Developing apparatus and image forming apparatus

1. A developing apparatus for use in an electrophotographic image forming apparatus, comprising:

a plurality of developing units configured to form corresponding developer images;

a frame configured to hold the plurality of developing units therein in position, the developing units being movable independently by a distance relative to the frame; and

an elastic sealing member secured to the frame and disposed between a side plate of each developing unit and the frame to seal a gap between the side plate and the frame after the developing unit has been attached to the frame, wherein when the developing unit moves over the distance relative to the frame, the elastic sealing member is deformable so that a surface of the elastic sealing member in contact with the side plate follows movement of the developing unit without slipping; wherein

each of the developing units includes a first transporting path configured to transport developer, and the frame includes a second transporting path configured to communicate with the first transporting path and to transport the developer further when a corresponding developing unit has been attached to the frame;

the elastic sealing member seals a gap between the first transporting path and the second transporting path when the corresponding developing unit is attached to the frame; and

the sealing member is compressed so that the sealing member, the gap, and the distance are related by T≧L 1 +L 2 , where T is the thickness of the sealing member when it is not compressed, L 1 is the distance, and L 2 is the gap.

2. An image forming apparatus which includes the developing apparatus according to claim 1 .

3. The developing apparatus according to claim 1 , further comprising an urging member configured to urge each of the developing units against the frame.

4. The developing apparatus according to claim 3 , wherein

the urging member is a coil spring that is mounted across the frame and each of the developing units;

the developing units are configured to support corresponding developer holding devices detachably attached to the developing units, each developer holding device including a memory element; and

the urging member is electrically conductive and includes a first portion and a second portion.

5. The developing apparatus according to claim 4 , wherein each of the developer holding devices includes a first terminal and the frame includes a second terminal, wherein the urging member electrically connects the first terminal and the second terminal.

6. The developing apparatus according to claim 5 , wherein the urging member includes a third portion electrically connected to the first terminal via a first conductive member, and a series connection of the first portion and second portion electrically connected to the second terminal via a second conductive member.

7. The developing apparatus according to claim 6 , wherein the distance and the coil spring are related by

L 3 ≧L 4 +L 1

where L 3 is the length of the coil spring when the coil spring is relaxed, L 4 is the length of the coil spring when the coil spring is fully compressed, and L 1 is the distance.

8. The developing apparatus according to claim 6 , wherein each of the developing units includes a projection that outwardly projects from each of the developing units,

wherein the third portion and the first conductive member fit over the projection.

9. The developing apparatus according to claim 1 , further comprising a movement mechanism configured to move the developing units.

10. A developing apparatus for use in an electrophotographic image forming apparatus, comprising:

a plurality of developing units configured to form corresponding developer images;

a frame configured to hold the plurality of developing units therein in position, the developing units being movable independently by a distance relative to the frame; and

an elastic sealing member secured to the frame and disposed between a side plate of each developing unit and the frame to seal a gap between the side plate and the frame after the developing unit has been attached to the frame, wherein when the developing unit moves over the distance relative to the frame, the elastic sealing member is deformable so that a surface of the elastic sealing member in contact with the side plate follows movement of the developing unit without slipping; and

an urging member configured to urge each of the developing units against the frame;

wherein the urging member is a coil spring that is mounted across the frame and each of the developing units;

each of the developing units includes a first transporting path configured to transport waste developer, and the frame includes a second transporting path configured to communicate with the first transporting path and to transport the waste developer further when a corresponding developing unit has been attached to the frame

the elastic sealing member seals a gap between the first transporting path and the second transporting path when the corresponding developing unit is attached to the frame; and

the sealing member is compressed so that the sealing member, the gap, and the distance are related by T≧L 1 +L 2 , where T is the thickness of the sealing member when it is not compressed, L 1 is the distance, and L 2 is the gap.

11. An image forming apparatus which includes the developing apparatus according to claim 10 .

12. A developing apparatus for use in an electrophotographic image forming apparatus, comprising:

a plurality of developing units configured to form corresponding developer images;

a frame configured to hold the plurality of developing units therein in position, the developing units being movable independently by a distance relative to the frame; and

an elastic sealing member secured to the frame and disposed between a side plate of each developing unit and the frame to seal a gap between the side plate and the frame after the developing unit has been attached to the frame, wherein when the developing unit moves over the distance relative to the frame, the elastic sealing member is deformable so that a surface of the elastic sealing member in contact with the side plate follows movement of the developing unit without slipping;

an urging member configured to urge each of the developing units against the frame;

wherein the urging member is a coil spring that is mounted across the frame and each of the developing units;

the developing units areconfigured to support corresponding developer holding devices detachably attached to the developing units, each developer holding device including a memory element; and

the urging member is electrically conductive and includes a first portion and a second portion.

13. The developing apparatus according to claim 12 , wherein each of the developer holding device includes a first terminal and the frame includes a second terminal, wherein the urging member electrically connects the first terminal and the second terminal.

14. The developing apparatus according to claim 13 , wherein the urging member includes a third portion electrically connected to the first terminal via a first conductive member, and a series connection of the first portion and second portion electrically connected to the second terminal via a second conductive member.

15. The developing apparatus according to claim 14 , wherein the distance and the coil spring are related by

L 3 ≧L 4 +L 1

where L 3 is the length of the coil spring when the coil spring is relaxed, L 4 is the length of the coil spring when the coil spring is fully compressed, and L 1 is the distance.

16. The developing apparatus according to claim 14 , wherein each of the developing units includes a projection that outwardly projects from each of the developing units,

wherein the third portion and the first conductive member fit over the projection.