Patent Application
20190118045
The present invention relates to a string set, a main string, and a cross string strung on a racket.
Generally, a badminton racket has a main string and a cross string strung such that the main string and the cross string intersect to form a face on which a shuttlecock is hit back. For each of the strings, there is known a string made by winding or braiding a side string around a multifilament core string and coating an outer surface. Various proposals to improve functions, such as durability, are made for such a string (for example, see Patent Document 1). For example, a string described in Patent Document 1 has improved string durability by adding a metal powder, such as titanium, in a coating agent.
As shots in badminton, there are known a shot called a hairpin and a shot called a cut smash. The hairpin is a shot that lightly repels a shuttle (shuttlecock) that is dropped near a net back into an opponent's court. The cut smash is a shot that uses a face of a racket to cut the shuttlecock that flies over the head so as to drop the shuttlecock near the net in the opponent's court. These shots require different functions in the string, and thus, it has been difficult to improve a hairpin performance (spinning performance) and a cut smash performance at the same time.
The present invention has been made in consideration of such a point, and it is an objective of the present invention to provide a string set, a main string, and a cross string that ensure improving a hairpin performance and a cut smash performance.
A string set of the present invention is a string set strung on a racket as a main string and a cross string. The string set includes a first string and a second string. The first string is strung as any one of the main string and the cross string. The first string has a small surface friction force and a small diameter. The second string is strung as another one of the main string and the cross string. The second string has a larger surface friction force and a larger diameter than the surface friction force and the diameter of the first string.
With this configuration, the second string has the large surface friction force and the large diameter, and thus, a friction force as well as a contacted area with a shuttlecock increases. Accordingly, a spin is easily applied to the shuttlecock repelled when a hairpin is shot, thereby improving the hairpin performance. The first string has the small surface friction force and the small diameter, and thus, a friction force as well as a contacted area between the first string and the second string decreases. Accordingly, the first string and the second string easily moves relatively when a cut smash is shot, thereby improving the cut smash performance. Thus, distributing functions to the first string and the second string ensures obtaining both the hairpin performance, which is improved by the large surface friction force and outer diameter of the string, and the cut smash performance, which is improved by the small surface friction force and outer diameter of the string, at the same time.
In the string set of the present invention, the first string is the cross string, and the second string is the main string. With this configuration, in addition to obtaining both the hairpin performance and the cut smash performance at the same time, it is possible to compensate the shortage of a feeling of shuttlecock hitting (repulsion) caused by the increased outer diameter of the main string by decreasing the outer diameter of the cross string. Increasing the outer diameter of the main string, which is susceptible to an edge breakage, ensures lowering an edge breakage probability.
In the string set of the present invention, a friction force at which the second string moves with respect to the first string is 2.2 [N] or less. With this configuration, the second string easily moves with respect to the first string, thereby ensuring improving the cut smash performance.
In the string set of the present invention, the first string has an outer diameter that is 94% or less of an outer diameter of the second string. With this configuration, even when the second string is made to have a large diameter and the hairpin performance is improved, the second string can be made to easily move with respect to the first string, thereby ensuring improving the cut smash performance.
In the string set of the present invention, the first string and the second string form a face of the racket, and the face has a surface friction force of 9 [N] or more. With this configuration, the surface friction force on the face increases, and therefore, a spin is easily applied to a shuttlecock repelled on the face.
In the string set of the present invention, the second string includes a coating film, and at least a superficial layer of the coating film of the second string has a property to increase a grip force corresponding to an increase in film thickness. With this configuration, the film thickness of at least the superficial layer of the coating film of the second string increases the grip force, thereby ensuring the increased surface friction force of the second string.
In the string set of the present invention, at least the superficial layer of the coating film of the second string is formed of polyurethane or rubber. With this configuration, a simple configuration ensures the increased surface friction force of the second string.
A cross string of the present invention is a cross string strung on a racket while intersecting with a main string, and the cross string has a smaller surface friction force and a smaller diameter than a surface friction force and a diameter of the main string.
With this configuration, the cross string is made to have a smaller surface friction force and a smaller diameter than the surface friction force and the diameter of the main string, thereby decreasing a friction force as well as a contacted area between the strings. Accordingly, the main string easily moves with respect to the cross string when a cut smash is shot, thereby improving the cut smash performance. Even when the main string having the large surface friction force and the large diameter makes it easy to apply a spin, and thus, the hairpin performance is improved, the main string sufficiently moves with respect to the cross string, and thus, the cut smash performance is not lowered. Thus distributing the functions to the main string and the cross string ensures obtaining both the hairpin performance, which is improved by the large surface friction force and outer diameter of the string, and the cut smash performance, which is improved by the small surface friction force and outer diameter of the string, at the same time.
A main string of the present invention is a main string strung on a racket while intersecting with a cross string, and the main string has a larger surface friction force and a larger diameter than a surface friction force and a diameter of the cross string.
With this configuration, the main string is made to have a larger surface friction force and a larger diameter than the surface friction force and the diameter of the cross string, thereby increasing a friction force as well as a contacted area between the shuttlecock and the main string. Accordingly, a spin is easily applied to the shuttlecock repelled when a hairpin is shot, thereby improving the hairpin performance. Even when the cross string having the small surface friction force and the small diameter makes it easy for the main string to move, and thus, the cut smash performance is improved, the surface friction force of the main string is sufficiently large, and thus, the hairpin performance is not lowered. Thus distributing the functions to the main string and the cross string ensures obtaining both the hairpin performance, which is improved by the large surface friction force and outer diameter of the string, and the cut smash performance, which is improved by the small surface friction force and outer diameter of the string, at the same time.
According to the present invention, using the first string having the small surface friction force and the small diameter in combination with the second string having the large surface friction force and the large diameter ensures improving the hairpin performance and the cut smash performance.
The following describes a string set according to an embodiment with reference to the accompanying drawings.
As illustrated in
As shots in badminton, there are known a shot called a hairpin and a shot called a cut smash. The hairpin is a shot that uses the face 54 of the racket 50 to lightly repel the shuttlecock back to near a net in an opponent's court. In this case, the shuttlecock is repelled with the face 54 of the racket 50 in an approximately horizontal, and when the shuttlecock is hit as if being scuffed, a spin is applied to the repelled shuttlecock, and thus, the shuttlecock is returned to the opponent's court along a nearly vertical trajectory. The cut smash is a shot that uses the face 54 to hit the shuttlecock as if cutting the shuttlecock so as to drop the shuttlecock near the net in the opponent's court. In this case, the face 54 obliquely hits the shuttlecock. The main string 21 is moved by the shuttlecock, and the main string 21 gives a rotation to the shuttlecock when returning, and thus, the shuttlecock is returned to the opponent's court along a sharply dropping trajectory.
As the comparative example illustrated in
Meanwhile, as illustrated in
Thus, increasing the string gauges of the strings 41 and 42 and the friction force improves the hairpin performance but lowers the cut smash performance. Decreasing the string gauges of the strings 41 and 42 and the surface friction force improves the cut smash performance but lowers the hairpin performance. Since the hairpin performance and the cut smash performance are in a trade-off relationship, it has been difficult to improve the hairpin performance and the cut smash performance at the same time when the identical strings 41 and 42 are used for the main string and the cross string. In addition, there have occurred disadvantages, such as increasing the string gauges degrades the feeling of shuttlecock hitting, but conversely, decreasing the string gauges causes an easy edge breakage, and further, increasing the surface friction force makes it hard to string.
Therefore, in the embodiment, functions of the hairpin performance and the cut smash performance are distributed to the main string 21 (second string) having a large surface friction force and a large diameter and the cross string 22 (first string) having a small surface friction force and a small diameter. Then, the disadvantage caused by the increased string gauge of the main string 21 and surface friction force is improved by decreasing the string gauge of the cross string 22 and the surface friction force. Conversely, the disadvantage caused by the decreased string gauge of the cross string 22 and surface friction force is improved by increasing the string gauge of the main string 21 and the surface friction force.
Specifically, as illustrated in
Meanwhile, as illustrated in
Furthermore, a shortage of the feeling of shuttlecock hitting (repulsion) caused by the increased string gauge of the main string 21 is compensated by decreasing the string gauge of the cross string 22. Meanwhile, the easy edge breakage caused by the decreased string gauge of the cross string 22 is compensated by increasing the string gauge of the main string 21, which is in particular susceptible to the edge breakage. Furthermore, the difficulty in stringing caused by the increased surface friction force of the main string 21 is compensated by decreasing the surface friction force of the cross string 22.
The following describes the string set according to the embodiment in detail.
As illustrated in
Around the structure 13 in the string shape, polyamide or the like coats an inner side, and subsequently, polyurethane coats a superficial layer to form the coating film 16 with a predetermined film thickness. That is, the coating film 16 is configured of a two-layer structure of a coating layer inside (inner layer) and a coating layer outside (superficial layer). The coating layer outside has a friction force (friction coefficient) higher than that of the coating layer inside. It should be noted that the coating film 16 may be formed only of the polyurethane. It should be noted that in the following description, a film thickness t of the coating film 16 of the main string 21 indicates a thickness from an outermost surface of the structure 13 in the string shape.
While it is not illustrated in detail, the cross string 22 is formed approximately similarly to the main string 21 except that a coating film is formed only of the polyamide and an outer diameter of a structure in the string shape is small. Unlike the main string 21, the cross string 22 has a superficial layer of the coating film formed of the polyamide as well, thereby having the surface friction force smaller than that of the main string 21. It should be noted that, while a material of the core string and the side string of the main string 21 and the cross string 22 is not limited, for example, the polyamide, polyester, and the like are used.
Next, the hairpin performance will be described.
As illustrated in
When the film thickness of the polyurethane indicated on the horizontal axis in
When the string gauge indicated on the vertical axis in
When the film thickness of the polyurethane is large, increasing a grip force to the shuttlecock increases the surface friction force of the string. When the string gauge is large, increasing a contacted area between the surface of the string and the cork leather of the shuttlecock increases the surface friction force of the string. Thus, in the embodiment, by adjusting the film thickness of the polyurethane and the string gauge, an appropriate friction force is given to the surface of the string. It should be noted that, the above-described string friction force is measured using Autograph AG-IS (made by SHIMADZU CORPORATION), for example, by sliding a weight having a cork leather attached on a contact surface on the string surface strung on a racket.
Specifically, as illustrated in
Next, in order to select an optimum material, superficial layers of the coating film were formed using three kinds of materials, polyamide to which a terpene resin is added, polyurethane with an excellent production stability, and rubber with an excellent friction. Then, surface friction forces of the strings were measured, and the surface friction forces were compared with the surface friction force of the string whose superficial layer of the coating film 16 was formed of the polyamide. Common condition was that the string gauge was 0.67 [mm] and the film thickness of the superficial layer of the coating film 16 was 10 [μm]. As a result, a result illustrated in Table 1 was obtained. The terpene resin is a tackifying resin made by processing turpentine and an orange oil as a raw material.
The surface friction force of the string that used the polyamide to which the terpene resin is added was 7.6 [N] and was greater than 6.3 [N] of the surface friction force of the string that used the polyamide, but was less than 9 [N] where a spin is easily applied. In contrast to this, the surface friction forces of the strings that used the polyurethane and the rubber were 12.5 [N] and 21.4 [N], respectively, and were greater than 6.3 [N] of the surface friction force of the string that used the polyamide, and further, were equal to or more than 9 [N] where a spin is easily applied. From this, it was found that a sufficient friction force can be obtained by using the polyurethane and the rubber as the coating agent.
Accordingly, upon applying a spin to the shuttlecock with the string, it is preferred that the polyurethane or the rubber is used as the material of the superficial layer of the coating film 16. Furthermore, from the aspect of processing stability, it is more preferred to use the polyurethane. It should be noted that the material of the superficial layer of the coating film is not limited to the above-described materials, and any materials may be used as long as the surface friction force of the string becomes 9 [N] or more. For example, it is possible to even use the polyamide and the polyamide to which the terpene resin is added as the material of the coating film by adjusting the film thickness of the coating film 16 and a size of the string gauge to make the surface friction force of the string 9 [N] or more. When the surface friction force of the string is 9 [N] or more, a material identical to that of an inside of the coating film, for example, the polyamide may form the superficial layer.
Next the cut smash performance will be described.
As illustrated in
Here, by repeating test hitting while the cross string gauge was changed, it was found that the player felt it was easy to apply a cut smash when the main string moving amount was 6.0 [mm] or more. Measurement of the friction force when the main string at this time moved was 2.2 [N] or less. Therefore, the friction force of the cross string gauge and the cross string at which the friction force when the main string moved became 2.2 [N] or less was checked. Then, the results illustrated in
Specifically, as illustrated in
The force gauge 97 is mounted to an electric slider 98, and is slid at a tension speed of 600 [mm/min] and for a movement distance of 100 [mm]. Then, slidability is measured. That is, the friction force when the main string moves is a relative friction force generated when the cross string 81 to which the weight weighing 300 [g] is attached is slid with respect to the main string 82 to which the weight weighing 1000 [g] is attached in a state where the cross string 81 is in contact with the main string 82 at the plurality of intersecting positions 85 (fifteen positions in the embodiment).
As illustrated in
As illustrated in
Next, the feeling of shuttlecock hitting and the edge breakage probability will be described.
As illustrated in
In contrast to this, when the main string gauge was 0.67 [mm] and the cross string gauge was 0.61 [mm], a repulsion similar to that of when both the main string gauge and the cross string gauge were 0.63 [mm] was obtained. That is, the repulsion better than that of when both the main string gauge and the cross string gauge were 0.67 [mm] was obtained. Thus, it was confirmed that even when the main string gauge was increased, decreasing the cross string gauge ensured obtaining a sufficient repulsion.
As illustrated in
In contrast to this, when the main string gauge was 0.67 [mm] and the cross string gauge was 0.61 [mm], the edge breakage probability decreased down to approximately 32%. Increasing the main string gauge and decreasing the cross string gauge tremendously lowers the edge breakage probability. This is considered because the edge breakage is typically more likely to occur in the main string, and the size of the main string gauge affects the edge breakage probability easier than the size of the cross string gauge affects the edge breakage probability. Thus, it was confirmed that even when the cross string gauge was decreased, increasing the main string gauge ensured lowering the edge breakage probability.
From the results in
Next, a stringability will be described. Usually, when the main string and the cross string are strung on a racket, the main string is strung on the racket, and then, the cross string is strung so as to thread through the main string. In view of this, the stringability changes depending on a threadability of the cross string through the main string in a state where the main string is strung on the racket.
As illustrated in
In contrast to this, when the cross string with the nylon coating was used, a friction force when the cross string was threaded through the main string was 3.0 [N] or less with the cross string gauge in a range of 0.55 to 0.70 [mm], and thus, slidability of the cross string was good. Accordingly, when the cross string is coated with ordinary nylon to reduce the surface friction force, the stringability improves. Thus, it is possible to compensate the lowered stringability caused by the increased surface friction force of the main string in order to improve the hairpin performance by decreasing the surface friction force of the cross string.
While the following further describes the present invention in detail based on working examples, these are described for explanation, and the scope of the present invention is not limited to the following working examples.
Strings having a string gauge of 0.67 [mm] and film thicknesses of the polyurethane of 0 [μm], 4 [μm], and 6 [μm] were prepared, and actual test hitting evaluations of a hairpin were executed. Ten intermediate to advanced players in the age group of twenties to fifties evaluated spin capabilities into six levels of “excellent,” “good.” “slightly good,” “normal.” “slightly poor,” and “poor.” As a result, the result illustrated in Table 2 was obtained.
The string with the film thickness of the polyurethane of 0 [μm] was evaluated as a reference (normal). In contrast to this, when the film thickness of the polyurethane was 4 [μm], nine players evaluated as “good,” and only one player evaluated as “poor.” When the film thickness of the polyurethane was 6 [μm], four players evaluated as “excellent,” three players evaluated as “good,” two players evaluated as “slightly good,” and only one player evaluated as “slightly poor.” That is, nine out of ten players evaluated that it spun better than “normal” with both strings with the polyurethane film thicknesses of 4 [μm] and 6 [μm]. Thus, it was obtained the evaluation that a spin was easily applied with the polyurethane film thicknesses of 4 [μm] and 6 [μm], that is, the surface friction force of 9 [N] or more (see
Next, cross strings having cross string gauges of 0.65 [mm], 0.63 [mm], 0.61 [mm], and 0.58 [mm] and a main string having a main string gauge of 0.67 [mm] and a polyurethane film thickness of 10 [μm] were prepared, and actual test hitting evaluations of a cut smash were executed. Here, the main string and the cross string were strung at 23 pounds on a racket, NR900 (made by YONEX CO., LTD.). Ten intermediate to advanced players in the age group of twenties to fifties evaluated cut smash capabilities into five levels of “good.” “slightly good,” “normal.” “slightly poor,” and “poor.” As a result, the result illustrated in Table 3 was obtained.
When the size of the cross string gauge was 0.65 [mm], two players evaluated as “good,” two players evaluated as “slightly good,” two players evaluated as “normal,” and four players evaluated as “slightly poor.” When the size of the cross string gauge was 0.63 [mm], two players evaluated as “good,” four players evaluated as “slightly good,” three players evaluated as “normal,” and one player evaluated as “slightly poor.” When the size of the cross string gauge was 0.61 [mm], two players evaluated as “good.” five players evaluated as “slightly good.” two players evaluated as “normal,” and one player evaluated as “slightly poor.” When the size of the cross string gauge was 0.58 [mm], seven players evaluated as “good,” and three players evaluated as “slightly good.” That is, equal to or more than the half evaluated any of the strings with the cross string gauges sized 0.63 [mm], 0.61 [mm], and 0.58 [mm] as higher than “normal.”
As described above, in the string set 20 according to the embodiment, using the main string 21 having a larger surface friction force and a larger diameter than those of the cross string 22 increases the friction force as well as the contacted area between the shuttlecock and the main string 21. Accordingly, a spin is easily applied to the shuttlecock repelled when a hairpin is shot, thereby improving the hairpin performance. Using the cross string 22 having a smaller surface friction force and a smaller diameter than those of the main string 21 decreases the friction force as well as the contacted area between the main string 21 and the cross string 22. Accordingly, the main string 21 is easily moved with respect to the cross string 22 when a cut smash is shot, thereby improving the cut smash performance. Thus, distributing functions to the main string 21 and the cross string 22 ensures obtaining both the hairpin performance, which is improved by the large surface friction force and outer diameter of the string, and the cut smash performance, which is improved by the small surface friction force and outer diameter of the string, at the same time.
It should be noted that, the present invention is not limited to the above-described embodiment, and can be variously changed to embody. In the above-described embodiment, size, shape, direction, and the like illustrated in the attached drawings are not limited to those, and may be appropriately changed in a range that can provide the effects of the present invention. Moreover, the present invention may be appropriately changed to embody without departing from a scope of the object of the present invention.
For example, in the embodiment, while the structure 13 in the string shape is configured by braiding the side strings 12a and 12b around the core string 11, the structure 13 in the string shape may be configured only of the core string 11. While it is configured such that the side strings 12a and 12b are braided around the core string 11, it may be configured such that only one layer of the side string is wound around the core string 11. Furthermore, two layers of the side string may be wound around and string gauges (outer diameter) of the first layer and the second layer of the side strings may be different.
In the embodiment, the core string 11 and the side strings 12a and 12b may be configured of any of a multifilament and a monofilament, and a count is not limited. When the core string 11 is the monofilament, the cross-sectional surface is not limited to a circular shape, and the cross-sectional surface may be polygonal (such as a pentagonal shape). Furthermore, a hollow thread may be used for the core string 11 and the side strings 12a and 12b.
In the embodiment, while the strings 21 and 22 have a configuration of being formed of the synthetic fiber, the configuration is not limited to this. The structure 13 in the string shape of the strings 21 and 22 may be formed of a natural string made of a natural fiber, such as a sheep casing and a whale's muscle.
In the embodiment, while there has been described the configuration in which the polyamide is coated on the cross string 22, it is not limited to this configuration. The coating film of the cross string 22 may be formed in any way as long as it is possible to improve the cut smash performance by having a friction force smaller than that of the main string 21 so as to cause the main string 21 to easily move.
In the embodiment, while it is configured to use the string having the small friction force and the small diameter for cross string and the string having the large friction force and the large diameter for main string, the configuration is not limited to this. It is possible to obtain both the hairpin performance and the cut smash performance at the same time even when a string having a small friction force and a small diameter is used for main string and a string having a large friction force and a large diameter is used for cross string.
This application is based on Japanese Patent Application No. 2016-089286 filed on Apr. 27, 2016, and the disclosure of which is incorporated herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-089286 | Apr 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/006675 | 2/22/2017 | WO | 00 |
