US3493463A - Process and apparatus for forming a high strength band along the length of a paper web - Google Patents

Description

Feb. 3, 1970 a -R 7 3,493,463

P-RocEss AND APPARATUS FOR FORMING A HIGH STRENGTH BAND ALONG THE LENGTH OF A PAPER WEB Filed May L0, 1966 2 Sheets-Sheet l m V LI 8 m Q/ |"\r CD N 56 i s LL l a I i IGH STRENGTH P R WEB 2 Sheets-Sheet 2 Feb. 3, 1970 o. B. BAKER AND APPARATUS FOR PO NG PROCESS BAND ALONG THE LENGTH A Filed May 10, 1966 United States Patent 3,4ii3,463 PROCESS AND APPARATUS FOR FORMING A HIGH STRENGTH BAND ALONG THE LENGTH OF A PAPER WEB Donald B. Baker, Foxboro, Mass, assignor to Bird Machine Company, South Walpole, Mass, a corporation of Massachusetts Filed May 10, 1966, Ser. No. 548,921 Int. Cl. D21h /02; D21f 1/06 US. Cl. 162109 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to papermaking, and in particular to the problems arising from the susceptibility of paper webs or sheets to breakage. In high speed papermaking, to mention only one example, a break in the traveling web is a very serious and costly event.

A principal object of the invention is to improve papermaking to decrease the problems of breakage. A particular object is to provide a simple and inexpensive means of decreasing breakage problems in the initial stages of the papermaking operation, while another object is to decrease breakage problems which occur in the later stages of manufacture and use of the paper. Another particular object is to provide improved paper products.

According to the invention it is realized that means can be provided for confining the introduction of strengthened paper stock or strength additives to the stock to selected narrow regions of the head box before the stock reaches the forming surface, and that the breakage characteristics of the paper can be greatly improved by the appropriate location of such narrow regions, despite the absence of the special stock from most of the body of the paper.

Because a relatively small amount of the more expensive stock is required (which, in important instances can be reused) the invention is applicable to the making of low grade papers such as newsprint, catalogue grad and coated stock.

The invention has particular importance to the problem of breakage of the web at the point of removal from the forming wire. For this purpose there is introduced a narrow band of additive material of sufiicient width to extend from the formed or deckle edge inwardly beyond the line of action of the deckle edge trim squirt or cutter. Accordingly, when the deckle edge is removed, the margin of the web will still contain additive material such as faster drying or reinforcing fibers which ensure that the freshly-laid web can be separated from the wire at the couch roll, and transferred to the following equipment. After the main body is dried, and thus strengthened, it is possible to trim off the remainder of the band, reprocess it, and use it again, either as part of the make-up for the main body or for the edge region.

It is contemplated, however, that at least a portion of the strengthened edge will be preserved in the finished web, where it will lessen tear problems in subsequent operations, such as in running the web through printing presses. Indeed, it is appreciated that, in its broadest aspect, the invention is applicable to the strengthening of 3,493,463 Patented Feb. 3, 1970 edges of newsprint rolls and the like formed from center portions of the web. In this instance the web from the paper machine is taken up on a reel. Later it is rewound while passing through a slitting device to form two or more rolls. According to this aspect of the invention the means introducing the narrow band of additive material at the head box is aligned with the line of action of the slitter, so that additive material is present on both sides of the slit line, to strengthen the margins of the two freshly-cut edges.

According to another aspect of the invention, to achieve undisruptive introduction of the additive material or strengthened stock to the head box, the material should be introduced as a fiuid suspension through an opening of predetermined width in the head box. Advantageously this opening takes the form of a submerged opening into the head box connected to a supply of additive fluid, or it advantageously takes the form of a supply pipe which supplied the entire stock demand for a given narrow width of the web, this stock being of greater strength qualities than the stock supply for the major portion of the web. When a bafiie device is employed in the main body flow of the head box to assist in establishing a boundary, it should be specially constructed and arranged to provide an undisruptive profile in the flow direction, and terminate in advance of the slice outlet, to prevent the formation of a discontinuity in the formed web.

Advantageously, where it is necessary to limit the width-wise spread of additive material or strengthe ed stock, the point of mergence is located close to the slice, in a region of convergence of the stock as it approaches the slice. Advantageously the additive material is caused to be mixed throughout the depth of the stock by the time it reaches the forming wire.

It is contemplated that additive material or strengthened stock can be introduced into otherwise conventional head box arrangements of the various known types, with little structural modification being required, and with the desirable feature of adjustability, to conform to various needs in the papermaking operation.

These and other objects and features will be understood from the following description and with reference to the drawings wherein:

FIG. 1 is a perspective view of a paper machine incorporating a preferred embodiment of a narrow band fiow device;

FIG. 2 is a rear view of the head box of FIG. 1 taken on lines 2-2;

FIG. 3 is a cross-sectional view of the head box of FIG. 1 taken on lines 33, on an enlarged scale;

FIG. 3a is a cross-sectional view of the baflle taken on lines 3a3a of FIG. 3;

FIGS. 4 and 5 are rear and cross-sectional side views, respectively, of another embodiment.

The invention will now be described in detail.

It is appreciated that edge regions or margins of paper webs or sheets having a local increase in strength quality relative to the main body of the paper result in considerable decrease in breakage problems because stresses which produce breakage usually concentrate in these regions, and the possibility of load-sharing in opposite widthwise directions, which is present in the main body of a web, is not present in the edge regions.

Referring to the drawings head box 10 having inlet means 12 produces a flow of stock through slice 14 onto forming wire 16 of a Fourdrinier paper machine. Preceding the couch roll 18 the deckle edge D of the formed web W is cut away by a high presure jet of liquid from nozzle 22, known as a trim squirt.

At the couch roll the web, with trimmed edge E, leaves the wire under the influence of tension T.

According to the invention a narrow band fiow device is provided to impart to the formed web W an integral strengthened band B of for example 3 inches width. Band B extends inwardly beyond line L, the line of action of the trim squirt and accordingly a margin M of strengthened material defines edge E, and resists breakage of the web as it leaves the wire.

The trimmed-off deckle edge D, which, for example may be one inch in width, continues around the couch roll 18 and is removed from the wire 16 with a spray into pit 24, from which it is removed to a reprocessing device, thence, as indicated by dotted lines, is reused as a strengthening material in the formation of the Web.

The Web proceeds from the couch roll 18 through the press and dryer sections, not shown, and then moves through a slitter 26 at which a further portion P, for example of one inch width, is trimmed off to produce the finished edge of the web. Advantageously strengthened band B extends inwardly of line of action L of the slitter 26, thus leaving a margin M on the web, for example of one inch width, to provide strength for further processing and use of the web.

In this embodiment the narrow band flow device comprises a special feed conduit 30 and a bafiie 32 which defines an inlet zone for the strengthening material closely adjacent to, but spaced from the slice 14. In the embodiment shown the bafiie comprises a vertical sheet member resting upon the bottom and forward wall of the head 'box, and defines with the end wall of the head box a slotform passage. Stock supplied to the head box through inlet 12 passes into the band-forming region between the baffie and end Wall and proceeds to the forming surface. Additional stock, containing material having increased strength potential relative to the stock of inlet 12 is also introduced to the band-forming region, advantageously with the opening 31 of feed conduit 30 located in the floor 11 of the head box, submerged relative to stock in the head box, and directed forwardly as shown, so that the entering flow has a substantial component in the direction of the slice.

In this embodiment it is advantageous to locate the bafiie 32 inwardly of line L as shown, to ensure that the band B is of suflicient width. The forward edge 33 of the baffle is advantageously very narrow, see FIG. 3a, and is spaced rearwardly from the slice to avoid disruption of the flow at the slice and to ensure that the strengthened bank B is integral with the main body of the web. The leading edge 35 of the baflie is rounded and the bafiie as a whole presents a streamlined profile, see FIG. 3a.

The opening 31 of feed 30 is located near the rearward edge of the bafiie, so that there is an opportunity of mixing throughout the depth and alignment of the flow along the extent of the baflie, so that the strengthening material will be found throughout the width and depth of the band B when it reaches the forming wire.

It is contemplated that the location and size of the opening 31 and the location of the battles may be made adjustable for those machines which make paper to various specifications. Likewise it is contemplated that a pair of these bafiles, suitably spaced apart, and combined with a suitable supply 30, may 'be located in the head box at the center-line or other region where a band of strengthened material is desired.

It will be appreciated that the flow device may take various forms, depending upon the quality of the web desired and the particular construction of the head box. In some situations it is contemplated that the strengthening material can be introduced along the upper wall of the slice, or through an inlet located between the upper and lower Walls. In other situations it is contemplated that the baffie may be omitted, relying upon the directional capability of the special feed pipe, and its proximity to the slice, to confine the strengthening material to the desired band width.

It is also contemplated that the special feed can be introduced within a rectifier roll located closely adjacent the slice, with suitable confining bafiies.

Referring to FIGS. 4 and 5, in this embodiment the head box supply is formed by a substantial number of parallel feed pipes 120. They may be provided with spreader sections in their outlet region, to form a head box, or the more conventional head box as shown may be employed. For the introduction of the special strengthening material a means, illustrated by strengthening material pipe 130, is provided to cause the flow in selected pipes 120a to have the desired increased strength properties, these selected pipes being aligned with the desired lines for the formed web.

Whatever specific details are employed, it is advantageous that the supply opening be submerged, and that no opportunity he presented for the entry or entrainment of air.

It is important also that the flow device be constructed and arranged so that the strengthening material is introduced in a hydraulically undisruptive manner, i.e. with flow direction having a substantial component in the direction of the slice and with any objects in the fiow path having narrow or streamlined form to permit smooth fiow thereby.

The invention is contemplated to be of particular importance to the production of newsprint and the like, in which the main body is made up for instance of ground wood and 20% sulphite, and a flow of sulphite fiber slurry is added by the flow device to make the band contain a substantially higher percentage of sulphite stock, for example as much as 50%. It will be understood that such stock not only adds strength due to the substantially longer length of the fibers; also because of the lower amount of fines, the overall band dries more quickly and is therefore in a dryer, hence stronger, condition at the couch roll.

In the case of such papers, the trimmed off edge margins, containing e.g. 50% sulphite fibers, may be reprocessed and employed as part of the sulphite constituent of the main feed. By this means, operation according to the invention requires little increase in the cost of the pulp.

While the additive material should be different from the main body of the web, the difference may take numerous forms. Thus in certain processes, the main reason for breakage may be the presence of shives in the stock, and the strengthening material may be quantities of the same stock which have been subjected to an extra screening process for the removal of the shives.

The invention is also contemplated to be of use with other papermaking procedures, e.g. the production of nonwoven fabrics in which the strengthening substance may comprise synthetic materials or fibers.

While the invention may be advantageously employed to produce narrow bands, in some instances bands of substantial width may be formed, or hands in which there is a gradual variation in the Widthwise direction in the various fiber content.

The paper product, as it emerges from slitter 26, FIG. 1, with the margin M comprising an integral strengthened band relative to the main body of the web, has many desirable uses. For example, if the web is bag stock, the margin M may be employed to define the edge of the bag opening, the place Where many bags are torn. Similarly, in the case of insulating butts for building construction, having paper margins which are nailed to the studding, reinforcement of the margins according to the invention will reduce the tendency to tear at the nail holes.

What is claimed is:

1. A papermaking process comprising the steps of:

directing a main stock flow from a headbox onto a moving forming surface;

directing a second stock flow through a path of confined Width, said second stock flow having strengthgiving properties greater than that of said main stock flow;

laterally merging said second stock flow with said main stock flow to form on said forming surface a web including an integral band of substantially greater strength properties than the major portions of said web; and

thereafter slitting said web along said band to provide on at least one side of the line of slitting a web product having an integral strengthened edge. 2. In papermaking in which a web is formed by depositing stock on a moving forming surface, the process comprising the steps of:

merging integrally with the flow of main stock to be deposited on said forming surface a flow of predetermined width of second stock having substantially greater strength potential than said main stock; and,

depositing said merged main and second stocks on said moving forming surface to form as an integral part of said web a band of said predetermined width having substantially greater strength properties than the major portion of said web and extending substantially parallel to the direction of movement of said forming surface.

3. The steps of claim 2 wherein said main stock is formed of fibrous paper stock comprising more than 50% ground wood fiber, and said second stock consists of a paper stock having a substantially greater quantity of non-ground wood substance than said main stock.

4. The steps of claim 2 wherein said main stock is formed of a given paper stock and said second stock consists of a paper stock produced by subjecting a portion of said given paper stock to an additional cleaning step for removal of shives.

5. In apparatus for forming a web comprising a headbox, means for supplying a main fiow of stock to said headbox, a slice, and a forming surface, the headbox being constructed and arranged to discharge said stock through said slice in a forming region to form a web on said forming surface, and means for severing the web along a line parallel to the direction of longitudinal extent of the web, that improvement comprising, in combination:

band forming means located in said forming region,

said band forming means including means for supplying stock having substantially greater strength potential than said main flow of said stock to a flow directing means, and said flow directing means positioned and constructed to introduce said stock of greater strength potential as an integral part of the flow of stock onto said forming surface, whereby said band forming means forms in the resulting web a band of increased strength relative to the main body of said web, extending substantially parallel to the direction of longitudinal extent of said web; and said means for severing said web along a line parallel to said direction of longitudinal extent of said web being positioned to sever said web within the boundaries of said band to provide a web edge margin of greater strength than the major portion of said web.

6. The apparatus of claim 5 wherein said means for severing said web includes deckle-edge trim apparatus mounted adjacent said forming surface with its line of action substantially parallel to the direction of movement of said forming surface and aligned between the inner and outer extremities of the effective action of said flow directing means whereby the resulting web can include a substantial portion of the width of said band lying inwardly of said line of action which can serve to strengthen said web when it is removed from said forming surface.

7. The apparatus of claim 5 wherein said means for severing said web includes a slitter located separate from said forming surface for slitting said web after it has been formed, said slitter being mounted with its line of action substantially parallel to the direction of longitudinal extent of and within the boundaries of said band.

8. The apparatus of claim 5 wherein said flow directing means comprises a baffle means within said headbox, preceding the slice, and defining a passage for said stock of greater strength potential separate from the main flow as the fluid approaches said slice.

9. The apparatus of claim 5 wherein said means for supplying stock includes a means for injecting into a narrow region of flow through said head box a strengthening substance, said means for injecting located in a region submerged with respect to said head box flow.

References Cited UNITED STATES PATENTS 1,909,150 5/1933 Bell-Irving et al. 162343 X 2,693,415 11/1954 Schur. 3,053,727 9/1962 Adomshick et al. 162-109 X S. LEON BASHORE, Primary Examiner R. D. BAJEFSKY, Assistant Examiner US. Cl. X.R.

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