Molten Corporation

Hajime Okimoto

Hideomi Shishido

Shigeo Doi

Masanori Hirakiuchi

A method for making a ball for sports comprises providing a round rubber tube, forming a reinforcing layer of a yarn wound about the tube, forming a rubber cover layer formed on the reinforcing layer, and vulcanizing the rubber cover layer to provide a carcass. In the method, the reinforcing layer is formed by winding, in combination, a covered yarn made of a urethane elastomer core thread wound thereabout with a synthetic resin filament or in combination with the synthetic resin filament and a yarn made of a member selected from the group consisting of cotton, polyesters and polyamides. The carcass may be attached with a skin layer made of a natural or artificial leather. Alternatively, the round rubber tube having the reinforcing layer may be attached with a skin layer.

Method for making balls for sports

A molding apparatus for injection-molding a hemispherical hollow body formed of a thermoplastic elastomer and having a valve formed integrally therewith. The apparatus includes a first mold having a hemispherical convex molding surface, a second mold having a hemispherical concave molding surface larger in size than the convex molding surface. The second mold is superposed on the first mold to form a molding cavity for the hollow body. A first valve mold is removably mounted at the center of the hemispherical convex molding surface of the first mold, for forming the valve and an inside and small-diameter portion of a valve rubber insertion hole of the valve. A second valve mold is removably mounted at the center of the hemispherical concave molding surface, for forming an intermediate and large-diameter portion of the valve rubber insertion hole and an outside and small-diameter portion thereof while forming a cavity for the valve in cooperation with the first valve mold. The second valve mold includes a diametrically-enlarged portion provided at a lower end of the second valve mold for downwardly pushing the formed hollow body when the second valve mold is engaged to the second mold after the second valve is removed from the second mold.

Ball for ball game and molding apparatus for forming the same

A ball for ball game, comprising a base body composed of two hemispherical hollow bodies formed by injection-molding a thermoplastic elastomer and bonded together to form a spherical hollow body, said base body containing and sealing compressed air injected therein through an air-injection valve provided at an appropriate portion of one of said two hemispherical hollow bodies, and a plurality of leather panels bonded by means of an adhesive to the surface of said base body, wherein a 10% tensile stress of said thermoplastic elastomer forming said base body ranges from 30 to 190 kg/cm.sup.2. Various properties of said ball such as shock-absorptivity, shape-maintaining property, impact resilience and the like can be set within appropriate ranges.

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Hiroshima, Japan

Hajime Okimoto