Process for forming shaped articles from cellulosic material bonded by a thermosetting resin

Claim 1

THE PROCESS OF PRODUCING A HOLLOW BOARD MEMBER HAVING PARALLEL OPPOSITE FACES OF LARGE AREA AND HAVING LONG HOLLOW PASSAGES THEREIN, EACH WITHIN THE THICKNESS OF THE BOARD AND SEPARATED FROM SAID FACES BY BODY PORTIONS OF THE BOARD, SAID PROCESS PRODUCING SAID BOARD FROM CELLULOSE FIBROUS MATERIAL IMPREGNATED WITH AND BOUND TOGETHER BY A CURED THERMOSETTING RESIN, WHEREIN SAID BOARD IS FORMED IN PART BY THE USE OF REMOVABLE ELONGATED CORE MEMBERS, RESPECTIVELY TO PRODUCE SAID PASSAGES, DURING THE FINAL PRESSING AND CURING OF THE BOARD, AND SAID PROCESS COMPRISING THE STEPS OF FORMING A PLURALITY OF THICK, COMPRESSIBLE, SHEET-LIKE MATS EACH HAVING LATERALLY AT LEAST THE AFORESAID AREA OF THE FINAL DESIRED SHAPED OF THE BOARD AND EACH COMPRISING A SUBSTANTIALLY HOMOGENEOUS MIXTURE OF CELLULOSIC FIBROUS MATERIAL AND AT LEAST ONE THERMOSETTING RESIN WHICH IS IN A SUBSTANTIALLY UNCURED STATE, ESTABLISHING A STACK CONSISTING ONLY OF SAID MATS IN SUPERPOSED RELATION AND SAID ELONGATED CORE MEMBERS AND HAVING THE CORE MEMBERS DISPOSED BETWEEN SUPERPOSED MATS, BETWEEN THE SPACED, PARALLEL, UPPER AND LOWER PLATENS OF A PRESS, WHEREIN SAID PLATENS ARE DISPOSED AT A SUBSTANTIALLY CONSTANT DISTANCE APART THROUGHOUT THEIR AREAS FOR ANY GIVEN SETTING OF SAID PRESS, SAID ESTABLISHMENT OF SAID STACK COMPRISING PLACING A FIRST MAT TO BE IN FLATWISE PARALLEL RELATION TO THE LOWER PLATEN, PLACING A PLURALITY OF THE ELONGATED CORE MEMBERS AT LATERALLY SPACED LOCALITIES ON THE UPPER SURFACE OF SAID FIRST MAT, TO FORM PASSAGES IN THE ULTIMATE BOARD, AND PLACING A SECOND MAT IN FLATWISE RELATION DIRECTLY ON SAID CORE MEMBERS AND SAID UPPER SURFACE OF THE FIRST MAT, ALL OF SAID ELONGATED CORE MEMBERS CONSISTING OF MATERIAL WHICH HAS A DIELECTRIC CONSTANT APPROXIMATING THAT OF THE RESIN-IMPREGNATED MATERIAL OF THE MATS WHEN SAID RESIN-IMPREGNATED MATERIAL IS COMPRESSED AS HEREINBELOW RECITED, SO THAT SUBSTANTIALLY UNIFORM DIELECTRIC HEATING OF ALL PARTS OF THE STACK BETWEEN THE PLATENS WILL OCCUR, NOTWITHSTANDING THE PRESENCE OF SAID CORE MEMBERS, SUPPLYING HEAT TO THE PLATENS TO BRING THEM TO AND HOLD THEM AT AN ELEVATED TEMPERATURE AT LEAST AT PORTIONS WHERE THEY COME INTO CONTACT WITH THE LOWER AND UPPER MATS OF SAID STACK, MOVING SAID PLATENS TOGETHER TO PROVIDE PHYSICAL COMPACTING PRESSURE ON THE RESIN-IMPREGNATED MATERIAL OF MATS IN THE STACK TO FORM A PRESSED BODY, AND THEREBY COMPACTING THE STACK TO THE AFORESAID THICKNESS DESIRED FOR THE BOARD, INCLUDING COMPACTING SAID FIRST AND SECOND MATS TO SURROUND THE SAID PLURALITY OF CORE MEMBERS BETWEEN THEM, SUPPLYING HIGH FREQUENCY ELECTRIC CURRENT SOLELY TO SAID PLATENS FOR DIELECTRIC HEATING OF THE SAID STACK TO GENERATE AND MAINTAIN A RESIN-CURING TEMPERATURE WITHIN THE COMPRESSED CELLULOSE-RESIN MIXTURE OF THE MATS IN THE STACK DURING THE PRESSING AND CURING THEREOF, TO PRODUCE AN ARTICLE WHEREIN THE RESIN IS CURED, AND REMOVING THE AFORESAID PLURALITY OF CORE MEMBERS FROM THE ARTICLE CONSTITUTED BY THE COMPRESSED AND CURED STACK, TO PRODUCE THE DESIRED BOARD MEMBER HAVING HOLLOW PASSAGES THEREIN.