阅读说明：本技术 球拍用弦线 (String for racket ) 是由 小泽佳佑 千叶慎一郎 于 2020-04-14 设计创作，主要内容包括：本发明目的在于能够使弦线强度良好,并提高击球的反弹性。一种球拍用弦线(10),其构成为具有芯丝(11)和设置在该芯丝的外周侧的多个侧丝(12),沿规定方向延伸。芯丝在包括中心轴位置(C)的区域具有弹性纤维(18)。弹性纤维设为与弦线的延伸的方向平行地延伸。因而,不捻入弹性纤维地进行设置,能够在拉设弦线的状态下将弹性纤维沿直线设置,良好地发挥伸缩方向的弹力,能够通过该弹力提高击球时的反弹性。(The invention aims to improve the strength of a string and improve the rebound of a striking ball. A string (10) for a racket, which is configured to have a core wire (11) and a plurality of side wires (12) provided on the outer peripheral side of the core wire and to extend in a predetermined direction. The core wire has an elastic fiber (18) in a region including the central axis position (C). The elastic fibers extend parallel to the direction in which the strings extend. Therefore, the elastic fiber can be provided in a straight line without twisting the elastic fiber, and the elastic fiber can be provided in a state where the string is pulled, so that the elastic force in the expansion and contraction direction can be favorably exerted, and the rebound at the time of hitting a ball can be improved by the elastic force.)

1. A string for a racket, which has a core filament and a plurality of side filaments provided on the outer peripheral side of the core filament and extends in a predetermined direction,

the core wire has an elastic fiber in a region including a central axis position, the elastic fiber extending parallel to the direction of extension.

2. A string for a racket as claimed in claim 1,

the core filament further has a core filament side portion wound in a spiral shape on an outer peripheral side of the elastic fiber.

3. A string for a racket as claimed in claim 1 or claim 2,

the elastic fiber is provided with a plurality of strips.

4. A string for a racket as claimed in any one of claims 1 to 3,

the ratio of the cross-sectional area of the elastic fiber to the cross-section of the entire racket string is set to be 10% or more and 40% or less.

Technical Field

The present invention relates to a string for a racket used for tennis, badminton, squash, and the like.

Background

In tennis and badminton rackets, strings are strung at the head surface. As a string for a racket, the following strings are widely used: the monofilament serving as a thin side yarn is wound around the outer side of the monofilament or multifilament serving as a core yarn.

As such a string, as disclosed in patent documents 1 and 2, a structure having a member with elastic core wires has been proposed. Specifically, the string of patent document 1 is configured as follows: a hollow portion is formed in the core wire (core material), and an elastic body made of urethane rubber or silicone rubber is provided in the hollow portion. The string of patent document 2 is formed of a multifilament in which core filaments (core bodies) are twisted and joined, and 2 to 3 pieces of filamentary rubber are mixed in the multifilament.

Documents of the prior art

Patent document

[ patent document 1 ] JP-A3-83568

[ patent document 2 ] JP-A-6-48719 (Kokai)

Disclosure of Invention

Problems to be solved by the invention

The string of patent document 1 is configured to be provided such that an elastic body is filled in the hollow portion. Therefore, although the elastic body can exhibit the same degree of rebound resilience against the shuttlecock as compared with a solid configuration without providing the hollow portion, the elastic body is less likely to expand and contract in the extending direction of the string, and the rebound resilience is less likely to be improved as compared with a solid configuration.

In the string of patent document 2, the string rubber is formed into a substantially spiral shape because the string rubber is twisted with other fibers. Therefore, even if the string is pulled and tightened in the pulling direction by the hitting ball, the spiral shape of the filament rubber is substantially maintained although it is slightly deformed in the extending direction. As a result, the filament rubber hardly exerts elastic force in the expansion and contraction direction, and thus it is difficult to improve the rebound.

Here, when the string is formed only of the filamentary rubber of patent document 2, there is a problem that the string cannot withstand the tension applied to 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 string for a racket, which has excellent strength even when elastic fibers are used, and can improve the rebound of a hit ball.

Means for solving the problems

In a racket string having a core filament and a plurality of side filaments provided on the outer peripheral side of the core filament and extending in a predetermined direction, the core filament has elastic fibers in a region including the position of the center axis, and the elastic fibers extend in parallel in the extending direction.

According to this configuration, the elastic fibers provided at the central axis position of the core wire extend in parallel in the extending direction of the string, that is, are provided without twisting the elastic fibers. This makes it possible to arrange the elastic fiber in a straight line with the string pulled, to exhibit elastic force in the expansion and contraction direction well, and to improve rebound at the time of hitting a ball by the elastic force. Further, by providing the elastic fiber in the core wire, the core wire including the elastic fiber is more likely to expand and contract in the extending direction than the conventional structure in which the elastic body is filled in the hollow portion of the core wire, and the elastic fiber can exhibit the elastic force well, contributing to improvement of the rebound resilience. Further, since the elastic fiber is provided in a region including the central axis position which is a part of the core yarn, the strength and the fracture durability of the portion other than the elastic fiber can be ensured satisfactorily.

In the racket string according to the present invention, the core filament preferably further includes a core filament side portion wound around an outer peripheral side of the elastic fiber. According to this configuration, the core yarn can be provided as a multifilament and can be provided at the center of the core yarn without twisting the elastic fiber. This makes it possible to exert the elastic force of the elastic fiber and to maintain the strength as a core yarn well.

In the racket string according to the present invention, the elastic fiber is preferably provided in a plurality of pieces. According to this configuration, the elastic force that can be exerted by the entire string can be adjusted by changing the number of elastic fibers, and further, the strength in the extending direction of the core yarn can be enhanced.

In the racket string according to the present invention, it is preferable that the ratio of the cross-sectional area of the elastic fiber to the entire cross-sectional area of the racket string is set to 10% or more and 40% or less. According to this numerical range, it is possible to satisfactorily achieve both the improvement of fracture durability and the improvement of rebound resilience, which are contradictory relationships.

Effects of the invention

According to the present invention, since the elastic fibers provided in the core wire extend in parallel to the extending direction of the strings, the strength can be improved and the rebound of a hit ball can be improved.

Drawings

Fig. 1 is a schematic perspective view of a part of a section of a chord line of the embodiment.

Fig. 2 is a cross-sectional view of the embodiment in chord.

Fig. 3 is a graph showing the relationship between the addition rate of the string and the breaking strength and the rebound resilience.

Detailed Description

Embodiments of the present invention will be specifically described below with reference to the drawings. The string of the present invention can be applied to various rackets such as badminton, tennis, squash, and the like if it is pulled on the frame of the racket to form a racket face.

Fig. 1 is a schematic perspective view of a part of a section of a string of the embodiment, and fig. 2 is a cross-sectional view of the string of the embodiment. As shown in fig. 1 and 2, the string 10 is configured to have: a core wire 11 located at the center and having a cross section forming a substantially circular outer periphery; and a plurality of side wires 12a, 12b spirally wound around the outer periphery side of the core wire 11; the chord line shown extends in a prescribed direction. The string 10 is formed in a circular shape in cross section. The core wire 11 is integrally bonded to the side wires 12a and 12 b. The side wires 12a and 12b are configured to weave around the core wire 11. The core wires 12a and 12b are formed by forming a plurality of side wires into 1 set, and are knitted so that 8 sets in the S-winding direction and 8 sets in the Z-winding direction cover the core wire 11.

After the inner coating layer 13a (not shown in fig. 1) is formed around the side wires 12a and 12b wound around the core wire 11, the surface coating layer 13b is formed. Thermoplastic resins can be used for all of the coating layers 13a and 13b, and particularly, polyamide resins and polyurethane resins are preferably used.

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

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

The core filament central portion 15 is comprised of a plurality of elastic fibers 18. In the present embodiment, the elastic fibers 18 are arranged so that 6 elastic fibers 18 surrounding the outer periphery of 1 elastic fiber 18 at the center converge. The elastic fibers 18 extend in parallel in the extending direction of the string 10 and are arranged as untwisted fibers that do not twist with each other. Therefore, in the region where the string 10 is pulled linearly along the racket not shown, the elastic fibers 18 are also arranged substantially linearly in the direction parallel to the pulling direction of the string 10.

Each elastic fiber 18 is a monofilament made of a synthetic fiber having low rubber elasticity (for example, 10MPa or less) and being greatly expanded and contracted with a small force. Specific examples thereof include polyurethane fibers, polyether-ester copolymer fibers, and polypropylene terephthalate fibers, which are formed by drawing at the time of production thereof.

The ratio of the cross-sectional area (sum) of all the elastic fibers 18 to the entire cross-section of the string 10 (hereinafter referred to as "addition rate") is preferably 10% or more and 40% or less, for reasons described later.

In the present embodiment, since the elastic fibers 18 can be arranged linearly in the direction parallel to the direction in which the string 10 is pulled, when the string 10 is extended and contracted, the elastic fibers 18 are also elastically extended and contracted in the extending direction by substantially the same length as the expansion and contraction. Therefore, when the string 10 is extended by hitting (hitting) the shuttlecock, the elastic fibers 18 can exert an elastic force in the restoring direction proportional to the amount of extension. In contrast, in the conventional configuration in which a thread-like rubber is twisted into a spiral shape in a core wire, when the string 10 is extended, the thread-like rubber contracts in the radial direction of the spiral, and is hard to elastically extend in the extending direction. Therefore, the conventional structure is difficult to exert a force in the direction of the elongation and recovery. As a result, in the string 10 of the present embodiment, the elastic force of the elastic fiber 18 can be applied to the shuttlecock more favorably than in the conventional structure when the shuttlecock strikes, and the rebound resilience as the strike of the shuttlecock can be improved.

In the conventional structure in which the hollow portion of the core wire is filled with the elastic body, the elastic body can exert a higher elastic force than the portion surrounding the elastic body in the core wire, but there is no great difference in the stretchability between them. In this regard, since the string 10 of the present embodiment uses the elastic fiber 18 having a large elasticity formed by stretching, the elastic fiber 18 can easily exert a force of recovering from elongation by hitting the shuttlecock, and the rebound resilience can be improved.

The elastic fibers 18 themselves have lower strength and durability than the core filament side portions 16 and the side filaments 12a, 12 b. However, since the portion is 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 can be configured to sufficiently ensure strength and durability. Further, by winding the core side portion 16 in a spiral shape, strength can be secured by the core side portion 16, stretchability can be exhibited, and the elastic force of the elastic fiber 18 can be exhibited satisfactorily.

Next, experiments for evaluating the rebound resilience and the durability performed on the string of the above embodiment will be described. In the experiment, as an example, 5 types (see fig. 3) of strings 10 in which the string 10 of the above embodiment was manufactured and the addition rate of the elastic fibers 18 was changed in a range of about 15 to 28%.

In addition, in the experiment, as a comparative example, a string in which the elastic fiber 18 was omitted from the constitution of the example was manufactured. Further, in the chord of the comparative example, the core wire 11 including the core wire center portion 15 is formed integrally as a multifilament by forming the multifilament of the core wire side portion 16 of the example. The examples and comparative examples were the same except for the conditions, and both the examples and comparative examples used a 23 pound tension to pull the string on the racquet for badminton.

Experiments for evaluating the rebound were performed on the strings of the examples and comparative examples. Further, for the strings of examples and comparative examples, experiments were conducted to measure the breaking strength of the strings for the purpose of evaluating durability. The measurement results are shown in fig. 3. Fig. 3 is a graph showing the relationship between the addition rate of the string and the breaking strength and the rebound resilience.

The rebound (strike) of the shuttlecock when struck, which the player experienced, was evaluated using a racket in which the strings of the examples and comparative examples were pulled. In this evaluation, the rebound of the comparative example is set as a "reference", and a state in which the player apparently experiences a difference in rebound from the "reference" is set as an evaluation of "hitting". Note that the evaluation between the "reference" and the "impact flight" is "slight impact flight", the evaluation of "impact flight" plus the difference between "impact flight" and "slight impact flight" is "large impact flight", and the evaluation of "large impact flight" plus the difference is "extraordinary impact flight". The evaluation is thus staged, and in the case where 5 types of strings 10 are pulled in the example, the scoring results of the players are plotted as "□" (open squares) in fig. 3.

In fig. 3, from the scoring results of the comparative example and the example, which are plotted, a curve obtained by the nonlinear least squares method is also plotted by a broken line on the curve, and the addition rate at the time of evaluation of less than "hit-and-fly" is less than 10%. Therefore, when the addition rate of the elastic fiber 18 is 10% or more, good rebound can be exhibited.

In the experiment for measuring the breaking strength of the string 10, the breaking strength of each string 10 of the example was measured by an autograph AGS-J (manufactured by shimadzu corporation). The measurement conditions were as follows JISL 1013: in 2010 edition "test method for chemical fiber filament", the sample fixing interval was 250mm, the drawing speed was 300mm/min, and the number of tests for each string 10 was 3 times each. Then, a straight line obtained by the least square method from each measurement result as an average value of the 3 tests is shown in fig. 3 by a thick solid line. Here, the lower limit of the breaking strength of the string of the shuttlecock that can withstand practical use is set to 200N. In fig. 3, the addition rate is greater than 40% when the breaking strength is less than 200N on a straight line obtained from the measurement result of the breaking strength. Therefore, when the addition rate is 40% or less, good fracture durability can be exhibited.

As described above, when the addition rate of the elastic fiber 18 is in the range R (see fig. 3) of 10% to 40%, both the rebound and the breaking durability can be exhibited well as in the string 10 of the example.

In addition, in the strings of examples and comparative examples, the elongation modulus for evaluating the rebound was measured. In the measurement of the elongation modulus, the string 10 was stretched 15% longer than the original length and held for 1 minute. Then, the recovery rate 3 minutes after the recovery to the original position was measured, and the case of complete recovery was taken as 100%. The larger the value of the elongation modulus (recovery rate), the stronger the force of bending and recovery, and the more the struck badminton can be struck. The string 10 having an addition rate of 18.5% as an example had an elongation modulus of 87.5%, and the string of the comparative example had an elongation modulus of 83.4%. Therefore, the example obtained the measurement result of hitting the shuttlecock well compared to the comparative example, and is evidence of the rebound evaluation based on the player experience described above.

The present invention is not limited to the above embodiments, and can be implemented with various modifications. In the above-described embodiments, the size, shape, orientation, and the like shown in the drawings are not limited thereto, and can be appropriately modified within a range in which the effects of the present invention are exhibited. Further, the present invention can be implemented by making appropriate changes without departing from the scope of the object of the present invention.

For example, the number of elastic fibers 18 may be appropriately changed to 1 (single), a plurality of fibers increased or decreased from 7, or the like. In this case, the elastic fiber 18 can be adjusted in thickness to exhibit good rebound. In the present invention, the number and thickness of the elastic fibers 18 can be selected and used as long as the elastic fibers 18 extend parallel to the extending direction of the string 10.

The center of the core filament central portion 15 formed of the elastic fiber 18 is shown in the figure as being located at the central axis position C of the string 10, but the present invention is not limited thereto, and these positions may be shifted.

The thickness, winding method, and lamination method of the core side portion 16 and the side wires 12a and 12b can be variously modified as long as the string 10 can be formed.

Industrial applicability

The string for racket of the present invention has excellent strength and can improve rebound effect of hitting ball.

The application is based on Japanese special application 2019-078689 applied on 4/17 in 2019. The entire contents of which are included herein.