SHEET STACKING DEVICE AND IMAGE FORMING APPARATUS

Abstract

A sheet stacking device includes a stacker, a conveyor, and a marking device. The stacker stacks transfer sheets. The conveyor conveys the transfer sheets toward the stacker in a sheet conveyance direction. The marking device includes a marker storage to store a marker, an ejection port to eject the marker, a marker conveyor to convey and eject the marker from the ejection port, and a guide to prevent the marker ejected from the ejection port from moving in a direction opposite to the sheet conveyance direction. The marking device places the marker on an uppermost sheet of each predetermined number of the transfer sheets on the stacker.

Claims

1. A sheet stacking device comprising: a stacker to stack transfer sheets; a conveyor to convey the transfer sheets toward the stacker in a sheet conveyance direction; a marking device including: a marker storage to store a marker; an ejection port to eject the marker; a marker conveyor to convey and eject the marker from the ejection port; and a guide to prevent the marker ejected from the ejection port from moving in a direction opposite to the sheet conveyance direction, wherein the marking device is configured to place the marker on an uppermost sheet of each predetermined number of the transfer sheets on the stacker.

2. The sheet stacking device according to claim 1, wherein the guide extends to a position below the uppermost sheet in a vertical direction orthogonal to the sheet conveyance direction.

3. The sheet stacking device according to claim 1, wherein the stacker is movable in a vertical direction orthogonal to the sheet conveyance direction, the guide is movable between an uppermost position and a lowermost position of the guide in the vertical direction in accordance with a vertical movement of the stacker, the guide has, when the guide is at the lowermost position: a lower end lower than the uppermost sheet; and an upper end higher than the ejection port.

4. The sheet stacking device according to claim 3, wherein the guide has: a plate having an L-shaped cross section having: a body having a slotted hole extending in a longitudinal direction of the guide; and a guide portion connected to the body at right angle, and a lower end of the guide portion extending downward below the body; and screws screwed into a side face of the marker storage through the slotted hole.

5. The sheet stacking device according to claim 4, wherein the stacker includes a sheet tray having a sheet placement surface to place the transfer sheets on the sheet placement surface, and the lower end of the guide portion contacts the sheet placement surface of the stacker.

6. The sheet stacking device according to claim 3, wherein the guide has: a plate having an L-shaped cross section having: a body extending in a longitudinal direction of the guide; a guide portion connected to the body at right angle, and a lower end of the guide portion extending downward below the body; and a support having a hole and fixed to a bent portion between the body and the guide portion; and a support pin fitted into the hole of the support and fixed to the marker storage to support the plate movable in the vertical direction.

7. The sheet stacking device according to claim 6, wherein the stacker includes a sheet tray having a sheet placement surface to place the transfer sheets on the sheet placement surface, and the lower end of the guide portion contacts the sheet placement surface of the stacker.

8. The sheet stacking device according to claim 1, further comprising: an air blower to blow an air to the transfer sheets conveyed to the stacker, wherein the marking device further includes another guide facing the guide across the ejection port to prevent the marker ejected from the ejection port from moving in the sheet conveyance direction.

9. The sheet stacking device according to claim 8, wherein the stacker is movable in a vertical direction orthogonal to the sheet conveyance direction, the guide and said another guide are movable in the vertical direction in accordance with a vertical movement of the stacker, a lower portion of the guide and another lower portion of said another guide are inclined with respect to the vertical direction, and a distance between the lower portion and said another lower portion increases downward.

10. The sheet stacking device according to claim 8, wherein the stacker is movable in a vertical direction orthogonal to the sheet conveyance direction, the guide and said another guide are movable in the vertical direction in accordance with a vertical movement of the stacker, the air blower stops blowing the air before the stacker starts moving downward, and the air blower starts blowing the air after the stacker finishes moving upward.

11. An image forming apparatus comprising: the sheet stacking device according to claim 1; and an image forming device disposed upstream from the sheet stacking device in the sheet conveyance direction to form images on the transfer sheets.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:

[0007] FIG. 1 is a schematic front view of an image forming apparatus;

[0008] FIG. 2 is a schematic front view of a sheet stacking device with a holder at a standby position;

[0009] FIG. 3 is a schematic plan view of a sheet stacking device with a holder at a standby position;

[0010] FIG. 4 is a schematic view of a lift used in a sheet stacking device;

[0011] FIG. 5 is a schematic front view of a sheet stacking device with a holder into which a leading end of a transfer sheet has been inserted by a predetermined amount;

[0012] FIG. 6 is a schematic front view of a sheet stacking device with a holder which has released a transfer sheet;

[0013] FIG. 7 is a schematic front view of a sheet stacking device with a holder which has released a transfer sheet of a small size;

[0014] FIG. 8 is a schematic side view of a sheet stacking device including a marking device;

[0015] FIG. 9 is a schematic front view of a sheet stacking device including a marking device;

[0016] FIGS. 10A and 10B are schematic views of a marking device;

[0017] FIGS. 11A to 11D are schematic views of a sheet stacking device including a marking device, illustrating a behavior of a marker;

[0018] FIGS. 12A to 12C are schematic views of a marking device according to a first embodiment of the present disclosure;

[0019] FIG. 13 is a schematic view of the marking device of FIGS. 12A to 12C, according to the first embodiment, and a sheet stacking device;

[0020] FIGS. 14A to 14C are schematic views of a marking device according to a second embodiment of the present disclosure;

[0021] FIGS. 15A to 15C are schematic views of a marking device according to a third embodiment of the present disclosure;

[0022] FIGS. 16A to 16C are schematic views of a marking device according to a fourth embodiment of the present disclosure;

[0023] FIGS. 17A to 17C are schematic views of a marking device according to a fifth embodiment of the present disclosure;

[0024] FIGS. 18A to 18C are schematic diagrams illustrating a behavior of a marker during raising and lowering operations of a guide and a second guide in the marking device of FIGS. 15A to 15C, according to the third embodiment;

[0025] FIGS. 19A to 19C are schematic diagrams illustrating a behavior of a marker during raising and lowering operations of a guide and a second guide in the marking device of FIGS. 17A to 17C, according to the fifth embodiment;

[0026] FIGS. 20A to 20C are schematic views of a marking device according to a sixth embodiment of the present disclosure; and

[0027] FIG. 21 is a flowchart of a series of operations of a sheet stacking device according to a seventh embodiment of the present disclosure.

[0028] The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

[0029] In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

[0030] Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0031] FIG. 1 illustrates an image forming apparatus 1. In FIG. 1, the image forming apparatus 1 includes a sheet feeding device 2 that stores a transfer sheet S as a recording medium, a sheet position correction device 3 that corrects a position of the transfer sheet S, and an image forming device 4 that forms an image on the transfer sheet S.

[0032] The image forming apparatus 1 further includes a sheet drying device 5 that dries an image formed on the transfer sheet S, a sheet cooling device 6 that cools the transfer sheet S, a sheet reverse device 7 that reverses the transfer sheet S, a first sheet stacking device 8 and a second sheet stacking device 9 that stack the transfer sheet S, and an control panel 10 that controls the above-described devices based on an instruction of a user.

[0033] The sheet feeding device 2 and the sheet position correction device 3 convey the transfer sheets S stacked and stored in the sheet feeding device 2 one by one. The sheet feeding device 2 includes a sheet size detection sensor 11 that detects the size of the transfer sheet S to be fed. Specifically, the sheet feeding device 2 includes multiple sheet size detection sensors 11 that detect the length and width of the transfer sheet S.

[0034] The sheet position correction device 3 adjusts the conveyance timing of the transfer sheet S so that the image forming device 4 forms an image at a predetermined position of the transfer sheet S based on size data of the transfer sheet S transmitted from the sheet size detection sensor 11.

[0035] The image forming device 4 is an inkjet recording device that discharges ink of each color of black (K), cyan (C), magenta (M), and yellow (Y) onto the transfer sheet S to form a full-color image on the transfer sheet S. The image forming device 4 includes liquid discharge devices 13K, 13C, 13M, and 13Y that discharge the above-described inks of the respective colors. The liquid discharge devices 13K, 13C, 13M, and 13Y are disposed around a drum roll 12 to form an inkjet image of each color on the transfer sheet S.

[0036] The sheet drying device 5 and the sheet cooling device 6 dry and then cool the inkjet image formed on the transfer sheet S. As a result, the inkjet image is held stably on the transfer sheet S.

[0037] The sheet reverse device 7 reverses the transfer sheet S by a switchback manner and conveys the transfer sheet S to the sheet position correction device 3 again, if desired, to switch the image forming surface of the transfer sheet S that faces the drum roll 12 from the front side to the back side of the transfer sheet S. The above-described respective devices are appropriately controlled in accordance with a user's operation via the control panel 10 to form an inkjet image on the transfer sheet S.

[0038] The inkjet printer that forms an inkjet image has been described as the image forming apparatus 1, but an image forming apparatus is not limited thereto, and may include an electrophotographic image forming unit as the image forming device 4. In this case, the image forming apparatus may include a fixing device that fixes a toner image on the transfer sheet S in place of the sheet drying device 5 and the sheet cooling device 6. Such an image forming apparatus may include components having the same or similar configuration as a typical image forming apparatus, and detailed descriptions thereof will be omitted.

[0039] The first sheet stacking device 8 will be described below. The first sheet stacking device 8 and the second sheet stacking device 9 are both ejection destinations to which the transfer sheet S is ejected in the image forming apparatus 1, and may have the same configuration or different configurations. In the following description, the first sheet stacking device 8 and the second sheet stacking device 9 are not different in configuration, and are different only in the ejection destination of the transfer sheet S.

[0040] The first sheet stacking device 8 illustrated in FIG. 2 includes a sheet tray 14 as a stacker, a sheet conveyance mechanism 15 as a conveyor that conveys the transfer sheet S to the sheet tray 14, and a guide mechanism 16 that grips a leading end of the transfer sheet S conveyed toward the sheet tray 14 and conveys the transfer sheet S to a downstream side in a sheet conveyance direction. The first sheet stacking device 8 further includes a sheet leading end detection sensor 17 that detects a leading end of the transfer sheet S on an upstream side of the sheet conveyance mechanism 15 in the sheet conveyance direction, and a bypass conveyance path 18 that conveys the conveyed transfer sheet S to the second sheet stacking device 9 disposed on a downstream side of the first sheet stacking device 8 in the sheet conveyance direction by bypassing the sheet tray 14.

[0041] After image formation, the transfer sheet S is stacked on the sheet tray 14. An initial position of the sheet tray 14 is located below the transfer sheet S fed by the sheet conveyance mechanism 15. The sheet tray 14 moves downward as the transfer sheet S is stacked on the sheet tray 14, and the position of the uppermost surface of a bundle of the transfer sheets S (i.e., a sheet bundle) stacked on the sheet tray 14 is continuously maintained at a height at which the transfer sheet S is ejected from the sheet conveyance mechanism 15 and smoothly stacked onto the uppermost surface of the sheet bundle on the sheet tray 14. A lift that raises and lowers the sheet tray 14 will be described later. A user pulls out the sheet tray 14 from the first sheet stacking device 8 to take out the transfer sheets S stacked on the sheet tray 14.

[0042] The sheet conveyance mechanism 15 includes a typical roller pair including a drive roller 15a and a driven roller 15b to convey the transfer sheet S conveyed from the image forming device 4 toward the sheet tray 14. The sheet conveyance mechanism 15 receives the transfer sheet S ejected by a supply roller pair 19 disposed at the most upstream position in the sheet conveyance direction in the first sheet stacking device 8, and conveys the transfer sheet S to the downstream side in the sheet conveyance direction.

[0043] The sheet leading end detection sensor 17 is disposed on the upstream side of the sheet conveyance mechanism 15 in the sheet conveyance direction, and detects the leading end of the conveyed transfer sheet S to output a signal.

[0044] The guide mechanism 16 is disposed on the downstream side of the sheet conveyance mechanism 15 in the sheet conveyance direction. The guide mechanism 16 conveys the transfer sheet S in the sheet conveyance direction at a speed higher than a sheet conveyance speed of the sheet conveyance mechanism 15 while holding the leading end of the transfer sheet S conveyed by the sheet conveyance mechanism 15. The guide mechanism 16 functions as a guide device that holds the leading end of the transfer sheet S and releases the leading end of the transfer sheet S at a release position to guide the conveyed transfer sheet S onto the sheet tray 14.

[0045] The guide mechanism 16 includes a rotatable endless conveyance belt 22 and a holder 23. The conveyance belt 22 is looped around a drive roller 20 and a driven roller 21. The holder 23 is attached to the conveyance belt 22 and moves along with the rotation of the conveyance belt 22. The drive roller 20 is driven by a motor 24, which is a variable speed stepper motor, to rotate the conveyance belt 22 at a variable rotation speed. The position of the holder 23 on the conveyance belt 22 can be grasped based on the number of steps of the motor 24.

[0046] As illustrated in FIG. 3, four conveyance belts 22 (i.e., conveyance belts 22a, 22b, 22b, and 22a) are arranged in parallel to each other in a sheet width direction of the transfer sheet S indicated by arrow B. Two holders 23 are arranged on each of the conveyance belts 22a, 22b, 22b, and 22a at positions which are point-symmetrical to each other in the circumferential direction of the conveyance belts 22. The holder 23 is attached to the outer circumferential surface of the conveyance belt 22 and moves along with the rotation of the conveyance belt 22. In FIG. 3, the transfer sheet S is conveyed in the sheet conveyance direction indicated by arrow A.

[0047] The first sheet stacking device 8 causes the holder 23 holding the transfer sheet S to release the transfer sheet S by using a speed difference between the sheet conveyance speed of the sheet conveyance mechanism 15 and the sheet conveyance speed of the guide mechanism 16. Thus, the released transfer sheet S is stacked on the sheet tray 14.

[0048] A blower fan 25 is disposed at a downstream portion of the guide mechanism 16 in the sheet conveyance direction. The blower fan 25 serves as an air blower that applies (blows) an airflow directed toward the sheet tray 14, i.e., directed downward, to the conveyed transfer sheet S. The blower fan 25 is constantly operated, and applies the airflow so as to press the transfer sheet S held by the holder 23 against the sheet tray 14.

[0049] As illustrated in FIG. 2, the holder 23 has an opening 23a into which the leading end of the transfer sheet S is inserted, and a nipping portion 23b that nips the leading end of the transfer sheet S inserted from the opening 23a. The force of the nipping portion 23b nipping the leading end of the transfer sheet S is set to be smaller than the friction force between the sheet conveyance mechanism 15 and the transfer sheet S. Thus, the nipping portion 23b allows the transfer sheet S to enter the holder 23 stopped at a standby position illustrated in FIG. 2 by the rigidity of the transfer sheet S conveyed by the sheet conveyance mechanism 15 and inserted from the opening 23a, and elastically holds the transfer sheet S.

[0050] The contact face of the holder 23 with the transfer sheet S is preferably formed of a material having high smoothness such as metal or resin. Such a material enables the holder 23 to smoothly hold the transfer sheet S.

[0051] The holder 23 is stopped at the standby position illustrated in FIG. 2 when receiving the transfer sheet S. The holder 23 starts conveying the transfer sheet S at a predetermined timing after the leading end of the transfer sheet S is detected by the sheet leading end detection sensor 17 and nipped by the nipping portion 23b. As described above, the holder 23 functions as a guide that moves in the sheet conveyance direction after holding the leading end of the transfer sheet S conveyed by the sheet conveyance mechanism 15 at the standby position to guide the conveyance of the transfer sheet S.

[0052] In the image forming apparatus 1, as illustrated in FIGS. 2 and 3, two holders 23 are disposed on the outer circumferential surface of the conveyance belt 22 in phases different from each other by 180 degrees. Accordingly, when the conveyance of the transfer sheet S is completed, one of the holders 23 is rotated by half as the conveyance belt 22 rotates, and the other holder 23 is positioned at the standby position and stopped. Thus, the two holders 23 are alternately moved to the standby position, so that the time until the holders 23 return to the standby position is shortened to enhance the conveyance cycle of the transfer sheet S.

[0053] In the image forming apparatus 1, as illustrated in FIG. 3, the four conveyance belts 22 are arranged in the sheet width direction, and the two holders 23 are disposed on each of the conveyance belts 22. Accordingly, the holder 23 can be downsized as compared with one or two conveyance belts 22 each provided with two holders. As a result, the inertial load of the holder 23 when the conveyance belt 22 rotates can be reduced, and the holding posture of the transfer sheet S can be stabilized by increasing the number of the holders 23.

[0054] The four conveyance belts 22a, 22b, 22b, and 22a are classified into end side conveyance belts 22a and 22a disposed at the respective end portions in the sheet width direction and center side conveyance belts 22b and 22b disposed between the end side conveyance belts 22a and 22a. The holders 23 are arranged so that the attaching positions in the sheet conveyance direction are different from each other between the end side conveyance belts 22a and 22a and the center side conveyance belts 22b and 22b. Specifically, the standby positions of the holders 23 on the center side conveyance belts 22b and 22b are located upstream of the standby positions of the holders 23 on the end side conveyance belts 22a and 22a in the sheet conveyance direction.

[0055] With the above configuration, the timing at which the holder 23 holds the transfer sheet S can be shifted between the end side conveyance belts 22a and 22a and the center side conveyance belts 22b and 22b, and thus the load when the transfer sheet S enters the holder 23 can be reduced. Further, the timing at which the holder 23 releases the transfer sheet S is also shifted, and thus the transfer sheet S can be kept in a stable posture.

[0056] As illustrated in FIG. 3, the sheet conveyance mechanism 15 includes two roller pairs each including the drive roller 15a and the driven roller 15b. Each roller pair has a narrow width that fits between the end side conveyance belt 22a and the center side conveyance belt 22b. In FIG. 3, the drive roller 15a is disposed on the upper surface side of the transfer sheet S, and the driven roller 15b is disposed on the lower surface side of the transfer sheet S, but the configuration of the drive roller 15a and the driven roller 15b is not limited thereto.

[0057] A lift that raises and lowers the sheet tray 14 will be described below. As illustrated in FIG. 4, a sheet bundle of the transfer sheets S is stacked on the sheet tray 14 via a pallet 26, and the sheet tray 14 can be raised and lowered by a lift 27. The lift 27 includes a pair of pulleys 28a and 28b, a pair of chains 29a and 29b, a pair of weights 30a and 30b, an upper limit detection sensor 31, and a lower limit detection sensor 32. The transfer sheet S may be directly stacked on the sheet tray 14 without using the pallet 26.

[0058] The pair of pulleys 28a and 28b are rotatably supported by a housing of the image forming apparatus 1 at positions above the sheet tray 14. The pulley 28a and the pulley 28b are separated from each other in the sheet conveyance direction indicated by arrow A. The pair of chains 29a and 29b are respectively wound around the corresponding pulleys 28a and 28b, and one ends of the chains 29a and 29b are connected to the sheet tray 14, and the other ends of the chains 29a and 29b are respectively connected to the corresponding weights 30a and 30b.

[0059] When the pulleys 28a and 28b rotate in a first direction (the pulley 28a rotates clockwise and the pulley 28b rotates counterclockwise in FIG. 4), the sheet tray 14 moves upward and the weights 30a and 30b move downward. On the other hand, when the pulleys 28a and 28b rotate in a second direction opposite to the first direction (the pulley 28a rotates counterclockwise and the pulley 28b rotates clockwise in FIG. 4), the sheet tray 14 moves downward and the weights 30a and 30b move upward.

[0060] The upper limit detection sensor 31 detects whether the uppermost transfer sheet S stacked on the sheet tray 14 reaches an upper limit position to which the transfer sheet S is allowed to be raised by the lift 27. The upper limit detection sensor 31 is disposed above the sheet tray 14. The upper limit detection sensor 31 is, for example, a reflective optical sensor including a light emitter that outputs light and a light receiver that receives the light, which is output from the light emitter and reflected by the transfer sheet S.

[0061] The upper limit detection sensor 31 outputs a detection signal to a controller when the transfer sheet S is on a detection optical path of the upper limit detection sensor 31, i.e., when the uppermost transfer sheet S stacked on the sheet tray 14 reaches the upper limit position. On the other hand, the upper limit detection sensor 31 does not output the detection signal when the transfer sheet S is not on the detection optical path. The upper limit detection sensor 31 may be a transmissive optical sensor instead of the reflective optical sensor. When the controller receives the detection signal of the upper limit position, the controller immediately stops a raising operation of the sheet tray 14.

[0062] The lower limit detection sensor 32 detects whether the sheet tray 14 reaches a lower limit position to which the sheet tray 14 is allowed to be lowered, with the transfer sheets S of the maximum capacity stacked on the sheet tray 14. The lower limit detection sensor 32 is disposed at a position facing the weight 30b when the sheet tray 14 is fully loaded. The lower limit detection sensor 32 is, for example, a reflective optical sensor similar to the upper limit detection sensor 31.

[0063] The lower limit detection sensor 32 outputs a detection signal to the controller when the sheet tray 14 is on a detection optical path of the lower limit detection sensor 32, i.e., when the sheet tray 14 is fully loaded and the sheet tray 14 reaches the lower limit position. On the other hand, the lower limit detection sensor 32 does not output the detection signal when the sheet tray 14 is not on the detection optical path. The lower limit detection sensor 32 may be a transmissive optical sensor instead of the reflective optical sensor. When the controller receives the detection signal of the lower limit position, the controller immediately stops a lowering operation of the sheet tray 14.

[0064] A sheet conveyance process by the first sheet stacking device 8 described above will be described below. The stacking of the transfer sheets S in the first sheet stacking device 8 and the stacking of the transfer sheets S in the second sheet stacking device 9 can be achieved by like configuration and control, and thus only the first sheet stacking device 8 will be described below.

[0065] First, the first sheet stacking device 8 acquires the size data including the length of the transfer sheet S to be conveyed and stacked. Specifically, the size data based on the length and width of the transfer sheet S detected by the sheet size detection sensor 11 or the size data of the transfer sheet S input by a user from the control panel 10 is used. Then, when the transfer sheet S on which an image is formed by the sheet feeding device 2, the sheet position correction device 3, and the image forming device 4 is conveyed to the first sheet stacking device 8, the supply roller pair 19 starts conveying the transfer sheet S, which is fed after the image is formed by the image forming device 4, and the sheet conveyance mechanism 15 is driven. At this time, the guide mechanism 16 is stopped in a standby state illustrated in FIG. 2 in which the holder 23 is stopped at the standby position, and the blower fan 25 starts blowing constantly at a constant air volume.

[0066] After that, the controller determines whether the sheet leading end detection sensor 17 has detected the leading end of the transfer sheet S. When the controller determines that the leading end of the transfer sheet S has been detected, the controller measures a first predetermined time which is an elapsed time from a leading end detection time of the transfer sheet S. The first predetermined time is determined in advance in accordance with the size of the transfer sheet S to be conveyed. When the first predetermined time has elapsed, the conveyance belt 22 starts rotating, and the holder 23 that has been stopped at the standby position starts moving in the sheet conveyance direction. At this time, since the conveyance speed of the transfer sheet S by the sheet conveyance mechanism 15 is faster than the moving speed of the holder 23, the leading end of the transfer sheet S enters the holder 23 from the opening 23a, and the leading end that has entered the holder 23 is nipped and held by the nipping portion 23b.

[0067] The controller controls the moving speed of the holder 23, i.e., the driving speed of the motor 24 to rotate the conveyance belt 22 so that the conveyance speed of the transfer sheet S by the sheet conveyance mechanism 15 and the moving speed of the holder 23 are equal to each other when the transfer sheet S has entered the holder 23. Accordingly, the leading end of the transfer sheet S enters the holder 23 due to the speed difference until the moving speed of the holder 23 becomes equal to the conveyance speed of the transfer sheet S by the sheet conveyance mechanism 15. The time from when the holder 23 starts moving until the transfer sheet S has entered the holder 23 is defined as a second predetermined time. At this time, the amount of the leading end of the transfer sheet S entering the holder 23 corresponding to the first and second predetermined times is a predetermined amount C illustrated in FIG. 5.

[0068] When the holder 23 holds the transfer sheet S, i.e., when the amount of the leading end of the transfer sheet S entering the holder 23 reaches the predetermined amount C, the controller accelerates the moving speed of the holder 23 (i.e., a first acceleration) and measures a third predetermined time corresponding to the size data of the transfer sheet S acquired in advance.

[0069] The sheet conveyance mechanism 15 and the guide mechanism 16 together start conveying the transfer sheet S with the speed difference between the conveyance speed of the transfer sheet S by the sheet conveyance mechanism 15 and the moving speed of the holder 23, which is generated by the first acceleration. At this time, the moving speed of the holder 23 becomes faster than the conveyance speed of the transfer sheet S by the sheet conveyance mechanism 15, and the holder 23 conveys the transfer sheet S while pulling the leading end of the transfer sheet S. As a result, the transfer sheet S can be prevented from bending (warping) as compared with the case of equal speeds (without the speed difference). During this conveyance, the force of the holder 23 holding the transfer sheet S is smaller than the friction force between the sheet conveyance mechanism 15 and the transfer sheet S. Accordingly, the transfer sheet S is gradually drawn out from the holder 23, but the holder 23 keeps holding the transfer sheet S from a holding position where the transfer sheet S is held to a releasing position where the transfer sheet S is released.

[0070] When the third predetermined time has elapsed after the holder 23 holds the transfer sheet S, the controller accelerates the moving speed of the holder 23 (i.e., a second acceleration). As a result, the moving speed of the holder 23 is increased, and the holder 23 releases the transfer sheet S. Even if the transfer sheet S is pulled out of the sheet conveyance mechanism 15 before the transfer sheet S is released from the holder 23, the transfer sheet S is released from the holder 23 by the inertial force of the transfer sheet S. FIG. 6 illustrates the transfer sheet S released from the holder 23. In FIG. 6, the holder 23 is accelerated at an acceleration position D of the second acceleration and releases the transfer sheet S at a release position E.

[0071] FIG. 7 illustrates a small-size transfer sheet S1, which has a smaller size than the transfer sheet S, used in the first sheet stacking device 8 instead of the transfer sheet S. As illustrated in FIG. 7, the controller adjusts the acceleration position D and the release position E in accordance with the small-size transfer sheet S1, and the small-size transfer sheet S1 is released from the holder 23 by the speed difference between the conveyance speed of the small-size transfer sheet S1 by the sheet conveyance mechanism 15 and the moving speed of the holder 23, which is generated by the second acceleration.

[0072] The transfer sheet S or the small-size transfer sheet SI that has been pulled out of the sheet conveyance mechanism 15 and has been released from the holder 23 receives the wind force from the blower fan 25, falls toward the sheet tray 14, and is stacked on the sheet tray 14.

[0073] When the transfer sheet S or the small-size transfer sheet S1 is released from the holder 23, the controller measures a fourth predetermined time corresponding to the size data of the transfer sheet S or the small-size transfer sheet S1 acquired in advance. When the fourth predetermined time has elapsed, the controller starts decelerating the holder 23 and stops the holder 23 at the standby position. After that, the controller determines whether an image forming operation in the image forming device 4 is completed. When the controller determines that the image forming operation is not completed, the controller determines whether the sheet leading end detection sensor 17 detects the leading end of the transfer sheet S, and the above-described operation is repeated until the image forming operation is completed. When the controller determines that the image forming operation is completed, the controller stops the operations of the sheet conveyance mechanism 15, the guide mechanism 16, and the blower fan 25.

[0074] FIG. 8 illustrates the sheet tray 14 of the first sheet stacking device 8 as viewed from the downstream side toward the upstream side in the sheet conveyance direction. In FIG. 8, a marking device 33 is disposed on the right side of the sheet tray 14, i.e., on the front side of the image forming apparatus 1. As illustrated in FIG. 8, the marking device 33 inserts a thin sheet marker 34 between bundles of the desired number of the transfer sheets S stacked on the sheet tray 14 such that the marker 34 protrudes from the bundles of the transfer sheets S to separate the bundles of the desired number of the transfer sheets S from one another. In the following description, an ejection object ejected from the marking device 33 is expressed as a marker. The marker 34 is, for example, a thin sheet medium, but the shape and material of the marker 34 are not limited.

[0075] As illustrated in FIG. 9, the marking device 33 is disposed at a position near the upstream end in the sheet conveyance direction of the transfer sheets S stacked on the sheet tray 14. If the marking device 33 is disposed near the downstream end in the sheet conveyance direction of the transfer sheets S stacked on the sheet tray 14, the conveyed transfer sheet S may not be stacked from directly above onto the sheet tray 14 but may be stacked while moving at a certain speed in the sheet conveyance direction. As a result, the transfer sheet S may move the marker 34 and drop the marker 34 from the bundle of the transfer sheets S. The marking device 33 will be described below with reference to FIGS. 10A and 10B.

[0076] In FIGS. 10A and 10B, the marking device 33 includes a marker storage 35 that stores a continuous marker 34 wound in a roll and a marker conveyor 36 that conveys the marker 34 from the marker storage 35 toward the outside. The marker 34 is used to sort the transfer sheets S based on image forming data set in the image forming apparatus 1. The marker storage 35 has a sealed box shape, and has an ejection port 35a at one position on a side face. The marker 34 is ejected to the outside through the ejection port 35a.

[0077] The marker conveyor 36 includes a roller pair 37 including a drive roller 37a and a driven roller 37b that sandwich and convey the marker 34, and a tension roller 38 that applies a tensile force to the marker 34. The drive roller 37a has a V-groove on the circumferential surface and is rotationally driven by a motor 39 which is described later. The driven roller 37b has an outer shape fitted into the V-groove of the drive roller 37a and is rotated following the rotation of the drive roller 37a. The tension roller 38, which is pressed against the marker 34 by a biasing member, applies a predetermined tension to the marker 34. The tension roller 38 is also rotated following the movement of the marker 34. The marker 34 is sandwiched and conveyed by the roller pair 37. With this configuration, the marker 34 that has passed through the roller pair 37 is bent into a V-shaped cross section, and the straightness of the marker 34 is maintained even after leaving the roller pair 37.

[0078] A cutter 40 is disposed between the roller pair 37 and the ejection port 35a to cut the marker 34 ejected through the ejection port 35a to the outside. The cutter 40 includes a fixed blade 40a disposed above the marker 34 passing across the cutter 40 and a movable blade 40b disposed below the marker 34 passing across the cutter 40. The movable blade 40b is moved upward by the motor 39, which is described later, and the fixed blade 40a and the movable blade 40b nip the marker 34 to cut the marker 34.

[0079] The motor 39 that drives the drive roller 37a and the movable blade 40b is disposed inside the marker storage 35. The motor 39 is rotatable forward and backward and is coupled to the drive roller 37a and the movable blade 40b via one-way clutches to drive the drive roller 37a or the movable blade 40b. The motor 39 operates in one of a forward rotation and a backward rotation to rotate the drive roller 37a, and operates in the other of the forward rotation and the backward rotation to move the movable blade 40b.

[0080] The first sheet stacking device 8 will be described in more detail below.

[0081] As illustrated in FIG. 11A, the transfer sheet S is conveyed to the first sheet stacking device 8. As illustrated in FIG. 11B, when the conveyed transfer sheet S reaches a predetermined position, the marking device 33 ejects the marker 34, cuts the marker 34 from the roll, and places the marker 34 on the uppermost transfer sheet S. After that, when the holder 23 conveys the transfer sheet S and releases the leading end of the transfer sheet S, the released transfer sheet S falls on the placed marker 34. At this time, as indicated by the outlined arrows in FIG. 11C, the transfer sheet S fans (i.e., generates a fan wind) when the transfer sheet S is placed on the uppermost transfer sheet S. The fan wind acts on the marker 34, and the marker 34 receiving the fan wind may fall from the sheet bundle as illustrated in FIG. 11D. Accordingly, the marker 34 does not function as a separator.

[0082] In a certain technique, the marker 34 is not cut and remains connected to the roll until the subsequent transfer sheet S completely falls onto the sheet bundle to prevent the marker 34 from being blown off. However, even in this technique, there is a limitation that an ejection height at which the marker 34 is ejected is preferably the same as the height of the uppermost transfer sheet S of the sheet bundle.

[0083] When the marker ejection height is away from the height of the sheet bundle, the end of the marker 34 connected to the roll is suspended and separated from the sheet bundle, and the end of the transfer sheet S placed on the marker 34 is lifted by the marker 34. As a result, the transfer sheet S may be defectively conveyed and stacked due to erroneous detection of the sheet stacking height. Further, the end of the marker 34 close to the roll after being cut may lean against the marking device 33, and the marker 34 may block the ejection port 35a of the marker 34, causing a marker ejection failure. In another case, the marker 34 leaning against the marking device 33 may be inserted into the sheet bundle with a small insertion amount, and thus the marker 34 may not reach the transfer sheet S of a small size.

[0084] In view of the foregoing, a description is given below of a configuration that solves the above-described situation.

[0085] FIGS. 12A to 12C illustrate a marking device 41 according to a first embodiment of the present disclosure. The marking device 41 is different from the marking device 33 illustrated in FIGS. 10A and 10B only in that the marking device 41 includes a guide 42, and the other configurations are the same.

[0086] The guide 42 is formed of a plate having an L-shaped cross section, and has a body 42a and a guide portion 42b. The body 42a has a slotted hole 42c extending in a longitudinal direction of the guide 42. The guide portion 42b, which is connected to the body 42a in a single piece, is bent at a substantially right angle with respect to the body 42a, and a lower end of the guide portion 42b extends downward below the body 42a.

[0087] The guide 42 is supported by two stepped screws 43, which are a fixed portion, fitted through the slotted hole 42c and screwed into one side face 35b of the marker storage 35. The guide 42, which is a movable portion, is vertically movable with respect to the marker storage 35. The guide 42 is guided by the slotted hole 42c, the stepped screws 43, and the one side face 35b during the vertical movement to construct a guide unit 44.

[0088] The guide 42 is lowered downward by its own weight within the range of the slotted hole 42c. The guide 42 is positioned at the lowest position when the stepped screw 43 contacts the inner face of the slotted hole 42c. When the guide 42 moves downward and occupies the lowermost position, as illustrated in FIG. 13, the lower end of the guide 42 is positioned below the uppermost transfer sheet S stacked on the sheet tray 14, and the upper end of the guide 42 is positioned above the ejection port 35a to guide the marker 34 to be ejected. The guide 42 may be positioned at the lowermost position by a stopper that stops lowering the guide 42 instead of the contact of the stepped screw 43 with the inner face of the slotted hole 42c. In FIG. 13, the lower end of the guide 42 contacts a sheet placement surface of the sheet tray 14 to stop lowering the guide 42, and thus the sheet tray 14 functions as a stopper.

[0089] The guide 42 is disposed on the left side of the ejection port 35a in FIG. 12B. The marking device 41 is disposed on the left side as viewed in the sheet conveyance direction, i.e., on the front side of the first sheet stacking device 8. The left side of the ejection port 35a in FIG. 12B corresponds to the upstream side in the sheet conveyance direction.

[0090] With the above-described configuration, when the transfer sheet S is placed on the uppermost transfer sheet S stacked on the sheet tray 14, even if the transfer sheet S generate the fan wind, and the fan wind acts on the marker 34 placed on the uppermost transfer sheet S to blow off the marker 34, the marker 34 is guided by the guide 42 disposed in the acting direction of the fan wind. Accordingly, the first sheet stacking device 8 can be provided in which the marker 34 is prevented from falling from the uppermost transfer sheet S, and the marker 34 can be placed on the sheet bundle without being affected by the fan wind.

[0091] In the above-described configuration, the guide 42 is vertically movable, but the guide 42 may be fixed. However, when the fixed guide 42 is applied to the sheet tray 14 including the lift 27, since the sheet tray 14 or the pallet 26 is raised to the position of the upper limit detection sensor 31, the guide 42 extending below the upper limit detection sensor 31 may interfere with the sheet tray 14 or the pallet 26. To prevent this interference, preferably, the guide 42 is vertically movable.

[0092] Further, as illustrated in FIG. 13, when the volume of the sheet bundle stacked on the sheet tray 14 is small, the sheet tray 14 approaches the marking device 41, but when the guide 42 is vertically movable, the guide 42 retreats upward while contacting the sheet tray 14, so that the above-described effects can be obtained while preventing the damage of the guide 42 due to interference. The marking device 41 and the guide 42 are disposed outside the stacking position of the transfer sheet S on the sheet tray 14.

[0093] FIGS. 14A to 14C illustrate a marking device 45 according to a second embodiment of the present disclosure. The marking device 45 is different from the marking device 41 in that a guide 46 is used instead of the guide 42, and the other configurations are the same.

[0094] The guide 46 is formed of a plate having an L-shaped cross section, and has a body 46a and a guide portion 46b which are a movable portion. The guide portion 46b, which is connected to the body 46a in a single piece, is bent at a substantially right angle with respect to the body 46a, and a lower end of the guide portion 46b extends downward below the body 46a. Supports 47 each having a semicircular hole are respectively fixed to two positions in the vertical direction of a bent portion between the body 46a and the guide portion 46b. A support pin 48 has a cross-sectional shape that fits into the semicircular hole of each of the supports 47. The support pin 48, which is a fixed portion, is fixed to an immovable portion of the first sheet stacking device 8 via a bracket. The guide 46 includes the body 46a, the guide portion 46b, the supports 47, and the support pin 48.

[0095] The guide 46 is supported by the support pin 48 fitted to the supports 47 and fixed to the immovable portion of the first sheet stacking device 8. The guide 46 is vertically movable with respect to the one side face 35b of the marker storage 35. The guide 46 is guided by the supports 47, the support pin 48, and the one side face 35b during the vertical movement to construct a guide unit 49. Although the support pin 48 has a semicircular cross-sectional shape and contacts the guide portion 46b to prevent the rotation of the guide 46 during the vertical movement, the support pin 48 may have a circular cross-sectional shape or may have another shape as long as the rotation is sufficiently prevented by the one side face 35b.

[0096] The guide 46 is lowered downward by its own weight, and the guide 46 is positioned at the lowermost position when a part of the guide 46 contacts a stopper. When the guide 46 moves downward and occupies the lowermost position, similarly to the guide 42, the lower end of the guide 46 is positioned below the uppermost transfer sheet S stacked on the sheet tray 14, and the upper end of the guide 46 is positioned above the ejection port 35a. The guide 46 may be positioned at the lowermost position by a stopper that stops lowering the guide 46. In FIG. 13, the lower end of the guide 46 contacts a sheet placement surface of the sheet tray 14 to stop lowering the guide 46, and thus the sheet tray 14 functions as a stopper.

[0097] With the above-described configuration, the effects similar to those of the first embodiment can be obtained, and the sliding resistance of the guide unit 49 can be reduced as compared with the guide unit 44 in the first embodiment, so that the vertical movement of the guide 46 can be performed well.

[0098] Each of the guide 42 and the guide 46 have a length in the vertical direction equal to or longer than a length L from the upper side of the ejection port 35a to a position lower than the detection position of the upper limit detection sensor 31 in FIG. 13.

[0099] Each of the guide 42 of the marking device 41 and the guide 46 of the marking device 45, which is vertically movable, is lowered by its own weight, but a guide may be pressed downward by a biasing member such as a spring, or a guide may be moved vertically by a driver such as a motor.

[0100] FIGS. 15A to 15C illustrate a marking device 50 according to a third embodiment of the present disclosure. The marking device 50 is different from the marking device 41 in that the marking device 50 further includes a second guide 51, and the other configurations are the same.

[0101] The second guide 51 is formed of a plate having an L-shaped cross section bent line-symmetrically to the guide 42 with respect to the Z-axis in FIG. 15B, and has a body 51a and a guide portion 51b. The body 51a has a slotted hole 51c extending in the longitudinal direction of the second guide 51, and the lower end of the guide portion 51b extends downward below the body 51a.

[0102] The second guide 51 is supported by two stepped screws 43 fitted through the slotted hole 51c. The second guide 51 is vertically movable with respect to the marker storage 35. The second guide 51 is guided by the slotted hole 51c, the stepped screws 43, and the one side face 35b during the vertical movement to construct a guide unit 52.

[0103] The second guide 51 is lowered downward by its own weight within the range of the slotted hole 51c. The second guide 51 is positioned at the lowest position when the stepped screw 43 contacts the inner face of the slotted hole 51c. Similarly to the guide 42, when the second guide 51 moves downward and occupies the lowermost position, the lower end of the second guide 51 is positioned below the uppermost transfer sheet S stacked on the sheet tray 14, and the upper end of the second guide 51 is positioned above the ejection port 35a to guide the marker 34 to be ejected.

[0104] The second guide 51 is line-symmetrical to the guide 42 with respect to the Z-axis in FIG. 15B. In other words, the second guide 51 is disposed at a position on the right side of the ejection port 35a in FIG. 15B and faces the guide 42 across the ejection port 35a.

[0105] With the above-described configuration, even if the air blowing from the blower fan 25 acts on the marker 34 placed on the uppermost transfer sheet S before the fan wind described above acts, the second guide 51 disposed in the acting direction of the air blowing from the blower fan 25 can prevent the marker 34 from moving. Accordingly, the first sheet stacking device 8 can be provided in which the marker 34 can be held between the guide 42 and the second guide 51, the marker 34 is prevented from falling from the uppermost transfer sheet S, and the marker 34 can be placed on the sheet bundle without being affected by the fan wind and the air blowing from the blower fan 25

[0106] FIG. 16 illustrates a marking device 53 according to a fourth embodiment of the present disclosure. The marking device 53 is different from the marking device 45 in that the marking device 53 further includes a second guide 54, and the other configurations are the same.

[0107] The second guide 54 is formed of a plate having an L-shaped cross section bent line-symmetrically to the guide 46 with respect to the Z-axis in FIG. 16B, and has a body 54a and a guide portion 54b which are a movable portion. The body 54a is connected to the guide portion 54b in a single piece, and the lower end of the guide portion 54b extends downward below the body 54a. Two supports 47, which are a movable portion, are fixed to a bent portion between the body 54a and the guide portion 54b in the vertical direction. The support pin 48, which is a fixed portion, fixed to an immovable portion of the first sheet stacking device 8 via a bracket is fitted into the supports 47. The second guide 54 includes the body 54a, the guide portion 54b, the supports 47, and the support pin 48.

[0108] The second guide 54 is supported by the support pin 48. The second guide 54 is vertically movable with respect to the one side face 35b. The second guide 54 is guided by the supports 47, the support pin 48, and the one side face 35b during the vertical movement to construct a guide unit 55.

[0109] The second guide 54 is lowered downward by its own weight, and the second guide 54 is positioned at the lowermost position when a part of the second guide 54 contacts a stopper. When the second guide 54 moves downward and occupies the lowermost position, similarly to the second guide 51, the lower end of the second guide 54 is positioned below the uppermost transfer sheet S stacked on the sheet tray 14, and the upper end of the second guide 54 is positioned above the ejection port 35a.

[0110] With the above-described configuration, the effects similar to those of the third embodiment can be obtained, and the sliding resistance of the guide unit 55 can be reduced as compared with the guide unit 52, so that the vertical movement of the second guide 54 can be performed well.

[0111] In each of the second guide 51 of the third embodiment and the second guide 54 of the fourth embodiment has a length corresponding to the length from the upper side of the ejection port 35a to the position below the detection position of the upper limit detection sensor 31.

[0112] Each of the second guide 51 of the marking device 50 and the second guide 54 of the marking device 53, which is vertically movable, is lowered by its own weight, but a guide may be pressed downward by a biasing member such as a spring, or a guide may be moved vertically by a driver such as a motor.

[0113] FIG. 17 illustrates a marking device 56 according to a fifth embodiment of the present disclosure. The marking device 56 is different from the marking device 50 in that the marking device 56 includes a guide 57 and a second guide 58 instead of the guide 42 and the second guide 51, and the other configurations are the same.

[0114] The guide 57 includes a body 57a, a guide portion 57b, and a slotted hole 57c, similarly to the guide 42. The guide 57 has a bent portion 57d at a portion near the lower end of the guide portion 57b. The bent portion 57d is inclined in a direction away from the second guide 58 as it goes downward. In other words, the guide 57 is different from the guide 42 only in that the guide 57 has the bent portion 57d bent from the guide portion 57b, and the other configurations are the same. The guide 57 is guided by the slotted hole 57c, the stepped screws 43, and the one side face 35b during the vertical movement to construct a guide unit 59.

[0115] The second guide 58 has a body 58a, a guide portion 58b, and a slotted hole 58c, similarly to the second guide 51. The second guide 58 has a bent portion 58d at a portion near the lower end of the guide portion 58b. The bent portion 58d is inclined in a direction away from the guide 57 as it goes downward. In other words, the second guide 58 is different from the second guide 51 only in that the second guide 58 has the bent portion 58d bent from the guide portion 58b, and the other configurations are the same. The second guide 58 is guided by the slotted hole 58c, the stepped screws 43, and the one side face 35b during the vertical movement to construct a guide unit 60. As described above, a lower portion (i.e., the bent portion 57d) of the guide 57 and a lower portion (i.e., the bent portion 58d) of the second guide 58 are inclined with respect to the vertical direction, and a distance between the lower portions of the guide 57 and the second guide 58 increases downward.

[0116] Effects of the fifth embodiment will be described below.

[0117] FIG. 18A illustrates the guide 42 and the second guide 51 lowered together. In FIG. 18A, the marker 34 is placed in the space between the guide 42 and the second guide 51 on the sheet bundle in the marking device 50 illustrated in the third embodiment. As illustrated in FIG. 18A, when an external force such as air blown from the blower fan 25 acts on the marker 34 placed on the sheet bundle or when the position of the marker 34 is unstable at the time of cutting the marker 34, the marker 34 may not be placed at a desired position on the sheet bundle and may lean against the guide portion 51b. In this case, when the sheet tray 14 is raised or lowered in preparation for the next image forming operation or in response to an input by an operator, the marker 34 lowered together with the sheet bundle on the sheet tray 14 once gets out of the space between the guide portions 42b and 51b and enters the space between the guide portions 42b and 51b again.

[0118] When the marker 34 leaning against the guide portion 51b gets out of the space between the guide portions 42b and 51b by the lowering of the sheet tray 14, the leaning marker 34 changes the posture from the state indicated by the broken line to the state indicated by the solid line, and thus the position of the marker 34 placed on the sheet bundle may change as illustrated in FIG. 18B. When the sheet tray 14 is raised from this state, the marker 34 whose position on the sheet bundle has been changed may not return into the space between the guide portions 42b and 51b, and as illustrated in FIG. 18C, the marker 34 may come into contact with the guide portion 51b. As a result, the marker 34 may fall from the sheet bundle and may not function as a marker.

[0119] FIG. 19A illustrates the guide 57 and the second guide 58 lowered together. In FIG. 19A, the marker 34 is placed in the space between the guide 57 and the second guide 58 on the sheet bundle in the marking device 56 illustrated in the fifth embodiment. In FIG. 19A, the marker 34 leans against the guide portion 58b. A case where the sheet tray 14 is raised and lowered from this state will be described below.

[0120] When the marker 34 leaning against the guide portion 58b gets out of the space between the guide portions 57b and 58b by the lowering of the sheet tray 14, the leaning marker 34 changes the posture from the state indicated by the broken line to the state indicated by the solid line, and thus the position of the marker 34 placed on the sheet bundle may change as illustrated in FIG. 19B.

[0121] When the sheet tray 14 is raised from the state illustrated in FIG. 19B, the marker 34 whose position on the sheet bundle has been changed contacts the inner face of the bent portion 58d of the second guide 58, is pushed by the inner face of the bent portion 58d, and is moved on the sheet bundle from the position indicated by the broken line to the position indicated by the solid line in FIG. 19C. As a result, the marker 34 enters the space between the guide portions 57b and 58b again as illustrated in FIG. 19C.

[0122] Accordingly, the situation in the third embodiment described above is prevented, and even if the marker 34 leaning against the guide portion 58b gets out of the space between the guide portions 57b and 58b, the marker 34 can be reliably returned to the space between the guide portions 57b and 58b to function as the marker 34.

[0123] In the above description of the effects, the marker 34 leans against the guide portion 51b and the guide portion 58b in FIGS. 18A and 19A, but the marker 34 may lean against the guide portion 42b and the guide portion 57b.

[0124] In the fifth embodiment, the bent portions 57d and 58d are added to the guide 42 and the second guide 51 of the marking device 50 to form the guide 57 and the second guide 58, respectively, but the bent portions 57d and 58d may be added to the guide 46 and the second guide 54 of the marking device 53 to form the guide 57 and the second guide 58, respectively. In this case, to prevent the support pins 48 from interfering with the bent portions 57d and 58d, respectively, for example, the bent portions 57d and 58d may have grooves into which the support pins 48 can be fitted, or brackets that separate the support pins 48 from the bent portions 57d and 58d may be provided.

[0125] FIG. 20 illustrates a marking device 61 according to a sixth embodiment of the present disclosure. The marking device 61 is different from the marking device 53 in that the marking device 61 includes a guide 62 and a second guide 63 instead of the guide 46 and the second guide 54, and the other configurations are the same.

[0126] The guide 62 has a body 62a formed of a plate having an L-shaped cross section and a guide portion 62b attached to the body 62a in a single piece. The guide portion 62b has a prismatic shape. The guide portion 62b extends downward below the body 62a, and an inclined face 62c is formed at a lower end of the guide portion 62b. The inclined face 62c is inclined in a direction away from the roller pair 37 as it goes downward, in other words, in a direction away from the second guide 63 as it goes downward. The body 62a and the guide portion 62b form a movable portion.

[0127] A support 64 including two support portions 64a each having a rectangular hole into which the guide portion 62b can be fitted is disposed at a bent portion of the body 62a. The guide portion 62b is guided by the support 64 so as to vertically move the guide portion 62b. The support 64, which is a fixed portion, is fixed to an immovable portion of the first sheet stacking device 8 via a bracket. The guide 62 is guided by the guide portion 62b, the support 64, and the one side face 35b during the vertical movement to construct a guide unit 66.

[0128] The second guide 63 is formed of a plate having an L-shaped cross section bent line-symmetrically to the guide 62 with respect to the Z-axis in FIG. 20B, and has a body 63a and a guide portion 63b attached to the body 63a in a single piece. The guide portion 62a has a prismatic shape. The guide portion 63b extends downward below the body 63a, and an inclined face 63c is formed at a lower end of the guide portion 63b. The inclined face 63c is inclined in a direction away from the guide 62 as it goes downward. The body 63a and the guide portion 63b form a movable portion.

[0129] A support 65 including two support portions 65a each having a rectangular hole into which the guide portion 63b can be fitted is disposed at a bent portion of the body 63a. The guide portion 63b is guided by the support 65 so as to vertically move the guide portion 63b. The support 65, which is a fixed portion, is fixed to an immovable portion of the first sheet stacking device 8 via a bracket. The second guide 63 is guided by the guide portion 63b, the support 64, and the one side face 35b during the vertical movement to construct a guide unit 67.

[0130] According to the sixth embodiment described above, the effects similar to those of the fifth embodiment can be obtained, and the apparatus configuration can be simplified to achieve cost reduction and downsize the apparatus.

[0131] In the sixth embodiment, each of the guide portions 62b and 63b has the prismatic shape, and each of the support portions 64a and 65a has in a rectangular hole corresponding to the prismatic shape. Alternatively, each of the guide portions 62b and 63b may have a cylindrical shape, and each of the support portions 64a and 65a may have a circular hole. The shape of the guide portion 62b and 63b and the shape of the holes of the support portion 64a and 65a corresponding to the guide portion 62b and 63b may be any shape as long as the guide 62 and the second guide 63 can be smoothly moved in the vertical direction.

[0132] The configuration of the sixth embodiment described above may be applied to the guide 46 in the second embodiment illustrated in FIGS. 14A to 14C. In this case, a guide portion similar to the guide portion 62b and a support similar to the support 64 are used instead of the guide portion 46b and the support pin 48. The body 46a and the guide portion form a movable portion, and the support forms a fixed portion.

[0133] The configuration of the sixth embodiment may be applied to the second guide 54 in the fourth embodiment illustrated in FIGS. 16A to 16C. In this case, a guide portion similar to the guide portion 62b and a support similar to the support 64 are used instead of the guide portion 54b and the support pin 48. The body 54a and the guide portion form a movable portion, and the support forms a fixed portion.

[0134] In the third to sixth embodiments described above, in a state where the marker 34 is placed on the uppermost transfer sheet S of the sheet bundle, when the sheet tray 14 is lowered by preparation for the next image forming operation or an operation by the operator, the marker 34 gets out of the space between the guide and the second guide. In this state, the function of guiding the marker 34 by the guide and the second guide does not work, and thus, when the blower fan 25 is operating, the marker 34 may be displaced or may fall from the sheet bundle. Operation control of the sheet stacking device for solving this situation will be described below as a seventh embodiment of the present disclosure.

[0135] FIG. 21 is a flowchart of an operation of the first sheet stacking device 8 according to the seventh embodiment.

[0136] As illustrated in FIG. 21, in step ST01, when the preparation of an image forming operation of the image forming apparatus 1 is completed, the initialization operations in portions including the first sheet stacking device 8 of the image forming apparatus 1 are completed, and the image forming apparatus 1 operates the blower fan 25. In step ST02, the image forming apparatus 1 determines whether the sheet tray 14 of the first sheet stacking device 8 is lowered by the operator of the image forming apparatus 1. When the image forming apparatus 1 determines that the lowering operation is not performed, in step ST03, the image forming apparatus 1 performs an image forming operation. In step ST04, when the image forming operation of one job is completed, in step ST05, the image forming apparatus 1 determines whether there is the next job.

[0137] In step ST05, when the image forming apparatus 1 determines that there is the next job, a controller of the image forming apparatus 1 for controlling the operation of the first sheet stacking device 8 sends a command to stop the operation of the blower fan 25, and then sends an operation command to lower the sheet tray 14 in order to perform an initialization operation. In step ST06, when the image forming apparatus 1 stops operating the blower fan 25 based on the command, in step ST07, the image forming apparatus 1 operates the lift 27 to lower the sheet tray 14 and position the sheet tray 14 at the lower limit position. Then, in step ST08, the image forming apparatus 1 performs the initialization operation of the first sheet stacking device 8.

[0138] In step ST07, when the sheet tray 14 is lowered to the lower limit position, the marker 34 placed on the sheet bundle in the previous job gets out of the space between the guide and the second guide of the marking device 41, 45, 50, 53, or 56. However, the image forming apparatus 1 stops operating the blower fan 25 before lowering the sheet tray 14. Accordingly, in step ST08, even when the image forming apparatus 1 performs the initialization operation, the external force due to the air blown from the blower fan 25 does not act on the marker 34. As a result, the marker 34 placed on the sheet bundle can be prevented from falling or being displaced.

[0139] In step ST08, when the initialization operation of the first sheet stacking device 8 is completed, the controller sends an operation command to raise the sheet tray 14, and, in step ST09, the image forming apparatus 1 operates the lift 27 to raise the sheet tray 14 toward a predetermined position. In step ST10, when the image forming apparatus 1 stops raising the sheet tray 14 and positions the sheet tray 14 at a predetermined position, the controller sends a command to start the operation of the blower fan 25, and, in step ST11, the image forming apparatus 1 starts operating the blower fan 25. After that, when the initialization operation is completed in all the portions of the image forming apparatus 1, in step ST12, the image forming apparatus 1 completes the preparation of the image forming operation, and, in step ST03, the image forming apparatus 1 performs the image forming operation. In step ST05, when the image forming apparatus 1 determines that there is no next job, the controller sends a command to stop the operation of the blower fan 25. Then, in step ST13, the image forming apparatus 1 stops operating the blower fan 25, and the image forming apparatus 1 enters the standby mode for the image forming operation.

[0140] In step ST02, when the image forming apparatus 1 determines that the operator of the image forming apparatus 1 has performed an operation to lower the sheet tray 14, the controller sends a command to stop the operation of the blower fan 25, and then sends an operation command to lower the sheet tray 14. In step ST14, when the image forming apparatus 1 stops operating the blower fan 25 based on the command, in step ST15, the image forming apparatus 1 operates the lift 27 to lower the sheet tray 14 and position the sheet tray 14 at the lower limit position.

[0141] In step ST16, the image forming apparatus 1 determines whether there is an operation to raise the sheet tray 14. When the image forming apparatus 1 determines that there is an operation to raise the sheet tray 14, the controller sends an operation command to raise the sheet tray 14, and, in step ST17, the image forming apparatus 1 operates the lift 27 to raise the sheet tray 14 toward a predetermined position. In step ST18, when the image forming apparatus 1 stops raising the sheet tray 14 and positions the sheet tray 14 at a predetermined position, the controller sends a command to start the operation of the blower fan 25, and, in step ST19, the image forming apparatus 1 starts operating the blower fan 25. Then, in step ST05, the image forming apparatus 1 determines whether there is the next job.

[0142] The marker 34 placed on the sheet bundle gets out of the space between the guide and the second guide of the marking device when the sheet tray 14 is lowered. According to the seventh embodiment described above, the image forming apparatus 1 stops operating the blower fan 25 before lowering the sheet tray 14. Accordingly, the marker 34 placed on the sheet bundle can be prevented from falling or being displaced.

[0143] In the above-described embodiments, the image forming apparatus 1 is an inkjet recording apparatus that forms full-color images, but an image forming apparatus is not limited thereto. The present disclosure is also adoptable to a copier, a facsimile machine, and a multifunction peripheral (MFP).

[0144] In the above-described embodiments, the transfer sheet S as a sheet is mentioned as a recording medium on which an image is formed, and the transfer sheet S is not limited a recording paper but also includes thick paper, a postcard, a rolled sheet, an envelope, plain paper, thin paper, coated paper, art paper, tracing paper, an overhead projector transparency (OHP sheet or OHP film), a resin film, and any other sheet-shaped material on which an image can be formed.

[0145] Aspects of the present disclosure are, for example, as follows.

[0146] Aspect 1

[0147] A sheet stacking device includes a stacker on which transfer sheets are stacked and a conveyor that conveys the transfer sheets toward the stacker in a sheet conveyance direction. The sheet stacking device further includes a marking device that ejects and places a marker on an upper surface of an uppermost sheet for each predetermined number of the transfer sheets stacked on the stacker. The marking device includes an ejection port from which the marker is ejected, a marker storage that stores the marker, a marker conveyor that conveys the marker to eject the marker from the ejection port, and a guide that guides the marker ejected from the ejection port to prevent the marker from moving in a direction opposite to the sheet transport direction.

[0148] In other word, a sheet stacking device includes a stacker, a conveyor, and a marking device. The stacker stacks transfer sheets. The conveyor conveys the transfer sheets toward the stacker in a sheet conveyance direction. The marking device includes a marker storage to store a marker, an ejection port to eject the marker, a marker conveyor to convey and eject the marker from the ejection port, and a guide to prevent (block) the marker ejected from the ejection port from moving in a direction opposite to the sheet conveyance direction. The marking device places the marker on an uppermost sheet of each predetermined number of the transfer sheets on the stacker.

[0149] Aspect 2

[0150] In the sheet stacking device according to Aspect 1, the guide guides the marker to a position below the uppermost sheet.

[0151] In other word, the guide extends to a position below the uppermost sheet in a vertical direction orthogonal to the sheet conveyance direction.

[0152] Aspect 3

[0153] In the sheet stacking device according to Aspect 1 or 2, the stacker is vertically movable, and the guide is vertically movable in accordance with a vertical movement of the stacker. When the guide is located at a lowermost position, a lower portion of the guide is located at a position below the uppermost sheet and an upper portion of the guide is located at a position above the ejection port.

[0154] In other word, the stacker is movable in a vertical direction orthogonal to the sheet conveyance direction. The guide is movable between an uppermost position and a lowermost position of the guide in the vertical direction in accordance with a vertical movement of the stacker. The guide has, when the guide is at the lowermost position, a lower end lower than the uppermost sheet and an upper end higher than the ejection port.

[0155] Aspect 4

[0156] In the sheet stacking device according to Aspect 3, the guide is guided by a guide unit to move vertically

[0157] In other word, the guide has a plate and screws. The plate has an L-shaped cross section having a body having a slotted hole extending in a longitudinal direction of the guide and a guide portion connected to the body at right angle. A lower end of the guide portion extends downward below the body. The screws are screwed into a side face of the marker storage through the slotted hole.

[0158] Further, the stacker includes a sheet tray having a sheet placement surface to place the transfer sheets on the sheet placement surface. The lower end of the guide portion contacts the sheet placement surface of the stacker.

[0159] Aspect 5

[0160] In the sheet stacking device according to Aspect 3 or 4, the guide includes a fixed portion and a movable portion. When the guide is located at an uppermost position, an upper portion of the guide is located below an upper end of the marker storage.

[0161] In other word, in the sheet stacking device according to Aspect 3, the guide has a plate and a support pin. The plate has an L-shaped cross section having a body, a guide portion, and a support. The body extends in a longitudinal direction of the guide. The guide portion is connected to the body at right angle. A lower end of the guide portion extends downward below the body. The support has a hole and is fixed to a bent portion between the body and the guide portion. The support pin is fitted into the hole of the support and fixed to the marker storage to support the plate movable in the vertical direction.

[0162] Further, the stacker includes a sheet tray having a sheet placement surface to place the transfer sheets on the sheet placement surface. The lower end of the guide portion contacts the sheet placement surface of the stacker.

[0163] Aspect 6

[0164] The sheet stacking device according to any one of Aspects 1 to 5, further includes an air blower that applies an airflow in a direction toward the stacker to the transfer sheets being conveyed. The marking device includes a second guide that guides the marker ejected from the ejection port to prevent the marker from moving in the sheet conveyance direction, at a position facing the guide via the ejection port.

[0165] In other word, the sheet stacking device according to any one of Aspects 1 to 5, further includes an air blower to blow an air to the transfer sheets conveyed to the stacker. The marking device further includes another guide facing the guide across the ejection port to prevent (block) the marker ejected from the ejection port from moving in the sheet conveyance direction.

[0166] Aspect 7

[0167] In the sheet stacking device according to Aspect 6, the stacker is vertically movable, and the guide and the second guide are vertically movable in accordance with a vertical movement of the stacker. The guide and the second guide are formed such that portions thereof in the vicinity of lower end portions thereof are inclined or bent in a direction away from each other as it goes downward.

[0168] In other word, the stacker is movable in a vertical direction orthogonal to the sheet conveyance direction, and the guide and said another guide are movable in the vertical direction in accordance with a vertical movement of the stacker. A lower portion of the guide and another lower portion of said another guide are inclined with respect to the vertical direction, and a distance between the lower portion and said another lower portion increases downward.

[0169] Aspect 8

[0170] In the sheet stacking device according to Aspect 6, the stacker is vertically movable, and the guide and the second guide are vertically movable in accordance with a vertical movement of the stacker. The air blower stops blowing the airflow before the stacker starts a lowering operation. The air blower operates after a raising operation of the stacker is completed.

[0171] In other word, the stacker is movable in a vertical direction orthogonal to the sheet conveyance direction, and the guide and said another guide are movable in the vertical direction in accordance with a vertical movement of the stacker. The air blower stops blowing the air before the stacker starts moving downward, and the air blower starts blowing the air after the stacker finishes moving upward.

[0172] Aspect 9

[0173] In the sheet stacking device according to Aspect 7, the air blower stops blowing the airflow before the stacker starts a lowering operation. The air blower operates after a raising operation of the stacker is completed.

[0174] Aspect 10

[0175] An image forming apparatus includes the sheet stacking device according to any one of Aspects 1 to 9.

[0176] In other word, an image forming apparatus includes the sheet stacking device according to any one of Aspects 1 to 9 and an image forming device disposed upstream from the sheet stacking device in the sheet conveyance direction to form images on the transfer sheets.

[0177] As describes above, according to one aspect of the present disclosure, the marker is guided by the guide arranged in a direction of the action of the fan wind. Accordingly, the marker is prevented from falling from the uppermost transfer sheet, and the sheet stacking device can be provided which places the marker on the sheet bundle without being affected by the fan wind and the air blown from the air blower.

[0178] The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.