JP2000343804A - Stencil printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of re-transposition scumming due to undried ink in the case of resupplying a one-side printed sheet and double-side printing, to shorten a waiting time from an end of the one-side printing to the resupplying, and to prevent a decrease in image quality due to an ink insufficiency on a printing surface of the one-side printed sheet. SOLUTION: A sheet supply rotor 46 is brought into contact with a printing surface of a one-side printed sheet P2 to be resupplied of one component of a double-side printing sheet supply unit 10, and a pressure contact rotor 66 is rotated while being brought into pressure contact with the rotor 46. When an undried ink is transferred from the printing surface of the sheet P2 to be resupplied to the rotor 46, the undried ink is thinly uniformly extended on surfaces, of both the members of the rotor 46 and the rotor 66, dried, and almost all the ink is not transferred from the rotor 66 to a printing surface of next one-side printed sheet P2, thereby preventing re-transposition scumming of the sheet P2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically re-feeding a single-sided printed sheet discharged and stacked on a discharge tray after printing on one side is completed, and re-feeding the sheet on the other side. The present invention relates to a stencil printer capable of performing automatic double-sided printing for printing.

[0002]

2. Description of the Related Art Conventionally, various types of stencil printing apparatuses which automatically perform double-sided printing using one printing drum have been proposed. For example, Japanese Patent Application Laid-Open No. 7-81202 discloses a stencil printing apparatus. JP-A-8-91710, JP-A-9-1880
No. 57, for example.

In the stencil printing apparatus described in the above publication,
The single-sided printed paper that has been printed on one side is ejected and stacked on the output tray, and the output tray is moved to the re-feeding position facing the paper feed unit for double-sided printing. The paper is re-fed by the two-sided printing paper feed unit to perform printing on the other side.

However, in the stencil printing apparatuses described in JP-A-7-81202 and JP-A-8-91710, when undried ink is present on the printing surface of a single-side printed paper, the undried ink is The ink transferred to the paper supply member (for example, a paper supply roller or a separation roller) in contact with the printing surface of the single-sided printed paper in the paper supply unit for duplex printing, and the ink transferred to the paper supply member is transferred from the paper supply member to the next single-sided printing. A so-called re-transfer stain occurs in which the paper is transferred to the printed surface of the used paper and the printed surface is stained.

Therefore, in the stencil printing apparatuses described in JP-A-7-81202 and JP-A-8-91710, after printing on one side is completed, printing on the other side is started. In addition, a waiting time of 4 to 5 minutes is provided so that the ink adhering to the printing surface of the one-sided printed paper is sufficiently penetrated.
I try to dry it.

Further, in the stencil printing apparatus described in Japanese Patent Application Laid-Open No. 9-188057, in order to prevent the occurrence of retransfer smears, the stencil printing apparatus is provided on the conveyance path of a single-side printed sheet immediately after printing on one side is completed. Has a re-transfer prevention mechanism. The mechanism to prevent re-transfer is a mechanism to remove undried ink from the printing surface of the one-side printed paper, a mechanism to dry the printing surface of the one-side printed paper by heat, and a mechanism to prevent re-transfer to the printing surface of the one-side printed paper A mechanism for applying a treatment liquid is mentioned.

Further, the paper feeding member such as the paper feeding roller and the separation roller is formed of a material having a property of repelling ink, for example, silicone rubber or ethylene tetrafluoride resin, so that the transfer of the ink to the paper feeding member is reduced. It is also considered to make it happen.

[0008]

However, in the stencil printing apparatuses described in JP-A-7-81202 and JP-A-8-91710 described above, after printing on one side is completed, the other side is used. Before starting printing on one side, 4
Since a waiting time of up to 5 minutes is required, the work efficiency of the double-sided printing operation is reduced.

In the stencil printing apparatus described in Japanese Patent Application Laid-Open No. Hei 9-188057, when a mechanism for removing undried ink from the printing surface of a single-sided printed paper is provided as a re-transfer prevention mechanism, the ink may not be printed. When the ink does not penetrate the paper sufficiently, the ink is removed, so part of the ink required for image formation is removed, resulting in insufficient ink on the printing surface, insufficient image density, and insufficient solid filling. Image quality degradation occurs.

When a mechanism for drying with heat is provided as a mechanism for preventing retransfer, a large amount of power is required to dry undried ink that has not sufficiently penetrated paper immediately after printing. The consumption increases.

When a mechanism for applying a re-transfer treatment liquid to the printing surface of a single-sided printed sheet is provided as a re-transfer prevention mechanism, maintenance such as replenishment or replacement of the processing liquid is required.
It is complicated.

Further, regarding the fact that the paper feed roller and the separation roller, which are paper feed members, are formed of a material having a property of repelling ink, for example, silicone rubber and ethylene tetrafluoride resin, the paper feed roller and the separation roller Must secure a certain coefficient of friction to separate and feed the paper,
It is not practical to use a material having a small coefficient of friction, such as silicon rubber or ethylene tetrafluoride resin.

In view of the above, the present invention provides a method for automatically reversing single-sided printed paper discharged and stacked on a paper discharge tray to perform double-sided printing. The transfer of ink to the rotating body for paper feed that comes into contact with the paper, and the transfer of ink from the rotating body for paper feed to the printing surface of the next single-sided printed paper can be prevented. It is an object of the present invention to provide a stencil printing apparatus which can shorten the waiting time until sheet feeding, and does not cause a decrease in image quality, an increase in power consumption, and a complicated maintenance.

[0014]

According to the first aspect of the present invention,
The printing unit discharges and loads the single-sided printed paper on which one-side printing has been performed on the first discharge tray, and removes the first-side printed paper on which the single-sided printed paper is discharged and stacked. The sheet is moved to a sheet re-feeding position by the two-sided printing sheet feeding section, and the single-side printed sheets on the first discharge tray are separately fed one by one toward the printing section, and the other of the single-side printed sheets is fed. A stencil printing apparatus capable of automatic double-sided printing in which double-sided printed paper on which printing on one side has been performed in the printing unit is discharged and stacked on a second discharge tray, And a press-contact rotating body that rotates while being pressed against a sheet-feeding rotary body that is in contact with the printing surface of the single-sided printed paper that is to be re-fed.

Therefore, when the rotating body for feeding comes into contact with the printing surface of the single-sided printed sheet to be re-fed and the undried ink transfers from the printing surface to the rotating body for feeding, The rotating rotator is rotated while being pressed against, so that the undried ink transferred to the rotator for feeding is thinly and uniformly spread on the surfaces of both the rotator for feeding and the rotator. However, the thin and uniformly spread undried ink has an increased contact area with the air to promote drying. The moisture of the ink and the oil phase component remain on the surfaces of both the rotating member and the rotating member, and the dried ink pigment and the oil phase component are fed. Transfer from the rotating body for printing to the printing surface of the next single-sided printed paper, or
Even if the image is transferred, the transfer amount is very small, so that re-transfer contamination of the single-side printed paper is prevented.

By providing such a pressure contact rotating body, the ink adhering to the printing surface of the one-side printed sheet is sufficiently permeated and dried from the end of the one-side printing to the start of refeeding. This eliminates the need to wait until the master unit used in the printing unit has finished making and winding the master sheet, so that the sheet can be fed again immediately, thereby improving the work efficiency of the duplex printing operation.

Further, the reason why the undried ink transfers due to the contact of the rotating body for feeding with the printing surface of the single-sided printed paper and not immediately after the printing is performed, but the single-sided printed paper is re-fed. By this time, a predetermined time has elapsed, and the required amount of ink has already penetrated into the printing surface of the single-sided printed paper. For this reason, even if the undried ink is transferred to the rotary member for paper feeding, the ink does not run out on the printing surface of the single-sided printed paper, and the image quality does not deteriorate, such as insufficient image density and insufficient solid filling. .

Further, since the one-side printed paper is not heated and dried in order to prevent re-transfer contamination of the one-side printed paper, no increase in power consumption is caused and no re-transfer prevention treatment liquid is used. No complicated maintenance is required.

According to a second aspect of the present invention, in the stencil printing machine according to the first aspect, there is provided a drying unit for drying a surface of the rotating body for feeding and a surface of the pressing rotating body.

Therefore, the ink which has been thinly and uniformly spread on the surfaces of both the rotating member for feeding and the rotating member for press-contact is further dried by the drying means, and the next transfer of the single-sided printed paper is performed again. Dirt is more reliably prevented.

The power consumption of the drying means can be made extremely smaller than the power consumption required for directly drying the printing surface of the single-sided printed paper.

According to a third aspect of the present invention, in the stencil printing apparatus according to the first or second aspect, the stencil printing apparatus is located downstream of the double-sided printing paper supply unit along a paper supply direction of the single-sided printed paper. An ink removing unit is provided for removing undried ink on the printing surface of the single-sided printed paper.

Therefore, when the ink is left in the plate cylinder of the printing unit for a long time, the viscosity of the ink is greatly reduced, and the amount of ink adhering to the printing surface of the one-side printed paper is larger than usual. In such a case, even if the undried ink passes through the contact point with the paper feed rotary body without being transferred to the paper feed rotary body, the wet ink is removed by the ink removing means. Therefore, transfer of the undried ink to the transfer member in the transfer process of the re-fed single-sided printed paper is prevented, and occurrence of retransfer contamination in the transfer process is prevented.

According to a fourth aspect of the present invention, there is provided the stencil printing apparatus according to the first, second or third aspect, wherein the first discharge tray, the second discharge tray, the double-sided printing sheet feeding unit, and the double-sided printing. And a double-sided printing unit, which unitizes a single-sided printed sheet re-fed from the paper feeding unit toward the printing unit. It is detachably attached to it.

Therefore, by preparing a double-sided printing unit as an option and attaching the double-sided printing unit as necessary, it is possible to switch between a stencil printing apparatus dedicated to single-sided printing and a stencil printing apparatus capable of automatic double-sided printing.

[0026]

FIG. 1 shows a first embodiment of the present invention.
A description will be given with reference to FIG. 1 and 2 are front views showing the entire structure of a stencil printing apparatus, FIG. 3 is a front view showing a part of a second paper feed unit for re-feeding single-side printed paper, and FIG.
FIG. 9 is a front view illustrating another part of the sheet feeding unit.

The printing apparatus main body 1 of the stencil printing apparatus includes:
A porous cylindrical plate cylinder 2, which is rotationally driven about an axis, movably provided at a position which comes into contact with and separates from the outer peripheral surface of the plate cylinder 2, and is rotationally driven about an axis parallel to the axis of the plate cylinder 2; A cylindrical impression cylinder 3, a plate making section 5 for making a master 4 wound around the outer peripheral surface of the plate cylinder 2, and an impression cylinder for swinging the impression cylinder 3 to a position where the plate cylinder 2 and the impression cylinder 3 come and go. A swing mechanism 6, a plate discharging unit 7 that peels the used master 4 from the plate cylinder 2 and discharges the plate, a sheet feeding table 8, a first sheet feeding unit 9, a second sheet feeding unit 10 that is a sheet feeding unit for duplex printing, A first paper discharge tray 11, a second paper discharge tray 12, and the like are provided. In the upper part of the printing apparatus main body 1,
A document reading unit 13 is provided.

The plate making section 5 includes a platen roller 14 that is driven to rotate by a stepping motor (not shown), a thermal head 15 having a number of heating elements and pressed against the outer peripheral surface of the platen roller 14, and is wound in a roll. It comprises a holding shaft 16 for holding the master base paper 4a thus cut, a cutter 17 for cutting the master 4 to a predetermined length, a conveying roller 18 for conveying the master 4 toward the plate cylinder 2, and the like. In the plate making section 5, the master base paper 4a is pulled out by rotating the platen roller 14, and the thermal head 15
Are generated according to the image data, and thereby the master 4 having the heat-melted perforations formed into a predetermined image pattern is made. The master 4 that has been made is cut into a predetermined length by a cutter 17 and wound around the outer peripheral surface of the plate cylinder 2.

A clamper 19 connected to an opening / closing mechanism (not shown) is provided on the outer peripheral surface of the plate cylinder 2 so as to be openable and closable. The master 4 conveyed from the plate making section 5 is clamped by the clamper 19 by rotating to the closing position at the timing of (1).

Inside the plate cylinder 2, an ink pipe 20 which is located on the axis of the plate cylinder 2 and also serves as a support shaft for rotatably supporting the plate cylinder 2, and an inner peripheral surface of the plate cylinder 2. An ink roller 21 that is driven to rotate in the same direction as the plate cylinder 2 with a minute gap, a doctor roller 22 disposed with a minute gap between the ink roller 21 and the outer peripheral surface of the ink roller 21 are provided. In a portion sandwiched between the outer peripheral surface of the ink roller 21 and the outer peripheral surface of the doctor roller 22, an ink reservoir 23 for storing the ink supplied from the ink pipe 20 is formed.

The impression cylinder swinging mechanism 6 includes a shaft 2 that supports the impression cylinder 3.
An arm 25 to which the arm 4 is attached, a fulcrum shaft 26 for rotatably supporting one end of the arm 25, and a spring 2 attached to the other end of the arm 25 for urging the impression cylinder 3 toward the plate cylinder 2.
7. A solenoid (not shown) for rotating the arm 25 in a direction in which the impression cylinder 3 is separated from the plate cylinder 2 and the like.

The impression cylinder 3 is formed to have the same diameter as the plate cylinder 2,
In addition, a portion where the outer peripheral surface of the impression cylinder 3 and the outer peripheral surface of the plate cylinder 2 come into contact with each other is synchronously driven at the same peripheral speed (rotation direction is opposite direction), and is a printing unit 28. A concave portion 29 is formed on the outer peripheral surface of the impression cylinder 3 to avoid collision with the clamper 19 during synchronous rotation with the plate cylinder 2.
A biting claw 30 for holding the leading end of the fed paper (unprinted paper P1, single-sided printed paper P2, which will be described later) is provided rotatably.

The first paper feed unit 9 includes a call roller 31 and
It is composed of a paper feed roller 32 and a separation roller 33,
The sheets (unprinted sheets) P1 stacked on the sheet feeding table 8 are separated and fed one by one. A transport roller 34 that transports the paper toward the print unit 28 is disposed on a paper transport path between the first paper supply unit 9 and the print unit 28.

Between the impression cylinder 3 and the first discharge tray 11 and the second discharge tray 12, printed paper (one-side printed paper P2, both-side print paper, which will be described later) is placed on the impression cylinder 3. And a peeling claw 35 for peeling off the paper from the first
A paper discharge transport mechanism 36 for discharging paper onto the paper discharge tray 11 or the second paper discharge tray 12 is provided.

The plate discharging section 7 includes a peeling roller 37 for holding the used master 4 wound around the outer peripheral surface of the plate cylinder 2 and peeling the used master 4 from the outer peripheral surface of the plate cylinder 2 by pulling.
It is composed of a plate discharge storage box 38 for storing the peeled master 4 and the like.

The first discharge tray 11 and the second discharge tray 12
Are fixed vertically with respect to a rack 39 extending vertically. Rack 39
Is engaged with a pinion 42 driven by a motor (not shown), and the pinion 42 is driven to rotate by the first rotation.
The discharge tray 11 and the second discharge tray 12 are moved up and down integrally. When the first discharge tray 11 and the second discharge tray 12 rise, the first discharge tray 11 faces the discharge position of the discharge conveyance mechanism 36. When the first paper discharge tray 11 and the second paper discharge tray 12 are lowered, the second paper discharge tray 12 faces the paper discharge position by the paper discharge transport mechanism 36, and the first paper discharge tray 11 becomes the second paper supply tray. It faces the part 10.

The first discharge tray 11 is provided with an end fence 43 which is slidable in the horizontal direction. A horizontally extending rack 44 is connected to the lower end of the end fence 43, and a pinion 45 driven by a motor (not shown) meshes with the rack 44, and a pinion 4 is provided.
The end fence 43 is slid in the horizontal direction by the rotation driving of the end fence 43. When the end fence 43 slides toward the second paper feed unit 10, the first paper output tray 1
1 is a single-sided printed sheet P2 discharged and stacked on
The sheet is moved to a position where the sheet can be fed again by the sheet feeding unit 10 (see FIG. 2).
reference).

The second paper feeding unit 10 directs the paper P (one-side printed paper) P2, which has been discharged and stacked on the first paper discharge tray 11 and has been printed on one side, to the printing unit 28. The separation roller 46, which is a rotating body for paper feeding,
It comprises a call roller 47, a paper feed roller 48, a paper pressing roller 49, a paper stopper plate 50, and the like. A guide plate 51 for guiding the single-side printed paper P2 and a plurality of pairs of transport rollers 5 are provided between the second paper supply unit 10 and the printing unit 28.
2 and a drive mechanism (not shown) for rotating these transport rollers 52 is provided.

As shown in FIG. 3, the paper pressing roller 49 is attached to a rack 54 extending vertically. In this attachment, a vertically long slot 55 is formed in the rack 54, and the central shaft 56 of the paper pressing roller 49 is fitted into the slot 55 so as to be vertically movable.
This is performed by attaching a spring 57 to the central shaft 56 for urging the paper pressing roller 49 downward (in a direction of pressing the paper). A pinion 58 driven by a motor (not shown) meshes with the rack 54, and the sheet press roller 49 moves up and down together with the rack 54 by rotating the pinion 58.

A slitter 59 is attached to the central shaft 56 of the paper pressing roller 49, and the slitter 59 moves up and down integrally with the paper pressing roller 49 as the paper pressing roller 49 moves up and down the long hole 55. I do. A sensor 60 for detecting the position of a slitter 59 that moves up and down is provided on the rack 54.
Is mounted, and the pressing force of the paper pressing roller 49 against the one-side printed paper P2 is controlled to be constant. The material of the paper pressing roller 49 includes a single-sided printed paper P
In order to prevent the transfer of ink even when pressed against the printing surface of No. 2, silicon rubber or ethylene tetrafluoride resin, which is a material having a property of repelling ink, is used.

The paper stopper plate 50 is rotatably provided with a support shaft 61 as a fulcrum, and the single-side printed paper P2 moved to the second paper supply unit 10 side by the end fence 43.
(A solid line position shown in FIGS. 1 and 2), and a position (a two-dot chain line position shown in FIG. 2) away from the end surface of the single-sided printed sheet P2 and allowing refeeding. To rotate. For this rotation, a rotation means (not shown) such as a solenoid is used. When the paper stopper plate 50 is rotated to the position shown by the two-dot chain line, the separation roller 4
A notch (not shown) for avoiding collision with 6 is formed.

As shown in FIG. 4, the separation roller 46 is rotatably attached to one end of a swing arm 63 that swings with the support shaft 62 as a fulcrum. A spring 64 is attached to the swing arm 63 so as to urge the single-sided printed sheet P <b> 2 re-fed from the direction of pressing the printing surface of the sheet P <b> 2. A solenoid 65 is connected to the other end of the swing arm 63.

In the vicinity of the separation roller 46 in the swing arm 63, a press contact rotating roller 66 as a press contact rotating body is rotatably mounted. The pressing rotation roller 66 is pressed against the separation roller 46 and rotates together with the rotation of the separation roller 46. The material of the pressure contact rotating roller 66 may be any material as long as it has a smooth surface and can secure a certain degree of oil resistance and water resistance. For example, urethane rubber or the like whose friction coefficient is reduced by surface treatment can be used.

At a position near the pressure contact rotating roller 66, a blower fan 67 as drying means for drying the surface of the pressure contact rotating roller 66 and the surface of the separation roller 46 is disposed.

Further, in the vicinity of the press-contact rotating roller 66, an ink wiping sheet 68, a supply shaft 69 and a winding shaft 70 of the ink wiping sheet 68, a rotatable pressing roller 71, and a rotation auxiliary roller driven to rotate by a motor. 72 and the like are provided. The ink wiping sheet 68 is made of a material such as a fine-grained nonwoven fabric. Ink wiping sheet 68
4B is pressed against the outer peripheral surface of the press-contact rotating roller 66 as shown in FIG. 4B, and is taken up in the direction of the arrow by the driving of the winding shaft 70, so that the drying adheres to the outer peripheral surface of the press-contact rotary roller 66. Wipe off the pigment and oil phase components of the ink.
At the time of wiping by the ink wiping sheet 68, the rotation assisting roller 72 is pressed against the pressure contact rotating roller 66 and is rotationally driven, whereby the pressure contact rotating roller 66 is rotated in the direction indicated by the arrow, and the entire surface of the pressure contact rotating roller 66 is rotated. Is wiped by the ink wiping sheet 68.

In such a configuration, first, the outline of the double-sided printing process will be described. When printing is started after designation of double-sided printing, setting of the number of prints, etc., the first document is read by the document reading unit 13, and the master 4 corresponding to the read image data is made by the plate making unit 5 to make a plate. Then, the master 4 is wound around the outer peripheral surface of the plate cylinder 2. Then, the unprinted paper P1 loaded on the paper feed table 8 is transferred to the first paper feed unit 9
, One side of the unprinted sheet P1 separated and fed is printed by the printing unit 28, and the one-side printed sheet P2 on which this printing has been performed is first discharged. The paper is discharged and stacked on the tray 11 (see FIG. 1).

When the printing of the set number of sheets is completed, the first discharge tray 11 and the second discharge tray 12 are lowered, and the end fence 43 is slid toward the second paper supply unit 10 so that the first discharge tray 11 slides toward the second paper supply unit 10. The single-sided printed paper P2 discharged and stacked on the paper discharge tray 11 moves to a position where the second paper supply unit 10 can re-feed the paper (see FIG. 2).

Immediately after the printing of the set number of single-sided printed sheets P2 is completed, the used master 4 wound around the plate cylinder 2 is discharged, and the next document is read by the document reading unit 13. According to the read image data, a new master 4 is made in the plate making section 5 and the master 4 is wound around the outer peripheral surface of the plate cylinder 2.

Then, after the new master 4 is wound around the outer peripheral surface of the plate cylinder 2, the single-sided printed paper P2 on the first discharge tray 11 is separated and fed one by one by the second paper feed unit 10 ( Re-feeding), and the printing unit 28
Is printed on the other side of the single-sided printed sheet P2, and the double-sided printed sheet (not shown), which has been printed on both sides, is printed by the second printing tray 12 The paper is discharged and stacked.

The single-sided printed paper P2 by the second paper feed unit 10
When paper is re-fed, as shown in FIG. 3B, the paper pressing roller 49 descends and the single-sided printed paper P2 is lightly pressed from above. When the single-sided printed paper P2 is fed and the number of sheets stacked on the first discharge toilet 11 decreases, the paper pressing roller 49 and the slitter 59 descend accordingly, and the decrease is detected by the sensor 60. And the sensor 60
The pinion 58 is driven to lower the rack 54 on the basis of the detection result, and by this control, a constant pressing force always acts on the one-side printed sheet P2 from the sheet pressing roller 49 at the time of refeeding. are doing.

When the single-sided printed sheet P2 is fed by the second sheet feeding unit 10, the calling roller 47 and the sheet feeding roller 4
8 is pressed against the unprinted surface, so that the transfer of the undried ink does not occur between the call roller 47 and the paper feed roller 48. However, since the separation roller 46 comes into contact with the printing surface of the single-side printed paper P2, the undried ink on the printing surface transfers to the separation roller 46.

When the undried ink is transferred from the printing surface of the single-side printed paper P2 to the separation roller 46, the separation roller 4
6 is rotated while being pressed against the roller 6, so that the undried ink transferred to the separation roller 46 is thin and uniform on the surfaces of both the separation roller 46 and the pressure contact rotation roller 66. The undried ink that has been thinly and uniformly spread has an increased contact area with air, and drying is promoted by blowing air from the blowing fan 67. Then, the separation roller 46 and the pressing roller 6
The pigment of the dried ink and the oil phase component remain on the surfaces of the two members, and the dried ink pigment and the oil phase component are separated from the separation roller 46 to the next single-sided printed paper P2.
Is hardly transferred to the printing surface, or even if transferred, the amount is very small, so that re-transfer stain of the single-side printed paper P2 is prevented.

By using such a pressure contact rotating roller 66 to prevent retransfer contamination of the single-sided printed paper P2, it is possible to prevent the paper P2 from being reprinted after the one-sided printing is completed.
There is no need to wait until the ink adhering to the printing surface of the single-sided printed paper P2 has sufficiently penetrated and dried, and the plate making unit 5
The re-feeding can be performed immediately after the master making of the master 4 and the winding of the master 4 around the plate cylinder 2 are completed. The time required for plate making and winding of No. 4 is about one minute, and the work efficiency of the double-sided printing operation is improved.

It is not immediately after printing is performed that the undried ink is transferred by the pressing roller 66 contacting the printing surface of the single-side printed paper P2, but rather immediately after printing.
A predetermined period of time has passed before is fed again, and the required amount of ink has already penetrated into the printing surface of the single-side printed paper P2. For this reason, even if the undried ink is transferred to the press-contact rotating roller 66, the ink does not run out on the printing surface of the single-side printed paper P2, and the image quality does not deteriorate, such as insufficient image density and insufficient solid filling. .

In order to prevent the accumulation of the pigment and the oil phase component of the ink on the surface of the pressure contact rotating roller 66 and to surely prevent the occurrence of retransfer stain, the surface of the pressure contact rotating roller 66 is wiped with an ink wiping sheet 68. I do. This wiping operation is performed immediately before re-feeding of the single-side printed sheet P2 or immediately after re-feeding is completed. As shown in FIG. 4B, the swing arm 63 is driven by driving the solenoid 65. Is pivoted around the support shaft 62, and the press-contact rotating roller 66 is
Is pressed against the ink wiping sheet 68 at a position opposing the roller, and the press contact rotating roller 66 is pressed against the rotation assisting roller 72. Then, the take-up shaft 70 is driven to rotate to wind up the ink wiping sheet 68 in the direction shown by the arrow, and the rotation assisting roller 72 is driven to rotate to rotate the press-contact rotating roller 66 in the direction shown by the arrow. By such a wiping operation, the pigment and the oil phase component of the ink adhering to the surface of the pressure contact rotating roller 66 are wiped off.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, when the undried ink remains on the printing surface of the single-side printed paper P2 that has passed through the location of the separation roller 46, the ink removing sheet 73 that is an ink removing unit that removes the undried ink is used. It is provided.

The ink removal sheet 73 includes a drive roller 74
And a plurality of driven rollers 75 and a plurality of support rollers 76, and rotates in the direction indicated by the arrow. Then, the ink removal sheet 73 comes into contact with the printing surface of the single-side printed paper P2 to be re-fed at a position facing the transport roller 52, so that the undried ink on the printing surface of the single-side printed paper P2 is removed. It is removed by the sheet 73. As a material of the ink removing sheet 73,
As described in JP-A-1-91074, the ink (emulsion ink) has a porosity that separates the ink (emulsion ink) into a pigment and other components and removes the ink from the printing surface of the printed matter, and also includes a material other than the separated pigment. A sheet having a holding layer for absorbing and holding the components, or a member having a critical surface tension of 30 dyne / cm or more, as described in Japanese Patent Application No. 10-85643, is suitable.

Further, by bringing the ink wiping sheet 68 into pressure contact with the surface of the ink removing sheet 73, the ink attached to the ink removing sheet 73 can be wiped. Immediately before re-feeding of the single-sided printed paper P2 or immediately after re-feeding is completed, as shown in FIG. 5B, by bringing the press contact rotating roller 66 into contact with the ink removing sheet 73, The pigment and the oil phase component of the ink adhered to the surface of the pressure contact rotating roller 66 can be wiped off.

In such a configuration, by providing the ink removing sheet 73, the viscosity of the ink is greatly reduced due to the ink being left in the plate cylinder 2 for a long period of time, and the ink is removed from the printing surface of the single-side printed paper P2. For example, when the amount of ink adhering to the separation roller 46 is larger than usual, even if the undried ink passes through the contact portion with the separation roller 46 without being transferred to the separation roller 46, the undried ink is removed from the ink removal sheet 73. To be removed. For this reason, in the process of re-feeding the single-sided printed paper P2, the undried ink on the printing surface is removed by the guide plate 51, the transport roller 52, the impression cylinder 3 of the re-feed transport mechanism 53.
The transfer of the transferred ink to the printing surface of the next single-side printed paper P2 is prevented, and the occurrence of retransfer stains is prevented.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. The printing apparatus main body 77 of the stencil printing apparatus according to the present embodiment includes a plate cylinder 2, an impression cylinder 3, a plate making section 5, an impression cylinder swinging mechanism 6, a plate discharge section 7, a sheet feeding table 8, and a first sheet feeding section 9. , A paper discharge tray 78 and the like. Further, a double-sided printing unit 79 is provided in which the first paper output tray 11, the second paper output tray 12, the second paper supply unit 10, the re-feeding conveyance mechanism 53, and the like are unitized. Body 7
7 is detachably attached. When attaching the duplex printing unit 79 to the printing apparatus main body 77,
After removing the discharge tray 78, the duplex printing unit 7
9 is attached.

In such a configuration, a double-sided printing unit 79 is prepared as an option, and the double-sided printing unit 79 is attached as necessary, so that a stencil printing apparatus dedicated to single-sided printing can be used. You can switch to Further, the printing apparatus main body 77 is shared between a stencil printing apparatus dedicated to one-sided printing and a stencil printing apparatus to which a double-sided printing unit 79 is attached and capable of automatic double-sided printing.

[0062]

According to the stencil printing apparatus according to the first aspect of the present invention, the rotation of the stencil printing apparatus, which is a part of the two-sided printing paper feed unit and which comes into contact with the printing surface of the reprinted single-sided printed paper, It has a pressure contact rotating body that rotates while being pressed against the body, so when the undried ink is transferred to the sheet feeding rotating body that is in contact with the printing surface of the single-sided printed paper to be re-fed, this paper feeding rotation The undried ink transferred to the rotator for feeding is spread thinly and evenly on the surfaces of both the rotator for feeding and the rotator by rotating the pressing rotator while being pressed against the body. The ink is hardly transferred from the rotator for paper feeding to the printing surface of the next single-sided printed paper, or the transfer is very small. The generation of dirt can be prevented, and the occurrence of retransfer dirt can be prevented. This eliminates the need for a long waiting time before re-feeding, which can improve the efficiency of double-sided printing work. Not immediately after printing
After the required amount of ink has been infiltrated into the printing surface after a predetermined time has elapsed since printing, even if the undried ink has transferred to the rotating body for paper feeding, the ink is printed on the printing surface of the single-sided printed paper. The image quality can be maintained without running short.

According to the second aspect of the present invention, in the stencil printing machine according to the first aspect, since there is provided a drying unit for drying the surface of the rotating body for feeding and the surface of the pressing rotating body, the rotating body for feeding is provided. The ink spread thinly and uniformly on the surfaces of the two members, the pressing and rotating body, is further promoted by the drying means, and the re-transfer stain of the next single-side printed paper can be more reliably prevented. .

According to a third aspect of the present invention, in the stencil printing machine according to the first or second aspect, the one-sided printing apparatus is located on the downstream side of the two-sided printing paper feeding unit along the feeding direction of the one-sided printed paper. Since there is an ink removing unit that removes undried ink on the printed surface of the printed paper, the undried ink is fed when the amount of ink adhering to the printed surface of the one-sided printed paper is larger than usual. Even if the paper passes through the contact point with the paper feed rotary body without being transferred to the paper rotary body, the undried ink can be removed by the ink removing means, and the reprinted single-sided printed paper is conveyed. It is possible to prevent the occurrence of retransfer contamination in the step performed.

According to the invention described in claim 4, according to claim 1,
4. The stencil printing machine according to 2 or 3, wherein the first discharge tray, the second discharge tray, the double-sided printing paper supply unit, and the single-sided printed paper re-fed from the double-sided printing paper supply unit are sent to the printing unit. A double-sided printing unit is provided, which unitizes a re-feeding conveyance mechanism that conveys the paper toward the unit.Since this double-sided printing unit is detachably attached to the printing apparatus main body, a double-sided printing unit is prepared as an option. By attaching this double-sided printing unit as needed, it is possible to easily switch between a stencil printing apparatus dedicated to single-sided printing and a stencil printing apparatus capable of automatic double-sided printing.

[Brief description of the drawings]

FIG. 1 is a front view showing the entire structure of a stencil printing apparatus according to a first embodiment of the present invention.

FIG. 2 is a front view showing the entire structure of the stencil printing machine in a state where single-sided printed paper is re-fed.

FIG. 3 is a front view showing a mounting structure of a paper pressing roller.

FIG. 4 is a front view showing a mounting structure of a separation roller, a press-contact rotating roller, and an ink wiping sheet.

FIG. 5 is a front view showing an attachment structure of an ink removing sheet in a stencil printing apparatus according to a second embodiment of the present invention.

FIG. 6 is a front view showing the entire structure of a stencil printing apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Double-sided printing paper feed part 11 1st paper discharge tray 12 2nd paper discharge tray 28 Printing part 46 Paper supply rotating body 53 Re-feeding conveyance mechanism 66 Press-contact rotating body 67 Drying means 73 Ink removing means 77 Printer main body 79 Double-sided printing unit P2 Single-sided printed paper

Claims (4)

[Claims] A first-side printed sheet on which printing on one side has been performed in a printing unit is discharged and stacked on a first discharge tray, and the first-side printed sheet is discharged and stacked on the first discharge tray; (1) moving the discharge tray to a re-feeding position by the two-sided printing paper feed unit, separating and feeding the single-side printed paper on the first discharge tray toward the printing unit one by one; In a stencil printing apparatus capable of automatic double-sided printing, in which double-sided printed paper on which printing on the other side of printed paper has been performed in the printing unit is discharged and stacked on a second discharge tray, The printing apparatus further comprises a press-contact rotating body that rotates while being pressed against a sheet-feeding rotating body that is a part of the double-sided printing sheet feeding unit and contacts a printing surface of the single-sided printed sheet to be re-fed. Stencil printing machine. 2. The stencil printing machine according to claim 1, further comprising a drying unit for drying a surface of the rotating body for feeding paper and a surface of the rotating body for press-contact. 3. An ink removing means for removing undried ink on a printing surface of the single-sided printed paper, which is located downstream of the double-sided printing paper supply unit in a direction of feeding the single-sided printed paper. The stencil printing apparatus according to claim 1, further comprising: 4. The printing unit according to claim 1, wherein the first discharge tray, the second discharge tray, the double-sided printing paper supply unit, and the single-sided printed paper re-fed from the double-sided printing paper supply unit are sent to the printing unit. 3. A double-sided printing unit in which a re-feeding transport mechanism for transporting the paper toward the unit is provided, and the double-sided printing unit is detachably attached to the printing apparatus main body. 3. The stencil printing machine according to 3.