JP3177427B2 - Sheet conveying device and sheet processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet processing apparatus such as a printer, a copier, a facsimile, a scanner, etc., for example, a single-sided printing apparatus having only a single-sided sheet conveying path in the image forming apparatus main body. 1. Field of the Invention The present invention relates to a sheet conveying device used for performing double-sided printing with an image forming apparatus having specifications. Here, the sheet processing apparatus is a general term for an apparatus having a sheet processing unit that performs a predetermined process (for example, forming an image, reading an image, and the like) on sheets fed one by one. ing.

[0002]

2. Description of the Related Art Some image forming apparatuses (sheet processing apparatuses) such as printers, copiers, and facsimile machines have only a single-sided printing sheet conveyance path in the main body of the image forming apparatus. Some apparatuses can perform double-sided printing by installing an optional sheet conveying apparatus for double-sided printing (sheet conveying apparatus).

[0003] Here, the sheet conveying device for double-sided printing detachably mounted on the image forming apparatus main body, reverses the front and back surfaces of the first-side printed sheet discharged from the image forming apparatus main body, and reverses the image forming apparatus. It fulfills the function of transporting into the body. Normally, the reversal of the front and back surfaces of the printed sheet on the first side is performed by a switchback transport unit (a pair of rollers capable of normal and reverse rotation) that changes the transport state from normal transport to switchback transport. The front and back sides of the printed sheet on the first side are reversed during switchback conveyance.

In the case of a conventional sheet conveying apparatus for double-sided printing, (1) the state in which the switchback conveying means is already driven in the normal conveying state when the sheet on which the first side has been printed is discharged from the image forming apparatus main body. It is in. Also,
(2) The switchback transport means for transporting the sheet printed on the first surface in a switchback manner transports the sheet printed on the first surface in a straight line.

[0005]

However, when the above-described conventional sheet conveying device (sheet conveying device for double-sided printing) is used, jams are likely to occur or printing on the second surface cannot be performed accurately. There is a problem.

That is, the first-side printed sheet discharged from the image forming apparatus main body is often skewed, but in the above-described conventional example, the first-side printed sheet is in a state where the skew is not corrected. Since the sheet is normally conveyed by the switchback conveying means as it is, the skew amount gradually increases, and for example, a jam easily occurs in the retreat path.

Further, a regulating means (one-sided conveyance reference) for regulating the position in the width direction of the first-side printed sheet conveyed by the switchback conveyance means is provided. Since the printed first-side printed sheet is traveling straight, there are some sheets whose side edges in the width direction cannot contact the regulating means. Since such a sheet is conveyed to the image forming unit without being restricted in the width direction, printing on the second surface cannot be performed accurately. This is because, in the image forming unit, printing on the second surface is started from a position corresponding to the regulated position by the regulating means.

Accordingly, the present invention has been made in view of the above circumstances, and it is difficult for a skewed sheet to be jammed even with a skewed sheet. It is an object of the present invention to provide a sheet conveying device that can reliably perform position control in the width direction.

[0009]

According to the present invention, there is provided a switch for conveying a first processed sheet discharged from a sheet processing apparatus main body into a sheet processing apparatus main body after normal conveyance. In a sheet transport apparatus provided with a back transport unit, the switchback transport unit has a pair of rollers that can rotate forward and reverse, and the pair of rollers is a first roller that is discharged from the sheet processing apparatus main body.
The rotation-processed sheet is brought into contact with the nip to form a predetermined amount of loop, and the rotation is stopped until the skew state of the sheet is corrected by forming the loop. When the loop is formed and the skew state is corrected, the sheet is rotated in a predetermined direction and the sheet is normally conveyed.

[0010] The present invention is characterized in that the speed at which the switchback conveying means normally conveys the sheet is higher than the moving speed of the sheet discharged from the sheet processing apparatus main body.

Further, the switchback conveyance means is configured to skew the sheet during switchback conveyance.

Further, the sheet is skewed when the nip line of one of the rollers in the pair of rollers is inclined during switchback conveyance.

When the pair of rollers is driven in the normal transport direction, the nip lines of both rollers are in a parallel state.

Further, the sheet is skewed by moving one of the pair of rollers in the axial direction by a predetermined amount during switchback conveyance.

Further, when the pair of rollers is driven in the normal transport direction, the roller moved in the axial direction returns to the original position.

Further, the present invention is characterized in that it has a one-side reference conveyance path for changing the skewed state of the sheet conveyed by the switchback conveyance means to the straight state.

Further, the first sheet through which a sheet having a small width is passed.
And a second one-sided reference transport path through which a sheet having a large width passes is formed in the same path.

Further, there is provided a sheet processing apparatus characterized in that the above-mentioned sheet conveying device is mounted on a sheet processing apparatus main body.

Further, when the above-mentioned sheet conveying apparatus is mounted on the sheet processing apparatus main body, the printing operation in the second mode becomes possible, and the first processed sheet is fed into the sheet conveying apparatus, and the sheet is conveyed. The first processed sheet sent from the apparatus is transported to a sheet processing unit.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows the overall configuration of an image forming apparatus (laser beam printer) equipped with a sheet conveying apparatus for double-sided printing according to the present invention. FIG. 2 shows the configuration of a sheet transport apparatus for double-sided printing according to the present invention.

The image forming apparatus 100 shown in FIG. 1 has a single-sided printing specification in which the image forming apparatus main body 101 has only sheet conveying paths P1, P3, P4, P5, and P6 for single-sided printing. However, as shown, by mounting the optional double-sided printing sheet conveying device 200 at a predetermined position of the image forming apparatus main body 101, double-sided printing becomes possible.

Here, the overall configuration of the image forming apparatus 100 will be described along the flow of recording sheets in the single-sided printing mode when the optional double-sided printing sheet conveying device 200 is not mounted.

At the bottom of the image forming apparatus main body 101, a paper feed cassette 110 is installed.
The recording sheets S stacked and stored in the sheet 10 are fed one by one toward the transfer unit.

In the paper feed cassette 110, a support shaft 1 at the rear end is provided.
An intermediate plate 112 that is rotatable up and down around the center 11 and whose distal end is pushed up by a push-up spring 113 is provided. A large number of recording sheets S are stacked on the middle plate 112.

The recording sheets S stacked in the sheet feeding cassette 110 are sequentially fed out from the uppermost sheet by a half-moon-shaped feeding roller 120 which makes one rotation counterclockwise in the drawing. Then, only the uppermost sheet of the recording sheet S fed by the feeding roller 120 is separated by the separation claw 114.

The recording sheet S fed by the feeding roller 120 reaches the registration roller pair 122 that is stopped rotating through the path P1. At this time, the conveying roller pair 121
Transports the recording sheet S.

The pair of conveying rollers 121 temporarily stops rotating when a predetermined amount of loop is formed on the recording sheet S when the leading end of the recording sheet S abuts the nip of the pair of registration rollers 122. By forming this loop, the skew state of the recording sheet S is corrected.

The recording sheet S that has been corrected for the skew state is
In the process unit 140, the photosensitive drum 141 is rotated by a registration roller pair 122 which starts rotating at a timing of aligning the position of the toner image on the photosensitive drum 141 rotating clockwise in FIG.
Is transferred to the transfer section between the transfer roller 123 and the transfer roller 123. At this time,
The recording sheet S passes through the path P3. The toner image on the photosensitive drum 141 rotating clockwise is sequentially transferred to the sheet surface of the recording sheet S sent to the transfer unit.

The laser beam L emitted from the laser scanner unit 130 is irradiated on the photosensitive drum 141 rotating clockwise. Thereby, an electrostatic latent image is sequentially formed on the photosensitive drum 141,
The latent image is visualized by toner supplied from a developing unit (not shown).

The toner image-transferred sheet S being conveyed by the photosensitive drum 141 and the transfer roller 123 is sent to the fixing device 150 through a path P4. The transferred toner image is fixed on the sheet surface by being heated and pressed while passing through the nip between the fixing roller 151 and the pressure roller 152.

The recording sheet S which has been subjected to the fixing process of the toner image by the fixing device 150 is discharged outside the apparatus. In the case of the image forming apparatus 100, two types of discharge modes can be selected. Has become. One is face-down discharge in which the print surface is discharged downward, and the other is face-up discharge in which the print surface is discharged upward.

For example, when performing face-down discharge, the discharge tray 102 that can be opened and closed in the vertical direction about the support shaft 103 is closed as shown by the solid line, and the flapper 160 passes the path P5. Is set to the position shown by the solid line. By doing so, the recording sheet S conveyed by the paper discharge roller pairs 153 and 154 passes through the path P5, is discharged out of the apparatus by the paper discharge roller pair 170, and is formed on the upper surface of the image forming apparatus main body 101. Are stacked on the discharge tray 101a.

When performing face-up paper discharge, the discharge tray 102 is opened as shown by the dotted line, and the flapper 160 is set at the position shown by the dotted line where the path P6 opens. By doing so, the recording sheet S conveyed by the discharge roller pairs 153 and 154 passes through the path P6 and is discharged out of the apparatus via the discharge port 104.
The paper is stacked on the open paper discharge tray 102.

The setting position of the flapper 106 that opens and closes the paths P5 and P6 automatically changes in conjunction with the opening and closing operation of the paper discharge tray 102. That is, when the closed discharge tray 102 is opened to the position shown by the dotted line, the flapper 1 set at the position shown by the solid line is opened.
Numeral 60 rotates counterclockwise around the support shaft 161 and is set at the position shown by the dotted line. In this case, the flapper 160 is constantly urged clockwise by a spring or the like (not shown). When the open paper discharge tray 102 is closed as shown by the solid line, the flapper 160 set at the position shown by the dotted line is rotated clockwise by the urging force of the spring or the like to be set at the position shown by the solid line. You.

When double-sided printing is performed by the image forming apparatus 100, as shown in FIG.
1. The double-sided printing sheet conveying device 200 of the present invention is mounted at a predetermined position. Here, the sheet conveying device body 20
1 is a part of the fixing device 150 of the image forming apparatus main body 101.
Space 1 formed between the paper cassette 110
01b (see FIG. 2). As described above, when a part of the sheet conveying apparatus main body 201 is inserted into the space 101b, the sheet conveying apparatus 200 for double-sided printing is automatically locked with respect to the image forming apparatus main body 101. When the double-sided printing transport device 200 is pulled out with a certain force, the locked state is released.

When the sheet conveying device 200 for double-sided printing according to the present invention is mounted on the image forming apparatus main body 101, the sheet discharge tray 102 must be closed.
Therefore, in the image forming apparatus 100 in a state in which double-sided printing can be performed, the recording sheet S cannot be discharged onto the discharge tray 102 for face-up discharge, and all the recording sheets S after printing are face-down. The paper is discharged onto the paper discharge tray 101a for paper discharge.

Next, with reference to FIGS. 1 and 2, the structure of the sheet conveying apparatus 200 for double-sided printing according to the present invention will be described.

The sheet transporting apparatus 200 for double-sided printing is provided with flapper switching means capable of automatically changing the setting position of the flapper 160 in the main body 101 of the image forming apparatus. This flapper switching means includes a lever member 280 that can rotate up and down around a support shaft 281.
And a solenoid 282 whose plunger 282a contracts in the direction of the arrow when the solenoid is turned on. One end (cam follower) 280 a of the lever member 280 is connected to a cam member 162 fixed on a support shaft 161 of the flapper 160.
Is in contact with Also, the other end 280 of the lever member 280
b is linked to the tip of the plunger 282a in a link by a connecting shaft 283.

When the plunger 282a is reduced with the solenoid on, the lever member 280 rotates clockwise about the support shaft 281 and the cam follower 280 is rotated.
a presses the cam member 162. As a result, the cam member 162 rotates counterclockwise, and the flapper 160 is set at the position where the path P6 is opened as shown in FIG. When performing double-sided printing, the flapper 160 is first set at this position so that the first-side printed sheet S can enter the sheet conveying apparatus 200 for double-sided printing.

When the plunger 282a extends when the solenoid is off, the lever member 280 rotates counterclockwise about the support shaft 281 and the cam follower 28
The pressing force of 0a is released. Thereby, the cam member 16
2 rotates clockwise, and the flapper 160 is set at a position to open the path P5 as shown by the solid line in FIG. After the first-side printed sheet S passes through the path P6 during double-sided printing, the flapper 160 is set at this position so that the second-side printed sheet S can pass through the path P5. Also, the flapper 160 is always set at this position during one-sided printing.

In the sheet conveying apparatus 200 for double-sided printing, the front and back sides of the first-side printed sheet S discharged from the discharge port 104 of the image forming apparatus main body 101 are turned over and conveyed into the image forming apparatus main body 101. Switchback transport means 260 and 261 are provided. The switchback transporting means 260 and 261 reverses the front and back surfaces by normally transporting the first-side printed sheet S and then performing switchback transport. Where 260
Numeral denotes a transport roller which can be rotated forward and reverse by driving from the motor M1, and 261 is a transport roller which rotates following the transport roller 260 in contact therewith. The first-side-printed sheet S is conveyed between the conveying roller 260 and the conveying roller 261. The transport roller 261 is in contact with the transport roller 260 at a predetermined pressure by the urging force of the spring 262.
Further, the transport roller 260 is attached to the sheet transport apparatus main body 201 side, and the transport roller 261 is attached to the openable / closable cover 212 side that can be opened and closed about the support shaft 211.

The first-side printed sheet S discharged from the discharge port 104 of the image forming apparatus main body 101 passes through the path P7.
And reaches the transport roller 260, and the leading end of the sheet enters the nip between the transport roller 260 and the transport roller 261. At this time, since the conveyance roller 260 has stopped rotating, the first-side printed sheet S being continuously discharged is curled in a wide space upstream of the path P7. Due to the formation of the curl, the skew state of the first surface printed sheet S is corrected. FIG. 7 shows the first-side printed sheet S when the skew correction has been completed.

In the upstream portion of the transport roller 260,
A reversing flapper 251 is provided. The flapper 251 normally closes the downstream portion of the path P7 as shown in FIG. In this case, the flapper 251 rotates clockwise around the support shaft 250 by its own weight of the light shielding member 252 connected to the flapper 251, and is in contact with the positioning member 215 provided on the cover member 212. . Then, when the side surface 251a is pressed by the front end of the first surface printed sheet S moving downstream, as shown in FIG. 7, the sheet S rotates counterclockwise around the support shaft 250 and passes through the path. 7 is opened to allow the sheet S to pass through.

As shown in FIG. 7, when the flapper 251 opens the path 7, the light blocking member 252 interlocking with the rotation of the flapper 251 moves on the optical path of the photo interrupter 240 (between the light emitting unit 241 and the light receiving unit 242). And the photo interrupter 240 is turned on. When the photointerrupter 240 is turned on, it can be detected that the first-surface-printed sheet S is passing through the flapper 251. Further, when the state in which the flapper 251 opens the path P7 changes to a state in which the path P7 is closed, the light shielding member 2 is closed.
52 interrupts the optical path of the photo interrupter 240. As a result, the photo interrupter 240 is turned off. When the photointerrupter 240 is turned off, it can be detected that the rear end of the sheet S on which the first surface has been printed has passed the flapper 251.

The transport roller 260 rotates counterclockwise when the predetermined amount of curl is formed on the first-side printed sheet S, and performs normal transport of the first-side printed sheet S. The first surface printed sheet S moving downstream by this conveyance enters the path P8 while traveling straight. In this case, the transport speed of the transport roller 260 is higher than the transport speed of the pair of paper discharge rollers 153 and 154. By doing so, the skew correction loop of the first-side printed sheet S is rapidly eliminated, and the curling at the rear end of the sheet is less likely to occur, and the transportability during switchback transport described later is improved. . FIG. 8 shows the first-side printed sheet S which is normally conveyed by the conveying roller 260.

Immediately after the trailing edge of the sheet has passed the flapper 251 (at this point, the photo interrupter 240 is turned off, and the flapper 251 closes the path P7), the transport roller 260 rotates clockwise to the first position. The switchback conveyance of the sheet S on which the surface is printed is performed. FIG. 9 shows the first-side printed sheet S on which the switchback conveyance is started. The first-side printed sheet S that has been switched back enters the reversing path P9 while being guided by the side surface 251b of the flapper 251 closing the path P7, and proceeds downstream. By passing through the path P9, the front and back surfaces of the first-side printed sheet S are reversed. The first surface printed sheet S passing through the path P9 is skewed rightward (toward the front side in the drawing) in the sheet conveying direction by the action of the conveying rollers 261.

FIGS. 3 and 4 show the detailed configuration of the switchback transport means (transport roller 260 and transport roller 261). FIG. 3 is a front view as viewed from the left side of FIG.

The transport roller 260 comprises a plurality of rollers 260-1 to 260-4 arranged at a predetermined interval. Rollers 261-1 to 261-4 are respectively provided on the rollers 260-1 to 260-4 with springs 262-1 to 262-
4 and is in contact.

The rollers 261-1 to 261-4 are rotatably mounted on support plates 263, 264 provided on the cover member 212. In this case, the roller 261-1
261-4 (the right axis in the figure) 261
a is fitted into a circular hole 264a, and the other shaft (left shaft in the figure) 261a is an elongated oval hole 263a that is long in the vertical direction.
It is fitted in.

The transport rollers 261-1 to 261- when the switchback transport unit corrects the skew of the first-side printed sheet S, and when the normal transport of the skew-corrected first-side printed sheet S is performed. 4 is in the state of FIG. That is, the left shaft 261a is in contact with the lower end of the oval hole 263a to form the gap G. At this time, the rollers 261-1 to 261-1
261-4 nip line and rollers 260-1 to 260-4
Nip lines are parallel. Therefore, the roller 261-
The front end of the first surface printed sheet S on which the skew correction is performed by the rollers 1-26-1-4 and the rollers 260-1 to 260-4 is entirely aligned at the same position. In addition, the roller 261-
The first surface printed sheet S that is normally conveyed while being sandwiched between the rollers 1-26-1 and rollers 260-1 to 260-4 travels straight.

FIG. 4B shows that the switchback transport means is the first
The state of the conveyance rollers 261-1 to 261-4 when performing the switchback conveyance of the sheet S on which the surface has been printed is illustrated. When the first-side printed sheet S is transported in a switchback manner, the rollers 260-1 to 260-4 rotate clockwise in FIG. For this reason, the roller 260
Roller 261-1 that rotates following the rotation of -1 to 260-4
The left shaft 261a in the movable state of 261-4 moves upward, and the nip line of the rollers 261-1 to 261-4 is inclined rightward and downward. As a result, the first-side printed sheet S conveyed by the switchback is skewed.

The switch-back conveying means terminates the switch-back conveyance (the first-side printed sheet S is moved by the rollers 260-1 to 260-4 and the rollers 261-1 to 261-4).
4A), and returns to the initial state of FIG. 4A for skew correction and normal conveyance of the next sheet. This state can be obtained by rotating the rollers 260-1 to 260-4 by a predetermined amount in the counterclockwise direction in FIG.

The first surface printed sheet S that has passed the path P9 after the switchback has passed the path P10 in the main body 271 of the positioning device 270 (photointerrupter 29).
0), then passes through path P2 and passes path P1
And is sent to the pair of registration rollers 122 whose rotation is stopped. Hereinafter, the first-side printed sheet S whose front and back surfaces have been inverted by the double-sided printing sheet conveying device 200 will be described.
Is similarly conveyed at the time of printing on the first side, and after the steps of printing on the second side and fixing the same toner image, are discharged onto the discharge tray 101a outside the apparatus by the discharge roller pair 170. .

Here, the configuration and functions of the positioning device 270 will be described with reference to FIGS.
FIG. 6 is a cross-sectional view in the direction of arrows X1 and X2 in FIG.

The positioning device 270 is for adjusting the first-surface-printed sheet S, which has been skewed in the path P9, to advance straight on the basis of one-sided conveyance. While the first-side printed sheet S is moving in the path P10, the entire one side end (the front end in FIG. 5) in the width direction comes into contact with the transport reference plane. Here, a path P10-1 dedicated to a sheet SA having a large width and a path P10-2 dedicated to a sheet SB having a small width are provided.
10-1 passes through the sheet S with a small width
B passes through the path P10-2. These sheets SA and SB are both skewed conveying means (conveying rollers 272-1 and skewed rollers 273-1, conveying rollers 272-2 and skewed 273-
It is sent obliquely to 2).

The path P10-1 has a flat guide surface 27.
1a and a vertical guide surface (one-sided conveyance reference surface) 271c. The path P10-2 includes a planar guide surface 271b and a vertical guide surface 271d. Between the two paths P10-1 and P10-2, the path P10-
The sheet SB having a small width moving in the sheet 2 is the path P1.
A partition wall 271e is formed to prevent the partition wall 271 from entering the area 0-1. Also, each path P10-1,
The inclined guide surface 27 is provided at the sheet introduction portion of P10-2.
1f and 271g are formed.

The sheet SA having a large width passing through the path P9 is guided by the guide surface 271f while passing through the path P1.
0-1 and moves on the guide surface 271a while the oblique feeding means moves one end in the width direction to the guide surface 27a.
1c. FIG. 6A shows that the sheet SA passes the path P10.
-1 indicates a state in which it is moving. Also, pass P
The small-sized sheet SB that has passed through No. 9 is the guide surface 2
While entering the path P10-2 while being guided by 71g, one side end in the width direction is brought into contact with the guide surface 271d by the above-described oblique transporting means while moving on the guide surface 271b.
FIG. 6C shows a state where the sheet SB is moving in the path P10-2.

The large-size sheet SA passing through the path P10-1 is, for example, an A4 size or LTR size sheet, and the small-size sheet S passing through the path P10-2.
B is a sheet of B5 size and EXEC size, for example. In this case, the A4 size has a smaller width size than the LTR size, and the A5 size has a smaller width size than the EXEC size. Therefore, the guide surfaces 271c and 271d of the paths P10-1 and P10-2 and one end in the width direction are connected. Is large, but the magnitude of this distance can be reduced by obliquely feeding the first-side printed sheet S to be switched back.

Next, the structure of the skew feeding means for skew feeding the first-side printed sheet S moving in the path 10 will be described.

The skew conveying means includes conveying rollers 272-1 and 272-1.
272-2 and oblique feed rollers 273-1 and 273-2. The transport rollers 272-1 and 272-2 are provided with roller shafts 272 that are oriented in a direction orthogonal to the sheet transport direction.
a, 272b. The roller shaft 272a,
Reference numeral 272b is rotatably attached to the main body 271 via bearings 275 and 276. Both roller shafts 272
a and 272b are connected by an endless belt 279 wound around pulleys 277 and 278. The drive of the motor M2 is performed by the roller shaft 27 via the gears 281 and 280.
2a and 272b, the conveying rollers 272-
1, 272-2 rotate clockwise in FIG.

The oblique feed rollers 273-1 and 273-2 are in contact with the transport rollers 272-1 and 272-2 at a predetermined pressure. The rollers 273-1 and 273-2 are the main body 2
It is supported by a leaf spring 274 attached to the base 71 and is urged by the leaf spring 274. As a result, the rollers 273-1 and 273-2 move the rollers 272-1 and 272-1.
It rotates following the rotation of 272-2. In addition, roller 273-
The nip lines of 1,273-2 are rollers 272-1,272
-2 is inclined with respect to the nip line. As a result, the rollers 272-1 and 272-2 and the roller 27
1st which is pinched and conveyed by 3-1 and 273-2
The surface printed sheet S is the guide surface 271c, 271d
You will be able to approach in the direction.

The path P7 includes guide members 224, 213, and 2
The path P8 is formed by the guide member 21.
4, 201c and 201d, and the path P9 is formed by the guide members 201a and 201b. The guide member 224 is attached to the cover member 220. The guide members 213 and 214 are
2 attached. Guide members 201a, 201
b and 201c are attached to the main body 201. The guide member 201d is a bottom plate of the main body 201.

The cover members 220 and 212 are for performing a jam processing. When a jam occurs in the main body 201, the cover members 220 and 212 are opened to perform the jam processing. The cover member 212 can be opened and closed about the support shaft 211. The cover member 220 is coupled to the cover member 212 via a coupling shaft 223. The coupling shaft 223 is fitted in an arc-shaped hole 217 formed in the guide member 213. The cover member 220 is normally urged in a counterclockwise direction by a torsion spring 222 attached to the shaft 221 such that the coupling shaft 223 is located at the upper end of the arc-shaped hole 217. The set position of the cover member 220 is detected by the photo interrupter 230. When the light blocking unit 225 does not block the optical path between the light emitting unit 23121 and the light receiving unit 232 in the state of FIG. 2, the photo interrupter 230 is on, and it is detected that the cover member 220 is at the correct position.

<Second Embodiment> FIGS. 11 and 12 show another configuration example (1) of the switchback transport means.

Here, the skew of the printed sheet S on the first side during switchback conveyance is performed by conveying rollers 261-1 to 261-2.
61-4, without tilting the nip line.
２６０260-4 is slid in the axial direction, and
The oblique feed is performed by changing the position with respect to 1-1 to 261-4.

The shaft 260 of the rollers 260-1 to 260-4
a is a bearing 266 with respect to the supporting members 265a and 265b.
a and 266b so as to be rotatable and slidable. The drive of the motor M1 is transmitted to the shaft 260a via the helical gear 267. The helical gear 267 is fitted non-rotatably with respect to the shaft 260a, and is non-slidable with respect to the shaft 260a by regulating members 268a and 268b.

FIGS. 11 (a) and 11 (b) show the set positions of the rollers 260-1 to 260-4 during skew correction and during normal conveyance. At this time, the rollers 260-1 to 260-
No. 4 is located at approximately the same position as the rollers 261-1 to 261-4, and the helical gear 267 is located at a distance H from the bearing 266a. Therefore, the first surface printed sheet S normally conveyed while being sandwiched between the rollers 260-1 to 260-4 and the rollers 261-1 to 261-4 advances straight.

FIGS. 12A and 12B show the set positions of the rollers 260-1 to 260-4 during switchback conveyance. When the helical gear 267 rotates in a predetermined direction, the helical gear 267 receives a force in the thrust direction from a mating helical gear (not shown) and slides by the gap H. Thereby, axis 2
60a slides in the direction of the arrow,
The set position of 260-4 changes as shown. When the switchback transport is performed at this position, the first-side printed sheet S is skewed.

<Third Embodiment> FIGS. 13 and 14 show another configuration example (2) of the switchback transport means.

Here, the skew feeding of the first-side printed sheet S during switchback conveyance is performed by using conveyance rollers 261-1 and 261-2.
Without tilting the nip line of 61-4, each transport roller 260-
1 to 260-4 are slid in the axial direction to transport the roller 2
The oblique feed is performed by changing the position with respect to 61-1 to 261-4.

Each of the rollers 260-1 to 260-4 has a shaft 26
0a so as to be rotatable. And
The amount of rotation is regulated by fitting the guide shaft 260d on the shaft 260a side into the spiral groove 260c formed in the boss 260b.

FIGS. 13 (a) and 13 (b) show the set positions of the rollers 260-1 to 260-4 during skew correction and during normal conveyance. At this time, the rollers 260-1 to 260-
Reference numeral 4 is at substantially the same position as the rollers 261-1 to 261-4, and the guide shaft 260d is located at one end of the spiral groove 260c.

At this time, even if the rollers 260-1 to 260-4 rotate in a predetermined direction, the guide shaft 260d is
0c, the rollers 260-1 to 260-2
The position of 60-4 does not change. Therefore, the roller 260-
The first-surface-printed sheet S conveyed while being sandwiched between the rollers 1-261-4 and the rollers 261-1 to 261-4 travels straight.

FIGS. 14A and 14B show the set positions of the rollers 260-1 to 260-4 at the time of switchback. When the shaft 260a rotates in a predetermined direction from the state shown in FIG. 13, the guide shaft 260d located at the position shown in FIG. 13 moves in the spiral groove 260c.
Reference numeral 60-2 slides a predetermined amount to the right in the figure, and the set position changes. When the switchback transport is performed at this position, the first-side printed sheet S is skewed.

[0076]

As described above, in the sheet conveying apparatus of the present invention, a predetermined amount of loop is formed by abutting the leading end of the first processed sheet discharged from the sheet processing apparatus body against the nip. The skew state of the sheet is corrected by forming the loop. That is, since the skew correction of the sheet is performed by the switchback conveying means, the jam is less likely to occur. Also, there is no need to provide a dedicated means for correcting skew.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional side view showing an overall configuration of an image forming apparatus (laser beam printer) equipped with a sheet conveying device for double-sided printing of the present invention.

FIG. 2 is a vertical sectional side view showing a configuration of a sheet conveying apparatus for double-sided printing of the present invention.

FIG. 3 is a front view showing a configuration of a switchback unit in the sheet transporting apparatus for double-sided printing.

FIG. 4 shows a state in which the switchback means is normally transported (FIG. 4 (a)
) And a partially enlarged front view illustrating the operation and functions during switchback conveyance (FIG. 13B).

FIG. 5 is a partially cutaway plan view showing a configuration of a final conveyance path section in the sheet conveyance device for double-sided printing.

FIG. 6 is a vertical sectional front view illustrating the configuration, operation, and function of the final transport path unit.

FIG. 7 is a vertical cross-sectional side view showing a state in which a sheet having been printed on a first surface moves within the sheet transporting apparatus for double-sided printing.

FIG. 8 is a vertical cross-sectional side view showing a state in which a sheet having been printed on a first surface moves in the sheet conveying apparatus for double-sided printing.

FIG. 9 is a vertical cross-sectional side view showing a state in which the sheet having been printed on the first side moves in the sheet transporting apparatus for double-sided printing.

FIG. 10 is a vertical cross-sectional side view showing a state in which a sheet having been printed on a first surface moves in the sheet transporting apparatus for double-sided printing.

FIG. 11 is a front view (FIG. 11 (a)) and a vertical sectional side view (FIG. 11 (b)) for explaining the operation and functions of another configuration example (1) of the switchback means during normal transport.

12 is a front view (FIG. 1) for explaining the operation and function of another configuration example (1) of the switchback means during switchback conveyance.
2 (a)) and a longitudinal side view (FIG. 12 (b)).

FIG. 13 is a front view (FIG. 13 (a)) and a vertical cross-sectional side view (FIG. 13 (b)) illustrating the operation and functions of another configuration example (2) of the switchback means during normal transport.

14 is a front view (FIG. 1) for explaining the operation and function of another configuration example (2) of the switchback means during switchback transport.
4 (a)) and a longitudinal side view (FIG. 14 (b)).

[Explanation of symbols]

101 Image Forming Apparatus Main Body (Sheet Processing Apparatus Main Body) 200 Double-Sided Printing Sheet Conveying Apparatus (Sheet Conveying Apparatus) 260 Conveying Roller (Switchback Conveying Means) 261 Conveying Roller (Switchback Conveying Means) )

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B65H 29/58 B65H 9/14

Claims (11)

(57) [Claims] A first sheet discharging device for discharging the sheet from the main body of the sheet processing apparatus;
In a sheet transporting apparatus including a switchback transporting unit that performs switchback transporting into the sheet processing apparatus main body after normal transporting the reprocessed sheet, the switchback transporting unit includes a pair of rollers that can rotate forward and backward, The roller pair forms a predetermined amount of loop by abutting the leading end of the first processed sheet discharged from the sheet processing apparatus main body on the nip, and forms the loop to reduce the skew state of the sheet. A sheet conveying device which is in a rotation stopped state until the sheet is corrected, and rotates in a predetermined direction to normally convey the sheet when a predetermined amount of loop is formed on the sheet and the skew state is corrected. . 2. The apparatus according to claim 1, wherein a speed at which the switchback conveying means normally conveys the sheet is higher than a moving speed of the sheet discharged from the sheet processing apparatus main body. 2. The sheet conveying device according to 1. 3. The sheet conveying apparatus according to claim 1, wherein the switchback conveying means skews the sheet during switchback conveyance. 4. The sheet conveying apparatus according to claim 3, wherein the sheet is skewed when the nip line of one roller of the pair of rollers is inclined during switchback conveyance. 5. The sheet conveying apparatus according to claim 4, wherein when the pair of rollers is driven in the normal conveying direction, the nip lines of both rollers are in a parallel state. 6. The sheet conveying device according to claim 3, wherein the sheet is skewed by moving one of the rollers in the axial direction during switchback conveyance by a predetermined amount. 7. The sheet conveying apparatus according to claim 6, wherein when the pair of rollers is driven in the normal conveying direction, the roller moved in the axial direction returns to the original position. 8. The sheet conveying apparatus according to claim 3, further comprising a one-sided reference conveying path for changing a skewed state of the sheet conveyed by the switchback conveying means into a straight traveling state. 9. A first one-side reference conveyance path through which a sheet having a small width is passed, and a second reference conveyance path through which a sheet having a large width is passed.
9. The sheet conveying apparatus according to claim 8, wherein the one-side reference conveying path is formed in the same path. 10. A sheet processing apparatus comprising the sheet conveying apparatus according to claim 1 mounted on a sheet processing apparatus main body. 11. When the sheet conveying apparatus according to any one of claims 1 to 9 is mounted on a sheet processing apparatus main body, a printing operation in a second mode can be performed, and
Feeding the processed sheet into the sheet conveying device,
The sheet processing apparatus is configured to convey the first processed sheet sent from the sheet conveying apparatus to a sheet processing unit.