Sheet stacking apparatus, sheet processing apparatus and image forming apparatus Number:7,419,150 from the United States Patent and Trademark Office (PTO) owispatent A sheet stacking apparatus includes an intermediate process tray stacked with sheets, a trailing end lever movable upward from a pressing position in which to press the sheets on the intermediate process tray, a lever stopper regulating the upward movement of the trailing end lever, and an adjusting mechanism changing the regulating position of the trailing end lever by the lever stopper in accordance with a sheet stacking height of the sheets stacked on the intermediate process tray, wherein the adjusting mechanism keeps substantially constant a distance to the regulating position from the pressing position of the trailing end lever irrespective of the sheet stacking height of the sheets stacked on the intermediate process tray.<H processing, apparatus, Sheet, stacking, , 7419150.html, Patent, pto, 7419150

Title: Sheet stacking apparatus, sheet processing apparatus and image forming apparatus

Abstract: A sheet stacking apparatus includes an intermediate process tray stacked with sheets, a trailing end lever movable upward from a pressing position in which to press the sheets on the intermediate process tray, a lever stopper regulating the upward movement of the trailing end lever, and an adjusting mechanism changing the regulating position of the trailing end lever by the lever stopper in accordance with a sheet stacking height of the sheets stacked on the intermediate process tray, wherein the adjusting mechanism keeps substantially constant a distance to the regulating position from the pressing position of the trailing end lever irrespective of the sheet stacking height of the sheets stacked on the intermediate process tray.

Patent Number: 7,419,150 Issued on 09/02/2008 to Kushida, et al.

Inventors: Kushida; Hideki (Moriya, JP), Kamiya; Daisaku (Abiko, JP)
Assignee: Canon Kabushiki Kaisha (Tokyo, JP)

Appl. No.: 11/442,322

Filed: May 30, 2006

Foreign Application Priority Data


Jun 10, 2005 [JP]			2005-171720
Aug 15, 2005 [JP]			2005-235556
Mar 31, 2006 [JP]			2006-096492

Current U.S. Class: 270/58.07 ; 270/58.08; 270/58.11; 270/58.12; 270/58.27

Current International Class: B65H 37/04 (20060101)

Field of Search: 270/58.07,58.08,58.11,58.12,58.27 271/220,221

References Cited [Referenced By]

U.S. Patent Documents


5419545	May 1995	Hutson
5467974	November 1995	Ishiwata et al.
6145825	November 2000	Kunihiro et al.
6412774	July 2002	Saito et al.
6427997	August 2002	Hirota et al.
6601846	August 2003	Saito et al.
6634641	October 2003	Yamakawa et al.
7014183	March 2006	Tamura et al.
7152856	December 2006	Kamiya et al.
2002/0113362	August 2002	Saito et al.
2005/0082735	April 2005	Nakamura et al.
2005/0084308	April 2005	Nakamura et al.
2005/0179190	August 2005	Kamiya et al.
2006/0017209	January 2006	Kushida et al.
2006/0017218	January 2006	Kawata et al.
2006/0019811	January 2006	Ikeda et al.
2006/0061032	March 2006	Kamiya et al.
2006/0208411	September 2006	Saito et al.
2006/0214346	September 2006	Terao et al.
2007/0035082	February 2007	Kushida
2007/0057425	March 2007	Kamiya

Foreign Patent Documents


11-130338	May., 1999	JP

Primary Examiner: Crawford; Gene O.
Assistant Examiner: Nicholson, III; Leslie
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto

Claims

What is claimed is:

1. A sheet stacking apparatus comprising: a sheet stacking portion which stacks a sheet; a sheet pressing member which presses the sheet on said sheet stacking portion in a pressing position and which is movable upward about an axis by abutting a sheet that is delivered onto said sheet stacking portion; a regulating member which regulates the upward movement of said sheet pressing member about the axis; and an adjusting mechanism which changes a regulating position where said sheet pressing member is regulated by said regulating member in accordance with a sheet stacking height of the stacked sheets and keeps substantially constant a distance to the regulating position from the pressing position of said sheet pressing member irrespective of the sheet stacking height.

2. A sheet stacking apparatus according to claim 1, further comprising: a stopper which receives a trailing end of the stacked sheets; and a sheet conveying guide which guides the sheet to said stopper, wherein said sheet pressing member is provided between said sheet conveying guide and said stopper, and a distance between said sheet conveying guide and a sheet stacking surface of said sheet stacking portion is changed in linkage with the change of the regulating position of said sheet pressing member.

3. A sheet stacking apparatus according to claim 2, wherein the sheet pressing position of said sheet pressing member is set in the vicinity of a downstream side of said stopper.

4. A sheet stacking apparatus according to claim 2, wherein said stopper and said sheet pressing member are movable in the direction intersecting the sheet delivery direction.

5. A sheet stacking apparatus according to claim 2, further comprising: another sheet pressing member which is provided in symmetry with said sheet pressing member in the direction intersecting the sheet delivery direction; and another sheet conveying guide which is provided in symmetry with said sheet conveying guide in the direction intersecting the sheet delivery direction.

6. A sheet stacking apparatus according to claim 5, wherein said sheet pressing member and said sheet conveying guide are driven by the same drive unit, and a distance to the regulating position from the pressing position in which said sheet pressing member presses the sheet and a distance up to an end portion of said conveying guide from a sheet uppermost surface on said sheet stacking portion, are made substantially constant.

7. A sheet stacking apparatus according to claim 1, wherein said regulating member is provided integrally with a rotary shaft rotating corresponding to the sheet stacking height.

8. A sheet stacking apparatus according to claim 1, further comprising: a biasing member which biases said regulating member toward the regulating position of said sheet pressing member, wherein said sheet pressing member can resist said biasing member and move said regulating member upward.

9. A sheet stacking apparatus according to claim 8, wherein said regulating member is rotatably provided at said rotary shaft rotating corresponding to the sheet stacking height, said biasing member is provided between said regulating member and said rotary shaft so as to bias said regulating member in said regulating position of said sheet pressing member, and said regulating member is regulated in the regulating position of said sheet pressing member by a rotation regulating mechanism which is provided between said rotary shaft and said regulating member.

10. A sheet stacking apparatus according to claim 1, wherein at least said sheet pressing member in said sheet pressing member and said regulating member is movable in a direction intersecting a sheet delivery direction.

11. A sheet processing apparatus which executes processing on a sheet, comprising: a sheet stacking portion which stacks the sheet; a sheet pressing member which presses the sheet on said sheet stacking portion in a pressing position and which is movable upward about an axis by abutting a sheet that is delivered onto said sheet stacking portion; a regulating member which regulates the upward movement of said sheet pressing member about the axis; and an adjusting mechanism which changes a regulating position where said sheet pressing member is regulated by said regulating member in accordance with a sheet stacking height of the stacked sheets and keeps substantially constant a distance to the regulating position from the pressing position of said sheet pressing member irrespective of the sheet stacking height.

12. A sheet processing apparatus according to claim 11, further comprising: a stopper which receives a trailing end of the stacked sheet; and a sheet conveying guide which guides the sheet to said stopper, wherein said sheet pressing member is provided between said sheet conveying guide and said stopper, and a distance between said sheet conveying guide and a sheet stacking surface of said sheet stacking portion is changed in linkage with the change of the regulating position.

13. A sheet processing apparatus according to claim 11, wherein said regulating member is provided integrally with a rotary shaft rotating corresponding to the sheet stacking height.

14. A sheet processing apparatus according to claim 11, further comprising: a biasing member which biases said regulating member toward the regulating position of said sheet pressing member, wherein said sheet pressing member can resist said biasing member and move said regulating member upward.

15. A sheet processing apparatus according to claim 11, wherein a moving area of said sheet pressing member is set in a position where said sheet pressing member does not interfere with said binding unit.

16. A sheet processing apparatus according to claim 11, wherein said binding unit is movable in a direction intersecting the sheet delivery direction.

17. An image forming apparatus comprising: an image forming portion which forms an image on a sheet; and a sheet processing apparatus which executes processing on the sheet on which the image is formed by said image forming portion, said sheet processing apparatus comprising: a sheet stacking portion which stacks the sheet; a binding unit which binds the stacked sheets; a sheet pressing member which presses the sheet on said sheet stacking portion in a pressing position and which is movable upward about an axis by abutting a sheet that is delivered onto said sheet stacking portion; a regulating member which regulates the upward movement of said sheet pressing member about the axis; and an adjusting mechanism which changes a regulating position where said sheet pressing member is regulated by said regulating member in accordance with a sheet stacking height of the stacked sheets and keeps substantially constant a distance to the regulating position from the pressing position of said sheet pressing member irrespective of the sheet stacking height.

18. An image forming apparatus according to claim 17, further comprising: a stopper which receives trailing ends of the stacked sheets; and a sheet conveying guide which guides the sheets to said stopper, wherein said sheet pressing member is provided between said sheet conveying guide and said stopper, and a distance between said sheet conveying guide and a sheet stacking surface of said sheet stacking portion is changed in linkage with the change of the regulating position.

19. An image forming apparatus according to claim 17, wherein said regulating member is provided integrally with a rotary shaft rotating corresponding to the sheet stacking height.

20. An image forming apparatus according to claim 17, further comprising: a biasing member which biases said regulating member toward the regulating position of said sheet pressing member, wherein said sheet pressing member can resist said biasing member and move said regulating member upward.

21. An image forming apparatus comprising: an image forming portion which forms an image on a sheet; a sheet stacking portion which stacks the sheet bearing the image formed by said image forming portion; a sheet pressing member which presses the sheet on said sheet stacking portion in a pressing position and which is movable upward about an axis by abutting a sheet that is delivered onto said sheet stacking portion; a regulating member which regulates the upward movement of said sheet pressing member about the axis; and an adjusting mechanism which changes a regulating position where said sheet pressing member is regulated by said regulating member in accordance with a sheet stacking height of the stacked sheets and keeps substantially constant a distance to the regulating position from the pressing position of said sheet pressing member irrespective of the sheet stacking height.

22. An image forming apparatus according to claim 21, further comprising: a stopper which receives trailing ends of the stacked sheets; and a sheet conveying guide which guides the sheets to said stopper, wherein said sheet pressing member is provided between said sheet conveying guide and said stopper, and a distance between said sheet conveying guide and a sheet stacking surface of said sheet stacking portion is changed in linkage with the change of the regulating position.

23. An image forming apparatus according to claim 21, further comprising: a biasing member which biases said regulating member toward the regulating position of said sheet pressing member, wherein said sheet pressing member can resist said biasing member and move said regulating member upward.

24. A sheet stacking apparatus comprising: a sheet stacking portion which stacks conveyed sheets; a sheet pressing member which is movable upward about an axis by abutting the conveyed sheet and which presses the sheets on said sheet stacking portion in a pressing position; and an adjusting mechanism which changes an upper limit position where the upward movement of said sheet pressing member about the axis is regulated, wherein a conveying path space for the conveyed sheet is provided in a gap between the pressing position and the upper limit position, and wherein the adjusting mechanism changes the upper limit position so as to prevent the conveying path space from narrowing by an increase of the sheet stacking height of the stacked sheets.

25. A sheet stacking apparatus according to claim 24, further comprising: a regulating member which regulates said sheet pressing member in the upper limit position.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a sheet stacking apparatus in which sheets are sequentially delivered to and stacked on a sheet stacking tray, and more particularly to a sheet stacking apparatus capable of guiding the sheets to a alignment stopper surface on the sheet stacking tray and pressing the sheets against on the sheet stacking tray by substantially constant pressing force irrespective of a sheet stacking height, also to a sheet processing apparatus of which an apparatus main body includes the present sheet stacking apparatus, and further to an image forming apparatus.

2. Related Background Art

An image forming apparatus that forms an image on a sheet, a binding device that binds a sheet bundle and a sheet processing apparatus that processes the sheets such as a punching apparatus that punches the sheet bundle, have hitherto included a sheet stacking apparatus sequentially stacked with the sheets. In this case, the majority of these apparatuses have a sheet tacking apparatus in which the sheets are stacked on the sheet stacking tray in a way that reduces floating of the sheet in consideration of curling of the sheet. Note that the image forming apparatus is exemplified such as a copying machine a laser beam printer, a facsimile and a multifunction apparatus having functions of these apparatuses.

A sheet stacking apparatus 1302 shown in FIG. 45 is provided in a binding device 1300 for binding the sheets formed with images. This sheet stacking apparatus 1302 is constructed so that a sheet bundle is formed by sequentially stacking the sheets on an intermediate process tray 1330 defined as a sheet stacking tray provided within a binding device 1300, a stapler 1301 moving along an edge of the sheet bundle staples the sheet bundle at a plurality of points, and thereafter the stapled sheet bundle is delivered to a stack tray 1622 from the intermediate process tray 1330.

An operation of binding the unillustrated sheet bundle at two points, which is stacked on the intermediate process tray 1330, will be explained with reference to FIG. 46.

The sheets discharged out of the apparatus main body of the image forming apparatus are delivered sheet by sheet to the intermediate process tray 1330, and upstream-side ends (trailing ends) of the sheets in a sheet delivery direction are made to abut on an abutment support surface 1331a of a trailing end stopper 1331 by a pull-in paddle 1360 rotating in an arrow-headed direction and a knurled belt 1608 of a delivery roller 1320a configuring a first delivery roller pair 1320, thereby aligning the trailing ends of the sheets. Further, both sides of the sheets are widthwise aligned by first and second alignment members 1340, 1341 getting close to the sheets from the both sides of the sheets.

With a repetition of these operations, the plurality of sheets stacked on the intermediate process tray 1330 becomes a sheet bundle of which the trailing ends and the side ends are aligned. Thereafter, the on-standby stapler 1301 moves to first and second stapling positions along the trailing ends of the sheet bundle, and staples the sheet bundle in the respective stapling positions.

Thus, the sheet stacking apparatus 1302 including the intermediate process tray 1330 is configured in the way that alignment of the trailing end portions of the sheet involves pulling back the sheets toward the trailing end stopper 1331 by a pullback mechanism composed of the pull-in paddle 1360, the knurled belt 1608, etc and making the sheets abut on the trailing end stopper 1331. Normally, the sheet formed with a toner image might, however, change in its water content amount when the toner image is heated, pressurized and thus fixed by a fixing unit within the apparatus main body of the image forming apparatus, or depending on a using environment. Therefore, a buckling phenomenon occurs on the sheet. Namely, the sheet might be warped (curled).

The thus-curled sheet and a sheet that is small in thickness and low in rigidity are, when abutting on the trailing end stopper 1331 on the intermediate process tray 1330, buckled and disturb the alignment of the sheet bundle. Such being the case, the following configurations of the trailing end stopper are taken as measures against a failure of alignment of the sheets on the intermediate process tray 1330.

A trailing end stopper 1332 shown in FIG. 47 includes an abutting surface 1332a provided with a plurality of grooves 1332b and a plurality of protruded strip members 1332c, which prevent the sheet from being pushed up along the abutting surface 1332a.

A trailing end stopper 1333 shown in FIG. 48 includes a downwardly-inclined elastic film 1334 provided at an upper portion thereof, thereby invariably pressing the sheet trailing end portion against on the intermediate process tray 1330 (see FIG. 46).

A trailing end stopper 1335 shown in FIG. 49 includes a movable pressing member 1336 that presses the sheet in the vicinity of the trailing end stopper 1335. The pressing member 1336, after the sheets have abutted on the trailing end stopper 1335, presses the sheet bundle against on the intermediate process tray 1330, thereby flattening the sheets in a way that presses down the curled sheets (refer to Japanese Patent Application Laid-Open No. H11-130338).

The trailing end stopper 1332 illustrated in FIG. 47 takes a low-cost/space-saving structure with a small number of components, however, is unable to positively flatten the sheet by pressing the curl, since the curled sheet is held in an as-curled state by the grooves 1332b and the protruded strip members 1332c.

Further, such poor alignment property arose that a deviation occurs in the aligning position of the trailing end of the sheet due to recessed and protruded portions of the plurality of grooves 1332b and the plurality-of protruded strip members 1332c.

Further, when the widthwise alignment of the sheet is done by the first and second alignment members 1340, 1341 (see FIG. 46), it follows that the sheet moves in the widthwise direction in a state where the trailing end of each sheet enters the recessed portion of the groove 1332b and the recessed portion between the protruded strip members 1332c. Consequently, frictional resistance occurs between the sheet railing end and the recessed portion and retards the widthwise movement of the sheet, and the sheet can not be aligned widthwise exactly. Moreover, when the number of stacked sheets increases, an excessive load is applied to a motor for moving the first and second alignment members 1340, 1341 due to the frictional resistance, which is a cause for deteriorating the widthwise alignment property.

The trailing end stopper 1333 shown in FIG. 48 has a simple structure including the elastic film 1334 and is capable of enhancing the alignment property of the trailing end of the sheet by pressing down the curled sheet. The elastic film 1334 has elasticity, and hence, when the number of the stacked sheets increases, the pressing force rises when the sheet enters. Conversely, if set so that the pressing force of the elastic film 1334 becomes proper when the number of the stacked sheets increases, the elastic film 1334 lacks the pressing force when the number of the stacked sheets decreases. Therefore, a relationship between the pressing force when the sheet enters and the pullback force of the knurled belt 1608 gets unstable.

For example, as shown in FIG. 50A, if the pressing force by the elastic film 1334 becomes larger than the pullback force of the knurled belt 1608 when the number of the stacked sheets rises, an upper sheet Pa is unable to reach the trailing end stopper 1333, and the alignment property of the sheet trailing end can not be enhanced. Further, as illustrated in FIG. 50B, when the number of the stacked sheets decreases, the pressing force by the elastic film 1334 becomes smaller than the pullback force of the knurled belt 1608, and almost no pressing force acts on the sheet. Hence, the sheet Pa might be pushed up and buckled along the abutting support surface 1333a. It is considered for preventing the buckling to increase the elastic force of the elastic film 1334. If the elastic force is increased, however, it follows that the phenomenon illustrated in FIG. 50A occurs also when the number of the stacked sheets decreases. Therefore, such a problem arises that a pullback optimal area depicted in a hatching portion in FIG. 51 is narrowed. Moreover, the buckling property and the pull back resistance change on a sheet-by-sheet basis depending on surface resistance based on a sheet material and on a difference in thickness, and hence it is highly difficult to have configurations flexible to various types of sheets.

Further, in the trailing end stopper 1335 shown in FIG. 49, the pressing member 1336 stands by in positions designated by Al, A2, A3 corresponding to a sheet stacking height in the vicinity of the trailing end stopper 1335 and descends, thus pressing the sheet P. Therefore, the pressing member 1336 stands by in any one of these positions, and, when a gap between the uppermost sheet and an undersurface 1336a of the pressing member 1336 gets narrowed due to the increase in the number of the stacked sheets, the largely curled sheet is hard to enter this gap and might be jammed therein.

Moreover, the pressing member 1336 is constructed to move up and down perpendicularly to the sheet in the vicinity of the trailing end stopper 1335. Hence, in a view of the trailing end stopper as viewed from the front surface thereof in FIG. 49, it is required that a position of the stapler 1301 (see FIG. 46) and a position of the pressing member 1336 be deviated in the right-and-left directions in FIG. 49. Accordingly, in order for the pressing member 1336 to press the most effective and closest portion to the trailing end stopper, the stapler 1301 must be retreated backward (on the right side in FIG. 49) not to interfere with the pressing member 1336 when the pressing member 1336 performs pressing or must be provided outside the stapling positions of the stapler in the direction perpendicular to the sheet surface in FIG. 49.

Moreover, the pressing member 1336 shown in FIG. 49, if scheming to press the entire sheet widthwise area, is upsized in the retreat configuration described above and is therefore often disposed at a central portion serving as a non-stapling area, wherein the pressing member 1336 is unable to press the both end portions of the sheet which correspond to the stapling positions, and there is a case of causing a decline of the alignment property about the both side ends of the trailing end of the sheet.

Further, when in a two-point stapling mode, the stapler passes through the central portion of the trailing end of the sheet and moves to the stapling positions on a deep side. Hence, if the pressing member 1336 is disposed at the central portion, after temporarily retreating backward (on the right side in FIG. 49), the stapler moves to a position that is not overlapped as viewed from the front surface and further moves on the deep side. Moreover, the operation is also the same when moving to an anterior side from the deep side. Therefore, the stapler moving mechanism is required to enable the stapler to move in biaxial (X-axis, Y-axis) directions, and consequently the structure gets complicated. Moreover, the stapler moves in the biaxial directions, so that staple processing time elongates. Still further, standby time of the image forming apparatus increases corresponding to this elongated processing time, and productivity for forming the images decreases. It should be noted that the sheet stacking apparatus illustrated in FIG. 49 configures, together with the stapler 1301, a sheet processing apparatus.

As discussed above, the conventional sheet stacking apparatus can not press the sheet bundle by the substantially constant pressing force irrespective of the sheet stacking height. The conventional sheet stacking apparatus can not restrain especially the curled sheet from floating.

Yet further, the sheet processing apparatus has such a problem that processing operation time is long in terms of a layout of the pressing member and the stapler of the sheet stacking apparatus.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sheet stacking apparatus capable of pressing a sheet bundle by substantially constant pressuring force regardless of a sheet stacking height.

It is another object of the present invention to provide a sheet processing apparatus capable of reducing the sheet processing time by including the sheet stacking apparatus capable of surely processing the sheet bundle.

It is still another object of the present invention to provide a sheet processing apparatus that improves a sheet stacking property and a sheet alignment property of all types of sheets ranging from a thin sheet to a thick sheet without depending on thickness of the sheet by including the sheet stacking apparatus capable of surely processing the sheet bundle.

It is yet another object of the present invention to provide a sheet processing apparatus that improves the sheet stacking property and the sheet alignment property without depending on a curling direction and a size of the sheet by including the sheet stacking apparatus capable of surely processing the sheet bundle.

It is a further object of the present invention to provide an image forming apparatus that improves productivity of image formed sheets by including the sheet stacking apparatus capable of surely processing the sheet bundle.

To accomplish the above objects, a sheet stacking apparatus according to the present invention comprises a sheet stacking portion stacked with sheets, a sheet pressing member movable upward from a pressing position in which to press the sheets on the sheet stacking portion, a regulating member regulating the upward movement of the sheet pressing member, and an adjusting mechanism changing the regulating position of the sheet pressing member by the regulating member in accordance with a sheet stacking height of the sheets stacked on the sheet stacking portion, wherein the adjusting mechanism keeps substantially constant a distance to the regulating position from the pressing position of the sheet pressing member irrespective of the sheet stacking height of the sheets stacked on the sheet stacking portion.

The sheet stacking apparatus according to the present invention further comprises a stopper receiving and stopping trailing ends of the sheets stacked on the sheet stacking portion, and a sheet conveying guide provided on the side opposite to the stopper with the sheet pressing member being interposed therebetween and guiding the sheets to the stopper, wherein a distance between the sheet conveying guide and a sheet stacking surface of the sheet stacking portion is changed in linkage with a change of the regulating position of the sheet pressing member.

The sheet stacking apparatus according to the present invention further comprises a stopper receiving and stopping trailing ends of the sheets stacked on the sheet stacking portion, and a sheet conveying guide provided on the side opposite to the stopper with the sheet pressing member being interposed therebetween and guiding the sheets to the stopper, wherein a distance between the sheet conveying guide and a sheet stacking surface of the sheet stacking portion is changed in linkage with a change of the regulating position.

The sheet stacking apparatus according to the present invention further comprises a biasing member biasing the regulating member to the regulating position of the sheet pressing member, wherein the sheet pressing member can move the regulating member more upward than the regulating position, resisting the biasing member.

To accomplish the above objects, a sheet processing apparatus according to the present invention comprises a sheet stacking apparatus stacked with sheets and a binding unit binding upstream-side end portions, in a sheet delivery direction, of the sheets stacked in the sheet stacking portion of the sheet stacking apparatus, wherein the sheet stacking apparatus is any one of the sheet stacking apparatuses described above.

In the sheet stacking apparatus according to the present invention, a moving area of the sheet pressing member of the sheet stacking apparatus is set in a position that does not interfere with the binding unit.

In the sheet stacking apparatus according to the present invention, the binding unit is capable of adjusting a position in a direction intersecting the sheet delivery direction.

To accomplish the above objects, an image forming apparatus according to the present invention comprises an image forming portion forming an image on a sheet and a sheet stacking apparatus stacked with the sheets formed with the images by the image forming portion, wherein the sheet stacking apparatus is any one of the sheet stacking apparatuses described above.

To accomplish the above objects, an image forming apparatus according to the present invention comprises an image forming portion forming an image on a sheet and a sheet processing apparatus executing processing on the sheets formed with the images by the image forming portion stage, wherein the sheet processing apparatus is any one of the sheet processing apparatuses described above.

In the sheet stacking apparatus according to the present invention, the adjusting mechanism can keep substantially constant the distance from the pressing position of the sheet pressing member to the regulating position irrespective of the sheet stacking height of the sheets stacked on the sheet stacking portion. Therefore, in the sheet stacking apparatus, the sheet pressing member can press the sheet bundle by the substantially constant pressing force irrespective of the sheet stacking height.

In the sheet stacking apparatus according to the present invention, in combination with the sheet pressing member, the sheet alignment property with respect to the stopper can be enhanced by keeping substantially constant the distance between the sheet conveying guide and the sheet uppermost surface on the sheet stacking portion irrespective of the sheet height on the sheet stacking portion.

To be specific, the sheet stacking apparatus according to the present invention is configured so that for example, as shown in FIG. 44A, even if the sheet with its trailing end abutting on the stopper is upwardly curled, the sheet pressing member temporarily escapes upward, after receiving the sheet between the sheet pressing member and the sheet stacking portion, then descends and presses the sheet. Therefore, the sheet stacking apparatus according to the present invention is capable of enhancing the sheet alignment property even if the sheet is upwardly curled.

Further, the sheet stacking apparatus according to the present invention is configured so that for instance, as illustrated in FIG. 44B, even if the sheet with its trailing end abutting on the stopper is downwardly curled, in a position where the sheet conveying guide presses a vertex portion (a swollen portion) of a middle portion of the downward-curled sheet, the sheet abuts on the stopper while flattening the curled sheet. Therefore, the sheet stacking apparatus according to the present invention can enhance the sheet alignment property even if the sheet is downwardly curled.

Moreover, the sheet stacking apparatus is configured so that in the case of the sheet having a curling amount that is larger than an upward escapement (clearance) amount of the sheet pressing member, the sheet pressing member is regulated from moving upward and, after receiving the sheet being between the sheet pressing member and the sheet stacking portion in a way that restrains the sheet from being curled, presses the sheet. Hence, the sheet stacking apparatus according to the present invention can enhance the sheet alignment property even if the sheet has a large curling amount.

In the sheet stacking apparatus according to the present invention, the sheet pressing member is movable together with the regulating member more upward than the regulating position, resisting the biasing member. Therefore, the curl of the sheet having the large curling amount, since the sheet pressing member is moved more upward than the regulating position of the sheet pressing member, resisting the biasing member, is mended by resilience of the biasing member. Hence, the sheet stacking apparatus according to the present invention can enhance the sheet alignment property even if the sheet has the large curling amount.

The sheet processing apparatus according to the present invention includes the sheet stacking apparatus that enhances the sheet alignment property and can therefore execute the process of precisely binding the sheet bundle by the binding unit.

The image forming apparatus according to the present invention includes the sheet stacking apparatus that enhances the sheet alignment property and can therefore increase the productivity of forming the images on the sheets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an image forming apparatus in an embodiment of the present invention as viewed in a sheet delivery direction;

FIG. 2 is a plan schematic view of a side stitch processing apparatus;

FIG. 3 is a front view of the side stitch processing apparatus;

FIG. 4 is a schematic plan view of a mechanism for moving a stapler;

FIG. 5 is a plan view showing an intermediate process tray and an alignment member moving mechanism in the side stitch processing apparatus;

FIG. 6 is a plan view showing a sheet stacking apparatus in a first embodiment of the present invention;

FIG. 7A is a perspective view showing an external configuration of the sheet stacking apparatus in the first embodiment; FIG. 7B is a front view thereof;

FIG. 8 is a plan view of the sheet stacking apparatus;

FIG. 9A a plan view of a positional relationship between a stapler and a trailing end stopper, showing a case of stapling corners of a sheet bundle; FIG. 9B is a plan view showing a case of stapling a trailing end of the sheet bundle;

FIG. 10 is a perspective view showing a layout relationship between the trailing end stopper and a trailing end level;

FIG. 11 is an explanatory view showing an operation when in a non-sort mode in a finisher;

FIG. 12 is an explanatory view showing an operation of delivering the sheet to the intermediate process tray when in a staple mode in the finisher;

FIG. 13 is an explanatory view showing an operation after delivering the sheet to the intermediate process tray when in a staple sort mode in the finisher;

FIG. 14 is an explanatory view showing an operation pf delivering the sheet bundle from the intermediate process tray when in the staple sort mode in the finisher;

FIG. 15 is an explanatory view showing a superposed state of the sheets in a buffer roller of the finisher;

FIG. 16 is an explanatory view showing the superposed state of the sheets in the finisher;

FIG. 17 is an explanatory view showing an operation of delivering the superposed sheets to the intermediate process tray in the finisher;

FIG. 18 is an explanatory view showing an operation when the superposed sheets are stacked on the intermediate process tray in the finisher;

FIG. 19 is a view showing a deviation between the sheets;

FIG. 20 is a view showing a state enabling the fourth sheet to be received;

FIG. 21 is an explanatory view showing an operation of delivering the sheets to the intermediate process tray when in the sort mode of the finisher;

FIG. 22 is a view showing a state where the sheets are stacked on the intermediate process tray when in the sort mode of the finisher;

FIG. 23 is a view when the sheet stacks are offset-stacked;

FIG. 24 is a plan view of the intermediate process tray, showing positions of first and second alignment members in a two-point stapling mode of the stapler;

FIG. 25 is a plan view of the intermediate process tray when the sheets are aligned widthwise by the first and second alignment members;

FIG. 26 is a plan view of the intermediate process tray when the sheets are aligned widthwise by the first and second alignment members in the case of offset-stacking;

FIG. 27 is an explanatory view of an operation till ten sheets are stacked in the sheet stacking apparatus in the first embodiment of the present invention;

FIG. 28 is an explanatory view of an operation till twenty sheets are stacked in the sheet stacking apparatus in FIG. 27;

FIG. 29 is an explanatory view of an operation till thirty sheets are stacked in the sheet stacking apparatus in FIG. 27;

FIG. 30 is an explanatory view of an operation till ninety sheets are stacked in the sheet stacking apparatus in FIG. 27;

FIG. 31A is an explanatory view of the operation till the ten sheets are attacked in the sheet stacking apparatus in a second embodiment of the present invention, showing a case where the trailing end of the sheet is curled upward; FIG. 31B is an explanatory view showing a case where the middle portion of the sheet is curled upward;

FIG. 32 is an explanatory view of an operation till twenty sheets are stacked in the sheet stacking apparatus in FIG. 31;

FIG. 33 is an explanatory view of an operation till thirty sheets are stacked in the sheet stacking apparatus in FIG. 31;

FIG. 34 is an explanatory view of an operation when ninety sheets are stacked in the sheet stacking apparatus in FIG. 31;

FIG. 35A is a perspective view showing an external configuration of the sheet stacking apparatus in a third embodiment; FIG. 35B is a front view thereof;

FIG. 36 is an explanatory view of an operation till ten sheets are stacked in the sheet stacking apparatus in the third embodiment of the present invention;

FIG. 37 is an explanatory view of an operation when ten sheets are stacked in the sheet stacking apparatus in FIG. 36;

FIG. 38 is an explanatory view of an operation when twenty sheets are stacked in the sheet stacking apparatus in FIG. 36;

FIG. 39 is an explanatory view of an operation when ninety sheets are stacked in the sheet stacking apparatus in FIG. 36;

FIG. 40 is an explanatory view of an operation when ten sheets are stacked in the sheet stacking apparatus in a fourth embodiment of the present invention;

FIG. 41 is an explanatory view of an operation when ten sheets are stacked in the sheet stacking apparatus in FIG. 40;

FIG. 42 is a graph showing a relationship between the number of stacked sheets, a position of a trailing end lever and a rotational angle of a lever stopper;

FIG. 43 is a table showing a count value per sheet that is set according to a thickness of the sheet, and a displacement value of the lever stopper;

FIG. 44A is an explanatory view representing an effect of the embodiment of the present invention, showing a case where the trailing end of the sheet is curled upward; FIG. 44B is an explanatory view showing a case where the trailing end of the sheet is curled downward;

FIG. 45 is a sectional view showing a conventional finisher;

FIG. 46 is a schematic front view of the sheet processing apparatus;

FIG. 47 is a perspective view of an external configuration of a conventional trailing end stopper;

FIG. 48 is a perspective view of the external configuration of the conventional trailing end stopper;

FIG. 49 is a front view of a conventional sheet processing apparatus;

FIGS. 50A and 50B are front views showing a trouble in the trailing end stopper of the conventional sheet processing apparatus;

FIG. 51 is a view showing a pullback area in the conventional sheet processing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A sheet stacking apparatus, a sheet processing apparatus and an image forming apparatus incorporating this sheet apparatus into an apparatus body in embodiments of the present invention, will hereinafter be described with reference to the drawings. It should be noted that numerical values taken in the description are reference numerical values but do not limit the present invention. Further, the components marked with the same reference numerals and symbols have the same configurations, and repetitive explanations thereof shall properly be omitted.

(Image Forming Apparatus)

A black-and-white/color copying machine 110 defined as an image forming apparatus will be explained with reference to FIG. 1. The black-and-white/color copying machine 110 includes a main body 100 of the black-and-white/color copying machine (which will hereinafter simply be termed [the copying machine]) and a finisher 600. The finisher 600 is connected to the main body 100 of the copying machine, and has a saddle stitch processing device 200, a side stitch processing device 300 defined as the sheet processing apparatus, and a sheet-bundle spine processing device 400. The saddle stitch processing device 200 and the sheet-bundle spine processing device 400 configure a saddle stitch bookbinding processing apparatus 700. Therefore, a sheet discharged from the copying machine main body 100 can be processed online. Note that the finisher 600 might be employed as an option. Hence, the copying machine main body 100 can be used as a single unit. Further, the finisher 600 and the main body 100 may be integrally configured (one united body).

Photosensitive drums 101a to 101d serving as image forming portions respectively for yellow, magenta, cyan and black, transfer four-color toner images onto the sheets supplied from cassettes 107a to 107d within the main body 100, and the image-transferred sheets are conveyed to a fixing unit 11 in which to fix the toner images and then discharged outside the copying machine.

(Finisher)

Referring to FIG. 1, the sheets discharged from the main body 100 of the copying machine are conveyed to the finisher 600. The finisher 600 executes a variety of sheet post-processes such as a process (a alignment process) of sequentially taking in the sheets discharged from the main body 100 of the copying machine and aligning the plurality of taken-in sheets into one bundle of sheets, a stapling process of stapling a rear edge (an upstream-side edge in a sheet conveying direction) of the sheet bundle by use of a stapler 301, a punching process of punching holes in the vicinity of the rear edge of the taken-in sheets, a sorting process, a non-sorting process, a folding process of folding the sheet bundle and a bookbinding process. The finisher 600 in the first embodiment is capable of executing at least the alignment process.

The finisher 600 has an entrance roller pair 602 for guiding the sheets discharged from the main body 100 of the copying machine 110 to the interior. A changeover flapper 601 for selectively guiding the sheets to a side stitch bookbinding path X or a saddle stitch bookbinding path Y is provided on a downstream side of this entrance roller pair 602.

The sheets guided to the side stitch bookbinding path X are fed toward a buffer roller 605 via a conveying roller pair 603. The conveying roller pair 603 and the buffer roller 605 are capable of rotating in forward and reversed directions. A punch unit 650 is provided between the conveying roller pair 603 and the buffer roller 605. The punch unit 650 operates as the necessity may arise and punches the holes in the vicinity of the rear edge of the conveyed sheet.

The buffer roller 605 is a roller wound with a predetermined number of stacked sheets fed to an outer periphery of this buffer roller 605. The sheets fed to the buffer roller 605 are stacked on a sample tray 621 or stacked on an intermediate processing tray (which will hereinafter be simply referred to as a processing tray) 330 within the side stitch processing device 300 through a changeover flapper 611 disposed downstream.

The sheets stacked as a sheet bundle on the process tray 330, after being subjected to the alignment process, the stapling process, etc according to the necessity, are delivered onto a stack tray 622 by delivery rollers 380a, 380b. The stapling process of stapling the sheet bundle stacked on the process tray 330 involves using the stapler 301. The stapler 301 staples portions corresponding to an angular portion (corner) and a rear portion of the sheet bundle. Note that the side stitch processing device 300 will be explained later on.

On the other hand, the sheet guided by the changeover flapper 601 is accommodated in an accommodation guide 220 by a conveying roller pair 213, and is further conveyed till the front edge of the sheet abuts on an unillustrated elevation type sheet positioning member. Further, two pairs of staplers 218 (only one stapler is illustrated because of their being viewed in superposition) are provided in the middle of the accommodation guide 220. The stapler 218 staples the center of the sheet bundle in cooperation with an anvil 219 facing the stapler 218.

A pair of folding rollers 226a, 226b is provided downstream the staplers 218. A protruding member 225 is provided in a position that faces the folding roller pair 226. A front edge of the protruding member 225 faces a nip of the folding roller pair 226. The pair of folding rollers 226a, 226b and the protruding member 225 configure a sheet bundle folding apparatus 201 for folding the sheet bundle.

When folding the sheet bundle stapled by the stapler 218, the unillustrated sheet positioning member descends so that a stapling position of the sheet bundle comes to face a central position (nip) of the folding roller pair 226 after finishing the stapling process. Next, the protruding member 225 protrudes toward the sheet bundle, whereby the sheet bundle is pushed in between the folding roller pair 226 (in between the nip), then conveyed while being nipped by the folding roller pair 226 and is folded by two. Accordingly, the sheet bundle becomes a saddle-stitched booklet. It is to be noted that the sheet bundle might also be folded without being saddle-stitched.

The sheet bundle, which has been saddle-stitched in the booklet, is conveyed as it is to the sheet-bundle spine processing device 400 by the protruding member 225 and by a bookbinding bundle conveying belt 401. The sheet-bundle spine processing device 400 neatly sets the sheet bundle so that the crease thereof takes an exactly folded shape by pressing a folding portion of the rear surface of the sheet bundle from both of the surfaces, and flattens the rear portion of the rear surface folded portion. Finally, the sheet bundle is delivered to and thus placed in the folding sheet bundle stack tray 480.

Next, the side stitch processing device 300 serving as the sheet processing apparatus in the first embodiment of the present invention will be described.

A stapler 301 serving as a binding unit and components peripheral to this stapler 301 will be explained with reference to FIGS. 2 and 3.

The stapler 301 is fixed onto a slide support anvil 303. Rolling rollers 304, 305 are provided under the slide support anvil 303. The slide support anvil 303 is guided by the rollers 304, 305 and a guide rail groove 307 on a stapler moving base 306, thus moving along the rear edges of the sheets stacked in the intermediate process tray 330 (as indicated in a direction of an arrowhead Y).

The stapler 301 is, as shown in FIG. 2, kept in a posture inclined at a predetermined angle a at the corner of the sheets stacked in the intermediate process tray 330. The inclined angle .alpha. is set at approximately 30 degrees but can be varied by changing the shape of the guide rail groove 307. Further, the stapler moving base 306 is provided with an unillustrated position sensor for detecting a home position of the stapler 301. Normally, the stapler 301 stands by in the home position designated by a symbol A, which is anterior to the apparatus (as viewed from a user).

A moving mechanism for moving the stapler 301 in the Y-direction will be described with reference to FIG. 4.

A belt support portion 311 is provided under the slide support anvil 303. The belt support portion 311 is attached to a moving belt 308 extending in the peripheral direction between belt pulleys 309a, 309b disposed at side end portions of a moving area for the stapler 301. Further, a drive motor 310 connected to the belt pulley 309a is disposed under the slide support anvil 303. Accordingly, the stapler 301 is supported on the slide support anvil 303 and is therefore reciprocated together with the slide support anvil 303 in the Y-directions while being tugged by the moving belt 308 of which a circulating direction is changed depending on forward and reversed rotations of the drive motor 310.

A processing tray unit will be explained with reference to FIGS. 1 and 3.

The processing tray unit is constructed of the intermediate process tray 330, the conveying guide 312, a trailing end stopper 331, first and second alignment portions 340, 341, a rocking arm (guide) 350, a pull-in paddle 360, a sheet-bundle delivery roller pair 380, a trailing end lever 332 and a lever stopper 333.

The intermediate process tray 330 is obliquely disposed with its downstream side (the left side in FIG. 3) directed upward and with its upstream side directed downward (the right side in FIG. 3) with respect to the sheet bundle delivery direction. The trailing end stopper 331 is disposed at the lower end portion, defined as the upstream side, of the intermediate process tray 330. The pull-in paddle 360 and the first and second alignment portions 340, 341 are disposed at the middle portion of the intermediate process tray 330. Moreover, the pull-in paddle 360, the sheet-bundle delivery roller pair 380 and the rocking arm 350, which will be described later on, are disposed at the upper end portion, defined as the downstream side, of the intermediate process tray 330, specifically substantially in an upper area portion of the of the unit configuration.

Then, a sheet P delivered from the first delivery roller pair 320 (see FIG. 3) slides on a stacking surface 330c of the intermediate process tray 330 or on the sheet stacked on the intermediate process tray 330 till a trailing end (the upstream end in the delivery direction) of the sheet P abuts on an abutting support surface 331a of the trailing end stopper 331 by dint of the inclination of the intermediate process tray 330 and by action of the pull-in paddle 360 that will be described hereafter.

Further, one lower delivery roller 380a configuring the sheet-bundle delivery roller pair 380 is disposed at the end portion of the intermediate process tray 330 on the downstream side, and the other upper delivery roller 380b thereof is disposed at the tip portion of the lower surface of the rocking arm 350. The upper delivery roller 380b gets apart from and gets close to the lower delivery roller 380a. The pair of delivery rollers 380a, 380b is rotated in the forward and reversed direction by a drive motor M380.

The first and second alignment portions 340, 341 and the components peripheral thereto are explained with reference to FIG. 5.

The first and second alignment portions 340, 341 have a couple of first and second side stoppers 340a, 341a that align the both side ends (which are the edges in the sheet delivery direction) of the sheets stacked in the intermediate process tray 330. Further, the first and second alignment portions 340, 341 have a moving mechanism 345 for moving the sheet bundle of which the trailing end side and the lateral end sides are aligned in the crosswise direction of the sheet with respect to the intermediate process tray 330.

The first and second side stoppers 340a, 341a are disposed in a face-to-face relationship independently at the lower portion and the upper portion (which correspond to the both side ends of the sheet P) in FIG. 5 above the intermediate process tray 330. The first and second side stoppers 340a, 341a include alignment surfaces 340aa, 341aa that press the sheet side end perpendicularly against the surface of the intermediate process tray 330, and rack-and-gear portions 340b, 341b that sustain the undersurface of the sheet. The rack-and-gear portions 340b, 341b are respectively disposed on the lower surface side of the intermediate process tray 330 through a couple of guide grooves 330a, 330b parallel with each other. The guide grooves 330a, 330b extend through the intermediate process tray 330 in the widthwise direction of the sheet P.

The moving mechanism 345 has a first rack-and-gear portion 340b linked to the first side stopper 340a, a pinion gear 343, the second rack-and-gear portion 341b linked to the second side stopper 341a, a pinion gear 344, and first and second drive motors M340, M341 capable of each independently driving these first and second rack-and-gear portions 340b, 341b and the pinion gears 343, 344.

Then, the first and second rack-and-gear portions 340b, 341b mesh with the pinion gears 343, 344, whereby the first and second alignment portions 340, 341 can move independently in the widthwise direction of the sheet P with respect to the intermediate process tray 330. Namely, the alignment surfaces 340aa, 341aa are disposed in the face-to-face relationship on the upper surface side of the intermediate process tray 330, and the respective rack-and-gear portions 340b, 341b are so assembled as to be movable in the alignment direction on the lower surface side of the intermediate process tray 330.

Then, the individual pinion gears 343, 344 driven so as to be rotatable in the forward and reversed directions by the respective drive motors M340, M341 mesh with the rack-and-gear portions 340b, 341b. The first and second side stoppers 340a, 341a are moved in the alignment direction by the drive motors M340, M341. Herein, unillustrated position-sensors for detecting the home position are disposed at the first and second side stoppers 340a, 341a. With the position sensors, in a normal case, the first side stopper 340a stands by in the home position set at the lower end portion, while the second side stopper 341a stands by in the home position set at the upper end portion.

The rocking arm 350 will be explained with reference to FIG. 3.

The rocking arm 350 rotates in the up-and-down directions while being supported on a support shaft 351. The rocking arm 350 is provided with the upper delivery roller 380b abutting on the lower delivery roller 380a of the sheet-bundle delivery roller pair 380. The sheet-bundle delivery roller pair 380 is disposed on the downstream side in the sheet delivery direction from the support shaft 351. When a position in which the upper delivery roller 380b abuts on the lower delivery roller 380a is the home position, the rocking arm 350 is detected by the unillustrated position sensor.

Then, the rocking arm 350, normally when each individual sheet P is delivered onto the intermediate process tray 330, rotates upward, and the upper delivery roller 380b comes to an open state away from the lower delivery roller 380a. As a result, the sheet-bundle delivery roller pair 380 hinders neither the delivery operation of the sheet P to the intermediate process tray 330 by the pull-in paddle 360 that will be described later on nor a widthwise alignment operation by the first and second alignment portions 340, 341.

In such a structure, when the sheet is delivered onto the intermediate process tray 330, the rocking arm 350 rotates upward and separates the upper delivery roller 380b from the lower delivery roller 380a, thereby setting the sheet-bundle deliver