JP2008100028A - Soft tennis ball and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient soft tennis ball manufacturing method which is simple in manufacturing processes, does not depend on the skill of a worker, and suppresses the generation of a man-caused defective product. <P>SOLUTION: The edge parts G, L of two uniform and thick semispherical bodies, which are molded by temporary heating and vulcanizing, are made to adhere each other with an adhesive after filling a foam agent L inside the semispherical bodies, and then, molded by heating and vulcanizing. One semispherical body is obtained by filling rubber, being the same in quality as that of a ball body part, in a mold where a small recession is molded to form a valve part, so as to integrally molding the semispherical body of the ball body and the valve part by heating and vulcanizing. When the right and left semispherical bodies are molded with the rubber respectively different in color, the symmetrical color ball for practice, where the joint surfaces are uniformly and linearly joined, is manufactured by using the manufacturing method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a soft tennis ball and a manufacturing method thereof.

Conventional soft tennis ball manufacturing is based on a single vulcanization. There are roughly the following three types of methods for molding a rubber sheet before vulcanization into a spherical shape.
(1) A curved sheet that is formed into a disk shape by stacking two upper and lower curved sheets extruded in a bowl shape by an extrusion molding machine.
(2) A rubber sheet that has been cut into a figure 8 shape is bonded together in order to form a shape close to a sphere.
(3) A curved sheet formed by extruding a long cylinder that has been extruded into a cylinder by an extrusion molding machine into 3-4cm widths to make a short cylinder, and extruding it separately into a bowl on both sides of the cylinder Are molded into a shape close to a sphere.
In any of the methods, after molding, a female-female mold (both concave molds) is loaded and heat vulcanization molding is performed.

The common disadvantage of these molding methods is that even if the rubber sheet is uniformly stretched, it is a soft rubber sheet before vulcanization, so various forces are applied during the molding process such as lamination, and the sheet thickness is uniform. It is that the nature is impaired. This can be said to have been the biggest problem in soft tennis balls, where the uniform thickness of the ball body has a large effect on stable flight, bounce and rotation of the ball. The fact that the skill level of the workers is easily reflected directly in the quality of the ball is also a big problem in modern Japan where it is difficult to secure skilled workers.

Another prior art relates to a valve portion that fills the ball body with air by inserting a needle-type pneumatic needle. This valve portion is separately vulcanized and molded, and after being bonded to an unvulcanized soft ball body rubber sheet with an adhesive, vulcanization molding is performed again when the ball body is vulcanized.
In a soft tennis ball where a strong impact at the time of impact is applied to the ball body, especially this valve part, the adhesive strength of this part is very important, and the conventional manufacturing method may cause problems with this adhesive strength. It was. Moreover, this is a process in which a lot of manufacturing time and defective products are generated in the production of the factory.

Also, in various practice processes in ball games, many practice methods are taken in which the color of a certain part of the ball is changed, the rotation of the ball is clearly confirmed, and training of moving vision is taken into consideration. Among various color combinations, it is said that the most clearly visible rotation of the ball is a ball whose color is clearly divided into the left and right halves of the sphere. However, the color composition that is most visible is greatly different depending on the use environment of each ball game. In many ball games, this symmetrical ball is used in practice, but that type of ball is not used in soft tennis practice. In particular, although it is a symmetrical color ball that seems to be optimal for practice of cut serve that is popular in soft tennis, the reason why it is difficult to produce is the above-mentioned production methods (1) to (3). It is possible to assign different colors to the left and right only with the production method (1), but due to the production method of soft rubber before vulcanization, the adhesive surfaces of the different colors are completely non-uniform, and the product value is apparent. There is also a problem.

In addition, the following patent documents 1 and 2 and the nonpatent literature 1 can be mentioned as a well-known technique relevant to this invention.
Japanese Patent Application No. 9-252589 Japanese Patent Application No. 2002-371365 http: // www. showa-rubber. co. jp / product / akaemu. html Showa Rubber Co., Ltd. Product Information Akaem Rotating Ball

The present invention sets the following three problems in order to solve the above problems.
1. Development of a production method that can uniformly mold the thickness of the soft tennis ball rubber.
2. Development of a manufacturing method that eliminates the need to attach the valve part to fill the ball body with air.
3. Development of a manufacturing method that uses rubbers of different colors for each hemisphere of the ball body and the joint surfaces can be joined evenly and linearly.
These inventions are also simple in terms of the production process, and it is also an object to reduce the generation of defective and artificial artifacts efficiently without being influenced by the skill level of workers.

After filling and compressing solid rubber into two types of male-female molds (one with a convex shape and the other with a concave shape), the first heat vulcanization molding is performed in that state. To produce hemispheres of uniform thickness. There are two types of molds, one for a hemisphere without an air-filling valve portion and the other for a hemisphere with a valve portion. The edges of the hemispheres thus manufactured are filled with a foaming agent and then bonded with an adhesive, and then heated for the second time by another female / female mold (both concave molds). Perform sulfur molding. What is produced in this way is a soft tennis ball having a uniform thick body and a highly accurate sphere.

Also, one of two types of male and female molds has a small concave part formed in the center for forming an air-filling valve part, and this part is made of the same material as the ball body part. Is carefully filled and integrally heated and vulcanized together with the hemisphere of the ball body. By doing so, it is possible to manufacture an integrally molded soft tennis ball having a valve portion that is strong against impact and never peels off. The ball inner surface convex portion of the valve portion is fitted with an O-shaped ring to strongly tighten the air hole from the outside, thereby preventing air leakage of the ball.

Furthermore, when each hemisphere of the ball body is heat-vulcanized and molded with rubber of different colors, a practice color soft tennis ball with different colors on the left and right sides can be manufactured in which the joining surfaces are joined evenly and linearly.

As described above, the present invention does not exist in the conventional soft tennis ball manufacturing method, and by performing the heat vulcanization molding twice, the ball thickness is uniform, and stable flight / rotation and bouncing with less shake are achieved. Soft tennis balls can be produced. Also, by adopting a manufacturing method in which the air filling valve is vulcanized and integrally molded with the same material as the ball body, it becomes possible to produce a soft tennis ball whose valve part is strong against impact and never peels off. .

All of these production methods make it possible to minimize the occurrence of defective products in the production process without using skilled workers, and to produce soft tennis balls efficiently and quickly.

In addition, a clear straight line allows the ball to be color-coded with different colors symmetrically, creating a new ground for practice methods in the field of soft tennis ball practice.

The present invention will now be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a male and female mold for a hemisphere without a valve portion for the first heat vulcanization molding of the soft tennis ball of the present invention and the ball body after the heat vulcanization molding.
The first vulcanization mold consists of a male part A and a female part B. After being extruded into a rod shape by an extrusion molding machine, the rubber solid C (Fig. 2) cut to a specified weight is moved up and down. The shape like C1 is created by compression vulcanization molding. A cross-sectional view of hemisphere C2 obtained by cutting C1 created in this way at E and E1 is (FIG. 3).
The cross-sectional view (FIG. 3) of the hemisphere C2 at this point has a uniform thickness, and the hemisphere has an almost perfect shape.

FIG. 4 is a cross-sectional view of the other hemisphere C4 processed in the same manner. The biggest difference is that the valve portion H for inserting the air needle is integrally molded at the same time. In the sectional view of the mold on this side (FIG. 5), a small recess H1 for molding the valve is formed in the male part A1, and a rubber material having the same components as the ball body is carefully filled in the ball H1. The valve portion H is molded by integrally heating and vulcanizing with the main body.
The valve portion H is fitted with an O-shaped ring O to strongly tighten the air hole from the outside, thereby preventing air leakage of the ball.
FIG. 4 is a cross-sectional view of C4 obtained by cutting the portion C3 thus heat-vulcanized and molded at locations J and J1 (FIG. 4).

The G-G1 and K-K1 surfaces of the edge portions of the respective hemispheres C2 and C4 thus heat-vulcanized are sanded and bonded together with an adhesive. At that time, the foaming agent L is simultaneously loaded inside. Both I formed into a sphere by bonding the respective hemispheres are loaded into female molds M and N (FIG. 6), and heat vulcanization molding is performed again. By this processing step, the bonded surfaces of G-K1 and K-G1 are completely bonded, and a truly spherical, uniform and strong soft tennis ball is completed.

  Sectional drawing of the male-female metal mold | die for hemispheres which does not have the valve | bulb part for 1st time heat vulcanization moldings, and the ball main body after the 1st time heat vulcanization molding.   Sectional drawing of the solid body for ball | bowl main bodies loaded with the male-female metal mold | die for hemispheres which does not have the valve | bulb part for the 1st heating vulcanization molding.   Sectional drawing of the hemisphere of the direction which does not have the valve | bulb part of a ball | bowl main body.   Sectional drawing of the hemisphere of the direction which has the valve | bulb part of a ball | bowl main body.   Sectional drawing of the male-female metal mold | die for hemispheres which has the valve | bulb part for 1st heating vulcanization moldings, and the ball main body after the 1st heating vulcanization molding.   Sectional drawing of the metal mold | die for the 2nd heating vulcanization molding of the ball main body which became a sphere by bonding each hemisphere together, the foaming agent with which it was loaded inside, and both.

Explanation of symbols

A A male die for a hemisphere without a valve portion for the first heat vulcanization molding.
A1 A male mold for a hemisphere having a valve portion for the first heat vulcanization molding.
B A female mold for a hemisphere without a valve portion for the first heat vulcanization molding.
B1 A female mold for a hemisphere having a valve portion for the first heat vulcanization molding.
C Rubber solid for ball body.
C1 A hemisphere of a ball body without a valve portion after the first heat vulcanization molding.
C2 The hemisphere of the ball body without the valve part after the first heat vulcanization molding is cut at E-E1 part.
C3 The hemisphere of the ball body with the valve portion after the first heat vulcanization molding.
C4 The hemisphere of the ball body with the valve part after the first heat vulcanization molding is cut at J-J1 part.
E The part of the ball body where the hemisphere without the valve part is cut.
E1 A part of the ball body where the hemisphere without the valve is cut.
G Edge part for bonding hemisphere without ball part of ball body.
G1 Edge part that bonds the hemisphere without the valve part of the ball body.
H Valve part to insert air needle.
H1 A concave portion of a mold for heat-vulcanizing a valve portion into which an air needle is inserted.
I A ball body made into a sphere by pasting the hemispheres together.
J A place where the hemisphere with the valve part of the ball body is cut.
J1 A part that cuts the hemisphere with the valve part of the ball body.
K An edge part that bonds the hemisphere with the valve part of the ball body.
K1 Edge part that bonds the hemisphere with the valve part of the ball body.
L Foaming agent.
M Upper part of the second heating vulcanization mold.
N Lower part of the second heating vulcanization mold.
O O-ring fitted to the valve part.

Claims (3)

After filling and compressing solid rubber into two types of male-female molds (one with a convex shape and the other with a concave shape), the first heat vulcanization molding is performed in that state. To produce hemispheres of uniform thickness. There are two types of molds: a hemisphere without an air filling valve part and a hemisphere with a valve part. The edges of the hemispheres manufactured in this way are filled with a foaming agent inside and then adhered with an adhesive, and another female and female mold (both concave molds) is used for the second time. A soft tennis ball having a uniform thick body and a highly accurate sphere manufactured by heat vulcanization molding and a method for manufacturing the same. One of the two types of male-female molds has a small concave part in the center to form an air-filling valve, and this part is filled with the same rubber material as the ball body. Then, a soft tennis ball having a valve portion which is manufactured by integrally heating and vulcanization molding together with a hemisphere of the ball body and has a valve portion which is strong against impact and never peels off, and a manufacturing method thereof. An O-shaped ring is fitted to the convex portion on the ball inner surface side of the valve portion to prevent air leakage. A color soft tennis ball for practice with different colors, which can be produced when each hemisphere is heat-cured and molded with rubber of different colors, and the joint surfaces are joined evenly and linearly, and its manufacturing method.

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