Sheet treating apparatus and image forming apparatus therewith

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet treating apparatus and an image forming apparatus therewith, particularly to the sheet treating apparatus and the image forming apparatus therewith, which perform binding treatment to a sheet stack formed by alignment of the treated sheets by using binding means.

2. Related Background Art

Conventionally, in the image forming apparatus such as a copying machine, a printer, and a facsimile, in order to reduce time and effort necessary for treatments such as binding and punching to the sheets such as copy paper in which an image is already formed, some image forming apparatuses includes the sheet treating apparatus which sequentially takes the sheet to selectively perform the treatments such as the binding and punching to the sheet.

For example, Japanese Patent Application Laid-Open No. H11-322160 discloses the sheet treating apparatuses in which a predetermined sheet stack is formed by aligning the sheets sequentially discharged from the image forming apparatus and stapling (binding) treatment is performed to the sheet stack.

In the sheet treating apparatus disclosed in Japanese Patent Application Laid-Open No. H11-322160, for example, the sheets sequentially discharged from the image forming apparatus are temporarily accommodated in a treating tray, the sheets are aligned to form the sheet stack, the stapling treatment is performed to the sheet stack by a stapler provided in the treating tray, and the sheets are discharged from the treating tray to a stack tray to stack the sheets.

The conventional sheet treating apparatus and image forming apparatus therewith include alignment means such as an alignment plate which aligns the sheets stacked in the treating tray at a predetermined alignment position before the stapling treatment is performed. The sheets are aligned at the predetermined alignment position by the alignment means, which improves appearance of the sheet stack in which the stapling treatment is performed.

In performing the alignment of the sheets on the treating tray, when the discharged sheets have the same sizes, the alignment operation can be performed with no trouble. However, when the alignment operation is performed to the sheet stack in which the sheets having the different sizes are mixed, it is necessary that the alignment operation is performed by aligning the sheets having the different sizes with the sheets having a certain size.

When the alignment operation is performed by aligning the sheets having the different sizes with the sheet having the maximum size, because a movement distance to the alignment plate is short in the maximum-size sheet, when the small-size sheet is moved toward a direction of the alignment plate by the same amount as for the maximum-size sheet in aligning the small-size sheet, sometimes the small-size sheet does not reach the alignment plate. Therefore, in this case, the sheets cannot securely be aligned.

When the stapling treatment is performed to the sheet stack in a state that the sheets are not securely aligned, the stapling treatment cannot securely be performed to the sheet stack, or the stapling treatment cannot be performed at an appropriate position in the sheet stack. Accordingly, there is generated the problem that the appearance of the sheet stack becomes worsened.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the invention is to provide a sheet treating apparatus and an image forming apparatus therewith which can securely perform stapling (binding) treatment even to a sheet stack, in which the sheets having different sizes are mixed, and improve appearance of the sheet stack when the stapling (binding) treatment is performed to the sheet stack.

In order to achieve the object, a sheet treating apparatus of the invention having sheet stacking means for stacking a sheet to be treated, the sheet treating apparatus which forms a sheet stack by aligning the sheets conveyed to the sheet stacking means and performs binding treatment to the aligned sheet stack by binding means, the sheet treating apparatus includes a side-end regulation member which is provided on a side of a width direction orthogonal to a sheet conveying direction of the sheet stacking means, the side-end regulation member regulating an end-portion position in the width direction of the sheet; and moving means for moving the sheet in the width direction to cause the sheet to abut-on the side-end regulation member, in which the moving means moves the sheet in the width direction to cause the sheet to abut on the side-end regulation member in each time when the sheet is conveyed to the sheet stacking means such that the end portions in the width directions of the sheets whose lengths differ from one another in the width direction are aligned.

In a sheet treating apparatus according to the invention, it is possible that the moving means moves the sheet in the width direction by a distance corresponding to the length in the width direction.

In a sheet treating apparatus according to the invention, it is possible that the sheet treating apparatus further includes holding means for holding the sheet abutting on the side-end regulation member, in which the moving means moves the sheet in the width direction to cause the sheet to abut on the side-end regulation member in each time when the sheet is conveyed to the sheet stacking means, in the state that the sheet abutting on the side-end regulation member is held by the holding means.

In a sheet treating apparatus according to the invention, it is possible that the moving means separates the sheet having a predetermined length in the width direction from the side-end regulation member by a predetermined distance in the width direction, after the moving means causes the sheet to abut on the side-end regulation member.

In a sheet treating apparatus according to the invention, it is possible that the binding means is configured to be movable in the width direction to a predetermined position where the sheets are bound, the predetermined position being separated from the side-end regulation member by a predetermined distance.

In a sheet treating apparatus according to the invention, it is possible that the moving means includes sheet conveying means for conveying the conveyed sheet in the opposite direction to the sheet conveying direction, the sheet conveying means being provided in a side-end portion on the upstream side in the sheet conveying direction of the sheet stacking means, the sheet conveying means causing the sheet to abut on the side-end regulation member which regulates a position in the sheet conveying direction of the sheet; and driving means for moving the sheet conveying means in the width direction in the state that the sheet abuts on the sheet conveying means.

Further, an image forming apparatus of the invention includes an image forming apparatus main body which has an image forming portion for forming an image in a sheet; and the above-described sheet treating apparatus which treats the sheet in which the image is formed by the image forming portion.

In an image forming apparatus according to the invention, it is possible that the image forming apparatus further includes detection means for detecting any one of the end portion in the width direction of the sheet, a central portion of the sheet, and an arbitrary position of the sheet, in which the moving means moves the sheet in the width direction by a distance corresponding to a distance between the side-end regulation member and any one of the end portion in the width direction of the sheet, the central portion of the sheet, and the arbitrary position of the sheet.

In an image forming apparatus according to the invention, it is possible that the moving means moves the sheet in the width direction based on information on a length in the width direction of the sheet from the image forming apparatus main body.

Further, an image forming apparatus of the invention which forms a sheet stack by aligning sheets conveyed an image forming portion to sheet stacking means and performs binding treatment to the aligned sheet stack by binding means, the image forming apparatus includes a side-end regulation member which is provided on a side of a width direction orthogonal to a sheet conveying direction of the sheet stacking means, the side-end regulation member regulating an end-portion position in the width direction of the sheet; and moving means for moving the sheet in the width direction to cause the sheet to abut on the side-end regulation member, in which the moving means moves the sheet in the width direction to cause the sheet to abut on the side-end regulation member in each time when the sheet is conveyed to the sheet stacking means such that the end portions in the width directions of the sheets whose lengths differ from one another in the width direction are aligned.

According to the invention, the sheet is abutted on the side-end regulation member in each time when the sheet is conveyed to the sheet stacking means such that the end portions in the width directions of the sheets whose lengths differ from one another in the width direction are aligned. Accordingly, the binding treatment can be performed even to a sheet stack in which the sheets having different sizes are mixed, and the appearance of the sheet stack can be improved when the stapling (binding) treatment is performed to the sheet stack.

Still other objects of the present invention, and the features thereof, will become fully apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a configuration of an image forming apparatus including a sheet treating apparatus according to an embodiment of the invention;

FIG. 2 is a view explaining the configuration of the sheet treating apparatus;

FIG. 3 is a view showing a state in which a sheet is discharged onto a treating tray of the sheet treating apparatus;

FIG. 4 is a view explaining offset rollers and conveying rollers in the sheet treating apparatus;

FIG. 5 is a view explaining a mechanism for driving the offset roller, the conveying roller, a sheet stack discharging member, and a sheet clamping member in the sheet treating apparatus;

FIGS. 6A, 6B, and 6C are views explaining operation of the offset roller and operation of the sheet associated with the operation of the offset roller;

FIGS. 7A and 7B are first views explaining the operation of the sheet clamping member;

FIGS. 8A and 8B are second views explaining the operation of the sheet clamping member;

FIG. 9 is a view showing the state in which the sheet stack discharge member discharges a sheet stack to a stack tray;

FIG. 10 is a block diagram showing the configuration of a control portion of the sheet treating apparatus;

FIG. 11 is a flowchart explaining a part of sheet treating operation of the sheet treating apparatus;

FIG. 12 is a flowchart explaining the remaining parts of the sheet treating operation of the sheet treating apparatus;

FIG. 13 is a view showing the state in which a stapling treatment is performed to the sheets offset by the offset roller;

FIG. 14 is a view showing the state in which the stapling treatment is performed with a stapler unit which can move the sheets offset by the offset roller in a sheet conveying direction; and

FIG. 15 is a view showing the state in which the stapling treatment is performed with the stapler unit which can move the sheets offset by the offset roller in a sheet width direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the accompanying drawings, a preferred embodiment of the invention will be described in detail.

FIG. 1 is a sectional view showing a configuration of an image forming apparatus including a sheet treating apparatus according to an embodiment of the invention. In FIG. 1, the reference character A denotes an image forming apparatus, the reference numeral 500 denotes an image forming apparatus main body, the reference numeral 300 denotes an automatic document feeder (ADF) provided on an upper surface of the image forming apparatus main body 500, and the reference numeral 400 denotes a sheet treating apparatus which treats the sheet discharged from the image forming apparatus A.

In FIG. 1, the reference numeral 120 denotes a reader portion (image input apparatus) which converts the original into image data, and the reference numeral 200 denotes a printer portion. The printer portion 200 has sheet cassettes 204 and 205. The printer portion 200 outputs the image data as a visible image onto the sheet according to a print command.

In the image forming apparatus A having the above configuration, when the original is read to form the image, the original placed on the auto document feeder (ADF) 300 is conveyed onto a platen glass surface 102 one by one.

When the original is conveyed to a predetermined position on the glass surface 102, a lamp 103 is lit in the reader portion 120, and a scanner unit 101 is moved to irradiate the original with the lamp 103. Reflected light from the original is input to a CCD image sensor portion 109 through mirrors 105, 106, and 107 and a lens 108. Normal digital processing is performed by electric processes such as optoelectric conversion in the CCD image sensor portion 109.

The image signal to which the electric processes are performed is converted into a modulated light signal by an exposure control portion 201 in the printer portion 200, and a photosensitive drum 202 is irradiated with the light signal. Then, a latent image is formed on the photosensitive drum 202 by the irradiation light. The latent image is developed by a developing device 203, which allows a toner image to be formed on the photosensitive drum 202.

A sheet S is conveyed from the sheet cassette 204 or 205 in synchronization with a front end of the toner image. The toner image is transferred to the sheet S with a transfer portion 206. Then, the toner image transferred to the sheet S is fixed with a fixing portion 207, and the sheet S to which the toner image is fixed is discharged outside the apparatus by a sheet discharging portion 208.

The sheet S output from the sheet discharging portion 208 is conveyed to a sheet treating apparatus 400. In the sheet treating apparatus 400, the sheets S are sorted according to an operation mode previously specified, and the treatments such as binding are performed.

When the images sequentially read are output in both sides of one sheet S, the sheet S of which the toner image is fixed onto one side by the fixing portion 207 is guided to a path 215 once by switching a direction switching member 209 to a direction shown by broken lines of FIG. 1, and then the sheet S is conveyed to a turn-over path 212 through a path 218 by switching a direction switching member 217 to broken lines and by switching a direction switching member 213 to broken lines.

After a rear end of the sheet S passes through the direction switching member 213, the direction switching member 213 is switched to solid lines to reverse a rotating direction of a roller 211, which guides the sheet S to a path 210. Then, the sheet S is conveyed to the transfer portion 206 to form the image on the backside of the sheet S.

In addition to sorting operation for sorting the sheets S, the sheet treating apparatus 400 has a stapling function in which a stapler unit performs binding operation. As shown in FIG. 2, the sheet treating apparatus 400 includes a treating tray 410 and a stack tray 421. The treating tray 410 treats the sheets S sequentially discharged from the image forming apparatus main body 500. The sheet stack treated on the treating tray 410 is finally stacked on the stack tray. The sheet stack having the number of sheets corresponding to the number of original sheets is formed on the treating tray 410, and each sheet stack is discharged to the stack tray 421.

In FIG. 2, the reference numeral 401 denotes a sheet receiving portion which receives the sheet S discharged from the image forming apparatus main body 500. After the sheet receiving portion 401 receives the sheet S, the sheet S is detected by an entrance sensor 403, and the sheet S is conveyed by conveying rollers 405 and offset rollers 407. Then, as shown in FIG. 3, the sheet S is conveyed onto the treating tray 410 which is of sheet stacking means. The sheet S stacked on the treating tray 410 is detected by a sheet stack discharge sensor 415 shown in FIG. 2.

At this point, the offset rollers 407 which are of sheet conveying means is held about an offset roller arm 406 in the state being able to be lifted and lowered. The offset roller arm 406 is vertically movable about a shaft 406a shown in FIGS. 4 and 5. When the sheet S is conveyed to the treating tray 410, the offset rollers 407 are moved upward through the offset roller arm 406, which allows the sheet S to be conveyed onto the treating tray 410 without being interrupted by the offset rollers 407.

The offset roller arm 406 can be lifted and lowered by a pickup solenoid 433 while the shaft 406a acts as a fulcrum. That is, the offset rollers 407 are lifted and lowered through a down lever 433a by turning on and off the pickup solenoid 433.

As shown in FIG. 5, the offset rollers 407 are driven through belts 431a and 431b by the conveying motor 431. The conveying motor 431 also drives the conveying rollers 405. When the conveying motor 431 is rotated, the offset rollers 407 are rotated (hereinafter, referred to as reversely rotated) in a conveying direction or the reverse direction according to the amount of rotation of the conveying motor 431.

In the embodiment, the entrance sensor 403 detects the sheet S, and the pickup solenoid 433 is turned off after the sheet S is moved to a predetermined position away from the entrance sensor 403. Therefore, the offset rollers 407 are lowered by deadweight to land on the sheet S. Then, the offset rollers 407 are rotated in a conveying direction for a predetermined time, and the offset rollers 407 are reversely rotated after the predetermined time elapses.

The reverse rotation allows the sheet S to abut on a sheet rear-end stopper 411 to perform alignment of the sheet S in the conveying direction. The sheet rear-end stopper 411 is of a side-end regulation member for regulating the position of the sheet S in the conveying direction. The sheet rear-end stopper 411 is vertically provided on the upstream side in the conveying direction of the treating tray 410.

In FIG. 4, the reference numeral 416 denotes a positioning wall which is of the side-end regulation member for regulating the end position of the sheet S in direction (hereinafter referred to as width direction) orthogonal to the conveying direction of the sheet S. The reference numeral 420 denotes a stapler unit which is of binding means for performing stapling treatment to the sheet stack formed on the treating tray 410. The stapler unit 420 is arranged near the positioning wall of the treating tray 410. An offset motor 432, which is of driving means and can rotate and reversely rotate, drives the offset rollers 407 through a rack 406c and a pinion 406a. Therefore, the offset rollers 407 can be moved in the width direction to be brought close to the positioning wall 416. The offset motor 432 and the offset rollers 407 constitute moving means.

When the offset rollers 407 are brought close to the positioning wall 46, the sheet S in which the alignment of the conveying direction is performed by abutting on the sheet rear-end stopper 411 is moved to the positioning wall 416 by frictional force of the offset rollers 407, and the sheet S is positioned in the width direction. After the sheet S abuts on the positioning wall 416, the offset rollers 407 are moved while sliding on the sheet S, and then the offset rollers 407 are stopped.

Thus, since the offset rollers 407 are provided, as shown in FIG. 6A, the sheet S discharged on the treating tray 410 is conveyed toward the stack tray side by the offset rollers 407 rotated in the sheet conveying direction. Then, as shown in FIG. 6B, the sheet S is returned to the sheet rear-end stopper 411 by the reverse rotation of the offset rollers 407, and the rear end of the sheet S abuts on the sheet rear-end stopper 411 to perform the alignment of the sheet S.

FIGS. 6A, 6B, 6C, 7A, 7B, 8A and 8B, and 13 differ from FIG. 4 in the configuration in which the offset rollers 407 are arranged inside the offset roller arm 406. However, the difference is only the design matter. Accordingly, for the configurations shown in FIGS. 4, 6A, 6B, 6C, 7A, 7B, 8A and 8B, and 13, there is no difference in the functions and operations.

Then, as shown in FIG. 6C, the offset rollers 407 are moved along the shaft 406a toward the positioning wall side in the state being in contact with the sheet S, which allows the end portion in the width direction of the sheet S to abut on the positioning wall 416 to perform the alignment in the width direction of the sheet S.

In FIG. 5, the reference numeral 412 denotes a sheet clamping member which is of sheet stack holding means. The sheet clamping member 412 presses the rear-end portion of the aligned sheet S from the upper side by bias force generated by biasing means (not shown). As mentioned later, the alignment in the width direction of the sheet S is performed, and the rear-end alignment of the sheet S is performed. Then, when the offset rollers 407 is lifted by the pickup solenoid 433 as shown in FIG. 7A, the aligned sheet S is pressed from the upper side by the sheet clamping member 412 as shown in FIG. 7B.

The sheet S previously discharged (conveyed) to the treating tray 410 can be held at a predetermined position while the previously discharge sheet S is not affected by pull-in of the sheets S subsequently discharged (conveyed).

When the offset rollers 407 are reversely rotated, as shown in FIG. 8A, the sheet clamping member 412 is rotated upward so that the sheet S can be received. When the sheet S and the offset rollers 407 are moved in the width direction in order to perform the alignment of the end portion of the sheet S, as shown in FIG. 8B, the sheet clamping member 412 is rotated upward so as not to become a load against the movement of the sheet S.

In FIG. 5, the reference numeral 413 denotes sheet stack discharging member which is cited as an example of sheet stack discharging means. The sheet stack discharging member 413 discharges the treated sheet stack to the stack tray 421. The sheet stack discharging member 413 rotatably holds the sheet clamping member 412. In the state that the sheet clamping member 412 holds the aligned sheet stack or the sheet stack stapled after the alignment, the sheet stack discharging member 413 moves the sheet stack toward the stack tray 421 provided on the downstream side of the treating tray 410 as shown in FIG. 9.

When the sheet S reaches a front end portion of the treating tray 410 which is of a sheet discharging position shown by the solid line, a sheet stack SA on the stack tray 421 is released from the hold of the sheet clamping member 412, and the sheet stack SA is discharged and stacked on the stack tray 421. The sheet stack SA discharged and stacked on the stack tray 421 is held by a pressing member 421A shown in FIG. 2.

As shown in FIG. 5, a sheet stack discharging motor 430 transmits power to the sheet stack discharging member 413 through the rack and pinion, which allows the sheet stack discharging member 413 to travel between the position where the sheet S is discharged to the stack tray 421 and a home position near the sheet rear-end stopper 411. Usually the sheet stack discharging member 413 is fixed at the home position by magnetic excitation of the sheet stack discharging motor 430.

In FIG. 5, the reference numeral 434 denotes a clamping solenoid which rotates the sheet clamping member 412. The clamping solenoid 434 is turned on after the offset rollers 407 convey the sheet S, the clamping solenoid 434 is turned on when the offset rollers 407 stop the rotation, and the clamping solenoid 434 is turned on when the offset rollers 407 are moved in the width direction. The clamping solenoid 434 rotates the sheet clamping member 412 upward through a lever 434a and a releasing lever portion 412a provided in the sheet clamping member 412.

In the embodiment, after the sheet S is moved in the width direction, in order to correct the shift in the sheet conveying direction, the offset rollers 407 are reversely rotated again to end the alignment operation, which realizes the alignment with high accuracy. When the alignment treatment is ended for the specified number of sheets, the sheet clamping member 412 is closed by the clamping solenoid 434 to hold the sheet stack.

FIG. 10 is a block diagram showing the configuration of a control portion of the sheet treating apparatus 400. The reference numeral 100 denotes a CPU which is cited as an example of controlling means in the embodiment. The CPU 100 has a ROM 110. A program corresponding to a control procedure shown in FIGS. 11 and 12 and the like are stored in the ROM 110. The CPU 100 controls each portion while reading the program.

A RAM 121 is incorporated in the CPU 100. Action data and input data are stored in the RAM 121. The CPU 100 controls based on the program while referring to the data stored in the RAM 121. Input ports of the CPU 100 are connected to sensors such as the entrance sensor 403 and the sheet stack discharge sensor 415. Output ports of the CPU 100 are connected to motors and solenoids such as the conveying motor 431, the offset motor 432, the sheet stack discharging motor 430, the pickup solenoid 433, and the clamping solenoid 434. The CPU 100 controls loads of various motors and solenoids, which are connected to the output ports, based on the states of the sensors according to the program.

The CPU 100 includes a serial interface portion (I/O) 130. The serial interface portion (I/O) 130 transmits control data to and receives the control data from (a control portion of) the image forming apparatus main body 500, and the CPU 100 controls each portion based on the control data transmitted from (the control portion of) the image forming apparatus main body 500 through the serial interface portion (I/O) 130.

Because the image forming apparatus main body 500 grasps a size of the sheet S discharged from the sheet discharging portion 208, the control portion of the sheet treating apparatus 400 (CPU 100) including a microcomputer system conducts serial communication with the control portion of the image forming apparatus main body 500, which allows the size of the sheet S inserted on the treating tray 410 to be grasped.

Accordingly, the control portion of the sheet treating apparatus 400 (CPU 100) grasps the size of the sheet S in each time when the sheet S is discharged (conveyed) from the image forming apparatus main body, and the CPU 100 can control the amount of movement in the width direction of the offset rollers 407 by controlling the offset motor 432. Therefore, the offset rollers 407 can be moved by the amount according to the size of the sheet S inserted on the treating tray 410, and the side portion of the sheet S is abutted securely on the positioning wall 416.

In the embodiment, the sheet stack SA stacked on the stack tray 421 constitutes a part of the treating tray 410. Therefore, when the sheet stack SA is discharged from the treating tray 410, the stack tray 421 is lowered by a stack tray lifting/lowering motor (see FIG. 10) until the uppermost surface of the sheet stack SA stacked on the stack tray 421 corresponds substantially to the treating tray 410.

Then, sheet treating operation of the embodiment as configured above will be described referring to a flowchart shown in FIGS. 11 and 12.

When the image forming apparatus main body 500 starts the image forming operation, the CPU 100 of the sheet treating apparatus 400 (see FIG. 10) checks whether a sheet discharging signal is received from the image forming apparatus main body 500 or not (S100). When the sheet discharging signal is received (Y in S100), the pickup solenoid 433 is turned on (S110) to pull up the offset rollers 407 supported by the offset roller arm 406.

Then, the conveying motor 431 is turned on (S120) so that the conveying rollers 405 installed at a midpoint of a sheet discharging path can convey the sheet S in the direction similar to the sheet discharging direction of the image forming apparatus main body 500. When the front end of the initial sheet S passes through the entrance sensor 403, the entrance sensor 403 is turned on (Y in S130). Then, the sheet S reaches the conveying rollers 405, which allows the power to be transmitted from the conveying rollers 405. When the sheet S is separated from the sheet discharging portion 208 (see FIG. 1) in the image forming apparatus main body 500 (Y in S140), the delivery of the sheet S is completed.

While the conveying rollers 405 convey the sheet S to the treating tray 410, the pickup solenoid 433 is turned off (S150) before the sheet S passes completely through the conveying rollers 405. Then, the offset rollers 407 are caused to land on the sheet S by the deadweight. As shown in FIG. 6A, the offset rollers 407 convey the sheet S to the predetermined position (S160). When the sheet S is conveyed to the predetermined position (Y in S160), the rotation of the conveying motor 431 is stopped (S170), and the conveyance of the sheet S is stopped.

The clamping solenoid 434 is turned on at the time when the rotation of the offset rollers 407 is stopped (S180), and the sheet clamping member 412 installed at the home position near the sheet rear-end stopper 411 is opened as shown in FIG. 6B. Then, the conveying motor 431 is rotated in the opposite direction to the conveying direction to pull back the sheet S with the offset rollers 407 (S190), and the rear end of the sheet S is abutted on the sheet rear-end stopper 411.

In causing the rear end of the sheet S to abut on the sheet rear-end stopper 411, in consideration of skew of the sheet S generated when the sheet S is conveyed from the image forming apparatus main body 500, the amount of rotation of the offset rollers 407 is set so that the sheet S can be conveyed slightly longer than the distance between a point where the conveyance of the sheet S is stopped to perform switchback and the sheet rear-end stopper 411.

The size of the discharged sheet S is checked based on size information from the image forming apparatus main body 500 (S200), and the amount of offset movement according to the size of the discharged sheet S is computed. That is, the amount of offset movement which is of the amount of movement in the width direction of the sheet S is computed (S210). The amount of movement in the width direction of the sheet S is necessary for pressing the sheet S discharged on the treating tray 410 against the positioning wall 416.

The offset motor 432 is driven to start the offset movement of the offset rollers 407 (S220). In moving the offset rollers 407, the offset rollers 407 and the sheet S which is in contact with the offset rollers 407 are moved in the direction of the positioning wall 416 by the frictional force of the offset rollers 407. At this point, as shown in FIG. 8B, the sheet clamping member 412 is rotated upward so that the sheet clamping member 412 does not become the load against the movement of the sheet S.

As shown in FIG. 6C, the sheet S abuts on the positioning wall 416 by the offset movement operation of the offset rollers 407, which performs the alignment in the width direction of the sheet S. After the offset rollers 407 causes the sheet S to abut on the positioning wall 416, the offset rollers 407 is slightly moved while sliding on the sheet S and the offset rollers 407 is stopped. In order to correct the alignment shift in the conveying direction after the offset movement, the alignment operation in which the offset rollers 407 are reversely rotated again to pull back the sheet S is performed (S230), and the alignment of the first sheet S is completed.

When the alignment of the first sheet S is completed, the pickup solenoid 433 is turned on (S240) to lift the offset rollers 407 as shown in FIG. 7A, and the clamping solenoid 434 is turned off (S250). Therefore, as shown in FIG. 7B, the sheet clamping member 412 is closed the sheet S in which the alignment has been performed is nipped and held. As a result, the pull-in of the first discharge sheet by the subsequently discharged sheet S can be prevented.

Then, as shown in 7B, the offset rollers 407 are returned and moved to the home position by the offset motor 432 through the rack and pinion in the state being lifted (S260).

It is checked whether or not the sheet S accommodated on the treating tray 410 is the final sheet corresponding to the final page of the original to be copied (S270). When determined based on the information transmitted from the image forming apparatus main body 500 that the sheet S is not the final sheet S (N in S270), the flow returns to S100, and a sheet discharging signal sent from the image forming apparatus main body 500 is received. The flow is repeated until the final sheet S is accommodated in the treating tray 410.

In the configuration of the embodiment, the control portion (CPU 100) of the sheet treating apparatus 400 computes the amount of offset movement suitable for the sheet S while grasping the size of the sheet S at each time when the sheet S is discharged from the image forming apparatus main body 500. Accordingly, the sheet S with which the offset rollers 407 are in contact is subjected to the alignment treatment based on the computed amount of movement, and the sheet S is aligned with the positioning wall 416.

When determined that the sheet S is the final sheet S (Y in S270), since the sheet stack corresponding to the original to be copied is formed on the treating tray 410, it is checked whether the stapling treatment is selected or not (S280). When the stapling treatment is selected (Y in S280), the staple unit 420 is driven to perform the stapling treatment at a staple position shown in FIG. 13 (S290).

As shown in FIG. 13, even if the sheets S1 and S2 whose sizes differ from each other are mixed in the sheet stack stacked on the treating tray 410, each of the sheets S1 and S2 is subjected to the alignment treatment according to the size, so that the each of the sheets S1 and S2 is aligned with the positioning wall 416. Because the alignment position is one in which corner portions of the sheets S1 and S2 are inserted into the binding portion (not shown) of the stapler unit 420, the binding treatment is securely performed by the subsequent stapling treatment.

When the stapling treatment is not selected (N in S280), or after the stapling treatment is completed, the sheet stack discharging motor 430 causes the sheet stack discharging member 413 to proceed toward the direction of the stack tray 421 in the state that the sheet stack SA is held by the sheet clamping member 412, and the sheet stack SA is discharged (S300).

The movement (lowering) process of the stack tray 421 is performed in synchronization with the sheet stack discharging operation (S310), and the sheet stack discharging member 413 is returned to the home position (S320). In order to stop the rotation of the conveying rollers 405 and offset rollers 407, the conveying motor 431 is stopped (S330) and the pickup solenoid 433 is turned off (S340), which lowers the offset rollers 407 to end the series of the treatments.

As described above, in each time when the sheet S is conveyed to the stack tray 421, the offset rollers 407 causes the sheet S to abut on the positioning wall 416 to align the end portions in the width directions of the sheets S whose lengths in the width directions differ from one another. Therefore, even if the sheet stack SA includes the sheets S whose sizes differ from one another, the binding treatment is securely performed and the appearance of the sheet stack SA becomes better when the binding treatment is performed to the sheet stack SA. In moving the sheet S in the width direction to abut on the positioning wall 416, since the sheet S previously aligned is held by the sheet clamping member 412, disorder of the alignment is never generated.

In the embodiment, the fixed type stapler unit 420 for binding the sheet stack SA is used, and the stapler unit 420 is arranged near the positioning wall 416. The invention is not limited to the embodiment. It is also possible to use the movable type stapler unit 420 which can be moved in the sheet conveying direction or in the width direction.

When the movable type stapler unit 420 which can be moved in the sheet conveying direction is used, as shown in FIG. 14, the stapling treatment can be performed at another point in the sheet conveying direction of the sheet stack SA or at plural points in the sheet conveying direction.

When the movable type stapler unit 420 which can be moved in the width direction is used, the stapling treatment can be performed at another point in the width direction of the sheet stack SA or at plural points in the width direction. After the offset rollers 407 causes the sheet S having the predetermined size to abut on the positioning wall 416, the sheet S is separated from the positioning wall 416 to the wide direction in accordance with sheet size, and the movable type stapler unit 420 which can be moved in the width direction is moved to the predetermined position in the width direction. Therefore, as shown in FIG. 15, the sheet stack SA in which the sheets S1, S2, and S3 having the different sizes are mixed can be bound with respect to the center, and the appearance of the sheet stack SA becomes better when the binding treatment is performed.

In the embodiment, the offset rollers 407 is used as the sheet conveying means, the offset motor 432 is used as the driving means, and the sheet conveying means and the driving means constitute the moving means for moving the sheet S in the width direction. The invention is not limited to the embodiment. The same effects are obtained, when the moving means is constituted by the sheet conveying means for moving the member itself in the conveying direction to convey the sheet and the driving means for moving the sheet conveying means in the width direction.

In the embodiment, the CPU controls while reading the program written on the RAM (or the ROM), which is shown in the flowchart of FIGS. 11 and 12. However, the same effects are obtained when hardware performs the processes on the control program.

In the embodiment, the amount of offset movement is computed based on the sheet size information which is of the length information in the width direction of the sheet S discharged from the image forming apparatus main body 500. The invention is not limited to the embodiment. For example, the same effects are obtained, when detection means for detecting the length in the width direction of the sheet is provided in the sheet treating apparatus 400 to control the amount of offset movement of the offset roller 407 according to a detection signal from the detection means.

Further, foe example, the detection means for detecting any one of the end portion in the width direction of the sheet, the central portion of the sheet, and an arbitrary position of the sheet is provided, and the offset rollers 407 are moved in response to the detection signal from the detection means by the distance between the positioning wall 416 and any one of the end portion in the width direction of the sheet, the central portion of the sheet, and an arbitrary position of the sheet. Therefore, the same effects are obtained.

In the above descriptions, the CPU of the control portion provided in the sheet treating apparatus in the image forming apparatus controls the operations of the offset rollers and the like. It is also possible that the CPU of the control portion is provided in the image forming apparatus main body and the CPU controls the sheet treating operations of the offset rollers and the like.

The present invention has been explained by preferred embodiments thereof, but the present invention is by no means limited by such embodiments and is subject to any and all modifications within the scope and spirit of the appended claims.

This application claims priority from Japanese Patent Application No. 2004-122290 filed Apr. 16, 2004, which is hereby incorporated by reference herein.

Sheet treating apparatus and image forming apparatus therewith

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