Patent ID: 8768236

Claim:
A duplex image forming apparatus, comprising: an image forming part which forms an image on paper; a paper discharge part which reversely feeds the paper, in which the image has been formed on a first surface of the paper in the image forming part, so that the image is formed on a second surface of the paper, and discharges the paper on which the image is completely formed; and a duplex printing part having duplex rollers located upstream of a duplex sensor to feed the paper reversed from the paper discharge part toward the image forming part to form the image on the second surface of the paper, and to register the paper fed to form the image on the second surface, and the duplex sensor detects when the paper is caught in the duplex rollers and outputs a signal in response to the detection, wherein the paper discharge part includes a driving unit which has driving rollers and driven rollers to reversely feed the paper printed on the first surface to the duplex printing part and to discharge the paper printed on the first and second surfaces, and a separation unit to receive the signal from the duplex sensor and to separate the driven rollers and the driving rollers from each other in response to the received signal.