JP2000135851A - Option device for perfect printing, perfect printing method and reversing and paper resupply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable perfect printing to be easily performed in a short time dispensing with a makeup device or a printing plate delivery device belonging to a printing device for one side printing, on an option device for perfect printing by making two printing drums interchangeable. SOLUTION: A printing device 1 for one side printing is used with an option device 2 for perfect printing connected to a paper delivery aperture. In the option device 2 for perfect printing, a sheet S with a printed first surface delivered from the paper delivery aperture of the printing device 1 for one side printing is reversed so that the second surface is turned upward, by a reversing the paper resupply part 18. Further the second surface of the sheet S is printed by a printing drum 19 and delivered. Thus it is possible to perform the perfect printing easily and in a short time.

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 option device used in addition to a one-sided printing device, a two-sided printing method using a one-sided printing device and a two-sided printing option device, and And a reverse re-feeding device for reversing the front side printed paper discharged from the single-sided printing device and re-feeding it to the second single-sided printing device.

[0002]

2. Description of the Related Art In recent years, it has been required to reduce the amount of paper used and the storage space for printed materials by printing on both sides of the paper.

Conventionally, when performing double-sided printing, as a first example, first, the front side of all sheets is printed using a printing apparatus for single-sided printing, and then the operator turns the sheets over by hand and re-feeds the sheets. Then, the master is replaced and printing is performed on the back side of the sheet.

A second conventional example is disclosed in Japanese Patent Laid-Open No. 7-81.
There is a proposal of a stencil type stencil printing apparatus capable of double-sided printing described in Japanese Patent Publication No. 202-202. The apparatus proposed here is provided with an automatic refeeding function, and automatic refeeding by the operator in the first example is automated.

A third conventional example is disclosed in Japanese Patent Laid-Open No. 6-71.
There is a proposal of a "stencil printing apparatus" described in Japanese Patent Publication No. 996. The device proposed here has two printing drums, and these printing drums are arranged so that their outer peripheral surfaces can contact each other. The paper passes between these printing drums and is printed on both sides simultaneously.

[0006]

In the first example, the operator must re-feed the paper, which not only complicates the operation, but also causes the front-printed paper to be realigned and set again on the paper feed table. Requires skill and is a difficult task for an unskilled operator. Further, it takes a long time to complete the printing.

In the second example, re-feeding is automated, but the other steps are the same as in the first example. Time is long.

In the third example, although the time required until the printing is completed is short, it is difficult to separate the printed matter printed on both sides simultaneously from the printing drum, and the printed matter is conveyed after the separation. It is also difficult to avoid rubbing the image. Further, when printing is performed on only one side by this apparatus, the master must be mounted on one of the printing drums, so that the master is wasted.

An object of the present invention is to easily perform double-sided printing in a short time.

[0010]

According to a first aspect of the present invention, there is provided an optional apparatus for double-sided printing, comprising: a sheet conveying path on which a front side printed sheet printed on a front side by a single-sided printing apparatus is conveyed; A printing drum for backside printing for printing a part of the outer peripheral surface on a road and printing on the backside of the front side printed paper; and the front side printed paper discharged from the single side printing printing apparatus in the paper transport path. And a reverse re-feeding unit for turning the back side of the front side printed paper toward the printing drum side when placing on the print drum.

Therefore, double-sided printing can be performed by connecting to a single-sided printing apparatus.

According to a second aspect of the present invention, there is provided the optional device for double-sided printing according to the first aspect, wherein the print drum for front-side printing provided in the single-sided printing device is attached to and detached from the single-sided printing device. The printing drum for backside printing is detachable from the optional device for double-sided printing and the printing device for single-sided printing.

Therefore, plate discharging and / or plate feeding of the printing drum of the optional device for duplex printing can be performed by the printing device for simplex printing.

According to a third aspect of the present invention, there is provided the optional apparatus for double-sided printing according to the first or second aspect, wherein a registration roller is provided in a sheet transport path from the reverse re-feeding unit to the printing drum for backside printing. The printing drum for backside printing and the registration roller are driven to rotate in synchronization with a printing speed of the printing apparatus for single-sided printing.

Therefore, the printing speed of the optional device for double-sided printing matches the printing speed of the printing device for single-sided printing.

According to a fourth aspect of the present invention, there is provided the optional device for duplex printing according to the first, second or third aspect, wherein the reverse re-feeding section has a reversing direction whose axial direction is inclined with respect to the feeding direction. A sheet feeding roller is provided, and the sheet is turned over such that the front side printed sheet is folded back along the outer peripheral surface of the reversing re-feeding roller.

Therefore, the sheet can be easily inverted in a small space without temporarily stopping the sheet.

The invention according to claim 5 is the invention according to claims 1, 2, 3
5. The optional device for double-sided printing according to 4, wherein a discharge tray for loading the front-side printed paper discharged from the single-sided printing device is provided above the reverse re-feeding unit, and the single-sided printing is performed. And a lifting mechanism for raising and lowering the reverse re-feeding unit and the paper discharge tray with respect to the paper discharge port of the printing apparatus.

Therefore, even when the optional device for double-sided printing is installed, it is possible to cope with the discharge when printing only one side.

According to a sixth aspect of the present invention, there is provided the optional device for double-sided printing according to the fourth aspect, wherein an ink-absorbing material is wound around an outer peripheral surface of the reverse re-feed roller.

Therefore, surplus ink can be removed from the printing surface when the sheet is inverted.

According to a seventh aspect of the present invention, in the optional device for double-sided printing according to the fourth aspect, a plurality of minute projections are formed on an outer peripheral surface of the reverse re-feed roller.

Accordingly, the contact area between the printing surface and the reversing paper feed roller can be reduced.

According to an eighth aspect of the present invention, in the double-sided printing method, a printing drum for backside printing is mounted on a printing apparatus for single-sided printing.
The master for backside printing is made by the single-sided printing device, the plate is supplied to the printing drum for backside printing, and the printing drum for backside printing is taken out of the single-sided printing device and an optional device for double-sided printing is prepared. , A printing drum for surface printing is mounted on the printing apparatus for single-sided printing, a master for surface printing is made, and a plate is supplied to the printing drum for surface printing. And printing on the back side of the paper by the back side printing drum.

Therefore, according to the method for making the two printing drums compatible, the optional device for double-sided printing requires a plate making device and a plate discharging device provided in a conventional single-sided printing device. There is no need to provide, and the size is reduced.

According to a ninth aspect of the present invention, there is provided a reversing sheet re-feeding device.
A first connecting portion connected to a paper discharge port of the first single-sided printing device, and a paper supply direction substantially perpendicular to a paper discharging direction of the first single-sided printing device; A second connecting portion connected to a paper feed port of a second one-sided printing device, and a discharge direction of the first one-sided printing device and a paper feed direction of the second one-sided printing device. A reverse re-feeding roller whose axial direction is inclined with respect to the direction, so that the front side printed paper discharged from the first single-sided printing device is folded back along the outer peripheral surface of the reverse re-feeding roller. Then, the sheet is reversed and fed to the second single-sided printing device.

Therefore, two-sided printing can be performed by connecting two single-sided printing apparatuses.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. In this embodiment,
It is an example of an optional device for double-sided printing.

FIG. 1 is a plan view showing a state in which an optional device 2 for double-sided printing of the present invention is connected to a printing device 1 for single-sided printing. The printing apparatus 1 for single-sided printing and the optional apparatus 2 for double-sided printing are arranged such that the sheet conveyance directions are substantially orthogonal to each other. The structure of the printing apparatus 1 for single-sided printing is shown in the vertical front view of FIG. 2, and the structure of the optional apparatus 2 for double-sided printing is shown in the vertical left side view of FIG.

The printing apparatus 1 for single-sided printing is a stencil printing apparatus which is conventionally used, and includes a scanner unit 3 for reading an image of a document at an upper part of the apparatus, and a printing unit 4 below the scanner unit 3. The printing unit 4 includes a printing drum 5, and a press roller 6 can be pressed against the printing drum 5.

A paper feed path 8 is formed from the paper feed table 7 to the nip between the printing drum 5 and the press roller 6. A pair of registration rollers 9 for correcting the skew of the sheet S and sending the sheet S to a nip portion between the printing drum 5 and the press roller 6 at a predetermined timing are provided in the sheet feeding path 8.

From the nip portion between the printing drum 5 and the press roller 6 to the paper discharge port 10, a belt conveyor in which a plurality of belts 12 are hanged on a pair of transport rollers 11 arranged orthogonally to the paper transport direction. A paper discharge transport path 13 is provided, and transports the paper S while adsorbing it on the belt 12 by a suction fan 13a.

Above the paper feed path 8, there is provided a plate making device 14 for making a master M based on an image read by the scanner unit 3 and supplying the master M to the printing drum 5. Further, a plate discharging device 15 for stripping the master M from the printing drum 5 is provided above the sheet discharging conveyance path 13.

The printing drum 5 includes a master clamper 16 for fixing the master M.

The optional device 2 for double-sided printing includes a printing unit 1
7 and a reverse re-feeding unit 18. Printing unit 17
Has a printing drum 19 that is driven to rotate in synchronization with the printing speed of the printing apparatus 1 for single-sided printing. The printing drum 19 has the same shape and size as the printing drum 5 provided in the printing unit 4 of the printing apparatus 1 for single-sided printing. A press roller 20 can be pressed against the print drum 19. The printing drum 19 includes a master clamper 21 for fixing the master M.

A refeeding conveyance path 23 is formed from the refeeding port 22 to the nip between the printing drum 19 and the press roller 20. The refeeding conveyance path 23 is rotated in synchronization with the printing speed of the printing apparatus 1 for single-sided printing, corrects the skew of the sheet S, and moves a predetermined amount to the nip portion between the printing drum 19 and the press roller 20. A pair of registration rollers 24 that send out the sheet S at a timing are provided.

From the nip portion between the printing drum 19 and the press roller 20 to the final discharge port 25, as in the case of the single-sided printing apparatus 1, a pair of transport rollers 26 arranged orthogonally to the paper transport direction. A belt conveyor-shaped final discharge conveyance path 28 on which a plurality of belts 27 are hung is provided.
The sheet S is conveyed while being attracted to the belt 27 by the suction fan 28a.

Here, a paper transport path is formed by the re-feed transport path 23 and the final discharge transport path 28.

The printing section 17 has a paper discharge table 29 on which the sheets S discharged from the final paper discharge port 25 are stacked.

FIG. 4 shows the reversing sheet feeding section 18. The reverse re-feed unit 18 includes a belt conveyor-shaped intermediate conveyance path 32 in which a plurality of belts 31 are hung on a pair of rollers 30 orthogonal to the sheet discharge direction of the printing apparatus 1 for single-sided printing. A re-feed roller 33 having an axial direction of 45 ° with respect to the transport direction in the intermediate transport path 32 and the paper feed direction of the optional device 2 for duplex printing is provided on the intermediate transport path 32. The intermediate conveyance path 32 also has a suction fan 32a (see FIG. 2) for conveying the sheet S while adsorbing the sheet S on the belt 31.

A plurality of auxiliary rollers 35 supported by a rotating shaft 34 are in pressure contact with the reversing re-feed roller 33.

A reversing guide 36 is provided between the auxiliary rollers 35 so as to be close to the outer peripheral surface of the reversing re-feed roller 33 with a small gap therebetween. The reversing guide 36 guides the paper S to be folded back along the outer peripheral surface of the reversing re-feed roller 33, and changes the traveling direction of the paper S conveyed through the intermediate conveyance path 32 by 90 °.

The reverse re-feed section 18 includes a guide plate 37 for guiding the sheet S, which has been turned over by the reverse re-feed roller 33, the auxiliary roller 35, and the reverse guide 36, to the re-feed port 22.

Above such a reverse re-feeding section 18,
A paper discharge tray 38 is provided. The discharge tray 38
When performing single-sided printing in a state where the single-sided printing apparatus 1 and the double-sided printing option apparatus 2 are connected as shown in FIG. 1, the single-sided printing apparatus 1 is used to stack sheets S discharged. Things. An elevating mechanism 39 (see FIG. 5) is provided below the reversing and re-feeding unit 18, and the elevating mechanism 39 is used to selectively switch the reversing and re-feeding unit 18 or the discharge tray 38 to the discharge port 10. Adjust to height.

Here, the print drum 5 and the print drum 19 are provided with handles 40 and 41, respectively, and both are detachable from the apparatus main body. Further, since the print drum 5 and the print drum 19 have the same shape and size, the print drum 19 can be mounted on the printing apparatus 1 for single-sided printing.

In such a configuration, first, the printing drum 19 is mounted on the printing apparatus 1 for single-sided printing. Subsequently, the used master wound around the printing drum 19 is discharged by the plate discharging device 15, and the back side document is read by the scanner unit 3.
Based on the read image, the master M is made by the plate making device 14 to supply the plate. Then, the printing drum 19 is detached from the printing apparatus 1 for single-sided printing and mounted on the optional apparatus 2 for double-sided printing.

Next, the printing drum 5 is mounted on the printing apparatus 1 for simplex printing. An original for the front side is set in the scanner unit 3 and plate discharging, plate making, and plate feeding are performed in the same manner as the printing drum 19.

Next, the printing process will be described. The paper S fed from the paper feed table 7 is corrected for skew by the registration rollers 9, conveyed to the nip between the printing drum 5 and the press roller 6, and an image is printed on the surface of the paper S.

The sheet S on which front side printing has been performed is conveyed on the sheet discharge conveyance path 13, conveyed on the intermediate conveyance path 32, guided by the reversing guide 36, and folded back along the outer peripheral surface of the reversing re-feed roller 33. The sheet is turned over as described above, guided by the guide plate 37, and fed again from the sheet re-feeding port 22.

The registration roller 24 is driven to rotate in synchronization with the printing speed of the printing apparatus 1 for single-sided printing, and sends out the sheet S to the nip between the printing drum 19 and the press roller 20 at a predetermined timing. At this time, the back surface of the paper S is facing upward. Then, an image is printed on the back surface of the sheet S by the printing drum 19 that is driven to rotate in synchronization with the printing speed of the printing apparatus 1 for single-sided printing.

Paper S on which images are printed on both sides
Are conveyed through a final discharge conveyance path 28, discharged from the final discharge port 25, and stacked on a discharge table 29.

In this embodiment, when performing single-sided printing, the paper ejection tray 38 is adjusted to the height of the paper ejection outlet 10 by the elevating mechanism 39, and the paper S ejected from the paper ejection outlet 10 is ejected. The paper is loaded on the paper tray 38.

According to the present embodiment, double-sided printing can be easily performed in a short time. In addition, since it takes some time from printing on the surface to turning over, the ink dries, so that image rubbing hardly occurs. Further, the inconvenience that the ink is transferred to the reverse re-feed roller 33 and the ink is transferred again to the next sheet S is less likely to occur.

Here, if a material having a property of absorbing ink is wrapped around the outer peripheral surface of the reversing re-feed roller 33 of the present embodiment, even if there is ink remaining after drying, the ink is applied to the paper S. Is absorbed when it is turned over, so that image rubbing and ink re-transfer are less likely to occur.

Alternatively, if a plurality of minute projections are formed on the outer peripheral surface of the reverse re-feed roller 33 of this embodiment by, for example, etching or sheet metal drawing, the reverse re-feed roller 33 and the sheet S Since the ink is in point contact with the printed surface, even if there is ink remaining after drying, rubbing of the image and retransfer of the ink are less likely to occur. At this time,
The reverse re-feed roller 33 is driven to rotate at the same peripheral speed as the transport speed of the sheet 5.

Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the same portions as those described in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the present embodiment, two-sided printing can be performed using two single-sided printing devices by using an example of a reversing sheet feeding device. First, FIG.
FIG. 4 is a plan view showing a state in which two single-sided printing apparatuses 1h and 1r are connected. FIG. 7 is a vertical sectional front view of a first single-sided printing apparatus 1h for front side printing, and FIG. 8 is a vertical sectional left side view of a second single-sided printing apparatus 1r for back side printing.

The single-sided printing printer 1r for backside printing has a paper ejection tray 52, but the paper ejection tray is removed from the single-sided printing printer 1h for frontside printing.

Further, the reversing sheet re-feeding device 51 of this embodiment
Transfer the sheet S turned over by the reversing and re-feeding unit 18, the discharge tray 38, the elevating mechanism 39, and the reversing and re-feeding unit 18 to the registration roller 9 of the single-sided printing device 1 r for backside printing. And a re-feeding table 53 for transport. Then, the reversing sheet re-feeding device 51 is arranged such that the sheet re-feeding table 53 is located on the sheet feeding table 7. The re-feeding table 53 is also connected to the transport path 1.
3, 28 and 32 are provided.

Here, the intermediate conveyance path 32 provided in the reversing and re-feeding section 18 is connected to the discharge port 1 of the first single-sided printing apparatus 1h.
And also serves as a first connecting portion connected to 0.
Further, the re-feeding table 53 also serves as a second connecting portion connected to the sheet feeding port of the second single-sided printing apparatus 1r.

In such a configuration, first, the sheet S printed on the front side by the single-sided printing apparatus 1h for the front side printing is used.
Is turned over by the reversing and re-feeding unit 18 and the sheet conveyance direction is changed to a direction substantially perpendicular to the conveyance direction of the sheet S in the single-sided printing device 1h. It is transported to the printing device 1r for printing. And
When the back surface is printed, the paper S is stacked on the paper discharge tray 52. In this way, by turning over the sheet S in the re-turning and re-feeding section 18 in a direction substantially perpendicular to the transport direction, the apparatus space can be reduced.

According to this embodiment, if two or more printing apparatuses for single-sided printing are owned, double-sided printing can be easily performed in a short time only by replenishing the reversing and re-feeding apparatus 51. When not performing double-sided printing, the single-sided printing devices 1h and 1r can be used for single-sided printing.

[0063]

The double-sided printing optional device according to the first aspect of the present invention can perform double-sided printing by being connected to a single-sided printing device, so that a hand-held single-sided printing device can be used without wasting. This eliminates the need for the operator to perform re-feeding work, and further enables double-sided printing in a short time.

According to the second aspect of the present invention, plate discharging and / or plate feeding of the printing drum of the optional device for double-sided printing can be performed by the printing device for single-sided printing. The apparatus can be eliminated, and the size of the optional apparatus for duplex printing can be reduced.

According to the third aspect of the present invention, since the optional device for double-sided printing can be operated at the same printing speed as the printing speed of the single-sided printing device, the printing speed of the optional device for double-sided printing and the printing of the single-sided printing device can be improved. Paper jam due to speed mismatch can be prevented.

According to the fourth aspect of the present invention, since the sheet is turned upside down along the outer peripheral surface of the reversing and re-feeding roller, the apparatus for inverting the sheet tends to be large in size, and the sheet is temporarily stopped. It took a long time to flip the paper, but the paper can be easily flipped in a small space without pausing.

According to the fifth aspect of the present invention, since the discharge tray is provided above the reverse re-feeding unit, the discharge tray and the reverse re-feed unit can be moved up and down even when the optional device for duplex printing is installed. By doing so, it is possible to cope with paper discharge during printing on only one side.

According to the sixth aspect of the present invention, since the ink-absorbing material is wound around the reverse re-feed roller, excess ink can be removed from the printing surface at the time of reversing the sheet. Paper contamination due to transfer and re-transfer of the ink to the next paper can be prevented.

According to the seventh aspect of the present invention, since a plurality of minute projections are formed on the outer peripheral surface of the reversing and re-feeding roller, the contact area between the printing surface and the reversing and re-feeding roller can be reduced. Is transferred to the reversing re-feed roller and the ink is transferred again to the next sheet, thereby preventing paper contamination.

In the double-sided printing method according to the present invention,
Since the printing drum of the optional device for double-sided printing is mounted on the printing device for single-sided printing, plate making is performed, thereby eliminating the need for a plate-making device such as that provided by the printing device for single-sided printing conventionally used for the optional device for double-sided printing. The size of the device can be reduced.

If the reversing sheet feeding device according to the ninth aspect is used, printing can be performed by connecting two single-sided printing devices, so that double-sided printing can be easily performed in a short time. Furthermore, when not performing double-sided printing, each single-sided printing device can be used individually. Also,
If you have more than one single-sided printing device,
If only the reversing re-feeding device is newly provided, it is possible to cope with double-sided printing. Therefore, it is possible to reduce the area which must be newly secured as an installation space for the device for double-sided printing.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state in which an optional device for double-sided printing according to a first embodiment of the present invention is connected to a printing device for single-sided printing.

FIG. 2 is a vertical sectional front view showing the structure of a reversing sheet feeding unit and a single-sided printing apparatus of the optional apparatus for double-sided printing.

FIG. 3 is a left side view in vertical section showing the structure of an optional device for double-sided printing.

FIG. 4 is a plan view showing the reverse re-feeding unit in detail.

FIG. 5 is a vertical sectional front view showing an optional device for double-sided printing and a printing device for single-sided printing in a case where a reversing re-feeding unit is adapted for single-sided printing.

FIG. 6 is a plan view showing a state in which two single-sided printing apparatuses are connected in the reversing sheet feeding apparatus according to the second embodiment of the present invention.

FIG. 7 is a vertical sectional front view showing the structures of the reversing re-feeding device and the first single-sided printing device.

FIG. 8 is a longitudinal left side view showing the structure of the reversing re-feeding device and the second single-sided printing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Single-sided printing device 2 Optional device for double-sided printing 5 Print drum for front-side printing 10 Discharge port 18 Reverse re-feed unit 19 Print drum for reverse side printing 21 Master clamper 23 Paper transport path 24 Registration roller 33 Reverse re-feed Paper roller 38 Discharge tray 39 Elevating mechanism 1h First one-sided printing device 1r Second one-sided printing device 32 First connecting portion 51 Reverse refeeding device 53 Second connecting portion M Master S Paper

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B65H 29/58 B65H 29/58 C

Claims (9)

[Claims] 1. A sheet conveying path on which a front side printed sheet printed on a front side by a single-sided printing apparatus is conveyed, and a part of an outer peripheral surface is positioned on the sheet conveying path, and the back side of the front side printed sheet A printing drum for backside printing to be printed on the paper, and a backside of the frontside printed paper facing the printing drum when the frontside printed paper discharged from the one-sided printing device is placed on the paper transport path. An optional device for double-sided printing, comprising: a reverse re-feeding unit. 2. The printing drum for front-side printing provided in the printing apparatus for single-sided printing is used when the printing drum for front-side printing is detachable from the printing apparatus for single-sided printing. The optional device for double-sided printing according to claim 1, wherein the optional device for duplex printing is detachably attached to the optional device for printing and the printing device for single-sided printing. 3. A registration roller is provided in a sheet conveyance path from the reverse re-feeding unit to the printing drum for backside printing,
3. The optional device for double-sided printing according to claim 1, wherein the print drum for backside printing and the registration roller are driven to rotate in synchronization with a printing speed of the printing device for single-sided printing. 4. The reverse re-feeding section includes a reverse re-feed roller having an axial direction inclined with respect to a feeding direction, and the front side printed paper is fed along an outer peripheral surface of the reverse re-feed roller. The optional device for double-sided printing according to claim 1, 2 or 3, wherein the sheet is turned upside down. 5. A discharge tray for loading the front-side printed paper discharged from the single-sided printing printer, above the reversing and re-feeding unit, the discharge tray being provided at a discharge outlet of the single-sided printing device. The optional device for double-sided printing according to claim 1, further comprising an elevating mechanism for elevating and lowering the reverse re-feeding unit and the discharge tray. 6. The optional device for double-sided printing according to claim 4, wherein an ink-absorbing material is wound around the outer peripheral surface of the reversing re-feed roller. 7. The optional device for double-sided printing according to claim 4, wherein a plurality of minute projections are formed on an outer peripheral surface of the reverse re-feed roller. 8. A printing drum for backside printing is mounted on a printing apparatus for single-sided printing, a master for backside printing is made by the printing apparatus for single-sided printing, and a plate is supplied to the printing drum for backside printing. The printing drum for backside printing is taken out of the printing apparatus for single-sided printing, and is mounted on the optional apparatus for double-sided printing.The printing drum for front-side printing is mounted on the printing apparatus for single-sided printing, and a master for front-side printing is made. A printing method, wherein the plate is supplied to the printing drum for the front side printing, the printing is performed on the front side of the sheet by the printing drum for the front side printing, and the back side of the paper is printed by the printing drum for the back side printing. 9. A paper feeding direction substantially orthogonal to a first connecting portion connected to a paper discharge port of the first single-sided printing device and a paper discharging direction of the first single-sided printing device. Connected to a paper feed port of a second one-sided printing device installed as described above, and the discharge direction of the first one-sided printing device and the second one-sided printing device A reverse re-feed roller having an axial direction inclined with respect to a paper feeding direction of the printing apparatus, and an outer peripheral face of the reverse re-feed roller for printing the surface-printed sheet discharged from the first single-side printing printing apparatus; Reversing sheet feeding device that reverses the sheet so as to be folded back along the sheet and feeds the sheet to the second single-sided printing apparatus.