GB2044818A - Method and apparatus for producing corrugated combined board - Google Patents

Abstract

The plies of a faced corrugated board are bonded together while still wet from their manufacture. As shown, a first ply is laid on a travelling forming wire 1, and each subsequent ply is formed in close proximity to the travelling forming wire and brought into bonding engagement with the top surface of the previously formed ply on the travelling forming wire. The intermediate web ply 26 is doctored off either its forming roll 6 or a pick-off roll and is allowed to contact the preceding ply 4 in its characteristic corrugated configuration. A spray 27 of adhesive material is introduced onto the first ply 4 before the corrugated ply 26 is brought into contact and another adhesive spray 28 is introduced onto the top surface of the corrugating medium to bond it to the top ply. <IMAGE>

Description

SPECIFICATION Method and apparatus for producing corrugated combined board This invention relates to the production of corrugated combined board. More particularly, it relates to the production of corrugated combined board on a single papermaking machine. Sometimes this type of board is referred to by other names, such as box board, corrugated container board, container board and combined board. Herein, this product will be referred to as corrugated combined board, or box board, but the invention is intended to be applicable generally to the production of any board product having top and bottom liners, or linerboards, and an inner corrugated board, called corrugating medium in the papermaking industry, regardless of the name given to such a product. Typically, this kind of board is used to ship bulky products, such as appliances and furniture.

Traditionally, corrugated combined board has been manufactured by producing each of the layers separately on different papermaking machines and then producing the composite board by bringing all of the layers together on another machine and causing them to be adhesively bonded together. Indeed, in the papermaking industry, the inner corrugated layer for use in box board is a commercial product which is manufactured exclusively on some papermaking machines in some mills.

This "corrugating medium", as it is known in the trade, is produced in continuous sheets or webs and wound into rolls after it has been dried. The corrugations are then formed in the sheets by other machinery before the corrugating medium and top and bottom linerboards are brought together to form the box board.

Since box board is almost always comprised of three plies of layers it now takes several machines to produce all of the layers as well as additional machines to corrugate the inner layer and glue the several layers together to form the box board. Even if all of the layers were somehow produced on a single paper making machine, the overall production of box board would be reduced by one-third since each layer would have to be produced one at a time. In addition, each of the separate layers has to be dried separately which requires a considerable commitment in capital expenditure for drying apparatus as well as energy to dry the layers.

This invention obviates the aforementioned problems by forming all of the layers continuously, simultaneously and sequentially on a single papermaking machine. This is accomplished by laying and dewatering the individual board webs separately so that they are sufficiently formed to enable them to be adhesively secured to one another or to have corrugations formed in them, in the case of the corrugated inner layer, without falling apart.

According to the invention there is provided apparatus for the continuous production of multi-ply corrugated combined board, having at least a bottom linerboard and a top linerboard with an intermediate corrugating medium, from corresponding slurries of aqueous pulp fibre stock, the apparatus comprising: a looped foraminous forming wire for travelling and receiving an aqueous slurry or pulp fibres to form a bottom linerboard thereon; means for supplying an aqueous slurry of pulp fibres to the foraminous forming wire; means for forming a corrugating medium from a dilute aqueous slurry of pulp fibres, said means including a first foraminous surface for travelling, a former for supplying the aqueous slurry of pulp fibres to the first foraminous surface and means for removing the water from the slurry of pulp fibres to form the corrugating medium on the first foraminous surface; means for receiving the corrugating medium travelling on the first foraminous surface and producing corrugations therein, said means for producing the corrugations being disposed relative to the forming wire such that the travelling corrugating medium is thereafter brought into contact with the bottom linerboard; means for forming a top linerboard from a dilute aqueous slurry of pulp fibres, said means including a second foraminous surface for travelling, a former for supplying the aqueous slurry of pulp fibres to the second foraminous surface and means for removing the water from the slurry of pulp fibres to form the top linerboard on the second foraminous surface which is disposed to urge the top linerboard into contact with the corrugating medium web; and means for bonding the corrugating medium to the top and bottom linerboards to thereby form the corrugated combined board on the forming wire.

The invention also provides a method for the continuous production of a multi-ply corrugated combined board, having at least a bottom linerboard and a top linerboard with an intermediate corrugating medium, from corresponding slurries of aqueous pulp fibre stock, the method comprising the steps of: forming a bottom linerboard and conveying it upon a travelling foraminous forming wire; discharging an aqueous fibre slurry of corrugating medium stock upon a first travelling foraminous surface and dewatering the stock thereon to form the corrugating medium; removing the corrugating medium from the first foraminous surface and forming corrugations therein whereby said corrugated corrugating medium is formed at a speed substantially equal to the linear speed of the bottom linerboard on the foraminous forming wire; bonding the corrugating medium to the bottom linerboard; discharging an aqueous slurry of top linerboard stock upon a second travelling foraminous surface and dewatering the stock thereon to form the top linerboard; and bonding the top linerboard to the corrugating medium to thereby form the corrugated combined board on the forming wire.

In the manufacture of composite, multi-ply paper board products, it is important that the individual plies be of approximately the same moisture content. This is true regardless of whether the layers are bonded with an adhesive or ply bonded by the moisture in the adjacent webs. In ply bonding, the most effective bond is produced when both bonded layers have approximately the same moisture content at the lowest consistency while the webs are wet but capable of maintaining their integrity. Such a moisture level might range from about 6% bone dry to about 16% bone dry, depending on the type of forming equipment, machine speed and pulp stock used.

In this invention, each of the web plies may be separately laid, dewatered and formed in the same general area of a single papermaking machine. Accordingly, the moisture content of each web- play can be controlled so that all the webs will have approximately the same moisture content. In a preferred embodiment of the invention, the ply which is ta be the intermediate, or corrugating medium, ply is doctored off either its forming roll or a pickoff roll to form the characteristic flutes or corrugations. The first web formed is the bottom liner which is laid onto a travelling foraminous screen, such as a horizontally arra- yed fourdrinier wire. The forms producing the corrugating medium and top liner plies, respectively, are mounted above the fourdrinier wire one after the other.They are roll formers that dewater the web to the desired consistency in the 6% bone dry to about 16% bone dry (84% moisture) range. The corrugating medium is then doctored off and guided onto the bottom liner which is passing beneath on the fourdrinier wire. The next former is a roll former essentially identical to the former producing the corrugating medium and in turn places the top liner onto the corrugating medium. In the preferred embodiment, a spray of adhesive solution is applied to both the bottom liner and corrugating medium plies before the next ply is brought into contact with them in order to bond the plies into the composite corrugated combined board.

The moisture in the webs also helps bond the plies together by a phenomenon known as "ply-bonding" wherein the fibrils of the pulp fibres in one ply are attracted to the fibrils of the pulp fibres in the contiguous ply to cause the plies to bond together in much the same way that the individual fibres within a single ply, or web, comingle ta form the individual ply itself.

The composite board is then passed out of the forming section and into a dryer of conventional design. All plies are produced at the same time so that no warehouse storage is required for any previously made plies pending their being brought together on another machine to manufacture the corrugated combined board.

The following is a description of various embodiments of the invention, reference being made to the accompanying drawings in which: Figure 1 is a side elevational view of apparatus according to the invention, showing the bottom liner, corrugated, and top liner layers being formed and combined to produce box board, Figure 2 is a partial sectional view of the forming roll shell used in the corrugating medium and top liner formers shown in Fig.

1, and Figure 3 is a side elevational view of apparatus similar to Fig. 1 except that the corrugating medium is creped off an intermediate pick-off roll.

As shown in Fig. 1, a looped forming wire 1, such as is used commonly on a fourdriniertype papermaking machine, is shown travelling in the direction of arrow 22. A first water laid web 4 of fibres is formed and supported on top of the wire 1 from pulp fibre slurry discharged from a headbox 40, and is carried on the wire 1 in the same direction at the same speed. The headbox 40 and equipment, such as a breast roll 41, a couch roll 43 and a motor 42, for moving and guiding the fourdrinier forming wire 1 and depositing the first web 4 onto the forming wire, may take any one of several forms, all of them well known to those skilled in the art in the papermaking industry. As such, they are not shown in detail and will not be described in further detail. Web 4, which will become the bottom liner of the box board, is formed on the wire 1 as the water drains through.An hydraulic former 5 is mounted in position above the travelling forming wire 1 in such a manner that its forming roll 6 rotates in the direction of arrow 23 about a horizontal axis which is parallel to the plane of the travelling forming wire 1. The forming roll 6 is spaced above the surface of the travelling web 4. A supply header 7 supplies an aqueous slurry of stock fibres to a slice 14 which projects a thin stream of comingled fibres and water onto the surface of a foraminous element 11, such as a plastics or metal screen or fabric, which in turn is looped about the periphery of the cylindrical shell 9 of the forming roll 6, which shell has perforations 10 uniformly positioned over its operating surface to remove water from the newly laid layer of corrugating medium 8 and pass it into the interior of the forming roll. This is shown more clearly in Fig. 2. The foraminous fabric 11 is shown looped about the forming roll 6 and separate therefrom, but it could also be part of the integral construction of the roll 6 surface itself.

Beneath the inner peripheral surface of the forming roll shell 9 are three vacuum, or suction, boxes 15, 1 6 and 1 7. The suction in box 1 5 is less than in box 1 6 which in turn has a greater suction than box 1 7. Naturally, the aqueous slurry of board stock contains the most water at the point where it leaves the slice opening which extends arcuately over the forming roll surface, immediately above the suction box 15, and also extends across the width of the machine in the cross machine direction.The suction boxes 15, 1 6 and 1 7 similarly extend for substantially the entire length of the roll shell beneath the perforations 10 so as to remove the water for the entire width of the formed web 8 of corrugating medium.

Corrugating medium is usually made from chemical or semi-chemical wood pulps, straw or reclaimed paper stock in nominal grade weights of about 26 lbs/1000 ft2 and approximately 9 points thickness, although heavier weights are sometimes used. Most of the water is removed from the stock, to form the corrugating medium, over the suction boxes 1 5 and 1 6. Since the pulp board stock contains the most water when it is initially discharged from the slice opening onto the foraminous fabric 11 over the cylindrical forming roll, the vacuum in the first suction box 1 5 need not be great to effect substantial water removal and formation of the web on fabric 11. The web forms quite rapidly since board pulp stock is of a fairly high consistency (i.e.

about 1%-1.2% fibres for corrugating medium and about 0.5% fibres for liner, both by weight of fibres to weight of mix (wet basis)). The suction in the middle suction box 1 6 is higher in order to withdraw more of the remaining water through the resistance of the already formed board web. At the point where the web has reached the lower sector on the forming roll, the web has been dewatered to about 10%-16% bone dry and the suction in the last suction box 1 7 does not remove any appreciable amount of water, but is maintained at a lower level primarily to offset the centrifugal force on the web to hold it into position on the forming fabric 11.As the web reaches the region of the lower periphery of the forming roll 6, a doctor 18, which is bearing against the foraminous fabric 11, intercepts the newly formed web 8 along a line 26p and produces the corrugations 30 in the web which characterise corrugating medium.

The rotational speed of the forming roll 6 is such that the linear surface speed of the web 8 is greater than the linear surface speed of the bottom web 4 being carried on the forming wire 1. Thus, when the corrugations are produced in the web 8 by the doctor 18, there is enough web material to permit the formation of the corrugations in the web as well as a slight drape 26 between the location 26p on the forming roll where the doctor contacts the web and where the corrugated web falls into contact with the bottom web 4 at 26a.

In the preferred embodiment, the corrugating medium is adhesively secured to the bottom liner 4 and the top liner 1 9 which is produced on a second former 5'. This adhesive may be any suitable glue, such as latex or modified starch, and is applied by a spray from nozzles 27 and 28. As the corrugating medium 26 falls upon the adhesive on the bottom liner 4, the tips of the corrugations become adhered thereto. However, it should be noted that the bonding between the corrugating medium and the top and bottom liners is partly achieved without an adhesive under certain conditions. Such bonding is known in the paper trade as "ply-bonding" and is most likely to occur when the adjacent component webs have about the same moisture content and are more wet that dry. Also, it is best when the adjacent webs are of about the same stock composition.The fibrils of the still wet fibres on the adjacent webs comingle when the webs are pressed together and this effects a ply-bond. Essentially, the fibres in the adjacent webs cause the webs to combine in the same manner in which the fibres in a single web hold it together.

In both Figs. 1 and 3, the second, or downstream, former is identical to the former producing the corrugating medium. Therefore, the numerals referring to like components, items and features are designated with the same numerals as the former producing the corrugating medium, but the numerals are primed in order to designate the particular former being referred to. Further, in the embodiment shown in Fig. 3, the numerals referring to like compoments, items and features also have a subscript "a" for the same reason. The formers themselves in Figs. 1 and 3 are designated with separate numerals.

The downstream former 5', in the Fig. 1 arrangement, produces a top liner web 1 9 on a forming roll 6' which rotates in the direction of arrow 23' at a linear surface speed matching the linear speed of the bottom liner 4. The former 5' is mounted to bear against and deform the forming wire 1, bottom liner 4 and corrugating medium 26 downwardly over a portion of its arcuate surface between two guide rolls 2, 3 over which the forming wire and layers 4 and 26 pass as the upper liner 1 9 is pressed onto the upper flutes of the corrugating medium 26, which have been coated by the spray of adhesive from the nozzle 28. This positively effects adhesion between the top and bottom liners 19, 4, respectively, and the corrugating medium 26.

Although the plies are bonded together under the combined effect of the adhesive and the moisture in the plies themselves, the moisture will have the predominant bonding effect between the bottom liner and the corrugating medium while the adhesive will have the predominant bonding effect between the cor gating medium and the top liner. A suction box 20 is mounted beneath the forming wire 1 after the last guide roll 3 to ensure that the composite web remains an the forming wire for transfer into the drying section of the papermaking machine.The remainder of the papermaking machine downstrearh of the last former 5', which in this case consists primarily af drying, reeling and slitting apparatus, are of a design and configuration which are well known in the papermaking industry, as are their operationsl characteristics. Such apparatus forms no part of the present invention and, accordingly, will not be discussed in further detail.

A variation of the embodiment shown in Fig. 1 is illustrated in Fig. 3. The former 34 shown in Fig. 3 is identical -to the former 5 shown in Fig. 1 except that it is-turned aroundgso that its forming r.oll 6a rotates in a direction 32 opposite to that of the forming roll 6 on the former 5 shown in Fig. 1. The only operational difference between the formers 34.and 5 is the presence of a pick-off roll 25 on the former 34 which is mounted to nip against the corrugating medium web over the lower.portion of the forming roll 6a.sur- face, to pick-off the web 8a and reverse its direction so that it travels in the samedirec- tion as the bottom-liner 4.A doctor 1-fRa bears against the surface of-the -.pick-off.roll 2:5 to form the corrugations in the web 8a.along a line 26pabefore the web falls into contact with the travelling bottom liner 4.at 26aa.

The advantage of the use of the pick-off roll 25 is that the doctor then bears against its smooth, continuous cylindrical surface and does not touch the foraminous forming fabric 11 a as the doctor does on former 5 in Fig. 1.

This prevents wearing or tearing of the forming fabric.

In both of the embodiments shown in Figs.

1 and 3, the formation -of the webs in formers 34, 34' and 5, 5', respectively, is the same.

Also the same in both embodiments is the manner in which the adhesive is applied to the bottom liner and corrugating medium to effect bonding between the corrugating medium and the bottom and top liners to form the corrugated combined board. Either embodiment can be expected to produce this board at speeds of about 300 fpm to about 1 200 fpm. The moisture level in the bottom linerboard will range from about 88% to about 94%; the moisture level in the corrugating medium will range from about 84% to about 88%; and the moisture level in the top linerboard from about 86% to about 90%.

Clearly, this invention can be utilised to make more than three ply board. Merely by adding another corrugating medium former after the last liner former and then another liner former, a five ply corrugated combined board can be made.

Claims (14)

1. Apparatus for the continuous production of multi-ply corrugated combined board, having at least a bottom linerboard and a top linerboard with an intermediate corrugating medium, from corresponding slurries of aqueous pulp fibre stock, the apparatus comprising: a looped foraminous forming wire for travelling and receiving an aqueous slurry of pulp fibres to form a bottom linerboard thereon; means for supplying an aqueous slurry of pulp fibres to the foraminous forming wire; means for forming a corrugating medium from a dilute aqueous slurry of pulp fibres, said means including a first foraminous surface for travelling, a former for supplying the aqueous slurry of pulp fibres to the first foraminous surface and means for removing the water from the slurry of pulp fibres to form the corrugating medium on the first foraminous surface; means for receiving the corrugating medium travelling on the first foraminous surface and producing corrugations therein, said means for producing the corrugations being disposed relative to the forming wire such that the travelling corrugating medium is thereafter brought into contact with the bottom linerboard; means for forming a top linerboard from a dilute aqueous slurry of pulp fibres, said means including a second foraminous surface for travelling, a former for supplying the aqueous slurry of pulp fibres to the second foraminous surface and means for removing the water from the slurry of pulp fibres to form the top linerboard on the second foraminous surface which is disposed to urge the top linerboard into contact with the corrugating medium web; and means for bonding the corrugating medium to the top and bottom linerboards to thereby form the corrugated combined board on the forming wire.

2. The apparatus according to claim 1, wherein said first foraminous surface travels at a linear speed which is faster than the linear speed of the forming wire whereby the corrugated corrugating medium is travelling at the same speed as the bottom linerboard when they come into contact.

3. The apparatus according to claim 1 or claim 2, wherein at least one of said first or second foraminous surfaces include a separate foraminous fabric and a forming roll having a foraminous surface for receiving water from the aqueous slurry of pulp fibres to form the web thereon, said foraminous fabric being looped about the forming roll.

4. The apparatus according to any of claims 1 to 3, wherein said means for bonding the corrugating medium to the top and bottom linerboards include at least one nozzle for applying adhesive spray to the bottom linerboard and the corrugating medium whereby the corrugating medium web is adhesively secured to the top and bottom linerboards.

5. The apparatus according to any of claims 1 to 4, wherein said means for forming the corrugating medium and said means for forming the top linerboard each comprise a looped foraminous fabric and a rotatable forming roll having a foraminous surface disposed within the looped fabric, and a suction box within the forming roll for urging water from the aqueous slurry and through the fabric and roll surface to form the corrugating medium and top linerboard respectively on the foraminous fabrics.

6. The apparatus according to any of claims 1 to 5, wherein the means for receiving the corrugating medium comprise a doctor which bears against the travelling first foraminous surface to produce the corrugations in the corrugating medium.

7. The apparatus according to claim 6, further including a pick-off roll mounted in nipping engagement with the first travelling foraminous surface to thereby receive the corrugating medium, said doctor engaging the corrugating medium on the surface of the pick-off roll thereby to form the corrugations in the corrugating medium.

8. Apparatus according to claim 1, wherein said means for forming a corrugating medium comprise: (a) a rotatably mounted forming roll having a foraminous surface for receiving water therethrough, (b) a foraminous fabric, constituting said first foraminous surface, looped about the forming roll, (c) a pulp stock header and slice for supply ing a uniform aqueous dispersion of pulp fibres to the surface of the forami nous fabric to form the corrugating medium thereon, (d) at least one suction box operably posi tioned within the forming roll for urging water from the aqueous pulp slurry through the fabric and forming roll sur face to assist formation of the corrugat ing medium, (e) means for rotating the foraminous fabric so that the linear speed of the corrugat ing medium formed thereon is faster than the linear speed of the bottom linerboard on the forming wire; wherein said means for receiving the corrugating medium comprise a doctor for intercepting the corrugating medium and producing corrugations therein so that the corrugated corrugating medium travelling beyond the doctor travels at substantially the same linear speed as the bottom linerboard, said doctor being disposed relative to the corrugating medium former so that the corrugated corrugating medium falls upon the bottom linerboard; wherein said means for forming a top linerboard comprise: (a) a rotatably mounted forming roll having a foraminous surface for receiving water therethrough, (b) a foraminous fabric, constituting said second foraminous surface, looped about the forming roll, (c) a pulp stock header and slice for supply ing a uniform aqueous dispersion of pulp fibres to the surface of the forami nous fabric to form the top linerboard thereon, (d) at least one suction box operably posi tioned within the forming roll for urging water from the aqueous pulp slurry through the fabric and forming roll sur face to assist formation of the liner board, (e) means for rotating the foraminous fab ric, said foraminous fabric being urged against the corrugating medium on the bottom linerboard on the forming wire; and wherein said means for bonding the corrugating medium to the top and bottom linerboard comprise at least one spray nozzle operably disposed above both the bottom linerboard and corrugating medium for spraying an adhesive onto their surfaces whereby the corrugating medium is bonded to both the top and bottom linerboards thereby to form the corrugated combined board on the forming wire.

9. A method for the continuous production of a multi-ply corrugated combined board, having at least a bottom linerboard and a top linerboard with an intermediate corrugating medium, from corresponding slurries of aqueous pulp fibre stock, the method comprising the steps of: forming a bottom linerboard and conveying it upon a travelling foraminous forming wire; discharging an aqueous fibre slurry of corrugating medium stock upon a first travelling foraminous surface and dewatering the stock thereon to form the corrugating medium; removing the corrugating medium from the first foraminous surface and forming corrugations therein whereby said corrugated corrugating medium is formed at a speed substantially equal to the linear speed of the bottom linerboard on the foraminous forming wire; bonding the corrugating medium to the bottom linerboard; discharging an aqueous slurry of top linerboard stock upon a second travelling foraminous surface and dewatering the stock thereon to form the top linerboard; and bonding the top linerboard to the corrugating medium to thereby form the corrugated combined board on the forming wire.

1 0. The method according to claim 9, wherein the corrugating medium is formed on the first travelling foraminous surface at a linear speed which is faster than the linear speed of the bottom linerboard travelling on the forming wire.

11. The method according to claim 9 or claim 10, further including the step of receiving the corrugating medium from the first travelling foraminous surface on which it is formed and transferring the corrugating medium onto a separate travelling surface from which it is doctored to form the corrugations therein.

12. The method according to any of claims 9 to 11, wherein the bonding of the top and bottom linerboards to the corrugating medium includes the step of spraying an adhesive between the bottom linerboard and corrugating medium and between the top linerboard an.d corrugating medium to effect bonding therebetween.

1 3. The method according to any of claims 9 to 12, wherein the bottom linerboard, corrugating medium and top linerhoard are all dewatered to approximately the same dryness before being bonded together to form the composite corrugated combined board.

14. The method according to claim 13, wherein the moisture level of the webs ranges from about 84% to about 94%.

1 5. Apparatus for the continuous production of multi-ply corrugated combined board substantially as hereinbefore described w.ith reference to Figs.81 and 2, or Figs 2 and 3, of the accompanying drawings.

1 6. A method for the continuous production of multi-ply corrugated com.bined board substantially as hereinbefore described with reference to Figs. 1 and 2, or Figs 2 and 3, of the accompanying drawings.