EP0709184B1 - Apparatus for avoiding register differences - Google Patents

Abstract

The lining-up errors in the printers are measured at a numbers of printing speeds. The register corrections, which are necessary, are determined from these measurements which were carried out during actual printing tests. The corrections are incorporated taking the actual printing speeds into account. The register connections can also be established by building a theoretical model in which the rigidity of the drive train (R) of the printing machine is continuous. Register corrections are carried out taking the printing speeds into account as well as the load torque which the printing machine exerts on the main drive of the machine.

Description

The invention relates to a device for avoiding register differences according to the preamble of claim 1.

Modern sheetfed offset presses are usually controlled by speed DC drives, what their operation in allowed a wide speed range. Also be on today Sheetfed offset printing machine Print speeds of 15,000 sheets / h and achieved more. Operating a sheetfed offset press in wide speed range on the one hand and the achievable high Print speeds, on the other hand, require high levels of construction Effort to avoid register differences. In the the individual printing units printed in different colors must lie on the substrate in the correct position. Around just those that occur when the printing speed changes It is therefore known to be able to control register differences in the individual printing units in particular remotely adjustable devices to be provided for register adjustment. For page, circumference and Slant register correction can be done in particular by the plate cylinder compared to the blanket cylinders that interact with them be remotely adjustable.

When starting up a printing press, for example, from the basic speed in some cases, considerable press speeds occur Register differences. This not only applies to the acceleration phase, i.e. within the period in which the speed of the Printing machine is changed per unit of time, but also in ultimately reached steady state. The register differences that occur are due to the fact that in mechanical Drive train of the machine due to the speed-dependent load torque of the individual printing units a speed-dependent Torsion occurs. Depending on the rigidity of the mechanical Drive train, i.e. the elasticity of the performance transferring links between the individual printing units, it comes thus to register differences.

Traditionally, these register differences are compensated by that in particular on printed passports, pass marks, Passing crosses or the like just the passport differences individual sub-colors determined to each other and then control commands calculated for the necessary register corrections and these then brings to a halt. Especially for the circumferential register are the individual plate cylinders in the printing units in corrected their position so that the individual partial colors again to cover in the correct position. However, this has the disadvantage that at Such a procedure creates costly waste.

EP 0 446 641 A2 describes a position controller for the drive shafts a printing press known, by means of which a faulty Register accuracy during the acceleration of the printing press should be avoided. For this purpose, position signals at the different Shafts of the printing press formed and this with a Evaluation and control circuit on a constant phase position regulated. This previously known solution is probably for roll rotary printing machines with multiple drive motors can be used, but demonstrates appropriate transfer to a sheetfed offset press several printing units have significant disadvantages. So would have to the individual printing units or the plate cylinder axes, signal transmitter be attached with the highest resolution to position differences still being able to record which in the order of 1 / 100mm and lie below. Such signal generators are, however Can be used with a sheetfed offset press at all, very much expensive. A similar solution to register regulation Printing machines with multiple printing units during acceleration or delay also suggests DD-PS 115 069.

A multi-color sheetfed offset printing press is known from EP 0 571 159 A1 known in the case of the plate cylinders in the individual printing units remotely adjustable register correction devices are assigned. To determine the necessary setting commands for the register adjustment devices but also printed registration marks are scanned, what the disadvantage already made above Waste results.

The known register control systems for printing presses with several printing units therefore have in common that for register differences leading bearing differences of either printing unit parts relative to each other or to each other by printed passport marks , whereupon from it control commands to correct the register differences be determined. It is basically as disadvantageous to consider that a complex measurement technology is used must be to register errors or register differences first determine.

EP-A-0 081 186 describes a method for reducing register errors and a corresponding printing press for performing the method is known at which the printing press is driven by a common motor and Has facilities for register adjustment. It becomes functional Relationship between the torque delivered by the engine or one for the Torque characteristic size and that to maintain a flawless Necessary register shift determined and saved. This will the printing press at different printing speeds and the Register shifts recorded with the respective torque. When operating the Printing machine is then the register according to the torque according to the stored values. A disadvantage of this known design is that you work directly with the torque or a variable dependent on it. It is known in sheetfed offset presses that the driving torque, based on a single-revolution of the machine, around an average fluctuates, so that additional measures for smoothing or filtering when used this fluctuation must be provided, otherwise the short-term occurring Torque changes or current fluctuations for register operations to lead.

The object of the present invention is therefore a device for avoidance of register differences according to the preamble of claim to expand in such a way that the disadvantages listed above can be avoided.

This object is achieved by the characterizing features of claim 1. Further developments of the invention result from the subclaims.

According to an embodiment of the invention it is provided in pressure tests determine which register differences are at different printing speeds arise to then derive from this which register corrections for the individual Printing units at different printing speeds are necessary. In this way, a characteristic curve can be created for each printing unit can be determined, which indicates how large the particular to be carried out Correction of the circumferential register must be made in order to achieve the the printing unit under consideration caused register difference in the circumferential direction needs to be corrected. Such a variety of characteristic curves determined by tests are stored in the control according to the invention. It can also be provided, one for each printing unit Characteristic curve for different types of substrates or substrate thicknesses save. Instead of an empirical determination of the It is also print speed dependent register corrections possible to take the correction values through theoretical modeling Consideration of the rigidity of the drive train of the printing press perform.

Then, during printing, is carried out by the invention Control that depending on that detected by the control Print speed or a corresponding size in the individual printing units corrections of the circumferential register according to the associated characteristic curves are executed. The invention Control is available with a known register remote adjustment device in operative connection which corrects the circumferential register on the individual plate cylinders in the printing units for execution brings.

By the inventive, depending on the printing speed Correction of circumferential register errors in particular is avoided, that when the pressure speed changes, register differences in Circumferential direction sometimes occur on a considerable scale can. Of course, this invention Measure also register differences during the acceleration or Delay phase itself avoided because of the circumferential register correction via the remote register adjustment according to the current one Value of the printing speed, i.e. the speed of the printing press be carried out.

According to a preferred embodiment of the invention, that in addition to the measure described above, the value of the speed-controlled direct current drive of the printing press supplied current is detected and range register corrections in the individual printing units according to previously determined characteristics be carried out. In general, the register is in Corrects dependency of the load torque which the printing press opposed to the main drive. Again, pressure tests are used determines which register differences in the different Printing units are caused when the DC drive supplied motor current assumes different values. From these Registration differences are then in turn for the individual printing units Characteristic curves determined, which indicate which circumference register correction in the respective printing unit at a certain value of the motor current is necessary to a register difference in the circumferential direction avoid. The conversion of register differences in the circumferential direction corresponding control commands for a register adjustment device in The circumferential direction is known per se, so that a deeper one No need to go into this. In particular, can be provided be, from the register differences register correction values for the first printing unit to calculate the following printing units. The one in the first Color printed on the printing unit thus becomes the base color and the Registers in the following printing units are based on this standard color related corrected.

The invention is therefore preferably in the individual Printing units Corrective register corrections not only in dependence the printing speed but also depending on the motor current be performed. To do this, in turn, in pressure tests for a variety of values of printing speed and each different motor currents Correction of circumferential registers for the individual plate cylinders determined so that register differences in the circumferential direction avoided become. To be different at a given printing speed To be able to specify motor currents can be provided to attach braking devices to the individual printing units, at which the braking torque is adjustable. It is also conceivable To vary the load in the individual printing units - what a change in the motor current at a given printing speed has the consequence - by the pressure between the printing unit cylinders and / or the strength of cylinder lifts and / or the Ink viscosity is varied. It is also possible to Variation of the motor current at a given printing speed pressure tests at different machine temperatures mentioned above because the load moments of the bearings in one cold press are larger than at a machine temperature, which corresponds to the printing operation.

The pressure tests to be determined in the pressure tests described above Characteristic fields, which indicate which circumference register correction in the respective printing unit depending on the printing speed as well as the motor current are carried out in the invention Control stored, this being fed a signal which changes depending on the printing speed and further a further signal is supplied, which the value of the reproduces current motor current. For the current value of the Printing speed can be, for example, the signal from a tachometer generator be used. A line-guided converter for a DC drive provides the current speed value, however also available in digital form. For capturing the current Current value of the direct current drive can, for example, be the Armature current can be measured directly or accordingly on the converter provided value are applied.

The method according to the invention and a correspondingly designed one Control especially avoid register differences in Circumferential direction when the value of the printing speed changes and also in particular by changing the machine temperature in that empirically determined in the individual printing units Corrections to the circumferential register come to an end. It will takes advantage of the fact that the drive train is a Sheetfed offset printing machine with several printing units a certain Has torsional rigidity, i.e. at different load moments a predictable torsion between the individual printing units occurs. The occurring when the print speed changes Register differences have their cause in the fact that in one Load torque caused by the printing unit is a function of the speed, so the print speed is. When the print speed changes is not only the one to be fed into the drive train Performance greater, but also the load moments in the individual printing units. This results from predictable Register errors, register differences caused by the invention Procedure and a correspondingly trained control system Corrections to the circumferential register can be compensated again.

The register correction depending on the detected motor current value the DC drive also closes the fact Use that on the one hand the motor current (armature current) of a direct current drive proportional to the torque applied by the motor is when it is running at a specified speed. To the on the other hand, the drive torque is equal to the load torque the printing press, which is the sum of the individual load moments of the Printing units is. A warming that occurs during printing the machine thus leads to itself in the individual printing units changing load moments, so that at a given speed Current value of the DC drive changes. So that's also predictable by the current value, how big the due to torsion caused register differences in the individual printing units and therefore also how large the corresponding register corrections must be to compensate for them.

Furthermore, an exemplary embodiment is explained the invention with reference to the drawings.

Fig. 1

eine Bogenoffsetdruckmaschine mit Registerfernverstellung und einer erfindungsgemäßen Steuerung, welche mit dem Hauptantrieb der Druckmaschine in Verbindung steht, und

Fig. 2

prinzipiell ein Kennlinienfeld, welches den Zusammenhang der nötigen Umfangsregisterkorrekturen in einem Druckwerk als Funktion der Drehzahl sowie des Motorstroms wiedergibt.

It shows:

Fig. 1

a sheetfed offset printing machine with remote register adjustment and a control according to the invention, which is connected to the main drive of the printing press, and

Fig. 2

in principle a characteristic field, which shows the relationship between the necessary circumferential register corrections in a printing unit as a function of the speed and the motor current.

Fig. 1 shows the first four printing units of a sheetfed offset printing press. The plate cylinders P1 to P4 are with register adjustment devices R1 to R4 connected, which is a correction of the register position allow the plate cylinders P1 to P4 at least in the circumferential direction. The register adjustment devices R1 to R4 stand with one known register remote adjustment RS in operative connection, which the positioning drives of the register adjustment devices R1 controlled up to R4 according to specified data. Via an input station can also make corrections to the register remote RS be done manually.

The individual printing units are designed as a train of wheels R. Drive train interconnected by each double-sized spur gears of the impression cylinder G and the corresponding Transfer drums T is formed. The R and thus the individual printing units are powered by a DC motor M driven, its performance in the examples shown here Machine concept the power on the drive wheel one Feeding the transfer drum.

The DC drive M is designed as a converter Main drive HA controlled, this still with one Tachogenerator T is in operative connection with the DC motor M is coupled. In connection with the tachogenerator T the speed control of the DC motor M takes place

The control S according to the invention detects, for example, via the Main drive HA each have a signal that the speed n of the DC motor M or the printing speed of the printing press corresponds, and a signal that the motor current (armature current) IA of the DC motor M corresponds. In the controller S are for individual printing units characteristic curves, according to which in Dependence of the motor current IA and the speed (printing speed) n Adjustment values for the circumferential register of the plate cylinders P1 to P4 can be determined in the various printing units. The circumferential register corrections determined by the control S. through the remote register adjusters RS on the plate cylinder P1 brought up to P4. The setting of each Correction values for the circumferential register are made simultaneously to present current value of the motor current (armature current) IA as well the speed n (printing speed). It can also be provided to define the color printed in the first printing unit as the base color and carry out circumferential register corrections in the following printing units.

2 shows in principle a characteristic curve for a printing unit, according to which the e.g. empirically determined necessary corrections of the circumferential register ΔU as a function of speed n (printing speed) as well as the motor current IA. Is reproduced here, in principle, a characteristic field in the form of a skew in Direction of origin of the coordinate system. This Characteristic curve or this characteristic field gives the basic Again tendency that the circumferential register correction ΔU for a printing unit with increasing speed n even at a given speed value increases with increasing value of the motor current IA. Of the For the sake of simplicity, this is basically to be understood here Characteristic field of purely linear dependencies of the necessary circumferential register corrections ΔU as a function of the speed n or the motor current IA It is also shown that the characteristic field is only what begins at a level lying in the N-IA plane The reason for this is that for every speed n (printing speed) there is a certain minimum current IA. Correction of the circumference register with reverse sign and negative current (electric braking) are not shown.

In the exemplary embodiment described above, it was explained that that all printing units or all plate cylinders P1 to P4 of the printing units depending on the speed n and the motor current IA Corrected in the circumferential register direction. Of course however, it is also possible to make the circumferential register corrections provided according to the invention as a function of the speed n and the motor current IA can only be carried out in certain printing units. It would be It is therefore possible to always have the plate cylinder P1 in the first printing unit to keep the same register position and the intended Make register corrections in the following printing units.

Reference list

P1 to P4

Plate cylinder

R1 to P4

Register adjustment device

RS

Remote register adjustment

R

Gear train

G

Counter-pressure cylinder drive wheel

T

Drive wheel transfer cylinder

M

DC motor

HA

Main drive (converter)

TA

Tachometer generator

IA

Motor current

n

rotational speed

ΔU

Correction of the circumferential register

Claims (3)

1. Device for avoiding register differences on operating a printing press with several printing units, particularly for an offset sheet printing press, wherein the printing units have adjustment devices (R1 - R4) at least for the peripheral register and a control (S) which is operationally connected with the drive (HA, M) of the press is provided in which the operational condition of the main drive (HA) is sensed and corresponding to the signals of the main drive (HA) in combination with stored values in dependence on the operational condition, the register adjustment devices (R1 - R4) in the printing units are actuated, wherein the control (S) contains stored for a plurality of different print speeds (n) the necessary corrections for compensating register differences for the respective printing units, characterised in that the control (S) is in signal connection with a transmitter (TA) for the actual print speed (n), that the control (S) contains the correction values for the register differences as function of the print speed (n) and in combination with the signal of the transmitter (TA) brings them to adjustment.
2. Device according to Claim 1, characterised in that the register corrections necessary at the respective print speed (n) for compensation for register differences can be stored in the control (S) in the form of derived values.
3. Device according to Claim 1, characterised in that the necessary corrections for compensating register differences at the respective print speed (n) are determined by theoretical model formation taking

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