METALLIC SHEET SHAPE DETECTION AND APPARATUS THEREFOR

PURPOSE:To enable accurate detection of a shape of sheet uneffected by outside disturbances, by generating a local vibration on a metallic sheet and detecting it. CONSTITUTION:For detection of flatness of a thin sheet 2, a pulse generator 4 is driven to supply an electric current to the sheet 2 from a vibration exciting head for generation of a vibration. The current from the head 5 to the sheet 2 represents an impact current of a pulse form, leading to an electro-hammer effect. As application of an instantaneous external force becomes available based upon a relationship between magnetic flux and eddy current, a local vibration is excited on the sheet 2 and the vibration is detected by a detector 6 through a detecting head 7. This signal is then treated by a signal processing circuit 9 for frequency analysis, etc., however, at this moment. Such condition data as sheet feeding velocity, sheet thickness, sheet material, etc. are added and the signal is displayed on a displaying apparatus 11 through a displaying circuit 10. Further, a signal from the circuit 9 is transmitted to a form- controlling apparatus 12 also and a controlling command is issued to a bending apparatus etc. of a rolling mill 1.