Electrophotography – Document handling – Copy
Reexamination Certificate
2001-01-11
2003-04-08
Beatty, Robert (Department: 2852)
Electrophotography
Document handling
Copy
C399S124000
Reexamination Certificate
active
06546228
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese Patent Application Nos. JPAP2000-003000 filed on Jan. 11, 2000, JPAP2000-035757 filed on Feb. 14, 2000, and JPAP2000-391209 filed on Dec. 22, 2000, in the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that can conveniently be upgraded to a duplex image fonning apparatus.
2. Discussion of the Background
An electrophotographic image forming apparatus is widely used in various machines, such as copying machines, laser printers, facsimile machines, etc. In such electrophotographic image forming apparatus, an electrostatic latent image is formed on a photoconductive member and is developed, with toner, into a toner image, which is then transferred and fixed onto a recording sheet made of plain paper. As penetration of the electrophotographic image forming apparatus increases, requirements for a compact size and a light weight are increased.
In order to remain within the scope of the above requirements, various efforts have been made, such as, for example, a length of a sheet transfer path, for transferring a recording sheet inside the apparatus, has been shortened. In addition, an interior layout of the apparatus has been designed for a better machine handling in case of problems, such as a paper jam. For example, a sheet cassette is located at a lower part, fixing and ejection units are located on an upper part, and the above lower and upper parts are connected to each other with a vertical sheet-path. Furthermore, an operation panel is mounted on a front surface of the machine, typically in small-sized and mid-sized machines.
In addition, a requirement for a duplex printing function has recently been increased in connection with a movement of natural resource preservation. To cope with such a requirement, an image forming apparatus, employing the above-mentioned machine design, and which is capable of adopting an add-on duplex unit, has been developed. A published Japanese Unexamined Patent Application, No. 6-110274, described an example of such duplex image forming apparatus, as shown in FIG.
1
.
In the duplex image forming apparatus of
FIG. 1
, a sheet flipping unit
130
, for flipping a recording sheet during a duplex image forming process, is mounted on a top and front part of the apparatus. In the front side, the apparatus is provided with a manual sheet insertion guide
140
.
In the duplex image forming apparatus of
FIG. 1
, a recording sheet is transferred from a sheet cassette
141
during a duplex print mode, in which an image print is performed on both surfaces of the recording sheet. The recording sheet is stopped by registration rollers
142
and is restarted in synchronism with the rotation of a photoconductive drum
151
. After that, the recording sheet proceeds to a process unit
150
having the photoconductive drum
151
. When a recording sheet is inserted from the inlet of the manual sheet insertion guide
140
, the recording sheet also proceeds to the process unit
150
, via a manual sheet insertion path
143
.
In the process unit
150
, the recording sheet is subjected to an image forming process on its front surface and, as a result, the recording sheet has a toner image on the front surface. After that, the toner image is fixed with a heat fixing unit and is transferred upwardly. When a sensor
152
detects the leading edge of the recording sheet, a switch pawl
131
is turned to a position indicated by solid lines in FIG.
1
.
When the switch pawl
131
is at this position, the recording sheet is forwarded into the sheet flipping unit
130
. More specifically, the recording sheet is transported by a pair of switchback rollers
132
so that the leading edge of the recording sheet is ejected over a stacker
133
. When a sensor
134
detects the trailing edge of the recording sheet, the switchback rollers
132
are reverse rotated so that the recording sheet is reverse transferred towards an exit
136
through a sheet path
135
in the sheet flipping unit
130
. After that, the recording sheet again proceeds to the process unit
150
via the manual insertion path
143
. In the process unit
150
, the recording sheet is subjected to the image forming process, but on its back surface this time. As a result, the recording sheet is printed on both front and back surfaces.
After that, the recording sheet is guided to a pair of ejection rollers
137
by the switch pawl
131
, which is by now turned to a position indicated by dotted lines. The recording sheet is then ejected with the ejection rollers
137
onto stacker
133
.
As another example, a published Japanese Unexamined Patent Application, No. 7-261471, describes an image forming apparatus capable of having an add-on duplex unit. In this example, an opening to an outside is formed in a pair of sheet transfer paths downstream from a fixing unit in a sheet transfer direction. A duplex unit is attached to the image forming apparatus such that a sheet inlet is fit with the above opening. When the recording sheet is flipped, the leading edge of the recording sheet is ejected to an outside from the duplex unit or over an eject tray from the image forming apparatus.
In the above image forming apparatus, the operator is needed to open a front cover to deal with a paper jam or to exchange consumable items, since the apparatus has the design of the front operation panel and the vertical sheet transfer path, as described below. Therefore, if the duplex unit is attached to the front of the apparatus, the duplex unit becomes a severe obstacle and the inside accessibility of the apparatus is decreased.
In addition, a front design of the image forming apparatus would have a relatively large difference between those having the duplex unit and those having none. Accordingly, various components associated with the front design could not be unified and therefore, a consistency of machine model may become difficult.
Furthermore, in the image forming apparatus described in the published Japanese Unexamined Patent Application Nos. 6-110274 and 7-261471, a part of the recording sheet is temporarily ejected outside the apparatus and is reverse transferred during the sheet flipping process for the duplex image forming operation. Accordingly, there is a risk that the recording sheet is accidentally touched or held by anything, such as the operator, when the recording sheet is temporarily ejected outside the apparatus during the duplex image forming operation. As a result, the recording sheet may be jammed inside the apparatus. When the ejected part of the recording sheet touches other recording sheets stacked on the stacker, it is possible that other recording sheets may be pushed away.
SUMMARY OF THE INVENTION
The present invention provides a novel image forming apparatus. In one example, a novel image forming apparatus includes a sheet cassette, a first sheet path, a first sheet transfer mechanism, an image recording mechanism, an ejection mechanism, a second sheet path, and a sheet flipping mechanism. The sheet cassette is configured to contain a plurality of recording sheets. The sheet cassette is located at a lower part of the image forming apparatus. The first sheet path is arranged on a side of the apparatus. The first sheet transfer mechanism is configured to send a recording sheet one by one from the sheet cassette through the first sheet path. The image recording mechanism is configured to perform an image recording process relative to the recording sheet sent by the first sheet transfer mechanism. The ejection mechanism is configured to switch between an ejection process and a duplex recording process relative to a back surface of the recording sheet after completion of the recording process on a front surface of the recording sheet. The second sheet path is configured to receive the recording sheet from the ejection mechanism, wh
Hatta Hirotaka
Kosuge Katsuhiro
Motohashi Takeshi
Takemoto Hideyuki
Takiguchi Masashi
Beatty Robert
Ricoh & Company, Ltd.
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