A sheet processing apparatus is provided with a carry-in path for guiding a sheet from a carry-in entrance, a shift roller provided in the carry-in path to transport the sheet, while shifting, a carry-in roller positioned on the downstream side of the shift roller to carry the sheet from the carry-in path toward a collection tray, and a punch shift unit provided on the upstream side of the carry-in roller to process an end portion of the sheet in a processing position. The punch shift unit shifts in the same direction as the shift roller, a shift amount of the punch shift unit is set to be equal to a shift amount of the shift roller or more, and the end portion processing unit is thereby already positioned in an end portion processing position or a position near the processing position after shifting the sheet.

A medium transport device includes: a first transport unit that is provided in a first transport path, and nips and transports a medium by a pair of rotating bodies; a second transport unit that is provided in a second transport path different from the first transport path, and nips and transports a medium by a pair of rotating bodies; a first rotation drive unit that rotationally drives the pair of rotating bodies of the first transport unit; a second rotation drive unit that rotationally drives the pair of rotating bodies of the second transport unit; and a pressure contact force adjustment unit that is provided in at least one of the first transport unit or the second transport unit, and adjusts a pressure contact force of the pair of rotating bodies. When one of the first transport unit or the second transport unit nips and transports the medium, the pressure contact force adjustment unit adjusts the pressure contact force of the one transport unit that nips and transports the medium by utilizing a drive source of a rotation drive unit that provides no driving force for transporting the medium to the first transport unit or the second transport unit.

There is provided an intermediate unit including a transportation path along which a medium, on which printing has been performed by a printing unit that performs printing on the medium by using liquid, is transported to a post processing unit that performs post processing on the medium. The transportation path includes first and second inversion paths in which the medium is inverted upside down, respectively, the second inversion path being provided with a decurling unit that corrects curl of the medium, the first inversion path being not provided with the decurling unit, the first and second inversion paths being selectively used to invert the medium upside down according to printing data for the medium.

There is provided an intermediate unit including a transportation path along which a paper sheet, on which printing has been performed by a printing unit that performs printing on the paper sheet as a medium by using liquid, can be transported to a post processing unit that performs post processing on the paper sheet, in which the transportation path is provided with a drying unit that accelerates the drying of the paper sheet.

A sheet processing apparatus includes an intermediate tray on which a sheet is to be stacked, a stapler to execute stapling processing on the stacked sheet, a discharge tray on which the sheet subjected to the stapling processing by the stapler and discharged from the intermediate tray is to be stacked, a control unit, and a shift unit. The shift unit may shift the sheet to a position on the intermediate tray, wherein the position is outside of a range in which the stapling processing is to be executed. In a state where a first sheet and a second sheet are stacked on the intermediate tray and the second sheet is subject to the stapling processing, the control unit causes the shift unit to shift the first sheet on which the stapling processing is not executed, and causes the stapler to execute the stapling processing on the second sheet.

A sheet discharge device of the present invention includes discharge rollers configured to transport a sheet in a predetermined transport direction and to discharge the sheet to a discharge tray, and an upper discharge tray disposed above the discharge tray with a space being interposed therebetween. A bottom face of the upper discharge tray that faces the discharge tray includes a guide rib extending in an oblique direction inclined relative to the transport direction.

A sheet discharge device of the present invention includes discharge rollers configured to transport a sheet in a predetermined transport direction and to discharge the sheet to a discharge tray, and an upper discharge tray disposed above the discharge tray with a space being interposed therebetween. A bottom face of the upper discharge tray that faces the discharge tray includes a guide rib extending in an oblique direction inclined relative to the transport direction.

A drive transmission mechanism which transmits a rotational driving force to a roller to be shifted in directions of a rotational axis thereof is equipped with a rotary drive transmission member which is driven to rotate in a predetermined rotational direction, a holder which holds the roller in such a manner that the roller can slide freely in the rotational axis directions while rotating about the rotational axis, and a one-way clutch interposed between the rotary drive transmission member and the holder. The one-way clutch is configured to transmit a rotational driving force from the rotary drive transmission member to the holder, and also to permit the holder to rotate in the predetermined rotational direction relative to the rotary drive transmission member.

A medium transport device includes: a first transport unit on a front side and a first transport unit on a rear side that are respectively disposed in a front part and a rear part of a region having a length in a transport direction of a medium having a transportable minimum size and that transport the medium while nipping the medium; a second transport unit that is disposed between the first transport units and that transports the medium while nipping the medium and pulling the nipped medium outward in a width direction intersecting the transport direction; and a controller that performs control so that the medium transport device transports the medium while nipping the medium by using only the second transport unit when the medium is a thin medium having a thickness less than or equal to a predetermined thickness and so that the medium transport device transports the medium while nipping the medium by using the first transport units and the second transport unit when the medium is a medium other than the thin medium.

An image forming apparatus includes: a pair of rollers for conveying paper; a rocking mechanism for rocking the pair of rollers in a second direction orthogonal to a first direction, the first direction being a paper conveying direction; an upstream pair of rollers provided upstream of the pair of rollers in the paper conveying direction for conveying the paper; an upstream rocking mechanism corresponding to the upstream pair of rollers for rocking the upstream pair of rollers in the second direction; a first paper detector for detecting an end position of the paper in the second direction; and a controller controlling the rocking mechanism based on the paper end position to effect first rocking correction in which the pair of rollers is rocked, wherein the controller controls the upstream rocking mechanism to effect second rocking correction in which only the upstream pair of rollers is rocked.