JPS6391251A - Printing method and device - Google Patents

Abstract

PURPOSE:To print a pattern of varying repeat length on a running web without changing the diameter of a plate cylinder by comparing the distance between a set repeat length and a register mark and controlling the rotation of the plate cylinder based on an error signal of the distance. CONSTITUTION:A register mark 1 appears every one cycle on a running web 10 which is printed via a printing unit 50. This cycle is measured as a distance of the register mark by a distance measuring means 36, and a signal of the measurement value is transmitted to an arithmetic means 64. In the meantime, a signal of repeat length and a signal of distance which are set to a setting means 66 are compared and processed by the arithmetic means 64 to obtain an error signal. This error signal is sent to a control means 60, thereby adjusting the rotational speed of an electric motor 62 and obtaining a print of proper repeat length. Thus it is possible to print a pattern of varying repeat length on the running web without changing the diameter of the plate cylinder 42 substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a printing method and apparatus, and more particularly to a method and apparatus for printing patterns of different sizes on a running web.

(Prior Art) Various types of devices have been known that print on a moving web, and representative examples include rotary intaglio printing presses, lithographic printing presses, and
There are offset rotary printing presses and letterpress rotary printing presses.

However, when printing with different repeat lengths (one cycle length) using these printing machines, it was necessary to change the effective diameter of the plate cylinder at the same time as changing the printing plate. Therefore, plate cylinders of various diameters had to be provided. Particularly in the case of gravure printing, the printing pattern is etched directly onto the plate cylinder, so the entire plate cylinder must be replaced, and a large number of plate cylinders must be stored for each plate even if they have the same diameter. (There was a problem.

Therefore, due to the complexity of plate cylinder exchange and the long setup time, it is practically impossible to perform rotary printing of a desired repeat length at the same time, for example, in a line that manufactures corrugated board, which is a type of web. Therefore, it has become common practice to perform sheet-fed printing after cutting into corrugated cardboard sheets, and to perform off-line preprinting on corrugated board liners, although in a small number of cases.

It is known to print special patterns in-line with corrugated pole manufacturing (e.g. British Patent No. 125609).
(See Specification No. 7). This special pattern is a continuous pattern with no limited printing length, so it can be made by cutting the cardboard sheet from any point. Conversely, a pattern with arbitrary repeat length cannot be printed.

Note that the term "in-line" as used herein means [on the same line as the web processing line]. Moreover, the web is not limited to the corrugated liner, and of course includes kraft paper for bags, films, and the like.

Incidentally, regarding the invention related to the present invention, the present applicant has already filed an application, but the application has not yet been published (Japanese Patent Application No. 61-25367, Japanese Patent Application No. 61-7
1966, etc.).

(Problem that the invention attempts to solve) Accordingly, the objects of the present invention are as listed below.

■ To provide a method and apparatus for printing patterns of different repeat lengths on a running web without substantially changing the diameter of the plate cylinder.

To provide a method and apparatus for printing patterns of different repeat lengths in-line on a web such as a corrugated liner.

O To make the running speed of the running web and the circumferential speed of the plate cylinder different at a desired ratio.

■ Even if the circumferential speed of the plate cylinder and the running speed of the web are different,
To supply the amount of ink necessary for printing and obtain printing with appropriate density.

The purpose of the invention will become clear from the following description and drawings.

The gist of the present invention, which can quickly achieve the above object, is a printing method in which a plate cylinder is rotated asynchronously with the running speed of a running web, in which a repeat length to be printed is set and the printing is carried out on the web. A printing method characterized in that the distance between the registered register marks is measured, the distance between the register marks is compared with the repeat length, and the rotation of the plate cylinder is controlled based on an error signal, and the running speed of the running web. and a distance measuring means for measuring the distance between the register marks printed on the web; and a distance measuring means for measuring the distance between the register marks printed on the web. , comprising repeat length setting means, calculation means for obtaining an error signal by comparing the distance between the register marks and the repeat length, and control means for controlling the rotation of the plate cylinder based on the error signal. This is a printing device characterized by the following.

(Structure and operation of the invention) Details of the present invention will be described with reference to embodiments illustrated in the drawings, but it goes without saying that the present invention is not limited to these embodiments.

FIG. 1 is a block diagram showing a first embodiment of the apparatus of the present invention, in which an offset gravure coater is used as inking means. The web 1O held by the unwinder 20 is printed while running and then wound onto the rewinder 22. Web 10 rotatably held in an unwinder 20 as a web roll 16
While the web 10 is running while being pulled by the rewinder 22, the web 10 is pressed against the impression cylinder 40 by the nip roll 24, which is the running control means, so that the running web 10 does not slip.

In the present invention, since the web and the printing plate move asynchronously, slippage inevitably occurs between the web and the printing plate. In addition, as will be described later, the rotation of the plate cylinder, that is, the rotation of the printing plate, is controlled while measuring the distance between the metamarks to obtain the desired repeat length, so the web must be controlled so that it does not run abnormally. Must be.

In FIG. 1, the nip roll 2 is used as the travel control means.
4 is used, but the present invention is not limited to this, and the running of the web 10 can also be controlled by providing a brake on the unwinder 20 itself, for example. In addition, the impression cylinder 40 and the running web 1
In order to prevent the roller from slipping, the impression cylinder 40 itself may be a suction roll.

The running web 10 passes through a guide roll 32 and reaches an impression cylinder 40 .

Impression cylinder 40 brings running web 10 into contact with printing plate 44 on plate cylinder 42 . Since the printing plate 44 is a rotary printing machine, the printing plate 44 and the running web 1O have a substantially narrow line contact. In the present invention, the running web 10 and the printing plate 44 are in contact with a relatively small pressure called a kiss touch, and a cushion means 46 is arranged on the plate cylinder 42 side and/or the impression cylinder 40 side. (See Figure 2).

In order to achieve the kiss touch as described above, extremely fine adjustments are required, and if the thickness of the running web 10 differs locally, it is difficult to obtain an appropriate printing pressure. This is used as an overpressure prevention means to prevent large differences in printing pressure from occurring due to variations. The cushioning means 46 is usually attached to the plate cylinder 42, but it can of course be attached to the impression cylinder 40, and is not limited to an elastic body as shown in FIG. 2, and can blow compressed air onto the running web 10. You can do it like this.

Although there are a plurality of printing plates 44 in FIG. 2, it is also possible to integrate the entire printing plate into one printing plate.

The circumferential speed of the plate cylinder 42 and the speed of the running web 10 are as follows:
Instead of operating synchronously, they usually slip and operate asynchronously. However, coincidentally, the repeat length and plate cylinder 42
If the circumference matches the circumference, there is no need to slip it.

In this specification, the circumferential speed 1 of the first plate cylinder does not mean the circumferential speed of the plate cylinder 42 itself, but refers to the effective circumferential speed that indicates the substantial speed of the outer circumference of the printing plate 44. be. Further, the repeat length does not refer only to the length of the actual printed pattern, but is the length of one cycle including the length of the non-printed portion.

For example, if the running web 10 is a cardboard liner,
This corresponds to the length of the cardboard sheet when it is cut. FIG. 3 is a plan view of a sheet that has been printed and cut as appropriate, and the length indicated by symbol R is the actual repeat length.

FIG. 4 is a developed view of the printing plate 44.

As described above, when the printing plate 44 and the running web 1o slip and the speed of the running web 10 is higher than the circumferential speed of the plate cylinder, the printed pattern P is printed faster than the pattern P2 made on the printing plate 44. It appears extended in the circumferential direction of time. Conversely, when the speed of the running web 1o is lower than the circumferential speed of the plate cylinder, the printed pattern appears smaller than the pattern P2 made on the printing plate 44 in the circumferential direction during printing. This is thought to be because the printing plate 44 and the running web 10 are in line contact. Even if the pattern P2 on the printing plate 44 is enlarged or reduced to some extent, the printed pattern P is substantially not blurred. As a result of experimenting with flexographic printing, it was found that it could be fully put into practical use.

The dimensions of the printing pattern P and the printing plate pattern P2 differ by a certain ratio, and 几2 (circumferential dimension of the printing plate pattern P2) / It (circumferential direction dimension of the printing pattern P) is substantially the same as that of the plate cylinder. is equal to the rate of change in circumferential velocity.

A register mark 48 appears every cycle on the running web that has been printed via the printing unit 50. This cycle is measured as the distance between the register marks 48 by the distance measuring means 36, and the signal is transmitted to the calculating means 64.

On the other hand, the repeat length signal preset in the setting means 66 and the distance signal are compared by the calculation means 64 to obtain an error signal. This error signal is transmitted to the control means 60, the speed of the electric motor 62 is controlled, and printing with an appropriate repeat length is obtained.

Note that the operator stage 64, the setting means 64 and the control means 60
Of course, it is possible to integrate the two.

Further, the rotation control of the electric motor 62 does not have to be based only on the distance setting means 36, but may also be based on the rate of change.

When the circumferential dimension R of the printed pattern P is thicker than the circumferential dimension R2 of the pattern P2 on the printing plate 44, that is, when the rate of change is smaller than 1, apply a larger amount of ink onto the printing plate 44. Conversely, when the circumferential dimension R is smaller than the circumferential dimension R2, that is, when the rate of change is greater than 1, the ink application amount is adjusted to be smaller. In this way, the printed pattern P can have colors with appropriate density. There are various ways to adjust the ink; for example, the ink can be adjusted by using a doctor 56 that is in contact with the drawing roll 52, or by adjusting the viscosity of the ink 58.

When the viscosity of the ink 58 is high, the amount of ink applied is small, and when the viscosity of the ink 58 is low, the amount of ink applied is small.

The one shown in FIG. 1 is one example in which an offset gravure coater is applied as an inking means, and the drawing roll 52 has countless cells formed by photo-etching.
Excess ink is scraped off by a doctor 56. Therefore, as long as other factors remain unchanged, the amount of ink pumped up by the pumping roll 52 is constant per circumferential area of the pumping roll 52 and is directly proportional to the rotational speed, that is, the number of revolutions. In the present invention, the following adjustment is performed as one method for performing proper printing.

First, the shape of the cell, its depth, the viscosity of the ink, the density of the ink, and the thickness of the transfer roll are determined so that proper printing can be achieved when the rate of change of the circumferential speed is set to 1, that is, everything operates synchronously. Various factors such as quality, contact angle of the doctor, and contact pressure of the doctor are set.

In this setting, the plate cylinder 42 is driven by an electric motor 62, which is an example of a driving means, so that the plate cylinder 42 slips at a constant rate of change with respect to the running speed of the running web 10. At this time, the plate cylinder 42 and the transfer roll 54 rotate synchronously. That is, the peripheral speed of the plate cylinder 42 and the peripheral speed of the transfer roll 54 are the same.

Although the circumferential speed of the pumping roll 52 and the running speed of the running web 10 do not necessarily have to match,
If the ink is adjusted so that proper printing is performed when all the rollers rotate synchronously, a substantially appropriate amount of ink can be obtained by making the circumferential speed of the pumping roll 52 and the running speed of the web 100 the same.

To explain this in detail, first, the pumping roll 52
Since excess ink is scraped off by the doctor 56, a certain amount of ink is always on the top. Next, when the peripheral speed of the transfer roll 54 is smaller than the peripheral speed of the pumping roll 52, the thickness of the coating film on the transfer roll 54 is smaller than the thickness of the coating film when the speed is constant, and the amount of ink on the printing plate is It becomes a dog more than when moving at constant speed.

However, since the running speed of the web is higher than the circumferential speed of the plate cylinder, the ink on the printing plate is stretched and a pattern of appropriate density is obtained.

Conversely, when the circumferential speed of the transfer roll 54 is higher than the circumferential speed of the pumping roll 52, the coating film thickness on the transfer roll 54 and the printing plate 44 becomes small, resulting in an appropriate coating amount on the running web 10. It is.

The amount of ink on the printing plate 44 increases when the rate of change in the circumferential speed of the plate cylinder is less than 1, as in the case of two series, and decreases when it is greater than 1. For example, if the rate of change is 0.8,
The appropriate amount of ink on the printing plate 44 is about 1.25 times that in constant speed printing. Conversely, when the rate of change is 1.3, the appropriate amount of ink is about 0.75 times that of constant speed printing. Therefore, the rate of change in the peripheral speed of the plate cylinder and the amount of ink on the printing plate are substantially inversely proportional.

Note that the amount of ink on the printing plate 44 does not simply depend on the rate of change, but is also related to factors such as the ink affinity of the printing plate and the flow characteristics of the ink, so it is not an exact inversely proportional relationship.
There is an inversely proportional relationship.

Particularly when the web IO is a corrugated board liner and flexographic printing is performed, precise adjustment is not required, and sufficient practical printing can be obtained by adjusting inversely proportionally.

Distance measuring means 3 for measuring the distance between register marks 48
The distance signal obtained from 6 is transmitted to calculation means 64. On the other hand, the repeat length is set in the setting means 66,
The distance between the register marks detected by the distance measuring means 36 and the set repeat length are compared by the arithmetic means 66 to obtain an error signal, which is transmitted to the control means 60. A control signal processed based on this error signal is sent to the electric motor 62.
transmitted to. In this way, the electric motor 62 is subjected to acceleration/deceleration control.

The rate of change is constant while the same printing plate is used, and does not depend on the printing speed, that is, the running speed of the web. If the running speed increases, the circumferential speed of the plate cylinder also increases, and if the running speed decreases, the circumferential speed of the plate cylinder also decreases.

The rate of change in the circumferential speed of the plate cylinder can also be set by manually viewing what is recorded on the printing plate and operating the control unit, for example, by operating a variable resistor. In addition, the rate of change in the circumferential speed of the plate cylinder is recorded on the printing plate by creating an optical mark at the same time as the plate making, this is optically read by the recording detection means, and this signal is transmitted to the setting means 66 to automatically The rate of change can be set. Note that the recording of the rate of change is not limited to optical means, but may also be done by magnetic means, IC memory, mechanical recording means, etc. In short, it is important to record the rate of change so that it can be read when the printing plate is replaced. It is sufficient if it can be recorded somewhere on the edition.

The electric motor 62 drives the plate cylinder 42 at the rate of change of the peripheral speed. The rate of change in the circumferential speed is substantially equal to the ratio (R/R2) of the repeat length R of the printing pattern P to the circumferential dimension R2 of the printing plate 44.

The printed web 10 is heated with a heat roll 90 from the printed back side so as not to come into contact with the printed surface, and if necessary, the web 10 is heated and dried in a heating box 92 to ensure sufficient drying. The web 10 that has been subjected to this process is wound up by a rewinder 22 as required.

Although the beam winder 22 is used in FIG. 1, depending on the case, it is possible to cut the sheet into the desired length immediately after printing and drying, that is, in-line, without using the beam winder.Fixed points printed on the sheet The register mark 48, which is a cut mark, can be detected by a sensor and cut into a predetermined size using a rotary cutter, for example, to form the sheet.

Further, as means for heating the printing web 10, the heat roll 90 and/or the heat box 92 described above can be used, but the present invention is not limited thereto, and other means such as an infrared heater or microwave heating can of course be used.

In this specification, it has been explained that in principle, one plate cylinder is not replaced, but the present invention is not limited to this, and if printing accuracy is desired to be improved, two to four plate cylinders with different diameters may be prepared. In this case, the plate cylinder can be easily replaced by adopting a turret system.

Furthermore, although monochrome printing has been described as an embodiment of the present invention,
Of course, by using a plurality of printing units, multicolor printing is also possible.

In this specification, the flexographic printing method has been described, but
The method is not limited to this, and an offset method or an intaglio method is also possible. In the case of the offset method, a transfer means such as a blanket cylinder is interposed between the printing plate and the web, but it is also possible to change the speed between the printing plate and the transfer means to cause slippage. A slip may be provided between the transfer means and the web. In short, any material that can make the relative speed between the circumferential speed of the plate cylinder and the traveling web asynchronous can be used.

(Effects of the Invention) ■ As described above, the present invention makes it possible to change the repeat length of the printing pattern by changing the circumferential speed of the plate cylinder. The length can be made different.

■ If the web is a corrugated liner, patterns with different repeat lengths can be printed in-line because the plate change time can be shortened.

○ Operation during printing is simple because there is virtually no need to change the diameter of the plate cylinder.

(2) The size of printing plates can be fixed or limited to 2 to 4 types, so inventory management of printing plates is easy.

■ When printing on corrugated cardboard, it is possible to obtain high-strength corrugated cardboard without collapsing during printing.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention, FIG. 1 is a configuration diagram showing one embodiment of the device of the present invention, and FIG.
The figure is a sectional view of the main part, FIG. 3 is a plan view of the printed sheet, and FIG. 4 is a developed view of the printing plate. 10...Web, 20...Unwinder, 36
... distance measuring means, 40 ... impression cylinder, 42 ... plate cylinder, 44 ... printing plate, 46 ... cushion means, 48 ...
...Register mark, 50...Printing unit, 60.
. . . Control means, 64 . . Calculation means, 66 . . Setting means.

Claims (2)

[Claims] (1) In a printing method in which the plate cylinder is rotated asynchronously with the running speed of the running web, (a) setting the repeat length to be printed, and (b) measuring the distance between the register marks printed on the web. (c) obtaining an error signal by comparing the repeat length with the distance between the register marks, and (d) controlling the rotation of the plate cylinder based on this error signal. (2) In a device that performs printing by rotating a plate cylinder asynchronously with the running speed of a running web, (a) a printing plate for printing a pattern including a register mark on the web; (b) a printing plate for printing a pattern including a register mark on the web; (c) repeat length setting means; and (d) calculation means for comparing the distance between the register marks and the repeat length to obtain an error signal. and (e) a control means for controlling rotation of the plate cylinder based on the error signal.