Metal working

Claim 1

IN A TUBE FORMING MACHINE: MEANS FOR SUPPORTING AN ELONGATED BLANK; A ROLLER HEAD HAVING AN OPEN-CENTER CONFIGURATION TO ACCOMMODATE THE BLANK AND A TUBE MADE THEREFROM; MEANS MOUNTING SAID ROLLER HEAD FOR ROTATION ABOUT AN AXIS CO-AXIAL WITH THE AXIS OF THE BLANK; MEANS CONNECTED WITH THE BLANK FOR MOVING THE BLANK RELATIVE TO THE HEAD IN A DIRECTION ALONG THE BLANK AXIS; ROLLER MEANS FORMED IN THE SHAPE OF AN ANNULUS DISPOSED ON SAID HEAD, THE ROLLER MEANS HAVING A PAIR OF ANNULAR WORKING SECTIONS SURROUNDING SAID BLANK AND MAKING SIMULTANEOUS ENGAGEMENT WITH THE OUTSIDE OF THE BLANK RESPECTIVELY ON OPPOSITE SIDES OF THE BLANK AXIS, THE ENGAGEMENT AREAS OF THE WORKING SECTIONS BEING THE SAME RADIAL DISTANCE FROM THE BLANK AXIS AND LYING IN THE SAME RADIAL PLANE SO THAT THE WORKING FORCE ON ONE SECTION RADIALLY BALANCES THE WORKING FORCE OF THE OTHER SECTION; AND MOUNTING MECHANISM INCLUDING MEANS ROTATABLY CONNECTING SAID ANNULAR WORKING SECTIONS WITH THE HEAD FOR ROTATION RELATIVE TO THE HEAD ABOUT AXES RESPECTIVELY MAKING AN ACUTE ANGLE WITH SAID BLANK AXIS AND LYING IN A PLANE CONTAINING THE BLANK AXIS, THE AXES BEING SPACED FROM ONE ANOTHER IN SAID AXIAL PLANE, SAID BLANK AXIAL MOTION, SAIS HEAD ROTATION AND SAID WORKING SECTION ROTATION CAUSING EACH SAID WORKING SECTION TO PROGRESSIVELY ENGAGE THE BLANK ALONG A HELICAL PATH AROUND THE BLANK AXIS.