GB1600058A - Method and apparatus for regulating the printing in registry and in phase of preprinted webs - Google Patents

Description

(54) METHOD AND APPARATUS FOR REGULATING THE PRINTING IN REGISTRY AND IN PHASE OF PREPRINTED WEBS (71) We, WINDMÖLLER & HÖLSCHE1R, a Kommanditgesellschaft organised and existing under the laws of the Federal Republic of Germany, of 48-52 Münsterstrasse, 454 Lengerich, Westphalia, the Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a method of regulating the printing in registry and in phase of preprinted webs provided with register marks, wherein the web feed is controlled by the position of a pendulum roller which governs the web tension and wherein the errors in registry and phase are determined by comparing the signals from a photocell scanning the register marks with the signals given by means detecting the phase position of the cylinder of the printing mechanism relatively to the scanned register marks, as well as to an apparatus for performing this method.

In a method of this kind known from US-PS 3 326 436 but which only concerns the printing in registry of a web fed from an upstream printing mechanism to a second printing mechanism, the web tension is increased or reduced according to the detected departures in registry by a pair of rollers mounted on a pivotable lever, one of the rollers being driven by the central shaft of the printing press and enveloped in S formation by the web to be printed, being swung in the sense of increasing or reducing the web tension. Between the tensioning rollers which are enveloped in S formation and the last printing mechanism there is a pendulum roller which is pivotable by a pistoncylinder unit, freely rotatably mounted on a two-armed lever and, with associated control elements, adapted to regulate the web tension according to the detected departure in registry because pivoting of the tensioning rollers that are enveloped in S formation can only rapidly compensate an error in registry but the altered web tension between the second printing mechanism and the pair of rollers which are enveloped in S formation would soon adjust to the web tension upstream thereof, thereby making additional regulation necessary.

The regulation as known from US-PS 3 326 436 is suitable only for correcting and avoiding errors in registry, i.e. errors caused by elongation or contraction of the existing imprints and of the spaces therebetween.

Such errors are excluded by an increase or reduction in the web tension which result in a corresponding elongation or contraction of the web for setting the printing to be in registry.

Particularly in the case of the repeated printing of preprinted webs there is, apart from the problem of printing in registry, the problem of printing in phase, this resulting from the difficulty that even if the length of the preprinted imprints is correct, these imprints and the register marks have to be brought into the correct phase position in relation to the second impression cylinder.

Such errors in phase position cannot be corrected by the known register regulation because this only results in a change in the length of the preprinted imprints by increasing or reducing the web tension, but not to a change in the phase position of the preprinted imprints relatively to the second impression cylinder.

According to the present invention, there is provided a method of regulating the printing in registry and in predetermined format length of a preprinted web provided with printing marks, wherein the web feed is controlled by a drive motor, according to the position of a pendulum roller which governs the web tension, and wherein errors in registry and in format length are detected by comparing signals from a sensor scanning the printing marks with those from a means detecting the phase position of the cylinder of the printing mechanism in relation to the scanned printing marks, and wherein according to the detected deviation the web tension is increased or reduced temporarily and abruptly in order to achieve printing in registry, and in order to achieve printing in predetermined format length the web ten sion is increased and reduced progressively, and wherein according to the detected errors output signals are formed which simultaneously operate a fine adjusting valve and magnetic valves through adjustable time relays in order to adjust the pendulum roller position.

The invention further provides apparatus for performing this method comprising a feed means driven by a drive motor to withdraw the web from a supply reel, a pendulum roller movable by a piston-cylinder unit and controlling the web feed according to its deflection, and a comparator unit which compares the signals from a photocell scanning the printing marks on the web with the signals from means detecting the phase position of the cylinder of the printing mechanism in relation to the scanned printing marks and transmits signals according to the detected deviation, wherein the comparator unit is connected to a control unit which, as long as the comparator unit signals a control departure, gives pulses through adjustable time relays to a servo-motor which operates a cam plate controlling a fine pressure regulating valve which progressively increases or reduces the web tension by correspondingly raising or lowering the pressure in the piston-cylinder unit, the control unit also transmitting pulses to magnetic valves which temporarily and abruptly increase or reduce the pressure in the piston-cylinder unit. By means of the servo-motor or the cam plate, the fine pressure regulating valve is so set that the piston-cylinder unit gives the web a tension that is necessary for in-registry printing. The cam plate is in this case substantially in the central position.

If the comparator unit indicates a regulation departure, i.e. a change in the phase position of the register marks printed on the web in relation to the cylinder of the printing mechanism, there is either an error in registry or a phase error or both. To exclude these errors, the fine pressure regulating valve increases or reduces the pressure in the piston-cylinder unit, depending on whether the printed marks arrive too early or too late, i.e. whether an increase or reduction in the web tension is necessary to avoid the error in registry. Simultaneously with rotation of the cam plate acting on the fine pressure regulating valve, one of the two magnetic valves is actuated, whereby either a pressure of pressure medium increased with respect to the fine pressure regulating valve is momentarily applied to the piston of the piston-cylinder unit or the pressure at this position is reduced, so that the resulting jerk causes the web to slip relatively to the impression cylinder and phase errors are thereby compensated. Since the correction of phase errors is brought about by setting the correct phase position abruptly and thus more rapidly than inregister regulation, the superimposed modes of regulation cannot have opposite influences on one another over a prolonged time interval. The fine regulating valve brings about an integral regulation of the established web tension, the value of which approaches the impacts (differential impacts) bringing about the slip regulation, so that the differential regulation as well as the integral regulation are terminated as soon as the differential impacts causing the slip have disappeared or become imperceptibly small.

The invention permits the correction of registration errors as well as phase errors even though the means for eliminating both errors are actually oppositely directed. If for example the phase errors were to be compensated by constant elongation of the material, registration errors would result that would then have to be compensated, thereby resulting in hunting of the regulation.

An example of the invention will now be described in more detail with reference to the drawing, wherein: Fig. 1 is a diagrammatic representation of the combined registration slip regulation, and Fig. 2 is a web tension-time diagram.

A preprinted web 2 is withdrawn from a supply reel 1; it has printed marks 3 between the imprints (not shown). By means of a pair of feed rollers 4, 5, which is preceded by a guide roller, the web 2 is withdrawn.

The pair of feed rollers 4, 5 is driven by a drive motor 6. The web 2 passes over a pendulum roller 9 disposed between two guide rollers 7, 8 and freely rotatably mounted in two-armed levers 9.1 which are pivotable in the frame of the machine. The weight of the pendulum roller 9 is compensated in known manner by a counterweight. The preprinted web 2 is provided with further imprints by means of two printing mechanisms 10, 11 and is subsequently wound up on a supply reel 12. Upstream of the printing mechanism 10 and downstream of the printing mechanism 11 there are feeding means 13, 14 which are mechanically coupled to the printing mechanisms 10, 11 and which feed the web in synchronism with the printing mechanisms 10, 11. A photocell 15 scanning the printed marks 3 is disposed between the guide roller 8 and the feeding means 13.

ne cylinder of the printing mechanisms 10, 11 is mechanically connected to a contact switch 16 which indicates the phase position of the cylinder. The two signals given by the photocell 15 and the contact switch 16 are fed to a comparator unit 17 consisting of logic components.

One of the levers 9.1 of the pendulum roller 9 is articulated to the piston rod of a piston-cylinder unit 18 of which the cylinder is hinged to the frame of the machine.

Further, the lever 9.1 is connected to a potentiometer 19 by which the speed or torque of the drive motor 6 for the feed rollers 4, 5 is controlled in accordance with the angular position of the levers 9.1 or the deflection of the pendulum roller 9.

In the supply of pressure medium for the piston-cylinder unit 18 there are a fine pressure valve 20 and two magnetic valves 21, 22 which are connected in parallel. The fine pressure regulating valve 20 is actuated by a cam plate 25 which has linear characteristics and which is rotatable through a range of about 350C by a servo motor 24, the tappet of the fine pressure regulating valve 20 running on the cam face of the cam plate.

Upstream of the magnetic valve 21 there is a pressure regulating valve 23 with which the pressure of the pressure medium fed through the magnetic valve 21 can be set.

By means of the magnetic valve 22, the pressure upstream of the piston of the piston-cylinder unit 18 can be blown off to atmosphere.

The magnetic valves 21, 22 and the motor 24 are electrically connected to a control unit 26 which receives corresponding pulses from the comparator unit 17. The control unit 26 consists of two time relays 27, 28 with which the period of energisation of the servo-motor 24 can be separately set for both directions. The comparator unit 17 is connected to the control unit 26 by two lines 29, 30, of which the line 29 brings the command for increasing the web tension, allows the servo-motor 24 to start in the appropriate direction and permits the magnetic valve 21 to open momentarily. The line 30 brings the command for reducing the web tension.

This energises the magnetic valve 22 so that pressure medium can be blown off and the servo-motor 24 turns in a direction opposite to the first case. The time for which the motor 24 runs is limited by the adjustable time relays 27, 28. It can be reduced to practically zero so that integral regulation is similarly reduced and only predominantly differential pulses are applied to the pendulum roller 9.

Fig. 2 shows a web tension-time diagram.

The course of the web tension is indicated in full lines. Between the columns which obtain their characteristic form by the differential momentary increase or blow off of the pressure medium one can see the stepped course which is parallel to the base line and which is caused by the constant addition or withdrawal of pressure medium pressure by the cam-controlled fine pressure regulating valve.

WHAT WE CLAIM IS: 1. A method of regulating the printing in registry and in predetermined format length of a preprinted web provided with printing marks, wherein the web feed is controlled by a drive motor, according to the position of a pendulum roller which governs the web tension, and wherein errors in registry and in format length are detected by comparing signals from a sensor scanning the printing marks with those from a means detecting the phase position of the cylinder of the printing mechanism in relation to the scanned printing marks, and wherein according to the detected deviation the web tension is increased or reduced temporarily and abruptly in order to achieve printing in registry, and in order to achieve printing in predetermined format length the web tension is increased and reduced progressively, and wherein according to the detected errors output signals are formed which simultaneously operate a fine adjusting valve and magnetic valves through adjustable time relays in order to adjust the pendulum roller position.

2. Apparatus for performing a method according to claim 1 comprising a feed means driven by a drive motor to withdraw the web from a supply reel, a pendulum roller movable by a piston-cylinder unit and controlling the web feed according to its deflection, and a comparator unit which compares the signals from a photocell scanning the printing marks on the web with the signals from means detecting the phase position of the cylinder of the printing mechanism in relation to the scanned printing marks and transmits signals according to the detected deviation, wherein the comparator unit is connected to a control unit which, as long as the comparator unit signals a control departure, gives pulses through adjustable time relays to a servo-motor which operates a cam plate controlling a fine pressure reg- ulating valve which progressively increases or reduces the web tension by correspondingly raising or lowering the pressure in the piston-cylinder unit, the control unit also transmitting pulses to magnetic valves which temporarily and abruptly increase or reduce the pressure in the piston-cylinder unit.

3. A method of regulating the printing of preprinted webs substantially as hereinbefore described and with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. roller 9 is articulated to the piston rod of a piston-cylinder unit 18 of which the cylinder is hinged to the frame of the machine. Further, the lever 9.1 is connected to a potentiometer 19 by which the speed or torque of the drive motor 6 for the feed rollers 4, 5 is controlled in accordance with the angular position of the levers 9.1 or the deflection of the pendulum roller 9. In the supply of pressure medium for the piston-cylinder unit 18 there are a fine pressure valve 20 and two magnetic valves 21, 22 which are connected in parallel. The fine pressure regulating valve 20 is actuated by a cam plate 25 which has linear characteristics and which is rotatable through a range of about 350C by a servo motor 24, the tappet of the fine pressure regulating valve 20 running on the cam face of the cam plate. Upstream of the magnetic valve 21 there is a pressure regulating valve 23 with which the pressure of the pressure medium fed through the magnetic valve 21 can be set. By means of the magnetic valve 22, the pressure upstream of the piston of the piston-cylinder unit 18 can be blown off to atmosphere. The magnetic valves 21, 22 and the motor 24 are electrically connected to a control unit 26 which receives corresponding pulses from the comparator unit 17. The control unit 26 consists of two time relays 27, 28 with which the period of energisation of the servo-motor 24 can be separately set for both directions. The comparator unit 17 is connected to the control unit 26 by two lines 29, 30, of which the line 29 brings the command for increasing the web tension, allows the servo-motor 24 to start in the appropriate direction and permits the magnetic valve 21 to open momentarily. The line 30 brings the command for reducing the web tension. This energises the magnetic valve 22 so that pressure medium can be blown off and the servo-motor 24 turns in a direction opposite to the first case. The time for which the motor 24 runs is limited by the adjustable time relays 27, 28. It can be reduced to practically zero so that integral regulation is similarly reduced and only predominantly differential pulses are applied to the pendulum roller 9. Fig. 2 shows a web tension-time diagram. The course of the web tension is indicated in full lines. Between the columns which obtain their characteristic form by the differential momentary increase or blow off of the pressure medium one can see the stepped course which is parallel to the base line and which is caused by the constant addition or withdrawal of pressure medium pressure by the cam-controlled fine pressure regulating valve. WHAT WE CLAIM IS:

1. A method of regulating the printing in registry and in predetermined format length of a preprinted web provided with printing marks, wherein the web feed is controlled by a drive motor, according to the position of a pendulum roller which governs the web tension, and wherein errors in registry and in format length are detected by comparing signals from a sensor scanning the printing marks with those from a means detecting the phase position of the cylinder of the printing mechanism in relation to the scanned printing marks, and wherein according to the detected deviation the web tension is increased or reduced temporarily and abruptly in order to achieve printing in registry, and in order to achieve printing in predetermined format length the web tension is increased and reduced progressively, and wherein according to the detected errors output signals are formed which simultaneously operate a fine adjusting valve and magnetic valves through adjustable time relays in order to adjust the pendulum roller position.

2. Apparatus for performing a method according to claim 1 comprising a feed means driven by a drive motor to withdraw the web from a supply reel, a pendulum roller movable by a piston-cylinder unit and controlling the web feed according to its deflection, and a comparator unit which compares the signals from a photocell scanning the printing marks on the web with the signals from means detecting the phase position of the cylinder of the printing mechanism in relation to the scanned printing marks and transmits signals according to the detected deviation, wherein the comparator unit is connected to a control unit which, as long as the comparator unit signals a control departure, gives pulses through adjustable time relays to a servo-motor which operates a cam plate controlling a fine pressure reg- ulating valve which progressively increases or reduces the web tension by correspondingly raising or lowering the pressure in the piston-cylinder unit, the control unit also transmitting pulses to magnetic valves which temporarily and abruptly increase or reduce the pressure in the piston-cylinder unit.

3. A method of regulating the printing of preprinted webs substantially as hereinbefore described and with reference to the accompanying drawings.

4. Apparatus for regulating the printing

or preprinted webs constructed and arranged substantially as hereinbefore described and shown in the accompanying drawings.