Sheet processing device, image forming system, and method of additionally folding sheet bundle

1. A sheet processing device comprising:

a pressing device that presses a fold line part of a folded sheet bundle; and

a moving device that moves a pressing position of the pressing device in a fold direction of the folded sheet bundle, wherein

the pressing device includes a first pressing roller arranged on one side of a thickness direction of the folded sheet bundle, and a second pressing roller and a third pressing roller arranged on another side across the fold line part of the folded sheet bundle,

the pressing device is arranged in a state in which each of a first line and a second line is not parallel to the thickness direction of the folded sheet bundle, the first line connecting a rotational center of the first pressing roller and a rotational center of the second pressing roller, and the second line connecting the rotational center of the first pressing roller and a rotational center of the third pressing roller,

the second pressing roller and the third pressing roller are movable such that a distance between the rotational center of the second pressing roller and the rotational center of the third pressing roller changes only in the fold direction, and

the fold direction is orthogonal to the thickness direction.

2. The sheet processing device according to claim 1 , wherein the first pressing roller is positioned between the second pressing roller and the third pressing roller in the fold direction of the folded sheet bundle.

3. The sheet processing device according to claim 1 , wherein a shift amount of the rotational center position of the second pressing roller from a line drawn from the rotational center of the first pressing roller in the thickness direction of the folded sheet bundle is a same as a shift amount of the rotational center position of the third pressing roller from the line.

4. The sheet processing device according to claim 1 , wherein each of dimensions of the second pressing roller and the third pressing roller in the fold direction is smaller than a dimension of the first pressing roller in the fold direction.

5. The sheet processing device according to claim 1 , wherein the second pressing roller or the third pressing roller is movable in the fold direction with respect to the first pressing roller.

6. The sheet processing device according to claim 5 , wherein the second pressing roller or the third pressing roller is movable to a same position in the fold direction with respect to the first pressing roller.

7. The sheet processing device according to claim 5 , wherein the first pressing roller is arranged upstream or downstream with respect to the second pressing roller or the third pressing roller in the fold direction.

8. The sheet processing device according to claim 1 , further comprising a pressing state changing device that causes the pressing device to be in a pressing state and a press-releasing state.

9. An image forming system including a sheet processing device, the sheet processing device comprising:

a pressing device that presses a fold line part of a folded sheet bundle,

a moving device that moves a pressing position of the pressing device in a fold direction of the folded sheet bundle, and

the pressing device includes a first pressing roller arranged on one side of a thickness direction of the folded sheet bundle, and a second pressing roller and a third pressing roller arranged on another side across the fold line part of the folded sheet bundle, and the pressing device is arranged in a state in which each of a first line and a second line is not parallel to the thickness direction of the folded sheet bundle, the first line connecting a rotational center of the first pressing roller and a rotational center of the second pressing roller, and the second line connecting the rotational center of the first pressing roller and a rotational center of the third pressing roller, wherein

the second pressing roller and the third pressing roller are movable such that a distance between the rotational center of the second pressing roller and the rotational center of the third pressing roller changes only in the fold direction, and

the fold direction is orthogonal to the thickness direction.

10. A method of additionally folding a folded sheet bundle, comprising:

arranging a first pressing roller on one side of a thickness direction of the folded sheet bundle, and arranging a second pressing roller and a third pressing roller on another side of the thickness direction of the folded sheet bundle;

holding a fold line part of the folded sheet bundle between the first pressing roller and the second and the third pressing rollers;

moving the first, the second, and the third pressing rollers in a fold direction of the folded sheet bundle to additionally fold the fold line part of the folded sheet bundle in a state in which each of a first line and a second line is not parallel to the thickness direction of the folded sheet bundle, the first line connecting a rotational center of the first pressing roller and a rotational center of the second pressing roller, and the second line connecting the rotational center of the first pressing roller and a rotational center of the third pressing roller; and

moving the second pressing roller and the third pressing roller such that a distance between the rotational center of the second pressing roller and the rotational center of the third pressing roller changes only in the fold direction, wherein

the fold direction is orthogonal to the thickness direction.