JPH0433503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for coating a moving sheet of material with an adjustable thickness using a rod-shaped wiper approaching the application side of the sheet. The bar-shaped wiper is supported in the wiper bed and is pressed elastically with adjustable pressure onto the sheet to be coated evenly over the width of the coat.

In known devices of this kind (for example, DE 30 22 955 A1), a rod-shaped wiper is formed into a roller and is supported in an elastic wiper bed. A pressure means, for example a pressure tube containing compressed air, is provided between the wiper floor and the machine frame. This pressure tube presses a rolling bar wiper with variable pressure onto the material sheet to be coated for coating thickness adjustment and paint dosing. The roll-type rod-shaped wiper narrows the coating gap of a certain geometric shape for the paint, but the gap between the roll-type rod-type wiper and the sheet is narrowed when viewed from the exit side of the object to be coated, that is, in the sheet running direction. Behind the narrowest point, widening gaps can likewise occur here, and the surface of the application can become rough.

The basic problem of the invention is to develop a device of the kind described in the introduction, which makes it possible by simple means to maintain a high-quality coating layer and to make subtle changes in the coating weight. achieved. a) the wiper bar is configured as a wiper rung, which wiper rung is guided along a flat smooth surface on at least the exit side of the rigid wiper bed with slight friction; and b) faces the sheet to be applied. The end surface of the wiper crosspiece having a rectangular outline forms a coating gap that gradually narrows together with the sheet, and the end surface of the wiper crosspiece that forms this coating gap does not deform even if the pressing force changes, c. The front edge in the sheet traveling direction is straight and forms a sharp stripping edge; d. The wiper crosspiece is easily deflected in the area between the end surface and the stripping edge; e. The end surface has high wear resistance; f. Between the wiper crosspiece and the wiper floor. The structure is such that a pressing force is generated by the elastic pressing means.

The wiper bar is guided through the wiper floor with slight friction, allowing fine adjustment of the applied paint weight.
In this case, the elastic pressure means act directly on the flexible wiper bar in the region of the end face. This results in a very uniform application of the material sheet. The wiper crosspiece has the role of wiping away over-applied paint to achieve the desired thickness (paint weight). The paint therefore enters the application gap formed by the end face and the sheet supported by the opposing rollers at a high speed. As a result, the paint that accumulates in the coating gap creates a hydrodynamic pressure. This pressure results in an equilibrium condition for the pressure in the elastic pressure means. A high smoothness value is ensured by the sharp stripping edge on the end face of the wiper bar, which is in contact with the front edge in the direction of material sheet travel, while a construction with high wear resistance, which is characterized in particular by a high Witzkars hardness, ensures a high smoothness value. A long life of the end face is ensured. The inventive construction and arrangement of the wiper bar provides additional support rollers along which the material sheet moves and devices for adapting the wiper bar cross-section to the non-uniformities of the material sheet itself along the painting width. That also becomes unnecessary.

The wiper rungs can be guided between the parallel sliding surfaces of the wiper bed with little friction.

Advantageously, the coefficient of friction between the wiper rung and the wiper bed is approximately μ<0.1. As a result, the friction of the wiper bar against the wiper floor is extremely small compared to the pressure force of the wiper bar against the coated sheet.

The wiper crosspiece or wiper floor shall be made of steel, high-grade steel, or laminated aluminum at least in the smooth surface area, and the wiper floor and wiper crosspiece shall be made of red brass at least in the smooth surface area, and shall be treated with Teflon, hard nickel, or hard anodic electrolysis. It is convenient to oxidize.

Advantageously, the end face of the wiper rung extends essentially tangentially to the sheet to be coated at the stripping edge and has a radius of curvature from it, at least in the region of the stripping edge, of at least 4 mm, in particular 5 mm<R<250 It is convexly curved with a radius of curvature of mm, more particularly 20 mm<R<50 mm. Since the surface of the support roller remains unchanged, the geometry of the end face of the wiper bar determines the shape of the application gap. That is, it depends on how the paint approaches the narrowest point (the stripping edge) between the wiper bar and the sheet, and what the flow conditions are in that case. The wiper bar is pushed back by the pressure created in the application nip, which also depends on the shape of the application nip, so that the geometry of the end face can reduce the weight of the paint (i.e. the amount of paint remaining on the sheet after wiping off the excess amount). The final weight (based on the area of the wiper crosspiece end face) is also affected (grams/
m ² ). When this effect occurs, the rheological behavior of the paint also plays a decisive role, so different paints have different paint weights even if the degree of curvature is the same.

In order to approximate the radius of curvature, the end face can be formed by chamfer grinding. As a result, the end faces can optionally be finished particularly easily.

Advantageously, the width of the end face is between 8 and 60 mm. This width is determined by the weight of the paint. The greater the weight of the paint, the lower the flow pressure, the wider the edge width, and the shorter the wedge gap.
The wedge angle becomes smaller accordingly, and a stable equilibrium state is obtained.

In order to be able to easily switch to a wiper bar with a different end width, it is advantageous to insert a spacer between the rear edge of the wiper bar in the direction in which the material sheet travels and the wiper floor.

The tear-off edge of the wiper bar can be counter-ground to further improve the effect.

In order to achieve the necessary and sufficient flexibility of the wiper bar, the wiper bar is
It has a moment of inertia of 200 mm ⁴ <I<7000 mm ⁴ with respect to the axis of the book, perpendicular to the stripping edge and parallel to the coated sheet. Such a configuration of the wiper bar is achieved by having equidistant notches or equidistant notches and notches in the longitudinal direction.

The wiper rung can be made of tetrafluoroethylene, in which case the notch is unnecessary. Furthermore, the wiper bar can also be made of rubber-elastic material and can be provided with a wear-resistant padding on the end face.

In order to increase the wear resistance of the wiper rung, it is advantageous for the end face of the wiper rung to have a Witzkars hardness higher than 600 HV.

The end face of the wiper crosspiece may be chrome-plated, surface-hardened, nitrided, sprayed with ceramic oxide, laminated, anodized, or in the case of aluminum, preferably hard-coated or hard-nickel-plated. be.

In an advantageous embodiment of the wiper bar, the end face can be provided with a highly wear-resistant insert.

Furthermore, in the region of the end face, the wiper bar has a longitudinal recess on the side surface for forming a labyrinth seal against the wiper floor, which prevents paint from penetrating into the guide part facing the wiper floor.

The action of the elastic pressure means, especially the pressure tube, is based on the plane of the wiper floor that is essentially perpendicular to the sliding surface on the edge side in front of the direction of sheet travel, and the plane of the wiper crosspiece that is essentially parallel to this plane. It is particularly effective between

In a preferred embodiment, the pressure means and the wiper bar can also be formed in one piece.

Furthermore, a further sealed elastic pressure means, in particular a pressure tube, is preferably provided between the rear edge side of the wiper bar in the direction of sheet travel and the wiper floor. This sealing elastic pressure means, on the one hand, prevents the ingress of paint between the wiper bed and the wiper crosspiece, and on the other hand, after the equilibrium between the pressure of the fluid dynamic pressure and the pressure in the pressure means has been achieved, the said By increasing the pressure in the sealing elastic pressure means, the achieved stable state of the wiper bar can be fixed.

Advantageously, the sealing elastic pressure means and the wiper bar can be formed in one piece.

The hardness of the support roller is particularly 60 < Shore A < 95.
Advantageously, it has a rubber-elastic surface.

In order to apply to both sides of the material sheet, two wiper bars with mutually facing end faces with different radii of curvature can be provided if their coatings are different. By varying the radii of these end faces, a fixed ratio of the paint weights on both sides can then be established.
That is, from the total weight of paint applied to both sides, an amount determined by the radius of curvature is applied to each side. For example, apply one-third on one side and two-thirds on the other side. Of course, support rollers for guiding the coated material sheet into the coating area are unnecessary and not provided in this case. If the paint weight on both sides is the same, the radius is also the same.

In order to even out uneven application of the material sheet, pressure means can be added behind the pressure means for locally increasing the pressure force. It is then advantageous to arrange this additional pressure element in the wiper floor as an adjusting screw that engages with the sheet steel base.

Furthermore, it is advantageous to provide the wiper bar with a longitudinal slot open towards the material sheet, at the open end of which the end-faced insert piece is attached by means of locking means. The wiper bar with the longitudinal slot can then be divided lengthwise into several movable holding parts.

Finally, the wiper rung is partially pushed down to facilitate the removal of dirt, dust, which can form between the wiper rung and the material sheet and cause stripes and especially streaks on the material sheet. It is convenient to provide means. These means can be inserted into the wiper bed, advantageously keys which engage in the lateral ridges of the wiper bar.

The figures showing the embodiments will be explained in more detail.

In the device shown in FIG. 1, the sheet of material to be coated travels along support rollers 2 in the direction indicated by arrow A. In the device shown in FIG. A wiper bar 6 is slidably guided in the rigid wiper bed 3 between parallel sliding surfaces 4, 5. This wiper bar 6 has an end face 7 with a sharp tear-off edge 8, which is pressed against the coated sheet 1. By means of pressure means in the form of pressure tubes 9 between the wiper bed 3 and the wiper rung 6, the force with which the wiper rung 6 is pressed against the sheet 1 to be coated changes slightly.

The wiper crosspiece 6 can freely slide along the parallel sliding surfaces 4 and 5 of the wiper bed 3 in a direction toward the support roller 2 and in a direction perpendicular to this direction by the wiper bed 3. can be done.
No thermal twisting occurs in these directions. When applied to a sheet of paper, the paint typically heats up and the wiper bar 6 expands due to the heat. The wiper bar can freely expand both in the transverse direction to the seat 1 and in the direction of the seat 1. The wiper rung may heat up if it briefly contacts the uncoated sheet at the beginning of coating. That is, it can extend freely. The wiper bar 6 is arranged in the area of the end face 7 and the stripping edge 8 with respect to one axis, perpendicular to the stripping edge 8 and parallel to the coated sheet, in particular I (moment of inertia) = 200.
It has a relatively small moment of inertia I in the range mm ⁴ to 7000 mm ⁴ . Such a moment of inertia I can be achieved, for example, as follows. That is, as can be seen from FIG. 2, equidistant notches 10 and notches 11 are provided over the length of the wiper crosspiece 6. The cross-sectional area of the wiper bar is constant over the entire length of the wiper bar 6 up to a short distance measured from the tear-off edge 8. The bendability of the wiper bar 6 thus obtained is achieved either by selecting a suitable material or by appropriately narrowing the width of the wiper bar 6.

The end face 7 of the wiper bar 6 extends approximately tangentially to the coated sheet 1 at the stripping edge 8. In some of the illustrated embodiments, the end face 7 is at least in the region of the tear-off edge 8 at least 4 mm, in particular 5 to 250 mm, more in particular 20 mm, from this tear-off edge 8.
A curved and gradually narrowing application gap with a radius of curvature of ~50 mm is formed. This curvature is determined depending on the target range of paint weight and the rheological properties of the paint.

The wiper bar 6 further includes at least a curved end surface 7.
It has a surface with a Witzkars hardness that is harder than 600 HV in the range of 600 HV, increasing the wear resistance of the end face 7. For this purpose, the end face 7 of the wiper bar 6 is chromed, surface hardened, nitrided, laminated with ceramic oxide by spraying, anodized, hard coated in the case of aluminum, or hard nickel plated. can do.

The stripping edge 8 of the wiper bar 6 is always straight and has a sharp edge, and the surface of the applied paint after being brought to the desired paint weight with the wiper bar 6 is extremely smooth. An improvement in the stripping action is achieved, for example, by cutting the trailing edge of the stripping edge 8 at 12, as shown in FIG.

Another method of improving the wear resistance of the end face 7 of the wiper bar 6 is to form the end face 7 with a more wear resistant insert 13, as shown in FIG.

In order to prevent paint from entering the sliding guide between the wiper floor 3 and the wiper bar 6, or to minimize the penetration, the wiper bar 6 has a seal on the lower surface of the end surface 7 that leaks from the wiper floor 3. It has a longitudinal notch 14 for a labyrinth seal. This also limits the end face of the wiper crosspiece 6 to the wiper floor 3 at the same time.

The geometric configuration of the end face 7 of the wiper bar 6 is always constant in this embodiment of the wiper bar 6, regardless of its momentary pressing force. That is, the wiper crosspiece remains unchanged even if the pressing force is increased in order to reduce the amount of paint used.
That is, the pressing force is an important parameter along with the configuration of the end surface 7, the size of the curvature R, the sheet speed, the rheology of the paint, and the physical properties of the material sheet 1, and on the other hand, it is important that the end surface 7 is not deformed. First, the remaining amount of paint changes by the pressing force of the wiper bar 6, just as in the case of a scraper, without changing the shape of the coating gap. It is of utmost importance for uniform application of the paint on the sheet 1 that the application gap remains unchanged.

In the device described, an air-filled pressure tube 9 is used as the elastic pressure means for generating the pressure force. Due to its flexibility, the pressure tube 9 makes it possible to apply uniform pressure over the working width of the wiper bar 6 against the material sheet 1 moving on the support roller 2. The linear pressure applied by the tube pressure balances the fluid dynamic pressure below the end face 7 of the wiper bar 6. Therefore, the paint weight can be changed extremely slightly, uniformly, and steplessly by changing the tube pressure, and in this case, the fluid dynamic pressure and the wiper crosspiece can be applied at any position of the working width without adding a forming device. The same equilibrium condition is established between the pressures. This is a prerequisite for applying the paint to a uniform thickness.
The pressure tube 9 is configured in such a way that its forces are supported only against the rear face 15 of the wiper rung 6 and the pressure face 16 in the wiper floor 3 essentially parallel to this wiper rung. .

The wiper bar 6 and the pressure tube 9 can also be formed integrally. It must then be ensured that this unit has the necessary flexibility on the one hand and sufficient wear resistance on the other end face 7.

The combination of materials between the wiper floor 3 and the wiper crosspiece 6 must be selected so that the frictional force generated when the wiper crosspiece 6 slides is as small as possible. The frictional force resists the pressure of the pressure tube 9 and can therefore lead to hysteretic behavior when adjusting the paint weight. The normal forces on the wiper bar 6 result from the unavoidable shear stresses occurring during the application gap. The above-mentioned force applied to the wiper bar 6 is balanced by the air pressure inside the pressure tube 9. If the friction coefficient μ between the wiper bar 6 and the wiper floor 3 is set smaller or equal to 0.1, the frictional force generated is negligibly weak compared to the pressing force.

In order to obtain a desired coefficient of friction in the combination of the wiper floor 3 and wiper crosspiece 6, at least the sliding surface of the wiper floor 3 is made of steel or laminated aluminum, and the wiper crosspiece 6 is made of at least the sliding surface of steel or laminated aluminum. It can be either made of red brass or oxidized with Teflon coating, hard nickel coating or hard anodic electrolysis.

In order to coat both sides of the material sheet 1, instead of the support roller 2, another wiper bar 6 is arranged in addition to the first wiper bar 6 as follows. The wiper bar 6 is provided with its end faces facing each other and in contact with the material sheet 1 at the same height as its stripping edge 8 .

In the wiper rung in the wiper floor 3 shown in FIGS. 5 and 6, the wiper floor 3 has a stop rung 26, which is a flat slide for contact and smooth guidance of the wiper rung 6. It has a surface 4.

A further elastic pressure means in the form of a pressure tube 28 with a sealing effect is provided between the wiper floor 3 and the rear edge surface 27 of the wiper bar 6 in the direction of sheet travel. This pressure means can be used, on the one hand, to seal the wiper floor 3 and the wiper bar 6 to each other and, on the other hand, to fix the stable state of the wiper bar 6 by means of pressure reinforcement. The pressure tube 28 is pressed against the surface 27 of the spacer 29 adjacent to the wiper rung 6 and keeps the wiper rung 6 in the stable condition once set if the pressure is of a corresponding intensity. Furthermore,
A relatively narrow wiper bar 6 is used. In that case, a spacer 29 is added so that the narrow wiper crosspiece 6 can be replaced with a wider one.

6 and 7 show a further wiper bar 6 having a longitudinal slot 30 which is open towards the material sheet 1. In FIGS. An insert piece 31 with an end face 7 is attached to the open end of this longitudinal slot by a locking connection. The wiper bar 6 is then divided into several movable single holding parts 32.

In the embodiment shown in FIG.
Pressure tube 9 to compensate for uneven application of
A pressure member is added to the rear of the cylinder to locally increase the pressure. These pressure members are attached to the wiper floor 3 as adjustment screws 34 that engage with the steel plate base.
configured inside.

In the embodiment shown in FIG. 6, the wiper bar 6 is pushed down locally in order to remove dust and dust that is generated between the wiper bar 6 and the material sheet and creates striped patterns on the material sheet, especially due to coating. Means for this can be inserted into the wiper bed 3 and the wiper crosspiece 6
It is provided in the form of a key 36 that engages with the side protrusion 35 of the wiper bar 6, and by rotating this key 36, the wiper bar 6 is pushed down.

[Brief explanation of drawings]

1 is a partial sectional view of the device according to the invention; FIG. 2 is a side view and bottom view of the wiper bar of the device shown in FIG. 1; FIGS. 3 and 4 are other embodiments of the wiper bar. FIGS. 5 and 6 are side views, partially cut away, of a modified example of the device according to the invention, and FIG. 7 is a partial perspective view of a modified wiper crosspiece. Symbols in the figure: 1... Seat, 3... Wiper floor, 4...
3 sliding surface, 6... wiper crosspiece, 7... end surface of 6, 8
...Tear off edge, 9...Pressure means.

Claims (1)

[Scope of Claims] 1. Contacting the sheet application surface, which is supported in the wiper bed and is pressed elastically with adjustable pressure against the sheet to be applied uniformly over the application width. In an apparatus for coating a moving sheet with an adjustable coating thickness using a wiper bar, the wiper bar is configured as a wiper crosspiece 6, and this wiper crosspiece can be applied to a rigid wiper with slight friction. A smooth surface 4 on the floor 3 that is flat at least on the exit side
b The end face 7 of the wiper bar 6 having a rectangular outline facing the sheet 1 to be coated forms a coating gap that gradually narrows together with the sheet 1, and the edge surface 7 of the wiper bar 6 forming this coating gap The end surface does not deform even when the pressing force changes; c. The front edge of the end surface 7 of the wiper crosspiece 6 in the sheet traveling direction is straight and forms an acute-angled tearing edge 8; d. The wiper crosspiece 6 forms the edge surface 7. It is characterized in that it is easily bent in the region of the stripping edge 8, e, the end face 7 has high wear resistance, and f, a pressurizing force is generated between the wiper crosspiece 6 and the wiper floor 3 by the elastic pressurizing means 9. device to do. 2. Device according to claim 1), in which the wiper rung 6 is guided between parallel sliding surfaces 4, 5 of the wiper bed 3 with slight pressure. 3. The device according to claim 1) or 2), wherein the coefficient of friction between the wiper bar 6 and the wiper floor 3 is approximately μ<0.1. 4. At least the smooth surfaces 4, 5 of the wiper crosspiece 6 or the wiper floor 3 are made of steel, high-grade steel, laminated aluminum, red brass, or treated with Teflon;
The device according to claim 3), which is either laminated with a hard nickel layer or oxidized by hard anodic electrolysis. 5 The end face 7 of the wiper bar 6 extends approximately tangentially to the coated sheet 1 at the stripping edge 8 and is curved convexly from at least the region of the stripping edge 8, with a radius of curvature R 4 mm or more, in particular 5 mm<R<250 mm, more particularly 20 mm<R<50 mm. 6) The end face 7 is formed by chamfer grinding in order to approximate the radius of curvature.
The device described in. 7. The device according to any one of claims 1) to 6), wherein the end surface 7 of the wiper bar 6 has a width of 8 to 60 mm. 8. The device according to any one of claims 1) to 7), wherein a spacer 29 is inserted between the rear edge side surface 5 of the wiper crosspiece 6 in the sheet traveling direction and the wiper floor 3. 9. The device according to any one of claims 1) to 8), wherein the back surface of the tear-off edge of the wiper crosspiece 6 is ground. 10 A patent in which the wiper bar 6 has a cross-sectional moment of inertia I of 200 mm ⁴ < I < 7000 mm ⁴ in the region of the end face 7 and the stripping edge 8 in the direction perpendicular to the stripping edge 8 and parallel to the coated sheet 1 based on the axis. The device according to any one of claims 1) to 9). 11. The device according to any one of claims 1) to 10), wherein the wiper bar 6 has an equidistant notch 10 or an equidistant notch 10 and a notch 11 in the length direction thereof. 12. Claims 1) to 10) in which the wiper crosspiece 6 is made of polytetrafluoroethylene.
The device described in any one of . 13. The device according to any one of claims 1) to 10), wherein the wiper bar 6 is made of a rubber elastic material. 14. The device according to any one of claims 1) to 13), wherein the end face 7 of the wiper crosspiece 6 has a Witzkers hardness greater than 600 HV. 5 Whether the end surface 7 of the wiper crosspiece 6 is chrome plated, surface hardened, treated with nitric acid, laminated with ceramic oxide by spraying, electrolytically oxidized, or hard if made of aluminum. Claims 1) to 1 coated or hard nickel plated
The device according to any one of 4). 16. The device according to any one of claims 1) to 15), wherein the end surface 7 of the wiper bar 6 is formed by a highly wear-resistant insertion piece 13 inserted into the wiper bar 6. 17. The wiper crosspiece 6 has a longitudinal notch 14 on the lower side of the end surface 7 for forming a labyrinth seal for the wiper floor 3.
16). The device according to any one of 16). 18 the elastic pressure means 9 are essentially perpendicular to the sliding surface 4 of the wiper bed 3 on the front edge in the direction of sheet travel; Device according to any one of claims 1) to 17), which acts between the face 15 of the wiper bar 6. 19. The device according to any one of claims 1) to 18), wherein the elastic pressure means 9 is a compression tube. 20. The device according to any one of claims 1) to 18), wherein the elastic pressure means 9 and the wiper bar 6 are integrally constructed. 21. The device according to any one of claims 1) to 20), wherein the elastic pressure means 9 is a compression tube. 22. The device according to any one of claims 1) to 21), wherein the elastic pressure means 9 and the wiper bar 6 are integrally formed. 23. Device according to any one of claims 1) to 22), wherein the bearing roller 2 has a rubber-elastic surface, the hardness of which is in particular 60<shore<95. 24. According to any one of claims 1) to 22), two wiper bars having end faces 7 facing each other with different radii of curvature are provided for coating both sides of the material sheet 1 under different coating conditions. equipment. 25 The wiper bar 6 has a longitudinal slit 30 which is open towards the material sheet 1, and an insertion piece 31 having an end surface 7 is attached to the open end of this slit by a locking connection. The device according to any one of ranges 1) to 24). 26 A wiper rung 6 with a longitudinal slit 30 has a number of single movable holding parts 3 along its length.
Claims 1) to 2 are divided into 2.
5) The device described in any one of 5) above.