Method and apparatus for forming articles from plastic sheet material

Claim 1

A METHOD OF FABIRCATING DEEP DRAWN HOLLOW ARTICLES FROM THERMOPLASTIC RESING SHEETS WHICH COMPRISES CLAMPING A TERMOPLASTIC SHEET IN A FRAME, SOFTENING THE SHEET BY HEATING, PRELIMINARLY SHEET IN A FRAME, SOFTENING DRAWING THE SOFTENED SHEET THROUGH APPLICATION OF DIFFERENTIAL PRESSURE ONTO A MALE DIE HAVING A SHAPE APPROXIMATING THE DESIRED FINAL SHAPE OF THE ARTICLE AND HAVING EXTERNAL DIMENSIONS SOMEWHAT SMALLER THAN THE INTERNAL DIMENSIONS OF A CO-OPERATING FEMALE DIE, THE DIES BEING INITIALLY POSITIONED ADJACENT OPPOSITE SIDES OF THE SHEET AND THE MALE DIE HAVING A RECESS IN THE AREA WHICH IS IN OPPOSITELY DISPOSED SPACED RELATION RELATIVE TO THE RIM OF THE CO-OPERATING FEMALE DIE WHEN THE MALE DIE IS FULLY INSERTED IN THE FEMALE DIE AND INTO WHICH RECESS A PORTION OF THE SOFTENED SHEET US DRAWN, MOVING THE MALE AND FEMALE DIES RELATIVE TO EACH OTHER TO POSITION THE PORTION OF THE SHEET FOR FORMING THE ARTICLE IN THE CAVITY IN THE FEMALE DIE WHILE IT IS SUPPORTED ON HE MALE DIE, WITH THE PRELIMINARILY FORMED WHEET INCLUDING THE PORTION THEREOF WHICH HAS BEEN DRAWN INTO THE RECESS IN TYE MALE DIE BEING HELD OUT OF CONTACT WITH THE RIM OF THE FEMALE DIE SO AS TO AVOID PREMATURE CHILLING WHICH WOULD RESULT IN NON-UNIFORM STRETCHING OF THE ARTICLE FORMING PORTION OF THE SHEET, FORCING THE STILLSOFT SHEET INTO CONTACT WITH THE INTERIOR WALL DEFINING THE CAVITY IN THE FEMALE DIE BY DIFFERENTIAL PRESSURE SO AS TO EFFECT SUBSTANTIALLY INSTANTANEOUS TRANSFER OF ALL PARTS OF THE PRELIMINARILY DRAWN SHEET, AND COOLING THE SHEET TO SET THE RESIN WITH THE ARTICLE FORMING PORTION OF THE SHEET HAVING THE FINAL SHAPE OF THE CAVITY IN THE FEMALE DIE.

Claim 2

A METHOD OF FABIRCATING DEEP DRAWN HOLLOW ARTICLES FROM THERMOPLASTIC RESING SHEETS WHICH COMPRISES CLAMPING A TERMOPLASTIC SHEET IN A FRAME, SOFTENING THE SHEET BY HEATING, PRELIMINARLY SHEET IN A FRAME, SOFTENING DRAWING THE SOFTENED SHEET THROUGH APPLICATION OF DIFFERENTIAL PRESSURE ONTO A MALE DIE HAVING A SHAPE APPROXIMATING THE DESIRED FINAL SHAPE OF THE ARTICLE AND HAVING EXTERNAL DIMENSIONS SOMEWHAT SMALLER THAN THE INTERNAL DIMENSIONS OF A CO-OPERATING FEMALE DIE, THE DIES BEING INITIALLY POSITIONED ADJACENT OPPOSITE SIDES OF THE SHEET AND THE MALE DIE HAVING A RECESS IN THE AREA WHICH IS IN OPPOSITELY DISPOSED SPACED RELATION RELATIVE TO THE RIM OF THE CO-OPERATING FEMALE DIE WHEN THE MALE DIE IS FULLY INSERTED IN THE FEMALE DIE AND INTO WHICH RECESS A PORTION OF THE SOFTENED SHEET US DRAWN, MOVING THE MALE AND FEMALE DIES RELATIVE TO EACH OTHER TO POSITION THE PORTION OF THE SHEET FOR FORMING THE ARTICLE IN THE CAVITY IN THE FEMALE DIE WHILE IT IS SUPPORTED ON HE MALE DIE, WITH THE PRELIMINARILY FORMED WHEET INCLUDING THE PORTION THEREOF WHICH HAS BEEN DRAWN INTO THE RECESS IN TYE MALE DIE BEING HELD OUT OF CONTACT WITH THE RIM OF THE FEMALE DIE SO AS TO AVOID PREMATURE CHILLING WHICH WOULD RESULT IN NON-UNIFORM STRETCHING OF THE ARTICLE FORMING PORTION OF THE SHEET, FORCING THE STILLSOFT SHEET INTO CONTACT WITH THE INTERIOR WALL DEFINING THE CAVITY IN THE FEMALE DIE BY DIFFERENTIAL PRESSURE SO AS TO EFFECT SUBSTANTIALLY INSTANTANEOUS TRANSFER OF ALL PARTS OF THE PRELIMINARILY DRAWN SHEET, AND COOLING THE SHEET TO SET THE RESIN WITH THE ARTICLE FORMING PORTION OF THE SHEET HAVING THE FINAL SHAPE OF THE CAVITY IN THE FEMALE DIE.