METHOD AND DEVICE FOR COATING A METAL STRIP

Abstract

A method and a device for coating a metal strip with a coating material that is still liquid at first. During the coating, the coated metal strip runs through a roller pair. One of the rollers of the roller pair can be adjusted toward the other as a correction roller in order to eliminate a possible curvature of the metal strip. Then the metal strip runs through a blow-off apparatus for blowing off surplus coating. In order to prevent an uneven thickness distribution of the coating on the metal strip even when the correction roller of the roller pair has been adjusted, the actual position of the metal strip is controlled to a specified setpoint center position in the slot of the blow-off apparatus by an appropriate movement of the blow-off apparatus.

Claims

1-6. (canceled)

7. A method of coating a metal strip with a coating material, comprising: conducting the metal strip to be coated through a coating container filled with the liquid coating material, wherein the coating material adheres to the surface of the metal strip to be coated; conducting the coated metal strip through a slot of a blowing device, which is downstream of the coating container in the transport direction (R) of the metal strip, for blowing excess parts of the still liquid coating material off the surface of the metal strip; detecting the actual curvature of the metal strip after leaving the coating container; adjusting a correction roller, which is arranged within the coating container, against the metal strip for smoothing the metal strip when the amount of the actual curvature exceeds a predetermined permissible curvature threshold value, wherein the actual position of the metal strip in the slot of the blowing device changes due to the adjustment of the correction roller; regulating the actual position of the metal strip to a predetermined target centre position in the slot of the blowing device by displacing the blowing device in the plane transverse to the transport direction of the metal strip; the adjusted position of the correction roller or the change thereof is detected; and the displacement of the blowing device is carried out with consideration of the adjusted position of the correction roller.

8. The method according to claim 7, wherein the deviation of the actual position of the metal strip from its target centre position in the slot of the blowing device is detected; and the displacement of the blowing device is carried out as a function of the detected deviation.

9. The method according to claim 7, further comprising: stabilising the metal strip after leaving the coating container and the blowing device with the help of an electromagnetic stabilising device arranged above the blowing device.

10. A device for coating a metal strip with a coating material (300), comprising: a coating container with a correction roller, wherein the coating container is fillable with the liquid coating material, for conducting through the metal strip, and wherein the coating material adheres to the surface of the metal strip to be coated; a blowing device, which is arranged downstream of the coating container in the transport direction (R) of the metal strip, with a slot for conducting through the metal strip and for blowing excess parts of the still liquid coating material off the surface of the metal strip; a curvature sensor for detecting the actual curvature of the metal strip after leaving the coating container; a control device for adjusting the correction roller against the metal strip if the amount of the actual curvature exceeds a predetermined permissible curvature threshold value; a regulating device for regulating the actual position of the metal strip to the predetermined target centre position in the slot of the blowing device by displacing the blowing device in a plane transverse to the transport direction of the metal strip with the help of a displacing device; and a correction roller detection device for detecting the adjusted position of the correction roller or the change thereof; wherein the displacement of the blowing device is carried out with consideration of the adjusted position of the correction roller.

11. The device according to claim 10, further comprising: a position sensor for detecting the deviation of the actual position of the metal strip relative to the target centre position during passage through the slot of the blowing device due to the adjustment of the correction roller relative to the metal strip; and the displacement of the blowing device is carried out as a function of the detected deviation.

12. The device according to claim 10, further comprising: an electromagnetic stabilising device, which is arranged above the blowing device, for stabilising the metal strip after leaving the coating container and the blowing device.

Description

[0016] Accompanying the description are two figures, in which:

[0017] FIG. 1 shows the device according to the invention in an overall view; and

[0018] FIG. 2 shows a plan view of the slot of the blowing device.

[0019] The invention is described in detail in the following in the form of embodiments with reference to the mentioned figures. The same technical elements are denoted by the same reference numerals in both figures.

[0020] FIG. 1 shows the device 100 according to the invention for coating a metal strip 200 with a liquid coating material 300, for example zinc. For this purpose, the initially still uncoated metal strip 200 is conducted in transport direction R in a coating container 110 filled with the liquid coating material. Within the coating container 110 the metal strip 200 is deflected with the help of a deflecting roller so that it leaves the coating container upwardly. After the transit through the coating container, the still liquid coating material adheres to the metal strip 200.

[0021] A roller pair between which the coated metal strip is guided through is arranged downstream of the deflecting roller 115 in the transport direction R of the metal strip 200. The roller pair is typically arranged within the coating container 110 so that it is surrounded by the coating material 300 during performance of the coating process. One of the rollers is adjustable as a correction roller 160 towards the other roller of the roller pair so as to smooth the metal strip if an undesired curvature is present. For this purpose, the amount of curvature of the metal strip 200 is detected with the help of a curvature sensor 154 and compared with a predetermined curvature threshold value. The comparison can be carried out in a control device 190. If the amount of curvature of greater than the curvature threshold value then the correction roller is adjusted, under the control of the control device 190, relative to the metal strip.

[0022] Arranged downstream of the roller pair in transport direction R of the metal strip is a blowing device 120 which spans a slot 122 through which the metal strip 200 is guided. Excess coating material is blown off the surface of the metal strip 200 with the help of the blowing device.

[0023] In order that blowing onto the upper side and lower side of the metal strip 200 takes place uniformly it is important that the metal strip 200 runs through the slot 122 of the blowing device 120 in a predetermined target centre position 128, as symbolised in FIG. 2 in the form of the solid line in X direction. This target centre position is distinguished by, in particular, uniform spacings or spacing distributions from the inner edges of the slot 122 of the blowing device 120. Apart from the desired predetermined target centre position, possible undesired actual positions of the metal strip are also depicted, as dashed lines, in FIG. 2. Undesired actual positions for the metal strip are thus present, for example, if it is twisted relative to the target centre position or shifted parallelly in Y direction.

[0024] With further reference to FIG. 1 there can be seen above the blowing device 120 an electromagnetic stabilising device 140 which in turn has a slot 142 through which the metal strip 200 is similarly guided. It is also the case here that the metal strip 200 preferably runs through the slot 142 in a predetermined target centre position 128, as shown in FIG. 2, so that in desired manner the forces provided by the electromagnetic stabilising device 140 can have a uniform stabilising action on the metal strip 200.

[0025] A position sensor is provided for detecting a deviation of the actual position of the metal strip 200 from a predetermined target centre position in the slot 122 of the blowing device 120. In addition, a regulating device 180 is provided for regulating the actual position of the metal strip 200 to the predetermined target centre position in the slot 122 of the blowing device, as explained above with reference to FIG. 2, by displacing the blowing device 120 with the help of a displacing device 130. The displacement is carried out in a plane transverse to the transport direction R of the metal strip. The regulation is carried out in response to the deviation, which is detected by the position sensor 152, of the actual position from the target centre position of the metal strip 200. The regulation can optionally also be carried out with additional consideration of the amount of curvature of the metal strip detected by the curvature sensor 154.

[0026] The position sensor 152 and the curvature sensor 154 are both part of a metal strip detecting device 150. According to one embodiment, the function of the position sensor 152 and the curvature sensor 154 can be realised by a single, typically laser-supported, sensor device, also termed “laser” for short; the position sensor 152 and the curvature sensor 154 then form one constructional unit in the form of the sensor device or the metal strip detecting device.

[0027] According to a first alternative the displacement of the blowing device 120 can be carried out as a function of the detected deviation of the actual position of the metal strip from the predetermined target centre position in the slot 122 of the blowing device. In other words: if it is ascertained that the metal strip 200 does not run through the slot 122 in the target centre position 128 then the blowing device 120 is displaced with the help of the displacing device 130 in such a way that the metal strip again runs through the slot 122 of the blowing device in the predetermined target centre position 128 so as to ensure the desired uniform coating.

[0028] According to a second alternative or additionally the displacement of the blowing device 120 can also be carried out with consideration of the adjusted position, which is detected by a correction roller detecting device 165, of the correction roller 160 or the change thereof. For this purpose, the output of the correction roller detecting device 165 is also coupled to the input of the regulating device 180. In this way the displacement of the blowing device was improved with respect to a desired maximisation of uniformity during the coating. The correction roller detection device 165 can be constructed in the form of two encoders, each of which is seated on a respective drive of the correction roller 160.

[0029] The metal strip and correction roller detection devices 150, 165 are constructed to preferably recognise all conceivable deviations of an actual position of the metal strip from the desired target centre position. Amongst those is, in particular, a (parallel) shifting of the metal strip in X or Y direction or a rotation such as explained above with reference to FIG. 2. Accordingly, the displacing device 130—in the case of suitable control by the regulating device 180—is constructed to move the blowing device 120 in a desired manner in a plane transverse to the transport direction R of the metal strip, particularly to shift (parallelly) or to rotate, so as to realise transit of the metal strip in the target centre position. To that extent, the illustration of the displacing device 130 as a piston-cylinder unit is merely exemplifying, but not limiting.

REFERENCE NUMERAL LIST

[0030] 100 device [0031] 110 coating container [0032] 115 deflecting roller [0033] 120 blowing device [0034] 122 slot of the blowing device [0035] 128 target centre position of the metal strip in the blowing device or the electromagnetic stabilising device [0036] 130 displacing device [0037] 140 electromagnetic stabilising device [0038] 142 slot of the electromagnetic stabilising device [0039] 150 metal strip detecting device [0040] 152 position sensor [0041] 154 curvature sensor [0042] 160 correction roller [0043] 165 correction roller detecting device [0044] 180 regulating device [0045] 190 control device [0046] 200 metal strip [0047] 300 coating material [0048] R transport direction of the metal strip [0049] X width direction of the metal strip in target centre position [0050] Y direction transverse to the plane spanned by the metal strip [0051] Z direction perpendicular to the X-Y plane