JPH0530782Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a tennis racket with improved stability of the ball hitting surface (face surface). [Prior Art] Conventional tennis rackets are generally known to consist of an annular frame forming a face, a shaft formed integrally with the frame, and a grip portion formed at the lower end of the shaft. It is being As shown in FIG. 8, the thickness of the tennis racket in the direction perpendicular to the face surface is usually such that the grip part 31a is larger than the other parts, and the frame 1a and shaft 3a have approximately the same thickness (for example, around 20 mm). has been done. In the above-mentioned tennis racket, it is necessary to improve the stability of the face so that the face does not shake due to the impact when the ball is hit, and for this reason, it is necessary to increase the surface rigidity and moment of inertia of the face. It is being done. Conventionally, the frame 1a has been made of a material with a relatively high elastic modulus, such as carbon fiber-reinforced plastic, in order to increase the surface rigidity, or a separate member has been formed as a weight inside the frame 1a on both sides of the center of the face surface to increase the moment of inertia. It is also being installed. Furthermore, in order to improve the ball-hitting performance of the face surface, as shown in FIG. 9, the thickness of the frame 1b and shaft 3b in the direction perpendicular to the face surface is made larger than that of the grip portion 31b, thereby increasing the rigidity of the entire tennis racket. Tennis racquets with increased height are also known (e.g. United State
(See Patent No. 4, 664, 380). [Problem to be solved by the invention] In the conventional tennis racket mentioned above, if a separate member is attached to the inside of both sides of the center of the frame, the air resistance at the time of hitting the ball increases, and the stiffness of the separate member increases. There is a problem in that the curvature of the ball when hit is slightly different from the gut that is spread over other parts without a separate member, so that the feeling of hitting the ball differs depending on where the ball hits. In addition, in conventional tennis rackets that have increased overall rigidity of the frame and shaft, the rigidity in the ball hitting direction is set to be relatively large from the grip to the tip of the frame. The ball bends less when hit, making it difficult to apply spin to the ball when serving, for example. Furthermore, since the overall weight is relatively large, it becomes difficult to swing the tennis racket. This invention was made to solve such conventional problems, and the purpose is to provide a tennis racket that can improve the stability of the face and does not impair the ease of swinging. It is said that [Means for Solving the Problems] In order to achieve the above object, the tennis racket of this invention has an annular frame forming a ball-hitting surface, and the thickness of the frame in the direction perpendicular to the ball-hitting surface is equal to The frame width is the largest at the center both sides of the surface where the frame width is the largest, and becomes smaller as it goes toward the tip and grip side, and the center width of the ball hitting surface is the largest. The thickness of the frame in the direction parallel to the ball-hitting surface at the portion where the frame width dimension is maximum is greater than the thickness of the frame tip. [Function] According to the above configuration, the thickness in the direction perpendicular to the ball hitting surface at both the left and right end portions, which are the center sides of the frame and where the frame width dimension is maximum, is greater than the other portions of the frame. Since the thickness in the direction parallel to the ball hitting surface at both ends is also larger than the thickness at the tip of the frame, the moment of inertia around the vertical axis passing through the grip and the tip of the face surface can be made larger than that of a conventional tennis racket with the same thickness. It is also possible to increase the bending rigidity of the frame in the ball hitting direction, thereby improving the surface stability of the face surface. [Example] In FIG. 2, the face F is constituted by a gut 2 stretched around a substantially circular ring formed by the frame 1 and the yoke part 10, and the frame 1, the yoke part 10, and the end part grip part 3
The shaft 3 on which the shaft 1 is formed is integrally formed of a material such as fiber-reinforced plastic. As shown in FIG. 1, the frame 1 has different thicknesses in the direction perpendicular to the face surface F when viewed from the side. Sa and proximal end 1
The thickness is larger than the thickness c of No. 3. The thickness a of the tip 11 is set to be equal to the thickness d of the upper grip end 311 of the shaft 3, and the thickness b of the center side portions 12 is set to be equal to the thickness d of the grip upper end 311 of the shaft 3. The cross-sectional shape of the frame 1 is configured to gradually decrease from the central side portions 12 through the base end portion 13 to the grip upper end portion 311. The thickness b of the center side portions 12 is set to be approximately 1.3 to 1.8 times the thickness a of the tip portion 11 (for example, around 20 mm). If it exceeds 1.8 times, the weight will increase, and the face surface F will become heavy, resulting in poor balance and difficulty in swinging when hitting the ball. Further, the frame 1 is formed so that the cross section in the direction perpendicular to the face plane F has a flat shape with both ends pointed, as shown in FIGS. 3 to 5.
This reduces air resistance when hitting the ball. In the figure, reference numeral 14 indicates a groove for protecting the gut, and the groove 14 has the gut 2 penetrated through the grommet.
is located. In the tennis racket having the above structure, the thickness b of the left and right sides 12 of the center of the face is formed in a cross section larger than the thicknesses a and c of the other frame parts, so that the grip and the tip of the face are connected. The moment of inertia around the vertical axis (see Figure 2) X increases. When the value of this moment of inertia increases, it becomes difficult for the face surface to rotate around the above-mentioned vertical axis X, that is, it becomes difficult for the face surface F to shake. Therefore, even if the ball hits a position slightly shifted from the center of the face surface F in the left-right direction, the face surface F hardly moves, and the directional stability of the ball is improved. As a result, the width of the so-called sweet spot in the left-right direction can be increased. In this embodiment, the above moment of inertia is calculated from frame 1.
This is further increased by thickening not only the thickness b of the central side portions 12 in the direction perpendicular to the face surface F, but also the thickness on the face surface F side within a range that does not impede performance. In addition, since the thickness of the frame and shaft in the direction perpendicular to the face surface is set larger than that of conventional tennis rackets, the bending rigidity in the direction of ball hitting and the rigidity against torsion around the vertical axis of the tennis racket are increased by the thickness. It gets bigger accordingly. Not only that, but since the frame is thickest at its center, the surface rigidity of the face can be further increased. Furthermore, since the thickness of the shaft in the direction perpendicular to the face surface is smaller than that of the frame, it does not impair the generation of the subtle flex necessary to, for example, impart spin to the ball. Further, since the tip of the frame is set to have a smaller cross section than the other parts, the tip of the tennis racket will not become heavy and lose the balance of the tennis racket. In this way, the moment of inertia and surface rigidity of the face surface can be increased compared to conventional tennis rackets, which improves the stability of hitting the ball, and also prevents the tennis racket from impairing the ease of swinging. There isn't. In the above embodiment, the thickness in the direction perpendicular to the face surface is not limited to the case where the maximum thickness is at both sides of the center of the frame and forms the apex as shown in FIG. It may be formed as follows. Further, in the embodiment described above, a continuous taper is formed from the central side portions 12 of the frame 1 to the upper end 311 of the grip portion of the shaft 3, but the present invention is not limited to this. Alternatively, the taper may be formed so that the entire shaft portion has the same thickness. [Comparative Test Example] The tennis racket of the above example shown in FIG.
Surface stiffness and moment of inertia were measured using the conventional tennis racket shown in FIG. 8 and the conventional tennis racket shown in FIG. 9. These results are shown in Table 1. Regarding surface rigidity, deflection and torsion were measured. The deflection is measured by fixing the grip part 31 from above and below, as shown in FIG.
A load of 5 kg was applied to No. 1, and the amount of deflection at this loading point was measured. In addition, torsion measurement is performed by fixing the periphery of the grip 31 as shown in FIG.
A load of 4 kg was applied in opposite directions to each side of the center of the tennis racket, and the amount of twist around the vertical axis X of the tennis racket was measured. Regarding the moment of inertia, as shown in Figure 10, the tennis racket is suspended via a piano wire so that the vertical axis X is in the vertical direction, and the period T when it is rotated around the vertical axis is calculated as follows: = CT ² / The moment of inertia was calculated by 4π ² . Here C
is the torsion constant of the piano wire, and is determined in advance by testing with a wire whose moment of inertia is known. According to the test results shown in Table 1, the moment of inertia of the tennis racket of this invention is larger than either of the two conventional tennis rackets, and the amount of deflection and twisting are smaller. Furthermore, when we actually hit balls using the three types of tennis rackets shown in Table 1, we found that with the tennis racket of this invention it was easy to control the direction of the ball, while with the conventional tennis racket, although the control was fair, it was relatively It was heavy and difficult to swing, making it difficult to spin. Also, conventional tennis rackets are difficult to control.

【table】

[Effect of idea]

According to the tennis racket of this invention, the thickness in the direction perpendicular to the ball hitting surface at both the left and right end portions, which are the center sides of the frame and where the frame width dimension is maximum, is greater than the other portions of the frame. Since the thickness of this part in the direction parallel to the ball-hitting surface is also larger than the thickness of the frame tip, the moment of inertia around the vertical axis passing through the grip and the tip of the face surface can be made larger than that of a conventional tennis racket with the same thickness. In addition, the bending rigidity of the frame in the direction of ball hitting can be increased, thereby improving the surface stability of the face surface. Moreover, since it does not impair the weight balance or the flexibility of the shaft, there is no risk of impairing the ease of swinging.

[Brief explanation of the drawing]

Figure 1 is a side view showing an embodiment of this invention, Figure 2 is a side view showing an embodiment of this invention.
The figure is a front view of the tennis racket shown in Fig. 1, Fig. 3 is an explanatory cross-sectional view taken along the - line in Fig. 2, Fig. 4 is an explanatory cross-sectional view taken along the - line in Fig. 2, and Fig. 5 is an explanatory cross-sectional view taken along the - line in Fig. 2. 6 is an explanatory diagram of the method for measuring the amount of deflection, FIG. 7 is an explanatory diagram of the method for measuring the amount of twist, FIG. 8 is a side view of a conventional tennis racket, and FIG. 9 is a side view of another conventional tennis racket. , FIG. 10 is an explanatory diagram of the method for measuring the moment of inertia. 1... Frame, F... Face surface (ball hitting surface),
11...Tip part, 12...Central both sides, 13...
Proximal end.

Claims (1)

[Claims for Utility Model Registration] 1. In a tennis racket having an annular frame forming a ball-hitting surface, the thickness of the frame in the direction perpendicular to the ball-hitting surface is at both sides of the center of the ball-hitting surface, and the frame width dimension is the maximum. It is largest at the part where the frame width is the largest, and becomes smaller as it goes toward the tip side and the grip side. A tennis racket characterized in that the thickness of the frame in a direction parallel to the ball-hitting surface is greater than the thickness of the tip of the frame. 2 The thickness in the direction perpendicular to the ball hitting surface on both sides of the center of the ball hitting surface of the frame is 1.3 to 1.8 of the thickness of the tip.
2. The tennis racket according to claim 1, wherein the tennis racket is set in a double range.