JPS6050465B2 - Racket frame molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a racket having a cross-sectional structure in which a fiber-reinforced plastic (hereinafter abbreviated as FRP) forms an outer shell strength layer on the peripheral surface of the frame, and a core portion is made of foamed synthetic resin. Regarding the frame molding method, the molding of the FRP outer strength layer and the core are performed simultaneously with hot pressure molding using a mold.In addition, when molding the FRP outer strength layer, tension is applied to the reinforcing fibers in advance. By using an FRP thin rod-shaped strength member obtained by curing a liquid synthetic resin, it is possible to stabilize the alignment direction of reinforcing fibers and improve moldability.

Conventionally, in manufacturing an FRP racket frame having this type of outer shell structure, for example, semi-cured glass fiber or carbon fiber reinforcement is used to form an outer shell strength layer on the outer peripheral surface of a core material made of foamed synthetic resin. FRP molding material made of fibers, so-called prepreg, is wound and coated to form a frame molding rod of a predetermined length, and this frame molding rod is bent and fitted into a desired mold, or a core is formed. When making the racket frame hollow, a racket frame with a box-shaped cross-sectional structure whose outer shell layer is made of FRP is obtained by covering a tube or the like with prepreg and blowing high-pressure air into it to form it under heat and pressure. .

However, in the manufacturing method of a racket frame with such a conventional structure, since no tension is applied to the reinforcing fibers in the prepreg, the reinforcing fibers meander due to the flow of the remelted liquid synthetic resin during hot-press molding. The fiber arrangement may become irregular due to so-called swimming, and the reinforcing fibers may loosen due to the volumetric shrinkage phenomenon during polymerization and curing of liquid synthetic resin, which may cause the strength distribution of the FRP outer shell strength layer to deteriorate.・This becomes uneven and deviates from the initial product design value, resulting in a decrease in overall strength. This is especially noticeable in FRP that uses a mixture of reinforcing fibers with high elastic modulus such as carbon fiber, resulting in poor molding. There were various disadvantages, such as the tendency to cause curing, and the need for a long time for the liquid synthetic resin in the prepreg to harden. Therefore, in molding a racket frame having an outer shell structure in which an FRP strength layer is formed around the outer periphery of a foamed synthetic resin core, the present invention involves applying an uncured liquid synthetic resin to the cavity wall surface of a mold having a racket shape. A reinforcing member in the form of a thin rod of cured FRP serving as a reinforcing fiber member is arranged along the circumferential direction of the frame on the coating layer of the liquid synthetic resin to serve as a molding material for the FRP for the outer shell strength layer, and the mold is clamped. We attempted to eliminate the above-mentioned drawbacks of the conventional method by injecting a foamable liquid synthetic resin as a core material into the core space that will later be formed in the cavity of the mold, allowing the foam to harden, and at the same time heat-pressing the entire product. It is something to do. Hereinafter, the present invention will be explained based on the illustrated embodiment. As shown in FIG. It is integrally formed. This racket frame 1
As shown in the figures and FIG.
It has a box-shaped cross-sectional structure formed by 6, and
The outer shell strength layer FRP 6 has a plurality of thin rod-shaped reinforcing members 8 made of hardened FRP in a lateral direction (cut tension) in a synthetic resin layer 7 such as a gel coat layer on at least surfaces 6a and 6b facing the ball hitting direction. They are formed by arranging them in parallel in the frame circumferential direction and continuously disposing them in the circumferential direction of the frame. still,
figure. The middle part 9 is a yoke member installed on the neck part 3 of the racket frame 1. That is, in order to mold the above-mentioned racket frame, as shown in FIGS. 4 to 6, an upper die 10a1 having a racket shape, an upper die 10b, and an intermediate part are formed. Cavity 11 of mold 10 consisting of split mold 10c
An uncured liquid synthetic resin 12 that will become a gel coat layer is applied to the peripheral wall surface, and a reinforcing fiber material 13 such as thin glass cloth, glass mat, or semi-cured prepreg impregnated with liquid synthetic resin is applied in advance. A bundle of fibers is impregnated with uncured liquid synthetic resin (mainly epoxy resin) using the pultrusion molding method and cured under high tension. A plurality of thin rod-shaped reinforcing members 8 made of FRP are successively arranged in parallel in the circumferential direction of the frame on the side facing the ball hitting direction, and the molds are clamped (fourth
(See Figure and Figure 5).

Next, the core space 14 of the cavity 11 thus formed is filled with a foamable material such as a foam-curing polyurethane resin from the injection port 10d of the mold 10 corresponding to the end of the shaft portion of the racket frame. A racket frame as shown in FIGS. 1 to 3 is formed by injecting and filling a liquid synthetic resin 15, foaming it, and at the same time hot-pressing the entire structure (see FIG. 6). By the way, in the above-mentioned examples, the final hardened liquid synthetic resin applied to the peripheral wall surface of the cavity of the mold is either colored or colorless, or a combination of both, and in particular colored and colorless synthetic resins are used. When the two layers are applied, the colored one is applied as the outer layer.

In addition, FRP thin rod-shaped reinforcing members may be coated with liquid synthetic resin before being installed side by side, or may be partially or completely bound with supplementary fibers, or may be partially or partially bound with hot melt adhesive, etc. before fitting. The resin is temporarily attached to the coating layer of uncured liquid synthetic resin applied to the peripheral wall of the mold cavity.
Furthermore, the reinforcing fiber material is coated with FR in the liquid synthetic resin coating layer.
P Thin rod-shaped reinforcing members may be arranged in parallel and then interposed between the reinforcing members and the core material, and the types of fibers are as follows:
Glass, carbon, or organic fibers may be used alone or in combination. Therefore, according to the above-described molding method, in molding a racket frame having a box-shaped cross-section FRP outer shell strength structure made of a foamed synthetic resin core material, the heat of the FRP for the outer shell strength layer is Since compression molding and foam molding of the core material are carried out simultaneously, the reinforcing fiber material that constitutes the FRP for the outer shell strength layer and the hardened FRP thin rod-shaped reinforcing member are It is pushed into the liquid synthetic resin coating layer that becomes the gel coat layer applied to the peripheral wall of the mold cavity.
Moreover, moldability can be improved by applying pressure from the inside.

In addition, in the FRP for the outer shell strength layer, a reinforcing member in the form of a thin FRP rod, which is impregnated and cured with a terminally cured liquid synthetic resin while applying high tension to the fibers using a pultrusion molding method, is arranged to face at least the direction of the ball. Since a plurality of fibers are arranged in parallel on both sides of the racket frame, the fibers do not swim due to resin flow when hot-pressing the gel coat layer, and the direction of fiber arrangement can be stabilized. It is possible to effectively utilize the characteristics of the racket, and it is expected to improve the repulsion and durability of the racket.The molding time is also reduced by the curing time of the foamable liquid synthetic resin that is the core material, which is different from the conventional method. This method has excellent productivity and performance characteristics, such as being shorter than the hot pressure molding method for prepreg for FRP molding.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a racket frame according to the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of the ball hitting section taken along the line 1-1 in FIG. 1, and FIG. 3 is a shaft section taken along the line ■-■ in FIG. 4 to 6 show an embodiment of the racket frame molding means according to the present invention, and FIG. 4 is a perspective view of the mold, and FIGS. The figure is an explanatory diagram showing a molded state with a partially enlarged cross section taken along the line ■-■ in FIG. 4. DESCRIPTION OF SYMBOLS 1... Racket frame, 5... Core material, 6... FRP for outer shell strength layer 7... Gel coat layer, 8... F
RP thin rod-shaped reinforcing member, 10... mold, 11...
Cavity, 12... Uncured liquid synthetic resin, 14...
- Core space, 15... foamable liquid synthetic resin.

Claims (1)

[Scope of Claims] 1. A method for molding a racket frame, which comprises molding a racket frame in which the core portion is made of foamed synthetic resin and the outer strength layer is made of fiber-reinforced plastic in the following steps. (a) A step of applying an uncured liquid synthetic resin that will become a gel coat layer to the peripheral wall surface of the cavity of a racket-shaped mold. (b) On the uncured liquid synthetic resin coating layer, a thin rod-shaped reinforcing member made of fiber-reinforced plastic that is molded by hardening liquid synthetic resin that has been pre-impregnated into fibers while applying tension to the fibers is attached to the frame. A step of stacking and arranging in the circumferential direction and clamping the mold to form a core space, (c) a step of injecting and filling the foamable liquid synthetic resin into the core space, (d) a step of injecting and filling the foamable liquid synthetic resin. Along with foaming, this process involves hot-press molding and hardening the entire piece into one piece.