ROLLER LEVELER

PURPOSE:To improve efficiency of straightening by providing rolling-down cylinders to draw down large diameter straightener rolls and small diameter straightener rolls and providing high-pressure relief valves, low-pressure relief valves which are linked with the rolling-down cylinders and switching valves for switching their working. CONSTITUTION:Because a metal plate is rolled down with the small diameter straightener rolls 52 and large diameter straightener rolls 51 in the case of straightening of the metal plate, the valves are switched so as to operate the low-pressure relief valves 2 which are worked on the small diameter straightener rolls 52 with low mechanical strength by the switching valves 3. If excessive straightening torque is worked during straightening, the small diameter straightener rolls are prevented from mechanical damage by making the low-pressure relief valves 2 operate. In the case of the metal plate with more than a prescribed strength, the valves are switched so as to operate the high-pressure relief valves 1 which are worked on the large diameter straightener rolls 51 with the switching valves 3. Thus, efficiency of straightening can be improved because effective rolling draft can be applied to both of high straight material to be straightened and low strength material to be straightened. And the large diameter straightner rolls 51 and the small diameter straightener rolls 52 are protected from respective overload and the damage of mechanical system previously is prevented.