Patent ID: 7107903

Claim:
A sheet-fed printing press comprising: a photoelectric double sheet detector and an ultrasonic double sheet detector, both being adapted to output double sheet detected signal when they each have judged that two or more overlapped sheets are being fed; and a double-sheet-detector control part for automatically switching the photoelectric double sheet detector and the ultrasonic double sheet detector so as to employ the photoelectric double sheet detector as a double sheet detector for use in large quantity or successive printing when the ultrasonic double sheet detector output double sheet detected signal during test printing or during feeding a first printing sheet of successively fed printing sheets in large quantity or successive printing, and employ the ultrasonic double sheet detector as a double sheet detector for use in large or successive printing when the ultrasonic double sheet detector did not output double sheet detected signal during test printing or during feeding a first printing sheet of successively fed printing sheets in large quantity or successive printing.