Electrophotography – Internal machine environment – Forced air circulation
Reexamination Certificate
2002-04-23
2004-06-22
Grainger, Quana (Department: 2852)
Electrophotography
Internal machine environment
Forced air circulation
C399S122000
Reexamination Certificate
active
06754458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a printer and, in particular, to a shutter provided in a fixing device that is applied to the image forming apparatus.
2. Related Art
FIG. 11
shows a schematic sectional view of an image forming apparatus provided with a conventional fixing device. In the figure, reference numeral
101
denotes a scanner unit having optical means for irradiating a laser beam, which is emitted according to image information, and scanning means for scanning by the laser beam and
110
denotes a process cartridge incorporating main image forming means. A photosensitive drum
103
functioning as an image bearing member, a roller charger
104
made of semiconductive rubber, a developing device
105
for carrying toner
106
onto the photosensitive drum
103
to develop an electrostatic latent image thereon and a cleaner
108
for removing waste toner from the photosensitive drum
103
are integrally incorporated in and constitute the process cartridge
110
.
With the above-mentioned configuration, the photosensitive drum
103
in the process cartridge
110
is driven to rotate and the surface of the photosensitive drum
103
is uniformly charged by the roller charger
104
. Subsequently, a laser beam emitted by the scanner unit
101
is irradiated on the photosensitive drum
103
via a mirror
102
, whereby an electrostatic latent image is formed on the surface of the photosensitive drum
103
. Then, toner is supplied to the surface of the photosensitive drum
103
to visualize the electrostatic latent image as a toner image by the developing device
105
.
On the other hand, transferring materials (basis weight 64 to 216 g)
112
in a sheet feeding cassette
111
are separated piece by piece and supplied by a sheet feeding roller
113
. The supplied transferring material
112
is conveyed to a pair of registration rollers
115
along upper and lower guides
114
. The registration rollers
115
do not move until the transferring material
112
is supplied to them. When the transferring material
112
is supplied, its leading edge collides with the registration rollers
115
, whereby skew feeding of the transferring material
112
is corrected.
Subsequently, the registration rollers
115
convey the transferring material
112
to a transferring portion in such a manner as to synchronize the end of the toner image formed on the photosensitive drum
103
with the leading edge of the transferring material
112
. Further, a not-shown sheet feeding sensor is disposed in the vicinity of the registration rollers
115
. The sheet feeding sensor senses a sheet passing state or jam and the length of the transferring material
112
.
The transferring material
112
conveyed to the transferring portion as described above is applied a charge having a polarity opposite that of the toner by the transfer roller
107
from its back. As a result, the toner image formed on the photosensitive drum
103
is transferred to the transferring material
112
. The transferring material
112
with the toner image transferred thereon is conveyed to a fixing device
118
by a conveying roller
117
and a conveying guide
116
. The fixing device
118
fixes an unfixed toner image on the transferring material
112
by heat and pressure to form a recorded image thereon. Then, after the image is fixed, a conveying route is selected by a flapper
119
for the transferring material
112
, which is discharged to a discharge tray
120
or
121
.
Next, the fixing device
118
will be described.
The fixing device
118
is provided with a fixing roller
127
as a fixing body, a pressurizing roller
128
as a pressurizing body and a fixing inlet guide
130
.
The fixing device
118
employs a central reference for conveying the transferring material
112
, which has a width of A3 sheet (297 mm) as a maximum sheet passing size, with a sheet passing center of the device as a reference. The fixing device
118
of this type opens a fixing inlet shutter
123
′ as shown by solid lines to secure a conveying path when a transferring material is conveyed. In addition, when a transferring material is not conveyed, the fixing device
118
closes the fixing inlet shutter
123
as shown by broken lines to protect a user at the time of jam treatment.
However, in the conventional fixing device
118
provided with the fixing inlet shutter
123
, since an air path cannot be secured around the fixing device
118
when a transferring material is conveyed, there is no air path in the vicinity of its inlet as shown by arrows indicating a flow of air in FIG.
11
. As a result, temperature in the image forming apparatus increases to cause various harmful effects. In addition, a member of a complicated structure is required to secure an air path in an apparatus main body and, at the same time, retain heat of the fixing device
118
and protect a user at the time of jam treatment and the like, which causes increase of costs.
As means for coping with this problem, Japanese Patent Application Laid-Open No. 5-333614 describes securing of an air path by providing holes in a shutter.
Incidentally, in an image forming apparatus of this type, if an opening and closing member is provided in an apparatus main body, a part of the apparatus on the opening and closing member side tends to be exposed to the open air. Thus, for example, temperature further falls in a part of a fixing device on the opening and closing member side and unevenness of temperature occurs in the fixing device.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above-mentioned drawbacks, and it is an object of the present invention to provide an image forming apparatus that prevents unevenness of temperature in fixing means while controlling increase of temperature in an apparatus main body.
Another object of the present invention is to provide an image forming apparatus comprising: fixing means for heat-fixing an unfixed image on a recording material; a shutter movable to a first position for covering the fixing means and a second position retracting from the first position; and an opening and closing member that is openable and closable with respect to an image forming apparatus main body, in which: the shutter has a plurality of holes; when the opening and closing member is open, the shutter exists at the first position and, when the opening and closing member is closed, the shutter exists at the second position; and a size of the hole on the opening and closing member side of the shutter is smaller than a size of the hole on the opposite side of the opening and closing member.
Still another object of the present invention is to provide an image forming apparatus comprising: fixing means for heat-fixing an unfixed image on a recording material; a shutter movable to a first position for covering the fixing means and a second position retracting from the first position; and an opening and closing member that is openable and closable with respect to an image forming apparatus main body, in which: the shutter has a plurality of holes; when the opening and closing member is open, the shutter exists at the first position and, when the opening and closing member is closed, the shutter exists at the second position; and an interval of the holes on the opening and closing member side of the shutter is larger than an interval of the holes on the opposite side of the opening and closing member.
Still another object of the present invention is to provide an image forming apparatus comprising: fixing means for heat-fixing an unfixed image on a recording material; a shutter movable to a first position for covering the fixing means and a second position retracting from the first position; and an opening and closing member that is openable and closable with respect to an image forming apparatus main body, in which: the shutter has a plurality of holes; when the opening and closing member is open, the shutter exists at the first position and,
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grainger Quana
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