JP6812052B2 - Racket string - Google Patents

Description

The present invention relates to a racket string stretched on a racket frame.

Generally, as a badminton racket string, a string in which a side yarn is wound or braided around a core yarn of a multifilament to coat the outer surface, or a string in which the outer surface of the core yarn of the multifilament is coated is known. In such a racket string, various proposals have been made for coating agents in order to improve durability (see, for example, Patent Document 1). For example, in the racket string described in Patent Document 1, the durability of the string is improved while maintaining the original performance by adding a metal powder such as titanium to the coating agent.

Japanese Patent No. 3166031

By the way, as a badminton shot, a shot called a hairpin, which is used near the net, is known. The hairpin is a shot that lightly repels the shuttle (shuttle cock) dropped on the net to the opponent's court, and when you hit it like rubbing the cork of the shuttle on the net of your own court, it spins and makes complicated movements while the opponent It will be difficult for the opponent player to return the shuttle because it will fall near the net of the court. However, the hairpin largely depends on the skill of the player, and even if the highly durable racket string described in Patent Document 1 is used, it is difficult to appropriately spin the shuttle.

The present invention has been made in view of this point, and an object of the present invention is to provide a string for a racket capable of improving spin performance.

The racket string of the present invention has a thread-like structure and a coating film formed around the thread-like structure, and has a weight with cork leather in a state where the racket is stretched and horizontally arranged. The surface frictional force of the coating film measured as the static frictional force when a weight of 1 [kg] is slid is 9 [N] or more. With this configuration, the surface frictional force of the racket string is increased, so that the shuttle flipped by the racket string is easily spun.

In racquet string of the present invention, the coating layer is composed of the surface layer and the inner layer of the two-layer structure, the measured surface friction force of the surface to be measured under the same conditions is greater than the surface friction of the inner layer .. With this configuration, the coating film has a two-layer structure, and the spin performance can be improved on the surface layer of the coating film.

In the racket string of the present invention, at least the surface layer of the coating film has a property of increasing the grip force as the film thickness increases. With this configuration, the grip force is increased depending on the film thickness of the coating film, so that the surface frictional force of the racket string can be increased.

In the racket string of the present invention, the film thickness of at least the surface layer of the coating film is 2 [μm] or more. With this configuration, the grip force is increased depending on the film thickness of the coating film, so that the surface frictional force of the racket string can be increased.

In the racket string of the present invention, the outer diameter is 0.61 [mm] or more. With this configuration, the contact area between the shuttle and the racket string is increased, so that the surface frictional force of the racket string can be increased.

In the racket string of the present invention, at least the surface layer of the coating film is formed of polyurethane or rubber. With this configuration, the surface frictional force of the racket string can be increased with a simple configuration.

According to the present invention, the spin performance can be improved by increasing the surface frictional force of the racket string.

It is sectional drawing of the string of this embodiment. It is a figure which shows the relationship between the film thickness of polyurethane of this embodiment, and a string gauge. It is a figure which shows the relationship between the film thickness of polyurethane of this embodiment, and the surface friction force. It is a figure which shows the relationship between the string gauge of this embodiment, and the surface friction force. It is explanatory drawing of the measuring method of the surface friction force of this embodiment.

Generally, a racket for badminton is stretched with a racket string (hereinafter referred to as a string) in the vertical and horizontal directions, and the shuttle is hit back to the opponent's court by catching the shuttle on the face surface of the racket. As badminton shots, in addition to shots that strongly hit the shuttle such as clear and smash, hairpins that lightly hit the shuttle near the net are known. The hairpin is a badminton-specific shot in which the shuttle dropped from the opponent's court on the net is lightly flipped or rubbed on the face of the racket and returned to the opponent's court on the net, and the variation in the accuracy of the hairpin depends on the skill of the player. However, it was big.

As a factor that determines the accuracy of the hairpin, the degree of spin when the hairpin is struck is important. The spin depends on the friction between the surface of the string and the cork leather of the shuttle, but the proper amount of spin when hitting the hairpin has not been fully investigated. Therefore, the inventors of the present invention focused on the degree of spin on the hairpin, and repeated trial hits while changing the surface frictional force of the string. As a result, the player found the degree of spin on the hairpin. The surface frictional force of the string that feels good was identified.

Hereinafter, the structure of the string of the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of the string of the present embodiment. The cross-sectional structure of the string of the present embodiment is not limited to the configuration shown in FIG. 1, and can be changed as appropriate.

As shown in FIG. 1, the string 10 is configured by forming a coating film 16 around a thread-like structure 13 composed of a core thread 11 and side threads 12a and 12b. The thread-like structure 13 is formed by braiding side threads 12a and 12b around a core thread 11 of a multifilament. 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.

A coating film 16 having a predetermined film thickness is formed around the filamentous structure 13 by coating the inside with polyamide or the like and then coating the surface layer with polyurethane. That is, the coating film 16 is composed of a two-layer structure of an inner coating layer (inner layer) and an outer coating layer (surface layer), and the frictional force (friction coefficient) of the outer coating layer is higher than that of the inner coating layer. ing. The coating film 16 may be made of polyurethane only. The materials of the core yarn 11 and the side yarns 12a and 12b are not particularly limited, but for example, polyamide and polyester are used. In the following description, the film thickness t of the coating film 16 indicates the thickness of the filamentous structure 13 from the outermost surface.

Subsequently, with reference to FIG. 2, the relationship between the film thickness of polyurethane on the surface layer of the coating film and the string gauge will be described. FIG. 2 is a diagram showing the relationship between the film thickness of polyurethane and the string gauge of the present embodiment. In FIG. 2, the horizontal axis represents the film thickness of polyurethane on the surface layer of the coating film, and the vertical axis represents the string gauge (outer diameter). The coating film is formed of polyurethane and polyamide as described above, and it is possible to increase the film thickness of polyurethane on the surface layer by reducing the film thickness of the inner polyamide. The gauge also shows the outer diameter when towing 25 pounds.

As shown in FIG. 2, when the hairpin was repeatedly tested while changing the surface friction force of the string, the player easily applied a spin to the shuttle when the surface friction force of the string was 9 [N] or more, and when it was 12 [N] or more. I found that I felt it was easier to spin the shuttle. Therefore, when the relationship between the film thickness of the coating film having a string surface frictional force of 9 [N] or more and 12 [N] or more and the string gauge was investigated, the results shown in the figure were obtained. Here, a string having a surface frictional force of 9 [N] or more will be described as a spin region, and a string having a surface friction force of 12 [N] or more will be described as a high spin region.

When the film thickness of polyurethane shown on the horizontal axis of FIG. 2 is 0 [μm], the range R1 of the string gauge of about 0.80 [mm] -0.94 [mm] is the spin region, and the string gauge is about. The range R2 of 0.94 [mm] or more is a high spin region. When the film thickness of polyurethane is 8 [μm], the string gauge in the range of about 0.50 [mm] -0.65 [mm] is the spin region, and the string gauge is about 0.65 [mm]. ] The above range R4 is a high spin region. That is, as the film thickness of polyurethane increases, the region where spin is likely to be applied expands, and it is possible to obtain a surface frictional force of 9 [N] or more even if the string gauge is small.

When the string gauge shown on the vertical axis of FIG. 2 is 0.50 [mm], the range R5 having a film thickness of 8 [μm] or more is a spin region. When the string gauge is 0.80 [mm], the polyurethane film thickness is in the range of 0 [μm] -2 [μm] R6 is the spin region, and the polyurethane film thickness is in the range of 2 [μm] or more. R7 is in the high spin region. That is, as the string gauge becomes larger, the region where spin is likely to be applied expands, and it is possible to obtain a surface frictional force of 9 [N] or more even if the polyurethane film thickness is small. As described above, the larger the polyurethane film thickness and the string gauge, the wider the region where spin is likely to be applied.

When the polyurethane film thickness is large, the surface frictional force of the string increases due to the increased grip force against the shuttle. Further, when the string gauge is large, the contact area between the surface of the string and the cork leather of the shuttle is increased, so that the surface frictional force of the string is increased. As described above, in the present embodiment, an appropriate surface frictional force is imparted to the surface of the string by adjusting the film thickness of the polyurethane and the string gauge. For example, a weight with cork leather attached to the contact surface is slid on the string surface stretched on the racket, and the measurement is performed using Autograph AG-IS (manufactured by Shimadzu Corporation).

Specifically, as shown in FIG. 5, a racket 17 on which a string 10 is stretched is placed on a horizontal table 20, and a plate-shaped weight 32 (1 [kg]) with cork leather 31 is placed. .. One end of the wire rod 33 is attached to the weight 32, and the other end of the wire rod 33 is attached to the chuck 42 of the tensile tester 40 (Autograph AG-IS) via the pulley 41. As the chuck 42 rises, the weight 32 on the surface of the string 10 is pulled, and the frictional force generated between the string 10 and the cork leather 31 is measured as the tensile force of the tensile tester 40. That is, the surface frictional force of the string 10 is the frictional force when the weight 32 of the weight 1 [kg] with the cork leather 31 is slid against the string 10.

By the way, when the film thickness of polyurethane is 8 [μm] or more, the spin performance (surface frictional force) reaches a plateau, and the practical range of use of the string gauge is 0.70 [mm] or less. Therefore, in the string of the present embodiment, an appropriate polyurethane film thickness is specified at 8 [μm] or less, and an appropriate string gauge is specified at 0.70 [mm] or less.

Hereinafter, the relationship between the polyurethane film thickness and the surface frictional force and the relationship between the string gauge and the surface frictional force will be described. FIG. 3 is a diagram showing the relationship between the film thickness of polyurethane and the surface frictional force of the present embodiment. FIG. 4 is a diagram showing the relationship between the string gauge and the surface frictional force of the present embodiment. In FIG. 3, the horizontal axis represents the film thickness of polyurethane, and the vertical axis represents the surface frictional force of the string. Further, in FIG. 4, the horizontal axis represents the size of the string gauge, and the vertical axis represents the surface frictional force of the string.

As shown in FIG. 3, when the film thickness of the polyurethane was changed to 0 [μm] -10 [μm] using a string having a string gauge of 0.67 [mm], the film thickness was 0 [μm] -6. At [μm], the surface frictional force of the string increases sharply, and when the film thickness is 6 [μm] or more, the surface frictional force increases slowly. At this time, when the film thickness is 2 [μm] or more, the holding force against the shuttle becomes strong, and the surface frictional force of the string becomes 9 [N] or more, so that spin is easily applied. Further, when the film thickness exceeds 6 [μm], the holding force against the shuttle becomes stronger, and the surface frictional force of the string becomes 12 [N] or more, which makes it easier to apply spin.

As shown in FIG. 4, when the string gauges were changed using strings having a polyurethane film thickness of 0 [μm] -10 [μm], the string gauge became larger and the surface area of the string increased. Surface friction force increases. When the string gauge is 0.61 [mm] or more, the surface frictional force of the string is 9 [N] or more for a string having a polyurethane film thickness of 4 [μm] or more, and spin is easily applied. Further, when the string gauge is 0.67 [mm] or more, the surface frictional force of the string having a polyurethane film thickness of 2 [μm] or more is 9 [N] or more, and spin is easily applied, which is 6 [μm]. ] Or more, the surface frictional force of the string is 12 [N] or more, and spin is more easily applied.

From the above, the film thickness of the polyurethane on the surface layer of the coating film is preferably 2 [μm] or more, and particularly preferably 6 [μm] or more. The string gauge is preferably 0.61 [mm] or more, and particularly preferably 0.67 [mm] or more. As described above, the film thickness of polyurethane is preferably 8 [μm] or less at which the spin performance reaches a plateau, and the string gauge is preferably 0.70 [mm] or less, which is a practical range of use. Further, as will be described in detail later, even if the surface layer of the coating film is formed of rubber, it is possible to obtain sufficient spin performance with the same film thickness and string gauge.

Next, in order to select the optimum material, the surface friction force of the string is increased by forming the surface layer of the coating film with three types of polyamide with terpene resin added, polyurethane with excellent production stability, and rubber with excellent friction. It was measured and compared with the surface frictional force of the string on which the surface layer of the coating film was formed of polyamide. Further, as a common condition, the string gauge was set to 0.67 [mm], and the film thickness of the surface layer of the coating film was set to 10 [μm]. As a result, the results shown in Table 1 were obtained. Terpene resin is a tackifying resin processed from turpentine oil or orange oil.

The surface frictional force of the string using polyamide added with terpene resin is 7.6 [N], which is larger than the surface frictional force of 6.3 [N] of the string using polyamide, but spin is easily applied. It was less than 9 [N]. On the other hand, the surface frictional forces of the strings using polyurethane and rubber are 12.5 [N] and 21.4 [N], respectively, which is higher than the surface frictional force of 6.3 [N] of the strings using polyamide. It was 9 [N] or more, which made it easier to spin. From this, it was found that sufficient frictional force can be obtained by using polyurethane and rubber as coating agents.

Therefore, when spinning the shuttle with a string, polyurethane or rubber is preferably used as the material of the surface layer of the coating film. Further, from the viewpoint of processing stability, it is more preferable to use polyurethane. The material for the surface layer of the coating film is not limited to the above materials, and may be any material that makes the surface frictional force of the string 9 [N] or more. For example, even in the case of polyamide to which polyamide or terpene resin is added, the coating film can be coated by adjusting the film thickness of the coating film and the size of the string gauge to set the surface frictional force of the string to 9 [N] or more. It can be used as a material. Further, as long as the surface frictional force of the string is 9 [N] or more, the surface layer may be formed of the same material as the inside of the coating film, for example, polyamide.

(Example)
Hereinafter, the present invention will be described in more detail based on Examples, but these are described for the sake of explanation, and the scope of the present invention is not limited to the following Examples.

A string with a string gauge of 0.67 [mm] and a polyurethane film thickness of 0 [μm], 4 [μm], and 6 [μm] were prepared and a hairpin test hit evaluation was performed. Ten intermediate and advanced players in their 20s and 50s divide the degree of spin into 6 stages: "well hang", "hang", "somewhat hang", "normal", "somewhat not hang", and "not hang". Evaluated. As a result, the results shown in Table 2 were obtained.

The polyurethane having a film thickness of 0 [μm] was evaluated as a reference (usually). On the other hand, when the film thickness of polyurethane was 4 [μm], 9 people evaluated it as "hanging" and only 1 person evaluated it as "not hanging". In addition, when the film thickness of polyurethane is 6 [μm], 4 people evaluate it as "well hang", 3 people evaluate it as "hang", and 2 people evaluate it as "somewhat hang", and only 1 person says "it does not hang". evaluated. That is, for both strings having a polyurethane film thickness of 4 [μm] and 6 [μm], 9 out of 10 people evaluated that the spin was higher than "normal". As described above, when the film thickness of polyurethane is 4 [μm] and 6 [μm], that is, the surface frictional force is 9 [N] or more and 12 [N] (see FIG. 3), it is evaluated that spin is easily applied. ..

As described above, in the string 10 of the present embodiment, since the surface frictional force becomes large, the shuttle bounced by the string 10 is easily spun, and the hairpin performance can be improved.

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 attached 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, in the present embodiment, the thread-like structure 13 has a structure in which the side threads 12a and 12b are braided around the core thread 11, but it may be composed of only the core thread 11. Further, although the side yarns 12a and 12b are braided around the core yarn 11, only one side yarn may be wound around the core yarn 11. Further, the side yarns may be wound in two layers, and the gauges (outer diameters) of the side yarns of the first layer and the second layer may be different.

Further, in the present embodiment, the core yarn 11 and the side yarns 12a and 12b may be composed of either a multifilament or a monofilament, and the number is not limited. When the core yarn 11 is a monofilament, the cross section is not limited to a circular shape, and the cross section may be a polygon (for example, a pentagon). Further, hollow fibers may be used for the core yarn 11 and the side yarns 12a and 12b.

Further, in the present embodiment, the structure in which the string 10 is formed of synthetic fibers is not limited to this. The thread-like structure 13 of the string 10 may be formed of a natural string made of natural fibers such as sheep intestine and whale muscle.

Further, in the present embodiment, the string 10 is used for the warp and weft of the racket, but it may be used for any of the warp and weft.

The present invention is a racket string stretched on a racket frame, and has an effect that the spin performance when a hairpin is struck can be improved.

10 String 11 Core thread 12a, 12b Side thread 13 Thread-like structure 16 Coating film

Claims (6)

It has a filamentous structure and a coating film formed around the filamentous structure.
When the surface friction force of the coating film is 9 [N] or more, which is measured as the static friction force when a weight with a weight of 1 [kg] with cork leather is slid while being stretched on a racket and placed horizontally. A string for a racket that is characterized by being there. The coating layer is composed of the surface layer and the inner layer of the two-layer structure, in claim 1, wherein the measuring the surface friction force of the surface to be measured under the same conditions may be greater than the surface friction of the inner layer The listed racket string. The racket string according to claim 1 or 2, wherein at least the surface layer of the coating film has a property of increasing the grip force as the film thickness increases. The racket string according to claim 3, wherein at least the surface layer of the coating film has a film thickness of 2 [μm] or more. The racket string according to any one of claims 1 to 4, wherein the outer diameter is 0.61 [mm] or more. The racket string according to any one of claims 1 to 5, wherein at least the surface layer of the coating film is formed of polyurethane or rubber.

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