WO2020213599A1

WO2020213599A1 - Racket string

Info

Publication number: WO2020213599A1
Application number: PCT/JP2020/016423
Authority: WO
Inventors: 佳佑小澤; 慎一郎千葉
Original assignee: ヨネックス株式会社
Priority date: 2019-04-17
Filing date: 2020-04-14
Publication date: 2020-10-22
Also published as: JP2020174854A; TW202103756A; JP7280096B2; CN113710333A

Abstract

The objective of the present invention is to enable resilience when hitting a ball to be improved while providing satisfactory strength. A racket string (10) extending in a prescribed direction is configured to be provided with a core thread (11), and a plurality of side threads (12) provided on the outer circumferential side of the core thread. The core thread is provided with elastic fibers (18) in a region including a central axis position (C). The elastic fibers are provided in such a way as to extend parallel to the direction in which the string extends. The elastic fibers are therefore provided without being twisted, the elastic fibers are arranged in a straight line in a state in which the string has been stretched, and can thus satisfactorily exhibit an elastic force in the expanding and contracting direction, and the resilience when hitting a ball can be improved by means of said elastic force.

Description

Racket string

The present invention relates to a racket string used for tennis, badminton, squash, etc.

Tennis and badminton rackets have strings stretched over the face in a mesh pattern. As a string for a racket, a string in which a monofilament serving as a core yarn or a monofilament serving as a thin side yarn is wound around the outside of a multifilament is widely used.

As such a string, as disclosed in Patent Document 1 and Patent Document 2, a configuration having a member in which the core yarn has elasticity has been proposed. Specifically, the string of Patent Document 1 is configured by forming a hollow portion in a core thread (core material) and providing an elastic body made of urethane rubber or silicon rubber in the hollow portion. The string of Patent Document 2 is composed of a multifilament in which core threads (core bodies) are twisted and bonded, and the multifilament is composed of a mixture of two or three fine thread-like rubbers.

Jikkenhei 3-83568 Gazette Jikkenhei 6-48719

The string of Patent Document 1 has a configuration in which an elastic body is filled inside the hollow portion. For this reason, the resilience to the shuttle can be exhibited to the same extent as compared with the solid configuration without the hollow portion, but the elastic body is less likely to expand and contract in the extending direction of the string, and the elastic body repels the solid configuration. It becomes difficult to improve sex.

Further, in the string of Patent Document 2, since the fine thread-like rubber is twisted with other filaments, the fine thread-like rubber is formed into a substantially spiral shape. Therefore, even if the string is pulled in the extending direction by stretching and hitting a ball, the spiral shape of the fine thread-like rubber is slightly deformed in the extending direction of the string, but is generally maintained. As a result, it becomes difficult for the fine thread-like rubber to exert an elastic force in the expansion / contraction direction, which also makes it difficult to improve the resilience.

Here, when the string is composed only of the fine thread-like rubber of Patent Document 2, there is a problem that it cannot withstand the tension stretched on the racket.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a racket string capable of improving the resilience of a hit ball while maintaining good strength even when elastic fibers are used.

The racket string of the present invention is a racket string that includes a core thread and a plurality of side threads provided on the outer peripheral side of the core thread and extends in a predetermined direction. The core thread has a central axis position. The region including the elastic fiber is provided, and the elastic fiber extends parallel to the extending direction.

According to this configuration, the elastic fibers provided at the central axis position of the core yarn extend parallel to the extending direction of the string, that is, the elastic fibers are provided without twisting. As a result, the elastic fibers are linearly arranged in the state where the string is stretched, and the elastic force in the expansion / contraction direction can be satisfactorily exerted, and the elastic force can improve the resilience at the time of hitting the ball. Further, by providing the elastic fiber in the core thread, the core thread containing the elastic fiber can be easily expanded and contracted in the extending direction as compared with the conventional structure in which the hollow portion of the core thread is filled with the elastic body, and the elastic force of the elastic fiber can be increased. It can be exerted well and contribute to the improvement of resilience. Further, since the elastic fiber is provided in the region including the central axis position which is a part of the core yarn, the strength and cutting durability can be satisfactorily ensured in the portion other than the elastic fiber.

Further, in the racket string of the present invention, it is preferable that the core yarn further includes a core yarn side portion wound around the outer peripheral side of the elastic fiber. According to this configuration, the core yarn can be provided at the central axis position of the core yarn without twisting the elastic fibers while making the core yarn a multifilament. As a result, it is possible to maintain good strength as a core yarn while exerting the elastic force of the elastic fiber.

Further, in the racket string of the present invention, it is preferable that a plurality of the elastic fibers are provided. According to this configuration, the elastic force that can be exerted as the string as a whole can be adjusted by changing the number of elastic fibers, and it is possible to contribute to the improvement of the strength of the core yarn in the extending direction.

Further, in the racket string of the present invention, the ratio of the cross-sectional area of the elastic fiber to the cross section of the entire racket string may 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 contradictory relationships.

According to the present invention, since the elastic fiber provided in the core yarn extends in parallel with the extending direction of the string, it is possible to improve the resilience of the hit ball while improving the strength.

It is the schematic perspective view which made the string which concerns on embodiment partially cross-sectional view. It is sectional drawing of the string which concerns on embodiment. It is a graph which shows the relationship between the compounding ratio of a string, cutting strength and resilience.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The string of the present invention can be applied to various rackets such as badminton, soft tennis, tennis, squash, etc. as long as it is stretched over the frame of the racket to form a face.

FIG. 1 is a schematic perspective view of a part of the string according to the embodiment, and FIG. 2 is a cross-sectional view of the string according to the embodiment. As shown in FIGS. 1 and 2, the string 10 includes a core thread 11 which is located at the center and forms a substantially circular outer circumference in a cross section, and a plurality of strings wound spirally around the outer peripheral side of the core thread 11. The

side threads

12a and 12b are provided and are configured to extend in a predetermined direction. The outer shape of the string 10 is formed in a circular shape in a cross section. The core thread 11 and the

side threads

12a and 12b are integrally bonded. The

side threads

12a and 12b are formed by braiding around the core thread 11. The

side yarns

12a and 12b are formed into one set by a plurality of side yarns, and eight sets in the S winding direction and eight sets in the Z winding direction are braided so as to cover the core yarn 11.

The surface layer coating layer 13b is formed after the internal coating layer 13a (not shown in FIG. 1) is formed around the

side threads

12a and 12b wound around the core thread 11. A general thermoplastic resin can be used for each of the

coating layers

13a and 13b, and it is particularly desirable to use a polyamide resin or a polyurethane resin.

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

Here, the materials of the core yarn side portion 16 of the core yarn 11 and the

side yarns

12a and 12b are not particularly limited, but for example, polyamide, polyester and the like are used. In addition, it does not prevent the use of polyester (polybutylene terephthalate, polyethylene terephthalate, etc.), polyolefin, polyphenylene sulfide, polyetheretherketone, etc. in the core yarn side portion 16 and the

side yarns

12a, 12b.

The core thread center portion 15 is composed of a plurality of elastic fibers 18. In the present embodiment, the six elastic fibers 18 are arranged so as to converge around the outer periphery of one elastic fiber 18 which is the center. Each elastic fiber 18 extends parallel to the extending direction of the string 10 and is arranged as untwisted so as not to be twisted with each other. Therefore, in the region where the string 10 is linearly stretched on the racket (not shown), each elastic fiber 18 is also arranged substantially linearly in parallel with the stretching direction of the string 10.

As each elastic fiber 18, a monofilament made of synthetic fiber having low rubber elasticity (for example, 10 MPa or less) and greatly expanding and contracting with a small force is used. Specific examples include polyurethane fibers, polyether-ester copolymer fibers, and polytrimethylene terephthalate fibers, which are stretched and formed during the production thereof.

The ratio of the cross-sectional area (total) of all elastic fibers 18 to the cross section of the entire string 10 (hereinafter referred to as “blending ratio”) is preferably set to 10% or more and 40% or less, and the reason for this. Will be described later.

In the present embodiment, the elastic fibers 18 can be arranged in a straight line parallel to the extension direction of the string 10. Therefore, when the string 10 is expanded and contracted, the elastic fibers 18 also have substantially the same length as the expansion and contraction in the extension direction. It will elastically expand and contract. Therefore, when the string 10 is stretched by the impact (hit ball) of the shuttle, the elastic fiber 18 can exert the elastic force in the restoring direction of the stretched portion. On the other hand, in the conventional structure in which thread-like rubber is spirally twisted with a core thread, when the string 10 is stretched, the thread-like rubber contracts in the radial direction of the spiral and it becomes difficult to elastically stretch in the extending direction. .. Therefore, in the conventional structure, it becomes difficult to exert the force in the direction of restoring the elongation. As a result, in the string 10 of the present embodiment, the elastic force of the elastic fiber 18 can be applied to the shuttle better when the shuttle is hit, as compared with the conventional structure, and the resilience that causes the shuttle to fly is improved. Can be done.

Further, in the conventional structure in which the hollow portion of the core yarn is filled with an elastic body, the elastic body can exhibit higher elasticity than the portion surrounding the elastic body in the core yarn, but their elasticity is not significantly different. In this respect, since the elastic fiber 18 which is formed by stretching and has a large elasticity is used in the string 10 of the present embodiment, it becomes easy to exert the force to restore the elastic fiber 18 after it is elongated by the impact of the shuttle. Resilience can be improved.

The elastic fiber 18 itself has lower strength and durability than the core yarn side portion 16 and the

side yarns

12a and 12b. However, since it is partially arranged at the central axis position C of the core yarn 11, the strength and durability can be sufficiently ensured by the core yarn side portions 16 and the

side yarns

12a and 12b. Further, by winding the core thread side portion 16 in a spiral shape, the core thread side portion 16 can exhibit elasticity while ensuring strength, and the elastic force of the elastic fiber 18 can be satisfactorily exhibited.

Next, an experiment conducted to evaluate the resilience and durability of the string according to the above embodiment will be described. In the experiment, as an example, five types of strings 10 (see the graph in FIG. 3) in which the blending ratio of the elastic fibers 18 was changed within the range of about 15 to 28% in the string 10 of the above embodiment were used. Manufactured.

Further, in the experiment, as a comparative example, a string in which the elastic fiber 18 was omitted from the configuration of the example was manufactured. Then, in the string of the comparative example, the entire core yarn 11 including the core yarn central portion 15 was formed as a multifilament by the multifilament forming the core yarn side portion 16 of the example. Other conditions were the same for both Examples and Comparative Examples, and in both Examples and Comparative Examples, strings were stretched on a badminton racket with a tension of 23 pounds.

An experiment was conducted to evaluate the resilience of the strings of Examples and Comparative Examples. In addition, in order to evaluate the durability of the strings of Examples and Comparative Examples, an experiment was conducted to measure the cutting strength of the strings. The measurement result is shown in FIG. FIG. 3 is a graph showing the relationship between the blending ratio of strings and cutting strength and resilience.

Using the racket with the strings of the examples and comparative examples stretched, the resilience (flying) at the time of hitting the shuttle experienced by the player was evaluated. In this evaluation, the resilience in the comparative example was set as a "reference", and the state in which the player clearly experienced the difference in resilience with respect to the "criteria" was set as "fly". In addition, the evaluation between "standard" and "flying" is set as "slightly flying", the evaluation obtained by adding the difference between "flying" and "slightly flying" to "flying" is "flying greatly", and the difference is "flying greatly". The evaluation added to "fly big" was set as "very fly". The evaluation is divided into stages in this way, and the scoring results of the players when the five types of strings 10 in the examples are stretched are plotted with “□” (white squares) in the graph of FIG.

In the graph of FIG. 3, the curve obtained by the nonlinear least squares method from the scoring results of the plotted comparative examples and examples is also drawn by the dotted line. On the curve, when the evaluation is lower than the evaluation of "flying", the blending ratio is less than 10%. Therefore, good resilience can be exhibited when the blending ratio of the elastic fiber 18 is 10% or more.

In the experiment for measuring the cutting strength of the string 10, the cutting strength of each string 10 of the example was measured by Autograph AGS-J (manufactured by Shimadzu Corporation). The measurement conditions were based on JIS L1013: 2010 version "Chemical fiber filament yarn test method", and the sample gripping interval was 250 mm, the tensile speed was 300 mm / min, and the number of tests was 3 times for each string 10. Then, the straight line obtained by the least squares method from each measurement result which is the average value of the three tests is shown by a thick solid line in the graph of FIG. Here, the lower limit of the cutting strength that can withstand actual use in the badminton string is set to 200N. In the graph of FIG. 3, when the cutting strength is less than 200 N on a straight line obtained from the measurement result of the cutting strength, the blending ratio is more than 40%. Therefore, good cutting durability can be exhibited when the compounding ratio is 40% or less.

As described above, when the blending ratio of the elastic fiber 18 is in the range R (see FIG. 3) of 10% or more and 40% or less, both the resilience and the cutting durability are satisfactorily obtained as in the string 10 of the embodiment. Can be demonstrated.

Further, in the strings of Examples and Comparative Examples, the elongation elastic modulus was measured in order to evaluate the resilience. In such an extension modulus measurement, the string 10 was stretched to be 15% longer than its original length and held stretched for 1 minute. Then, the restoration rate was measured 3 minutes after returning to the original position, and the case of complete restoration was set to 100%. As for the elongation elastic modulus (restoration rate), the larger the value, the stronger the bending and restoring force, and the more distant the hit shuttle can be. As an example, the string 10 having a compounding ratio of 18.5% had an elongation elastic modulus of 87.5%, and the string of the comparative example had an elongation elastic modulus of 83.4%. Therefore, the measurement result that the shuttle flies better in the example than in the comparative example can be obtained, which supports the above-mentioned evaluation of resilience by the player's experience.

The present invention is not limited to the above embodiment, and can be modified in various ways. In the above embodiment, the size, shape, direction, etc. shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

For example, the number of elastic fibers 18 can be changed as appropriate, such as one (single) or a plurality of elastic fibers increased or decreased from seven. At this time, it is advisable to adjust the thickness of the elastic fiber 18 so that the resilience can be exhibited well. In the present invention, the number and thickness of the elastic fibers 18 can be selected and adopted as long as the elastic fibers 18 extend in parallel with the extension direction of the string 10.

Further, although the case where the center of the core thread center portion 15 formed of the elastic fiber 18 is located at the central axis position C of the string 10, the case is not limited to this, and the positions may be deviated. ..

Further, the thickness, winding form, and laminated form of the core thread side portion 16 and the

side threads

12a and 12b can be variously changed as long as they can be formed as the string 10.

The racket string of the present invention has the effect of improving the resilience of a hit ball while improving the strength.

This application is based on Japanese Patent Application No. 2019-078689 filed on April 17, 2019. All of this content is included here.

Claims

In a racket string that includes a core thread and a plurality of side threads provided on the outer peripheral side of the core thread and extends in a predetermined direction.
A string for a racket, wherein the core yarn includes elastic fibers in a region including a central axis position, and the elastic fibers extend in parallel with the extending direction.
The racket string according to claim 1, wherein the core thread further includes a core thread side portion that is spirally wound around the outer peripheral side of the elastic fiber.
The racket string according to claim 1 or 2, wherein a plurality of the elastic fibers are provided.
The racket according to any one of claims 1 to 3, wherein the ratio of the cross-sectional area of the elastic fiber to the cross section of the entire racket string is set to 10% or more and 40% or less. string.