JP2006347635A - Image forming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a waiting time from pressing of a descent button for pulling a tray out of a large capacity stacker to taking out of a sheet from the tray. <P>SOLUTION: An image forming system comprises: an elevating means for moving up/down a sheet loading stand; a descent setting means for selectively setting the moving down of the sheet loading stand; a first carrying path for carrying sheets to the sheet loading stand to load them on the stand; a second carrying path for carrying the sheets to deliver them to a sheet loading device which is connected to the subsequent stage; a third carrying path for carrying the sheet delivered from an image forming apparatus body to deliver them to a sub-delivery tray; a switching means switching among the first carrying path, a second carrying path, a third carrying path; and a control means for issuing a print stop command to the image forming device body when the moving down of the sheet loading stand is set by the descent setting means, and for making the switching means operate to switch from the first carrying path to the second carrying path or third carrying path and making the elevating means move down the sheet carrying stand. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming system having a sheet stacking device connected to an image forming apparatus such as a laser printer, a digital copier, a multi-function machine having a multi-function such as a printer, a copier, or a fax machine, or a post-processing apparatus. The present invention relates to an image forming system in which a plurality of sheet stacking devices capable of stacking a large amount of sheets discharged from an image forming device are connected in series.

  Conventionally, as a technique related to this type of image forming system, Patent Document 1 discloses a print stop determination unit that determines whether to stop printing, and a control that lowers a paper tray that can be moved up and down by the print stop determination unit. And a paper discharge device having the means.

Patent Document 1 discloses a paper discharge device provided with means for moving a paper tray to a paper loading position when a paper detection means for detecting the presence or absence of paper stacked on the paper tray detects a paper out condition. Has been.
JP-A-6-144687

  The paper discharge device disclosed in Japanese Patent Laid-Open No. 2004-26883 removes paper or resets paper when it stops printing, when it is detected that there is no paper in the paper feed device, or when a paper jam occurs in the paper feed unit. When it is detected that it is necessary, the paper tray is automatically moved to the paper loading position.

  However, in this paper discharge device, when an abnormality occurs in the transport means for transporting the printed paper to the paper tray or the paper tray lowering means for loading and lowering the transported paper on the paper tray, Waiting until all the paper is discharged onto the paper tray, the paper tray is lowered by the paper tray lowering means. In this case, a considerable time is required from the start of the operation of the paper tray lowering means until the paper on the paper tray is taken out.

  That is, the paper tray of the large-capacity stacker can be pulled out after the paper tray is lowered to the lowest position. However, even when the operator forcibly stops and wants to pull out the paper tray, the operator presses the stop button and shifts to the raising / lowering operation of the paper tray after the paper being printed from the image forming apparatus main body is completely discharged. Even when it is desired to quickly pull out the paper tray, a considerable amount of time is required for the completion of paper discharge from the main body of the image forming apparatus and the time for lowering the paper tray.

  The present invention is for solving the above-described problems, and shortens the time required from the start of the operation of the paper tray lowering means until the paper on the paper tray is taken out, and continues image formation and paper supply of the image forming apparatus main body. An image forming system including a sheet stacking device that enables the image forming system is provided.

The image forming system according to the present invention is an image forming system configured such that a plurality of sheet stacking apparatuses can be connected in series to the image forming apparatus body. The sheet stacking apparatus stacks and lifts the sheets discharged from the image forming apparatus body. A possible sheet stacking table, an elevating unit for moving the sheet stacking table up and down, a lowering setting unit for selecting and setting the lowering of the sheet stacking table, and a first transport path for transporting and stacking sheets on the sheet stacking table, A second conveyance path for conveying the sheet and discharging it to a sheet stacking apparatus connected to a subsequent stage; and a third conveyance path for conveying the sheet discharged from the image forming apparatus main body and discharging it to the sub discharge tray When the lowering of the sheet stacking table is set by the switching means for switching between the first conveying path, the second conveying path, and the third conveying path, and the lowering setting means, Control for notifying the image forming apparatus main body of a stop command, operating the switching unit to switch the first transport path to the second transport path or the third transport path, and lowering the sheet stacking table by the lifting / lowering unit And means.
In the image forming system of the present invention, a plurality of sheet stacking devices can be connected in series to the image forming apparatus main body, and the sheet stacking device stacks sheets discharged from the image forming apparatus main body. A sheet stacking table that can be moved up and down, a lifting unit that lifts and lowers the sheet stacking table, a lowering setting unit that selectively sets the lowering of the sheet stacking table, and a first transport that transports and stacks sheets on the sheet stacking table A path, a second transport path for transporting the sheet and discharging it to a sheet stacking apparatus connected to a subsequent stage, and a third transport for transporting the sheet discharged from the image forming apparatus main body and discharging it to the sub-discharge tray Switching means for switching the path, the first transport path, the second transport path, and the third transport path, and the disconnection of another sheet stacking apparatus connected to the subsequent stage are detected, and the front Control means for operating the switching means to switch the first transport path to the third transport path and discharging the sheets to the sub paper discharge tray when the lowering of the sheet stacking table is set by the lowering setting means; , Characterized by having.

  According to the present invention, the following effects can be obtained.

  (1) In an image forming system configured such that a plurality of sheet stackers can be connected in series to the image forming apparatus main body, when a stop button is pressed during an operation of stacking sheets on the sheet stacking table of the sheet stacker Of the plurality of sheet stacking apparatuses, the sheet stacking apparatus whose stop button has been pressed immediately switches the sheet conveyance, and discharges the remaining sheets to the connected sheet stacking apparatus via the second conveyance path and stops at the same time. The sheet stacking table of the sheet stacking apparatus whose button has been pressed immediately enters a lowering operation, so that the waiting time can be shortened.

  The remaining sheets discharged to the connected sheet stacking device are also waited for the removal of the remaining sheets stored in the connected sheet stacking device by lowering the sheet stacking table simultaneously with the completion of discharging. Time can be shortened.

  (2) In an image forming system in which a plurality of sheet stacking apparatuses can be connected in series to the image forming apparatus main body, when a stop button is pressed during an operation of stacking sheets on the sheet stacking table of the sheet stacking apparatus The first transport path for transporting and stacking the sheets on the sheet stacking table is immediately switched to the third transport path for discharging the sheets discharged from the image forming apparatus main body to the sub discharge tray, and the remaining sheets are transferred to the third transport path. At the same time as the sheet is discharged to the sub discharge tray via the conveyance path, the sheet stacking table of the sheet stacking apparatus whose stop button has been pressed immediately enters the lowering operation, so that the waiting time can be shortened.

  The present invention will be described below with reference to the drawings, but the description in this section is not limited to the technical scope of the claims and the meaning of terms.

  A sheet stacking apparatus and an image forming apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an image forming apparatus including an image forming apparatus main body A, a sheet stacking apparatus (hereinafter referred to as a large capacity stacker) B, an automatic document feeder DF, and a large capacity sheet feeding apparatus LT.

[Image forming device body]
The illustrated image forming apparatus main body A includes an image reading unit 1, an image processing unit 2, an image writing unit 3, an image forming unit 4, a paper feeding / conveying unit 5, and a fixing device 6.

  The image forming unit 4 includes a photosensitive drum 4A, a charging unit 4B, a developing unit 4C, a transfer unit 4D, a separating unit 4E, a cleaning unit 4F, and the like.

  The paper feeding / conveying means 5 includes a paper feeding cassette 5A, a first paper feeding means 5B, a second paper feeding means 5C, a conveying means 5D, a paper discharge roller 5E, and an automatic duplex copying paper feeding means 5F.

  An operation display unit 8 including an input unit and a display unit is disposed on the upper front side of the image forming apparatus main body A. An automatic document feeder DF is mounted on the upper part of the image forming apparatus main body A. A large-capacity stacker B is connected to the paper discharge roller 5E side of the left side of the image forming apparatus main body A shown in the figure.

  The document placed on the document table of the automatic document feeder DF is read on one or both sides of the document by the optical system of the image reading unit 1, and the photoelectrically converted analog signal is converted into an analog signal in the image processing unit 2. After processing such as processing, A / D conversion, shading correction, and image compression processing, the image is sent to the image writing unit 3.

  In the image writing unit 3, output light from the semiconductor laser is irradiated onto the photosensitive drum 4 </ b> A of the image forming unit 4 to form a latent image. In the image forming unit 4, processes such as charging, exposure, development, transfer, separation, and cleaning are performed.

  The sheet S fed by the first sheet feeding unit 5B of the sheet feeding cassette 5A is transferred to the sheet S by the transfer unit 4D. The sheet S carrying the image is fixed by the fixing device 6 and sent to the large-capacity stacker B from the paper discharge roller 5E. Alternatively, the single-sided image processed sheet S sent to the automatic double-sided copy paper feeding means 5D is again subjected to double-sided image processing in the image forming unit 4 and then discharged by the paper discharge roller 5E and sent to the large-capacity stacker B.

  The communication means 41 of the control means 40 arranged in the image forming apparatus main body A and the communication means 101 of the control means 100 arranged in the large-capacity stacker B are connected by a communication line 43, and input signals and control signals. Give and receive.

[Large capacity feeder]
The large-capacity sheet feeding device LT includes a sheet stacking unit 7A, a first sheet feeding unit 7B, and the like. The large-capacity sheet feeding device LT stacks and stores a large volume sheet S and feeds the sheet S to the image forming apparatus main body A.

[Large capacity stacker]
FIG. 2 is a front sectional view of the large-capacity stacker B showing the process of introducing the sheet S.

  The sheet S discharged from the image forming apparatus main body A and introduced into the inlet portion 11 of the large-capacity stacker B is nipped by the inlet roller 12, and is conveyed above the conveying path switching means G1 or below the first conveying path. It is conveyed to any of r1.

  The sheet S branched to the conveyance path r0 is nipped and conveyed by the conveyance roller 13, and is conveyed to either the third conveyance path r3 above the conveyance path switching unit G2 or the second conveyance path r2 below.

  The sheet S that has traveled to the third transport path r3 is discharged by the paper discharge roller 15 through the transport roller 14, and is stacked on the sub paper discharge tray 16 formed in the upper portion of the large-capacity stacker B.

  The sheet S that has traveled to the second conveyance path r <b> 2 is nipped and conveyed by the conveyance rollers 21 to 26, and is discharged to the outside by the paper discharge roller 27. Alternatively, it is sent to another post-processing device.

  The sheet S that has entered the first conveyance path r1 is nipped and conveyed by the conveyance roller 31, and is further gripped by a gripper 33 fixed to a rotating belt 32 with the leading end portion of the sheet S being moved leftward in the drawing. proceed.

  In the vicinity of the left end of the belt 32, a sheet front end regulating member 34 is waiting. The sheet leading edge regulating member 34 moves to a predetermined position corresponding to the size of the sheet S to be introduced and stops, and performs the leading edge alignment of the sheet S.

  When the leading edge of the sheet S comes into contact with the sheet leading edge regulating member 34, the gripper 33 is released and the sheet S falls and is placed on a sheet stacking table (hereinafter referred to as a tray) 35.

  The tray 35 is driven by an elevating drive means 36 including an elevating member such as a motor, a belt, or a wire, and moves up and down along a guide member 37.

  Display means 50 is disposed on the upper portion of the large capacity stacker B.

  FIG. 3 is a front sectional view of the large-capacity stacker B showing the process of stacking the sheets S.

  As the sheets S are sequentially stacked on the tray 35, the tray 35 is lowered by the lift driving means, and a signal indicating that the uppermost surface of the stacked sheets S has detected the initial position by the first sensor (first detection means) PS1. Stop and maintain the upper limit position.

  A first sensor PS1, a second sensor (second detection means) PS2A, PS2B, PS2C, PS2D, and PS2E (hereinafter referred to as a second sensor PS2) are vertically arranged in the vertical direction on the side of the guide member 37. Yes. Note that the number of second sensors PS2 is not limited to five.

  The first sensor PS1 detects the height of the top surface of the sheets S stacked on the tray 35 when the sheets S are not discharged. The second sensor PS <b> 2 detects the raising / lowering position of the tray 35 and sends a detection signal to the control means 100.

  FIG. 4 is a front sectional view of the large-capacity stacker B showing the process of taking out the sheet S to the outside.

  When taking out the sheet S accommodated in the large capacity stacker B, the operation display means 8 designates opening of the large capacity stacker B. By this designation, the lift drive means 36 lowers the tray 35.

  Below the large-capacity stacker B, a sheet transport carriage 38 having wheels 39 is movably disposed. The tray 35 is mounted in contact with the upper surface of the sheet conveying carriage 38, and the wire of the elevating drive means 36 continues to rotate, releasing the holding of the tray 35 and stopping.

  If the operator opens the front door of the large-capacity stacker B and manually or electrically pulls out the sheet conveyance carriage 38, the sheet S loaded on the tray 35 mounted on the sheet conveyance carriage 38 can be easily Can be taken out to the outside.

  FIG. 5 is an overall configuration diagram of an image forming system in which two large-capacity stackers B1 and B2 are connected to an image forming apparatus main body A in a column. FIG. 6 is a perspective view of the image forming system. Since the large-capacity stackers B1 and B2 have the same configuration, parts having the same function are denoted by the same reference numerals.

  The communication means 41 of the control means 40 arranged in the image forming apparatus main body A and the communication means 101 of the control means 100 arranged in the large-capacity stacker B1 are connected by a communication line 43, and input signals and control signals. Give and receive.

  When the sheet S introduced into the large-capacity stacker B1 and stacked on the tray 35 becomes full (for example, 5000 sheets) and the second sensor PS2E detects that the sheet stacking limit position is exceeded, the control unit 100 The sheet S discharged from the image forming apparatus main body A is switched from the first transport path r1 to the second transport path r2, transported, introduced into the large-capacity stacker B2 connected at the subsequent stage, and transported. Load on top.

  When the sheet S introduced into the large-capacity stacker B2 and stacked on the tray 35 becomes full (for example, 5000 sheets) and the second sensor PS2E detects that the sheet stacking limit position is exceeded, the control unit 200 The sheet S discharged from the image forming apparatus main body A is switched from the first transport path r1 to the second transport path r2 and transported and discharged.

  The sheets S can be sorted and accommodated in the large-capacity stackers B1 and B2 for each sheet size, sheet basis weight, and recording content of the sheet S discharged from the image forming apparatus main body A. Further, when a jam occurs in the first transport path r1 of the large capacity stacker B1, the sheet S can be stored in the tray 35 of the large capacity stacker B2 via the second transport path r2.

  FIG. 7 is an overall configuration diagram of an image forming system in which a sheet post-processing apparatus C and two large-capacity stackers B1 and B2 are connected in a column to the image forming apparatus main body A.

  The sheet post-processing apparatus C performs a punching process and various folding processes on the sheet S discharged from the image forming apparatus main body A. The sheet S discharged from the sheet post-processing apparatus C is introduced into the large-capacity stacker B1 and stacked on the tray 35. When the sheets S stacked in the large-capacity stacker B1 become full, the sheets S are stacked and accommodated in the large-capacity stacker B2 connected at the subsequent stage.

  When the sheets S stacked in the large capacity stacker B2 become full, the sheets S conveyed to the large capacity stacker B2 are discharged to the sub discharge tray 16. At this time, control is performed so that the sheet is not conveyed to the second conveyance path r2.

  Note that it is also possible to sort the sheets S and store them in the large-capacity stackers B1 and B2 for each sheet size, sheet basis weight, recording content, and post-processing type of the sheet S discharged from the sheet post-processing apparatus C.

  FIG. 8 is a plan view of the display means 50 arranged on the upper part of each main body of the large capacity stackers B1 and B2.

  The jam display unit 51 displays a position where a jam has occurred in the conveyance path in the large-capacity stacker B. The sheet size display unit 52 displays the sheet size of the sheet S carried into the large capacity stacker B. The sheet basis weight display unit 53 displays the basis weight of the sheet S carried into the large capacity stacker B. The full sheet amount limit display unit 54 displays the full load amount limit of the sheets S stacked on the tray 35, and warns, for example, by lighting a red lamp.

  The sheet stacking amount display unit 55 can display sheet stacking information during the sheet stacking operation that is stacked on the tray 35.

  A descent setting means (hereinafter referred to as a descent button) 56 is an operation button for forcibly driving the tray 35 to descent. The indicator lamp 57 displays the raising / lowering of the tray 35.

  FIG. 9 is a block diagram of control related to sheet stacking of the image forming apparatus main body A and the large-capacity stacker B.

  Hereinafter, the configuration related to the control and the outline of the operation will be described with reference to the block diagram.

  The control means 40 of the image forming apparatus main body A including a CPU or a sequencer is connected to a display means 81 including a touch panel or display means provided in the operation display means 8 and various switches. The display unit 81 displays a basic screen of the image forming apparatus main body A. For example, the size selection information (A4 size, B4 size, etc.) of the sheet size selection key 82 selected by the operator, the basis weight of the sheet, or the sheet weight An input information selection key 83 for setting sheet characteristic information such as thickness, a copy number setting key 84 for setting the number of copies, an application function key 85 for switching the basic screen to an application function screen, a copy start switch 86, paper discharge Operation information of switches such as the leading sheet stacking device setting key 87 and the sheet conveyance path selection key 88 can be read and stored in the memory 42 as necessary.

  Further, the control unit 40 is connected to the communication unit 41, and the sheet size information, sheet basis weight information, and sheet thickness information currently being discharged, which are stacking information of the image forming apparatus main body A, are transmitted via the communication unit 41. Thus, transmission to the communication unit 101 of the large-capacity stacker B connected to the image forming apparatus main body A is possible.

  A control unit 100 of the large-capacity stacker B composed of a CPU or a sequencer is connected to a first sensor PS1 that detects the sheet S and second sensors PS2A, PS2B, PS2C, PS2D, and PS2E that detect the position of the tray 35. The output signals of these sensors can be input.

  Further, a memory 102 is connected to the control means 100. Based on a sheet S stacking program stored in advance, the sheet S is removed from the large capacity stacker B as shown in FIGS. Is selected from among a third transport path r3 for discharging the sheet S, a second transport path r2 for discharging to a large-capacity stacker downstream in the transport direction (not shown), and a first transport path r1 for stacking sheets S in the large-capacity stacker B. Transport.

  Further, the control unit 100 is connected to the communication unit 101, and the stackable sheet size information (for example, A4 size) set in advance, which is the stacking information of the large capacity stacker B, and the sheet S on the tray 35 are stored. Full sheet information indicating whether or not the sheet is full, remaining sheet information indicating whether or not there is a remaining sheet in the tray 35, abnormality information indicating whether or not a jam has occurred, and the like are conveyed via the communication unit 101. Transmission is possible with the communication means 41 of the image forming apparatus main body A connected upstream in the direction. The communication unit 41 can receive the stacking information transmitted from the image forming apparatus main body A.

  FIG. 10 is a flowchart relating to the control of the large-capacity stacker. The conveyance control of the sheet S will be described using the image forming system shown in FIGS. Hereinafter, the tray 35 is also referred to as a tray.

  Step 1 During the sheet stacking operation, it is detected that a trouble such as a conveyance failure of the sheet S in the first conveyance path r1 occurs in any one of the large capacity stackers, for example, the large capacity stacker B1, and the jam display section of the display means 50 When it is confirmed that the message is displayed at 51, the operator depresses the lowering button 56 of the large-capacity stacker B1 where the trouble has occurred.

  Step 2 The control unit of the large-capacity stacker B1 where the trouble has occurred contacts the control unit 40 of the image forming apparatus main body A via the communication line 43 and notifies the image forming apparatus main body A of a paper feed stop command.

  Step 3 The communication line 43 and the control means detect whether the subsequent large-capacity stacker B2 is connected or not connected to the large-capacity stacker B1 where the trouble has occurred.

  Step 4 When it is confirmed that the subsequent large-capacity stacker B2 is connected, the first transport path r1 is immediately switched to the second transport path r2, and the remaining sheets S are routed through the second transport path r2. To discharge.

  Step 5 At the same time, the tray 35 of the large-capacity stacker B1 for which the lowering button 56 has been pressed is immediately started to descend. The waiting time can be shortened by switching to the second transport path r2 and starting to lower the tray 35.

  Step 6 When the tray 35 reaches the lowest lowered position, the full-scale door (not shown) of the large-capacity stacker B1 is opened, and the tray 35 on which the sheets S are stacked is pulled out. As a result, the sheet S can be taken out.

  Step 7 When the printing by the image forming apparatus main body A is completed and the discharge of the large-capacity stacker B2 connected at the subsequent stage of the sheet conveyance switching destination is completed, the lowering of the tray 35 is started.

  Step 8 When the tray 35 of the large-capacity stacker B2 connected to the rear stage reaches the lowest lowered position, the entire surface door (not shown) of the large-capacity stacker B2 connected to the rear stage is opened, and the tray 35 on which the sheets S are stacked is pulled out. As a result, the sheet S can be taken out.

  Step 9 The disconnection of the subsequent large-capacity stacker B2 to the large-capacity stacker B1 where the trouble has occurred is detected (large-capacity stacker B in FIG. 1, large-capacity stacker B2 in FIG. 5, large-capacity stacker B1 in FIG. 6). When the lowering of the tray 35 is set by the lowering button 56, the control unit operates the switching unit to switch the first transport path r1 to the third transport path r3, and discharges the sheet S to the sub discharge tray 16. .

  Step 10 At the same time, the tray 35 of the large capacity stacker B2 for which the lowering button 56 has been pressed is immediately started to descend.

  Step 11 When the tray 35 of the large-capacity stacker B1 reaches the lowest position, the unillustrated full surface door of the large-capacity stacker is opened, and the tray 35 on which the sheets S are stacked is pulled out. As a result, the sheet S can be taken out.

1 is an overall configuration diagram of an image forming apparatus including an image forming apparatus main body, a sheet stacking apparatus, an automatic document feeder, and a large capacity sheet feeding apparatus. FIG. 6 is a front sectional view of a large-capacity stacker showing a process for introducing a sheet. FIG. 6 is a front sectional view of a large-capacity stacker showing a process of stacking sheets. FIG. 3 is a front sectional view of a large-capacity stacker showing a process of taking out a sheet to the outside. 1 is an overall configuration diagram of an image forming system in which two large-capacity stackers are connected in series to an image forming apparatus main body. 1 is a perspective view of an image forming system. 1 is an overall configuration diagram of an image forming system in which a sheet post-processing device and two large-capacity stackers are connected in a column to an image forming apparatus main body. The top view of a display means. FIG. 3 is a block diagram of control related to sheet stacking of an image forming apparatus main body and a large-capacity stacker. The flowchart which concerns on control of a high capacity | capacitance stacker.

Explanation of symbols

8 Operating means 16 Sub-output tray 35 Sheet stacking tray (tray)
36 Lifting drive means 38 Sheet conveying cart 40, 100, 200 Control means 41, 101 Communication means 43 Communication line 50 Display means 51 Jam display section 52 Sheet size display section 55 Sheet load amount display section 56 Lowering setting means (down button)
57 indicator lamp 81 display means 87 discharge destination sheet stacking device setting key 88 sheet transport path selection key A image forming apparatus main body B, B1, B2 sheet stacking device (large capacity stacker)
G1, G2 transport path switching means S sheet r1 first transport path r2 second transport path r3 third transport path

Claims (2)

In the image forming system configured to connect a plurality of sheet stacking devices in series to the image forming apparatus main body,
The sheet stacking apparatus includes a sheet stacking table on which sheets discharged from the image forming apparatus main body can be stacked and moved up and down,
Elevating means for elevating and lowering the sheet stacking table;
Lowering setting means for selectively setting lowering of the sheet stacking table,
A first transport path for transporting and stacking sheets on the sheet stacking table;
A second conveyance path for conveying the sheet and discharging it to a sheet stacking device connected to a subsequent stage;
A third conveyance path for conveying a sheet discharged from the image forming apparatus main body and discharging the sheet to a sub discharge tray;
Switching means for switching between the first transport path, the second transport path, and the third transport path;
When the lowering of the sheet stacking table is set by the lowering setting means, a print stop command is notified to the image forming apparatus main body, and the switching means is operated to change the first transport path to the second transport path or the second transport path. An image forming system comprising: a control unit configured to switch to three transport paths and to lower the sheet stacking table by the lifting unit. In the image forming system configured to connect a plurality of sheet stacking devices in series to the image forming apparatus main body,
The sheet stacking apparatus includes a sheet stacking table on which sheets discharged from the image forming apparatus main body can be stacked and moved up and down,
Elevating means for elevating and lowering the sheet stacking table;
Lowering setting means for selectively setting lowering of the sheet stacking table,
A first transport path for transporting and stacking sheets on the sheet stacking table;
A second conveyance path for conveying the sheet and discharging it to a sheet stacking device connected to a subsequent stage;
A third conveyance path for conveying a sheet discharged from the image forming apparatus main body and discharging the sheet to a sub discharge tray;
Switching means for switching between the first transport path, the second transport path, and the third transport path;
When the disconnection of another sheet stacking device connected at the subsequent stage is detected and the lowering of the sheet stacking table is set by the lowering setting unit, the switching unit is operated to move the first transport path along the third transporting path. An image forming system comprising: a control unit that switches to a path and discharges a sheet to the sub-sheet discharge tray.

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