Sheet binding device and sheet post-processing apparatus including same

A sheet binding device, comprising:

• a processing tray on which a plurality of sheets conveyed thereto along a predetermined sheet entry direction are stacked;
• a movable reference plate that is disposed at a predetermined initial position at which the movable reference plate is capable of aligning the sheets by abutting edges of the sheets on a downstream side in an alignment direction that is opposite to the sheet entry direction, the movable reference plate being movable from the initial position in a sheet width direction that is orthogonal to the sheet entry direction;
• a stapling portion that is disposed opposite to the edges of the sheets, and that performs a stapling process of binding the plurality of sheets stacked on the processing tray with a staple needle at a predetermined position;
• a movement portion that causes the stapling portion to move, along the edges of the sheets, to a reference position that is located outward of the initial position in the sheet width direction and to at least one stapling position that is located inward of the initial position in the sheet width direction and at which the staple process is performed;
• a slide member on which the movable reference plate is mounted and that is reciprocatable along the sheet width direction;
• and
• a slide spring that biases the slide member in a direction in which the movable reference plate approaches the initial position,
• wherein
• the movement portion is capable of shifting orientation of the stapling portion to an inclined state inclined with respect to the edges of the sheets and to a parallel state parallel to the edges of the sheets,
• the slide member includes a movable engagement member that makes contact with a stapling-side engagement portion of the stapling portion when the stapling portion moves between the reference position and the stapling position,
• in a state in which the movable reference plate is disposed at the initial position, when the stapling portion is brought into the inclined state and moved from the reference position to the stapling position, the stapling-side engagement portion presses the movable engagement member, thereby causing the movable reference plate to move with the slide member inward in the sheet width direction against a biasing force of the slide spring,
• when the orientation of the stapling portion is shifted from the inclined state to the parallel state before the stapling portion reaches the stapling position, the stapling-side engagement portion separates from the movable engagement member, thereby causing the movable reference plate to move with the slide member outward in the sheet width direction due to the biasing force of the slide spring, so as to return to the initial position,
• when the orientation of the stapling portion is shifted from the parallel state to the inclined state while the stapling portion is moved from the stapling position to the reference position, the stapling-side engagement portion presses the movable engagement member, thereby causing the movable reference plate to move with the slide member inward from the initial position in the sheet width direction against the biasing force of the slide spring, and
• due to movement of the stapling portion to the reference position, the stapling-side engagement portion separates from the movable engagement member, thereby causing the movable reference plate to move with the slide member outward in the sheet width direction due to the biasing force of the slide spring, so as to return to the initial position.