JPH1036014A - Double side printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a paper guide mechanism for reversing the paper and to improve the reliability in paper running by making the direction of the paper conveying path unlimited, rotating and moving one of a pair of conveying rollers around the other roller to switch the recording paper conveying direction. SOLUTION: The paper P having an image on a surface thereof, is conveyed to a feeding-out roller 7 side by a driven side conveying roller 3b. When a rear end of the paper P is detected by a paper end detector 2, the rotation of the drive side conveying roller 3a is stopped, and the driven side conveying roller 3b is moved to a position for guiding the rear end of the paper P to the conveying roller 10b. The driving side conveying roller 3a and the feeding- out roller 7 are rotated to convey the paper P to the conveying rollers 10b, 10a, for reversing a front face and a rear face of the paper P. When it is detected that the rear end of the reversed paper P is removed from the drive side conveying roller 3a, by the paper end detector 2, the driven side conveying roller 3b is moved to a position to be guided to the feeding-out roller 7, and an image is formed on the rear face of the paper P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-sided printing apparatus, and more particularly, to a two-sided printing apparatus that prints on one side using cut paper, and then reverses the paper to perform printing on the back side.

[0002]

2. Description of the Related Art In a conventional double-sided printing apparatus, a recording sheet is usually reversed by opening and closing a gate also serving as a sheet guide.

Further, in order to reduce the space for reversing the recording paper, Japanese Patent Application Laid-Open No. 2-292075 proposes a method shown in FIG. Referring to FIG. 4, recording paper is supplied to a paper feed port 13 by a pickup roller 12. The supplied recording paper is further fed out by the gate roller 17 and the toner of the photoconductor 23 is transferred thereto.
The transferred toner is fixed by the fixing device 37, and the printing on one side is completed. When printing is not performed on the back surface, the sheet is conveyed toward the discharge roller 43 by the switching guide plate 41 and discharged outside the apparatus. When printing is also performed on the back surface, the sheet is conveyed in the direction of the sheet conveying roller 53 by the switching guide plate 41, and is sent upward by the sheet conveying roller 55 and the sheet pull-out roller 49. When the trailing edge detector 59 detects the trailing edge of the recording sheet, the sheet extracting roller 49 forms a roller gap.
The recording paper falls to the paper feed port 13 by its own weight, and is discharged to the outside of the apparatus by the discharge roller 43 through the printing process of the back surface.

[0004]

The above-described conventional double-sided printing apparatus has a problem that the size of the apparatus becomes large because a space for a gate also serving as a paper guide is required. Further, the method proposed in Japanese Patent Application Laid-Open No. 2-2920075 has a problem that the direction of the paper transport path is limited because the own weight of the recording paper is used.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-sided printing apparatus in which the size of a sheet guide mechanism for turning over a sheet is reduced and the direction of a sheet conveying path is not restricted, and the sheet traveling reliability is high.

[0006]

SUMMARY OF THE INVENTION A double-sided printing apparatus according to the present invention has a pair of transport rollers, and among the transport rollers, one of the rollers is rotated and the other roller is rotated to move the recording paper. The direction in which the recording paper is conveyed is switched between a direction in which the recording paper is discharged and a direction in which the recording paper being fed to the discharge side is fed again to the image forming means.

When printing on one side is completed and the paper exiting the image forming means enters the paper guide mechanism, the leading edge of the paper is guided in the discharge direction, and when printing is performed on the back side, the paper trailing edge detector detects the paper. When the trailing edge of the sheet is detected, the solenoid is urged, so that the driven transport roller slides on the circumference of the drive transport roller, and guides the trailing edge of the paper toward the image forming means.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

The paper end detector 2, the drive side transport roller 3a,
A paper guide mechanism that reverses the recording paper by the driven-side transport roller 3b, the arm 4, the solenoid 5, and the original position return spring 6 is configured. Both ends of the arm 4 are rotatably connected to rotating shafts of a driving-side transport roller 3a and a driven-side transport roller 3b, respectively. The movable shaft of the solenoid 5 is rotatably connected to the rotation support shaft of the driven-side conveyance roller 3b, and the rotation support shaft of the driven-side conveyance roller 3b is provided with an original position return spring 6. ON, O of energization of solenoid 5
The FF causes the driven-side transport roller 3b to slide on the roller circumference of the drive-side transport roller 3a around the rotation fulcrum A of the fixed drive-side transport roller 3a and to feed the incoming paper toward the discharge roller 7 side. Alternatively, it is fixed at a position leading to the transport roller 10b.

Next, the operation will be described with reference to FIGS. 1, 2 and 3. FIG.

FIG. 2 is a diagram showing the state of the paper guide mechanism when the paper is discharged. FIG. 3 is a diagram illustrating a state of the sheet guide mechanism when the sheet is transported to the image forming unit again for printing on the back surface of the sheet.

When the apparatus is set to the operation state of double-sided printing, the sheet P fed from the sheet bundle 11 by the sheet feeding roller 8 performs skew correction and cueing of print data by the timing roller 9, and the transfer roller 1a , Photoconductor 1b,
An image is formed on the surface of the sheet P by an image forming unit including a laser unit 1c, a developing unit 1d, a fixing unit 1e, and a charging roller 1f. Paper P with an image formed on its surface
Is transported to the paper guide mechanism by the fixing device 1e. The driven conveyance roller 3b is located at a position (FIG. 2) for guiding the leading end of the paper P toward the discharge roller 7, and conveys the paper P to the discharge roller 7. When the trailing edge of the sheet P is detected by the sheet edge detector 2, the rotation of the drive-side transport roller 3a is stopped after a predetermined time,
At the same time, the solenoid 5 is energized, the movable shaft of the solenoid 5 moves in the X direction, and the driven-side transport roller 3b is moved to a position (FIG. 3) where the rear end of the sheet P is guided to the transport roller 10b.
By rotating the drive side transport roller 3a and the discharge roller 7 in the Z direction, the paper P is transported by the transport roller 10b and the transport roller 10a.
Conveyed to. By this operation, the sheet on which the image is formed on the front side is turned upside down. By the paper edge detector 2,
When it is detected that the trailing end of the inverted sheet P has passed through the driving-side transport roller 3a, the power supply to the solenoid 5 is blocked, and the driven-side transport roller 3b is guided by the original position return spring 6 to guide the sheet to the discharge roller 7 ( Move to Fig. 2). An image is formed on the back surface of the inverted sheet P by the timing roller 9 and the image forming means described above, and the driving side transport roller 3a
And is discharged out of the apparatus by the discharge roller 7,
The operation of double-sided printing is completed.

[0014]

As described above, according to the present invention, since the space for the gate also serving as the paper guide is not required, the size of the paper guide mechanism for reversing the paper can be reduced, and at the same time, the direction of the paper transport path can be reduced. , There is an effect of improving the paper running reliability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a state of a sheet guide mechanism when a sheet is discharged.

FIG. 3 is a diagram illustrating a state of a sheet guide mechanism when a sheet is conveyed again to an image forming unit in order to print on the back surface of the sheet.

FIG. 4 is a diagram showing a conventional technique.

[Explanation of symbols]

 1a Transfer Roller 1b Photoconductor 1c Laser Unit 1d Developing Device 1e Fixing Device 1f Charging Roller 2 Paper End Detector 3a Driving Conveying Roller 3b Followed Conveying Roller 4 Arm 5 Solenoid 6 Original Position Return Spring 7 Discharge Roller 8 Feed Roller 9 Timing roller 10a Transport roller 10b Transport roller 11 Sheet bundle A Rotation fulcrum P Sheet

Claims (2)

[Claims] A sheet supply unit configured to supply recording paper to a paper supply port; and an image forming unit configured to form an image based on print data on a front surface and a back surface of the recording sheet taken into an apparatus main body by the paper supply unit. And a sheet discharging means for discharging the recording sheet on which an image is formed by the image forming means to the outside of the apparatus, the apparatus comprising a pair of conveying rollers, and one of the conveying rollers By rotating the other roller about the recording paper, the recording paper is discharged in one of a direction in which the recording paper is discharged and a direction in which the recording paper being fed to the discharge side is again fed into the image forming means. A double-sided printing device characterized by switching a transport direction. 2. A paper supply unit for supplying recording paper to a paper supply port, and an image forming unit for forming an image based on print data on front and back surfaces of the recording paper taken into the apparatus main body by the paper supply unit. And a paper discharging means for discharging the recording paper on which an image has been formed by the image forming means to the outside of the apparatus, wherein the leading end of the recording paper is directed in the discharging direction and the trailing end of the recording paper is directed in the direction of the image forming means. A paper guide mechanism that switches to any one of the following directions, wherein the paper guide mechanism includes a pair of transport rollers, and an arm that enables the driven roller of the transport roller to slide on the circumference of the drive roller. A double-sided printing apparatus, comprising: a solenoid for urging the arm; a return spring for returning the arm to an original position; and a sheet end detector for detecting a sheet end.