Sheet storage apparatus and image forming system including the same

A sheet storage apparatus comprising:

• a body housing;
• a sheet stacking tray supported in the body housing so as to be capable of ascending and descending, the sheet stacking tray being stacked with sheets;
• a pulley portion supported in the body housing so as to be rotatable about a rotation axis in forward and reverse directions;
• a wire having one end thereof fixed to the pulley portion and having another end thereof fixed to the sheet stacking tray, the wire suspending the sheet stacking tray via a pulley, the wire being reeled in as the pulley portion rotates in the forward direction and being reeled out as the pulley portion rotates in the reverse direction;
• a driving portion making the pulley portion rotate;
• a sensing portion sensing an ascent/descent position of the sheet stacking tray;
• and
• a control portion controlling the driving portion,
• wherein
• the sensing portion includes:
• a swing member supported so as to be swingable about a swing shaft as a fulcrum;
• a sensor sensing movement of the swing member toward and away from the sensor;
• and
• an urging member urging the swing member in a direction away from the sensor,
• with the wire wound up in the pulley portion, the wire is disposed in a pressing position extending along a tangential line common to the pulley portion and the pulley,
• the wire disposed in the pressing position presses the swing member against an urging force from the urging member such that the swing member approaches the sensor,
• with the wire completely unwound out of the pulley portion and hence with the sheet stacking tray disposed at a lowest position, the wire is disposed in a retracted position retracted from the pressing position,
• the wire disposed in the retracted position no longer presses the swing member and stays away from the sensor, and
• the control portion stops the driving portion on recognizing the swing member having moved away from the sensor.