Image forming apparatus having recovery process for jammed sheets

The present invention aims to provide a sheet conveying apparatus and an image forming apparatus having such a sheet conveying apparatus. If a sheet is jammed, the sheet is stopped in a sheet convey path at a position where the sheet can easily be removed by optimum treatment procedure. Sensors are disposed in a sheet convey path constituted by a plurality of units of an image forming apparatus portion and a sheet is stopped at an optimum position by a sheet position counter for recognizing the present position of the sheet in the sheet convey path.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a sheet treatment in an image forming 
apparatus such as a copying machine, a printer, a facsimile and the like. 
2. Related Background Art 
In the past, if a sheet is jammed on the way, clutches and motor for 
transmitting a driving force to a convey system are stopped immediately. 
The sheet stopped in a convey path is detected by a sensor for detecting 
the passage of the sheet, and a convey path unit including the sensor is 
displayed on a display. 
In order to improve the removal of the jammed sheet, techniques in which a 
sheet convey path is divided into a plurality of units which can be 
removably mounted on a main body of an image forming apparatus has 
recently been proposed. 
However, in the image forming apparatus having the plurality of units which 
can be removably mounted on the image forming apparatus as mentioned 
above, if the sheet is jammed when the convey drive system is stopped 
immediately, there is the danger of stopping the single sheet in two 
adjacent units. In such a case, if one of the units is drawn out, the 
jammed sheet will be torn. Further, as the sheet size becomes smaller, 
since the sheet convey path is curved more complicatedly, it is difficult 
to remove the jammed sheet. 
SUMMARY OF THE INVENTION 
The present invention aims to eliminate the above-mentioned conventional 
drawbacks, and has an object to provide a sheet conveying apparatus and an 
image forming apparatus having such a sheet conveying apparatus, in which, 
if a sheet is jammed, the jammed sheet is stopped at a position (in a 
sheet convey path) where the sheet can easily be removed, and the optimum 
treatment procedure can be displayed. 
To achieve the above object, a sheet conveying apparatus according to the 
present invention comprises a sheet convey means for conveying a sheet, a 
sheet detection means for detecting the passage of the sheet in a sheet 
convey path within which the convey means is disposed, a convey 
abnormality detecting means for detecting the abnormality in sheet 
conveyance in the sheet convey path, a sheet position counter for 
recognizing a position of the sheet in the sheet convey path, a sheet stop 
position determining means for determining a optimum stop position of the 
sheet on the basis of the sheet position counter, when the abnormality in 
sheet conveyance is detected by the convey abnormality detecting means, 
and a stop control means for stopping the sheet at the stop position 
determined by the sheet stop position determining means. 
Further, the stop control means serves to successively stop sheets situated 
at an upstream side of the stopped sheet (stopped in the sheet convey 
path) in a sheet conveying direction after the sheet (having the convey 
abnormality) was stopped. In addition, sheet position counter serves to 
recognize a tip end of the sheet. The sheet position counter may be 
renewed to a predetermined count value when the sheet passes through the 
sheet detection means. 
Further, a sheet conveying apparatus according to the present invention may 
comprise a sheet convey means for conveying a sheet, a sheet detection 
means for detecting the passage of the sheet in a sheet convey path within 
which the convey means is disposed, a convey abnormality detecting means 
for detecting the abnormality in sheet conveyance in the sheet convey 
path, a unit open/close detection means for detecting the fact that a 
first openable unit constituting a part of the sheet convey path is 
opened, a unit mount/dismount detection means for detecting the fact that 
a second removable unit constituting a part of the sheet convey path is 
mounted or dismounted, a display means for displaying a treatment 
procedure of the apparatus, a unit recognizing means for recognizing or 
identifying the unit including the sheet when the abnormality in sheet 
conveyance is detected by the convey abnormality detecting means, a 
display order determining means for determining the display order of the 
unit (to be treated) identified by the unit recognizing means, and a 
display control means for causing the display means to display the 
treatment procedure in the order determined by the display order 
determining means. 
An image forming apparatus according to the present invention includes the 
above-mentioned sheet conveying apparatus and comprises an image forming 
means for forming an image on the sheet conveyed by the sheet conveying 
apparatus in response to image information, a temporary contain means for 
temporarily containing the sheet on which the image was formed by the 
image forming means, and a display control means for causing the display 
means to display the fact that the sheet in the temporary contain means, 
when the temporary contain means is mounted in a condition that the 
available sheet remains in the temporary contain means, after the 
abnormality in sheet conveyance is detected by the convey abnormality 
detecting means. 
With the arrangement as mentioned above, in the sheet conveying apparatus 
according to the present invention, if the abnormality in sheet conveyance 
is detected by the convey abnormality detecting means, the present 
position of the sheet is recognized by the sheet position counter 
indicating the absolute position of the sheet in the sheet convey path, 
and the optimum stop position of the sheet is determined by the sheet stop 
position determining means. Then, the stop control means stops the sheet 
at the stop position determined by the sheet stop position determining 
means. In this way, the sheet can be stopped at the optimum stop position. 
Further, if the abnormality in sheet conveyance is detected by the convey 
abnormality detecting means, the unit including the sheet having 
abnormality is recognized or identified by the unit recognizing means, and 
the display order of the unit to be treated is determined by the display 
order determining means. Then, the display control means causes the 
display means to display the treatment procedure in the order determined 
by the display order determining means. In this way, the position of the 
unit including the stopped sheet can surely be recognized, and the jam 
treatment can be effected efficiently in accordance with the priority 
order. 
In addition, in the image forming apparatus according to the present 
invention, by utilizing the advantages of the sheet conveying apparatus, 
the image can be formed on the sheet effectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, the present invention will be concretely explained. As an example of 
an image forming apparatus having a sheet conveying apparatus according to 
the present invention, an electrophotographic copying machine will be 
described. 
In FIG. 1, the copying machine 1 includes a circulating automatic original 
feeding apparatus (RDF) 2 and an image forming apparatus portion 3. The 
automatic original feeding apparatus 2 can be combined with the image 
forming apparatus portion 3 appropriately. 
The image forming apparatus portion 3 has an upper original support glass 
(original resting plate) 5 below which there is provided an optical system 
(image reading means) 6. The optical system 6 includes an exposure lamp 
(original illumination lamp) 6a, a scan mirror 6b, a zoom lens 6c and a 
motor (not shown) so that an original is illuminated by the exposure lamp 
6a and light reflected from the original is incident to a photosensitive 
drum 7a through the scan mirror 6b and the zoom lens 6c. 
In order to direct the light reflected from the original to the 
photosensitive drum 7a, a method for shifting the optical system 6 such as 
the exposure lamp 6a while maintaining the original on the original 
support glass 5 or a method for shifting the original on the original 
support glass 5 while fixing the optical system 6 such as the exposure 
lamp 6a (flow reading mode) can be adopted. 
Below the optical system 6, there is provided an image forming portion 
(image forming means) 7 which includes the above-mentioned photosensitive 
drum 7a rotated in a direction shown by the arrow a, a high voltage unit 
7b, a blank exposure unit 7c, a potential sensor 7d, a developing device 
7e, a transfer charger 7f, a separation charger 7g and a cleaning device 
7h. These elements 7b to 7h are disposed around the photosensitive drum 
7a. The photosensitive drum 7a is rotated by a main motor (not shown); 
meanwhile, after the photosensitive drum is corona-charged by the high 
voltage unit 7b, the light reflected from the original is illuminated on 
the photosensitive drum through the optical system 6, thereby forming an 
electrostatic latent image on the drum. Then, the electrostatic latent 
image is developed by the developing device 7e to be visualized as a toner 
image. 
On the other hand, at a lower portion of the image forming apparatus 
portion 3, there are disposed a sheet supply cassette portion 9 including 
a first stage cassette 9a, a second stage cassette 9b, a third stage 
cassette 9c and a fourth stage cassette 9d. The cassette 9a to 9d are 
associated with sheet supply means 10a to 10d and 11a to lid for feeding 
out sheets (contained in the cassette 9a to 9d) from the cassette 9a to 
9d. Now, as an example, the sheet supply means associated with the third 
stage cassette 9c will be described. (The sheet supply means associated 
with the other cassettes have the same construction.) 
A pick-up roller 10c for feeding out the sheet(s) S from the cassette 9c is 
disposed above a sheet supply outlet of the cassette 9c, and a pair of 
separation rollers 11c comprised of a supply roller and a retract roller 
are disposed at a downstream side of the cassette 9c to separate and 
supply the sheet(s) fed out by the pick-up roller 10c one by one. In this 
way, a lowermost sheet S alone is separated from the other sheet(s) by the 
pair of separation rollers 11c. The separated sheet S is sent to a pair of 
regist rollers 13 disposed in front of the image forming portion 7 by 
means of a sheet convey means including pairs of convey rollers 12a, 12b, 
12c and 12d. 
Further, in the vicinity of the image forming portion 7, there is provided 
a multi manual insertion device 14 for conveying a sheet to the image 
forming portion 7 by manually inserting the sheet. At a downstream side of 
the image forming portion 7, there is provided a convey belt 15 for 
conveying the sheet (on which the image was formed) toward a downstream 
side. A fixing device 16 for fixing the toner image to the sheet S with 
heat is disposed at a downstream side of the convey belt 15. At a 
downstream side and in the vicinity of the fixing device 16, there is 
disposed a discharge flapper 17 for switching or selecting a discharge 
path A1 for discharging the sheet from the fixing device 16 out of the 
image forming apparatus portion 3 and a re-convey path A2 used in a sheet 
both-face recording mode or a sheet multi recording mode. And, a pair of 
discharge rollers 19 are disposed in the discharge path A1. 
Below the fixing device 16, there is provided a convey path 20 connected to 
the re-convey path A2, and, at a downstream side of the convey path 20, 
there are disposed a pair of temporary contain tray discharge rollers 21 
for discharging the sheet S into a temporary contain tray 23 for 
temporarily containing the imaged sheets S, and a discharge sensor 22 for 
detecting the sheet S discharged to the temporary contain tray 23. 
Incidentally, the discharge sensor 22 acts as both a sheet detection means 
for detecting the passage of the sheet S and a convey abnormality 
detecting means for detecting the abnormality in sheet conveyance. In the 
vicinity of the discharge sensor 22, a re-supply device 34 for 
successively re-supplying the sheets S contained in the temporary contain 
tray 23. 
In order that the temporary contain tray 23 helps to bring the sheet S to a 
re-supply separation belt 33 when the sheet S is re-supplied from the 
tray, as shown in FIG. 1, the temporary contain tray 23 is inclined at a 
predetermined angle, and a sheet re-supply roller 31 for re-supplying the 
sheet S is disposed in the vicinity of an outlet of the temporary contain 
tray 23. At a down stream side of the sheet re-supply roller 31, a 
re-supply feed roller 32 is urged against the re-supply separation belt 33 
so that the sheets S can be separated and re-supplied one by one. 
A multi flapper 36 is disposed at a downstream side and in the vicinity of 
the re-supply feed roller 32 and the re-supply separation belt 33, and, at 
a downstream side of the flapper 36, there are disposed an upwardly 
extending reverse rotation convey path 37 for reversely rotating (turning 
over) the imaged surface of the sheet S once so that images can be formed 
on the imaged surface of the sheet in a superimposed fashion in the multi 
recording mode, and a downwardly extending convey path 39 for reversely 
rotating the imaged surface of the sheet S so that an image can be formed 
on the other surface of the sheet S in the both-face recording mode. 
Depending upon the recording mode, by switching the multi flapper 36, the 
sheet S can be introduced into the reverse rotation convey path 37 or the 
convey path 39. 
The convey path 39 includes pairs of convey rollers 40a, 40b, 40c and 40d. 
Further, sensors 51, 52, 53, 54, 55, 56, 57 and 58 each acting as a sheet 
detection means for detecting the passage of the sheet S in the sheet 
convey path and a convey abnormality detecting means for detecting the 
abnormality in the sheet conveyance are disposed at predetermined 
positions in the sheet convey paths of the sheet convey means included in 
the image forming apparatus portion 3. 
FIG. 2 is a block diagram of a control device 100 of the copying machine 
having the sheet conveying apparatus according to the present invention. 
The control device 100 includes a CPU 101 for controlling the entire 
copying machine 1 in accordance with the control sequence (control 
program) stored in a ROM (read only memory) 102, the above-mentioned ROM 
102 for storing the control program, a RAM (random access memory) 103 
acting as a main memory for storing input data and used as a work area, 
and an I/O (input/output processor) 104 for outputting a control signal of 
the CPU 101 for the drive means such as the main motor and for receiving 
signals from the sensors and for sending the sensor signals to the CPU 
101. 
FIG. 3 shows an operation panel 200 provided on the image forming apparatus 
portion 3. A user mode key 601 is used by an operator to perform ON/OFF of 
auto (automatic) sort, ON/OFF of sheet removal before sorter, ON/OFF of 
skip both-face, ON/OFF of feeder manual insertion auto start, ON/OFF of 
cassette auto selection, ON/OFF of buzzer, change to smaller mode, setting 
of pre-heat mode, initialization of specification, change in standard 
mode, change in auto clear time, change in auto power off time, setting of 
weekly timer, setting of day of week/time, zoom fine adjustment, cleaning 
of feeder, cleaning of wire and the like. 
An all reset key 610 is depressed when the standard mode should be 
restored. A copy start key 605 is depressed when a copying operation is to 
be started. A clear key 604 is used when the set number of copies is 
cleared. A stop key 609 is depressed when the continuous copying operation 
is interrupted, so that, after the copying operation upon depressing this 
key is finished, the copying operation of the copying machine is stopped. 
A ten-key 608 is used when the number of copies is set. A guide key 62 is 
used to display explanation of functions corresponding to various keys on 
a message display 615. A pre-heat key 607 is depressed to change to a 
pre-heat mode and is constituted by a self-illumination key having a light 
emitting elements such as an LED so that, when the pre-heat mode is 
selected, this key is illuminated. 
An interruption key 606 is depressed when the copying operation is 
interrupted to perform another copying operation. Similar to the pre-heat 
key 607, this interruption key 606 is also constituted by a 
self-illumination key, and, thus, is illuminated when the interruption is 
effected. 
The message display (display means for displaying operation procedure of 
the machine) 615 has a touch panel of LCD (liquid crystal display) type 
for displaying information (characters and figures) regarding the copying 
operation with 240.times.320 dots. In a standard condition, the message 
display 615 displays a normal magnification change key, a same 
magnification key, a zoom key, a smaller key, a sheet selection key, a 
copy density key, a sorter key for selecting functions of a sorter, a 
both-face key for setting a mode regarding the both-face copy, and 
application mode keys for setting copy modes regarding application copies 
such as frame erase, staple margin, front page/bundle, contraction layout, 
enlargement layout, OHP sheet insertion between sheets, page sequence 
copy, multi copy, original mix, photograph, mode memory and the like. By 
touching a portion of the display corresponding to the specific key, a 
window regarding the contents of the touched key. Further, the operation 
sequence is displayed when the sheet jam or error is generated. 
FIGS. 4A to 4F are explanatory views for explaining original reading 
operations in a flow reading mode. First of all, the originals D are set 
in the automatic original feeding apparatus 2 (see FIG. 4A). When the copy 
start key 605 is depressed, the automatic original feeding apparatus 2 
supplies a lowermost sheet D2 (2) to the original reading portion 4 from 
right (FIG. 4A), and the image forming apparatus portion 3 shifts the 
optical system 6 to a center of the original support glass 5. The optical 
system 6 is then stopped at that position by an optical system locking 
means (not shown) (see FIG. 4B). 
When the lowermost sheet D2 is conveyed in front of the optical system 6 
(see FIG. 4C), an image signal is sent from the automatic original feeding 
apparatus 2 to the image forming apparatus portion 3, with the result that 
the exposure lamp 6a is illuminated and the regist rollers 13 are 
controlled in response to the image signal (see FIG. 4D). In this case, 
following to the lowermost sheet, a next sheet D1 (1) which was rested on 
the lowermost sheet D2 is sent to the original reading portion 4 from 
right. While the next sheet D1 is being exposed, the lowermost sheet D2 is 
discharged from left (see FIG. 4E). Then, the optical system 6 is returned 
to a home position and the next original D1 is discharged from left (see 
FIG. 4F). 
FIG. 5 is a perspective view showing an example that the sheet convey paths 
in the image forming apparatus portion 3 are divided into a plurality of 
units which can be removable or openable with respect to the image forming 
apparatus portion 3. FIG. 6 is a perspective view showing a condition that 
a right upper door unit 311 in FIG. 5 is opened and FIG. 7 is a 
perspective view showing a condition that a fixing convey unit 301 in FIG. 
5 is retracted toward a front side and dismounted from the image forming 
apparatus portion 3. 
In FIGS. 5 to 7, the reference numeral 301 denotes the fixing convey unit 
including various elements between the regist rollers 13 and the discharge 
rollers 19; 302 denotes a temporary contain tray unit including the 
temporary contain tray 23 and the re-supply device 34; 303 denotes a sheet 
re-supply convey unit including the pairs of convey rollers 40a to 40d for 
conveying the sheet S re-supplied from the temporary contain tray 23; and 
304, 305, 306 and 307 denote sheet supply cassette units including the 
first to fourth stage cassettes 9a-9d, respectively. The units can be 
retracted toward the front side to be dismounted from the image forming 
apparatus portion 3. 
The reference numeral 310 denotes a manual insertion cover unit including 
an openable convey path for the multi manual insertion device 14; and 311, 
312 denote an openable right upper door unit and an openable right lower 
door unit, respectively, which are obtained by dividing the vertically 
extending convey path (of the image forming apparatus portion 3) including 
the convey rollers 12a to 12d into two. The manual insertion cover unit 
310 and the door units 311, 312 can be opened around their fulcrums 
disposed at the rear side. As mentioned above, the units which can be 
dismounted or opened with respect to the image forming apparatus portion 3 
are provided with unit dismount detection means (not shown) or unit open 
detection means (not shown) which can detect the fact that the unit is 
dismounted or opened. By these detection means, information regarding the 
dismounting or opening of the unit is transmitted to the control device 
100. 
Further, the sheet S conveyed through the various units is detected by the 
sensors 22, 50 to 58. On the basis of the signals from these sensors, the 
unit to which the sheet actually belongs is recognized or identified by a 
unit recognizing means of the control device 100. Further, if the 
abnormality in conveyance of the sheet being conveyed through a certain 
unit, the unit to which the abnormal sheet actually belongs is recognized, 
and the abnormal unit is displayed on the message display (LCD) 615 on the 
operation panel 200, thereby commanding the optimum treatment procedure. 
Next, the control system of the copying machine 1 having the 
above-mentioned construction will be explained. FIG. 8 is a flow chart 
showing control task for controlling the sheet supplying operation in the 
image forming apparatus portion 3. First of all, when the copy start key 
605 is depressed, sheet supply task for controlling the conveyance of the 
sheet S is started (step S101), and a position count value Cc 
corresponding to a position of each sheet supply cassette unit 304 to 307 
in the sheet convey path is set in a position counter C for the sheet 
supply task (step S102). 
The position counter C is a sheet position counter for recognizing the 
present position of the sheet S in the sheet convey path of the image 
forming apparatus portion 3, and the counter value is so designed that, 
regarding the position of the regist roller pair 13 ("0" value in this 
point), an upstream side (sheet supply side) has a "minus" value and a 
downstream side (discharge side) has a "plus" value. Further, the position 
counter C is counted up by an encoder clock of the main motor for driving 
the convey means such as the convey rollers disposed in the sheet convey 
path of the image forming apparatus portion 3 or an internal timer clock 
(not shown), and the count value is subjected to calculation treatment in 
the control device 100. 
In the position counted C counted up by the encoder clock, the count value 
Cc corresponding to the position of each sheet supply cassette unit 304 to 
307 is a value obtained by dividing the actual distance between the 
position of the sheet supply cassette unit 304 to 307 and the regist 
roller pair 13 along the convey path by a moving distance corresponding to 
one (1) pulse of the encoder clock. The position counter C is designed to 
indicate the value calculated in the manner as mentioned above. 
Then, when a value obtained by subtracting the position count value Cc 
corresponding to the position of the sheet supply cassette unit 304 to 307 
from a count value Cp of the position counted C counted in the former 
sheet supply task control exceeds a count value Cb corresponding to a 
distance between a preceding sheet and a succeeding sheet along the sheet 
convey path (step S103), if the supply of a next sheet S is required (step 
S104), a next sheet supply task is started (step S101); whereas, if the 
supply of the next sheet S is not required, the sheet supply task is 
finished. 
Next, the details of the sheet supply task will be described. FIG. 9 is a 
flow chart showing the operation of the sheet supply task. First of all, 
when the sheet supply task is started, the fact that the sheet S passes 
through either one of the sensors 22, 50 to 58 disposed in the convey path 
(step S201). After the sheet S passes through a certain sensor, the value 
of the position counter C is corrected to an absolute position counter 
value Ca corresponding to the position of the sensor in question (step 
S202), and then, the convey means (convey rollers in the sheet convey 
path) to be then driven is turned ON and the convey means through which 
the sheet has already passed is turned OFF (step S203). 
Then, it is judged whether the sheet S is jammed or not by the sensors 22, 
50 to 58 (step S204). If the sheet is jammed in the sheet convey path, on 
the basis of the present count value Cx of the position counter C, the 
unit to which the jammed sheet belongs is calculated and the jammed unit 
is selected among the fixing convey unit 301, temporary contain tray unit 
302, re-supply convey unit 303, sheet supply cassette units 304 to 307, 
manual insertion cover unit 310, right upper door unit 311 and right lower 
door unit 312 (step S205). 
On the basis of the count information of the position counter C, the 
optimum stop position of the sheet S is determined by a sheet stop 
position determining means of the control device 100, and a stop position 
count value Cs of the position counter C corresponding to a predetermined 
optimum position where the sheet S is stopped in the unit in question is 
outputted. Then, the present count value Cx is subtracted from the stop 
position count value Cs (step S206). If a difference value Cd (between the 
values Cs and Cx) is reached (step S207), the convey means (such as the 
convey rollers) being driven is turned OFF by a stop control means, 
thereby stopping the sheet S at a desired position (step S208). For 
example, the sheet immediately in front of the regist roller pair 13 or 
the sheet being passed in a nip between the regist rollers 13 is stopped 
in a condition that a trail end portion of the sheet is pinched between 
the regist rollers 13, as shown in FIG. 1 by SR. In this case, the trail 
end of the sheet SR is completely included in the fixing convey unit 301 
(shown by the broken line), even when the fixing convey unit 301 is 
retracted toward the front side, the sheet is not torn. 
Further, since the sheet SR is stopped in the condition that it is pinched 
between the regist rollers 13, when the unit 310 is retracted, the sheet 
SR is surely be retracted together with the unit 301, with the result that 
the sheet is not trapped on the photosensitive drum 7a. Since the trail 
end portion of the sheet alone is pinched between the regist rollers 13, 
the sheet SR can easily be removed. 
Incidentally, even when the sheet SR has a maximum length among sheets 
available to the copying machine, by selecting a distance between a pair 
of fixing rollers 16a, 16b and the pair of regist rollers 13 so that a tip 
end is not pinched between the pair of fixing rollers 16a, 16b when the 
sheet is stopped at the predetermined position, the jammed sheet can 
easily be removed. 
Further, when the distance between the pair of fixing rollers 16a, 16b and 
the pair of regist rollers 13 is short, the pair of fixing rollers 16a, 
16b may be stopped before the tip end of the sheet SR reaches the pair of 
fixing rollers 16a, 16b. In this case, when the sheet is stopped at the 
predetermined position, the sheet SR is bent or curved between the fixing 
device 16 and the photosensitive drum 7a. 
Then, it is judged whether a succeeding sheet S exists at the upstream side 
of the stopped sheet S (step S209). If the succeeding sheet S exists, the 
jamming of the preceding sheet S is alarmed to the sheet supply task for 
the succeeding sheet S (step S210); whereas, if the succeeding sheet S 
does not exist, it is judged whether the present position count value Cx 
exceeds a count value Ci (of the position counter C) corresponding to a 
position of the separation charger 7g (step S211). 
If the present position count value Cx exceeds the count value Ci 
corresponding to the position of the separation charger 7g, post-rotation 
control of high voltage (in which the first charge, developing bias, post 
charge, transfer charge and separation charge are successively turned OFF) 
is started (step S212), and the program goes to a next task. Then, the 
sheet supply task is finished. The next task is started after a 
predetermined time is elapsed, if necessary. 
Next, display control for displaying information on the operation panel 200 
if the sheet S is jammed in the sheet convey path will be explained. FIG. 
10 is a flow chart showing control of jam display task. If the sheet S is 
jammed in the sheet convey path, the jam display task is started. First of 
all, the number n of sheets S remaining in the sheet convey path of the 
image forming apparatus portion 3 (excluding the sheets normally contained 
in the sheet supply cassette units 304 to 307) is calculated on the basis 
of the above-mentioned sheet supply task information, thereby determining 
the number Tn (n times) of sheet removal tasks regarding the jam treatment 
(step S301). 
Then, a unit number Ui of the unit to which the stopped sheet S belongs is 
calculated (step S302). The unit number Ui comprises first and second unit 
numbers which determine the priority order for effecting the jam treatment 
even if the sheet S is stopped between two adjacent units for any 
compelling reason. For example, regarding the sheet S stopped immediately 
in front of the pair of regist rollers 13, the right upper door unit 311 
shown in FIG. 6 is indicated by the first unit number which is the 
priority order for effecting the jam treatment and the fixing convey unit 
301 is indicating by second unit number which is the post order for 
effecting the jam treatment. That is to say, by commanding the operator to 
firstly effect the jam treatment regarding the unit indicated by the first 
unit number, the jammed sheet S can be removed easily and efficiently. 
Then, it is judged whether there is the priority unit Up. This is 
preferable when the sheet S is damaged so long as the sheet is not removed 
from the priority unit Up or when the stop position of the jammed sheet S 
cannot be judged correctly or when the sheet S is stopped between two 
adjacent units for any compelling reason. 
First of all, the temporary variable i for counting the removal number n of 
the sheets remaining in the sheet convey path of the image forming 
apparatus portion 3 is set to "1" (step S303), and it is judged whether 
the temporary variable i reaches the removal number n (step S304). If not, 
it is judged whether there is the predetermined priority unit Up (step 
S305). If there is the priority unit Up, a priority unit flag is set (step 
S306), and the temporary variable i is increased by 1 increment (step 
S307). Then, the sheet removal task is repeated by Tn times corresponding 
to the removal number n. If the priority unit flag is set (step S308), the 
sheet removal treatment (described later) is carried out (step S309), 
thereby removing the sheets to be removed in accordance with priority 
order. 
Then, the similar removal treatment is repeated regarding the remaining 
sheets. First of all, the temporary variable i is set to "1" (step S310), 
and it is judged whether the temporary variable i reaches the removal 
number n (step S311). If not, the sheet removal treatment (described 
later) is carried out (step S312), the temporary variable i is increased 
by 1 increment (step S313), and the sheet removal task is repeated by Tn 
times corresponding to the removal number n. Then, the sheet removal task 
control is finished. 
Next, the sheet removal treatment will be explained. FIG. 11 is a flow 
chart showing control of the sheet removal treatment. The display order of 
the units (for which the jam treatment is to be effected) recognized by 
the unit recognizing means is determined by the display order determining 
means of the control device 100, and the display control means causes the 
display means to display the jam treatment procedure on the message 
display 615. 
First of all, the display for demanding the jam treatment of the unit 
indicated by the first unit number (priority unit) is displayed on the 
message display (LCD) 615 of the operation panel 200 (step S401), and, it 
is judged whether the first unit is dismounted or opened by the operator 
(step S402). When the first unit is dismounted or opened, it is judged 
whether the sheet S can be detected by the sensor of the first unit, i.e., 
whether the sheet is detected by the sensor before the first unit is 
dismounted or opened and the sensor is turned OFF after the first unit is 
dismounted or opened (step S403). 
If the sensor is effective and is turned OFF, it is recognized that the 
sheet is removed by the operator, thereby finishing the sheet removal 
treatment control. To the contrary, in the other conditions, i.e., if the 
sensor is not effective or/and is turned ON, it is recognized that the 
sheet removal is not completed. In this case, in a step S404, it is judged 
whether the second unit number (post treatment order) is set (step S404). 
If the second unit number is not set, it is judged whether the sensor is 
effective (step S405). If the sensor is effective, it is judged again 
whether the first unit is dismounted or opened (step S402). 
On the other hand, if the second unit number is set, the display for 
demanding the jam treatment of the unit indicated by the second unit 
number is displayed on the message display 615 of the operation panel 200 
(step S406), and, it is judged whether the second unit is dismounted or 
opened by the operator (step S407). When the second unit is dismounted or 
opened, it is judged whether the sheet is detected by the sensor of the 
second unit and the sensor is turned OFF after the first unit is 
dismounted or opened (step S408). 
If the sensor is effective and is turned OFF, similar to the above, it is 
recognized that the removal of the sheet S is completed, thereby finishing 
the sheet removal treatment control. To the contrary, in the other 
conditions, i.e., if the sensor is not effective or/and is turned ON, it 
is recognized that the sheet removal is not completed. In this case, in a 
step S409, it is judged whether the sensor is effective. If the sensor is 
not effective, it is recognized that the removal of the sheet S is 
completed, thereby finishing the sheet removal treatment control. On the 
other hand, if the sensor is effective, it is judged again whether the 
second unit is dismounted or opened (step S407). 
Next, control of jam post treatment task for re-using the sheets S 
remaining in the temporary contain tray 23 when the sheet jam occurs will 
be explained. FIG. 12 is a flow chart showing the jam post treatment task. 
When it is recognized that the sheets S are remaining in the temporary 
contain tray 23 by the unit recognizing means, the display control means 
of the control device 100 causes the display means to display the 
treatment of the sheets S remaining in the temporary contain tray 23 on 
the message display 615. 
First of all, it is judged whether the sheets S are remaining in the 
temporary contain tray 23 (step S501). If there is no sheet in the 
temporary contain tray 23, the normal recovery data is calculated (step 
S506). On the other hand, if any sheet S is remaining in the temporary 
contain tray 23, it is judged whether the temporary contain tray 23 is 
mounted or dismounted after the entire jam treatment is completed (step 
S502). If the temporary contain tray 23 is mounted or dismounted, the 
treatment for the temporary contain tray 23 is displayed (step S503). 
Then, it is judged whether the temporary contain tray 23 is mounted or 
dismounted by the operator (step S504). After the temporary contain tray 
23 is mounted or dismounted, the treatment display is repeated until there 
is no sheet in the temporary contain tray 23 (step S505). After the sheet 
is completely removed from the temporary contain tray 23, the recovery 
data is calculated (step S506), and then the control of the jam post 
treatment task is finished. If the temporary contain tray 23 is mounted or 
dismounted by the operator even when the sheets S in the temporary contain 
tray 23 can be re-used, the treatment display is displayed as "non 
re-used". 
Next, control of a jam watch portion for monitoring or watching the jam 
occurrence will be explained, particularly, in connection with the flow 
reading mode. FIG. 13 is a flow chart showing the control of the jam 
watch. First of all, it is judged whether the copy start key 605 is 
depressed (step S601). When the copy start key 605 is depressed, it is 
judged whether the flow reading mode can be adopted or not on the basis of 
the original size and the copy magnification (step S602). 
If the flow reading is possible, a flow reading mode flag is set (step 
S603). If the flow reading mode flag is set (step S604), the jam 
occurrence in the circulating automatic original feeding apparatus (RDF) 2 
is monitored (step S605). If the sheet jam occurs in the automatic 
original feeding apparatus, the fact that the jam occurred is notified to 
the corresponding sheet supply task (in which the image is being formed) 
(step S606), and the monitoring is continued until the copy is finished 
(step S607). When the copy is finished, the jam monitoring operation of 
the jam watch portion is finished. That is to say, in the flow reading 
mode, if the sheet jam occurs in the automatic original feeding apparatus 
2, the sheet S (being imaged) corresponding to the jammed original is 
forcibly stopped, thereby preventing the non-imaged sheet from being 
discharged out of the copying machine. 
According to the present invention, since the sheet conveying apparatus has 
the above-mentioned construction and function, if the sheet is jammed, by 
stopping the sheet at a position where the jammed sheet can easily be 
removed, it is possible to display the treatment procedure for the optimum 
jam treatment. Further, since the stop position of the sheet in the sheet 
convey path is recognized by the position counter, the accuracy of the 
recognition of the jam treatment position is improved, thereby removing 
the jammed sheet positively and efficiently. In addition, in the image 
forming apparatus having such a sheet conveying apparatus, the image can 
be formed on the sheet conveyed by utilizing the advantage of the sheet 
conveying apparatus, and, if the sheet is jammed in the image forming 
apparatus, the jammed sheet can be removed positively and efficiently. 
As mentioned above, while the image is being formed under the flow reading 
control, if the abnormality in the original conveyance is detected by the 
original supply abnormality detection means, by forcibly stopping the 
sheet (being imaged), it is possible to prevent the mixture of the imaged 
sheets and the non-imaged sheets.