EP1502661B1 - Apparatus for applying a coating to plate-like workpieces - Google Patents

Description

The invention relates to the use of a device, wherein the device comprises an applicator roll (3), a metering device and at least one homogenization body (9,19) and wherein the application of a liquid application medium, in particular lacquer on flat workpieces by means of rolling on the workpiece applicator roll and which can be set to form a gap on the lateral surface of the applicator roll metering device, in particular in the form of a rolling on the applicator roll metering, takes place, such that above the gap between the applicator roll and metering a reservoir for the application medium is formed, its refilling by a supply line above the level the application medium takes place in the reservoir, wherein the refilling is carried out in particular by discontinuous pumps such as diaphragm pumps.

Such rolling machines and corresponding uses are known in many embodiments and for applying different application media. Their main field of application is the application of lacquer to plate-shaped workpieces, cf. EP 427 045 , The metering device usually consists of a metering roller which can be attached to the applicator roll; instead, it can consist of a squeegee, compare for example DE 100 30 310 , In both cases, an approximately V-shaped reservoir is formed above the gap, in which the application medium is kept at a certain minimum level. The frontal end of this reservoir is usually done by so-called end jaws, which are arranged on the front sides of the applicator roll.

The filling of the reservoir via a supply line with free outlet above the level of the application medium, usually in the middle of the machine. The capacity is adjusted so that a slightly larger amount is promoted, as it corresponds to the current need. The excess quantity of application medium returns to the circulation of the application medium via the upper edge of the lateral end jaws in return collecting lines to the pump container.

Investigations by the applicant have now shown that with high demands on the surface quality, especially when applying coatings with solids, sometimes optical irregularities in the surface texture occur and that these order errors may be related to the Nachfüllstoß occurring in discontinuous pumps.

Attempts by the applicant to even out the feed of the application medium into the reservoir, in particular by means of distribution channels with drain holes distributed over the roll width, did indeed result in a certain improvement. At the same time, however, spatial problems arose because the metering and application rollers usually pivotally mounted doctor blade attack, which can then collide with the distribution channel. In addition, the cleaning of the machine is very difficult.

DE 295 13 970 U1 and DE 296 10 446 U1 each show a device for applying a liquid to a fibrous web, which has at least one calming body, which partially dips into the application medium to avoid spattering at high order speed in the reservoir. A supply line for the application medium opens laterally next to the sedative body above the level of the application medium in the reservoir or is passed through the sedative body into the reservoir.

Another approach is from the non-generic JP 2001 070866 A known. There, a coating machine is described in which in a reservoir, in which the working medium is in direct contact with the workpiece to be coated, a completely immersed in the working medium Rotary roller or the like is arranged, which extends in the longitudinal direction over the entire width of the workpiece to be coated. A supply line for the application medium opens laterally next to the rotary roller below the level of the application medium in the reservoir. By turning the rotary roller in the reservoir, a more homogeneous coating is to be achieved.

Finally, out of the EP 0 643 928 A1 a device for coating a paper tape with adhesive, in which the adhesive is sprayed without the presence of a reservoir by means of nozzles directly on a Auftragungswulst.

Another prior art shows the EP-A-1216759 ,

Proceeding from this, the present invention has the object to improve a roller applicator device of the type described above in terms of coating quality, especially in those applications where the supply of the coating medium into the reservoir is carried out by discontinuous pumps, as in highly abrasive and aggressive Paints are necessary.

This object is achieved by the inventive use of a device of the type mentioned in such a way that in the reservoir at least one immersing in the application medium homogenizing body is arranged, which runs in the longitudinal direction approximately parallel to said gap and which is arranged in the vertical direction such that it its upper side emerges from the application medium, wherein the homogenizing body is arranged in the transverse direction so that its upper side is predominantly acted upon by the outflowing from the feed line application medium.

By this measure, the surge-like supply from the supply line no longer meets - at least not fully - on the free liquid surface of the reservoir, but this Nachfüllimpuls is completely or partially absorbed by the homogenizer and thus significantly weakened in its dynamics. The previously occurring disturbance in the paint flow of the reservoir is thus drastically reduced and the so-called glossy stripes on the product surface are reliably eliminated. In addition, the mentioned distribution channels and their complex cleaning accounts.

In order for the application medium to impinge on the homogenizing body, irrespective of its viscosity and its conveying speed, it is recommended that the supply line has at least one outlet directed towards the homogenizing body, but preferably a plurality of outlet openings arranged in succession in the splitting direction. These openings may extend almost the entire length of the reservoir.

With regard to the Homogenisierkörpers it is also recommended that it extends almost over the entire length of the reservoir, being preferably used for reasons of easier cleaning with a continuous body instead of several individual body. The shape of the homogenizing body is expediently circular-cylindrical. It can rotate in the reservoir - be it solely due to the forming flow, be it due to temporary contact with the application roller or the metering roller. Instead, however, the homogenizing body can also be arranged non-rotatably in the reservoir, for example as a wedge-shaped strip.

So that the homogenizing body can optimally fulfill its damping properties on the inflow of the application medium, it is recommended that it is stored floating in the reservoir at least in the vertical direction, preferably completely freely, so that it always emerges with its upper side from the application medium, regardless of the filling level. In order to be able to maintain this positioning for application media of widely varying specific weight, it is within the scope of the invention to use either differently sized homogenizing bodies or the homogenizing body is stored in a level control; which always keeps it in a partially submerged position, no matter how high the reservoir is filled and what specific weight the application medium has.

A particularly advantageous embodiment of the homogenizer is that it is designed as a hollow body and its interior is to be filled with different weights. As a result, its weight can be optimally adapted to the specific weight of the application medium, such that its ideal immersion position is ensured. The weights may be cylindrical inserts made of different materials, which are simply inserted axially into the likewise cylindrical homogenizing body, so that they are held in the interior of the homogenizing body in a friction-locked and / or positive-locking manner. Instead, the weights may also be loose fillers, such as granules.

So that the homogenizing body floating in the application medium does not abut against the rotating applicator roll, in particular is not jammed between two rolls, it may be expedient to limit the maximum sinking movement of the homogenizing body by stops. These stops can be mounted approximately in the reservoir and correspond either with the outer circumference of the homogenizer or with frontally centrally arranged pins or the like.

Suitably, the homogenizer is mounted at its outer ends vertically displaceable on the end-side end jaws of the reservoir. However, other storage options come into consideration for this; In principle, the homogenizing body can even be inserted into the reservoir completely free-floating.

Further investigations by the Applicant have shown that a considerable improvement in the surface quality of the applied medium can also be achieved by transferring the feed of the application medium into the interstice space between the doctor blade and the applicator roll, whereby the homogenizer body can then be dispensed with according to an arrangement not according to the invention , The doctor blade is then expediently arranged slightly lower on the circumference of the applicator roll, namely at the level of the resulting in the previously described design reservoir so that one reaches a sufficiently steep orientation of the interstice space between doctor blade and applicator roll.

Fig. 1

einen Ausschnitt aus einer Lackwalzmaschine im Querschnitt gemäß einer ersten Alternative;

Fig. 2

den gleichen Ausschnitt gemäß einer zweiten Alternative;

Fig. 3

eine Ansicht von oben;

Fig. 4

eine Stirnansicht mit dem Lagerschild für den Homogenisierkörper und

Fig. 5

einen Ausschnitt entsprechend Fig. 1 bei einer nicht erfindungsgemäßen Alternative.

Additional features will become apparent from the following description of an embodiment with reference to the drawings and the drawing itself; shows

Fig. 1

a section of a paint rolling machine in cross section according to a first alternative;

Fig. 2

the same section according to a second alternative;

Fig. 3

a view from above;

Fig. 4

an end view with the bearing plate for the Homogenisierkörper and

Fig. 5

a section accordingly Fig. 1 in an alternative not according to the invention.

In the FIGS. 1 and 2 can be seen a plate-shaped workpiece 1, on the upper side of a solid-based paint with a small layer thickness, to be applied in the embodiment of about 5 μ to about 20 μ. The application device initially has the usual structure, namely a lower transport roller 2 and an applicator roller 3 arranged above it, between which the product is conveyed through horizontally. The application roller 3 cooperates with a slightly smaller metering roller 4, such that a minimal gap arises between the two rollers, above which a paint reservoir 5 is located. The paint reservoir 5 is formed alongside by the two mutually facing peripheral surfaces of the applicator roller 3 and the metering roller 4, so that it receives an approximately V-shaped cross-section, whereas it is bounded at the end by not shown here, known per se end jaws.

At a distance above the reservoir one recognizes a feed line 6. It is connected to a discontinuous pump which is usual with lacquers with solids and pours the lacquer from above via a terminal opening 6a into the reservoir 5 FIG. 3 shows, the supply line 6 extends in the longitudinal direction of the reservoir, and only about about 1/3 of the reservoir length. This position of the discharge opening 6a, in conjunction with the delivery pulse, results in a relatively homogeneous mixing of the quantity of paint delivered downstream with the paint already present in the reservoir. Of course, the outflow opening can also protrude further into the central region of the reservoir length.

Finally one recognizes in the FIGS. 1 and 2 two scraper blade 7 and 8, which cooperate in a conventional manner with their associated metering roller 4 and applicator roll 3.

In so far, the rolling machine described has the known structure.

It is essential that in the reservoir 5, namely approximately below the feed line 6 a Homogenisierkörper 9 floats, which is arranged with a certain distance between two rollers and partially immersed in the standing in the reservoir paint, but protruding from the top of the paint. In FIG. 1 one recognizes that the paint coming from the feed line 6 for the most part does not fall directly into the reservoir 5, but strikes the homogenizing body 9. As a result, the homogenizing body absorbs the impulses resulting from the impulsive conveying characteristic of the pump and prevents their transfer to the Abströmspalt between applicator roller 3 and metering roller 4 and thus to the surface of the paint film on the workpiece.

At the in FIG. 1 As shown alternative, the homogenizing body consists of an approximately wedge-shaped strip, which tapers downwards and also retains this orientation, whereas it is preferably mounted floating in the vertical direction.

At the in FIG. 2 Instead, the homogenizing body shown instead consists of a round rod 19, which floats freely rotatable in the reservoir. This results in the following effect: As a result of the rotation of dosing and application roller - regardless of whether the rollers rotate the same or in opposite directions - usually also creates a circulation of the coating liquid to an axis parallel to the roller axes. This circulation of the coating liquid produces a rotation in the same direction of the rod-shaped homogenizing body 19 - possibly even more intensified by its tangential contact with one of the two rollers 3 or 4. Thus, the lacquer stream falling intermittently on the upper side of the homogenizing body is supplied to the reservoir 5 in a considerably uniform shape.

FIG. 4 shows an end view of the paint rolling machine. It recognizes there, in particular, a bearing plate for the end-face mounting of the homogenizing body 9 or 19. It consists of a bearing plate 10, which also forms the end-side end jaw for the rollers 3 and 4 at the same time. For this purpose, it has an approximately vertical, upwardly open slot 11, in which the axially projecting ends of the homogenizer 9 or 19 are mounted, in the case of the homogenizer 9 non-rotatable, in the case of the homogenizer 19 rotatable. In both cases, the homogenizer can be removed without additional tools up from the bearing plate 10, so that its cleaning is easily possible.

Fig. 5 shows a not inventive, alternative design, is dispensed with the Homogenisierkörper. Instead, the cooperating with the applicator roll 3 Abstreifrakel 8 is laid down further down and made steeper and the supply line 6 is no longer between the two squeegees, but between the doctor blade 8 and the applicator roll 3, so that in the gusset space formed there Paint reservoir 15 forms.

It is of course within the scope of the invention, the homogenizer also in the in Fig. 5 to use alternative shown.

In summary, the invention offers the advantage that by interposing a homogenizer in the form of a floating body or by the lateral displacement of the feed line between applicator roll and associated doctor blade direct bouncing of the effluent from the feed line application medium into the reservoir and the resulting disturbances of the inlet conditions in the dosing be avoided as far as possible. The previously occurring defects in the surface texture of the painted product are thereby reliably eliminated.

Claims (11)

1. The use of an apparatus, wherein the apparatus includes an applicator roller (3), a metering device and at least one homogenising body (9, 19) and wherein the application of a liquid coating medium, particularly paint, to flat workpieces (1) is effected by means of the applicator roller (3) rolling on the workpieces (1) and the metering device, which is positionable to form a gap at the peripheral surface of the applicator roller (3), particularly in the form of a metering roller (4) rolling on the applicator roller (3), such that produced above the gap between the applicator roller (3) and the metering device there is a reservoir (5) for the coating medium, which is filled by a supply line (6) above the level of the coating medium in the reservoir (5), whereby the filling is effected, in particular, by discontinuous pumps, such as membrane pumps, characterised in that the at least one homogenising body (9, 19) is disposed in the reservoir (5) dipping into the coating medium, which body extends in the longitudinal direction approximately parallel to the said gap and is arranged in the vertical direction such that its upper surface emerges out of the coating medium, wherein the homogenising body (9, 19) is so disposed in the transverse direction that its upper surface is impinged at least partially by the coating medium flowing out of the supply line (6).
2. The use as claimed in Claim 1, characterised in that the supply line (6) includes at least one outlet (6a) directed onto the homogenising body (9, 19).
3. The use as claimed in Claim 1, characterised in that the coating medium coming from the supply line (6) is distributed over a certain longitudinal section and impinges on the homogenising body (9, 19).
4. The use as claimed in Claim 1, characterised in that the homogenising body (9, 19) is of rod-like construction.
5. The use as claimed in Claim 1, characterised in that the homogenising body (9, 19) is mounted to be freely rotatable.
6. The use as claimed in Claim 1, characterised in that the homogenising body (9, 19) is mounted to be freely floating in the vertical direction.
7. The use as claimed in Claim 1, characterised in that it includes stops, which limit the downward movement of the homogenising body.
8. The use as claimed in Claim 1, characterised in that the homogenising body is constructed as a hollow body, which is to be filled with weights.
9. The use as claimed in Claim 1, characterised in that the homogenising body (9, 19) is mounted at its ends on closure flanges (10) of the reservoir (5).
10. The use as claimed in Claim 1, characterised in that the homogenising body (9, 19) is mounted so as to be freely removable in the upward direction.
11. The use as claimed in Claim 1, characterised in that a wiper blade (8) is arranged on the applicator roller (3) and that the supply (6) of the coating medium is positioned in the triangular space between the wiper blade (8) and applicator roller (3).

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