Billiard rubber

Abstract

A new technology for table tennis rubber is provided, which makes it easier to play spin balls and can provide a higher hitting speed. A table tennis rubber includes: a spongy sheet; and a rubber sheet that is laminated and adhered to the spongy sheet. The rubber sheet has a plurality of protrusions formed on the bonding surface of the main body of the rubber sheet and the spongy sheet. Among them, the rubber sheet has a thickness of 1.6 mm or less in the lamination direction of the spongy sheet, and ar / h is 52 or more, where ar represents the value of the area percentage (%) of the protrusion and the bonding surface, and h represents the value of the protruding height (mm).

Description

Technical Field

[0001] The present invention relates to a table tennis rubber for use when adhered to the main body of a table tennis racket. Background Art

[0002] Generally, a table tennis rubber is composed of a spongy sheet and a rubber sheet adhered to the spongy sheet. In a table tennis racket, the table tennis rubber accounts for a large part of its hitting performance.

[0003] Specifically, for example, a table tennis rubber needs to improve speed performance (the performance of providing a higher hitting speed) and spin performance (the performance of allowing a player to easily hit a spinning ball).

[0004] Therefore, in order to improve these performances, various rubbers different in constituent members, surface shape, etc. have been proposed, and so-called inverted rubbers are known as one of them.

[0005] An inverted rubber is composed of a spongy sheet and a rubber sheet laminated on the spongy sheet, and a plurality of protrusions are formed on the bonding surface of the rubber sheet and the spongy sheet. The inverted rubber obtains increased spin performance by providing a flat hitting surface with an increased ball contact area, and provides increased control performance (the performance of allowing a player to more reliably hit the ball in a desired direction) by reducing the compression stiffness of the entire rubber due to the protrusions biting into the spongy sheet, thereby providing a longer ball contact time.

[0006] On the other hand, inverted rubbers tend to cause energy loss of the ball because the protrusions biting into the spongy sheet during hitting reduces the elasticity. The energy loss causes a reduction in ball speed and is thus unpredictable.

[0007] In view of this, it has been proposed to improve the table tennis rubber also in terms of speed performance by adjusting the polymer properties as materials. For example, table tennis rubbers that enhance spin performance by mixing chemicals having good elastic properties or by mixing viscous substances in the rubber sheet have been previously proposed.

[0008] In addition, table tennis rubbers that improve speed performance by changing the shape of the protrusions in the rubber sheet have been previously proposed.

[0009] The applicant has also filed an application for a table tennis rubber including: a spongy sheet; and a rubber sheet laminated and adhered to the spongy sheet, the rubber sheet having a plurality of protrusions formed on the bonding surface of the main body of the rubber sheet and the spongy sheet (Patent Documents 1, 2).

[0010] Citation List

[0011] Patent Document

[0012] Patent Document 1: JP2013-17651

[0013] Patent Document 2: JP2021-45449 Summary of the Invention

[0014] Technical Problem

[0015] An object of the present invention is to provide a new technology for table tennis rubber that makes it easier to hit spin balls and can provide a higher hitting speed.

[0016] Solution to the Problem

[0017] From the perspective of the degree of freedom in product design, it is necessary to provide additional options for technologies that improve speed performance, spin performance, etc.

[0018] The present inventor diligently studied and found that, by means of the following configuration, improved speed performance and spin performance were achieved, thus completing the present invention: in this configuration, both the thickness of the rubber sheet and the value calculated by dividing the area percentage of the protrusions relative to the bonding surface by the height of the protrusions are within specific ranges.

[0019] The overview of the present invention is as follows.

[0020] [1] A table tennis rubber, comprising:

[0021] A spongy sheet; and

[0022] A rubber sheet that is laminated and adhered to the spongy sheet, the rubber sheet having a plurality of protrusions formed on the bonding surface of the main body of the rubber sheet with the spongy sheet,

[0023] wherein the rubber sheet has a thickness of 1.6 mm or less in the lamination direction of the spongy sheet, and

[0024] ar / h is 52 or more, where ar represents the value of the area percentage (%) of the protrusions relative to the bonding surface, and h represents the value of the height (mm) of the protrusions.

[0025] [2] The table tennis rubber according to [1], wherein ar / h is 55 or more.

[0026] [3] The table tennis rubber according to [1], wherein ar / h is 60 or more.

[0027] [4] The table tennis rubber according to any one of [1] to [3], wherein the protrusions have a height of 0.7 mm or less.

[0028] [5] The table tennis rubber according to any one of [1] to [4], wherein the rubber sheet has a thickness of 1.5 mm or less in the lamination direction of the spongy sheet.

[0029] [6] The table tennis rubber according to [5], wherein the rubber sheet has a thickness of 1.4 mm or less in the stacking direction of the spongy sheet.

[0030] [7] A table tennis racket, wherein the table tennis rubber according to any one of [1] to [6] is adhered to the main body of the racket.

[0031] Advantageous effects of the present invention

[0032] The present invention can provide a new technology for table tennis rubber, which makes it easier to hit spin balls and can provide a higher hitting speed. Description of the drawings

[0033] Figure 1 Figure 1 Is a perspective view of a table tennis racket to which the table tennis rubber of an embodiment of the present invention is adhered.

[0034] Figure 2 Figure 2 Is a cross-sectional view of the table tennis rubber of an embodiment of the present invention in the stacking direction.

[0035] Figure 3 Figure 3 Is a cross-sectional view of the rubber sheet in the table tennis rubber of an embodiment of the present invention in the stacking direction. Detailed implementation manners

[0036] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0037] Figure 1 Is a perspective view of a table tennis racket 100 according to this embodiment. As Figure 1 shown, the table tennis racket 100 includes a racket board 10 (the main body of the table tennis racket) and a table tennis rubber 20 adhered to the racket board 10.

[0038] The racket board 10 is made of wood, and the handle 14 is fixed to the portion of the racket board to be held during use by an adhesive. Although a cross-shaped racket board for double-sided hitting is shown in the drawing, the shape of the racket board in this embodiment is not limited thereto, and the racket board may be a straight-shaped racket board.

[0039] Figure 2 Is a cross-sectional view of the table tennis rubber 20 of this embodiment in the stacking direction. The table tennis rubber 20 of this embodiment is a so-called inverted rubber, and in this structure, it includes a spongy sheet 22 and a rubber sheet 24. The spongy sheet 22 and the rubber sheet 24 are stacked and adhered to each other to form an integral body. A plurality of protrusions 26 are formed at specific intervals on the bonding surface of the rubber sheet 24 with the spongy sheet 22.

[0040] ​​​​​​Each protrusion 26 has a substantially cylindrical shape with a vertex 261, which is visible as a substantially circular shape in a front view of the adhesive surface of the spongy sheet 22 (hereinafter, also simply referred to as the "front view"). The vertex 261 of the protrusion faces and contacts the spongy sheet 22, and the rubber sheet 24 is joined to the spongy sheet at the vertex 261 of the protrusion. Thus, the vertex 261 serves as the contact surface between the protrusion 26 and the spongy sheet 22. The ITTF Technical Handbook stipulates that "the pimples must be evenly spaced 60 degrees apart from each other along three sets of parallel lines". In addition, in the table tennis rubber of the present embodiment, the protrusions 26 can be evenly distributed on the adhesive surface in the same arrangement as described in the specification.

[0041] Here, the region of the rubber sheet 24 other than the protrusions 26 is referred to as the rubber sheet main body 23.

[0042] The surface 33 on the spongy sheet 22 side of the table tennis rubber 20 is adhered to the racket main body 10. The surface 35 on the rubber sheet 24 side serves as the hitting surface for the ball.

[0043] The overall shape of each protrusion 26 is not limited and can be the above-mentioned substantially cylindrical shape, or any other shape, such as a substantially frustum-conical shape, a shape combining and integrating a substantially frustum-conical vertex and a substantially cylindrical shape, and a shape combining and integrating a substantially cylindrical vertex and a substantially frustum-conical shape. The shape of the vertex of each protrusion is not limited and can be circular or polygonal, such as triangular and rectangular.

[0044] The spongy sheet 22 uses a polymer, examples of which include but are not limited to common natural rubber, polyisoprene, polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene-diene copolymer, ethylene-propylene copolymer, polychloroprene, isobutene-isoprene copolymer, styrenic thermoplastic elastomer, and olefinic thermoplastic elastomer. In particular, it is preferably produced using natural rubber, butadiene rubber, isoprene rubber, etc., and those skilled in the art can even appropriately select the chemicals to be mixed. The spongy sheet can have any properties without limitation, and, for example, the density, hardness, and foam size can be 0.1 to 0.7 g / cm 3 、10 to 70 (measured with the "ASKER Rubber Hardness Tester Type E" manufactured by Kobunshi Keiki Co., Ltd.) and 0.03 to 0.50 mm. To calculate the density of the spongy sheet 22, for example, the weight and volume are measured, and the measured weight is divided by the volume. The hardness of the spongy sheet 22 can be measured, for example, according to Standard No. JIS K6253.

[0045] Similarly, the rubber sheet 24 uses polymers, examples of which include but are not limited to common natural rubber, polyisoprene, polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene-diene copolymer, ethylene-propylene copolymer, polychloroprene, isobutene-isoprene copolymer, styrenic thermoplastic elastomer, and olefinic thermoplastic elastomer. In particular, it is preferably produced using natural rubber, butadiene rubber, isoprene rubber, etc., and those skilled in the art can even appropriately select the chemicals to be mixed. The rubber sheet 24 can have any properties without limitation. For example, the density and hardness can be 0.6 to 3.0 g / cm 3 and 20 to 65, respectively.

[0046] To calculate the density of the rubber sheet 24, for example, the weight is measured using an "Excellence XS analytical balance" manufactured by METTLER TOLEDO, and the measured weight is divided by the volume.

[0047] To obtain the hardness value of the rubber sheet 24, for example, the rubber sheet is measured using a "Micro Hardness Tester MD-1 Type A" manufactured by Kobunshi Keiki Co., Ltd. This hardness tester has a cantilever leaf spring for loading and can express the hardness as points from 0 to 100. The spring load at 0 points corresponds to 22 mN, the pressure at 100 points corresponds to 332 mN, and the indenter has a cylindrical shape with a diameter of 0.16 mm and a height of 0.5 mm. The hardness range of 20 to 65 shown as an example in this embodiment can also be expressed as a range of spring loads of, for example, 84.4 mN to 224.8 mN.

[0048] Figure 3 is a diagram showing Figure 2 the region surrounded by the dashed line m of the rubber sheet 24 of the table tennis rubber 20 in this embodiment.

[0049] Here, the thickness T (hereinafter, also simply referred to as thickness T or T) of the rubber sheet 24 on the spongy sheet 22 in the stacking direction is 1.6 mm or less. To improve the speed performance 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 based on the thickness of the rubber sheet main body 23 in the stacking direction and the height of the protrusion described later.

[0050] In this embodiment, ar / h is 52 or more, where ar represents the value of the area percentage (%) of the protrusion to the bonding surface (hereinafter, also referred to as the area percentage ar or simply ar), and h represents the value of the height (mm) of the protrusion (hereinafter, also referred to as the protrusion height h or h).

[0051] Here, the area percentage of the protrusion relative to the bonding surface refers to the ratio of the area per unit area of the portion of the protrusion 26 of the rubber sheet 24 that contacts the spongy sheet 22. The area percentage ar can be determined by calculation. For example, in the case where the apex of each protrusion is circular, it can be calculated using the following formula.

[0052] ar = (A / 2) 2 × π × 100 / ((A + B) 2 × sin(π / 3))

[0053] ar: Area percentage of the protrusion 26 with respect to the bonding surface (%)

[0054] A: Diameter (mm) of the portion of the protrusion 26 that contacts the spongy sheet (apex 261)

[0055] B: Distance (mm) between two adjacent protrusions 26

[0056] As described above, a structure with a thickness T of 1.6 mm or less and an ar / h of 52 or more provides improved speed performance and spin performance.

[0057] The value of ar / h is preferably 55 or more, more preferably 60 or more, because more improved speed performance and spin performance can be achieved.

[0058] The value of ar / h is not limited to this, but is preferably 130 or less.

[0059] The thickness T is similarly not limited to this, but is preferably 0.6 mm or more.

[0060] The height h of the protrusion is not limited to this, but is preferably 0.7 mm or less because more improved speed performance and spin performance can be achieved. The height h of the protrusion is not limited to this, but is preferably 0.45 mm or more.

[0061] The adjustment of the thickness T, area percentage ar, and height h of the protrusions in the rubber sheet 24 is not limited to a specific method, and those skilled in the art can appropriately set them, for example, by changing the mold.

[0062] Therefore, according to this embodiment, due to the structure of the rubber sheet with a thickness T of 1.6 mm or less and an ar / h of 52 or more, the table tennis rubber 20 can exhibit improved speed performance and spin performance.

[0063] Therefore, a table tennis racket configured with the table tennis rubber 20 of this embodiment allows the user to achieve increased hitting speed and higher spin on the hit, although the degree varies depending on the user.

[0064] Example

[0065] In the following, the table tennis rubber of the present embodiment will be described in more detail by way of examples; however, the present invention is not limited to these examples in any way.

[0066] Rubber sheets with different thicknesses T, area percentages ar, and protrusion heights h were prepared by molding the materials of the formulation shown in Table 1 using an 8-inch mixing roll and a vulcanizer. The production method is as follows.

[0067] First, the metal mold was heated to 152 °C, the materials were placed in the metal mold and pressurized to 10 MPa. Subsequently, pressure was applied for 471 seconds, and then the resulting product was taken out of the metal mold to obtain a rubber sheet.

[0068] [Table 1]

[0069] Polymer / Chemical Rubber Sheet Formula 1 Rubber Sheet Formula 2 Natural Rubber 100 Isoprene Rubber 100 Calcium Carbonate *1 15 15 Stearic Acid 1 1 Zinc Oxide 5 5 Sulfur *2 2.5 2.5 Catalyst 1 *3 0.4 0.4 Catalyst 2 *4 0.4 0.4 Total 124.3 124.3

[0070] (by mass)

[0071] *1 Calcium carbonate: NEOLIGHT SA300 produced by Takehara Chemical Industry Co., Ltd.

[0072] *2 Sulfur: Precipitated sulfur "Golden Flower" produced by Tsurumi Chemical Industry Co., Ltd.

[0073] *3 Catalyst 1: Nocceler DM-P produced by Ouchi Shinko Chemical Industry Co., Ltd.

[0074] *4 Catalyst 2: ACCEL D produced by Kawaguchi Chemical Industry Co., Ltd.

[0075] Each of the obtained rubber sheets was adhered to a sponge sheet derived from natural rubber having the hardness and density shown in Table 2; thus, the table tennis rubbers of the examples and comparative examples were prepared.

[0076] The speed performance and spin performance of the table tennis rubbers were evaluated.

[0077] [Table 2]

[0078] Hardness <![CDATA[Density [g / cm 3 > Sponge Sheet 36 0.41

[0079] The hardness was measured using an automatic rubber hardness tester P1 produced by Kobunshi Keiki Co., Ltd. The measurement method was based on JIS K 6253. The weight and volume were measured, and the density was calculated by "weight / volume".

[0080] Specifically, the evaluation was carried out according to the following procedure.

[0081] First, attach the rubber to a table inclined at 45 degrees using double-sided tape. Subsequently, a table tennis ball (manufacturer: Butterfly, product name: 3-star ball R40+) is hit onto the rubber using a table tennis ball machine. At that time, the ball speed and the ball rotation rate are set to 11.0 m / s and 150 rps, respectively. Use a camera (manufacturer: NAC Image Technology Co., Ltd., product name: MEMRECAM fx K4) from the moment immediately before the ball hits the rubber to the moment immediately after that (especially 10 ms before and after the impact).

[0082] Based on the obtained images, the ball speed and the ball rotation rate are calculated using analysis software (manufacturer: NAC Image Technology Co., Ltd., software: LAA Measurement) immediately before and after hitting the rubber. In addition, for the table tennis rubbers of the example and the comparative example, the "energy efficiency" of the hit is calculated based on the ball speed and the ball rotation rate determined before and after the hit. The results are shown in Table 3. Note that each of the "energy efficiency" values shown is calculated as the average of two shooting results.

[0083] Each of the determined energy efficiencies is a value indicating the hitting power, and the higher the energy efficiency value, the less energy the ball loses after the hit.

[0084] If the energy loss is small, the translational energy and the rotational energy of the ball before the hit are effectively transferred, thereby achieving a higher hitting speed. This leads to, for example, ease in high-speed travel and smashing.

[0085] If the energy loss is small, the translational energy and the rotational energy of the ball before the hit are effectively transferred, and thus enhanced rotational performance is also achieved. For example, this leads to ease in spinning, chopping, and serving the ball by rotation.

[0086] The energy efficiency is calculated according to the following formula.

[0087] [Formula 1]

[0088]

[0089] m: mass of the ball (kg)

[0090] v1: ball speed before impact (m / s)

[0091] v2: ball speed after impact (m / s)

[0092] I: moment of inertia of the ball (kg·m 2 )

[0093] ω1: ball rotation before impact (rad)

[0094] ω2: ball rotation after impact (rad)

[0095] [Table 3]

[0096]

[0097]

[0098] As can be seen from Table 3, the table tennis rubbers of these examples all have a structure with a thickness T of 1.6 mm or less and an ar / h of 52 or more, showing higher speed performance and spin performance.

[0099] List of Reference Numerals

[0100] 10: Racket board, 20: Table tennis rubber, 22: Sponge-like sheet, 24: Rubber sheet, 26: Protrusion, 100: Table tennis racket

Claims

1. A table tennis rubber, comprising: A spongy sheet; And A rubber sheet that is laminated and adhered to the spongy sheet, the rubber sheet having a plurality of protrusions formed on a bonding surface of a main body of the rubber sheet with respect to the spongy sheet, wherein the rubber sheet has a thickness of 1.6 mm or less in a lamination direction of the spongy sheet, and ar / h is 52 or more, where ar represents a value of an area percentage (%) of the protrusions with respect to the bonding surface, and h represents a value of a height (mm) of the protrusions.

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 protrusions have a height of 0.7 mm or less.

5. The table tennis rubber according to claim 1, wherein The rubber sheet has a thickness of 1.5 mm or less in the lamination direction of the spongy sheet.

6. A table tennis racket, wherein, The table tennis rubber according to any one of claims 1 to 5 is adhered to a main body of the racket.

Images