Coating Device and Method Using Rollers

Abstract

A coating device, comprising a supply roller having a first contact surface, and a counter-roller placed opposite the supply roller and a second contact surface substantially parallel to the first contact surface. The contact surfaces are at least a substrate width in width and maintain a mutual gap for receiving the substrate therein in contact with both contact surfaces. The supply roller and counter-roller are each rotatable about their central axis. A liquid is supplied to the supply roller. At least the contact surface of the supply roller or the counter-roller is axially adjustable along the central axis thereof. Adjusting means align an edge of the contact surface of the supply roller and the counter-roller with a side of the substrate. An opposite edge of the other of the supply roller and the counter-roller is aligned with an opposite side of the substrate.

Claims

1. Coating device for supplying a liquid to a substrate, particularly in the form of an optionally printed web, strip or sheet, comprising a supply roller having over a periphery thereof a first contact surface, and a counter-roller placed opposite the supply roller and having over a periphery thereof a second contact surface substantially parallel to the first contact surface, which contact surfaces are at least a substrate width in width and maintain a mutual gap for receiving the substrate therein in contact with both contact surfaces, wherein the supply roller and counter-roller are each rotatable about their central axis and supply means are provided for supplying a liquid to the contact surface of the supply roller, wherein at least the contact surface of at least one of the supply roller and the counter-roller is axially adjustable along the central axis thereof, and wherein adjusting means are provided for aligning an edge of the contact surface of the at least one of the supply roller and the counter-roller with a first longitudinal side of the substrate, wherein an opposite edge of the other of the supply roller and the counter-roller is aligned with an opposite, second longitudinal side of the substrate.

2. Coating device according to claim 1, wherein at least the contact surface of each of the supply roller and the counter-roller is axially adjustable, and wherein second adjusting means are provided in order to align an edge of the contact surface of the other of the supply roller and the counter-roller with a second longitudinal side, lying opposite the first longitudinal side, of the substrate.

3. Coating device according to claim 1, wherein at least the at least one, and preferably each, of the supply roller and the counter-roller is axially adjustable together with the contact surface thereof in order to align an edge of the contact surface with a longitudinal side of the substrate.

4. Coating device according to claim 1, wherein the at least one of the supply roller and the counter-roller comprises at least the supply roller and wherein the supply means are axially displaceable together with the supply roller.

5. Coating device according to claim 4, wherein the supply means are accommodated together with the supply roller fed thereby in a shared frame, which frame is coupled to the adjusting means for the purpose of performing an axial displacement parallel to the central axis of the supply roller.

6. Coating device according to claim 1, wherein the counter-roller comprises a second supply roller and is provided with second supply means for supplying a second liquid, optionally differing from the first liquid, to the second contact surface.

7. Coating device according to claim 1, wherein the supply means comprises a dosing unit, which is accommodated together with the supply roller fed thereby in the frame shared therewith, the dosing unit comprising a reservoir for holding a quantity of a liquid for supplying, and a pick-up roller which is arranged rotatably about a central axis thereof and comprises over a periphery thereof a take-up surface, and is able and configured to therewith enter into contact with a liquid held in the reservoir, wherein the pick-up roller and the supply roller are coupled to each other for the purpose of at least partially transferring the liquid from the take-up surface of the pick-up roller to at least substantially the whole contact surface of the supply roller.

8. Coating device according to claim 7, wherein the dosing unit comprises at least one transfer roller between the pick-up roller and the supply roller, which is arranged for rotation about a central axis thereof, and wherein the pick-up roller and the supply roller are coupled to each other with interposing of the at least one transfer roller for the purpose of transferring the liquid from the take-up surface of the pick-up roller to at least substantially the whole contact surface of the supply roller.

9. Coating device according to claim 1, wherein the adjusting means comprise one or more actuators and a control device, which actuators are individually controllable by the control device.

10. Coating device according to claim 9, wherein the actuators comprise one or more linear actuators with a linearly extendable drive rod which is coupled directly or indirectly to the relevant roller, particularly selected from a group of screw spindle/threaded cavity assemblies and pressure cylinders, particularly hydraulically or pneumatically fed pressure cylinders.

11. Coating device according to claim 9, wherein the control device is coupled to one or more sensors, particularly one or more optical sensors, which are able and configured to detect the first and second longitudinal side of the substrate, and wherein the control device is able and configured to extend one or more actuators on the basis of the longitudinal side detected by a sensor in order to align the edge of the contact surface of the relevant roller with the longitudinal side of the substrate detected by the sensor.

12. Method for supplying a liquid to a substrate, particularly in the form of an optionally printed web, strip or sheet of substrate, wherein the substrate is guided in a gap between a supply roller and a counter-roller and is brought into contact with opposite contact surfaces of respectively the supply roller and the counter-roller, wherein at least the supply roller is provided on a periphery thereof with the liquid, and wherein the liquid of at least the supply roller is supplied to the substrate, wherein at least the contact surface of at least one of the supply roller and the counter-roller is axially adjusted along a central axis thereof, and a first edge of the contact surface of that roller is aligned with a first longitudinal side of the substrate, wherein an opposite edge of the contact surface of the other of the supply roller and the counter-roller is or will be aligned with the opposite, second longitudinal side of the substrate.

13. Method according to claim 12, wherein at least the contact surface of both the supply roller and the counter-roller is adjusted axially along a central axis of the relevant roller, wherein a first edge of the contact surface of the one roller is aligned with the first longitudinal side of the substrate, and the opposite edge of the contact surface of the other of the supply roller and the counter-roller is aligned with the second longitudinal side of the substrate.

14. Method according to claim 12, wherein the edge of the contact surface of the at least one roller is lined up with the relevant longitudinal side of the substrate so that the opposite edges of the contact surfaces of the supply roller and the counter-roller at least substantially coincide with respectively the first longitudinal side and the second longitudinal side of the substrate.

15. Method according to claim 12, wherein the edge of the contact surface of the at least one roller is lined up with the relevant longitudinal side of the substrate so that the opposite edges of the contact surfaces of the supply roller and the counter-roller fall inside, particularly fall just inside, respectively the first longitudinal side and the second longitudinal side of the substrate.

Description

[0027] The invention will be further elucidated hereinbelow with reference to an exemplary embodiment and an accompanying drawing. In the drawing:

[0028] FIG. 1 shows a schematic representation of a roller system in an exemplary embodiment of the coating device according to the invention in side view;

[0029] FIG. 2 shows a top view of the supply rollers of the system of FIG. 1; and FIG. 3 shows a top view of the dosing and supply system of FIG. 1.

[0030] It is otherwise noted here that the figures are purely schematic and not always drawn to (the same) scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are designated in the figures with the same reference numeral.

[0031] FIG. 1 shows schematically a general setup of a coating device according to the invention. The coating device, also referred to as coater, can be applied to a substrate 1 in the form of individual strips of sheets, but can also be applied in a continuous printing process wherein the substrate 1 is formed by a long strip of substrate material which was unwound from a roll. Substrate 1 is guided into the device with infeed and throughfeed means 31, 32 provided for this purpose, and passes therebetween a set of rotating rollers 10, 20. At least one of the rollers 10, 20 is here a supply roller and is provided with supply means 11, 12, 15 whereby a liquid for applying can be applied to a lateral side of the substrate.

[0032] In this example the supply means comprise a reservoir 15 for holding therein a quantity of the liquid for applying, wherein a pick-up roller 12, usually referred to as fountain roller, enters into contact with the liquid. Pick-up roller 12 takes up an excess of liquid from reservoir 15 and is in turn in contact with an intermediate roller 11 which picks up a controlled quantity of liquid from pick-up roller 12. The intermediate roller can for this purpose be embodied with a carefully selected relief pattern of impressions (dimples), a shape, depth, size and density of which determine a take-up capacity. Such a roller is usually referred to as anilox roller. The present invention is however also suitable for a roller system wherein use is made of a smooth cylinder for the intermediate roller. It is optionally also possible to dispense with an intermediate roller, wherein use is for instance made of an anilox roller for the pick-up roller. In that case a possible surplus of liquid can be wiped off with a blade which is arranged in sliding contact with the relevant cylinder just after the contact with the liquid, optionally supplemented with a corresponding blade just before the contact with the liquid. More than one intermediate roller can also be applied, if desired.

[0033] All rollers 10, 11, 12, 20 are suspended rotatingly and motor-driven. The rotation directions are shown schematically in the figure. A peripheral speed of the rollers will usually be adjusted to a web speed or throughfeed speed of substrate 1, although a certain slip can be imparted here between successive contact surfaces by selecting a slightly higher or slightly lower peripheral speed than the adjacent contact surface. The rollers are usually embodied in steel, wherein a specific modified layer in the form of a carefully selected relief and/or a differing composition and/or material can be provided at the contact surface.

[0034] Finally, the liquid is transferred to the contact surface of supply roller 10 in the form of a thin film with a uniform thickness. The supply roller maintains a narrow gap with a counter-roller 20, such that the substrate 1, particularly paper, cardboard or plastic, is received therebetween under a certain pressure and the liquid film of supply roller 10 is transferred to the substrate at least substantially wholly and over the whole surface. The liquid provides for instance a glossy layer and comprises for this purpose a water-based or solvent-based varnish which is applied after a printing. The liquid can however also comprise a primer which is provided on the substrate prior to a printing, particularly in the case of paper or cardboard, in order to better adapt the substrate material and the ink to be applied to each other. The printing result can be improved here, and the ink consumption limited. The shown device can for instance also be applied downstream of a dryer for the printed material for the purpose of (re)humidifying and siliconization the substrate. And the device can also be utilized advantageously in other stages of a printing process.

[0035] Although a stand-alone smooth roller suffices in principle for counter-roller 20 in order to provide a counter-pressure to supply roller 10, a second supply roller is advantageously applied therefor, as in the shown example. This is provided in similar manner to first supply roller 10 with supply means 21, 22, 25, for a description of which reference is therefore made to the first supply means 11, 12, 15. For the second supply means use can be made here of the same liquid, although a different liquid or liquid composition can if desired also be applied for this purpose. The supply roller assembly 10, 20 thus provides the option of coating substrate 1 with a uniform liquid film on two sides in a single pass. It is here possible particularly to use a different liquid (composition) for a printed side or side to be printed than for an unprinted or more printed or less printed side.

[0036] In order to enable the device to adapt itself to an actual substrate width at least one of the supply roller 10 and the counter-roller 20 is laterally, axially adjustable with its contact surface along a central axis of the relevant roller. In this example the two supply rollers 10, 20 are embodied as such for axial adjustment, which is shown schematically in FIG. 2. This provides the option of adequately aligning a left-hand edge 10L of first supply roller 10 with the corresponding left-hand longitudinal side 1L of the substrate, and likewise aligning the right-hand edge 20R of the second supply roller with the right-hand longitudinal side 1R of the substrate in the same way. The width and position of the thus created overlap between the contact surfaces of the two supply rollers 10, 20 can thus in each case be adapted to an actual substrate width, without components having to be removed and switched for this purpose.

[0037] It has been found desirable here in practice to maintain a small margin in the order of one or several millimetres of the contact surface inside the longitudinal side of the substrate. The longitudinal side 1L, 1R of substrate 1 thus lies (just) clear of the respective contact surface 10, 20, whereby the longitudinal sides 1L, 1R will not experience any pressure from the rollers and will not cut into the contact surface 10, 20. It is also important here that direct contact or sight between the wet contact surfaces of the two supply rollers 10, 20 is thus avoided, as this could otherwise result in direct liquid-liquid contact resulting in undesired spraying or spattering. Substrate 1 is located where rollers 10, 20 ‘see’ each other, and where substrate 1 is not located, rollers 10, 20 do not ‘see’ each other. This provides a particularly practical and flexible arrangement whereby it is possible to anticipate a varying substrate width in rapid and simple manner.

[0038] In this example the respective supply means 11, 12, 15 and 21, 22, 25 for each of the two supply rollers 10, 20 form an independent dosing unit and are as such accommodated together with the supply roller 10, 20 to be fed thereby in a shared frame 110, 120, see FIG. 3. This frame 110, 120 forms as it were a cartridge having therein the dosing unit and the supply roller for the relevant side of substrate 1. The relevant cartridge 110, 120 is laterally displaceable as a whole by means of a linear actuator 115, 125 provided for this purpose. The overlap between the two supply rollers 10, 20 can thus be set by a corresponding lateral displacement of the relevant cartridge 110, 120 relative to the adjacent, fixed frame 100 of the device.

[0039] Actuators 115, 125 are for instance hydraulically or pneumatically controlled pressure cylinders, but can for instance also be formed by screw spindles which engage operatively inside threaded cavities provided for this purpose. If desired, all this can be controlled on the basis of predetermined preferred positions. These can for instance be imposed by a control device which is not further shown, and be entered by an operator. For this purpose the control device can be coupled to a user interface in the form of a screen with input means, whereby a setting of an actual substrate width and the overlap between the rollers 10, 20 corresponding therewith can be entered. Optical, acoustic or other sensors can optionally be provided here, which continuously monitor a correct mutual lining up of respectively roller edge 10L and substrate side 1L, and 20R and 1R, and generate a signal to the control device on the basis of which it can make adjustments, if necessary, when a variation is detected.

[0040] All in all, the invention thereby provides an extremely practical and valuable additional functionality to a coating device which can be utilized particularly universally. Although the invention has been further elucidated above on the basis of only a single exemplary embodiment, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art.

[0041] Use is thus made in the example of a dosing unit wherein the liquid is transferred from the pick-up roller to the supply roller by means of an intermediate roller. This is in particular what is usually referred to as a metering system. The pick-up roller comprises here a fountain roller and the intermediate roller an anilox roller, while a smooth cylinder is applied for the supply roller. An intermediate roller can however also be dispensed with in practice, wherein there will be direct contact between the pick-up roller and the supply roller. This is in particular what is usually referred to as a doctoring system, wherein the pick-up roller comprises an anilox roller and the supply roller a smooth cylinder. It is also possible to apply more than one intermediate roller.

[0042] Instead of a double-sided system, as described on the basis of the exemplary embodiment, the invention can advantageously also be applied for a single-sided coating, wherein the counter-roller will then usually be a smooth cylinder without further dosing and supply means for a liquid.