JP2001191629A - Stencil printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep an ink amount leaked out of pores on a master in an optimal value even when the different viscosity is generated by the evaporation of a water content from the ink, the kind of ink is different or the like so as to print excellently. SOLUTION: When the ink fed into a plate cylinder 2 is passed through between an ink roller 20 and a doctor roller 21, the doctor roller 21 is moved in the direction separating away from the ink roller 20 and then the viscosity of the ink can be sensed by the moving force applied to the doctor roller 21. Then the various adjustments, for instance the adjustments of varying the printing speed, varying the pore diameter of the master 9, varying the pressurizing force of a pressing body 5 and the like are carried out to keep the ink amount transferred onto a printing paper S at the optimum level regardless of the viscosity of the ink to obtain the high printing quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a stencil printing machine.

[0002]

2. Description of the Related Art Conventionally, a master is made by heat-melting and perforating a master base paper using a thermal head, and the master made is wound around the outer peripheral surface of a porous cylindrical plate cylinder.
Ink is supplied to the inner peripheral surface of the plate cylinder from an ink supply mechanism provided inside the plate cylinder, and the printing paper is pressed against the master wound around the outer peripheral surface of the plate cylinder with a pressing body, and bleeds from the perforated portion of the master. 2. Description of the Related Art A stencil printing apparatus that performs printing by transferring discharged ink to printing paper is widely known.

In such a stencil printing apparatus, if the amount of ink oozing out from the perforated portion of the master is large, the amount of ink transferred to the printing paper also becomes large, and the image on the printing paper bleeds. There is a problem that, when the printing papers are stacked, the ink of the lower printing paper shows off on the back surface of the upper printing paper. On the other hand, if the amount of ink that seeps out from the perforated portion of the master is small, the amount of ink transferred to the printing paper is also small, and there is a problem that the image on the printing paper is blurred.

[0004] The above-mentioned problems are greatly related to the viscosity of the ink and the pressing force of the pressing body.

[0005] In relation to the viscosity of the ink, when the viscosity of the ink is low, the ink easily oozes out of the perforated portion of the master, and the bleeding of the image and the show-through of the ink easily occur.
On the contrary, when the viscosity of the ink is high, the ink hardly oozes out from the perforated portion of the master, and the image is easily blurred.

Therefore, if the stencil printing apparatus is left for a long time without printing, the ink remaining in the printing drum will have a reduced viscosity due to evaporation of water, thereby causing image blurring. Also, show-through of the ink is likely to occur.

[0007] Further, when the viscosity of the ink is reduced due to an increase in temperature, or when a type of ink having a low viscosity is used, bleeding of an image or show-through of the ink is likely to occur.

When a large amount of printing is performed with a small amount of image, the ink is continuously stirred in the plate cylinder for a long time from when the ink is supplied into the plate cylinder to when the ink is transferred to printing paper. During this time, the evaporation of water is promoted during this time, the viscosity is reduced, and image bleeding and ink show-through are likely to occur.

In relation to the pressing force of the pressing body, as the pressing force increases, the amount of ink oozing out from the perforated portion of the master increases, and the bleeding of the image and the show-through of the ink tend to occur. Conversely, as the pressing force decreases, the amount of ink seeping out from the perforated portion of the master decreases, and image blurring tends to occur.

Therefore, conventionally, the leaving time of the stencil printing apparatus,
The temperature, the type of ink, and the like are input, and the pressing force of the pressing body is adjusted accordingly, so that the amount of ink that exudes from the perforated portion of the master and transfers to the printing paper is controlled to an optimum value.

[0011]

However, it is troublesome and time-consuming to input the stencil printing apparatus's leaving time, temperature, ink type, and the like.

According to the present invention, the water evaporates from the ink,
Provided is a stencil printing apparatus capable of performing good printing while maintaining the amount of ink oozing from a perforated portion of a master at an optimum value even when the viscosity of the ink is different due to a difference in the type of the ink. The purpose is to:

It is a further object of the present invention to provide a stencil printing apparatus capable of performing good printing while maintaining the amount of ink transferred to printing paper at an optimum value even when the printing speed is changed. I do.

[0014]

According to the first aspect of the present invention,
A plate making section for making a master by heating and punching a master base paper, a porous cylindrical plate cylinder in which the master is wound around an outer peripheral surface by being rotationally driven around an axis, and pressed against the outer peripheral surface of the plate cylinder. Press body, and an ink supply mechanism provided in the plate cylinder with an ink roller and a doctor roller. The ink supply mechanism supplies ink to the inner peripheral surface of the plate cylinder, In a stencil printing apparatus that performs printing by transferring ink oozing from a perforated portion of the master to the printing paper by pressing the printing paper with the pressing body against the master wound around the outer peripheral surface of the cylinder,
The ink roller is provided so as to be movable in the direction of coming into contact with and separating from the doctor roller, and the ink roller attached to the outer peripheral surface of the ink roller is separated from the ink roller when the ink passes through between the doctor roller and the ink roller. A moving force detecting unit for detecting a moving force acting in the direction to be moved is provided.

Accordingly, when the ink supplied into the plate cylinder passes between the ink roller and the doctor roller, the doctor roller moves in a direction away from the ink roller, and at this time, the moving force acting on the doctor roller is The moving force changes according to the viscosity of the ink, and the moving force is detected by the moving force detecting unit. That is, the viscosity of the ink can be known based on the detection result from the moving force detection unit. Therefore, by making various adjustments according to the viscosity of the ink, for example, changing the printing speed, changing the punching diameter of the master, changing the pressing force of the pressing body, etc., regardless of the viscosity of the ink, In addition, high print quality can be obtained by maintaining the amount of ink transferred to the printing paper at an optimum amount.

According to a second aspect of the present invention, there is provided the stencil printing apparatus according to the first aspect, further comprising a pressing force variable mechanism for changing a pressing force of the pressing body.

Therefore, the pressing force variable mechanism is driven based on the detection result from the moving force detecting section for detecting the moving force acting on the doctor roller (that is, the viscosity of the ink) to vary the pressing force of the pressing body. Accordingly, even when the ink viscosities differ, the amount of ink oozing out from the perforated portion of the master can be kept constant, and high print quality can be obtained regardless of the viscosity of the ink. In particular,
If the detection value of the moving force detector is high due to the high viscosity of the ink, drive the variable pressing force mechanism to increase the pressing force of the pressing body to promote the bleeding of ink from the perforated part of the master Let it. On the other hand, when the detection value of the moving force detecting unit is low due to the low viscosity of the ink, the variable pressing force mechanism is driven so that the pressing force of the pressing body is reduced, and the ink seeps out from the perforated portion of the master. Suppress.

According to a third aspect of the present invention, in the stencil printing apparatus according to the second aspect, the first pressing force variable control for automatically driving the variable pressing force mechanism based on a detection result from the moving force detection unit. Having means.

Therefore, the pressing force variable mechanism is automatically driven by the first pressing force variable control means based on the detection result from the moving force detecting section, so that the pressing force of the pressing member can be varied. Can be automatically performed, and even when the ink viscosities are different, the amount of ink oozing out from the perforated portion of the master can be kept constant, and high print quality can be reliably obtained.

According to a fourth aspect of the present invention, in the stencil printing apparatus according to the second or third aspect, a counter for counting the number of printed sheets, and a number of printed sheets until the ink already supplied in the plate cylinder is consumed. Means for determining the number of sheets to be printed from the size of the printing paper to be used; information from the counter; detection results from the moving force detection unit;
A second pressing force variable control unit that automatically drives the variable pressing force mechanism based on the determination result from the number-of-printed-sheets determining unit.

Here, when printing is started after the stencil printing apparatus has been left for a long time, the ink already supplied into the printing drum and left for a long time has its viscosity reduced due to evaporation of moisture. In many cases, the decrease in the viscosity can be detected based on the detection result from the moving force detection unit immediately after the start of printing. Also, how many prints are consumed by the ink already supplied in the plate cylinder (the ink whose viscosity has been reduced by evaporation of water), that is,
The number of prints before starting printing with the newly supplied ink (high-viscosity ink) can be determined by the first print number determination unit in accordance with the size of the printing paper.

Therefore, when the moving force detector detects that the viscosity of the ink has decreased at the start of printing, the pressing force of the pressing body is reduced to a value corresponding to the detection result, and The pressing force is automatically maintained by the second pressing force variable control means so that the pressing force is maintained until the number of printed sheets determined by the first printed sheet number determining means is reached, and then the pressing force of the pressing body is increased. Drive. As a result, the pressing force of the pressing body can be reduced until all the ink whose viscosity has been reduced due to the evaporation of the water in the plate cylinder is consumed, and the amount of the ink that leaks out from the perforated portion of the master can be suppressed. High printing quality can be obtained even when printing is started after leaving the stencil printing apparatus for a long time.

According to a fifth aspect of the present invention, in the stencil printing apparatus according to the second or third aspect, a document reading section for obtaining image data of the master by reading a document, a counter for counting the number of printed sheets, Second print number determining means for determining the number of prints until the ink already supplied in the cylinder is consumed, based on the image amount of the image data; and information from the counter and information from the moving force detector. A third pressing force variable control unit that automatically drives the variable pressing force mechanism based on a detection result and a determination result from the second print number determination unit.

Here, when printing is started after the stencil printing apparatus has been left for a long period of time, the ink already supplied into the plate cylinder and left for a long period of time has a reduced viscosity due to evaporation of moisture. In many cases, the decrease in the viscosity can be detected based on the detection result from the moving force detection unit immediately after the start of printing. Also, how many prints are consumed by the ink already supplied in the plate cylinder (the ink whose viscosity has been reduced by evaporation of water), that is,
The number of prints before starting printing with the newly supplied ink (high-viscosity ink) can be determined by the second print number determination unit based on the image amount of the image data. .

Therefore, when the moving force detecting section detects that the viscosity of the ink has decreased at the start of printing, the pressing force of the pressing body is reduced to a value corresponding to the detection result, and The pressing force is automatically maintained by the third pressing force variable control means so that the pressing force is maintained until the number of printed sheets determined by the second printed sheet number determining means is reached, and thereafter the pressing force of the pressing body is increased. Drive. As a result, the pressing force of the pressing body can be reduced until all the ink whose viscosity has been reduced due to the evaporation of the water in the plate cylinder is consumed, and the amount of the ink that leaks out from the perforated portion of the master can be suppressed. High printing quality can be obtained even when printing is started after leaving the stencil printing apparatus for a long time.

According to a sixth aspect of the present invention, in the stencil printing apparatus according to any one of the second to fourth aspects, a printing speed setting unit for setting a printing speed, information from the printing speed setting unit, and And a fourth pressing force variable control means for automatically driving the pressing force variable mechanism based on a detection result from the moving force detection unit.

Here, when the amount of ink seeping out from the perforated portion of the master is the same, the amount of ink transferred to the printing paper is small when the printing speed is high, and when the printing speed is low. Increases the amount of ink transferred to the printing paper. Therefore, when the printing speed is high, the amount of ink that seeps out of the perforated portion of the master is relatively increased, and when the printing speed is low, the amount of ink that seeps out of the perforated portion of the master is relatively small. Thus, the amount of ink transferred to the printing paper becomes constant regardless of the printing speed.

Therefore, when the printing speed is high, the pressing force of the pressing member is increased, and when the printing speed is low, the pressing force of the pressing member is reduced by the fourth pressing force variable control means. Automatically drive the variable mechanism. Thereby, even if the printing speed is different, the amount of ink transferred to the printing paper becomes constant, and high printing quality can be obtained.

[0029]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. FIG. 1 is a vertical sectional front view showing the entire structure of the stencil printing apparatus. In a main body case 1 of the stencil printing apparatus, a porous cylindrical plate cylinder 2 driven to rotate about an axis, a plate making section 3, a plate discharging section 4, and a pressing body disposed around the plate cylinder 2 are arranged. , A press roller 5, a registration roller 6, a suction conveyance mechanism 7, and the like. A scanner 8 serving as a document reading unit for reading a document is provided at an upper portion of the main body case 1.

The plate making section 3 is where the master 9 is made by drawing out the rolled master base paper 9a and subjecting it to heat-melting perforation. A holding shaft 10 for holding the rolled master base paper 9a, Platen roller 1 rotated and driven by a stepping motor (not shown)
1, a thermal head 12 pressed against the outer peripheral surface of a platen roller 11, a transport roller 13, a cutter 14, a reversing roller 15, a guide plate 16, and the like. By rotating the platen roller 11, the master base paper 9a is rotated.
Is pulled out of the roll state, and the pulled-out master base paper 9a is sandwiched between the platen roller 11 and the thermal head 12. At this time, the heating elements of the thermal head 12 generate heat in accordance with the image data of the original read by the scanner 8. Under the control, the master 9 is made. The master 9 that has been made is transported by the transport roller 13 and the reversing roller 15 and cut by the cutter 14 to a predetermined length.

The plate cylinder 2 is a member that is rotated by being wound around a master 9 that has been made. The outer peripheral surface of the plate cylinder 2 is connected to a stage 17 and an opening / closing mechanism (not shown) and can be opened and closed. And a large clamper 18. As shown in FIG. 1, when the clamper 18 is positioned below the guide plate 16, the rotation of the plate cylinder 2 is stopped, and at that position the clamper 18 is opened as shown by a two-dot chain line, and the master 9 is moved there.
Is transported, and the clamper 18 is closed at the timing when the leading end of the master 9 reaches between the stage 17 and the clamper 18, whereby the leading end of the master 9 is held between the stage 17 and the clamper 18. After the leading end of the master 9 is clamped, the master cylinder 9 is wound around the outer peripheral surface of the plate cylinder 2 by rotating the plate cylinder 2 in the direction of the arrow.

An ink supply mechanism 22 including an ink pipe 19, an ink roller 20, and a doctor roller 21 is provided inside the plate cylinder 2. The ink pipe 19 is located on the axis of the plate cylinder 2, and the plate cylinder 2 is rotatably supported by the ink pipe 19. The ink roller 20 is attached to a side plate (not shown) fixed to the ink pipe 19, and is driven to rotate in the same direction as the plate cylinder 2 as indicated by an arrow. The doctor roller 21 is rotatably supported by one end of a doctor arm 23 and is driven to rotate in a direction opposite to the direction of the ink roller 20. The other end of the doctor arm 23 is rotatably mounted on a side plate around a support shaft 24. That is, when the doctor arm 23 rotates about the support shaft 24, the doctor roller 21 moves in a direction in which the doctor roller 21 approaches and separates from the ink roller 20.

In a portion sandwiched between the outer peripheral surface of the ink roller 20 and the outer peripheral surface of the doctor roller 21, there is formed an ink pool 25 in a wedge-shaped space for storing the ink supplied to the inner peripheral surface of the plate cylinder 2. ing. The ink stored in the ink pool 25 adheres to the outer peripheral surface of the ink roller 20 when the ink roller 20 and the doctor roller 21 are driven to rotate, and the ink roller 20 and the doctor roller 21 are rotated.
At this time, a moving force acts on the doctor roller 21 in a direction to separate the doctor roller 21 from the ink roller 20. The direction in which the doctor roller 21 moves due to this moving force and the doctor arm 23
A load cell 26 which is a moving force detecting unit for detecting a moving force acting on the doctor roller 21 is disposed at a position facing the outer peripheral surface of the doctor roller 21.

The plate discharging section 4 is where the master 9 wound around the outer peripheral surface of the plate cylinder 2 is peeled off and discarded. The plate discharging roller 27 for peeling off the master 9 from the plate cylinder 2 and a housing for accommodating the peeled master 9 are provided. It is constituted by a box 28 and the like.

The press roller 5 is movable to a position where the press roller 5 comes into contact with or separates from the outer peripheral surface of the plate cylinder 2. When the press roller 5 contacts the outer peripheral surface of the plate cylinder 2 (more precisely, the press roller 5 is wound around the outer peripheral surface of the plate cylinder 2). This is a member for applying a pressing force to the master 9), and is rotatably held at one end of a pair of press arms 29. The other end of the press arm 29 is fixed to an arm shaft 30 rotatable around an axis. One end of a pressure arm 31 is fixed to one end of the arm shaft 30, and one end of a pressure spring 32 is connected to the other end of the pressure arm 31. A female screw portion is formed at the other end of the pressure spring 32, and a screw shaft portion of the pressure motor 33 is screwed into the female screw portion. Pressure arm 31
A cam follower 34 is rotatably mounted at a substantially central portion of the cam follower 34. A press cam 35 which rotates in synchronization with the plate cylinder 2 and comes into contact with and separates from the cam follower 34 at a predetermined timing is disposed near the cam follower 34. . The press arm 31 and the press arm 29 are configured to press the press roller 5 with the plate cylinder 2 by the urging force of an urging body (not shown).
Are urged in a direction to press against the outer peripheral surface.

The press cam 35 rotates and the cam follower 3 rotates.
4, the press arm 31 and the press arm 29 rotate counterclockwise about the arm shaft 30, and the press roller 5 separates from the outer peripheral surface of the plate cylinder 2. When the press cam 35 rotates and separates from the cam follower 34, the pressing arm 31 and the press arm 29 rotate clockwise about the arm shaft 30 by the urging force of the urging body, and the press roller 5 Is pressed against the outer peripheral surface of. Further, the pressure motor 33 is driven to drive the pressure spring 3.
2, the press arm 31 and the press arm 29 rotate about the arm shaft 30 as a fulcrum, and this rotation causes the press roller 5 to move in the direction of coming and coming from the outer peripheral surface of the plate cylinder 2, thereby The pressing force when the press roller 5 is pressed against the plate cylinder 2 can be changed. The press motor 33 and the press spring 32
A pressing force variable mechanism 36 for changing the pressing force of the pressure sensor is formed. A home position sensor 37 that detects the home position of the pressure spring 32 is disposed near the pressure spring 32.

The registration roller 6 temporarily stops conveyance of the printing paper S fed from a paper feeding tray (not shown), and feeds the printing paper S between the plate cylinder 2 and the press roller 5. It is a member that measures timing.

The suction conveyance mechanism 7 is a mechanism for conveying the printing paper S, which has been printed and has been separated from the plate cylinder 2 by the separation claw 38, onto a discharge tray 39, and at least one of the pair is driven to rotate. Transport rollers 40 and 41, transport roller 4
A transport belt 42 wound around 0 and 41, a suction fan 43 for attracting the printing paper S to the transport belt 42, and the like are provided.

FIG. 2 is a block diagram showing the electrical connection of a portion related to the variable pressing force of the press roller 5 in the control system of the stencil printing apparatus. The control system includes, as main components, a control unit 44 having a microcomputer configuration including a CPU and a memory. The control unit 44 includes a scanner 8, a load cell 26, a pressure motor 33, and the number of printed sheets. And a printing speed setting key 46 provided on the operation panel and serving as a printing speed setting unit for setting a printing speed.

Here, the stencil printing apparatus of this embodiment is
The control unit 44 includes a first pressing force variable control unit, a second pressing force variable control unit, and a first printed sheet number judging unit as various processes executed by the microcomputer operation.

The first pressing force variable control means detects the moving force acting on the doctor roller 21 when the ink passes between the ink roller 20 and the doctor roller 21 with the load cell 26, and based on the detection result, Pressurizing motor 33
The compression spring 32 is expanded and contracted by driving the compression arm 32.
This is a process of automatically changing the pressing force when the press roller 5 is pressed against the plate cylinder 2 by the rotation of the press cam 35 by rotating the roller 9 with the arm shaft 30 as a fulcrum.

More specifically, when the detected value of the load cell 26 is larger than the reference value (that is, when the viscosity of the ink is higher than the reference value), the pressure arm 31 and the press arm 29 are moved in accordance with the detected value. Is rotated clockwise by a predetermined angle around the arm shaft 30 to bring the press roller 5 close to the plate cylinder 2 and increase the pressing force when the press roller 5 is pressed against the outer peripheral surface of the plate cylinder 2. Thereby, even when the viscosity of the ink is high and the ink hardly oozes out of the perforated portion of the master 9, the pressing force of the press roller 5 is increased and the oozing of the ink from the perforated portion of the master 9 is promoted. For this reason, even when the viscosity of the ink is high, a sufficient amount of the ink can be oozed out of the perforated portion of the master 9, and it is possible to prevent blurring during printing.

On the other hand, when the detected value of the load cell 26 is smaller than the reference value (ie, when the viscosity of the ink is lower than the reference value), the pressing arm 31 and the press arm 29 are moved in accordance with the detected value. By rotating the press roller 5 away from the plate cylinder 2 by rotating the press roller 5 from the plate cylinder 2 by a predetermined angle around the fulcrum 30, the pressing force when the press roller 5 is pressed against the outer peripheral surface of the plate cylinder 2 is reduced. Accordingly, even when the viscosity of the ink is low and the ink easily oozes out of the perforated portion of the master 9, the pressing force of the press roller 5 is reduced and the oozing of the ink from the perforated portion of the master 9 is suppressed.
For this reason, even if the viscosity of the ink is low, it is possible to prevent the ink from bleeding out of a necessary amount from the perforated portion of the master 9, and to prevent the bleeding of the printed image and the occurrence of the offset of the ink.

The first print number determining means determines the number of prints until the ink already supplied into the plate cylinder 2 is consumed.
This is a process for judging from the size of the printing paper S to be used.

The second pressing force variable control means controls the viscosity of the ink already supplied into the plate cylinder 2 at the start of printing, such as when printing is started after the stencil printing apparatus has been left for a long time. Is a process for automatically changing the pressing force of the press roller 5 when the pressure is lower than a predetermined value.

Specifically, at the start of printing, the load cell 26
Is smaller than the reference value, the number of printed sheets is determined by the first printed sheet number determining means. Further, the press arm 31 and the press arm 29 are rotated counterclockwise in accordance with the detected value to separate the press roller 5 from the plate cylinder 2, and the press roller 5 is pressed against the outer peripheral surface of the plate cylinder 2. Pressure when pressing. Then, the state in which the pressing force of the press roller 5 is reduced is maintained until printing of the number of prints determined by the first number-of-prints determining means is completed. When the printing of the number of printed sheets is completed, the process is switched to the process by the first pressing force variable control unit described above.

FIG. 3 is a flowchart for explaining the control for varying the pressing force of the press roller 5. At the start of the printing operation, it is determined whether the detected value of the load cell 26 is equal to or greater than a predetermined value (step S1). When it is determined that the detected value of the load cell 26 is equal to or more than the predetermined value (Y in step S1), the ink already supplied into the plate cylinder 2 undergoes a drastic decrease in viscosity due to evaporation of moisture. The pressing force is controlled by the first pressing force variable control means (step S2).

On the other hand, when it is determined at the start of the printing operation that the detected value of the load cell 26 is equal to or smaller than the predetermined value (N in step S1), the ink already supplied into the plate cylinder 2 contains moisture. It is determined that the viscosity has significantly decreased due to evaporation or the like, and the pressing force is controlled by the second pressing force variable control means (step S3). Then, after the control of the pressing force by the second pressing force variable control means is started, it is determined whether the printing of the number of prints determined by the first printing number determination means is completed (step S).
4) When the process is completed (Y in step S4), the variable control of the pressing force by the second variable pressing force control means is switched to the variable control of the pressing force by the first variable pressing force control means.

In such a configuration, the load cell 26
The pressing force of the press roller 5 is varied in accordance with the viscosity of the ink detected in step (1). If the ink has a high viscosity and does not easily seep out from the perforated portion of the master 9, the pressing force of the press roller 5 is increased. In this way, the bleeding of the ink can be promoted. If the viscosity of the ink is low and the ink easily bleeds from the perforated portion of the master 9, the bleeding of the ink is performed by reducing the pressing force of the press roller 5. Can be suppressed.

For this reason, it is possible to prevent the amount of ink seeping out from the perforated portion of the master 9 from being reduced due to the high viscosity of the ink, thereby preventing the image printed on the printing paper S from being blurred. In addition, since the viscosity of the ink is low, it is possible to prevent a large amount of ink from oozing out from the perforated portion of the master 9 and bleeding the image printed on the printing paper S. It is possible to prevent show-through on the back surface. Therefore, irrespective of the viscosity of the ink, a high print quality can be obtained by keeping the amount of ink oozing out from the perforated portion of the master 9 constant.

If the viscosity of the ink already supplied into the plate cylinder 2 has decreased due to evaporation of water due to the stencil printing apparatus being left for a long time, the second pressing force variable control is performed. By controlling the pressing force by the means, the pressing force of the press roller 5 is kept small until all the ink already supplied in the plate cylinder 2 is consumed. For this reason, even if the load cell 26 detects that the viscosity of the newly supplied ink is high, the pressing force of the press roller 5 increases based on the detection result before the low-viscosity ink is consumed. Does not occur, and high printing quality can be obtained during printing after leaving the stencil printing apparatus for a long time.

In the present embodiment, the pressing roller 5 is controlled in accordance with the viscosity of the ink detected by the load cell 26.
The case of variably adjusting the pressing force has been described as an example,
In accordance with the viscosity of the ink detected by the load cell 26, other adjustments such as changing the printing speed, changing the perforated diameter of the master 9, and the like are performed, regardless of the viscosity of the ink. A high print quality may be obtained by keeping the amount of ink oozing from the ink constant.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. 1 to 3 are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments). The mechanical structure of the stencil printing apparatus of this embodiment and the electrical connection of the control system are the same as those of the stencil printing apparatus of the first embodiment. This embodiment is different from the first embodiment in various processes executed by the microcomputer in the control unit 44. In the present embodiment, the first pressing force variable control unit and the third pressing force It has a variable pressure control means and a second print number determination means.

The second print number determining means determines the number of prints until the ink already supplied in the plate cylinder 2 is consumed.
This is a process of making a determination based on the image amount of the image data of the document read by the scanner 8.

The third pressing force variable control means controls the viscosity of the ink already supplied into the plate cylinder 2 at the start of printing, such as when printing is started after the stencil printing apparatus has been left for a long time. Is a process for automatically changing the pressing force of the press roller 5 when the pressure is lower than a predetermined value.

Specifically, at the start of printing, the load cell 26
Is smaller than the reference value, the number of prints is determined by the second print number determination means. Further, the press arm 31 and the press arm 29 are rotated counterclockwise in accordance with the detected value to separate the press roller 5 from the plate cylinder 2, and the press roller 5 is pressed against the outer peripheral surface of the plate cylinder 2. Pressure when pressing. Then, the state in which the pressing force of the press roller 5 is reduced is maintained until the printing of the number of prints determined by the second number-of-prints determining means is completed. When the printing of the number of printed sheets is completed, the process is switched to the process by the first pressing force variable control unit described above.

FIG. 4 is a flowchart for explaining the control for changing the pressing force of the press roller 5. At the start of the printing operation, it is determined whether the detected value of the load cell 26 is equal to or greater than a predetermined value (step S11). When it is determined that the detected value of the load cell 26 is equal to or more than the predetermined value (Y in step S11), the ink already supplied into the plate cylinder 2 undergoes a significant decrease in viscosity due to evaporation of water and the like. Is determined not to be present, and the pressing force is controlled by the first pressing force variable control means (step S1).
2).

On the other hand, if it is determined at the start of the printing operation that the detected value of the load cell 26 is equal to or less than the predetermined value (N in step S11), the ink already supplied into the plate cylinder 2 contains water. It is determined that the viscosity has significantly decreased due to evaporation or the like, and the pressing force is controlled by the third pressing force variable control means (step S1).
3). Then, after the control of the pressing force by the third pressing force variable control means is started, it is determined whether or not the printing of the number of prints determined by the second printing number determining means is completed (step S14), and the process is ended. In this case (Y in step S14), the control is changed from the variable control of the pressing force by the third variable pressing force control means to the variable control of the pressing force by the first variable pressing force control means.

In such a configuration, when the viscosity of the ink already supplied into the plate cylinder 2 is reduced due to evaporation of water due to the stencil printing apparatus being left for a long time, the third printing is performed. By controlling the pressing force by the pressing force variable control means, the pressing force of the press roller 5 is kept small until all the ink already supplied in the plate cylinder 2 is consumed. For this reason, even if the load cell 26 detects that the viscosity of the newly supplied ink is high, the pressing force of the press roller 5 increases based on the detection result before the low-viscosity ink is consumed. Does not occur, and high printing quality can be obtained during printing after leaving the stencil printing apparatus for a long time.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. The mechanical connection of the stencil printing apparatus of this embodiment and the electrical connection of the control system are the first and second.
This is the same as the stencil printing machine of the embodiment. This embodiment is different from the first and second embodiments in that the control unit 4
4 are various processes executed by the microcomputer operation in the fourth embodiment. In the present embodiment, a fourth pressing force variable control unit is provided.

The fourth pressing force variable control means controls the signal (printing speed) from the printing speed setting key 46 and the detected value of the load cell 26 when the printing speed is changed by operating the printing speed setting key 46. Thus, the pressing force of the press roller 5 is automatically varied.

More specifically, control is performed such that the pressing force of the press roller 5 is increased when the printing speed is high, and the pressing force of the press roller 5 is reduced when the printing speed is low.

Here, when the viscosity of the ink is the same and the amount of bleeding of the ink from the perforated portion of the master 9 is the same, the ink transferred to the printing paper S when the printing speed is high. When the amount decreases and the printing speed is low, the amount of ink transferred to the printing paper S increases. For this reason, when the printing speed is high, the pressing force of the press roller 5 is increased to relatively increase the amount of ink oozing out from the perforated portion of the master 9, and when the printing speed is low, the press roller 5 By reducing the pressing force, the amount of ink that seeps out of the perforated portion of the master 9 is relatively reduced. Thereby, even when the printing speed is different, the amount of ink transferred to the printing paper S becomes the same, and high printing quality can be obtained.

FIG. 5 is a flowchart for explaining the control for changing the pressing force of the press roller 5. When the printing operation is started, the pressing force is controlled by the third pressing force variable control means based on the detection value of the load cell 26 and the signal from the printing speed setting key 46 (step S2).
1).

In such a configuration, even when printing is performed at a different printing speed, the pressing force of the press roller 5 can be changed to a magnitude corresponding to the printing speed, thereby printing at a different printing speed. In each case, high printing quality can be obtained while maintaining the amount of ink transferred to the printing paper S at an optimum value.

In the present embodiment, similarly to the first and second embodiments, when it is detected that the viscosity of the ink is lower than a predetermined value at the time of starting printing, the second embodiment is executed. The control of the pressing force by the second pressing force variable control means or the control of the pressing force by the third pressing force variable control means may be performed.

[0067]

According to the stencil printing apparatus of the first aspect of the present invention, the viscosity of the ink can be detected based on the detection result of the moving force detecting section. By adjusting, for example, changing the printing speed, changing the punching diameter of the master, changing the pressing force of the pressing body, etc., the amount of ink transferred to the printing paper is optimized regardless of the viscosity of the ink. A high print quality can be obtained by maintaining an appropriate amount.

According to the stencil printing apparatus of the second aspect, the stencil printing apparatus of the first aspect has a pressing force variable mechanism for changing the pressing force of the pressing body. By varying the pressing force of the body, even when the viscosity of the ink is different, the amount of ink oozing out from the perforated portion of the master can be kept constant, and high printing quality can be obtained regardless of the viscosity of the ink. .

According to the stencil printing apparatus of the third aspect, in the stencil printing apparatus of the second aspect, the first mechanism for automatically driving the pressing force variable mechanism based on the detection result from the moving force detecting unit. With the variable pressing force control means, the variable control of the pressing force of the pressing body according to the viscosity of the ink can be performed automatically, and the amount of ink oozing out from the perforated part of the master can be controlled regardless of the viscosity of the ink. High print quality can be reliably obtained by keeping the print quality constant.

According to the stencil printing apparatus according to the fourth aspect of the present invention, in the stencil printing apparatus according to the second or third aspect, a counter for counting the number of printed sheets and ink already supplied to the plate cylinder are consumed. The number of printed sheets up to the first printed sheet number determining means for determining the number of printed sheets from the size of the printing paper to be used, the information from the counter, the detection result from the moving force detecting section, and the determination result from the first printed sheet number determining means. And a second pressing force variable control means for automatically driving the pressing force variable mechanism based on the pressure. If the viscosity of the ink already supplied to the plate cylinder is reduced by evaporation of water, It is possible to reduce the pressing force of the pressing body until printing of the number of prints is completed until all the ink is consumed, thereby printing using the ink that has already been supplied into the plate cylinder and the viscosity has been reduced. To It is possible to obtain a high print quality even if the cormorant.

According to the stencil printing apparatus of the invention described in claim 5, in the stencil printing apparatus of claim 2 or 3, a document reading section for obtaining master image data by reading a document and counting the number of printed sheets. A counter, a second print number determining unit for determining the number of prints until the ink already supplied in the plate cylinder is consumed based on the image amount of the image data, and information from the counter and the moving force detecting unit. And a third pressing force variable control means for automatically driving the pressing force variable mechanism based on the detection result of the second printing number determination means and the determination result from the second printing number determination means. If the viscosity of the ink is reduced by evaporation of water, the pressing force of the pressing body can be reduced until the printing of the number of prints until all the ink is consumed can be reduced. High printing quality can be obtained even when printing is performed using ink whose viscosity has been reduced by being supplied into the plate cylinder, and especially when printing is performed even when the image data of the original image data is different. Quality can be obtained.

According to the stencil printing apparatus of the invention, in the stencil printing apparatus of any one of claims 2, 4 and 5, the printing speed setting section for setting the printing speed, and the printing speed setting section And a fourth pressing force variable control means for automatically driving the pressing force variable mechanism based on the information from the unit and the detection result from the moving force detecting unit. The pressing force of the body can be varied, so that even if the printing speed is different, the amount of ink transferred to the printing paper can be maintained at an optimum value, and high printing quality can be obtained.

[0073]

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating an electrical connection of a portion related to a variable pressing force of a press roller in a control system of the stencil printing apparatus.

FIG. 3 is a flowchart illustrating control for changing a pressing force of a press roller.

FIG. 4 is a flowchart illustrating control for changing a pressing force of a press roller according to a second embodiment of the present invention.

FIG. 5 is a flowchart illustrating control for changing a pressing force of a press roller according to a third embodiment of the present invention.

[Explanation of symbols]

 2 plate cylinder 3 plate making section 5 pressing body 8 original reading section 9 master 9a master base paper 20 ink roller 21 doctor roller 22 ink supply mechanism 26 moving force detecting section 36 variable pressing force mechanism 45 counter 46 printing speed setting section S printing paper

Claims (6)

[Claims] 1. A plate making section for making a master by heating and perforating a master base paper to make a master, a porous cylindrical plate cylinder which is driven to rotate around an axis and is wound around an outer peripheral surface thereof,
A press body pressed against the outer peripheral surface of the plate cylinder; and an ink supply mechanism provided in the plate cylinder including an ink roller and a doctor roller. The ink is applied to a surface of the plate, and the printing paper is pressed against the master wound around the outer peripheral surface of the plate cylinder by the pressing body, so that the ink oozing from the perforated portion of the master is transferred to the printing paper for printing. In the stencil printing apparatus, the ink roller is provided so as to be movable in the direction of coming into contact with and separating from the doctor roller, and the ink attached to the outer peripheral surface of the ink roller passes through the doctor roller when the ink passes through the doctor roller. A stencil printing apparatus, further comprising a moving force detecting unit for detecting a moving force acting in a direction to separate the roller from the ink roller. 2. The stencil printing apparatus according to claim 1, further comprising a pressing force variable mechanism that changes a pressing force of the pressing body. 3. The stencil printing apparatus according to claim 2, further comprising a first pressing force variable control unit that automatically drives the variable pressing force mechanism based on a detection result from the moving force detection unit. . 4. A counter for counting the number of printed sheets, and first printed sheet number determining means for determining the number of printed sheets until the ink already supplied in the plate cylinder is consumed from the size of the printing paper used. A second pressing force variable control means for automatically driving the pressing force variable mechanism based on information from the counter, a detection result from the moving force detection unit, and a determination result from the first printed sheet number determination means. The stencil printing apparatus according to claim 2, comprising: 5. A document reading section for obtaining image data of the master by reading a document, a counter for counting the number of printed sheets, and a counter for counting the number of printed sheets until the ink already supplied in the plate cylinder is consumed. A second print number determining unit that determines based on an image amount of the image data, based on information from the counter, a detection result from the moving force detection unit, and a determination result from the second print number determination unit. 4. The stencil printing apparatus according to claim 2, further comprising third pressing force variable control means for automatically driving the variable pressing force mechanism. 6. A printing speed setting unit for setting a printing speed,
4. A variable pressing force control means for automatically driving the variable pressing force mechanism based on information from the printing speed setting unit and a detection result from the moving force detecting unit. 6. The stencil printing apparatus according to any one of 2, 4 and 5.