Rubber for table tennis

Abstract

[Problem] To provide a novel technique for a rubber for table tennis which makes it easier to apply spin and can further increase the speed of a hit ball. [Solution] A rubber for table tennis includes: a sponge-like sheet; and a rubber sheet which is laminated and stuck on the sponge-like sheet and in which a plurality of projections are formed on a sticking surface of a rubber sheet body to the sponge-like sheet. The thickness of the rubber sheet in a lamination direction with the sponge-like sheet is 1.6 mm or less. When a value of an area ratio occupied by the sticking surface of the projections is taken as ar and a value of the height of the projections is taken as h, ar / h is 52 or more.

Description

Table Tennis Rubber

[0001] The present invention relates to a table tennis rubber that is attached to a table tennis racket body when used.

[0002] Table tennis rubbers are generally made up of a sponge sheet and a rubber sheet that is bonded to the sponge sheet. In a table tennis racket, the table tennis rubber plays a major role in its hitting performance.

[0003] Specifically, table tennis rubbers are required to have improved speed performance (the ability to hit the ball at a faster speed) and spin performance (the ability to make it easier for the player to apply spin to the ball).To this end, multiple types of rubbers with different components and surface shapes have been proposed with the aim of improving these performances, and one such type is the so-called inverted rubber.

[0004] An inverted rubber is composed of a sponge sheet and a rubber sheet laminated on the sponge sheet, with multiple protrusions formed on the surface of the rubber sheet where the rubber sheet is attached to the sponge sheet. Inverted rubbers have a flat hitting surface, which increases the contact area with the ball and improves spin performance. In addition, by having the protrusions dig into the sponge sheet and reducing the compression rigidity of the entire rubber, the contact time with the ball is extended, thereby improving control over the ball (the ability to hit the ball more reliably in the direction the player intends).

[0005] On the other hand, inverted rubbers tend to have reduced resilience due to the protrusions digging into the sponge sheet when hitting the ball, resulting in a loss of ball energy. This energy loss is undesirable because it reduces ball speed. For this reason, table tennis rubbers have been proposed that improve speed performance by adjusting the properties of the polymers used. For example, table tennis rubbers have been proposed that improve spin performance by incorporating chemicals that provide excellent resilience or by mixing adhesive substances into the rubber sheet. Table tennis rubbers have also been proposed that improve speed performance by changing the shape of the protrusions on the rubber sheet.

[0006] The applicant has also filed a patent application for a table tennis rubber comprising a sponge-like sheet and a rubber sheet laminated and attached to the sponge-like sheet, with multiple protrusions formed on the surface of the rubber sheet body that is attached to the sponge-like sheet (Patent Documents 1 and 2).

[0007] JP 2013-17651 A JP 2021-45449 A

[0008] An object of the present invention is to provide a new technology for a table tennis rubber that makes it easier to apply spin and increase the speed of the ball.

[0009] From the viewpoint of the degree of freedom in product design, there is a demand for more options for technologies that can improve speed performance, spin performance, etc. As a result of intensive research, the inventors have found that speed performance and spin performance can be improved by setting the thickness of the rubber sheet and the value obtained by dividing the area ratio of the protrusion adhesion surface by the protrusion height within a predetermined range, and have completed the present invention.

[0010] The gist of the present invention is as follows. [1] A table tennis rubber comprising: a sponge-like sheet; and a rubber sheet laminated and attached to the sponge-like sheet, the rubber sheet having a plurality of protrusions formed on the surface of the rubber sheet body that is attached to the sponge-like sheet, wherein the thickness of the rubber sheet in the direction of lamination with the sponge-like sheet is 1.6 mm or less, and where ar is the area ratio (%) of the protrusions to the attached surface and h is the height (mm) of the protrusions, ar / h is 52 or more. [2] The table tennis rubber according to [1], in which ar / h is 55 or more. [3] The table tennis rubber according to [1], in which ar / h is 60 or more. [4] The table tennis rubber according to any one of [1] to [3], in which the height of the protrusions is 0.7 mm or less. [5] The table tennis rubber according to any one of [1] to [4], in which the thickness of the rubber sheet in the direction of lamination with the sponge-like sheet is 1.5 mm or less. [6] The table tennis rubber according to [5], wherein the thickness of the rubber sheet in the direction of lamination with the sponge-like sheet is 1.4 mm or less. [7] A table tennis racket having the table tennis rubber according to any one of [1] to [6] attached to the racket body.

[0011] According to the present invention, a new technology can be provided for a table tennis rubber that makes it easier to apply spin and increase the speed of the ball.

[0012] The present invention relates to a table tennis racket having a table tennis rubber according to an embodiment of the present invention, a table tennis racket having a table tennis rubber according to an embodiment of the present invention, a table tennis racket having a table tennis rubber according to an embodiment of the present invention, a table tennis rubber according to an embodiment of the present invention, and a table tennis racket having a table tennis rubber according to an embodiment of the present invention.

[0013] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view of a table tennis racket 100 according to this embodiment. As shown in FIG. 1, the table tennis racket 100 is configured by attaching a table tennis rubber 20 to a blade 10 (table tennis racket body). The blade 10 is made of wood, and a grip 14 is fixed with adhesive to the portion of the blade that is held when in use. Note that the shape of the blade in this embodiment is a shakehand type for hitting with both hands, but is not limited to this and may also be a penholder type.

[0014] FIG. 2 is a cross-sectional view of the layering direction of the table tennis rubber 20 of this embodiment. The table tennis rubber 20 of this embodiment is a so-called backside soft rubber and includes a sponge-like sheet 22 and a rubber sheet 24. The sponge-like sheet 22 and the rubber sheet 24 are laminated and bonded together to form an integrated unit. Furthermore, a plurality of protrusions 26 are formed on the surface of the rubber sheet 24 that is bonded to the sponge-like sheet 22, spaced at predetermined intervals. The protrusions 26 have a generally cylindrical shape, with a generally circular apex 261 visible in a front view of the surface that is bonded to the sponge-like sheet 22 (hereinafter simply referred to as a front view). The apex 261 of each protrusion faces and contacts the sponge-like sheet 22, and the rubber sheet 24 is bonded to the sponge-like sheet 22 at the apex 261 of each protrusion. In other words, the apex 261 is the contact surface of the protrusions 26 with the sponge-like sheet 22. The ITTF Technical Leaflet stipulates that "the grains must be evenly distributed along three straight lines intersecting at 60-degree angles." In the table tennis rubber of this embodiment, the protrusions 26 can be evenly distributed on the adhesive surface in the same arrangement as described above. In this specification, the area of ​​the rubber sheet 24 excluding the protrusions 26 is referred to as the rubber sheet main body 23. The table tennis rubber 20 is bonded to the racket body 10 at the surface 33 facing the sponge sheet 22. The surface 35 facing the rubber sheet 24 is used as the hitting surface for the ball. The overall shape of the protrusions 26 may be, in addition to the generally cylindrical shape described above, generally truncated cone, a shape in which a generally cylindrical top is integrated with a generally cylindrical truncated cone, or a shape in which a generally cylindrical top is integrated with a generally cylindrical truncated cone, and is not particularly limited. The tops of the protrusions may also be circular or polygonal, such as triangular or rectangular, and are not particularly limited.

[0015] The polymer used for the sponge-like sheet 22 is not particularly limited, and examples thereof include ordinary natural rubber, as well as polyisoprene, polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene-diene copolymer, ethylene-propylene copolymer, polychloroprene, isobutylene-isoprene copolymer, styrene-based thermoplastic elastomer, and olefin-based thermoplastic elastomer. In particular, it is preferable to manufacture the sponge-like sheet using natural rubber, butadiene rubber, isoprene rubber, etc., and the chemicals to be blended can be appropriately selected by those skilled in the art. The properties of the sponge-like sheet are not particularly limited, but examples thereof include a density of 0.1 to 0.7 g / cm. ３ The sponge-like sheet 22 may have a hardness of 10 to 70 (measured using an "Asker Rubber Hardness Tester Type E" manufactured by Kobunshi Keiki Co., Ltd.), and a cell diameter of 0.03 to 0.50 mm. The density of the sponge-like sheet 22 may be calculated, for example, by measuring the weight and volume and dividing the weight by the volume. The hardness of the sponge-like sheet 22 may be measured, for example, in accordance with standard number JIS K 6253.

[0016] Similarly, the polymer used for the rubber sheet 24 is not particularly limited, and examples include ordinary natural rubber, as well as polyisoprene, polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene-diene copolymer, ethylene-propylene copolymer, polychloroprene, isobutylene-isoprene copolymer, styrene-based thermoplastic elastomer, and olefin-based thermoplastic elastomer. It is particularly preferable to manufacture the rubber sheet using natural rubber, butadiene rubber, isoprene rubber, etc., and the chemicals to be blended can be appropriately selected by those skilled in the art. The properties of the rubber sheet 24 are also not particularly limited, and examples include a density of 0.6 to 3.0 g / cm. ３The hardness of the rubber sheet 24 can be set to 20 to 65. The density of the rubber sheet 24 can be calculated by measuring the weight using, for example, an Excellence XS analytical balance manufactured by Mettler Toledo and dividing the weight by the volume. The hardness of the rubber sheet 24 can be obtained by measuring the rubber sheet using, for example, a Micro Rubber Hardness Tester MD-1 Type A manufactured by Kobunshi Keiki Co., Ltd. This hardness tester uses a cantilever leaf spring to apply load and can indicate a range from 0 to 100 points. The spring load is 22 mN at 0 point and 332 mN at 100 point, and the indenter dimensions are cylindrical with a diameter of 0.16 mm and a height of 0.5 mm. The hardness range of 20 to 65 exemplified in this embodiment can also be expressed as, for example, a spring load of 84.4 mN to 224.8 mN.

[0017] FIG. 3 is a diagram showing the area surrounded by the dashed line m in FIG. 2 of the rubber sheet 24 of the table tennis rubber 20 of this embodiment. In this embodiment, the thickness T of the rubber sheet 24 in the stacking direction with the sponge sheet 22 (hereinafter simply referred to as thickness T or T) is 1.6 mm or less. From the viewpoint of improving speed and spin performance, the thickness T is preferably 1.5 mm or less, more preferably 1.4 mm or less. The thickness T can also be calculated from the thickness of the rubber sheet body 23 in the stacking direction and the height of the protrusions, which will be described later. In this embodiment, when the area ratio (%) of the protrusions to the adhesive surface is ar (hereinafter simply referred to as area ratio ar or ar), and the height (mm) of the protrusions is h (hereinafter simply referred to as protrusion height h or h), ar / h is 52 or greater.

[0018] In this specification, the area ratio of the protrusions to the adhesive surface means the ratio of the area of ​​the contact portion of the protrusions 26 of the rubber sheet 24 with the sponge-like sheet 22 to the unit area. The area ratio ar can be obtained by calculation. For example, if the tops of the protrusions are circular, it can be calculated using the following formula: ar = (A / 2) ２ ×π×100 / ((A+B) ２× sin(π / 3)) ar: area ratio (%) of the protrusions 26 to the adhesion surface A: diameter (mm) of the contact portion (top 261) of the protrusions 26 with the sponge-like sheet B: distance (mm) between two adjacent protrusions 26

[0019] By setting the thickness T to 1.6 mm or less and the ar / h to 52 or more in this way, it is possible to improve the speed performance and spin performance.

[0020] The value of ar / h is preferably 55 or greater, more preferably 60 or greater, since this can further improve speed performance and spin performance. The value of ar / h is not particularly limited, but is preferably 130 or less. The thickness T is also not particularly limited, but is preferably 0.6 mm or greater. The height h of the protrusions is not particularly limited, but is preferably 0.7 mm or less, since this can further improve speed performance and spin performance. The height h of the protrusions is also not particularly limited, but is preferably 0.45 mm or greater.

[0021] The method for adjusting the thickness T, area ratio ar, and height h of the protrusions in the rubber sheet 24 is not particularly limited and can be set appropriately by a person skilled in the art, but can be done, for example, by changing the mold.

[0022] As described above, according to this embodiment, by setting the thickness T of the rubber sheet to 1.6 mm or less and ar / h to 52 or more, it is possible to improve the speed performance and spin performance of the table tennis rubber 20. As a result, by constructing a table tennis racket using the table tennis rubber 20 of this embodiment, it is possible to increase the speed of the ball and hit the ball with more spin, although this will vary depending on the individual user.

[0023] The table tennis rubber of this embodiment will be described in more detail below using examples, but the present invention is not limited to these examples in any way.

[0024] Using the materials listed in Table 1, rubber sheets with different thicknesses (T), area ratios (ar), and protrusion heights (h) were produced by molding using an 8-inch mixing roll and a vulcanization press. The production process was as follows: First, the mold was heated to 152°C, the materials were placed inside the mold, and a pressure of 10 MPa was applied. After applying pressure for 471 seconds, the rubber sheet was removed from the mold and the rubber sheet was obtained.

[0025]

[0026] Table tennis rubbers of the Examples and Comparative Examples were manufactured by laminating a sponge-like sheet made from natural rubber having the hardness and density shown in Table 2 to the obtained rubber sheet. The table tennis rubbers were used to evaluate speed performance and spin performance.

[0027]

[0028] Specifically, the evaluation was performed according to the following procedure. First, a rubber was attached to a table tilted at a 45-degree angle using double-sided tape. Next, a table tennis ball (manufacturer: Butterfly, product name: Three Star Ball R40+) was launched toward the rubber using a table tennis machine. The ball speed was set to 11.0 m / s and the spin rate to 150 rps. The ball was then photographed with a camera (manufacturer: NAC Image Technology Co., Ltd., product name: MEMRECAM fx K4) from just before to just after impact with the rubber (specifically, 10 ms before and after impact). The captured video was analyzed using analysis software (manufacturer: NAC Image Technology Co., Ltd., software: LAA Measurement) to calculate the ball speed and spin rate just before and just after impact with the rubber. Furthermore, the "energy efficiency" of the ball hit with the table tennis rubbers of the Examples and Comparative Examples was calculated from the obtained ball speed and spin rate just before and just after impact. The results are shown in Table 3. The "energy efficiency" was calculated from two photographs taken, and the average is shown.

[0029] The measured energy efficiency is a value that represents the power of the ball, and the higher this value, the less energy loss the ball has before and after hitting. When energy loss is low, the speed energy and rotation energy of the ball before hitting can be transferred efficiently, resulting in a faster ball speed. As a result, for example, it becomes easier to hit fast drives and smashes. Furthermore, when energy loss is low, the speed energy and rotation energy of the ball before hitting can be transferred efficiently, resulting in improved spin performance. As a result, for example, it becomes easier to hit drives, cuts, and serves with a lot of spin. Energy efficiency is calculated using the following formula.

[0030]

[0031] From Table 3, it can be seen that the table tennis rubbers of the examples having a thickness T of 1.6 mm or less and an ar / h of 52 or more exhibited higher speed performance and spin performance.

[0032] 10: Blade, 20: Table tennis rubber, 22: Sponge sheet, 24: Rubber sheet, 26: Protrusion, 100: Table tennis racket

Claims

1. A table tennis rubber comprising: a sponge-like sheet; and a rubber sheet laminated and attached to the sponge-like sheet, the rubber sheet having a plurality of protrusions formed on the adhesive surface of the rubber sheet body where the rubber sheet is attached to the sponge-like sheet, the thickness of the rubber sheet in the lamination direction with the sponge-like sheet being 1.6 mm or less, and where ar is the area ratio (%) of the adhesive surface occupied by the protrusions and h is the height (mm) of the protrusions, ar / h is 52 or more.

2. The table tennis rubber according to claim 1, wherein ar / h is 55 or more.

3. The table tennis rubber according to claim 1, wherein ar / h is 60 or more.

4. The table tennis rubber according to claim 1, wherein the height of the protrusions is 0.7 mm or less.

5. The table tennis rubber according to claim 1, wherein the thickness of the rubber sheet in the lamination direction with the sponge-like sheet is 1.5 mm or less.

6. A table tennis racket having the table tennis rubber according to any one of claims 1 to 5 attached to the racket body.

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