FI99038C - Device for coating a paper or board web - Google Patents

Abstract

Prior art devices for coating continuous strips of paper or cardboard (1) exist which have a counter-roller round which the paper or cardboard (1) passes, an application system (3) which applies an excess of coating material to the paper or cardboard (1), and a metering system (4) disposed a certain distance downstream from the application system (3) and fitted with a doctor blade. The application system (3) includes an application roller (8), driven to rotate, with a smooth surface which, together with the counter-roller (2), forms an application gap (9) to which excess coating material is fed in the same direction as the direction of motion of the paper or cardboard. The invention calls for the application roller (8) to have a diameter of 5 to 200 mm, preferably 10 to 150 mm, and to form together with the counter-roller (2) an application gap (9) of 0.01 to 2 mm, preferably 0.05 to 1 mm, these figures being in addition to the thickness of the paper or cardboard, and the rear side of the application roller (8) i.e. that remote from the counter-roller (2), rests, over the whole working width of the roller, against a mounting (12, 26, 27) which is rigid in the direction radial to the counter-roller (2) to prevent bending.

Description

99038

Device for coating a paper or board web

The invention relates to a device according to the preamble of claim 1 for coating a paper or board web.

Devices for coating paper or paperboard webs are known which have a counter-roll which pivotally guides the web and in which the counter-roll at the point where the web surrounds it has a spreading system which spreads excess coating material on the web and in which a feed element is arranged apart from the web. , which scrapes off the excess again up to the desired brush weight.

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In specific coating devices known from DE patent 36 23 402, the application system comprises a mechanically rotating application roller which, together with the counter roll, forms a coating gap into which an excess of coating material is fed from the web entry direction. An essential feature of this application system, described as a Flooded-Nip-Coater, is that there is a fixed gap between the counter roll and the application roller, so that the latter is not pressed against the web. In addition, the coating material is fed into the application gap at the lowest possible pressure; it is necessary to ensure that the application gap is evenly • · · ·:. ·. fully filled for reconstitution.

• · · ♦ ♦ · · • · DE application publication 37 35 889 explains the so-called Short-Dwell-Coater- • · € • · «* 30 devices with an application chamber open towards the counter roll, into which the coating material is fed at a higher pressure, and at the outlet end of which the counter roll is closed against the roll roll * · ·:::. The spreading chamber is used as a pre-dosing device, the outlet end of which is fitted with ... a roller squeegee rod with 35 circumferential grooves, which is pressed against the product web or counter roll by means of a pressure hose.

2 99038

Due to the ever-increasing web widths (8 m and more) in papermaking and the increasing machine speeds (800 m / min and more), the application rollers of roll application equipment must always have but larger diameters 5 to be stable enough to maintain the width of the application gap. constant, so that no disturbing tendencies must occur and, on the other hand, to avoid disturbing dynamic effects (vibrations). In addition to the large structural costs, the disadvantage of the large application roller diameter is that, due to the large construction volume, the dosing system has to be adapted to a relatively large distance from the application gap. The long penetration distance between application and raw material may result in higher minimum bar weights because the material penetrating the web can no longer be scraped off.

The object of the invention is to improve a species-specific coating device so that at high web speeds and high web widths, with a lower structural cost, a uniform application is achieved and the excess is also small.

This object is achieved according to the features of claim 1.

«*« • · · ·:. In addition to the lower structural costs, due to the smaller diameter of the • · · ** V spreading roller, the dosing system can be * 11! the system preferably fits a short distance behind the application system. The support of the spreading roller considerably reduces the bending effects due to its own weight or the ♦ hydrodynamics prevailing in the spreading gap, so that smaller gap widths can also be used so that, if desired, a smaller excess can be spread evenly.

....: 35

The application system according to the invention also has methodological advantages: 3,99038

The smaller diameter of the application roller results in a clearly lower hydrodynamic pressure in the application gap, especially in wide and high-speed devices. This results in less penetration of the coating material into the web, resulting in a beneficial effect on quality, especially at lower brush weights. Brushing errors due to film tears and the formation of stress lines are also significantly reduced.

The subclaims include preferred and highly preferred embodiments of the invention:

By placing the application roller in the bed according to claim 2, the bending effects are minimal and the elasticity of the system 15 can be set to the desired value.

In the embodiment according to claim 3, the elasticity of the application roller-holder of the system is sufficiently low to guarantee the stability of the gap against the hydrodynamic compression 20. In a highly preferred embodiment according to claim 4, there is no elasticity adversely affecting the stability of the gap, whereby in the event of disturbances, e.g. a through-adhesive point, the application roller can be flexible.

When the embodiment of claim 5 comprises: * [· 'ensuring that the application roller remains securely in the bed, claim 6 includes a preferred embodiment of the bed for lubricating and cleaning the application roller, preferably with water.

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The lip-shaped inner wall of the bed according to claim 7 keeps the spreading roller clean by scraping during rotation • · · ::; the contaminants adhering to it are removed.

Claim 8 includes a preferred structural embodiment of the bed of the spreading roll so that it can be replaced quickly and simply.

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The embodiment according to claim 9, which is provided with a guide plate, has the advantage that it can also be used to set larger spreading gap widths, without the need for uncovered points. The guide plate 5 separates the incoming coating material from the reversible coating material and thus prevents the vortices occurring in the application gap.

An embodiment provided with a guide plate fitted to the paint chamber according to claim 10 10 contributes to a smoothed, calmed supply of the coating material to the application gap.

The squeegee according to claim 11, arranged on the inlet side, in front of the application roller, considerably reduces the introduction of the coating material without the web.

The invention will be explained with reference to the drawing and a simplified exemplary embodiment shown therein, and in which Fig. 1 shows a side view of a coating device equipped with a spreading system according to the invention, in which the spreading roller is placed on a bed; Fig. 2 shows the spreading system in enlarged form; equipped with head; with a lapping device in which the spreading roller is supported by a base.

«·· · • · • ·« • · · ** V The coating device has a machine-operated counter roll 2 which pivotally controls the paper or board web 1, which in its area ♦ · · *** * 3 0 le with the web 1 rotates around it, a spreading system 3 is arranged and in the direction of travel of the web behind it, from it ... i * apart from the dosing system 4, in which the scraper element is * * «V: scraper knife 5. The scraper knife 5 is attached to its foot in a known direction towards the counter roll movable: 35 to the tearable tension beam 6. The tensioning beam 6 is placed in the reversible tine bar 7, whereby the scraper knife 5

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5 99058 The clamping force and the blade angle (= the angle between the scraper 5 and the tangent of the counterblade 2) can be adjusted.

The spreading system 3 shown enlarged in Fig. 2 comprises a spreading roller 8 connected to a machine-driven rotating system, having a diameter of 5 to 200 mm, preferably 10 to 150 mm, arranged parallel to the axis of the counter roll 2 so that it and the web 1 remain at the narrowest point. a spreading gap 9 of 0.01 to 2 mm wide, preferably 0.05 to 1 mm 10 wide. The smallest gap with respect to the counter roll 2 therefore depends on the thickness of the paper or board of the web 1. The spreading roller 8 extends in axial length at least over the length of the counter roll 2, i.e. over the maximum web width. It is made primarily of steel and has a smooth jacket surface 15 and is supported against bending on its rear side opposite its counter-plate 2, over its entire working width, i. along its entire length. In the embodiment according to Figures 1 and 2, the spreading roll 8 is placed in a bed 10, 11 open towards the counter roll 2, which is a limitedly elastic, rubber-like material. In the present example, the bed 10, 11 is made of rubber and consists of two mirror-symmetrical parts 10, 11 arranged in the holder 12 and movable towards and away from each other.

25 The holder 12 runs in the same way as the bed 10, 11 throughout the work; . ·, Over water and is made of a rigid material such as • · · • * Y aluminum. In the present embodiment example is

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• · · “Y is a slot in the middle of the holder 12 running radially against the • counter roll 2 and is fitted to a U-shaped bracket · * '30 13 which is screwed to a pivotable cross member 14.

On one side there is a pressure hose 15 between the holder 12 and the support 13 on the other side over the working width, by means of which

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'' ί Both parts of the holder 12 can be pressed towards each other so that the bed 10, 11 holds the spreading roller 8 securely in place. In order to be able to rotate the spreading roller 8 as smoothly as possible between the two parts of the holder 12, despite the compressive force thus produced, the inner walls of the bed 10, 11 are molded so that they rest only in places against the spreading roller 8. It is preferred that the at least one inner wall is shaped in the shape of an axially extending lip so that the impurities adhering thereto as the application roller 8 rotates can be scraped off. In addition, open channels 16 have been machined into the inner walls towards the spreading roller 8, to which water is introduced as a lubricating and cleaning medium during use.

In order to keep the spreading roller 8 firmly in place, the bed 10, 11 rotates around its outer circumference by at least 180 °. In order to replace the spreading roller 8, the pressure is released from the pressure hose 15, by means of which both parts 10, 11 of the bed open and the spreading roller 8 can be removed.

It is essential for the invention that the spreading roller 8 is positioned over the entire working width in such a way that the set gap width of the spreading gap 9 is maintained under the hydrodynamic pressure. In the embodiment shown in Figures 1 and 2, the bed 10, 11 is held in place by an application roller 8, which bed is fitted to a holder 12 constructed rigidly radially with respect to the roller 2 and positioned immovable and inflexible in the working position. In order to maintain the gap width, in this embodiment, the application roller 8 - bed 10, 11 - holder 12 of the system has a restoring force in the radial direction. . a deflection away from the counter roll 2 of at least 25 1 · 106N · x · y, preferably more than 5 · 106N x · y; ···: where x = axial length of the spreading roller [m] and y = radial deflection [m] away from the counter roll 2.

• · • «· • ·» • · »· *: * · In order for the application roller 8 to be able to follow the web 1 in a case of disturbance, e.g. when the thick: * i? 0 adhesive point passes through the web 1, to a limited extent, , 11 - the return force of the holder 12 is preferably further less than 2 · 107N * x · ** · y, preferably less than 1 · 107N · x · y, where x = axial length of the application roller [m] and y = radial deflection [m] away from the counter roll 2. This low elasticity avoids damage and does not adversely affect the stability of the application gap 9.

li 7 99038 The supply of coating material to the application slot 9 takes place via a supply channel 17 on the inlet side, which is formed by a guide plate 18 extending close to the application gap 9 and the inlet side of the holder 12 or the circumference of the application roller 8. The feed channel 5 in the spreading slot 9 runs at an acute angle to the tangent of the counter roll 2. It is connected to a color chamber 19 extending over the entire working width, into which the coating material is introduced via a distribution pipe 20 connected to the inlet side. The rear side of the guide plate 18 away from the spreading roller 8 is constructed as a back-casting surface 10 for the additional coating material. The guide plate 18 thus separates the coating material conveyed to the application slot 9 from the return material in the excess feed. Thus, vortices in the coating material are avoided, and the excess ratio can be adjusted to a lower value or the Levi-15 slit can be adjusted to a higher value, and without uncovered spots. The recycled coating material is collected in the ink tank 21 and returned to the ink chamber 19.

A color guide 19 is arranged in the color chamber 19 and extends radially over the working width and relative to the counter roll 2 and ends a short distance from the bottom of the chamber. The guide plate 22 forms a channel 23 with the outlet wall of the color chamber 19 with a slit-shaped inlet opening which terminates in the feeds channel 19. It, as a dam wall opposite the distribution pipe 20, prevents the feed coating material from pressure and the flow conditions prevailing here and in the spreading gap 9 ···. At the same time, the guide plate 22 allows the paint chamber 19 to be towed, and without any irregularities in the supply of coating material into the application slot 9. Thus can be removed from the coating material - * !!! unwanted air bubbles.

On the inlet side, in front of the spreading roller, there is a short distance from the guide plate 18 and a scraper knife 24 arranged approximately parallel thereto, the tip of which rests against the web 8 99038 1. The scraper knife is drawn in Figures 1 and 2, but can also be used in the embodiments of Figures 3 and 4. A scraper knife 24 extending over the entire width of the web removes the air adhering to the surface of the web 1 before the web 1 passes into the application slot 9. The air transferred from the web 1 to the coating material leads to undesirable irregularities in the coating image after dosing. The negative effects due to the incoming air can be considerably reduced by means of a scraper knife 18 and / or by removing air 10 from the coating material in the paint chamber 19.

The application systems according to Figures 3 and 4 in each case comprise an application roller 8 with a larger diameter between 50 and 200 mm, preferably between 50 and 150 mm. Spreading rollers 8 of this type 15 are suspended on roller pins on their end sides on center bearings which are attached to both sides of the body. In addition, a support bearing 26, 27 is arranged between the cross member 14 and the spreading roller 8, which extends over the entire working width (i.e. along the length of the spreading roller 8) and which prevents the spreading roller 8 from bending due to its own weight and / or hydrodynamic pressure in the spreading slot 9.

. , The support bearing 26, 27 is preferably shaped on the side of the spreading roller 8 • 25 so that the spreading roller 8 is supported on its surface. Each support bearing 26, 27 is made of a hard material with low friction with respect to the spreading roller 8, in particular of hard rubber or rubber-like plastic, if the spreading roller 8 is coated with carbide, e.g. .

• · 1 (: 30 chromed, or it is hard metal if the application roller 8 is coated with rubber or rubber-like plastic.

The surface of the support bearing 27 according to Fig. 4 resting against the spreading roller 8 is constructed according to the bed 10, 11 35 according to Fig. 2 on the inlet and outlet side in the shape of a lip, so that impurities adhere to it when the spreading roller 8 rotates; be scraped off. The support bearing 27 is formed with channels 28 open in the direction of the spreading roller 8 and running in the axial direction thereof, to which a lubricant and cleaning agent, e.g. water, can be introduced during use.

5 Depending on the application, the spreading roller 8 is rotated machine-driven with respect to the counter roll 2 of the counter roll.

The co-operative use of the spreading roller 8 has the advantage that the spreading roller 8 additionally sucks material from the feed channel 17 and thus contributes to filling the spreading gap 9. In continuous use of Vas-10, the film tearing phenomena and the formation of the tension line are preferably reduced. The circumferential speed of the application roller 8 when applied is greater than 0 m / min and less than 100 m / min, preferably between 2 and 20 m / min.

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The application system 3 is thus able to apply even small excesses evenly to the web 1. The scraper knife 5 of the subsequent dosing system 4 scrapes off the excess again up to the desired brush weight and then leads it 20 back to the ink tank 25.

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Claims (11)

An apparatus for coating a cardboard or paper web (1), comprising: a counter roll (2) controlling the web (1) pivotally a coating system (3) which coats the web (1) with an excess of coating material; and a dosing system (4) provided with a rake element (5) adapted behind the coating system separate from this,. . : wherein the coating system (3) comprises a mechanical root. a coating coating roller (8) having a smooth casing surface, which, with the counter roll (2), forms a coating gap (9) in which from the inlet side of the web is led an excess of coating material, characterized in that the coating roller (8) has a diameter of 5 - 200 mm, preferably 10 - 150 mm, "" - with the counter roll (2) forms a coating roll (9) of 0.01 - · ·::: 2 mm, preferably 0.05 - 1 mm, depending on the paper or cardboard's thickness, and 35. is supported against bending over its entire working width from the rear side opposite the counter roll (2) by means of a rigidly placed rigid holder (12, 27, 28) radially disposed against the counter roll (12, 27, 28). working position. Device according to claim 1, characterized in that the coating roll (8) is placed in a flat (10, 11) which runs across the working width and is open to the counter roll (2), made of limited elastic, rubbery material, and fitted into the holder ( 12). Device according to Claim 2, characterized in that the restoring force of the system coating roll (8) - bed (10, 11) - holder (12) against radial bending away from the counter roll (2) is at least 1 10¾ · xy, preferably more than 5 · 10¾ · x · y, in which x = the coating roll axial length [m] and y = the radial bend [m] away from the counter roll (2). 4. Apparatus according to claim 3, characterized in that the restoring force of the system coating roll 20 (8) - bed (10, 11) - holder (12) is less than 2 · 107N · x · y, preferably less than 1 · 107N · xy. in which x = the axial length of the coating roll [m] and y = the radial bend [m] away from the counter roll (2). ; 25 Device according to any of claims 2 - 4, characterized in that the bed (10, 11) covers the coating choice. then (8) in an area of at least 180 ° along its circumference. • · · · • i Device according to any one of claims 2 to 5, characterized in that the bed (10, 11) has one or more channels (16) open to the coating roller (8), which runs on the bed. · · * · * * Rally with the shaft of the coating roller (8). · »· ♦» · • · Device according to any of claims 2 to 6, characterized in that at least one of the inner walls of the bed (10, 11) supporting the coating roll (8) is constructed as an axially extending lip. 14 99038 Apparatus according to any of claims 2 to 7, characterized in that the bite consists of two parts (10, 11) placed in the holder (12) for shaking and removing the coating roll (8), and which are movable against and from each other. 5 Device according to any of claims 1-8, characterized in that on the inlet side of the coating roll (8), a guide plate (18) extending near the coating slot (9) is formed and which forms a feeder channel (17) with the side of the holder (12) on the inlet side or the circumference of the roller (8) and forms a sharp angle with the key of the counter roll (2), and the rear side of which against the coating roll (8) is designed as a drainage surface for the excess of coating material. 10. Apparatus according to any one of claims 1 to 9, characterized in that on the inlet side of the coating roll (8) a feeder channel (17) extending near the coating slot (9) is connected to a color chamber. (19) provided with a coating tube (20) for coating material, wherein a guide plate (22) which extends across the working width and radially against the counter roll (2) adjusts in the ink chamber (19) and terminates in the vicinity of the bottom of the ink chamber (19). and forming with the wall on the outlet side of the ink chamber a channel (23) having a slot-shaped inlet opening opening into the feeder channel (17). • ·· · • «* • · · · 11. Device according to any one of claims 1 - 10, characterized in that on the inlet side in front of the coating roll (8) is adapted a creator (24) running over the entire web width and the tip of which rests against the web. (1). I t '»· i •« · «• · · • · li