JP7105565B2 - Tire vulcanization mold and vent plug - Google Patents

Description

An embodiment of the present invention relates to a tire vulcanization mold vent plug and a tire vulcanization mold including the vent plug.

In the tire vulcanization mold, a large number of exhaust holes, that is, vent holes, are provided on the molding surface that contacts the outer surface of the tire. is discharged to the outside through Vent holes are sometimes fitted with vent plugs to prevent the formation of rubber projections called spews.

For example, Patent Document 1 discloses a cylindrical housing fitted into a vent hole, a stem that is inserted into the housing and moves in the axial direction to serve as a valve body that opens and closes the opening of the housing, and an opening of the housing. A vent plug is disclosed with a spring that biases the stem into an open state.

A vent plug with such a spring vent mechanism opens the opening of the housing at the initial stage of vulcanization molding to discharge air to the outside, and after the tire comes into contact with the molding surface, the contact pressure is used to move the stem. Pushing against the bias of the spring closes the opening in the housing, thereby preventing spew.

Conventionally, in this type of vent plug, both the shape of the opening of the housing and the contour shape of the outer circumference of the head portion of the stem fitted therewith are circular. However, in the case of a circular shape, the stem can rotate freely with respect to the housing, and misalignment tends to occur. Therefore, when the opening of the housing is closed, a gap is generated between the opening and the head of the stem. , rubber may protrude. In particular, when tires are mass-produced, wear of the housing and stem tends to increase the gap, which can cause malfunction of the vent plug due to protruding rubber.

Patent document 2 describes that the shape of the housing and stem of the vent plug is non-circular. However, in this document, the opening of the housing and the head of the stem are fixed by welding at one or more points on the circumference, and the portion other than the welded portion is a gap for exhaust through which air passes. It is not described that the opening of the housing and the head of the stem have the same shape in the spring vent.

Further, Patent Document 3 discloses a vent plug having a cylindrical plug holder mounted in a vent hole and a plug head fitted inside thereof, in which the seating portion of the plug holder and the head portion of the plug head are separated. It is described that the cross-sectional shape is formed in the same polygonal shape. However, this document forms a slit in the head portion of the plug head and utilizes the slit as a passage for exhausting air from the inside of the mold. It does not suggest suppression of misalignment between the opening of the stem and the head of the stem.

Japanese Unexamined Patent Application Publication No. 2011-116012 JP 2014-058046 A JP 2009-255485 A

In view of the above points, an embodiment of the present invention suppresses the occurrence of a gap between the opening of the housing and the head of the stem when the opening of the housing in the vent plug having a spring vent mechanism is closed, thereby preventing the protrusion of the rubber. An object of the present invention is to provide a vent plug for a tire vulcanization mold that can be suppressed.

A vent plug for a tire vulcanization mold according to an embodiment of the present invention includes a cylindrical housing mounted in a vent hole provided in a tire vulcanization mold, and a tubular housing inserted into the housing to move in the axial direction. and a spring that biases the stem toward the inside of the mold so that the opening is open. The stem has a head for opening and closing the opening at one end in the axial direction. It is what is done.

A tire vulcanization mold according to an embodiment of the present invention is a tire vulcanization mold provided with a vent hole for discharging air accumulated between the mold and the tire during tire vulcanization molding, wherein the vent hole The vent plug is attached.

According to the embodiment of the present invention, the shape of the opening of the housing and the contour shape of the outer periphery of the head of the stem are the same non-circular shape. It is possible to suppress the generation of a gap between the head of the stem and the protrusion of the rubber.

Cross-sectional view of a tire vulcanization mold according to one embodiment Sectional view showing the vent plug of the first embodiment mounted in the vent hole of the same mold (A) is a front view of a vent plug according to an example of the first embodiment in a closed state as seen from inside the mold, and (B) and (C) are front views according to other examples. Sectional view of the vent plug according to the second embodiment (A) is a front view of a vent plug in a closed state according to an example of the second embodiment as seen from inside the mold, and (B) to (D) are front views according to other examples. Sectional view of a vent plug according to the third embodiment

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a mold 10 according to one embodiment. This mold 10 is a mold for vulcanizing and molding a pneumatic tire, that is, a tire vulcanizing mold. The mold 10 has an annular tread mold portion 12 for molding the tread portion of the tire, a pair of upper and lower side mold portions 14, 14 for molding the sidewall portion of the tire, and the bead portion of the tire. A pair of upper and lower bead rings 16, 16 for forming a cavity 18, which is a space for molding a pneumatic tire.

A large number of vent holes 22 communicating with the outside of the mold 10 are provided on the mold inner surface 20 which is a molding surface for molding the tire outer surface. The vent hole 22 is an exhaust hole for discharging air accumulated between the mold 10 and the tire during vulcanization molding of the tire, and is a hole having a circular cross section in this example.

FIG. 2 shows the exhaust structure according to the first embodiment, and a vent plug 24 is attached to the vent hole 22 for suppressing spew formation on the tire surface while allowing exhaust. A vent plug 24 is attached to the opening to the mold inner surface 20 in the vent hole 22 .

The vent plug 24 is configured as a so-called spring vent. Specifically, the vent plug 24 includes a cylindrical housing 26 mounted in the vent hole 22, a stem 28 as a valve body inserted into the housing 26, and the stem 28 facing the inside of the mold 10. and a biasing spring 30 . The vent plug 24 may be attached by, for example, fitting the housing 26 into the vent hole 22 and then inserting the stem 28 into the housing 26 together with the spring 30 .

The housing 26 has a tubular shape with an exhaust path 32 inside, and the exhaust path 32 is formed by the hollow portion thereof. In this example, the housing 26 has a cylindrical outer peripheral surface so as to fit inside the vent hole 22 having a circular cross section.

Housing 26 has an opening 34 into mold 10 at one end (upper end). The opening 34 of the housing 26 has a top surface (upper surface) 34A facing the cavity 18, and the top surface 34A is flush with the mold inner surface 20. As shown in FIG. An inner surface 34B of the opening 34 is formed in a reverse tapered shape in which the opening area gradually increases toward the cavity 18 side, and constitutes a valve seat.

The housing 26 has a brim-shaped stopper 36 protruding inward (that is, radially inward) at the end (lower end) opposite to the opening 34 , and the lower end of the stem 28 is located on the inner peripheral side of the stopper 36 . A through hole 38 is provided through which the part penetrates.

The stem 28 is a valve body that opens and closes the opening 34 of the housing 26 by moving in the housing 26 in its axial direction X (vertical direction in FIG. 2), thereby opening and closing the exhaust passage 32 . More specifically, the stem 28 is biased toward the inside (upward in FIG. 2) of the mold 10 by a spring 30, so that the opening 34 is opened and the spring is pushed by the tire during tire vulcanization molding. By being pressed toward the outside (downward in FIG. 2) of the mold 10 against the biasing force of 30, the opening 34 is closed.

The stem 28 has a columnar body portion 40 extending in the axial direction X of the housing 26 and a head portion 42 as a valve portion for opening and closing the opening 34 of the housing 26 .

The head 42 has a larger outer diameter than the body 40 at one end (upper end) in the axial direction of the stem 28 (same as the axial direction X of the housing 26). It has a reverse tapered outer peripheral surface 42A whose outer diameter gradually increases toward the tip so that it can be fitted into the tapered inner surface 34B to close the opening 34 . Further, the head 42 has a flat top surface (tip surface) 42B facing the cavity 18 .

At the other end (lower end) of the stem 28 in the axial direction, a retaining projection 44 is provided to prevent the stem 28 from coming off inside the mold 10 . The retainer projection 44 is formed to protrude outward (that is, radially outward) at the lower end portion of the body portion 40 extending downward through the inside of the stopper 36 of the housing 26 . The retainer projection 44 has a larger diameter than the through hole 38 inside the stopper 36 , and therefore prevents the stem 28 from coming off upward, that is, inside the mold 10 by abutting against the stopper 36 .

A spring 30 is disposed between the housing 26 and the stem 28 and biases the stem 28 toward the inside of the mold 10 so that the opening 34 of the housing 26 is open. In this example, the spring 30 is a coil spring arranged to surround the trunk portion 40 of the stem 28 and is interposed between the head portion 42 and the stopper 36 to bias the stem 28 .

Therefore, the stem 28 is mounted so as to be able to reciprocate in the axial direction X via the spring 30, and the spring 30 is allowed to move only until the retainer projection 44 comes into contact with the stopper 36 of the housing 26 and is locked. It is biased toward the cavity 18 side by an elastic force, and in this state, a gap 46 for exhaust is formed between the head 42 and the opening 34 of the housing 26 .

In this embodiment, the opening 34 of the housing 26 has a non-circular opening (that is, the cross-sectional shape), and the head portion 42 of the stem 28 that fits into the opening 34 has an outer contour shape (that is, The cross-sectional shape) has the same non-circular shape as the opening shape. Here, "non-circular" means non-circular, and includes, for example, polygonal and elliptical shapes. Polygons include concave polygons as well as convex polygons, and thus may be, for example, a star. In addition, "the same non-circular shape as the opening" includes a similar shape, and normally, the outer peripheral contour shape of the head 42 is adjusted so that the head 42 fits inside the opening 34. It is formed slightly smaller than the opening shape of the opening 34 in consideration.

Since the inner surface 34B of the opening 34 is formed in a reverse tapered shape as described above, the opening 34 is formed in a reverse tapered shape with a non-circular cross section. Similarly, the head 42 is also formed in a reverse tapered shape with a non-circular cross section because the outer peripheral surface 42A thereof is formed in a reverse tapered shape.

As shown in FIG. 3(A), in one example, the opening 34 of the housing 26 has a regular hexagonal shape, and the peripheral contour shape of the head portion 42 of the stem 28 fitted therein also has a regular hexagonal shape. is making

As shown in FIG. 3B, in another example, the opening 34 of the housing 26 has a square shape, and the peripheral contour shape of the head portion 42 of the stem 28 fitted therein is also square. is making

As shown in FIG. 3(C), in still another example, the opening 34 of the housing 26 has an elliptical opening shape, and the peripheral contour shape of the head 42 of the stem 28 fitted therein is also elliptical. It has a shape.

When manufacturing a pneumatic tire using the mold 10 configured as described above, after setting an unvulcanized tire (green tire) in the mold 10 and closing the mold, a bladder (not shown) arranged inside is removed. The unvulcanized tire is vulcanized and molded by inflating, pressing the tire against the mold inner surface 20, and maintaining it in a heated state.

At that time, the tire is vulcanized while exhausting the air accumulated between the tire and the mold 10 through the vent hole 22.例文帳に追加Specifically, when the tire is pressed against the inner mold surface 20, the stem 28 of the vent plug 24 is initially positioned with its head 42 open relative to the opening 34 of the housing 26, as shown in FIG. Therefore, the air in the cavity 18 flows into the vent hole 22 through the gap 46 between the head 42 and the opening 34 and is exhausted to the outside of the mold 10 . After that, when the tire reaches the mold inner surface 20, the tire presses the top surface 42B of the stem 28, and the stem 28 is pushed in to eliminate the gap 46 and close the opening 34, so that the vent hole 22 is closed. intrusion of rubber material into the

In this embodiment, the shape of the opening 34 of the housing 26 and the contour shape of the outer circumference of the head 42 of the stem 28 are non-circular, so that when the opening 34 is closed, the head 42 and the opening It is possible to suppress the occurrence of a gap with 34, and suppress the protrusion of the rubber.

More specifically, the opening 34 of the housing 26 and the head 42 of the stem 28 fitted therewith are non-circular, so that the rotation of the stem 28 within the housing 26 is restricted, and misalignment is less likely to occur. Therefore, when the opening 34 of the housing 26 is closed, a gap is less likely to occur between the opening 34 and the head portion 42 of the stem 28, thereby suppressing protrusion of the rubber. Therefore, malfunction of the vent plug 24 due to protrusion of the rubber can be suppressed.

FIG. 4 is a diagram showing an exhaust structure according to the second embodiment. The second embodiment differs from the first embodiment in that a convex portion 48 is provided on the top surface 42B of the head portion 42 of the stem 28 of the vent plug 24 .

A central portion of the top surface 42</b>B of the head portion 42 is provided with a protrusion 48 that protrudes upward, that is, into the cavity 18 . Therefore, recesses corresponding to the protrusions 48 are formed on the tire surface, and the design of the tire can be improved. In addition, malfunction of the vent plug 24 can be easily detected at an early stage by using the concave portion formed on the tire surface as a mark.

The cross-sectional shape of the convex portion 48 (the same planar shape as viewed from the inside of the mold) is not particularly limited, and may be circular, but may be non-circular to further improve the design of the tire. For example, as shown in FIG. 5A, as an example, the cross-sectional shape of the convex portion 48 may be a cross (plus) shape. As another example, the cross-sectional shape of the protrusion 48 may be a negative shape as shown in FIG. 5B, a rhombus as shown in FIG. It may be star-shaped, and various polygonal shapes can be adopted. Moreover, although not shown, the cross-sectional shape of the convex portion 48 may be an elliptical shape, and various shapes such as a heart shape, letters, and symbols can be adopted.

The cross-sectional shape of the projection 48 may be the same as or different from the cross-sectional shape of the opening 34 of the housing 26 and the head 42 of the stem 28 .

In the second embodiment, other configurations and effects are the same as those in the first embodiment, and description thereof will be omitted.

FIG. 6 is a diagram showing an exhaust structure according to the third embodiment. The third embodiment is different from the first embodiment in that a recess 50 is provided in the top surface 42B of the head 42 of the stem 28 in the vent plug 24 .

That is, a concave portion 50 is formed in the central portion of the top surface 42B of the head portion 42 . Therefore, a convex portion corresponding to the concave portion 50 is formed on the tire surface, and the design of the tire can be improved. In addition, the malfunction of the vent plug 24 can be easily detected at an early stage by using the convex portion formed on the tire surface as a mark.

The cross-sectional shape of the concave portion 50 (same as the planar shape when viewed from the inside of the mold) is not particularly limited, and may be a circular shape, or a non-circular shape to further improve the design of the tire. Specifically, similar to the protrusion 48, the cross-sectional shape of the recess 50 may be a cross (plus) shape, a minus shape, a diamond shape, a star shape, or various polygonal shapes. Moreover, an elliptical shape may be used, and various shapes such as a heart shape, characters, symbols, etc. may be adopted. Also, the cross-sectional shape of the recess 50 may be the same as or different from the cross-sectional shapes of the opening 34 of the housing 26 and the head 42 of the stem 28 .

In the third embodiment, other configurations and effects are the same as those in the first embodiment, and description thereof will be omitted.

Although several embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Tire vulcanization mold, 22... Vent hole, 24... Vent plug, 26... Housing, 28... Stem, 30... Spring, 34... Opening, 42... Head, 42B... Top surface, 48... Convex part, 50... Concave portion

Claims (3)

A cylindrical housing mounted in a vent hole provided in a tire vulcanization mold, and a valve body that is inserted into the housing and moves in the axial direction to open and close the opening of the housing into the mold. and a spring that biases the stem toward the inside of the mold so that the opening is in an open state,
The stem has a head that opens and closes the opening at one end in the axial direction, the opening of the opening has a non-circular shape, and the outer peripheral contour of the head has the same non-circular shape as the opening. and
The stem has a convex portion on the top surface of the head portion, and the convex portion has a central portion of the top surface that protrudes with respect to a planar peripheral portion, and the cross-sectional shape of the convex portion is is a shape different from the outer peripheral contour shape of the head,
Vent plug for tire vulcanization mold. 2. The vent plug for a tire vulcanization mold according to claim 1 , wherein both the opening shape and the outer peripheral contour shape are polygonal or elliptical. A tire vulcanization mold provided with a vent hole for discharging air accumulated between the mold and the tire during tire vulcanization molding, wherein the vent plug according to claim 1 or 2 is attached to the vent hole. Tire vulcanization mold.

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