JPH03264358A - Method and device for phase control of web - Google Patents

Abstract

PURPOSE:To make it possible to control a phase and a pitch of a travelling web by controlling a torque using a brake provided on a feed roller. CONSTITUTION:A preprinted web 1 is bound on a feed roller 2 and register marks are inscribed on the preprint at equal intervals. The feed roller 2 is provided with a brake 3 for controlling the rotation so as to generate a control torque which is approximately proportional to a current or an air pressure. The web 1 is provided with plate cylinder 5 - 8 for follow-up printing of different colors which are driven to rotate by a main motor 9. The plate cylinder 5 is provided with an encoder 10 for measuring a rotational position, and a scan head 11 for detecting the register marks and a tension sensor 12 of the web 1 are provided upstream at a predetermined distance from the plate cylinder 5. Outputs of the encoder 10, scan head 11, and tension sensor 12 are inputted to a controller 13. The controller 13 controls are tension of the web 1 by means of a control torque of the brake 3 in order to make it possible to detect the marks when the rotational position of the plate cylinder 5 comes to a predetermined position. A length of a printing pitch is detected by changes of a phase deviation of the register marks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a web phase control method and apparatus for controlling the phase of a web by correcting expansion and contraction that occurs in the web when overprinting or the like is performed on the web.

[Conventional technology]

When performing multi-color printing, the remaining several colors are printed (hereinafter referred to as additional printing) on the printing paper that has been printed with several colors in the first printing (hereinafter referred to as pre-printing). The length of the print varies depending on various conditions such as the surrounding environment such as temperature and humidity, mechanical factors such as the dryer, and the elapsed time of 2 hours. If additional printing is performed in such a state, the final print and the additional printing will be out of sync with each other. In order to solve this misalignment, the rotation of the travel drive roller has conventionally been controlled. This example will be explained using FIG.

The main drive motor 9 rotates the feed roller 14 and the plate cylinder 5 to transport the web 1. Register marks are written on the web at equal pitches. The rotational position of the plate cylinder 5 and the register mark detection data are input to the phase control section 15, the phase change and pitch are determined from the phase deviation data, and the phase control section 15 generates a phase/pitch control signal. The signal is output to the correction motor 16, and the planetary gear mechanism 17 performs control regarding both phase and pitch. If the correction by the planetary gear mechanism 17 is rapid, paper breaks or sag occurs, so a tension detector 12 is provided, and a tension monitoring device W1B issues an alarm when the tension exceeds a set value.

[Problems to be Solved by the Invention] According to such a configuration, the correction motor 16, the planetary gear mechanism 17, etc. are required, resulting in a complicated mechanical configuration and increased manufacturing cost. Furthermore, when converting a printing machine that was conventionally designed without taking additional printing into consideration into a machine capable of additional printing, the cost is high due to the large number of parts to be modified.

The present invention has been made in view of the above-mentioned problems, and provides a method and apparatus for controlling the phase of a web in order to perform predetermined processing on the web based on marks written on the web at regular intervals using a simple flI command. The purpose is to provide

[Means to solve the problem]

In order to achieve the above object, the web phase control method of the present invention utilizes a rotational braking device provided on the supply roller. A web whose phase is changed by controlling the tension applied to the web based on marks written on the web at regular intervals when the web is subjected to a predetermined process by a processing device that rotates at the same circumferential speed as the web speed. In the phase control method, the rotational position of the processing device, the mark passing through a predetermined position, and the tension of the web are detected, and the mark is detected when the processing device reaches the predetermined rotational position. It is characterized in that rotation of the supply roller is braked. Further, the web phase control device of the present invention includes a supply roller wound with a web having marks written at predetermined intervals, a running drive roller that unwinds the web from the supply roller and drives the web, and a running speed of the web. a processing device that rotates at the same circumferential speed and performs a predetermined process on the web; a rotational position meter that measures the rotational position of the processing device; and a mark detector that is placed at a predetermined position from the processing device and detects the mark. , a tension meter for measuring the tension of the web, a brake for braking the rotation of the supply roller, and a mark detector for detecting the mark when the rotational position of the processing device reaches a predetermined position. A control section that controls the braking force of the brake is provided.

[Function] Since the web is composed of film, paper, etc., it expands and contracts with changes in temperature and humidity. For this reason, when marks are written on the web at regular intervals, the interval between the marks expands and contracts. For this reason, if additional printing is performed using the mark as a reference and, for example, with a plate cylinder having the same circumference as when the mark was written, color misregistration will occur. Therefore, the relationship between the circumference of the processing device such as the plate cylinder and the mark interval is
To maintain the same relationship as when writing marks and when printing additional prints, when the web is shrinking, the tension is increased and stretched, and when it is stretching, the tension is loosened and the web is shortened. Note that the web runs with a constant tension applied between the running drive roller and the supply roller. The supply roller is equipped with a rotary braking device (C) in order to maintain this constant tension or to stop rotation due to inertia when unwinding of the web is stopped, but the braking force of this braking device must be adjusted. The web can be expanded and contracted. In other words, if the rotational position of the processing device is detected and the tension of the web is controlled by the braking device so that marks on the running web are always detected when the rotational position reaches a predetermined position, the circumference of the processing device and the web tension can be controlled. Since the lengths between marks can be maintained in a constant relationship, it is possible to correct for expansion and contraction due to temperature and humidity of the web. Further, the initial phase deviation or the phase deviation due to disturbance is corrected by integrating the stroke difference between the plate cylinder and the web due to tension changes.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

This embodiment shows an apparatus for peel-printing four colors on a preprinted web. A preprinted web 1 is wound around a supply roller 2. Register marks are written at equal intervals on this preprint. Note that a part of a preprinted pattern may be used as the register mark. The paper feed roller 2 is provided with a brake 3 for braking its rotation, which generates a braking torque approximately proportional to current or air pressure. The web 1 is pulled and driven by a take-up roller 4 and is taken up with a predetermined tension applied thereto. On the web 1, four pairs of plate cylinders for printing different colors are installed in order from left to right in the drawing: plate cylinder 59, plate cylinder 6, plate cylinder 7, and plate cylinder 8, and each plate cylinder 5 to 8 is It is rotationally driven by one main motor 9. The plate cylinder 5L is provided with an encoder 10 for measuring the rotational position, and a scanning head 11 for detecting register marks and a web l are provided at a predetermined distance upstream from the plate cylinder 5.
A tension sensor 12 is provided to detect the tension.

The control unit 13 includes an encoder 10. scanning head 11
The tension of the web 1 is controlled by the braking torque of the brake 3 so that the mark is detected when the output of the tension sensor 12 is input and the rotational position of the plate cylinder 5 reaches a predetermined position. This is because the length of the printing pinch is detected by the change in the phase deviation of the register mark.

In other words, if the pre-print printing pitch is shorter than the add-on printing pitch, increase the tension and lengthen the pre-print printing pinch to match the add-on printing pinch, and in the opposite case, reduce the tension and shorten the printing pinch for add-on printing. to prevent color shift. Initial phase deviations not caused by printing pinches and deviations due to disturbances are corrected by integrating the travel difference between the plate cylinder and the web using tension.

Next, the operation of the control section 13 will be explained.

The web 1 is unwound from a paper feed roller 2 with a constant tension T. This tension T is approximately the same value as the tension during printing. However, during add-on printing, the web 1 expands and contracts with respect to the web 1 during pre-printing due to differences in ambient conditions such as temperature and humidity.

This appears as an expansion or contraction in the length between register marks. The relationship between the elongation and tension of the web 1 is expressed by the following equation.

χ− to △T −−−−−−−−−(1) Constant △T: amount of increase in tension (a reference tension T is applied to the web 1, and this represents the tension added to or subtracted from this T) The relationship between tension T and brake torque τ is expressed by the following equation. Ru.

τ=T・tenτ. to------(2) τ=T・
−−−−−−−−−−−−(3) D: Winding diameter τ of paper feed roller 2: Mechanical loss of torque Here, τ varies depending on various conditions such as speed, that is, winding diameter, and is constant. is not the value of τ. is generally small, so if it is omitted, it becomes equation (3).

The relationship between the brake torque τ and the brake signal i is as shown in the following equation. Here, the brake signal i is assumed to be an air pressure or current value for driving the brake, or a value proportional to these numbers.

τ=A (i −i, )−−−−−−−(4)τ
=A-1------------(5) A: Constant 10: Bias value for signal i.

A linear relationship can be obtained between the signal i and the signal i within a certain range.

Bias value 10 is small and can be omitted (5)
It can be expressed as the formula.

Using the above relationship, the brake torque τ control signal i is determined by the following equation so that the amount of expansion and contraction X of the web 1 becomes zero.

1 i=to, (ΔT+　　　　r△Tdt)+αXtenT.

g (△χ)−−−−−−−11−(6) KP: Proportional gain T1: Integral time ΔX=Xi ~x i−+ −−−−−−−(7) ΔX
represents the difference in change in distance between adjacent register marks.

The first term in equation (6) is PI control for ΔT, and the second and third terms are correction signals based on register mark deviation.

Next, a method of calculating the register mark deviation X from the encoder IO and the scanning hand 11 will be explained. The encoder 10 rotates in the same manner as the plate cylinder 5, and outputs the rotational position. Assuming that the encoder 10 outputs 100 pulses per revolution, if an address from 0 to 99 is attached to the pulse, that address indicates the position. If a register mark is written on the web 1 every rotation of the plate cylinder during preprinting, the pinch of the register mark will be the same as the circumference of the plate cylinder. Therefore, if the scanning head 11 detects a register mark when the encoder 10 is at a predetermined address, for example, address 50, and the scanning head 11 detects the register mark again when the next rotational position reaches address 50, the web 1 will cause expansion and contraction. In this case, x=0.

Further, if a register mark is detected when the web 1 reaches address 49, this indicates that the web 1 has shortened, and if a register mark is detected when the web 1 reaches the 51st address, this indicates that the web 1 has expanded. Therefore, the address where the register mark is first detected is set as a reference address, and X can be determined as a value proportional to the difference between this reference address and the address where the register mark is detected. Details such as determining the address using the signal of the encoder 10 and detecting it by providing a gate are given in Japanese Patent Publication No. 62-58878 and Japanese Patent Publication No. 63-28758.
It is stated in the No.

By the way, the winding diameter of the paper feed roller 2 shown in equations (2) and (3) decreases as the web is unwound. There is a linear tension control calculation method to control the tension of such a diameter.In this method, when a disturbance is detected in an equilibrium state during control, the output changes in proportion to the amount of disturbance, regardless of the size of the winding or unwinding diameter. is given to return to equilibrium. On the other hand, the brake torque is proportional to the control signal i as shown in equation (5). Further, as shown in equation (3), the torque generated by the brake is expressed as the product of the unwinding radius or the winding radius and the tension.

Therefore, in the case of constant tension control with constant tension, the torque is proportional to the unwinding or winding diameter. Since this torque is proportional to the control signal i as described above, the control signal i is proportional to the winding diameter. When a disturbance is detected here, an output change proportional to the amount of disturbance is performed in the linear tension control calculator, and when the winding diameter is large, the control signal i
is large, so the tension change is small, and when the winding diameter is small, the control signal i is small, so the tension change is large. As described above, since the gain of the control loop changes depending on the winding diameter, the control operation becomes unstable. In order to prevent this, the loop gain of the control system can always be kept constant by outputting the output of the linear tension control calculator through a calculator having an exponential current characteristic such as a diode. Details are described in Japanese Patent Publication No. 54-42064.

Although this embodiment is a device for preventing color misregistration during post-addition printing, if the plate cylinders 6 to 8 are removed and the plate cylinder 5 is used as a label cutter or a perforation machine, it is possible to perform lael punching and perforation processing. In addition, there is no need for a mechanical mechanism such as a planetary gear mechanism for phase control, and if there is an existing tension detector, it can be used to perform phase control.

〔Effect of the invention〕

As is clear from the above description, the present invention provides an inexpensive phase control method and device because the phase and pinch of the running web are controlled by controlling the torque using the brake inherent in the supply roller. can do.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram explaining a conventional technique. 1----Web 2-m=Paper feed roller 3--
- Brake 4-11 Take-up roller 5 6.
7.8--One plate cylinder 9-m-Main motor

Claims (2)

[Claims] (1) When the web is subjected to a predetermined process by a processing device that rotates at the same circumferential speed as the running speed of the web unwound from the supply roller and driven to run by the running drive roller, marks are written on the web at regular intervals. In a web phase control method for controlling the phase of the web based on marks, the rotational position of the processing device, the mark passing a predetermined position, and the tension of the web are detected, A method for controlling the phase of a web, characterized in that rotation of the supply roller is braked so that the mark is detected when the feed roller reaches a position. (2) A supply roller that winds a web with marks written at predetermined intervals, a traveling drive roller that unwinds the web from this supply roller and drives it to travel, and a traveling drive roller that rotates at the same circumferential speed as the traveling speed of the web and a processing device that performs a predetermined process, a rotational position meter that measures the rotational position of the processing device, a mark detector that is placed at a predetermined position from the processing device and detects the mark, and a mark detector that measures the tension of the web. a tension meter, a brake that brakes the rotation of the supply roller, and a control unit that controls the braking force of the brake so that the mark detector detects the mark when the rotational position of the processing device reaches a predetermined position. A web phase control device comprising: