JPS5854970A - Racket frame and production thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention relates to the structure of a racket frame having an outer shell structure made of fiber reinforced plastics (hereinafter abbreviated as FRP) and its manufacturing method.
By using foamed synthetic resin as the matrix resin of RP, specifying the type of synthetic resin or the type of reinforcing fiber, and forming a colored synthetic resin layer on the outermost surface, it is possible to improve the elasticity due to impact when hitting the ball. A racket frame that reduces wave propagation and is lightweight, durable, and has good appearance is obtained.

Conventionally, in manufacturing this type of FRP racket frame, organic fibers such as glass fibers, carbon fibers, or mixed fibers thereof are added to a core forming material made of a foamed synthetic resin with a rectangular cross section that has been separately foamed in advance. A frame molding material obtained by covering and surrounding an uncured FRP molding material (prepreg) consisting of a non-foamed thermosetting synthetic resin matrix with reinforcing fibers is placed in a heated desired mold. It is well known that the ball hitting part and the shaft part of the frame are formed into an FRP outer shell structure having a so-called box-shaped cross section by placing the ball inside the ball and performing hot pressure molding after mold clamping.

However, with such conventional racket frame manufacturing methods, the center core forming material relies on the foamed synthetic resin core forming material to maintain the shape of the inner circumferential surface of the FRP outer shell during hot press molding. When the thickness of the uncured non-foamed FRP molding material that is covered and surrounded by the outer periphery is increased, the amount of compressive deformation of the core is increased due to the pressurizing action after mold clamping.
The shape retention of the cross-section of the FRP outer shell after molding deteriorates, resulting in uneven strength distribution throughout the frame, as well as an increase in overall weight, so it is necessary to reduce the wall thickness of the FRP molding material. For this reason, only thin-walled FRP outer shell structures can be obtained, and if the frame is damaged by external force such as when hitting a ball, it will have a large effect on the rigidity of the entire frame, which will be fatal in terms of durability. Furthermore, the propagation of the vibrations generated by the impact when hitting the ball was large, leading to various problems such as severe wrist fatigue.

This invention aims to eliminate the above-mentioned conventional drawbacks, and will be described below based on the illustrated embodiments.

As shown in FIGS. 1 to 3, / in the figure is a racket frame molded by a molding means described later, and the frame ball-striking part! , the shaft portion including the throat portion 3 is continuously integrally molded. As shown in the figure, the racket frame/top, frame ball-striking part is a thermoplastic foamed synthetic resin center // and a carbon fiber reinforced foamed synthetic resin that covers and surrounds the outer peripheral surface of the center core l/. (Hereinafter, foamed CFR
It is formed into a single box-shaped outer shell structure with a cross section of 2 (abbreviated as P)/2, while the shaft part has a central center // in a direction parallel to the ball hitting surface of the frame, as shown in Figure 3. It has a double box-shaped outer shell structure with a cross section arranged side by side, and a non-foamable fiber-free synthetic resin layer /3 colored in an appropriate color is formed on the outermost surface thereof.

That is, the above-mentioned racket frame/
To manufacture this, a rod-shaped core forming material with a rectangular cross section made of a thermoplastic foamed synthetic resin that has been separately foamed is treated in an uncured state with a foamable synthetic resin matrix having carbon fibers as reinforcing fibers on the outer peripheral surface of the material. A frame molding material is preformed by covering and surrounding the foamed CFRP molding material in an unfoamed state, and then the rod-shaped frame molding material is coated with an uncured non-foamed colored synthetic resin on the mold surface. It is obtained by placing the mold in a heated mold, and after the mold is clamped, heat and pressure foaming is performed to integrate the whole.

By the way, the foamed CFRP used in this invention is made of thermosetting synthetic resin such as epoxy resin, unsaturated polyester resin, phenol resin, or polyimide resin, or polyamide resin, polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, or 7.2 Using a thermoplastic synthetic resin matrix with acrylonitrile-butadiene-styrene resin and continuous or short carbon fibers and a conventional blowing agent.
It is made by foaming at a volume magnification of ~6 times, and when covering and surrounding such a foamed CFRP molding material (prepreg) in a core forming material, prepreg with continuous fibers aligned in one direction is used. For example, prepare a sheet and a short fiber mat prepreg sheet, and alternately stack several continuous fiber prepreg sheets sandwiched between the short fiber mat prepreg sheets to obtain the desired thickness. If the fiber direction of the continuous fibers is arranged along the longitudinal direction of the core forming material and the circumferential direction of the frame frame, closed cells will be formed when the matrix resin foams in the mold during hot-press molding. Since the short fiber mat layer facilitates the freedom to expand, expand, move, or develop in the stacking direction, foaming pressure can be used effectively, and the distribution and size of closed cells are less uneven, and the shape of the outer shell layer can be maintained. It has excellent shapeability and can evenly distribute the fibers themselves.

In addition, the thickness of the colored synthetic resin layer in the above example was 0.
/~0.1m, and the thickness of the outer shell of foamed CFRP is 3~r
It is appropriately selected within the range of mti.

Therefore, according to the above-mentioned racket frame according to the present invention, since foamed CFRP is used as the strength layer of the outer shell having a box-shaped cross section, the thickness of the strength layer can be increased compared to the conventional structure. Even if it receives the same amount of trauma from external force when hitting a ball, it will have little effect on the overall rigidity, and it can be expected to be lighter, and since the outer shell has a bubble structure, it will not be elastic due to the impact when hitting the ball. Since waves can be refracted, reflected, and interfered with by bubbles, the propagation of vibrations can be reduced.

It also causes less wrist fatigue. In addition, since a colored synthetic resin layer is formed on the surface of the frame, the openings of the air bubbles on the surface of the foamed CFRP are not exposed to the outside surface, and the frame surface can be finished with a smooth surface, improving the appearance. In addition, the frame surface is less likely to become dirty, and the black foamed CFRP can be prevented from absorbing infrared rays, thereby preventing a decrease in durability due to material deterioration. Furthermore, since the uncured foamed CFRP molding material is foamed and hardened in the mold during molding, the shape of the outer shell is well maintained by using foaming pressure, and the entire frame is This has excellent practical effects, such as making the intensity distribution uniform.

FIG. 1 is a perspective view showing an embodiment of the racket frame according to the present invention, FIG. 2 is an enlarged sectional view of the frame's ball-hitting part taken along the line ■-■ in FIG. 1, and FIG. FIG. 3 is an enlarged cross-sectional view of the shaft portion.

/ Racket frame //...Middle core/, 2-
．． Foamed CFRP layer /3...Colored synthetic resin layer Patent applicant Nippon Musical Instruments Fukuzo Co., Ltd. Figure 1, Figure 2, Figure 3, Figure 3 A?

Claims (2)

[Claims] (1) A cross-sectional box consisting of a core made of thermoplastic foamed synthetic resin, an outer shell made of carbon fiber-reinforced foamed synthetic resin on the outer peripheral surface of the core, and a colored synthetic resin layer coated on the surface of the outer shell. A racket frame with a mold structure. (2) A core forming material made of a thermoplastic foamed synthetic resin that has been previously foamed is surrounded with an uncured carbon fiber reinforced foamed synthetic resin molding material that has not been foamed to form a frame molding material. 1. A method for manufacturing a racket frame, which comprises the steps of: 1) placing the frame molding material in a heated mold in which an uncured colored synthetic resin layer has been previously formed on the mold surface, and heating and pressurizing the material;