CN113978108A - Multicolor web printing press and printing method thereof - Google Patents

Abstract

The invention discloses a multicolor web printing machine, which comprises four pairs of color group units which are sequentially arranged along the advancing direction of web at intervals, wherein the rear ends and the front ends of the four pairs of color group units are provided with a paper feeding tension device and a paper discharging tension device in a one-to-one correspondence manner; each pair of color group units consists of two printing devices which have the same color and are arranged in tandem at intervals; each printing device comprises a first plate cylinder, a second plate cylinder, a first rubber cylinder, a second rubber cylinder, two automatic plate changing devices and two automatic cleaning devices. The first and second plate cylinders are fixedly mounted; the first rubber cylinder and the second rubber cylinder are correspondingly connected with the first clutch machine and the second clutch machine one by one and are in clutch pressure with the first printing plate cylinder and the second printing plate cylinder; the two automatic plate changing devices are close to the first plate cylinder and the second plate cylinder in a one-to-one correspondence manner when the first rubber cylinder and the second rubber cylinder are separated from the press cylinder, and the two automatic cleaning devices are close to the first rubber cylinder and the second rubber cylinder in a one-to-one correspondence manner. The invention also discloses a printing method capable of switching printing varieties without stopping.

Description

Multicolor web printing press and printing method thereof

Technical Field

The invention relates to a multicolor web printing press and a printing method thereof.

Background

The traditional web printing machine generally comprises four printing devices, wherein each printing device is of one color and comprises a first rubber cylinder, a second rubber cylinder, a first printing plate cylinder and a second printing plate cylinder, a printing gap is formed between the first rubber cylinder and the second rubber cylinder, a web can movably penetrate through the printing gap, the first printing plate cylinder and the second printing plate cylinder can be separated from the first rubber cylinder and the second rubber cylinder in a one-to-one correspondence mode, the central position of the first rubber cylinder is unchanged, the central position of the second rubber cylinder is changed when the second rubber cylinder is separated from the first rubber cylinder, the paper stops moving when the first rubber cylinder and the second rubber cylinder are separated from the first rubber cylinder and the second rubber cylinder, and the distance between the first rubber cylinder and the second rubber cylinder is about 1mm when the first rubber cylinder and the second rubber cylinder are separated from the first rubber cylinder and the second rubber cylinder, so that the paper cannot rub against the first rubber cylinder and the second rubber cylinder, and normal printing is affected. Such a printing press operates all the printing units together to perform printing during printing. As the times grow, the production requirements of printing plants are changing today. In the past, the demand of single printing products is large in a period of time, and the types of the printing products are few. The demand of single printing products is reduced, and the types of the printing products are increased. Due to such a requirement, the conventional printing machine needs to be stopped after printing one kind of printed matter, then the rubber cylinder is cleaned, the printing plate on the printing plate cylinder is replaced, and then the printing machine is started up and debugged, so that the second kind of printed matter can be printed again. Typically this process takes a half hour or more. The more products that need to be printed, the more time is spent.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a multicolor web printing machine and a printing method thereof, which can realize the switching of printing varieties under the state of no stop and improve the production efficiency.

One technical scheme for achieving the purpose of the invention is as follows: a multicolor web printing press comprising four pairs of color group units, wherein,

the four color group units are sequentially arranged at intervals along the advancing direction of the roll paper, a paper feeding tension device is arranged at the rear end of each color group unit, and a paper discharging tension device is arranged at the front end of each color group unit;

each pair of color group units consists of two printing devices with the same color, the two printing devices are arranged in tandem at intervals, and the gap is the same as that between the four pairs of color group units;

each printing device comprises a first plate cylinder, a first rubber cylinder, a second plate cylinder, a second rubber cylinder, two automatic plate changing devices and two automatic cleaning devices, wherein the first rubber cylinder is in clutch pressure with the first plate cylinder;

the first plate cylinder and the second plate cylinder fixedly span on two side wall plates of the printing machine;

the first rubber cylinder and the second rubber cylinder are connected with the first clutch mechanism and the second clutch mechanism in a one-to-one correspondence mode, so that a printing gap is formed between the first rubber cylinder and the second rubber cylinder when the first rubber cylinder and the first plate cylinder are pressed together and between the second rubber cylinder and the second plate cylinder when the second rubber cylinder and the second plate cylinder are pressed together, and the roll paper can movably pass through the printing gap; the first rubber cylinder and the second rubber cylinder are also pressed away from the first printing plate cylinder when pressed away; the second rubber cylinder and the first rubber cylinder are also pressed against the second printing plate cylinder when pressed against each other, and the gap between the first rubber cylinder and the second rubber cylinder is more than 2mm when pressed against each other;

an automatic plate changing device is close to the first plate cylinder when the first rubber cylinder is separated from the first plate cylinder through a pushing mechanism; the other automatic plate changing device is close to the second plate cylinder when the second rubber cylinder is separated from the second plate cylinder through the other pushing mechanism;

an automatic cleaning device is against the first rubber cylinder when the first rubber cylinder and the first printing plate cylinder are separated and pressed through a moving mechanism; and the other automatic cleaning device leans against the second rubber cylinder when the second rubber cylinder is separated from and pressed against the second printing plate cylinder through the other moving mechanism.

The above multicolor web printing press wherein a middle tension device is provided in the middle of the four pairs of color group units.

The multicolor web printing press described above, wherein each printing unit further includes a first water roller and a first ink roller that are clutched to press the first plate cylinder and a second water roller and a second ink roller that are clutched to press the second plate cylinder.

The other technical scheme for realizing the purpose of the invention is as follows: a printing method of a multicolor web printing machine based on the invention comprises the following printing modes:

the switching printing mode of two kinds of four-color printing products comprises the following steps:

step one, mounting printing plates of first four-color prints in a first plate cylinder and a second plate cylinder of a former printing device in a four-color pair unit, and mounting printing plates of second four-color prints in a first plate cylinder and a second plate cylinder of a latter printing device in the four-color pair unit;

step two, the first rubber cylinders and the second rubber cylinders in the previous printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the first rubber cylinders and the second rubber cylinders in the next printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the pressing gap is more than 2mm, and the web movably penetrates through the printing gap of the previous printing device in the four color pair unit to print the first four-color printing product;

step three, during switching, the first rubber cylinders and the second rubber cylinders in the former printing device in the four pairs of color group units are correspondingly disengaged and pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the disengagement and pressing gaps are more than 2mm, at the moment, the tension of the web is kept through the paper feeding tension device, the middle tension device and the paper discharging tension device, then the first rubber cylinders and the second rubber cylinders in the latter printing device in the four pairs of color group units are correspondingly engaged and pressed through the first clutch mechanisms and the second clutch mechanisms one by one, and the web movably penetrates through the printing gaps of the latter printing device in the four pairs of color group units to print a second four-color printed product;

the switching printing mode of three kinds of four-color printed products comprises the following steps:

step one, mounting printing plates of first four-color prints in a first plate cylinder and a second plate cylinder of a former printing device in a four-color pair unit, and mounting printing plates of second four-color prints in a first plate cylinder and a second plate cylinder of a latter printing device in the four-color pair unit;

step two, the first rubber cylinders and the second rubber cylinders in the previous printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the first rubber cylinders and the second rubber cylinders in the next printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the pressing gap is more than 2mm, and the web movably penetrates through the printing gap of the previous printing device in the four color pair unit to print the first four-color printing product;

step three, the first rubber cylinders and the second rubber cylinders in the former printing device in the four color pair unit are correspondingly disengaged through the first clutch mechanisms and the second clutch mechanisms one by one, and the disengagement gap is more than 2mm, at the moment, the tension of the web is kept through the paper feeding tension device, the middle tension device and the paper discharging tension device, then the first rubber cylinders and the second rubber cylinders in the latter printing device in the four color pair unit are correspondingly engaged through the first clutch mechanisms and the second clutch mechanisms one by one, and the web movably penetrates through the printing gap of the latter printing device in the four color pair unit to print the second four-color printed product; meanwhile, two automatic cleaning devices in the previous printing device in the four pairs of color group units respectively lean against the first rubber roller and the second rubber roller in a one-to-one correspondence manner through a moving mechanism for cleaning; the first water roller and the first ink roller in the previous printing device in the four-couple color group unit are both disengaged from the first plate cylinder, and the second water roller and the second ink roller are both disengaged from the second plate cylinder; two automatic plate changing devices in the previous printing device in the four-pair color group unit respectively approach the first plate cylinder and the second plate cylinder one by one through a pushing mechanism to change the printing plates of the third four-color printing product;

step four, when switching is to be carried out, a first water roller and a first ink roller in a previous printing device in the four color pair unit are firstly closed with a first printing plate cylinder to carry out dampening solution and ink blending on the first printing plate cylinder, and a second water roller and a second ink roller are firstly closed with a second printing plate cylinder to carry out dampening solution and ink blending on the second printing plate cylinder;

step five, during switching, the first rubber cylinders and the second rubber cylinders in the next printing device in the four pairs of color group units are correspondingly disengaged and pressed through the first clutch mechanisms and the second clutch machines one by one, the disengagement gap is more than 2mm, the tension of the web is kept through the paper feeding tension device, the middle tension device and the paper discharging tension device at the moment, then the first rubber cylinders and the second rubber cylinders in the previous printing device in the four pairs of color group units are correspondingly engaged and pressed through the first clutch mechanisms and the second clutch machines one by one, and the web movably penetrates through the printing gap of the previous printing device in the four pairs of color group units to print a third four-color printed product;

by analogy, the switching printing mode of at least two single-color prints, the switching printing mode of at least two double-color prints, the switching printing mode of at least two three-color prints and the switching printing mode of at least two four-color prints can be realized.

The multicolor web printing machine and the printing method thereof have the following characteristics: the printing process can be kept without stopping the machine when the printing variety is changed, the preparation work of the next printing product can be done when the previous printing product is printed, and the printing can be switched to another printing product for printing immediately after the printing of one printing product is finished, so that the preparation time for switching the printing products is effectively saved.

Drawings

FIG. 1 is a schematic block diagram of a multicolor web printing press of the present invention;

FIG. 2 is a schematic view of the structure (nip) of each printing unit in the multicolor web printing press of the present invention;

FIG. 3 is a schematic view of the structure of each printing unit in the multicolor web printing press of the present invention (plate change state and cleaning state when off-impression);

fig. 4 is a schematic view of the structure of each printing unit in the multicolor web printing press of the present invention (on-press inking state).

Detailed Description

The invention will be further explained with reference to the drawings.

Referring to fig. 1 to 4, the multicolor web printing press of the present invention includes four pairs of color group units 10, 20, 30, 40, the four pairs of color group units 10, 20, 30, 40 being sequentially arranged at regular intervals along the advancing direction of a web 50; each pair of colour group units consists of two printing devices of the same colour, arranged at a distance in tandem and at the same pitch as the four pairs of colour group units 10, 20, 30, 40.

A paper feed tension device 11 is provided at the rear end (paper feed side) of the four color pair unit 10, 20, 30, 40, and a middle tension device 12 is provided in the middle of the four color pair unit 10, 20, 30, 40, that is, the middle tension device 12 is provided between the second color pair unit 20 and the third color pair unit 30; a paper discharge tension device 13 is provided at the leading end (paper discharge side) of the four color pair units 10, 20, 30, 40.

The four pairs of color group units 10, 20, 30, 40 of the present embodiment are respectively two black printing devices 10a, 10b, two blue printing devices 20a, 20b, two red printing devices 30a, 30b, and two yellow printing devices 40a, 40b in color, and the two black printing devices 10a, 10b, the two blue printing devices 20a, 20b, the two red printing devices 30a, 30b, and the two yellow printing devices 40a, 40b are arranged from the rear to the front.

The eight printing devices are identical in structure, and each printing device comprises a first plate cylinder 21, a first rubber cylinder 22, a second plate cylinder 23 and a second rubber cylinder 24, wherein the first rubber cylinder 22 is in clutch pressure with the first plate cylinder 21, the second rubber cylinder 23 is in clutch pressure with the second plate cylinder 23, a first water roller 211 and a first ink roller 212 are in clutch pressure with the first plate cylinder 21, a second water roller 231 and a second ink roller 232 are in clutch pressure with the second plate cylinder 23, two automatic plate changing devices 25 and two automatic cleaning devices 26; wherein the content of the first and second substances,

the first plate cylinder 21 and the second plate cylinder 23 fixedly straddle the two side wall plates of the printing press;

the first rubber cylinder 22 and the second rubber cylinder 24 are connected with the first clutch mechanism 220 and the second clutch mechanism 240 in a one-to-one correspondence manner, so that the first rubber cylinder 22 and the first plate cylinder 21 form a printing gap h1 when being pressed together and the first rubber cylinder 2 and the second rubber cylinder 24 form a printing gap h1 when the second rubber cylinder 23 and the second plate cylinder 23 are pressed together, and the web 100 movably passes through the printing gap h1 (see fig. 2); the first rubber cylinder 22 and the second rubber cylinder 24 are also pressed away from the first plate cylinder 21 when pressed away; the second rubber cylinder 24 and the first rubber cylinder 22 are also separated from the second plate cylinder 23 when separated, and the gap h2 between the first rubber cylinder 22 and the second rubber cylinder 24 when separated is more than 2mm (see fig. 3);

an automatic plate changing device 25 approaches the first plate cylinder 21 by a pushing mechanism 250 when the first blanket cylinder 22 is disengaged from the first plate cylinder 21; the other automatic plate changing device 25 approaches the second plate cylinder 23 by another pushing mechanism 250 when the second blanket cylinder 24 is disengaged from the second plate cylinder 23;

an automatic cleaning device 26 is attached to the first blanket cylinder 22 by a moving mechanism 260 when the first blanket cylinder 22 is disengaged from the first plate cylinder 21; the other automatic cleaning device 26 is pressed against the second blanket cylinder 24 by the other moving mechanism 260 when the second blanket cylinder 24 is disengaged from the second plate cylinder 23.

The multicolor web printing press of the present invention has the following features:

1) four pairs of color group units are adopted, each pair of color group units consists of two printing devices with the same color, the two printing devices are arranged in tandem at intervals, and the distance between the two printing devices is the same as that between the four pairs of color group units; if the roll paper is not arranged at intervals, stress points of the roll paper are distributed unevenly, and the roll paper with overlarge stress point distance is easy to vibrate; the use of printing units at intervals best ensures web stability.

2) Because the web paper of the multicolor web printing machine of the invention always keeps moving at a high speed in the whole printing process, the situation that the web tension disappears can be generated when the subsequent cylinders are not pressed together because the printing cylinders are pressed away in the switching process of the printing modes.

3) Because the web in high-speed movement can vibrate, if the separation distance of the printing cylinder is not large enough, the vibrating web can rub against the printing cylinder, and normal printing is influenced. Therefore, the invention increases the pressure-separating distance of the printing cylinder, ensures that the roll paper can pass through smoothly and does not influence normal printing.

4) After the two rubber rollers are separated, the automatic cleaning device is moved onto the rubber rollers by utilizing a moving mechanism to clean the rubber rollers. Meanwhile, a pushing mechanism device is used for enabling the automatic plate changing device to be close to the upper plate cylinders to change the printing plates on the two plate cylinders.

5) The rubber roller is cleaned, and after the printing plate is replaced, the preparation work before printing is basically finished. After the printing of the previous type of printing product is finished, when the printing of the previous type of printing product is finished and the printing is ready to be switched, the water roller and the ink roller are closed, because the rubber cylinder and the plate cylinder are still in a pressure-separated state at the moment, and because the central position of the plate cylinder is not changed in the pressure-separated state, the water roller and the ink roller can be close to the plate cylinder as in the printing state. After the water and ink rollers are placed against the plate cylinder, the dampening solution and ink are conditioned on the plate cylinder, which is a short time since the plate cylinder is running at high speed.

The printing method of the multicolor web printing machine of the invention is based on the multicolor web printing machine of the invention and comprises the following printing modes:

switching printing modes of two four-color prints (see fig. 1 and 4), comprising the steps of:

firstly, printing plates of a first four-color printing product are arranged in a first plate cylinder 21 and a second plate cylinder 23 of a former printing device 10a, 20a, 30a and 40a of four color pair units 10, 20, 30 and 40, and printing plates of a second four-color printing product are arranged in a first plate cylinder 21 and a second plate cylinder 23 of a latter printing device 10b, 20b, 30b and 40b of four color pair units 10, 20, 30 and 40;

secondly, the first rubber cylinders 22 and the second rubber cylinders 24 in the previous printing devices 10a, 20a, 30a and 40a in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240 one by one, and the first rubber cylinders 22 and the second rubber cylinders 24 in the next printing devices 10b, 20b, 30b and 40b in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240 one by one, and the pressing-off gap h2 is more than 2mm, so that the web 50 movably passes through the printing gaps h1 of the previous printing devices 10a, 20a, 30a and 40a in the four color pair units 10, 20, 30 and 40 to print the first four color prints;

step three, when switching, the first rubber cylinders 22 and the second rubber cylinders 24 in the previous printing devices 10a, 20a, 30a, 40a in the four pairs of color group units 10, 20, 30, 40 are correspondingly released through the first clutch mechanisms 220 and the second clutch mechanisms 240 one by one, and the releasing gap h2 is more than 2mm, at this moment, the tension of the roll paper 50 is maintained through the paper feeding tension device 11, the middle tension device 12 and the paper discharging tension device 13, then the first rubber cylinders 22 and the second rubber cylinders 24 in the latter printing devices 10b, 20b, 30b and 40b in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240, so that the web 50 movably passes through the printing gaps h1 of the latter printing devices 10b, 20b, 30b and 40b in the four color pair units 10, 20, 30 and 40 to print the second four-color printing;

the switching printing mode of three kinds of four-color printed products comprises the following steps:

firstly, printing plates of a first four-color printing product are arranged in a first plate cylinder 21 and a second plate cylinder 23 of a former printing device 10a, 20a, 30a and 40a of four color pair units 10, 20, 30 and 40, and printing plates of a second four-color printing product are arranged in a first plate cylinder 21 and a second plate cylinder 23 of a latter printing device 10b, 20b, 30b and 40b of four color pair units 10, 20, 30 and 40;

secondly, the first rubber cylinders 2 and the second rubber cylinders 24 in the previous printing devices 10a, 20a, 30a and 40a in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240 one by one, the first rubber cylinders 22 and the second rubber cylinders 24 in the next printing devices 10b, 20b, 30b and 40b in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240 one by one, the pressing-off gap h2 is more than 2mm, and the web 50 movably passes through the printing gaps h1 of the previous printing devices 10a, 20a, 30a and 40a in the four color pair units 10, 20, 30 and 40 to print the first four color prints;

step three, the first rubber cylinders 22 and the second rubber cylinders 24 in the previous printing devices 10a, 20a, 30a, 40a in the four pairs of color group units 10, 20, 30, 40 are correspondingly released and pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240 one by one, and the releasing and pressing gaps are more than 2mm, at this moment, the tension of the roll paper 50 is maintained by the paper feeding tension device 11, the middle tension device 12 and the paper discharging tension device 13, then the first rubber cylinders 22 and the second rubber cylinders 24 in the latter printing devices 10b, 20b, 30b and 40b in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240, so that the web 50 movably passes through the printing gaps h1 of the latter printing devices 10b, 20b, 30b and 40b in the four color pair units 10, 20, 30 and 40 to print the second four-color printing; meanwhile, the two automatic cleaning devices 26 in the previous printing devices 10a, 20a, 30a, 40a in the four pairs of color group units 10, 20, 30, 40 are respectively leaned against the first blanket cylinder 22 and the second blanket cylinder 24 to clean the blanket in a one-to-one correspondence manner by a moving mechanism 260; the first water roller 211 and the first ink roller 212 in the preceding printing couple 10a, 20a, 30a, 40a in the four couple unit 10, 20, 30, 40 are both decoupled from the first plate cylinder 21, and the second water roller 231 and the second ink roller 232 are both decoupled from the second plate cylinder 23; the two automatic plate changing devices 25 in the previous printing devices 10a, 20a, 30a, 40a in the four-pair color group units 10, 20, 30, 40 are respectively close to the first plate cylinder 21 and the second plate cylinder 23 through a pushing mechanism 250 to change the printing plates of the third four-color printing products in a one-to-one correspondence manner;

step four, when switching is to be performed, the first water roller 211 and the first ink roller 212 in the previous printing device 10b, 20b, 30b, 40b in the four pairs of color combination units 10, 20, 30, 40 are firstly closed with the first plate cylinder 21 to perform dampening solution and ink blending on the first plate cylinder 21, and the second water roller 231 and the second ink roller 232 are firstly closed with the second plate cylinder 23 to perform dampening solution and ink blending on the second plate cylinder 23;

step five, when switching, the first rubber cylinders 22 and the second rubber cylinders 24 in the next printing devices 10b, 20b, 30b, 40b in the four pairs of color group units 10, 20, 30, 40 are pressed off one by the first clutch mechanisms 220 and the second clutch mechanisms 240, and the pressing off clearance h2 is more than 2mm, at this moment, the tension of the roll paper 50 is maintained by the paper feeding tension device 11, the middle tension device 12 and the paper discharging tension device 13, then the first rubber cylinders 22 and the second rubber cylinders 24 in the previous printing devices 10a, 20a, 30a and 40a in the four color pair units 10, 20, 30 and 40 are correspondingly pressed by the first clutch mechanisms 220 and the second clutch mechanisms 240, and the web 50 movably passes through the printing gaps h1 of the previous printing devices 10a, 20a, 30a and 40ab in the four color pair units 10, 20, 30 and 40 to print a third four-color printing product;

by analogy, the switching printing mode of at least two single-color prints, the switching printing mode of at least two double-color prints, the switching printing mode of at least two three-color prints and the switching printing mode of at least two four-color prints can be realized.

The above embodiments are provided only for illustrating the present invention and not for limiting the present invention, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and therefore all equivalent technical solutions should also fall within the scope of the present invention, and should be defined by the claims.

Claims (4)

1. A multicolor web printing press comprising four pairs of color group units, characterized in that,

the four color group units are sequentially arranged at intervals along the advancing direction of the roll paper, a paper feeding tension device is arranged at the rear end of each color group unit, and a paper discharging tension device is arranged at the front end of each color group unit;

each pair of color group units consists of two printing devices with the same color, the two printing devices are arranged in tandem at intervals, and the gap is the same as that between the four pairs of color group units;

each printing device comprises a first plate cylinder, a first rubber cylinder, a second plate cylinder, a second rubber cylinder, two automatic plate changing devices and two automatic cleaning devices, wherein the first rubber cylinder is in clutch pressure with the first plate cylinder;

the first plate cylinder and the second plate cylinder fixedly span on two side wall plates of the printing machine;

the first rubber cylinder and the second rubber cylinder are connected with the first clutch mechanism and the second clutch mechanism in a one-to-one correspondence mode, so that a printing gap is formed between the first rubber cylinder and the second rubber cylinder when the first rubber cylinder and the first plate cylinder are pressed together and between the second rubber cylinder and the second plate cylinder when the second rubber cylinder and the second plate cylinder are pressed together, and the roll paper can movably pass through the printing gap; the first rubber cylinder and the second rubber cylinder are also pressed away from the first printing plate cylinder when pressed away; the second rubber cylinder and the first rubber cylinder are also pressed against the second printing plate cylinder when pressed against each other, and the gap between the first rubber cylinder and the second rubber cylinder is more than 2mm when pressed against each other;

an automatic plate changing device is close to the first plate cylinder when the first rubber cylinder is separated from the first plate cylinder through a pushing mechanism; the other automatic plate changing device is close to the second plate cylinder when the second rubber cylinder is separated from the second plate cylinder through the other pushing mechanism;

an automatic cleaning device is against the first rubber cylinder when the first rubber cylinder and the first printing plate cylinder are separated and pressed through a moving mechanism; and the other automatic cleaning device leans against the second rubber cylinder when the second rubber cylinder is separated from and pressed against the second printing plate cylinder through the other moving mechanism.

2. The multicolor web printing press according to claim 1, wherein a middle tension device is provided in the middle of the four pairs of color group units.

3. The multicolor web printing press according to claim 1, wherein each printing unit further comprises a first water roller and a first ink roller clutched to the first plate cylinder and a second water roller and a second ink roller clutched to the second plate cylinder.

4. A printing method of a multicolor web printing press based on the multicolor web printing press according to claim 1, characterized in that the printing method comprises the following printing modes:

the switching printing mode of two kinds of four-color printing products comprises the following steps:

step one, mounting printing plates of first four-color prints in a first plate cylinder and a second plate cylinder of a former printing device in a four-color pair unit, and mounting printing plates of second four-color prints in a first plate cylinder and a second plate cylinder of a latter printing device in the four-color pair unit;

step two, the first rubber cylinders and the second rubber cylinders in the previous printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the first rubber cylinders and the second rubber cylinders in the next printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the pressing gap is more than 2mm, and the web movably penetrates through the printing gap of the previous printing device in the four color pair unit to print the first four-color printing product;

step three, during switching, the first rubber cylinders and the second rubber cylinders in the former printing device in the four pairs of color group units are correspondingly disengaged and pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the disengagement and pressing gaps are more than 2mm, at the moment, the tension of the web is kept through the paper feeding tension device, the middle tension device and the paper discharging tension device, then the first rubber cylinders and the second rubber cylinders in the latter printing device in the four pairs of color group units are correspondingly engaged and pressed through the first clutch mechanisms and the second clutch mechanisms one by one, and the web movably penetrates through the printing gaps of the latter printing device in the four pairs of color group units to print a second four-color printed product;

the switching printing mode of three kinds of four-color printed products comprises the following steps:

step one, mounting printing plates of first four-color prints in a first plate cylinder and a second plate cylinder of a former printing device in a four-color pair unit, and mounting printing plates of second four-color prints in a first plate cylinder and a second plate cylinder of a latter printing device in the four-color pair unit;

step two, the first rubber cylinders and the second rubber cylinders in the previous printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the first rubber cylinders and the second rubber cylinders in the next printing device in the four color pair unit are correspondingly pressed through the first clutch mechanisms and the second clutch mechanisms one by one, the pressing gap is more than 2mm, and the web movably penetrates through the printing gap of the previous printing device in the four color pair unit to print the first four-color printing product;

step three, the first rubber cylinders and the second rubber cylinders in the former printing device in the four color pair unit are correspondingly disengaged through the first clutch mechanisms and the second clutch mechanisms one by one, and the disengagement gap is more than 2mm, at the moment, the tension of the web is kept through the paper feeding tension device, the middle tension device and the paper discharging tension device, then the first rubber cylinders and the second rubber cylinders in the latter printing device in the four color pair unit are correspondingly engaged through the first clutch mechanisms and the second clutch mechanisms one by one, and the web movably penetrates through the printing gap of the latter printing device in the four color pair unit to print the second four-color printed product; meanwhile, two automatic cleaning devices in the previous printing device in the four pairs of color group units respectively lean against the first rubber roller and the second rubber roller in a one-to-one correspondence manner through a moving mechanism for cleaning; the first water roller and the first ink roller in the previous printing device in the four-couple color group unit are both disengaged from the first plate cylinder, and the second water roller and the second ink roller are both disengaged from the second plate cylinder; two automatic plate changing devices in the previous printing device in the four-pair color group unit respectively approach the first plate cylinder and the second plate cylinder one by one through a pushing mechanism to change the printing plates of the third four-color printing product;

step four, when switching is to be carried out, a first water roller and a first ink roller in a previous printing device in the four color pair unit are firstly closed with a first printing plate cylinder to carry out dampening solution and ink blending on the first printing plate cylinder, and a second water roller and a second ink roller are firstly closed with a second printing plate cylinder to carry out dampening solution and ink blending on the second printing plate cylinder;

step five, during switching, the first rubber cylinders and the second rubber cylinders in the next printing device in the four pairs of color group units are correspondingly disengaged and pressed through the first clutch mechanisms and the second clutch machines one by one, the disengagement gap is more than 2mm, the tension of the web is kept through the paper feeding tension device, the middle tension device and the paper discharging tension device at the moment, then the first rubber cylinders and the second rubber cylinders in the previous printing device in the four pairs of color group units are correspondingly engaged and pressed through the first clutch mechanisms and the second clutch machines one by one, and the web movably penetrates through the printing gap of the previous printing device in the four pairs of color group units to print a third four-color printed product;

by analogy, the switching printing mode of at least two single-color prints, the switching printing mode of at least two double-color prints, the switching printing mode of at least two three-color prints and the switching printing mode of at least two four-color prints can be realized.

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