JPH0634845B2 - Method for manufacturing fiber-reinforced plastic bat - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bat used for baseball, softball, etc., and relates to a method for producing a durable bat.

(Prior Art) In recent years, a baseball bat made of reinforced plastic or a bat for softball has sufficient strength in a grip portion, a hitting portion, and the like and has a good quality and a well-balanced bat. Various configurations have been attempted for the purpose of obtaining.

For example, as shown in Japanese Examined Patent Publication No. 49-28614 shown in FIG. 6, using a tube 12 having an uneven wall thickness of an arbitrary material as a base, the reinforced plastic layer 6 is also thick at the portion that is hit by a hit ball, and the impact is directly received. The non-uniform portion has a non-uniform hollow so that the non-existing portion has a thin wall structure or JP-A-53-
As shown in 19231, it has a bat shape of a thermoplastic resin, and a resin-impregnated glass fiber is wrapped around the outer periphery of a hollow core material provided with an air supply pipe, and hot-press molding is performed with a mold, and compressed air is compressed into air. It is known that a glass fiber fed from a supply pipe and wound around the outer periphery of the core material is brought into close contact with a mold by air pressure to form an ERP layer of a bat.

(Problems to be Solved by the Invention) These conventional methods have the following problems.

That is, the former tube 12 having a non-uniform wall thickness is used as a base body, the outer periphery thereof is formed into a bat shape with the reinforced plastic layer 6, and the inside has a hollow having an unequal inner diameter, so that the reinforced plastic layer 6 also has an unequal wall thickness. In the case of molding the bat, when the internal pressure is applied by injecting compressed air or the like into the hollow portion inside the bat to form the bat, the internal shape is not uniform, and the wall thickness of the tube is also uneven, The thick part of the tube is difficult to spread due to the internal pressure, and the pressure may concentrate on the thin part to break, so it is difficult to apply the internal pressure evenly to the whole, and the shape of the process of arranging the fibers on the outer periphery of the tube is complicated. Therefore, there are drawbacks such that it is troublesome to dispose and the cost is high. Further, in the latter case where a bat-shaped hollow core material is formed from a thermoplastic synthetic resin and glass fibers are wound around the outer periphery of the core material to be molded, the hollow core material must be molded in advance. Therefore, the hollow core material needs to have a thickness such that it is softened by being heated and an internal pressure is applied.Therefore, the thickness must be naturally reduced. When it is wound, since sufficient rigidity cannot be obtained, sufficient tension cannot be applied to cover it, and the glass fiber may become wrinkled inside. If the FRP layer is thin, it is easy to tear and therefore the internal pressure is not evenly applied. If the FRP layer is thick, the thermosetting synthetic resin forming the glass fiber layer and the thermoplastic forming the hollow core material are used. Synthetic resins are difficult to mix and cause concentration of stress due to impact, which has a drawback that the strength as a bat decreases.

(Means for Solving Problems) In view of these conventional drawbacks, the present invention relates to a method for forming a bat having excellent workability and durability.

To explain the features of the present invention with reference to the drawings, the bat 1 of the present invention shown in FIG. 1 is used for forming a bat outer shell made of a prepreg on the outer periphery of a mandrel 7 having a substantially bat shape in advance as shown in FIG. After arranging the material 3, the mandrel 7 is extracted to make it hollow, and the tube 2 of an arbitrary material having elasticity is inserted into the hollow portion, and then arranged in the mold 4 having a desired bat shape. After tightening, a gas or liquid such as compressed air 5 is injected into the tube 2, the tube is expanded, and the bat outer shell molding material 3 is subjected to thermocompression molding along the mold with internal pressure to form a bat. In the method, the tube 2 is characterized in that it has a double structure in which two tubes are superposed as shown in FIG.

The material of the tube may be a tube made of a thermoplastic synthetic resin such as natural rubber, nylon, polyester, polyethylene, polypropylene, or polyvinyl chloride, or may be a laminate of these materials.

(Function) According to the method of the present invention, when a bat is molded by internal pressure using a tube having elasticity, the tube is doubled so that the bat outer shell molding material has adhesiveness and the like. Even if the outer tube in contact with the bat outer shell molding material is broken, the inner tube is present, so there is no fear of compressed air leaking. Since the thickness can be used effectively enough, pressure is applied evenly over the entire bat during molding, and there is no concern that the outer shell layer of the bat will be non-uniform, and a bat with good quality and excellent durability should be formed. You can Further, since the tube has a simple structure in which two tubes are superposed on each other, it can be easily manufactured and has good workability.

(Effect of the Invention) In the method for producing a bat by the internal pressure of the present invention,
While expanding the tube, the bat outer shell molding material is heated and pressed so that the bat outer shell molding material follows a mold having a bat shape. Therefore, the tube is exposed to heat and pressure and is also in contact with the molding material resin. In addition, the shape of the bat differs greatly between the hitting part and the grip part (the maximum diameter part is about 4 times the minimum diameter part), and if the tube is made too thick, it will not spread easily in the bat shape, and it will be too thin. However, it is necessary that the resin be strong enough to withstand the adhesiveness of the molding resin.
Since the base tube is doubled, the thickness can be such that the internal pressure effectively acts, and the outer tube that is in direct contact with the bat outer shell molding material is placed on the outer circumference of the tube. Even if the outer shell molding material is torn by adhesiveness such as resin or wrinkles are formed, compressed air leaks during thermocompression molding after placing it in the mold and compressed air leaks and molding fails Because of the wrinkles, it is possible to prevent that the internal pressure is not evenly applied to the entire inside of the bat during molding with a mold, and a bat having a uniform thickness and high durability can be obtained.

[Brief description of drawings]

1 to 5 are views for explaining the method of the present invention, and FIG. 6 is a view for showing one conventional method. 1: Vat, 2, 12: Tube, 3: Bat outer shell molding material, 4: Mold, 5: Compressed air, 6: Reinforced plastic layer, 7: Mandrel.

Claims (1)

[Claims] 1. A bat outer shell molding material composed of a prepreg is provided on the outer periphery of a substantially bat-shaped mandrel, the mandrel is extracted to make it hollow, and a tube made of an arbitrary material having elasticity is inserted into the hollow part. Then, after placing in a mold having a desired bat shape and clamping the mold, gas or liquid is injected into the tube, the tube is expanded, and the bat outer shell molding material is spread along the mold by internal pressure. A method for producing a bat made of fiber reinforced plastics, characterized in that the tube is doubled in the method for producing a bat by thermocompression molding.