JP2003146502A - Paper sheet conveyance device for electrophotographic arrangement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive paper sheet conveyance device capable of dispensing with a valve unit because a structure of the valve unit is complicated and the valve unit is expensive and preventing slack of a paper sheet when performing paper sheet return operation. SOLUTION: This paper sheet conveyance device is composed of a transfer part for transferring toner forming characters and images onto a paper sheet, a nipping roller unit positioned in the front of the transfer part and nipping a paper sheet by a pair of rollers having a drive source to rotate and convey it, and a vacuum belt unit and a suction blower positioned in the rear of the transfer part and composed of a drive shaft rotatable by the same drive source as the nipping roller unit, a vacuum belt provided with a plurality of holes, and a belt drive roller transmitting a driving force of the drive shaft to the vacuum belt to convey a paper sheet by air suction. A member for regulating the direction of driving and transmission of the belt drive roller of the vacuum belt unit into the direction of paper sheet feeding only is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device for an electrophotographic apparatus.

2. Description of the Related Art An electrophotographic printing apparatus using continuous printing paper will be described. In recent years, since conventional tractor transportation in a printer using continuous printing paper is costly, pinless paper that does not require processing of holes for tractor pins has been used.

FIG. 3 is a schematic view of an electrophotographic printing apparatus for carrying pinless paper in the prior art. The photosensitive drum 1 rotates, a high voltage is applied to the charger 2, and the surface of the photosensitive drum 1 is uniformly charged. ON / OFF of the optical unit 3 in which character data and graphic data converted into dot images are composed of semiconductor lasers, light emitting diodes, etc.
Light is emitted onto the photosensitive drum 1 as an OFF signal. As a result, a so-called electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image is developed by the developing device 4 to form a toner image on the photosensitive drum 1. The toner image is transferred to the sheet 5 by the action of the transfer unit 7 that applies an electric charge having a polarity opposite to that of the toner image on the back side of the sheet 5. As shown in FIG. 4, the transfer unit 7 includes a transfer device 7a, a retractor 7b that is a paper guide, and a retractor paper guide 7c. When printing (shown in broken lines), the toner 5
The retractor 7b comes into contact with the photosensitive drum 1 through the paper 5 so as to be easily transferred to the photosensitive drum 1. Further, at the time of non-printing (shown by a solid line), the retractor 7b and the retractor paper guide 7c are separated from the photosensitive drum 1 together with the paper 5 from the drum 1.

Before the transfer of the paper 5, the nipping roller unit 6
After being passed through the transfer unit 7, the vacuum belt unit 10 conveys the toner image to the fixing unit 9 via the buffer 8. The fixing unit 9 melts and fixes the toner image on the sheet 5 and conveys the toner image. Further, during the printing stop operation, the sheet conveyance in the fixing unit 9 is stopped before the conveyance in the vacuum belt unit 10 so that the sheet 5 is not torn. At the time of printing and at the time of stopping, the buffer 8 applies tension to the sheet 5 by a spring or the like so that the sheet 5 does not sag. The sheet 5 is nipped by the driving nip roller 6a and the driven nip roller 6b, and is nipped and conveyed by the rotation of the driving nip roller 6a by the drive source 13. At the time of the printing stop operation, the nip roller unit 6 and the vacuum belt unit 10 convey the paper 5 in the reverse direction of paper feeding in preparation for the next printing operation. Therefore, the paper 5 is returned to the next print start position.
The vacuum belt unit 10 includes a belt drive roller 10a, a belt drive shaft 10b, a vacuum chamber 10c, a vacuum belt 10d, a vacuum hose 10e, a valve unit 11, and a suction blower 12 shown in FIG. The vacuum belt 10d is driven by a drive source 13 via a belt drive shaft 10b,
It is rotated in the sheet conveying direction by a. Further, the vacuum belt 10d has holes all around, and the suction blower 12
The suction force (static pressure) is transferred via the valve unit 11 and the vacuum hose 10e while sucking the sheet 5 in the vacuum chamber 10c.

At the time of printing, it is necessary to apply an appropriate tension to the sheet 5 at the transfer section 7. If the vacuum belt unit 10 and the nipping roller unit 6 are driven by the drive source 13 at the same paper conveyance speed, and the diameter of the belt driving roller 10a is smaller than that of the driving nipping roller 6a due to variations in parts or the like, the paper 5 is conveyed due to the difference in conveyance amount. Sags near the transfer section 7. Here, since the vacuum belt unit 10 conveys the sheet only by air suction, the sheet can be conveyed while sliding even when the sheet conveying speed is high. Therefore, by increasing the diameter of the belt driving roller 10a of the vacuum belt unit 10 and increasing the sheet conveyance amount, the sheet 5 is applied with tension.

Further, the sheet 5 is a retractor 7b of the transfer section 7.
Thus, printing is performed in a state of being brought into contact with the photosensitive drum 1.

After the printing is stopped, the retractor 7b of the transfer section 7 is separated from the photosensitive drum 1. Since the photosensitive drum 1 is charged, an electrostatic force acts on the sheet 5 and the sheet 5 is not separated from the photosensitive drum 1. Therefore, the retractor paper guide 7c is designed to project. As a result, the paper path length between the nip roller unit 6 and the vacuum belt unit 10 does not change, and the paper 5 can be separated from the drum 1 together with the retractor 7b.

However, when the paper 5 is returned to the next print start position at the time of the print stop operation, the paper feed amount of the vacuum belt unit 10 is increased, so that the retractor paper guide 7c has no effect and the vicinity of the transfer portion 7 is eliminated. The paper 5 sags. As a result, the sheet 5 temporarily separated from the photosensitive drum 1 by the retractor 7b comes into contact with the photosensitive drum 1 again, and the sheet is soiled by the residual toner on the photosensitive drum 1. Therefore, the valve 11 is used as a paper slack preventing means.

At the time of printing, the valve 11 is opened and the suction static pressure of the suction blower 12 is transmitted to the vacuum belt unit 10. During the printing stop operation, the valve 11 is closed and the vacuum belt unit 10 loses the conveying force because the suction static pressure is cut off. Therefore, the paper 5 is conveyed by the nipping roller unit 6 without sagging under the tension of the buffer 8.

[0009]

The valve unit has a complicated structure and is expensive. SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-priced sheet transporting device, in which a valve unit is eliminated, and it is possible to prevent the sheet from slackening during a sheet returning operation.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a sheet is sandwiched between a transfer section for transferring toner on which characters and images are formed onto a sheet and a pair of rollers located in front of the transfer section and having a drive source. A nipping roller unit that rotates and conveys, a belt driving shaft located behind the transfer unit and rotatable by the same drive source as the nipping roller unit, a vacuum belt having a plurality of holes, and a driving force of the driving shaft. In a paper conveying device consisting of a vacuum belt unit and a suction blower that can convey paper by air suction consisting of a belt driving roller that transmits the belt to the vacuum belt, the drive transmission direction of the belt driving roller of the vacuum belt unit is restricted to the paper feeding direction only. It is characterized in that a member is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a case where a one-way clutch is used as a member for restricting a drive transmission direction only to a sheet feeding direction will be described with reference to FIGS. 1 and 2, the same parts as those in FIG. 3 are denoted by the same reference numerals.

The carrying device comprises the same as that shown in FIG. Further, as shown in FIG. 1, a one-way clutch 14 is provided between the belt drive roller 10a and the belt drive shaft 10b of the vacuum belt unit 10. Alternatively, as shown in FIG. 2, a one-way clutch 14 is provided between the belt drive shaft 10b of the vacuum belt unit 10 and the drive source 13. At the time of printing, the one-way clutch 14 transmits the driving force from the driving source 13 in the sheet feeding direction. As a result, the vacuum belt 10
It is possible to convey the paper in the suction state.

When the printing operation is stopped and the paper 5 is returned to the printing start position, the one-way clutch 14 does not transmit the driving force. Therefore, the sheet 5 is returned to the print start position along the retractor 7b and the retractor 7c separated from the photosensitive drum 1, with the tension applied by the buffer 8. Therefore, by mounting the one-way clutch 14, it is possible to prevent the paper 5 from sagging with an inexpensive structure.

[0014]

According to the present invention, since the nipping roller unit performs the paper returning operation in the state where the tension of the buffer acts, the slack of the paper does not occur, and the same effect as the valve unit can be obtained with a simple and inexpensive structure. Is obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a sheet conveying device of the invention.

FIG. 2 is a schematic configuration diagram showing a configuration of a sheet conveying device of the invention.

FIG. 3 is a schematic configuration diagram showing a configuration of a conventional paper transport device.

FIG. 4 is a schematic configuration diagram of a conventional transfer unit.

[Explanation of symbols]

1 ... Photosensitive drum, 2 ... Charger, 3 ... Optical unit, 4 ...
Developing device, 5 ... Paper, 6 ... Nip roller unit, 6a ...
Drive nip roller, 6b ... driven nip roller, 7 ... transfer section,
7a ... Transfer device, 7b ... Retractor, 7c ... Retractor paper guide, 8 ... Buffer, 9 ... Fixing unit, 10 ...
Vacuum belt unit, 10a ... Belt drive roller, 10b ... Belt drive shaft, 10c ... Vacuum chamber, 10d ... Vacuum belt, 10e ... Vacuum hose, 11 ... Valve, 12 ... Suction blower, 13 ... Drive source, 14 ... One-way clutch.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Terakado             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. (72) Inventor Hidenori Iwanaga             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. F term (reference) 3F103 AA02 BC02 BC06 DA01                 3F105 AA02 AB04 BA02 BA16 BA27

Claims (3)

[Claims] 1. A transfer unit for transferring toner on which characters or images have been formed to a sheet, and a nipping roller unit for nipping and conveying the paper by a pair of rollers having a drive source located in front of the transfer unit. A belt drive shaft located behind the transfer unit and rotatable by the same drive source as the nip roller unit, a vacuum belt having a plurality of holes, and a belt drive for transmitting the drive force of the drive shaft to the vacuum belt. In a sheet conveying device including a vacuum belt unit that can convey sheets by air suction consisting of rollers and a suction blower, a member that restricts the drive transmission direction of the belt driving roller of the vacuum belt unit only to the sheet feeding direction is provided. Paper transport device for electrophotographic device. 2. A sheet conveying device for an electrophotographic apparatus according to claim 1, further comprising a member disposed between the belt driving shaft and the belt driving roller for restricting a drive transmission direction only in a sheet feeding direction. apparatus. 3. Between the drive source and the belt drive shaft,
The sheet conveying device of the electrophotographic apparatus according to claim 1, further comprising a member that restricts the drive transmission direction only to the sheet feeding direction.