Image forming apparatus

An image forming apparatus of the present invention includes a main body, a fixing device arranged in the main body and supported so that it can be pulled out of the main by for fixing an image formed on one side of a paper, a duplex device arranged in the main body and supported so that it can be pulled out of the main body for once housing a paper having an image fixed on one side and taking it out with the other side having no image fixed facing toward the fixing device; and a coupling unit for coupling so that the fixing device and the duplex device can be pulled out of the main body simultaneously.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an image forming apparatus, which serves 
as an electronic copying machine, equipped with a duplex device enabling 
the copying of both sides of a paper. 
2. Description of the Related Art 
There is a model of an image forming apparatus, which is an electronic 
copying machine, provided with a so-called duplex copying function to copy 
an image on one side of a paper and then, copy another image on the other 
side. 
This kind of an image forming apparatus is equipped with an automatic 
duplex device which takes a paper with a developer image fixed on one side 
by a fixing device once via an auxiliary conveying path, inverse it to 
change its fixing side and carrying it out again between a 
photo-conductive drum and a transfer charger. 
To be concrete, there is a converting (sorting) gate between a fixing 
device and a paper receiving tray and this paper receiving tray is 
arranged at one of the sorted destinations and the automatic duplex device 
is arranged at the other sorted destination via the auxiliary conveying 
path. 
An electronic copying machine equipped with such the automatic duplex 
device adopts such a structure that, in order to suppress the increase in 
the installing space of the main body, the automatic duplex device is 
arranged almost immediately below the fixing device and these fixing 
device and the automatic duplex device are connected each other by the 
auxiliary conveying path. 
The auxiliary conveying path is formed in a sharp curved state so as to 
convey a paper almost in a U-turn state. As a result, such a phenomenon 
called a jam that a paper is jammed in the auxiliary conveying path tends 
to be caused. 
As the indication of "JAM" is shown on the operation panel at this time, 
worker is required to remove a jammed paper. Actually, the length of the 
auxiliary conveying path is shorter than that of a paper and a part of a 
paper left in the auxiliary conveying path and the remainder of the paper 
is left in the fixing device and/or the automatic duplex device. 
The fixing device and the automatic duplex device are so arranged that they 
can be pulled cut of the main body, while the auxiliary conveying path 
comprising conveyor rollers and guide plates is fixed to the main body. 
So, worker pulls out the fixing device or the automatic duplex device to 
this side and remove a jammed paper or takes out the jammed paper by 
inserting his hand into the main body and takes out the jammed paper 
without pulling out the devices. 
However, even when the fixed device and the automatic duplex device are 
pulled out, as a part of a paper is left in the auxiliary conveying path 
in the main body, the paper tends to be cut in the main body. If so, the 
portion of the paper left in the main body must be taken out and it 
becomes very troublesome to take out the paper left in the main body. 
If the hand is inserted into the main body from the first or later, the 
inside of the main body is not visible and there is the possibility that 
the hand may touch other component elements and is injured or other 
component elements may be damaged. 
Further, there are some models in which a fixing device and an automatic 
duplex device are arranged in series along a paper conveying path and an 
auxiliary conveying path is omitted. Even in this case, such devices are 
separately taken out if a paper is jammed and there are the same problems 
as shown above. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an image forming 
apparatus which assures the safe and fast removing of a paper when jammed 
between a fixing device and an automatic duplex device, thus improving the 
workability and safety and securing reliability of the apparatus. 
According to the present invention, an image forming apparatus is provided. 
The image forming apparatus comprises a main body; a fixing device 
arranged in the main body for fixing an image formed on one surface of a 
paper, the fixing device being supported so that it can be pulled out of 
the main body; a duplex device arranged in the main body for once housing 
paper having a fixed image on one surface and conveying with the other 
surface having no fixed image faced toward the fixing device, the duplex 
device being supported so that it can be pulled out of the main body; and 
coupling means for coupling the fixing device and the duplex device so 
that they can be simultaneously pulled out of the main body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, a preferred embodiment of an image forming apparatus of the 
present invention will be described with reference to the attached 
drawings. 
FIG. 1 shows an electronic copying machine which serves as an image forming 
apparatus. A photo-conductive drum 1 which serves as an image carrier is 
arranged in a main body S. This photo-conductive drum 1 is connected to a 
driving source (not shown). 
Around the photo-conductive drum 1, there are arranged a main charger 2, an 
exposing portion 4, a developing device 5, a transfer charger 6, a 
separation charger 7, a cleaning device (not shown) and a charge 
elimination lamp (not shown) along the rotating direction of the 
photo-conductive drum 1. 
On the top of the main body S of the copying machine, a document table 10 
comprising a glass plate for placing documents is provided and an optical 
unit 8 is arranged between the document table 10 and the exposing portion 
4. 
On the bottom of the main body S, a paper supply device 13 is arranged. The 
paper supply device 13 is composed of a plurality of cassettes 11, each of 
which is for containing paper in different sizes, and a paper supply belt 
12. 
On the top of the uppermost cassette of the paper supply device 13, an 
automatic duplex unit (hereinafter referred to as ADU) 14 is arranged. At 
the sides of these ADU 14 and the paper supply device 13, a large capacity 
cassette 15 is arranged and on the top of this large capacity cassette 15, 
a manual paper supply device 16 is arranged. 
At the paper supply side of each cassette 11 of the paper supply device 13, 
the ADU 14, the large capacity cassette 15 and the manual paper supply 
device 16, a paper conveying device 17 is arranged. The paper conveying 
device 17 conveys paper supplied from the cassette 11, the ADU 14, the 
large capacity cassette 15 or the manual paper supply device 16 to an 
aligning roller pair 18 which is arranged at the lower side of the 
developing device 5. At the paper conveying side of the aligning roller 
pair 18, the transfer charger 6 is arranged. 
As shown in the enlarged view of FIG. 2, at the side of the separation 
charger 71 a conveyor belt 19 is arranged to convey paper. At the 
conveying end of the conveyor belt 19, a fixing device 20 is arranged and 
further, on the side of the main body, a paper receiving tray 21 is 
mounted. 
Between the paper receiving tray 21 and the fixing device 20, a converting 
gate 22 is provided. The paper receiving tray 21 is arranged at one of the 
sorted destination of the converting gate 22 and the ADU 14 is provided at 
the other sorted destination via an auxiliary conveying path 23. 
Between the fixing device 20 arranged at the inlet side of the auxiliary 
conveying path 23 and the converting gate 22, a first paper jam detector 
24 is arranged and at the inlet side of the ADU 14 provided at the outlet 
side of the auxiliary conveying path 23, a second paper jam detector 25 is 
arranged. 
The first and the second paper jam detectors 24 and 25 are electrically 
connected to a controller 26 and further, electrically connected to an 
operation panel (not shown) from the controller 26. 
When judged the paper jam, the controller 26 indicates such a message as, 
for instance, "PAPER JAMMED IN U-TURN SECTION AT EXIT SIDE. PULL OUT THE 
KNOB AND PROCESS JAMMED PAPER." or "PAPER JAMMED. PULL OUT KNOB THAT IS 
LIGHTED AND PROCESS JAMMED PAPER." on the operation panel. 
As shown in FIG. 3 and FIG. 4, when the front cover of the main body of the 
apparatus is opened, the modular units of fixing device 20, auxiliary 
conveying path 23 and ADU 14 can be seen. 
The paper supply device 13, the photo-conductive drum 1 and the main 
charger 2 are also made modular units, respectively; moreover the detailed 
explanation will be omitted here. 
The fixing device 20, the auxiliary conveying path 23 and the ADU 14 are 
supported movably on a guide rail 30 that is provided along the 
longitudinal direction of the main body S. That is, they can be pulled out 
to this side (the front surface side) from the main body S along the guide 
rail 30. 
A handle 31 is mounted on the front panels of the fixing device 20 and the 
ADU 14, respectively. These handles 31 are used when performing the 
maintenance of the fixing device 20 and the ADU 14. 
On the front panel of the fixing device 20 only, a dial 32 for the jam 
processing is provided. This dial is connected mechanically to a specified 
conveyor roller arranged in the fixing device so as to eject a jammed 
paper to the outside by manually rotating this dial when processing the 
jammed paper. 
On the front panel of the auxiliary conveying path 23, a knob 41 comprising 
a coupling mechanism 40 that is described later is mounted. One end of the 
knob 41 is pivoted on the front panel and the other end is a free end and 
is able to freely rotate. At the end of the pivoted side, there is 
provided an indicator 42 such as an LED which is connected to the 
controller 26, comprising an informing means jointly with an indicator on 
the operation panel. 
As shown in FIG. 5, the knob 41 is supported rotatably on the front panel 
of the auxiliary conveying path 23. A shaft 43 connected to the rotating 
end of the knob 41 is extended toward the rear surface of the auxiliary 
conveying path 23. 
At the middle section of the shaft 43, a positioning member 44 is provided. 
This positioning member 44 is a rectangular dowel member and a slit 45 is 
provided at its one side. The slit 45 of the positioning member 44 engages 
with a frame 46 that is projecting from the main body S in the normal 
state where the free end of the knob 41 hangs down. In this engaged state, 
the coupling mechanism 40 and the longitudinal position of the auxiliary 
conveying path 23 are controlled. 
As shown in FIG. 6, the auxiliary conveying path 23 is able to change its 
position in the longitudinal direction freely together with the coupling 
mechanism 40 only when the slit 45 of the positioning member 44 is 
separated from the frame 46 of the main frame by rotating the knob 41 in 
the direction of arrow. 
As shown in FIG. 5 and FIG. 6, a pressuring member 47 having a curved 
surface Sa which is partially formed in the circular arc shape is provided 
at the other end of the shaft 43. This pressuring member 47 is in a right 
angled triangle in the prescribed plate thickness, its side equivalent to 
the oblique side is the curved surface Sa and the shaft 43 penetrates near 
the right angle portion soft the pressuring member 47. 
The curved surface Sa of the pressuring member 47 is kept in contact with a 
hook plate 49 at which upper and lower ends a tension spring 48 hooked, 
respectively. The other end of each tension spring 48 hooks at the 
prescribed portion of the auxiliary conveying path 23. 
In the normal state where the free end of the knob 41 is hanging down, the 
hook plate 49 is elastically compressed by the elastic force of the 
pressuring member 47 so as to contact a point near the top of the curved 
surface Sa. When the knob 41 is rotated against the elastic force of the 
tension spring 48, the tip of the curved surface Sa of the pressuring 
member 47 is displaced to contact the hook plate 49 against the elastic 
force of the tension spring 48 and thus, the hook plate is displaced. When 
the knob 41 is rotated in the original direction even slightly, the 
elastic force of the tension spring 48 acts again to return the knob 41 to 
the prescribed state automatically. 
A hook 50 having a sharp shaped tip is projected from the hook plate 49. 
This tip of the hook 50 is inserted into holes 51 and 52 provided on the 
fixing device 20 and the ADU 14, respectively when the hook plate 49 is 
displaced by the pressuring member 47. In the state where the hook plate 
49 returned to the original position, the tip of the hook 50 comes out of 
the holes 51 and 52 and has no longer related to each other. 
Thus, a hook mechanism F is composed of parts ranging from the shaft 43 to 
the hook 50 excepting the knob 41. 
When a document is set on the document table 10 and the copy switch is 
turned ON, the optical unit 8 exposes and scans the document surface and a 
document image is formed on the surface of the photo-conductive drum 1 in 
the exposing portion 4. 
The surface of the photo-conductive drum 1 is charged previously by the 
main charger 2 and the document image is formed in an electrostatic latent 
image. When the photo-conductive drum 1 is rotated and the electrostatic 
latent image portion faces the developing device 5, a developer is 
supplied from the developing device 5 and the latent image is developed. 
Further, simultaneously with the start of copying, a paper designated by, 
for instance, the paper supply device 13 is supplied via the paper 
conveying device. If the supply of paper from the large capacity cassette 
15 is designated, as a matter of course, a paper is supplied from the 
large capacity cassette 15. 
A supplied paper is conveyed between the photo-conductive drum 1 and the 
transfer charger 6 timely by the aligning roller pair 18 and a developer 
image is transferred on the top of the paper by the transfer charger 6. 
The paper with the developer image transferred on its top is separated from 
the photo-conductive drum 1 by the action of the separation charger 7 and 
conveyed on the conveyor belt 19. Then, the paper is led to the fixing 
device 20 wherein the image is fixed and the paper with the developer 
image fixed on its top is ejected in the paper receiving tray 21. 
The photo-conductive drum 1 continues to rotate successively. The area from 
where the paper was separated by the separation charger 7 is faced to the 
cleaning device and a residual toner is wiped and removed from the drum 
surface, discharged by the charge elimination lamp and is faced to the 
main charger again and the actions described above are repeated. 
The duplex copying is executed as shown below when it is directed. 
That is, the processes from when a paper is led to the fixing device 20 
until a fixed image is obtained on its top surface are the same as 
described above. 
Under this state, the converting gate 22 is displaced so as to lead the 
paper with the fixed image obtained on its top surface to the auxiliary 
conveying path 23. So, this paper is led to the ADU 14 by way of the 
auxiliary conveying path 23. 
The ADU 14 is located under the fixing device 20 and the auxiliary 
conveying path 23 is formed almost in the U-shaped state and therefore, 
when the paper is led to the auxiliary conveying path 23, its fixed image 
surface is faced to the paper receiving tray 21 side. 
When this paper is led to the ADU 14, the fixed image surface is faced 
downward. Under this state, the paper is conveyed from one end to the 
other end in the ADU 14 and further, when conveyed in the U-turn state, it 
is housed in the bottom of the apparatus. At this time, the fixed image 
surface is faced upward and the non-fixed image surface comes to the down 
side. 
After paper in the number of sheets designated for the duplex copying are 
housed in the ADU 14 successively and accumulated, the image forming on 
the non-fixing image surface is carried out. 
First, the ADU 14 acts to supply accumulated paper. This paper is led to 
the aligning roller pair 18 by way of the paper conveying device 17, where 
the paper is aligned and timely supplied between the photo-conductive drum 
1 and the transfer charger 6. 
As the ADU 14 is located immediately below the photo-conductive drum 1, the 
paper is conveyed in the U-turn state. Accordingly, even if the fixed 
image surface is at the upper side and the non-fixed image surface is at 
the lower side when carried out from the ADU 14, the paper is reversed 
when supplied to the photo-conductive drum 1 so that the non-fixing image 
surface comes to the upper side and the fixed image surface comes to the 
lower side. 
A developer image that is developed is transferred on the upper surface 
side of a paper by the transfer charger 6. That is, a developer image is 
formed on the surface that has so far no fixed image. The paper having a 
transferred developer image is led to the fixing device 20 again and the 
image is fixed and is ejected in the receiving tray 21 in the two side 
copied state. 
While the duplex copying is functioning, the first paper jam detector 24 
detects the leading edge of a paper conveyed from the fixing device 20. 
Further, the second paper jam detector 25 detects the trailing edge of a 
paper that is conveyed on the auxiliary conveying path 23 and is 
introducing into the ADU 14. 
The controller 26 counts a time from the detection of the leading edge of a 
paper by the first paper jam detector 24 to the detection of the trailing 
edge of a paper by the second paper jam detector 25 and computes whether 
this counted time is within the predetermined time. 
If the time detected by the first and the second paper jam detectors 24 and 
25 is above the prescribed time, the controller 6 judges that the paper 
jam was taken place in the auxiliary conveying path 23, stops a series of 
copying actions, makes an applicable indication and lights the indicator 
42 provided at the knob 41 of the coupling mechanism 40. 
Worker performs the works according to the indications on the operation 
panel. That is, the front panel of the main body S is opened by worker. As 
the indicator 42 of the knob 41 is already ON, worker is able to check 
which knob should be rotated easily. 
As shown in FIG. 5, when the knob 41 of which free end faces downward is 
rotated counterclockwise by 90.degree. as shown in FIG. 6, the hook 
mechanism F connected to the knob 41 is engaged with the fixing device 20 
and the ADU 14. 
When the knob 41 is pulled out by worker to this side without changing its 
position, the fixing device 20 and the ADU 14 are pulled out to this side 
together with the auxiliary conveying path provided with the coupling 
mechanism 40. 
Even when a part of the paper jammed in the auxiliary conveying path 23 is 
in the fixing device 20 or the ADU 14, the paper is pulled out in the 
jammed state. So, by rotating, for instance, the dial 32, worker takes out 
the jammed paper. 
The jammed paper can be taken out certainly without leaving any of it in 
the main body S. Furthermore, as all the devices can be pulled out at one 
time and the easy work, the simple removal of a paper in the jammed state 
and high safety are assured. 
After removing the jammed paper, when the knob 41 is pushed back into the 
main body S by grasping it without changing its posture, the auxiliary 
conveying path 23, the fixing device 20 and the ADU 14 move simultaneously 
and return to the prescribed positions, respectively. 
When the knob 41 is restored in the original state and the front panel is 
closed, the duplex copying function starts again. 
Further, in the above embodiment, a paper is conveyed in the U-turn state 
by providing the auxiliary conveying path 23 between the fixing device 20 
and the ADU 14; however, it is not limited to this and needless to say, 
this invention is also applicable to an electronic copying machine in 
which the fixing device 20 and the ADU 14 are arranged in series along a 
paper conveying path. 
As described above, according to the present invention, it is possible to 
get such effects that the work to remove a paper jammed between the fixing 
device and the ADU 14 can be made safely and quickly and thus, workability 
and safety are improved and reliability is secured.