1. Field of the Invention
The present invention relates to a sheet stacking mechanism for successively stacking sheets being carried in from a carry-in opening on the upper surface of a sheet placing table, a sheet folding device, a sheet post-processing apparatus and an image forming apparatus provided with the sheet stacking mechanism.
2. Description of the Related Art
Some of image forming apparatuses include post-processing apparatuses such as a sheet middle-folding device as disclosed in Japanese Unexamined Patent Publication No. 2002-167120. A sheet stacking mechanism is provided in this sheet middle-folding device. However, since this sheet stacking mechanism has a mere construction of providing a pair of carry-in rollers at a carry-in opening for sheets, there is a likelihood that, upon receiving a sheet fed from the sheet post-processing apparatus, the trailing end of this sheet comes into contact with the leading end of a succeeding sheet, thereby causing a jam.
As means for solving such a problem, a processing tray includes a sheet stocking portion having a paddle for pressing a sheet in a guiding path for guiding the sheet, and a succeeding sheet is further stocked with the trailing end of the previously stocked sheet pressed by the paddle, for example, in Japanese Unexamined Patent Publication No. 2001-171889 although this technology is not applied to a sheet middle-folding device as described above. Accordingly, an occurrence of a jam caused by the collision of sheets can be prevented and even folded sheets can be stocked without causing any jam. This publication discloses that a high-speed processing can be carried out since the above makes it unnecessary to stop the conveyance of sheets during the application of stapling as a post-processing to a stack of sheets.
Further, Japanese Patent Publication No. 3423462 discloses the arrangement of a paddle for pressing an upstream end of a stapled stack of sheets with respect to a sheet discharging direction in a discharge tray.
However, even with the technologies disclosed in the latter two publications, if a sheet is stacked in an unstable state such as a curled state upon being stored, it is difficult to solve problems such as the switch of sheets (disorder in numbering) caused by a succeeding sheet having slipped in a clearance between the curled sheet and the sheet right below it or a tray and an occurrence of a jam caused by the collision of sheets. There have been also problems such as a loud hitting sound (noise) of the paddle when the stacked sheets are moved toward one end by the paddle in order to prevent the above switch of sheets.
USPTO Backgrounds
USPTO Backgrounds