Patent ID: 7571909

Claim:
A sheet treating apparatus for treating sheets discharged from an image forming apparatus, and being accommodated in a space formed in an image forming apparatus, said sheet treating apparatus comprising: plural sheet stacking devices which stack treated sheets discharged from the image forming apparatus; a moving device which moves said plural sheet stacking devices independently of each other; and a driving unit which generates driving power for moving said plural sheet stacking devices by said moving device; a limiting device which limits transmission of the driving power from said driving unit to said moving device when a torque in moving said sheet stacking device exceeds a predetermined torque; a sensor device which detects that an uppermost sheet stacking device among said plural sheet stacking devices reaches an upper limit position of said sheet stacking device; and a control device which stops moving of the uppermost sheet stacking device in case said sensor device detects that the uppermost sheet stacking device reaches the upper limit position within a predetermined time after the uppermost sheet stacking device moves toward the upper limit position by said moving device, and stops moving of the uppermost sheet stacking device in case said sensor device does not detect that the uppermost sheet stacking device reaches the upper limit position even after a lapse of the predetermined time.