Post-handling apparatus and image forming system

A post-handling apparatus having an aligning tray configured to receive a sheet from an image forming apparatus; an ejected sheet tray located adjacent to the aligning tray; a conveyer configured to convey the sheet on the aligning tray to the ejected sheet tray; and a sheet presser configured to press a sheet previously ejected onto the ejected sheet tray against the ejected sheet tray. The sheet presser presses the sheet previously ejected to the ejected sheet tray when a leading edge of a sheet currently conveyed to the ejected sheet tray falls down on the ejected sheet tray, and is in a receding position receding from the ejected sheet tray when a trailing edge of the sheet currently conveyed to the ejected sheet tray falls down on the ejected sheet tray.

This application claims benefit of priority to Japanese Patent Application No. 2014-190926 filed Sep. 19, 2014, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a post-handling apparatus and an image forming system, and more particularly to a post-handling apparatus configured to handle sheets ejected from an image forming apparatus and an image forming system comprising the post-handling apparatus.

As an example of post-handling apparatuses configured to handle sheets ejected from an image forming apparatus, a post-handling apparatus disclosed in Japanese Patent Laid-Open Publication No. 2007-145528 is well known. Such a conventional post-handling apparatus handles sheets ejected from an image forming apparatus and ejects the sheets to an ejected sheet tray of the post-handling apparatus. The ejected sheet tray conventionally has a mechanism to move up and down the ejected sheet tray depending on the load on the ejected sheet tray.

Meanwhile, it is suggested that the mechanism to move up and down the ejected sheet tray depending on the load on the ejected sheet tray be omitted from the ejected sheet tray in order to downsize the post-handling apparatus. However, omitting the mechanism from the ejected sheet tray may cause a problem that when a sheet is newly ejected onto the ejected sheet tray, sheets previously ejected onto the ejected sheet tray fall therefrom due to impact with the sheet newly coming to the ejected sheet tray.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a post-handling apparatus that prevents sheets previously ejected onto an ejected sheet tray from falling therefrom due to impact with a sheet newly coming to the ejected sheet tray, and an image forming system comprising the post-handling apparatus.

According to a first aspect of the present invention relates to a post-handling apparatus for handling sheets ejected from an image forming apparatus, and the post-handling apparatus comprises: an aligning tray configured to receive a sheet from the image forming apparatus; an ejected sheet tray located adjacent to the aligning tray; a conveyer configured to convey the sheet on the aligning tray to the ejected sheet tray in a sheet ejecting direction; and a sheet presser configured to press a sheet previously ejected onto the ejected sheet tray against the ejected sheet tray, wherein the sheet presser presses the sheet previously ejected onto the ejected sheet tray when a leading edge, with respect to the sheet ejecting direction, of a sheet currently conveyed to the ejected sheet tray falls down on the ejected sheet tray, and is in a receding position receding from the ejected sheet tray when a trailing edge, with respect to the sheet ejecting direction, of the sheet currently conveyed to the ejected sheet tray falls down on the ejected sheet tray.

According to a second aspect of the present invention relates to an image forming system, and the image forming system comprises: the post-handling apparatus described above; and an image forming apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

General Structure of Image Forming System and Post-Handling Apparatus; See FIGS.1-3

An image forming system1and a post-handling apparatus3according to an embodiment of the present invention are hereinafter described with reference to the drawings. In the following description, the direction in which an image forming apparatus2ejects a sheet is referred to as a positive side in x-direction or a positive x-direction, and a direction opposite thereto is referred to as a negative side in x-direction or a negative x-direction. The direction in which a rear-side aligning plate29pushes a sheet or a stack of sheets P to an ejected sheet tray35is referred to as a positive side in y-direction or a positive y-direction, and a direction opposite thereto is referred to as a negative side in y-direction or a negative y-direction. In this embodiment, the y-direction is orthogonal to the x-direction and the vertical direction.

As illustrated inFIG. 1, the image forming system1comprises an image forming apparatus2, a post-handling apparatus3and an image reading apparatus100. The image forming system1further comprises a control unit4inside the image forming apparatus2as illustrated inFIG. 2, and the control unit4controls the image forming apparatus2, the post-handling apparatus3and the image reading apparatus100.

The image forming apparatus2comprises an imaging unit5configured to form toner images by a conventional electrophotographic process. Sheets P are fed from a sheet feeder section one by one, and the toner images are transferred to the sheets P at a transfer section12one by one. The imaging unit5may be configured to form a full-color toner image or to form a monochromatic toner image. Further, if the imaging unit5is configured to form a full-color toner image, the imaging unit5may be a tandem type or a four-cycle type. The sheets P that received toner images at the transfer section12undergo a heating treatment at a fixing unit14for fixation of toner thereon, and the sheets P are ejected from the image forming apparatus2one by one through a pair of ejection rollers16. The ejection of each sheet from the image forming apparatus2is detected by a sheet ejection sensor60located near an exit of the image forming apparatus2.

The post-handling apparatus3is an apparatus configured to handle, for example, align and/or staple the sheets P ejected from the image forming apparatus2. As illustrated inFIG. 3, the post-handling apparatus3comprises an aligning tray21, a leading-edge support member23, a trailing-edge support member25, a front-side aligning plate27, a rear-side aligning plate29, a stapler31, and an ejected sheet tray35. The ejected sheet tray35is located adjacent to the aligning tray21and more specifically at the positive side in y-direction of the aligning tray21.

A basic process carried out by the post-handling apparatus3is described below. Each printed sheet P ejected from the exit of the image forming apparatus is received on the aligning tray21and is conveyed to a predetermined position on the aligning tray21while being aligned by use of the leading-edge support member23, the trailing-edge support member25, the front-side aligning plate27and the rear-side aligning plate29. The aligned stack of sheets P is stapled by a stapler31as needed. The sheet P or the stack of sheets P conveyed to the predetermined position on the aligning tray21is pushed out to the ejected sheet tray35by the rear-side aligning plate29. This is a basic process carried out by the post-handling apparatus3.

Detailed Structure Around Ejected Sheet Tray; See FIGS.4-6

As illustrated inFIG. 4, the post-handling apparatus3further comprises a sheet ejection sensor37configured to detect a sheet or a stack of sheets ejected onto the ejected sheet tray35, and sheet pressers39configured to hold the ejected sheet or the ejected stack of sheets on the ejected sheet tray35. As illustrated inFIG. 5, the post-handling apparatus3still further comprises a motor43serving as a drive source of the sheet pressers39, a shaft45configured to transmit the drive force from the motor43to the sheet pressers39, and a monitoring system47configured to monitor the rotation of the shaft45.

The sheet ejection sensor37is fitted in a dent made in the upper surface of the ejected sheet tray35. When a sheet P or a stack of sheets P ejected from the aligning tray21covers the upper surface of the ejected sheet tray35, the sheet ejection sensor37detects a sheet on the ejected sheet tray35. Then, the sheet ejection sensor37sends a signal indicating the state to the control unit4.

The sheet pressers39are to prevent one or more sheets P previously ejected onto the ejected sheet tray35from falling from the ejected sheet tray35due to collision with one or more sheets P newly ejected thereto. The sheet pressers39are also to prevent the sheets P already ejected onto the ejected sheet tray35from curling, thereby preventing the sheets P from increasing in volume on the ejected sheet tray35. As seen inFIG. 4, each of the sheet pressers39is substantially J-shaped when viewed from the x-direction. Respective one ends of the sheet pressers39are fixed to the shaft45such that the sheet pressers39are capable of rotating along with the shaft45. With the rotation of the sheet pressers39, the respective other ends of the sheet pressers39hit and press the upper surface of the sheet or the stack of sheets P on the ejected sheet tray35. In this embodiment, a total of four sheet pressers39are fixed to the shaft45.

The motor43is a drive source of the rotation of the sheet pressers39. The motor43is activated at appropriate times under control of the control circuit4. As illustrated inFIG. 5, the motor43is located around a corner of the ejected sheet tray35at the negative end in x-direction and the negative end in y-direction. The motor43is enclosed in sheet metal.

The shaft45is a round bar extending in the x-direction and is located at the negative end in y-direction of the sheet ejected tray35. As described above, the sheet pressers39are fixed to the shaft45. A first end of the shaft45is connected to the motor43via a gear. Accordingly, the shaft45transmits the force supplied from the motor43to the sheet pressers39. Additionally, near a second end of the shaft45, a closure plate47a, which is a component of the monitoring system47, is provided.

The monitoring system47, as illustrated inFIG. 6, comprises the closure plate47aand a shaft sensor47b. As mentioned above, the closure plate47ais fixed to a portion of the shaft45near the second end. The closure plate47ais a sector plate, and its main surfaces in a sector form are perpendicular to the x-direction. The shaft sensor47bis an optical sensor having a light emitting element and a light receiving element. The shaft sensor47bis shaped like a right-angled U having an open upper side when viewed from the y-direction. In the monitoring system47having this structure, the closure plate47acuts across the open side of the right-angled U shape of the shaft sensor47bas the shaft45rotates. In this moment, the closure plate47ablocks light coming from the light emitting element of the shaft sensor47b. In this way, the monitoring system47monitors the rotation of the shaft45.

Sheet Ejection from Post-Handling Apparatus

Sheet ejection from the post-handling apparatus3is described below. In the following description, a sheet which has not been ejected completely onto the ejected sheet tray35is referred to as a sheet P1, and a sheet which has been ejected completely onto the ejected sheet tray35is referred to as a sheet P2. In the following, a case where a sheet P1is ejected from the aligning tray21to the ejected sheet tray is considered.

A sheet P1ejected from the image forming apparatus2is received on the aligning tray21and then ejected therefrom to the ejected sheet tray35by the rear-side aligning plate29. In this moment, if there are any sheets P2on the ejected sheet tray35, as illustrated inFIG. 7, the sheet pressers39press the upper surface of the stack of sheets P2. However, while the sheet P1is coming from the aligning tray21to the ejected sheet tray35, the sheet pressers39move back in a receding position. The following description is focused on this point.

Initially, as illustrated inFIG. 8, before a sheet P1is ejected from the image forming apparatus2to the aligning tray21, the sheet pressers39are hidden in holes G formed at the negative side in y-direction of the ejected sheet tray35, that is, are located in the receding position. When the sheet ejection sensor37detects a sheet or a stack of sheets P2on the ejected sheet tray35, a signal is sent to the control unit4. Thereafter, at a time when the sheet P1is ejected from the image forming apparatus2to the aligning sheet21, the motor43is activated. Thereby, the sheet pressers39rotate along with the shaft45and come out of the holes G. Then, as illustrated inFIG. 7, the sheet pressers39press the upper surface of the sheet or the stack of sheets P2on the ejected sheet tray35. Accordingly, when the leading edge E1of the sheet P1falls down on the sheet or the stack of sheets P2on the ejected sheet tray35, the sheet or the stack of sheets P2is already pressed by the sheet pressers39. Therefore, the sheet P1passes over the sheet pressers39and falls down on the sheet or the stack of sheets P2.

While the sheet P1is passing over the sheet pressers39, the sheet pressers39start receding into the holes G. As illustrated inFIG. 9, a point of time T1when the sheet pressers39start the receding movement is Δt earlier than a reference time T2, wherein Δt is a period of time required for a movement of the sheet pressers39from the ejected sheet tray35into the holes G, and T2is a point of time when the trailing edge of the sheet P1comes out of the aligning tray21. Accordingly, as illustrated inFIG. 10, when the trailing edge E2of the sheet P1comes out of the aligning tray21, the receding movement of the sheet pressers39has been already completed. The point of time T2when the trailing edge E2of the sheet P1comes out of the aligning tray21is approximated from a point of time when the rear-side aligning plate29reaches the positive end in y-direction of the aligning tray21. The period of time Δt required for a movement of the sheet pressers39from the ejected sheet tray35into the holes G is determined from a value preliminarily stored in the control unit4.

After completion of the ejection of the sheet P1, the sheet pressers39start coming to a position again to press the upper surface of the stack of sheets P2on the ejected sheet tray35. In this regard, the control unit4perceives the travel distance (rotation angle) of the sheet pressers39from information sent from the monitoring system47. If the travel distance is smaller than a predetermined value, the control unit4determines that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity of the ejected sheet tray35.

When the control unit4determines that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity of the ejected sheet tray35, the control unit4stops the image forming apparatus2from starting a next image forming process. Also, an interface IF provided on the image forming apparatus2displays information that sheets have been stacked on the ejected sheet tray35up to the limit of loadable capacity, that is, information that the ejected sheet tray35is full. Further, the control unit4keeps the sheet pressers39pressing the upper surface of the stack of sheets P2. In other words, the control unit4prohibits the sheet pressers39from receding.

However, if there is a sheet P1remaining on the aligning tray21, the control unit4permits ejection of the sheet P1from the aligning sheet tray21in order to complete the ejection of the sheet P1from the post-handling apparatus3. In this regard, when the leading edge E1of the sheet P1comes out of the aligning tray21to the ejected sheet tray35, the sheet pressers39press the upper surface of the stack of sheets P2on the ejected sheet tray35. While the sheet P1is being ejected from the aligning tray21to the ejected sheet tray35, the sheet pressers39move to the receding position. Thus, if there is a sheet P1remaining on the aligning tray21, the control unit4once cancels the prohibition of the receding movement of the pressers39. Then, after completion of the ejection of the sheet P1from the post-handling apparatus3, the sheet pressers39come to a position again to press the upper surface of the stack of sheets P2on the ejected sheet tray35.

Thereafter, when the user discharges the stack of sheets P2from the ejected sheet tray35, the control unit4receives information from the sheet ejection sensor37that there are no sheets on the ejected sheet tray35. In response, the control unit4permits the image forming apparatus2to start a next image forming process and returns the display screen on the interface IF to a normal screen. Further, the control unit4returns the sheet pressers39to the receding position.

Incidentally, if a receding movement of the sheet pressers39from the ejected sheet tray35by order of the control unit4is not completed within a predetermined period of time, the control unit4takes a process depending on whether there is a sheet on the ejected sheet tray35.

If a receding movement of the sheet pressers39from the ejected sheet tray35by order of the control unit4is not completed within a predetermined period of time and if there is a sheet on the ejected sheet tray35, the control unit4takes a process similar to the process the control unit4carries out when the control unit4has determined that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity. Specifically, the control unit4stops the image forming apparatus2from starting a next image forming process and drives the interface IF to display information that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity. This permits a user to perceive the problem, for example, that a sheet P1is stuck between the sheet pressers39in the middle of a receding movement and the exit of the post-handling apparatus3as illustrated inFIG. 11, and the user can remove the sheet P1.

If a receding movement of the sheet pressers39from the ejected sheet tray35by order of the control unit4is not completed within a predetermined period of time and if there are no sheets on the ejected sheet tray35, the control unit4determines that any component relating to the sheet pressers39has a defect. Then, the control unit4stops the image forming apparatus2from staring a next image forming process and drives the interface IF to display information that any component relating the sheet pressers39has a defect.

Control of Sheet Ejection

In a procedure of controlling sheet ejection, first, an MFP controller401of the control unit4obtains information from the user interface IF provided on the image forming apparatus2, a computer terminal PC, and the sensors provided in the image forming apparatus2and the post-handling apparatus3. In accordance with the information, an engine controller402of the control unit4controls image formation in the image forming apparatus2and ejection of a printed sheet P from the image forming apparatus2. A post-handling controller403of the control unit4activates the motor43for the support members, the aligning plates and the pressers39, and other members to carry out sheet ejection. In the following, a control flow is described with reference toFIGS. 13 through 19.

Main Routine

First, the main routine of the control procedure illustrated inFIGS. 13 through 15is described. The main routine starts at a time of issuance of an image forming command from the control unit4, that is, at a time of determination to eject a sheet from the image forming apparatus2.

At step MS1of the main routine, the control unit4determines the position of sheet pressers39from the signal sent from the monitoring system47. If the control unit4determines that the sheet pressers39are not in the receding position (home position), the control procedure goes to step MS2, and if the control unit4determines that the sheet pressers39are in the receding position, the control procedure goes to step MS7.

At step MS2of the main routine, the control unit4activates the motor43to start moving the sheet pressers39to the receding position.

At step MS3of the main routine, the control unit4starts a timer A1. The timer A1is to count down a predetermined time T3from the time of starting a receding movement of the sheet pressers39. The predetermined time T3, which is stored in the control unit4, is a period of time required for a movement of the sheet pressers39from the ejected sheet tray35to the receding position plus a predetermined margin.

At step MS4of the main routine, the control unit4determines whether the predetermined time T3has passed. When the control unit4determines that the predetermined time T3has passed, the control procedure goes to step MS5. The control procedure stands by at step MS4until the predetermined time T3has passed.

At step MS5of the main routine, the control unit4stops the motor43to stop the receding movement of the sheet pressers39.

At step MS6of the main routine, the control unit4determines the position of the sheet pressers39from the signal sent from the monitoring system47. If the control unit4determines that the sheet pressers39are in the receding position (home position), the control procedures goes to step MS7of the main routine. If the control unit4determines that the sheet pressers39are not in the receding position, the control procedure goes to step FS1of a first subroutine, which will be described later. In a case where the control procedure goes from step MS6of the main routine to step FS1of the first subroutine, the control procedure thereafter returns from the first subroutine to step MS2of the main routine or ends.

At step MS7of the main routine, the control unit4determines from the signal sent from the sheet ejection sensor37whether there are any sheets P2on the ejected sheet tray35. If the control unit4determines that there are no sheets P2on the ejected sheet tray35, the control procedure stands by at this step until the control unit4determines that there is a sheet P2on the ejected sheet tray35, that is, until a sheet has been ejected from the post-handling apparatus3. When the control unit4determines that there are any sheets P2on the ejected sheet tray35, the control procedure goes to step MS8of the main routine.

At step MS8of the main routine, the control unit4determines from the signal sent from the sheet ejection sensor60located near the exit of the image forming apparatus2whether ejection of a sheet P1from the image forming apparatus2onto the aligning tray21of the post-handling apparatus3has been started. When the control unit4determines that ejection of a sheet P1from the image forming apparatus2onto the aligning tray21has been started, the control procedure goes to step MS9. The control procedure stands by at step MS8until sheet ejection onto the aligning tray21is started.

At step MS9of the main routine, the control unit4activates the motor43to start moving the sheet pressers39to the ejected sheet tray35.

At step MS10of the main routine, the control unit4starts a timer A2. The timer A2is to count down a predetermined time T4from the time of starting a movement of the sheet pressers39to the ejected sheet tray35. The predetermined time T4, which is stored in the control unit4, is a period of time required for a movement of the sheet pressers39from the receding position to the ejected sheet tray35plus a predetermined margin.

At step MS11of the main routine, the control unit4determines whether the predetermined time T4has passed. When the control unit4determines that the predetermined time T4has passed, the control procedure goes to step MS12. The control procedure stands by at step MS11until the predetermined time T4has passed.

At step MS12of the main routine, the control unit4stops the motor43to stop the movement of the sheet pressers39to the ejected sheet tray35. At the same time, the rear-side aligning plate29starts moving toward the ejected sheet tray35.

At step MS13of the main routine, the control unit4determines whether the rear-side aligning plate29has passed a predetermined position on the aligning tray21. As illustrated inFIG. 16, the predetermined position is a position at a distance L1in the negative y-direction from the positive end in y-direction of the aligning tray21, that is, from the exit of the post-handling apparatus3. The distance L1is obtained by v×Δt, where v denotes the travel speed of the rear-side aligning plate29, and Δt denotes the period of time required for a movement of the sheet pressers39from the ejected sheet tray35to the receding position. When the control unit4determines that the rear-side aligning plate29has passed the predetermined position on the aligning tray21, the control procedure goes to step MS14. The control procedure stands by at step MS13until the rear-side aligning plate29has passed the predetermined position on the aligning tray21.

At step MS14of the main routine, the control unit4activates the motor43to start a movement of the sheet pressers39to the receding position. Therefore, when the trailing edge E2of the sheet P1being ejected from the aligning tray21falls down on the ejected sheet tray35, the sheet pressers39have already receded from the ejected sheet tray35, and there is no possibility that the sheet pressers39get stuck between the previously ejected sheet P2and the newly ejected sheet P1.

At step MS15of the main routine, the control unit4activates a timer A3. The timer A3is to count down the predetermined time T3from the time of starting a movement of the sheet pressers39to the receding position. As mentioned above, the predetermined time T3is stored in the control unit4and is a period of time required for a movement of the sheet pressers39from the ejected sheet tray35to the receding position plus a predetermined margin.

At step MS16of the main routine, the control unit4determines whether the predetermined time T3has passed. When the control unit4determines that the predetermined time T3has passed, the control procedure goes to step MS17. The control procedure stands by at step MS16until the predetermined time T3has passed.

At step MS17of the main routine, the control unit4stops the motor43to stop the movement of the sheet pressers39to the receding position.

At step MS18of the main routine, the control unit4determines the position of the sheet pressers39from the signal sent from the monitoring system47. If the control unit4determines that the sheet pressers39are in the receding position (home position), the control procedure goes to step MS19of the main routine. If the control unit4determines that the sheet pressers39are not in the receding position, the control procedure goes to step FS1of the first subroutine, which will be described later. In a case where the control procedure goes from step MS18of the main routine to step FS1of the first subroutine, the control procedure thereafter returns from the first subroutine to step MS14of the main routine or ends.

At step MS19of the main routine, the control unit4determines whether the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21, that is, whether the sheet P1has been completely ejected from the aligning tray21. When the control unit4determines that the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21, the control procedure goes to step MS20. The control procedure stands by at step MS19until the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21. It is determined from the travel distance of the rear-side aligning plate29whether the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21.

At step MS20of the main routine, the control unit4activates the motor43to start a movement of the sheet pressers39to the ejected sheet tray39.

At step MS21of the main routine, the control unit4starts a timer A4. The timer A4is to count down the predetermined time T4from the time of starting a movement of the sheet pressers39to the ejected sheet tray35. As mentioned above, the predetermined time T4is stored in the control unit4and is a period of time required for a movement of the sheet pressers39from the receding position to the ejected sheet tray35plus a predetermined margin.

At step MS22of the main routine, the control unit4determines whether the predetermined time T4has passed. When the control unit4determines that the predetermined time T4has passed, the control procedure goes to step MS23. The control procedure stands by at step MS22until the predetermined time T4has passed.

At step MS23of the main routine, the control unit4stops the motor43to stop the movement of the sheet pressers39to the ejected sheet tray35.

At step MS24of the main routine, the control unit4determines whether sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity. If the control unit4determines that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity, the control procedure goes to step SS1of a second subroutine, which will be described later. If the control unit4determines that sheets have not been stacked on the ejected sheet tray35up to the limit of loading capacity, the control procedure goes to step MS25.

At step MS25of the main routine, the control unit4determines whether a next sheet is to be ejected from the image forming apparatus2. If there is a next sheet to be ejected from the image forming apparatus2, the control procedure returns to step MS2. If there is no sheet to be ejected from the image forming apparatus2, the control procedure ends.

First Subroutine

The first subroutine illustrated inFIG. 17is a routine that is selected in a case where a movement of the sheet pressers39to the receding position by order of the control unit4is not completed within a predetermined period of time.

At step FS1of the first subroutine, the control unit4determines from a signal sent from the sheet ejection sensor37whether there are any sheets P2on the ejected sheet tray35. If the control unit4determines that there are no sheets P2on the ejected sheet tray35, the control procedure goes to step FS2. If the control unit determines that there are any sheets P2on the ejected sheet tray35, the control procedure goes to step FS3.

At step FS2of the first subroutine, the control unit4stops the image forming apparatus2from starting a next image forming process. Also, the control unit4drives the interface IF provided on the image forming apparatus2to display information that a component relating to the sheet pressers39has a defect. Thereafter, the control procedure ends.

At step FS3of the first subroutine, the control unit4stops the image forming apparatus2from starting a next image forming process. Also, the control unit4drives the interface IF provided on the image forming apparatus2to display information that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity, that is, display information that the ejected sheet tray35is full. Further, the control unit4prohibits the sheet pressers39from moving to the receding position.

At step FS4of the first subroutine, the control unit4determines from the signal sent from the sheet ejection sensor37whether there are any sheets P2on the ejected sheet tray35. If the control unit4determines that there are any sheets P2on the ejected sheet tray35, the control procedure stands by at this step until the control unit4determines that there are no sheets P2on the ejected sheet tray35, that is, until a user removes the sheets P2from the ejected sheet tray35. When the control unit4determines that there are no sheets P2on the ejected sheet tray35, the control procedure goes to step FS5.

At step FS5of the first subroutine, the control unit4permits the image forming apparatus2to start a next image forming process. Also, the control unit4returns the display screen of the interface IF provided on the image forming apparatus2to a normal screen. Further, the control unit4cancels the prohibition of a receding movement of the sheet pressers. Thereafter, the control procedure returns to step MS2or step MS14of the main routine or returns to step SS5of the second subroutine, which will be described below.

Second Subroutine

The second subroutine illustrated inFIGS. 18 and 19is a routine that is selected in a case where the control unit4determines that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity.

At step SS1of the second subroutine, the control unit4stops the image forming apparatus2from starting a next image forming process. Also, the control unit4drives the interface IF to display information that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity. Further, the control unit4prohibits the sheet pressers39from moving to the receding position.

At step SS2of the second subroutine, the control unit4determines from signals sent from sensors and other devices provided around the aligning tray21whether there is a sheet P1on the aligning tray21. If the control unit4determines that there is a sheet P1on the aligning tray21, the control procedure goes to step SS3. If the control unit4determines that there are no sheets P1on the aligning tray21, the control procedure goes to step SS16.

At step SS3, the control unit4cancels the prohibition of a receding movement of the sheet pressers39. Substantially at the same time as the cancellation of the prohibition of a receding movement of the sheet pressers39, the control unit4drives the rear-side aligning plate29of the aligning tray21to move toward the ejected sheet tray35. Thereby, the sheet P1on the aligning tray21is moved from the aligning tray21toward the ejected sheet tray P1.

At step SS4of the second subroutine, the control unit4determines whether the rear-side aligning plate29has passed the predetermined position on the aligning tray21. As mentioned above, the predetermined position is a position at a distance L1in the negative y-direction from the positive end in y-direction of the aligning tray21, that is, from the exit of the post-handling apparatus3. When the control unit4determines that the rear-side aligning plate29of the aligning tray21has passed the predetermined position, the control procedure goes to step SS5. The control procedure stands by at step SS4until the rear-side aligning plate29of the aligning tray21has passed the predetermined position.

At step SS5of the second subroutine, the control unit4activates the motor43to start a movement of the sheet pressers39to the receding position. Accordingly, when the trailing edge E2of the sheet P1falls down on the ejected sheet tray35, the sheet pressers39has receded from the ejected sheet tray35into the receding position, and there is no possibility that the sheet pressers39are stuck between the previously ejected sheet P2and the sheet P1newly coming to the ejected sheet tray35.

At step SS6of the second subroutine, the control unit4starts a timer A5. The timer A5is to count down the predetermined time T3from the start of a movement of the sheet pressers39toward the receding position. As mentioned above, the predetermined time T3is stored in the control unit4and is a period of time required for a movement of the sheet pressers39from the ejected sheet tray35to the receding position plus a predetermined margin.

At step SS7of the second subroutine, the control unit4determines whether the predetermined time T3has passed. When the control unit4determines that the predetermined time T3has passed, the control procedure goes to step SS8. The control procedure stands by at step SS7until the predetermined time T3has passed.

At step SS9of the second subroutine, the control unit4determines the position of the sheet pressers39from the signal sent from the monitoring system47. If the control unit4determines that the sheet pressers39are in the receding position (home position), the control procedure goes to step SS10of the second subroutine. If the control unit4determines that the sheet pressers39are not in the receding position, the control procedure goes to step FS1of the first subroutine. In a case where the control procedure goes from the step SS9of the second subroutine to the first subroutine, the control procedure thereafter returns from the first subroutine to the second subroutine or ends.

At step SS10of the second subroutine, the control unit4determines whether the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21, that is, whether the sheet P1has been completely ejected from the aligning tray21. When the control unit4determines that the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21, the control procedure goes to step SS11. The control procedure stands by at step SS10until the rear-side aligning plate29has reached the positive end in y-direction of the aligning tray21.

At step SS11of the second subroutine, the control unit4activates the motor43to start a movement of the sheet pressers39toward the ejected sheet tray35.

At step SS12of the second subroutine, the control unit4starts a timer A6. The timer A6is to count down the predetermined time T4from the time of starting a movement of the sheet pressers39toward the ejected sheet tray35. As mentioned above, the predetermined time T4is stored in the control unit4and is a period of time required for a movement of the sheet pressers39from the receding position to the ejected sheet tray35plus a predetermined margin.

At step SS13of the second subroutine, the control unit4determines whether the time T4has passed. When the control unit4determines that the time T4has passed, the control procedure goes to step SS14. The control procedure stands by at step SS13until the time T4has passed.

At step SS14of the second subroutine, the control unit4stops the motor43to stop the movement of the sheet pressers39toward the ejected sheet tray35.

At step SS15of the second subroutine, the control unit4prohibits the sheet pressers39from receding.

At step SS16of the second subroutine, the control unit4determines from the signal sent from the sheet ejection sensor37whether there are any sheets P2on the ejected sheet tray35. If the control unit4determines that there are any sheets P2on the ejected sheet tray35, the control procedure stands by at this step until the control unit4determines that there are no sheets P2on the ejected sheet tray35, that is, until a user has removed the sheets P2from the ejected sheet tray35. When the control unit4determines that there are no sheets P2on the ejected sheet tray35, the control procedure goes to step SS17.

At step SS17of the second subroutine, the control unit4permits the image forming apparatus2to start a next image forming process. Also, the control unit4returns the display screen of the interface IF to a normal screen. Further, the control unit4cancels the prohibition of a receding movement of the sheet pressers39. Thereafter, the control procedure goes to step MS25of the main routine.

Advantageous Effects

In the image forming system1and in the post-handling apparatus3, when the leading edge E1of a sheet P1or a stack of sheets P1newly coming to the ejected sheet tray35falls down on the ejected sheet tray35, the sheet pressers39press the sheets P2previously ejected onto the ejected sheet tray35. Thereby, in the image forming system1and in the post-handling apparatus3, it is possible to prevent the sheets P2previously ejected onto the ejected sheet tray35from falling from the ejected sheet tray35due to collision with the sheet or the stack of sheets P1newly coming to the ejected sheet tray35. Also, it is possible to prevent the sheets P2previously ejected onto the ejected sheet tray35from becoming out of alignment due to collision with the sheet or the stack of sheets P1newly coming onto the ejected sheet tray35.

In the image forming system1and in the post-handling apparatus3, further, since the sheet pressers39press the sheets P2ejected onto the ejected sheet tray35, it is possible to prevent the sheets P2from curling, thereby preventing the sheets P2from increasing in volume on the ejected sheet tray35.

Moreover, in the image forming system1and in the post-handling apparatus3, when the trailing edge E2of the sheet or the stack of sheets P1falls down on the ejected sheet tray35, the sheet pressers39have already receded from the sheet ejected tray35, and therefore, there is no possibility that the sheet pressers39are stuck between the sheets P2previously ejected onto the ejected sheet tray35and the sheet or the stack of sheets P1newly coming onto the ejected sheet tray35.

In the image forming system1and in the post-handling apparatus3, the amount of sheets P2loaded on the ejected sheet tray35is derived from the travel distance of the sheet pressers39from the receding position to the upper surface of the sheets P2on the ejected sheet tray35. Therefore, it is not necessary to provide the image forming system1or the post-handling apparatus3with an additional system configured to figure out the amount of sheets P2loaded on the ejected sheet tray35. Thus, in the image forming system1and the post-handling apparatus3, figuring out the amount of sheets P2loaded on the ejected sheet tray35based on the movement of the sheet pressers39results in space saving and a reduction in cost.

As illustrated inFIG. 11, if the sheet or the stack of sheets P1is stuck between the exit of the post-handling apparatus3and the sheet pressers39, the movement of the sheet pressers39cannot be completed. In order to address this trouble, if a movement of the sheet pressers39to the receding position by order of the control unit4is not completed within the predetermined time and if there are any sheets P2on the ejected sheet tray35, the control unit4drives the interface IF provided on the image forming apparatus2to display information that sheets have been stacked on the ejected sheet tray35up to the limit of loading capacity. By the display, the user can possibly perceive that a sheet or a stack of sheets P1is stuck between the exit of the post-handling apparatus3and the sheet pressers39and remove the sheet or the stack of sheets P1therefrom.

In a case where a movement of the sheet pressers39to the receding position by order of the control unit4is not completed within the predetermined time, the control unit4takes different procedures depending on whether there are any sheets on the ejected sheet tray35. This control contributes to a decrease in the frequency of calling a serviceman of a maintenance agency for maintenance of the image forming apparatus2and the post-handling apparatus3or the image forming system1, compared to a case of adopting a control procedure in which the control unit4drives the interface IF to display information that a component relating to the sheet pressers39has a defect regardless of whether there are any sheets on the ejected sheet tray35.

Modification

An image forming system1A and a post-handling apparatus3A according to a modification are different from the image forming system1and the post-handling apparatus3according to the above-described embodiment in the condition of starting the control procedure for sheet ejection from the post-handling apparatus. According to the modification, the control procedure is started on the condition that the post-handling apparatus3A or the image forming system1A is started.

By setting a start of the post-handling apparatus3A or the image forming system1A as the condition for a start of the control procedure, the sheet pressers39can be returned to the receding position (home position) before the control unit4issues an image forming command. Therefore, at a time of issuance of an image forming command, the main routine starts from step MS7, and a series of actions from image formation to sheet ejection from the post-handling apparatus3can be performed more smoothly.

Other Embodiments

Post-handling apparatuses and image forming systems according to the present invention are not limited to the embodiment and the modification described above. For example, the control unit4may be provided not in the image forming apparatus2but in the post-handling apparatus3.

Although the present invention has been described in connection with the embodiment and the modification above, it is to be noted that various changes and modifications may be obvious to those who are skilled in the art. Such changes and modifications are to be understood as being within the scope of the invention.