Patent ID: 8109495

Claim:
A spine formation device comprising: a sheet conveyer that conveys a bundle of folded sheets in a sheet conveyance direction with a folded portion of the bundle of folded sheets forming a front end portion of the bundle of folded sheets; a contact member disposed downstream from the sheet conveyer in the sheet conveyance direction, the contact member including, a contact surface extending in a first direction perpendicular to the sheet conveyance direction, against which the folded portion of the bundle of folded sheets is pressed, and a first row of grooves to house a projection projecting from the folded portion of the bundle of folded sheets, provided in the contact surface, extending in a second direction parallel to the folded portion of the bundle of folded sheets, the first row of grooves including at least a first pair of grooves inclined in different directions with an interval therebetween varying in size with location of the grooves in the first direction; a driving unit to move the contact member in the first direction relative to the folded portion of the bundle of folded sheets; a first sandwiching unit disposed downstream from the sheet conveyer in the sheet conveyance direction, the first sandwiching unit squeezing the bundle of folded sheets in a direction of thickness of the bundle of folded sheets with the folded portion pressed against the contact member; a second sandwiching unit disposed downstream from the first sandwiching unit in the sheet conveyance direction, the second sandwiching unit forming a spine of the bundle of folded sheets by squeezing a bulging of the bundle of folded sheets created between the first sandwiching unit and the contact member; a discharge unit to discharge the bundle of folded sheets to a discharge tray; and a controller operatively connected to the sheet conveyer, to the first and second sandwiching units, and to the driving unit, the controller causing the driving unit to move the contact member to change the size of interval between the first pair of grooves at a position in the first direction, aligned with the projection projecting from the folded portion of the bundle of folded sheets.