A sheet processing apparatus includes: a second conveying roller pair that receives and conveys a sheet conveyed by a first conveying roller pair; a first folding roller pair that forms a first fold on the sheet; and a first rotation unit capable of rotating the second conveying roller pair and the first folding roller pair. One roller of the second conveying roller pair and one roller of the first folding roller pair are a common roller shared therebetween. The second conveying roller pair causes the sheet to be deflected and guided to the first folding roller pair, and the first folding roller pair forms the first fold on the deflected sheet by rotating the first rotation unit in a certain direction in a state in which the sheet is held by the first conveying roller pair and the second conveying roller pair.

A sheet processing apparatus includes: a second conveying roller pair that receives and conveys a sheet conveyed by a first conveying roller pair; a first folding roller pair that forms a first fold on the sheet; and a first rotation unit capable of rotating the second conveying roller pair and the first folding roller pair. One roller of the second conveying roller pair and one roller of the first folding roller pair are a common roller shared therebetween. The second conveying roller pair causes the sheet to be deflected and guided to the first folding roller pair, and the first folding roller pair forms the first fold on the deflected sheet by rotating the first rotation unit in a certain direction in a state in which the sheet is held by the first conveying roller pair and the second conveying roller pair.

The folding roller includes a rotation axis and at least a gripping member extending longitudinally along the folding roller, controlled by at least a piezoelectric actuator. The piezoelectric actuator causes a pivoting movement of the gripping member about its pivoting axis parallel to the rotation axis of the folding roller.

The folding roller includes a rotation axis and at least a gripping member extending longitudinally along the folding roller, controlled by at least a piezoelectric actuator. The piezoelectric actuator causes a pivoting movement of the gripping member about its pivoting axis parallel to the rotation axis of the folding roller.

A sheet folding device includes a folding path, a positioning member, a first folding roller, a second folding roller, a folding blade, a guide path, and a conveying roller. The positioning member is to support a leading edge of a sheet fed along the folding path and align the sheet at an initial folding position. The first folding roller is to engage with the second folding roller to form a folding nip. The folding blade is to move to an insertion position to push the sheet on the folding path into the folding nip. The guide path is provided around the first folding roller to return the sheet that has passed through the folding nip to the folding path. The conveying roller is to partially rotate around the first folding roller, to engage with the first folding roller to form a conveying nip and to feed the sheet along the guide path.

A sheet pressing device includes a carry-in port that receives a Z-folded sheet having two folds; an additional folding roller disposed downstream of the carry-in port to press the fold; a lower folding guide having a pedestal disposed opposite to the additional folding roller; a first moving mechanism that moves the additional folding roller between a pressing position at which the additional folding roller is made to approach the pedestal and a retreat position at which the additional folding roller is moved relative to the pedestal from the pressing position; a second moving mechanism that moves the additional folding roller along the fold; and a control part. The control part controls the second moving mechanism so as to increase the number of times the additional folding roller is moved along the fold when a sheet section is positioned between the additional folding roller and the fold.

Provided is a sheet folding apparatus for folding sheets, including: a feeding-roller pair; a loop-forming space provided downstream from the feeding-roller pair, for forming a sheet loop; a pushing member for pushing the looped sheet; a folding-roller pair for nipping a prescribed part of the sheet pushed by the pushing member, thereby to fold the sheet; and a path provided between the feeding-roller pair and the folding-roller pair, for guiding the sheet fed from the feeding-roller pair toward the loop-forming space.

Provided is a sheet folding apparatus for folding sheets, including: a feeding-roller pair; a loop-forming space provided downstream from the feeding-roller pair, for forming a sheet loop; a pushing member for pushing the looped sheet; a folding-roller pair for nipping a prescribed part of the sheet pushed by the pushing member, thereby to fold the sheet; and a path provided between the feeding-roller pair and the folding-roller pair, for guiding the sheet fed from the feeding-roller pair toward the loop-forming space.

A sheet folding apparatus includes a conveyance member to convey a sheet from an ejection member at a first speed lower than a conveyance speed by the ejection member or a second speed substantially same as or higher than the conveyance speed; a registration member; a pair of first and second rollers to rotate in forward and reverse directions; a plurality of folding rollers downstream from the second roller, to rotate in forward and reverse directions to fold the sheet; and circuitry to determine whether the sheet is equal to or smaller than a reference length from an exit position from the ejection member to a folding start position downstream from the pair of the first and second rollers. The circuitry performs first-speed folding when the sheet is equal to or smaller than the reference length and performs second-speed folding when the sheet is longer than the reference length.

A sheet folding apparatus includes a conveyance member to convey a sheet from an ejection member at a first speed lower than a conveyance speed by the ejection member or a second speed substantially same as or higher than the conveyance speed; a registration member; a pair of first and second rollers to rotate in forward and reverse directions; a plurality of folding rollers downstream from the second roller, to rotate in forward and reverse directions to fold the sheet; and circuitry to determine whether the sheet is equal to or smaller than a reference length from an exit position from the ejection member to a folding start position downstream from the pair of the first and second rollers. The circuitry performs first-speed folding when the sheet is equal to or smaller than the reference length and performs second-speed folding when the sheet is longer than the reference length.