racket

Abstract

To excellently exhibit both control performance and flicking performance so as to soften an impact feeling.SOLUTION: A racket (10) includes a frame (15) forming a ball hitting surface due to a stretched string, and a shaft (13) formed between the frame and a grip (12). The shaft includes a shaft body (20) continuing from the upper edge of the grip, a throat (21) continuing from the upper edge of the shaft body and branched into two from the upper edge to the frame, and a cave-in part (30) and a non-cave-in part (31) formed at both surface sides in the thickness direction of the shaft body. The cave-in part extends upward adjacently to the upper edge of the grip, and the non-cave-in part is formed in a region sandwiched by the upper edge of the cave-in part and the bottom edge of the throat.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a racket, and more particularly to a soft tennis racket. [Background technology]

[0002] In racket sports such as tennis, a player swings a racket to hit a ball. The racket has a grip that the player holds, a shaft with the grip attached to one end, and a loop-shaped frame attached to the other end of the shaft. Strings are stretched in a lattice pattern inside the frame, and the strings form a hitting surface for hitting the ball (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-261914 Summary of the Invention [Problem to be solved by the invention]

[0004] To enhance the accuracy and performance of a player's play, rackets are required to have both improved ball control and repulsion. Control refers to the ease with which a player can control a ball, and improving performance can be achieved by making the hitting surface less likely to wobble when hitting the ball. Therefore, to improve control, rackets generally employ a shaft design that makes it less likely for the shaft to twist.

[0005] In addition, repulsion performance is the initial velocity of the ball when it is hit, and performance can be improved by making the ball leave the club quickly upon impact. Therefore, to improve repulsion performance, a shaft design that makes it less likely to bend is generally adopted.

[0006] Therefore, in order to improve both control performance and repulsion performance, it is possible to design a shaft with increased rigidity to suppress shaft flex and twist. However, simply increasing the shaft rigidity increases the impact felt by the player when hitting the ball, making it difficult to evaluate each of the above performance characteristics.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a racket that can exhibit both good controllability and good repulsion performance, and can also reduce the feeling of impact. [Means for solving the problem]

[0008] The racket of the present invention is a racket comprising a frame on which strings are stretched to form a hitting surface, and a shaft formed between the frame and a grip, wherein the shaft comprises a shaft body connected to the upper end of the grip, and a recessed portion and a non-recessed portion formed on both thickness-wise sides of the shaft body, the recessed portion extending upward adjacent to the upper end of the grip, and the non-recessed portion formed in at least the area sandwiched between the upper end of the recessed portion and the lower end of the frame. [Effects of the Invention]

[0009] According to the present invention, the non-depressed portions are formed in the shaft, which suppresses twisting of the shaft and makes the hitting surface less likely to wobble, thereby improving ball control. Furthermore, the non-depressed portions suppress shaft flex, while the depressed portions prevent excessive suppression of this flex. In other words, the depressed and non-depressed portions can moderately suppress shaft flex. This moderate shaft flex increases the initial velocity of the ball when hit, improving repulsion performance and mitigating the feeling of impact when hitting the ball. In this way, the depressed and non-depressed portions of the shaft simultaneously improve both ball control and repulsion performance, while mitigating the feeling of impact when hitting the ball. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are external views of a racket according to an embodiment in one mode of use, with FIG. 1A being a front view of the racket and FIG. 1B being a side view of the racket. [Figure 2] FIG. 2 is a partial schematic perspective view of the racket. [Figure 3] FIG. 1B is a partially enlarged view of FIG. 1A. [Figure 4] FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Figure 5] 10 is a graph showing the results of fluid analysis of the embodiment and a second comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that, although the following describes an example in which the present invention is applied to a soft tennis racket, the application of the present invention is not limited to this and can be changed. For example, the present invention may be applied to a tennis racket for hard tennis, a squash racket, etc.

[0012] Fig. 1 is an external view of a racket according to an embodiment of the present invention in one mode of use, with Fig. 1A being a front view of the racket and Fig. 1B being a side view of the racket. Note that for the sake of convenience, some components have been omitted from the following figures.

[0013] 1, a racket 10 includes a head 11, which is the part that hits the ball, a grip 12, which is the part that a player holds the racket 10, and a shaft 13 that is formed between the head 11 and the grip 12. The head 11 and the shaft 13 are formed by molding a hollow cylinder made of, for example, a fiber-reinforced resin, but they may also be solid and filled with a foam material, or made of wood or metal.

[0014] In the following description, as shown by the arrows in Figure 1, the longitudinal direction of the racket 10 is referred to as the up-down direction, with the side where the head 11 is located referred to as the upper side and the side where the grip 12 is located referred to as the lower side. Furthermore, the direction perpendicular to the up-down direction on the hitting surface of the racket 10 (i.e., on a plane along the hitting surface) is referred to as the left-right direction, and the direction perpendicular to the hitting surface of the racket 10 is referred to as the front-rear direction. The left-right direction refers to the width direction of the racket 10 and may be referred to as the width direction in the following description, and the front-rear direction refers to the thickness direction of the racket 10 and may be referred to as the thickness direction in the following description.

[0015] The head 11 includes a frame 15 having a loop shape similar to an ellipse that is long in the vertical direction, and a string (not shown) is stretched around the frame 15 in a grid pattern to form a ball-hitting surface (face) on the inside. The outer peripheral surface 15a of the frame 15 is provided with a groove 16 that is recessed in the center in the thickness direction. The groove 16 is provided continuously along the circumferential direction of the frame 15. The frame 15 is provided with a plurality of holes 17 through which the string is inserted. These multiple holes 17 are formed so as to penetrate from the bottom of the groove 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.

[0016] The shaft 13 includes a shaft body 20 that is connected to the upper end of the grip 12 and extends linearly in the vertical direction. The shaft 13 also includes a throat 21 that is connected to the upper end of the shaft body 20 and that branches into two from the upper end of the shaft body 20 toward the frame 15 when viewed from the front-to-rear direction. A yoke 18 that forms part of the frame 15 is formed between the left and right throats 21. The throat 21 is formed in a shape that curves gently in an arc between the grip 12 and the head 11.

[0017] An opening 23 that is open in the front-to-rear direction is formed between the yoke 18 of the frame 15 and the left and right throats 21 of the shaft 13. Here, as also shown in FIG. 2, the area adjacent to the opening 23 is an opening-forming surface 25. FIG. 2 is a partial schematic perspective view of the racket. The opening-forming surface 25 forms the inner peripheral surface of the throat 21, and this inner peripheral surface is formed to bulge toward the opening 23. The opening-forming surface 25 also forms the lower end 23a of the opening 23. This lower end 23a is the boundary position between the shaft body 20 and the throat 21 in the up-down direction, and this boundary position is the upper end of the shaft body 20 and the lower end of the throat 21.

[0018] At the upper end of the shaft body 20, an opening-side recess 27 is formed, continuing to the opening-forming surface 25. The opening-side recess 27 is formed on both sides in the thickness direction of the shaft body 20. The opening-side recess 27 is formed so that its width dimension gradually decreases downward in the up-down direction. Furthermore, the opening-side recess 27 is formed so that its depth (recess width) gradually decreases downward in the thickness direction.

[0019] The shaft 13 further includes a recessed portion 30 and a non-recessed portion 31 formed on both sides of the shaft body 20 in the thickness direction.

[0020] The recessed portion 30 extends upward adjacent to the upper end of the grip 12 and is recessed in a direction that reduces the thickness of the shaft body 20. The recessed portion 30 is formed so that its width dimension gradually decreases upward in the vertical direction. Specifically, when viewed from the front-to-rear direction, the recessed portion 30 is formed over the entire left-to-right direction of the shaft body 20 near the grip 12. Furthermore, when viewed from the front-to-rear direction, the recessed portion 30 has a pair of left and right inclined edges that gradually approach each other upward from the grip 12, and a semicircular arc-shaped upper edge (upper end) that connects the inclined edges.

[0021] Fig. 3 is a partially enlarged view of Fig. 1A. As shown in Fig. 3, the upper edge of the recessed portion 30 is formed above the center position C in the vertical direction of the shaft body 20. In other words, the recessed portion 30 is formed in an area of ​​more than half of the shaft body 20 in the vertical direction.

[0022] The non-depressed portion 31 is formed on both sides of the shaft body 20 in the thickness direction, extending in an X-shape when viewed from the front-to-rear direction. The portion of the non-depressed portion 31 that is sandwiched between the upper end of the depressed portion 30 and the lower end of the opening-side recess 27 is defined as an intermediate portion 31a in the up-down direction. Furthermore, the non-depressed portion 31 is formed extending from the intermediate portion 31a to both the left and right sides of the opening-side recess 27 and to both sides of the depressed portion 30 in the up-down direction. The region in the non-depressed portion 31 where the intermediate portion 31a is formed is also the region sandwiched between the upper end of the depressed portion 30 and the lower end of the throat 21.

[0023] The intermediate portion 31a is formed at a position including the center portion in the left-right direction of the shaft body 20. Since the upper edge of the recessed portion 30 is formed above the center position C in the up-down direction of the shaft body 20, the intermediate portion 31a adjacent to and above the upper edge is also formed above the center position C in the up-down direction of the shaft body 20.

[0024] The shaft body 20 has an area in the vertical direction where neither the depressed portion 30 nor the opening-side recess 27 is formed, due to the intermediate portion 31a of the non-depressed portion 31. In other words, the depressed portion 30 and the opening-side recess 27 are formed apart in the vertical direction via the intermediate portion 31a, and the intermediate portion 31a also has a shape formed by raising between the depressed portion 30 and the opening-side recess 27.

[0025] Fig. 4 is a cross-sectional view taken along line AA in Fig. 1A. As shown in Fig. 4, the cross-sectional shape of the shaft body 20, which is perpendicular to the up-down direction in the region where the non-depressed portion 31 is formed, is formed into a substantially octagonal shape. The non-depressed portion 31 is formed by both the front and rear sides (both sides in the thickness direction) of the octagon.

[0026] Here, the octagon formed by the cross section of the shaft body 20 has inclined surfaces 33 formed on both the front-rear and left-right sides. The front-rear width of each inclined surface 33 is set within a range of 25 to 35% of the entire front-rear width of the shaft body 20, and the left-right width of each inclined surface 33 is set within a range of 25 to 35% of the entire left-right width of the shaft body 20.

[0027] In the region where the recess 30 is formed, the cross section perpendicular to the up-down direction is formed to be substantially octagonal, and both the front and rear sides are recessed as shown by the dotted lines in FIG.

[0028] Next, an analysis of the stiffness of the shaft in both the bending direction and the twisting direction will be described. This analysis was performed on the racket of the above embodiment and first to third comparative examples, which have shaft shapes different from those of the above embodiment.

[0029] In the first comparative example, the shaft body 20 of the above embodiment does not have a non-depressed portion 31, but has a depressed portion 30 that continues vertically from the opening-side recess 27. In the second comparative example, the shaft body 20 of the above embodiment does not have a depressed portion 30, but has a cross-sectional shape perpendicular to the vertical direction that is substantially rectangular. In the third comparative example, the shaft body of the second comparative example has a cross-sectional shape perpendicular to the vertical direction that is substantially octagonal. Note that the first comparative example has a conventional, common shape, and the shapes of the second and third comparative examples and the embodiment were designed to improve on this shape of the racket.

[0030] In the analysis, the racket grip was fixed, a predetermined load was applied in the front-to-back direction to the upper end of the frame, and the amount of deformation in the front-to-back direction at the upper end of the frame was measured as the amount of flex.Similarly, the racket grip was fixed, and a predetermined load was applied in opposite front-to-back directions to the left and right sides of the frame, and the amount of deformation in the front-to-back direction at both the left and right ends of the frame was measured as the amount of torsion.

[0031] In the measurements carried out for the embodiment and each comparative example, the value of the amount of flex and twist of the first comparative example was set to 100, and the amounts of flex and twist of the other comparative examples and the embodiment were measured as relative values ​​to the first comparative example. The measurement results are shown in Table 1 below.

[0032] [Table 1]

[0033] As shown in Table 1, the second and third comparative examples and the embodiment all had smaller amounts of flex and torsion than the first comparative example, and both flexural rigidity and torsional rigidity were increased. However, the second comparative example had too little flex compared to the first comparative example. As a result, the flexural rigidity of the second comparative example was too high, resulting in a strong impact feeling when hitting the ball and making it unpractical.

[0034] The third comparative example had a smaller amount of flex than the first comparative example, but a larger amount of flex than the second comparative example, allowing for a moderate increase in flex rigidity. Therefore, the third comparative example was able to increase the initial velocity of the ball at impact, exhibiting good repulsion performance and reducing the impact feeling at impact. However, the third comparative example had a slight change in the amount of torsion compared to the first comparative example, and was unable to sufficiently increase torsional rigidity. Therefore, the third comparative example experienced wobble on the hitting surface, making it impossible to improve control performance compared to the first comparative example.

[0035] The embodiment had the same amount of flex as the third comparative example, and the flex rigidity was appropriately increased, allowing for good ball-hitting performance and a reduced sense of impact when hitting the ball. Furthermore, the embodiment was able to reduce the amount of torsion compared to the first and third comparative examples, and torsional rigidity was sufficiently increased. As a result, the embodiment was able to prevent the ball-hitting surface from wobbling when hitting the ball, allowing for good controllability. Therefore, the embodiment was able to simultaneously improve both ball-hitting controllability and ball-hitting performance while reducing the sense of impact when hitting the ball.

[0036] Furthermore, a fluid analysis was performed on the shafts of the embodiment and the second comparative example. In this fluid analysis, the drag values ​​were analyzed when wind was blown from the front for one second under the same conditions on each of the shafts of the embodiment and the second comparative example. The results are shown in Figure 5. Figure 5 is a graph showing the results of the fluid analysis of the embodiment and the second comparative example.

[0037] In the graph of Figure 5, if the average value of the drag force of the second comparative example is set to 100, the average value (relative value) of the drag force of the embodiment is 94. Therefore, the second comparative example has a shaft with a substantially rectangular cross-sectional shape, while the embodiment with a substantially octagonal cross-sectional shape was able to reduce air resistance by approximately 6%. As a result, the embodiment can improve swingability and swing speed more than the second comparative example.

[0038] In the above embodiment, the upper end of the depressed portion 30 is formed above the vertical center position C of the shaft body 20, so that the formation range of the depressed portion 30 can be secured so as to maintain an appropriate level of bending rigidity. Moreover, the formation position and range of the non-depressed portion 31 in the vertical direction can be set so as to exhibit good torsional rigidity. Therefore, it is possible to exhibit both good ball control performance and good ball repulsion performance.

[0039] Furthermore, the width of the left and right recessed portions 30 gradually decreases upward, and the non-recessed portions 31 extend in an X-shape, which also contributes to the excellent bending rigidity and torsional rigidity.

[0040] The present invention is not limited to the above-described embodiment, and various modifications can be made to the embodiment. In the above-described embodiment, the size, shape, direction, etc. shown in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate without departing from the scope of the object of the present invention.

[0041] For example, the shapes and positions of the recessed portion 30 and the non-recessed portion 31 can be modified in various ways as long as the non-recessed portion 31 is formed in the area sandwiched at least between the upper end of the recessed portion 30 and the lower end of the throat 21 and can perform the same function as in the above embodiment.

[0042] Furthermore, shaft 13 may not have a bifurcated throat 21, but may have a single shaft body 20 extending vertically whose upper end is connected to the lower end of frame 15. In such a configuration, non-depressed portion 31 is formed in at least the area sandwiched between the upper end of depressed portion 30 and the lower end of frame 15. With such a configuration, both control performance and repulsion performance can be exhibited well, and the feeling of impact can be reduced, as in the above embodiment. [Industrial Applicability]

[0043] The present invention is a racket that can exhibit both excellent controllability and repulsion performance, and has the effect of mitigating the feeling of impact. [Explanation of symbols]

[0044] 10: Racket 12: Grip 13: Shaft 15: Frame 20: Shaft body 21: Throat 30: Depression 31: Non-depressed area C: Vertical center position

Claims

1. A racket comprising a frame on which strings are stretched to form a hitting surface, and a shaft formed between the frame and a grip, The shaft includes a shaft body connected to an upper end of the grip; a recessed portion and a non-recessed portion formed on both sides of the shaft body in the thickness direction, the recess extends upward adjacent an upper end of the grip; The racket is characterized in that the non-depressed portion is formed at least in an area sandwiched between an upper end of the depression portion and a lower end of the frame.

2. The shaft further includes a throat that is connected to an upper end of the shaft body and that branches into two branches from the upper end toward the frame, 2. The racket according to claim 1, wherein the non-depressed portion is formed at least in an area sandwiched between an upper end of the depression and a lower end of the throat.

3. 3. The racket according to claim 1, wherein the upper end of the recessed portion is formed above the center position in the vertical direction of the shaft body.

4. 3. The racket according to claim 1, wherein the width of the recessed portion gradually decreases toward the top.

5. 3. The racket according to claim 1, wherein the non-depressed portion is formed to extend in an X-shape when viewed in the thickness direction of the shaft body.

6. 3. The racket according to claim 1, wherein the non-depressed portion has a cross section perpendicular to the up-down direction that is substantially octagonal.

Images