JPH04344662A - Both-side paper feeding device - Google Patents

Abstract

PURPOSE:To reduce the set-off of toner when a laminated and stacked transfer paper where copying has been finished on its one side is fed again. CONSTITUTION:This is the both-side paper feeding device of a lower side paper feeding system, which is provided with a pressure plate 31 for pressuring the bundle of the stacked transfer papers 8, and a pickup roller 29 which is provided with a semicircular roller 28 which cooperates with the plate 31 and successively feeds the lowermost paper of the bundle of the transfer papers 8 toward a frictional separation part 41. In this device, a pressure regulating means for regulating pressure acting between the plate 31 and the pickup roller 29 at the time of feeding the paper, for example, a pressure regulating means 31c which is obtained by forming the part of the pressure surface 31a of the plate 31 opposed to the apex of the pickup roller in a recessed shape is provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided paper feeding device that is installed in a double-sided copying machine and temporarily stores transfer paper on which front side copies have been made and refeeds the paper for back side copying or composite copying.

0002

2. Description of the Related Art First, let us consider the case where double-sided copying is performed using a double-sided copying machine equipped with an RDH (circulating document feeder).
Copy productivity differs depending on whether the paper feeding method of the duplex paper feeding device (double-sided tray) is an upper paper feeding method or a lower paper feeding method. In order to increase copy productivity, it is preferable to use a lower paper feeding method as the paper feeding method in the duplex tray.

Furthermore, when refeeding paper from the double-sided tray, a separation mechanism is required to avoid double feeding. For example, if an air separation method is used, it requires space for a fan and duct piping to supply air, and has the drawbacks of high noise during air suction, and high power consumption because it requires a dedicated fan. . In this respect, the frictional separation method does not require a fan or duct, and can be constructed compactly using a roller pair structure, etc., and is advantageous in terms of noise generation and power consumption.

[0004] From this point of view, a friction separation system and a bottom paper feeding system are generally used. In this case, a pick-up roller with a half-moon roller shape is used so as not to hinder the progress of the transfer paper when it is stacked on the double-sided tray.

[0005]

[Problem to be Solved by the Invention] However, in a double-sided paper feeding device that feeds paper from the bottom using such a frictional separation method, the copied side of the transfer paper after single-sided (front side) copying is facing up. Laminated in condition. After a predetermined number of sheets have been stacked, the sheets are fed starting from the lowest sheet, but at this time, there is In areas where pressure is applied to the loaded transfer paper stack, friction between the fed transfer paper and the transfer paper above it causes some of the toner transferred and copied onto the top surface of the fed transfer paper.
It is reflected on the non-copy side (the side to be copied for the second time) of the transfer paper above it, causing stains on the back side. As a result, the copy quality in double-sided copying is impaired. This is undesirable because even during composite copying in which copies are made twice on the same side, the back side becomes stained.

[0006]

[Means for Solving the Problems] A friction separation unit includes a pressure plate that presses a stacked bundle of transfer paper, and a half-moon-shaped roller that cooperates with the pressure plate to separate the lowest paper of the stack of transfer paper. In a bottom-feed type double-sided paper feeding device that is provided with a pickup roller that sequentially feeds paper toward The length of the pressure regulating means in which the pressure plate's pressing surface facing the pick-up roller apex is formed into a concave shape, and the arcuate surface of the half-moon roller that contacts the transfer paper, is the length from the tip of the stacked transfer paper to the friction separation part. Pressure regulating means of substantially identical construction were provided.

[0007]

[Function] When feeding paper, the pressure regulating means
Since the pressure between the pickup rollers is relaxed, the friction between the transfer sheets is also eased, and the show-through of the toner image is reduced. Such pressure regulating means can be achieved, for example, by forming a recess on the pressure side of the pressure plate to release the pressure, or by shortening the length of the arcuate surface of the half-moon roller on the pickup roller side to reduce the time during which pressure is applied. This can be easily achieved by regulating the

[0008]

Embodiment A first embodiment of the present invention will be explained based on FIGS. 1 to 5. FIG. 2 shows an example of a double-sided copying machine to which the present invention is applied.
2 is provided. This RDH 2 feeds the stacked originals 3 one by one onto the contact glass 1 starting from the lowest one, and returns them to the top of the stack of originals after exposure is completed. A photoreceptor 4 is provided inside the main body, and a lens 6 forms an image of the document on the contact glass 1 that has been subjected to slit exposure scanning by an exposure illumination unit 5 . The photoreceptor 4 is uniformly charged, and the electrostatic latent image formed by exposing the original image is developed by the developing unit 7. The developed toner image is transferred onto the selectively fed transfer paper 8 by the action of the transfer charger 9, then conveyed by the conveyor belt 10, fixed via the fixing unit 11, and then discharged. During double-sided copying, after being fixed, the reversing unit 12 performs reversing processing to replace the leading and trailing edges, and the selective ejection unit 13 transfers the sheet onto the duplex tray 15 of the duplex paper feeder 14 according to the size of the transfer paper. Once the sheets are ejected, they are stacked. That is, the paper is ejected with the copy side facing upward. Therefore, by refeeding the paper from this double-sided tray 15, a transfer operation is performed on the back side, resulting in a double-sided copy.

Note that during composite copying, the transfer paper 8 is not reversed by the reversing unit 12 and is transferred to the double-sided tray 15.
The paper is discharged and stacked on top, and copies are made on the same side by refeeding the paper.

The structure and operation of the double-sided sheet feeding device 14, which uses a friction separation type and a lower side sheet feeding type, will now be described with reference to FIG. FIG. 1(a) shows the stacking state, and FIG. 1(b) shows the state of refeeding. First, the operation when stacked will be explained. The leading edge of the transfer paper 8 that has passed through the reversing unit 12 is detected by the entrance sensor 21, and then transferred to the selective discharge unit 13.
guide plate 2 from the gate position according to the transfer paper size.
2 and is ejected toward the double-sided tray 15 side. On the table 23 of the double-sided tray 15, there is provided a leading end shifting roller 25 supported by a rotatable arm 24, and is set to always rotate clockwise during the stacking operation of the transfer paper 8. . Therefore, the transfer paper 8 discharged onto the table 23 is further sent forward by the leading edge shifting roller 25, and is stopped when it hits a stopper 26 for regulating the position of its leading edge. Tip gathering roller 25
The contact/non-contact control for the table 23 is, for example,
Each sheet is controlled by turning on and off a solenoid (not shown) at an appropriate timing based on the detection timing of the entrance sensor 21. This is the tip adjustment roller 25
This is to prevent the paper from buckling due to constant contact with the transfer paper 8. (Since the leading edge of the transfer paper 8 is stopped by the stopper 26, the leading edge shifting roller 25 is constantly in contact with and rotates in this state.) paper will buckle). Additionally, jogger fences 27 are provided on the left and right sides of the table 23, and are jogged by a stepping motor (not shown) or the like to align the stacked transfer papers in the left and right direction. The driving timing of this jogger fence 27 is also performed based on the detection timing of the entrance sensor 21. By repeating such operations, a specified number of transfer sheets 8 are stacked on the table 23 of the double-sided tray 15 with their leading edges and left and right sides aligned.

Next, the operation at the time of paper refeeding will be explained. Re-feeding of the stacked transfer sheets 8 is basically carried out by a pickup roller 2 having a half-moon roller 28 with a D-shaped cross section and intermittently contacting the lower surface of the transfer sheets through the notch opening of the table 23.
9, this is performed as lower paper feeding. Prior to refeeding the paper after stacking, it is necessary to press the leading end of the transfer paper 8 corresponding to the pickup roller 29. For this reason, a pressure plate 31 is provided above, which is rotatable with respect to the support shaft 30. During the stack operation, the pin 32 provided on the pressure plate 31 is lifted by the arm 26a of the stopper 26 (always urged counterclockwise by the return spring 33), as shown in FIG. 1(a). It is opened to the stack of transfer paper. When pressurizing for paper refeeding, a solenoid 35 connected to the stopper 26 via the connecting link 34 is turned on, rotating the stopper 26 clockwise and retracting the tip of the stopper 26 away from the surface of the table 23. , a gap is formed between them through which the transfer paper 8 can pass. In this way, by rotating the stopper 26, the arm portion 26a
is separated from the pin 32, the pressure plate 31 rotates counterclockwise around the support shaft 30 due to the restoring force of the pressure spring 36, and the pressure surface 31a on the tip side is positioned on the stacked transfer paper. Pressure is applied to the pickup roller 29 side.

The shaft hole 31b that fits into the support shaft 30 has an elongated hole shape with ample space in the vertical direction, so that even if the thickness of the loaded transfer paper bundle changes, the pressure applied by the pressure surface 31a can be stably performed. It is configured to be

In this pressurized state, the pickup roller 29 rotates to re-feed the paper. first,
When a paper feed signal is input, a paper feed clutch (not shown) is turned on and drives the feed roller 42 of the friction separation unit 41.
to communicate. The pickup roller 29 is connected to the feed roller 42 by gears 43, 44, and 45, and the pickup roller 29 also rotates when the paper feed clutch is turned on. Due to the cooperative action of the rotating pickup roller 29 and the pressure plate 31, the lowest transfer paper 8
The sheet is sent out and is conveyed and re-feeded by the feed roller 42 and pull-out roller 46 in the front. At this time, a reverse roller 47 that does not rotate is in contact with the feed roller 42, and when two or more sheets of transfer paper are fed from the pickup roller 29 side, the friction at the nip portion prevents the advance of the paper other than the lowest paper. You will have to block it and separate only one piece.

When the transfer paper 8 is gripped by the pair of pull-out rollers 46, the paper feed clutch is turned off and the drive is stopped. However, a one-way clutch 48 provided on the shaft of the feed roller 42 continues to rotate due to the frictional force of the advancing transfer paper 8, and does not become a load. On the other hand, since the pickup roller 29 must always stop at a fixed position, the filler 4 provided coaxially with the pickup roller 29 as shown in FIG.
When the home sensor 50 detects the home position by 9,
The clutch is disengaged and the cam follower 53, which is biased by a spring 52 as shown in FIG. 4, is engaged with the cam 51 provided coaxially with the pickup roller 29, thereby stopping at a fixed position.

By repeating such operations, when all the stacked transfer sheets have been fed out, the solenoid 35 is turned off, the sheet refeeding operation is completed, and the state is returned to a state in which stacking operation is possible.

FIG. 5 is a timing chart showing an example of processing for A4 size transfer paper.

However, in this embodiment, as shown in FIG. 1, the pressure surface 31a of the pressure plate 31 is not flat;
At the time of paper refeeding, the apex facing portion of the pull-up roller 29 (half-moon roller 28) is curved to form a concave portion 31c on the opposite side of the pull-up roller 29, thereby forming a pressure regulating means.

Therefore, when refeeding the stacked transfer paper, pressure is applied between the pickup roller 29 and the pressure plate 31, but the concave portion 31c is opposed to the apex portion of the pickup roller 29 where the highest pressure is applied during the paper feeding operation. The paper is fed in a state where the pressure is relieved. Therefore, when the pressure surface 31a is flat, the paper is fed under strong pressure and the transfer paper 8
Although toner show-through occurs due to friction between the concave portions 31c and
By easing the pressure caused by this, such toner show-through can be eliminated or significantly reduced. Therefore, good double-sided copies can be obtained.

Next, a second embodiment of the present invention will be explained with reference to FIG. In this embodiment, the pick-up roller 29 side is devised so that the length (circumferential length) L1 of the circular arc surface 55a in contact with the lower surface of the transfer paper is aligned between the tip of the transfer paper 8 and the rollers 42 and 47, which are aligned by the stopper 26. A half-moon-shaped roller 55 that is approximately equal to or slightly longer than the length L2 between the two parts is used. Here, the semicircular roller 55 is in a stopped state as shown in FIG.

In such a configuration, the pressure plate 3
By rotating the pickup roller 29 under the pressure of the transfer sheet 1, the sheet feeding operation of the lowest transfer sheet 8 is performed. Here, in the case of the half-moon-shaped roller 28 shown in FIG. 1 etc., the transfer paper 8
Even after the pressure plate 31 is sent between the rollers 42 and 47,
However, in the case of the semicircular roller 55 of this embodiment, when the fed transfer paper 8 is held in the nip between the rollers 42 and 47, the arcuate surface 55a is short, so the semicircular roller 55 continues to act. No pressure is applied from the roller 55 side. That is, compared to the case of the half-moon-shaped roller 28, since the time (length) during which pressure is applied is restricted to a shorter time with the half-moon-shaped roller 55, there is a possibility that toner is imprinted due to friction between the transfer paper 8. It will be significantly reduced. In this way, the arc surface 55
Even if the length of a is shortened, L1≧L2 and roller 4
The paper feeding function up to the nip portion between 2 and 47 times is not impaired.

[0021]

Effects of the Invention As described above, the present invention is provided with a pressure regulating means for regulating the pressure acting between the pressure plate and the pick-up roller during paper feeding, so that one side of the sheet that has been layered when refeeding is provided. It is possible to reduce the frictional force that acts between copied transfer sheets, reduce toner bleed-through, and improve copy quality. This can be easily realized by forming a concave portion to release the pressure, or by making the length of the arcuate surface of the half-moon roller on the pickup roller side shorter to limit the time during which the pressure is applied.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the present invention, in which (a) is a cross-sectional view when stacking, and (b) is a cross-sectional view when paper refeeding starts.

FIG. 2 is a schematic diagram of the entire double-sided copying machine.

FIG. 3 is a perspective view of a pickup roller.

FIG. 4 is a front view of a pickup roller and a cam follower.

FIG. 5 is a timing chart.

FIG. 6 shows a second embodiment of the present invention, in which (a) is a cross-sectional view when stacking, and (b) is a cross-sectional view when paper refeeding starts.

[Explanation of symbols]

8 Transfer paper 28 Half-moon-shaped koro 29 Pick up roller 31 Pressure plate 31a Pressure surface 31c concavity 41 Friction separation part 55 Half-moon-shaped roller 55a Arc surface

Claims (3)

[Claims] 1. A pressure plate that presses a stack of transfer paper bundles, and a half-moon-shaped roller that cooperates with the pressure plate to sequentially move the lowest paper of the transfer paper stack toward a friction separation part. A double-sided sheet feeding device of a lower side feeding type, which is provided with a pickup roller for feeding the sheet, characterized in that a pressure regulating means is provided for regulating the pressure acting between the pressure plate and the pickup roller during sheet feeding. Double-sided paper feeder. 2. The double-sided paper feeding device according to claim 1, wherein a portion of the pressure surface of the pressure plate facing the pickup roller is formed into a concave pressure regulating means. 3. A claim characterized in that the length of the arcuate surface of the half-moon-shaped roller that contacts the transfer paper is approximately the same as the length from the tip of the stacked transfer paper to the friction separation part. The double-sided paper feeding device according to item 1.