JPH10211761A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a desired printing density by altering a nip width of a press roller to a plate cylinder while preventing generation of an impact sound at the time of bringing the roller into pressure contact with a printing sheet on the cylinder. SOLUTION: This printer resets a roller support member 25 for supporting a press roller 5 by a reset spring 41 to bring it into contact with a contact member 37 provided at a pressurizing member 28, and alters a position of the member 37 to alter a reset position of the member 25, thereby altering a separating distance of the roller 5 from a plate cylinder 2. And, the member 25 is pressed by the member 37 when the member 28 is driven to the cylinder 2 side at a predetermined stroke to steadily bring the roller 5 into contact with a printing sheet on the cylinder 2, and a nip width of the roller to the cylinder 2 is regulated in response to the distance of the roller 5 from the cylinder 2, thereby obtaining a desired printing density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing machine which feeds printing paper in alignment with a pre-made master wound on a rotatable plate cylinder, and presses the printing paper against the plate cylinder via a master by a press roller. The present invention relates to a printing apparatus that transfers ink supplied to a master onto printing paper.

[0002]

2. Description of the Related Art In this type of printing apparatus, the viscosity of ink and the printing speed, that is, the number of rotations of a plate cylinder, due to a change in environmental temperature affect the printing density. In addition, the outer periphery of the plate cylinder is provided with a peeling claw for peeling the printing paper wrapped around the plate cylinder. However, if the printing density is too high, the printing paper is difficult to separate from the plate cylinder and adheres to the peeling nail. Ink sticks to the printing paper, causing stains on the nails. Furthermore, if the print density is too high, the drying time becomes longer, and if printed papers are overlaid, there is a problem in that ink adheres to the print papers and the print papers become dirty, and the operator's hands become dirty.

Therefore, in order to keep the printing density constant, when the printing speed is low or the viscosity of the ink is low, the pressing force of the printing paper against the plate cylinder is reduced, or the nip width of the printing paper against the plate cylinder is reduced. On the other hand, when the printing speed is high or the viscosity of the ink is high, the pressing force of the printing paper against the plate cylinder or the nip width is increased. There are several different methods for changing the pressing force and the nip width.

For example, as described in JP-A-5-162430, a belt press roller formed by winding an endless belt around two rollers is pressed against a plate cylinder, and the endless belt is adjusted by adjusting the interval between the rollers. A method in which the surface tension of the endless belt and the nip width of the printing paper with respect to the plate cylinder are changed by changing the belt tension.
No. 07, JP-A-2-151473, etc., a member for supporting the press roller is urged by a spring, and the strength of the spring is adjusted to press the press roller against the plate cylinder. As described in Japanese Patent Publication No. Hei 5-74475, the voltage applied to an actuator such as a solenoid for driving a member supporting the press roller toward the plate cylinder is changed to apply a force to the plate cylinder. For adjusting the pressing force of the press roller.

[0005] The above-mentioned apparatus using a belt press roller achieves the purpose of obtaining a desired print density, but has a problem that the apparatus becomes complicated and large in size as compared with a structure using a single press roller. Further, since the force of the spring that urges the member supporting the press roller is changed to change the pressure contact force of the press roller against the plate cylinder, the force of the spring acts when the press roller contacts the plate cylinder. A collision sound is generated. When the viscosity of the ink is high or printing is performed at a high speed, the pressing force must be considerably increased, so that there is a problem that the collision sound becomes high. Similarly, when changing the voltage applied to the actuator that drives the member supporting the press roller, there is a problem that the collision noise increases in proportion to the magnitude of the pressing force of the press roller against the plate cylinder.

As described above, Japanese Patent Application Laid-Open No. 48-732 discloses a method in which a press roller (pressure roller) is pressed against a plate cylinder without depending on the strength of a spring or the driving force of an actuator.
No. 20 is disclosed. More specifically, a holding member for supporting a press roller (pressure roller) is swingably provided, and a driven rod supported reciprocally on a straight line passing in the vicinity of the holding member is biased in one direction by a spring. And
The driven rod is provided with a rotator that comes into contact with the cam and a rotatable operating member that operates when printing paper is supplied, and the rotation of the cam that comes into contact with the rotator causes the driven rod to reciprocate, thereby performing printing. When the paper is supplied, the holding member is pressed by the operating member that rotates on the driven rod, and the press roller is pressed against the plate cylinder.

[0007]

Problems to be Solved by the Invention JP-A-48-7322
Japanese Patent Application Publication No. JP-A No. 0-110,027 discloses a cam driven by a motor and a roller contacting the cam to move a holding member holding a press roller toward the plate cylinder, even if only the main component configuration is viewed. This requires a driven rod having an armature, an operating member rotatably attached to the driven rod, a detecting member for displacing the operating member when supplying printing paper, and the like, so that the number of parts is large and the structure is complicated. In addition, by changing the position of the rotator that contacts the cam on the driven rod, the pressing force of the press roller against the plate cylinder is adjusted. Although not specifically disclosed, it is not easy to change the position of the trochanter. Also, it seems more difficult to adjust the position of the trochanter steplessly along the longitudinal direction of the driven rod. That is, it is extremely difficult to adjust the pressing force of the press roller against the plate cylinder in a stepless manner.

The present invention suppresses the collision noise by pressing the press roller against the plate cylinder without depending on the inertia, and changes the nip width of the press roller with respect to the plate cylinder with a simple structure having a small number of parts. It is an object of the present invention to provide a printing device that can perform the printing.

[0009]

According to a first aspect of the present invention, there is provided a rotatable plate cylinder for holding a prepressed master on an outer peripheral surface, and a press roller rotatably supported to approach and separate from the plate cylinder. A roller support member freely provided, a return spring for returning the roller support member to a return position away from the plate cylinder, and a reciprocation driven by a pressure driving unit to move to the plate cylinder side with a constant stroke. A movable pressurizing member, which is supported by the pressurizing member so as to be adjustable in position, determines a return position of the roller support member against a return force of the return spring, and the pressurizing member is disposed on the plate cylinder side. And a contact member that presses the roller support member toward the plate cylinder when driven.

Therefore, the roller supporting member supporting the press roller comes into contact with the contact member by the return force of the return spring, and the return position is determined. When the pressing member is driven by the pressing driver, the roller supporting member is pressed by the contact member and moves in the plate cylinder direction, so that the press roller is pressed against the plate cylinder. Changing the position of the contact member on the pressing member to change the return position of the roller support member changes the separation distance of the press roller from the plate cylinder, but the stroke of the pressing member pressing the roller support member is constant. Therefore, the nip width of the press roller with respect to the plate cylinder is adjusted according to the separation distance of the press roller with respect to the plate cylinder.

According to a second aspect of the present invention, in the first aspect of the present invention, there is further provided a contact member drive source for driving the contact member in the position changing direction. Accordingly, the position of the contact member is changed by driving the contact member drive source, and the nip width of the press roller with respect to the plate cylinder is adjusted. In this case, the operation of the contact member drive source can be controlled by inputting a control signal, so that the nip width can be easily adjusted.

According to a third aspect of the present invention, the operation of the contact member drive source is controlled based on the rotation speed of the plate cylinder in the second aspect of the invention. Therefore, it is possible to automatically adjust the nip width of the press roller with respect to the plate cylinder in accordance with the number of rotations (printing speed) of the plate cylinder which affects the print density.

According to a fourth aspect of the present invention, the operation of the contact member drive source is controlled based on the environmental temperature information in the second aspect of the invention. Therefore, although the viscosity of the ink changes due to the change in the environmental temperature, it is possible to automatically adjust the nip width of the press roller with respect to the plate cylinder in accordance with the environmental temperature which affects the print density.

According to a fifth aspect of the present invention, in the first, second, third or fourth aspect, the press roller is formed of a soft elastic material. Accordingly, since the amount of elastic deformation of the press roller increases, the amount of change in the nip portion of the press roller with respect to the plate cylinder increases.

According to a sixth aspect of the present invention, in the first, second, third, or fourth aspect, an oil-resistant protective film is formed on the surface of the press roller. Therefore, the press roller is less likely to be permanently deformed and is less likely to be soiled.

[0016]

An embodiment of the present invention will be described with reference to the drawings. First, a plate cylinder 2 around which a master 1 having been made is wound is provided rotatably. Around the plate cylinder 2, a master 1 is heated and perforated to make a plate, and a plate making section 3 for feeding the master 1 to the plate cylinder 2 and a printing sheet fed from a sheet feeding section (not shown) are provided. A pair of registration rollers 4 for transporting the master 1 wound around the plate cylinder 2 in a timely manner, and a press roller 5 for pressing the printing paper fed from the registration rollers 4 onto the plate cylinder 2 via the master 1
And a peeling claw 6 for peeling printed printing paper from the plate cylinder 2
And a paper discharge unit 7 for storing the printing paper peeled by the peeling claws 6.

The press roller 5 has a metal shaft covered with a soft elastic body. As the soft elastic body, for example, soft nitrile rubber having a rubber hardness of about 10 to 25 °, chloroprene rubber, urethane rubber, or a foamed material thereof is used. Is formed. When the inside is foamed, the soft elastic body may form a solid surface layer, and this solid film may be used as a protective film. Also,
The outer diameter of the press roller 5 is set to about １ ／ to の of the outer diameter of the plate cylinder 2 in order to secure a nip width with respect to the plate cylinder 2.

The plate making section 3 is provided with a conveying path 8 for the master 1.
The platen 9 is driven to rotate along the
A thermal head 10 supported so as to be able to freely contact and separate from the master 1, a fixed blade 11 and a movable blade 12 for cutting the master 1, a pair of transport rollers 13, 14, a guide plate 15 for supporting the master 1 from below, and the like. Is formed. Roll core 1 a of master 1, platen 9, transport rollers 13, 1
Reference numerals 4 and the like are rotatably supported by side plates (not shown) of a main body case of the printing apparatus.

The plate cylinder 2 has a non-opening portion 2a and an opening portion 2a.
b are formed. The opening 2b is provided with a mesh screen formed of a resin or metal net. The plate cylinder 2 has flanges (not shown) fixed to both ends thereof rotatably supported by an ink pipe 16 fixedly supported on a side plate of the printing apparatus, and is driven clockwise. Inside the plate cylinder 2, an ink roller 17 and a doctor roller 18 that come into contact with the inner peripheral surface of the plate cylinder 2 are rotatably provided with a slight gap therebetween. An ink reservoir 20 for receiving ink dropped from a supply hole 19 formed at the lower end of the ink pipe 16 is formed in a wedge-shaped space between the ink reservoir 20 and the ink reservoir 20. Ink is supplied to the ink pipe 16 from an ink pack (not shown) provided outside the plate cylinder 2. A stage 21 and a clamper 22 for holding the leading end of the master 1 at the non-opening portion 2a are attached to the outer peripheral surface of the plate cylinder 2. The stage 21 is formed of a magnetic material and has a length along the axial direction of the plate cylinder 2. The clamper 22 is rotatably supported on a clamper shaft 23 disposed along the longitudinal direction of the stage 21 as a support shaft.

The press roller 5 is rotatably supported by one end of a roller support member 25 which rotates integrally with the arm shaft 24. In the present embodiment, the roller support member 25 is divided into a plurality of arms 25a and 25b fixedly fitted to the arm shaft 24, respectively, and these arms 25a and 25b are formed integrally and continuously. May be. In addition, a pin 26 is provided at an end of the arm shaft 24 at an intermediate portion.
Pressing member 2 having a cam follower 27 at its lower end
8 are rotatably fitted. A pressing drive unit 29 for driving the pressing member 28 has a projection 31 on a part of the outer periphery, and a cam 31 that rotates in synchronization with the rotational movement of the plate cylinder 2.
And a spring 32 for urging the pressing member 28 clockwise about the arm shaft 24.

Further, a locking member 33 for holding the pressing member 28 by engaging with the pin 26 is
Is provided so as to be rotatable around the center. This locking member 33
Is urged clockwise by a spring (not shown). Such a locking member 33 is connected to a plunger 36 of a solenoid 35.

Further, the pressing member 28 supports an axial contact member 37 which contacts the end of the arm 25b of the roller support member 25. The pressing member 28 has a forward / reverse rotatable driving motor 3 as a driving source for the contact member.
8 is fixed, and a gear 39 is directly connected to the drive motor 38. The contact member 37 has a male screw shape, and a gear 40 meshing with the gear 39 is screwed around its outer periphery. The gear 40 is supported in a state where the gear 40 is prevented from moving in the axial direction. The contact member 37 is prevented from rotating in the rotational direction by a structure to be described later, and is supported by the pressing member 28 so that the position can be freely changed in the axial direction. And
The arm 25b of the roller support member 25 is connected to the arm shaft 24 by a return spring 41 stretched between the arm 25b and the pressing member 28.
And is in contact with the lower end of the contact member 37 in a counterclockwise direction. Thereby, the pressing member 28 and the arm 2
5b rotates together with it.

Here, the support structure of the contact member 37 is shown in FIG. As can be seen from the upper side of the pressing member 28, a groove 42 is formed along the axial direction on the outer periphery of the shaft-shaped contact member 37, and a ridge 43 slidably fitted in the groove 42. Are formed on the pressing member 28. The groove 42 and the ridge 43
By this, the contact member 37 is allowed to move only in the axial direction.

Next, FIG. 3 shows an electronic circuit. CPU44
In R, fixed data such as a program is written.
An OM 45, a RAM 46 in which variable data is written, and an input / output interface 47 are connected. The drive motor 38 is connected to the output side of the interface 47. A pulse motor is used as the drive motor 38, and the motor sensor 4 for detecting the initial position thereof is used.
8, a panel switch 49 for inputting various operation commands, a rotation sensor 50 for detecting the rotation speed of the plate cylinder 2, a temperature sensor 51 for detecting the environmental temperature in the printing apparatus, and the like are connected to the input side of the interface 47. I have. And CPU
44 is a panel switch 49 and various sensors 48, 50,
The rotation direction of the drive motor 38 and the number of drive pulses are controlled based on the information from 51. A table for the control is stored in the ROM 45 or the like.

Next, the operation will be described. When a document is set on a document reading unit (not shown) and a start signal is issued by pressing a start button or the like, the plate cylinder 2 is driven counterclockwise by a motor (not shown). In this process,
The master 1 wound up to that time by the plate cylinder 2 is peeled off by a plate discharging device (not shown) and discarded, and the plate cylinder 2 is stopped when the clamper 22 reaches almost directly above. At the time of this stop, the clamper 22 rotates in the opening direction about the clamper shaft 23 and is maintained in the plate feeding standby state.

When the original is sent to the original reading unit and the image is read, and the read image is formed on the CCD sensor,
The image data (analog data) converted to an electric signal by the CCD sensor is converted to digital data by an A / D converter, and output to the thermal head 10 via a plate making control device or the like. That is, the heating elements arranged in a line in the thermal head 10 are selectively energized based on image data, and the platen 9 and the transport rollers 13 and 14 are driven to transport the master 1 to the plate cylinder 2 side. . As a result, dots are formed in the master 1 by punching based on the image data.

At this time, the platen 9, the transport rollers 13,
When it is determined that the tip of the master 1 has reached the clamper 22 by counting the number of steps of the stepping motor for driving the clamper 14, the clamper 22 is closed by an opening / closing device (not shown), and the tip of the master 1 is connected to the clamper 22 and the plate. It is clamped between the stage 21 on the body 2. continue,
The plate cylinder 2 is driven clockwise at a peripheral speed substantially equal to the transport speed of the master 1 to wind the master 1 around the outer periphery of the plate cylinder 2. Then, when it is determined from the number of steps of the stepping motor that plate making is completed, the movable blade 12 is operated to cut the master 1, and the platen 9 and the transport rollers 13, 14 are stopped. And
By further rotating the plate cylinder 2, the winding of the master 1 around the plate cylinder 2 is completed.

When the winding of the master 1 around the plate cylinder 2 is completed, the printing paper stacked on the paper feeding tray (not shown) is fed by the separation paper feeding device, and the printing paper is The sheet is conveyed between the plate cylinder 2 and the press roller 5 by a registration roller 4 that rotates in synchronization with the rotation. At the time of printing, the printing paper is pressed against the outer periphery of the plate cylinder 2 by the press roller 5.

The operation of bringing the press roller 5 into and out of contact with the printing paper on the plate cylinder 2 is performed as follows. In the state shown in FIG. 1, the cam follower 27 of the pressing member 28 is pressed by the projection 30 of the cam 31, and the pin 26 and the locking member 33 are engaged with each other. The movement of the roller support member 25 is stopped, the roller support member 25 is stopped by the return force of the return spring 41 at the return position where the arm 25b contacts the lower end of the contact member 37, and the press roller 5 is separated from the plate cylinder 2.

The cam 31 starts rotating when the printing paper is fed between the plate cylinder 2 and the press roller 5 in synchronization with the rotation movement of the plate cylinder 2. The release is performed while the projection 30 of the cam 31 is riding on the cam follower 27. That is, when the solenoid 35 is excited in the state shown in FIG. 1, the plunger 36 is sucked downward, the locking member 33 rotates counterclockwise about the support shaft 34, and the engagement with the pin 26 is released. You. Therefore, when the cam 31 rotates counterclockwise and the protrusion 30 separates from the cam follower 27, the pressing member 28 rotates clockwise about the arm shaft 24 by the urging force of the spring 32, Since the end of the contact member 37 presses the arm 25b of the roller support member 25, the roller support member 25 rotates clockwise integrally with the pressing member.
In this case, since the cam follower 27 rotates along the outer peripheral surface of the cam 31 by the spring 32, the stroke of the pressing member 28 is always set to a predetermined value. At this time, the relationship between the elastic coefficient of the press roller 5 and the spring constant of the spring 32 is maintained so that the cam follower 27 does not float from the outer peripheral surface of the cam 31.

As described above, when the roller supporting member 25 rotates clockwise integrally with the pressing member 28, the press roller 5 comes into contact with the plate cylinder 2. The cam 31 is a plate cylinder 2
Is configured to make one rotation in the counterclockwise direction when one rotation is made. Therefore, the fed printing paper is the one shown in FIG.
As shown in (1), the press roller 5 presses against the outer periphery of the plate cylinder 2, and the ink that has permeated the perforated portion of the master 1 from within the plate cylinder 2 is transferred (printed) to printing paper.

Since the solenoid 35 is shut off just before the end of one rotation of the cam 31, the locking member 33 is
It returns clockwise around 4. Then, the pressing member 28
Is returned by the protrusion 30 of the cam 31 in the counterclockwise direction, the locking member 33 is engaged with the pin 26. When the pressing member 28 returns in the counterclockwise direction, the roller support member 25 is moved by the return force of the return spring 41 to the arm shaft 24.
At the same time, the press roller 5 returns from the plate cylinder 2 to return in the counterclockwise direction. At this time, the separation distance of the press roller 5 from the plate cylinder 2 depends on the return position of the roller support member 25, and the return position is determined by the length of the contact member 37 projecting downward from the pressing member 28. .

The projecting length of the contact member 37 downward is as follows:
The CPU 44 determines, based on the initial position of the drive motor 38 determined by the detection signal from the motor sensor 48, the number of rotations of the plate cylinder 2 (corresponding to the printing speed) detected by the detection signal of the rotation sensor 50, or The drive motor 3 is controlled by the temperature detected by the temperature sensor 51 (corresponding to the viscosity of the ink).
8 and the number of drive pulses thereof are determined. That is, since the gear 40 is rotated by the rotation of the drive motor 38, the contact member 37 moves upward or downward to change the return position of the roller support member 25.

As described above, the contact member 3 on the pressing member 28
When the return position of the roller support member 25 is changed by changing the position of the roller 7, the separation distance of the press roller 5 from the plate cylinder 2 is changed, but the stroke of the pressing member 28 pressing the roller support member 25 is constant. Therefore, the nip width of the press roller 5 with respect to the plate cylinder 2 is adjusted according to the separation distance of the press roller 5 with respect to the plate cylinder 2.

Specifically, in the state shown in FIG. 1, when the length of the downwardly projecting portion of the contact member 37 is increased, the separation distance of the press roller 5 from the plate cylinder 2 is reduced, and the approach distance is reduced. Roller support member 2 for a fixed stroke from the position
Since the roller 5 is rotated by being pressed by the contact member 37, the press roller 5 moves toward the plate cylinder 2 even after contacting the printing paper on the plate cylinder 2. As a result, the press roller 5 is elastically deformed largely, and presses the printing paper against the plate cylinder 2 with a large nip width.

Conversely, when the downward projecting length of the contact member 37 is shortened, the separation distance of the press roller 5 from the plate cylinder 2 becomes longer, and the roller support from the separated position by a fixed stroke. Since the member 25 is rotated by being pressed by the contact member 37, the amount of movement of the press roller 5 toward the plate cylinder 2 after the press roller 5 contacts the printing paper on the plate cylinder 2 is reduced. Thus, the press roller 5 presses the printing paper against the plate cylinder 2 with a small nip width.

As the nip width of the press roller 5 against the plate cylinder 2 increases, the pressing force of the press roller 5 against the plate cylinder 2 increases.
2, the length is obtained by the length of pressing the roller support member 25 in the direction of the plate cylinder 2 based on the changed position of the press roller 5 with respect to the plate cylinder 2 which has been changed. The strength of the spring 32 may be a minimum necessary limit for driving the pressing member 28 in the direction of the plate cylinder 2. Moreover, since the strength of the spring 32 is offset by the strength of the return spring 41, the press roller 5 can be gently brought into contact with the printing paper on the plate cylinder 2. Therefore, it is possible to suppress the generation of the collision sound.

Further, a pressurizing system for pressing the roller supporting member 25 toward the plate cylinder 2 detects the supplied printing paper as in the conventional example described in, for example, JP-A-48-73220. Since there is no need for a member to be displaced, the number of parts can be reduced and the structure can be simplified.

[0039]

According to the first aspect of the present invention, there is provided a return spring for returning a roller supporting member for supporting a press roller in a direction away from the plate cylinder, and the plate having a constant stroke driven by a pressure driving unit. A reciprocating pressurizing member that moves to the barrel side, and a position that is adjustable by the pressurizing member to determine the return position of the roller support member against the return force of the return spring; A contact member that presses the roller support member against the plate cylinder when driven to the cylinder side, so that the roller support member that has returned to the return position by separating the press roller from the plate cylinder is a pressing member. Is driven by the contact member to move in the direction of the plate cylinder, so that the press roller is pressed against the plate cylinder. In this case, when the return position of the roller supporting member is changed by changing the position of the contact member on the pressing member, the separation distance of the press roller from the plate cylinder is changed, but the pressing member presses the roller supporting member. Since the stroke is constant, the nip width of the press roller with respect to the plate cylinder can be adjusted according to the separation distance of the press roller with respect to the plate cylinder. Thereby, the print density can be adjusted to a desired density. When the nip width is increased, the pressing force of the press roller against the plate cylinder increases as a result, but this pressing force presses the roller support member in the direction of the plate cylinder based on the separated position of the press roller relative to the changed plate cylinder. Since the roller support member moves toward the plate cylinder against the return force of the return spring, the press roller can be gently brought into contact with the printing paper on the plate cylinder. it can. Therefore, it is possible to suppress the generation of the collision sound. Further, a pressing system that presses the roller supporting member toward the plate cylinder side includes:
Since there is no need for a member for detecting and displacing the supplied printing paper as in the related art, the number of components can be reduced and the structure can be simplified.

According to the second aspect of the present invention, the apparatus further comprises a contact member driving source for driving the contact member in the direction of changing the position. Is changed, and the nip width of the press roller with respect to the plate cylinder is adjusted. In this case, since the operation of the contact member drive source can be controlled by inputting a control signal,
The nip width can be easily adjusted.

According to the third aspect of the present invention, the operation of the contact member drive source is controlled based on the number of revolutions of the plate cylinder. , The nip width of the press roller with respect to the plate cylinder can be automatically adjusted.

According to the fourth aspect of the present invention, since the operation of the drive source for the contact member is controlled based on the environmental temperature information, the viscosity of the ink changes with the change of the environmental temperature.
It is possible to automatically adjust the nip width of the press roller with respect to the plate cylinder according to the environmental temperature that affects the print density.

According to the fifth aspect of the present invention, since the press roller is formed of a soft elastic body, the amount of elastic deformation of the press roller increases, so that the change amount of the nip portion of the press roller with respect to the plate cylinder increases. In addition, the adjustment range of the print density can be widened.

According to the sixth aspect of the present invention, since the oil-resistant protective film is formed on the surface of the press roller, it is possible to prevent permanent deformation of the press roller and to prevent the press roller from becoming dirty.

[Brief description of the drawings]

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

FIG. 2 is a plan view illustrating a relationship between a pressing member and a roller supporting member.

FIG. 3 is a block diagram showing an electronic circuit.

FIG. 4 is a vertical sectional front view showing a state where a press roller is pressed against a plate cylinder with a small nip width.

FIG. 5 is a vertical sectional front view showing a state in which a press roller is pressed against a plate cylinder with a large nip width.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Master 2 Plate cylinder 5 Press roller 25 Roller support member 28 Pressure member 29 Pressure drive unit 37 Contact member 38 Contact member drive source 41 Return spring

Claims (6)

[Claims] 1. A rotatable plate cylinder for holding a plate-making master on an outer peripheral surface, a roller support member rotatably supporting a press roller and provided so as to approach and separate from the plate cylinder. A return spring that returns the roller support member to a return position away from the plate cylinder; a reciprocating pressure member that is driven by a pressure driving unit and moves toward the plate cylinder with a constant stroke; The roller support member is supported by a member so as to be position-adjustable to determine the return position of the roller support member against the return force of the return spring, and the roller support member is moved when the pressurizing member is driven to the plate cylinder side. And a contact member for pressing the plate cylinder side. 2. The printing apparatus according to claim 1, further comprising: a contact member driving source for driving the contact member in a position changing direction. 3. The printing apparatus according to claim 2, wherein the operation of the drive source for the contact member is controlled based on the number of rotations of the plate cylinder. 4. The printing apparatus according to claim 2, wherein the operation of the contact member drive source is controlled based on the environmental temperature information. 5. The printing apparatus according to claim 1, wherein the press roller is formed of a soft elastic body. 6. The printing apparatus according to claim 1, wherein an oil-resistant protective film is formed on a surface of the press roller.