JP2519996Y2 - Racket frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a racket frame in which air resistance received by the frame when swinging the racket is reduced.

(Prior Art) A racket frame (hereinafter referred to as a frame) generally includes a hitting portion, a shaft portion, and a grip portion. Examples of molding materials include wood, metal, and fiber reinforced plastic.

The widths of these frames in the ball striking direction, that is, the side surface widths of the frames were substantially constant.

However, recently, in order to make the natural frequency of the frame closer to the frequency of the ball so that the vibration of the frame can be used to promote the acceleration of the ball when hitting the ball on the hitting surface, There is a racket called a thick racket in which the side width of the frame is partially or entirely wider than the conventional width.

These rackets are also called mid-size and large-size, and are larger than the area of a conventional ball striking surface by about 30 to 80%.

As described above, the sweet spot can be increased by making the area of the hitting surface wide, and the hitting becomes easier. In addition, by increasing the width of the side surface of the frame in whole or in part, the vibration frequency of the ball and the natural frequency of the frame are close to each other, and thereby the repulsion characteristic of the ball can be improved.

On the other hand, however, there has been a drawback that the air resistance is increased by widening the area of the ball striking face and widening the side width of the frame.

(Problems to be solved by the invention) The following are possible causes of air resistance generated when the racket is swung.

One is the trajectory during the swing. That is, when actually hitting the ball with the racket, the frame makes a rotational movement.

There are also problems such as the height of the net on the terrace court, the gravity applied to the ball, and the operation for imparting spin to the ball, and the trajectory of the frame has some angle with respect to the ground. Therefore, the air flow to the frame during swing is not always in the direction perpendicular to the ball striking face,
In other words, the air flow during the swing has some angle with respect to the center axis of the ball striking direction in the cross section of the frame cut perpendicularly to the ball striking surface. Especially in soft tennis, this is often the case.

The other is the width of the frame in the gut insertion direction, that is, the front width. That is, at the time of swing, a boundary layer having a lower flow velocity than the surroundings is generated near the surface of the frame due to the viscosity of air, the flow velocity in the boundary layer is gradually reduced, and the boundary layer is separated from the surface of the frame. At that time, vortices are generated in the rear side of the frame with respect to the ball striking direction to generate a region having a lower pressure than the front side of the frame, and the pressure difference between the front side and the rear side of the frame causes air resistance.

The causes of these air resistances are that the front width of the frame is large and the side width is large, and the air striking surface area is large. Therefore, the longer the frame length, the more the air resistance. Resistance increases.

(Means for Solving the Problem) Therefore, the present invention provides a frame at the time of hitting by making the cross-sectional shape of the frame and the angle formed by the central axis of the cross-section and the axis perpendicular to the hitting surface different from that of the conventional one. An object of the present invention is to provide a frame in which the air resistance is reduced, the swing speed of the racket is increased, swinging out is facilitated, and the movement of the racket with respect to the ball is accelerated.

A means for solving the above problems and achieving the object will be described with reference to an example in which a hitting portion which is a part of a frame is implemented.

The frame of the present invention shown in FIG. 1 comprises a ball striking portion 2, a shaft portion 3 and a grip portion 4.

Then, as shown in FIG. 2, in the cross section obtained by cutting the hitting portion in a direction perpendicular to the hitting surface, the maximum width T of the front surface width of the hitting portion which is the width in the gut insertion direction of the hitting portion.
Is set on one of the left and right cross sections Y1 and Y2 of the gut insertion hole 6, that is, on the Y1 side in this embodiment. And the radius of curvature R1 on the front side on the Y1 side is 1/2 to 1/5 of the maximum width T, the outer shape of Y2 is gradually narrowed from the portion of the maximum width T toward R2, and the gut net surface is the center. It has an asymmetric shape.

Further, the central axis line M in the longitudinal direction in the cross section is a vertical axis passing through the center of gravity with respect to the axis where the geometrical moment of inertia in the front width direction passing through the center of gravity of the cross section is minimum.
The axis is inclined by 5 to 45 degrees with respect to the axis Z perpendicular to the ball striking face 5.

The racket having such a structure is suitable for a case where the forehand has a large stroke or a case of soft tennis.

Although not shown in the drawings, the present invention can be applied to the shaft portion and the grip portion in addition to the hitting portion.

Further, the air resistance can be further reduced by roughening the surface of the frame.

(Operation) When the racket is swung, air resistance is large with respect to the front width and the side width of the frame. This air resistance is applied to the traveling direction when the portion having the maximum width T is swung, that is, to the Y1 side in this embodiment, and the shape of the rear side is gradually narrowed toward the rear, and the air resistance of the rear side of the frame is increased. The negative pressure region generated by the vortex can be reduced, and the air resistance can be reduced by reducing the pressure difference between the front and the rear of the frame.

By arranging the central axis M in the range of 5 degrees to 45 degrees with respect to the axis Z perpendicular to the ball striking surface, the central axis M during swing becomes substantially parallel to the air flow, and the side surface of the frame The resistance of the air received in the width can be reduced.

Furthermore, by roughening the surface of the frame, the flow in the boundary layer near the frame surface at the time of swing is made turbulent, and separation of the boundary layer becomes difficult to separate from the surface,
The peeling point moves rearward, the negative pressure region on the rear side is reduced, and air resistance can be reduced.

(Effect) As described above, in the frame of the present invention, the cross-sectional shape of the frame is such that the maximum width portion of the frame front width is the gut insertion hole 6
On either the left or the right, and the width gradually narrows from the maximum width portion toward the rear, and the central axis M in the longitudinal direction is set to 5
By tilting from the axis Z perpendicular to the ball striking surface at an angle of 45 to 45 degrees, if the side with the maximum width is set as the traveling direction during the swing, the air flow during the swing may be blocked by the side width of the frame. Since the eddy generated on the rear side of the frame due to the turbulence of the air is conventionally reduced and the negative pressure region formed when the vortex is separated from the surface of the frame can be reduced, the air flow becomes smooth and the air resistance can be reduced.

Further, by roughening the frame surface, the flow in the boundary layer near the frame surface is made turbulent, the boundary layer becomes difficult to separate from the surface, the separation point moves backward, and The negative pressure area is reduced and the air resistance can be reduced.

Thus, the frame of the present invention can minimize air resistance during swing, which is beneficial for play.

[Brief description of drawings]

The drawing shows an example in which the present invention is applied to a hitting portion, and FIG. 1 is a front view. 2 is a cutaway end view of the main part, and FIG. 3 is FIG. 1A-
It is an A line cutting end view. 1: racket frame, 2: ball striking part, 3: shaft part, 4: grip part, 5: ball striking surface, 6: gut insertion hole, T: maximum width of frame front width, R1: radius of curvature, R2: rear end, M: longitudinal center axis of the frame, Z: vertical to the ball striking face, Y1, Y2: left and right cross sections with respect to the gut insertion hole.

Claims (2)

(57) [Scope of utility model registration request] 1. In the cross-sectional shape of the frame whose side face width is larger than the front face width and which is cut in a direction perpendicular to the ball striking face, the portion of the maximum frame front face width is either left or right with respect to the gut insertion hole. On one side, the front width gradually narrows from the maximum width portion to the other side, and the central axis M in the longitudinal direction of the cross section forms an angle of 5 to 45 degrees with the surface perpendicular to the ball striking face. Racket frame characterized by being inclined. 2. The racket frame according to claim 1, wherein the entire surface or an arbitrary portion of the surface of the racket frame is roughened.