A controller of a sheet stacking device executes tray elevating processing and sheet stacking processing. The tray elevating processing is processing in which when a sensor detects an uppermost sheet, the controller once lowers a stacking tray, and lifts the stacking tray until the sensor detects the uppermost sheet. The sheet stacking processing is processing in which the controller arranges a guide arm at an advanced position to guide the sheet, arranges the guide arm at a retracted position before a rear end of the sheet passes the sheet discharge portion, and stacks the sheet on the stacking tray after the rear end of the sheet passes the sheet discharge portion. The controller executes the tray elevating processing in a state where the guide arm is disposed at the advanced position during the execution of the sheet stacking processing.

A sheet processing device includes a stapling unit that cuts off excess parts of a staple at a normal processing position, a container that stores the excess parts, the container having an upper end portion with an opening and being disposed below the stapling unit, a pair of electrodes disposed at a portion of a side wall of the upper end portion, the portion corresponding to the normal processing position, the pair of electrodes being exposed to inside the container, and a control unit for detecting that the excess parts in the container have reached the upper end portion when the pair of electrodes is short-circuited.

Disclosed is a post-processing apparatus couplable to an image forming apparatus. The post-processing apparatus comprises: a paper discharging roller to convey, from a conveying path, a first paper discharged from the image forming apparatus, to a standby path connected to the conveying path, and convey the first paper from the standby path and a second paper discharged from the image forming apparatus from the conveying path, to an intermediate loading part, in a state in which a leading end of the first paper toward the intermediate loading part protrudes more than a leading end of the second paper toward the intermediate loading part to process the first paper and the second paper.

A post-processing apparatus that rotates a rotation paddle in which a fin having flexibility is cantilevered by a holder to apply a conveying force along a rotation direction to a sheet to align the sheet, wherein the holder includes a recess in which a peripheral surface part from a support position of the fin to an upstream side in the rotation direction is recessed from a circumscribed circle of the holder, and when the fin elastically turns while being pressed against the sheet with rotation of the rotation paddle, turning of the fin is allowed until the fin comes into contact with a surface of the recess.

A post-processing device includes a discharge port through which a sheet is discharged, an intermediate tray, a discharge tray and an air sending part. The air sending part includes an upper air sending member, an upper switching member, a lower air sending member, a lower switching member and a controller. The upper air sending member generates a downward air flow from above the discharge port. The upper switching member is distributable the air flow generated by the upper air sending member to above the intermediate tray and to above the discharge tray. The lower air sending member generates an upward air flow from below the discharge port. The lower switching member is distributable the air flow generated by the lower air sending member to below the intermediate tray and to above the discharge tray. The controller controls the upper switching member and the lower switching member.

A sheet processing device includes a stapling unit that cuts off excess parts of a staple at a normal processing position, a container that stores the excess parts, the container having an upper end portion with an opening and being disposed below the stapling unit, a pair of electrodes disposed at a portion of a side wall of the upper end portion, the portion corresponding to the normal processing position, the pair of electrodes being exposed to inside the container, and a control unit for detecting that the excess parts in the container have reached the upper end portion when the pair of electrodes is short-circuited.

A controller of a sheet stacking device executes tray elevating processing and sheet stacking processing. The tray elevating processing is processing in which when a sensor detects an uppermost sheet, the controller once lowers a stacking tray, and lifts the stacking tray until the sensor detects the uppermost sheet. The sheet stacking processing is processing in which the controller arranges a guide arm at an advanced position to guide the sheet, arranges the guide arm at a retracted position before a rear end of the sheet passes the sheet discharge portion, and stacks the sheet on the stacking tray after the rear end of the sheet passes the sheet discharge portion. The controller executes the tray elevating processing in a state where the guide arm is disposed at the advanced position during the execution of the sheet stacking processing.

A bundle of printing media by eco-stapling often has a smaller thickness than a bundle of printing media by needle stapling by the thickness corresponding to an amount of used staples, although they have the same number of printing media, and there is room capable of stacking bundles in many cases in the eco-stapling. According to an embodiment, when a printing medium that has undergone an image forming process is taken in, stapling processing is performed on the printing medium, and then the printing medium is discharged to the tray, the following process is performed. That is, when the process is performed in accordance with instructed stapling processing, and the printing medium that has undergone the process is discharged outside the apparatus, the amount of printing media stacked on the tray is controlled in accordance with instructed stapling processing.

Disclosed is a post-processing apparatus couplable to an image forming apparatus. The post-processing apparatus comprises: a paper discharging roller to convey, from a conveying path, a first paper discharged from the image forming apparatus, to a standby path connected to the conveying path, and convey the first paper from the standby path and a second paper discharged from the image forming apparatus from the conveying path, to an intermediate loading part, in a state in which a leading end of the first paper toward the intermediate loading part protrudes more than a leading end of the second paper toward the intermediate loading part to process the first paper and the second paper.

A sheet post-processing device includes a conveying member, a processing tray, a processing section, a reference plate, an alignment member, and a frame. The processing tray stacks sheets carried in by the conveying member. The alignment member moves the sheet carried in onto the processing tray in an alignment direction so as to aid alignment of the sheets. The alignment member includes a roller holder, an alignment roller, and a guide member. The guide member has a sheet guide part protruding from a swinging end of the roller holder to the downstream side in the alignment direction than the alignment roller. When the number of the sheets placed on the processing tray varies, an angle of the guide member with respect to the roller holder varies so that a distance between a top sheet placed on the processing tray and the sheet guide part becomes substantially constant.