Thickness control system for rolling mill

In a thickness control system for a rolling mill having a hydraulic roll gap control system for setting a roll gap between upper and lower work rolls for rolling a workpiece passing from an uncoiling reel on an entry side of said work rolls to a coiling reel on an exit side of said rolls, motor means including reel motor tension controllers for driving said coiling and uncoiling reels at speeds maintaining constant tension on said workpiece on the entry and exit sides of said work rolls, a mill module control unit for outputting an instruction signal to said hydraulic roll-gap control system on the basis of any difference between a reference rolling pressure and an actual rolling pressure during rolling detected by a load cell, the improvement comprising a tension controller separate from the tension controllers for said reels and disposed on at least said entry side of said work rolls, said separate tension controller comprising:

• a tension detector for detecting the tension applied to the workpiece, means for applying a force directly to said workpiece to tension same, and means for adjusting the tension in said workpiece by varying the force exerted by said force applying means on said workpiece in response to a difference between a predetermined reference tension and the tension detected by said tension detector whereby any fluctuation in tension of said workpiece in response to a predetermined change in said roll gap is immediately detected and tension restored by said tension controller independently of operation of said reel drive tension contollers.