JPH08155055A - Ball for ball game and its production - Google Patents

Abstract

PURPOSE: To improve the durability of a ball for ball games having a sewn structure. CONSTITUTION: Self-shrinkable yarn 9 which is shrunk by heating or water absorbing is used as sewing yarn for plural sheets of leather panels 2, 3 constituting a leather skin layer 5 of a soccer ball, etc. This self-shrinkable yarn is shrunk by heating or water absorbing after the production of the ball. As a result, strong tightening force is obtd. in the sewn part of the leather panels and the opening of stitches does not arise even after long-term use. Initial game performance is retained without degradation and the enlargement of the ball is suppressed, by which the durability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball game ball such as a soccer ball, and more particularly to a ball game ball having a sewn structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a ball game ball having an air-filled structure such as a soccer ball, a handball, a volleyball and a dodgeball, the ends of a plurality of leather panels are bent inward and the bent parts are sewn together with a thread to form a spherical shape as a whole. There is known a ball structure ball (referred to as a sewing ball) having a sewn structure in which a hollow spherical rubber tube is housed in the leather skin layer (for example, Jitsukaihei 2-136660). .

1 to 3 show an example of a soccer ball 1 having a sewn structure, and 20 hexagonal leather panels 2 and 2 are shown.
... and twelve pentagonal leather panels 3, 3 ... are sewn together at their ends with a thread 4 to form a leather skin layer 5, and a hollow spherical elastic rubber having low air permeability such as latex and butyl rubber is formed therein. A tube 6 made of Compressed air is enclosed in the tube 6 via a valve (not shown).

Natural leather or synthetic leather is used as the leather panels 2, 2 ,. Normal leather panel 2,
A reinforcing cloth layer 7 is formed on the back surface of 3 by adhering a cotton cloth or a polyester / cotton mixed cloth with an adhesive such as a two- to four-layer latex. In the following description, the leather panels 2 and 3 are referred to as the reinforcement. The one including the cloth layer 7.

As shown in FIG. 3, the leather panels 2, 2, ..., 3, 3 are provided with a large number of sewing holes 8, 8 ... At the periphery thereof, and the thread 4 is passed through the sewing holes 8, 8. Then, the two leather panels 2 and 2 are sewn together. As the thread 4, polyester thread, cotton thread, hemp thread, nylon thread, or the like is used.

On the other hand, a high shrinkage polyester fiber which shrinks by several 10% by heat treatment is also known (for example,
Japanese Patent Publication No. 51-40170). In this publication, polyethylene terephthalate unstretched fiber is used in a hot water bath at 60 to 70 ° C for 2.5
A method for producing a highly shrinkable polyester fiber is described, in which the material is stretched to 2.9 times, cooled to 40 ° C or less after stretching, supplied to a crimper to be crimped, and then dried at 45 ° C or less after crimping.
Such high shrinkage polyester fiber is 30% in hot water at 70 ℃.
It is explained that the above shrinkage ratio can be obtained. other than this,
For high shrink polyester shrink yarn, Japanese Patent Publication No. 51-40171
There is an invention disclosed in Japanese Patent Publication No. 52-43931.

On the other hand, there is also known a wet shrinkable polyvinyl alcohol (hereinafter referred to as PVA) fiber which shrinks by several 10% by water absorption treatment (for example, Japanese Utility Model Publication No. 63-15353). The wet shrinkable PVA fiber disclosed in this publication is usually dry or wet spun using PVA having a polymerization degree of 300 to 2400 and a fighting degree of 90 to 99.9 mol% as a raw material, and contains water in an atmosphere of 130 ° C or lower. It is described that it may be obtained by stretching it 1.5 times or more and then drying, and then heat treatment in a tension state after drying, and in the case of a wet method, a refining treatment for salt removal may be subsequently performed. This wet shrinkage P
VA fiber can be used for 10 seconds within 30 seconds when immersed in water at 40 ° C or less.
It is stated that it shrinks by ~ 60%.

[0008] Fibers that have a high shrinkage effect of 10% or more when subjected to treatment such as heating or water absorption as described above,
It is called self-shrinking thread. Generally, the chemical fiber shrinks by heating, but its value is extremely small and usually about 2 to 3%.

[0009]

A ball having a sewn structure is
For example, in the case of a soccer ball, the ball bites into the foot at the time of kicking, and it is easy to use high technology in shooting, dribbling, passing, etc., and it has the advantage that it is excellent in competition performance, but it has the drawback of poor durability. Similarly, for handballs, volleyballs, and dodgeballs, sewn balls have excellent grip (easiness to grasp) and are therefore easy to control, have a stable trajectory without throwing irregularly when thrown, and have little pain on the body. However, there is a problem in durability as described above. That is, as the sewing ball is used repeatedly, the sewn portion expands (referred to as the seam opening 11) as shown in FIG. 4, and the ball expands and deforms. To give an example,
Six size 5 soccer balls (initial circumference 685 mm)
After using it in soccer practice, games, etc. for a month, its circumference was enlarged to 705 mm to 710 mm. On the other hand, the ball of the pasting structure (same size) with excellent durability was 700 mm.

Here, the ball having a sticking structure means a reinforcing layer for preventing a spherical shape from enlarging by winding a nylon tube of several thousand m evenly on a rubber tube, and a thin rubber layer on the reinforcing layer. It is made by sticking multiple leather panels, and is usually called a sticking ball. Since this pasted ball has a reinforcing layer, it has excellent durability, but it does not feel good when hitting a ball, etc., and is inferior in competitive performance to a sewn ball. Often used as a game ball.

The present invention provides a sewn ball having improved durability without impairing high playing performance such as grip and ball controllability.

[0012]

A ball for ball game according to the present invention comprises a hollow spherical rubber tube housed in a leather skin layer formed by stitching a plurality of leather panels in a spherical shape with threads, In a ball for ball game in which compressed air is injected into a tube through an air injection valve, the thread is a self-shrinking thread that is shrink-treated after sewing.

Further, in the ball for ball game according to the present invention, the self-shrinking yarn is made of a self-shrinking yarn which shrinks by heating.

Further, in the ball for ball game according to the present invention, the self-shrinking yarn which shrinks by heating is made of a highly shrinkable polyester fiber.

Further, in the ball for ball game according to the present invention, the self-shrinking yarn is made of a self-shrinking yarn which shrinks by absorbing water.

Further, in the ball for ball game according to the present invention, the self-shrinking yarn which shrinks by absorbing water is composed of a wet shrinkable PVA fiber.

In the ball game ball according to the present invention, the leather skin layer is composed of a plurality of hexagonal leather panels and pentagonal leather panels, and the ball game ball can be a soccer ball or a handball. is there.

In the ball game ball according to the present invention, the leather skin layer is composed of a plurality of substantially rectangular leather panels, and the ball game ball can be a volleyball or a dodge ball.

The method for producing a ball for ball game according to the present invention comprises:
A step of forming a hollow spherical rubber tube, a step of sewing a plurality of leather panels in a spherical shape with a self-shrinking thread that shrinks by heating to form a leather skin layer, and storing the tube in the leather skin layer And a step of heat-treating the leather skin layer to heat-shrink the self-shrinking yarn.

Further, in the method for producing a ball for ball game according to the present invention, the self-shrinkable yarn which shrinks by heating is made of a highly shrinkable polyester fiber.

Also, in the method for producing a ball game ball according to the present invention, the leather skin layer sewn with the heat shrinkable self-shrinking thread comprises a plurality of hexagonal leather panels and pentagonal leather panels. The game ball can be a soccer ball or a handball.

Further, in the method for producing a ball game ball according to the present invention, the leather skin layer sewn by the heat shrinkable self-shrinking thread is composed of a plurality of substantially rectangular leather panels. It can be volleyball or dodgeball.

The method of manufacturing a ball for ball game according to the present invention comprises:
A step of forming a hollow spherical rubber tube, a step of forming a leather skin layer by stitching a plurality of leather panels in a spherical shape with a self-shrinking thread that shrinks by absorbing water, and a step of storing the tube in the leather skin layer , Is included.

Further, the method for producing a ball for ball game according to the present invention is obtained by adding the step of storing the tube in the leather skin layer and then wetting the self-shrinking yarn with water to shrink the tube. Is.

Further, in the method for manufacturing a ball for ball game according to the present invention, the self-shrinking yarn which shrinks by absorbing water is wet shrinkable PVA.
It consists of fibers.

Further, in the method for producing a ball for ball game according to the present invention, the leather skin layer sewn by the self-shrinking yarn which shrinks by absorbing water is composed of a plurality of hexagonal leather panels and pentagonal leather panels. The game ball can be a soccer ball or a handball.

Further, in the method for producing a ball game ball according to the present invention, the leather skin layer sewn with the self-shrinking yarn which shrinks by absorbing water is composed of a plurality of substantially rectangular leather panels, It can be volleyball or dodgeball.

[0028]

[Function] The self-shrinking thread, after sewing the leather panels together,
Shrink processing is performed. The contracted thread tightly tightens the leather panels to each other and suppresses seam opening and enlargement of the leather skin layer.

When the self-shrinking yarn is a self-shrinking yarn that shrinks by heating, it is heat-treated after sewing, and the self-shrinking yarn is made to shrink, so that the leather panels are strongly tightened together. After heating, the shrinkage of the yarn is maintained even when the temperature is returned to room temperature.

When the heat-shrinkable self-shrinking yarn is made of a high shrinkage polyester fiber, a high and constant shrinkage ratio is obtained.

When the self-shrinking thread is made of a self-shrinking thread which shrinks by absorbing water, it is made to shrink by absorbing rainwater or the like during use after sewing or by being forcibly absorbed by water, thereby making the leather Tighten the panels together. The shrinkage of the yarn is maintained even after drying after absorbing water.

The self-shrinking yarn which shrinks by absorbing water has a wet shrinkability P
When made of VA fibers, a high and constant shrinkage is obtained.

When the leather surface layer is composed of a plurality of hexagonal leather panels and pentagonal leather panels, the seam opening is suppressed and the grip, ball control, kicking or throwing required for a soccer ball or a handball is thrown. The performance of the race, such as the stability of the trajectory, is maintained.

When the leather surface layer is composed of a plurality of substantially rectangular leather panels, the seam opening is suppressed in the same manner as described above, and the grip, ball controllability, hitting and throwing required for volleyball or dodgeball are required. Competition performance such as trajectory stability is maintained.

[0035]

EXAMPLE As shown in FIGS. 1 to 3, 20 pieces of hexagonal panels 2, 2 ... And 12 pieces of pentagonal panel are cut by cutting natural leather or synthetic leather having a reinforcing cloth layer 7 adhered to the back surface thereof. Three
3 are formed, a plurality of sewing holes 8 are formed in the peripheral edge, and the panels 2, 2, ..., 3, 3 are sewn with the self-shrinking thread 9 to form a spherical leather skin layer 5, and A rubber tube 6 was housed to make a No. 5 soccer ball 1. The synthetic leather refers to leather-like material artificially produced by imitating natural leather using a resin such as polyurethane resin or PVA resin.

As the self-shrinking yarn 9, a highly shrinkable polyester fiber which shrinks by heating, for example, Soku latex (registered trademark, manufactured by Teijin Ltd.) can be used. The heat treatment is performed by immersing the soccer ball 1 in boiling water at 100 ° C. or by housing it in a heated mold. The yarn 9 instantly shrinks by 50% when immersed in boiling water in a state where no tension is applied to the yarn alone (no load). Further, this yarn 9 has a high shrinkage stress. For example, when shrinkage yarn having a total denier number of 12,000 denier is shrunk by 10% in boiling water, the tightening force increases by about 1 kg. It is maintained even if the temperature is lowered and returned to room temperature. In addition, it has a high strength retention rate even after shrinkage.

FIG. 5 shows the results of measuring the circumference (ball circumference) when a soccer ball 1 was prepared using 12,000 denier self-shrinking yarn 9 and treated at different heating temperatures for 10 minutes each. As shown by the curve A, there is almost no change in the circumference at 60 ° C, and the circumference at 80 ° C is about 2.6 mm compared to 60 ° C.
About 0.4% smaller. As a comparative example, a curve B shows the value of the circumference of a ball produced using a conventional non-shrink yarn (11,500 denier). Since this conventional ball should not be affected by temperature, it should have a curve close to horizontal, but in reality it was slightly (about 0.15%) enlarged. From this, by using the self-shrinking thread 9,
It can be seen that the seams are tightly tightened and the circumference of the ball is slightly smaller.

The self-shrinking thread 9 shrinks by heating and strongly tightens the sewn portions of the leather panels 2 and 3. Due to this tightening, partial loosening at the time of sewing, individual differences in sewing strength among sewing manufacturers, etc. are eliminated, and a constant and strong tightening force is obtained. According to the experiments by the inventors, the circumference of each of the 100 soccer balls before and after the shrinkage treatment was measured and the standard deviation thereof was calculated.As a result, the value before treatment was 1.733 and the value after treatment was 0.
Got 966. The standard deviation after the treatment is about 55% before the treatment, which means that the range of the variation of the circumference is narrowed to 1 in about 2 minutes.

FIG. 6 shows the results of a durability test when a soccer ball 1 was produced using the self-shrinking yarn 9 and heated at 80 ° C. for 10 minutes in a thermostatic chamber to shrink. The durability test
It is a test of repeatedly compressing a ball to 33% of its diameter. As shown by the curve A, in the compression test of 30,000 times (equivalent to about 6 months of use), the circumference increases from 665 mm to 676 mm,
The rate of increase was 1.7%. At this time, no seam opening was observed, and there was no problem in using. On the other hand, the curve B shows a sewing ball using a conventional non-shrinkable thread, and in the same compression test, the circumference increased from 665 mm to 684 mm (increase rate of 2.9%). At this time, the ball has a seam opening,
It hindered the competition and could not be used. A curve C shows the durability test result on the pasted ball, and it can be seen that the sewing ball (curve A) according to the example of the present invention has durability close to that of the pasted ball. In order to facilitate the comparison with the example balls, the conventional example balls corresponding to the curves B and C had a circumference at the start of the test equal to that of the example balls.

Next, a method of manufacturing the soccer ball according to the above embodiment will be described. As shown in FIG. 3, first, the leather panel is cut into 20 hexagonal panels 2, 2 by cutting natural leather or synthetic leather having a reinforcing cloth layer 7 adhered to the back surface thereof.
And twelve pentagonal panels 3, 3 ... Next, a plurality of sewing holes 8 are formed on the periphery of each panel. These panels are manually sewn together using the aforementioned self-shrinking thread 9 to form a spherical leather skin layer 5.

The rubber tube 6 is formed by heating and vulcanizing butyl rubber. At the same time as molding, a valve for enclosing air in the tube 6 is formed. The tube 6 is accommodated in the leather skin layer from the unsewn portion of the leather skin layer 5, which is left on only one side. A small circular opening 10 (FIG. 1) is formed in the center of one panel 2 of the leather skin layer 5, and the valve of the tube 6 is positioned in this opening 10 and the peripheral portion of the valve is the leather skin layer. 5 Bonded to the back side. The adhesion between the leather skin layer 5 and the tube 6 is only around this valve,
In other parts, the two are separated. After storing the tube 6, the unsewn portion of the leather skin layer 5 is sewn.

The ball 1 thus sewn together is housed in a mold having a spherical cavity matching the outer shape of the ball 1, and is filled with compressed air of a predetermined pressure at 80 ° C.
It is heated for 10 minutes. As a result, the self-shrinking yarn 9 shrinks, and the leather panels 2 and 3 are joined with a strong tightening force. This heat treatment is performed by using a heating die, for example, by setting the ball internal pressure to 0 to 0.3 kg / cm ² and 80 to 80 in a constant temperature bath.
The same contraction effect can be obtained by placing the film in air at 90 ° C for 30 minutes or more.

Examples of the self-shrinkable yarn 9 that shrinks by heating include acrylic fibers, acetate fibers, vinylidene fibers, nylon fibers, in addition to the above-described highly shrinkable polyester fibers.
It is possible to use a yarn in which a shrinkage effect is imparted by subjecting polyvinyl chloride fiber, polyethylene fiber, polypropylene fiber to special treatment such as draw crimping.

In the above embodiments, the self-shrinkable yarn 9 is described as a yarn which shrinks by heating. However, instead of this, a self-shrinkable yarn 9 which shrinks by absorbing water can be used. The case where the shrinkable yarn 9 is used will be described. As such self-shrinking yarn 9, a wet shrinkability P
VA fiber such as high shrinkage vinylon, Cremona (registered trademark,
Kuraray Co., Ltd.) can be used.

The water absorbing type self-shrinking yarn 9 is kept at room temperature (20 ° C.).
Shrinks about 30% in water instantly. Further, this shrinkable yarn 9 has a high shrinkage stress, and for example, even if a water absorbing shrinkable yarn of 12,000 denier is loaded with 300 g and pulled to absorb water,
Shrink more than%. The high tightening force due to shrinkage is maintained even after drying.

Table 1 shows the results of measuring the circumference when a soccer ball was produced using 12,000 denier self-shrinking yarn 9, immersed in water, subjected to water absorption treatment, and then dried. For reference, the results of a soccer ball using a conventional non-shrink yarn (11,500 denier) are also shown. As can be seen from this table, the shrinkage rate of the soccer ball of the example was 1.0%, which was higher than the shrinkage rate of 0.3% of the soccer ball of the conventional example. It is assumed that even the conventional soccer ball slightly shrinks due to the drying of the leather panel.

[0047]

[Table 1]

The self-shrinking thread 9 shrinks by absorbing water,
Tighten the sewn parts of the leather panels 2 and 3. As a result, partial loosening at the time of sewing, individual differences in sewing strength among sewing manufacturers, etc. are eliminated, and a constant and strong tightening force can be obtained. That is, the same effect as in the case of using the above-described heat shrinkable self-shrinking yarn can be obtained.

FIG. 7 shows the results of the durability test when the soccer ball 1 was produced using the water-absorbing type self-shrinking yarn 9, and the self-shrinking yarn 9 was shrunk by drying after absorbing water. The durability test is the same as the above-mentioned test. As shown by the curve A, in the compression test of 30,000 times, the circumference increased from 670 mm to 683 mm, and the increase rate was 1.9%. At this time, no seam opening was observed, and there was no problem in using.
Curve B shows the result of the sewing ball using the conventional non-shrink thread, the circumference increases from 670mm to 688mm (increase rate 2.7
%), A seam opening occurred, which hindered the game and made the ball unusable. Curve C is the test result for the pasted ball. It can be seen that the sewing ball (curve A) according to the example of the present invention has durability close to that of the pasted ball. As the balls of the conventional example corresponding to the curves B and C, those having the same circumference as that of the example ball at the start of the test were used in order to facilitate comparison with the example ball similar to the above example.

In the final step of manufacturing the soccer ball 1, the self-shrinking yarn 9 is forcibly immersed in water to shrink the self-shrinking yarn 9, and the binding force between the leather panels is strengthened.
However, it is also possible to sell the soccer ball to the customer in a state where it is not subjected to the water-absorption contraction treatment, and when the customer uses the soccer ball, the self-contraction yarn 9 gets wet and is naturally contracted by rainwater.

In the above embodiment, a soccer ball in which 20 hexagonal leather panels and 12 pentagonal leather panels are sewn together has been described. In addition to this, 30 hexagonal leather panels and 12 pentagonal leather panels are used. It can also be applied to soccer balls stitched together. It can also be applied to a handball having a leather skin layer with the same pattern as a soccer ball. It is also effective when applied to a volleyball in which twelve or eighteen rectangular panels are sewn together to form a leather skin layer, particularly a beach volleyball and a dodgeball. In FIG. 8, eighteen elongated rectangular leather panels 12, 12, ... Are arranged in parallel, and three are prepared as one set, and six sets are arranged on a spherical surface so that the arrangement directions of each set are orthogonal to each other. 1 shows a beach volleyball 14 having a leather skin layer 13 stitched together.

[0052]

According to the present invention, a self-shrinking thread that shrinks by heating or absorbing water is used as a sewing thread for a ball game ball having a sewn structure, and a shrinking treatment is performed after the ball is manufactured, so that the leather panels are made uniform. Can be combined with a strong tightening force. Therefore, the seams do not open even after repeated use, grip, ball control,
High performance such as stability of trajectory at the time of kicking or pitching can be maintained, and a ball with soft feel and less pain when hitting the body can be realized. Further, since the increase in circumference is suppressed and a stable shape can be maintained for a long period of time, it is possible to prevent enlargement, which was a defect of the sewing ball, and to significantly improve durability.

According to the present invention, even if there are individual differences in the sewing strength of the thread before shrinking, the self-shrinking thread is made to shrink by heating the skin layer or absorbing water after sewing the leather panel. However, the difference is eliminated, a constant and high tightening force is obtained, and stable durability can be obtained.

Further, according to the present invention, by using the high shrinkage polyester fiber or the wet shrinkable PVA fiber as the self-shrinking yarn, a high and constant shrinkage ratio can be obtained and the mechanical strength thereof is sufficient. It is most suitable for ball game balls that are used under severe usage conditions such as the application of a strong external force.

Further, according to the present invention, since the seam opening is hardly generated after sewing, the groove formed in the seam is held for a long period of time. Therefore, the grip and ball controllability obtained by this seam are not impaired, and they are useful when applied to soccer balls, handballs, volleyballs and dodgeballs.

[Brief description of drawings]

FIG. 1 is a front view of a soccer ball for explaining a conventional example and an example of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a perspective view showing one step of a sewing operation.

FIG. 4 is a cross-sectional view showing a state in which a seam opening has occurred.

FIG. 5 is a curve diagram showing a circumference-heating temperature characteristic.

FIG. 6 is a curve diagram showing a circumference-compression test frequency characteristic of a soccer ball using a heat-shrinkable self-shrinking yarn.

FIG. 7 is a curve diagram showing a circumference-compression test frequency characteristic of a soccer ball using a water-absorption shrinkage type self-shrinking yarn.

FIG. 8 is a front view of a beach volleyball for explaining an embodiment of the present invention.

[Explanation of symbols]

 1 ………… Soccer ball 2,3,12 ………… Leather panel 4 ………… Yarn 5,13 ………… Leather skin layer 6 ……… Tube 8 ……… Suture hole 9 ……… Self-shrinking thread 11… …… Seams open 14 ………… Beach volleyball

Claims (17)

[Claims] 1. A hollow spherical rubber tube is housed in a leather skin layer formed by sewing a plurality of leather panels in a spherical shape with threads, and compressed air is injected into the tube through an air injection valve. In the ball game ball as described above, the thread is a self-shrinking thread that is shrink-processed after sewing. 2. The ball for ball game according to claim 1, wherein the self-shrinking yarn is made of a self-shrinking yarn that shrinks when heated. 3. The ball for ball games according to claim 2, wherein the self-shrinking yarn is made of highly shrinkable polyester fiber. 4. The ball for ball game of claim 1, wherein the self-shrinking yarn is formed of a self-shrinking yarn that shrinks by absorbing water. 5. The self-shrinking yarn is composed of a wet shrinkable polyvinyl alcohol fiber.
Balls for ball games described 6. The leather surface layer is composed of a plurality of hexagonal leather panels and pentagonal leather panels, and the ball for ball game is a soccer ball or a handball. Ball game described in 7. The leather skin layer comprises a plurality of substantially rectangular leather panels, and the ball for ball game is a volleyball or a dodgeball.
5. The ball for ball game according to any one of 5 to 5. 8. A step of forming a hollow spherical rubber tube, wherein a plurality of leather panels are sewn into a spherical shape by a self-shrinking thread that shrinks by heating to form a leather skin layer, and the above-mentioned inside of the leather skin layer is formed. A method for producing a ball for ball games, comprising: a step of housing a tube; and a step of heat-treating the leather skin layer to heat-shrink the self-shrinking yarn. 9. The method for manufacturing a ball for ball game according to claim 8, wherein the self-shrinking yarn is made of a self-shrinking yarn that shrinks when heated. 10. The method for manufacturing a ball for ball games according to claim 9, wherein the self-shrinking yarn is made of highly shrinkable polyester fiber. 11. The leather surface layer is composed of a plurality of hexagonal leather panels and pentagonal leather panels, and the ball for ball game is a soccer ball or a handball. Method for manufacturing ball for ball game described in 12. The ball game according to claim 8, wherein the leather skin layer comprises a plurality of substantially rectangular leather panels, and the ball game ball is a volleyball or a dodge ball. For balls 13. A step of forming a hollow spherical rubber tube, a plurality of leather panels are sewn into a spherical shape by a self-shrinking thread that shrinks by absorbing water to form a leather skin layer, and the above-mentioned inside of the leather skin layer is formed. A method of manufacturing a ball for ball game, including a step of storing a tube. 14. The method for producing a ball for ball games according to claim 13, further comprising the step of wetting the self-shrinking thread with water to shrink the tube after housing the tube in the leather skin layer. 15. The method for producing a ball for ball game according to claim 13, wherein the self-shrinking yarn is made of wet shrinkable polyvinyl alcohol fiber. 16. The leather surface layer comprises a plurality of hexagonal leather panels and pentagonal leather panels, and the ball for ball game is a soccer ball or a handball. Method for manufacturing ball for ball game described in 17. The ball game according to claim 13, wherein the leather skin layer is composed of a plurality of substantially rectangular leather panels, and the ball game ball is a volleyball or a dodge ball. For balls