A sheet processing apparatus includes a conveying portion conveying sheets; a stack portion staking the sheets; a first regulating portion regulating a position of a sheet bundle on the stack portion in a crossing direction; a second regulating portion regulating a position of a sheet bundle in the conveying direction; a first binding device moving in the crossing direction so that the first binding device moves between first and second sides of the sheet processing apparatus and to bind an upstream end portion of a sheet bundle by a staple at a plurality of positions in the crossing direction; a second binding device binding an upstream end portion of a sheet bundle, where the second regulating portion has contacted without a staple; and a controller causing, in a case that the first binding device binds a sheet bundle, the second binding device to be positioned outside the sheet bundle.

A recording-medium binding device includes a first tooth row including plural teeth and a second tooth row including plural teeth. The first and second tooth rows include a central region and end regions. The plural teeth of each of the first and second tooth rows include at least one tooth disposed in the central region and at least one tooth dispose in each of the end regions. In a process of pinching the recording medium batch, the at least one tooth of the first tooth row in the end region and the at least one tooth of the second tooth row in the end region pinch the recording medium batch earlier than the at least one tooth of the first tooth row in the central region and the at least one tooth of the second tooth row in the central region.

A recording-medium binding device includes a first tooth row including plural teeth and a second tooth row including plural teeth. The first and second tooth rows include a central region and end regions. The plural teeth of each of the first and second tooth rows include at least one tooth disposed in the central region and at least one tooth dispose in each of the end regions. In a process of pinching the recording medium batch, the at least one tooth of the first tooth row in the end region and the at least one tooth of the second tooth row in the end region pinch the recording medium batch earlier than the at least one tooth of the first tooth row in the central region and the at least one tooth of the second tooth row in the central region.

A binding device includes a first pressing member that presses a recording-medium stack from one surface side of the recording-medium stack, a second pressing member disposed at a position opposed to the first pressing member to press the recording-medium stack from the other surface side of the recording-medium stack, and a reduction part provided in at least one pressing member of the first pressing member and the second pressing member to reduce creases in recording media of the recording-medium stack in a binding operation when a number of the recording media in the recording-medium stack is smaller than a maximum number of recording media to be bound by the first pressing member and the second pressing member.

A sheet binding device includes a binding operation unit including a first tooth-shaped member that has plural arrayed teeth, a second tooth-shaped member that has plural arrayed teeth and binds sheets by biting the first tooth-shaped member to clamp the sheets in cooperation with the first tooth-shaped member, and a link structure that opens and closes the first tooth-shaped member and the second tooth-shaped member to perform a binding operation, and two side frames that are arranged to hold the binding operation unit therebetween and to support the binding operation unit on both sides of the binding operation unit.

A sheet binding device includes a binding operation unit including a first tooth-shaped member that has plural arrayed teeth, a second tooth-shaped member that has plural arrayed teeth and binds sheets by biting the first tooth-shaped member to clamp the sheets in cooperation with the first tooth-shaped member, and a link structure that opens and closes the first tooth-shaped member and the second tooth-shaped member to perform a binding operation, and two side frames that are arranged to hold the binding operation unit therebetween and to support the binding operation unit on both sides of the binding operation unit.

There is provided a binding member. The binding member includes: an upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials; and a lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in side surfaces of the recesses of one toothed part, when the upper toothed part and the lower toothed part are engaged, surfaces wide in a direction parallel to the pressing direction of the toothed parts are formed so as to be provided gaps between the upper toothed part and the lower toothed part.

There is provided a binding member. The binding member includes an upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials; and a lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in some of parts of inclined surfaces of the toothed part which form the recesses, second curved surfaces having the centers of curvature on the opposite sides of the inclined surfaces to the centers of curvature of first curved surfaces which form the recesses are formed.

In a cross section shape of the toothed part, in gaps formed between a recesses and a projections when a upper toothed part and a lower toothed part are engaged without a bundle of recording materials, when the distances between the recesses and the projections in a pressing direction of the toothed part at positions where the distances from a center lines of the projections in a direction perpendicular to the pressing direction of the toothed part to the surfaces of the projections in the direction perpendicular to the pressing direction of the toothed part are a distance L1 are H1, and the distances between the recesses and the projections at positions where the distances from the center lines to surfaces of the projections in the direction perpendicular to the pressing direction of the toothed part are H2, a combination of L1 and L2 satisfies H1 is smaller than H2.

There is provided a binding member. An upper toothed part having projections and recesses for forming irregularities in a bundle of recording materials. A lower toothed part having projections and recesses for forming irregularities in the bundle of recording materials and forming a pair with the upper toothed part. In at least one of the upper toothed part and the lower toothed part, in a cross section shape of the toothed part, the recesses of the toothed part have depressed areas depressed from virtual lines which are extensions of inclined surfaces of the toothed part.