Method of manufacturing resin retainer having two annular sections

A method of manufacturing a resin retainer having two annular sections, by injection molding,

• the retainer having a shape in which annular sections in pair, which are separated from each other in an axial direction, are connected by a plurality of columns provided in a circumferential direction of the annular sections at an equal interval,
• the injection molding being performed using an injection molding die that includes:
• a fixed-side cavity forming mold;
• a movable-side cavity forming mold;
• and
• slide cores,
• the fixed-side cavity forming mold having:
• a first axial mold surface that is in contact with an axial end surface of a first annular section of the annular sections of the retainer;
• and a first protruding portion protruding from the first axial mold surface,
• the movable-side cavity forming mold having:
• a second axial mold surface that is in contact with an axial end surface of a second annular section of the annular sections of the retainer;
• and a second protruding portion protruding from the second axial mold surface,
• one of the fixed-side cavity forming mold and the movable-side cavity forming mold having an inner periphery molding surface that is in contact with an inner peripheral surface of the retainer, and
• each of the slide cores, which has:
• an outer periphery molding surface that is in contact with an outer peripheral surface of the retainer;
• and a pocket-forming protruding portion for forming a pocket between the columns adjacent to each other,
• the method comprising:
• a molten resin material charging step of charging a molten resin material in a cavity of the injection molding die for molding the resin retainer, after the fixed-side cavity forming mold, the movable-side cavity forming mold, and the slide core are closed and clamped;
• a molten resin material cooling step of cooling and solidifying the molten resin material that has been charged in the cavity in the molten resin material charging step;
• a slide core sliding step of sliding the slide cores in a radially outward direction to extract the pocket-forming protruding portions of the slide cores from the pockets of the resin retainer in a state where a parting surface between the fixed-side cavity forming mold and the movable-side cavity forming mold is not opened, after the molten resin material charging step and the molten resin material cooling step are performed;
• a mold opening step of opening the parting surface by moving the movable-side cavity forming mold relative to the fixed-side cavity forming mold, after the slide core sliding step is performed;
• and
• a molded article taking-out step of taking the resin retainer molded in the cavity of the injection molding die out from the injection molding die, after the mold opening step is performed.