JPH0649339B2 - Method for producing partially colored hollow rubber balls - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method of making hollow rubber balls, such as partially colored softball baseballs.

[Prior Art] Recently, as a hollow rubber ball such as a softball ball, a ball whose surface is partially colored is provided.

In such a hollow rubber ball, a predetermined portion of the surface of the ball is colored by painting, or a coloring piece is attached to a predetermined portion of the surface of the ball, and the coloring piece is heated and pressed. A method of integrally fixing to the surface of the ball is adopted.

[Problems to be Solved by the Invention] However, in the means for providing the colored portion by painting, there is a problem in that the colored portion is worn out early with use of the ball, and the colored portion becomes unclear or easily disappears.

Further, in a means for sticking a coloring piece on the surface of the ball and pressing and fixing the coloring piece while heating, the peripheral edge of the coloring piece overhangs due to the pressurization and the boundary between the coloring part and other parts There is a problem that the lines are distorted or unclear and the appearance deteriorates. Especially when the surface of the ball has a design, it is almost difficult to clearly distinguish the boundary between the design and the colored portion.

The present invention has been made by paying attention to such a point, and a hollow rubber ball capable of obtaining a hollow rubber ball having a good appearance by clearly dividing a boundary between a colored portion and a non-colored portion without disturbance or distortion. The object of the present invention is to provide a manufacturing method of.

[Means for Solving the Problems] In order to achieve such an object, the present invention has a molding chamber in a first vulcanizing mold in which a convex portion corresponding to a portion of a ball to be colored is provided on an inner surface. A ball element body made of unvulcanized rubber is inserted into the inside of the ball element body, and the ball element element is heated and expanded, and by this expansion, a concave portion corresponding to the convex portion is formed on the surface of the ball element element, and Before the vulcanization reaction of the body is completed, the ball element body is taken out from the first vulcanization mold, and the concave portion of the ball element body is colored with a predetermined color and the depth of the concave portion is increased. A coloring piece made of unvulcanized rubber having a smaller thickness than that is embedded, and then the ball element is inserted into the molding chamber of the second vulcanization mold and heated, and this heating causes the ball element and the Then expand the coloring pieces and complete the vulcanization reaction. It is the one.

[Operation] When the ball element inserted into the molding chamber of the second vulcanization mold is heated, the surface of the ball element is first brought into close contact with the inner surface of the molding chamber, and in this state, the coloring piece in the recess is removed. It expands and adheres to the inner surface of the molding chamber, so that the peripheral edge of the coloring piece does not project to the surface side of the ball element body, and the boundary line between the coloring part and the non-coloring part is clear without distortion or distortion. It is clearly formed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 1 is a first vulcanizing mold and 2 is a second vulcanizing mold, both of which are upper molds 1a. 2a and lower mold 1b. 2b
And the upper mold 1a. 2a and lower mold 1b. 2b
By joining and, a spherical molding chamber 3.4 is formed inside each vulcanization mold 1.2. And the first
On the inner surface of the molding chamber 3 of the vulcanizing mold 1, for example, a strip-shaped convex portion 5 corresponding to the portion of the ball to be colored is integrally provided.

Reference numeral 6 shown in FIG. 3 is a hollow ball element body made of unvulcanized rubber having a diameter smaller than that of the molding chamber 3. The inside of the ball element body 6 is decomposed by heating. A large amount of gas generating chemicals is pre-filled.

Next, a process of manufacturing the hollow rubber ball will be described.

First, as shown in FIG. 3, the ball element body 6 is inserted into the molding chamber 3 of the first vulcanization mold 1. Then, in this state, the ball element body 6 is heated through the vulcanization mold 1 for a predetermined time. By this heating, the chemicals enclosed in the ball body 6 are decomposed to generate a large amount of gas, and the ball body 6 expands due to the pressure of this gas and the thermal expansion of the rubber itself, and the outer surface of the ball body 6 is molded. The chamber 3 is closely adhered along the inner surface thereof, and the vulcanization reaction of the rubber of the ball element body 6 proceeds with this heating. However, this vulcanization reaction is stopped by cooling the vulcanization mold 1 in the middle of its completion. Then, the vulcanization mold 1 is opened and the ball element body 6 is taken out.

The ball body 6 is formed into a shape corresponding to the molding chamber 3, that is, a spherical shape having a concave portion 7 corresponding to the convex portion 5 of the molding chamber 3 on the surface as shown in FIG. Then,
The inside of the recess 7 is polished to remove foreign matters and dirt, and a band-shaped coloring piece 8 made of unvulcanized rubber colored in a predetermined color is embedded in the recess 7. The thickness t of the coloring piece 8
Is slightly thinner than the dimension of the depth h of the recess 7, as shown in FIG. 5, for example, if the depth h of the recess 7 is 3 mm, the thickness t of the coloring piece 8 is about 2 mm, Therefore, a slight space 9 remains between the surface of the coloring piece 8 and the opening surface of the recess 7.

Thereafter, as shown in FIG. 6, the ball element body 6 is inserted into the second vulcanization mold 2 molding chamber 4. Then, the ball element body 6 is heated for a predetermined time through the vulcanization mold 2. Due to this heating, the ball element body 6 expands due to the increase of the internal pressure, and as shown in FIG. 7, the entire surface of the ball element body 6 except the recess 7 is brought into close contact with the inner surface of the molding chamber 4. Then, after that, the coloring piece 8 in the recess 7 expands so as to fill the space 9 and comes into close contact with the inner surface of the molding chamber 4. A pressure increase inside the ball element body 6 also contributes to this close contact, and therefore, even when the design of the projection 8a is provided on the surface of the coloring piece 8 as shown in FIG. it can. Moreover, the vulcanization reaction of the ball element 6 is restarted by the heating at this time, and then the vulcanization reaction of the coloring piece 8 is further started. Then, after a while, the vulcanization reaction of the ball element body 6 and the coloring piece 8 is completed, and the coloring piece 8 is integrally bonded to the ball element body 1
A hollow rubber ball a as shown in the figure is completed.

According to such a manufacturing process, under the condition that the surface of the ball body 6 is in close contact with the inner surface of the molding chamber 4, the coloring piece 8 in the recess 7 expands and is in close contact with the inner surface of the molding chamber 4, Therefore, the peripheral edge of the coloring piece 8 does not project to the surface side of the ball element body 6, the boundary line between the coloring part and the non-coloring part is formed clearly and without distortion and distortion, and has a good appearance. The rubber ball a can be obtained. Since the coloring piece 8 is integrally bonded to the ball element body 6 in a state of being embedded in the recessed portion 7, the bonding strength is strong, and, for example, in the case of a soft baseball that is hit hard. Even if there is, since the coloring piece 8 has a sufficient thickness, there is an advantage that it can be almost semipermanently prevented from disappearing due to abrasion.

[Effects of the Invention] According to the present invention as described above, the boundary line between the colored portion and the non-colored portion can be clearly formed without any disturbance or distortion, and a hollow rubber ball having a good appearance can be obtained. The coloring piece is firmly bonded to the ball, and the disappearance due to wear is almost semipermanently prevented.

[Brief description of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is a front view of a completed hollow rubber ball, Fig. 2 is a cross-sectional view of first and second vulcanizing dies, and Fig. 3 is a first vulcanization mold. FIG. 4 is a sectional view showing a state in which the ball element is inserted into the vulcanizing die, FIG. 4 is a front view of the ball element after being molded by the first vulcanizing die, and FIG. FIG. 6 is a sectional view showing a state in which a piece is laid, and FIG. 6 is a sectional view showing a state in which the ball element is inserted into a second vulcanizing mold,
FIG. 7 is a cross-sectional view showing a state in which the coloring piece in the recess expands, and FIG. 8 is a cross-sectional view showing a state in which a projection is provided as a design on the surface of the coloring piece. 1 ... 1st vulcanization mold, 2 ... 2nd vulcanization mold, 3.4
...... Molding chamber, 5 ... projection, 6 ... ball element, 7 ... recess, 8 ... coloring piece.

Claims (1)

[Claims] 1. A ball element body made of unvulcanized rubber is inserted into a molding chamber of a first vulcanizing mold having a convex portion corresponding to a portion to be colored of a ball provided on an inner surface thereof. The ball element is heated and expanded to form a concave portion corresponding to the convex portion on the surface of the ball element by this expansion, and the ball element is first expanded before the vulcanization reaction of the ball element is completed. Removed from the vulcanization mold of, into the recess of the ball element,
A coloring piece made of unvulcanized rubber which is colored with a predetermined color and is thinner than the depth of the recess is embedded, and then the ball element is inserted into the molding chamber of the second vulcanizing mold. A method for producing a partially colored hollow rubber ball, characterized in that the ball element body and subsequently the coloring piece are expanded by the heating and the vulcanization reaction is completed.