INSPECTING DEVICE FOR PRINTED MATTER

摘要

PURPOSE:To prevent false abnormality detection during an increase or decrease in printing speed by providing a printing speed monitoring circuit to a printed matter inspecting device which inputs each picture element of the pattern of printed matter and compares pattern information of every picture element with reference information. CONSTITUTION:A printing form 3 supplied by a rolled take-up form 2 is printed in four colors on its top and reverse surfaces by a printing part 1 and carried. Pattern information IS on the form 3 is scanned by a detecting part 4 on the basis of timing pulses TP from a rotary encoder fitted to the plate drum or blanket, and the scan data is inputted to an abnormality decision circuit 6. An abnormality signal ES outputted by the circuit 6 is transferred to the speed monitoring circuit 7. In the circuit 7, a speed arithmetic circuit 10 calculates the current speed variable Vn on the basis of the pulses TP and clock pulses CP. An addition absolute value circuit 13 calculates the quantity of speed variation of the variable Vn and a comparing circuit 14 compares it with a reference value from a shift circuit 12 and outputs a constant speed signal TS when the difference is within a permissible range. Thus, false abnormality detection in an increase or decrease in printing speed is prevented.