Sheet stacking device and sheet processing apparatus

Abstract

In a sheet stacking device including a sheet stacking section, a holding member for holding sheets on the sheet stacking section, and a driving device for moving the holding member to the holding position and retreating position, the holding of the holding member which retreats when a sheet is being fed in and which holds the sheet when the sheet has reached, is canceled on the basis of approaching information of a succeeding sheet.

Description

This application is based on Japanese Patent Application No. 2006-233323 filed on Aug. 30, 2006 in Japanese Patent Office, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a sheet stacking device and a sheet processing apparatus and more particularly to an art for suppressing uplift of sheets of paper at the sheet stacking step.

In a copier and a printing device, sheets of paper with images formed are stacked on a stacking device, and when conducting post-processing to the stacked sheets of paper or stacking a large amount of sheets of paper, a sheet holding device for suppressing uplift of sheets of paper is often used.

In Patent Document 1, a sheet stacking device for suppressing uplift of sheets of paper and aligning sheets of paper by using a switching gate for switching between a holding position for holding sheets of paper and a guiding position for guiding entry of sheets of paper and by using a moving aligning member for pressing the rear ends of sheets of paper is proposed.

In Patent Document 1, the switching gate is set at the position for guiding entry of sheets of paper at the sheet entry stage, and is set at the sheet holding position at the stage of arrival of sheets of paper at the sheet stacking section, and then is set at the position for guiding at the sheet entry stage after finishing of alignment by the aligning member, that is, at the position for guiding entry of sheets of paper.

When continuously conveying sheets of paper and stacking many sheets of paper on the sheet stacking section, the aforementioned step is executed repeatedly.

In the sheet stacking device in Patent Document 1, the sheet holding is canceled when the alignment is finished, so that the elapsed time becomes long until the next sheet reaches the sheet stacking section and the holding member starts to hold the sheet of paper, thus the sheet of paper may be uplifted.

Therefore, a problem arises that a sheet bundle becomes thick and some troubles occur in the post processing for the sheet bundle and the quality of a booklet prepared by the bookbinding process is deteriorated.

Further, due to uplift of sheets of paper, satisfactory alignment may not be realized.

Patent Document 1: Unexamined Japanese Patent Application Publication No. 2001-322760

SUMMARY

One aspect of the present invention is as indicated below.

1. A sheet stacking device including a sheet stacking section, a holding member for holding sheets on the sheet stacking section, and a driving device for moving the holding member to the holding position and retreating position, wherein:

the sheet stacking device further has a control device for controlling the driving device, and the control device sets the holding member at the retreating position at the stage of conveying sheets to the sheet stacking section, sets the holding member at the holding position at the stage of arrival of sheets at the sheet stacking section, and furthermore, on the basis of information of approaching of a succeeding sheet to the sheet stacking section, the control device controls to set the holding member at the retreating position.

2. A sheet processing apparatus including a sheet stacking device of above item 1 and a processing device for processing sheets stacked thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing the whole image forming system relating to the embodiment of the present invention.

FIG. 2 is a drawing showing the constitution of a reverse section 40 and a sheet stacking section 50 of a bookbinding device B.

FIG. 3 is a drawing showing the drive control system of a holding member 510.

FIG. 4 is a flow chart of drive control of the holding member 510.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be explained referring to a preferred embodiment shown in the drawings. However this invention is not limited to the preferred embodiment.

FIG. 1 is a view of the entire image forming system relating to a preferred embodiment of the present invention.

The image forming system includes image forming apparatus A and bookbinding apparatus B.

Image forming apparatus A electrophotographically forms images on sheets and is equipped with image forming section A1, document feeder A2, and image reader A3.

Image forming section A1 has charging unit 2, exposing unit 3, developing unit 4, transfer unit 5A, separating unit 5B, and cleaning unit 6 around drum-shaped photoreceptor 1. These electrophotographic units perform charging, exposure, development, and transferring in order to form a toner image on the surface of photoreceptor 1 and an image on sheet S1.

Sheets S1 are stored in three sheet supply trays 7A, and delivered one by one from sheet supply trays 7A to transfer unit 5A. Sheet S1 receives a toner image there from photoreceptor 1 by transfer unit 5A.

Sheet S1 with a toner image transferred on it is delivered through fixing unit 8 and fixed there. Fixed sheet S1 is ejected by ejection rollers 7C or delivered to sheet re-feeding path 7E.

For face-down sheet ejection of one-side printing, face-up sheet ejection of one-side printing or front side image forming of both-side image forming, switching gate 7D switches to guide sheet S1. That is, when sheet S1 is ejected with its face up, switching gate 7D delivers sheet S1 straight. When sheet S1 is ejected with its face down or when sheet S1 has images on both surfaces, switching gate 7D delivers sheet S1 downward.

When sheet S1 is ejected with its face down, sheet S1 is guided downward, switched back to move up, and ejected by ejection rollers 7C.

In the both-side image forming, sheet S1 is guided downward, turned upside down with a switchback, delivered again to a transfer section which includes transfer unit 5A through the sheet re-feeding path 7E, and receives another image on the other surface of the sheet.

Document feeder A2 feeds documents one by one to a reading position. Image reader A3 reads the image on a document which is fed from document feeder A2 or placed on document table 9 and generates an image signal.

Bookbinding apparatus B is an apparatus which bundles plural sheets sent from image forming apparatus A into a bundle of sheets, bonds a cover sheet to the sheet bundle to form a booklet. On the following explanation, the sheet on which an image is formed in image forming apparatus A and which is fed to bookbinding apparatus B is called sheet S1, the cover sheet is called cover sheet S2 and the booklet wherein sheets are bonded with the cover sheet is called booklet S3.

The bookbinding apparatus B described in the figure is an example of sheet processing apparatuses and the sheet processing apparatuses include various types of sheet processing apparatuses such as a processing apparatus for stapling a bundle of sheets with staples and a tape-binder which binds a bundle of sheets with a tape.

Bookbinding apparatus B is equipped with reverse section 40, sheet stacking section 50, adhesive coating section 60, a bonding device to bond a cover sheet to a bundle of sheets (composed of cover sheet supporting section 90), further with conveying section 10, sheet ejection tray 20, cover sheet storage section 80 and booklet ejecting section 100.

Sheet S1 ejected from image forming apparatus A is delivered to switching gate 11 in conveying section 10. The switching gate 11 changes sheet paths to send sheet S1 to sheet ejection tray 20 via ejection path 12 or to reverse section 40. In the non-bookbinding mode, sheets S1 are ejected to sheet ejection tray 20.

In the bookbinding mode, sheet S1 is sent to reverse section 40 via conveying path 13, switched back by reverse section 40, and delivered to sheet stacking section 50. A preset number of sheets S1 are stacked in sheet stacking section 50 and when the preset number of sheets S1 have been stacked, sheet stacking section 50 is rotated and the bundle of sheets S1 is held almost vertically.

Adhesive coating section 60 applies adhesive to the bottom surface of bundle of sheets S1 which is held vertically by sheet stacking section 50.

Cover sheet S2 is brought into contact with the bundle of sheets S1 which has been coated with adhesive to be bonded to it by means of the bonding device.

Booklet S3 made by bonding cover sheet S2 to the bundle of sheet S1 is ejected to booklet ejecting section 100.

In the bookbinding device B, a sensor SE1 for detecting sheets S1 in the sheet entrance section, a sensor SE2 for detecting the sheets S1 in the sheet ejection section to the sheet reverse section 40, a sensor SE3 for detecting the sheets S1 in the feed-in section (the neighborhood on the upstream side of the sheet receiving section) of the sheet stacking section 50, and a sensor SE4 on the bottom of the sheet stacking section 50 are installed.

On the basis of sheet detection signals of the sensors SE1 to SE4, sheet conveyance control and process control are executed in the bookbinding device B.

FIG. 2 is a drawing showing the constitution of the reverse section 40 and sheet stacking section 50 of the bookbinding device B.

The sheets S1 conveyed on a conveying path 13 are ejected by sheet ejection rollers 14 and moved up on an inclined reverse guide 402 via conveying rollers 401, and then the conveying rollers 401 invert the rotation and convey the sheets S1 downward.

Numeral 406 indicates conveying rollers for conveying the sheets S1 from the reverse section 40 to the sheet stacking section 50.

The sheets S1 conveyed downward are dropped and stacked on the sheet stacking section 50. The sheet stacking section 50 includes a support plate 502 and a receiver plate 506 and the sheets S1 which have moved down in the reverse section 40 are supported by the support plate 502 and receiver plate 506 in the inclined state.

The sheets S1 sequentially ejected from an image forming apparatus A are stacked on the sheet stacking section 50 and a sheet bundle SS is formed. The number of the sheets S1 composing the sheet bundle SS is set by the setting section (not illustrated) of the image forming apparatus A. Numeral 505 indicates an aligning plate for aligning the side edges of sheets.

Numeral 510 indicates a holding member for suppressing uplift of the sheets S1 conveyed into the sheet stacking section 50 and it is installed in the sheet feed-in section of the sheet stacking section 50. The holding member holds the sheets S1 conveyed into the sheet stacking section 50 at the solid line position and moves to the dotted line position, thereby retreats from the conveying path of the sheets S1 to the sheet stacking section 50, and enables entry of the sheets S1 into the sheet stacking section 50.

At the stage of completion of stacking the sheets S1 of the number of sheets composing the sheet bundle SS, a holding plate 503 operates and holds the bundle of the sheets S1.

The sheet stacking section 50 rotates around a shaft 501 while holding the bundle of the sheets S1 and changes the state of the bundle of the sheets S1 from the inclined state to the perpendicular state.

FIG. 3 is a drawing showing the drive control system of the holding member 510.

When a plunger 512 is pulled by turning on a solenoid 511, a shaft 510A to which the holding member 510 is fixed is rotated clockwise in FIG. 3, thus the holding member 510 is set at the holding position. When the solenoid 511 is turned off, the plunger 512 moves in the direction of the arrow to rotate the shaft 510A, and the holding member 510 retreats to the dotted line position shown in FIG. 2, thus the conveying path for conveying the sheets S1 to the sheet stacking section 50 is formed. Although the holding member 510 is composed of two pieces in the figure, it can be composed of one piece, of course. Therefore the singular name is generically used for the holding member 510 in this document.

At the stage of conveying the sheets S1 into the sheet stacking section 50, the holding member 510 is set at the dotted retreating position shown in FIG. 2, thus the sheet feed-in path into the sheet stacking section 50 is formed, and at the stage of having stored the sheets S1 in the sheet stacking section 50, the holding member 510 is set at the solid line position shown in FIG. 2 and holds the sheets S1.

Such drive control of the holding member 510 is executed by a control device 513. The drive control of the holding member 510 will be explained by referring to FIG. 4.

FIG. 4 is a flow chart of the drive control.

At STEP 1, existence of sheets in the sheet stacking section 50 is checked. STEP 1 is executed on the basis of a sheet detection signal of the sensor SE4 installed on the bottom of the sheet stacking section 50.

When there are some sheets S1 in the sheet stacking section 50, as explained later, the holding member 510 is set at the working position (YES at STEP 1), while there are no sheets S1 (NO at STEP 1), the solenoid 511 is off, and the holding member 510 is at the dotted line position, and the sheet feed-in path to the sheet stacking section 50 is formed (STEP 2).

By passing detection signal of a sheet rear end by the sensor SE3, conveying of sheets into the sheet stacking section 50 is detected (STEP 3), and the aligning member 505 is driven (STEP 4), and the solenoid 511 is operated, and the holding member 510 is rotated to the solid line position shown in FIG. 2 and is set at the sheet holding position. By doing this, uplift of the sheets S1 newly introduced into the sheet stacking section 50 is eliminated.

The number of sheets stacked in the sheet stacking section 50 is counted on the basis of the sheet detection signal of the sensor SE3 and at the stage of arrival of the counted value at the set number indicating the number of sheets S1 composing the sheet bundle SS (YES at STEP 6), the process goes to the bookbinding process at STEP 7.

When the counted value does not arrive at the set number of sheets (NO at STEP 6), at STEP 11, whether succeeding sheets are approaching the stacking section 50 or not is monitored. However when a stop signal is received at the previous stage (YES at STEP 8), the holding member 510 is set at the retreating position (STEP 9).

The stop signal at STEP 8 is a stop signal received by a control device CR mainly from the image forming apparatus A, and as a case that such a stop signal is sent, there are a case that the sheets S1 on the sheet supply tray 7A (shown in FIG. 1) of the image forming apparatus A have been all fed out and a case that a jam occurs in the image forming apparatus A. In addition, there are cases that a failure such as a jam occurs in the bookbinding device B and cover sheets S2 have been all fed out.

When the stop signal is received (YES at STEP 8), the holding member 510 is set at the retreating position (STEP 9). After waiting for and receiving a stop cancelling signal (STEP 10), the holding member 510 is set at the holding position (STEP 11).

When there is no stop signal at STEP 8 or after STEP 11, the holding member 510 is set at the holding position and in this state, whether or not the next sheet S1 is approaching the sheet stacking section is monitored (STEP 12).

The monitoring at STEP 12 is executed on the basis of the passing detection signal of the rear end of sheets S1 by the sensor SE2 installed on the upstream side of the reverse section 40. Namely, STEP 12 is a step for detecting approaching information of conveying the sheets S1 to the sheet stacking section 50 and for obtaining the approaching information, a detection signal of the sensor SE2 installed on the upstream side is used instead of the sensor SE3 installed in the neighborhood of the feed-in section of the sheet stacking section 50.

When approaching of sheets to the sheet stacking section 50 is detected, the process is returned to STEP.2, and the holding member 510 is set and retreated at the dotted line position shown in FIG. 2, and the sheet feed-in path to the sheet stacking section 50 is formed.

At the control step shown in FIG. 4, the sheets stored in the sheet stacking section 50 are held by the holding member 510. Uplift of the sheets is eliminated, and the sheets are continuously held immediately before the next sheet enters and at the stage of detection of approaching of the next sheet S1, the holding is canceled. Thus the sheets held once are prevented from uplifting, and a sheet bundle in a state in which the sheets and sheets are closely adhered to each other or a state close to this state is formed.

Therefore, the problem is solved that the quality of a booklet bound by conducting processing to the sheet bundle is deteriorated.

The approaching information of the sheets S1 to the sheet stacking section 50 is obtained from a sensor installed on the upstream side of the sheet stacking section 50, for example, SE2. However the approaching information can be obtained from a sensor other than SE2. For example, a detection signal of the sensor SE1 installed in the sheet entrance section of the bookbinding device B can be used. In this case, control is executed for canceling the holding of the holding member 510 after a lapse of a predetermined period of time after the sheet detection signal of the sensor SE1 comes.

According to the present invention, the holding of the sheet holding member is canceled on the basis of the sheet approaching information to the sheet stacking section, so that the sheet holding is continued immediately before arrival of the sheets at the sheet stacking section, and the period of time when the holding is cancelled is shortened. As a result, uplift of sheets in the sheet stacking section is prevented, and a sheet bundle composed of sheets closely adhered to each other is formed, and the post processing is performed smoothly, and the quality of output of the sheet processing apparatus such as a booklet prepared by processing the sheet bundle is improved.

Claims

1. A sheet stacking device comprising:

a sheet stacking section;

a holding member for holding a sheet on the sheet stacking section;

a driving device for moving the holding member between a holding position and a retreating position; and

a control device for controlling the driving device,

wherein the control device sets the holding member in the retreating position while a sheet is being conveyed to the sheet stacking section and sets the holding member in the holding position when the sheet has arrived at the sheet stacking section and then sets the holding member in the retreating position based on information of approaching of a subsequent sheet to the sheet stacking section.

2. The sheet stacking device of claim 1,

wherein the information of approaching is a sheet detection signal from a first sensor equipped in an upstream position of the sheet stacking section.

3. The sheet stacking device of claim 1,

wherein the control device controls to set the holding member in the holding position based on a sheet detection signal of a second sensor equipped in a position which is vicinity of a receiving section of the sheet stacking section and is upstream of the sheet stacking section.

4. The sheet stacking device of claim 3, further comprising:

a first sensor equipped in an upstream position of the sheet stacking section for transmitting a sheet detection signal which is the information of approaching; and

wherein the first sensor detects a sheet on an upstream side of the second sensor.

5. The sheet stacking device of claim 1,

wherein the control device controls to set the holding member from the holding position to the retreating position based on a stop signal for stopping the sheet stacking device and set the holding member in the holding position based on a stop cancelling signal.

6. A sheet processing apparatus comprising:

the sheet stacking device of claim 1; and

a processing device for applying processing to a sheet stacked thereon.