JP2001037919A - Racket frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a racket frame which is excellent in attenuation ability to vibration under normal conditions of use for a string used. SOLUTION: There are provided a head part including a yoke part 11, two throat parts, a shaft part and a grip part on a racket frame. An vibration attenuation material 21 and the first protective material 13 are installed on the yoke part 11. There are provided a band 23 and a cylinder 25 on the vibration attenuation material 21. There are provided a hard band 27 and a hard cylinder 29 on the first protective member 13. The cylinder 25 and the head cylinder 29 are inserted in string ports which are punched on the yoke part 11. Dynamic viscoelastic loss factor tanδ which is measured in a condition of which frequency of the vibration attenuation material 21 is 10 Hz and temperature of the same is -5 deg.C is over 0.3% and below 2.3%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a racket frame used for ball games such as hard tennis, soft tennis, and badminton.

[0002]

2. Description of the Related Art Bamboo, light metal and the like have been used for hard tennis rackets in the old days, but in recent years, fiber reinforced resin has been mainly used. Since the fiber reinforced resin has a high specific strength and a high degree of design freedom, the weight of the tennis racket can be reduced while maintaining the strength. Tennis rackets made of fiber reinforced resin are also suitable for mass production.

[0003] When a player hits a ball with a tennis racket, vibrations are generated in a racket frame and a string (also referred to as "gutt"). This vibration is transmitted to the player's body through the grip and gives the player discomfort. The vibration is also considered to be a cause of so-called tennis elbow. In particular, when the ball is hit in a portion other than the sweet area of the ball striking face (face), severe vibration is generated, and the player is seriously damaged.

[0004] The tennis racket made of the above-mentioned fiber reinforced resin has a higher vibration damping property than a metal tennis racket or the like. However, even the tennis racket made of the fiber reinforced resin does not have a sufficient vibration damping property. The problems of tennis elbow etc. have not been completely solved. Moreover, in recent years, tennis rackets made of fiber reinforced resin have been further reduced in weight and length by increasing the strength and elasticity of the fibers, but the vibration damping properties have been reduced due to the reduction in weight and length. There is a tendency to do so. Further improvement in vibration damping properties is also desired for tennis rackets made of fiber reinforced resin.

Japanese Patent Application Laid-Open No. 10-337812 discloses a tennis racket in which an ionomer resin film is interposed in a fiber-reinforced resin laminate having an epoxy resin as a matrix. Since the ionomer resin is more excellent in vibration damping property than the epoxy resin, the vibration damping property of the tennis racket is improved by the interposition of the ionomer resin film. However, the vibration of the racket frame is mainly attenuated by the ionomer resin film, and the vibration of the string is hardly attenuated.

Japanese Patent Laid-Open Publication No. Sho 60-168473 discloses a tennis racket in which a vibration absorber made of a flexible elastic body or a viscoelastic body is wound around a string to improve the vibration damping performance of the string. ing. However, the material of the vibration absorber is not sufficiently considered and its vibration damping performance is not sufficient. Further, since the vibration absorber is not fixed to the racket frame, it takes time and effort to remove and reattach the string every time the string is replaced, and there is a risk of loss when the string is removed. Further, since the weight of the vibration absorber is about 5 to 15 g, the moment of inertia of the tennis racket increases accordingly. Therefore, this tennis racket is difficult for players to handle.

[0007] Japanese Utility Model Publication No. 4-15235 discloses a tennis racket in which the vibration damping performance of a string is enhanced by inserting a vibration absorbing material made of, for example, silicone rubber into a gut through hole (string hole). Have been. However, even with this tennis racket, the study of the material of the vibration absorbing material is still insufficient, and the vibration damping performance is not satisfactory. In addition, silicone rubber is flexible and deforms when the string is stretched, so not only workability is poor, but also the contact state between the string and the vibration absorbing material is not stable, and the vibration absorbing material improves vibration damping performance. It is hard to contribute as expected.

[0008] The dynamic viscoelastic loss factor tan
A tennis racket in which the vibration damping of the string is enhanced by inserting a gut protective material having a δ within a predetermined range is disclosed in JP-A-61-73675 and JP-A-62-53.
No. 69 and Japanese Patent Application Laid-Open No. 62-5370. However, the dynamic viscoelastic loss coefficient tan δ of these gut protective materials is usually determined under the conditions where a tennis racket is used (that is, at room temperature and when the string frequency is 500
From 600 Hz), the vibration damping performance under normal conditions is not sufficient.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a racket frame excellent in damping ability of a string to be stretched under normal use conditions. It is an issue.

[0010]

According to the present invention, there is provided a racket frame provided with a head portion having a plurality of string holes formed therein, wherein at least a part of the string holes has a frequency of 10 Hz. And the temperature is -5 ° C
Dynamic viscoelastic loss coefficient tan δ measured under the condition
A racket frame provided with a vibration damping material of 3 or more and 2.3 or less is provided.

According to the knowledge of the present inventor, the normal tension (5
Room temperature (25 ° C)
Is about 500 to 600 Hz. On the other hand, the frequency is 10 Hz and the temperature is −5 ° C.
According to the law of temperature-frequency conversion, the dynamic viscoelastic loss coefficient tan δ (hereinafter, also simply referred to as “tan δ”) is measured at room temperature at a frequency of 500 to 60
This corresponds to the condition of 0 Hz, which is almost equal to the frequency of the primary vibration of the string. Therefore, when the string is stretched on the racket frame of the present invention, the vibration of the string generated at room temperature is efficiently attenuated by the vibration damping material. The vibration damping material in which tan δ falls within the above range under the measurement conditions of a frequency of 10 Hz and a temperature of −5 ° C. has not been present in the above-described conventional racket frame. Note that the above-mentioned temperature-frequency conversion law is obtained by superimposing a dynamic viscoelastic curve when the frequency is fixed and the temperature is changed with a curve when the frequency is changed. Ideally, tan δ is measured under the condition of a frequency of 500 to 600 Hz at room temperature. However, since it is impossible to measure under this condition, this conversion law is used.

Preferably, the complex elastic modulus E * of the vibration damping material measured at a frequency of 10 Hz and a temperature of -5 ° C. is 1 × 10 ⁸ dyn / cm ² or more and 50 × 10 ⁸ d.
yn / cm ² or less. In a so-called thick racket in which the thickness of the racket frame in the out-of-plane direction (perpendicular to the hitting surface) is large and the weight is reduced, the out-of-plane secondary natural frequency is 500 to 600.
Hz. This natural frequency approximately matches the natural frequency of the string. By setting the complex elastic modulus E * within the above range, a string whose natural frequency matches the out-of-plane secondary natural frequency of the racket frame can easily function as a dynamic vibration absorber for the racket frame. Therefore, not only the vibration of the string but also the vibration damping performance of the racket frame can be enhanced.

[0013] Preferably, the Shore A hardness of the vibration damping material is 60 or more and 95 or less. Thereby, the workability at the time of string stretching is enhanced while the vibration damping performance is maintained.

Preferably, the number of string holes into which the vibration damping material is inserted is at least 3% and at most 90% of the total number of string holes. Thereby, the vibration damping performance of the string is efficiently enhanced.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Embodiments of the present invention will be described in detail. FIG. 1 is a front view showing a part of a racket frame 1 according to an embodiment of the present invention, together with a string 3. The racket frame 1 is for hard tennis, and has a head portion 5, two throat portions 7, and a shaft portion 9. The head portion 5 has an outline of a striking surface, and its cross-sectional shape is substantially elliptical. One end of each of the two throat portions 7 extends from the head portion 5 and merges with each other at the other end. The shaft portion 9 extends from a place where the two throat portions 7 and 7 join, and is formed continuously and integrally with the throat portion 7. The portion of the head portion 5 sandwiched between the two throat portions 7 is a yoke portion 11. A first protection member 13 described later in detail is mounted on the yoke portion 11 of the head portion 5. Further, a second protective member 17 described later in detail is mounted near the upper end (top portion 15) in FIG. Although not shown, a grip portion is formed at the rear end of the shaft portion 9 continuously and integrally with the shaft portion 9. Further, although not shown, the left and right ends of the head portion 5 (side portions 1)
9) is provided with a third protective material described in detail later. Racket frame 1 is preferably made of fiber reinforced resin. Preferably, the racket frame 1 is hollow.

FIG. 2 is a perspective view showing the vibration damping member 21 mounted on the racket frame 1 of FIG. The vibration damping member 21 includes a band 23 and a plurality of cylinders 25 standing upright from the band 23. The band 23 and the cylinder 25 are integrally formed from the same material. As will be described in detail later, the cylinder 25 is inserted into a string hole of the racket frame 1. For this reason, the outer diameter of the cylinder 25 is equal to or slightly smaller than the inner diameter of the string hole. As described in detail later, the string 3
Is inserted. Therefore, the inner diameter of the cylindrical body 25 is equal to or slightly larger than the outer diameter of the string 3.

The vibration damping member 21 is formed from an elastic material. Dynamic viscoelastic loss coefficient ta of this elastic material measured at a frequency of 10 Hz and a temperature of -5 ° C.
nδ is 0.3 or more and 2.3 or less. Thereby, the vibration damping performance of the string 3 is enhanced. In particular,
The string 3 made of synthetic fiber is stretched at 50 × 45 pounds, and the string 3 is left to stand in an environment of 24 ° C. and 55% of humidity for 48 hours to have a vibration damping rate of 0.22% or more. If tan δ is less than 0.3, the vibration damping performance of the string 3 may be insufficient. On the other hand, when tan δ exceeds 2.3, an uncomfortable feeling may be easily generated at the time of hitting the ball. From these viewpoints, tan δ is preferably from 0.3 to 2.3.

The tan δ is measured by a viscoelasticity measuring device (Viscoelasticity spectrometer “DVA200 improved type” manufactured by Shimadzu Corporation). The measurement condition is that the frequency is 10
Hz, the jig is tensile, and the heating rate is 2 ° C./mi.
n, the initial strain is 2 mm, and the displacement amplitude is ± 12.5 μm. The dimensions of the test piece (dumbbell) are 4.0 mm in width, 1.66 mm in thickness, and 30.0 mm in length. 5m at both ends of this test piece
Since m is chucked, the length of the displaced portion of the test piece is 20.0 mm.

Examples of the elastic material having a tan δ within the above range include a composition in which a thermoplastic elastomer is blended in a range of 5 to 80 parts by weight with 100 parts by weight of rubber such as natural rubber, butyl rubber, and acrylonitrile butadiene rubber. Can be Suitable thermoplastic elastomers include triblock copolymers having a polystyrene block and a vinyl-polyisoprene block (for example, Kuraray's trade name “Hybler”), cashew-modified phenolic resins (for example, Sumitomo Durez's trade name “Sumi”). Light Resin PR-1
2687 ”). Further, instead of or together with these thermoplastic elastomers, a large amount of rubber (for example, 6
A composition to which 0 to 120 parts by weight of carbon black is added can also be suitably used.

Further, as another elastic material having tan δ within the above range, a modified polymer composition can be mentioned. This composition comprises polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polymethyl methacrylate, polyvinylidene fluoride, polyisoprene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer And an acrylonitrile-butadiene copolymer, a styrene-butadiene copolymer, a polybutadiene, a natural rubber, and other polymers mixed with an active ingredient that increases the amount of dipole moment. This active ingredient includes those having a large amount of dipole moment itself, and those having a small amount of dipole moment itself but having an effect of increasing the amount of dipole moment of the composition when mixed with a polymer. It is. Specific active ingredients include cyclohexane, benzothiazole, dicyclohexylamine,
Cyclohexylamine, higher fatty acids and the like can be mentioned, and these can be used alone or in combination of two or more.

Further, a filler such as mica, glass piece, glass fiber, carbon fiber, calcium carbonate, barlite, precipitated barium sulfate, a corrosion inhibitor, a dye, an antioxidant, a stabilizer, a wet A composition to which an agent or the like is added in an appropriate amount can also be suitably used.

The frequency of the vibration damping material 21 is 10 Hz.
And the complex elastic modulus E measured at a temperature of −5 ° C.
* Indicates 1 × 10⁸dyn / cm^TwoMore than 50 × 10⁸dy
n / cm^TwoThe following is preferable, and 3 × 10⁸dyn / cm^TwoLess than
Upper 35 × 10⁸dyn / cm ^TwoThe following are particularly preferred. S
Tring 3 functions as a dynamic vibration absorber for racket frame 1
In order to achieve this, the vibration damping material 21 acts as a kind of spring.
The complex elastic modulus E * is less than the above range.
Then, the vibration damping material 21 should be out of the optimal range as a spring.
Of racket frame 1 and insufficient attenuation of out-of-plane secondary vibration
It may be. Conversely, the complex elastic modulus E *
Beyond the above range, the vibration damping material 21 is similarly used as a spring.
Out of plane of racket frame 1 out of the optimal range of
In addition to insufficient vibration damping, vibration damping
The material 21 cannot follow the movement of the string 3
The vibration damping of the ring 3 may be insufficient.
You.

The Shore A hardness of the vibration damping material 21 is 6
It is preferably from 0 to 95, particularly preferably from 70 to 92. If the hardness is less than the above range, the vibration damping member 21 is likely to be deformed at the time of string stretching, and the workability may be reduced. Conversely, if the hardness exceeds the above range, it may be difficult to maintain the value of tan δ described above.

FIG. 3 is an enlarged exploded front view showing the vicinity of the yoke portion 11 of the racket frame 1 of FIG. A vibration damping material 21 and a first protection material 13 are mounted on the yoke portion 11. The vibration damping member 21 is of the type shown in FIG. 2 and includes four cylinders 25. First protective material 13
Is made of a hard material such as a synthetic resin. The first protective material 13 is
The rigid band 27 and two standing upright from both ends of the rigid band 27
And a plurality of hard cylinders 29.
And the hard cylinder 29 are integrally formed from the same material. Six string holes 31 are formed in the yoke portion 11. In the entire racket frame 1, a total of 70 string holes 31 are formed, for 32 for warp and 38 for weft.

The vibration damping member 21 is attached to the string hole 3
1 is achieved by inserting the cylindrical body 25 from the outside to the inside of the yoke portion 11. The attachment of the first protection member 13 is achieved by inserting the hard cylindrical body 29 into the string hole 31. That is, of the six string holes 31, the cylinder 25 of the vibration damping material 21 is inserted in four of the string holes 31 near the center, and the hard cylinder 29 of the first protection material 13 is inserted in the other two of them. Be worn. When the string 3 is stretched, the string 3 is inserted through the cylinder 25 and the rigid cylinder 29. Outside (back side) of the band 23 of the vibration damping material 21
Is covered by the hard band 27,
The outside of the string 3 does not directly contact the folded string 3. This prevents the band 23 from being broken by the load from the string 3. When the tennis ball is hit by the racket frame 1, the vibration generated in the string 3 is attenuated by the vibration damping material 21.

The band 23 is made of an elastic material as described above and is flexible. Therefore, even if the pitch of the cylindrical body 25 slightly deviates from the pitch of the string holes 31,
Is deformed, the cylindrical body 25 can be inserted into the string hole 31. Further, the band 23 is interposed between the yoke portion 11 and the first protective material 13, and suppresses resonance between the yoke portion 11 and the first protective material 13.

The material of the first protection member 13 is a vibration damping member 21.
From the viewpoint of protecting the rubber, those having a high elastic modulus at room temperature are suitable. Specifically, the complex elastic modulus E measured at a frequency of 10 Hz and a temperature of 25 ° C. (normal temperature)
* Is 2.0 × 10 ⁸ dyn / cm ² or more and 120 × 10
⁸ dyn / cm ² or less, especially 10 × 10 ⁸ dyn / c
m ² or more 100 × ¹⁰ 8 dyn / cm ² or less being preferred. If the complex elastic modulus E * is less than the above range, the first protection member 13 may become weak and the protection of the vibration damping member 21 may be insufficient. Conversely, when the complex elastic modulus E * exceeds the above range, the deformation of the first protective member 13 becomes difficult, and it may become difficult to follow the head portion 5. Specific examples of the material used for the first protective material 13 include polyamide (especially nylon 11, nylon 12), polyether block amide, and the like.

FIG. 4 is an enlarged exploded front view showing the vicinity of the top portion 15 of the racket frame 1 of FIG. The vibration damping member 21 and the second protection member 17 are mounted on the top portion 15. The vibration damping member 21 is of the type shown in FIG. 2 and includes eight cylinders 25. Second protective material 17
Is equivalent to the first protective material 13 shown in FIG. The second protective member 17 includes a hard band 27 and the hard band 2.
The rigid band 27 and the rigid cylinder 29 are integrally formed of the same material.

The vibration damping member 21 is mounted on the string hole 3
This is achieved by inserting the cylindrical body 25 into the top part 1 from the outside to the inside of the top part 15. The attachment of the second protection member 17 is achieved by inserting the hard cylinder 29 into the string hole 31. That is, eight of the string holes 31 of the head portion 5 near the tip end are provided with the vibration damping material 21.
Of the second protection member 17 is inserted into the other string hole 31. String 3
Is stretched, the string 3 is inserted through the cylinder 25 and the rigid cylinder 29. The vibration of the string 3 is attenuated by the cylindrical body 25. The second protection member 17 plays a role of protecting the vibration damping member 21 as in the first protection member 13 shown in FIG. The second protection member 17 also serves to protect the top portion 15 when the racket frame 1 comes into contact with the ground during a swing, for example. In this sense, the second protection member 17 is also called a bumper.

FIG. 5 is an enlarged exploded front view showing the vicinity of the right side portion 19 of the racket frame 1 of FIG.
The side portion 19 includes a vibration damping material 21 and a third protection material 33.
Is installed. The vibration damping member 21 is of the type shown in FIG. 2 and includes nine cylinders 25. The material of the third protection member 33 is the same as that of the first protection member 13 shown in FIG. The third protective member 33 is composed of a hard band 27 and a number of hard cylinders 29 rising from the hard band 27. The hard band 27 and the hard cylinder 29 are integrally formed of the same material. Is formed.

The vibration damping member 21 is mounted on the string hole 3
1 is achieved by inserting the cylindrical body 25 from the outside to the inside of the side portion 19. The attachment of the third protection member 33 is achieved by inserting the hard cylindrical body 29 into the string hole 31. That is, the cylinder 25 of the vibration damping material 21 is inserted into nine of the string holes 31 of the side portion 19, and the hard cylinder 29 of the third protection material 33 is inserted into the other string holes 31. You. When the string 3 is stretched, the string 3 is inserted through the cylinder 25 and the rigid cylinder 29. The vibration of the string 3 is attenuated by the cylindrical body 25. The third protective member 33 plays a role of protecting the vibration damping member 21 as in the first protective member 13 shown in FIG. Although the right side portion 19 is shown in FIG. 5, the vibration damping material 21
And the third protection member 33 is mounted.

In the racket frame 1 shown in FIGS. 1 to 5, the vibration damping material 21 is mounted on the yoke portion 11, the top portion 15, and the side portions 19 on both sides. The position is not limited to this. For example, the vibration damping material 21 may be mounted only on the yoke portion 11, only on the top portion 15, or only on the side portions 19 on both sides. Further, the vibration damping material 21 may be attached to the yoke 11 and the top 15, may be attached to the yoke 11 and the side 19, or may be attached to the top 15 and the side 19. You may. Further, the vibration damping material 21 may be attached near a middle point between the yoke part 11 and the side part 19 or near a middle point between the top part 15 and the side part 19. In addition,
The vibration damping material 21 is dispersed at a plurality of locations of the head section 5,
In addition, it is preferable to be mounted symmetrically with respect to the center axis from the viewpoint of improving the vibration damping performance.

In the racket frame 1 shown in FIGS. 1 to 5, the yoke 11
, Eight of the top part 15 and eighteen of the side parts 19 on both sides (9 on each side),
Is inserted. That is, the ratio of the number of string holes 31 in which the cylindrical body 25 is inserted to the number of all string holes 31 (hereinafter also referred to as “insertion ratio”) is:
43%. String hole 31 into which cylinder 25 is inserted
The position and the number can be variously changed, but even if changed, from the viewpoint of maintaining the vibration damping performance, the vibration damping members 21 are arranged so that the insertion ratio is 3% or more, particularly 5% or more. Preferably. In addition, the higher the insertion ratio, the higher the vibration damping performance is. Therefore, the upper limit does not need to be particularly defined. However, if the upper limit is too high, the effect reaches a peak and the cost is uneconomical. Since the string hole 31 for insertion is required, the insertion ratio is preferably 90% or less, particularly preferably 80% or less.

FIG. 6 is a perspective view showing a vibration damping member 35 of a racket frame according to another embodiment of the present invention. The vibration damping member 35 includes a cylindrical body 37 and a flange 39. This vibration damping material 35 is formed from the same material as the vibration damping material 21 shown in FIG.
When this vibration damping material 35 is used, the string holes 3
The cylindrical body 37 is inserted into 1. The flange 39 functions as a positioning stopper at the time of insertion. Further, the flange is interposed between the head portion 5 and the protective material, and suppresses the resonance between the two.

[0035]

EXAMPLES Hereinafter, the effects of the present invention will be clarified based on examples, but it is needless to say that the present invention should not be construed as being limited based on the description of the examples.

Example 1 Five unidirectional prepreg sheets, in which the matrix was an epoxy resin and the reinforcing fibers were carbon fibers, were wound around a mandrel, and the mandrel was pulled out to produce a lay-up. This was heated in a mold at 145 ° C. and an internal pressure of 7 kgf / cm ² for 50 minutes. A string hole 32 for warp is formed in the obtained molded body.
(16 × 2) and 38 string holes for weft (19
× 2).

On the other hand, 100 parts by weight of butyl rubber (trade name “IIR268” of Nippon Synthetic Rubber Co., Ltd.), 60 parts by weight of ISAF carbon black (trade name “Dia I” of Mitsubishi Chemical Corporation), a polystyrene block and a vinyl-polyisoprene block 20 parts by weight of a triblock copolymer (trade name "HIBLER HVS-3" of Kuraray Co., Ltd.), 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 1 part by weight of sulfur, a vulcanization accelerator (Ouchi Shinko Chemical) Company's product name "Noxeller TE
T ") and 1.5 parts by weight of another vulcanization accelerator (trade name" Noxeller CZ "of Ouchi Shinko Chemical Co., Ltd.) were crosslinked to form a rubber composition comprising 0.5 parts by weight, as shown in FIG. A vibration damping material including a cylindrical body and a band was molded. The length of the cylinder is 15
mm. The tan δ of this vibration damping material measured at a frequency of 10 Hz and a temperature of −5 ° C. is 0.5
6, and the complex elastic modulus E * is 6.33 × 10 ⁸ dyn /
cm ² and a Shore A hardness of 74. This vibration damping material was mounted on the yoke, the top, and both side portions of the above-mentioned molded body. Specifically, the cylindrical body was inserted into four string holes in the yoke part, eight string holes in the top part, and 18 (9 × 2) string holes in the side part. The insertion ratio is 42.9%.

Next, a first protective material, a second protective material, and a third protective material made of nylon 12 (trade name: RILSON BMN-P20, manufactured by ATIO Corporation) are provided on each of the yoke, head, and side. Was attached. Each of these protective members is provided with a predetermined number of rigid cylinders, and is configured such that the rigid cylinders are inserted into the string holes where the cylinders of the vibration damping material are not inserted. The frequency of these protective materials is 10
The complex elastic modulus E * measured at a frequency of 25 Hz and a temperature of 25 ° C. was 71.3 × 10 ⁸ dyn / cm ² .
Further, an end cap and a grip tape were attached to the grip portion to obtain a rigid tennis racket frame of Example 1. This racket frame had a weight before string stretching of 210 g, a length of 27.5 inches, a thickness of 28 mm, a balance of 375 mm, and a face area of 115 inch ² .

Example 2 The shape of the vibration damping material was such that the individual cylinders were not integrated as shown in FIG. 6, and the blending amount of carbon black was not used without the high blur HVS-3. Was changed to 100 parts by weight, and a racket frame of Example 2 was obtained in the same manner as in Example 1. The flange shape of this vibration damping material was a square with a side of 4.5 mm, and the thickness was 1.0 mm. The tan δ of this vibration damping material measured at a frequency of 10 Hz and a temperature of −5 ° C. was 0.35, and the complex elastic modulus E * was 12.3 × 10 ⁸ dyn / cm ² . And a Shore A hardness of 90.

Example 3 A racket frame of Example 3 was obtained in the same manner as in Example 1 except that the cylinder of the vibration damping material was inserted only into the four string holes of the yoke. The insertion ratio is 5.7%.

Example 4 The weight was changed to 168 g and the balance was changed to 3 by changing the reinforcing form of the carbon fiber.
A racket frame of Example 4 was obtained in the same manner as Example 1 except that the thickness was set to 95 mm.

Example 5 The prepreg sheet and the mold used were changed to a weight of 267 g and a thickness of 23 mm.
A racket frame of Example 5 was obtained in the same manner as Example 1 except that the balance was set to 343 mm.

Example 6 The prepreg sheet and the mold used were changed to a weight of 297 g and a length of 27.5.
Inch, thickness 18mm, balance 316m
m, and the racket frame of Example 6 was obtained in the same manner as in Example 1 except that the face area was 105 inch ² .

Comparative Example 1 A racket frame of Comparative Example 1 was obtained in the same manner as in Example 1 except that the material of the vibration damping material was nylon 12, which was the same as the material of the protective material. Note that the vibration damping material and the protection material were integrally formed. The tan δ of this vibration damping material measured at a frequency of 10 Hz and a temperature of −5 ° C. is 0.05, and the complex elastic modulus E
* Was 178 × 10 ⁸ dyn / cm ² and Shore A hardness was 98.

Comparative Example 2 A racket frame of Comparative Example 2 was obtained in the same manner as in Example 1 except that the material of the vibration damping material was fluorinated silicone. The tan δ of this vibration damping material measured at a frequency of 10 Hz and a temperature of −5 ° C. was 0.11, and the complex elastic modulus E * was 0.19.
× 10 ⁸ dyn / cm ² , and Shore A hardness was 43.

Comparative Example 3 A racket frame of Comparative Example 3 was obtained in the same manner as in Example 1 except that the material of the vibration damping material was a polyester-based polyurethane. The tan δ of this vibration damping material measured at a frequency of 10 Hz and a temperature of −5 ° C. is 0.28, and the complex elastic modulus E *
Was 1.2 × 10 ⁸ dyn / cm ² and the Shore A hardness was 55.

[Measurement of String Vibration Damping Factor] A 1.35 mm gauge string (trade name “ATP Tour Classic” manufactured by Babora Co., Ltd.) made of polyamide resin was used for the racket frame of each of Examples and Comparative Examples for 60 pounds. Stretched. Then, a position 150 mm from the grip end was fixed with a vise, and the laser was reflected at the center of the ninth weft yarn from the top to measure the vibration attenuation rate. Specifically, a transfer function is obtained by FFT from a voltage signal that measures the force of an impulse hammer through an amplifier and a voltage signal that measures the speed of reflection of a laser on a string through a laser Doppler velocimeter, Thus, the frequency of resonance was analyzed, and the vibration damping rate was calculated. The results are shown in Table 1 below.

[Measurement of Out-of-Plane Secondary Natural Frequency of Racket Frame] A racket frame on which a string was not stretched was hung with a string, and an accelerometer was attached to a shaft portion. Then, the shaft on the back side of the accelerometer was vibrated with an impact hammer. The out-of-plane secondary natural frequency was determined from the input vibration measured by the force pickup meter attached to the impact hammer and the response vibration measured by the acceleration pickup meter. The results are shown in Table 1 below.

[Measurement of Out-of-Plane Secondary Damping Rate of Racket Frame] The input vibration and response were measured in the same manner as the above-described method of measuring the out-of-plane secondary natural frequency except that a racket frame with strings was used. The out-of-plane secondary damping rate was determined from the vibration. The results are shown in Table 1 below.

[Evaluation of Workability] The workability when string was stretched on each racket frame was evaluated. When inserting the string into the cylinder, the case where the cylinder moves along with the string and enters the racket frame, or the case where the cylinder extends in the racket frame direction and is bitten into the string hole is referred to as " X ". A case where such a problem did not occur was marked as “○”. The results are shown in Table 1 below.

[0051]

[Table 1]

In Table 1, in Comparative Examples 1, 2 and 3 in which a vibration damping material having a tan δ smaller than 0.3 measured at a frequency of 10 Hz and a temperature of -5 ° C. was used. The racket frame is inferior in the vibration damping performance of the string. In contrast, this tan δ is 0.3
The racket frame of each embodiment that is 2.3 or less is
Excellent vibration damping performance of the string. From these experimental results, the superiority of the racket frame of the present invention was confirmed. As described above, the vibration damping material excellent in the vibration damping performance of the string is particularly a long lightweight tennis racket (27 inches or more in length and 1 weight in which string vibration is a problem).
60 to 270 g).

Although the present invention has been described in detail by taking a racket frame for hard tennis as an example, the present invention can be applied to various racket frames such as a racket frame for soft tennis and a racket frame for badminton. It is.

[0054]

As described above, the racket frame of the present invention has an excellent damping ability against vibration under the normal use condition of the string to be stretched. A player using this racket frame rarely feels discomfort due to vibration when hitting a ball, and the occurrence of tennis elbow is suppressed.

[Brief description of the drawings]

FIG. 1 is a front view showing a part of a racket frame according to an embodiment of the present invention together with strings.

FIG. 2 is a perspective view illustrating a vibration damping material mounted on the racket frame of FIG. 1;

FIG. 3 is an enlarged exploded front view showing the vicinity of a yoke portion of the racket frame of FIG. 1;

FIG. 4 is an enlarged exploded front view showing the vicinity of a top portion of the racket frame of FIG. 1;

FIG. 5 is an enlarged exploded front view showing the vicinity of a right side portion of the racket frame of FIG. 1;

FIG. 6 is a perspective view illustrating a vibration damping member of a racket frame according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Racket frame 3 ... String 5 ... Head part 7 ... Throat part 9 ... Shaft part 11 ... Yoke part 13 ... First protective material 15 ... Top part 17 ... Second protective material 19 ... Side part 21,35 ... Vibration damping material 23 ... Band 25,37 ... Cylinder 27 ... Hard band 29 ... Hard cylinder 31 ... string hole 33 ... third protective material 39 ... flange

Claims (4)

[Claims] 1. A racket frame provided with a head portion having a plurality of string holes, wherein at least some of the string holes are measured at a frequency of 10 Hz and a temperature of -5 ° C. A racket frame in which a vibration damping material having a dynamic viscoelastic loss coefficient tan δ of 0.3 or more and 2.3 or less is inserted. 2. A frequency of 10 Hz and a temperature of -5 ° C.
The complex elastic modulus E * of the vibration damping material measured under the conditions of
But 1 × 10⁸dyn / cm^TwoMore than 50 × 10 ⁸dyn
/ Cm^TwoThe racket frame according to claim 1, which is:
M 3. The racket frame according to claim 1, wherein the Shore A hardness of the vibration damping material is 60 or more and 95 or less. 4. The number of string holes into which the vibration damping material is inserted is 3% or more and 90% of the total number of string holes.
The racket frame according to any one of claims 1 to 3, which is as follows.