EP0580478A1 - Asymmetrical papermakers fabric and papermaking device using such a fabric - Google Patents

Abstract

The cloth consists of a single-layer fabric comprising weft yarns (7) interlaced with warp yarns (8) of flattened cross-section, forming floats (9) on the right (good) face (10) in contact with the paper sheet. The cloth is mounted alternately around drive and idle rolls, the wrong (back) face (12) of the cloth being in contact with the rolls of one type, and the sheet being in contact with the rolls of the other type. <IMAGE>

Description

The present invention relates to a paper manufacturing device comprising a canvas transporting the sheet moving on two series of rollers arranged alternately in contact with the sheet supported by the right side, then in contact with the reverse side of the canvas, the rollers of the 'one of the series being in contact with the sheet and the rollers of the other series being in contact with the back of the fabric, the rollers of one of the series being wholly or partly motor, the rollers of the other series being non-motor, the fabric comprising basic yarns arranged in a single layer in the direction perpendicular to the direction of movement of the canvas, called basic weft yarns and wires arranged in the direction of movement of the canvas called yarns chain.

The present invention relates in particular to the manufacture of paper in the dryer section where the rollers are all or partly heated.

When the sheet of paper passes accompanied by the canvas from rollers located on one side of the canvas to rollers located on the other side of the canvas, the sheet is in direct contact with the rollers on a series and only with the canvas on the other series.

When the rollers of one series are motor (in whole or in part) while the rollers of the other series are non-motor, extensions and compressions of the felt occur around the neutral line generally located in the middle some cobweb.

These extensions and compressions are transmitted to the sheet which risks being torn by overvoltage or relaxed.

This results in a limitation of the performance of the machine and an increase in production costs.

The device according to the invention making it possible to reduce these drawbacks is characterized in that uses a canvas whose warp threads are of flattened section and define floats on the right side of the canvas intended to come into contact with the sheet of paper and knees on the reverse side of the canvas.

The fabric used is not very thick since it comprises only a single layer of basic weft threads and the warp threads are of flattened section.

In addition, this fabric is asymmetrical so that the neutral line is very close to the right side in contact with the sheet of paper.

It follows that the right side of the canvas and therefore the sheet will undergo little extension and compression.

Preferably, the fabric consists of a single layer of base weft yarns in monofilaments of large diameter D (0.6 to 1 mm), which ensures good stability of the fabric.

The armours are for example satins, twills, derivatives of one or the other or combinations of satins, twills or satins and twills, the objective being to have the longest floats possible without degrade the stability of the fabric and have the desired air permeability.

As the warp threads are side by side, the air permeability is only due to lateral air leaks in the interstices created by the warp and weft threads.

The advantage of flat hair is to have a thinner fabric and moreover allows to have a low permeability.

Such a fabric with flat warp threads defining floats on the face of the fabric in contact with the sheet of paper is known in itself from document PCT-A-91/04374.

To obtain the even lower permeability necessary when the speed of the machines is high, or when the sheet is very fragile, these gaps are plugged with weft threads of smaller section than those of large diameter used for the structure of base by altering more or less the geometry of the interlacing of the flat warp threads with the basic weft threads. These threads, which can be monofilaments (single, twisted, cables), multifilaments (single, twisted), multi or monofilaments sheathed with thermoplastic polymers or threads of flattened section, are inserted during the weaving operation. These weft threads preferably have a round or three-lobed section to best fill the interstices.

Thus when using a single weft thread of round section, the diameter d of this section will be chosen equal to 0.20D ≦ d ≦ 0.4D.

To improve the asymmetry of the canvas, the warp threads are woven with the following cycle:
a primary interlacing constituted by the passage of the warp yarn below a basic weft yarn and one or more secondary interleaving constituted by the passage of the warp yarn below a small weft yarn, said primary interlacing and secondary being separated by floats formed by the passage of the warp yarn over several basic weft yarns and the small weft yarn (s) included between these basic weft yarns.

The contact between the fabric and the sheet is also improved because the area occupied by the warp threads on the face of the sheet is even greater.

It is possible for certain applications to have several groups of warp threads woven differently.

A first group of warp threads are woven with the following pattern:

Passage below a basic weft yarn followed by passage above several basic weft yarns and the small weft yarn (s) included between said basic weft yarns.

A second group of warp threads are woven with the following pattern:
- secondary interlacing constituted by the passage below a small weft yarn followed by the passage above several basic weft yarns and small weft yarns comprised between said basic weft yarns.

A third group of warp threads are woven with the following pattern:

A primary interlacing constituted by the passage of the warp yarn below a basic weft yarn and one or more secondary interlacing constituted by the passage of the warp yarn below a small weft yarn, said primary and secondary interlacing being separated by floats formed by the passage of the warp yarn over several basic weft yarns and of the small weft yarn (s) included between these basic weft yarns. The floats framing the primary interlacing can also pass over the small weft threads framing the basic weft yarn of the primary interlacing.

These fabrics can include the three groups of threads or a combination of only two groups.

When using warp threads without primary interlacing (second group) this allows a good contact surface and a high asymmetry of the fabric.

To further increase the asymmetry of the canvas and its qualities of contact with the paper sheet, the small weft threads disposed between the basic weft threads are replaced by flat weft threads which are arranged above the weft threads. based.

The invention will now be described in more detail, with reference to particular embodiments cited by way of nonlimiting example and represented by appended tops.

Figure 1 shows the device according to the invention.

Figure 2 shows a known canvas.

FIG. 3 represents a detail of FIG. 2.

FIG. 4 represents a side view of a fabric according to the invention.

FIG. 5 represents the assembly of a warp thread of the fabric of FIG. 4.

Figure 6 shows another canvas according to the invention.

FIG. 7 represents the assembly of a warp thread in the fabric of FIG. 6.

FIG. 8 represents a side view of the fabric of FIG. 6.

FIG. 9 represents a variant of FIG. 7.

FIG. 10 represents a different weaving of a warp thread.

FIG. 11 represents another variant of the fabric using weaving of warp threads according to FIG. 10.

FIG. 12 represents a variant of FIGS. 7 and 9.

FIG. 13 represents another variant of FIG. 5.

FIG. 14 represents another variant of FIG. 9.

FIG. 15 represents another variant of FIG. 10.

The paper manufacturing device according to the invention (see FIG. 1) comprises two series 1, 2 of rollers.

The rollers 3 of the first series 1 are motor and the rollers 4 of the second series 2 are non-motor. A fabric 5 carrying on its right side a sheet of paper 6 is wound alternately around the rollers 3, 4 of the two series 1, 2. The sheet 6 is in contact direct with the rollers 3 of the first series 1 and the reverse side of the fabric 5 is in contact with the rollers 4 of the second series 2.

The fabric 5 (see FIG. 2) consists of basic yarns 7 arranged in a single layer in the direction perpendicular to the direction of the machine, called basic weft yarns and of yarns 8 arranged in the direction of the machine, called basic yarns. chain.

The basic weft yarns 7 are synthetic monofilaments of large diameter D (0.6 to 1 mm). The warp threads 8 are synthetic monofilaments of flattened section, for example oval and preferably rectangular.

The ratio between the width l of the wires 8 and their thickness is preferably greater than 3.

The warp threads 8 are juxtaposed so that if there are n warp threads per meter of width, we have n x l = 1 m.

The warp threads 8 pass over three basic weft threads 7, then below a single basic weft thread 7 and so on.

The warp threads 8 thus define floats 9 on the face side 10 of the fabric 5 and knees 11 on the reverse face 12 of the fabric.

The floats 9 are more or less long depending on whether the wires 8 pass over three, four etc ... weft wires. The longer the floats 9, the more asymmetrical the fabric 5. Their length is limited by the stability of the fabric 5.

The floats 9 for each warp yarn 8 are offset to form satins, twills or a combination of the two.

The contact between the sheet 6 and the right side 10 of the fabric 5 is very good since the warp threads 8 are flat and there is a lot of float 9.

In addition, since the warp threads 8 are side by side, there is a low permeability.

The residual permeability is due to lateral air leaks in the interstices 13 created in the vicinity of the face side 10 between the warp threads 8 and the basic weft threads 7 (see FIG. 3).

To reduce this permeability, these interstices 13 are plugged (see FIGS. 4 and 5) using small weft threads 14.

These wires 14 have a cross section smaller than the cross section of the basic weft wires 7, their diameter d is between 0.2 and 0.4D.

These threads 14 can be monofilaments or multifilaments. The pattern of the warp threads 8 is unchanged, they pass below a basic weft thread 7 and then above three basic weft threads 7, as well as two small weft threads 14 located between said three threads. base frame 7.

In FIGS. 6 to 8 a canvas is shown, the asymmetrical nature of which is greater.

The warp threads 8 are mounted with the following pattern:
a primary interlacing 15 constituted by the passage of the warp yarn 8 below a basic weft yarn 14 and one or more secondary interlacing constituted 16 by the passage of the warp yarn 8 below a small weft yarn 14, said primary and secondary interleaving being separated by floats 9, formed by the passage of the warp thread 8 above several basic weft threads 7 and of the small threads 14 included between these basic weft threads 7.

The patterns are shifted from warp to warp to form, for example, a satin or twill or a combination of the two.

The face side 10 which includes the floats 9 ensures very good contact with the sheet.

This contact is better than that of the fabric of FIG. 2 because the hollows (a) of the secondary interleaving 16 are less important than the hollows (b) due to the primary interlacing, 15.

It also follows a more accentuated asymmetry between the floats 9 of the face 10 and the knees 11 of the reverse 12.

According to a variant shown in FIG. 9, the weaving cycle of the warp threads 8 comprises a primary interlacing 15 and two secondary interlacing 16.

Obviously, a group of warp threads can be woven as in FIG. 5 and another group as in FIGS. 7 or 9.

FIG. 10 shows a weaving of warp threads in which there are only secondary interlacing 16 followed by floats 9.

The fabric of FIG. 11 has a group of warp yarns woven as in FIG. 10 and a group of warp yarns woven as in FIG. 5.

The warp threads 8 of the two groups are alternated. Such a canvas is very asymmetrical and has excellent contact with the sheet.

One could obviously replace the group of woven threads according to FIG. 5 with a group of woven threads according to FIG. 7 or 9.

We could also have three groups of warp threads, a group woven according to FIG. 5, a group woven according to FIG. 7 or 9 and a group woven according to FIG. 10.

FIG. 12 shows a variant of FIGS. 7 and 9.

The flat warp threads 8 define floats 9 on either side of a primary interlacing 15 which also pass over the small weft threads 14 framing the basic weft thread 7 of the primary interlacing 15.

The asymmetry of the canvas is thus improved as well as its surface condition.

It is therefore possible to replace the groups of warp yarns woven according to FIGS. 7 or 9 by groups of warp yarns woven according to FIG. 12.

Figures 13, 14 and 15 are variants of Figures 5, 9 and 10 in which the small weft son 14 have been replaced by flat weft son 14 '.

Each flat weft son 14 surmounts a base weft thread 7 and has a width 1 substantially equal to the diameter D of the base weft son. The height h of the flat wires is for example between 0.2 and 0.4 l.

In FIG. 13 the warp thread 8 passes below a basic weft thread 7 and the flat weft thread 14 'associated with the basic weft thread 7 and then above three basic weft threads 7 and associated flat weft threads 14 '. The warp threads define floats on the right side 10 and knees 11 on the reverse side 12.

In FIG. 14, the warp thread passes under a basic weft thread 7 and the associated flat weft thread 14 ', which defines a primary interlacing 15'. Then the warp thread 8 passes over three basic weft threads 7 with their associated flat weft threads 14 ′, then the warp thread passes below the flat weft thread 14 ′ and above the associated base frame 7 defining a secondary interlacing 16 ′.

The warp thread 8 passes over three basic weft threads with their associated flat threads and then below a flat weft thread defining a second secondary interlacing 16 '.

Then the thread passes over three basic weft threads with their associated flat weft threads 14 'before starting the cycle again with a primary interlacing 15'.

The number of secondary interlaces can obviously be equal to 1 in this case there are two floats 9 for a knee 11.

In FIG. 15 the warp thread 8 only forms secondary interlaces 16 ′.

You can weave a canvas using only the weaving in Figure 13 or only the weaving in Figure 14. You can also use a group of woven warp threads as in Figure 13, a group of woven yarns as in Figure 13. FIG. 14 and a group of warp threads woven as in FIG. 15 or only two groups taken from these three.

The use of flat weft threads 14 'increases the asymmetry of the fabric and improves the surface condition.

Claims (24)

1) Device for manufacturing paper comprising a canvas (5) transporting the sheet (6) moving over two series (1, 2) of rollers (3, 4) arranged alternately in contact with the sheet (6) supported by the right side (10), then in contact with the reverse side (12) of the fabric (5), the rollers of one of the series being in contact with the sheet and the rollers of the other series being in contact with the reverse (12) of the fabric (5), the rollers of one of the series being wholly or for the most part motor, the rollers of the other series being non-motor, the fabric (5) comprising basic wires arranged in a single layer in the direction perpendicular to the direction of movement of the fabric, called basic weft yarns (7) and yarns arranged in the direction of movement of the fabric, called warp yarns (8),
characterized in that the warp threads (8) are of flattened section and define floats (9) on the right side (10) of the fabric and knees (11) on the reverse side (12) of the fabric. 2) Device according to claim 1, characterized in that the interstices (13) between the basic weft threads (7) and the warp threads (8) in the vicinity of the face face (10) are blocked by small wires weft (14) of smaller section than that of the base weft yarns (7). 3) Device according to one of claims 1 or 2, characterized in that the warp threads (8) are woven with the following pattern: passage below a basic weft thread (7) followed by passage to above several basic weft threads (7). 4) Device according to claim 2, characterized in that the warp threads (8) are woven with the following pattern:
- passage below a basic weft yarn (7) followed by passage above several basic weft yarns (7) and the weft yarn (s) (14) included between said basic weft yarns ( 7). 5) Device according to claim 4, characterized in that the warp threads (8) also pass over the small weft threads (14) adjacent to the basic weft threads (7) below which these warp threads (8) pass. 6) Device according to claim 2, characterized in that the warp threads are woven with the following cycle:
- a primary interlacing (15) formed by the passage of the warp thread (8) below a base weft thread (7) and one or more secondary interlacing (16) constituted by the passage of the warp thread ( 8) below a small weft thread (14), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of the warp thread (8) over several threads of base weft (7) and of the small thread (s) (14) included between these base weft threads (7). 7) Device according to claim 6, characterized in that the floats (9) framing the primary interlacing (15) also pass over the small weft threads (14) framing the weft threads (7) of said primary interlacing (15 ). 8) Device according to claim 1, characterized in that the basic weft son (7) are surmounted by flat weft son (14 ') of width substantially equal to the diameter of the base weft son (7). 9) Canvas for the manufacture of paper comprising basic threads arranged in a single layer in the direction perpendicular to the direction of movement of the machine, called basic weft threads (7) and threads of flattened section arranged in the direction of movement of the machine, called warp threads (8), which define floats (9) on the right side (10) of the canvas intended to come into contact with the sheet of paper (6), at least some of these threads chain defining knees (11) on the reverse side (12).
characterized in that the gaps (13) between the basic weft threads (7) and the warp threads (8) in the vicinity of the face side (10) are blocked by small weft threads (14) of smaller section than that of the basic weft threads (7). 10) Canvas according to claim 9, characterized in that the warp threads (8) are woven with the following pattern: passage below a basic weft thread (7) followed by the passage over several son of base frame (7). 11) Canvas according to claim 9, characterized in that the warp threads (8) are woven with the following cycle:
- a primary interlacing (15) formed by the passage of the warp thread (8) below a base weft thread (7) and one or more secondary interlacing (16) constituted by the passage of the warp thread ( 8) below a small weft thread (14), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of the warp thread (8) over several threads of base weft (7) and of the small thread (s) (14) included between these base weft threads (7). 12) Canvas according to claim 9, characterized in that a first group of warp threads (8) are woven with the following pattern. - passage below a basic weft yarn (7) followed by passage above several basic weft yarns (7) and the small weft yarn (s) (14) included between said basic weft yarns (7), - and that a second group of warp threads (8) are woven with the following cycle: - a primary interlacing (15) formed by the passage of the warp thread (8) below a base weft thread (7) and one or more secondary interlacing (16) constituted by the passage of the warp thread ( 8) below a small weft thread (14), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of the warp thread (8) over several threads base frame (7) and or small basic weft threads (14) included between these basic weft threads (7),
the warp threads (8) of the two groups being regularly distributed with respect to each other. 13) Canvas according to claim 9, characterized in that a first group of warp threads (8) are woven with the following pattern: - passage below a basic weft yarn (7) followed by passage above several basic weft yarns (7) and the small weft yarn (s) (14) included between said basic weft yarns (7),
a second group of warp threads (8) are woven with the following pattern. - secondary interlacing (16) consisting of the passage below a small weft yarn (14) followed by the passage above several basic weft yarns (7) and small weft yarns (14) included between said basic weft yarns, the warp yarns (8) of the two groups being regularly distributed with respect to each other. 14) Canvas according to claim 9, characterized in that a first group of warp threads (6) are woven with the following cycle:
- a primary interlacing (15) formed by the passage of the warp thread (8) below a base weft thread (14) and one or more secondary interlacing (16) constituted by the passage of the warp thread ( 8) below a small weft thread (14), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of the warp thread (8) over several threads of base weft (7), and of the small thread (s) (14) included between these base weft threads (7). 15) Canvas according to claim 9, characterized in that a first group of warp threads (8) are woven with the following pattern: - passage below a basic weft yarn (7) followed by passage above several basic weft yarns (7) and the small weft yarn (s) (14) included between said basic weft yarns (7), - a second group of warp threads (8) are woven with the following pattern: - secondary interlacing (16) consisting of the passage below a small weft yarn (14) followed by the passage above several basic weft yarns (7) and small weft yarns (14) included between said basic weft yarns and a third group of warp yarns (8) are woven with the following cycle: - a primary interlacing (15) formed by the passage of the warp thread (8) below a base weft thread (14), and one or more secondary interleaving (16) constituted by the passage of the warp thread (8) below a small weft thread (14), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of the warp thread (8) over several basic weft yarns (7) and of the small yarn (s) (14) included between these weft and basic yarns (7),
the warp threads (8) of the three groups being regularly distributed with respect to each other. 16) Canvas according to one of claims 11, 12, 14 or 15 characterized in that the floats (9) framing the primary interlacing (15) also pass over the small weft threads (14) framing the weft threads (7) of said primary interleaving (15). 17) Canvas for the manufacture of paper comprising basic threads arranged in a single layer in the direction perpendicular to the direction of movement of the machine, called basic weft threads (7) and flat threads arranged in the direction of displacement of the machine, called warp threads (8), which define floats (9) on the right side (10) of the fabric intended to come into contact with the sheet of paper (6), at least some of these warp threads defining knees (11) on the reverse side (12), characterized in that the basic weft threads (7) are surmounted by flat weft threads (14 ') of width substantially equal to the diameter of the basic weft threads (7). 18) Canvas according to claim 17, characterized in that the warp threads (8) are woven with the following pattern; passage below a basic weft yarn (7) and the associated flat weft yarn (14 '), followed by passage over several basic weft yarns (7) and their flat weft yarns associates (14 '). 19) Canvas according to claim 17, characterized in that the warp threads (8) are woven with the following cycle:
- a primary interlacing (15 ') formed by the passage of the warp thread (8) below a base weft thread (7) and one or more secondary interlacing (16') constituted by the passage of the warp (8) below a flat weft thread (14), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of warp thread (8) above several basic weft yarns (7) and flat weft yarns (14 ') associated with these basic weft yarns (7). 20) Canvas according to claim 17, characterized in that a first group of warp threads (8) are woven with the following pattern. - passage below a basic weft yarn (7) followed by the passage above several basic weft yarns (7) and associated flat weft yarns (14 ') - and that a second group of warp threads (8) are woven with the following cycle: - a primary interlacing (15) formed by the passage of the warp thread (8) below a base weft thread (7) and one or more secondary interlacing (16) constituted by the passage of the warp thread ( 8) below a flat weft thread (14 '), said interlacing primary and secondary (15, 16) being separated by floats (9) formed by the passage of the warp thread (8) over several basic weft threads (7) and associated flat weft threads (14 ') with these basic weft yarns (7),
the warp threads (8) of the two groups being regularly distributed with respect to each other. 21) Canvas according to claim 17, characterized in that a first group of warp threads (8) are woven with the following pattern: - passage below a basic weft yarn (7) followed by passage above several basic weft yarns (7) and flat weft yarns (14) associated with said basic weft yarns (7) ,
a second group of warp threads (8) are woven with the following pattern. - secondary interlacing (16 ') consisting of the passage below a flat weft thread (14') followed by the passage above several basic weft threads (7) and associated flat weft threads (14) to said base weft threads, the warp threads (8) of the two groups being regularly distributed with respect to each other. 22) Canvas according to claim 17, characterized in that a first group of warp threads (6) are woven with the following cycle:
- a primary interlacing (15 ') formed by the passage of the warp thread (8) below a base weft thread (14) and one or more secondary interlacing (16') constituted by the passage of the warp (8) below a flat weft thread (14 '), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of warp thread (8) above of several basic weft threads (7), and flat weft threads (14 ') associated with these basic weft threads (7). 23) Canvas according to claim 17, characterized in that a first group of warp threads (8) are woven with the following pattern: - passage below a basic weft yarn (7) followed by the passage above several basic weft yarns (7) and flat weft yarns (14 ') associated with said basic weft yarns (7 ). - A second group of warp threads (8) are woven with the following pattern: - secondary interlacing (16 ') consisting of the passage below a flat weft yarn (14') followed by the passage above several basic weft yarns (7) and flat weft yarns (14 ') associated with said basic weft threads (7) and a third group of warp threads (8) are woven with the following cycle: - a primary interlacing (15 ') formed by the passage of the warp thread (8) below a base weft thread (14), and one or more secondary interlacing (16') constituted by the passage of the thread warp (8) below a flat weft thread (14 '), said primary and secondary interlacing (15, 16) being separated by floats (9) formed by the passage of warp thread (8) to the above several basic weft threads (7) and flat weft threads (14 ') associated with said basic weft threads (7),
the warp threads (8) of the three groups being regularly distributed with respect to each other. 24) Canvas according to one of claims 11 to 16, characterized in that the warp threads (8) also pass over the small weft threads (14) adjacent to the base weft threads (7) below from which said warp threads (8) pass.

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