Electrophotography – Image formation – Development
Reexamination Certificate
1999-12-21
2001-10-23
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S267000, C399S272000
Reexamination Certificate
active
06308035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing device that is applicable to, for instance, electrophotographic copying machines.
2. Description of the Related Art
A developing device of this type, equipped with a developing magnet roller and upper and lower mixers, circulates developer along upper and lower conveying paths by rotating the upper and lower mixers and develops images by supplying developer to the developing magnet roller from a developer accumulating portion via the upper conveying path.
Further, after developing images, residual developer remaining on the developing magnet roller is recovered and conveyed along the lower conveying path.
By the way, the developer accumulating portion and the lower conveying path are communicated with each other and developer tends to leak from the developer accumulating portion to the lower conveying path. Leakage (flow) of developer to the lower conveying path is prevented because developer is retained by the magnetic force of a conveying pole located close to the developer accumulating portion of the developing magnet roller.
However, in conventional developing devices, developer is retained by the magnetic force of the conveying pole and if the magnetic force of the conveying pole drops, the developer leaks (flows) from the developer accumulating portion to the lower conveying path and the circulation of developer is unbalanced. That is, there was such a defect that developer in the upper conveying path decreases, amount of developer supplied to the developing magnet roller via the developer accumulating portion drops and in the worst case, developer may not be supplied.
Further, when the magnetic force of the conveying pole is too high, used developer is drawn in the developer accumulating portion from the lower conveying path and an image density is apt to drop.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a developing device that is capable of preventing leakage (flow) of developer from a developer accumulating portion to a lower conveying path without relying on the magnetic force of a conveying pole and drawing-up of used developer from a lower conveying path.
According to the present invention, a developing device is provided. The developing device comprises a developing roller configured to supply developer to a developing portion, a first conveying path configured to guide a moving of the developer and from which the developer is supplied by the developing roller to the developing portion, a first mixer configured to mix the developer while the developer is moving along the first conveying path, a second conveying path configured to guide the moving of the developer, wherein a residual developer left on the developing roller is recovered to the second conveying path and conveyed to the first conveying path, a second mixer configured to mix the developer while the developer is moving along the second conveying path, and a partition member arranged between the developing roller and the first conveying path to prevent leakage of the developer from between the developing roller and the first conveying path to the second conveying path directly, wherein one end of the partition member is brought in contact with the developing roller.
REFERENCES:
patent: 4940014 (1990-07-01), Saijo et al.
patent: 5758240 (1998-05-01), Ito et al.
patent: 5991583 (1999-11-01), Nozawa
patent: 6035168 (2000-03-01), Masuda et al.
patent: 6122472 (2000-09-01), Sako et al.
patent: 6144829 (2000-11-01), Miyasaka et al.
patent: 5-333691 (1993-12-01), None
Foley & Lardner
Royer William J.
Toshiba Tec Kabushiki Kaisha
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