JP2004065862A - Badminton racket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a generation rate of a defective product; and to strengthen adhesive strength of a T-shaped joint and a shaft by reducing the possibility of causing positional dislocation between these members after fitting the T-shaped joint and the shaft. <P>SOLUTION: This badminton racket is formed by joining a frame and the shaft via an adhesive by inserting an upper end part of a hollow shaft 2 into a vertical shaft part 6 of the T-shaped joint by inserting horizontal both shoulder parts 5 of the T-shaped joint 4 into hollow both end parts of the frame 1 formed in an elliptic shape. A plurality of ribs 9 are formed in the shaft direction on an outside surface of the vertical shaft part of the T-shaped joint. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
According to the present invention, the horizontal shoulders of the T-shaped joint are inserted into the hollow ends of the oval frame, and the upper end of the hollow shaft is inserted into the vertical shaft of the T-shaped joint. The present invention relates to a badminton racket that is formed by bonding together through an adhesive.
[0002]
[Prior art]
Conventionally, as this type of badminton racket, those related to Japanese Utility Model No. 2-19163 have been publicly known. In order to manufacture this known badminton racket, an adhesive such as a liquid epoxy resin is first attached to the T-shaped joint, and then the vertical shaft portion of the T-shaped joint is inserted into the upper end opening of the hollow shaft and the gold Insert the horizontal shoulders of the T-joint into the hollow ends of the oval frame in the mold, and then reinforce the FRP resin tape around the outer periphery of the joint between the shaft and the frame to close the mold. It was thermoformed.
[0003]
[Problems to be solved by the invention]
However, the outer diameter (diameter) of the vertical shaft portion of the conventional joint in order to facilitate the work of inserting the T-joint into the upper end opening of the shaft and so that the adhesive is sufficiently distributed between the T-joint and the shaft. Are formed smaller than the inner diameter (diameter) of the hollow shaft by about 0.2 mm to 0.3 mm. For this reason, the fitting between the T-joint and the shaft is relatively loose, and once the vertical shaft portion of the T-joint is inserted into the upper end opening of the shaft, it is slightly pulled when installed in the mold. Even if an external force in the direction is applied, the shaft is slightly displaced (for example, several mm) in the direction in which the shaft is pulled out from the T-shaped joint. When a badminton racket is manufactured with such a displacement, stress concentrates on the portion of the T-joint vertical shaft that protrudes from the top end of the shaft during use, and the joint at that portion breaks. Has occurred.
[0004]
In addition, when a highly viscous adhesive such as epoxy resin is attached to the T-joint and inserted into the upper end opening of the shaft, the vertical shaft, for example, of the T-joint is precisely concentric with the opening of the shaft. It is almost impossible to insert it on top, and it is usually inserted in an eccentric state. Therefore, the adhesive attached to the outer periphery of the T-shaped joint is scraped off by the end of the shaft on the eccentric side, and becomes thin. There is a problem that the force may be reduced, and the torsional resistance of the shaft to the frame becomes weak.
[0005]
The present invention has been made in view of the above problems, and its purpose is to reduce the possibility of occurrence of defective products by reducing the possibility of misalignment between the T-joint and the shaft after fitting. An object of the present invention is to provide a badminton racket that is reduced and has an enhanced adhesive force between a T-shaped joint and a shaft.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, the horizontal shoulders of the T-shaped joint are inserted into the hollow ends of the oval frame, and the upper end of the hollow shaft is connected to the vertical shaft of the T-shaped joint. In the badminton racket in which the frame and the shaft are joined via an adhesive by insertion, a plurality of ribs are formed in the axial direction on the outer surface of the vertical shaft portion of the T-joint.
[0007]
Due to the presence of the rib, once the T-joint is inserted into the upper end of the shaft, if the rib dimensions are defined such that the upper end of the rib is in close contact with the inner surface of the hollow opening of the shaft, the T-joint is once attached to the shaft. After insertion to the predetermined position of the hollow opening of the shaft, the shaft does not shift in the direction of pulling out from the joint with a slight external force, so it is possible to reduce the occurrence of defective products due to positional shift between the joint and the shaft as much as possible after manufacturing. it can.
[0008]
In addition, since there are a plurality of the ribs, the vertical shaft portion of the joint is inserted correctly and concentrically with respect to the upper end opening of the shaft. The adhesive is not scraped off by the portion and the adhesive is almost uniformly attached to the outer periphery of the vertical shaft portion of the joint, so that the adhesive effect is not reduced as in the conventional case.
[0009]
In addition, the presence of the ribs increases the adhesion area of the T-joint to the shaft as compared to the case without the conventional ribs, so that the adhesive strength between the two is greater than in the conventional case.
[0010]
Preferably, 2 to 8 ribs are formed in the axial direction of the vertical shaft portion, thereby further reducing the possibility of positional deviation between the T-joint and the shaft, and the bonding area of the vertical shaft portion. Can be increased to further increase the bonding effect.
[0011]
Preferably, the ribs are formed such that the width and height of the ribs gradually decrease from the upper side to the lower side of the vertical shaft portion, whereby the vertical shaft portion of the T-joint is inserted from the upper end of the shaft. Becomes easy.
[0012]
Also preferably, ribs in the longitudinal direction are formed on the upper surfaces of the horizontal shoulders of the T-shaped joint. More preferably, a plurality of the longitudinal ribs are formed. As a result, for the same reason as described above, the adhesive area between the horizontal shoulders of the T-joint and the hollow ends of the frame increases, and the adhesive strength between the two can be increased.
[0013]
Preferably, the height of the rib is 0.1 to 1.0 mm. When the rib height is increased to some extent and the T-joint is inserted into the upper end of the shaft, if the rib partially bites into the inner surface of the hollow opening of the shaft, in addition to the adhesive effect described above, The joint strength between the T-shaped joint and the shaft is greatly improved.
[0014]
Preferably, a boundary portion between the upper end portion of the vertical shaft portion of the T-shaped joint and the shoulder portion is formed as a tapered surface, and an upper end opening portion of the hollow shaft is formed on the substantially same tapered surface. It is. And preferably, the said taper surface of the said boundary part is formed in the range of curvature radius 0.5-5.0 mm.
[0015]
As a result, the T-joint itself is strengthened, and the upper end opening of the shaft and the T-joint are brought into close contact with each other, thereby further improving the coupling strength between them.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a front view of a badminton racket frame according to the present invention. The badminton racket frame is composed of a frame part 1, a shaft part 2, and a grip part 3 in appearance.
As shown in FIGS. 2 and 3, the frame portion 1 and the shaft portion 2 are coupled to each other by a T-type joint 4 incorporated therein.
The frame portion 1 and the shaft portion 2 are FRP hollow tubular bodies mainly composed of carbon fibers, and the T-joint 4 is made of a metal such as an aluminum alloy.
[0017]
The T-shaped joint 4 includes substantially horizontal shoulder portions 5-5 and a vertical shaft portion 6 extending downward from the center of these shoulder portions. The cross-sectional shape of each horizontal shoulder portion 5 is the cross-sectional shape of the frame portion 1. The cross-sectional shape of the vertical shaft portion is the same circle as the cross-sectional shape of the shaft portion 2.
[0018]
A single rib (small projection) 7 is formed over the entire length in the longitudinal direction at the center of the flat upper surface of the horizontal shoulder 5-5, and this rib is gradually lowered toward both ends. It is preferable to facilitate insertion into opening portions at both ends of the frame which will be described later. Further, the end portions of both shoulder portions are tapered small-diameter end portions 8-8 for easy insertion into both hollow end portions of the frame.
[0019]
Four ribs (small protrusions) 9 are formed along the axial direction at equal intervals on the outer peripheral side surface of the vertical shaft portion 6, and the lower end of the vertical shaft portion 6 is a tapered small-diameter end portion 10. The height of the rib 7 of the shoulder portion and each rib 9 of the vertical shaft portion 6 is 0.1 to 1.0 mm. This dimension is determined by the relationship with the inner diameter of the shaft portion 2. In any case, when the vertical shaft portion 6 of the T-joint is inserted into the shaft from the upper end of the hollow shaft 2, the four ribs described above are used. 9, the vertical shaft portion 6 needs to be closely fitted into the hollow shaft. Therefore, when the inner diameter of the hollow shaft is constant, increasing the height of the rib reduces the diameter of the vertical shaft portion of the T-shaped joint, and when the height of the rib exceeds 1.0 mm, Since the diameter becomes too small to maintain the required strength, the height of the rib is limited to 1.0 mm. On the other hand, if the height of the rib is less than 0.1 mm, the effect of providing the rib described later cannot be achieved.
[0020]
It is preferable that the width and height of each rib 9 in the vertical shaft portion of the T-shaped joint be gradually reduced from the top to the bottom of the vertical shaft portion 6. This facilitates the operation of inserting the vertical shaft portion 6 of the T-joint into the upper end opening of the shaft 2.
[0021]
Further, the boundary portion 11 between the horizontal shoulder portion 5 and the vertical shaft portion of the T-shaped joint 4 is formed as a tapered surface. Correspondingly, the inner peripheral surface 12 of the upper end opening of the hollow shaft 2 into which the vertical shaft portion 6 is inserted is countersunk so as to have the same tapered surface as the tapered surface of the boundary portion 11. Thus, when the vertical shaft portion 6 of the T-shaped joint 4 is inserted from the upper end opening of the hollow shaft 2, the tapered surface of the boundary portion 11 and the tapered surface of the upper counterbore portion 12 of the hollow shaft are in close contact with each other. It has become. Further, the strength of the T-shaped joint 4 itself is increased by the tapered surface of the boundary portion 11.
[0022]
The radius of curvature of the tapered surface of the boundary portion 11 of the T-shaped joint 4 is in the range of 0.5 to 5.0 mm, and if the radius of curvature becomes larger than this radius of curvature, the shaft formed to match this radius of curvature. The counterbore of the tip becomes large, and the strength of the tip of the shaft is too low. On the other hand, if the radius of curvature is less than 0.5 mm, an improvement in strength due to the close contact between the tip of the shaft and the boundary 11 of the T-shaped joint 4 cannot be expected.
[0023]
Next, a process for forming a badminton racket using the above-described T-shaped joint will be described. As shown in FIG. 3, a preformed aluminum alloy T-shaped joint is immersed in a molten epoxy resin prepared as an adhesive. Then, an epoxy resin is adhered to the outer surface of the T-shaped joint. Next, the vertical shaft portion 6 of the joint 4 is inserted from the upper end opening portion of the FRP hollow shaft until the boundary portion 11 of the joint comes into contact with the upper end counterbore portion 12 of the shaft.
[0024]
At this time, the dimensions are set so that the four ribs 9 formed on the outer surface of the vertical shaft portion 6 are press-fitted in close contact with the inner peripheral surface of the hollow shaft 2. This prevents the joint 4 from being displaced from the shaft 2 by a slight external force.
[0025]
Next, both horizontal shoulder portions 5 and 5 of the T-shaped joint 4 are inserted into the opening portions at both ends of the FRP frame 1 made of carbon fiber previously formed into an oval hollow shape. At this time, since the rib 7 formed at the center of the upper surface of the shoulder is in close contact with the inner wall surface of the opening of the frame, the engagement between the joint 4 and the frame is ensured and the bias of the adhesive is prevented, and the desired adhesive strength is achieved. Can be definitely obtained. Next, a belt-like FRP prepreg is wound around the connecting portion between the frame 1 and the shaft 2 that is the outer periphery of the T-shaped joint portion. In this state, the T-shaped joint portion is inserted into the mold, and the mold is closed and heat-molded.
[0026]
In the badminton racket manufactured as described above, as shown in FIG. 2, the frame 1 and the shaft are firmly connected via the T-shaped joint 6, and the connecting portion is covered with the FRP resin layer 13.
[0027]
The present invention is not limited to the above-described embodiment, and the number of ribs 9 formed on the vertical shaft portion may be a plurality, preferably 8 or less. Moreover, the rib 7 of a horizontal shoulder part does not need to be one, and you may provide multiple pieces.
[0028]
【The invention's effect】
As described above, in the badminton racket of the present invention, a plurality of ribs 9 are formed on the outer surface of the vertical shaft portion 6 of the T-shaped joint 4 in the axial direction, and the vertical portion is inserted into the upper end portion of the hollow shaft 2. Therefore, when the T-joint is inserted into the upper end of the shaft, if the rib dimensions are defined so that the upper end of the rib is in close contact with the inner surface of the hollow opening of the shaft, the T-joint is once opened in the hollow of the shaft. After insertion to a predetermined position of the part, the shaft does not shift in the direction of pulling out from the joint with a slight external force, so that the generation of defective products due to the positional shift between the joint and the shaft can be reduced as much as possible.
[0029]
In addition, since there are a plurality of the ribs described above, the vertical shaft portion of the joint is inserted correctly and concentrically with respect to the upper end opening of the shaft. The adhesive is not scraped off by the portion and the adhesive is almost uniformly attached to the outer periphery of the vertical shaft portion of the joint, so that the adhesive effect is not reduced as in the conventional case.
[0030]
Furthermore, since the area of adhesion of the T-joint to the shaft increases due to the presence of the ribs compared to the case without the conventional ribs, the adhesive strength between the two becomes larger than in the conventional case.
[Brief description of the drawings]
FIG. 1 is a front view of a badminton racket to which the present invention is applied.
FIG. 2 is a cross-sectional view of a main part showing a connecting portion between a frame part and a shaft part of a badminton racket that is a main part of the present invention.
FIG. 3 is a front view of a T-shaped joint applied to the present invention.
FIG. 4 is a bottom view of the T-shaped joint shown in FIG.
DESCRIPTION OF SYMBOLS 1 Frame part 2 Shaft part 4 T-shaped joint 5 Shoulder part 6 Vertical shaft part 7 Longitudinal rib 9 Axial rib 11 Boundary part 12 Counterbore part

Claims (8)

Insert the horizontal shoulders of the T-joint into the hollow ends of the oval frame, and insert the upper end of the hollow shaft into the vertical shaft of the T-joint. A badminton racket, wherein a plurality of ribs are formed in an axial direction on an outer surface of the vertical shaft portion of the T-joint. The badminton racket according to claim 1, wherein 2 to 8 ribs are formed in an axial direction of the vertical shaft portion. 3. The badminton racket according to claim 1, wherein the ribs are formed so that the width and height of each rib gradually decrease from above to below the vertical shaft portion. The badminton racket according to any one of claims 1 to 3, wherein ribs in the longitudinal direction are formed on the upper surfaces of the horizontal shoulder portions of the T-shaped joint. The badminton racket according to claim 4, wherein a plurality of the ribs in the longitudinal direction are formed. The badminton racket according to any one of claims 1 to 5, wherein a height of the rib is 0.1 to 1.0 mm. A boundary portion between the upper end portion of the vertical shaft portion of the T-shaped joint and the shoulder portion is formed as a tapered surface, and an upper end opening portion of the hollow shaft is formed in a substantially identical tapered surface. The badminton racket according to any one of claims 1 to 6. The badminton racket according to claim 7, wherein the tapered surface of the boundary portion is formed within a radius of curvature of 0.5 to 5.0 mm.

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