EP1927697A1 - Calendar for processing a sheet of material - Google Patents

Abstract

The calendar (1) has a printing device (21) applied against an effective direction of a force unit of a charging pressure. The printing device is connectable and disconnectable in dependence of a load-conditional adjustable line force in a nip (3) that is limited by a bending-controlled roller (4) i.e. end roller. A fluid supply unit e.g. supply lines (17, 18, 22) and delivery line (23), is provided, where the fluid supply unit supplies a hydraulic and/or lubricating medium to bearings (15) and the printing device. The printing device is formed by an annular space.

Description

The invention relates to a calender for the treatment of a web according to the preamble of claim 1.

Such calenders are for example off DE 32 01 635 C2 or DE 196 50 576 C2 known. Thereafter, both or at least one of the two end rollers of a roller stack are formed as a bending-controlled roller. The bending-controlled rollers serve to eliminate short- and long-wave profile defects in the roll transverse direction, which can follow from the roll construction and / or the material to be treated. The entire profiling is carried out exclusively by hydraulic means, wherein the force elements of the hydraulic bearing assembly can be controlled in groups or individually. In addition to the correction width and the positioning accuracy, the size of the local line force correction, ie the correction potential, is of decisive importance for the effects in the transverse profiling.

To optimize the correction potential is known, the bending-controlled roller with form at least two continuous, completely filled rows of force elements. The nip-facing force elements are individually controlled. For this purpose, rearwardly directed force elements of the at least second row of force elements produce a uniform preload pressure over the entire length of the roller. This uniform biasing pressure of the at least second row of force elements causes the element pressures of the force elements facing the nip to be artificially increased. In this way, greater pressure and power reserves are available for local profile corrections. The provision of an at least second row of force elements is structurally complex. In addition, flex-controlled rollers with at least a second row of force elements require higher drive power, which increases the operating costs of the calender.

To optimize the correction potential is also off DE 38 20 974 C3 known, in addition to a nip facing series of hydraulic power elements that are individually controlled and thereby produce selectable element pressures to pressurize the annulus between the roll carrier and roll shell with a defined oil pressure, the so-called annular chamber pressure. From the interaction between element pressure and annular chamber pressure can be generated as a result of two different local forces. Either the element pressure is greater than the surrounding annular chamber pressure, so that via a pressure mountain, a force effect to the nip takes place, or the element pressure is smaller than the surrounding annular chamber pressure, so that via a pressure hole, a force effect takes place away from the nip. The force elements can thus work both as overpressure elements and as vacuum elements. The disadvantage here is that the bending-controlled roller with oil-filled annular chamber requires higher drive power due to swirl losses of the oil in the annular chamber.

The object of the invention is therefore to provide a calender according to the preamble of claim 1, which is inexpensive in operation and also low maintenance.

This object is solved by the features of claim 1.

As a result, a calender is provided which activates and deactivates a printing device for increasing the correction potential for profile errors as a function of the height of the load-dependent adjustable line force in the nip limited by the bending-controlled roller. Geometry errors of the rolls as well as due to the web conditional profile errors, in particular differences in thickness, differences in basis weight and moisture differences in the roll transverse direction can be corrected.

According to the invention, it has been recognized that the height of the preload pressure or of the annular chamber pressure is of subordinate importance for the consumed drive power. Decisive for an increased drive power is the oil contained in the annular chamber, which causes high vortex losses. The pressure device causes additional oil gets into the annular chamber of the bending-controlled roller. If at least one second row of force elements is preferably formed, friction losses result and additional oil enters the annular space of the roller. If an oil-filled annular chamber or an oil-filled annular space is preferably formed, there is a particularly high level of oil in the roller. According to the invention it is therefore provided that the oil, which passes through the nipabwärtsgerichtete forces generating pressure device additionally in the annulus of the bending-controlled roller, can get there only in certain operations of the calender.

In order to reduce the drive power, the at least one two-mode bending controlled roller is formed by an on or off pressure device. Depending on the currently driven line force in a calender, the corresponding operating mode is activated, thus minimizing the energy requirement for the operation of the calender. A reduction in drive power of up to 30% at high web speeds of about 2000 m / min is possible.

The connection of a printing device is preferably only to provide enough correction potential for line force corrections for small line forces available. By means of the element pressures of the force elements can be compared to by a printing device generated bias so-called pressure holes are generated.

In the area of higher line forces, the correction potential of the bending-controlled roll can be obtained solely from the element pressures of the force elements. The element pressures are then so high that it is sufficient for negative profile corrections to lower the oil pressures in the force elements. According to the invention, it is therefore provided that an additional printing device for generating a correction potential is then switched off. As higher line forces, values in the range of 10 to 200 N / mm are to be considered depending on the paper.

It is further preferred that the connection and disconnection of the printing device controls an adjustable scraper, which is pivotable adjacent to the inner circumference of the roll shell when switching off the printing device in a doctor position and can be pivoted away from the doctor position when the printing device. It is particularly preferred that the positioning of the scraper is self-regulating by the ability to connect and disconnect the printing device.

It is furthermore preferred that the pressure device is formed either by hydrostatic support dies directed backwards relative to the hydraulic bearing arrangement and / or by an annular space which can be acted upon by a selectable oil pressure between the roll shell and the carrier. The pressure device by means of supporting punches allows the setting of a uniform or locally uneven biasing pressure, but at the expense of increased design complexity. The oil pressures adjustable with an oil-filled annulus require uniform preload pressures. The setting of a large correction potential, however, by means of a simple structural design.

The force elements and the pressure device preferably operate hydraulically, for which purpose at least one liquid or oil supply is provided. The force elements can be designed as hydrostatic support elements or sealing elements.

Further embodiments of the invention are described in the following description and the dependent claims.

• Fig. 1 zeigt schematisch einen Teilbereich eines Kalanders mit einer teilweise im Längsschnitt dargestellten biegegesteuerten Walze als eine Endwalze gemäß einem ersten Ausführungsbeispiel,
• Fig. 2 zeigt schematisch einen Schnitt nach A-A gemäß Fig. 1 mit einem in eine Rakelposition geschwenkten Abstreifer,
• Fig. 3 zeigt schematisch einen Schnitt nach A-A gemäß Fig. 1 mit einem aus einer Rakelposition weggeschwenkten Abstreifer,
• Fig. 4 zeigt schematisch einen Schnitt nach A-A gemäß Fig. 1 mit einem aus einer Rakelposition selbstregelnd weggeschwenkten Abstreifer,
• Fig. 5 zeigt schematisch einen Teilbereich eines Kalanders mit einer teilweise im Längsschnitt dargestellten biegegesteuerten Walze als eine Endwalze gemäß einem zweiten Ausführungsbeispiel,
• Fig. 6 zeigt schematisch einen Querschnitt der Fig. 5 mit einem in eine Rakelposition geschwenkten Abstreifer,
• Fig. 7 zeigt in einem Diagramm die Antriebsleistung in Abhängigkeit von der Geschwindigkeit für eine biegegesteuerte Walze mit zu- und abgeschalteter Druckeinrichtung.

The invention will be explained in more detail with reference to the embodiments illustrated in the accompanying drawings.

• Fig. 1 shows schematically a portion of a calender with a partially longitudinally illustrated bending-controlled roller as an end roller according to a first embodiment,
• Fig. 2 schematically shows a section according to AA Fig. 1 with a scraper pivoted into a doctoring position,
• Fig. 3 schematically shows a section according to AA Fig. 1 with a scraper pivoted away from a squeegee position,
• Fig. 4 schematically shows a section according to AA Fig. 1 with a scraper pivoted away from a squeegee position self-regulating,
• Fig. 5 shows schematically a portion of a calender with a partially longitudinally illustrated bending-controlled roller as an end roller according to a second embodiment,
• Fig. 6 schematically shows a cross section of Fig. 5 with a scraper pivoted into a doctoring position,
• Fig. 7 shows a diagram of the drive power as a function of the speed for a bending-controlled roller with on and off pressure device.

Fig. 1 refers to a calender 1 for the treatment of a web, in particular a paper or board web or a tissue web, with at least one roll stack 2. The roll stack 2 has at least two rollers which form nips 3 loadable with line forces between in each case two rolls. The nip 3 or passes through a web, not shown, at a certain web speed to be subjected to a pressure treatment and optionally temperature treatment. For two-sided treatment of the web For example, the at least one roll stack 2 can have a selectable number of rolls with an interchangeable gap or at least two roll stacks arranged behind one another or one above the other, wherein the change of the fabric web side is then preferably carried out between the at least two roll stacks. The load level can be formed vertically, horizontally or with a selectable inclination to the vertical.

At least one end roll of a roll stack 2, here a lower roll of the roll stack 2, is designed as a bending-controlled roll 4. Adjacent to the bending-controlled roller 4, a conventional hard or soft roller 9 is arranged to form a hard or soft nip 3 with the bending-controlled roller 4, which can also be formed as a hard or soft roller. The number of nips 3 in the roll stack 2 is selectable and depends on the type of web, in particular a paper type, and the calendering parameters. Also, two-roll stack with two nip 3 forming bending-controlled rollers 4, which are hard and / or soft formable, can be provided.

The bendable roller 4 has a rotatable roller shell 5, the outer periphery 6 forms a working roll circumference. The roll shell 5 is formed as a roll tube or roll shell. The length of the roll shell 5 is penetrated or penetrated by a stationary crosshead, the stationary support 7, which leaves a distance from the inner periphery 8 of the roll shell 5. The roll shell 5 surrounds an annular space 12, in which the carrier 7 is arranged. The carrier 7 is rotatably with its ends 10 in each case a bearing 13 and optionally mounted pivotably.

The bearings 13 of the bending-controlled roller 4 and pins 11 of the conventional roller 9 are guided in a roll stand, not shown, and can be pressed against each other by load devices, not shown. As a result of this, line forces can be adjusted. The load can also be alternatively or additionally adjustable by a stroke of the roll mantle 5 relative to the carrier 7.

The roller shell 5 is rotatable relative to the carrier 7 and is supported at its two ends in each case in a peripheral bearing unit 14.

Between the carrier 7 and the roll shell 5, a hydraulic bearing assembly 15 for supporting the roll shell 5 along at least one effective region is arranged, which is formed by individual along a roll length axially juxtaposed bearings, each having a radially movable force element 16 for transmitting controllable element pressures the inner shell peripheral surface 8 of the roll shell 5. The force elements 16 each pressure medium with adjustable pressure can be supplied to hydraulically radially movable as a piston elements in a cylinder blind bore 19 which abut with a correspondingly shaped end face 20 on the inner circumference 8 of the roll shell 5. The force elements 16 are provided for pressure transmission between roll shell 5 and support 7, wherein the pressure medium for contact pressure and hydrostatics is used, depending on the design of the force elements 16 as, for example, hydrostatic support elements or sealing elements with common or separate liquid supply via leads 17, 18. Die Power elements 16 face the nip 3.

The bending-controlled roller 4 further comprises at least one pressure device 21, by means of which against the direction of action of the force elements 16, a biasing pressure can be applied. The biasing pressure is, as it were, directed backwards with respect to the pressure direction of the force elements 16. The printing device 21 can be switched on and off as a function of the height of the load-dependent adjustable line force in the nip 3 bounded by the bending-controlled roller 4. Preferably, the printing device 21 can be switched on under load-induced line forces below a line force of 10 to 200 N / mm, in particular 20 up to 100 N / mm.

According to the first exemplary embodiment, the pressure device 21 is formed by the annular space 12 which can be acted upon by a selectable oil pressure between the roll shell 5 and the carrier 7. The annular space 12 is at the ends by not illustrated axial seals sealed and can be filled via a supply line 22 with hydraulic fluid from a reservoir 24. Via a line 23, the pressure fluid can be returned to the reservoir 24. In line 23 is a pressure relief valve 25, which allows to set and maintain a predetermined pressure in the annulus 12, the so-called annulus pressure. The pressure fluid is removed from the reservoir 24 and, via a pump 26 which is connected to the supply line 22, to pressure, preferably 40 to 60 bar, brought. The annulus pressure generates a bias voltage from which the flex-controlled roller 4 obtains its correction potential. Namely, two different local force effects can be generated from the interaction between element pressure and annulus pressure, namely a pressure island towards the nip 3, if the element pressure is greater than the surrounding annulus pressure, or a pressure hole, if the element pressure is smaller than the surrounding annulus pressure. In the area of high load-related line forces, in particular for line forces above 20 to 100 N / mm, the correction potential of the bending-controlled roller 4 can be obtained solely from the element pressures. The element pressures are then so high that it is sufficient for negative profile corrections to lower the oil pressures in the force elements 16. It must then be generated no pressure holes on the printing device 21. The pump 26 for activation of the printing device 21 is therefore switched on and off.

Fig. 4 schematically shows the entering in the annular space 21 during oil filling turbulence, which is connected to a drive power consumption. In Fig. 7 the drive power is shown as a function of the speed. Shown dashed lines is the drive power with connected pressure device. The solid line shows the drive power when the printing device is switched off. At web speeds below 500 m / min, the drive power consumption is about the same in both cases. At a web speed of about 2000 m / min, the drive power is reduced by about 30%, when the power consumption portion caused by a pressure device, in particular vortex and / or friction loss, is eliminated.

In a known manner, finally, each cylinder blind bore 19 of a force element 16 can be fed individually or in zones via a supply line 17, 18 with pressure medium, wherein the supply is effected via a control device 35. The pressure medium is removed from the reservoir 24 and brought via a pump 36 to pressure.

According to a second in the Fig. 5 and 6 illustrated embodiment, a pressure device 40 with respect to the force elements 16 backward directed hydrostatic support stamp 37, which preferably produce a uniform bias and are arranged adjacent to each other in a row. Alternatively, the support stamp 37 may be formed as a hydraulic sealing elements. The hydrostatic support punches 37 are preferably connected to a common supply supply and discharge line 22, 23. The support stamps 37 can be activated and deactivated. The shutdown takes place by retracting the support punches 37, whereby mechanical and hydraulic friction losses and the outlet overflowing oil in support on the inner circumference 8 of the roll shell 5 omitted, which otherwise have a power consumption when driving the roller 4 result. Fig. 6 shows the retracted position of a support punch 37 in the annular space 12, so that no contact exists to the inner periphery 8 of the roll shell fifth

By means of the hydrostatic support dies 37, a nipabwärtsgerichtete force can be generated along the roll length as well as with an oil-filled annular space 21, in which an oil pressure is built up. The oil-filled annulus 21 has the advantage that the roll shell 5 maintains a substantially round shape despite set nipabwärts directed forces, while using hydrostatic support die 37 of the roll shell 5 is deformed from the circular shape when adjusting nipabwärts directed forces. The hydrostatic support stamp 37 can be formed in a known manner. For the retraction of the support stamp 37 may be provided a mechanical or hydraulic retraction device. According to Fig. 6 For example, the mechanical retraction device is formed by a tension spring 41.

As already to the embodiment of Fig. 1 to 4 described, the scraper 27 is preferably zurückstell- or retractable via a connection of the printing device 40 from a doctor position. When the mechanical or hydraulic retraction device 41 becomes effective, ie deactivation of the support punches or hydraulic sealing elements, the wiper 27 is placed in the doctoring position, if it is not preferably set permanently in the doctoring position. This can be done selbstregelnd or by coupling a Abstreiferbetätigung and actuation of the retraction device.

The bending-controlled roller 4, which is designed with a pressure device 21, 40, has at least one scraper 27 which can be adjusted in a doctoring position adjacent to the inner circumference 8 of the roller jacket 5. The scraper 27 is arranged in the annular space 12. According to the invention it is provided that the scraper 27 is formed such that the scraper 27, when switching the printing device 21, 40 back from a doctor position, in particular pivots back. It is particularly preferred that the recoverability of the doctor blade position is self-regulating. For this purpose, the scraper 27 preferably has an actuating device 28, which responds to the effectiveness of the printing device 21, 40. According to the in the FIGS. 1 to 6 illustrated embodiment, the scraper 27 is designed as a two-armed lever. A in the doctor position adjacent to the inner circumference 8 of the roll shell 5 alignable lever arm is hinged to a tension spring 29 here. Contrary to the tensile force of the tension spring 29 operates an actuator 28, for example, an inflatable tube which is connected to a pneumatic supply line 30 with pump 31. When oil filling the annular space 12, the actuator 28 is deactivated, here by squeezing the tube, so that the scraper 27 under the tensile force of the tension spring 29 from the doctor position (see. Fig. 2 ) is swung away, as in Fig. 3 is shown. The scraper 27 may not only be pivotable, but also designed to be displaceable.

The scraper 27 is a guide surface 34 and a stripped liquid receiving collecting space 33 associated with outflow 32. The drain 32 is preferably connected to a drain 38 which can be selectively opened or closed by an actuator 39. If the pressure device 21, 40 is switched on, the actuator 39 is closed. If the printing device 21, 40 is switched off, the actuator 39 is opened. As an actuator 39 is used in particular a valve.

Claims (12)

A calender for treating a web, in particular a paper or board web or a tissue web, with at least one roll stack, the at least two rollers forming nips with line forces and at least one end roller having a bending-controlled roller, and the bending controllable roller formed is provided with a rotatable roll shell interspersed by a fixed support, a hydraulic bearing arrangement between support and roll shell formed by individual along a roll length axially juxtaposed bearings, each having a radially movable force element for transmitting controllable force element pressures on an inner circumferential surface the roll mantle, and with at least one against the direction of action of the force elements a biasing pressure coatable printing device, characterized in that the pressure device (21, 40) is switched on and off depending on the level of loading gsbedingt adjustable line force in the nip (3) bounded by the bending-controlled roller (4). Calender according to claim 1, characterized in that the pressure device (21, 40) is switchable under load-related line forces below a line force of 10 to 200 N / mm. Calender according to claim 1 or 2, characterized in that at least one liquid supply (17, 18; 22, 23) is provided, which supplies the bearings (15) and the pressure device (21, 40) with pressure and / or lubricating fluid. Calender according to one of Claims 1 to 3, characterized in that the pressure device (21) is formed by an annular space (12), which can be acted upon by a selectable oil pressure, between the roll shell (5) and the carrier (7). Calender according to one of claims 1 to 3, characterized in that the pressure device (40) relative to the hydraulic bearing assembly (15) comprises backward directed hydrostatic support punches or hydraulic sealing elements (37) along the roller (4). Calender according to claim 5, characterized in that the hydrostatic support punches or hydraulic sealing elements (37) are retractable by means of a mechanical or hydraulic retraction device. Calender according to claim 6, characterized in that a tension spring (41) is provided as the mechanical retraction device. Calender according to one of claims 1 to 7, characterized in that with a pressure device (21, 40) formed bending-controlled roller (4) at least one in a doctor blade position adjacent the inner circumference (8) of the roll shell (5) adjustable scraper (27) , Calender according to claim 8, characterized in that the scraper (27) is retractable via a connection of the printing device (21, 40) from a doctor position. Calender according to claim 8 or 9, characterized in that the scraper (27) is associated with a guide surface (34) and a collecting chamber receiving the stripped liquid (32). Calender according to one of claims 1 to 10, characterized in that the force elements (16) are designed as hydrostatic support punches. Calender according to one of claims 1 to 11, characterized in that the force elements (16) are designed as hydraulic sealing elements.

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