STRAIGHTENING METHOD AND DEVICE FOR ROUND CROSS SECTION STOCK BY ROLL GROUP HAVING DIFFERENT DIAMETER

PROBLEM TO BE SOLVED: To restrain a slip between rolls and stock to a minimum by providing another driving unit besides a main roll driving unit on the output shaft of a differential gear connected to driving systems of A group and B group in a drum type roll. SOLUTION: The differential gear 3 is connected to driving shafts 2 and 1 of respective distributors 6 and 7 of A group 4 and B group 5 in the drum type roll having different roll diameters. The differential gear 3 is driven with a main motor 9 via a reduction gear 8. After stock is bitten into rolls 4 and 5, the differential gear 3 is operated to make the peripheral speed of A group 4 and B group 5 of rolls tune. The number of revolution of input shafts 1 and 2 is measured with revolution number detectors 12 and 13. The number of revolution at the time of biting stock and tuning to the differential gear 3 is stored in a sequence controller. Before a succeeding stock to be straightened is bitten, the difference in the rotary speed of rolls is corrected with a peripheral steed tuning motor 14 based on this value. Then, the peripheral speed of rolls is always allowed to tune. Wear of rolls 4 and 5 is reduced and the generation of defects in the stock is prevented.