Patent ID: 9434570
Filing Date: 2016-09-06
CPC Classification: B65H

Claim Text:
1. A sheet processing device, comprising: an exit tray on which ejected sheets or ejected sheet sheaves subjected to stapling are stacked; a sheet alignment mechanism configured to align, when at least a sheet is ejected, the sheets in a manner to be in contact with and catch opposite edges of the sheets stacked on the exit tray from a base end side of the exit tray; a lifting controller configured to lift up and down the exit tray so that a height of a corner of a topmost surface of the sheet sheaves, the corner being raised by staple parts formed in the stapling, is kept constant; and a control section, wherein when stapling is performed and a sheet sheaf is ejected, the sheet alignment mechanism comes in contact with a first point and a second point on a topmost surface of the sheet sheaves stacked on the exit tray to detect a height difference between the first and second points, the first point is located in a raised region of the topmost surface of the sheet sheaves, the raised region being raised by accumulation of the staple parts, the second point is located in a flat region of the topmost surface of the sheet sheaves, the sheet alignment mechanism includes a pair of alignment members and a detection mechanism one of the pair of alignment members comes in contact with the first point, the other of the pair of alignment members comes in contact with the second point, the one and the other of the pair of alignment members are each independently rotatable about an axial line in a shifting direction orthogonal to an ejection direction in which a sheet is ejected and to a stacking direction in which a sheet is stacked, and each have play to make difference in amount of rotation between the one and the other of the pair of alignment members when driven at the same amount of rotation, the play is set such that the difference in amount of rotation is equal to or larger than a specific amount, the specific amount indicates an amount of rotation referenced for determining that the height difference exceeds an allowable limit, the control section controls the other of the pair of alignment members to rotate until the other of the pair of alignment members is enabled to detect the specific amount in a state in which the one of the pair of alignment members is in contact with the first point, the detection mechanism detects the difference in amount of rotation between the one and the other of the pair of alignment members as the height difference between the first and second points.