Patent GB-1340265-A (GB)
Title: Device for automatic thickness control of rolled strips
IPC: B21B37/62
Filed: 1971-04-22
Abstract: 1340265 Rolling NOVOSIBIRSKY METALLURGICHESKY ZAVOD IMENI AN KUZMINA 22 April 1971 10664/71 Heading B3M [Also in Divisions B4-B5 and G2-G3] A rolling mill has an automatic thickness  control which comprises an hydraulic pistoncylinder unit 6, 7 between the work roll chocks 2 of each frame 1 in a closable hydraulic system which includes a damping piston-cylinder unit 8, 9, a closable valve 11 and a positive feedback circuit in which any pressure changes in the system are measured and which has a correcting piston-cylinder unit 20, 21 or (54), (55), Fig. 3 (not shown), to back-up the pressure changes. The roll chocks 2 are adjusted by a screw 4 driven by an electric motor 5 with the valve 11 open and the system pressurized. After adjustment the valve is closed to seal the hydraulic system and increase the rigidity of the roll stand. The system forms a prestressing circuit. When the thickness of the rolled material allows the rolls to move together the hydraulic pressure in the system increases. The increase is measured by a meter in the positive feedback circuit which causes a further pressure increase to move the rolls apart to their original separation. The opposite procedure applies if the rolls are moved apart by the material being rolled. The damping unit 8, 9 has its piston 9 biased against the hydraulic pressure by a spring 10 to prevent rapid movement of the chocks after the exit of the rolled material. In one embodiment, Fig. 1, the positive feedback circuit comprises a spool valve 13, 14 under the control of the hydraulic pressure in the system and a spring 17 connected between the spool and an adjustable lever 18. The lever is also connected to the piston 19 of an actuating unit 12 controlled by fluid pressure supplied through the valve 13, 14. The piston 19 is integral with the piston 20 of the correcting hydraulic cylinder 21. The pivot 22 of the lever 18 is set so that when the hydraulic system is closed the spool 14 occupies its neutral position. During rolling a rise in pressure in the system due to movement of the rolls towards each other moves the spool rightward and the valve supplies fluid to move the pistons 19, 20 leftwards to increase the pressure in the system further and move the rolls apart. The movement of the pistons also moves the lever 18 to alter the biasing of the spring so that the spool moves to its neutral position again. The increase in the rigidity of the mill using the closed hydraulic system increases the amplitude of pressure variations in the system and the movement of the rolls can be stabilized using a piston-cylinder unit 41 between the back-up roll chocks and the fluid pressure in the unit is controlled by a spool valve 37, 38 moved by the fluid pressure of the closed system and spring biasing 39. The device 40 is adjustable to vary the spring-biasing for different strip widths. In a second embodiment, Fig. 2, the positive feedback circuit is electromechanical and comprises a magnetoanisotropic force transmitter 23 with a piston 24 connected to the hydraulic system, a comparator 25 fed with a reference voltage, an amplifier 26 and a divider 27 fed with a feedback co-efficient K. The output of the divider 27 is fed to a comparator 28 which also receives a signal indicating the position of the piston 33 of the correcting hydraulic cylinder 34. The output of the comparator is used to drive an electric motor 30 linked by a screw and nut 32 to the piston 33. The stabilization is provided by an electromechanical arrangement connected electrically to the amplifier 26 of the feedback circuit. The arrangement includes a motor 45, a screw and nut 32 and a piston-cylinder unit 42, 43 connected to the piston-cylinder unit 41 between the back up chocks. The mill may alternatively have a stabilizing arrangement which drives the motor 5 of the mill screw 4. A programmed correction control can be included in the mill to change the pressure in the closed system in dependence on machining inaccuracy of the working rolls. The control, Fig. 3 (not shown), includes a pulse transmitter (46) connected to a counter (47). The counter has a converter to change the pulses into a code indicating the angular position of the roll. The amplifier (26) of the feedback circuit sends signals to a control unit (48) which also receives the code signals. A memory unit 49 memorizes the change of fluid pressure as a function of the angular position of the rolls. The memory unit is charged by using the mill with the working rolls in contact. The signal from the control unit (48) is connected to an electromechanical converter (53) linked with a correcting hydraulic unit (54), (55). The mill may be used for metal, paper or synthetic film.