1. Field of the Invention
The present invention relates to a sheet processing apparatus and image forming apparatus and more particularly to the sheet processing apparatus and image forming apparatus which perform a processing of binding a sheet bundle having a front cover and a back cover.
2. Description of the Related Art
In recent years, diversification of information has been accelerated and accompanied by this, an opportunity for a person to output a content having a high confidentiality from a printer which is an example of the image forming apparatus individually and possess it has been increased. Such an output needs to be treated so that the content thereof cannot be seen easily by other people.
To solve this problem, there have been invented a plurality of methods for blocking a bookbound matter from being opened so that the content is hard to see by binding a fore edge, or an end opposite to a bound end of the bookbound matter temporarily (see Japanese Patent Application Laid-Open Nos. 2004-284750 and 9-165136).
FIG. 18A illustrates an example of the method for blocking bookbound matter from being opened. Folded sheets S having perforations b at a bent portion are overlaid and the fore edge is bound with binding devices, for example, needles SP to make the bookbound matter double-leaved. In the meantime, this bookbound matter can be seen by separating across the perforations b.
The bookbound matter shown in FIG. 18B is double-leaved by binding the fore edge of sheet bundles SA each side-stitched, using the needles SP. This bookbound matter allows its content to be seen by removing the needles SP which bind the fore edges.
However, in case of the conventional bookbound matter formed in this way, if the binding devices are removed to see the content thereof, it is difficult to return the state to the original bound condition. Particularly, in case of a bookbound matter having a large number of sheets, once the double-leaved sheets are released, it cannot be double-leaved again using a marketed stapler and if the fore edges are bound with the stapler again, a plurality of holes are made in the bookbound matter, thereby producing a bad appearance of the sheets.
Further, when any binding device is removed from the fore edge to release the double-leaved sheets, if no care is taken, the sheet might be torn out or bent.
Accordingly, the present invention has been achieved in views of such a circumstance and the present invention intends to provide a sheet processing apparatus and image forming apparatus capable of producing double-leaved sheets and released that binding condition, without use of any binding device.