Patent ID: 7445209

Claim:
A sheet feeding apparatus comprising: a stacker for stacking a sheet, a transport guide for guiding the sheet from the stacker to a predetermined processing position situated under the stacker, said transport guide having a U-turn shape portion, first and second transport devices arranged in the transport guide before the U-turn shape portion for transporting the sheet, a sheet size recognition device for recognizing length of the sheet placed on the stacker in a transport direction, an ultrasonic double feed detection device arranged between the first transport device and the second transport device for detecting a double feed of sheets, said double feed detection device comprising an oscillating element and a receiving element facing each other to allow the sheet to pass therebetween and detecting the double feed while the sheet is being transported, a transport length detection device formed separately from the ultrasonic double feed detection device, said transport length detection device detecting a transport length of the sheet transported by the first and second transport devices from a leading edge of the sheet to a trailing edge of the sheet, a comparison device for comparing the length of the sheet recognized by the sheet size recognition device and the transport length of the sheet detected by the transport length detection device, and a judgment device for judging the double feed of the sheets based on both of a comparison result from the comparison device and a detection result from the double feed detection device.