Copier with automatic document feed having jam prevention function

An apparatus with a document feeder for sequentially copying plural sheets of documents. When a document longer than a predetermined length is detected by a sensor, a stopper for aligning the document at a predetermined position is withdrawn in order to prevent the document from being damaged. At the same time, an indicator is turned on, warning the operator of jamming.

BACKGROUND OF THE INVENTION 
This invention relates to an electrostatic copier which automatically feeds 
and delivers documents to be copied. 
In order to copy a plurality of documents with a conventional copier, each 
document should be manually set on a platen glass located in the upper 
portion of the apparatus, and also removed from the platen glass to be 
replaced by the next document. However, this exchange of the documents is 
a very troublesome job when copying many documents. 
Recently a new apparatus, which is called an automatic document feeder, has 
been developed. The procedure of feeding documents by the automatic 
document feeder will be described as follows. After a plurality of 
documents to be copied are set at a prescribed position on the automatic 
document feeder, the documents are automatically conveyed sheet by sheet 
onto the prescribed position on the platen glass. The document is exposed 
on the platen glass. After exposure, the document is automatically 
delivered. The automatic document feeder is used either as a built-in 
device of the copier or as an optional accessory to the conventional 
copier as occasion demands. 
The procedure of copying a plurality of documents by an electrostatic 
copier equipped with this kind of automatic document feeder is as follows. 
A plurality of documents to be copied are initially stacked at the 
prescribed position on the automatic document feeder and the copy button, 
which is mounted on the operation panel of the copier, is pressed. Then, 
the document feeding mechanism of the automatic document feeder is 
activated and a sheet of document, the uppermost or the lowermost of a 
pile of documents on the document feeder, is conveyed onto the platen 
glass. The conveyed document is stopped at the prescribed position on the 
platen glass by the stopping device which protrudes a little from the 
platen glass surface. After the document is thus aligned at the prescribed 
position on the platen glass, the optical scanning unit installed just 
below the platen glass moves and exposes the document from the underside 
to the light of a lamp. The reflected light from the document is projected 
on the surface of the photoreceptor. Then, a document image is formed by a 
series of electrophotographic processes. Likewise afterward, each of the 
documents are automatically conveyed and processed as described above. 
This type of copier is usually designed to copy those documents belonging 
to a predetermined size group, as an example B5 and A4, the upper size 
limitation of this size group being A4 here. 
And problems are caused by a careless setting of a document which is longer 
than the upper size limitation, which we call long document hereafter in 
the specification, to the document feeder. In this case, when the copying 
operation starts, the long document is conveyed onto the platen glass, and 
after the leading edge of the document is halted by the stopping device, 
the trailing portion of the document is still conveyed by the feed roller. 
As a result, the leading edge of the document is damaged or the trailing 
portion of the document is bent and wound around the feed roller, which 
may cause jamming of the apparatus in addition to damage of the document. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved 
electrostatic copier with a document feeder which can prevent a document 
from being damaged when it is fed onto the platen glass. In order to 
attain the object described above, when a long document is detected by a 
sensor, the document stopping device is withdrawn and at the same time the 
indicator which warns the operator of jamming turns on. Another example to 
attain the object of the invention is that when a long document is 
detected, the document stopping device is withdrawn and the document is 
continuously discharged from the apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings, an exemplary embodiment of the invention will be 
described below. 
FIG. 1 is a schematic illustration of one of the examples of the 
electrostatic copier of the invention. A paper feed unit which contains a 
plurality of recording papers and is capable of rising and falling, and a 
sorter which can automatically sort copied recording papers, are installed 
in this example. However, these two units are not essential to the present 
invention. In the electrostatic copier illustrated in FIG. 1, the platen 
glass 2 is mounted on the upper portion of the apparatus 1. On the 
underside of the platen glass 2, the exposure unit 3 is installed which 
can be horizontally reciprocated to expose the document, which is not 
shown in the drawing, on the upper surface of the platen glass 2. 
In the middle portion of the apparatus 1, is the photoreceptor drum 4 to 
bear a latent image on its surface. The following units are placed around 
the photoreceptor drum 4: the electrostatic charging unit 5, the 
developing unit 6, the transfer and separating unit 7, and the cleaning 
unit 8. 
The recording paper feed unit 10 is connected to the right side of the 
apparatus 1. The recording paper feed unit 10 is equipped with the lifting 
base 11 on which a plurality of recording papers can be stacked. The hand 
feeding unit 12 is mounted on the upper portion of the recording paper 
feed unit 10. At the uppermost portion of the recording paper unit 10, the 
recording paper feed roller 13 is mounted which comes into contact with 
the uppermost recording paper stacked on the lifting base 11. This 
recording paper feed roller 13 is driven by a motor not shown in the 
drawing. Furthermore, the double-feed preventing mechanism 14 is placed 
ahead of the recording paper feed roller 13 in the direction of paper 
conveyance. Between the double-feed preventing mechanism 14 and the 
transfer and separating unit 7 placed close to the photoreceptor drum 4, 
the recording paper passage 16 and the second recording paper feed roller 
(the resisting roller) 15 which stops and holds a conveyed recording paper 
for a while before feeding again, are placed. In the left portion of the 
apparatus, the fixing unit 17 is installed. Between the fixing unit 17 and 
the photoreceptor drum 4, the conveying unit 18 is installed which conveys 
the recording paper after transfer. 
Furthermore, the sorter 20 is connected to the left side of the apparatus 1 
and the automatic document feeder 21 is mounted on the upper portion of 
the apparatus 1. The numeral 22 is a hopper to supply toner to the 
developing unit 6. The numeral 23 is a stand to adjust the height of the 
delivery roller 24 which delivers a recording paper from the apparatus 1 
with the height of the sorter 20. 
The detailed structure of the recording paper feed unit 10 is illustrated 
in FIG. 2. The lifting base 11 of the recording paper feed unit 10 is 
connected via fixture members 27a and 27b to the stainless steel wire 26 
(shown by a chain line) which is stretched by the pulleys 25a, 25b, 25c, 
25d, 25e, and 25f. When the motor 28 is rotated normally or reversely, the 
lifting base 11 rises or falls in the arrowed direction in accordance with 
the motion of the stainless steel wire 26. The movable recording paper 
feed roller 13 is located at the upper left portion of the recording paper 
feed unit. The double feed preventing mechanism, the details of which will 
be described below, is located ahead of the recording paper feed roller 
13. The double feed preventing mechanism comprises: a pair of rollerS 30, 
31 Which are placed ahead of the recording paper feed roller 13 in the 
paper feeding direction; the belt 32 which is stretched between the roller 
30 and the roller 31; the tension roller 33 which presses the belt 32 from 
above: and the conveyance roller 36 which presses the belt 32 from below. 
The passage 16 is provided ahead of the double feed preventing mechanism 
and at the end of the passage a pair of rollers, the second recording 
paper feed rollers 15 (the resisting rollers) are provided. The conveyance 
roller 36 is driven by the same motor (not shown in the drawing) as that 
which drives the recording paper feed roller 13. 
The hand feeding unit 12 is provided in the vicinity of the recording paper 
feed roller 13 which is placed at an upper part of the lifting base 11. 
The hand feeding board 37 of the hand feeding unit 12 can move between the 
raised position illustrated by a chain line and the lowered position 
illustrated by a solid line. When the hand feeding board 37 of the hand 
feeding unit 12 is moved from the raised position to the lowered position, 
the mode changes from the automatic feeding mode to the hand feeding mode 
and the mode change is electrically detected by the photo coupler (not 
shown in the drawing). At the same time, the lever 38 which is integrally 
moved with the hand feeding board 37, is moved from the position 
illustrated by a solid line to the position illustrated by a chain line. 
When the lever 38 is moved, the recording paper feed roller 13 is lifted 
since the support lever 40 of the press roller 39 which holds the 
recording paper feed roller 13 at the lower position shown in the drawing, 
is pushed up. Accordingly, when the tip 37a of the hand feeding board 37 
is moved from the position shown by a solid line to the position shown by 
a chain line, the lower surface of the recording paper feed roller 13 is 
positioned to the same surface as the upper surface of the tip 37 a of the 
hand feeding board 37. 
As a result, when the recording paper feed roller 13 is positioned at the 
raised position, the uppermost recording paper of a stack on the lifting 
base 11 is not fed but left on the stack, and the uppermost recording 
paper of a plurality of recording papers on the hand feeding board 37 of 
the hand feeding unit 12, is fed. 
The automatic document feeder 21, which is illustrated in FIG. 3 in detail, 
is placed on the platen glass 2 which is provided on the upper surface of 
the electrostatic copier 1. The document tray 50 is provided on the right 
side of the document feeder 21. 
The automatic document feeder 21 is equipped also with a pair of rollers 
51, 52 which are placed on the platen glass 2 at a prescribed interval. 
The belt 53 is stretched between the roller 51 and the roller 52. The belt 
is pressed against the upper surface of the platen glass 2 by the press 
rollers 54. The double feed preventing mechanism 60 is placed between the 
belt 53 and the document tray 50 and comprises a pair of rollers 56, 57 
between which the belt 55 is stretched, the tension roller 58 which 
presses the belt 55 from above, and the conveying roller 59 which presses 
the belt 55 from below. The passage 61 is provided ahead of the double 
feed preventing mechanism 60 in the document feeding direction. A pair of 
feed rollers 62 (the resisting rollers) are provided at the tip of the 
passage. A document is conveyed to be inserted between the belt 53 and the 
platen glass 2 by a pair of rollers 62. Optical sensor PS.sub.1 is placed 
close to the feed rollers 62 in the downstream portion of document flow. 
The document stopping device 63 for positioning a document on the platen 
glass is provided at the downstream end of the platen glass 2 with an 
angle to the platen surface. This stopping device 63 is pressed against 
the platen glass 2 by the spring 64. On the other hand, the stopping 
device 63 is connected with the rod of the plunger 65. When the plunger 63 
is activated, the tip of the stopping device 63 protrudes above the platen 
glass surface as the plunger force is stronger than the spring force. The 
numeral 66 is a guide for an exposed document. The numeral 67 is a 
document delivery tray. Optical sensor PS, which detects a jammed 
documents, is provided at a point halfway along the guide. 
Referring to FIG. 1, a recording paper which has been fixed by the fixing 
unit 17 which is provided in the electrostatic copier 1, is delivered by 
the delivery roller 24 and sorted by the roller 70 of the sorter 20 to be 
stored in the bin 71 of the sorter The recorded paper to be stored into 
the bin 71, is sorted on right and left with regard to the paper delivery 
direction. Accordingly, the recorded paper is sorted into two groups in a 
bin. 
The following is to explain the motion of a copier as an example of the 
embodiments of this invention. 
FIG. 4 is a part of the control circuit diagram of the electrostatic copier 
of the invention. FIG. 5 is a timing chart of the signals which relate to 
the control of the copier. 
At first, several documents are placed on the document tray 50 of the 
automatic document feeder 21 and a plurality of recording papers are 
placed on the lifting base 11 of the recording paper feed unit 10. At this 
moment, the hand feeding unit 12 is at the raised position as illustrated 
by a chain line in FIG. 2. 
By pressing the copying button after the selection of automatic feeding 
mode, document conveyance motor 60 begins to rotate, and the first 
document sheet on the document tray 50 of the automatic document feeder 21 
is conveyed by the conveying roller 59 to the platen glass. 
At the same time the plunger 65 is activated and the stopper 63 protrudes 
from the surface of the platen glass. 
In the mean, time the conveyed document transfers through the passage 61 to 
a pair of feed rollers 62 to be stopped and wait there for a while. 
After the predetermined time, the document is sent from the feed roller 62 
onto the platen glass 2 and conveyed further on the platen glass 2 by the 
belt 53 driven by the motor 69 to the predetermined position, where it is 
hampered and stopped by the stopping device 63, the tip of which is 
protruded above the surface of the platen glass 2. The document is then 
exposed on the platen glass 2 by the exposure unit 3. The reflected light 
from the document is transmitted through a group of mirrors 9 to the 
photoreceptor drum 4 which is electrostatically charged by the 
electrostatic charging unit 5, and the electrostatic latent image is 
formed on the surface of the photoreceptor drum 4. After that, the latent 
image is developed by the developing unit 6 and sent to the transfer and 
separating unit 7. 
During this interval the uppermost recording paper of the recording paper 
stack on the lifting base 11 of the recording paper feed unit 10 is 
conveyed by the recording paper feed roller 13. At that time, double 
feeding is prevented by the double feed preventing mechanism 14. When the 
leading edge of the recording paper reaches at the second recording paper 
feed roller 15, the recording paper is halted and kept waiting in the 
passage 16. 
The electrostatic latent image formed on the photoreceptor drum 4 by a 
sequence of electrophotographic processes is conveyed to the transfer and 
separating unit 7 in accordance with the rotation of the drum 4, then the 
recording paper in the passage 16 is sent to the transferring position by 
the second recording paper feed roller 15. The image is transferred onto 
the recording paper by the transfer and separating unit 7, and the 
recording paper is separated from the drum 4 by the transfer and 
separating unit 7. After that, the recording paper is conveyed to the 
fixing unit 17 by the conveying member 18. After the image is fixed on the 
recording paper, the recording paper is conveyed into the sorter 20 by the 
delivery roller 24. 
The recording paper on which the image is recorded, is delivered to the bin 
71 by the roller 70. Since the bin 7 is moved at this moment upwards and 
downwards by a drive unit not shown in the drawing, the recording paper is 
delivered to the bin 71 in order. 
The first document exposed on the platen glass 2 is conveyed along the 
guide 66 of the automatic document feeder 21 onto the upper surface of the 
delivery tray 67. While this motion is conducted, the second document is 
sent out from the document tray 50. After that, the same motions are 
repeated to copy the succeeding documents. The recorded papers are sorted 
by the sorter 20 and stored in each bin. 
To copy a document of different size on a recording paper of different size 
at a time point t.sub.1 in the half way or after the completion of the 
automatic feeding mode described above, the hand feeding board 37 which is 
in the raised position as shown by a chain line in FIG. 2, is pushed down 
to the lowered position as shown by a solid line in FIG. 2. 
The electrostatic copier is switched from the automatic feeding mode to the 
hand feeding mode by this motion, and the output of the photo coupler 100 
changes as shown in FIG. 5 (A), from L to H in this example. At the same 
time, the recording paper feed roller 13 is raised by the action of the 
lever 38 in FIG. 2. 
When the hand feeding mode is detected in this way, the motor 28 to drive 
the lifting base 11 is reversely rotated for a short time according to the 
direction from the controller 200 as shown in FIG. 5 (F). As a result, the 
lifting base 11 is lowered a little and the recording paper feed roller 13 
is kept at the raised position by a mechanism not shown in the drawing. 
For that reason, the recording papers are smoothly fed along the hand 
feeding board 37 in the hand feeding mode. 
When the copy button is pressed after that, the uppermost recording paper 
on the hand feeding board 37 is fed by the recording paper feed roller 13 
and conveyed to the second recording paper feed roller 15 through the 
double feed preventing mechanism 14 in the same way as the recording paper 
stacked on the lifting base 11. Then, the recording paper is fed by the 
second recording paper feed roller 15 at a predetermined time so that an 
image can be transferred on the recording paper by the transfer and 
separating unit 7. 
When the hand feeding board 37 is raised again after the hand feeding copy 
mode is completed, the output of the photo coupler 100 varies again as 
shown in FIG. 5 (A). It varies from H to L in this case. Accordingly, the 
motor 28 to lift the lifting base 11 is normally rotated for a short time 
and the lifting base 11 is raised to the original position. 
The above are the copying motions when the document size is within the 
predetermined upper limitation. The copying motions when a long document 
which is longer than the said limitation is put on the document tray 50 by 
mistake, will be explained referring to the flow chart in FIG. 6. 
In both the automatic feeding mode and the hand feeding mode, when the copy 
button is pressed, the automatic document feeder 21 operates in the same 
way as when a standard size document is put on document tray 50. The 
document conveyance motor 68 is rotated (F-1) and the first document is 
conveyed by the conveying roller 59. At the same time, the plunger 65 is 
activated and the tip of the stopping device 63 protrudes above the 
surface of the platen glass 2 (F-2). 
When the leading edge of the document passes through optical sensor 
PS.sub.1, a timer built in the controller 200 starts. When the time 
counted by the timer exceeds the passing time of the maximum standard size 
document, the controller 200 judges that the document is a long document 
(F-3) and turns off the activator of the plunger, wherein the passing time 
means the time consumed from the passing of the document's leading edge to 
the passing of the document's trailing edge. The tip of the stopping 
device 63 is withdrawn from the surface of the platen glass 2 by turning 
off the activator of the plunger (F-4). At this moment, the document 
conveyance motor 68 and the belt driving motor 69 which drives the belt 
53, are stopped (F-5), and the jam indicator on the display panel is 
turned on (F-6). 
Since the tip of the stopping device 63 is withdrawn before the long 
document's leading edge comes into contact with it, its leading edge is 
not damaged. Since the document conveyance motor 68 and the belt driving 
motor 69 are stopped, the long document is not deformed and a jam is not 
caused. 
When the operator recognizes that the indicator is turned on, he can remove 
the long document by opening the cover. 
As explained above, in the present invention, when a long document is 
detected by the automatic document feeder, the document stopping device is 
withdrawn and at the same time document feeding is stopped and the jam 
indicator is turned on. Therefore, damage of the long document can be 
surely prevented. 
In the example shown in FIG. 7, after a long document is detected (F-3) and 
the stopping device is withdrawn from the surface of the platen glass 2, 
the document conveyance motor 68 and the belt driving motor 69 which 
drives the belt 53 are kept operating. Thus, the long document passes 
through the guide 66 and is delivered onto the document delivery tray 67. 
When optical sensor PS, detects the trailing edge of the long document and 
the controller 200 judges that delivery of the long document has been 
completed (F-7), the document conveying motor 68 and the belt driving 
motor 69 are stopped (F-8). After that, the indicator on the display panel 
is turned on, which indicates the document is too long to be copied (F-9). 
Since the stopping device 63 is withdrawn before the leading edge of the 
long document comes into contact with the stopping device 63, the 
document's leading edge is not damaged. Furthermore, since the long 
document is completely discharged from the apparatus, it is not necessary 
to open the cover of the apparatus to remove the long document. 
As explained above, in this example, when the automatic document feeder 
detects that the document is a long document, the document stopping device 
is withdrawn and the document is discharged from the apparatus. As a 
result, the document can be prevented from being damaged.