| 摘要 |
PROBLEM TO BE SOLVED: To detect the double feed when paper sheets of various thickness and length are conveyed in a mixed state. SOLUTION: A length of paper sheet delivered in each job is independently detected and stored. When the double feed does not occur, the length of the paper measured in each job is constant, for example, a first sheet is 200 mm, a second sheet is 200 mm, a third sheet is 220 mm, a fourth sheet is 250 mm, a fifth sheet is 200 mm, and a sixth sheet is 220 mm. On the other hand, when the double feed occurs on the second sheet in a third job, for example, a result of the detection of the length of the paper in delivering the second sheet becomes 300 mm, which is different from the result of the former length of 200 mm. The double feed is determined when a value different from the former length is detected.
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