JP6943632B2 - racket - Google Patents

Description

The present invention relates to a racket, particularly a racket for soft tennis.

In racket sports such as tennis, the player swings the racket and hits the ball. The racket includes a grip gripped by the player, a shaft provided with the grip on one end side, and a frame formed on the other end side of the shaft in a loop shape. Strings are stretched in a grid pattern on the inside of the frame, and a ball striking surface for hitting a ball is formed by the strings (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-261914

Recently, the contact time between the ball and the string at the time of hitting has become shorter due to the speeding up of the swing speed of the racket and the speeding up of the hitting ball. For this reason, the so-called ball holding performance (hold feeling) is lowered, and it tends to be difficult for the player to control the hit ball.

Here, in order to lengthen the contact time between the ball and the string, it is conceivable to increase the pitch of the string or decrease the tension of the string. In this case, the surface pressure of the ball striking surface formed by the string can be lowered to prolong the contact time between the ball and the string, but the shot feeling is blurred by the player, and as a result, the controllability can be sufficiently improved. There is a problem that it disappears.

Further, as another configuration for lengthening the contact time, a configuration in which the rigidity of the frame or shaft is reduced to significantly increase the bending of the racket is also conceivable. However, in this case, it takes time for the bent racket to return to its original shape. Therefore, even if the player swings to hit the ball in the desired hitting direction, the ball is hit at a deviation from the desired hitting direction, which also causes a problem that the controllability cannot be sufficiently improved.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a racket capable of prolonging the contact time between the ball and the string at the time of hitting the ball and improving the controllability of the hitting ball. ..

The racket of the present invention is a racket including a frame in which strings are stretched to form a ball striking surface and a shaft formed between the frame and the grip, and is between the frame and the shaft. Is formed, a joint portion for joining these is formed, an opening surrounded by the frame and the shaft is formed, a region adjacent to the opening is defined as an opening formation region, and the string is inserted through the joint portion. A hole is formed, and recesses are formed on both sides of the hole and the opening forming region and sandwiching the center position in the thickness direction.

According to this configuration, since the recess is formed in the joint portion that joins the frame and the shaft, the rigidity of the joint portion can be reduced and the joint portion can be easily deformed at the time of hitting a ball. As a result, the frame is easily deformed so as to be twisted with respect to the shaft, the contact time between the ball and the string can be lengthened, the ball holding performance can be improved, and the controllability can be improved. Further, only the rigidity of the joint portion can be reduced as compared with the conventional structure in which the recess is not formed, in other words, the rigidity of the frame and the shaft can be maintained as compared with the conventional structure. As a result, it is possible to prevent the amount of bending deformation of the frame or shaft at the time of hitting the ball from changing, and it is possible to prevent the controllability from being lowered.

Further, in the racket of the present invention, the shaft includes a throat that bifurcates from the grip toward the frame , and the joint portion and the recess extend along the extension direction of the throat. good. According to this configuration, the recess can be formed over a wide range of the joint portion, and the rigidity at the joint portion can be better reduced.

Further, in the racket of the present invention, the joint portion is provided with a pair of inclined surfaces that approach each other from both sides in the thickness direction toward the outside when the throat is viewed in a cross section orthogonal to the extension direction, and the recess is provided. May be formed on each of the pair of inclined surfaces. According to this configuration, since the joint portion forms an inclined surface, the cross-sectional shape of the joint portion is approximated to a triangular shape having each inclined surface as a hypotenuse. As a result, the reduction in rigidity at the joint can be better achieved, and the above-mentioned actions and functions can be more satisfactorily exhibited.

Further, in the racket of the present invention, it is preferable that the width of the recess in the direction orthogonal to the extending direction is formed so as to increase from both ends of the extending direction toward the center. According to this configuration, by changing the width of the concave portion, it is possible to adopt a design in which the rigidity of the joint portion is adjusted according to the width of the concave portion in the extending direction of the joint portion. In addition, it is possible to obtain a visual effect in which the rigidity reduction can be achieved most in the central portion where the width of the recess is maximum.

Further, in the racket of the present invention, a groove portion having the hole on the bottom side is formed on the outer peripheral side of the frame and the joint portion, and the groove portion is continuously formed by the frame and the joint portion. It is preferable that the groove portion formed in the joint portion has a larger groove depth than the groove portion formed in the frame. According to this configuration, the rigidity of the joint can be reduced not only by the shape of the recess but also by the shape of the groove.

According to the present invention, since the recess is formed in the joint portion where the frame and the shaft are joined, the contact time between the ball and the string at the time of hitting the ball can be lengthened, and the controllability of the hit ball can be improved.

It is an external view of one usage mode of the racket according to the embodiment, FIG. 1A is a front view of the racket, and FIG. 1B is a side view of the racket. It is a partial schematic perspective view of the racket. FIG. 1A is a cross-sectional view taken along the line AA of FIG. 1A. It is explanatory drawing of the deformation operation of a racket at the time of hitting a ball. It is a graph which shows the rate of change of a frame angle at the time of hitting a ball. FIG. 5 is a schematic cross-sectional view of a joint portion of Examples 1 to 3 and Comparative Examples 1 to 4.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the following, an example in which the present invention is applied to a racket for soft tennis will be described, but the application target is not limited to this and can be changed. For example, it may be applied to a tennis racket for hard tennis, a racket for squash, and the like.

FIG. 1 is an external view of one usage mode according to the racket of the embodiment, FIG. 1A is a front view of the racket, and FIG. 1B is a side view of the racket. In each of the following figures, some configurations are omitted for convenience of explanation.

As shown in FIG. 1, the racket 10 includes a head 11 which is a portion for hitting a ball, a grip 12 which is a portion where a player grips the racket 10, and a shaft 13 formed between the head 11 and the grip 12. It has. In the following description, as shown by an arrow in FIG. 1, the side in which the head 11 is located is the upper side and the side where the grip 12 is located is the lower side in the longitudinal direction of the racket 10. Further, the direction orthogonal to the longitudinal direction on the ball striking surface of the racket 10 (that is, on the plane along the ball striking surface) is the width direction (or the left-right direction), and the direction orthogonal to the ball striking surface of the racket 10 is the thickness direction (that is, the thickness direction). Alternatively, it is in the front-back direction).

The head 11 includes a loop-shaped frame 15 that resembles an ellipse that is long in the vertical direction, and a striking surface (face) is formed inside by stretching strings (not shown) in a grid pattern on the frame 15. The outer peripheral surface 15a of the frame 15 is provided with a groove portion 16 having a recessed central portion in the thickness direction. The groove portion 16 is continuously provided along the circumferential direction of the frame 15. The frame 15 is provided with a plurality of holes 17 through which strings are inserted. The plurality of holes 17 are formed so as to penetrate from the bottom side of the groove portion 16 on the outer peripheral surface 15a of the frame 15 to the inner peripheral surface 15b. A plurality of holes 17 are provided along the circumferential direction of the frame 15.

The frame 15 is formed so that the position where the left-right width is maximum is above the center position in the vertical direction. As a result, the so-called sweet spot can be set above the vertical center position of the frame 15.

The shaft 13 includes a throat 20 bifurcated from the grip 12 toward the head 11 when viewed from the front-rear direction, and a yoke 18 forming a part of the frame 15 is formed between the left and right throats 20. .. The throat 20 is formed in a shape that curves in an arc shape between the grip 12 and the head 11.

Here, a joint portion 24 for joining these is integrally formed between the upper end of the throat 20 and the left and right sides (left and right sides of the yoke 18) below the frame 15. The joint portion 24 is formed so as to overlap the forming position of the frame 15 in the vertical direction, and the lower portion of the frame 15 is formed so as to bulge outward. Further, the joint portion 24 is provided in a shape that extends along the extending direction of the curved throat 20. Further, the joint portions 24 are provided on both ends of the yoke 18 in the extending direction. Also in the joint portion 24, the groove portion 16 formed in the frame 15 is continuously formed, and the groove portion 16 is also formed through the hole 17 for inserting the string.

An opening 25 that opens in the front-rear direction is formed surrounded by the yoke 18 in the frame 15 and the left and right throats 20 in the shaft 13. Here, as shown in FIG. 2, the region adjacent to the opening 25 is referred to as the opening forming region 26. FIG. 2 is a partial schematic perspective view of the racket. The opening forming region 26 includes an opening inner peripheral surface 27 extending along the front-rear (thickness) direction on the opening 25 side of the left and right throats 20, the yoke 18, and the joint portion 24, and a throat connected to the opening inner peripheral surface 27. It has 20 and an opening adjacent surface 28 located on the opening 25 side of the maximum front-rear width forming position 29 of the joint portion 24. The front-rear width on the opening adjacent surface 28 is smaller than the front-rear width at the maximum front-rear width formation position 29, and is formed so as to be recessed from the maximum front-rear width formation position 29.

The frame 15, the shaft 13, and the joint portion 24 are formed by molding a hollow cylindrical body made of, for example, a fiber reinforced resin, but the frame 15, the shaft 13, and the joint portion 24 may be filled with a foam material, or may be made of wood or metal, instead of being hollow. You may.

Recesses 30 are formed in each of the left and right joints 24. The left and right joints 24 and recesses 30 have the same structure except that the positions and orientations are symmetrical. Therefore, in the following description, the specific configuration of the joint portion 24 and the recess 30 on the left side will be described, and the description of the joint portion 24 and the recess 30 on the right side will be simplified or omitted.

FIG. 3 is a cross-sectional view taken along the line AA of FIG. 1A. As shown in FIG. 3, the joint portion 24 includes a pair of inclined surfaces 24a on both sides in the thickness direction. The pair of inclined surfaces 24a are viewed from both sides in the front-rear (thickness) direction toward the outside (left in FIG. 3) when viewed in the cross section of FIG. 3 (cross section orthogonal to the extending direction of the throat 20). Formed to approach. More specifically, the front-rear inclined surfaces 24a are formed on the inclined surfaces so as to approach each other from the maximum front-rear width forming position 29 toward the front-rear end sides of the groove portion 16 in the inside-out direction of the joint portion 24.

Recesses 30 (rear recesses are not shown in FIG. 2) are formed on each of the front and rear inclined surfaces 24a. The recess 30 is formed at a position and shape symmetrical with respect to the front-rear (thickness) direction center position C of the joint portion 24 on the front-rear inclined surface 24a. Further, the recess 30 is formed so as not to protrude from the inclined surface 24a, in other words, is formed at a position away from the groove portion 16, the hole 17, and the opening forming region 26.

As shown in FIG. 2, the outer peripheral edge shape of the recess 30 is formed into an elongated shape that extends along the extending direction of the throat 20, and is formed so that the width in the direction orthogonal to the extending direction changes. ing. Specifically, the width is formed so as to increase from both ends in the extension direction toward the center to form a triangular shape. The triangular vertices of the recess 30 are formed on both sides of the throat 20 in the extending direction and inside in the intermediate portion in the extending direction.

Subsequently, with reference to FIG. 4, the deformation operation of the racket at the time of hitting a ball will be described. 4A to 4C are explanatory views of the deformation operation of the racket at the time of hitting a ball. As shown in FIG. 4A, for example, in the ground stroke of soft tennis, when the ball B is to be driven to rotate, the ball B is hit with the width direction of the frame 15 directed in the vertical direction in the drawing. In this hit, the racket 10 is often moved from the bottom to the top in order to apply drive rotation during the swing. At this time, in order to gain an area for rolling or rubbing the ball B on the ball striking surface F, the striking position of the ball B tends to be upward in FIG. 4A of the ball striking surface F. Further, in order to apply the drive rotation, there is a tendency to incline the flying ball B so as to cover the ball striking surface F from above.

Then, as shown in FIG. 4B, when the ball B hits the ball striking surface F, the frame 15 is elastically deformed so as to be twisted in the direction of arrow R1 in the figure due to the impact force generated at that time. Then, the elastic deformation is restored, and as shown in FIG. 4C, the twist is returned so that the frame 15 rotates in the direction of the arrow R2 in the drawing. By twisting back in the direction of the arrow R2, the drive rotation is applied to the ball B in contact with the ball striking surface F.

In the present embodiment, the rigidity of only the joint portion 24 can be reduced by forming the recess 30 as compared with the racket which does not form the recess 30 which is the conventional structure. As a result, it is possible to easily cause the racket 10 to be deformed as shown in FIG. Specifically, due to the decrease in rigidity of the joint portion 24, the amount of twisting deformation in the direction of arrow R1 in FIG. 4B can be increased, and the amount of return in the direction of arrow R2 in FIG. 4C can be increased accordingly. ..

By deforming in this way, even an advanced player with a high swing speed can prolong the contact time between the ball B and the ball striking surface F, and can improve the ball holding performance (holding feeling). As a result, when the player hits the ball, it is possible to gain time to operate the hitting direction, and the range of the hitting direction can be expanded to hit the ball at a wide angle.

Further, since the amount of twisting deformation and the amount of return thereof become large, it is possible to apply more drive rotation to the ball B, and it is possible to improve the drive performance of the racket 10. Further, by increasing the twisting deformation, the hitting surface F when twisted to the maximum can be made more upward, and the trajectory of the hitting ball can be raised to improve the flying performance.

Further, by providing the recess 30 only in the joint portion 24, the joint portion 24 is easily deformed when a force due to the hitting ball is applied to the hitting surface F, but the rigidity of the frame 15 and the shaft 13 itself remains the same. It is possible to prevent a decrease in repulsion performance at the time of hitting a ball. Moreover, the deformation of the frame 15 and the shaft 13 itself can be made the same as those of the conventional structure, and the bending method and the amount of bending thereof are the same as those of the conventional structure, and the control performance due to the change of the bending is improved. The drop can be avoided. For example, when an attempt is made to hit a ball in the straight direction, it is possible to prevent the ball from being hit in a direction deviated from the straight direction, and it is possible to maintain good controllability.

Here, in the above description, the case where the hitting position of the ball B is upward in FIG. 4A of the ball striking surface F has been described, but an experiment was conducted in the case where the hitting position of the ball B is downward in the figure. In this experiment, the ball was hit by a highly reproducible robot that swings the racket in the same manner as the player, and the hitting surface and the ball at the time of hitting were measured with a high-speed camera (5,000 Hz). In this measurement, the number of rotations of the ball and the behavior of the racket were evaluated. As the racket, a racket formed in the same manner as in the above embodiment and a racket having a conventional structure in which the recess 30 is not formed in the racket were used.

Comparing the rotation speeds of the balls between the racket of the embodiment and the racket of the conventional structure, the rotation speeds of the balls in the embodiment were about 27% higher than those in the conventional structure. The behavior of the racket is as shown in the graph shown in FIG. FIG. 5 is a graph showing the rate of change of the frame angle at the time of hitting a ball. In the graph of FIG. 5, the circle mark and the solid line indicate the embodiment, and the triangle mark and the dotted line indicate the conventional structure. As can be understood from the graph of FIG. 5, the embodiment has a larger twist than the conventional structure, and the time for the twist to occur is longer. It can be inferred that the direction of twisting is such that the frame (ball striking surface) is tilted in the direction in which it is turned down, and the frame is swung up in this state, so that the drive rotation is likely to be applied.

Subsequently, in order to evaluate the difference in rigidity depending on the shapes of the joints and recesses of the above embodiment, the rigidity was calculated and compared with the shapes of Examples 1 to 3 and Comparative Examples 1 to 4 shown in FIG. FIG. 6 is a schematic cross-sectional view of the joints of Examples 1 to 3 and Comparative Examples 1 to 4. FIG. 6 is a cross-sectional view of the joint portion 24 at the same position as in FIG. Further, in FIG. 6, in all the examples and comparative examples, the rigidity was calculated and compared in the case where the frame 15 adjacent to the joint portion 24 was omitted and the solid structure was used.

In Examples 1 to 3, the joint portion 24 has a shape in which a pair of inclined surfaces 24a and a groove 16 are formed as in the above embodiment, and the joint portion 24 has a thickness t of about 13.5 mm and a front-rear width h. It was set to 19 mm. In Examples 1 to 3, the depth d of the groove 16 is different, the depth d of Example 1 is 2.5 mm, the depth d of Example 2 is 3 mm, and the depth d of Example 3 is 5 mm. bottom. The joint portion 124 of Comparative Example 1 was reshaped so as to have a region substantially parallel to the front surface 124b and the rear surface 124c with respect to Example 1, and the formation of the recess 30 of Example 1 was omitted. Further, the joint portion 124 of Comparative Examples 2 to 4 formed an inclined surface 124a similar to the inclined surface 24a of Examples 1 to 3, but had a shape in which the formation of the recess 30 was omitted. Regarding the groove 16, the depth d of Comparative Examples 1 and 2 was 2.5 mm, the depth d of Comparative Example 3 was 3 mm, and the depth d of Comparative Example 4 was 5 mm.

Table 1 below shows the relative values of the cross-sectional rigidity (second moment of area with respect to the axis extending in the left-right direction) of Examples 1 to 3 and Comparative Examples 2 to 4 when the value of the cross-sectional rigidity of Comparative Example 1 is 100. show.

As can be understood from the results in Table 1, with respect to the joint portions 24 and 124, the rigidity of Examples 1 to 3 in which the recesses 30 are formed can be reduced by 10% or more as compared with Comparative Examples 2 to 4. As a result, by forming the recess 30, the amount of twisting deformation shown in FIG. 4 can be increased, the contact time between the hitting surface and the ball at the time of hitting the ball can be lengthened, and the control performance can be improved. In addition, since the amount of return of the twisting deformation is large, the ball can be rubbed greatly with the ball striking surface, and the drive rotation performance can be improved.

In comparison between Comparative Example 1 and Comparative Examples 2 to 4, it can be understood that forming the inclined surface 124a on the joint portion 124 contributes to a decrease in the rigidity of the joint portion 124. Therefore, even in the joint portion 24 of the embodiment, by forming the joint portion 24 to have an inclined surface 24a, the cross-sectional rigidity can be reduced and the above-mentioned torsional deformation can be largely secured.

Further, according to the results of Examples 1 to 3 and Comparative Examples 2 to 4, the value of the cross-sectional rigidity becomes smaller when the depth d of the groove 16 is larger, although it is slight. As a result, for example, the groove portion 16 formed in the joint portion 24 has a larger groove depth than the groove portion 16 formed in the frame 15, thereby lowering the cross-sectional rigidity value of the joint portion 24 and twisting. It can be easily deformed.

The present invention is not limited to the above embodiment, and can be modified in various ways. In the above embodiment, the size, shape, direction, etc. shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

For example, the shape of the joint portion 24 is not limited to the shape of the above embodiment. As an example, the shape of the joint portion 124 in Comparative Example 1 of FIG. 5 may be adopted, and recesses 30 may be formed on both front and rear surfaces of the joint portion 124. However, it is advantageous to form the recess 30 on the inclined surface 24a of the joint portion 24 as in the above embodiment in that the recess 30 is easily twisted and deformed due to the decrease in the cross-sectional rigidity, and the above-mentioned effect can be obtained better. Become.

Further, the shape of the recess 30 can be changed in various ways. For example, the joint portion 124 is formed in a rectangular shape or an oval shape extending in the extending direction, or divided into a plurality of portions with respect to one inclined surface 24a. You may.

The present invention is a racket, and has an effect that the contact time between the ball and the string at the time of hitting the ball can be lengthened.

10 Racket 12 Grip 13 Shaft 15 Frame 16 Groove 17 Hole 20 Throat 24 Joint 24a Inclined surface 25 Aperture 26 Aperture formation area 30 Recess

Claims (5)

A racket including a frame in which strings are stretched to form a ball striking surface and a shaft formed between the frame and the grip.
A joint is formed between the frame and the shaft to join them.
An opening surrounded by the frame and the shaft is formed, and a region adjacent to the opening is designated as an opening forming region.
A hole through which the string is inserted is formed in the joint portion, and recesses are formed on both sides of the hole and the opening forming region and sandwiching the center position in the thickness direction. A featured racket. The shaft comprises a throat that bifurcates from the grip towards the frame.
The racket according to claim 1, wherein the joint portion and the concave portion extend along the extending direction of the throat. The joint comprises a pair of sloping surfaces that approach the throat outward from both sides in the thickness direction when viewed in cross section orthogonal to the extension direction.
The racket according to claim 2, wherein the recesses are formed on each of the pair of inclined surfaces. The racket according to claim 2 or 3, wherein the width of the recess in the direction orthogonal to the extending direction is formed so as to increase from both ends of the extending direction toward the center. A groove having the hole on the bottom side is formed on the outer peripheral side of the frame and the joint portion.
The claim is characterized in that the groove portion is continuously formed by the frame and the joint portion, and the groove portion formed in the joint portion has a groove depth larger than that of the groove portion formed in the frame portion. The racket according to any one of items 1 to 4.

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