Method of making rigid laminate of thermoplastic sheets having increased load-bearing ability

Claim 1

A METHOD OF MAKING A LAMINATE OF RIGID THERMOPLASTIC HEAT-FORMABLE SHEET MATERIAL COMPRISING PROVIDING A LEAST TWO SHEETS OF SUCH RIGID THERMOPLASTIC MATERIAL, PLACING ON A SURFACE OF ONE SUCH SHEET AT A PRESELECTED AREA A LAYER OF PARTING MATERIAL, DISPOSING AN AIR-COMDUCTING MEANS ON THE SHEET LEADING FROM THE PARTING MATERIAL TO THE EDGE OF THE SHEET, ASSEMBLING THE TWO THERMOPLASTIC SHEETS IN FACE-TO-FACE RELATIONSHIP WITH THE PARTING MATERIAL AND AIR-CONDUCTING MEANS SANDWICHED BETWEEN THE THERMOPLASTIC SHEETS, APPLYING HEAT AND PRESSURE TO UNITE THE THERMOPLASTIC SHEET TOGETHER AT THEIR CONTACTING FACES, HEATING THE RESULTING LAMINATE TO A TEMPERATURE AT WHICH THE THERMOPLASTIC MATERIAL CAN READILY BE DRAWN INTO A DESIRED SHAPE, DISPOSING THE THUSHEATED LAMINATE BETWEEN MOLD MEMBERS WHICH CONFINE THE LAMINATE AGAINST OUTWARDLY EXPANSION EVERYWHERE EXCEPT AT THE AREA OF SAID PARTING LAYER, AT WHICH AREA AT LEAST ONE OF THE MOLD MEMBERS IS PROVIDED WITH AN ENLARGED CAVITY, AND APPLYING DIFFERENTIAL PRESSURE TO THE HEATED LAMINATE TO PRODUCE A THERMOPLASTIC DEFORMATION OF AT LEAST ONE OF THE THERMOPLASTIC SHEETS AT THE SAID AREAR INTO THE SHAPE OF SAID ENLARGED CAVITY WITHOUT PRODUCING THERMOPLASTIC DEFROMATION OF THE REMAINDER OF THE LAMINATE, WHEREBY THERE IS FORMED A HOLLOW SECTION BETWEEN THE THERMOPLASTIC SHEETS AT THE SAID PARTING LAYER WHEREBY THE RIGIDITY OF THE LAMINATE IS INCREASED.

Claim 2

A METHOD OF MAKING A LAMINATE OF RIGID THERMOPLASTIC HEAT-FORMABLE SHEET MATERIAL COMPRISING PROVIDING A LEAST TWO SHEETS OF SUCH RIGID THERMOPLASTIC MATERIAL, PLACING ON A SURFACE OF ONE SUCH SHEET AT A PRESELECTED AREA A LAYER OF PARTING MATERIAL, DISPOSING AN AIR-COMDUCTING MEANS ON THE SHEET LEADING FROM THE PARTING MATERIAL TO THE EDGE OF THE SHEET, ASSEMBLING THE TWO THERMOPLASTIC SHEETS IN FACE-TO-FACE RELATIONSHIP WITH THE PARTING MATERIAL AND AIR-CONDUCTING MEANS SANDWICHED BETWEEN THE THERMOPLASTIC SHEETS, APPLYING HEAT AND PRESSURE TO UNITE THE THERMOPLASTIC SHEET TOGETHER AT THEIR CONTACTING FACES, HEATING THE RESULTING LAMINATE TO A TEMPERATURE AT WHICH THE THERMOPLASTIC MATERIAL CAN READILY BE DRAWN INTO A DESIRED SHAPE, DISPOSING THE THUSHEATED LAMINATE BETWEEN MOLD MEMBERS WHICH CONFINE THE LAMINATE AGAINST OUTWARDLY EXPANSION EVERYWHERE EXCEPT AT THE AREA OF SAID PARTING LAYER, AT WHICH AREA AT LEAST ONE OF THE MOLD MEMBERS IS PROVIDED WITH AN ENLARGED CAVITY, AND APPLYING DIFFERENTIAL PRESSURE TO THE HEATED LAMINATE TO PRODUCE A THERMOPLASTIC DEFORMATION OF AT LEAST ONE OF THE THERMOPLASTIC SHEETS AT THE SAID AREAR INTO THE SHAPE OF SAID ENLARGED CAVITY WITHOUT PRODUCING THERMOPLASTIC DEFROMATION OF THE REMAINDER OF THE LAMINATE, WHEREBY THERE IS FORMED A HOLLOW SECTION BETWEEN THE THERMOPLASTIC SHEETS AT THE SAID PARTING LAYER WHEREBY THE RIGIDITY OF THE LAMINATE IS INCREASED.