Undercut processing mechanism

An undercut processing mechanism (30) in a molding device (1) for molding an article (P) to be molded with a stationary mold (11) and a movable mold (14), the molded article (P) having an undercut portion (P3) formed inside it in a circumferential direction thereof at a time of punching out the molded article (P) and brought to a detachable state, comprising:

• an undercut mold core (60) comprising plural split cores (61) that line one another in an entire circumferential direction to correspond in position to an inner peripheral surface of the undercut portion (P3), the split cores (61) comprising inner split cores (61a) and outer split cores (61b) formed to line alternately, the inner split cores (61a) abutting on one another and formed on an inner side and the outer split cores (61b) coming close to one another along an outer side of the inner split cores (61a) when the split cores (61) have been reduced in diameter toward an center axis of the undercut portion (P3);
• slide members (50) radially disposed and opposed to the center axis of the undercut portion (P3) in a state in which each of the slide members (50) supports each of the split cores (61) of the undercut mold cores (60) on a leading end thereof;
• a holder (40) provided integrally with the stationary mold (11) or movable mold (14) for housing the slide members (50) slidably between a molding position at which the split cores (61) supported on the leading ends of the slide members (50), respectively, line one another in the entire circumferential direction and a demolding position at which the split cores (61) are reduced in diameter one another toward the center axis of the undercut portion (P3);
• and
• guide means (46) disposed in the holder (40) for guiding, at the time of punching out the molded article (P), the slide members (50) to move simultaneously in a punching-out direction parallel to the center axis of the undercut portion (P3) and in a direction escaping from the undercut portion (P3) toward the center axis of the undercut portion (P3), respectively, along an inclination direction from the molding position to the demolding position.