Sheet accumulation apparatus and image formation apparatus including the apparatus

A sheet accumulation apparatus, comprising:

• a tray moving device having a first fork member and elevatably provided at a lower side of a paper ejection opening for sequentially discharging sheets;
• a tray device detachably disposed on the first fork member for mounting the sheets ejected from the paper ejection opening;
• a driving device for moving the tray moving device up and down under the paper ejection opening;
• an installation frame equipped with the tray moving device and the driving device, and having side frames;
• and
• a carrier device which receives the tray device from and provides the tray device to the first fork member at an attachment/detaching position at which the tray moving device is lowered in the sheet accumulation apparatus to carry the tray device outside the apparatus,
• wherein the carrier device includes a hand truck frame with a second fork member for mounting the tray device, a transport wheel formed immediately beneath the second fork member, and an operation handle connected to the hand truck frame for operating the hand truck frame, and
• the side frames form a guide for guiding the second fork member to align with the first fork member and are arranged such that when the tray device is transferred between the tray moving device and the carrier device at the attachment/detachment position, upper surfaces of the first and second fork members are aligned side by side and are located at a substantially same plane.