Developer supply device with wall between chambers having two heights

1. A developer supply device, comprising:

a roller configured to carry developer, extending in a first direction the first direction being in a direction of a rotation axis of the roller and horizontal when the developer supply device is in use;

a casing in which a first room and a second room are defined, the roller being disposed in the first room, the second room being configured to store the developer;

a wall extending over a length of the casing in the first direction, the first room and the second room being partitioned by the wall, an opening being formed above the wall over the length of the wall when the developer supply device is in use; and

an agitator configured to convey the developer from the second room to the first room, the agitator including a shaft and a rotating member fixed to the shaft, the shaft being rotatably supported by the casing and configured to rotate in the second room;

wherein the wall is divided into:

end portions which are both end portions, in the first direction, of the wall and having a first height at upper ends of the end portions; and

a central portion defined as a portion, between the end portions, having a predetermined length in the first direction and having a second height which is higher than the first height, the central portion having an upper end that is continuous with the upper ends of the end portions,

wherein the agitator is configured to convey the developer from the second room to the first room through at least a portion of the opening which is formed above at least the central portion of the wall,

wherein the developer conveyed over the wall accumulates in the first room,

wherein the roller is configured to collect the developer accumulated in the first room, and

wherein the rotating member of the agitator includes a central conveyance portion corresponding to the central portions of the wall and end conveyance portions respectively corresponding to the end portions of the wall, each of the end conveyance portions including a mesh part,

wherein the central conveyance portion has a different shape than the end conveyance portions so that a force to convey the developer from the second room to the first room is stronger by the central conveyance portion than by the each end conveyance portion,

wherein superfluous developer accumulated in the first room returns to the second room through at least portions of the opening which are formed above the end portions of the wall.

2. The developer supply device according to claim 1 , wherein the roller includes a shaft and a carrying part disposed around the shaft of the roller and configured to carry the developer,

wherein, when Dcr is a length of the carrying part of the roller in the first direction, Dwl is a length of the central portion of the wall in the first direction, and Daj is a length of the rotating member of the agitator in the first direction, the developer supply device satisfies a following relationship:

Dcr>Dwl≧Daj.

3. The developer supply device according to claim 2 , further comprising a developer supplying member disposed between the roller and the wall and configured to supply the developer to the roller,

wherein the developer supplying member includes a shaft and a supplying part disposed around the shaft of the developer supplying member and configured to supply the developer,

wherein, when Dsp is a length of the supplying part of the developer supplying member in the first direction, the developer supply device satisfies a following relationship:

Dcr≧Dsp>Dwl≧Daj.

4. The developer supply device according to claim 1 , wherein the central conveyance portion has a different shape than the end conveyance portions.

5. The developer supply device according to claim 1 , wherein a circumferential surface of the roller is disposed near the wall with an interval.

6. The developer supply device according to claim 1 , wherein the rotation axis of the roller is disposed above the highest portion of the central portion of the wall when the developer supply device is in use.

7. The developer supply device according to claim 1 , further comprising a restricting member fixed to the casing and configured to remove a part of the developer carried by the roller so as to restrict an amount of the developer carried by the roller,

wherein the restricting member contacts a circumferential surface of the roller above the first room, downstream side of a movement direction of the circumferential surface of the roller and upstream side of a development position where the developer is supplied by the developer supply device.

8. The developer supply device according to claim 7 , wherein the restricting member directs the removed developer to the second room.

9. The developer supply device according to claim 1 , further comprising side seal members disposed on both ends of the opening in the width direction to prevent leakage of the developer from the opening.

10. The developer supply device according to claim 1 , further comprising a lower seal member disposed on a lower end of the first room when the developer supply device is in use, to prevent leakage of the developer from the lower end of the first room.

11. The developer supply device according to claim 1 , wherein the roller is a brush roller including:

a roller body having a circumferential surface; and

a brush layer formed on the circumferential surface to carry the developer.

12. The developer supply device according to claim 11 , further comprising a restricting member fixed to the casing and configured to remove a part of the developer carried by the roller so as to restrict an amount of the developer carried by the roller,

wherein the restricting member includes:

a fixing part fixed to the casing; and

a restricting part formed in an edge of the fixing part, the restricting part extending towards a central axis of the roller to contact the brush layer.

13. The developer supply device according to claim 1 , wherein the roller comprises a development roller configured to contact a photoconductive drum and supply the developer to the photoconductive roller on which an electrostatic latent image is formed.

14. The developer supply device according to claim 1 , further comprising a development roller,

wherein the roller comprises a supplying roller configured to contact the development roller and supply the developer to the development roller.

15. The developer supply device according to claim 2 , wherein Daj is equal to a length of the rotating member of the agitator between a first end and a second end in the first direction.

16. The developer supply device according to claim 1 , wherein the agitator is arranged inside the second room.

17. The developer supply device according to claim 1 , wherein the wall is disposed between the roller and the agitator in a direction perpendicular to the first direction.

18. A developer supply device, comprising:

a roller configured to carry developer, extending in a first direction the first direction being in a direction of a rotation axis of the roller and horizontal when the developer supply device is in use;

a casing in which a first room and a second room are defined, the roller being disposed in the first room, the second room being configured to store the developer;

a wall extending over a length of the casing in the first direction, the first room and the second room being partitioned by the wall, an opening being formed above the wall over the length of the wall when the developer supply device is in use; and

an agitator configured to convey the developer from the second room to the first room, the agitator including a shaft and a rotating member fixed to the shaft, the shaft being rotatably supported by the casing and configured to rotate in the second room;

wherein the wall is divided into:

end portions which are both end portions, in the first direction, of the wall and having a first height at upper ends of the end portions; and

a central portion defined as a portion, between the end portions, having a predetermined length in the first direction and having a second height which is higher than the first height, the central portion having an upper end that is continuous with the upper ends of the end portions,

wherein the agitator is configured to convey the developer from the second room to the first room through at least a portion of the opening which is formed above at least the central portion of the wall,

wherein the developer conveyed over the wall accumulates in the first room,

wherein the roller is configured to collect the developer accumulated in the first room, and

wherein the rotating member of the agitator includes a central conveyance portion corresponding to the central portions of the wall and end conveyance portions respectively corresponding to the end portions of the wall, each of the end conveyance portions including a plurality of penetrating holes,

wherein the central conveyance portion has a different shape than the end conveyance portions so that a force to convey the developer from the second room to the first room is stronger by the central conveyance portion than by the each end conveyance portion,

wherein superfluous developer accumulated in the first room returns to the second room through at least portions of the opening which are formed above the end portions of the wall.