Electrophotography – Image formation – Development
Patent
1999-05-03
2000-11-07
Pendegrass, Joan
Electrophotography
Image formation
Development
399284, G03G 1508
Patent
active
06144829&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a developing device for use in an electrophotographic apparatus which is applicable for use with printers, facsimile apparatuses, copying machines, and the like.
The configuration of a known developing device is shown in FIG. 6. Referring to FIG. 6, reference numeral 1 denotes a developing roll for forming a thin layer of electrically charged tonor thereon and transporting the tonor to a photosensitive member; 2 denotes a transport roll for transporting the tonor to the developing roll 1; 3 denotes a tonor transporting vane for agitating the tonor and transporting the tonor to the transport roll; 5 denotes a regulating blade for regulating the amount of the tonor attaching onto the developing roll 1; 6 denotes a tonor storage for storing tonor; 9 denotes tonor; and 10 denotes a photosensitive member 10.
In a conventional developing device of the one-component type, the photosensitive member 10 is generally disposed so that at the tonor transfer position, it moves downward, and the developing roll 1, with a tonor thin layer formed thereon, is also arranged to rotate downward at the tonor transfer position facing the photosensitive member 10 to perform development.
The tonor 9 within the tonor storage 6 is transported to the transport roll 2 by the rotating tonor transporting vane 3. As the transport roll 2, a conductive or semiconductive foam roll is generally used. The tonor 9 transported to the transport roll 2 is further transported to the developing roll 1 by the rotating transport roll 2. The amount of tonor is regulated by the regulating blade 5 provided on the developing roll 1 and the tonor is electrically charged by friction with the regulating blade 5 to form a thin layer of charged tonor on the developing roll 1. The developing roll 1 with the charged tonor thin layer formed thereon, when brought into contact with or into the vicinity of the photosensitive member 10, develops an electrostatic latent image on the photosensitive member 10.
In the configuration of the developing device of FIG. 6, because the developing roll 1 is located below the regulating blade 5, tonor can be supplied in a stabilized manner to the regulating position of the regulating blade 5 located on the surface of the developing roll 1. Further, since the tonor which has become a surplus by the action of the regulating blade 5 can escape into the space above the regulating blade, a flow of tonor shown by an arrow 28 in the drawing is produced, and, thereby, the surplus tonor is returned, in a stabilized manner, to the transport roll 2 and the tonor storage 6 so as to be circulated. Thus, a stabilized tonor supply to the regulating blade 5 and the recovery of the surplus tonor can both be achieved, so that the tonor is prevented from stagnating or solidifying.
On the other hand, in the case of a developing device of a nonmagnetic one-component type in which the photosensitive member 10 is positioned to move upward at the tonor transfer position, it is necessary to cause the developing roll 1 with a tonor thin layer formed thereon also to rotate upward to perform development at the tonor transfer position facing the photosensitive member 10. Since, in this case, it is necessary to dispose the regulating blade 5 below the developing roll 1, it becomes difficult to supply the tonor to the regulating position of the regulating blade 5 on the surface of the developing roll 1 in a stabilized manner. Further, since the surplus tonor provided by the regulating blade 5 falls below the developing roll 1 due to gravity, it becomes difficult to form a circulating path as shown by the arrow 28 in FIG. 6 within the developing device.
A developing device for performing development using a developing roll 1 with a tonor thin layer formed thereon, which is rotated upward at the tonor transfer position facing the photosensitive member 10, is disclosed in the Japanese Patent Laid-open No. Hei 5-158345. The configuration of this developing device is shown in FIG. 7. Reference numerals
REFERENCES:
patent: 5701563 (1997-12-01), Fukida et al.
patent: 5722021 (1998-02-01), Iwao
patent: 5815775 (1998-09-01), Miyasaka et al.
Miyasaka Toru
Okano Tadashi
Oonishi Kazushige
Saito Masahiko
Takeya Shoji
Hitachi , Ltd.
Pendegrass Joan
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