Soft tennis racket frame

Abstract

To improve a striking power while maintaining a centroid position.SOLUTION: A soft tennis racket frame (10) has: a total mass MA of 215 g or more and 265 g or less; a centroid position BP, as a distance between a lower end of a grip (13) and a centroid position of the whole racket frame, of 280 mm or more and 295 mm or less; a swing weight SW (kg cm2), as an inertia moment of the racket frame with a lower end side of the grip defined as a fulcrum, of 225 or less; and a ratio A1 of a performance swing weight PSW to a swing weight SW, of 1.12 or less, where the performance swing weight is an index value of a weight feeling during swing calculated by the following numerical expression 1. (numerical expression 1) PSW=C1*SW+C2*MA+C3*BP, where, in the numerical expression 1, 0.37≤C1≤0.48, 0.41≤C2≤0.52, 0≤C3≤0.11, and C1+C2+C3=1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a racket frame for soft tennis using a ball made of highly elastic rubber. [Background technology]

[0002] In soft tennis, a player swings a racket to hit a ball. The racket is equipped with 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] JP 2009-261914 A Summary of the Invention [Problem to be solved by the invention]

[0004] In soft tennis rackets, there is a demand for improving the power of shots in order to enhance the advantage of play. In order to improve power, it is considered to move the center of gravity toward the upper end of the racket, making it so-called top-heavy, so that the centrifugal force can be utilized to hit the ball strongly.

[0005] However, since a top-heavy racket reduces maneuverability and makes it difficult to control the ball, there is a conflicting demand to maintain the center of gravity position. Therefore, the inventor discovered that it is possible to improve the power of a hit by maintaining the center of gravity position and setting the index value of the weight feeling during a swing according to the mass change on the grip side within a predetermined range.

[0006] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a soft tennis racket frame that can improve the power of hitting the ball while maintaining the position of the center of gravity. [Means for solving the problem]

[0007] A soft tennis racket frame according to one embodiment of the present invention is a soft tennis racket frame including, in order from top to bottom, a frame body, a shaft, and a grip that extend in an annular shape, and wherein the soft tennis racket frame has an overall mass MA of 215 g or more and 265 g or less, a center of gravity position BP that is the distance between the lower end of the grip and the overall center of gravity position of the soft tennis racket frame is 280 mm or more and 295 mm or less, and a swing weight SW (kg cm ) that is the moment of inertia of the soft tennis racket frame with the lower end side of the grip as a fulcrum. 2 ) is 225 or less, and the ratio A1 of the performance swing weight PSW, which is an index value of the weight feeling during a swing calculated by the following formula 1, to the swing weight SW is 1.12 or less.

[0008] A soft tennis racket frame according to another embodiment of the present invention is a soft tennis racket frame including, in order from top to bottom, a frame body, a shaft, and a grip that extend in an annular shape, and wherein the soft tennis racket frame has an overall mass MA of 215 g or more and 265 g or less, a center of gravity position BP that is the distance between the lower end of the grip and the overall center of gravity position of the soft tennis racket frame is 250 mm or more and 280 mm or less, and a swing weight SW (kg cm) that is the moment of inertia of the soft tennis racket frame with the lower end side of the grip as a fulcrum. 2 ) is 215 or less, and the ratio A1 of the performance swing weight PSW, which is an index value of the weight feeling during a swing calculated by the following formula 1 to the swing weight SW, is 1.17 or less.

[0009] A soft tennis racket frame according to still another embodiment of the present invention is a soft tennis racket frame including, in order from top to bottom, a frame body, a shaft, and a grip that extend in an annular shape, wherein the soft tennis racket frame has an overall mass MA of 200 g or more and 245 g or less, a center of gravity position BP that is the distance between the lower end of the grip and the overall center of gravity position of the soft tennis racket frame is 270 mm or more and 300 mm or less, and a swing weight SW (kg cm) that is the moment of inertia of the soft tennis racket frame with the lower end side of the grip as a fulcrum. 2 ) is 205 or less, and the ratio A1 of the performance swing weight PSW, which is an index value of the weight feeling during a swing calculated by the following formula 1, to the swing weight SW is 1.15 or less. (Formula 1) PSW = C1 SW + C2 MA + C3 BP However, in the above formula 1, 0.37≦C1≦0.48, 0.41≦C2≦0.52, 0≦C3≦0.11, and C1+C2+C3=1 Effect of the Invention

[0010] According to the present invention, while maintaining the same center of gravity as a conventional soft tennis racket, the sense of weight felt by the player during swing can be increased, thereby improving the power of hits. [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B are external views of a racket frame according to an embodiment, FIG. 1A being a front view of the racket frame, and FIG. 1B being a side view of the racket frame. [Diagram 2] 1B is a front view similar to FIG. 1A, showing one variation of the racket frame of FIG. 1. [Diagram 3] 1B is a front view similar to FIG. 1A, showing one variation of the racket frame of FIG. 1. [Figure 4] 1 is a diagram showing a racket frame according to an embodiment as viewed from above. [Diagram 5] FIG. 2 is a schematic exploded perspective view of a cap forming a grip. [Figure 6] FIG. 6A is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 6B is a cross-sectional view similar to FIG. 6A of a conventional racket frame. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiments, and can be appropriately modified within the scope of the present invention. For the sake of convenience, some components are omitted in the following drawings.

[0013] Fig. 1 is an external view of one aspect of a racket frame according to an embodiment, Fig. 1A is a front view of the racket frame, and Fig. 1B is a side view of the racket frame. As shown in Fig. 1, a soft tennis racket frame (hereinafter referred to as "racket frame") 10 includes a frame body 11, a shaft 12, and a grip 13, which extend in an annular shape in the longitudinal direction.

[0014] In this embodiment, the racket frame 10 may be referred to as a "racket" in some cases, and is configured with no strings (not shown) stretched inside the frame body 11. When strings are stretched in a lattice pattern inside the frame body 11, a hitting surface for striking a ball is formed by the strings.

[0015] In the claims and the description of this specification, unless otherwise specified, the longitudinal direction of the racket frame 10 is the up-down direction, the side where the frame body 11 is located is the upper side, and the side where the grip 13 is located is the lower side, as shown by the arrow in FIG. 1. Thus, the frame body 11, the shaft 12, and the grip 13 are provided in this order from top to bottom. In addition, the direction perpendicular to the hitting surface described above is the front-back direction, the front side of the paper in FIG. 1A (the left side of the paper in FIG. 1B) is the front side, and the opposite side is the back side. Furthermore, on the hitting surface (i.e., on a plane along the hitting surface), the direction perpendicular to the up-down direction is the left-right direction, and the left and right sides are based on the view when the front side of the racket frame 10 is viewed from the front side as shown in FIG. 1A.

[0016] The frame body 11 is formed in a loop shape similar to an ellipse long in the up-down direction when viewed from the front-back direction, and is sometimes referred to as a head. The outer peripheral surface 11a of the frame body 11 is provided with a groove portion 11b whose center in the front-back direction is recessed. The groove portion 11b is provided continuously along the circumferential direction of the frame body 11. The frame body 11 is provided with a plurality of holes (not shown) through which the string is inserted. The plurality of holes are formed penetrating from the bottom side of the groove portion 11b on the outer peripheral surface 11a of the frame body 11 to the inner peripheral surface 11c, and are provided side by side in the circumferential direction of the frame body 11.

[0017] A plurality of grommets 21 to 24 are attached to the frame body 11 from its outer periphery. For example, in this embodiment, four grommets are provided, an upper grommet 21, a left grommet 22, a right grommet 23, and a lower grommet 24. As for the attachment area, the upper grommet 21 is provided from a position in the 10 o'clock direction of the frame body 11 to a position in the 2 o'clock direction of the frame body 11 when viewed from the front and back direction. The left and right grommets 22 and 23 are provided from the vicinity of both the left and right ends of the upper grommet 21 to positions reaching the lowest holes formed on the left and right side surfaces of the frame body 11. The lower grommet 24 is provided on the yoke 16 described later. Note that the lengths of the grommets 21 to 23, except for the lower grommet 24, along the circumferential direction of the frame body 11 may be changed according to various conditions.

[0018] Each of the grommets 21-24 can be, for example, a molded body obtained by injection molding a thermoplastic resin. Each of the grommets 21-24 includes a plurality of tubular parts (not shown) that pass through holes formed in the frame body 11, and band-like parts 21a-24a that are connected to the base of each tubular part and extend in the circumferential direction of the frame body 11. A string is inserted into the inside of the tubular parts.

[0019] The band-shaped portions 21a-23a of the grommets 21-23, except for the lower grommet 24, are provided to fit into the groove portions 11b in the outer peripheral surface 11a of the frame body 11, and form an area along the outer peripheral surface 11a of the frame body 11. The width in the front-back direction of the band-shaped portions 21a-23a is set to be larger than or the same as the width in the front-back direction of the groove portion 11b, and smaller than the width in the front-back direction of the frame body 11. Note that the upper grommet 21 is configured to include a portion formed to increase the width in the front-back direction of the band-shaped portion 21a, and this configuration will be described later.

[0020] The shaft 12 has a throat 15 that branches into two branches from the grip 13 toward the frame body 11 when viewed from the front-rear direction, and a yoke 16 that forms part of the frame body 11 is formed between the left and right throats 15. The throat 15 is formed in a shape that curves in an arc between the grip 13 and the frame body 11. An opening that opens in the front-rear direction is formed between the yoke 16 of the frame body 11 and the left and right throats 15 of the shaft 12.

[0021] Here, joints 17 that join the upper end of throat 15 to both the left and right sides below frame main body 11 (both the left and right sides of yoke 16) are integrally formed between them. Joints 17 are formed so as to overlap with the formation position of frame main body 11 in the up-down direction, and are formed so as to bulge the lower part of frame main body 11 outward. Also, joints 17 are provided on both ends of yoke 16 in the extension direction.

[0022] The frame body 11, shaft 12 and joint 17 may be formed into a hollow cylindrical body made of, for example, fiber-reinforced resin or metal, or may be made into a solid structure by filling the inside of the hollow body with foam or making it out of wood.

[0023] The grip 13 is the part where the player holds the racket frame 10. The cross section of the grip 13 perpendicular to the up-down direction is formed into an octagonal shape. The grip 13 includes a core 13a having a cross section corresponding to the octagonal shape, and leather 13b made of synthetic leather or natural leather wrapped around the outer periphery of the core 13a. The lower end side of the grip 13 is formed by a cap 19. The configuration around the cap 19 will be described later.

[0024] 2 and 3 are front views similar to FIG. 1A, showing one variation of the racket frame of FIG. 1. The racket frame 10 of FIG. 2 has a different shape of the shaft 12 when viewed from the front and back directions compared to the racket frame 10 of FIG. 1. More specifically, the length of the throat 15 of the shaft 12 of the racket frame 10 of FIG. 1 is shorter than that of the racket frame 10 of FIG. 2, and the center of gravity of the entire racket frame 10 is shifted upward (toward the upper end of the frame body 11). As a result, the racket frame 10 of FIG. 1 is a variation that emphasizes strokes that can make the upper part feel heavier in soft tennis play, and is a variation suitable for rear court players. Hereinafter, the racket frame 10 of FIG. 1 may be referred to as a "stroke-emphasizing racket frame."

[0025] The racket frames 10 in FIG. 1 and FIG. 2 are formed to have substantially the same shape except for the shaft 12.

[0026] Comparing the racket frame 10 in Fig. 1 and Fig. 2, the racket frame 10 in Fig. 2 has a longer throat 15 than the racket frame 10 in Fig. 1, and the center of gravity of the entire racket frame 10 is shifted downward (closer to the grip 13). As a result, the racket frame 10 in Fig. 2 is a variation that emphasizes volleys, which can reduce the sense of weight in the upper part when playing soft tennis, and is suitable for forward players. Hereinafter, the racket frame 10 in Fig. 2 may be referred to as a "volley-oriented racket frame."

[0027] Also, the racket frame 10 in FIG. 3 has a different shape of the frame body 11 when viewed from the front and back directions from the racket frame 10 in FIG. 1. More specifically, the racket frame 10 in FIG. 3 has a maximum width position at the bottom, and the center of gravity of the entire racket frame 10 is slightly lower (closer to the grip 13) than the racket frame 10 in FIG. 1. On the other hand, the racket frame 10 in FIG. 3 has a center of gravity of the entire racket frame 10 slightly higher (closer to the upper end of the frame body 11) than the racket frame 10 in FIG. 2. Therefore, the racket frame 10 in FIG. 3 has a center of gravity located midway between the centers of gravity of the racket frames 10 in FIG. 1 and FIG. 2, and is a variation that can respond well to both strokes and volleys on average in soft tennis play. Hereinafter, the racket frame 10 in FIG. 3 may be referred to as an "average-oriented racket frame."

[0028] 1 to 3, the total mass MA, the center of gravity BP, the swing weight SW, and the ratio A1 (PSW / SW) of the performance swing weight PSW to the swing weight SW are set within the ranges described below. Note that each value is a measured value or a calculated value when no strings are strung on the racket frame 10.

[0029] [Stroke-oriented racket frame (see Figure 1)] Mass MA: 215g or more and 265g or less Center of gravity position BP: 280mm or more and 295mm or less Swing weight SW: 225 or less Ratio A1:1.12 or less [Volley-focused racket frame (see Figure 2)] Mass MA: 215g or more and 265g or less Center of gravity position BP: 250mm or more and 280mm or less Swing weight SW: 215 or less Ratio A1:1.17 or less [Racket frame for average players (see Figure 3)] Mass MA: 200g or more and 245g or less Center of gravity position BP: 270mm or more and 300mm or less Swing weight SW: 205 or less Ratio A1:1.15 or less

[0030] Mass MA is the mass of the entire racket frame 10.

[0031] The center of gravity position BP is the distance between the lower end of the grip 13 and the overall center of gravity position (center of gravity point) of the racket frame 10 in the up-down direction.

[0032] The swing weight SW is the moment of inertia of the racket frame 10 with the lower end of the grip 13 as the fulcrum. The unit of the swing weight SW is (kg cm 2 The swing weight SW is measured by holding the lower end of the grip 13 with a clamp equipped with a rotating shaft, rotating the grip by a predetermined angle against the force of an elastic body attached to the rotating shaft, and then swinging the racket frame 10 like a pendulum with the rotating shaft as the fulcrum due to the force of the elastic body. The value of the oscillation period during this oscillation is measured, and the swing weight SW is calculated from the oscillation period.

[0033] The performance swing weight PSW is an index value of the weight felt during a swing, and is a value calculated using the above-mentioned swing weight SW, mass MA, and center of gravity position BP of the racket frame 10 and the following formula 1. PSW = C1 SW + C2 MA + C3 BP (Formula 1) C1: First contribution rate C2: Second contribution rate C3: Third contribution rate However, C1+C2+C3=1

[0034] Here, the first to third contribution rates C1 to C3 are set in the following ranges so that the performance swing weight PSW corresponds more accurately to the sense of weight during a swing than the swing weight SW. 0.37≦C1≦0.48 0.41≦C2≦0.52 0≦C3≦0.11 However, C1+C2+C3=1

[0035] When setting the first to third contribution rates C1 to C3 within the above ranges, the order of priority is the first contribution rate C1, the second contribution rate C2, and the third contribution rate C3.

[0036] In formula 1, the performance swing weight PSW is calculated by multiplying the mass MA, center of gravity position BP, and swing weight SW of the racket frame 10 by the first to third contribution rates C1 to C3. Therefore, in formula 1, the calculation result of the performance swing weight PSW increases or decreases according to the change in the center of gravity position BP when the mass on the grip 13 side changes. As a result, the performance swing weight PSW is a value that accurately corresponds to the sense of weight felt by the player during the swing.

[0037] In the racket frame 10 of this embodiment, in any of the stroke-oriented, volley-oriented, and average-oriented variations, the mass MA and center of gravity BP are the same or similar to those of the conventional racket frame 10 of the corresponding variation. On the other hand, the swing weight SW and the performance swing weight PSW, which indicates the sense of weight during swing, are larger than those of the conventional racket frame 10 in any of the variations. In addition, in the racket frame 10 of this embodiment, the ratio A1 obtained by dividing the swing weight SW by the performance swing weight PSW is smaller than that of the conventional racket frame 10 in any of the variations.

[0038] As a result, the racket frame 10 of each variation of this embodiment increases the sense of weight felt by the player during swing, allowing the player to hit the ball harder by utilizing centrifugal force, improving the power (force) of the hit. Moreover, since the mass MA and center of gravity position BP can be maintained at values ​​close to those of the conventional racket frame 10, a decrease in operability can be suppressed and good control performance of the hit can be maintained. In this way, this embodiment can simultaneously maintain control performance and improve the power of the hit.

[0039] In this embodiment, when the mass MA, center of gravity position BP, swing weight SW, performance swing weight PSW, and ratio A1 are set within the above-mentioned ranges, the weights of the upper grommet 21 and grip 13 are increased compared to the conventional case. Furthermore, in addition to this increase in weight, the increased weight is made up for by reducing the weight of the components other than the upper grommet 21 and grip 13, and the strength of the frame body 11 is improved along with this weight reduction. Below, a structure for increasing the weight of the upper grommet 21, a structure for increasing the weight of the grip 13, and a structure for improving the strength of the frame body 11 will be described.

[0040] 1A and 4, the upper grommet 21 provided in the upper half of the frame body 11 has bumper portions 21b formed on both the left and right sides.

[0041] Bumper portions 21b are formed on both sides of band-shaped portion 21a in the front-rear direction, and are formed to have a width equal to or slightly larger or smaller than the overall width of frame body 11 in the front-rear direction, and have a width corresponding to the overall width of frame body 11. In a conventional soft tennis racket frame, the area of ​​upper grommet 21 that runs along outer peripheral surface 11a of frame body 11 is formed only by band-shaped portion 21a. Therefore, by forming bumper portion 21b on upper grommet 21 as in this embodiment, the weight can be increased by the amount of bumper portion 21b, and bumper portion 21b constitutes an upper weight-increasing portion.

[0042] In this embodiment, bumper portion 21b is formed in a range between approximately 10 o'clock and approximately 11 o'clock on frame body 11 and a range between approximately 1 o'clock and approximately 2 o'clock on racket frame 10 when viewed from the front and back. This makes it possible to effectively protect the parts of racket frame 10 that are particularly likely to come into contact with the surface of a tennis court. In addition, a plurality of dimples are formed on the outer peripheral surface of upper grommet 21 to reduce air resistance and, in turn, to improve the ease of swinging.

[0043] Returning to Fig. 1, the cap 19 forming the lower end side of the grip 13 is attached so as to cover the lower end side of the core 13a of the grip 13, and the leather 13b is wound around the outer peripheral surface. Fig. 5 is a schematic exploded perspective view of the cap forming the grip. As shown in Fig. 5, the cap 19 has a recessed portion 19a formed by depressing the lower end surface, and a plate-shaped member B is attached to the inside (bottom) of the recessed portion 19a. Although not shown, a logo mark or the like is displayed on the plate-shaped member B.

[0044] Here, even in a conventional soft tennis racket frame, a plate-like member is attached to the cap 19. The plate-like member B of this embodiment can be made thicker or have a larger specific gravity than a conventional plate-like member, or can be formed by stacking two plates to increase its weight, and the lower weight-increasing portion is constituted by the plate-like member B.

[0045] Fig. 6A is a cross-sectional view taken along line AA in Fig. 1A. Fig. 6A is a cross-sectional view of the frame body 11 taken along a plane perpendicular to the extending direction of the frame body 11. As shown in Fig. 6A, the inner peripheral surface 11c of the frame body 11 is formed by a bulging surface portion 31. The outer peripheral surface 11a of the frame body 11 is formed by a pair of inclined surface portions 32, and the groove portion 11b of the frame body 11 is formed by a groove forming surface 33. Thus, the frame body 11 has a pointed shape in which the width of the frame body 11 in the inner and outer directions gradually narrows toward both the front side and the back side.

[0046] 6A, the bulging surface portion 31 has a front end (one end in the front-back direction) located closest to the front of the frame main body 11, and a rear end (the other end in the front-back direction) located closest to the rear of the frame main body 11. The bulging surface portion 31 is formed in an arc shape with a middle portion in the front-back direction bulging most inward. The pair of inclined surface portions 32 are formed so as to approach the groove forming surface 33 from both sides in the front-back direction.

[0047] The bulging surface portion 31 is formed continuously in the circumferential direction of the loop-shaped frame main body 11. For example, the bulging surface portion 31 can be formed around the entire circumference of the frame main body 11, or can be formed in a region extending from one of the joints 17 on both the left and right sides through the upper part of the frame main body 11 to the other of the joints 17 on both the left and right sides.

[0048] In the cross-sectional view of Fig. 6A, the width Wb of the bulging surface portion 31 in the inside-outside direction of the frame main body 11 is formed to be 1 / 3 or less of the overall width Wa of the frame main body 11. Here, Fig. 6B shows a cross-sectional view of a frame main body 111 of a comparative structure. In the comparative structure of Fig. 6B, the bulging surface portion 131 forming the inner peripheral surface of the frame main body 111 is formed to have a width Wd of the bulging surface portion 131 in the inside-outside direction of the frame main body 111, which is 1 / 2 of the overall width Wc of the frame main body 111.

[0049] A simulation was performed in which a load was applied from both the left and right sides toward the center (deflection direction) to the entire frame body 111, 11 of the comparative structure in Fig. 6B and the above embodiment. It was confirmed that the rigidity in the deflection direction was 19% higher in the above embodiment than in the comparative structure in Fig. 6B. This makes it possible to improve the strength of the frame body 11, and to maintain its strength even when the frame body 11 is made lighter.

[0050] The present invention is not limited to the above-described embodiment, and can be modified in various ways. In the above-described embodiment, the size, shape, direction, and the like shown in the attached 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 purpose of the present invention.

[0051] For example, the shaft 12 is not limited to the configuration in the above embodiment, and may not be bifurcated.

[0052] Furthermore, the shape of bumper portion 21b of upper grommet 21 is not limited to that in the above embodiment, and the position at which it is formed may be changed as appropriate in the circumferential direction or the front and back directions of frame main body 11. [Industrial Applicability]

[0053] The present invention relates to a soft tennis racket frame that can increase the index value of the weight feeling during a swing and thereby improve the power of the ball hit. [Explanation of symbols]

[0054] 10: Racket frame (soft tennis racket frame) 11: Frame body 11a: Outer surface 11c: Inner surface 12: Shaft 13: Grip 17:Joint part 19: Cap 21: Upper grommet (grommet) 21b: Bumper section (upper weight increase section) 31:Bulging surface part B: Plate-shaped member (lower weight increase part)

Claims

1. A soft tennis racket frame including a frame body, a shaft, and a grip extending in an annular shape from top to bottom in this order, The overall mass MA of the soft tennis racket frame is 215 g or more and 265 g or less, a center of gravity BP, which is the distance between the lower end of the grip and the overall center of gravity of the soft tennis racket frame, is 280 mm or more and 295 mm or less; The swing weight SW (kg cm) which is the moment of inertia of the soft tennis racket frame with the lower end side of the grip as a fulcrum ２ ) is 225 or less; A soft tennis racket frame, characterized in that a ratio A1 of a performance swing weight PSW, which is an index value of a weight feeling during a swing calculated by the following formula 1, to the swing weight SW is 1.12 or less. (Formula 1) PSW=C1.SW+C2.MA+C3.BP However, in the above formula 1, 0.37≦C1≦0.48, 0.41≦C2≦0.52, 0≦C3≦0.11, and C1+C2+C3=1.

2. A soft tennis racket frame including a frame body, a shaft, and a grip extending in an annular shape from top to bottom in this order, The overall mass MA of the soft tennis racket frame is 215 g or more and 265 g or less, a center of gravity BP, which is the distance between the lower end of the grip and the overall center of gravity of the soft tennis racket frame, is 250 mm or more and 280 mm or less; The swing weight SW (kg cm) which is the moment of inertia of the soft tennis racket frame with the lower end side of the grip as a fulcrum ２ ) is 215 or less; A soft tennis racket frame, characterized in that a ratio A1 of a performance swing weight PSW, which is an index value of a weight feeling during a swing calculated by the following formula 1, to the swing weight SW is 1.17 or less. (Formula 1) PSW=C1.SW+C2.MA+C3.BP However, in the above formula 1, 0.37≦C1≦0.48, 0.41≦C2≦0.52, 0≦C3≦0.11, and C1+C2+C3=1.

3. A soft tennis racket frame including a frame body, a shaft, and a grip extending in an annular shape from top to bottom in this order, The overall mass MA of the soft tennis racket frame is 200 g or more and 245 g or less, a center of gravity BP, which is the distance between the lower end of the grip and the overall center of gravity of the soft tennis racket frame, is 270 mm or more and 300 mm or less; The swing weight SW (kg cm) which is the moment of inertia of the soft tennis racket frame with the lower end side of the grip as a fulcrum ２ ) is 205 or less; A soft tennis racket frame, characterized in that a ratio A1 of a performance swing weight PSW, which is an index value of a weight feeling during a swing calculated by the following formula 1, to the swing weight SW is 1.15 or less. (Formula 1) PSW=C1.SW+C2.MA+C3.BP However, in the above formula 1, 0.37≦C1≦0.48, 0.41≦C2≦0.52, 0≦C3≦0.11, and C1+C2+C3=1.

4. the frame main body has a bulging surface portion, one end of which in a front-back direction is located closest to the front of the frame main body and the other end of which in a front-back direction is located closest to the rear of the frame main body when viewed in cross section on a plane perpendicular to the extending direction thereof, and which forms an inner peripheral surface of the frame main body; 4. A soft tennis racket frame as claimed in any one of claims 1 to 3, characterized in that the bulging surface portion is formed to have a width of 1 / 3 or less of the overall width of the frame body in the inward and outward direction of the frame body when viewed in cross section on a plane perpendicular to the extension direction of the frame body.

5. A joint portion for joining the frame body and the shaft is formed on both the left and right sides, 5. The soft tennis racket frame according to claim 4, characterized in that the bulging surface portion is formed in an area extending from one of the joints on both the left and right sides of the frame body through the upper part of the frame body to the other of the joints on both the left and right sides.

6. a grommet having an area along an outer peripheral surface of the frame body; A cap forming a lower end of the grip, The grommet is provided in an upper half of the frame body with an upper weight increase portion having a width corresponding to the overall width of the frame body in the front-back direction, 4. The soft tennis racket frame according to claim 1, wherein a plate-shaped lower weight increase portion is attached to a lower end surface of the cap.

Images