Method of brazing

Claim 1

IN THE METHOD OF BRAZING METAL SKIN SHEETS TO A CELLULAR METAL CORE HAVING COMMUNICATION BETWEEN ADJACENT CELLS OF SAID CORE, THE STEPS COMPRISING FORMING A SANDWICH BY PLACING A SKIN SHEET ON EACH FACE OF SAID CORE WITH A LAYER OF BRAZING MATERIAL DISPSED BETWEEN THE CORE AND EACH SHEET, SEALING THE PERIPHERAL EDGES OF SAID SANDWICH, ALTERNATELY INTRODUCING SUBSTANTIALLY NONOXIDIZING GAS INTO SAID SANDWICH AND WITHDRAWING THE SAME WITH THE FINAL WITHDRAWAL OF GAS SERVING TO PROVIDE A VACUUM WITHIN SAID SANDWICH WHEREBY THE COMPONENTS OF SAID SANDWICH ARE FORCED FIRMLY AND UNIFORMLY TOGETHER, HEATING SAID SANDWICH TO A TEMPERATURE SUFFICIENT TO MELT SAID BRAZING MATERIAL, COOLING SAID SANDWICH TO ALLOW SOLIDIFICATION OF THE MELTED BRAZING MATERIAL TO BOND SAID SKIN SHEETS TO SAID CORE WITH SAID VACUUM BEING MAINTAINED DURING SAID HEATING AND COOLING, AND LOCATING SAID SANDWICH BETWEEN A PAIR OF DIES CONFORMING TO THE CONTOUR OF THE SANDWICH AND SPACED APART A DISTANCE WHICH IS FORMED .003 INCH TO .010 INCH GREATER THAN THE THICKNESS OF THE SANDWICH DURING THE COOLING PERIOD TO PREVENT WARPING AND DISTORTING OF THE SANDWICH DURING COOLING WHILE PREVENTING EXCESSIVELY HIGH DIE PRESSURE ON SAME.