JPH0335350Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention is based on fiber-reinforced plastics (hereinafter referred to as
This invention relates to a racket frame such as a tennis racket whose outer shell is FRP (abbreviated as FRP).

[Prior art and its problems] Conventionally, in a racket frame having this type of FRP outer shell structure, the cross-sectional shape of the frame stringing part 2 of the racket frame body 1 is However, around the core layer 3 made of foam or honeycomb material made of polyurethane resin, polyethylene resin, etc., an FRP layer 4 made of reinforcing fibers such as glass fiber, carbon fiber, Kevlar, or boron fiber is attached with equal thickness. It has a closed cross-sectional structure.

However, in the case of a racket frame with such a conventional structure, the entire circumference in the closed cross-sectional direction is
Since it is made of a single thin FRP layer of about 1.6 mm, the direction of the solid line arrow that acts on the FRP layer 4 on one side of the outer peripheral surface 2a of the frame stringing section 2, where the strings are folded in a U-turn shape, is particularly strong. There was a problem that the rigidity was insufficient for the tension of the gut, and sufficient buckling strength could not be obtained, resulting in insufficient tensile strength and elasticity.

[Purpose of the invention] This invention was made under the above circumstances, and its purpose is to be lightweight, increase rigidity against gut tension, and improve vibration damping characteristics. Our goal is to provide racket frames.

[Summary of the invention] In order to achieve the above-mentioned object, this invention is a racket frame whose outer shell is made of FRP with a closed cross section, in which the FRP has a foam core material on the entire circumference or part of the closed cross section. The structure consists of a sandwich structure interposed between FRP layers.

In this case, it is preferable that the FRP has a sandwich structure over the entire length or part of the length in the circumferential direction of the frame.

[Embodiments of the invention] This invention will be described below based on the embodiments shown in FIGS. 1 to 3. In the illustrated embodiment of this invention, the same reference numerals are used for the parts having the same structure as the conventional structure shown in FIGS. 4 and 5, and the explanation thereof will be omitted.

FIG. 1 shows a first embodiment of the racket frame according to this invention.
The outer shell FRP layer 4 of the frame stringing part 2 is formed of first and second FRP layers 41 and 42, and both FRP
A foamed core material 31 is interposed between the layers 41 and 42 so that the entire circumference in the closed cross-sectional direction exhibits a sandwich structure, and is formed over the entire length or a part of the length in the frame circumferential direction.

By the way, the racket frame having the above structure has, for example, when considering the tensile strength with respect to the string tension at the outer circumferential surface portion 2a of the frame stringing portion 2.
The thickness of the first and second FRP layers 41 and 42 is 0.8 mm,
If the thickness of the foam core material 31 is 1.0 mm, the buckling strength will be improved compared to the conventional one made of a single 1.6 mm thick FRP layer shown in Fig. 5, and the buckling strength will be approximately 1.0 mm without increasing the weight. It is expected that the rigidity will be doubled, and the foam core material 31 interposed between the FRP layers 41 and 42 can significantly attenuate the propagation of vibrations and shocks when the ball is hit.

Furthermore, FIG. 2 shows a second embodiment according to this invention, in which the outer circumferential surface portion 2a side of the frame stringing portion 2 is
It has a structure in which only the FRP layer 4 has a sandwich structure.

Furthermore, FIG. 3 shows a third embodiment of this invention, in which both the front and back FRP layers 4 facing the ball-hitting surface side of the frame stringing section 2 have a sandwich structure.

In addition, in the embodiment of this invention, the outer shell
Although the FRP has a sandwich structure for the frame stringing part, it is of course possible to apply it to the entire length from the frame stringing part to the shaft part and grip part.

In the above example, the weaving and knitting forms of the FRP reinforcing fibers forming the outer shell structure of the racket frame include roving, plain weave cloth, twill cloth,
Bias cloth etc. can be used alone or in combination of two or more types, and even if any type of reinforcing fiber is used alone or in a composite layered form of two or more types, the effect of this structure is Furthermore, the reinforcing fibers in various forms are preferably made of carbon, glass, or high modulus organic fibers, either alone or in combination of two or more. It is also valid in case. The matrix synthetic resin impregnated into the reinforcing fibers is preferably an epoxy resin, an unsaturated polyester resin, or an epoxy acrylate resin.

[Effects of the invention] As explained above, according to this invention, the entire circumference or part of the outer shell FRP in the closed cross-sectional direction is made into a sandwich structure in which the foam core material is interposed between the FRP layers. Even with a full-thickness outer shell FRP, the rigidity and buckling strength can be improved due to the sandwich effect between the FRP layers.

In addition, if the core between the FRP layers is a non-strength material and
Since it is made of a foam core material that has a negligible weight increase compared to FRP materials, it can be used without increasing weight.
This has excellent effects in that it can be expected to be lighter in weight and can improve vibration damping characteristics when hitting a ball.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a frame stringing part showing a first embodiment of a racket frame according to this invention;
FIG. 2 is a sectional view showing a second embodiment of this invention, FIG. 3 is a sectional view of a third embodiment of this invention, and FIG. 4 is an explanatory diagram showing an example of a conventional racket frame. FIG. 5 is an enlarged sectional view of the frame stringing section taken along the line A-A in FIG. 4. 1... Racket frame body, 2... Frame stringing part, 2a... Outer peripheral surface part, 4... FRP layer, 4
1, 42...FRP layer, 31...foam core material.

Claims (1)

[Claims for Utility Model Registration] (1) In a racket frame whose outer shell is made of FRP with a closed section, the FRP is a sandwich frame with a foam core material interposed between the FRP layers all or part of the circumference in the direction of the closed section. A racket frame characterized by its structure. (2) The racket frame according to claim 1, wherein the FRP has a sandwich structure over the entire length in the circumferential direction of the frame. (3) The racket frame according to claim 1, wherein the FRP has a sandwich structure for a part of the length in the circumferential direction of the frame.