Electrophotography – Document handling – Copy
Reexamination Certificate
2001-12-17
2003-09-16
Tran, Hoan (Department: 2852)
Electrophotography
Document handling
Copy
Reexamination Certificate
active
06622002
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, a printer, a facsimile, and an MFP (multifunction printer), and in particular to an image forming apparatus having a duplex recording function.
2. Description of Related Art
There have conventionally been proposed various constructions where duplex recording functions are given to image forming apparatuses, such as a copying machine, a printer, and a facsimile. A conventional image forming apparatus will be described by taking a facsimile as an example.
FIG. 7
is an overall construction diagram of a facsimile having a duplex recording function according to a conventional technique.
In
FIG. 7
, the front of the main body of apparatus
100
is rightward in
FIG. 7
(in th direction indicated by the arrow A). An image reading portion
300
is provided in the upper part of the apparatus, an image forming portion
101
is provided in the approximately center part thereof, and a sheet feeding portion
110
is provided in the lower part thereof. Also, duplex recording unit
200
including surface reversing means and a re-feed and transporting path is provided between the image forming portion
101
and the sheet feeding portion
110
. Further, on the upper surface of the apparatus, there is arranged an operation portion
130
that includes buttons and a display portion that are not shown in FIG.
7
.
In the image reading portion
300
, an original S stacked on an original stacking tray
301
is fed by a separation roller pair
302
. After image information is read by a contact-type image sensor
303
, the original S is delivered to an original delivery tray
304
. The read image information is transmitted by a communication means (not shown) or is sent to the image forming portion
101
, which then records the image information on a sheet.
The image forming portion
101
has a process cartridge
102
that is constructed by integrating a photosensitive drum
103
that is an image bearing member, a charging means
104
, a developing means
105
, and a cleaning means
106
. Also, an optical means
107
is arranged above the process cartridge
102
. The optical means
107
irradiates a laser beam onto the photosensitive drum
103
, which has been uniformly charged by the charging means
104
, according to the image information. In this manner, an electrostatic latent image is formed. The electrostatic latent image is visualized by the developing means
105
, thereby forming a toner image. After the toner image is transferred to a fed sheet by a transferring means
108
, residual toner on the photosensitive drum
103
is removed by the cleaning means
106
.
A sheet is fed from the sheet feeding portion
110
provided in the lower part of the apparatus or from a multi-feeding portion
115
provided in a side part of the apparatus. The sheet feeding portion
110
is capable of stacking and storing sheets on a feeding tray
111
and the sheets are separated and fed by a feeding roller
112
and a separation roller pair
113
one by one. In this manner, each sheet is fed to a registration roller pair
114
on the upstream side of the image forming portion
101
. As to the multi-feeding portion
115
, sheets are inserted by opening a multi-tray
116
and are fed to the registration roller pair
114
by a multi-separation portion
117
.
The registration roller pair
114
transports each sheet in synchronism with the toner image on the photosensitive drum
103
. After the toner image is transferred to the sheet by a nip between the photosensitive drum
103
and the transferring means
108
, a transporting means
118
transports the sheet to a fixing means
119
, which then applies heat and pressure to the sheet. In this manner, the toner image is permanently fixed. The transporting path of the sheet, on which the toner image has been fixed, is switched by a flapper
120
. If the image formation is to be finished, the sheet is delivered to the outside of the apparatus. If an image is to be recorded on the second side, the sheet is re-fed to the image forming portion
101
by the duplex recording unit
200
.
If the image formation is to be finished, the sheet is delivered to any one of two delivery trays
122
and
123
so that the recording surface faces down (face-down delivery). The delivery trays
122
and
123
are provided between the image forming portion
101
and the image reading portion
300
. The selection between the delivery trays
122
and
123
is performed by a flapper
121
according to the control performed for the sheet to be delivered.
If an image is to be recorded on the second side, the sheet is guided by the flapper
120
to the duplex recording unit
200
connected to a back delivery portion
124
. The sheet is delivered from the back delivery portion
124
so that the recording surface faces up (face-up delivery), and is transported by a surface reversing roller pair
202
from a duplex transporting path
201
to a surface reverse path
203
. Following this, when the trailing edge of the sheet reaches the vicinity of the surface reversing roller pair
202
, the transport direction is reversed and the sheet is transported to a re-feed and transporting path
204
, with the trailing edge being transported thereto first. Then, the sheet is further transported by a transporting roller pair
205
to a feeding roller pair
109
on the main body side. After an image is recorded on the second side in the same manner as above, the sheet is delivered to the delivery tray
122
or
123
.
Here, the duplex recording unit
200
is mountable to and detachable from the main body of the apparatus (in the direction indicated by the double-headed arrow K), which makes it possible for a user to pull out the duplex recording unit
200
to remove a jamming sheet or the like from the duplex recording unit
200
.
To perform duplex recording in the manner described above, it is required to reverse a sheet delivered from the main body of the apparatus. Therefore, the surface reverse path
203
having a U-turn shape is formed with the aforementioned conventional construction, which means that the duplex recording unit
200
significantly projects backward from the apparatus. Accordingly, the size of the apparatus is increased by the amount of this projection B. This results in problems that a production cost is increased and an installation space is also increased.
Also, the surface reverse path
203
and the re-feed and transporting path
204
are formed below the image forming portion
101
, so that the overall height of the apparatus is also increased by the height C required to form these paths. This increase of the apparatus height results in the increase of a size of the apparatus, which in turn increases a production cost. The increase of the apparatus height also increases the heights of the original stacking tray
301
, the original delivery tray
304
, the delivery trays
122
and
123
, an operation panel of the operation portion
130
, and the like. Accordingly, this problem particularly becomes serious in the case of a desktop-type apparatus that is used on a desk.
Meanwhile, as a means for reducing the size of the apparatus, there may be reduced the radius of the U-turn portion; through which a sheet passes when it is fed from the re-feed and transporting path
204
to the feeding roller pair
109
on the apparatus main body side, or there may be reduced the radius of the U-turn portion of the surface reverse path
203
. However, if the radius of such U-turn portions are reduced, this increases the resistance that occurs during the transport of a sheet. As a result, there are various adverse effects. For instance, jams tend to occur, particularly when thick sheets are used. Also, the reliability of sheet transportation is reduced and the sheets that are usable are limited to thin sheets.
SUMMARY OF THE INVENTION
In view of these problems, the object of the present invention is to provide a desktop-type image forming apparatus having a duplex
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Tran Hoan
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