JPS6351266A - Control for web tension of belt type printing machine - Google Patents

Abstract

PURPOSE:To prevent the color discrepancy by varying the speed of a pulling roller on the basis of the variation value of the output of a tension sensor installed between a final stage printing unit of a belt type multicolor printing machine and a roller for pulling a web. CONSTITUTION:An independent printing unit 22 is formed by laying an endless belt 14 onto which a printing press 16 is attached, between a printing trunk 10 and an adjusting trunk 12 in free mounting and demounting. A plurality of printing units 22 are set in series, and a web 20 is supplied from the printing unit 22 on the upstream side. The web 20 on which printing is completed is pulled by a pulling roller 30 through a heating section 24, guide roller 26, and a tension detecting means 34, and taken up onto a taking-up device 28. The speed of the pulling roller 30 is adjusted on the basis of the variation of the tension detected by the tension detecting means 34. Therefore, color discrepancy is prevented to improve the precision in multicolor printing.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a method for controlling web tension in a belt-type printing press.

Prior Art It has long been desired in the industry to perform high-speed printing on paper rolls and other continuous sheets (hereinafter referred to as "web J") at arbitrary printing lengths without cutting them. On the corrugator line that produces corrugated cardboard, long core paper and liner are each rolled out from a roll, and the liner is bonded to the top of the corrugated corrugation of the core paper to produce single-sided and double-sided corrugated cardboard. At this time, if it is possible to print an arbitrary length on the surface of a long liner in advance, compared to the conventional printing after cutting, it is possible to improve the printing finish and avoid a decrease in the compressive strength of the corrugated board. It's actually convenient.

However, in ordinary transfer printing machines, the size of the printing surface applied to a continuous sheet is generally determined by the circumferential dimension of the plate cylinder, and therefore it is impossible to print larger than the entire circumferential dimension of the plate cylinder. Furthermore, when printing with a printing plate having a circumferential dimension or less, there is a drawback that a margin is created between adjacent printing surfaces of a continuous sheet every time the plate cylinder rotates, resulting in large waste.

Belt type printing machines have been proposed as a means to solve these drawbacks. In other words, this belt type printing machine is as shown in Fig. 4.

It comprises a plate cylinder 10 and an adjustment cylinder 12 disposed so as to be able to adjust the distance between the axes with respect to the plate cylinder 10, and the plate cylinder 1° and adjustment cylinder 12
2, an endless belt 1 made of synthetic resin film between
4 is detachably wound and rotated in the negative direction. Desired printing plates 16 are pasted on the surface of this endless belt 14 in an appropriate arrangement pattern, and this endless belt 14 is rotated and connected to an impression cylinder 18 disposed close to the plate cylinder 10. Continuous web 20 between
The continuous web can be printed by passing it through the web. In this way, the belt-type printing press does not require its printing length to depend on the circumferential dimension of the plate cylinder, as in conventional rotary printing presses.

By simply changing the lengths of the endless belt and the printing plate, it is possible to print a continuous web at any printing length.

Therefore, if the belt-type printing machine is used, it is possible to print the liner of the above-mentioned corrugated line with any size and length, which is suitable.

To apply multicolor printing to this continuous web.

A belt-type printing machine having the above-described structure is used as an independent printing unit 22, and as shown in FIG. By passing the continuous web 20 through the continuous web 20, desired color printing is performed.

Problems to be Solved by the Invention In this type of multicolor printing, the printing speed between each printing unit 22 is strictly adjusted to prevent color unevenness, color shift, etc. from occurring.

However, the endless belt 14 of a belt-type printing press that constitutes each printing unit 22 is generally long, and therefore the printing length on the web 2o in each unit is the portion printed by the printing press using the plate cylinder. It is longer than the . Therefore, in the above-mentioned multicolor printing machine in which a plurality of belt-type printing machines are arranged in series, in the process of passing the web 20 and performing multicolor printing, an error occurs in the flow direction of the web, and this causes the color This often results in unevenness and color shift, which impairs the accuracy of multicolor printing. In particular, this error in the flow direction increases cumulatively as the printing units are placed on the downstream side, and this type of color misregistration cannot be completely corrected only by adjusting the speed of each printing unit; Although this is a serious error, it remains unresolved and remains at present.

However, recently, even in the field of printing for corrugated cardboard sheets, there has been an increasing demand for further increasing the accuracy of multicolor printing.

In particular, with the spread of POS systems that convert various data such as price, quantity, manufacturer, etc. into barcodes, it has become necessary to print barcodes on the corrugated cardboard sheets.
In this case, improving printing accuracy has become a top priority in order to eradicate reading errors.

Purpose of the Invention The present invention has been proposed in view of the above-mentioned problems and to suitably solve the problems.The present invention is a method of applying multicolor printing to a web using a multicolor printing machine having a large number of belt type printing machines arranged. The purpose of this invention is to eliminate errors in the web running direction that conventionally occur, and to achieve highly accurate multicolor printing without color misregistration.

Means for Solving the Problems In order to overcome the above-mentioned problems and achieve the intended purpose, the present invention provides a plate cylinder and an adjustment cylinder disposed on the plate cylinder such that the distance between the axes can be freely adjusted. An endless belt having a desired printing plate pasted thereon is removably wound between the plate cylinder and the adjustment cylinder to constitute a belt-type printing machine as an independent printing unit, and this printing unit is In a multicolor printing machine that prints multiple colors on a continuous web by arranging multiple units in series, the continuous web that has been set up, consisting of the final printing unit, is actively directed toward the winder using a tension roll. When the web is pulled out, a means for detecting the tension during the running of the web is provided in the running path of the web between the printing unit at the final stage and the tension roll, and the fluctuation value of the web tension detected by this means is provided. It is characterized in that the speed of the tension roll is controlled to vary as a basis.

EXAMPLE Next, a method for controlling web tension in a belt-type printing press according to the present invention will be described below in relation to an apparatus for preferably carrying out the method. FIG. 1 shows an example of a multicolor printing press that implements the method of the present invention, in which an independent printing unit 22 employs the above-mentioned belt type printing press.

The last printing unit 22 downstream in the machine direction of the web
After passing through a heating section 24 for drying the ink immediately after printing, the continuous web 20 sent out from It is supplied towards the web winder 28.

The tension on the web 20 in this case is provided by a tension roll 30 arranged between the guide roll 26 and the web winder 28. That is, the tension roll 3o is driven by a motor 32 shown in FIG. 3, rotates in a predetermined direction, and tensions and supplies the web 20 toward the downstream side.

For the motor 32, a model that can perform variable speed control with high accuracy using, for example, an inverter is selected and used.

Next, in the running path of the web 2o and between the printing unit 22 at the final stage and the tension roll 30, a means 34 for detecting the tension during running of the web 2o is provided. As the web tension detection means 34, for example, a differential transformer type tension detector is suitably used. That is, the differential transformer type tension detector 34 has a leaf spring inside, and functions as a transducer that converts the displacement due to the load applied to the leaf spring into an electrical signal using the differential transformer.

For example, as shown in FIG. 1, it is preferable to arrange a tension detection roll 36 on the deck 25, and the roll 36 is supported by bearings 40, 40 at both ends of the rotating shaft 38. . Furthermore, this bearing 40, 40
are respectively supported by the detector 34, and as a result, two detection means are disposed at both shaft ends of the detection roll 36. Note that the detectors 34 and 34 convert the vector sum of the tension transmitted through the roll 36 into pressure, and further convert it into an electrical signal, and the surface output signal is the tension shown in FIG. 3 in the added state. The signal is input to the control circuit 42.

FIG. 3 shows a tension control circuit 42 using tension detection means 34.
2 is a block diagram showing an example, and the illustrated motor 32 serves as a common drive source for rotating the tension roll 30 as described above. In this tension control circuit 42, the motor 32 is always driven at a set speed according to a reference set value input by the operator. However, if the tension of the web 2o changes during running, this is converted into a pressure change in the detectors 34, 34, and further converted into an electrical signal and input to the tension control circuit 42. This tension control circuit 42 sends a control signal to the motor 32 in response to the tension fluctuation value of the web 20, and instantaneously speeds up or decelerates the motor 32 relative to the set speed.

Operation of the Invention Next, the operation of the web tension control method for a belt-type printing press according to the present invention constructed as described above will be explained. As shown in FIG. 1, in a multicolor printing machine in which a plurality of printing units 22 each consisting of a belt printing machine are arranged in series, a continuous web 20 is placed between the plate cylinder 10 and the impression cylinder 18 of each unit 22. The paper is passed through the paper and the required multicolor printing is sequentially applied.

In this case, as described above, due to the fact that the endless belt 14 is generally long, the printing unit 2 on the downstream side
2, the printing error tends to accumulate and expand. This error manifests itself in the printing portion of the web 2o with phenomena such as color shift, and also appears in the form of fluctuations in the tension of the web 20 on the downstream side. When the tension of the web 20 fluctuates in this manner, the tension fluctuation is converted into a pressure change in the detectors 34, 34, and further converted into an electrical signal. This electrical signal is input to the tension control circuit 42, which sends a control signal to the motor 32 in accordance with the tension fluctuation value of the web 20, and instantly speeds up or decelerates the motor 32 from the set speed. The tension of the web 20 is maintained at a predetermined reference value.

Effects of the Invention As explained above, according to the present invention, the tension of the web passing through each unit in a multicolor printing machine can be maintained at a predetermined reference value at all times on the downstream side, thereby improving multicolor printing. It is possible to eliminate printing errors and achieve highly accurate multicolor printing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a multicolor printing press in which the web tension control method for a belt-type printing press according to the present invention is suitably implemented, and FIG. 2 is a diagram showing the arrangement of a tension detector suitably used in the method of the present invention. FIG. 3 is a block diagram of a control circuit, and FIG. 4 is a basic schematic configuration diagram of a belt-type printing press according to the prior art. 1o... plate cylinder 12... adjustment cylinder 14...
Endless belt 16...Print plate 20...Continuous web
22... Printing unit 28... Web winder 3
0...Tension roll 32...Motor 34.
... Tension detection means patent applicant Isoe Iron Works Co., Ltd. FIo, 3 -ra9Q- FIo, 4

Claims (1)

[Claims] An endless belt (14) comprising a plate cylinder (10) and an adjustment cylinder (12) disposed on the plate cylinder (10) so that the distance between the axes can be freely adjusted, and on which a desired printing plate (16) is attached. is removably wound between the plate cylinder (10) and the adjustment cylinder (12) to constitute a belt-type printing machine as an independent printing unit (22), and this printing unit (22) is In a multicolor printing machine in which a plurality of units are arranged in series to perform multicolor printing on a continuous web (20), a printed continuous web (20) is sent out from a printing unit (22) at the final stage.
) toward the winder (28) by the tension roll (30), when the web (20) is in the traveling path and between the final printing unit (22) and the tension roll (30). A means (34) for detecting the tension of the web (20) during running is provided between the web (20) and the means (34).
34) A web tension control method for a belt-type printing press, characterized in that the speed of the tension roll (30) is controlled to be changed based on the tension variation value of the web (20) detected by 34).