Patent ID: 8794622

Claim:
A sheet stacking device comprising: a sheet stacking unit provided in a body and configured to be movable upward and downward and to stack the sheets discharged by a discharge portion; an elevation unit configured to raise and lower the sheet stacking unit; a door provided on the body and configured to be opened when sheets stacked on the sheet stacking unit are removed; a detection portion configured to detect the door being open; a drive source configured to drive the elevation unit; and a transmission unit transmitting a driving force of the drive source to the elevation unit to raise and lower the sheet stacking unit, the transmission unit comprising: a ratchet provided in a drive force transmitting route to transmit the drive force from the drive source to the elevation unit; a lock portion configured to be able to regulate the ratchet so as to interrupt a transmission of the drive force to raise the sheet stacking unit when the lock portion contacts the ratchet to regulate the ratchet; and an actuating portion configured to release the lock portion from the ratchet while being supplied with a driving current based on a detection of the door being closed by the detecting portion and to contact the lock portion to the ratchet without being supplied with the driving current based on a detection of the door being open by the detecting portion, wherein, in a state where the door is closed, the actuating portion releases the lock portion from the ratchet to transmit the drive force to the elevation unit to raise and lower the sheet stacking unit via the drive force transmitting route, and in a state where the door is open, the actuating portion brings the lock portion into contact with the ratchet to transmit to the elevation unit only the driving force to lower the sheet stacking unit via the drive force transmitting route.