WO2005108085A1

WO2005108085A1 - A control system and a method for a printing press

Info

Publication number: WO2005108085A1
Application number: PCT/SE2005/000526
Authority: WO
Inventors: Birger Hansson
Original assignee: Baldwin Jimek Ab
Priority date: 2004-05-07
Filing date: 2005-04-13
Publication date: 2005-11-17
Also published as: SE0401184D0; SE0401184L; DE112005001047T5; SE526315C2

Abstract

A method of improving the printing quality in a printing press (1), where signals indicative for the temperature at selected locations in the printing press (1) are utilized to control the amount of fountain solution supplied from a dampening device (7a) of the printing press (1) in relation thereto.

Description

A CONTROL SYSTEM AND A METHOD FOR A PRINTING PRESS

TECHNICAL FIELD The present invention relates to a control system and a method for improving the printing quality in a printing press .

BACKGROUND OF THE INVENTION It is well known in the printing industry that the ambient temperature in the vicinity of printing presses affects the printing quality, see e.g. GB-A-1 014 574. It is well known in the printing art that fountain solution is required for the offset printing process. The higher the temperature in the vicinity of a printing press is, the quicker fountain solution vaporizes, so that the printing quality deteriorates in an unpredictable manner. To compensate the vaporization the printer adds more fountain solution. The initial starting up of a printing press in room temperature consumes a certain amount of fountain solution. During the continued printing process the blanket cylinders of the printing press are heated and the fountain solution vaporizes quicker. The vaporization of fountain solution in a printing press is due to the generation of heat in the printing press. The heat generated in the printing press originates mainly from the friction between their cylinders and from the rotary friction of the cylinder bearings. The vaporization of fountain solution is a non-linear function relative to the temperature of the ambient air of the printing press. The vaporization together with the fountain solution consumption at the initial starting of the printing press forces the printer to continuously make manual adjustments of the printing press to increase the amount of fountain solution as the temperature is increasing by the heat generation. The wear of the printing plates increases and a varying toning is received. There are known different ways of controlling the temperature at printing presses to reduce the problems of the heat generation. One solution to the problem of heating is disclosed in US-B2-6 505 557, where a process temperature control system for a rotary printing press is equipped with conventional lithography printing plates or waterless printing plates by using its hollowed ink roller train to receive internal coolant and where the ink is the cooling medium. The system includes non-contact ink temperature sensors coupled to a temperature controller, which controls the flow of cooling medium. Another solution to the problem of heating is proposed in US-B-6 571 711, where a cooling system for a printing press includes a fan and a cooling element such as a chilled water coil. The printing press includes ink cylinders, a blanket cylinder, an impression cylinder, and one or more transfer cylinders. The fan generates an airflow toward a cylinder. The airflow is within a predetermined temperature range and of a sufficient magnitude to maintain the cylinder within a critical temperature range to prevent or minimize substrate distortion. Yet another solution is disclosed in US-B1-5 178 064, where a thermal regulator is provided for blowing tempered air on a printing form in an offset printing press to ensure that the property of the printing form is maintained at a optimum. The problem with the prior art solutions is that they are relatively expensive and therefore primarily can be used in larger or more advanced printing presses or that they require additional equipment such as blowing fans or cooling devices arranged inside the printing cylinder complicating the constructing. SUMMARY OF THE INVENTION The object with present invention is to provide a solution to the problems caused by heating in a printing press without adding additional structural components to the printing press. This object is achieved by a control system and a method for improving the printing quality in a printing press, where the amount of fountain solution supplied from a dampening device is controlled as a function of the measured temperature in the printing press. Further embodiments of the invention are defined in the dependent claims .

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in further detail below under reference to the accompanying drawings, in which: Fig. la shows an overview of a printing press with a control system for controlling the supply of fountain solution according to the present invention; Fig. lb shows an overview of a control system for controlling the supply of fountain solution according to the present invention; and Fig. 2 shows a flowchart over the steps of controlling the supply of fountain solution according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. la shows an overview of a printing press 1 including a plurality of printing towers 2, each printing tower 2 including for example eight printing units 3. In Fig. lb a printing unit 3 is schematically shown, where the printing unit comprises an ink tray 6a, an ink train 6b, a dampening device or spray bar 7a, a fountain solution train 7b, a printing cylinder 12, a blanket cylinder 5, a blanket 13 and a paper web 14. The ink contained in the ink tray 6a is transferred to the printing cylinder 12 and to the print areas thereof by the ink train 6b. The fountain solution contained in the dampening device 7a is sprayed to a first cylinder of the fountain solution train 7b and further transferred by other cylinders in the fountain solution train 7b to the printing cylinder 12 and to the non print areas thereof. The print of the printing cylinder 12 is transferred to the paper web via the blanket cylinder 5. Temperature sensors 8 are arranged in the vicinity of the blanket cylinder 5 and/or in the printing unit 3. The sensors.8 can be arranged at many different locations. There can be arranged one sensor 8 for every blanket cylinder 5 in the printing press 1, several sensors 8 arranged along the axial direction of every blanket cylinder 5, sensors 8 arranged only at particularly located blanket cylinders 5 in the printing press 1 or combinations thereof. The sensors 8 that can be either analog or digital are connected to a control unit 9 by communication arrangements 10, and are preferably of a self-cleaning type. The control unit 9 that typically is included in or connected to the printing unit control unit includes electronic devices for receiving input signals from the sensors 8, devices for analyzing the input signals, devices for selecting output/control signals in accordance with the received input signals and devices for transferring output signals to the dampening device/devices 7. There can be provided one control unit 9 for each printing unit 3 or one control unit for every two or more printing units 3. The control unit 9 is connected to the dampening device 7 by a communication arrangement 11. The communication arrangements 10, 11 for connecting the sensors 8 and the dampening devices 7 to the control unit 9 can be cables, optical communication devices (e.g. infrared transmission) or short range radio communication devices (e.g. Bluetooth). The sensors 8 can be using any known contact or non- contact (e.g. infrared) temperature measuring method. The temperature of the ambient air can be measured or the temperature of the surface of the blanket cylinders 5 or other surfaces can be measured. The temperature measurement of the surface of the blanket cylinder 5 is more accurate than the temperature measurement of the ambient air that is affected by air streams, but also more difficult to perform due to the rotation of the blanket cylinder 5. Naturally, a better printing quality is received if the temperature is measured along the entire printing path of the paper web in the printing press 1 so that the optimal supply of fountain solution can be achieved at every printing unit 3. This is .possible to achieve with a multitude of sensors 8 arranged at each blanket cylinder 5, and preferably with at least four sensors 8 arranged at each blanket cylinder 5 for covering all printing options (full, half or quarter web) . However, having a multitude of sensors makes the printing press too expensive and probably not much better than with fewer sensors arranged at selectively chosen positions. The temperature sensors 8 are therefore arranged at strategically located and selected points in the printing press 1. These strategic points can be upper positions of the blanket cylinders 5 in the printing towers 2, blanket cylinders 5 that are used for most printing options etc. The control unit 9 is provided with reference data based on dampening characteristics, dampening tables and algorithms for establishing control signals. The reference data is based on a base graph of a certain temperature, e.g. 20 °C, with an offset temperature depending on the temperature on the blanket cylinder and/or the ambient air. The input signals from the sensors 8 are compared with the stored reference data by the control unit 9 to establish a temperature probability matrix for selecting the best parameters for the fountain solution to get the appropriate output/control signals to achieve the optimal printing quality. The output/control signals are transferred to the dampening device 7. The control unit 9 is typically included in the comprehensive control system for the printing unit or the printing press. The signals transferred from the sensors 8 can be provided with a tag so that the control unit 9 can identify from which sensor 8 the input signals are sent. The input signals can also be transferred according a selected transfer protocol to establish a common interface between the sensors 8 and the controls unit or units 9. The output signals to the dampening device can be arranged in the same way. It is important to have tags on the transferred signals if wireless communication arrangements 10, 11 are used to transfer the input and output signals between the sensors 8, control units 9 and the dampening devices 7, but also if single control units 9 control a plurality of printing units 2. In Fig. 2 the steps of supplying fountain solution as a function of the temperature in the printing press 1 are shown. First the temperature is measured by the sensors 8, step 100, and then the input signals from the sensors 8 are transferred to the control unit or units 9 via the communication arrangements 10, step 110. The input signals are analyzed in relation to reference data stored in the control units 9, step 130, and the preferred parameters for achieving the optimal quality at the printing locations are selected, step 140. The preferred parameters or the output signals are transferred via the communication arrangement 11 to the dampening device or devices 7, step 150, and the fountain solution supply parameters of the dampening device or devices 7 are changed according to the new control signals, step 160. The control process is finally restarted, step 170, to continually measure temperature from the sensors 8 and controlling the supply of the fountain solution from the dampening device or devices 7 accordingly. It should be appreciated that the control of the supply of fountain solution based on the measured temperature in a printing press is not the only control function of the fountain solution supply, but a damp curve is also used and the temperature is an offset in respect of the damp curve . It should also be appreciated that a single sensor can control the supply of fountain solution to several dampening devices, and that the sensors can be located in any position in the printing press, e.g. can the sensors be located in the vicinity of other cylinders or rollers an not only the blanket cylinder such as cylinders or rollers included in the ink train, fountain solution train or the printing cylinder. The invention is not limited to the above-described examples or to the drawings showing examples of embodiments, but can be varied within the scope of the appended claims.

Claims

1. A control system for improving the printing quality in a printing press (1) , having at least one dampening device (7a) for the_; supply of fountain solution characterized by temperature sensors (8) selectively arranged in the printing press (1) and a control unit (9) for controlling the amount of fountain solution supplied from at least one dampening device (7a) in response to signals from the sensors (8), and where the sensors (8) are arranged to measure the temperature of the ambient air in the printing press (1) .

2. A control system according to claim 1, wherein the sensors (8) are arranged in the vicinity of the blanket cylinders (5) of the printing press (1) .

3. A control system according to any preceding claim, wherein the sensors (8) are arranged along the longitudinal direction of the blanket cylinders (5) .

4. A control system according to any preceding claim, wherein at least one sensor (8) is connected to one control unit (9) .

5. A control system according to any preceding claim, wherein the control unit (9) is connected to at least one dampening device (7a) .

6. A method of improving the printing quality in a printing press (1), where signals indicative for the temperature at selected locations in the printing press (1) are utilized to control the amount of fountain solution supplied from a dampening device (7a) of the printing press (1) in relation thereto, wherein the method includes the following steps:

- selectively arranging temperature sensors (8) in the selectively chosen locations in the printing press (1) ; - connecting the sensors (8) to a control unit (9) ;

- connecting the control unit (9) to at least one dampening device (7) arranged in the printing press (1) ;

- measuring the temperature at the selected locations by the sensors (8) and transferring the signals indicative of the temperature to the control unit (9);

- analyzing the signals with pre-stored reference data in the control unit (9) , selecting control/output signals based on the analysis; and

- transmitting the control/output signals to the at least one dampening device (7a) to regulate the amount of fountain solution supplied from the at least one dampening device (7a) .

7. A method for regulating the temperature according to claim 6, further including the following step:

- selectively arranging the temperature sensors (8) in the vicinity of a blanket cylinder (5) in the printing press ( 1) ; and/or

- selectively arranging the temperature sensors along the longitudinal .direction of the blanket cylinder (s) (5) in the printing press (1); and/or

- selectively arranging the temperature sensors in the printing press (1) to measure the ambient air in the printing press (1) .