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 conveyance device includes a registration roller pair including a first roller and a second roller, configured to form a nip by the first roller and the second roller, and configured to correct a skew of a sheet conveyed thereto by allowing the sheet to abut the nip. The first roller includes an outer peripheral surface with a groove portion, the groove portion being formed in a region in which a corner portion of a sheet abuts the outer peripheral surface, and causing a part of the outer peripheral surface to be concave and another part of the outer peripheral surface to be convex in an axial direction.

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.

A sheet folding device, which is included in an image forming system and uses a sheet folding method, includes first and second drive motors, a first sheet conveyor driven by the first drive motor and configured to receive and convey a sheet toward a downstream side of a sheet conveying direction, a second sheet conveyor driven by the second drive motor and configured to receive the sheet conveyed from the first sheet conveyor and to convey the sheet to the downstream side of the sheet conveying direction, and a controller configured to fold the sheet to a predetermined folding length set according to an amount of conveyance of the sheet by the second sheet conveyor while the sheet is being held between the first and second sheet conveyors, and to perform a feedback control with an integral gain to the second drive motor.

In some examples, a sheet processing machine includes at least one infeed system including at least one transport means including at least one upper holder and at least one lower holder. The at least one transport means can be and/or is arranged in at least three states: a maximally closed state corresponding to a minimal distance, a minimally closed state corresponding to a maximal distance, and an at least one mean state corresponding to at least one mean distance between at least one upper holding surface at least of the respective upper holder, and at least one lower holding surface of the lower holder of the at least one transport means that is assigned to the respective upper holder. During a machine cycle, the at least one transport means has each of the minimally closed state, the maximally closed state, and the at least one mean state at least once.

A paper aligning mechanism and an image generating device having the same are provided, the paper aligning mechanism is arranged on a calibration path of the image generating device, the calibration path is arranged between a paper assigning mechanism and a paper-feeding mechanism of the image generating device, and the paper aligning mechanism has at least two calibrating swingarms arranged spacedly. Each of the calibrating swingarms has an arm portion and a pivoting axle portion arranged on the arm portion to pivotally connect the arm portion to the image generating device. The arm portion has an extending segment and a limiting segment extended from the extending segment, the limiting segment is downward extended along the calibration path toward an exit of the calibration path to be swingable and to block the exit of the calibration path.

According to an embodiment, a sheet processing apparatus includes a transport unit and a holding unit. The transport unit transports a first sheet to a first position. The transport unit transports a second sheet, which is transported after the first sheet, to a second position displaced to the upstream side of a sheet transport direction relative to the first position. The transport unit transports a third sheet, which is transported after the second sheet, to a third position displaced to the downstream side of the sheet transport direction relative to the second position. In the case where the second sheet is transported to the second position, the holding unit holds the first sheet at the first position. In the case where the third sheet is transported to the third position, the holding unit holds the second sheet at the second position.

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 paper guide mechanism that facilitates operation without easily allowing deviation of a wide guide unit. In a paper guide mechanism (10), a position-holding member (13) holds the widthwise position of a widthwise moving member (12) by bringing a first fixing-side locking section (11e) and a first moving-side locking section (13d) into contact with each other on a surface perpendicular to a direction of movement of the widthwise moving member (12) even in a case in which the widthwise moving member (12) is about to move in any direction along the width direction. The position-holding member (13) has a movement-restricting section (13e). The movement-restricting section (13e) restricts the movement of the position-holding member (13) in an orientation in which the first fixing-side locking section (11e) and the first moving-side locking section (13d) are moved away from each other by bringing the position-holding member (13) into contact with a second surface of a supporting member (11) on a side opposite to a first surface.

A paper conveying apparatus and an image forming apparatus are described which can appropriately convey a sheet when the sheet is restarted after forming a loop. The paper conveying apparatus includes a conveying roller pair in the upstream side of a loop roller pair, a stepping motor for rotationally driving the conveying roller pair, and a processor for controlling rotation of the stepping motor by controlling pulse signals and excitation current supplied to the stepping motor. This processor halts rotation of the conveying roller pair by stopping output of the pulse signals when loop formation of the sheet is completed, and switches the excitation current to a lower current value which is lower than a reference current value at which excitation is turned on.