Patent Application
20230159297
The present invention relates to a sheet discharge apparatus that discharges a sheet and an image forming system that forms an image on a sheet.
A sheet processing device (also referred to as a finisher) that performs processes, such as sorting, binding, and alignment, on sheets having images formed thereon has been developed as an option for image forming apparatuses, such as electrophotographic copying machines and laser beam printers. Some sheet processing devices have the configuration in which when continuously processes a plurality of sheet bundles, the sheet processing device temporarily stops receiving a sheet from an image forming apparatus to wait for the end of the previous sheet bundle process. In this case, the productivity (the throughput) of the image forming system decreases.
Therefore, a method is proposed for stacking a sheet received from the image forming apparatus in the sheet processing device to temporarily hold (buffer) the sheet during processing a sheet bundle and after the processing of sheet bundle is finished, placing the sheet on a processing tray as a sheet bundle. Japanese Patent Publication No. 06-099070 describes the configuration in which a sheet received from an image forming apparatus is held using two conveying paths branched inside a finisher, and the two sheets are overlapped and stacked on a processing tray.
However, if the sheet conveying speed is increased to further improve the productivity of the image forming system, the sheet is discharged at high speed from the image forming apparatus or the sheet processing device and, thus, it is likely that the placement positions of the sheets discharged to the discharge destination, such as a discharge tray, are not the same.
According to one aspect of the present invention, a sheet discharge apparatus includes a first stacking member provided outside an apparatus main body, a first conveying device disposed in a first conveying path extending toward the first stacking member in the apparatus main body, wherein the first conveying device conveys a sheet to the first stacking member, a discharge device configured to receive the sheet conveyed by the first conveying device and discharge the sheet to the first stacking member, wherein the discharge device discharges a plurality of the sheets each conveyed from the first conveying device in the form of a bundle of sheets, a sheet processing device configured to receive a sheet that is not discharged by the discharge device and processes the received sheet, a second stacking member provided outside the apparatus main body, wherein the sheet processed by the sheet processing device is stacked on the second stacking member, and a controller configured to control the first conveying device and the discharge device to perform a bundle discharge operation for discharging the bundle of sheets from the discharge device onto the first stacking member. The controller sets a discharge speed at which a sheet is discharged by the discharge device to a first discharge speed when the bundle of sheets includes a first number of sheets and sets the discharge speed to a second discharge speed that is lower than the first discharge speed when the bundle of sheets includes a second number of sheets that is greater than the first number of sheets.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Exemplary embodiments of the present invention are described below with reference to the accompanying drawings.
The image forming apparatus 1 includes an electrophotographic image forming unit 8 for forming an image, and a feeding device 6 for feeding sheets to the image forming unit 8 one by one. The image forming unit 8 is a cartridge integrally incorporating a photosensitive drum 9, which is an image bearing member (an electrophotographic photosensitive member), and a charging device and a developing device for performing an electrophotographic process by acting on the photosensitive drum 9. A scanner unit 15 serving as an exposure device is disposed above the image forming unit 8, and a transfer roller 10 serving as a transfer device is disposed at a position facing the photosensitive drum 9. A fixing device 11, discharge rollers 12a, and reverse rollers 12b are disposed above the transfer roller 10. The fixing device 11 has a heat fixing configuration and includes, for example, a cylindrical film, a heater unit that includes a heater and that is disposed inside the film, and a pressure roller in pressure contact with the heater via the film.
A plurality of feeding devices 6 for feeding sheets are disposed below the image forming unit 8. Each of the feeding devices 6 includes a cassette 6a serving as a storage unit (a storage box) for storing a plurality of sheets and a feeding unit 6b for feeding sheets one by one from the cassette 6a.
When the image forming apparatus 1 performs an image forming operation, the surface of the photosensitive drum 9 is uniformly charged by the charging device in the image forming unit 8, and the scanner unit 15 emits a laser beam to the surface of the photosensitive drum 9 on the basis of image information and forms an electrostatic latent image. The electrostatic latent image is developed (visualized) with toner serving as a developer supplied from the developing device, and a toner image is formed on the surface of the photosensitive drum 9.
In parallel with the operation performed by the image forming unit 8, sheets are fed one by one from the cassette 6a by the feeding unit 6b in any of the feeding devices 6 and are conveyed toward registration rollers 7. After correcting the skew of the sheet, the registration rollers 7 feed the sheet to a transfer portion between the photosensitive drum 9 and the transfer roller 10 in synchronization with the formation of the toner image by the image forming unit 8. Then, the toner image is transferred from the photosensitive drum 9 to the sheet in the transfer portion.
The sheet that has passed through the transfer portion is delivered to the fixing device 11. In the fixing device, when the sheet is nipped by the film and the pressure roller and passes through a fixing nip (a nip between the heater unit and the pressure roller), the toner on the sheet is heated and pressurized. Thus, a toner image is fixed onto the sheet.
In the case of single-sided printing, the sheet that has passed through the fixing device 11 is discharged from the image forming apparatus 1 by the discharge rollers 12a and is received by the relay unit 14. In the case of double-sided printing, the sheet having a toner image formed on the first side and having passed through the fixing device 11 is guided by the reverse rollers 12b, is switched back by the reverse rollers 12b, and is conveyed again to the registration rollers 7 via a re-conveying path 13. Thereafter, an image is formed on a second side opposite to the first side by passing through the transfer portion and the fixing device 11, and the sheet is delivered to the relay unit 14 by the discharge rollers 12a.
The image reading device 2 is attached to the top of the image forming apparatus 1. The image reading device 2 includes a reading sensor 2s that reads image information from an original and an original conveying unit that conveys the originals one by one to the reading sensor 2s. The image forming apparatus 1 can perform both a copying operation of forming an image based on image information acquired by the image reading device 2 and a printing operation of forming an image based on image information received from the outside of the image forming apparatus 1.
According to the present embodiment, the relay unit 14 is disposed in a space (also referred to as an internal discharge space) between the image forming apparatus 1 and the image reading device 2 in the vertical direction (the vertical direction when the image forming system 1S is installed on a horizontal plane). The relay unit 14 conveys the sheet discharged from the image forming apparatus 1 in a substantially horizontal direction viewed from the front side, toward the sheet processing apparatus 4 that is installed alongside of the image forming apparatus 1 on a common installation surface with the image forming apparatus 1. The relay unit 14 includes a sheet sensor 52 serving as a detection unit for detecting passage of a sheet. The sheet sensor 52 is, for example, a reflective photosensor that emits infrared light onto the conveying path and detects light reflected by a sheet passing through the conveying path to determine the presence of the sheet. While the image forming system 15 including the relay unit 14 is used as an example, a sheet may be delivered directly from the image forming apparatus 1 to the sheet processing apparatus 4.
Furthermore, the image forming apparatus 1 includes a display unit 5 (an operation unit, an operation display unit) that serves as a user interface of the image forming system 1S. The display unit 5 has a function of displaying the operation status of the system, such as paper jamming and malfunction and an instruction for the user to perform an operation, such as replacement of consumables in the apparatus and removal of a jammed sheet. The user can operate the touch panel function of a display of the display unit 5, numeric keys, and the like to perform various settings and provide instructions to the image forming system 1S.
Note that the configuration of the image forming apparatus is not limited to the direct transfer system illustrated in
The sheet processing apparatus 4 includes a sheet processing device 71 that processes a sheet. The sheet processing apparatus 4 has a function of discharging, as a processing result, sheets that are received from the image forming apparatus 1 and are processed by the sheet processing device 71. Alternatively, the sheet processing apparatus 4 can discharge, as a processing result, sheets received from the image forming apparatus 1 without performing a binding process.
The sheet processing apparatus 4 includes a receiving path 81, an internal discharge path 82, a first discharge path 83, and a second discharge path 84 as conveying paths for conveying sheets. Furthermore, the sheet processing apparatus 4 includes, as discharge destinations for discharging sheets, an upper discharge tray 25 and a lower discharge tray 37 each protruding outward from an apparatus main body 4A (a housing in which the receiving path 81, the internal discharge path 82, the first discharge path 83, and the second discharge path 84 are provided) to the outside of the apparatus main body 4A. The receiving path 81 is a conveying path for receiving a sheet from the image forming apparatus 1 and conveying the sheet, and the internal discharge path 82 is a conveying path for conveying a sheet toward the sheet processing device 71. The first discharge path 83 is a conveying path for discharging a sheet to the upper discharge tray 25, and the second discharge path 84 is a conveying path for discharging a sheet to the lower discharge tray 37. As described above, according to the present embodiment, the receiving path 81 and the first discharge path 83 form a first conveying path toward the upper discharge tray 25 serving as a first stacking member, and the internal discharge path 82 is provided as a second conveying path that branches from the first conveying path. In addition, the second discharge path 84 is provided as a third conveying path extending from the sheet processing device 71 toward the lower discharge tray 37 serving as a second stacking member.
The receiving path 81 has, disposed therein, inlet rollers 21, pre-branch rollers 22, and an inlet sensor 27. The first discharge path 83 has, disposed therein, discharge and reverse rollers 24 as a reversal conveying unit. The internal discharge path 82 has, disposed therein, internal discharge rollers 26, intermediate conveying rollers 28, kickout rollers 29, and a pre-intermediate stacking sensor 38. The second discharge path 84 has bundle discharge rollers 36 disposed therein. The pre-branch rollers 22 serve as a first conveying device of the present embodiment, the discharge and reverse rollers 24 serve as a second conveying device of the present embodiment, and the internal discharge rollers 26 serve as a third conveying device of the present embodiment. Each of the inlet rollers 21, the pre-branch rollers 22, the discharge and reverse rollers 24, the internal discharge rollers 26, the intermediate conveying rollers 28, the kickout rollers 29, and the bundle discharge rollers 36 is a roller pair in which the rollers are in contact with each other at the circumferential surface to form a nip that nips and conveys a sheet. The discharge and reverse rollers 24 also serve as a discharge device for discharging a sheet.
Both the inlet sensor 27 and the pre-intermediate stacking sensor 38 are examples of a sheet detection unit for detecting the passage of a sheet at a predetermined detection position in the conveying path in the sheet processing device. As the inlet sensor 27 and the pre-intermediate stacking sensor 38, a reflective photosensor, for example, is used that emits infrared light to the inside of the conveying path and detects the light reflected by the sheet passing through the conveying path to determine the presence of the sheet.
The sheet conveying path in the sheet processing apparatus 4 is described below. A sheet conveyed from the image forming apparatus 1 via the relay unit 14 is received by the inlet rollers 21 of the sheet processing apparatus 4 and is conveyed to the pre-branch rollers 22 through the receiving path 81. The inlet sensor 27 detects the sheet at a detection position between the inlet rollers 21 and the pre-branch rollers 22. The pre-branch rollers 22 conveys the sheet received from the inlet rollers 21 toward the first discharge path 83.
At a predetermined time point after the inlet sensor 27 detects the passage of the trailing edge of the sheet, the pre-branch rollers 22 accelerate the sheet conveying speed to a speed higher than that of the relay unit 14. Alternatively, the sheet conveying speed of the inlet rollers 21 may be set higher than that of the relay unit 14, and the sheet conveying speed may be accelerated by the inlet rollers 21 upstream of the pre-branch rollers 22. In this case, it is desirable to install a one-way clutch between the conveying roller of the relay unit 14 and a motor that drives the conveying roller so that the conveying roller runs idle even if the sheet is pulled by the inlet rollers 21.
When the sheet discharge destination is the upper discharge tray 25, the discharge and reverse rollers 24 discharge the sheet received from the pre-branch rollers 22 to the upper discharge tray 25. In this case, the discharge and reverse rollers 24 decelerate the discharge speed to a predetermined discharge speed at a predetermined time point after the trailing edge of the sheet moves past the pre-branch rollers 22.
When the sheet discharge destination is the lower discharge tray 37, the discharge and reverse rollers 24 performs switchback conveyance of the sheet received from the pre-branch rollers 22 to convey the sheet to the internal discharge path 82. That is, the discharge and reverse rollers 24 convey the sheet toward the outside of the sheet processing apparatus 4 in the discharge direction and reverse their rotation directions to convey the sheet in the opposite direction before the trailing edge of the sheet in the discharge direction moves past the discharging and reversing rollers 24. A check valve 23 is provided at a branching portion (between the pre-branch rollers 22 and the discharge and reverse rollers 24) where the internal discharge path 82 branches from both the receiving path 81 and the first discharge path 83 upstream of the discharge and reverse rollers 24 in the discharge direction. The check valve 23 functions as a guide (a restricting member) that restricts the backward movement of the sheet switched back by the discharge and reverse rollers 24 to the receiving path 81. That is, the discharge and reverse rollers 24 reverse the conveying direction of the sheet after the trailing edge of the sheet in the discharge direction moves past the check valve 23 to perform switchback conveyance.
The internal discharge rollers 26, the intermediate conveying rollers 28, and the kickout rollers 29 disposed in the internal discharge path 82 sequentially pass the sheet received from the discharge and reverse rollers 24 to the next rollers to convey the sheet toward the sheet processing device 71. The pre-intermediate stacking sensor 38 detects the sheet positioned between the intermediate conveying rollers 28 and the kickout rollers 29. The pre-intermediate stacking sensor 38 is, for example, a reflective photosensor that emits infrared light to the inside of the conveying path and detects the light reflected by the sheet passing through the conveying path to determine the presence of the sheet.
The sheet processing apparatus 4 includes a superposition processing unit 4B including the discharge and reverse rollers 24 and the internal discharge rollers 26 and can perform an operation to superpose a plurality of sheets conveyed from the image forming apparatus 1 one on top of another by using the superposition processing unit 4B. According to the present embodiment, the superposition processing unit 4B holds, in the internal discharge path 82, a first sheet conveyed through the receiving path 81 by using the discharge and reverse rollers 24 and the internal discharge rollers 26. Subsequently, the superposition processing unit 4B superposes a second sheet conveyed through the receiving path 81 on the first sheet. The superposition processing unit 4B also has a function of outputting the superposed sheets onto the upper discharge tray 25 (superposed discharge) and a function of conveying the superposed sheets to the sheet processing device 71 (a buffer function). The configuration and operation of the superposition processing unit 4B are described in detail below.
After aligning the plurality of sheets received from the internal discharge path 82, the sheet processing device 71 performs a binding process at a predetermined position of the sheet bundle. The sheet processing device 71 includes a stapler 50 as processing equipment and an upper intermediate stacking guide 31 and a lower intermediate stacking guide 32 that constitute an intermediate stacking member (a processing tray) on which sheets to be processed are stacked.
A vertical alignment reference plate 39 serving as a reference member is disposed at the downstream end of the sheet processing device 71 in the conveying direction of the kickout roller 29. The position of the sheet bundle in the vertical direction (the conveying direction) is aligned by bringing the edges of the sheets in the conveying direction into contact with the vertical alignment reference plate 39. A half-moon roller 33 rotatably supported by the upper intermediate stacking guide 31 is provided downstream of the pressing guide 56.
The half-moon roller 33 is a moving member (a paddle member, a conveying member) for bringing the sheet that has passed through the kickout rollers 29 into contact with the vertical alignment reference plate 39. After the trailing edge of the sheet moves past the pre-intermediate stacking sensor 38, the half-moon roller 33 conveys the sheet toward the vertical alignment reference plate 39 at a predetermined time point. The contact pressure of the half-moon roller 33 against the sheet is adjusted to such an extent that the half-moon roller 33 slips on the sheet when the sheet is in contact with the vertical alignment reference plate 39. A flexible pressing guide 56 is fixed to the upper intermediate stacking guide 31 and presses the sheet in the sheet processing device 71 downward with a predetermined pressure to prevent the sheet from lifting. Furthermore, a bundle pressing flag 30 is rotatably supported downstream of the kickout rollers 29 to prevent the trailing edge of the sheet from lifting so that the trailing edge of the sheet already stacked in the sheet processing device 71 does not interfere with the leading edge of the succeeding sheet discharged by the kickout rollers 29.
When the alignment of a predetermined number of sheets on the intermediate stacking member is finished, the stapler 50 performs a binding operation. Then, the bundle discharge guide 34 serving as an extrusion member driven by a guide drive unit 35 moves in a direction from the standby position illustrated in
Both the upper discharge tray 25 and the lower discharge tray 37 are movable vertically relative to the housing of the sheet processing apparatus 4. Sheet presence sensors 51 and 53 for detecting the presence/absence of a sheet on a tray are disposed on the upper discharge tray 25 and the lower discharge tray 37, respectively. The sheet presence sensors 51 and 53 are, for example, reflective photosensors that determine the presence/absence of a sheet by emitting infrared light upward from the tray stacking surface and detecting reflected light from the sheets. The sheet processing apparatus 4 further includes a sheet surface detection sensor that detects the upper surface position of the sheets (the sheet stack height) on each of the upper discharge tray 25 and the lower discharge tray 37.
When the sheet surface detection sensor detects a sheet, the corresponding one of the upper discharge tray 25 and the lower discharge tray 37 tray is lowered in an A2 or B2 direction. When the sheet presence sensor 51 or 53 detects that the sheet has been removed from the upper discharge tray 25 or the lower discharge tray 37, the tray is raised in the A1 or B1 direction. The upper discharge tray 25 and the lower discharge tray 37 are controlled to move up and down according to the number of stacked sheets so that the upper surfaces of the stacked sheets are positioned below the discharge and reverse rollers 24 and the bundle discharge rollers 36 in the vertical direction, respectively. According to the present embodiment, the upper discharge tray 25 serving as the first stacking member and the lower discharge tray 37 serving as the second stacking member are controlled to be raised and lowered by motor drive. However, the upper discharge tray 25 and the lower discharge tray 37 may be configured so as to be raised and lowered by an urging unit, such as a spring.
The stapler 50 is an example of the processing equipment. For example, a sorting mechanism for sorting sheets and a center-folding processing unit for center folding a plurality of sheets and perform saddle stitch book binding may be provided.
The sheet conveyed by the inlet rollers 21 is guided to the pre-branch rollers 22 by the upper inlet guide 40 and the lower inlet guide 41. The inlet sensor 27 is disposed on the upper inlet guide 40. As the inlet sensor 27, a reflective photosensor can be used that determines the presence of a sheet at the detection position by emitting infrared light to the receiving path 81 and detecting reflected light from the sheet. In this case, a hole having a diameter greater than the diameter of the spotlight of the inlet sensor 27 is formed in a portion of the lower inlet guide 41 facing the inlet sensor 27 so that the infrared light is not reflected when a sheet does not pass through the receiving path 81.
The check valve 23 is disposed downstream of the pre-branch rollers 22 and at a portion where the receiving path 81 and the internal discharge path 82 branch from the first discharge path 83. The check valve 23 is rotatably supported by the upper internal discharge guide 46 via a rotating shaft 23a. In addition, the check valve 23 is always urged by a spring (not illustrated) in a C2 direction (the clockwise direction in
The discharge and reverse rollers 24 consist of an upper roller 24a and a lower roller 24b. According to the present embodiment, driving force is input to both the upper roller 24a and the lower roller 24b, and the rotations of the upper roller 24a and the lower roller 24b are always synchronized.
The discharge and reverse rollers 24 are configured to contact each other (a close operation) and separate from each other (an open operation) by a plunger solenoid 45. More specifically, one end of a separation lever 44 is connected to the roller shaft of the upper roller 24a, and the separation lever 44 is supported by a lever fulcrum shaft 44a in a rotatable manner with respect to the upper reverse guide 42. A solenoid connection shaft 44b provided at the other end of the separation lever 44 is connected to a plunger of the plunger solenoid 45.
When the plunger solenoid 45 is powered on, the plunger is attracted in a D1 direction by a magnetic force. Thus, the separation lever 44 rotates in an E1 direction, and the discharge and reverse rollers 24 are separated from each other (the nip of the roller pair is released). When the plunger solenoid 45 is powered off, the upper roller 24a is brought into contact with the lower roller 24b by the biasing force of a pressure spring 48 connected to the roller shaft of the upper roller 24a, and the discharge and reverse rollers 24 are in contact with each other (the nip is closed). At this time, the separation lever 44 rotates in the E2 direction as the upper roller 24a moves, and the plunger of the plunger solenoid 45 moves in the D2 direction.
The internal discharge rollers 26 form a roller pair adjacent to the discharge and reverse rollers 24 in the sheet conveying direction in the internal discharge path 82. The roller pair is capable of forward rotation and reverse rotation. That is, the internal discharge rollers 26 can convey a sheet in both the direction from the discharge and reverse rollers 24 to the sheet processing device 71 (hereinafter referred to as a G1 direction) and the direction from the sheet processing device 71 to the discharge and reverse rollers 24 (hereinafter referred to as a G2 direction).
The hardware configuration of the image forming system 1S according to the present embodiment is described below with reference to
A main control unit 603 controls the sheet processing apparatus 4. A signal line 604 is a signal line for serial command transmission to transmit a command from the video controller 601 to the engine control unit 602 by serial communication, and a signal line 605 is similarly used to transmit a command from the video controller 601 to the main control unit 603. A signal line 606 is a signal line for serial status transmission to transmit status data from the engine control unit 602 to the video controller 601 by serial communication in response to a command, and a signal line 607 is similarly used to transmit status data from the main control unit 603 to the video controller 601. To perform an image forming operation, the video controller 601 transmits serial commands to the engine control unit 602 and the main control unit 603 and receives status data from the engine control unit 602 and the main control unit 603. Thus, the video controller 601 performs control. In this way, when a plurality of apparatuses are connected and the image forming system 1S operates, the video controller 601 manages the control and status of each of the apparatuses and ensures the consistency of the operations performed by the apparatuses.
The main control unit 603 includes a central processing unit (CPU) 608 that controls various operations performed by the sheet processing apparatus 4 and a random access memory (RAM) 609 that temporarily stores control data necessary for the operations performed by the sheet processing apparatus 4.
The main control unit 603 further includes a nonvolatile read only memory (ROM) 610 that stores programs and control tables necessary for the operation performed by the sheet processing apparatus 4. The main control unit 603 further includes a communication unit 611 for communicating with the video controller 601, a system timer 612 that generates timings necessary for various controls, and an input and output (I/O) port 613 that inputs and outputs control signals from and to various units of the sheet processing apparatus 4. The main control unit 603 is a control integrated circuit (IC) to which the above-described elements are connected via a bus 614.
Input signals from the inlet sensor 27 and the sheet presence sensors 51 and 53 of the upper discharge tray 25 and the lower discharge tray 37 are transmitted to the main control unit 603 via input circuits 615, 626, and 628, respectively. The control signals from the main control unit 603 are transmitted to an inlet motor 641, a pre-branch motor 642, a discharge and reverse motor 643, an internal discharge motor 644, and the plunger solenoid 45 via drive circuits 618, 619, 620, 621, and 623, respectively. Thus, the driving of actuators is controlled.
The functional blocks of the present embodiment are described below with reference to
The sensor controller 720 is a unit for inputting signals from the inlet sensor 27 and the sheet presence sensor 51 of the upper discharge tray 25 to the sheet conveying controller 701. The sheet conveying controller 701 includes a superposed conveying controller 711 and a sheet count controller 712. The sheet conveying controller 701 controls the motor controller 721 and the solenoid controller 722 on the basis of the input from the sensor controller 720 to achieve the operations performed by the superposition processing unit 4B, the upper discharge tray 25, and the lower discharge tray 37. The superposed conveying controller 711 controls conveyance of a sheet to the superposition processing unit 4B and the upper discharge tray 25 while managing the position of the sheet on the basis of mainly the input from the sensor controller 720. The sheet count controller 712 determines the timing of discharging the superposed sheets to the upper discharge tray 25 on the basis of the maximum number of sheets that can be superposed by the superposition processing unit 4B (the number of superposable sheets) and the current number of superposed sheets.
The inlet motor 641 drives the inlet rollers 21, the pre-branch motor 642 drives the pre-branch rollers 22, and the discharge and reverse motor 643 drives the discharge and reverse rollers 24. The internal discharge motor 644 drives the internal discharge rollers 26, and the plunger solenoid 45 drives the separation lever 44. The operations performed by these elements to be driven are described in detail below.
An overview of a bundle discharge operation (a superposed discharge operation) in which the superposed conveying controller 711 superposes and discharges a plurality of sheets by the superposition processing unit 4B is described with reference to
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
Thus, the operation of superposing and discharging the two sheets S1 and S2 while aligning the two sheets S1 and S2 in the superposition processing unit 4B (the superposed discharge operation) is completed. When the image forming operation is continuously performed on a large number of sheets, two-sheet bundles are stacked on the upper discharge tray 25 by repeating the above-described superposed discharge operation.
Advantages of the present embodiment are described below, compared with the case where the sheets S1 and S2 are discharged one by one without being subjected to the superposed discharge operation. When the sheets S1 and S2 are discharged one by one, the positions and postures of the sheets S1 and S2 that have passed through the discharge and reverse rollers 24 may be lost before the sheets S1 and S2 land on the upper surface of the upper discharge tray 25 or the upper surface of the sheets on the upper discharge tray 25. This is because while falling down, each of the sheets S1 and S2 receives air resistance and, thus, moves in all directions as viewed from above.
In contrast, according to the present embodiment, the positions of the sheets S1 and S2 are aligned in the sheet conveyance direction and the sheets S1 and S2 are superposed in advance and are discharged, so that the positions and postures of the sheets S1 and S2 are less likely to be lost.
When the sheet bundle discharged through the superposed discharge operation is compared with the sheets discharged one by one, the projected areas of the sheet (bundle) and the single sheet as viewed from above are the same, but the weight of the sheet bundle is two times the weight of the single sheet. For this reason, the sheet bundle is less susceptible to air resistance. As a result, even when the sheet discharge speed of the discharge and reverse rollers 24 is increased to improve the productivity of the image forming system 1S and the productivity of the sheet processing apparatus 4, a degradation of the sheet stackability can be avoided.
While the above description has been made with reference to the conveyance of two sheets, the sheet processing apparatus 4 of the present embodiment can perform a superposed discharge operation to align the positions of three or more sheets, superpose the sheets on top of another in the superposition processing unit 4B, and discharge the sheets to the upper discharge tray 25.
When the superposed discharge operation is performed for three sheets, two sheets S1 and S2 are first superposed in the same procedure as described above with reference to
As a result, after the sheet bundle S′ is temporarily stopped while being held by the internal discharge rollers 26 in the internal discharge path 82, when the predetermined time T_wait elapses since the inlet sensor 27 detected the trailing edge of the third sheet S3, the internal discharge rollers 26 convey the sheet bundle S′ in the G2 direction. Thereafter, the discharge and reverse rollers 24 that have been open is closed, so that the three sheets S1, S2, and S3 are nipped by the discharge and reverse rollers 24 at the same time. When the trailing edge of the sheet S3 passes through the check valve 23, a sheet bundle is formed in which both the leading edges and the trailing edges of the three sheets S1, S2, and S3 are aligned.
When the number of sheets in the superposed discharge operation is three, the sheet bundle is directly discharged in the G2 direction by the discharge and reverse rollers 24 and is stacked on the upper discharge tray 25. When the number of sheets in the superposed discharge operation is four or more, the discharge and reverse rollers 24 convey the sheet bundle again in the G1 direction and repeats the same operations as in
The sheet count controller 712 manages the number of sheets to be superposed in the superposition processing unit 4B on the basis of the number of sheets superposable by the superposition processing unit 4B and information regarding the sheet to be conveyed. That is, the sheet count controller 712 determines whether the sheet conveyed to the superposition processing unit 4B is immediately discharged to the upper discharge tray 25 or is superposed on top of another.
As an example of the determination technique, let N denote the number of superposable sheets by the superposition processing unit 4B. Then, the sheet count controller 712 generates a sheet bundle of N−1 sheets and discharges the sheet bundle to the upper discharge tray 25. Only when the sheet count controller 712 determines that the Nth sheet is the last sheet, the number of sheets to be superposed is set to N. In this way, the sheet count controller 712 prevents discharge of the Nth sheet to the upper discharge tray 25 as one sheet.
As a specific example, the number of superposable sheets by the superposition processing unit 4B is five in the configuration example according to the present embodiment. In this case, the sheet count controller 712 repeatedly performs the superposed discharge operation for four sheets and stacks a sheet bundle of the four sheets on the upper discharge tray 25. At this time, if the sheet count controller 712 determines that the fifth sheet is the last sheet and the last sheet is discharged as one sheet if the superposed discharge operation for four sheets is repeated to the end, a superposed discharge operation for five sheets including the last sheet is performed, and the sheets are discharged to the upper discharge tray 25. If the last sheet is superposed on another sheet even after the superposed discharge operation for four sheets is performed to the end, the sheet bundle is discharged to the upper discharge tray 25 when the sheet bundle including the last sheet is formed.
That is, when executing a job of discharging a predetermined number of sheets to the upper discharge tray 25, the sheet count controller 712 changes the number of sheets in a bundle formed through the superposed discharge operation in accordance with a predetermined number of sheets so that each of the predetermined number of sheets is always included in a sheet bundle of two or more sheets formed through the superposed discharge operation and is discharged to the upper discharge tray 25. As a result, it is possible to prevent a single sheet from being discharged to the upper discharge tray 25 and, thus, prevent a degradation of the sheet stackability. Note that the technique for controlling the number of sheets in the superposed discharge operation is not limited thereto. Any technique that avoids discharge of a single sheet can be employed. For example, in the above-described example, the number of sheets in the successive superposed discharge operations may be four, . . . , four, three, and two.
The timing management (a method for obtaining T_wait described above) is described that is performed by the superposed conveyance controller 711 to align the leading edges of the sheets S1 and S2 in the superposition processing unit 4B.
In
Let T_merge denote the elapsed time from A to D. Let T1 denote the time required for the pre-branch rollers 22 to accelerate from the speed V1 to the speed V2 (the elapsed time from A to B). Let T2 denote the time from acceleration of the pre-branch rollers 22 to the speed V2 until start of the rotation of the internal discharge rollers 26 (the elapsed time from B to C). As can be seen from the definitions of T1, T2 and T_wait, T_wait=T1+T2. Let T3 denote the time required for the stopped sheet S1 to accelerate to the speed V2 with a constant acceleration (the elapsed time from C to D).
Let X2 denote the distance that the sheet S1 moves from the position in
X2=(V2×T3)/2 (1).
In addition, let X1 denote the distance that the sheet S2 moves from the position in
X1=(V1+V2)×T1/2+V2×(T2+T3) (2).
From the positional relationship between the sheets S1 and S2 at the time in
L1−X1=L2−X2−Kt (3).
Substituting equations (1) and (2) into equation (3) and expanding and rearranging the equation yields the following equation:
L1−L2+Kt=(T½)×V1+(T½+T2+T 3/2)×V2 (4).
Substituting T_wait=T1+T2 into the above equation (4) and rearranging the equation, the waiting time T_wait from when the trailing edge of the sheet S2 passes the inlet sensor 27 to when the internal discharge rollers 26 start conveying the sheet S1 is given for the protrusion amount Kt by the following equation:
T_wait=(L1−L2+Kt)/V2−(T½)×V1/V2+(T1−T3)/2 (5).
To align the leading and trailing edges of the sheets S1 and S2 and superpose the sheets S1 and S2, the waiting time T_wait can be calculated by setting Kt=0 in the above equation (5). By starting the conveyance of the sheet S1 by the internal discharge rollers 26 on the basis of the calculated T_wait, the sheet bundle S′ in which the leading and trailing edges of the sheets S1 and S2 are aligned can be formed. In addition, by using the same value of T_wait when three or more sheets are superposed, a sheet bundle in which the leading and trailing edges of the sheets are aligned can be formed.
An example of a method for controlling the sheet processing apparatus 4 that achieves the superposed discharge operation described with reference to
In the following description, the term “first sheet” refers to a sheet conveyed first to the sheet processing apparatus 4 among the sheets to be superposed in the superposition processing unit 4B to form a sheet bundle. For example, when four sheets are superposed and discharged to the upper discharge tray 25, the sheet conveyed to the sheet processing apparatus 4 after the last sheet of the preceding sheet bundle (that is, the (4n+1)th sheet) is the first sheet. The term “last sheet” refers to a sheet that is conveyed to the sheet processing apparatus 4 last among the sheets to be superposed in the superposition processing unit 4B to form a sheet bundle (that is, the 4nth sheet in the above example).
In step S101, rotation of the inlet rollers 21 and the pre-branch rollers 22 is started at the speed V1. Thereafter, the processing proceeds to step S102. If the inlet rollers 21 and the pre-branch rollers 22 are already rotating at the speed V1, the rotation of the rollers is continued.
In step S102, it is determined whether the current sheet is a first sheet. If Yes, then the processing proceeds to step S103, and if No, the processing proceeds to step S106.
In step S103, the discharge and reverse rollers 24 are brought into contact with each other, and the rotation of the discharging and reversing rollers 24 is started in a direction in which the first sheet is conveyed toward the upper discharge tray 25 (the G2 direction) at the speed V1 (refer to the sheet S1 in
In step S104, it is determined whether the trailing edge of the first sheet has passed the inlet sensor 27. If Yes, the processing proceeds to step S105, and if No, the processing proceeds to step S104.
In step S105, the pre-branch rollers 22 and the discharge and reverse rollers 24 are accelerated to the speed V2 (refer to the sheet S1 in
In step S106, it is determined whether the trailing edge of the current sheet (one of the second and succeeding sheets) has passed the inlet sensor 27. If Yes, the processing proceeds to step S107, and if No, the processing proceeds to step S106.
In step S107, the pre-branch rollers 22 and the discharge and reverse rollers 24 are accelerated to the speed V2. As a result, the conveying speed of the current sheet is accelerated from the speed V1 to the speed V2 (refer to the sheet S2 in
In step S108, it is determined whether a predetermined time T_wait has elapsed since the time the trailing edge of the current sheet passed the inlet sensor 27. If Yes, the processing proceeds to step S109, and if No, the processing proceeds to step S108.
In step S109, rotation of the internal discharge rollers 26 is started again in the direction in which the sheet is conveyed toward the discharge and reverse rollers 24 (the F2 direction) at a speed V2 (refer to the sheet S1 in
In step S110, at the time the conveying speed of the sheets (a bundle) conveyed by the internal discharge rollers 26 and the conveying speed of the current sheet become equal, the upper roller 24a of the discharge and reverse rollers 24 is moved in the E2 direction so as to come into contact with the lower roller 24b (refer to
In step S111, it is determined whether the current sheet is the last sheet. If Yes, the processing proceeds to step S112, and if No, the processing proceeds to step S116.
In step S112, the sheet bundle including the last sheet is discharged to the upper discharge tray 25 (refer to
In step S113, when the trailing edge of the sheet bundle reaches the distance L from the discharge and reverse rollers 24, the conveying speed of the discharge and reverse rollers is changed to the speed V3, and the sheet bundle is discharged to the upper discharge tray 25. According to the present embodiment, the discharge speed V3 is set according to the number of sheets in a sheet bundle to be discharged.
In step S114, it is determined whether the trailing edge of the sheet bundle has passed through the discharge and reverse rollers 24. If Yes, the processing proceeds to step S115, and if No, the processing proceeds to step S114.
In step S115, the pre-branch rollers 22 is decelerated to the speed V1, and the discharge and reverse rollers 24 and the internal discharge rollers 26 are stopped. Thus, the flow ends. If the current sheet is the last sheet in the job (if no more sheets are conveyed from the image forming apparatus 1), the inlet rollers 21 and pre-branch rollers 22 are also stopped in step S115.
In step S116, it is determined whether the trailing edge of the current sheet (a sheet other than the last sheet) has passed through the check valve 23. If Yes, the processing proceeds to step S117, and if No, the processing proceeds to step S116.
In step S117, the discharge and reverse rollers 24 and the internal discharge rollers 26 are temporarily stopped (refer to the sheet S1 in
In step S118, rotation of the discharge and reverse rollers 24 and rotation of the internal discharge rollers 26 are started in a rotation direction for conveying the sheets (the bundle) in the direction after reversal (the F1 direction, G1 direction) at the speed V2 (refer to the sheet S1 in
In step S119, it is determined whether the leading edge of the sheets (the bundle) has passed through the internal discharge rollers 26. If Yes, the processing proceeds to step S120, and if No, the processing proceeds to step S119.
In step S120, the upper roller 24a is separated from the lower roller 24b of the discharge and reverse rollers 24. The processing proceeds to step S121.
In step S121, at the position where the leading edge of the sheets (the bundle) has passed through the internal discharge rollers 26 and has been conveyed by a predetermined distance, the pre-branch rollers 22 is decelerated to the speed V1, and the discharge and reverse rollers 24 and the internal discharge rollers 26 are stopped. Thus, the flow ends. As a result, the sheets (the bundle), which are the target of the superposed discharge operation and are still superposed on other sheets, are held while being nipped by the internal discharge rollers 26 (refer to the sheet S1 in
As described in step S113, according to the present embodiment, the discharge speed V3 is set according to the sheet bundle to be discharged. The reason for this setting is described below with reference to
For this reason, if the discharge speed V3 is constant regardless of the number of sheets in a bundle, variations occur in the flight distance of the sheet bundle from the discharge and reverse rollers 24, as illustrated in
Therefore, according to the present embodiment, the discharge speed V3 is set according to the number of sheets in a bundle to be discharged to avoid the above-described issues.
As illustrated in
That is, when the number of sheets in the sheet bundle is a first number of sheets (for example, 2 sheets), the discharge speed V3 is set to a first discharge speed (for example, a discharge speed V32). When the number of sheets in the sheet bundle is a second number of sheets that is greater than the first number of sheets (for example, 3 sheets), the discharge speed V3 is set to a second discharge speed that is lower than the first discharge speed (for example, a discharge speed V33).
As a result, regardless of the number of sheets in the bundle, the sheet bundle can be discharged to the target position, improving the stackability. Note that the discharge speed V3 can be changed by the time the trailing edge of the sheet bundle passes through the discharge and reverse rollers 24 at the latest.
Instead of changing the discharge speed V3 according to the number of sheets in the bundle, a threshold may be set for the number of sheets in a bundle. For example, when the number of sheets in the bundle is 2 or 3, the discharge speed V3 may be set to the first discharge speed. When the number of sheets in the bundle is 4 (which is greater than or equal to the threshold), the discharge speed V3 may be set to the second discharge speed (in this case, the threshold is 4 sheets). The discharge speed V3 can be appropriately set according to the discharge angle of the discharge and reverse rollers 24, the positional relationship between the upper discharge tray 25 and the discharge and reverse rollers 24, and the like.
In some cases, the flight distance changes according to the basis weight of the sheet, giving an impact on the stackability. For example,
Accordingly, when a bundle (a first sheet bundle) consisting of a plurality of sheets of a first basis weight is formed, the discharge speed V3 is set to a third discharge speed. When a bundle (a second sheet bundle) consisting of a plurality of sheets with a second basis weight (the sheets with a basis weight that is less than the first basis weight) is formed, the discharge speed V3 is set to a fourth discharge speed. The fourth discharge speed is set so as to be greater than the third discharge speed.
In addition, in some cases, the flight distance varies according to the size of the sheet, giving an impact on the stackability. In this case, the setting of the discharge speed V3 may be changed according to the sheet size and the number of sheets in the same manner as described above. Furthermore, in some cases, the curl direction of the sheets varies according to the print mode (for example, double-sided printing or single-sided printing) or the medium type (
As described above, according to the present embodiment, when a plurality of sheets that are continuously conveyed are discharged onto the first stacking member, the superposition processing unit 4B can superpose the plurality of sheets while aligning the edges of the sheets and, thereafter, discharge the sheets. As a result, the stackability of the sheets on the first stacking member can be improved while maintaining the productivity. In addition, when the superposition processing unit 4B superposes a plurality of sheets while aligning the edges of the sheets and, thereafter, discharge the sheets, the discharge speed can be changed according to the number of sheets that form the bundle. As a result, the flight distance of the sheet bundle discharged onto the first stacking member from the discharge and reverse rollers 24 can be made constant and, thus, the sheet stackability can be improved.
While the configuration example of the present embodiment has been described with reference to the maximum number of sheets that can be superposed by the superposition processing unit 4B (the number of superposable sheets) being five, the number of superposable sheets can be appropriately changed according to the particular configuration of the superposition processing unit 4B and the performance required for the superposition processing unit 4B.
The superposition processing unit 4B of the present embodiment can also operate as a buffer unit that superposes and holds sheets received from the image forming apparatus 1 while the sheet processing device 71 is processing sheets. By performing the buffer operation, collision of sheets in the sheet processing device 71 is avoided without decreasing the productivity of the image forming apparatus 1. As a result, the productivity of the image forming system 1S is improved.
When the buffer operation is performed, the operation performed by the superposition processing unit 4B is basically common to the superposed discharge operation, except that the bundle of superposed sheets is conveyed to the sheet processing device 71 via the internal discharge path 82. That is, in the operations illustrated in
In the buffer operation, a protrusion amount Kt (
As described above, the superposition processing unit 4B of the present embodiment has the function of performing a superposed discharge operation when discharging sheets to the outside of the sheet processing apparatus 4 without the processing performed by the sheet processing device 71 and also has the function of buffering sheets to be processed by the sheet processing device 71. As a result, the size and cost of the apparatus can be reduced as compared with the configuration including two mechanisms for superposing sheets in order to achieve the above-described two functions.
According to the present embodiment, the internal discharge path 82 serving as the second conveying path communicates with the sheet processing device 71. However, a configuration in which the second conveying path communicates with a discharge destination other than the sheet processing device 71 may be employed. For example, the sheet processing device 71 may be removed, and a sheet conveyed via the internal discharge path 82 may be discharged to the lower discharge tray 37 without being processed. Alternatively, an configuration may be employed in which the second conveying path has a dead end and does not communicate with the outside of the sheet processing apparatus 4.
In addition, while the present embodiment has been described with reference to the sheet discharge apparatus of the sheet processing apparatus 4 provided separately from the image forming apparatus 1, the present technology is applicable to a sheet discharge apparatus that discharges a sheet from the image forming apparatus 1 or other apparatuses that handle sheets.
In addition, according to the present embodiment, the bundle discharge rollers 36 for discharging the sheets processed by the sheet processing device 71 to the lower discharge tray 37 can be applied as the discharge device. When the bundle discharge rollers 36 discharge a sheet bundle, the discharge speed may be appropriately set according to the number of sheets that form the sheet bundle.
The present invention can be also implemented by performing the following processing. That is, a program that provides at least one of the functions of the above-described embodiment is supplied to a system or apparatus via a network or a storage medium, and at least one processor of the computer of the system or apparatus reads and executes the program. Alternatively, the present invention is implemented by using a circuit (for example, an application specific integrated circuit (ASIC)) that provides the at least one function.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2021-189216 filed Nov. 22, 2021, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-189216 | Nov 2021 | JP | national |
