Improved method of and apparatus for automatically controlling the thickness of metal strips, especially metal foils, in rolling mills

摘要

601,214. Automatic control systems for rolling-mills. NEHER, Ltd., R. V. April 11, 1944, No. 6690. Convention date, March 4, 1943. [Class 38 (iv)] In the rolling of foil, particularly of aluminium or its alloys, the thickness of the product leaving the mills is continuously measured by means which automatically control the setting of parts of the mill to maintain the thickness control within prescribed limits. The control device consists of a measuring device 2 that creates eddy currents in the foil 1 ; the strength of the magnetic field due to the currents being used for the thickness measurement by apparatus 3 comprising a high-frequency amplifier and a galvanometer. When the permitted thickness variation is exceeded and current is switched on which by means of an amplifying relay 4 operates a reversing relay 5 causing rotation of an auxiliary motor 6 in one direction or the other. This may actuate a control 7 for regulating the speed of an A.C. motor driving the rolling-mill or it may control a brake for varying the back tension of the foil entering the mill. The tension of the foil on the leaving side of the mill may be controlled.