METHOD FOR MANUFACTURING TWO-SIDED LAMINATED CARDBOARD, AS WELL AS TWO-SIDED LAMINATED CARDBOARD MANUFACTURED BY SUCH A METHOD

Abstract

In manufacturing two-sided laminated cardboard (1) in a laminating apparatus (10), by controlling band tensions of a first outer layer (11) and a second outer layer (12), a torque difference between an exerted first torque (Q1) in an upper roller (21) and an exerted second torque (Q2) in a lower roller (22) is controlled towards a pre-determined value (ΔQ) of said torque difference, while at the same time a torque addition sum of the first torque and the second torque is controlled towards a pre-determined constant value (Q) of said torque addition sum. Thus the invention provides an effective and reliable solution for counteracting concaveness or convexness, in the conveying direction (MD), of the two-sided laminated cardboard (1) to be manufactured.

Claims

1. A method for manufacturing two-sided laminated cardboard, wherein on both sides of an intermediate cardboard layer a first outer layer and a second outer layer, respectively, are laminated, and wherein during said laminating: the intermediate layer is conveyed in a conveying direction through a laminating apparatus; the first outer layer is glued together with the upper side of the intermediate layer by means of a rotating upper roller under exertion of a first torque, and the second outer layer is glued together with the lower side of the intermediate layer by means of a rotating lower roller under exertion of a second torque; a measuring roller measures a measured band tension, in the conveying direction, of the intermediate layer being conveyed; for the purpose of a taut running of the intermediate layer, the intermediate layer being conveyed is kept at a pre-determined constant operational band tension in the conveying direction in dependence of said measured band tension and in dependence of said pre-determined constant operational band tension; and for the purpose of counteracting concaveness or convexness, in the conveying direction, of the two-sided laminated cardboard to be manufactured, band tensions of the first outer layer and the second outer layer are controlled; wherein in said controlling of said band tensions of the first outer layer and the second outer layer: a torque addition sum of the first torque and the second torque is controlled towards a pre-determined constant value of said torque addition sum, said pre-determined constant value being obtained from experience; and a torque difference between the first torque and the second torque is controlled towards a pre-determined value of said torque difference, said pre-determined value of said torque difference being obtained from experience, while maintaining said controlling of said torque addition sum towards said pre-determined constant value of said torque addition sum.

2. A two-sided laminated cardboard, manufactured by the method according to claim 1 in said laminating apparatus.

Description

[0026] Hereinafter the invention is further elucidated with reference to a non-limiting example embodiment, and with reference to the schematical FIG. 1 in the appended drawing.

[0027] FIG. 1 schematically shows, in side view, an example of a part of a laminating apparatus during execution of an example of an embodiment of a method for manufacturing two-sided laminated cardboard according to the invention.

[0028] FIG. 1 further comprises a control scheme for executing the concerned example of the method. This control scheme is formed by dash line arrows which are connecting a number of measuring and control symbols with one another. In the control scheme, the highly schematically depicted part 4 is a PID controller which uses set values and measured values that play a role in the method according to the invention.

[0029] FIG. 1 shows the laminating apparatus 10 for manufacturing two-sided laminated cardboard 1, wherein on both sides of the intermediate cardboard layer 2 the first outer layer 11 and the second outer layer 12, respectively, are laminated by means of gluing with glue 3. During laminating the intermediate layer 2 is conveyed through the laminating apparatus 10 in the conveying direction MD. Therein, the first outer layer 11 is glued by means the upper roller 21 at the upper side of the intermediate layer 2, and the second outer layer 12 is glued by means of the lower roller 22 at the lower side of the intermediate layer 2. The upper roller 21 is driven by the shown first motor 31, under exertion of a first torque Q1. The lower roller 22 is driven by the shown second motor 32, under exertion of a second torque Q2. The shown measuring roller 23 measures the band tension, in the conveying direction MD, of the intermediate layer 2 being conveyed.

[0030] For the purpose of a taut running of the intermediate layer 2 the intermediate layer 2 is kept at the pre-determined constant operational band tension T in the conveying direction MD. This is controlled in dependence of the band tension measured by the measuring roller 23 and in dependence of the pre-determined constant operational band tension T.

[0031] For the purpose of counteracting concaveness or convexness in the conveying direction MD of the two-sided laminated cardboard 1 to be manufactured, the band tensions of the first outer layer 11 and the second outer layer 12 in the conveying direction MD are controlled. Therein, the addition sum Q1+Q2 of the first torque Q1 and the second torque Q2 are controlled towards the pre-determined constant value Q. In other words, the control is such that eventually Q1+Q2=Q applies. Therein, also the torque difference between the first torque Q1 and the second torque Q2 is controlled towards the pre-determined value ΔQ of said torque difference, while maintaining said controlling of said torque addition sum towards said pre-determined constant value Q. As seen in FIG. 1, this is realized in the shown example in that the torque Q1 of the first motor 31 is controlled towards ½Q+½ΔQ, and the torque Q2 of the second motor 32 is controlled towards ½Q−½ΔQ. Accordingly, in the shown example the torque addition sum Q1+Q2 and the torque difference Q1−Q2 are controlled as follows:

Q1+Q2=(½Q+½ΔQ)+(½Q−½ΔQ)=Q, and

Q1−Q2=(½Q+½ΔQ)−(½Q−½ΔQ)=ΔQ.

[0032] It has appeared that, thanks to using this “torque difference control, wherein total torque is kept equal”, a practically realizable and effective corrective flatness control is obtained, wherein a corrective control action has no consequences for band running and band tension of the intermediate cardboard layer, and wherein the pleat and breakage risk of the glued outer layers is minimized.