WOVEN STRUCTURED FABRIC

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit, under 35 U.S.C. § 119(e), of provisional patent application No. 63/695,451, filed September 17, 2024, this application also claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 102024130 209.7, filed October 17, 2024; the prior applications is herewith incorporated by reference in its entirety.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a woven fabric for use in a machine to produce a fiber web, preferably a tissue web. The woven fabric has a machine direction and a transverse direction, as well as a paper side and a machine side, wherein the paper side is formed of warp and weft yarns, wherein the warp and weft yarns are interwoven with one another in a weave pattern. The paper side has a plurality of twill lines, wherein each twill line is formed by a plurality of adjacent warp yarn floats.

Such woven fabrics are known, e.g., from applicant’s application U.S. patent publication 2023/0011606 A1, which is referenced herein.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a novel woven structure for such a woven fabric in order to improve the softness and hand feel of tissue papers produced on TAD machines, for example, using such a woven fabric.

The object is achieved by a woven fabric according to the independent claim.

Proposed is a woven fabric for use in a machine to produce a fiber web, preferably a tissue web. The woven fabric has a machine direction and a transverse direction, as well as a paper side and a machine side. The paper side is formed of warp yarns and weft yarns, which are interwoven with one another in a weave pattern, and the paper side has a plurality of twill lines. Each twill line is formed by a plurality of adjacent warp yarn floats. The invention is characterized in that the twill lines are completely or substantially formed by warp yarns floating across seven successive weft yarns and adjacent warp yarn floats overlapping over a length of four weft yarns.

In advantageous embodiments, it may be provided for the warp yarns to float across seven successive weft yarns and each two adjacent warp yarn floats overlapping over the length of four weft yarns, thereby forming straight, parallel twill lines. (First embodiment; see below).

In similarly advantageous alternative embodiments, it may be provided for the twill lines to be formed only across a certain interval length of weft yarns by warp yarns floating across seven successive weft yarns and each two adjacent warp yarn floats overlapping over a length of four of the weft yarns, while turning points are provided at the interval ends, at which this pattern is interrupted. (Second embodiment; see below).

In this respect, it may be particularly advantageous for the interval length between the turning points to be more than 15 weft yarns, in particular more than 20 weft yarns.

As such, it may be provided for the twill lines to follow a zigzag or wave shape.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a woven structured fabric, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an illustration showing a woven fabric from the prior art;

FIGS. 2 and 3 are illustrations each showing the woven fabric according to aspects of a first embodiment of the invention; and

FIG. 4 an illustration showing the woven fabric according to aspects of a second embodiment of the invention.

All figures are oriented so that warp direction K extends from vertically above, and weft direction S extends horizontally.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be explained in more detail below by way of the figures.

First embodiment

The warp yarns float across seven successive weft yarns.

Adjacent warp yarns “overlap” with weft yarns.

The term “overlap” means that a warp yarn W1 and its left neighbor, warp W2, float across a length of the same four weft yarns I, II, III and IV, while warp W1 passes below weft V and warp W2 passes below weft X.

In other words: the weave pattern of adjacent warp yarns is offset by three weft yarns.

If a warp passes over wefts I-VII, the first neighbor passes over wefts IV-X and the second neighbor passes over wefts VII to XIII.

Woven fabrics according to this first embodiment have a diagonal pattern of twill lines. As shown in FIG. 2, these may extend from the lower left to the upper right or, as shown in Fg.3, extend from the lower right to the upper left.

These twill lines structure the woven fabric, in a voluminous manner in the grooves and in a compacted manner at the floats or beads. The main property of the woven fabric is that, during the creping process, the continuous warp of warp nodes results in a soft, smooth web.

Second embodiment

FIG. 4 shows a woven fabric according to a second embodiment of the invention by way of example. As such, the second embodiment may be seen as a variation of the first embodiment. While the first embodiment generates diagonal twill lines extending from the lower left to the upper right (FIG. 2) or from the lower right to the upper left (FIG. 3), the second embodiment is somewhat of a combination of the two.

For a certain number of wefts, the warp pattern corresponds to the example of FIG. 2, wherein the twill lines extend from the lower left to the upper right.

At a turning point T1, the pattern changes to the warp pattern from the example of FIG. 3 in which the twill lines extend from the lower right to the upper left.

At a further turning point T2, the pattern switches back to the example of FIG. 2. As a result, a wave or zigzag pattern of the twill lines is achieved.

The second embodiment is substantially also produced by the design principle of the first embodiment.

The warp yarns float across seven successive weft yarns.

Adjacent warp yarns “overlap” over a length of four weft yarns.

However, to achieve the change of direction, this principle needs to be modified at turning points T1, T2. Here, waft W3 only floats across three wefts, while warp W4 floats across nine wefts (see FIG. 4).

The wave pattern of the second embodiment has the same effect as the diagonal pattern of the first embodiment. The woven fabric is structured, in a voluminous manner in the grooves and in a compacted manner at the floats or beads. The main property of the woven fabric is that, during the creping process, the continuous warp of warp nodes result in a soft, smooth sheet.

The design can be adapted easily by changing the number of wefts between turning points T1, T2.

Usually, it is advantageous to have these turning points T1, T2 at regular intervals. In the example of FIG. 4, there is a turning point T1, T2 every 17 wefts. This number may vary. The intervals should not be much shorter, but it might still be possible to have a turning point every 15 wefts. In many applications, longer intervals may also be chosen. A turning point T1, T2 every 20 wefts, every 25 wefts or even every 30 wefts may be advantageous.

While a regular interval of the turning points is usually preferred, it should be noted that the invention is not limited thereto. It is also possible to have changing intervals. For example, the interval between turning point T1 and turning point T2 may be 15 wefts, while the interval between turning point T2 and a subsequent turning point T3 may be 20 wefts. A person skilled in the art will appreciate that many other combinations are possible.

Although the woven fabrics according to the aspects of the present invention may basically be used in any machine to produce tissue paper, they are preferably employed in a so-called through-air drying (TAD) machine. These machines are used to produce high-quality tissue paper. The quality of the tissue paper is mainly determined by the volume, softness and hand feel of the tissue paper.

The former for TAD tissue usually requires a more sophisticated technology than a wet-pressed tissue machine. The former configuration is usually a twin-wire former with a fixed forming roller. The forming wires are important for TAD products. The web is formed with an initial consistency of about 0.1% of solids (1000 kg of water for each single kg of fiber). The rest of the machine then dries the web to the desired final dryness, wherein the final moisture is generally 5% or less depending on the product.

The web is then transferred to a TAD fabric (=TAD wire), wherein a vacuum box or vacuum roller is used for transfer of the web. It is known that the design of the TAD fabric can heavily influence the properties of the product to be produced.

The TAD wire guides the web across one or more through-air driers to the smoothing cylinder. While transferring the sheet to the TAD fabric, the vacuum box or the roller may be used to form the sheet into the TAD fabric. As described above, the woven fabrics according to the invention provide a considerably advantage in terms of the softness and hand feel of the tissue. The three-dimensional character is chosen such that the proportion of sheet deformation on the TAD fabric is maximized. This increases the apparent volume of the web.

The TAD system must be large and very efficient to dry the web moving at a speed of up to 1,500 m per minute. As the retention time of a typical 16-feet TAD cylinder is less than a second, extremely high drying rates are required, and the TAD system must be designed for such high drying rates.

The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention:

S Weft direction

K Warp direction

W1, W2 Warp yarns

W3, W4 Warp yarns

I, II, II, IV, V Weft yarns

X Weft yarn

T1 Turning point

T2 Turning point