The invention relates to blow molding of an article having an inwardly projecting hollow boss with a closed end. A portion of a molten parison conforms to the shape of a fixed pin projecting from the face of a mold part to thereby form the hollow boss. The invention includes an apparatus comprising a...http://www.google.es/patents/US6605247?utm_source=gb-gplus-sharePatente US6605247 - Blow molding process
