SE514421C2 - Press, and press section and machine for producing webs which comprise said press - Google Patents

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

15 20 25 30 35. ~ _ ... -. _,. rr - «,; _ fy“ f «f; 3 * _. , rr rr f t '_ I,. . fr:; r <*, Q r, _ _ r, t:. .ÜHL ¿¿ç °. a f '2. . - - .f .1 ff N as mentioned is that the steam which develops in the vicinity of the hot surface closest to the fibrous web of the heat transfer device by its expansion helps to squeeze out substantially all the remaining water in the fiber web into the filt which is in contact with the fiber web. Another theory is that the reduced viscosity of the water due to the high temperature, in combination with the high temperature water (> 100 ° C) evaporates quickly at a rapidly reduced pressure which occurs when the web leaves the press nip and the pressure thus returns to normal atmospheric pressure. leads to high dry contents being obtained in the paper web.

In the said SE 7803 672-0 a burner supplies heat to one roller in a press, which press has two rotating rollers. The heat is applied to the mantle surface of the roller just before the press nip. The patent specification states that the roller can have a surface layer with low thermal conductivity so that the surface layer can thereby maintain a high temperature.

U.S. Pat. No. 4,738,752 discloses an elongated, heated press nip in which the fibrous web meets a hot surface which is formed by a rotatable press roll or a metal strip which runs in a loop around a number of guide rollers. The press roll and the belt are heated by a heating device. The press roll may have a first coaxial layer and a second coaxial layer, which later layer extends around the first layer and has a thermal conductivity coefficient greater than that of the first layer. The first layer may consist of ceramic, while the second, outer 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 form a unified body.

A problem when a roller of the described, known types is heated from the outside is that the outer layer will be hotter than the layer or layers located inside the outer layer, which is firmly connected to the nearest inner layer. The outer layer will therefore expand more than the inner layer so that stresses arise between the two layers. If the roller is homogeneous, the same differences arise in expansion and stresses between the outer and inner parts, which merge into each other without a definite limit. To reduce the risk of damage to the roller due to such voltage differences, the initial heating of the roller must take place slowly. Another problem is that it is difficult to maintain the geometric axis of the roll across the machine direction due to difficulties in maintaining the same temperature along the mantle surface of the roll as on the ends.

Since the mantle surface and the gables cannot expand freely independently of each other, large stresses arise between them, so that the mantle surface becomes arched outwards or inwards. _ ._ <- -x. n 'H' i “'(I- f' <- t '<: -» - =' _. - <= .__ 'i' f, _ _ _ ~ «* f _ l .. = - _ m .ac 1, -. - <K Å i. .- <~, g, »~ '' ^ f - '" if-tr - <' * ° 'i 0 i _ Mr.> ~ - v. «I '*. ~ F - -“ f. I »*“ (,' u * u; re 1. _ 3 _ VU.. T across the machine direction. Since even the inner layer or portion of the roll will absorb some of added heat energy, the heating costs become high.

A disadvantage of a metal strip as a heat transfer device is that it must be arranged in a loop between at least two rollers, which constitutes a space-consuming configuration. In order to be able to clean the surface of the belt with a doctor blade, a counter-roller must be arranged inside the belt loop in the middle of the doctor blade. A further disadvantage is that the belt usually cannot be coated with layers to achieve certain release properties and certain thermal conductivity properties.

In the production of tissue paper, which has lower basis weights and which is used, for example, for the manufacture of kitchen paper, paper towels and other hygiene products, it is a common desire that the bulk, ie. the ratio between the volume and the weight of the paper, should be substantially higher than for other paper, as high-bulk paper has a desirable combination of softness and high absorbency. In conventional papermaking, a continuous fiber web is formed from a pulp suspension with an initial very high water content on a wire by dewatering. The moist web runs through a press section comprising one or two presses, each with at least one press nip, where additional water is forced out of the web.

In a conventional wet press, however, there is always a certain wetting of the web at the outlet of the press nip and when the presses are compressed in an unfavorable manner during said pressing, the paper properties achieved by the pressing do not remain fully, but after the web has been dried in a drying section, a relatively large and compact tissue web with a lower bulk than desired is obtained. In the manufacture of paper, cardboard and board, a drying section with a large number of alternating drying cylinders and guide rollers, around which the adjacent web runs, is usually used.

This large number of cylinders and rollers gives an unfavorable length to the paper machine.

In the manufacture of tissue paper, a Yankee cylinder has hitherto usually been used for the main drying of the web. The conditions of a Yankee cylinder are different from those of a conventional wet press, for example direct dewatering of the formed fibrous web takes place not only by pressing but largely by thermal drying of the web.

However, some attempts have been made to make tissue paper with a bulk, which is significantly elevated from the previously obtained one. For example, U.S. Patent No. 3,806,406 discloses a method and apparatus for forming a high bulkhead. v »f v '<* É <_» _? .- »_-_ f. p '_, _ A I _ f n. ~ ...: 53 ^ f4 = -.> 42%: - _: ~ - 1: »ß 4 'i'. ^ “.I tissue paper. The wet web is advanced on a igenom lt through a press nip between a press roll and a heated Yankee cylinder. Since the compression of the fi web thus gives rise to an undesirably low bulk for tissue, the Yankee cylinder described in US-A-3,806,406 has been attempted to reduce the pressurized surfaces of the ban web. The Yankee cylinder has a mantle surface with alternately raised and lowered surface portions, which form a relief pattern for application to the web. Essentially only the parts of the web which abut against the raised surface portions are compressed in the press nip, while the intermediate parts are left relatively unaffected. Substantially the entire drying of the web takes place thermally by heat supply from the heated Yankee cylinder, while the tissue web is kept in an xt position relative to said surface portions. A certain pre- or post-drying of the web can also take place by means of blow molding, if required. The web thereby obtains a specific embossing pattern consisting of compressed and non-compressed portions, which correspond to the current pattern of the mantle surface. Pattern embossing of a moist fi berbana and drying of the embossed fi berbana without destroying the resulting structure gives high bulk, while the structure remains even after the fi berbana has been allowed to absorb water.

However, the Yankee cylinder has a couple of significant disadvantages. It has a large diameter, which is why it is very bulky. When using a Yankee cylinder, it is difficult to achieve the very high temperatures used in impulse drying. This is because the Yankee cylinder is heated from the inside by steam, which consequently means that the entire Yankee cylinder must be heated, with high energy costs as a result. Although the steam inside the cylinder can have a very high temperature, only about 95 ° C - 100 ° C is obtained on the outer surface of the cylinder. The relatively low temperature means that the web must be in contact with the Yankee cylinder for a longer period of time, which is the reason for its large diameter, and that the Yankee cylinder often has to be supplemented with either pre- or post-drying, sometimes both. Some of the above-mentioned problems concerning temperature differences between different parts of a heated roller and the unfavorable stresses which arise therefrom may be considered valid even for the heated Yankee cylinder.

OBJECT AND FEATURES OF THE INVENTION The object of the present invention is to provide a press which has at least one press nip with an improved heat transfer device, which press at least substantially reduces the above-mentioned problems so that both the favorable effects of impulse drying and embossing can be better utilized. way than has previously been possible. The press according to the invention is characterized in that - the heat transfer device consists of a - heatable sleeve included in the counter roll, which encloses the roll body, and has an outer jacket surface for co-operation with the opposing press device, and - that the outer jacket surface of the sleeve comprises a number , which are arranged in a pattern for a generation of a pattern element corresponding to a pattern image in the path.

FIGURE OF THE FIGURE The invention is explained in more detail in the following with reference to the drawings.

Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 is a perspective view of parts of a press, comprising a press with a counter-roller and a shoe press roller, which counter-roller has a rigid sleeve, the diameter of which is shown to be greatly exaggerated and on which the outer circumferential surface of the sleeve shows part of a pattern. shows a cross-section of the shoe press according to fi gl where a fi berban runs through a press nip formed by the counter roll and the shoe press roll. shows a cross-section of the shoe press according to fi g. 2, but with an alternative stretching of the banber web, through which the web is arranged to follow a longer distance around the sleeve after the press nip. and 4a shows a detail enlargement of the pattern according to a first embodiment. and Sa shows a detail magnification of the pattern according to a second embodiment. and 6a shows a detail enlargement of the pattern according to a third embodiment. and 7a shows a detail enlargement of the pattern according to a fourth embodiment. shows a press with a counter-roller and a shoe press roller similar to that in Figure 1, but which counter-roller has an flexible sleeve according to a second embodiment, in which flexible sleeve a part of a pattern is shown. a detail enlargement of the pattern according to fi g is displayed. 8 according to a first embodiment. 10 15 20 25 30 35 5; f- .ån fl u 'f “r i r ~ f“ I: i u! ,. ,, _ __ _ _. .. |. Fig. 10 shows a detailed enlargement of the pattern according to fi g. 8 according to a second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENT Figures 1 and 2 schematically show parts of a press 1, which is part of a press section in a machine for producing a continuous web 2 of cellulosic carrier material.

The invention is particularly, but not exclusively, applicable to paper machines for producing low basis weight paper, i.e. tissue. However, the paper machine may be designed for the production of any other paper grades. The press 1 comprises a rotatably mounted counter-roller 3; a pressing device 5 cooperating therewith, for forming a press nip 4; and a liner 6, which is in direct contact with the web 2 and which is preferably capable of receiving from the web 2 and carrying liquid in fl surface form and in gaseous form out of the press nip 4. The counter roll 3 comprises a stable cylindrical roller body 7, which has shaft pins 8, see figure 1, for rotatable bearing of the counter roller 3 in bearing housings not shown. The roller body 7, which is arranged to rotate about an axis of rotation 9, has a circumferential surface with a circular cross-section. In the embodiment shown, the press 1 consists of a shoe press with an extended press nip 4 and the press 5 of a shoe press roll, which comprises a pressure shoe 10 and an impermeable flexible jacket 11, which jacket 11 is fixedly mounted on rotatable peripheral end portions 12. The pressure shoe 10 has a concave surface 13, see figure 2 or 3, for pressure-generating cooperation with the convex selection body 7 of the counter-roller 3 to obtain the extended press nip 4. The jacket 11 runs through the press nip 4 in sliding contact with the concave surface 13 of the pressure shoe 10. Alternatively, the flexible jacket 11 can run in a loop around a number of rollers (not shown), in which loop the pressure shoe 10 is thus mounted.

The lining 6 of the shoe press 1 is arranged to run in an endless loop around a plurality of guide rollers (not shown) and through the extended press nip 4. The fibrous web 2 is carried by the lining 6 up to the pressing nip 4 and is then separated from said lining 6 or the nip 4, to abut against and accompany the counter roll 3 around a predetermined part of the mantle surface 14 of the counter roll 3. Alternatively, the web runs in an open pull before the press nip, ie. without the support of the cladding. The web can also be separated from the counter-roller 3 directly after the press nip 4, so that the web runs completely free of any support.

Two alternative web sections for the cable web 2 after the press nip 4 are shown in Figures 2 and 3. In the web line shown in Figure 2, the fibrous web 2 is arranged to abut and accompany only a small surface section of the mat surface 14 of the counter roll 3. fi berbanan 2 arranged to accompany the counter roll 3 of the counter roller 3 during abutment against the counter surface 3 of the counter roller 3 for a substantially longer distance, ie. over a considerably larger surface section, than in the embodiment shown in Figure 2. The larger the surface section against which fi berbanan 2 abuts, the more heat is transferred to fi berbanan 2, so that a higher dry matter content is thus obtained in weban 2. The surface section over which fi berbanan 2 is arranged to follow, (including the new length) has a length in the direction of rotation, determined by its sector with the angle ot, see fi gures 2 and 3, which are suitably within the range (10 ° to 300 °), depending on the post-drying required to reach the desired dry matter content.

The liner 6 usually consists of a press, but also a permeable process belt, which has through openings and possibly recesses or extending between them, can be used, as well as an impermeable belt with recesses of suitable depth, shape and stretch. The mentioned recesses fi are located on the side facing the fi berbanan 2. The mentioned openings and / or recesses are arranged to receive and carry liquid from the fi berbanan 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 embossed pattern, which embossing increases the bulk of the web 2. Instead of a permeable band or impermeable band, an open and a closed wire, respectively, which have a sealing layer facing away from the web 2, can be used. The press shown with a shoe press 1 is the preferred embodiment, but also other types of presses are included in the invention, such as for instance a press comprising a conventional, cylindrical press roll arranged against the roller and cooperating with it.

The press 1 also comprises a movable device 15 for continuous transfer of heat to the web 2 as it passes through the press nip 4, and a heating device 16 for heating said heat transfer device 15 from its outside to the desired operating temperature at start-up and thereafter for constantly recurring or continuous heating. below dri fi to maintain this driñ temperature. The heating device 16, which may be fixed or movable, e.g. oscillating, is arranged at a predetermined place or within a predetermined interval the dry press nip 4 for heating the circumference of the heat transfer device 15, e.g. about 30 ° - 330 ° before the inlet to the press nip 4, ie. also in the vicinity of the outlet from the press nip 4 for an improved utilization of the space around the counter-roller 3, which is possible since the heat loss from the heat transfer device 15 before the contact with the moist web 2 is relatively small. 10 15 20 25 30 35. According to the present invention, the counter-roller 3 comprises a heatable sleeve, which forms the said heat transfer device 15. The sleeve 15 encloses at least the entire axial part of the cylindrical roller body 7 acting for the press nip 4 and is arranged so that it can expand relative to the roll body 7 during said heating before the press nip 4 without adverse stresses thereby arising in the sleeve 15. The sleeve 15 has an inside 17, which is arranged to be brought into contact with the roll body 7 within the zone of the press nip 4, and an outside which constitutes the above-mentioned the sheath surface 14 of the counter-roller 3, around which the fiber web 2 is included during abutment.

The sleeve 15 is free from mechanical, adhesive or any other such existing, oxidizing connection which would prevent a free expansion of the sleeve 15 axially and / or radially relative to the cylindrical roller body 7 outside the press nip 4, i.e. where heating takes place, and which connections would instead give rise to unfavorable stresses in the sleeve 15.

Flat circular rings 18 are coaxially mounted at the end surfaces of the cylindrical roller body 7, which rings 18 have a slightly larger outer diameter than the cylindrical roller body 7 for forming axial end stops 19 for the sleeve 15 during the passage of the sleeve 15 through the press nip 4. At the shown The rings 18 are circular fl, 1 of which is arranged to run in a groove 20, which is arranged in the inside 17 of the sleeve 15, parallel to the end plane of the sleeve 15. Even during operation, the heat, axially expanding sleeve 15 is free from contact with one or both of these end stops 19 in order to also avoid axial stresses in the sleeve 15 in the zone of the press nip 4 so that the straightness of the cylindrical shell surface 14 can be ensured.

The sleeve 15 is thus fi independent i 'in existing, locking connections in all directions to be allowed to expand stress-free during heating both axially and radially relative to the cylindrical roller body 7. During drive val the roller body 7 is arranged to press the sleeve 15 in a contact point 21 within the zone of the press nip 4 at the pressure shoe 10 pressure generating interaction with the roller body 7 to form a sufficiently large ficrafting force in said contact point 21 between the roller body 7 and the sleeve 15 so that the sleeve 15 is driven around by the roller body 7 at the same speed as at said contact point 21, see Figures 2 and 3.

The sleeve 15 can be designed as a rigid, dimensionally stable sleeve, see especially fi gures 1-3, or alternatively as an ibel flexible sleeve 15, which is thus not dimensionally stable, see especially fi gur 8. 10 15 zo, 25 30 35 In Figures 1-3, the sleeve 15 schematically as a cylindrical, rigid, dimensionally stable sleeve 15 with an outer surface 14 which constitutes the outer surface of the rigid sleeve 15 and with an inner surface 17 which has a constant, circular cross-section. However, the diameter of the rigid sleeve 15 is shown to be greatly exaggerated in relation to that of the roller body 7. The sleeve 15 shown in Figures 1-3 thus has a certain wall thickness, measured between the inside 17 and the jacket surface 14, in all arbitrary cross-sections between the sleeve 15 parallel end faces. The wall thickness of the sleeve 15 is chosen depending on each specific use with varying wishes about the properties of the sleeve 15, for example that the wall thickness is optimized for as fast heating of the loose sleeve 15 as possible and for maintaining the straightness of the jacket surface 14 across the machine. The wall thickness of the sleeve 15 is large enough so that the sleeve 15 is rigid and dimensionally stable, i.e. is at least self-supporting so that, resting on a flat surface, it retains its radius all around and does not collapse into a round shape. Preferably, it is so rigid and dimensionally stable that it is not appreciably deformed by normal stresses during assembly and during operation. The rigid sleeve 15 has a sufficient wall thickness to withstand the large stresses in the press nip 4, which can arise due to radius differences between the different construction elements.

During drive fi the rigid sleeve 15 is arranged to rotate about its own axis of rotation, i.e. center axis 22, which is eccentrically located relative to the axis of rotation 7 of the roller body 7 or center axis 9, the eccentric displacement, i.e. the distance between these shafts 9, 22, corresponds to half the difference between the outer diameter of the roller body 7 and the inner diameter of the sleeve 15, i.e. the radius difference. It is understood that in a starting position, when the pressure shoe 10 and the counter-roller 3 are displaced vertically from each other a distance corresponding to said diameter difference, the sleeve 15 is suspended on the roller body 7 and thus has its center axis 22 located below the center axis 9 of the roller body 7. The sleeve 15 is completely loose in relation to the roller body 7 for a simplified replacement of the sleeve 15 in that a required gap for axial removal of the sleeve 15 is thus present between the pressing device 5 and the roller body. 7.

The concave surface 13 of the pressure shoe 10 has a radius which is adapted to the radius of the rigid, cylindrical sleeve 15. The sleeve 15 is so firm and stable that it itself has a pressing function by actuation from the roller body 7, i.e. the pressure from the roller body 7 at the shorter contact point 21 compared to the length of the press nip 4 is propagated forwards and backwards, seen in the direction of rotation, through the sleeve 15 to the press nip 4 so that the length of the nip 4 becomes approximately as long as the width of the pressure shoe 10. As a section of the rigid sleeve 15 passes the pressure shoe 10, a slight deformation will occur in this passing section due to differences between the inner radius of the sleeve 15 and the outer radius of the roll body 7, which slight change, however, disappears as soon as the pressure ceases after the press nip 4, and no harmful stresses arise in the rigid sleeve 15 due to it being thick enough to withstand this load. The rigid sleeve 15 therefore still fulfills the property "unstable" as defined in this description.

The diameter difference between the outer diameter of the roller body 7 and the inner diameter of the sleeve 15 is so determined that a small gap 23 is arranged to be formed at the side of the roller body 7 from the press nip 4 opposite. Thanks to this free space 23 inside the sleeve 15, only small amounts of heat will be consumed by the roller body 7. During operation, this air-containing space 23 has the shape of a crescent moon. Only in the zone for the press nip 4 does a transfer of heat from the sleeve 15 to the roller body 7 take place within the surface of the contact point 21, but the amounts of heat consumed here are still small, since the contact surface here constitutes a very small proportion of the circumferential surface. one surface to another. In general, the temperature of the hot jacket surface 14 of the sleeve 15 at the inlet to the press nip 4 can be in the range 150 ° C - 400 ° C.

Because the rigid, cylindrical sleeve 15 remains round during operation, a constant distance between the sleeve 15 and the heating device 16 is maintained at a constant operating temperature.

The wall thickness of the rigid sleeve 15 is generally in the range 5 - 100 mm, preferably 15-40 mm. The difference between the inside diameter of the rigid sleeve 15 and the outside diameter of the roller body 7 is generally in the range 0.01 - 100 mm, preferably 0.5 - 10 mn, measured at room temperature. During operation, when the rigid sleeve 15 is hot, this diameter difference is of course larger. The smaller the wall thickness of the sleeve 15, the faster a high surface temperature is achieved without high stresses arising by the mass to be heated in the radial direction decreasing correspondingly.

In the embodiment with a flexible sleeve 15, see Figure 8, this can also be included in a shape-changing cylinder, which is lethal to an applied outer collar fi, i.e. the sleeve 15 is shape-changing upon passage through the press nip 4, but substantially retains its non-self-supporting cross-sectional shape thereafter when the outer collar ceases or is moved along the circumferential surface 14 of the sleeve 15 upon rotation of the sleeve 15. The visible sleeve 15 generally has a wall thickness in the range 0.4 - 5.0 mm, preferably 0.8 - 2.3 mm.

The difference between the inner circumference of the visible sleeve 15 and the outer circumference of the roller body 7 is generally in the range 0 -100-1t mm, preferably 0.1 - 10-1: 10. . ,. - «. <F '4- _ - -_. .,,. _-, f .f r-c r <.. z <: - 'j, -.:*I* e, <2; E; - _ '' »» I 4 '«_' '_ S f 1 i. ur * fi,. “Nya -,. '_ f-. ,, = t 1- ~ _ _H u., .. <1 c <ß __ I.,,. t. _,, _ r r I “_ mm, measured at room temperature. During operation, when the visible sleeve 15 is hot, this difference in circumference is of course greater. Because the sleeve 15 is flexible, a cleaning scraper can be arranged in a suitable place so that the sleeve 15 is bent towards the roller body 7, which will act as an abutment. The flexible sleeve 15 is further från 'i from any moments between fi iktionskrafis and the sleeve handling is considerably facilitated when using the flexible embodiment of sleeve 15.

The above-described, rigid or visible sleeve 15, which is impermeable, i.e. impermeable, may be replaced by a further embodiment of sleeve, namely a permeable, rigid or flexible sleeve 15 for, for example, facilitating the detachment of the outer web from the sleeve 15 and for a simplified cleaning of said sleeve 15. The permeable sleeve 15 may be a metallic wire shaped into a cylinder, such as may be of bronze. The permeable sleeve 15 may, however, be any form of suitable permeable element which may be formed into a cylinder, including disc-shaped elements which are joined together end to end with a seam, for example a certain length of sheet metal, in which a pattern of continuous slots, openings or holes 35 are provided for forming said cylindrical, permeable sleeve 15. The slots can then be arranged so that when stretching the plate in its plane they expand to form a network of openings, for example elliptical, after which the ends of the plate are joined together with a weld.

With a permeable sleeve 15 it is desired to achieve a reduction in the risk of delamination, especially for medium and high weight paper webs, and for the web to adhere to the jacket surface 14 of the sleeve 15 and the loosening can be further facilitated, if desired, by arranging nozzles (not shown) at a position downstream of the web release point for strong lu fi blowing towards the ñber track, directly or through the sleeve. Furthermore, with a permeable patterned sleeve 15, it is generally easy to detach the berban 2 unscathed 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 jacket surface 14, air knives (not shown) can be arranged in suitable places at the outlet from the press nip 4. However, it is known that the web 2 easily releases from the jacket surface 14 of the sleeve 15 at temperatures above 200 ° C.

If desired, the lu jet may be constituted by or co-operate with the hot gases from a gas burner, or the like. All fibers adhered to the sleeve will be immediately burned to ash and carried away by the gas jet. The heating of the wire by means of the hot gases also reduces the need for, for example, electromagnetic heating of the sleeve. In a embodiment not shown, the roller body 7, which is enclosed by the permeable sleeve 15, may consist of a roller having a first blowing zone, at which the web is detached from the sleeve, and a second blowing zone arranged downstream of this first blowing zone. in the direction of rotation of the sleeve for cleaning the permeable sleeve. If desired, a suction zone can also be provided at the impulse pressure nip to remove steam and to reduce the risk of delamination. For example, the roller with at least one blowing zone can have a suction zone located in the press nip.

According to the present invention, the sleeve 15 further comprises a number of pattern elements 24, which are arranged on, down in or through the outer, web-bearing mantle surface 14 of the sleeve 15, see 1 or 8. The pattern elements 24 are arranged in a predetermined pattern, preferably a relief pattern 25. , for application to the web 2 so that a pattern element 24 corresponds to a pattern image, i.e. embossing, is generated in the ñber web 2 as it passes through the press nip 4 together with the cladding 6.

The embossing gives lasting positive property changes in the web 2, among other things, the bulk of the web 2 increases by 50 - 150%, compared with conventional pressing with a smooth counter-roll.

The pattern elements 24, see Figures 4 - 7a and 9 - 10, are arranged to be formed by depressions in the outer surface 14 of the sleeve 15, which depressions are preferably arranged to form, in relation to each other, raised or lowered surface portions 26, 27, see Figures 4 - 7a. The pattern elements 24 may be uniformly distributed, but all, some or individual pattern elements 24 may also be arranged, individually or in groups at a desired distance from each other, that together they form each other predetermined pattern 25, for example in the form of structures, symbols, urer gures or ordinary decors, such as breaks, numbers, letters, trademarks, names or other images. All, some or a single pattern element 24 may have an elliptical, circular, rectangular, square or other polygonal shape, e.g. triangular, or have any other conceivable geometric shape which is considered suitable for obtaining the desired pattern in the current fi track 2.

In the embodiment with raised or recessed surface portions 26, 27, see Figures 4 - 7a, the raised surface portions 26, which are arranged between said recessed surface portions 27, may for example have two, faceted, conical, arched or other convex in I cross-sectional shapes or portions. Correspondingly, the recessed surface portions 27 may comprise, for example, fl ata, multifaceted or curved, hollowed out or otherwise concavely shaped finite cross-sectional shapes or portions. The pattern elements 24 may also, instead of the radially submerged surface portions 27 of the radially articulated surface of the sleeve 15, comprise a larger number of through-holes, drilled or otherwise suitably received holes 35, which extend through the wall of the sleeve 15. to form a desired penile pattern 25, see gurus 9 and 10, or a combination of both raised and lowered surface portions 26, 27 and through holes 35 (not shown). The pattern elements 24 are arranged in size and number so that the raised surface portions 26, which are in pressing contact with the outer web 2, together form a substantial part of the total casing surface 14, preferably between 20 - 50% of the casing surface 14.

The pattern elements 24 may further be arranged so as to form continuous grooves with even distribution over the mantle surface 14, stripes of fls of closely spaced adjacent continuous grooves, which stripes of grooves are thus mutually separated by a relatively larger distance, or intimate final groups of elements in the jacket surface 14, which pattern elements 24 are arranged in the direction of rotation of the sleeve 15, at an angle to the direction of rotation of between 10 ° to 80 ° diagonally from one or both end surfaces of the sleeve 15 to the opposite or the opposite, or substantially transversely to the direction of rotation. The grooves, lanes or groups may be straight or wavy, e.g. sinusoidal or zigzag shaped, and the distance between them may vary, or between two adjacent and mutually parallel grooves, stripes or groups be fi xt, fi from 1 to 5 mm, while the groove width is suitably in the range 0.5 - 2.0 mm with a groove depth within the range 0.1 to 2.0 mm. The pattern elements 24 can then be comprised of, for example, radially finite grooves, through grooves or other finely recessed or through recesses, which are formed by means of mechanical, laser or chemical processing of the casing surface by means of, for example, etching, drilling, turning, electrolytic pickling or at least a shorter etching. piece down into the mantle surface of the sleeve 15 from its outside 14.

Seen in a cross-section of the sleeve 15, the height difference, i.e. the radius difference, between the raised and the lowered surface portions 26, 27 in the range 0.1 - 2.0 mm, while the width of the raised surface portions 26 is suitably in the range 0.5 - 5 mm.

When the web 2 passes through the press nip 4, essentially only those parts of the web which abut against the raised surface portions 26 are compressed in the press nip 4, while the intermediate parts of the web are left relatively unaffected.

In the figures 4 - 7a and 9 - 10 described below, in particular a number of different embodiments of patterns 25 for the casing surface 14 of a sleeve 15 are shown, which sleeve 15 can be either rigid or flexible. In the embodiments shown in Figures 4 - 7a, the sleeve 15 is impermeable, but may as above also be designed as a permeable sleeve 15, for example by its construction, for example comprising a net or wire structure, or by the arrangement of said through hole 35, see Figures 9 and 10.

The invention is thus in no way limited to the specially shown embodiments, but any other configuration of pattern elements 24 for embossing predeterminable patterns 25 in the web 2 as above falls within the invention tank.

Figures 4 and 4a show schematically in view and cross-section a detail of a pattern 25 according to a first embodiment, which pattern 25 comprises pattern elements 24 in the form of a number of straight and mutually parallel grooves 28, which divide the sleeve surface into elongate, alternately raised and submerged 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 two wall surfaces 31, 32 converging from the bottom surface 29 to the top surface 30 extend. The corners between the surfaces 29, 31 and 30, respectively 29, 32 and 30, are shown in figure 4a as being completely straight, but can also be designed with a small radius for rounding said corners. In the cross section shown in Figure 4a, the width and the height difference of the two surface portions 26, 27 are illustrated by the markings a, b and c, which widths and height difference are within the above-mentioned range. The grooves 28 in the embodiment shown extend in the direction of rotation of the sleeve around its entire circumference in endless rings, but may in another embodiment, not shown, instead have a certain fixed angle to the end plane of the sleeve. Figures 5 and 5a show schematically in view and cross-section a detail of a pattern 25 according to a second embodiment, which pattern 25 comprises pattern elements 24 similar to the grooves 28 shown in the first embodiment, but which, unlike these, have wall surfaces 31, 32 which are mutually parallel and which extend between a bottom surface 29 and a top surface 30 at a right angle thereto.

Figures 6 and 6a show schematically in view and cross-section a detail of a pattern 25 according to a further embodiment, which pattern 25 comprises pattern elements 24 in the form of grooves 28 similar to those shown in the first and second embodiments above, but which in contrast to these have rounded bottom surface 29, see figure 6a, and flat top surfaces 30 on the raised surface portions 26 thus formed between the grooves 28.

Figures 7 and 7a show schematically in view and cross-section a detail of a pattern 25 according to a further embodiment, which pattern 25 comprises pattern elements 24, 10 which are constituted by two groove groups 33, 34, each of which comprises a plurality of respective groups of mutually parallel grooves 28, which groove groups 33, 34 extend in a first group 33 from the first to the second end face of the sleeve, and in a second group 34 n from the second end face of the sleeve to the first, the two the track groups 33, 34 intersect at an angle of between 10 ° to 170 °. Both groove groups 33, 34 have a concavely rounded bottom surface 29. The two groove groups can also, in an embodiment not shown, have different angles to the end surface of the sleeve in order to avoid that the same strip in the cladding is compressed turns or turns.

Figure 9 schematically shows in detail a detail according to a first embodiment of a continuous pattern 25 of a permeable sleeve 15, which pattern 25 comprises pattern elements 24, which consist of substantially circular holes 35 running through the cross section of the sleeve 15. The holes are arranged in line with each other at a predetermined mutual distance and at a certain predetermined angle to the direction of rotation of the sleeve 15, diagonally from one end surface of the sleeve 15 to the other. The width of the holes, the angle, the mutual distance between each hole in the line and the distance between said lines are within the above-mentioned range.

Figure 10 schematically shows in detail a detail according to a second embodiment of a continuous pattern 25 of a permeable sleeve 15, which pattern 25 comprises pattern elements 24, similar to the holes 35 shown in the first embodiment, but which, unlike these, have rectangular form.

The patterned sleeve 15 can be homogeneous, i.e. be made of one and the same material straight through without layers, or consist of two or more, uniformly continuous layers of different materials, of which at least one layer functions as at least carrier for the other layer or layers. Like the rigid sleeve 15, the flexible one can consist of two or two layers.

Thus, since the rigid sleeve 15 consists of fl your layers, one layer is a support layer with the main function as a stabilizing carrier with a sufficiently large wall thickness so that the support layer can be provided with e.g. a surface layer with desired or desired properties.

The support layer may be provided on its outside with a surface layer of a suitable material in order to obtain the desired release capacity and / or a desired thermal conductivity of the jacket surface 14 of the cylindrical sleeve 15. A special thermal conductivity of the jacket surface 14 may be desirable to control the heat supply. fi berbanan 2 10 15 15 20 25 30 35 iåirórïztfåli and thus prevent delamination of the web 2. Delamination is the phenomenon when the ñberban 2 bursts, when it leaves the press nip 4 due to the vapor pressure inside the web 2 being greater than the cohesive forces in lane 2 can withstand.

The cylindrical roller body 7 can be provided on its outer surface with a surface layer of one or more suitable materials to increase the abrasion resistance and / or increase the corrosion resistance and / or to achieve an insulation so that the amount of heat transferred from the sleeve to the cylindrical roller body 7 is further reduced. within the press nip 4. Alternatively or additionally, the sleeve 15 on its inside 17 may have such a surface layer (not shown).

Suitable materials for obtaining a surface layer with the desired emissivity and the desired thermal conductivity can be mentioned alumina, chromium oxide and zirconia-based ceramics. Suitable materials to increase abrasion resistance are tungsten and chrome carbides as well as chrome steel. Suitable materials to increase corrosion resistance are nickel, chromium and cobalt based alloys. Suitable insulating materials are zirconia-based ceramics. Suitable materials for a homogeneous sleeve (ie without layers) and for the support layer of a sleeve consisting of at least two layers can be mentioned ductile iron, cast steel and weldable high-strength structural steels.

Any suitable heating device 16 can be used, although an induction heater is currently preferred. Examples of other heating devices 16 are electric heaters, infrared heaters, laser heaters and gas burners.

The roller body 7 of the press 1 can be a so-called solid roller, which is modified according to the invention, but a bending compensated roller can also be used. Because the contact surface between the hot sleeve 15 and the shell body of the bending compensated roller is small, some heat is transferred to the roller. Sufficient heat can be dissipated with the oil in the roll to maintain a reasonable temperature and thus a sufficiently high viscosity of the oil to achieve a satisfactory function of the roll.

The temperature of the web 2 can be raised before the press nip 4 by arranging one or two steam boxes in the light loop and / or near the free side of the web 2. Preheating of the wet web 2 gives a lower viscosity of the water, which facilitates the extraction of this from the outer web at the press nip After the press nip 4, further drying devices can also be arranged, such as for instance one or two blow dryers, for more gradual drying of the web 2.

In the embodiment with a loose, rigid sleeve 15, the advantage is obtained that the casing surface can be coated to improve the release properties, the heat transfer to the paper and to reduce unwanted heat rad radially inwardly into the sleeve 15. By making the rigid sleeve 15 the wall thickness 15 of the sleeve 14, which is in contact with the web 2, is treated as a conventional press roll surface to be cleaned, if necessary, with a cleaning device 36, for example a doctor blade, a metal brush or by nozzles for blowing air. In the embodiment with loose, fl visible sleeve. 15, an easily mounted heat transfer device is obtained. In the embodiment with a loose, permeable sleeve 15, the advantages are obtained that the risk of partial annealing at certain paper qualities is minimized by a suction zone being arranged at the counter-roller for removing the steam and that facilitating the release of the web from the sleeve by air blowing is allowed and that a cleaning with of a cleaning device 36 in front of a burner for burning off stuck fibers is made possible. In addition, it is easier to handle the sleeve.

With the invention described above, a press section is obtained comprising one or more presses 1 with press nip 4 in succession for impulse drying, which is energy-efficient and dimensionally stable in the press nip 4, which press nip 4 comprises a counter roll 3 with a heat transfer device 15 in the form of a loose , patterned sleeve 15 for faster and more efficient heating than with conventional rollers, since a smaller mass is heated. In addition, no problems arise with stresses in the counter-roller 3, so that its straightness is maintained. A fi berbana 2, which has been rapidly dried at a sharply elevated temperature in connection with the embossing of a structured pattern therein, as is the case with the present invention, retains its structure after drying even during liquid absorption, which also means that the advantageous product properties obtained by the patterning , such as high bulk, high softness, good extensibility and high liquid absorption are maintained.

Due to the fast drying in the impulse press 1 and due to the lack of a long conventional drying section and / or a large Yankee cylinder, the advantages of a higher paper production and a lower energy cost are obtained. In the production of tissue, a softer and more bulky tissue is obtained through the patterned sleeve 15.

Through the pattern elements 24, i.e. the present through holes and / or finite depressions, outlets and spaces are obtained for the steam formed at the press nip 4 10 15 20 25 30 with a reduction of the steam pressure and thus also of the risk of delamination in the web 2. However, this mainly applies to paper other than tissue, as tissue lets the steam through. The main task of the pattern elements 24 is, however, to structure the web 2 according to the current pattern in the mantle surface 14, whereby some further favorable effects are obtained. The steam penetrating through the web 2 is considered to provide more advantageous unloading properties for the web 2 against the sleeve 15. The total contact surface of the web 2, which is heated by the sleeve 15, is significantly increased, so that the drying is considerably accelerated, while the total contact surface exposed to pressure of the sleeve 15 is instead considerably reduced down to 20 - 50% of the total web surface 2 before the press nip 4, and that the tissue web 2 is allowed to expand by the steam in the cavity of the pattern 25, so that a structured and thus more fluid, ie. bulkier, product obtained. When depressing the web 2 in the cavities, ie. the submerged surface portions 27 and the through holes 35, the web 2 is protected from getting stuck by it against the hot roller, i.e. sleeve 15, formed the vapor, which constitutes a previously unknown eiïelct.

The drying section normally constitutes a substantial length of the conventional paper machine, so that an advantageous shortening of the paper machine is also obtained, since the total length of the pressing and drying sections is substantially reduced compared to the previous constructions.

It will be appreciated that the number, size, material and shape of the elements and details included in the press, for example the roller body 7, the sleeve 15 and the pattern elements 24 are adapted to the press device (s) 5 and the fi berbana 2 currently present. The press device 5 can thus be comprised of one of several different types of press device 5, for example a conventional press roll, an open or closed shoe press roll or any other suitable press roll. The order of magnitude of the sleeve 15, i.e. its outer diameter, is usually over about 1.0 meter. The sleeve 15 may be made by any of the methods of sintering, casting, cold pressing, rolling and welding.

Claims (33)

10 15 20 25 30 35 <z. . r * / 7 PATENT REQUIREMENTS A press in a machine for setting up a continuous web (2) of cellulosic material, comprising iii I - a press device (5) - a rotatably mounted counter-roller (3), which comprises a cylindrical roller body (7) and is arranged to cooperating with the press device (5) form a press nip (4), - an endless liner (6), which is arranged to run through the press nip (4) in contact with the web (2) and preferably has the ability to receive and carry liquid from the web (2), and - means (15, 16) for heating the web (2) in the press nip (4), which heating means (15, 16) comprise - a movable heat transfer device (15) for transferring heat to the web (2) in the press nip (4), and - at least one heating device (16) for heating the heat transfer device (15), characterized in that the heat transfer device (15) consists of a p - heatable sleeve included in the counter roller (3), which encloses the roller body (7) , and has an outer jacket surface (14) for co-operation with the opposing press device (5), and - that the outer jacket surface (14) of the sleeve (15) comprises a number of pattern elements (24), which are arranged in a pattern (25) for a generation of a pattern element (24) corresponding to a pattern image in the web (2). Press according to claim 1, characterized in that the sleeve (15) is cylindrical and arranged to loosely enclose the roller body (7) for expansion in relation to the roller body (7) during said heating before the press nip (4). Press according to Claim 1 or 2, characterized in that the sleeve '(15) is designed as a rigid and with the exception of deformation caused by heat expansion, dimensionally stable sleeve (15). Press according to claim 3, characterized in that the rigid sleeve (15) is impermeable. Press according to claim 3, characterized in that the rigid sleeve (15) is permeable. Press according to Claim 1 or 2, characterized in that the sleeve is designed as a flexible, deformable sleeve (15). 10 15 20 25 30 35 .w «. Press according to Claim 6, characterized in that the removable sleeve (15) is impenetrable. Press according to Claim 6, characterized in that the removable sleeve (15) is permeable. Press according to one of Claims 1 to 8, characterized in that the sleeve (15) consists of a certain length of sheet metal which is joined, end to end, to a cylinder. Press according to one of the boards 1 to 4, 6, 7 or 9, characterized in that the pattern elements (24) consist of depressions in the jacket surface (14) of the sleeve (15), which depressions are arranged to form, in relation to each other, raised or sunk surface portions (26). , 27) in a relief pattern (25), and which pattern elements (24) are arranged in size and number so that the raised surface portions (26), which are in pressing contact with the ban berbanan (2), together form a substantial part of the total the mantle surface (14), preferably between about 20 to about 50% of the mantle surface (14). 11. ll. Press according to claim 10, characterized in that one, some or all of the raised surface portions (26) are comprised of eight, multifaceted, conical, arched or other convex cross-sectional shapes or portions and that one, some or all of the recessed surface portions (26) 27) consists of flat, multifaceted or curved, hollowed out or otherwise concavely shaped, radially finite cross-sectional shapes or sections. Press according to one of the preceding claims, characterized in that all, some or a single pattern element (24) has an elliptical circular, or rectangular, square or other polygon in front. A press according to any one of the preceding claims, characterized in that the pattern elements (24) are uniformly distributed or that all, some or individual pattern elements (24) are so arranged, individually or in groups at a desired distance from each other, that they are together arranged to form structures, symbols, urer gures or decors, such as rasters, silos, letters, trademarks, names or other images, which constitute approximate patterns (25). Press according to one of Claims 1 to 3, 5, 6, 8 or 10, characterized in that the pattern elements (24) consist of 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 (3 5). 15. Press according to any one of claims 1 - 11 or 14, characterized in that the pattern elements (24) consist of continuous grooves (28) with even distribution over the mantle surface (14), or strips of fls at close distances next to each other. continuous grooves (28), which stripes of grooves (28) are thus mutually separated by a relatively larger distance, or intermittent, finite groups of pattern elements (24), which are arranged in the direction of rotation of the sleeve (15), at an angle to the direction of travel between 10 ° to 80 ° diagonally from one or both end faces of the sleeve (15) to the opposite or the opposite and which grooves (28), stripes or groups are straight or wavy, e.g. sinusoidal or zigzag shaped. Press according to one of Claims 1 to 9, characterized in that the pattern elements (24) consist of straight and mutually parallel grooves (28) which extend in the direction of rotation of the sleeve around its entire circumference in endless rings which divide the outer surface of the sleeve into 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 converging or at a right angle to these parallel wall surfaces (31 , 32) extends from the bottom surface (29) towards the top surface (30). Press according to claim 15 or 16, characterized in that the grooves (28) have a certain fixed angle to the end plane of the sleeve (15) within a range of about 10 ° to about 170 °. Press according to claim 15, 16 or 17, characterized in that the distance between the grooves (28), the grooves or the groups is in a range of about 1 to about 5 mm, while the groove width is in a range of about 0.5 to about 2.0 mm with a groove depth within one in the range of about 0.1 to about 2.0 mm. J 'i Press according to any one of claims 11 - 18 in combination with claim 10, characterized in that the height difference between the raised and the lowered surface portions (26, 27), seen in a cross section through the sleeve (15), is within a range of about 0.1 to about 2.0 mm, while the width of the raised surface portions (26) must be within a range of about 0.5 to about 5 mm. Press according to one of Claims 1 to 11, characterized in that the pattern elements (24) consist of two groove groups (33, 34), each of which comprises a plurality within rr r. _. ... ~. .__- ._ 10 15 20 25 30 35 respective groups of mutually parallel grooves (28), which groove groups (33, 34) extend in a first group (33) fi from the first to the second end surface of the sleeve (15), and in a second group (34) from the second end surface of the sleeve (15) to the first, the two groove groups (33, 34) intersecting at an angle of between about 10 ° to about 170 °. Press according to claim 20, characterized in that the two groove groups (33, 34) have different angles to the end surface of the sleeve (15) in order to avoid that the same strip in the cladding (6) is compressed turn after turn. Press according to Claim 6 or 8, characterized in that the permeable sleeve (15) consists of a metallic wire formed into a cylinder. Press according to any one of the preceding claims, characterized in that the press (1) consists of a shoe press with an extended press nip (4), the press device 5 being a shoe press roll, which comprises a pressure shoe (10) with a concave surface (13) to obtain the elongated press nip (4), and an impermeable ibel visible sheath (11), which A is arranged to run through the press nip (4) in sliding contact with the concave surface (13). Press according to one of Claims 1 to 22, characterized in that it comprises a roller press with two mutually arranged, cooperating cylindrical press rollers, of which the counter-roller (3) constitutes one, while the other is constituted by a conventional cylindrical press roller. . _ Press according to any one of the preceding claims, characterized in that the web (2) is arranged to abut against and accompany the casing surface (14) a certain predetermined surface section, which surface section has a length in the direction of travel, determined by its sector with the angle ot, which is in a range of about 10 ° to about 300 °. ' Press according to any one of the preceding claims, characterized in that the heating device (16) is arranged within a predetermined range, which is within about 30 ° to about 330 ° before the inlet to the press nip (4). Press according to any one of the preceding claims, characterized in that the roller body (7) consists of a roller having a first blowing zone, at which the web (2) is detached from the sleeve (15), and a second blowing zone arranged downstream of this first blowing zone in the direction of rotation of the sleeve (15) for cleaning the sleeve (15). 10 15 20 tä-izä 23 Press according to one of the preceding claims, characterized in that the cover (6) consists of a strip with recesses arranged to receive and carry liquid from the web (2) out of the press nip (4) and to give the web (2 ) an imprint in the form of an embossed pattern (25). i - Press according to claim 22, characterized in that the heating device (16) consists of a burner, which also cleans the sleeve (15) by burning fi residual residues and the like. IN Press according to one of the preceding claims, characterized in that the sleeve (15) is manufactured by one or more of the methods of sintering, casting, cold pressing, rolling and welding. Press section, characterized in that it comprises at least one press (1) according to any one of claims 1 - 30. 32. A machine for preparing a paper web (2) of low basis weight, for example tissue or other soft paper; characterized in that it comprises at least one press (1) 'according to claims 1 - 30. A machine for producing a paper or paperboard web (2), characterized in that it comprises at least one press according to any one of claims 1 to 30.