Sheet stacking device and printing apparatus

A sheet stacking device include a guide unit and a blower. The guide unit receives a downstream end of a sheet in a sheet conveyance direction and guides the sheet downstream in the sheet conveyance direction. The blower blows air toward the sheet guided by the guide unit. A region of the blower from which the air is blown is changeable in response to a size of the sheet.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2021-009055, filed on Jan. 22, 2021, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Aspects of the present disclosure relates to a sheet stacking device and a printing apparatus.

Description of the Related Art

A certain printing apparatus includes a sheet stacking device including a guide unit. The guide unit holds a downstream end of a sheet with a guide part and guides the sheet downstream in a sheet conveyance direction. The printing apparatus may further include a blower that blows air toward the sheet near a sheet ejection port when the sheet is ejected.

SUMMARY

Embodiments of the present disclosure describe an improved sheet stacking device that includes a guide unit and a blower. The guide unit receives a downstream end of a sheet conveyed in a sheet conveyance direction and guides the sheet downstream in the sheet conveyance direction. The blower blows air toward the sheet guided by the guide unit. A region of the blower from which the air is blown is changeable in response to a size of the sheet.

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. In addition, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described below with reference to the accompanying drawings. First, a printing apparatus1as a liquid discharge apparatus according to a first embodiment of the present disclosure is described with reference to FIG.1.FIG.1is a schematic view of the printing apparatus1.

The printing apparatus1includes a loading unit10to load a sheet P, a pretreatment unit20, a printing unit30as an image forming unit, a drying unit40, an ejection unit50, and a reverse mechanism60. In the printing apparatus1, the pretreatment unit20applies, as required, pretreatment liquid onto the sheet P forwarded (supplied) from the loading unit10, the printing unit30applies liquid to the sheet P to perform printing on the sheet P, the drying unit40dries the liquid adhering to the sheet P, and the sheet P is ejected to the ejection unit50.

The loading unit10includes a lower loading tray11A and an upper loading tray11B to accommodate a plurality of sheets P and feeders12A and12B to separate and forward the sheets P one by one from the lower and upper loading trays11A and11B, thereby supplying the sheets P to the pretreatment unit20.

The pretreatment unit20includes, e.g., a coater21as a treatment-liquid applicator that coats a printing surface of the sheet P with, for example, treatment liquid having an effect of agglomerating colorant of ink to prevent bleed-through.

The printing unit30includes a drum31and a liquid discharger32. The drum31is a bearer (rotator) that bears the sheet P on the circumferential surface of the drum31and rotates. The liquid discharger32discharges liquid toward the sheet P borne on the drum31.

The printing unit30further includes transfer cylinders34and35. The transfer cylinder34receives the sheet P from the pretreatment unit20and forwards the sheet P to the drum31. The transfer cylinder35receives the sheet P conveyed by the drum31and forwards the sheet P to the drying unit40.

The transfer cylinder34includes a sheet gripper to grip a leading end of the sheet P conveyed from the pretreatment unit20to the printing unit30. The sheet P thus gripped is conveyed as the transfer cylinder34rotates. The transfer cylinder34forwards the sheet P to the drum31at a position opposite the drum31.

Similarly, the drum31includes a sheet gripper on the surface thereof, and the leading end of the sheet P is gripped by the sheet gripper of the drum51. The drum31has a plurality of suction holes dispersedly on the surface of the drum31, and a suction unit generates suction airflows directed inward from suction holes of the drum31.

On the drum31, the sheet gripper grips the leading end of the sheet P forwarded from the transfer cylinder34, and the sheet P is attracted to and borne on the drum31by the suction airflows by the suction unit. As the drum31rotates, the sheet P is conveyed.

The liquid discharger32includes discharge units33(discharge units33A to33D) to discharge liquids. For example, the discharge unit33A discharges liquid of cyan (C), the discharge unit33B discharges liquid of magenta (M), the discharge unit33C discharges liquid of yellow (Y), and the discharge unit33D discharges liquid of black (K). Further, the liquid discharger32may include a discharge unit33that discharges special liquid, that is, liquid of spot color such as white, gold, or silver.

The discharge operation of each of the discharge units33of the liquid discharger32is controlled by a drive signal corresponding to print data. When the sheet P borne on the drum31passes through a region facing the liquid discharger32, the respective color liquids are discharged from the discharge units33, and an image corresponding to the print data is printed on the sheet P.

The drying unit40dries the liquid applied onto the sheet P by the printing unit30. Thus, a liquid component such as moisture in the liquid evaporates, and the colorant contained in the liquid is fixed on the sheet P. Additionally, curling of the sheet P is restrained.

The reverse mechanism60reverses, in switchback manner, the sheet P that has passed through the drying unit40in duplex printing. The reversed sheet P is fed back to the upstream side of the transfer cylinder34through a conveyance passage61of the printing unit30.

The ejection unit50serves as an example of a sheet stacking device according to the present disclosure and includes a stacker501and a sheet conveyor502. A plurality of sheets P is stacked on the stacker501. The sheets P conveyed through the reverse mechanism60is sequentially stacked and held on the stacker501.

A sheet stacking device500according to the first embodiment of the present disclosure is described with reference toFIG.2.FIG.2is a schematic side view of the sheet stacking device500.

The sheet stacking device500includes the stacker501on which a sheet bundle PB (i.e. a bundle of the sheets P) is stacked. The stacker501includes a table511, a leading end fence512(e.g., a sheet jogger), a trailing end fence513, and side fences on both sides of the stacker501. The sheet bundle PB is stacked on the table511. The side fences are disposed on opposite sides in a direction perpendicular to a direction of conveyance of the sheet P indicated by arrow D inFIG.2(i.e., a sheet conveyance direction).

The sheet stacking device500further includes conveyance roller pairs521and522and a guide unit523. The conveyance roller pairs521and522convey the sheet P fed from the reverse mechanism60. The guide unit523receives a leading end (downstream end) of the sheet P conveyed from the conveyance roller pair522toward the stacker501, and guides the sheet P downstream from the conveyance roller pair522in the sheet conveyance direction.

The guide unit523includes an endless belt530and guide parts541. The endless belt530is looped around a drive roller531and a driven roller532. The guide parts541are attached to the belt530.

In the guide unit523, the belt530circumferentially rotates around the drive roller531and the driven roller532after an elapse of a predetermined period of time from a timing of detection of the sheet P at an upstream of the conveyance roller pair522. Then, the leading end of the sheet P is inserted into the guide part541due to a difference between a linear velocity of the guide part541and a linear velocity of the conveyance roller pair522. For example, the linear velocity of the guide parts541is smaller than the linear velocity of the conveyance roller pair522. Then, as the belt530rotates around the drive roller531and the driven roller532, the guide part541moves downstream in the sheet conveyance direction (leftward direction inFIG.2) while holding the leading end of the sheet P to guide the sheet P.

The guide part541has a gap wider than the thickness of the sheet P and does not have gripping force to grip the sheet P The leading end of the sheet P is merely inserted into the gap of the guide part541. The guide part541also has a function of guiding the leading end of the sheet P and reducing flapping of the sheet P in a part of the sheet P from the leading end to a middle portion of the sheet P. The guide part541may include a clip having the gripping force for gripping the leading end of the sheet P.

When the guide part541reaches a guide end position, the linear velocity of the guide part541is set higher than the linear velocity of the conveyance roller pair522. Thus, the leading end of the sheet P is separated from the guide part541and falls onto the stacker501to be stacked.

The sheet stacking device500further includes a blower550for blowing air toward the sheet P. The blower550is disposed inside the loop of the endless belt530in the vertical direction as viewed in the cross-section. As the blower550blows air to the sheets P, the stacked sheets P are pressed, and air accumulated between the sheets P is pushed out to the outside of the sheets P.

Next, the guide unit523and the blower550according to the first embodiment is described with reference toFIGS.3to4.FIG.3is a plan view of the guide unit523, andFIG.4is a side view of the guide unit523.

In the guide unit523, multiple belts530(four in the present embodiment) are disposed at intervals in the direction perpendicular to the sheet conveyance direction. Each of the multiple belts530is looped around the drive roller531and the driven roller532. The multiple drive rollers531are coaxial with each other, the multiple driven rollers532are coaxial with each other, and each belt530circumferentially rotates at the same linear velocity. Each belt530is provided with the guide parts541.

The blower550includes fans551F1to551F12serving as airflow generators that blow air. Hereinafter, the fans551F1to551F12are also collectively referred to as “fans551”, and one of the fans551F1to551F12is referred to as a “fan551” unless distinguished. The fans551are arranged in three lines in the sheet conveyance direction and each line of the fans551is disposed between the belts530side by side in the direction perpendicular to the sheet conveyance direction.

That is, the belt530is divided into the multiple belts530to move the guide parts541, and the multiple belts530are disposed at the intervals. Each fan551of the blower550is disposed adjacent to the belt530in the direction perpendicular to the sheet conveyance direction. Accordingly, the size of the guide unit523can be downsized as compared with a case in which the fans551(blower550) are disposed above the belt530.

Here, a sheet Pa having the maximum size, a sheet Pb having the medium size, and a sheet Pc having the minimum size are stacked at the respective stacking positions in the stacker501as illustrated inFIG.3. At that time, as viewed in the plan view (as viewed in the direction perpendicular to the surface of the sheet P), the fans551F1to551F3are disposed at positions facing only the sheet Pa having the maximum size. Similarly, the fans551F4to551F6are disposed at positions facing the sheet Pa having the maximum size and the sheet Pb having the medium size.

Similarly, the fans551F7,551F9,551F10, and551F12are disposed at positions facing the sheet Pa having the maximum size and the sheet Pb having the medium size, and portions of the fans551F7,551F9,551F10, and551F12face the sheet Pc having the minimum size. Similarly, the fans551F8and551F11are disposed at positions facing all of the sheet Pa having the maximum size, the sheet Pb having the medium size, and the sheet Pc having the minimum size. Accordingly, the blower550can change the fans551F1to551F12to be driven, so that a region of the blower550from which air is blown is changeable.

A configuration for controlling fans551according to the present embodiment is described with reference to a block diagram inFIG.5. A fan controller701causes the multiple fans551F1to551F12of the blower550to rotate. The fan controller701receives the size of the sheet P to be guided (i.e., sheet size data), and selects the fans551to be rotationally driven in response to the size of the sheet P to be guided.

As described above, the fan controller701selects (changes) one or more of the fans551to be rotationally driven from the multiple fans551F1to551F12so as to change the region of the blower550from which air is blown in response to the size of the sheet P to be guided to blow the air within an area of the sheet P to be guided.

For example, the fans551F1to551F12are rotationally driven to blow air within the area of the sheet Pa having the maximum size to guide the sheet Pa having the maximum size. The fans551F4to551F12are rotationally driven to blow air within the area of the sheet Pb having the medium size to guide the sheet Pb having the medium size. At that time, as viewed in plan view, the fans551F1to551F3positioned outside the sheet Pb having the medium size are not used. Therefore, air is not blown outside the sheet Pb. The fans551F8and551F11are rotationally driven to blow air within the area of the sheet Pc having the minimum size to guide the sheet Pc having the minimum size. At that time, as viewed in plan view, the fans551F1to551F6entirely facing an area outside the sheet Pc having the minimum size and the fans551F7,551F9,551F10, and551F12partially facing the area outside the sheet Pc are not used. Therefore, air is not blown outside the sheet Pc. Thus, air is blown within the area of the guided sheet P, and air is not blown outside the guided sheet P, thereby stably guiding the sheet P.

Further, the fan controller701receives the weight of the sheet P to be guided (i.e., sheet weight data), and changes an amount of air (flow rate) blown from the driven fans551of the blower550in response to the weight of the sheet P to be guided. For example, the fan controller701changes a duty ratio of pulse-width modulation (PWM) control or changes a rotation speed to drive the fans551, thereby changing the amount of blowing air.

For example, as illustrated inFIG.4, when a sheet Pd is heavier than a sheet Pe, the fan controller701controls the fans551so that the amount of blowing air to the sheet Pd is greater than the amount blowing air to the sheet Pe. Thus, buckling of the sheet P having low stiffness can be prevented, thereby stably guiding the sheet P.

Next, a second embodiment of the present disclosure is described with reference toFIG.6.FIG.6is a schematic side view of the guide unit523and the blower550according to the second embodiment. In the present embodiment, guide rails553are disposed in the direction perpendicular to the sheet conveyance direction so as to penetrate through the loops of the multiple belts530. The guide rails553movably supports a fan holder554, and the fans551included in the blower550is mounted (held) on the fan holder554. That is, the fan holder554as a holder holding the blower550is movable in the direction perpendicular to the sheet conveyance direction in the loops of the multiple belts530. Accordingly, the fan holder554is drawn in the direction perpendicular to the sheet conveyance direction to pull out the multiple fans551together.

Next, a third embodiment of the present disclosure is described with reference toFIG.7.FIG.7is a schematic plan view of the guide unit523according to the third embodiment. In the present embodiment, the blower550includes one airflow generator or multiple airflow generators (for example, the fans551in the above-described embodiment), and further includes a shutter561that opens and closes a region through which the airflow generated by the airflow generator passes to change the region from which air is blown. In the example inFIG.7, the shutter561covers the region of the fans551F1to551F3illustrated inFIG.3, thereby opening a region562facing the sheet Pb so that air can pass therethrough. Thus, the number of airflow generators (e.g., the fans551) can be reduced as compared with the first embodiment.

Here, an example of an opening and closing mechanism of the shutter561is described with reference toFIGS.8A and8B.FIGS.8A and8Bare schematic plan views of the opening and closing mechanism of the shutter561. The shutter561is movably held by guides570. The shutter561is moved along the guides570by a cam572attached to a cam shaft573. The shutter561is pressed against the cam572by springs571. The shutter561has an opening561a, and an opposing member581having an opening581ais disposed facing the shutter561(on the side facing the sheet P). The opposing member581has the opening581athrough which the blower550blows air.

In the opening and closing mechanism, when the cam572is in the state illustrated inFIG.8A, the shutter561is at the open position where the opening561aof the shutter561coincides with the opening581aof the opposing member581by biasing force of the springs571. At that time, the air blown by the blower550is blown toward the sheet P. On the other hand, as illustrated inFIG.8B, as the cam572is rotationally driven to move the shutter561against the biasing force of the springs571, the shutter561is at the closed position where the opening561aof the shutter561does not coincide with the opening581aof the opposing member581. At that time, air is not blown toward the sheet P from the blower550.

A fourth embodiment of the present disclosure is described with reference toFIGS.9and10.FIG.9is a schematic side view of the guide unit523and the blower550according to the fourth embodiment.FIG.10is a schematic plan view of the guide unit523and the blower550according to the fourth embodiment. In the present embodiment, the blower550includes a chamber552and a pump555that pumps air into the chamber552. In the chamber552, an opening581A or581B through which air is blown out is disposed at each of positions G1to G12. The positions G1to G12correspond to the positions of the fans551F1to551F12described in the above embodiment. The openings581B are disposed at the center and the openings581A are disposed on both sides in the direction perpendicular to the sheet conveyance direction.

As illustrated inFIG.9, shutters561A and shutters561B that open and close the openings581A and the openings581B, respectively, are movably disposed in the chamber552. Cams572A and cams572B are pressed against the shutters561A and the shutters561B, respectively. Similarly to the third embodiment, each of the shutters561A and561B is biased by a biasing member such as a spring to be pressed against the corresponding cam572A or572B.

That is, in the direction perpendicular to the conveyance direction of the sheet P, the cams572A drive the shutters561A to open and close the openings581A on both sides, and the cams572B drive the shutters561B that open and close the openings581B at the center. The cam572A is attached to a camshaft573A, and the cam572B is attached to a camshaft573B. Thus, an open area of the opening581A on both sides, which the shutter561A opens and closes, and an open area of the opening581B at the center, which the shutter561B opens and closes, can be controlled independently.

Note that the printing unit30of the printing apparatus1in each of the above-described embodiments ma fix toners onto the sheet P to perform a desired printing operation to the sheet P instead of discharging liquid such as ink onto the sheet P to perform the desired printing operation.

A material of the sheet P to be conveyed is not limited to a paper, and the sheet stacking device according to the present disclosure may also be applied to an apparatus to convey a plastic film, cloth, metal sheet, and the like.

As described above, according to the present disclosure, the sheet can be stably guided.