SHEET STACKING DEVICE, SHEET POST-PROCESSING DEVICE, AND IMAGE FORMING SYSTEM

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2019-140728 filed Jul. 31, 2019, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a sheet stacking device, a sheet post-processing device including the sheet stacking device, and an image forming system including the sheet post-processing device.

There is known a sheet post-processing device having a post-processing mechanism that performs post-processing such as a stapling process or a punching process after image formation. The sheet post-processing device is equipped with a sheet stacking device including a discharge roller pair that discharges a sheet after the post-processing, and a stacking tray on which sheets discharged by a discharge roller pair are stacked. As the sheet stacking device, there is known a device including an aligning mechanism for aligning sheets stacked on the stacking tray in a sheet width direction perpendicular to a sheet discharge direction.

For instance, in the conventional sheet stacking device, when the amount of sheets stacked on the stacking tray increases, an alignment member pair is moved down, and a position of the alignment member pair is controlled so that the alignment member pair contacts the sheets on the stacking tray. In this way, even if the sheets stacked on the stacking tray is curled (curved), the sheets can be securely aligned.

SUMMARY

A sheet stacking device according to one aspect of the present disclosure includes a sheet discharge outlet, a discharge roller pair, a stacking tray, and an aligning mechanism. A sheet is discharged from the sheet discharge outlet. The discharge roller pair discharges the sheet from the sheet discharge outlet. The stacking tray is disposed below a downstream side of the sheet discharge outlet in a sheet discharge direction, so that the sheet discharged from the sheet discharge outlet by the discharge roller pair is stacked on the stacking tray. The aligning mechanism aligns the sheets stacked on the stacking tray in a sheet width direction perpendicular to the sheet discharge direction. The aligning mechanism includes a pair of alignment members and a pair of height detectors. The pair of alignment members are capable of moving independently of each other in the sheet width direction and in an up and down direction, and contact side edges in the sheet width direction of the sheets stacked on the stacking tray from both sides in the sheet width direction, so as to align the sheets in the sheet width direction. The pair of height detectors detect heights of the sheets on both sides in the sheet width direction by allowing the pair of alignment members to contact an upper surface of the sheets at vicinities of the side edges of the sheets. The pair of alignment members are is capable of correcting heights of the pair of alignment members individually when aligning the sheets, on the basis of the heights of the sheets detected by the pair of height detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front cross-sectional diagram illustrating a schematic structure of an image forming system of an embodiment of the present disclosure.

FIG. 2 is a partial front cross-sectional diagram illustrating a sheet stacking device and its vicinity in a sheet post-processing device of the embodiment of the present disclosure.

FIG. 3 is a perspective view of a sheet stacking device of the embodiment of the present disclosure.

FIG. 4 is a front cross-sectional diagram illustrating an alignment member and its vicinity in the sheet stacking device of the embodiment of the present disclosure.

FIG. 5 is a perspective view of the alignment member and its vicinity in the sheet stacking device of the embodiment of the present disclosure.

FIG. 6 is a perspective view illustrating a cylindrical part and its vicinity of the alignment member of the sheet stacking device of the embodiment of the present disclosure.

FIG. 7 is a perspective view illustrating the cylindrical part and its vicinity of the alignment member of the sheet stacking device of the embodiment of the present disclosure.

FIG. 8 is a schematic front view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where the alignment member is at a first position.

FIG. 9 is a schematic front view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where the alignment member is at a second position.

FIG. 10 is a schematic front view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where one of the alignment members contacts an upper surface of sheets.

FIG. 11 is a schematic front view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where the other alignment member contacts the upper surface of the sheet.

FIG. 12 is a perspective view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a sheet height detection state.

FIG. 13 is a schematic front view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where one of the alignment members is moved to an alignment position.

FIG. 14 is a schematic front view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where the other alignment member is moved to the alignment position.

FIG. 15 is a perspective view of the sheet stacking device of the embodiment of the present disclosure, as a diagram illustrating a state where heights of the alignment members are adjusted individually on the basis of sheet heights.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure is described with reference to the drawings. Note that the present disclosure is not limited to the following description.

FIG. 1 is a front cross-sectional diagram illustrating a schematic structure of an image forming system 301 of the embodiment. The image forming system 301 includes an image forming apparatus 101 and a sheet post-processing device 201.

The image forming apparatus 101 is, for example, a so-called monochrome multifunction peripheral having functions such as printing, scanning (image reading), and facsimile transmitting. Note that the image forming apparatus 101 may be, for example, an apparatus such as a copier or a printer, and it may be an apparatus that supports color printing.

As illustrated in FIG. 1, the image forming apparatus 101 includes a document feeder unit 103 disposed on an upper surface of its main body 102, and an image reader unit 104 disposed in the main body 102 below the document feeder unit 103. The image reader unit 104 reads an image of a document loaded on the document feeder unit 103 or an image of a document placed on a not shown contact glass on the upper surface of the image reader unit 104.

The image forming apparatus 101 further includes a sheet feeding unit 105, a sheet conveying unit 106, an exposure unit 107, an image forming unit 108, a transfer unit 109, a fixing unit 110, a sheet discharge unit 111, and a main body controller 112.

The sheet feeding unit 105 stores a plurality of sheets S and sending out the sheet S after separating one by one. The sheet conveying unit 106 conveys the sheet S sent out from the sheet feeding unit 105 to the transfer unit 109 and the fixing unit 110, and further delivers the sheet S after fixing, to the sheet discharge unit 111 or to the sheet post-processing device 201. The exposure unit 107 emits a laser beam controlled based on image data to the image forming unit 108.

The image forming unit 108 includes a photosensitive drum 1081 as an image carrier and a development device 1082. In the image forming unit 108, the laser beam emitted from the exposure unit 107 forms an electrostatic latent image of a document image on a surface of the photosensitive drum 1081. The development device 1082 supplies toner to this electrostatic latent image to develop the image, so that a toner image is formed. The transfer unit 109 transfers the toner image formed by the image forming unit 108 on the surface of the photosensitive drum 1081 to the sheet S. The fixing unit 110 heats and presses the sheet S with the transferred toner image so that the toner image is fixed to the sheet S.

The sheet S after fixing is sent to the sheet discharge unit 111 or to the sheet post-processing device 201. The sheet discharge unit 111 is disposed below the image reader unit 104. The sheet discharge unit 111 has an opening at the front, and the sheet after printing (printed matter) is taken out from the front side. The sheet post-processing device 201 will be described later.

The main body controller 112 includes a CPU, an image processor, and a storage unit, which are not shown, and other not shown electronic circuits and components. The CPU controls operations of the individual units of the image forming apparatus 101 on the basis of control programs and data stored in the storage unit, so as to perform processes related to the functions of the image forming apparatus 101. The sheet feeding unit 105, the sheet conveying unit 106, the exposure unit 107, the image forming unit 108, the transfer unit 109, and the fixing unit 110 respectively receive instructions from the main body controller 112 and perform printing on the sheet S in a cooperative manner. The storage unit is constituted of a combination of a nonvolatile storage device such as a program read only memory (ROM) and a data ROM, and a volatile storage device such as a random access memory (RAM), which are not shown, for example.

The sheet post-processing device 201 is connected to a side face of the image forming apparatus 101 in a detachable and attachable manner. Note that the sheet post-processing device 201 can be connected not only to the multifunction peripheral but also to other apparatus such as a copier or a printer, for example. As illustrated in FIG. 1, the sheet post-processing device 201 includes a sheet conveyance inlet 202, a sheet discharge passage 203, an intermediate roller pair 204, a processing tray 205, a post-processor 206, a sheet stacking device 1, and a post-processing controller 207. Note that in the following description about the sheet post-processing device 201, the direction from the right to the left in FIG. 1 is referred to as a “sheet discharge direction”.

The sheet conveyance inlet 202 is formed and opens on a side surface facing the image forming apparatus 101. The sheet S after fixing, which is delivered to the sheet post-processing device 201, passes through the sheet conveyance inlet 202 and is conveyed to an inside of the sheet post-processing device 201.

The sheet discharge passage 203 extends laterally from the sheet conveyance inlet 202 to above the processing tray 205 in a direction apart from the image forming apparatus 101 (in the left direction in FIG. 1).

The intermediate roller pair 204 is disposed on the downstream side in the sheet discharge direction of a punching unit 2061 (described later) in the sheet discharge passage 203. Rotation axes of the intermediate roller pair 204 extend in the sheet width direction perpendicular to the sheet discharge direction (in the direction perpendicular to paper of FIG. 1). A plurality of the intermediate roller pairs 204 are arranged with spaces along the sheet width direction. The intermediate roller pairs 204 convey the sheet S, which is conveyed in the sheet discharge passage 203, to a sheet discharge outlet 2 (described later) on the further downstream side.

The processing tray 205 is disposed below the downstream side of the sheet discharge passage 203 in the sheet discharge direction. In other words, the processing tray 205 is positioned just below the downstream side of the intermediate roller pairs 204 in the sheet discharge direction. A sheet loading surface of the processing tray 205 has an inclination ascending toward the downstream side in the sheet discharge direction. A plurality of sheets S conveyed to the processing tray 205 through the sheet discharge passage 203 are loaded on the processing tray 205, and post-processing is performed on them.

The post-processor 206 performs a predetermined post-processing on the sheets S that are conveyed through the sheet discharge passage 203. The post-processor 206 includes the punching unit 2061 and a stapling unit 2062, for example.

The punching unit 2061 is disposed at an intermediate part of the sheet discharge passage 203 between the sheet conveyance inlet 202 as an upstream end and a downstream end in the sheet discharge direction. The sheet post-processing device 201 performs a punching process on the sheet S conveyed in the sheet discharge passage 203, using the punching unit 2061, so that punch holes can be formed.

The stapling unit 2062 is disposed on the upstream side of the processing tray 205 in the sheet discharge direction. The sheet post-processing device 201 performs a stapling process (binding process) on the sheets S loaded on the processing tray 205, using the stapling unit 2062, so that the sheets can be bound.

The sheet stacking device 1 is disposed on the downstream side of the processing tray 205 in the sheet discharge direction. The sheet stacking device 1 includes a discharge roller pair 3, and a stacking tray 5. The discharge roller pair 3 is disposed at a downstream end of the processing tray 205 in the sheet discharge direction. The stacking tray 5 is disposed below the downstream side of the discharge roller pair 3 in the sheet discharge direction. The sheets S after finishing the post-processing on the processing tray 205 are discharged by the discharge roller pair 3 onto the stacking tray 5 and are taken out. Note that if the post-processing by the stapling unit 2062 is not performed, the sheet S is not stacked on the processing tray 205 but is conveyed to the stacking tray 5. A detailed structure of the sheet stacking device 1 will be described later.

The post-processing controller 207 includes a CPU and a storage unit, which are not shown, and other not shown electronic circuits and components. The post-processing controller 207 is connected to the main body controller 112 in a communicable manner. The post-processing controller 207 receives instructions from the main body controller 112, and uses the CPU to control operations of individual units of the sheet post-processing device 201 on the basis of control programs and data stored in the storage unit, so as to perform processes related to functions of the sheet post-processing device 201. The sheet discharge passage 203, the intermediate roller pair 204, the processing tray 205, the post-processor 206, and the sheet stacking device 1 respectively receive instructions from the post-processing controller 207 and perform post-processing on the sheets S in a cooperative manner. Note that the post-processing controller 207 is an example of the “controller” recited in claim 1 of the present disclosure. The “controller” may be separately disposed in the sheet stacking device 1 itself.

Next, a detailed structure of the sheet stacking device 1 is described with reference to FIGS. 2, 3, 4, and 5. FIG. 2 is a partial front cross-sectional diagram illustrating the sheet stacking device 1 and its vicinity in the sheet post-processing device 201. FIG. 3 is a perspective view of the sheet stacking device 1. FIG. 4 is a front cross-sectional diagram illustrating an alignment member 61 and its vicinity in the sheet stacking device 1. FIG. 5 is a perspective view illustrating the alignment member 61 and its vicinity in the sheet stacking device 1. FIGS. 6 and 7 are perspective views illustrating a cylindrical part 611 and its vicinity in the alignment member 61 of the sheet stacking device 1.

Note that in the following description about the sheet stacking device 1, the direction from the right to the left in FIGS. 2 and 4 is referred to as the “sheet discharge direction” and is shown by an arrow line Dd. Further, the “sheet width direction” perpendicular to the sheet discharge direction is the direction perpendicular to papers of FIG. 2 and FIG. 4, and is shown by an arrow line Dw in FIGS. 3 and 5.

As illustrated in FIG. 2, the sheet stacking device 1 includes the sheet discharge outlet 2, the discharge roller pair 3, an arm part 4, the stacking tray 5, and an aligning mechanism 6.

The sheet discharge outlet 2 is disposed on the downstream side of the intermediate roller pair 204 in the sheet discharge direction Dd, and on the downstream side of the processing tray 205 in the sheet discharge direction Dd. The discharge roller pair 3 is disposed at the sheet discharge outlet 2. The sheets S after finishing the post-processing on the processing tray 205 are discharged onto the stacking tray 5 through the sheet discharge outlet 2.

The discharge roller pair 3 is disposed at the sheet discharge outlet 2. The discharge roller pair 3 discharges the sheet S from the sheet discharge outlet 2. Rotation axes of the discharge roller pair 3 extend in the sheet width direction Dw. A plurality of the discharge roller pairs 3 are arranged with spaces along the sheet width direction Dw. In this embodiment, as illustrated in FIG. 3, two discharge roller pairs 3 are disposed. The discharge roller pair 3 includes a pair of a lower side discharge roller 31 and an upper side discharge roller 32.

The lower side discharge roller 31 is connected to a not shown discharge drive unit and can rotate in a forward direction for discharging the sheet S onto the stacking tray 5 and in a backward direction for sending the sheet S onto the processing tray 205. The upper side discharge roller 32 contacts the lower side discharge roller 31 and is driven to rotate.

The upper side discharge roller 32 is supported by the arm part 4. The arm part 4 extends in the sheet discharge direction Dd, and supports the upper side discharge roller 32 in a rotatable manner, at one end on the downstream end in the sheet discharge direction Dd.

The arm part 4 is supported by the sheet post-processing device 201 in a rotatable manner about the rotation shaft 41 extending in the sheet width direction Dw, at one end on the upstream end in the sheet discharge direction Dd. The arm part 4 is connected to a not shown arm drive unit, and is swung in the up and down direction about the rotation shaft 41 with a free end that is the one end supporting the upper side discharge roller 32. This swinging of the arm part 4 causes the upper side discharge roller 32 to contact or separate from the lower side discharge roller 31. As illustrated in FIGS. 2 and 3, the pair of upper side discharge roller 32 and the lower side discharge roller 31 contact each other at their circumferential surfaces, and hence a nip 3N is formed for discharging the sheet S from the sheet discharge outlet 2.

The sheet S discharged from the sheet discharge outlet 2 by forward rotation of the discharge roller pair 3 is stacked on the stacking tray 5. Further, the nip 3N of the discharge roller pair 3 holds the sheet S, and in the state where the upstream end of the sheet S in the discharge direction is apart from a nip 204N of the intermediate roller pair 204, the discharge roller pair 3 is rotated backward. Then, the sheet S is conveyed onto the processing tray 205.

The stacking tray 5 is disposed below the downstream side of the sheet discharge outlet 2 in the sheet discharge direction Dd. A sheet stacking surface 51 of the stacking tray 5 has an inclination ascending toward the downstream side in the sheet discharge direction Dd. The upstream end of the stacking tray 5 in the sheet discharge direction Dd is positioned below the sheet discharge outlet 2. A sheet receiving wall 1a is disposed on the upstream side of the stacking tray 5 in the sheet discharge direction Dd. The stacking tray 5 can be moved substantially vertically in the up and down direction by a not shown drive unit. The sheet S discharged from the sheet discharge outlet 2 by the discharge roller pair 3 is stacked on the stacking tray 5. The stacking tray 5 is a final discharge place of the sheet S, in the sheet post-processing device 201.

The stacking tray 5 has a recess 52. The recess 52 is recessed downward from the sheet stacking surface 51 of the stacking tray 5. The recess 52 is disposed on each side of the stacking tray 5 in the sheet width direction Dw with respect to a middle part in the sheet width direction Dw. In general, when performing the aligning operation for aligning the sheets S in the sheet width direction Dw, the aligning operation is performed in the state where a lower part of the alignment member 61 described later is in the recess 52 as illustrated in FIG. 2.

As illustrated in FIGS. 2 and 3, the aligning mechanism 6 is disposed above the sheet discharge outlet 2 on the downstream side thereof in the sheet discharge direction Dd, and on each side in the sheet width direction Dw. The aligning mechanism 6 aligns the sheets S stacked on the stacking tray 5 in the sheet width direction Dw perpendicular to the sheet discharge direction Dd. The operation of the aligning mechanism 6 is controlled by the post-processing controller 207, for example.

The aligning mechanisms 6 are disposed to form a pair on both sides of the sheets S stacked on the stacking tray 5 in the sheet width direction Dw. The pair of aligning mechanisms 6 includes an aligning mechanism 6F disposed on the front side of the sheet stacking device 1 and an aligning mechanism 6B disposed on the back side of the same with respect to the sheets S. Unless it is necessary to specify, the suffixes F and B representing front and back, respectively, may be omitted.

Each of the pair of aligning mechanisms 6 includes the alignment member 61, a slide mechanism 7, a lifting mechanism 8, and a height detector 62. In other words, the aligning mechanisms 6 include a pair of alignment members 61 and a pair of height detectors 62. The pair of aligning mechanisms 6 have the basically same structure except that the alignment members 61 align the sheets S in the opposite directions in the sheet width direction Dw.

The alignment member 61 is disposed on the downstream side of the sheet discharge outlet 2 in the sheet discharge direction Dd and on one end side of the stacking tray 5 in the sheet width direction Dw. The alignment member 61 is held by a carriage 72 described later of the slide mechanism 7. The alignment member 61 has a plate-like shape that extends in the sheet discharge direction Dd and has a substantially L shape viewed from the sheet width direction Dw. The alignment member 61 includes the cylindrical part 611 and a sheet contact part 612.

The cylindrical part 611 is disposed at an upstream end in the sheet discharge direction Dd and the upper end of the alignment member 61, and extends in the sheet width direction Dw. The cylindrical part 611 has a through hole 6111 extending in the sheet width direction Dw, in which a rotation shaft 721 of the carriage 72 is inserted. The cylindrical part 611 is supported by the rotation shaft 721 of the carriage 72 in a rotatable manner. In other words, the alignment member 61 can rotate about the rotation shaft 721 with respect to the carriage 72. A more detailed structure of the cylindrical part 611 will be described together with description of the lifting mechanism 8 described later.

The sheet contact part 612 is disposed at a downstream side part of the alignment member 61 in the sheet discharge direction Dd and in an area facing the sheets S stacked on the stacking tray 5. The sheet contact part 612 contacts the side edges of the sheets S stacked on the stacking tray 5 in the sheet width direction Dw from one end side in the sheet width direction Dw.

The pair of alignment members 61 can be moved independently of each other, in the sheet width direction Dw and in the up and down direction, by the slide mechanism 7 and the lifting mechanism 8.

The slide mechanism 7 is disposed above the sheet discharge outlet 2. The slide mechanism 7 includes a guide shaft 71, the carriage 72, and a not shown width direction drive unit.

The guide shaft 71 is disposed at an upper part of the slide mechanism 7, extends in the sheet width direction Dw, and is supported by the sheet post-processing device 201.

The guide shaft 71 penetrates the carriage 72 in the sheet width direction Dw, and the carriage 72 is supported by the guide shaft 71. The carriage 72 can move in the sheet width direction Dw along the guide shaft 71. The carriage 72 includes the rotation shaft 721 and holds the alignment member 61 via the rotation shaft 721.

The width direction drive unit may be constituted of, for example, an endless moving belt extending in the sheet width direction Dw, to which the carriage 72 is attached, a pulley around which the moving belt is wound, a drive motor for rotating the pulley, and the like. Alternatively, the width direction drive unit may be constituted of, for example, a rack extending in the sheet width direction Dw, a pinion attached to the carriage 72 so as to engage with the rack, a drive motor for rotating the pinion, and the like.

The slide mechanism 7 can move the carriage 72 holding the alignment member 61 in the sheet width direction Dw along the guide shaft 71 by operating the drive motor of the width direction drive unit. In other words, the slide mechanism 7 moves each of the pair of alignment members 61 in the sheet width direction Dw. In this way, the pair of alignment members 61 contact the side edges in the sheet width direction Dw of the sheets S stacked on the stacking tray 5 from both sides in the sheet width direction Dw, so as to align the sheets S in the sheet width direction Dw.

The lifting mechanism 8 is disposed inside the carriage 72 and outside the sheet discharge outlet 2 in the sheet width direction Dw. The lifting mechanism 8 includes an output gear 81, an intermediate gear 82, a drive transmission gear 83, a drive shaft 84, an input gear 85, and a drive motor 86.

An output gear 81 is disposed at a bottom inside the carriage 72. The output gear 81 has a through hole 811 extending in the sheet width direction Dw, in which the rotation shaft 721 of the carriage 72 is inserted, and is supported by the carriage 72. The output gear 81 is disposed coaxially with the cylindrical part 611 of the alignment member 61, and can rotate about the rotation shaft 721 extending in the sheet width direction Dw.

The output gear 81 has a protrusion 812. The protrusion 812 is disposed on a side face of the output gear 81, which faces the cylindrical part 611 of the alignment member 61, and protrudes toward the cylindrical part 611 in the sheet width direction Dw. The protrusion 812 is formed in a sector shape having a center at the axis viewed from the sheet width direction Dw, for example. For instance, two protrusions 812 are disposed at symmetric positions with respect to the axis center.

The cylindrical part 611 has recesses 6112. The recesses 6112 are disposed at a side face of the cylindrical part 611 facing the output gear 81, and recess toward inside of the cylindrical part 611 in the sheet width direction Dw. The recess 6112 is formed in a sector shape having a center at the axis viewed from the sheet width direction Dw, for example. A perimeter of the recess 6112 in a radial direction opens in a circumferential surface of the cylindrical part 611. For instance, two recesses 6112 are disposed at symmetric positions with respect to the axis center.

The protrusion 812 of the output gear 81 is inserted in the recess 6112 of the cylindrical part 611 along the sheet width direction Dw (see FIG. 8). A central angle of the recess 6112 having a sector shape viewed from the sheet width direction Dw is larger than that of the protrusion 812 having a sector shape similarly. For instance, the recess 6112 is formed to have a central angle of 90 degrees, and the protrusion 812 can move about the rotation shaft 721 within a movable area Ar of approximately 60 degrees in the recess 6112. In other words, the pair of alignment members 61 are attached to one end and the other end of the rotation shaft 721 respectively in a rotatable manner with a predetermined play in the rotation direction.

The intermediate gear 82 is disposed above the output gear 81 inside the carriage 72, and is supported by the carriage 72. The intermediate gear 82 is engaged with the output gear 81 and can rotate about an axis extending in the sheet width direction Dw.

The drive transmission gear 83 is disposed above the intermediate gear 82 inside the carriage 72 and is supported by the carriage 72. The drive transmission gear 83 is engaged with the intermediate gear 82. The drive transmission gear 83 is disposed coaxially with the drive shaft 84 and can rotate around an axis extending in the sheet width direction Dw.

The drive shaft 84 is disposed in the middle of the carriage 72 in the up and down direction, extends in the sheet width direction Dw, and is supported by the sheet post-processing device 201 in a rotatable manner. The drive shaft 84 penetrates the carriage 72 in the sheet width direction Dw, and the drive transmission gear 83 is disposed coaxially with the drive shaft 84. The carriage 72 can move in the sheet width direction Dw along the guide shaft 71 with respect to the drive shaft 84 and does not rotate together with the drive shaft 84. The drive transmission gear 83 can move together with the carriage 72 in the sheet width direction Dw with respect to the drive shaft 84, and rotates following the rotation of the drive shaft 84.

The input gear 85 is disposed on one end side of the sheet discharge outlet 2 in the sheet width direction Dw, and is fixed to one end of the drive shaft 84 in the sheet width direction Dw. The input gear 85 is disposed coaxially with the drive shaft 84 and can rotate about an axis extending in the sheet width direction Dw.

The drive motor 86 is disposed on one end side of the sheet discharge outlet 2 in the sheet width direction Dw. The drive motor 86 is constituted of a stepping motor or the like, for example. A rotation shaft of the drive motor 86 is provided with a not shown drive gear. The drive gear of the rotation shaft of the drive motor 86 is engaged with the input gear 85.

Note that a not shown one-way rotary member is disposed between the rotation shaft of the drive motor 86 and the input gear 85. During rotation of the drive motor 86, if the input gear 85 and the drive shaft 84 stop rotating so that a load is generated due to contact between the alignment member 61 and the sheet S, the drive motor 86 idles due to the one-way rotary member's action. In this way, the drive motor 86 can be prevented from being broken.

The lifting mechanism 8 operates the drive motor 86, and hence can rotate the alignment member 61 about the rotation shaft 721 extending in the sheet width direction Dw, via the input gear 85, the drive shaft 84, the drive transmission gear 83, the intermediate gear 82, and the output gear 81. In this way, the sheet contact part 612 of the alignment member 61 moves in the up and down direction. In other words, the lifting mechanism 8 can move the alignment member 61 in the up and down direction.

The height detector 62 is disposed on the one end side of the sheet discharge outlet 2 in the sheet width direction Dw, for example. The height detector 62 includes a magnetic or optical angle detection sensor 621 including a rotary encoder or a resolver, and can detect a rotation angle of the alignment member 61 that rotates about the rotation shaft 721. In other words, the height detector 62 can detect a position of the alignment member 61 in the up and down direction.

As described above, the lifting mechanism 8 can move the alignment member 61 in the up and down direction. Then, the height detectors 62 detect heights of the sheets S at both sides in the sheet width direction Dw, by allowing the pair of alignment members 61 to contact the upper surface of the sheets S stacked on the stacking tray 5 near the side edges of the sheets S.

Next, an operation of the sheet stacking device 1 is described with reference to FIG. 3 as well as FIGS. 8 to 15. Note that for convenience sake of description, FIGS. 8, 9, 10, 11, 13, and 14 show a front view of only one of the pair of alignment members 61 and, on the right side thereof, enlarged cross-sectional views of the protrusion 812 of the output gear 81 and the cylindrical part 611, for describing a positional relationship of the alignment member 61. Further, suffixes F and B representing front and back, respectively, of the sheet stacking device 1 with respect to the sheets S are added for the alignment member 61, as necessary.

Usually every time when one sheet S is discharged onto the stacking tray 5, the sheet stacking device 1 performs the aligning operation of the sheets S stacked on the stacking tray 5. In this case, as illustrated in FIG. 3, the aligning mechanism 6 allows the pair of alignment members 61 to contact the side edges in the sheet width direction Dw of the sheets S stacked on the stacking tray 5 from both sides in the sheet width direction Dw. Note that a distance between the pair of alignment members 61 in the sheet width direction Dw is determined in advance on the basis of a size of the sheets S stacked on the stacking tray 5.

As illustrated in FIG. 3, a part of the sheets S stacked on the stacking tray 5 may be curved, and hence a curled part Sc may be generated. For this reason, when a print job is finished, or every time when a predetermined number of sheets S are discharged onto the stacking tray 5, the sheet stacking device 1 performs height detection of the sheets S stacked on the stacking tray 5 using the pair of height detectors 62, and can perform the aligning operation by correcting the heights of the pair of alignment members 61 individually from each other.

FIG. 8 is a schematic front view of the sheet stacking device 1, as a diagram illustrating a state where the alignment member 61 is at a first position P1. As illustrated in FIG. 8, the post-processing controller 207 first controls each of the pair of alignment members 61 to move to the first position P1 facing the side edges in the sheet width direction Dw of the sheets S stacked on the stacking tray 5. The first position P1 of the pair of alignment members 61 is a position of the pair of alignment members 61 in the normal aligning operation, in which the alignment member 61 is close to the stacking tray 5 in the up and down direction, and the lower part thereof is in the recess 52. The first position P1 of the pair of alignment members 61 is a position outside the side edges of the sheets S in the sheet width direction Dw, in which the alignment member 61 does not contact the sheets S.

The post-processing controller 207 stops rotation of the protrusion 812 of the output gear 81 of the lifting mechanism 8 at a predetermined position corresponding to the first position P1. Each of the pair of alignment members 61 tries to rotate in a counterclockwise direction in FIG. 8 due to gravity action, but one end part in the circumferential direction of the recess 6112 of the cylindrical part 611 abuts the protrusion 812 so that the rotation stops at the first position P1.

FIG. 9 is a schematic front view of the sheet stacking device 1, as a diagram illustrating a state where the alignment member 61 is at a second position P2. Next, as illustrated in FIG. 9, the post-processing controller 207 controls the lifting mechanism 8 to move each of the pair of alignment members 61 from the first position P1 to the second position P2 above the sheets S. The second position P2 of the pair of alignment members 61 is set to a sufficiently high position taking into account the number of sheets S and the curl.

The post-processing controller 207 allows the protrusion 812 of the output gear 81 of the lifting mechanism 8 to rotate in a clockwise direction in FIG. 9 from the first position P1 by 50 degrees, for example, to be at the second position P2. When the cylindrical part 611 is rotated by the protrusion 812, each of the pair of alignment members 61 is rotated about the rotation shaft 721 and is moved to the second position P2.

The movable area Ar of the protrusion 812 in the recess 6112 illustrated in FIG. 8 is 60 degrees, and the rotation angle from the first position P1 to the second position P2 is 50 degrees. Therefore, after being at the second position P2, even when the alignment member 61 soon contacts the sheet S and stops its rotation, the protrusion 812, which continues to rotate after that until reaching the position corresponding to the first position P1, does not contact the opposite end of the recess 6112 in the circumferential direction. In this way, an overload does not occur, and a breakage of the output gear 81 or the cylindrical part 611 can be prevented.

Next, the post-processing controller 207 controls the slide mechanism 7 to move each of the pair of alignment members 61 to inside in the sheet width direction Dw so as to be positioned at a third position P3 (see FIG. 10) facing the upper surface of the sheets S. Here, the post-processing controller 207 controls the angle detection sensor 621 of the height detector 62 to detect a position (angle) of the alignment member 61 at the third position P3 in the up and down direction, and stores the same as an initial value.

FIG. 10 is a schematic front view of the sheet stacking device 1, as a diagram illustrating a state where one alignment member 61F contacts the upper surface of the sheets S. Next, as illustrated in FIG. 10, the post-processing controller 207 controls the lifting mechanism 8 to move each of the pair of alignment members 61 downward from the third position P3 so as to contact the upper surface of the sheets S. As illustrated in FIG. 3, if the sheets S stacked on the stacking tray 5 have a curved part, i.e. a curled part Sc on the front side, the front side alignment member 61F contacts the upper surface of the sheets S earlier than a back side alignment member 61B does (see FIG. 10).

The post-processing controller 207 allows the protrusion 812 of the output gear 81 of the lifting mechanism 8 to rotate from the third position P3 in the counterclockwise direction in FIG. 10. Due to gravity applied to each of the pair of alignment members 61, the cylindrical part 611 rotates together with the protrusion 812, and hence each of the pair of alignment members 61 is rotated about the rotation shaft 721 toward the upper surface of the sheets S. When the front side alignment member 61F contacts the upper surface of the sheets S, it stops at the contact position Pt.

Note that when the front side alignment member 61F contacts the upper surface of the sheets S and stops at the contact position Pt, the protrusion 812 of the output gear 81 of the lifting mechanism 8 continues to rotate in the counterclockwise direction in FIG. 10. In this way, the back side alignment member 61B is rotated about the rotation shaft 721 toward the upper surface of the sheets S.

FIG. 11 is a schematic front view of the sheet stacking device 1, as a diagram illustrating a state where the other alignment member 61B contacts the upper surface of the sheets S. FIG. 12 is a perspective view of the sheet stacking device 1, as a diagram illustrating a sheet height detection state. As illustrated in FIG. 3, if the sheets S stacked on the stacking tray 5 have no curled part and are flat on the back side, the back side alignment member 61B contacts the upper surface of the sheets S at a normal height (see FIGS. 11 and 12). When the back side alignment member 61B contacts the upper surface of the sheets S, it stops at the contact position Pt.

Note that when the back side alignment member 61B contacts the upper surface of the sheets S and stops at the contact position Pt, the protrusion 812 of the output gear 81 of the lifting mechanism 8 continues to rotate in the counterclockwise direction in FIG. 11. After that, the protrusion 812 rotates to a position corresponding to the first position P1, and stops.

Next, the post-processing controller 207 controls the angle detection sensor 621 of the height detector 62 to detect a position (angle) in the up and down direction of each of the pair of alignment members 61 that has stopped. In addition, the post-processing controller 207 controls the angle detection sensor 621 to detect a rotation angle of each of the pair of alignment members 61 from the third position P3 stored as the initial value to the contact position Pt. Then, the post-processing controller 207 derives an alignment position Pa of each of the pair of alignment members 61 (see FIGS. 13 and 14) after correcting the height on the basis of the rotation angle.

If the sheets S have no curled part and are flat, the first position P1 may be set as the alignment position Pa of the back side alignment member 61B without the correction.

FIG. 13 is a schematic front view of the sheet stacking device 1, as a diagram illustrating a state where one of the alignment members 61B is moved to the alignment position Pa. Next, as illustrated in FIG. 13, the post-processing controller 207 positions the back side alignment member 61B at the alignment position Pa. If the back side of the sheets S stacked on the stacking tray 5 is flat, for example, the post-processing controller 207 sets the alignment position Pa of the back side alignment member 61B to the first position P1, and positions the alignment member 61B.

The post-processing controller 207 stops the rotation of the protrusion 812 of the output gear 81 of the back side lifting mechanism 8 at a predetermined position corresponding to the first position P1 that is the alignment position Pa. The back side alignment member 61B stops at the first position P1 as the alignment position Pa, when one end of the recess 6112 of the cylindrical part 611 in the circumferential direction abuts the protrusion 812 due to gravity action.

FIG. 14 is a schematic front view of the sheet stacking device 1, as a diagram illustrating a state where the other alignment member 61F is moved to the alignment position Pa. Next, as illustrated in FIG. 14, the post-processing controller 207 positions the front side alignment member 61F at the alignment position Pa. The alignment position Pa of the back side alignment member 61B is corrected in the height on the basis of the rotation angle of the front side alignment member 61F from the third position P3 to the contact position Pt with the sheet S. The post-processing controller 207 positions the front side alignment member 61F at the alignment position Pa after correcting the height.

The post-processing controller 207 stops the rotation of the protrusion 812 of the output gear 81 of the front side lifting mechanism 8 at a predetermined position corresponding to the alignment position Pa after correcting the height. The front side alignment member 61F stops at the alignment position Pa after correcting the height, when one end of the recess 6112 of the cylindrical part 611 in the circumferential direction abuts the protrusion 812 due to gravity action.

FIG. 15 is a perspective view of the sheet stacking device 1, as a diagram illustrating a state where the heights of the alignment members 61 are individually corrected on the basis of the sheet heights. Next, as illustrated in FIG. 15, the post-processing controller 207 performs the aligning operation for aligning the sheet S in the sheet width direction Dw at the alignment position Pa.

The post-processing controller 207 controls the slide mechanism 7 to move the back side alignment member 61B in the sheet width direction Dw at the first position P1 as the alignment position Pa, so as to contact the side edges in the sheet width direction Dw of the sheets S stacked on the stacking tray 5. Further, the post-processing controller 207 controls the slide mechanism 7 to move the front side alignment member 61F in the sheet width direction Dw at the alignment position Pa after correcting the height, so as to contact the side edges in the sheet width direction Dw of the sheets S stacked on the stacking tray 5. The alignment member 61F on the front side, where the sheets S has the curled part Sc, contacts the side edges of the sheets S in the sheet width direction Dw at a position higher than the alignment member 61B on the back side, where the sheets S are flat.

As described above, the aligning mechanism 6 can individually correct the heights of the pair of alignment members 61 so that the pair of alignment members 61 face the side edges of the sheet S when aligning the sheets S, on the basis of the heights of the sheets S detected by the pair of height detectors 62. With this structure, even if the sheets S stacked on the stacking tray 5 are curled (curved) so that the height thereof is different between both sides in the sheet width direction Dw, the heights of the pair of alignment members 61 can be corrected individually. The heights of the pair of alignment members 61 can be individually adjusted to the heights of the sheets S in accordance with the heights of the sheets S detected by the pair of height detectors 62. In this way, the alignment members 61 can contact the side edges of the sheets S in the sheet width direction Dw in accordance with the heights of the curled sheet S, and the sheets S on the stacking tray 5 can be appropriately aligned. In other words, a decrease in alignment property of the sheets S stacked on the stacking tray 5 or dropping of the same from the stacking tray 5 can be prevented.

Further, with the structure described above, the pair of alignment members 61 can rotate about the rotation shaft 721 extending in the sheet width direction Dw, independently of each other. Further, the height detector 62 detects the height of the sheets S on the basis of the rotation angle of the alignment member 61. In this way, the heights of the sheets S can be easily detected by rotating the alignment members 61. In addition, the heights of the sheets S can be detected with fine resolutions. Therefore, the heights of the pair of alignment members 61 can be appropriately adjusted to the heights of the sheets S.

Note that if a difference between the height of the sheets S detected by one of the pair of height detectors 62 and the height of the sheet detected by the other of the pair of height detectors is a predetermined value or larger, the discharging of the sheets S from the sheet discharge outlet 2 is stopped. With this structure, if the sheets S are curled (curved) to such an extent that the movement of the alignment member 61 in the up and down direction does not work, it is possible to stop stacking the sheets S on the stacking tray 5. It is possible to prevent stacking on the stacking tray 5 of the sheets S that are largely curled so that a decrease in alignment property or dropping from the stacking tray 5 may occur.

Further, according to the embodiment described above, each of the pair of alignment members 61 is attached to the rotation shaft 721 in a rotatable manner with a predetermined play in the rotation direction. Further, the post-processing controller 207 allows each of the pair of alignment members 61 to move from the first position P1 to the second position P2, and further to the third position P3, controls the angle detection sensor 621 to detect the rotation angle from the third position P3 to the contact position Pt at which the alignment member 61 contacts the upper surface of the sheets S and stops, derives the alignment position Pa after correcting the height based on the rotation angle, and performs the aligning operation for aligning the sheets S in the sheet width direction at the alignment position Pa. With this structure, only by rotating the alignment member 61 about the rotation shaft 721 so as to move downward, the contact position Pt of the alignment member 61 with the sheets S can be detected. In this way, it is not necessary to use a sensor for detecting contact of the alignment member 61 with the sheets S. Therefore, cost reduction of the apparatus can be achieved, and the alignment position Pa of the alignment member 61 can be easily derived.

Further, according to the embodiment described above, the sheet post-processing device 201 includes the sheet stacking device 1 having the structure described above. In this way, in the sheet post-processing device 201, if the height of the sheets S stacked on the stacking tray 5 is different between both sides in the sheet width direction Dw, the heights of the pair of alignment members 61 can be adjusted individually to the heights of the sheets S. Therefore, in the sheet post-processing device 201, the alignment members 61 can contact the side edges of the sheets S in the sheet width direction Dw in accordance with the heights of the sheets S, and the sheets S on the stacking tray 5 can be appropriately aligned.

Further, according to the embodiment described above, the image forming system 301 includes the sheet stacking device 1 having the structure described above. In this way, in the image forming system 301, if the height of the sheets S stacked on the stacking tray 5 is different between both sides in the sheet width direction Dw, the heights of the pair of alignment members 61 can be adjusted individually to the heights of the sheets S. Therefore, in the image forming system 301, the alignment members 61 can contact the side edges of the sheets S in the sheet width direction Dw in accordance with the heights of the sheets S, and the sheets S on the stacking tray 5 can be appropriately aligned.

Although the embodiment of the present disclosure is described above, the scope of the present disclosure is not limited to the embodiment, but can be variously modified within the scope of the invention without deviating from the spirit thereof.

For instance, in the embodiment described above, the lifting mechanism 8 rotates the alignment member 61 about the rotation shaft 721 so as to move in the up and down direction, but this mechanism is not a limitation. For instance, the lifting mechanism 8 may be one that moves the alignment member 61 to slide substantially vertically in the up and down direction, or to slide in the up and down direction along the normal direction to the sheet stacking surface 51 of the stacking tray 5.

Further, in the embodiment described above, the image forming apparatus 101 of the image forming system 301 is the image forming apparatus for monochrome printing, but this type is not a limitation. For instance, the image forming apparatus may be an image forming apparatus for color printing.

SHEET STACKING DEVICE, SHEET POST-PROCESSING DEVICE, AND IMAGE FORMING SYSTEM

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