Patent ID: 8593649

Claim:
A defect detector for corrugated cardboard flutes, said defect detector comprising: an optical projector configured to project, to traveling flutes, an inspection light having an effective line of which the length is about one pitch of flutes inclined slightly so that a tip of a normal flute mountain is positioned on or slightly under a posterior end of the effective line and simultaneously a slope of an adjacent normal flute mountain is positioned on an anterior end side of the effective line; an optical receiver comprising a light-receiving element configured to receive the inspection light reflected by a flute mountain to output information corresponding to a light-receiving position; a normal or abnormal determining means for, if the light-receiving position detected from the information output by the light-receiving element is within an allowable range Wp, determining that the height of the flute is “normal”, and if the light-receiving position is out of the allowable range Wp, determining that the height of the flute is “abnormal”; and an allowable range shifting means for shifting the allowable range Wp of the light-receiving position to adjust the allowable range Wh of the flute height based on a corrugation type of the corrugated cardboard flutes.