EP1473064A1

EP1473064A1 - Blade of a table tennis racket and table tennis racket

Info

Publication number: EP1473064A1
Application number: EP03292617A
Authority: EP
Inventors: Kimihiko Tamasu
Original assignee: Tamasu Co Ltd
Current assignee: Tamasu Co Ltd
Priority date: 2003-04-30
Filing date: 2003-10-21
Publication date: 2004-11-03
Also published as: JP2004329303A; CN1541737A

Abstract

A blade and a table tennis racket are provided, which have a level of repulsive force required by each player by a simple structure at low cost without greatly changing the feeling of impact transmitted to the player through the racket. Also provided are a blade and a table tennis racket that allow easy adjustment of variation of the flexural elastic modulus. A blade of a table tennis racket includes a plurality of piled base plates which are piled each other and a fiber sheet provided between two adjacent ones of these piled base plates. The fiber sheet is nonwoven fabric containing fibers aligned substantially unidirectionally. An angle formed by the alignment direction of the fibers and a longitudinal direction of the blade is set in accordance with the flexural strength of the blade.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a blade which is a main part of a table tennis racket, as well as to a table tennis racket which comprises the blade.

2. Description of the Related Art

It is demanded that a table tennis racket have various performances, for example, high level of repulsive force with respect to a ball hit by the racket. Fig. 5A shows the table tennis racket having such a performance.

As shown in Fig. 5A, the table tennis racket has a blade 91 and a grip member 92 attached to an end portion of the blade 91.

Fig. 5B shows a cross section view of the blade 91 in the thickness direction thereof. As shown in Fig. 5B, the blade 91 is formed by piling five base plates 93. Between the adjacent base plates 93, a woven material sheet 94 in the form of sheet shown in Fig. 6A is provided.

Fig. 6B shows the details view of the woven material sheet 94, in which a portion circled with broken line in Fig. 6A is enlarged. As shown in Fig. 6B, the woven material sheet 94 is formed as textile obtained by regularly intersecting yarn of fiber material. As the fiber material, continuous fiber such as aramid fiber or carbon fiber is used.

Moreover, the woven material sheet 94 is hardened by thermoplastic resin in order to keep its sheet-like shape.

According to the above structure of the table tennis racket, the flexural elastic modulus of the blade 91 can be increased by providing the woven material sheet 94 between the adjacent base plates 93. Thus, it is possible to provide the table tennis racket having high level of repulsive force for a ball hit by the racket.

On the other hand, in order to adjust the flexural elastic modulus of the table tennis racket, a method was proposed in which the material of the base plate 93 was changed (Japanese Patent Laid-Open Publication No. 2000-342732).

According to the method described in the above patent publication, the base plate 93 is formed of composite polymer material having porous structure reinforced by various types of particles, thereby changing the flexural elastic modulus.

In recent years, preferences of respective table tennis players with respect to the performances of the table tennis racket have been changed with the improvement of skill of each table tennis player. Concretely, it is demanded that the table tennis racket have flexural elastic modulus varies depending on the personality, ability and strategy of each player.

However, since the woven material sheet 94 has the structure in which continuous fibers are crossed as described above, the flexural elastic modulus cannot be greatly changed only by changing the orientation of the woven material sheet 94 with respect to the base plates 93.

Moreover, in a case where the continuous fibers are crossed, the thickness of the fiber sheet increases at the crossings, thus increasing the thickness of the blade. This increase of the blade thickness may increase the thickness of the assemble racket, or may increase the amount of adhesive used for making the woven material sheet 94 adhere to the base plate 93 so as to increase the total weight of the racket. Therefore, in some cases, the table tennis racket having satisfactory performances cannot be supplied.

Furthermore, in the conventional table tennis racket, the flexural elastic modulus cannot be greatly changed only by changing the orientation when adhering the woven material sheet 94 with respect to the base plates 93. Therefore, in a case where the thickness of the base plate 93 that forms the table tennis racket is varied to cause variation of the flexural elastic modulus, the adjustment of flexural elastic modulus may be difficult.

Furthermore, according to the table tennis racket described in the patent publication mentioned above, the material for the racket should be changed for each racket. Such a change can be causing a lot of trouble of manufacturing the racket, thus increasing the manufacturing cost.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a blade and a table tennis racket that can have a level of repulsive force required by each player by a simple structure at low cost without greatly changing the feeling of impact transmitted through the racket to the player.

It is another object of the present invention to provide a blade and a table tennis racket that can allow easy adjustment of variation of the flexural elastic modulus.

In order to achieve the above objects, a blade of a table tennis racket according to the present invention includes: a plurality of piled base plates which piled each other; and a fiber sheet provided between two adjacent ones of the plurality of base plates, wherein the fiber sheet is made of nonwoven fabric containing fibers aligned substantially unidirectionally and an angle formed by an alignment direction of the fibers and a longitudinal direction of the blade is set in accordance with flexural strength of the blade.

As material for the fibers, aramid fibers, polyarylate fibers, metal fibers, glass fibers, and carbon fibers can be used.

The above blade can be applied to any one of a penholder type racket and a shake-hand type racket.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a outline perspective view of a table tennis racket according to an embodiment of the present invention;

Fig. 2A is an exploded perspective view of a blade according to the embodiment of the present invention;

Fig. 2B is a partially enlarged view of a fiber sheet;

Fig. 3 is an exploded perspective view of a table tennis racket used in Example;

Fig. 4A is a cross-sectional view of the table tennis racket used in Example in the longitudinal direction thereof;

Fig. 4B is top view of the table tennis racket used in Example;

Fig. 5A is a perspective view of a conventional table tennis racket;

Fig. 5B is a cross-sectional view of a conventional blade;

Fig. 6A is a perspective view of a conventional entire fiber sheet; and

Fig. 6B is a partially enlarged view of the conventional fiber sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 is a outline perspective view of a table tennis racket (shake-hand type) according to an embodiment of the present invention. In Fig. 1, the reference numeral 11 denotes a blade of the table tennis racket.

This blade 11 is formed by a blade part 11a onto which a rubber sheet 12 is placed to adhere and a grip mounting part 11b which forms a grip together with a grip members 13.

On one surface of the rubber sheet 12 that does not adhere to the blade 11, a number of cylindrical convex protrusions (not shown) are formed.

The grip member 13 has a so-called FL flare shape in which the center of gravity is located at the top end of the grip member 13 and which fits a palm of a player who holds this racket.

Next, the structure of the blade 11 will be described with reference to Fig. 2A. Fig. 2A is an exploded perspective view of the blade 11.

An inner plate 31 serves as a base plate that defines the shape of the table tennis racket. As the material for the inner plate 31, obeche (Ayous), Japanese linden, Japanese cypress, Willow, and the like can be used.

Fiber sheets 32 for increasing flexural elastic modulus of the blade 11 are placed on and adhere to both surfaces of the inner plate 31 with adhesive. As the adhesive, epoxy resin thermosetting adhesive is used.

On the surface of each fiber sheet 32 that does not adhere to the inner plate 31, an outer plate 33 is placed to adhere to the fiber sheet 32. As the material for the outer plate 33, obeche (Ayous), Japanese linden, Japanese cypress, Willow, and the like can be used just like the inner plate 31. As the adhesive for making the outer plate 33 adhere to the fiber sheet 32, epoxy resin thermosetting adhesive is used.

The fiber sheet 32 is formed by nonwoven fabric including fibers that are aligned substantially unidirectionally, as shown in Fig. 2B. As the material for the fiber sheet 32, fiber material that may be light and strong in addition to excellent other properties can be used.

Examples of the material for the fiber sheet 32 include carbon fibers, aramid fibers, polyarylate fibers, glass fibers, metal fibers, and the like.

Here, it is assumed that an angle formed by the direction along which the fibers forming the fiber sheet 32 are aligned and the longitudinal direction of the blade 11 is represented by . Since the fibers of the fiber sheet 32 are aligned unidirectionally, the flexural elastic modulus of the blade 11 can be adjusted by changing the angle .

Moreover, if the flexural elastic modulus of the plate constituting the blade 11 is varied between the plates, the flexural elastic modulus of the blade 11 as a whole can be adjusted by changing the orientation of the fiber sheet 32 when the fiber sheet 32 is made to adhere to the inner plate 31. Thus, the blade 11 having a level of flexural strength required by a player can be supplied to the player.

In addition, the fiber sheet 32 is nonwoven fabric in which the fibers are unidirectionally aligned. Thus, the fiber sheet 32 is lighter than the conventional fiber sheet 94 in a case where both

sheets

32 and 94 are made of the same material, because the fiber sheet 32 contains no crossing of the fibers. Therefore, by sandwiching the fiber sheet 32 between the inner plate 31 and the outer plate 33, the weight of the blade 11 can be reduced.

Moreover, the fiber sheet 32 is nonwoven fabric and has no texture unlike woven fabric. Thus, the possibility that the adhesive enters the texture can be eliminated and it is therefore possible to reduce the amount of the adhesive. Accordingly, the weight of the blade 11 can be reduced.

Furthermore, the fiber sheet 32 contains no crossing of the fibers. Thus, the fiber sheet 32 can be made thinner than the conventional fiber sheet 94. This can reduce the thickness of the blade 11.

According to the present embodiment, the flexural elastic modulus can be adjusted without changing the materials of the inner plate 31 and the outer plate 33 which form the blade 11. Thus, it is possible to provide a plurality of table tennis rackets that give approximately the same feeling of impact (echo) at hitting but are different in repulsive force severally.

Moreover, it is not necessary to change the materials of the inner plate 31 and the outer plate 33 when a plurality of table tennis rackets that are different in flexural elastic modulus severally are manufactured. Thus, the manufacturing cost can be reduced.

In the present embodiment, the number of the outer plates 33 is two. However, the number of the outer plates 33 is not limited to two. For example, four outer plates 33 may be used.

When the number of the outer plates 33 is changed as mentioned above, the flexural elastic modulus of the blade 11 is changed. However, according to the present embodiment, the flexural elastic modulus of the blade 11 can be adjusted by changing the orientation when adhering the fiber sheet 32 with respect to the inner plate 31. Therefore, it is not necessary to carefully consider the relationship between the flexural modulus and the number of the outer plates 33, thus the freedom of design increases.

In addition, the shape of grip member may be formed to be AN anatomic, CO conic, or ST straight.

[Examples]

As described above, the angle formed by the longitudinal direction of the blade and the alignment direction of the fibers forming the fiber sheet is assumed to be .

In order to investigate the relationship between the angle  and the flexural elastic modulus of the blade, the following experiment was done.

The structure of the blade is described with reference to Fig. 3. Fig. 3 is an exploded perspective view of a blade 21 according to this example.

In this example, the blade 21 is formed by one inner plate 41, two fiber sheets 42, and two outer plates 43. At the bottom of the blade 21, a pair of grip members 45 are attached.

The inner plate 41 is made of Ayous and has a thickness of 3.2 mm. The surface of the inner plate 41 has the grain extending in a direction perpendicular to the longitudinal direction of the table tennis racket.

The fiber sheets 42 are placed on both surfaces of the inner plate 41 and adhere to the respective surfaces with epoxy resin thermosetting adhesive.

As the material for the fiber sheet 42, carbon fiber is used. In detail, as carbon fiber TORAYCA (trademark), available from Toray Industries, Inc., which is 0.22 g/m in weight per unit length is used.

The outer plate 43 is made of Ayous and has a thickness of 0.8 mm. The surface of the outer plate 43 has the grain extending along the longitudinal direction of the table tennis racket.

The table tennis racket having the above blade 21 is described with reference to Figs. 4A and 4B. Fig. 4A shows a cross section view of the table tennis racket in the longitudinal direction thereof, and Fig. 4B is a top view of the table tennis racket. Note that a rubber sheet to be placed on the blade 21 is omitted in Figs. 4A and 4B.

The length L1 from the top end to the grip end of the table tennis racket is 260 mm. The length L2 of the racket in the thickness direction at the grip end is 25 mm. The length L3 of the racket in the thickness direction at the top end is 6 mm.

The top end of each grip member 45 is tapered toward the blade 21 so as to form a tapered portion 45a. The length L4 of the tapered portion 45a in the longitudinal direction of the racket is 15 mm. The portion of the grip member 45 other than the tapered portion 45a has the length L5 of 85 mm.

The length L6 of the racket in the thickness direction at the top end of the tapered portion 45a is 8 mm. The length L7 of the racket in the lateral direction L7 is 150 mm.

In addition, the grip member 45 was obtained by cutting a block of plywood composed of a plurality of plies of Ayous, each of which has a thickness of 6 mm, into a grip shape.

When the flexural elastic modulus of the table tennis racket having the above structure was measured, the results as shown in Table 1 were obtained.

In the actual measurement, the flexural elastic modulus was measured by performing flexural test for a flat rectangular plate having a size of 40 mm x 150 mm which was cut from the blade 21.

More specifically, the flexural elastic modulus was measured by three point bending test in which the flat plate was supported at both ends in the longitudinal direction and the load was applied to the center of the flat plate in the longitudinal direction. As the tester, Strograph V10-C (Toyo Seiki Seisaku-sho, Ltd.) was used.

	0°	45°	90°
Flexural elastic modulus (N/mm)	31.4	19.6	17.6

As shown in Table 1, the flexural elastic modulus was 31.4 N/mm when  was equal to 0°; the flexural modulus was 19.6 N/mm when  was equal to 45°; and the flexural modulus was 17.6 N/mm when  was equal to 90°.

As is apparent from the above experimental results, the flexural elastic modulus becomes smaller as the angle  increases, whereas the flexural elastic modulus becomes larger as the angle  decreases.

Thus, the flexural elastic modulus of the blade can be adjusted by changing the angle . Therefore, it is possible to provide the blade and the table tennis racket that have a level of repulsive force required by each player.

As described above, according to the present invention, the flexural elastic modulus of the blade can be changed only by adjusting the alignment direction of the fibers in the fiber sheet with respect to the base plate. Thus, it is possible to provide the blade and the table tennis racket that have a level of the repulsive force required by the player.

Moreover, the flexural elastic modulus of the blade and the table tennis racket can be increased by arranging the fiber sheet with respect to the inner plate of the blade in such a manner that the alignment direction of the fibers in the fiber sheet is substantially parallel to the longitudinal direction of the table tennis racket.

Claims

A blade of a table tennis racket comprising:

a plurality of base plates which piled each other; and

a fiber sheet provided between two adjacent ones of the plurality of piled base plates, wherein

said fiber sheet is made of nonwoven fabric containing fibers aligned substantially unidirectionally, and

an angle formed by an alignment direction of said fibers and a longitudinal direction of the blade is set in accordance with flexural strength of the blade.
A blade of a table tennis racket comprising:

a plurality of base plates which piled each other; and

a fiber sheet provided between two adjacent ones of the plurality of piled base plates, wherein

said fiber sheet is made of nonwoven fabric containing fibers aligned substantially unidirectionally, and

an angle formed by an alignment direction of said fibers and a longitudinal direction of the blade is set in accordance with predetermined flexural strength of the blade.
The blade of a table tennis racket according to claim 1 or 2, wherein the alignment direction of said fibers is approximately parallel to the longitudinal direction of said blade.
The blade of a table tennis racket according to any one of claims 1 to 3, wherein said fibers are any one of aramid fibers, polyarylate fibers, glass fibers, metal fibers, and carbon fibers.
A table tennis racket comprising the blade according to any one of claims 1 to 4.