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 modem 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 support 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 wearability.

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 support surface adapted to receive and support 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 support surface adapted to receive and support 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 support 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 first 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 support 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 support 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 support surfaces so that the paper slurry as introduced between the support 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 part 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 support 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 departs the area of forming roll 14, it is supported by the support surface of inner forming belt 16 as it is transported to press felt 24 where it is picked up and transported 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 support surface 31 formed of longitudinal or machine direction yarns 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 support 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 support surface 35 adjacent the outer edges thereof.

Beads 38,39 comprise an extrusion of or a monofilament yarn 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 support 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 support 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 exerted 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 support 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 support 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 support surface 35 along one edge. The opposite edge of support 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 support 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 departing from the spirit or scope of the following claims.