Illegal-sheet-material detection apparatus in sheet material manufacturing machine

An abnormal sheet material detecting apparatus for use in a sheet material processing machine which is adapted to pass at intervals a given portion of every single sheet of material and to pick up the sheets, one by one, from a plurality of sheet materials, each one having approximately the same property, comprising:

• a detecting circuit including a sensor for detecting a predetermined portion of a single sheet material at a given position in accordance with the amount of light transmitted through said single sheet material, with said amount of light being a variable value from sheet to sheet;
• a first memory circuit for storing, in sequence, the detected value of each of said variable value of transmitted amount of light with respect to each of said single sheet material output from said detecting circuit and for outputting a representative signal;
• a second memory circuit for storing an output signal from said first memory circuit after at least said single sheet material is passed through said sensor provided within said detecting circuit for detecting the transmitted amount of light;
• a comparison circuit for outputting signals, each corresponding to the difference between said detected and memorized value of said transmitted amount of light with respect to the nth (n being an integer of 1 or more) single sheet material stored within said second memory circuit and said detected and variable value for said transmitted amount of light with respect to the n+1th single sheet material, said output signal provided when the detecting circuit determines a difference beyond a predetermined upper and lower limit;
• and
• a discrimination circuit for outputting an abnormal condition detecting signal when said output signal of said comparison circuit is continued beyond a predetermined time period.