JP2001030605A - Stencil printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stencil printer capable of reducing the image doubling printing, the printed image slippage and the stain of a printing paper. SOLUTION: An intermediate feeding device 17 for feeding printing papers 22 from an upstream side printing section E1 for printing using an upstream side plate cylinder to a downstream side printing section E2 using a downstream side plate is provided between a plate cylinder 1A positioned on the upstream side in the paper feeding direction X and a plate cylinder 1B positioned on the downstream side. In the case where the printing paper 22 is shorter than the interval L between the upstream side plate cylinder and the downstream side plate cylinder, the paper feeding speed V of the intermediate feeding device is switched over and controlled in compliance with the passing state of the printing paper 22 on the upstream side printing section E1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil printing machine provided with an intermediate conveying device for conveying printing paper.

[0002]

2. Description of the Related Art In a stencil printing machine in which a plurality of plate cylinders are juxtaposed at intervals in the sheet conveying direction, a plate cylinder provided on the upstream side in the sheet conveying direction and a plate cylinder provided on the downstream side in the sheet conveying direction. And an intermediate transport device that transports the printing paper from the upstream plate cylinder to the downstream plate cylinder.

When the printing paper conveyed by the intermediate conveyance device passes through an upstream printing section where printing is performed using the upstream printing drum, the printing paper is arranged to face the upstream printing cylinder with a paper conveyance path interposed therebetween. The ink image is transferred from the master wound on the outer peripheral surface of the upstream plate cylinder by receiving the printing pressure from the printing pressure member,
When passing through a downstream printing unit where printing is performed using the downstream plate cylinder, the downstream plate cylinder receives printing pressure from a printing pressure member disposed opposite to the downstream plate cylinder with the sheet transport path interposed therebetween. The ink image is transferred from the master wound on the outer peripheral surface of the ink jet printer.

In such a stencil printing apparatus having a plurality of plate cylinders, for example, in order to perform multicolor printing of two colors, a master on which a perforated image corresponding to the first color image is formed, and a second color image are formed. A master on which a perforated image corresponding to a plate is made is wound around each of the outer peripheral surfaces of the upstream and downstream plate cylinders, and inks of different colors are supplied to the inner peripheral surfaces of the plate cylinders and printed. The paper feed timing for feeding paper and each plate cylinder are rotated in synchronization, and the paper transport speed at which the printing paper is transported by the intermediate transport device is set to be approximately the same as the print rotation speed at which the plate cylinder rotates during printing. The printing corresponding to the color is performed by one paper feeding operation.

A problem with a stencil printing apparatus capable of simultaneous multicolor printing is that the ink transferred to the printing paper in the upstream printing section adheres to the master of the downstream plate cylinder, and the adhered ink is then transferred to the master. This is to cause so-called image double printing or the like, which is transferred when printing on the transported printing paper. This phenomenon is characterized in that the amount of double printing changes due to the influence of the printing rotation speed of the plate cylinder and the paper transport speed of the intermediate transport device.

In the case of stencil printing, the printing paper is pressed against the plate cylinder by the printing pressure member to transfer the ink image onto the printing paper. Therefore, the size of the image area depends on the size of the ink image and the size of the printing paper. However, there is a change in the amount of ink transferred to the printing paper. Due to the viscosity of the ink, the time at which the printing paper adheres to the plate cylinder at the time of printing peels off from the plate cylinder varies depending on the amount of ink that is transferred. As a result, the timing of feeding the sheet to the downstream printing unit is shifted. The shift in the feeding timing causes a variation in the print timing from the downstream plate cylinder to the printing paper, and causes problems such as a print image shift and image double printing.

[0007]

Therefore, the paper transport speed of the intermediate transport device is made higher than the printing rotation speed of the plate cylinder,
A speed difference is intentionally generated between the paper conveyance speed and the printing rotation speed, and the printing paper that has passed through the upstream printing section is conveyed while being pulled by the intermediate conveyance device using the speed difference, thereby reducing the printing paper. The applicant of the present invention has proposed an invention in which the occurrence of a print image shift, image double printing, or the like is suppressed by suppressing slack or a shift of a transfer start position of a print sheet by an intermediate transfer device.

In the case where the paper transport speed of the intermediate transport device is higher than the printing rotation speed of the plate cylinder, if the length of the printing paper is longer than the interval between the upstream plate cylinder and the downstream plate cylinder, the upstream printing section is moved. Even if the leading end of the passed printing paper reaches the downstream printing section, the trailing end is located at the upstream printing section. That is, since the trailing edge of the sheet is sandwiched between the upstream plate cylinder and the printing pressure member, after the leading edge of the sheet reaches the downstream printing section, the sheet transport speed of the intermediate transport device changes the printing rotation of the plate cylinder. Even if the printing speed is higher than the speed, the printing paper is in a state of being pulled by the upstream plate cylinder. For this reason, printing paper longer than the interval between the upstream plate cylinder and the downstream plate cylinder will slide on the intermediate conveyance device, and will not be slackened before the downstream plate cylinder, without switching the paper conveyance speed. Good.

However, when the length of the printing paper is shorter than the interval between the upstream plate cylinder and the downstream plate cylinder, the leading end of the paper reaches the downstream printing unit even if the rear end of the paper passes through the upstream printing unit. If the paper transport speed is still high,
Printing paper is conveyed quickly toward the downstream plate cylinder,
The print timing from the downstream plate cylinder to the printing paper varies, causing an image misalignment, or the printing paper is slackened before the downstream plate cylinder due to the speed difference between the printing rotation speed of the downstream plate cylinder and the paper transport speed. This may cause the loosened printing paper to come into contact with the downstream plate cylinder and cause image stains. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a stencil printing apparatus capable of reducing image double printing, print image deviation, and stain on printing paper.

[0010]

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a method in which a plate cylinder located on the upstream side in the sheet conveying direction and a plate cylinder located on the downstream side in the sheet conveying direction. Stencil printing provided with an intermediate transport device that transports printing paper from an upstream printing unit where printing using an upstream plate cylinder is performed to a downstream printing unit where printing using a downstream plate cylinder is performed In the apparatus, when the printing paper passing through the upstream printing unit is shorter than the interval between the upstream printing cylinder and the downstream printing cylinder, a switching unit that switches the paper conveyance speed of the intermediate conveyance device according to the passing state of the printing paper. It is characterized by having. Since the paper transport speed of the intermediate transport device is controlled according to the passing state of the printing paper shorter than the interval between the upstream plate cylinder and the downstream plate cylinder passing through the upstream printing section, the paper has passed through the upstream printing section. Variations in the conveyance start position of the printing paper in the intermediate conveyance device are adjusted.

According to a second aspect of the present invention, in the stencil printing apparatus according to the first aspect, when the printing paper is passing through the upstream printing section, the paper transport speed is higher than the printing rotation speed of the upstream printing drum. After the printing paper has passed through the upstream printing section, the switching means performs switching control so that the paper transport speed is substantially equal to the printing rotation speed of the downstream plate cylinder. For this reason, when a printing sheet shorter than the interval between the upstream plate cylinder and the downstream plate cylinder is passing through the upstream printing unit, the leading end of the sheet is pulled by the intermediate conveyance device, and the conveyance delay and slack of the printing sheet are eliminated. . When the printing paper finishes passing through the upstream printing unit, the paper transport speed is reduced so as to be substantially equal to the printing rotation speed of the downstream plate cylinder, so that the short printing paper reaches the downstream printing unit quickly. Thus, the shift of the transport timing to the downstream printing section is suppressed. Further, since there is no speed difference between the printing rotation speed of the downstream plate cylinder and the paper conveyance speed of the intermediate conveyance device, the slack of the printing paper generated before the downstream plate cylinder is suppressed by this speed difference.

The invention described in claim 3 is the first or second invention.
The stencil printing apparatus according to the above, further comprising a paper detecting unit for detecting the printing paper being transported, wherein the switching unit determines a passing state of the printing paper based on a detection signal from the paper detecting unit and switches the paper transport speed. It is characterized by. For this reason, the paper transport speed of the intermediate transport device can be switched during the printing operation, and the responsiveness of the speed switching is improved.

The invention according to claim 4 is the first or second invention.
In the stencil printing apparatus described above, the stencil printing apparatus includes a paper size detecting unit that detects a size of the printing paper, and an angle detecting unit that detects a rotation angle of the upstream plate cylinder or the downstream plate cylinder, and the switching unit detects the paper size. It is characterized in that the passage state of the printing paper is determined based on the paper size detected by the means and the angle information detected by the angle detecting means, and the paper transport speed is switched. For this reason, the timing of feeding the printing paper printed by the upstream printing section to the downstream printing section is appropriately adjusted, and image double printing and print image deviation are extremely reduced, and printing in front of the downstream plate cylinder is performed. The occurrence of paper slack is suppressed.

According to a fifth aspect of the present invention, there is provided the first or second aspect.
In the stencil printing apparatus described in the above, a passing time setting means in which a trailing end passage time is set according to a sheet size in which a trailing end of the printing paper passes through the upstream printing section, and a paper size detection for detecting a paper size of the printing paper Means for switching, based on the sheet size detected by the sheet size detecting means, the passage time setting means to select a rear end passage time corresponding to the paper size, and the selected rear end passage time The paper transport speed is switched after elapse of the time.
Therefore, since the trailing time of the printing paper is set before printing based on the paper size, it is not necessary to detect the passing state of the printing paper during printing, and the paper detection for detecting the printing paper being transported is performed. This eliminates the need for a unit, thereby reducing the number of components, and also reduces switching failures in the paper transport speed due to a failure in the paper detection unit.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A stencil printing apparatus according to the present invention
As shown in FIG. 1, a plate cylinder (hereinafter, referred to as "plate cylinder outer peripheral surface 1Aa") provided on the upstream side in the sheet transport direction X and having a plate-making master 33a wound thereon. Upstream drum cylinder 1A) and a plate cylinder provided downstream of the sheet conveying direction X and having a master 33b formed therearound wound around its outer peripheral surface (hereinafter referred to as "plate cylinder outer peripheral surface 1Ba"). (Hereinafter referred to as “downstream plate cylinder 1B”) in the sheet transport direction X
Is a so-called double-cylinder type that is arranged side by side from the upstream side to the downstream side to enable simultaneous multicolor printing.
A and the intermediate conveying device 17 disposed between the downstream plate cylinder 1B
Can be switched.

The stencil printing apparatus includes an upstream plate cylinder 1A, a downstream plate cylinder 1B, and an intermediate conveying device 17 together with the upstream plate cylinder 1A.
And press rollers 9 a and 9 b as printing pressure members respectively opposed to the downstream plate cylinder 1 </ b> B, a paper feed unit 20 that feeds printing paper 22, and discharge of printed printing paper 22 as a paper discharge unit This is a well-known thermosensitive digital stencil integrated stencil printing apparatus including a paper ejection device 35 that ejects paper onto the tray 37, plate making and feeding units 41A and 41B, and plate making units 42A and 42B.

The plate making and feeding units 41A and 41B hold an unprinted master wound in a roll shape (not shown) between a thermal head and a platen roller to make an image corresponding to an image signal while making an upstream plate cylinder. This is a well-known configuration in which the sheet is conveyed toward the printing drum 1A and the downstream plate cylinder 1B, respectively. In this embodiment, the plate making and feeding section 41A forms a plate making image according to the image signal of the first color, and the plate making and feeding section 41B forms a plate making image according to the image signal of the second color. When the stencil printing apparatus is provided with a document reading unit, the image signal obtained by reading the document set in the document reading unit is used as an image signal used for plate making. An image signal corresponding to an image to be printed input from the information processing device may be used, or
Both may be used as appropriate.

The plate discharging sections 42A and 42B have a well-known structure (not shown) provided with a plate discharging roller pair, a plate discharging conveying belt, a plate discharging roller, a plate discharging box, a compression plate, and the like, and are used on the plate cylinder outer peripheral surfaces 1Aa and 1Ba. The masters 33a and 33b are separated and discarded.

The plate making operation by the plate making units 41A and 41B and the plate discharging operation by the plate discharging units 42A and 42B are executed by operating the plate making start key 72 shown in FIG.

The upstream plate cylinder 1A and the downstream plate cylinder 1B have a well-known porous cylindrical shape and are rotatably supported around drum shafts 2a and 2b which also serve as ink supply shafts. The upstream plate cylinder 1A and the downstream plate cylinder 1B are connected to a plate cylinder drive motor 63 as a drive unit shown in FIG. 2 via a power transmission mechanism (not shown). At the rotation speeds V1 and V2, the motor rotates at a constant speed in the clockwise direction in FIG.

Openable and closable clampers 5a, 5b for clamping the leading ends of the masters 33a, 33b are provided on one generatrix of the plate outer peripheral surfaces 1Aa, 1Ba, respectively.
The clampers 5a and 5b are pivotally mounted on the upstream plate cylinder 1A and the downstream plate cylinder 1B by clamper shafts 6a and 6b, respectively, and are opened and closed at predetermined positions at predetermined positions by opening and closing means (not shown). ing. The predetermined time is a time when the leading ends of the masters 33a and 33b are opened or pinched during plate discharging or plate making.

Inside the upstream plate cylinder 1A and the downstream plate cylinder 1B, ink supply means 45A and 45B for supplying ink to the plate cylinder inner peripheral surfaces 1Ab and 1Bb are provided, respectively. The ink supply means 45A and 45B are provided on the drum shaft 2a,
2b, ink rollers 3a and 3b which slidably contact the plate cylinder inner peripheral surfaces 1Ab and 1Bb to supply ink, and ink rollers 3a and 3b.
a, doctor rollers 4a, 4b disposed opposite to each other,
It includes wedge-shaped ink reservoirs Ia and Ib formed between the ink roller 3a and the doctor roller 4a and between the ink roller 3b and the doctor roller 4b, respectively.
2b has a known configuration in which ink is supplied to the ink reservoirs Ia and Ib. In this embodiment, the ink pool I
a is supplied with, for example, magenta ink as the first color ink, and the ink reservoir Ib is supplied with, for example, black ink as the second color ink.

Below the upstream plate cylinder 1A, a press roller 9a as a printing pressure member for pressing the printing paper 22 fed from the paper feed unit 20 against the master 33a of the upstream plate cylinder 1A, which has been made, is provided. It is arranged to face the side plate cylinder 1A.
Between the press roller 9a and the upstream plate cylinder 1A, an upstream printing section E1 on which printing is performed using the upstream plate cylinder 1A is configured. Below the downstream plate cylinder 1B, a press roller 9b as a printing pressure member for pressing the printing paper 22 that has passed through the upstream printing section E1 against the master 33b of the downstream plate cylinder 1B that has been made is provided with the downstream plate cylinder 1B. They are arranged facing each other.
Between the press roller 9b and the downstream plate cylinder 1B, a downstream printing unit E2 for performing printing using the downstream plate cylinder 1B is formed.

The paper supply unit 20 includes a paper supply tray 21 on which print papers 22 are stacked, a call roller 23 disposed above the paper supply tray 21, and separates and supplies the print papers 22 one by one. A pair of separation rollers 24 and 25 and a separation plate 26 are provided, and when the call roller 23 rotates clockwise, the uppermost print sheet 22 of the paper feed tray 21 is sent out, and the separation roller pairs 24 and 25 and the separation plate are separated. This is a well-known configuration in which the sheet 26 is separated into one sheet by the cooperation of the plate 26 and fed in the sheet transport direction X. The paper feed tray 21 is provided with a plurality of paper size detection sensors 46 as paper size detection means for detecting the size of the printing paper 22.

The separation roller pair 24, 25 and the upstream printing unit E1
Between the printing paper 22 fed from the paper feeding unit 20
Pair of registration rollers 29 and 30 for adjusting the timing of entry into the upstream printing section E1, and upper and lower guide plates 2
7, 28 are arranged. Printing paper 22 fed
Is transported to a pair of registration rollers 29, 30 through a paper transport path formed between the guide plates 27, 28, and the registration rollers 29, 30 are used to transfer the image position of the plate-making image on the upstream plate cylinder 1A to the printing paper. The paper is fed at the timing when the position of the print job 22 coincides with the position of the upstream printing unit E1.

The press rollers 9a, 9b are connected to the shafts 10a, 1
Arm members 11a and 11b provided to be swingable at 0b
Are rotatably supported by one of the swinging ends, respectively.
It is provided on the outer peripheral surfaces 1Aa and 1Ba of the plate cylinder so as to be able to freely contact and separate. The arm members 11a and 11b are locked with tension springs 13a and 13b for applying a printing pressure by the press rollers 9a and 9b to the upstream plate cylinder 1A and the downstream plate cylinder 1B. The other swing ends of the arm members 11a and 11b are pressed against the contour peripheral surfaces of the press roller cams 12a and 12b by the urging forces of the tension springs 13a and 13b, respectively. The press roller cams 12a and 12b are used for printing paper 2 fed from the paper feeding unit 20 by the printing pressure driving unit 86 shown in FIG.
2 and the rotations of the upstream plate cylinder 1A and the downstream plate cylinder 1B are synchronized with the rotation of the upstream plate cylinder 1A and the downstream plate cylinder 1B, and the clampers 5a and 5b are rotated by the upstream printing unit E1 and the downstream printing unit. The cam profile separates the press rollers 9a and 9b from the upstream plate cylinder 1A and the downstream plate cylinder 1B when the sheet passes through E2 and when the printing paper 22 is not fed. For this reason, the upstream printing unit E1 and the downstream printing unit E2
Then, the press rollers 9a and 9b press the print paper 22 against the plate cylinder outer peripheral surfaces 1Aa and 1Ba, and
2 is printed.

In the vicinity of the upstream printing section E1 and the downstream printing section E2, the printing paper 22 printed by the upstream printing section E1 and the downstream printing section E2 is transferred from the upstream plate cylinder 1A and the downstream plate cylinder 1B. Well-known air knife 7 that separates and separates
a and 7b are arranged.

The paper discharge device 35 is disposed between the downstream printing section E2 and the paper discharge tray 37 disposed at the most downstream in the paper transport direction X. The paper discharging device 35 includes a pair of rollers 3.
A conveyor belt 40 wound between the conveyor belts 8 and 39, and a suction fan 36 for applying a suction action to the conveyor belt 40 are provided, and drive a paper discharge system drive unit 87 and a fan drive unit 88 shown in FIG. By controlling, the conveyor belt 40 is rotated in the counterclockwise direction in FIG. 1, and the suction fan 36 is rotated to generate a suction force.
The printing paper 22 that has passed through the printer is brought into close contact with the transport belt 40 and is transported toward the discharge tray 37.
The transport belt 40 is provided with a print rotation speed V1 of the upstream plate cylinder 1A.
It is designed to be driven in synchronization with the upstream plate cylinder 1A at substantially the same transport speed as that described above.

Between the upstream plate cylinder 1A and the downstream plate cylinder 1B, there is arranged an intermediate transport device 17 for transporting the printing paper 22 from the upstream printing section E1 to the downstream printing section E2.
The intermediate transport device 17 includes a driven roller 14 disposed near the upstream printing section E1 and a driving roller 15 disposed near the downstream printing section E2, around which a porous transport belt 16 is wound. Below the belt 16, a suction fan 18 is arranged. The intermediate transfer device 17 is shown in FIG.
The transfer belt 1 is controlled by a control unit 34 as a switching unit, and the control unit 34 uses the control unit 34 according to the passing state of the printing paper 22 passing through the upstream printing unit E1.
6, the paper transport speed V of the printing paper 22 is controlled, and the fan drive unit 88 shown in FIG.
8 to generate a suction force, so that the upstream printing section E1
The printing paper 22 that has passed through is brought into close contact with the transport belt 16 and is transported toward the downstream printing section E2.

The stencil printing apparatus according to the present invention includes an operation panel 70 shown in FIG. On the operation panel 70,
Numeric keypad 71 for setting the number of prints, plate making, plate feeding,
A plate making start key 72 for activating each operation up to the printing, a printing start key 73 for setting activation of each operation up to the printing process, a paper size setting key 47 serving as a paper size setting unit, A digital display 74 for displaying an operation state and numerical data is provided.

Control means 34 as switching means shown in FIG.
Is a central processing unit (hereinafter referred to as “CPU”) 80,
A read-only storage device (hereinafter referred to as “ROM”) 81;
Read / write storage device (hereinafter referred to as “RAM”) 82
The main part is constituted by a well-known microcomputer connected by a signal bus. The control means 34 includes each key of the operation panel 70 and the stencil making system driving unit 8 for operating the stencil making units 41A and 41B.
3. Plate discharging system drive unit 8 that operates plate discharging units 42A and 42B
4. a paper feed system drive unit 85 for operating the paper feed unit 20, a printing pressure system drive unit 86 for operating the press rollers 9a and 9b to approach and separate,
Paper discharge system drive unit 87 for operating paper discharge device 35, fan 1
8, a paper size detection sensor 46, a paper passage sensor 56 as paper detection means for detecting the printing paper 22 being conveyed, and a plate cylinder speed for detecting the printing rotation speed V1 of the upstream plate cylinder 1A. A plate cylinder speed detecting sensor 48 as a detecting unit and a belt speed detecting sensor 49 as a conveying speed detecting unit for detecting the sheet conveying speed V of the conveying belt 16 are connected to each other. An off signal and a data signal are transmitted and received to control the entire system operation of the apparatus.

The plate cylinder drive motor 63 is connected to the upstream plate cylinders 1A and 1B via power transmission means (not shown).
The upstream plate cylinder 1A and the downstream plate cylinder 1B rotate at the same rotational speed. The plate cylinder speed detection sensor 48
It is a known rotary encoder provided on the output shaft of the plate cylinder drive motor 63, and the print rotation speed V of the upstream plate cylinder 1A is
1 is detected, and the detection result is input to the control means 34 via the pulse detection device 92.

As shown in FIG. 3, the belt speed detecting sensor 49 detects the driving roller 1 around which the transport belt 16 is wound.
5 is a rotary encoder having a disk 49a having a slit fixed to an output shaft 57a of a transport drive motor 57 for driving the disk drive 5, and a photo interrupter 49b provided with a light source and a light receiving element provided between the disks 49a. is there.

The paper passage sensor 56 is a transmission type optical sensor disposed near the driven roller 14 and
2 is on, the print paper 22
Is turned off when the signal passes and is no longer detected.

The output shaft 57a of the transport drive motor 57 has
The drive gear 59a is fixed. The large-diameter gear 59b meshing with the drive gear 59a is fixed to a support shaft 60 on which a pulley 61a is mounted. The pulley 61a is connected to a pulley 61b fixed to the shaft 150 of the driving roller 15 via an endless belt 62. The rotation output of the transport drive motor 57 is transmitted to the shaft 150 by such a transmission mechanism. A stepping motor is used as the transport driving motor 57, and the frequency of the motor is changed by changing the frequency to the motor according to a control signal from the control unit 34 to change the paper transport speed V of the transport belt 16. It is supposed to.

The transport drive motor 57 and the plate cylinder drive motor 6
3 is a control means 3 via driving circuits 89 and 90, respectively.
4 and the driving state thereof, that is, the sheet conveyance speed V of the conveyance belt 16 and the printing rotation speed V1 of the upstream plate cylinder 1A are detected by the belt speed detection sensor 49 and the plate cylinder speed detection sensor 48, respectively. The detection information is input to the control means 34 via the pulse detection devices 91 and 92.
In the control means 34, input information from each sensor and CPU
The result of the calculation at 80 is temporarily stored in the RAM 82, and the information is read out at an appropriate time.

The paper transport speed V of the transport belt 16 is approximately 1.0 to 1.2 times the print rotational speed V1 of the upstream plate cylinder 1A or the print rotational speed V2 of the downstream plate cylinder 1B. It is controlled. Further, in this embodiment, since the upstream plate cylinder 1A and the downstream plate cylinder 1B are rotated by the plate cylinder drive motor 63 which is the same driving means, the printing rotational speed V
The print rotation speed V2 can be detected by detecting the print rotation speed V1 with the plate cylinder speed detection sensor 48.

The ROM 81 stores in advance programs relating to operations such as start, stop, timing, and the like of the apparatus and each drive unit, and necessary data, and also stores a speed control program of the intermediate conveyance device shown in FIG. ing. In the data, the distance between the drum shafts 2a and 2b (hereinafter referred to as "inter-plate cylinder distance L"), which is the distance between the upstream plate cylinder 1A and the downstream plate cylinder 1B shown in FIG. 2
2 size data.

The speed control of the intermediate conveyance device 17 in this embodiment and the state of the printing paper 22 at that time will be described. It is assumed that the processes such as plate discharging, plate making, and plate feeding have already been completed, and The description will focus on speed control.

In the speed control program of the intermediate conveyance device 17 shown in FIG. 4, in step A1, the printing paper 22 is input from the paper size detection sensor 46 and the paper size setting key 47.
Paper size information, and from this information print paper 2
The paper size and orientation of No. 2 are recognized, and the process proceeds to step A2. In step A2, the print start key 73 is turned on / off.
If it is determined that the print start key 73 is turned off and the print start key 73 is pressed, and the print start key 73 is turned on, the process proceeds to step A3. In step A3,
The length of the printing paper 22 in the paper transport direction X is compared with the plate-to-cylinder distance L. If the length of the printing paper 22 is shorter than the plate-to-cylinder distance L, the process proceeds to step A4. If it is longer than the plate cylinder distance L, the process proceeds to step A5.

In step A4, the frequency to the transport drive motor 57 is varied to perform output control (rotation control).
Speed-up control is performed until the sheet conveying speed V of the conveying belt 16 becomes about 1.2 times faster than the printing rotation speed V1 of the upstream plate cylinder 1A. Then, based on a signal from the belt speed detection sensor 49, the sheet conveying speed V of the conveying belt 16 is changed to the upstream plate cylinder 1A.
When the print rotation speed is about 1.2 times (predetermined speed) higher than the print rotation speed V1, the state is maintained.

Here, the state of the printing paper 22 will be described. The shift in the feeding timing of the printing paper 22 with respect to the downstream printing unit E2 is mainly due to the increase or decrease in the amount of ink adhering to the printing paper 22 due to the size and size of the print image printed on the printing paper 22 in the upstream printing unit E1. It is. If the ink amount, the paper transport speed V of the transport belt 16 and the printing rotation speed V1 of the upstream plate cylinder 1A are balanced, as shown in FIG. 5, the printing paper 22 in the upstream printing unit E1 is pressed. When the air passes through the roller 9a, it is peeled off from the upstream plate cylinder 1A by the action of the air jetted from the air knife 7a, is immediately attracted to the transport belt 16 and is transported toward the downstream printing unit E2. However, when this balance is lost, as shown in FIG.
A is not immediately peeled off, but is peeled off by the tip of the air knife 7a, and the tip of the printing paper 22 is loosened above the transport belt 16 as shown by a solid line in FIG. Then, the landing point of the printing paper 22 on the transport belt 16 is different from that in the well-balanced state shown by the broken line in FIG. Since the transport belt 16 has already been driven in the paper transport direction X at this time, the difference between the landing points is that the timing of feeding the sheet to the downstream printing unit E2 is delayed by the interval W. In FIG. 7, reference numeral 22a indicates the leading end of the printing paper 22 with a delay, and reference numeral 22b indicates the leading end of the printing paper 22 conveyed at normal timing.

Therefore, if the paper transport speed V of the transport belt 16 is controlled to be about 1.2 times faster than the printing rotation speed V1 of the upstream plate cylinder 1A as in the present embodiment, the upstream printing unit E1 will not be able to reach 1 The image area on which the color ink image is printed is large, and the leading end 22a of the printing paper 22, which has been delayed from being peeled off from the upstream plate cylinder 1A, is quickly sent to the downstream printing unit E2. At this time, the rear end of the printing paper 22 is still pressed by the press roller 9a and the upstream plate cylinder 1 in the upstream printing section E1.
8, the printing paper 22 whose leading end is slackened is stretched and conveyed, as shown in FIG. For this reason, variations in the transport position of the leading end of the printing paper 22 are eliminated, the timing of sending the paper to the downstream printing unit E2 can be corrected, and image double printing can be eliminated.

The control for increasing the paper conveying speed V is as follows.
In step A6, the rear end of the printing paper 22 is moved to the upstream printing section E1.
Is performed until it is detected by the sheet passage sensor 56.
Then, as shown in FIG. 9, when the trailing edge of the printing paper 22 passes through the upstream printing unit E1 and the paper passage sensor 56 detects the passage of the trailing edge of the printing paper 22 in step A6, the process proceeds to step A7. The frequency to the transport drive motor 57 is again varied to perform output control (rotation control), and the speed is reduced until the paper transport speed V of the transport belt 16 becomes equal to the printing rotational speed V2 of the downstream plate cylinder 1B. . When the paper transport speed V of the transport belt 16 becomes equal to the printing rotation speed V2 of the downstream plate cylinder 1B based on a signal from the belt speed detection sensor 49, the state is maintained and the routine returns.

As shown in FIG. 9, when the length of the printing paper 22 is shorter than the plate-to-cylinder distance L, the leading end of the printing paper 22 remains at the leading end even if the rear end of the printing paper 22 passes through the upstream printing section E1. Since the sheet has not reached the downstream printing section E2, if the sheet transport speed V is kept high, the printing paper 22 is moved to the downstream printing section E2.
, And the print timing from the downstream plate cylinder 1B to the printing paper 22 varies, causing an image shift. However, in this embodiment, as soon as the rear end of the printing paper 22 passes through the upstream printing section E1, the deceleration control for the paper transport speed V is performed.
1 is suppressed from being rapidly conveyed to the downstream printing unit E2, and image double printing and image misalignment can be reduced. Further, since the paper transport speed V controlled to be decelerated is equal to the print rotational speed V2 of the downstream plate cylinder 1B, the paper transport speed V and the print rotational speed V2
The slack of the printing paper 22 in front of the downstream plate cylinder 1B caused by the difference in speed between the printing plate 22 and the downstream printing drum 1B is eliminated, and the image stain generated by the contact of the loose printing paper 22 with the downstream printing drum 1B is eliminated. Can be reduced.

Printing paper 2 conveyed to downstream printing section E2
2 is the second color ink image is printed, the air knife 7
By the action of b, it is peeled off from the downstream plate cylinder 1B, and as shown by a broken line in FIG. 9, is immediately attracted to the transport belt 40 of the paper discharge device 35 and discharged to the paper discharge tray 37 shown in FIG.

On the other hand, the printing paper 2 in the paper transport direction X
If the length of the transport belt 1 is larger than the plate cylinder distance L, in step A5, as in step A4,
6 is the printing rotation speed V of the upstream plate cylinder 1A.
Until the transfer driving motor 57 becomes about 1.2 times as large as 1
(Rotation control) is performed, and the paper transport speed V of the transport belt 16 is about 1.2 times (predetermined speed) the printing rotational speed V1 of the upstream plate cylinder 1A based on a signal from the belt speed detection sensor 49. When the speed is increased, the state is maintained and a predetermined number of prints are performed.

The printing paper 22 longer than the plate cylinder distance L is
Even if the front end reaches the downstream printing section E2, the rear end is located in the upstream printing section E1 and is sandwiched between the upstream plate cylinder 1A and the press roller 9a. After the leading edge of the printing paper 22 reaches
Even if the paper transport speed V is higher than the printing rotation speed V1 of the upstream plate cylinder 1A, the printing paper 22 is pulled by the upstream plate cylinder 1A. Therefore, the printing paper 22 longer than the inter-plate cylinder distance L slides on the transport belt 16, does not slack before the downstream plate cylinder 1B, and does not switch the paper transport speed V from high speed to low speed. good.

As described above, when the printing paper 22 has the plate cylinder distance L
When the printing paper 22 is passing through the upstream printing unit E1, the paper conveyance speed V is set to be higher than the printing rotation speed V1 of the upstream plate cylinder 1A when the printing paper 22 passes through the upstream printing unit E1. By performing switching control to make the paper transport speed V substantially equal to the printing rotation speed V2 of the downstream plate cylinder 1B, the transport delay of the printing paper 22 and the slack on the transport belt 16 and before the downstream printing unit E2 are performed. Can be suppressed.

The printing paper 22 in step A3
Is automatically determined by the control means 34 based on the detection information from the paper size detection sensor 46, so that the paper transport speed V can be automatically switched without setting the paper size one by one, and the operability is good. In addition, paper size setting key 4
7, the size of the printing paper 22 can be manually set when the paper size detection sensor 46 fails, and the reliability of the apparatus can be improved.

FIG. 10 shows another form of the speed control program for the intermediate transfer device 17. The speed control program detects the rotation angle of the upstream plate cylinder 1A, and determines the passing state of the printing paper 22 based on the paper size detected by the paper size detection sensor 46 and the detected angle information. The paper transport speed V is switched, and the speed control program of the intermediate transport device 17 shown in FIG.
It is stored in M81. As an angle detecting means for detecting the rotation angle of the upstream plate cylinder 1A, a plate cylinder speed detection sensor 4
8, the rotation angle of the upstream plate cylinder 1A is detected.

Hereinafter, the speed switching control of the sheet conveying speed V by the speed control program of the intermediate conveying device 17 shown in FIG. 10 will be described, but detailed description of steps having the same contents as those of the program shown in FIG. 4 will be omitted.

In the speed control program of the intermediate conveyance device 17 shown in FIG. 10, the printing paper 22 is input from the paper size detection sensor 46 and the paper size setting key 47 in step B1.
The print start key 73 is pressed in step B2 to turn on the paper size information in step B3.
Proceed to. In step B3, the length of the printing paper 22 in the paper transport direction X is compared with the distance L between plate cylinders. If the length of the printing paper 22 is shorter than the distance L between plate cylinders, the process proceeds to step B4.
In step B4, the rotation angle of the upstream plate cylinder 1A after the print start key 73 is turned on is determined by the plate cylinder speed detection sensor 4.
8 and the output to the transport drive motor 57 is varied (rotation control) in step B5 to control the paper transport speed V of the transport belt 16 to the upstream plate cylinder 1A.
The printing speed is controlled to be about 1.2 times faster than the printing rotation speed V1. When the sheet conveying speed V becomes about 1.2 times (predetermined speed), this state is changed to the printing paper 2 in step B7.
2 until the rotation angle of the upstream plate cylinder 1A becomes equivalent to the rear end passage time.

In step B7, when the plate cylinder rotation angle detected by the plate cylinder speed detection sensor 48 is equivalent to the rear end passage time of the printing paper 22, the rear end of the printing paper 22 is moved to the upstream printing section E1. Step B
In step 8, the frequency to the transport drive motor 57 is changed again to perform output control (rotation control) until the paper transport speed V of the transport belt 16 becomes equal to the printing rotational speed V2 of the downstream plate cylinder 1B. Deceleration control is performed. When the paper transport speed V of the transport belt 16 becomes equal to the printing rotation speed V2 of the downstream plate cylinder 1B based on a signal from the belt speed detection sensor 49, the state is maintained and the routine returns.

On the other hand, if the length of the printing paper 22 is longer than the plate-to-cylinder distance L in step B3, the process proceeds to step B6, and the paper transport speed V of the transport belt 16 is reduced in the same manner as in step B5. Output control (rotation control) of the transport drive motor 57 is performed until the print rotational speed V is about 1.2 times higher than the print rotational speed V1. When the printing speed is about 1.2 times (predetermined speed) higher than the printing rotation speed V1 of the plate cylinder 1A, the state is maintained and the routine returns.

As described above, when the printing paper 22 has the plate cylinder distance L
When the printing paper 22 is passing through the upstream printing unit E1, the paper conveyance speed V is set to be higher than the printing rotation speed V1 of the upstream plate cylinder 1A when the printing paper 22 passes through the upstream printing unit E1. By performing switching control to make the paper transport speed V substantially equal to the printing rotation speed V2 of the downstream plate cylinder 1B, the transport delay of the printing paper 22 and the slack on the transport belt 16 and before the downstream printing unit E2 are performed. Can be suppressed. Further, in the present embodiment, the passage time during which the rear end of the printing paper 22 passes through the upstream printing unit E1, that is, the passage state, is determined using the plate cylinder rotation angle input from the plate cylinder speed detection sensor 48. The paper passage sensor 56 becomes unnecessary, the number of components can be reduced, the cost can be reduced, and the switching failure of the paper conveyance speed V due to the failure of the paper passage sensor 56 is reduced.

FIG. 11 shows another form of the speed control program of the intermediate transfer device 17. The speed control program selects the trailing edge passage time based on the paper size from the passage time setting means set according to the paper size as the trailing edge passage time when the trailing edge of the printing paper 22 passes through the upstream printing section E1. At the same time, the paper transport speed V is switched after the passage of the selected rear end passage time, and the speed control program of the intermediate transport device 17 shown in FIG.
It is stored in the OM 81. The passing time setting means is a map in which the optimum rear end passing time of the printing paper 22 according to the paper size is obtained in advance by experiment or the like and stored, and is stored in the ROM 81 shown in FIG.

The speed switching control of the sheet conveying speed V by the speed control program of the intermediate conveying device 17 shown in FIG. 11 will be described below, but detailed description of the steps having the same contents as those of the speed control program shown in FIG. 4 will be omitted. I do.

According to the speed control program of the intermediate conveyance device 17 shown in FIG. 11, in step C1, the printing paper 22 is input from the paper size detection sensor 46 and the paper size setting key 47.
The print start key 73 is pressed in step C2 to turn on the paper size information in step C3.
Proceed to. In step C3, the length of the printing paper 22 in the paper transport direction X is compared with the distance L between plate cylinders. If the length of the printing paper 22 is shorter than the distance L between plate cylinders, the process proceeds to step C4.
In step C4, a trailing edge passage time corresponding to the sheet size is selected from a map (not shown), and the process proceeds to step C5. The trailing edge passage time selected in step C4 is the time when the trailing edge of the printing paper 22 finishes passing through the upstream printing section E1 after the print start key 73 is turned on.

In step C5, the transport drive motor 5
Output control (rotation control) by changing the frequency to 7,
When the paper transport speed V of the transport belt 16 is controlled to increase by about 1.2 times faster than the printing rotation speed V1 of the upstream plate cylinder 1A, and when the paper transport speed V becomes about 1.2 times faster,
This state is continued until the rear end passage time selected in step C7 is reached. Then, in step C7,
The trailing edge passage time is measured by a timer (not shown), and when the selected trailing edge passage time elapses, it is determined that the trailing edge of the printing paper 22 has passed the upstream printing section E1, and the process proceeds to step C8. And the output control (rotation control) is performed again, and the speed is reduced until the sheet conveyance speed V of the conveyance belt 16 becomes equal to the printing rotation speed V2 of the downstream plate cylinder 1B. When the paper transport speed V of the transport belt 16 becomes equal to the printing rotation speed V2 of the downstream plate cylinder 1B based on a signal from the belt speed detection sensor 49, the state is maintained and the routine returns.

On the other hand, if the length of the printing paper 22 is longer than the plate-to-cylinder distance L in step C3, the process proceeds to step C6, and the paper transport speed V of the transport belt 16 is reduced in the same manner as in step C5. Output control (rotation control) of the transport drive motor 57 is performed until the print rotational speed V is about 1.2 times higher than the print rotational speed V1. When the printing speed is about 1.2 times (predetermined speed) higher than the printing rotation speed V1 of the plate cylinder 1A, the state is maintained and the routine returns.

As described above, when the printing paper 22 has the plate cylinder distance L
When the printing paper 22 is passing through the upstream printing unit E1, the paper conveyance speed V is set to be higher than the printing rotation speed V1 of the upstream plate cylinder 1A when the printing paper 22 passes through the upstream printing unit E1. By performing switching control to make the paper transport speed V substantially equal to the printing rotation speed V2 of the downstream plate cylinder 1B, the transport delay of the printing paper 22 and the slack on the transport belt 16 and before the downstream printing unit E2 are performed. Can be suppressed. Further, in the present embodiment, by storing the trailing edge passage time according to the sheet size in advance as a map, the upstream printing unit E1
Is determined by determining the passage time during which the rear end of the printing paper 22 passes, that is, the passing state, so that the paper passage sensor 56 becomes unnecessary, the number of parts can be reduced, the cost can be reduced, and the paper due to the failure of the paper passage sensor 56 can be reduced. Transfer speed V
Switching failure is reduced.

In each of the above-described embodiments, the frequency supplied to the transport drive motor 57 is changed to switch the paper transport speed V. As a means for switching the paper transport speed V, the transport drive motor 57 shown in FIG. And a shaft 150 of the drive roller 15 are provided with a speed change means composed of a gear train or a group of pulleys. The speed change means is driven according to the sheet size of the printing paper 22 to change the speed ratio, and The paper transport speed V may be switched. In each embodiment, the center distance between the drum shafts 2a and 2b is described as the plate cylinder distance L, but may be the center distance between the upstream printing unit E1 and the downstream printing unit E2.

In each of the embodiments, the upstream plate cylinder 1A and the downstream plate cylinder 1B are rotated by the common plate cylinder drive motor 63, but the upstream plate cylinder 1A and the downstream plate cylinder 1B are individually rotated. You may make it rotate using a drum drive motor. In this case, two plate cylinder speed detection sensors 48 are provided to provide the print rotation speed V of the upstream plate cylinder 1A and the downstream plate cylinder 1B.
1, V2 or the rotation angle may be detected.

In each of the embodiments described above, the stencil printing apparatus capable of multicolor printing is provided with two plate cylinders, the upstream plate cylinder 1A and the downstream plate cylinder 1B, but the number of plate cylinders is two. The four plate cylinders are arranged in parallel from the upstream side to the downstream side in the paper transport direction X, and yellow, magenta, cyan, and black inks are sequentially arranged from the upstream side for each plate cylinder. And a stencil printing apparatus capable of performing full-color printing. Also in this case, the intermediate conveyance devices 21 are respectively arranged between the adjacent plate cylinders, and the paper conveyance speed V of each intermediate conveyance device 21 is set such that printing is performed by the plate cylinder located upstream of each intermediate conveyance device. When the printing paper 22 is passing through the printing section,
When the paper transport speed V is higher than the print rotation speed, and the rear end of the printing paper 22 passes through each upstream printing section, the paper transport speed V is increased by the printing rotation of the plate cylinder located downstream of each intermediate transport device. By performing the speed switching control so as to be substantially equal to the speed, the same effect as in the above-described embodiment can be obtained.

In each of the above-described embodiments, a stencil printing apparatus integrated with a thermosensitive digital stencil has been described as an example. However, the stencil printing apparatus to which the present invention is applied is not limited to such a configuration. Parts having no parts 41A and 41B and the plate discharging parts 42A and 42B, each of which is made by a plate making apparatus provided separately from the main body of the stencil printing apparatus, is wound around each plate cylinder, and is used from each plate cylinder after printing. It goes without saying that the present invention may be applied to a stencil printing machine for peeling off the masters 33a and 33b.

[0067]

According to the first aspect of the present invention, the paper transport speed of the intermediate transport device is controlled in accordance with the state of passage of printing paper shorter than the distance between plate cylinders passing through the upstream printing section. In addition, variations in the transport start position of the printing paper that has passed through the upstream printing section in the intermediate transport device are covered, and in particular, image double printing can be reduced.

According to the second aspect of the present invention, while the printing paper shorter than the plate cylinder distance is passing through the upstream printing section, the leading end of the printing paper is pulled by the intermediate conveyance device, and the paper conveyance delay and the printing are delayed. The slack of the paper is eliminated, the timing of feeding the printing paper printed by the upstream printing unit to the downstream printing unit is appropriately adjusted, and the image double printing and the print image deviation can be reduced. After the printing paper has passed through the upstream printing section, the paper transport speed is reduced so as to be substantially equal to the printing rotation speed of the downstream plate cylinder, so that the printing paper does not reach the downstream printing section quickly. As a result, the shift of the transport timing to the downstream printing section is suppressed, and the speed difference between the printing rotation speed of the downstream plate cylinder and the paper transport speed of the intermediate transport device disappears. The slack of the printing paper in the foreground is suppressed, and the stain on the printing paper can be reduced.

According to the third aspect of the present invention, the paper transport speed of the intermediate transport device can be switched during the printing operation, and the response of control is improved.

According to the fourth aspect of the present invention, the time when the printing paper passes through the upstream printing section can be known from the paper size and the rotation angle of the plate cylinder, and the printing paper printed by the upstream printing cylinder can be known. The timing of feeding the image to the downstream printing section is appropriately adjusted, and image double printing and print image deviation are extremely reduced.

According to the fifth aspect of the present invention, in the stencil printing apparatus according to the first or second aspect, the passage time of the printing paper passing through the upstream printing section is determined based on the paper size set before the start of printing. Since it is set in advance before printing, it is not necessary to detect the passing state of the printing paper during printing, and the paper detection means for detecting the printing paper being conveyed becomes unnecessary, and the paper detection is performed while reducing the number of parts. It is possible to reduce the speed control switching operation failure of the sheet conveyance speed due to the malfunction of the means.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a stencil printing apparatus according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a switching unit according to the present invention and a configuration of each unit connected to the switching unit.

FIG. 3 is a partially enlarged perspective view illustrating a configuration of a sheet transport speed detecting unit and a configuration of an intermediate transport device.

FIG. 4 is a flowchart illustrating one form of speed control of the intermediate conveyance device.

FIG. 5 is a side view showing an operation of the stencil printing apparatus and a state in which printing paper is peeled off from an upstream printing drum in an appropriate state.

FIG. 6 is a side view showing the operation of the stencil printing apparatus and a state in which the timing of peeling of the printing paper from the upstream plate cylinder is delayed.

FIG. 7 is an enlarged view illustrating a difference in a landing point of a printing sheet on an intermediate conveyance device.

FIG. 8 is a side view illustrating a state in which printing paper is transported by the intermediate transport device.

FIG. 9 is a side view showing a state in which the printing paper is conveyed to the downstream printing section and a state in which the printing paper passes through the downstream printing section.

FIG. 10 is a flowchart illustrating another form of speed control of the intermediate conveyance device.

FIG. 11 is a flowchart illustrating another form of speed control of the intermediate conveyance device.

[Explanation of symbols]

1A upstream plate cylinder 1B downstream plate cylinder 17 intermediate transport device 22 printing paper 34 switching means (control means) 46 paper size detection means 48 angle detection means (plate cylinder speed detection means) 56 paper detection means E1 upstream printing section E2 Downstream printing section L Distance between upstream plate cylinder and downstream plate cylinder V Paper transport speed V1 Printing rotational speed of upstream plate cylinder V2 Printing rotational speed of downstream plate cylinder X Paper transport direction

Claims (5)

[Claims] An image forming apparatus is provided between a plate cylinder located on an upstream side in a sheet conveying direction and a plate cylinder located on a downstream side in a sheet conveying direction,
In a stencil printing machine provided with an intermediate conveyance device for conveying printing paper from an upstream printing section where printing is performed using an upstream plate cylinder to a downstream printing section where printing is performed using a downstream plate cylinder, When the printing paper passing through the side printing unit is shorter than the interval between the upstream plate cylinder and the downstream printing cylinder, there is provided switching means for switching the paper transport speed of the intermediate transport device according to the passing state of the printing paper. A stencil printing machine characterized by the following. 2. The stencil printing apparatus according to claim 1, wherein said switching means sets said paper transport speed higher than a printing rotation speed of an upstream printing drum when said printing paper is passing through an upstream printing unit. A stencil printing apparatus, wherein after the printing paper has passed through the upstream printing section, switching control is performed so that the paper conveyance speed is substantially equal to the printing rotation speed of the downstream printing drum. 3. A stencil printing apparatus according to claim 1, further comprising a paper detecting means for detecting a printing paper being conveyed, wherein said switching means is configured to output said printing paper based on a detection signal from said paper detecting means. A stencil printing apparatus characterized in that the sheet conveying speed is switched by judging a passing state of the sheet. 4. A stencil printing apparatus according to claim 1, wherein the paper size detecting means for detecting the size of the printing paper and the angle detecting means for detecting the rotation angle of the upstream printing drum or the downstream printing drum. The switching unit determines the passing state of the printing paper based on the paper size detected by the paper size detecting unit and the angle information detected by the angle detecting unit, and switches the paper transport speed. A stencil printing apparatus characterized by the above-mentioned. 5. A stencil printing apparatus as claimed in claim 1, wherein said trailing edge of said printing paper passes through an upstream printing section, and said trailing edge passing time is set according to the size of said paper. Paper size detection means for detecting the paper size of the paper, the switching means based on the paper size detected by the paper size detection means, the rear end passage time according to the paper size from the passage time setting means And a stencil printing apparatus that switches the paper transport speed after the selected rear end passage time elapses.