Cage-roll unit for metal pipe forming

A cage roll unit for use in a metal pipe forming mill train for progressively forming a flat metal sheet into a round form along a mill line extending along the mill train by means of forming rolls, said cage roll unit comprising:

• a cross rail extending perpendicular to the mill line;
• a pair of movable bases slidably supported on said cross rail so as to be slidable therealong, one on each side of the mill line;
• driving mechanisms connected to said bases for moving said bases back and forth along said cross rail;
• a pair of stands, one mounted on each movable base;
• at least two pairs of cage rolls rotatably mounted on said stands and facing said mill line and defining a pass for the metal sheet being formed, one pair on each side of said mill line, each pair having an upper and a lower cage roll, the corresponding cage rolls on each stand being opposed to each other, said lower cage rolls having a curved profile opening upwardly and inwardly toward the center of the pass and the upper cage rolls having a curved profile opening downwardly and inwardly toward the center of the pass, at least the upper cage rolls being mounted on said stands for pivoting movement about an axis parallel to said mill line for adjusting the position of said upper cage rolls relative to the center of the pass;
• and
• a support roll rotatably disposed between the stands for supporting the metal sheet being formed from below.