Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
1999-08-25
2001-10-02
Grainger, Quana M. (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S274000, C399S284000
Reexamination Certificate
active
06298203
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus which can be used with a forming apparatus such as an electrophotographic copying machine, an electrophotographic printer and the like.
2. Related Background Art
In image forming apparatuses of electrophotographic type or electrostatic type, an electrostatic latent image formed on an image bearing body such as an electrophotographic photosensitive body or an electrostatic recording dielectric body is visualized by a developing apparatus as a toner image.
As an example of such developing apparatuses, various dry one-component developing apparatuses have been proposed and put to a practical use. However, in all of such developing apparatuses, it is difficult to form a thin toner (one-component developer) layer on a developer bearing body.
Nowadays, since improvement in resolution and clearness of an image have been requested, development regarding method and apparatus for forming a thin toner layer is inevitable and some attempts have been proposed.
For example, as disclosed in Japanese Patent Application Laid-open No. 54-43038, an elastic blade (regulating member) made of metal or rubber abuts against a developing sleeve (developer bearing body) so that, by passing toner through an abutment area between the elastic blade and the developing sleeve to regulate the toner, a thin toner layer is formed on the developing sleeve and adequate triboelectricity is applied to the toner by friction generated in the abutment area.
In this case, when nonmagnetic toner is regulated by the elastic blade, a toner supplying member for supplying the toner onto the developing sleeve must be provided additionally. The reason is that, although magnetic toner can be supplied onto the developing sleeve by a force of a magnet disposed within the developing sleeve, the nonmagnetic toner cannot be supplied by such a magnetic force.
Now, an example of a conventional color laser printer as a conventional multi color electrophotographic image forming apparatus will be described with reference to FIG.
6
.
Within a main body of an image forming apparatus, there are disposed an image bearing body unit
101
, a laser scanner portion
105
, a developing unit
106
of rotary type, a transfer unit
107
, a sheet feeding unit
108
and a fixing device
109
and the like.
The image bearing body unit
101
includes an image bearing body (electrophotographic photosensitive drum)
102
rotated in an counter-clockwise direction shown by the arrow, a charging device
103
and a cleaning device
104
and constitutes a process cartridge detachably attachable to the main body of the image forming apparatus.
The developing unit
106
includes four developing devices
106
Y,
106
M,
106
C,
106
B containing four color (yellow, magenta, cyan and black) toners. The four color developing devices are rotatably mounted on a rotary
106
b
rotated in a clockwise direction around a shaft
106
a
. The shaft
106
a
is provided with a revolution gear around which rotation gears are meshed, so that, in synchronism with the movement of the rotation gears, the developing devices
106
Y,
106
M,
106
C,
106
B are rotated, thereby maintaining the postures of the developing devices constant.
The developing devices
106
Y,
106
M,
106
C,
106
B are constituted as a developing cartridge detachably attachable to the rotary
106
b.
The transfer unit
107
mainly includes a transfer drum
107
a
rotated in a clockwise direction shown by the arrow, so that a transfer material P fed from the sheet feeding unit
108
can be wound around the transfer drum
107
a
and be conveyed by the transfer drum.
The sheet feeding unit
108
includes a sheet feeding cassette
108
a
disposed at a lower part of the main body of the image forming apparatus, a sheet feeding roller (pick-up roller)
108
b
for feeding out the transfer materials P from the sheet feeding cassette, and a sheet path
108
c
including a one sheet separation and feed roller, a turn roller and registration rollers, so that the transfer material P is fed to the transfer drum
107
a
of the transfer unit
107
at a predetermined control timing.
When the rotating image bearing body
102
of the image bearing body unit
101
is subjected to uniform charging treatment effected by the charging device
103
with a predetermined polarity and potential and laser scan exposure L (corresponding to predetermined image information) effected by the laser scanner portion
105
, an electrostatic latent image corresponding to the predetermined image information is formed on the peripheral surface of image bearing body.
The electrostatic latent image is developed as a toner image by a predetermined developing device of the developing unit
106
. In image formation, among the developing devices
106
Y,
106
M,
106
C,
106
B of the developing unit
106
, the developing device corresponding to the latent image is stopped at a position opposed to the image bearing body
102
, and the developing device is pressed against the image bearing body
102
by a pressurizing mechanism so that a developing sleeve
106
S is positioned to be opposed to the surface of the image bearing body
102
with a small gap therebetween. In the development, bias is applied to the developing sleeve
106
S and the developing sleeve is rotated, thereby developing the latent image formed on the image bearing body
102
as a toner image. The toner image is transferred onto the transfer material P wound around the peripheral surface of the transfer drum
107
a.
The cleaning device
104
serves to remove residual toner from the surface of the image bearing body after the transferring operation.
In case of a full-color image, four color (yellow, magenta, cyan and black) toner images successively formed on the image bearing body
102
are successively transferred onto the same transfer material P wound around the peripheral surface of the transfer drum
107
a.
The transfer material P to which the toner images were transferred is separated from the surface of the transfer drum
107
a
and then is introduced into the fixing device
109
, where the toner images are melted and mixed by receiving permanent fixing to form a full-color toner image. Thereafter, the transfer material is discharged out of the image forming apparatus.
FIG. 7
is an enlarged schematic sectional view of the developing apparatus (developing cartridge). The developing devices
106
(Y, M, C, B) have the same constructions and each has a developing container
91
containing nonmagnetic toner (one-component developer) T, a rotating developing sleeve (developer bearing body)
92
disposed at an opening portion of the developing container, an elastic regulating blade
93
abutting against the developing sleeve with the interposition of the developer, an elastic roller (developer supplying member for supplying the developer to the developing sleeve)
94
, and a toner feed mechanism
95
and the like.
More specifically, in this conventional developing apparatus, within the developing container
91
containing the nonmagnetic toner (one-component developer) T, there is provided the elastic roller
94
using foam material such as polyurethane foam or sponge or a fur brush which abuts against the developing sleeve
92
at a position upstream of the elastic regulating blade
93
in a rotational direction of the developing sleeve
92
, so that, by rotating the elastic roller
94
in a direction shown by the arrow F, the toner T is supplied onto the developing sleeve
92
.
The elastic regulating blade
93
comprises an elastic blade portion and a support metal plate for supporting the blade portion, and the support metal plate is pinched between a holding metal plate
68
of the developing container
91
and a pressing metal plate
69
. The holding metal plate
68
, elastic regulating blade
93
and pressing metal plate
69
are positioned by a positioning boss
27
b
integral with the developing container
91
.
The toner T supplied to the developing sleeve
92
by the
Fujita Akiyoshi
Hashimoto Kouji
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grainger Quana M.
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