Process of manufacturing fibrous sheet covered plywood

Claim 1

THE IMPROVEMENT IN THE PROCESS OF MANUFACTURING FIBROUS SHEET COVERED PLYWOOD THE FACE OF WHICH PLYWOOD ADJACENT THE FIBROUS SHEET CONTAINS SURFACE DEFECTS, WHICH COMPRISES THE STEPS OF IMPREGNATING A PAPER SHEET HAVING A BASIS WEIGHT, WHEN DRY, WITHIN THE RANGE OF FROM 110 TO 210 POUNDS FOR 500 SHEETS 24 AND 36 INCHES, AND A DENSITY WITHIN THE RANGE OF FROM .55 TO .80 GRAM PER CUBIC CENTIMETER, WITH A THERMOSETTING ALDEHYDE RESIN TO PROVIDE A RESIN CONTENT IN SAID SHEET, AFTER DRYING, WITHIN THE RANGE OF FROM ABOUT 5 TO 35% OF THE WEIGHT OF THE DRY IMPREGNATED SHEET; DRYING THE RESIN-CONTAINING SHEET; HEATING SAID DRY, RESIN-CONTAINING SHEET TO CURE THE RESIN CONTAINED THEREIN TO SUCH AN EXTENT THAT WHEN A SECTION OF THE CURED SHEET IS PRESSED BETWEEN A FLAT, METALLIC, BACKING PLATE AND A FLAT, METALLIC, DIE PLATE, BOTH APPROXIMATELY 8 INCHES BY 8 INCHES SQUARE, SAID DIE PLATE HAVING OVER THE GREATER PORTION OF ITS SURFACE CONCENTRIC LANDS 5/64 OF AN INCH IN WIDTH, SPACED APART BY CONCENTRIC GROOVES 3/32 OF AN INCH IN WIDTH, WITH A FORCE OF ABOUT 12,800 POUNDS, UNIFORMLY DISTRIBUTED OVER THE PLATE, THE SHEET BEING HEATED DURING THE PRESSING OPERATION TO A TEMPERATURE OF ABOUT 300* F. WHILE MAINTAINED UNDER PRESSURE FOR A PERIOD OF SIX TO EIGHT MINUTES, SAID SHEET IS FREE OF VISIBLE MARKS CORRESPONDING TO THE DIE PATTERN ON THE SIDE THEREOF OPPOSITE TO THE SIDE IN CONTACT WITH THE DIE SURFACE; PLACING AT LEAST ONE PLY OF SAID CURED SHEET OVER THE EXPOSED FACE OF ONE OF THE OUTER VENEERS OF A PLYWOOD ASSEMBLY WHICH FACE CONTAINS SURFACE DEFECTS, WHEN THAT ASSEMBLY IS PLACED IN A PLYWOOD PRESS; PROVIDING A GLUE LINE ADHESIVE INTERMEDIATE THE RESIN-CONTAINING SHEET AND THE ADJACENT VENEER; AND FINALLY SUBJECTING SAID ASSEMBLY, IN SAID PRESS, TO PRESSURE WITHIN THE RANGE OF FROM ABOUT 150 TO 300 POUNDS PER SQUARE INCH AND A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 260 TO 325* F. TO EFFECT THE JOINING OF THE PLIES OF THE PLYWOOD ASSEMBLY AND THE ATTACHMENT OF THE CURED RESINCONTAINING SHEET TO THE SURFACE VENEER SOLELY BY THE ADHESIVE ACTION OF SAID GLUE LINE.