DE4026774A1 - Paper polishing roller assembly giving high speed working - has hard top and bottom rollers with a soft cladding at the centre rollers for high-speed working - Google Patents

Abstract

The multi-roller polishing roller assembly has at least four rollers on a vertical stack where the bearing mountings at the ends of each roller are at the same gap from each other in all the rollers. The top and bottom rollers are both hard, and the two centre rollers have a soft cladding. Two rollers, operating in the same direction but not next to each other, act as roller bending compensation rollers, with pressure zones directed at the other rollers with a normal rigid bending action. Three rollers are on moving bearing mountings which can be subjected to pressure to adjust the linear forces between the rollers. ADVANTAGE - The assemly occupies relatively little space, allows the paper web to be thread through simply, and gives a high speed working.

Description

The present invention relates to a multi-roll calender for the treatment of sheet-like goods, in particular of paper webs, by means of four in a common press plane stacked rollers.

Machines for smoothing paper webs and the like web-like goods have long been known, in particular also under the name of calender. These consist of a plurality superimposed rollers between which the Paper web passes under pressure.

According to the state of the art, there is a so-called super calender with 10 to 14 rolls stacked on top of each other known, with the principle of gradual line force increase from top to bottom nip use is made. The steps or levels of line force increase correspond to their own weight of the rollers, which alternate a hard surface (e.g. made of chilled cast iron) or a soft, elastic surface (e.g. overlay made of paper or a fibrous fabric) exhibit. With these soft rollers you can achieve two advantages:

• - in the event that the thickness of the to be processed Paper web varies across the surface (Cloudy, screen mark), the roller surface dodge. . . it can be used on the surface  the paper web considers uniformity improve smoothness;
• - When passing through a press nip between two rollers are created between the surfaces of a "hard" and a "soft" Roll existing roller pair a relative movement . . . the paper web adheres to the surface the soft roller and is so through the relative movement on the other hand by the hard Surface of the conjugate roller polished.

The super calender consists of viewed from top to bottom alternating hard and soft rollers, so is only one side of the paper web is polished and you get it a glossy paper on one side. To paper with the same To get shine on both sides, in the roller stack, in the lower area, two soft ones Rollers arranged one above the other. With that the so far brought unpolished paper side to the hard rollers and the polished on the soft rollers. . . The result is a paper web polished on both sides (cf. US-PS 45 01 197).

The known super calenders are subject to their Resilience thermal limits, in particular in that the soft rollers on each of their Revolutions must pass two press nips. With that in particular the working speeds are limited, and to 50% relative to the case that only one press nip to happen.

Based on this or based on it, matt or Developed soft smoothing, where every soft roller only turns past a press nip and consequently in Connection with paper machines up to the highest machine speeds can keep up (see. US-PS 46 06 264).  

These smoothing systems have the disadvantage that they are relatively large Need space, because instead of one Stack a plurality of roller pair stations necessary is. Doing so, on both sides of a paper web to get the same shine, the soft rollers of Station to station between upper and lower position switch.

The object underlying the present invention exists - based on the aforementioned state of the art - in specifying a multi-roll calender that at relative small space requirement and relatively simple paper guidance operated up to the highest web or paper speeds can be, taking both sides of the subject to be treated Good, especially both sides of a paper web can be polished to approximately the same gloss.

The above-mentioned task is characterized by the one in Part of claim 1 specified combination of features solved.

As a result of the equidistant positioning (feature a) the Rolls reached in one and the same press level (stacking level), that even then over the entire width of the multi-roll smoothing unit equal line force distribution is guaranteed if all Rollers are bent by the same amount; this deflection can be positive or negative, i.e. H. convex or be concave relative to the machine floor. In principle means this is that, contrary to the prior art, at the same line forces over the entire web width in all press nips only with straight rollers are possible on the bearings and in the pressure chambers via targeted and coordinated force application of the rollers also on rollers bent by the same amounts in all three columns the same line force distribution over the Width arises.

According to feature b) care is taken that the gutter in no nip between two hard rollers  runs through, and that the top and bottom of the gutter equally polished.

Due to the specific allocation or arrangement of the deflection compensation rollers (Feature c) ensures that the line force between the two middle rollers is kept small, so that there is no significant dynamic stress on the roller supports arises when passing through the middle press nip. The preferred line force in the middle gap is 10 to 25 ° the line forces in the upper and lower press nip.

The movable bearing of three rollers (feature d) finally ensures that with variable line forces always the same deflection of all rollers and thus an equal line force distribution across the width of the multi-roller smoothing unit can be adjusted.

Around the goal, about the same gloss on both sides of a paper web to achieve, the pressing force in the two outer press nips of the multi-roller smoothing unit are approximately the same. This is - according to claim 2 - achieved in that the two Rolls without deflection compensation are made approximately equally stiff are.

In general, all of the rollers are cylindrical. To where appropriate Giving a paper web side more shine is - according to the patent claim 3 - the hard roller, not as a deflection compensating roller is trained with a certain positive Crowning. Ultimately, the line force in the press nip associated with this roller increases and a fine adjustment relative paper gloss on both sides of the web.

According to a special version - cf. Claim 4 - is intended to store the top roller firmly in a frame, while the three lower rollers can then be moved vertically. With this type of construction, the multi-roller smoothing unit opens with the Dead weight of the rollers, so that no additional means of displacement required are.  

In the event that a smaller in the middle press nip Line force is aimed for, the two middle ones soft rollers supported on their bearing blocks against each other, in particular by means of hydraulic cylinders - cf. Claim 5. This ensures that it is brought about same bending lines of all rolls, d. H. same Line force distribution over the entire width of the Multi-roll smoothing units in all three press nips on the Bearing points of one of the two soft rollers only one relatively little additional force required is.

In principle, it is possible to use the deflection compensation rollers press from bottom to top or from top to bottom allow. In the first case - cf. Claim 6 - the top roller is a rigid roller and the bottom one Deflection compensation roller; in the second case is - cf. Claim 7 - the top roller is a deflection compensation roller and the bottom one is a rigid roller. This enables the paper web to travel from above down (according to claim 6) or - alternatively - From the bottom up (according to claim 7).

Is - according to claim 8 - in the direction of the the first rigid roller looks at the web-like material operation and the second rigid roller increasingly driven, so the paper web between the first and second press nips tightened. This increases operational safety and product quality.

As an alternative, these latter specifications also serve one the paper web between the first and the second press nip opposite drying device - cf. Claim 9. The web shrinks due to drying, which also leads to a tightening.  

The bearing forces to act on the bearing points of the Rollers, as well as those for the operation of the deflection compensation rolls required internal pressures are - according to claim 10 - in a coordinated manner in one determined appropriately programmed control computer and then preferably automatically entered into the load system.

The invention will now be described with reference to the drawing explained. This shows in

Fig. 1 shows a first embodiment of a multi-roll calender in a basic representation;

Fig. 2 shows a second embodiment of a multi-roll calender in a basic representation;

Fig. 3 is a multi-roll calender of the type shown in Fig. 1, installed in a frame.

In Fig. 1, a multi-roll calender 1 is shown, in which the direction of passage of a paper web 2 is oriented from top to bottom. The multi-roll calender 1 consists of four rolls stacked one above the other in a press plane (stacking plane), the two outer rolls (roll 11 and roll 14 ) of which have a hard surface; the two inner, intermediate rollers (roller 12 and roller 13 ) are covered with a soft pad 3 .

These four rollers 11. . . 14 form three press nips I, II and III in the common press plane through which the paper web 2 is guided or pulled one after the other.

The first (upper) press nip I is thus formed by a hard - 11 - and a soft - 12 roll; the second (middle) press nip II is formed by the two soft rollers 12 and 13 ; the third (lower) press nip III is formed by the second soft roller 13 and the second hard roller 14 .

The soft roll 12 determining the first press nip I and the hard roll 14 determining the third press nip III are each designed as deflection compensation rolls. These each have inner pressure zones 121 and 141 , the effect of which is such that, in relation to the common press nip I or III, they influence the adjacent rollers 11 and 13 , respectively. (The deflection compensation rollers themselves are described in their details, for example, in EP 00 43 119 B1.)

The material web to be treated, in particular paper web 2 , is thus passed through the press nips I, II and III through the multi-roll smoothing unit 1 and treated in succession, on both sides. In order to tighten this paper web 2 between the first and the second press nip I / II, if necessary, the uppermost hard roller 11 is braked and at the same time the soft rigid roller 13 is driven more intensely. The same goal is served by a drying device 4 , which is opposite the paper web 2 after passing through the first press nip I. With this drying device 4 , for example, air is blown onto the paper web 2 , so that the paper web shrinks and tightens in the process. Such a streamlining can u. U. become necessary when the line force in the second press nip II is set relatively low, so that there is no significant dynamic stress on the roller supports 3 in the press nip II.

The deformation work between the two soft rollers 12, 13 is only half as large as between a hard and a soft roller. However, this deformation work can be further reduced if a lower line force is set in the second press nip II by means of the pressure zones 121 and 141 mentioned than in the other two press nips I and III.

In addition, it should be noted that the two rigid rollers 11 and 13 have approximately the same stiffness. This size, which corresponds to the product of the modulus of elasticity (in N / mm²) and the moment of inertia (in mm⁴), should not differ more than in the ratio 2 to 3 if the same smoothness or gloss is desired on both sides of the paper web 2 . A targeted or conscious improvement in the smoothness of the paper web on one side compared to the other can also be achieved in that the hard rigid roller is positively cambered.

In Fig. 2, a multi-roll smoothing unit 1 'is shown, in which the paper web 2 - runs counter to the direction of travel according to Fig. 1 - from bottom to top and at the same time the arrangement of the rollers is reversed from top to bottom. In both of these calendering units according to FIG. 1 or 2, the direction of web travel can of course also be selected against the direction of the arrow shown.

The first press nip I 'is formed in Figure 2 by a hard rigid roller 11' and a soft deflection compensating roller 12 ' ; the second press nip II 'is formed by the pairing of the last-mentioned soft deflection compensation roller 12' and a soft rigid roller 13 ' ; the third press nip III 'is formed by the last-mentioned soft rigid roller 13' and a further, but hard deflection compensation roller 14 ' . The sequence of the individual rolls stacked one on top of the other ultimately corresponds to that according to the multi-roll calender 1 according to FIG. 1, this quasi reversal of the rolls also corresponding to the inner pressure zones 121 ' and 141' of the deflection compensation rolls 12 ' and 14' in the same direction from bottom to top , So are directed towards the adjacent roller 11 ' or 13' . Analogous to the multi-roll calender 1 according to FIG. 1, the soft deflection compensation roll 12 'is opposite a drying device 4 , namely after the first press nip I', so that the paper web 2 between the first and the second press nip I 'or II' are tightened can.

FIG. 3 shows the multi-roll smoothing unit 1 shown in a basic illustration in FIG. 1, specifically installed in a (frame) frame 100 . The first rigid rigid roller 11 delimiting the first press nip I is in this case firmly installed via bearing blocks 101 by means of screws 102 and is driven (or braked) by a motor via a drive pin 103 .

The lowermost roller, that is to say the deflection compensation roller 14 , is in turn movably supported on the frame 100 by means of two support brackets 104 and is pressed upwards by means of pressure cylinders 105 in the direction of the adjacent soft rigid roller 13 . This deflection compensation roller 14 has a fixed axis 106 around which a roller shell with a hard surface rotates. This roller shell is driven by two drive pinions with drive pins 107 and 108 .

The soft rigid roller 13 forming the third press nip III together with the deflection compensation roller 14 is in turn mounted in two bearing blocks 109 and is driven (or braked) via a drive pin 110 . Pressure cylinders 111 are provided between the bearing blocks 104 and 109 for the rollers 13 and 14 forming the third press nip III, via which correction forces can be transmitted to the soft rigid roller 13 .

The soft rigid roller 13 lies opposite the soft deflection compensation roller 12 in order to form the second press nip II. This is supported in support frames 112 and is pressed against the uppermost hard rigid roller 11 by pressure cylinders 113 . These pressure cylinders 113 are supported on the bearing blocks 109 for the soft rigid roller 13 .

The soft deflection compensation roller 12 has a fixed axis 114 which is driven by pinions and drive pins 115, 116 . The pinions drive, in a manner known per se, a toothed ring connected to the rotating roller jacket of the soft deflection compensation roller 12 . The support brackets 112 for the soft deflection compensation roller 12 can be pressed down by means of pressure cylinders 117 pressing against the bearing brackets 101 for the first rigid roller 11 .

The bearing or support brackets 104, 109 and 112 for the movably mounted rollers 12, 13 and 14 are each mounted or guided in slide guide pieces 118 on the frame 100 . In practical operation of the multi-roller smoothing unit 1 , ie the generally bent rollers, corresponding bearing forces a _i can be determined via said pressure cylinders 105, 111, 113 and 117 , via which in conjunction with those in the pressure zones of the deflection compensation rollers 12 and 14 respectively the width of the multi-roll calender 1 viewed in all three press nips I, II, III an equal line force distribution is adjustable. Instead of the pressure cylinders mentioned, power means acting directly from the frame 100 on the bearings 109, 112 of the middle rollers 12 or 13 can also be used; instead of the slide guides 118 mentioned , it is also possible, for example, to use pressure levers movable about fixed pivot points.

It is essential that all the rollers of the multi-roll calender 1 are mounted at least approximately equidistically, ie with the same distance between the two roller bearings, and that the bearings of the movably mounted rollers are subjected to bearing forces in accordance with the current operating conditions in such a way that the forces are optimal Operation required equal line force distribution over the entire width of the multi-roll smoothing unit 1 can be set. The current bearing forces to be introduced are determined in a control computer 150 . This is programmed in accordance with the complex system of equations, ie the laws of elastomechanics and the deflection of the rolls in a multi-roll smoothing unit 1 and links the quantities corresponding to the dead weight forces, the resulting line forces and the deflection-free line forces; As mentioned, the control computer 150 also determines the respective internal pressures P ₁₂ and P _{14 of} the deflection compensation rolls 12 and 14, respectively. The introduction of the bearing forces a ₁₂ , a ₁₃ , a ₁₄ to the movably mounted rollers 12, 13, 14 takes place via force elements which are arranged on both sides of the rollers 12, 13, 14 and are functionally coupled to the corresponding bearing points. In the example of FIG. 3, the bearing force introduced on the roller 12 results as the differential force of the pressure cylinders 113 and 117 . The bearing force introduced into the roller 13 is the differential force of the pressure cylinders 113 and 111 , and the force acting on the bearing of the roller 14 is the differential force of the pressure cylinders 105 and 111 . The control computer 150 controls the contact forces of the pressure cylinders 105, 111, 113 and 117 as well as the pressures of the pressure zones 121 and 141 of the rollers 12 and 14 via supply lines (not shown).

As an alternative to the multi-roll smoothing unit 1 shown in FIG. 3, instead of the top roller 11 , any other roller 12 or 13 or 14 can also be firmly connected to the frame 100 . The top roller 11 is then vertically movable and the control computer 150 must be reprogrammed accordingly.

The mathematical-theoretical model of the bearing support forces (e.g. a ₁₂ , a ₁₃ , a ₁₄ ) and the entire line force range is as follows:

First you see those that appear as additive constants mass forces acting outside the web width, apply for equal line force distribution in all press nips following Equations:

P _I , P _II , P _III mean the line forces in the press nips I, II and III, and

f the deflection across the width of the paper web,
s the stiffness of the rotating roller body (s = E · I),
c is a constant, namely c = L⁴ (1 + 24/5 U / L) with L as the paper web width and U as the distance from the paper web edge to the center of the bearing support,
_{E is} the dead weight of the rotating part of the roller within the width of the paper web, expressed as a line load (kN / m),
_{H is} the hydraulic force of the pressure zones of the deflection compensation rollers (kN / m) related to the paper web width.

The term

defines the required exterior Bearing force, expressed as Line force in kN / m (and without compensation force for overhanging masses).

The actual bearing force is then

(With F _Ü as the dead weight for overhanging masses);
L is the paper web width.

With this system of equations, the same linear force distribution results in all press nips I, II, III if the same value for the deflection f is selected for each roller. By specifying a certain value for the deflection f, the system of equations can be solved perfectly starting with the roller 11 and ending with the roller 14 .

The above system of equations can also be used if necessary the influence of shear deformation is expanded, and in accordance with the applicable mechanical relationships. The actual bearing force is in this case

Mean

f = f ₁ + f ₂ the deflection,
A the shear cross section of the respective roller,
G the sliding module,
L the press length and
µ the shear distribution number, where applies

δ = d / D

With

d = inner roll diameter,
D = roller outer diameter.

Claims (10)

1. Multi-roll smoothing unit for the treatment of web-like material, in particular paper webs, by means of four rollers stacked one above the other in a common press plane, characterized in that

• a) all rolls are mounted equidistantly, ie with the same distance between the two bearings of the rotating roll body,
• b) the top and bottom rollers are each hard rollers and the two inner rollers are each covered with a soft pad,
• c) two non-adjacent rollers are deflection compensating rollers which act in the same direction and which have pressure zones acting in the direction of the two other rigid rollers which normally deflect, and
• d) three of the rollers are movably mounted in the press plane and can be acted upon by adjustable bearing forces acting in the press plane.

2. Multi-roll calender according to claim 1, characterized, that the two rigid rollers essentially have the same rigidity. 3. Multi-roll calender according to claim 1 or 2, characterized, that the hard rigid roller is positively cambered. 4. Multi-roll calender according to one of claims 1 to 3, characterized, that the top roller is firmly in a rack is stored. 5. Multi-roll calender according to one of claims 1 to 4, characterized, that the two inner rollers on their bearings relative to each other, especially with hydraulic cylinders are supported. 6. Multi-roll smoothing unit according to one of claims 1 to 5, characterized in that the top roller is a rigid roller and the bottom is a deflection compensation roller ( Fig. 1). 7. Multi-roll calender according to one of claims 1 to 5, characterized in that the top roller is a deflection compensation roller and the bottom one is a rigid roller ( Fig. 2). 8. multi-roll calender according to claim 6 or 7, characterized, that in the direction of flow of the web-like material looks at the first rigid roller braked and the second rigid roller reinforced are driven.   9. multi-roll calender according to claim 6 or 7, characterized, that in the direction of the web-shaped Considered good between the first two Press columns arranged a drying device is. 10. Multi-roll calender according to one of claims 1 to 9, characterized, that the moveable at the bearing points stored rollers effective bearing forces and the Internal pressure of the deflection compensation rollers via a suitably programmed control computer are adjustable so that one over the Width of the rollers matched the same Line force distribution in all three nips arises.