GB2139261A

GB2139261A - Method and device for controlling the edge of a paper web formed on a travelling foraminous wire

Info

Publication number: GB2139261A
Application number: GB08233604A
Authority: GB
Inventors: Umberto Bollani
Original assignee: Beloit Corp
Current assignee: Beloit Corp
Priority date: 1982-11-25
Filing date: 1982-11-25
Publication date: 1984-11-07
Also published as: GB2139261B

Abstract

An edge of a paper web formed on a travelling foraminous wire (1) from stock issuing from the slice of a headbox (3) is separated before the stock engages the wire by means of a blade (5) positioned parallel to the machine direction. The edge material is collected and conveyed away so that it can be used. <IMAGE>

Description

SPECIFICATION Method and device for controlling the edge of a paper web formed on a travelling foraminous wire The present invention relates to improvements in papermaking machines, and more particularly to a method and device for separating the marginal edge of a paper web formed on a travelling wire wherein the web is single layer or multiple layered.

In a papermaking machine, the sheet or web is formed by depositing one or more layers of stock, which consists of fibres in an aqueous suspension, on to a travelling wire.

The stock is normally derived from wood or other vegetable fibres, and the suspension of stock is delivered onto the travelling wire by head-boxes having slice openings and positioned along the wire. The layers of stock which are formed in this manner have longitudinal edges which are not perfectly even or regular, both from the standpoint of their geometry and their dimension, and these edges must therefore be made even and regular after the head-boxes have deposited the web on the wire. This is frequently done by means of devices which employ water jets which are directed onto the edges of the layers on the wire in order to separate the most irregular marginal portions from the web. The scrap which is generated by this separation arrangement is collected by ducts, and the material of the scrap is used for additional stock.

Methods and devices used heretofore for trimming or forming the edge of a travelling web have encountered disadvantages. First, they do not allow complete and useful recovery of the scrap material which is derived from the separated edge. This is because the usual edge forming device, which is located a considerable distance downstream of the headbox, separates the marginal portions of the single layer or the multi-layered web in a single operation, and when multiple layers are used, each of the layers normally comprises fibres of a different type and quality. That is, where multiple layer paper is made, one layer may be made of fibres that have unique tear strength, and another layer made of fibres that have unique softness. If the edge from the multiple layers is separated, this mixes the fibres so that they cannot be used to make either layer.It is almost impossible to separate the fibres of the various layers after they have been intermixed and their subsequent use is considerably limited.

Accordingly, an object of the invention is to provide a method and device for adjusting and trimming the edge of one or more continuous layers of paper delivered by headboxes, and which enables the marginal portions of the edges of these layers to be separated while at the same time making it possible to completely reuse the fibres of the scrap stock separated from the edge of the web.

A further object of the invention is to provide a device for trimming the edge of a travelling paper web being formed which can be associated with the headbox and provides for separation at an eariy stage of the formation.

According to the invention, there is provided a method of controlling the edge of a paper web formed on a travelling foraminous wire from stock issuing from a slice opening of a head box comprising the steps of separating the marginal edge of a layer of stock as it leaves the slice opening, and collecting the material of said marginal edge by conveying it into a collector.

The invention also provides a device for controlling the edge of a paper web formed on a travelling foraminous wire from stock issuing from a slice of a headbox comprising blade means positioned to intersect the path of travel of the stock as it leaves the slice opening to be deposited on a travelling foraminous wire and separate an edge from the flow of stock, and means for subsequently removing the separated edge material.

The following is a detailed description of an embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a diagrammatic side view of a device constructed and operated in accordance with the present invention, Figure 2 is a plan view of the device of Figure 1, Figure 3 is a more detailed view of the device of Figure 1 showing a portion of the device substantially enlarged, and Figure 4 is a diagrammatic representation of a part of a papermaking machine wherein a multi-layered web is formed and one of the layers is trimmed.

In a continuous paper web manufacturing apparatus, a continuous foraminous wire 1, Figures 1 and 2, is provided for forming the web and is positioned to receive one or more layers of stock, consisting of fibres in an aqueous suspension, normally wood fibres.

Each layer is delivered through the slice opening 2 of a corresponding headbox 3 to which a suitable quantity of the stock is delivered for continuous flow of stock through the slice opening. The slice opening 2 is positioned above the wire so that the stock leaving the slice opening spouts at a predetermined flow rate and forms a layer 4 of predetermined thickness on the wire, as may be seen in Figure 3.

The device according to the invention includes at least one flat blade 5 disposed in a plane perpendicular to the plane of the wire and in a plane extending in the machine direction which is also essentially perpendicu lar to the plane of the layer of stock leaving the slice opening. The blade has a sharp front edge 6 which is configured so that it makes contact with the front edges 7 of the slice opening, Figure 3, touching both the upper and lower slice lip and the blade may be configured at its leading edge so that it actually projects into the slice opening.

As the layer of stock leaves the slice opening 2, the blade is located in a predetermined position relative to the width of the web so as to be able to separate the marginal edge portion of at least one edge of the layer 4 from the remainder of the web. Two blades 5 will normally be disposed with one on each side of the slice opening 2 in order to separate both lateral marginal portions of the edges of the layer 4 from the remainder of the web.

The device also includes means for conveying the separated marginal portions into suitable containers or to scrap utilisation devices.

These means can comprise an assembly of walls arranged to define actual conduits indicated overall by 8, Figures 1 and 2. These can comprise, for example, lower, upper and side walls 11, 12 and 1 3 respectively, Figure 3, which define a conduit of rectangular crosssection with the lower wall receiving the marginal portion 14 of the layer 4 when this is separated from the remainder of the web.

The blade 5 is conveniently fixed to one of the side walls 1 3 of the conduit as illustrated.

The conduit formed in this manner can open into a collection hopper 15, Figures 1 and 2, arranged to convey the scrap generated, as a result of the separation, into a predetermined zone.

The device also comprises means for transversely adjusting the position of the blade in a cross-machine direction in order to adjust the width of the marginal portion of the edge which is separated from the web. These means can comprise a flat guide 16, Figure 3, fixed to the frame of the headbox 3, and a slide 1 7 slidable on said guide and to which the assembly of walls 11, 1 2 13 and the blade 5 are fixed. The slide 1 7 can be provided with slots 1 8 through which the shanks of locking capscrews 1 9 are inserted. In addition, the wall assembly can be connected to a plate 20, Figure 2, which can be fixed in a predetermined position relatively to a bar 21 by capscrews 22 inserted through slots 23.

In operation, one or more headboxes (two headboxes 30 and 31 being shown in Figure 4) can be disposed along atravelling wire such that, as shown in Figure 4, there are delivered fibre suspension layers 32 and 35 respectively of which the first is deposited directly on the wire 1, and the second is deposited onto the top of the preceding layer.

The edge separating device is located at 34 and is arranged to separate the edge from the second layer. This device is connected to the headbox 31, and a similar device can also be associated with the other head box 30, or alternatively a device may be provided for the headbox 30 and not for the headbox 31.

Production lines may be employed comprising more than two headboxes for generating multi-layer sheets and separating devices such as the device 34 associated with one or more of the head boxes.

In the example illustrated in Figure 4, the layer 35 is deposited by the headbox 31 on top of the layer 32 which is deposited by the headbox 30. As soon as the layer 35 leaves its slice opening, the edges are separated by the actions of blades 5 of the device 34. The edges are shown as the lateral strips 14, Figure 3, leaving the main web in the centre.

The edges comprise irregular marginal portions and the central web has remaining edges which are straight and regular. The removed strips are conveyed through conduits 8 defined by the walls 11, 1 2 and 1 3 to a reutilisation zone and the web is deposited onto the previously formed layer 32.

The web comprising the two layers formed in this manner can pass through a zone 36 in which suitably directed water jets 37 are directed to separate the marginal portions of the first layer in a conventional manner. Thus, if the two layers are formed of diff-erent fibres, the trimmed edges of fibres are maintained separate so that they can be reutilised.

The remaining multi-layered web ham uniform straight edges.

If the first headbox 30 were also provided with a separator device 34, the web comprising the layers 32 and 35, which is formed downstream of the second head box 31, would already be perfectly regular at its edges, and thus it would not be necessary to use the conventional device including the jets 37.

Thus, it is not only possible to obtain perfect regularity of the edge of the resultant web whatever the number of layers which make up the web, but also the fibres of each of the layers, which normally are of different types, are collected separately with the advantage of being able to reuse them in the most suitable manner taking account of their physical and chemical characteristics.

Claims

1. A method of controlling the edge of a paper web formed on a travelling foraminous wire from stock issuing from a slice opening of a head box comprising the steps of separating the marginal edge of a layer of stock as it leaves the slice opening, and collecting the material of said marginal edge by conveying it into a collector.

2. A method according to claim 1, wherein the marginal edge of the layer of stock is separated by a blade located in a predetermined position and adjusted along the emerging width of the layer leaving the slice opening in accordance with the width of the edge to be removed.

3. A method according to claim 1, wherein a first layer is deposited on a travelling wire and a marginal edge of a second layer is separated with the second layer being positioned on the first and the marginal edge separated before the second layer is placed on the first.

4. A device for controlling the edge of a paper web formed on a travelling foraminous wire from stock issuing from a slice of a headbox comprising blade means positioned to intersect the path of travel of the stock as it leaves the slice opening to be deposited on a travelling foraminous wire and separate an edge from the flow of stock, and means for subsequently removing the separated edge material.

5. A device according to claim 4, wherein said blade means comprise a thin blade positioned along the path travelled by the stock as it leaves a slice opening of a headbox with the blade extending parallel to the flow of stock and in a position to intersect the flow of stock and separate one edge from the layer of stock, and wherein conveying means are positioned adjacent the blade location receiving the material of the edge which is separated by the blade.

6. A device according to claim 4 or claim 5, including means for adjusting the blade relative to the slice opening while maintaining the blade in a predetermined cross-machine direction.

7. A device according to any of claims 4 to 6, wherein the conveying means include an assembly of walls arranged to provide conduits for the separated paper web edge.

8. A device according to any of claims 4 to 7, wherein the slice opening is a part of a headbox formed with vertical walls and wherein the blade is mounted on one of said walls.

9. A device according to any of claims 4 to 8, wherein the blade has a shape such that it remains in contact with the front surface of the slice lip defining said slice opening.

10. A device according to any of claims 4 to 9, including means for adjusting the crossmachine direction of the blade to change the width of edge removed from the web to be formed on the wire.

11. A method of controlling the edge of a paper web formed on a travelling foraminous wire substantially as hereinbefore described with reference to the accompanying drawings.

1 2. A device for controlling the edge of a paper web formed on a travelling foraminous wire substantially as hereinbefore described with reference to the accompanying drawings.