EP1556218A2

EP1556218A2 - Doctor blade devices for a strip-producing or strip-processing machine

Info

Publication number: EP1556218A2
Application number: EP03778236A
Authority: EP
Inventors: Johannes Boppel; Peter Wilhelm Kurt Leidig
Original assignee: Koenig and Bauer AG
Current assignee: Officine Meccaniche Giovanni Cerutti SpA
Priority date: 2002-10-19
Filing date: 2003-10-20
Publication date: 2005-07-27
Anticipated expiration: 2023-10-20
Also published as: EP1554122A1; US20060096476A1; EP1554208B1; WO2004037538B1; EP1997759B1; ATE435180T1; EP1655257B1; WO2004037698B1; ATE337255T1; JP2006502937A; AU2003286098A1; WO2004037539A2; EP1655257A1; ES2306904T3; DE50309490D1; EP1556218B1; CN1705608A; WO2004037539B1; WO2004037696A3; WO2004037538A1

Abstract

A folding element for a printing press, or sheet handler, has the folding guide (03) with a microporous surface to generate an air cushion and thereby prevent mechanical contact between the guide and the sheets. The pore size is less than 500 microns and the pores are evenly distributed over the surface of the guide. Air is blown through the porous surface from inside the hollow guide.

Description

description

Doctor devices of a web-producing or processing machine

The invention relates to doctor blade devices of a web-producing or processing machine according to the preamble of claim 1 or 2.

A chambered doctor blade is known from DE 43 30 681 A1, wherein an ink-permeable body for ink application can be placed on an anilox roller and brought into physical contact. The color-permeable body can be a porous material such. B. be sintered metal.

US 5423468 A shows a guide element for webs, which has an inner body with bores and an outer body made of porous, air-permeable material. By applying compressed air to the guide element from the inside, the web is guided contactlessly on a pleasure pad.

The doctoring devices are used in particular on gravure printing machines (of all kinds) in order to strip off the excess ink from the forme cylinder so that only ink remains in the cells. It is important that the doctor blade does not destroy and damage the surface of the forme cylinder. This is achieved in the currently usual doctor blade devices by the doctor blade being made of a softer steel (easy to replace and used as a wearing part in the printing house) and the forme cylinder being coated with a wear-resistant surface (in illustration gravure, e.g. chrome).

So that the doctor blade, also called doctor blade, does not run in, the conventional doctor blade is moved back and forth evenly on the surface of the forme cylinder to evenly wear the doctor blade. The invention has for its object to provide doctor devices.

The object is achieved by the features of claim 1 or 2.

The advantages that can be achieved with the invention are, in particular, that a low-wear doctor device has been created. The squeegee system that is common today is replaced by a squeegee, at the point of contact of which with the forme cylinder, an air cushion is created, so that there is no direct contact between the squeegee and the forme cylinder. There is therefore no wear between the squeegee and the forme cylinder, since the air cushion prevents direct contact. It is also no longer necessary to move the squeegee sideways. The additional coating of the forme cylinder with chrome can also be omitted if necessary. An air cushion can also be formed on the ink-carrying side to prevent contamination.

By designing the openings as micro-openings, the air flow over the effective length of the squeegee is greatly evened out. It is advantageous that - in contrast to openings in the millimeter range - there is essentially no "blowing effect" but only an air cushion, since otherwise the color dries in the wells and can no longer be transferred to the paper web. It is therefore not included an "air knife" comparable, in which an air jet is used, for. B. scraping off the color.

By means of air outlet openings with diameters in the millimeter range, forces (momentum of the beam) are selectively effective, while the distribution of micro-openings with a high hole density primarily has the effect of a trained air cushion. The cross-section of holes previously used was, for example, 1 to 3 mm, whereas for the micro-openings the cross-section was at least a power of ten smaller. This creates significantly different effects. In contrast to squeegees with openings or bores of opening cross-sections in the range of millimeters and a hole spacing of several millimeters, a much more homogeneous surface structure is advantageously created when micro-openings are formed on the surface. Micro-openings are understood here to mean openings on the surface of the doctor blade which have a diameter of less than or equal to 500 μm, advantageously less than or equal to 300 μm, in particular less than or equal to 150 μm. A “hole density” for the area provided with the micro-openings is at least one micro-opening per 5 mm ² (= 0.20 / mm ² ), advantageously at least one micro-opening per 3.6 mm ² (= 0.28 / mm ² ).

In addition, in the case of micro-openings, the volume flow exiting per unit area is reduced in such a way that a leakage flow can also be reasonably small, even in peripheral areas or areas that are not currently being used, even without area-wise covering.

Further advantages are that an exchange is not required, or at least less often, and that there is much less contamination.

The new doctor blade is now executed in a version with microporous material so that the doctor blade body made of metal, plastic or similar rigid materials has an air chamber into which a fluid under pressure, e.g. B. compressed air is pressed. On the side of the squeegee body, which faces the forme cylinder, there are even holes through which the compressed air can escape. So that a uniform air cushion is created without direct flow on the outside, the doctor blade is coated with a microporous material layer or a similarly fine-porous material, which creates a uniform load-bearing air layer. In the second embodiment, the micro-openings are designed as openings in micro-holes.

The geometry of the squeegee is to be carried out so advantageously that the squeegee cutting edge is in one steeper angle lies against the forme cylinder and the ink is peeled off from the forme cylinder without a direct blowing effect.

The micro-openings can advantageously be designed as open pores on the surface of a porous, in particular microporous, air-permeable material or as openings of through-holes with a small cross-section which extend through the wall of a supply chamber to the outside.

In order to achieve a uniform distribution of air emerging at the surface of the material in the case of the use of microporous material, without simultaneously requiring high layer thicknesses of the material with high flow resistance, it is expedient that the doctor blade has a solid, air-permeable carrier on which the microporous material is applied as a layer. Such a carrier can be acted upon by compressed air which flows out of the carrier through the microporous layer and thus forms an air cushion on the surface of the doctor blade.

This carrier can in turn be porous with a better air permeability than that of the microporous material; however, it can also be formed from a flat material or molded material which encloses a cavity and is provided with air passage openings. Combinations of these alternatives are also possible.

In order to achieve a uniform air distribution, it is also desirable that the thickness of the layer corresponds at least to the distance between adjacent openings of the carrier.

If micro-bores are used, an embodiment is advantageous in which the side of the doctor facing a roller or a cylinder and having the micro-openings is designed as one or more inserts in a carrier. In further training, the insert can be detachably and, if necessary, exchangeably connected to the carrier. So is cleaning and / or an exchange of inserts of different types of micro perforations to adapt to different job widths possible.

Further applications in doctor blade devices for doctoring off ink or ink contamination, doctor blade on the anilox roller or anilox roller in flexo or anilox machines (in packaging machines)

Exemplary embodiments of the invention are shown in the drawings and are described in more detail below.

Show it:

Figure 1 is a schematic section through a printing unit with doctor device.

FIG. 2 shows an enlarged cross-sectional illustration of the doctor device from FIG. 1 with porous material;

3 shows a second embodiment of the doctor device;

FIG. 4 shows an enlarged cross-sectional illustration of the doctor device from FIG. 3 with porous material; FIG.

FIG. 5 shows an enlarged cross-sectional illustration of the doctor device from FIG. 1 with micro bores; FIG.

FIG. 6 shows an enlarged cross-sectional illustration of the doctor device from FIG. 3 with micro bores. The printing unit shown in FIG. 1 in a simplified section, in particular gravure printing unit, comprises a rotary body 01, e.g. B. a roller 01 or a cylinder 01, in particular a forme cylinder 01, an ink pan 02, into which the forme cylinder 01 is immersed and from which it takes color when it rotates, an impression roller 03, which in a known manner as one with an elastic Material such as rubber-coated, rotatable cylinder 03 is carried out, and a doctor device 04, doctor blade 04 for short.

The doctor blade 04 is arranged, based on the direction of rotation of the forme cylinder 01 in the counterclockwise direction in FIG. 1, on the way from the ink tray 02 to a printing gap formed between the forme cylinder 01 and impression roller 03, through which a web 06 to be printed, in particular a material web 06, is led. The doctor blade 04 has a hollow interior 07 which extends over its entire length and can be acted upon by compressed air through a connector 05 attached to a rear side.

On the side facing away from the forme cylinder 01, the inner space 07 is delimited by dense metal sheets, the surface facing the forme cylinder 01 has a plurality of openings 10, in particular micro-openings 10, at least in the area interacting with the forme cylinder 01 (see FIG. 2) which in operation from the interior 07, z. B. cavity 07, in particular a chamber 07 designed as a pressure chamber 07, pressurized fluid against the environment, for. B. a liquid, a gas or a mixture, especially air, flows. A corresponding supply of compressed air into the cavity 07 is not shown in the figures.

In a first embodiment for the micro-openings 10 (FIGS. 1 to 4), these are open pores on the surface of a porous, in particular micro-porous, air-permeable material 09, e.g. B. made of an open-pore sintered material 09, in particular made of sintered metal 09. The pores of the air-permeable porous material 09 have an average diameter (average size) of less than 150 μm, for. B. 5 to 50 microns, in particular 10 - 30 microns. The material 09 has an irregular, amorphous structure.

The cavity 07 of the doctor blade 04 can, at least on its area interacting with the forme cylinder 01, be essentially formed solely from a body which closes off the cavity 07 on this side from porous solid material (i.e. without further load-bearing layers of appropriate thickness). This essentially self-supporting body is then designed with a wall thickness of greater than or equal to 2 mm, in particular greater than or equal to 3 mm.

In order to achieve a uniform distribution of air emerging on the surface of the microporous material 09, without simultaneously requiring high layer thicknesses of the material 09 with a correspondingly increased flow resistance, it is provided in a first embodiment (FIG. 2) that the doctor blade 04 has a solid, at least partially air-permeable carrier 08, in particular carrier body 08, on which the microporous material 09 is applied as a layer 09. Such a carrier body 08 can be pressurized with compressed air, which flows out of the carrier body 08 through the microporous layer 09 and thus forms an air cushion on the surface of the doctor blade 04. In a preferred embodiment, the porous material 09 is thus not designed as a load-bearing solid body (with or without a frame construction), but rather as a coating 09 on a carrier material, in particular metallic, which has openings 15 or through openings. "Non-load-bearing" layer 09 in conjunction with the carrier body 08 is - in contrast to, for example, "load-bearing" layers known from the prior art - a structure, the layer 09 covering its entire layer length and entire layer width in each case on a large number of support points the support body 08 supports. The carrier body 08 has z. B. on its interacting with the layer 09 width and length each have a plurality of unrelated bushings 15, z. B. holes 15 on. This embodiment is clearly different from an embodiment in which a porous material extending over the entire active surface is self-supporting over this distance is supported only in one end area on a frame or support, and therefore must have a corresponding strength.

In the exemplary embodiment shown, the carrier material essentially absorbs the weight, shear, torsion, bending and / or shear forces of the squeegee, which is why a corresponding wall thickness (for example greater than 3 mm, in particular greater than 5 mm) of the carrier body 08 and / or an appropriately stiffened construction is selected. The porous material 09 outside the bushing 15 has z. B. a layer thickness that is less than 1 mm. A layer thickness between 0.05 mm and 0.3 mm is particularly advantageous.

A proportion of the open area in the area of the effective outer surface of the porous material 09, here denoted by degree of opening, is between 3% and 30%, preferably between 10% and 25%. In order to achieve a uniform air distribution, it is also desirable that the thickness of the layer 09 corresponds at least to the distance between adjacent openings in the bores 15 of the carrier body 08.

In the first embodiment (FIG. 2), the interior 07 on the side facing the forme cylinder 01, at least in the region of a metering edge 11, is delimited by the carrier body 08 or the wall 12 which is frequently broken. This or these carries on its or its outside the layer 09 made of microporous material 09. The carrier body 08 can be a piece of flat material or shaped material, such as a punched sheet or a stiff wire mesh, which is perforated many times; however, a three-dimensional, air-permeable body such as an open-pore metal foam etc. is also possible. In the exemplary embodiment, the openings are shown as bores 15 connecting the cavity 07 with the layer 09.

The choice of material, dimensioning and pressurization are selected such that 1-20 standard cubic meters per m ² , in particular 2 to 15 standard cubic meters per m ² , emerge from the air outlet surface of the sintered material 09 per hour. The is particularly advantageous Air outlet from 3 to 7 standard cubic meters per m ² .

The sintered surface from the cavity 07 is advantageously subjected to an excess pressure of at least 1 bar, in particular more than 4 bar. It is particularly advantageous to apply an overpressure of 5 to 7 bar to the sintered surface.

The side of the squeegee 04 facing the forme cylinder 01 has the metering edge 11, which can be adjusted to the surface of the forme cylinder 01 with an adjustable gap width, and between the metering edge 11 and the ink tray 02 a continuous sloping wall 12 which extends into one of the Ink tray 02 surrounding receptacle 13 extends into and on which ink stripped by the dosing edge 11 from the surface of the forme cylinder 01 can flow into the receptacle 13.

The perforated carrier body 08 extends into the dosing edge 11, so that compressed air can penetrate from the interior 07 to the dosing edge 11 and microporous layer 09 surrounding the dosing edge 11 can emerge evenly with a small layer thickness. Air forms at the tip of the metering edge 11 directly opposite the forme cylinder 01, on the surface of which a thin air cushion, which is extremely homogeneous thanks to the microporous layer 09, prevents direct physical contact between the metering edge 11 and the forme cylinder 01. As a result, the dosing edge 11 and the printing plates mounted on the forme cylinder 01 or the self-locking forme cylinder 01 are practically free from frictional wear, while the effect of the doctor blade 04 is practically the same as that of a conventional doctor blade with fixed or flexible lips.

Air can also flow homogeneously through the microporous layer 09 covering the carrier body 08 in the region of the wall 12. This prevents paint stripped off by the metering edge 11 from collecting on the wall 12 and leading to a jam in front of the metering edge 11. Even if the color used is highly viscous, it can Do not wet wall 12 and drip off it drop by drop.

The throughput of compressed air required per unit area of the wall 12 is less than that required at the level of the metering edge 11. Such different flow rates can be achieved by appropriately selecting the number of bores 15 and their relative cross-sectional area in the carrier body 08 as well as the thickness of the microporous layer 09 or the porosity of the layer 09. That means in the area of the metering edge 11 the density of the bores 15 (hole density) must be greater and / or the thickness of the layer 09 must be smaller than in the area of the wall 12. Regulation is also possible via the air volume and / or the air pressure.

Air that has passed through one of the bores 15 of the carrier body 08 tends to be distributed in the pores of the microporous layer 09 both towards its surface and laterally, parallel to the surface. If one assumes that the flow resistance in the microporous layer 09 is isotropic, the air which has passed through a bore 15 in the carrier body 08 is also distributed isotropically in the layer 09. In order to create a homogeneous, gapless air cushion on the surface of the layer 09, air must escape on its entire surface, even in those areas below which there is an impermeable surface area of the carrier body 08. For this purpose, the thickness of the microporous layer 09 can be at least as large as an average distance between adjacent bores 15 on the surface of the carrier body 08.

The wall thickness of the carrier body 08 at least in the area bearing the layer 09 is, for. B. greater than 3 mm, in particular greater than 5 mm.

However, the carrier body 08 can itself also be made of porous material, but with better air permeability -z. B. a larger pore size - than that of the microporous material of the layer 09. In this case, the Openings of the carrier 08 through open pores in the area of the surface, and the feedthroughs 15 through the channels formed randomly via the porosity inside. The carrier body 08 can, however, also be formed from any flat material or shaped material which surrounds the cavity 07 and is provided with passages 15. Combinations of these alternatives are also possible.

The internal cross section of a feed line, not shown, for supplying the compressed air to the turning bar is less than 100 mm ² , preferably it is between 10 and 60 mm ² .

FIG. 3 shows a second embodiment with a doctor device 14 modified with respect to doctor 04, e.g. B. Squeegee 14. Components shown in FIG. 3 that have the same reference numerals as FIG. 1 are identical to the corresponding components already written with reference to FIG. 1. The tip of the doctor blade 14 is shown in Fig. 4 on an enlarged scale in section. A housing of the doctor blade 14 is formed by an angularly bent inner plate 16 and an approximately parallel outer plate 17, which is repeatedly broken through on an end face 18 facing the forme cylinder 01 and an underside 19 adjoining the inner plate 16. The end face 18 and page 19, e.g. B. underside 19, carry the microporous layer 09. The doctor blade 14 is provided to be placed against the forme cylinder 01 with its edge 22 delimited by the end face 18 and underside 19. Size, cross-sectional area and density of the bore 21, z. B. Breakthroughs 21 in the region of the edge 22 acting as a metering edge 22 are defined such that, as in the case of FIGS. 1 and 2, a homogeneous air cushion is formed between the edge 22 and the surface of the forme cylinder 01, which makes direct contact of the doctor blade 14 with the forme cylinder 01 prevented. On the underside 19, the density and / or cross-sectional area of the bores 21 is greater, smaller or the same as in the area of the edge 22, so that an intensive air flow emerges here, which strips paint from the bottom side 19 through the edge 22 from the forme cylinder 01. and hurls in the direction of the collecting container 13. The one shown in Fig. 3 Configuration there is no direct connection between the edge 22 of the doctor blade 14 and the collecting container 13, which is why between the doctor blade 14 and the collecting container 13 there is still a collecting screen 23 which is hit by thrown off ink drops and on which they can flow downwards. The collecting screen 23 can also have a surface facing the forme cylinder 01 made of air-flowed microporous material 09 on a perforated carrier 08 corresponding to the wall 12 of the doctor blade 04 from FIG. 1.

In a second embodiment (Fig. 5 and 6) for the micro-openings 03, these are designed as openings through holes 24, in particular micro-holes 24, which are characterized by a z. B. formed as a pressure chamber 07 cavity 07 delimiting wall 26, z. B. chamber wall 26, extend outwards. The holes 24 have z. B. a diameter (at least in the region of the openings 10) of less than or equal to 500 μm, advantageously less than or equal to 300 μm, in particular between 60 and 150 μm. The degree of opening is z. B. at 3 to 25%, especially at 5 to 15%. A hole density is at least 1/5 mm ² , in particular at least 1 / mm ² up to 4 / mm ² . The wall 26 thus has a microperforation, at least in an area opposite the forme cylinder 01. The microperforation advantageously extends, as in the first exemplary embodiment, the bushings 15 and layer 09, at least in the effective area between the doctor blade 04 and the forme cylinder 01.

A wall thickness influencing the flow resistance of the chamber wall 26 containing the bores 24 is, for. B. at 0.2 to 3.0 mm, advantageously at 0.2 to 1.5 mm. in particular from 0.3 to 0.8 mm. A reinforcing structure (not shown), for example a carrier, in particular a metal carrier, extending in the longitudinal direction of the doctor 04, on which the chamber wall 26 is supported at least in sections or at points, can be arranged in the interior of the doctor 04, in particular in the cavity 07. FIG. 6 shows the second embodiment of the doctor blade 04 from FIG. 3 in the embodiment with micro bores 24 from FIG. 5.

For the execution of the micro-openings 03 as openings of holes 24 z. B. an excess pressure in the chamber 07 of 0.5 to 2 bar, in particular from 0.5 to 1.0 bar is advantageous.

The bores 24 can be cylindrical, funnel-shaped or with another special shape (eg in the form of a Laval nozzle).

The microperforation, i.e. H. The holes 24 are preferably produced by drilling using accelerated particles (for example liquid such as water jet, ions or elementary particles) or using electromagnetic radiation with a high energy density (for example light using a laser beam). Production using an electron beam is particularly advantageous.

The side facing the forme cylinder 01 of the wall 26 having the bores 24, for. B. a wall made of stainless steel, in an advantageous embodiment has a dirt and / or paint-repellent finish. It has a coating, not shown, which does not cover the openings 10 or bores 24 - for. B. nickel or advantageously chromium - which z. B. is additionally processed - e.g. B. structured with micro ribs or a lotus flower effect or preferably mirror polished).

In one variant, the wall having the bores is designed as one insert or several inserts in a carrier. The insert can be fixed or changeable to the carrier. The latter is advantageous with regard to cleaning or exchanging inserts of different types of microperforations to adapt to different colors, printing forms etc. LIST OF REFERENCE NUMBERS

01 rotating body, cylinder, roller, forme cylinder

02 paint tray

03 cylinder, impression cylinder

04 Squeegee device, squeegee

05 sockets

06 web, material web

07 interior, cavity, chamber, pressure chamber

08 carrier, carrier body

09 layer microporous; Material, breathable, microporous; Sintered material; Sintered metal, coating

10 opening, micro opening

11 dispensing edge

12 wall

13 collecting container

14 Squeegee device, squeegee

15 implementation, drilling

16 inner sheet

17 outer panel

18 end face

19 bottom, side

20 -

21 hole, opening

22 edge, dispensing edge

23 fall arrest

24 hole, micro hole

25 -

26 wall, chamber wall

Claims

Expectations

1. doctor device (04; 14) of a printing press with a metering edge (11; 22) which can be set against a co-operating rotating body (01), characterized in that the doctor device (04) at least in the region of its metering edge (11; 22) has a multiplicity of openings (10) for the exit of a pressurized, gaseous fluid, which in operation forms a gaseous cushion between the metering edge (11; 22) and a surface of the rotating body (01).

2. Doctor device (04; 14) of a printing press with a metering edge (11; 22) which can be set against a co-operating rotating body (01), characterized in that the doctor device (04; 14) at least in the region of its metering edge (11; 22) has microporous, air-permeable material (09).

3. Doctor device according to claim 2, characterized in that the microporous material (09) has on its outer surface a plurality of openings (10) for the discharge of a pressurized, gaseous fluid, which in operation is a gaseous cushion between the metering edge (11 ; 22) and a surface of the rotating body (01).

4. Doctor device according to claim 1 or 3, characterized in that the openings (10) are designed as micro-openings (10) with a diameter of less than 500 microns.

5. Doctor device according to claim 1, characterized in that the openings (03) are designed as open pores of a porous material through which the fluid flows (09).

6. Doctor device according to claim 2 or 5, characterized in that the pores of the fluid-permeable porous material (09) has an average diameter of

5 to 50 μm, in particular 10 to 30 μm.

7. Doctor device according to claim 2 or 5, characterized in that the porous material (09) is designed as an open-pore sintered material (09), in particular as a sintered metal (09).

8. Doctor device according to claim 2 or 5, characterized in that an opening degree on the outward surface of the porous material (09) is between 3% and 30%, preferably between 10% and 25%.

9. Doctor device according to claim 2 or 5, characterized in that the microporous material (09) is designed as a layer (09) on a load-bearing, but at least partially fluid-permeable carrier (08).

10. Doctor device according to claim 9, characterized in that the carrier (08) on its side facing the layer (09) has at least one supporting surface connected to the layer (09) and a plurality of openings for supplying the fluid into the layer (09 ) having.

11. Doctor device according to claim 10, characterized in that the layer (09) in the region of the wing has a thickness of less than 1 mm, in particular from 0.05 mm to 0.3 mm.

12. Doctor device according to claim 9, characterized in that the carrier (08) on its with the layer (06) cooperating width and length each have a plurality, in particular non-contiguous, bushings (15).

13. Doctor device according to claim 9, characterized in that a wall thickness of the carrier (08) or at least the wall (09) carrying the wall is greater than 3 mm, in particular greater than 5 mm.

14. Doctor device according to claim 9, characterized in that the carrier (08) is formed at least partially from a porous material (09) with a better air permeability than the microporous material (09).

15. Doctor device according to claim 9, characterized in that the carrier (08) is formed at least in part from a flat material which surrounds a cavity (07) and is provided with openings.

16. Doctor device according to claim 9, characterized in that the microporous material (09) has a layer thickness which corresponds at least to the distance between adjacent openings of the carrier (08).

17. Doctor device according to claim 9, characterized in that the carrier (08) simulates the outer contour of the metering edge (11).

18. Squeegee device according to claim 1, characterized in that the openings (10) are designed as outwardly directed openings (10) of microbores (24) in a wall (26) delimiting the squeegee (04) towards the outside towards the rotating body (01) are.

19. Doctor device according to claim 18, characterized in that a diameter of the openings (10) is less than or equal to 300 microns, in particular between 60 and 150 microns.

20. Doctor device according to claim 18, characterized in that a Wall thickness of the wall (26) is 0.2 to 3.0 mm.

21. Doctor device according to claim 18, characterized in that a hole density, ie a number of openings (10) per unit area, for the area provided with the micro-bores (10) is at least 0.2 / mm ² .

22. Doctor device according to claim 1 or 6, characterized in that

1 - 20 standard cubic meters of air per hour escape to one square meter of the lateral surface with the openings (10).

23. Squeegee device according to claim 1 or 3, characterized in that 2-15, in particular 3-7, standard cubic meters of air per hour emerge on a square meter of the lateral surface having the openings (03).

24. Doctor device according to claim 2 or 5, characterized in that the porous material (06) is acted upon from the inside with at least 1 bar overpressure.

25. Doctor device according to claim 2 or 5, characterized in that the porous material (06) from the inside with more than 4 bar, in particular with 5 to 7 bar, excess pressure is applied to the fluid.

26. Doctor device according to claim 1 or 3, characterized in that a feed line for supplying the fluid to the guide element (01) has an internal cross section of less than 100 mm ² , in particular between 10 and 60 mm ² .

27. Doctor device according to claim 1 or 3, characterized in that the pressurized fluid is designed as compressed air.

28. Doctor device according to claim 1 or 3, characterized in that the Part of the doctor blade (04) carrying openings (10) is designed as a releasable insert on a carrier.

29. Doctor device according to claim 1 or 3, characterized in that a wall (12) of the component (04) which projects beyond the metering edge (11) also has openings (10) for the exit of the fluid.

30. Doctor device according to claim 18 and 25, characterized in that the wall (12) is also formed by the carrier (08) coated with the microporous material (09).

31. Doctor device according to claim 1 or 3 and claim 25, characterized in that the fluid permeability per unit area at the metering edge (11) is higher than on the wall (12).

32. Doctor device according to claim 1, 3 or 25, characterized in that a region of maximum fluid permeability is present on a side (19) of the metering edge (11) facing an ink collecting container.