Patent ID: 7425001

Claim:
A sheet handling apparatus comprising: a sheet stacker for stacking sheets, separating means for separating and feeding the sheets stacked on the sheet stacker, a register roller disposed adjacent to the separating means, said register roller forming a loop to the sheet transferred from the separating means for correcting a skew of the sheet, an ultrasonic wave sensor composed of a wave sending sensor and a wave receiving sensor and arranged between the separating means and the register roller obliquely relative to a sheet transfer surface therebetween, judging means electrically connected to the wave receiving sensor and having means for taking an output signal from the wave receiving sensor for a predetermined time beginning from a time that the loop of the sheet is removed since the register roller starts rotating from a stopping condition thereof until a trailing edge of the sheet moves away from nipping of the separating means, said judging means detecting a double feed of the sheet based on the output signal for said predetermined time, and control means electrically connected to the judging means and the register roller for controlling the register roller to stop and rotate.