DUMPING UNIT FOR A PRESS

Abstract

A damping unit for a press has means for applying a clamping solution to a printing form and means for setting the quantity of damping solution applied. At least one sensor is provided for registering the quantity of damping solution actually applied to the printing form. By means of a comparison with a predefined quantity of damping solution, the quantity of damping solution on the printing form can be regulated.

Description

FIELD OF THE INVENTION

The invention relates to printing devices, and more particularly to a damping unit for a printing press.

BACKGROUND OF THE INVENTION

In planographic printing processes, it is generally known to wet the non-printing points of a printing form with damping solution and to wet the printing points with ink. The metering of the damping solution is controlled by the control desk. In the case of film damping units, the rotational speed of the damping solution distributor is driven and the quantity of damping solution across the web width is controlled manually by means of pressure changes between dip roll and damping solution distributor. In the case of nozzles and centrifugal damping units, the quantity of damping solution can be controlled via the spraying frequency of the nozzles or via the valve opening in the case of turbo damping units.

In the case of controlled metering of the quantity of damping solution, it is disadvantageous that erroneous settings can occur.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to improve the metering of the quantity of damping solution on a printing form.

In a damping unit according to the invention, the quantity of damping solution on the printing plate is advantageously regulated. Moreover, a damping unit according to the invention is advantageously self-teaching and compensates automatically for changes on the roll coatings as a result of swelling or shrinkage.

When starting up a new print job, the optimal settings can be stored, and, during the next such job, can be read back again into the control/regulating device of the damping unit as presetting data.

Furthermore, the laborious determination of what is known as a “damping run-up curve” for different materials can be dispensed with, since the rotational speed of the damping unit and, likewise, the imprint widths of the dip roll can be regulated via a control signal of the damping unit according to the invention.

Moreover, with a damping unit according to the invention, smearing, scumming and color build-up can be detected in good time and therefore the wastage can advantageously be reduced.

Preferred embodiments of the invention are described in greater detail below with reference to the schematic drawings, in which:

BRIEF DESCRIPTION THE DRAWING(S)

FIG. 1 shows a film damping unit in an embodiment according to the invention;

FIG. 2 shows adjusting devices of the film damping unit;

FIG. 3 shows a spray damping unit in another embodiment according to the invention; and

FIG. 4 shows a centrifugal damping unit in yet another embodiment according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, the principle according to the invention is applied to an embodiment using a film damping unit, illustrated as a detail from a press is a plate cylinder 1, which normally interacts with a transfer cylinder. On the plate cylinder 1 there is a printing form, which is provided with ink-accepting and ink-repelling regions. A damping solution is applied to the ink-repelling regions. In order to measure the damping solution layer thickness, a sensor 2 is provided, which is operatively connected to a control/regulating device 3. A value of the damping solution layer thickness or quantity can be predefined in the control and regulating device 3.

Since the quantity of damping solution which is applied to the plate cylinder 1 depends firstly on the pressure between a dip roll 9 and a damping solution distributor 8 and on the oblique adjustment of the dip roll with respect to the damping solution distributor and on the damping solution distributor speed, the predefined value 4 results in a set point for the pressure between the dip roll 9 and damping solution distributor, a set point for the oblique adjustment of the dip roll with respect to the damping solution distributor and a set point for the damping solution distributor speed. From the signal from the sensor 2, the control and regulating device 3 determines the respective actual values of the pressure between the dip roll and damping solution distributor, the actual value of the oblique adjustment of the dip roll and the damping solution distributor speed. Following a comparison between set points and actual values, the deviations determined are readjusted by means of appropriate regulating devices 5.

In order to adjust the pressure between the dip roll 9 and the damping solution distributor roll 8, two motors 6a, b are provided, which are able to adjust the roll mountings, preferably via spindles. A further motor 6c is provided for the oblique adjustment of the dip roll, and a motor 6d is driven in order to regulate the damping solution distributor speed. The achievement of the predefined value 4 is manifested by the production of what is known as a good sheet. The latter has the desired print quality and the values for the control variables a, b, c and d adjusted for this purpose can be stored and later read back again into the control and regulating device 3 for the production of a similar job. Instead of a single sensor 2, a plurality of sensors 2 can also be provided, which are arranged distributed over the width of the printing form. The result is an evaluation of different regions of the printing form, and it is possible to regulate the corresponding regions differently as well.

In order to regulate to the predefined value 4, each control variable a, b, c, d can be regulated on its own or in conjunction with one or more others.

FIG. 2 illustrates the possible adjustments of the film damping unit in a side view. The dip roll 9 applies the damping solution to a damping solution distributor roll 8, which applies the damping solution to the printing form on the plate cylinder 1 via an applicator roll 7. In order to adjust the pressure between the dip roll 9 and the distributor roll 8, adjusting motors 6a, b are provided, which are able to adjust the position of the roll mountings, preferably via spindles. For the purpose of adjusting the dip roll 9 obliquely with respect to the distributor roll 8, an adjusting motor 6c is provided, which likewise acts on the mounting of the dip roll 9, preferably via a spindle drive.

FIG. 3 illustrates an application of the principle according to the invention in an embodiment that uses a spray damping unit. In the case of a spray damping unit, the damping solution is sprayed via a spraying bar having a plurality of nozzles onto a damping solution distributor roll, which transfers the damping solution to the plate cylinder via a damping solution applicator roll. The quantity of damping solution may be influenced by the cycle frequency 10 and the cycle period 11 of the spraying. Furthermore, influence can also be exerted on the damping solution layer thickness via the damping solution distributor roll rotational speed 12 and the damping solution applicator roll rotational speed 13. As in the preceding exemplary embodiment, a sensor 2 is also provided here, which passes the actual value of the damping solution layer thickness on to a control/regulating device 3. The control and regulating device 3 breaks down the actual value into an actual value of the cycle frequency 10, cycle period 11, damping solution distributor rotational speed 12 and speed of the damping solution applicator roll 13. These actual values are compared with the associated set points i, l, g, h, which result from the predefined value of the quantity of damping solution. Following a comparison between the set points and the actual values, the corresponding deviations are readjusted. As soon as the first “good sheet” is produced, the ideal settings have been reached and can be stored. These values are read back into the control and regulating device 3 again for the next similar job and used as predefined values for the various settings.

An embodiment of a centrifugal damping unit according to the invention is illustrated in FIG. 4. In the case of centrifugal damping units, the damping solution is thrown onto a damping solution distributor without contact by a rotor, or directly onto the plate cylinder 1. Adjustable shields are provided in order to meter the quantity of damping solution. It is also possible for the damping solution distributor rotational speed or the rotational speed of the damping solution applicator roll to be used for metering. As in the preceding exemplary embodiments, a sensor 2 determines the damping solution layer thickness on the plate cylinder 1, and passes it on to a control and regulating device 3. The control and regulating device 3 breaks down the actual value of the damping solution layer thickness into an actual value for the shield position, damping solution distributor rotational speed and the speed of the damping solution applicator roll. A predefined value for the quantity of damping solution can be entered into the control and regulating device, which is broken down into set points i, j, k for the shield position, damping solution distributor rotational speed and damping solution applicator roll rotational speed. Following a comparison between the individual set points and actual values, the various settings can be readjusted by controllers 5i, j, k. As soon as the first good sheet is produced, the ideal settings have been reached and can be stored in a memory in order later to be read back in a manner analogous to the preceding exemplary embodiments.

Claims

1. A method for adjusting the quantity of fountain solution in a centrifugal dampening system of a printing machine wherein movable shutters having a shutter position, a rotating damping solution distributor, and a rotating damping solution applicator roll are provided for adjusting the quantity of fountain solution, the method comprising: determining a coating thickness of the fountain solution via at least one sensor;providing a signal indicative of the coating thickness from the at least one sensor to a control and regulation device;based on the signal from the at least one sensor, determining via the control and regulation device an actual values for the shutter position, damping solution distributor rotational speed and damping solution applicator roll rotational speed; andcomparing the determined thickness to a predetermined thickness, and recording the determined actual values for shutter position, damping solution distributor rotational speed and damping solution applicator roll rotational speed as set-point values for the predetermined thickness when the determined thickness is equal to the predetermined thickness.

2. The method according to claim 1, wherein the at least one sensor includes a plurality of sensors distributed across the width of the printing plate to determine the coating thickness of the fountain solution.

3. The method according to claim 1, wherein the centrifugal dampening system further comprises at least one dampening oscillator roller and one dampening form roller.

4. The method according to claim 1, further comprising reading back and applying the set-point values when a desired thickness is the predetermined thickness.

5. A printing machine comprising: a centrifugal dampening system including movable shutters having a shutter position, a rotating damping solution distributor, and a rotating damping solution applicator roll;at least one sensor for determining a coating thickness of a fountain solution and providing a signal indicative of the coating thickness;a control and regulation device for receiving the signal indicative of the coating thickness and configured to determine actual values for the shutter position, damping solution distributor rotational speed and damping solution applicator roll rotational speed, compare the determined thickness to a predetermined thickness, and record the determined actual values for shutter position, damping solution distributor rotational speed and damping solution applicator roll rotational speed as set-point values for the predetermined thickness when the determined thickness is equal to the predetermined thickness.

6. The printing machine according to claim 5, wherein the at least one sensor includes a plurality of sensors distributed across the width of the printing plate to determine the coating thickness of the fountain solution.

7. The printing machine according to claim 5, wherein the centrifugal dampening system further comprises at least one dampening oscillator roller and one dampening form roller.

8. The printing machine according to claim 5, wherein the control and regulation device is further configured to read back and apply the set-point values when a desired thickness is the predetermined thickness.

9. A controller for adjusting a quantity of fountain solution in a centrifugal dampening system of a printing machine, wherein movable shutters having a shutter position, a rotating damping solution distributor, and a rotating damping solution applicator roll are provided for adjusting the quantity of fountain solution, the controller including computer-readable instructions stored on a computer-readable medium, the instructions comprising instructions for: determining a coating thickness of the fountain solution via at least one sensor;providing a signal indicative of the coating thickness from the at least one sensor to a control and regulation device;based on the signal from the at least one sensor, determining via the control and regulation device an actual values for the shutter position, damping solution distributor rotational speed and damping solution applicator roll rotational speed; andcomparing the determined thickness to a predetermined thickness, and recording the determined actual values for shutter position, damping solution distributor rotational speed and damping solution applicator roll rotational speed as set-point values for the predetermined thickness when the determined thickness is equal to the predetermined thickness.

10. The controller according to claim 9, wherein the at least one sensor includes a plurality of sensors distributed across the width of the printing plate to determine the coating thickness of the fountain solution.

11. The controller according to claim 9, wherein the centrifugal dampening system further comprises at least one dampening oscillator roller and one dampening form roller.

12. The controller according to claim 9, wherein the instructions further comprise instructions for reading back and applying the set-point values when a desired thickness is the predetermined thickness.