WO2017082015A1 - Racquet string - Google Patents

Abstract

The present invention is configured so that an advantage can be obtained by forming a hollow section and durability can be increased. A racquet string (10) is configured provided with a core yarn (11) and a plurality of side yarns (12) wrapped on the outer peripheral side of the core yarn. The core yarn is provided with a solid-core section (20) formed in a prescribed region including a center axis position (C), and a plurality of hollow sections (21) formed around the solid-core section and extending in the extension direction of the core yarn. An odd number of hollow sections are formed, and the hollow sections are disposed at equal angles with the solid-core section as a center.

Description

Racket string

The present invention relates to a racquet string used for tennis, badminton, squash and the like, and more particularly to a racquet string in which a plurality of side yarns are wound around the outer periphery of a core yarn.

In tennis and badminton racquets, strings are stretched in mesh on the face portion. In addition, as a string for racquet, a string in which a monofilament which becomes a core yarn and a monofilament which becomes a thin side yarn around the outside of a multifilament are widely used. Such strings are generally referred to as "monofilament type" when the core yarn is a monofilament, and "multifilament type" when the core yarn is a multifilament.

As a monofilament type string, as disclosed in Patent Document 1, a structure in which a hollow portion is formed at a central axis position of a core yarn is proposed. By forming such a hollow portion, advantages can be obtained such that the elasticity of the string can be increased to improve the vibration absorbing performance at the time of hitting a ball.

Japanese Patent Application Publication No. 2005-237877

However, in the string of Patent Document 1, when a force is applied in the radial direction in the cross section, there is a problem that the hollow portion is easily crushed in the radial direction. This hollow portion is likely to be crushed at the intersection of the warp and weft of the string, and is also easily generated at the time of hitting a ball, and there is a problem that the durability of the string is reduced by such crushing.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a racquet string capable of obtaining an advantage by forming a hollow portion and capable of enhancing the durability.

The racquet string according to the present invention is a racquet string extending in a predetermined direction, wherein a solid portion formed in a predetermined region including a central axis position and a periphery of the solid portion are formed in the extension direction. And a plurality of hollow portions extending. In the racquet string according to the present invention, the racquet string includes a core yarn and a plurality of side yarns wound around the outer periphery of the core yarn, wherein the core yarn is in a predetermined area including the central axis position. A solid portion is formed, and a plurality of hollow portions formed around the solid portion and extending in the extending direction of the core yarn are characterized.

According to these configurations, the central axis position is a solid portion, and a hollow portion is formed around the solid portion. Therefore, the string radial direction (thickness) with respect to the hollow portion by stretching on a racket or hitting a ball Direction) It can control that strong force acts from both sides. As a result, the hollow portion can be made difficult to be crushed, and while it is possible to obtain advantages such as the vibration absorbing action at the time of hitting a ball, it is possible to prevent the stress concentration from becoming large due to the crushing and to prevent the deterioration of durability. . In addition, since a plurality of hollow parts are formed around the solid part, it is possible to reduce the opening area of each hollow part while earning the total sum of the opening areas of the hollow parts, which also makes it difficult to crush the hollow part. can do.

Further, in the racquet string of the present invention, it is preferable that the formation number of the hollow portions is an odd number, and the hollow portions are disposed at equal angles around a solid portion. According to this configuration, it is possible to distribute the hollow portions around the solid portion and prevent the two hollow portions from being aligned in the diameter direction of the string. Thereby, even if a force in the diametrical direction is applied to one of the plurality of hollow portions by tensioning on the racket or the like and the temporary collapse occurs, it is suppressed that a large force acts on the other hollow portions from the diametrical direction. can do. As a result, simultaneous collapse of the two hollow portions can be avoided, and the advantages of the hollow portions can be more easily exhibited.

Further, in the racquet string of the present invention, the number of hollow portions may be any of 3, 5, and 7. According to this configuration, the size and layout of the hollow portion can be maintained in a well-balanced manner, stress concentration on the hollow portion can be alleviated better, the durability can be improved, and the hollow portion is maintained. The advantages of can be demonstrated well.

Further, in the racket string of the present invention, the plurality of hollow portions may be formed in the same shape. According to this configuration, even if the circumferential direction of the string changes, the performance of the hollow portion in terms of hitting can be stabilized without changing.

In the racquet string of the present invention, the ratio of the opening area of the hollow portion to the entire cross section of the racquet string may be 3.0% or more and 8.0% or less. According to this numerical range, it is possible to favorably achieve both the improvement of the cutting durability and the improvement of the feel at impact, which are opposite to each other.

According to the present invention, since the solid portion is formed at the central axis position and the plurality of hollow portions are formed around the solid portion, the advantage of forming the hollow portion can be obtained, and the durability can be enhanced. be able to.

It is a cross-sectional view of the string which concerns on 1st Embodiment. It is a cross-sectional view of the string which concerns on comparison structure. It is a cross-sectional view of the string which concerns on 2nd Embodiment. It is a graph which shows the relationship between the hollow rate of a string, natural frequency, and cutting strength. It is a graph which shows the relationship between the gauge of a string, and natural frequency.

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 soft tennis, tennis, badminton, squash, etc. as long as it is stretched on the frame of the racket to form a face.

First Embodiment
FIG. 1 is a cross-sectional view of a string according to a first embodiment. As shown in FIG. 1, the string 10 has a core yarn 11 located at the center and forming a circular outer periphery in a cross section, and a plurality of side yarns 12 spirally wound around the outer periphery of the core yarn 11. And a resin coating layer 13 formed on the outer periphery thereof, and the outer shape is formed in a circular shape in a cross section. The core yarn 11 and the side yarn 12 are integrally bonded by an adhesive.

For the core yarn 11, a monofilament made of synthetic fiber is used, and it is preferable to use polyamide fiber of nylon 6 and nylon 66. Further, monofilaments, multifilaments or multimonofilaments made of synthetic fibers are used as the side yarns 12, and it is preferable to use polyamide fibers of nylon 6 and nylon 66. It is preferable to use a polyamide resin as the resin coating layer 13. The use of polyester (polybutylene terephthalate, polyethylene terephthalate or the like), polyolefin, polyphenylene sulfide, polyetheretherketone or the like in the core yarn 11 and the side yarn 12 does not occur.

The core yarn 11 includes a solid portion 20 formed in a predetermined area including the central axis position C, and a plurality of hollow portions 21 formed around the solid portion 20. In other words, in the core yarn 11, as shown by a two-dot chain line in FIG. 1, a region having a substantially circular cross section in the inside of the plurality of hollow portions 21 is a solid portion 20. The solid portion 20 and the plurality of hollow portions 21 are formed to extend in the extending direction of the core yarn 11, respectively.

The number of hollow portions 21 formed is an odd number, and in the first embodiment, five hollow portions 21 are formed. The five hollow portions 21 are disposed at equal angular intervals (approximately every 72 °) around the solid portion 20. Therefore, all the hollow portions 21 have a positional relationship in which no other hollow portion 21 exists on the line L (dotted line in FIG. 1) connecting the hollow portion 21 and the central axis position C. Also in the radial direction of the core yarn 11, a plurality of lines do not line up.

The five hollow portions 21 are formed in an inner peripheral shape that is substantially the same, and in the first embodiment, are formed in a substantially square shape in a cross section. Specifically, it has an elongated shape so as to be pointed outward in the radial direction of the core yarn 11, including two sides forming an inner angle substantially at right angles and two sides forming an inner angle forming an obtuse angle at the opposite angle. It is done. The five hollow portions 21 have substantially the same distance from the central axis position C, and the distances from the outer periphery of the core yarn 11 are also set substantially the same.

The ratio (hereinafter referred to as “hollow ratio”) of the open area (total sum) of all the hollow portions 21 in the entire cross section of the string 10 is set to 3.0% or more and 8.0% or less Preferably, the reason is mentioned later.

Subsequently, the deformation of the hollow portion 21 when the string 10 is stretched will be described in comparison with the comparative structure of FIG.

In the string 10, when it is stretched in a mesh shape on the frame (not shown) of the racket, it receives a pulling force in the extending direction. At the same time, at the intersections of the warp yarns and weft yarns stretched in a mesh, compressive force is applied from both sides in the diameter direction in the cross section. In addition, even when hitting with a racket, the string 10 receives compressive force from both sides in the diameter direction in the cross section. Such a compressive force acts on the string 10 from various directions by the change in the circumferential direction of the stretched string 10 if it is in the diametrical direction in the cross section. Here, as an example, the case where a compressive force acts in the direction of arrow F in FIG. 1 will be considered.

When such a compressive force acts, the hollow portion 21 at the top of FIG. 1 is deformed so as to be crushed in the vertical direction which is the diameter direction. However, since the other four hollow portions 21 are not located on the line of the arrow F on which the compressive force acts, the compressive force acting is extremely weak, and the deformation of the hollow portion 21 can be suppressed. That is, the four hollow portions 21 not on the line of the arrow F can maintain the open state. Since the two hollow portions 21 do not line up in the diameter direction even if the diametrical position where the compressive force acts changes, at least four hollow portions 21 can be maintained in the open state as described above.

Moreover, in the first upper hollow portion 21, the compressive force from below acts via the solid portion 20. For this reason, it is presumed that the force for deforming the hollow portion 21 so as to be crushed is dispersed in the solid portion 20, and the deformation amount of the crushing is reduced. In addition, it is assumed that the solid portion 20 acts as a base to support the No. 1 upper hollow part 21 against the compression force from above, and the No. 1 upper No. hollow part 21 is less likely to be crushed. Therefore, even if it is in the hollow portion 21 at the top, it is in a state where deformation so as to be crushed is suppressed.

Here, the five hollow portions 21 are formed at intervals of about 72 ° with respect to the axial center position C in the cross section and have the same shape, so that the acting position of the compressive force shown by the arrow F in FIG. When changing every multiple of 72 °, the hollow portion 21 is deformed as described above. Depending on the change in the diameter position where the compressive force acts, all the hollow portions 21 may not overlap with the diameter position. In this case, the crushing deformation of the hollow portion 21 can be better suppressed.

FIG. 2 is a cross-sectional view of a string according to a comparison structure. In the string 10A according to the comparison structure, the formation position and the shape of the hollow portion 21 of the string 10 in the first embodiment are changed, and one hollow portion 21A is formed at the axial center position C of the core yarn 11A. Configured In the string 10A having such a comparison structure, when a compressive force acts in the direction of the arrow F in the same manner as described above, the hollow portion 21A becomes flat as shown by the two-dot chain line in the figure (vertical direction) Both sides will be crushed. The reason is that the hollow area 21A is located at the axial center position C, and the open area of the hollow area 21A is large.

Stress is concentrated and generated on the left and right sides of the hollow portion 21A which is crushed, and cracks are generated from the portion where the stress is concentrated, which has adverse effects such as reduction in durability and cutting strength. On the other hand, in the string 10 of the first embodiment, each opening area can be reduced while earning the total sum of the opening areas of the hollow portions 21, and crushing of each hollow portion 21 is suppressed as described above. As in the comparative structure, stress can be prevented from being concentrated. As a result, it is possible to avoid the occurrence of a crack at a stress concentration portion such as a comparative structure, and to improve the performance of durability and cutting strength. As a result, the life of the string 10 can be extended, and high performance can be maintained over a long period of time, and the frequency of replacement can be reduced to reduce the cost burden.

Here, by forming a plurality of hollow portions 21 in the core yarn 11 as in the string 10, a string in which the core yarn 11 without forming the hollow portion 21 becomes solid (hereinafter referred to as "solid string") There are advantages compared to the following.

By forming the hollow portion 21, it is possible to make the gauge (diameter dimension) thicker without changing the weight per unit length as compared with a solid string. As a result, the contact area between the string 10 and the ball (shuttle) can be expanded, and the controllability and the drivability can be enhanced, and the strength of the hitting ball can be increased. In addition, when the string 10 having the same gauge as the solid string is formed, the ease of displacement of the string 10 can be enhanced by the formation of the plurality of hollow portions 21 to realize high repulsion by restoration, and light and crisp Good hitting feel can be obtained and hitting sound can be increased.

Such an advantage can not be obtained with a solid string, and also becomes difficult to obtain when the hollow portion 21A is crushed as in the comparison structure. That is, the above-mentioned advantage can be said to be a distinctive and remarkable effect obtained by forming a plurality of hollow portions 21 like the above-mentioned string 10.

Second Embodiment
Next, a second embodiment different from the first embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view of a string according to a second embodiment. In the second embodiment, the components common to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The string 10 according to the second embodiment has three hollow portions 31 formed in a core yarn 11. The three hollow portions 31 are disposed about every 120 ° at equal angular intervals around the solid portion 20. Therefore, also in the second embodiment, all the hollow portions 31 have a positional relationship in which no other hollow portion 31 exists on the line L (dotted line in FIG. 3) connecting the hollow portion 31 and the central axis position C. A plurality of hollow portions 31 do not line up in the radial direction of the core yarn 11 in any hollow portion 31.

The three hollow portions 31 are formed in an inner peripheral shape that is substantially the same, and in the second embodiment, are formed in a substantially triangular shape in a cross section. Specifically, the shape is a substantially isosceles triangle, the base is located on the central axis position C side, and is concentrically curved with the core yarn 11, and the internal angle of the other two sides becomes an obtuse angle, and the radial direction of the core yarn 11 It is formed to be located outside. Further, the three hollow portions 31 have the same distance from the central axis position C, and the distance from the outer periphery of the core yarn 11 is also set to be the same. The three hollow portions 31 are formed closer to the central axis position C than at the hollow portion 21 of the first embodiment and at a position away from the outer periphery of the core yarn 11.

In addition, the ratio of the opening area (sum total) of all the hollow parts 31 occupied in the cross section of the core yarn 11 whole is also set to 3.0% or more and 8.0% or less.

Grooves 11 a formed on the outer peripheral surface of the core yarn 11 on the outer side in the radial direction of each hollow portion 31 are formed in a V-shaped cutout. The formation of the groove 11a may be omitted, and the core yarn 11 may form a substantially cylindrical outer periphery.

According to the second embodiment as well, the same effect as that of the first embodiment can be obtained, and since the number of hollow portions 31 formed is reduced, the mold can be simplified, etc. Can be facilitated.

Subsequently, an experiment conducted to evaluate the feel at impact, the hitting sound, and the durability of the string according to the first embodiment will be described. In the experiment, the strings of the first embodiment shown in FIG. 1 are manufactured as Examples 1 and 2. In Example 1, the hollow ratio of the hollow portion 21 is 4.2%, and in Example 2, 2 · 3. Set to%. Moreover, the string which made the core yarn 11 solid as a comparative example was manufactured. The other conditions were the same in each example and comparative example.

In order to evaluate the feel at impact and the hitting sound for the strings of Examples 1 and 2 and the Comparative Example, an experiment was performed to measure the natural frequency of the strings. Moreover, in order to evaluate durability with respect to the string of Example 1, 2, the experiment which measures the cutting | disconnection strength of a string was conducted. The measurement results are shown in FIGS. 4A and 4B. FIGS. 4A and 4B are graphs showing the relationship between the hollow rate of a string and the natural frequency and the breaking strength. FIG. 4A shows the measurement results of the natural frequency and cutting strength of a string stretched on a tennis racket. FIG. 4B shows the measurement results of the natural frequency and cutting strength of a string stretched on a soft tennis racket.

In the experiment to measure the natural frequency of the string, the strings of Examples 1 and 2 and the Comparative Example are stretched by a tension of 50 pounds on a tennis racket and by a tension of 30 pounds on a soft tennis racket. It was stretched. Then, an acceleration sensor was attached to the grip portion of the racket thus stretched, and an FFT analyzer DS-2000 (manufactured by Ono Sokki Co., Ltd.) was used for output analysis of the acceleration sensor. The string intersection point was impacted with an impulse hammer, and the obtained time-axis vibration waveform was subjected to Fourier transform to measure the first-order natural frequency of the string. The measurement results are shown in FIGS. 4A and 4B.

Further, using the racquet in which the strings of Examples 1 and 2 and Comparative Example were stretched, the feel at impact and the impact sound at the time of hitting the ball experienced by the player were evaluated. In this evaluation, Example 1 in which the hollow ratio is 4.2% is the best, then Example 2 in which the hollow ratio is 2.3% is preferable, and the comparative example is inferior to the first example. The amount of change in the natural frequency at which the player who feels it feels hitting feel and the change in hitting sound is about 10 Hz or more. In the graphs of FIG. 4A and FIG. 4B, the hollow ratio to the value obtained by subtracting 10 Hz from the natural frequency of Example 1 is about 3% on the straight line obtained by the least squares method from the measurement results of the natural frequency. Therefore, when the hollow ratio is 3.0% or more, a good hitting feel can be obtained with a high hitting sound. The difference between Examples 1 and 2 is assumed to be due to the hollow ratio and not to be influenced by the number of hollow portions formed.

In the experiment for measuring the cutting strength of the string, the cutting strength of the strings of Examples 1 and 2 was measured with Autograph AGS-J (manufactured by Shimadzu Corporation). The measurement conditions conform to JIS L1013: 2010 edition "Chemical fiber filament yarn test method", and the sample gripping distance was 250 mm, the tensile speed was 300 mm / min, and the number of tests was 3 times. The measurement result which becomes an average value of three tests is shown to FIG. 4A and FIG. 4B. The lower limit value of cutting strength that can withstand practical use of a string is 300N. In the graphs of FIG. 4A and FIG. 4B, the hollow ratio when the cutting strength is less than 300 N on the straight line connecting the measurement results of the cutting strength is 8% or more. Therefore, when the said hollow rate will be 8.0% or less, favorable cutting | disconnection durability can be exhibited. As described above, when the hollow ratio is 3.0% or more and 8.0% or less, both of the improvement in cutting durability and the improvement in shot feeling, which are in a contradictory relationship, can be favorably realized.

FIG. 5 is a graph showing the relationship between the gauge of the string and the natural frequency. In order to examine the relationship between the gauge of the string and the presence or absence of the hollow portion in the core yarn, the string (core yarn is solid) of three comparative examples in which the gauges are 1.15 mm, 1.2 mm, and 1.25 mm. The string of Example 1 having a gauge of 1.25 mm was prepared. Then, in the same manner as described above, the natural frequency was measured by stretching on a soft tennis racket. The measurement results are shown in FIG.

As can be understood from the graph of FIG. 5, the characteristic vibration measured in Example 1 in which the hollow portion is formed in the core yarn as compared with the comparative example in which the core yarn is solid under the condition of a gauge of 1.25 mm. The value of the number increases. Therefore, if the gauges are the same, it is lighter when the hollow portion is formed, and a good feel on impact can be obtained, and the impact sound can be increased.

Further, in the graph of FIG. 5, straight lines obtained by the least squares method are drawn from the measurement results of the natural frequencies of the comparative example. On this straight line, the gauge which becomes the same as the natural frequency of Example 1 whose gauge is 1.25 mm is 1.215 mm. That is, at the same natural frequency, the gauge can be made thicker in Example 1 in which the hollow portion is formed in the core yarn, as compared to the comparative example in which the core yarn is solid. This makes it possible to expand the contact area between the string and the ball (shuttle) while maintaining the feel at impact and the impact sound.

The present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above embodiment, the size, shape, direction, and the like shown in the attached drawings are not limited to the above, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, without departing from the scope of the object of the present invention, it is possible to appropriately change and implement.

For example, even if the number of hollow portions 21 and 31 formed in the core yarn 11 is seven, the same effects as those in the above-described embodiments can be obtained. Also, the number of hollow portions 21 and 31 may be changed to an even number, but two hollow portions 21 in the diameter direction of the core yarn 11 may be arranged at equal angles centering on the solid portion 20 as an odd number. 31 is advantageous in that two hollow parts can be prevented from collapsing simultaneously. Furthermore, the number of hollow portions 21 and 31 may be an odd number of 9 or more, but the number of formations of 3, 5 and 7 can improve the balance between the size of hollow portions 21 and 31 and the layout. Durability and hit performance can be exhibited well.

Further, the opening shape of the hollow portions 21 and 31 is not limited to the illustrated configuration example, and may be changed from the viewpoint of processability, hitting performance, and durability.

In the string 10, all the side yarns 12 wound around the core yarn 11 may be omitted. In this case, a monofilament made of synthetic fiber is used for the string 10, and it is preferable to use polyester. However, it does not prevent using polyamide fiber of nylon 6 and nylon 66.

The racquet string of the present invention has an effect that durability can be enhanced while forming a hollow portion.

This application is based on Japanese Patent Application No. 2015-221973 filed on November 12, 2015. All this content is included here.

Claims (6)

In a racket string extending in a predetermined direction,
A racquet string comprising: a solid portion formed in a predetermined region including a central axis position; and a plurality of hollow portions formed around the solid portion and extending in the extending direction. In a racquet string comprising a core yarn and a plurality of side yarns wound around the outer periphery of the core yarn,
The core yarn includes a solid portion formed in a predetermined region including a central axis position, and a plurality of hollow portions formed around the solid portion and extending in the extending direction of the core yarn. A racket string featuring The number of formation of the said hollow part is an odd number, and it arrange | positions at equal angle centering | focusing on a solid part, The string for rackets of Claim 1 or 2 characterized by the above-mentioned. The string for a racket according to claim 3, wherein the number of hollow portions is 3, 5, or 7. The string according to any one of claims 1 to 4, wherein the plurality of hollow portions are formed in the same shape. The ratio of the opening area of the said hollow part occupied in the cross section of the whole string for racquets is 3.0%-8.0%, It is characterized by the above-mentioned. Racket string.

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