EP1645685A1 - Calender roll and method for driving a calender roll - Google Patents

Abstract

A papermaking calendar drum has a mantle (2) incorporating a number of heating ducts (8) at regular intervals and linked to a heat fluid inlet and outlet. The ducts have supplementary temperature regulators (23, 25, 32, 33) with heating elements that facilitate setting different temperatures between the individual ducts. Each individual duct has a temperature regulator coupled to an electrical heating element. The electrical heating element is inductive, microwave or infrared. The temperature regulation system rotates with the calendar drum. also claimed is a commensurate operating process.

Description

The invention relates to a calender roll having a roll shell having a plurality of Heizmittelkanäle 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 having a plurality of Heizmittelkanäle through which directs 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 medium, for example hot water, hot oil or steam, through the heating medium channels. The Heizmittelkanäle are formed as peripheral holes. In general, two adjacent Heizmittelkanäle be used to first direct the heating medium in an axial direction through the roll shell and then back in the adjacent Heizmittelkanal. 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 similar problem also arises in rolls whose shell is formed only of a material, such as steel (KSTV). If the jacket has peripheral holes whose distance from the surface is not the same everywhere, a difference of 1 mm in the distance to the surface can cause a temperature difference on the surface of a few ° C, for example 6 ° C, for a bad heat conductor such as KSTV. Basically, any temperature distribution which is non-uniform on average over the circumference poses the risk of thermally induced deflection, which leads to a tendency to vibrate.

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 sometimes considerable balance weights with masses of several 100 kg must be used, which are also still attached in the axial center of the roll shell have to. 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 in a calender roll of the type mentioned above in that at least one flow path has a tempering, which sets the temperature of the heating means through this flow path to a different value than the temperature 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 temperature of the heating medium, the more heat is supplied to the roll shell in the region of this heating medium channel. Accordingly, the temperature rises locally here. In another Heizmittelkanal heating medium is supplied at a lower temperature. 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 caused by the different temperatures difference in the circumferential direction of the roll shell rotates with in operation with the roll shell. By selectively adjusting 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 tempering rotates with the roller. Thus, a temperature distribution is generated in the circumferential direction of the roller, which rotates with the roller. A return deflection of the roller produced by the temperature distribution is thus maintained.

It is also advantageous if the tempering device acts on an inlet to the propellant channel. This has the advantage that practically over the entire length of the Heizmittelkanals the heating means with the increased or lowered temperature is supplied. This keeps stresses that may be generated by uneven temperature distribution in the axial direction small. In addition, there is usually more space available in the area of the inlet. The inlet is often designed as a radial channel in the roll neck. You can now modify the roll neck accordingly and provide the heater there without having to engage excessively in the structure of the roll shell.

Alternatively or additionally, however, it can also be provided that the tempering device is applied to a section the Heizmittelkanals acts. If necessary, this section can also cover the entire length of the heating medium channel. Such a training is particularly recommended if you want to ensure at longer rolls that the temperature differences between the beginning of a Heizmittelkanals and its end are not too large.

In an advantageous embodiment, the tempering device is designed as a heating device. In addition, heat is supplied to the heating medium in order to locally increase the temperature of the roll shell in the circumferential direction. In many cases, it is easier to increase a temperature by a heating device than to lower a temperature by a cooling device.

The heating device preferably has an ohmic heating resistor. In an ohmic heating resistor, a higher temperature is simply generated by passing electrical current through it. This stream can be adjusted easily. With the adjustment of the current can influence the desired increase in temperature take.

It is preferred that the heating resistor flows around the heating medium. The heating resistor is thus within the heating medium. In this way, the heat supplied is completely absorbed by the heating means, so it is not lost in the environment.

Alternatively or additionally, the heater may include an inductive heater that acts on material that limits the flow path. An inductive heater typically operates on alternating current and generates a magnetic field, which in turn generates eddy currents in conductive materials. By using such conductive materials to confine the flow path, one can heat the walls of the flow path and thus also the heating means.

In a further alternative or additional embodiment, the heating device may have a microwave heating. A microwave heating acts directly on the heating means, which should be liquid in this case. In particular, when used as heating medium water, can be with a microwave heating cause a relatively rapid and accurate increase in temperature.

Finally, it is also possible that the heater has an infrared heater. An infrared heater works with radiation. For example, one can arrange such a radiation source within a heating medium channel or at its beginning. The radiation then heats the heating medium flowing through and the surrounding areas of the flow path in the desired manner.

It is also advantageous if the flow path has a flow-influencing device, the heat transfer from the heater to the heating means affected. For example, the flow-influencing device may generate turbulence. These turbulences can be used to actually allow as much of the heating means as possible to come into contact with hot surfaces of the heater. In addition, one can influence the flow rate of the heating medium with such a flow-influencing device. The flow rate in turn affects the heat transfer from the heating means to the roll shell.

Preferably, the flow-influencing device is adjustable. By adjusting the device so you can change the heat transfer from the heater to the heating means and the heating means on the roll shell so that there is the desired temperature distribution in the circumferential direction of the roll shell. This temperature distribution leads to a deflection, which counteracts the "natural" deflection of the roll, which results from an uneven distribution of material.

The object is achieved in a method of the type mentioned fact that one generates a heat supply, which varies in the circumferential direction between a minimum and a maximum by tempering the heating means in different Heizmittelkanälen different, and the minimum and maximum with the calender roll to rotate.

As stated above in connection with the calender roll, this procedure 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 medium channel at a first temperature and through another heating medium channel at a second temperature different from the first temperature. In the area of the heating medium channel with the higher temperature 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, by a Heizmittelkanal on the inside of the deflection in the initial state heating means at a higher temperature than by a Heizmittelkanal on the outside of the deflection. As a result, the deflection in the initial state is at least partially compensated. The higher temperature of the Heating means leads to a slight increase in temperature on the inside of the deflection. As a result, the roller expands more in the axial direction than on the outside, so that in the initial state (heated roller without different volume flows) occurred deflection is compensated again.

Preferably, the calender roll is heated to an operating temperature, determines a resulting deflection and adjusts the temperatures in the Heizmittelkanälen so that the deflection is regressed. 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. It is also possible to calculate which temperature of the heating means (at a given flow rate) is required to reach this local temperature of the roll. This temperature can now be determined by arranging temperature-influencing means in the individual flow paths, for example a heating or cooling device, a heating device being preferred.

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

verschiedene Ausführungsformen von Temperiereinrichtungen in einer Walze,

Fig. 4

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

Fig. 5

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

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

various embodiments of tempering devices in a roller,

Fig. 4

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

Fig. 5

the radial deformation of the calender roll in the operating conditions shown in Fig. 4.

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 in the form of peripheral holes intended. 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 Heizmittelkanälen 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 brought to a higher overall 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, now the heating medium, which by the Heizmittelkanäle 8, 9 flows, additionally influenced by a temperature control, which may have different configurations. These different embodiments are shown in Fig. 3a to 3e. In each case a single type of tempering device is shown in each figure. However, it is readily possible to combine several or even all types of tempering with each other, if necessary or should be favorable.

Elements which correspond to those of Figs. 1 and 2 are provided with the same reference numerals.

Fig. 3a shows first a radial channel 17, is supplied by the heating means from the heating medium connection 10 to the heating medium channel 8. In this radial channel 17, an ohmic resistor 23 is arranged, which is supplied via a supply device 24 with a predetermined electrical current and a predetermined electrical voltage. The supply device 24 in turn receives its electrical energy via a feedthrough not shown, which is guided for example by the roll neck 4 and the stub shaft 6.

When current flows through the ohmic resistor 23, its temperature increases. Accordingly, the ohmic resistor 23 outputs heat to the heating means flowing through the radial passage 17 to the heating medium passage 8. The temperature increase does not have to be excessively large. A temperature increase of, for example, 5 to 10 ° C is readily sufficient, as will be explained below.

Of course, such an ohmic resistor 23 can also be supplied without contact from the outside with electrical energy. For this purpose, the supply device 24 may be formed, for example, as a secondary side of a transformer and arranged in the stub shaft 7, on the outside of which then the primary side of the corresponding transformer is arranged.

In FIG. 3 a, the ohmic resistor 23 is arranged in the radial channel 17. But it is also possible to arrange the ohmic resistor 23 in the heating medium channel 8, as shown in Fig. 3b. Again, the ohmic resistance 23 is in the midst of the Heizmittelstromes so that it can deliver the heat that he generates virtually completely to the Heizmittelstrom.

An insert 19 is inserted into the heating medium channel 8 at the end face of the roll mantle 2. After disassembly of the roll neck 4, this end face 20 is freely accessible, so that the insert 19 can optionally be replaced. The insert 19 abuts against a step 21, which is formed by an increase in the diameter of the heating medium channel 8. In the insert 19, a flow-influencing device in the form of a throttle valve 22 is arranged. With the help of the throttle valve 22, which is shown here only schematically, it is possible to selectively supply the heating means to the resistor 23. It may be enough to simply swirl the heating means in the region of the ohmic resistor 23, so that one can ensure that as much heating means as possible actually comes into contact with the ohmic resistor 23. A heat transfer by heat conduction in the heating means is then required only to a lesser extent.

FIG. 3 c shows a further alternative, in which the heating device is formed by an inductive heater 25. The inductive heating 25 has two coil pairs 26, 27, which are supplied with an alternating voltage. The frequency of this AC voltage is adjustable. The roll shell 2 is electrically conductive. Accordingly, the alternating magnetic field generated by the coils 26, 27 generates eddy currents in the roll shell, which lead to a heating of the roll shell and thus to a heating of the liquid flowing through the Heizmittelkanal 8. The heating by eddy currents can be locally controlled relatively accurately, so that here also targeted a temperature increase can be made by heating the heating medium at certain positions in the circumferential direction of the roller.

Fig. 3c shows that in the vicinity of the radial channel 17, a corresponding coil assembly 28, 29 may be provided, so that the heating means can be heated when flowing through the radial channel 17 already.

The inductive heating with its coils 26-29 is shown here only schematically. To accommodate the coils here, one will edit both the roll shell 2 and the roll neck 4 accordingly, for example, provided with recesses for receiving the coils 26-29.

FIG. 3d shows a further possibility for heating the liquid flowing through individual heating medium channels 8. Provided here is an ultrasonic generator 30, which acts on the radial channel 17 by flowing liquid, such as water. The ultrasound generator 30 interacts with a second transmitter 31. Both transmitters together form an ultrasonic heater 32. The ultrasonic heater 32, in a manner known per se, causes liquid molecules to oscillate and thereby leads to an increase in the temperature of the liquid flowing through. This temperature increase is specifically limited to individual Heizmittelkanäle 8, so that one obtains a non-uniform temperature distribution over the circumference of the roller.

FIG. 3 e shows a further possibility of heating the liquid flowing through within individual heating medium channels 8. Provided is an infrared heater 33, for example an IR emitter, which acts on the heating medium channel 8 flowing through the liquid.

As mentioned above, all heaters can be combined. It is also possible to use a cooling device instead of a heating device in order to locally lower the temperature of the heating medium in certain heating medium channels 8, 9. The effects of such Heater devices (or cooling devices) are considered below regardless of the type of heater.

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.

Now, if you change the temperature of the heating medium in individual Heizmittelkanälen and, for example, at 0 ° heating medium at a higher temperature by the Heizmittelkanäle 8, 9 passes, as at 180 ° (relative to the circumferential angle), and between the temperature of the heating medium steadily decreases, 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 be ensured by a targeted adjustment of the temperature of the heating medium in the Heizmittelkanälen 8, 9 that results from the non-uniform heat supply of Heizmittelkanäle 8, 9, a temperature distribution, which leads to a deflection of the calender roll 1, 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 mantle more strongly on the inner side of the deflection, ie, it conducts heating means at a higher temperature through the heating medium channels 8, 9. Thus, the heaters are arranged in heating medium channels which lie on the "inside" of the uncompensated concave bend.

As shown above, the necessary temperature differences are not large. One can therefore produce them within the roll by means of suitable heating devices. Of course, a temperature difference can also be generated by cooling the heating means at certain circumferential positions.

Claims (17)

Calender roll having a roll shell having a plurality of Heizmittelkanäle 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, characterized in that at least one flow path Tempering device (23, 25, 32, 33), which sets the temperature of the heating means through this flow path to a value other than the temperature of the heating means by another flow path. Calender roller according to claim 1, characterized in that the tempering device (23, 25, 32, 33) rotates with the roller (1). Calender roller according to claim 1 or 2, characterized in that the tempering device (23, 25, 32, 33) acts on an inlet (17) to the heating medium channel (8). Calendering roller according to one of claims 1 to 3, characterized in that the tempering device (23) acts on a portion of the heating medium channel (8). Calender roller according to one of claims 1 to 4, characterized in that the tempering device (23, 25, 32, 33) is designed as a heating device. Calender roller according to claim 5, characterized in that the heating device has an ohmic heating resistor (23). Calender roller according to claim 6, characterized in that the heating resistor (23) flows around heating means. Calender roll according to one of claims 5 to 7, characterized in that the heating device has an inductive heater (25) which acts on material which limits the flow path. Calendering roller according to one of claims 5 to 8, characterized in that the heating device has a microwave heater (32). Calendering roller according to one of claims 5 to 9, characterized in that the heating device has an infrared heater (33). Calender roll according to one of Claims 5 to 10, characterized in that the flow path has a flow-influencing device (22) which influences a heat transfer from the heating device (23) to the heating means. Calender roller according to claim 11, characterized in that the flow-influencing device (22) is adjustable. A method of operating a calender roll having a roll shell having a plurality of heating medium 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 by varying the heating means in different Heizmittelkanälen differently , And you can rotate the minimum and the maximum with the calender roll. Method according to Claim 13, characterized in that the minimum and the maximum are generated offset by 180 ° relative to one another. A method according to claim 13 or 14, characterized in that , in dependence on a deflection of the calender roll in an initial state, the heating medium is conducted through a heating medium channel at a first temperature and through another heating medium channel at a second temperature different from the first temperature. A method according to claim 15, characterized in that one passes through a Heizmittelkanal on the inside of the deflection in the initial state heating means at a higher temperature than through a Heizmittelkanal on the outside of the deflection. Process according to Claim 15 or 16, characterized in that the calendering roller is heated to an operating temperature, a resultant deflection is determined and the temperatures in the heating medium passages are adjusted so that the deflection is restored.

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