Apparatus for collecting sheets and apparatus for forming images

1. A sheet collection apparatus including a collection tray for receiving a discharged sheet and shifting, comprising:

a discharge unit adapted to discharge a sheet;

a shift rail provided in the discharge unit to permit a shift of the collection tray corresponding to a sheet collection amount of the collection tray;

a drive member adapted to shift the collection tray along the shift rail; and

an extension rail capable of being added and set onto the shift rail to extend a shift range of the collection tray,

wherein the extension rail is provided with a load reduction member that reduces a load of the collection tray for receiving a sheet and shifting.

2. The sheet collection apparatus according to claim 1 , wherein each of the shift rail and the extension rail is comprised of a gear constituting a part of the drive member provided in the collection tray, a rack that engages in the gear, and a slide rail that slide-holds the collection tray, and the load reduction member is comprised of a compression spring that receives a load of the collection tray.

3. The sheet collection apparatus according to claim 1 , further comprising a limit sensor to detect a shift limit position of the collection tray.

4. An image formation apparatus including a collection tray for receiving a discharged sheet and shifting, comprising:

an apparatus frame including an image formation section;

a discharge unit disposed above the image formation section, the discharge unit performing processing on a sheet subjected to image formation from the image formation section to discharge;

a shift rail attached to the discharge unit to support a shift of the collection tray that shifts corresponding to a collection amount of discharged sheets;

a drive member attached to the collection tray to shift the collection tray along the shift rail;

an extension rail capable of being added and set onto a side portion of the apparatus frame to extend a shift range of the collection tray; and

a control unit for controlling the shift of the collection tray,

wherein the discharge unit is configured to be able to shift to a first position to shift the collection tray in a range of the shift rail, and a second position shifted to a sheet discharge direction to enable the collection tray to shift in a range in which the shift rail and the extension rail are continued along the side portion of the apparatus frame, above the image formation section, and

when the discharge unit is shifted to the second position along the side portion of the apparatus frame, the control unit detects the shift of the discharge unit, and controls the collection tray to be capable of shifting in the shift range extended from the shift rail to the extension rail.

5. The image formation apparatus according to claim 4 , wherein in order to reduce a load of the collection tray for receiving a sheet and shifting, the extension rail is provided with a spring member that comes into contact with the collection tray during a descent of the collection tray to reduce a load of the collection tray.

6. The image formation apparatus according to claim 5 , wherein the extension rail and the spring member are made a unit.

7. The image formation apparatus according to claim 4 , wherein the extension rail is beforehand attached to the side portion of the apparatus frame.

8. The image formation apparatus according to claim 4 , wherein the extension rail is attached to the discharge unit additionally.

9. The image formation apparatus according to claim 4 , wherein the extension rail is comprised of a slide rail that holds the collection tray to enable a shift, and an extension rack that meshes with a drive gear provided in the collection tray to shift the collection tray.

10. The image formation apparatus according to claim 5 , further comprising a limit sensor to detect a shift limit position of the collection tray.