Method and apparatus for preparing polyurethane foam sandwich structure

Claim 1

A METHOD OF PRODUCING A MULTI-LAYER STRUCTURE COMPRISING UPPER AND LOWER FACING SHEETS AND A CORE LAYER OF PREDOMINANTLY CLOSED CELL POLYURETHANE FOAM WHICH METHOD COMPRISES THE STEPS OF: (A) COATING AN ADVANCING FACING SHEET WITH A POLYURETHANE FOAM-FORMING COMPOSITION; (B) COMBINING SAID COATED FACING SHEET WITH A SECOND FACING SHEET TO PROVIDE AN ADVANCING AND EXPANDING SANDWICH COMPRISING UPPER AND LOWER FACING SHEETS AND AN INTERMEDIATE LAYER OF RISING FOAM-FORMING COMPOSITION; (C) SUBJECTING SAID ADVANCING AND EXPANDING SANDWICH TO POSITIVE BUT YIELDABLE PRESSURE IN A PLURALITY OF SUCCESSIVELY INDEPENDENT APPLICATIONS DURING AT LEAST THE MAJOR PORTION OF THE PERIOD OF RISE OF THE FOAM-FORMING COMPOSITION, SUCH PRESSURE APPLICATIONS BEING OVER A PLURALITY OF SUCCESSIVELY ADJACENT AREAS OF THE UPPER FACING SHEET AND BEING SUFFICIENT TO SUPPRES GAS FROM THE FOAM-FORMING FROM LODGING AT THE INTERFACE OF THE FOAM AND UPPER FACING SHEET BUT INSUFFICIENT TO CAUSE CRUSHING OF THE FOAM; AND (D) THERAFTER CURING THE FULLY RISEN POLYURETHANE FOAM TO PROVIDE A MULTI-LAYER STRUCTURE IN WHICH THE DISTRIBUTION OF GAS CELLS THROUGHOUT THE THICKNESS OF THE POLYURETHANE FOAM LAYER IS MORE NEARLY UNIFORM AND IN WHICH BOTH UPPER AND LOWER FACING SHEETS ARE FIRMLY BONDED TO THE POLYURETHANE FOAM CORE BY REASON OF SAID PRESSURE APPLICATIONS.

Claim 2

A METHOD OF PRODUCING A MULTI-LAYER STRUCTURE COMPRISING UPPER AND LOWER FACING SHEETS AND A CORE LAYER OF PREDOMINANTLY CLOSED CELL POLYURETHANE FOAM WHICH METHOD COMPRISES THE STEPS OF: (A) COATING AN ADVANCING FACING SHEET WITH A POLYURETHANE FOAM-FORMING COMPOSITION; (B) COMBINING SAID COATED FACING SHEET WITH A SECOND FACING SHEET TO PROVIDE AN ADVANCING AND EXPANDING SANDWICH COMPRISING UPPER AND LOWER FACING SHEETS AND AN INTERMEDIATE LAYER OF RISING FOAM-FORMING COMPOSITION; (C) SUBJECTING SAID ADVANCING AND EXPANDING SANDWICH TO POSITIVE BUT YIELDABLE PRESSURE IN A PLURALITY OF SUCCESSIVELY INDEPENDENT APPLICATIONS DURING AT LEAST THE MAJOR PORTION OF THE PERIOD OF RISE OF THE FOAM-FORMING COMPOSITION, SUCH PRESSURE APPLICATIONS BEING OVER A PLURALITY OF SUCCESSIVELY ADJACENT AREAS OF THE UPPER FACING SHEET AND BEING SUFFICIENT TO SUPPRES GAS FROM THE FOAM-FORMING FROM LODGING AT THE INTERFACE OF THE FOAM AND UPPER FACING SHEET BUT INSUFFICIENT TO CAUSE CRUSHING OF THE FOAM; AND (D) THERAFTER CURING THE FULLY RISEN POLYURETHANE FOAM TO PROVIDE A MULTI-LAYER STRUCTURE IN WHICH THE DISTRIBUTION OF GAS CELLS THROUGHOUT THE THICKNESS OF THE POLYURETHANE FOAM LAYER IS MORE NEARLY UNIFORM AND IN WHICH BOTH UPPER AND LOWER FACING SHEETS ARE FIRMLY BONDED TO THE POLYURETHANE FOAM CORE BY REASON OF SAID PRESSURE APPLICATIONS.