Overlapped-sheet detection apparatus

An overlapped-sheet detection apparatus comprising:

• a forwarding roller rotating while making contact with sheets to forward the sheets in a conveying direction on a conveying path;
• a shifting roller provided at a position where said shifting roller and said forwarding roller pinch at said sheets,
• said shifting roller being configured to shift said sheets if said sheets are overlapped and to follow a rotation of said forwarding roller if said sheets are not overlapped;
• driving torque means for supplying said shifting roller with driving torque to shift said sheets;
• a first sensor provided closer to an entrance than to said forwarding roller to detect a rear edge portion of said sheets in the conveying direction;
• a second sensor provided between said first sensor and said forwarding roller to detect the rear edge portion of said sheets in the conveying direction;
• and
• discrimination means for judging whether said sheets are overlapped or not from a period of time taken between detection of the rear edge portion by said first and that of the rear edge portion by second sensor.

An overlapped-sheet detection apparatus comprising:

• a forwarding roller rotating while making contact with sheets to forward the sheets in a conveying direction on a conveying path;
• a shifting roller provided at a position where said shifting roller and said forwarding roller pinch at said sheets,
• said shifting roller being configured to shift said sheets if said sheets are overlapped and to follow a rotation of said forwarding roller if said sheets are not overlapped;
• driving torque means for supplying said shifting roller with driving torque to shift said sheets;
• detection means for detecting rotation speeds of said shifting roller;
• and
• discrimination means for judging that said sheets are overlapped when a difference between said rotation speed of said shifting roller and that of said forwarding roller is greater than a threshold value.

An overlapped-sheet detection apparatus comprising:

• a forwarding roller rotating while making contact with sheets to forward the sheets in a conveying direction on a conveying path;
• a shifting roller provided at a position where said shifting roller and said forwarding roller pinch at said sheets,
• said shifting roller being configured to shift said sheets if said sheets are overlapped and to follow a rotation of said forwarding roller if said sheets are not overlapped;
• driving torque means for supplying said shifting roller with driving torque to shift said sheets;
• detection means for detecting rotation speeds of said shifting roller;
• first discrimination means for judging that said sheets are overlapped when a difference between said rotation speed of said shifting roller and that of said forwarding roller is greater than a threshold value;
• a first sensor provided closer to an entrance of the conveying path than to said forwarding roller to detecting a rear edge portion of said sheets in said conveying direction;
• a second sensor provided between said first sensor and said forwarding roller to detect said rear edge portion of said sheets in said conveying direction;
• and
• second discrimination means for judging whether said sheets are overlapped or not from a period of time taken between detection of the rear edge portion by said first and that of said rear edge portion by second sensor.