WO2000079043A1

WO2000079043A1 - Press

Info

Publication number: WO2000079043A1
Application number: PCT/SE2000/001280
Authority: WO
Inventors: Ingmar Andersson; Malin Kilian; Bertil ANDRÉN
Original assignee: Metso Paper Karlstad Aktiebolag
Priority date: 1999-06-17
Filing date: 2000-06-19
Publication date: 2000-12-28
Also published as: EP1194637A1; CA2376768A1; AU5862800A; SE9902318D0; SE514421C2; SE9902318L

Abstract

A press in a machine for the production of a continuous web (2) of cellulosic fibrous material, comprising a press device (5), a rotatably journalled counter roll (3), which comprises a cylindrical roll body (7) and is arranged to form a press nip (4) in cooperation with the press device, and endless clothing (6), that is arranged to run through the press nip in contact with the web and preferably has ability to receive and carry away liquid from the web, and devices (15, 16) for heating the web in the press nip, which heating devices comprise a movable heat transferring device (15) for transferring heat to the web in the press nip, and at least one heating apparatus (16) for heating the heat transferring device. According to the invention the heat transferring device consists of a heatable sleeve, which is an integral part of the counter roll and encloses the roll body, and which has an external mantle surface (14) for cooperation with the opposite press device, and said external mantle surface of the sleeve comprises a number of imprinting elements (24), which are arranged in a pattern (25) for a in the fibrous web generating a pattern imprint corresponding to the imprinting elements.

Description

PRESS

TECHNICAL FIELD

The present invention relates to a press in a machine for the production of a continuous web of cellulosic fibrous material, comprising

(a) a press device;

(b) a rotatable counter roll having a cylindrical roll body forming a press nip with the press device;

(c) an endless clothing extending through the press nip for carrying the web through the press nip, said clothing having the ability to receive and carry away liquid from the web; and

(d) devices for heating the web in the press nip, said heating devices including

(da) a movable heat transferring device for transferring heat to the web in the press nip; (db) at least one heating apparatus for heating the heat transferring device.

PROBLEM PRESENTATION AND PRIOR ART

Pressing of a wet fibrous web in a press at an elevated temperature and at a high pressure has been found to result in a number of favorable effects, for instance highly increased dewatering rate. The technique, which is called impulse technique, impulse pressing or impulse drying, is described in SE-7803672-0, equivalent to US-4,324,613. The top pressures that the method described therein uses lie within the interval 3 - 8 MPa and the surface temperatures between about 150 °C to about 350 °C at a cylinder in a press nip of conventional type. In this case, "conventional press nip" means a press nip, in which two rolls with cylindrical cross-section are co-operating against each other under pressure. However, because of the short press nip, the dwell time for the paper web in this type of press nip is only some few milliseconds, and this dwell time is too short for it to derive advantage from the favorable effects of pressing at high temperature under simultaneously high pressure. Therefore, it has also been proposed to utilize impulse drying in a heated shoe press, wherein the press nip is extended to about 20 to 30 cm, so that the dwell time for the heat treatment becomes considerably longer.

Consequently, at impulse drying, high temperature and high pressure are combined under a short time period in order to give very high thermal flows to the web. A heat transferring tool in the form of the mantle surface of a steel or cast iron roll, which transfers heat to the fibrous web, achieves top thermal flows within the interval 2 - 8 MW/m², which results in very high dewatering rates. The mechanism that is the cause of these high dewatering rates with accompanying high dry solids contents is not yet entirely clear. One theory that has been submitted is that the vapor, which develops near the surface of the heat transferring device closest to the fibrous web, through its expansion helps to extrude substantially all remaining water in the fibrous web into the felt that is in contact with the fibrous web. Another theory is that the reduced viscosity of the water, caused by the high temperature, in combination with the fact that water of high temperature (>100 °C) evaporates fast at a rapidly reduced pressure, which occurs when the web leaves the press nip and the pressure returns to normal atmospheric pressure, results in that high dry solids contents in the paper web is obtained.

In said SE 7803672-0 a burner supplies heat to one of the rolls in a press, which press has two rotating rolls. The heat is supplied onto the mantle surface of the roll immediately before the press nip. The patent states that the roll can have a surface layer with low capacity of heat transmission so that the surface layer thereby can keep a high temperature.

The patent US-4, 738,752 describes an extended, heated press nip, in which the fibrous web encounters a hot surface, which is formed of a rotatable press roll or a metal belt, that runs in a loop around a plurality of guide rolls. The press roll and the belt are heated by a heating apparatus. The press roll may have a first coaxial layer and a second coaxial layer, which second layer extends around the first layer and has a coefficient of thermal conductivity that is larger than that of the first the layer. The first layer may be of ceramics, while the second, external layer consists of metal and has a thickness of 0.0127 - 1.27 cm. The layers are in intimate contact with each other and together they constitute a uniform body.

When a roll of the described, known types is heated from the outside, one problem is that the external layer will become warmer than the layer or the layers that is located inside of the external layer, which is firmly connected with the next inner layer. The external layer will therefore expand more than the inner layer so that tensions will occur between the two layers. If the roll is homogeneous the same differences in expansion and tensions between the external and the internal sections, which merge into each other without a determined boundary, will arise. In order to reduce the risk for damages in the roll from said difference in tensions the initial heating of the roll must be done slowly. Another problem is that it is difficult to keep the geometrical shape of the roll in the cross machine direction because of the difficulties in maintaining the same temperature along the mantle surface of the roll and on the roll heads. Since the mantle surface and the heads can not expand freely and independently of each other, large tensions occur between them and the mantle surface becomes curved outwards or inwards across the machine direction. Since also the internal layer or part of the roll will absorb some of the heat energy supplied, the heating costs become high.

One disadvantage of using a metal belt as a heat-transferring device is that it must be arranged in a loop between at least two rolls, which constitutes a configuration that is space requiring. In order to clean the surface of the belt with a doctor blade, a counter roll must be arranged inside of the belt loop opposite the doctor blade. Another disadvantage is that the belt usually can not be coated with layers in order to achieve certain properties of release and certain thermal conductivities.

In production of soft paper, of lower basis weight and which for instance is used for making household paper, paper towels and other hygiene products, it is a common wish that the bulk, i.e. the relationship between the volume and the weight of the paper, shall be substantially higher than for other papers, as paper with high bulk has a desirable combination of softness and high power of absorption. In conventional production of paper, a coherent fibrous web is formed on a wire by dewatering a pulp suspension with initially very high water content. The moist web runs through a press section comprising one or more presses, each with at least one press nip, in which additional water is pressed out of the web. However, in a conventional wet press a certain re- wetting of the web always occurs at the outlet of the press nip and moreover the fibers are pressed together in a disadvantageous way at said pressing, the desired properties of the paper obtained by the pressing do not remain in full, but a relatively flat and compact soft paper web with lower bulk than desired is obtained after the web has dried in a drying section. In the manufacturing of paper, board and cardboard, usually a drying section is used which has a large number of alternating drying cylinders and guide rolls, around which the moist web runs. This large number of cylinders and rolls gives the paper machine a disadvantageous length. In the manufacture of soft paper, usually a Yankee dryer has hitherto been used for the main drying of the web. The conditions at an Yankee dryer differ from those at a conventional wet press, for instance the dewatering of the formed fibrous web is not merely done by pressing but largely by thermal drying of the web.

However, certain attempts have been made to manufacture soft paper with a bulk that is substantially increased from the one obtained earlier. For instance, in the patent US-A- 3,806,406 is described a procedure and a device for forming a high bulk soft paper web. The wet web is transported on a felt through a press nip between a press roll and a heated Yankee dryer. Since the compressing of the fibrous web consequently results in a for soft paper unwanted low bulk, it has been tried in the Yankee dryer described in US-A-3, 806,406 to reduce the surfaces of the fibrous web that are exposed to pressure in the press. The Yankee dryer has a mantle surface with alternately raised and lowered surface portions, which constitute a relief pattern for placing against the web. Substantially, only the parts of the web that are in contact with the raised surface portions are compressed in the press nip, while the parts in between are left relatively unaffected. On the whole, the entire drying of the web is done thermally by supplying heat from the heated Yankee dryer, while the soft paper web is maintained in a fixed position relative to the said surface portions. If required, a certain pre-drying or after-drying of the web can be done as well by through-air drying. Thereby, the web obtains a certain embossing pattern that consists of compressed and non- compressed portions, which equals the current pattern of the mantle surface. Pattern imprinting of a moist fibrous web and drying of the imprinted fibrous web without destroying the procured structure gives a high bulk and, simultaneously, the structure remains even after the fibrous web has absorbed water.

However, the Yankee dryer has some essential disadvantages. It has a large diameter, why it is very bulky. In using a Yankee dryer, it is hard to achieve the very high temperatures that are being exploited in impulse drying. This is due to that the Yankee dryer is heated from its interior by steam, which consequently leads to that the entire Yankee dryer must be heated up, with high energy costs as a consequence. Despite the fact that the steam inside the drum can have a high temperature, the external mantle surface of the drum reaches only about 95 °C - 100 °C. The relatively low temperature partly leads to that the web must be in contact with the Yankee dryer under a longer time period, which is the reason for its big diameter, partly to that the Yankee dryer often must be completed with either pre-drying or after-drying, occasionally both. Some of the problems mentioned above concerning the differences in temperature between different parts of a heated roll and the unfavorable tensions which then occur, may be considered to be valid also for the heated Yankee dryer.

OBJECT AND FEATURES OF THE INVENTION

The object of the present invention is to achieve a press, which has at least one press nip with an improved heat transferring device, which press at least substantially reduces the problems mentioned above so that the favorable effects of both the impulse drying and of the pattern imprinting, which have been stated above, can be utilized in a better way than possible earlier.

The press according to the invention is characterized in that said heat transferring device includes a heatable sleeve, which is an integral part of the counter roll and encloses the roll body; said sleeve having an external mantle surface for cooperation with the press device; and a plurality of imprinting elements arranged in a pattern being provided on said external mantle surface of the sleeve for a generating in the fibrous web a pattern imprint corresponding to the pattern of the imprinting elements.

LIST OF FIGURES

The invention will be described in more detail hereinafter with reference to the drawings.

Fig. 1 is a perspective view of parts of a press comprising a press with a counter roll and a shoe press roll, which counter roll has a rigid sleeve which has a diameter that is shown highly exaggerated, part of a pattern being shown on the external mantle surface of the sleeve. Fig. 2 is a cross sectional view of the shoe press according to fig. 1 in which a fibrous web runs through a press nip which is formed by the counter roll and the shoe press roll. Fig. 3 is a cross sectional view of the shoe press according to fig. 2, but with an alternative run of the fibrous web, by which the web is arranged to follow a longer section around the sleeve after the press nip. Figs. 4 and 4a are enlarged scale views of the pattern according to a first embodiment. Figs. 5 and 5a are enlarged scale views of the pattern according to a second embodiment. Figs. 6 and 6a are enlarged scale views of the pattern according to a third embodiment. Figs. 7 and 7a are enlarged scale views of the pattern according to a fourth embodiment. Fig. 8 is a perspective view of a press with a counter roll and a shoe press roll similar to the view shown in figure 1, but with the counter roll having a flexible sleeve according to a second embodiment, part of a pattern being shown on the flexible sleeve. Fig. 9 is an enlarged scale view of the pattern according to fig. 8 according to a first embodiment.

Fig. 10 is an enlarged scale view of the pattern according to fig. 8 according to a second embodiment.

DETAILED EMBODIMENT DESCRIPTION In figures 1 and 2, there are schematically shown parts of a press 1 , which is part of a press section in a machine for the production of a continuous web 2 of cellulosic fibrous material. The invention is particularly but not exclusively applicable to paper machines for the production of paper with low basis weight, i.e. soft paper. However, the paper machine can be designed for the production of any other paper grade. The press 1 comprises a rotatably journalled counter roll 3; a cooperating press device 5 for forming a press nip 4, and a clothing 6 that is in direct contact with the fibrous web 2 and which preferably has the ability to receive liquid in fluid state and gaseous state from the web 2 and to carry it out of the press nip 4. The counter roll 3 comprises a rugged cylindrical roll body 7 which has stub shafts 8, see figure 1, for rotatable journalling of the counter roll 3 in bearing houses, not shown. The roll body 7, which is arranged rotatably around an axis of rotation 9, has a mantle surface with a circular cross-section. In the embodiment shown, the press 1 is constituted of a shoe press with an extended press nip 4 and the press device 5 of a shoe press roll, comprising a press shoe 10 and an impermeable flexible jacket 11, which jacket 11 is fixed at rotatable peripheral roll head parts 12. The press shoe 10 has a concave surface 13, see figures 2 or 3, for generating pressure under cooperation with the convex roll body 7 of the counter roll 3 and for achieving the extended the press nip 4. The jacket 11 runs through the press nip 4 in sliding contact with the concave surface 13 of the press shoe 10. Alternately, the flexible jacket 11 may run in a loop around a plurality of rolls (not shown) and, consequently, in which loop the press shoe 10 is mounted. The clothing 6 of the shoe press 1 is arranged to run in an endless loop around a plurality of guide rolls (not shown) and through the extended press nip 4. The fibrous web 2 is supported on the clothing 6 up to the press nip 4 and is then separated from said clothing 6 after the press nip 4. Instead it bears on and is carried by the counter roll 3 around a predetermined section of the mantle surface 14 of the counter roll 3. Alternatively, the web runs in an open draw before the press nip, i.e. unsupported of the clothing. The web may also be separated from the counter roll 3 directly after the press nip 4, so that the web runs entirely free from any support.

In figures 2 and 3 there are shown two alternative runs for the fibrous web 2 after the press nip 4. In the web run shown in figure 2, the fibrous web 2 is arranged to bear on and to enclose only a small surface section of the mantle surface 14 of the counter roll 3. In the web run shown in figure 3, the fibrous web 2 is arranged to follow and to be in contact with the mantle surface 14 of the counter roll 3 over a substantially longer section, i.e. over a considerably larger surface section than in the embodiment shown in figure 2. By arranging the fibrous web 2 to contact a greater proportion of the mantle surface, more heat can be transferred to the web, and therefore a higher dry solids content can be achieved in the web. The surface section over which the fibrous web 2 is arranged to follow, (including the nip length) has a length in the direction of circulation, determined by its sector having the angle α, see the figures 2 and 3, which preferably is within the interval (10° to 300°), depending on the after-drying that is needed in order to achieve the desired dry solids content.

The clothing 6 usually consists of a press felt, but also a permeable process belt that has through going openings and possibly recesses located between these can be used, like an impermeable belt with recesses of suitable depth, shape and orientation. Said recesses exist on the side that is facing the fibrous web 2. Said openings and/or recesses are arranged to receive and transfer liquid from the fibrous web 2 out of the press nip 4. The openings and/or the recesses also give the web 2 an impression in the form of an imprinted pattern, which imprint increases the bulk of the web 2. Instead of a permeable or impermeable belt, an open or closed wire that has a sealing layer that is turned from the web 2 can be used. The press shown, comprising a shoe press 1 , is the preferred embodiment, but the invention also comprises other types of press devices, as for instance a press comprising a conventional, cylindrical press roll against which the counter roll is arranged and with which it is cooperating.

Further, the press 1 comprises a movable device 15 for continuous transfer of heat to the fibrous web 2, when this passes through the press nip 4, and a heating apparatus 16 for heating said heat transferring device 15 from its exterior to the desired operating temperature at startup and then for a continual or continuous heating during operation in order to maintain this operating temperature. The heating apparatus 16, which can be fixed or movable, e.g. oscillating, is arranged at a predetermined location or within a predetermined interval upstream of the press nip 4 in order to heat the circumference of the heat transferring device 15, e.g. around 30° - 330° ahead of the inlet of the press nip 4, i.e. also near the outlet of the press nip 4 for more-efficient utilization of the space around the counter roll 3, which is possible because the heat loss from the heat transferring device 15 before the contact with the moist web 2 is comparatively small.

According to the invention, the counter roll 3 comprises a heatable sleeve, which forms said heat-transferring device 15. The sleeve 15 encloses at least the entire axial portion of the cylindrical roll body 7 active in the press nip 4 and is so arranged that it can expand freely in relation to the roll body 7 at said heating before the press nip 4 without causing unfavorable tensions in the sleeve 15. The sleeve 15 has an interior surface 17, which is arranged to be brought in contact with the roll body 7 within the zone of the press nip 4, and an exterior surface, that constitutes the mantle surface 14 of the counter roll 3 mentioned above, around which the fibrous web 2 runs carried by the surface. The sleeve 15 is free from mechanical, adherence or any other such permanent, fixing connections, which would block a free expansion of the sleeve 15 in the axial and/or radial direction in relation to the cylindrical roll body 7 outside the press nip 4, i.e. where heating occurs, and which connections on the contrary would give rise to unfavorable tensions in the sleeve 15.

Flat annular rings 18 are coaxially mounted at the end surfaces of the cylindrical roll body 7, which rings 18 have a somewhat larger outer diameter than the cylindrical roll body 7 to form axial end stops 19 for the sleeve 15 during the passage of the sleeve 15 through the press nip 4. In the embodiment shown, the rings 18 constitute annular flanges (see figure 1), of which one is arranged to run in a groove 20, that is arranged on the inside 17 of the sleeve 15, parallel with the end face of the sleeve 15. Even during operation, the sleeve 15, which is expanded axially by the heat, is free from contact with one of or both of these end stops 19 in order to avoid also axial compressive stresses in the sleeve 15 in the zone of the press nip 4, so that the straightness of the cylindrical mantle surface 14 can be ensured.

Consequently, the sleeve 15 is completely free from permanent locking connections in all directions in order to allow the sleeve 15 to expand axially as well as radially in a stress free manner in relation to the cylindrical roll body 7 during heating. During operation, the roll body 7 is arranged to press and hold the sleeve 15 at a place of contact 21 within the zone of the press nip 4 at the press shoe 10 for generating pressure in cooperation with the roll body 7 to form a friction force in said place of contact 21 between the roll body 7 and the sleeve 15 large enough to ensure that the sleeve 15 will be rotated by the roll body 7 and at the same speed at said place of contact 21 (see figures 2 and 3).

The sleeve 15 may be a rigid sleeve that is stable in shape, (see especially figures 1-3), or alternatively as a flexible sleeve 15, that consequently is not stable in shape (see especially figure 8).

In figures 1-3 the sleeve 15 is schematically illustrated as a cylindrical, rigid, sleeve 15 that is stable in shape and has an exterior 14 that constitutes the rigid mantle surface of the sleeve 15 and an interior 17 that has a constant, circular cross-section. When the sleeve 15 is heated to its desired operating temperature, the interior surface 17 has a larger diameter than the outer diameter of the cylindrical roll body 7, as shown in the drawings. However, the diameter of the rigid sleeve 15 is shown highly exaggerated in relation to the roll body 7. Consequently, the sleeve 15 shown in figures 1-3 has a certain wall thickness, measured between the inner side 17 and the mantle surface 14, in every cross-section arbitrary between parallel end faces of the sleeve 15. The wall thickness of the sleeve 15 is selected after the specific use with varying demands for the properties of the sleeve 15. For instance, the wall thickness is optimized for heating the loose sleeve 15 as quickly as possible and for keeping the straightness of the mantle surface 14 across the machine. The wall thickness of the sleeve 15 is large enough to make the sleeve 15 rigid and stable in shape, i.e. is at least self-supporting, so that, resting on a flat supporting surface, it will maintain its radius on all sides and will not collapse to oval shape. Preferably, it is so rigid and so stable in shape that it will not be considerably deformed by normal tensions at assembling and during operation. The rigid sleeve 15 has a sufficient wall thickness in order to resist the large tensions in the press nip 4, which can arise from the differences in radius between the different construction elements.

During operation the rigid sleeve 15 is arranged to rotate around its own axis of rotation, i.e. its central axis 22, which is situated eccentrically in relation to the axis of rotation or central axis 9 of the roll body 7. The eccentricity, i.e. the distance between these axes 9 and 22, equals half of the difference between the outer diameter of the roll body 7 and the inner diameter of the sleeve 15, i.e. the difference in radius lengths. When the press shoe 10 and the counter roll 3 are displaced vertically away from each other by a distance corresponding to this radius difference, the sleeve 15 will hang on the roll body 7 and its central axis 22 will be situated beneath the central axis 9 of the roll body 7. In this condition the sleeve 15 is entirely loose in relation to the roll body 7 for a simplified change of the sleeve 15 in that a necessary space for the axial removal of the sleeve 15 thus exists between the press device 5 and the roll body 7.

It is possible to size the inner diameter of the sleeve 15 in relation to the outer diameter of the roll body 7 such that at room temperature the sleeve forms a tight or interference fit about the roll body, yet when heated up to its operating temperature the sleeve expands sufficiently to become loose about the roll body. In this situation, removal of the sleeve must be performed while the sleeve is heated sufficiently to enable it to be slid axially off the roll body; similarly, installation of a new sleeve would require heating of the sleeve to expand it sufficiently to allow it to be slid axially onto the roll body.

The concave surface 13 of the press shoe 10 has a radius that is adjusted to the radius of the rigid, cylinder-shaped sleeve 15. The sleeve 15 is so rigid and stable that it self will exert a press function by the action of the roll body 7, i.e. the pressure from the roll body 7 at the shorter place of contact 21, compared to length of the press nip 4, is propagated forward and backward, seen in the direction of rotation, through the sleeve 15 to the press nip 4, so that the length of the press nip 4 becomes about equal to the width of the press shoe 10. When a section of the rigid sleeve 15 passes the press shoe 10, a minor change in the shape of the passing section will occur caused by differences in length between the inner radius of the sleeve 15 and the outer radius of the roll body 7. These minor changes in shape, however, will disappear as soon as the pressure is relieved after the press nip 4, and some harmful tensions do not occur in the rigid sleeve 15 because it is thick enough to resist this load. Therefore, the rigid sleeve 15 still fulfills the requirement for being "stable in shape" as it is defined in this description.

During operation when the sleeve is heated to its operating temperature, the difference in diameter between the outer diameter of the roll body 7 and the inner diameter of the sleeve 15 is so determined that a free space 23 is formed at that side of the roll body 7 that is opposed to the press nip 4. Thanks to this free space 23 inside the sleeve 15 only minor heat quantities will be consumed of the roll body 7. During operation, this air containing space 23 has the shape of a crescent. Only in the zone of the press nip 4 within the surface of the place of contact 21 a transfer of heat from the sleeve 15 to the roll body 7 occurs, but the heat quantities that are consumed here yet are small, since the contact surface here constitutes a diminutive portion of the peripheral surface and the fact that the heat is transported from one surface to another. In general, the temperature on the hot mantle surface 14 of the sleeve 15 at the inlet to the press nip 4 may be within the interval 150 °C - 400 °C.

Because the rigid, cylinder-shaped sleeve 15 remains round during operation, a constant distance between the sleeve 15 and the heating apparatus 16 is maintained with constant operating temperature.

Generally, the wall thickness of the rigid sleeve 15 is 5 - 100 mm, preferably 15 - 40 mm. Preferably, at room temperature the sleeve fits closely or with an interference fit about the roll body, and when heated to its operating temperature the sleeve expands to have a greater inside diameter than the outside diameter of the roll body. The difference between the internal diameter of the rigid sleeve 15 and the external diameter of the roll body 7 when the sleeve is heated during operation generally is 0.01 - 100 mm, preferably 0.5 - 10 mm. The less the wall thickness of the sleeve 15 is, the faster a high surface temperature is achieved and this without high tensions occurring, because the mass which must be heated in the radial direction decreases in degree accordingly.

In the embodiment with a flexible sleeve 15 (see figure 8) this can be a deformable cylinder, which will yield when exposed to an external load, i.e. the sleeve 15 will deform at the passage through the press nip 4, but will substantially recapture its not self- supporting cross sectional shape thereafter when the external load is released or is moved along the mantle surface 14 during the rotation of the sleeve 15. Generally, the flexible sleeve 15 has a wall thickness within the interval 0.4 - 5.0 mm, preferably 0.8 - 2.3 mm. The difference between the internal circumference of the flexible sleeve 15 and the external circumference of the roll body 7 during operation in general is within the interval of about 0 - 100-π mm, preferably about 0.1 - 10-π mm. Since the sleeve 15 is flexible, a cleaning doctor may be arranged at a suitable place so that the sleeve 15 will be deflected against the roll body 7, which will function as a counter member. Furthermore, the flexible sleeve 15 is free from any torque from frictional forces, and the sleeve handling is facilitated considerably by using the flexible embodiment of the sleeve 15.

The rigid or flexible sleeve 15 described above, which is impermeable, i.e. impervious, can be replaced by another embodiment of sleeve, namely a permeable, rigid or flexible sleeve 15. For instance, this will facilitate the release of the fibrous web from the sleeve 15 and will simplify the cleaning of said sleeve 15. The permeable sleeve 15 may consist of a metallic fabric formed into a cylinder, which e.g. may be of bronze. However, the permeable sleeve 15 can consist of any form of suitable permeable elements, that can be formed into a cylinder, including plate-shaped elements, which are attached to each other, end part to end part with a seam, for instance a certain length of metal plate, in which a pattern of through going elongated slots, openings or holes 35 are made to form said cylindrical, pervious sleeve 15. The elongated slots may be so arranged that they by stretching of the plate in its plane expands to form a net of openings, for instance elliptical ones, after which the end parts of the plate are attached to each other by a welded joint.

With a permeable sleeve 15 the desire is to achieve a reduction of the risk of delamination, especially for paper webs of medium and high basis weights, and not to cause the web to get stuck on the mantle surface 14 of the sleeve 15. In addition, the releasing may be facilitated, if desired, by the provision of spray nozzles (not shown) for blowing air powerfully, directly or through the sleeve, against the fibrous web at a position downstream of the web releasing point. Furthermore, with a permeable imprinted sleeve 15 it is normally easy to loosen the fibrous web 2 unharmed from the sleeve 15 and to clean the sleeve 15 from remaining fibers. In order to facilitate the release of the web 2 from the mantle surface 14, air-knives (not shown) may be provided at suitable locations at the outlet from the press nip 4. It is known, however, that the web 2 loosens easily from the mantle surface 14 of the sleeve 15 at temperatures over 200 °C. If desired, the air jet may consist of or cooperate with the hot gases from a gas burner, or the like. All fibers stuck to the sleeve will immediately be burnt to ashes and will be carried away by the jet of gas. Furthermore, the heating of the fabric by the hot gases decreases the need of electromagnetic heating of the sleeve.

The roll body 7, which is enclosed by the permeable sleeve 15, may (in a not shown embodiment) consist of a roll that has a first blow zone at which the web is detached from the sleeve, and a second blow zone, which is arranged downstream of said first blow zone in the direction of rotation of the sleeve, for cleaning of the permeable sleeve. If desired, also a suction zone may be arranged at the nip of the impulse press for removing vapor and for reduction of the risk of delamination. For instance, the roll with at least one blow zone may have a suction zone situated in the press nip.

Furthermore and according to the present invention the sleeve 15 comprises a plurality of imprinting elements 24, which are arranged on, in or through the external, web carrying mantle surface 14 of the sleeve 15 (see figures 1 or 8). The imprinting elements 24 are arranged in a predetermined pattern, preferably a relief pattern 25, for placing against the fibrous web 2 so that a pattern imprint, i.e. imprinting, is generated in the fibrous web 2 according to the imprinting elements 24 when said fibrous web 2 runs through the press nip 4 together with the clothing 6. The imprinting causes positive and remaining changes in the properties of the web 2, inter alia the bulk of the web 2 increases with 50 - 150 %, compared to conventional pressing with a smooth counter roll.

The imprinting elements 24 (see figures 4 - 7a and 9 - 10) are formed by recesses in the mantle surface 14 of the sleeve 15, which recesses preferably are arranged to constitute, in relation to each other, raised or lowered surface portions 26, 27 (see the figures 4 - 7a). The imprinting elements 24 may be uniformly distributed, but all, some or one specific imprinting element 24 may also be so arranged, separate or in groups at a desired spacing from one another, that they together constitute any other predetermined pattern 25, for instance in the form of structure, symbols, figures, or common decors, such as grids, digits, letters, trademarks, names or other depicting. All, some, or one specific imprinting element 24 may be of elliptical, circular, rectangular, square or other polygon shape, e.g. triangular, or may be of any another imaginable geometrical shape, which is considered reasonable for obtaining the desired pattern 25 in the fibrous web 2 to be produced.

In the embodiment with raised or lowered surface portions 26, 27 (see figures 4 - 7a), the raised surface portions 26, which are arranged between said lowered surface portions 27, may for instance have flat, multi-faceted, tapered, arched or other convex cross-sectional shapes or parts. Accordingly, the lowered surface portions 27 comprise flat, multi-faceted or curved, hollowed out or in another way concave formed finite cross-sectional shapes or parts.

The imprinting elements 24 may also, instead of the surface portions 27, which are lowered finitely in the radial direction in the mantle surface 14 of the sleeve 15, comprise a great plurality of through going, drilled or in any other suitable way produced holes 35, which extend through the wall of the sleeve 15 to form a desired permeable pattern 25 (see figures 9 and 10), or a combination of both raised and lowered surface portions 26, 27 and through holes 35 (not shown). The imprinting elements 24 are so arranged in size and number that the raised surface portions 26, that are in pressing contact with the fibrous web 2, together constitute an essential portion of the total mantle surface 14, preferably between 20 - 50 % of the mantle surface 14.

Furthermore, the imprinting elements 24 may be arranged so that they form continuous grooves with even spacing across the mantle surface 14, bands of several continuous grooves arranged near each other, which bands of grooves thus are mutually separated by a proportionately greater distance, or intermittent and finite groups of elements in the mantle surface 14, which imprinting elements 24 are arranged in the direction of circulation of the sleeve 15, with an angle to the direction of rotation of between 10° to 80° diagonally from one or both of the end surfaces of the sleeve 15 to one or both of the opposed end surfaces, or substantially across the direction of circulation. The grooves, bands of grooves or the groups may be straight or waved, e.g. sine or zigzag shaped, and the distance between them can vary, or between two adjacent and mutually parallel grooves, bands or groups be fixed, from 1 to 5 mm, while the grooves have a width between about 0.5 to 2.0 mm and a depth of about 0.1 to 2.0 mm. The imprinting elements 24 may for instance be comprised of radially finite channels, through going notches or other finite recesses or through going recesses which are formed with the aid of mechanical, laser or chemical working of the mantle surface by for instance milling, boring, turning, electrochemical pickling or etching at least a short distance down in the mantle surface of the sleeve 15 from its outside 14.

Seen in a cross-section of the sleeve 15, the difference in altitude, i.e. the difference in radius, between the raised and the lowered surface portions 26, 27 lies within the interval 0.1 - 2.0 mm, while the width of the raised surface portions 26 suitably lies within the interval 0.5 - 5 mm. At the passage of the web 2 through the press nip 4 substantially only the parts of the web, which are in contact with the raised surface portions 26, will become compressed in the press nip 4, while the parts of the web in between are left relatively unaffected.

In the figures 4 - 7a and 9 - 10 described below, there are especially shown a number of different embodiments of patterns 25 for the mantle surface 14 of a sleeve 15, which sleeve 15 can be either rigid or flexible. In the embodiments shown in figures 4 - 7 the sleeve 15 is impermeable, but according to what is mentioned above it may also be designed as a permeable sleeve 15, for instance through its construction, for instance comprising a net or fabric structure, or by the arrangement of said through holes 35 (see the figures 9 and 10). Consequently, the invention is in no way limited to the especially shown embodiments, but any other configuration of imprinting elements 24 for imprinting of predetermined patterns 25 in the fibrous web 2 according to what is mentioned above falls within the inventive concept.

In figures 4 and 4a there is schematically shown, in view and cross-section, a detail of a pattern 25 according to a first embodiment, which pattern 25 comprises imprinting elements 24 in the form of a plurality of straight and mutually parallel grooves 28, which divide the mantle surface of the sleeve in elongated, alternately raised and lowered surface portions 26, 27. The surface portions 26, 27 have, seen in a cross-section through the sleeve, a flat bottom surface 29 and a flat top surface 30, respectively, between which convergent wall surfaces 31, 32 extend from the bottom surface 29 towards the top surface 30. The corners between the surfaces 29, 31 and 30, and also 29, 32 and 30, are shown in figure 4a as being entirely straight, but they may also be designed with a small radius for rounding said comers. In the cross-sectional view shown in figure 4a, the width and the difference in altitude of the two surface portions 26, 27 are illustrated with the markings a, b and c, which widths and differences in altitude are within the interval mentioned above. The grooves 28 in the shown embodiment extend in the direction of rotation of the sleeve around its entire circumference in endless rings, but in another embodiment (not shown) they may instead have a certain determined angle to the end face of the sleeve.

In figures 5 and 5 a there is schematically shown, in view and cross-section, a detail of a pattern 25 according to another embodiment, which pattern 25 comprises imprinting elements 24 similar to the grooves 28 that are shown in the first embodiment, but which differ in that they have wall surfaces 31, 32, which are mutually parallel, and which extend perpendicularly between a bottom surface 29 and a top surface 30.

In figures 6 and 6a there is schematically shown, in view and cross-section, a detail of a pattern 25 according to another embodiment, which pattern 25 comprises imprinting elements 24 in the form of grooves 28 similar to the ones that are shown in the first and the second embodiment above, but which differs in having a roundish bottom surface 29 (see figure 6a) and flat top surface 30 at the raised the surface portions 26 thus formed between the grooves 28.

In figures 7 and 7a there is schematically shown, in view and cross-section, a detail of a pattern 25 according to another embodiment, which pattern 25 comprises imprinting elements 24, which consists of two groups of grooves 33, 34, which each comprise a plurality of grooves 28, which are mutually parallel within the respective group, which groups of grooves 33, 34 extend in a first group 33 from the first to the second end surface of the sleeve, and in a second group 34 from the second end surface of the sleeve to the first, at which the two groups of grooves 33, 34 cross each other at an angle of between 10° to 170°. Both groups of grooves 33, 34 have a concave roundish bottom surface 29. The two groups of grooves may also, in an embodiment not shown, have different angles to the sleeve end surface in order to avoid that the same bands in the clothing are compressed turn after turn.

In figure 9 there is schematically shown in perspective view a detail according to a first embodiment of a through going pattern 25 of a permeable sleeve 15, which pattern 25 comprises imprinting elements 24, which consist of substantially circular and through going holes 35 extending in the thickness direction of the sleeve 15. The holes are arranged at a predetermined mutual spacing, successively in line and at a certain determined angle to the direction of rotation of the sleeve 15, going diagonally from one end surface of the sleeve 15 to the other. The width of the holes 35, the angle, the mutual spacing between the holes in the line plus the spacing between said lines lie within the interval mentioned.

In figure 10 there is schematically shown in perspective view a detail according to a second embodiment of a through going pattern 25 of a permeable sleeve 15, which pattern 25 comprises imprinting elements 24, similar to the holes 35 that are shown in the first the embodiment, but which differ in that they have a rectangular shape.

The imprinted sleeve 15 may be homogeneous, i.e. be represented by one and the same material straight through without any layers, or consist of two or several uniform and coherent layers of different materials, of which layers at least one functions as a carrier for one or all of the other layers. Like the rigid sleeve 15, the flexible one may consist of two or more layers.

Consequently, when the rigid sleeve 15 consists of several layers, one of the layers is a supporting layer with the default function to be a stabilizing carrier with a sufficient wall thickness to provide the supporting layer with e.g. a surface layer with desired properties.

The exterior surface of the supporting layer may be provided with a surface layer of a suitable material in order to obtain the desired release ability and/or a desired capacity of heat transmission of the mantle surface 14 of the cylinder-shaped sleeve 15. A special capacity of heat transmission of the mantle surface 14 may be desirable in order to control the supply of heat to the fibrous web 2 and to prevent delamination of the web 2. Delamination is the phenomenon when the fibrous web 2 bursts at exiting the press nip 4, because the steam pressure inside the web 2 is greater then what the bonding forces in the web 2 can withstand.

The cylindrical roll body 7 may be provided with a surface layer of one or several suitable materials on its mantle surface in order to increase the resistance to wear and/or increase the corrosion-resistance and/or to achieve an insulation so that the heat, which is being transferred from the sleeve to the cylindrical roll body 7, is additionally reduced within the press nip 4. Alternately or furthermore, the sleeve 15 may have such a surface layer (not shown) on its interior 17 side. As suitable materials, in order to obtain a surface layer with the desired release ability and desired capacity of heat transmission, aluminum oxide, chromium oxide and zirconium oxide based ceramics can be used. Suitable materials in order to increase the resistance to wear are carbides of wolfram and/or chrome, and chrome steel. Suitable materials in order to increase the corrosion resistance are alloys based on one or more of nickel, chrome, and cobalt. Suitable insulation materials are zirconium oxide based ceramics. As suitable materials for a homogeneous sleeve (i.e. without layers) and for the supporting layer of a sleeve consisting of at least two layers we can mention nodular-iron, cast steels and weldable high-strength structural steels.

Any suitable heating apparatus 16 may be used, although an induction heater presently is preferred. Examples of other heating apparatus 16 are electric heaters, infrared heaters, laser heaters and gas burners.

The roll body 7 of the press 1 may be a so-called solid press roll, which has been modified according to the invention, but a deflection compensated roll may also be used. Since the contact surface between the hot sleeve 15 and the mantle body of the deflection compensated roll is small, only a little heat is transferred to the roll. Enough heat can be removed with the oil in the roll in order to enforce a reasonable temperature and thereby a high enough viscosity in the oil to achieve a satisfying function of the roll.

The temperature of the web 2 can be increased before the press nip 4 by arranging one or more steam boxes in the felt loop and/or near the free side of the web 2. Preheating of the wet web 2 gives a lower viscosity of the water, this facilitates the pressing of water out of the fibrous web at the press nip 4. Additional drying devices may also be arranged after the press nip 4, as for instance one or more through-air drying machines, for more high-grade drying of the web 2.

In the embodiment with a loose, rigid sleeve 15, the advantage is obtained that the mantle surface may be coated to enhance the release properties, the heat transfer to the paper, and to reduce unwanted thermal flow radially inwards of the sleeve 15. By making the wall thickness of the rigid sleeve 15 large enough, the mantle surface 14 of the sleeve 15, which is in contact with the web 2, may be treated like a conventional press roll surface in order to be cleaned, when it is necessary, with a cleaning device 36, for instance a doctor blade, a metal brush or by spray nozzles for air blowing. In the embodiment with a loose, flexible sleeve 15, a heat-transferring device is achieved which is easy assembled. In the embodiment with a loose, permeable sleeve 15, the you achieve the advantages of minimizing the risk of delamination of certain paper grades, since a suction zone may be provided at the counter roll for removal of the steam, and also a release of the web from the sleeve is facilitated since through-blowing of air is possible, and cleansing is made possible with the aid of a cleaning device 36 in the form of a burner for burning off sticky fibers. Furthermore, the handling of the sleeve is made easier.

With the invention described above, a press section is achieved comprising one or more presses 1 for impulse drying with press nips 4 arranged in succession, which press section is power saving and has a stable geometry in the press nip 4, which press nip 4 comprises a counter roll 3 with a heat transferring device 15 in the form of a loose, imprinted sleeve 15 for faster and more efficient heating than with conventional rolls since less mass is heated. Furthermore, no problems with tensions in the counter roll 3 occur, wherefore its straightness is maintained. A fibrous web 2 which has been dried rapidly at a highly increased temperature in conjunction with imprinting of a structured pattern 25 in the web, which is done in the present invention, keeps its structure after the drying even after absorption of liquid, whereby also the advantageous product characteristics achieved by the imprinting, such as high bulk, great softness, favorable stretchability and high liquid absorption are maintained.

By the fast drying in the impulse press 1 and by the lack of a long conventional drying section and/or a large Yankee dryer the advantages of a high paper production and a lower energy cost is achieved. In production of soft paper, a softer paper with more bulk is obtained by means of the imprinted sleeve 15.

Through the imprinting elements 24, i.e. the through going holes and/or the finite recesses in question, outlets and space, respectively, for the steam are created in the press nip 4. This results in a reduction of the steam pressure and, thereby, also a reduction of the risk of delamination in the web 2. However, this is mostly for applicable primarily to other papers than soft paper, since soft paper lets the steam through. The main task of the imprinting elements 24 is, however, to structure the web 2 in accordance with the used pattern on the mantle surface 14, whereby some additional favorable effects are achieved. The steam that penetrates through the web 2 is considered to give the web 2 more advantageous release properties against the sleeve 15. The total contact surface of the fibrous web 2, which is heated by the sleeve 15, increases substantially, so that the drying is considerably faster, while the total contact surface, which is exposed to pressure from the sleeve 15, instead is considerably reduced down to 20 - 50 % of the total web surface 2 ahead of the press nip 4. In addition, the steam allows the soft paper web 2 to expand in the recesses of the pattern 25, so that a product is achieved that is structured and thereby fluffier, i.e. has more bulk. At the depression of the web 2 into the cavities, i.e. the lowered surface portions 27 and the through going holes 35, the web 2 is protected from sticking by the steam film, which is formed against the heating roll, i.e. the sleeve 15, which is an hitherto unknown effect.

Normally the drying section constitutes an essential length of the conventional paper machine, why an advantageous reduction in the length of the paper machine also is achieved when the total length of the press and the drying sections is substantially reduced compared to earlier designs.

It is realized that the number of, the size, the material and the shape of the elements and details which are comprised in the press, for instance the roll body 7, the sleeve 15 and the imprinting elements 24, are to be adapted to the press device or devices 5 and to the fibrous web 2 to be imprinted and dried. The press device 5 may thus be comprised of one of several different types of press devices 5, for instance a conventional press roll, an open or a closed shoe press roll, or any another suitable press roll. The size of the sleeve 15, i.e. its outer diameter, is usually over about 1.0 meter. The sleeve 15 may be manufactured by one or more of the methods sintering, casting, cold pressing, milling and welding.

Claims

1. A press in a machine for the production of a continuous web (2) of cellulosic fibrous material, comprising (a) a press device (5);

(b) a rotatable counter roll (3) having a cylindrical roll body (7) forming a press nip (4) with the press device (5);

(c) an endless clothing (6) extending through the press nip (4) for carrying the web (2) through the press nip, said clothing having the ability to receive and carry away liquid from the web (2); and

(d) devices (15, 16) for heating the web (2) in the press nip (4), said heating devices (15, 16) including

(da) a movable heat transferring device (15) for transferring heat to the web (2) in the press nip (4); (db) at least one heating apparatus ( 16) for heating the heat transferring device (15), (dc) said heat transferring device (15) including a heatable sleeve, which is an integral part of the counter roll (3) and encloses the roll body (7); said sleeve having an external mantle surface (14) for cooperation with the press device (5); and a plurality of imprinting elements (24) arranged in a pattern (25) being provided on said external mantle surface (14) of the sleeve (15) for a generating in the fibrous web (2) a pattern imprint corresponding to the pattern of the imprinting elements (24).

2. A press as claimed in claim 1, wherein the sleeve (15) is generally cylindrical and is mounted about the roll body (7) in such a manner as to allow the sleeve (15) to freely expand relative the roll body (7) upon heating and thermal expansion of the sleeve (15).

3. A press as claimed in claim 1 or 2, wherein the sleeve (15) is a substantially rigid sleeve (15).

4. A press as claimed in claim 1, 2 or 3, wherein the sleeve (15) fits closely about the roll body (7) at room temperature and expands when heated by the heating apparatus (16) so as to become loose about the roll body (7).

5. A press as claimed in claim 3 or 4, wherein the rigid sleeve (15) is impermeable.

6. A press as claimed in claim 3 or 4, wherein the rigid sleeve (15) is permeable.

7. A press as claimed in claim 1 or 2, wherein the sleeve is a flexible, deformable sleeve (15).

8. A press as claimed in claim 7, wherein the flexible sleeve (15) is impermeable.

9. A press as claimed in claim 7, wherein the flexible sleeve (15) is permeable.

10. A press as claimed in any one of claims 1 to 9, wherein the sleeve (15) consists of a length of metal plate having two ends joined to each other to form a cylinder.

11. A press as claimed in any one of claims 1 to 5, 7, 8 or 10, wherein the imprinting elements (24) include recesses in the mantle surface (14) of the sleeve (15), said recesses forming, in relation to one another, raised or lowered surface portions (26, 27) in a relief pattern (25), and being so arranged in size and number that the raised surface portions (26), that will be in pressing contact with the fibrous web (2), together constitute an essential portion of the total mantle surface (14), preferably between about 20 % to about 50 % of the mantle surface (14).

12. A press as claimed in claim 11, wherein one, some or all of the raised surface portions (26) are of flat, multi-faceted, tapered, arched or other convex cross-sectional shapes, and wherein one, some or all of the lowered surface portions (27) are of flat, multi- faceted, tapered arched or other concave cross-sectional shapes.

13. A press as claimed in any one of the preceding claims, wherein all, some, or one of the imprinting elements (24) is of elliptical or circular shape, or of rectangular, square or other polygon shape.

14. A press as claimed in any one of the preceding claims, wherein the imprinting elements (24) are uniformly distributed, or form structures, symbols, figures or decors, as raster, digits, letters, trademarks, name or other depicting, which constitute said pattern (25).

15. A press as claimed in any one of claims 1 to 4, 6, 7, 9 or 11, wherein the imprinting elements (24) include through holes (35), which extend through the wall of the sleeve (15) to form a desired permeable pattern (25), or a combination of both raised and lowered surface portions (26, 27) and through holes (35).

16. A press as claimed in any one of claims 1 to 12 or 15, wherein the imprinting elements (24) include

(a) continuous grooves (28) uniformly distributed over the mantle surface (14), or (b) bands of a plurality of continuous grooves (28) arranged adjacent each other, said bands of grooves (28) being spaced apart by greater distances than the distance between the grooves inside a band, or

(c) intermittent and finite groups of imprinting elements (24),

(d) which extend substantially in the direction of rotation of the sleeve (15), but with an angle to the direction of rotation of between 10° to 80° diagonally from one or both of the end surfaces of the sleeve (15) to one or both of the opposed end surfaces, and said grooves (28), bands or groups being straight or wave shaped, e.g. sine or zigzag shaped.

17. A press as claimed in any one of claims 1 to 10, wherein the imprinting elements (24) include straight and parallel grooves (28) extending in the direction of rotation of the sleeve around its entire circumference in endless rings and dividing the mantle surface of the sleeve in alternately raised and lowered surface portions (26, 27), which, seen in a cross-section through the sleeve, have a flat bottom surface (29) and a flat top surface (30), between which two parallel wall surfaces (31, 32) extend from the bottom surface (29) towards the top surface (30) and converge or form right angles with the flat bottom surface (29) and the flat top surface (30).

18. A press as claimed in claim 16 or 17, wherein the grooves (28) form an angle of about 10° to about 170° with the end faces of the sleeve (15).

19. A press as claimed in claim 16, 17 or 18, wherein the distance between the grooves (28), bands or groups is about 1 to about 5 mm, and wherein the grooves (28) have a width between about 0.5 to about 2.0 mm and a depth of about 0.1 to about 2.0 mm.

20. A press as claimed in any one of claims 12 to 19 in combination with claim 11, wherein the difference in height between the raised and the lowered surface portions (26, 27), is about 0.1 to about 2.0 mm, while the width of the raised surface portions (26) suitably is about 0.5 to about 5 mm.

21. A press as claimed in any one of claims 1 to 12, wherein the imprinting elements (24) include two groups of grooves (33, 34), each group including a plurality of parallel grooves (28), and the grooves (33, 34) in a first group (33) extending from the first to the second end surface of the sleeve (15), while in a second group (34) the grooves extend from the second end surface of the sleeve (15) to the first, so that the two groups of grooves (33, 34) cross each other at an angle of between 10° to 170°.

22. A press as claimed in claim 21, wherein the two groups of grooves (33, 34) form different angles with the end surfaces of the sleeve (15), whereby a formation of streaks in the clothing (6) caused by continual compression turn after turn is avoided.

23. A press as claimed in claim 7 or 9, wherein the permeable sleeve (15) consists of a metallic fabric formed into a cylinder.

24. A press as claimed in any one of the preceding claims, wherein the press (1) is a shoe press having an extended press nip (4), where the press device (5) is a shoe press roll including a press shoe (10) with a concave surface (13) for forming the extended press nip (4) with the counter roll (3), and an impermeable flexible jacket (11) extending through the press nip (4) rotatably supported by the concave surface (13).

25. A press as claimed in any one of claims 1 to 23, wherein the press device (5) is a conventional cylindrical press roll.

26. A press as claimed in any one of the preceding claims, wherein the web (2) is intended to wrap the mantle surface (14) over a rotational angle of about 10° to about 300°.

27. A press as claimed in any one of the preceding claims, wherein the heating apparatus (16) is located between about 30° to about 330° ahead of the inlet to the press nip (4).

28. A press as claimed in any one of the preceding claims, wherein the roll body (7) has a first blow zone for detaching the web (2) from the sleeve (15), and a second blow zone downstream of said first blow zone for cleansing of the sleeve (15).

29. A press as claimed in any one of the preceding claims, wherein the clothing (6) is a belt having recesses for receiving and carrying liquid from the fibrous web (2) out of the press nip (4) and for giving the web (2) an impression in the form of an imprinted pattern (25).

30. A press as claimed in claim 23, wherein the heating apparatus (16) is a burner, which also cleanses the sleeve (15) through combustion of fiber residues and the like.

31. A press as claimed in any one of the preceding claims, wherein the sleeve ( 15) is manufactured by one or more of the methods sintering, casting, cold pressing, milling and welding.

32. A press section including at least one press (1) as claimed in any one of claims 1 to 31.

33. A machine for the production of a paper web (2) with low basis weight, for instance tissue or other soft paper, and comprising at least one press (1) as claimed in any one of claims 1 to 31.

34. A machine for the production of a paper or board web (2), and comprising at least one press as claimed in any one of claims 1 to 31.