This application claims priority to and the benefit of Japanese Patent Application No. 2020-101333, filed on Jun. 11, 2020, the entire disclosure of which is incorporated herein by reference.
The present invention relates to rackets for use in, for example, tennis.
When a player hits a ball with a tennis racket, the racket vibrates. The vibration propagates to the player, thereby causing discomfort to the player.
Japanese Laid-Open Patent Application Publication No. 2002-045444 discloses a racket frame including a fiber reinforced layer and a vibration absorber. The vibration absorber is inserted in the fiber reinforced layer. The vibration absorber can suppress the vibration that propagates to the player.
The vibration absorber disclosed in Japanese Laid-Open Patent Application Publication No. 2002-045444 has insufficient adhesion to the fiber reinforced layer. Such a vibration absorber impairs the stiffness of the frame. A racket that is inferior in stiffness is also inferior in rebound performance.
An object of the present invention is to provide a racket that is not only capable of suppressing the vibration that propagates to the player, but also has excellent stiffness.
A racket according to the present invention includes a frame. The frame includes a fiber reinforced layer and a vibration damper joined to the fiber reinforced layer. The fiber reinforced layer includes a reinforcement fiber and a matrix whose base material is an epoxy resin. A material of the vibration damper is a polymer composition whose base material is a styrene-isoprene-styrene block copolymer or an acrylic elastomer.
In the racket according to the present invention, the vibration damper damps vibration that occurs at the frame. Therefore, vibration that propagates to a player using the racket can be suppressed. This allows the player to have an excellent feel at impact. The vibration damper is excellent in adhesion to the epoxy resin of the fiber reinforced layer. Therefore, the vibration damper does not significantly impair the stiffness of the racket. The racket not only provides an excellent feel at impact, but also has excellent stiffness.
The frame may include a head, two throats, and a shaft. Preferably, each throat includes the vibration damper.
Preferably, a thickness of the vibration damper is greater than or equal to 0.10 mm but less than or equal to 1.00 mm.
Hereinafter, the present invention is described in detail based on preferred embodiments with appropriate reference to the accompanying drawings.
The frame 4 includes a head 14, two throats 16, and a shaft 18. The head 14 forms the contour of a face 20 (the face 20 will be described below in detail). The front shape of the head 14 is substantially an ellipse. The major axis direction of the ellipse coincides with the axial direction Y of the tennis racket 2. The minor axis direction of the ellipse coincides with the width direction X of the tennis racket 2. One end of each throat 16 is continuous with the head 14. Each throat 16, at the vicinity of the other end thereof, merges with the other throat 16. The throats 16 extend from the head 14 to the shaft 18. The shaft 18 extends from the location where the two throats 16 merge together. The shaft 18 is formed so as to be continuous with, and integrated with, the throats 16. A portion of the head 14, the portion being positioned between the two throats 16, is a yoke 22. The frame 4 is hollow.
The main material of the frame 4 is a fiber reinforced resin. In the present embodiment, the matrix resin of the fiber reinforced resin is a thermosetting resin. The thermosetting resin is typically an epoxy resin. The fibers of the fiber reinforced resin are typically carbon fibers. The fibers are long filament fibers.
As shown in
The head 14 further includes a plurality of holes 26. Each hole 26 extends through the head 14. The plurality of holes 26 are arranged over substantially the entire periphery of the head 14.
The grip 6 is formed by a tape wound around the shaft 18. The grip 6 suppresses a slip between a hand of a player and the tennis racket 2 when the tennis racket 2 is swung. The end cap 8 is attached to the end of the grip 6.
As shown in
The grommet 10 is attached to the head 14. In a state where the grommet 10 is attached to the head 14, the base 28 is accommodated in the grommet groove 24. The base 28 may partly protrude from the grommet groove 24. Further, in the state where the grommet 10 is attached to the head 14, the pipes 30 extend through the respective holes 26.
As shown in
In the present embodiment, the vibration damper 36 is laminar. The vibration damper 36 is surrounded by the fiber reinforced layer 34. The vibration damper 36 is disposed in the outer side of the throat 16 in the width direction (the right side in
The vibration damper 36 is formed of a polymer composition. The polymer composition contains a base polymer. The polymer composition may contain additive agents as necessary.
The base polymer of the vibration damper 36 is typically a styrene-isoprene-styrene block copolymer. The styrene-isoprene-styrene block copolymer contains a polystyrene block as a hard segment and a polyisoprene block as a soft segment. One example of a sheet molded from the styrene-isoprene-styrene block copolymer is “KRAIBON” (trade name) available from Gummiwerk KRAIBURG GmbH & Co. KG.
The vibration damper 36 whose base material is the styrene-isoprene-styrene block copolymer has excellent damping performance. When a player hits a ball with the tennis racket 2, the frame 4 vibrates. The vibration damper 36 gradually decreases the amplitude of the vibration. In the case of the tennis racket 2, the amplitude of the vibration that propagates to the player is small. Therefore, the player feels less discomfort when hitting the ball with the tennis racket 2. The tennis racket 2 provides an excellent feel at impact.
As previously described, in the present embodiment, the vibration damper 36 is present in each throat 16. When the player hits a ball with the face 20, vibration is generated at the head 14, and the vibration is damped by the throat 16. Then, the damped vibration propagates to the player.
Since the styrene-isoprene-styrene block copolymer has excellent vibration damping performance, even though the vibration damper 36 is thin, the vibration damper 36 can contribute to the feel at impact. The thin vibration damper 36 does not significantly impair the stiffness of the frame 4.
The styrene-isoprene-styrene block copolymer is excellent in adhesion to epoxy resins. Therefore, the vibration damper 36 can be firmly joined to the fiber reinforced layer 34. The firm joining can contribute to the stiffness of the frame 4. The tennis racket 2 having excellent stiffness has excellent rebound performance. The player can hit a fast shot by using the tennis racket 2. The firm joining can also contribute to the durability of the tennis racket 2.
Another base polymer suitable for use in the vibration damper 36 is an acrylic elastomer. The acrylic elastomer contains an acrylic resin block as a hard segment and a soft segment. One example of a sheet molded from the acrylic elastomer is “PIEZON” (trade name) available from TITECS JAPAN Inc.
The vibration damper 36 whose base material is the acrylic elastomer has excellent damping performance. When a player hits a ball with the tennis racket 2, the frame 4 vibrates. The vibration damper 36 gradually decreases the amplitude of the vibration. In the case of the tennis racket 2, the amplitude of the vibration that propagates to the player is small. Therefore, the player feels less discomfort when hitting the ball with the tennis racket 2. The tennis racket 2 provides an excellent feel at impact.
Since the acrylic elastomer has excellent vibration damping performance, even though the vibration damper 36 is thin, the vibration damper 36 can contribute to the feel at impact. The thin vibration damper 36 does not significantly impair the stiffness of the frame 4.
The acrylic elastomer is excellent in adhesion to epoxy resins. Therefore, the vibration damper 36 can be firmly joined to the fiber reinforced layer 34. The firm joining can contribute to the stiffness of the frame 4. The tennis racket 2 having excellent stiffness has excellent rebound performance. The player can hit a fast shot by using the tennis racket 2. The firm joining can also contribute to the durability of the tennis racket 2.
In
The total of the lengths Le of all the vibration dampers 36 in the tennis racket 2 is preferably greater than or equal to 50 mm, more preferably greater than or equal to 80 mm, and particularly preferably greater than or equal to 100 mm.
Preferably, the Shore A hardness of the vibration damper 36 is higher than or equal to 40 but lower than or equal to 95. The vibration damper 36 having the Shore A hardness of higher than or equal to 40 does not significantly impair the stiffness of the frame 4. In light of this, the Shore A hardness of the vibration damper 36 is more preferably higher than or equal to 45, and particularly preferably higher than or equal to 50. An excellent feel at impact can be achieved by the vibration damper 36 having the Shore A hardness of lower than or equal to 95. In light of this, the Shore A hardness of the vibration damper 36 is more preferably lower than or equal to 90, and particularly preferably lower than or equal to 87. The Shore A hardness of the vibration damper 36 is measured by using a test piece that contains the same material as that of the vibration damper 36. The measurement is performed in compliance with the “JIS K 6253-3” standards.
Preferably, the elongation rate at break (hereinafter, simply referred to as “elongation rate”) of the vibration damper 36 is higher than or equal to 200%. An excellent feel at impact can be achieved by the vibration damper 36 having the elongation rate of higher than or equal to 200%. In light of this, the elongation rate is more preferably higher than or equal to 240%, and particularly preferably higher than or equal to 260%. The elongation rate is measured by a tensile test. The tensile test is performed in compliance with the “JIS K 6251” standards.
Hereinafter, one example of a method of manufacturing the tennis racket 2 according to the present invention is described with reference to
By rotating the mandrel, the prepreg 38b is wound around the prepreg 38a. As a result of the winding, the prepreg 38b has a tubular shape. Each film 40 is sandwiched between the prepreg 38a and the prepreg 38b. Another prepreg 38 or prepregs 38 is/are wound around the prepreg 38b as necessary.
After the mandrel is removed from the tube, the tube and the prepregs 38 are set in a mold. In the mold, gas is injected into the tube, thereby inflating the tube. The prepregs 38 are pressed against the cavity surface of the mold by the inflation. The prepregs 38 are heated to cure the matrix resin. A molded article is obtained by the curing. The molded article has a reverse shape of that of the cavity surface.
The holes 26 are drilled in the molded article. The molded article is further subjected to treatments such as surface polishing and painting, and thereby the frame 4 is obtained. Components such as the grip 6 and the grommet 10 are attached to the frame 4. Further, the string 12 is stretched on the frame 4, and thus the manufacturing of the tennis racket 2 is completed. The vibration damper 36 of the left-side throat 16 is formed by one film 40. The vibration damper 36 of the right-side throat 16 is formed by the other film 40.
The tennis racket includes a fiber reinforced layer 44, a first vibration damper 46, and a second vibration damper 48. The fiber reinforced layer 44 includes a plurality of reinforcement fibers and a matrix. The reinforcement fibers are typically carbon fibers. The material of the matrix is a resin composition whose base material is an epoxy resin. The first vibration damper 46 is surrounded by the fiber reinforced layer 44. The second vibration damper 48 is surrounded by the fiber reinforced layer 44. The fiber reinforced layer 44 is present between the first vibration damper 46 and the second vibration damper 48. The second vibration damper 48 is spaced apart from the first vibration damper 46.
The material, thickness, and physical properties of the first vibration damper 46 are the same as those of the vibration damper 36 shown in
When a player hits a ball with the tennis racket, the frame vibrates. The first vibration damper 46 and the second vibration damper 48 gradually decrease the amplitude of the vibration. In the case of this tennis racket, the amplitude of the vibration that propagates to the player is small. Therefore, the player feels less discomfort when hitting the ball with the tennis racket. The tennis racket provides an excellent feel at impact.
The tennis racket includes a fiber reinforced layer 52, a first vibration damper 54, and a second vibration damper 56. The fiber reinforced layer 52 includes a plurality of reinforcement fibers and a matrix. The reinforcement fibers are typically carbon fibers. The material of the matrix is a resin composition whose base material is an epoxy resin. The first vibration damper 54 is surrounded by the fiber reinforced layer 52. The position of the first vibration damper 54 is shifted from the center of the throat 50 toward the outer side in the width direction (the right side in
The material, thickness, and physical properties of the first vibration damper 54 are the same as those of the vibration damper 36 shown in
When a player hits a ball with the tennis racket, the frame vibrates. The first vibration damper 54 and the second vibration damper 56 gradually decrease the amplitude of the vibration. In the case of this tennis racket, the amplitude of the vibration that propagates to the player is small. Therefore, the player feels less discomfort when hitting the ball with the tennis racket. The tennis racket provides an excellent feel at impact.
The tennis racket includes a fiber reinforced layer 60 and a vibration damper 62. The fiber reinforced layer 60 includes a plurality of reinforcement fibers and a matrix. The reinforcement fibers are typically carbon fibers. The material of the matrix is a resin composition whose base material is an epoxy resin. In the cross section of
When a player hits a ball with the tennis racket, the frame vibrates. The vibration damper 62 gradually decreases the amplitude of the vibration. In the case of this tennis racket, the amplitude of the vibration that propagates to the player is small Therefore, the player feels less discomfort when hitting the ball with the tennis racket. The tennis racket provides an excellent feel at impact.
The tennis racket includes a fiber reinforced layer 66 and a vibration damper 68. The fiber reinforced layer 66 includes a plurality of reinforcement fibers and a matrix. The reinforcement fibers are typically carbon fibers. The material of the matrix is a resin composition whose base material is an epoxy resin. The vibration damper 68 is laminated on the inner surface of the fiber reinforced layer 66. The material, thickness, and physical properties of the vibration damper 68 are the same as those of the vibration damper 36 shown in
When a player hits a ball with the tennis racket, the frame vibrates. The vibration damper 68 gradually decreases the amplitude of the vibration. In the case of this tennis racket, the amplitude of the vibration that propagates to the player is small Therefore, the player feels less discomfort when hitting the ball with the tennis racket. The tennis racket provides an excellent feel at impact.
When a player hits a ball with the tennis racket 70, the frame vibrates. The vibration damper 74 gradually decreases the amplitude of the vibration. In the case of the tennis racket 70, the amplitude of the vibration that propagates to the player is small. Therefore, the player feels less discomfort when hitting the ball with the tennis racket 70. The tennis racket 70 provides an excellent feel at impact.
The material, thickness, and physical properties of the first vibration damper 86 are the same as those of the vibration damper 36 shown in
When a player hits a ball with the tennis racket 82, the frame vibrates. The first vibration damper 86 and the second vibration damper 88 gradually decrease the amplitude of the vibration. In the case of the tennis racket 82, the amplitude of the vibration that propagates to the player is small. Therefore, the player feels less discomfort when hitting the ball with the tennis racket 82. The tennis racket 82 provides an excellent feel at impact.
The tennis racket shown in
A tennis racket of Example 2 was obtained in the same manner as in Example 1, except that a different commercially available sheet (trade name “PIEZON”) was used as the vibration damper. The material of the vibration damper is a polymer composition whose base material is an acrylic elastomer.
A tennis racket of Comparative Example 1 was obtained in the same manner as in Example 1, except that a different commercially available sheet was used as the vibration damper. The material of the vibration damper is a polymer composition whose base material is chlorinated polyethylene.
A tennis racket of Comparative Example 2 was obtained in the same manner as in Example 1, except that the tennis racket of Comparative Example 2 includes no vibration damper.
Tennis rackets of Examples 3 to 8 were obtained in the same manner as in Example 1, except that the position of the vibration damper was varied as shown in Table 2 below.
Players did a rally by using each tennis racket. The players evaluated the rebound performance (flight), vibration absorption performance, feel at impact, and control performance of each racket. The evaluation results are shown in Tables 1 and 2 below.
In Tables 1 and 2, the greater the numerical value, the higher the evaluation.
It is clear from Tables 1 and 2 that the tennis racket in each Example is well-balanced in various performances. These evaluation results clearly indicate the superiority of the present invention.
The racket according to the present invention can be used in various sports, such as soft tennis, squash, and badminton. The foregoing description is in all aspects illustrative, and various modifications can be made without departing from the essential features of the invention.
Number | Date | Country | Kind |
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2020-101333 | Jun 2020 | JP | national |