded tire, which may reduce the merchantability.

  Therefore, a method has been attempted in which an air vent hole (vent hole), which is a minute hole, is generally provided in the mold and gas is extracted behind the mold (for example, see Patent Document 1).

JP-A-8-267457

In the tire molding die disclosed in Patent Document 1, vent holes are formed in the inner corners of the recesses along the protrusions oriented in the circumferential direction that define the recesses on the mold surface.
Gas that tends to accumulate in the corners of the recesses can be extracted to the outside by a vent hole provided in the inner corners of the recesses, and the generation of bears can be prevented.

However, at the time of vulcanization molding, unvulcanized rubber penetrates into the vent holes, and spews, which are rubber whisker-like projections, protrude from the tread surface of the tire tread.
Since this spew is one of the causes that deteriorate the initial performance of the tire, trimming is performed to cut off the spew, but as the work process increases, some protrusions may remain due to trimming, reducing the appearance quality. As well as affecting the initial performance of the tire.

  The present invention has been made in view of the above points, and the object of the process is that the spew generated by the air vent hole at the time of vulcanization molding does not protrude from the tread surface of the tire, and there is no need for trimming work. This is to provide a tire molding die that can be maintained and the initial performance of the tire can be maintained well.

In order to achieve the above object, a tire molding die according to the present invention is:
A plurality of partial molds are combined at the time of tire molding to form an annular overall mold,
The mold surface for molding the tire tread of the partial mold has a recess defined by a protrusion that forms a land portion of the tire tread,
In a tire molding mold in which a vent hole is formed which is perforated from the bottom surface of the concave portion toward the outer peripheral surface of the partial mold and communicates with the outside.
From the bottom surface of the recess of the vent hole to a predetermined depth, has a buried hole,
A cylindrical body having a shaft hole having a smaller diameter than the vent hole passes through the central axis,
The cylindrical body is embedded in the bottom surface of the concave portion, the proximal-side embedded portion is embedded in the embedded hole,
The cylindrical body includes a slit that communicates the shaft hole and the outer peripheral space of the cylindrical body at least at a distal end side portion other than the proximal-side embedded portion.

  According to this configuration, when the unvulcanized rubber of the raw tire is pressed against the mold surface during vulcanization molding, the unvulcanized rubber flows into the concave portion of the mold surface, and the tip side portion of the implanted cylindrical body is Although encased in unvulcanized rubber, until the unvulcanized rubber fills the recess, the slit of the cylindrical body planted on the bottom surface of the recess communicates with the vent hole through the shaft hole and draws air to the outside. And the occurrence of bears can be prevented.

  Since the unvulcanized rubber covers the outer periphery of the tip side portion of the cylindrical body, the same long hole as the outer shape of the tip side portion of the cylindrical body is formed in the land portion of the tire tread and the shaft hole of the cylindrical body However, since unvulcanized rubber penetrates, spews are formed, which are rubber whisker protrusions that protrude from the bottom of the long hole, but the shaft hole is smaller in diameter than the vent hole, so the spew that is formed by the conventional vent hole Shorter than the spew that forms.

Therefore, the spew formed by the small-diameter shaft hole of the cylindrical body protrudes from the bottom surface of the elongated hole, and its protruding length is short, so that the spew is accommodated in the elongated hole so as not to protrude from the tread surface of the tire tread. Can do.
Therefore, it is not necessary to trim the spew, the appearance quality is maintained, and the initial performance of the tire can be maintained well.

In the above configuration,
The slit may be continuous from at least one axial end of the tip end portion of the cylindrical body to the tip opening at the other end.

According to this configuration, the slit is formed continuously from at least one end in the axial direction of the distal end portion of the cylindrical body to the distal end opening at the other end. Therefore, the slit is formed by the spew and slit formed by the axial hole of the cylindrical body. The formed thin plate-like fins are integrally formed continuously, and the spew and the fin are extracted together at the time of die cutting, so that it is possible to avoid the spew being cut off along with the fin as much as possible.
Therefore, it is possible to prevent as much as possible that the spew and fins are broken and the clogged parts are left behind in the shaft hole and slit of the cylindrical body.

In the above configuration,
A plurality of the slits may be formed in the circumferential direction of the shaft hole.

  According to this configuration, since a plurality of slits are formed in the circumferential direction of the shaft hole, a spew formed by the shaft hole of the cylindrical body and a plurality of fins formed by the plurality of slits are integrally formed continuously. In addition, the spew and the plurality of fins are extracted without being broken when the mold is cut, and the shaft hole of the cylindrical body is less likely to be clogged.

In the above configuration,
The slit may have a slit width that gradually increases from one end in the axial direction of the tip end portion of the cylindrical body to the tip opening at the other end.

  According to this configuration, since the slit gradually increases in width from one end in the axial direction of the tip end portion of the cylindrical body to the end opening at the other end, the fins are smoothly extracted during die cutting, and At the same time, tearing can be avoided with certainty, so that the shaft hole of the cylindrical body can be prevented from being clogged with certainty.

In the above configuration,
The cylindrical body may be cast and implanted in a bottom side portion of the concave portion of the partial mold.

  According to this configuration, the cylindrical body is cast and planted on the bottom side portion of the concave portion of the partial mold, so that the cylindrical body can be firmly planted on the bottom surface of the concave portion of the partial mold. Easy to do.

In the above configuration,
The cylindrical body has a male screw shape on the outer peripheral surface of the proximal-side embedded portion,
The partial mold has a female screw shape on the inner peripheral surface of the embedded hole,
The cylindrical body may be planted such that the external thread shape of the embedded portion on the base end side is screwed into the internal thread shape of the embedded hole of the partial mold.

  According to this configuration, the cylindrical body has a male screw shape on the outer peripheral surface of the proximal-side embedded portion, the partial mold has a female screw shape on the inner peripheral surface of the embedded hole, Since the male thread shape of the embedded part on the base end side is screwed into the female thread shape of the embedding hole of the partial mold, the cylindrical body can be easily detached and the shaft hole of the cylindrical body is clogged. When it occurs, it can be easily replaced with a new cylindrical body.

In the above configuration,
The embedding hole may be formed with an inner diameter enlarged from a bottom surface of the concave portion of the vent hole to a predetermined depth.

  According to this configuration, the embedded hole is formed so that the inner diameter is enlarged from the bottom surface of the concave portion of the vent hole to a predetermined depth, so that the cylindrical body can be firmly connected by being connected to the vent hole.

In the above configuration,
The vent hole may be formed at least at the corner of the recess.

  According to this configuration, since the vent hole is formed at least at the corner of the concave portion, the cylindrical body that is implanted in the vent hole formed at the corner of the concave portion is provided with a gas that easily collects at the corner of the concave portion. Through the vent hole, it is possible to reliably prevent the occurrence of bears.

  According to the present invention, the proximal-side embedded portion of the cylindrical body in which the shaft hole having a smaller diameter than the vent hole passes through the central axis is embedded in the embedded hole formed from the bottom surface of the concave portion of the vent hole to a predetermined depth. Since the cylindrical body is implanted in the bottom surface of the recess, and the cylindrical body is formed with a slit that communicates the outer peripheral space of the cylindrical hole and the cylindrical hole at least at the distal end side portion other than the proximal-side embedded portion, When molding, until the unvulcanized rubber fills the recess, the slit of the cylindrical body planted on the bottom surface of the recess communicates with the vent hole through the shaft hole, and air can be extracted to the outside, generating bears Can be prevented.

  In addition, the spew formed by the small-diameter shaft hole of the cylindrical body protrudes from the bottom surface of the elongated hole, and the protruding length is short, so that the spew is accommodated in the elongated hole so as not to protrude from the tread surface of the tire tread. Therefore, it is not necessary to trim the spew, the appearance quality is maintained, and the initial performance of the tire can be maintained well.

1 is a perspective view showing an overall configuration of a tire molding die according to an embodiment of the present invention. It is a perspective view of one segment of the tire mold. It is a section perspective view of one division part cut and cut out one division among a plurality of divisions where a crevice of a mold surface of a partial mold was divided. It is an expansion perspective view of a vent piece. It is a cross-sectional perspective view of the part of the tire shape | molded by the 1 division part and partial division part of a partial metal mold | die. It is the cross-sectional perspective view which expanded the principal part of FIG. It is a perspective view which shows the three modifications of a vent piece. It is a perspective view which shows another three modifications of a vent piece. It is a perspective view which shows another modification of a vent piece. It is a cross-sectional perspective view of 1 division part of the partial metal mold | die of another embodiment. It is an expansion perspective view of a vent piece. It is a perspective view which shows the two modifications of a vent piece. It is a cross-sectional perspective view of the 1 division part of the partial mold which shows the example by which nine vent pieces were planted in the recessed part where the mold surface of the partial mold was divided.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 is a perspective view showing an overall configuration of a tire molding die 1 according to the present embodiment.
The tire molding die 1 is composed of a plurality of fan-shaped segments 2 (9 in FIG. 1) divided in the circumferential direction.

Each segment 2 is movable in the radial direction of the tire mold 1, and FIG. 1 shows a state in which each segment 2 has moved outward.
In this state, the green tire 3 is stored in the center of the tire molding die 1 and the segments 2 are moved all at once in the central direction, whereby an annular molding die is formed. Is vulcanized.

FIG. 2 is a perspective view of one segment 2 of the tire molding die 1.
One segment 2 is configured by combining a holder 4 and a plurality of aluminum alloy partial molds 5 (three in the figure) held by the holder 4.
On the mold surfaces of the adjacent partial molds 5, circumferential ridges 6 that are continuous along the tire circumferential direction, and lateral ridges 7 are formed at positions that partition the mold surfaces of the respective partial molds 5. Yes.
The recesses 8 defined by these ridges 6 and 7 form land portions on the tire tread surface.

The concave portion 8 formed by being partitioned by the protrusions 6 and 7 on the mold surface of the partial mold 5 is rectangular, and the depth h of the concave portion 8 is 10.0 mm.
FIG. 3 is a cross-sectional perspective view of a section obtained by cutting and cutting one section among a plurality of sections in which the concave portions of the mold surface of the partial mold 5 are sectioned.

  In the rectangular recess 8, vent holes 9, which are air vent holes, are drilled from the bottom surface 8 s of the recess 8 toward the back surface (outer peripheral surface) of the partial mold 5. Vent pieces 10 each having a cylindrical shape are planted.

The vent piece (cylindrical body) 10 is a steel material, and is integrally cast when the aluminum alloy partial mold 5 is cast.
Therefore, by casting the vent piece 10 in the partial mold 5, it is possible to easily plant the vent piece 10 firmly on the bottom surface 8 s of the concave portion 8 of the partial mold 5.
The partial mold 5 is manufactured by a gypsum casting method, and the vent hole 9 connected to the vent piece 10 is formed by a casting method.

The vent piece 10 is a cylindrical body having a shaft hole 11 passing through a central axis.
FIG. 4 is an enlarged perspective view of the vent piece 10. Referring to FIG. 4, the vent piece 10 has a length L of 10.0 mm, an outer diameter Do of 1.6 mm, and a shaft hole 11. This is a cylindrical body having an inner diameter Di of 0.6 mm.

The vent piece 10 has a base-side embedded portion 10b and a tip-side portion 10a other than the base-side embedded portion 10b formed in a straight line when planted on the bottom surface 8s of the recess 8 of the mold surface. Yes.
The length La of the distal end side portion 10a in the vent piece 10 is 6.0 mm, and the length Lb of the proximal side embedded portion 10b is 4.0 mm.

In the distal end portion 10a of the vent piece 10, three slits 12 are formed in the radial direction from the shaft hole 11 so as to communicate with the shaft hole 11 and the outer peripheral portion.
The slit 12 is formed in a straight line continuously from one end in the axial direction of the tip end portion 10a of the vent piece 10 to the tip opening at the other end.

Each slit 12 has a proximal slit width Sb at one end in the axial direction of 0.08 mm, a distal slit width Sa at the distal end opening at the other end is 0.12 mm, and the slit width gradually increases from the proximal end side to the distal end side. It becomes the first opening which becomes big.
The three slits 12 are formed at equal intervals in the circumferential direction of the shaft hole 11.

The vent piece 10 is manufactured by a laser lamination sintering method using maraging steel (MASIC).
Then, deposits and the like inside the shaft hole 11 and the slit 12 can be removed by cleaning with a medium such as dry ice blast.

Four such vent pieces 10 are implanted on the bottom surface 8s of the recess 8 by embedding the proximal-side embedded portions 10b in the vent holes 9 drilled in the four corners of the recess 8 of the mold surface.
FIG. 3 is a cross-sectional perspective view of one section, which is cut along a cross section passing through the center of each axial hole of two vent pieces 10 that are planted in the radial direction.

The inner diameter Dv of the vent hole 9 is 1.2 mm, and at the depth of 4.0 mm from the bottom surface 8 s of the recess 8 of the vent hole 9, there is a buried hole 9 b whose inner diameter is increased to 1.6 mm.
That is, since the base side embedded portion 10b of the vent piece 10 is integrally cast and implanted in the bottom surface side portion of the bottom surface 8s of the concave portion 8 of the partial mold 5, the shape of the embedded hole 9b is the vent piece 10b. The vent piece 10 is connected to the vent hole 9 and can be firmly planted.

Therefore, the inner diameter Dv (1.2 mm) of the vent hole 9 is smaller than the outer diameter Do (1.6 mm) of the vent piece 10 and larger than the inner diameter Di (0.6 mm) of the shaft hole 11 of the vent piece 10 (FIG. 6). reference).
That is, the inner diameter Di (0.6 mm) of the shaft hole 11 of the vent piece 10 is smaller than the inner diameter Dv (1.2 mm) of the vent hole 9.

When the proximal-side embedded portion 10b of the vent piece 10 is embedded in the embedded hole 9b in the bottom surface 8s of the concave portion 8 of the mold surface, and the vent piece 10 is implanted in the bottom surface 8s of the concave portion 8, The distal end side portion 10 a protrudes from the bottom surface 8 s of the recess 8.
Therefore, the three slits 12 of the tip end portion 10 a of the vent piece 10 communicate with the vent hole 9 through the shaft hole 11.

In the vulcanization molding, when the mold surface of the mold is pressed against the unvulcanized rubber of the raw tire, the unvulcanized rubber flows into the concave portion 8 of the mold surface, so that the distal end portion 10a of the planted vent piece 10 is not yet formed. The three slits 12 of the vent piece 10 planted at the four corners of the recess 8 are pivoted until the unvulcanized rubber spreads from the center of the recess 8 to the periphery and fills the recess 8. The state of communicating with the vent hole 9 through the hole 11 is maintained, and all the air can be extracted without causing gas accumulation.
Therefore, a bare due to gas accumulation is not formed on the molded tire surface, and the merchantability is not deteriorated.

Since the unvulcanized rubber covers the outer periphery of the tip end portion 10a of the vent piece 10, the depth of the land portion 20r of the tire 20 is increased by the tip end portion 10a of the vent piece 10 with reference to FIGS. Since a circular hole 20a of 6.0 mm (length La of the tip end portion 10a) is formed and unvulcanized rubber enters the shaft hole 11 and slit 12 of the tip end portion 10a of the vent piece 10, the shaft hole The spew 21 protrudes from the bottom surface 21b of the circular hole 20a by the unvulcanized rubber that has entered into the circular hole 20a and is formed in the circular hole 20a. The thin plate-like fins 22 are formed radially.
The spew 21 is integrally formed with rubber around the circular hole 20a in the tire land portion and three fins 22.

  Referring to FIG. 6, 0.6 mm of the inner diameter Di of the shaft hole 11 of the vent piece 10 is smaller than 1.2 mm of the inner diameter Dv of the vent hole 9, so that the protruding length Ls of the spew 21 formed to protrude. Is shorter than the spew projection length (about 10.0 mm) formed by the conventional vent hole and about 5.0 mm together with the fins 22.

When the rubber is removed from the mold, the spew 21 and the three fins 22 come out from the shaft hole 11 and the slit 12 of the vent piece 10 in the mold release direction (axial direction).
Since the slit 12 is straight and has a slit that gradually increases from the base side to the tip side, the fin 22 can be smoothly removed, and the spew 21 integrated with the three fins 22 is also a fin. It can be avoided as much as possible that it is easy to escape with 22 and torn along the way.
Therefore, it is possible to prevent as much as possible that the spew 21 and the fins 22 are cut off in the middle, and the portions separated in the shaft hole 11 and the slit 12 of the vent piece 10 remain and cause clogging. .

As shown in FIG. 6, the spew 21 protrudes from the bottom surface 20b of the circular hole 20a by about 5.0 mm and is formed in the circular hole 20a, so that the depth is 6.0 mm (the length La of the tip side portion 10a). ) And the spew 21 does not protrude from the tread (the surface of the land portion 20r) 20f of the tire 20.
Therefore, there is no need to trim the spew 21, the appearance quality is maintained, and the initial performance of the tire can be maintained well.

  When the tire is vulcanized and molded using the vent piece 10, the number of molded tires until the shaft hole 11 and the slit 12 of the vent piece 10 are clogged is about 2000, and the vent piece is not used. Although it does not reach the case of a conventional vent hole alone, it has sufficient durability.

In the vent piece which is a cylindrical body as described above, the outer diameter Do is preferably 1.0 to 2.0 mm.
If the outer diameter Do <1.0 mm, it will be difficult to fix to the mold, and if the outer diameter Do> 2.0 mm, the diameter of the circular hole formed in the tire will increase and the rubber properties will decrease. is there.

The inner diameter Di of the shaft hole of the vent piece is preferably 0.3 to 1.2 mm.
If the inner diameter Di <0.3 mm, the shaft hole is likely to be clogged, and if the inner diameter Di> 1.2 mm, the spew protrusion length increases and may protrude considerably from the tread surface of the tire. Because there is.

The slit width average Sav of the slit widths Sa and Sb is preferably 0.06 to 0.20 mm.
If the slit width average Sav is less than 0.06 mm, there is a high possibility that the spew will be cut off when the rubber is removed. If the slit width average Sav is greater than 0.20 mm, the spew is increased by increasing the spew length. This is because there is a possibility that it will protrude considerably from the tread surface of the tire.

The length La of the tip side portion of the vent piece is preferably 2.0 to 10.0 mm.
If the length La <2.0 mm of the distal end side portion 10a, the spew easily protrudes from the tread surface of the tire, and if the length La> 10 mm of the distal end side portion 10a is greater than the circular hole formed in the tire. This is because the depth is increased and the rubber properties are lowered.

The length Lb of the base end side embedded portion of the vent piece is preferably 3.0 to 5.0 mm.
If the length Lb <3.0 mm of the base side embedded portion, the fixing force to the mold is insufficient, and if the length Lb> 5.0 mm of the base side embedded portion, the material cost increases and the cost increases. Because it becomes.

The vent piece 10 is a cylindrical body and has three slits 12 formed straight in the axial direction. A modification of the vent piece 10 of the cylindrical body is shown in FIG.
7 (1), the vent piece 30 is a cylindrical body having a shaft hole 31, and three slits 32 are formed in the distal end portion 30a other than the proximal embedded portion 30b embedded in the mold. However, the slit 32 is not straight in the axial direction but is formed in a spiral shape having a very steep gradient (an extremely large spiral angle).

Each of the slits 32 has a first opening in which the slit width gradually increases from the proximal end side to the distal end side.
Since the slit 32 is open first and the spiral of the slit 32 has an extremely steep slope, the fin formed by the slit 32 can be smoothly extracted when the rubber is removed.

  The vent piece 30 has substantially the same effect as the vent piece 10, that is, the spew formed by the shaft hole 31 of the vent piece 30 does not protrude from the tread surface of the tire 20, does not need to be trimmed, and has a good appearance quality. The initial performance of the tire can be maintained well.

  It should be noted that the slit is formed from the tip opening at the tip of the vent piece, so that the tip opening may be deformed and opened in a funnel shape when cleaning with media such as dry ice blast. In the piece 30, the slit 32 is formed in a spiral shape from the front end opening of the front end side portion 30 a, so that it is possible to substantially reliably prevent the front end opening from opening and deforming during cleaning.

A vent piece 40 which is a modification shown in FIG. 7B will be described.
4, the vent piece 40 is formed in a radial direction from the shaft hole 41 in the distal end side portion 40a, whereas the sectional shape perpendicular to the axial direction of the slit 12 of the vent piece 10 shown in FIG. The cross-sectional shape of the slit 42 is a fan shape.
In addition, the slit is not formed in the base end side embedded part 40b of the vent piece 40.
The fins formed by the slits 42 have a fan-shaped cross section and are thickened outwardly and firmly support the spew. Therefore, it is possible to prevent spew from being broken when removing the rubber.

The vent piece 50 which is a modified example shown in FIG. 7 (3) has the same cross-sectional shape as the vent piece 40 shown in FIG. 7 (2), and is formed in the radial direction from the shaft hole 51 in the tip side portion 50a. The cross-sectional shape of the slit 52 is fan-shaped, and the cross-sectional fan-shaped slit 52 is formed in a spiral shape instead of being straight in the axial direction.
It should be noted that no slit is formed in the proximal-side embedded portion 50b of the vent piece 50.
Therefore, it is possible to suppress as much as possible that the tip opening is opened and deformed when cleaning with media such as dry ice blasting.

Although the above vent pieces 10, 30, 40, 50 are cylindrical bodies, modified examples of other shapes of cylindrical bodies will be described with reference to FIG.
The vent piece 60 shown in FIG. 8 (1) is a hexagonal cylindrical body in which a shaft hole 61 is formed on the central axis of a hexagonal column having six ridges each having a hexagonal cross section. Three slits 62 communicating with the outer peripheral space of the shaft hole 61 and the hexagonal cylindrical body are formed in the radial direction from the shaft hole 61 toward every other three ridgelines.

Since the vent piece 60 forms a hexagonal cylinder, a hexagonal hole is formed in the land portion of the tire by the tip side portion 60a of the vent piece 60.
Compared with the cylindrical body of the vent piece 10 shown in FIG. 4, the vent piece 60 is a hexagonal cylinder and only the outer shape is different. Therefore, the same effect is achieved and the spew is formed in a hexagonal hole in the land portion of the tire. Therefore, it is not necessary to perform spew trimming work, the appearance quality is maintained, and the initial performance of the tire can be maintained well.

The vent piece 70 shown in FIG. 8 (2) is formed with four ridges 70r extending in the axial direction at equal intervals in the circumferential direction and sandwiching the ridge 70v therebetween, and a shaft hole 71 on the central axis. In the formed cylindrical body, slits 72 that communicate the shaft hole 71 and the outer peripheral space of the cylindrical body are formed straight in the axial direction in the four concave ridges 70v in the distal end portion 70a. .
The base-end-side embedded part 70b of the vent piece 70 is also formed with four protruding ridges 70r projecting in the circumferential direction.
And this vent piece 70 can have an effect substantially the same as the vent piece 60 shown by FIG. 8 (1).

The vent piece 80 shown in FIG. 8 (3) is a cylinder in which a section perpendicular to the axial direction forms an arcuate surface and a long portion piece 80p extending in the axial direction has a three-piece outer peripheral surface facing each other. It is a striated body.
The proximal-side embedded portions 80b of the three long pieces 80p are bonded to each other in the vicinity, and a substantially circular proximal-side shaft hole 81b is formed at the center, and the distal end side of the three pieces of the long pieces 80p. In the portion 80a, a slit 82 is formed between adjacent long pieces 80p, 80p, and a tip side shaft hole 81a having a star shape simulating a star that emits light in three directions is formed in the center. The shaft hole 81a and the base end side shaft hole 81b communicate with each other.

The proximal-side embedded portions 80b of the three long pieces 80p are bonded to each other in the vicinity so as to be integrally cast into the mold.
The vent piece 80 can achieve substantially the same effect as the vent piece 60 shown in FIG. 8 (1), the long piece 80 p can be easily manufactured, and the vent piece 80 can be easily configured. it can.

Next, a vent piece 90 which is still another modification will be described with reference to FIG.
The vent piece 90 is a cylindrical body having the same dimensions as the vent piece 10 shown in FIG. 4, and the proximal-side embedded portion 90b is formed with a proximal-side shaft hole 91b having the same inner diameter Di.
However, the distal end side portion 90a is formed only with three slits 92 in the radial direction from the axial center, and a small diameter distal end side shaft hole 91a is formed at the central portion where the three slits 92 are gathered. The shaft hole 91a communicates with the base end side shaft hole 91b.

The distal end slit width Sa and the proximal end slit width Sb of the slit 92 have the same dimensions as the vent piece 10.
When such a vent piece 90 is implanted in the bottom surface of the concave portion of the mold surface, three slits 92 are formed in the vent hole via the distal end side axial hole 91a and the proximal end side axial hole 91b. It is possible to evacuate air without causing gas accumulation during communication and vulcanization molding.

A small-diameter spew is formed by the tip-side shaft hole 91a, and three fins are formed in the radial direction around the spew.
Since the tip-end side shaft hole 91a at the center of the three slits 92 has a small diameter, the spew formed is short and about 2.0 mm together with the fins.

A circular hole with a depth of 6.0 mm is formed on the land portion of the tire by the tip side portion 90 a of the vent piece 90, but the spew and fin are formed into a circular hole by projecting about 2.0 mm from the bottom surface of the circular hole. Therefore, it does not protrude from the tread of the tire.
Therefore, it is not necessary to perform spew trimming work, appearance quality is maintained, and initial tire performance can be maintained well.

At the time of rubber release, the tip side shaft hole 91a at the center of the three slits 92 has a small diameter, so when the formed spew comes off, the end tends to remain, but the spew projection length is short. The clogging of the distal end side shaft hole 91a is suppressed.
Nevertheless, clogging is likely to occur as compared to the vent piece 10, and when the tire is vulcanized and molded using the vent piece 90, the number of molded tires until clogging is about 500.

Next, a tire molding die 100 according to another embodiment will be described with reference to FIGS.
The tire molding die 100 has the same structure as that of the tire molding die 1 shown in FIGS. 1 and 2, and the concave portion 108 on the mold surface of the partial die 105 having the same shape as in FIG. FIG. 10 shows a cross-sectional perspective view of a section obtained by cutting and cutting out one section among a plurality of sections.

  Vent holes 109 are drilled at four corners on the bottom surface side portion of the bottom surface 108s of the recess 108 defined by the circumferential protrusion 106 and the lateral protrusion 107 on the mold surface of the partial mold 105. The base end side embedded portion 110b of the vent piece 110 is embedded in the embedded hole 109b on the bottom surface 108s side, and the four vent pieces 110 are implanted on the bottom surface 108s of the concave portion 108.

The vent piece 110 has a shape as shown in FIG.
The vent piece 60 shown in FIG. 8 (1) is a hexagonal cylinder having a hexagonal column-shaped central axis having six linearly extending ridgelines having a hexagonal cross section, and a shaft hole 61 formed at the tip. Three slits 62 are formed in the side portion 60a in the radial direction so as to communicate the shaft hole 61 and the outer peripheral space of the hexagonal cylindrical body.

The vent piece 110 has a shape obtained by twisting and deforming the vent piece 60.
That is, the vent piece 110 is a twisted cylindrical body having a shaft hole 111 formed in the central axis, a hexagonal cross section, and six ridge lines formed in a spiral shape. Three slits 112 communicating with the hole 111 and the outer peripheral space of the cylindrical body are also formed in a spiral shape.

The base-end-side embedded portion 110b of the vent piece 110 also has six ridge lines formed in a spiral shape and a male screw shape on the outer peripheral surface.
The embedding hole 109b drilled in the bottom surface 108s of the recess 108 in the partial mold 105 has a female screw shape corresponding to the male screw shape of the vent piece 110 on the inner peripheral surface.

Therefore, as shown in FIG. 10, the vent piece 110 has a base-side embedded portion 110 b having a male screw shape screwed into an embedded hole 109 b having a female screw shape of the partial mold 105, and the bottom surface 108 s of the recess 108. To be planted.
Thus, since the vent piece 110 is screwed into the embedding hole 109b in the bottom surface 108s of the concave portion 108, the vent piece 110 can be easily attached and detached, and when the shaft hole 111 of the vent piece 110 is clogged. It is possible to easily replace the vent piece 110 with a new one.

In the vent piece 110, as in the vent piece 60 shown in FIG. 8 (1), the spew formed by the shaft hole 111 does not protrude from the tread surface of the tire, and there is no need to trim the spew. The appearance quality is maintained and the initial performance of the tire can be maintained well.
Further, in the vent piece 110, since the slit 112 is formed in a spiral shape from the distal end opening of the distal end side portion 110a, the opening of the distal end opening is prevented from being deformed as much as possible during cleaning by dry ice blasting or the like. .

FIG. 12 shows a modified example of a twisted cylindrical vent piece. The vent piece 120 shown in FIG. 12 (1) has a shape obtained by twisting and deforming the vent piece 70 shown in FIG. 8 (2). I am doing.
Four ridges 120r, dents 120v, and slits 122 around the shaft hole 121 of the vent piece 120 are spirally formed.
The slit 122 is formed in the tip side portion 120a of the vent piece 120.

The helical twist of the four ridges 120r of the proximal-side embedded portion 120b of the vent piece 120 forms a male screw shape.
Therefore, since the vent piece 120 can be easily detached from the mold, when the shaft hole 121 of the vent piece 120 is clogged, it can be easily replaced with a new vent piece 120.

Further, the vent piece 130 shown in FIG. 12 (2) has a shape obtained by twisting and deforming the vent piece 80 shown in FIG. 8 (3).
That is, the vent piece 130 is formed by combining three elongated portions 130p whose cross section perpendicular to the axial direction forms an arcuate surface together with three slits 132 in a spiral manner.
The slit 132 is formed in the distal end side portion 130a, and the distal end side shaft hole 131a in the shape of a three-pointed star in the distal end side portion 130a communicates with a substantially circular proximal end side axial hole 131b.

The helical twist of the three long portion pieces 130p of the proximal-side embedded portion 130b of the vent piece 130 forms a male screw shape.
Therefore, since the vent piece 130 can be easily detached from the mold, when the shaft hole 131 of the vent piece 130 is clogged, it can be easily replaced with a new vent piece 110.

  In the embodiment described above, four vent pieces are embedded in the vent hole perforated in the four corners of the rectangular concave portion of the partial mold, and four embedded portions are implanted on the bottom surface of the concave portion. However, not only the four corners of the recess, but also a vent hole may be provided in the center and a vent piece may be planted.

FIG. 13 shows an example.
Vent pieces 160 are implanted in the four corners of the bottom surface 158s of the rectangular recess 158 defined by the circumferential protrusion 156 and the lateral protrusion 157 on the mold surface of the partial mold 155 of the tire molding mold 150, respectively. In addition, one vent piece 162 is planted in the center, and four vent pieces 161 are planted between one central vent piece 162 and four vent pieces 160, respectively.

The length of the vent pieces 160, 161, 162 protruding from the bottom surface 158s of the recess 158 is longer in the order of the vent pieces 160, 161, 162, and the central vent piece 162 is the longest.
The vent pieces 160, 161, 162 used here have the same shape as the vent piece 40 shown in FIG.
Each vent piece 160, 161, 162 is embedded in the position of the vent hole 159, and the shaft hole communicates with the vent hole 159.

  The vent pieces 162 at the center other than the four corners and the vent piece 161 around the center flow in first from the center of the recess 158 when unvulcanized rubber flows into the recess 158 during vulcanization molding. The unvulcanized rubber is rectified by the vent pieces 162 and 161 having a large projecting length planted in the center and the vicinity of the center, and can be distributed evenly from the center to the periphery of the recess 158, and the gas reservoir The air can be surely extracted without causing any occurrence.

  Further, since the vent pieces 160, 161, 162 are planted from the center to the periphery on the bottom surface 158s of the concave portion 158, the land portion of the tire tread is guided to the vent pieces 160, 161, 162 when the rubber is removed. Therefore, it is possible to suppress deformation and deformation of the rubber.

  As described above, the tire molding die according to the embodiment of the present invention has been described. However, the aspect of the present invention is not limited to the above embodiment, and can be implemented in various aspects within the scope of the gist of the present invention. Including things.

For example, the material of the vent piece is steel, but it can be cemented carbide or various ceramics.
The shape of the tubular body of the vent piece may be various shapes other than those described in the above embodiment.

DESCRIPTION OF SYMBOLS 1 ... Tire molding die, 2 ... Segment, 3 ... Raw tire, 4 ... Holder, 5 ... Partial die, 6 ... Circumferential ridge, 7 ... Lateral ridge, 8 ... Recess, 8s ... Bottom, 9 ... Vent hole, 9b ... Embedded hole,
10: Vent piece (cylindrical body), 10a: Tip side portion, 10b: Base side embedded portion, 11 ... Shaft hole, 12 ... Slit,
20 ... Tire, 20r ... Land, 20a ... Round hole, 20b ... Bottom, 21 ... Spew, 22 ... Fin,
30 ... Vent piece, 30a ... Tip side portion, 30b ... Base end side embedded portion, 31 ... Shaft hole, 32 ... Slit,
40 ... Vent piece, 40a ... Tip side portion, 40b ... Base end side embedded portion, 41 ... Shaft hole, 42 ... Slit,
50 ... Vent piece, 50a ... Tip side portion, 50b ... Base end side embedded portion, 51 ... Shaft hole, 52 ... Slit,
60 ... Vent piece, 61 ... Shaft hole, 62 ... Slit,
70 ... Bent piece, 70r ... Projected ridge, 70v ... Concave ridge, 70a ... Front end side portion, 70b ... Base end embedded portion, 71 ... Shaft hole, 72 ... Slit,
80 ... vent piece, 80p ... long piece, 81 ... shaft hole, 82 ... slit,
90 ... Vent piece, 90a ... Tip side portion, 90b ... Base end side embedded portion, 91a ... Tip side shaft hole, 91b ... Base end side shaft hole, 92 ... Slit,
100 ... Tire molding die, 105 ... Partial die, 106 ... Circumferential ridge, 107 ... Lateral ridge, 108 ... Recess, 109 ... Vent hole,
110 ... Vent piece, 111 ... Shaft hole, 112 ... Slit,
120 ... Bent piece, 120r ... Convex section, 120v ... Concavity section, 121 ... Shaft hole, 122 ... Slit,
130 ... Bent piece, 130p ... Long piece, 131 ... Shaft hole, 132 ... Slit,
150 ... Tire molding die, 155 ... Partial die, 156 ... Circumferential ridge, 157 ... Lateral ridge, 158 ... Recess, 159 ... Vent hole,
160, 161, 162 ... Vent piece.

Claims (8)

A plurality of partial molds are combined at the time of tire molding to form an annular overall mold,
The mold surface for molding the tire tread of the partial mold has a recess defined by a protrusion that forms a land portion of the tire tread,
In a tire molding mold in which a vent hole is formed which is perforated from the bottom surface of the concave portion toward the outer peripheral surface of the partial mold and communicates with the outside.
From the bottom surface of the recess of the vent hole to a predetermined depth, has a buried hole,
A cylindrical body having a shaft hole having a smaller diameter than the vent hole passes through the central axis,
The cylindrical body is embedded in the bottom surface of the concave portion, the proximal-side embedded portion is embedded in the embedded hole,
The cylindrical mold has a slit for connecting the shaft hole and the outer peripheral space of the cylindrical body at least at a distal end side portion other than the base side embedded portion.   The tire molding die according to claim 1, wherein the slit is continuous from at least one axial end of the tip side portion of the cylindrical body to a tip opening at the other end.   The tire molding die according to claim 2, wherein a plurality of the slits are formed in a circumferential direction of the shaft hole.   4. The tire molding metal according to claim 2, wherein a width of the slit gradually increases from one end in the axial direction of the tip end portion of the cylindrical body to a tip opening at the other end. 5. Type.   The tire molding die according to any one of claims 1 to 4, wherein the cylindrical body is cast and planted in a bottom side portion of the concave portion of the partial die. . The cylindrical body has a male screw shape on the outer peripheral surface of the proximal-side embedded portion,
The partial mold has a female screw shape on the inner peripheral surface of the embedded hole,
5. The cylindrical body according to claim 1, wherein the male thread shape of the embedded portion on the base end side is screwed into the female thread shape of the embedding hole of the partial mold. A tire molding die according to claim 1.   The tire molding die according to any one of claims 1 to 6, wherein the embedding hole has an inner diameter enlarged from a bottom surface of the concave portion of the vent hole to a predetermined depth.   The tire molding die according to any one of claims 1 to 7, wherein the vent hole is formed at least at a corner of the recess.

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