Electrophotography – Image formation – Development
Reexamination Certificate
2000-10-05
2002-06-11
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S359000
Reexamination Certificate
active
06405009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus capable of recycling residual toner on the photosensitive drum surface after forming an image in an image forming method such as electrophotography. More specifically, the invention relates to an image forming apparatus, in which recovered toner is not used as it is, but its external additive concentration is returned to an appropriate level to turn it into recycled toner with the same properties as fresh toner, and recycle this recycled toner.
2. Description of the Related Art
Conventionally, image forming apparatuses using electrophotography are widely used. In electrophotography, an electrostatic latent image, which has been formed on the surface of a photosensitive drum serving as an electrostatic latent image carrier, is developed with toner, transferred onto a sheet of recording paper or the like and ejected. In such an apparatus, the toner on the photosensitive drum is not necessarily transferred entirely to the sheet, and some of it remains on the surface of the photosensitive drum. After the residual toner that has remained on the photosensitive drum has been removed in a cleaning step, it is recovered in a toner container, such as a toner bottle, and disposed of. That is to say, in conventional methods, recovered toner is not recycled.
In recent years, image forming apparatuses have become much faster, and the number of images printed per unit time has grown very high, so that also the amount of residual toner has grown to large quantities. The principle component of the residual toner is a binder resin, and disposing large quantities thereof may lead to environmental pollution.
Under these circumstances, there has been much talk in recent years about pollution of the environment and the efficient use of natural resources, so that a strong demand for the recycling of residual toner in image forming apparatuses has developed.
One method that is used for this is to supply the toner that has been eliminated or recovered in a cleaning step as it is to a developing unit via conveying means.
FIGS. 15A and 15B
show a conventional image forming apparatus
200
that can recycle residual toner.
FIG. 15A
shows the general configuration of this conventional image forming apparatus
200
, which can recycle residual toner.
FIG. 15B
is a magnification showing the general configuration of the image forming portion of the image forming apparatus
200
shown in FIG.
15
A.
The image forming portion of the image forming apparatus
200
includes a charging unit
202
, an exposure device
203
, a developing unit
204
, a transfer device
205
, a peel-off device
208
, a cleaning device
206
, and a discharger
207
arranged around a rotatable cylindrical photosensitive drum
201
serving as an electrostatic latent image carrier and having an organic photoconducting photosensitive layer, as well as a toner recycling portion
209
, which conveys the residual toner that has been recovered with the cleaning device
206
to the developing unit
204
.
The image formation is carried out in the following order. To carry out an image formation, the photosensitive drum
201
is first rotated in the arrow direction A, and the surface of the photosensitive drum
201
is charged uniformly with the charging unit
202
. Then, the exposure device
203
exposes photosensitive drum
201
in correspondence with the original document. This forms on the surface of the photosensitive drum
201
an electrostatic latent image corresponding to the original document. In the developing unit
204
, this electrostatic image is made visible by supplying toner with a developing roller
204
d
. The toner image is transferred by the transfer device
205
onto a transfer material, such as a piece of paper, which has been conveyed from a paper feed portion
210
. After the transfer material, onto which the toner has been transferred, has been subjected to a fixing process with the fixing device
211
, it is ejected out of the image forming apparatus.
After the transfer step, the residual toner that has remained on the surface is scraped off the photosensitive drum
201
with a cleaning blade
206
a
of the cleaning device
206
, and the charge on the surface of the photosensitive drum
201
is eliminated with the discharger
207
. Then, the surface of the photosensitive drum
201
is uniformly charged again with the cleaning unit
202
, and the above steps are repeated.
The residual toner that has been recovered by the cleaning device
206
is conveyed through the toner recycling portion
209
, which is provided with a screw, to the developing unit
204
, is mixed with the toner that has accumulated in the developing unit
204
while being stirred, and is used again for making electrostatic latent images on the photosensitive drum
201
visible. The replenishing of fresh toner is performed from a toner cartridge
212
, serving as a toner supply portion, provided at the top of the developing unit
204
.
In the above-described series of image forming steps, matter generated by the corona charging and foreign matter, such as paper particles or talc, which is contained in the paper sheets or other transfer material, adheres to the surface of the photosensitive drum
201
, in addition to the residual toner. In the image forming apparatus shown in
FIGS. 15A and 15B
, if foreign matter, such as particles of the paper sheets or toner coagulates, is conveyed through the toner recycling portion
209
to the developing unit
204
together with the toner, then this may adversely influence the following image forming steps, and when foreign matter is supplied together with the toner to the surface of the photosensitive drum
201
, a decline of the image quality, such as blank spots in the image, may occur. There is also the possibility that the surface of the photosensitive drum
201
is damaged. Consequently, to recycle the residual toner that has been recovered, it was necessary to recycle the residual toner by some means.
A technique that has been proposed to solve this problem is to carry out a recycling process, in which the recovered toner is passed through a lattice-shaped filter (mesh), and foreign matter mixed into the recovered toner is eliminated, as for example in the image forming -method disclosed in Japanese Unexamined Patent Publication JP-A 8-185101 (1996). This technique also carries out a process in which the separatability of the foreign matter from the recovered toner is improved. With this technique, it is possible to obtain a recycled toner that can maintain a high image density from beginning to end, and without covering of the document with toner and toner scattering.
In the toner cartridge disclosed in Japanese Unexamined Patent Publication JP-A 6-130810 (1994), a residual toner storage tank for collecting residual toner is coupled to and formed in one piece with a fresh toner storage tank for supplying fresh toner to the developing unit. The residual toner is mixed with the fresh toner, and this toner mixture of residual toner and fresh toner is supplied to the developing unit via a conveyance duct, and thereby recycled. A wall in which holes with small diameter are formed or a lattice-shaped wall is provided between the residual toner storage tank and the fresh toner storage tank, which prevents that foreign matter or residual toner particles with large particle diameter are transferred to the fresh toner storage tank. Furthermore, this cartridge also improves the conveyability and the chargeability of the residual toner by mixing the fresh toner and the residual toner while stirring.
Although this toner cartridge improves the properties of the residual toner, the properties of the fresh toner, which is mixed with the residual toner, deteriorate. Therefore, it cannot provide a mixed toner of high quality. The reason for this is that not only are impurities mixed into the recovered residual toner, but the composition of the toner itself changes. That is to say, the residual toner's co
Inoue Atsushi
Masuda Jitsuo
Sakai Takashi
Shinkawa Kouji
Yamanaka Takayuki
Nixon & Vanderhye P.C.
Royer William J.
Sharp Kabushiki Kaisha
LandOfFree
Image forming apparatus including system for recycling toner does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus including system for recycling toner, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus including system for recycling toner will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2979324