JP2005335823A - Paper carrying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict fluctuation of paper carrying speed due to a pair of register rollers even in a case that a pair of feed rollers and the pair of register rollers are disposed in line on a paper carrying passage. <P>SOLUTION: This paper carrying device is provided with the pair of feed rollers 4 to separate and carry the paper 2 fed from a supply paper tray 1 sheet by sheet, and the pair of register rollers 5 to actuate at prescribed timing after correction of skew of the paper 2 to hold and carry the paper 2 to the subsequent stage side. The pair of feed rollers 4 and the pair of register rollers 5 are disposed in line on a paper carrying passage. The device is also provided with a rotatable carrying roller 11 disposed on the carrying passage 6 between the feed rollers 4 and the register rollers 5, and a buffer mechanism 12 to energize the carrying roller 11 toward the carrying passage 6, and support it in such a way that it is movable to the opposite side to the energized side in accordance with tension generated at the paper 2 being carried on the carrying passage 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet conveying device used for a copying machine, a printer device, and the like.

In general, a copying machine, a printer device, and the like are equipped with a paper transport device for transporting paper stored in a paper feed tray to an image forming unit that transfers a toner image onto the paper.
As a sheet conveying device, for example, one configured as shown in FIG. 9 is widely known. In the illustrated sheet conveying apparatus, a pickup roll 23 that feeds out a sheet 22 from a sheet feeding tray 21, a feed roll pair 24 that conveys the sheet 22 fed out to the pickup roll 23 on each leaf, and its feed A takeaway roll pair 25 disposed on the rear side of the sheet conveying direction with respect to the roll pair 24 and a registration roll pair 26 disposed on the rear side of the takeaway roll pair 25 are further provided. Then, when the paper 22 is fed out from the feed roll pair 24 one by one, the takeaway roll pair 25 abuts against the registration roll pair 26 that is nipping and transporting the paper 22 toward the rear side and stopped. Thus, after correcting the skew (inclination) of the sheet, the registration roll pair 26 starts rotating in accordance with the operation timing of the image forming unit (not shown), and the sheet 22 is directed toward the image forming unit on the rear side. It is designed to be nipped and conveyed.

  Incidentally, in recent years, there has been a strong demand for miniaturization, low power consumption, low price, and the like for copying machines and printer devices. Along with this, some paper transport devices eliminate the takeaway roll pair, and the feed roll pair and the registration roll pair are arranged side by side on the paper transport path (for example, see Patent Document 1). ).

JP 2002-255403 A

By the way, in the paper transporting device in which the feed roll pair and the registration roll pair are arranged side by side, there is no takeaway roll pair, so there is a possibility that the following problems may occur when transporting the paper.
Usually, in a paper transport device, after a skew loop is generated in the paper by abutting against the registration roll pair and the skew of the paper is corrected, the registration roll pair starts rotating operation in accordance with the operation timing of the image forming unit. To the image forming unit. At this time, the feed roll pair sandwiches and conveys the sheet in the same manner as the registration roll pair, but stops rotating before the trailing edge of the sheet passes in order to prevent double feeding of the sheet. Therefore, after the rotation of the feed roll pair is stopped, only the registration roll pair is rotating, so the bending loop that has occurred in the paper gradually disappears, and then the tension is applied between the registration roll pair and the feed roll pair. Will occur. The tension generated in the paper can be a factor that increases the sliding resistance during paper conveyance. Further, at the timing when the bending loop is completely eliminated, an impact on the paper is also involved.
If there is no takeaway roll pair, the influence of such sliding resistance and impact on the paper directly affects the registration roll pair. Due to the influence, the conveyance of the sheet by the pair of registration rolls may cause a speed fluctuation, and the sheet may not be conveyed at a constant speed. This disturbance in the sheet conveyance speed in the pair of registration rolls causes an image formation defect due to a deviation in the sheet conveyance timing to the image forming unit, specifically, color deviation, smear, and the like.

  Therefore, the present invention avoids the occurrence of speed fluctuations in the conveyance of paper by the pair of registration rolls as much as possible even when the feed roll pair and the registration roll pair are arranged side by side on the paper conveyance path. It is an object of the present invention to provide a paper transport device that can handle the above.

  The present invention is a sheet conveying device devised to achieve the above object. That is, a pair of feed rolls that transports the paper fed out from the paper feed tray every leaf, and corrects the skew of the paper by abutting the paper and then operates at a predetermined timing to pinch the paper to the rear side A pair of registration rolls for conveyance, and a conveyance path for the sheet between the feed roll pair and the registration roll pair is curved, and the feed roll pair and the registration roll pair are arranged side by side on the conveyance path. A paper transporting apparatus provided on the transport path between the feed roll pair and the registration roll pair, and a rotatable transport roller disposed inside a curve in the transport path; While urging the transport roller toward the outer side of the curve in the transport path, the tension generated in the paper transported by the transport roller through the transport path It is characterized in comprising a buffer mechanism for supporting so as to move toward the center of the arc curvature draw of the transport path in response.

  According to the paper transport device having the above configuration, the feed roll pair and the registration roll pair are arranged side by side on the paper transport path. Here, “arranged side by side” means that a pair of feed rolls and a pair of registration rolls are adjacent to each other on the transport path, and no other roll pair exists between them. However, instead of the roll pair, a conveyance roller supported by the buffer mechanism is disposed on the conveyance path between the feed roll pair and the registration roll pair. Therefore, even when the paper is stuck between the feed roll pair and the registration roll pair, the shock that can be applied to the paper is mitigated by the buffer mechanism moving the conveyance roller. In addition, since the transport roller is rotatable, it rotates according to the transported paper, and even when tension is generated between the registration roll pair and the feed roll pair, It can suppress that sliding resistance increases.

  In the paper transport device according to the present invention, even when the feed roll pair and the registration roll pair are arranged side by side on the paper transport path, the transport roller supported by the buffer mechanism includes the feed roll pair and the registration roll pair. Since it is arranged on the conveyance path between the two, it is possible to suppress the influence of sliding resistance, impact, etc. on the paper directly on the registration roll pair as much as possible, and paper conveyance by the registration roll pair can be performed at a constant speed. It becomes like this. Therefore, according to the paper transport device of the present invention, by arranging the feed roll pair and the registration roll pair side by side on the transport path, the copying machine or the printer device on which the paper transport device is mounted can be downsized and reduced in consumption. In addition to making it possible to easily realize power savings and lower prices, the paper transport speed can be stabilized by using a pair of registration rolls. As a result, the paper transport timing is shifted to the image forming unit. By doing so, it is possible to satisfactorily form an image on a sheet.

  Hereinafter, a sheet conveying apparatus according to the present invention will be described with reference to the drawings. The paper conveying apparatus described here is used by being mounted on a copying machine, a printer apparatus, or the like. Since the copying machine, the printer apparatus, or the like is realized by a publicly known technique, the description thereof will be given here. Is omitted.

[First Embodiment]
First, a first embodiment of a paper conveying apparatus according to the present invention will be described.

  FIG. 1 is a schematic diagram illustrating an example of a schematic configuration of a sheet conveying device according to the first embodiment. In the illustrated sheet conveying apparatus, a pickup roll 3 that feeds out a sheet 2 from a sheet feeding tray 1, a feed roll pair 4 that conveys the sheet 2 that has been fed out to the pickup roll 3 on each leaf, and its feed A registration roll pair 5 is provided on the rear side of the sheet conveying direction with respect to the roll pair 4. That is, the feed roll pair 4 and the registration roll pair 5 are arranged side by side on the conveyance path 6 of the paper 2, and no takeaway roll pair is arranged between them. The conveyance path 6 is formed to be curved between the feed roll pair 4 and the registration roll pair 5 by a conveyance guide 6a for guiding the sheet, a leaf spring-shaped mylar 6b for controlling the sheet posture, and the like. ing. Further, an image forming unit 7 such as a copying machine or a printer that transfers a toner image onto the paper 2 is disposed on the rear side in the paper transport direction with respect to the registration roll pair 5.

  Furthermore, in addition to the above-described configuration, the paper transport device according to the present embodiment includes a transport roller 11 and a buffer mechanism 12 as a characteristic configuration.

  The conveyance roller 11 is rotatably disposed on the conveyance path 6 between the feed roll pair 4 and the registration roll pair 5 and inside the curve in the conveyance path 6. In addition, it is desirable to arrange | position the conveyance roller 11 to the vertex vicinity of the arc which the curve of a conveyance path | route draws.

  The buffer mechanism 12 urges the transport roller 11 toward the outside of the curve in the transport path 6, and the transport roller 11 is curved in the transport path 6 according to the tension generated in the paper transported through the transport path 6 described later. The carrier roller 11 is supported so that it can move toward the center of the arc drawn by.

  Here, the transport roller 11 and the buffer mechanism 12 will be described in more detail. FIGS. 2 and 3 are schematic diagrams illustrating an example of a configuration of main parts of the sheet conveying device according to the first embodiment.

  As shown in FIG. 2A, the transport roller 11 does not have a drive source, but is a roller-like one that is rotatably supported via a rotating shaft 13 and a bearing 14. On the other hand, the buffer mechanism 12 includes a support member 15 of the transport roller 11 and an elastic member 16 built in the support member 15.

  Among these, the elastic member 16 is formed of a coil spring that biases the rotating shaft 13 of the transport roller 11, for example. By having this elastic member 16, in the buffer mechanism 12, as shown in FIG. 2B, when the conveying roller 11 is urged toward the curved outer side, and a force is applied from the urging destination side (see FIG. The elastic member 16 is compressed and the conveyance roller 11 is retracted inside the support member 15. That is, the buffer mechanism 12 shown in FIG. 2 supports the transport roller 11 itself so that it can move.

  The buffer mechanism 12 is not necessarily required to move the transport roller 11 itself. That is, as shown in FIG. 3A, the buffer mechanism 12 may be one in which the elastic member 16 is sheathed on the support member 15. In the buffer mechanism 12 configured in this way, as shown in FIG. 3B, when the conveying roller 11 is urged together with the support member 15 toward the curved outer side, and a force is applied from the urging destination side ( The elastic member 16 is compressed, and the conveyance roller 11 moves inward together with the support member 15. That is, the buffer mechanism 12 shown in FIG. 3 supports the support member 15 of the transport roller 11 so that it can move.

  2 and 3, the elastic member 16 does not necessarily need to be a coil spring. That is, other elastic members such as a leaf spring, rubber, and sponge may be used as long as the conveying roller 11 can be urged and compressed by an external force.

  However, regardless of the type of the elastic member 16, the buffer mechanism 12 has the elastic member 16 regardless of the difference in configuration such as whether the conveyance roller 11 itself moves or whether the conveyance roller 11 moves together with the support member 15. Even after the transport roller 11 is compressed and moved, the transport roller 11 is supported so that the outer periphery of the transport roller 11 is in contact with the paper transported through the transport path 6 in order to reduce sliding resistance as described later. It shall be comprised so that it may do.

  Next, an example of processing operation in the sheet conveying apparatus configured as described above will be described. 4 to 6 are schematic diagrams illustrating an outline of processing operation examples in the sheet conveying apparatus.

  In the paper transport device, the following processing operation is performed when transporting the paper stored in the paper feed tray 1 to the image forming unit 7 that transfers the toner image onto the paper. That is, as shown in FIG. 4, when the pickup roll 3 feeds the paper 2 from the paper feed tray 1, the paper 2 is fed to the side of the registration roll pair 5 that has stopped rotating while the feed roll pair 4 is rolling every leaf. Transport toward. Then, the skew of the sheet 2 is corrected by causing the leading end of the sheet 2 to abut the registration roll pair 5 and causing the sheet 2 to bend. At this time, the mylar 6b in the transport path 6 is bent by the bending loop generated in the paper 2 (see the broken line in the figure).

  Thereafter, as shown in FIG. 5, in the paper transport device, the registration roll pair 5 starts rotating in accordance with the operation timing of the image forming unit 7, and the paper 2 is nipped and transported toward the image forming unit 7 on the subsequent stage side. . At this time, the sheet is conveyed while being sandwiched between both the feed roll pair 4 and the registration roll pair 5. However, the feed roll pair 4 stops its rotation before the trailing edge of the paper 2 passes through the pickup roll 3 in order to prevent double feeding of the paper. For this reason, after the rotation of the feed roll pair 4 is stopped, only the registration roll pair 5 is rotating, so that the bending loop generated in the sheet 2 is gradually eliminated while being assisted by the reaction force of the mylar 6b. Then, the sheet 2 comes into contact with the outer periphery of the transport roller 11 that is biased toward the curved outer side of the transport path 6 by the buffer mechanism 12.

  After that, if only the registration roll pair 5 continues to rotate, the bending loop generated in the paper 2 is completely eliminated between the feed roll pair 4 and the registration roll pair 5 and tension is generated in the paper 2. .

  At this time, since the conveyance roller 11 in contact with the paper 2 is supported by the buffer mechanism 12, if tension is generated between the feed roll pair 4 and the registration roll pair 5, the paper 2 is as shown in FIG. Depending on the tension, the elastic member 16 moves toward the center of the arc drawn by the curvature of the transport path 6, that is, toward the direction in which the elastic member 16 is compressed. Even after the elastic member 16 is compressed and the transport roller 11 moves, the outer periphery of the transport roller 11 is in contact with the paper 2 and the transport roller 11 rotates in accordance with the transported paper 2. .

  That is, after the rotation operation of the feed roll pair 4 is stopped, the sheet 2 is conveyed toward the image forming unit 7 between the feed roll pair 4 and the registration roll pair 5 by the rotation operation of only the registration roll pair 5. In addition, at this time, the sheet 2 is transported in a state where tension is generated and in contact with the outer periphery of the transport roller 11 that is driven to rotate. When the trailing edge of the sheet 2 passes through the registration roll pair 5, the registration roll pair 5 stops rotating in preparation for skew correction of the next sheet 2.

  As described above, since the sheet conveying apparatus described in the present embodiment includes the conveying roller 11 and the buffer mechanism 12, the series of processing operations described above, that is, for conveying the sheet 2 to the image forming unit 7 is performed. Even when the paper 2 is stuck between the feed roll pair 4 and the registration roll pair 5 in the processing operation, the shock that can be applied to the paper 2 is reduced by the buffer mechanism 12 moving the transport roller 11. Can do. In addition, since the transport roller 11 is rotatable, the transport roller 11 rotates according to the transported paper 2, and even if tension is generated between the feed roll pair 4 and the registration roll pair 5, the paper It can suppress that the sliding resistance at the time of conveying 2 increases.

  Therefore, according to the paper transport device described in the present embodiment, even when the feed roll pair 4 and the registration roll pair 5 are arranged side by side on the transport path 6, the sliding resistance and the impact on the paper 2 are affected. Thus, it is possible to suppress the influence of the above and the like directly on the registration roll pair 5 as much as possible, and the sheet conveyance by the registration roll pair 5 can be performed at a constant speed. For this reason, the feed roll pair 4 and the registration roll pair 5 are arranged side by side on the transport path 6 so that the copying machine, the printer apparatus, etc. on which the paper transport device is mounted can be reduced in size, reduced in power consumption, reduced in price, etc. Can be easily realized, and even in such a case, the sheet conveyance speed can be stabilized by the registration roll pair 5, and as a result, the deviation of the sheet conveyance timing to the image forming unit 7 can be avoided and the sheet 2 can be prevented. Thus, it is possible to satisfactorily form an image.

[Second Embodiment]
Next, a second embodiment of the paper conveying apparatus according to the present invention will be described. However, the description of the same contents as those in the first embodiment described above is omitted.

  FIG. 7 is a schematic diagram illustrating a configuration example of a main part of the sheet transport device according to the second embodiment. As shown in FIG. 7A, in the paper conveyance device described here, the buffer mechanism 12 ′ supports the first elastic member 16 a that urges the rotation shaft 13 of the conveyance roller 11 and the conveyance roller 11. And a second elastic member 16b for urging the support member 15. The elastic members 16a and 16b have different elastic coefficients. That is, the buffer mechanism 12 'is configured using two elastic members 16a and 16b having different elastic coefficients.

  In the buffer mechanism 12 'configured as described above, when a force is applied from the urging destination side of the transport roller 11 (see the arrow in the figure), the elastic members 16a and 16b have different elastic coefficients, and therefore FIG. As shown in FIG. 7, after the first elastic member 16 a is compressed and the conveying roller 11 is retracted inside the support member 15, the second elastic member 16 b is compressed as shown in FIG. The support member 15 moves inward. Or, conversely, after the second elastic member 16 b is compressed and the support member 15 moves inward, the first elastic member 16 a is compressed and the transport roller 11 is retracted into the support member 15.

  Even in the case where such a buffer mechanism 12 ′ and the transport roller 11 supported by the buffer mechanism 12 ′ are arranged, the sheet transport apparatus has a sliding resistance, an impact, etc. with respect to the sheet 2 as in the case of the first embodiment described above. Can be suppressed as much as possible to the registration roll pair 5 and the sheet conveyance speed by the registration roll pair 5 can be stabilized.

  Moreover, in the paper transport apparatus described in the present embodiment, the buffer mechanism 12 'is configured using the two elastic members 16a and 16b having different elastic coefficients, so that it can flexibly cope with various paper transports. become. Various types of paper can be used for the paper quality, thickness, size, and the like. When such various papers are transported, it is considered that the tension generated on the papers, that is, the external force applied to the transport roller 11 is also various. However, if the elastic coefficients of the elastic members 16a and 16b are different, it is difficult to realize with the single elastic member 16, for example, one is compressed at a light load and both are compressed when it is not sufficient. It becomes possible to perform a flexible response. That is, it is very suitable for the conveyance of various sheets in order to stabilize the sheet conveyance speed by the registration roll pair 5.

  In addition, although the two elastic members 16a and 16b were mentioned here as an example, the number of elastic members is not limited to this, and may be three or more.

[Third Embodiment]
Next, a third embodiment of the paper conveying apparatus according to the present invention will be described. However, also here, the description of the same contents as those of the first or second embodiment described above is omitted.

  FIG. 8 is a schematic diagram illustrating a configuration example of a main part of the sheet transport device according to the third embodiment. In the illustrated sheet conveying apparatus, the conveying roller 11 is not simply supported rotatably, but is driven by a drive motor 17. This drive motor 17 starts or stops the rotation operation of the transport roller 11 independently of the drive source that drives the feed roll pair 4, that is, without depending on the start / stop of the rotation operation in the feed roll pair 4. To get. Further, the drive by the drive motor 17 is supported by the transport roller 11 so as to be movable, so that the drive roller 17 is transmitted to the transport roller 11 via the pulley 18 and the drive transmission belt 19 to correspond to the movement.

  In the sheet conveying apparatus configured as described above, since the conveying roller 11 is driven by the drive motor 17, when the sheet 2 is stuck between the feed roll pair 4 and the registration roll pair 5, This is very suitable for reducing sliding resistance. In other words, the conveyance roller 11 positively assists the conveyance of the paper 2, thereby further reducing the conveyance load as compared with the case where the conveyance roller 11 is simply supported so as to be freely rotatable, and further register roll pairs 5. Can stabilize the paper conveyance speed.

  By the way, it is desirable to always drive the transport roller 11 by the drive motor 17 from the viewpoint of reducing the transport load. However, continuous driving is not preferable from the viewpoints of power consumption, noise, temperature in the apparatus, and the like. Therefore, it is desirable to drive the transport roller 11 at the timing described below. The drive motor 17 starts driving the transport roller 11 at the same time as the registration roll pair 5 starts operating at the latest. That is, the registration roll pair 5 starts rotating operation in synchronization with the operation timing of the image forming unit 7, but the conveying roller 11 starts rotating operation at least at the timing. As a result, when the registration roll pair 5 nipping and conveying the sheet, the conveyance roller 11 is driven to reliably assist the sheet conveyance, so that the sheet conveyance speed by the registration roll pair 5 is very stable. Is preferred. Further, the drive motor 17 conveys at any point in time from when the trailing edge of the sheet passes through the feed roll pair 4 to when the feed roll pair 4 starts feeding (clamping conveyance) of the next sheet. The driving of the roller 11 is stopped. If the trailing edge of the sheet passes through the feed roll pair 4, the nipping state of the sheet by both the feed roll pair 4 and the registration roll pair 5 is eliminated. This is because the paper conveyance speed can be stabilized. Further, after the feed roll pair 4 starts feeding the next sheet, the skew of the sheet is corrected. However, when the skew is corrected, the skew is sufficiently corrected only by the feed roll pair 4 alone. Therefore, it is not necessary to drive actively.

  When the transport roller 11 is driven by the drive motor 17, for example, a one-way clutch (not shown) is provided coaxially with the transport roller 11, and the pulley 18 on the shaft of the transport roller 11 is coupled with the coupling. It is also conceivable that the pulley 18 on the shaft of the conveying roller 11 is provided with a so-called one-way function. With such a configuration, when the drive motor 17 is driven, the one-way clutch or the one-way function is locked and the transport roller 11 rotates, but when the drive motor 17 is stopped, the one-way clutch or the one-way function is released and the transport roller 11 is released. Rotates idly. For this reason, even when the drive motor 17 is stopped, there is no adverse effect on the travel of the paper on which the transport roller 11 is transported.

  In the first to third embodiments described above, preferred specific examples of the present invention have been described. However, the present invention is not limited to the contents described in these embodiments. That is, the present invention can be appropriately changed without departing from the gist thereof, and can be realized by appropriately combining the contents described in the first to third embodiments, for example.

FIG. 3 is a schematic diagram illustrating a schematic configuration example in the first embodiment of the paper conveying apparatus according to the present invention. FIG. 3 is a schematic diagram (part 1) illustrating a configuration example of a main part of the paper transport device according to the first embodiment of the paper transport device according to the present invention. FIG. 6 is a schematic diagram (part 2) illustrating a configuration example of a main part of the paper transport device according to the first embodiment of the paper transport device according to the present invention. FIG. 6 is a schematic diagram (part 1) illustrating an outline of a processing operation example in the first embodiment of the sheet conveying device according to the invention. FIG. 6 is a schematic diagram (part 2) illustrating an outline of a processing operation example in the first embodiment of the sheet conveying device according to the invention. FIG. 6 is a schematic diagram (part 3) illustrating an overview of an example of a processing operation in the first embodiment of the sheet conveying device according to the present invention. It is a schematic diagram which shows the example of a principal part structure of the paper conveying apparatus in 2nd Embodiment of the paper conveying apparatus which concerns on this invention. It is a schematic diagram which shows the example of a principal part structure of the paper conveying apparatus in 3rd Embodiment of the paper conveying apparatus which concerns on this invention. FIG. 10 is a schematic diagram illustrating a schematic configuration example of a conventional paper conveyance device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Paper feed tray, 2 ... Paper, 3 ... Pickup roll, 4 ... Feed roll pair, 5 ... Registration roll pair, 6 ... Conveyance path, 7 ... Image forming part, 11 ... Conveyance roller, 12, 12 '... Buffer mechanism, DESCRIPTION OF SYMBOLS 15 ... Support member, 16 ... Elastic member, 16a ... 1st elastic member, 16b ... 2nd elastic member, 17 ... Drive motor

Claims (7)

A pair of feed rolls that transport the paper fed from the paper feed tray every leaf, and correct the skew of the paper by abutting the paper and operate at a predetermined timing to nipping and transport the paper to the subsequent stage side A pair of registration rolls, and a conveyance path of the sheet between the feed roll pair and the registration roll pair is curved, and the feed roll pair and the registration roll pair are arranged side by side on the conveyance path. A paper transport device,
A rotatable transport roller disposed on the transport path between the feed roll pair and the registration roll pair and inside the curve in the transport path;
The conveyance roller is urged toward the outside of the curve in the conveyance path, and the conveyance roller is directed toward the center side of the arc drawn by the curvature of the conveyance path according to the tension generated in the paper conveyed through the conveyance path. And a buffer mechanism for supporting the sheet so that it can be moved. The buffer mechanism is configured so that the outer periphery of the transport roller is in contact with the paper transported through the transport path even after the transport roller has moved toward the center of the arc drawn by the curvature of the transport path. The sheet conveying apparatus according to claim 1, wherein The paper transport device according to claim 1, wherein the buffer mechanism supports the transport roller so that the transport roller itself can move. The paper transport device according to claim 1, wherein the buffer mechanism supports the transport roller so that a support member of the transport roller can move. 5. The sheet conveying device according to claim 1, wherein the buffer mechanism is configured using a plurality of elastic members having different elastic coefficients. The paper transport device according to claim 1, 2, 3, 4, or 5, wherein the transport roller is driven by a drive source different from a drive source that drives the feed roll pair. The sheet conveying apparatus according to claim 6, wherein the conveying roller is driven at least when the pair of registration rolls starts an operation at a predetermined timing.

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