Apparatus having detachment unit for binding unit

An image forming apparatus comprising:

• an image forming unit configured to form an image on a sheet;
• and
• a processing unit configured to process the sheet on which an image is formed by the image forming unit, wherein the processing unit includes:
• a binding unit including:
• a first portion having a plurality of protrusions, and
• a second portion having a plurality of concaves,
• wherein the binding unit is configured to bind a sheet bundle by the plurality of protrusions nipping the sheet bundle with the plurality of concave, and
• a detachment unit having a flat surface and configured to urge the bound sheet bundle by bringing the flat surface into contact with the bound sheet bundle toward the second portion such that the bound sheet bundle is detached from at least one of the plurality of protrusions in a case where the first portion and the second portion move apart to release the sheet bundle from nipping,
• wherein, when viewed from a thickness direction of the bound sheet bundle, the detachment unit includes first, second, and third edges that surround and oppose to the plurality of protrusions, and
• wherein the detachment unit is provided on the first portion.

A apparatus comprising:

• a binding unit including:
• a first portion having a plurality of protrusions, and
• a second portion having a plurality of concaves,
• wherein the binding unit is configured to bind a sheet bundle by the plurality of protrusions nipping the sheet bundle with the plurality of concaves;
• a detachment unit configured to urge the bound sheet bundle toward the second portion such that the bound sheet bundle is detached from at least one of the plurality of protrusions in a case where the first portion and the second portion move apart to release the sheet bundle from nipping;
• and
• a driving unit configured to move the detachment unit to a first position and a second position protruding more than the first position toward the second portion.