WO2001060595A1

WO2001060595A1 - Plastic sheet material

Info

Publication number: WO2001060595A1
Application number: PCT/IB2001/000196
Authority: WO
Inventors: Dante Valenti
Original assignee: Vame Di Valenti Dante
Priority date: 2000-02-16
Filing date: 2001-02-15
Publication date: 2001-08-23
Also published as: AU3045101A; ITBO20000070A1; IT1320881B1

Abstract

A plastic sheet material (F) has a pair of opposite parallel faces, a first face (10) and a second face (11). Two separate groups of interconnections, a first interconnection group (14) and a second interconnection group (15), run and cross between the first face (10) and second face (11), so as to define and delimit a series of voids (13). The first interconnection group (14) forms a triangular wave (140), while the second interconnection group (15) forms a trapezoidal wave (150).

Description

PLASTIC SHEET MATERIAL

TECHNICAL FIELD

The present invention relates to plastic sheet materials and in particular relates to thin sheet or laminated materials, used for packaging or covering.

BACKGROUND OF THE INVENTION

Plastic material sheeting is useful particularly for boxes, cases, containers and recipients for packaging articles and/or products, e.g. food stuff.

For this purpose, the plastic sheet materials must have a considerable resistance to compression and pressure, so as to maintain its conformation unchanged, and at the same time, they cannot be heavy.

Moreover, the above mentioned resistance and lightness must be obtained with limited production costs in relation to product physical properties ..

Many attempts have been made hitherto to obtain plastic sheet materials, which are highly resistant and light at the same time.

For instance, FR-A-2 235 785 describes a semi-rigid plastic sheet material, as shown in Figure 1, including a pair of opposed faces, a first face 1 and a second face 3, between which run elongated voids 4, the voids being defined by interconnections 5 between the two opposite faces .

The cross sectional shape of at least some of the voids is hexagonal . The disadvantage of this type of plastic sheet material lies in the fact that the portions B of width L, corresponding to the voids 4 , and thus having weak resistance to compression., are relevant with reference to the width LI of the portions A corresponding to the interconnections 5, which have greater resistance to compression .

This increases the probability of the structure being broken in the region of the portions B, due to the compression stresses or during creasing by forming, which can be obtained only by heat-welding and with little homogeneity and precision.

The publication O-A-91/16243 describes a plastic sheet material including a pair of opposite faces, a first face 6 and a second face 7, between which run elongated voids 8, the voids being arranged so that there are a series of uninterrupted interconnections 9 between the two opposite faces .

The cross sectional shape of the voids is such that there is a substantial absence of sharp corners.

This document describes in particular a plastic sheet material, having a structure shown in Figure 2.

The dimensions and shape of the voids are such that the interconnections are thin elements which form two saw- tooth wave joined one another where they cross.

Thus, the interconnections between the opposite faces form a criss-cross structure, which run between the voids.

Each interconnection runs in a generally diagonal direction making an angle of between 30 and 60 degrees; the angle shown in Figure 2 is of 45°. Figures 3 and 4 show other types of known structures of plastic sheet materials, having voids and interconnections of different geometrical shapes between two opposite faces . For instance, Figure 3 shows a plastic sheet material, having a structure of "I"-type, in which opposite faces, a first face 100 and a second face 30, are separated by lateral support elements 50, parallel each to another.

Figure 4 shows a plastic sheet material having a "V"-type pattern 60.

The publication WO-A-97/25197 describes also plastic sheet materials, whose interconnections between the opposite faces define polygonal structures, such as hexagons or octagons . The presence of voids between the opposite surfaces of the plastic sheet material allows to reduce the total weight of the material, maintaining its physical properties unchanged.

The voids run in practice parallel to one another and run the length of the plastic sheet material, thus the material can be produced by extrusion from a suitable die, a processing technique which is cheaper than laminating process .

The presence of interconnections between the opposite surfaces of the plastic sheet material, with geometrical pattern defined by the particular conformation of the die being used, somehow provides a resistance to compression and pressure stresses to which the plastic sheet material is subjected during its use. However, the interconnections provide a good resistance to compression and pressure stresses only where they touch the opposed faces of the plastic sheet material and in the crossing zones.

Known plastic sheet materials, as the ones previously described, on one hand have obtained a considerable lightness, maintaining at the same time a sufficient resistance to compression and pressure stresses, yet, on the other hand, they present considerable disadvantages.

These disadvantages are shown mainly during creasing necessary to obtain collapsible containers. Actually, due to the voids and to the regular structure of the interconnections, the known plastic sheet materials are heterogeneous in longitudinal direction, i.e. in the direction of the voids extension.

The heterogeneousness is the result of alternation of longitudinal portions of weaker resistance to compression, indicated with B in Figures from 1 to 4 corresponding to the voids of width L, and the longitudinal portions of stronger resistance, indicated with A in the same figures and corresponding to longitudinal contact planes between the opposite surfaces and the relative interconnections.

This evident heterogeneousness in longitudinal direction causes the lack of a continuous and homogeneous series of longitudinal portions having similar resistance to compression. This continuity is necessary to make creasing by forming, by cold cutting, without causing partial collapsing of the whole structure.

The lack of subsequent longitudinal portions having similar resistance to compression causes also imprecision in making the creasing in the desired point. Actually, when the creasing is being formed in a predetermined position of the material, the creasing is possibly offset, so that it will be formed in a position where the material resistance to compression is weaker with respect to the desired position.

Consequently, if the creasing is to be formed in the region of a longitudinal portion of higher resistance, as the above mentioned portions A, the creasing is offset sideways to a portion of weaker resistance, as the above mentioned portions B.

This causes the beginning of collapsing of the whole structure .

Therefore, due to the above mentioned disadvantages, known plastic sheet materials are creased only by heat-welding, which is extremely expensive and imprecise with respect to the cold cutting.

SUMMARY OF THE INVENTION

The main object of the present invention is to propose a plastic sheet material, whose structure allows to outweigh all the above mentioned disadvantages.

Another object of the present invention is to propose a plastic sheet material, whose structure is simple due to the combination of voids and interconnections, and which is light and resistant to compression and pressure.

A further object of the present invention is to propose a plastic sheet material which is substantially homogeneous in its longitudinal portions and thus can be adapted to different creasings necessities, assuring high precision standard and low working costs, as well as better homogeneousness of the creasings obtained either by cold cutting or by heat welding.

A still further object of the present invention is to propose a plastic sheet material, in which the width of the longitudinal portions with weaker resistance to compression (voids) is not relevant with respect to the width of the longitudinal portions with higher resistance (interconnections) .

The above mentioned objects are wholly obtained, in accordance with the content of the claims, by means of a plastic sheet material, including a pair of opposed parallel faces, a first face and a second face, between which run a series of elongated voids, the voids running the length of said plastic sheet material, the plastic sheet material including two separate groups of interconnections, a first interconnection group and a second interconnection group, extending and crossing between said first face and said second face, so as to define and delimit said voids.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristic features of the present invention will be pointed out in the following description of a preferred, but not only embodiment, with reference to the enclosed of drawings, in which:

Figures from 1 to 4 show cross sectional views of prior art different types of plastic sheet materials, as previously described;

Figure 5a shows a cross sectional view of the structure of the proposed plastic sheet material, and Figure 5b shows a cross sectional view of ar_ exemplifying, but not exclusive embodiment of the structure of the plastic sheet material .

BEST MODES OF CARRYING OUT THE INVENTION

With reference to Figures 5a and 5b, reference F indicates the plastic sheet material proposed by the preseπ invention .

The plastic sheet material F includes two opposite faces, parallel to each other, namely a first face 10 and a second face 11, respectively, between which run tvc different groups of interconnections, namely a first interconnection group 14 and a second interconnection group 15. The above mentioned first interconnection group 14 and the second interconnection group 15 extend, crossing each other, between the first face 10 and the second face 11 of the plastic sheet material F and define voids 13 by intersecting reciprocally. The voids 13 run, parallel to one another, the length cf the plastic sheet material F, inside thereof.

The geometrical cross sectional shape of the firs- interconnection group 14 forms a triangular wave 14C, which extends crosswise between the opposite faces, namely the first face 10 and the second face 11, of the plastic sheet material F.

The geometrical cross sectional shape of the second interconnections group 15 forms a trapezoidal wave 150, which extends crosswise between the opposite faces, namely the first face 10 and the second face 11, of the plastic sheet material F. The opposite vertexes of the triangular wave 140, first vertexes 141 and second vertexes 142 join alternately with the opposite faces of the plastic sheet material F, the first face 10 and the second face 11, respectively. The first vertexes 141 and the second vertexes 142 of the triangular wave are equidistant by a step P.

The constant step P, as shown in the Figures, can be e.g. 7mm long.

It is evident that, according to other embodiments, the step P can be of different length.

The vertex angle of the first vertexes 141 and the second vertexes 142 of the triangular wave 140, as shown in the Figures, is of 98,80 degrees.

The vertex angle amplitude can vary in relation to the distance between the opposite faces, the first face 10 and the second face 11, of the plastic sheet material F.

The opposite minor bases, first base 151 and second base 152, of the above mentioned trapezoidal wave 150, join alternately with the opposite faces of the plastic sheet material F, the first face 10 and the second face 11, respectively, while the inclination of the relative oblique sides 153 make an angle of 59,74 degrees with respect to the opposite first face 10 and second face 11.

The opposite minor first bases 151 and second bases 152 have the same 3,5mm length.

Due to the contemporary presence of a first group of triangular wave-like interconnections and a second group of trapezoidal wave-like interconnections, extending crosswise between the opposite faces of the plastic sheet material and crossing as described above, the plastic sheet material is substantially homogeneous along subsequent longitudinal portions.

The substantial homogeneous property is obtained by the sequence of longitudinal portions of identical or similar resistance to compression and pressure.

This substantial longitudinal continuity allows to obtain creasing by cold cutting along predetermined longitudinal portions with high precision, avoiding lateral offsets of the creasing. Actually, the creasing can be obtained in any longitudinal portion, because there is always a similar resistance to compression, instead of alternating portions with stronger resistance and portions with weaker resistance, like in known, previously described, materials. The contemporaneous presence of the two groups of interconnections and voids 13 not only gives to the plastic sheet material a considerable standard of substantial homogeneousness along subsequent longitudinal portions, but also lightness. The proposed plastic sheet material is advantageously extremely light, and, at the same time, considerably resistant to compression and pressure.

It is also to be pointed out that the proposed plastic sheet material is advantageously, substantially homogeneous along subsequent longitudinal portions, which present similar values of resistance to compression: this assures obtaining, by cold cutting, of extremely precise creasing lines along the predetermined sections .

It is to be highlighted that in the proposed plastic sheet material, the width of the longitudinal portions with weaker resistance to compression (voids) is not relevant with respect to the width of the longitudinal portions with bigger resistance (interconnections), which definitely reduces the possibility of the structure breaking due to compression stresses. The structure of the proposed plastic sheet material is simple and extremely reliable in relation to its performance .

Moreover, it is to be pointed out that the proposed plastic sheet material can be obtained by extrusion and the production costs are very low.

It is understood that what above, has been described as a pure, not limitative example, therefore, possible variants of the details, as well as the changes of the characteristic parameters of the two groups of interconnections, in particular the step between the opposite vertexes and the vertex angle of the triangular wave, or the inclination of the oblique sides or the length of the opposite minor bases of the trapezoidal wave, remain within the protective scope of the present technical solution, as described above and claimed hereinafter .

Claims

1. A plastic sheet material, including a pair of opposed parallel faces, a first face (10) and a second face (11), between which run a series of elongated voids (13) , the voids running the length of said plastic sheet material, the plastic sheet material including two separate groups of interconnections, a first interconnection group (14) and a second interconnection group (15) , extending and crossing between said first face (10) and said second face (11) , so as to define and delimit said voids (13) .

2. A plastic sheet material as claimed in claim 1, wherein the geometric shape of said first group of interconnections (14) forms a triangular wave (140), said triangular wave which extends crosswise between said opposed first face (10) and second face (11) .

3. A plastic sheet material as claimed in claim 2, wherein said triangular wave (140) has opposite first vertexes

(141) and second vertexes (142), said first vertexes (141) and second vertexes (142) joining alternately with said opposed first face (10) and second face (11) respectively.

4. A plastic sheet material as claimed in claim 3, wherein between said first vertexes (141) and second vertexes

(142) there is a 7 mm distance (P) .

5. A plastic sheet material as claimed in claim 3, wherein said first vertexes (141) and said second vertexes (142) of said triangular wave make each one an angle of 98,80 degrees .

6. A plastic sheet material as claimed in claim 1, wherein said second group of interconnections (15) forms a trapezoidal wave (150), said trapezoidal wave extending crosswise between said opposite first face (10) and second face (11) .

7. A plastic sheet material as claimed in claim 6, wherein said trapezoidal wave (150) includes opposite first minor bases (151) and second minor bases (152) joined alternately with said opposite first face (10) and second face (11), respectively.

8. A plastic sheet material as claimed in claim 6, wherein said trapezoidal wave has oblique sides (153) with an inclination of 59,74° with respect to said opposite first face (10) and second face (11) .

9. A plastic sheet material as claimed in claim 7, wherein said opposite first minor bases (151) and second minor bases (152) have a same 3,5mm length (L) .

10. A plastic sheet material as claimed in claim 1, wherein said first group of interconnections (14) forms a triangular wave (140), said triangular wave (140) extending crosswise between said opposite first face (10) and second face (11), whereas said second group of interconnections (15) forms a trapezoidal wave (150), said trapezoidal wave (150) extending crosswise between said opposite first face (10) and second face (11) .

11. A plastic sheet material as claimed in claim 10, wherein said first vertexes (141) and said second vertexes (142) of said triangular wave make each one an angle of 98, 80 degrees.

12. A plastic sheet material as claimed in claim 10, wherein said triangular wave (140) has opposite first vertexes (141) and second vertexes (142) joined alternately with said opposite first face (10) and second face (11), respectively.

13. A plastic sheet material as claimed in claim 12, wherein between first vertexes (141) and second vertexes (142) there is a 7 mm distance (P) .

14. A plastic sheet material as claimed in claim 12, wherein said first vertexes (141) and said second vertexes (142) of said triangular wave make each one an angle of 98,80 degrees.

15. A plastic sheet material as claimed in claim 10, wherein said second group of interconnections (15) forms a trapezoidal wave (150), said a trapezoidal wave (150) extending crosswise between said opposite first face (10) and second face (11) .

16. A plastic sheet material as claimed in claim 10, wherein said trapezoidal wave (150) includes opposite first minor bases (151) and second minor bases (152) joined alternately with said opposite first face (10) and second face (11) , respectively.

17. A plastic sheet material as claimed in claim 15, wherein said trapezoidal wave (150) includes oblique sides (153) with an inclination of 59,74° with respect to said opposite first face (10) and second face (11) .

18. A plastic sheet material as claimed in claim 16, wherein said first minor bases (151) and second minor bases (152) have a same 3,5 mm length (L) .

19. A plastic sheet material as claimed in claim 1, wherein between said opposite first face (10) and second face (11) there is a 6 mm distance (D) .

20. A plastic sheet material as claimed in claim 1, obtained by extrusion through a die.