Patent ID: 7954809

Claim:
A sheet post-processing apparatus, comprising: a discharge member for discharging a sheet; a discharge tray being movable up and down and for stacking sheets discharged from the discharge member successively thereon; a sheet detector for detecting that the sheet is discharged from the discharge member; and a sheet hold member being capable of changing states between a hold state in which the sheet hold member holds a top surface of sheets discharged to the discharge tray and a release state in which the hold is released, wherein the discharge tray is capable of moving up and down between a hold position where the top surface of the sheets is held by the sheet hold member which is in the hold state and a wait position which is lower than the hold position and where the top surface of the sheets is not held by the sheet hold member which is in the hold state, with the discharge tray situated at the hold position and with the sheet hold member holding the sheet stacked on the discharge tray, discharge of the sheet onto the discharge tray is started, and when the sheet detector detects completion of the sheet discharge, the sheet hold member changes state from the hold state to the release state and the discharge tray moves down from the hold position to the wait position, then, the sheet hold member changes to the hold state and the discharge tray moves up to the hold position, and thereby the top surface of the sheets is held by the sheet hold member.