Method and device for forming at least two paper sheets

Abstract

The invention relates to method for forming at least two different paper sheets from a single paper tambour, comprising the following steps: - measuring at least two parameters of the sheet material (1) of the paper tambour, wherein the at least two parameters are measured in a plurality of regions (1-1, 1-2,..., 1-9) across the sheet material (1), - determining quality indicators based on the parameters using a processing unit, - storing the quality indicators in a memory along with the positional information of the corresponding regions (1-1, 1-2,...,1-9), - comparing the quality indicators with at least two predefined quality requirement profiles in a comparison unit, and selecting regions (1-1, 1-2,...,1-9), - forming at least two different paper sheets (3, 4) by cutting at least one selected region (1-1, 1-2,...,1-9) from the sheet material (1) of the paper tambour using a cutting device. The invention further relates to a device for performing this method.

Description

[0001] Method and device for forming at least two paper sheets

[0002] The present invention relates to a method and a device for forming at least two different paper sheets from a single paper tambour as set forth in the independent claims.

[0003] Modern paper production is a highly industrialized process, with large amounts of paper material being produced in relatively short periods of time. State-of-the-art paper mills produce paper sheets with widths of 4 m and above at a production speed of 400 m / min and above. In a final step of the paper sheet production, the obtained material is wound up to large rolls of material, so-called paper tambours. These tambours are used for intermediate storage of the material; before being delivered to a customer, the tambours are cut up into smaller pieces of sheet material, which then may again be wound up to form product rolls, also called paper reels.

[0004] Due to commonly occurring instabilities in the paper production process, the physical and / or chemical parameters of the sheet material on one paper tambour usually underlie certain variations. Paper parameters such as moisture or basis weight may vary across the lateral extension of the sheet material, or some areas may contain holes or stains, whereas others do not.

[0005] While some deviations of the paper parameters be tolerated by customers, complaints will be provoked if the permissible limits are exceeded. Therefore, it is known in the art that a relevant parameter of the sheet material is measured and only those areas of the paper are processed into product reels, which fulfill the customer’s quality requirements. Regions, which are out of the required range, are discarded as waste.

[0006] However, such practice cannot completely rule out complaints, as other parameters, which have not been considered in the quality control, may not be in line with the customer’s requirements. Additionally, depending on the customer’s requirements, large amounts of paper may be discarded, which reduces productiveness of the paper mill.

[0007] The present invention has been made in view of the above circumstances; it particularly aims at mitigating the conflict of goals involving the desired decrease of waste material, while keeping up the product quality for each customer.

[0008] This goal is achieved by a method and a device according to the independent patent claims.

[0009] In the present invention, the particular fact has been considered that a producer of paper material usually has different customers, which all have different requirements regarding the quality of the supplied paper material. For example, one customer may be very sensitive to stains on the paper surface, but less sensitive to the homogeneity of the material thickness. In contrast, another customer may have lower demands as regards stains, but higher ones concerning material thickness.

[0010] It has now been surprisingly found that these variations in different customers’ quality requirements may be used for the benefit of solving the above-mentioned conflict of goals.

[0011] In the method and the device of the invention, selected parameters of the paper can be measured during or after the production of a paper sheet material. This may be done using measurement devices, which are known in the art, such as a moisture measurement device, a thickness measurement device, or a camera system for detection of surface defects, such as holes and stains. It will be appreciated that a parameter may be directly obtained via the measurement or it may be derived from the measurement. For example, the moisture content of the paper can be directly obtained as a measurement result. In contrast, an example for a parameter derived from the measurement is the number of holes; the measurement itself delivers a photograph of the sheet material; using digital processing, the number of holes is then calculated.

[0012] The parameters are determined along with positional information concerning the region where the measurement has been performed. Such positional information may comprise coordinates, which indicate the measurement position on the sheet material.

[0013] Preferably, each measured parameter is assigned to a certain region on the paper sheet, wherein the region is of fixed position and size. If multiple measurements within a certain region have been performed, the measurement data may be processed for further use, such as by calculating averages from all measurements that have been performed in a certain region. It is preferable that the regions are not overlapping and that each point of a sheet material is assigned to one single region.

[0014] Each of the parameters may then be used to determine a quality indicator for a certain property of the paper sheet. Determining the quality indicators is preferably done by comparing the value of the parameter with at least two given ranges of this parameter. The quality parameter may thus indicate that the value of the parameter is within an acceptable range or if a predefined limit is exceeded.

[0015] The quality indicators therefore are at least binary values, but also more than two states for each quality indicator are possible such as “optimal” if the parameter is within an optimal range, “warning” if the parameter is out of the optimal range, but still within an acceptable range, and “out of limit” if the value even exceeds the limits of the acceptable range.

[0016] The quality indicators may also be numeric values into which the measured parameters are transformed. In certain aspects, the quality indicators may also be unprocessed and identical with the parameters. The location of the regions with their corresponding quality indicators may be stored in a memory. In particular, the analyzed sheet material may be wound up to a paper tambour after all required measurements have been performed with the quality information being available upon request. This way, the tambours with the corresponding quality indicators can be kept until further use.

[0017] The present invention now employs predefined quality requirement profiles which are assigned to each potential customer (also referred to as target or recipient) of the produced paper material or product. The quality requirement profiles contain information in relation each customer’s requirement regarding the paper quality. The information contained in the quality requirement profiles preferably relates to the parameters that have been measured.

[0018] To give an example, the quality requirement profile may contain information regarding a customer’s tolerance towards variations of paper basis weight, paper moisture, and holes in the sheet material, if these three parameters are measured in the method of the invention. The quality requirements represented by two profiles may particularly be different.

[0019] The quality indicators of each region are then compared with the quality requirement profiles and it is determined if a region matches at least one of the profiles. Based on the result of the comparison, each region may be assigned to one customer and the paper sheet may be cut into different sheet areas.

[0020] It will be appreciated that one paper sheet may be composed of a plurality of adjacent regions, without performing cuts between the regions. However, all regions within a single paper sheet should fulfill a certain quality requirement profile. Such sheets may also be referred to as product sheets. The product sheets may be wound up to yield rolls or reels, which then can be delivered to a certain customer.

[0021] Regions, which do not fulfill any of the quality requirement profiles, may be discarded. Recycling of the discarded waste regions may be performed, by re-suspending the paper material and introducing the pulp into the paper mill. An optimization step may be provided, where the number of waste regions and / or the amount of waste material is minimized.

[0022] In summary, using the method and / or device of the invention may allow a reduction of the number of claims by at least 20%. Alternately or additionally, it may be possible to reduce the percentage of waste material by at least 2% in relation to the complete amount of produced paper material.

[0023] Further aspects may be taken into account for assigning the regions to the recipients, such as the amount of material required by a recipient and / or the size of paper sheets required by a recipient. Those aspects may be taken into consideration during an optimization step.

[0024] The invention preferably relates to a method for forming at least two different paper sheets from a single paper tambour, comprising the following steps:

[0025] - measuring at least two parameters of the sheet material of the paper tambour, wherein the at least two parameters are measured in a plurality of regions across the sheet material using a measurement system,

[0026] - determining quality indicators based on the parameters using a processing unit,

[0027] - storing the quality indicators in a memory along with the positional information of the corresponding regions,

[0028] - comparing the quality indicators with at least two predefined quality requirement profiles in a comparison unit, and selecting regions in which the quality indicators are in accordance with at least one quality requirement profile,

[0029] - forming at least two different paper sheets (3, 4) by cutting at least one selected region from the sheet material of the paper tambour using a cutting device.

[0030] It may be provided, that the step of determining the quality indicators comprises:

[0031] - comparing the value of a parameter with at least two associated parameter ranges, and

[0032] - selecting the quality indicator depending on which of the parameter ranges encloses the value of the parameter. It may be provided, that a quality requirement profile comprises information in relation to the quality indicators which are required by a certain target and / or recipient of the paper sheet.

[0033] It may be provided, that one quality indicator is determined from each parameter, and / or wherein two or more parameters are merged to form a merged parameter before determining a quality indicator from the merged parameter.

[0034] It may be provided, that each quality requirement profile reflects the quality requirements of a certain target and / or recipient of the paper sheet.

[0035] It may be provided, that a paper sheet where all regions are in accordance with a quality requirement profile is a product sheet.

[0036] It may be provided, that a product sheet is composed of a plurality of adjacent selected regions.

[0037] It may be provided, that a paper sheet where at least one region is not in accordance with a quality requirement profile is a waste sheet, wherein the waste sheet is discarded and optionally recycled.

[0038] It may be provided, that prior to cutting, an optimization step is performed such that the area of waste sheet is minimized.

[0039] It may be provided, that measuring the parameters is performed in an at least partially unwound state of the sheet material, wherein the sheet material is wound up to a tambour after measuring the parameters, and wherein prior to cutting, the paper tambour is at least partially unwound.

[0040] It may be provided, that after cutting the sheet material, an obtained paper sheet, in particular a product sheet, is wound up to a reel. It may be provided, that the parameters are selected from one or more of the following properties of the sheet material: moisture; basis weight; thickness; opacity; roughness; whiteness; defects, such as contaminations or holes; quantity of chemical substances.

[0041] It may be provided, that the regions are non-overlapping, and / or wherein the regions are of predefined size.

[0042] The invention preferably also relates to a device for forming at least two different paper sheets from a single paper tambour, comprising:

[0043] - a measurement system for measuring at least two parameters of the sheet material of the paper tambour, wherein the at least two parameters are measured in a plurality of regions across the sheet material,

[0044] - a processing unit for determining quality indicators based on the parameters,

[0045] - a memory for storing the quality indicators along with the positional information of the corresponding regions,

[0046] - a comparison unit for comparing the quality indicators with at least two predefined quality requirement profiles, and for selecting regions in which the quality indicators are in accordance with a quality requirement profile,

[0047] - a cutting device for forming at least two different paper sheets by cutting at least one selected region from the sheet material of the paper tambour.

[0048] It may be provided, that the measurement system comprises one or more of the following measurement devices: moisture sensor; weight sensor; thickness sensor; light transmission and / or reflection sensor; camera system; chemical sensor.

[0049] It may be provided, that the processing unit, the memory, and the comparison unit are part of a computing unit.

[0050] Further features of the present invention are apparent from the claims, the drawing and the description of the exemplary embodiment.

[0051] In the following, a preferred embodiment of the method of the present invention will be explained based on a simplified example. The example is merely intended to illustrate specific aspects of the present invention, without being intended to limit the scope of protection, which is solely determined by the patent claims.

[0052] Fig. 1 illustrates by way of example a paper sheet material 1 in unwound state and its way to a plurality of sheet regions obtained by the method of the invention.

[0053] Except otherwise used, the reference numerals in the drawing denotes the following features: Sheet material 1 ; regions 1-1 , 1-2, ... , 1-9; paper sheet 2; product sheet 3; first product sheet 3’; second product sheet 3”; third product sheet 3”’; waste sheet 4.

[0054] In the present exemplary method of the invention, the sheet material 1 is composed of a plurality of virtual regions, only nine of which, namely regions 1-1 to 1-9, are depicted in Fig. 1 . Parameters of the sheet material are measured in each of the regions. The parameters, which are measured in the present example, are paper moisture M, paper basis weight W, and number of holes H. The measurement system of the device to perform this method therefore comprises a moisture sensor, a weight sensor, and a camera system with corresponding data processing device in order to detect holes in the paper sheet.

[0055] All measurements are performed directly after the production of the sheet material 1 in the paper mill, before winding the sheet material 1 up to form a tambour.

[0056] Using the measurement system, the parameters are determined for each of the regions, forming a data matrix containing the parameters of each region along with the positional information of each region. Such data matrix is represented in Table 1 below.

[0057] The parameters moisture M and basis weight B are averages from multiple measurement points within one region, but otherwise used without further processing. The number of holes H is determined from visual images of the regions using a suitable data processing system known in the art, such that the parameter H is a derivative from the actual measurement data. Table 1: Data matrix obtained via the localized measurement of parameters of the sheet material

[0058] The paper sheet is wound up to a tambour until further use, with the data matrix being stored.

[0059] In the next step, the parameters are used to determine quality indicators QI for each of the regions. In order to do this, it is determined if the parameters lie within predefined parameter ranges, wherein each of the ranges corresponds to a certain quality indicator. The scheme, which has been used in the present example, is illustrated in Table 2 below.

[0060] Table 2: Scheme for determination of the quality indicators QI

[0061] The quality indicators QI and the underlying ranges are empirically selected based on the known requirements of different customers. By comparing the parameter ranges of the quality indicators with the parameters measured in each region, respective quality indicators QI for each region can be determined, as illustrated in the matrix of Table 3 below.

[0062] Table 3: Data matrix containing quality indicators for each region of the sheet material

[0063] The obtained data matrix is now compared with the quality requirement profiles of the customers. In this exemplary embodiment, only two potential customers are considered for simplification. The quality requirement profiles of the two customers or recipients of the sheet material are depicted in Table 4 below.

[0064] Table 4: Quality requirement profiles of the potential recipients

[0065] The recipients only accept paper sheets having the above quality indicators QI. Sheets having other quality indicators would be rejected. Recipient A accepts larger variations concerning moisture M and holes H compared to recipient B. However, recipient B is more tolerant towards variations of weight W as compared to recipient A. Now, the data matrix with the quality indicators is compared with the quality requirement profiles. From the comparison, it follows that regions 1-2, 1-3, 1-4, 1-5, 1-6, and 1-8 fulfill the quality requirement of recipient B. Regions 1-2, 1-3, 1-5, 1-6, and 1-9 fulfill the quality profile demanded by recipient A. The remaining regions, namely 1-1 and 1-7 do not fulfill any of the two quality requirement profiles. In Fig. 1 , regions, which fulfill the quality requirements of recipients A and B, are marked using bold solid lines; regions fulfilling the quality requirements of recipient A are marked using dashed lines; regions fulfilling the quality requirements of recipient B are marked using dotted lines.

[0066] Based on the comparison, the regions can be assigned to the respective recipients. During an optimization step, additional requirements can be taken into account, such as the amount of paper material required by each recipient. This way, regions, which fulfill the quality requirement profile of both recipients, can be assigned based on the customers’ actual needs. Additional parameters to be taken into account during optimization may also be the number of cuts required to divide the paper sheet among the recipients, or the number of adjacent regions, which fulfill a certain profile.

[0067] In the present example, the sheet material 1 is cut into five separate paper sheets 2, whereby three paper sheets 2 are product sheets 3. The first product sheet 3’ consists of regions 1-2, 1-5, and 1-7; the second product sheet 3” consists of region 1-4; the third product sheet 3”’ consists of regions 1-3, 1-6, and 1-9. The first and second product sheets 3’, 3” fulfill the quality requirement profile of recipient B; the third product sheet 3”’ fulfills the quality requirement profile of recipient A. Regions 1-1 and 1-7 do not fulfill any of the quality requirement profiles and these regions are therefore waste sheets 4.

[0068] The product sheets 3 are wound up to reels for delivery to the respective customers. The waste sheets 4 are recycled in reintroduced into the paper production process.

[0069] In the example described above, all data processing steps, such as processing the measurement parameters, storing the parameters, determining the quality indicators, comparing the quality indicators with the quality requirement profiles, as well as assigning the selected regions to the recipients, are performed in a single processing device such as a computer.

Claims

Claims1 . A method for forming at least two different paper sheets having different qualities from a single paper tambour, comprising the following steps: a. measuring at least two parameters of the sheet material (1 ) of the paper tambour using a measurement system, wherein the at least two parameters are measured in a plurality of regions (1 -1 , 1 -2, ... , 1 -9) across the sheet material (1 ), b. determining quality indicators based on the parameters using a processing unit, c. storing the quality indicators in a memory along with the positional information of the corresponding regions (1 -1 , 1 -2, ... ,1 -9), d. comparing the quality indicators with at least two predefined quality requirement profiles in a comparison unit, and selecting regions (1 -1 , 1 -2, ... , 1 -9) in which the quality indicators are in accordance with at least one quality requirement profile, e. forming at least two different paper sheets (3, 4) by cutting at least one selected region (1 -1 , 1 -2, ... , 1 -9) from the sheet material (1 ) of the paper tambour using a cutting device.

2. The method according to claim 1 , wherein the step of determining the quality indicators comprises:- comparing the value of a parameter with at least two associated parameter ranges, and- selecting the quality indicator depending on which of the parameter ranges encloses the value of the parameter.

3. The method according to claim 1 or 2, wherein a quality requirement profile comprises information in relation to the quality indicators which are required by a certain target and / or recipient of the paper sheet (3, 4).

4. The method according to any of claim 1 to 3, wherein one quality indicator is determined from each parameter, and / or wherein two or more parameters aremerged to form a merged parameter before determining a quality indicator from the merged parameter.

5. The method according to any of claims 1 to 4, wherein each quality requirement profile reflects the quality requirements of a certain target and / or recipient of the paper sheet (3, 4).

6. The method according to any of claims 1 to 5, wherein a paper sheet where all regions (1-1 , 1-2, ... , 1 -9) are in accordance with a quality requirement profile is a product sheet (3, 3’, 3”, 3”’).

7. The method according to claim 6, wherein a product sheet (3, 3’, 3”, 3”’) is composed of a plurality of adjacent selected regions (1 -1 , 1-2, ... , 1 -9).

8. The method according to any of claims 1 to 7, wherein a paper sheet where at least one region (1 -1 , 1-2, ... , 1 -9) is not in accordance with a quality requirement profile is a waste sheet (4), wherein the waste sheet (4) is discarded and optionally recycled.

9. The method according to claim 8, wherein prior to cutting, an optimization step is performed such that the area of waste sheet (4) is minimized.

10. The method according to any of claims 1 to 9, wherein measuring the parameters is performed in an at least partially unwound state of the sheet material (1 ), wherein the sheet material (1 ) is wound up to a tambour after measuring the parameters, and wherein prior to cutting, the paper tambour is at least partially unwound.11 . The method according to any of claims 1 to 10, wherein after cutting the sheet material (1 ), an obtained paper sheet (3, 4), in particular a product sheet (3, 3’, 3”, 3”’), is wound up to a reel.

12. The method according to any of claims 1 to 11 , wherein the parameters are selected from one or more of the following properties of the sheet material (1 ):moisture; basis weight; thickness; opacity; roughness; whiteness; defects, such as contaminations or holes; quantity of chemical substances.

13. The method according to any of claims 1 to 12, wherein the regions (1-1 , 1-2, ... ,1- 9) are non-overlapping, and / or wherein the regions (1-1 , 1-2, ... , 1 -9) are of predefined size.

14. A device for forming at least two different paper sheets having different qualities from a single paper tambour, comprising: a. a measurement system for measuring at least two parameters of the sheet material (1 ) of the paper tambour, wherein the at least two parameters are measured in a plurality of regions (1 -1 , 1-2, ... , 1 -9) across the sheet material (1 ), b. a processing unit for determining quality indicators based on the parameters, c. a memory for storing the quality indicators along with the positional information of the corresponding regions (1-1 , 1-2, ... ,1 -9), d. a comparison unit for comparing the quality indicators with at least two predefined quality requirement profiles, and for selecting regions (1-1 , 1-2, ... ,1 -9) in which the quality indicators are in accordance with a quality requirement profile, e. a cutting device for forming at least two different paper sheets (3, 4) by cutting at least one selected region (1 -1 , 1-2, ... , 1 -9) from the sheet material (1 ) of the paper tambour.

15. The device according to claim 14, wherein the measurement system comprises one or more of the following measurement devices: moisture sensor; weight sensor; thickness sensor; light transmission and / or reflection sensor; camera system; chemical sensor.

16. The device according to claim 14 or 15, wherein the processing unit, the memory, and the comparison unit are part of a computing unit.

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