EP1100993A1

EP1100993A1 - Roller group

Info

Publication number: EP1100993A1
Application number: EP99939959A
Authority: EP
Inventors: Heinz-Michael Zaoralek; Jürgen KRÜGER; Bernd Eppli; Julien Tenelsen
Original assignee: Schwaebische Huettenwerke Automotive GmbH
Current assignee: SHW Casting Technologies GmbH
Priority date: 1998-06-29
Filing date: 1999-06-28
Publication date: 2001-05-23
Anticipated expiration: 2019-06-28
Also published as: EP1100993B1; WO2000000694A1; CA2335924C; DE59908593D1; JP2002519532A; DE19828722C2; DE19828722A1; US6588332B1; CA2335924A1

Abstract

The invention relates to a roller group for a calender provided for processing material webs. The roller group is comprised of at least two rollers respectively having a roller body made of a cast or forged ferrous material. At least one of the roller bodies is made of a chilled cast iron or a chilled cast form. One or more rollers can comprise a covering made of an elastic material, for example, a polymeric plastic. Although the outer diameter of the rollers can vary, the deflection of the rollers is essentially the same when solely supported in the antifriction bearings thereof. In order to produce corresponding rollers, the actual average moduli of elasticity of all roller bodies are measured and the inner diameters of the central drilled holes are, in particular, calculated according to this measurement after the essential processing steps of the roller bodies, i.e., for example, after casting, rough turning, predrilling and optionally, after drilling peripheral holes. The invention also relates to methods for influencing the deflection of the rollers in a targeted manner by selecting corresponding materials which depict the relationships of material structures in the roller body, or by the targeted placement of ballast in the central drilled hole or also in specific peripheral drilled holes of the roller bodies.

Description

Patent application "roller group"

Task

Modern multi-roll calenders, in which hard, heated and soft, plastic-covered rolls are used at the same time, could be used particularly effectively for the smoothing of paper if the central rolls were raised in their bearings so far that the roll gap underneath relieved them of their own roll weight becomes. It would then be possible to apply the same line pressure from zero to the maximum pressure in all nips by exerting pressure on the entire roller package by means of a lower and upper pressure roller. However, this can only be achieved if all rolls in the calender have largely the same bending lines, if they are held in the bearings on the journal and are only bent by their own weight.

The suggestion to equip a calender with such rolls goes e.g. from U.S. Patent No. 5,438,920. In it, the intermediate rolls are described as rolls in which the shape of the natural deflection line, caused by its own weight, is largely the same. However, the patent does not show how such rolls can be produced with largely the same bending lines. This is in no way trivial and is not readily possible for the average specialist, even if he considers the basic relationships between the weight of a bending beam, its moment of inertia, the modulus of elasticity of the beam material and the distance between the supports (see e.g. Hütte, 28th revised edition, publisher von Wilhelm Ernst and Son, Berlin 1955, pp. 876 - 892).

Also in PCT patent application WO 95/14813 it is only pointed out that the bending lines which are produced by gravity in each center roll must be dimensioned such that their shapes are largely the same. With regard to the question of how this can be accomplished, the applicant merely gives an indication that the center rollers "have been selected in this way". Such selection processes are known, for example, in the manufacture of balls with largely the same diameters for precision ball bearings. However, it is hardly economically feasible for calender rolls to produce a larger number of rolls and to select those whose natural bending lines largely match. A similar task consists of so-called doubling calenders for the production of multi-layer tissue webs. In such a two-roll calender, two or more separately manufactured layers of fine paper tissues together _¬ quantitative results and can be easily compressed. This creates a multi-layered End _¬ product such as toilet paper or paper towels. The line pressure in Wal _¬ zenspalt is far lower than it by the mere placement of the top roll it would evidence _¬ example. Here, too, the nip has to be largely relieved of the weight of the top roller. So that the pressure profile in the roll gap is uniform, it is also advantageous to use rolls with largely matching bending lines. The state of the art here is to produce the rolls from the same material and with the same geometry and to accept the inevitable variations in the material properties in terms of their effect on the bending lines. In another embodiment, a naturally durchbie by its own weight _¬ constricting roller is combined with another, the bending line can be adjusted by an inner hy _¬ cally acting adjustment of the first. However, this is a complex and correspondingly expensive solution.

State of the art

In general, it can be said that, in the strict sense, rollers with the same deflection have so far not been available. This is due to a number of technical limitations:

1) Heated rolls in any form of calender for the paper industry are made almost exclusively with bodies made of chilled cast iron. An economical production of chilled cast iron rolls is only possible within certain diameters _¬ rows, since each roll diameter must be cast in a corresponding set of cast iron molds - so-called molds. Typically, these diameters are graded in two inch increments. Usual diameters for multi-roll calenders are accordingly: e.g. 505 mm, 560 mm, 610 mm, 660 mm, 710 mm, 760 mm, 812 mm, 860 mm, 915 mm.

2) The production results in a certain tolerance range of the outer diameter of the rolls. As usual in the industry, this has adjusted to +/- 1% of the roller diameter. Since the maximum deflection of the roller is inversely proportional to the moment of inertia of the roller cross section, and this in turn is proportional to the 4th power of the roll diameter, this tolerance means a difference in the deflection of +/- 4% in otherwise identical rolls.

3) Chilled cast iron is a so-called inhomogeneous material. The physical properties vary except due to the composition also due to geringfügi _¬ gen differences in the microstructure. On separately cast or even mitgegosse _¬ nen samples measured material properties only a limited ge _¬ precise meaning for the effective structure in the roll body itself. Deviations _¬ have gen the modulus of elasticity of samples due to the inhomogeneity and the tolerance of the measurement process to just a few percent accurate can be measured have an inversely proportional effect on the deflection. The specific density has a directly proportional influence. Material properties measured in this way cannot be used as the basis for the design.

4) The cooling rate during casting, which is decisive for the thickness of the pure fright ("white iron") and the so-called transition zone, also has a strong influence on the material parameters. Since the pure white iron has a modulus of elasticity of 180,000 N / mm ² and the gray core iron typically about 100,000 N / mm ² , deviations in the relative distribution of the two components lead to variations in the average modulus of elasticity and thus also to a different one Deflection.

5) There are similar variations in the case of long rollers in the axial direction, since the roller bodies are cast upright in the mold.

6) The associated polymer-related rolls should preferably be designed with a diameter of the finished roll that comes close to that of the heated, hard rolls or corresponds to an adjacent diameter in the standard series. Then hard and soft rollers can be mixed in any order in the calender, which gives the papermaker greater flexibility when setting up his calender when smoothing. The outer diameter of the roll core is thus determined by the thickness of the polymer layer. When using the usual roller materials, such as gray cast iron or nodular cast iron, the production of such rollers with identical bending lines is very difficult because the moduli of elasticity are very different. 7) In operation, the polymer layer of the elastic rolls must refinished _¬ the. Depending on the type of layer, it loses up to 15 mm in thickness until the layer is renewed. Since the layer only contributes to the weight of the roller, but not to the rigidity, this means that the "worn" roller deflects less than the new roller.

The opposite is true for the chilled cast iron roller. Although the roll is reduced only slightly _¬ fügig in diameter when it is sharpened, but the number of grinding operations is relatively high. In the course of the life of the roller, the white layer of fright is significantly reduced. However, since this greatly influences the deflection of the roll due to their high modulus of elasticity, will be at ei _¬ nem grinding this layer the deflection gradually increase.

8) The modulus of elasticity of both chilled cast iron and other iron materials is temperature-dependent. While hard rolls usually at temperatures of about 120 ° C and operated higher, the polymer-based Walzenkör _¬ are heated uniformly by at most. Also result in operation under _¬ schiedliche bending lines.

9) Finally - especially when the polymer covered rollers - even bauartbe _¬-related differences of significance. For example, rollers are drilled peripherally or with a displacer in the central bore.

Description of the invention

The invention relates to a group of substantially the same bending rolls and the procedural _¬ ren for manufacturing such a roller group. As rolls with the same bending he is referred to _¬ according to those rolls which have largely identical deflections. Deflection f is understood to mean the vertical deflection of the roll axis when the roll bends in the middle of the roll body and in relation to the position of the roll axis at the web ends. While the bending line can only be measured in a very complex manner, the following shows _various ways of determining the deflection. For the beabsichtig _¬ th purpose of identifying and influencing the deflection can with sufficient accuracy _¬ that replacing the elastic line.

Such a roller group consists of at least two, if it is one Multi-roll calender is made up of a plurality of rolls arranged one above the other, at least one of which has a roll body made of chilled cast iron or hard chilled cast iron, as well as other rolls with roll bodies also made of chilled cast iron or chilled cast iron or of a cast iron with lamellar, vermicular or spherical graphite formation, which then have a elastic cover are provided. The rollers are enclosed by an upper and lower roller, the deflection of which can be adjusted by hydraulic fittings and which also make it possible to vary the line pressure exerted on the roller group. The problems of different deflection can be neglected for small rolls with a diameter less than 500 mm and a ratio of web length: diameter less than 7.

In such a roller group, a distinction must be made between a so-called reference roller and the rollers dependent thereon. This does not include the top and bottom rollers because their deflection can be changed not only by the weight, but actively by pressure settings in the hydraulic components.

According to the invention, the reference roller is a chilled or shell chilled roller that has a central hole with a wall thickness between 100 and 300 mm and a natural deflection under the influence of gravity when suspended in its bearings, which are arranged on the pins, between 0.1 and 0.2 mm per meter of web length. The diameter of the central bore lies approximately in the middle of an area, the upper end of which is determined by the minimum wall thickness of the roller body and the lower end of which is determined by the lowest possible roller weight.

The other rollers in the roller group can be made of chilled cast iron or chilled cast iron, but can also be made of other suitable materials. If they are provided with an elastic coating, they will generally consist of cast iron, but can also consist of forged steel. Their weight without a pin corresponds to the shape! G = G _{re (} χ E x J xf / (E _ref χ J _re , χ f _fef )

Here are:

G _ref = weight of the reference roller body (N)

(without spigot) in the area of the web length LE _re = modulus of elasticity of the reference roller body

(N / m ² ) J _re , = moment of inertia of the cross-section of the reference roller body (m ⁴ ) f, _{e (} = deflection of the reference roller (m) E = modulus of elasticity (N / m ² )

J = moment of inertia of the roll cross-section (m ⁴ ) f = desired deflection (m)

Your central hole corresponds to the formula:

Bore diameter = (D ⁴ - G x K _G / (fx E)) ^{1 4}

as far as the roller body has no peripheral bores. With peripheral bores:

Bore diameter = (D ⁴ - Z _p x D _p ² x (D _p ² + 2 χ T _p ² ) - G χ K _G / (fx E)) ' ^Λ

Here are:

G = weight of the roller body (N) in the area of the web length

E = modulus of elasticity (N / m ² )

D = outer diameter (m) f = desired deflection (m)

KG = group constant (m ³ ) according to equation (3) Zp = number of peripheral holes

D _p = diameter of the peripheral bores (m)

T _p = pitch circle (m) of the peripheral holes

If these are rollers with elastic covers, these covers have a thickness of between 10 and 30 mm and a supporting metallic body with the diameter

D = D _rel - 2 x (dp - ap)

Here are:

D _{re (} = relative diameter (m) dp = thickness of the new polymer cover (m) ap = maximum possible wear of the polymer cover (m).

The same applies to the diameter D.

D = (16 ^χ G ^χ K _G / (15 χ E χ f _{re (} )) ^{1 4}

with the final D as the next diameter to be produced economically.

Here are:

G = weight of the roller body (N) in the range of

Web length LE = desired modulus of elasticity (N / m ² ), e.g. 180,000 for gray cast iron with spherical graphite f _{re (} = deflection (m) of the reference roller KG = group constant (m ³ ) according to the following equation:

K _G = (5 / (6 ^χ π)) x L ³ x (1 + 2.4 x (LM-L) / L + 2 x (D, _ef / L) ² ) Here are: π = circle constant (3.14159 ...)

L = web length of the roller group (m)

LM = bearing center distance of the roller group (m)

D _{re (} = diameter of the reference roller (m)

So that the arrangement of the rolls in the calender can be designed relatively freely, rolls are used which are essentially the same in their outer diameters. Undesirable vibrations of the rollers can be avoided if they are dimensioned so that they do not have to be operated in the vicinity of the semi-critical speed. Finally, for even more precise determination of the deflection, all the rollers can be provided with fibers or bodies in the central bore or the peripheral bores, which can also be fed in or out or adjusted during operation.

The production of a corresponding roller group is described below:

The determination of the roll diameter for rolls of a multi-roll calender begins with the chilled cast rolls, because this should be done after the maximum permissible deflection. It is determined by the technical possibilities of deflection compensation of the top and bottom rolls, which are usually available in multi-roll calenders. A chilled cast iron roll is expediently designated as the reference roll. The outer diameter and the diameter of the central bore, which each larger roller has to reduce weight, should be approximately in the middle of the respective tolerance or feasibility areas.

A permissible range for the deflection is then determined within the scope of the expected scatter of the elasticity module. This range can be narrowed down by compensating for the effect of different moduli of elasticity on the deflection by modifying the diameter of the central bore. The deflection of a roller suspended in the bearings is determined by the weight of the roller body, the modulus of elasticity of the roller material and the moment of inertia of the roller cross section. The reduction in the size of the central bore increases the weight and increases the moment of inertia, but the latter only to a lesser extent, so that the roll deflection can be increased by reducing the bore.

Within the usual manufacturing tolerances of cast iron or chilled cast iron rolls, the outer diameter of the roll body can fluctuate by +/- 1% due to the manufacturing process. This tolerance can be limited with a certain additional effort, which is generally avoided because an adjustment to different roll diameters in the calender is possible in a simple manner. This relatively small span can be used for the production of rolls that are largely identical in bending, because a variation of the outside diameter of only +/- 1% changes the deflection of the roll under its own weight by approx. - / + 2%.

However, when finalizing the outer diameter, it must be taken into account that the diameter is reduced by regrinding during the use of the roller. Possibly. a compromise can be found in that the service life of the roller and thus the allowable regrinding allowance is reduced.

According to the invention, the diameter D of the roller body to be provided with a polymer cover is to be determined in accordance with the stress on the cover and its durability. In the case of very high loads caused by line pressure, speed of rotation and temperatures or less durable covers, you will opt for the largest possible roll diameter. A material with a low modulus of elasticity between 90,000 and 120,000 N / mm ² is then used with regard to the desired bending uniformity.

Conversely, if the elastic cover or a highly resilient elastic cover material is subjected to low loads, a smaller roller diameter can be provided. Then an elastic modulus between 170,000 and 185,000 N / mm ^{2 should} preferably be used. According to the invention, a cast iron is used for medium loads, the modulus of elasticity of which is in a wide range between 130,000 and 160,000 N / mm ² .

Part of the invention is therefore also the possibility of influencing the modulus of elasticity of cast iron in large roll bodies in accordance with the requirements for the production of rolls with largely the same deflections. It largely depends on the graphite embedded in the iron structure. If this is designed in the form of lamellae (gray cast iron), a notch effect occurs when the tensile load is applied, which weakens the base material and greatly reduces the modulus of elasticity. It is then 100,000 N / mm ² and less. The alloying of magnesium changes the surface tensions in the liquid state to such an extent that the graphite is spherically shaped (spheroidal iron). The reduction in the modulus of elasticity of the base material is then only slight. Values up to 185,000 N / mm ² are achieved.

According to the invention, the inoculation technique and the magnesium doping are now modified so that intermediate forms of lamellar and spherical occur during the graphite precipitation (vermicular cast iron). These intermediate forms make it possible to adjust the modulus of elasticity of the material in a range between 110,000 and 170,000 N / mm ² - preferably between 130,000 and 160,000 N / mm ² - exactly as is required based on the specifications. However, the technology is burdened with a relatively large spread of the decisive material properties, because even the smallest variations in alloy and vaccination have a significant impact on the elastic modulus. Therefore, an exact determination of the actual elastic modulus of rolls is of special importance not only for the roll itself, but also as a basis for the material decisions to be made continuously in future cases.

From the core diameter and the constructionally possible diameters of the central bores, the bending formula results in a range for the permissible moduli of elasticity of the roller material. The size of the bore is limited upwards by the profile disturbance in the edge region of the roller, which results from the fact that the roller body is ovalized under a line load, but also by the necessity of accommodating heating or cooling holes in the roller body, which is the smoothing process requires or increase the durability of elastic plastic covers. In the case of rolls with large outside diameters, the bore is also limited downwards to limit the roll weights. According to the invention, the diameter D of the roll body for rolls of largely the same curvature with an elastic cover is used

D = D _rel - 2 x (dp - ap)

selected.

Here are:

D _rei = relative diameter (m) dp = thickness of the new polymer covering (m) ap = max. possible wear of the polymer cover (m).

The relative diameter D _rel corresponds approximately to the case of rollers with an elastic cover with basic bodies from cast iron with lamellar graphite the next highest in the series of standard diameter in cast iron with spheroidal graphite un _¬ endanger the next lowest or in the series of standard diameter at a roller base body made of cast iron with vermicular graphite roughly the diameter _¬ By the reference roll. Since these materials - unlike shell _¬ cast iron - the machining allowance can be chosen freely, apart from economic considerations, this specification is only a guideline.

The finished diameter D of the roller body is to be chosen as it is from the formula

D = (16 XGXK _G / (15 χ E χ f _ref )) ^{1 4}

the next diameter to be produced economically.

Here are:

G = weight of the roller body (N) in the range of

Web length LE = desired modulus of elasticity (N / m ² ), eg 180,000 for gray cast iron with spherical graphite f ref = deflection (m) of the reference roller

KG = group constant (m ³ ) according to the following equation

K (5 / (6 ^χ π)) x L ³ x (1 + 2.4 x (LM-L) / L + 2 x (D _ref / L) ² ) Here are: π = circle constant (3.14159 ...)

L = web length of the roller group (m)

LM = bearing center distance of the roller group (m)

D _ref = diameter of the reference roller (m)

Since the weight G of the roller body depends on its diameter, it must be finally determined by iteration or further calculation.

Since the material parameters, e.g. the modulus of elasticity, cannot be determined with sufficient precision from small samples, it is finally part of the invention that the average modulus of elasticity of the entire roller body is determined and controlled in the course of the manufacturing process by bending tests of the entire roller body, which in each case gives points of reference for the further processing of the roller body be won. For this purpose, the roller body is supported and bent by the application of defined forces. The bending of the whole body is measured. All material properties that change over the cross-section, e.g. the modulus of elasticity and the specific density are thus recorded together and simultaneously. The actual mean modulus of elasticity can be calculated from this. With progressive machining of the chilled cast body (rough turning of the surface, central drilling, introduction of peripheral drilling), these measurements can be repeated if necessary and a somewhat final mean elastic modulus can be determined, for which the exact diameter of the central drilling can then be determined, which produces the desired deflection . The following applies without peripheral drilling:

Bore diameter = (D ⁴ - G x K _G / (fx E)) ^{, 4}

With peripheral bores:

Bore diameter = (D ⁴ - Z _p x D _p ² x (D _p ² + 2 x T _p ² ) - G x K _G / (fx E)) ^%

Here are:

G = weight of the roller body (N) in the area of the web length E = modulus of elasticity (N / m ² )

D = outer diameter (m) f = desired deflection (m)

KG = group constant (m ³ ) according to the above equation

Z _p = number of peripheral holes

Dp = diameter of the peripheral bores (m)

T _p = pitch circle (m) of the peripheral holes

As a method of measuring the deflection of the entire roll body in various _¬ which Fertigungszuständeπ example, be used according to the invention:

Light beam method:

The roller body, the weight of which was previously determined to a precision of 0.5% using a precision balance, is supported at the ends on roller stands. On the upper _¬ side of the roller body is in the center of a light source - such as a laser - mounted axially parallel and divided whose beam sensors path is directed to two, each of which is attached to the roll ends. The radial position of the points of impact on the sensors is recorded. After rotating the roller body by 180 °, the displacement of the radial position of the impact points is measured a second time. These displacements are a measure of twice the value of the deflection of the roll body in the middle of the roll under its own weight. With the measured values for the outer and inner diameter of the roller body, as well as the distance between the roller blocks and the sensors, the exact average elastic modulus of the roller body can then be determined.

G x L ³ / (38.4 χ fx J)

Here are:

E = modulus of elasticity in (N / m ² )

G = weight of the roller body (N) in the area of the web length L L = distance between the rollers (m)

= measured change in deflection (m)

J = moment of inertia of the roll cross-section (m ⁴ )

The light beam method has the advantage that a measurement can also be carried out on a finished roller if the roller can be rotated in its own bearings. The equation for determining the modulus of elasticity is then: 6 χ K _G χ π / (32 χ L xfx J)

Here are:

Weight force of the roller body (N) in the area of the web length L

K _G group constant (m ⁴ ) according to the above equation π circle constant (3.14159 ...)

L path length (m) f measured change in deflection (m)

J moment of inertia of the roll cross-section (m ⁴ )

Measuring bar method:

A rigid measuring beam is placed on the roll body in the axial direction, whereby it is supported by supports at the roll ends. A distance measuring device, e.g. a dial gauge measures the distance of the roller body to the measuring bar in the middle of the roller. If a defined vertical force is now exerted on the roller body in the middle of the roller, it deforms that roller body, but not the measuring beam. The exact average modulus of elasticity can be calculated directly from the change in the distance between the measuring bar and the roller body in the middle of the roller and the dimensions of the roller body:

E = P x L ³ / (48 xfx J)

Here are:

E = modulus of elasticity (N / m ² )

P = applied force (N)

L = distance between the supports (m) f = measured change in deflection (m)

J = moment of inertia of the roll cross-section (m ⁴ )

Since the modulus of elasticity of cast iron materials depends on the load, the measurement should be repeated under different force levels. Measuring bridge method:

The measurement can also be carried out similarly to the measuring beam method if the roller body is supported at the ends on a stable surface. _¬ measuring bridge at the ends and in the middle of the roller body, the vertical Ver _¬ can shift measured at these points in space by applying a defined verti cal _¬ force. Any elastic yielding of the supports can thus be eliminated by calculation. The formula for determining the average Elastizi _¬ tätsmoduls corresponds to the formula (7), wherein the deflection f is determined as follows:

f - (f, + f ₂ ) / 2

Are there

L display in the middle of the roll (m) nf ₂ = display at the end of the roll (m)

Natural frequency method:

From the measured natural frequency of a bending beam, which is supported on both ends on _¬ , it can be seen via the simple relationship

^f = g / (4 x π ² xn ² )

the deflection in weight and therefore the exact average Elasti _¬ zitätsmodul determine the roll body.

Here are: π = circular constant (3.14159 ...) n = natural frequency (1 / s) g = gravitational acceleration (= 9.81 m / s ² )

With regard to the application of these measurement methods according to the invention, it is common that even larger systematic errors of the respective measurement method are irrelevant, as long as the measurement results deliver reproducible results with an accuracy of <1%. The for the roll group produced according to the invention my same same deflection may differ absolutely from the measurement, the rollers can still _¬ with each other at substantially equal deflections _¬ forth are provided.

It has so far been in the production of calender rolls for Papierindu _¬ stry only common in exceptional cases, to determine the exact weight of the rolls by weighing. Because of no small expense in determining the high roller weights weighing will lead to individual rolling bodies rarely Runaway _¬. Usually approximately Berechnuπgsformeln, the values on experiential _¬ are based.

For peripherally drilled rolls of the roll group with elastic cover, e.g. the following formula for the weight force G of the entire roller can be applied with an accuracy of a few percent

G = 60000 x (D ² - B) x L

Here are:

D = diameter (m) of the roller body B = bore diameter (m) L = web length (m)

For the production and operation of all roll groups with largely the same deflections to establish the exact rolling weights, however, as indicated in the applicable measurement methods, important because these due to the different roll diameter, the elastic covers which specific under _¬ retired union material weights and to Generation of largely identical deflections to be dimensioned central bores can fluctuate considerably. According to the invention, the roll weights of the new rolls are therefore to be exactly determined by calibrated precision carriages and to be used as a basis for the determination of the diameter of the central bore. It is also advisable to add the weights to the roll documentation. The change of the roller weights during operation wear conditional by eg finishing able to be tracked on this basis with sufficient accuracy _¬ to. As mentioned above, the deflection of calender rolls changes over the course of their operational use. In rollers from chilled cast the hard and disproportionately contributing because of their high modulus of elasticity to the bending stiffness of the roller is chilled layer Ringert gradually ver _¬ by re _¬ gelmäßiges regrinding. The deflection of these rollers increases accordingly. In the case of rolls with an elastic cover, this hardly contributes to the bending stiffness of the roll. However, it increases the roll weight. If this relation - what happens at regular intervals _¬ - refinished, reduces the roll weight and deflection.

A further change in the deflection resulting in variations in operating _¬ ture due to the decreasing with increasing temperature Elastizitätsmo _¬ duls. Depending on the desired smoothing result, the temperature of the heating rollers and the line pressure in the calender are increased. While the temperature of the heated rollers from chilled cast by means of a liquid or gaseous Wärmeträ _¬ transfer medium, which passes through the roller body, is directly affected, increased pressure increases the flexing into the elastic case. The thus produced Rei _¬ bung heat leads to temperature increases of the cover and the roll body. This is why they are often equipped with cooling options. Both effects are the reason that it is not possible to design the rollers in a roller group so that these, under all operating conditions and for the whole groove _¬ wetting time of the rolls just like deflections comprise, although the manufacturing method of the invention described above, a very precise manufacturing enables. Two extreme situations can be described for the roller group. Once the delivery state at temperatures in the vicinity of the other _¬ ambient temperature and on the other the respective state at the maximum wear of the working layer and maximum operating temperature of the heated chilled rolls. If the rolls had corresponding deflections under the influence of gravity in the delivery state, the deflections would drift further and further apart with increasing wear and increasing temperature of the heated chilled cast iron rolls. It is according to the invention provided about adjusting the deflection of the rolls with resilient coverings in the delivery state initially somewhat Staer _¬ ker. For this, the deflections are related to each other Ver _¬ ratio calculation:

Deflection chilled cast roller: Deflection polymer roller In the delivery state, this ratio should be <1 and in the state of the maximum wear and operating temperature> 1. By appropriately determining the finished diameter of the holes, όie extreme conditions can preferably be set so that they have approximately the same absolute distance from 1. This ensures that the deflections are always largely the same even with any combination of rollers within the group.

This can also be achieved by designing the finished diameter of the bores in such a way that the following condition is approximately fulfilled:

^f H HWW11 •• ^' ' PWΪι == f τ _{P 2} ? :: f τι _HW2

Here are: ^f HWi = deflection of the chilled cast iron roll (m) i = deflection of the polymer roll (m) each in new condition at ambient temperature

/ 2 = deflection of the polymer roller (m) ^f HW2 = deflection of the chill cast roller (m) in each case in the state of maximum wear and at maximum operating temperature of the chill cast roller.

Claims

Expectations

1. roller group for a calender for processing material webs, best _¬ starting from at least two rolls, each with a roller body from a ge _¬ cast ferrous material, of which at least one consists of a Hartguß- or Schalenhartgußwerkstoff and the other either also from Hartguß- or chill casting or consist of a cast iron with lamellar, vermicular or spherical graphite and can be provided with an elastic cover, with at least one screwed pin, with diameters of the roller bodies> 500 mm, with a ratio of web length: diameter> 7, with a bearing the rollers in rolling bearings in the area of the pins,

characterized in that

the roller body made of chilled or hard chilled cast material (reference roller) has a central hole with a wall thickness between 100 mm and 300 mm

as well as a natural deflection f _ref under the influence of gravity and with support in the roller bearings between 0.1 and 0.2 mm per meter of track length,

and the final bore diameter of the rolling body to be determined of the other rollers, taking into account their own weight G in the region of the web length L and their mean modulus of elasticity E so that arise f essentially the same amounts for the deflection, for example by satisfying the sliding _¬ chung :

Bore diameter = (D ⁴ - G x K _G / (fx E)) ^1/4

Are there

G = weight of the roller body (N) in the range of

Web length LE = modulus of elasticity (N / m ² )

D = outer diameter (m) of the roller body f = desired deflection (m), largely the same as f _ref

K _G = group constant (m ³ ) according to the following equation: KQ = (5 / (6 ^χ π)) x L ³ x (1 + 2.4 x (LM-L) / L + 2 x (D _ref / L) *)

Here are: π = circle constant (3.14159 ...)

L = web length of the roller group (m)

LM = bearing center distance of the roller group (m)

D _ref = diameter of the reference roller (m)

2. roller group according to claim 1,

characterized in that

the roll body of the present therein rolls are equipped with peripheral bores being _¬ through which a liquid or condensable gaseous Wärmeträ _¬ can be passed ger for heating, cooling or tempering, and the finished central hole diameter of the roller bodies, taking into account their egg _¬ gengewichtes G and its mean modulus of elasticity E are determined such that there are essentially equal amounts for the deflection f, for example by satisfying the following equation:

Bore diameter = (D ⁴ - Z _p x D _p ² x (D _p ² + 2 x T _p ² ) - G x K _G / (fx E)) ^{y «}

In addition to claim 1:

Z _p = number of peripheral holes

^D p = diameter (m) of the peripheral holes T _p = pitch circle (m) of the peripheral holes

3. roller group according to claims 1 and 2,

characterized in that

existing rollers provided with elastic covers have such covers with a thickness between 10 and 30 mm.

4. roller group according to claims 1 to 3,

characterized in that

the weights G of the roller bodies without pins which are not reference rollers essentially satisfy the following equation in the region of the web length L:

GG _ref x E ^χ J xf / (E _ref χ J _ref xf _ref )

Here are:

G _ref - weight of the reference roller body (N)

(without spigot) in the area of the web length LE _ref = modulus of elasticity of the reference roller body

(N / m ² ) ef = moment of inertia of the cross section of the

Reference roll body (m ⁴ ) fref = deflection of the reference roll (m) E = modulus of elasticity (N / m ² )

J = moment of inertia of the roll cross-section (m ⁴ ) desired deflection (m)

5. roller group according to claims 1 to 4,

characterized in that

the body of the reference roller is made of a material other than chilled cast or chilled cast.

6. roller group according to claims 1 to 4,

characterized in that

other materials, for example ge _¬ forged steel, can be used for the roller bodies which are not reference _rollers .

7. roller group according to claims 1 to 4,

characterized in that

in so far as departing from the made there determinations that the ratio _¬ se of the deflection of chilled rollers: polymer rollers in the mint To _¬ stand at low operating temperatures the ratios of polymer rollers: chilled rolls are substantially equal in the state of maximum acceptable wear at high operating temperatures of the chilled rolls.

8. roller group according to at least one of the preceding claims,

characterized in that

all or individual rollers are provided with a displacer in the central bore, between which and the inside of the bore of the roller body flows a heat transfer medium.

9. roller group according to at least one of the preceding claims,

characterized in that

the outer diameters of the rollers are essentially the same.

10. roller group according to at least one of the preceding claims,

characterized in that

the weight of at least one roller is reduced by additional axial bores, which are preferably arranged close to the neutral fiber of the roller wall.

11. roller group according to claims 1 to 10,

characterized in that

the central bore and / or the additional axial drillings with a Bal _¬ load material, eg water or a granular medium, are filled completely or partially.

12. A method for producing a roller group according to claims 1 to 4,

characterized in that

using the characteristic values of the reference roller developed according to the mechanical engineering specifications and taking into account the conditions set out in claim 1, the body diameter of the roller cores to be provided with a polymer cover _¬ essentially according to the equation

D = D _rel - 2 x (dp - ap)

^{with: D} rei = relative diameter (m) dp = thickness of the new polymer cover (m) ap = max. possible wear of the polymer cover (m)

is determined, whereby the relative diameter for roller bodies made of spheroidal graphite cast iron is approximately the next lower in the series of standard diameters (approx. -0.05 m), for roller base bodies made of gray cast iron with lamellar graphite that roughly the next higher in the series of standard diameters ( about about + 0.05 m) and cast iron with vermicular graphite rolls from that of the reference roll, or equivalent for any of the following materials substantially sliding _¬ chung:

D = (16 XGXK _G / (15 x E xf _ref )) ^{1 4}

Here are:

G = weight (N) of the roller body in the area of the web length LE = modulus of elasticity of the roller body (N / m ² ), for example 180,000 for gray cast iron with spherical graphite ^f ref = deflection (m) of the reference roller

KG = group constant (m ³ ) according to the following equation:

KQ = (5 / (6 * π)) x L ³ x (1 + 2.4 x (LM-L) / L + 2 x (D _ref / L) ² )

Here are:

π = circle constant (3.14159 ...)

L = web length of the roller group (m)

LM = bearing center distance of the roller group (m)

D _ref = diameter of the reference roller (m)

13. A method for producing a roller group according to claims 1 to 4 and 12,

characterized in that

the maximum permissible bore diameter of the central bore of the roller body is also determined taking into account the maximum permissible ovalization of the roller body according to the operating specifications.

14. A method for producing a roller group according to claims 1 to 4 and 12,

characterized in that

for adjusting the bending equality of the rollers from chilled cast iron or chilled cast the resulting moment of inertia of roller cross-section by reducing the outer diameter within the usual manufacturing tolerance of +/- 1% _¬ changed is changed.

15. A method for producing a roller group according to claims 1 to 4 and 12,

characterized in that

is the substantial equality of the bending rolls in the roll group characterized Herge _¬ provides that firstly the actual mean modulus of elasticity of the roller body is determined in the course of their manufacture by measuring the bend resulting from the dead weight or when applying at least one external force or determining the natural frequency and then the finished outer diameter of the roller body within the usual manufacturing tolerances of +/- 1 % and the finished inner diameter of the bore of the roller body are determined and generated in _{accordance with} the respective local elastic moduli.

16. A method for producing a roller group according to claims 1 to 4 and 12,

characterized in that

when determining the deflection in subsequent operation the BE in the peripheral bores or holes in the central introduced amount of heat transfer _¬ true, is controlled separately and taken into account.

17. A method for producing a roller group according to claim 6,

characterized in that

the partial or complete filling of the rollers with the fiber is carried out and changed after completion.

18. A method for producing a roller group according to claims 1 to 4 and 12,

characterized in that

in order to avoid undesirable vibrations of the rollers the individual Wal _¬ Zen groups of the rollers are dimensioned so that they need not be operated in the vicinity of the semi-critical speed.