EP1389523B1 - Printing or coating machine - Google Patents

Abstract

The coating assembly e.g. at an offset printing press, to coat the paper with a varnish or ink, has a dosing unit (5) with a chamber to contain the liquid coating medium under pressure and open towards the screened application roller (3). A pressure sensor registers the pressure in the chamber (24) at the chamber doctor (4), linked to the printing press control. The control is coupled to the pump in the coating feed line (7), which develops the pressure. Surplus coating medium is carried out of the chamber by a return flow line (8) by gravity back to the reservoirs.

Description

The invention relates to a printing machine or a coating machine.

[State of the art]

A coating device of this kind is made EP 0 619 186 A1 for coating substrates with a coating fluid, such as paint or paint, known in a printing press. This coating device consists of a pressure cylinder leading to the printing material, a forme cylinder and a metering system associated with the forme cylinder, formed from a screened applicator roller and a chambered doctor blade coupled to this applicator roller. The interior of the chambered doctor blade is filled with coating fluid, in which a feed pump is connected on the line side to a reservoir for the coating fluid of the chambered doctor blade and a suction pump of the chambered doctor blade connected to this reservoir on the line side is arranged downstream.

The disadvantage here is that in the processing of certain coating fluids in the housing interior of the chambered blade a coating quality affecting foaming may occur. This foaming arises for example by turbulence and / or temperature or pressure-related viscosity changes of the coating fluid in the housing interior (chamber) of the chambered doctor blade and / or in that on the wells or cells of the rotating rasterized application roller (anilox roller) air into the housing interior of the chambered doctor blade is "introduced". This results in an insufficient filling of the wells (cells) on the circumference of the screened application roller, which may for example lead to different layer thicknesses, different degrees of gloss or partially to defects on the substrate.

To avoid the "entrainment" of air in the interior of a chambered doctor blade is according to EP 0 629 501 A1 the arrangement of stripping means within the housing interior of a chambered doctor blade known. These stripping means are preferably liquid-permeable stripping means, for example brushes, which strip away the air in the cells or cells of the applicator roll. In addition to chamber doctor blade and screened application roller, this coating device comprises a reservoir for the provision of a defined amount of coating liquid, eg paint or printing ink. From this reservoir, a supply line for the coating liquid leads to the chamber doctor blade, wherein in the supply line, a feed pump is integrated. From the chamber doctor blade performs a return line for excess coating liquid to the reservoir, wherein in the return line, a suction pump is integrated. In the housing interior of the chamber doctor blade by means of the pumps in the coating liquid, a positive pressure state is to be avoided and a vacuum pressure value below the atmospheric pressure can be maintained.

Out WO01 / 10645A a coating device is known, which comprises a counter-pressure cylinder, a forme cylinder, an applicator roller with metering system and a circulation line system for a liquid medium received in a reservoir. The circulating line system connected to the metering system has a supply and a return line with pumps. In order to reduce set-up times when using different media, the supply and return lines and at least the parts of the pump contacted by the medium are arranged so that they can be released quickly. With regard to the pressure conditions in Umlaufleitungs- or dosing no information can be found.

Furthermore, it is off EP-A-0 461 426 a pressurized liquid ink delivery system for a planographic printing press. The press includes a blanket cylinder, a plate cylinder, a dampening unit and an inking unit. A metering roller of the inking unit, which is followed by a color roller train, a chamber doctor blade is assigned. The chambered doctor blade is connected to a circulatory system with a reservoir for the ink. In the supply line of the circulation system, a feed pump is arranged, which promotes the ink to the chamber of the chamber doctor blade under pressure. From the chamber doctor blade excess, under constant pressure ink flows by return line in the reservoir. The entire circulation system including reservoir is thus under pressure. At the chambered doctor blade, a pressure sensor is arranged, which is connected to a machine control. The machine control is connected in terms of circuitry with the feed pump.

OBJECT OF THE INVENTION

The invention is based on the object to provide a printing or coating machine of the type described above, which avoids the disadvantages mentioned above, which allows more uniform filling of the cells on the screened applicator roll with coating fluid, in particular with an overpressure which can be generated in the chamber of a chambered doctor blade has a simple structure.

The object is achieved according to the invention by the training features of claim 1. Further developments will become apparent from the dependent claims.

A first advantage of the coating device is due to the fact that a sensor coupled in circuit-wise with a machine control is arranged on the chambered doctor blade for detecting the overpressure in the chamber (housing interior). In addition to detecting the pressure in the chamber, the sensor is used in conjunction with the machine control (setpoint / actual value) to supply a coating or cleaning fluid by means of a feed pump into the chamber of the chambered doctor blade. The supply of coating fluid to the chamber doctor blade during the coating job takes place continuously or by means of machine control and feed pump preferably intermittently. During a coating job, an overpressure in the interior, in particular of the chamber, of the chamber doctor blade always remains constant, which is kept constant in an adjustable range. Ensuring a defined overpressure improves the uniform filling of the cells located on an anilox roller or screened applicator roller and simultaneously counteracts the undesired entry of air into the chamber. Due to the overpressure in the chamber of the chambered doctor blade, the liquid medium, especially the coating fluid, is better pressed into the cells of the adjacent screened application roller and at the same time a liquid seal is formed outside the chambered doctor blade exposed lateral surface (with normal air pressure) of the application roller. This counteracts the "entrainment" of air into the chamber of the chambered doctor during the rotation of the rasterized applicator roll.
The feed pump is connected on the line side to a reservoir for the supply of the coating fluid and is arranged upstream of the chamber doctor blade. The return of excess coating fluid from the chambered doctor blade is done by the gravity principle and thus without a suction pump in this reservoir.

An additional advantage is that the screened application roller has an open grid structure in the form of cells or wells. Under an open grid structure is on the outer surface of the applicator roller interconnected arrangement (for example, by channels or a special screening) to understand cells or wells. In this open grid structure, the coating fluid from the housing interior, ie the chamber, the chambered doctor blade in the cells (wells) of the applicator roll and - passed through the channels or the special interconnected grid - under the doctor blades of the chambered doctor blade as fluid flow, ie by a plurality of arranged on a squeegee blade formed by the respective squeegee throttle gap (constrictions formed by doctor blade, associated cells (wells) and webs (ie support surface (web top surface) of the doctor blade) of the rasterized applicator roll is thus counteracted the "entrainment" of air On the exposed lateral surface of the applicator roller, the speed energy resulting from the pressure energy (in the chamber of the chambered doctor blade) is converted into friction after the flow through the throttling points markedly reduced fluid flow and thus the remaining fluid flow on the rotating applicator roller is calmed on the circumference the coating fluid to be processed (paint, paint) suitable, but it is also in this procedure, a cleaning fluid for flushing the lines or chamber doctor blade used.

A further advantage is that at least all lines (supply / return line) - preferably as a set - are arranged detachably within the coating device and, for example, when changing the coating fluid against preferably a second set of at least lines are interchangeable. Such a set of lines is preferably cleanable outside the coating device and can be used again if necessary. In the processing of different coating fluids, the respective chamber doctor blade is preferably additionally exchangeable and, if required, can be cleaned outside the coating device. Alternatively, the lines and the chamber doctor blade are at least pre-cleaned within the coating device with a cleaning fluid. As a result, set-up times are noticeably reduced when changing the coating fluid within this device.

It is also advantageous that complex circulation piping systems with switching valves, etc. are obsolete, so that only a supply line and a return line as a line system with a arranged exclusively in the supply line, preferably reversible feed pump with the chambered doctor blade can be coupled. The arrangement of a suction pump is obsolete, since the return of coating fluid into the reservoir takes place on the principle of gravity. As a result, a set-up time reduction, for example when replacing the line system, can still be achieved. In the delivery pump, at least the parts in contact with the coating medium are exchangeable. In the preferred use of peristaltic pumps, an exchange of pump parts refers only to the arranged in the pump pump hose.

Furthermore, it is advantageous that a plurality of line systems can be used if different coating media are used. In this case, a line system can be used exclusively for one and the same coating medium. In a preferred embodiment, the line systems - if necessary, including the pump parts and as needed the chambered doctor blade - for the respective coating medium.

[Examples]

Fig. 1

eine Offsetdruckmaschine mit zwei Beschichtungseinrichtungen,

Fig. 2

eine Beschichtungseinrichtung mit einem Dosiersystem (Seitenansicht),

Fig. 3

eine Ausbildung gem. Fig.2 (Rückansicht).

The invention will be explained in more detail using an exemplary embodiment. Here are shown schematically:

Fig. 1

an offset printing machine with two coating devices,

Fig. 2

a coating device with a dosing system (side view),

Fig. 3

an education gem. Fig.2 (Rear view).

A sheet-fed rotary printing machine is according to Fig. 1 shown in rows. Several offset printing units for multi-color printing are strung together with printing cylinders and connected to each other with transfer cylinders or turning systems. In the Fig. 1 shown partial view of such a printing machine is used, inter alia, the inline finishing. Only a last offset printing unit I with a plate cylinder 10, a blanket cylinder 11 and a printing cylinder 1 as a sheet guiding cylinder is shown. The plate cylinder 10 is associated with an inking unit and possibly a dampening unit, which will not be discussed in detail here.

The offset printing unit I is downstream in the conveying direction 6, a first coating unit II, for example, a painting or flexographic printing, which is formed by a forme cylinder 2 and a metering system 5. The metering system 5 consists of a chambered doctor blade 4 and a screened applicator roller 3 operatively connected thereto. The chambered doctor blade 4 extends with a chamber 24 which is open toward the applicator roller 3 parallel to the roller axis of the applicator roller 3 substantially over its full width.

In the conveying direction 6, a drying system 12, for example an infrared or UV dryer, which is assigned to an adjacent sheet guiding cylinder (printing cylinder 1 or transfer cylinder 9), is arranged downstream of the first coating unit II. The drying system 12 is followed in the conveying direction 6 by a second coating unit II, for example a coating unit, with forme cylinder 2 and metering system 5, again formed by a chambered doctor blade 4 and a screened applicator roller 3. The printing cylinder 1 of the offset printing units I, the coating units II and the dryer system 12 are by means of Transfer cylinder 9 interconnected for sheet transport.

The second coating unit II follows in the conveying direction 6, a boom 14, which feeds the sheet-shaped substrate by means of circulating conveyor system 13 in a known manner to a delivery pile and deposits there. The blanket cylinder 11 in the offset printing unit I carries a blanket, the form cylinder 2 of the coating units II preferably carry a flexible high-pressure plate or a blanket. The sheet guiding cylinders 1, 9, the forme cylinder 2 with associated, screened applicator roller 3 and the chambered doctor blade 4 are mounted in side frames 15.

The chamber doctor blade 4 is formed with a first and a second doctor blade (doctor blade) 22, 23. Further, the chambered doctor blade 4 has laterally arranged seals, so that a known interior, a chamber 24, for receiving a liquid medium, preferably of coating fluid, alternatively of cleaning fluid, and for simultaneous wetting of the screened applicator roll 3 (over the width ).
The chamber doctor blade 4 is preferably formed in the direction of rotation of the applicator roll 3, each with a positive and a negative on the lateral surface of the screened applicator roll 3 employed doctor blades 22, 23. The chamber doctor blade 4 is coupled to at least one supply line 7 and at least one return line 8 for the supply of the coating fluid used.

Depending on the format width and several feed and return lines 7, 8 can be arranged on the chambered doctor blade 4. Preferably, in this case only one feed pump 16 is required, so that between a respective reservoir 17,18,19 and the Delivery pump 16 a single supply line 7 is arranged. Between the feed pump 16 and the chamber doctor blade 4, the supply line 7 is divided into a plurality of supply lines 7 (partial strands) which feed the liquid medium to the chambered doctor blade 4 at various locations (over the format width). In the return lines 8, a plurality of partial strands of return lines 8 are preferably arranged on the chamber doctor blade 4, which open into a common return line 8 before immersion in a respective reservoir 17,18,19.

Preferably, as the coating fluid, varnish, e.g. aqueous dispersion varnish, printing ink, e.g. Flexographic ink, processable or it is a cleaning fluid processable. The coating fluid, alternatively the cleaning fluid, is in the coating operation, alternatively in cleaning operation, constantly under an overpressure in the interior of the chambered doctor blade 4 and in the cells of the chamber 24 located in the area of the lateral surface of the screened, rotating applicator roller third

At the chambered doctor blade 4 at least one pressure sensor 21 is arranged, which is connected in circuit technology with a machine control 20 of the processing machine. The machine control 20 is connected in terms of circuitry to a feed pump 16 which is arranged exclusively in a feed line 7 (or coupled to the feed line 7). The pressure sensor 21 is used for preferably non-contact sensing of the pressure conditions in the chamber 24 of the chamber doctor blade 4. Alternatively, as a pressure sensor 21 submersible sensors for level measurement in the chamber 24 can be used. The signals of the pressure sensor 21 can be processed by means of the machine control 20 and via this machine control 20, the feed pump 16 is operable.

By means of the feed pump 16 is in the chambered doctor blade 4, specifically the chamber 24, an overpressure in a range of approximately 0 to 1.5 bar can be generated and the medium, coating fluid or cleaning fluid, by means of return line 8 by the principle of gravity in a reservoir 17, 18, 19 traceable. The respective medium is always returned to the corresponding reservoir 17 or 18 or 19 of the return line 8 from which it was removed via the supply line 7. The overpressure in the chamber 24 is individually adjustable manually or automatically depending on the liquid medium used. For example, a coating fluid having a lower gauge pressure and a cleaning fluid having a higher gauge pressure are fed to the chamber 24.

Within the coating device, the chamber doctor blade 4 with feed and return line 7,8 is arranged quickly detachable. When processing different coating fluids, a corresponding chamber doctor blade 4 and in particular a supply and return line 7, 8 are preferably interchangeable for each coating fluid.

In a preferred embodiment, the screened application roller 3 on the lateral surface on an open structure of cells. Similar structures are known on a roll shell of Haschur engravings. In such a structure, preferably in the form of cells with rotationally symmetric arranged engraving on the roll shell, these cells are interconnected, so that the pressurized liquid medium, for example coating fluid, is received in these cells and in addition to the adjacent cells on the lateral surface the application roller 3 forms a fluid flow. This fluid flow also takes place in the area of the doctor blades 22, 23, ie the doctor blades 22, 23 are underflowed by the respective fluid in the region of the cells and channels.

Rollers which can be used as raster application rollers 3 having such an open structure are, for example, from Praxair Surface Technologies, D-40880 Ratingen (head office: Praxair Inc., Danbury, USA), for example under the name TIF, ART, etc., known.

In coating operation, the recirculation of the circulating coating fluid from the chambered doctor blade 4 takes place via the return line 8 according to the gravity principle. If necessary, in the return line 8, a throttle, preferably a manually or automatically controllable valve for adjusting the flow rate can be arranged. In a preferred embodiment of this valve is connected in circuit technology with the machine control 20.

Each reservoir 17-19 accommodates a liquid medium, preferably of a different kind. For example, the reservoir 17 has an aqueous dispersion varnish, the reservoir 18 a UV varnish and the reservoir 19 receives a cleaning fluid. The number of Reservoir 17-19 is not limited to the present example.

The supply line 7, return line 8, the metering system 5, in particular the chamber doctor blade 4, as well as at least the parts of the feed pump 16, which are in contact with the respective liquid medium, are arranged quickly detachable within the coating device.

When processing different coating fluids in the coating device, for example during a paint change, the entire circulating line system (supply line 7, return line 8), the chambered doctor blade 4 and depending on the order, the roaster applicator roller 3 and at least come into contact with the liquid medium parts of the feed pump sixteenth among themselves exchangeable for previously cleaned parts.
This means that these elements can be quickly removed from the coating unit II and are interchangeable with another circulatory system (supply line 7, return line 8), another chamber doctor blade 4 and, if necessary, with an applicator roller 3 with a different pumping volume and at least the relevant parts of the feed pump 16. In this case, feed line 7 and return line 8 can be brought into functional connection with the respectively associated reservoir 17 or 18 or 19.
If there is still a liquid medium in the chambered doctor blade 4, this can be returned to the correspondingly assigned reservoir 17, 18, 19 before the exchange of the abovementioned elements.
Preferably, the feed pump 16 is designed to switch to suction mode.
The feed pump 16 is preferably designed as a peristaltic pump with easily accessible pump head for changing the supply line 7 within the peristaltic pump.

• ein Schlauch-Pumpensystem, bei dem nur die Zuführleitung 7 (Schlauch) im Pumpenkopf austauschbar ist,
• ein Verdränger-Pumpensystem, bei dem der mit dem jeweiligen Medium in Kontakt kommende Pumpenkopf austauschbar ist,
• ein Impeller-Pumpensystem, bei dem der Impeller austauschbar ist,
  ein Pumpenzylindersystem, bei dem nur der mit dem Medium in Kontakt kommende Zylinderteil austauschbar ist und das Steuerteil in der Beschichtungseinrichtung verbleibt.

For the promotion of the liquid media (coating or cleaning fluid) are various feed pumps 16 are available. By way of example, the following variants are to be enumerated:

• a hose-pump system in which only the supply line 7 (hose) in the pump head is exchangeable,
• a positive-displacement pump system in which the pump head coming into contact with the respective medium is exchangeable,
• an impeller pump system in which the impeller is replaceable,
  a pump cylinder system in which only the cylinder part coming into contact with the medium is interchangeable and the control part remains in the coating device.

In a further development, a pulsation damper (depending on the type of pump) is arranged between the outlet of the feed pump 16 and the chambered doctor blade 4 in the feed line 7.

The supply and return line 7,8, the chamber doctor blade 4 and at least the parts of the feed pump 16 contacted by the medium, in particular coating fluid, can be cleaned within the coating device, for example with cleaning fluid fed from one of the reservoirs 17-19. Preferably, the supply and return line 7,8, the chamber doctor blade 4 and the relevant parts of the feed pump 16 outside the coating device can be cleaned.

The exemplified coating device is not limited to the above embodiment. Rather, such coating devices are also in coating machines - for example DE 298 18 148 U1 known - or in printing machines with printing units for multi-color printing combined with a coating device - for example EP 0 574 124 A1 , known - used. Alternatively, according to DE 197 29 985 A1 respectively. DE 197 29 977 A1 Coating equipment can be used directly in otherwise suitable for offset printing units of a printing press.

[REFERENCE LIST]

1

pressure cylinder

2

form cylinder

3

applicator roll

4

chambered doctor blade

5

dosing

6

conveying direction

7

feed

8th

Return line

9

transfer cylinder

10

plate cylinder

11

Blanket cylinder

12

dryer system

13

conveyor system

14

boom

15

side frame

16

feed pump

17

reservoir

18

reservoir

19

reservoir

20

machine control

21

pressure sensor

22

First doctor blade

23

Second squeegee blade

24

chamber

I

Offset printing

II

coating plant

Claims (8)

1. Printing or coating machine with an impression cylinder (1), a forme cylinder (2), a rastered applicator roller (3) and fitted thereto a chamber doctor (4) which can be set on and off with a first and a second doctor blade (22, 23) and lateral limiters with the purpose of forming a chamber (24) open towards the applicator roller (3) for the receipt of a liquid medium, wherein within the chamber (24) an excess pressure can be generated and the chamber doctor (4) is linked with a circulating lead system with feed and return leads (7, 8) for liquid medium received in a reservoir (17, 18, 19), wherein:

   - a pressure sensor (21) is arranged on the chamber doctor (4) for determining the excess pressure in the chamber (24) and this pressure sensor (21) is linked by circuit technology with a machine control (20) of the printing or coating machine,

   - the machine control (20) is linked with a feed pump (16) arranged exclusively in the feed lead (7) and, by means of the feed pump (16), the excess pressure of the liquid medium in the chamber (24) of the chamber doctor (4) can be generated

   - the signals of the pressure sensor (21) can be processed by means of the machine control (20) and, via this machine control (20), the feed pump (16) can be driven, and

   - in the return lead (8), a valve for the adjustment of the throughflow is arranged and the excess medium can be fed back to the reservoir (17, 18, 19) from the chamber (24) by means of the return lead (8) under gravity.
2. Printing or coating machine according to Claim 1, characterised in that the rastered applicator roller (3) has on its cover surface an open structure of cells connected to one another.
3. Printing or coating machine according to Claim 1, characterised in that the feed pump (16) can be switched over to suction operation.
4. Printing or coating machine according to Claim 1 and 3, characterised in that before an exchange of chamber doctor (4) and feed and return leads (7, 8) any liquid medium located in the chamber (24) can be fed back into a corresponding reservoir (17, 18, 19).
5. Printing or coating machine according to Claim 1, characterised in that the feed pump (16) is a hose pump receiving the feed lead (7).
6. Printing or coating machine according to at least Claim 1, characterised in that the feed and return leads (7, 8), the chamber doctor (4) as well as at least the parts of the feed pump (16) contacted by the medium can be cleaned outside of the coating unit.
7. Printing or coating machine according to at least Claim 1, characterised in that, in the direction of rotation of the driveable rastered applicator roller (3), the first doctor blade (22) lies against it as a closing doctor and the second doctor blade (23) as a working doctor of the chamber doctor (4).
8. Printing or coating machine according to Claim 1, characterised in that the valve is connected by circuit technology with the machine control (20).

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