DE3525950A1 - Roller for the thermal treatment of a web of material, and the use thereof - Google Patents

Abstract

For treating a web of material, for example for smoothing a paper web, an externally heated tubular roller (1) is used. To reduce the heat flux between the outer surface and the inside of the shell (6), where there are heat-sensitive components (3), the roller shell is built up from a plurality of concentric radial zones (9, 10, 11), at least one of the zones, for example the middle zone (11), consisting of a heat-insulating material of low thermal conductivity. This heat-insulating zone (11) can, for example as a continuous layer, consist of ceramic, porcelain or heat-resistant plastic, or of individual pieces of such material with interposed air- or gas-filled chambers, or of continuous air- or gas-filled grooves or channels, where the latter can be filled by a porous material. <IMAGE>

Description

ROLLER FOR THERMAL TREATMENT OF A

TRACK AND THE USE OF IT The invention relates to a roller for Treatment of a web of material with a tubular roll shell and its use.

In the thermal treatment of webs with such rollers, especially when smoothing paper or cardboard webs, when processing Textile webs or when rolling metal foils, strips or sheets is common a temperature of at least 200 ° C is required on the outer surface of the roller. The heat required to heat up the roll surface can come from outside e.g. be applied with an impingement heater or with one, at least in the Outer zone electrically conductive roll jacket with eddy current heating. the The outer zone of rollers for the uses mentioned must usually have a sufficient hardness and have strength and must generally have a smooth surface. Such rollers are for example made of hard cast iron or made of made of a material with similar properties. As these materials, however usually have a relatively high thermal conductivity in the range of 50 W / m.K, the heat applied to the outer surface of the roll shell penetrates quickly into the roll shell and heats the entire roll to a similar temperature. In principle, however, an extreme temperature only occurs on the outer surface of the roller needed.

In addition, the inside of the roll shell is often temperature-sensitive Components are provided. For example, the rollers are perfect for handling the web is often designed as deflection compensation rollers, where the Roll shell is rotatable around a fixed support and the inner surface of the Roll shell by means of suitable support elements against this carrier with a controllable Force are supported. These support elements can be purely mechanical, magnetic, pneumatic or in a particularly advantageous manner hydraulically against the inner surface of the Roll shell be supported, as for example in US 3 802 044 or a number further patents described. However, such rollers have critical parts on, which as a rule can only be used up to temperatures of 1000 C to a maximum of 1500 C. are, for example, bearings, seals, valves or lubricants. With hydrostatic Support elements a hydraulic pressure medium is also required, i.e. in the case of water under atmospheric pressure, only temperatures below 1000 C are permitted and even with the usual pressure oils a maximum of about 1400 C. The heat dissipation at such deflection compensation rollers with hydrostatic support sources is-moreover predetermined by the pressure medium throughput through the storage pockets of the support elements and cannot be varied freely.

It is therefore necessary that the one penetrating the inside of the roller from the outside To reduce heat flux in order to place the inside of the roll mantle on another, e.g. to maintain a lower temperature that does not exceed the permitted values allowed.

Similar conditions exist when the treatment of a web of material must take place at a low temperature, for example below 0 ° C, since the corresponding Parts of deflection compensation rollers usually only at temperatures above Freezing point work perfectly.

It has already been proposed to overcome these drawbacks execute the entire roller from a poorly thermally conductive material, for example made of ceramic or a porous material. Such materials can, however difficult to process and hardly with the required properties in terms of hardness, Establish strength and smoothness with reasonable effort.

It has also already been proposed to provide channels in the roll shell, in which a coolant or a heating medium circulates and the excess heat energy discharges. In the case of a rotating roll, however, the operation of such a cooling system is constructive very complex and also prone to failure. Also will although the heat flow between the inside and outside of the roller is reduced, it remains the energy consumption of the heating remains high and is sometimes even higher the values without roller cooling.

To eliminate the mentioned disadvantages of the prior art the invention has the task of designing a roller of the type mentioned at the outset in such a way that that even with an increased or decreased temperature of the outside of the roll the temperature inside the roll shell does not exceed the specified operating values or falls below.

According to the invention, the object is achieved in that the roll shell has at least one concentric zone with lower thermal conductivity than at least one other concentric zone.

Through this zone of low thermal conductivity, the heat flow of the outer surface to the inside of the roll shell is reduced so much that the still Thermal energy passing through can be dissipated from the interior without difficulty can, for example, through the natural heat dissipation through the pressure oil when using hydrostatic support elements. The other zones of the roll shell can be made of other materials with higher thermal conductivity, which optimally meet other requirements.

In a particularly advantageous embodiment of the invention, can the roller an outer zone from a hard one Metal with smooth Have surface and a likewise metallic inner zone, the inner surface of which serves as a running surface for hydrostatic support elements, with a heat-insulating Intermediate layer. This intermediate layer can advantageously be made of a solid material with lower thermal conductivity, e.g. consist of ceramic or porcelain Gas or air chambers or a combination of both. Another decrease in Heat transfer can be achieved in that provided in the roll shell Cavities are filled with a fibrous or porous material, so that the influence of thermal radiation and convection is switched off or reduced.

It is particularly favorable between the two metallic tubes to provide heat-insulating intermediate pieces with air gaps, the intermediate pieces are attached to the inner tube by means of an elastic intermediate layer in order to to compensate for different thermal expansions of the different zones.

In a preferred embodiment, the roll shell is made of composed of two concentric parts, being on the outside of the inner one Part in the circumferential direction or helically arranged grooves or Bars are provided that form air chambers when the two parts are assembled are filled with a foam or fiber material.

The webs can be aligned radially, or a little at an angle placed in order to be able to absorb thermal expansion.

The invention is based on the exemplary embodiments shown in the figures explained in more detail. FIG. 1 shows a roller with a heat-insulating intermediate layer, FIG. 2 shows a roller with heat-insulating elements and gas chambers, and FIG. 3 shows one Roller with heat-insulating elements and porous filling, FIG. 4 a roller with inner circumferential grooves, FIG. 5 a roller with gas-filled channels, FIG. 6 a Roller arrangement with impingement flow heating, FIG. 7 a roller arrangement with eddy current heating.

In the roll shown in Figure 1, a roll shell 1 is means Rolling bearings 5 rotatable about a fixed carrier 2 mounted in a frame 4 stored.

The inner surface 6 of the roll shell 1 is by means of a series of radially movable, hydrostatic support elements 3 supported with respect to the carrier 2. Between the support elements 3 and the carrier 2 pressure spaces 7 are formed, which with a suitable pressure medium, e.g.

Oil are supplied so that the support elements 3 against the roll shell 1 are pressed and effect a deflection compensation of the roller. Instead of the shown However, hydrostatic support elements can also support elements other designs can be used, e.g.

hydrodynamic, magnetic, pneumatic or mechanical, by means of Support elements supported by spring force or one or more pressure chambers. Also the The type of storage of the support elements on the inside of the jacket can vary be, for example, as shown, as a hydrostatic bearing with a Pressure medium supplied storage pocket 8 on the storage area 6, or as a classic, hydrodynamic plain bearing or as a roller bearing. Direct storage 5 of the roll shell 1 on the carrier 2 can optionally also be dispensed with, i.e. the roll shell 1 can also only be placed on the carrier by means of the support elements 3 be stored.

In the example shown, the roll shell 1 consists of several concentric ones Zones built. The outer zone 9 consists of metal, for example made of hard cast iron with a hard, smooth surface and sufficient strength. You can use a suitable impingement heating or eddy current heating easily to a required Temperature of 200 - 2500 C can be heated. The inner zone 10 of the roll shell is also made of metal, for example from a steel with high thermal Thermal expansion. The thermal conductivity of the inner and outer zone lies in this in the order of magnitude of 15 or 50 W / m.K. Between the two that conduct heat well Zones is a concentric to these, heat-insulating zone 11 with essential lower thermal conductivity provided to the heat transfer between the outer Zone in the inner zone or vice versa. Suitable Materials for the intermediate zone are, for example, ceramic or porcelain a thermal conductivity of 1 - 5 W / m.K. Also temperature-resistant plastic, for example based on silicone or in the manner of polyimides with an even lower thermal conductivity in the range of 0.2 - 0.5 W / m.K can be used if a slightly lower temperature resistance can be accepted. With a little less heat input, if necessary also a metal or another material with particularly low thermal conductivity can be used as the intermediate layer 11.

It should be noted that instead of providing three zones, also another one Number of concentric zones may be appropriate. For example, a metallic outer zone or a metallic inner zone can be dispensed with, provided The circumstances allow it, i.e. the outer surface is compatible with the material web and the inner surface has sufficiently good running properties for the support elements having. In any case, one of the concentric zones must have a low thermal conductivity exhibit.

In the case of the rollers described above with several concentric The problem with layers of different material is that the different Materials usually show different thermal expansion. It is useful to combine such materials, which taking into account their working temperature have a thermal expansion that is as similar as possible. If this is due to material-technical establish is not possible, it can be advantageous, at least not to design one of the layers with extreme thermal expansion as a continuous layer, but rather as an interrupted zone consisting of separate individual parts.

Figure 2 shows such an example in which the outer metal layer 9 and the inner metal layer 10 are formed as continuous tubes, while the heat insulating intermediate layer 11 consists of individual pieces 18, which between the two tubes 9 and 10 are clamped. Between each ceramic or Porcelain pieces 18 are air- or gas-filled spaces 12, which also has excellent thermal insulation properties and a particularly low one Have a heat conduction coefficient of about 0.03 W / m.K. These pieces can be used as individual blocks or designed as ceramic rings running in the circumferential direction be, or as axially parallel ceramic rods.

The ceramic or porcelain spacers 18 can be on the outside of the inner metal tube 10 by means of elastic intermediate layers 25 made of a suitable temperature-resistant elastomer be attached. So that the different Thermal expansion of the three layers 9, 10 and 11 are balanced and compensated.

The elastic intermediate layer 25 can also be used as a continuous jacket be carried out on the inner metal tube 10.

To avoid being in the air or gas-filled spaces 12 a heat transfer takes place by convection or by thermal radiation, it can, as shown in Figure 3, be expedient through a suitable porous material 13 to be filled, for example by a foam or by a suitable fiber material such as rock wool, asbestos or materials with similar characteristics. At the same time, this example shows that unfavorable Effects of different thermal expansion of the outer zone 9 and the inner zone 10 can be avoided in that the inner zone consists of several, in the axial direction rings 10.1, 10.2, 10.3 and 10.4 lying one behind the other with intervening Sealing rings 14 consists. Each of these rings 10.1-10.4 forms a raceway for a corresponding support element 3.

Figure 4 shows an embodiment in which on a separate Intermediate layer made of solid, heat-insulating material can be dispensed with. Of the Roll shell 1 is made up of an outer tube 9 and an inner tube 10. In the outer surface of the inner tube 10 are circumferential, annular or screw-shaped grooves or grooves 15 screwed or milled, so that only thin webs 19 remain. After making these grooves 15, the two Tubes 9 and 10 inserted into one another and shrunk onto one another, so that the grooves 15 now form good heat-insulating spaces. To improve the effect the grooves 15 can in turn be filled with porous material. Both tubes 9 and 10 can out be made of such material that the problem the different thermal expansion is significantly reduced. The grooves or grooves can also be provided on the inside of the outer tube 9, the effect is equal to. Instead of being oriented in the radial direction, the webs 19 can also be inclined to be so that different thermal expansions of the both pipes 9 and 10 can be collected.

Figure 5 shows a roller in section perpendicular to the axis, the Roll shell 16 consists of a single tube in which in a central zone a plurality of axially parallel bores or channels 17 are provided which in turn can be filled with air or with a porous material. The channels 17 here form the heat-insulating zone of the roll shell. Also plays here the thermal expansion hardly plays a role.

FIG. 6 shows a roller arrangement for the pressure treatment of a web of material 22 at elevated temperature. This arrangement consists of a rotatable roller 23 with a roller tube with a heat-insulating intermediate zone, the surface of which by means of Impingement heating in an air box 20 by means of hot air to a desired temperature, for example 2500 C is heated. The counter roller 24 can be as a solid or as Tube roller can be designed with or without a heat-insulating intermediate layer. By the force acting on the support elements 3 is thereby a Pressure treatment applied at a temperature between 200 and 2500 C.

The web of material can be a paper web and the roller arrangement serve as a smoothing mechanism. However, other applications are also possible, such as pressure treatment a textile web at elevated temperature or the rolling of metal foils or strips.

Figure 7 shows another arrangement, with the heating of the surface the roller 23 by means of an eddy current heater 21, which has a medium frequency in the range e.g. operated between 1 and 5 kHz. To such eddy current heating To be able to use, the outer zone of the roller 23 must be made of electrically conductive material consist, i.e. made of metal, which usually also has good thermal conductivity having.

There are also other methods of heating the outer surface of the roller possible. When treating a web of material with pressure at a low temperature, appropriate Provide measures to cool the outer surface of the roller, e.g. to make it too strong To counteract heating of the rolling stock during the rolling process.

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Claims (19)

Claims 1. Roller for treating a web (22) with a tubular roll shell (1), characterized in that the roll shell (1) at least one concentric zone (11, 12, 13, 15, 17,) with lower thermal conductivity has as at least one other concentric zone (9, 10, 16,). 2. Roller according to claim 1, characterized in that the zone (11, 12, 13, 17,) with lower thermal conductivity between an outer zone (9, 16,) with greater thermal conductivity and an inner zone (10, 16,) with also greater thermal conductivity is arranged. 3. Roller according to claim 1 or 2, characterized in that the Zone (11) with lower thermal conductivity than layer made of ceramic, porcelain, heat-resistant plastic or the like is formed. 4. Roller according to claim 1 or 2, characterized in that the Zone with lower Thermal conductivity of cavities (12, 13, 15, 17,). 5. Roller according to claim 4, characterized in that the zone (11) with lower thermal conductivity between two zones (9, 10) with greater thermal conductivity is arranged and separated by cavities (12), heat-insulating pieces (18) having. 6. folds according to claim 5, characterized in that between the heat insulating pieces (18) and the outer surface of the inner zone (10) a elastic intermediate layer (25) is provided. 7. Roller according to one of claims 4-6, characterized in that the cavities (13, 15, 17) with a porous material such as foam, fiber or the like are filled out. 8. Roll according to one of claims 1 - 7, characterized in that at least one of the zones (10, 11) composed of several individual parts (10.1-10.4, 18) is. 9. Roll according to claim 8, characterized in that between the Parts (10.1, 10.2, 10.3, 10.4), from which a zone (10) is composed, sealing elements (14) are provided. 10. Roll according to claim 4 or 7, characterized in that on the outside of an inner zone (10) grooves (15) are provided, which cavities with lower thermal conductivity. 11. Roll according to claim 4 or 7, characterized in that on the inside of an outer zone grooves are provided, which cavities with form lower thermal conductivity. 12. Roll according to claim 10 or 11, characterized in that the Grooves are separated by webs (19) inclined against the radial direction. 13. Roll according to claim 1, characterized in that the roll shell consists of a tubular part (16) with greater thermal conductivity, in which In the middle zone, longitudinal bores (17) parallel to the axis are provided. 14. Roll according to one of claims 1 - 13, characterized in that that the inside (6) of the tubular roll shell (1) is supported by support elements (3) is supported against a stationary carrier (2). 15. Roller according to claim 14, characterized in that the support elements (3) as radially movable, hydraulic support elements formed are attached to the inside by means of a pressure chamber (7) supplied with pressure medium (6) of the roll shell (1) are pressed. 16. Roll according to claim 15, characterized in that the support elements (3) a hydrostatic bearing surface with at least one bearing pocket supplied with pressure medium (8) which cooperates with the inner surface (6) of the roll shell (1). 17. Use of the roller according to one of claims i -16 for pressure treatment a web (22) at a temperature different from the inside of the roll. 18. Use of the roller according to claim 17 for the pressure treatment of a Web (22) at elevated temperature, the roll shell (1) on a predetermined Temperature is heated and the heated roller (23) with a counter pressure element (24) exerts a certain pressure on the web (22). 19. Use according to claim 18 for smoothing a paper web (22).