EP1935643B1 - Method for controlling a rotary press and rotary press - Google Patents

Description

The present invention relates to a method for controlling a rotary press for printing a web of material, the press being of the type comprising printing units each having at least one impression and drive roll of the web , the press comprising at least one tape drive cylinder disposed downstream of the printing units in the running direction of the web.

During printing operations, a print tape travels in tension and at high speed on the printing and driving rolls and on the or each downstream driving roll.

The printing and driving rolls and the downstream driving rollers are in contact with the web and rotated so that they contribute to driving the web. The printing and driving cylinders also print the tape by depositing ink thereon.

In case of breaking of the web downstream of a printing unit, the tape loses its tension and tends to adhere to the printing cylinders of the printing unit, because of the ink which covers them. The tape may wrap around one of the printing cylinders, which can very quickly cause damage to the printing unit due to tape layers accumulating in the print unit. 'impression.

DE 196 00 110 A1 proposes to brake one or more functional units as quickly as possible according to the maximum available torque of the electric motors of the functional units.

An object of the invention is to limit the risk of damage to printing units in case of breakage of the band.

To this end, the subject of the invention is a method for controlling a rotary press of the aforementioned type according to claim 1.

The invention also relates to a rotary press according to claim 9.

• la figure 1 est une vue schématique d'ensemble d'une presse rotative ;
• les figures 2 et 3 sont des vues schématiques d'une unité d'impression de la presse de la figure 1, dans deux configurations distinctes ; et
• les figures 4 à 6 sont des graphiques illustrant différents procédés de commande de la presse de la figure 1.

The invention and its advantages will be better understood on reading the description which will follow, given solely by way of example, and with reference to the appended drawings, in which:

• the figure 1 is a schematic overview of a rotary press;
• the Figures 2 and 3 are schematic views of a press printing unit of the figure 1 in two distinct configurations; and
• the Figures 4 to 6 are graphs illustrating different methods of controlling the press of the figure 1 .

The figure 1 illustrates a rotary press 2 for printing a strip 4 of material, for example a strip of paper.

During the printing operations, the band 4 passes through the press 2, in tension and at high speed, following a path of movement, from left to right on the figure 1 , as illustrated by the arrow S.

In the remainder of the description, the terms "upstream" and "downstream" refer to the direction of travel of the web 4 in the press 2 along its path of travel.

The press 2 comprises a plurality of functional units, including, successively from upstream to downstream, a reeling unit 6, printing units U1, U2, U3 and U4, a drying unit 8, a unit 10 and a folding and / or receiving unit 12.

Units 8, 10 and 12 are optional.

The unwinding unit 6 makes it possible to unroll the strip 4 from a reel. Each printing unit U1, U2, U3, U4 makes it possible to print the double-sided tape 4. The drying unit 8 makes it possible to dry the strip 4 after it has been printed. The cooling unit 10 is used to cool the strip 4 after drying. The folding unit 12 makes it possible to fold the band 4, for example to form notebooks.

As shown on the Figures 2 and 3 , each printing unit U1, U2, U3 and U4 is double and comprises two printing groups 14 and 16 disposed on either side of the strip 4 for a double-sided printing thereof.

Each of the printing units 14 and 16 comprises a blanket printing cylinder 18, a plate cylinder 20, and an inking cylinder 22 of parallel axes.

In a manner known per se, each printing unit U1, U2, U3, U4 comprises a mechanism (not shown) for supporting and moving the cylinders 18, 20, 22 of the printing units 14 and 16 between a pressure configuration ( figure 2 ) and a pressure-free configuration ( figure 3 ).

In pressure configuration ( figure 2 ), the cylinders 18 of the printing units 14 and 16 are brought together and clamp the strip 4 between them. The cylinder 20 of each of the groups 14 and 16 is applied against the cylinder 18 of this group, and the cylinder 22 of each of the groups 14 and 16 is applied against the cylinder 20 of this group.

During the printing operations, the groups 14 and 16 are in pressure configuration. The cylinder 22 deposits ink on one or more plate (s) carried (s) by the cylinder 20 and imposed according to the pattern to be printed, and the or each plate deposits the ink in the pattern determined on a blanket carried by the cylinder 18, which deposits the ink on one side of the strip 4.

In an off-press configuration ( figure 3 ), the rolls 18 are spaced from each other by a gap e sufficient to allow the band 4 to pass, that is to say a gap e greater than the thickness of the band 4.

The pressure-free configuration makes it possible to intervene on the printing unit U1, U2, U3, U4 for maintenance operations, for example to change the plates, blankets or cylinders.

As shown on the figure 3 in the non-pressure configuration in each of the groups 14 and 16, the cylinder 20 is spaced from the cylinder 18, and the cylinder 22 is spaced from the cylinder 20.

Alternatively, in the off-press configuration, the cylinders 18 of the groups 14 and 16 are spaced apart but the cylinders 18, 20 and 22 of the same group 14, 16 are kept applied to each other.

Returning to figure 1 , the unwinding unit 6 has roll deflection cylinders 24 which are free to rotate.

The drying unit 8 comprises means for heating the strip 4 to dry the ink deposited on the strip 4.

The cooling unit 10 comprises rolls 26 for deflecting the band 4.

The folding unit 12 comprises, in the example illustrated, in a manner known per se a cone 28 for folding the band 4 for example along a longitudinal fold line. The folding unit 12 comprises several pairs of cylinders 30, arranged upstream and downstream of the folding cone 28. The two cylinders 30 of each pair pinch the band 4 between them.

The units U1, U2, U3, U4, 10 and 12 have devices 32 for driving their cylinders 18, 26 and 30, each of these units having its own device 32.

Each device 32 comprises one or more motors. For example, the device 32 of each of the printing units U1, U2, U3 and U4 comprises a motor common to the two printing units 14 and 16, a motor for each printing unit 14 and 16, or a motor for each of the cylinders 18 and 20, and possibly 22.

The press 2 has a detection device 34 associated with each of the units U1, U2, U3, U4, 10, 12, and a central control system 36 for all of these units.

Each detection device 34 is able to emit a measurement signal representative of the angular position or the angular velocity of the cylinders 18, 26, 30 of the corresponding unit.

The control system 36 is connected to the detection devices 34 to receive the measurement signals emitted by them, and is connected to the drive devices 32 to send them control signals after processing of the measurement signals.

During the printing operations, the rolls 18, 26 and 30 are in contact with the band 4 and rotated each by the device 32 of their unit U1, U2, U3, U4, 10, 12. These cylinders 18, 26 and 30 cause the strip 4 to move in the press 2.

The rotation of the rolls 18, 26 and 30 must be synchronized, on the one hand, to ensure the running of the strip 4 in tension between the different units of the press 2, and, on the other hand, to ensure the correct impression of the band 4, without offset between the images printed by the different printing units U1, U2, U3, U4.

For this purpose, the control system 36 slaves the cylinders 18, 26 and 30 in angular position and / or in angular velocity and ensures their synchronized rotation.

It happens that the band 4 breaks during the printing operations, due to the mechanical and thermal stresses it undergoes, and often because of a defect of the band 4.

In a manner known per se, the press 2 has detectors 38 breaking tape along the path of the strip 4. The press 2 comprises for example a detector 38 between each pair of adjacent units.

The detectors 38 are detectors of a known type, and for example optical detectors capable of detecting a break in the band 4 by the modification of a light beam reflected by the band 4 or crossing the band 4 because of the loss. of tension of the band 4.

In case of rupture of the strip 4 downstream of a printing unit, the band 4 tends to adhere to the cylinders 18 of this printing unit because of the ink which covers these cylinders 18. Thus, the band 4 tends to curl on one of two.

The accumulation of the strip 4 wound on a cylinder 18, between the cylinder 18 and the cylinder 20 of the same printing unit or between the cylinder 18 and the cylinder 18 of the other printing unit of the unit of printing, risk of damaging these cylinders, plates or blankets carried by these cylinders, or the printing unit as a whole, or to prevent the operation of the press 2 for a variable delay due to the pollution of the press 2 by pieces of the band 4.

The replacement of a cylinder, its plate or its blanket, and the restarting of the printing unit are tedious and expensive.

In order to protect the printing units U1, U2, U3 and U4, in case of breakage of the belt 4, an emergency stop of the press 2 during which the drive rolls of the machine are braked is applied. press 2, for example by applying them a braking resisting torque using the motors of the driving devices 32.

The figure 4 is a graph representing the running speed (y-axis) of the drive rolls of the press 2, as a function of time (x-axis).

The speed of travel of a driving cylinder is the running speed applied by this drive cylinder to the belt 4, which is substantially equal to the product of the angular velocity of this cylinder by its radius.

On the figure 4 in a normal operating phase, between times T0 and T1, the drive rolls are driven in a synchronized manner, at the same constant scrolling speed V0.

On detection of a rupture of the strip 4 at time T1, an emergency stop step of the press 2 is implemented by braking the drive rolls of the press 2 by applying a braking torque using the motors of the devices 32.

From the beginning of the emergency stop, the printing units 14, 16 of the printing units U1, U2, U3 and U4 are moved in an unpressurized configuration to disengage the cylinders 18 of the band 4.

In addition, a differential braking stage of the drive rolls of the press 2 is implemented.

In particular, in the differential braking stage, the rolls of the printing units U1, U2, U3 and U4 are slowed down, and in particular their rolls 18, faster than the drive rolls 26, 30 of the units 10, 12 arranged downstream of the printing units U1, U2, U3 and U4.

Thus, as represented on the figure 4 , the cylinders 18 of the printing units U1, U2, U3 and U4 are stopped at the instant T2, before the driving rollers 26, 30 of the units 10, 12, which are stopped at a time T3.

For example, the drive rolls of the printing units U1, U2, U3 and U4 are stopped in 3 seconds, while the drive rolls 26, 30 of the units 10, 12 are stopped in 10 seconds.

The faster braking of the rolls 18 makes it possible to limit a winding thickness of the strip 4 around these rolls 18, and consequently limits the risk of damage to these rolls 18 and the printing units U1, U2, U3 and U4.

The drive motors of the rolls 18 are generally dimensioned more strongly than the motors of the other drive rolls of the press 2, because of the greater resistant torques encountered by the rolls 18. The faster braking of the rolls 18 is therefore possible. without structural modifications of the press 2, and only by a modification of the programming of the emergency stop of the control system 36.

In the mode of implementation of the figure 4 , the cylinders 18 of the printing units U1, U2, U3 and U4 are slowed synchronously with each other, and stop at the same time T2. The drive cylinders of the units 10 and 12 are also stopped in synchronism with each other, and stop at the same time T3.

In an alternative embodiment according to the invention illustrated on the figure 5 at the detection of the breaking of the web at the instant T1, a prior synchronized braking step is implemented, in which the rolls 18 of the printing units U1, U2, U3 and U4 and the rolls 26 are slowed down. , Units 10, 12 in a synchronized manner, while moving the printing units 14 and 16 of the printing units U1, U2, U3 and U4 in an off-press configuration.

Once the pressure-free configuration is reached, at a time T4, the differential braking step is implemented as before, braking the rollers 18 more rapidly than the rolls 26 and 30.

The cylinders 18 stop at a time T5, before the cylinders 26, 30 which stop at time T3.

The prior step of synchronized braking avoids causing new breaks in the band 4 due to different slowdowns of the band 4 increasing the voltage in the band 4.

Advantageously, to accelerate the stopping of the printing units U1, U2, U3, U4, the differential braking stage begins as soon as the spacing between the cylinders 18 of each printing unit U1, U2, U3, U4 is greater than the thickness of the strip 4, without waiting to have reached the configuration off pressure.

In another embodiment illustrated on the figure 6 at detecting the break at the instant T1, the printing units 14 and 16 of the printing units U1, U2, U3 and U4 are maintained in pressure configuration, and the cylinders 18 of the units of the printing units are slowed down. printing U1, U2, U3 and U4 differentially.

In a first variant illustrated on the figure 6 the rolls 18 of each of the units U1, U2 and U3 are braked more rapidly than those of the adjacent printing unit U2, U3 and U4 located downstream respectively.

Thus, the slowing speed of the printing units U1, U2, U3 and U4 is decreasing from upstream to downstream. As a result, the tension of the web 4 is increased between each pair of adjacent printing units between which the web 4 is still stretched, which is the case if the breaking point of the web 4 is not between the two printing units of said pair.

A sufficient increase in the voltage makes it possible to break the band 4 again between the two adjacent printing units, which limits the length of band 4 that can be wound on the cylinders 18 of these printing units.

Thus, for example, if the band 4 breaks initially between the drying unit 8 and the cooling unit 10, the band 4 will be broken due to the differential braking at three secondary breaking points between the units U1 and U2. units U2 and U3, and units U3 and U4.

In a second variant, the rolls of printing units U1, U2, U3 and U4 located upstream of the breaking point are braked faster than the rolls of printing units U1, U2, U3 and U4 located downstream of the point a break.

The risk of winding downstream of the breaking point is less important because the downstream band 4 continues to be driven downstream by the units of the press 2 located downstream of the breaking point. Therefore the differential braking only of the printing units upstream of the breaking point greatly limits the risks of winding.

In this second variant, the cylinders of printing units U1, U2, U3 and U4 located upstream of the breaking point are slowed synchronously with each other, or differentially between them, according to the first variant.

The rolls of the printing units U1, U2, U3 and U4 located downstream of the breaking point are slowed down at the same speed or faster than the rolls of the press units 2 situated downstream of the printing units U1, U2 , U3 and U4.

In addition, the risks of winding are greater when the rupture of band occurs in a zone A ( figure 1 ) of the press 2 between the printing unit U1 furthest upstream and the cooling unit 12, only when the strip breaking occurs in a zone B, downstream of the zone A.

Therefore, during an emergency stop, a differential braking step is implemented when a break in the band 4 is detected in the zone A, and the differential braking step is not used when a tape break is detected in zone B.

If during the emergency stop of the press 2 without differential braking is detected a new rupture of the band 4in the zone A, it then implements a differential braking step.

A differential braking step is implemented according to any one of the embodiments and any one of the variants described above.

Claims (9)

1. Process for control of a rotary press (2) for printing a strip (4) of material, the press (2) being of the type comprising printing units (U1, U2, U3 and U4), each one having at least one impression and feed cylinder (18) for the strip (4), the press comprising at least one feed cylinder for the strip (4), arranged downstream from the printing units (U1, U2, U3 and U4) in the direction of unwinding the strip (4),
   wherein, in normal operation, the said impression and feed cylinders (18) and the or each downstream feed cylinder (26, 30) are driven in a synchronised manner and, in the event of breakage of the strip (4), a stage of differential braking of the said impression and feed cylinders (18) and of the or each downstream feed cylinder (26, 30) is used,
   characterised in that, in the event of breakage of the strip (4), a prior stage of synchronised braking is used, at which the said impression and feed cylinders (18) and the or each downstream feed cylinder (26, 30) are braked in a synchronised manner, then the differential braking stage is used and in that, at the synchronised braking stage, within each printing unit (U1, U2, U3, U4), each impression and feed cylinder (18) is moved away from an associated counter-pressure cylinder (18) provided for holding the strip (4) against the impression and feed cylinder (18) and the differential braking stage is started when each impression and feed cylinder (18) is moved away from the associated counter-pressure cylinder (18) by a predetermined minimum distance.
2. Process according to claim 1, wherein, at the differential braking stage, at least part of the impression and feed cylinders (18) is braked more rapidly than the or each downstream feed cylinder (26, 30).
3. Process according to claim 1 or 2, wherein, at the differential braking stage, the impression and feed cylinders (18) are braked in a synchronised manner.
4. Process according to any of claims 1 to 3, wherein, at the differential braking stage, the impression and feed cylinders (18) are braked in a differential manner.
5. Process according to claim 4, wherein, at the differential braking stage, the impression and feed cylinders (18) situated upstream from a point of breakage of the strip (4) are braked more rapidly than the impression and feed cylinders (18) situated downstream from the point of breakage.
6. Process according to claim 5, wherein, at the differential braking stage, the impression and feed cylinders (18) situated upstream from the point of breakage are braked in a synchronised manner.
7. Process according to any of the preceding claims, wherein each printing unit (U1, U2, U3, U4) has two printing groups (14, 16), each comprising an impression and feed cylinder (18), the impression and feed cylinder (18) of each printing group (14, 16) forming a counter-pressure cylinder for the impression and feed cylinder (18) of the other printing group (14, 16) to hold the strip (4) against the impression and feed cylinder (18) of the said other printing group (14, 16).
8. Process according to any of the preceding claims, characterised in that each impression and feed cylinder (18) is a blanket cylinder of a printing group (14, 16) also having a plate cylinder (20).
9. Rotary press (2) of the type comprising a plurality of printing units (U1, U2, U3, U4), each having at least one printing group (14, 16) comprising an impression and feed cylinder (18) for a strip (4) to be printed and a counter-pressure cylinder (18) for holding a strip (4) to be printed between the counter-pressure cylinder (18) and the impression and feed cylinder (18), the press (2) also comprising at least one feed cylinder (26, 30) for the strip (4), arranged downstream from the printing units (U1, U2, U3, U4) in the direction of unwinding of the strip (4), characterised in that it comprises means (32) of driving the impression and feed cylinders (18) and the downstream feed cylinders (26, 30) and control means (34, 36, 38), adapted and programmed for using a control process according to any of the preceding claims.

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