Patent ID: 7531119

Claim:
A method of manufacturing a boot for a constant-velocity universal joint, the boot having a plurality of thick portions adapted to concave portions of a casing of a tripod joint and formed to protrude toward a center direction and a plurality of thin portions formed between adjacent thick portions, the method comprising the steps of: preparing a primary molded member having a large-diameter side end portion, a small-diameter side end portion, a bellows portion formed between the large-diameter side end portion and the small-diameter side end portion and constituted of repeatedly arranged large-diameter portions and small-diameter portions, and a tapered portion formed between the large-diameter side end portion and the small-diameter portion in a vicinity of the large-diameter side end portion in the bellows portion, holding the small-diameter portion in the vicinity of the large-diameter side end portion between an inner peripheral surface of a mold disposed in an outer peripheral side of the primary molded member and an outer peripheral surface of a core mold disposed in the large-diameter side end portion, forming a secondary molding space constituted of a thick portion molding space molding the thick portion and a thin portion molding space molding the thin portion between a large-diameter side end portion inner peripheral surface of the primary molded member and a core mold outer peripheral surface, injecting a molten material to the secondary molding space; and molding a secondary molded portion constituting the plural thick portions and the plural thin portions on the large-diameter side end portion of the primary molded member, the step of injecting the molten material to the secondary molded portion including the steps of: a first step for applying a pressure of the molten material injected into the secondary molding space to an inner surface of the tapered portion of the primary molded member; a second step for expanding the tapered portion compressed in a thickness direction by the pressure of the molten material toward a direction of the small-diameter portion; and a third step for pressure-contacting the small-diameter portion held between the mold inner peripheral surface and the core mold outer peripheral surface onto the core mold outer peripheral surface by the expanding of the tapered portion.