JP2001204854A - End cap and racket frame on which end cap is mounted - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give vibration absorbing function to an end cap mounted on a racket end. SOLUTION: The end cap is formed of a material which resonates with the vibration of a racket to give vibration absorbing function to the end cap. That is, the end cap is formed of a material which has a complex modulus of 3×107 to 50×108 dyn/cm2 measured under the condition of frequency 10 Hz and temperature range 5-15 degrees C and a visco-elasticity loss efficient tanδ of 0.1 to 2.3. A through-hole is provided in a cover portion of the end cap for easy flexibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end cap attached to a racket frame for hard tennis, soft tennis, etc., and a racket frame to which the end cap is attached, and more particularly to a racket frame made of fiber reinforced resin or metal. The end cap attached to the rear end of the grip is improved to improve the vibration absorption and shock absorption of the grip portion gripped by the player without increasing the weight of the racket frame.

[0002]

2. Description of the Related Art In recent years, racket frames have become the mainstream of fiber-reinforced resins, taking advantage of their features such as light weight, high rigidity, high strength and durability. In addition, the development of racket frames made of aluminum alloy and titanium alloy is also in progress. Usually, the racket frame is integrally formed from a thermosetting resin reinforced with high-strength, high-modulus fibers such as carbon fibers. Alternatively, it is formed by processing a light alloy tube into a frame shape, and fixing a plastic connecting portion after heat treatment. Although these materials have high rigidity and are excellent, they have a problem that vibrations are easily generated when subjected to an impact, and a tennis elbow or the like is easily given to a player.

[0003] For those using the above thermosetting resin,
Racket frames made of fiber reinforced thermoplastic resin using continuous fibers as reinforcing fibers have also been provided. This racket frame reflects the high toughness of the thermoplastic resin and obtains shock resistance and vibration damping properties, etc., which cannot be obtained with the above-mentioned thermosetting resin racket frame or light alloy racket frame such as aluminum. be able to. However,
In general, thermoplastic resins have a greater environmental dependency of elastic modulus than thermosetting resins, and racket frames have the disadvantage that characteristics such as rigidity are liable to change depending on the use environment.

In recent years, there has been an increasing demand for lighter rackets, and rackets of 250 g or less have been provided, and rackets of 230 g or less have been studied. As described above, as the weight becomes lighter, improvement in shock absorption and vibration damping properties has been desired. However, if the weight increase is large in order to improve the vibration damping property and the shock absorbing property, it becomes impossible to achieve both the light weight and the vibration damping property and the shock absorbing property.

As a racket of this type for improving vibration damping, a weight is partially arranged on a racket frame, and the vibration of the frame is suppressed by synchronizing with the vibration of the frame, so that the function of a dynamic vibration absorber (dynamic damper) is achieved. A racquet frame having a structure utilizing the same has been proposed.

For example, Japanese Patent Laid-Open No. 62-192182 discloses a racket frame in which a vibration absorber having a rod having a mass attached to a free end supported by a viscoelastic member is installed on a racket frame body. A device in which a vibration absorbing device is attached to a racket frame body has been proposed.
In the above-mentioned vibration absorbing device, the rod of the dynamic vibration absorber resonates at the time of hitting the ball and moves up and down, and the compression and shear deformation of the low resilience rubber is caused by this movement, the vibration energy is radiated, and the vibration is damped. Is what you do. In addition, Japanese Unexamined Patent Publication No.
In a tennis racket of -52030, attention is paid to the vibration of about 100 Hz, and the dynamic vibration absorber is arranged at the antinode of the vibration of the racket frame.

[0007]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 62-19 / 1987
The racket frame vibration absorbing device disclosed in No. 2182 can only resonate with either the primary vibration or the secondary vibration of the racket frame. Although the vibration mode of the racket frame has many degrees of freedom and is complicated, the vibration absorbing device can absorb only a specific frequency, and the vibration mode of the racket frame also has in-plane vibration. However, resonance of in-plane vibration is difficult and cannot be absorbed. Further, when the vibration absorbing device is installed on a racket frame, there is a problem that the weight increases. Also,
As a result of mounting the vibration absorbing device on a racket frame and conducting a test, the rod of the vibration absorbing device hit the inner wall of the frame, and in fact, contrary to the intended purpose, a large vibration was felt.

On the other hand, in a tennis racket described in Japanese Patent Laid-Open No. 49-52030, vibration of about 100 Hz is absorbed, but other vibrations are not considered. In addition, the dynamic vibration absorber requires weight, and the entire racket becomes heavy. In addition, when the dynamic vibration absorber comes out of the grip end, there is a problem that the dynamic vibration absorber easily hits the body when hitting a ball.

As described above, any of the conventionally proposed dynamic vibration absorbers added to the racket frame only contributes to the damping of a specific vibration mode of the racket, and is optimal for the vibration characteristics of the racket. However, there is a problem that it is difficult to perform a proper matching and that the weight increases.

The present invention has been made in view of the above-mentioned problems, and a dynamic vibration absorber capable of coping with various vibration modes of a racket is mounted on a racket frame without increasing the weight, and the dynamic vibration absorber is provided with a ball. The objective is to be able to absorb the impact transmitted to the player's arm and elbow when hitting.

[0011]

In order to solve the above-mentioned problems, the present invention focuses on an end cap attached to a rear end (racquet end) of a grip portion of a racket frame, and attaches the end cap to a dynamic vibration absorber. It has a function. That is, the material of the end cap attached to the grip end located at the antinode of the vibrations (out-of-plane primary, secondary vibration and in-plane vibration) of the various modes of the racket frame is a material that resonates with the vibrations of the various modes, In particular, the cover of the end cap is made flexible so as to function as a dynamic vibration absorber by vibrating the cover, thereby improving vibration damping and shock absorption. In addition, a dynamic vibration absorber is not added to the racket frame, and the end cap itself is a dynamic vibration absorber, thereby achieving both reduction in weight and improvement in vibration damping and shock absorption.

That is, the present invention provides a frequency of 10 Hz, a temperature of 5
The complex elastic modulus measured under the condition of any temperature within the range of １５15 ° C. is 3 × 10 ⁷ to 50 × 10 ⁸ dyn / cm.
^The end cap is made of a material in the range of No. 2 and includes a tubular portion fitted around the outer peripheral surface of the grip rear end of the racket frame and a lid portion covering the rear end surface of the grip.

The material of the end cap has a complex elastic modulus within the above range at a frequency of 10 Hz and a temperature of 5 ° C. to 15 ° C., and has a viscoelastic loss coefficient tan δ measured under the same conditions. Is in the range of 0.1 to 2.3.

When measuring the viscoelasticity, the temperature condition should be 5 to 1
The reason for specifying the range of 5 ° C. is due to the frequency-temperature conversion rule, which is an empirical rule for measuring viscoelasticity. According to this rule of thumb, one order of frequency is considered to correspond to a temperature of 10 ° C. Out-of-plane primary vibration of racket frame is 100-200
Hz, and the out-of-plane secondary vibration is about 400 to 500 Hz. Further, the in-plane vibration is affected by the string tension and is in the range of 300 to 800 Hz. Therefore, attention is focused on 5 to 15 ° C., which is 10 to 20 ° C. lower than room temperature.

Therefore, the complex material having a complex elastic modulus of 3 × 10 ⁷ to 50 × 10 ⁸ measured by viscoelasticity under the conditions of a frequency of 10 Hz and a temperature of 5 to 15 ° C.
dyn / cm ² , preferably 1.0 × 10 ⁸ to 30 × 1
When set to the range of 0 8 ^dyn / cm ^2, the combined end cap to the vibration of various vibrational modes of the racket frame, it is possible to resonate. If the complex elastic modulus is out of the above range, it becomes difficult to resonate with the vibration of the racket frame in various vibration modes.

Further, as described above, the material of the end cap is set such that tan δ which is a loss coefficient of viscoelasticity measurement at 10 Hz in the range of 5 to 15 ° C. is 0.1 to 2.3, preferably 0.3 to 2.3. 2.0. this is,
Forced vibration generated when hitting a ball with a racket is 1
It can be said that it is within the range of 00 to 1000 Hz. Therefore, by setting tan δ in the above temperature range to a range of 0.1 to 2.3, it is possible to efficiently suppress the force (acceleration) generated by the impact. If tan δ is less than 0.1, the attenuation of vibration is poor, and if it exceeds 2.3, the player does not have a firm feeling when holding.

FIG. 13 shows the relationship between the transfer function relating to the vibration of the frame and the complex elastic modulus and the loss coefficient. FIG.
(A) shows the vibration of the frame body,
(B) shows the vibration when the end cap whose complex elastic modulus is within the range of the present invention is attached, and (C) shows the vibration when the end cap whose complex elastic modulus and loss coefficient are within the range of the present invention is attached. Indicates vibration. The intensity ratio (dB) of (A) is large and the peak is sharp, so that the vibration hardly stops and the vibration hardly attenuates. On the other hand, the intensity ratio (dB) of (B) is reduced, the peaks are dispersed, and the vibration is easily stopped, and the vibration damping property is improved. further,
The intensity ratio (dB) of (C) is very small, the intensity is weak, and there is no sharp peak, so that the vibration damping property is greatly improved. From this relationship, when the complex elastic modulus of the end cap is within the range of the present invention, the vibration damping property can be enhanced. Further, when the complex elastic modulus and the loss coefficient are within the range of the present invention, the vibration damping property is significantly increased. Will be enhanced.

The end cap is generally located at a portion corresponding to the palm for the player, and by increasing tan δ at a predetermined frequency, it becomes possible to greatly increase the shock absorption, and the end cap is transmitted to the player. Shock can be reduced.

The thickness of the lid of the end cap is 0.3
~ 6.0 mm (more preferably 2.0-5.0 mm)
mm), and is constant or partially changed within this range. The rigidity of the lid can be specified by the thickness and the complex elastic modulus of the lid, and the lid can function as a dynamic vibration absorber adapted to the vibration of the racket frame. That is, when the thickness of the lid portion exceeds the above range, not only does the performance of the dynamic vibration reducer decrease, but also when the thickness increases, there is a problem that the thickness increases. On the other hand, if it is thinner than the above range, it is easily broken, which is not preferable in terms of strength.

The end cap may be one in which the cylindrical portion and the lid portion are integrally formed, or may be formed as a separate body and detachably connected. In the case of this separate end cap, the lid portion is formed from the material having the complex elastic modulus, but the cylindrical portion may be formed from another material.

It is preferable that one or a plurality of through holes are provided in a part of the lid. By providing the through-holes in this manner, the lid can be more easily bent, and can easily resonate with the vibration of the racket frame,
The function as a dynamic vibration absorber can be promoted. It is also preferable that the shape of the through hole is non-linearly symmetric about the axis parallel to the racket face. Due to the non-linear symmetry, the vibration of the lid can generate not only a direction perpendicular to the plate but also a vibration with a torsional behavior. As a result, it is possible to cope with a multi-degree (complex) vibration mode of the racket frame.

Further, the cover has a diameter of 1 to 4 mm and a length of 3 to 2 mm.
A protrusion protruding inside 0 mm may be provided. By providing the projections in this way, it is possible to promote the twisting behavior without increasing the weight significantly. Furthermore, the position of this projection can promote torsional vibration of the lid by removing the center of the lid.

Further, the lid may be provided with a concentrated weight portion of 1 to 3 g. Specifically, it is preferable to provide a concentrated weight portion by burying an object having a large specific gravity in the lid. If the weight exceeds 3 g, the vibration of the lid does not match the frequency of the frame, while if it is less than 1 g, the torsional behavior cannot be promoted.

As the material for forming the end cap,
The following are mentioned. (1) Thermoplastic polyurethane (for example, ICI Polyurethane Co., Ltd., trade name “Avalon 90AB”) (2) Styrene-based elastomer (3) Ionomer (for example, Mitsui Dupont Corp., trade name “Himilan 1605”, “Himilan 1702”) (4) Water (5) Compound rubber based on natural rubber, butyl rubber, acrylonitrile butadiene, etc. Specifically, 100 parts of rubber material are polystyrene and vinyl polyisoprene Is combined with 5
To 80 parts by weight, and the polystyrene and vinyl polyisoprene combined block copolymer (for example,
Kuraray's trade name “HIBLER”) In addition, not only the above block copolymer in which polystyrene and vinyl polyisoprene are bonded, but also various other thermoplastic resins (for example, Sumitomo Purez's trade name “Sumilite Resin PR”)
In addition, as an additive, norbornene is synthesized from ethylene and cyclopentadiene, and a polymer structure having a five-membered ring and a double bond in a main chain obtained by ring-opening polymerization of this norbornene is added in a large amount. A rubber-like oil-extended polymer to which an extender oil has been added may be added. (6) Triblock copolymer having a polystyrene block and a vinyl-polyisoprene block (for example, Kuraray's trade name “Hybler”) alone or a mixture thereof. Examples of the mixture include inorganic fillers such as mica and calcium carbonate, polystyrene, polypropylene, HDPE, E
Polymer blended with VA, ABS, etc. (7) Cashew-modified phenol resin (for example, Sumitomo Purez Co., Ltd. product name "Sumilite Resin PR-1268")
7)) (8) Polymer alloy type material composed of multiple polymers including ester-based polymer and halogen-based polymer (for example, “Elastage”, trade name of Tosoh Corporation) (9) Modification of thermoplastic resin and rubber Formulation. For example, polyvinyl chloride, polyethylene, polypropylene, ethylene vinyl acetate copolymer, polymethyl methacrylate, polyvinylidene fluoride, polyisoprene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, NB
Polymer materials such as R, SBR, butadiene rubber, natural rubber, isoprene rubber, and blends thereof are used as the main components, and mica, glass pieces, glass fiber, carbon fiber, calcium carbonate, bar light,
A compound to which substances such as precipitated barium sulfate, corrosion inhibitors, dyes, antioxidants, stabilizers, wetting agents, etc. are added as required. (10) A blend of a polymer and an active ingredient The active ingredient is a substance having a large amount of its own dipole moment, or a dipole of a base material having a small amount of its own dipole moment being added. A substance that increases the amount of moment. Suitable active ingredients include cyclohexane, benzothiazole, dicyclohexylamine,
Examples thereof include cyclohexylaniline and higher fatty acids, which may be used alone or in combination of two or more. Specific examples of the polymer to which the active ingredient has been added include chlorinated polyethylene-modified materials (for example, CLU Co., Ltd. product names "Ulenein" and "Diporgy Film")

Further, the present invention provides a racket frame to which the above-mentioned end cap is attached. The racket frame employing this end cap is particularly suitable for a light weight racket frame in which it is usually difficult to improve the vibration damping property. However, if the weight is too small, there is a limit in improving the vibration damping property. Specifically, the present invention can be suitably applied to a racket frame whose weight (mass excluding strings) is 180 g or more and 305 g or less.
Further, the present invention is also suitably used for a racket frame having a total length of 660 mm to 737 mm from the viewpoint that the natural frequency of the entire racket frame and the natural frequency of the handle member can be easily adjusted.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an end cap and a racket frame to which the end cap is attached according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the racket frame is
It has a head part 1, a throat part 2, a shaft part 3, a grip part 4, and a yoke part 5, and an end cap 10 is attached to a rear end opening of the grip part 4. The frame body 8 constituting the head portion 1, the throat portion 2, the shaft portion 3 and the grip portion 4 is formed of a hollow pipe made of fiber reinforced resin.

FIGS. 2A and 2B show the end cap 10 of the first embodiment. The end cap 10 includes an octagonal cylindrical portion 11 that fits over the rear end outer peripheral surface of the grip portion 4 and an octagonal lid portion 12 that closes the rear end opening of the grip 4. The cap 10 has a cylindrical portion 11
And the lid 12 are integrally formed.

The end cap 10 has a frequency of 10H.
z, the complex elastic modulus E * measured under the temperature condition of 5 to 15 ° C. is 3 × 10 ⁷ to 50 × 10 ⁸ dyn / c.
m ² , the viscoelastic loss factor measured under the same conditions is t
It is formed from a material having an δ in the range of 0.1 to 2.3. The material is formed from a mixture of one or more of the above (1) to (10).

The lid 12 has a thicker portion 12a at its outer peripheral portion which is in contact with the end face of the grip portion 4, and has a thick portion 12a at other portions, and a step 12c as a thin portion 12b. Protrusions 12d protruding from the inner surface are provided at opposing portions of the step 12c, and these protrusions 12d are
In the opening. The lid 12 has a thickness of the thick portion 12a and the thin portion 12b of 1.0 to 6.0 mm.
Within the range. The protrusion 12d has a protrusion amount of 3 to 2
It is within the range of 0 mm.

One or a plurality of through holes 13 are provided in the thin portion 12b for closing the grip opening of the lid portion 12. In the first embodiment, an upper line X and a lower line Y are set with a line parallel to the face surface S surrounded by the head unit 1 as an axis L as a symmetry axis.
Are provided with a pair of through holes 13a and 13b. These two through-holes 13a and 13b have a curved shape on the inside because an oval-shaped closing portion 14 is left in the center, and have a polygonal shape on the outside parallel to the octagon of the outer shape. Hereinafter, the shape shown in FIG. 2 is referred to as an (A) shape.

The thickness of the cylindrical portion 11 is in the range of 0.3 to 6 mm, and the diameter of the cylindrical portion 11 is reduced so as to closely fit the outer peripheral surface of the grip portion 4. The end cap 10 composed of the cylindrical portion 11 and the lid portion 12 is attached by fitting the cylindrical portion 11 to the outer peripheral surface of the grip portion 4 and fitting the projection 12a of the lid portion 12 inside. (Not shown) and is fixed to the frame body 8.

As described above, the end cap 10 of the present invention
Is provided with a through hole 13 to reduce the weight, and has a configuration opposite to that of a conventional racket frame having the function of a dynamic vibration absorber in which a mass adding material is attached to add weight. When the weight is reduced by providing the through hole 13 in the end cap 10 as in the present invention, the end cap 10 is easily bent, and the material for forming the end cap is a material that easily resonates with the vibration of the frame main body in various vibration modes. The end cap works effectively as a dynamic vibration absorber, reducing weight and vibration damping,
It is possible to achieve both the improvement of the shock absorbing property.

FIGS. 3 to 7 show a through hole 1 provided in the lid 12.
3 shows a modification of the first embodiment in which the shape and position of No. 3 are changed. The shape of the lid 12 in FIGS. 3 to 7 is changed to (B), (C), or (D).
(E) and (F).

In the shape shown in FIG. 3B, one X-shaped through-hole 13 is provided, and the intersection is located at the center of the lid 12. The (C) shape shown in FIG. 4 is provided with through-holes 13 a and 13 b having three sides parallel to the outer shape of the lid 12 symmetrically with respect to the axis L above and below the lid 12. The (D) shape shown in FIG. 5 has an octagonal through hole 13 a in the center of the lid 12.
The rectangular frame 13c protrudes from below, and has a rectangular through hole 13d provided in the square frame 13c.

The (E) shape shown in FIG. 6 has a connecting portion 13e projecting from one side of an octagonal frame-shaped through-hole 13a from the outer periphery, and is connected to a central portion 13f surrounded by the octagonal frame-shaped through-hole 13a. It has a shape. The (F) shape shown in FIG. 7 has a through hole 13 composed of three sides parallel to the outer shape on both left and right sides of the axis L.
a, 13b.

In the above (D), (E) and (F), the upper and lower sides are non-linearly symmetrical with respect to the axis L. In this way, the non-linearly symmetrical vibration can generate torsional vibration, and Can be resonated in response to a complex vibration mode having multiple degrees of freedom.

FIG. 8 shows a second embodiment, in which the cover 12 is not provided with a through hole. However, as in the first embodiment,
The outer periphery of the lid 12 is made thick and the inside is made thin.

FIG. 9 shows a third embodiment, in which the cover 12 is not provided with a through-hole, but is provided with a number of protrusions 14 protruding inward. The protrusion 14 has a diameter of 1 to 4 mm and an amount of protrusion of 3 to 29 mm. The number of the protrusions 14 is different between the upper part and the lower part with respect to the axis L so as to generate torsional vibration.

It goes without saying that the through holes 13 shown in FIGS. 2 to 7 may be provided, and the projections 14 may be provided at required positions. That is, FIG. 10 shows a fourth embodiment, in which a lid 12 is provided with a through-hole 13 and a projection 14 protruding inward.

FIG. 11 shows a fifth embodiment in which a lid 12 is provided with a through hole 13 and a concentrated weight 16 made of tungsten or the like is attached to the inner surface above the axis L. Note that a projection may be provided.

Hereinafter, Examples 1 to 11 and Comparative Examples 1 to 3 of the racket frame of the present invention will be described in detail. Note that the racket shape, length, and face area were the same for both the examples and comparative examples. Maximum thickness of racket frame is 2
The length was 8 mm, the length was 28 inches, and the face area was 115 square inches.

(Example 1) A mandrel having a diameter of 14 mm was passed through a 66 nylon tube, and an epoxy resin impregnated carbon fiber prepreg (trade name “T800, P2053-12” manufactured by Toray Industries, resin content 30%) was placed on the nylon tube. Were laminated to obtain a laminate. At this time, the fiber angles of the prepreg were set to 0 °, 22 °, 30 ° and 90 °. The laminate and the yoke member were arranged in a mold having a racket frame-shaped cavity, and a connection portion with the yoke was wrapped with a CF prepreg to reinforce 15 g. In this state, the mold was clamped and the nylon tube was heated at 150 ° C. for 40 minutes while the internal pressure was 69 N / cm ² to obtain a molded body. The yoke was formed by winding a carbon fiber prepreg impregnated with an epoxy resin around a polystyrene resin. The weight of the molded low frame was 167 g.

The end cap was made of 100% by weight of Kuraray “HIBLER HVS-3” as a material, and mica 25 was used.
What mixed the weight% was used. This material was injection molded to form an end cap. The lid of the end cap had the shape of (E) above. The thickness of the lid was 4.2 mm except for the cylindrical part. In addition, φ2.5 mm and a length of 10 m are set at 2/3 from the lower edge to the upper edge of the inner surface of the lid.
m projections were provided.

Example 2 Example 1 was the same as Example 1 except that the lid of the end cap had the shape of (D) and 2 g of tungsten was arranged at the same position as the projection of Example 1. No projection is provided on the lid. Example 3 Example 3 was the same as Example 1 except that the lid of the end cap had the shape of (F) and no projection was provided. (Example 4) This is the same as Example 3 except that the shape of the lid of the end cap was changed to (C). (Example 5) This is the same as Example 1 except that the shape of the lid of the end cap was changed to (G). (Example 6) This is the same as Example 2 except that the shape of the lid of the end cap was changed to (G). (Example 7) The same as Example 1 except that "AVALON90" made of polyester-based polyurethane was used as the material of the end cap, and the thickness of the lid portion was 4.5 mm. (Example 8) The same as Example 1 except that Tosoh "Elastage IO42" was used as the material of the end cap, and the thickness of the lid was 2.3 mm. (Example 9) Example 3 except that the shape of the lid of the end cap was (G) and the thickness of the lid was 6.4 mm.
Is the same as (Example 10) Example 3 except that the shape of the lid of the end cap was (G) and the thickness of the lid was 0.7 mm.
Is the same as (Example 11) The same as Example 1 except that the weight of the low frame was 137 g, and the weight of the racket product without the string and with the end cap attached was 194 g.
And

Comparative Example 1 The procedure of Example 9 was repeated except that the material of the end cap was “PEBAX6333” manufactured by Atochem. Note that the material of the end cap is one generally used as a material of the end cap. (Comparative Example 2) The same as Example 9 except that the material of the end cap was silicon rubber. Silicon rubber, which is a material for the end cap, is generally softer than the material used for the end cap. (Comparative Example 3) The same as Comparative Example 1 except that the low frame weight was 138 g.

The weight of the end caps and the weight of the tennis racket to which the end caps were attached in the above Examples and Comparative Examples were as shown in Table 1 below. Further, the complex elastic modulus E * and the viscoelastic loss coefficient tanδ of the end cap material used were as shown in Table 1 below.

[0048]

[Table 1]

As shown in Table 1, out-of-plane primary vibration damping rate, out-of-plane secondary vibration damping rate, in-plane vibration damping rate, and elbow acceleration of the tennis rackets of Examples 1 to 11 and Comparative Examples 1 to 3 ( G)
Was measured.

(Measurement of Out-of-Plane Primary Vibration Damping Factor) A string (trade name “VF International Tour” manufactured by Babora Co., Ltd.) is provided on each racket frame with a warp 551b and a weft 481.
It was stretched with the tension of b. The strings are stretched in order to make accessories such as bumpers and grommets adhere to the racket frame. Unless these accessories are in close contact with the racket frame, abnormal measurement may not be possible due to the occurrence of abnormal resonance. This racket frame is suspended at the upper end of the head unit 1 with a string 51 as shown in FIG. 12A, and an accelerometer 53 is fixed to one joint between the head unit 1 and the throat unit 2 perpendicularly to the frame surface. did. In this state, as shown in FIG. 12B, the other joint of the head 1 and the throat 2 was vibrated by the impact hammer 55. The input vibration (F) measured by the force pickup meter attached to the impact hammer 55 and the response vibration (α) measured by the acceleration pickup meter 53 are input to the frequency analysis device 57 (manufactured by Hewlett-Packard, Inc.) via the amplifiers 56A and 56B. It was input to a dynamic single analyzer HP3562A) and analyzed. The transfer function in the frequency domain obtained by the analysis was obtained, and the frequency of the racket frame was obtained. The vibration damping ratio (ζ) was obtained from the following equation and was defined as an out-of-plane primary vibration damping rate. The measurement was performed on five racket frames, and the average value was calculated as shown in Table 1 above.
Shown in

Ζ = (1/2) × (△ ω / ωn) To = Tn / √2

(Measurement of Out-of-Plane Secondary Vibration Damping Factor) The racket frame with the strings stretched as described above is shown in FIG.
As shown in (c), the upper end of the head was hung with a string 51, and an accelerometer 53 was fixed to a continuous point between the throat portion 2 and the shaft portion 5 perpendicularly to the frame surface. In this state, the frame on the back side of the accelerometer 53 was vibrated with an impact hammer. Then, the damping rate was calculated by the same method as the out-of-plane primary vibration damping rate, and was set as the out-of-plane secondary vibration damping rate. Table 1 shows the average values measured for the five racket frames of each example and comparative example.

(Measurement of In-Plane Vibration Attenuation Rate) FIG. 12D shows a racket frame on which strings are stretched as described above.
As shown in FIG. 5, the racket is turned downward, and the confluence of the shaft portion 3 and the throat portion 2 is suspended by a string 51, and the head portion 1
The accelerometer 53 was fixed to one side of the maximum width position of the frame so as to be parallel to the frame surface (face surface S).
In this state, the throat section 3 was vibrated with an impact hammer. Then, the damping rate was calculated by the same method as the out-of-plane primary vibration damping rate, and was set as the in-plane secondary vibration damping rate. Table 1 shows the average values measured for the five racket frames of each example and comparative example.

(Measurement of Impact Acceleration at Elbow) Using the frequency analyzer and the acceleration pickup used for the vibration measurement shown in FIG. 12, an acceleration pickup was attached to the bone portion of the elbow of the player. The player held the racket with his hand and kept still until just before hitting the ball. The end cap was held against the lower left part of the right palm. In this state, the acceleration of the elbow when the ball was hit against the center of the face surface at a speed of 30 m / sec was measured. The acceleration with respect to time was measured, and the maximum peak of the acceleration was read.
Table 1 shows the average values measured for the five racket frames of each example and comparative example.

As shown in Table 1, the rackets of Examples 1 to 12 have a high out-of-plane primary vibration damping rate of 1.09 to 0.63 while maintaining a light weight of 194 g to 226 g.
The out-of-plane primary vibration damping rate of 0.31 of Comparative Example 1 and Comparative Example 3 to which the end cap generally used in the related art is attached,
It was considerably higher than 0.30. Similarly,
The out-of-plane secondary vibration damping rate was also as high as 1.41 to 0.63, and was considerably higher than the out-of-plane secondary vibration damping rates of Comparative Examples 1 and 3 of 0.40 and 0.37. . Furthermore, the in-plane vibration damping rate was as high as 1.58 to 0.75, which was considerably higher than the in-plane vibration damping rates of Comparative Examples 1 and 3 of 0.39 and 0.36. In particular, the lightest embodiment 11 is the out-of-plane 1
Next, it was recognized that the secondary and in-plane vibration damping rates were high, and the lighter the weight, the higher the vibration damping rate. On the other hand, in Comparative Examples 1 and 3, the weight of Comparative Example 3 was lower than that of Comparative Example 1 in vibration damping rate, and it was recognized that the vibration damping rate became worse with weight reduction. Also, when the end cap of Comparative Example 2 was formed of soft silicon, the out-of-plane primary, secondary, and in-plane vibration damping rates were slightly higher than those of Comparative Examples 1 and 3; 1
It was confirmed that the effect of improving the vibration damping function was low by simply forming the end cap with a soft material.

Further, as for the impact given to the elbow of the player, as shown in the measured value of the elbow acceleration, the seventh and eighth embodiments are shown.
Examples 7 and 8 were small in the range of 1.1 to 1.6, except for
Also, 4.6 and 3.5 are drastically reduced as compared with 8.6 to 12.8 of Comparative Examples 1 to 3. From these results, it was confirmed that the use of the end cap of the present invention can reduce the impact given to the player.

[0057]

As is apparent from the above description, the end cap of the present invention itself functions as a dynamic vibration absorber, and can attenuate the vibration of the racket frame and absorb the impact. In particular, the end cap is made of a material that can resonate with vibrations of various vibration modes (out-of-plane primary vibration, out-of-plane secondary vibration, and in-plane vibration) generated when the racket frame hits a ball. Vibration damping and shock absorption can be enhanced.

Conventionally, when a dynamic vibration absorber is added to a racket frame, there is a problem that the weight increases. However, in the present invention, the end cap itself functions as a dynamic vibration absorber, so that the weight increases. Absent. Furthermore, by providing a through hole in the lid of the end cap to reduce the weight, vibration absorption and shock absorption can be further improved, and the racket frame that reduces the weight has a vibration absorption and shock absorption function. Can be compatible.

As described above, the racket frame of the present invention is attached to the racket end, and has an improved end cap that comes into direct contact with the player's hand.
It can be a racket frame excellent in weight reduction, vibration damping property and shock absorption, and is suitably used as a racket frame for hard tennis and soft tennis. In particular, it is optimal for hard tennis, in which intense vibration occurs when hitting a ball.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a racket frame.

FIG. 2 shows the first embodiment, wherein (A) is a perspective view of an end cap, and (B) is a front view of a lid.

FIG. 3 is a front view showing a modification of the first embodiment.

FIG. 4 is a front view showing another modification of the first embodiment.

FIG. 5 is a front view showing another modification of the first embodiment.

FIG. 6 is a front view showing another modification of the first embodiment.

FIG. 7 is a front view showing another modification of the first embodiment.

FIG. 8 is a front view of a lid of an end cap according to a second embodiment.

FIG. 9 is an end cap according to a third embodiment (A).
Is an inner view, and (B) is a sectional view.

FIG. 10 is a sectional view of an end cap according to a fourth embodiment.

FIG. 11 is a sectional view of a main part of an end cap according to a fifth embodiment.

12A to 12D are diagrams illustrating a method of measuring a vibration damping rate.

FIG. 13 is a diagram illustrating a relationship between a transfer function of a frame body and a complex elastic modulus and a loss coefficient of an end cap.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head part 2 Throat part 3 Shaft part 4 Grip part 10 End cap 11 Cylindrical part 12 Cover part 13 Through-hole 14 Projection

Claims (8)

[Claims] 1. A material having a complex elastic modulus in the range of 3 × 10 ⁷ to 50 × 10 ⁸ dyn / cm ² measured under the conditions of a frequency of 10 Hz and a temperature within a range of 5 to 15 ° C. And an end cap comprising: a tubular portion that is formed from an outer peripheral surface of the racket frame, the lid portion covering the rear end surface of the grip; 2. The material of the end cap has a frequency of 1
The complex elastic modulus is in the above-mentioned range in the entire range of 0 Hz and a temperature of 5 ° C. to 15 ° C., and the viscoelastic loss coefficient tan δ measured under the same conditions is in the range of 0.1 to 2.3. The end cap according to claim 1. 3. The end cap according to claim 1, wherein the thickness of the lid is constant or partially changed within a range of 0.3 to 6.0 mm. 4. The end cap according to claim 1, wherein one or a plurality of through holes are provided in a part of the lid. 5. The cover has a diameter of 1 to 4 mm and a length of 3 to 20 mm.
The end cap according to any one of claims 1 to 4, further comprising a projection protruding inward from the inside of the end cap. 6. The end cap according to claim 1, wherein the lid has a concentrated weight portion of 1 to 3 g. 7. The end cap according to claim 1, comprising a mixture containing a triblock copolymer having a polystyrene block and a vinyl polyisoprene block. 8. A racket frame to which the end cap according to claim 1 is attached.