JPH03112573A - Racket - Google Patents

Abstract

PURPOSE:To perform a rapid and effective damping of impact vibration during striking of a ball by a method wherein a vibration suppressing material is located to the shaft part of a racket and in the vicinity of a center of gravity point. CONSTITUTION:A vibration suppressing material 5 is mounted to the one of shafts 3 and in the vicinity of the center of gravity line of a racket comprising a gut 1, a frame 2, shafts 3, and a grip 4. The vibration suppressing material 5 may be mounted on the shaft 3 in a shape being symmetrical about the central line of the racket, but it is rather higher in a damping effect and preferable that the vibration suppressing material is located asymmetrically and especially mounted on only either the right or left shaft 3 based on the central line. A material being the same as a material, e.g. wood, aluminium alloy, FRP, of which the frame, the shafts, and the grip of the racket are formed may be used for the vibration suppressing material, but a substance, such as a metal, e.g. iron, copper, lead, and stainless steel, and ceramics, having high specific gravity is preferable. Further, a resin material having high vibration damping capacity is also preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a racket, particularly a tennis racket, which significantly suppresses impact vibrations when hitting a ball and allows comfortable play.

(Prior Art) Generally, the frames of rackets such as hard tennis rackets in which the sweet spot is a problem are made of lightweight, strong and rigid materials.

That is, wood, aluminum alloy, fiber-reinforced synthetic resin (FRP), etc. are used as the aggregate for such rackets. Although these materials inherently have relatively good vibration damping properties, they are not always sufficient in their ability to rapidly and effectively reduce impact vibrations when a ball is hit.

Additionally, "stabilizers" have been proposed and commercially available for the purpose of reducing and mitigating impact vibrations when hitting a ball.

This "stabilizer" is a rubber or soft synthetic resin molded product inserted between the racket guts or crimped onto the gut surface.

This "stabilizer" is quite effective in suppressing the vibrations of the guts themselves, but it does not attenuate the vibrations propagated from the guts to the frame by the function of the frame itself.

(Problem to be solved by the invention) In other words, in the conventional racket, the vibration propagated to the frame during impact vibration when hitting a ball is transmitted to the arm and elbow through the shaft and grip, causing damage to the wrist, arm, elbow, etc. This resulted in accumulated fatigue. In particular, if the ball is hit off the center of the gut (the so-called sweet spot), the player may experience unpleasant vibrations or tingling.

In view of the drawbacks of conventional rackets, the present invention is capable of rapidly and effectively attenuating impact vibrations when hitting a ball.
To provide a racket, especially a tennis racket, which allows players to play comfortably and reduces fatigue in their arms and elbows.

(Means for solving problems) The following measures will be taken to achieve the above objectives.

That is, the racket of the present invention is a racket consisting of a gut part, a frame part, a shaft part, and a grip part, and a racket having a weight of 1/7 to 1/80 of the weight of the racket in the shaft part of the racket and near the center of gravity. It is characterized by the addition of vibration suppressing material.

(Function) The present invention is applicable to rackets such as squash, tennis,
This relates to rackets with guts, such as tennis rackets, that hit a ball that is relatively heavy compared to the weight of the racket, and especially rackets such as hard tennis rackets that have a problem with the sweet spot. It has been surprisingly discovered that when a vibration suppressing material is attached to the shaft portion of the racket near the center of gravity, the impact vibrations transmitted from the gut when hitting a ball are extremely effectively damped.

FIG. 1 is a schematic diagram showing an example of the racket of the present invention. In this example, a normal racket consisting of a gut 1, a frame 2, a shaft 3 and a grip 4 has a vibration suppressing material 5 attached to one side of the shaft 3 near the center of gravity.

The vibration suppressing material 5 may be attached to the shaft 3 symmetrically with respect to the center line of the racket, but it may be attached more asymmetrically, especially only on one of the shafts 3, either left or right with respect to the center line. It is preferable to attach it to the center because the damping effect is greater.

Such vibration suppressing materials include wood, aluminum alloy, and FRP that make up the frame, shaft, and grip of the racket.
Although the material may be the same as the above, metals such as iron, copper, lead, and stainless steel, and materials with high specific gravity such as ceramics are preferable.

Furthermore, it is also preferable to use a damping resin material with high vibration damping ability as the vibration suppressing material. Such a vibration-damping resin material can be processed into various shapes such as a desired shape, such as a protrusion shape, a plate shape, and a film shape, so that it is easy to attach it to the shaft 3, which is preferable.

The vibration suppressing material 5 may be installed by pasting a plate-like vibration suppressing material on the shaft 3, by wrapping a film-like vibration suppressing material around the shaft 3, or by incorporating it into the aggregate of the shaft 3. It is preferable to use a vibration suppressing material in the form of a protrusion because it has good damping characteristics.

It is important to attach the vibration suppressing material 5 to the shaft 3 near the center of gravity as shown in FIGS. 1 to 3; even if it is attached at other positions, the vibration damping effect will be small. The vibration damping effect can be achieved at any position near the center of gravity. In particular, it is preferable to use a protrusion-like shape as shown in FIG. 1.2, which is attached to the surface of one of the shafts 3 toward the inside, since it has excellent vibration damping characteristics.

The vibration suppressing material 5 has a weight of 1/7 to 1/8 of the weight of the racket.
0 weight, preferably 1/10 to 1/40 weight. Specifically, in the case of a hard tennis racket, a vibration suppressing material of about 5 to 50 g, preferably about 10 to 45 g, exhibits preferable vibration damping characteristics.

In the present invention, as described above, by attaching the vibration suppressing material 5 having a specific weight to the shaft 3 on the center of gravity of the racket, the impact vibration propagated from the racket 1 to the frame 2 is rapidly attenuated by the shaft 3. However, the propagation to the grip 4 was successfully suppressed.

The above-mentioned vibration-damping resin material will be explained as the vibration-suppressing material 5 to be attached to the racket of the present invention.

Such vibration-damping resin materials include, for example, compounds of rubber or synthetic resin with relatively high specific gravity, compounds in which these resins are blended with metals with high specific gravity such as lead or metal fibers, and materials that can be heated at temperatures ranging from room temperature to 100°C. A thermosetting resin composition whose main components are an epoxy resin that has fluidity at room temperature to 100 °C, a polyamide resin that has fluidity at room temperature to 100 °C, and at least one inorganic filler selected from graphite, ferrite, and mica. Resin materials are preferably used.

That is, the above-mentioned resin composition has a high degree of freedom in processing;
The flexible resin material exhibits excellent vibration damping effects after hardening.

For example, a thermosetting resin material made of such a resin composition can be attached to the frame, shaft, or grip of a racket in the form of putty, and then left at room temperature or heated to harden. It is also possible to attach a product that has been cured and molded in advance using a molding machine, such as a plate or a film.

In the above-mentioned resin composition, the epoxy resin having fluidity at room temperature to 100°C is a resin having at least two or more glycidyl ether groups, preferably two or more glycidyl ether groups.
Viscosity at 5°C is 1-300 poise, epoxy equivalent is 10
It is preferable to have a molecular weight of 0 to 500 and a molecular weight of 200 to 1000.

Specifically, for example, Epicote 828.827.83
4.807 (manufactured by Yuka Shell Chemical Co., Ltd.), etc. can be used.

In addition, as a polyamide resin having fluidity at room temperature to 100°C, preferably the viscosity at 25°C is 3 to 2000.
Those having a poise and amine value of 100 to 800 are suitable because they act effectively as a curing agent for the epoxy resin and as an agent for imparting flexibility to the resin after curing. Specifically, for example, Tomide #225-X, #215-X, #225 (
Above, manufactured by Fuji Kasei Co., Ltd.), Persamide 930.115
(manufactured by General Mills), Epon-V15 (
(manufactured by Shell) etc. can be used.

Such polyamide resin acts as a curing agent for epoxy resin, but in order to shorten the curing time and sufficiently progress the curing of the molded product, a commonly used curing agent for epoxy resin can be used in combination. . Such curing agents include aliphatic amines such as triethyltetramine, propatoolamine, aminoethylethanolamine, aromatic amines such as P-phenylenediamine, tris(dimethylamine)methylphenol, benzylmethylamine, and even phthalic anhydride. , a carboxylic acid such as maleic anhydride, and the like can be used. The amount of the curing agent to be added may be sufficient for curing, taking into consideration the epoxy equivalent, amine equivalent, and acid equivalent.

In addition, the inorganic fillers filled in these resins include graphite,
It is at least one selected from ferrite and mica. Among such inorganic fillers, graphite is preferably used because it has excellent impact vibration suppressing properties, and furthermore,
Among these, those having an aspect ratio of 3 to 70 are preferred. The aspect ratio is a value obtained by dividing the diameter of a graphite particle by its thickness, and those in the above range have excellent wettability with resin and excellent mixing characteristics.

The above components are preferably blended in the following proportions.

That is, the blending amount of polyamide resin with respect to 100 parts of epoxy resin is 100 to 800 parts, more preferably 2 parts.
00 to 500 parts, and the inorganic filler is 30 to 120 parts, more preferably 40 to 100 parts, based on 100 parts of the total amount of these resins (including monoglycidyl ether, which will be described later). .

In addition, it is preferable to further blend a monoglycidyl ether compound into the above-mentioned resin composition, since it is possible to provide a damping resin material that is extremely flexible and has excellent processability. Particularly preferably, the epoxy equivalent is 80 to 400 and the molecular weight is 8.
A monoglycidyl ether compound having a molecular weight of 0 to 400 is preferable. Specifically, octadecyl glycidyl ether, phenyl glycidyl ether, butylphenyl glycidyl ether, etc. can be preferably used. Such a compound has the advantage that the viscosity of the provided resin composition can be adjusted to be extremely effective for use in the form of a putty.

The compounding amount of this compound is preferably 5 to 45 parts, more preferably 10 to 25 parts, per 100 parts of the epoxy resin.

Among such vibration-damping resin materials, those having a vibration loss coefficient of 0.02 or more at room temperature are preferred because they have a large damping effect on impact vibrations from guts.

The above-mentioned vibration loss coefficient is measured as follows.

That is, after pasting a 10 mm thick synthetic resin onto a 5 mm thick steel plate using a two-component adhesive, the adhesive was left for 24 hours to harden, and then the MI
Measure the vibration damping waveform according to LP-22581B,
Find the vibration loss coefficient (η) using the following formula.

a, Attenuation rate (DECAY RATE) Do (dB/
5ec)=(F/N) 20 log(At/A2
) b, effective attenuation factor (EFFECTIVI! DEC
AY RATE)De (dB/5ec)-DO-
DBC0 critical attenuation rate (PERCENT CRITI)
CAL DAMPING) C/Cc (%) = (18
3xDe)/F where, F: Natural frequency N of the sample bonded disk; Number of calculated periods A1: Maximum amplitude in N A2: Minimum amplitude in N Do: Damping rate DB of sample bonded disk : Damping rate d of the original disc, vibration loss coefficient (η) η = (C/Cc) 150 The vibration damping resin material of the present invention has the above-mentioned vibration loss coefficient, more preferably from 50 Hz at room temperature of 20°C. It is preferable that the value is 0.04 or more in a frequency range of 5 kHz.

The method for measuring the apparent vibration loss coefficient of a racket is as follows.

In other words, a micro-acceleration pickup was attached to the center of the grip of a racket equipped with vibration suppression material, the tip of the frame was tapped with a hammer, and the attenuation waveform of the vibration was measured using an FFT analyzer (manufactured by Ono Sokki ■). The vibration loss coefficient (η) of the waveform is measured using a microcomputer (manufactured by NEC Corporation) according to the formula of MIL-P-22581B.

According to this method, the vibration loss coefficient of the grip 4 is preferably 0.01 or more, preferably 0.02 or more from the viewpoint of both vibration damping effect and productivity. In other words, if the vibration loss coefficient is less than 0.01, there is a tendency for the racket to lose its superiority over conventional rackets, and unpleasant vibrations will propagate when the ball is hit off the sweet spot.

When making a resin molded product from a resin composition consisting of the above-mentioned components, first, the epoxy component (epoxy resin, monoglycidyl ether compound) and the polyamide component (polyamide resin, curing agent, inorganic filler) are separately separated. A method is used in which the two components are mixed in the system, and then the two are mixed together at the end. The above-mentioned method is also adopted when the resin composition is used in the form of a putty. In either case, it is preferable to use a mixer for high viscosity to mix gently and uniformly so as not to introduce air bubbles.

Curing of such a resin composition varies depending on the type of epoxy resin, curing agent, and polyamide resin used, but the curing temperature is between room temperature and
It can be cured and molded into a resin by coating or using a molding device into a desired shape under a temperature condition of 100°C.

Mounting in the present invention includes methods such as mounting, fixing, laminating, or covering.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A resin material made of a resin composition having the following formulation is used as a damping material.

(Resin composition) Epoxy resin 13.6 parts (Epicote #828, manufactured by Yuka Shell Epoxy Co., Ltd.) Octadecyl glycidyl ether 2.7 parts Amide resin
31.9 parts (Tomide #225-X
, manufactured by Fuji Kasei Co., Ltd.) Tris(dimethylamide)methylphenol 1. 8 parts graphite 50.0 parts A damping plate with a thickness of 10 mm was made using the resin composition having the above composition. When the vibration loss coefficient of this plate was measured at room temperature of 20°C using the method described above, it was found that the vibration loss coefficient from 50Hz to 5K
It was -0.05 in the frequency range of Hz.

The above resin composition was molded and cured to obtain a damping plate. This plate was cut into a substantially triangular shape with a base of 50 mm and a height of 50 mm, and was attached to the shaft of the racket near the center of gravity using adhesive, as shown in FIG.

The weight increase of this racket was 20g.

This racket was measured using the aforementioned apparent vibration loss coefficient measurement method in which a pick-up was attached to the center of the grip and the tip of the frame was tapped, and the results shown in Table 1 were obtained.

Example 2 Instead of the damping plate of Example 1, a copper plate with a thickness of 1.2 a+m was cut out in the same shape as in Example 1, and then attached using screws and nuts in the same manner. The weight increase of this racket was 21g.

The apparent vibration loss coefficient of this racket was measured in the same manner as in Example 1, and the results shown in Table 1 were obtained.

Example 3 Instead of the damping plate of Example 1, a piece of pine wood with a thickness of 10 mm was cut out in the same shape as in Example 1, and then attached using screws and nuts in the same manner. The weight increase of this racket was 10g.

The apparent vibration loss coefficient of this racket was measured in the same manner as in Example 1, and the results shown in Table 1 were obtained.

Example 4 The damping plate of Example 1 was cut into a substantially equilateral trapezoid with a base of 60 mm and a height of 30 mm, and was attached to the shaft of the racket near the center of gravity using adhesive as shown in FIG.

The weight increase of this racket was 19g.

The apparent vibration loss coefficient of this racket was measured in the same manner as in Example 1, and the results shown in Table 1 were obtained.

As is clear from Table 1, the rackets of Examples 1 to 4 all had higher apparent vibration loss coefficients than the blank racket of the comparative example, and were evaluated as having a lighter and softer feel at impact. Met. In the comparison between Example 4 and Example 1, Example 1 was evaluated as being good.

Table 1 In the table, the feel at impact was determined by asking 20 tennis players to rate the feel of the ball when they hit it into the following four grades.

△: Fair, O: Good, ◎: Very good (Effects of the invention) The present invention provides a racket that has a function of extremely well damping the transmission of impact vibrations when hitting a ball from the gut to the frame, shaft, and grip. It is something to do.

According to this racket, there is no unpleasant vibration or tingling when the ball is hit off the sweet spot, and it also satisfactorily reduces fatigue in the arms and elbows caused by impact vibrations, thereby reducing fatigue in the wrists, arms, and elbows. There is no accumulation and you can play comfortably.

[Brief explanation of drawings]

1 to 3 are all examples of the racket of the present invention,
Fig. 1 shows an example in which a protruding vibration suppressing material is attached to the shaft part, and Fig. 2 shows an example in which another protruding vibration suppressing material is attached.
FIG. 3 shows an example in which the vibration suppressing material is attached to the shaft portion symmetrically with respect to the center line. 1: Gut 2: Frame 3: Shaft 4: Grip 5: Vibration suppression material

Claims (2)

[Claims] (1) In a racket consisting of a gut section, a frame section, a shaft section, and a grip section, 1/7 to 1/7 of the weight of the racket is located at the shaft section of the racket and near the center of gravity.
A racket characterized by having a vibration suppressing material with a weight of 80 mm. (2) Claim (1) in which the vibration suppressing material is provided in a symmetrical or asymmetrical weight relationship with respect to the center line of the racket.
) Racket listed.