GB2078802A

GB2078802A - A Fourdrinier Wire Screen

Info

Publication number: GB2078802A
Application number: GB8021698A
Authority: GB
Original assignee: SCHOELLER DUEREN METALLTUCH
Current assignee: SCHOELLER DUEREN METALLTUCH
Priority date: 1980-07-02
Filing date: 1980-07-02
Publication date: 1982-01-13

Abstract

A Fourdrinier wire screen has a twill weave and the warp wires 1 are bent or cranked round the weft wires 2 and are kept close to each other, on the running face and the weft wires (2) are also bent whereby the ratio of the spacing (a) of the warp wires to the warp wire diameter (d) is increased.

Description

SPECIFICATION A Fourdrinier Wire Screen The present invention relates to a Fourdrinier twill wire screen for a paper-making machine, having a single-thread weave structure on the paper face and in which the warp wires are bent round weft wires and are disposed side-by-side, touching or nearly touching each other.

A description of such a Fourdrinier metal wire screen is to be found in German Offenlegungsschrift (DOS) 2,530,110. Using a wire screen, as described in DOS 2,530,1 10, the paper-making machine may be operated for a longer period without changing the screen than is the case, for example, with the wire screen described in German Auslegeschrift (DAS) 1,1 1 1,151, and without any essential decrease in the dewatering effect throughout that longer period.

One purpose of these prior art paper-making machine screens was to increase the quality, and more specially the printing quality, of papers produced on them.

However, this purpose is not fully effected with the suggestions made in DOS 2,530,1 10, because in this case, on having the warp wires bent round the straight weft wires and generally touching each other, and having a single-thread wire weave on the paper face, the paper is produced with surface markings so that it does not attain the standard required for very highquality papers, because the screen is not fine enough.

One aim of the present invention is to provide a Fourdrinier wire screen, which, while having the improved working life of a screen as described in DOS 2,530,1 10, at least descreases the surface marking on paper produced on the screen and at best avoids any surface marking on the paper.

According to the present invention a Fourdrinier twill wire screen, having a singlethread weave structure on its paper face and in which the warp wires are bent round the weft wires and are disposed side-by-side, touching or nearly touching each other, is characterised in that while keeping the liquid-tight or tight positioning of the warp wires with respect to each other on the running face, the weft wires are also bent or cranked and the ratio of the spacing between adjacent warp wires bent round a given weft wire, to the warp wire diameter is increased.

According to the invention, the number of wire cross-overs which arise on the paper side of the screen (i.e. the side used for supporting the paper pulp) is increased, this, in turn, reducing the risk of surface marking and thereby increasing the quality of the paper which can be produced thereon.

The increase in the said ratio of the spacing of the joining warp wires to the warp wire diameter may be produced in a number of different ways.

For example, in one embodiment of the invention, use may be made of an at least fourharness twill weave. Two or more warp wires can be grouped together in the weave, or the effect of a pair of warp wires can be obtained by using a single flat wire for the warp.

The invention will now be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a view of part of one embodiment of a Fourdrinier wire screen in accordance with the invention with a four-harness twill weave, the view being of the upper or paper face of the screen, Figure 2 is a view of the screen of Figure 1 as seen from the lower or running face of the screen, Figure 3 is a section on the line Ill-Ill of Figure 1, Figure 3a is a section on the line Illa--llla of Figure 1, Figure 4 is a view of part of a second embodiment of Fourdrinier wire screen in accordance with the invention having a twill weave in which the warp wires are grouped together in pairs, also of the paper face of the screen, Figure 5 is a view of the screen of Figure 4 as seen from the running screen, Figure 6 is a section on the line VI--VI of Figure 4, and Figure 7 is a modified section on the line VII- VII of Figure 6, in which each pair of warp wires has been replaced by a single flat wire.

In each of Figures 1, 2, 4 and 5 the wires 1 drawn from top to bottom of the drawings are the warp wires, and these are bent or cranked round the horizontally drawn (weft) wires 2, to produce a screen from a four-harness twill weave. The weft wires 2 are also bent or cranked whereby the bent parts 3 of the warp wires extend upwards as far as a plane E (see Figure 3) of the upper face of the screen which defines the paper face for the paper pulp or stuff. From Figure 1 it can be seen that the ratio of the spacing "a" between adjacent warp wires bent round a given weft wire to the warp wire diameter "d" has been increased (to something around six in the illustrated case) compared to that expected in the case of a singlethread wire weave.

A similar increase in the stated ratio can be seen in Figures 4 and 5. In these Figures, the warp wires 1 are grouped together in pairs, and a pair of wires 1 may be replaced by a flat wire 4 as shown in Figure 7.

The area of available screen openings per unit area of a Fourdrinier screen in accordance with the invention can be of the order of 20%.

Claims

1. A Fourdrinier twill wire screen, having a single-thread weave structure on its paper face in which the warp wires are bent round the weft wires and are disposed side-by-side, touching or nearly touching each other, characterised in that while keeping the liquid-tight or tight positioning of the warp wires with respect to each other on the running face, the weft wires are also bent or cranked and the ratio of the spacing between

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A Fourdrinier Wire Screen The present invention relates to a Fourdrinier twill wire screen for a paper-making machine, having a single-thread weave structure on the paper face and in which the warp wires are bent round weft wires and are disposed side-by-side, touching or nearly touching each other. A description of such a Fourdrinier metal wire screen is to be found in German Offenlegungsschrift (DOS) 2,530,110. Using a wire screen, as described in DOS 2,530,1 10, the paper-making machine may be operated for a longer period without changing the screen than is the case, for example, with the wire screen described in German Auslegeschrift (DAS) 1,1 1 1,151, and without any essential decrease in the dewatering effect throughout that longer period. One purpose of these prior art paper-making machine screens was to increase the quality, and more specially the printing quality, of papers produced on them. However, this purpose is not fully effected with the suggestions made in DOS 2,530,1 10, because in this case, on having the warp wires bent round the straight weft wires and generally touching each other, and having a single-thread wire weave on the paper face, the paper is produced with surface markings so that it does not attain the standard required for very highquality papers, because the screen is not fine enough. One aim of the present invention is to provide a Fourdrinier wire screen, which, while having the improved working life of a screen as described in DOS 2,530,1 10, at least descreases the surface marking on paper produced on the screen and at best avoids any surface marking on the paper. According to the present invention a Fourdrinier twill wire screen, having a singlethread weave structure on its paper face and in which the warp wires are bent round the weft wires and are disposed side-by-side, touching or nearly touching each other, is characterised in that while keeping the liquid-tight or tight positioning of the warp wires with respect to each other on the running face, the weft wires are also bent or cranked and the ratio of the spacing between adjacent warp wires bent round a given weft wire, to the warp wire diameter is increased. According to the invention, the number of wire cross-overs which arise on the paper side of the screen (i.e. the side used for supporting the paper pulp) is increased, this, in turn, reducing the risk of surface marking and thereby increasing the quality of the paper which can be produced thereon. The increase in the said ratio of the spacing of the joining warp wires to the warp wire diameter may be produced in a number of different ways. For example, in one embodiment of the invention, use may be made of an at least fourharness twill weave. Two or more warp wires can be grouped together in the weave, or the effect of a pair of warp wires can be obtained by using a single flat wire for the warp. The invention will now be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a view of part of one embodiment of a Fourdrinier wire screen in accordance with the invention with a four-harness twill weave, the view being of the upper or paper face of the screen, Figure 2 is a view of the screen of Figure 1 as seen from the lower or running face of the screen, Figure 3 is a section on the line Ill-Ill of Figure 1, Figure 3a is a section on the line Illa--llla of Figure 1, Figure 4 is a view of part of a second embodiment of Fourdrinier wire screen in accordance with the invention having a twill weave in which the warp wires are grouped together in pairs, also of the paper face of the screen, Figure 5 is a view of the screen of Figure 4 as seen from the running screen, Figure 6 is a section on the line VI--VI of Figure 4, and Figure 7 is a modified section on the line VII- VII of Figure 6, in which each pair of warp wires has been replaced by a single flat wire. In each of Figures 1, 2, 4 and 5 the wires 1 drawn from top to bottom of the drawings are the warp wires, and these are bent or cranked round the horizontally drawn (weft) wires 2, to produce a screen from a four-harness twill weave. The weft wires 2 are also bent or cranked whereby the bent parts 3 of the warp wires extend upwards as far as a plane E (see Figure 3) of the upper face of the screen which defines the paper face for the paper pulp or stuff. From Figure 1 it can be seen that the ratio of the spacing "a" between adjacent warp wires bent round a given weft wire to the warp wire diameter "d" has been increased (to something around six in the illustrated case) compared to that expected in the case of a singlethread wire weave. A similar increase in the stated ratio can be seen in Figures 4 and 5. In these Figures, the warp wires 1 are grouped together in pairs, and a pair of wires 1 may be replaced by a flat wire 4 as shown in Figure 7. The area of available screen openings per unit area of a Fourdrinier screen in accordance with the invention can be of the order of 20%. Claims

1. A Fourdrinier twill wire screen, having a single-thread weave structure on its paper face in which the warp wires are bent round the weft wires and are disposed side-by-side, touching or nearly touching each other, characterised in that while keeping the liquid-tight or tight positioning of the warp wires with respect to each other on the running face, the weft wires are also bent or cranked and the ratio of the spacing between adjacent warp wires bent round a given weft wire, to the warp wire diameter is increased.

2. A Fourdrinier wire screen as claimed in claim 1, characterised in that the twill weave is at least a four-harness twill weave.

3. A Fourdrinier wire screen as claimed in claim 1 or claim 2, characterised in that the warp wires are grouped together in groups of two or more.

4. A Fourdrinier wire screen as claimed in any preceding claim, characterised in that the said ratio is of the order of six.

5. A Fourdrinier wire screen as claimed in claim 1 or claim 2, characterised in that the warp wires are in the form of single flat wires.

6. A Fourdrinier wire screen as claimed in any preceding claim, in which the area of available screen openings per unit area of the screen is of the order of 20%.

7. A Fourdrinier wire screen substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 3a, Figures 4 to 6 or Figures 4 to 6 as modified by Figure 7 of the accompanying drawings.

New Claims or Amendments to Claims filed on 23 March, 1981.

New or Amended Claims: Claim 6 deleted, appendant claim renumbered.