EP0532813B1 - Panelstructure of corrugated paperboard with these layers - Google Patents

Abstract

The invention belongs to the field of laminated products and relates to a corrugated cardboard sheet with triple corrugations. Corrugated cardboard sheet comprising three layers of corrugations, of which the two outer ones (1_ and 3_) and an inner one (2_) are separated by a sheet of cardboard, chiefly characterised in that, in the case of a given thickness (E) of the sheet, the outer layers (1_ and 3_) are crisscrossed by a trellis consisting of the inner layer (2_). The thicknesses (e1 and e3) of the outer layers are substantially equal, the thickness (e2) of the inner layer being at least equal to half of the total thickness (E) of the sheet. Application to the field of packaging and wrapping. <IMAGE>

Description

The present invention is in the field of laminate products, and more particularly relates to a triple corrugated corrugated cardboard plate.

We know thick corrugated sheets with triple grooves of the kind that combine three strata of grooves of equal thickness, as disclosed for example in document FR-A-1 488 484, Du of those that combine three strata asymmetrical grooves, the different strata being separated or covered by a sheet of strong paper.

The object of the present invention is in particular to increase the overall rigidity of a corrugated cardboard sheet of this type.

To this end, according to the present invention, a corrugated board of the kind in question is characterized in that the outer layers are thinner than the inner layer.

In other words, for a given thickness of the plate, its external layers, playing the role of structured structures, that is to say of parts working in traction, are braced like trusses or I-beams for example, by a trellis formed by the central layer, so that, as in beams or other structural elements, the tensile strength of the external layers is generally translated for the corrugated board, inne resistance to bending; Now it turns out that in the manufacture of corrugated cardboard, corrugations of small amplitude (thin layer) are also of small spacing, which results in a relatively high density structure, while conversely corrugations of large amplitude (very thick stratum) are of great spacing, and consequently of lower density. Thus the structure proposed by the invention is quite similar to that of a set of trusses with parts higher density external and lower density central part.

According to a more specific characteristic arrangement, the outer layers are of substantially equal thicknesses, while the thickness of the inner layer is at least equal to half the total thickness of said corrugated cardboard plate. In other words, the thickness of any of the outer layers is at most equal to half the thickness of the inner layer, and by substantially equal thicknesses is meant that the ratio between the thickness of a of the outer layers and the thickness of the other outer layer is between 0.75 and 1.35.

As an exemplary embodiment, the thickness of the internal layer is equal to 6.5 millimeters and the thickness of the plate is equal to 12 millimeters, the external layers having a thickness in the order of 3 millimeters.

• La figure 1 est inne vue en coupe d'une plaque de carton ondulé à trois cannelures d'égales épaisseurs, de l'art antérieur.
• La figure 2 est une vue en coupe d'une autre plaque de carton ondulé à triple cannelure dissymétrique relevant aussi de l'art antérieur.
• La figure 3 est une vue en coupe d'une plaque de carton ondulé à triple cannelure conforme à la présente invention.

The present invention will be better understood and details will be apparent from the description which will be given of a preferred embodiment, in relation to the figures in the appended plate, in which:

• Figure 1 is a sectional view of a corrugated cardboard plate with three grooves of equal thickness, of the prior art.
• Figure 2 is a sectional view of another corrugated cardboard plate with asymmetrical triple groove also falling within the prior art.
• Figure 3 is a sectional view of a triple corrugated corrugated cardboard sheet according to the present invention.

• La figure 4 est une vue en perspective de la plaque de la figure 3.

Figures 1 to 3 are accompanied by a box schematically illustrating the differences in density of the strata, for each of the section views.

• FIG. 4 is a perspective view of the plate of FIG. 3.

In all of the figures, we can recognize a cardboard plate with a triple groove made up of sheets of corrugated paper, such as 6 between and glued against flat sheets of paper such as 7.

It appears clearly by comparing the arrangement of the layers 1, 2, 3 and 1 ', 2', 3 'of the corrugated sheets of triple corrugation of FIGS. 1 and 2, relating to the prior art, with that of the plate of FIG. 3 pertaining to the invention, all these plates being of equal total thicknesses E, that the plate of the invention comprises external strata 1 '' and 3 '', of thicknesses e1 and e3, much thinner, but of higher density than the internal layer of thickness e2, which gives this plate its so-called structured structure.

   Grâce à la disposition caractéristique de l'invention il a été constaté un accroissement considérable de la résistance à la flexion.The thicknesses of the strata the plate of the invention preferably meet the definitions given above, namely: $$\begin{array}{c}\begin{array}{c}\text{0.75 ≦ e1 / e3 ≦ 1.35 and}\\ \text{e2 ≧ E / 2}\end{array}\end{array}$$

Thanks to the characteristic arrangement of the invention, a considerable increase in the flexural strength has been observed.

In fig. 4, a particular cardboard plate pertaining to the invention has the following dimensional characteristics: e1 = 3 mm, e2 = 6.5 mm, e3 = 4 mm, the total thickness E being 13.5 mm. The distances between the crests and the undulations are respectively d1 = 6.4 mm, d2 = 15 mm, d3 = 7.5 mm.

Claims (5)

1. A three-ply corrugated cardboard sheet comprising two outer layers (1'' and 3'') of corrugations and an inner layer (2'') of corrugations, the said layers being separated and/or covered by a sheet of cardboard, characterised in that the outer layers (1'', 3'') are thinner than the inner layer (2'').
2. A corrugated cardboard sheet according to claim 1, wherein the thickness (e1 or e3) of one of the outer layers (1'' or 3'') is at maximum equal to half the thickness (e2) of the inner layer (2'').
3. A corrugated cardboard sheet according to claim 1, wherein the outer layers (1'' and 3'') have substantially equal thicknesses (e1 and e3), the ratio of these thicknesses being between 0.75 and 1.35.
4. A corrugated cardboard sheet according to any one of the preceding claims, wherein the thickness (e2) of the inner layer (2'') is equal to 6.5 millimetres.
5. A corrugated cardboard sheet according to any one of the preceding claims, wherein the inner layer (2'') has a thickness (e2) at least equal to half the total thickness (E) of said sheet of corrugated cardboard.

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