JP2753484B2 - Tennis racket frame - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tennis racket frame having an outer shell layer made of at least a non-woody material such as metal or fiber-reinforced plastic. [Related Art] Recently, tennis racket frames using a metal material such as steel or an aluminum alloy, or a high-strength, high-modulus long-fiber reinforced plastic material such as glass fiber or carbon fiber are increasing. The overall weight of such a tennis racket was about 365 g when the gut was stretched, and the inertia moment around the grip was about 450 g · cm · sec in most cases.
In recent years, the weight has been reduced, and when the gut is stretched, there are cases where the weight is 300 g or less and the inertia moment is 350 g · cm · sec ² or less. However, no change in hoop rigidity (rigidity in the direction toward the center of the wheel) was observed even when the weight was reduced. [Problems to be Solved] The repulsion performance of the tennis racket was largely affected by the moment of inertia around the grip of the racket and the hoop rigidity of the face portion. There has been a problem of a decrease in repulsion performance. SUMMARY OF THE INVENTION It is an object of the present invention to provide a tennis racket frame that can improve the rebound performance while reducing the weight, and that can meet the required characteristics relating to the weight of the player. Means for Solving the Problems To achieve the above object, the present invention relates to a tennis racket frame having a hollow outer shell layer made of metal or fiber-reinforced plastic. When the axis passing through the center of gravity and orthogonal to the face is defined as the x-axis, and the axis passing through the center of gravity and orthogonal to the x-axis is defined as the y-axis, at least the cross section 2 of the frame defining the face
The ratio Ix / Iy of the next moments Ix and Iy is set to 0.25 to 0.35, and a weight adding member is mounted on the outer peripheral surface of the top of the frame. [Operation] By reducing Ix / Iy, the hoop rigidity decreases in proportion to Ix / Iy at the same bending rigidity, and the rebound performance is improved. Further, by attaching the weight adding member to the outer peripheral surface of the frame top, the moment of inertia can be added to a maximum with a minimum weight, and the rebound performance is further improved. Embodiments Preferred embodiments of the present invention will be described below with reference to the drawings. 1 and 2, the frame 1 has an outer shell layer 10 made of fiber reinforced plastic, and a gut 3 is stretched in an area defining the face surface 2 of the frame 1. The frame 1 may be formed of metal. The hollow interior of the outer shell layer 10 may be filled with a lightweight foam material such as polyurethane foam, or may remain as a hollow portion. A grommet (gut protection material) (not shown) is mounted in the recess 11 of the outer shell layer 10, and the gut 3 is inserted through the grommet. The location of the recess 11 forms the outer peripheral surface of the frame 1. An axis passing through the center of gravity O of the cross section of the outer shell layer 10 of the frame 1 and orthogonal to the face surface 2 is defined as an x-axis.
When the axis perpendicular to the axis is the y-axis, at least the second moments of area Ix and Iy of the frame 1 that define the face surface 2
Is set to 0.25 to 0.35. More preferably, it is set to 0.25 to 0.32. A weight addition member 4 is mounted on the outer peripheral surface of the top of the frame 1. The weight of the weight adding member 4 is preferably about 2 to 5% of the total weight of the racket in which no gut is stretched. For example, when the racket weighs 330 g or less, preferably 280 to 320 g in a state where no gut is stretched, the weight adding member 4 preferably has a weight of about 6 to 16 g. As shown in FIGS. 3 to 5, the weight adding member 4 is a band-shaped member, and has a hole 4A for inserting a grommet (not shown) in the center thereof. The line indicated by TL in FIG. 3 is located at the top center of the racket. Two specific embodiments of the present invention (products 1 and 2 of the present invention shown in FIGS. 7 and 8) and a conventional racket equipped with a weight-adding member 4 similar to that of the present invention 3 The repulsion rate of each of the three comparative products 1 to 3 was tested. FIG. 7 (Example 1) and FIG. 8 show specific examples for realizing a second moment of area ratio of 0.25 to 0.35 as such examples 1 and 2 of the present invention.
A cross-sectional shape and dimensions of a frame made of fiber reinforced plastic as shown in FIG.
The frames of the comparative products 1 to 3 have cross-sectional shapes as shown in FIGS. 9 to 11, and are each made of fiber reinforced plastic. As can be seen from these figures, the dimensions of the cross-sectional shapes of the actual product and the comparative product are different, so
Are different. In this experiment, as shown in FIG.
The grip hand (the initial velocity V ₁ of the Rakento this time is zero), bumping ball launch from machine racket was determined speed ratio of the racquet and ball (rebound rate). Figure 6 in v ₁ is the incident velocity of the ball was about 28 m / sec. The v ₂ is a reflection speed of the ball. Also, V ₂
Is the speed after the racket hits the ball, the repulsion is calculated by the following equation. Incidentally, V ₂ is the speed at which racquet is moved rearwardly by the impact of the ball after the ball impact. When the experiment was performed in this manner, the results shown in the following table were obtained. The racket weight in this table is the weight when no gut is stretched. As is evident from the experimental results, the products of the present invention 1 and 2 were compared with the comparative product 1 in rebound rate.
~ 3 won. [Effect] As described above, according to the present invention, the axis passing through the center of gravity of the cross section of the outer shell layer of the frame and orthogonal to the face surface is represented by x.
When the y-axis is the axis passing through the center of gravity and orthogonal to the x-axis, at least the ratio Ix / Iy of the second moment of area Ix to Iy of the frame defining the face is set to 0.25 to 0.35, The weight addition member is mounted on the top outer peripheral surface of, so that the hoop stiffness is Ix / Iy at the same bending stiffness by reducing the ratio of the second moment of area Ix / Iy.
And the repulsion performance was improved. In addition, since the weight adding member is mounted on the outer peripheral surface of the top of the frame, the moment of inertia can be maximized with a minimum weight, and the rebound performance is further improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a preferred embodiment of the present invention, FIG. 2 is a sectional view of an outer shell layer, FIG. 3 is a sectional view taken along the line IV-IV, FIG. 5 is a sectional view taken along the line VV in FIG. 3, FIG. 6 is an explanatory view for experimenting the repulsion rate, FIG. 7 and FIG. 9 to 11 are sectional views showing comparative products 1 to 3, respectively. 1 ... frame, 2 ... face surface, 4 ... weight adding member, 10 ... outer shell layer of frame.

Claims (1)

(57) [Claims] In a tennis racket frame having a hollow outer shell layer made of metal or fiber-reinforced plastic, an axis passing through the center of gravity of the cross section of the outer shell layer of the frame and orthogonal to the face surface is set as an x-axis, and similarly, an x-axis is passed through the center of gravity. The ratio Ix / Iy of the second moment of area Ix to Iy of the frame defining at least the face surface when the axis perpendicular to the axis is the y-axis is 0.25.
A racket frame with a weight setting of 0.35 and a weight-adding member attached to the outer periphery of the top of the frame.