KR20170050345A - Shaft for badminton racket and badminton racket comprising of the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a shaft for a badminton racket and a badminton racket including the same, wherein at least an upper portion and a lower portion of the shaft for a badminton racket according to the present invention are formed in a cross- The high torsional resistance that suppresses the torsional vibration of the head portion and the good elastic characteristic that gives the excellent feeling of stability at the time of hitting the ball are balanced without sacrificing sufficient mechanical strength against impact at the time of high-speed swing and hit by the shuttlecock, The badminton rackets are lightweight, flexible enough to withstand the mechanical strength, have excellent controllability and fast swing characteristics, and exhibit an excellent shuttlecock "feeling of holding".

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a shaft for a badminton racket and a badminton racket including the same,

The present invention relates to a shaft for a badminton racket and a badminton racket including the same, and more particularly, to a badminton racquet having a shaft for a badminton racket and a badminton racket including the same, At least the upper portion and the lower portion of the upper and lower portions are formed in a plurality of cross-sectional shapes so as to provide a good elasticity to the badminton racquet so as to give a high degree of stability to the badminton racquet while having high torsional resistance The center portion is a cylindrical badminton racket shaft and a badminton racket including the same.

The prototype of the badminton game was a game where a ball made of sheepskin in the Punah region of India was played with the palm of a hand. The British officer in India introduced the Puna game in the badminton village of the grotto of England after returning home. It was transformed into a game where a bird's feathers were inserted into corks and sent out with a racket. The name of the badminton village was settled as the name of the game.

Badminton is an athletic sport where a shuttlecock is hit by a racket over a net and the shuttlecock has a special aerodynamic nature from its morphological features. Air resistance. The shuttlecock typically produces a variety of changes from 0 to 260 km / h, especially over 300 km / h. The combination of a white shuttlecock with a changeable line and an elegant rhythm is the ultimate in physical artistry And it has been adopted as a formal sport for the Olympic Games in the summer of 1992.

Such a badminton is a gentlemanly movement that requires a whole body movement consisting of running, leaping, body rotation and flexion and extension, and is carried out without physical contact with the net at the center. Since it is an indoor game, Can be freely controlled according to the physical capacity and characteristics of the individual, has no adherence to the ages of men and women, has a great value as a recreation, and does not require a large cost for facilities and equipment .

Especially badminton competition requires to hit the shuttlecock in a relatively narrow coat, so players need more agile and faster swinging action than a game like tennis.

Therefore, the badminton racket has to be structured to meet the player's agile and quick swing motion, so that the condition required for the badminton racket is not only lightweight but also maintains a moderate degree of flexibility, .

In order to enable the high speed swing, which is the most important feature of badminton, it is necessary to be able to minimize the resistance by the wind during the swing but to be lightweight, and also to have sufficient mechanical strength and torsional resistance to withstand high- , But since these elements require mutually conflicting characteristics, it is not easy to satisfy all of these elements at the same time, and therefore a proper combination of these elements is important.

Concretely, there is a problem that weight reduction for achieving excellent controllability and high-speed swing characteristics, flexible elasticity of moderate degree, and minimized structure of wind pressure area are premised on sacrifice of mechanical strength.

Especially in badminton rackets, shafts are one of the key factors that plays a key role in the power transmission of badminton racquets. Shafts generate strong repulsive force due to their elasticity at the impact of shuttlecock, .

Generally, the stiffness of the shaft increases as the stiffness increases and the control surface rises as the flexible surface increases. As the balance point becomes head heavy, the power surface rises and the headlight light has been considered to be very difficult to achieve harmonization because of the elevated control surfaces, so these elements have been chosen to suit the individual's wrist power and swing speed.

Further, the direction of the bending vibration of the shaft, which has a decisive influence on the stroke, must be made in the direction of the swing motion after the impact of the shuttlecock due to the swing and in the opposite direction thereof, and the bending vibration in the left- Can not do it.

Thus, the deflection of the shaft affects the RB, and the deflection of the shaft appropriately distributes the swing power, so that the elasticity is added at the time of impact of the shuttlecock, so that the shuttlecock is instantaneously attached to the head of the badminton racket, feeling of holding '.

For the above reasons, conventionally, a material made of aluminum alloy or steel has been mainly used as a material of the shaft. However, recently, except for a low-priced product, the metal material as described above is hardly used. A prepreg which is a composite material of semi-hardened "Stage" impregnated or processed with a thermosetting resin such as an epoxy resin or a phenol resin as a matrix after the surface treatment of a light carbon fiber or the like is used , Excellent physical properties such as strength, stiffness, corrosion resistance, fatigue life, abrasion resistance, impact resistance, light weight, vibration damping property, high elasticity and inelasticity.

A typical badminton racquet shaft using a prepreg as described above is formed of a hollow cylindrical structure having a diameter of about 7.0 mm, about 7.2 mm, or about 7.5 mm, and a polyepoxy or poly Ester or polyphenol paint layer.

The production of the racket shaft for badminting using such a prepreg is carried out by winding the prepreg strip in a winding manner or in a full-bodied manner, and the winding method is easy to manufacture and the production cost is relatively low While there is a problem that the balance strength and torsional strength of the one strength are low, the method of making the whole feed is a method mainly used for a golf shaft, and it has an advantage of excellent strength balance and a somewhat high torsional rigidity. However, There is a problem that it is relatively high.

As mentioned above, the badminton racket shaft requires a proper combination of mutual advantages such as moderate stiffness, moderate bending resilience, and good torsional resistance, and each individual needs to be aware of his or her athletic ability, physical condition, And the like, and selects an appropriate one of the above-mentioned elements having a high weighting factor corresponding to itself.

8 and 9, the conventional badminton racket 100 'includes an elliptical frame 11 for minimizing a wind pressure area during a swing and a gut, which is installed longitudinally and laterally in the frame 11, a cylindrical shaft 1 ', a T-shaped connector 25 and a grip 30. The head 10 is made of a synthetic resin,

The both end portions 11a of the frame 11 and the upper end portion 1a 'of the shaft 1' are connected to both the side branch portions 25a and the lower branch pipe portions 25b of the T- Respectively.

The grip 30 includes a main body 31 formed of wood and having a butt 33 at its distal end and a front cap 33 and an end cap 34 at the front and rear ends thereof, On the outer surface of the main body 31, a grip tape 35 is wound.

The lower end of the shaft 1 'is fitted in a through hole (not shown) formed in the main body 31 and is formed in a direction orthogonal to the through hole (not shown) in the area of the front cap 33 And is fixed by a key (not shown) fitted in the through hole (not shown).

However, since the shaft 1 'of the conventional badminton racket 100' as described above is entirely formed in a cylindrical shape, when the strength of the shaft 1 'is made flexible, not only the power resistance is inferior but also the torsional resistance When the shuttlecock is impacted on the area adjacent to the frame 11 which is deviated from the central portion of the head 10, the torsional vibration becomes strong, which may cause deviation or error in the traveling line of the shuttlecock. On the other hand, 1 ') is stiffened, the power and the resistance to torsion are improved. However, when the swing speed is insufficient, it is difficult to transfer enough kinetic energy to the shuttlecock, .

Therefore, in the conventional cylindrical shaft 1 ', it is difficult to harmonize the strength, elasticity and torsional resistance characteristics of the shaft 1'.

Korean Patent Registration No. 1366583 (Feb. 18, 2014) discloses a shaft having an elliptical cross section or a shaft having a plurality of elliptical shaft sections having an elliptical cross section formed on a shaft having a circular section in order to increase the above- The badminton racket having the above-described conventional elliptical shaft has excellent torsional resistance, but the flexibility of the shaft in the hitting direction is excessively increased, so that the power and the power of the swing are inferior at the time of swing In addition, there is a problem that the area of the wind pressure due to the shaft is increased.

  Korean Patent Laid-Open Publication No. 10-2012-0056740 (Apr. 24, 2012) discloses a badminton racket having a shaft having a partition wall. However, it is difficult to manufacture a shaft in which a plurality of partition walls are formed in the through- The flexibility or strength of the strength is undermined, so that not only the controllability is deteriorated but also there is a concern that the beginner may be injured by the wrist.

Korean Registered Patent No. 1366583 (Feb. Korean Patent Laid-Open No. 10-2012-0056740 (2012.06.04.)

Accordingly, it is a first object of the present invention to provide a safety device capable of suppressing the torsional vibration of the head portion even when the shuttlecock is offset from the center portion of the head frame, thereby providing a high torsional resistance capable of transmitting the shuttlecock to an intended accurate position, The present invention relates to a badminton racquet shaft, and more particularly, to a badminton racquet shaft having a good elasticity characteristic that gives a badminton racquet a moderate degree of flexibility.

A second object of the present invention is to provide a shaft for a badminton racket having a sufficiently strong mechanical strength capable of withstanding a high-speed swing and an impact upon hitting a shuttlecock while minimizing wind pressure resistance during swing.

A third object of the present invention is to provide a shaft for a badminton racket having a controllability and a high-speed swing characteristic with a flexible degree of elasticity and a moderate degree of weight, without sacrificing mechanical strength, in addition to the above objects.

A fourth object of the present invention is to provide a shaft for a badminton racket capable of imparting a superior feeling of holding to a shuttlecock in addition to all of the above objects.

A fifth object of the present invention is to provide a badminton racket to which the shaft according to the above-described objects is applied.

According to a preferred aspect of the present invention for achieving the first to fourth objects of the present invention, a shaft for a badminton racket in which a through hole is formed in the longitudinal direction, A shaft for a badminton racket having a polygonal upper end portion and a lower cylindrical portion integrally formed therewith is formed integrally with the shaft for a badminton racket having a length ratio of a cylindrical upper portion = 1: 0.15 to 0.20: 0.85 to 0.80 / RTI >

According to another aspect of the present invention, there is provided a shaft for a badminton racquet having a through hole formed in a longitudinal direction thereof, And a shaft portion in a central region between the polygonal upper end portion and the polygonal lower end portion and a lower lower portion of the polygonal lower end portion integrally formed with the shafts for the badminton racket, Shaft for Badminton racquet is provided which has a length of cylindrical part: a length of polygonal lower end part: length ratio of stab part = 1: 0.15 to 0.20: 0.40 to 0.45: 0.15 to 0.20: 0.15 to 0.25.

The polygonal upper end portion and the lower end portion are formed to have an octagonal shape and the diameter of the cylindrical portion is formed to have a diameter in contact with an octagonal end face of the octagonal upper end portion and the lower end portion, have.

The above-mentioned plug portion may be formed in a cylindrical shape.

In addition, the boundary between the polygonal upper end portion and the lower end portion and the cylindrical portion may be gradually changed.

In addition, the boundary between the polygonal lower end portion and the mounting portion may be gradually changed.

The shaft for badminton racket described above may be formed of a thermosetting molding of carbon fiber prepreg.

In order to achieve the fifth object of the present invention, a badminton racket including a shaft for a badminton racket is provided according to a preferred embodiment of the present invention.

The multi-angle upper end portion and the lower end portion of the shaft for a badminton racket described above may be formed in an octagonal shape.

In this case, the vertical portion of the T-shaped joint is inserted into the through hole of the upper end of the polygonal upper end of the shaft for badminton racket, the wing portion of the T-shaped joint is fitted to both ends of the frame forming the head of the badminton racket, The joint and regions adjacent thereto can be coated with a prepreg and cured to form a neck.

Both ends of the frame may be formed in a hollow shape having a flat elliptical shape.

The shaft for a badminton racket according to the present invention has a high torsional resistance that suppresses the torsional vibration of the head portion and a good elasticity that gives an excellent stability feeling in the hit without sacrificing a sufficient mechanical strength for impact at the time of high- The badminton racket adopts this characteristic, and it is lightweight without any sacrifice of mechanical strength, it has moderate elastic resilience with excellent controllability and fast swing characteristics, and has a superior shuttlecock "feeling of holding" .

1A, 1B and 1C are a perspective view, a plan view and a bottom view, respectively, of a shaft for badminton racket according to the present invention.
FIG. 2 is a plan view of a badminton racket according to the present invention to which a shaft for a badminton racket according to the present invention shown in FIG. 1A is applied.
Figs. 3A and 3B are partially enlarged perspective views of the neck adjacent region and the grip adjacent region of Fig. 2, respectively.
4 is a perspective view of FIG. 3A.
5 is a perspective view of FIG. 3B.
6 is a perspective view of a frame and a neck portion of the head shown in Fig.
7 is a typical cross-sectional structural view of the neck connecting portion.
8 is a top view of a typical badminton racket.
Figure 9 is a front perspective view of the neck connection of Figure 8;

As used throughout this specification, the term " polygonal " is defined to mean a polygonal cross-section of at least hexagonal, and specifically includes hexagonal, octagonal, polygonal, It is defined to mean a sieve, and in particular is octagonal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings.

1A, 1B, and 1C are a perspective view, a plan view, and a bottom view, respectively, of a shaft 1 for a badminton racket according to the present invention.

In the illustrated example, the shaft 1 for a badminton racket according to the present invention is different from the conventional shaft in which the cross-sectional shape is formed entirely cylindrically, The lower end portion 4 and the cylindrical portion 3 at the center thereof are integrally formed with the lower end portion of the polygonal upper end portion 2 and the lower end of the polygonal lower end portion 4, A through hole 6 is formed in the lower part 4 and the part 5 at the same time.

The shaft 1 for a badminton racket according to the present invention can be made of a composite prepreg using a composite prepreg, as in the usual case, but it is preferably manufactured in a cost- The shaft 1 for a badminton racket according to the present invention has a diameter of about 7.0 mm to about 7.5 mm and a diameter of the through hole 6 of about 2.5 to 3.8 mm, And a polyepoxy or polyester or polyphenol paint layer having a thickness of about 0.3 mm may be coated on the surface.

It is needless to say that the above-described prepreg woven carbon (graphite) fiber, boron fiber and the like used for manufacturing the shaft 1 for a badminton racket according to the present invention may be used.

The shaft 1 for a badminton racket according to the present invention includes the shaft 1 for the badminton racket described above and the length of the polygonal upper end portion 2: the length of the cylindrical portion 3: the length of the polygonal lower end portion 4: 0.15 to 0.20: 0.40 to 0.45: 0.15 to 0.20: 0.15 to 0.25, and particularly preferably 1: 0.17 to 0.18: 0.43 to 0.45: 0.17 to 0.18: 0.20 to 0.22 Lt; / RTI >

The present invention is not limited to this configuration. In some cases, only the polygonal upper end portion 2 and the cylindrical portion 3 are integrally formed with each other And it is also within the scope of the present invention.

In this case, the length ratio of the shaft 1 for a badminton racket: the polygonal upper end portion 2: the length of the cylindrical portion 3 is in the range of 1: 0.15 to 0.20: 0.85 to 0.80, 0.17 to 0.18: 0.83 to 0.82.

 In the shaft 1 for badminton racket according to the present invention, when the length ratio of the polygonal upper end portion 2 to the entire length of the shaft 1 for badminton racket is less than 0.15, there is a fear that the torsional resistance is unsatisfactory Inversely, if it exceeds 0.20, the flexibility or elasticity of the shaft 1 for badminton racket may be excessively lowered, which is not preferable.

In the shaft 1 for a badminton racket according to the present invention, even when the polygonal lower end portion 4 is provided, the length ratio of the polygonal lower end portion 4 to the entire length of the shaft 1 for badminton racket, Is in the range of 1: 0.15 to 0.20. When the length ratio of the polygonal lower end portion 4 to the entire length of the shaft 1 for badminton racket is less than 0.15, torsional resistance may be unsatisfactory, which is not preferable , And conversely, if it exceeds 0.20, the flexibility or elasticity of the shaft 1 for badminton racket may be excessively lowered, which is not preferable.

The polygonal lower end portion 4 is fixed in contact with the front cap 32 of the grip 30.

On the other hand, the lower end of the cylindrical portion 3 in the case where the polygonal lower end portion 4 is present or the polygonal lower end portion 4 is not present is formed in a through hole (not shown) formed in the grip 30 And is firmly fixed by a key (not shown) inserted into another through hole (not shown) formed perpendicular to the main body 31 of the grip 30 with respect to the through hole (not shown).

It should be noted that the shape of the above-mentioned plug 5 may be generally hollow, cylindrical, or may be polygonal.

In the shaft 1 for a badminton racket according to the present invention in which the polygonal lower end portion 4 and the pin portion 5 are formed, the length ratio of the shaft 1 for the badminton racket: cylindrical portion 3 If it is less than 0.40, the elasticity of the shaft 1 for badminton racket may be undesirably lowered. Conversely, if it exceeds 0.45, it may adversely affect the torsional resistance, which is also undesirable.

The shape of the polygonal upper end portion 2 and / or the polygonal lower end portion 4 of the shaft 1 for a badminton racket according to the present invention may be various shapes such as a hexagonal, octagonal, However, it may be preferable that the octagonal shape is used in particular in terms of easiness of fabrication and increase of torsion resistance.

On the other hand, the diameter of the cylindrical portion 3 may be any of those in which the diameter of the cylindrical portion 3 is circumscribed or in contact with the end face of the polygonal upper end portion 2 and / or the lower end portion 4, It may be desirable to have a diameter in the form of being in contact with the end faces of the polygonal upper end portion 2 and / or the lower end portion 4 in terms of imparting resistance.

In addition, the shape of the through hole 6 which passes through the entire length of the shaft 1 for a badminton racket is generally circular in cross section, but this is not restrictive and optional in the present invention.

It should be noted that the shape of the outer periphery of the plug 5 may also be formed in a cylindrical shape, but it may be formed in any other polygonal shape.

The length of the lower end portion of the plug 5 or the cylindrical portion 3 inserted into the grip 30 has a length ratio of 0.15 to 0.25 with respect to the entire length of the shaft 1 for badminton rackets, If the ratio of the length of the bottom portion of the cylindrical portion 3 to the length of the bottom portion of the cylindrical portion 3 with respect to the entire length of the shaft 1 for badminton racket is less than 0.15, Conversely, if the ratio exceeds 0.25, the total weight of the badminton racket 100 is increased, which may cause deterioration of usability, which is also undesirable.

It is preferable that the boundary region between the polygonal upper end portion 2 and / or the lower end portion 4 and the cylindrical portion 3 and / or the plug portion 5 is gradually changed so that the division can not be clearly distinguished. In order to reduce the influence on the flexibility or elasticity of the shaft 1 for badminton racket according to the present invention.

The shaft 1 for badminton racket described above may be formed of a thermosetting molded product obtained by winding a carbon (graphite) fiber prepreg or a boron fiber prepreg and then heat-curing the same.

Next, a badminton racket 100 according to the present invention to which a shaft 1 for a badminton racket according to the present invention is applied will be described.

FIG. 2 is a plan view of a badminton racket 100 according to the present invention to which a shaft 1 for a badminton racket according to the present invention of FIGS. 1A and 1B is applied. A neck 20 in which a polygonal upper end portion 2 of a shaft 1 for badminton racket according to the present invention is joined to the frame 10 and a shaft 20 for a badminton racket according to the present invention, (See reference numeral 5 in FIG. 1A) or the polygonal lower end portion 4 located below the polygonal lower end portion 4 of the shaft 1 for a badminton racket according to the present invention does not exist And a grip 30 in which the lower end of the cylindrical portion 3 is inserted.

The grip 30 is formed of a hard wood and has a front cap 32 and an end cap 34 attached to a front end and a rear end of a main body 31 having a butt 33 formed at an end thereof, 31 and the end cap 34 are gripped with a grip tape 35 for improving grip feeling.

Reference numeral 16 denotes a grommet as an elastic cushioning member against the tightening force of a gut (not shown) attached to the frame 10.

 Next, a configuration in which the shaft 1 for a badminton racket according to the present invention is assembled and applied to the neck 20 will be described first with reference to FIG.

In the illustrated example, the shaft 1 for a badminton racket according to the present invention is fitted to the hollow both ends 14 of the frame 11 constituting the head 10 via the T-shaped joint 21, Reinforced cured layer 22 formed by wrapping the prepreg reinforcing ribs in the prepreg reinforcing ribs and curing and surface-treating the regions.

The vertical portion 21a of the T-shaped joint 21 is fitted in the through hole 6 of the polygonal upper end portion 2 of the shaft 1 for a badminton racket according to the present invention, The wings 21b of the T-shaped joint 21 are fitted to the hollow both ends 14 of the frame 10 forming the head 10 and the T-shaped joint 21 and the frame 10, A carbon (graphite) fiber prepreg is coated on the region adjacent to the hollow both ends 14 and a hardened prepreg reinforcing hardened layer 22 is formed to thereby form the neck 20 as a whole.

The hollow upper and lower ends 14 of the frame 10 are formed in a flat elliptical shape so that a smooth overall appearance can be imparted when the coating is cured with a carbon (graphite) fiber prepreg.

The prepreg-cured layer 12 of the frame 10 may have a circular shape or an elliptic shape for minimizing the wind pressure area, and the core 13 may be present therein. The core 13 may be made of various lightweight materials, but is typically formed by filling polyurethane foam.

The neck 20 of the badminton racket 100 according to the present invention is formed such that the outer shape of the polygonal upper end portion 2 of the shaft 1 for a badminton racket according to the present invention is formed in a plurality of normal shapes, The cured layer 22 also has a polygonal shape as a whole. As a result, as shown in Fig. 3A, the neck portion 20 is formed in a polygonal shape, specifically, an octagonal shape, and the polygonal upper end portion 2 The polygonal image gradually disappears and the cylindrical portion 3 is changed to a cylindrical shape.

3A, reference numeral 15 denotes a gut through hole 15 formed in the grommet 16.

3B is a view showing the case where the polygonal lower end portion 4 is formed above the grip 30 and is in a state in which the plug portion 5 is inserted into the grip (refer to reference numeral 30 in FIG. 2) A polygonal lower end portion 4 is formed above and adjacent to the tapped cap 32, and a polygonal shape is gradually removed therefrom, thereby showing a state in which the cylindrical portion 3 in a cylindrical shape is located.

The conventional structure in which the above-mentioned plug 5 or the lower end of the cylindrical portion 3 is fixed in the grip 30 has already been described above, so that further detailed description thereof will be omitted.

3 is a perspective view of FIG. 3B. FIG. 6 is a perspective view of the frame 10 and the neck portion 20 of the head 10 of FIG. 2 without gutting. FIG. And these drawings are merely illustrative of the actual product state, and the construction thereof has already been described in detail, so that further description of each component will be omitted.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention Which is also within the scope of the present invention.

1: Shaft according to the present invention
2: polygonal upper end portion 3: cylindrical portion
4: polygonal lower end portion 5:
6: Through the hole
100: Badminton racket according to the present invention
10: Head
11: Frame 12: prepreg cured layer
13: core 14: hollow (positive) end
15: gut through hole 16: grommet
17: gut or string
20: Neck
21: T-shaped joint 21a:
21b: wing portion 22: prepreg reinforcing hardening layer
30: grip
31: main body 32: front cap
33: butt 34: end cap
35: Grip tape

Claims (11)

A shaft for a badminton racket in which a through hole is formed in the longitudinal direction,
A polygonal normal upper end portion having a cross-sectional shape formed generally in a polygonal shape and a cylindrical portion below the polygonal upper end portion are integrally formed,
Shaft for badminton racket described above: length of polygonal upper end portion: length ratio of cylindrical portion = 1: 0.15 to 0.20: 0.85 to 0.80. A shaft for a badminton racket in which a through hole is formed in the longitudinal direction,
A cylindrical upper end portion and a polygonal lower end portion which are formed in a polygonal cross-sectional shape and a cylindrical portion in a central region between the polygonal upper end portion and the polygonal lower end portion and a lower portion of the polygonal lower end portion,
The badminton rackets for badminton racket described above are as follows: Length of polygonal upper end part: Length of cylindrical part: Length of polygonal lower part: Length ratio of pin part = 1: 0.15 to 0.20: 0.40 to 0.45: 0.15 to 0.20: 0.15 to 0.25 shaft. 3. The apparatus according to claim 1 or 2, wherein the polygonal upper end portion and the lower end portion are formed to have an octagonal shape and the diameter of the cylindrical portion is formed to have a diameter in contact with an octagonal end face of the octagonal upper end portion and the lower end portion, Wherein the through hole is formed in a circular through-hole. The badminton racquet shaft according to claim 2, wherein the rack is cylindrical. The badminton racquet shaft according to claim 1 or 2, wherein the boundary between the polygonal upper end portion and the lower end portion and the cylindrical portion is gradually changed. 3. The badminton racquet according to claim 2, wherein the boundary between the polygonal lower end portion and the pin portion is gradually changed. The badminton racquet according to any one of claims 1 to 3, wherein the shaft for the badminton racket is constituted by a thermosetting molding of a carbon fiber prepreg. A badminton racket including a shaft for a badminton racket according to any one of claims 1 to 3. The badminton racquet according to claim 8, wherein the multi-angled upper end portion and the lower end portion of the shaft for badminton racket are generally formed in octagonal angles. 9. The badminton racket according to claim 8, wherein a vertical portion of the T-shaped joint is inserted into the through hole of the polygonal upper end portion of the shaft for badminton racket, the wing portion of the T-shaped joint is fitted to both ends of the frame forming the head of the badminton racket, A badminton racquet wherein the T-shaped joint and adjacent regions thereof are coated with a prepreg and cured to form a neck. The badminton racquet according to claim 10, wherein both ends of the frame are formed in a hollow shape having a flat elliptical shape vertically.

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