Sheet processing apparatus and image forming system which corrects a curl

A sheet processing apparatus including: a humidifier that humidifies a sheet; a curl correcting section that corrects a curl by applying mechanical bending force on a sheet; and a control section that causes humidification by the humidifier and curl correction by the curl correcting section to be possible for a prescribed sheet, and causes either one of humidification by the humidifier and curl correction by the curl correcting section to be possible for sheets other than the prescribed sheet.

RELATED APPLICATION

This application is based on Japanese Patent Application No. 2008-158901 filed with Japanese Patent Office on Jun. 18, 2008, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a sheet processing apparatus that corrects a curl of a sheet and to an image forming system equipped with the sheet processing apparatus.

2. Description of Related Art

Image forming by an electrophotographic process is one for forming an image through a process wherein a toner image is formed by charging, light exposure and developing, then, the toner image thus formed is transferred onto a sheet, and the toner image thus transferred onto the sheet is fixed, as is known widely.

In a fixing step in this process, toner is fused by heat and pressure so that an image is fixed on a sheet, and in this occasion, there is presented a phenomenon that moisture is vaporized by heat from the sheet.

There is further presented a phenomenon that a sheet absorbs moisture from the open air when the sheet is exposed to the open air.

Since a rate of occurrence of these evaporation, absorption and radiation of moisture on a surface of the sheet is different from that on the other side of the sheet, there is a problem that waviness and curls are caused on the sheet.

Sheets having waviness and curl cause troubles for conveyance, processing and stacking in a sheet processing apparatus that is connected to an image forming apparatus, and they become obstacles for processing and storage for sheets such as an increase in a volume of sheets bundled by binding processing, thus, a technology to correct sheet curls has been developed.

Namely, Unexamined Japanese Patent Application Publication No. 4-338060 and Unexamined Japanese Patent Application Publication No. 5-309971 disclose a technology to correct curls by applying mechanical bending force for a sheet on a sheet conveyance path, and Patent Document 2 discloses a technology to select an air volume of a fan in accordance with a sheet type and image density and to radiate moisture of a sheet.

Though an extent of curl correction can be selected in accordance with a sheet type in the structure described in Unexamined Japanese Patent Application Publication No. 4-338060, it has been found that curls cannot be corrected sometimes by adjustment of mechanical bending force alone even if bending force is adjusted, because sheets are of various types.

For example, it has been found that curls can be corrected by applying strong force in the case of a thick sheet, but, in the case of a thin sheet, it is difficult to correct curls by mechanical bending force alone, and it is difficult to correct curls by bending force alone in the case of fine-quality sheets for printing.

It has been further found that curls cannot be corrected by radiating moisture of a sheet alone, in a similar manner, in the structure described in Unexamined Japanese Patent Application Publication No. 5-309971.

SUMMARY

One aspect of the present invention is as follows.

Item 1. A sheet processing apparatus comprising: a humidifier that humidifies a sheet; a curl correcting section that corrects a curl by applying mechanical bending force on the sheet; and a control section that causes humidification by the humidifier section and curl correction by the curl correcting section to be possible for a prescribed sheet, and causes either one of humidification by the humidifier and curl correction by the curl correcting section to be possible for sheets other than the prescribed sheet.

Item 2. An image forming system comprising an image forming apparatus to form an image on a sheet, the sheet processing apparatus described in the Item 1, and a post-processing apparatus for post-processing the sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of the embodiment relating to the present invention will be explained as follows, referring to the drawings, in which the scope of the invention is not limited by the terminologies used in the specifications.

In the following explanation, a wording of the width direction means the direction perpendicular to the direction in which the sheets are conveyed.

Further, the upper reaches means the side from which a sheet is conveyed in the sheet conveyance direction, while, the lower reaches means the side toward which a sheet is conveyed.

Further, the upward curl means a curl that is convex on a certain surface side of a sheet conveyed in a sheet processing apparatus, while, the downward curl means a curl that is convex on the side that is opposite to the upward curl, namely, the curl that is convex on the side opposite to the certain surface of the sheet to be conveyed.

In the structure described later, an upward curl means a curl that is convex on the side of an image forming surface, for example, and a downward curl means a curl that is concave, for example, on the side of an image forming surface.

Further, the curl correction for correcting a curl by applying mechanical bending force on a sheet is also described as a curl adjustment.

FIG. 1is a sectional view of a sheet processing apparatus.

Sheet processing apparatus B has therein entrance conveyance path HR1representing an entrance conveyance path through which a sheet is conveyed, humidification conveyance path HR2representing a humidification conveyance path on which humidifying section110(humidifier) is arranged, correction conveyance path HR3representing a curl correcting conveyance path having thereon curl correcting section120(including curl correcting section130, curl correcting section140and curl correcting section150), exit conveyance path HR4representing an exit conveyance path through which a sheet is ejected to a post-process and bypass conveyance path HR5for bypassing the humidification conveyance path HR2(humidifying section).

Sheet S on which an image has been formed in image forming apparatus A (which will be explained later) is fed to entrance101of sheet processing apparatus B to be introduced to the entrance conveyance path HR1.

Then, humidifying processing is carried out in the humidifying section110of the humidification conveyance path HR2for the sheet S which undergoes curl correction processing at the curl correcting section130, the curl correcting section140or the curl correcting section150on the correction conveyance path HR3, to be ejected from the exit conveyance path HR4.

Further, in case of need, the bypass conveyance path HR5that bypasses off switching section H12between the entrance conveyance path HR1and the humidification conveyance path HR2, and joins at switching section H23between the humidification conveyance path HR2and the correction conveyance path HR3, which makes it possible to bypass the humidifying section110.

In the entrance conveyance path HR1, the sheet S is conveyed by roller R1, and in the humidification conveyance path HR2, the sheet S is conveyed by rollers R2-R5.

Further, in the correction conveyance path HR3, the sheet S is conveyed by rollers R6-R10, while, in the exit conveyance path HR4, the sheet S is conveyed by rollers R11.

Incidentally, the following explanation will be given under the assumption that the surface of the sheet S on which an image has been formed faces upward in the illustration at entrance101.

The sheet processing apparatus B is capable of practicing a mode without processing that conducts no processing by sheet processing apparatus B, a humidifying mode that conducts only humidifying processing, a first curl correction mode that conducts only curl correction and a second curl correction mode that conducts humidification and curl correction.

In the mode without processing, the bypass conveyance path HRS which will be explained later is selected by switching gate102, and correction conveyance paths HR31and HR41which will be explained later are selected respectively by switching gate138and switching gate148.

Owing to the foregoing, the sheet S advances to the bypass conveyance path HR5from the entrance conveyance path HR1, and passes through correction conveyance path HR31, correction conveyance path HR41, correction conveyance path HR3and exit conveyance path HR4to be ejected without being processed.

In the humidifying mode, humidification conveyance path HR2which will be explained later is selected by switching gate102, and correction conveyance paths HR31and HR41are selected respectively by switching gates138and148.

Owing to this, the sheet S advances to the humidification conveyance path HR2from the entrance conveyance path HR1, and passes through correction conveyance path HR31, correction conveyance path HR41, correction conveyance path HR3explained later and exit conveyance path HR4, after being processed in terms of humidification in the humidifying section110, to be ejected.

A mode to carry out curl correction includes a mode to conduct upward curl correction, a mode to conduct downward curl correction and a mode to correct both upward curl and downward curl.

In the mode for conducting correction for upward curls, humidification conveyance path HR2or bypass conveyance path HR5is selected by switching gate102, correction conveyance path HR32explained later is selected by switching gate138and correction conveyance path HR41is selected by switching gate148.

Owing to this, the sheet S advances to the humidification conveyance path HR2or to the bypass conveyance path HR5from the entrance conveyance path HR1, and passes through correction conveyance path HR41, correction conveyance path HR3, and exit conveyance path HR4, after being corrected in terms of upward curls by the curl correcting section130, to be ejected.

In the mode for conducting correction for downward curls, humidification conveyance path HR2or bypass conveyance path HR5is selected by switching gate102, correction conveyance path HR31is selected by switching gate138and correction conveyance path HR42is selected by switching gate148.

Owing to this, the sheet S advances to the correction conveyance path HR42from the entrance conveyance path HR1, by passing through the humidification conveyance path HR2or bypass conveyance path HR51and bypass conveyance path HR31, and passes through correction conveyance path HR3and exit conveyance path HR4after being corrected by curl correcting section140in terms of downward curls, to be ejected.

In the mode to correct both upward and downward curls, the humidification conveyance path HR2or bypass conveyance path HR5is selected by switching gate102, correction conveyance path HR31which will be explained later is selected by switching gate138, correction conveyance path HR41is selected by switching gate148, and curl correcting section150is caused to operate.

Owing to the foregoing, the sheet S advances to the correction conveyance path HR3from the entrance conveyance path HR1, by passing through the humidification conveyance path HR2or bypass conveyance path HRS, bypass conveyance path HR31and bypass conveyance path HR41, and passes through correction conveyance path HR3and exit conveyance path HR4after being corrected by curl correcting section150explained later in terms of upward and downward curls, to be ejected.

Meanwhile, the mode to correct both upward and downward curls may also be of the structure wherein upward curls and downward curls are corrected by the curl correcting section130and the curl correcting section140.

The second curl correction mode that conducts humidification and curl correction includes a mode to conduct corrections for upward curls and a mode to conduct corrections for downward curls.

In the mode conducting corrections for upward curls, humidification conveyance path HR2is selected by switching gate102, correction conveyance path HR32is selected by switching gate138, and correction conveyance path HR41is selected by switching gate148.

Owing to this, the sheet S advances to the humidification conveyance path HR2from the entrance conveyance path HR1, and is corrected in terms of upward curls by curl correcting section130after being processed in terms of humidification by humidifying section110, and then, it passes through correction conveyance path HR3and exit conveyance path HR4, to be ejected.

In the mode conducting corrections for downward curls, humidification conveyance path HR2is selected by switching gate102, correction conveyance path HR31is selected by switching gate138, and correction conveyance path HR42is selected by switching gate148.

Owing to this, the sheet S advances to the humidification conveyance path HR2from the entrance conveyance path HR1, and is corrected in terms of downward curls by curl correcting section140after being processed in terms of humidification by humidifying section110, and then, it passes through correction conveyance path HR3and exit conveyance path HR4, to be ejected.

Incidentally, as stated above, switching gate102switches between sheet conveyance paths (the first conveyance path extending from entrance conveyance path HR1toward humidification conveyance path HR2, and the second conveyance path extending from entrance conveyance path HR1toward bypass conveyance path HR5).

On the humidification conveyance path HR2, there is arranged humidifying section110that humidifies sheet S.

The humidifying section110is formed as a unit which can be drawn out of an apparatus through a guide by a guide rail.

On the lower portion of the humidifying section110, there is arranged tank130that supplies water to the humidifying section110, and the tank130is capable to be drawn out of an apparatus through a guide by guide rails130A and130B.

In correction conveyance path HR3, there is arranged curl correcting section120correcting curls of sheets wherein there are arranged curl correcting section130for correcting upward curls representing the first curl correcting section that corrects curls by applying mechanical bending force from the first surface side of a sheet, curl correcting section140for correcting downward curls representing the second curl correcting section that corrects curls by applying mechanical bending force from the first surface side and from the second surface side on the opposite side and curl correcting section150for correcting upward and downward curls representing the third curl correcting section that corrects curls by applying mechanical bending forces from the first surface side and from the second surface side of the sheet alternately.

Thus, upward curls are corrected to be flat by operations of the curl correcting section130, downward curls are corrected to be flat by operations of the curl correcting section140and both upward and downward curls are corrected to be flat by operations of the curl correcting section150.

The humidifying section110and the curl correcting section120will be explained in detail as follows.

Humidification conveyance path HR2is formed to be U-shaped, and sheet S advances downward almost vertically from entrance conveyance path HR1(not shown), then, it makes a U-turn to advance upward vertically, and humidifying section110is arranged at the portion that is an upper part of the humidification conveyance path HR2to which the sheet S advances.

The humidifying section110has a pair of humidifying sections arranged respectively to face the humidification conveyance path HR2, namely, has humidifying section110A on the left side in the drawing and humidifying section110B on the right side, and the humidifying section110A has humidifying roller111A, water-supply roller112A and water-supply tank114A, while, the humidifying section110B has humidifying roller111B, water-supply roller112B and water-supply tank114B.

The water-supply roller112A is in contact with the humidifying roller111A, and the water-supply roller112B is in contact with the humidifying roller111B, while, the water-supply roller112A is soaked in water W contained in the water-supply tank114A, and the water-supply roller112B is soaked in water W contained in the water-supply tank114B.

Further, the humidifying roller111A and the humidifying roller111B which face each other are in contact with each other, and they rotate in the directions of their own arrows to humidify sheet S by giving water while conveying the sheet S.

Each of113A and113B represents a water-adjusting member, and the water-supply roller112A is squeezed by the water-adjusting member113A and the water-supply roller112B is squeezed by the water-adjusting member113B, so that water content of each of the water-supply roller112A and the water-supply roller112B may be regulated.

For the humidifying rollers111A and111B and for the water-supply rollers112A and112B, there are used single-layer structured or multiple-layer structured rollers made of elastic materials such as solid rubber that is not foaming and foaming rubber or multiple-layer structured rollers each being of the structure in which fibers are wound around rubber.

The humidifying roller111A is composed of shaft core111Aa made of metal and of rubber layer111Ab formed on the shaft core111Aa, and the humidifying roller111B is composed of shaft core111Ba made of metal and of rubber layer111Bb formed on the shaft core111Ba.

The water-supply roller112A is composed of shaft core112Aa made of metal and of rubber layer112Ab formed on the shaft core112Aa, and the water-supply roller112B is composed of shaft core112Ba made of metal and of rubber layer112Bb formed on the shaft core112Ba.

For the water-adjusting members113A and113B, there is used a rotating (that rotates in the direction of an arrow when it rotates) or fixed round bar. It is further possible to use a tabular blade, as the water-adjusting members113A and113B.

Water W in tank130is drawn up by a pump (not shown) into water-supply tanks114A and114B through feed water pipe116A, and it flows back from overflow pipe116B to the tank130through overflowing, whereby, water levels respectively in the water-supply tanks114A and114B are maintained to be constant.

Meanwhile, the water-supply tank114A is communicated with the water-supply tank114B, and water levels in both of them are kept to be constant.

In the humidifying processing, the humidifying rollers111A and111B and water-supply rollers112A and112B are rotated in the directions shown by their own arrows, to conduct humidifying processing by giving water to both sides of sheet S.

Since both the humidifying rollers111A and111B are arranged to be bilaterally symmetric about humidification conveyance path HR2as illustrated, and both the water-supply rollers112A and112B are arranged to be bilaterally symmetric about humidification conveyance path HR2as illustrated, a water-supply channel covering from water-supply tank114A to humidifying roller111A and a water-supply channel covering from water-supply tank114B to humidifying roller111B are the same in terms of a shape and a length.

Therefore, equal supplies of water are conducted to sheet S from its both sides. In addition, an equal amount of water in the direction of a thickness of sheet S is supplied to sheet S, and flatness of sheet S is kept favorably, because the sheet S is humidified in humidification conveyance path HR2that goes up vertically.

The symbols117A and117B represent fans that blow a dried wind against both sides of sheet S, and blowing a dried wind against sheet S by fans117A and117B causes excessive water to evaporate from sheet S that is immediately after humidification, and prevents that water is accumulated on an conveyance path forming member such as a conveyance roller.

FIG. 3is an enlarged illustration of a curl correcting section.

Curl correcting section120correcting curls by applying mechanical bending force on a sheet is one that applies mechanical force (bending force) in the direction from a convex portion to a concave portion (in the direction opposite to curls) and corrects curls by the bending force to correct curls.

The curl correcting section120has therein curl correcting section130that corrects the upward curls, curl correcting section140that corrects downward curls and curl correcting section150(FIG. 4) mentioned later which corrects both upward and downward curls.

The curl correcting section130has therein small-diameter roller (for example, radius of7mm)131, a pair of belt-drive rollers132and133, belt134trained about the belt-drive rollers132and133, spring hooking shaft135, pressure spring136that presses belt134through the small-diameter roller131in the direction (arrow) opposite to the conveyance path for a sheet, and first correction extent adjusting section137that urges the spring hooking shaft135in the direction (arrow) opposite to that of a conveyance path for a sheet to change stress of the pressure spring136and adjusts an extent of curl correction for a sheet.

In the curl correcting section130, when switching gate138that switches conveyance paths is at the position shown by one-dot chain lines, correction conveyance path HR31that does not pass through the curl correcting section130is selected, while, when the switching gate138is at the position shown by solid lines, correction conveyance path HR32that passes through the curl correcting section130is selected.

Further, the switching gate138is turned on or turned off by a control section which will be explained later, depending on a thickness and a type of a sheet and on the direction of a curl.

Since the correction conveyance path HR31has a large radius of curvature (for example, radius 60 mm) as is illustrated, curls are not corrected when sheet S conveyed in the direction of an arrow passes through the correction conveyance path HR31.

In contrast to this, when sheet S passes through correction conveyance path HR32formed by small-diameter roller131and by belt134, bending force by the small-diameter roller131and by the belt134is applied on the sheet S, and curls on the sheet S are corrected.

Sheet S having thereon an image formed on the upper surface in entrance101and having upward curls (namely, upward convex form in entrance101) is in a posture wherein its image surface faces downward obliquely on the right side, in the curl correcting section130(namely, convex form facing downward obliquely on the right side).

Therefore, the sheet having upward curls, namely, having a convex form facing downward obliquely on the right side receives urging force in the direction opposite to the direction of the convex form by small-diameter roller131(namely, bending force caused by small-diameter roller131and by belt134), when the sheet passes through correction conveyance path HR32along the belt134.

As a result, upward curls are corrected to be in a shape of a flat plate.

Further, this urging force can be adjusted by the first correction extent adjusting section137, and is changed by a control section explained later, depending on a thickness and a type of a sheet.

The curl correcting section140has therein small-diameter roller (for example, radius of 7 mm)141, a pair of belt-drive rollers142and143, belt144trained about the belt-drive rollers142and143, spring hooking shaft145, pressure spring146that presses belt144through the small-diameter roller141in the direction opposite to the conveyance path for a sheet, and second correction extent adjusting section147that urges the spring hooking shaft145in the direction opposite to that of a conveyance path for a sheet to change stress of the pressure spring146and adjusts an extent of curl correction for a sheet.

In the curl correcting section140, when switching gate148that switches conveyance paths is at the position shown by one-dot chain lines, correction conveyance path HR41that does not pass through the curl correcting section140is selected, while, when the switching gate148is at the position shown by solid lines, correction conveyance path HR42that passes through the curl correcting section140is selected.

Further, the switching gate148is turned on or turned off by a control section which will be explained later, depending on a thickness and a type of a sheet and on the direction of a curl.

Since the correction conveyance path HR41has a large radius of curvature (for example, radius 60 mm) as illustrated, curls are not corrected when sheet S conveyed in the direction of an arrow passes through the correction conveyance path HR41.

In contrast to this, when sheet S passes through correction conveyance path HR42formed by small-diameter roller141and by belt144, bending force by the small-diameter roller141and by the belt144is applied on the sheet S, and curls on the sheet S are corrected.

Sheet S having thereon an image formed on the upper surface in entrance101and having downward curls (namely, forming a convex form facing downward in entrance101) is in a posture wherein its image surface faces downward obliquely on the left side, in the curl correcting section140(namely, a convex form facing upward obliquely on the right side in curl correcting section140).

Therefore, the sheet having downward curls, namely, having a convex form facing upward obliquely on the right side receives urging force in the direction opposite to the direction of the convex form by small-diameter roller141(namely, bending force caused by small-diameter roller141and by belt144), when the sheet passes through correction conveyance path HR42along belt144and curls are corrected.

As a result, downward curls are corrected to be in a shape of a flat plate.

Further, this urging force can be adjusted by the second correction extent adjusting section147, and is changed by a control section explained later, depending on a thickness and a type of a sheet.

FIG. 4is an enlarged illustration of curl correcting section150.

Belt155and belt156are rotatable while they are in contact with each other on the correction conveyance path HR3side.

Inside the belt155, there are provided small-diameter rollers158which are smaller than belt-drive rollers151and152movably, and inside the belt156, there are provided small-diameter rollers159which are smaller than belt-drive rollers153and154movably.

Third correction extent adjusting section161that urges small-diameter roller158toward opposing belt156(direction of arrow a) and adjusts curl correction extent for the sheet is connected to the small-diameter roller158.

Fourth correction extent adjusting section162that urges small-diameter roller159toward opposing belt155(direction of arrow b) and adjusts curl correction extent for the sheet is connected to the small-diameter roller159.

Owing to the foregoing, the third correction extent adjusting section161urges small-diameter roller158, and the fourth correction extent adjusting section162urges small-diameter roller159, and when the belt155and the belt156form a shape of a zigzag (two-dot chain lines zigzag conveyance path HR6), sheet S that is interposed between the belt155and the belt156to be conveyed receives bending force in both directions alternately, thus, upward curls and downward curls are corrected.

Urging force of the third correction extent adjusting section161and that of the fourth correction extent adjusting section162are caused to be capable of being adjusted by a control section, and desired urging force in accordance with an extent of curl of a sheet to be conveyed is generated, whereby, a sheet having a curl with optional extent can be made to be in a shape of a flat plate.

Further, when the third correction extent adjusting section161does not urge small-diameter roller158and the fourth correction extent adjusting section162does not urge small-diameter roller159, and each of belt155and belt156becomes to be linear (one-dot chain line), sheet S interposed between the belt155and the belt156to be conveyed does not receive bending force, and curls are not corrected.

Incidentally, when upward curls and downward curls are corrected all the time, it is also possible to fix small-diameter roller158and small-diameter roller159respectively at positions shown with broken lines, by providing neither the third correction extent adjusting section161nor the fourth correction extent adjusting section162.

Owing to the foregoing, the belt155and the belt156become to be in a form of zigzag (two-dot chain line-zigzag conveyance path HR6), and sheet S interposed between the belt155and the belt156to be conveyed receives bending force constantly in both directions alternately, whereby, upward curls and downward curls are corrected constantly.

In addition, it is also possible to increase the number of steps in a form of zigzag by providing a plurality of pairs each including small-diameter roller158and small-diameter roller159, which makes it possible to correct curls gradually, therefore, this method can be used favorably for correcting curls on the sheets which are difficult to be corrected at a time, like the sheets, for example, having great basis weight.

Conveying sheet S nipped by belts while urging it in a zigzag form as stated above makes it possible to correct upward curls and downward curls to be in a shape of a flat plate.

FIG. 5is an illustration of an image forming system having therein image forming apparatus A, sheet processing apparatus B and sheet finisher C.

The image forming apparatus A has an image forming section wherein charging section2, image-wise exposure section (writing section)3, developing section4, transfer section5A, neutralizing section5B and cleaning section6are arranged around image carrier1that rotates.

In the image forming section, the charging section2carries out uniform charging on a surface of the image carrier1, then, exposure scanning based on image data obtained through reading of a document by a laser beam of the image-wise exposure section3is conducted to form a latent image after uniform charging is carried out on the surface of the image carrier1, and a toner image is formed on a surface of the image carrier1after the latent image is subjected to reversal development by the developing section4.

Sheet S fed out of sheet storage section7A is sent to a transfer position. In the transfer position, the toner image is transferred onto the sheet S by the transfer section5A.

After that, electric charges on the reverse side of the sheet S are eliminated by the neutralizing section5B, and the sheet S is separated from the image carrier1to be conveyed by conveyance section7B, and is heated and fixed by fixing section8to be ejected from sheet ejection roller7C.

The fixing section8has therein heat roller8A, pressure roller8E that comes in pressure contact with the heat roller8A and heater8C, and an unfixed toner image is heated by the heat roller8A that is heated by the heater8C, thus, toner is fused and the toner image is fixed on the sheet S.

When forming images on both sides of sheet S, the sheet S that has been subjected to heating and fixing by the fixing section8is detached from an ordinary sheet ejection path by conveyance path switching plate7D, then, is caused to switchback in reversing conveyance section7E to be reversed inside out, and passes through the image forming section again, thus, an image is formed on the reverse side of the sheet S.

Then, the sheet S is ejected to the outside of an apparatus from sheet ejection roller7C through fixing section8. The sheet S ejected from the sheet ejection roller7C is sent to sheet processing apparatus B.

Developing agents still staying on a surface of image carrier1even after image processing are removed by cleaning section6so that the surface is prepared to be ready for following image forming.

On operation section SA representing a setting section, a curl correction setting screen (FIGS. 7 and 8described later) that sets correction conditions for curls in sheet processing apparatus B is displayed, and information by an operator such as basis weight of a sheet is set.

Then, information thus set is transmitted to sheet processing apparatus B by an unillustrated communication section.

Meanwhile, in a storage section of image forming apparatus A, information that displays the curl correction setting screen is stored in advance.

Then, information that displays a curl correction setting screen is read out of the storage section as occasion demands, and the curl correction setting screen is displayed on a display screen such as a touch panel provided on operation section SA.

Incidentally, when manufacturing and marketing, for example, image forming apparatus A and sheet processing apparatus B individually, it is also possible to store information to display a curl correction setting screen in sheet processing apparatus B in advance in a storage section of sheet processing apparatus B, and when the image forming apparatus A is connected with the sheet processing apparatus B, to transmit information that displays a curl correction setting screen from sheet processing apparatus B to image forming apparatus A through a communication section of the sheet processing apparatus B and a communication section of the image forming apparatus A, so that the information may be stored in a storage section of the image forming apparatus A.

An explanation of the sheet processing apparatus B will be omitted here, because it has already been given earlier.

Sheet finisher C is composed of sheet conveyance section210, sheet ejection section220, cover supplying section230, sheet bundle storing section240, sheet bundle conveying section250, paste coating section260, cover pasting section270, cover-folding section280and booklet ejecting section290.

The respective sections are arranged on a tandem placement basis vertically, in a main body of the sheet finisher C.

Sheet S ejected from the sheet processing apparatus B is stored temporarily at the prescribed position of sheet bundle storage section240of the sheet finisher C, and is stacked one after another.

A sheet bundle composed of sheets S in the prescribed number is formed in sheet bundle storage section240, then, the sheet bundle is sent to sheet bundle holding section250where paste is coated on a bottom surface of the sheet bundle by paste coating section260, when the sheet bundle holding section250rotates to be almost vertical, thus, a sheet bundle is tied up.

A cover is supplied from cover pasting section270to the sheet bundle thus tied up to be put together, and the cover is folded by cover-folding section280, whereby, a booklet is formed.

The booklet thus formed is ejected out of sheet finisher C by booklet ejecting section290.

Though the explanation has been given under the condition of a finished image forming system, it is naturally possible to complete an image forming system finally by connecting sheet processing apparatus B to image forming apparatus A later, or by connecting sheet processing apparatus B and sheet finisher C to image forming system some other day.

The foregoing has been an explanation for structures of the image forming apparatus A, the sheet processing apparatus B and the sheet finisher C, and control of the sheet processing apparatus B will be explained as follows.

FIG. 6is a block diagram for the control relating to curl correction of sheet processing apparatus B.

Control section Cb of the sheet processing apparatus B has therein nonvolatile storage section M in which control program for total sheet processing apparatus b is stored in advance, RAM that stores various types of data temporarily, CPU that reads out control programs one after another, and causes RAM to store and to practice, interface unit I/O that conducts interface with various types of input and output members and communication section CCb that communicates with communication section CCa of image forming apparatus A and with communication section CCc of sheet finisher C.

In the nonvolatile storage section M, there are stored programs described in a flow diagram explained later, and information that displays curl correction setting screen that is described later, in advance.

Then, CPU reads out programs described on a flow diagram described later as occasion demands, and practices control relating to curl correction.

Switching gate102is controlled by CPU through interface unit I/o to switch a conveyance path for a sheet to humidification conveyance path HR2or to bypass conveyance path HR5.

Switching gate138is controlled by CPU through interface unit I/O to switch a conveyance path for a sheet to correction conveyance path HR31or to correction conveyance path HR32.

Switching gate148is controlled by CPU through interface unit I/O to switch a conveyance path for a sheet to correction conveyance path HR41or to correction conveyance path HR42.

With respect to humidifying section110, drive motor (not shown) that drives humidifying roller111A and humidifying roller111B and a pump (not shown) are controlled by CPU through interface unit I/O, and a sheet is humidified.

With respect to curl correcting section130, first correction extent adjusting section137is controlled by CPU through interface unit I/O, and urging force to correct upward curls is adjusted.

With respect to curl correcting section140, second correction extent adjusting section147is controlled by CPU through interface unit I/O, and urging force to correct downward curls is adjusted.

With respect to curl correcting section150, third correction extent adjusting section161and fourth correction extent adjusting section162are controlled by CPU through interface unit I/O, and urging forces to correct upward and downward curls are adjusted.

Communication section CCb communicates with communication section CCa of image forming apparatus A and with communication section CCc of sheet finisher C, and gives and receives various types of information.

Setting condition information relating to curl correction set by curl correction setting screen P displayed on an operation section (not shown) of image forming apparatus A is transmitted to sheet processing apparatus B through communication section CCa and communication section CCc, to be used for the following flow processing.

FIG. 7is an illustration of a curl correction setting screen.

FIG. 7is a basic screen of a curl correction setting screen, and it shows a curl correction setting screen on the occasion where plain paper and basis weight 60 g/m2or more are set respectively by the following sheet type setting section P11and basis weight setting section P12.

When a prescribed sheet, namely, plain paper and basis weight 60 g/m2or more are displayed in the case of job setting, and are set on a curl correction setting screen representing a basic screen of a curl correction setting screen, plain paper and basis weight 60 g/m2or more transmit to curl correction setting screen P representing a curl correction setting screen in the case of setting. However, in this case, contents displayed remain unchanged.

An occasion wherein plain paper and basis weight 60 g/m2or more are set will be explained as follows.

The curl correction setting screen P is divided into setting section P1that sets information relating to a sheet and curl adjusting section P2that sets information relating to curl correction (adjustment).

The setting section P1is divided into sheet type setting section P11that sets a sheet type and basis weight setting section P12that sets basis weight, and in the sheet type setting section P11, sheet types, for example, plain paper and color paper or the like (in the drawing, plain paper is set) are set, and in basis weight setting section P12, basis weight, for example, less than 60 g/m2(less than 59 g/m2or less in illustration), 60 g/m2or more (60 g/m2or more in illustration) are set.

Curl adjusting section P2is divided into curl adjustment setting section P21that sets an extent of curl adjustment and sets whether adjustment of upward curls or adjustment of downward curls and humidification setting section P22that sets whether conducting humidification or conducting no humidification (ON key P23, OFF key P24).

The curl adjustment setting section P21has +2 key and +1 key which adjust an extent of upward curl adjustment (namely, adjusting upward curls to be in the direction of a flat plate), and an extent of upward curl adjustment is set by +2 key and +1 key, and has −2 key and −1 key which adjust an extent of downward curl adjustment (namely, adjusting downward curls to be in the direction of a flat plate), and an extent of downward curl adjustment is set by −2 key and −1 key, and adjustments for both upward curls and downward curls are set by 0 key that adjusts both upward curls and downward curls to be in the direction of a flat plate.

Meanwhile, (+1) of curl correction extent (intensity) key Q223is a key for correcting relatively small upward curls and curls of a sheet having low stiffness, while, (+2) is a key for correcting severe upward curls and curls of a sheet having high stiffness.

Further, (−1) of curl correction extent (intensity) key Q223is a key for correcting relatively small downward curls and curls of a sheet having low stiffness, while, (−2) is a key for correcting severe downward curls and curls of a sheet having high stiffness.

Further, in humidification setting section P22, right or wrong for practice of humidification is set by selection of ON key P23or OFF key P24.

Incidentally, when setting neither curl adjustment setting section P21nor humidification setting section P22, curls are not corrected.

Owing to the foregoing, when a prescribed sheet, namely, basis weight 60 g/m2or more is set at sheet basis weight setting section P12, setting for curl correction and setting for humidification processing become possible, in accordance with key operations relating to curl correction and humidification processing thereafter.

FIGS. 8aand8bare illustrations of a curl correction setting screen for a thin sheet.

FIG. 8ais a diagram of curl correction setting screen Q1that is transited when a sheet other than a prescribed sheet, namely, plain paper (P11) having basis weight less than 60 g/m2(P12) is set, in curl correction setting screen (FIG. 7) representing a basic screen of curl correction setting screen that is displayed in the case of setting a job, or when “PREVIOUS” key is set in the following curl correction setting screen Q2.

FIG. 8bis a diagram of curl correction setting screen Q2that is transited when “NEXT” key is set in the curl correction setting screen Q1.

InFIG. 8a, curl correction setting screen Q1is divided into setting section Q11that sets information relating to sheets and humidification setting section Q113(ON key Q114, OFF key Q115) that sets whether conducting humidification or not, and it has a “NEXT” key.

A key relating to humidification processing is displayed as stated above, and setting about humidification processing is made possible, in the same way as that explained by referring toFIG. 7.

Further, by setting the “NEXT” key, it is possible to transit to the following curl correction setting screen Q2.

Further, when humidification setting ON key0114is selected in curl correction setting screen Q1, operations of the “NEXT” key are made to be impossible, resulting in an inability to perform curl adjustment processing.

When humidification setting OFF key Q115is selected, operations of the “NEXT” key are made possible, and curl setting screen Q2shown inFIG. 8bis displayed by operating the “NEXT” key.

Then, setting of curl correction extent (intensity) by curl correction extent (intensity) key Q223is made possible, and curl adjustment processing is carried out by the setting.

InFIG. 8b, curl correction setting screen Q2is divided into setting section Q21that sets information relating to sheets and curl adjusting section Q22that sets curl correction, and it has a “PREVIOUS” key.

Curl correction extent (intensity) keys Q223(+2-0-−2 keys) are displayed on curl adjusting section Q22, so that setting about curl correction extent (intensity) is made possible, in the same way as that explained by referring toFIG. 7.

Namely, when humidification ON key Q114of humidification setting section Q113is selected, humidification processing only is made possible, while, when humidification setting OFF key Q115is selected, curl correction only is made possible.

Further, by setting the “PREVIOUS” key, it is possible to transit to the previous curl correction setting screen Q1, thus, fresh start for setting is made possible.

When a sheet other than a prescribed sheet in terms of basis weight, namely a sheet having basis weight of less than 60 g/m2is selected by a basis weight setting key as stated above, it is possible to make setting of curl correction only to be possible, or to make setting of humidification processing only to be possible, depending on key operations relating to curl correction and humidification processing thereafter.

Owing to this, it is possible to practice curl correction only, or humidification processing only.

Meanwhile, in the curl correction setting screen P, curl correction setting screen Q1and curl correction setting screen Q2which are displayed on operation section SA of image forming apparatus A, the occasion where neither curl adjustment nor humidification setting is set corresponds to the mode of no processing (processing by sheet processing apparatus B is not conducted), the occasion where curl adjustment is not set and humidification setting only is set corresponds to the mode of humidification (humidification processing only is conducted), the occasion where humidification setting is not set and curl adjustment only is set corresponds to the first curl correction mode (that conducts curl correction only), and the occasion where both of curl adjustment and humidification setting are set corresponds to the second curl correction mode (that conducts humidification and curl correction).

Namely, in the operation section SA of image forming apparatus A, it is possible to set information relating to the job including, for example, a mode without processing, a humidification mode, a first curl correction mode and a second curl correction mode.

Thus, owing to the setting, the sheet processing apparatus B makes the curl correction possible in a mode without processing, a humidification mode, a first curl correction mode or a second curl correction mode.

Further, in the curl correction setting screen P and curl correction setting screen Q2, the occasion where +2 key or +1 out of keys for +2-0-−2 of curl adjustment section is set, corresponds to the mode to conduct the upward curls correction, the occasion where −2 key or −1 key is set, corresponds to the mode to conduct the downward curls correction, and the occasion where 0 key is set, corresponds to the mode to conduct correction of the both (upward and downward) curls.

Namely, in the operation section SA of image forming apparatus A, it is possible to set information relating to the job including, for example, a mode to conduct upward curl correction, a mode to conduct downward curl correction and a mode to conduct both upward and downward curls correction.

Thus, owing to the setting, the sheet processing apparatus B makes the curl correction possible in a mode to conduct upward curl correction, or a mode to conduct downward curl correction, or a mode to conduct both upward and downward curls correction.

FIG. 9is a flow chart of the control concerning curl correction of sheets in image forming apparatus A.

First, an outline of control flow concerning curl correction for sheets in image forming apparatus A will be explained, referring toFIGS. 9,6and7, before explaining control flow for correcting curls of sheets in sheet processing apparatus B.

1. Display of Curl Correction Setting Screen: Step S11

For example, in setting a job, curl correction setting screen display information that displays a setting screen (curl correction setting screen•FIG. 7) concerning curl correction is read out from a storage section of image forming apparatus A, to cause a display screen such as a touch panel provided on operation section SA to display curl correction setting screen P to advance to the following step.

2. Basis Weight Reading of Basis Weight Setting Section P12: Step S12

An operator sets information concerning basis weight, humidification and curl correction on curl correction setting screen P displayed on a display screen.

Information concerning curl correction including basis weight that is set by basis weight setting section P12is read to be stored in a storage section such as RAM, to advance to the following step.

3. Judgment for Whether Basis Weight is Not Less than 60 g/m2or Not: Step S13

A judgment for whether the basis weight thus read is not less than 60 g/m2or not is made, and when the basis weight is not less than 60 g/m2(Yes), curl correction setting screen P is caused to be displayed continuously, to advance to step S18, and when the basis weight is less than 60 g/m2(No), the curl correction/setting screen P is caused to transit to curl correction setting screen Q1, to advance to the following step.

4. Judgment of Presence or Absence of Humidification: Step S14

In curl correction setting screen Q1, when ON key Q114of humidification setting section Q113is set (Yes), a flow advances to the following step and when OFF key Q115of humidification setting section Q113is set (No), curl correction setting screen Q1is caused to transit to curl correction setting screen Q2, to advance to step S16.

5. Transmission of Information for Humidification Present: Step S15

Information of humidification present is transmitted to communication section CCb of sheet processing apparatus B through communication section CCa, to advance to END.

6. Judgment for Presence or Absence of Curl Adjustment: Step S16

In curl correction setting screen Q2, when curl adjusting section Q22is set (Yes), curl correction extent (intensity) key Q223(+2-0-−2 keys) of curl adjusting section Q22is read, to advance to the following step, and when curl adjusting section Q22is not set (No), a flow advances to END.

7. Transmission of Information of Curl Adjustment Present: Step S17

Information of curl correction present and information of curl correction extent (+2-0-−2) are transmitted to communication section CCb of sheet processing apparatus B through communication section CCa, to advance to END.

8. Judgment for Presence or Absence of Curl Adjustment: Step S18

In curl correction setting screen P (FIG. 7), when curl adjusting section P2is set (Yes), curl correction extent (intensity) key P21/Q223(+2-0-−2 keys) of curl adjusting section P2is read, to advance to the following step, and when curl adjusting section P2is not set, a flow advances to step S20(No).

9. Transmission of Information of Curl Adjustment Present: Step S19

Information of curl correction present and information of curl correction extent (+2-0-−2) are transmitted to communication section CCb of sheet processing apparatus B through communication section CCa, to advance to the following step.

10. Judgment of Presence or Absence of Humidification Step S20

In curl correction setting screen P, when ON key P23of humidification setting section P22is set (Yes), a flow advances to the following step, and when OFF key P24of humidification setting section P22is set, and a flow advances to END.

11. Transmission of Information of Humidification Present Step S21

Information of humidification present is transmitted to communication section CCb of sheet processing apparatus B through communication section CCa, to advance to END.

Incidentally, when manufacturing and marketing image forming apparatus A and sheet processing apparatus B individually, to systemize by combining both of them later, a flow of control concerning curl correction for sheets in image forming apparatus A may be stored either in the sheet processing apparatus B, or, it may be transmitted to image forming apparatus A by a communication section to be stored in the image forming apparatus A in the case of the combination of the image forming apparatus A and the sheet processing apparatus B.

Step S13and steps S18-S21make it possible to set both curl adjustment and humidification in the case of the basis weight of 60 g/m2or more, namely, in the case of the prescribed sheet, whereby, both curl adjustment and humidification are made possible.

Further, when basis weight is less than 60 g/m2, namely, when a sheet is other than a prescribed sheet, one of curl adjustment and humidification can be set, thereby, one of the curl adjustment and the humidification are made possible.

FIG. 10is a flow chart of the control concerning curl correction of sheets in sheet processing apparatus B.

A flow for the control to correct curls of sheets will be explained as follows, referring toFIG. 10.

1. Acquisition of Information Concerning Curl Adjustment: Step S101

Image forming apparatus A receives transmitted information concerning curl adjustment, and stores it in RAM and advances to the following step.

Incidentally, information concerning curl adjustment includes information about humidification present transmitted in the step S15, information of curl correction present and curl correction extent information (+2-0-−2) transmitted in step S17, information of curl correction present and curl correction extent information (+2-0-−2) transmitted in step S19and information about humidification present transmitted in step S21.

2. Judgment for Information for Presence of Humidification: Step S102

Information concerning curl adjustment received from RAM is read out, and when information for presence of humidification is present (Yes), a flow advances to the following step for conducting humidification processing, and when information for presence of humidification is not present (No), a flow advances to step S104.

Water is pumped up by a pump (not shown) or the like into water-supply tanks114A and114B, then, humidifying rollers111A and111B are rotated by a drive motor (not shown) that rotates the humidifying rollers111A and111B, thus, a sheet passing through the humidifying rollers is coated with water (humidification), and a flow advances to the following step.

4. Judgment for Information for Presence of Curl Correction: Step S104

Information concerning presence or absence of curl correction received from RAM is read out, and when information for presence of curl correction is present (Yes), a flow advances to the following step for reading out information of curl correction extent, and when information for presence of humidification is not present (No), a flow advances to END.

5. Acquisition of Information Concerning Curl Collection Extent: Step S105

Information concerning curl correction extent (+2-0−2) is read out, and when information of curl correction extent is positive (+2, +1) (Yes), a flow advances to the following step for conducting processing for upward curl correction, and when information of curl correction extent is not positive (No), a flow advances to step S107.

6. Practice of Correction Processing for Upward Curl: Step S106

Switching gate138is operated so that a sheet is caused to pass through correction conveyance path HR32. Then, small-diameter roller131is caused to urge first correction extent adjusting section137with urging force in accordance with curl correction extent information (+2, +1), to advance to END.

When curl correction extent information +1 is set in this case, the small-diameter roller131is caused to urge by relatively small urging force, while, when curl correction extent information +2 is set, the small-diameter roller131is caused to urge by great urging force.

7. Acquisition of Curl Correction Extent Information: Step S107

Information concerning curl correction extent (+2-0-−2) is read out, and when information of curl correction extent is negative (−2, −1) (Yes), a flow advances to the following step for conducting processing for downward curl correction, and when information of curl correction extent is not negative (No), a flow advances to step S109for conducting processing of correction for both upward and downward curls.

8. Practice of Correction Processing for Downward Curl: Step S108

Switching gate148is operated so that a sheet is caused to pass through correction conveyance path HR42. Then, small-diameter roller141is caused to urge second correction extent adjusting section147with urging force in accordance with curl correction extent information (−2, −1), to advance to the following step.

When curl correction extent information −1 is set in this case, the small-diameter roller141is caused to urge by relatively small urging force, while, when curl correction extent information −2 is set, the small-diameter roller141is caused to urge by great urging force.

9. Practice of Correction Processing for Both Upward and Downward Curls: Step S109

Third correction extent adjusting section161and fourth correction extent adjusting section162are caused to operate so that a sheet is urged by small-diameter rollers158and159in the direction opposite to the curl direction, and a flow advances to END.

In steps S104-S109, it is possible to correct curls by at least one of the first curl correcting section, the second curl correcting section and the third curl correcting section which were mentioned earlier, depending on a curl correcting method set by an operator. Owing to the foregoing, curls can be corrected by using different mechanical bending forces (step S101and steps S104-Step109) and humidifications (step S102and step S103) for different purposes depending on sheet types and basis weights (step S11-step S21). Therefore, it is possible to prevent occurrence of troubles in conveyance, processing and in integration all caused by the curls, resulting in provision of a sheet processing apparatus wherein required maintenance time caused by abnormal processing is shortened and high productivity is realized, and of an image forming system having the sheet processing apparatus.