PURPOSE: To enable a defect at a steel-band butt welding portion to be detected automatically and readily and accurately.
CONSTITUTION: A center line of a visual sensor which divides an area 4 into two portions is matched to a welding line 7 at a steel-band butt welding portion and then a difference between an amount of left reflection light and that of right reflection light is detected for the welding line 7 on a surface of two butted steel bands 6 by a visual sensor 1. A camera 2 of the visual sensor 1 is allowed to run along the welding line 7 at an upper portion of the steel bands 6 by a certain height a difference between the amount of left reflection light and that of right reflection light of the area 4 is measured and a voltage signal is output to the welding line 7, and this voltage signal value and a reference value when there are no welding defects which are set previously are compared by an operation mechanism 8, thus enabling a welding defect to be detected according to a difference between the voltage signal value and the reference value.
NAKASHIO SATORU
SAIJO YOSHIO
SHIMADA TAKASHI
NOJIMA HIROFUMI
SHINOHARA MASANORI
Next Patent: MARKING DEVICE FOR FLAW PORTION ON STRIP