Patent ID: 8398078

Claim:
A post-processing device, comprising: a pair of feed rollers configured to feed a sheet of medium in a feed direction while sandwiching the sheet of medium therebetween; a tray configured to stack the sheet of medium fed by the pair of feed rollers in a stacking direction; and a sheet aligning mechanism configured to cause the sheet of medium stacked on the tray to move in a shift direction perpendicular to the feed direction and the stacking direction, such that the sheet of medium is aligned, wherein the sheet aligning mechanism comprises: a pair of alignment members including a pair of alignment surfaces configured to push an end of the sheet of medium in the shift direction, the pair of alignment surfaces extending into a region above the tray in the stacking direction; an alignment member support configured to support the pair of alignment members such that each of the pair of alignment members is rotatable about a rotation shaft extending in the shift direction and rectilinearly movable in the shift direction, within a region on a side closer to the sheet of medium stacked on the tray with respect to the stacking direction; a driving mechanism configured to cause the pair of alignment members to rotate about the rotation shaft extending in the shift direction and to rectilinearly move in the shift direction; a first detector configured to detect whether the pair of alignment members has moved to a rotational waiting position provided for the pair of alignment members, the rotational waiting position being a part of a rotational range in which the pair of alignment members is rotatable about the rotation shaft extending in the shift direction; a second detector configured to detect whether the pair of alignment members has moved to a rectilinear waiting position provided for the pair of alignment members, the rectilinear waiting position being a part of a rectilinear range in which the pair of alignment members is movable in the shift direction; and a post-processing controller configured to cause the driving mechanism to correct a rotational angle and an amount of rectilinear movement based on signals sent from the first detector and the second detector, wherein one rotation shaft about which one of the air of alignment embers rotates is configured to be spaced away a distance from the other rotation shaft about which the other one of the pair of alignment members rotates.