Textiles: weaving – Fabrics – Drier felts
Patent
1992-10-20
1994-10-25
Falik, Andrew M.
Textiles: weaving
Fabrics
Drier felts
439411, D03D 1300, D03D 1500, D03D 1100
Patent
active
053580141
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCES TO RELATED APPLICATIONS
This application is a national phase application of PCT/AT/00060 filed Apr. 23, 1991 and based upon an Austrian Application A1037/90 filed May 8, 1990 under the International Convention.
1. Field of the Invention
The invention relates to a fabric of synthetic monofilaments for use as a drain web in a paper machine, more particularly the invention relates to a paper making screen having warp threads and three layers of weft threads connecting these warp threads.
2. Background of the Invention
In order to increase the wear toleration of a papermaking screen or feet, fabrics with a higher number of healds were constructed; this increases the floating length of the weft threads on the operating side while largely maintaining the visual aspect of the surface geometry on the paper side. Thus, a relatively greater proportion of the length of the operating-side weft threads is available for abrasion.
Problems with this construction arise because the weft threads, floating over longer stretches, cause a pronounced marking of the papers, especially in the case of fast-running machines, as a result of turbulence created when the wire moves over stationary draining elements, such as foils, wet suction boxes or other suction boxes.
DE-A-2 445 185 describes a three-layer fabric corresponding to the above-mentioned type. Two adjoining layers each, tied by their respective warp threads, are connected by means of separate strings.
The strings are formed as warp threads connecting two layers in such a manner that in the finished wire the surface of the top layer is not absolutely planar so that the different levels of the surface result in a high degree of wire markings on the paper.
U.S. Pat. No. 4,941,514 describes a four-layer fabric in which the weft threads are tied by warp threads extending through all layers. In this known fabric, permeability is reduced at the center of the fabric because the apertures between the fabric elements are smaller. The draining capacity of the fabric is thus diminished. This is even more compounded by the fact that fibers which penetrate the fabric due to the larger apertures existing on the paper side of the fabric clog the smaller apertures at the center of the fabric even more strongly.
OBJECTS OF THE INVENTION
It is the object of the present invention to prevent markings and to use wires equipped with weft threads of extended floating ability on the operating side even in fast machines running at velocities of more than 400 m/min. Still another object is to improve the drainage capacity as much as possible.
Yet another object of the present invention is to accentuate the curve of the bottom weft layer toward the operating side so that more volume of the bottom weft thread can be abraded on the operating side.
SUMMARY OF THE INVENTION
This is achieved by having the weft threads, which are tied in groups, being connected both by warp threads running only through the two top layers and warp threads running through all three layers.
The thus tied middle weft layer creates a wider space between the mat surface and the stationary carrying elements of the paper machine so that the turbulence effects of the bottom weft threads, which float for longer stretches, do not reflect on the mat.
The wider space disturbs the turbulences and damps their effect on the mat. This phenomenon is due to the unobstructed space of the wire construction, which narrows upward in a vertical direction. Practically markings not observed. As a result of the unobstructed space narrowing upward in a vertical direction, the drainage effect is not impaired.
In a fabric according to the invention, every weft thread of the bottom layer is grasped by two, preferably not adjoining, warp threads from below and pulled upward towards the warp threads located between the weft threads of the middle layer which acts as a support so that the curve facing the outside of the wire can e maximally developed.
In a preferred embodiment of the invention, four weft threads of the top layer c
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Dubno Herbert
Falik Andrew M.
Hutter & Schrantz AG
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