JPH01167164A - Sheet uncurler - Google Patents

Abstract

PURPOSE:To reduce the cost by providing front and rear pair rollers, a decurl gap formed between the pair rollers and a control section for stopping the front carry rollers when a sheet passes through the pair rollers and decurling the sheet. CONSTITUTION:A sheet 50 is curled at the inlet of a sheet carry path 47 such that the intermediate section thereof stretches to the right along the sheet carry path 47. When the sheet 50 is placed between carry rollers 48, 49, a control section stops the forward carry roller 49 for a predetermined time and feeds the sheet 50 by means of the rearward carry roller 48. By such arrangement, the sheet 50 is bent in reverse direction from curling direction of the sheet 50 thus decurling the sheet 50. Thereafter, the sheet 50 is carried into an intermediate tray.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a paper curl correction device for copying machines, laser printers, and the like.

[Conventional technology]

2. Description of the Related Art Recently, double-sided copying has been increasingly used in copiers, laser copiers, laser printers, etc. for purposes such as saving paper and making documents more compact, and as a result, the number of devices having an automatic double-sided copying function has also increased.

FIG. 4 shows an example of a copying machine capable of automatic double-sided copying. During copying, the original 1 is placed on the original placing table 3 by an automatic original feeder 2 or the like, and each part of the original 1 is sequentially irradiated with a light source included in the optical means 4, so that light corresponding to the image of the original 1 is emitted. An image is exposed onto photoreceptor 5. Photoreceptor 5
is charged by the charger 6 prior to exposure, so
An electrostatic latent image is formed on the photoreceptor 5 by the above exposure, and then the electrostatic latent image is developed by toner supplied to the surface of the photoreceptor 5 from the developing device 7 to form a toner image. .

Paper (not shown) is fed to the photoreceptor 5 from a manual paper feeder 8 or one of the paper feed cassettes 10 and 11 via registration rollers 12, and the toner image on the photoreceptor 5 is transferred to a transfer device 13.
After being transferred onto a sheet of paper, the sheet is peeled off from the photoreceptor 5 by an electrostatic peeling device 14 and a peeling claw 15, and is transported to a fixing device 17 by a transporting means 16. Fixing device 1
After the toner image is fixed on the paper in step 7,
In the single-sided copy mode, the paper is sent to the paper transport path 20 by the switching gate 18, and the sorted paper is discharged from the paper transport path 20 via the device 21 onto the paper discharge tray 22.

In addition, in the case of double-sided copying mode, the paper on which the image has been fixed on one side by the fixing device 17 is transferred from the switching gate 18 to the paper transport path 23, the switching gate 24, and the paper transport path 2.
5 to the intermediate tray 26, the paper is first discharged to the intermediate tray 26, and then sent from the intermediate tray 26 to the registration rollers 12 via the paper transport path 27, the switching gate 24, and the paper transport path 28. Copying to the other side is then performed in the same manner as described above.

Furthermore, in the composite copying mode, the paper that has been fixed by the fixing device 17 passes through the switching gate 18 and the paper transport path 23.
, are directly sent to the registration rollers 12 by the switching gate 24 and the paper conveyance path 28 without passing through the intermediate tray 26.

By the way, in the above-mentioned copying machine, a large amount of heat is applied to the paper by the fixing device 17, so that the fixing device 17
If the paper 29 is foreign paper or relatively thick, the paper 29 with the image 29a copied on one side is usually placed with the middle part facing downward, as shown in FIG. 5(a). If the paper 29 is a domestic paper or is relatively thin, the paper 29 will usually have curls in the direction in which the middle part extends upward, as shown in FIG. 5(b). There is a tendency to occur. In the case of double-sided copying mode, the paper 29 curls along the curved direction of the paper transport paths 23 and 25 when it is guided to the intermediate tray 26 via the paper transport paths 23 and 25, and is discharged to the intermediate tray 26. In both foreign and domestic papers, a curl occurs in which the middle part protrudes downward, as shown in FIG. 5(a). In particular, in the case of domestic paper, the curling direction due to the heat of the fixing device 17 and the curling direction due to the curvature of the paper transport paths 23 and 25 are the same, so the curling when ejected to the intermediate tray 26 is quite large. Become.

However, if the paper 29 curls in such a way that the middle part bulges downward, it may cause a paper jam when being ejected to the intermediate tray 26, or a paper feed failure when refeeding from the intermediate tray 26. may occur. Also, intermediate tray 2
When the paper 29 re-fed from 6 reaches the photoreceptor 5, the paper 29 is curled so that the middle part bulges downward, so when copying to the other side of the paper 29, There is a risk that a transfer failure or a failure of peeling of the paper 29 from the photoreceptor 5 may occur, or a paper jam may occur when the paper enters the fixing device 17, or the paper 29 may have wrinkles or folded corners in the fixing device 17. be.

Therefore, as shown in FIG. 6, a switch bank section 33 is provided in the paper transport path 32 between the fixing device 30 and the intermediate tray 31, and the switch bank section 33 turns the paper upside down and then discharges it to the intermediate tray 31. When this is done, the direction in which the paper 29 curls when it is ejected to the intermediate tray 31 is such that the intermediate portion thereof extends upward, as shown in FIG. 5(b). In this way, if the paper 29 is curled in such a direction that the middle portion of the paper 29 protrudes upward, if the paper jams when being ejected to the intermediate tray 31, failure to refeed the paper from the intermediate tray 31 is less likely to occur.

[Problem that the invention seeks to solve]

However, in the apparatus shown in FIG. 6, there still remain problems such as paper jams in the intermediate tray 31 under conditions where curling is likely to occur, such as at high temperatures and high humidity.
After paper is re-fed from
As shown in Figure 5(a), the curl direction of No. 9 is the direction in which the middle part protrudes downward, so the above-mentioned problems such as poor transfer and peeling when copying the other side are eliminated. It is difficult to do. Moreover, the switchback part 3
3, there is also a drawback that the structure becomes complicated.

In addition, in order to reduce the curling of paper due to the curvature of the paper transport path, a relatively long straight paper transport path is provided behind the fixing device, and the paper ejected from the fixing device is It is conceivable to change the direction of the paper after sufficient heat has been dissipated, but in that case, there is a problem of increasing the size of the apparatus.

It is also conceivable to angle the pair of upper and lower rollers for conveyance immediately after the fixing device in the direction of curl correction with respect to the curved direction of the paper conveyance path, but it is difficult to obtain a sufficient curl correction effect with this alone.

Furthermore, it is conceivable to provide heaters above and below the heat roller in the fixing device, but in this case, although curling of the paper is reduced, there arises a problem of increased cost.

[Means for solving problems]

In order to solve the above-mentioned problems, the paper curl correction device according to the present invention includes a pair of front and rear transport rollers provided in the paper transport path, and a paper transport path between the two transport rollers.
A curl correction gap formed by expanding the middle part of the curled paper in the opposite direction to the extending direction, and a transport roller on the front side in the paper traveling direction when the paper passes through the pair of transport rollers. The present invention is characterized by comprising a control section that corrects the curl by stopping the paper for a predetermined period of time to bend the paper in the direction opposite to the direction of the curl within the curl correction gap.

[For production]

According to the above configuration, when the paper approaches both of the pair of transport rollers, the front transport roller is stopped for a predetermined period of time as viewed in the direction in which the paper travels, and the paper is transported by the front transport roller. By feeding the paper forward in the traveling direction using the rear conveyance roller while holding it in a stopped state, the paper is bent in the opposite direction to the curling direction within the curl correction gap, thereby preventing the curling of the paper. be corrected.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 to 3.

FIG. 2 shows a copying machine having an automatic double-sided copying function and equipped with the curl straightening device of the present invention. A transfer device 40 and an electrostatic peeling device 41 are arranged below the photoreceptor 38. Note that the configuration and operating principle of the peripheral portion of the photoreceptor 38 are basically the same as those of the conventional example shown in FIG. 4, so detailed explanations will be omitted.

A fixing device 42 is installed behind the photoreceptor 38, and further includes:
A paper detection switch 43 is provided behind the fixing device 42 to detect passage of paper. Paper detection switch 43
The paper that has passed through is sent to the reversing claw 45 via the transport roller 44, and then the reversing claw 45 transports the paper to the paper ejection section through a paper transport path (not shown) or a plurality of paper guides 46, 46, . . . The paper is guided to an intermediate tray 53 (described later) (to be fed into one of the paper conveyance paths 47).

As shown in FIG. 1(a), in the paper conveyance path 47,
A pair of front and rear transport rollers 48 and 49 are arranged with an interval shorter than the front and back length of the paper 50, and both transport rollers 48 and 4
9 are rotated by a drive motor (not shown) in a direction in which the paper can be conveyed to the intermediate tray 53 side.

Paper guides 46 and 46 are provided at positions immediately after the transport roller 48 between the transport rollers 48 and 49 in a direction opposite to the direction in which the intermediate portion of the paper 50 that curls at the entrance of the paper transport path 47 extends. In other words, the curl correction cavity 51 is formed by expanding the paper conveyance path 47.

Further, in this copying machine, the paper 50 is transported by both conveying rollers 48 and 4.
9, by stopping the conveyance roller 49 on the front side in the direction of travel for a predetermined period of time, the paper 50 is bent in the direction opposite to the curling direction within the curl correction cavity 51, thereby causing the paper 50 to A control unit such as a microcomputer is provided to correct the curl.

A Wl extension roller 52 is arranged at the end of the paper conveyance path 47 . An intermediate tray 53 is installed diagonally below the kicking roller 52, and the sheet on which one side has been copied is discharged from the kicking roller 52 to the intermediate tray 53. Paper feed rollers 54 and 55 for refeeding the paper 50 from the intermediate tray 53 are provided below the kicking roller 52, and the paper 50 refeed from the intermediate tray 53 is passed through a plurality of paper guides 56.・56
..., and a plurality of conveyance rollers 57, 57,
The registration roller 60 is
The photoreceptor is fed to the photoreceptor 38 again via the .

In the above configuration, when double-sided copying is performed, the paper 50 is supplied from a paper feed section (not shown) to the photoreceptor 38 via the registration rollers 60, where the toner image is transferred to one side, and then fixed. The above-mentioned toner image is fixed on the paper in the bag W42. After passing through the paper detection switch 43, the paper 50 is fed into the paper transport path 47 by the reversing claw 45, and the paper 50 is moved along the curved direction of the paper transport path 47 at the entrance of the paper transport path 47, as shown in FIG. As shown in (a), the intermediate portion curls in the direction of extending rightward in the figure.

Next, when the paper 50 approaches both the transport rollers 48 and 49, the above-mentioned control section stops the transport roller 49 on the front side in the paper traveling direction for a predetermined period of time, thereby causing the first transport roller 49 to stop.
As shown in Figure (b), while the paper 50 is held in a stopped state by the front transport roller 49, the rear transport roller 4
At step 8, the paper 50 is fed forward in the traveling direction, and the paper 50 is bent in the direction opposite to the curling direction of the paper 50 within the curl correction cavity 51, thereby correcting the curl of the paper 50.

Here, the timing to stop the conveyance roller 49 is, for example,
As shown in FIG. 3, t2 seconds elapse from t1 seconds after the paper detection switch 43 is turned off due to the rear end of the paper 50 leaving the paper detection switch 43. Note that when the paper 50 is once ejected to the intermediate tray 53 and then re-fed, the paper 50 is fed from the rear end, so in order to smoothly re-feed the paper from the intermediate tray 53, it is especially necessary to It is desirable to set the timing at which the conveyance roller 49 stops so that the curl at the rear end of the paper 50 is corrected intensively.

The paper 50, the curl of which has been corrected in the curl correction cavity 51, is conveyed to the intermediate tray 53 by the paper conveyance path 47, and is then discharged there. Thereafter, the paper 50 is re-fed by the paper feed rollers 54 and 55, and is fed to the photoreceptor 38 via the paper conveyance path 58 via the registration rollers 60, and copying is performed on the other side. The paper 50 that has been copied on both sides is conveyed from the reversing claw 45 to the above-mentioned paper discharge section.

Note that the copying machine equipped with the curl correction device of the above embodiment is of a type in which the paper 50 curls in the direction in which the intermediate portion thereof protrudes downward on the intermediate tray 53 when the curl correction is not performed. As mentioned above, if the middle part of the paper 50 curls downward on the intermediate tray 53, it may be due to a paper jam in front of the intermediate tray 53, a paper refeed failure from the intermediate tray 53, etc. The present invention is particularly effective for copying machines of the above-mentioned type, since these problems are likely to occur. However, the curl correction device of the present invention can also be applied to a copying machine in which the paper 50 curls on the intermediate tray 53 in a direction in which the middle portion bulges upward when the curl correction is not performed. .

Further, in the above embodiment, a curl straightening device attached to a copying machine was described, but the curl straightening device of the present invention can also be attached to equipment other than a copying machine, such as a laser printer or a laser copier.

〔Effect of the invention〕

As described above, the paper curl correction device according to the present invention has the following features:
A curl correction method formed by a pair of front and rear transport rollers provided in the paper transport path and a bulge in the paper transport path between the two transport rollers in the opposite direction to the direction in which the middle portion of the curled paper extends. When the paper passes through the curl correction gap and the pair of conveyance rollers, the paper is bent in the opposite direction to the curling direction within the curl correction gap by stopping the front conveyance roller in the paper traveling direction for a predetermined period of time. This configuration also includes a control section that causes the curl to be straightened.

As a result, when the paper approaches both of the above-mentioned pair of transport rollers, the front transport roller is stopped for a predetermined period of time as viewed in the direction in which the paper travels, and the front transport roller holds the paper in a stopped state. By feeding the paper forward in the direction of travel using the conveyance roller on the rear side, the paper is bent in the opposite direction to the direction of the curl within the curl correction gap, and the curl of the paper is corrected. This has the effect that the curl of paper can be sufficiently corrected using a simple and inexpensive curl correction device.

[Brief explanation of the drawing]

1 to 3 show examples of the present invention, in which FIG. 1(a) is an enlarged explanatory diagram showing a state in which curling occurs on paper, and FIG. 1(b) shows curling of paper. An enlarged explanatory diagram showing the state of correction; Fig. 2 is an explanatory diagram showing the overall configuration;
The figure is a time chart showing when the conveyance roller stops.
The figure is an explanatory diagram showing a conventional example, Figures 5(a) and (b) are explanatory diagrams showing the curling direction of foreign paper and domestic paper, respectively, due to the heat of the fixing device, and Figure 6 is an explanatory diagram of another conventional example. It is a diagram. 47 is a paper conveyance path, 48 and 49 are a pair of conveyance rollers, 5
0 is paper, and 51 is a curl correction void. Figure 1 (a) Figure 1 (b)

Claims (1)

[Claims] 1. A paper transport path is formed by a pair of front and rear transport rollers provided in the paper transport path, and a bulge between the two transport rollers in the opposite direction to the direction in which the middle portion of the curled paper extends. When the paper passes through the curl correction gap and the pair of conveyance rollers, the paper is moved in the direction opposite to the curling direction within the curl correction gap by stopping the front conveyance roller in the paper traveling direction for a predetermined period of time. 1. A paper curl straightening device, comprising: a control section for straightening curls by bending the paper.