JP2019123148A - Tire vulcanization mold and vent plug - Google Patents

Abstract

To suppress protrusion of rubber when an aperture of housing in a vent plug having a spring vent mechanism is closed.SOLUTION: A vent plug 24 for tire vulcanization mold has a cylindrical housing 26 installed to a vent hole 22, a stem 28 which becomes a valve body opening and closing the aperture 34 thereof by insertion to the housing, and a spring 30 energizing the stem 28 toward a mold inside so that the aperture 34 is at an open state. The stem 28 has a head 42 opening and closing the aperture 34 at one terminal of an axis direction, in which an aperture shape of the aperture 34 is a non-circular shape, and an outer peripheral contour shape of the head 42 is the non-circular shape same as the aperture shape.SELECTED DRAWING: Figure 3

Description

  Embodiments of the present invention relate to a vent plug for a tire vulcanizing mold and a tire vulcanizing mold provided with the same.

  In a tire vulcanizing mold, a large number of exhaust holes, ie, vent holes, are provided on a molding surface in contact with the outer surface of the tire, and air accumulated between the tire and the molding surface during vulcanization molding can be vent holes. Through the discharge to the outside. A vent plug may be attached to the vent hole to prevent formation of a rubber protrusion called spew.

  For example, in Patent Document 1, a cylindrical housing fitted in a vent hole, a stem serving as a valve element that opens and closes an opening of the housing by being axially inserted into the housing, and an opening of the housing And a spring for biasing the stem to open.

  The vent plug having such a spring vent mechanism opens the opening of the housing and discharges the air to the outside at the initial stage of vulcanization molding, and after the tire comes in contact with the molding surface, the contact pressure is used to make the stem By pushing against the biasing force of the spring, the opening of the housing is closed, thereby preventing the occurrence of spew.

  Heretofore, in this type of vent plug, both the opening shape of the opening of the housing and the outer peripheral contour shape of the head of the stem fitted thereto have a circular shape. However, in the case of a circular shape, the stem can rotate freely with respect to the housing, and misalignment easily occurs, so that when the opening of the housing is closed, a gap is generated between the opening and the head of the stem. , Extrusion of rubber may occur. In particular, at the time of mass production of the tire, the gap between the housing and the stem tends to be large due to wear, which also causes the malfunction of the vent plug due to the protrusion of 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 gap between the opening of the housing and the head of the stem is fixed by welding at one or more points on the circumference, and a gap for exhausting air through the portion other than the weld. 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, in Patent Document 3, in a vent plug including a cylindrical plug holder mounted in a vent hole and a plug head fitted inside thereof, a seating portion of the plug holder and a head portion of the plug head It is described that the cross-sectional shape is formed in the same polygonal shape. However, this document forms a slit portion in the head portion of the plug head and uses the slit portion as a passage for exhausting the inside of the mold, and does not relate to the spring vent but a housing for the spring vent. It does not suggest misalignment suppression between the opening of the stem and the head of the stem.

JP, 2011-116012, A JP, 2014-058046, A JP, 2009-255485, A

  In view of the above, the embodiment of the present invention suppresses the generation 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 protruding the rubber. It is an object of the present invention to provide a tire vulcanizing mold vent plug that can be suppressed.

  A tire vulcanizing mold vent plug according to an embodiment of the present invention includes: a cylindrical housing mounted in a vent hole provided in the tire vulcanizing mold; and axial movement by inserting into the housing. A stem serving as a valve body for opening and closing an opening of the housing into the mold; and a spring biasing the stem toward the inside of the mold so that the opening is in an open state, The stem has a head for opening and closing the opening at one end in the axial direction, the opening shape of the opening is non-circular, and the outer peripheral contour of the head is non-circular the same as the opening. It is nothing.

  A tire vulcanizing mold according to an embodiment of the present invention is a tire vulcanizing mold including a vent hole for discharging air accumulated between the mold and the tire at the time of tire vulcanization molding. The vent plug is mounted.

  According to the embodiment of the present invention, the opening shape of the opening of the housing and the outer peripheral contour shape of the head of the stem have the same non-circular shape, thereby closing the opening of the housing and the opening The generation of a gap between the stem and the head can be suppressed, and the protrusion of rubber can be suppressed.

Sectional view of a tire vulcanizing mold according to one embodiment Sectional drawing which shows the vent plug of 1st Embodiment with which the vent hole of the same metal mold | die was mounted | worn (A) is a front view seen from the inside of the mold in the closed state of the vent plug according to an example in the first embodiment, (B) and (C) are front views according to another example Cross-sectional view of a vent plug according to a second embodiment (A) is a front view seen from the inside of the mold in the closed state of the vent plug according to an example in the second embodiment, (B) to (D) are front views according to another example Cross-sectional view of a vent plug according to a third embodiment

  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 an embodiment. The mold 10 is a mold for vulcanizing and forming a pneumatic tire, that is, a tire vulcanizing mold. The mold 10 molds an annular tread mold 12 for molding a tread of a tire, a pair of upper and lower side molds 14 and 14 for molding a sidewall of a tire, and a bead of a tire And a pair of upper and lower bead rings 16, 16 to form a cavity 18 which is a molding space of the 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 the air accumulated between the mold 10 and the tire at the time of tire vulcanization molding, and in this example, is a hole having a circular cross section.

  FIG. 2 is a view showing an exhaust structure according to the first embodiment, and a vent plug 24 for preventing spew formation on the tire surface while being capable of exhausting is attached to the vent hole 22. The vent plug 24 is attached to an 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 has 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 spring 30 for biasing. The mounting of the vent plug 24 may be performed by, for example, fitting the housing 26 into the vent hole 22 and then inserting and attaching the stem 28 together with the spring 30 into the housing 26.

  The housing 26 has a tubular shape having the exhaust passage 32 inside, and the hollow portion forms the exhaust passage 32. In this example, the housing 26 has a cylindrical outer peripheral surface so as to be fitted in the vent hole 22 having a circular cross section.

  The housing 26 has an opening 34 into the mold 10 at one end (upper end). The opening 34 of the housing 26 has a top surface (upper surface) 34 A facing the cavity 18, and the top surface 34 A is flush with the mold inner surface 20. The 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, and constitutes a valve seat.

  The housing 26 has a hook-like stopper 36 projecting inward (i.e., radially inward) at the end (lower end) opposite to the opening 34, and the lower end of the stem 28 on the inner peripheral side of the stopper 36 A through hole 38 through which the portion passes is provided.

  The stem 28 is a valve body that opens and closes the opening 34 of the housing 26 by moving in the axial direction X (vertical direction in FIG. 2) in the housing 26 and accordingly opens and closes the exhaust passage 32. In detail, the stem 28 is urged toward the inside (upper side in FIG. 2) of the mold 10 by the spring 30 to open the opening 34, and the spring is applied by the tire at the time of tire vulcanization molding. By being pressed against the biasing force of 30 toward the outside (downward in FIG. 2) of the mold 10, the opening 34 is closed.

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

  The head 42 has an outer diameter larger than that of the trunk 40 at one end (upper end) of the stem 28 in the axial direction (the same as the axial direction X of the housing 26). In order to be able to engage with the tapered inner surface 34B and close the opening 34, there is provided a reverse tapered outer peripheral surface 42A whose outer diameter gradually increases toward the tip. Further, the head 42 has a top surface (tip surface) 42B facing the cavity 18 formed in a planar shape.

  The other end (lower end) of the stem 28 in the axial direction is provided with a retaining projection 44 for preventing the stem 28 from coming off to the inside of the mold 10. The retaining projection 44 is formed to project outward (i.e., radially outward) at the lower end portion of the body portion 40 which extends downward through the inside of the stopper 36 of the housing 26. The retaining projection 44 is larger in diameter than the through hole 38 on the inner side of the stopper 36, and therefore, by coming into contact with the stopper 36, the stem 28 is prevented from coming out upward, that is, to the inside of the mold 10.

  The 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 disposed so as to surround the body 40 of the stem 28, and is interposed between the head 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 limited to the extent that the retaining projection 44 abuts on the stopper 36 of the housing 26 and is locked. It is biased toward the cavity 18 by an elastic force, and in this state, a gap 46 for exhausting air is formed between the head 42 and the opening 34 of the housing 26.

  In the present embodiment, the opening shape (i.e., the cross-sectional shape) of the opening 34 of the housing 26 is non-circular, and the outer peripheral contour of the head 42 of the stem 28 fitted in the opening 34 (i.e., The cross-sectional shape has the same non-circular shape as the opening shape. Here, "non-circular" means that it is not circular, and includes, for example, polygonal and elliptical shapes. The polygons include not only convex polygons but also concave polygons, so they may be, for example, star-shaped. In addition, “the same non-circular shape as the opening shape” includes similar shapes, and generally, the outer peripheral contour shape of the head 42 has a tolerance or the like so that the head 42 fits inside the opening 34 In consideration of this, it is formed to be slightly smaller than the opening shape of the opening 34.

  As described above, since the inner surface 34B of the opening 34 is formed in the reverse taper shape, the opening 34 is formed in the reverse taper shape with a non-circular cross section. Similarly, since the outer peripheral surface 42A of the head portion 42 is also formed in an inverse taper shape, the head portion 42 is also formed in an inverse taper shape with a non-circular cross section.

  As shown in FIG. 3A, in one example, the opening 34 of the housing 26 has a regular hexagonal shape, and the outer peripheral contour of the head 42 of the stem 28 fitted thereto is also regular hexagonal I am

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

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

  When manufacturing a pneumatic tire using the mold 10 composed of the above, after setting and closing a non-vulcanized tire (green tire) in the mold 10, a bladder (not shown) disposed inside is used. The unvulcanized tire is vulcanized and molded by expanding the tire, pressing the tire against the inner surface 20 of the mold and holding it in a heated state.

  At that time, the tire is vulcanized and molded while exhausting air accumulated between the tire and the mold 10 through the vent holes 22. Specifically, when the tire is pressed against the mold inner surface 20, initially, as shown in FIG. 2, the stem 28 of the vent plug 24 has its head 42 in an open position relative to the opening 34 of the housing 26, as shown in FIG. Because of this, 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. Thereafter, when the tire reaches the mold inner surface 20, the tire presses the top surface 42B of the stem 28 to push the stem 28 into the gap 46 and close the opening 34. Infiltration of the rubber material is prevented.

  In the present embodiment, the opening shape of the opening 34 of the housing 26 and the outer peripheral outline shape of the head 42 of the stem 28 are non-circular, whereby the head 42 and the opening when the opening 34 is closed It is possible to suppress the generation of the gap with the V. 34 and to suppress the protrusion of the rubber.

  Specifically, the non-circular shape of the opening 34 of the housing 26 and the head 42 of the stem 28 fitted thereto restricts the rotation of the stem 28 in the housing 26 and makes it difficult to cause misalignment. Therefore, when the opening 34 of the housing 26 is closed, a gap is less likely to be generated between the opening 34 and the head 42 of the stem 28, and rubber protrusion can be suppressed. Therefore, the malfunction of the vent plug 24 due to the protrusion of rubber can be suppressed.

  FIG. 4 is a view showing an exhaust structure according to a 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 in the vent plug 24.

  At a central portion of the top surface 42 B of the head portion 42, a convex portion 48 that protrudes upward, that is, into the cavity 18 is provided. Therefore, the recessed part corresponding to the convex part 48 will be formed in the tire surface, and the designability of a tire can be improved. Moreover, it is easy to detect the malfunctioning of the vent plug 24 at an early stage by making the recessed part formed in the tire surface into a mark.

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

  Further, 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, the other configurations and effects are the same as those of the first embodiment, and the description will be omitted.

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

  That is, a recess 50 is formed in the center of the top surface 42B of the head 42. Therefore, the convex part corresponding to the concave part 50 will be formed in the tire surface, and the designability of a tire can be improved. Moreover, it is easy to detect the malfunction of the vent plug 24 at an early stage by using the convex part formed on the tire surface as a mark.

  The cross-sectional shape (the same as the planar shape viewed from the inside of the mold) of the recess 50 is not particularly limited, and may be circular, but it may be non-circular to further improve the design of the tire. Specifically, similar to the convex portion 48, the cross-sectional shape of the concave portion 50 may be a cross (plus) shape, a minus shape, a rhombic shape, or a star shape, and various polygonal shapes can be adopted. The shape may be elliptical, and furthermore, various shapes such as a heart shape, characters, and symbols can be adopted. Also, the cross-sectional shape of the recess 50 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 third embodiment, the other configurations and effects are the same as those of the first embodiment, and the description will be omitted.

  While certain embodiments have been described above, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

DESCRIPTION OF SYMBOLS 10 Tire vulcanizing mold 22 vent hole 24 vent plug 26 housing 28 stem 30 spring 34 opening 42 head 42B top surface 48 convex portion 50: Recess

Claims (5)

A cylindrical housing mounted in a vent hole provided in a tire vulcanizing mold, and a valve element inserted into the housing and axially opening and closing 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 open,
The stem has a head for opening and closing 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. Are doing,
Vent plug for tire vulcanizing mold.   The tire vulcanizing mold vent plug according to claim 1, wherein both the opening shape and the outer peripheral contour shape are polygonal or elliptical.   The tire vulcanizing mold vent plug according to claim 1, wherein the stem has a convex portion on the top surface of the head.   The tire vulcanizing mold vent plug according to claim 1, wherein the stem has a recess on a top surface of the head. A tire vulcanizing mold comprising a vent hole for discharging air accumulated between the mold and a tire during tire vulcanization molding, wherein the vent hole according to any one of claims 1 to 4 Tire vulcanizing mold equipped with a plug.

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