JPH01288559A - Paper reversing device - Google Patents

Abstract

PURPOSE:To prevent the generation of jamming by installing a pressing means for pressing the rear edge of a paper under pressure towards the nipping part of the second roller along the surface of the second roller when the rear edge of the paper is separated from the nipping part of the first roller pairs and smoothly reversing-transporting the rear edge of the paper from the first roller pairs to the second roller pairs. CONSTITUTION:When the rear edge of a paper which is transported by the first roller pairs (33, 34) and transported into a paper reversing guide part 37 is separated from the nipping parts of the first roller pairs (33, 34), the rear edge of the paper is sent under pressure towards the nipping parts of the second roller pairs (34, 35) along the surface of the second roller 34 by a pressing means (elastic plate) 40. Therefore, the rear edge of the paper is transferred onto the second roller pairs (34, 35) from the first roller pairs (33, 34) without slipping on the second roller, and reversing-transported smoothly, and the generation of jamming, etc. is prevented, and the paper is discharged onto a stacker.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a paper reversing device used in a paper processing apparatus such as an image forming apparatus.

[Conventional technology]

2. Description of the Related Art In image forming apparatuses such as copying machines and printers, a paper reversing device is used to store sheets on which images have been sequentially formed into a stacker in the order in which they were formed.

Conventionally, such a paper reversing device was developed by Japanese Patent Publication No. 61-231.
As disclosed in Japanese Patent Application No. 46, etc., the paper discharged from the fixing processing section of the image forming apparatus, etc. is once transferred to the paper reversing guide section by a first roller pair consisting of a first roller and a second roller. Then, the trailing edge of the paper is moved along with the rotation of the second roller to the second roller pair consisting of the second roller and the third roller, and the paper is reversed at the paper reversal guide section. There is known a structure in which sheets are conveyed in opposite directions by a second pair of rollers and sequentially discharged to a stacker.

[Problem to be solved by the invention]

However, in a paper reversing device using such a paper reversing guide, the paper carried in from the first pair of rollers is charged due to frictional contact between the pair of rollers, the paper guide, etc. electrification due to friction between the sheet being carried into the sheet reversing guide section and the sheet that was previously brought in and reversed, and as a result, the sheet is stuck to the sheet reversing guide section and It becomes difficult for the trailing edge of the paper discharged from the roller pair to bear its own weight, and as a result, the trailing edge of the paper slips on the second roller and the transition to the second roller pair does not occur smoothly, resulting in a jam. There was a problem.

In particular, when paper is curled by a paper processing device such as a pressure transfer device or a heat roll fixing device, slippage on the roller is more likely to occur because the trailing edge of the paper is less likely to come into contact with the second roller. , the transition becomes difficult and jams are likely to occur.

The present invention has been made in order to solve the above-mentioned problems in conventional paper reversing devices. prevents slipping on the rollers of
It is an object of the present invention to provide a paper reversing device capable of smoothly reversing and transporting paper and discharging it to a stacker.

[Means and operations for solving the problem] In order to solve the above-mentioned problems, the present invention provides a first roller and a second roller that transport paper discharged from a paper processing device in a first direction. a first pair of rollers, a paper reversing guide section that guides the paper in a second direction from the first conveyance direction by the first roller pair; a second roller pair consisting of a second roller and a third roller that are conveyed in a direction substantially opposite to the conveyance direction by the roller pair; In a paper reversing device that transfers the paper to the second roller pair via the second roller, when the trailing edge of the paper leaves the nip portion of the first roller pair, the trailing edge of the paper is transferred to the second roller pair. A side surface pressing means is provided to forcefully feed the sheet along the surface of the roller toward the nip portion of the second pair of rollers.

With this configuration, when the trailing edge of the sheet conveyed by the first pair of rollers and carried into the sheet reversing guide section leaves the nip section, it is immediately forcibly pressed onto the surface of the second roller by the pressing means. The trailing edge of the paper is transferred from the first roller pair to the second roller pair without slipping on the second roller pair.
The paper is transferred to a pair of rollers, is smoothly reversed and conveyed, and can be discharged to a stacker without jamming or the like.

〔Example] Examples will be described below.

First, a first example will be described. FIG. 1 is a schematic sectional view showing the overall configuration of an image forming apparatus to which the present invention is applied, and this configuration example shows a printer configured using an ion flow type recording head.

In the figure, ■ is a dielectric drum, 2 is the dielectric drum 1
a recording head for forming an electrostatic charge image on the dielectric drum 1 by emitting an ion flow modulated in accordance with the image signal to be recorded in a dont shape; The developing device 4 is a transfer roller for transferring the toner image on the drum 1 onto a sheet of paper. 5 is a cleaning blade for removing toner remaining on the dielectric drum 1''2 after transfer; 6 is a paper feed tray disposed on the side of the apparatus main body 7; and 8.9 is a blade for separating and feeding the paper 10 from the tray 6. Paper feed roller and retard for feeding, 11.12. 13.
14 is a paper conveyance guide, 15.16 is a paper conveyance roller,
17.18 is a post-transfer conveyance guide; 19 is a fixing unit that fixes the transferred toner image by heat and pressure; 20 is a reversal discharge unit for reversing and discharging the sheet on which the toner image has been fixed;
21 is a stacker that stores the ejected paper. In this configuration example, the post-transfer conveyance guides 17, 18, the fixing section 19, and the reversing and discharging section 20 are supported by a unit frame (not shown) that can be pulled out from the apparatus main body 7 in the paper ejection direction, so that they can be pulled out integrally. It is configured.

As shown in FIG. 2, the fixing unit 19 includes a heat roll 25 which is rotatably supported by a frame via a hair ring and has a halogen lamp disposed inside, and a heat roll 25 which is also rotatably supported and pressed against the heat roll 25. and a driven roll 26 coated with silicone rubber. A blade 27 for removing paper dust and offset toner is placed in pressure contact with the outer peripheral surface of the heat roll 25.

Further, a heat roll peeling claw 28 is swingably supported by a claw shaft 29, and is disposed such that its tip abuts against the heat roll 25 by a biasing means (not shown).

Reference numeral 30 indicates an upper paper guide, and 31 indicates a lower paper guide, which are each fixed to the reverse side plates 32 (only one of which is shown) so that the downstream side in the conveyance direction is higher.

33 is a first reversing roller, 34 is a second reversing roller, and 35 is a third reversing roller, each of which is supported by the reversing side plates 32 so as to be able to rotate once, and the first and second reversing rollers 33, 3
4, and the second and third reversing rollers 34.35° are in contact with each other and constitute a first roller pair and a second roller pair, each of which is connected to a drive system (not shown) and rotates in the direction of the arrow. is configured to do so. In this embodiment, each pair of rollers is arranged with three rollers spaced apart from each other.

In this embodiment, the first and second reversing rollers 33.
34 is the nip point, the heat roll 25 and the driven roll 2
The line l connecting the nip point of 6 is 1.16 with respect to the horizontal line.
Further, the line m connecting the centers of both reversing rollers 33 and 34 is arranged at an angle of 20 degrees with respect to the vertical line.

Reference numeral 37 denotes a paper reversing guide section, which, as shown in FIG. 39, and the paper reversing guide section 37.
is arranged at an angle of 25 degrees with respect to the vertical line. 40 An elastic body made of a plate spring such as a thin stainless steel plate bent at the middle part in a dogleg shape. One end of the elastic body is fixed to the upper paper guide 30 or its vicinity as appropriate and extends in the paper conveyance direction. The middle part has first and second reversing rollers 33.3
The other free end reaches the upper part of the nip part of the second roller pair, and the extension line of the free end is located in the gap between the three first roller pairs consisting of four rollers. Guide section 3
It is configured to intersect at a substantially right angle to the paper entry plate 38 of No. 7.

The biasing force per unit width of the elastic body 40 is the first
The stiffness is slightly larger than the stiffness of the unit width of the paper transported by the pair of rollers, and is set to an extent that does not impede the paper transport force.

Reference numerals 41 and 42 designate static elimination brushes, and the static elimination brush 41 touches the reversing side plates 32 in the vicinity of the intersection of the paper conveyance direction by the first and second reversing rollers 33 and 34 and the paper reversing guide section 37.
The static elimination brush 42 is supported and attached to the
is supported by the bent end portion of the paper entry plate 38 of the paper reversal guide section 37.

A paper discharge guide 43 is fixed to the unit frame and guides the reversed paper conveyed by the second and third reversing rollers 34.35 to the paper discharge rollers 44.45. The paper ejection rollers 44 and 45 are both rotatably supported by the unit frame, and the upper paper ejection roller 44
The driving force is transmitted from a drive system (not shown).

The reverse side plates 32 are integrated by a tie plate (not shown), and are swingably supported by the shaft of the upper paper discharge roller 44.

Next, the operation of the image forming apparatus configured as described above will be explained. Paper 10 stacked in paper feed tray 6
The sheets are separated and conveyed one by one by the feed roller 8 and the retard 9, and are guided by the sheet conveyance guides 11, 12, 13, and 14 to reach the nip portion between the dielectric drum 1 and the transfer roller 4. Here, the toner image on the dielectric drum 1 is pressure-transferred to the paper 10, and the leading edge of the paper advances to wrap around the dielectric drum 1 and is peeled off by the upper peeling claw 17a, and only the leading edge of the paper is guided to the upper paper guide 17. As the paper progresses a little, the paper gradually loses its stiffness to its own weight and is guided by the lower paper guide 18. As long as the stiffness of the paper is stronger than its own weight,
Since only the leading edge of the paper is guided by the upper paper guide 17 directed downward, there is nothing that touches the unfixed image surface, and therefore the paper is conveyed to the fixing section 19 without any disturbance or staining of the image.

The paper 10 conveyed to the fixing section 19 is guided to an inlet chute 50 and sandwiched between a heat roll 25 and a driven roll 26, and the toner is melted and fixed by heat and pressure. After fixing, the paper advances so as to be wrapped around the heat roll 25, and is peeled off by the heat roll peeling claw 28 and advances. At this time, the leading edge of the paper is curled upward as shown by the two-dot chain line in FIG. 2, and the leading edge of the paper is guided so as to become higher downstream in the conveyance direction, so that the paper is guided smoothly.

If the paper is configured to be guided downward as shown in FIG. 1
A waving phenomenon occurs at 0a.

The paper further advances and is conveyed by the first reversing roller 33 and the second reversing roller 34 to the paper entry plate 38 of the paper reversing guide section 37.
collide with The entry angle of the paper at this time is the paper entry angle of the paper entry plate 38.
It is determined by the angle of the line m connecting the centers of the first reversing roller 33 and the second reversing roller 34, and in this embodiment, it is 45 degrees as shown in FIG. If this intrusion angle increases, not only will the leading edge of the paper be damaged by the collision, but also the leading edge of the paper will be damaged by the paper reversing guide section 3 first, as shown in FIG. 5(A).
[Sheet 10c that was carried in and reversed] Ob causes a problem in that the leading edge of the paper 10c that is carried in is pulled in and is ejected without being reversed. Furthermore, in order to reduce the entry angle, as shown in FIG. 5(B), if the angle formed by the line m connecting the centers of the first reversing roller 33 and the second reversing roller 34 is increased, The end slips on the second reversing roller 34 and the third reversing roller 35
A problem occurs in which the data cannot be transferred to the other side. On the other hand, if the angle of the paper reversing guide section 37 is increased in order to reduce the entry angle, the paper reversing guide section 37 will be laid down horizontally, resulting in a problem that the installation space for the paper reversing device will become larger. Therefore, it is generally desirable to keep the entry angle between 30 and 60 degrees. The present invention completely prevents slippage on the second reversing roller 34, which may occur even when the entry angle is set to this level, and ensures reliable reversing conveyance.

By the way, before the sheet 10 conveyed by the first roller pair consisting of the first reversing roller 33 and the second reversing roller 34 enters the paper entry plate 38, its leading end abuts against the elastic body 40. As mentioned above, the biasing force per unit width of the elastic body 40 is set to be slightly larger than the stiffness per unit width of the paper 1o, but the biasing force per unit width of the elastic body 40 is set to be slightly larger than the stiffness strength per unit width of the paper 1o. Since the stiffness of the sheet is larger than the biasing force of the entire elastic body 40, even if the leading edge of the paper comes into contact with the elastic body 4o, it will not be bent by the biasing force of the elastic body 40 and will be transported by the first pair of rollers. While keeping the direction, figure 6 (
It is transported as shown in A). and paper reversing guide section 3
The paper that has reached the paper thrust plate 38 of No. 7 rises along the paper thrust plate 38 by the conveying force of the first and second reversing rollers 33 and 34, and is conveyed to the wire paper receiving section 39.

When the trailing edge of the paper leaves the nip between the first and second reversing rollers 33 and 34, there is nothing to hold the trailing edge of the paper and it becomes free, so the trailing edge of the paper is immediately moved by the elastic body 40 to the second roller pair. is urged toward the nip portion of the roller, and is forced along the surface of the second reversing roller 34 to exceed the intermediate position between the nip portions of the first and 20th roller pairs shown in FIG. 6(B). . When the trailing edge of the paper reaches a position beyond the intermediate portion of both nip portions of the second reversing roller 34, the edge portion comes into pressure contact with the surface of the second reversing roller 34, so that the rotation of the second reversing roller 34 is stopped. It is reliably transferred toward the nip portion of the second pair of rollers without slipping along with it.

As described above, the pressing force per unit width of the elastic body 40 is set to be a little stronger than the stiffness of the paper, but within a range that does not impede the conveying force of the paper. Until the trailing edge of the paper leaves the reversing guide part 37, it does not affect the conveyance of the paper toward the reversing guide part 37. When the trailing edge of the paper leaves the nip part of the first pair of rollers, the Since the trailing edge of the paper is force-fed along the surface of the second reversing roller 34 by the biasing force, the trailing edge of the paper is pushed onto the first reversing roller 34 due to curls of the paper itself and curls caused by pressure transfer and heat roll fixing. It is possible to reliably prevent the situation where the vehicle slips.

When the trailing edge of the paper is transferred to the nip portion of the second roller pair consisting of the second and third reversing rollers 34 and 35, the paper carried into the paper reversing guide section 37 is reversed by the second roller pair. The sheet is conveyed from the rear end side, passes through the sheet discharge guide 43, and is discharged and stored in the sheet discharge stacker 21 by the sheet discharge rollers 44 and 45.

In addition, in this sheet reversal conveyance process, the sheet conveyed by the first roller pair consisting of the first and second reversal rollers 33 and 34 is moved near the position where it collides with the paper entry plate 38 of the sheet reversal guide section 37. Since the electricity is not removed by the electricity removal brush 41, it rises along the paper entry plate 38. Electric charges generated by frictional contact with the paper entry plate 38 or with the paper that has been previously carried in and reversed due to the upward movement are eliminated by a static elimination brush 42 disposed at the tip of the paper entry plate 38. be done. Invert again and paper entry plate 38
Since the charges generated on the sheet of paper descending along the direction are eliminated by the two static eliminating brushes 4L and 42, the sheet of paper is effectively prevented from sticking to the paper entry plate 38 due to charging.

By the way, since the elastic body 40 in this first embodiment is configured to press the paper 10 with the tip of a leaf spring, the paper 10
When the curl of the paper 10 is particularly large, the trailing edge of the paper 10 may exceed the tip of the elastic body 40 and ride on top of the elastic body 40, as shown in FIG. Sometimes. In order to overcome this problem, as shown in FIG. 8, the tip of the leaf spring is formed by bending it upward almost parallel to the paper entry plate 38 above the nip of the second pair of rollers. Escape prevention part 40'
By using the elastic body 40' having a
The rear end of the roller can be reliably fed into the nip portion of the second pair of rollers.

Further, in the embodiments described above, the elastic bodies 40 and 40' are used as means for pressing the side surface of the paper, but other members and means may be used.

FIG. 9 shows a second embodiment of the invention.

In the figures, the same members as in the first embodiment are designated by the same reference numerals, and their explanations will be omitted. In this embodiment, a nozzle 46 that discharges an air stream is used as a means for pressing the side surface of the paper, and a second nozzle is used to press the side surface of the paper 10 downstream of the first pair of rollers.
The direction of the nip portion of the 0 roller pair, or the direction of the third roller 3
A plurality of nozzles 46 are provided in parallel in the axial direction of the roller at positions for discharging airflow in the direction 5, and are connected to an air supply device (not shown). With this configuration, an air stream is ejected from the nozzle 46 to the side surface of the paper 10 that has been conveyed by the first pair of rollers, and the paper 10 is pressed, but the direction of movement of the paper 10 is largely changed due to the stiffness of the paper itself. is never added. However, the trailing edge of paper 10 is
When the sheet 10 leaves the nip of the pair of rollers, the trailing edge of the sheet 10 is immediately forced by air pressure toward the nip of the second pair of rollers along the second roller. In this embodiment, since the nozzle 46 is provided outside the paper transport path, there is an advantage that the pressing means does not become an obstacle to paper transport or cause a jam.

(Effects of the Invention) As described above based on the embodiments, according to the present invention, when the trailing edge of the paper leaves the nip portion of the first pair of rollers, the trailing edge of the paper is immediately moved to the surface of the second roller. 2nd along
Since a pressing means is provided for force feeding in the direction of the nip portion of the pair of rollers, a simple structure ensures that the trailing edge of the paper slips when it passes from the first pair of rollers to the second pair of rollers via the second roller. Therefore, reversal conveyance can be carried out smoothly, and occurrence of jams etc. can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a configuration example of an image forming apparatus to which a paper reversing device according to the invention is applied, and FIG. 2 is a sectional view showing a first embodiment of the paper reversing device according to the invention. FIG. 3 is an enlarged perspective view thereof, FIG. 4 is a perspective view showing a discharged sheet in which the undulating phenomenon has occurred, and FIGS. 5 (A) and (B) show an example of inappropriate arrangement of the reversing roller. Explanatory diagram, Figure 6 (A), (
B) is an explanatory diagram showing the reversing conveyance operation according to the first embodiment, FIG. 7 is an explanatory diagram showing an example of failure of the reversing operation, and FIG.
The figure is an explanatory diagram showing an improved example of the first embodiment, and FIG.
FIG. 2 is an explanatory diagram showing a second embodiment of a paper reversing device according to the present invention. In the figure, 20 is a reversing discharge section, 33 is a first reversing roller, 34 is a second reversing roller, 35 is a third reversing roller, and 37
Reference numeral 40 indicates a paper reversing guide, 38 a paper entry plate, 40°40' an elastic body, and 46 a nozzle. = 21-

Claims (1)

[Claims] 1. A first roller pair consisting of a first roller and a second roller that conveys paper discharged from a paper processing device in a first direction; a paper reversing guide section that guides the paper from the first transport direction to a second direction; and a second paper reversing guide section that transports the paper reversed from the paper reversing guide section in a direction substantially opposite to the transport direction of the first pair of rollers. Laura and the third
and a second roller pair consisting of a roller, and a paper reversing device configured to transfer the trailing edge of the paper discharged from the first roller pair to the second roller pair via the second roller. , a pressing means for pressing the side surface of the paper from the first roller side toward the second roller side near the downstream side of the nip portion of the roller pair when the paper is conveyed by the first roller pair; and configured to force feed the trailing edge of the paper along the surface of the second roller toward the nip portion of the second roller pair immediately when the trailing edge of the paper leaves the nip portion of the first pair of rollers. A paper reversing device characterized by: 2. A first roller pair consisting of a first roller and a second roller that conveys the paper discharged from the paper processing device in the first direction, and from the first conveyance direction by the first roller pair. a paper reversal guide unit that guides the paper in a second direction; a second roller that transports the paper reversed from the paper reversal guide unit in a direction substantially opposite to the transport direction of the first pair of rollers;
and a second roller pair consisting of a roller, and a paper reversing device configured to transfer the trailing edge of the paper discharged from the first roller pair to the second roller pair via the second roller. , a pressing means is provided that constantly presses the downstream side of the nip portion of the sheet passing through the nip portion of the first pair of rollers in the direction of the third roller, so that the rear end of the sheet passes through the nip portion of the first pair of rollers. A paper reversing device characterized in that the paper reversing device is configured to force-feed the rear end of the paper toward a third roller when the paper is separated from the paper. 3. The pressing means is an elastic member whose free end is arranged so as to cross the paper conveyance path on the downstream side of the nip portion of the first pair of rollers, and the pressing means is an elastic member whose free end is arranged to cross the paper conveyance path downstream of the nip portion of the first pair of rollers, and the pressing means Claim 1 characterized in that the free end presses the side surface of the paper by being bent by the paper.
Or the paper reversing device described in 2. 4. Claim 3, wherein the elastic member is a leaf spring having a bent portion at its free end that presses the paper, and the bent portion is configured to abut against a side surface of the paper. Paper reversing device as described. 5. The pressing means is comprised of a nozzle that discharges an air flow, and is configured to press the downstream side surface of the sheet passing downstream of the nip portion of the first pair of rollers with the air flow. The paper reversing device according to claim 1 or 2.