JP2005073785A - tennis racket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve flight performance without impairing the rigidity of a tennis racket.
A racket frame made of a fiber reinforced resin composed of a sleeve of a prepreg laminate is provided, and gut holes are provided in the head portion surrounding the striking surface of the racquet frame with a gap in the longitudinal direction of the frame. A tennis racket in which an inner gut hole drilled on the inner peripheral side of the head portion and an outer gut hole drilled on the outer peripheral side are penetrated perpendicularly to the longitudinal direction of the frame, On the inner peripheral side, there are provided recesses centered on some of the inner gut holes, and the recesses have dimensions in the frame length direction at both ends in the frame thickness direction orthogonal to the ball striking surface. It is set to be shorter than the dimension in the frame length direction at the center of the frame.
[Selection] Figure 1

Description

  The present invention relates to a tennis racket, and in particular, reduces the weight without impairing the rigidity of the racket frame, and widens the sweet area with high resilience.

  In recent years, there has been a growing demand for rackets that can achieve high flight performance even with little effort, especially for women and seniors. In particular, it is required to increase the rebound of the racket to increase the flight distance while maintaining the light weight, and to increase the spin area by expanding the sweet area to improve the operability. In addition, in-plane rigidity is regarded as important for athletes in order to obtain stability of the ball striking face.

Various proposals have been made for these demands. For example, in Utility Model Registration No. 3090850 (Patent Document 1), as shown in FIGS. 12A and 12B, the portion of the gut hole H on the inner peripheral surface side Fa of the face portion (head portion) F of the racket frame. In addition, it has been proposed to form a concave portion 1 that is recessed from the surroundings and to form a raised convex portion 2 between adjacent concave portions 1 to expand the movable range of the gut and increase the resilience. .
However, Patent Document 1 does not consider the influence of the formation of the concave portion 1 on the frame strength and the problems in molding. When the concave portion 1 is formed on the entire circumference of the head portion, the rigidity in the in-plane direction is low. It is considered that the surface stability is lowered. Moreover, although it is described that the shape of the recessed part 1 is a rectangle, stress tends to concentrate on the recessed part 1 in a rectangle, and the fall of durability becomes a problem.

Further, in Japanese Patent No. 2991129 (Patent Document 2), as shown in FIG. 13, a groove 3 extending in the longitudinal direction of the frame is formed in at least a part of the inner peripheral surface Fa of the face F of the racket frame. It has been proposed to provide a curved portion closer to a straight line than an arc having a radius of 150 mm in the cross-sectional shape when the face portion F is cut along the ball striking surface, thereby aligning the gut length and expanding the sweet area. .
However, in the configuration shown in Patent Document 2, the cross-sectional peripheral length of the face portion F increases, resulting in an increase in the weight of the frame, resulting in a decrease in operability and durability by extending the groove portion 3 in the longitudinal direction of the frame. This is a problem. In particular, the formation of the groove portion 3 causes a sudden change in the cross-sectional shape of the frame and is easily damaged, and this tendency becomes more remarkable when the weight is reduced. Further, since the sleeve-shaped laminate is curved in accordance with the frame shape for molding, if the difference between the inner peripheral length and the outer peripheral length of the face portion is large, a bent wrinkle is always generated on the inner peripheral side. Therefore, there is a problem that cracks and cracks are likely to occur.

Furthermore, in Japanese Patent Laid-Open No. 2000-61004 (Patent Document 3), as shown in FIG. 14, the diameter r1 of the outer gut hole 4 of the face part F of the racket frame is formed smaller than the diameter r2 of the inner gut hole 5. It is proposed to extend the sweet area by extending the gut effective length.
However, in the configuration shown in Patent Document 3, when it is necessary to further increase the diameter r2 of the inner gut hole 5 due to the demand for weight reduction, the strength around the inner gut hole 5 may be reduced.

  Further, in Japanese Patent Application Laid-Open No. 7-155407 (Patent Document 4), a groove portion 6 having a U-shaped cross section, a V-shaped cross section, or a U-shaped cross section is formed along the inner peripheral surface side of the face portion of the racket frame. Thus, there has been proposed a device that enables a smooth swing by reducing the air resistance. However, if it is set as the structure of patent document 4, it has the same problem as the said patent document 2. FIG.

In addition to the method of providing grooves and recesses on the inner peripheral surface of the face portion surrounding the ball striking surface as described above, the following method may be adopted in order to improve the resilience performance.
(1) Increase the moment of inertia by adding weight.
(2) Widen the hitting surface.
(3) Increase out-of-plane rigidity while decreasing out-of-plane rigidity.
However, in the method (1), the operability is lowered and it is against the request for weight reduction. In the method (2), when the striking surface is increased, the weight and the moment of inertia increase. The method (3) involves a change in the laminated structure and cross-sectional shape of the prepreg constituting the racket frame, and there is a problem that the strength decreases when the elasticity is increased, and the weight increases when the strength is taken into consideration.

In order to improve vibration absorption, the following means have been conventionally taken.
(1) A thermoplastic resin excellent in vibration absorption is used as the fiber reinforced resin constituting the frame. (2) Install the dynamic damper.
(3) In the laminate of prepregs constituting the frame, a vibration damping material is interposed between the layers.
(4) Wear a string damping material such as rubber grommet.
However, in (1), it is difficult to reduce the weight due to the strength of the material, and the environment dependency is large. (2) is accompanied by an increase in weight. (3) reduces the rigidity of the frame. In (4), the string damping material used in the past only attenuates the vibration of the string alone and does not contribute much to the vibration damping of the frame.

Thus, there is much room for improvement in order to obtain a tennis racket that can be reduced in weight without reducing rigidity and strength, has good resilience, and has excellent vibration damping properties.
Utility Model Registration No. 3090850 Japanese Patent No. 2911129 JP 2000-61004 A Japanese Unexamined Patent Publication No. 7-155407

  The present invention has been made in view of the above-mentioned problems. The main object of the present invention is to provide a tennis racket that achieves high flight performance while having high rigidity and high strength, and further provides a tennis racket that has high vibration damping properties. It is a subject to be followed.

In order to solve the above-described problems, the present invention includes a fiber reinforced resin racket frame formed of a sleeve of a prepreg laminate, and a gut hole is provided in the longitudinal direction of the frame with a head portion surrounding the hitting surface of the racket frame. The gut hole is a tennis racket in which an inner gut hole drilled on the inner peripheral side of the head portion and an outer gut hole drilled on the outer peripheral side are penetrated perpendicularly to the longitudinal direction of the frame. There,
On the inner peripheral side of the head portion, a recess centered on a part of the inner gut hole is provided, and the recess has dimensions in the frame length direction on both ends in the frame thickness direction orthogonal to the striking surface. The tennis racket is characterized by being set shorter than the dimension in the frame length direction at the center in the frame thickness direction.

As described above, by forming the recess around the inner gut hole, the effective length of the string can be extended and the movable area of the string can be expanded, so the resilience is improved and the flight distance of the ball is extended. The sweet area can be expanded to improve operability.
Also, the racket frame is formed by winding a plurality of prepregs around a mandrel and laying up a laminated sleeve, filling it into a mold cavity, bending it according to the shape of the racket frame, pressurizing and heating. Has been. Since the sleeve is curved and filled in the cavity, in particular, in the head portion surrounding the ball striking face, bending and wrinkles are inevitably formed on the inner peripheral side due to the difference between the inner peripheral length and the outer peripheral length. It tends to cause cracks and cracks.
In the present invention, as described above, the difference between the inner peripheral length and the outer peripheral length of the head portion can be reduced by changing the size of the concave portion between the center side and both end sides in the frame thickness direction. It is possible to improve the durability of the racket frame by suppressing the occurrence of the above. In particular, since both ends of the recess in the frame thickness direction have little contribution to the resilience performance and rebound area expansion, by reducing the width dimension on both ends in the thickness direction, both the resilience performance and durability are balanced. Can be improved. Furthermore, by making the recess have the above shape, unlike the case where the recess has a rectangular shape, the frame cross-sectional shape does not change rapidly, and frame damage due to stress concentration can be prevented.

The positions where the recesses are provided are substantially elliptical and oval corners, that is, when the top surface is 12 o'clock when the ball striking surface is viewed as a clock face, the range from 1 o'clock to 2 o'clock, and 10 o'clock to 11 o'clock. When the recesses are formed in the gut holes in the four areas, the time range, 4 o'clock to 5 o'clock, and 7 o'clock to 8 o'clock, the effective length of the strings is aligned, effectively increasing the resilience, The spot can be enlarged.
Further, when the concave portion is formed in the head portion corresponding to the maximum horizontal width portion of the head portion at 3 o'clock and 9 o'clock and the maximum vertical width portion at 12 o'clock and 6 o'clock, the string passing through the gut hole provided in the concave portion is a sweet area In order to pass through, the resilience of the sweet area can be effectively increased.

The concave portion has a substantially elliptical shape in which the maximum width in the frame longitudinal direction is shorter than the maximum width in the frame thickness direction.
When the concave portion has a substantially elliptical shape as described above, the change in the cross-sectional shape of the frame can be relaxed compared to the case of a perfect circle shape, and stress concentration can be suppressed and the durability of the frame can be enhanced. Further, by setting the major axis of the concave portion in the frame thickness direction, it is possible to effectively absorb wrinkles that are likely to occur particularly in the frame thickness direction during frame molding. On the other hand, by setting the minor axis of the concave portion in the longitudinal direction of the frame, it is possible to avoid the concave portion formed for each gut hole from continuing in a groove shape, and to suppress a decrease in rigidity and strength of the frame.
Specifically, the major axis of the recess is preferably 10 mm or more and 20 mm or less, and the minor axis is preferably 5 mm or more and 10 mm or less.

It is preferable that a curved surface that protrudes toward the ball striking surface is formed on the inner peripheral surface of the face portion other than the portion where the concave portion is formed.
That is, when a curved surface that protrudes in the direction opposite to the concave portion forming direction is formed, at least on the inner surface of the concave portion forming region, irregularities are continuously formed in the longitudinal direction of the frame to increase the inner peripheral length of the frame. The difference becomes even smaller. As a result, generation of wrinkles that cause cracks and cracks can be suppressed.

The depth of the recess is gradually reduced from the periphery of the recess to the deepest position, with the position of the inner gut hole being the deepest position.
Furthermore, the depth of the recess is preferably such that the cross-sectional shape of the recess in the frame thickness direction is substantially linear with a radius of curvature of 50 mm or more.
The depth of the concave portion refers to a depth from a virtual inner side surface that is continuous with the inner side surface of the face portion where no concave portion is formed.
Thus, by not forming an extremely deep recess on the inner surface side of the frame but rather forming it as shallow as the cross-sectional shape of the recess in the racket thickness direction becomes substantially linear, it is possible to prevent stress concentration. Accordingly, it is possible to maintain rigidity with an appropriate balance while improving flying performance by increasing the effective length of the string and preventing wrinkles by increasing the inner peripheral length of the frame.

The cross-sectional width at the central portion in the thickness direction of the head portion other than the recessed portion forming portion is within the range of 12 mm or more and 18 mm or less, and the maximum depth of the recessed portion is within the range of 1 mm or more and 7 mm or less. The difference from the maximum depth of the recess is 10 mm or more.
If the frame width of the head portion is less than 12 mm, the rigidity is low, and if it exceeds 18 mm, the weight increases. Further, when the depth of the recess is less than 1 mm, improvement in resilience is hardly observed, and when the depth exceeds 7 mm, the shape change is abrupt and causes a decrease in strength. Furthermore, by making the difference between the frame width of the head part and the maximum depth of the recess 10 mm or more, it is possible to improve the flight performance and increase the rigidity of the frame by increasing the degree of freedom of the string while maintaining a balance. can do.

It is preferable that a groove in the longitudinal direction is provided on the surface of the outer peripheral part of the frame of the head part at least on the side opposite to the recessed part forming portion, and a viscoelastic member is attached to the groove.
By attaching the viscoelastic member in this way, it is possible to absorb the vibration of the string at the time of hitting the ball and the vibration of the frame in contact with the string. In addition, the head has a large curvature in the range from 1 o'clock to 2 o'clock, from 10 o'clock to 11 o'clock, from 4 o'clock to 5 o'clock, and from 7 o'clock to 8 o'clock. From the viewpoint, the concave portion cannot be formed deeply, and there is a limit to the extension of the effective length of the string. However, by attaching the viscoelastic member to the outer surface of these four regions, the resilience is achieved by the spring effect utilizing the elasticity. Can be supplemented, and both flight performance and vibration damping can be improved.

The viscoelastic member includes a plurality of cylindrical portions that pass through the string and a band portion that connects the cylindrical portions, and has a shape in which a plurality of holes that pass through the cylindrical portion are formed in the band portion, and the band portion is It is mounted in the groove provided on the outer peripheral surface of the frame, and is interposed between the band-shaped grommet cover having rigidity and the frame.
The viscoelastic member is preferably a rubber material, but may be HYBRAR + PP or natural rubber.
The thickness of the band portion of the viscoelastic member is preferably 1 mm or more and 6 mm or less from the viewpoint of securing elasticity and suppressing weight increase. The viscoelastic member has a complex elastic modulus of 2.0 × 10 ⁷ dyn / cm ² or more and 1.0 × 10 ¹⁰ dyn measured under a measurement condition of a frequency of 10 Hz and a temperature of 0 ° C. to 10 ° C. / Cm ² is preferable. If this is less than 2.0 × 10 ⁷ dyn / cm ² , stress concentration occurs on the racket frame, and the frame tends to be damaged. If the frame is larger than 1.0 × 10 ¹⁰ dyn / cm ² , a sufficient spring This is because the resilience is not improved because the effect cannot be obtained, and the natural frequency becomes too high, resulting in a decrease in vibration damping.

  As described above, according to the tennis racket according to the present invention, by forming the recess centered on the gut hole at the required position on the inner peripheral surface of the head portion of the racket frame, the movable area of the string is expanded. The resilience at the time is improved, the flying performance is improved, and the expansion of the sweet area and the resilience in the sweet area can be further enhanced. In addition, by forming the recesses in a rectangular shape, the width in the frame longitudinal direction on both ends in the frame thickness direction is shorter than the width in the frame longitudinal direction on the center side in the frame thickness direction, for example, an elliptical shape. The difference between the inner and outer peripheral lengths of the frame, which causes wrinkles at the time of frame molding, is reduced, and cracks and cracks can be prevented to increase durability and strength. Therefore, it is possible to improve both the flying performance / operability and the rigidity / strength of the tennis racket in a well-balanced manner.

  Furthermore, the above-mentioned concave portion has an elliptical shape, the depth is not less than 1 mm and not more than 7 mm, and the sectional shape obtained by cutting the concave portion in the frame thickness direction is a substantially linear shape having a curvature radius of 50 mm or more, thereby preventing an extreme change in rigidity. Thus, a decrease in durability due to stress concentration can be suppressed. Moreover, the rigidity fall of a flame | frame can be suppressed by making the difference of the depth of a recessed part and frame cross-sectional width 10 mm or more.

  In addition, by attaching a viscoelastic member to the outer surface side of the recessed portion forming portion of the frame, it is possible to ensure high flight performance and rigidity while attenuating unpleasant vibration during hitting.

Hereinafter, an embodiment of a tennis racket of the present invention will be described with reference to the drawings.
In all of the embodiments described below, the tennis racket 10 is a hard tennis racket, and the racket frame 11 is formed of a sleeve made of a prepreg laminate.

In the present embodiment, the racket frame 11 is a mandrel (in which a CF prepreg (Toray T300, 700, 800, M46J)) using carbon fiber as a reinforcing fiber and a matrix resin as an epoxy is covered with an internal pressure tube made of 66 nylon. 14.5), the prepreg angles are inclined at 0 °, 22 °, 30 °, and 90 ° in the axial direction to form a layup, and the mandrel is extracted from the layup and set in a mold. The mold is clamped, heated to 150 ° C., heated for 30 minutes, and at the same time, an air pressure of 9 kgf / cm ² is applied to the internal pressure tube, and the pressure is maintained.

  1 to 3 show the tennis racket according to the first embodiment. As shown in FIG. 1A, the racket frame 11 includes a head portion 12, a throat portion 13, a shaft portion 14, and a grip portion 15 that are continuously arranged. The both ends of the yoke portion 16 are connected to the throat portions 13 on both sides to form a gut stretch portion surrounding the hitting surface 21 together with the head portion 12. The head portion 12 is provided with a plurality of gut holes 25 through which the strings S are inserted so as to penetrate in the width direction perpendicular to the longitudinal direction of the frame. Specifically, the gut hole 25 includes an inner gut hole 20 drilled in the inner peripheral portion 12a and an outer gut hole 19 drilled in the outer peripheral portion 12b. The gut holes 20 and 19 are provided so as to penetrate the same line. Yes. On the surface of the outer peripheral portion 12b of the head portion 12, a gut groove portion 17 is continuously formed in the circumferential direction, and a wide protective material groove portion 18 is formed in a region where the viscoelastic member 22 is mounted.

  In the head portion 12, the thickness D in the direction orthogonal to the ball striking surface 21 is 28 mm, the cross-sectional width W at the central portion in the frame thickness direction is 13 mm to 18 mm (13 mm in the first embodiment), and the area of the ball striking surface 21 is 116 square. The gut hole 25 (the outer gut 19 and the inner gut hole 20) has a hole diameter set in a range of 3.6 mm to 4.0 mm.

  The viscoelastic member 22 has a shape including a plurality of cylindrical portions 22a that pass through the gut holes 22c through which the strings S are inserted, and a band portion 22b that connects the cylindrical portions 22a. ing.

  When the head portion 12 of the racket frame 11 is a clock face and the top is 12 o'clock, a plurality of inner depth portions 12a in the 3 o'clock and 9 o'clock regions have a maximum depth d of 2 mm around the inner gut hole 20. The recesses 31 are formed at intervals. “Depth d” refers to the depth from the virtual inner side surface that is continuous with the inner side surface 12a of the portion where the recess 31 is not formed, and the same applies to all the following embodiments, examples, and comparative examples. It is.

  As shown in FIG. 1 (B), the recess 31 has an elliptical shape centered on each inner gut hole 20, with the major axis 31a in the frame thickness D direction and the minor axis 31b in the frame longitudinal direction. The major axis 31a is 20 mm and the minor axis 31b is 10 mm. The cross-sectional shape obtained by cutting the recess 31 perpendicularly to the frame length direction is formed to be a substantially straight line having a curvature radius of 100 mm as shown in FIG.

  Of the inner peripheral portion 12a of the head portion 12 of the racket frame 11, the inner peripheral portion 12a where the concave portion 31 is not formed is a curved surface raised on the inner side of the ball striking surface as shown in FIG. Yes. Thereby, on the inner peripheral portion 12a in the 3 o'clock and 9 o'clock regions where the concave portion 31 is formed, a curved arc-shaped convex portion 32 is formed between the adjacent concave portions 31 as shown in FIG. doing.

  In the tennis racket having the above-described configuration, a recess 31 centered on each gut hole 20 is formed in the inner peripheral portion 12a of the 3 o'clock and 9 o'clock region of the racket frame 11 to thereby form the string S of the 3 o'clock and 9 o'clock region. Therefore, the repulsive force of the hitting surface 21 in the sweet area can be increased, and the flight distance of the ball can be effectively extended.

On the other hand, by forming the recess 31 in an elliptical shape that is longer in the thickness direction and shorter in the frame length direction, the plurality of recesses 31 can be formed at intervals in the frame length direction. Concave portions 31 and convex portions 32 are alternately formed in 12a, and the inner peripheral length of the frame 11 can be increased. Accordingly, the difference between the inner and outer peripheral lengths, which is a cause of wrinkles at the time of molding, can be reduced, so that the strength of the frame 11 can be increased by preventing cracks and cracks.
Further, the major axis 31a is arranged in the frame thickness D direction to effectively cover the wrinkles that are likely to occur in the thickness D direction, while the minor axis 31b is arranged in the longitudinal direction of the frame to reduce the recessed area as much as possible. Therefore, the rigidity reduction of the frame 11 can be suppressed.
Further, since the recess 31 is elliptical, as shown in FIG. 1B, the width w1 in the frame longitudinal direction on both ends in the frame thickness D direction of the recess 31 is the frame at the center in the frame thickness D direction. Since the width is shorter than the width w2 in the longitudinal direction and the difference between the inner and outer peripheral lengths of the frame 11 can be reduced from this point as well, the generation of wrinkles that cause cracks and the like can be suppressed.
Furthermore, since the cross-sectional shape of the concave portion 31 is substantially linear, as shown in FIG. 2, the shape does not change from the inner gut hole 20 toward the peripheral edge 31c of the concave portion 31, and therefore stress due to an extreme change in rigidity. Concentration can be suppressed and the strength and durability of the frame 11 can be increased.

  4A and 4B show a tennis racket according to a second embodiment of the present invention, in which four corner portions of the head portion 12 of the racket frame 11 having a cross-sectional width W of 13 mm, that is, from 1 o'clock to 2 o'clock. Area, 4 o'clock to 5 o'clock, 7 o'clock to 8 o'clock, 10 o'clock to 11 o'clock A plurality of recesses 31 having d of 4 mm are formed at intervals. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

In the present embodiment, the recess 31 is formed around the inner gut hole 20 of the four regions where the effective length of the string S is the shortest, so that the effective length of the string S is uniform and the string movable area is effectively reduced. Can be enlarged. Thereby, the resilience is improved and the flight distance is extended, and the sweet spot is enlarged to improve the operability.
Further, the cross-sectional shape of the recess 31 in the frame thickness D direction is an arc shape as shown in FIG. 4B, but the radius of curvature is 50 mm, and the change in rigidity does not appear extremely, preventing stress concentration. Strength reduction can be suppressed.

FIG. 5 shows a tennis racket according to a third embodiment of the present invention. Each inner gut hole 20 is formed in the inner peripheral portion 12a of the 12 o'clock and 6 o'clock region of the head portion 12 of the racket frame 11 having a sectional width W of 13 mm. And a plurality of recesses 31 having a maximum depth d of 4 mm are formed at intervals. Since the shape and other configurations of the recess 31 are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.
Also in the third embodiment, the repulsive force in the sweet area of the ball striking surface 21 can be effectively increased.

6A and 6B show the main part of a tennis racket according to the fourth embodiment of the present invention.
A plurality of recesses 31 having a maximum depth d of 4 mm centering on each inner gut hole 20 are formed in the inner peripheral portion 12a of the 3 o'clock and 9 o'clock region of the head portion 12 of the racket frame 11 having a cross-sectional width W of 13 mm. They are formed at intervals. In addition, the viscoelastic member 23 is attached to the protective material groove 18 of the outer peripheral portion 12b at a position corresponding to the formation region of the recess 31, and the viscoelastic member 23 is attached between the frame 11 and the grommet cover 22. .
The viscoelastic member 23 has a shape in which the cylindrical portion 23c is protruded from the periphery of the insertion hole 23a provided at an interval in the band portion 23a, and is formed of silicon rubber, and the thickness of the band plate 23a is 5 mm. The grommet cover 22 that covers the viscoelastic member 23 has an insertion hole 22 a at a position corresponding to the insertion hole 23.

  In the present embodiment, in addition to improving the resilience by forming the concave portion 31 on the inner surface 12a of the 3 o'clock and 9 o'clock regions of the head portion 12, by attaching the viscoelastic member 23 to the outer peripheral portion 12b of the same region, The resilience can be further enhanced by utilizing the elasticity of the elastic member 23, and the ball flight performance can be effectively increased. At the same time, the string S and the vibration / impact of the frame can be absorbed and attenuated by the viscoelastic member 23, so that a good shot feeling can be obtained and the occurrence of tennis elbow can be prevented.

  As shown in Table 1 below, Examples 1 to 12 and Comparative Examples 1 to 3 were prepared, and the tennis racket was measured for rigidity, breaking strength, durability, coefficient of restitution, vibration damping, and an actual hit test was also performed. . In these examples and comparative examples, the shape around the gut hole 20 formed in the inner peripheral portion of the head portion, the depth of the recess 31, the position where the recess 31 is formed, the cross-sectional width W of the frame 11, and the viscoelastic member The presence / absence or type of 23 was varied. About the structure of the other racket frame 11, all the Examples and the comparative examples were the same as the racket frame 11 of the tennis racket of the above embodiment, and the frame weight and the frame balance were set as shown in Table 1.

The complex elastic modulus in Table 1 is representative of the values measured at a temperature of 5 ° C. among the values measured under the following conditions using a FT Rheospectr made by Rheology.
Sample: width 5 mm x length 30 mm x thickness 2 mm
Length of the deformed part in the sample: 20 mm (5 mm between both ends of 30 mm in length)
Initial strain: 10% (2mm)
Amplitude: 12 μm
10Hz frequency
Temperature: 0 ° C to 10 ° C
Mode: Tensile mode

(Example 1)
The depth d of the recess 31 is 2 mm, the cross-sectional width W of the frame 11 is 13 mm, and the other configurations are the same as those of the first embodiment. That is, the recess 31 is formed in an oval shape having a major axis of 20 mm and a minor axis of 10 mm around the inner gut hole 20 in the 3 o'clock and 9 o'clock regions of the head portion 12, and the depth d of the recess 31 and the frame The difference from the sectional width W of 11 was 11 mm.
(Example 2)
The configuration is the same as that of the first embodiment. That is, the depth d of the recess 31 is 4 mm different from that of the first embodiment, the cross-sectional width W of the frame 11 is 13 mm, and the difference between the depth d of the recess 31 and the cross-sectional width W of the frame 11 is 9 mm.
(Example 3)
The depth d of the concave portion 31 was 6 mm, the cross-sectional width W of the frame 11 was 13 mm, and the difference between the depth d of the concave portion 31 and the cross-sectional width W of the frame 11 was 7 mm. The other configurations are the same as those of the first embodiment.
Example 4
The depth d of the recess 31 was 6 mm, the cross-sectional width W of the frame 11 was 18 mm, and the difference between the depth d of the recess 31 and the cross-sectional width W of the frame 11 was 12 mm. The other configurations are the same as those of the first embodiment.

(Example 5)
The configuration is the same as that of the second embodiment. That is, the cross-sectional width W of the frame 11 is set to 13 mm, and the recess 31 is formed in the inner gut hole in the region of 1 to 2 o'clock, 4 o'clock to 5 o'clock, 7 o'clock to 8 o'clock, 10 o'clock to 11 o'clock. An elliptical shape having a major axis of 20 and a major axis of 20 mm, a minor axis of 10 mm, and a depth d of 4 mm was formed, and the difference between the depth d of the recess 31 and the cross-sectional width W of the frame 11 was 9 mm.

(Example 6)
The configuration is the same as that of the third embodiment. That is, the cross-sectional width W of the frame 11 is 13 mm, and the recess 31 has a major axis of 20 mm and a minor axis of 10 mm with the inner gut hole 20 at the center at 12 o'clock and 6 o'clock of the head 12 and a depth d. The difference between the depth d of the concave portion 31 and the cross-sectional width W of the frame 11 was 9 mm.

(Example 7)
The configuration is the same as that of the fourth embodiment. That is, the viscoelastic member 23 was attached to the outer surface side of the 3 o'clock and 9 o'clock regions of the frame 11 having the same configuration as that of the second embodiment. The viscoelastic member 23 was formed of silicon rubber, the thickness of the band portion 23a was 5 mm, and the complex elastic modulus measured under the above conditions was 1.41 × 10 ⁷ dyn / cm ² .
(Example 8)
The viscoelastic member 23 was molded by SBR, and the complex elastic modulus measured under the above conditions was 5.07 × 10 ⁷ dyn / cm ² . Other configurations were the same as those in Example 7.
Example 9
The viscoelastic member 23 is molded by blending 100 parts of SBR, 40 parts of carbon black and 1.5 parts of sulfur, the thickness of the band part 23a is 2 mm, and the complex elastic modulus measured under the above conditions is 3. 86 × 10 ⁸ dyn / cm ² . Other configurations were the same as those in Example 7.
(Example 10)
The viscoelastic member 23 is molded by blending 100 parts of SBR, 40 parts of carbon black and 1.5 parts of sulfur, the thickness of the band part 23a is 5 mm, and the complex elastic modulus measured under the above conditions is 3. 86 × 10 ⁸ dyn / cm ² . Other configurations were the same as those in Example 7.
(Example 11)
The viscoelastic member 23 is molded by blending 100 parts of SBR, 40 parts of carbon black and 1.5 parts of sulfur, the thickness of the band part 23a is 8 mm, and the complex elastic modulus measured under the above conditions is 3. 86 × 10 ⁸ dyn / cm ² . Other configurations were the same as those in Example 7.
(Example 12)
The viscoelastic member 23 was molded from 11-nylon, the thickness of the band portion 23a was 5 mm, and the complex elastic modulus measured under the above conditions was 1.45 × 10 ¹⁰ dyn / cm ² . Other configurations were the same as those in Example 7.

(Comparative Example 1)
The concave portion 31 was not formed in the racket frame 11 having a cross-sectional width of 13 mm, and the viscoelastic member 23 was not attached.
(Comparative Example 2)
In the 3 o'clock and 9 o'clock regions of the head portion 12 of the frame 11 having a cross-sectional width of 13 mm, as shown in FIG. 7, the inner gut hole 20 had a diameter of 5 mm and no recess was formed. The viscoelastic member 23 was not attached.
(Comparative Example 3)
An elliptical recess 31 having a major axis of 20 mm, a minor axis of 10 mm, and a depth d of 4 mm is formed over the entire circumference of the inner surface 12a of the head 12 of the frame 11 having a cross-sectional width of 13 mm. did.

(Measurement of lateral pressure stiffness)
As shown in FIG. 8, the side pressure stiffness is measured by holding the tennis racket with the tennis racket 10 of the example and the comparative example facing sideways and the striking surface 21 vertical. In this state, a load of 784N was applied to the side 12s of the upper head portion 12 by the flat plate P, the spring constant was calculated from the displacement at the time of loading, and the lateral pressure stiffness was measured.

(Measurement of ball striking surface stiffness)
As shown in FIG. 9, the ball striking surface stiffness (out-of-plane stiffness) is measured by placing the tennis rackets 10 of the example and the comparative example horizontally and receiving the top 12t of the head portion 12 with a jig 61 (R15). In addition, the position of the throat portion 13 from the both sides of the throat portion 13 to the yoke portion 16 was received and supported by a jig 62 (R15) at a position 340 mm away from the top 12t. In this state, a load of 784 N is applied from above to the position 170 mm away from the receiving jig 61 in the direction of the receiving jig 62, and the spring constant is calculated from the displacement at the time of loading. The ball striking face stiffness was calculated and measured.

(Measurement of maximum coefficient of restitution)
As shown in FIG. 10, the coefficient of restitution is such that the tennis racket 10 of the example and the comparative example is stretched with a tension of 60 pounds in length and 55 pounds in width and each tennis racket 10 is free in a vertical state. The grip portion 15 was fixed softly, a tennis ball was made to collide with the ball striking surface at a constant velocity V1 (30 m / sec) from the ball launcher on the ball striking surface 21, and the velocity V2 of the bounced ball was measured. The restitution coefficient is the ratio (V2 / V1) between the firing speed V1 and the rebound speed V2, and the larger the restitution coefficient, the better the ball flies.

(Measurement of out-of-plane primary vibration damping rate)
As shown in FIG. 11 (A), the upper end of the head portion 12 is lifted by a string 51 as shown in FIG. 11A, and an acceleration pickup meter 53 is placed at one continuous point between the head portion 12 and the throat portion 13. It was fixed perpendicular to the ball striking surface. In this state, as shown in FIG. 11B, the other continuous point of the head portion 12 and the throat portion 13 was vibrated with an impact hammer 55. An input vibration (F) measured by a force pickup meter attached to the impact hammer 55 and a response vibration (α) measured by an acceleration pick-up meter 53 are subjected to a frequency analysis device 57 (manufactured by Hewlett-Packard Company, dynamics) through amplifiers 56A and 56B. Single analyzer HP3562A) was input and analyzed. The transfer function in the frequency domain obtained by the analysis was obtained, and the frequency of the tennis racket was obtained. The vibration damping ratio (ζ) was obtained from the following equation, and used as the out-of-plane primary vibration damping rate. Table 1 shows the average values measured for the racket frames of the examples and comparative examples.

ζ = (1/2) × (Δω / ωn)
To = Tn × √2

(Measurement of out-of-plane secondary vibration attenuation rate)
As shown in FIG. 12C, the upper end of the head portion 12 is suspended by a string 51, and the acceleration pickup meter 53 is fixed perpendicularly to the ball striking surface at a continuous point between the throat portion 13 and the shaft portion 14. In this state, the frame 11 on the back side of the acceleration pickup meter 53 was vibrated with an impact hammer 55. Then, the attenuation rate was calculated by a method equivalent to the out-of-plane primary vibration attenuation rate, and the out-of-plane secondary vibration attenuation rate was obtained. Table 1 shows the average values measured for the racket frames of the examples and comparative examples.

(Measurement of fracture strength)
The breaking strength was set to the same test conditions as the measurement of the lateral pressure rigidity, a load was applied until the frame side broke, and the load at the time of occurrence of breaking was measured.

(Durability measurement)
A ball with a ball speed of 55 m / s was placed at a position 18 cm from the top position of the hitting surface 21 to check whether the frame 11 was damaged.

(Actual hit evaluation)
A questionnaire survey was conducted on racket flight, control, and operability. Table 1 shows the average score of 43 middle and advanced players (women who meet the requirements of playing tennis for more than 10 years and currently playing for more than 3 days a week), with a maximum score of 5. Indicated.

As can be seen from Table 1, the tennis rackets of Examples 1 to 12 in which the oval or perfect circular recesses are formed in the required portions of the frame all have high rigidity, breaking strength and durability, but also have a coefficient of restitution. High evaluation was obtained that both flying and operability were good in the actual hit evaluation. Moreover, it turned out that each Example except Example 12 among Examples 7-12 which attached the viscoelastic member has a high vibration damping factor, and there are few vibrations and impacts also from actual hit | damage evaluation.
On the other hand, it was found that Comparative Example 1 in which no concave portion was formed had no problem in rigidity and strength, but had a low coefficient of restitution and poor flying performance. Further, Comparative Example 2 in which the diameter of the gut hole was increased and Comparative Example 3 in which the recesses were formed on the entire periphery of the frame had a high coefficient of restitution but a low rigidity, strength, and durability.

Further, the vibration damping rate of Example 12 in which the complex elastic modulus of the viscoelastic member is larger than 1.0 × 10 ¹⁰ dyn / cm ² is almost the same as those of other Examples 1 to 6 in which no viscoelastic member is attached, Even in the actual hit evaluation, the result that vibration and impact were particularly small was not obtained. Further, in Example 11 in which the thickness of the band-shaped substrate of the viscoelastic member was 6 mm or more, the result that the operability was low in the actual hit evaluation was obtained.

The tennis racket which concerns on 1st embodiment of this invention is shown, (A) is a schematic front view of a racket, (B) is the figure which looked at the recessed part of the racket frame from the frame inner surface. It is sectional drawing which cut | disconnected the recessed part formation location of the racket frame shown in FIG. 1 in the frame thickness direction. It is sectional drawing which cut | disconnected the location which has not formed the recessed part of the racket frame shown in FIG. 1 in the frame thickness direction. The tennis racket which concerns on 2nd embodiment of this invention is shown, (A) is a schematic front view of a racket, (B) is sectional drawing which cut | disconnected the recessed part formation location in the frame thickness direction. It is a schematic front view of the racket frame of the tennis racket which concerns on 3rd embodiment of this invention. The principal part of the tennis racket which concerns on 4th embodiment of this invention is shown, (A) is principal part sectional drawing, (B) is a principal part disassembled perspective view. 6 is a cross-sectional view in the frame thickness direction of a recessed portion formation portion of Comparative Example 2. FIG. It is the schematic which shows the measuring method of the side pressure rigidity of a tennis racket. It is the schematic which shows the measuring method of the ball striking surface rigidity of a tennis racket. It is the schematic which shows the measuring method of the coefficient of restitution of a tennis racket. (A), (B), and (C) are schematic views showing a method of measuring the vibration attenuation rate of the racket frame. It is a figure which shows a prior art example. It is a figure which shows another prior art example. It is a figure which shows another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Tennis racket 11 Racket frame 12 Head part 12a Inner peripheral part 12b Outer peripheral part 18 Gut hole 19 Outer gut hole 20 Inner gut hole 21 Hitting surface 23 Viscoelastic member 23a Belt part 31 Recessed part 31a Long diameter 31b Short diameter 23 Viscoelastic member W Frame Section width D Frame thickness

Claims (7)

A racket frame made of fiber reinforced resin composed of a sleeve of a prepreg laminate is provided, and a gut hole is provided in the head portion surrounding the striking surface of the racquet frame with a gap in the longitudinal direction of the frame. A tennis racket in which an inner gut hole drilled on the inner peripheral side and an outer gut hole drilled on the outer peripheral side are penetrated perpendicularly to the longitudinal direction of the frame,
On the inner peripheral side of the head portion, a recess centered on a part of the inner gut hole is provided, and the recess has dimensions in the frame length direction on both ends in the frame thickness direction orthogonal to the striking surface. The tennis racket is characterized by being set shorter than the dimension in the frame length direction at the center in the frame thickness direction.   2. The tennis racket according to claim 1, wherein the concave portion has a substantially elliptical shape in which a maximum width in a frame longitudinal direction is narrower than a maximum width in a frame thickness direction.   3. The tennis racket according to claim 1, wherein a curved surface that protrudes toward the ball striking surface is formed on an inner peripheral surface of the face portion other than a portion where the concave portion is formed.   The tennis according to any one of claims 1 to 3, wherein the depth of the concave portion is such that the position of the inner gut hole is a deepest position, and the depth is gradually reduced from the peripheral edge of the concave portion to the deepest position. racket.   The tennis racket according to any one of claims 1 to 4, wherein the recess contour in a cross section perpendicular to the length direction of the frame is substantially linear with a radius of curvature of 50 mm or more.   The frame width orthogonal to the frame thickness direction of the head portion is in the range of 12 mm to 18 mm, the maximum depth of the recess is in the range of 1 mm to 7 mm, and the difference between the frame width and the maximum depth of the recess The tennis racket according to any one of claims 1 to 6, wherein the length is 10 mm or more.   7. The device according to claim 1, wherein a groove in the longitudinal direction is provided at least on the opposite side of the recessed portion forming portion on the outer peripheral surface of the head, and a viscoelastic member is attached to the groove. Tennis racket.

Images