EP4043356A1 - Bi-material packaging made from plastic and cardboard or another bio-sourced material with cover. - Google Patents

Abstract

Packaging in particular suitable for containing foodstuffs, comprising on the one hand a container (1) of plastic-type material provided with a polygonal bottom (4) and a continuous peripheral wall comprising a plurality of flat faces (5), the upper edge (6) of said peripheral wall delimiting an opening and being provided with a polygonal peripheral rim (7) extending radially outwards provided with a gutter (8) capable of cooperating with a peripheral bead (21) of a cover (2) by fitting the rod (21) into the said gutter (8), and on the other hand an outer coating (40) made of cardboard-type material or other bio-sourced material adjusting at least in contact of the faces (5) of the container (1) and fixed between the gutter (8) and the part of said faces (5) adjacent to the edge (6). The polygonal rod (21) and the gutter (8) have a correspondence of shape for elastic interlocking by frictional contact of at least a fraction of their walls, except at the level of the corners of the ring (21) of the cover (2) which have a recess (22) in their inner wall, eliminating contact with the inner wall of the gutter (8) in each angular region.

Description

The present invention is in the field of packaging, and more particularly trays and boxes in particular intended to contain food. These packages have a container offering an interior space delimited by a bottom and lateral sides, they are generally made of plastic material, for example by thermoforming. In the context of the invention, they are bi-material with an outer covering of cardboard-type material and they comprise a means of closure by means of a cover having a snap ring in a gutter of the peripheral rim of the container.

As part of the French and European strategy to reduce plastic in packaging, we are trying to reduce the quantity of plastic used in the manufacture of trays, boxes and other containers. This is in particular the reason for the use of external coatings of the cardboard or bio-sourced type specific to the packaging of the invention. One of their functions is to reinforce the rigidity of the packaging, and they therefore make it possible, if necessary, to thin the thickness of the plastic walls and therefore to minimize the quantity of plastic used and to be recycled. In the rest of the text, it will generally be enough to mention materials of the cardboard type, but the bio-sourced materials, which in this case are technical equivalents, are included in the invention.

Solutions comprising a structure of the cardboard type are less easy to manufacture, and pose multiple problems, for example related to the automation of the chains and to the production rates, since it is necessary to combine two materials with very different properties. This is particularly the case when, as in the packaging configuration of the invention, the cardboard-type part is not glued to the plastic tray - a solution which makes their separation and consequently their recycling much more difficult - but is maintained by mechanical connection means resulting from the shape of the plastic packaging. Such a configuration makes the two materials easily separable manually, but singularly complicates the manufacture.

The cardboard-type coating, in the form of cardboard surrounding at least the sides of the container, is thus retained in particular by wedging between the gutter aforementioned peripheral and the walls of the container, and the thermoforming of the plastic must be done in consideration of the fact that the cardboard-like coating is already in place in the mould. This pre-positioning and the configuration of the cardboard part have implications in manufacturing, for example in the angular regions when the packages are polygonal in appearance. This must be taken into account in the design of the shape of the packaging.

Furthermore, the cardboard-like coating placed in the mold is liable to react to the actual thermoforming operations, which involve deformations of a plastic sheet. These deformations, which operate in multiple directions, generate forces and stresses which also apply to the cardboard-type material, which must however be maintained throughout manufacture in the shape that it is intended to be given in relation to the molded plastic. This shape is notably defined by the positioning given to the cardboard-type covering when it is initially positioned in the mould.

The interdependence between the manufacturing requirements and the structure of the bi-material packaging leads to an invention covering several objects: the packaging itself, which has characteristics resulting from the manufacturing constraints mentioned above, a particular manufacturing process such packaging adapted to the existence of two materials, and finally certain aspects of the thermoforming mold making it possible to obtain these bi-material packaging.

The product, in short, is a packaging in particular capable of containing food, comprising a container of plastic-type material provided with a polygonal bottom and a continuous peripheral wall comprising a plurality of flat faces. The upper edge of said peripheral wall delimits an opening and is provided with a polygonal peripheral rim extending radially outwards. This rim is provided with a gutter capable of cooperating with a peripheral bead of a lid by fitting the bead into said gutter. It also comprises an outer covering of the cardboard type or other bio-sourced material adjusting at least in contact with the faces of the container and fixed between the gutter and the part of said faces adjacent to the border.

According to the invention, the polygonal rod and the gutter have a shape match for elastic interlocking by frictional contact of at least one fraction of their walls, except at the level of the angles of the bead of the cover which have a clearance in their internal wall, eliminating contact with the internal wall of the gutter in each angular region.

The clearances made in the male rod at the corners or angles of the cover prevent any contact and aim to eliminate any possibility of collision between them in the angular zones of the rod and the gutter. These clearances are necessary for the proper functioning of the packaging, since they guarantee that the operations of opening and closing the lid on the container can be carried out without obstacles.

In practice, when a cardboard-like covering with a polygonal bottom is preformed in the mold - for example in the case of right angles in rectangular packaging - a kind of point or angular spur forms at the corners. the corner edge where the side edges of the adjacent sides of the cardboard type covering meet. The plastic sheet during thermoforming adapts somehow to this edge over the height of the cardboard-like coating, but the existence of a sharp angle can lead to the formation of folds in the plastic sheet, which do not fit snugly over the cardboard-like covering in these areas. In this case, if the contour of the male bead of the cover were molded to correspond to the theoretical contour of the female gutter, as on the rest of the circumference of the packaging, there would be a collision due to the obstacles constituted by these folds, and impossibility to close the lid properly.

This is the reason why the angular zones of the male bead of the lid have these recesses or clearances: they actually make it possible to absorb potential thermoforming defects in the corners of the box, or simply to take account of the extra thicknesses resulting from the angular configuration. According to one possibility, each clearance is rounded and therefore creates a reserve of space in front of each surface of an angular zone of the interior wall of the gutter.

Furthermore, in the packaging of the invention, the gutter may have, in each rectilinear section between the angular regions, at least one bulge protruding from its internal wall, encroaching into the volume of the gutter and fitting into a recess of corresponding shape made in the portion of the ring provided to fit therein.

These bulges result, as will be seen in more detail below, from a configuration of the mold specifically provided to prevent the cardboard-like coating from bending during the thermoforming of the plastic. Thus, in particular during the suction resulting from the establishment of a vacuum in part of the mould, the plastic sheet is deformed and exerts a force on the cardboard-type coating when the peripheral gutter is formed in the rim of the container. The gutter is in fact molded between the outside of the parts of the walls of the cardboard-type covering which protrude from a cavity of the mold and the peripheral edge of said mold. The constraints applying to the cardboard type coating are in fact multiple, because in addition to the suction on one side of the mould, there is an overpressure obtained by blowing compressed air on the other side.

According to one possibility, the bulge can take the form of a ramp originating in the edge of the internal wall of the gutter and extending to the bottom of the latter where the encroachment in the volume of the gutter is then maximum. . It should be noted that the use of a mold configuration which creates these bulges makes it possible to use a cardboard of reduced thickness, since it is intended to oppose folding. The use of a substantially thicker cardboard type coating could accommodate a mold lacking this specific configuration, which will be detailed below.

The second object of the invention relates to the process for manufacturing the packaging described above, and it essentially comprises the following steps:

- inserting the cardboard type coating or other bio-sourced material into the cavity of a thermoforming mold comprising a recess corresponding at least partially to the shape of the container;

- Positioning of said coating of cardboard type or other bio-sourced material so that its upper peripheral edge protrudes from the recess by a distance equal to the depth of the gutter;

- conveying a continuous strip of a plastic film between the cavity and a counter-mold of a thermoforming mould;

-displacements for closing the thermoforming mold of said impression and of the counter-mold in the direction of one another and of the plastic film;

- molding of the plastic film after closing the cavity and the counter-mold, by moving at least one molding core from the counter-mold, and by simultaneously producing an overpressure at the level of the counter-mold and a depression at the level of the imprint.

During the manufacturing process, the plastic sheet is notably molded around an upper edge of the cardboard-type covering, which is in fact fixed to the plastic packaging by wedging between the external gutter and the upper part of the faces of the container. The upper edge of the cardboard-like coating is therefore used, in the invention, as an internal wall of the mold which gives part of its shape to the plastic sheet during thermoforming. The heated plastic sheet is in fact deformed, during molding, around said upper peripheral edge of the cardboard-like coating, by the combined action in the mold of the displacement of a mobile core, an overpressure of a side and a depression on the other side. During the operation, the plastic sheet is therefore molded on either side of an upper peripheral band of the cardboard-like coating, a band which protrudes from the recess of the impression and which the thermoformed sheet encloses and jams, thereby securing it to the plastic wrapper.

In practice, the rim of the recess of the cavity of the thermoforming mold further comprises teeth distributed over its periphery, protruding from the recess by a distance equal to the depth of the gutter, a first face of which is in the extension of the wall of the recess which it overhangs, and a second face opposite the first face is in the form of a ramp starting from the upper edge of the tooth. The latter therefore has a section of triangular appearance of maximum thickness at its base, located at the level of said rim of the recess.

These teeth make it possible, as mentioned, to prevent the strip of the cardboard-like coating which protrudes from the recess from bending during the thermoforming of the plastic sheet. The plastic sheet in fact exerts a non-negligible force on the cardboard when it invests the peripheral space between the upper edge of the carton which protrudes from the recess on the one hand, and the peripheral vertical edge of the mold on the other hand, at the time of creation of the gutter. This force is actually multiple, because it is also caused by a suction due to the depression of the thermoforming mold on the cavity side and by the injection of compressed air under overpressure on the other side. The existence of these teeth makes it possible to keep the upper edge of the cardboard-type coating fixed, a condition which would require, in the absence of the teeth, the use of a more rigid cardboard and/or of greater thickness.

Other aims and advantages of the present invention will appear during the description which will follow relating to embodiments which are given only by way of indicative and non-limiting examples.

• La figure 1 représente une vue en perspective d'un emballage conforme à l'invention, couvercle fermé ;
• La figure 2 montre, en vue perspective, l'emballage de la figure précédente avec le couvercle ouvert ;
• La figure 3 montre une section transversale du même emballage ;
• La figure 4 en montre un détail agrandi, au niveau de l'emboîtement couvercle/conteneur encerclé dans la figure précédente ;
• La figure 5 illustre une coupe C-C de la figure 3 ;
• La figure 6 représente un agrandissement d'un coin de la figure 5 ;
• La figure 7 montre une vue en section d'un coin de l'emballage fermé ;
• La figure 8 représente une partie d'un moule de thermoformage, comprenant une empreinte femelle avec des évidements pour le conteneur et le couvercle ;
• La figure 9 en illustre un détail agrandi, au niveau du coin de l'évidement pour le conteneur ;
• La figure 10 reprend la figure 8 avec un revêtement de type carton positionné dans l'empreinte du moule du conteneur ; et
• La figure 11 montre un agrandissement équivalent à celui de la figure 9, avec l'empreinte du moule du conteneur revêtu du revêtement de type carton ou cartonnette.

The understanding of this description will also be facilitated by referring to the attached drawings, which explain the particularities of the packaging of the invention and its manufacture, and in which:

• The figure 1 shows a perspective view of a packaging according to the invention, lid closed;
• The figure 2 shows, in perspective view, the packaging of the previous figure with the lid open;
• The picture 3 shows a cross section of the same package;
• The figure 4 shows an enlarged detail, at the lid/container interlocking circled in the previous figure;
• The figure 5 illustrates a CC cut of the picture 3 ;
• The figure 6 represents an enlargement of a corner of the figure 5 ;
• The figure 7 shows a sectional view of a corner of the closed package;
• The figure 8 shows part of a thermoforming mould, comprising a female cavity with recesses for the container and the lid;
• The figure 9 illustrates an enlarged detail, at the corner of the recess for the container;
• The figure 10 take it back figure 8 with a cardboard-like liner positioned in the mold cavity of the container; and
• The figure 11 shows a magnification equivalent to that of the figure 9 , with the impression of the mold of the container coated with the coating of the cardboard or cardboard type.

With reference first to figures 1 to 7 , the packaging of the invention comprises a container 1 hinged to a lid 2, the container 1 having a bottom 4 in this case rectangular and four faces 5 forming a continuous peripheral wall and whose upper edge 6 extends radially towards the outside by a rim 7 provided with a peripheral gutter 8. A cardboard or cardboard type covering 40 de facto hugs the outer faces of the bottom 4 on the one hand and the side faces 5 on the other hand. The upper edge of the cardboard or cardboard type covering 40 is crimped between the gutter 8 and a upper part - a strip - of the side faces 5.

Hinged lid 2 is able to close elastically on container 1, with the aid of homologous profiles for gutter 8 and a rod 21 of lid 2, which are clipped into each other, one being a female profile (the gutter 8) and the other a male profile (the rod 21) within the meaning of this closure system. This is what appears more particularly in the section view of the picture 3 and in the enlargement of the figure 4 . The cover 2 and the container 1 are, in this configuration, connected by a hinge 3 integral with these two volumes, obtained by the same operation of thermoforming a plastic sheet.

Over the entire periphery of the packaging, the cardboard-type coating 40 is therefore wedged between the gutter 8 and the upper parts of the faces 5 of the container 1 (see in particular in figure 4 ), which materialize between them a reception slot of substantially constant thickness, which allows an effective mechanical peripheral retention over the entire periphery of the container 1. faces 5 have overlapping portions, at the corners, since there is room for only one thickness of cardboard. This wedging solution has multiple advantages, including that of eliminating any need for the use of a chemically polluting adhesive material (glue) and of reducing the quantity of cardboard to strictly necessary dimensions. In the corners, the adjacent edges of the side panels of the cardboard-type covering 40 are therefore in theory in linear contact along an edge 41.

At this inclined contact edge 41, the thermoforming of the plastic sheet can give rise to some difficulties, insofar as the plastic does not necessarily follow very precisely the spur formed by the inclined end edges of the two adjacent sides of the cardboard-like liner 40 which join at this line, and undesirable creases may occur. One of the aspects of the invention makes it possible to avoid the impossibility of closing the lid due to the existence of an extra thickness causing a collision between the rod 21 and the gutter 8 in this zone, which would not fail to produce if the rod 21 had everywhere a homologous male profile of the female profile of the gutter 8 for the snap-type elastic friction closure which is implemented in the invention.

In the CC cut appearing in figure 5 , as defined in picture 3 , illustrating the position of the rod 21 inside the gutter 8, examination of the corners (see figure 5 and in particular in figure 6 which shows an enlargement of the circled corner of the figure 5 ) shows that there is a clearance 22 at the junction 41 of the edges of the side panels of the cardboard type covering 40. The 4 corners of the rod 21 have this clearance 22, giving the closure system an additional free space in the angles to avoid at best excessive friction and at worst prohibitive obstacles to closure, in the event of formation of folds or extra thickness during thermoforming.

The result appears in the section view of the figure 7 , taken at the level of a corner: there remains a spacing between the inner wall of the recess 22 and the outer point of the spur formed in the upper part of the junction edge of the two adjacent side edges of the panels of the cardboard-type covering 40.

Another characteristic of the invention appears in the preceding figures: the gutter 8 has, in the internal wall (proximal to the useful volume of the container 1) of each rectilinear part separating the angles, bulges 81 encroaching into the volume of the gutter 8 ( see in particular picture 2 ). These bulges 81 fit in practice into corresponding recesses 23 made in the rectilinear portions of the rod 21 at equivalent locations. These reliefs result in fact from a peculiarity linked to the manufacture, namely the existence of growths which are placed in the thermoforming mold to prevent the upper parts of the cardboard-like liner 40 do not bend during thermoforming, as mentioned above.

One of the two parts of the thermoforming mold is shown in the following figures 8 to 11. This is the mold part 100 comprising the female cavity for the container 1 and the lid 2. A first recess 101 makes it possible to thermoform the container 1, and a second recess 102 makes it possible to mold the lid 2. A strip of plastic film (not shown) is therefore positioned, at the time of manufacture, above the cavity with double recess 101, 102. The female part 100 of the mold is moved, in a conventional manner, towards the plastic film and in the direction of the mold part comprising male cores (not shown), which is placed above the film and also moves in the opposite direction in the direction of the film strip and the recesses 101, 102 of the part 100. The thermoforming results from their interaction, and makes it possible to deform the heated plastic strip to the shape given by said molds, so as to obtain the packaging of the preceding figures .

The cavity 100 for molding the container 1 has a peripheral shoulder 110 at the edge (see figures 8 and 9 ) making it possible, as will be seen below, to mold the gutter 8. The enlargement of the figure 9 shows this even more clearly, and highlights teeth 111 distributed along the peripheral edge joining the recess 101 and said shoulder 110.

These teeth 111 have a first face which is in the extension of the walls of the recess 101, and a second face which connects their upper edge to the shoulder 110. The base of the teeth 111 constitutes their thickest part, the section of the teeth 111 being triangular in shape. They therefore mold the bulges 81 of the gutters 8 according to a corresponding volume: the bulge 81 substantially takes the form of a ramp emerging from the edge of the internal wall of the gutter 8, which corresponds in the mold to the upper edge of the strip 44 of the cardboard-like liner 40 and to the upper edge of the tooth 111, the ramp then extending to the bottom of the gutter at the base of the tooth 111, where the encroachment in the volume of gutter 8 is maximum.

The figures 10 and 11 are identical to the two previous ones, except that the cardboard-like coating 40 is positioned in the cavity 101, and the sheet plastic is thermoformed. In this case, as is particularly clear in figure 11 , the upper part of said cardboard-like covering 40 protrudes from the cavity 101: an upper peripheral strip 44 of the cardboard-like covering 40 in fact creates a solid wall between the interior volume of the recess 101 and the shoulder 110, leading to isolate a peripheral channel 112 making it possible to mold the gutter 8. This strip 44 rests on the teeth 111 distributed at the periphery of the recess 101, and which protrude therefrom by a height equal to said residual strip 44 .

In practice, they prevent the cardboard from bending towards the flat surface of the shoulder 110, due to the forces in action during the molding, and which are, as mentioned, of several orders: the forces due to the plastic film which deforms, a depression at the level of the cavities of the mold 100, which sucks up the plastic sheet, and finally an overpressure at the level of the upper counter-mold, which pushes said sheet into the cavities 101, 102 and into the peripheral channel 112. In the absence of the teeth 111 , these forces would run the risk, unless thick cardboard was used, of folding the upper part forming the peripheral strip 44 of the cardboard-like covering 40 against the shoulder, and the gutter 8 could not be molded. Their presence creates the bulges 81 in the gutter 8 thermoformed from the plastic sheet.

On the edge of the recess 102 of the cover, a peripheral bead 120 is used to mold the ring 21. It comprises, at locations calculated to correspond to those of the teeth 111, notches 121 allowing the molding of the recesses 23 of the internal wall of the ring 21 of the cover 2, intended to cooperate with the bulges 81 of the gutter 8, which they house in practice in the closed state of the cover 2 on the container 1.

The examples of shapes appearing in the figures are not exhaustive of the invention, which also encompasses variants in particular but not exclusively for the gutter 8 and its possible sections (same for the rod 21), for the shape and the geometric volume of the container 1 and its lid 2, and where appropriate for the shape and number of the corresponding bulges 81 and recesses 23, clearances 22, teeth 111, etc.]

Claims (6)

Packaging in particular suitable for containing foodstuffs, comprising on the one hand a container (1) of plastic-type material provided with a polygonal bottom (4) and a continuous peripheral wall comprising a plurality of flat faces (5), the upper edge (6) of said peripheral wall delimiting an opening and being provided with a polygonal peripheral rim (7) extending radially outwards provided with a gutter (8) capable of cooperating with a peripheral bead (21) of a lid (2) by fitting the rod (21) into the said gutter (8), and on the other hand an outer covering (40) made of a material of the cardboard type or other bio-sourced material adjusting at least in contact of the faces (5) of the container (1) and fixed between the gutter (8) and the part of the said faces (5) adjacent to the edge (6), characterized in that the polygonal rod (21) and the gutter (8) have a shape match for elastic engagement by frictional contact of at least a fraction of their walls is, except at the corners of the ring (21) of the cover (2) which have a recess (22) in their inner wall, eliminating contact with the inner wall of the gutter (8) in each angular region. Packaging suitable for containing food according to Claim 1, characterized in that the recess (22) is rounded. Packaging suitable for containing food according to one of the preceding claims, characterized in that the gutter (8) has, in each rectilinear section between the angular regions, at least one bulge (81) projecting from its internal wall, encroaching into the volume of the gutter (8) and fitting into a recess (23) of corresponding shape made in the portion of the rod (21) intended to fit therein. Packaging suitable for containing foodstuffs according to the preceding claim, characterized in that the bulge (81) takes the form of a ramp originating in the edge of the internal wall of the gutter (8) and extending to the bottom of the latter where the encroachment in the volume of the gutter (8) is maximum. Process for manufacturing packaging with container and lid according to the preceding claims, characterized in that it comprises the following steps: - inserting the cardboard type coating or other bio-sourced material (40) into the cavity (100) of a thermoforming mold comprising a recess (101) corresponding at least partially to the shape of the container (1); - Positioning of said cardboard type coating or other bio-sourced material (40) so that its upper peripheral edge protrudes from the recess (101) by a distance equal to the depth of the gutter (8); - conveying a continuous strip of a plastic film between the cavity (100) and a counter-mold of a thermoforming mould; - displacements for closing the thermoforming mold of said cavity (100) and of the counter-mold in the direction of one another and of the plastic film; - molding of the plastic film after closing the cavity (100) and the counter-mold, by moving at least one molding core from the counter-mold, and by simultaneously producing an overpressure at the level of the counter-mold and a depression at the cavity (100). Thermoforming mold cavity for carrying out the method according to the preceding claim, characterized in that the rim of the recess (101) of the cavity (100) of the thermoforming mold comprises teeth (111) distributed over its periphery, projecting from the recess (101) by a distance equal to the depth of the gutter (8), a first face of which is in the extension of the wall of the recess (101) which it overhangs, and a second face opposite the first face is in the form of a ramp starting from the upper edge of the tooth (111).

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