Patent Publication Number: US-2022234848-A1

Title: Sheet stacking device and printing apparatus

Description:
CROSS-REFERENCE TO RELMED 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. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a schematic view of a printing apparatus as a liquid discharge apparatus according to a first embodiment of the present disclosure; 
         FIG. 2  is a schematic side view of a sheet stacking device according to the first embodiment of the present disclosure; 
         FIG. 3  is a schematic plan view of a guide unit and a blower according to the first embodiment: 
         FIG. 4  is a schematic side view of the guide unit and the blower according to the first embodiment; 
         FIG. 5  is a block diagram illustrating a configuration for controlling fans of the blower according to the first embodiment; 
         FIG. 6  is a schematic side view of a guide unit and a blower according to a second embodiment of the present disclosure; 
         FIG. 7  is a schematic plan view of a guide unit and a blower according to a third embodiment of the present disclosure; 
         FIGS. 8A and 8B  are schematic plan views illustrating an example of an opening and closing mechanism of a shutter according to the third embodiment; 
         FIG. 9  is a schematic side view of a guide unit and a blower according to a fourth embodiment of the present disclosure; and 
         FIG. 10  is a schematic plan view of the guide unit and the blower according to the fourth embodiment. 
     
    
    
     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 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent 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 the same function, operate in a similar manner, and achieve a similar result 
     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. 
     Embodiments of the present disclosure are described below with reference to the accompanying drawings. First, a printing apparatus  1  as a liquid discharge apparatus according to a first embodiment of the present disclosure is described with reference to FIG.  1 .  FIG. 1  is a schematic view of the printing apparatus  1 . 
     The printing apparatus  1  includes a. loading unit  10  to load a sheet P, a pretreatment unit  20 , a printing unit  30  as an image forming unit, a drying unit  40 , an ejection unit  50 , and a reverse mechanism  60 . In the printing apparatus  1 , the pretreatment unit  20  applies, as required, pretreatment liquid onto the sheet P forwarded (supplied) from the loading unit  10 , the printing unit  30  applies liquid to the sheet P to perform printing on the sheet P, the drying unit  40  dries the liquid adhering to the sheet P, and the sheet P is ejected to the ejection unit  50 . 
     The loading unit  10  includes a lower loading tray  11 A and an upper loading tray  11 B to accommodate a plurality of sheets P and feeders  12 A and  12 B to separate and forward the sheets P one by one from the lower and upper loading trays  11 A and  11 B, thereby supplying the sheets P to the pretreatment unit  20 . 
     The pretreatment unit  20  includes, e.g., a coater  21  as 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 unit  30  includes a drum  31  and a liquid discharger  32 . The drum  31  is a bearer (rotator) that bears the sheet P on the circumferential surface of the drum  31  and rotates. The liquid discharger  32  discharges liquid toward the sheet P borne on the drum  31 . 
     The printing unit  30  further includes transfer cylinders  34  and  35 . The transfer cylinder  34  receives the sheet P from the pretreatment unit  20  and forwards the sheet P to the drum  31 . The transfer cylinder  35  receives the sheet P conveyed by the drum  31  and forwards the sheet P to the drying unit  40 . 
     The transfer cylinder  34  includes a sheet gripper to grip a leading end of the sheet P conveyed from the pretreatment unit  20  to the printing unit  30 . The sheet P thus gripped is conveyed as the transfer cylinder  34  rotates. The transfer cylinder  34  forwards the sheet P to the drum  31  at a position opposite the drum  31 . 
     Similarly, the drum  31  includes a sheet gripper on the surface thereof, and the leading end of the sheet P is gripped by the sheet gripper of the drum  51 . The drum  31  has a plurality of suction holes dispersedly on the surface of the drum  31 , and a suction unit generates suction airflows directed inward from suction holes of the drum  31 . 
     On the drum  31 , the sheet gripper grips the leading end of the sheet P forwarded from the transfer cylinder  34 , and the sheet P is attracted to and borne on the drum  31  by the suction airflows by the suction unit. As the drum  31  rotates, the sheet P is conveyed. 
     The liquid discharger  32  includes discharge units  33  (discharge units  33 A to  33 D) to discharge liquids. For example, the discharge unit  33 A discharges liquid of cyan (C), the discharge unit  33 B discharges liquid of magenta (M), the discharge unit  33 C discharges liquid of yellow (Y), and the discharge unit  33 D discharges liquid of black (K). Further, the liquid discharger  32  may include a discharge unit  33  that discharges special liquid, that is, liquid of spot color such as white, gold, or silver. 
     The discharge operation of each of the discharge units  33  of the liquid discharger  32  is controlled by a drive signal corresponding to print data. When the sheet P borne on the drum  31  passes through a region facing the liquid discharger  32 , the respective color liquids are discharged from the discharge units  33 , and an image corresponding to the print data is printed on the sheet P. 
     The drying unit  40  dries the liquid applied onto the sheet P by the printing unit  30 . 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 mechanism  60  reverses, in switchback manner, the sheet P that has passed through the drying unit  40  in duplex printing. The reversed sheet P is fed back to the upstream side of the transfer cylinder  34  through a conveyance passage  61  of the printing unit  30 . 
     The ejection unit  50  serves as an example of a sheet stacking device according to the present disclosure and includes a stacker  501  and a sheet conveyor  502 . A plurality of sheets P is stacked on the stacker  501 . The sheets P conveyed through the reverse mechanism  60  is sequentially stacked and held on the stacker  501 . 
     A sheet stacking device  500  according to the first embodiment of the present disclosure is described with reference to  FIG. 2 .  FIG. 2  is a schematic side view of the sheet stacking device  500 . 
     The sheet stacking device  500  includes the stacker  501  on which a sheet bundle PB (i.e. a bundle of the sheets P) is stacked. The stacker  501  includes a table  511 , a leading end fence  512  (e.g., a sheet jogger), a trailing end fence  513 , and side fences on both sides of the stacker  501 . The sheet bundle PB is stacked on the table  511 . 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 in  FIG. 2  (i.e., a sheet conveyance direction). 
     The sheet stacking device  500  further includes conveyance roller pairs  521  and  522  and a guide unit  523 . The conveyance roller pairs  521  and  522  convey the sheet P fed from the reverse mechanism  60 . The guide unit  523  receives a leading end (downstream end) of the sheet P conveyed from the conveyance roller pair  522  toward the stacker  501 , and guides the sheet P downstream from the conveyance roller pair  522  in the sheet conveyance direction. 
     The guide unit  523  includes an endless belt  530  and guide parts  541 . The endless belt  530  is looped around a drive roller  531  and a driven roller  532 . The guide parts  541  are attached to the belt  530 . 
     In the guide unit  523 , the belt  530  circumferentially rotates around the drive roller  531  and the driven roller  532  after an elapse of a predetermined period of time from a timing of detection of the sheet P at an upstream of the conveyance roller pair  522 . Then, the leading end of the sheet P is inserted into the guide part  541  due to a difference between a linear velocity of the guide part  541  and a linear velocity of the conveyance roller pair  522 . For example, the linear velocity of the guide parts  541  is smaller than the linear velocity of the conveyance roller pair  522 . Then, as the belt  530  rotates around the drive roller  531  and the driven roller  532 , the guide part  541  moves downstream in the sheet conveyance direction (leftward direction in  FIG. 2 ) while holding the leading end of the sheet P to guide the sheet P. 
     The guide part  541  has 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 part  541 . The guide part  541  also 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 part  541  may include a clip having the gripping force for gripping the leading end of the sheet P. 
     When the guide part  541  reaches a guide end position, the linear velocity of the guide part  541  is set higher than the linear velocity of the conveyance roller pair  522 . Thus, the leading end of the sheet P is separated from the guide part  541  and falls onto the stacker  501  to be stacked. 
     The sheet stacking device  500  further includes a blower  550  for blowing air toward the sheet P. The blower  550  is disposed inside the loop of the endless belt  530  in the vertical direction as viewed in the cross-section. As the blower  550  blows 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 unit  523  and the blower  550  according to the first embodiment is described with reference to  FIGS. 3 to 4 .  FIG. 3  is a plan view of the guide unit  523 , and  FIG. 4  is a side view of the guide unit  523 . 
     In the guide unit  523 , multiple belts  530  (four in the present embodiment) are disposed at intervals in the direction perpendicular to the sheet conveyance direction. Each of the multiple belts  530  is looped around the drive roller  531  and the driven roller  532 . The multiple drive rollers  531  are coaxial with each other, the multiple driven rollers  532  are coaxial with each other, and each belt  530  circumferentially rotates at the same linear velocity. Each belt  530  is provided with the guide parts  541 . 
     The blower  550  includes fans  551 F 1  to  551 F 12  serving as airflow generators that blow air. Hereinafter, the fans  551 F 1  to  551 F 2  are also collectively referred to as “fans  551 ”, and one of the fans  551 F 1  to  551 F 12  is referred to as a “fan  551 ” unless distinguished. The fans  551  are arranged in three lines in the sheet conveyance direction and each line of the fans  551  is disposed between the belts  530  side by side in the direction perpendicular to the sheet conveyance direction. 
     That is, the belt  530  is divided into the multiple belts  530  to move the guide parts  541 , and the multiple belts  530  are disposed at the intervals. Each fan  551  of the blower  550  is disposed adjacent to the belt  530  in the direction perpendicular to the sheet conveyance direction. Accordingly, the size of the guide unit  523  can be downsized as compared with a case in which the fans  551  (blower  550 ) are disposed above the belt  530 . 
     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 stacker  501  as illustrated in  FIG. 3 . At that time, as viewed in the plan view (as viewed in the direction perpendicular to the surface of the sheet P), the fans  551 F 1  to  551 F 3  are disposed at positions facing only the sheet Pa having the maximum size. Similarly, the fans  551 F 4  to  551 F 6  are disposed at positions facing the sheet Pa having the maximum size and the sheet Pb having the medium size. 
     Similarly, the fans  551 F 7 ,  551 F 9 ,  551 F 10 , and  551 F 12  are disposed at positions facing the sheet Pa having the maximum size and the sheet Pb having the medium size, and portions of the fans  551 F 7 ,  551 F 9 ,  551 F 10 , and  551 F 12  face the sheet Pc having the minimum size. Similarly, the fans  551 F 8  and  551 F 11  are 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 blower  550  can change the fans  551 F 1  to  551 F 12  to be driven, so that a region of the blower  550  from which air is blown is changeable. 
     A configuration for controlling fans  551  according to the present embodiment is described with reference to a block diagram in  FIG. 5 . A fan controller  701  causes the multiple fans  551 F 1  to  551 F 12  of the blower  550  to rotate. The fan controller  701  receives the size of the sheet P to be guided (i.e., sheet size data), and selects the fans  551  to be rotationally driven in response to the size of the sheet P to be guided. 
     As described above, the fan controller  701  selects (changes) one or more of the fans  551  to be rotationally driven from the multiple fans  551 F 1  to  551 F 12  so as to change the region of the blower  550  from 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 fans  551 F 1  to  551 F 12  are 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 fans  551 F 4  to  551 F 12  are 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 fans  551 F 1  to  551 F 3  positioned outside the sheet Pb having the medium size are not used. Therefore, air is not blown outside the sheet Pb. The fans  551 F 8  and  551 F 11  are 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 fans  551 F 1  to  551 F 6  entirely facing an area outside the sheet Pc having the minimum size and the fans  551 F 7 ,  551 F 9 ,  551 F 10 , and  551 F 12  partially 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 controller  701  receives 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 fans  551  of the blower  550  in response to the weight of the sheet P to be guided. For example, the fan controller  701  changes a duty ratio of pulse-width modulation (PWM) control or changes a rotation speed to drive the fans  551 , thereby changing the amount of blowing air. 
     For example, as illustrated in  FIG. 4 , When a sheet Pd is heavier than a sheet Pe, the fan controller  701  controls the fans  551  so 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 to  FIG. 6 .  FIG. 6  is a schematic side view of the guide unit  523  and the blower  550  according to the second embodiment. In the present embodiment, guide rails  553  are disposed in the direction perpendicular to the sheet conveyance direction so as to penetrate through the loops of the multiple belts  530 . The guide rails  553  movably supports a fan holder  554 , and the fans  551  included in the blower  550  is mounted (held) on the fan holder  554 . That is, the fan holder  554  as a holder holding the blower  550  is movable in the direction perpendicular to the sheet conveyance direction in the loops of the multiple belts  530 . Accordingly, the fan holder  554  is drawn in the direction perpendicular to the sheet conveyance direction to pull out the multiple fans  551  together. 
     Next, a third embodiment of the present disclosure is described with reference to FIG,  7 .  FIG. 7  is a schematic plan view of the guide unit  523  according to the third embodiment. In the present embodiment, the blower  550  includes one airflow generator or multiple airflow generators (for example, the fans  551  in the above-described embodiment), and further includes a shutter  561  that 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 in  FIG. 7 , the shutter  561  covers the region of the fans  551 F 1  to  551 F 3  illustrated in  FIG. 3 , thereby opening a region  562  facing the sheet Pb so that air can pass therethrough. Thus, the number of airflow generators (e.g., the fans  551 ) can be reduced as compared with the first embodiment. 
     Here, an example of an opening and closing mechanism of the shutter  561  is described with reference to  FIGS. 8A and 8B .  FIGS. 8A and 8B  are schematic plan views of the opening and closing mechanism of the shutter  561 . The shutter  561  is movably held by guides  570 . The shutter  561  is moved along the guides  570  by a cam  572  attached to a cam shaft  573 . The shutter  561  is pressed against the cam  572  by springs  571 . The shutter  561  has an opening  561   a,  and an opposing member  581  having an opening  581   a  is disposed facing the shutter  561  (on the side facing the sheet P). The opposing member  581  has the opening  581   a  through which the blower  550  blows air. 
     In the opening and closing mechanism, when the cam  572  is in the state illustrated in  FIG. 8A , the shutter  561  is at the open position where the opening  561   a  of the shutter  561  coincides with the opening  581   a  of the opposing member  581  by biasing force of the springs  571 . At that time, the air blown by the blower  550  is blown toward the sheet P. On the other hand, as illustrated in  FIG. 8B , as the cam  572  is rotationally driven to move the shutter  561  against the biasing force of the springs  571 , the shutter  561  is at the dosed position where the opening  561   a  of the shutter  561  does not coincide with the opening  581   a  of the opposing member  581 . At that time, air is not blown toward the sheet P from the blower  550 . 
     A fourth embodiment of the present disclosure is described with reference to  FIGS. 9 and 10 .  FIG. 9  is a schematic side view of the guide unit  523  and the blower  550  according to the fourth embodiment.  FIG. 10  is a schematic plan view of the guide unit  523  and the blower  550  according to the fourth embodiment. In the present embodiment, the blower  550  includes a chamber  552  and a pump  555  that pumps air into the chamber  552 . In the chamber  552 , an opening  581 A or  581 B through which air is blown out is disposed at each of positions G 1  to G 12 . The positions G 1  to G 12  correspond to the positions of the fans  551 F 1  to  551 F 12  described in the above embodiment. The openings  581 B are disposed at the center and the openings  581 A are disposed on both sides in the direction perpendicular to the sheet conveyance direction. 
     As illustrated in  FIG. 9 , shutters  561 A and shutters  561 B that open and close the openings  581 A and the openings  581 B, respectively, are movably disposed in the chamber  552 . Cams  572 A and cams  572 B are pressed against the shutters  561 A and the shutters  561 B, respectively. Similarly to the third embodiment, each of the shutters  561 A and  561 B is biased by a biasing member such as a spring to be pressed against the corresponding cam  572 A or  572 B. 
     That is, in the direction perpendicular to the conveyance direction of the sheet P, the cams  572 A drive the shutters  561 A to open and close the openings  581 A on both sides, and the cams  572 B drive the shutters  561 B that open and close the openings  581 B at the center. The cam  572 A is attached to a camshaft  573 A, and the cam  572 B is attached to a camshaft  573 B. Thus, an open area of the opening  581 A on both sides, which the shutter  561 A opens and closes, and an open area of the opening  581 B at the center, which the shutter  561 B opens and closes, can be controlled independently. 
     Note that the printing unit  30  of the printing apparatus  1  in 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. 
     The above-described embodiments are illustrative and do not limit the present disclosure. 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 disclosure.