Method and apparatus for blow molding hollow thermoplastic articles

Claim 1

A PROCESS FOR BLOW MOLDING HOLLOW TUBULAR PLASTIC ARTICLES, COMPRISING THE STEPS OF: EXTRUDING A TUBULAR THERMOPLASTIC PARISON AND LOCATING IT BETWEEN A PAIR OF OPENED MOLD HALVES AND IN SURROUNDING RELATIONSHIP TO A BLOW PIN; CLOSING SAID MOLD HALVES TO PRESS ONE END OF THE PARISON INTO TIGHT CONFORMING RELATIONSHIP TO THE EXTERIOR OF THE BLOW PIN AND TO PINCH CLOSED THE OTHER END OF SAID PARISON; INTRODUCING BLOWING AGENT THROUGHSAID BLOW PIN TO EXPAND SAID PARISON OUTWARDLY AND INTO CONTACT WITH THE INTERIOR WALLS OF SAID MOLD HALVES; CLOSING THE END OF SAID PARISON ADJACENT SAID BLOW PIN TO SEAL OFF COMMUNICATION BETWEEN SAID BLOW PIN AND THE INTERIOR OF SAID PARISON; PINCHING SAID EXPANDED PARISON ALONG A LINE COINCIDING WITH THE SURFACE OF THE MOLD, SAID PINCHING STEP PRODUCING A RELATIVELY THIN WEB SEPARATING SAID EXPANDED PARISON FROM THE PORTION OF SAID PARISON TO CONTACT WITH SAID BLOW PIN;