EP1719559A1 - Doctor blade holder - Google Patents

Abstract

The bed has a continuous groove in an axial direction to hold a rotatable metering rod (3) that is pressed against a moving surface (8) and meters and equalizes a liquid to a pasty medium applied to the moving surface. The bed uses a material including a homogeneous mixture of specific percentages of polyethylene and wax of animal, vegetable, mineral and synthetic origins, where the wax is either solid or liquid at room temperature. The material has a low coefficient of friction and is inserted into the bed as an insert part. A pressing unit is arranged in an upper part of the bed. An independent claim is also included for a method of production of parts of a metering unit used in a production of a fibrous web.

Description

The invention relates to a doctor bed formed as a profile strip with a continuous groove in the axial direction for receiving a rotary metering rod which can be pressed against a running surface and dosed on the running surface applied liquid to pasty medium and / or equalized, the running surface in direct Order of the medium is one side of a paper, cardboard or other fibrous web and for indirect application is the surface of a transfer element, which transfers the application medium to the fibrous web

Such a doctor bed of a metering, doctoring or equalizing unit is already known from various documents. On the DE-A1 3022 955 should be referenced here. The doctor bar is held in a doctor bed of rubber-elastic material. But other homogeneous materials of the doctor bed, such as polyethylene and polyurethane are known.

In most cases, the doctor bed has on its rear side facing away from the metering rod a pressing element (pressure hose) for pressing against the running surface. With the pressure element or the pressure hose, the thickness of the metered film on the running surface can be adjusted and varied via the pressure in the pressure hose. In addition, the doctor bed contains flushing channels into which a rinsing or lubricating fluid, eg. As water is introduced. As a result, the bearing of the metering rod can be lubricated and thinned and possibly penetrated application medium.

The smooth or profiled metering rod rotating in the doctor bed causes considerable wear of the doctor bed. The precisely manufactured doctor beds must therefore be replaced frequently, which causes considerable costs and effort.

The wear is all the greater or the friction conditions are unfavorable, the more the doctor bed is pressed in the region of the doctor rod receiving groove against the doctor blade to the doctor rod on the one hand over its entire length (machine width) to better lead and on the other hand said penetration of To prevent application medium. Here then an enormously high drive power of the rotating metering rod is necessary, which in turn causes high costs.

The invention is therefore based on the object to provide an improved with respect to the friction conditions doctor bed or an improved material.

The object is achieved by the characterizing features of claims 1 to 3 and 10.

The invention provides materials or material combinations which have a significantly lower coefficient of friction than the materials used hitherto.

According to the first solution (claim 1) is a material consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a solid at room temperature or liquid wax of animal, vegetable, mineral or synthetic origin, according to the second solution (claim 2) a material consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a solid at room temperature or liquid fat of animal origin and according to the third solution (claim 3) a material consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a natural or synthetic oil proposed.

• Gleitmittelkonzentrate von Kohlenwasserstoffwachsen;
• Carbonsäuren und deren Amide aber auch Carbonsäureester, - teils auch Alkohole, wie z.B.: HECOSLIP;
• Paraffin Wachse, wie z.B.: AdSperse;
• Fischer Tropsch - Wachse;
• Mikrowachse, wie z.B.: Petrolatum, EnHance, Sasobit;
• Rohparaffine, wie z.B.: Rubitherm;
• Vaseline, wie z.B.: Hellfrisch Vaseline;
• Weißöl;
• Silikonöl;
• Wachsöle;
• Bitumenadditive, wie z.B.: Scenti;
• Synthetisches Wachse, wie z.B.: Hydrowax, Sasolwax;
• Stearine, wie z.B.: Varacid, VaraNat;
• Naturwachse;
• Gelwachse, wie z.B. VaraGel.

The following waxes, greases or oils (some of whose product names are indicated) are suitable for the material combination according to the invention:

• Lubricant concentrates of hydrocarbon waxes;
• Carboxylic acids and their amides but also carboxylic acid esters, - partly also alcohols, such as: HECOSLIP;
• Paraffin waxes, such as: AdSperse;
• Fischer Tropsch - waxes;
• Microwaxes, such as: Petrolatum, EnHance, Sasobit;
• Crude paraffins, such as: Rubitherm;
• Vaseline, such as: Bright Vaseline;
• White oil;
• Silicone oil;
• Wax oils;
• Bitumen additives, such as: Scenti;
• Synthetic waxes, such as: Hydrowax, Sasolwax;
• Stearins, such as: Varacid, VaraNat;
• Natural waxes;
• Gel waxes, such as VaraGel.

It is envisaged that the production of inventive, wear-resistant "ultra high molecular weight" polyethylene (UHMW-PE) via sintered presses. The production process for example doctor beds requires a stress-free production of the plastic block, which can be achieved for example by appropriate Abkühlkurven.
Oils, liquid waxes and liquid fats tend to accumulate locally at room temperature compared to solid waxes and fats during compaction (at 220 bar) and at a press temperature of 250 ° C. A stepwise compression with specially different temperature levels prevents the removal of the liquid. A homogeneous incorporation of the slip additives in finely dispersed form takes place in the melt.

There is no immediate compression at full temperature, but only with pressureless placement of the press ram and short full Temperature load is achieved a melted skin draw, wherein the inner life is still in pure powder form, wetted with liquid rests. Only then is the pressure increased at low temperature and the material pressed. A lower temperature is therefore chosen so as not to allow the liquid to flow down too quickly, but to be able to compact it immediately in the powder (temperature increase = viscosity reduction).

The claim 10 specifies the use of material combinations according to the invention consisting of polyethylene with proportions by weight of waxes or fats or oils, in addition to the already described doctor blade of any design and size for the production of so-called Rakelabstreifleisten (such is the arrangement forth in the post-published DE 10 2004 028 754 described) and also application nozzles and deck boundary elements (such an element is in the post-published DE 10 2004 028 755 described) can be used in an applicator.
In addition, the material combinations described can also be used for support bodies for the application nozzles and metering or doctor units. However, the application for doctor beds is considered preferable.

• erhöhte Standzeit des Rakelbettes,
• geringere Antriebsleistung des Rakelstabes ist erforderlich,
• eine höhere Anpresskraft bei gleicher Antriebsleistung ist möglich, wodurch bessere Auftragsprofile in Querrichtung erreicht werden
• die Möglichkeit der Anbringung eines zusätzlichen Anpress- bzw. Abdichtelementes innerhalb des Rakelbettes, wodurch eine gleichmäßigere Betriebsweise der Dosiereinheit erreicht sowie Ablagerungen in den Spülkanälen des Rakelbettes vermindert werden und dabei dennoch die Antriebsleistung nicht erhöht werden muss.

As advantages apply to the doctor beds:

• increased service life of the doctor bed,
• lower drive power of the metering rod is required
• a higher contact force with the same drive power is possible, whereby better job profiles in the transverse direction can be achieved
• the possibility of attaching an additional pressing or sealing element within the doctor bed, whereby a more uniform operation of the metering unit achieved and deposits in the purge channels of the doctor bed can be reduced and yet the drive power does not need to be increased.

It should also be noted that not the complete doctor blade bed must be made of the combination of materials according to the invention, but it may be useful if this particular material in the form of a sectionally inserted and extending in the axial direction insert part, as in the post-published DE 10 2004 024 079 specified, is manufactured. This insert is then frictionless with respect to the rest (normal material eg rubber-elastic material or PU or PE).

So far, the fats, waxes and oils proposed here have been used only in the production of detergents or certain paints. The suitability for the formation of homogeneous mixtures for said components, however, has turned out to be surprising and it is the merit of the inventors to have recognized this.

Further advantageous embodiments of the invention will become apparent from the dependent claims.

The invention will be explained below with reference to application examples.

Figur 1:

einen Querschnitt durch ein Rakelbett

Figur 2:

einen Querschnitt durch eine Auftragsdüse, die auf einem Tragkörper sitzt

Figur 3:

eine Ansicht auf ein weiteres Rakelbett

Figur 4:

einen Querschnitt durch Dosiereinheit mit anderem Rakelbett

The schematic representations show:

FIG. 1:

a cross section through a doctor bed

FIG. 2:

a cross section through an applicator nozzle, which sits on a support body

FIG. 3:

a view on another doctor bed

FIG. 4:

a cross section through metering with another doctor bed

The same reference numerals in the individual figures designate the same or equivalent elements.

FIG. 1 shows a metering unit 1, which can also be used as a doctor blade, or as a doctor blade. Egalisiereinheit 1 can be designated. It is used for dosing, doctoring off or equalizing a previously applied to a running surface application medium and has an inventive doctor bed 2 and a metering rod 3 as a metering, doctoring or leveling on. The metering rod 3 is rotatably received in an axially extending groove 4, which is adapted to the shape of the metering rod, or has a rotary drive 5. The more firmly the metering rod 3 is received in the groove 4, the higher must normally be the drive power. In the doctor bed in the example two to metering rod 3 open flush channels 6 are incorporated, in which a rinsing liquid can be introduced for lubricating the rotating metering rod 3 and also to reduce the penetration of application medium in the interior of the doctor bed 2.

With a pressure element 7, the doctor bed 2 including the doctor blade 3 against a running surface 8, which is a direct application of a web side of a fibrous web and indirect application, the surface of a transfer element which emits the application medium 9 to the fibrous web, pressed while the thickness d determined the applied medium. As a pressure element 7 is usually a pressure hose on the adjustable internal pressure, the contact force F is set.

The doctor bed 2 is inventively made of a combination of materials consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a solid or liquid at room temperature wax of animal, vegetable, mineral or synthetic origin, in particular consisting from long-chain fatty alcohols and fatty acids or carnauba wax and paraffin.

In a second variant, the doctor bed 2 is made of a combination of materials consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a solid at room temperature or liquid fat of animal origin, such as stearins.

In a third variant, the doctor bed 2 is made of a material combination consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a natural or synthetic oil, which also with thickeners up to 40% by weight can be offset, manufactured.

The chosen material combinations ensure due to the low friction coefficient better friction conditions than before, so that either the previous drive power can be miniert or an additional contact element 10 in the doctor bed 2 - can be accommodated in its upper part 2.1 in a groove 11, whereby the metering rod 3 by this additional Pressing on the one hand is better stored and on the other hand, a better tightness against penetrating application medium 9 is achieved. This would normally only be possible with increased drive power of the metering rod 3, but this is compensated by application of the proposed material.

It should be added that the additional pressing element 10 is formed as a pressure hose, the. If the pressure hose is pressurized with air, the upper part 2.1 presses against the metering rod 3 and the advantages mentioned above are achieved.

From Figure 1 is still a cover strip 12 for the said pressure hose, i. the pressing or sealing member 10 can be removed. The cover strip serves as protection for the pressure hose and is screwed to the doctor bed 2. In case of pressure loss in the pressure hose 10, the metering rod 3 is still held in the groove 4 by the cover strip 12 fixed in or on the doctor bed 2, so that no unintentional ejection of the metering rod 3 is possible.

FIG. 2 shows a further example of application of the material according to the invention, ie the material combination.

Shown is an applicator device 13, in which an applicator nozzle 15 is placed on a hollow cylindrical support body 14 here. The application nozzle 15 consists of two nozzle lips 15.1 and 15.2, which between them a metering gap 15.3 for applying the application medium 9 on the running in the direction L surface 8. Both the application nozzle 15, and the support body 14 are made of the combination of materials according to the invention and thereby guarantee a long service life.

It should also be mentioned that also so-called (not shown) limiting elements, which are also referred to as Randbegrenzer or as a format delimiter, and as the name implies, a bar-free edge and a specific format or order width on the running surface 8 during their Establish production and / or finishing, can be made from the material of the invention.

So far, it was the case that due to the contact of the limiting element with the high-speed surface 8 and the high friction of this element, but also the roller cover of the running surface 8 has been partially damaged. By the material according to the invention, the disadvantages mentioned are significantly reduced and also increases the service life of said components.

FIG. 3 shows a further example of application of the material according to the invention, ie the material combination. It is again a dosing unit 1 with doctor bed 2 and stored therein, rotary squeegee 3. The squeegee bed 2 is not completely made of the material combination according to the invention, but as the perspective view shows, the material combination W _k in the form of only partially used and insert member 16 extending in the axial direction. This insert member 16 may be distributed centrally, or in the outer regions or in multiple numbers over the length of the doctor bed 2, and be in relation to the rest of the material W _ü (ie normal material such as rubber-elastic material or PU or PE) has the advantageous properties described (eg, is less friction).

FIG. 4 shows that the doctor bed 2 of a dosing unit 1, consisting or as described in FIG. 3, at least partially consisting of the material combination W _k according to the invention, may have a different shape than that shown in FIGS. 1 and 3. It can be seen that the doctor bed 2 with the low-friction material has a relatively small cross-section with respect to the metering rod 3 and is removably inserted in a larger holder 17. It is also conceivable that the holder 17 is made of the material combination W _k .

LIST OF REFERENCE NUMBERS

1

dosing

2

doctor bed

2.1

top

3

doctor bar

4

groove

5

rotary drive

6

irrigation channel

7

presser

8th

running surface

9

application medium

10

additional contact pressure element

11

groove

12

cover strip

13

applicator

14

supporting body

15

applicator

15.1

die lip

15.2

die lip

15.3

die gap

16

insert

17

holder

F

contact force

L

direction

d

thickness

W _K

Material combination

W _u

remaining material

Claims (10)

Doctor bed (2) formed as a profiled strip with a continuous groove in the axial direction (4) for receiving a rotary metering rod (3) which is pressed against a running surface (8) and on the running surface (8) applied liquid to pasty medium ( 9) metered and / or equalized, wherein the running surface (8) for direct application of the medium one side of a paper, cardboard or other fibrous web and indirect application is the surface of a transfer element, which the application medium (9) to the Fibrous web transfers,
characterized in that
for its production a material or a material combination (W _k ) is provided, consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a solid at room temperature or liquid wax of animal, vegetable, of mineral or synthetic origin. Doctor bed (2) formed as a profiled strip with a continuous groove in the axial direction (4) for receiving a rotary metering rod (3) which is pressed against a running surface (8) and on the running surface (8) applied liquid to pasty medium ( 9) metered and / or equalized, wherein the running surface (8) for direct application of the medium one side of a paper, cardboard or other fibrous web and indirect application is the surface of a transfer element, which the application medium (9) to the Fibrous web transfers,
characterized in that
for its production a material or a material combination (W _k ) is provided, consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a solid at room temperature or liquid fat of animal origin. Doctor bed (2) formed as a profiled strip with a continuous groove in the axial direction (4) for receiving a rotary metering rod (3) which is pressed against a running surface (8) and on the running surface (8) applied liquid to pasty medium ( 9) metered and / or equalized, wherein the running surface (8) for direct application of the medium one side of a paper, cardboard or other fibrous web and indirect application is the surface of a transfer element, which the application medium (9) to the Fibrous web transfers
characterized in that
for its production a material or a material combination (W _k ) is provided, consisting of a homogeneous mixture of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a natural or synthetic oil. Doctor bed according to claim 1,
characterized in that
the waxes consist of long-chain fatty alcohols and fatty acids or are carnauba waxes and paraffins. Doctor bed according to claim 2,
characterized in that the fats are stearins. Doctor bed according to claim 3,
characterized in that
the oil is provided with thickeners up to 40% by weight. Doctor bed according to one or more of claims 1 to 6,
characterized in that
the material or the material combination (W _k ) has a low coefficient of friction and, if desired, only as an insert (16) in the doctor bed (2) is integrated. Doctor bed according to one or more of claims 1 to 7,
characterized in that
an additional contact pressure element (10) in the upper part (2.1) of the doctor bed (2) is arranged, wherein for a pressure hose is selected. Doctor bed according to one or more of claims 1 to 8,
characterized in that
as protection for the contact pressure element (10) a cover strip (11) on the doctor bed (2) is fixed. Use of a material in the form of a homogeneous mixture consisting of 70 to 99.8% polyethylene and 0.2 to 30% by weight of a wax, oil or fat, a) for the production of parts of a metering unit (1), in particular a doctor bed (1), designed as a profile strip with a continuous groove in the axial direction for receiving a rotatable metering rod which can be pressed against a running surface and acts as a metering element, b) for producing parts, such as an applicator nozzle (15) and the application width limiting edge elements of a device (13) for applying a liquid or pasty medium on a running surface (8), wherein the surface upon direct application, the surface of a paper, Cardboard or other fibrous web and, in the case of indirect application, the surface of a transfer element which delivers the application medium (9) to the fibrous web, c) for producing a support body (14) for the application device (13) or the application nozzle (15) and / or for the dosing unit (1).

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