JPH04161175A - Tennis ball - Google Patents

Abstract

PURPOSE:To enable even a beginner to easily handle the above ball by consisting its cover of specific needle felt and forming the ball having the thickness of the core, the weight of the ball and the outside diameter of the ball which are respectively specific. CONSTITUTION:This ball is formed by constituting its cover of the needle felt having 450 to 600g/m<2> METSUKE and specifying the thickness of the core to 2.2 to 3.0mm, the weight of the ball to 40 to 54g and the outside diameter of the ball to 6.35 to 6.67cm. Such tennis ball which enables children and beginners to easily handle the ball, accelerates the improvement in tennis and allows the smooth shifting to a play with an ordinary tennis ball after the improvement to some extent is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to tennis balls. More specifically, it relates to a tennis ball that is light, soft, and easy to handle even for children and beginners.

[Conventional technology]

Tennis balls have standards set by the ITF (International Tennis Federation), and unless they pass these standards, they cannot be used in official matches, so most commercially available tennis balls pass the TTF standards. is a ball,
Not only professionals and advanced tennis players, but also general tennis players.
I'm using this ball.

Here, the rTF standards are as follows.

Weight 56.7-58.5g Outer diameter
6.35~6.67cm Forward deformation amount 5.6~7.41 Return deformation amount 8.
9-10.8■Rebound 135-147
C11 Also, there are tennis balls on the market that do not meet the ITF standards as practice balls, but these balls also do not meet the ITF standards.
It does not deviate greatly from the F standard, but the characteristics are I
It is almost the same as a ball that passes the TF standard.

These balls have the advantage of being able to play quickly because they have a moderate impact and high ball speed for those who have progressed to a certain level, but when used by children and beginners, they feel hard and heavy. Also, since the ball speed is high, it is difficult to handle the ball, making it difficult to maintain a rally.

As a result, their progress slows down and they decide that tennis is not an interesting sport, giving up on improving or moving on to other sports.

Furthermore, Japanese Patent Application Laid-Open No. 61-41385 proposes a tennis ball with an outer diameter that is about 3 to 11% larger than a normal ball, but because this ball has a large resistance, the ball speed in the air is slow. However, the weight is 54-58.5g.
It is difficult to handle because it is heavy and the impact force is not much different from a regular ball.

[Problem to be solved by the invention]

As mentioned above, tennis balls that pass the ITF standard and conventional tennis balls for practice are hard, heavy, and fast, making it difficult for children and beginners to handle the ball, making it difficult to improve their skills.

Therefore, the present invention solves the above problems and
Easy to handle for children and beginners, promotes improvement, and,
To provide a tennis ball that causes less discomfort when transitioning to play with a normal tennis ball after a certain degree of skill is achieved.

[Means to solve the problem]

The present invention provides a tennis ball, ■ a cover with a basis weight of 450 to 6;
00g/m2 needle felt, ■The core thickness (wall thickness) is 2.2~3.0cm, ■The pole weight is 4.
0~54g, and ■Ball outer diameter 6.35~6.6
By setting the length to 7 cm, the above objective was achieved.

That is, by making the core thickness 2.2 to 3.0 cm thinner than normal balls, the ball is made lighter and softer, and the cover that covers the core is made with a fabric weight of 450 to 600 g, which is light and highly elastic. / rrr's needle felt makes it easier for the cover to follow the deformation of the core, reducing impact and suppressing ball speed, making it easier for children and beginners to handle, promoting their improvement, and to some extent. This is designed to reduce the sense of discomfort when transitioning to playing with a regular tennis ball after improving.

The present invention will be described in detail as follows.

As mentioned above, all commercially available tennis balls, including tennis balls that pass the ITF standard, are hard (and heavy) and have high ball speeds, so for those who have progressed to a certain level, they have a moderate impact and are suitable for speedy play. Although it has the advantage of being playable, it feels heavy and hard for children and beginners, and the ball speed is too fast, making it difficult to handle the ball and making it difficult to sustain rallies.

As a result, tennis feels like a difficult and uninteresting sport.

Therefore, Japanese Utility Model Application Publication No. 64-42067 proposes a tennis ball with a thinner core, lower rubber hardness, and lower internal pressure. However, the cover of this tennis ball is made of woven felt (melton) with low elongation, which is used in regular tennis balls, resulting in a combination of a core that is too soft and a cover that has little elongation. Since the deformation of the ball is significantly suppressed by the cover, the impact becomes large, and since the internal pressure of the ball is low, there are problems in that the flight is poor and the rebound is too low. Therefore, in the case of this tennis ball, the purpose of reducing the impact is not fully achieved, and the low rebound may cause a feeling of discomfort when transitioning to playing with a regular tennis ball after improving. Become.

Therefore, the present invention solves the problems that children and beginners feel about balls that pass ITF standards, makes the ball easier to handle, and promotes their improvement in tennis. The goal is to provide a tennis ball that allows a smooth transition to play.

For children and beginners, the problems with balls that pass ITF standards are high impact (i.e., the ball is hard (and heavy)) and too much speed (i.e., the ball travels too fast). Therefore, it is necessary to solve this problem without changing other factors as much as possible.

Therefore, in the present invention, by reducing the thickness of the core to 2.2 to 3.0 mm, the ball is made lighter and softer, and the cover that covers this core is made of light and highly elastic needle felt. By using this, the cover can follow the deformation of the core, reducing the impact.
And try to keep the ball speed down.

In other words, in the case of the woven felt used in conventional tennis balls, cotton yarn is used for the warp, which suppresses elongation and cannot follow the deformation of the core. The characteristics of the developed core are not fully utilized.

On the other hand, the needle felt used in the present invention has a light basis weight of 450 to 600 g/m, has no directionality when expanding and contracting like woven felt, and has extremely high elasticity, so that the cut 1 is centered at the core. Since the deformation of the core can be fully followed and the deformation of the core is not suppressed, the impact does not become large.

By the way, the specifications of the woven felt (melton) used in conventional tennis ball covers are as follows.

Warp: 100% cotton Weft: wool and nylon (7:3.6:4, etc.) Weave (650-800 g/28 pieces of weave) Sateen weave density: over 200 warp/10CI, under 200 width/10C11 needle Felt is made by placing a fiber web on top of a base fabric, piercing it with many needles, and intertwining the fibers.

The needle felt used in the present invention has a basis weight of 450 to 600 g/%, which is 0° lighter than conventionally used woven felt.A base fabric is usually used for this needle felt. However, the material of this base fabric is polyester, etc., and it does not easily suppress elongation like the cotton thread used in woven felt.
The density of the base fabric is preferably 150 fibers/10 ci or less in both length and width), but the base fabric is not necessarily required.

In the present invention, the basis weight of needle felt is 450 to 6.
00 g/n (but this requires a basis weight of 450 g/n (if it is less, the density will become smaller and there is a risk of problems with durability etc.), and if the basis weight is less than 600 g/n. This is because if it exceeds nf, the density becomes too large and becomes hard.

The thickness of the core must be 2.2 to 3.0 mm, particularly preferably 2.4 to 2.8 mm. Core thickness is 2
．． If it is thinner than 2■, the ball becomes too soft, causing problems such as so-called air leakage becoming faster and internal pressure decreasing. Also, if the core thickness is thicker than 3.0 mm,
It will be harder and heavier, and will be no different from balls that pass ITF standards.

The weight of the ball must be 40-54g, and 4
A ball weight of 3 to 50 g is particularly preferable; if the ball weight is less than 40 g, it is too light and cannot be used as a tennis ball (hard tennis ball).
The ball will have different properties and its trajectory will be unstable. Furthermore, if the ball weighs more than 54 g, it will be too heavy and the impact will be large.

The outer diameter of the ball is set to 6.35 to 6.67 (], which is the same as the ITF standard.This is to solve the problem that the ball that passes the ITF standard is hard, heavy, and has too high speed. For example, it will be easier to transition to playing with a regular tennis ball after you have improved if you do not change other factors as much as possible.
This is because it is better to match the ball size to ITF standards.

The internal pressure of the ball may also be increased to about 0.6 to 1.0 kg/cd relative to atmospheric pressure, as in a normal tennis ball.

The internal pressure of the ball (however, the degree of pressurization relative to atmospheric pressure) is 0.6
If it is lower than kg/d, the rebound will be low and the flight will be poor. Furthermore, when the internal pressure of the ball is higher than 1.0 kg/cd, the ball becomes hard, which affects the outer diameter of the core and the strength of the joint.

And, by using the above configuration, the rebound is
It can be made from 135 to 147C11 according to the F standard.

〔Effect of the invention〕

The tennis ball of the present invention is light and soft, so there is little impact, and its weight is moderately light, so the speed decreases moderately in the air, making it easy for children and beginners to handle, making it easier to continue rallies. As a result, tennis becomes more interesting and you will improve faster.

In addition, since the internal pressure of the ball is kept normal, and the ball's outer diameter and rebound also pass ITF standards, it does not significantly impair the characteristics of normal tennis, so you can transition to playing with a normal tennis ball after you have improved to a certain extent. There is little discomfort when doing so.

Therefore, if you start practicing with this child Nispol, tennis will become more interesting (and you will improve faster), so you will be less likely to give up on improving or move on to other sports because tennis is a difficult and uninteresting sport.

In addition, this tennis ball does not feel any different from a regular tennis ball, so people who have progressed to a certain level can enjoy playing tennis at a leisurely pace, and even elderly people with poor physical strength can enjoy playing tennis. can.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Six types of tennis balls were produced according to the specifications shown in Table 1, and were used to evaluate impact, ball speed, and the like.

The results are shown in Table 1.

Comparative Example 1 uses woven felt for the cover! A tennis ball that passes the TF standard is selected, and it is clarified how the tennis ball of the present invention differs in impact and ball speed from a ball that passes the ITF standard. In Comparative Example 2, needle felt was used for the cover to produce a tennis ball that was lighter in weight than the ball of the present invention and had a thicker core. In Comparative Example 3, needle felt was used for the cover and heavier than the invented ball,
A tennis ball with a thicker core was also produced, and the differences in impact, ball speed, etc. with the tennis ball of the present invention are shown.

The rubber composition used to make the core was 100 parts by weight of natural rubber, 12 parts by weight of zinc oxide, 20 parts by weight of hard clay, 40 parts by weight of magnesium carbonate, and 1 part by weight of stearic acid. , 3.5 parts by weight of sulfur, 2.0 parts by weight of promoter M and promoter D
The accelerator M is 2-mercaptobenzothiazole and the accelerator is diphenylguanidine.

To make the core, the rubber composition with the above formulation is made into a sheet,
It was molded into a rond shape using an extruder, put into a mold for half shells, and compression molded at 160°C for 2 minutes to produce half shells, and a gas generating agent was placed in the recess of one of the pair of half shells. The half shell was filled with ammonium chloride and sodium nitrite, and the other half shell was superimposed on the half shell to form a spherical shape.The half shell was placed in a core mold and compression molded at 150°C for 12 minutes. A tennis ball was produced by covering the core with a cover, placing it in a ball mold, and compression molding it at 140° C. for 18 minutes.

The specifications of the needle felt used for the tennis ball covers of Examples 1 to 3 and Comparative Examples 2 to 3 are as follows.

Fabric weight: Approximately 510 g/a Base fabric: Polyester Density: Approximately 90 vertical lines/101 horizontal lines/10 cm The specifications of the woven felt used for the tennis ball cover of Comparative Example 1 are as follows.

Warp: 100% cotton Weft: Wool: Nylon (7:3') Weight: approx. 750
g / A structure = 8 pieces Sateen weave density: Approximately 230 pieces vertically / l0C11 Approximately 190 lines horizontally / 10 cm In Table 1, impact, ball speed, characteristics, etc. are evaluated based on children and beginners, so The tennis ball of Comparative Example 1, which passes the ITF standard, is evaluated as having a large impact and a high ball speed. On the other hand, the tennis balls of Examples 1 to 3 are lighter, softer, and have slower ball speeds than the tennis ball of Comparative Example 1, which passes the ITF standard, but they are considered preferable for children and beginners. Therefore, as shown in Table 1, the hardness, weight, and ball speed are all appropriate.
It is rated as easy to handle. Incidentally, the rebound described in Table 1 was measured by the following method.

Rebound: A ball is dropped from a height of 254 cm onto a concrete surface, and the height of the rebound is measured.

Claims (1)

[Claims] 1. A tennis ball having a hollow core and a cover covering the core, (1) the cover is made of needle felt with a basis weight of 450 to 600 g/m^2, and (2) the core is made of needle felt. A tennis ball having a thickness of 2.2 to 3.0 mm, (3) a ball weight of 40 to 54 g, and (4) a ball outer diameter of 6.35 to 6.67 cm.