Sheet feed cassette and image forming apparatus using the same

1. A sheet feed cassette comprising:

a main container on which sheets are mounted;

a sub container slidably attached to the main container;

first slidable portions that are disposed on sidewalls of each of the main container and the sub container, and that are formed in a U-shape;

a rear end guide that is disposed on the sub container, that regulates a rear end of the sheets, and that is slidable in a direction of an extraction and a retraction of the sub container from the main container; and

a size detector that is coupled with the rear end guide, and that detects a size of the sheets, the size detector comprising:

a hole for allowing a rotary motion;

a continuous groove formed in a zigzag;

a pin disposed on the rear end guide;

a sensor; and

an uneven part for detecting a radial position of said size detector,

wherein the hole mates with the main container, and

wherein the pin is disposed in the continuous groove.

2. The sheet feed cassette according to claim 1 further comprising:

second slidable portions that are disposed on sheet mounting planes of the main container and the sub container, and that are formed in an L-shape.

3. The sheet feed cassette according to claim 1 further comprising:

a locking member that positions the sub container in a direction of an extraction and a retraction from the main container.

4. The sheet feed cassette according to claim 3 , wherein the locking member is formed so as to be elastically deformable when attached into the main container.

5. The sheet feed cassette according to claim 1 , further comprising:

a main container bottom cover that is disposed on a bottom of the main container beneath the size detector; and

a sub container bottom cover that is disposed on a bottom of the sub container beneath the size detector, and that slides with the sub container,

wherein the size detector is disposed on bottom rear portions of the main container and the sub container.

6. The sheet feed cassette according to claim 1 , wherein the sub container includes a grip for extraction of the sheet feed cassette from an image forming apparatus.

7. The sheet feed cassette according to claim 1 further comprising:

a rotary axis that is disposed on left and right top sides of the sub container, and that rotatably supports a cover covering a top opening of the sub container.

8. An image forming apparatus comprising the sheet feed cassette according to claim 1 .

9. The sheet feed cassette according to claim 1 , wherein the first slidable portions are formed in an angular U-shape.

10. The sheet feed cassette according to claim 1 , wherein the first slidable portions are disposed on upper portions of the sidewalls of the main container and the sub container.

11. A sheet feed cassette comprising:

a main container on which sheets are mounted:

a sub container slidably attached to the main container:

first slidable portions that are disposed on sidewalls of each of the main container and the sub container, and that are formed in a U-shape; and

second slidable portions that are disposed on sheet mounting planes of the main container and the sub container, such that the second slidable portions of the main container comprise an S-shape or a reversed S-shape and the second slidable portions of the sub container comprise an L-shape.

12. The sheet feed cassette according to claim 1 , wherein the first slidable portions are nested such that the slidable portions of the main container rest upon the slidable portions of the sub container.

13. The sheet feed cassette according to claim 3 , wherein the locking member further comprises a peg which fits into one of a plurality of through holes located in the sidewalls of the main container and the sub container.

14. The sheet feed cassette according to claim 13 , wherein the peg further comprises:

a head portion;

a shaft portion connected to said head portion; and

a claw portion connected to said shaft portion,

wherein said shaft portion has a portion of lower thickness along one plane perpendicular to an axis of said shaft, and

wherein said claw portion is elastically deformable, such as to allow insertion into a hole with a diameter smaller than that of a diameter of said claw portion.

15. A sheet feed cassette comprising:

a main container on which sheets are mounted;

a sub container slidably attached to the main container;

first slidable portions that are disposed on sidewalls of each of the main container and the sub container, and that are formed in a U-shape; and

a locking member that positions the sub container in a direction of an extraction and a retraction from the main container;

wherein the locking member further comprises a peg which fits into one of a plurality of through holes located in the sidewalls of the main container and the sub container, and

wherein the through hole in the sidewall of the main container comprises a long slot, running along a length of the sidewall of the main container in an extension and a retraction direction, comprising rounded portions on an end of said through hole, a size of said rounded portions being greater than a size of an other portion of said through hole.

16. The sheet feed cassette according to claim 1 , wherein the U-shape comprises three sides including an upper part in a direction horizontal to a sheet mounting side and two sides in a direction vertical to the sheet mounting side.

17. The sheet feed cassette according to claim 1 , wherein the first slidable portions are disposed on upper portions of the sidewalls along a sliding direction of the main container and the sub container.