WO1994013554A1

WO1994013554A1 - Packaging material of dewatered pulp

Info

Publication number: WO1994013554A1
Application number: PCT/DK1993/000420
Authority: WO
Inventors: Torben Rasmussen
Original assignee: Brødrene Hartmann A/S
Priority date: 1992-12-10
Filing date: 1993-12-10
Publication date: 1994-06-23
Also published as: AU5694294A; DK148792D0

Abstract

In a packaging material made from dewatered pulp, said material being generally in sheet or web form and comprising a number of mutually intersecting, rectilinear rows of hollow posts (2), the main new feature is that at least one side wall (3) of each hollow post (2) converges towards the remaining side walls and/or forms such an angle (4) with the general plane of the material, that when the hollow posts on one piece of the material are inserted in the hollow posts on another piece of the material, the outside surface on said side wall or side walls (3) in said other piece enters into engagement with the inside surface of said side wall or side walls (3) in said first piece in such a manner, that the bringing together of said outside and inside surfaces will produce a locking interengagement between them. With this arrangement, a number of pieces of packaging material may be joined together so as to form sheets or webs of larger dimensions, especially for use as an intermediary layer between a packaged article and e.g. a corrugated-paper box, the dimensions of which usually differ from the dimensions of the moulds, with which articles of pulp are manufactured.

Description

PACKAGING MATERIAL OF DEWATERED PULP

TECHNICAL FIELD

The present invention relates to a packaging material of the kind set forth in the preamble of claim 1.

BACKGROUND ART

A packaging material of the kind referred to above is disclosed in US Patent Specification No. 1,958,050. In the packaging material thus known, the hollow posts consist of pyramid-like projections, the side walls of which form an angle of the order of magnitude 45° with the general plane of the material. If such a packaging material is pro¬ duced in the known manner by using moulds for casting or deposition by suction having finite length and width, it will be very difficult to use the material as an intermediary layer between a packaged article and e.g. a corrugated-paper box, in which the article is placed with a view to being dispatched, unless the dimensions of the article or the corrugated-paper box do not happen to correspond to those of the mould.

DISCLOSURE OF THE INVENTION

On this background, it is the object of the invention to improve the known material mentioned above in such a manner that the hollow posts can be utilized to build an intermediary layer of arbitrary size from two or more pieces of material, and this object is achieved with a packaging material of the kind referred to initially, according to the invention additionally exhibiting the features set forth in the characterizing clause of claim 1.

With hollow posts shaped in the manner indicated in the claim, it is possible to bring the hollow posts into locking interengage ent with each other, so that the effect referred to above is achieved, as will be evident in more detail from the following detailed portion of the present description.

The invention also relates to a web of material of arbitrary length consisting of packaging material according to the invention, and this web of material is characterized as set forth in claim 11.

Advantageous embodiments of the packaging material and the web of material according to the invention, the effects of which are explained in more detail in the follow¬ ing detailed portion of the present specification, are set forth in claims 2-10 and 12 respectively.

BRIEF DESCRIPTION OF THE DRAWING

In the following detailed portion of the present description, the invention will be explained in more detail with reference to the exemplary embodiment of a packaging material according to the invention shown in the drawing, in which

Figure 1 in isometric perspective and on a slightly reduced scale shows a piece of packaging material according to the invention,

Figure 2 on a scale one half of that in Figure 1 shows how a number of layers of packaging material according to the invention may be placed on top of each other to form packaging material of greater thickness, and Figure 3 on a scale double that of Figure 1 is a sectional view at right angles to the general plane of the packaging material through two hollow posts having been brought into locking interengagement by inserting one hollow post into the other.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The segment of an exemplary embodiment of a packaging material according to the present invention shown in Figure

1 consists of a base material 1, generally of planar or web shape, shaped integrally with a number of hollow posts 2, in the figure protruding upwardly. The hollow posts 2 are placed in mutually intersecting, rectilinear rows with a constant pitch.

In a manner known per se, the packaging material according to the invention is produced by dewatering pulp, i.e. dewatering a watery slurry of fibre material, e.g. having been produced by shredding paper waste. The combined dewatering and shaping may occur in different ways, but in the present case it is preferred to use the so-called suction moulding, consisting in that a mould, that is permeable to water but not to fibres, is immersed with one side in the slurry while at the same time applying sub-atmospheric press¬ ure to the opposite side, so that a fibre layer is deposited on the mould. The material can be removed from the mould in various known ways, that do not have to be described here, since they do not directly relate to the invention.

In the exemplary embodiment shown, the hollow posts 2 are formed with four side walls 3, inclined inwardly and upwardly from the base material 1 at an angle 4 with the latter and terminated by an end wall 5, preferably in the manner shown extending substantially parallel to the base material 1.

As shown in Figure 3, the angle 4 is of such a mag¬ nitude, that a hollow post 2 on one piece of base material 1 may be inserted in a hollow post 2 on another piece of base material 1, the side walls 3 being wedged against each other in the process. In this manner, a locking engagement is produced between the two hollow posts inserted in each other, i.e. a force substantially greater than corresponding to the weight of the material itself is required to pull one of the hollow posts out from the other. The angle 4 will depend on the wall thickness of the hollow posts and of the surface properties of the material, but it will norm¬ ally be possible to choose this angle between approximately 75° and approximately 90°. Persons skilled in this art will know how to perform the requisite computations and experi¬ ments with a view to finding the most suitable magnitude of the angle 4 in each case.

In the exemplary embodiment shown, the hollow posts 2 are generally square-shaped as seen in section parallel with the base material 1 and are placed in rows crossing each other at right angles, but it lies within the scope of the invention to use hollow posts with other shapes, e.g. in the form of regular triangles or hexagons as seen in a section parallel with the base material 1, in which case the rows will have to intersect each other at mutual angles of 60°.

In the exemplary embodiment shown, the hollow posts 2 are shown as also being symmetrical about planes at right angles to the main plane of the base material 1, but it does also lie within the scope of the present invention to give the hollow posts a more or less asymmetric shape rela¬ tive to such planes or corresponding planes. What is import¬ ant is that at least one of the side walls extend in such a manner that the wedging-engagement effect referred to above is achieved. Due to the special method used when producing suction- moulded pulp articles, the packaging material according to the invention will preferably be produced in pieces having a finite length and width corresponding to the maximum pos¬ sible size of the suction moulds used. If there is a need for a packaging material with a greater surface area, this need can easily be met by interconnecting a number of the pieces so produced to form an article with large area, such as e.g. a web of material of indefinite length capable of being wound on a drum and later divided into pieces with lengths corresponding to the application desired in each case. If the interconnecting is performed by making each piece of material engage with each of the preceding and the succeeding pieces of material with one half of its length, a web of material will be produced, the base material of which pre- dominantly will have a thickness corresponding to twice the thickness of the base material 1 , thus appearing with sub- stantially constant thickness and generally homogeneous bending elasticity.

Pulp material of the kind referred to here is known to be flexible in a manner similar to that of thick paper or thin carton or cardboard. This property is not always advantageous, when the packaging material according to the invention is to be used as an intermediate layer in the manner referred to initially, as the flexibility can make the material difficult to control, especially when a number of pieces of material have been joined so as to form an article with a large area. This disadvantage is avoided by means of ribs 1 , of which one may be seen in Figure 1 , form¬ ing bridges between each hollow post 2 and the adjacent post. The ribs 7 make the material more rigid, and in ad- dition provides the advantage of preventing unintentional interlocking of two pieces of material placed on top of each other, e.g. in a stack. The strength of the ribs 7 is, however, so small that they may easily be broken, when two pieces of material are to be placed in interlocking engage- ment.

To make it easier to divide the packaging material, the base material 1 may as shown comprise weakening lines 6, e.g. in the form of perforations, of sufficiently low strength to make it possible to tear the base material 1 apart along these weakening lines without damaging the hollow posts 2.

As shown in Figure 2, a number of layers of packaging material may be placed on top of each other with every second layer inverted so as to form a packaging material of multiple thickness, that may - if necessary - be made more rigid by glueing or cementing the pieces of material to each other. Since the base material 1, as will be realized by having a closer look of Figure 1, constitutes a grid with a mesh size corresponding to the size of the hollow posts 2, the pieces of material shown in Figure 2 as being stacked on top of each other will not "fall down into each other", as this will be prevented by the base material 1.

LIST OF PARTS

Claims

C L A I M S :

1. Packaging material made from dewatered pulp, said material being generally in sheet or web form and comprising a number of mutually intersecting, rectilinear rows of hollow posts (2) , characterized in that at least one side wall (3) of each hollow post (2) converges towards the remaining side walls and/or forms such an angle (4) with the general plane of the material, that when the hollow posts on one piece of the material are inserted in the hollow posts on another piece of the material, the outside surface on said side wall or side walls (3) in said other piece enters into engagement with the inside surface of said side wall or side walls (3) in said first piece in such a manner, that the bringing together of said outside and inside surfaces will produce a locking interengagement between them.

2. Packaging material according to claim 1, charact¬ erized in that said mutual angle (4) amounts to approximately 75° to 90°.

3. Packaging material according to claim 1 or 2, characterized in that the angle (4) has substantially the same magnitude for all side walls in each hollow post (2) .

4. Packaging material according to any one or any of the claim 1-3, characterized in that the hollow posts (2) are shaped in such a manner that the rows, in which the hollow posts (2) are situated, form such mutual angles, and that the pitch distance between the individual pockets (2) in each row has such a magnitude, that hollow posts in a first piece of the material may be brought into locking engagement with hollow posts in a second piece of the mate¬ rial at at least two different mutual angles between the pieces of material as measured about an axis at right angles to the general plane of both pieces.

5. Packaging material according to claim 4, charact¬ erized in that the angle between the rows is 90°, and that the hollow posts as seen in section parallel to the general plane of the material are at least approximately square- shaped .

6. Packaging material according to claim 4, charact¬ erized in that the angle between the rows is 60°.

7. Packaging material according to claim 6, charact¬ erized in that the hollow posts as seen in section parallel to the general plane of the material are shaped at least approximately like regular triangles.

8. Packaging material according to claim 6, charact¬ erized in that the hollow posts as seen in section parallel to the general plane of the material are shaped at least approximately like regular hexagons.

9. Packaging material according to any one or any of the claims 1-8, characterized by weakening lines (6) formed in at least some of the interspaces between the hollow posts (2) or the rows of same, said weakening lines allowing the material to be torn apart without the hollow posts being deformed.

10. Packaging material according to any one or any of the claims 1-9, characterized by stiffening ribs (7) of low strength connecting the outside of the parts of the side wall (3) of each hollow post (2) situated closest to the base material (1) with the corresponding parts of each ad¬ jacent post (2) and with the base material (1) .

11. Web of material of arbitrary length of packaging material according to any one or any of the claims 1-10, characterized in that it consists of a number of pieces each having finite length and width joined by locking inter¬ engagement between at least the pockets situated closest to the overlapping edges of the individual pieces of material.

12. Web of material according to claim 10, charact¬ erized in that, with the exception of the first and last pieces of material, each piece of material is in locking engagement with the preceding and the succeeding piece of material with at least approximately one half of its extent in the longitudinal direction of the web.