Patent Grant
10814188
This application claims priority on Patent Application No. 2018-83991 filed in JAPAN on Apr. 25, 2018. The entire contents of this Japanese Patent Application are hereby incorporated by reference.
The present invention relates to tennis rackets.
JP2002-306639 discloses a tennis racket having an enlarged sweet area. In the tennis racket, the length L1 of the minimum interval between longitudinal strings and the length L2 of the minimum interval between transverse strings are each set within a predetermined range, and the ratio (L2/L1) of the length L2 to the length L1 is further set to be not less than 1.50 and not greater than 2.80.
Conventionally, the mainstream swing in regulation-ball tennis is classical swing. In the classical swing, when a tennis racket hits a ball, the tennis racket is swung such that a hand grip portion and a tip portion thereof move substantially parallel to each other. Meanwhile, in recent years, modern swing is the mainstream swing. In the modern swing, when a tennis racket hits a ball, the tennis racket is swung such that a tip portion thereof moves faster than a hand grip portion thereof. In the modern swing, a ball is hit at the vicinity of the tip portion that moves fast, whereby the ball can be strongly hit.
In a conventional tennis racket, the sweet spot is located substantially at the center of the ball-hitting face. In the tennis racket, the resilience performance at the vicinity of a tip portion is inferior to that of a center portion. For the conventional tennis racket, there is room for improvement from the viewpoint of strongly hitting a ball at the vicinity of the tip portion. For the conventional tennis racket, there is also room for improvement from the viewpoint of application to the modern swing.
An object of the present invention is to provide a tennis racket having, at a tip side from the center of a ball-hitting face thereof, an area having high resilience performance.
In a tennis racket according to the present invention, longitudinal strings extending in a longitudinal direction and transverse strings extending in a transverse direction intersect each other to form a plurality of meshes. At a center, in the transverse direction, of a head, a ratio of an area St of a tip mesh located closest to a tip in the longitudinal direction relative to an area Sc of a center mesh located at a center in the longitudinal direction is not less than 1.6. The center mesh is formed in a rectangular shape having short sides in the longitudinal direction and long sides in the transverse direction.
Preferably, from the center mesh to the tip mesh, an area of each mesh is set so as to be not larger than an area of a mesh adjacent thereto at a tip side.
Preferably, from the center mesh to the tip mesh, the area of the mesh gradually increases from the center toward the tip.
Preferably, pitches between the longitudinal strings are constant in the transverse direction.
Resilience amounts at positions at which a distance Y from a top of the head is 6 cm, 9 cm, 12 cm, and 15 cm are denoted by Hb6, Hb9, Hb12, and Hb15, respectively. In this case, preferably, among the resilience amounts Hb6, Hb9, Hb12, and Hb15, a minimum resilience amount is not less than 0.98 times of a maximum resilience amount.
Preferably, the area Sc of the center mesh is not less than 70 mm2.
Preferably, a number of the longitudinal strings is not less than 16 and not greater than 18, and a number of the transverse strings is not less than 18 and not greater than 20.
In the tennis racket according to the present invention, since the center mesh is formed in a rectangular shape, the ratio (St/Sc) of the area St of the tip mesh to the area Sc of the center mesh is increased without extremely decreasing the area of the center mesh. Since the ratio (St/Sc) is increased, high resilience performance is exhibited at the tip side.
The following will describe in detail the present invention based on preferred embodiments with appropriate reference to the drawings.
The racket frame 4 includes a head 12, a pair of throats 14, and a shaft 16. The head 12, the pair of throats 14, and the shaft 16 are connected to each other. The head 12 extends in a curved manner so as to be bent back at the upper side. A pair of lower ends of the head 12 are connected to each other via the yoke 8. In this manner, the head 12 and the yoke 8 form an annular portion 18 having a substantially elliptical shape.
Each throat 14 extends downward from the lower end of the head 12. The throats 14 extend toward the shaft 16 in directions in which the throats 14 come close to each other. Both end portions of the racket frame 4 extend downward further from the pair of throats 14. Both end portions are joined to each other. The joined end portions form the shaft 16. The grip 10 is formed at the outer side of the shaft 16.
The string 6 is stretched on the annular portion 18 of the racket frame 4. The string 6 stretched on the annular portion 18 forms a plurality of longitudinal strings 20 and a plurality of transverse strings 22. These longitudinal strings 20 and these transverse strings 22 form a ball-hitting face 24. The ball-hitting face 24 has a substantially elliptical shape surrounded by the annular portion 18. The major axis direction of the ball-hitting face 24 is the longitudinal direction of the tennis racket 2. The minor axis direction of the ball-hitting face 24 is the transverse direction of the tennis racket 2.
In the tennis racket 2, the string 6 forms, for example, 16 longitudinal strings 20, and, for example, 19 transverse strings 22. Each longitudinal string 20 extends in the longitudinal direction inside the annular portion 18. Each transverse string 22 extends in the transverse direction inside the annular portion 18. These longitudinal strings 20 and these transverse strings 22 intersect each other to form a plurality of meshes 26. The shape of each mesh 26 is a quadrangle surrounded by the longitudinal strings 20 and the transverse strings 22.
A point P1 represents the point of intersection of the annular portion 18 (head 12) and the center line Ly at the upper side. In the present invention, the point P1 is also referred to as a top of the head 12. A point P2 represents the point of intersection of the annular portion 18 (yoke 8) and the center line Ly. A point P3 represents one point of intersection of the annular portion 18 (head 12) and the center line Lx in the transverse direction. A point P4 represents the other point of intersection of the annular portion 18 (head 12) and the center line Lx in the transverse direction.
In
In the present invention, the mesh 26 in which the center position P0 is located, among a large number of meshes 26, is referred to as a center mesh 26c. In addition, in the present invention, at the center in the transverse direction, the mesh 26 that is closest to the top (point P1) of the head 12 is referred to as a tip mesh 26t.
In the tennis racket 2, the longitudinal intervals y8 to y11 are set so as to have the same magnitude. The longitudinal interval y gradually increases from the longitudinal interval y8 toward the longitudinal interval y1. Similarly, the longitudinal interval y gradually increases from the longitudinal interval y11 toward the hand grip side.
In
In
In the tennis racket 2, the areas S8, S9, S10, and S11 are set so as to have the same magnitude. In other words, the areas S8, S10, and S11 are set so as to have the same magnitude as the area Sc. Furthermore, the area S gradually increases from the area S8 toward the area St. Similarly, the area S gradually increases from the area S11 toward the hand grip side.
The tennis racket 2 is placed on a test stand 28. The test stand 28 has a flat placement surface 30. The placement surface 30 is a flat surface that extends in the horizontal direction. The head 12 and the yoke 8 are placed on the placement surface 30. The tennis racket 2 is placed such that the ball-hitting face 24 is parallel to the placement surface 30. In other words, the tennis racket 2 is placed such that the longitudinal strings 20 and the transverse strings 22 extend parallel to the placement surface 30. The tennis racket 2 is fixed to the test stand 28 by a cramp that is not shown.
In
In the testing method for resilience performance, a tennis ball is caused to freely fall from a position having a predetermined height H from the ball-hitting face 24 at the position of the distance Y. The tennis ball that has collided against the ball-hitting face 24 at the point Pf is rebounded. A resilience amount Hb of the rebounded tennis ball is measured. The resilience amount Hb is obtained as a maximum reach height of the tennis ball. The resilience amount Hb is obtained as a height from the ball-hitting face 24. The ratio (Hb/H) of the height Hb to the height H may be obtained. The ratio (Hb/H) is used as resilience performance. When the ratio (Hb/H) is greater, the resilience performance is higher. In this testing method, a tennis ball that complies with the ITF standards is used. In the testing method for resilience performance, the height H is set to 254 cm. The heights H and Hb are each measured as a distance from the ball-hitting face 24 to the lower position (lower end position) of the tennis ball. The heights H and Hb are each measured as a direct distance in the thickness direction of the tennis racket 2.
As shown in
A mesh 26 having a large area S can bend more greatly when a tennis ball collides with the tennis racket 2, than a mesh 26 having a small area S. The greater bending produces greater resilient force. In the tennis racket 2, resilience performance at the tip side is improved by increasing the area ratio (S/Sc).
In the tennis racket 2, a resilience amount Hb6 at a position at which the distance Y from the top is 6 cm, a resilience amount Hb9 at a position at which the distance Y from the top is 9 cm, and a resilience amount Hb12 at a position at which the distance Y from the top is 12 cm are each larger than a resilience amount Hb15 at the position at which the distance Y is 15 cm. In the tennis racket 2, the resilience amount Hb6, the resilience amount Hb9, and the resilience amount Hb12 at the tip side of the ball-hitting face 24 are larger than the resilience amount Hb15 at the center mesh 26c. On the other hand, in the conventional tennis racket, the resilience amount Hb decreases as the distance Y from the top decreases.
In the tennis racket 2, the longitudinal interval y9 at the center mesh 26c is set so as to be less than the transverse interval x1 at the center mesh 26c. Although not shown, the magnitude of the longitudinal interval at the center mesh is generally set so as to be greater than that of the transverse interval at the center mesh in the conventional tennis racket. Accordingly, in the tennis racket 2, the ratio (St/Sc) of the area St at the tip mesh 26t to the area Sc at the center mesh 26c can be greater than that in the conventional tennis racket.
In the tennis racket 2, the ratio (St/Sc) is increased and set so as to be not less than 1.6. In the tennis racket 2, the ratio (St/Sc) is greater than that in the conventional tennis racket. In the tennis racket 2 having a great ratio (St/Sc), high resilience performance is obtained at the vicinity of the tip mesh 26t. The tennis racket 2 can strongly hit a ball at the vicinity of the tip portion.
The area S of the mesh 26 preferably increases gradually from the center side toward the tip side. In other words, from the center mesh 26c to the tip mesh 26t, the area S of the mesh 26 preferably increases gradually from the center toward the tip. Accordingly, a sudden change in resilience performance is inhibited. Thus, the resilience performance is made uniform from the center of the ball-hitting face 24 to the vicinity of the tip.
In the tennis racket 2, the area Sc of the center mesh 26c, the area S8 of the mesh 26 adjacent to the center mesh 26c at the tip side, the area S10 of the mesh 26 adjacent to the center mesh 26c at the hand grip side, and the area S11 of the mesh 26 adjacent to the mesh 26 having the area S10 at the hand grip side are set so as to have the same magnitude. In the present invention, the area S does not necessarily have to gradually increase from the center mesh 26c to the tip mesh 26t. From the viewpoint of making the resilience uniform, the areas S of meshes 26 adjacent to each other in the longitudinal direction may be partially set so as to be equal to each other. Furthermore, from the viewpoint of obtaining high resilience at the tip side, the area St of the tip mesh 26t only needs to be larger than the area Sc of the center mesh 26c, and the area S of each mesh 26 only needs to be not larger than the area S of the mesh 26 adjacent thereto at the tip side.
The conventional tennis racket is configured such that the transverse interval x gradually increases from the center side toward the outer side in the transverse direction. In the tennis racket 2, the longitudinal strings 20 are stretched at equal intervals x1 from one end toward the other end in the transverse direction. In other words, the pitches between the longitudinal strings 20 are constant. Accordingly, the area Sc of the center mesh 26c is inhibited from becoming extremely small even when the longitudinal interval y9 at the center mesh 26c is decreased. A mesh 26 having an excessively small area S decreases the resilience performance. In the tennis racket 2, even when the longitudinal interval y is decreased, since the longitudinal strings 20 are stretched at equal intervals x1, the resilience performance is not greatly deteriorated. The tennis racket according to the present invention is not limited to a tennis racket in which the transverse intervals x between the longitudinal strings 20 are equal. In the tennis racket, the transverse interval x may gradually increase or gradually decrease from the center side toward the outer side in the transverse direction.
From the viewpoint of inhibiting resilience performance from being deteriorated at the vicinity of the center mesh 26c, the area Sc of the center mesh 26c is preferably not less than 70 mm2, further preferably not less than 90 mm2, and particularly preferably not less than 110 mm2.
Furthermore, uniform resilience performance is obtained from the center to the vicinity of the tip by decreasing the differences among the resilience amount Hb6, the resilience amount Hb9, the resilience amount Hb12, and the resilience amount Hb15. From the viewpoint of obtaining uniform resilience performance, among the resilience amount Hb6, the resilience amount Hb9, the resilience amount Hb12, and the resilience amount Hb15, the minimum resilience amount is preferably not less than 0.98 times of the maximum resilience amount.
The tennis racket 2 has excellent resilience performance at the tip side. The tennis racket 2 is particularly suitable for modern swing.
From the viewpoint of increasing the resilience performance at the tip side, the present invention is particularly suitable for the tennis racket 2 in which the longitudinal width of the annular portion 18 is larger than the transverse width thereof.
The tennis racket 2 has a string pattern composed of 16 longitudinal strings 20 and 19 transverse strings 22, but the string pattern according to the present invention is not limited thereto. For example, the present invention can be similarly applied to a tennis racket having a string pattern composed of 16 longitudinal strings 20 and 18 transverse strings 22, 16 longitudinal strings 20 and 20 transverse strings 22, or the like. The present invention is suitable in the case where the number of longitudinal strings 20 is not less than 16 and not greater than 18 and the number of transverse strings 22 is not less than 18 and not greater than 20.
The following will show the effects of the present invention by means of examples, but the present invention should not be construed in a limited manner based on the description of these examples.
[Comparison Test]
A tennis racket A shown in
Tennis rackets B and C in each of which the face size, the string pattern, the center position, and the area ratio (S/Sc) of each mesh were as shown in Table 1 were prepared.
Commercially-available tennis rackets D to M were prepared. The face sizes, the string patterns, the center positions, and the area ratios (S/Sc) of each mesh of these tennis rackets were as shown in Tables 1 and 2.
In the tennis rackets of Examples 1 to 3, the ratios (St/Sc) of the tip mesh St to the center mesh Sc were 1.83, 1.77, and 1.71, respectively. On the other hand, in the tennis rackets of the Comparative Examples, the ratio (St/Sc) was at most 1.54. Also from this fact, it is obvious that, in the tennis racket according to the present invention, the ratio (S/Sc) is greater than that in the conventional tennis racket. From the viewpoint of exhibiting high resilience performance at the vicinity of the tip, the ratio (S/Sc) is preferably not less than 1.6 and further preferably not less than 1.7.
[Resilience Amount Test]
The aforementioned tennis racket A of Example 1 was prepared. In addition, the tennis rackets D to H of Comparative Examples 1 to 5 were prepared as examples of conventional commercially-available products.
[Evaluation of Resilience Performance]
These tennis rackets were evaluated for resilience performance by using the testing method for resilience performance in
As shown in Table 3, the tennis racket A of Example 1 has better resilience at the tip side than the conventional tennis rackets. In addition, the difference in resilience amount is decreased from the position at which the distance Y is 6 cm to the position at which the distance Y is 15 cm. Among the resilience amount Hb6, the resilience amount Hb9, the resilience amount Hb12, and the resilience amount Hb15, the minimum resilience amount Hb6 is not less than 0.98 times of the maximum resilience amount Hb12.
[Sensuous Test]
A tennis racket N according to the present invention was prepared as Example 4. In the tennis racket N, the intervals between the longitudinal strings were made uniform, and the intervals between the transverse strings were small at the center side and gradually increased toward the outer side. In Table 4, M1, M3, M6, M9, M12, M15, and M18 each represent what number from the tip side the mesh is, similar to Table 1. In Table 4, the ratios (S/Sc) of the meshes of M1, M3, M6, M9, M12, M15, and M18 are shown.
A tennis racket P of Comparative Example 11 was prepared as an example of a commercially-available product. In the tennis racket P, the intervals between the longitudinal strings and the intervals between the transverse strings were small at the center side and gradually increased toward the outer side. In Table 4, the ratios (S/Sc) of the meshes of M1, M3, M6, M9, M12, M15, and M18 of the tennis racket P are shown.
Tennis rackets Q, R, and S were produced in the same manner as Example 1, except the intervals between the longitudinal strings, the intervals between the transverse strings, and the ratio (S/Sc) were as shown in Table 4. In the tennis racket Q, the shape of each mesh was a square.
[Sensuous Evaluation]
An advanced player made sensuous evaluation for these tennis rackets. The advanced player made evaluations for the size of the sweet area, the magnitude of vibration transmitted to the hand, and ease of providing spin, and made an overall evaluation. The results are shown in Table 4. The results are each indicated as a value with the value of Comparative Example 11 being a reference value 50. A higher value indicates a better result. The overall evaluation is represented as a value at five levels with the value of Comparative Example 11 being a reference value 3. The higher the value is, the better the result is.
In the tennis racket N of Example 4, the area Sc of the center mesh was made relatively large while the ratio (St/Sc) was made great. Accordingly, the tennis racket N of Example 4 has excellent vibration absorption at a wide ball-hitting face from the vicinity of the center to the vicinity of the tip. The tennis racket N also has excellent ease of providing spin. The tennis racket N is highly rated as compared to the tennis rackets of the Comparative Examples. From the evaluation results, advantages of the present invention are clear.
The method described above can be applied to a wide range of rackets for regulation-ball tennis.
The above descriptions are merely illustrative examples, and various modifications can be made without departing from the principles of the present invention.
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| 2018-083991 | Apr 2018 | JP | national |
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