A sheet folding apparatus for folding sheets comprising a curved conveyance path along which the sheets are moved successively in first and second opposite directions, the curved conveyance path being such that the sheets cannot naturally register to reach a folding position by simple effect of gravity, wherein to register the sheets before to fold them transport rollers having loaded the sheets in the first direction moves back in the second opposite direction for compressing the sheets against an adjustable low stop member to generate an elastic deformation of the sheets sufficient to compensate friction in the curved conveyance path and automatically register the sheets.

A medium transport device includes a feeding unit that transports a medium, a stack portion that receives the medium transported by the feeding unit between a support surface for supporting the medium in an inclined posture in which a downstream side in a transport direction is directed downward and an opposing surface opposing the support surface and stacks the medium, an alignment portion that aligns a downstream end of the medium stacked in the stack portion, a paddle that is provided between the feeding unit and the alignment portion in the transport direction and moves the medium toward the alignment portion by rotating while being in contact with the medium, and a control unit that controls an operation of the paddle, in which the control unit controls the operation of the paddle according to a condition.

A medium transport device includes a feeding unit that transports a medium, a stack portion that receives the medium transported by the feeding unit between a support surface for supporting the medium in an inclined posture in which a downstream side in a transport direction is directed downward and an opposing surface opposing the support surface and stacks the medium, an alignment portion that aligns a downstream end of the medium stacked in the stack portion, a paddle that is provided between the feeding unit and the alignment portion in the transport direction and moves the medium toward the alignment portion by rotating while being in contact with the medium, and a control unit that controls an operation of the paddle, in which the control unit controls the operation of the paddle according to a condition.

A sheet folding apparatus includes: a conveying roller conveying a sheet in a predetermined conveying direction; a folding roller pair disposed downstream of the conveying roller in the conveying direction and rotating while nipping a predetermined position of the sheet to form a fold; a conveying path for conveying the sheet in the conveying direction from the conveying roller to the folding roller pair; an abutting member moving downstream in the conveying direction and abutting against the predetermined position of the sheet to bend the sheet downstream; and a loop space where the sheet is bent between the conveying roller and folding roller pair in a direction crossing the conveying direction. The folding roller pair stops while nipping a front end of the sheet fed from to form a loop of the sheet in the loop space, and the abutting member moves to abut against the loop.

The present invention is to provide an image forming system including a sheet folding processing apparatus and a sheet pressing apparatus capable of performing additional folding processing without decreasing productivity. The sheet pressing apparatus of the present invention includes a pressing roller including a pressing surface configured to press a fold line part of a folding processed sheet conveyed from a carry-in port in a thickness direction of the sheet and a guide portion configured to guide the folding processed sheet so that the fold line part is positioned at the pressing surface, a nipping member configured to nip the fold line part between the pressing surface and the nipping member, a first moving unit configured to move the pressing roller to a nipping position at which the fold line part is nipped between the nipping member and the pressing roller and a retracting position.

In order to enable a sheet end portion to be properly guided to a nip portion in performing folding processing a plurality of times, provided are a transport path including a guide face to guide a transported sheet, a rotating body pair which nips the sheet transported to the transport path by a nip portion to rotate, a folding blade that pushes the sheet to the nip portion of the rotating body pair, and a blade guide member including a guide portion for pushing one end of the sheet to the nip portion when the folding blade pushes the sheet to the nip portion, and a shift section that shifts the folding blade and the blade guide member in a push direction for pushing to the nip portion and in a return direction opposite to the push direction.

In order to enable a sheet end portion to be properly guided to a nip portion in performing folding processing a plurality of times, provided are a transport path including a guide face to guide a transported sheet, a rotating body pair which nips the sheet transported to the transport path by a nip portion to rotate, a folding blade that pushes the sheet to the nip portion of the rotating body pair, and a blade guide member including a guide portion for pushing one end of the sheet to the nip portion when the folding blade pushes the sheet to the nip portion, and a shift section that shifts the folding blade and the blade guide member in a push direction for pushing to the nip portion and in a return direction opposite to the push direction.

A sheet post-processing apparatus includes a stacker, a pair of folding rollers having a nip portion therebetween, and a blade. A sheet is stacked on the stacker. The blade is configured to fold the sheet in half by pushing the sheet stacked on the stacker into the nip portion of the pair of folding rollers. The pair of folding rollers are configured to switch between a first posture and a second posture. In the first posture, the sheet is pushed into the nip portion by the blade. In the second posture, a feeding direction of the sheet is different from that in the first posture.

A sheet post-processing apparatus includes a stacker, a pair of folding rollers having a nip portion therebetween, and a blade. A sheet is stacked on the stacker. The blade is configured to fold the sheet in half by pushing the sheet stacked on the stacker into the nip portion of the pair of folding rollers. The pair of folding rollers are configured to switch between a first posture and a second posture. In the first posture, the sheet is pushed into the nip portion by the blade. In the second posture, a feeding direction of the sheet is different from that in the first posture.

A sheet folding processing device includes a folding processing mechanism that includes a folding roller pair for forming a plurality of folds on the sheet conveyed in a predetermined sheet conveying direction to produce Z-fold, additional folding rollers and a lower folding guide. The additional folding rollers and the lower folding guide are arranged on the downstream side of the folding roller pair in the sheet conveying direction to face each other and cooperate with each other to press the folds. The interval between the folding roller pair and the additional folding rollers is determined such that when the leading fold as viewed in the sheet conveying direction is pressed between the additional folding rollers and the lower folding guide, the sheet part having a plurality of layers of sheet where the sheet is folded between the additional folding rollers can also be held between the folding roller pair.