A binding device includes a first pushing member that includes protrusions along one direction and that pushes a recording-material bundle as a result of pushing the protrusions against one of surfaces of the recording-material bundle, the protrusions disposed side by side in a direction that intersects the one direction; and a second pushing member that includes protrusions along the one direction and that pushes the recording-material bundle as a result of pushing the protrusions against the other surface of the recording-material bundle, the protrusions disposed side by side in the direction that intersects the one direction, wherein, in at least one end portion in the one direction of each protrusion of at least one of the first pushing member and the second pushing member, a hollow is disposed in a top portion of each protrusion.

There is provided a binding processing device including:

a first pressing member including a convex portion formed by a curved surface with a curvature and protruding toward a sheet bundle; and

a second pressing member including a concave portion formed by a curved surface with a curvature and configured to be combined with the convex portion through the sheet bundle, the second pressing member configured to press the sheet bundle sandwiched between the first and second pressing members, wherein

in a state where the convex portion of the first pressing member and the concave portion of the second pressing member are combined with each other, a gap is formed between the convex portion and the concave portion in a cross section of the first and second pressing members along a pressing direction, and

the gap has a volume larger than a volume of the sandwiched sheet bundle.

There is provided a binding processing device including:

a first pressing member including a convex portion formed by a curved surface with a curvature and protruding toward a sheet bundle; and

a second pressing member including a concave portion formed by a curved surface with a curvature and configured to be combined with the convex portion through the sheet bundle, the second pressing member configured to press the sheet bundle sandwiched between the first and second pressing members, wherein

in a state where the convex portion of the first pressing member and the concave portion of the second pressing member are combined with each other, a gap is formed between the convex portion and the concave portion in a cross section of the first and second pressing members along a pressing direction, and

the gap has a volume larger than a volume of the sandwiched sheet bundle.

A recording-medium binding device includes a first tooth row that includes teeth arranged in a tooth arrangement direction and a second tooth row that includes teeth, that is to be engaged with the first tooth row, and that cooperates with the first tooth row to bind recording media by pinching a batch of the recording media. In the tooth arrangement direction, the first and the second tooth rows have first and second ranges. In the first range, an engaging height is a first engaging height, and a width of an effective tooth top is a first effective tooth top width. In the second range, the engaging height is a second engaging height that is smaller than the first engaging height, and a width of an effective tooth top is a second effective tooth top width that is larger than the first effective tooth top width.

A recording-medium binding device includes a first tooth row that includes teeth arranged in a tooth arrangement direction and a second tooth row that includes teeth, that is to be engaged with the first tooth row, and that cooperates with the first tooth row to bind recording media by pinching a batch of the recording media. In the tooth arrangement direction, the first and the second tooth rows have first and second ranges. In the first range, an engaging height is a first engaging height, and a width of an effective tooth top is a first effective tooth top width. In the second range, the engaging height is a second engaging height that is smaller than the first engaging height, and a width of an effective tooth top is a second effective tooth top width that is larger than the first effective tooth top width.

A binding member is provided and includes: upper teeth having a tooth form configured to form a convex-concave portion on a recording material bundle; and lower teeth having a tooth form configured to form the convex-concave portion on the recording material bundle, and paired with the upper teeth. At least one of the upper teeth and the lower teeth includes: a first tooth row having a first tooth form having a first shape suitable for binding a first binding number of sheets; and a second tooth row having a second tooth form having a second shape suitable for binding a second binding number of sheets which is smaller than the first binding number of sheets.

A binding member is provided and includes: upper teeth having a tooth form configured to form a convex-concave portion on a recording material bundle; and lower teeth having a tooth form configured to form the convex-concave portion on the recording material bundle, and paired with the upper teeth. At least one of the upper teeth and the lower teeth includes: a first tooth row having a first tooth form having a first shape suitable for binding a first binding number of sheets; and a second tooth row having a second tooth form having a second shape suitable for binding a second binding number of sheets which is smaller than the first binding number of sheets.

A recording-medium binding device includes first and second tooth groups. The first tooth group includes first and second tooth rows. The second tooth group includes third and fourth tooth rows. The third tooth row to be engaged with the first tooth row forms, together with the first tooth row, a first tooth row pair. The fourth tooth row to be engaged with the second tooth row forms, together with the second tooth row, a second tooth row pair. A second engaging height in the second tooth row pair is smaller than a first engaging height in the first tooth row pair. A second effective tooth top width in the second tooth row pair is larger than a first effective tooth top width in the first tooth row pair.

A recording-medium binding device includes first and second tooth groups. The first tooth group includes first and second tooth rows. The second tooth group includes third and fourth tooth rows. The third tooth row to be engaged with the first tooth row forms, together with the first tooth row, a first tooth row pair. The fourth tooth row to be engaged with the second tooth row forms, together with the second tooth row, a second tooth row pair. A second engaging height in the second tooth row pair is smaller than a first engaging height in the first tooth row pair. A second effective tooth top width in the second tooth row pair is larger than a first effective tooth top width in the first tooth row pair.

An image forming system includes an image forming unit configured to form an image on a sheet and provided in an apparatus body, a first sheet processing device provided in a first housing and configured to perform a first binding processing, without using a needle, on the sheet that is formed with the image and stacked, and a second sheet processing device provided in a second housing that is different from the first housing and configured to perform a second binding processing, using a needle, on the sheet that is formed with the image and stacked. The first housing and the second housing are mounted on the apparatus body. At least a portion of the first housing is positioned within a range exclusively occupied by a rectangular space defined by a maximum outer dimension of the apparatus body. The second housing is positioned outside the rectangular space.