TWI833944B - Net string for racket - Google Patents

Abstract

The net string for rackets of the present invention has good strength and can improve the rebound of the ball. A racket string (10) is constructed including a core string (11) and a plurality of side strings (12) provided on the outer peripheral side of the core string and extending in a predetermined direction. The core wire has elastic fibers (18) in a region including the central axis position (C). The elastic fibers are arranged to extend parallel to the extending direction of the mesh wires. In this way, the elastic fibers are arranged without being twisted, and the elastic fibers are arranged in a straight line with the mesh wires stretched, so that the elastic force in the expansion and contraction direction can be well exerted, and the elastic force can be used to improve the rebound when playing ball.

Description

Net string for racket

The present invention relates to racket strings used in tennis, badminton, squash, etc.

In a tennis or badminton racket, a mesh-shaped string is provided on the surface of the racket. Furthermore, as a net string for a racket, a net string in which a monofilament serving as a thin side string is wound around an outer side of a monofilament or a multifilament serving as a core string is widely used.

As the above-mentioned mesh cord, as disclosed in Patent Document 1 or Patent Document 2, a structure of a member in which the core cord has elasticity is proposed. Specifically, the network cable in Patent Document 1 has a hollow portion formed in a core wire (core material), and an elastic body made of polyurethane rubber or silicone is provided in the hollow portion. The network cable in Patent Document 2 is composed of multifilaments in which core wires (cores) are twisted and combined, and 2 to 3 thin linear rubbers are mixed with the multifilaments. [Prior technical literature] [Patent Document]

Patent document 1: Japanese Utility Model Publication No. 3-83568 Patent document 2: Japanese Utility Model Publication No. 6-48719

[Problem to be solved by the invention]

The mesh cord in Patent Document 1 has a hollow portion filled with an elastic body. Therefore, compared with a solid structure that does not provide a hollow portion, it becomes difficult for the elastic body, which can exert the same degree of resilience as a badminton ball, to expand and contract in the extending direction of the net string, and it becomes more difficult to improve the resilience than a solid structure.

Furthermore, in the mesh wire of Patent Document 2, thin linear rubber is twisted with other threads, so that the thin linear rubber is formed into a rough spiral shape. Therefore, even when the net cord is pulled in the extending direction due to stretching or playing ball, the spiral shape of the thin linear rubber still roughly maintains the net cord to be slightly deformed in the extending direction. As a result, it becomes difficult for the thin linear rubber to exert elastic force in the expansion and contraction direction, making it difficult to improve the resilience.

Here, when the string is composed of only the thin linear rubber of Patent Document 2, there is a problem that the tension placed on the racket cannot be loaded.

In view of the above circumstances, the present invention aims to provide a racket string that can improve the resiliency of the ball even if elastic fiber is used. [Means used to solve problems]

The racket string of the present invention is a racket string including a core string and a plurality of side strings provided on the outer periphery of the core string and extending in a predetermined direction. The characteristic is that the core string is in a region including the position of the central axis. Elastic fibers are provided, and the elastic fibers extend parallel to the above-mentioned extending direction.

With this configuration, the elastic fibers arranged at the central axis of the core wire extend parallel to the extension direction of the mesh wire, that is, the elastic fibers are arranged without being twisted. Thereby, the elastic fiber is arranged linearly in the state of stretching the net cord, and the elastic force in the expansion and contraction direction can be well exerted, and the elastic force can be used to improve the rebound when playing ball. In addition, elastic fibers are arranged in the core thread, and compared with the conventional structure in which the hollow portion of the core thread is filled with elastomer, the core thread including the elastic fiber easily expands and contracts in the extending direction, and the elastic force of the elastic fiber can be effectively exerted to improve the resilience. In addition, the elastic fiber is provided in a region including the central axis position that is part of the core yarn, so good strength and cutting durability can be ensured in parts other than the elastic fiber.

Furthermore, in the racket string of the present invention, the core string may further include a core side portion wound around the outer periphery of the elastic fiber. With this configuration, the core wire is a single filament and the elastic fiber is not twisted and can be arranged at the central axis position of the core wire. This allows the elasticity of the elastic fiber to be exerted while maintaining good core strength.

Furthermore, the racket string of the present invention may be provided with a plurality of elastic fibers described above. With this structure, changing the number of elastic fibers can not only adjust the elastic force that the entire network cable can exert, but also increase the strength in the extending direction of the core cable.

Furthermore, in the racket string of the present invention, the proportion of the cross-sectional area of the elastic fiber in the entire cross-section of the racket string can be set to 10% or more and 40% or less. According to this numerical range, it is possible to satisfactorily achieve both the improvement of cutting durability and the improvement of resilience, which are inverse relationships. [Effects of the invention]

According to the present invention, the elastic fibers provided on the core string extend parallel to the extending direction of the net string, so it has good strength and improves the rebound of the ball.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the net string of the present invention only needs to be stretched on the frame of the racket to form the racket surface, and can be applied to various rackets such as badminton, soft tennis, tennis, and squash.

FIG. 1 is a schematic perspective view showing a partial cross-section of the network cable according to the embodiment, and FIG. 2 is a cross-sectional view of the network cable according to the embodiment. As shown in FIGS. 1 and 2 , the network cable 10 is provided with: a core wire 11 located in the center and forming a substantially circular cross-section on the periphery, and a plurality of side wires 12 a and 12 b spirally wound around the outer periphery of the core wire 11 , forming a structure that moves in a predetermined direction. extend out. The shape of the network cable 10 is circular in cross section. The core wire 11 and the side wires 12a and 12b are adhered together. The side wires 12a and 12b are grouped around the core wire 11. The side wires 12a and 12b are composed of a plurality of side wires as one group, and eight groups in the S winding direction and eight groups in the Z winding direction are arranged to cover the core wire 11.

After the inner coating 13a (not shown in FIG. 1 ) is formed around the side wires 12a and 12b of the core wire 11, the surface coating 13b is formed. All thermoplastic resins can be used for each coating layer 13a and 13b, and polyamide resin and polyurethane resin are particularly preferred.

The core wire 11 has a two-layer structure including a core wire center portion 15 at the central axis position C, and core wire side portions 16 provided on the outer side of the core wire center portion 15 . The core wire side portion 16 is formed by laminating a plurality of layers of spirally wound multifilaments in the radial direction of the core wire 11 on the outer peripheral side of the core wire center portion 15 .

Here, the material of the core side portion 16 of the core wire 11 and the side wires 12a and 12b is not limited, but for example, polyamide, polyester, or the like can be used. In addition, polyester (polybutylene terephthalate, polyethylene terephthalate, etc.), polyolefin, polyphenylene sulfide, and polyether may also be used for the core wire side portion 16 and the side wires 12a and 12b. Ether ketone etc.

The core core portion 15 is composed of a plurality of elastic fibers 18 . In this embodiment, six elastic fibers 18 are arranged to be bundled around the periphery of one elastic fiber 18 serving as the center. Each elastic fiber 18 extends parallel to the extending direction of the mesh wire 10 so as to be arranged without twisting each other. Therefore, in the area where the net cord 10 is stretched linearly on the racket (not shown), each elastic fiber 18 is also disposed substantially linearly parallel to the direction in which the net cord 10 is stretched.

Each elastic fiber 18 is a monofilament made of a synthetic fiber that has lower elasticity than rubber (for example, 10 MPa or less) and can expand and contract greatly with a small force. Specific examples include polyurethane fibers, polyetherester copolymer fibers, and polytrimethylene terephthalate fibers, which are formed by stretching during their production.

The proportion of the cross-sectional area (total) of all the elastic fibers 18 in the entire cross-section of the mesh cord 10 (hereinafter referred to as the "mixing ratio") is preferably set to 10% or more and 40% or less. The reason for this will be described later.

In this embodiment, the elastic fibers 18 can be arranged in a straight line parallel to the extension direction of the mesh cord 10. Therefore, when the mesh cord 10 expands and contracts, the elastic fibers 18 also elastically extend in the extending direction with approximately the same length as the expansion and contraction. shrink. Thereby, when the net string 10 is elongated due to the impact of the badminton (playing the ball), the elastic fiber 18 can exert elastic force in the direction of recovery of the elongation. In contrast, in the conventional structure in which linear rubber is twisted into a spiral shape using core wires, when the mesh wire 10 is extended, the linear rubber shrinks in the radial direction of the spiral, making elastic expansion in the extending direction difficult. Therefore, it becomes difficult for the conventional structure to exert force in the direction of restoring elongation. Therefore, compared with the conventional structure, the net string 10 of this embodiment can better act on the shuttlecock when the shuttlecock is struck by the elastic force of the elastic fiber 18, thereby improving the rebound of the shuttlecock.

Furthermore, although the conventional structure in which the hollow portion of the core wire is filled with elastomer can exert a higher elastic force than the elastomer portion surrounding the core wire, the elasticity is not different. In this regard, since the net string 10 of this embodiment uses elastic fibers 18 formed by stretching and having large elasticity, the elastic fibers 18 can easily exert the force of recovery after elongation when a shuttlecock is struck, thereby improving the resilience.

The elastic fiber 18 itself has lower strength and durability than the core side portion 16 and the side wires 12a and 12b. However, since it is partially disposed at the central axis position C of the core wire 11, the core wire side portion 16 and the side wires 12a and 12b are configured to ensure sufficient strength and durability. In addition, by winding the core side portion 16 in a spiral shape, the strength of the core side portion 16 can be ensured and stretchability can be exerted, and the elastic force of the elastic fiber 18 can be well exerted.

Next, an experiment performed to evaluate the resilience and durability of the network cable related to the above embodiment will be described. In the experiment, the mesh cord 10 of the above-mentioned embodiment was used as an example, and the mesh cord 10 of 5 types (refer to the graph in FIG. 3 ) in which the blending ratio of the elastic fiber 18 was changed in the range of about 15 to 28% was produced.

In addition, in the experiment, a comparative example was produced in which the elastic fiber 18 was omitted from the structure of the Example. In addition, in the mesh cord of the comparative example, the core cord 11 including the core cord center portion 15 is formed entirely into a multifilament yarn using the multifilament yarn that forms the core cord side portions 16 of the embodiment. Other conditions are the same as those in the Examples and Comparative Examples. Along with the Examples and Comparative Examples, the net string is stretched on the badminton racket with a tension of 23 pounds.

An experiment was conducted to evaluate the resilience of the network cables of Examples and Comparative Examples. Furthermore, in order to evaluate the durability of the network cables of Examples and Comparative Examples, an experiment was conducted to measure the cutting strength of the network cables. The measurement results are shown in Figure 3. FIG. 3 is a graph showing the relationship between the mixing ratio of the network cable, the cutting strength and the resilience.

Using a racket with the strings of Examples and Comparative Examples stretched, the rebound (bounce) of badminton felt by the players during impact was evaluated. This evaluation is set based on the rebound properties of the comparative example as the "baseline", and the state in which the player clearly feels the difference in rebound properties relative to the "baseline" is defined as "bounce". Also, let the evaluation between "standard" and "bounce" be "slightly bounced", and let the difference between "bounce" and "bounce" added to the evaluation of "bounce" be "larger bounce". , assuming that the difference plus "larger bounce" is evaluated as "extreme bounce". The evaluation is divided into several stages as described above, and the point collection results of the players in the case where the 5-type network cable 10 is installed in the embodiment are plotted with "□" (blank corners) in the graph of Figure 3 .

The graph in FIG. 3 is a curve calculated by the nonlinear least squares method and drawn as a dotted line from the plotted point sampling results of the comparative examples and the examples. On this curve, the coordination rate at the time of evaluation is less than 10% as "bounce". Therefore, when the above-mentioned blending ratio of the elastic fiber 18 is 10% or more, good resilience can be exerted.

In an experiment to measure the cutting strength of the network cable 10, the cutting strength of each network cable 10 of the Example was measured using AUTO-GRAPH AGS-J (manufactured by Shimadzu Corporation). The measurement conditions are based on JIS L1013: 2010 edition "Test Methods for Chemical Fiber Threads". Samples are taken at an interval of 250mm, the tensile speed is 300mm/min, and the number of tests is 3 times for each network cable 10. Furthermore, a straight line calculated by the least square method from each measurement result which is the average value of three tests is shown as a thick solid line in the graph of FIG. 3 . Here, the lower limit of the actual cutting force that a badminton volleyball string can withstand is 200N. In the graph of FIG. 3 , when the cutting strength is less than 200N on a straight line calculated from the measurement results of the cutting strength, the mixing ratio is 40%. Therefore, when the above-mentioned mixing ratio is 40% or less, good cutting durability can be exhibited.

As explained above, when the blending ratio of the elastic fiber 18 is in the range R (see FIG. 3 ) of 10% to 40%, the mesh cord 10 of the embodiment can exhibit both resilience and cutting durability well.

In addition, for the mesh yarns of Examples and Comparative Examples, the elastic modulus of elasticity should be measured to evaluate elasticity. The measurement of the relevant elongation elastic modulus is to extend the mesh wire 10 to 15% longer than the original length and maintain it in the extended state for 1 minute. After that, the recovery rate after 3 minutes of returning to the original position is measured, and the complete recovery is regarded as 100%. The larger the elongation elasticity (recovery rate) value, the stronger the bending recovery force becomes, allowing the struck shuttlecock to fly farther. The mesh cord 10 of the Example has a blend ratio of 18.5% and has an elongation elasticity of 87.5%, while the mesh cord of the Comparative Example has an elongation elasticity of 83.4%. Therefore, the measurement result of good bounce of the shuttlecock obtained by comparing the embodiment with the comparative example becomes the basis for the evaluation of the rebound of the player's body sensation.

In addition, the present invention is not limited to the above-described embodiment, and can be implemented with various modifications. In the above-mentioned embodiment, the size, shape, direction, etc. shown in the accompanying drawings are not limited thereto, and may be appropriately changed within the scope of exerting the effects of the present invention. Others can be appropriately modified and implemented within the scope that does not deviate from the purpose of the present invention.

For example, the number of elastic fibers 18 may be one (odd number) or a plurality of elastic fibers 18 increased or decreased from seven, etc., and may be appropriately changed. At this time, the thickness of the elastic fiber 18 can be adjusted to exhibit good resilience. In the present invention, as long as the elastic fibers 18 extend parallel to the extending direction of the mesh wire 10, the number and thickness of the elastic fibers 18 can be selected.

In addition, although the center axis position C of the mesh cord 10 is shown as being centered on the core core portion 15 formed of the elastic fiber 18, the invention is not limited to this, and these positions may be offset.

In addition, the thickness of the core wire side portion 16 and the side wires 12a and 12b, the winding form, and the lamination form can be changed in various ways as long as the network cable 10 can be formed. [Industrial availability]

The racket string of the present invention has the effect of obtaining good strength and improving the rebound of the ball.

This application is based on Japanese Special Application No. 2019-078689, which was filed on April 17, 2019. All its contents are included.

10: Net string for racket 11:Core wire 12a: Lateral line 13b: Surface coating 13a: Internal coating 15: Core wire center part 16: Core wire side 18: Elastic fiber C: Central axis position

[Fig. 1] is a schematic perspective view showing a partially cross-sectional view of the network cables related to the embodiment. [Fig. 2] is a cross-sectional view of a network cable according to the embodiment. [Fig. 3] is a graph showing the relationship between the mixing ratio of the network cable, the cutting strength, and the resilience.

10: Net string for racket

11:Core wire

12a: Lateral line

12b: Side line

13b: Surface coating

15: Core wire center part

16: Core wire side

18: Elastic fiber

C: Central axis position

Claims (4)

A net string for rackets, which is provided with: a core string, and a plurality of side strings arranged on the peripheral side of the core string and extending in a predetermined direction, characterized in that: the above-mentioned core string is provided with polyurethane fiber and polyether ester copolymer in the area including the central axis position. The elastic fiber is composed of at least one of polypropylene fiber and polytrimethylene terephthalate fiber, and the elastic fiber extends parallel to the above-mentioned extending direction. The racket string according to claim 1, wherein the core string further includes core side portions spirally wound around the outer periphery of the elastic fiber; wherein the side strings are composed of a plurality of side strings as one group. Eight groups in the S winding direction and eight groups in the Z winding direction cover the aforementioned core wires. The racket string according to claim 1 or claim 2, wherein a plurality of elastic fibers are provided. The racket string according to Claim 1 or 2, wherein the proportion of the cross-sectional area of the elastic fiber in the entire cross-section of the racket string is set to 10% or more and 40% or less.

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