JP2003320058A - Frame for badminton packet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a badminton racket frame of light weight improved in a deflection characteristic of a shaft and provided with the shaft of high impact resilience. <P>SOLUTION: In this badminton racket frame of which the shaft 2 is connected to an elliptic-ring-shaped hollow tubular frame 1 each other via joints 4, 4a the joint 4 has a recess 5 engaged with and bonded to an upper end outer circumferential part of the shaft, and both shoulder parts 7, 7 extended substantially horizontally from both sides of the recess to be engaged with and bonded to an inner part of the frame. The shaft 2 is preferably a hollow tubular shaft, and a central lower face part of the joint 4a is engaged with and inserted into an upper end tube of the shaft, and the recess 5 is brought into an annular recess 5a engaged with an upper end of the shaft. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a badminton racket frame in which a shaft and a hollow tubular frame formed in an elliptical ring are connected to each other through a joint.

[0002]

2. Description of the Related Art As a conventional badminton racket frame, the one disclosed in Japanese Utility Model Laid-Open No. 60-99965 is known. In this known badminton racket, a T-shaped joint consisting of a pair of tubular horizontal supports and a tubular vertical support is used as a joint, and the horizontal support is inserted into the openings at both ends of the tubular frame, and the vertical support is provided with a hollow tubular shaft. Is fitted and inserted into the upper end of the frame, and the outer periphery of the joint between the frame and the shaft is coated with a fiber reinforced resin.

[0003]

As the T-type joint, a solid structure made of metal is actually used. However, in order to reliably join the shaft and the frame with such T-type joint. It is necessary to form its vertical support relatively long and insert and bond it in the shaft relatively long. For this reason, the weight of the joint formed of aluminum alloy can be reduced as much as possible.
It weighed 6g, which was an obstacle to reducing the overall weight of the badminton racket.

Further, since the vertical support portion of the T-shaped joint is inserted and adhered inside the shaft, the torsion torque (rotation torque) of the frame joined by this T-joint with respect to the shaft is equal to that of the inner peripheral surface of the shaft and the joint. It is applied to the outer peripheral surface of the vertical support, and it is necessary to lengthen the adhesive surface in the axial direction in order to counter this twisting torque, which makes the shaft rigid at the joint insertion part without bending. Next, the bending characteristics of the shaft were diminished.

Furthermore, in a badminton racket using a T-shaped joint, the upper end of the shaft terminates at substantially the same level as the lower end surface of the frame and cannot enter the frame, so the effective length of the shaft is gripped. It was limited from the top of the part to the bottom of the frame.

The present invention has been made in view of the above problems, and an object thereof is to improve the weight by improving a joint portion for interconnecting a shaft and a hollow tubular frame formed in an elliptical ring shape. Another object of the present invention is to provide a badminton racket frame which improves the bending characteristics of the shaft and enables high resilience of the shaft.

[0007]

In order to achieve the above object, according to the present invention, there is provided a badminton racket frame in which a shaft and a hollow tubular frame formed in an elliptical ring are connected to each other through a joint. The joint has a recess that fits and adheres to the outer peripheral portion of the upper end of the shaft, and both shoulders that extend substantially horizontally from both sides of the recess and that are fitted and bonded to the inside of the frame. As described above, the joint of the present invention can be made smaller than the conventional T-joint. Further, since the joint of the present invention is fitted and bonded to the outer peripheral portion of the upper end of the shaft, when the bonding area between the shaft and the joint is made the same as that of the conventional one, in the present invention, the bonding length of the joint in the shaft direction is reduced. Can be shorter than before.

Regarding the torsional torque, in the present invention, the adhesive surface between the outer peripheral surface of the shaft and the inner peripheral surface of the recess of the joint receives the torsional torque of the frame. Since the distance is increased by an amount corresponding to the wall thickness of the shaft, the twisting torque of the frame can be countered with a smaller bonding area than before. Therefore, it is not necessary to make the depth of the recessed portion longer than in the vertical supporting portion of the conventional T-joint. With the above characteristics, the size (volume) of the joint can be reduced and the weight can be reduced. Moreover, since the axial length of the bonded portion between the shaft and the joint can be shortened, the flexural characteristics of the shaft can be improved. Furthermore, since the upper end of the shaft is inserted near the center of the inside of the frame, the effective utilization length of the shaft can be increased and a high resilience of the shaft can be obtained.

[0009] Preferably, in the badminton frame of the present invention, the shaft is a hollow tubular shaft, and the central lower surface of the joint is inserted into the upper end tube of the shaft so that the concave portion fits into the upper end of the shaft. Is to As a result, the bonding area between the shaft and the upper end of the joint can be increased without increasing the vertical length of the joint, so that the rigidity of the frame in the torsional direction with respect to the shaft is increased and the surface stability of the frame is improved. Can be improved.

Preferably, in the above badminton frame of the present invention, the upper end surface of the joint is formed as a substantially flat surface or a slightly curved surface connecting the shoulder portions, and the shoulder portions have a lower center from both ends thereof. It is to form a taper surface toward. As a result, the axial length of the inner peripheral surface of the recess of the joint portion can be increased within a limited size, and the adhesion area with the outer peripheral surface of the shaft can be increased.

Further, preferably, in the badminton frame of the present invention, the tapered surface is formed in a concave shape toward the upper end surface side of the joint, whereby the bonding area between the joint and the shaft is maintained at a predetermined value. However, the weight of the joint can be further reduced.

More preferably, in the above badminton frame of the present invention, lower end portions of both ends of the frame fitted to the shoulder portion of the joint are formed as inclined surfaces corresponding to the tapered surfaces, and the inclined surfaces are the tapered surfaces. The frame is assembled to the joint in a state of abutting against the joint, and a joint coating material is coated in a substantially T shape on the outer periphery of the joint between the shaft and the frame. This further improves the connection between the frame and the joint, and also improves the connection between the frame and the shaft.

[0013]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 3
1 shows a first preferred embodiment of the present invention, FIG. 1 shows a badminton racket frame, 1 is a hollow tubular frame formed in an elliptical ring shape, 2 is a hollow shaft, 3 is a grip part ing. The hollow tubular frame 1 and the hollow shaft 2 are made of a fiber-reinforced thermosetting resin (FRP) mainly containing carbon fibers.

The frame 1 and the shaft 2 are connected via a joint 4 as shown in FIG. As shown in the vertical cross-sectional view of FIG. 3, the joint extends from the cylindrical recess 5 that fits into the outer peripheral portion of the upper end of the shaft 2, the ceiling surface 6 of the recess 5 and the left and right sides of the recess 5 to the outside. And a tapered portion 8-8 extending from the tubular shoulder portions 7-7 to the open end of the tubular recess 5.

The upper surface where the ceiling surface 6 and the two cylindrical shoulders 7-7 are integrated is preferably a curved surface along the elliptic curve of the frame 1, whereby the frame 1 will be described later. The upper surface of the joint 4 housed inside is in close contact with the inner peripheral surface of the frame. Further, the taper portion 8 may be a linear taper portion, but it is preferably a taper surface slightly concave toward the ceiling surface 6 side.

The joint 4 is made of metal, non-metal, resin made of thermoplastic resin, or thermosetting resin. Its weight is within the range of 0.8 g to 1.9 g. If the weight is less than 0.8g, the desired strength cannot be obtained, and 1.9g
If it exceeds, it will not be possible to meet the demand for weight reduction of the racket frame. When the joint 4 of the present invention is formed of an aluminum alloy as in the conventional case, the weight is 1.5 g, which is 0.1 g lighter than the conventional T-type joint of 1.6 g.

The axial length P of the recess 5 is 4.35.
When the length is less than 4.35 mm, it is not possible to obtain a sufficient adhesive area with the shaft 2 so that a desired torsion torque cannot be obtained and 6.00 mm is set in the range of mm to 6.00 mm. If exceeded, the joint cannot be built into the frame.

To connect the frame 1 to the shaft 2 using the joint 4, the recess 5 of the joint 4 is fitted to the upper end of the shaft 2 with an adhesive. Then
The free ends of the elliptical curved frame 1 are fitted to the left and right shoulders 7-7 of the joint with an adhesive. At this time, it is preferable that a portion of the lower end of the free end of the frame 1 that abuts the left and right tapered surface portions 8-8 of the joint 4 is formed in a tapered shape so as to be in close contact with the tapered surface portion 8-8. . Then, the outer periphery of the joint portion between the frame 1 and the shaft 2 is wrapped with a prepreg tape 9 of carbon fiber and thermosetting resin, heat-treated to cure the resin, and then polished to finish as shown in FIG.

4 and 5 show a second preferred embodiment of the present invention, in which the shape of the joint 4a is different from that of the first embodiment. That is, in this embodiment, the central lower surface portion 10 of the ceiling surface 6a of the joint 4a projects downward, and the upper end portion of the concave portion 5 is formed as an annular concave portion 5a, and the annular concave portion 5a, as shown in FIG. That is, the upper end of the shaft 2 is closely fitted. The downward projection length of the central lower surface portion 10 is preferably about 2.0 mm, and the weight when this joint is made of an aluminum alloy is 1.57 g.

In the second embodiment, the recesses 5 and 5a of the joint are adhered to the outer peripheral surface and the inner peripheral surface of the upper end of the shaft, and the adhesion area of both is larger than that in the first embodiment, and the joint 4a is also used. Is partially inserted into the upper end of the shaft 2, and the connection between the two is stronger than in the first embodiment. Other configurations are the same as those in the first embodiment.

In the badminton racket frame having the above-mentioned structure, the tip of the shaft 2 is brought into the axial position of the tubular frame by adopting the above-mentioned joints 4 and 4a. The effect of this is that, if the length of the badminton frame, the size of the frame and the length of the grip are constant, the effective length that contributes to the bending of the shaft is the rear end of the shaft in the case of the present invention. From the grip tip position to the position where the front end of the shaft intersects the axis of the frame. On the other hand, when the frame and the shaft are connected by the conventional T-joint, the effective length of the shaft is from the grip tip position to the position intersecting the lower surface of the frame. That is, in the case of the present invention, the effective length of the shaft becomes longer by the outer radius of the tubular frame than in the conventional T-joint. Strain energy (longitudinal elastic modulus of the shaft) E stored in the shaft due to the bending of the shaft at the time of hitting the ball is given by the following equation.

[0022]

[Equation 1] P: load applied to the tip of the shaft E: longitudinal elastic modulus of the shaft I: second moment of area of the shaft L: effective length of the shaft

As is clear from the above equation, by increasing the shaft effective length (L), more strain energy can be obtained. In the present invention, as a result of the effective shaft length becoming longer than that of the conventional one by an amount corresponding to the outer radius of the tube of the frame 1, about 7% more strain energy than that of the conventional one is stored and high resilience is enabled.

[0024]

As described above, in the badminton racket frame of the present invention, the size (volume) of the joint can be reduced and the weight can be reduced. Moreover, since the axial length of the bonded portion between the shaft and the joint can be shortened, the flexural characteristics of the shaft can be improved. Furthermore, since the upper end of the shaft is inserted near the center of the inside of the frame, the effective utilization length of the shaft can be increased and a high resilience of the shaft can be obtained.

If the shaft is a hollow tubular shaft and the lower central surface of the joint is fitted into the upper end pipe of the shaft so that the concave portion is an annular concave portion fitted to the upper end of the shaft, the joint is Since the bonding area between the shaft and the upper end of the joint can be increased without increasing the length in the vertical direction, the rigidity of the frame in the torsional direction with respect to the shaft can be increased to improve the surface stability of the frame. it can.

[Brief description of drawings]

FIG. 1 is a plan view of a badminton racket frame to which the present invention is applied.

FIG. 2 is a vertical cross-sectional view of a connecting portion between a frame and a shaft of a badminton racket frame to which the joint according to the first embodiment of the present invention is applied.

FIG. 3 is a vertical cross-sectional view showing the joint of FIG.

FIG. 4 is a vertical cross-sectional view of a connecting portion between a frame and a shaft of a badminton racket frame to which a joint according to a second embodiment of the present invention is applied.

5 is a vertical cross-sectional view showing the joint of FIG.

[Explanation of symbols]

1 frame 2 shafts 3 grip 4, 4a joint 5 recess 6 ceiling 7 shoulder 8 Tapered part

Claims (5)

[Claims] 1. A badminton racket frame in which a shaft and a hollow tubular frame formed in an elliptical ring shape are connected to each other through a joint, wherein the joint has a recess for fitting and adhering to the outer periphery of the upper end of the shaft. A badminton racket frame, characterized in that the badminton racket frame comprises substantially horizontal portions extending from both sides of the concave portion and both shoulder portions fitted and bonded inside the frame. 2. The shaft is a hollow tubular shaft, and the central lower surface portion of the joint is fitted and inserted into an upper end pipe of the shaft, and the recessed portion is an annular recessed portion fitted to the upper end of the shaft. The badminton racket frame according to claim 1, wherein 3. An upper end surface of the joint is formed as a substantially flat surface or a slightly curved surface connecting the both shoulder portions,
The badminton racket frame according to claim 1 or 2, wherein the both shoulder portions are formed in a tapered surface from both ends thereof toward the lower center. 4. The badminton racket frame according to claim 3, wherein the tapered surface is formed in a concave shape toward the upper end surface side of the joint. 5. The lower end portions of both ends of the frame fitted to the shoulder portion of the joint are formed on an inclined surface corresponding to the tapered surface, and the frame is formed in a state where the inclined surface is in contact with the tapered surface. The badminton racket frame according to claim 3 or 4, wherein the badminton racket frame is assembled in a joint, and a joint coating material is coated in a substantially T shape on an outer periphery of a joint portion between the shaft and the frame.