FI112515B - The thermo roll - Google Patents

Description

112515

The present invention relates to a thermal roller for paper or the like, in particular a calender roll having channels for conveying a heating medium, such as liquid or steam, within the roll.

Generally, the calenders comprise superimposed rolls with a nip formed between them. The calender may comprise one or more pairs of nip forming rolls. The rollers may have a hard or soft surface. The rolls 10 may be unheated or heated thermo rolls. The medium used for heating the rolls may be liquid or vapor, for example, water, steam or oil. The choice of medium depends on e.g. the desired surface temperature of the thermal roll. The web passes through nipples formed by pairs of rollers and with this treatment e.g. the thickness variations of the web are reduced, the surface roughens and the web becomes thinner.

Heating of known thermal rollers is generally arranged by circulating the heated medium inside the roll. The earliest solutions consisted of 20 channels passing through the center of the roll and parallel to the longitudinal axis of the roll. Hot oil or the like was introduced into the duct through one end of the roll and drained out of the roll through the opposite end of the roll.

One known heating of a thermal roller is arranged such that 25 heating media are introduced into the annular region formed between the roll shell and the shaft at one end of the roll. The medium may be led out of the roll at the opposite end of the roll, or may be provided with a passage so that it returns through the center passage of the shaft to the same end of the shaft from which it was led inside the roll.

: 30 The heating of the roll may be arranged around the periphery of the roll casing by means of channels arranged at even intervals parallel to the axial direction of the roll. The ducts are generally 20-60 mm from the surface of the roll and normally have a diameter of 25-50 mm. The number of channels varies from 15 to 50 pendants. In addition to the peripheral passages, the roll has a passageway extending through the center of the roll, along the longitudinal axis of the roll.

2 112515

A solution is also known in which a conical displacement body is inserted inside the duct, which is intended to increase the flow rate of the heating medium in the duct and thereby to equalize the surface temperature of the roll.

The passage of the heating medium may be arranged in the ducts in different ways. In mono-pass type rollers, the medium passes in at one end of the roll and out at the opposite end. In duo-pass type rollers, the medium, usually a liquid, is introduced into the channel inside the roll at one end of the roll and returns to the same end along the second channel connected to the first channel 10. In tri-pass type rollers, the medium first passes to one end of the roll, thence to the other channel, to the other end, and to the opposite channel, from the third channel, from where it was introduced. In Tri-pass II type rollers, the two-channel liquid medium is combined with the third channel, thereby increasing the flow rate of the liquid-15. The liquid returns to the same end from where it was led inside the roll.

Thermal rolls are known e.g. EP 333688, US 4,658,486 and US 4,920,623.

20

Known problems with thermal rollers include uneven surface temperature and unevenness of the roll surface due to uneven heat distribution. The surface temperature of the roll is uneven in both machine and transverse directions. The transverse surface temperature unevenness is due to a decrease in the temperature of the heating medium as it circulates in the ducts. Since, in all known solutions, the channels are parallel to the axial direction of the thermal roll, they are also parallel to the two roll contact points, i.e. the nip line, formed between the thermal roll and its counter roll. The surface of the thermal roller is warmer than where the heating medium passing through the channel is directly below the surface and therefore the thermal expansion at the surface of the roller is different locally. Thus, the shape of the roll becomes angular, which, when periodically repeated, causes vibration and noise. Especially as machine speeds increase and multi-nip calendars become more common, nipple vibration has become a 35 bad problem.

For example, Tri-pass II type rollers have been found to have a machine-to-transverse variation of about 2 µm, which is however sufficient to provide a 3112515 excitation for nipple vibration. Due to the angularity of the roll, the polymer coatings are flattened and the paper is labeled. The medium passing inside the roll also cools as the farther it flows from the source of the warm medium. In known solutions, the flow rate of the medium 5 should be increased with respect to the surface temperature, but the problem arises e.g. medium switch size. The known solutions thus seek to find a compromise between the flow rate of the medium and the uniformity of the surface temperature.

The above-mentioned problems can be reduced with the thermal roller according to the invention. The thermal roller according to the invention is characterized in that the thermal roller comprises channels which form an angle with the longitudinal straight line of the roll passing through the center of the roll.

The thermal roller according to the invention has a more uniform surface temperature than the known solutions. The channels for transporting its heating medium are not parallel to the nip line, whereby the parallel deflections of the roll do not coincide with the nip line.

The uniformity of the surface temperature requires that the channels carrying the heating roller heating media are suitably distributed in the vicinity of the roll surface. Changes in the surface temperature also occur in the axial direction of the roll, so that in order to equalize the temperature throughout the surface, it is also necessary to take into account that the medium releases heat to the roll. 25, and thus cools as it passes through the channels, Usually, the channels are made in a roll so that they are drilled at each end of the roll and the bores meet in the middle of the roll. In this case, the ducts are constant in diameter and extend in a straight line over at least the portion drilled at one end of the roll.

: ·:: 30

In the thermal roller of the invention, the problem of cooling the medium v is solved by drilling the channels obliquely so that the end of the channel from which the heating medium is introduced is farther from the roll surface than the other end of the channel, i.e. the channel distance from the surface decreases. The distance of the individual channels from the surface of the roll at the same longitudinal point of the roll may vary to provide an optimal temperature distribution.

4 112515 The ducts carrying the heating medium are located relatively close to the surface of the roll to provide good heat transfer from the roll to the paper. Thermal expansion at the ducts causes a surface irregularity in the roll surface. If the channels are drilled such that they form an angle with the nip line formed between the two rolls, the shape unevenness is distributed more evenly in the nip. As a result, several channels are continuously passing through the nip line forming an angle with the nip line. Preferably, the angle is from 1 ° to 5 °. The channels can also be drilled in the form of an arrow pattern, whereby the sub-channels drilled at each end of the roll 10 meet at an angle. When the channels are at an angle to the nip line, the distance of the individual channels from the roll surface varies slightly due to the circular surface shape of the roll.

A thermal roller can also be used to solve the problems of both flat surface temperature and thermal expansion. The channels are drilled into the roll casing so that they form an angle with the nip line, and the distance of the individual passage from the roll surface varies depending on its longitudinal position on the roll. In this case, the deformation caused by the channels enters the nip line at an angle and at the same time the distance of the channels 20 from the surface of the roll decreases in the flow direction of the heating medium (except for the distance variation due to the circular

The flow of medium through the channels can be arranged in the same way. 25 as set forth in the prior art section of the application.

For example, the channels whose distance from the surface of the roll decreases in the direction of flow of the heating medium may be connected at one end to similar channels. When the heating medium is introduced into the channels approaching the roll surface in the medium flow direction, at one end they may be connected to the channels which also approach the roll surface in the medium flow direction. In this case, the interconnected: channels are crosswise within the roll and the frozen medium can be i: removed from the roll at the same end of the roll as it is fed in.

"When the arrow 35 in Figures channel arrangement is also possible that each half of the arrow at an angle to the nip line of the individual channels and the halves away from the surface of the heating roller is reduced: ··: tysväliaineen flow direction.

112515

The invention will now be described with reference to the accompanying drawings, in which Figures 1a, 2a, 3a and 4a show a side view of a part of the roll, and Figures 1b, 1c, 2b, 2c, 3b, 3c, 4b, 4c, 4d showing rolls.

Not all details are shown in the illustrations to maintain their clarity. For the same reason, only eight channels are shown in the figures, although the number is generally higher. Figures 1a-1c illustrate an embodiment of the invention in which the distance of the individual channel 1 from the surface of the roll 2 varies. Fig. 1a shows a side view of a portion of the roll 2 and shows that the channels 1 are conically disposed within the shell of the roll 2, i.e. the channels 1 form an angle with the axial straight line L of the roll passing through the center 15 of the roll. The individual duct 1 runs in a straight line within the roll 2 such that the portion of the duct 1 through which the hot heating fluid, generally the oil, enters the duct is farther from the roll surface than the portion of the duct where the heating fluid is colder. Thus, the surface temperature of the rolls 20 of the rolls 20 remains very constant because the colder liquid flows closer to the surface than the warmer one. Fig. 1b shows a cross-sectional AA located near the end from which the hot heating fluid is arranged to flow into the conduit 1. The conduits 1 are then farther from the roll surface than the cross-section BB shown in Fig. 1c, which is near the opposite end of the roll; then the channels 1 are close to the surface of the roll.

Figures 2a-2c illustrate an embodiment of the invention. When the thermal roller 2 and its counter roll (not shown) form a nip through which the paper web or the like passes through the calendering treatment, a nip line extending over the length of the rolls is provided at the point of contact with the rolls, and wider Γ: range when at least one of the nip forming rolls is soft. meäpintainen. The channel 1 shown in Figures 2a-2c is made so that it

': 35 forms a straight line L passing through the center of roll 2

with the nip line formed between the two rollers. In Fig. 2a, a portion of roll 2 is shown in side elevation showing the oblique ducts 1 relative to the nipple. polymer coatings and paper web marking. Figure 5 2b shows a cross-sectional view C-C and Figure 2c a cross-sectional view D-D, showing that the channels pass obliquely inside the roll relative to the nip line and straight through the center of the roll L.

Figures 3a-3c illustrate an embodiment of the invention in which the channels 10 1 form an angle with the nip line and the distance of the individual channels from the surface of the roll 2 decreases in the flow direction of the heating medium. In Figure 3a, a portion of the roll is shown in side view. Figures 3b and 3c show cross-sections E-E and F-F showing that the distance of the individual channels 1 from the roll surface varies and forms an angle with the nip line 15. The cross-section E-E is close to where the heating medium is fed into my duct.

Figures 4a-4d show an embodiment of the invention in which the channel 1 forms an arrow pattern. The arrow pattern has the advantage that the vibration of the roll 2 and the resulting noise are substantially reduced, the channels are easier to meet in the center of the roll, and the error due to the circular shape of the roll at the distance from the roll surface is small. Both halves of the arrow pattern form an angle with the nip line. Figure 4a shows a side view of a portion of the roll 2. Figure 4b shows a cross-sectional view G-G, Figure 4c a cross-section H-H and Figure 4d a cross-section I-1. The cross-sectional images show the angle with which the arrow pattern forms at each nip line.

The foregoing does not limit the embodiments of the invention, but may vary within the scope of the claims. From the embodiments described above, new embodiments may be combined. The heating medium and its direction of passage in the ducts and the interconnection of the ducts may vary as necessary. In addition to heating, the channels described in the application may also be used for transporting a cooling medium, for example in polymer-coated rolls. However, in this case, the distance of the channels from the surface is arranged in a manner suitable for cooling. Some of the channels in the roll may be parallel to the axial direction of the roll. In addition to the calendars 7112515, the thermal roll of the invention can also be used with a press portion of a papermaking machine or the like. The main point of the present invention is that the surface temperature of the thermal roller is uniform and the surface irregularities of the roll surface are uniformly distributed over the nip line so as to cause as few problems as possible in the handling of the paper web or the like.

Claims (4)

112515 A thermo roll (2) for processing paper or the like, in particular a calendar roll having channels (1) for controlling the temperature of the roll. For transporting a female within a roll, characterized in that the thermal roll (2) comprises drilled channels (1) forming an angle with the longitudinal straight line (L) of the roll passing through the center of the roll. Thermal roll according to Claim 1, characterized in that the distance of the channels (1) from the surface of the roll (2) is arranged to decrease in the flow direction of the roll warming medium. Thermal roll according to Claim 1 or 2, characterized in that the channels (1) form an angle with the nip line 15 of the nip between the two rolls. Thermal roll according to Claim 3, characterized in that the angle between the channels (1) and the nip line of the nip between the two rolls is 1 ° to 5 °. 20> *>? · T · «# I * 112 51 &