WO2001004413A1 - Edge cut system for papermaking fabrics - Google Patents

Abstract

Forming belts in combination with a forming section of a papermaking machine which act to form a paper sheet of prescribed width. The combination includes an outer forming belt (10) comprising a continuous porous fabric having a support surface (31) adapted to receive and support a sheet of paperforming slurry (22) during its formation into a sheet during passage about a forming roll of the forming section. The outer forming belt cooperates with an inner forming belt (16) which also comprises a porous continuous fabric and a support surface (35) adapted to receive and support the sheet of paperforming slurry during its formation into a sheet. First and second edge cutting elements (38', 39') which act to engage and cut the slurry sheet along opposed edges into a desired width during its formation into a sheet as it passes through the forming section. At least one of the cutting elements comprises a continuous polyurethane bead or filament bonded with the support surface adjacent an edge of one of the outer and inner forming fabrics. The continuous bead or filament, when compressed between the support surfaces as the belts pass about the forming roll, cuts the newly formed paper sheet to have at least one sharp defined edge.

Description

EDGE CUT SYSTEM FOR PAPERMAKING FABRICS

Background of the Invention

The instant invention is directed to paper forming belts for use in the forming

section of a papermaking machine. Each of the forming belts including a forming surface

which carries or co-operates with an edge trimmer during formation of paper on the suppoπ

surfaces of the forming belts.

The use of paper edges or cutters co-operating with paper forming cloth is well

known, however, none of the known arrangements are satisfactory with today's paper

forming machines. U.S. Patent 709,228 to Kron shows a wire fabric which includes

metallic strips woven lengthwise therein. The metal strips divide the paper lengthwise.

U.S. Patent 3,652,390 discloses a Fourdrinier fabric with a pair of polyethylene edging

bands of about 1/4" thick which prevent drainage therethrough. These bands, which are

disposed to wear, serve to define the edges of the paper. U.S. Patent 4,576,681 utilizes a

narrower wire 31 in combination with a wider felt 12. The edges of the narrower wire act

to size the paper widthwise. Each known arrangement either was not designed to or does

not perform satisfactorily with modern papermaking equipment.

It is an object of the present invention to provide a forming belt which is wear

resistant.

Another object of the invention is the provision of a forming belt which carries

an edge cutting or edge forming band. Another object of the invention is a pair of forming belts which co-operate to form a paper sheet with defined edges.

Another object of the invention is a pair of forming belts which carry a continuous bead of polyurethane bonded with the support surface.

Another object of the invention is to bond with the suppoπ surface of the

forming fabrics a shaped continuous polyurethane monofilament which acts as an edge cutter

or shaping member.

Another object of the invention is the provision of an edge cutting bead secured

with the support surface of the forming belt which has superior wearabiliry.

Summary of the Invention

The instant invention is directed to co-operating forming belts in combination

with a forming section of a papermaking machine. The combination includes an outer

forming belt comprising a plurality of longitudinal and transverse yarns intermeshed to form

a continuous porous fabric. The outer belt is formed with a suppoπ surface adapted to

receive and suppoπ paper forming slurry during its formation into a paper sheet as it is

passed about a forming roll of the forming section. Also, an inner forming belt comprising

a plurality of longitudinal and transverse yarns intermeshed to form a porous continuous

fabric. The inner belt is formed with a suppoπ surface adapted to receive and suppoπ the

paper forming slurry during its formation into a paper sheet as it is passed about the forming

roll and through said forming section. First and second edge cutters which act to engage the slurry sheet along opposed

edges and cut it to a desired width during its passage through the forming section are

provided. At least one of the first and second cutters, comprises a continuous bead of

synthetic material bonded with the suppoπ surface of one of the outer and inner forming

fabrics . Continuous beads may comprise a continuous polyurethane monofilament or it may

comprise a continuous extrusion of polyurethane. The continuous polyurethane bead may

also form both the first and second cutters. The monofilaments may be bonded with either

or both forming belts.

In an alternative arrangement, one of the f rst and second cutters may comprise

a needle shower arranged along a second edge of the inner forming fabric.

The forming belts may be woven single layer of polyester yarns. One of the

forming belts may be formed two ply with the outer ply being formed of polyester

monofilaments while the inner ply is formed of nylon monofilament, or polyester

monofilament, or alternating nylon and polyester monofilaments.

The invention also is directed to forming belts which are adapted to form paper

slurry into a paper sheet of prescribed width in the forming section of a papermaking

machine. The belts include an outer belt and inner belt formed of interwoven synthetic

yarns having a paper suppoπ surface and a running surface. The forming surfaces of the

outer and inner belts are adopted to be in overlaying position during the paper sheet forming

operation.

First and second edging members may comprise first and second continuous

synthetic beads which are bonded with the suppoπ surface of at least one of the inner and outer forming belts. These edging members are arranged longitudinally of and adjacent

opposed lateral edges of the suppoπ surfaces so that the paper slurry as introduced between

the suppoπ surfaces and compressed into a paper sheet has its opposed edges are cut at the

desired width. The beads may comprise polyurethane monofilaments having a cross-section of one of round, triangular, and square. Alternatively, they may comprise a pair of

polyurethane extrusions.

Description of the Drawings

The construction designed to carry out the invention will hereinafter be described, together with other features thereof.

The invention will be more readily understood from a reading of the following

specification and by reference to the accompanying drawings forming a pan thereof,

wherein an example of the invention is shown and wherein:

Figure 1 is a schematic side view of the forming belts and a forming section of

a papermaking machine;

Figure 2 is a cut-away end view of a first arrangement of the forming fabrics

of the invention;

Figure 3 is similar to Figure 2 showing a second belt arrangement;

Figure 4 is similar to Figure 2 showing a third belt arrangement; and,

Figure 5 is similar to Figure 2 showing a fourth belt arrangement. Description of a Preferred Embodiment

Referring now to the drawings, the invention will now be described in more detail.

Figure 1 is a diagrammatic view of the forming section of a papermaking

machine. Forming section A includes an outer forming section which includes an outer

forming belt 10 which passes about a plurality of guide rolls 12 and forming or press roll

14. Forming section A also includes an inner forming section with inner forming fabric 16

passing about guide rolls 18 and about forming roll 14 inwardly of outer belt 10 so that the

paper forming slurry is compressed between the inner and outer belts substantially upon

delivery to the belts.

There are a plurality of knock off showers, not shown, arranged about the path

of each forming belt 10, 16. These showers act to clean any fibrous residue from the guide

rolls and suppoπ belts prior to the paper forming slurry being delivered and after the

removal of the paper sheet. The removed slurry residue is returned to a holding tank and

recycled as forming slurry.

Head box 20 is located adjacent forming roll 14 and is positioned to deliver a

stream of paper forming slurry 22 into the gap formed where outer and inner forming belts

10, 16 come together and pass around press roll 14. Here, the slurry is compressed to

remove a majority of the liquid and is formed into a sheet.

In practice, it is difficult to deliver a stream of slurry which is formed into paper

with sharp longitudinal edges. The instant invention is directed to edge cutters which define

sharp edges during forming of the paper sheet. As the paper emerges from between belts 10 and 16 and depaπs the area of forming roll 14, it is suppoπed by the support surface of inner forming belt 16 as it is

transpoπed to press felt 24 where it is picked up and transpoπed into the press section. A

needle shower or shower cutter 26 may be disposed, as shown, adjacent press felt 24. Also,

trim removal or knock off showers 28 are shown adjacent the inner surface of inner forming

belt 16 beyond the pick-up area of press felt 24. Other knock off showers, which are not

shown, are provided about the paths of both outer and inner forming belts 10 and 16.

Turning now to Figures 2-5 the edge trimming arrangement according to the

invention is shown.

A first arrangement of the edge cutting system of the invention is shown in

Figure 2. In this arrangement, the outer forming belt 10 is shown as a forming fabric

having a suppoπ surface 31 formed of longitudinal or machine direction yams 30

intermeshed with transverse yarns 32. In the arrangement shown, yarns 30 and 32 comprise

interwoven monofilament polyester yarns. Alternatively, these yarns may be formed of

other synthetic material such as nylon or polyethylene or a combination thereof. Also, they

may be multi-filament and may be interlaced by other than weaving.

Inner forming belt 16 is shown as a forming fabric having a suppoπ surface 35

which is formed of longitudinal yarns 34 interlaced with transverse yarns 36. In the

arrangement shown, yarns 34 and 36 comprise interwoven monofilament polyester yarns.

Alternatively, these yarns may be formed of other synthetic material such as nylon or

polyethylene. Also, they may be multi-filament and may be interlaced by other than

weaving. Inner forming belt 16 includes a pair of edge cutting elements in the form of

longitudinal beads 38, 39 bonded to suppoπ surface 35 adjacent the outer edges thereof.

Beads 38, 39 comprise an extrusion of or a monofilament yam of polyurethane having a substantially circular or a shaped cross-section which, when bonded, are caused to embed in the interstices of the fabric.

The fabric forming suppoπ belts 10, 16 are each formed with a desired porosity

within the range of 100-800 CFM.

As shown, paper forming slurry 22 has been deposited between support surfaces

31 and 35 to extend substantially across the width of forming belts 10, 16 and on each side

of edge cutting elements 38, 39. As the suppoπ surfaces are pressed together by forming

roll 14 the slurry at the edges is separated by the edge cutting elements and the paper which

is formed between the edge cutting elements is formed with smooth and sharp longitudinal

edges.

Due to the pressure exeπed by forming roll 14, the interaction between the press

belts and the effect of the chemicals used to form the paper forming slurry, these belts and

especially the edge cutting elements are subject to wear and degradation. It has been found

that polyurethane is especially resistant to degradation and wear.

Also, in order for the cutting element to form a sharp uniform edge on the

paper, it has been found that the axis of the cutting element should extend substantially

along a single plane during cutting. Also, in order that the cutting element is firmly secured

with the forming belt, it has been found that it should be imbedded in the fabric of the belt. As a result, the cutting element is bonded to the suppoπ surface of the forming belt in such a manner as to also penetrate into a bond with the belt forming yarns.

In a second arrangement shown in Figure 3, a pair of forming belts 10 and 16

are formed and arranged relative to each other as in Figure 2. Like elements are identified

with numerals. In Figure 3, the cutting elements or beads 38' and 39' extend longitudinally

and are bonded to the suppoπ surface 31 of outer forming fabric 10 in similar manner as

beads 38, 39 are bonded with fabric 16. The beads shown in Figure 3 are shaped with a

triangular cross-section. It is anticipated that they could also be round or square.

Figure 4 depicts a third arrangement of the invention. Again, outer and inner

forming fabrics 10 and 16 are formed as in Figure 2. Cutting element 38' is bonded with

outer forming fabric 10 while cutting element 39' is bonded with inner forming fabric 16.

Again, forming fabrics 10 and 16 are formed as in Figure 2 with like members identified

with like numerals. Again, the cutting elements employed may have any of the above

described cross-sectional shapes.

Figure 5 depicts yet another arrangement of the invention. Here, only inner

forming fabric 16 is shown. A single cutting element 38 is shown bonded with suppoπ

surface 35 along one edge. The opposite edge of suppoπ surface 35 is shown with no

cutting element.

In operation, cutting element 38 severs paper forming slurry 22 along a first

edge at press roll 14 as above described. The opposite slurry edge is pressed out and

remains engaged with the paper sheet in an unfinished condition until forming fabric 16

passes beneath needle shower 26 where it is cut in the usual manner. The remainder of the operation is as previously described. Again, cutting member 38 may have a cross-section of any disclosed shape.

Each arrangement disclosed has selected individual advantages. In the

arrangements of Figures 2 and 3, should one of the outer or inner forming fabric be

subjected to more wear than the other, the cutting elements may be placed on the suppoπ

surface of least wear. In Figure 3, should one side of the forming fabrics be subject to more

wear than the other, the sides selected to carry the cutting elements can be adjusted

accordingly. In Figure 4, the width of the paper can be easily adjusted by axially

positioning needle shower 26.

While a preferred embodiment of the invention has been described using specific

terms, such description is for illustrative purposes only, and it is to be understood that

changes and variations may be made without depaπing from the spirit or scope of the

following claims.

Claims

What is claimed is:

1. Forming belts in combination with a forming section of a papermaking machine for forming a paper sheet of prescribed width, said combination comprising:

an outer forming belt comprising a plurality of longitudinal and transverse yarns

intermeshed to form a continuous porous fabric, said outer belt having a suppoπ surface

adapted to receive and suppoπ paper forming slurry during its formation into a paper sheet

during passage about a forming roll of said forming section;

an inner forming belt comprising a plurality of longitudinal and transverse yarns

intermeshed to form a porous continuous fabric, said inner belt having a suppoπ surface

adapted to receive and suppoπ said paper forming slurry during its formation into said paper

sheet during passage about said forming roll and through said forming section;

first and second edge cutting elements adapted to engage said sheet along

opposed edges, said cutting elements being adapted to cut said sheet into a desired width

during said passage through said forming section;

at least one of said first and second cutting elements comprises a continuous

bead of synthetic material bonded with said suppoπ surface adjacent an edge of one of said

outer and inner forming fabrics; wherein,

said continuous bead when compressed between said suppoπ surfaces of said

outer and inner forming fabrics during passage about said forming roll cuts said sheet

forming a sharp defined edge.

2. The forming belts of claim 1 wherein continuous bead comprises a

continuous polyurethane monofilament.

3. The forming belts of claim 1 wherein said continuous bead comprises a polyurethane extrusion.

4. The forming belts of claim 1 wherein each of said first and second edge cutting elements comprise a continuous polyurethane monofilament bonded with said suppoπ surface of one of said outer and inner belts.

5. The forming belts of claim 4 wherein each said polyurethane

monofilament is bonded with said support surface of one of said outer and inner forming

belts.

6. The forming belts of claim 1 wherein said continuous bead has a cross- section of one of round, square, and triangular.

7. The forming belts of claim 1 wherein one of said first and second cutting

elements comprise a needle shower arranged along a second edge of said inner forming belt.

8. The forming belts of claim 1 wherein said outer and inner forming belts

are woven.

9. The forming belts of claim 8 wherein said longitudinal and transverse

yarns of at least said inner forming belt are formed of polyester.

10. The forming belts of claim 8 wherein at least one of said inner and outer

forming belts is formed two ply with said yarn forming the outer ply are formed of

polyester monofilaments and the yarns forming the inner ply are formed of one of polyester,

nylon, and a combination of polyester and nylon monofilament.

11. Forming belts adapted to form paper slurry into a paper sheet of

prescribed width in the forming section of a papermaking machine including: an outer belt formed of interwoven synthetic yarns having a paper suppoπ surface and a running surface;

an inner belt formed of interwoven synthetic yarns having a paper suppoπ surface and a running surface;

said forming surfaces of said outer and inner belts being adopted to be in

overlaying position during the paper sheet forming operation;

first and second edging members comprising first and second continuous

synthetic beads bonded with said suppoπ surface of at least one of said inner and outer

forming belts, said edging members being arranged longitudinally of and adjacent opposed lateral edges of said suppoπ surfaces; whereby,

paper slurry introduced between said suppoπ surfaces is compressed into a paper

sheet with opposed edges of said sheet being simultaneously cut at a desired width.

12. The forming belts of claim 11 wherein said continuous beads comprise

polyurethane monofilaments having a cross-section of one of round, triangular, and square.

13. The forming belts of claim 11 wherein said continuous beads comprise

a pair of polyurethane extrusions.