Sheet postprocessing device and image forming system including the sheet postprocessing device

A sheet postprocessing device comprising:

• a sheet conveyance path through which a sheet is conveyed in a specified conveyance direction;
• a sheet tray which includes an upstream-side stacking part placed on an upstream side and a downstream-side stacking part placed on a downstream side, each in the conveyance direction, and on which the sheet having passed through the sheet conveyance path is stacked to a specified number;
• a carry-in guide which is placed on an upstream side of the sheet tray and at a downstream end of the sheet conveyance path in the conveyance direction, and which carries the sheet onto the sheet tray through the sheet conveyance path;
• a processing part which is placed within a range from the upstream-side stacking part to the downstream-side stacking part in the conveyance direction, and which performs specified postprocessing on the sheets stacked on the sheet tray;
• a discharge member which is placed on a downstream side of the processing part in the conveyance direction, and which discharges the sheets, which have been subjected to the postprocessing, to the downstream side of the conveyance direction;
• a blower device which blows off air from upstream side to downstream side of the conveyance direction and toward between an upper surface of an uppermost sheet out of the sheets stacked on the sheet tray and a lower surface of the sheet carried from the carry-in guide onto the sheet tray;
• and
• an intermediate conveyance part which is provided at a position within a range from the upstream-side stacking part to the downstream-side stacking part in the conveyance direction, and through which the sheet passes below the processing part, wherein
• the intermediate conveyance part includes:
• an upstream part including a first clearance through which the sheet passes;
• and
• a downstream part placed on a downstream side of the upstream part and including a second clearance through which the sheet passes,
• a size of the second clearance in a planar direction perpendicular to a surface of the sheet is wider than the first clearance in the planar direction, and
• the intermediate conveyance part further includes:
• an upstream-side guide plate which is placed at a position overlapping with the processing part in the conveyance direction and on an upstream side of the processing part, and which is opposed to the sheet tray in the planar direction;
• and
• a downstream-side guide plate which is placed on a downstream side of the processing part in the conveyance direction and downward of the processing part, and which is opposed to the downstream-side stacking part in the planar direction,
• the first clearance is formed between the upstream-side guide plate and the sheet tray, and
• the second clearance is formed between the downstream-side stacking part and the downstream-side guide plate.