The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2012-269750 filed in Japan on Dec. 10, 2012.
1. Field of the Invention
The present invention relates to a sheet stacking device, an image forming system, and a sheet stacking method, and more particularly concerns a sheet stacking device that aligns and stacks sheets of a recording medium such as paper, recording paper, transfer paper, or transparency (hereinafter simply referred to as “sheets”) delivered into the sheet stacking device when the sheets are discharged, an image forming system including the sheet stacking device and an image forming apparatus such as a copier, a printer, a facsimile, or a digital multifunction peripheral, and a sheet stacking method performed by the sheet stacking device.
2. Description of the Related Art
Conventionally, sheet processing apparatuses that perform various processing, e.g., postprocessing such as alignment, stapling, folding, and bookbinding, on sheets discharged from an image forming apparatus are widely known and used. Hereinafter, such a sheet processing apparatus that performs post processing is referred to as a sheet post processing apparatus. In recent years, variety of sheets desired to be processed by this type of sheet post processing apparatus has become noticeably wide. In particular, it has become more common to perform printing using a color image forming apparatus on a sheet of coated paper (hereinafter, “coated paper”) that produces a visually-superior image for a brochure, a leaflet, or the like. Coated paper generally has the following properties:
1) high surface smoothness;
2) high inter-sheet clinging force; and
3) low stiffness (Clark method).
These properties can make coated paper less favorable in terms of sheet stackability.
A technique utilizing a return roller for preventing such unfavorable stacking and stacking discharged sheets at a normal position is already known.
Meanwhile, an apparatus that utilizes a pressing member for preventing sheets from being misaligned on a sheet discharge tray is also already known. As an example of an apparatus that uses such a pressing member, a technique disclosed in Japanese Laid-open Patent Application No. 2004-284786 is known.
According to this technique, a sheet stacking device including an output tray, onto which image-formed sheets are to be discharged and stacked, and a pressing member that presses a trailing end portion in a direction, in which the sheets are discharged onto the output tray, is configured as follows. The output tray is movable a preset amount in a direction perpendicular to the sheet discharging direction to perform offset output. The pressing member is moved in synchronization with an offset operation of the output tray.
The conventionally-employed return roller can move back a sheet to a normal position as described above; however, the return roller cannot prevent a phenomenon that a subsequent sheet electrostatically clings to a preceding sheet and pushes out the preceding sheet. Furthermore, when a sheet discharge tray is shifted for offset sorting, an aligned state of the sheets in the sheet discharge tray cannot be maintained with the return roller.
To maintain the aligned state of the sheets, a combination of the pressing member disclosed in Japanese Laid-open Patent Application No. 2004-284786 and the return roller can be employed. The combination of the return roller and the pressing member allows, even when the sheet discharge tray is shifted, holding sheets at the normal position by moving back the sheets to the normal position with the return roller and causing the pressing member to hold the sheets at the position.
However, arranging the return roller and the pressing member in the sheet discharging unit requires space for accommodating them and space for mounting drive mechanisms that drive the return roller and the pressing member, respectively. When the sheet discharging unit is required to have such space, it naturally follows that the sheet discharging unit is increased in size.
Under the circumstances, there is a need for a technique for preventing a sheet from being pushed out by another sheet or misaligned due to electrostatic inter-sheet clinging using a compact device.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
A sheet stacking device includes: a stacking unit that stacks thereon a sheet discharged in a sheet discharging direction; a conveying unit that performs a moving-back operation of conveying the stacked sheet in a direction opposite to the sheet discharging direction; a pressing unit that performs a pressing operation of pressing the conveyed sheet; and a driving unit that drives the conveying unit and the pressing unit by a same driving source.
An image forming system includes the sheet stacking device as described above.
A sheet stacking method includes: stacking a sheet discharged in a sheet discharging direction on a stacking unit; performing, by a conveying unit, a moving-back operation of conveying the stacked sheet in a direction opposite to the sheet discharging direction; and performing, by a pressing unit, a pressing operation of pressing the conveyed sheet. The conveying unit and the pressing unit are driven by a same driving source. Switching between operation of the conveying unit and operation of the pressing unit is performed in response to a rotating direction of the driving source. After a preceding sheet is discharged and the moving-back operation is completed, the pressing operation is started. The pressing unit withdraws from a pressing position before a trailing end of a subsequent sheet is discharged.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
According to an aspect of the present invention, a return roller and a pressing member are driven by a single driving source. The pressing member presses a trailing end of a discharged sheet in an ideal state, in which the discharged sheet has been moved back by the return roller.
A preferred embodiment of the present invention is described below with reference to the accompanying drawings via comparison with a configuration of a conventionally-employed sheet post processing apparatus, on which the embodiment is based.
An embodiment of the present invention is described below with reference to the accompanying drawings.
Referring to
In the present embodiment, the image forming apparatus PR is an electrophotographic image forming apparatus as described above, but not limited thereto. Any known image forming apparatus, e.g., of an inkjet type or a thermal transfer type, can be used as the image forming apparatus PR. In the embodiment, the image processing circuit, the optical writing device, the developing device, the transfer device, and the fixing device make up an image forming unit.
The sheet post processing apparatus PD is attached to a side of the image forming apparatus PR. A sheet discharged from the image forming apparatus PR is guided into the sheet post processing apparatus PD. The sheet post processing apparatus PD includes a conveying path A, a conveying path B, a conveying path C, a conveying path D, and a conveying path H. The sheet is conveyed to the conveying path A that includes a postprocessing unit (in the present embodiment, a punch unit 50 that is a punching unit) that performs postprocessing on a single sheet.
The conveying path B is a conveying path that extends from the conveying path A and leads to an upper tray 201. The conveying path C is a conveying path that leads to a shift tray 202. The conveying path D is a conveying path that leads to a processing tray F (hereinafter, also referred to as “side-stitching tray”) where alignment, staple binding, and the like are performed. The conveying paths are configured such that a sheet conveyed to the conveying path A is then directed to one of the conveying paths B, C, and D by a bifurcating claw 15 and a bifurcating claw 16.
The sheet post processing apparatus can perform various sheet processing, such as hole punching (using the punch unit 50), sheet alignment and side stitching (using jogger fences 53 and a side-stitching stapler S1), sheet alignment and saddle stitching (using a saddle-stitching upper jogger fence 250a, a saddle-stitching lower jogger fence 250b, and a saddle-stitching stapler S2), sheet offset sorting (using the shift tray 202), and center folding (using a folding plate 74 and folding rollers 81). The conveying path A and one of the conveying paths B, C, and D extending from the conveying path A are selected depending on processing to be performed. The conveying path D includes a sheet holding unit E. The side-stitching tray F, a saddle-stitching/center-folding tray G, and the sheet-discharging conveying path H are arranged downstream of the conveying path D.
The conveying path A is upstream of each of the conveying path B, the conveying path C, and the conveying path D. An entry sensor 301 that detects a sheet received from the image forming apparatus PR is arranged on the conveying path A. Entry rollers 1, the punch unit 50, a punch waste hopper 50a, conveying rollers 2, and the first and second separating claws 15 and 16 are arranged in this order along the conveying path A downstream of the entry sensor 301. The first and second bifurcating claws 15 and 16 are held at orientations (initial state) illustrated in
When the sheet is to be directed to the conveying path B, the state illustrated in
When the sheet to be directed to the conveying path C, the first and second solenoids are turned on (the second bifurcating claw 16 is oriented upward in its initial state) from the state illustrated in
When the sheet is to be directed to the conveying path D, the first solenoid that drives the first bifurcating claw 15 is turned on and the second solenoid that drives the second bifurcating claw 16 is turned off, thereby putting the first and second bifurcating claws 15 and 16 in the upwardly pivoted state. In this state, the sheet is delivered between the conveying rollers 2 and then between conveying rollers 7 toward the conveying path D. The sheet delivered to the conveying path D is delivered to the side-stitching tray F. Sheets aligned and stapled on the side-stitching tray F are directed by a guide member 44 to one of the conveying path C along which the sheets are to be conveyed to the shift tray 202 and the saddle-stitching/center-folding tray (hereinafter, also referred to as “saddle stitching tray”) G where the sheets undergo folding and the like. When a sheet bundle PB is to be delivered to the shift tray 202, the sheet bundle PB is discharged through the pairs of sheet delivery rollers 6 onto the shift tray 202. The sheet bundle PB delivered to the saddle-stitching tray G is folded and stapled on the saddle-stitching tray G and conveyed along the sheet-discharging conveying path H to be discharged through lower sheet discharging rollers 83 onto a lower tray 203.
A bifurcating claw 17 is arranged on the conveying path D and held in a state illustrated in
When sheet alignment and side stitching are to be performed on a sheet delivered to the conveying path D, the sheet is delivered by the sheet-stapling-discharging rollers 11 to the side-stitching tray F. Sheets delivered one sheet by one sheet are stacked on the side-stitching tray F. Each time a sheet is stacked in this operation, sheets are aligned in a longitudinal direction (the sheet conveying direction) by a tapping roller 12 against a trailing-end reference fence 51 and aligned in a lateral direction (the direction perpendicular to the sheet conveying direction; also referred to as the “sheet width direction”) against the jogger fences 53. The side-stitching stapler S1, which is a stapling unit, is driven to perform stapling in response to a stapling signal fed from a central processing unit (CPU) 101, which will be described later, in an interval between jobs, i.e., an interval between the last sheet of the sheet bundle PB and the first sheet of a subsequent sheet bundle. Immediately after the stapling, the stapled sheet bundle PB is conveyed by an ejecting belt 52 (see
As illustrated in
A home position (HP) of the ejecting tabs 52a is detected by an ejecting-belt HP sensor 311. The ejecting-belt HP sensor 311 is switched on and off by the ejecting tabs 52a provided on the ejecting belt 52. The ejecting tabs 52a are arranged on an outer circumferential surface of the ejecting belt 52 at positions where the ejecting tabs 52a face each other, and alternately convey the sheet bundle PB held in the side-stitching tray F. It is also possible to rotate the ejecting belt 52 in reverse as required, thereby aligning leading ends of sheets of the sheet bundle PB held in the side-stitching tray F in the conveying direction with one of the ejecting tabs 52a that is on standby to move the sheet bundle PB and a back surface of the other one of the ejecting tabs 52a.
Reference numeral 110 in
In
Referring back to
Configurations of these elements are described in detail below. The conveying mechanism 35 includes a drive shaft 37 and a roller 36, to which a driving force of the drive shaft 37 is transmitted via a timing belt. The roller 36 and the drive shaft 37 are connected and supported by an arm in such a manner that the roller 36 can pivot about the drive shaft 37 serving as a pivot support. The roller 36 of the conveying mechanism 35 is driven to pivot via a cam 40 that is rotated about a rotary shaft by a motor (not shown). The conveying mechanism 35 includes a driven roller 42 at a position where the driven roller 42 faces the roller 36. The conveying mechanism 35 applies a conveying force to the sheet bundle PB by pinching the sheet bundle PB between the driven roller 42 and the roller 36 and pressing the sheet bundle PB with an elastic member.
The turn conveying path, along which the sheet bundle PB is turned from the side-stitching tray F to the saddle-stitching tray G, is provided between the ejecting rollers 56 and an inner surface of the guide member 44 on the side where the guide member 44 faces the ejecting rollers 56. The guide member 44 is driven to pivot about a pivot support on a driving force transmitted to the guide member 44 from a bundle-route-switching driving motor 161 (see FIG. 2). When conveying the sheet bundle PB from the side-stitching tray F to the shift tray 202, the guide member 44 pivots clockwise in
As illustrated in
Upper bundle conveying rollers 71 and lower bundle conveying rollers 72 are arranged in an upper portion and a lower portion of the upper bundle-conveyance guide plate 92, respectively. The saddle-stitching upper jogger fences 250a are arranged along side surfaces of the upper bundle-conveyance guide plate 92 in a manner to straddle the rollers 71 and 72. Similarly, saddle-stitching lower jogger fences 250b are arranged along side surfaces of the lower bundle-conveyance guide plate 91. The saddle-stitching stapler S2 is arranged at a position where the saddle-stitching lower jogger fences 250b are provided. The saddle-stitching upper jogger fences 250a and the saddle-stitching lower jogger fences 250b are driven by a drive mechanism (not shown) and perform alignment in the direction (sheet width direction) perpendicular to the sheet conveying direction. The saddle-stitching stapler S2 includes two stapler units that are spaced from each other a predetermined distance in the sheet width direction. Each stapler unit includes a pair of a clincher unit and a driving unit.
A movable trailing-end reference fence 73 extends across the lower bundle-conveyance guide plate 91. A moving mechanism including a timing belt and a drive mechanism for the timing belt allows the movable trailing-end reference fence 73 to move in the sheet conveying direction (i.e., the vertical direction in
The center folding mechanism positioned at substantially center of the saddle-stitching tray G includes the folding plate 74, the folding rollers 81, and the conveying path H, along which the folded sheet bundle PB is conveyed. Referring to
In the present embodiment, a detection lever 501 for detecting a stack height of the center-folded sheet bundle PB is arranged on the lower tray 203 to be pivotable on a fulcrum 501a. A sheet level sensor 505 detects an angle of the detection lever 501. Ascending/descending of the lower tray 203 and tray-full detection of the same are performed based on the detected angle.
However, a sheet discharge tray having such a configuration can cause the problem described above when the sheet P has high smoothness as does coated paper. For example, when a subsequent sheet P2 is discharged onto the shift tray 202 where a preceding sheet P1 is already placed as illustrated in
Therefore, the configuration of the sheet discharging unit illustrated in
Referring to
The pressing members 14 perform a pressing operation only when coated paper is fed. The CPU 101 of the sheet post processing apparatus PD makes determination, which will be described later, as to whether or not a sheet being fed is coated paper based on sheet-type information transmitted from the image forming apparatus PR, and controls the operation.
After completion of the sheet alignment in the conveying direction and in the width direction, the pressing members 14 press a trailing end of the subsequent sheet P2 as illustrated in
A drive mechanism 18 includes a first shaft 19a, a second shaft 19b, a return-roller driving motor 20 that drives the first shaft 19a to rotate, a drive gear 20a, a driven gear 20b, first to third gears 21, 22, and 23, and cams 24.
The return-roller driving motor 20 has the drive gear 20a on a distal end of a rotating shaft of the motor 20. The drive gear 20a can rotate the first shaft 19a either forward or in reverse by meshing with the driven gear 20b attached to a shaft end of the first shaft 19a.
The first gear 21 arranged on the first shaft 19a can mesh with the second gear 22 arranged on the second shaft 19b, thereby transmitting a driving force of the return-roller driving motor 20 to the second shaft 19b. One-way clutches are arranged on the first and second gears 21 and 22. The one-way clutch locks during rotation in respective directions opposite to each other.
A pair of the third gears 23 are arranged to be symmetric with respect to the conveyance center of the sheet P and fixed onto the second shaft 19b. Accordingly, the third gears 23 are rotated by rotation of the second shaft 19b. The third gears 23 drive the pair of cams 24 by meshing with gear portions of the cams 24 arranged on the first shaft 19a. The cams 24 rotate only when the third gears 23 rotate because the cams 24 are not fixed onto the first shaft 19a. The pair of pressing members 14 is rotatably supported on a support shaft 14d. The pair of cams 24, which are freely-rotatably mounted on the first shaft 19a, moves (causes to swing) the respective pressing members 14 between a pressing position and a withdrawn position.
The drive mechanism 18 configured as described above uses the return roller motor 20 as a driving source. The return rollers 13 are fixed onto projections projecting from a circumferential portion of the first shaft 19a as illustrated in
When a moving-back operation of the return rollers 13 is completed, the pressing operation is started by rotating the return-roller driving motor 20 in reverse (in a direction indicated by arrow R3) as illustrated in
The drive mechanism configured as described above allows obtaining favorable alignment accuracy. This is because the preceding sheet P1 clinging due to inter-sheet close contact is pressed in a state where the preceding sheet P1 has been moved back by the return rollers 13. Furthermore, reduction in size and cost can be achieved because the return rollers 13 and the pressing members 14 are driven by the same single driving source. Switching between the moving-back operation of the return rollers 13 and the pressing operation of the pressing members 14 can be performed only by switching the rotating direction of the return-roller driving motor 20 between forward and reverse.
The above-described control is executed in accordance with program defined by program codes stored in a ROM (not shown). The CPU 101 reads out the program codes and loads them into a RAM (not shown), and executes the program defined by the program codes while using the RAM as a working area and a data buffer.
The trailing-end-pressing setting process is performed in the following manner. When an “ON” option 105b is selected from a configuration screen 105a for the trailing-end-pressing setting process on the operation panel 105 illustrated in
More specifically, at default settings, when coated paper is selected, the pressing using the pressing members 14 is set to “ON”. Accordingly, whether or not “forced pressing (using the pressing members 14) OFF” is selected is determined before the pressing is set to “ON” (Step S103). If “forced pressing OFF” is selected (YES in Step S103), the pressing operation using the pressing members 14 is set to “OFF” (Step S104). Then this routine ends.
If “forced pressing OFF” is not selected (NO in Step S103), the pressing operation using the pressing members 14 is set to “ON” (the return-roller driving motor 20 is to be rotated in reverse; Step S105) to cause a sheet to be pressed and held. Then this routine ends.
When a paper type other than coated paper is selected, the pressing operation is set to “OFF” at the default settings. Accordingly, whether or not “forced pressing ON” is selected is determined (Step S106). If “forced pressing ON” is selected (YES in Step S106), the return-roller driving motor 20 is rotated in reverse (Step S105). If “forced pressing ON” is not selected (NO in Step S106), this routine ends while setting the pressing members 14 to be left in the withdrawn state (Step S107).
When a “NO” option 105c is selected on an air-blowing-mode screen, a normal sheet discharging operation is to be performed without performing the pressing operation.
As described above, in the embodiment, when a user selects paper-type information from the operation panel 105, the pressing operation is set to “ON” at the default settings. However, it is possible to cause the pressing operation not to be performed by selecting “forced pressing OFF”. At the default settings, the pressing operation is not performed when ordinary paper is selected. However, it is possible to cause the pressing operation to be performed on ordinary paper by selecting “forced pressing ON”.
As described above, the embodiment provides the following advantages.
1) The sheet stacking device includes: the shift tray 202 (stacking unit) that stacks thereon a sheet discharged in the sheet discharging direction; the return rollers 13 (conveying unit) that perform the moving-back operation of conveying the stacked sheet P in the direction opposite to the sheet discharging direction; the pressing members 14 (pressing unit) that drives the return rollers 13 and the pressing members 14 by the return-roller driving motor 20 (the same single driving source). Accordingly, the sheet stacking device can press the preceding sheet P1 with the pressing members 14 when the subsequent sheet P2 is discharged, and move back the subsequent sheet with the return rollers 13 by using the single driving source. The pressing operation can prevent the sheet from being pushed out due to electrostatic inter-sheet clinging. As a result, favorable alignment accuracy can be obtained. Furthermore, because the return rollers 13 and the pressing members 14 are driven by the single driving source, the device is not increased in size, and can be provided as a compact device.
2) The driving unit includes the first and second gears 21 and 22 and the one-way clutches (switching unit) that switch between operation of the return rollers 13 and operation of the pressing members 14 in response to a rotating direction of the return-roller driving motor 20. Accordingly, switching between the operations can be performed with a simple configuration.
3) The pressing unit includes the pressing members 14 that are driven by the cams 24 attached to the first shaft 19a, the second gear 22 attached to the second shaft 19b that drives the cams 24, and the first gear 21 that transmits rotation of the first shaft 19a to the second shaft 19b. The conveying unit includes the return rollers 13 that are attached to the first shaft 19a and rotates in synchronization with the first shaft 19a. Accordingly, the effect provided by 1) can be obtained with a simple configuration.
4) The switching unit includes the one-way clutches for the first gear 21 and the second gear 22 that lock during rotation in respective directions opposite to each other. Accordingly, the effect provided by 2) can be obtained with a simple configuration.
5) The pressing members 14 are pivotably supported on the support shaft 14d. Rotation of the cams 24 in one rotational direction moves the pressing members 14 between the pressing position (the position in
6) The sheet stacking device includes the CPU 101 (control unit) that controls driving of the return-roller driving motor 20. The CPU 101 causes the pressing members to operate based on paper-type information about the sheet to be discharged (
7) The pressing members 14 start the pressing operation when the preceding sheet P1 is discharged and the moving-back operation of the return rollers 13 is completed, and withdraw before the trailing end of the subsequent sheet P2 is discharged. Accordingly, the sheet is prevented from being pushed out due to electrostatic inter-sheet clinging. As a result, favorable alignment accuracy can be obtained.
8) A user can configure setting as to whether or not to perform the pressing operation of the pressing members 14 from the operation panel 105 (operating unit). Accordingly, whether or not to perform the pressing operation on the sheet P can be controlled as desired by the user (
The shift tray 202 is an example of “stacking unit” in the appended claims; the return rollers 13 are an example of “conveying unit”; the pressing members 14 are an example of “pressing unit”; the sheet post processing apparatus PD is an example of “sheet stacking device”; the return-roller driving motor 20 is an example of “driving source”; the first and second shafts 19a and 19b, the first to third gears 21, 22, and 23, the cams 24, and the one-way clutches are an example of “driving unit”; reference numeral 14d denotes “support shaft”; the CPU 101 is an example of “control unit”; the operation panel 105 is an example of “operation unit”; reference symbol P denotes “sheet”; reference symbol P1 denotes “preceding sheet”; reference symbol P2 denotes “subsequent sheet”; the system including the image forming apparatus PR and the image post processing apparatus PD is an example of “image forming system”.
According to the embodiment, it is possible to prevent a sheet from being pushed out by another sheet and/or misaligned due to electrostatic inter-sheet clinging using a compact device.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
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2012-269750 | Dec 2012 | JP | national |
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Number | Date | Country | |
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20140159301 A1 | Jun 2014 | US |