Method for making integral containers having precisely parallel vertical walls

Claim 1

A METHOD OF FORMING, FROM THERMOPLASTIC MATERIAL CHARACTERIZED BY SHRINKAGE WHICH CONTINUES DURING THE COOLING AND SETTING PROCESS, AN INTEGRAL CONTAINER HAVING PRECISELY PARALLEL VERTICAL WALLS COMPRISING THE STEPS OF: SELECTING A SHEET OF THERMOPLASTIC MATERIAL; PREHEATING AT LEAST A PORTION OF SAID SHEET OF MATERIAL; PREHEATING A FEMALE DIE; HEATING A MALE DIE TO A PRESELECTED TEMPERATURE AND THEREAFTER MAINTAINING THE MALE DIE AT SAID TEMPERATURE; MOVING THE PREHEATED MATERIAL AND FEMALE DIE RELATIVE TO ONE ANOTHER TO BRING THE MATERIAL INTO CONTACT WITH THE PERIPHERY OF THE FEMALE DIE; VACUUM DRAWING THE MATERIAL INTO THE FEMALD DIE; LOWERING THE MALE DIE INTO THE FEMALE DIE TO PRESS THE MATERIAL BETWEEN THE MALE AND FEMALE DIES ABOUT THE PERIPHERY OF THE FEMALE DIE TO THEREBY FORM A CONTAINER RIM OF INCREASED THICKNESS AND DENSITY; FLUID PRESSURE FORMING THE MATERIAL WITHIN THE FEMALE DIE AND THE MALE DIE; DELIVERING COOLING FLUID TO THE INTERIOR OF THE FEMALE DIE TO COOL EXPOSED PORTIONS OF THE MATERIAL WHICH ARE IN CONTACT WITH THE MALE DIE, THE MATERIAL IN THE REGION OF THE CONTAINER RIM BEING PROTECTED FROM THE COOLING FLUID BY BEING COMPRESSED BETWEEN THE HEATED MALE AND THE FEMALE DIES, THE MATERIAL IN THE REGION OF THE CONTAINER RIM THEREBY REMAINING IN AN EXPANDED AND SOFTENED CONDITION; AND STRIPPING THE THUS FORMED CONTAINER FROM THE MALE DIE AND ALLOWING THE RIM REGION THEREOF TO SET.

Claim 2

A METHOD OF FORMING, FROM THERMOPLASTIC MATERIAL CHARACTERIZED BY SHRINKAGE WHICH CONTINUES DURING THE COOLING AND SETTING PROCESS, AN INTEGRAL CONTAINER HAVING PRECISELY PARALLEL VERTICAL WALLS COMPRISING THE STEPS OF: SELECTING A SHEET OF THERMOPLASTIC MATERIAL; PREHEATING AT LEAST A PORTION OF SAID SHEET OF MATERIAL; PREHEATING A FEMALE DIE; HEATING A MALE DIE TO A PRESELECTED TEMPERATURE AND THEREAFTER MAINTAINING THE MALE DIE AT SAID TEMPERATURE; MOVING THE PREHEATED MATERIAL AND FEMALE DIE RELATIVE TO ONE ANOTHER TO BRING THE MATERIAL INTO CONTACT WITH THE PERIPHERY OF THE FEMALE DIE; VACUUM DRAWING THE MATERIAL INTO THE FEMALD DIE; LOWERING THE MALE DIE INTO THE FEMALE DIE TO PRESS THE MATERIAL BETWEEN THE MALE AND FEMALE DIES ABOUT THE PERIPHERY OF THE FEMALE DIE TO THEREBY FORM A CONTAINER RIM OF INCREASED THICKNESS AND DENSITY; FLUID PRESSURE FORMING THE MATERIAL WITHIN THE FEMALE DIE AND THE MALE DIE; DELIVERING COOLING FLUID TO THE INTERIOR OF THE FEMALE DIE TO COOL EXPOSED PORTIONS OF THE MATERIAL WHICH ARE IN CONTACT WITH THE MALE DIE, THE MATERIAL IN THE REGION OF THE CONTAINER RIM BEING PROTECTED FROM THE COOLING FLUID BY BEING COMPRESSED BETWEEN THE HEATED MALE AND THE FEMALE DIES, THE MATERIAL IN THE REGION OF THE CONTAINER RIM THEREBY REMAINING IN AN EXPANDED AND SOFTENED CONDITION; AND STRIPPING THE THUS FORMED CONTAINER FROM THE MALE DIE AND ALLOWING THE RIM REGION THEREOF TO SET.