METHOD AND SYSTEM FOR PRODUCING COMPOSITE STRIPS OR COMPOSITE SHEETS

Abstract

The invention relates to a method of making composite strips and composite sheets of at least one first outer layer (1) of metal, one second outer layer (2) of metal, and at least one core layer (3) of plastic between the outer layers (1, 2) and bonded unitarily thereto, a first metal strip (4) for the first outer layer (1), a second metal strip (5) for the second outer layer (2), and a plastic web (6) for the core layer (6) being laminated together and continuously bonded unitarily into a composite strip by application of pressure and/or heat, the first metal strip (4) and the second metal strip (5) being heated before the lamination and/or during the lamination, characterized by the fact that, after lamination and bonding of the metal strips (4, 5), an actual transverse curvature of the composite strips is measured, and that the temperature of the first metal strip (4) and/or of the second metal strip (5) is carried out before the lamination and/or during the lamination as a function of the actual transverse curvature. Furthermore, the invention relates to a system for carrying out the method with a transverse curvature sensor (15).

Claims

1. A method of making a composite strip and composite sheet of at least one first outer layer of metal, one second outer layer of metal and at least one core layer of plastic that is between the outer layers and bonded unitarily, the method comprising the steps of: feeding a first metal strip for the first outer layer, a second metal strip for the second outer layer, and a plastic web for the core layer to a laminater that continuously laminates the metal strips and plastic web unitarily into a composite strip by application of pressure and/or heat, preheating the first metal strip and the second metal strip in respective presenters upstream of or in the laminater, and after lamination and bonding of the metal strips, measuring an actual transverse curvature of the composite strips, and regulating the temperature of the first metal strip and/or of the second metal strip as a function of the actual transverse curvature upstream of or in the laminater.

2. The method defined in claim 1, wherein the transverse curvature is adjusted by a closed loop control to a specified target transverse curvature.

3. The method defined in claim 2, wherein a value of zero is the target transverse curvature.

4. The method defined in claim 2, wherein a manipulated variable of the control loop is the temperature of the first metal strip and/or of the second metal strip upstream of or in the laminater.

5. The method defined in claim 1, wherein, for temperature regulation of the metal strip before the lamination, one or a plurality of operating parameters of the respective preheater is/are adjusted.

6. The method defined in claim 1, wherein at least one furnace is used as a preheater.

7. The method defined in claim 1, wherein the metal strips are laminated together by interposing the plastic web between the rollers of a calender.

8. The method defined in claim 7, wherein, for temperature regulation of the metal strips, the temperature of the rollers is varied.

9. The method defined in claim 1, wherein the temperature of the first metal strip and/or of the second metal strip is measured by at least one respective sensor.

10. The method defined in claim 1, further comprising the step of: passing the composite strip after lamination through a heating and pressing device, one or a plurality of transverse curvature measurements being carried out between the laminater and the heating and pressing device and/or downstream of the heating and pressing device.

11. The method defined in claim 4, wherein the values for the manipulated variable to be adjusted in the event of a deviation of the actual transverse curvature from the target transverse curvature are determined using a mathematical model that comprises at least the strip thickness, the width of the strip, the thermal expansion coefficient, and/or the temperature differential between the metal strips.

12. A system for making a composite strip or sheet that is made of at least one lower outer layer of metal, one upper outer layer of metal, and one core layer of plastic that is between the outer layers and that is bonded unitarily thereto, the system comprising at least one first preheater for the first metal strip, one second preheater for the second metal strip; a laminater in which the metal strips are laminated together by interposing a plastic web; at least one transverse curvature sensor that measures an actual transverse curvature of the composite strip downstream of the laminater, and a control and adjusting device that controls the temperature of the first metal strip and/or of the second metal strip before and/or during lamination as a function of the measured actual transverse curvature.

13. The system defined in claim 12, wherein the transverse curvature sensor is a sensor operating with or without contact.

14. The system defined in claims 12, further comprising: a first second temperature sensor for the second metal strip upstream of and/or in the laminater.

Description

[0035] In the following, the present invention is described in further detail with reference to a drawing illustrating only one embodiment. In the figures,

[0036] FIG. 1 is a simplified cross section through a composite strip or composite sheet;

[0037] FIG. 2 is a greatly simplified schematic view of a system for making a composite strip; and

[0038] FIG. 3 shows a modified embodiment of the system as in FIG. 2.

[0039] The system illustrated in FIGS. 2 and 3 enables the manufacture of a composite strip or sheet that are made of at least one lower outer layer 1 of metal, one upper outer layer 2 of metal, and at least one core layer 3 of plastic between the outer layers 1, 2, the outer layers 1, 2 being bonded unitarily to the plastic core layer 3 (see FIG. 1).

[0040] For making such composite strips according to FIG. 1, a first metal strip 4 for the lower outer layer and an upper metal strip 5 for the upper outer layer and a plastic web 6 for the core layer are thus supplied to the systems of FIGS. 2 and 3. The first metal strip 4, the second metal strip 5, and plastic web 6 are continuously laminated together and continuously bonded to one another unitarily using pressure and/or heat. For the process according to the present invention, the metal strips 4 and 5 are thus the starting material for making a composite strip. These are for example strips of steel, for example electrolytically galvanized and optionally oiled steel strips. Alternatively, strips of aluminum or other metals can however also be used. Preferably, such metal strips 4, 5 can first be pretreated in that they are continuously coated on one face with an adhesive agent. This is not shown in the figures.

[0041] The system illustrated in FIGS. 2 and 3 as a rule has at least one unillustrated unwinder for the first metal strip 4 and an also unillustrated unwinder for the second metal strip 5 and, moreover, an also unillustrated unwinder for the plastic web 6. In addition, a rewinder may be provided for the finished composite strip. This is also not shown.

[0042] Furthermore, the system has a first preheater 7 for the first metal strip 4, a second preheater 8 for the second metal strip 5, and a laminater 9 in which the metal strips 4 and 5 are laminated together and connected to one another. A heating and pressing device 10 downstream of the laminater 9 finishes the bonding between outer sheets 4 and 5 and the interposed plastic web.

[0043] Here, the preheater 7 and the preheater 8 are furnaces, for example strip flotation furnaces. In them, the metal strips 4 and 5 are preheated to a specific temperature.

[0044] Here according to FIG. 1, the laminater 9 is a roller assembly or calender having an upper roller 11 and a lower roller 12, and these rollers 11 and 12 can be heated. In the embodiment according to FIG. 1, only one post-heating furnace 13, which also can be a strip flotation furnace, is illustrated as the heating and pressing device 10.

[0045] To this end, FIG. 2 shows a first embodiment of the present invention where the two the metal strips 4 and 5 and the plastic web 6 are simultaneously laminated together and bonded to each other with the plastic web 6 being fed directly to where the metal strips 4 and 5 merge, the plastic web thus being introduced into the gap between the two converging metal strips.

[0046] Moreover, the metal strips 4 and 5 in the system can be locally connected in another strip connecting device 14 when starting up the process at a strip leading end. Such a connection of the two strips takes place in a start-up process, particularly preferably without interposed plastic web. The connection can be done for example by punching, riveting (clinching), welding, and/or adhesive bonding. Such strip connectors are known from process lines for making metal strips. In the case of the described system, the strip connectors are optionally at the laminater or in the travel direction of the strip downstream of the laminater and upstream of the heating and/or pressing device. With this additional local strip connection at the leading end of the metal strips or at the leading end of the strip of one of the metal strips, a delamination of this region downstream is prevented by the laminating line. The start-up process can overall be optimized to ensure that, when passing through the laminating line and in particular the heating and optionally pressing units from the upstream end, the two surfaces of the continuous workpiece are formed by metal strips and not by the plastic strip.

[0047] According to the present invention, it is now particularly important that the laminater 9 be downstream of a transverse curvature sensor 15 that can measure an actual transverse curvature of the composite strip manufactured in the laminater. According to the present invention, the temperature of the first metal strip 4 and/or of the second metal strip 5 is controlled before the lamination and/or during the lamination as a function of the measured actual transverse curvature. According to the present invention, potentially resulting transverse curvatures in the composite strip subsequently are thus not corrected by suitable measures, but the formation of transverse curvatures is instantly inhibited by suitably influencing the temperature regulation of the metal strips, and that is preferably by control engineering measures.

[0048] To this end, the system has a controller or adjusting device, which is not illustrated, that regulates the temperature of the first metal strip 4 and/or the second metal strip 5 before the lamination and/or during the lamination as a function of the actual transverse curvature.

[0049] Particularly preferably, the transverse curvature is adjusted in a closed loop control to a predetermined desired transverse curvature, the target transverse curvature preferably specifying the value zero. As the manipulated variable of such a control loop, the temperature of the first metal strip and/or the second metal strip is regulated prior to the lamination or during the lamination. Hence, if within the course of the measuring a deviation of the measured actual transverse curvature from the specified target transverse curvature (for example zero) is detected, the adjusting device generates a correction signal for the manipulated variable so that the temperature of the first metal strip and/or of the second metal strip is varied. With the aid of a closed loop control, the actual transverse curvature can then be corrected to the specified target transverse curvature.

[0050] For regulating the temperature and, for this reason, the temperature of the respective metal strip in the course of an adjustment process, for example, the operating parameters of the preheater and thus of the furnace 7 and/or 8, can be adjusted.

[0051] Alternatively, for regulating the temperature and, for this reason, the temperature of the respective metal strip, the temperature of the rollers 11 and 12 of the laminater can be varied or adjusted.

[0052] It is always ensured that the temperatures of the metal strips are set in such a manner that, within the course of bonding, a composite strip free of transverse curvature can be produced.

[0053] In this instance, the temperatures of the two metal strips do not necessarily have to be identical because the metal strips, after leaving the furnaces 7 and 8, pass through different spaces and also the extent of wrap around the rollers 11 and 12 are not identical. Thus, within the context of the method according to the present invention, neither absolute temperatures of the metal strips nor, in particular, identical temperatures are decisive, but the temperatures merely have to be set relative to each other so that a composite strip free of transverse curvatures results in the composite. This is because the temperature in the sandwich panel is homogenized during the lamination (in the calender 9) and/or after lamination. To the extent that the lower outer strip 4 is colder before laminating than the upper outer strip 5, it would be heated in the calender 9 and/or in the post-heating furnace 13 relative to the upper strip, and this would result in a longitudinal expansion of lower outer strip 4 in the direction of the strip width relative to upper outer strip 5. The difference in transverse width between the two outer strips results in a barrel-like transverse curvature that is prevented according to the present invention by a targeted variation in temperature before or during lamination. In this instance, it is within the scope of the present invention that a first temperature sensor 16 is provided downstream of the first furnace 7 and that a second temperature sensor 17 downstream of the second furnace 8. Here according to FIG. 2, a transverse curvature sensor 15 is spaced downstream from the laminater 9 and upstream of the heating and pressing device 10 or downstream of the postheating furnace 13. Alternatively, it is however also within the scope of the present invention to provide a transverse curvature sensor 15 downstream of the post-heating furnace 13 or downstream of the heating and pressing device 10.

[0054] FIG. 3 shows a modified embodiment of the present invention where the lamination of the metal strips 4 and 5 and of the plastic web 6 is carried out in two steps. To this end, the laminater 9 preferably has a first laminater 9a that laminates plastic web 6 with the first metal strip 4 (for example the lower metal strip), and a second laminater 9b that laminates the second metal strip 5 (for example the upper metal strip) with the plastic web 6 on or at the first metal strip 4. The first laminater 9a, in turn, is a roller assembly or calender having an upper roller 11a and a lower roller 12a. The second laminater 9b, in turn, is a roller assembly or calender having an upper roller 11a and a lower roller 12a. There are also preheaters 7 and 8. Moreover, a further heater 7 is provided for the first metal strip 4 downstream of first laminater 9a. A transverse curvature sensor 15 that is used in connection with the roller already described in FIG. 2, is downstream of the laminater 9 and, in the shown embodiment, downstream of the second laminater 9b. Optionally, this transverse curvature sensor 15 could also be downstream of the post-heating furnace 13 or between post-heating furnace 13 and calender 19.

[0055] This is because the heating and pressing device 10 connected downstream from the laminater 9, here according to FIG. 2, has a heater 10, for example a furnace 13, a pressing device and optionally a further heater, for example a furnace 20, and optionally a cooling device 21 connected downstream. Optionally, an additional transverse curvature sensor 15 can be downstream from the heating and pressing device 10. This additional transverse curvature sensor 15 can be used merely for checking purposes. Alternatively, it is also within the scope of the present invention to use this additional transverse curvature sensor 15 in combination with the transverse curvature sensor 15 for redundant adjustment control.

[0056] In turn, a temperature sensor 16 is assigned to the first metal strip 4 and, also, a temperature sensor 17 is assigned to the second metal strip 5. A further temperature sensor 18 can be provided at the second metal strip 5.

[0057] Independent from the described differences between the embodiments according to FIGS. 2 and 3, also here according to FIG. 3, an adjustment of the transverse curvature is carried out in that, when the measured actual transverse curvature deviates from

[0058] A predetermined target transverse curvature, a correction signal for the manipulated variable is generated, in turn the temperature of the first metal strip and/or of the second metal strip being controlled as a manipulated variable before the lamination or during the lamination.

[0059] In this instance, it is categorically possible to influence the temperature regulation of the first metal strip as well as also the temperature regulation of the second metal strip during adjustment. Preferably, only the temperature of one of the metal strips, for example the upper metal strip, is however regulated as the manipulated variable for the adjustment.