Electrophotography – Document handling – Copy
Reexamination Certificate
2002-03-14
2003-09-09
Ngo, Hoang (Department: 2852)
Electrophotography
Document handling
Copy
C399S316000
Reexamination Certificate
active
06618576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image forming apparatus such as a copying machine, a printer or a facsimile apparatus for effecting image formation by the electrophotographic process or the electrostatic recording process.
2. Description of Related Art
In an image forming apparatus such as a copying machine for effecting image formation by the electrophotographic process, the productivity (the number of prints per unit time) of the apparatus is a very important measure, and in recent years, higher productivity has been required. On the other hand, a higher quality of the output image of the image forming apparatus also is an important measure, and a high quality of image has also been required.
So, in recent years, in order to achieve an improvement in the productivity of the image forming apparatus, design has come to be made so as to transport a transfer material such as paper at a higher speed, but to obtain an output image of high quality, it is particularly important to transport the transfer material such as paper stably to a transferring portion between a photosensitive drum and transferring means (such as a transferring roller).
Particularly when the transfer material is thick paper (cardboard) or the like, if the leading edge of the transfer material (cardboard) is not struck against a predetermined position on the photosensitive drum so that the transfer material fails to be transported to the transferring portion, the transporting speed becomes unstable, and this has sometimes led to a case where the output image is disturbed and the quality of image is reduced particularly when the output image is a halftone image or the like.
So, there is conceived an image forming apparatus in which, as shown in
FIG. 16
of the accompanying drawings, a charge eliminating brush member
103
, a transport regulating member
104
and an upper transfer guide
105
are installed downstream of a pair of registration rollers
100
provided upstream of a transferring portion (not shown) in the transport direction of a transfer material so that the transfer material can be transported to the transferring portion with the leading edge thereof stably struck against the predetermined position on a photosensitive drum.
FIG. 16
shows the background art of the present invention.
The pair of registration rollers
100
are comprised of an upper registration roller
101
and a lower registration roller
102
rotatably brought into pressure contact with each other, and a registration nip portion N is formed between the upper registration roller
101
and the lower registration roller
102
.
The pair of registration rollers
100
once stops a transfer material P transported from a feed cassette (not shown) at the registration nip portion N, and are rotatively driven in timed relationship with the formation of a toner image on the photosensitive drum (not shown) to thereby transport the transfer material P to the downstream transferring portion.
The charge eliminating brush member
103
is comprised of a brush portion
103
b
supported by a brush supporting portion
103
a
. The transport regulating member
104
has a transport guide portion
104
a
inclined in the transport direction of the transfer material P. The distal end of the top
104
b
of the transport guide portion
104
a
with which the transporting transfer material P contacts is obliquely downwardly bent with respect to the transport direction of the transfer material P. The top
104
b
of the transport guide portion
104
a
is located a little above with respect to the horizontal direction in the registration nip portion N.
Downstream of the transport regulating member
104
in the transport direction of the transfer material, there is provided an upper transfer guide
105
for causing the transfer material P being transported to contact with the predetermined position on the photosensitive drum and guiding it to the transferring portion.
The transfer material P nipped and transported by the registration nip portion N between the pair of registration rollers
100
as described above contacts with the brush portion
103
b
of the charge eliminating brush member
103
and has its charges eliminated thereby, and the leading edge of the charge-eliminated transfer material P strikes against the inclined surface of the transport guide portion
104
a
of the transport regulating member
104
and is guided to the upper transfer guide
105
while contacting with the top
104
b
. The upper transfer guide
105
guides the leading edge of the transfer material P so as to strike against the predetermined position on the photosensitive drum. The transfer material P, which has struck against the predetermined position on the photosensitive drum, is transported to the transferring portion between the photosensitive drum and transferring means, and the toner image on the photosensitive drum is transferred to the transfer material P.
By the transport regulating member
104
being provided downstream of the pair of registration rollers
100
as described above, the leading edge of the transfer material P stably contacts with the predetermined position on the photosensitive drum and is directed to the transferring portion. Consequently, the transport of the transfer material P to the transferring portion is stabilized, whereby even if as described above, a halftone image is transferred in the transferring portion by the use of a transfer material such as cardboard disadvantageous to transport, a good output image can be obtained.
Now, in the above-described image forming apparatus, the charge eliminating brush member
103
having the brush portion
103
b
for eliminating the charges of the transfer material P is provided upstream of the transport regulating member
104
, but there has been a case where as the number of prints increases, the brush portion
103
b
contacting with the transfer material P comes off the brush supporting portion
103
a
or the brush portion
103
b
breaks from the surface of the brush supporting portion
103
a.
This is because during the transport of the transfer material P, the transfer material P contacts with the brush portion
103
b
, whereby the brush portion
103
b
flexes in the transport direction of the transfer material P, whereby a load is repetitively applied to the root of the brush portion
103
b
which is exposed from the surface of the brush supporting portion
103
a
. Further, during the transport of the transfer material P, the transfer material P contacts with the brush portion
103
b
, whereby the brush portion
103
b
is sandwiched between the transfer material P and the transport guide portion
104
a
, whereby the load applied to the brush portion
103
b
becomes great, and the brush portion
103
b
becomes liable to come off or break.
As described above, the brush portion
103
b
has the role of eliminating the charges of the transfer material P upstream of the transferring portion, but will become incapable of appropriately eliminating the charges of the transfer material P before transfer if the brush portion
103
b
comes off or breaks as described above. If the transfer material P is charged, uneven transfer may occur during the transfer of the toner image in the transferring portion. This uneven transfer appears as a density difference particularly in a halftone image, and is a conspicuous phenomenon.
Also, the brush portion
103
b
has electrical conductivity and therefore, if the brush portion
103
b
comes off or breaks, it will scatter in the image forming apparatus, and if the scattered brush portion
103
b
contacts with an electrical contact portion in the image forming apparatus, electrical leak will be caused and the image forming apparatus may come not to operate normally.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus in which the coming-off or break of a charge eliminating member by sheet supply endurance can be prevented and the charges of a recording material can be stably elimi
Kanari Kenji
Nakata Yasuhiro
Yuminamochi Takayasu
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Ngo Hoang
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