Patent ID: 8023880

Claim:
A sheet post-processing apparatus comprising: a standby tray having a pair of tray members to be able to move to make a sheet discharged from an image forming apparatus stand by; a processing tray arranged under the standby tray; a paddle configured to beat down a sheet from the standby tray to the processing tray; a processing mechanism to perform post-processing for the sheet; a sheet discharge tray to load the sheet, the sheet discharge tray tilted such that the discharge direction front end of the sheet is positioned higher than the discharge direction rear end thereof; a feed pawl to discharge, via a discharge path, the sheet from the processing tray to the discharge tray; a plurality of ejection rollers to discharge the sheet from the processing tray to the discharge tray; a motor to drive the plurality of ejection rollers in a first direction and in a second direction, where the second direction is counter to the first direction; a rear end supporting mechanism arranged on the discharge direction rear end side of the sheet discharge tray, where the rear end supporting mechanism has stationary portions and movable portions that can slide to extend upwardly from the stationary portions; and an electromagnetic clutch forming part of a drive link mechanism between the motor and the movable portions, wherein when the electromagnetic clutch is on and the ejection rollers are rotated in the first direction by the motor, the movable portions are driven to a first position to facilitate discharge of the sheet along the discharge path, and wherein when the electromagnetic clutch is on and the ejection rollers are rotated in the second direction by the motor, the movable portions are driven to a second position where the movable portions block the discharge path to prevent a rear end of a sheet on the discharge tray from contact with the ejection rollers.