Forming openings into hollow chambers in plastic moldings produced by gas injection

摘要

An opening can be formed in an end of a molding by a tool insert (6) which moves forward through the molding wall into the gas-formed hollow cavity (8) where it forces the still-molten purged material onto the adjacent molding sidewall. An opening can also be produced in the molding sidewall by a further tool insert (5) which moves forward to punch an area (10) out of the wall and press the punched part onto the opposing wall. Preferred Features: Tool inserts (6) for forming openings in the ends of moldings are mandrels with pointed ends which can penetrate the molding wall and move into the hollow chamber (8). The end of the mandrel is completely enclosed by melt before being moved forward and purged melt pushed onto the sidewall may be used to seal the gas injection opening. The mandrel is completely retracted after melt solidification to allow demolding. The tool insert (5) for forming openings in the molding sidewall is a pin whose head is flush with the molding cavity wall or projects into the cavity. Forward movement of the pin breaks through the thin solidified skin of a molding and removes an area of the wall. The punched out area can again be used to seal the gas injection point. Inserts for forming openings with internal threads or undercuts comprise pointed mandrels or pins moving inside sleeves (7) or collapsible cores whose outer profile forms the thread or undercut. Openings may be produced by inserts which are pressed in by mandrel or core and remain in or on the molding.