Method of pressure welding metal sheets

Claim 1

IN THE FABRICATION OF A HOLLOW ARTICLE BY INFLATION OF AN INTEGRAL METAL SHEET FORMED BY UNIFICATION OF TWO SUPERPOSED METAL COMPONENT SHEETS, SAID SUPERPOSED SHEETS BEING A RELATIVELY LESS PLASTIC FIRST METAL COMPONENT SHEET AND A RELATIVELY MORE PLASTIC SECOND METAL COMPONENT SHEET WHEREIN UPON ROLLING SAID SECOND SHEET ELONGATES TO A GREATER EXTENT RELATIVE TO SAID FIRST SHEET, THE METHOD COMPRISING, INTERPOSING BETWEEN THE ADJACENT SURFACES OF SAID SUPERPOSED METAL SHEETS A PATTERN OF STOPWELD MATERIAL DEFINING A CORRESPONDING SYSTEM OF TUBULAR PASSAGES; AND PRESSURE WELDING THE ASSEMBLY OF COMPONENT SHEETS BY ROLLING THEM BETWEEN MILL ROLLS IN THE ABSENCE OF RELATIVE MOVEMENT BETWEEN ADJACENT PORTIONS OF SAID COMPONENT SHEETS OPPOSITE THEIR INTERFACE EXTENDING IN THE PORTION OF THE BITE OF SAID MILL ROLLS COMMON TO SAID COMPONENT SHEETS WHILE SAID COMPONENT SHEETS ARE CONSTRAINED AGAINST MISALIGNMENT AND WITH THE REMAINING UNROLLED PORTIONS OF SAID SHEETS FREE TO MOVE LONGITUDINALLY RELATIVE TO EACH OTHER.