GB2536456A

GB2536456A - Open faced cup and dome core board for automatic decorative sheet lamination

Info

Publication number: GB2536456A
Application number: GB1504510.7A
Authority: GB
Inventors: John Clement Adie Victor
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-03-17
Filing date: 2015-03-17
Publication date: 2016-09-21
Also published as: GB201504510D0

Abstract

The board comprises at least two embossed plies 4, 5, laminated either side of a smooth centre ply 6. The embossed plies have predominantly alternating cup 3 and dome 2 embossed shapes across and along the sheet, with a dome in the place of a cup at regular intervals to form clusters 1 of domes or projections on the outer faces of the board. The laminated board may have additional plies alternating between planar and embossed, there always being an embossed ply on each outer edge. An alternative embodiment there is no central flat layer, a tow-ply board whereby the embossed plies are adhered directly to each other at the top of the projections. The plies are preferably composed of a cellulose based fibre. The relative vertical position of embossed plies is preferably offset so that the clusters do not coincide in order to avoid soft spots in the 3-ply board. The pattern of the embossing prevents the sheets from settling in close contact when stacked thus facilitating the automatic feeding of the sheets.

Description

Open faced cup and dome middle board for automatic sheet laminating

Background

It is known that globular embossed paperboard middles can be used as the core onto which un-embossed smooth outer facings can be adhered to produce high bulk laminated boards (HBLB) which are very light in ratio to their thickness and are used for the production of such items as displays, packaging and showcards. Prior art is disclosed in GB24465876 (Adie) granted on 04 October 2011 and this is recognised and referred to in the current invention.

Here follows a description of the preferred embodiment of the current invention.

The pattern of embossed plies is typically but not exclusively a series of substantially hemispherical embossings (Dome) projecting from the top surface of the paper with the same pattern of domes projecting from the opposite side of the paper. The underside of each dome is typically but not exclusively in the form of a hollow, substantially hemispheric embossing (Cup). These embossed papers are adhered in layers of typically but not exclusively even numbers which have intervening sheets of flat paper between each pair of embossed plies. The cups and domes are typically but not exclusively arranged alternately in a grid pattern with lines of domes and alternating cups positioned typically but not exclusively perpendicular to each other checker board style such that the black squares would indicate the positions of domes and the white squares of cups.

HBLB boards (GB24465876 Adie) usually, but not exclusively, have smooth outer faces on both sides which are intended to be printed by any method which permits the board to remain flat.

However, there is a need to be able to apply decorative facings to typically but not exclusively both sides of the HBLB board as a sheet fed process. This is particularly important when paper sheets are printed and then need to be laminated to sheets of board. It is also important when fancy, coloured, decorative or special purpose facings need to be adhered to the boards.

The most commonly used adhesives for sheet lamination are water based and the presence of the water causes problems with the stability and flatness of the finished HBLB laminated boards which the current invention seeks to overcome.

When water based adhesive is applied to the smooth facing of the HBLB or to the decorative paper sheet which is to be laminated to it and the two are combined with pressure, the moisture in the adhesive causes the facing paper of the board to swell, cockle and distort. This effect is more extreme in HBLB compared to smooth solid board because the contact area between the smooth facings and the embossed middle plies is very much less. The added moisture from the adhesive is transferred away from the smooth facing paper into the core middle only where there is contact between the tops of the embossed domes of the middle and the outer facing paper.

This contact area is typically, but not exclusively, less than 10% of the surface area of the smooth outer facing paper of the HBLB. Thus, 90% of the outer facing paper remains saturated with moisture which cannot be absorbed by contact with a middle and this causes swelling of the paper fibre resulting in cockling and distortion as well as curl as the finished lamination dries.

For this reason the post manufacture decorative sheet lamination of HBLB is usually unsatisfactory.

The way to overcome this is to make HBLB without the smooth outer facings so that the embossed core middle becomes the outer surfaces on which to laminate the decorative outer sheets. This is referred to as "open faced" board In this means the adhesive is applied to the tops of the embossed plies of the board and the smooth decorative outer sheets applied. The moisture added to the finished laminated board is in proportion to the area of the tops of the embossed domes in contact with the decorative outer sheets, which is typically, but not exclusively, less than 10% of the total area of the sheet. Thus, the amount of moisture added during lamination of open face HBLB is only 10% of that when laminating on to a smooth faced HBLB. The result is to substantially reduce the adverse effects of adding the additional moisture when decorative sheet laminating.

However, open faced HBLB sheets present problems in stacking as they come off the production line and during machine feeding in subsequent processing such as on a sheet laminating machine. The exposed embossed pattern of the open faced surfaces of the material intermesh from sheet to sheet so preventing them from sliding over each other as would be needed for automatic stacking and feeding systems.

Automatic sheet feeding and stacking mechanisms, typically rely on jets of air to float the sheets and keep them separate from the underlying sheets. When open faced HBLB sheets settle in a stack, the air is squeezed out from between the sheets so that the area of contact between the sheets is substantially 100%. During automatic sheet feeding, vacuum suckers are designed to lift the edge of the top sheet on the stack so that air jets can introduce air under the top sheet and permit it to be floated off the stack. This cannot happen with open faced HBLB and automatic feeding is impossible.

Various methods have been tried to overcome this problem by the use of means to prevent the sheets of open faced HBLB from settling into close surface contact in a stack sufficiently to impair automatic sheet feeding.

Each means has one or more disadvantages which make it unsatisfactory. Amongst these means are the following: 1. Make open faced HBLB with a different size or pattern of embossed domes on one face of the sheet compared to the other so that the resulting mismatch would prevent the sheets interlocking.

The disadvantage is that the stability of the finished laminated board is reliant on the board being substantially the same in construction from side to side. Because of the different amounts of adhesive and therefore moisture being picked up during lamination by the different patterns of emboss there is an imbalance in added moisture. In addition the different embossed shapes would impart different physical characteristics to the two sides of the finished board in terms of smoothness, stiffness and compressibility.

More or less contact area between the embossed facings and the smooth paper liners will result in different levels of moisture, and therefore stability, because the adhesive is applied to the tops of the embossed domes.

It would be possible to vary the size or spacing of the domes of the embossed pattern to ensure that the surface contact area of the tops of the domes is substantially the same on both faces of the sheet even though the patterns are different. This would alter the physical characteristics of the laminated board from side to side because the pattern of embossing determines the smoothness and crush resistance of the board.

Another method is to space the domes in a random pattern so that some are closer together and others further apart. This has the disadvantage that across the sheet there would be variation in the crush resistance, rigidity and mechanical strength of the finished laminated board.

2. Use the same embossing pattern but made so that the embossed pattern of the open faced HBLB on one side of the sheet at an angle of, typically, 45 degrees compared to the opposing side.

The problem is that sheets can slew and twist when handled or machine fed and patterns coincide and interlock. This jams the automatic feed systems of machines such as laminating machines.

Statement of Invention

To overcome these problems, the current invention proposes a double sides open faced board using a novel pattern of cups and domes embossing which is such that the sheets cannot settle in close contact and machine handling is possible. At the same time the benefits of HBLB (GB24465876 Adie) are substantially retained.

There now follows a statement of invention in the preferred embodiment.

The preferred embodiment is an open faced two sides board made up of two outer embossed plies adhered to a smooth centre ply making a composite board of three plies. In the preferred embodiment of the invention the embossing is in the shape of cups and domes of which the size and spacing of the cups and domes is substantially the same as that used to make HBLB with smooth facings.

In the preferred embodiment: On the first face of the embossed ply the first line of alternating cups and domes running in the cross machine direction, has every fourth cup replaced by a dome of the same dimensions as those either side of it.

This extra dome sits at the centre of 5 domes in a cruciform cluster.

Preferably the horizontal spacing between the cups and domes is uniform.

Preferably on the first side of the embossed ply, counting in the long machine direction, every eighth line of alternating cups and domes shall have every fourth cup replaced by a dome of the same dimensions as those either side of it.

Preferably the lines of cups and domes shall form a grid pattern so that when rotated by degrees the cups and domes are spaced the same across and along the sheet. In the preferred embodiment of the invention the embossed plies are arranged so that both sides of the 3 ply sheet has first side embossings, which contain the extra domes, as outer faces.

In the preferred embodiment of the current invention the second side embossing of the plies are adhered to the smooth centre ply.

In the preferred embodiment of the current invention the patterns of the embossed plies are the same both sides of the 3 ply board except that they are offset in position in both the cross and long machine directions by half the measure of the repeat of the emboss pattern.

Advantages The patterns of embossing on both outer faces of the 3 ply composite sheet are substantially the same so giving uniform and balanced moisture pick up, rigidity, compressibility and other physical characteristics to each side whilst preventing handling problems caused by the sheets settling into close contact as occurs in prior art.

During decorative sheet lamination, there is a negligible adverse effect on the moisture content of the current invention compared to open faced HBLB made according to known prior art disclosed in GB24465876 (Adie) as there are only an extra 6.3% more domes on the outer facings of the invention compared to the prior art. This restricts the additional moisture pick up to a level which has no practical adverse effect on the finished board whilst maintaining the benefits of the prior art.

Because the embossing patterns are aligned in parallel to the machine direction there is no tendency to slew and jam during machine feeding.

Introduction to drawings

Open faced cup and dome core board for sheet lamination using automatic sheet handling made up in the preferred embodiment of 3 plies.

The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Fig 1 shows the plan view of the current invention, being a 3 ply 2 sides open faced board composed of smooth un-embossed ply with cup and dome embossed plies adhered both sides to form the outer facings of the 3 ply board.

The dotted line A -A denotes the position of the cross sectional view described in Fig. 2.

The dotted line B -B denotes the position of the cross sectional view described in Fig. 3.

The embossings shown on the plan view are alternate raised domes (2) and depressed cups (3), whose pattern is uniform except for the addition of extra domes which replace cups to form cruciform clusters (1). The extra domes at the centre of the clusters on the sheet are spaced apart at an interval of 4 domes and 3 cups in the cross machine direction, repeating at the same interval measured in the long machine direction.

Fig. 2 shows the cross section view of the current invention taken along the line A -A shown in Fig. 1.

The embossings shown on the cross section view are alternate raised domes (2) and depressed cups (3), whose pattern is uniform except for the addition of a extra domes which replace cups to form a cruciform clusters (1).

The 3 ply construction of the current invention is made up of first (4) and second (5) embossed plies which are adhered to a smooth centre ply (6). The embossed patterns of the top ply (4) and the bottom ply (5) do not match when seen in cross section because the embossed plies are offset horizontally by 50% of the repeat of the emboss pattern in both the long and cross machine directions in order to avoid soft spots created by the coincidence of clusters (1) on both sides of the sheet.

Fig. 3 shows the cross sectional view of the current invent taken along the line B -B. This view shows the position of the embossing pattern which is offset in both the long and cross machine directions by 50% of the repeat as referred to in Fig. 2.

Fig. 4 shows the cross sectional view of 2 sheets of the current invention of a 3 ply open faced embossed board (7 and 8) as they appear when stacked one on top of the other.The air space between the sheets (9) is created by action of the clusters of domes preventing close vertical intermeshing of the sheets. In prior art the absence of the clusters of domes of the current invention permit the sheets to closely intermesh resulting in substantially 100% surface to surface contact which leads to difficulty in separating the sheets.

Fig. 5 shows the cross sectional view of the shape of the embossings on an embossed ply. The first side (10) of the ply has extra domes; the second side (11) has extra cups as shown in Figs. 1, 2 and 3. The first side (10) forms the outer facing sides of the 3 ply board. The second side (11) is adhered to the centre ply of the 3 ply board.

Claims

Claims 1. An open faced 3 ply laminated board comprising a smooth centre ply adhered to first and second embossed outer plies having raised projections.
2. The laminated board of claim 1, further comprising a second smooth ply and a third embossed ply having raised projections such that the 5 plies are attached to each other in alternate layers of smooth and embossed plies with the outer plies being embossed plies.
3. The laminated board of claims 1 and 2, further comprising additional plies of embossed and plain plies adhered to each other in alternating layers of smooth and embossed plies up to any number of plies, there being always 2 outer facings of embossed plies.
4. The laminated board of claims 1 to 3, wherein the embossed plies have rows of alternating raised and lowered projections.
5. The laminated board of claims 1 to 4, wherein the embossed plies have rows in the cross machine direction of the sheet of alternating raised and lowered projections except that every fourth lowered projection is replaced by a raised projection to form a cluster of raised projections.
6. The laminated board of claims 1 to 5, wherein the embossed plies have alternating raised and lowered projections except that every fourth lowered projection is replaced by a raised projection in every eighth row measured in the long machine direction the sheet.
7. The laminated board in claims 1 to 6, wherein the clusters are offset in horizontal position relative to one another by means of the position of the plies relative to one another.
8. The laminated board in claims 1 to 7, wherein the degree of offset is 50% of the repeat pattern distance in the cross machine direction.
9. The laminated board in claims 1 to 8, wherein the degree of offset is 50% of the repeat pattern distance in the long machine direction.
10. The laminated board in claims 1 to 9, wherein the plies are composed of cellulose based fibre.
11. The laminated board in claims 1 to 9, wherein the plies are composed of any material other than cellulose based fibre.
12. The laminated board in claims 1 to 11, wherein the shape of the projections of embossing is different to cup and dome.
13. The laminated board of claims 1 to 12, wherein the dimensions of the embossings may be such that the distance from the top of the projections in the first side to the top of the recessed shapes in the second side may be in the range from 1 to 100 millimetres.
14. The laminated board of claims 1 to 13, wherein the distance between the edges of the projected and recessed shapes in the embossed pattern is in the range from 0.1 to 100 millimetres.
15. The laminated board of claims 1 to 14, wherein the projected shapes are substantially hemispherical (domes).
16. The laminated board of claims 1 to 15, wherein the recessed shapes are substantially hemispherical (cups).
17. The laminated board of claims 1 to 16, wherein the extra domes which replace cups to form clusters are spaced at intervals of 4 domes and 3 cups.
18. The laminated board of claims 1 to 17 wherein, the embossed plies are arranged so that the position of the clusters in each sheet may or may not coincide vertically. e
19. The laminated board of claims 1 to 18, wherein there is no smooth centre ply but the embossed plies are adhered to each other at the top of the protections in the embossings.
20. The laminated board of claims 1 to 19, wherein the spacing of the domes and cups may vary and not be uniform.
21. The laminated board of claims 1 to 20, wherein the spacing of the domes and cups may vary from side to side of the sheet.20 25 30 35 40 45 50