Winding – tensioning – or guiding – Unwinding – With detector – indicator – or control
Patent
1996-09-26
1998-06-23
Nguyen, John Q.
Winding, tensioning, or guiding
Unwinding
With detector, indicator, or control
242534, B65H 2600, B65H 1808, B65H 4300, B65H 6300
Patent
active
057693536
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present application relates to a method of initiating the premature replacement of a material web, especially a paper web, that is unwound from a spool.
2. Description of the Prior Art
The term "spool" refers here to reels and winding cores of cardboard or metal.
In all winding processes, especially in the paper industry, larger and larger rolls are striven for. This is true of both diameter and width. However, winding technology runs into physical limits, which make it impossible to completely utilize the wound web material. Inside the rolls, i.e., in the so-called core region, defects such as web tears, core breaks and crepe folds occur directly on or directly above the spool. These phenomena are referred to hereinafter as "faults." Faults are all the more difficult to deal with because the statistical frequencies with which they occur fluctuate sharply.
This results inevitably in web breaks in downstream processing machines, accompanied by shutdowns and material losses. For safety reasons, therefore, not all of the material on a roll is subjected to further processing. Instead, a considerable quantity of leftover paper is left on the spool and must be recycled as spoilage.
As Juehe reports in the German reference "Practical Experiences in Producing Wide Gravure Printing Rolls with a Large Diameter" ("Praxiserfabrungen bei der Herstellung breiter Tiefdruckrollen mit grossem Durchmesser") in Paper (Das Papier) Vol. 45, 1991, No. 10a, pp. V73-V78, attempts have already been made to make the faults, e.g., winding folds and ridges, that occur during winding visible to the human eye by means of stroboscopic lighting. Nonetheless, a significant number of large rolls continue to be wound around clinic rollers for control purposes, in order to obtain information on the possible presence of faults whose development has not been detectable from the outside. The aforementioned reference also indicates that "problems near the spool (core breakers)" evidently do not arise until the web material is unrolled, and thus cannot be detected during winding.
Temperature changes discovered during the unwinding of a large reel (namely, a systematic temperature increase near the reel core, resulting from pressure change) as well as bending stresses and sliding movements detected in the core have led to the idea of developing another test and assessment process for winding technology. The characteristics of winding quality mentioned in the above article include roll hardness, roll structure, roll surface and roll shape (p. V76, right-hand column). An impetus to develop a method to detect existing faults is not found in this reference.
SUMMARY OF THE INVENTION
The present invention is based on the object of providing a process that permits the early detection of faults occurring in the core region during the production of rolls having large diameters and large web widths, especially in the paper industry, so that it is possible to manufacture large rolls that can be utilized up to the point of their physical winding limits and to minimize the number of remnant layers that must be left on the spool.
The inventors have realized that certain temperature phenomena can occur inside a certain area of the paper web layers located next to the spool. These phenomena allow the early recognition of faults to be exploited and permit a roll change to be initiated before the faults cause a rip in the web. The temperature phenomena in question are measurement points or areas with temperatures raised by a few tenths of a degree C. These hotter points or areas are not to be confused with the ring-shaped temperature phenomena also observed in the central region. These ring-shaped areas are higher in temperature than the web layers located farther from the spool.
Utilizing this newly obtained knowledge, the invention therefore suggests, in order to attain the stated object, a process for initiating the premature replacement of a web to be unwound from a spool, especially a paper web, whi
REFERENCES:
"Das Papier" Oct. 1991, pp. 73-78, H.H. Juhe, Praxiserfahrungen mit Grossen Durchmesser.
Juhe Hans-Helmut
Rauhut Matthias
Nguyen John Q.
Stora Feldmuhle AG
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