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.

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 when an end portion of the at least one pressing member is pressed against the recording-medium stack.

A sheet processing apparatus includes a conveying portion, a stack portion on which sheets conveyed by the conveying portion are stacked, a first regulating portion regulating a position of a sheet bundle stacked on the stack portion in a crossing direction, a second regulating portion regulating a position of a sheet bundle on the stack portion in a conveying direction, a first binding device moved in the crossing direction and binding a corner portion of a sheet bundle by a staple, a second binding device binding a corner portion of a sheet bundle without a staple, and a controller positioning the first binding device and binding a corner portion of a sheet bundle by the first binding device. The controller also moves the second binding device and binds a corner portion of a sheet bundle without a staple by the second binding device.

A sheet processing device has a binding unit that applies water to a crimping range of sheets and then crimps the sheets. The sheet processing device includes a processing tray on which sheets are placed, a pair of pressure teeth (pressure teeth and receiving teeth) that crimps the sheets placed on the processing tray at a crimping position with the sheets interposed therebetween, and a water application member (cylinder and piston) that applies water to the crimping position before crimping by the pressure teeth. When the number of sheets placed on the processing tray is equal to or less than a predetermined number, the sheets are crimped by the pressure teeth without water application; while when the number of sheets placed on the processing tray exceeds the predetermined number, the sheets are crimped by the pressure teeth after water application.

The present invention is to provide a sheet processing device including: a receiving tray capable of accommodating therein a sheet having, at a part thereof, a protruding portion and a sheet not having the protruding portion in a mixed state; a first binding member that binds the accommodated sheet bundle at a substantially center thereof in a sheet conveying direction; a folding section that folds the sheet bundle bound by the first binding member in two; and a second binding member that binds protruding portions of the sheet bundle folded by the folding section on a fore edge side of the sheet bundle. With this configuration, the fore edge side of the folded and saddle-stitched sheet bundle can be bound by temporary binding. Thus, a sheet processing device capable of ensuring the security of a saddle-stitched sheet bundle can be provided.

There is provided a sheet post-processing apparatus capable of performing eco-stapling processing to prevent a decrease in binding force by the thickness of a sheet with a simple arrangement by changing a stapling count depending on the grammage and size of a sheet and the number of sheets in consideration of the change in binding force caused by the sheet size.

A sheet processing apparatus includes a binding unit including a first portion and a second portion and configured to nip a sheet bundle between the first portion and the second portion to deform the sheet bundle in a thickness direction to bind the sheet bundle, and a detachment unit configured to push the bound sheet bundle toward the second portion to detach the bound sheet bundle from the first portion.