Thermoplastic pre-forms which are obtained as a result of expansion of parisons in a pre-form blow mold are transformed into bottles or analogous hollow shaped articles in a final blow mold. The first stage of transformation involves mechanical stretching of the pre-form in the cavity of the final mold...http://www.google.es/patents/US4177239?utm_source=gb-gplus-sharePatente US4177239 - Blow molding method
