JP2595299Y2 - Extrusion dies - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion die for forming a desired cross-sectional shape of a tire to be reused by replacing tread rubber consumed by use with new tread rubber, that is, a so-called retread tire. Things.

[0002]

2. Description of the Related Art As shown in FIG. 1a, a tread rubber of a retread tire is charged by feeding a rubber-kneaded sheet-like raw rubber into a cylinder of an extruder and rotating a screw in the cylinder. The raw rubber is sent out in the direction of the tip of the cylinder, and is formed into a predetermined cross-sectional shape through an extrusion die provided in the cylinder head. The formed tread rubber is stuck via a strong adhesive onto a belt or carcass ply from which the used tread rubber has been removed from the tire. By vulcanizing the attached tread rubber, it becomes possible to use it as a retread tire.However, when the thickness of the end of the tread rubber is large at the time of this vulcanization, rubber flow tends to occur, The rubber adhesive force is reduced, and as a result, the rubber may peel off due to repetition of bending due to load rolling, causing a failure. For this reason, research for reducing the thickness of the tread rubber has been conducted. For example, to optimize conditions such as the number of rotations of the screw, the amount of raw rubber to be charged into the cylinder, and the speed at which the tread rubber extruded from the cylinder is loaded on the conveyor and pulled out, the thickness of the tread rubber end is reduced. Useful for

[0003]

By optimizing the above conditions, the end thickness of the tread rubber is set to a medium thickness (4).
mm) can be controlled, but in order to reduce the rubber flow during vulcanization and obtain a desired thin thickness (3 mm or less) to obtain a sufficient adhesive force, the above conditions must be optimized. Even if it was attempted, defects such as so-called ear breaks and tears occurred, and it was not possible to mold a tread rubber having a stable end thickness.

Therefore, an object of the present invention is to make it possible to produce a tread rubber having an end portion thickness less than that of a conventional one by forming an opening shape of an extrusion die in consideration of the viscosity of raw rubber and the like.

[0005]

According to the present invention, a pair of hypotenuses 2 are provided.
A short upper base 3 extending between both hypotenuses 2, a lower base 4 longer than the upper base 3, and an extended side of the hypotenuse 2 forming a narrow entry corner 5 between both ends of the lower base 4. In the extrusion die having a deformed trapezoidal opening 7 surrounded by the extension 6, the extended side 6 is divided into an area 8 adjacent to the hypotenuse 2 and an area 9 adjacent to the end A forming the minimum gap S of the entry corner 5. In the area 9 adjacent to the end A of the insertion corner 5, the area rises with a larger slope than the slope of the area 8 adjacent to the hypotenuse 2, and the vertex T
Through the enlarged gap 10 to the area 8 adjacent to the hypotenuse 2
The extrusion die is characterized by being formed as follows.

[0006] Fig. 1a shows an extruder equipped with an extrusion die, and Fig. 1b shows an example of the extrusion die of the present invention with a front opening. 2a and 2b illustrate details of the corners of the extrusion die of the present invention. In the figure, 1 is an extrusion die, 2 is a hypotenuse, 3 is an upper bottom, 4 is a lower bottom, 5 is a corner, 6 is an extended side, 7
Is an opening, 8 is a region adjacent to the hypotenuse, 9 is a region adjacent to the corner end A, and 10 is an enlarged gap.

[0007] The devised extrusion die 1 shown in Fig. 1b comprises a pair of hypotenuses 2, a short upper base 3 protruding between both hypotenuses on both sides in the width direction, and a lower base 4 longer than the upper base 3. And a modified trapezoidal opening 7 surrounded by the extended side 6 of the oblique side 2 forming a narrow corner 5 between both ends of the lower base 4, and the extended side 6 is defined as an area adjacent to the oblique side 2. 8 and
A region 9 adjacent to the end A forming the minimum gap S of the corner 5
And rises in the area 9 adjacent to the end A with a larger slope than the slope of the area 8 adjacent to the hypotenuse 2,
An enlarged gap 10 is formed to reach the region 8 adjacent to the hypotenuse 2 through the vertex T.

Assuming that the height measured perpendicularly to the lower base 4 from the bisecting point P of the area 8 and the area 9 is H, this height H is set to be 1 to 4 times the minimum gap S of the entry corner 5. Is preferred. If the magnification is less than 1 time, defects such as ear breakage are likely to occur, and if it exceeds 4 times, the thickness of the end cannot be reduced. In addition, when the tread rubber end is set to 2 mm or less, which is 1/2 or less of the related art, the minimum gap S of the inset corner 5 is:
0.8 ~ narrower than the conventional extrusion die (3mm)
Preferably, it is 1.5 mm. Also, the position of the point P,
The position of the intersection Q between the hypotenuse 2 and the area 8 adjacent to the hypotenuse 2 can be appropriately selected as long as it is within the range of the above-mentioned claims. Particularly, when the thickness of the end portion of the tread rubber is reduced to 2 mm or less. When the length Px measured parallel to the lower bottom 4 from the end A of the corner 5 is 10 mm, the length Py measured perpendicular to the lower bottom 4 is 4 to 12 mm, and the end of the corner 5 is When the length Qx measured parallel to the lower base 4 from the portion A is 20 mm, the length Qy measured perpendicular to the lower base 4 is preferably set to 6 to 15 mm. The rising inclination angle α of the enlarged gap 10 is more preferably in the range of 30 to 60 ° with respect to the lower base 4 and larger than the inclination angle β of the region 8 adjacent to the hypotenuse 2 by 10 ° or more. If the inclination angle α is less than 30 °, the ear is cut or the ear is easily broken, and if it is more than 60 °, the thickness of the rubber end cannot be reduced. When the inclination angle α is less than 10 ° as compared with the inclination angle β, ear breakage or tearing tends to occur. The cross-sectional shape between the end A of the entry corner 5 and the vertex T, between the vertex T and the bisecting point P, and between the bisecting point P and the intersection Q was linear in FIG. A curved shape may be used as long as the condition is satisfied. In the case of a curved cross section between the corner A and the vertex T or between the bisecting point P and the intersection Q, the rising inclination angle α
Is the inclination angle with respect to the lower base of a straight line connecting the corner end A and the point B separated by 5 mm along the shape of the opening 7 from the corner end A. The inclination angle β is the bisection point P and the bisection point An angle of inclination with respect to the lower base of a straight line connecting 5 mm away from P along the shape of the opening 7 and point R

[0009]

The extruding die of the present invention rises in the area 9 adjacent to the end A of the insertion corner 5 of the extension side 6 with a larger inclination than the inclination of the area 8 adjacent to the hypotenuse 2 to form the vertex T. By forming an enlarged gap 10 that passes through to the area 8 adjacent to the hypotenuse 2, the thickness of the end of the tread rubber, which could not be reduced due to defects such as cut edges and broken ears in a conventional extrusion die. Can be reduced to a thickness of 3 mm or less.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of an extrusion die according to the present invention will be described with reference to the drawings. The extrusion die used in Example 1 is a devised extrusion die 1 having a corner as shown in FIG. 2A, a pair of hypotenuses 2, a short upper bottom 3 having both sides in the width direction extending between both hypotenuses 2, This upper bottom 3
A modified trapezoidal opening 7 surrounded by a lower base 4 longer than the lower base 4 and an extended side 6 of the hypotenuse 2 forming a narrow corner 5 between both ends of the lower base 4. Is divided into an area 8 adjacent to the hypotenuse 2 and an area 9 adjacent to the interior corner end A forming the minimum gap S of the interior corner 5, and the area 9 adjacent to the interior corner end A is divided into the hypotenuse 2 The height H (2.0 mm) measured perpendicularly to the lower bottom 4 from the bisected point P from the above bisecting point P as compared with the inclination of the region 8 adjacent to the minimum gap S (1. An enlarged gap 10 is formed extending through a vertex T which is 1.3 times as large as 5 mm) to reach an area 8 adjacent to the hypotenuse 2. The rising inclination angle α of the enlarged gap 10 was 35 ° with respect to the lower base 4, and the inclination angle β of the region 8 adjacent to the hypotenuse 2 was 16 ° with respect to the lower base 4. The lengths Px and Py measured between the inner corner end A and the bisected point P horizontally and vertically with the lower base 4 are 10 mm and 4.7 mm, respectively.
mm, the inner corner end A, the hypotenuse 2 and the area 8 adjacent to the hypotenuse 2
, The lengths Qx and Qy measured horizontally and vertically with the lower base 4 were 20 mm and 7.6 mm, respectively. The cross-sectional shapes between the corner A and the vertex T, between the vertex T and the bisecting point P, and between the bisecting point P and the intersection Q were all straight lines.

The extrusion die used in Example 2 is shown in FIG.
A devised extrusion die having a corner shown in FIG.
3.0 mm, the minimum gap S of the inset corner 5 is 0.8 mm,
The inclination angle α is 50 °, the inclination angle β is 16 °, and the lengths Px and Py are 10 mm and 6.8 m, respectively.
m and the lengths Qx and Qy are 20 mm and 9.7 m, respectively.
Except for m, it is almost the same as the extrusion die used in Example 1.

The extrusion die used in Example 3 has a height H of 3.0 mm and a minimum gap S of the corner 5 of 2.0 m.
m, the inclination angle α is 60 °, and the inclination angle β is 16 °
And the lengths Px and Py are 10 mm and 12 m, respectively.
m and the lengths Qx and Qy are 20 mm and 14.8, respectively.
Except for mm, it is almost the same as the extrusion die used in Example 1.

The extrusion die used in Example 4 has a height H of 0.5 mm and a minimum gap S at the corner 5 of 1.0 m.
m, the inclination angle α is 30 ° with respect to the lower base 4, the inclination angle β is 16 °, and the lengths Px and Py are 10
mm, 4.8 mm, and the lengths Qx, Qy are each 20.
It is almost the same as the extrusion die used in Example 1 except that the diameter was set to 7.7 mm and 7.7 mm.

The extrusion die used in the conventional example is a conventional extrusion die having a front surface of the extrusion die shown in FIG. 3A and a corner having no enlarged gap shown in FIG. 3B.
Is 0 mm, the minimum gap S of the inset corner 5 is 3.0 mm, the inclination angle α is 11 ° with respect to the lower base 4, and the inclination angle β is 1
6 °, the lengths Px and Py are each 10 mm,
4.9 mm, the lengths Qx and Qy are each 20 mm,
Except that it was 7.8 mm, it was almost the same as the extrusion die used in Example 1.

Table 1 shows the end thickness of the tread rubber molded using the above five types of extrusion dies. No defects such as cut ears and broken ears occurred during the molding.

[0016]

[Table 1]

From the results shown in Table 1, in Examples 1 to 4, the end thickness of the tread rubber can be reduced to 3 mm or less as compared with the conventional example. In Examples 1 to 2 and 4 having particularly preferable shapes, the thickness of the end portion can be reduced to 1/2 or less of the conventional example.

[0018]

According to the present invention, in the region 9 adjacent to the end A of the corner 5 of the extension side 6, the region rises with a larger inclination than the inclination of the region 8 adjacent to the hypotenuse 2, and the vertex T By forming an enlarged gap 10 extending to the area 8 adjacent to the hypotenuse 2 through the through-hole, the thickness of the tread rubber end portion which could not be thinned due to defects such as ear breakage and ear breakage in the conventional extrusion die. Can be reduced to 3 mm or less, the rubber flow at the time of vulcanization of the end of the tread rubber used for the retreaded tire can be reduced, and sufficient adhesive strength with a belt or the like to which the tread rubber is attached can be obtained. It has become possible to provide a retreaded tire which can prevent peeling of the tread rubber end portion and has few troubles.

[Brief description of the drawings]

FIG. 1A is a side view of an extruder with an extrusion die attached, and FIG. 1B is a front view showing an example of a devised extrusion die.

FIG. 2A is a detailed view of a corner of the inventive extrusion die used in Example 1, and FIG. 2B is a detailed view of an inside corner of the inventive extrusion die used in Example 2.

FIG. 3 (a) is a front view of a conventional extrusion die used in a conventional example, and FIG. 3 (b) is a detailed view of a corner of the conventional extrusion die shown in FIG.

[Explanation of symbols]

 1 extrusion die 2 hypotenuse 3 upper base 4 lower base 5 inset corner 6 extended side 7 opening 8 area adjacent to hypotenuse 2 9 area adjacent to end A of inset corner 5 10 enlarged gap

Continuation of the front page (56) References JP-A-61-94735 (JP, A) JP-A-2-269032 (JP, A) JP-A-2-212134 (JP, A) JP-A-61-94735 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 47/00-47/96

Claims (1)

(57) [Scope of request for utility model registration] 1. A pair of hypotenuses (2), a short upper base (3) extending between both hypotenuses (2), a lower base (4) longer than the upper base (3), and a lower base (4). An extrusion die (1) having a deformed trapezoidal opening (7) surrounded by the extended side (6) of the hypotenuse (2) forming a narrow corner (5) between both ends of the extrusion die (4). (6) is divided into an area (8) adjacent to the hypotenuse (2),
The area (9) adjacent to the edge (A) forming the minimum gap (S) of the corner (5) is bisected into the edge (A) of the corner (5).
In the area (9) adjacent to the area (9), the area (8) rises at a larger inclination than the inclination of the area (8) adjacent to the hypotenuse (2), passes through the vertex (T), and is adjacent to the hypotenuse (2). An extrusion die characterized by forming an enlarged gap (10) leading to (1).