When duplex printing non-rectangular sheets of printable media, the sheets require proper registration to prevent misalignment of front and back images. This is ensured by: determining relative orientations of three different edges of a sheet being transported towards print station on a first pass; registering the sheet on the first pass by aligning one of the edges with respect to a predetermined alignment direction; printing a first image on a first side of the registered sheet; flipping the sheet on a second pass; registering the flipped sheet by aligning one of the edges with respect to a predetermined alignment direction; and printing a second image on a second side of the registered, flipped sheet aligned with the first image based on the determined relative orientations.

The present invention provides a conveyor mechanism for conveying sheets. The conveyor mechanism comprises a movable conveyor body, a drive mechanism, and an adjustment system configured to detect and correct skewing of the conveyor body, comprising one or more markers provided on or in the conveyor body, a sensor arrangement for detecting each marker at two or more discrete positions, and a processor to determine the skewing of the conveyor body. The conveyor body and the drive mechanism of the conveyor mechanism are mounted on a movable conveyor frame, and the adjustment system includes a frame shifting device comprising one or one or more actuator for shifting or moving the conveyor frame relative to a fixed framework. The invention also provides a related method of correcting skewing in a conveyor mechanism for conveying sheets along a transport path.

A sheet conveying device includes a sheet detection unit and a position adjusting mechanism. The position adjusting mechanism is disposed on a downstream side of the sheet detection unit in a sheet conveying direction in the sheet conveying path, includes an adjusting roller pair, and performs skew correction and positional displacement correction of a sheet, while conveying the sheet. The sheet conveying path includes a first conveying roller pair disposed on an upstream side of the position adjusting mechanism in the sheet conveying direction, and a curved part disposed between the adjusting roller pair and the first conveying roller pair, which curves in an S shape so as to be convex in a front and back side direction of the sheet alternately at different positions in the sheet conveying direction. The adjusting roller pair nips and conveys the sheet together with the first conveying roller pair.

An image forming apparatus, including: a sheet cassette; an image former; a fixer; a discharge tray; a conveyor configured to convey a sheet along a conveyance passage; a return conveyor configured to convey the sheet from a branch position between the fixer and the discharge tray to a merge position between the sheet cassette and the image former along a return passage which is branched from the conveyance passage at the branch position, passes below the sheet cassette, and merges with the conveyance passage at the merge position; a switchback roller disposed between the branch position and the discharge tray in the conveyance passage and configured to convey the sheet to the discharge tray when it rotates forwardly and to the return passage when it rotates backwardly; and an intermediate conveyance roller disposed in the return passage at a height level intermediate between the fixer and the sheet cassette.

A sheet processing system according to an embodiment includes a tray that supports a sheet on opposite sides of the sheet orthogonal to a conveyance direction of the sheet. The tray includes a first adjustable support and second adjustable support positioned opposite the first adjustable support in the direction orthogonal to the conveyance direction of the sheet. A skew sensor detects a skew angle of the sheet conveyed to the tray. A corner sensor detects positions of each corner on a front end in the downstream direction of the sheet conveyed to the tray. A controller controls movement of the first and second adjustable supports based on the detected skew angle and the detected positions of each corner on the front end of the sheet conveyed to the tray so that the sheet is conveyed to the tray without jamming.

An image forming apparatus includes an image forming unit, a reversing roller pair, a moving unit, and an obtaining unit. The image forming unit forms an image on a sheet. The reversing roller pair nips the sheet having the image, rotates in a first direction, and then rotate in a second direction and conveys the sheet. The moving unit moves the reversing roller pair. The obtaining unit obtains the sheet length. If a first sheet having a first length is reversed and conveyed, the moving unit moves the reversing roller pair conveying the first sheet in the width direction by a first moving amount. If a second sheet having a second length greater than the first length is reversed and conveyed, the moving unit moves the reversing roller pair conveying the second sheet in the width direction by a second moving amount smaller than the first moving amount.

An image formation device includes: a registration roller pair configured to shift sheet in a second direction perpendicular to a first direction of a sheet feeding direction while holding the sheet; a feeding section provided upstream of the registration roller pair in the first direction and including a feeding belt configured to convey the sheet to the registration roller pair; a first air adjustment section configured to perform air suction or blowing for the sheet conveyed by the feeding belt; and a control section configured to switch between a first operation of controlling, when the sheet is conveyed by the feeding belt, the first air adjustment section to suck the sheet with air and a second operation of controlling, when the sheet is swung by the registration roller pair, the first air adjustment section to blow air on the sheet.

A sheet conveying device includes a blocking member having a blocking surface with which a leading end of a sheet that is being conveyed comes into contact for obliquity correction. The blocking member is rotated by being pushed by the sheet against an urging force of a positioning unit that positions the blocking member to be in the standby position. The blocking member is rotatable to be in a sheet-passage-allowing orientation in which the sheet is allowed to pass. When a trailing end of the sheet that is being conveyed has passed the blocking member, the blocking member that is in the sheet-passage-allowing orientation rotates in a same direction as a sheet conveyance direction and is positioned to be in a standby position.

A sheet conveying device, which is incorporated in an image forming apparatus, includes a first detector to detect an angle deviation of a recording medium to a sheet conveying direction, a second detector to detect a lateral shift of the recording medium to a width direction, a third detector to detect at least one of the angle deviation and the lateral shift after correction of the angle deviation detected by the first detector and the lateral shift detected by the second detector, and a rotary body to perform a primary movement by (1) rotating in the sheet conveying direction and returning to a reference position and by (2) moving in the width direction and returning to the reference position, and a secondary movement by performing at least one of (1) and (2) after the primary movement.

An image-forming apparatus contains an image-forming portion, a first conveying portion that is arranged at an upstream side of the image-forming portion along a sheet conveying direction, a second conveying portion that is arranged at an upstream side of the first conveying portion along the sheet conveying direction and a control portion. The control portion controls the first conveying portion to move a pair of registration rollers along a direction that is orthogonal to the sheet conveying direction while the pair of registration rollers nips the sheet when conveying the sheet to the image-forming portion. The control portion controls the second conveying portion to move one of the pair of conveying rollers along the direction that is orthogonal to the sheet conveying direction while the pair of conveying rollers does not nip the sheet.