Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-12-09
2004-11-16
Chen, Sophia S. (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S254000, C399S258000
Reexamination Certificate
active
06819882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a powder stirring device used in an image forming device, such as a photocopier or a printer.
2. Description of the Related Art
An image forming device, such as a photocopier or a printer, develops images in the following way. First, images are optically read and electrostatic images are formed on the surface of a photosensitive body. Next, powder-type toner is attached to the electrostatic images and is then transferred to a piece of paper. Such a process of developing images is performed in a development unit included in an image forming device.
In general, toner is contained in a toner cartridge under a predetermined pressure to be maintained in a solid state. Powder-type toner can be provided to a development unit after transferring the toner from the toner cartridge to a reserve tank to supply toner and then stir it with a powder stirring device in the reserve tank. An image forming device having such a structure has been disclosed in Japanese Patent Laid-Open Publication No. hei 3-217879. Here, the toner cartridge and the reserve tank may be integrated into one body or may be used separately.
FIG. 1
is a diagram illustrating a conventional image forming device, such as a printer. Referring to
FIG. 1
, toner contained in a toner cartridge
31
is provided to a reserve tank
32
and stirred therein so that it becomes powdery. Next, the toner is provided from a supply roller
33
of the reserve tank
32
to a development unit
34
. The fine-grained toner is attached to electrostatic images formed on a drum of the development unit
34
and is finally transferred to a piece of paper as an image.
In order to regularly attach toner to the electrostatic images formed on the drum of the development unit
34
, the amount of the toner needs to be controlled by stirring the toner in the reserve tank
32
with air, in order to reach a powdery state and thus the toner regularly spreads in the direction of the length of the supply roller
33
. Accordingly, a powder stirring device to stir toner and convey it in the direction of the length of the supply roller
33
is installed in the reserve tank
32
.
FIG. 2
is a diagram illustrating the structure of a conventional reserve tank. Referring to
FIG. 2
, when grain-type toner is supplied from a toner discharger
42
formed at the lower part of a toner cartridge
41
to a toner supplier
44
formed at the surface of a reserve tank
43
, the grain-type toner is mixed with air by two stirring screws
45
and
46
so that it becomes powdery.
The powdery toner is circulated by the two stirring screws
45
and
46
so that it can be repeatedly moved along the direction of the length of the reserve tank
43
and can be regularly spread to the reserve tank
43
, as marked by the arrows in FIG.
2
. The toner stirred by the stirring screws
45
and
46
is sent to a development unit (not shown) for development. A supply roller
47
is installed near the stirring screw
45
to supply toner to the development unit. The amount of toner in the reserve tank
43
is measured by a toner sensor
48
, which includes a piezoelectric vibrator, so that a certain amount of toner required for development can always be saved in the reserve tank
43
.
However, in the structure of the conventional powder stirring device, toner cannot be effectively stirred because the toner may attach to the surface of the stirring screws
45
and
46
. In particular, in the case of a small-sized image forming device, since the capacities of a reserve tank
43
and the amount of air in the reserve tank
43
are very small, toner may more easily attach to the surface of the stirring screws
45
and
46
, and thus it is much more difficult to effectively stir the toner with air. In addition, the stirring screws
45
and
46
have a very complicated structure and are very expensive. It is also very difficult to manufacture the stirring screws
45
and
46
to be compact.
In the case of an image forming device, such as a printer, since the reserve tank
43
has a small capacity, toner in the reserve tank
43
is used up faster, and thus it is necessary to frequently detect how much toner is left in the reserve tank
43
. However, a piezoelectric sensor, which is conventionally used as a toner sensor
48
, measures the amount of toner based on vibration frequencies that vary depending on the amount of toner attached to the piezoelectric sensor, and thus it is impossible to measure the amount of toner in real time. In other words, a small-sized image forming device, such as a printer, has a small reserve tank and can print images very quickly. However, it is almost impossible to maintain an appropriate amount of toner in the reserve tank
43
, unless the amount of toner in the reserve tank is measured often.
SUMMARY OF THE INVENTION
Accordingly, it is an aspect of the present invention to provide a powder stirring device which has a simple structure and can effectively stir toner.
It is another aspect of the present invention to provide a powder stirring device which measures the amount of toner left in a reserve tank in real time.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention may be achieved by providing a powder stirring device, which stirs toner to be provided to a development unit of an image forming device. The powder stirring device includes a stirring element which is supported in a reserve tank, temporarily storing the toner. The stirring element is arranged away from a rotation axis of the reserve tank or a region adjacent to the rotation axis, so as to be capable of rotating in the reserve tank.
The stirring element may be formed in a bar shape and arranged in parallel with the rotation axis of the reserve tank. The stirring element may be formed in a crank or a spiral shape.
The stirring device may include a pair of bars, which are symmetrically arranged with respect to the rotation axis of the reserve tank and are parallel to the rotation axis of the reserve tank, and ribs, which are formed along the rotation circumference of the pair of bars and are slantingly connected to the pair of bars.
The powder stirring device may further include a unit to detect the amount of toner in the reserve tank. The unit to detect the amount of toner in the reserve tank may be an optical sensor which detects the amount of light passing through a region in the reserve tank where toner is stirred.
The powder stirring device may further include a supply roller which is provided in the vicinity of the stirring element to provide toner to the development unit. The stirring element may be arranged so that its rotation circumference contacts the supply roller.
REFERENCES:
patent: 5189474 (1993-02-01), Miya et al.
patent: 5287151 (1994-02-01), Sugiyama
patent: 5701563 (1997-12-01), Fukuda et al.
patent: 6424812 (2002-07-01), Hsu
patent: 6591079 (2003-07-01), Ota et al.
patent: 60-238874 (1985-11-01), None
patent: 3-217879 (1991-09-01), None
patent: 11-143201 (1999-06-01), None
patent: 11-231634 (1999-08-01), None
Chen Sophia S.
Staas & Halsey , LLP
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