JP2006176245A - Paper sheet conveyor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper sheet conveyor capable of rapidly eliminate double feed without manually taking out any double-fed paper sheet (a white paper or the like) or without performing any preliminary feed. <P>SOLUTION: The paper sheet conveyor is capable of conveying a paper sheet or an original at a predetermined speed and separating a preceding paper 21 and a succeeding paper 22 which are double-fed. The paper sheet conveyor comprises an upstream side roller 4, a downstream side roller 6 which is adjacent to the upstream side roller 4 and arranged at a spacing below the length in the conveying direction of a paper sheet 2, a first detector 5 which forms a pair with the upstream side roller 4 to detect a preceding end and a succeeding end of the preceding paper 21 and the succeeding paper 22, and a second detector 7 which forms a pair with the downstream side roller 6 to detect the preceding end and the succeeding end of the preceding paper 21 and the succeeding paper 22. When the first detector 5 detects the preceding end of the conveyed preceding paper 21 and cannot detect the succeeding end thereof, the rotation of the downstream side roller 6 is continued, the conveyance of the preceding paper 21 is continued, the upstream side roller 4 is stopped, and the succeeding paper 22 is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a paper transport device, and in particular, in a paper transport device that transports paper of a printer or a copying machine by a transport roll at a constant interval and at a constant speed, it detects the double feed of the paper and controls rotation / stop of the transport roll. The present invention relates to a paper transport device that can separate papers that have been double fed and continue paper feeding.

Conventionally, when a double feed of paper (white paper, etc.) of a printer or a copying machine is detected, the paper feed is stopped and the double fed paper is taken out.
On the other hand, Patent Document 1 discloses an automatic document feeder that continuously conveys a document without taking out the double-fed document. Specifically, after detecting a double feed of a document, the subsequent document is fed forward and returned to the document tray so that the document tray can supply the double feed document, and then the paper adjacent to the document exit is scanned. The double feed is released by increasing the pressure of the roller. The reason for increasing the pressure of the winding roller only at the time of releasing the double feed is that if a high pressure is always applied to the winding roller, the roller may be broken or the original may be damaged.
Japanese Patent Laid-Open No. 5-105281 (FIG. 3, paragraph 0095)

However, in conventional printers and copiers, even if double paper feed is detected, the double-fed paper must be taken out, and it takes time and effort to eliminate the double feed.
Further, in Patent Document 1, if double feed of a document is detected, double feed is eliminated without requiring manual work. However, it takes time to skip the document. For example, if the 99th and 100th of 100 originals are double-fed, 99 sheets need to be fed forward, so even if the copying process is 1 sheet / second, the waiting time is as long as 99 seconds. It will be time.
SUMMARY OF THE INVENTION An object of the present invention is to provide a paper transport apparatus that can quickly eliminate double feeding without manually taking out the double-fed paper and without feeding the original document. Accordingly, an object of the present invention is to provide a paper transport apparatus that can be used for transporting a document.

In the present invention, when double feeding is detected near a certain roller, only the preceding paper is passed through the roller, but the succeeding paper is stopped to prevent the succeeding paper from passing through the roller.
Further, when the passage of the preceding paper is detected in the vicinity of the roller adjacent to the roller and downstream thereof, the conveyance of the succeeding paper is resumed.
The succeeding sheet whose conveyance has been resumed is once again stopped at a predetermined position and conveyed in synchronization with the printing process or the copying process.
Note that if the passage of the preceding paper alone is not detected near the downstream roller, the preceding paper itself is being double fed, and the paper transport device is stopped.

  Specifically, the present invention is a paper transport device capable of transporting a paper at a constant speed and separating a preceding paper and a succeeding paper to be fed, and is adjacent to an upstream roller and the upstream roller. A first roller for detecting the leading edge and the trailing edge of each of the preceding paper and the succeeding paper, which is provided corresponding to the downstream roller disposed at an interval smaller than the length in the conveyance direction of the paper and the upstream roller. And a second detector provided corresponding to the downstream roller and detecting the leading edge and the trailing edge of the preceding paper and the succeeding paper, and the first detector is conveyed. If the leading edge of the preceding paper that has been detected is detected but the trailing edge cannot be detected, the downstream roller continues to rotate and continues to convey the preceding paper, while the upstream roller is stopped and the succeeding paper is stopped. Equipped with a control device to stop To.

Further, the present invention is characterized in that the first detector is disposed close to the upstream roller.
According to the present invention, there is provided the sheet conveying apparatus according to the first invention, wherein the second detector is disposed in proximity to the downstream roller.
The present invention also provides a memory for storing the timing at which the leading edge and the trailing edge of the sheet are detected, and a sheet of paper as the first detector or the second sensor based on the timing at which the leading edge of the preceding sheet is detected. The rotation and stop of the upstream roller and the downstream roller are controlled on the basis of a timer that counts a predetermined time required to pass through the detector, and the output of the timer and the contents of the memory. And a CPU.
Further, in the present invention, when the first detector detects the leading edge of the preceding paper and does not detect the trailing edge of the preceding paper even after the predetermined time has elapsed, the CPU detects the upstream of the upstream paper. The side roller is stopped.

In the present invention, when the second detector detects the trailing edge of the preceding paper after the predetermined time has elapsed after detecting the leading edge of the preceding paper, the CPU detects the upstream roller. The conveyance of the succeeding paper is resumed by re-rotating.
In the present invention, when the second detector detects the leading edge of the succeeding paper, the CPU temporarily stops the downstream roller, and the trailing edge of the preceding paper and the leading edge of the succeeding paper are It is characterized by re-rotating from a certain distance.
According to the present invention, if the second detector detects the leading edge of the preceding paper and does not detect the trailing edge of the preceding paper even after the predetermined time has elapsed, the CPU detects the upstream of the upstream paper. The side roller and the downstream roller are stopped.
In the present invention, the first detector and the second detector each include a light source and a light detector arranged on one surface side of the paper, and light from the light source is reflected by the paper. It is characterized by detecting whether or not.

  According to the present invention, the first detector and the second detector include a light source disposed on one surface side of the sheet and a photodetector disposed on the other surface side of the sheet. And detecting whether light from the light source is blocked by the paper.

  According to the present invention, it is possible to quickly eliminate the double feed without manually taking out the double-fed paper and without feeding the original in the idle state. Accordingly, it is possible to provide a paper transport device that can be used for transporting printing paper and documents.

Hereinafter, embodiments of the invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram of a paper transport device. The sheet conveying apparatus of this embodiment is used in a printing sheet supply system in an image forming apparatus such as a so-called MFP used as a printer, a facsimile machine, or a copier.
The state of the preceding paper 21 and the succeeding paper 22 relating to the multifeed shown in FIG. 1 is a state in which the preceding paper 21 is conveyed while the succeeding paper 22 is stopped. The preceding paper is conveyed to the stage where the leading edge of the paper 22 is slightly overlapped, and represents a state immediately before the double feed is canceled.
Hereinafter, each part of the sheet conveying apparatus will be described.
A large number of sheets having predetermined dimensions are stacked on the sheet tray 1. Since the A4 size, B4 size, and other sizes are different, a paper tray 1 having a predetermined specification is prepared for each.
The paper 2 is usually the bottom or top one of the stacked ones.
The separation roller 3 is a transport roller for taking out the paper 2 to the outside of the paper feed tray 1, and is a pair of rollers that rotate reversely with the paper 2 interposed therebetween.
The upstream roller 4 is a conveyance roller for conveying the paper 2 conveyed from the separating roller 3 further downstream. It should be noted that the arrangement interval between the separation roller 3 and the upstream roller 4 is set to be less than the length in the conveyance direction of the minimum size paper 2 so that the paper 2 of various sizes can be transferred from the separation roller 3 to the upstream roller 4. To.
The downstream roller 6 is a conveyance roller for conveying the sheet 2 conveyed from the upstream roller 4 further downstream. It should be noted that the arrangement interval between the upstream roller 4 and the downstream roller 6 is set to be less than the length in the conveyance direction of the paper 2 having the smallest dimension, whereby the paper 2 having various dimensions can be transferred to the upstream roller 4 and the downstream roller 6. It can be done.

In FIG. 1, a sheet 2 is fed from a sheet feed tray 1 in which sheets of minimum dimensions are stacked.
The first detector 5 that functions as a double feed detector is a paper sensor disposed between the upstream roller 4 and the downstream roller 6. For example, the first detector 5 includes a light source and a light detector. Is incident on the paper 2 to detect the presence or absence of reflected light. Although not shown, the first detector 5 includes a light source disposed on one side of the sheet 2 and a photodetector disposed on the other side of the sheet. It may be a method of detecting whether or not the light is blocked by the paper 2.
When double feeding occurs, the trailing edge cannot be detected even after a predetermined time has elapsed after detecting the leading edge of the preceding paper 21 related to double feeding. Here, the fixed time is a time that will be required for one sheet 2 conveyed at a constant speed to pass through the first detector 5. For example, when A4 size paper 2 is laterally fed at a conveyance speed of 600 mm / s, the predetermined time is 210 mm / 600 mm / s (= 350 ms).

In FIG. 1, the first detector 5 is disposed close to the downstream side of the upstream roller 4. Here, the close arrangement means that the first detector 5 is arranged as close as possible to the extent that it does not contact the upstream roller.
The arrangement interval between the upstream roller 4 and the downstream roller 6 is set to be less than the length in the conveyance direction of the paper 2 having the smallest dimension, and the first detector 5 detects the leading edge of the preceding paper 21, and then the above-mentioned fixed interval. After the elapse of time, the leading edge of the preceding paper 21 has already passed the downstream roller 5, and the succeeding paper 22 follows the preceding paper 21. Therefore, if the first detector 5 cannot detect the trailing edge of the preceding paper 21 after the predetermined time has elapsed after the leading edge of the preceding paper 21 is detected, it can be understood that double feeding has occurred. In the method of this embodiment, when the deviation is zero, double feeding cannot be detected.

The discharge roller 8 is a transport roller for transporting the paper 2 transported from the downstream roller 6 further downstream and delivering it to a printer unit or a copy unit (not shown). The arrangement interval between the downstream roller 6 and the discharge roller 8 is set to be less than the length in the conveyance direction of the minimum size paper 2 so that the paper 2 of various sizes can be transferred from the downstream roller 6 to the discharge roller 8. To.
The second detector 7 that functions as a separation detector is a paper sensor disposed between the downstream roller 6 and the discharge roller 8, and has the same configuration as the first detector 5.
If the time difference between the time when the leading edge of the paper 2 is detected and the time when the trailing edge is detected is a predetermined time based on the signal from the second detector 7, it is determined that the preceding paper 21 has been separated from the succeeding paper 22. be able to.

In FIG. 1, the second detector 7 is disposed close to the downstream side of the downstream roller 6. The arrangement interval between the downstream roller 6 and the discharge roller 8 is set to be less than the length in the conveyance direction of the paper 2 having the minimum dimension, and the above-described fixed time period after the second detector 7 detects the leading edge of the preceding paper. After the lapse, the trailing edge of the preceding paper 21 should have reached the second detector 7. Conversely, when the preceding paper 21 is not separated from the succeeding paper 22 due to the arrangement of the second detector 7, the paper conveying device is stopped and the paper 2 is prevented from being discharged from the discharge roller 8. It becomes possible to do.
The configuration of the sheet conveying device has been described above with reference to FIG. 1, but the embodiment is not limited to this.

First, the first detector 5 and the second detector 7 do not have to be arranged close to the upstream roller 5 and the downstream roller 7, respectively. The first detector 5 and the second detector 7 may be arranged upstream or downstream of the upstream roller 5 and upstream or downstream of the downstream roller 7, respectively, and can be arranged in four types. It is. However, if the second detection device 7 is arranged on the downstream side of the discharge roller 8, the preceding paper 21 may be discharged from the discharge roller 8 when the preceding paper 21 itself is being fed in a multiple manner. The first detector 5 and the second detector 7 may be a pressure sensor or a capacitance sensor. Furthermore, the first detector 5 may be an optical sensor, and the second detector 7 may be a capacitance sensor.
Moreover, the diameter, material, etc. of each roller do not necessarily need to be the same. Further, an auxiliary roller may be arranged between the above-described rollers for stable conveyance of the paper 2 or the like. Further, the paper 2 is not limited to the printing paper, and may be a document to be read.

FIG. 3 is a block diagram of a control unit that controls rotation / stop of the transport rollers 3, 4, 6, and 8.
The control unit 90 stores a memory 91 that stores the timing at which the leading edge and the trailing edge of the sheet 2 are detected, and a sheet of paper 2 based on the timing at which the leading edge of the preceding sheet 21 is detected as the first detector or A timer 92 that counts a predetermined time required to pass through the second detector, a rolling roller 3, an upstream roller 4, and a downstream side based on the output of the timer 92 and the contents of the memory 91 A CPU 93 that controls the rotation or stop of the roller 6 and the discharge roller 8 via the output I / F 95 and the roller driving unit 100 is provided.

FIG. 2 is a timing chart of signals output from the first detector 5 and the second detector 7, showing the timing of double feed detection and separation control by the control of the control unit 90. The horizontal axis is the time axis, and the vertical axis is the high level and the low level, but this is not particularly shown.
FIG. 2A is a timing chart of signals output from the first detector 5 and the second detector 7 when there is no double feed. In this case, the separating roller 3, the upstream roller 4, the downstream roller 6, and the discharge roller 8 are all rotating.
First, timings t1 to t9 on the time axis will be described mainly in relation to the first detector 5.
For simplicity, the distance between the first detector 5 and the second detector 7 is assumed to be equal to the length of the paper 2 in the transport direction.
Further, the interval between the preceding paper 21 and the succeeding paper 22 is assumed to be equal to the length of the paper 2 in the conveyance direction.
Further, the first detector 5 and the second detector 7 are arranged close to the upstream roller 4 and the downstream roller 6 (as shown in FIG. 1, the first detector 5 and the second detector 7). Are arranged as close as possible so as not to contact the upstream roller 4 and the downstream roller 6, respectively.

2A and 2B, timing t1 is timing when the first detector 5 detects the leading edge of the preceding paper 21.
Timing t <b> 2 is timing when the first detector 5 detects the trailing edge of the preceding paper 21.
Timing t3 is timing when the upstream roller 5 stops.
Timing t <b> 4 is timing when the first detector 5 detects the leading edge of the succeeding paper 22.
Timing t5 is timing when the upstream roller 5 resumes rotation.
Timing t <b> 6 is timing when the first detector 5 detects the trailing edge of the succeeding paper 22.
Timing t7 is a timing at which the second detector 7 detects the leading edge of the succeeding paper 22 and stops the succeeding paper 22.
Timing t8 is timing when the first detector 5 re-transports the succeeding paper 22.
Timing t9 is a timing at which the first detector 5 detects the leading edge of the paper 2 following the succeeding paper 22.
In the case of no double feed, the signal of the second detector 7 is a signal obtained by delaying the signal of the first detector 5 by a time difference (t2−t1).

FIG. 2B shows the output signals of the first detector 5 and the second detector 7 when there is a double feed, and the states of the upstream roller 4 and the downstream roller 6 (the high level is rotating, the low level is low). It is a timing chart showing that the level is stopped.
First, the signal of the first detector 5 will be described.
The first detector 5 detects the leading edge of the preceding paper 21 at timing t1, which is the same as in the case of no double feed. However, the first detector 5 cannot detect the trailing edge of the preceding paper 21 even after the timing t2, and the upstream roller 4 stops rotating by the control unit 90. For the time being, The output signal remains high.
The first detector 5 detects the trailing edge of the succeeding paper 22 at a timing t6 after the upstream roller 5 is rotated again, and the output signal becomes a low level. Here, the timing t6 is before the timing t8. The time difference (t8−t6) depends on the difference between the leading edge of the preceding paper 21 and the leading edge of the succeeding paper 22 in the double feed state. In addition, when the deviation is zero, double feeding cannot be detected.
Further, at timing t9, the first detector 5 detects the leading edge of the sheet 2 following the succeeding sheet 22 as usual.

Next, the signal of the second detector 7 will be described.
The second detector 7 detects the leading edge of the preceding paper 21 at timing t2, which is the same as in the case of no double feed.
Further, the second detector 7 should detect the trailing edge of the preceding paper 21 at timing t4 (except when the preceding paper 21 itself is double-feeding). The same. Even when the preceding paper 21 itself is conveyed with the leading ends of the two sheets 2 matched, the second detector 7 detects the trailing edge of the preceding paper 21 at timing t4.
Further, the second detector 7 detects the leading edge of the succeeding paper 22 at timing t7. This is because the upstream roller 4 resumes rotation and the succeeding paper 22 has been conveyed.
At timing t6, the leading edge of the succeeding paper 22 has not yet reached the downstream roller. Therefore, the leading edge of the succeeding paper 22 is detected at timing t7 after timing t6. Further, since the succeeding sheet 22 has followed the preceding sheet with a delay of a distance shorter than the length of the sheet 2 in the transport direction, the leading end of the succeeding sheet 22 is detected at a timing t7 before the normal timing t8. The time difference (t8−t7) is a time interval for stopping the succeeding paper 22 in order to synchronize with the printing process or the copying process.

Next, the state of the upstream roller 4 will be described.
The upstream roller 4 stops rotating at a timing t3 slightly delayed from the timing t2. The time difference (t3−t2) is a time required to determine that the feed is a double feed, and the smaller the better.
Since the leading edge of the succeeding paper 22 stops on the upstream side of the upstream roller 4 due to the stop of the upstream roller 4, the preceding paper 21 and the succeeding paper 22 can be separated thereafter. Note that it is not necessary to stop the roller 3. The reason for this is that the double feed elimination process is completed up to timing t9, and the conveyance of the sheet 2 following the succeeding sheet 22 returns to the normal state.

  The upstream roller 4 resumes rotation at a timing t5 slightly delayed from the timing t4. The reason is that the control unit 90 finds that the preceding sheet 21 has been conveyed by only one sheet at timing t4 (except when the two sheets 2 are completely overlapped and integrated). This is because it is determined that the preceding sheet and the succeeding sheet 22 have been separated. The time difference (t5−t4) is a time required for the separation determination, and is preferably as small as possible.

Next, the state of the downstream roller 6 will be described.
The downstream roller 6 stops rotating at the timing t7 and restarts after a time difference (t8−t7). As a result, the timing at which the first detector 7 detects the trailing edge of the succeeding paper 22 can be aligned with the timing t9 when there is no double feed, and the double feed is synchronized with the printing process or the copying process. The conveyance of the succeeding paper 22 can be resumed.
Note that if the downstream roller 6 is stopped at the timing t7, the leading edge of the succeeding paper 22 stops on the upstream side of the downstream roller 6, and therefore the rotation of the discharge roller 8 may be continued.
Although not shown, when the second detector 7 does not detect the trailing edge of the preceding paper 21 at the timing t4, the preceding paper 21 itself has been double-feeded, so that the rotation of all the rollers is stopped. It is necessary to take out the stacked preceding paper.

As described above, the operation of the sheet conveying device has been described based on the output signals of the first detector 5 and the second detector 7 with reference to FIG. 2, but the embodiment is not limited to this. .
First, the distance between the first detector 5 and the second detector 7 may not be equal to the length of the paper 2 in the transport direction.
Further, the interval between the preceding paper 21 and the succeeding paper 22 may not necessarily be equal to the length in the transport direction of the paper 2 depending on the printing process or the like.
Further, as already described in the description of FIG. 1, the first detector 5 and the second detector 7 may not be arranged in the immediate vicinity of the upstream roller 4 and the downstream roller 6, respectively.
The first detector 5 and the second detector 7 can be arranged at any position on the upstream side or downstream side of the upstream roller 5 or on the upstream side or downstream side of the downstream roller. Different types of arrangements are possible.

The memory 91 provided in the control unit 90 stores each timing shown in FIG. 2 in a predetermined area via the input I / F and the CPU 93.
In addition, the timer 92 measures the above-mentioned fixed time based on an instruction from the CPU 93.
Accordingly, when the first detector 5 cannot detect the trailing edge of the preceding paper 21 at the timing t3 shown in FIG. 2, the CPU 93 stops the upstream roller 4.
When the second detector 7 detects the trailing edge of the preceding paper 21 at the timing t4 shown in FIG. 2, the upstream roller 4 is rotated again by the CPU 93.
When the second detector 7 detects the leading edge of the succeeding paper 22 at the timing t7 shown in FIG. 2, the downstream roller 6 is stopped by the CPU 93, and the trailing edge of the preceding paper 21 is detected. The succeeding paper 22 is rotated again at a timing t8 when the leading edge of the succeeding paper 22 becomes a certain distance.
If the second detector 7 cannot detect the trailing edge of the preceding paper 21 at the timing t4 shown in FIG. 2, all the rollers (the rolling roller 3, the upstream roller 4, the downstream roller 6, The discharge roller 8) is stopped by the CPU 93.

FIG. 4 is a flowchart in a case where multifeed detection and separation are performed by software.
First, in S10, it is determined by the CPU 93 based on the signal from the first detection means 5 whether or not the double feed of the paper 2 is detected. Here, the double feed refers to a state in which the leading edge of the preceding paper 21 and the leading edge of the succeeding paper 22 are misaligned and conveyed together.
If the double feed of the paper 2 is not detected in S10, the detection of the double feed of the paper 2 is awaited.
On the other hand, if double feeding of the paper 2 is detected in S10, the process proceeds to S20.

In S20, the conveyance of the preceding paper 21 is continued and the conveyance of the subsequent paper 22 is stopped.
In the subsequent S30, the time required for the preceding paper 21 to finish passing through the second detector 7 is the above-mentioned fixed time (the time required for one sheet 2 to pass through the second detector 7). ) Is determined by the CPU 93.
In S30, if the time required for the preceding paper 21 to finish passing through the second detector 7 exceeds the predetermined time described above, the double feed has not been eliminated even if it passes through the first detector 5. The process proceeds to S35.
In S35, in order to prevent the sheet 2 from being discharged from the discharge roller, the sheet conveying device is stopped and all the processes are ended. Thereafter, the stacked sheets 2 are taken out.
On the other hand, in S30, when the time required for the preceding paper 21 to finish passing through the second detector 7 is the above-described fixed time, the process proceeds to S40.

In S40, since it is confirmed that the preceding paper 21 and the succeeding paper 22 are separated, the transport of the succeeding paper 22 is resumed, and the time when the leading edge of the succeeding paper 22 is detected by the second detector 7 (timing t7). Then, the succeeding paper 22 is temporarily stopped.
In S50, at the timing t8 when the second detector 7 will detect the leading edge of the succeeding sheet 22 when there is no double feed, the transport of the succeeding sheet 22 is resumed and the subsequent process is synchronized with the printing process or the copying process. The paper 22 is discharged from the paper transport device, the double feed process is completed, and all the processes are completed. After that, it automatically returns to normal conveyance processing.

FIG. 3 is a conceptual diagram of a paper transport device. It is a timing chart of the output signal etc. of a 1st detector and a 2nd detector. It is a block diagram of the control part which controls rotation and a stop of an upstream roller and a downstream roller. 6 is a flowchart for eliminating double feeding of paper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper feed tray 2 Paper 21 Prior paper 22 Subsequent paper 3 Rolling roller 4 Upstream roller 5 First detector 6 Downstream roller 7 Second detector 8 Discharge roller 90 Control part 91 Memory 92 Timer 93 CPU 94 Input I / F (interface)
95 Output I / F (interface)
100 Roller drive

Claims (10)

In a paper transport device that transports paper used as a print document or print paper,
An upstream roller;
A downstream roller disposed on the downstream side of the upstream roller at a distance less than the length of the sheet in the conveyance direction;
A first detector that is provided corresponding to the upstream roller and detects a leading edge and a trailing edge of each of the preceding paper and the succeeding paper;
A second detector provided corresponding to the downstream roller and detecting the leading edge and the trailing edge of each of the preceding paper and the succeeding paper;
When the first detector detects the leading edge of the preceding paper that has been conveyed but cannot detect the trailing edge, it continues the rotation of the downstream roller to continue the conveyance of the preceding paper, And a control device for stopping the succeeding paper by stopping the upstream roller. The sheet conveying device according to claim 1,
The paper transporting apparatus, wherein the first detector is disposed close to the upstream roller. The sheet conveying device according to claim 1,
The paper transporting apparatus, wherein the second detector is disposed close to the downstream roller. The sheet conveying device according to claim 1, wherein the control device includes:
A memory for storing the timing of detecting the leading edge and the trailing edge of the paper;
A timer that counts a certain time required for one sheet to pass through the first detector or the second detector based on the timing at which the leading edge of the preceding sheet is detected;
A sheet conveying apparatus comprising: a CPU that controls rotation or stop of the upstream roller and the downstream roller based on the output of the timer and the contents of the memory. The sheet conveying device according to claim 4,
After the first detector detects the leading edge of the preceding paper, after the predetermined time has passed, if the trailing edge of the preceding paper cannot be detected,
The sheet conveying device, wherein the CPU stops the upstream roller. The sheet conveying device according to claim 5,
When the second detector detects the trailing edge of the preceding paper after the predetermined time has elapsed after detecting the leading edge of the preceding paper,
The CPU is configured to restart the conveyance of the succeeding sheet by re-rotating the upstream roller. The sheet conveying device according to claim 6,
When the second detector detects the leading edge of the succeeding paper,
The CPU further stops the downstream roller and causes the downstream roller to rotate again after the trailing edge of the preceding paper and the leading edge of the succeeding paper have reached a certain distance. The sheet conveying device according to claim 4,
When the second detector cannot detect the trailing edge of the preceding paper after the predetermined time has elapsed after detecting the leading edge of the preceding paper,
The CPU is configured to stop the upstream roller and the downstream roller. The sheet conveying device according to claim 1,
The first detector and the second detector are:
A light source and a photodetector disposed on one side of the paper;
A paper conveying apparatus that detects whether or not light from the light source is reflected by the paper. The sheet conveying device according to claim 1,
The first detector and the second detector are:
A light source disposed on one side of the paper;
A photodetector disposed on the other side of the paper,
A paper conveying apparatus that detects whether or not light from the light source is blocked by the paper.

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