Sheet processing apparatus, image forming system, and non-transitory computer readable medium

A sheet processing apparatus comprising:

• a vertically movable tray that moves vertically in accordance with an amount of stacked folded sheets which are transported and stacked thereon;
• a setting clamp that presses an upstream portion of a stacked sheet in a transport direction;
• a plate disposed above the vertically movable tray;
• a recognizing unit that recognizes a predetermined height state of a sheet stacked on the vertically movable tray;
• and
• a controller that controls the vertically movable tray so as to, in response to a recognition of the predetermined height state of the sheet by the recognizing unit, move the vertically movable tray upward, press a downstream portion of the sheet in the transport direction, which is stacked on the vertically movable tray, against the plate, and subsequently move the vertically movable tray downward.

An image forming system comprising:

• an image forming unit that forms an image on a transported sheet;
• a folding processing unit that performs folding processing on the sheet on which the image is formed by the image forming unit;
• a vertically movable tray that stacks the sheet subjected to the folding processing and that is vertically movable;
• a plate that is disposed above the vertically movable tray and that does not move in accordance with transport of a folded sheet;
• a recognizing unit that recognizes a predetermined height state of the sheet stacked on the vertically movable tray;
• and
• a controller that controls the vertically movable tray so as to, in response to a recognition of the predetermined height state of the sheet by the recognizing unit, move the vertically movable tray upward, press the sheet stacked on the vertically movable tray against the plate, and subsequently move the vertically movable tray downward, wherein the plate does not move during a period spanning from when the folded sheet is transported to the vertically movable tray to when the sheet stacked on the vertically movable tray is pressed against the plate.