EP0195276B1 - Deflector for a lamelliform freely floating viscous coating material - Google Patents

Abstract

A deflecting device includes a deflecting electrode (13), which is disposed at a spacing below a lip nozzle (11.1), from which the viscous coating material (10.2, 10.1) flowing freely in the form of a sheet is emerging, and which extends over the entire width of the coating material sheet. This deflecting electrode includes an electrode arrangement (31), the exposure region of which facing the sheet surface is subdivided into a number of electrode elements (33) which taper outwardly to a point. When placed under a voltage, the electrode arrangement (31) provides an ion stream directed towards the surface of the coating material sheet. The impact of this ion stream on the surface of the coating material sheet (10.2) imparts to the latter a change in direction ( alpha ) towards the deflecting electrode (13), so that a flat substrate (5.1) running horizontally towards the deflected coating material sheet (10.1) impinges on the sheet (10.1) at an acute angle ( beta ). The impact of the substrate (5.1) on the sheet (10.1) at an acute angle causes a smooth, undulation-free application of the coating material to the substrate surface.

Description

The present invention relates to a deflection device for lamellar free-flowing viscous coating material according to the preamble of patent claim 1.

It is already known from CH-A-435 048 to use a so-called lacquer or slot casting machine for applying liquid (viscous) coating material to flat, horizontal surfaces of a substrate. The main field of application of such machines is the coating of flat panels made of wood, metal, plastic, etc., cut to formats with practically any desired, but preferably rectangular, outline shape. The problem causing the invention is to be demonstrated on panel-shaped substrate bodies, hereinafter simply referred to as panels.

The plates are on a horizontal transport path, e.g. B. fed to a conveyor belt of a processing station in which they are moved under a pouring head emitting the viscous coating material in the form of a calibrated liquid lamella. Such a machine is designed for continuous operation, the liquid lamella flowing practically vertically downwards in the direction of a collecting container, in which coating material not used for a coating process is collected and returned to the casting head by means of a pump. A distance is preferably maintained between two successive plates, so that the coating can start exactly at the leading edge and end at the trailing edge, and no bridges of coating material result between adjacent plates.

Since the plates, which are preferably 10 - 40 mm thick, are provided with run-on and outlet surfaces that are perpendicular to the surface of the plate and pass under the casting head at a speed of approximately 50 m / min, there is a risk that the coating material lamella of approx 3/100 mm to approx. 6/100 mm thick begins to oscillate or flutter due to the pressure of the air stowed on the plate on the inlet side and the vacuum on the outlet side. Due to the instability, mainly due to the build-up of air dust, a wavy cross-sectional shape is created on the coating material lamella, which results in surface irregularities in the coating in the starting area of the plate. Since a smoothing operation on the still liquid coating material is almost impossible, expensive reworking must be provided to achieve a clean edge area. The outlet-side vacuum does not have any disadvantageous consequences with regard to the coating appearance; however, it complicates the lamella separation at the end of the coated plate and favors the formation of a standing wave on the coating material lamella, which now faces the subsequent plate.

Experiments have shown that the corrugation of the coating material lamella on the starting side of the plate to be coated can practically disappear if an acute angle is maintained between the plate surface and the lamella surface in the running directions of the plate and the lamella. It is assumed that this measure prevents the build-up of an air stagnation zone on the plate start-up side, since the ram air can flow down freely from the wedge space that forms in front of the plate start-up side. The initial contact of the flattened lamella surface with the plate surface is thus "soft". The subsequent covering of the plate surface by the coating material slat already inclined in the direction of passage of the plate can take place without a major change in direction in the slat material.

When reaching the plate drain edge, the suction effect on the back of the plate has the effect that the lamella is sucked into the plate edge and torn off immediately below the edge when the plate continues to run. It can be assumed that by separating the lamella below the plate edge, the lamella course remains stable and the leading edge of the following plate runs against a flat lamella surface.

The problem, however, is to deflect a coating material lamella at an acute angle to a flat substrate surface while maintaining the horizontal delivery of the substrates to be coated or the plates mentioned on a transport device. It should be taken into account here that on the one hand the use of a horizontally running transport device offers significant operational advantages compared to one with rising and / or falling movement sections, but on the other hand a liquid lamella flowing out of a casting head can only naturally flow vertically for physical reasons. One possibility for the contactless deflection of a liquid lamella, which is only 3 - 6 hundredths of a millimeter thick, is to direct air currents below the casting head against the lamella surface in such a way that the lamella changes its direction of travel as desired. Apart from the fact that it is extremely difficult to generate sufficiently stable surface currents which ensure a flat slat guidance, such air curtains have a tendency to change the liquid surface, e.g. B. to oxidize and / or dry out. A particular disadvantage would be a reduced adhesiveness to the substrate body or the plate surfaces.

The object of the invention is therefore to propose a deflection device for lamellar free-flowing viscous coating material with which the above-mentioned problem can be reliably solved in a simple manner.

The solution to this problem according to the invention can be read out from patent claim 1. Embodiments are defined by the dependent claims.

• Fig. 1 schematisch eine herkömmliche Lackgiessmaschine in Seitenansicht, versehen mit einer erfindungsgemässen Ablenkvorrichtung für freifliessendes Beschichtungsmaterial,
• Fig. laschematisch den Ansatz- und Abreissvorgang beim Auftragen der Beschichtung auf einem Substrat,
• Fig. 1 beine Ausführungsvariante der Ablenkvorrichtung nach Fig. 1,
• Fig. 2 eine erste Ausführungsform einer in der Ablenkvorrichtung verwendbaren Elektrodenanordnung zur Erzeugung einer gegen die "Aussenfläche" der Beschichtungsmateriallamelle gerichteten lonenströmung, im partiellen Längsschnitt (11-11 in Fig. 3),
• Fig. 3 die Elektrodenanordnung nach Fig. 2 im Schnitt nach der Linie III-III,
• Fig. 4 eine zweite Ausführungsform der Elektrodenanordnung ähnlich der Fig. 2, ebenfalls im partiellen Längsschnitt (IV-IV in Fig. 5), und
• Fig. 5 die Elektrodenanordnung nach Fig. 4 im Schnitt nach der Linie V-V.

The invention is explained below with reference to the drawing, for example. Show it:

• 1 schematically shows a conventional paint casting machine in a side view, provided with a deflection device according to the invention for free-flowing coating material,
• 1 shows the approach and tear-off process when the coating is applied to a substrate,
• 1 shows a variant embodiment of the deflection device according to FIG. 1,
• 2 shows a first embodiment of an electrode arrangement that can be used in the deflection device for generating an ion flow directed against the “outer surface” of the coating material lamella, in partial longitudinal section (11-11 in FIG. 3),
• 3 shows the electrode arrangement according to FIG. 2 in section along the line III-III,
• Fig. 4 shows a second embodiment of the electrode arrangement similar to Fig. 2, also in partial longitudinal section (IV-IV in Fig. 5), and
• Fig. 5 shows the electrode arrangement according to Fig. 4 in section along the line VV.

The paint casting machine shown schematically in FIG. 1 contains within a machine frame 1 a delivery-side (first) conveyor arrangement 2, and an outlet-side (second) conveyor arrangement 3, which are separated from one another by a so-called pouring gap 4 explained later. The conveyor arrangements 2 and 3 are preferably longitudinally structured, synchronous conveyor belts which ensure that the substrates 5.1, 5.2 and 5.3 to be coated are guided in a stable manner by the machine. The minimum width of the casting gap 4 is given both by the length of the substrates 5.1, 5.2, etc. and also by the design and operation of a coating arrangement, generally designated 6, and can be made narrower or wider by mutual approximation or removal of the conveyor arrangements 2, 3.

The coating arrangement 6 essentially consists of a schematically shown casting head 7, a deflection device 9 according to the invention for a coating material lamella 10.1, and a collecting device 8 for coating material not applied to substrates 5.1, 5.2 etc. The casting head 7 of a known embodiment essentially comprises a storage container 7.1 for receiving liquid single- or multi-component coating starting material with a high dielectric constant and an elongated flat nozzle 11 on the bottom of the storage container 7.1. The length dimension of their casting lips 11.1 is matched to the coating width on the substrates 5.1, 5.2, etc., and their passage width can be adjusted to the desired thickness of the coating material lamella 10.1 by a calibration device 12. This thickness is usually in the range from 0.02 to 0.08 mm. The lamella flow rate from the flat nozzle 11 and the surface stability essentially depend on the viscosity of the coating starting material. A flat, uniform, level drain from the flat nozzle 11 is assumed, with the formation of an initially vertically downward flowing lamella section 10.2.

By means of a deflecting electrode 13 described later, the coating material lamella 10.1 can be given a deflecting effect by means of an ion beam emanating from the deflecting electrode 13, by means of which the lamella 10.1 experiences on the surface of the ion impact zone on a surface inclination a against the electrode 13. This path inclination can be set by applying a voltage adapted to the desired inclination angle to the electrode 13. The path inclination a is expediently chosen such that the coating material lamella 10.1 does come as close as possible to the inner deflection area 3.1 of the outlet-side (second) conveyor arrangement 3, but is not attracted to it. Such a risk exists due to the ionization of the electrode-side surface of the lamella 10.1. If, as shown, no substrate (e.g. 5.1) bridges the casting gap 4, the lamella 10.1 runs obliquely through the gap 4 against a first inclination-adjustable (double arrow 14.1) collecting flap 14. It is important that the lamella 10.1 so impinges on the flap 14 so that the flowing coating material can flow from the flap surface into a collecting trough 15 without a tendency to jam. This can effectively counteract the occurrence of wave and flutter movements at the lower end of the lamella 10.1.

When the deflection electrode 13 is switched off, the coating material lamella 10.3 flows according to the interrupted line in a vertical direction immediately before the inner deflection area 2.1 of the (first) delivery arrangement 2 on the delivery side onto a second one Collecting flap 16 in the collecting trough 15. Like the first collecting flap 14, this flap is also appropriately inclined so that the freely running coating material lamella 10.3 flows from the flap surface into the collecting trough 15 without a tendency to jam. A return pump 17 recovers the coating material collected in the collecting trough 15 at appropriate time intervals via a pipeline 18 into the trough 7.1 of the pouring head 7.

1, the coating material lamella (sections 10.2, 10.3) is first brought to the desired thickness of 0.03 to 0.06 mm and uniform outflow from the casting head 7 by adjusting the flat nozzle 11. The lamella runs essentially vertically downwards (broken line 10.3). Then the deflection electrode 13 is aligned by adjusting its support device 19 and, by applying a high voltage, a potential is applied which is capable of causing a deflection of the lamella section 10.1 below the electrode 13 by an acute angle α. After commissioning of the delivery and discharge-side conveyor arrangements 2 and 3, a first substrate, in FIG. 1, the plate 5.1 into the casting gap 4 and with surface covering of the surface of the plate 5.1 with coating material at a speed of 40-60 m / min passed through the casting gap 4 in the direction of arrow A.

The resulting coating process in its individual phases I to IV is shown schematically in FIG. 1a. As soon as the leading edge 5.1 'touches the lamella 10.1 starting at the angle β = 90 ° -a (phase I), the latter tears off along this edge. The edge 5.1 'is expediently sharp in order to achieve a defined break line 21. Due to the air jam 22 prevailing under the break line 21, the downward-oriented and rapidly downward falling slat section 10.1 'at its upper end is pushed slightly away from the end face of the plate 5.1 (broken lines), so that an end face coating and thus undesired reworking are eliminated.

The forward movement speed of the plate 5.1 and the flow speed of the coating material lamella must be coordinated with one another in such a way that the lamella is slightly stretched when it is placed on the plate surface in order to achieve a clean coating 23. As a result, the initial run-up angle β is slightly reduced to β 'during the coating operation (phase 11), i.e. the lamella 10.1 starts somewhat flatter when coating. This state continues until the plate trailing edge 21 'is reached (phase 111). There, supported by a drainage edge vacuum, the lamella 10.1 breaks off and, due to the now free air access according to arrow 24, it returns to its original inclination β (phase IV) without occupying the plate drainage side 5.1 ". See also the Plate 5.3 in Fig. 1 on the conveyor assembly 3rd

In the event that the coating material lamella 10.1 cannot be deflected sufficiently by a single deflection electrode 13, a deflection device 9 'with two (or more) deflection electrodes 13', 13 "according to FIG. 1b can be used. The references provided with an index mark denote parts 1, which are identical to those of Fig. 1. The casting head 7 'can in principle be of the same design as that of Fig. 1. Likewise, the two deflection electrodes 13', 13 "can be of the same design, or at most different. The change in path inclination a 'and a "caused by the two deflection electrodes 13', 13" are set analogously to the procedure described for FIG. 1. Both deflecting electrodes 13 ', 13 "are built on position-changing support devices 19' which, together with an electrode potential adjustment, allow the desired section-wise change in web inclination to be set. The coating material lamella 10.1 'hits when it flows into substrate spaces, as is also shown with reference to FIG. 1 , again at an acute angle onto the collecting flap 14 'in order to avoid drain backflow.

Two examples of the structure of the deflection electrode 13 or 13 ', 13 "can be seen from FIGS. 2 to 5. In both embodiments, the cavity of an elongated, in principle U-shaped, profiled insulating housing 30 is generally 31 and 31, respectively The insulating housing 30 is expediently provided with flange elements 32 for fastening the deflection electrode on a schematically illustrated support device 19.

The electrode arrangement of the embodiment according to FIGS. 2 and 3 essentially consists of a series of approximately prismatic electrode bodies 33 made of a material with high electrical resistance (of the order of 50 MQ. Cm). The electrode bodies 33 have the cross-sectional shape of an approximately isosceles, slender triangle, the base of which rests on a height compensation and spacer 34, and the tip of which is flush at the level of the top of the housing. The tip regions 35 of all the electrode bodies 33 lie in the longitudinal direction of the deflection electrode 13 on a straight line which runs essentially parallel to the longitudinal axis of the housing. The electrode bodies 33 with a width of 1 to 2 cm (viewed in the longitudinal direction of the electrode) are separated from one another by insulating intermediate layers 36 with a thickness of 1.5 to 3 mm and, according to FIG. 2, are connected or fed in parallel with one another by a continuous conductor rod 37. Through the Splitting the entire electrode length into a larger number of discrete sections corresponding to the electrode bodies 33 is intended on the one hand to ensure that the charge field distribution along the electrode 13 is as uniform as possible. On the other hand, the resulting division of the total cross-section of the electrode body is intended to keep the contact current strength low in order to prevent spark formation in relation to counter-polar components.

The insulating intermediate layers 36 have a thickness of 1.5 to 3 mm and consist of a dimensionally stable material which, together with a casting resin filling the free spaces 38 in the housing 30, can form an integral body. The intermediate insulating layers 36 are expediently centered at least in the height compensation piece 34 in grooves 39 in order to achieve a uniform structure of the electrode arrangement 31.

In the embodiment according to FIGS. 4 and 5, an insulating housing 30 is again used, which is constructed on a support arrangement 19 by means of flange means 32. An electrode arrangement 31 'is installed in the housing cavity. This essentially consists of a central, longitudinal insulating material support wall 40, high-resistance parallel-fed individual resistors 41 arranged on both sides thereof, and a series of prismatic electrode bodies 43 of approximately triangular cross section made of a material with a preferably high electrical resistance. The latter are each plugged onto a pointed contact element 44, so that they are ohmically connected to the outer end of the associated individual resistor 41. The individual resistors 41 with resistance values of 50 to 100 MQ are connected at a lateral distance from the supporting wall 40 to the common feed rail 42 and the contact elements 44 in such a way that they lie alternately to the side of the supporting wall 40. Their outer boundary areas are so far apart that these areas simultaneously center the supporting wall 40 and the triangular tips of the electrode bodies 43 within the insulating housing 30 on the longitudinal plane of the electrodes. The triangular tips of the electrode bodies 43 are again approximately at the level of the top of the housing.

The electrode bodies 43 have a width of approximately 10-20 mm (viewed in the longitudinal direction of the electrodes) and are separated from one another by insulating intermediate layers 45. The latter can be inserted into grooves 46 on the upper side of the support wall 40 for uniform spacing. This results, as already described with reference to FIGS. 2, 3, in turn, an optimally uniform charge field distribution along the electrode 13. Through the individual feeding of the electrode bodies 43 via the high-resistance resistors 41, it is also possible to keep the contact current strength low and thus the Eliminate the risk of spark formation against oppositely polar components.

The intermediate insulating layers 45 can be made of the same material as the intermediate insulating layers 36 of FIG. 2, and the free spaces remaining in the housing cavity between the housing walls and the components of the electrode arrangement 31 'are filled with a casting resin 47.

The deflection electrode 13, which is divided into discrete length sections in the manner described, makes it possible to achieve an optimally uniform field distribution along the deflection electrode 13. Different field strength levels between adjacent electrode sections resulting from inhomogeneities in the individual electrode bodies 33, 43 and / or resistance values which are unequal due to tolerance in the high-resistance individual resistors 41 are locally limited. Level differences from uneven surface loads on the electrode due to dirt, dust and / or moisture are within the operationally permissible limits. In applications where graded field strength levels are necessary or expedient, electrical separation of the feed conductors of individual or groups of electrode bodies 33, 43 from neighboring areas can easily be provided.

The above-described deflecting device for lamellar free-flowing viscous coating material can be used wherever the coating material is to be brought into a second (deflected) flow direction without contact from a first (stock) flow direction. Due to the possibility of operating the deflection electrodes with very low local contact currents, the deflection device according to the invention can also be used safely when processing coating materials with easily flammable solvents.

Claims (11)

1. Deflector for a lamellar viscous dielectric coating material freely flowing downwards from a reservoir (7.1) via a lip nozzle (11.1.) in the direction of a coating zone 4 situated vertically thereunder, and at least one deflector electrode (13) situated at a certain distance underneath the lip nozzle (11.1) and at a distance from the surface of the coating material lamella (10.2) and extending over at least the entire width of the coating material lamella and having an electrode arrangement of which that exposure zone which faces towards the said surface contains a number of electrode elements (33; 43) converging outwards at an acute angle, characterized by the fact that the electrode arrangement (31), when subjected to voltage, is intended to supply an ionic current which flows towards the surface of the coating material lamella and of which the arrival on the surface of the coating material lamella (10.1) causes the latter to change direction towards the defector electrode (13); and that underneath the coating zone (4) a collecting flap (14) which is situated in a collecting vat (15) for coating material not used for the coating process and which extends over at least the entire width of the lamella is provided to enable the coating material lamella (10.1) deflected by the deflector electrode (13) to be guided in a reflux-free manner into the collector vat (15).

2. Deflector in accordance with Claim 1, characterized by the fact that the said collector flap (14) is pivotably mounted (14.1) in order to obtain the optimum angle of ascent (y) for the stabilization of the coating material lamella (10.1).

3. Deflector in accordance with Claim 1 or 2, characterized by the fact that the collecting vat (15) contains a further collector flap (16) to enable a non-deflected coating material lamella (10.3) to be guided into the collector vat (15) in a reflux-free manner.

4. Deflector in accordance with Claim 1, characterized by the fact that the electrode arrangement (31) of the deflector electrode (13) is accommodated inside a channel-shaped elongated insulating housing (30) in which it is cast in one piece, that the electrode arrangement

(31) is provided with a series of a number of mainly prismatic electrode bodies (33; 43) of a low-conductivity material, which are spatially separated from one another by intermediate insulating layers (36, 46), that the electrode bodies (33; 43) are provided with a longitudinally orientated scarfing (35) and that all scarfings (35) are aligned in relation to one another and situated on a substantially straight line parallel to the longitudindal axis.

5. Deflector in accordance with Claim 1 or 4, characterized by the fact that all electrode bodies (33) or groups thereof are directly connected with a conductor bar (37) which is common to them or which continues the whole way through in sections.

6. Deflector in accordance with Claim 1 or 2, characterized by the fact that the electrode bodies (33, 43) consist of a material with a resistance of the order of 50 M Q /cm.

7. Deflector in accordance with Claim 1 or 4, characterized by the fact that all electrode bodies (43) or groups thereof are directly connected via a high-ohmic individual reistor (41) to a common or sectionally continuous feeder bar (42).

8. Deflector in accordance with Claim 7, characterized by the fact that the individual resistors (41) have resistances in the range 50-100 MQ.

9. Deflector in accordance with Claim 1 or 4, characterized by the fact that the electrode arrangement (31') of the deflector electrode (13) has a central supporting wall (40) of insulating material to which the individual resistors (41) are affixed between a feeder bar (42) and an upper contact element (44) and that the electrode body (43) is placed on the associated contact element (44) and in ohmic contact therewith.

10. Deflector in accordance with Claim 6, characterized by the fact that the electrode bodies (33; 43) have a width of 1-2 cms as viewed in the longitudinal direction of the electrodes and that the intermediate insulating layers (36,45) provided between adjacent electrode bodies (33; 34) have a thickness of 1.5 to 3 mm.

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