EP0013994A1 - Multi-ply endless drainage screen and method for making endless a multi-ply drainage screen - Google Patents

Abstract

A multiple-layer spliced drainage sieve belt for use in paper pulp drying, in which the ends of respective layers of sieve fabric are spliced together separately, the seams being staggered along the length of the belt. Various types of seams may be utilized, among them a woven seam which does not differ from the other portions of the sieve belt.

Description

The invention relates to a multilayer, endless drainage sieve according to the preamble of claim 1 and a method for making a multilayer drainage sieve endless according to the preamble of claim 9.

From DE-OS 2 455 184 multi-layer drainage screens, namely paper machine screens are known. These drainage screens should preferably be woven endlessly. However, they can also be woven flat and then made endless in a suitable manner. However, it is not disclosed how flat woven, multi-layer drainage screens can be made endless.

The problem of making endless does not arise with round-woven drainage screens. In the case of round-woven screens, however, there is the disadvantage that the screen length is predetermined and there are generally fewer possible variations with regard to the fabric number and the number of wefts, so that the dewatering performance can only be set to a limited extent. Endless weaving therefore requires a very large machine park in order to be able to meet customer specifications. Flat-woven paper machine screens, on the other hand, can be produced with a single weaving machine in any length. By varying the number of shots and the wire diameter, customer requirements can be better met. These advantages of flat weaving generally outweigh the disadvantages associated with making endless. There is therefore a need for multi-layer, endless ones Drainage screens and for a process for the continuous making of multilayer drainage screens.

In principle, a multi-layer drainage screen can be made endless in the same way as a single-layer drainage screen, for example by simply sewing it together with a sewing machine, by means of a fabric connection seam (DE-OS 2 700 390) or a pin seam. Basically, it is also possible to make a multilayer drainage screen endless with a woven seam, as is generally known for single-layer drainage screens. A device for making a single-layer drainage screen endless is described in DE-AS 1 710 205. When a multilayer sieve is made endless by a woven seam, the binding chain can even be woven in the area of the woven seam. In practice, however, it has been shown that such a multilayer woven seam can hardly ever be produced without defects.

DE-OS 2 429 162 discloses a method for making multilayer screens endless, in which several zones are provided in order to increase the flexibility of a seam, which is in principle a plug-in seam, in which the warp threads are freed from at least one weft position. The disadvantage of multi-layer screens made endless in this way is that the drainage performance in the seam area is significantly lower than in the rest of the screen.

DE-OS 2 707 705 discloses a method for making a multilayer fabric endless, in which free fabric flaps of different layers overlap and are made endless by sewing, stapling, gluing or a Velcro fastener. However, this type of connection does not guarantee sufficient freedom of marking.

The object of the invention is a multi-layer, endless drainage screen, in which the drainage performance in the seam area deviates as little as possible from the drainage performance of the rest of the screen, and in a method for making a multilayer, flat-woven drainage screen endless.

This object is achieved by the features characterized in claim 1 and the method steps characterized in claim 9.

Preferred embodiments of the invention are the subject of the dependent claims.

The individual layers are preferably stitched at offset locations, which results in a particularly uniform drainage.

At least one layer is preferably connected by a woven seam or made endless. Such sieves are particularly suitable for the production of paper, since the structure of the woven seam does not differ from that of the rest of the sieve, so that the seam does not form in the paper.

A particularly preferred embodiment of the invention consists in a multi-layer, in particular two-layer drainage screen, in which each layer is individually made endless by a woven seam.

• Fig. 1 das Herstellen einer Webnaht bei einem einlagigen Entwässerungssieb und
• Fig. 2 und 3 das Endlosmachen der ersten bzw. zweiten Lage eines zweilagigen Entwässerungssiebes.

Embodiments of the invention are explained below with reference to the drawing. Show it

• Fig. 1, the production of a woven seam in a single-layer drainage screen and
• 2 and 3, the making of the first and second layers of a two-layer dewatering screen endless.

The drainage screen according to the invention can be of any type of flat-woven drainage screen. It can have a plain weave, twill or satin weave or weave derived from it. The warp and weft threads can be made of any suitable material, e.g. Made of metal (phosphor bronze) or plastic (polyester, polyamide). Part of the warp and / or weft threads can consist of plastic and another part of metal. The drainage screen can also be coated.

The drainage sieve according to the invention consists of several layers which are connected to one another by a so-called binding chain. Each layer is a complete fabric in itself. The individual layers can differ in the type of weave, the size of the repeat and / or the material. The drainage screen contains at least two layers, but can also have three or more layers. In general, the top layer, namely the paper-bearing layer, consists of a fabric with a higher number of warp and weft threads per cm and of finer threads. The diameter of the warp threads of a certain layer can differ from the diameter of the weft threads of the same layer. The warp threads of a particular layer do not have to have the same diameter, for example they can be thicker in the edge area or thick and thin warp threads can alternate with one another. The same applies to the weft threads of a layer.

For the dewatering sieve according to the invention, any dewatering sieve that consists of several layers and is woven flat is therefore possible.

• 1. Endlosweben (Webnaht);
• 2. Übernähen der beiden Enden einer Lage mit einer Nä.h-maschine;
• 3. Stecknaht. Es sind verschiedene Ausführungsformen einer Stecknaht bekannt und zum Beispiel in den DE-OSen 24 29 162, 25 42 905 und 27 00 390 beschrieben.
• 4. Schweissen oder Kleben, wobei gegebenenfalls die Schweissnaht noch schlaufenweise übernäht werden kann.
• 5. Überlappung der beiden Enden ohne feste Verbindung der Enden.

Since a dewatering screen runs as an endless belt over two rollers, a flat-woven dewatering screen must be made endless. In the multi-layer drainage screen according to the invention, the individual layers are made endless separately. Any process that is suitable for making a single-layer dewatering screen endless can be used to make the individual layers endless. The individual layers can be made endless using the following methods:

• 1. Endless weaving (woven seam);
• 2. Sew over the two ends of a layer with a sewing machine;
• 3rd pin seam. Various embodiments of a plug seam are known and are described, for example, in DE-OSes 24 29 162, 25 42 905 and 27 00 390.
• 4. Welding or gluing, where appropriate the weld seam can still be sewn over in loops.
• 5. Overlap of the two ends without a fixed connection of the ends.

The connection points (seams) of the individual layers can lie one above the other. However, the connection points of the individual layers are preferably offset from one another in the longitudinal direction of the screen. This results in a particularly uniform drainage performance.

The seam can run perpendicular to the longitudinal direction of the screen. The ends of a layer are sewn with a Sewing machine, welding, gluing or similarly made endless or the ends of a layer overlap, the seam or connection can also run obliquely to the longitudinal direction of the screen.

To connect the two ends of a layer, it is generally necessary to remove the binding chain in a certain area, for example 10 or 20 cm wide, along the joint. After the individual layers have been sewn or joined, it is usually not necessary to retract the binding chain in these areas.

In the case of three-layer and multi-layer drainage screens, not all layers generally have to be stitched or firmly connected. Depending on the application, it may be sufficient if only two layers are sewn, for example the top and bottom layers. The top layer is preferably always sewn, since the paper pulp lies on it. The ends of the non-firmly bonded layers can overlap or butt each other. If the ends of the lowest layer, that is to say the layer which comes into contact with the rollers, are not firmly connected, the ends of this layer preferably overlap. The end of the lowermost layer pointing in the running direction is covered by the other end of the wire and therefore does not come into contact with the rollers. The two ends can be chosen to be of any length. However, the end pointing in the running direction is preferably cut off as short as possible and overlapped by the other end of the screen by a few centimeters or more.

Even with two-ply screens, it is possible to have only one ply to sew, generally this is the top layer as it carries the pulp. In order to avoid rapid wear of the lower layer, it is expedient that the two unconnected ends of the lower layer in turn overlap in such a way that the end of the lower layer pointing in the running direction between the upper layer and the opposite end End of the lower layer.

With certain types of seams, several layers can be made endless at the same time with one seam. For example, two layers can be made endless at the same time by sewing over with a sewing machine. Another example is the method described in DE-OS 24 29 162, with which several layers can be made endless by a seam. The invention also relates to multilayer, continuous drainage screens in which a corresponding number of groups of layers are made endless by at least two seams. Each group of layers is made endless by a single seam.

If a layer is made endless by a woven seam and the other or the other layers with another seam, for example a pin seam, it is advantageous to first carry out the non-woven seam and lastly the woven seam, since the width of a woven seam can be controlled more precisely. However, considerable difficulties arise in the manufacture of the woven seam in that the seam that has already been produced is used to produce the woven seam with special needs. If the seams are offset against each other, the production of the woven seam is hindered by the other fabric layers.

To explain the difficulties that arise when the weaving seam is carried out last, the manufacture of a weaving seam in a single-layer fabric will first be described with reference to FIG. 1. At the ends of the fabric 1, 2 to be connected, the warp threads are first exposed to about 10 cm by removing weft threads. The fabric ends prepared in this way are clamped on a tension table 3, the fabric ends, that is to say the weft threads 7, 8 remaining in the fabric, being exactly parallel at a certain distance of, for example, 8 cm. The distance is generally a whole Numerical multiple of the weave repeat and is equal to or less than the length of the fringe-like warp thread ends (here 10 cm). Almost all of the warp threads are now removed from a strip previously cut off from the fabric, the width of which corresponds exactly to the distance between the fabric ends (in the present case 8 cm). The warp threads are left at one end of the strip so that the weft threads hold together. The fringe-like protruding warp thread ends 9 of the two fabric ends 1, 2 and the weft threads 5 of the previously cut-off fabric strip, which have been freed of the warp threads, are now intertwined. For this purpose, a device can be used, as described in DE-AS 1 710 205. For this purpose, the exposed weft threads are drawn into heald frames, so that with the exposed weft threads a weaving shed can be formed, into which the warp thread ends projecting like fringes from the fabric ends are inserted. From the function of this device, the exposed weft threads are the warp and the fringe-like warp thread ends of the fabric are the weft.

A warp beam is not required in this device, since the warp threads left in the fabric strip hold the exposed weft threads together. The end of the fabric strip, in which the warp threads are left, is held in place by a suitable clamping device. The finished part of the woven seam takes over the function of the goods tree. The frayed warp thread ends 9 are entered and pricked by hand. The two opposite warp thread ends 9 are at a certain point, the so-called stitch place 10, inside the seam down or up or one end down and the other out and cut off. The points at which the warp thread ends are brought out are arranged in a certain pattern within the woven seam. This pattern is essential for the tensile strength of the woven seam. The basic idea is to achieve as large an overlap as possible of adjacent, opposite warp thread ends. The piercing points 10 of adjacent warp thread ends should accordingly be offset in the longitudinal direction of the sieve.

In the case of a two-layer screen, first, as shown in FIG. 2, the first layer 11 is woven endlessly, the ends of the second layer 12, which is located under the first layer, hanging down. The first layer can then be endlessly woven essentially as described for a single-layer sieve and in connection with FIG. 1.

After the endless weaving of the first layer 11, the sieve is turned for reasons of easier access, so that the second layer 12 comes to lie on top. This is shown in FIG. 3. The second layer 12 can no longer be woven endlessly in the same way as the first layer 11, since the weaving harness cannot be arranged between the fabric ends 13, 14 to be connected. This difficulty can be avoided by arranging the harness not next to the sieve plane, but instead placing it next to the sieve and lifting it out of the sieve plane so that it is on the side of the sieve that is opposite the first layer 11 that has already been sewn . The distance of the Weave harness from the sieve level must be at least large enough that the exposed weft wires 5, which form the compartment, lie in their deep position just in the sieve level or slightly above the sieve level. However, this path can only be followed for screen widths up to approximately 80 cm. With wider sieves, the harness cannot be placed next to the sieve. The weaving harness must then be arranged at a correspondingly greater distance from the sieve plane, so that the shaft frames do not touch the already sewn first layer 11 in their lowest position.

A corresponding procedure is followed in the event that the woven seams are offset from one another in the longitudinal direction of the sieve. If both layers are made endless by woven seams, the procedure for producing both woven seams must be as described above in connection with FIG. 3.

• 1. Obere Lage: Webnaht. Untere Lage: Stecknaht mit Fremdmaterial, das in das Gewebe eingeflochten ist. Dieses Fremdmaterial kann aus Metall,Polyester, Polyamid und dergleichen bestehen.
• 2. Obere Lage: Webnaht. Untere Lage: Mit Nähmaschine zusammengenäht.
• 3. Obere Lage: Webnaht. Untere Lage: Siebenden sind verschweisst und mit Nähdraht schlaufenweise übernäht.
• 4. (Besonders bevorzugte Ausführungsform) Obere Lage: Webnaht Untere Lage: Nicht genahtet, an der unteren Lage wird ein entgegen der Laufrichtung zeigendes längeres Siebstück am vorderen Teil der Naht belassen. Dieses Siebstück überdeckt das in Laufrichtung zeigende abgeschnittene Siebstück, das vom hinteren Nahtteil ausgeht. In den obigen Fällen 1 bis 4 verlaufen die Nähte jeweils in Schussrichtung und können die Nähte übereinander liegen oder in Längsrichtung versetzt sein.
• 5. Das Entwässerungssieb wird diagonal zerschnitten und die obere und die untere Lage werden für sich getrennt schlaufenweise vernäht. Die Nähte können übereinander liegen oder versetzt sein.
• 6. Obere Lage: Webnaht. Untere- Lage: Eingenä.hte Naht gemäss DE-OS 24 29 162 (Stecknaht in mehreren Zonen, in denen die Kettfäden von mindestens einer Schusslage befreit sind) oder gemäss DE-OS 27 00 390 (Bandnaht, ähnlich Spiralnähten mit Hohlsaumband) oder gemäss DE-OS 25 42 950 (zurückgewobene Stecknaht).
• 7. Eine Lage ist verklebt oder verschweisst, während die andere Lage durch eine Webnaht endlos gemacht ist.

The following seam combinations have proven particularly useful when making two-layer drainage screens endless:

• 1. Upper layer: woven seam. Bottom layer: push-in seam with foreign material that is woven into the fabric. This foreign material can consist of metal, polyester, polyamide and the like.
• 2. Upper layer: woven seam. Bottom layer: Sewn together with a sewing machine.
• 3. Upper layer: woven seam. Lower layer: the ends of the sieve are welded and sewn over with loops of sewing wire.
• 4. (Particularly preferred embodiment) Upper layer: Woven seam Lower layer: Not sewn, on the lower layer a longer sieve piece pointing in the opposite direction is left on the front part of the seam. This screen piece covers the cut screen piece pointing in the running direction, which starts from the rear seam part. In the cases 1 to 4 above, the seams run in the weft direction and the seams can lie one above the other or be offset in the longitudinal direction.
• 5. The drainage screen is cut diagonally and the upper and lower layers are sewn separately in loops. The seams can be on top of each other or offset.
• 6. Upper layer: woven seam. Lower layer: Sewn-in seam according to DE-OS 24 29 162 (plug-in seam in several zones in which the warp threads are freed from at least one weft layer) or according to DE-OS 27 00 390 (band seam, similar to spiral seams with hemstitch band) or according to DE-OS 25 42 950 (woven seam).
• 7. One layer is glued or welded, while the other layer is made endless by a woven seam.

With three and multi-layer drainage screens, there are similar combinations of different seam types. When choosing a specific seam for a layer, the material from which this layer is made may have to be taken into account. For example, not all are suitable Materials for welding and gluing. Layers made of polyamide can be welded, whereas this is not possible with polyester.

Example: 1

The endlessization of a two-ply sieve by two superimposed woven seams is described.

The upper layer has a four-strand cross twill weave, the warp threads have a diameter of 0.20 mm and the warp number is 28 / cm. The weft threads have a diameter of 0.24 mm and the number of wefts is 22 / cm.

The lower layer has a three-twill weave and consists of warp threads with a diameter of 0.35 mm and weft threads with a diameter of 0.40 mm. The warp number is 14 / cm and the weft number 11 / cm.

The binding chain is pulled in single binding and has a diameter of 0.17 mm. The binding chain number is 4.7 / cm.

A cross stripe of 15 cm warp length is cut off from one end of the sieve for a center piece to be used later. The number of shots on both ends of the screen and in the center piece must match exactly. The binding chain is cut out between the two sieve layers at a depth of 20 cm and removed so that no chain residue remains.

The lower layer of the sieve is now woven endlessly (weaving seam) so that the seam width is approx. 6 cm in the warp direction. For this purpose, the weft threads are removed in a 20 cm wide area from the two ends of the lower layer, so that warp thread fringes of 20 cm length are created. The sieve is then clamped on a seaming device, similar to that described in DE-AS 1 710 205. A strip is now selected from the middle section, which contains 65 weft wires and is connected to the repeat of the layer ends, in accordance with the seam width of 6 cm. These 65 weft wires are now drawn into the three-twill repeat of the seaming machine. By forming the weaving harness of the seaming machine, the first warp thread fringe of the two ply ends can now be braided into the open shed and the warp thread fringes are pricked at a location that is close to the first ply end, that is, they are led out. After advancing the weaving harness by one switching step, the second warp thread fringes are braided in and brought out at a piercing point which is relatively far away from the first layer end. The other warp thread fringes are woven in and pierced in a corresponding manner. After the weaving seam of the lower layer has been completed, the sieve is removed from the seaming device, turned so that the layer that has not yet been connected points upward, and clamped again.

The upper layer is now woven endlessly, as was explained in connection with the lower layer, that is to say in the ends of the layers to be connected Weft wires removed and the warp threads in the middle. The weft threads of the middle piece are now drawn in in the four-twine repeat, the number of threads drawn in now being 128 so that the woven seam of the upper layer has the same width as the woven seam of the lower layer.

Since the sieve was fixed before it was made endless and thus the offsets of the warp threads and weft threads are fixed, the warp thread fringes and the weft threads of the middle piece fit together as in the sieve, so that the weave repeat of the sieve continues within the seam. There is therefore no seam marking in the paper produced by means of the dewatering screen.

After the interlacing of the warp fringes and the weft threads, the warp thread fringes which are guided outside are cut off.

Claims (11)

1. Two- or multi-layer, endless drainage screen, in which the layers are connected by a binding chain, characterized in that at least two layers or two groups of layers are sewn separately. 2. Drainage sieve according to claim 1, characterized in that the seams of the individual layers or groups of layers are offset in the longitudinal direction of the sieve. 3. Drainage sieve according to claim 1 or 2, characterized in that at least one seam is a woven seam. 4. Drainage sieve according to claim 1, characterized in that all the layers are made endless by a woven seam. 5. Drainage sieve according to claim 3 or 4, characterized in that the warp thread ends are led out on the non-paper-bearing side in the woven seam of the paper-bearing layer. 6. Drainage sieve according to one of claims 1 to 3 or 5, characterized in that the ends of a layer or some layers butt butt and are not made endless, while the other layers are made endless. 7.Dewatering screen according to one of claims 1 to 3, 5 or 6, characterized in that the lowermost layer is not made endless and the end of the lowermost layer pointing in the running direction of the screen overlaps with the end of the lowermost layer pointing counter to the running direction of the screen and between them and the other layers is arranged. 8. Drainage sieve according to claim 7 with two layers, characterized in that the upper layer is made endless by a woven seam. 9. A method for making a two- or multi-layer drainage screen endless according to claim 1 to 8, characterized in that the one layer is made endless in a manner known per se and that the second layer or the further layers are made endless by a woven seam. 10.The method according to claim 9, wherein for producing the woven seam at both ends of the fabric, the warp threads are exposed by removing the weft threads to a certain length, the fabric ends are clamped exactly parallel at a certain distance and the exposed warp threads are interwoven with weft threads by using a A harness is formed from the weft threads from the weft threads, characterized in that the weft threads are led out of the part of the woven seam already formed from the sieve plane at such an angle that the deep weft threads lie in the sieve plane or above. 11. The method according to claim 10, characterized in that the angle at which the weft threads are led out of the sieve plane is so large that the weaving harness does not touch the already endless layer or, in the case of offset seams, the other sieve layers.

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