JP2000042145A - Racket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase strength so as to prevent the outer peripheral part of the racket frame from being recessed by releasing stress concentration applied to the outer peripheral part of a racket frame by a string. SOLUTION: In a racket having a frame part 1 with a large number of string through-holes 3 formed, curved protruding faces 7 are formed on the frame outer peripheral surface between the adjacent string through-holes, and independent eyelets or eyelets continuously formed in belt shape are mounted to the string through-holes to strain the string.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a racket for tennis, badminton, and the like, and more particularly to an improvement in a frame portion of such a racket.

[0002]

2. Description of the Related Art An enlarged frame portion of a conventional badminton racket is shown in FIG.
Insertion holes 3 for inserting the strings 2 at predetermined intervals
The insertion holes 3 are provided with eyelets (grommets) 4 made of synthetic resin. An annular flange 4 a is integrally formed on the outer end of each eyelet 4, and the inner surface of the flange 4 a is in contact with the outer peripheral surface of the frame 1. The string 2 is stretched to the frame portion 1 between adjacent eyelets 4 as shown.

[0003]

However, in such a conventional racket, when the string 2 is stretched through the eyelet 4, opposing corners (flanges) as shown by arrows in FIG. Part), the string is repeatedly pulled up with high strength several times, or the string 2 breaks during use, or the outer periphery of the frame between adjacent eyelets 4-4 is depressed And sometimes the racket became unusable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to alleviate the concentration of stress applied to the outer peripheral portion of a racket frame by the above strings, so that the strings are not easily cut. An object of the present invention is to provide a racket having increased strength so that the outer periphery of the racket frame does not collapse.

[0005]

In order to achieve the above object, in a racket according to the present invention, in a racket having a frame portion in which a number of string insertion holes are formed, the racket has a curved outer peripheral surface between adjacent string insertion holes. That is, a convex surface is formed.

As a result, the stress caused by the string stretched through the adjacent string insertion hole is received and dispersed not only by the corner of the string insertion hole but also by the curved convex surface. The strength of the depressed portion of the string is greatly increased, so that the string is not repeatedly pulled up with the high strength several times, or the string is not broken during use, and the frame portion does not buckle due to the tension of the string. .

In the case where an eyelet having a flange at an outer end is attached to each of the adjacent string insertion holes, the top of the convex surface is projected more outward than the flange of the eyelet. It is.

Thus, the stress caused by the string which is stretched through the eyelet mounted on the adjacent string insertion hole is received and dispersed by the curved convex surface as well as the eyelet flange located at the corner of the string insertion hole. Therefore, the same effect as in the above case can be obtained.

In the case of a tennis racket, it is preferable to mount a synthetic resin eyelet formed integrally and continuously with a band-shaped portion in the string insertion hole. In this case, the center of the band-shaped portion is attached to the eyelet. It can be made thinner than both ends to reduce the weight.

[0010] Preferably, the pressure receiving strength of the convex portion can be increased by projecting the convex portion substantially in a spherical shape along both the length direction and the thickness direction of the frame portion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The same parts as those in the conventional example are denoted by the same reference numerals.

FIG. 1 is a front view showing a cross section of about 2/3 of an upper portion of a frame portion 1 when the present invention is applied to a badminton racket. In order to avoid complicating the drawing, the position of a string insertion hole 3 is shown. Is indicated by a single line. FIG. 2 is a perspective view showing a flat state before the frame portion is bent as shown in FIG. 1, and FIG.
FIG. 2 is a partially enlarged cross-sectional view of the top part of FIG.

In FIG. 1, a frame portion 1 of a badminton racket is formed by bending a hollow pipe into an oval shape in a front view, and a hollow shaft 5 is integrally connected to a lower end thereof. On both sides of the top of the frame portion 1 as a center, a concave groove 6 is formed along the outer periphery until reaching a position slightly below the geometric center of the frame portion 1. Further, the frame portion 1 is provided with a string insertion hole 3 over substantially the entire circumference except for a joint portion with the shaft. Each of the string insertion holes 3 is inserted with a synthetic resin eyelet 4 (grommet) having a flange 4a at the outer end.

According to the embodiment of the present invention, an outwardly protruding arc-shaped convex surface 7 is provided between the string insertion holes 3 on the upper outer peripheral portion corresponding to about one third of the perimeter of the oval frame portion 1. It is integrally formed along the length direction of the frame portion 1. FIG. 4 is a cross-sectional view of the convex surface 7 taken along line aa and line bb in FIG. The height of the convex surface is lower than the height of the side walls on both sides of the concave groove 6 and higher than the eyelet flange 4a attached to the string insertion hole 3, so that the string is preferably attached to the frame. The reason is that the outer peripheral portion of the string is substantially housed in the side walls on both sides of the concave groove 6 when the string is pulled up.

The frame portion 1 having the convex surface 7 formed as described above
When the string 2 is inserted with a predetermined tension to form a gut surface, as shown in FIG. 3, the string 2 inserted between the adjacent eyelets 4 has at least the flanges 4a, 4a of the opposing eyelets 4. Because of the contact with the top of the convex surface 7, the stress applied by the string as in the prior art is applied to the eyelet collar 4.
a, 4a.

Hereinafter, the mechanical strength of the product of the present invention in which the convex portion 7 is formed on the frame portion 1 of the badminton racket as in the above-described embodiment, and the conventional product which is different from the product of the present invention only in that the convex surface is not formed. Table 1 shows the results of the measurements for the ratios. The product weight of both the product of the present invention and the conventional product is 92.0 g.

[0017]

[Table 1]

In the above table, the "load" of "longitudinal fracture" is the load applied from the top of the frame downward until the frame is plastically deformed, and the "bending amount" is that the frame portion was deformed in the vertical direction at that time. Indicates the amount. Further, the “depression strength of the string insertion hole” indicates a load applied to the string until the space between the insertion holes buckles in a state where the string is inserted.

As is clear from the results in Table 1 above, the product of the present invention increases the load of longitudinal break by 7% and the amount of deflection by 5% as compared with the conventional product, and the convex portion formed on the frame portion 1 increases the frame portion. It can be seen that the stiffness and toughness have increased.
In addition, it can be seen that the depression strength of the string insertion hole is significantly increased by 23% due to the convex surface formed on the frame portion 1.

Further, when the curved portion 2a of the string 2 in FIG. 3 is compared with the curved portion 2b of the string in FIG. 8, it is understood that the angle of 2a is obtuse, and the stress applied to the string itself is dispersed in the present invention. .

FIG. 5 shows a second embodiment of the present invention suitable for application to a tennis racket.

This embodiment differs from the first embodiment in that the eyelets 4 attached to the string insertion holes are not independent as in the previous embodiment, as shown by hatching in FIG. The other points are the same as the previous embodiment in that they are continuously formed integrally with the band portion 4b.

In this embodiment, the eyelet band 4b is convexly curved along the convex surface 7 of the frame, and the string 2 is received by the convexly curved band 4b. The stress applied to the frame portion 1 when the frame 2 is pulled up is dispersed in the curved band portion,
The stress does not concentrate on the upper end corner of the eyelet 4 as before.

FIG. 6 shows a modification of the second embodiment shown in FIG. 5. In this modification, the thickness of the band portion 4c of the eyelet 4 is not uniform as shown in FIG. Is formed thinner than both ends, and when the string 2 is pulled up, the string 2
It is curved in a letter shape.

In this modification, the outer peripheral surface of the string 2 is housed in the concave groove 6 formed in the frame portion 1 so that the outer end of the string does not come into contact with the ground or the floor surface when the racket is used so as not to be damaged. In this case, the depth of the groove can be made shallower than in the case of FIG.

FIG. 7 is a central longitudinal sectional view of a convex surface showing a modified example of the convex surface 7 formed on the frame portion 1.
Is not only convex along the length direction of the frame portion 1 but also convex along the thickness direction of the frame,
Since the convex surface has a substantially spherical shape, the strength can be increased as compared with the case where only the convex shape is formed along the length direction of the frame portion 1 as in the above embodiment.

[0027]

As described above, in the racket according to the present invention, in a racket having a frame portion in which a number of string insertion holes are formed, a curved convex surface is formed on the outer peripheral surface of the frame between adjacent string insertion holes. Therefore, the stress caused by the raised string is received and dispersed by the curved convex surface, so that the strength of the depressed portion between the string insertion holes on the outer peripheral portion of the frame is greatly enhanced, and the string is stretched at a high strength several times. Repeat,
Alternatively, it is possible to prevent the string from being broken during use and the frame portion from buckling due to the tension of the string. Further, the rigidity and toughness of the racket frame can be increased by greatly increasing the breaking strength of the frame portion and increasing the amount of bending.

[Brief description of the drawings]

FIG. 1 is a front view showing a case in which the present invention is applied to a badminton racket, and showing a cross section of about 部 of an upper portion of a frame portion.

FIG. 2 is a perspective view showing a flat state before a frame portion is curved as shown in FIG. 1;

FIG. 3 is a partially enlarged cross-sectional view of the top part of FIG. 1 showing a state where eyelets are attached to each of the string insertion holes of the frame portion and the strings are inserted.

FIGS. 4 (a) and (b) respectively show a in FIG.
Sectional drawing in the -a line and the bb line.

FIG. 5 is a partially enlarged sectional view similar to FIG. 3, showing a second embodiment of the present invention.

FIG. 6 is a partially enlarged sectional view showing a modification of the second embodiment of the present invention.

FIG. 7 is a central longitudinal sectional view of a convex surface showing a modification of the convex surface 7 formed on the frame portion 1;

FIG. 8 is an enlarged cross-sectional view showing a top portion of a frame portion of a conventional badminton racket. Reference Signs List 1 frame part 2 string 3 string insertion hole 4 eyelet (grommet) 6 concave groove 7 convex surface

Claims (5)

[Claims] 1. A racket having a frame portion in which a number of string insertion holes are formed, wherein a curved convex surface is formed on an outer peripheral surface of the frame between adjacent string insertion holes. 2. An eyelet having a flange at an outer end is attached to each of the adjacent string insertion holes, and a top of the convex surface protrudes outward from the flange of the eyelet. The racket according to claim 1. 3. The racket according to claim 1, wherein said plurality of string insertion holes are provided with synthetic resin eyelets formed integrally and continuously with a band-shaped portion. 4. The racket according to claim 3, wherein a center portion of the strip portion is formed thinner than both end portions thereof. 5. The racket according to claim 1, wherein the projection is formed along both the length direction and the thickness direction of the frame portion.