JPH106588A - Both side printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the switch back mechanism of a both side printer so as to improve the printing speed. SOLUTION: A paper is guided to a discharging side A by a switching gate 7 when it is only for one side printing so as to be discharged by a discharging roller 6 and piled on a paper stacker 13. If the other side is to be printed, the switching gate 7 is oriented to the direction shown by the broken line. The paper is guided in direction B by the switching gate 7 so as to be discharged on a reverse plate 8. A fixer 5 comprises a heat roller having a heat source and a pressure roller for applying pressure on the paper. Furthermore, a reverse roller 9 is integrated so as to be contacted with the pressure roller. The paper discharged on the reverse plate 8 is fed into the apparatus again by the pressure roller and the reverse roller 9 with the paper rear end entering a portion where the pressure roller and the reverse roller 9 are contacted for the self weight and the pressure roller rotation.

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 for printing on the front and back surfaces of a cut sheet.

[0002]

2. Description of the Related Art Conventionally, as a double-sided printing apparatus of this type, for example, one shown in FIG. 3 has been proposed in Japanese Patent Application Laid-Open No. 62-280183. Referring to FIG. 3, the sheet printed on one side is fixed by a fixing unit 21, discharged onto a reverse plate 23 by a sheet discharge roller 22, and then, from the rear end of the sheet by a reverse roller 24 serving as a switchback mechanism. It is sent to again. Immediately after the reverse roller 24, a paper path switching gate 25 is provided. One paper path is again led to the printing unit, and the other paper path is led to the paper stacker 26. The sheet on which printing is performed on only one side is guided to the sheet stacker 26 by the operation of the switching gate 25. The sheet to be printed on the opposite side is sent out again from the rear end of the sheet to the printing section by the operation of the switching gate 25, and the opposite side is printed. After the paper printed on both sides is fixed by the fixing device 21, the paper is discharged by the paper discharge roller 22. Here, after the sheet is discharged onto the reverse plate 23 again, the sheet is pulled in again from the rear end of the sheet by the reverse roller 24. Here, the switching gate 25 is operated, and the sheet is discharged to the sheet stacker 26 side. By repeating the above operation, double-sided printing can be performed continuously.

[0003]

The above-mentioned conventional double-sided printing apparatus has the following problems.

[0004] The first problem is that since a reverse roller for reversing the paper is provided behind the fixing device, the paper path is lengthened and the printing speed is reduced.

[0005] The second problem is that the reverse mechanism requires a pair of rollers for conveyance and a roller for reversal, so that the mechanism is complicated.

An object of the present invention is to provide a double-sided printing apparatus in which the printing speed is increased and the reverse mechanism is simplified.

[0007]

According to a double-sided printing apparatus of the present invention, a sheet printed on one side in a printing section is fixed by a fixing device, and then the sheet is printed again for printing and fixing on the opposite side. A reverse roller leading to the section is integrated with the fixing device.

By integrating the reverse roller with the fixing device, it is possible to immediately reverse the sheet discharged from the fixing device nip portion, that is, immediately after the fixing device,
A path system shorter than the conventional paper path is possible.

Further, since a pair of rollers for conveyance is not required in the reverse mechanism, the number of parts is reduced and the mechanism is simplified.

[0010]

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

Referring to FIG. 1, a sheet fed by a pick roller 1 of a sheet feeding section is conveyed to a registration roller 3 by a feed roller 2, cueed by the registration roller 3, and conveyed to a printing section. . Only the photosensitive drum 4 is shown as a printing unit. The toner image on the photosensitive drum 4 is transferred to a sheet by a transfer roller 12, and the transferred toner image is fixed on the sheet by a fixing device 5.

When printing is performed on only one side of the sheet on which the toner image is fixed, the sheet is guided to the discharge side A by the switching gate 7, discharged by the discharge roller 6, and stacked on the sheet stacker 13.

The sheet to be printed on the opposite side is guided in the direction B by the operation of the switching gate 7 and is discharged onto the reverse plate 8. Then, the sheet is trailed by the reverse roller 9 integrated with the fixing device 5. Again into the device. The paper fed into the apparatus is conveyed by the reverse feed roller 10, the skew is corrected by the skew correction roller 11, the cue is again performed by the registration roller 3, and the paper is conveyed to the photosensitive drum 4. The toner image on the opposite surface is transferred from the photosensitive drum 4 to a sheet by a transfer roller 12,
The transferred toner image is fixed on the sheet by the fixing device 5. The sheet on which double-sided printing and fixing have been completed is guided by the sheet path switching gate 7 in the direction of the discharge side A, discharged by the discharge roller 6 and stacked on the sheet stacker 13 as in the case of only one-sided printing.

FIG. 2 is a sectional view of a mechanism for switching back a sheet.

Referring to FIG. 2, the switching gate 7 and the reverse roller 9 will be described in detail.

When printing the toner image on one side on the opposite side of the sheet fixed by the fixing unit 5, a switching gate 7 for switching the sheet path is provided by a solenoid or the like (not shown).
In the direction shown by the broken line. The sheet is guided in the direction B by the switching gate 7 and discharged onto the reverse plate 8. The fixing device 5 includes a heat roller 5a having a heat source and a pressure roller 5b for applying pressure to a sheet. Further, a reverse roller 9 is integrated with the pressure roller 5b. The paper discharged onto the reverse plate 8 enters the portion where the pressure roller 5b and the reverse roller 9 are in contact with each other by its own weight and the rotation of the pressure roller 5b, and enters the apparatus by the pressure roller 5b and the reverse roller 9. Will be sent again.

[0017]

As described above, the first effect of the present invention is that the paper path can be shortened and the printing speed is increased by integrating the reverse roller with the fixing device.

A second effect of the present invention is that the integration of the reverse roller with the fixing device eliminates the need for a pair of transport rollers in the switchback mechanism, thereby simplifying the switchback mechanism. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a switchback mechanism according to the present invention.

FIG. 3 is a cross-sectional view of a conventional switchback mechanism.

[Explanation of symbols]

 Reference Signs List 1 pick roller 2 feed roller 3 registration roller 4 photosensitive drum 5 fixing device 5a heat roller 5b pressure roller 6 discharge roller 7 switching gate 8 reverse plate 9 reverse roller 10 reverse feed roller 11 skew correction roller 12 transfer roller 13 paper stacker

Claims (3)

[Claims] 1. A reverse roller for fixing a sheet printed on one side in a printing unit by a fixing unit and then guiding the sheet to the printing unit again for printing and fixing on the opposite side is integrated with the fixing unit. A double-sided printing apparatus characterized in that: 2. A double-sided printing apparatus comprising a reverse roller for guiding a sheet printed on one side in a printing section by a fixing device and then guiding the sheet to the printing section again for printing and fixing on the opposite side. A double-sided printing apparatus, wherein the reverse roller is integrated with the fixing device. 3. A sheet printed on one side in a printing section is fixed by a fixing device including a heat roller and a pressure roller, and then the sheet is again transferred to the printing section for printing and fixing on the opposite side. A two-sided printing apparatus, wherein a reverse roller for guiding is integrated so as to be in contact with the pressure roller.