JP7653271B2 - Paper feeder - Google Patents

Description

The present invention relates to a paper feeder that discharges sheets in which a double feed or other problem has been detected to a specified discharge section.

Conventionally, in a paper feed device installed in an image forming apparatus or a paper feed device connected to an image forming apparatus that supplies sheets, it is known that when a paper jam occurs, stuck sheets in the transport path or overlapping sheets transported in an overlapping state are forcibly discharged to an exit section (escape section) to eliminate the need to remove stuck sheets or overlapping sheets.

For example, in Patent Documents 1 and 2, a multi-feed detection sensor that detects multi-feeds, a dedicated discharge section for removing multi-fed sheets from a transport path leading to 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.

JP 2011-42469 A JP 2018-199565 A

In the devices disclosed in Patent Documents 1 and 2, when the overlapping detection sensor detects the overlapping of sheets, the leading edge of the overlapped sheet may pass through the branching position that guides the sheet to the discharge section. Also, when a jam occurs downstream of the branching position of the conveyance path including the image forming device, the leading edge of the sheet following the jammed sheet may pass through the branching position and remain 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 remaining in the conveyance path in addition to the jammed sheet and overlapping sheet, and this removal work is troublesome.

The present invention aims to provide a paper feeder that can reduce the amount of work required to remove overlapping sheets and stuck sheets that occur in the transport path.

The paper feeding device of the present invention comprises a transport path for guiding a sheet , a sheet transport means for transporting a sheet along the transport path , a discharge section from which the sheet is discharged , and a guide means for switching the path of the sheet between a direction in which the sheet transported along the transport path heads downstream in the transport direction of a branch position provided midway along the transport path, and a direction from the branch position of the transport path toward the discharge section.When the leading edge of the sheet passes the branch position and stops on the transport path , and the distance between the leading edge of the sheet and the branch position is within a predetermined distance, the sheet transport means moves the leading edge of the sheet upstream of the branch position, and the guide means switches the path of the sheet toward the discharge section , and the sheet is transported by the sheet transport means toward the discharge section.

According to the above-mentioned paper feeding device, even if the leading edge of a specific sheet stops after passing the branching position to the discharge section due to double feeding or blockage, the specific sheet can be discharged to the discharge section by moving it back upstream, so the work required to remove the specific sheet due to double feeding or blockage can be reduced. In addition, the number of times the device is stopped due to transport problems can be reduced, thereby increasing productivity.

1 is a cross-sectional view showing an overall configuration of an image forming system including a paper feeder according to the present invention; FIG. 2 is a block diagram showing a control configuration of the image forming system. FIG. 2 is a cross-sectional view showing a main configuration of the paper feed device. FIG. 2 is a cross-sectional view showing the arrangement of various sensors in the paper feeder; 13A and 13B are explanatory diagrams showing a normal discharge operation in the first multifeed process. 13A and 13B are explanatory diagrams showing a backward operation in the first multifeeding process. 13A and 13B are explanatory diagrams showing a discharging operation after retreating in the first multiple feeding process. 10A and 10B are explanatory diagrams showing a state in which the leading edge of the multi-fed sheets reaches within an allowable distance and outside the allowable distance; FIG. 11 is an explanatory diagram showing a start-up state of a first jam removal process. 11A and 11B are explanatory diagrams illustrating a retracting operation of a sheet and a discharging operation of a sheet in a first jam clearing process; 13A and 13B are explanatory diagrams showing a backward movement of the sheets in the second multi-feeding process. 13A and 13B are explanatory diagrams showing a sheet discharging operation in the second multi-feeding process. 13A and 13B are explanatory diagrams illustrating a retracting operation of a sheet in the second jam removal process. 11A and 11B are explanatory diagrams illustrating a sheet discharging operation in the second jam removal process. 11 is a cross-sectional view showing a structure for preventing a sheet from jamming during a backward movement. 11 is a flowchart of sheet processing in the event of multiple feeding or a jam. 13A and 13B are explanatory diagrams of another embodiment of the sheet retreat portion.

The embodiment of the present invention will be described in detail below with reference to the attached 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 other types such as an inkjet type, not limited to an electrophotographic type.

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 sheets can be fed from each storage unit toward the image forming device 101. In addition to plain paper, thin paper, thick paper, and the like, plastic sheets and the like can be used as the types of sheets.

Figure 2 is a block diagram showing the control configuration and mutual connection relationship of the image forming apparatus 101 and the paper feeder DK in the image forming system 100. The image forming apparatus 101 is equipped with a control means (control unit) CON0 that controls the sheet transport and image formation process, an operation unit 102, and an informing means (display unit) 103. The first paper feed unit DK1 and the second paper feed unit DK2 that constitute the paper feeder DK are each equipped with a control unit (CON1, CON2) that controls the transport and feeding of sheets, sheet detection means (sheet sensors S1-S13 and double feed sensors DFS1-DFS3) that are arranged at predetermined positions on the transport path and detect the transport state of the sheets, transport motors M1-M14, lift motors M15-M17, solenoid SOL, etc. The sheet sensors S1-S13 detect the leading edge of the sheet being transported, and the double feed sensors DFS1-DFS3 detect whether or not there is double feeding of sheets. In the paper feed device DK, the control unit CON1 of the first paper feed unit DK1 and the control unit CON2 of the second paper feed unit DK2 are electrically connected to each other. In addition, the paper feed device DK and the image forming device 101 are electrically connected to each other via the control unit CON1 of the first paper feed unit DK1 and the control unit CON0 of the image forming device 101.

As shown in FIG. 1, the image forming device 101 conveys various sheets fed from the internal paper feed section 20 (multiple paper feed cassettes 21) and multiple storage compartments in the paper feed device DK (first paper feed unit DK1, second paper feed unit DK2) in a separated state one by one to the image forming section 10. After an image is formed on the sheet in the image forming section 10, the sheet is discharged from the discharge tray 29.

The first paper feed unit DK1 is provided with a through-path section TP that relays and transports sheets fed from the second paper feed unit DK2 to the image forming device 101.

The operation unit 102 is used to select 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 to specify the printing method, number of copies to be printed, etc. The display unit 103 also 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 a double feed of sheets. It is also possible to remotely operate the operation unit 102 from an external information terminal such as a PC or smartphone, without directly operating the operation unit 102.

The image reading device 2 provided in the image forming apparatus 101 reads the document image by irradiating light from a scanning optical system light source onto the document placed on the platen 3 and inputting the reflected light into a CCD. An automatic document feeder (ADF) 4 can also be connected to the image reading device 2, so that the document set on the tray 5 can be automatically transported to the 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, etc.

The paper feed section 20 includes a plurality of paper feed cassettes 21 that store various types of sheets, a pickup roller 22, and a pair of separation and transport rollers 25. The sheets stored in the paper feed cassettes 21 are separated one by one by the pickup roller 22 and the pair of separation and transport rollers 25, which move up and down and rotate at a predetermined timing.

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. In addition, the sheet fed from the paper feed device DK joins the image formation transport path TR00 via the transport roller pair 54 and the connection path TR6 provided in the first paper feed unit DK1, and is transported into the image forming device 101.

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 rotates, 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.

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

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

The control unit CON0 has a CPU, ROM, and RAM. The CPU controls each part while reading a program corresponding to the 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 aforementioned programs, etc.

The operation unit 102 of the image forming device 101 sets image forming conditions, such as sheet size, color or monochrome printing, number of copies to be printed, single-sided or double-sided printing, and enlarged or reduced printing.

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

The first paper feed unit DK1 includes a first transport path TR10 consisting of multiple storage containers LO1-LO3, multiple transport paths TR1-TR5 extending from the upstream side to the downstream side, a sheet transport means consisting of multiple transport roller pairs arranged on each transport path, sheet sensors S1-S13, double feed sensors DFS1-DFS3, motors M1-M17, a through path section TP, etc. In this embodiment, the three storage containers LO1-LO3 are arranged in three tiers in the vertical direction, and a through path section 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 section TP and double feed sensor DFS3.

Sheets fed from the upper storage LO1 are transported to the transport path TR1, sheets fed from the middle storage LO2 are transported to the transport path TR2 that merges with the transport path TR1, and sheets fed from the lower storage LO3 are transported to the transport path TR3. Sheets transported from the second paper feed unit DK2 via the through path section TP are transported to the transport path TR4. In addition, the transport paths TR1, TR3, and TR4 merge at the junction J1, are transported through the transport path TR5 to the transport roller pair 54, and merge with the image formation transport path TR00 in the image forming device 101 via the connection path TR6.

As shown in FIG. 4, the transport path TR1 after merging with the transport path TR2, the through path section TP, and the transport path TR3 are provided with double feed sensors DFS1 to DFS3 for detecting double feed of sheets. The sheets detected as double fed by the double feed sensors DFS1 to DFS3 (hereinafter referred to as double fed sheets) are transported to the transport path TR5. Below the transport path TR5, a downstream discharge section (first escape section) ES1 for discharging the double fed sheets is provided. The double fed sheets are 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 transport path TR5. Details of the process when double feed is detected will be described later.

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

As shown in FIG. 3, storage LO1 has a sheet feeding section 40a that feeds sheets toward the image forming device 101, and a stacking tray 44a on which multiple 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 as the stacked sheets are fed.

The sheet feeding section 40a is equipped with a first sheet conveying means consisting of a pickup roller 43a, a separation conveying roller pair 41a consisting of a conveying roller and a retard roller, a conveying roller pair 42a, etc. The pickup roller 43a and the separation conveying roller pair 41a are rotated and driven by a conveying motor M1, and the conveying roller pair 42a is rotated and driven by a conveying motor M2. In addition, the sheet feeding section 40a is provided with a sheet sensor S1 that detects 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 that detects the leading edge of the sheet on the upstream side of the conveying roller pair 42a in the conveying direction.

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 reason, the pickup roller 43a is positioned near the leading edge of the sheet in the sheet transport direction so that it can apply an appropriate amount of pressure to the top sheet on the stacking tray 44a. Then, the pickup roller 43a rotates to feed out the top sheet.

When two or more overlapping sheets are fed from the pickup roller 43a, that is, when two or more sheets are fed overlappingly, the separation conveying roller pair 41a separates the sheets and conveys only one of them.

The sheet separated and conveyed by the separation conveying roller pair 41a is conveyed to the conveying path TR1 by the conveying roller pair 42a. A plurality of conveying roller pairs driven to rotate by conveying motors M7 and M8 are arranged on the conveying path TR1. As shown in FIG. 4, the conveying path TR1 is also arranged with a sheet sensor S7 that detects the leading edge of the sheet on the upstream side in the conveying direction, and a sheet sensor S8 that detects the leading edge of the sheet on the downstream side in the conveying direction.

Storage cabinets LO2 and LO3 have sheet feeding units 40b and 40c that feed sheets toward image forming device 101, stacking trays 44b and 44c on which multiple sheets are stacked, and lifting mechanisms 45b and 45c. Note that the configuration of sheet feeding units 40b and 40c and transport motors M3 to M6 are the same as those of sheet feeding unit 40a, and the configuration of lifting mechanisms 45b and 45c and lifting motors M16 and M17 are the same as those of lifting mechanism 45a, so a description thereof will be omitted.

In the through-path section TP, the sheet is transported through the device by a conveyor 50 that is driven to rotate by a transport motor M14. In addition, a double-feed sensor DFS3 is disposed in the through-path section TP upstream of the conveyor 50 in the transport direction, which detects whether two or more sheets are being fed in the through-path section TP.

The sheet transported by the conveyor 50 is transported into the transport path TR4 by a pair of transport rollers 51, which is rotated by a transport motor M12, and a pair of transport rollers 52, which is rotated by a transport motor M13.

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.

The transport paths TR1, TR3, and TR4 join at a junction J1 and are connected to the transport path TR5. The transport path TR5 includes a pair of transport rollers 53 that is driven to rotate by a transport motor M10 and a pair of transport rollers 54 that is driven to rotate by a transport motor M11. The sheet sent out by the pair of transport rollers 54 is transported to the image forming device 101 via a connection path TR6.

In addition, a sheet sensor S10 that detects the leading edge of the sheet near the upstream side of the pair of transport rollers 53 and a sheet sensor S11 that detects the leading edge of the sheet near the upstream side of the pair of transport rollers 54 are arranged on the transport path TR5. A flapper FL1 is arranged on the transport path TR5. This flapper FL1 is provided at a branch position DP that blocks the connection path TR6 leading to the image forming device 101 and opens the first escape section ES1, and is switched between a position that blocks the connection path TR6 and an open position that opens the first escape section ES1 by turning a solenoid SOL ON/OFF.

The first escape section ES1 is provided below the transport paths TR3, TR5 for transporting sheets from the storage unit LO3 to the image forming device 101, below the connection path TR6, and below the junction J1 with the transport paths TR1, TR2, 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, TR5, which is a wide range from a position adjacent to the image forming device 101 to a position adjacent to the storage unit LO3. In other words, the length in the transport direction of the sheets passing through the transport paths TR3, TR5 in the first escape section ES1 is the length from the transport path TR3 to the junction J1, via the flapper FL1, and to the connection path TR6.

The second paper feed unit DK2 includes a second transport path TR20 consisting of multiple storage compartments LO1-LO3, multiple transport paths TR1-TR5 extending from the upstream side to the downstream side, a second sheet transport means consisting of multiple 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 the downstream connection path TR26. The second escape section ES2 is provided below the connection path TR26 connected to the first paper feed unit DK1, and double-fed or jammed sheets are discharged by switching the flapper FL2. The configuration and arrangement of the storage units LO1 to LO3, the pairs of transport rollers arranged on each transport path, the sheet sensors S1 to S13, the double feed sensors DFS1 and DFS2, the motors M1 to M17, etc. are the same as those of the first paper feed unit DK1.

Next, the 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 a multi-feed.

When a specific sheet (hereafter referred to as a multi-fed sheet) PP for which a multi-fed has been detected passes through a branching position DP to the escape section and stops, there are two types of multi-fed processing: a first multi-fed processing in which only the leading edge of the multi-fed sheet PP is moved back in the direction opposite to the conveying direction and then discharged to the escape section, and a second multi-fed processing in which the entire multi-fed sheet PP is moved back in the direction opposite to the conveying direction and then discharged to the escape section. The multi-fed sheet PP is in a state in which a leading sheet Pa that is advanced and a trailing sheet Pb are overlapping the leading sheet Pa.

Jam processing is a process that is performed when a sheet transported to the image forming device 101 becomes jammed (jammed) for some reason and the sheet sensors S1 to S13 detect the stop of the sheet being transported. This jam processing includes a first jam processing in which, when a specific sheet (hereafter referred to as a retained sheet) whose transport has been stopped when a jam has occurred passes through a branch position DP to the escape section of the paper feeder DK and stops, only the leading edge of the retained sheet is moved back in the direction opposite to the transport direction and then discharged to the escape section, and a second jam processing in which the entire retained sheet is moved back in the direction opposite to the transport direction and then discharged to the escape section.

The above-mentioned multiple feed processing and jam processing are performed by the control units CON0, CON1, and CON2 of the image forming device 101, the first paper feed unit DK1, and the second paper feed unit DK2, respectively. Below, the sheet processing in the first paper feed unit DK1 is explained, but the same applies to the second paper feed unit DK2.

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 a multifeed is detected via transport path TR1 or TR2, the same applies when a multifeed is detected via transport path TR3.

As shown in FIG. 5A, in the first multiple feed process, the pair of transport rollers 53 is driven by a transport motor M10 that can switch between forward rotation, which feeds the sheet in the normal transport direction, and reverse rotation, which feeds the sheet in the opposite direction to the transport direction. In addition, sheet evacuation sections LP1 and LP2 are provided on the transport paths TR12 and TR3 upstream of the nip position RP1 of the sheet by the pair of transport rollers 53 to temporarily retreat and evacuate the leading edge of the sheet for which multiple feed has been detected. These 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 protruding a part of the transport guide (not shown) that forms the transport path outward.

The process when the double feed sensor DFS1 detects double feed of sheets is described below. First, it is determined whether the sheet sensor S10 arranged near the upstream side of the flapper FL1 is OFF, i.e., whether it detects the leading edge of the double-fed leading sheet Pa (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 upstream 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 to the connection path TR6 and switches to the conveying direction TD2 toward the first escape section ES1. In this way, the double-fed sheets PP are discharged to the first escape section ES1 (ST02). At that time, if there is a sheet (stagnant sheet) stuck in the transport path upstream of the double-fed sheet PP (No in ST03), the stuck sheet is also discharged to the first escape section ES1 (ST02). If there are no more stuck sheets (Yes in ST03), the transport and discharge operations to the first escape section ES1 are stopped (ST04).

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 located, as shown in FIG. 6A, and the transport 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 (ST05). In this retreat 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 retreat operation is possible, and if the arrival position RP2 is further downstream and the passing distance ED exceeds the allowable distance AD, it is determined that the retreat operation is not possible. The passing distance ED can be calculated based on the amount of rotation of the conveying roller pair 53 from when the leading edge of the leading sheet Pa is detected by the sheet sensor S10 until it reaches the arrival position RP2.

When it is determined that the backward operation is possible, the backward operation is executed (ST06). In this backward operation, as shown in FIG. 6B, the pair of transport rollers 53 is rotated by an amount of drive corresponding to the passing distance ED in the direction opposite to the normal transport direction, i.e., in the direction returning the sheet to the upstream side. This returns the leading edge of the leading sheet Pa to the nip position RP1 of the pair of transport 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. Then, as shown in FIG. 7, the flapper FL1 is switched to the transport direction TD2 toward the first escape section ES1, and the double-fed sheets PP are discharged (ST02). The retained sheets are also discharged in succession.

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

In the backward movement determination process in this embodiment, the allowable distance AD is set to approximately 20 mm. In other words, the sheet evacuation section LP1 has a storage space that can accommodate the sheet even if it bends by approximately 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 transport 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.

When the double feed sensor DFS2 detects a double feed of sheets fed from the storage unit LO3, the first double feed process is performed via the sheet evacuation section LP2 formed in the transport path TR3.

9 and 10 show jam processing in the case where the sheet P1 fed from the first paper feed unit DK1 to the image forming apparatus 101 jams on the transport path TR00 in the above configuration. FIG. 9 shows a state where the leading edge P2a of the following sheet (retained sheet) P2 stopped at the first paper feed unit DK1 passes through the branch position DP by the flapper FL1 and stops when a jam occurs in the image forming apparatus 101 and the transport 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 branch 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 where it is nipping the retained sheet P2. 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 caused by the return 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 switching the flapper FL1 to block the conveying path TR6.

On the other hand, if the leading edge P2a of the retained sheet P2 exceeds the allowable distance AD, it is determined that the backward movement is not possible, and the retained sheet P2 is removed by opening a specified transport path, etc.

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

As shown in Figures 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 that they can rotate forward and backward, respectively. Note that in the second multiple feed processing and second jam processing, since the entire sheet is moved back, there is no need to provide the sheet evacuation sections LP1 and LP2 as described above.

In the second multi-feed process, the multi-feed is detected by the multi-feed sensor DFS1, and if the sheet sensor S10 is OFF, it is determined that at least the leading edge of the leading sheet Pa of the multi-fed sheets PP has not passed through the branch position DP by the flapper FL1. This determination causes the flapper FL1 to switch to a direction that blocks the transport path TR6, and the multi-fed sheets PP are discharged to the first escape section ES1.

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 transport 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, if the leading edge of the leading sheet Pa is within the allowable distance AD, as shown in FIG. 8, it is determined that the retreat operation is possible.

When it is determined that the backward operation is possible, the backward operation is executed. In this backward operation, as shown in FIG. 11B, the conveying roller pairs 53, 55, and 56 are 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 an amount equivalent 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 is moved backward as if sliding in the opposite direction to the conveying direction as the conveying roller pairs 53, 55, and 56 rotate in the opposite direction. Then, as shown in FIG. 12, the flapper FL1 is switched to the first escape section ES1 side, and the conveying roller pairs 53, 55, and 56 switch from reverse rotation to forward rotation, and the overlapped sheet PP in which the leading sheet Pa and the trailing sheet Pb overlap is discharged.

The second jam processing is a processing when the sheet P1 conveyed from the first paper feed 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. After that, 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.

In the second double feed process and second jam process, the entire double-fed or jammed sheet is moved back a specified amount, which may cause the sheet to 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, allowing the sheet to smoothly pass the following sheet that has reached the conveying path TR12. The same applies to the other conveying roller pairs 53, 55.

In the above embodiment, the transport paths TR12 and TR3 upstream of the nip position RP1 of the sheet by the transport roller pair 53 are provided with sheet evacuation sections LP1 and LP2 for temporarily retracting and evacuating the leading edge of the sheet for which double feeding has been detected, as shown in FIG. 17. 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 just before the transport roller pair 53.

DK Paper feeding device DK1 First paper feeding unit DK2 Second paper feeding unit CON0, CON1, CON2 Control unit ES1 First escape unit ES2 Second escape unit M1-M14 Transport motor M15-M17 Lifting motor S1-S13 Sheet sensor DFS1-DFS3 Double feed sensor TR00 Image formation transport path TR10 First transport path TR20 Second transport path TR1-TR5 Transport paths TR6, TR26 Connection paths J1 Junction TP Through path unit FL1, FL2 Flapper (switching member)
LO1, LO2, LO3 storage DP branch position TD1, TD2 transport direction P1, P2 sheet PP multi-fed sheet Pa leading sheet Pb trailing sheet LP1, LP2, LP3 sheet evacuation section AD allowable distance ED passing distance RP1 nip position RP2 arrival position 19 discharge roller pair 20 paper feed section 21 paper feed cassette 22 pickup roller 25 separation transport roller pair 29 discharge tray 31 transport roller pair 33 registration roller pair 40a, 40b, 40c sheet feed section 41a separation transport roller pair 42a transport roller pair 43a pickup roller 44a, 44b, 44c stacking tray 45a, 45a, 45c lifting mechanism 50 conveyor 51 to 56 Conveying roller pair 100 Image forming system 101 Image forming apparatus 102 Operation unit 103 Display unit

Claims (6)

A conveying path for guiding the 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. The paper feeding device according to 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 transport failure occurs in the sheet. a double feed sensor provided upstream of the branching position for detecting double feed of the 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. a sheet sensor for detecting a sheet transported along the transport path upstream of the branch position ;
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 . 2. The sheet feeding device according to claim 1 , further comprising a notification means for notifying an error when the leading edge of the sheet exceeds the predetermined distance and feeding is stopped. 2. The sheet feeding device according to claim 1, further comprising a sheet evacuation section for accommodating a flexure of the sheet moved by the sheet transport means, the sheet evacuation section being disposed upstream of the branching position in the transport path .

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