Electrophotography – Diagnostics – Document handling
Reexamination Certificate
2000-04-28
2001-02-06
Pendegrass, Joan (Department: 2852)
Electrophotography
Diagnostics
Document handling
C399S401000, C271S301000
Reexamination Certificate
active
06185380
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image (including characters and the like) on a recording medium (plain paper, coat paper, an OHP (Over Head Projector) sheet, glossy paper, a glossy film, a color-image-only paper, a cut sheet, such as a postcard or an envelope) after which the image is fixed and discharged. The present invention relates to an image forming apparatus, such as a printer, a facsimile machine, a copying machine or the like, for mainly using an electrophotographic technology to form a color image on a recording medium, fix the color image and discharge the recording medium. More particularly the present invention relates to a fixing technology for use in the image forming apparatus capable of forming either matte or glossy images on two sides of a recording medium. Further, the present invention relates to a paper discharge passage of the image forming apparatus.
The present application is based on Japanese Patent Application Nos. Hei. 9-203850, Hei. 9-203851, Hei. 9-282810, Hei. 9-282811, Hei. 9-282812, Hei. 9-282813, Hei. 9-282814 which are incorporated herein by reference.
2. Description of the Related Art
In general, image forming apparatuses have widely been known which incorporate a fixing unit for conveying a recording medium while heating and applying pressure to the recording medium. The apparatus is arranged such that a non-fixed image formed by a developer, such as toner, is formed on the surface of the recording medium after which the recording medium is allowed to pass through a fixing unit having a pair of rollers so that an image is fixed to the recording medium.
Devices for use with an image forming apparatus of the above-mentioned type have been known, for example, as in Japanese Patent Publication No. 5-48917 and Japanese Patent Publication No. 6-68646. These devices attempted to improve the fixing characteristic by selectively (as necessary) allowing a recording medium to pass through a fixing unit two times.
One of the two types of the image forming apparatuses which has been disclosed in Japanese Patent Publication No. 6-68646 has a double-side mode for forming images on two sides of a recording medium and a single-side mode for forming an image on either side of the recording medium. When a glossy image is formed on an OHP film in the single-side mode, the OHP film is allowed to pass through the fixing unit two times. Thus, a glossy image can be obtained.
Specifically, the apparatus disclosed in Japanese Patent Publication No. 6-68646 has a structure in which a plurality of recording mediums, on which images are formed on one side, are temporarily accumulated in an intermediate tray so that images can be formed on both sides of the recording medium, in the double-side mode. Each recording medium is again supplied from the intermediate tray to the image forming portion so as to form an image on the other side. Thus, images are formed on both sides of each recording medium. However, when a glossy image is formed on an OHP film, a plurality of the OHP films are temporarily accumulated in the intermediate tray. Then, each OHP film is again fed to the fixing unit from the intermediate tray. But, when a plurality of OHP films are stacked and accumulated in the intermediate tray, the OHP films easily adhere to one another. Because the OHP films easily adhere to one another, there arises a clogging problem in the feeding operation, or undesirable stacking easily takes place.
Further, when a separating agent is applied to the fixing roller, in Japanese Publication No. 6-68646, the separating agent adheres to the surface of the recording medium. Since the recording medium in the form of a resin sheet, such as an OHP sheet, has a poor oil absorbing characteristic, the OHP sheets furthermore easily adhere to one another when the OHP sheets are stacked on the intermediate tray. Thus, problems easily arise in the feeding operation, or stacking easily takes place. Also, since a space for the paper feeding tray is required, there arises another problem in that the size of the apparatus cannot be reduced.
When a color image is formed, toner images in a plurality of colors (for example, yellow, magenta, cyan and black) superimposed on the recording medium must be melted and fixed. Since a great heat capacity is required, a known fixing unit is structured such that a recording medium is allowed to pass through the fixing unit at relatively low speed. See for example, Japanese Patent Publication No. 6-40235.
An image forming apparatus capable of forming images on two sides of paper sheets, a two-side copying machine as disclosed in Japanese Patent Publication No. 61-11865, for example, has been known.
As shown in FIG.
9
(
a
), a typical double-side copying machine has a structure that an original document
1
is irradiated with a lamp
2
. Reflected light is imaged on a photosensitive drum
3
so that an electrostatic latent image is formed on the photosensitive drum
3
. The electrostatic latent image is visualized into a powder image or the like by a developing unit
4
so as to be transferred to copying paper
7
fed from paper feeders
5
and
6
. The powder image is then fixed to the copying paper
7
by a fixing unit
8
. The copying paper
7
is allowed to pass through a passage
9
, and is then moved to a right-side/reverse-side converting unit
10
. If a single-side final copy is desired, the copying paper
7
is allowed to pass through a paper-discharge passage
11
and a deflector
12
. The copying paper
7
is then discharged to the upper surface of a paper-discharge tray
13
disposed on the body of the apparatus.
If a double-side final copy is desired, the copying paper
7
having a powder image formed by the fixing unit
8
is allowed to pass through the passage
9
, and is then moved to the right-side/reverse-side converting unit
10
. After the leading end of the copying paper
7
has temporarily been introduced into the paper-discharge passage
11
, the copying paper
7
is moved inversely such that the copying paper
7
is allowed to pass through an inverse passage
14
. Thus, the copying paper
7
is stacked and accommodated in an accommodating portion
15
. The operation for stacking copying paper in the accommodating portion
15
continues until images are copied on one side of a predetermined number of paper sheets.
After the operation for copying one side of all of the copying paper sheets has been completed, the copying paper
7
stacked in the accommodating portion
15
is allowed to pass through a re-feeding passage
17
by a paper-supply roller
16
so as to again be moved to the photosensitive drum
3
. A powder image is then formed on the other side, after which the copying paper
7
passes through the fixing unit
8
as well as the right-side/reverse-side converting unit
10
and is moved to the paper-discharge passage
11
.
FIG.
9
(
b
) is a diagram showing an example of the right-side/reverse-side converting unit described above. The right-side/reverse-side converting unit has a drive roller
18
and conveying rollers
19
,
20
disposed at the inlet and outlet portions thereof. A drive roller
21
and a movable roller
22
are disposed in the rear of the right-side/reverse-side converting unit. A deflecting plate
23
is disposed between the drive roller
18
and the drive roller
21
. The deflecting plate
23
is rotatively supported by a shaft
23
a
such that the deflecting plate
23
is always urged clockwise by a spring (not shown).
The operation of the right-side/reverse-side converting unit will now be described.
(i) When the copying paper
7
moved from the fixing unit
8
through the passage
9
is moved to the paper-discharge passage
11
, all of the rollers are rotated in a direction (forward direction) indicated by an arrow shown in the drawing. Thus, the copying paper
7
discharged from the fixing unit
8
is moved to the paper-discharge passage
11
by the drive roller
18
, the conveying roller
19
, the drive roller
Abe Nobumasa
Fujisawa Kazutoshi
Ishiwatari Tahei
Okumura Naoyuki
Shiraki Takayuki
Pendegrass Joan
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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