EP1619303A1 - Calender roll and method for driving a calender roll - Google Patents

Abstract

The channels contain devices (18) differentiating the volumetric flowrate of thermal fluid between them. The device is a constriction; preferably it is an adjustable throttling valve. The device (18) includes a pump. A roller casing (2) end face is connected to a stub shaft (4), the device being located near this connection. The device is an insert (19) in the thermal fluid channel. At the insert location, the channel cross section is enlarged (20) : Volumetric flowrate is differentiated between channels, by +-50% at most. Locations of minimum and maximum heat transfer are set; these rotate with the roller and are displaced by 180[deg]. Thermal medium flowrate differentiation is a function of roller flexure, thus on the inside of the curvature, a greater volumetric flow is passed than on its outside. To carry out compensation, the roller is heated to operational temperature. Its flexure is determined. The volumetric flowrate in the heating channels is then adjusted in order to compensate the flexure, removing it. An independent claim is included for the corresponding method of operation.

Description

The invention relates to a calender roll having a roll shell having a plurality of heating channels, which are distributed in the circumferential direction, and a Heizmittelanschlußanordnung for supplying and discharging a heating means, each Heizmittelkanal is part of a flow path, which is in communication with the Heizmittelanschlußanordnung. Furthermore, the invention relates to a method for operating a calender roll with a roll shell, which has a plurality of heating channels through which one passes a heating medium.

Calenders serve for the calendering of a paper or board web. The web is guided by nips, which are formed by two cooperating rollers. Of these rollers usually carries an elastic cover. This roller is called a "soft roller". The other roller is designed as a hard, smooth roller. It is usually heated, so that the web can be acted upon not only with an increased pressure, but also with an elevated temperature. Heated calender rolls are also used in so-called wide-nip calenders, in which the heated, hard roll interacts with a shoe roll or a circulating belt.

The heating of such a roll is effected by passing a heating means, such as hot water, hot oil or steam, through the heating channels. The heating channels are designed as peripheral bores. In general, two adjacent heating channels are used to first direct the heating means in an axial direction through the roll shell and then back in the adjacent heating channel. Accordingly, the inflow and outflow of the heating medium can be done by a single roll neck.

In some rolls, however, heating not only leads to the desired increased surface temperature, but causes vibrations. This can be observed especially in rolls that are formed of different layers. For example, if a roll mantle comprises a core of chilled casting provided with an outer froth layer of white cast, then it is extremely difficult during the course of manufacture to ensure that each layer has exactly the same thickness in the circumferential direction. After completion of the roll jacket, it is possible to ensure that the roll externally has a cylindrical shape, for example by twisting and grinding. However, this cylinder shape is guaranteed only in the cold state. At an elevated temperature there is a risk that the shape of the roll will change because the individual materials have different coefficients of thermal expansion. If the layers do not have a constant thickness in the circumferential direction, then this may cause the roll to become slightly small sags. This then leads to vibrations during operation, which can lead to considerable problems even at low speeds.

A possible solution to this problem is to heat the roll to operating temperature and to grind it around hot. However, this requires a considerable manufacturing effort. In addition, a wet grinding is not possible when hot, but it must be gefinished consuming with a grinding belt to achieve the desired surface roughness Ra <0.1 microns.

The balancing, are fixed in the additional masses in or on the roller, is not always possible, because in some cases considerable balancing weights must be used with masses of several 100 kg, which also still need to be fixed in the axial center of the roll shell. In addition, a balancing mass is usually suitable only for a certain speed.

The invention has for its object to enable as undisturbed operation.

This object is achieved with a calender roll of the type mentioned above in that at least one flow path has a flow-influencing means which causes a volume flow of the heating means results through this flow path, which differs from the flow rate of the heating means by another flow path.

With this embodiment, it is possible to produce different temperatures in the circumferential direction of the roll shell. The greater the volume flow, i. the mass of heating medium flowing through the heating channel per time is the more heat is supplied to the roll shell in the area of this heating channel. Accordingly, the temperature rises locally here. In another heating channel, a lower volume flow of the heating medium is supplied. Accordingly, only a smaller amount of heat is supplied here and the temperature rises to a lower value. This is not true only when the roller is at rest. The supplied by the different volume flow temperature difference in the circumferential direction of the roll shell rotates with in operation with the roll shell with. By the targeted adjustment of the temperature difference, the deflection can be at least partially compensate, which occurs for other reasons at a higher temperature, for example, by the different material thicknesses of the individual layers of the roll shell. The additional production cost is relatively low. This gives a roller that can work without unbalance and runout during operation. The possible speed range for the operation of the roller is increased compared to a roll balanced only by masses.

Preferably, the flow-influencing device is designed as a throttle. With a throttle to create an increased flow resistance in the flow path. So if you want to conduct through a heating channel less heating, then it is sufficient to arrange a throttle in the flow path, which is part of the corresponding heating channel.

It is preferred that the throttle is designed as an adjustable throttle. An adjustable throttle has an adjustable flow resistance. By an adjustable throttle, the flow resistance can be adjusted relatively accurately to the required size. The throttle can also be adjusted from the outside, e.g. manually or remotely controlled, so that you can set the desired volume flow without disassembly of the roller.

Alternatively or additionally, it may be provided that the flow-influencing device has a pump. With a pump, an increased volume flow through the heating channel can be promoted. It is also possible to arrange a pump and a throttle in series in order, for example, to be able to supply a plurality of heating channels with the same pump, but nevertheless to be able to set the volume flows through the individual heating channels differently. The pump can be supplied in different ways. For example, you can contact without supplying an electrical energy or you can use the supplied heating medium to drive pumps for some heating channels. The energy required to drive the pumps is then removed from a portion of the heating means so that it flows through other heating channels at a lower flow rate.

Preferably, the roll shell is connected at least one end face with a roll neck and the flow-influencing means is arranged in the region of the connection between the roll shell and the roll neck. By a simple disassembly of the roll neck from the roll shell then the flow-influencing device is easily accessible. It can be installed and removed or replaced. An adjustment of the flow-influencing device is easily possible if the roll neck is separated from the roll shell.

Preferably, the flow-influencing device is arranged in an insert. If the roll neck is dismantled from the roll shell, then you have to install only at the desired flow paths a corresponding insert. The size of this insert, i. the external dimensions, can be the same everywhere, even if the flow-influencing device accommodated in an insert is designed differently from insert to insert. This simplifies the production.

It is preferred that the insert is inserted into the Heizmittelkanal. The Heizmittelkanal is easily accessible on the front side of the roll shell.

Preferably, the Heizmittelkanal in the region of the insert on an enlarged cross-section. This has the additional advantage of being used at one stage can lie, which is formed by the cross-sectional reduction of the Heizmittelkanals on its usual cross-section. The insert is thus held with sufficient stability in the heating medium channel.

Preferably, the volume flows in different flow paths differ by a maximum of ± 50%, preferably by a maximum of ± 20%. The different heat supply causes in the circumferential direction of the roller seen a temperature distribution that is not constant. This is desired. Where more heating medium is supplied, a higher temperature is created than where less heating medium is supplied. The temperature differences must not be so great that they lead to a different calendering of the treated web. By limiting the differences in the volume flows to ± 50% or even ± 20%, ie a deviation of an average value by 50% and 20% upwards and downwards, but ensures that the temperature differences on the surface of the roller do not get too big.

The object is achieved in a method of the type mentioned above in that one generates a heat supply, which varies in the circumferential direction between a minimum and a maximum and you can rotate the minimum and maximum with the calender roll.

As stated above in connection with the calender roll, this method produces a thermal Deformation of the roll, which specifically counteracts the deflection caused by the heating of the roll and possibly non-uniform material distributions. Accordingly, the operation of the roller can be made trouble-free.

Preferably, one generates the minimum and the maximum offset by 180 ° to each other. This has the greatest effect in compensating a deflection.

Preferably, depending on a deflection of the calender roll in an initial state, the heating medium is passed through a heating channel with a first volume flow and through another heating channel with a second volume flow, which differs from the first volume flow. In the region of the heating channel with the larger of the two volume flows of the roll shell is heated more and expands accordingly stronger. In this case, one can create a secondary deflection that can be superimposed on the primary deflection that results from the heating of the roll mantle as a whole.

Preferably, a larger volume flow is passed through a heating channel on the inside of the deflection in the initial state than through a heating channel on the outside of the deflection. As a result, the deflection in the initial state is at least partially compensated. The larger volume flow leads to a slight increase in temperature on the inside of the deflection. As a result, the roller expands in the axial direction stronger than on the outside, so that in the initial state (heated roller without different flow rates) occurred deflection is compensated again.

Preferably, the calender roll is heated to an operating temperature, determines a resulting deflection and adjusts the volume flows in the heating channels so that the deflection is formed back. This procedure can be carried out with a stationary or slowly rotating roller. Of course, you can also rotate the roller at operating speeds, even if this is unfavorable. From the deflection one can determine, for example, the different lengths of the roll shell on the outside of the deflection and on the inside of the deflection. This difference in length must now be compensated by different thermal expansions. The required temperatures can be calculated. One can also calculate which volume flow of the heating medium (at a given temperature) is required to reach this temperature. This volume flow can now be predefined by arranging flow-influencing means in the individual flow paths.

Preferably, volumetric flows are generated by the heating channels, which differ by a maximum of ± 50%, preferably by a maximum of ± 20%. In this case, the temperatures are different over the circumference of the roll shell. However, the differences are still within a tolerable range.

Fig. 1

eine schematische Darstellung einer beheizbaren Kalanderwalze im Schnitt I-I nach Fig. 2,

Fig. 2

einen Schnitt II-II nach Fig. 1,

Fig. 3

eine schematische Darstellung des Zusammenhangs zwischen einem Wärmeübergangskoeffizienten α und der Strömungsgeschwindigkeit des Heizmediums,

Fig. 4

eine Temperaturverteilung über den halben Umfang der Kalanderwalze in zwei verschiedenen Betriebsweisen,

Fig. 5

die radiale Verformung der Kalanderwalze in den in Fig. 4 dargestellten Betriebszuständen,

Fig. 6

eine vergrößerte Teilansicht der Kalanderwalze,

Fig. 7

die Ansicht nach Fig. 6 mit einer festen Drossel und

Fig. 8

die Ansicht nach Fig. 6 mit einer veränderbaren Drossel.

The invention will be described below with reference to preferred embodiments in conjunction with the drawings. Herein show:

Fig. 1

a schematic representation of a heatable calender roll in section II of Fig. 2,

Fig. 2

a section II-II of Fig. 1,

Fig. 3

a schematic representation of the relationship between a heat transfer coefficient α and the flow rate of the heating medium,

Fig. 4

a temperature distribution over half the circumference of the calender roll in two different modes of operation,

Fig. 5

the radial deformation of the calender roll in the operating states shown in FIG. 4,

Fig. 6

an enlarged partial view of the calender roll,

Fig. 7

the view of FIG. 6 with a fixed throttle and

Fig. 8

the view of FIG. 6 with a variable throttle.

Fig. 1 shows a calender roll 1 in a schematic longitudinal section. The calender roll 1 has a roll shell 2, which encloses an interior space 3. At both ends of the roll shell 2 is provided with roll necks 4, 5, which also close the interior 3. Each roll neck 4, 5 carries a stub shaft 6, 7, with which the calender roll 1 can be hung in the stiffening of a calender.

In the roll shell 2 are distributed in the circumferential direction more Heizmittelkanäle 8, 9 provided in the form of peripheral bores. The Heizmittelkanäle are connected to a Heizmittelanschlußanordnung 10 in connection, which is formed in the left roll neck 4 (based on the illustration of FIG. 1). The Heizmittelanschlußanordnung 10 has an inlet 11 and a drain 12, which are connected by a rotary feedthrough 13 with a heat source (not shown). Through the inflow 11 heating medium, such as hot water, hot oil or steam, are fed into the Heizmittelkanal 8. After flowing through the longitudinal extent of the roll shell 2, the heating medium flows through an adjacent Heizmittelkanal back to the Heizmittelanschlußanordnung and from there to the outside. The connection of adjacent heating channels 8, 9 takes place in a manner not shown in the right roll neck 5. Due to the steady influx of hot heating means, the calender roll 1 is a total of one brought higher temperature. Surface temperatures of such a calender roll are in the range of 60 ° C to 200 ° C.

If the calender roll 1 has been heated to its operating temperature, then it may occasionally happen that it bends. The deflection is at a calender roll with a length of the roll shell 2 of 7 m, for example, 0.2 mm. This deflection leads to an imbalance, which leads to significant vibration problems during operation.

In order to defuse or even eliminate these vibration problems, the heating medium is no longer conducted uniformly through all the heating medium channels 8, 9, but the volumetric flow of the heating medium is influenced by at least one heating medium channel 8, 9. The effect should be explained with reference to FIGS being represented.

Fig. 3 shows first for three different temperatures of the heating means of 150 ° C, 200 ° C and 250 ° C, the dependence of the heat transfer coefficient α as a function of the speed w of the heating medium. This speed can be equated in first approximation with the flow rate. At a temperature of 200 ° C, the heat transfer coefficient α at a speed of 1 m / s is about 1000 W / m ² K. At a speed of 2 m / s, the heat transfer coefficient α is about 1750 W / m ² K. The faster the Heating medium flows through the Heizmittelkanäle 8, 9, the more Heat is delivered to the roll shell 2 and the more strongly heats up the roll shell in the region of the corresponding Heizmittelkanals 8, 9. This will now be illustrated with reference to FIGS. 4a and 4b.

Fig. 4a shows the surface temperature over half the circumference of the calender roll 1. Shown is a wavy curve, which has its maximum at the points of the surface (seen in the circumferential direction), in which heating medium channels 8 are arranged, through which the heating means of the Heizmittelanschlußanordnung 10th flow away. The minima are located where the heating medium 9 flows back through Heizmittelkanäle. The temperature differences between maximum and minimum are of the order of about 1 ° C.

If you now change the volume flow of the heating medium and, for example, at 0 ° a larger volume flow through the Heizmittelkanäle 8, 9 passes, as at 180 ° (relative to the circumferential angle), and between the flow continuously decrease, then there is a temperature distribution over the Circumference, as shown in Fig. 4b. At 0 ° circumferential angle, the average temperature is about 177 ° C. At 180 ° circumferential angle, the average temperature is about 174 ° C.

The effects can be seen in FIG. 5. Fig. 5a shows the radial expansion of the roll shell in the event that the roll shell 2 is heated uniformly in the circumferential direction. The radial strain at the Top (at 0 ° circumferential angle) is about + 1 mm, represented by a curve 14. The radial expansion at the bottom, ie at 180 ° circumferential angle, is about - 1 mm, represented by the curve 15. The center line of the roller, represented by the curve 16 experiences no displacement. The increase in diameter at the left edge is due to the roll neck 4. This "ox yoke" effect is known per se and will not be explained further here. Fig. 5 shows the corresponding radial expansion only for one half (seen in the axial direction) of the roller.

In Fig. 5b, the situation is now shown when the roll shell heated non-uniformly over its circumference. It can be seen that the curve 14 ', which indicates the radial deformation on the upper side of the roll, ie at 0 ° circumferential angle, increases towards the axial center of the roll by about 1.35 mm. At the bottom of the roller (curve 15 '), the radial deformation is less pronounced than in Fig. 5a. Here, the deformation is only about 0.95 mm. Also, the center line (curve 16 ') deforms by about 0.192 mm, which is almost 0.2 mm, about which the roller would be deformed due to its uncompensated deflection, which would be due to uniform heating.

It can now by a targeted adjustment of the volume flows through the heating channels 8, 9 ensure that results from the non-uniform supply of the heating channels 8, 9 with heating means a temperature distribution, which leads to a deflection of the calender roll. 1 leads, which is opposite to the deflection without additional measures.

This is conveniently done so that the calender roll 1 is first heated to its operating temperature, for example, sets a surface temperature of 175 ° C. The resulting deflection of the calender roll 1 can be determined by measurement. From this deflection results in a difference in length between the outside of the deflection and the inside of the deflection. This difference in length can now be eliminated by heating the roll jacket more strongly on the inside of the bend, thus conducting a larger flow of heating medium through the heating medium passages 8, 9. Since the dependence of the heat transfer coefficient α on the speed or the volume flow is known (see Fig. 3), the volumetric flow, which is required to bring the inside of the deflected roller to the desired temperature, so that the roller again is straightened. The volume flows deviate by a maximum of ± 50%, preferably by ± 20%.

With this procedure, it is only necessary to grind the calender roll 1 in the cold state and to balance.

FIGS. 6 to 8 show how to adjust the volume flow through a heating channel 8.

Fig. 6 shows the roll shell 2 with its roll neck 4. Through the roll neck 4, more precisely through a radial channel 17, heating medium is fed to the heating medium channel 8. Fig. 6 shows a situation in which the heating medium supply is unthrottled. This is the "normal" state, as it is known from heated rolls.

If one now knows that one must lower the Heizmittelstrom by the Heizmittelkanal 2 to a certain value, then you can install a throttle 18 in the Heizmittelkanal 8. Of course, you can install the throttle 18 elsewhere in the flow path from which the Heizmittelkanal 8 forms a part. The position shown in Fig. 7 but is advantageous.

The throttle 18 is formed on an insert 19. The insert 19 is inserted into the end face 20 of the roll shell 2, to which also the roll neck 4 is attached. After disassembly of the roll neck 4, this end face 20 is freely accessible, so that the insert can be inserted into the roll shell 2. For this purpose, the heating medium channel 8 has an increase in diameter 20, which forms a step 21. At the stage 21 of the insert 19 comes to the plant.

FIG. 8 shows a modified embodiment in which a throttle 18 is likewise formed in an insert 19. While the throttle 18 in Fig. 7 is a fixed throttle, the throttle 18 in Fig. 8, an adjustment 22, so that the throttle resistance of the throttle 18 is adjustable. This adjustment can, if necessary, be adjusted from the outside, for example with a suitable tool.

The throttles 18 lead to a reduction in the volume flow through the Heizmittelkanäle 8, 9. In a manner not shown, you can also use a pump that leads to an increase in the volume flow through certain Heizmittelkanäle 8, 9.

Despite the different heating in the circumferential direction, there are no negative effects. The polygon effect has not changed compared to known rolls, which are uniformly heated in the circumferential direction. The temperature difference is obviously so small that there are no differences in the calendering of a paper web.

Claims (15)

Calender roll having a roll shell having a plurality of heating channels distributed in the circumferential direction and a heating means connection arrangement for supplying and removing a heating means, each heating medium channel being part of a flow path communicating with the heating means connection arrangement, characterized in that at least one flow path is one flow-influencing means (18) which causes a volume flow of the heating means results through this flow path, which differs from the volume flow of the heating means by another flow path. Calender roller according to claim 1, characterized in that the flow-influencing device (18) is designed as a throttle. Calender roller according to claim 2, characterized in that the throttle is designed as an adjustable throttle. Calendering roller according to one of claims 1 to 3, characterized in that the flow-influencing device (18) comprises a pump. Calender roll according to one of claims 1 to 4, characterized in that the roll shell (2) is connected at at least one end face to a roll neck (4) and the flow-influencing device (18) in the region of the connection between the roll shell (2) and the roll neck (4) is arranged. Calender roller according to one of claims 1 to 5, characterized in that the flow-influencing device (18) is arranged in an insert (19). Calender roller according to claim 6, characterized in that the insert (19) is inserted into the heating medium channel (8). Calender roller according to Claim 7, characterized in that the heating medium channel (8) has an enlarged cross section (20) in the region of the insert (19). Calender roller according to one of claims 1 to 8, characterized in that the volume flows in different flow paths differ by a maximum of ± 50%. Method for operating a calender roll with a roll shell having a plurality of heating channels through which a heating medium is passed, characterized in that one generates a heat supply which varies in the circumferential direction between a minimum and a maximum and the minimum and the maximum with the calender roll to rotate. Method according to Claim 10, characterized in that the minimum and the maximum are generated offset by 180 ° relative to one another. A method according to claim 10 or 11, characterized in that , depending on a deflection of the calender roll in an initial state, the heating medium passes through a heating channel with a first volume flow and through another heating channel with a second volume flow, which differs from the first volume flow. A method according to claim 12, characterized in that a larger volume flow is conducted through a heating channel on the inside of the deflection in the initial state than through a heating channel on the outside of the deflection. A method according to claim 12 or 13, characterized in that the calender roll is heated to an operating temperature, determines a resulting deflection and adjusts the volume flows in the heating channels so that the deflection regresses. Method according to one of claims 12 to 14, characterized in that one generates volume flows through the heating channels, which differ by a maximum of ± 50%.

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