Method and apparatus for manufacturing corrugated paperboard

Abstract

A method for manufacturing corrugated paperboard is disclosed. The method comprises: directing a corrugating medium from a corrugating medium supply roll to a pair of corrugating rolls; and operating the pair of corrugating rolls to corrugate the corrugating medium; wherein each corrugating roll is operated at ambient temperature; and wherein the step of operating the pair of corrugating rolls to corrugate the corrugating medium comprises forming a fluted web in which the corrugating medium substantially conforms around a plurality of corrugator peaks and is spaced from a plurality of corrugator troughs in at least one of the pair of corrugating rolls.

Claims

1. A method for manufacturing corrugated paperboard, the method comprising: directing an unheated corrugating medium from a corrugating medium supply roll to a pair of corrugating rolls comprising a first corrugating roll and a second corrugating roll; operating the pair of corrugating rolls to corrugate the unheated corrugating medium; employing a vacuum system to retain the unheated corrugating medium, when corrugated into a fluted web, on the second corrugating roll for a predefined part of a revolution; and bonding a first liner to a first side of the fluted web to form a single-faced web whilst the fluted web is retained on the second corrugating roll by the vacuum system; wherein each corrugating roll is operated at ambient temperature; wherein manufacturing the corrugated paperboard is without the use of a heat source, at least up to and including formation of corrugations in the unheated corrugating medium; wherein a diameter of the first corrugating roll is at least 20% less than a diameter of the second corrugating roll; and wherein the vacuum system holds the flutes of the fluted web in place, against resilient forces urging the unheated corrugating medium to spring back to a flat configuration, at least from formation of the fluted web until the first liner is bonded to the fluted web.

2. The method of claim 1 wherein the step of operating the pair of corrugating rolls comprises spacing the pair of corrugating rolls and/or applying pressure such that corrugator peaks of the first corrugating roll are spaced from corrugator troughs of the second corrugating roll when the pair of corrugating rolls are meshed together.

3. The method of claim 1 wherein at least one of the pair of corrugating rolls comprises a series of corrugations having a height that is at least 10% larger than a target flute height for the unheated corrugating medium and/or wherein at least one of the pair of corrugating rolls comprises a series of corrugations having a height to pitch ratio of at least 0.5 or at least 0.6.

4. The method of claim 1 wherein at least one of: the corrugating medium supply roll or a press roll, is operated at ambient temperature; optionally wherein all rolls employed in the manufacture of the corrugated paperboard are operated at ambient temperature.

5. The method of claim 1 wherein the unheated corrugating medium has a moisture content consistent with ambient conditions when passed through the pair of corrugating rolls.

6. The method of claim 1 comprising manufacturing corrugated paperboard without the use of steam, at least up to and including formation of corrugations in the unheated corrugating medium.

7. The method of claim 1 further comprising bonding a second liner to a second side of the fluted web to form a double-faced web.

8. The method of claim 1 wherein the bonding is by PVA glue.

9. A corrugated paperboard manufactured by the method of claim 1.

10. An apparatus for manufacturing corrugated paperboard, the apparatus comprising: a pair of corrugating rolls comprising a first corrugating roll and a second corrugating roll configured to corrugate an unheated corrugating medium when operated at ambient temperature; and a vacuum system configured to retain the unheated corrugating medium, when corrugated into a fluted web, on the second corrugating roll for a predefined part of a revolution; and a first bonding assembly arranged for bonding a first liner to a first side of the fluted web to form a single-faced web whilst the fluted web is retained on the second corrugating roll by the vacuum system; wherein the apparatus is configured to manufacture the corrugated paperboard without the use of a heat source, at least up to and including formation of corrugations in the unheated corrugating medium; wherein a diameter of the first corrugating roll is at least 20% less than a diameter of the second corrugating roll; and wherein the vacuum system is configured to hold the flutes of the fluted web in place, against resilient forces urging the unheated corrugating medium to spring back to a flat configuration, at least from formation of the fluted web until the first liner is bonded to the fluted web.

11. The apparatus according to claim 10 wherein the first bonding assembly comprises a press roll and wherein the press roll is configured to be operated at ambient temperature.

12. A corrugated paperboard manufactured using the apparatus of claim 10.

13. The method of claim 1 wherein the diameter of the first corrugating roll is at least 25%, 30%, 40%, 50%, 60 or 75% less than the diameter of the second corrugating roll.

Description

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) Some embodiments of the disclosure will now be described by way of example only and with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a schematic view of an apparatus for manufacturing corrugated paperboard in accordance with the present disclosure.

(3) FIG. 2 shows an enlarged view of the corrugating medium passing through the corrugating rolls of the apparatus of FIG. 1.

(4) FIG. 3 shows an exploded view of a glue station as employed in the apparatus of FIG. 1.

(5) FIG. 4 illustrates a method for manufacturing corrugated paperboard in accordance with the present disclosure.

(6) FIGS. 5A and 5B show, respectively, plan and side elevation views of a sheet of corrugated paperboard manufactured in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) Generally speaking, the disclosure provides an apparatus and method for manufacturing corrugated paperboard without the use of heat, at least up to and including formation of a fluted web.

(8) Some examples of the solution are given in the accompanying figures.

(9) FIG. 1 shows an apparatus 100 for manufacturing corrugated paperboard in accordance with the present disclosure. The apparatus 100 comprises a pair of corrugating rolls 102a and 102b configured to corrugate a corrugating medium 104 when operated at ambient temperature (e.g. not actively heated or cooled from within). The corrugating medium 104 is a large sheet of paper provided on a corrugating medium supply roll 106. As shown in FIG. 1, the corrugating medium 104 is directed to the first corrugating roll 102a via a directional roller 108a. However, in other embodiments, the corrugating medium 104 may be directed to the first corrugating roll 102a directly from the corrugating medium supply roll 106 or any number of directional rollers may be provided in the path of the corrugating medium 104. The corrugating medium supply roll 106 and directional roller 108a are also operated at ambient temperature (e.g. not heated from within).

(10) The corrugating medium 104 is forced between meshing teeth of the pair of corrugating rolls 102a and 102b to form an undulating fluted web 110, as will be described in more detail below with respect to FIG. 2. The corrugating rolls 102a and 102b are configured to pull the corrugating medium 104 from the corrugating medium supply roll 106 to form the fluted web 110. The fluted web 110 is retained on the corrugating roll 102b by a vacuum force applied from within the corrugating roll 102b to suck air, along with the corrugating medium 104, inwardly through small holes (not shown) in the outer surface of the corrugating roll 102b. The vacuum force retains the fluted web 110 on the corrugating roll 102b for a predefined part of a revolution and ensures the fluted web 110 is brought into contact with a bonding agent from a first bonding station 112a before being bonded to a first liner 114 via a first press roll 116a. Taken together, the first bonding station 112a and first press roll 116a may be considered as a first bonding assembly arranged for bonding the first liner 114 to a first side of the fluted web 110 to form a single-faced web 120.

(11) The first liner 114 is a large sheet of paper provided on a first liner supply roll 118. As shown in FIG. 1, the first liner 114 is directed to the first press roll 116a via two directional rollers 108b and 108c. However, in other embodiments, the first liner 114 may be directed to the first press roll 116a directly from the first liner supply roll 118 or any number of directional rollers may be provided in the path of the first liner 114. The first liner supply roll 118 and directional rollers 108b and 108c are also operated at ambient temperature.

(12) The bonding agent may be a thermoplastic glue such as polyvinyl acetate (PVA) glue. This is preferable to starch glue, which significantly wets the fluted web and liner, making it more likely to tear, increasing drying time and reducing the overall strength of the paperboard. PVA glue, on the other hand, is not as wet and can cure rapidly at ambient temperature, further reducing the need for heat.

(13) The single-faced web 120 is then directed from the corrugating roll 102b to a second bonding assembly arranged for bonding a second liner 122 to a second side of the fluted web 110 to form a double-faced web 126. The second bonding assembly comprises a second bonding station 112b and a second press roll 116b. In the embodiment, shown in FIG. 1 a directional roller 108d is provided between the second bonding station 112b and the second press roll 116b. In other embodiments, no directional rollers may be required between the second bonding station 112b and the second press roll 116b or multiple directional rollers may be provided. Also, in this embodiment, no directional rollers are provided between the corrugating roll 102b and the second bonding station 112b. In other embodiments, one or more directional rollers may be provided between the corrugating roll 102b and the second bonding station 112b.

(14) The second liner 122 is a large sheet of paper provided on a second liner supply roll 124. As shown in FIG. 1, the second liner 122 is directed to the second press roll 116b directly.

(15) However, in other embodiments, the second liner 122 may be directed to the second press roll 116b via one or more directional rollers. The second liner supply roll 124 and directional roller 108d are also operated at ambient temperature.

(16) In some embodiments, the second liner 122 may not be required and the output from the apparatus 100 may be the single-faced web 120. In other words, the second bonding assembly may not be required.

(17) In some embodiments, the apparatus 100 may be configured to produce corrugated paperboard having multiple layers of corrugated material and/or liner material by feeding the single-faced web 120 or double-faced web 126 through additional equipment configured to bond additional layers in a similar manner to that described above.

(18) As shown in FIG. 1, the apparatus 100 may be relatively compact. Advantageously, each corrugating roll 102a, 102b is configured for operation at ambient temperature, which may be a temperature of less than 60 degrees Celsius. This significantly reduces complexity of the apparatus 100 and its energy consumption when compared to systems requiring heated corrugating rolls, which are typically heated to well in excess of 100 degrees Celsius (e.g. 180 degrees Celsius). Furthermore, there may be no need to heat any of the components of the apparatus 100, further reducing energy consumption.

(19) In addition, no steam is required to wet the corrugating medium 104 to make it more pliable prior to forming the fluted web 110. This further reduces energy consumption as well as eliminating the need for a lengthy drying time, thereby allowing the apparatus 100 to be compact. Furthermore, the absence of steam means the corrugated paperboard may be less likely to warp as this is believed to be caused by different drying times in different areas of the corrugated paperboard.

(20) Although the corrugating rolls 102a and 102b are shown as approximately the same size in FIG. 1, this need not be the case. In fact, it may be advantageous for a first (e.g. lower) corrugating roll 102a to have a smaller diameter than a second (e.g. upper) corrugating roll 102b as this reduces the number of meshing corrugations which can help to prevent tearing of the corrugating medium (e.g. because less paper is stretched when the corrugations are formed). In an example, the first corrugating roll 102a may have a diameter of approximately 120 mm, while the second corrugating roll 102b may have a diameter of approximately 550 mm. In more general terms, the diameter of the first corrugating roll 102a may be 10%, 20%, 25%, 30%, 40%, 50%, 60 or 75% less than the diameter of the second corrugating roll 102b. Advantageously, the second corrugator roll 102b is the larger of the pair of corrugating rolls to allow a longer drying time for the glue when deposited on the corrugating medium.

(21) FIG. 2 shows an enlarged view 200 of the corrugating medium 104 passing between the corrugations in the corrugating rolls 102a and 102b of the apparatus 100 of FIG. 1. As illustrated, the corrugating medium 104 substantially conforms around corrugator peaks 202a, 202b and is spaced from corrugator troughs 204a, 204b in each of the corrugating rolls 102a, 102b. This arrangement may be due to the spacing between the pair of corrugating rolls 102a, 102b and/or may be due to an application of a predefined pressure on at least one of the corrugating rolls 102a, 102b such that corrugator peaks 202a of a first roll 102a are spaced by a distance s from corrugator troughs 204b of a second roll 102b when the pair of corrugating rolls 102a, 102b are meshed together.

(22) In some embodiments, at least one of the corrugating rolls 102a, 102b may have a series of corrugations having a height h from corrugator trough 204a, 204b to corrugator peak 202a, 202b that is at least 10% larger than a target flute height for the corrugating medium 104 when formed into the fluted web 110. For example, to achieve a flute height of 3 mm, a corrugation height h of 3.6 mm may be used, and the corrugator peaks 202a of the first roll 102a may be spaced from the corrugator troughs 204b of the second roll 102b by approximately 0.6 mm. To achieve larger flutes, an even larger corrugation height h may be used.

(23) In some embodiments, the first roll 102a may have a different corrugation height to the second roll 102b. In other embodiments, the first roll 102a may have the same corrugation height as the second roll 102b but may be backed off from close engagement by a reduced pressure applied to one or both rolls 102a, 102b.

(24) In some embodiments, the series of corrugations in one or both corrugating rolls 102a, 102b may have a height h to pitch p ratio of at least 0.5, at least 0.6 or approximately 0.65. Such ratios are significantly larger than for conventional apparatus, which may have a ratio of between 0.3 and 0.4. Accordingly, to achieve a similar flute pitch, the apparatus 100 employs a significantly larger corrugation height.

(25) It has been determined that each of the above features, individually and collectively may help to prevent tearing of the corrugating medium 104 as it is forced between the corrugations in the corrugating rolls 102a and 102b. Traditional corrugators use heat and/or steam to make the corrugating medium 104 more pliable to prevent tearing. However, in the proposed non-heated ambient apparatus 100, it has been found that tearing that can be prevented (or at least minimised) by one or more of the above features. In particular, it is believed that not forcing the corrugating medium 104 to the base of the corrugating troughs 104a, 104b helps to reduce strain in the corrugating medium 104 which can lead to tearing.

(26) Furthermore, the described arrangement may form larger, flatter areas at the peaks of the fluted web 110, which may provide a more effective surface for bonding to the liner material.

(27) FIG. 3 shows an exploded view of a bonding station 112a, 112b as employed in the apparatus of FIG. 1. Each bonding station 112a, 112b comprises a glue roll 300 comprising a series of circumferential flange-like ring protrusions 302 at even intervals along the axial length of the glue roll 300. Each end of the glue roll 300 is configured to lock into a drive gear 304a, 304b configured with recesses to engage in the corrugations of the corrugating roll 102b such that rotation of the corrugating roll 102b causes the glue roll 300 to rotate at the same circumferential speed. On rotation, the protrusions 302 of the glue roll 300 are configured to pass through a glue reservoir provided in a trough 306 before passing through a comb 308 to remove excess glue from the glue roll 300. Further rotation of the glue roll 300 will apply glue present on each of the protrusions 302 to the outer peaks of the fluted web 110 when retained on the corrugator roll 102b. The series of protrusions 302 will form a series of glue dots along the length of each peak in the fluted web 110, the spacing between the protrusions 302 determining the spacing between the glue dots. The comb 308 may be adjustable in order to regulate an amount of glue applied to the fluted web 110 and different configurations of protrusions 302 may be employed to vary the size and/or spacing of the glue dots. Other types of bonding stations 112a, 112b may be provided.

(28) It will be understood that the glue dots on the fluted web 110 will facilitate bonding with a liner material 114, 122 when the liner material is pressed by a press roll 116a, 116b into contact with the fluted web 110 as shown in FIG. 1 in both the first and second bonding stations 112a, 112b.

(29) FIG. 4 illustrates a method 400 for manufacturing corrugated paperboard in accordance with the present disclosure. The method 400 comprises a first step 402 of directing a corrugating medium 104 from a corrugating medium supply roll 106 to a pair of corrugating rolls 102a, 102b; and a second step 404 of operating the pair of corrugating rolls 102a, 102b to corrugate the corrugating medium 104, wherein each corrugating roll 102a, 102b is operated at ambient temperature.

(30) FIGS. 5A and 5B show, respectively, plan and side elevation views of a sheet of corrugated paperboard 500 manufactured in accordance with the present disclosure. The sheet of corrugated paperboard 500 is cut to form a large rectangular cuboid having a first liner 502 bonded on a first side of a fluted web 504 and a second liner 506 bonded on a second side of the fluted web 504.

(31) Advantageously, the corrugated paperboard 500 is believed to have less tendency to warp due to the absence of heat and steam from the manufacturing process. In addition, the corrugated paperboard 500 may be stronger than in the prior art, for the same weight of paper, when made using the described method, as the absence of heat in the process will retain the paper strength. Moreover, the flatter peaks of the fluted web 504 will ensure the paperboard has flatter outer surfaces, and the combination of flatter peaks and PVA glue may enable a stronger bond than in the prior art.

(32) Embodiments of the present disclosure can be employed in many different industries to make corrugated paperboard for a variety of applications including but not limited to packaging.

(33) The skilled person will understand that in the preceding description and appended claims, positional terms such as above, along, side, etc. are made with reference to conceptual illustrations, such as those shown in the appended drawings. These terms are used for ease of reference but are not intended to be of limiting nature. These terms are therefore to be understood as referring to an object when in an orientation as shown in the accompanying drawings.

(34) Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure, which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in any embodiments, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.