Paper making and fiber liberation – Apparatus – Running or indefinite length product forming and/or treating...
Reexamination Certificate
2002-05-14
2004-06-22
Fortuna, José A. (Department: 1731)
Paper making and fiber liberation
Apparatus
Running or indefinite length product forming and/or treating...
C162S374000, C162S353000, C162S354000, C162S352000, C162S351000, C162S366000
Reexamination Certificate
active
06752909
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and a system for monitoring a paper machine's drainage element, which includes at least one ceramic.
2. Description of the Related Art
A suction box used in a system for monitoring a paper machine's drainage element is known, for example, from German patent specification DE-PS 233 618 and European patent registration EP 0 831 173 A2 (PB10359 EP).
Not enough rinse water during the start up phase of the machine for manufacturing a fibrous web (especially a paper, cardboard, or tissue web) from a fibrous suspension can lead to overheating of the drainage elements. The resulting thermal load can be particularly damaging when thermal tensions arise in the ceramic, which could lead to a fracture in the ceramic, or when glued points between the ceramic and the main body soften, thereby creating the danger that the ceramic may slide or detach.
In general, there are two different possibilities that could lead to failure of a ceramic:
1. The adhesive remains stable and the ceramic breaks due to the direct thermal load on the ceramic.
2. The ceramic itself would withstand the thermal load, but the adhesive becomes soft and the small individual ceramic plate protrudes in one area progressively into the wire. This leads to a greater thermal load, resulting in fracture.
Of course, a combination of both cases may also occur. For case 1, the temperature is measured close to the surface of the ceramic; for case 2, the temperature is measured on the adhesive point. Due to the constantly increasing machine speeds, even a short period of insufficient cooling, which can never be ruled out under practical operational conditions, could lead to destruction of the ceramic.
Although the article “Auswahlkriterien für Keramik-Beläge in schnelllaufenden Papiermaschinen unter Berüicksichtigung ihres Einflusses auf die Konstanz der Siebpartie”, written by K. D. Fuchs and published in, among other publications, Wochenblatt für Papierfabrikation 23/24, 2000, (pages 1631-1635, especially page 1633, left column) mentions simulation experiments with which thermal elements are used to measure the temperature on the lining surfaces in the wet section (sheet formation unit) and in the press section, the article deals primarily with the criteria for selecting ceramic coatings. Moreover, apparently temperature was measured only on the surface of the ceramic.
SUMMARY OF THE INVENTION
A machine for manufacturing a fibrous web, and, more particularly, a paper, cardboard, or tissue web, from a fibrous suspension, with a sheet forming area in which the developing fibrous web is led by way of at least one porous fabric, especially a mesh screen, over at least one suction box that has a main box that has at least one connection, including a line, to at least one vacuum source. The at least one suction box also has at least one suction box covering that is formed by at least two drainage elements, especially drainage rails, that run laterally to the machine's running direction, border a suction slit, and each of which has one main body and at least one ceramic, whereby preferably each of the at least one suction slits in both edge zones of the fabric is bordered by a format slide that has a main body and at least one ceramic. The term sheet-forming unit includes both a former, for example, a twin-wire former or a hybrid former, as well as a wire section, especially a Fourdrinier wire part.
The present invention provides an improved machine for manufacturing a fibrous web from a fibrous suspension with which is ensured economical and reliable monitoring of the affected drainage elements and with which possible damage is avoided. An advantage of the invention is simple and economical subsequent installation and exchange of temperature sensors on existing drainage elements.
According to the present invention, a machine for manufacturing a fibrous web from a fibrous suspension accomplishes this task with at least one drainage element and/or format slide that exhibits a removable edge piece inside which at least one temperature sensor is integrated.
These temperature sensors can be used to measure the temperature in the ceramic and/or the temperature at an adhesive point between the ceramic and the related main body and/or the temperature in the main body, thereby ensuring economical and reliable monitoring of the affected drainage elements and avoidance of potential damages.
The removable edge piece also creates the ideal condition both for simple and economical subsequent installation of a temperature measurement system as well as rapid and economical exchange of temperature sensors on existing drainage elements.
There are two primary preferred temperature measurement positions. In the first form, the temperature sensor is placed in the ceramic close to the ceramic surface, where the maximum temperature appears, and on any desired position above the section of the width of the drainage element that is wetted by the fabric. The maximum temperature usually appears on edges, where the fabric contacts it or runs off. For this reason, temperature measurement without mechanical contact with the so-called “hot” spot (using infrared for example) is not practical. For this reason, a second promising form involves arranging the temperature sensor in a recess in the ceramic. The recess in the ceramic is normally created before sintering (when the ceramic is still green). The advantage of this method of production is that it does not contribute to internal stresses in the ceramic or in the area around the recess or opening. The recess can be created especially during a molding process.
A temperature measurement is generally practical in the machine's direction of operation only at the following locations:
a) at the beginning and end of a drainage element, for example, at the first and last drainage rails of a suction box,
b) especially where there is a high vacuum and/or a fabric guide with a rail or a lining,
c) in general anywhere there is a high specific pressure of the fabric on the ceramic and/or
d) where there is insufficient lubrication caused by low drainage or the absence of spray water.
Accordingly, a temperature sensor is planned for at least one of the mentioned locations, as needed.
It is also advantageous when several temperature sensors are arranged laterally to the machine's running direction at an appropriate distance from each other. The distance between the measurement points can be approximately 500 mm, for example. Thermocouples are the preferred temperature sensor type because they have historically demonstrated satisfactory price/performance, operational safety and maintenance characteristics.
The preferred material for the main body of the drainage element is glass fiber-reinforced plastic. This type of material has proven its value in the paper industry.
From the perspective of costs and process technology, the ceramic of the drainage element and/or the format slide is shaped like a small ceramic plate and has a height of 1 mm to 10 mm, preferably from 2 mm to 6 mm.
The format slide can be slid laterally relative to the machine's running direction in order to facilitate simple adjustment of the width of an individual suction zone and thereby the suction box's individual suction surface.
The format slide includes either one part or several parts, each preferably with a constant height. Both variations of the format slide can be equipped with at least one height adjustment mechanism, whereby the preferred design of the height adjustment mechanism consists of at least one adjustment screw together with the accompanying locking screw.
In another embodiment, height adjustment can be accomplished through mutual sliding of the format slide with the drainage element. In order to avoid or reduce by the greatest degree possible damage and/or wear to the fabric running over the drainage element, the format slide has an extension that extends in the direction of the middle of the machine and pref
Boden Herbert
Fitzke Helmut
Haase Christoph
Halmschlager Günter
Haunlieb Herbert
Fortuna Jos'e A.
Voith Patent GmbH
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