JPH01185272A - Manufacture of racket frame or stick - Google Patents

Abstract

PURPOSE:To enhance productivity of the racket frame or stick stated in the caption and improve reduction of weight, rigidity and strength thereof in a slim configuration by setting a core covered with reinforcing continuous fibers in a metallic mold, injecting or extruding preheated and molten thermoplastic resin through an injection port provided on the metallic mold and hardening and taking the resin out of the mold. CONSTITUTION:A plurality of reinforcing continuous fiber layer 2 are spread along the outer periphery of a core 1, then the core 1 covered with the reinforcing continuous fiber layers 2 is set in a metallic mold 3. The metallic mold 3 consists of a left-hand metallic mold 31 and a right-hand metallic mold 32 and both right and left-hand molds 32, 31 are constructed to be capable of being opened and closed. The left-hand mold 31 and the right-hand mold 32 are closed and thermoplastic resin preheated and molten in a cylinder 5 is injected or extruded in the mold through an injection port 4 provided on the right-hand mold 32, then cooled and taken out of the mold. The thermoplastic resin is either one of such substances as a homopolymer of polyphenylene oxide or a blend consisting of nylon and polystylenic resin, or liquid crystal polymer, polycarbonate, acetal resin or terpolymer composed of acrylonitrile-butadiene-stylene and so forth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing racket frames for tennis, badminton, squash, racquetball, etc., and furthermore, sticks for gateball.

[Conventional technology]

Conventionally, for example, in tennis racket frames, it was necessary to increase the frame area in order to widen the sweet area and improve control of the ball, so fiber was used as a material to meet the demands for a frame with high strength and light weight. Racket frames are manufactured using reinforced plastics (FRP). A racket frame using FRP is convenient for reducing weight and increasing size, and has a large degree of freedom in design. The manufacturing method for FRP racket frames involves laminating a large number of so-called prepregs, which are semi-hardened reinforcing fibers impregnated with thermosetting resin, around the outer periphery of a core material such as a foam or tube, and then heating and hardening them in a mold. There are two methods: a core material whose outer periphery is coated with reinforcing fibers is placed in a mold, the mold is closed, a thermosetting resin is injected through an injection port attached to the mold, and the thermosetting resin is heated and cured; A method in which reinforcing fibers coated around the outer periphery of a core material are impregnated with a thermosetting resin and heated and cured in a mold, or a combination of these methods, and a thermoplastic resin pellet containing reinforcing short fibers or long fibers. Methods of preheating, injection, cooling, demolding, etc. are known (Japanese Patent Laid-Open No. 61-45780
JP-A-61-45782, JP-A-61-
167513).

[Problem to be solved]

Among conventional methods for manufacturing FRP racket frames, methods using thermosetting resins have a problem in that heating and curing takes a long time. One of the countermeasures is to shorten the curing time of thermosetting resin, but in that case,
There has been a problem that the shelf life (shell life) of prepreg is short and the gel time is short. Another countermeasure is to speed up the mold usage cycle by heating and curing in a short time that allows demolding, and post-curing in an oven after demolding. Although the heating time in the mold was short, no significant effect could be expected due to the post-curing time.

On the other hand, in the case of a method of preheating, injecting, cooling, and demolding thermoplastic resin pellets containing reinforcing short fibers or long fibers, the molding time can be significantly shortened, but the rigidity and strength of FRP are reduced. The stiffness required for the racket, due to very low
In order to develop strength, the wall must be made thicker, and there was a problem in that it could not meet the recent trend in rackets, which is the desire for slim-shaped and lightweight rackets.

Therefore, this invention addresses the problem of long-term curing of FRP that occurs when thermosetting resin is used, and the low rigidity and low strength of FRP that occurs when thermoplastic resin containing short fibers or long fibers is used. The purpose of the present invention is to solve the problems and provide a method for manufacturing a lightweight racket frame or a stick used for gateball, etc., which has high productivity, slim shape, high rigidity, and high strength.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes a step of coating the outer periphery of a core material with a layer of reinforcing continuous fibers, a step of setting the core material covered with the reinforcing continuous fibers in a mold, and a step of covering the outer periphery of a core material with a layer of reinforcing continuous fibers, A process consisting of the process of closing the mold and injecting or extruding the preheated and melted thermoplastic resin from an injection port attached to the mold, and the process of cooling and hardening the thermoplastic resin in the mold and removing it from the mold. It is.

[Effect]

In this invention, since the thermosetting resin FRP is not used, there is no problem regarding long-term hardening, and since the thermoplastic resin FRP containing short fibers or long fibers is not used, the slim shape and weight reduction are achieved. This eliminates the problems of low rigidity and low strength, and makes it possible to obtain racket frames and sticks with improved productivity, slim shape, light weight, rigidity, and strength.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the drawings.

First, as shown in FIG. 1, the outer periphery of the core material 1 is covered with a plurality of reinforcing continuous fiber layers 2, and then, as shown in FIG. Set in mold 3. The mold 3 is composed of a left mold 3 and a right mold 32, and the left and right molds 31 and 32 are configured to be openable and closable. The left mold 31 and the right mold 32 are closed, and the thermoplastic resin preheated and melted in the cylinder 5 is injected or extruded from the injection port 4 attached to the right mold 32, and then cooled and demolded.

As the core material 1, a synthetic resin foam, for example, a specific gravity of 0.0 is used.
4 to 0.1 polyurethane foam, acrylic foam, or a tube made of synthetic resin or elastomer is used.

Further, as the reinforcing continuous fiber layer 2, fibers such as glass, carbon, Kevlar (aramid), boron, silicon carbide, ceramic, alumina, etc. can be used alone or in combination. These continuous fibers may be used singly or in combinations of woven (cloth), knitted (knit), m'1Ji (braid), non-woven unidirectionally aligned (UD) fibers, and the like.

The reinforcing continuous fiber layer 2 coated on the outer periphery of the core material 1 and set in the mold 3 is not yet impregnated with resin. As shown in FIG. 3, as a means for covering the outer periphery of the core material 1 with the reinforcing continuous fiber layer 2, usable reinforcing continuous fibers 21 are wound around a plurality of bobbins 5, and a braider (knitting machine) is used. ), and the reinforcing continuous fibers 21 are knitted onto the core material 1 which has been cut into a length of 1.6 m in advance. In addition, as another covering means, as shown in Fig. 4, a unidirectional sheet-like material obtained by knitting or weaving reinforcing continuous fibers, or fixing in places with polymer material tape or adhesive is available. Wrap the core material 1 around the core material 1 with a piece (UD) etc. 22 that are aligned. As another covering means, as shown in FIG. 5, a tube-shaped article 23 may be prepared in advance from reinforcing continuous fibers, and the core material 1 may be inserted into this tube-shaped article 23.

To insert the core material 1 coated with the reinforcing continuous fiber layer 2 into the mold 3, insert the core material 1 into the mold 3 in a shape that follows the cavity of the mold 3.
, and if necessary, reinforcing continuous fibers N2 may be partially added to the necessary portions of the bent frame. After the core material 1 covered with the reinforcing continuous fiber layer 2 is set in the mold 3, the mold 3 is closed, and the preheated and melted thermoplastic is poured into the cylinder 5 through the injection port 4 attached to the mold 3. By injecting or extruding the resin, the resin is spread throughout the mold 3, and after impregnating the reinforcing continuous fiber layer 2 with the resin, it is cooled and demolded. At this time, by applying internal pressure before the resin cooling step, it is possible to obtain a resin layer with a uniform thickness and a molded product with no voids or sink marks on the surface. As a method of applying internal pressure, a method of using a foamable core material for the core material 1, a method of expanding a synthetic resin or elastomer tube with air, etc. can be adopted.

The thermoplastic resin injected into the mold 3 from the injection port 4 may be a homopolymer of polyphenylene oxide, a blend (alloy) with nylon or polystyrene resin, a liquid crystal polymer, polycarbonate, an acetal resin, or acrylonitrile-butadiene-styrene. It is desirable to use a thermoplastic resin that is a copolymer or the like and has a low viscosity in a molten state and is excellent in moldability of thin portions and impregnation into the reinforcing continuous fiber layer 2. Furthermore, reinforcing short fibers, long fibers, fillers, etc. can be included in advance in these thermoplastic resin pellets, etc., but this increases the viscosity in the molten state and improves the formability and reinforcement of thin parts. This is not necessarily preferable since it tends to impede impregnation into the continuous fiber layer 2.

In addition, as a manufacturing method using FRP consisting of a combination of the reinforcing continuous fiber layer 2 and a thermoplastic resin, a so-called prepreg in which the reinforcing continuous fibers are pre-impregnated with a thermoplastic resin, as is usually done in the case of thermoplastic resins, is used. The method of laminating a large number of sheets around the outer periphery of a core material was extremely difficult because, unlike thermosetting resins, prepregs are extremely rigid. One solution to this problem is that even though it is possible to preheat and semi-melt the prepreg to reduce its rigidity, it cools down to near room temperature while being laminated around the outer periphery of the core material, causing the rigidity to recover. Another countermeasure is to laminate multiple sheets of prepreg made of thermoplastic resin with relatively low melting and softening temperatures around the core material at temperatures close to the limits of lamination work, and then heat them in a mold. A product was obtained by molding, cooling, and demolding, but there was a problem that it would become heated and deformed in the trunk of a car during the summer.

In the illustrated embodiment, the manufacturing of a racket frame has been described, but it is of course possible to manufacture a stick for gateball or the like in this manner.

〔effect〕

As explained above, according to the present invention, the problem of long-time curing in thermosetting resins is solved, and since FRP, which is a thermoplastic resin containing short fibers or long fibers, is not used, the invention has a slim shape and is lightweight. This eliminates the problems of low rigidity and low strength that occur when the product is used, and improves productivity as well as lightness, rigidity, and strength with a slim shape. In addition, unlike those using prepreg, even non-experts can easily set the mold, and fiber layers can be added partially to areas that require modification during mold setting, making work easier. In addition, productivity is improved and finishing accuracy is also excellent.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the core material covered with a reinforcing fiber layer, Figure 2 is a perspective view showing the core material shown in Figure 1 placed in a mold, and Figure 3 is the same as Figure 1. FIG. 4 is a perspective view showing another means for making the thing shown in FIG. 1, and FIG. 5 shows still another means for making the thing shown in FIG. 1. FIG. 1...Core material, 2...Continuous fiber layer for reinforcement, 3...Mold, 4...Inlet. Applicant Brideston Co., Ltd. Agent Patent Attorney Masu 1) Takeo

Claims (1)

[Claims] 1. A step of coating the outer periphery of the core material with a layer of reinforcing continuous fibers, a step of setting the core material coated with the reinforcing continuous fibers in a mold, and closing the mold. Manufacturing of racket frames or sticks consists of a process of injecting or extruding preheated melted thermoplastic resin from an injection port attached to the mold, and a process of cooling and hardening the thermoplastic resin in the mold and removing it from the mold. Method.