1. Field of the Invention
The present invention relates to a sheet post-processing apparatus that performs post-processing for a sheet on which an image has been formed in an image forming apparatus such as a copier, a printer, or a composite device.
2. Description of the Related Art
In recent years, there was developed a sheet post-processing apparatus, which is disposed adjacent to the sheet discharge section of an image forming apparatus main body for the purpose of performing post-processing for a sheet on which an image has been formed in the image forming apparatus. The sheet post-processing apparatus performs post-processing for a sheet, such as sorting of printed sheets discharged from the image forming apparatus or stapling thereof. The sheet post-processing apparatus performs post-processing for a succeeding sheet after completion of the post-processing for a preceding sheet. In order for the sheet post-processing apparatus to wait until the post-processing for a preceding sheet has been completed, an apparatus in which a retreating path is formed in the middle of a path reaching to a stapler is disclosed in Japanese Patent Publication (Kokoku) No. H6-99070.
However, in the case where the retreating path is formed in the middle of a path reaching to a stapler as described above, the length of a sheet path extending from the discharge section of the image forming apparatus main body to the stapler is increased. This may prevent size reduction of the entire apparatus.
In light of the above, an apparatus in which a processing tray for use in staple processing and a standby tray which retains a sheet to be supplied to the processing tray in a standby mode are vertically provided to reduce the length of the sheet path has been proposed. In this apparatus, a sheet is dropped from the standby tray and is supplied onto the processing tray. Further, such an apparatus has a sheet discharge tray on which a sheet discharged from the standby tray or processing tray is placed and a rear end guide that supports the rear end of the sheet on the discharge tray between the discharge tray.
However, if deformation of a sheet occurs when the sheet is discharged from the standby tray or processing tray to the sheet discharge tray, the sheet is caught by the rear side which may result in sheet jamming. Further, if the rear guide contacts a sheet when the sheet is aligned on the processing tray, the rear guide serves as resistance too adversely affecting the sheet alignment performance.
Further, in some cases, the sheet discharge tray is slid on the side surface of the post-processing apparatus main body, with the sheet placed thereon, so as to be disposed adjacent to the position of the standby tray or processing tray. If the rear end of the sheet on the discharge tray is slipped from the upper end of the rear guide at this time, the sheet may be fed back to the processing tray or standby tray side.
To cope with the above problems, a small-sized sheet post-processing apparatus that prevents sheet jamming from occurring when the sheet is discharged from the standby tray or processing tray to the discharge tray without adversely affecting the sheet alignment performance made in the processing tray has been desired. Further, a sheet post-processing apparatus that prevents the sheet placed on the discharge tray from being fed back to the backside at the time of the slide of the discharge tray has been desired.