FI120216B - Method for lubricating a paper / board or finishing machine's bend-compensated heated roller - Google Patents

Description

A method for lubricating a deflection compensated heated roll of a paper / board or finishing machine

The present invention relates to a method for lubricating a deflection-compensated heated roll of a paper / board or finishing machine, which roll includes an inner shaft having a cylindrical center portion having an axial pin at each axial end surrounded by a radial clearance in the outer casing at its axial ends, radially inwardly extending end flanges disposed about a counter-axis pivot in which the heating medium is recirculated from the outside of the roll through the inner axis of the inner shaft to the inner periphery of the inner shaft and to the inner periphery of the outer shell; back to the outside of the roll, wherein the roll has been bombarded on the outside of the center of the inner shaft or the inner surface of the outer shell, whereby the inner surface of the roll outer shell settles under contact with the inner with the outer surface of the shaft substantially throughout its axial length.

In many parts of a paper / board or finishing machine, the rolls of the machine become loaded so that the load causes the rolls to bend. In the case of nip rolls, the deflections affect the uniformity of the nip load and, in the case of the guide rolls, the uniformity of the tension of the controlled web. The guide rollers are used e.g. guiding the metal belt of the fibrous web, fabrics and the metal belt calender.

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In cases where the deflections become excessive, the deflections should be compensated to reduce uneven loading. The known technique is to use the so-called. deflection compensated rolls, or simply use bombing on rolls, wherein the roll diameter profile corrects the load difference caused by the roll deflection line. However, bombardment cannot be used on a guide roll of a tissue or metal belt, since the surface speed differences produced by the difference in diameter on the roll cause rapid wear of the tissue or metal belt. A so-called "paperboard" fabric has been developed for paper machine fabrics. a center-supported roller having a roller divided into an inner shaft and an outer jacket, and the outer jacket being supported centrally to an inner shaft. In this case, the outer sheath bends under load-5 so that the difference in tension caused by the deflection of the other rolls is offset.

However, the belt guide rollers of the metal belt calender cannot be made as centrally supported rolls because the belt load is too high and the rolls need to be heated. This is solved by making the roll so that it is divided into an inner shaft 10 and a shell and the outer surface of the inner shaft or the inner surface of the shell is bomb-shaped. In this case, the outer shell of the roll rolls freely on the surface of the inner shaft and, when loaded, due to the deflection of the inner shaft, the outer shell over its entire axial length contacts the inner shaft. In the volume between the shaft and the sheath, a medium for warming the roll, preferably a heat transfer oil, passes.

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Figure 1 shows one such deflection compensated roll as disclosed in the applicant's previous Finnish patent application FI20065824. The roller 10 comprises an shaft 12 formed by a cylindrical center portion 12c and center shaft 12c at each end of shaft 20s 12a, 12b mounted on end bearings 13a, 13b. The central portion 12c of the shaft 12 is bombarded and fitted with a cylindrical jacket 11 supported at both ends by end pieces 20a, 20b to the ends of the central portion 12c of the shaft 12. Each end piece 20a, 20b is secured by bolts 21b to the ends of the sheath 11. Each end piece 20a, 20b 25 is further sealed with seals 31a, 31b to the end of the housing 11 and seals 30a, 30b to the shaft pin 12a, 12b. Each end piece 20a, 20b is disposed around the shaft pin 12a, 12b such that the fitting permits a small amount of radial movement. The end pieces 20a, 20b move with the shell 11 slightly radially relative to the shaft pins 12a, 12b in a situation where the shell 11 30 is subjected to external loading.

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A first passage 40 is formed through one end of the roll pin 12b of the roll 10, extending axially spaced from the opposite end of the roll end end 20a, where it branches into a plurality of radial passageways 41. These radial passageways 41 extend into the space 12c of the shaft . In addition, a second channel 50 is formed through the shaft pin 12b which surrounds the first channel 40 and extends axially inside the end piece 20b at the shaft pin 12b, where it branches into radial channels 51. These radial channels 51 also open to the center portion 12 of the shaft 12c. mode. Along the first passage 40, oil can be supplied to the space 42 between the center 12c of the shaft 12 and the shell 11 near the opposite end piece 20a, from where the oil is led back through the grooves on the outer surface of the center 12c to the end piece 20b. The first passageway 40 may 15 consist of a tube.

The roll 10 becomes or pum compensated as a result of bombardment of the center 12c of the shaft 12. In the unloaded condition, the inner surface of the sheath 11 is attached to the outer surface of the central portion 12c of the shaft 12 at the center of the central portion 12c, but the ends of the central portion 12c have a small gap between the inner surface of the shell 11 and the outer surface of the central portion 12c. When the roll shell 11 is externally loaded, e.g. with another roll, the center 12c of the shaft 12 begins to deflect from the center and at a given load the deflection of the inner shaft is such that the inner surface of the outer shell 11 abuts the outer surface 25 of the center shaft 12c. The roll bombardment may be dimensioned such that the outer surface of the sheath 11 becomes straight under the desired loading conditions.

The surface velocity of the roll is constant, since the sheath can be manufactured in the form of tubes of 30 diameters in diameter. This prevents slipping between the outer surface and the metal belt contact. Instead, the contact between the inner surface of the sheath 11 and the outer surface of the inner part 12 4 of the inner shaft 12 causes slippage due to bombardment and this contact requires lubrication. As the process requirements require that the roll be heated to temperatures above 200 ° C, the lubricity (viscosity) of the heat transfer oil is not good enough.

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It is an object of the present invention to provide a method for reliably lubricating the contact between the inner surface of such or puma compensated roll shell portion and the outer surface of the inner shaft. To achieve this object, the process of the invention is characterized in that the process utilizes a heating medium to which a solid lubricant has been added.

The heating medium used for the heat transfer, preferably the oil, is further admixed with a solid lubricant which is mixed with the oil in powder form. The concentration of additive 15 is 1-5% by volume. Tungsten disulfide (WS2), molybdenum disulfide (MoS2) or graphite powders may be used as additives. In the export-front situation, the lubricant in the oil is rolled onto the rolling surface, filling the surface roughness volume, thus preventing the occurrence of a limit lubrication. In addition, a thin film of lubricant with low shear strength is formed on the surface. The lubricant film on the surface of the slip is sheared at the hips and the shear strength of the inner shaft and sheath material is thereby not exceeded. The additive detached from the surface drifts back into the oil cycle and the substance in the oil cycle re-adheres to the surface upon rolling contact.

25 Em. lubricants are chemically inert to very high temperatures where they do not affect the properties of the base oil. Nor are they soluble in oil, but remain small particles in the oil. For this reason, it is preferred that the particles have a small size, preferably less than about 1.5 microns. However, in the case of an oil heating system, the insoluble matter of the particles does not pose a problem since the system preferably does not contain a reservoir where the particles can be separated from the oil but the oil circulates continuously in the system. However, pipeline design should take into account that the pipeline will not be constructed with downward facing branches with low flow rates, e.g. less than about 0.2 m / s. In these situations, solid particles can settle to the bottom of the tube and can cause the tube to become clogged and, in addition, the lubricant content of the oil decreases.

Claims (4)

6 A method for lubricating a deflection compensated heated roll of a paper / board or finishing machine comprising an inner shaft 5 (12) having a cylindrical center portion (12c) having at each axial end a shaft pin (12a, 12b) surrounded by a central portion radial play, the outer jacket (11) having at its axial ends radially inwardly extending end flanges (20a, 20b) disposed about a respective shaft pin (12a, 12b), in which the heating medium 10 is circulated from the outside of the roll through the inner heating medium 40, 41) into the heating medium space (42) between the outer surface of the inner shaft center and the inner surface of the outer shell, and back to the inner shaft inner face (51) and back (50) to the outer rotation of the inner core shaft (12c) or the outer shell (11). brewed, with the inner casing of the roll outer casing The device in contact with the outer surface of the inner shaft, when loaded, contacts substantially the entire axial length, characterized in that the method uses a heating medium to which a solid lubricant has been added. Method according to claim 1, characterized in that the solid lubricant is added in powder form. Process according to claim 1 or 2, characterized in that the lubricant is selected from the group consisting of tungsten disulfide (WS2), molybdenum disulfide (MoS2) and graphite powder. Method according to one of Claims 1 to 3, characterized in that the solid lubricant is added in an amount of 1-5% by volume of the heating medium. 7