SEAM DETECTOR FOR SHEET INCLUDING METAL FOIL

摘要

PURPOSE:To make it possible for sure to detect a seam that has been electrically insulated and also to provide improved easiness of operation and simplification of electric circuit by setting up and a specified relation to the width of the seam the distance between a pair of coils that are opposed with a sheet inbetween them and the coil diameter. CONSTITUTION:A seam 3' is detected 9 by the electromagnetic induction method as a sheet 3 including a metal foil which has an electrically insulated seam 3' and the thickness of which is 20mu or less is made to travel. In this case, a pair of coils 2 and 4 that are opposite to each other with the sheet 3 inbetween them are provided and the distance between the coils and their diameters are set at below 2/3 of the seam 3' or over the width of the seam 3'. With this arrangement, the seam 3' is detected for sure by the induction voltage in each of the coils.