A sheet alignment device includes a roller that moves a sheet on a sheet transport route so that a side edge of the sheet abuts against an alignment member, a first one-way clutch that transmits a first rotative driving force for making a roller support device pivot upward with respect to the shaft of the roller support device, when a motor rotates in a first direction, a first torque limiter that disconnects the transmission of the first rotative driving force, when a rotation control device limits the rotation of the shaft, a second one-way clutch that rotates with a second rotative driving force, and making the roller support device pivot downward, when the motor is stopped, and a second torque limiter that stops the rotation of the shaft, by being subjected to a rotational torque of the second one-way clutch.

A method for aligning a sheet in a feeder of a sheet-processing machine, where the sheet that is clamped between feed rollers and counterpressure rollers is delivered to a sheet transport device is aligned laterally during this process. First, the sheet is laterally aligned by clamping between feed and counterpressure roller pairs, and a slide to which the feed rollers are mounted, is moved with the clamped sheet transversely to the transport direction in a first direction. Second, the counterpressure rollers are raised from the sheet after the sheet has been gripped by the sheet transport device and before the slide with the feed rollers is moved back to its original position. The return movement of the slide takes place while the sheet, which is no longer clamped, is still present in the region between the feed and counterpressure roller pairs.

A sheet post-processing device includes a conveying member, a processing tray, a processing section, a reference plate, an alignment member, a holder drive unit, and a control unit. The alignment member includes a paddle holder, and an alignment paddle having a paddle main body supported in a rotatable manner at the paddle holder, and a paddle part protruding from the paddle main body. The holder drive unit moves the alignment paddle in a reciprocating manner, between a reference position to separate the paddle part above a top sheet and an acting position to allow the paddle part to contact with the top sheet. The control unit sets a second acting position when the paddle part contacts with the sheet at n1-th time, to be higher than a first acting position when the paddle part contacts with the sheet at m1-th time, where 1m1<n1 holds.

A sheet separation device includes a sheet separation unit, a displacement detector, a displacement adjuster, and a controller. The sheet separation unit performs a sheet separating operation and a sheet inserting operation. The displacement detector detects a displacement amount of the two-ply sheet when the two-ply sheet is displaced in a width direction of the two-ply sheet and detects a displacement amount of the inner sheet. The displacement adjuster adjusts the displacement of the two-ply sheet in the width direction before the sheet separating operation, based on the displacement amount of the two-ply sheet in the width direction detected by the displacement detector. The controller causes the displacement adjuster to adjust relative positions of the two-ply sheet and the inner sheet between the sheet separating operation and the sheet inserting operation, based on the displacement amount of the inner sheet in the width direction detected by the displacement detector.

A sheet conveyance apparatus includes a first conveying rotary member pair, an abutment portion, a first skewing rotary member pair, a second skewing rotary member pair, a switching mechanism, and a control unit. The control unit executes a first mode of controlling the second skewing rotary member pair to be in a nipping state in a sheet oblique conveyance state which is a state from when the first skewing rotary member pair starts an oblique conveyance of the sheet having been conveyed by the first conveying rotary member pair until an edge portion in a width direction of the sheet abuts the abutment portion, and a second mode of controlling the second skewing rotary member pair to be in a non-nipping state in the sheet oblique conveyance state.