EP0520332B1 - Printing press with a printing form to be deleted - Google Patents

Printing press with a printing form to be deleted Download PDF

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Publication number
EP0520332B1
EP0520332B1 EP92110378A EP92110378A EP0520332B1 EP 0520332 B1 EP0520332 B1 EP 0520332B1 EP 92110378 A EP92110378 A EP 92110378A EP 92110378 A EP92110378 A EP 92110378A EP 0520332 B1 EP0520332 B1 EP 0520332B1
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EP
European Patent Office
Prior art keywords
printing
forme
printed image
printing form
electrode
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Expired - Lifetime
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EP92110378A
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German (de)
French (fr)
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EP0520332A1 (en
Inventor
Asbjorn John Kanck
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Manroland AG
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MAN Roland Druckmaschinen AG
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Publication of EP0520332A1 publication Critical patent/EP0520332A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C1/00—Forme preparation
    • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
    • B41C1/1066—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by spraying with powders, by using a nozzle, e.g. an ink jet system, by fusing a previously coated powder, e.g. with a laser
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N3/00—Preparing for use and conserving printing surfaces
    • B41N3/006—Cleaning, washing, rinsing or reclaiming of printing formes other than intaglio formes

Definitions

  • the present invention relates to a printing press with an erasable printing form, a method for imaging the printing form with a printed image deposit and a method for removing the printed image deposit from the printing form.
  • the printed image deposit is removed by a heating process which is also known per se, this requires the printing form to be removed from the printing unit and heated in an oven at a suitable temperature for a certain time in order to remove the printed image deposit.
  • a heating process is not suitable for executing it within the printing unit because the application of a heating jacket or a similar device is necessary in order to liquefy the print image deposit and to remove it from the printing form.
  • a printing press with an imageable printing form clamped on a forme cylinder is known.
  • a print image deposit is sprayed onto the printing form from nozzles of a print head.
  • the printing form can also be deleted.
  • laminate or layered sheets are known which are produced in an impregnation or hot-pressing process and are then imaged under heat by a carrier, for example a cotton or silk ribbon, as used in typewriters. High-frequency fields are used for heating.
  • the figure shows a device that is used to apply a print deposit 2 to the surface of a printing form 1 by melting and then to remove the print deposit from the printing form 1 again.
  • the printing form 1 carries the printed image deposit 2 on its outer surface, while it is itself applied to the outer surface of a rotatable forme cylinder 3.
  • a curved electrode 4, which belongs to a high-frequency induction heater 5, is arranged in the vicinity of the printing form 1, its distance from the printing form 1 can be changed. If energy is supplied to the high-frequency induction heater 5, voltage is also present at the electrode 4.
  • the forme cylinder 3 serves as the counter electrode. If the printing form consists of a metal, the forme cylinder 3 is preferably conductively connected to it.
  • the forme cylinder 3 is preferably at ground potential.
  • the printing form 1 can also consist of a non-conductive material, for example ceramic.
  • the printed image deposit 2 can preferably be sprayed onto the printing form 1 from one nozzle or from a plurality of nozzles, for example arranged side by side.
  • a liquid medium sprayable through the nozzle or nozzles contains volatile components, as will be described below.
  • the melting and the removal of the printed image deposit 2 are independent of the method by which the liquid medium was applied beforehand, and that these methods can also be used in connection with electrostatographic methods for producing a print template.
  • a hydrophobic precipitate 2 is applied; if it has a hydrophobic surface, a hydrophilic printed image deposit 2 is applied.
  • the electrode 4 of the high-frequency induction heater 5 is circular-arc-shaped and is at a certain distance from the printing form 1.
  • the frequency and the operating time of the induction heater 5 more or less superficial heating can be achieved of the lithographic printing plate 1 in order to effectively heat the printed image deposit 2 on its surface from the inside out.
  • the print image deposit 2 is melted on the surface of the printing form 1 before it becomes internally coherent. This avoids the formation of bridges within the printed image deposit 2, which could lead to its premature destruction during the printing process.
  • the liquid medium which can be sprayed on from the nozzle or the nozzles to form the print image precipitate 2 is composed, for example, as follows: Styrene maleic anhydride 12 g ammonia 5 g Bactericide 2 g dye 2 g Diethylene glycol diethyl ether 30 g water 949 g
  • styrene maleic anhydride is the heat-fusible component.
  • Styrene maleic anhydride is soluble in an aqueous alkaline medium.
  • the dye is used only to produce a visually visible print image deposit 2. It is not necessarily part of the liquid medium.
  • the bactericide and the diethylene glycol diethyl ether are only relevant for the application through the nozzle and are of no importance for the resulting print image precipitation 2.
  • the printing form 1 is, for example, an aluminum plate with a granular surface, which is attached to the form cylinder 3.
  • the resulting printed image precipitate 2 is now solidified by melting on the surface of the printing form 1 by means of the induction heater 5, the induction heater 5 being able to be operated at variable frequencies in the kHz range.
  • the electrode 4, to which the voltage is applied is located, for example, at a distance of 6 mm. Since the electrode 4, for example, does not cover the entire width of the surface of the printing form 1, it is moved parallel to the longitudinal axis of the form cylinder 3, for example at a speed of 0.5 cm / s by a stepping motor 6. At a frequency of 140 kHz, the power is 1.5 kW.
  • the forme cylinder 3 rotates accordingly, so that the electrode 4 passes over the forme cylinder 3 again in the next step parallel to its longitudinal axis in the other direction.
  • the printed image deposit 2 is melted on the entire surface of the printing form 1. If, as shown in the figure, the electrode 4 extends, for example, over a quarter of the circular section of the forme cylinder 3, the forme cylinder 3 needs to be rotated three times more, for a quarter of its circumference, in order to deposit the printing forme 1 over its entire surface with a constant print image to provide.
  • the print image deposit 2 is to be removed again. After removing excess ink, a reflow process is carried out again.
  • the distance between the surface of the printing form 1 and the electrode 4 is chosen to be smaller than when the print image precipitate 2 solidifies. In this case it is, for example, 4 mm in order to remove the print image deposit 2 and to prepare the printing form 1 for the next imaging process.
  • the energy supply per unit of time is used to detach the print image precipitate 2 1.6 kW increased while the frequency is 150 kHz.
  • the distances between the electrode 4 when applying and when removing the printed image deposit 2 are chosen to be the same.
  • An electrode in the form of a circular arc is again used as the electrode 4.
  • a flat electrode which has only a slight extension in the circumferential direction of the forme cylinder 3 and extends over the entire length of the lateral surface. It is at a distance of 5 mm from the surface of the printing form 1. With an energy supply of 3 kW per time unit and a frequency of 150 kHz, the printed image deposit 2 is melted. The forme cylinder 3 is rotated at a speed of 1 cm / s when applying and at a speed of 0.5 cm / s when removing the print image deposit 2. In this case, the stepper motor 6 is not required.
  • the distance between the electrode 4 and the printing form 1 can be adapted accordingly in accordance with the desired heating depth of the heating into the interior of the printing form 1 starting from the electrode 4; the frequencies and the energy supply can also be adapted in accordance with the various printing forms 1 that can be used. For example, cleaning of the printing form 1, which in any case requires more energy than the application of the printed image deposit 2 on it, can be carried out at a higher frequency than the application of the printed image deposit 2.
  • the invention can also be used when the printing form 1 is not applied to the form cylinder 3.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacture Or Reproduction Of Printing Formes (AREA)
  • Ink Jet Recording Methods And Recording Media Thereof (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
  • Printing Methods (AREA)

Description

Die vorliegende Erfindung bezieht sich auf eine Druckmaschine mit einer löschbaren Druckform, ein Verfahren zum Bebildern der Druckform mit einem Druckbildniederschlag und ein Verfahren zum Entfernen des Druckbildniederschlags von der Druckform.The present invention relates to a printing press with an erasable printing form, a method for imaging the printing form with a printed image deposit and a method for removing the printed image deposit from the printing form.

Es ist bekannt, Druckbildniederschläge auf der Oberfläche einer hydrophilen lithographischen Druckform aufzubringen und derartige Druckbildniederschläge durch die Anwendung von Wärme zu fixieren. Außerdem ist es bekannt, derartige Druckbildniederschläge von der Oberfläche der Druckform nach Beendigung des Druckprozesses wieder zu entfernen. Insbesondere ist es aus CA-P-10 75 300 bekannt, mittels eines elektrostatographischen Verfahrens einen Druckbildniederschlag auf einem elektrostatographischen Übertragungsmedium zu erzeugen, den Druckbildniederschlag anschließend auf die Oberfläche einer lithographischen Druckform aufzubringen und mittels Wärme auf ihr zu fixieren. Nachdem der Druckbildniederschlag für das Bedrucken einer Bedruckstoffbahn gedient hat, wird er anschließend von der Oberfläche der lithographischen Druckform mittels eines Lösungsmittels unter Anwendung von Reibung entfernt. Dieses Verfahren hat einige Nachteile, insbesondere ist der Schritt zur Entfernung des Bildes von der Druckform sehr aufwendig, da er die gleichzeitige Anwendung eines geeigneten Losungsmittels und von Reibung erfordert. Dies ist ein mühsamer und zeitaufwendiger Vorgang, der darüber hinaus die Oberflächenkörnung der lithographischen Druckform verschlechtern kann und beträchtlich die Hydrophilie der Druckform verringert.It is known to deposit printed image deposits on the surface of a hydrophilic lithographic printing form and to fix such printed image deposits by the application of heat. In addition, it is known to remove such print image deposits from the surface of the printing form after the printing process has ended. In particular, it is known from CA-P-10 75 300 to generate an image deposit on an electrostatographic transfer medium by means of an electrostatographic method, to subsequently apply the image deposit to the surface of a lithographic printing form and to fix it on it by means of heat. After the printed image precipitate has been used for printing on a printing material web, it is then removed from the surface of the lithographic printing plate by means of a solvent using friction. This process has some disadvantages, in particular the step of removing the image from the printing form is very complex since it requires the simultaneous use of a suitable solvent and friction. This is a tedious and time consuming process which can also degrade the surface grain of the lithographic printing form and significantly reduce the hydrophilicity of the printing form.

Zusätzlich muß, wenn dieser Vorgang innerhalb des Druckwerkes ausgeführt wird, darauf geachtet werden, daß das Lösungsmittel ausschließlich mit der Oberfläche der Druckform in Berührung kommt und unter gar keinen Umständen die Druckfarbe in dem Farbkasten des Druckwerks kontaminiert. Darüber hinaus sind derartige Lösungsmittel allgemein umweltschädigend und haben einen niedrigen Flammpunkt.In addition, if this process is carried out within the printing unit, care must be taken that the solvent only comes into contact with the surface of the printing form and under no circumstances contaminates the printing ink in the ink fountain of the printing unit. In addition, such solvents are generally harmful to the environment and have a low flash point.

Wenn andererseits der Druckbildniederschlag nach einem ebenfalls an sich bekannten Erwärmungsprozeß entfernt wird, so erfordert dies, die Druckform aus dem Druckwerk herauszunehmen und in einem Ofen bei einer geeigneten Temperatur für eine bestimmte Zeit zu erwärmen, um den Druckbildniederschlag zu entfernen. Ein derartiger Prozeß ist deswegen nicht dazu geeignet, ihn innerhalb des Druckwerks auszuführen, weil das Anbringen eines Erwärmungsmantels oder einer ähnlichen Vorrichtung notwendig ist, um den Druckbildniederschlag zu verflüssigen und von der Druckform zu entfernen.On the other hand, if the printed image deposit is removed by a heating process which is also known per se, this requires the printing form to be removed from the printing unit and heated in an oven at a suitable temperature for a certain time in order to remove the printed image deposit. Such a process is not suitable for executing it within the printing unit because the application of a heating jacket or a similar device is necessary in order to liquefy the print image deposit and to remove it from the printing form.

Bei bekannten Verfahren zur Aufbringung eines Druckbildniederschlags auf einer Druckform ist nachteilhaft, daß die Erwärmung primär zur Bildung eines verfritteten Niederschlags anstelle einer gewünschten Adhäsion des den Druckbildniederschlag bildenden Materials auf der Druckform führt.In known methods for applying a printed image deposit to a printing form it is disadvantageous that the heating primarily leads to the formation of a fretted precipitate instead of a desired adhesion of the material forming the printed image deposit on the printing form.

Aus der EP 0 298 580 A 2 ist eine Druckmaschine mit einer in ihr bebilderbaren auf einem Formzylinder aufgespannten Druckform bekannt. Zur Bebilderung wird ein Druckbildniederschlag aus Düsen eines Druckkopfs auf die Druckform aufgesprüht. Die Druckform ist auch löschbar.From EP 0 298 580 A 2 a printing press with an imageable printing form clamped on a forme cylinder is known. For the purpose of imaging, a print image deposit is sprayed onto the printing form from nozzles of a print head. The printing form can also be deleted.

Aus derr LU 73 769 A sind Laminat- oder Schichtplatten bekannt, die in einem Imprägnier- oder Heißpreßvertahren erzeugt werden, und anschließend von einem Träger, beispielsweise einem Baumwoll- oder Seidenband, wie es bei Schreibmaschinen Verwendung findet, unter Wärme bebildert werden. Zur Erwärmung dienen Hochfrequenzfelder.From LU 73 769 A, laminate or layered sheets are known which are produced in an impregnation or hot-pressing process and are then imaged under heat by a carrier, for example a cotton or silk ribbon, as used in typewriters. High-frequency fields are used for heating.

Es ist die Aufgabe der vorliegenden Erfindung, die Nachteile des Standes der Technik zu überwinden und eine Druckmaschine zu schaffen, in der mittels Wärme ein Druckbildniederschlag von außen auf eine Druckform aufgebracht werden kann, der zu einer starken und vollständigen Adhäsion mit der Druckform führt und der sich nach Beendigung des Druckauftrags anschließend wieder innerhalb der Druckmaschine entfernen läßt, sowie Verfahren zum Bebildern der Druckform mit einem Druckbildniederschlag sowie zur Entfernung dieses Druckbildniederschlags zu schaffen, die innerhalb der Druckmaschine durchgeführt werden.It is the object of the present invention to overcome the disadvantages of the prior art and to provide a printing press in which a printed image deposit can be applied to the outside of a printing form by means of heat, which leads to strong and complete adhesion to the printing form and which can then be removed again within the printing press after completion of the print job, and to create methods for imaging the printing form with a print image deposit and for removing this print image deposit, which are carried out within the printing press.

Die Aufgabe wird, wie in Patentanspruch 1 bzw. 5, 7 oder 8 angegeben, gelöst.The object is achieved as specified in claim 1 or 5, 7 or 8.

Außerdem ist es möglich, das Aufschmelzen des Druckbildniederschlags auf der Druckform gleichzeitig mit der Aufbringung des Druckbildniederschlags durchzuführen. Mit einigen Anpassungen an die entsprechenden Verfahrensbedingungen läßt sich der gleiche Apparat verwenden, um einerseits den Druckbildniederschlag aufzubringen und ihn nach Beendigung eines Druckprozesses zu entfernen, ohne Lösungsmittel oder Reibung verwenden zu müssen.In addition, it is possible to melt the print image deposit on the printing form simultaneously with the application of the print image deposit. With some adjustments to the corresponding process conditions, the same apparatus can be used, on the one hand, to deposit the printed image and to remove it after the end of a printing process, without having to use solvents or friction.

Nachstehend wird die Erfindung anhand der einzigen Figur in einem Ausführungsbeispiel erläutert. Die Figur zeigt eine Vorrichtung, die verwendet wird, um einen Druckbildniederschlag 2 auf der Oberfläche einer Druckform 1 durch Schmelzen aufzubringen und anschließend den Druckbildniederschlag von der Druckform 1 wieder zu entfernen. Die Druckform 1 trägt den Druckbildniederschlag 2 auf ihrer äußeren Oberfläche, während sie selbst auf der äußeren Oberfläche eines drehbaren Formzylinders 3 aufgebracht ist. Eine gebogene Elektrode 4, die zu einer Hochfrequenz-Induktionsheizung 5 gehört, ist in der Nähe der Druckform 1 angeordnet, ihr Abstand zu der Druckform 1 läßt sich verändern. Wenn der Hochfrequenz-Induktionsheizung 5 Energie zugeführt wird, liegt auch an der Elektrode 4 Spannung an. Als Gegenelektrode dient der Formzylinder 3. Wenn die Druckform aus einem Metall besteht, ist der Formzylinder 3 vorzugsweise leitend mit ihr verbunden. Vorzugsweise liegt der Formzylinder 3 auf Massepotential. Die Druckform 1 kann jedoch auch aus einem nicht leitenden Material, beispielsweise Keramik, bestehen.The invention is explained below with reference to the single figure in an exemplary embodiment. The figure shows a device that is used to apply a print deposit 2 to the surface of a printing form 1 by melting and then to remove the print deposit from the printing form 1 again. The printing form 1 carries the printed image deposit 2 on its outer surface, while it is itself applied to the outer surface of a rotatable forme cylinder 3. A curved electrode 4, which belongs to a high-frequency induction heater 5, is arranged in the vicinity of the printing form 1, its distance from the printing form 1 can be changed. If energy is supplied to the high-frequency induction heater 5, voltage is also present at the electrode 4. The forme cylinder 3 serves as the counter electrode. If the printing form consists of a metal, the forme cylinder 3 is preferably conductively connected to it. The forme cylinder 3 is preferably at ground potential. However, the printing form 1 can also consist of a non-conductive material, for example ceramic.

Der Druckbildniederschlag 2 läßt sich gemäß der vorliegenden Erfindung vorzugsweise aus einer Düse oder aus mehreren, beispielsweise nebeneinander angeordneten Düsen auf die Druckform 1 aufsprühen. Ein durch die Düse oder die Düsen aufsprühbares flüssiges Medium enthält flüchtige Komponenten, wie nachfolgend noch beschrieben wird. Es versteht sich jedoch, daß das Aufschmelzen und das Entfernen des Druckbildniederschlags 2 unabhängig davon sind, nach welchem Verfahren das flüssige Medium vorher aufgebracht wurde, und daß sich diese Verfahren auch in Verbindung mit elektrostatographischen Methoden zur Herstellung einer Druckvorlage verwenden lassen.According to the present invention, the printed image deposit 2 can preferably be sprayed onto the printing form 1 from one nozzle or from a plurality of nozzles, for example arranged side by side. A liquid medium sprayable through the nozzle or nozzles contains volatile components, as will be described below. However, it goes without saying that the melting and the removal of the printed image deposit 2 are independent of the method by which the liquid medium was applied beforehand, and that these methods can also be used in connection with electrostatographic methods for producing a print template.

Wenn die Druckform 1 eine hydrophile Oberfläche hat, wird ein hydrophober Druckbildniederschlag 2 aufgebracht; wenn sie eine hydrophobe Oberfläche hat, wird ein hydrophiler Druckbildniederschlag 2 aufgebracht.If the printing form 1 has a hydrophilic surface, a hydrophobic precipitate 2 is applied; if it has a hydrophobic surface, a hydrophilic printed image deposit 2 is applied.

Gemäß der vorliegenden Erfindung ist die Elektrode 4 der Hochfrequenz-Induktionsheizung 5 kreisbogenförmig und befindet sich in einem gewissen Abstand zu der Druckform 1. Durch Steuerung der an ihr anliegenden Spannung, der Frequenz und der Betriebsdauer der Induktionsheizung 5 läßt sich eine mehr oder weniger oberflächliche Erwärmung der lithographischen Druckform 1 erzielen, um den Druckbildniederschlag 2 auf ihrer Oberfläche wirksam von innen heraus aufzuwärmen. Dadurch wird der Druckbildniederschlag 2 auf der Oberfläche der Druckform 1 aufgeschmolzen, bevor er innerlich zusammenhängend wird. Dadurch werden Brückenbildungen innerhalb des Druckbildniederschlags 2 vermieden, die zu dessen vorzeitiger Zerstörung während des Druckprozesses führen könnten.According to the present invention, the electrode 4 of the high-frequency induction heater 5 is circular-arc-shaped and is at a certain distance from the printing form 1. By controlling the voltage applied to it, the frequency and the operating time of the induction heater 5, more or less superficial heating can be achieved of the lithographic printing plate 1 in order to effectively heat the printed image deposit 2 on its surface from the inside out. As a result, the print image deposit 2 is melted on the surface of the printing form 1 before it becomes internally coherent. This avoids the formation of bridges within the printed image deposit 2, which could lead to its premature destruction during the printing process.

Das aus der Düse oder den Düsen aufsprühbare flüssige Medium zur Bildung des Druckbildniederschlags 2 ist beispielsweise folgendermaßen zusammengesetzt: Styrolmaleinsäureanhydrid 12 g Ammoniak 5 g Bakterizid 2 g Farbstoff 2 g Diethylenglykoldiethylether 30 g Wasser 949 g The liquid medium which can be sprayed on from the nozzle or the nozzles to form the print image precipitate 2 is composed, for example, as follows: Styrene maleic anhydride 12 g ammonia 5 g Bactericide 2 g dye 2 g Diethylene glycol diethyl ether 30 g water 949 g

Bei diesem flüssigen Medium ist Styrolmaleinsäureanhydrid die durch Wärme aufschmelzbare Komponente. Styrolmaleinsäureanhydrid ist in einem wäßrigen alkalischen Medium löslich. Der Farbstoff dient ausschließlich zur Erzeugung eines visuell sichtbaren Druckbildniederschlags 2. Er ist nicht notwendigerweise Bestandteil des flüssigen Mediums. Das Bakterizid und der Diethylenglykoldiethylether sind nur für die Aufbringung durch die Düse relevant und haben keinerlei Bedeutung für den aus der Druckfarbe schließlich entstehenden Druckbildniederschlag 2. Die Druckform 1 ist beispielsweise eine Aluminiumplatte mit einer körnigen Oberfläche, die auf dem Formzylinder 3 befestigt ist.In this liquid medium, styrene maleic anhydride is the heat-fusible component. Styrene maleic anhydride is soluble in an aqueous alkaline medium. The dye is used only to produce a visually visible print image deposit 2. It is not necessarily part of the liquid medium. The bactericide and the diethylene glycol diethyl ether are only relevant for the application through the nozzle and are of no importance for the resulting print image precipitation 2. The printing form 1 is, for example, an aluminum plate with a granular surface, which is attached to the form cylinder 3.

Der auf diese Weise entstandene Druckbildniederschlag 2 wird nun durch Aufschmelzen auf der Oberfläche der Druckform 1 mittels der Induktionsheizung 5 verfestigt, wobei sich die Induktionsheizung 5 bei veränderlichen Frequenzen im kHz-Bereich betreiben läßt. Die Elektrode 4, an der die Spannung anliegt, befindet sich beispielsweise in einem Abstand von 6 mm. Da die Elektrode 4 beispielsweise nicht die ganze Breite des der Oberfläche der Druckform 1 überdeckt, wird sie parallel zur Längsachse des Formzylinders 3 beispielsweise mit einer Geschwindigkeit von 0,5 cm/s von einem Schrittmotor 6 bewegt. Bei einer Frequenz von 140 kHz liegt die Leistung bei 1,5 kW. Nachdem die Elektrode 4 jeweils die ganze Breite der Oberfläche der Druckform 2 überfahren hat, dreht sich der Formzylinder 3 entsprechend weiter, so daß die Elektrode 4 den Formzylinder 3 im nächsten Schritt wiederum parallel zu seiner Längsachse in der anderen Richtung überfährt. Auf diese Weise wird, nachdem sich der Formzylinder 3 jeweils um den der Bogenlänge der Elektrode 4 entsprechenden Kreisabschnitt vorwärts gedreht hat, der Druckbildniederschlag 2 auf der gesamten Oberfläche der Druckform 1 aufgeschmolzen. Wenn sich die Elektrode 4, wie in der Figur dargestellt, beispielsweise über ein Viertel des Kreisabschnitts des Formzylinders 3 erstreckt, so bedarf es einer dreimaligen Weiterdrehung des Formzylinders 3 um ein Viertel seines Umfangs, um die Druckform 1 über ihrer gesamten Oberfläche mit einem beständigen Druckbildniederschlag zu versehen.The resulting printed image precipitate 2 is now solidified by melting on the surface of the printing form 1 by means of the induction heater 5, the induction heater 5 being able to be operated at variable frequencies in the kHz range. The electrode 4, to which the voltage is applied, is located, for example, at a distance of 6 mm. Since the electrode 4, for example, does not cover the entire width of the surface of the printing form 1, it is moved parallel to the longitudinal axis of the form cylinder 3, for example at a speed of 0.5 cm / s by a stepping motor 6. At a frequency of 140 kHz, the power is 1.5 kW. After the electrode 4 has run over the entire width of the surface of the printing form 2, the forme cylinder 3 rotates accordingly, so that the electrode 4 passes over the forme cylinder 3 again in the next step parallel to its longitudinal axis in the other direction. In this way, after the forme cylinder 3 has rotated forward by the circular section corresponding to the arc length of the electrode 4, the printed image deposit 2 is melted on the entire surface of the printing form 1. If, as shown in the figure, the electrode 4 extends, for example, over a quarter of the circular section of the forme cylinder 3, the forme cylinder 3 needs to be rotated three times more, for a quarter of its circumference, in order to deposit the printing forme 1 over its entire surface with a constant print image to provide.

Nachdem die Druckform 1 anschließend für einen Offset-Druckprozeß verwendet worden ist, soll der Druckbildniederschlag 2 wieder entfernt werden. Nach Entfernung überschüssiger Druckfarbe wird erneut ein Aufschmelzprozeß durchgeführt. In diesem Fall wird der Abstand zwischen der Oberfläche der Druckform 1 und der Elektrode 4 kleiner als beim Verfestigen des Druckbildniederschlags 2 gewählt. Er beträgt in diesem Falle beispielsweise 4 mm, um den Druckbildniederschlag 2 zu entfernen und die Druckform 1 für den nächsten Bebilderungsprozeß vorzubereiten.After the printing form 1 has subsequently been used for an offset printing process, the print image deposit 2 is to be removed again. After removing excess ink, a reflow process is carried out again. In this case, the distance between the surface of the printing form 1 and the electrode 4 is chosen to be smaller than when the print image precipitate 2 solidifies. In this case it is, for example, 4 mm in order to remove the print image deposit 2 and to prepare the printing form 1 for the next imaging process.

In einem anderen Ausführungsbeispiel wird zum Ablösen des Druckbildniederschlags 2 die Energiezufuhr je Zeiteinheit auf 1,6 kW erhöht, während die Frequenz 150 kHz beträgt. Die Abstände der Elektrode 4 beim Aufbringen und beim Entfernen des Druckbildniederschlags 2 werden gleich gewählt. Als Elektrode 4 dient wieder eine kreisbogenförmig ausgebildete Elektrode.In another exemplary embodiment, the energy supply per unit of time is used to detach the print image precipitate 2 1.6 kW increased while the frequency is 150 kHz. The distances between the electrode 4 when applying and when removing the printed image deposit 2 are chosen to be the same. An electrode in the form of a circular arc is again used as the electrode 4.

In einem weiteren Ausführungsbeispiel wird eine flache Elektrode verwendet, die in Umfangsrichtung des Formzylinders 3 nur eine geringe Ausdehnung hat und sich über die gesamte Länge der Mantelfläche erstreckt. Sie hat einen Abstand von 5 mm zu der Oberfläche der Druckform 1. Bei einer Energiezufuhr je Zeiteinheit von 3 kW und einer Frequenz von 150 kHz wird der Druckbildniederschlag 2 aufgeschmolzen. Dabei wird der Formzylinder 3 mit einer Geschwindigkeit von 1 cm/s beim Aufbringen und mit einer Geschwindigkeit von 0,5 cm/s beim Entfernen des Druckbildniederschlags 2 gedreht. In diesem Fall ist der Schrittmotor 6 nicht erforderlich.In a further exemplary embodiment, a flat electrode is used which has only a slight extension in the circumferential direction of the forme cylinder 3 and extends over the entire length of the lateral surface. It is at a distance of 5 mm from the surface of the printing form 1. With an energy supply of 3 kW per time unit and a frequency of 150 kHz, the printed image deposit 2 is melted. The forme cylinder 3 is rotated at a speed of 1 cm / s when applying and at a speed of 0.5 cm / s when removing the print image deposit 2. In this case, the stepper motor 6 is not required.

Entsprechend der gewünschten Erwärmungstiefe der von der Elektrode 4 ausgehenden Erwärmung in das Innere der Druckform 1 kann der Abstand zwischen der Elektrode 4 und der Druckform 1 entsprechend angepaßt werden; ebenfalls lassen sich die Frequenzen und die Energiezufuhr entsprechend den verschiedenen Druckformen 1, die sich verwenden lassen, anpassen. So läßt sich beispielsweise das Reinigen der Druckform 1, welches auf jeden Fall mehr Energie benötigt als das Aufbringen des Druckbildniederschlags 2 auf ihr, bei einer höheren Frequenz durchführen als das Aufbringen des Druckbildniederschlags 2.The distance between the electrode 4 and the printing form 1 can be adapted accordingly in accordance with the desired heating depth of the heating into the interior of the printing form 1 starting from the electrode 4; the frequencies and the energy supply can also be adapted in accordance with the various printing forms 1 that can be used. For example, cleaning of the printing form 1, which in any case requires more energy than the application of the printed image deposit 2 on it, can be carried out at a higher frequency than the application of the printed image deposit 2.

Die Erfindung läßt sich auch verwenden, wenn die Druckform 1 nicht auf dem Formzylinder 3 aufgebracht ist.The invention can also be used when the printing form 1 is not applied to the form cylinder 3.

Claims (8)

  1. Printing machine having an erasable hydrophilic or hydrophobic printing forme (1) applied to a forme cylinder (3), and a printing head having at least one nozzle for applying a hydrophobic or a hydrophilic liquid medium for producing a printed image deposit (2) on the printing forme (1), the liquid medium having a heat-fusible component, characterised in that the printing machine has a heating means (5) arranged near the forme cylinder (3) by which the component can be fixed on the printing forme (1) as a printed image deposit (2) and removed from it.
  2. Printing machine according to claim 1, characterised in that the printing forme (1) is a metallic printing forme (1), in particular of aluminium.
  3. Printing machine according to claim 2, characterised in that the heating means is an induction heating means (5).
  4. Printing machine according to claim 3, characterised in that the induction heating means (5) can be operated at a variable frequency.
  5. Process for the imaging of the erasable printing forme (1) in the printing machine according to claim 3 or 4, characterised in that it supplies high-frequency electrical energy to the printed image deposit (2) by means of an electrode (4) which is at a first distance from the printing forme (1).
  6. Process according to claim 5, characterised in that the electrode (4) is moved by a stepper motor (6) parallel to the longitudinal axis of a forme cylinder (3) on which the printing forme is applied.
  7. Process for removing the printed image deposit (2), applied according to claim 5 or 6, from the printing forme (1), characterised in that the electrode (4) is at a second distance from the printing forme (1) which is smaller than the first distance whilst the same electrical energy is supplied.
  8. Process for removing the printed image deposit (2), applied according to claim 5 or 6, from the printing forme (1), characterised in that the electrode (4) is at the first distance from the printing forme (1) for a period which is longer than the one during the application of the printed image deposit (2).
EP92110378A 1991-06-28 1992-06-19 Printing press with a printing form to be deleted Expired - Lifetime EP0520332B1 (en)

Applications Claiming Priority (2)

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AUPK699391 1991-06-28
AU6993/91 1991-06-28

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EP0520332A1 (en) 1992-12-30
DE59205729D1 (en) 1996-04-25
US5213041A (en) 1993-05-25
JPH05185575A (en) 1993-07-27

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