JPH0838652A - Racket - Google Patents

Abstract

PURPOSE:To effectively lessen the air resistance at the time of swinging a racket by providing this racket with a head frame delineating a gut extension part and a shaft including a grip part and forming plural pieces of recesses on the surfaces. CONSTITUTION:This tennis racket has the head frame delineating the gut extension part 1 and the shaft 3 including the grip part. In such a case, the surfaces, particularly the inner peripheral side surface 2a and the outer peripheral side surface 2b of the head frame 2 are provided with the recesses 4a, 4b having edge part contour shapes over nearly the entire periphery of the head frame 2. These recesses 4a, 4b are formed to one kind or plural kinds of nearly circular shapes of a diameter 0.5 to 10.0mm and depth 0.1 to 3.0mm or one kind or plural kinds of nearly elliptic shapes of a major axis length 0.5 to 30.0mm, minor axis length 0.4 to 25.0mm and depth 0.1 to 3.0mm. As a result, the peeling of boundary layers is sufficiently delayed and the air resistance is effectively lowered at the time of swinging the racket.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gut-stretched racket for badminton, squash, racket ball, tennis, etc., and particularly, it effectively reduces air resistance when swinging the racket. It is a thing.

[0002]

2. Description of the Related Art A racket of this kind having a head frame defining a gut tension portion and a shaft including a grip portion, particularly a tennis racket, is used for the purpose of reducing air resistance and improving swing-out. The so-called thick racket, which has a thicker head frame and a streamlined cross-sectional profile, has become popular, and such a head frame structure has been adopted for badminton rackets.

[0003]

However, in a tennis racket with a thick head frame, the resilience of the ball becomes too high and the controllability deteriorates, resulting in a blurred shot feeling However, there is a disadvantage that the mechanical strength of the head frame is reduced. Here, the mechanical strength means a racket strength capable of withstanding an impact generated when a ball is hit, and this mechanical strength is usually evaluated by a three-point bending test of a head frame. Further, in the badminton racket, the racket speed during smash reaches 45 to 65 m / s in the central portion of the head frame, so that the air resistance cannot be sufficiently reduced only by the streamlined sectional contour shape. It was

The present invention has been made as a result of investigations aimed at solving such problems of the prior art, and an object of the present invention is an inconvenience resulting from increasing the thickness of the head frame. It is an object of the present invention to provide a racket that can effectively reduce the air resistance of the head frame during swinging of the racket without causing the occurrence of swinging, and can effectively increase both swing-out ease and swing-out speed.

[0005]

A racket according to the present invention comprises a head frame defining a gut stretched portion and a shaft including a grip portion, the surface of which has a substantially circular contour or a substantially elliptical contour. A plurality of one kind or two or more kinds of depressions having a polygonal shape are formed.

Preferably, the recess is formed only in the head frame, and preferably, the recess is formed substantially in the top half of the head frame.

When the outer peripheral surface of the head frame is covered with a bumper to protect the head frame body from external damage, it is preferable to form a recess in each of the bumper and the head frame itself. .

More preferably, the plurality of recesses are one or more kinds of substantially circular recesses having a diameter of 0.5 to 10.0 mm and a depth of 0.1 to 3.0 mm, or have a long length. The axial length is 0.5 to 30.0 mm and the minor axial length is 0.
4 to 25.0 mm and a depth of 0.1 to 3.0 mm, by one or more kinds of substantially elliptical depressions, or
The contour shape is a polygonal depression.

[0009]

In this racket, when the player swings the racket to move the head frame and the shaft at high speed in the air, the dents formed in the head frame, bumper, etc. form the laminar flow boundary formed on their surfaces. The layer will be transitioned to a turbulent boundary layer to make boundary layer separation less likely to occur and to bring the separation point to the rear side of the air flow compared to the prior art. For this reason, the negative pressure region generated on the rear side of the separation point is effectively reduced, the pressure difference between the front side and the rear side of the head frame and the like is reduced, and the air resistance is effectively reduced. . Therefore, the player can swing the racket at a higher speed.

When the recess is formed only in the head frame, the racket can be sufficiently exerted with the required effect, and the man-hour for processing the recess-forming projection on the racket molding die can be effectively reduced. This can be achieved, and this is particularly remarkable when the depression is formed only in approximately half of the top side of the head frame where the swing speed is highest.

When the plurality of depressions are formed of one or more types of substantially circular depressions, the total area of the depressions on the racket can be made sufficiently large, and the depressions can be formed. It is possible to easily form the convex portion of the mold. In this case, the diameter of the depression is 0.5 to 10.0 mm, especially 1.5 to 3.0 mm.
It is preferable to set it as the range.

That is, if the diameter is less than 0.5 mm, the degree of surface irregularities due to dimple formation is reduced, the effect on the air flow is reduced, and the total area of dimples formed on the surface is secured. It is necessary to form a large number of dimples, which is disadvantageous in terms of processing, and the depth of the dimples is inevitably shallow.
Difficulty in processing including painting increases. On the other hand, if it exceeds 10.0 mm, the surface roughness is still small even if the depression is provided, and the depression cannot fully exhibit its original function.

By the way, the depth of the depression is 0.1 to 3.0.
mm is preferable, and when it is less than 0.1 mm,
Similar to the case described above, the effect of the dimples on the air flow is reduced, and the difficulty in processing including coating is increased. On the other hand, if it exceeds 3.0 mm, a negative pressure is generated in the dimples, which in turn increases the air resistance, and waviness is generated in the reinforcing fiber layer forming the racket, which lowers the racket strength and further causes dimples. Since the thickness of the racket at the bottom of the racket becomes thin, the racket strength is reduced.

When the plurality of depressions are formed by one or more kinds of substantially elliptical depressions, the total area of the dimples can be increased and the surface roughness can be effectively increased. As a result, the effect of arranging the dimples on the racket surface can be enhanced.

Here, the major axis length of the depression is 0.5 to 30.
0mm and minor axis length 0.4 to 25.0mm,
The diameter of the circular recess is almost the same as described above, and the effect on the air flow can be sufficiently increased, and the number of dimples to be processed and other processing advantages can be provided.

Further, when the plurality of dents are formed by polygonal dents, the dimples can be effectively arranged on the racket frame as in the case of the ellipse, and the dimple edge can be formed. The effect of the air flow is increased by making the portion acute.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an essential part of a tennis racket according to an embodiment of the present invention. The racket includes a head frame 2 defining a gut tension portion 1 and a shut 3 including a grip portion (not shown). At the surface of the head frame 2, in particular, the inner peripheral surface 2a thereof
Further, recesses 4a and 4b having a substantially circular edge contour shape are provided on each of the outer peripheral surface 2b over substantially the entire circumference of the head frame 2. The depressions 4a and 4b are also formed on the back side of the drawing in the same manner.

Further, in this example, the depressions can be provided not only on the head frame 2 but also on the surface of the shaft 3 excluding the grip portion, and in the racket posture shown in the drawing, in particular, on each of the left and right surfaces. The portion where the recess is formed may be the entire peripheral surface of the head frame 2 or, in addition, the entire peripheral surface of the shaft 3 excluding the grip portion.

On the other hand, it is possible to form the recess on the top side of the head frame 2, in other words, only on approximately the half of the upper end side of FIG. 1, and further, the recesses 4a, which have a circular contour shape, are formed. It is also possible to replace 4b with a substantially elliptical recess or a polygonal recess, or to arrange two or more types of circular, elliptical, and polygonal recesses in combination.

FIG. 2 shows the outer peripheral surface 2 thus formed.
It is a sectional perspective view which expands and shows the hollow 4b of b. Here, the circular recesses 4b which have the same diameter are equal in the circumferential direction on the curved surface of each side which separated the gut hole formation groove 5. They are formed in one row at intervals, and the bottom wall of each recess 4b here can be a curved bottom type, a two-step bottom type, or a flat bottom type, as illustrated in the sectional view of FIG. In addition, a pan bottom type, a conical bottom type, or the like can be used. Further, such a shape of the edge portion of the depression 4b may be a shape in which a sharp edge line portion as shown in FIG. 3 is chamfered and removed.

Here, the diameters and intervals of the recesses 4b can be appropriately changed depending on the circumferential position of the head frame 2, and various sizes of recesses 4b can be formed in a mixed manner.

Although not shown here, the inner surface 2a of the head frame 2 generally has an outer surface 2a.
At a position corresponding to the recess 4b formed in b, a recess 4a having a shape and size corresponding to the recess 4b is formed.

Here, when the racket is made of fiber reinforced resin, the above depressions can be formed simultaneously with molding by providing a convex portion on the molding surface of the molding die, and the racket material It can be formed by engraving afterwards, adjusting the thickness of the coating film at the time of painting, etc., for aluminum rackets, and can also be formed by embossing after molding. be able to.

FIG. 4 is a diagram schematically showing the function of the depression as described above with respect to the head frame. When the racket of the embodiment swings at a high speed, as shown in FIG. 4 (a), Each of the depressions 4a and 4b functions to give a disturbance to the laminar boundary layer and promote its transition to the turbulent boundary layer, which makes it difficult for the boundary layer to separate and also the scale of separation. Since it becomes smaller, FIG.
The negative pressure region V generated on the rear side of the separation point is effectively reduced as compared with the conventional technique shown in FIG. Therefore, in the racket of the embodiment, the air resistance acting on the head frame is effectively reduced, and the player can swing the racket at a higher speed. Note that this is more effective as the area where the depression is formed becomes wider.

FIG. 5 is a view showing another embodiment of the present invention, in which a head frame 2 is provided with a bumper 6 which covers the outer peripheral surface of the head frame 2 over substantially the entire circumference thereof or over substantially the half of the top side thereof. It is attached, and FIG.
In the example shown in (a), the circular recess 4b is formed on the surface of the bumper 6 in the same manner as described above. It should be noted that the inner surface 2a of the head frame 2 has a structure shown in FIG.
As shown in (b), this also forms a circular depression 4b similar to that described above.

In the example shown in FIG. 5C, the edge contours of the recess 7b formed on the surface of the bumper 6 and the recess formed on the inner peripheral surface 2a of the head frame 2 are substantially elliptical. It was done.

Also in these embodiments, by effectively suppressing the separation of the boundary layer under the action of the depressions 4a, 4b and 7b, it is possible to obtain the same action and effect as the above-mentioned embodiment.

FIG. 6 is a view showing still another embodiment of the present invention, in which the bumper 6 covering the outer peripheral surface of the head frame 2 is provided on each side of the bumper 6 separated from the gut hole forming groove 8. Two types of depressions, large and small, having an elliptical contour shape 9
b is formed densely, and this is the same for the inner peripheral surface 2a of the head frame.

According to this, since more sufficient disturbance can be given to the laminar boundary layer, the air resistance during the swing of the racket can be reduced more effectively.

FIG. 7 shows an example of application of the present invention to a badminton racket. As in the case of a tennis racket, the inner surface 12a and the outer circumference of the head frame 12 for partitioning the gut extension 11 are separated. Each of the side surfaces 12b is formed with a substantially elliptical recess 14a, 14b. FIG. 7B shows the recess 1 of the outer peripheral surface 12b.
4b is an enlarged perspective view showing 4b. FIG.

Also in this application example, the depressions 14a, 1
4b can effectively contribute to the reduction of air resistance as in the case described above. It should be noted that the recesses of the badminton racket can be modified in the same manner as described for the tennis racket.

[0032]

As described above, according to the present invention, the plurality of recesses provided on the surface of the racket sufficiently delay the separation of the boundary layer during the swing of the racket,
Ease of swinging the racket by effectively reducing the air resistance of the head frame etc. without causing inconveniences such as deterioration of controllability and blurring of shot feeling caused by thickening the head frame And the swing-out speed can be increased.

Here, when the recess is formed only in the head frame, the number of man-hours required for forming the recess can be effectively reduced, and this can be achieved only in almost half of the top side of the head frame. This is more noticeable when the depression is formed.

The same applies to the case where the outer peripheral surface portion of the head frame is covered with a bumper so as to protect the head frame itself, and a recess is formed in each of the bumper and the head frame itself. is there.

By the way, when the outline shape of the edge of the recess is substantially circular, it is relatively easy to form the protrusion forming the recess in the mold for forming the racket by an NC processing machine or the like. If the size of the formed recess is within a predetermined range, sufficient disturbance is given to the laminar boundary layer, and the air resistance reducing effect is obtained.

If it is formed into an almost elliptical shape,
It is possible to further increase the total area of the portion where the depression is arranged, and the air resistance reducing effect is further increased.

Further, in the case of a polygonal shape, the contour of the depression can be formed at an acute angle, and the total area of the portion where the depression is arranged can be widened to the maximum, thereby disturbing the air flow. The effect is even greater than with an elliptical depression.

[Brief description of drawings]

FIG. 1 is a plan view of essential parts showing a tennis racket according to an embodiment of the present invention.

FIG. 2 is a cross-sectional perspective view showing an outer peripheral side surface depression of FIG. 1 in an enlarged manner.

FIG. 3 is a cross-sectional view illustrating the shape of a recess bottom wall.

FIG. 4 is a streamline diagram schematically showing the function of a depression.

FIG. 5 is a cross-sectional perspective view showing another embodiment.

FIG. 6 is a sectional perspective view showing still another embodiment.

FIG. 7 is a diagram showing an example of a badminton racket.

[Explanation of symbols]

 1, 11 Gut tension part 2, 12 Head frame 2a, 12a Inner peripheral surface 2b, 12b Outer peripheral surface 3 Shaft 4a, 4b, 7b, 9b, 14a, 14b Recess 5,8 Gut hole forming groove

Claims (7)

[Claims] 1. A racket comprising a head frame defining a gut stretched portion and a shaft including a grip portion, and having a plurality of recesses formed on the surface thereof. 2. The racket according to claim 1, wherein the recess is formed in the head frame. 3. The racket according to claim 1, wherein the recess is formed substantially in a half portion on the top side of the head frame. 4. The racket according to claim 2, wherein the outer peripheral surface portion of the head frame is covered with a bumper, and recesses are formed in each of the bumper and the head frame itself. 5. The plurality of depressions have a diameter of 0.5 to 1
The racket according to any one of claims 1 to 4, which is constituted by one or more kinds of substantially circular recesses having a depth of 0.0 mm and a depth of 0.1 to 3.0 mm. 6. The major axis length of the plurality of depressions is 0.5.
3. A single or plural kinds of substantially oval-shaped depressions each having a length of -30.0 mm, a short axis length of 0.4-25.0 mm, and a depth of 0.1-3.0 mm. The racket according to any one of 4. 7. The racket according to claim 1, wherein the plurality of depressions are formed by depressions having a polygonal outline shape.