FI77493B - TORKFILT ELLER -VIRA. - Google Patents

Description

1 77493

Drying felt or wire - Torkfilt eller

The invention relates to a wire for use as a drying felt for a paper machine according to the preamble of claim 1.

In the above-mentioned technical field, there are numerous descriptions of drying felts and drying felt fabrics. Despite the large amount of usable material, an ideal drying wire has not yet been obtained.

In recent years, dry wires have been developed which are wholly or partly constructed of monofilament yarns. However, such wires are not satisfactory when used as drying felts. Monofilament yarns are susceptible to wear and moisture thermal hydrolysis. In known constructions, load-bearing monofilament yarns can deteriorate very rapidly in the machine direction under certain operating conditions, so that the service life of the drying felt is reduced.

It is an object of the present invention to improve hitherto known wires.

According to the present invention, the above-mentioned object is solved as described in the characterizing part of claim 1.

In the fabrics of the present invention, when used as drying blankets, the paper web to be dried is supported transversely to the machine direction. The machine direction monofilament yarns are thus protected from direct contact with the lateral element. The total age of the drying felt is considerably increased compared to blankets in which the machine direction monofilament yarns are in contact with the paper web to be dried.

2 77493

The present invention will be described in more detail below with reference to the accompanying drawings, in which:

Figure 1 shows a cross-section of a part of a preferred embodiment of a wire according to the present invention.

Figure 2 shows a schematic side view of a part of the drying section of a paper machine.

Figure 1 shows, on a large scale, a side view of a part of a wire 10 according to the invention. to a plane forming the outer surface of the wire 10. Preferably at least 50%, preferably all or substantially all of the protrusions 16 are located in the same plane. The deposits 18 are located on a separate plane inside the plane provided with the protrusions 16.

The second tortuous layer 20 of monofilament yarns 14 'transverse to the machine direction forms the second outside of the wire 10, which also comprises protrusions 16' and depressions 18 'in its side profile. Several or at least two protrusions 16 'are located in one plane forming the outer surface (preferably at least 50% and preferably all protrusions 16' are located on the outer surface). The deposits 18 'are located in one separate plane inside the plane formed by the protrusions 16'.

A number of machine direction monofilament yarns 22 is disposed between the outer wire side, which consists of an outer plane formed by the protuberances 16, 16 'and intersecting the plane with respect to the transverse yarns 14, 14' with locations that are protrusions 16, the deposition 18 and, respectively, the protuberances 16 ', 3 77493 between the levels of the sediments 18 '. As shown in Figure 1, the peaks of the load-bearing yarns 22 in the machine direction are located below the protrusions 16, 16 'at the point where they intersect with the yarns 14, 14' transverse to the machine direction and thus do not come into contact with the paper web 24 on the wire 10 when the wire 10 is used as a drying felt for a paper machine. The web 24 rests on protrusions 16 of yarns transverse to the machine direction. It should be noted that the greatest wear of the dry wire yarns occurs in the monofilament yarns in contact with the web 24. Therefore, it is not necessary to protect the yarns 22 'by protrusions 16' on the opposite side of the paper web, although it wears out. 22 are located outside the layer 20 as they pass through the layer 20.

In the wire 10, the machine direction yarns 22 of the layer 12 are connected to the yarns 22 of the layer 20, and the paired yarns are moved somewhat from each other vertically, where they pass over the yarns 14, 14 'transverse to the machine direction. The fabric form has four groups of yarn pairs 22 transverse to the machine direction. One pair intersects with a yarn 14, 14 'transverse to every fourth machine direction, and this is repeated. Preferably, the machine direction yarns extend over at least one yarn transverse to the machine direction, under at least one yarn transverse to the next machine direction, and over at least one yarn transverse to the next machine direction before going down to join the lower machine direction transverse yarn layer. with the upper yarn layer transverse to it, whereby the yarns parallel to the machine and the yarns transverse to it are combined in a repetitive shape. Of course, the fabric will be such that the association between the machine direction yarns and the upper machine direction transverse yarn layer becomes such that the upper surfaces of the machine direction transverse upper layer yarns over which the machine direction yarns extend are relatively higher in the direction away from the wire end. and the visible surfaces of the machine direction yarn portions in the upper plane below which the machine direction transverse yarns pass are proportionally lower in the opposite direction, with planar differences protecting the visible tops of the machine direction yarns from contact with the paper web contacting the upper machine direction transverse yarn surface.

The yarns 14, 14 'and 22 may be monofilament yarns made of a synthetic polymeric resin. The yarns 14 and 14 'may also be multifilament yarns. Such multi- and monofilament yarns are represented by polyester, polyamide, polyolefin, polyaramide, polyimide and the like yarns. Typically, such yarns have a diameter of 0.2 to 1.0 mm and are preferred for the fabrics of the invention.

After the wires of the present invention are woven, they are heat treated to stabilize the wire and pull the yarns to their desired relative position. The machine direction yarns 22 are pulled inwardly from the outer surface of the fabric 10, and this pressure compresses the yarn locations 18, 18 'so that the protrusions 16, 16' protrude onto the outer surface of the wire, as previously described. The degree of heat treatment to achieve the desired construction of the wire 10 will, of course, vary with the properties of the yarns 14, 14 'and 22. However, the optimal periods, temperatures and stresses to which the 5 77493 wire is exposed in the heat treatment can be determined by one skilled in the art by experimenting with different yarn materials. In general, the heat treatment can be performed at about 65 to 190 ° C for 15 to 60 minutes. Wires such as the present invention can be woven flat and their ends joined together by conventional methods known to those skilled in the art. The wires thus joined are easy to use as drying felts in the drying section 30 of the paper machine, as shown in Fig. 2. Figure 2 shows a paper web 24 pressed against an endless wire 34 according to the present invention against steam cylinders 32 as it is passed through a drying section 30.

The following examples illustrate best practices for carrying out and using the present invention, but are not to be construed as limiting.

Example 1

The wire is made of double woven from polyester monofilament yarns with a diameter of 0.51 mm in the machine direction (24 pcs / 2.5 cm) and polyamide monofilament yarns with a diameter of 0.51 mm in the machine direction (24 pcs / 2.5 cm), ie a total of 48 machine direction yarn per 2.5 cm interwoven with polyester monofilament yarns transverse to the machine with a diameter of 0.51 mm (48 pieces / 2.5 cm; 24 pieces at the top, 24 pieces at the bottom). After the heat treatment, a wire is obtained with only yarns extending transversely to the machine direction on the outer surface or at the outermost level of the wire. A representative portion of the fabric produced is subjected to physical experiments. The physical properties that appear are shown in Table 1.

Example 2 This is not an example of the present invention, but has been made for comparison. The wire is woven into double weave 6 77493 (4 warp and 8 weft yarns) with machine direction yarns and cross-yarns as follows:

Machine direction yarns - 24 pcs / 2.5 cm 0.51 mm diameter polyester monofilament yarns, 24 pcs / 2.5 cm 0.51 mm diameter polyamide monofilament yarns arranged in a "two and two" arrangement.

Wefts in the machine direction - 25 pieces of twine yarns transverse to 2.5 cm polyester monofilament with a diameter of 0.51 mm, 12.5 up, 12.5 down.

After the heat treatment, a wire is obtained in which the machine direction yarns are in the upper plane or outside the wire where they intersect or cross the transverse yarns.

A representative portion of the wire was examined for its physical anines. The results of the study are presented in Table 1 below.

Table 1 Wire preparation method

Example 1______Example 2

Weight, g / cm2 (oz / ft2): 0.11 (3.70) 0.09 (3.0)

Thickness, mm (inches): 2.11 (0.083) 2.16 (0.085)

Air permeability: 436,700 (measured with Frazier; ft ^ / min. Air / ft2 at pressure drop of 1/2 "H2O)

Breaking strength: kg / cm (lbs / inch) in the machine direction 204 (1140) 165 (923) transverse to the machine direction 170 (950) 91 (512) 7 77493

Thermal stability (Heat plate smoothing) (177 ° C * 3 ° C) __Example 1___ Example 2_____

Surface Remaining Surface Remaining

Exposure fracture fracture time strength elongation strength elongation in hours kg / cm (lbs / w) _% ___ kg / cm (lbs / 1 *) __% ____ 0 204 (1140) 100 165 (923) 100 25 200 ( 1120) 98 160 (898) 97 50 195 (1090) 96 155 (866) 94 75 198 (1110) 97 152 (851) 92 100 201 (1125) 99 150 (841) 91 150 199 (1115) 98 140 (785) ) 43

Abrasion resistance according to Taber1

In the direction of the machine In the transverse direction

Nylon Polyester% ice% ice%

Eg 1 ___ kg / thread_with kq / thread with kg / thread__

New 7.9 - 10.0 - 7.7 500 rounds. 7.7 98 10.0 100 6.4 83 1000 rev. 7.0 91 10.3 100+ 5.8 76

EsinK_2

New 8.2 - 10.3 - 9.5 500 rounds. 4.6 57 7.6 74 8.8 93 1000 rev. 2.5 31 4.8 47 8.6 90

Those skilled in the art will recognize that the embodiments described above may be varied in many ways without departing from the following inventive ideas set forth in the claims. For example, the wire of the present invention can be woven with different filler weaves to provide wires with different permeabilities, which is valuable to those skilled in the art.

Claims (2)

8 77493 A wire (10) for use as a drying felt for a paper machine, comprising a first tortuous layer (12) of yarns (14) transverse to the direction of the machine, which provide protrusions (16) and depressions (18) on the outer surface of the wire, a plurality of protrusions (16) to the first outer surface plane, and the depositions (18) are located on the first inner surface plane, a second tortuous layer (20) of yarns (14 ') transverse to the machine direction forming protrusions (16 ·) and depositions (18 ·) on the second outer surface of the wire, with most protrusions ( 16 ') are arranged on the second outer surface plane and the deposits (18') on the second inner surface plane, and a plurality of machine direction monofilament yarns (22) between the first and second outer surface planes, characterized in that the monofilament yarns (22) are woven together in machine direction transverse yarns (14). , 14 ') in the first and second outer surface planes and woven together with yarns (14, 14') transverse to the machine direction. in the first and second layers (12, 20) at locations between the outer and inner surface planes of at least the second said first and second layers (12, 20) and at locations inside the outer surfaces of said first and second layers (12, 20), the yarns (22) in the deposits (18,18 ') are in a different plane from the outwardly directed protrusions (16,16') of the yarns (14,14 ') and that the distance between the planes containing the yarns (22) is smaller than that of the yarns (14,14') ') the distance between the planes containing the protrusions. Wire according to Claim 1, characterized in that the machine direction yarns (22) are woven together with the transverse yarns (14, 14 ') at locations between the outer and inner surface planes of each layer (12, 20).