Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
1999-05-12
2001-02-13
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C356S429000, C427S009000, C118S419000, C162S263000
Reexamination Certificate
active
06188077
ABSTRACT:
The present invention relates to a method of analyzing at least one property of a paper web manufactured in a defined paper machine from which jumbo rolls are supplied.
The invention also relates to a measuring machine for analyzing at least one property of a paper web manufactured in a defined paper machine from which jumbo rolls are supplied.
The manufacture of paper comprises a large number of part processes, each of which affects inter alia the quality of the product. The paper shall have certain properties in accordance with the customer's wishes. Furthermore, the properties shall be constant, i.e. shall lie within defined limits, in order to achieve uniform quality. Although the properties can be specified at the time of ordering, the manufacturer by experience usually believes he knows what the product should be like in order to comply with the wishes of the customer, and the manufacturer then determines internal specifications for the part processes and their parameters in an endeavour to follow these.
However, the information currently available concerning quality properties of the paper supplied by a paper machine is extremely limited. The information is based on the measurement of very small quantities of the paper in a reel for delivery to a customer and it must be assumed that the properties measured in these small, restricted amounts of paper are representative for all the paper in the reel. This circumstance constitutes an essential obstacle to the technical development of paper and paper products.
The measuring system of a paper machine measures less than 0.5% of the total surface of the paper web which is to make up a jumbo roll. Furthermore, the measurement is performed diagonally over the paper web and detailed information disappears since the results are converted to mean values. However, such detailed information is of great significance to the properties of the final product. The properties of the paper are also determined in the laboratory on cut samples representing less than 0.1 per mille of the total area of the paper web which is to make up a jumbo roll.
The object of the present invention is to eliminate the above-mentioned problems.
The method according to the invention is characterized in that a jumbo roll from said paper machine is placed in a measuring machine, that the paper web is conveyed from an unreeling section for the jumbo roll, through a measuring section to a reeling section for winding the paper web to form a new reel, that a first measuring sequence is performed which comprises feeding the paper web in a plurality of steps having the same predetermined length, and measuring said property in the measuring section, when the paper web is stationary, within a web-width measuring area which in the machine direction corresponds, or substantially corresponds to said step length, by scanning traversing a measuring sensor, in order to measure said property from one edge of the paper web to the other within said measuring area, and that the measured values recorded by the measuring sensor are transmitted to a computer unit for processing and conversion of the measured values to a visual form which indicates variations of the property within an area of the paper web defined by said steps. According to a preferred embodiment of the invention the measured values are converted to graphic form, and most preferably are presented by cartogram.
The measuring machine according to the invention is characterized in that it comprises an unreeling section to support and rotatably journalling a jumbo roll from said paper machine, a reeling section for winding the paper web of the jumbo roll to form a new reel and a measuring section situated between them through which the paper web passes, that the measuring section comprises traversing scanners having a measuring sensor for measuring said property, that the reeling section includes drive means for stepwise movement of the paper web through the measuring section, and that the measuring section includes a computer unit for storing the measured values recorded by the measuring sensor and processing these values for visual presentation of variations of the property.
The use of the method and the measuring machine according to the invention entails an advanced total analysis of the paper web which enables a practically complete and two-dimensional representation of the properties of the paper web in a jumbo roll to be obtained with a resolution of 1 cm
2
. The information obtained through the advanced total analysis of the paper web is useful in many contexts.
The information can be used as follows, for instance:
A. For in-house process development. It provides a clearer representation of the function mode of various process apparatus and their interaction than has been possible previously and in this way form the basis for making improvements.
B. For in-house product development. It facilitates opportunities for developing a paper with the properties desired by the customer and creates new possibilities of more accurately and distinctly mapping out and documenting paper properties.
C. For customer process development. It offers customers an excellent basis on which to determine the setting of their conversion equipment and opportunity to improve this.
D. For customer product development. The properties of the paper supplied greatly influence the quality of the customer's final product. The information enables the customer to make better assessments than before, and more clearly inform the supplier what paper properties are required in order to achieve a satisfactory final product.
The invention involves that a comprehensive, fine-scale measurement to be performed of a web-width area until the variation pattern of the properties appear. This comprehensive, fine-scale measurement means that every small surface unit within said web-width area is measured. One such small surface unit for said first measuring sequence, using present-day measuring equipment, is 1 cm
2
.
The values measured are processed directly by a computer unit which presents the result in the form of a topographical map, i.e. a cartogram, preferably coloured, in which each colour represents a certain value of the properties. The cartogram may reveal an undesired irregularity in a measured property which may be caused by errors in the operating parameters set and/or in construction elements of the paper machine from which the paper web under analysis comes. A cartogram over a grammage analysis may, for instance, reveal regularly occurring diagonal larger or smaller areas with increased grammage in comparison with the adjacent areas, which may originate from preparation of the pulp fed to the paper machine. A grammage cartogram showing recurrent round patches in a certain pattern may be caused by deficiencies in the wire section, e.g. the dewatering system. Keeping the pulp in a pulp vessel at the wrong level may result in a grammage cartogram with large patches. A grammage cartogram in which grammage variations appear in a striped pattern may be caused by a pulp pump which is not centred so that small pulses occur in the pulp as it is pumped out of the headbox. Advantageously, the effect of rebuilding a paper machine can easily be verified by comparing cartograms obtained before and after the rebuilding.
The properties that may be of interest for analysis and measurement in accordance with the invention are grammage, thickness, moisture content, ash content, strength and optical properties of the paper web.
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Lind Bengt
Lind Ella-Britt
Allen Stephone B.
Lind Ella-Britt
Nixon & Vanderhye P.C.
Stora Kopparbegs Bergslags AB
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