Electrophotography – Image formation – Development
Reexamination Certificate
2002-10-29
2003-12-30
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S262000, C399S263000
Reexamination Certificate
active
06671481
ABSTRACT:
BACKGROUND
In an electrophotographic imaging process a dry toner (“toner”) is fused to a sheet of imaging media (such as paper or a transparency, for example) to generate an image on the imaging media. This process is well understood in the art, and is accomplished using an electrophotographic imaging apparatus such as a printer, a photocopier, a facsimile machine, or a multi-function apparatus which performs one or more of the processes of printing, photocopying, or printing facsimiles. Toner is typically provided to an imaging producing section of the imaging apparatus from a toner reservoir, which can be a removable toner cartridge or a replenishable reservoir which is resident within the imaging apparatus.
Toner generally includes color particles (generally microscopic particles such as carbon or colored plastic). Toner can also include carrier particles. In certain instances, the color particles are capable of carrying an electrostatic charge, allowing them to be moved by an electrostatic process from the toner reservoir to an image producing section of the imaging apparatus. In other applications, the carrier particles carry an electrostatic charge to thereby facilitate movement of the color particles. (It should be noted that by “color” we mean to include black, as well as other colors.)
In the electrophotographic imaging process toner is moved from a toner reservoir to the image producing section of the imaging apparatus. The image producing section includes a photosensitive conductor, or photoconductor, which is typically a drum or a roller. The photoconductor can be selectively exposed by an energy source, such as a pulsed laser, to electrostatically produce a portion of an image on the photoconductor. Toner particles from the toner reservoir are then either repelled or attracted to the photoconductor, based on the relative electrostatic charge differential there between. For example, if a photoconductor is initially charged with a positive electrical charge and then portions thereof are exposed to produce a lesser positive charge (or a neutral or negative charge), then positively charged toner will be attracted to the exposed areas, and repelled from the non-exposed areas. The toner is then electrostatically transferred from the photoconductor to either a sheet of imaging media, or to an intermediate transfer carrier (such as a belt or a drum) which subsequently transfers the toner to imaging media. The toner is then fused to the sheet of imaging media in a fusing section of the imaging apparatus, and the media is then deposited in an output tray. The imaging apparatus thus further includes a media transfer section to facilitate movement of the imaging media from a media supply point to the toner transfer point, and thence to the fusing section and the output tray. Because toner generally is made from near-microscopic particles, it takes on the form of a powder. The toner resident within a toner reservoir will thus tend to settle and densify over time due to gravity. However, for the electrophotographic imaging process to be particularly effective, the toner needs to be available to the photoconductor in an essentially fluidic state during the imaging process. Fluidizing the toner allows better distribution of the toner over the photoconductor, and also helps to ensure that any carrier particles are well distributed among color particles. Accordingly, most toner reservoirs include an agitator which agitates or “stirs” the toner at least during the electrostatic imaging process.
To better understand the present invention, a brief reference will be made to a conventional prior art developing device using a toner cartridge, shown in FIG.
1
. As depicted, a toner cartridge
1
stores a toner (not shown) therein. The cartridge
1
has a casing or housing
2
which defines a toner reservoir
19
, and which accommodates an agitator
3
and a magnetic roller
4
. The agitator
3
is rotated to agitate the toner existing in the housing
2
. The housing
2
is formed with a plurality of toner outlets
5
, only one of which can be seen in
FIG. 1. A
developing device
6
has a casing
7
which includes a toner storing section, or hopper as referred to hereinafter,
8
. An agitator
9
is rotatable in the hopper
8
for agitating the toner existing in the hopper
8
. A toner inlet
10
is formed in a portion of the casing
7
which faces the toner outlets
5
of the housing
2
. A developing roller
11
causes the toner to deposit thereon. A doctor blade
12
causes the toner to form a thin layer on the surface of the developing roller
11
. An intermediate roller
13
is held in contact with the developing roller
11
, so that the toner is transferred from the developing roller
11
to the intermediate roller
13
. A photoconductive element in the form of a drum
14
is held in contact with the intermediate roller
13
. The toner is transferred from the intermediate roller
13
to the drum
14
in order to develop a latent image electrostatically formed on the drum
14
. The resulting toner image is transferred from the drum
14
to a paper or similar recording medium “M” by an image transfer unit
15
. A cleaning unit
16
cleans the surface of the drum
14
after the image transfer. A charger
17
uniformly charges the surface of the drum
14
. An exposing device
18
exposes the charged surface of the drum
14
imagewise so as to form the latent image.
The agitator
3
of the toner cartridge
1
of
FIG. 1
can be provided with a flexible blade
20
which can conform to the shape of the interior of the housing
2
as the agitator
3
rotates in the direction indicated by the arrows. While some toner cartridges have toner reservoirs with complex interior shapes, generally the cross sectional shape of the toner reservoir area can be described as non-square in cross section. This non-square geometry helps to maintain contact between the flexible blade
20
and the walls of the toner reservoir. Accordingly, toner storage volume in the toner reservoir is impacted by not being able to use a geometry that is more square or rectangular in cross section than prior art toner reservoirs. That is, it is not always possible to maximize the toner storage volume within the available space in a toner cartridge, since prior art toner reservoirs are generally configured to ensure that prior art agitators will be able to access the entire toner reservoir. Put another way, toner cartridges are typically configured to fit within an imaging apparatus based on the presence of ancillary components located within the imaging apparatus. The exterior dimensions imposed on a toner cartridge by these ancillary components thus define a maximum toner reservoir volume which can be achieved in a toner cartridge. Yet prior art toner agitators do not always allow the maximum available volume to be utilized due to the need to accommodate the limitations of prior art agitators.
In addition to toner cartridges which do not include the photoconductor (as depicted in FIG.
1
), other prior art toner cartridges are known which incorporate the photoconductor. One such example is depicted in
FIG. 2
, which shows a toner cartridge
30
having a housing
31
which defines a toner reservoir
32
in which is located an agitator
34
. Toner from within the toner reservoir
32
egresses through outlet opening
35
to a hopper area
36
. An application roller
38
applies toner from the hopper area
36
to the optical photoconductor (“OPC”)
40
, which has been charged by charge roller
42
. A scraper blade
44
removes any residual toner from the OPC
40
after toner has been transferred from the OPC
40
to a sheet of imaging media (not shown), and the residual toner is stored in a waste storage area
46
. Agitator
34
of toner cartridge
30
is depicted in a front view in FIG.
3
. As can be seen, the agitator
34
includes two blade portions
50
which are supported by, but distal from, a central shaft
48
, thus creating open areas
52
. The open areas
52
allow the toner to “fluff” or volumize as it is agitated
Costello Daniel E.
Terry James P.
Tupper Paxton J.
Hewlett--Packard Development Company, L.P.
Royer William J.
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