Paper feeder

Abstract

To provide a paper feeding device that can reduce a work of taking off overlapped feed sheets and accumulated sheets generated in a conveyance passage.SOLUTION: A paper feeding device comprises: a sheet conveyance passage extending from an upstream side toward a downstream side; a conveying roller pair that conveys a sheet along the conveyance passage; a first escape part ES1 that branches specific sheets (overlapped fed sheets) PP overlappingly fed and accumulated, at a branching position DP provided in the middle of the conveyance passage and ejects the sheets; and a flapper FL1 which is provided at the branching position DP, and switches a passage of sheets to a direction toward the downstream side and a direction toward the first escape part ES1. When tips of the overlappingly fed sheets PP pass through the branching position DP and then stop, the tips of the overlappingly fed sheets are retreated to an upstream side of the branching position DP, and then a passage of the flapper FL1 is switched to a passage toward the first escape part ES1 and the sheets are ejected.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a sheet feeding device that discharges a sheet in which a double feed or the like has been detected to a predetermined discharge section. [Background technology]

[0002] Conventionally, in a paper feeding device installed in an image forming apparatus or a paper feeding device connected to an image forming apparatus to supply sheets, it is known that when a paper jam occurs, stuck sheets in the transport path or multi-fed sheets that are transported in an overlapping state are forcibly discharged to an ejection section (escape section) to eliminate the task of removing the stuck sheets or multi-fed sheets.

[0003] For example, in Patent Documents 1 and 2, a multi-feed detection sensor that detects multi-feeding, a dedicated discharge section for removing multi-fed sheets from a transport path toward an image forming device, and a discharge path that branches off from the transport path at a branch position provided on the outlet side of a paper feeding device that communicates with the image forming device and guides the sheets to the discharge section are provided. Then, multi-fed sheets detected as multi-fed by the multi-feed detection sensor are discharged to the discharge section via the discharge path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-42469 A [Patent Document 2] JP 2018-199565 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the devices disclosed in Patent Documents 1 and 2, when the double feed detection sensor detects the double feed of the sheets, the leading edge of the double-fed sheets may pass through a branching position that guides the sheets to a discharge section. underWhen a jam occurs on the upstream side, the leading edge of the sheet following the jammed sheet may pass the branch position and become stuck there. In such a case, even if there is a function to automatically discharge the sheets to the discharge section, the user must remove all the sheets stuck in the conveyance path in addition to the jammed sheet and the overlapped sheets, and this removal work is troublesome.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a sheet feeding device that can reduce the amount of work required to remove overlapped sheets or stuck sheets that occur in the transport path. [Means for solving the problem]

[0007] The paper feeder according to the present invention , S R Guide to a conveying path; and a sheet conveying means for conveying a sheet along the conveying path. , S R is discharged A discharge portion and the When a sheet is conveyed along a conveying path, the sheet is conveyed downstream of a branch position provided in the middle of the conveying path in the conveying direction. The direction and , from the branching position of the conveying path a direction toward the discharge portion; 、 and a guide means for switching the path of the sheet. The tip of the sheet Passing through the branch point On the conveying path Stop If the distance between the leading edge of the sheet and the branching position is within a predetermined distance, Tip of the rod Before The sheet conveying means conveys the sheet to the upstream side of the branch position. move and then the sheet path is switched by the guide means to a direction toward the discharge portion. , S The sheet is then conveyed to the discharge section by the sheet conveying means. Transported towards do. Effect of the Invention

[0008] According to the above-mentioned paper feeding device, even if the leading edge of a specific sheet due to double feeding or clogging passes the branch position to the discharge section and stops, the specific sheet can be discharged to the discharge section by moving the specific sheet backward upstream, so that the work of removing the specific sheet due to double feeding or clogging can be reduced. Also, the number of times the device is stopped due to poor transport can be reduced, thereby increasing productivity. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an overall configuration of an image forming system including a paper feeder according to the present invention; [Diagram 2] FIG. 2 is a block diagram showing a control configuration of the image forming system. [Diagram 3] FIG. 2 is a cross-sectional view showing a main configuration of the paper feed device. [Figure 4] FIG. 2 is a cross-sectional view showing the arrangement of various sensors in the paper feeder; [Diagram 5] FIG. 11 is an explanatory diagram showing a normal discharge operation in the first multi-feeding process. [Figure 6] FIG. 11 is an explanatory diagram showing a backward operation in the first multifeeding process. [Figure 7] FIG. 13 is an explanatory diagram showing a discharging operation after retreating in the first multiple feeding process. [Figure 8] 1A is an explanatory diagram showing a state where the leading edge of a multi-fed sheet reaches within an allowable distance and FIG. 1B is an explanatory diagram showing a state where the leading edge of a multi-fed sheet reaches outside the allowable distance. [Figure 9] FIG. 11 is an explanatory diagram showing a starting state of a first jam removal process. [Figure 10] 11A and 11B are explanatory views showing a retreating operation of a sheet and a discharging operation of a sheet in a first jam clearing process; [Figure 11] 13 is an explanatory diagram showing a backward operation of the sheets in the second multi-feeding process. FIG. [Figure 12] 13A and 13B are explanatory diagrams showing a sheet discharging operation in the second multi-feeding process. [Figure 13] 13 is an explanatory diagram showing a retreating operation of a sheet in the second jam removal process. FIG. [Figure 14] 13A and 13B are explanatory diagrams showing a sheet discharging operation in the second jam removal process. [Figure 15] 11 is a cross-sectional view showing a structure for preventing a sheet from jamming during a backward movement. [Figure 16] 11 is a flowchart of sheet processing in the event of multiple feeding or a jam. [Figure 17] 13A and 13B are explanatory diagrams of another embodiment of the sheet retreat portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows the overall configuration of an image forming system 100 including an image forming apparatus 101 and a paper feeder DK of the present invention that can be connected to the image forming apparatus 101. In this embodiment, the paper feeder DK has a two-stage configuration of a downstream paper feed unit (first paper feed unit) DK1 and an upstream paper feed unit (second paper feed unit) DK2, but the number of stages of paper feed units is not limited and may be a configuration in which multiple independent paper feed units are connected. In the following description, a laser printer system using an electrophotographic method will be described as an example of the image forming apparatus 101. Note that the image forming apparatus 101 may be a copier, facsimile, multifunction machine, etc. other than a printer, and may be of another type such as an inkjet type, not limited to an electrophotographic type.

[0011] The first paper feed unit DK1 and the second paper feed unit DK2 each have a plurality of storage sections (storage units) capable of storing a plurality of sheets, and can feed sheets from each storage unit toward the image forming apparatus 101. Note that types of sheets that can be used include plain paper, thin paper, thick paper, and plastic sheets.

[0012] 2 is a block diagram showing the control configuration and mutual connection relationship of the image forming apparatus 101 and the sheet feeding device DK in the image forming system 100. The image forming apparatus 101 includes a control means (control unit) CON0 for controlling the conveyance of sheets and the execution of image forming processing, an operation unit 102, and a notification means (display unit) 103. The first sheet feeding unit DK1 and the second sheet feeding unit DK2 constituting the sheet feeding device DK each include a control unit (CON1, CON2) for controlling the conveyance and feeding of sheets, sheet detection means (sheet sensors S1 to S13 and double feed sensors DFS1 to DFS3) disposed at predetermined positions on the conveyance path and detecting the conveyance state of the sheets, conveyance motors M1 to M14, lift motors M15 to M17, a solenoid SOL, and the like. The sheet sensors S1 to S13 detect the leading edge of the sheet being conveyed, and the double feed sensors DFS1 to DFS3 detect the presence or absence of double feed of sheets. In the sheet feeding device DK, the control unit CON1 of the first sheet feeding unit DK1 and the control unit CON2 of the second sheet feeding unit DK2 are electrically connected to each other. Also, the sheet feeding device DK and the image forming device 101 are electrically connected to each other via the control unit CON1 of the first sheet feeding unit DK1 and the control unit CON0 of the image forming device 101.

[0013] 1, the image forming apparatus 101 conveys various sheets fed from a paper feed section 20 (plurality of paper feed cassettes 21) and a plurality of storage containers in a paper feed device DK (first paper feed unit DK1, second paper feed unit DK2) in a separated state one by one to an image forming section 10. Then, after an image is formed on the sheet in the image forming section 10, the sheet is discharged from a discharge tray 29.

[0014] The first sheet feeding unit DK1 is provided with a through-path portion TP that relays and conveys the sheets fed from the second sheet feeding unit DK2 to the image forming apparatus 101.

[0015] The operation unit 102 selects the sheets to be fed to the image forming unit 10 from the paper feed unit 20, the first paper feed unit DK1, or the second paper feed unit DK2, and also specifies the printing method, the number of copies to be printed, etc. The display unit 103 displays which storage unit of the paper feed unit 20, the first paper feed unit DK1, or the second paper feed unit DK2 the sheets are being fed from, and whether or not there is any double feeding of sheets. It is also possible to remotely operate the operation unit 102 from an information terminal such as an external PC or smartphone, without directly operating the operation unit 102.

[0016] The image reading device 2 provided in the image forming apparatus 101 irradiates light from a scanning optical system light source onto a document placed on a platen 3, and inputs the reflected light into a CCD to read the document image. An automatic document feeder (ADF) 4 can be connected to the image reading device 2, and a document set on a tray 5 can be automatically transported to a reading section of the image reading device 2 to read the document image. The read document image is then converted into an electrical signal and transmitted to a laser scanner 13 of the image forming section 10, which will be described later. Note that the laser scanner 13 may also receive image data sent from an external terminal device or the like.

[0017] The paper feed section 20 includes a plurality of paper feed cassettes 21 for storing various types of sheets, a pickup roller 22, and a pair of separation and conveyance rollers 25. The sheets stored in the paper feed cassette 21 are separated one by one by the pickup roller 22 and the pair of separation and conveyance rollers 25, which move up and down and rotate at a predetermined timing.

[0018] The image formation transport path TR00 includes a transport roller pair 31 and a registration roller pair 33. The sheet guided from the transport roller pair 31 by the registration roller pair 33 is sent to the image forming section 10 at a predetermined timing. The sheet fed from the sheet feeding device DK joins the image formation transport path TR00 via the transport roller pair 54 and a connection path TR6 provided in the first sheet feeding unit DK1, and is transported into the image forming apparatus 101.

[0019] The image forming unit 10 includes a photosensitive drum 11, a charger 12, a laser scanner 13, a developing unit 14, a transfer unit 15, a cleaner 17, etc. During image formation, the photosensitive drum 11 is rotated, and first, the surface of the photosensitive drum 11 is uniformly charged by the charger 12. Then, the charged photosensitive drum 11 is irradiated with laser light from the laser scanner 13, which is emitted in response to an image signal, to form an electrostatic latent image on the photosensitive drum 11. Furthermore, the electrostatic latent image thus formed on the photosensitive drum 11 is visualized as a toner image by the developing unit 14.

[0020] Thereafter, the toner image on the photosensitive drum 11 is transferred onto a sheet by a transfer unit 15. Furthermore, the sheet onto which the toner image has been transferred is transported to a fixing unit 16 where the toner image is fixed, and then the sheet is discharged onto a discharge tray 29 via a pair of discharge rollers 19.

[0021] When a toner image is formed on the back surface of the sheet, the sheet discharged from the fixing device 16 is transported to a switchback path 18. Then, in a state where the sheet is turned over by the switchback path 18, the sheet is transported again to the transfer device 15 of the image forming unit 10. The sheet with the toner image transferred to the back surface is transported to the fixing device 16, where the toner image is fixed, and then the sheet is discharged to a discharge tray 29 by a pair of discharge rollers 19. Note that any residual toner remaining on the photosensitive drum 11 after the transfer is removed by a cleaner 17.

[0022] The control unit CON0 has a CPU, a ROM, and a RAM. The CPU controls each part while reading a program corresponding to a control procedure stored in the ROM. In addition, working data and input data are stored in the RAM, and the CPU performs control by referring to the data stored in the RAM based on the above-mentioned programs, etc.

[0023] In the operation unit 102 provided in the image forming apparatus 101, image forming conditions, such as sheet size, color / monochrome printing, number of copies to be printed, single-sided / double-sided printing, enlarged / reduced printing, and other printing conditions are set.

[0024] Next, the details of the sheet feeding device DK will be described with reference to Figures 3 and 4. Note that the first sheet feeding unit DK1 and the second sheet feeding unit DK2 have the same configuration except for the through path section TP, so the description will be based on the first sheet feeding unit DK1.

[0025] The first paper feed unit DK1 includes a first transport path TR10 consisting of a plurality of storage containers LO1-LO3, a plurality of transport paths TR1-TR5 extending from the upstream side to the downstream side, a sheet transport means consisting of a plurality of transport roller pairs arranged on each transport path, sheet sensors S1-S13, double feed sensors DFS1-DFS3, motors M1-M17, a through path part TP, etc. In this embodiment, the three storage containers LO1-LO3 are arranged in three tiers in the vertical direction, and the through path part TP is provided between the lower storage container LO3 and the middle storage container LO2. The second paper feed unit DK2 does not include the through path part TP and the double feed sensor DFS3.

[0026] A sheet fed from the upper storage LO1 is transported to the transport path TR1, a sheet fed from the middle storage LO2 is transported to the transport path TR2 that merges with the transport path TR1, and a sheet fed from the lower storage LO3 is transported to the transport path TR3. A sheet transported from the second paper feed unit DK2 via the through path section TP is transported to the transport path TR4. The transport paths TR1, TR3, and TR4 merge at a junction J1, are transported to the transport roller pair 54 through the transport path TR5, and merge with the image formation transport path TR00 in the image forming apparatus 101 via a connection path TR6.

[0027] As shown in Fig. 4, the conveying path TR1 after merging with the conveying path TR2, the through path section TP, and the conveying path TR3 are provided with double feed sensors DFS1 to DFS3 for detecting double feed of sheets, respectively. Then, the sheet in which the double feed is detected by the double feed sensors DFS1 to DFS3 (hereinafter, referred to as a double fed sheet) is conveyed to the conveying path TR5. Below the conveying path TR5, a downstream discharge section (first escape section) ES1 for discharging the double fed sheet is provided. The double fed sheet is discharged to the first escape section ES1 by switching the path by a switching member (flapper) FL1 provided in a guide means provided on the conveying path TR5. Details of the process when a double feed is detected will be described later.

[0028] Sheets fed from storage units LO1 to LO3 are transported to a connection path TR6 via transport paths TR1, TR3, and TR4. Each part of the first paper feed unit DK1 is controlled by a control unit CON1. ​​The control unit CON1 has a CPU, a ROM, and a RAM. The control unit CON1 can communicate with a control unit CON0 of the image forming apparatus 101, and controls the timing of sheet feeding and the like by communicating with the control unit CON0.

[0029] 3, storage LO1 has a sheet feeding section 40a that feeds sheets toward image forming apparatus 101, and a stacking tray 44a on which a plurality of sheets are stacked. The stacking tray 44a can be raised and lowered in the vertical direction by a lifting mechanism 45a driven by a lifting motor M15. The stacking tray 44a is lowered to a predetermined position when sheets are stacked, and gradually rises when the stacked sheets are fed.

[0030] The sheet feeding section 40a includes a first sheet conveying means including a pickup roller 43a, a separation conveying roller pair 41a including a conveying roller and a retard roller, and a conveying roller pair 42a. The pickup roller 43a and the separation conveying roller pair 41a are rotated by a conveying motor M1, and the conveying roller pair 42a is rotated by a conveying motor M2. The sheet feeding section 40a also includes a sheet sensor S1 for detecting the leading edge of the sheet on the downstream side of the separation conveying roller pair 41a in the conveying direction, and a sheet sensor S2 for detecting the leading edge of the sheet on the upstream side of the conveying roller pair 42a in the conveying direction.

[0031] The pickup roller 43a is provided above the stacking tray 44a and contacts the top sheet of the sheets stacked on the raised stacking tray 44a to feed it. For this purpose, the pickup roller 43a is disposed near the leading edge of the sheet in the sheet conveying direction so as to be able to apply an appropriate pressure to the top sheet on the stacking tray 44a. Then, the pickup roller 43a rotates to feed out the top sheet.

[0032] When two or more overlapping sheets are fed from the pickup roller 43a, that is, when two or more overlapping sheets are fed, the pair of separation and conveyance rollers 41a separates the sheets and conveys only one sheet.

[0033] The sheet separated and conveyed by the separation conveying roller pair 41a is conveyed to a conveying path TR1 by a conveying roller pair 42a. A plurality of conveying roller pairs rotated by conveying motors M7 and M8 are arranged on the conveying path TR1. As shown in FIG. 4, a sheet sensor S7 for detecting the leading edge of the sheet on the upstream side in the conveying direction and a sheet sensor S8 for detecting the leading edge of the sheet on the downstream side in the conveying direction are arranged on the conveying path TR1.

[0034] Storage cabinets LO2 and LO3 have sheet feeding units 40b and 40c that feed sheets toward image forming apparatus 101, stacking trays 44b and 44c on which a plurality of sheets are stacked, and lifting mechanisms 45b and 45c. Note that the configurations of sheet feeding units 40b and 40c and conveying motors M3 to M6 are similar to those of sheet feeding unit 40a, and the configurations of lifting mechanisms 45b and 45c and lifting motors M16 and M17 are similar to those of lifting mechanism 45a, and therefore descriptions thereof will be omitted.

[0035] In the through-path section TP, the sheet is transported through the device by a conveyor 50 driven by a transport motor M14. In addition, in the through-path section TP, a double-feed sensor DFS3 is disposed upstream of the conveyor 50 in the transport direction to detect whether or not two or more sheets are being fed in the through-path section TP.

[0036] The sheet conveyed by the conveyor 50 is conveyed into a conveying path TR4 by a conveying roller pair 51 rotated and driven by a conveying motor M12 and a conveying roller pair 52 rotated and driven by a conveying motor M13.

[0037] A sheet sensor S12 that detects the leading edge of the sheet on the upstream side of the conveying roller pair 51 in the conveying direction, and a sheet sensor S13 that detects the leading edge of the sheet on the upstream side of the conveying roller pair 52 in the conveying direction are arranged on the conveying path TR4.

[0038] The conveying paths TR1, TR3, and TR4 join at a joining point J1 and are connected to a conveying path TR5. A pair of conveying rollers 53 rotated by a conveying motor M10 and a pair of conveying rollers 54 rotated by a conveying motor M11 are arranged on the conveying path TR5, and a sheet sent out by the pair of conveying rollers 54 is conveyed to the image forming device 101 via a connection path TR6.

[0039] Also, a sheet sensor S10 that detects the leading edge of the sheet in the vicinity of the upstream side of the pair of conveying rollers 53 and a sheet sensor S11 that detects the leading edge of the sheet in the vicinity of the upstream side of the pair of conveying rollers 54 are disposed on the conveying path TR5. A flapper FL1 is disposed on the conveying path TR5. This flapper FL1 is provided at a branch position DP that blocks the connection path TR6 leading to the image forming apparatus 101 and opens the first escape portion ES1, and is switched between a position that blocks the connection path TR6 and an open position that opens the first escape portion ES1 by turning a solenoid SOL ON / OFF.

[0040] The first escape section ES1 is provided below the transport paths TR3 and TR5 for transporting sheets from the storage container LO3 to the image forming device 101, below the connection path TR6, and below the junction J1 of the transport paths TR1, TR2, and TR3. As shown in Fig. 3, the first escape section ES1 has a discharge area for overlapped sheets in the transport direction of the sheets transported on the transport paths TR3 and TR5, which is a wide range from a position adjacent to the image forming device 101 to a position adjacent to the storage container LO3. In other words, the length in the transport direction of the sheets passing through the transport paths TR3 and TR5 in the first escape section ES1 is the length from the transport path TR3 to the connection path TR6 via the junction J1 and the flapper FL1.

[0041] The second sheet feed unit DK2 includes a plurality of storage containers LO1-LO3, a second transport path TR20 consisting of a plurality of transport paths TR1-TR5 extending from the upstream side to the downstream side, a second sheet transport means consisting of a plurality of transport roller pairs arranged on each transport path, sheet sensors S1-S13, double feed sensors DFS1, DFS2, and motors M1-M17. The second transport path TR20 merges with the first transport path TR10 via a downstream connection path TR26. The second escape section ES2 is provided below the connection path TR26 connected to the first sheet feed unit DK1, and double-fed or jammed sheets are discharged by switching the flapper FL2. The configurations and arrangements of the storage containers LO1-LO3, the plurality of transport roller pairs arranged on each transport path, the sheet sensors S1-S13, the double feed sensors DFS1, DFS2, and the motors M1-M17 are the same as those of the first sheet feed unit DK1.

[0042] Next, details of the sheet processing in the present invention will be described. The sheet processing includes a multi-feed processing for when a multi-feed is detected, and a jam processing for when a jam occurs other than the multi-feed.

[0043] The multiple feed processing includes a first multiple feed processing in which only the leading edge of the multiple feed sheet PP is moved backward in the direction opposite to the conveying direction and then discharged to the escape section when a specific sheet (hereinafter referred to as the multiple feed sheet) PP in which multiple feeding has been detected passes through a branch position DP to the escape section and stops, and a second multiple feed processing in which the entire multiple feed sheet PP is moved backward in the direction opposite to the conveying direction and then discharged to the escape section. The multiple feed sheet PP is in a state in which a leading sheet Pa that is fed forward and a trailing sheet Pb are overlapped on the leading sheet Pa.

[0044] Jam processing is a process that is performed when a sheet conveyed to the image forming apparatus 101 becomes jammed (jammed) for some reason and the sheet sensors S1 to S13 detect the stop of the sheet being conveyed. This jam processing includes a first jam processing in which only the leading edge of the retained sheet is moved backward in the direction opposite to the conveying direction and then discharged to the escape section when a specific sheet (hereinafter, the retained sheet) whose conveyance has been stopped when a jam has occurred passes through a branch position DP to the escape section of the sheet feeding device DK and stops, and a second jam processing in which the entire retained sheet is moved backward in the direction opposite to the conveying direction and then discharged to the escape section.

[0045] The above-mentioned multiple feed processing and jam processing are executed by the control units CON0, CON1, and CON2 provided in the image forming apparatus 101 and the first and second sheet feeding units DK1 and DK2, respectively. Below, the sheet processing in the first sheet feeding unit DK1 will be described, but the same applies to the second sheet feeding unit DK2.

[0046] The first multifeed process will be described with reference to the state diagrams of Figures 5 to 8 and the flowchart of Figure 16. Note that while Figure 5 shows a case where multifeed is detected via the transport path TR1 or TR2, the same applies when multifeed is detected via the transport path TR3.

[0047] As shown in Fig. 5(a), in the first multifeed process, a pair of conveying rollers 53 is driven by a conveying motor M10 that can switch between forward rotation for conveying a sheet in a normal conveying direction and reverse rotation for conveying a sheet in a direction opposite to the conveying direction. In addition, sheet evacuation sections LP1 and LP2 for temporarily retreating and retreating the leading edge of a sheet for which a multifeed has been detected are provided on the conveying paths TR12 and TR3 upstream of a nip position RP1 of the sheet by the pair of conveying rollers 53. The sheet evacuation sections LP1 and LP2 have a storage space that can accommodate the leading edge of the retreated sheet in a bent state. The storage space can be formed by projecting a part of a conveying guide (not shown) forming the conveying path outward.

[0048] Hereinafter, a process when the overlapped feed sensor DFS1 detects overlapped feeding of sheets will be described. First, it is determined whether the sheet sensor S10 arranged near the upstream side of the flapper FL1 is OFF, that is, whether the leading edge of the overlapped leading sheet Pa is detected (ST01). If the sheet sensor S10 is OFF (Yes in ST01), it is determined that the leading edge of the leading sheet Pa has not reached the branch position DP and is on the upstream side of the flapper FL1, as shown in FIG. 5(a). In this state, as shown in FIG. 5(b), the flapper FL1 arranged at the branch position DP blocks the conveying direction TD1 toward the connection path TR6 and switches to the conveying direction TD2 toward the first escape section ES1. In this way, the overlapped sheet PP is discharged to the first escape section ES1 (ST02). At that time, if there is a sheet (retained sheet) retained in the conveying path upstream of the overlapped sheet PP (No in ST03), the retained sheet is also discharged to the first escape section ES1 (ST02). Thereafter, if there are no more retained sheets (Yes in ST03), the conveyance and discharge operations to the first escape portion ES1 are stopped (ST04).

[0049] On the other hand, if the sheet sensor S10 is ON (No in ST01) after the double feed is detected by the double feed sensor DFS1, it is determined that the leading edge of the leading sheet Pa has already reached the downstream side beyond the branch position DP where the flapper FL1 is disposed, as shown in FIG. 6(a), and the conveyance of the double-fed sheet PP is stopped. Then, a retreating operation determination process is performed to determine whether the leading edge of the leading sheet Pa can be retreated to the upstream side of the branch position DP (ST05). In this retreating operation determination process, as shown in FIG. 8, if the passing distance ED of the leading edge of the leading sheet Pa from the nip position RP1 of the conveying roller pair 53 to the downstream arrival position RP2 is within a predetermined range (allowable distance) AD, it is determined that the leading edge of the leading sheet Pa can be retreated, and if the arrival position RP2 is further downstream and the passing distance ED exceeds the allowable distance AD, it is determined that the leading edge of the leading sheet Pa cannot be retreated. The passing distance ED can be calculated based on the rotational drive amount of the conveying roller pair 53 from the detection of the leading edge of the leading sheet Pa by the sheet sensor S10 until the leading edge of the leading sheet Pa reaches the arrival position RP2.

[0050] If it is determined that the backward operation is possible, the backward operation is executed (ST06). In this backward operation, as shown in FIG. 6(b), the pair of conveying rollers 53 is rotated by a drive amount equivalent to the passing distance ED in the direction opposite to the normal conveying direction, that is, in the direction returning the sheet to the upstream side. This causes the leading edge of the leading sheet Pa to return to the nip position RP1 of the pair of conveying rollers 53. At this time, the bent portion caused by the backward movement of the leading sheet Pa is temporarily accommodated in the sheet evacuation section LP1. Thereafter, as shown in FIG. 7, the flapper FL1 is switched to the conveying direction TD2 toward the first escape section ES1, and then the double-fed sheets PP are discharged (ST02). The retained sheets are also discharged in succession.

[0051] If it is determined in the backward operation determination process (ST05) that the backward operation is not possible, the transport operation of the double-fed sheets PP is stopped (ST07), and the double-fed sheets PP are displayed as a jam on the display unit 103 of the image forming apparatus 101, or an alarm sound is sounded, or other error information is notified to the user (ST08). When the jam occurs, the jammed double-fed sheets PP and the stuck sheets are removed by opening and closing a transport guide (not shown) of a predetermined transport path.

[0052] In the backward operation determination process in this embodiment, the allowable distance AD ​​is set to about 20 mm. That is, the sheet evacuation section LP1 has a storage space that can accommodate the sheet even if it is bent by about 20 mm. Note that the allowable distance AD ​​is an example, and is not limited to this, and can be set appropriately depending on the length of the conveying path, the position of the sheet sensor, etc. Also, the storage space of the sheet evacuation section LP1 is set according to the allowable distance AD.

[0053] When the multi-feed sensor DFS2 detects a multi-feed of the sheets fed from the storage container LO3, the first multi-feed process is performed via the sheet evacuation section LP2 formed in the transport path TR3.

[0054] 9 and 10 show jamming processing when the sheet P1 fed from the first sheet feeding unit DK1 to the image forming apparatus 101 jams on the conveying path TR00 in the above configuration. FIG. 9 shows a state in which the leading edge P2a of the following sheet (retained sheet) P2 stopped at the first sheet feeding unit DK1 passes through the branching position DP by the flapper FL1 and stops when a jam occurs in the image forming apparatus 101 and the conveying operation stops. In this state, as shown in FIG. 8, if the passing distance ED when the leading edge P2a of the retained sheet P2 passes through the branching position DP and stops is within the allowable distance AD, as shown in FIG. 10(a), the conveying roller pair 53 is rotated in the opposite direction to the normal conveying direction, that is, in the direction returning the retained sheet P2 to the upstream side, by an amount equivalent to the passing distance ED. At this time, the conveying roller pair 55 on the upstream side of the conveying roller pair 53 is in a state in which the retained sheet P2 is nipped. As a result, the leading edge P2a of the retained sheet P2 is returned to the nip position RP1 of the conveying roller pair 53, and the deflection of the retained sheet P2 is temporarily accommodated in the sheet evacuation section LP1. Then, as shown in FIG. 10(b), the retained sheet P2 can be discharged to the first escape section ES1 by blocking the conveying path TR6 by switching the flapper FL1.

[0055] On the other hand, if the leading edge P2a of the retained sheet P2 exceeds the allowable distance AD, it is determined that the retreating operation is not possible, and the retained sheet P2 is removed by opening a predetermined conveying path or the like.

[0056] Next, the second multi-feed processing and the second jam processing will be described with reference to Figs. 11 to 14. In the first multi-feed processing and the first jam processing, only the leading edge of the multi-fed sheet or the retained sheet that could not be discharged toward the first escape portion ES1 is temporarily moved backward toward the upstream side of the flapper FL1 and then discharged toward the first escape portion ES1. In contrast, in the second multi-feed processing and the second jam processing, the entire sheet that could not be discharged toward the first escape portion ES1 is moved backward so as to slide toward the upstream side by a predetermined amount and then discharged toward the first escape portion ES1.

[0057] 11 to 14, in the second multiple feed processing and second jam processing, in addition to the conveying roller pair 53, the conveying roller pair 54 arranged on the connection path TR6 and the conveying roller pairs 55 and 56 arranged on the conveying path TR12 are driven by the conveying motor M11 and the conveying motor M8 so as to be capable of rotating forward and reverse, respectively. Note that in the second multiple feed processing and second jam processing, since the entire sheet is moved backward, there is no need to provide the sheet evacuation sections LP1 and LP2 as described above.

[0058] In the second multi-feed process, if the multi-feed sensor DFS1 detects the multi-feed and the sheet sensor S10 is OFF, it is determined that at least the leading edge of the first sheet Pa of the multi-feed sheets PP has not passed through the branch position DP by the flapper FL1. Based on this determination, the flapper FL1 is switched to a direction to block the conveying path TR6, and the multi-feed sheets PP are discharged to the first escape section ES1.

[0059] On the other hand, if the sheet sensor S10 is ON after the double feed is detected by the double feed sensor DFS1, it is determined that the leading edge of the leading sheet Pa has already reached the downstream side beyond the branch position DP, as shown in Fig. 11(a), and the conveyance of the double-fed sheet PP is stopped. Then, a retreat operation determination process is performed to determine whether the leading edge of the leading sheet Pa can be retreated to the upstream side of the branch position DP. In this retreat operation determination process, as shown in Fig. 8, if the leading edge of the leading sheet Pa is within the allowable distance AD, it is determined that the retreat operation is possible.

[0060] When it is determined that the backward movement is possible, the backward movement is executed. In this backward movement, as shown in FIG. 11B, the conveying roller pair 53, 55, 56 is rotated in the opposite direction to the normal conveying direction, that is, in the direction returning the leading sheet Pa to the upstream side by the amount corresponding to the passing distance ED. As a result, the entire overlapped sheet PP in which the leading sheet Pa and the trailing sheet Pb overlap each other is moved backward as if sliding in the opposite direction to the conveying direction with the reverse rotation of the conveying roller pair 53, 55, 56. Thereafter, as shown in FIG. 12, the flapper FL1 is switched to the first escape portion ES1 side, and the conveying roller pair 53, 55, 56 is switched from reverse rotation to forward rotation, so that the overlapped sheet PP in which the leading sheet Pa and the trailing sheet Pb overlap each other is discharged.

[0061] The second jam processing is a processing when the sheet P1 conveyed from the first sheet feeding unit DK1 to the image forming apparatus 101 jams on the conveying path TR00. As shown in FIG. 13(a), when a jam occurs in the image forming apparatus 101 and the conveying operation stops, if the leading edge P2a of the sheet P2 passes through the branch position DP and stops, as shown in FIG. 8, if the leading edge P2a of the sheet P2 is within the allowable distance AD, as shown in FIG. 13(b), the conveying roller pair 53 is rotated in the opposite direction to the normal conveying direction, that is, in the direction returning the sheet to the upstream side by the amount corresponding to the passing distance ED. As a result, the entire sheet P2 is returned to the upstream side by the passing distance ED. Thereafter, as shown in FIG. 14, the flapper FL1 is switched to the first escape section ES1 side, and the conveying roller pairs 53, 55, and 56 are switched from reverse rotation to forward rotation, and the sheet P2 is discharged.

[0062] In the second double feed process and the second jam process, the double-fed or jammed sheet is moved back by a predetermined distance, so that the sheet may pass the following sheet. To prevent jamming due to such passing, for example, as shown in Fig. 15, one of the conveying roller pair 56 is separated to widen the conveying path TR12, so that the following sheet that has reached the conveying path TR12 can smoothly pass the sheet. The same applies to the other conveying roller pairs 53 and 55.

[0063] In the above embodiment, the sheet evacuation sections LP1 and LP2 for temporarily retreating and evacuating the leading edge of a sheet for which double feeding has been detected are provided on the transport paths TR12 and TR3 upstream of the nip position RP1 of the sheet by the transport roller pair 53. Instead of providing these two sheet evacuation sections LP1 and LP2, a single shared sheet evacuation path LP3 may be provided downstream of the junction J1 of the transport paths TR12 and TR3 and before the transport roller pair 53, as shown in FIG. [Explanation of symbols]

[0064] DK Paper Feeder DK1 1st feed unit DK2 2nd Paper Feed Unit CON0, CON1, CON2 control section ES1 First escape section ES2 Second Escape Section M1~M14 Conveyor motor M15~M17 Lift motor S1~S13 Sheet sensors DFS1~DFS3 Double feed sensor TR00 Image formation transport path TR10 First transport route TR20 Second transport route TR1~TR5 transport path TR6, TR26 connection path J1 Junction TP Through Pass Section FL1, FL2 flappers (switching members) LO1, LO2, LO3 Storage DP branch position TD1, TD2 conveying direction P1, P2 sheets PP multi-feed sheet Pa first sheet Pb Rear Sheet LP1, LP2, LP3 Sheet evacuation area AD Allowable Distance ED passing distance RP1 Nip Position RP2 Arrived position 19 Discharge roller pair 20 Paper feed section 21 Paper feed cassette 22 Pickup roller 25 Separation and conveying roller pair 29 Output Tray 31 Transport roller pair 33 Registration roller pair 40a, 40b, 40c Sheet feeding section 41a Separation and conveyance roller pair 42a conveying roller pair 43a Pickup roller 44a, 44b, 44c Loading Tray 45a, 45a, 45c Lifting mechanism 50 Conveyor 51~56 Conveyor roller pair 100 Image forming system 101 Image forming device 102 Operation section 103 Display section

Claims

1. A conveying path for guiding a sheet; a sheet conveying means for conveying a sheet along the conveying path; a discharge section to which the sheet is discharged; a guide means for switching a path of the sheet conveyed along the conveying path between a direction toward a downstream side of a branching position provided in the middle of the conveying path in a conveying direction and a direction toward the discharge section from the branching position of the conveying path, When the leading edge of the sheet passes the branching position and stops on the conveying path, and the distance between the leading edge of the sheet and the branching position is within a predetermined distance, the leading edge of the sheet is moved upstream of the branching position by the sheet conveying means, the sheet path is switched by the guide means to a direction toward the discharge section, and then the sheet is conveyed toward the discharge section by the sheet conveying means.

2. A paper feeding device as described in Claim 1, wherein the sheet whose leading edge has passed the branch position and stopped on the transport path is a sheet that has been stopped on the transport path when a sheet transport problem occurs.

3. A double feed sensor is provided upstream of the branch position and detects double feed of sheets, 2. The sheet feeding device according to claim 1, wherein the sheet whose leading edge has passed the branch position and stopped in the transport path is a multi-fed sheet whose multi-fed state has been detected by the multi-feed sensor.

4. A sheet sensor is provided upstream of the branch position to detect a sheet being transported along the transport path, 2. The sheet feeding device according to claim 1, wherein the distance traveled by the sheet through the branching position is determined based on the detection of the leading edge of the sheet by the sheet sensor.

5. A paper feeding device as described in claim 1, further comprising an alarm means for notifying error information when the leading edge of the sheet exceeds the specified distance and transport stops.

6. A paper feeding device as described in claim 1, further comprising a sheet evacuation section upstream of the branching position in the conveying path for accommodating deflection of the sheet moved by the sheet conveying means.

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