Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-08-07
2003-09-02
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S312000
Reexamination Certificate
active
06615016
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an image forming apparatus, for example, a copying machine, a facsimile machine, a printer, or the like, which forms an image with the use of an electrophotographic method or an electrostatic recording method. It also relates to a transfer medium bearing member employed by such an image forming apparatus.
In an image forming apparatus, for example, an electrophotographic image forming apparatus, the peripheral surface of a cylindrical electro-photographic photoconductive member (photoconductive drum) as an image bearing member is uniformly charged, and an electrostatic latent image is formed on the uniformed charged surface in accordance with image formation data. This electrostatic latent image is visualized with the use of developer; a so-called toner image is formed. Then, the toner image is transferred from the photoconductive drum onto a piece of transfer medium (recording medium), and is fixed to the transfer medium, to obtain a copy or a print.
Some of the image forming apparatuses are color image forming apparatuses capable of forming a full-color image as well as a monochromatic image. These color image forming apparatuses can be divided into two groups according to the manner in which a full-color image is formed. In one group, a color image forming apparatus comprises a plurality of image forming stations, each of which has its own photoconductive drum, and in each of which a toner image, which is different in color from the toner image formed in the other stations, is formed on the photoconductive drum. A plurality of the thus formed toner images different in color are consecutively transferred in layers onto the same recording medium borne on a transfer medium bearing member, to form a full-color image. In the other group, a color image forming apparatus comprises only a single image forming station with a single photoconductive drum. In a full-color image forming operation, a plurality of tone images different in color are formed in succession on the same photoconductive drum after the preceding toner image is transferred onto the recording medium borne on a transfer medium bearing member. In these groups of image forming apparatuses, recording medium is conveyed by a transfer bearing member, for example, an endless belt suspended around a plurality of rollers, a cylinder formed by stretching a sheet of specific material around a cylindrical skeletal frame, or the like.
FIG. 3
shows the general structure of an example of a color image forming apparatus. An image forming apparatus
100
comprises a plurality of image forming stations Py, Pm, Pc, and Pk. In each image forming station, a toner image different in color from the toner image formed in the other stations is formed. The toner image formed in each station is consecutively transferred onto the same recording medium to form a color image.
The image forming apparatus comprises a transfer belt
51
as a transfer medium bearing member, which is an endless belt and is suspended around four rollers: a driving roller
52
and three supporting rollers
53
a
,
53
b
, and
53
c
. Located above the transfer belt
51
in this embodiment are four image forming stations Py, Pm, Pc, and Pk for forming yellow, magenta, cyan, and black images, correspondingly. Since the four image forming stations Py, Pm, Pc, and Pk are the same in structure, the structures of the image forming stations will be described in detail with reference to the image forming station Py for forming a toner image of a first color (yellow). In the drawings, the elements in each image forming station, which are the same in function as those in the other stations, are given the same referential codes, but are differentiated from those in the other stations by addition of subscripts y, m, c, and k, correspondingly to the referential codes Py-Pk for the yellow, magenta, cyan, and black image forming stations.
Referring to
FIG. 4
, the image forming station Py for the first color has a cylindrical photoconductive member (photoconductive drum)
1
y
as an image bearing member. During an image forming operation, the photoconductive drum
1
y
is rotationally driven in the direction indicated by an arrow mark A by a driving means (unshown), and the peripheral surface of the photoconductive drum
1
y
is uniformly charged by a magnetic brush type charging apparatus as a charging means. Then, the charged photoconductive drum
1
y
is exposed to an image exposure light L representing the yellow component of an original, by an exposing apparatus (LED based scanning apparatus)
3
y
. As a result, an electrostatic latent image in accordance with the inputted image formation data is formed on the peripheral surface of the photoconductive drum
1
y
. Next, the electrostatic latent image on the photoconductive drum
1
y
is developed into a yellow toner image by a developing apparatus
4
y.
At the same time as the yellow toner image on the photoconductive drum
1
y
reaches a transfer nip between the peripheral surface of the photoconductive drum
1
y
and a transfer belt
51
, a recording medium P, for example, a piece of recording paper, which is fed into the image forming apparatus main assembly from a recording medium cassette
80
as a recording medium storage by a sheet feeding roller
81
or the like, is delivered to the transfer nip by a registration roller
82
. In the transfer nip, electrical charge, which is opposite in polarity to the toner, is applied to the recording medium P, on the reverse side, that is, the side on which the image is not going to be transferred and is in contact with the transfer belt
51
, by a transfer charge blade
54
as a transfer charging device charged with transfer bias. As a result, the toner image on the photoconductive drum
1
y
is transferred onto the transfer medium P, on the top side. A transferring apparatus
5
(belt type transferring apparatus) comprises the transfer belt
51
, rollers
52
,
53
a
,
53
b
, and
53
c
, and transfer charge blades
54
y
-
54
k.
After the transfer of the yellow toner image onto the recording medium P, the recording medium P is conveyed to the image forming station Pm for a second color (magenta), as the transfer belt
51
moves in the direction indicated by an arrow mark f.
The image forming station Pm for the second color is the same in structure as the image forming station Py for the first color. Thus, the same processes as those carried in the image forming station Py are carried out in the image forming station Pm. That is, a latent image is formed on the photoconductive drum
1
m
, and the magenta developing apparatus
4
m
develops the latent image into a magenta toner image with the use of magenta toner. Then, the magenta toner image is transferred onto the recording medium P, in a manner to be layered on the yellow toner image, by the function of the transfer charge blade
54
m
, in the transfer nip.
Next, a cyan toner image and a black toner image are formed in the image forming stations Pc for a third color and the image forming station Pk for a fourth color, respectively, and are transferred onto the recording medium P by the transfer charge blades
54
c
and
54
k
, in a manner to be layered on the preceding two toner images, in the corresponding image forming stations. Consequently, a color image, or a composite of four layers of toner images different in color, is formed on the recording medium P. At this point, the color image is yet to be fixed.
After the transfer of the four toner images onto the recording medium P, the recording medium P is conveyed to a fixing apparatus
6
which comprises a fixing roller
6
a
containing a heating means, and a driving roller
6
b
. In the fixing apparatus
6
, the toner images on the recording medium P are fixed, as a permanent full-color image, to the surface of the recording medium P by the application of heat and pressure by the fixing roller
6
a
and driving roller
6
b
. After the fixation of the toner images, the recording medium P is discharged int
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grainger Quana M.
LandOfFree
Transfer medium bearing member and image forming apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transfer medium bearing member and image forming apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transfer medium bearing member and image forming apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3056831