JPS6148385A - Tennis ball - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to tennis balls, and more particularly to tennis balls that play more slowly than standard tennis balls.

Conventional technology Tennis has been a popular sport for decades.

However, tennis' popularity peaked in the 1970s, and mass participation in the sport has declined since this time.

One of the main reasons why many tennis players lose interest and give up on the sport is the perceived difficulty of the sport and the perceived low level of skill of the players.

Many people find that reaching and maintaining a standard of tennis skill requires a substantial amount of playing time, and many people find that reaching and maintaining a standard of tennis skill requires a substantial amount of playing time. It has no time or relevance.

Problems with Inventions Several attempts have been made to make the game of tennis easier. For example, in 1976 Sportink introduced a tennis ball called the ``Australian'', which was described as a ball that played slower than a standard tennis ball to make for longer exchanges and a more enjoyable game. The slow play is due to the lower air pressure and coefficient of restitution compared to the standard ball. However, this ball is not popular because it lacks vivacity and is heavy on the racket. This is thought to be due to the feeling of

The unpressurized tennis pole, which generally plays slower than a standard tennis ball, has the same drawbacks as the Australian ball. Tren h-ren pressureless Kapor has improved high repulsion. However, this ball lacks vigor due to its high impact velocity, which makes it feel heavy and dead against the racket.

SUMMARY OF THE INVENTION The present invention provides a new tennis ball that is slower to play than a standard tennis ball and is more bouncy than a standard tennis ball. The diameter of the ball is about 6 to 11 percent larger than the diameter of a standard ball, so the ball flies through the air more slowly and is more clearly visible than a standard ball. This new ball is slower than the standard ball, so when you hit it with more force or higher over the net, the new ball will fall more steeply.

Therefore, this new ball is more forgiving, allows for a greater margin of error, requires less skill, and allows for longer exchanges than a drifting ball.

Although the new ball is slower, the new ball has increased vivacity as measured by rebound and coefficient of restitution. This new ball is larger than the standard ball, but due to its thinner core, it weighs the same. Therefore, the ball feels light and lively compared to the racket.

The invention will now be described according to embodiments shown in the accompanying drawings.

EXAMPLE Tennis ball 10 is comprised of a core 11 made of rubber or other elastic material and a felt cover 12.

Core 11 is conventionally molded, but the diameter and thickness of core 11 differs from that of a standard tennis ball core, as will be explained in more detail below. The felt cover 12 is made from ilM woven felt. The weight of felt is 746g/m2 (2
4759/rn2(+
4 ounces/square yard). felt cover 12
The thickness of the standard tennis ball is approximately 6.05 mm (
0.120 inch) and approximately 2. +9 mrn
(0.094 inch).

A standard tennis ball has dimensions, weight, and rebound according to the following United States Tennis Association specifications:

``The ball must have a uniform outer surface and be white or yellow in color. If there is a seam, the seam must be seamless to complete.

The ball must have a diameter of at least 6.35 cm (2.5 inches) and no more than 6.6 y crrL (2 A inches), and a weight of at least 56.7.9 (2 ounces) and 58.5 g (2 ounces). Must be less than or equal to The bounce of the ball is
254 crtt (100 inches) more than 135 cm (53 inches) when dropped onto a concrete platform,
Must be no larger than 147 cm (58 inches). The forward deformation of the ball is 0.56α (0.220 inch) or more at a load of 8.165 kg (18 pounds), 0
．． 74 CTL (0.290 inch) or less, return deformation is 0.89 engineering (o, 35° inch) or more, t, 08
cm (0.a 25 inches) or less. The two deformation values must be the average of three separate readings along the six axes of the ball, and the two individual readings or o. , o 8c1rL (0.o 3 o inch)
It must not be higher than that. All tests for bounce and size and deformation shall be performed in accordance with International Lawn Tennis Federation (L, T, F) regulations. Approximately 3-11%
A ball with a larger outer diameter can play slower than a standard pole, and if the weight of the ball is kept at standard weight by reducing the thickness of the core, the larger ball has surprisingly better bounce and rebound. It was found that Traditionally, tennis balls, which are played more slowly than standard balls, have insufficient rebound and feel heavier on rackets. However, balls made according to this invention have better rebound and coefficient of restitution than standard balls.

Therefore, the ball of this invention feels light and cheerful against the racket.

The following table compares the physical customization of a standard tennis ball and a ball made in accordance with the present invention that is about 1 factor and about 15 factors larger than the standard ball.

The larger ball showed a better coefficient of restitution as the impact velocity increased. However, the increase was not linear and the optimum increase was obtained at a size increase of about 4.6%. The change in coefficient of restitution from the standard ball to the 4.6% larger ball at 70 feet/second (70 feet/second) is +0.45, which is 4.6
The change in coefficient of restitution from a % larger ball to a 15% larger ball is +0.18.

The observed increase in coefficient of restitution with ball size may be caused by a number of factors. 1. The thin walls of large balls experience less stress at a given bending moment, so less energy is dissipated. 2. When the ball becomes large with thin walls, it becomes more like an air spring and less like a rubber spring. Of course, air has a much lower attenuation coefficient than a comb.

3. The time interval for Tsukuda B meal is indicated by a large ball. It means that the amount of displacement, and therefore the energy dissipation, becomes smaller.

The displacements of the various balls are as follows.

Changes in small play ability and heavy sensation as they increase are not linear with dimension. 4 from standard ball.
The change in displacement to the 6th larger ball is +0.65, 4.
The change in displacement from a ball that is 6% larger to a ball that is 15 times larger is +0.57. Figure 2 shows the trajectory of the flight of handrails of various sizes fired by a tennis ball gun at the same velocity and firing angle. This is computer simulation. Due to tennis ball guns firing balls of different sizes slightly differently and balls of specific sizes inconsistently, or due to uncontrollable various spins, winds, etc. '[i
iJ controlled takes are difficult to obtain. but,
The accuracy of computer simulation is verified by actual firing of balls of each size. In Figure 2, a standard tennis ball is 23.8
m (78 ft) away at a speed of 35,7 rn/s (117 ft/s) that allows it to fall onto another
seconds) and is fired from the baseline of one side of the tennis court at an angle. The firing angle in FIG. 2 is 5.60°.

It will be understood that this means that as the ball grows, the ball will not fly far beyond the baseline, but will fall inside the baseline.

Figures 3 and 4 are identical to Figure 2. However, the firing velocity and angle in Figure 6 are 29.3 m7 seconds (96 ft/sec) and 9.2 degrees, and the firing velocity and angle in Figure 4 are 23.2 m1 seconds (76 ft/sec). ) and 16.9
°.

FIG. 5 is a computer simulation of the flight paths of balls of various sizes launched at the same velocity and at different angles that allow the ball to fall from one baseline onto the other. The ball gets bigger;
Therefore, it will be understood that the ball can be launched high above the net and fall in the same place. Therefore, the margin for error increases as the ball size increases. The rate of fire in Figure 5 is 29-5 mh (96 ft/sec).

Figures 6 and 7 are the same as Figure 5, or the firing speed is 23
．． 2 m1 sec (76 ft/sec) and 20.1 m/sec (
66 feet/second).

Play testing was used to determine acceptable balls. Testing by tennis players in actual playing conditions is important because the acceptable performance of tennis equipment is based more on ``feel'' and perceived conditions than under expected conditions. Play testing shows that a ball that is 1.2% larger than a standard pole does not exhibit sufficiently different play customization than in a standard ball.

The 4.6% larger ball was noticeably slower than the standard ball, and players felt they were able to hit the larger ball with more precision and control, had longer exchanges, and had more time to spot the ball. These same characteristics were exhibited by balls that were 8 and 1.2% larger than the standard ball, but felt heavier to players with balls that were 1.2% larger than the standard ball.

On the other hand, a ball that was 15% larger than the standard ball was not sufficient. The 15% larger ball was too slow and heavy, and players felt they could not hit the ball with enough force.

Furthermore, a ball that is 15 factors larger will be affected more by spin, and such a ball will bend more when a player applies spin to the ball.

It is known that the spin of a ball is proportional to the moment of inertia of the ball. The skin moment of the spherical shell is expressed as: ≈2/3 MR2. However, M is the mass and R is the outer radius. As the radius increases, the moment of inertia increases in proportion to the square of the radius. Therefore, a ball that is 15 factors larger will bend more when spin is applied to the ball.

Therefore, the player can play 266% ~ + more than a standard ball.
1.2% greater range of the ball increases accuracy and allows for longer exchanges. Balls that are 4.6% and 8% larger are better than balls that are j L2 % larger, and optimal play is obtained with balls that are 4.6 factors larger.

In the foregoing description, the detailed description of the specific embodiments of this invention is for illustrative purposes only, and many details given herein may depart from the spirit and scope of this invention. It will be understood that considerable changes may be made by the operator.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway view of a tennis ball made in accordance with the present invention, and FIG. 2 is a diagram showing the flight of a tennis ball of moderate dimensions hit from the baseline at the same angle Z and velocity. Figure 3.4 is a diagram similar to Figure 2 of a tennis ball of the same size hit at a slow speed; Figure 5 is a diagram showing various tennis balls hit from the baseline at the same speed but at different angles. Figures 6-7 are similar views to Figure 5 for tennis balls of various sizes hit at low speeds. In the figure, 1o: tennis ball, 11: core, 1
2: Feltkaha FIG, 1

Claims (1)

[Claims] 1. Consisting of an elastic core and a felt cover attached to the outer surface of the core, the ball has an outer diameter of approximately 6.83 cm (2.
689 inches) to approximately 7.40 cm (2.915 inches). 2. The tennis ball of claim 1, wherein the ball weighs between about 54g and about 58.5g. 3. Core thickness is approximately 0.30cm (0.118 inch)
2. The tennis ball of claim 1, wherein the tennis ball is within a range of about 0.25 cm (0.100 inch). 4. The thickness of the felt cover is approximately 0.24cm (0.09cm)
The tennis ball according to claim 1, which has a diameter of 4 inches. 5. The weight of the felt cover is approximately 474.6g/m^2 (
14 ounces per square yard). 6. The tennis ball of claim 1, wherein the ball has a coefficient of restitution of about 0.651 to about 0.675 at 21.4 m/sec (70 ft/sec). 7. The tennis ball of claim 1, wherein the ball has an outer diameter within the range of about 6.83 cm (2.689 inches) to about 7.19 cm (2.830 inches). 8. The tennis ball of claim 1, wherein the ball has an outer diameter within the range of about 6.96 cm (2.741 inches) to about 7.19 cm (2.830 inches). 9. The tennis ball of claim 1, wherein the ball has an outer diameter of approximately 6.96 cm (2.741 inches). 10. Consisting of an elastic core and a felt cover attached to the outer surface of the core, the outer diameter of the ball is approximately 6.83 cm (
2.689 inches) to approximately 7.40 cm (2.915 inches), and the ball weight ranges from approximately 54 grams to approximately 5.5 grams.
A tennis ball weighing 8.5 g and having a core thickness within the range of about 0.30 cm (0.118 inch) to about 0.25 cm (0.100 inch). 11. The thickness of the felt cover is approximately 0.24cm (0.0
11. The tennis ball according to claim 10, wherein the tennis ball has a diameter of 94 inches. 12. The weight of the felt cover is approximately 474.6g/m^2
(14 ounces/square yard)
Tennis ball described in item 0. 13. The tennis ball of claim 10, wherein the ball has a coefficient of restitution of about 0.651 to about 0.675 at 70 feet/second. 14. The outer diameter of the ball is within the range of approximately 6.83 cm (2.689 inches) to approximately 7.19 cm (2.830 inches), and the core thickness is approximately 0.30 cm (0.118 inches) to approximately 7.19 cm (0.118 inches). 11. The tennis ball of claim 10, wherein the tennis ball is within about 0.106 inches. 15. The outer diameter of the ball is within the range of approximately 6.96 cm (2.741 inches) to approximately 7.19 cm (2.830 inches), and the core thickness is approximately 0.29 cm (0.113 inches) to approximately 7.19 cm (0.113 inches). 11. The tennis ball of claim 10, wherein the tennis ball is within about 0.106 inches. 16. The tennis ball of claim 10, wherein the ball has an outer diameter of about 6.96 cm (2.741 inches) and a core thickness of about 0.29 cm (0.113 inches).