JP4405431B2 - Paper transport device and paper transport method - Google Patents

Description

The present invention is a sheet conveying apparatus for conveying paper (sheet transfer medium such as transfer paper), and relates the sheet conveying apparatus in an image forming equipment having integrally or separately.

  As this type of technology, for example, the technology disclosed in Patent Document 1 is known. In this document, a branching claw is arranged in the conveyance path, and after the trailing edge of the sheet passes through this, the conveyance roller is reversed to guide the trailing edge of the sheet to the sheet accommodating portion to retain the sheet. There is described a sheet processing apparatus configured to be transported in an overlapping manner. In this paper processing apparatus, it is also possible to convey two or more sheets in a superimposed manner by repeating the above operation.

  Patent Document 2 discloses a conveying unit that conveys a sheet to a discharge port along a conveying path, a staying unit that temporarily retains the sheet on the conveying unit, and a sheet that is conveyed by the conveying unit. Sheet processing having determination means for determining whether or not the paper is special paper, and, when the sheet conveyed by the conveyance means is special paper, a staying number limiting means for limiting the number of sheets retained by the staying means An apparatus is described.

Further, Patent Document 3 discloses a paper discharge tray for directly stacking paper discharged from the image forming apparatus or stacking a post-processed paper bundle, a post-processing tray for post-processing the paper bundle, In the sheet post-processing apparatus including a first transport path from the entrance portion toward the paper discharge tray and a second transport path branched from the first transport path and toward the post-processing tray, A paper post-processing apparatus, wherein a switching claw is provided on the conveyance path, and a staying conveyance path branched from the first conveyance path by the switching claw and joined to the second conveyance path is provided. Is described.
Japanese Patent Laid-Open No. 2004-001998 JP 2001-097631 A JP-A-11-199128

  By the way, in the technique described in Patent Document 1, when the trailing edge of the sheet is guided to the sheet accommodating portion and the sheet is retained, the sheet is conveyed in the reverse direction until the leading edge of the sheet protrudes several millimeters from the conveying roller, that is, the state where it does not pass. The sheet is stopped at the position, and is rotated forward immediately before the leading edge of the next sheet reaches the conveying roller, and the overlapping conveyance is performed with as little deviation as possible between the respective sheets.

  By the way, in order to increase productivity in the paper processing apparatus as in the conventional example, it is necessary to increase the paper conveyance speed. Therefore, when the stopped first sheet is transported so as not to be misaligned with the second sheet, the second sheet reaches the transport roller holding the first sheet. Sometimes it is necessary to start driving the transport rollers. However, it takes time until the conveyance roller starts driving and the conveyance speed of the first sheet reaches the same speed as that of the second sheet. Therefore, the second sheet has a speed difference between the leading edge and the trailing edge of the sheet, which may cause a large deflection of the sheet and possibly damage the sheet.

  Also, before the second sheet reaches the conveying roller holding the first sheet, the conveying roller is driven so that the speed of the first sheet is the same as the speed of the second sheet. In this case, since the first sheet advances first, a large shift occurs between the first and second sheets. If the misalignment is large as described above, it takes time for paper alignment in the next process, which causes a decrease in productivity, and there is a possibility that inconveniences such as folding of the edge of the paper may occur during paper alignment.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to maintain high productivity and to enable sheet conveyance and sheet processing without fear of sheet breakage. is there.

In order to achieve the object, the first means branches the first conveyance path for guiding the sheet conveyed from the preceding apparatus to the processing tray and the first conveyance path, and temporarily retracts the sheet. A second conveying path that is provided, a branching claw that is provided at the branched portion and guides the trailing edge of the sheet to the second conveying path when conveyed in the reverse direction after the trailing edge of the sheet has passed, The first conveying means provided in the first conveyance path and from the branching claw to the preceding apparatus side, and the first conveying means provided in the first conveyance path and from the branching claw to the processing tray side. and second conveying means, provided with, in the sheet conveying device having a function of conveying superimposed with trailing sheet the second previous row paper which has been temporarily saved in the conveying path of the conveying said second Means to convey the preceding paper in the direction opposite to the processing tray side and to the second conveyance path. When retracted, the preceding paper is clamped by the second transport means, and the leading edge of the succeeding paper by the first transport means before the leading edge of the succeeding paper reaches the second transport means. Control means for stopping the conveyance is provided.
The second means includes a first conveyance path that guides the sheet conveyed from the preceding apparatus to the processing tray, and a second conveyance path that branches from the first conveyance path and temporarily retracts the sheet. A branching claw that is provided at the branched portion and guides the second conveyance path when a sheet that has passed through the portion is conveyed in the reverse direction; and the branching claw in the first conveyance path. First conveying means provided on the preceding apparatus side, and second conveying means provided on the processing tray side from the branching claw in the first conveying path, In the paper transport apparatus having a function of transporting the preceding paper that has been temporarily retracted to the second transport path while superimposing the succeeding paper on the succeeding paper, the second transporting unit reverses the preceding paper from the processing tray side. When the second transport path is temporarily retracted to the second transport path. Control means for holding the preceding paper by the means and stopping the conveyance of the succeeding paper by the first conveying means when the leading edge of the succeeding paper reaches the second conveying means. Features.
The third means is characterized in that, in the first or second means, the control means restarts the conveyance of the preceding paper and the following paper when the conveyance of the following paper is stopped.
The fourth means is any one of the first to third means, wherein the control means decelerates the transport speed of the succeeding paper before the leading edge of the succeeding paper reaches the second transport means. The sheet is conveyed while being superposed on the preceding sheet in a decelerated state.
A fifth means is the fourth means wherein the control means increases the transport speed of the preceding paper and the following paper when the leading edge of the following paper reaches the second transport means position. It is characterized by making it.
A sixth means is the fourth means, wherein the control means carries the succeeding paper into the second conveying means at a speed at which the succeeding paper is carried into the first conveying path from the preceding apparatus, and It is characterized in that it is transported in superposition with paper.
The seventh means is characterized in that, in any one of the fourth to sixth means, means for allowing the trailing paper to bend is provided upstream of the conveying means in the paper conveying direction.
According to an eighth means, in the seventh means, the means for allowing the bending is a guide plate facing a sheet surface constituting the conveyance path of the first conveyance path, and an upstream side of the guide plate in the sheet conveyance direction. For supporting the guide plate in a swingable manner, an elastic urging member for elastically urging the guide plate in the closing direction at all times, and regulating the position of the free end of the guide plate to convey the paper And a stopper for ensuring the conveyance width of the sheet.
A ninth means is characterized in that the image forming apparatus includes a paper conveying apparatus according to any one of the first to eighth means.
The tenth means includes: a first conveyance path that guides the sheet conveyed from the preceding apparatus to the processing tray; a second conveyance path that branches from the first conveyance path and temporarily retracts the sheet; A branching claw that is provided at the branched portion and guides the second conveyance path when a sheet that has passed through the portion is conveyed in the reverse direction; and the branching claw in the first conveyance path. First conveying means provided on the preceding apparatus side, and second conveying means provided on the processing tray side from the branching claw in the first conveying path, In the paper transport method for transporting the preceding paper temporarily retracted to the second transport path by superimposing it on the succeeding paper, the second transport means transports the preceding paper in a direction opposite to the processing tray side. , When the second conveying means is temporarily retracted to the second conveying path, The preceding sheet is interposed, the leading end of the trailing sheet is characterized by stopping the conveyance by the first conveying means of said trailing sheet before reaching the second transport means.
The eleventh means includes a first conveyance path that guides the sheet conveyed from the preceding apparatus to the processing tray, and a second conveyance path that branches from the first conveyance path and temporarily retracts the sheet. A branching claw that is provided at the branched portion and guides the second conveyance path when a sheet that has passed through the portion is conveyed in the reverse direction; and the branching claw in the first conveyance path. First conveying means provided on the preceding apparatus side, and second conveying means provided on the processing tray side from the branching claw in the first conveying path, In the paper transport method for transporting the preceding paper temporarily retracted to the second transport path by superimposing it on the succeeding paper, the second transport means transports the preceding paper in a direction opposite to the processing tray side. , When the second conveying means is temporarily retracted to the second conveying path, The preceding sheet is interposed, the leading end of the trailing sheet is characterized in that stopping conveyance by the first conveying means of said trailing sheet when it reaches the second conveying means.

  In the embodiment described later, the first transport path is the first and second lower transport paths 2b and 2c, the second transport path is the prestack path 2d, and the transport means is the second and third transport paths. The roller (pair) 6 and 7, the switching means is the switching claw 9, the branching point is 2h, the control means is the CPU 32, and the means for allowing deflection is the guide plate 100, the torsion spring 101, the stopper 102 and the support shaft 103. Each corresponds.

According to the present invention, a large deflection occurs in the paper to succeeding when superimposed transport, thereby preventing damaging the paper.

  Embodiments of the present invention will be described below with reference to the drawings.

1. First Embodiment <Overall Configuration>
FIG. 1 is a diagram illustrating a schematic configuration of an image forming system including a sheet processing apparatus and an image forming apparatus according to an embodiment of the present invention. The image forming system according to the present embodiment includes an image forming apparatus 1 that forms an image on a sheet, which is a sheet-like recording medium, and various post-processing such as alignment and binding with respect to the sheet discharged from the image forming apparatus 1 Is basically composed of a sheet post-processing apparatus 2 as a sheet processing apparatus for performing the above. The image forming apparatus 1 includes any one of a copier having a function of forming an image on a sheet, a printer, a facsimile, or a complex machine in which these functions are combined. Since the image forming apparatus having these functions is a known one, and the function of this image forming apparatus is not the gist of the present invention, description thereof is omitted here. In addition to the alignment and binding functions, the sheet post-processing apparatus 2 has functions such as punching and folding. These are known configurations, and the specifications of the sheet post-processing apparatus 2 are as follows. It is set accordingly.

  The paper post-processing device 2 basically includes a receiving port 2a, lower transport paths 2b and 2c, an upper transport path 2f, a prestack path 2d, a paper processing unit 18, a paper discharge roller 16, a paper discharge port 15, and a paper discharge tray 3. It is configured. The receiving port 2a is an opening for receiving paper from the paper discharge port 1a of the image forming apparatus 1, and an inlet sensor S1 and an inlet roller pair 4 are provided in the paper transport path 2g following the receiving port 2a.

  The sheet conveyance path 2g on the downstream side of the entrance roller pair 4 is a lower conveyance path 2b, 2c for guiding the sheet to the sheet processing unit 18 side (hereinafter, the first lower conveyance on the upstream side from the branch point 2h where the switching claw 9 is provided). The path 2b, the downstream side is referred to as the second lower transport path 2c), and the upper transport path 2f (details are omitted in the figure) that leads directly to the paper discharge outlet 15 side, and branches to that branch point The claw 2e is arranged. This branching claw 2e is driven by a stepping motor (not shown) to switch the paper transport path.

  The first lower transport path 2b is provided with a sensor S2 and a first transport roller 5 for detecting the paper in the lower transport path 2b from the upstream side in the paper transport direction, and a prestack path 2d is provided at the lower end portion in the paper transport direction. Are provided so as to function as a guide when the switching claw 9 moves backward at the branch point. The second lower conveyance path 2c is a conveyance path from the branch point 2h to the sheet processing unit 18, and the second and third conveyance roller pairs 6 and 7 are arranged, and the tray discharge is disposed on the most downstream side. Eight pairs of rollers are provided. In the following description, a pair of roller pairs is omitted.

  The sheet processing unit 18 aligns the sheet conveyance direction, the staple tray 14 on which sheets are discharged and stacked, the alignment fence 10 that aligns the direction orthogonal to the sheet conveyance direction of the sheets stacked on the staple tray 14, and the sheet conveyance direction. On the trailing edge fence 11, the tapping roller 14 a that brings the paper discharged on the staple tray 14 toward the trailing edge fence 11, the stapler 12 that binds the bundle of sheets aligned on the staple tray 14, and the staple tray 14. The discharge mechanism 13 includes a discharge belt 13 that discharges a bound sheet bundle and a pair of discharge claws 13a and 13b. The discharge belt 13 is stretched between the discharge roller 19 and the driven roller 19a, and discharges a sheet bundle from the discharge port 15 onto the discharge tray 3 by one of the discharge claws 13a and 13b. At that time, a predetermined pressing force is received from the paper discharge roller 16 by releasing the paper discharge roller 16 provided on the free end side of the paper discharge lever 17 supported swingably on the support shaft 17a. The sheet bundle is reliably conveyed.

<Control configuration>
FIG. 2 is a block diagram showing a control configuration of the image forming system according to the present embodiment.
In the figure, a control device 31 is composed of a microcomputer having a CPU 32, an I / O interface 33, and the like, and includes switches on the control panel of the image forming apparatus 1 main body, an inlet sensor SN1, a sensor SN2, and other sensors. Is input to the CPU 32 via the I / O interface 33. The CPU 32 controls various motors and solenoids based on the input signals. Further, the stapler 12 also controls a stapler drive motor and a stapler moving motor (not shown) to drive a staple needle at a predetermined position of the sheet according to an instruction from the CPU 32 and execute a binding operation of the sheet bundle.

  The sheet post-processing device 2 is controlled by the CPU 32 executing a program written in a ROM (not shown) while using a RAM (not shown) as a work area. Data necessary for control and processing is stored in the EPROM 34 in addition to the RAM.

<Operation>
FIG. 22 is an explanatory diagram showing the basic concept of the present invention. That is, as described above, it is necessary to increase the paper transport speed when increasing productivity. In the case where the prestacked first sheet and the second sheet are transported with less misalignment, as shown in FIG. 22A, the first sheet (preceding sheet) P1 is moved to the prestack path 2d. When the leading edge of the second sheet (following sheet) P2 reaches the nip of the second conveying roller 6 as shown in FIG. The driving of the roller 6 is started, and the first and second sheets P1, P2 are stacked and conveyed. At this time, even if the driving of the second transport roller 6 is started, the second transport roller 6 does not immediately reach the transport speed of the second sheet, but the speed increases as the transport speed increases. It takes time to reach. For this reason, the second sheet P2 has a slow conveyance speed at the leading edge and a high conveyance speed at the trailing edge, which may cause the sheet to bend and damage the sheet P2, as shown in FIG. Is expensive.

  Further, in order not to damage the paper P2, the driving of the second transport roller 6 is started before the leading edge of the second paper P2 reaches the second transport roller 6, and the first sheet When the paper P1 is transported and the second paper P2 reaches the second transport roller 6, the transport speed of the first paper P1 is controlled to be equal to the transport speed of the second paper P2. As a result, it is possible to prevent bending, but as shown in FIG. 22 (d), a large deviation L occurs between the leading edge of the first sheet P1 and the leading edge of the second sheet P2.

  Since the path width is about 2 to 3 mm and it is necessary to transport a B5 horizontal (182 mm) size sheet, the deflection is about 4 mm between the first and second transport rollers 5 and 6 at a distance of 175 mm. However, if it is larger than this, there is a high possibility of causing a paper jam or damaging the paper.

  The present embodiment is an example in which the deviation L can be reduced without reducing productivity from such a point.

<< 1 copy >>
The paper output from the image forming apparatus 1 is carried into the paper post-processing apparatus 2 through the paper discharge port 1a and the receiving port 2a. The paper carried into the paper post-processing device 2 is detected by the entrance sensor SN1, and is transported through the paper transport path 2g by the entrance roller 4. The switching direction of the branching claw 2 e is instructed by the CPU 32 of the control device 31 in accordance with a sheet processing instruction transmitted from the image forming apparatus 1. Therefore, when the sheet is conveyed to the sheet processing unit 18 side, the sheet is first guided to the first lower conveying path 2b by rotating the branching claw 2e in the counterclockwise direction (the state shown in FIG. 1). The sheet guided to the first lower conveyance path 2b rotates the switching claw 9 counterclockwise by the conveyance force of the sheet provided by the entrance roller 4 and the first conveyance roller 5, thereby reducing the sheet conveyance space. Secure. As a result, the sheet is guided from the space secured as described above to the second lower conveyance path 2c side, and then passed through the second and third conveyance rollers 6 and 7 to the staple tray 14 by the tray discharge roller 8. The paper is ejected.

  The discharged paper leaves the nip of the tray paper discharge roller 8, lands on the staple tray 14, and then falls by its own weight in the direction of arrow B. At the same time, it is knocked down by the hitting roller 14 a and the rear end in the transport direction is aligned by the rear end fence 11. Then, the trailing edge of the sheet is detected in advance by the sensor SN2, and the width direction is aligned by the alignment fence 10 after a time during which the sheet conveyance direction can be aligned. By repeating this operation, a large number of sheets are aligned one by one.

<< In the case of two or more parts >>
In the case of 1 part, it operates as described above, but in the case of 2 parts or more, it operates as follows.

  The interval between sheets output from the image forming apparatus 1 is constant, and the interval between jobs is also constant. When the first copy is output from the image forming apparatus 1, signals such as the paper size, number of sheets, transport speed, and processing mode are sent. When the signal is received by the sheet post-processing device 2, the number of sheets to be stacked, the acceleration point, the acceleration linear velocity, the retrograde point, and the stop point at the time of stacking are determined. These determinations are made by a CPU of a control circuit described later.

(1) When the length of the paper in the transport direction is B5 horizontal size (182 mm) or more and less than B5 vertical size (257 mm) First, the length of the paper in the transport direction is B5 horizontal size (182 mm) or more B5 vertical 3A to 3D show a processing operation for a sheet having a size less than 257 mm. Details of the operation at that time are shown in FIGS.

  The leading sheet P1 of the job output from the image forming apparatus 1 is conveyed by the entrance roller 4 and the first conveying roller 5 of the sheet post-processing apparatus 2, and the trailing edge of the sheet passes through the branching claw 9 and passes through FIG. (The distance α from the branch point 2h (corresponding to almost the tip of the branch claw 9)). At this time, when it is necessary to reverse the sheet by a signal from the image forming apparatus 1, the second conveyance roller 6 and the third conveyance roller 7 once stop and further reverse rotation in the clockwise direction shown in the drawing. At that time, the branching claw 9 functions and the paper is guided to the prestack path 2d and prestacked. The branching claw 9 is always elastically biased so that the prestack path is opened at the time of reverse feeding of the paper at a low pressure (pressure that can be rotated by a space sufficient for the paper to pass through as described above). Yes. The distance transported to the prestack path 2d is measured by a pulse count or a timer from the sensor SN2 disposed immediately before in the transport direction of the first transport roller 5, and the counted number or time is measured. Based on the control timing, the sheet is stopped when the trailing edge of the sheet (at the leading edge of the sheet conveyance during reverse feeding) is the same position. At this time, as shown in FIG. 3B and FIG. 4A, the sheet is nipped by the nip of the second conveying roller 6 and stopped in a state where it protrudes from the nip several mm (distance β-5 mm). ing. In order to reduce the pop-out amount β as much as possible, the sensor SN2 is disposed as close as possible to the reverse point to reduce the conveyance error and to stop the sheet with high accuracy. If the stop can be performed with high accuracy, the pop-out amount β can be reduced to the utmost limit, thereby reducing the deviation when the paper is superposed on the next sheet and transporting it, thereby improving the alignment on the staple tray 14.

  Next, as shown in FIG. 3C, the second sheet P <b> 2 is conveyed by the first conveying roller 5. When the leading edge of the second sheet is conveyed upstream from the second conveyance roller 6 to a position of a predetermined distance γ, for example, 20 mm, based on the detection information of the sensor SN2, as shown in FIG. 4 and the first transport roller 5 are temporarily stopped, and then re-driven as shown in FIG. 4C. At the same time, the second and third transport rollers 6 and 7 are rotated in the counterclockwise direction. The conveyance of the sheets stacked in the lower conveyance path 2c and the stack path 2d is started. Since the first sheet of the job is re-conveyed as shown in FIG. 3D while being nipped by the nip of the third conveying roller 7, the leading edge of the first sheet of the job is more than the leading edge of the second sheet. Two sheets are simultaneously discharged onto the staple tray 14 in the preceding state. The discharged sheet bundle is rotated by the discharge belt 13 installed parallel to the sheet conveyance direction at the center of the staple tray 14, and a pair of discharge claws 13 a and 13 b installed at symmetrical positions of the discharge belt 13. Moves in the direction of arrow B, strikes the leading edge of the paper protruding from the back of one discharge claw 13, aligns two sheets and drops them to the trailing edge fence 11, and the deviation in the conveying direction is aligned. Accordingly, post-processing can be performed without reducing the productivity and binding quality of the main body of the image forming apparatus 1.

  The above is the conveyance situation in the case of two sheets. If two or three sheets are stacked according to the processing contents in the staple tray 14 to earn a job, it is possible to perform post-processing without dropping the CPM of the main body by repeating the above operation.

  In this embodiment, the timing for re-conveying the paper that has been waiting in the prestack path 2d is set at a position 20 mm upstream of the second conveyance roller 6 as described above, but this timing is not necessarily limited. The position does not have to be 20 mm from the second conveyance roller 6 and is based on the condition that the leading edge of the (N + 1) th sheet does not enter the second conveyance roller 6 during the slow-up of the second conveyance roller 6. A position as close to the second conveying roller 6 as possible (for example, 5 mm) is preferable. Even if the leading edge of the (N + 1) th sheet is transported after abutting against the second transporting roller 6, there is no problem if there are no leading scratches, flexure scratches, etc., in that case, 0 mm.

  FIG. 5 is a timing chart showing the operation timing of the leading edge and the trailing edge of the second (following) sheet when the operations of FIGS. 3 and 4 are performed, and FIG. 6 is an inlet roller corresponding to the timing chart of FIG. 4 is a timing chart showing operation timings of the first conveyance roller 5 and the second conveyance roller 6.

  In FIG. 5, F indicates the leading edge of the sheet and B indicates the trailing edge of the sheet. In FIG. 5, the vertical axis is the position, the distance from the receiving port 2a carried into the paper post-processing apparatus 2 is taken in mm, the horizontal axis is time, and the inlet sensor S1 is cut off at the tip. The elapsed time from is taken in ms. In this embodiment, it temporarily stops at the T1 position (position of 600-20 mm from the entrance) 20 mm upstream of the second conveyance roller 6 in the nip sheet conveyance direction. This state is the paper position in FIG. At this time, as shown in FIG. 5, the entrance roller 4 and the first transport roller 5 are temporarily increased immediately before the stop timing (650 mm / s → 950 mm / s) to minimize time loss when stopped. ing. At the time of re-conveying, the entrance roller 4 and the first conveying roller 5 are re-driven, and the second conveying roller 6 starts to be driven from the stopped state, and is superposed on the first (preceding) sheet so as to overlap the staple tray. It is conveyed to the 14 side. The sheet conveyance speed by these drives is 750 mm / s. Since the entrance roller 4 and the first transport roller 5 have the same drive source, they are driven at the same timing and the same transport speed. Further, since the sheet is conveyed without being bent, the relative positional relationship between the sheet leading edge F and the sheet trailing edge B is always constant. Further, a control procedure for this operation is shown in a flowchart of FIG. 14 described later.

  FIG. 7 shows that when the stop position γ is 0 mm, that is, after the leading edge F of the second (following) sheet is stopped at the nip of the second conveying roller 6, it is re-conveyed with the preceding sheet P1. FIG. 8 is a timing chart showing the operation timing of the leading edge and the trailing edge of the sheet at that time, FIG. 9 is an inlet roller 4 corresponding to the timing chart of FIG. 6 is a timing chart showing the operation timing of the second transport roller 6.

  The parameters shown in FIGS. 6 and 7 are the same as those shown in FIGS. 4 and 5, and the leading edge F of the second (following) paper P <b> 2 is the second transport roller 6 as shown in FIGS. 7A and 8. When the nip position is reached, the sheet (first transport roller 5) temporarily stops as indicated by T2. The second conveying roller 6 starts conveying when the sheet stops. At the same time, as shown in FIGS. 7B, 8 and 9, the first conveying roller 5 and the entrance roller 4 which have once been stopped after being accelerated are also started to rotate again from the stopped state. The paper stacked on the staple tray 14 side together with the (preceding) paper P1 is conveyed. In this case, the deviation L between the preceding paper P1 and the following paper P2 is obtained by subtracting the paper thickness from the protruding amount β of the preceding paper P1 from the nip of the second transport roller 6 shown in FIG. Almost equal to the distance.

  The speed relationship is the same as that described with reference to FIGS. 4 and 5 except that the stop position of the second sheet extends to the nip position of the second conveyance roller 6. In this example, the stop position of the second (following) sheet P2 is set to the nip position of the second conveyance roller 6. Further, a control procedure for this operation is shown in a flowchart of FIG.

  As described above, when the second sheet P2 is temporarily stopped at the position where the leading edge of the second sheet is stopped at the nip position of the second transport roller 6, the first sheet P1 and the second sheet P2 are stopped. The shift amount L of the paper P2 can be minimized, and more paper can be prestacked. Thereby, productivity can be improved.

  In the example described so far, the first sheet P1 is conveyed without stopping to the position shown in FIG. 3A, for example, and the second and third conveying rollers 6 and 7 are reversed from the position to form the sheet. Is reversely moved in the direction of the pre-stack path 2d, and then stopped at the pre-stack position to wait for the second sheet P2 to be loaded. You may stop once before reaching or when reaching 6. By controlling in this way, the same control can be performed without distinguishing between the first sheet and the second and subsequent sheets, so that the control is simplified and a decrease in reliability can be prevented. A control procedure for this operation is shown in the flowchart of FIG.

  Even when the first sheet P1 does not need to be prestacked (for example, when sheets are conveyed from a low-productivity apparatus or when one sheet is processed), It can also be controlled to stop once before or when the leading edge of the sheet reaches the second conveying roller 6. Also in this case, the same control can be performed without distinguishing for each sheet, so that the control is simplified and a decrease in reliability can be prevented.

(2) In the case of paper of B5 vertical size or larger Next, processing operations of paper of B5 vertical size (257 mm) or larger are shown in FIGS.
When a paper of B5 vertical size or larger is conveyed, the second conveying roller 6 is operated in the direction of the arrow to release the pressure in advance. Since the distance between the first conveyance roller 5 and the third conveyance roller 7 is set to be shorter than the B5 vertical size within a range of several mm to 10 mm, there is no problem even if the pressure of the second conveyance roller 6 is released. Be transported. In such a state, the operation of the second conveying roller 6 as described above is performed by the third conveying roller 7 as an operation of less than the B5 vertical size, and prestacking is performed.

  That is, when it is necessary to reverse the sheet by a signal from the image forming apparatus 1, if the sheet size is B5 vertical size or more, first, the pressure of the second conveying roller 6 is released to open the nip, and the first The two transport rollers 6 are not related to the sheet transport. In this state, the first sheet P1 of the job output from the image forming apparatus 1 is conveyed by the entrance roller 4 and the first conveyance roller 5 of the sheet post-processing apparatus 2, and the rear end of the sheet passes through the branching claw 9. It is transported to the position 10 (a) (distance α from the branch point 2h). The third conveying roller 7 once stops and further reverses in the clockwise direction in the figure. At that time, the branching claw 9 functions and the paper is guided to the prestack path 2d and prestacked. The distance transported to the prestack path 2d is measured by a pulse count or a timer from the sensor SN2 disposed immediately before in the transport direction of the first transport roller 5, and the counted number or time is measured. Based on the control timing, the sheet is stopped when the trailing edge of the sheet (at the leading edge of the sheet conveyance during reverse feeding) is the same position. In this example, the rear end of the sheet is set to stop at the same position relative to the second conveyance roller 6 as compared with the case of the sheet less than B5 length with respect to the second conveyance roller 6. That is, as shown in FIG. 10B, the sheet stops in a state where it protrudes from the nip of the third conveying roller 7 to the downstream side in the distance β conveying direction.

  Next, as shown in FIG. 10C, the second sheet P <b> 2 is conveyed by the first conveying roller 5. When the leading edge of the second sheet is conveyed upstream from the third conveyance roller 7 to a predetermined distance, for example, a position of 20 mm, based on the detection information of the sensor SN2, the third conveyance roller 7 is counterclockwise. Rotation is started, and conveyance of the sheets stacked on the second lower conveyance path 2c and the stack path 2d is started. Also in this case, the leading sheet of the job is re-conveyed as shown in FIG. 10D while being nipped by the nip of the third conveying roller 7, so the leading edge of the leading sheet of the job is the second sheet. Two sheets are simultaneously discharged onto the staple tray 14 in a state preceding the leading edge of the sheet. The discharged sheet bundle strikes the leading edge of the sheet protruding at the back of one discharge claw 13 as described above, aligns two sheets and drops to the trailing edge fence 11 to align the deviation in the transport direction. Thus, post-processing can be performed without reducing the productivity and binding quality of the image forming apparatus 1 main body.

  In the case of the transport situation with two sheets as described above, if it is necessary to stack two sheets and three sheets of paper and earn a gap between jobs as in the case described above, the CPM of the main body is lowered by repeating the above operation. It is possible to carry out post-processing.

(3) Second and third transport roller driving mechanism and second transport roller pressure release mechanism If the pressure of the second transport roller 6 is not released when pre-stacking sheets of B5 vertical size or larger, It is necessary to carry out reverse conveyance to the position of 5 mm upstream from the 2nd conveyance roller 6 similarly to the paper of less than B5 vertical size, and to stop. In other words, the longer the paper is, the longer the reverse conveyance distance becomes, and the next paper cannot enter the second conveyance roller 6, so that high productivity cannot be handled.

  In the example described in (2) above, the pressure release of the second conveying roller 6 is performed by moving the driven roller 6b in the direction of the arrow in FIG. 11, but the pressure release is performed by moving the driving roller 6a. Also good. 11 to 13 are views showing the driving mechanism and the pressure releasing mechanism of the second and third transport rollers 6 and 7, FIG. 11 is a front view, FIG. 12 is a side view, and FIG.

  As shown in FIGS. 11 and 12, the second transport roller 6 transmits the driving force of the motor 22 to the pulley 21 via the belt 23, and further rotates by obtaining the driving force from the idler 20. 7 rotates by obtaining a driving force directly via the pulley 7a. The idler 20 and the gear 6a are connected by a link 24, and the gear 6a rotates around the idler 20 when the second transport roller 6 moves in the direction of the arrow in FIG. At that time, since the link 24 is connected to the idler 20 and the gear 6a, the distance between both axes does not change.

  The moving mechanism of the second transport roller 6 in the direction of the arrow is constituted by a cam. As shown in FIG. 13, the cam is composed of a pulley 26, a pin 26a erected on the side surface of the pulley 26, and a lever 25 having a long hole 25a in which the pin 26a is loosely fitted. The lever 25 is engaged with the shaft 6 c of the driving roller 6 a of the second transport roller 6. In this configuration, when the pulley 26 obtains a driving force from the motor 27 and rotates clockwise or counterclockwise, the pin 26a slides along the long hole 25a, and the lever 25 is perpendicular to the shaft 6c. Move in any direction. FIG. 13A shows a pressurized state, and FIG. 13B shows a pressure released state. That is, according to the rotation of the pulley 26, the pin 26a rotates around the rotation center of the pulley 26, and the lever 26 performs a linear motion with respect to the driven roller 6b by a distance corresponding to the diameter of the rotation locus, so that the driving roller 6a. Is moved toward and away from the driven roller 6b. The stroke of the drive roller 6a (distance of linear movement) is set according to the path width of the transport path (distance in the direction perpendicular to the paper surface). As a result, when prestacking a sheet of B5 vertical size or larger, the second transport roller pair 6 can be operated without being present.

(4) Control Procedure FIG. 14 shows a control procedure of the operation for temporarily stopping the succeeding paper P2 at the position γ on the upstream side in the paper transport direction of the second transport roller 6 described with reference to FIGS. It is a flowchart. This procedure is executed by the CPU 32 using the RAM as a work area according to a program stored in a ROM (not shown).

  As shown in FIG. 14, when the sheet stops before the second conveying roller 6, first, each control element is initialized (step S1), and the inlet sensor S1 is turned on (step S2). 4 and the first transport roller 5 are driven (step S3). Next, when the sensor S2 disposed between the branch claw 2e and the first conveying roller 5 is turned on (step S4), it is checked whether or not the first sheet of the prestack is present (step S5). If it is the first sheet of the prestack, the second and third transport rollers 6 and 7 are driven to move the paper along the second lower transport path 2c (step S6). Then, the rear end of the sheet passes through the sensor S2, the sensor S2 is turned OFF (step S7), and the rear end of the sheet reaches the downstream side by a predetermined distance α from the position of the free end of the switching claw 9 (branch point 2h). At the time (step S8), the first to third transport rollers 5, 6, and 7 are stopped (step S9). Next, after confirming the stop of the first to third transport rollers 5, 6 and 7 (step S10), the second and third transport rollers 6 and 7 are reversed (step S11).

  When the leading edge of the preceding sheet reaches the downstream side of the distance β from the nip of the second conveyance roller 6 by the reverse rotation of the second and third conveyance rollers 6 and 7 (step S12), the second and third conveyance rollers 6 and 7 are stopped (step S13). By the reverse rotation of the second and third transport rollers 6 and 7, the rear end side of the preceding sheet waits on the prestack path 2d side, and after the stop of the second and third transport rollers 6 and 7 is confirmed ( In step S14), the process returns to step S3 to wait for the next sheet to be conveyed.

  On the other hand, if it is not the first sheet of the pre-stack in step S5, in other words, if it is the second sheet or later, the leading edge of the sheet is positioned upstream from the nip of the second transport roller 6 by a distance γ (for example, 20 mm). Then (step S15), the first conveyance roller 5 is stopped (step S16), and after the first conveyance roller 5 is stopped (step S17), it is checked whether or not there is a prestack request (step S18). If there is a prestack request, the first to third transport rollers 5, 6 and 7 are driven (step S19), and the processes after step S7 are executed. On the other hand, if there is no pre-stack request in step S18, the first to third transport rollers 5, 6, and 7 are driven (step S20), and the processes after step S2 are executed.

  FIG. 15 is a flowchart showing a control procedure of the operation of stopping the paper P2 that is followed by the nip of the second conveyance roller 6 described with reference to FIG. This procedure is equivalent to the control in which γ in step S15 in the flowchart of FIG. 14 is set to 0, except for the determination process in which the leading edge of the following paper P2 stops at the nip position of the second transport roller 6 in step S15a. 14 is the same as the process shown in FIG.

  FIG. 16 is a flowchart showing a control procedure of the operation of stopping both the first sheet (leading sheet) P1 and the second sheet (following sheet) P2 at the second conveying roller 6 position. In this procedure, steps S5-S7 and S19 are deleted from the control procedure shown in FIG. 15, and steps S31 and S32 are provided between steps S17 and S18. Therefore, in this control procedure, when the sensor SN2 is turned on in step S4, it is checked whether or not the leading edge position of the sheet has reached the nip position of the second conveying roller 6 (step S15a), and the position has been reached. If it is determined that the first conveying roller 5 is stopped (step S16), and if the first conveying roller 5 is confirmed to be stopped (step S17), the first to third conveying rollers 5, 6, 7 are used. Is driven (step S31). When the sensor SN2 is turned off and the trailing edge of the sheet has passed the sensor SN2 (step S32), the presence or absence of a prestack request is checked (step S18), and if there is no prestack request, the first to third transport rollers 5 , 6 and 7 and the tray paper discharge roller 8 are driven (step S20), and the next paper is awaited. On the other hand, if there is a prestack request, the processing of steps S8 to S14 is executed, and the next paper is awaited.

  According to this embodiment, the conveyance roller to be reversed according to the paper size is selected, in other words, the branch point of the first and second conveyance paths of the conveyance roller that applies the conveyance force according to the paper size in the conveyance direction. Or the position where the paper is stopped (longer paper is more downstream) according to the paper size in the transport direction when moving the preceding paper backwards. It is possible to reverse the feed time and minimize the dead time when transporting to the staple tray side, which can reduce the time between sheets even when the paper is long in the transport direction. In addition, it is possible to cope with an increase in image forming speed.

2. Second Embodiment In the above-described first embodiment, when prestacking is performed, the second (following) sheet is once upstream of the processing distance upstream from the nip position of the second conveying roller 6 or the nip. Stop, carry in the first (preceding) paper into the pre-stack path 2d, and stack and carry the second (following) paper, and perform one copy on the staple tray 14 Time is saved so that the sheet is not conveyed to the staple tray 14 side during the process. On the other hand, once the motor is stopped, a rise time is required to reach a constant speed when re-driving. Therefore, once the following paper is completely stopped, it takes time to reach the constant speed when transport is started again. Will take. For this reason, if the gap between the sheets is shortened as described above, the motor may not be able to rise to a constant speed until the next sheet is conveyed. Therefore, in this embodiment, the following paper is decelerated at a predetermined timing without being stopped, and is conveyed while being overlapped with the preceding paper.

  Note that the present embodiment is configured in substantially the same manner as the first embodiment except that the following paper is not temporarily stopped and the change of the conveyance timing due to the fact that the paper is not stopped. Therefore, only different points will be described. .

  FIG. 17 is an operation explanatory diagram of the sheet post-processing apparatus 2 according to the present embodiment, and FIG. 18 is a diagram illustrating a mechanism for allowing the sheet to bend. FIG. 17A shows a state in which the rear end side of the preceding paper P1 is retracted to the prestack path 2d and the front end protrudes about 5 mm (distance β) downstream from the nip of the second conveying roller 6 and stops. . When the succeeding sheet P2 does not stop before the second conveying roller 6 or at the nip, the second conveying roller 6 causes the following sheet P2 to be second conveyed as shown in FIG. Re-rotation is started immediately before reaching the nip of the roller 6 or when the nip is reached. At that time, the second conveyance roller 6 starts rotating from the stopped state, and the leading edge of the following paper P2 is restrained by the second conveyance roller 6 until reaching the same linear velocity as the subsequent paper P2 after increasing the speed. As a result, the sheet P2 following upstream from the nip of the second conveying roller 6 is bent. Since the paper conveyance path has only a gap for conveying one or several sheets of paper, bending occurs in the conveyance path, and when the trailing edge of the following paper P2 is further conveyed, A jam occurs. The bending is as described with reference to FIG.

  Therefore, in the present embodiment, as shown in FIG. 17C, a space for absorbing the bending, in other words, for bending in the conveyance path can be formed. That is, as shown in FIG. 18 as a side view (FIG. 15 (a) Q direction arrow view), the mechanism for allowing this bending is supported by the support shaft 103 so as to be swingable on the upstream side in the sheet conveying direction. A guide plate 100, a torsion spring 101 that elastically urges the guide plate 100 toward the second lower conveyance path 2c around the support shaft 103, and a stopper 102 of the guide plate 100. It is provided in the second lower conveyance path 2c just before the conveyance direction of the conveyance roller 6c. The stopper 102 regulates the position of the guide plate 100 to form a gap of about 2 mm as the width of the conveyance path, thereby ensuring a function as a paper conveyance path.

  In the second embodiment having such a mechanism, as shown in FIG. 17C, for example, the following sheet P2 is sandwiched between the nips of the second transport roller 6 that has been re-driven, and the second transport is performed. While the roller 6 is accelerated and reaches a predetermined conveyance speed, the guide plate 100 is rotated in the counter arrow Q direction by bending to widen the conveyance path width of the second lower conveyance path 2c. As a result, the following sheet P2 is conveyed by the second conveying roller 6 without causing a sheet jam, and is further discharged to the staple tray 14 via the third conveying roller 7 and the tray discharge roller 8.

  Timings for performing such operations are shown in timing charts of FIGS. In this timing chart, the entrance roller 4 and the first transport roller 5 are once decelerated to increase the speed in synchronization with the re-drive of the second transport roller 6. FIG. 19 shows the operation of FIG. FIG. 20 is a timing chart showing the operation timing of the leading edge and the trailing edge of the second (following) sheet P2 in the case of performing, FIG. 20 is the inlet roller 4, the first conveying roller 5 and the second corresponding to the timing chart of FIG. 6 is a timing chart showing the operation timing of the transport roller 6.

  In FIG. 19, F indicates the leading edge of the sheet and B indicates the trailing edge of the sheet. In FIG. 19, the vertical axis represents the position, that is, the distance from the receiving port 2 a carried into the paper post-processing apparatus 2 in mm, and the horizontal axis represents the time in ms. In this embodiment, the second transport roller 6 is re-driven from the T3 position (position of 600-20 mm from the entrance) 20 mm upstream of the second transport roller 6 in the sheet transport direction. At this time, as shown in FIG. 20, the entrance roller 4 and the first conveying roller 5 are temporarily accelerated immediately before the T3 timing (650 mm / s → 950 mm / s) to minimize time loss. It is suppressed. Then, the speed is reduced from 950 mm / s to 270 mm / s at the T3 position, and the speed is increased from 270 mm / s to 750 mm / s in a short time in synchronization with the re-driving of the second conveying roller 6. During this time, the second conveying roller 6 has not yet reached 750 mm / s, and during this time, the bending is gradually eliminated, and the trailing edge of the sheet passes through the nip of the first conveying roller 5 to completely eliminate the bending. When the period T5 is completed, the preceding sheet P1 and the following sheet P2 are overlapped and conveyed on the second lower conveying paths 2b and 2c after the first conveying roller 5. Accordingly, the sheet is bent from the time when the following sheet P2 contacts the nip of the second conveying roller 6 (at a position 600 mm from the entrance) until the period T5 is passed, but the sheet is overlapped and conveyed without causing a jam. Is possible.

  This timing chart is for the case where the entrance roller 4 and the first transport roller 5 are once decelerated, and even when the entrance roller 4 and the first conveying roller 5 are not decelerated at all, the mechanism shown in FIG. 18 can be used. However, it is necessary to set the re-transport start timing of the second transport roller 6 slightly earlier than the timing shown in FIG. Further, the control procedure itself is equivalent to the flowchart of FIG. 14 in the first embodiment. However, in accordance with the timing charts of FIGS. 19 and 20, the control procedure is decelerated without stopping the first transport roller 5 in step S17. When the first conveying roller is decelerated to a linear speed of 270 mm / s in step S18, the first conveying roller 5 is accelerated and the second and third conveying rollers 6 and 7 are driven again. .

  The control procedure of the operation in the second embodiment is shown in the flowchart of FIG. The flowchart shown in FIG. 21A is such that the roller switching process is performed as step S21 between step S1 and step S2 in the flowchart of FIG. 14, and the roller switching process is performed according to the procedure of FIG. Executed.

  That is, as shown in FIG. 21A, when this control procedure is started, first, each control element is initialized (step S1), and the switching operation of the second transport roller 6 is executed (step S21). The roller switching subroutine in step S21 checks the size of the paper carried in from the image forming apparatus 1 side as shown in FIG. 21B (step S211). If the size in the paper transport direction is less than B5 vertical, Since the second transport roller 6 is used (case (1) above), the motor 27 is driven to pressurize the second transport roller 6 so that the paper can be transported by the second transport roller 6 ( Step S213). Although the paper size has been described above, it is transmitted from the image forming apparatus 1 side before paper conveyance.

  After the second transport roller 6 is switched to the transport position, when the entrance sensor S1 is turned on (step S2), the process between step S3 and step S20 is performed according to whether the pre-stack or the number of the job. And execute. No processing is as described with reference to the flowchart of FIG.

  If the paper size is B5 length or more in step S21, the second transport roller 6 is switched to the separated state in step S212 in FIG. 21B, and the second transport roller 6 is not used ((2) above). Case) mode. Therefore, the motor 27 is driven to move the driving roller 6a of the second transport roller 6 away from the driven roller 6b so that the second transport roller 6 is not involved in transport. And the function of the 2nd conveyance roller 6 in the flowchart of Fig.21 (a) is made to substitute for the 3rd conveyance roller 7. FIG. Accordingly, after step S2, the processing of the second transport roller 6 is executed by the third transport roller 7. As a result, when the size in the transport direction is B5 length or more, the third transport roller 7 performs the same operation as the second transport roller 6 when the paper is less than B5 length.

  Other parts that are not particularly described are configured in the same manner as the first embodiment and function in the same manner.

  According to this embodiment, it is not necessary to stop the subsequent paper when the paper is superposed and conveyed, so that it is possible to cope with the first embodiment by shortening the paper interval time and speeding up the image formation. can do.

1 is a diagram illustrating a schematic configuration of an image forming system including a sheet processing apparatus and an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image forming system in FIG. 1. FIG. 10 is an operation explanatory diagram illustrating a processing operation for a sheet having a length in the sheet conveyance direction of B5 horizontal size (182 mm) or more and less than B5 vertical size (257 mm). It is a figure which shows the detail of operation | movement of FIG. FIG. 5 is a timing chart showing the operation timing of the leading and trailing edges of the paper that follows when performing the operations of FIGS. 3 and 4. FIG. 6 is a timing chart showing operation timings of an entrance roller, a first transport roller, and a second transport roller corresponding to the timing chart of FIG. 5. FIG. 10 is an explanatory diagram illustrating an operation when the leading edge of a succeeding sheet is transported again with the preceding sheet after stopping at the nip of the second transport roller. 7 is a timing chart showing the operation timing of the leading edge and the trailing edge of the sheet when the leading edge of the succeeding sheet stops at the nip of the second conveying roller when the operation of FIG. is there. FIG. 9 is a timing chart showing operation timings of an entrance roller, a first transport roller, and a second transport roller corresponding to the timing chart of FIG. 8. FIG. 10 is an operation explanatory diagram illustrating a processing operation for a sheet of B5 vertical size (257 mm) or more. It is a front view which shows the drive mechanism and pressure release mechanism of a 2nd and 3rd conveyance roller. It is a side view which shows the drive mechanism and pressure release mechanism of a 2nd and 3rd conveyance roller. It is operation | movement explanatory drawing which shows the drive mechanism and pressure release mechanism of a 2nd and 3rd conveyance roller. FIG. 5 is a flowchart showing a control procedure of an operation for temporarily stopping a succeeding sheet at a position upstream of the second conveying roller in the sheet conveying direction described with reference to FIGS. 3 and 4; FIG. FIG. 8 is a flowchart showing a control procedure of an operation for stopping a sheet that follows at the nip of the second conveyance roller described with reference to FIG. 7. FIG. 10 is a flowchart illustrating a control procedure of an operation for stopping both the preceding sheet and the following sheet at the second conveyance roller position. FIG. 10 is an operation explanatory diagram of a sheet post-processing apparatus according to a second embodiment. It is a Q direction arrow directional view of Drawing 17 (a). It is a timing chart which shows the operation | movement timing of the front-end | tip of a paper and the rear end of the paper to follow in the case of performing operation | movement of FIG. FIG. 20 is a timing chart showing operation timings of the entrance roller, the first transport roller, and the second transport roller corresponding to the timing chart of FIG. 19. FIG. It is a flowchart which shows the control procedure of the operation | movement in 2nd Embodiment. It is explanatory drawing which shows the fundamental view of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper post-processing apparatus (paper processing apparatus)
2b First lower transport path 2c Second lower transport path 2d Pre-stack path 2e Branch claw 2f Upper transport path 2h Branch point 4 Entrance roller 5 First transport roller 6 Second transport roller 7 Third transport roller 8 Tray discharge roller 9 Switching claw 14 Stipple tray 18 Paper processing unit 31 Controller 32 CPU
100 Guide plate 101 Torsion spring 102 Stopper 103 Support shaft

Claims (11)

A first transport path that guides a sheet transported from the preceding apparatus (hereinafter simply referred to as “sheet”) to the processing tray, and a second branch that branches from the first transport path and temporarily retracts the sheet. And a branching claw that is provided at the branched portion and guides the trailing edge of the sheet to the second conveying path when the trailing edge of the sheet passes and is conveyed in the reverse direction. A first conveying means provided in the conveying path and from the branching claw to the preceding apparatus side; and a second conveying means provided in the first conveying path and from the branching claw to the processing tray side. Conveying means;
With
A function of superimposing and transporting preceding paper (hereinafter referred to as “preceding paper”) temporarily retracted to the second transport path with subsequent paper (hereinafter referred to as “following paper”). In a paper transport device having
When the preceding sheet is conveyed in the direction opposite to the processing tray by the second conveying unit and temporarily retracted to the second conveying path, the preceding sheet is sandwiched by the second conveying unit, A sheet conveying apparatus comprising: a control unit that stops conveyance of the following sheet by the first conveying unit before a leading edge of the following sheet reaches the second conveying unit . A first conveyance path that guides the sheet conveyed from the preceding apparatus to the processing tray, a second conveyance path that branches from the first conveyance path and temporarily retracts the sheet, and the branched portion A branching claw that is provided and guides the second conveyance path when the sheet that has passed through the portion is conveyed in the reverse direction; and within the first conveyance path from the branching claw to the preceding apparatus side A first conveying means provided; a second conveying means provided on the processing tray side from the branch claw in the first conveying path;
With
In the paper transport apparatus having a function of transporting the preceding paper that has been temporarily retracted to the second transport path with the succeeding paper,
When the preceding sheet is conveyed in the direction opposite to the processing tray by the second conveying unit and temporarily retracted to the second conveying path, the preceding sheet is held by the second conveying unit, line feed tip is the second of said trailing sheet of the first conveying means paper transportation device for you, characterized in that it comprises a control means for stopping the conveyance by the time it reaches the conveying means. 3. The sheet conveying apparatus according to claim 1, wherein the control unit resumes conveying the preceding sheet and the succeeding sheet when conveyance of the following sheet is stopped . The control means decelerates the conveyance speed of the succeeding paper before the leading edge of the succeeding paper reaches the second conveying means, and conveys the preceding paper while being superposed on the preceding paper. The sheet conveying apparatus according to claim 1 . 5. The paper according to claim 4 , wherein the control means increases the transport speed of the preceding paper and the succeeding paper when the leading edge of the following paper reaches the second transport means position. Conveying device. The control means carries the succeeding paper into the second transport means at a speed at which the succeeding paper is carried into the first transport path from the pre-stage device, and transports the succeeding paper in superposition with the preceding paper. The sheet conveying apparatus according to claim 4 . 7. The sheet conveying apparatus according to claim 4 , further comprising a unit that allows the trailing sheet to bend on the upstream side in the sheet conveying direction of the conveying unit. The means for allowing the bending includes a guide plate facing a sheet surface constituting the conveyance path of the first conveyance path, and a support for swingably supporting the guide plate on the upstream side in the sheet conveyance direction of the guide plate. A shaft, an elastic biasing member that elastically biases the guide plate in the closing direction, and a stopper for restricting the position of the free end of the guide plate and securing a transport width for transporting paper. and sheet conveying apparatus according to claim 7, wherein the are. An image forming apparatus comprising the sheet conveying device according to claim 1 . A first conveyance path that guides the sheet conveyed from the preceding apparatus to the processing tray, a second conveyance path that branches from the first conveyance path and temporarily retracts the sheet, and the branched portion A branching claw that is provided and guides the second conveyance path when the sheet that has passed through the portion is conveyed in the reverse direction; and within the first conveyance path from the branching claw to the preceding apparatus side A first conveying means provided; a second conveying means provided on the processing tray side from the branch claw in the first conveying path;
With
In the paper transport method for transporting the preceding paper that has been temporarily retracted to the second transport path in a superimposed manner with the following paper,
When the preceding sheet is conveyed in the direction opposite to the processing tray by the second conveying unit and temporarily retracted to the second conveying path, the preceding sheet is held by the second conveying unit, paper transporting method conveyance by the first conveying means of said trailing sheet you wherein <br/> be stopped before the leading edge of the row paper reaches the second conveying means. A first conveyance path that guides the sheet conveyed from the preceding apparatus to the processing tray, a second conveyance path that branches from the first conveyance path and temporarily retracts the sheet, and the branched portion A branching claw that is provided and guides the second conveyance path when the sheet that has passed through the portion is conveyed in the reverse direction; and within the first conveyance path from the branching claw to the preceding apparatus side A first conveying means provided; a second conveying means provided on the processing tray side from the branch claw in the first conveying path;
With
In the paper transport method for transporting the preceding paper that has been temporarily retracted to the second transport path in a superimposed manner with the following paper,
When the preceding sheet is conveyed in the direction opposite to the processing tray by the second conveying unit and temporarily retracted to the second conveying path, the preceding sheet is held by the second conveying unit, paper transporting method conveyance by the first conveying means of said trailing sheet you wherein <br/> be stopped when the leading end of the row sheet has reached the second conveying means.

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