Electrophotography – Image formation – Development
Reexamination Certificate
1999-11-19
2002-02-12
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S260000, C399S263000
Reexamination Certificate
active
06347207
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a developing unit for use in an image forming apparatus such as a laser printer, copier, facsimile machine etc., and in particular relates to a technology for replenishing, as required, the toner for image development to the developer hopper as a part of a developing unit.
(2) Description of the Prior Art
An image forming apparatus such as a laser printer, copier, facsimile machine utilizing the electrophotographic technique, has an image forming portion for forming a desired image on a sheet for recording. In this image forming portion, the surface of a photoreceptor as an image bearer is uniformly electrified with charge of a particular polarity and then is illuminated with an optical image so as to form a static latent image corresponding to the image. For the purpose of visualizing this static latent image, the image forming portion includes a developing unit and other components. The developing unit is configured of a developer hopper holding a developer and having a developing roller for replenishing the developer to the developing position where the developing roller opposes the photoreceptor. Further, since the toner in the developer hopper is consumed, a toner replenishing device for supplying the toner to the developer hopper as necessary is arranged adjacent to the developer hopper.
In a developing unit of the above type, if the toner reserve container for replenishing the developer to the developer hopper is arranged on the top, the developing unit would be bulky as to its height so a waste space would arise inside the image forming apparatus, thus making the whole image forming apparatus bulky. For this reason, the toner reserve container is horizontally arranged adjacent to the developer hopper to reduce the height of the developing unit, thus making the developing unit into a thinned configuration and hence making it possible to configure a compact image forming apparatus as a whole by eliminating the unnecessary space which would arise inside the image forming apparatus.
An example of such a developing unit is disclosed in Japanese Patent Application Laid-Open Sho No. 63-213877. In this developing unit, the toner reserve container is arranged at the side of the developing hopper and has a conveying element that conveys and agitates the toner inside the toner reserve container so that the conveying element feeds (replenishes) the toner into the toner replenishing portion from which the toner is replenished to the developer hopper.
Japanese Patent Application Laid-Open Hei No. 10-123815 has proposed a developing unit having a toner replenishing device having a simpler configuration compared to the developing unit disclosed in the aforementioned publication. This developing unit
60
comprises, as shown in
FIG. 1
, a developer hopper
61
which incorporates an agitating roller
62
for agitating the developer stored in developer hopper
61
and a developing roller
63
for conveying the developer to the developing area that opposes the photoreceptor. Further, a toner reserve container
64
is horizontally arranged at the side of developer hopper
61
. Toner reserve container
64
stores toner
69
for replenishment and incorporates an agitator
65
that agitates and conveys the stored toner
69
.
Formed between developer hopper
61
and toner reserve container
64
is a toner supply opening
66
, at which a toner replenishing roller
67
made up of sponge for replenishing the toner into developer hopper
61
is positioned. The agitator
65
is rotated in the direction of the arrow in the drawing during toner replenishment so as to feed the toner to replenishing roller
67
whilst agitating the toner stored in toner reserve container
64
.
Agitator
65
is configured of rotational, agitating vanes (a pair of plates arranged on both sides) with a conveying sheet
68
of a flexible sheet-like element, attached atone end of the vanes. Accordingly, as agitator
65
is turned, conveyer sheet
68
scoops up the toner
69
accumulated or stored at the bottom of toner reserve container
64
whilst agitating it and collects the toner thereover to feed it to replenishing roller
67
. During this, the toner
69
covering the sheet is supplied to replenishing roller
67
by making use of the force of action that causes conveying sheet
68
to restore itself due to its own flexibility.
In a developing unit of this kind, toner reserve container
64
is arranged at the side, and the agitator
65
is provided in the toner reserve container
64
, whereby toner
69
in toner reserve container
64
can be conveyed completely to toner replenishing roller
67
. Thus, the toner storage volume can be increased by enlarging the developing unit horizontally while the height of the developing unit can be suppressed.
In the developing unit shown in
FIG. 1
, since toner reserve container
64
is horizontally arranged at the side of developer hopper
61
, there is no increase in height. However, if the toner storage volume of toner reserve container
64
is further increased, the height cannot but increase.
If toner reserve container
64
is enlarged only in the horizontal direction in order to increase the toner storage volume, agitator
65
shown in
FIG. 1
cannot agitate and convey the toner well enough. That is, if the distance of conveying sheet
68
from the fixed end to the distal end is set long enough to convey the toner in the vertical direction, it is difficult to secure good enough performances of agitation and conveyance of the toner in the lateral direction. As a result, the toner inside toner reserve container
64
cannot be completely used and a certain toner will remain unused. Further, the remaining toner is not agitated and hence the toner gathers into a mass in the stationary area, which may then be fed into the agitatable area by some reason such as vibration, for instance, and hence the aggregation may be fed to replenishing roller
67
. When such a toner aggregation is fed to developer hopper
61
, it may cause development failures, or other deficiencies.
For these reasons, in the apparatus disclosed in Japanese Patent Application Laid-Open Hei No. 10-123815, the rotary shaft
65
a
of agitator
65
is set off-centered closer to the developer hopper
61
side while conveying sheet
68
when it is positioned horizontally is formed long enough so that its front end reaches the right side wall (rear wall) of toner reserve container
64
in
FIG. 1
, whereby toner supply can be stabilized while securing a desired amount of toner for replenishment and eliminating toner stagnation. In
FIG. 1
, a reference numeral
71
designates a regulating element for limiting the developer adhering to developing roller
63
to the predetermined amount and
72
designates a concentration detector for detecting the toner concentration of the developer in developer hopper
61
.
Here, in accordance with the toner replenishing device having a configuration shown in
FIG. 1
, toner
69
in toner reserve container
64
is adapted to be scooped up and fed to the replenishing portion from above to replenishing roller
67
. In contrast to this, those disclosed in Japanese Patent Application Laid-Open Hei No. 6-236110 and Japanese Patent Application Laid-Open Hei No. 7-271163 are configured so that the toner in the toner reserve container is scooped up and fed from below. In these cases where the toner is fed in such a manner, the rotary shaft of the agitator needs to be positioned above the replenishing portion so that the configuration inevitably tends to be greater in height.
Here, the developing unit having a configuration shown in
FIG. 1
, particularly, agitator
65
rotatably provided in toner reserve container
64
for toner replenishment is configured to be symmetrical with respect to rotary shaft
65
a
. In other words, agitator
65
is set so that the distance from the center of rotary shaft
65
to either end is constant, and conveying sheet
68
is attached to one of the ends.
Therefore, when agit
Funayama Naotaka
Ishiguro Yasuyuki
Nagata Tsutomu
Nishino Toshio
Otsuka Yoshinori
Royer William J.
Sharp Kabushiki Kaisha
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