JP2011177369A - Tennis ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tennis ball to largely bound with small time degradation in the bounds when the ball is used. <P>SOLUTION: The tennis ball includes a core 10 and felt 12 covering the core. The core is molded in pressurized atmosphere so that the inner pressure of the core is higher than the atmospheric pressure. The felt is formed of a nonwoven fabric. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tennis ball having a core and a felt covered with a core as a skin (melton). More specifically, the present invention relates to a tennis ball in which the internal pressure of the core is higher than atmospheric pressure.

  As shown in FIG. 1, a tennis ball having a core 10 and a felt 12 covered with the core is used. Usually, the core is formed into a spherical shape with rubber, the felt is formed in a substantially bowl shape, and two felts are bonded to the core with a rubber adhesive. In FIG. 1, reference numeral 14 denotes a joint where the rubber adhesive is exposed between two felts.

  As a tennis ball, the internal pressure of the ball is approximately twice the atmospheric pressure, and the pressure ball (pressured ball) to which a repulsive force is applied is made the same as the atmospheric pressure, and the rubber thickness is increased. By doing so, there is a non-pressurized ball (non-pressure ball) imparted with a repulsive force.

  As a method for producing a pressurized ball, a chemical (ammonium chloride tablet, sodium nitrite tablet and water) is placed inside the core during molding of the core, and nitrogen gas is generated by the chemical reaction of the chemical to increase the internal pressure of the core. (In this specification, this method is referred to as “chemical method”. For example, refer to Patent Documents 1 and 2.) and a method of increasing the internal pressure of the core by molding the core in a pressurized atmosphere (in this specification, This method is referred to as “natural method” (for example, see Patent Document 2).

  As the above-mentioned felt for tennis balls, woven felt (weave felt) or needle felt is used (see Patent Document 3). Woven felt is obtained by fluffing the surface of a woven fabric, and is produced by raising and shrinking raw material. Needle felt is a non-woven fabric with a fluffed surface, and is produced by performing needle processing on a raw material dough.

  A tennis ball using a woven felt for the outer skin (in this specification, this ball is referred to as a “woven felt ball”) is a tennis ball using a needle felt for the outer skin (in this specification, this ball is referred to as a “needle felt ball”). It is superior in terms of performance, but it is mainly used for games because the felt is easy to fluff and wears easily. On the other hand, the needle felt ball is less used for practicing because it is less expensive than the woven felt ball because the felt is less fuzzy and less likely to wear.

  On the other hand, tennis courts include an un-to-car court made of red soil, an omni coat made of artificial grass with sand, a clay coat made of soil, a hard coat made of rubber on concrete, and a carpet coat made of carpet-like material ( For indoor use) and glass courts made of natural turf.

JP 2007-167 A JP 2004-194860 A Japanese Patent Laid-Open No. 2003-154037

  Patent Document 1 described above describes that a woven felt or a needle felt is used as a melton in a pressure ball manufactured by a chemical method (this ball is referred to as a “chemical pressure ball” in this specification). .

  However, the chemical pressure ball using the needle felt has a problem that the bounce of the ball is small. According to Rule 3 of the Tennis Rules, “The bounce of a ball must be not less than 134.62 cm and not more than 147.32 cm when the ball falls from a height of 254.00 cm onto a hard flat surface such as concrete.” It is prescribed. In addition, the chemical pressure ball using woven felt has a problem that the deterioration with time of bounce during use of the ball is large. Furthermore, the chemical pressure ball has a problem of lacking consideration for the environment because a chemical is used for pressurization.

  On the other hand, among each of the above-mentioned courts, there are courts in which it is preferable to use a ball having a high felt durability because the felt of the tennis ball tends to fluff. For example, a carpet coat. Therefore, it is preferable to use the needle felt ball described above for such a coat. However, when forming a needle felt ball, there is a problem that wrinkles are likely to occur particularly in the peripheral portion of the felt (in the vicinity of the joint).

  The present invention has been made in view of the above circumstances, and has as its first object to provide a tennis ball that has a large bounce of the ball and a small bounce of the bounce during use of the ball and is favorable to the environment. To do.

  In addition, the present invention has been made in view of the above circumstances, and the bounce of the ball is large, the deterioration with time of the bounce during use of the ball is small, and it is preferable for the environment, and moreover, the felt is not easily wrinkled during molding. The second object is to provide a tennis ball.

  In order to achieve the first object, the present invention provides, as a first invention, a tennis ball having a core and a felt covered with the core, wherein the core is molded in a pressurized atmosphere. The tennis ball is characterized in that the internal pressure is made higher than the atmospheric pressure, and the felt is formed of a nonwoven fabric.

  In order to achieve the second object of the present invention, as the second invention, in the tennis ball of the first invention described above, the felt has a bending resistance value measured by a cantilever method of 15 cm or less. A tennis ball is provided.

  In the above-mentioned chemical method, two half shells are bonded together in a state where an ammonium chloride tablet, a sodium nitrite tablet and water are put into one core forming half shell, and this is vulcanized. At the time of sulfuration, the tablet and water are heated, and nitrogen gas is generated by a chemical reaction between ammonium chloride and sodium nitrite, but water remains in the core. And, due to the water inside the core, the chemical pressure ball using needle felt is considered to have a small bounce of the ball.

  In addition, since the above-mentioned woven felt uses cotton which is easily stretched as a material, the woven felt ball is easily stretched during play. Accordingly, it is considered that the deterioration of the bounce over time when the ball is used increases because the core is greatly bent as the felt stretches during play and the core easily deteriorates.

  On the other hand, the tennis ball of the first invention is not formed by the chemical method of the core, but is formed by the natural method of forming the core in a pressurized atmosphere. It is thought that the bounce of the ball will not be small due to the internal water. In the present specification, a pressure ball manufactured by a natural method is referred to as a “natural pressure ball”.

  The tennis ball of the first invention uses a felt made of nonwoven fabric. Felt made of non-woven fabric uses polyester fiber, which is a material that is difficult to stretch, so it is difficult to stretch during play. Therefore, in the tennis ball of the first invention, the core does not bend greatly during play, and the core is not easily deteriorated. Therefore, it is considered that the deterioration with time of bouncing when using the ball is reduced. However, the felt material is not limited to polyester fiber, and any material that does not easily stretch may be used.

  Further, the tennis ball of the second invention has a felt bending resistance value of 15 cm or less measured by the cantilever method, so that the felt has flexibility, and therefore, when the tennis ball is molded, the felt is less likely to be wrinkled. Conceivable.

  The tennis ball of the first aspect of the invention is preferable for the environment because the bounce of the ball is large, the deterioration of the bounce with the passage of time is small, and no chemical is used for pressurization.

  The tennis ball of the second invention is preferable for the environment because the bounce of the ball is large, the deterioration of the bounce with the use of the ball is small, and no chemical is used for pressurization. Is unlikely to occur. That is, according to the second invention, it is possible to obtain a ball with excellent aesthetics, and to effectively prevent irregular ball jumps due to felt wrinkles.

It is a partial cross section front view which shows an example of a tennis ball. It is explanatory drawing of a cantilever method. It is a graph which shows a time-dependent change of ball hardness when a tennis ball is hit | damaged to a concrete wall with a ball hitting machine. It is a graph which shows the relationship between the incident speed and repulsive force of a ball when a tennis ball is hit | damaged to a concrete wall with a ball hitting machine.

  Hereinafter, the present invention will be described in more detail. More specifically, in the first and second inventions, the core is molded by the natural method. More specifically, a half shell serving as a core of a ball is charged in a molding die, and a constant pressure (pressurized atmosphere) is provided in the die. It is possible to carry out the process by molding the core while maintaining the above.

In the second invention, the cantilever method refers to a method for evaluating the stiffness of a woven fabric defined in the JIS-L-1096 stiffness A method. In this cantilever method, the bending resistance of the test piece is measured by the following procedures (A) to (D) (see FIG. 2). The smaller the value of the bending resistance measured by the cantilever method, the softer the sample.
(A) A test piece 20 having a length of 15 cm and a width of 2 cm is prepared.
(A) As shown in FIG. 2 (a), a test piece 20 is placed on a smooth horizontal table 24 having a 45 ° inclined surface 22 on one end side. At this time, the one end side short side 26 of the test piece 20 is aligned with one end of the horizontal base 24 on the inclined surface 22 side, and the position of the other end side short side 28 of the test piece 20 is read on a scale.
(C) The test piece 20 is slid gently in the direction of the slope 22, and the test is performed when the lateral center of the one end side short side 26 of the test piece 20 is in contact with the slope 22 as shown in FIG. The position of the short side 28 on the other end side of the piece 20 is read with a scale.
(D) The movement distance L of the short side 28 on the other end side of the test piece 20 when the short side 26 on the one end side of the test piece 20 is in contact with the inclined surface 22 as described above is the bending resistance (unit: cm).

  In the second invention, when the value of the bending resistance of the felt measured by the cantilever method exceeds 15 cm, that is, when the moving distance L reaches 15 cm without the one end side short side 26 of the test piece 20 being in contact with the inclined surface 22, The felt becomes too hard, and the felt tends to wrinkle when forming a tennis ball. A more preferable value of the bending resistance is 7.0 to 15 cm, particularly 12.5 to 14.4 cm in that wrinkles are less likely to occur in the felt during molding of the tennis ball.

  In the first and second inventions, polyester-based fibers can be suitably used as the material for the nonwoven fabric forming the felt. This is because the felt formed of polyester fiber is difficult to stretch during play as described above.

  In the second invention, the felt softness measured by the cantilever method can be set to the above-mentioned value by treating the fiber forming the felt with a softening agent for fibers and applying a soft finish to the fiber. The fiber softener imparts flexibility to the fiber, and an appropriate one is selected according to the material of the fiber.

  Examples of the main component of the fabric softener include a cationic surfactant such as a polyamide type cationic surfactant, a quaternary ammonium salt type cationic surfactant, a nonionic / cationic surfactant, and an ester type nonionic anion. Surfactant, nonionic / anionic surfactant, higher alcohol anionic surfactant, wax / nonionic / anionic surfactant, anionic surfactant such as wax / nonionic / weak anionic surfactant, polyhydric alcohol Nonionic surfactants, polyhydric alcohol ester type nonionic surfactants, polyether type nonionic surfactants, wax / nonionic surfactants, nonionic interfaces such as waxes / weak cations / nonionic surfactants Activators, silicone oils, modified silicone oils and the like can be mentioned.

  Particularly preferred as the main component of the fabric softener is a polyamide-type cationic surfactant. By using this, a soft soft texture can be imparted to the fiber, and the hue change and color fastness can be fastened. The effect that a fiber with little fall of can be obtained is acquired. When the polyamide-type cationic surfactant is used for a polyester fiber, the above effect can be obtained particularly effectively.

  Examples of the treatment method using the fiber softener include, but are not limited to, a method of immersing felt raw fiber or felt in a fiber softener diluted with water.

  When producing the felt of the tennis ball of the second invention, the felt may be produced with fibers previously treated with a fiber softener, and after the felt is produced, the felt may be treated with a fiber softener.

  More preferably, the tennis balls of the first and second inventions are formed into needle felt balls. As a result, it is possible to obtain a tennis ball that can be suitably used in a court (for example, a carpet court) in which it is preferable to use a ball having a high felt durability because the felt is easily fluffed.

  The needle felt mentioned above can produce the needle felt which is the nonwoven fabric with which the surface fuzzed by performing the needle process which pierces a needle | hook with the needle punch apparatus, for example to the raw material cloth | flour obtained by mixing a fiber.

  Further, the needle felt described above may have a single layer structure or a multilayer structure. As the needle felt having a multilayer structure, for example, a base layer made of polyester fiber or acrylic fiber and a felt layer made of nylon fiber or a mixture fiber of wool and nylon are laminated. In the case where such a multi-layer needle felt is treated with a fiber softener, the main component of the fiber softener may be selected so that the fibers of all layers can be softened.

Example 1
(A) Tennis balls 1 to 5 having the specifications shown in Table 1 were produced. The definitions and measurement methods of hardness, return hardness, bounce, and ball internal pressure in Table 1 are as follows. The numerical values in Table 1 are average values of 12 balls. From Table 1, even if the felt is the same material (for example, needle felt), the bounce of the ball is different when the core is different. Specifically, the natural pressure ball using the needle felt uses the needle felt. It can be seen that the bound tends to be larger than that of the chemically pressurized ball.
・ Ball 1: Needle felt bonded to a core molded by the natural method.
-Ball 2: Needle felt bonded to a core molded by the natural method.
Ball 3: A needle formed by bonding a needle felt to a core formed by a chemical method.
Ball 4: A woven felt bonded to a core formed by a chemical method.
Ball 5: A woven felt bonded to a core molded by the natural method.
Definition of hardness / Measurement method: Deformation amount of the ball when a constant load (18 pounds = 8.165 kg) is applied to the ball.
・ Definition of return hardness ・ Measurement method: After applying a constant load (18 lbs = 8.165 kg) to the ball and measuring the hardness, the ball was compressed to a deformation of 1 inch (2.54 cm) and then released. The amount of deformation at the time of 18 pound load.
・ Definition and measurement method of bounce: The amount of bounce when a ball is dropped on a concrete floor from a height of 1 inch (254 cm) on the floor.
・ Definition / measurement method of ball internal pressure: Pressure amount obtained by measuring ball internal pressure using a pressure gauge for measuring internal pressure.

(A) Change in Ball Hardness over Time The change in ball hardness over time when the balls 1 to 5 were hit against a concrete wall with a ball hitting machine (bazooka) was examined. The results are shown in FIG. The numerical value of FIG. 3 is an average value of three balls. From FIG. 3, natural pressure balls (balls 1 and 2) using needle felt are chemical pressure balls (ball 3) using needle felt, chemical pressure balls (ball 4) using woven felt, woven It can be seen that the time-dependent deterioration (sagging) of the ball hardness during use is small and the time-dependent deterioration of the bounce during use is small compared to a natural pressure ball (ball 5) using a felt.

(C) Repulsion The relationship between the incident speed of the ball and the repulsive force when the balls 1 to 5 were hit against the concrete wall by a ball hitting machine (bazooka) was examined. In the measurement of the repulsive force, the repulsive force was calculated from the incident velocity and the reflection velocity when the ball was launched at the impact velocity set by the impact testing machine and hit the concrete wall. The results are shown in FIG. The numerical value of FIG. 4 is an average value of three balls. From FIG. 4, natural pressure balls (balls 1 and 2) using needle felt are chemical pressure balls (ball 3) using needle felt, chemical pressure balls (ball 4) using woven felt, woven It can be seen that the repulsive force of the ball is larger and the bounce of the ball is larger than the natural pressure ball (ball 5) using the felt.

(Example 2)
The bending resistance of felts of the following samples A1 to A10, B1 to B10, C1 to C4, and D1 to D4 was measured by a cantilever method. In this case, the measurement was performed by the procedures (a) to (d) described above. Further, the thickness and the bending resistance of the sample were expressed by average values of five test pieces prepared from each sample. The treatment with the fabric softener was performed by immersing the felt in a fabric softener diluted with water and then drying. The main component of the fabric softener was a polyamide-type cationic surfactant. Felt with back paste is a pre-coated rubber adhesive for adhering the felt to the core on the back of the felt. Felt without back paste means that the adhesive is applied to the back of the felt. It is not applied. In addition, a sample whose sample direction is the vertical direction is a test piece cut out with the vertical direction of the sample as the long side direction, and a sample whose sample direction is the horizontal direction is cut out with the horizontal direction of the sample as the long side direction. Test piece. The results are shown in Tables 2-5.

[sample]
A1: Needle felt A (no softener treatment, no back glue, longitudinal direction).
A2: Needle felt A (no softener treatment, no back glue, lateral direction).
A3: Needle felt A (without softener treatment, with back paste, longitudinal direction).
A4: Needle felt A (without softener treatment, with back paste, lateral direction).
A5: Needle felt A (with softener treatment / no back glue / longitudinal direction).
A6: Needle felt A (with softener treatment, no back glue, lateral direction).
A7: Needle felt A (with softener treatment / with back paste / longitudinal direction).
A8: Needle felt A (with softener treatment, back paste, lateral direction).
A9: Needle felt A (with softener treatment / with back paste / longitudinal direction).
A10: Needle felt A (with softener treatment / with back paste / lateral direction).
B1: Needle felt B (no softener treatment, no back glue, longitudinal direction).
B2: Needle felt B (no softener treatment, no back glue, lateral direction).
B3: Needle felt B (without softener treatment, with back paste, longitudinal direction).
B4: Needle felt B (without softener treatment, with back paste, lateral direction).
B5: Needle felt B (with softener treatment / no back glue / longitudinal direction).
B6: Needle felt B (with softener treatment, no back paste, lateral direction).
B7: Needle felt B (with softener treatment / with back paste / longitudinal direction).
B8: Needle felt B (with softener treatment, back paste, lateral direction).
B9: Needle felt B (with softener treatment / with back paste / longitudinal direction).
B10: Needle felt B (with softener treatment / with back paste / lateral direction).
C1: Woven felt C (no softener treatment, no back glue, longitudinal direction).
C2: Woven felt C (no softener treatment, no back glue, lateral direction).
C3: Woven felt C (without softener treatment, with back paste, longitudinal direction).
C4: Woven felt C (without softener treatment / with back paste / lateral direction).
D1: Woven felt D (no softener treatment, no back glue, longitudinal direction).
D2: Woven felt D (no softener treatment, no back glue, lateral direction).
D3: Woven felt D (without softener treatment / with back paste / longitudinal direction).
D4: Woven felt D (without softener treatment, with back paste, lateral direction).

[felt]
Needle felt A: The material is a mixture of wool and nylon, and the base is polyester.
-Needle felt B: The material is a mixture of wool and nylon, and the base is polyester.
-Woven felt C: The material is a mixture of wool and nylon, and the base is cotton.
-Woven felt D: The material is a mixture of wool and nylon, and the base is cotton.

From Tables 2 to 5, the following can be understood.
(A) In the case of the same sample, the felt treated with the fiber softener is softer than the felt not treated with the fiber softener.
(B) Since the woven felt is a woven fabric, the bending resistance differs depending on the sample direction. However, since the needle felt is a nonwoven fabric, there is no difference in bending resistance depending on the sample direction.
(C) Since the woven felt differs in the bending resistance depending on the sample direction, the bending resistance cannot be measured with the felts of C3 and D3, but wrinkles are not generated in the felt due to the lateral flexibility.
(D) No difference in the stiffness of the felt due to the difference in the thickness of the felt.

Next, the tennis ball shown in FIG. 1 was produced according to the following procedure.
(1) Felts of samples A1 to A10, B1 to B10, C1 to C4, and D1 to D4 were punched into a substantially bowl shape.
(2) The two felts described above were bonded to the outer periphery of a spherical core made of a crosslinked rubber with a rubber adhesive to produce a tennis ball.

  As a result, the felt having a bending resistance value of 15 cm or less was not wrinkled during the production of the tennis ball. On the other hand, the felt having a bending resistance value of more than 15 cm was wrinkled in the felt during the production of the tennis ball.

DESCRIPTION OF SYMBOLS 10 Core 12 Felt 14 Joint 20 Test piece 22 Slope 24 Horizontal stand 26 One end short side 28 of test piece The other end short side L of test piece L Movement distance

Claims (6)

  A tennis ball having a core and a felt covered with the core, wherein the core is formed in a pressurized atmosphere so that an internal pressure is higher than atmospheric pressure, and the felt is formed of a nonwoven fabric. A tennis ball characterized by being.   The tennis ball according to claim 1, wherein the felt is a needle felt.   The tennis ball according to claim 1, wherein the felt is made of polyester fiber.   The tennis ball according to any one of claims 1 to 3, wherein the felt has a bending resistance value of 15 cm or less as measured by a cantilever method.   The tennis ball according to claim 4, wherein the fibers forming the felt are treated with a fabric softener.   The tennis ball according to claim 5, wherein a main component of the softener is a polyamide-type cationic surfactant.

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