Sheet processing device, image forming system, and sheet processing method

An image forming system comprising:

• a sheet processing device;
• and
• an image forming apparatus configured to form an image on a sheet, wherein the sheet processing device includes:
• a stacking unit configured to stack thereon one or more conveyed sheets;
• a staple unit configured to staple a bundle of sheets stacked on the stacking unit;
• a moving unit configured to move the staple unit to a staple position;
• and
• a projecting and retrieving unit configured to project and retrieve the stacking unit in a space overlapped with a motion space for the staple unit to move therein, wherein:
• the stacking unit includes a fixed tray and a movable tray,
• the projecting and retrieving unit projects and retrieves the movable tray along the fixed tray,
• the projecting and retrieving unit retrieves the movable tray from the motion space, in order to move the staple unit by the moving unit, and the moving unit as well as the projecting and retrieving unit are driven by the same drive source.

A sheet processing method capable of realizing one-position parallel stapling, one-position slanted stapling, and two-position stapling, implemented by a sheet processing device which includes:

• a stacking unit configured to stack thereon one or more conveyed sheets;
• a staple unit configured to staple a bundle of sheets stacked on the stacking unit;
• a moving unit configured to move the staple unit to a staple position;
• and a projecting and retrieving unit configured to project and retrieve the stacking unit in a space overlapped with a motion space for the staple unit to move therein, wherein the stacking unit includes a fixed tray and a movable tray, the projecting and retrieving unit projects and retrieves the movable tray along the fixed tray, the projecting and retrieving unit retrieves the movable tray from the motion space, in order to move the staple unit by the moving unit, and the moving unit as well as the projecting and retrieving unit are driven by the same drive source, the method comprising:
• projecting maximally the stacking unit by the projecting and retrieving unit, and disposing the staple unit at a first staple position located outside of the motion space, when stacking the sheets on the stacking unit;
• stapling the bundle of sheets at the first staple position, after projecting maximally the stacking unit and disposing the staple unit at the first staple position, if the one-position parallel stapling is to be performed;
• rotating the staple unit by an angle corresponding to a staple angle for the slanted stapling, retrieving the stacking unit by the projecting and retrieving unit to a position where the stacking unit does not hinder a rotation of the staple unit, and stapling the bundle of sheets at a second staple position, after projecting maximally the stacking unit and disposing the staple unit at the first staple position, if the one-position slanted stapling is to be performed;
• rotating the staple unit to a position where a staple needle of the staple unit becomes parallel to a rear end of the bundle of sheets, retrieving the staple unit maximally by the projecting and retrieving unit to a position where the stacking unit does not hinder the motion of the staple unit, and stapling the bundle of sheets at a third staple position and a fourth staple position, after projecting maximally the stacking unit and disposing the staple unit at the first staple position, if the two-position stapling is to be performed.