Sheet feeding device and image forming apparatus

Abstract

Discharging subsequent sheets that are not being fed in a double feed to the escape transport path may increase the number of sheets that are discarded. [Solution] The system comprises a first loading section, a second loading section, and a third loading section for loading sheets; a first feeding means and a second feeding means for feeding sheets; a double-feed detection means for detecting double feeding; a first transport means, a second transport means, and a third transport means for transporting sheets; a first transport path and a second transport path through which sheets pass; and a control unit for controlling the transport of sheets. When the double-feed detection means detects double feeding of the first sheet, the control unit stops the transport of the second sheet, which is fed by the second feeding means and follows the first sheet, discharges the first sheet to the third loading section, then feeds the third sheet loaded in the first loading section from the first feeding means, and resumes the transport of the second sheet, which had been stopped.

Description

Technical Field

[0001] The present invention relates to a sheet feeding device and an image forming apparatus including the sheet feeding device.

Background Art

[0002] Generally, in an image forming apparatus that forms an image on a sheet such as a printer, when feeding a sheet, a phenomenon called "double feed" in which a plurality of sheets are fed in an overlapping state is known. When double feed occurs, among the sheets conveyed while overlapping (hereinafter also referred to as double-fed sheets), the sheets that are blank sheets on which no image is formed are discharged as blank sheets.

[0003] Particularly, when performing a binding process or a stapling process on a sheet on which an image is formed, a blank sheet is interposed in the bound or stapled product. Therefore, in Patent Document 1, a double-feed detection means is mounted on a conveyance path through which the fed sheet passes, and when a double-fed sheet is detected, the double-fed sheet is discharged to an escape conveyance path provided so as to branch from a normal conveyance path toward an image forming unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when detecting a double-fed sheet with a double-feed detection means, there may be a case where a subsequent sheet following the double-fed sheet has already started to be fed. In that case, after discharging the subsequent sheet that is not a double feed to the escape conveyance path, the feeding is restarted. That is, by discharging the subsequent sheet that is not a double feed to the escape conveyance path, there is a risk of increasing the number of sheets to be discarded.

[0006] Therefore, the object of the present invention is to provide a sheet feeding device that reduces the discharge of subsequent sheets that have already started to be fed when a double-fed sheet is discharged to an escape conveying path. [Means for solving the problem]

[0007] One aspect of the present invention includes a first loading section for loading sheets, a first feeding means for feeding sheets loaded in the first loading section, a double-feed detection means for detecting double feeding of sheets fed from the first feeding means, a first transport means provided downstream of the double-feed detection means in the sheet transport direction for transporting sheets fed by the first feeding means, a second loading section for loading sheets, a second feeding means for feeding sheets loaded in the second loading section, a second transport means for transporting sheets fed by the second feeding means, a third transport means provided downstream of the first and second transport means in the sheet transport direction for transporting sheets, a first transport path through which sheets pass from the first feeding means to the third transport means in the sheet transport direction, and a branch from the first transport path The system comprises: a second transport path provided at a branch point through which a sheet detected by the double-feed detection means passes; a third loading section provided downstream of the second transport path in the sheet transport direction for loading the sheet detected by the double-feed detection means; and a control unit that controls the transport of the sheet by the first feeding means, the second feeding means, the first transport means, the second transport means, and the third transport means, wherein when the double-feed detection means detects a double-feed of the first sheet, the control unit stops the transport of the second sheet that is fed by the second feeding means and follows the first sheet, discharges the first sheet to the third loading section, then feeds the third sheet loaded in the first loading section from the first feeding means, and resumes the transport of the second sheet that had been stopped. [Effects of the Invention]

[0008] According to the present invention, when a double-feed sheet is discharged to an escape conveyor path, the discharge of subsequent sheets that have already started to be fed can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] Diagram showing the overall configuration of printer 1 according to Embodiment 1 [Figure 2] Diagram showing the configuration of the control unit of the paper deck according to Embodiment 1 [Figure 3] Enlarged view of the feed unit to the transport roller pair according to Embodiment 1 [Figure 4] A diagram showing the ultrasonic reception level according to Embodiment 1. [Figure 5] Flowchart of the double feed detection process by the control unit according to Embodiment 1 [Figure 6] Conveying control of the double-feed sheet and the subsequent sheet when a double-feed sheet is detected according to Embodiment 1 [Figure 7] Timing chart of the double-feed sheet and the subsequent sheet when a double-feed sheet is detected according to Embodiment 1 [Figure 8] Flowchart of double-feed processing by the control unit according to Embodiment 1 [Figure 9] Flowchart of the transport restart process by the control unit according to Embodiment 1 [Modes for carrying out the invention]

[0010] The best mode for carrying out the present invention will be described below with reference to the drawings.

[0011] [Embodiment 1] <Image forming apparatus> Figure 1 is a cross-sectional view showing the overall configuration of the printer 1, which is an image forming apparatus in this embodiment. As shown in Figure 1, the printer 1, which is an image forming apparatus, is configured to include an apparatus body 100, which is the main body of the image forming apparatus that forms images on sheets, and a paper deck 101, which is a sheet feeding device that feeds sheets to the apparatus body 100. The paper deck 101 is connected to the apparatus body 100 and is equipped with large-capacity stackers 110a to 110c that can hold more sheets than the sheet cassettes 61 to 64 inside the apparatus body 100.

[0012] The device body 100 has an image reading unit 21 with a scanning optical system for reading images at the top of the device body, and an image forming unit 22 for forming images on a sheet at the bottom of the image reading unit 21. Below the image forming unit 22, there are multiple sheet cassettes 61 to 64 that house front-loading type sheets that can be inserted and removed from the front of the device body.

[0013] The image forming unit 22 includes image forming stations 23Y, 23M, 23C, and 23K that form images of yellow Y, magenta M, cyan C, and black K. The image forming stations 23Y to 23K are tandem-type image forming units arranged side by side along the intermediate transfer belt 31. The yellow image forming station 23Y consists of a photosensitive drum 11Y and, around this photosensitive drum 11Y, a charging device 12Y, an exposure device 13Y, a developing device 14Y, a primary transfer roller 35Y, and a cleaning blade 15Y.

[0014] The charging device 12Y charges the surface of the photosensitive drum 11Y to a predetermined potential, and the exposure device 13Y forms an electrostatic latent image on the surface of the photosensitive drum 11Y, which has been uniformly charged by the charging device 12Y. The developing device 14Y develops the electrostatic latent image formed on the photosensitive drum 11Y with toner to form a toner image. The primary transfer roller 35Y forms a primary transfer nip between the photosensitive drum 11Y and the intermediate transfer belt 31, and is configured to transfer the toner image on the photosensitive drum 11Y onto the intermediate transfer belt 31 by applying a transfer bias. The cleaning blade 15Y is configured to contact the surface of the photosensitive drum 11 downstream of the primary transfer nip to remove residual toner remaining on the photosensitive drum 11Y after the primary transfer.

[0015] Note that the other image forming stations 23M to 23K have basically the same configuration as the yellow image forming station 23Y mentioned above, except for the toner color used, so their explanation will be omitted.

[0016] The intermediate transfer belt 31 forms a secondary transfer unit T2 that transfers the image formed on the intermediate transfer belt 31 to a sheet together with the secondary transfer inner roller 32 and the secondary transfer outer roller 41 on the downstream side of the black image forming station 23K. Further, a fixing device 5 is provided downstream in the sheet conveyance direction of the secondary transfer unit T2, and the unfixed image on the sheet is fixed to the sheet by being pressurized and heated by this fixing device 5.

[0017] As described above, for example, when the printer 1 prints an image read by the image reading unit 21, the read image information is photoelectrically converted, and images of each color are formed at the image forming stations 23Y to 23K. Then, the images formed at the image forming stations 23Y to 23K are primarily transferred so as to be superimposed on the intermediate belt, and this image is secondarily transferred to a sheet fed from the sheet cassettes 61 to 64 or the paper deck 101 at the secondary transfer unit T2.

[0018] Next, the sheet onto which the image has been transferred at the secondary transfer unit T2 is applied with heat and pressure by the fixing device 5 to fuse the toner image, and if it is in the single-sided image forming mode according to the user's specification, it is discharged outside the apparatus from the discharge port 50. Also, if it is in the double-sided image forming mode, the sheet is conveyed to the reverse conveyance path 52, and in order to reverse the front and back of the sheet, the leading end and the trailing end of the sheet in the sheet conveyance direction are reversed. Then, the reversed sheet is conveyed again to the image forming unit 22 through the double-sided conveyance path 85, and an image is formed on the back surface of the sheet.

[0019] <Paper Deck> Next, the configuration of the paper deck 101 will be explained in detail. As shown in Figure 1, the paper deck 101 is equipped with sheet loading sections 110a to 110c (first loading section 110a, second loading section 110c) which have a larger capacity than the sheet cassettes 61 to 64 provided in the main body 100 of the device. It is also equipped with feeding sections 120a to 120c (first feeding means 120a, second feeding means 120c) corresponding to each sheet loading section 110a to 110c. The feeding sections 120a to 120c are suction conveying means that use a fan (not shown) to handle the sheets on the sheet loading sections 110a to 110c, and then use a belt to suction and convey them, thus constituting a feeding means for feeding the sheets loaded in the sheet loading sections 110a to 110c.

[0020] Furthermore, the paper deck 101 is equipped with a sheet transport path 250, which is a first transport path that guides sheets fed from the sheet loading sections 110a to 110c to the main body of the device 100. It is also equipped with an escape transport path 251, which is a second transport path that branches off from the sheet transport path 250 and guides sheets to an escape tray 232 provided on the upper surface of the paper deck 101. Multiple transport roller pairs 205 to 214 (first transport means 205, second transport means 207, third transport means 214) are arranged on the sheet transport path 250 to transfer the fed sheets to the main body of the device 100.

[0021] In this embodiment, the sheet transport path refers to the path through which the sheet passes, as shown below. This path is from when the sheet is fed from the sheet loading sections 61-64 or 110a-110c, until the image is formed on the sheet, and until the sheet is discharged outside the device (in this embodiment, until it is discharged from the discharge port 50). The sheet transport path 250 constitutes the sheet transport path in the paper deck 101.

[0022] On the other hand, the escape transport path 251 branches upward from the sheet transport path 250 at the branching point 231 downstream of the transport roller pair 213, and the transport roller pair 215 is positioned on the escape transport path 251. The sheets transported by the transport roller pair 215 are discharged into the escape tray 232, which is located at the end of the escape transport path 251 and on the upper surface of the paper deck 101.

[0023] Furthermore, the paper deck 101 is equipped with transport roller pairs 216-220, and an additional paper deck can be connected to the right side of the paper deck 101, allowing for paper feeding from the expanded paper deck as well.

[0024] Furthermore, downstream of the transport roller pairs 205, 206, and 207 that feed the sheets from the feeding sections 120a, 120b, and 120c to the sheet transport path 250, there are double-feed detectors 233a, 233b, and 233c, which serve as double-feed detection means for detecting double feeding of sheets. The escape tray 232 is a double-feed sheet discharge section to which sheets in which double feeding has been detected are discharged via an escape transport path that branches off from the middle of the sheet transport path. Sheets in which double feeding has been detected by the double-feed detectors 233a, 233b, and 233c are discharged to the escape tray 232.

[0025] In this embodiment, the double-feed detectors 233a, 233b, and 233c are composed of an ultrasonic transmitting sensor and an ultrasonic receiving sensor, and when sheets overlap, they determine that a double-feed has occurred based on the degree of attenuation of the ultrasonic waves passing through the sheets. Furthermore, the double-feed detection method does not necessarily have to use an ultrasonic sensor; for example, it may be composed of an optical sensor or the like.

[0026] <Paper Deck Control Unit> The configuration of the control device 300, which serves as the control unit for the paper deck 101, will be explained using Figure 2. As shown in Figure 2, the control device 300 includes a CPU 301 as a calculation means for performing various calculations, and a ROM 302 and RAM 303 that constitute a storage unit. The RAM 303 functions as the working area of ​​the CPU 300, and the ROM 302 stores various programs used to control the paper deck 101. Here, the CPU 301, ROM 302, and RAM 303 are connected by a bus 304.

[0027] Furthermore, the control device 300 is connected to double-feed detection devices 233a, 233b, and 233c, which serve as double-feed detection means. The control device 300 is also connected to a first drive motor 234a that drives the conveyor belt that picks up and conveys the sheets of the conveyor roller pairs 205-214 and the feeding sections 120a, 120b, and 120c. The control device 300 is also connected to a second drive motor 234b that drives the conveyor roller pairs 216-220 and a third drive motor 234c that drives the conveyor roller pair 215. In addition, the control device 300 is also connected to a conveyor switch 235. This conveyor switch 235 is provided at the branching section 231 so as to be movable between a first and second position and has a solenoid as a drive source to change the posture of the switching member. When the switching member is in the first position, it guides the sheet to the sheet conveyor path 250, and when it is in the second position, it guides the sheet to the escape conveyor path 251.

[0028] Here, the ROM 302 stores a double-feed processing program P1 that is executed when the double-feed detectors 236a to 236c detect a double-feed sheet. In this embodiment, the double-feed detector 233a detects a double-feed of a sheet fed from the sheet loading unit 110a. Similarly, the double-feed detector 233b detects a double-feed of a sheet fed from the sheet loading unit 110b, and the double-feed detector 233c detects a double-feed of a sheet fed from the sheet loading unit 110c.

[0029] <Double feed detection in the paper deck's feeding section> Figure 3 is an enlarged view of the vicinity from the feeding unit 120a to the transport roller pair 212. Figures 3(a), 3(b), and 3(c) show the process of the sheet 400 being fed and transported from the feeding unit 120a in chronological order.

[0030] As described above, the double feed detector 233a consists of an ultrasonic oscillating sensor and an ultrasonic receiving sensor. The ultrasonic waves emitted from the ultrasonic oscillating sensor are received by the ultrasonic receiving sensor, and the CPU 301 determines whether or not a double feed has occurred based on the attenuation level of the ultrasonic waves. Therefore, since it is necessary to emit, receive, and determine ultrasonic waves, a predetermined amount of time is required for one double feed detection. In this embodiment, this series of times (sampling time) is set to 25 ms. In addition, the transport speed of the sheet 400 in this embodiment is set to 1000 mm / sec. Figure 3(a) shows the timing of starting double feed detection. Double feed detection starts when the leading edge of the sheet 400 in the transport direction has moved a predetermined distance past the double feed detector 233a. The leading edge of the sheet is prone to excessive flapping due to transport vibrations, making it highly likely to falsely detect a double feed. Therefore, double feed detection starts when the sheet 400 has moved a predetermined distance (flapping stabilization distance) past the double feed detector. In this embodiment, this predetermined distance is set to 20 mm.

[0031] While a double feed is being detected, the sheet 400 continues to be transported, passing through the state shown in Figure 3(b), and finally reaching the double feed detector 233a with respect to the transport direction of the sheet 400, as shown in Figure 3(c). The time it takes to go from the state in Figure 3(a) to the state in Figure 3(c) varies depending on the length of the sheet 400 in the transport direction, so the number of double feed detections Cmax varies depending on the length of the sheet 400 in the transport direction. Cmax can be calculated using equation (1).

[0032]

number

[0033] In equation (1), in this embodiment, Cmax is the number of double feed detections, L is the length of the sheet 400 in the transport direction (mm), b is the flutter stabilization distance (20 mm), V is the transport speed (1000 mm / sec), and S is the sampling time (25 msec).

[0034] Next, Figure 4 shows the received ultrasonic level for each detection count C by the double-feed detectors 233a, 233b, and 233c. In single-feed mode, i.e., when there is no double-feeding, the ultrasonic is received at a high level with little attenuation (single-feed level region in the figure). In double-feed mode, the ultrasonic is attenuated and received at a low level (double-feed level region in the figure). Therefore, a threshold is set for the received level (dotted line in the figure), and the CPU 301 determines that a reception level above this threshold is single-feed, and a reception level below this threshold is double-feed. In other words, Figure 4 shows that the CPU determines that the sheet is double-feeding on the third double-feed detection (C=3).

[0035] Next, the operation of the double-feed detection process performed by the CPU 301 will be explained using Figure 5. This flow is executed each time a sheet is fed from the sheet stacking units 110a, 110b, and 110c. In this embodiment, the explanation will be given for the case where a sheet is fed from the sheet stacking unit 110a.

[0036] In S300, the CPU 301 initializes the double-feed detection count C and Cmax. C is the count value of the current detection number and is stored in RAM 303. C is initially set to 1. Cmax is the maximum number of double-feed detections. In this embodiment, since double-feed detection is performed multiple times in the transport direction of the fed sheet, this number becomes Cmax. For example, if it is A4 paper, substituting the transport direction length of 297 mm into equation (1), Cmax becomes 11.

[0037] In S301, the CPU 301 waits until the sheet is transported to a position where double-feed detection can begin. Specifically, it waits until the sheet 400 is transported to the state shown in Figure 3(a).

[0038] In S302, the CPU301 starts reading using the double-feed detection sensor. As described above, the ultrasonic waves emitted from the ultrasonic oscillation sensor are received by the ultrasonic receiving sensor, and the reception level of the received ultrasonic waves is read by the receiving sensor.

[0039] In S303, CPU301 determines whether or not it is a double feed. As mentioned above, it determines whether or not it is a double feed based on the ultrasonic attenuation level.

[0040] If a double feed is detected in S303 (Yes in the diagram), CPU301 performs post-double feed processing in S304. Then, in S305, CPU301 performs transport restart processing. Post-double feed processing and transport restart processing will be explained later. If it is determined in S303 that there is no double feed (No in the diagram), CPU301 increments C in S306. Then, in S307, CPU301 determines whether C has become greater than Cmax. If it is determined in S307 that C has become greater than Cmax (Yes in the diagram), CPU301 terminates the double feed detection process. If it is determined in S307 that C has not become greater than Cmax (No in the diagram), CPU301 performs double feed detection again.

[0041] <Sheet transport control after detecting double-feed sheets> Next, Figure 6 shows the control of transporting the double-feed sheet after detecting the double-feed sheet, and the subsequent sheets that have already started feeding and are stuck in the sheet transport path. In this printing job, for example, one sheet is fed from the sheet stacking unit 110a, one sheet is fed from the sheet stacking unit 110c, and then one sheet is fed from the sheet stacking unit 110a, and so on, with alternating feeding.

[0042] Figure 6(a) shows the case where the first sheet is fed from the sheet loading unit 110a and the double-feed detector 233a determines that it is a double-feed. This first sheet is referred to as the double-feed sheet 501. At this time, the subsequent single-feed sheet 502 has already been fed from the sheet loading unit 110c. In this case, the double-feed sheet 501 is discharged into the escape tray 232, but if the subsequent single-feed sheet 502 is also discharged into the escape tray 232, the number of sheets to be discarded will increase.

[0043] Therefore, when the double-feed sheet 501 is ejected, the subsequent single-feed sheet 502 is stopped on the sheet transport path, as shown in Figure 6(b). Then, as shown in Figure 6(c), after the re-feed sheet 503 for the double-feed sheet 501 is fed from the sheet loading section 110a, the transport of the single-feed sheet 502, which had been stopped, is resumed. This makes it possible to resume the print job without increasing the number of sheets discarded other than the double-feed sheet. Note that since the print job resumes from the double-feed sheet, the resumption process is the same whether the double-feed occurs on the first sheet or on the second or subsequent sheets, so no distinction is made.

[0044] Next, Figure 7 shows a timing chart for the sheet transport of the double-feed sheet and the subsequent sheet after double-feed sheet detection. Each timing (a), (b), and (c) in Figure 7 indicates the timing of the sheet position shown in Figures 6(a), (b), and (c), respectively.

[0045] In Figure 7, the job execution status is indicated as High when the job is running and as Low during other periods. The double-feed detection determination status is indicated as High when the double-feed detector 233a detects a double-feed and as Low during other periods. The transport roller pair 205 drive status is indicated as High when the transport roller pair 205 is being driven and as Low during other periods. Similarly, the transport roller pair 207 drive status is indicated as High when the transport roller pair 207 is being driven and as Low during other periods.

[0046] Furthermore, time T1 is the time from the start of transporting the double-feed sheet until the transport roller pair 207 stops, and this information is necessary to control the timing of restarting the drive of the transport roller pair 207. This control will be explained later.

[0047] <Post-fetching processing after detecting a double-fetched sheet> Next, we will explain the details of the post-double feed processing performed by the CPU 301 after detecting a double feed of sheets, using Figure 8. Figure 8 shows the operation of the double feed processing performed by the CPU 301 in the post-double feed processing shown in Figure 5.

[0048] First, in S700, the CPU 301 performs a transport path switch (251). Specifically, it switches the orientation of the switching member of the branch section 231 to the second position. In S701, it drives the transport roller pair 215. This makes it possible to discharge the sheet 400 that has been transported on the escape transport path 251 into the escape tray 232.

[0049] In S702, roller pairs other than those in the double-feed sheet transport path are stopped. Specifically, in Figure 6, transport roller pairs 206-211, 214, and 216-220 are stopped.

[0050] In S703, the time T1 from the start of transport of the double-feed sheet to the stop of transport of the transport roller pair is recorded.

[0051] In S704, the CPU 301 waits until the double-feed sheet 400 is discharged into the escape tray 232. Specifically, it waits until the sheet detection sensor 240 located downstream of the transport roller pair 215 detects the rear end of the sheet 400. When the rear end of the sheet 400 is detected by the sheet detection sensor 240, it determines that the sheet 400 has been discharged into the escape tray 232.

[0052] In S705, it checks if the job during double feeding has been canceled. If it has been canceled (No. in the diagram), S706 drives the transport roller pair, and in S707, the CPU 301 waits until the sheets that have accumulated in the sheet transport path are discharged into the escape tray 232.

[0053] In S708, the CPU 301 stops the transport roller pair 215. In S709, the transport path switching (250) is performed. This returns the orientation of the switching member of the branching section 231 to the first position. After that, the CPU 301 finishes the post-double feed processing.

[0054] <Processing to resume transport after detecting a double-feed sheet> Next, we will explain the details of the transport restart process that the CPU 301 executes after detecting a double feed of sheets, using Figure 9. Figure 9 shows the operation of the transport restart process performed by the CPU 301 in the post-double feed processing shown in Figure 5.

[0055] In S800, it is determined whether the job during double feeding has been canceled. If it has not been canceled and the same job is to be resumed (indicated by No. in the diagram), S801 starts transporting the re-fed sheet in order to feed the sheet again. At this time, the subsequent sheet that has already been fed is already on the sheet transport path and not on the sheet loading section 110, so the transport timing needs to be adjusted to follow the re-fed sheet.

[0056] Therefore, in S802, the CPU 301 waits until time T1 has elapsed, and then in S803, it resumes transporting the subsequent sheet to follow the re-fed sheet. Here, time T1 is the time in the previous job from when the double-fed sheet started to transport until the subsequent sheet moved to its current stopping position. In other words, even if the distance between the re-fed sheet and the subsequent sheet is the same as during normal transport, this occurs after time T1 has elapsed since the re-fed sheet started to feed. Therefore, by delaying the resumption of transport of the subsequent sheet by time T1, the subsequent sheet can be transported with the same distance between sheets as during normal transport.

[0057] If a job during double-feeding is canceled in S800 (Yes in the diagram), a new job is started in S804. After that, CPU301 terminates the transport restart process.

[0058] As in this embodiment, when a double-feed sheet is discharged to the escape tray, subsequent sheets that have already been fed are stopped on the transport path, and transport is resumed when the next re-feed sheet is re-feeded. This allows the job to be resumed without increasing the number of sheets that are discarded in addition to the double-feed sheet.

[0059] Furthermore, in the above-described embodiment, the double-feed sheet is fed from the sheet loading section 110a and the subsequent sheet is fed from the sheet loading section 110c. However, the present invention is concerned with transport control when the subsequent sheet has already been fed when the double-feed sheet is detected. In other words, the sheet loading section to which the sheets are fed is not limited to the above combination. Also, in the above-described embodiment, only the paper deck 101 was used, but it may also include feeding from the sheet loading section of an extended paper deck, as explained in Figure 1. [Explanation of Symbols]

[0060] 110a, 110b, 110c Loading section (1st loading section, 2nd loading section) 120a, 120b, 120c Feeding section (first feeding means, second feeding means) 233a, 233b, 233c Double feed detector (double feed detection means) 205, 206, 207 Conveyor rollers (first conveying means, second conveying means) 214 Conveyor roller (third conveying means) 231 Branching point 232 Escape Tray (Third Loading Section) 250-sheet conveying path (first conveying path) 251 Escape transport path (second transport path) 300 Control device (control unit)

Claims

1. The first loading section for loading the sheets, A first feeding means for feeding the sheets loaded in the first loading section, A double-feed detection means for detecting double feeding of sheets fed from the first feeding means, A first conveying means is provided downstream of the double-feed detection means in the sheet conveying direction and conveys the sheet fed by the first feeding means, The second loading section for loading the sheets, A second feeding means for feeding the sheets loaded in the second loading section, A second conveying means for conveying the sheet supplied by the second feeding means, A third conveying means is provided downstream of the first and second conveying means in the sheet conveying direction and conveys the sheet, A first transport path through which the sheet passes from the first feeding means to the third transport means in the sheet transport direction, A second transport path is provided, branching off from the first transport path, through which the sheet detected by the double-feed detection means passes. A third loading section is provided downstream of the two transport paths in the sheet transport direction and loads sheets detected by the double-feed detection means, The system comprises a control unit that controls the transport of the sheet by the first feeding means, the second feeding means, the first transport means, the second transport means, and the third transport means, When the double-feed detection means detects a double-feed of the first sheet, the control unit stops the transport of the second sheet that is being transported by the second feeding means and is following the first sheet, discharges the first sheet to the third loading section, then transports the third sheet loaded in the first loading section from the first feeding means, and resumes the transport of the second sheet that had been stopped. A sheet feeding device characterized by the following features.

2. If the double-feed detection means does not detect a double-feed of the first sheet, the control unit will transport the second sheet without stopping the transport of the second sheet that is fed by the second feeding means and that follows the first sheet. The sheet feeding device according to feature 1.

3. It has a storage unit that stores the time from the start of transport of the first sheet by the first transport means to the stop of transport of the second sheet by the second transport means, as detected by the double-feed detection means, The control unit restarts the transport of the second sheet, which had been stopped after the time stored by the storage unit had elapsed since the start of the third sheet's feeding. A sheet feeding device according to claim 1, characterized in that...

4. The control unit, when the double-feed detection means detects a double-feed of the first sheet and the job is canceled, discharges the sheets remaining in the first transport path to the third loading unit. The sheet feeding device according to feature 1.

5. A sheet feeding device according to any one of claims 1 to 4, An image forming unit that forms an image on a sheet fed by the sheet feeding device, An image forming apparatus equipped with the following features.

Images