A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.

With a cover in a closed position, a first internal gear and a first spur gear do not mesh with each other, and a second internal gear and a second spur gear do not mesh with each other. When the cover rotates by a predetermined angle around a first support shaft from the closed position, the first internal gear and the first spur gear start to mesh with each other. When the cover rotates by a predetermined angle around a second support shaft from the closed position, the second internal gear and the second spur gear start to mesh with each other.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.

A sheet folding apparatus including a folding roller, a positioning member, a push member, and a shift member. The folding roller including a pair of rollers to rotatably engage with each other to form a folding nip. The positioning member to support a first end of a printing medium which is fed along a folding path and to arrange the printing medium in an initial folding location. The push member to move to an insertion location to push the printing medium on the folding path into the folding nip, and to move to a retreat location. The shift member, located at an exit of the folding nip, to selectively guide the printing medium to a guide path to return the printing medium having passed through the folding nip to the folding path, the guide path being provided around at least one of the pair of rollers.

With a cover in a closed position, a first internal gear and a first spur gear do not mesh with each other, and a second internal gear and a second spur gear do not mesh with each other. When the cover rotates by a predetermined angle around a first support shaft from the closed position, the first internal gear and the first spur gear start to mesh with each other. When the cover rotates by a predetermined angle around a second support shaft from the closed position, the second internal gear and the second spur gear start to mesh with each other.

A sheet folding apparatus including a folding roller, a positioning member, a push member, and a shift member. The folding roller including a pair of rollers to rotatably engage with each other to form a folding nip. The positioning member to support a first end of a printing medium which is fed along a folding path and to arrange the printing medium in an initial folding location. The push member to move to an insertion location to push the printing medium on the folding path into the folding nip, and to move to a retreat location. The shift member, located at an exit of the folding nip, to selectively guide the printing medium to a guide path to return the printing medium having passed through the folding nip to the folding path, the guide path being provided around at least one of the pair of rollers.

A lead-in path through which a sheet is led in; a first branch path and a second branch path which branch from the lead-in path; a first switchback path which extends from the first branch path; a second switchback path which extends from the second branch path; a first joining path and a second joining path through which the switched-back sheet is transported; and a lead-out path which extends from a joining point at which the first joining path and the second joining path join with each other, are provided. The lead-out path passes through between the first switchback path and the second switchback path. A first connection point at which the first switchback path and the first joining path are connected to each other is disposed above a second connection point at which the second switchback path and the second joining path are connected to each other.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.

A medium transport unit includes an upstream route in which a print sheet is transported, a first switchback route, a second switchback route, a first guide route, a second guide route, a guide flap configured to switch the route so that the print sheet in the upstream route is transported either toward the first guide route or toward the second guide route, a first discharge route from which the print sheet in the first switchback route is discharged, a second discharge route from which the print sheet in the second switchback route is discharged, and a downstream route passing between the first switchback route and the second switchback route and having an upstream end connected to a junction of downstream ends of the first discharge route and the second discharge route.