EP0440140A2 - Roll for smoothing apparatus or calender - Google Patents

Abstract

The present invention proposes a roller (10) for smoothing units or calenders, which is provided with one, preferably with two, in particular screwed-on pins (2a, 2b) and a roller body (1), and a closed central inner bore with an enlarged diameter having; a liquid heat transfer medium is passed through the roll in peripheral channels (6) near the roll surface; and near the central bore, which is enlarged in diameter, further axial bores (7) of small diameter are provided, through which the heat transfer medium is guided, for example to the one spigot, which is usually the inlet spigot, flows back and is disposed of from the roller to be tempered externally again.

Description

The present invention relates to a roller for a calender or a calender according to the preamble of claim 1.

Such rollers are used for the production and processing of material webs, in particular for smoothing paper webs. Rolls of large dimensions in which a heat transfer medium is guided through bores (peripheral bores) running directly below the surface of the roller body are becoming increasingly important in recent times. This makes it possible to keep the path of heat from the heat transfer medium to the roll surface through the roll wall short and to enable effective heat transfer.

Comparable rollers of conventional diameter can be found in DE-GM 84 36 546, DE-GM 84 10 839 and EU-OS 158 220 based on the two utility models. This has a roller body, peripheral bores on the roller body for the flow of a fluid heat transfer medium, a flange pin for each end of the roller body, supply and discharge lines for the fluid heat transfer medium in at least one flange pin and recesses for the distribution of the fluid heat transfer medium from the supply lines to the peripheral holes and from the peripheral holes to the discharge lines.

As has been said, larger dimensions have recently become increasingly important for comparable rolls. The large diameters of these rollers are caused by correspondingly high line pressures. Excessive bending and excessive bending alternating stresses can only be avoided by increasing the section modulus of the roll. This is proportional to the fourth power of the roller diameter.

On the other hand, to keep the weight of the rolls manageable, these rolls are manufactured with enlarged central inner bores. However, this configuration has disadvantages in several ways:

Without further measures, the inner bore is filled with the heat transfer fluid during operation. This is not only expensive, but also has to be heated each time the calender is started and cooled each time it is shut down. This is not only a waste of energy, but also means an extension of the corresponding heating and cooling processes and thus an extension of the operational readiness.

By enlarging the inner bore by boring, the residual stress distribution of the chilled cast iron rolls changes in such a way that the tensile residual stresses increase in the bore wall. This is certainly desirable for high-performance heating operation, since the superimposed thermal stress is the reverse of the distribution of the residual stress and the stress level is reduced when the two stress distributions are superimposed. In the heating phase, however, the temperature increase in the outer roller shell due to the hot heat transfer medium in the peripheral bores only follows the temperature increase in the inner roller shell with a certain delay. This applies in the same way to the expansion of the roller material at the points listed. Due to the faster expanding roller material of the shell, the roller bore is put under additional tension. Knowing this connection, the permissible heating speeds are therefore greatly restricted, e.g. to 0.5 ° C per minute. This means a significant increase in waiting times until operational readiness. At an operating temperature of the roller of 250 ° C e.g. The heating-up time, starting from 20 ° C room temperature, takes almost eight hours.

When a paper web is torn off and a new paper web is subsequently reintroduced onto the roller, the thermal loads change very quickly. Given the low permissible rates of change in temperature, it is practically impossible to react to these changes with the heating. The result is undesirable fluctuations in quality or thickness in the paper web.

Finally, the following circumstance is disadvantageous: there are countries in which containers with internal pressure below certain Conditions fall under the very restrictive local ordinances on pressure vessels, although they are so oversized in terms of wall thickness that they are again considered machine parts in other countries. For chilled cast iron rollers, this could mean considerable approval problems if the regulations were interpreted closely, because the material "chilled cast iron" is not standardized in the relevant regulations. Due to the pump pressure to convey the heat transfer fluid and the own vapor pressure, even when using heat transfer oils, pressures inside the roll are significantly higher than the ambient pressure, which is why the above-mentioned regulations should also be observed here.

It is the object of the present invention to largely eliminate the disadvantages of the prior art listed above and also to achieve further desired technical improvements; in particular, a generic roller is to be proposed which is essentially stress-free, can be brought to the desired temperature relatively quickly and, in the process, requires a small amount of heat or coolant fluid.

This object is achieved for a generic roller by the features in the characterizing part of claim 1.

Useful features of the roller according to the invention are defined by the features in the subclaims.

In the roller according to the invention, further axial bores with a small diameter are provided near the inner bore, which has an enlarged diameter, in which a heat or cold medium for tapping, through which the Carrier medium has been introduced into the roller, flows back.

Since the rollers in question are generally driven rollers, the carrier liquid must be returned to the relevant pin after being introduced through the inlet pin and flowing through the peripheral bores and removed via double sealing heads. The other pin is not available for this because it is required to drive the roller. The additional axial bores of small diameter that are additionally provided are very advantageous for returning the heat transfer fluid to the inlet spigot, since on the one hand this eliminates the usually regularly provided central roller bore and on the other hand additional weight savings are possible.

A displacer provided in the inner bore with its enlarged diameter in the roller is usually shrunk into the roller body. In other words, the roller body is raised to a temperature which entails a certain increase in the diameter, in particular the inner diameter, of the roller. The displacement body is then pushed into the central bore of the roller body. The displacer is either a tube welded at both ends or an open tube at both ends, which is sealed with closures after the shrinking process. When the roller body is subsequently cooled, the roller body presses firmly against the displacement body.

If the central bore in the roller body is completely closed by sealing washers, the displacement body can be completely dispensed with. This measure has the valuable advantages that the roller according to the invention can be manufactured much more easily and in a shorter time. In addition, the total weight of the roller can be reduced further as a result. The reliability of the roller in terms of tightness also increases.

If the heat transfer medium is returned to the inlet pin after one or three passages through one or more peripheral channels and through one or more of the further axial bores, the heat or coolant initially flows through the central hole of the inlet pin into the roller and passes through connecting channels preferably to every third of the peripheral bores and flows through them in the axial direction along the roller. At the other end, the carrier medium flows through connecting channels into an adjacent peripheral bore or into one of the other axial bores of small diameter. In principle, the carrier medium can be passed axially several times through the roller body before it is disposed of via the further axial bores of small diameter and the subsequent entry pin. The disposed carrier medium is then brought back to the desired temperature outside the roller and fed to the roller again. The inlet pin is usually provided with a double sealing head.

In the preferred configuration, three peripheral channels are connected to one another and to one of the further axial channels or bores for returning the carrier medium near the central bore. The radial arrangement of the peripheral channels or bores compared to the other axial bores has the advantage that the thermal compressive stresses in the interior of the roll are further reduced can be. This can be justified as follows: Because heat is removed from the surface of the roller, the heat transfer fluid also cools down during the repeated passage through the peripheral bores. With the triple-pass version listed above, the heat transfer fluid has reached its lowest temperature in the heating roller. Due to the return via the further axial bores in the inner roll area, the heat transfer medium warms up again somewhat due to the higher average temperature of the roll. In doing so, it removes some of the heat transferred from the inside of the roll and thus slightly reduces the inside temperature of the roll. This leads to a leveling of the temperature profile which lies against the roller in the axial direction. The reduced thermal compressive stresses also make a significant contribution to the operational safety of the roller.

Viewed globally, there is a blatant reduction in the volume of heat transfer fluid (or coolant fluid) required for temperature control of the roller for all embodiments of the roller according to the invention.

In addition, both the radially inner and the radially outer regions of the roller body are simultaneously brought to the desired temperature during the heating phase. Thermal stresses from temporary temperature differences are avoided from the outset. This enables much faster heating times. Calculations have shown that it is possible to increase the heating rate to 4 ° C per minute. The heating-up time is reduced to just under an hour.

In addition, when the paper web is torn off and the subsequent reintroduction of another paper web, it is advantageously better possible to adapt the rapidly changing heating output and thus to ensure the uniformity of the production or the paper quality.

Finally, it is also a global advantage of all embodiments according to the present invention that the central bore, which has an enlarged diameter, is not filled with heat transfer fluid which is under pressure. It is therefore no longer inevitable to design the roller body as a pressure vessel. The exclusive use of bores with small diameters can be used as the basis for calculation methods for pipes, which greatly simplifies the design and, if necessary, the acceptance of the heated peripherally drilled rolls in view of the above-mentioned approval problems.

Fig. 1

eine Ausführungsform einer Walze, bei der ein Verdrängerkörper die erweiterte zentrale Bohrung vollständig ausfüllt, in einer längs axial aufgeschnittenen Darstellung, wobei der Schnitt entlang des Schnittgraphen D-D, dargestellt in Fig. 3, verläuft;

Fig. 2

einen Teilquerschnitt für die Walze gemäß Fig. 1 entlang der Schnittebene C-C; und

Fig. 3

eine Querschnittsdarstellung in zwei Schnittebenen (A-A, B-B) für die Walze gemäßt Fig. 1.

In the following, the present invention is to be discussed on the basis of preferred exemplary embodiments with reference to the attached figures, further features and advantages being disclosed. Show it:

Fig. 1

an embodiment of a roller, in which a displacer completely fills the enlarged central bore, in a longitudinally cut open representation, the section running along the section graph DD, shown in Fig. 3;

Fig. 2

a partial cross section for the roller of Figure 1 along the section plane CC. and

Fig. 3

2 shows a cross-sectional representation in two sectional planes (AA, BB) for the roller according to FIG. 1.

1 shows an embodiment of the roller according to the invention, which is generally identified by reference number 10.

The roller 10 is provided with an enlarged central bore which is completely filled with a displacer 4. The roller body 1 of the roller 10 is provided with peripheral channels or bores 6 near the roller surface. The peripheral channels 6 are connected to further axial channels or bores 7 via connections 6c. These further axial bores 7 are in turn connected via an annular space 3 to the pin 2a, through which the heat transfer medium is introduced into the roller body 1 or disposed of therefrom.

In Fig. 1 it is indicated in the drawing that instead of a displacer 4, the expanded central bore can also be easily welded closed, for example, with sealing caps 8, which enables the roller 10 to be manufactured more easily.

The heat transfer fluid is introduced into the roller body 1 via the inlet pin 2a. Here, the heat transfer fluid is supplied to the peripheral channels 6 via connections 6e. Via connections 6b to adjacent peripheral channels 6 or via a connection 6c to the further axial channels 7, the heat transfer fluid is then passed through the roller body 1 a further time either close to the roll surface or close to the surface of the enlarged central bore. The cooled or used heat transfer fluid is disposed of from the roller 10 via the inlet pin 2a in order to be brought back to the desired temperature outside the roller.

The partial cross section C-C according to FIG. 2, which is applied to the roller end on which the drive pin 2b is provided, again illustrates the connection geometry of the peripheral channels 6 and the further axial bores 7 with one another. With the reference numeral 12 are fasteners, for. B. screws, bolts or the like, with which the displacer 4 is connected to the roller body 1 of the roller 10. The connecting lines 6b allow fluid to be exchanged between adjacent peripheral channels 6. The radially extending connecting lines 6c ensure the return of the heat transfer fluid from the peripheral channels 6 to the further axial channels 7.

In the embodiment shown in FIG. 2, the heat transfer fluid is passed through three peripheral channels 6 near the roller surface, in order to then be returned through an axial channel 7 near the surface of the enlarged central bore to the inlet pin 2a.

The cross section shown in FIG. 3 through the roller body according to FIG. 1 shows two sectional planes. The cuts are made at the end of the roller 10 at which the entry pin 2a is located.

Section AA shows essentially the same features as are shown from section CC in FIG. 2. However, instead of the radially extending connecting lines 6c here are also radially extending Connecting lines 6d are provided, which connect the further axial channels or bores 7 to the annular space 3, from which the cooled or used heat transfer fluid is returned to the inlet pin 2a. The annular space 3 is connected to the return line 5.

The lower section B-B in FIG. 3 shows the connection of every third peripheral channel 6 to the heat carrier feed 9 via connecting lines 6b. The peripheral bores 6 are connected to one another via connecting lines 6a.

The sectional graphic D-D clarifies along which the cut shown in FIG. 1 runs through the roller body 1 of the roller 10.

The flow diagram for the carrier liquid and the peripheral channels or bores 6 and through the further axial bores 7 or through the entire roller results from the combination of FIGS. 2 and 3 as follows:

After the heat transfer fluid has entered the roller body via the inlet pin 2a or the feed line 9 running through it (FIG. 1), the heat transfer fluid is introduced into every third peripheral channel 6 via the connecting lines 6e (FIG. 3). The heat transfer fluid is now conveyed in the axial direction through the peripherally running channels 6 in order to be transferred at the roller end of the drive pin 2b (FIG. 2) via connecting lines 6a into adjacent peripheral channels 6. The heat transfer fluid is again axially passed through the roller body 1 through this adjacent peripheral channel 6. At the roller end of the inlet peg 2a, the heat transfer fluid is transferred once more via a circumferentially extending connecting line 6a into an adjacent peripheral bore. After an additional axial passage through a further adjacent peripheral bore 6, the heat transfer fluid is passed on to the further axial bores 7 via radially extending connecting lines 6c (FIG. 1, FIG. 2). After the heat transfer fluid has passed through the further axial bores 7, it is conveyed into the annular space 3 via the radially inwardly extending connecting lines 6d. From the annular space 3, the cooled or used heat transfer fluid is passed via the disposal line 5 through the inlet pin 2a from the roller 10.

Claims (6)

Roller for a calender or a calender a) with a roller body, b) with a flange pin on each end of the roller body, c) with a closed central bore in the roller body, and d) with peripheral channels formed near the roll surface in the roll body for the passage of a fluid heat or cold carrier, characterized in that e) in the roller body (1) near the central bore further axial channels (7) of small diameter are provided for the passage of the heat or cold medium. Roll according to claim 1, characterized in that the central bore is completely filled with a displacement body. Roller according to claim 1, characterized in that the central bore is closed by sealing washers (8). Roller according to one of claims 1 to 3, characterized in that the heat or cold carrier flows back through the further axial channels (7) of small diameter to the flange pin (2a) through which the heat or cold carrier flows into the roller (10 ) has occurred. Roller according to one of claims 1 to 3, characterized in that the heat or cold carrier flows back through the peripheral channels (6) to the flange pin (2) through which the heat or cold carrier has entered the roller (10) . Roll according to one of claims 1 to 5, characterized in that the heat or cold carrier flows through the peripheral channels (6) and the further axial channels (7) one to three times.

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