Method for producing shaped multilayer bodies

Claim 1

IN A METHOD OF PRODUCING A CURVED SHAPED UNITARY BODY OF PREDETERMINED CONFIGURATION, THE STEPS OF FORMING A STACK COMPRISING AT LEASE TWO SOLID THERMOPLASTIC COVER SHEETS AND AT LEAST ONE CELLULAR THERMOPLASTIC SHEET INTERPOSED BETWEEN SAID COVER SHEETS, WITH LAYERS OF LATENTLY ADHESIVE MATERIAL RESPECTIVELY, INTERPOSED BETWEEN ADJACENT THERMOPLASTIC SHEETS, SAID LATENTLY ADHESIVE MATERIAL BEING ADAPTED TO BECOME ACTIVELY ADHESIVE AT THE MOLDING TEMPERATURE OF SAID THERMOPLASTIC SHEETS; GRIPPING SAID STACK ALONG AN ANNULAR PORTION THEREOF BUT LIGHTLY, SO AS TO HOLD SAID SHEETS OF SAID STACK TOGETHER WHILE PERMITTING SLIDING MOVEMENT OF SAID SHEETS RELATIVE TO EACH OTHER UNDER THE INFLUENCE OF DIFFERENT LATERAL TENSION EXERTED ON SAID ANNULAR PORTIONS OF SAID SHEETS, RESPECTIVELY, SO THAT DUE TO SAID SLIDING MOVEMENT OF SAID GRIPPED SHEET PORTIONS STRETCHING OF THE RESPECTIVE SHEETS WILL BE EVEN THROUGHOUT THE TENSIONED PORTIONS THEREOF AND THE SAME WILL BE OF EVEN CROSS-SECTIONAL DIMENSIONS; AND SUBJECTING THE PORTION OF SAID STACK SURROUNDED BY SAID GRIPPED ANNULAR PORTION TO DEEP DRAWING TO SAID PREDETERMINED CONFIGURATION AT THE MOLDING TEMPERATURE OF SAID THERMOPLASTIC SHEETS,THEREBY ACTIVATING SAID LATENTLY ADHESIVE LAYER AND EXERTING DIFFERENT TENSION ON THE GRIPPED ANNULAR PORTIONS OF SAID SHEETS, RESPECTIVELY, CAUSING DIFFERENT LATERAL SLIDING MOVEMENT OF SAID ANNULAR PORTIONS OF SAID SHEETS, RESPECTIVELY, INWARDLY TOWARD THE PORTION THEREOF WHICH IS SUBJECTED TO DEEP DRAWING, THEREBY SUBSTANTIALLY PREVENTING DISTORTION OF THE CROSS SECTIONAL DIMENSIONS OF SAID SHEETS DURING DEEP DRAWING OF THE SAME.