Method of manufacturing resin boot for constant-velocity universal joint

A manufacturing method in which a boot main body primarily molded of a resin is held in an injection mold, a molten resin material is injected/charged in a secondary molding space formed in the injection mold in this state, portions having different thicknesses are secondarily molded on an other-end annular fastening portion of the boot main body to constitute a boot for a constant-velocity universal joint, formed of the resin, and thereafter the boot for the constant-velocity universal joint, formed of the resin, can be removed from the injection mold, the manufacturing method comprising the steps of:

• holding the primarily molded resin boot main body from the outside by divided molds;
• holding the boot main body from the inside by a core;
• injecting/charging a molten resin material into a secondary molding space constituted of a thick portion molding space and a thin portion molding space formed between the core and the other-end annular fastening portion, between the divided molds and the other-end annular fastening portion, or between the core and the divided molds via the other-end annular fastening portion by a runner mechanism;
• and
• removing, from the core, the resin boot for the constant-velocity universal joint in which the molten resin material is charged into the secondary molding space to integrally and secondarily mold portions having different thicknesses, constituted by combining a thickness of the molten resin material in the secondary molding space with that of the boot main body, on the other-end annular fastening portion by an ejection mechanism,
• the runner mechanism being provided with injecting/charging gates for injecting/charging the molten resin materials onto optional one or a plurality of positions of the secondary molding space,
• the ejection mechanism being provided with a plurality of ejectors in positions avoiding the injecting/charging gates of the runner mechanism, wherein predetermined ejecting forces are applied onto lower end surfaces of the portions having different thicknesses in the other-end annular fastening portion of the resin boot for the constant-velocity universal joint from the plurality of ejectors to remove the resin boot for the constant-velocity universal joint from the core.