Die apparatus for forming hollow plastic structure

Claim 1

A STAMPING ASSEMBLY COMPRISING, IN COMBINATION, A PAIR OF COOPERATING DIE MEMBERS SUPORTED TO BE MOVED TOWARD AND AWAY FROM EACH OTHER, A SHEET CARRYING AND CLAMPING FRAME REMOVABLY SUPPORTED BETWEEN SAID DIE MEMBERS, SAID FRAME COMPRISING COOPERATING FRAME MEMBERS COUPLED TOGETHER TO BE MOVED APART TO RECEIVE THEREBETWEEN IN SPACED RELATIONSHIP TWO PLASTIC SHEETS; MEANS OPERABLE TO HOLD SAID FRAME MEMBERS TOGETHER TO GRIP AND SUPPORT THEREBETWEEN TWO HEATED PLASTIC SHEETS IN SPACED-APART SUBSTANTIAL PARALLELISM SAID DIE MEMBERS HAVING ASSOCIATED THEREWITH MEANS ADAPTED TO SUPPORT SAID FRAME WITH SPACED OPPOSED AREAS OF SAID SHEETS SURROUNDED BY SAID FRAME DISPOSED BETWEEN SAID TWO DIE MEMBERS IN THE LINE OF MOVEMENT OF SAID DIE MEMBERS RELATIVE TO EACH OTHER WHEREBY OPPOSED AREAS OF SAID SHEETS ARE URGED AND SEALED TOGETHER AT PREDETERMINED POINTS WITHIN THE BOUNDARY OF SAID FRAME MECHANISM OPERABLE TO CREATE A DIFFERENTIAL IN AIR PRESSURE WITHIN THE SPACE BETWEEN THE TWO PLASTIC SHEETS AND THE OUTER FACES OF THE SHEETS OPOSED TO THE WORKING FACES OF THE DIE MEMBERS TO CAUSE OPPOSED AREAS OF THE SHEETS WITHIN THE FRAME TO BE HELD APART AND AGAINST THE FACES OF THE DIE MEMBERS TO FORM A HOLLOW PLASTIC STRUCTURE.