DE102020105480A1 - Seam for a perforated plastic film - Google Patents

Abstract

The invention relates to a covering for a device for the production and / or processing of a fibrous web, comprising a plastic film (100), the top side (104) facing the fibrous web, an underside facing away from the fibrous web and a plurality of through openings (102) which are from the top (104) to the bottom, wherein the plastic film (100) further has at least one seam which extends from a first side edge (114) of the plastic film (100) to a second side edge opposite the first side edge (114) of the plastic film (100) and by means of which a first longitudinal end of the plastic film (100) is connected to an opposite second longitudinal end of the plastic film (100) for making the plastic film (100) endless, the seam having a first seam line on the upper side (104) of the Plastic film (100) and a second seam line on the underside of the plastic film (100) and wherein the first seam line and / or the second seam line is / are arranged in such a way that they substantially do not intersect any through openings (102). The invention also relates to a device with such a covering and a manufacturing method for such a covering.

Description

The invention relates to a covering for a device or machine for producing and / or processing a fibrous web, comprising a plastic film that has a top side facing the fibrous web, an underside facing away from the fibrous web and a plurality of through openings extending from the top to the bottom extend, wherein the plastic film further has at least one seam which extends from a first side edge of the plastic film to a second side edge of the plastic film opposite the first side edge, and by means of which a first longitudinal end of the plastic film with an opposite second longitudinal end of the plastic film for making endless the plastic film is connected, wherein the seam comprises a first seam line on the top of the plastic film and a second seam line on the underside of the plastic film. The invention further relates to a device for producing a fibrous web, in particular a tissue paper web, with such a covering and a method for producing such a covering.

It has been known for a long time to produce coverings for paper machines or the like from perforated plastic films instead of fabrics, although such coverings have so far been rarely found in practice. For example in the WO 2015/185278 A1 is described, such a covering can be produced in that a plastic film, in the form of a laminated polymer film arrangement, is perforated by means of punching. Furthermore, it is proposed to close a substantially flat basic structure, which comprises the perforated plastic film or consists of it, with the aid of a seam connection element to form an endless belt.

Although the use of a seam connection element has the advantage that the covering can be closed within the device or machine, this is - depending on the design of the device - not absolutely necessary The arrangement and density of the perforations.

A known solution to this problem provides to dispense with a separately formed seam connection element and instead to produce the seam, for example, by means of a form-fitting connection of the two longitudinal ends of the plastic film, for example by welding. Such weld seams are for example in the patent, which also goes back to the applicant EP 2 734 672 B1 described.

However, it has been observed that there is sometimes increased wear of such coverings in the area of the weld seam.

It is the object of the present invention to provide a covering which does not have the problem described above or at least has only to a reduced extent.

This object is achieved by the features of the independent claims, the dependent claims having advantageous developments of the present invention as their subject.

Thus, according to claim 1, a covering mentioned at the beginning is proposed which is particularly characterized in that the first seam line and / or the second seam line is or are arranged in such a way that they essentially do not intersect or cut through openings.

It is to the merit of the inventors to have recognized that increased wear of the covering in the area of the seam of the plastic film, which can lead to a failure of the covering in the machine, is directly related to the formation of the first and / or second seam line. It could be observed that the quality of the seam is the better, the fewer through-openings are cut by the first and / or second seam line. The results are best when neither the first nor the second suture line intersects any through openings. So far, no consideration has been given to whether or how many through openings were cut by the first and / or second seam line.

A positive side effect of the present invention is that the handling of the perforated plastic film before and during the production of the seam is safer. If the first and / or second seam line intersects or cut through openings, the affected longitudinal end has a sawtooth-like structure on which injuries can easily be sustained.

In the context of the present invention, the term “fibrous web” is to be understood broadly when in doubt. It includes webs made of natural and / or synthetic fibers. In addition to paper and cardboard webs, the present invention is particularly concerned with tissue webs. However, webs made of nonwoven or nonwovens can also be understood under the term “fibrous webs”.

A “multiplicity of through openings” is to be understood here as a large number of through openings, ie the covering has a number of through openings which is beyond a thousand and can be up to several million. The function of the passage openings can be to give the plastic film - and thus the covering - a certain permeability in order to be able to withdraw water from the fibrous web transported on it when the covering is used as intended. Alternatively or additionally, however, the through openings can also be provided to give the fibrous web transported on them a structure. This is particularly important in the manufacture of tissue products in order to increase the so-called bulk of the tissue.

When it is said that the covering comprises a plastic film, the covering can preferably be formed essentially exclusively from the plastic film. Alternatively, however, the covering can also have further components if required, such as one or more layers of staple fibers, for example if the covering is a press felt.

The covering according to the invention can either have only one seam or also several seams. In particular, it is conceivable to provide the covering - similar to the chain of a tank - with a large number of seams. In this way, coverings of different lengths and widths can be manufactured relatively easily from film webs of predefined width. If the seams of the plastic film do not have a weak point compared to the other areas of the covering, in particular due to increased wear, it is irrelevant for the quality of the covering how many seams are present.

The “first seam line” is the line that can be seen on the top of the plastic film from the seam, whereas the “second seam line” is a line that can be seen on the underside of the plastic film from the seam. These two seam lines preferably run parallel to one another. They can also be arranged directly one above the other in the direction of the thickness of the plastic film. However, this is not mandatory. On the contrary, it can be advantageous if the two opposite longitudinal ends of the plastic film, which are to be connected to one another by means of the seam, are or are prepared in such a way - for example by means of a profile cutter - that they have an enlarged contact surface for the formation of the seam . In this case, the first and the second seam line, viewed in the direction of the thickness of the plastic film, will usually not lie directly one above the other.

According to the invention, the first and / or second seam line essentially does not intersect or intersect any through openings. In this context, the term “essentially” means that the first and / or second seam line intersects or cuts through holes less than 10%, preferably less than 5%, more preferably less than 1% and even more preferably none at all. cut, which partially or completely lie in a fictitious corridor that extends on both sides of the said seam line with a width of twice the average diameter of the passage openings. If the passage openings in the plastic film all have the same diameter, the corridor has a width that is four times as large as this diameter, namely twice the diameter to the left of the seam line concerned and twice the diameter to the right of the seam line concerned.

An advantageous development of the present invention provides that the first and / or second seam line runs in a straight line between the first side edge of the plastic film and the second side edge of the plastic film. This enables a relatively simple preparation of the seam area, whereby it should be noted that the two longitudinal ends of the plastic film to be connected are to be designed to be complementary to one another.

Alternatively, however, it is also possible that the first and / or second seam line does not run in a straight line between the first side edge of the plastic film and the second side edge of the plastic film. Instead, the gradient can be zigzag, for example. The first and second seam lines can run parallel to one another.

Furthermore, it has proven to be advantageous if the first and the second seam line run parallel to one another, whereby they enclose an angle to the first and / or second side edge which differs from 90 °. In this way, the entire seam line does not hit elements of the machine at the same time, such as deflection rollers, cleaning devices, etc., which are usually oriented in the cross-machine direction.

The covering according to the invention can in particular be designed to contour the fibrous web transported on it when used as intended. The person skilled in the art understands the term “contouring” in this context to mean that the finished fibrous web has a pattern or embossing that can be clearly recognized with the naked eye even from a distance. The through-openings can represent areas for the fibrous web in which the latter is less strongly pressed and thus compressed, so that the shape of the through-openings is permanent as elevations in the fibrous web emerging. In the case of a tissue web in particular, this leads, on the one hand, to an improved haptic and optical impression of the fibrous web, and, on the other hand, to an improved absorbency due to the increased bulk.

It can be provided, in particular in order to achieve a noticeable contouring of the fibrous web, that some or all of the through openings have a clear opening of an area that corresponds to a circle with a diameter between 1 mm and 5 mm, with some or all of the through openings preferably essentially the Have the shape of a cylinder, more preferably the shape of a straight circular cylinder. However, the shape of the openings does not necessarily have to be that of a straight circular cylinder. The size of the area of the passage opening is of primary importance in order to achieve good contouring of the fibrous web. The area of a circle with a diameter D between 1mm and 5mm can easily be calculated using ^{the formula A = π * D 2/4.}

Tests have also shown that very satisfactory results can be achieved if the open area on the upper side and / or underside (in the case of through openings in the form of straight circular cylinders, the open area of the upper side corresponds to the open area of the lower side) is less than 20%, preferably between 5% and 15%. Other tests with covers that have a larger open area, for example an open area of 40%, turned out to be significantly worse.

The plastic film can be an extruded plastic film which has one or more layers. For example, the plastic film can consist of three or four individually extruded, stretched and then laminated plastic layers, each individual layer being, for example, 250 μm thick. At least one plastic layer can also have reinforcing elements, such as, for example, reinforcing threads, and / or such reinforcing elements can be arranged between the plastic layers. The covering can consist of the plastic film over the entire width and only have a single seam, in particular a transverse seam, in order to make the covering endless. Alternatively, the covering can also consist of several parts of the plastic film, the parts being connected to one another at corresponding seams.

In a first variant, the closed surface on the top and / or bottom of the plastic film can be designed to be essentially smooth. The term “closed area” here means the area of the plastic film that remains between the passage openings. Alternatively, however, according to a second variant, it is possible for the closed surface to be structured on the top of the plastic film. It is thus possible not only to contour the fibrous web through the through openings, but also to structure it, at least to a certain extent, in the area in between. The structuring of the closed surface can be achieved, for example, by etching shapes. In contrast to contouring, structuring only results in very fine depressions or elevations in the finished fibrous web, which can no longer be seen with the naked eye and from a distance.

Another aspect of the present invention is aimed at the use of the clothing according to the invention in a device or machine for structuring a tissue web. Specifically, a device for producing a fibrous web, in particular a tissue paper web, is claimed which comprises: a forming section for forming the fibrous web, the forming section comprising a gap former with a headbox, a first covering and a second covering; a press section for pressing the formed fibrous web, the press section comprising a first press element and a second press element which together form a press nip through which, when the device is used as intended, the first covering, a third covering and the fibrous web in between are passed; and a drying section for further drying the pressed fibrous web, the drying section comprising a drying cylinder to which the fibrous web transported on the third clothing is transferred, a transfer device for this purpose together with the drying cylinder forming a transfer nip through which the fibrous web can be used when the device is used as intended and the third covering are guided, the third covering being the covering according to the invention described above.

An advantageous further development of the device according to the invention provides that the first press element is a suction roll with a suctioned circumferential section over which the first covering and the fibrous web transported on the first covering are guided before reaching the press nip. By designing the first press element as a suction roll, the fibrous web is pre-dewatered by the suction system before it passes through the press nip, so that it enters the press nip with a higher dry content compared to a variant in which the fibrous web has not previously been suctioned. This makes it possible to apply a lower pressing force to the fibrous web in the press nip of the press section exercise to achieve the desired dry content at the end of the press nip. In this way, a relatively large bulk of the fibrous web can be achieved with the simultaneous use of relatively inexpensive technology for the two pressing elements of the press section.

1. a) Bereitstellen einer Kunststofffolie mit einer Oberseite und einer der Oberseite gegenüberliegenden Unterseite, sowie mit einem ersten Seitenrand und einem dem ersten Seitenrand gegenüberliegenden zweiten Seitenrand;
2. b) Einbringen einer Vielzahl von Durchgangsöffnungen in die Kunststofffolie, welche sich von der Oberseite zu der Unterseite der Kunststofffolie erstrecken;
3. c) Vorbereiten eines ersten Längsendes der Kunststofffolie und eines dem ersten Längsende der Kunststofffolie gegenüberliegenden zweiten Längsendes für die Ausbildung einer Naht zum Endlosmachen der Kunststofffolie;
4. d) Erzeugen einer Naht, indem die beiden vorbereiteten Längsenden der Kunststofffolie miteinander verbunden werden;

wobei die Vorbereitung in Schritt c) derart erfolgt, dass eine erste Nahtlinie auf der Oberseite der Kunststofffolie und/oder eine zweite Nahtlinie auf der Unterseite der Kunststofffolie im Wesentlichen keine Durchgangsöffnungen schneidet bzw. schneiden.Yet another aspect of the present invention relates to a method for producing a covering according to the invention as described above, comprising the following steps:

1. a) providing a plastic film with a top side and a bottom side opposite the top side, as well as with a first side edge and a second side edge opposite the first side edge;
2. b) introducing a multiplicity of through-openings in the plastic film which extend from the top to the bottom of the plastic film;
3. c) preparing a first longitudinal end of the plastic film and a second longitudinal end opposite the first longitudinal end of the plastic film for the formation of a seam for making the plastic film endless;
4. d) creating a seam in that the two prepared longitudinal ends of the plastic film are connected to one another;

wherein the preparation in step c) takes place in such a way that a first seam line on the upper side of the plastic film and / or a second seam line on the underside of the plastic film essentially does not cut or cut through openings.

In view of the large number of through-openings in the plastic film and in view of the fact that the through-openings are often not all arranged in exact rapport to one another due to unavoidable manufacturing tolerances, it is relatively difficult to avoid that the first and / or second seam lines are essentially nonexistent Through openings cuts or cut. For this reason, it is proposed in a further development of the production method according to the invention that sensor means, in particular optical sensor means such as a camera, are used for the preparation in step c), the signal of the sensor means being used to align the first and / or second seam line to determine. For example, a digital camera can be used to send image data to a computer, which uses image recognition software to recognize the passage openings and determines one or more cutting lines, which later form the first or second seam line and which as few or essentially no passage openings as possible cuts or cut. The computer can then preferably control a cutting device in order to carry out the corresponding cut, for example by means of a laser. If more than one possible cutting line has been determined, it can be advantageous if these are shown to a user so that the user can decide which of the cutting lines should be selected.

Since relatively large through-openings are required for structuring the fibrous web, that is to say a relatively large amount of material has to be removed, it is proposed that the through-openings be made in step b) by means of punching. The drilling of the holes by means of a laser, for example, or the introduction of the through openings by means of an etching process is also possible, but is less preferred.

It can be advantageous if the preparation in step c) includes chamfering, in particular profile milling, of the first and second longitudinal ends of the plastic film, so that the first longitudinal end and the second longitudinal end touch a contact surface to form the seam in step d) , which is larger than an area which is defined by the width and thickness of the plastic film. For possible contact surfaces, reference is made to the disclosure already mentioned at the beginning EP 2 734 672 B1 referenced, which goes back to the applicant and whose content is hereby referred to.

An advantageous development of the method according to the invention provides that the seam is produced in step d) by integrally connecting the two prepared longitudinal ends of the plastic film to one another, preferably by welding, more preferably by laser welding, in particular laser transmission welding. Here, an absorber material can be applied to at least one of the longitudinal ends to be welded in order to support the formation of the integral connection.

Optionally, the two longitudinal ends can be aligned with one another before and / or during the creation of the seam by means of a positioning aid. For example, positioning pins can be used for this purpose, which at least partially penetrate through bores of both longitudinal ends of the plastic film, which are located one above the other in the seam area.

• 1 das Einbringen von Durchgangsöffnungen in eine Kunststofffolie mittels Stanzen;
• 2 einen Abschnitt der mit Durchgangsöffnungen versehenen Kunststofffolie;
• 3 die Kunststofffolie vor dem Zuschneiden;
• 4 die Kunststofffolie nach dem Zuschneiden;
• 5 einen Querschnitt durch die Kunststofffolie an ihren beiden zu verbindenden Längsenden, nachdem diese durch Fräsen für die Naht vorbereitet wurden;
• 6 eine schematische Darstellung, wie die Naht geschlossen wird bzw. ist;
• 7 die fertige Bespannung mit der Naht;
• 8 einen ersten möglichen Verlauf für eine Nahtlinie;
• 9 einen zweiten und dritten möglichen Verlauf für eine Nahtlinie;
• 10 eine Maschine bzw. Vorrichtung mit der erfindungsgemäßen Bespannung.

On the basis of exemplary embodiments, some advantageous features of the invention are explained in more detail below, reference being made to the drawings, which are not true to scale. The features mentioned can be implemented advantageously not only in the combination shown, but also individually combined with one another will. The figures, which are not to scale, show in detail:

• 1 the introduction of through openings in a plastic film by means of punching;
• 2 a portion of the plastic film provided with through openings;
• 3 the plastic film before cutting;
• 4th the plastic film after cutting;
• 5 a cross section through the plastic film at its two longitudinal ends to be connected after they have been prepared for the seam by milling;
• 6th a schematic representation of how the seam is closed or is;
• 7th the finished covering with the seam;
• 8th a first possible course for a seam line;
• 9 a second and third possible course for a seam line;
• 10 a machine or device with the covering according to the invention.

The figures are described in more detail below. 1 illustrates how in a plastic sheet 100 by means of a punching device SV a multitude of through openings 102 be introduced. As in 1 indicated, the plastic film 100 several, for example 3 or 4, separately extruded and then laminated together plastic layers. The individual plastic layers can, for example, have a thickness between 200 μm and 300 μm, preferably about 250 μm. The through openings 102 can, as in 2 shown, be designed in the form of straight circular cylinders, which are distributed evenly, namely, for example, checkerboard. However, other shapes and / or other arrangements or distributions of the through openings are possible 102 just as conceivable. The through openings 102 extend continuously from a top 104 the plastic film 100 , which in the intended use of the finished covering 200 the fibrous web transported on it FB facing to one of the top 104 opposite bottom 106 the plastic film 100 . The through openings 102 are preferably dimensioned such that the finished covering 200 is suitable, the fibrous web transported on it FB to contour. Good results could be achieved with diameters between 1mm and 5mm, for example with 1.3mm or 3.0mm.

Furthermore, tests have shown that the covering has a large open area 200 , such as an open area of about 40%, gives far less satisfactory results compared to a smaller open area, especially an open area of no more than 20%. Good results have been achieved with an open area of the order of 8% -11%. This means that the through openings 102 preferably only 8% -11% of the top 104 or the bottom 106 the plastic film 100 turn off.

On the fibrous web FB facing top 104 the closed surface can optionally be designed to be essentially smooth or slightly structured in order to create finer structures in the fibrous web FB memorize. Such structuring 108 can for example by etching in the top 104 to be engraved.

After the production and perforation of the plastic film 100 For example, these can be temporarily stored as roll goods before they are made into the finished covering 200 is further processed. Alternatively, however, it can also be processed further directly.

Around the perforated plastic film 100 to the finished covering 200 further processing is a first longitudinal end 110 the plastic film 100 and one to the first longitudinal end 110 opposite second longitudinal end 112 the plastic film 100 for the formation of a seam for making the plastic film endless 100 prepared. The preparation can include the step that the two longitudinal ends 110 , 112 are initially cut parallel to one another, the respective cut preferably being straight from a first side edge 114 the plastic film 100 to one of the first margin 114 opposite second margin 116 the plastic film 100 runs. The corresponding cutting lines SL are in 3 indicated, whereas 4th the pre-cut plastic film 100 shows. The respective cut can be produced, for example, by means of a laser. The two cutting lines run SL preferably not orthogonal to the first side edge 114 or the second margin 116 , but at an angle other than 90 °. This means that the later seam also runs along the finished covering 200 not parallel to the transverse direction QR the covering 200 but at an angle to it, as in 7th is shown. This has the advantage that stationary machine elements or sections of such machine elements, over or past which the clothing 200 in the intended use the same is performed, and which is in the transverse direction QR the covering 200 or extend the machine, do not come into contact with or act on the seam over its entire length at the same time. This allows the covering to run smoothly 200 achieved and a wear and tear on the covering 200 and / or the said machine elements are reduced.

After cutting the two side margins 114 , 116 these can still be reworked, in particular with the aim of enlarging a contact area for the formation of the seam, in particular a weld seam. For this purpose, it is particularly useful to use the cut side margins 114 , 116 to be reworked using a milling cutter. For example, the two side margins 114 , 116 in this way each be provided with a bevel in opposite directions, as shown in 5 is shown. The bevel preferably faces the top 104 or the bottom 106 the plastic film 100 an angle between 2 ° and 8 °, more preferably an angle of approximately 4 °. Alternatively, profile milling cutters with more complex geometry can of course also be used. Please refer to the one already mentioned at the beginning EP 2 734 672 B1 referenced, which goes back to the applicant and which discloses various profile shapes, which are hereby incorporated by reference.

The in 5 The illustrated embodiment are the chamfers or bevels on the two opposite longitudinal ends 110 , 112 the plastic film 100 brought into contact or overlap with each other and then welded together to form the finished covering 200 to train. The welding can also be carried out by means of a laser, a laser light-absorbing auxiliary medium, such as an auxiliary medium known under the brand name “ClearWeld”, preferably being applied to at least one of the two bevels or bevels prior to welding. Furthermore, the two longitudinal ends can be aligned with one another by means of a positioning aid before and / or during the welding. Positioning pins, for example, can be used as a positioning aid, which are completely or partially inserted into the through openings 102 of the overlapping longitudinal ends 110 , 112 are or are introduced.

The seam thus formed has a first seam line 118 on the top 104 the plastic film 100 and a second suture line 120 on the bottom 106 the plastic film 100 as shown schematically in 6th is shown. The first seam line lies through the bevel or slope 118 and the second seam line 120 in the direction of the thickness of the plastic film 100 not directly on top of each other, but are offset from one another. 7th shows the finished covering again in a view at an angle from above. Here is only the first seam line of the seam 108 on the top 104 to recognize.

According to the present invention, when preparing the first longitudinal end 110 the plastic film 100 and the first longitudinal end 110 opposite second longitudinal end 112 the plastic film 100 for the formation of the seam for making the plastic film endless 100 made sure that the first seam line 118 on the top 104 the plastic film 100 and / or a second seam line 120 on the bottom 108 the plastic film 100 essentially no through openings 102 cuts or cut. For this purpose, the cutting line can or can SL that is the first longitudinal end 110 the plastic film 100 is assigned, and / or the cutting line SL that the second longitudinal end 112 the plastic film 100 is assigned, preferably both cutting lines SL , are placed in such a way that there are essentially no through openings 102 cuts or cut. Then, for example, by milling, starting from the respective cutting line SL , a material area with a triangular cross-section can be removed in order to form the bevel or bevel at the respective longitudinal end (cf. 5 ). The one on the plastic film 100 the remaining tip corresponds to the respective cutting line SL . It should be noted at this point that the tip does not actually have to be completely pointed, but can also be flattened or rounded in practice, in particular for manufacturing reasons. However, such a flattening or rounding should preferably turn out to be very small, that is to say only in a thickness range of the plastic film 100 , which is a maximum of 1/10, preferably a maximum of 1/20 of the total thickness of the plastic film 100 corresponds to.

8th shows a section of the already perforated, but not yet cut to size, plastic film 100 with a pattern of evenly, namely checkerboard-like arranged through openings 102 . In this case the cutting line could be relatively simple SL orthogonal to the first page margin 114 be placed in such a way that these are none of the through openings 102 cuts. This is in 8th indicated by a corresponding line. However, for the reasons explained above, it is more advantageous for the cutting line not to be orthogonal to the first side edge 114 or the second margin 116 but with an angle other than 90 °. Two such possible courses of the cutting line SL are in 9 indicated.

As it is due to the large number of through holes 102 in the perforated plastic film 100 and taking into account certain manufacturing tolerances when perforating is not very easy, the exact position of the cutting lines SL in 9 To determine, it is proposed to use optical sensor means, such as a digital camera, which transfer their signal to a computer which preferably controls the cutting process, ie controls the laser, for example.

Finally, with reference to 10 Another exemplary device for producing a structured fibrous web, in particular a structured tissue paper web, is described, which uses the above-described covering according to the invention 200 includes.

The device 10 includes a forming section 12th for forming a fibrous web FB , one to the forming section 12th subsequent press section 14th for pressing the formed fibrous web FB and one to the press section 14th subsequent dryer section 16 for further drying of the pressed fibrous web FB . The fibrous web FB is in 10 shown as a dashed line.

To form the fibrous web FB First, a fiber suspension, which consists mainly of water and only has a small proportion of fibers, is passed through a headbox 18th in a gap between a first covering 20th and a second covering 22nd a so-called gap former. In this embodiment, the first covering 20th be a felt, i.e. a covering which has at least one layer of staple fibers, whereas the second covering 22nd can be a woven forming fabric. The first covering 20th , the second covering 22nd and the fibrous web disposed therebetween FB are together with a certain tension over a forming roll 24 out, which is preferably vacuumed in order to at least partially suck off the water pressed from the pulp suspension. After leaving the gap in the forming section 12th the formed fibrous web follows FB the first covering 20th to the press section 14th .

The press section 14th comprises a first pressing element 26th , which is preferably designed as a suction roll, and a second pressing element 28 , which, as in this embodiment, is preferably designed as a shoe press and thus a stationary shoe 30th and one around the shoe 30th rotating press jacket 32 having. The shoe 30th has a concave curved surface which is the convex surface of the first pressing member 26th or the suction roll 26th facing and adapted to this. The first pressing element 26th and the second pressing member 28 together form an extended press nip through which the first covering 20th , a third covering, which is the covering according to the invention 200 acts, and the fibrous web arranged therebetween FB be run together.

The suction roll 26th comprises an evacuated peripheral portion 36 , which is only indicated schematically here. In this embodiment, the evacuated peripheral portion 36 for example over about 90 ° of the circumference of the suction roll 26th extend. It ends either in front of or, as here, preferably within the extended press nip, that of the first press element 26th and the second pressing member 28 is trained. The first covering 20th , the third covering 200 and the fibrous web disposed therebetween FB are jointly over at least a large part, ie over at least 45 °, preferably over at least 60 °, of the evacuated circumferential section 36 guided. By the tension of the third covering 200 , which should be at least 10kN, experiences the fibrous web FB in addition to the suction through the suction roll 26th before reaching the press nip of the press section 14th an efficient pre-drainage. Thus, the dry content of the fibrous web is FB relatively high even before reaching the press nip. On the one hand, this has the consequence that the actual press, in particular the shoe press, can be designed to be simpler and therefore more cost-effective. On the other hand, the higher dry content of the fibrous web has an effect FB in front of the press nip also has a positive effect on the contouring of the fibrous web FB out. Because of the higher dry content, the material of the fibrous web has FB In particular in the more densely compressed areas in the press nip, a higher resistance force and thus a larger bulk at the end.

After leaving the press nip of the press section 14th the first covering separate 20th and the third covering 200 from each other, the fibrous web FB continue on the third covering 200 to be led. In order to reliably achieve this separation, it is advantageous if the evacuated peripheral section 36 the suction roll 26th ends before the end of the extended press nip. It is also advantageous if the around the shoe 30th rotating press jacket 32 one of the third covering 200 and the fibrous web FB Has facing surface which is essentially smooth, in particular free of grooves or the like, is formed. This allows through the third covering 200 therethrough, at least if the same is made permeable, a negative pressure on the fibrous web FB act, which the fibrous web FB on the third covering 200 holds.

The contouring and possibly finer structuring of the fibrous web FB through the third covering 200 takes place not only in the press nip between the first press element 26th and the second pressing member 28 , but to a lesser extent beforehand in the section of the evacuated circumferential section 36 the suction roll 26th over which the first covering 20th , the third covering 200 and the fibrous web disposed therebetween FB be guided about it together.

After leaving the press nip, the fibrous web follows FB the third covering 200 and is carried out with this via a deflection roller 46 which can be vacuumed to ensure a secure hold of the fibrous web FB on the third covering 200 to ensure when deflecting, to the dryer section 16 guided. The dryer section 16 includes a transfer device 48 , by means of which the fibrous web FB from the third covering 200 to the drying cylinder also mentioned above 50 is passed. From the drying cylinder 50 is in 10 only one section shown. It can be designed as a so-called Yankee cylinder and have a steam hood or Yankee hood, not shown here. After further drying of the fibrous web FB on the surface of the drying cylinder 50 can the fibrous web FB by means of a creping doctor from the surface of the drying cylinder 50 and then either further processed or refined or wound up directly.

The transfer device 48 preferably comprises just like the second pressing element 28 the press section 14th a fixed shoe 52 , which one to the drying cylinder 50 has facing and adapted to this concave surface, and one around the shoe 52 rotating press jacket 54 . In contrast to the rotating press jacket 32 of the second pressing element 28 shows the press jacket 54 the transfer device 48 does not have a substantially smooth surface, but preferably comprises a multiplicity of grooves or the like, in particular circumferential grooves, in order to pass over the through openings 102 the third covering 200 the fibrous web FB in a transfer gap between the transfer device 48 and drying cylinders 50 to ventilate, so that there is no suction between the third covering 200 and the fibrous web FB can arise and the fibrous web FB the smooth surface of the drying cylinder 50 after leaving the transfer gap reliably continues. This enables the reliable transfer of the fibrous web FB from the third covering 200 onto the surface of the drying cylinder 50 can be achieved without particularly large pressing forces on the fibrous web FB by means of the transfer device 48 having to exercise. As a result, not only can the transfer device be made technically simpler and thus more cost-effective, but the outer wall of the drying cylinder can also be 50 be made thinner, as this only has to withstand lower compressive forces. A thinner version of the wall of the drying cylinder 50 However, in addition to material and thus cost savings, it also means better heat transfer from the interior of the drying cylinder 50 through its wall into the fibrous web 50 . Thus, the device according to the invention 10 can be operated in a very energy-efficient and thus cost-efficient manner.

In comparison to this, such an energy-efficient operation is possible with one from the prior art, for example the US 8,414,741 B2 The usual device is not possible, since the third covering should be made smooth and preferably impermeable here. Because of the lack of the possibility of rear ventilation of the fibrous web in the transfer nip, the transfer of the fibrous web from the third clothing to the surface of the drying cylinder is extremely difficult in practice with this known device. This not only means that higher pressure forces and thus a more stable design of the drying cylinder are necessary in the transfer nip, but also larger quantities of chemicals have to be used with which the third covering is sprayed to make it easier to detach the fibrous web from it. In addition, there is the need to thoroughly clean the third clothing before it is passed through the press nip of the press section. The distance or the length of the third covering between the press nip of the dryer section and the transfer nip of the transfer device must also be relatively long so that the fibrous web has sufficient time to remove the moisture film that forms after the press nip between the fibrous web and the smooth and impermeable third covering to suck in again so that it does not prevent the fibrous web from detaching from the third covering through its suction effect. However, a large length of the third covering between the press nip and the transfer nip leads to higher costs. In addition, re-moistening of the fibrous web after the press nip is energetically counterproductive, since this water that has been absorbed again has to be removed from the fibrous web again by more power in the dryer section. These disadvantages from the prior art can be avoided or at least reduced with the device described here.

List of reference symbols

10

contraption

12th

Form ierpartie

14th

Press section

16

Dryer section

18th

Headbox

20th

first covering (forming fabric)

22nd

second covering (felt)

24

Forming roll

26th

first press element (suction roll)

28

second press element (shoe press)

30th

Shoe (fixed)

32

Press jacket (rotating)

36

evacuated peripheral portion (of the suction roll 26)

46

Deflection roller

48

Transfer device

50

Drying cylinder (Yankee cylinder)

52

Shoe (fixed)

54

Press jacket (rotating)

100

Plastic film

102

Through opening

104

Top

106

bottom

108

structuring

110

first longitudinal end

112

second longitudinal end

114

first margin

116

second margin

118

first seam line

120

second seam line

200

(third or finished) covering

FB

Fibrous web

SL

Cutting line

SV

Punching device

QR

Transverse direction

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2015/185278 A1 [0002]
• EP 2734672 B1 [0004, 0030, 0039]
• US 8414741 B2 [0054]

Claims (16)

Covering (200) for a device (10) for producing and / or processing a fibrous web (FB), comprising a plastic film (100), the top side (104) facing the fibrous web (FB) and an underside facing away from the fibrous web (FB) (106) and a plurality of through openings (102) which extend from the top (104) to the bottom (106), wherein the plastic film (100) furthermore has at least one seam which extends from a first side edge (114 ) the plastic film (100) extends to a second side edge (116) of the plastic film (100) opposite the first side edge (114) and by means of which a first longitudinal end (110) of the plastic film (100) with an opposite second longitudinal end (112) of the plastic film (100) for making the plastic film (100) endless, the seam having a first seam line (118) on the top (104) of the plastic film (100) and a second seam line (120) on the bottom rside (106) of the plastic film (100), characterized in that the first seam line (118) and / or the second seam line (120) is or are arranged such that they essentially do not intersect or intersect any through openings (102) . Covering (200) Claim 1 , characterized in that the first and / or second seam line (118, 120) runs in a straight line between the first side edge (114) of the plastic film (100) and the second side edge (116) of the plastic film (100). Covering (200) Claim 2 , characterized in that the first and second seam lines (118, 120) run parallel to one another, enclosing an angle that differs from 90 ° to the first and / or second side edge (114, 116). Covering (200) according to one of the preceding claims, characterized in that the covering (200) is designed to contour the fibrous web (FB). Covering (200) according to one of the preceding claims, characterized in that some or all of the through openings (102) have a clear opening of an area which corresponds to a circle with a diameter between 1 mm and 5 mm, some or all of the through openings (102) preferably essentially have the shape of a cylinder, more preferably the shape of a straight circular cylinder. Covering (200) according to one of the preceding claims, characterized in that the open area on the top (104) and / or the bottom (106) of the plastic film (100) is less than 20%, preferably between 5% and 15% . Covering (200) according to one of the preceding claims, characterized in that the plastic film (100) is an extruded plastic film (100) which has one or more layers. Covering (200) according to one of the preceding claims, characterized in that the closed surface on the top (104) and / or bottom (106) of the plastic film (100) is essentially smooth. Covering (200) according to one of the Claims 1 to 7th , characterized in that the closed surface is structured on the top (104) of the plastic film (100). Device (10) for producing a fibrous web (FB), in particular a tissue paper web, comprising: - a forming section (12) for forming the fibrous web (FB), the forming section (12) being a gap former with a headbox (18) and a first covering (20) and a second covering (22); - A press section (14) for pressing the formed fibrous web (FB), the press section (14) comprising a first pressing element (26) and a second pressing element (28) which together form a press nip through which, when the device is used as intended ( 10) the first covering (20), a third covering (200) and the fibrous web (FB) between them are guided; and - a drying section (16) for further drying the pressed fibrous web (FB), the drying section (16) comprising a drying cylinder (50) to which the fibrous web (200) transported on the third clothing (200) is transferred, for this purpose a transfer device (48) together with the drying cylinder (50) forms a transfer nip through which the fibrous web (FB) and the third covering (200) are guided when the device (10) is used as intended, characterized in that the third covering (200 ) is a covering (200) according to one of the preceding claims. Device (10) according to Claim 10 , characterized in that the first pressing element (26) is a suction roll with a suctioned peripheral section (36) over which the first covering (20) and the fibrous web (FB) transported on the first covering (20) are guided before reaching the press nip . Method for producing a covering (200) according to one of the Claims 1 to 9 , comprising the following steps: a) providing a plastic film (100) with a top side (104) and a bottom side (106) opposite the top side (104), and with a first side edge (114) and a first side edge (114) opposite second side edge (116); b) introducing a multiplicity of through openings (102) into the plastic film (100), which passages extend from the top (104) to the bottom (106) of the plastic film (100); c) preparing a first longitudinal end (110) of the plastic film (100) and a second longitudinal end (112) of the plastic film (100) opposite the first longitudinal end (110) for the formation of a seam for making the plastic film (100) endless; d) creating a seam in that the two prepared longitudinal ends (110, 112) of the plastic film (110) are connected to one another; characterized in that the preparation in step c) takes place in such a way that a first seam line (118) on the top (104) of the plastic film (100) and / or a second seam line (120) on the bottom (106) of the plastic film (100 ) essentially does not cut or cut any through openings (102). Procedure according to Claim 12 , characterized in that sensor means, in particular optical sensor means such as a camera, are used for the preparation in step c), the signal of the sensor means being used to determine the alignment of the first and / or second seam line (118, 120) . Procedure according to Claim 12 or 13th , characterized in that the introduction of the through openings (102) in step b) takes place by means of punching. Method according to one of the Claims 12 to 14th , characterized in that the preparation in step c) comprises milling the first and second longitudinal ends (110, 112) of the plastic film (100), so that the first longitudinal end (110) and the second to form the seam in step d) Touch the longitudinal end (112) with a contact surface which is larger than an area which is defined by the width and thickness of the plastic film (110). Method according to one of the Claims 12 to 15th , characterized in that the seam in step d) is produced by the two prepared longitudinal ends (110, 112) of the plastic film (100) being materially connected to one another, preferably by welding, more preferably by laser welding, with the two longitudinal ends (110 , 112) are aligned with one another by means of a positioning aid before and / or during the creation of the seam.

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