Sheet stacking tray, sheet stacking apparatus, and image forming system

A sheet stacking tray comprising:

• a first conveyor configured to sequentially convey a plurality of sheets ejected to the sheet stacking tray, in a sheet conveyance direction to form a sheet bundle;
• a second conveyor disposed downstream from the first conveyor in the sheet conveyance direction;
• a sheet stopper pivotable between a protruding position and a lowered position, the sheet stopper being configured to block the plurality of sheets conveyed by the first conveyor to form the sheet bundle when the sheet stopper is at the protruding position, the sheet stopper being configured to allow the formed sheet bundle to pass when the sheet stopper is at the lowered position;
• a first full-load detector configured to detect that the sheet bundle blocked by the sheet stopper is fully loaded;
• and
• a second full-load detector configured to detect that a leading edge of the sheet bundle conveyed by the second conveyor has reached a downstream end portion of the second conveyor in the sheet conveyance direction;
• a plurality of motors configured to:
• maintain the sheet stopper at the protruding position to block the sheet conveyed by the first conveyor until the first full-load detector outputs a signal indicating that the sheet bundle is fully loaded;
• shift the sheet stopper to the lowered position to allow the sheet bundle to pass when the first full-load detector outputs the signal indicating that the sheet bundle is fully loaded;
• drive the first conveyor and the second conveyor together to convey the sheet bundle when the sheet stopper shifts to the lowered position;
• and
• stop the second conveyor and drive only the first conveyor, when the second full-load detector detects the leading edge of the sheet bundle.