ES2967948T3 - Bi-material container made of plastic and cardboard or other material of biological origin with a cover - Google Patents

Abstract

Container especially indicated for containing food, which comprises on the one hand a container (1) made of plastic-type material provided with a polygonal bottom (4) and a continuous peripheral wall that comprises a plurality of flat faces (5), the upper edge being (6) of said peripheral wall that delimits an opening and that is provided with a polygonal peripheral edge (7) that extends radially outwardly provided with a gutter (8) capable of cooperating with a peripheral rod (21) a cover (2 ) fitting the rod (21)) into said gutter (8), and on the other hand an outer cover (40) made of cardboard-type material or other material of biological origin that fits at least to the contact faces (5) of the container (1) and fixed between the gutter (8) and the part of said faces (5) close to the edge (6). The polygonal rod (21) and the gutter (8) have a shape correspondence for the elastic interlocking by friction contact of at least a fraction of their walls, except in the corners of the ring (21) of the cover (2) that They have a free space (22) on their interior wall, eliminating contact with the interior wall of the gutter (8) in each angular region. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Bi-material container made of plastic and cardboard or other material of biological origin with a cover

The present invention relates to the field of packaging, and more particularly to trays and boxes, in particular intended to contain food. These containers have a container that offers an internal space delimited by a base and side sides, they are generally made of plastic material, for example, by thermoforming. In the context of the invention, they are bi-materials with an outer cover made of cardboard material and comprise a closure means for each lid that has a rib that engages in a channel on the peripheral edge of the container.

As part of the French and European strategy to reduce plastic in packaging, the aim is to reduce the amount of plastic used in the manufacture of trays, boxes and other containers. This is in particular the reason for the use of cardboard or external liners of biological origin specific to the packaging of the invention. One of its functions is to reinforce the rigidity of the packaging and therefore allow, if necessary, to thin the thickness of the plastic walls and therefore minimize the amount of plastic that is used and needs to be recycled. In the rest of the text, the term “cardboard materials” is generally mentioned, but materials of biological origin, which in this case are technical equivalents, are included in the invention.

Solutions that include a cardboard structure are less easy to manufacture and pose multiple problems, for example, related to the automation of assembly lines and production speeds since two materials with very different properties must be combined. This is particularly the case when, as in the packaging configuration of the invention, the cardboard-type part is not attached to the container made of plastic, a solution that makes its separation and, consequently, its recycling much more difficult. but it is maintained by means of mechanical connection that result from the shape of the plastic container. Such a configuration makes the two materials easily separated manually, but in particular complicates manufacturing. GB 1,264,811 A shows a molded plastic container attached to a cardboard lid carrying printed material.

The cardboard cover, in the form of a board that surrounds at least the sides of the container, is therefore retained, in particular by wedging between said peripheral channel and the walls of the container, and the thermoforming of the plastic must be done taking into account that the cardboard cover is already placed in the mold. This pre-positioning and configuration of the carton part has impacts on manufacturing, for example in the corner regions when the packages are polygonal. It must be taken into account in the design of the shape of the container.

Furthermore, the cardboard cover placed in the mold is capable of reacting with actual thermoforming operations, which involves deformations of a plastic sheet. These deformations, which occur in multiple directions, generate forces and tensions that are also applied to the cardboard-type material, which, however, must be maintained throughout manufacturing in the intended shape in relation to the molded plastic. This shape is defined in particular by the positioning given to the cardboard cover when it is initially placed in the mould.

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

In summary, the product is a packaging in particular capable of containing food, comprising a container made of plastic material provided with a polygonal base 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 edge that extends radially outwards. This edge is provided with a channel capable of cooperating with a peripheral ring of a cover that engages the rib in said channel. Furthermore, it comprises an outer cover made of cardboard or other material of biological origin that fits at least in contact with the faces of the container and is fixed between the channel and the part of said faces adjacent to the edge.

According to the invention, as described in claim 1, the polygonal rib and the channel coincide in shape to elastically engage by frictional contact of at least a part of their walls, except in the corners of the rib of the cover which have a free space on its inner wall, eliminating contact with the inner wall of the channel in each corner region.

The clearances made in the male rib at the corners or angles of the cap prevent any contact and are intended to eliminate any possibility of collision between them in the corner areas of the rib and channel. These clearances are necessary for the container to function correctly since it guarantees that the operations of opening and closing the lid on the container can be carried out without obstacles.

In practice, when a carton cover with a polygonal base is preformed in the mould, for example in the case of right angles in rectangular containers, an angular jar or point is formed on the corner flange at the corners where they meet. the side edges of the adjacent panels of the cardboard cover. The plastic sheet during thermoforming has problems fitting into this edge over the height of the cardboard cover, but the existence of a well-marked angle can lead to the formation of folds of the plastic sheet, which do not fit perfectly to the cardboard cover in these areas. In this case, if the contour of the male rib of the lid was molded to correspond to the theoretical contour of the female channel, as in the rest of the perimeter of the container, a collision would occur due to the obstacles formed by these folds, and the lid would be unable to close properly.

This is why the corner areas of the male rib of the lid have these recesses or free spaces: they actually allow potential thermoforming defects in the corners of the box to be absorbed, or simply to take into account the resulting additional thicknesses. of the corner configuration. According to one possibility, each recess is rounded and therefore creates a reserve space opposite each surface of a corner area of the inner wall of the channel.

Furthermore, in the package according to the invention, the channel may have, in each straight segment between the corner regions, at least one protuberance projecting from its inner wall that projects into the volume of the channel and fits into a correspondingly formed recess made in the part of the rib provided to engage therewith.

These protrusions result, as will be seen in greater detail later, from a mold configuration specifically designed to prevent the cardboard cover from bending during thermoforming of the plastic. Therefore, particularly during the suction resulting from producing a negative pressure in a part of the mold, the plastic sheet deforms and exerts a force on the cardboard cover when the peripheral channel is formed at the edge of the container. In fact, the channel is molded between the exterior of the portions of the walls of the cardboard cover that extend beyond a cavity of the mold and the peripheral edge of said mold. In fact, the stresses applied to the cardboard cover are multiple since in addition to the suction on one side of the mold, there is a positive pressure obtained by blowing compressed air on the other side.

According to one possibility, the bulge takes the form of a ramp that begins at the edge of the inner wall of the canal and extends to the base of the canal, where the projection into the volume of the canal is at a maximum. It should be noted that using a mold configuration that creates these protrusions makes it possible to use a thinner board thickness as it is provided to oppose folding. Using a substantially thicker cardboard cover could accommodate a mold without this specific configuration which will be detailed below.

The second object of the invention, as described in claim 5, refers to the method for manufacturing the containers described above, and essentially comprises the following steps:

- inserting the cover made of cardboard or other material of biological origin into the cavity of a thermoforming mold comprising a recess corresponding at least partially to the shape of the container;

- placing said cover made of cardboard or other material of biological origin in such a way that its upper peripheral edge protrudes from the recess by a distance equal to the depth of the channel;

- transporting a plastic film as a continuous web between the cavity and a countermold of a thermoforming mold;

- to close the thermoforming mold, move said cavity and the countermold between each other and the plastic film;

- molding the plastic film after closing the cavity and the countermold, moving at least one molding core of the countermold and simultaneously producing a positive pressure in the countermold and a negative pressure in the cavity.

During the manufacturing process, the plastic sheet is molded in particular around an upper edge of the cardboard cover, which is secured to the plastic container by pressure between the outer channel and the top of the container faces. Therefore, the top edge of the cardboard cover is used in the invention as an inner wall of the mold that gives a part of its shape to the plastic sheet during thermoforming. In fact, the heated plastic sheet is deformed during molding around said peripheral upper edge of the cardboard cover by the combined action in the mold of the movement of a moving core of a positive pressure on one side and a negative pressure on the other side. Accordingly, during operation, the plastic sheet is molded on both sides of an upper peripheral strip of the carton cover, this strip protrudes from the recess in the cavity and the thermoformed sheet grips and presses thereby securing it to the packaging. plastic.

In practice, the edge of the recess of the thermoforming mold cavity comprises teeth distributed over its periphery, these teeth protrude from the recess for a distance equal to the depth of the channel, and of which the first face is in the extension of the wall of the protruding recess, and a second face opposite the first face is ramp-shaped starting from the upper edge of the tooth. Consequently, the tooth has a triangular cross section of maximum thickness at its base located at said edge of the recess.

These teeth make it possible, as mentioned, to prevent the cardboard cover strip protruding from the recess from folding during thermoforming of the plastic sheet. In fact, the plastic sheet exerts a non-negligible force on the cardboard when it fills the peripheral space between the upper edge of the cardboard that projects beyond the recess on the one hand, and the peripheral vertical edge of the mold on the other hand at the moment in which the channel is created. This force is actually multiple as it is also produced by suction due to the negative pressure of the thermoforming mold on the cavity side and by the injection of compressed air under positive pressure on the other side. The existence of these teeth makes it possible to keep the top edge of the cardboard cover fixed, a condition that would require, in the absence of teeth, the use of a cardboard that is more rigid and/or of greater thickness.

Other objects and advantages of the present invention will become apparent throughout the following description relating to embodiments which are provided only as indicative and non-limiting examples.

The understanding of this description will also be facilitated with reference to the attached figures, which explain the characteristics of the container of the invention and its manufacture, and where:

Figure 1 shows a perspective view of a container according to the invention, with the lid closed;

Figure 2 shows, in perspective view, the container of the previous figure with the lid open;

Figure 3 shows a cross section of the same container;

Figure 4 shows an enlarged detail of the lid/container attachment in a circle in the previous figure;

Figure 5 shows a section C-C of Figure 3;

Figure 6 shows an enlargement of a corner of Figure 5;

Figure 7 shows a sectional view of a corner of the closed container;

Figure 8 shows a part of a thermoforming mold, comprising a female cavity with recesses for the container and lid;

Figure 9 shows an enlarged detail at the corner of the recess for the container;

Figure 10 repeats Figure 8 with a cardboard cover placed in the container mold cavity; and Figure 11 shows an enlargement equivalent to that of Figure 9 with the container mold cavity lined with the cardboard cover.

Referring first to Figures 1 to 7, the container of the invention comprises a container 1 hinged to a lid 2, the container 1 has a base 4, in this case a rectangular shape, and four faces 5 forming a continuous peripheral wall and whose upper edge 6 extends radially outwards along an edge 7 provided with a peripheral channel 8. A cardboard cover 40 encompasses the outer faces on one side of the base 4 and, on the other hand, the lateral faces 5. The edge top of the cardboard cover 40 is corrugated between the channel 8 and a top part, a strip, of the side faces 5.

The hinged lid 2 is capable of being elastically closed on the container 1, using homologous profiles for the channel 8 and a rib 21 of the lid 2, which are held together, one of which is a female profile (the channel 8) and the another is a male profile (rib 21) in the sense of this closure system. This is more particularly evident in the sectional view of Figure 3 and in the enlargement of Figure 4. In this configuration, the lid 2 and the container 1 are connected by a hinge 3 formed by a single piece with these two volumes, obtained through the same operation of thermoforming a plastic sheet.

Throughout the periphery of the container, the cardboard cover 40 is therefore wedged between the channel 8 and the upper parts of the faces 5 of the container 1 (see in particular in Figure 4), which forms between them a groove of receiving of substantially constant thickness, allowing effective mechanical peripheral retention throughout the periphery of the container 1. However, this mode of fastening prevents the cardboard cover panels 40 from covering the faces 5 that have overlapping portions, in the corners, as there is only room for a single thickness of cardboard. This pressure solution has multiple advantages, including eliminating any need to use chemically contaminating adhesive material (glue) and reducing the amount of cardboard to strictly necessary dimensions. Therefore, at an angle, the adjacent edges of the side panels of the cardboard cover 40 are in theory in linear contact along a flange 41.

At this inclined contact lip 41, thermoforming the plastic sheet can create some difficulties, to the extent that the plastic does not necessarily follow very close to the bottle formed by the inclined terminal edges of the two adjacent panels of the cover 40 of cardboard that join together on this line, and undesirable folds can form. One of the aspects of the invention makes it possible to avoid an inability to close the lid due to the existence of an additional thickness that causes a collision between the rib 21 and the channel 8 in this area, which would not occur if the rib 21 at all The points had a male profile that joins the female profile of channel 8 for flexible friction closure of the snap-fit type implemented in the invention.

In the cross section C-C appearing in Figure 5, as defined in Figure 3, which shows the position of the rib 21 within the channel 8, examining the corners (see Figure 5 and in particular in Figure 6 showing An enlargement of the circled corner in Figure 5) shows that there is a free space 22 at the junction 41 of the edges of the side panels of the cardboard cover 40. The four corners of the rib 21 have this clearance 22, giving the closure system additional clearance at the angles to avoid excessive friction at best and obstacles that are prohibitive to close at worst, in case additional creases or thicknesses are created during thermoforming.

The result appears in the sectional view of Figure 7, taken in a corner: there is a gap between the inner wall of the free space 22 and the outer tip of the bottle formed at the top of the joining flange between two adjacent side edges of the Cover 40 cardboard panels.

Another feature of the invention appears in the previous figures; The channel 8 has, on the inner wall (proximal to the working volume of the container 1), each rectilinear part separating the angles, the protuberances 81 being in the volume of the channel 8 (see in particular in Figure 2). These protuberances 81 effectively fit into corresponding recesses 23 made in the rectilinear portions of the rib 21 at equivalent locations. These reliefs actually result from a manufacturing-related feature, namely the existence of protrusions that are placed in the thermoforming mold to prevent the top portions of the cardboard cover 40 from bending 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. Therefore, a strip of plastic film (not shown) is placed, at the time of manufacture, above the double recess cavity 101, 102. The female mold part 100 moves, in a conventional manner, towards the plastic film and towards the mold part comprising male cores (not shown), which are placed on top of the film and also move in the opposite direction to 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, to obtain the container of the previous figures .

The cavity 100 for molding the container 1 comprises, on the edge, a peripheral shoulder 110 (see Figures 8 and 9) making it possible, as will be seen later, to mold the channel 8. The enlargement of Figure 9 shows even more clearly and highlights the teeth 111 distributed along the peripheral edge that joins the recess 101 and said shoulder 110.

These teeth 111 have a first face that is in the extension of the walls of the recess 101, and a second face that connects its upper edge to the shoulder 110. The base of the teeth 111 constitutes its thickest part, the cross section of the teeth 111 is triangular in shape. Therefore, mold the protuberances 81 of the channels 8 according to a corresponding volume: the protuberance 81 has substantially the shape of a ramp originating at the edge of the inner wall of the channel 8, which corresponds in the mold to the upper edge of the strip 44 of the cardboard cover 40 and to the upper edge of the tooth 111, the ramp then extending as the base of the channel, at the base of the tooth 111, where the projection in the volume of the channel 8 is at a maximum.

Figures 10 and 11 are identical to the previous two, except that the cardboard cover 40 is placed in the cavity 101, and the plastic sheet is thermoformed. In this case, as is particularly evident in Figure 11, the upper part of said cardboard cover 40 protrudes from the cavity 101: an upper peripheral strip 44 of the cardboard cover 40 forms a solid wall between the interior volume of the recess 101 and the shoulder 110, which results in isolating a peripheral channel 112 making it possible to mold the channel 8. This strip 44 rests on the teeth 111 distributed on the periphery of the recess 101, and which protrudes from it for a height equal to said strip residual 44.

In practice, they prevent the cardboard from bending towards the flat surface of the shoulder 110 due to the forces in action during molding, and which are as mentioned of several kinds: the forces due to the plastic film being deformed, a negative pressure in the cavities of the mold 100, which sucks the plastic sheet, and finally a positive pressure in the upper countermold, which pushes said sheet towards the cavities 101, 102 and into the peripheral channel 112. In the absence of teeth 111, these Forces, if not using thick cardboard, can bend the upper part that forms the peripheral strip 44 of the cardboard cover 40 against the shoulder, and the channel 8 could not be molded. Their presence creates the protuberances 81 in the channel 8 thermoformed from the plastic sheet.

At the edge of the recess 102 of the lid, a peripheral bead 120 is used to mold the rib 21. It comprises, in locations calculated to correspond to those of the teeth 111, the notches 121 that make it possible to mold the recesses 23 of the inner wall of the rib 21 of the lid 2, intended to cooperate with the protuberances 81 of the channel 8, which in practice are housed in the closed state of the lid 2 in the container 1.

The illustrative shapes that appear in the figures are not exhaustive of the invention, which also covers variants, in particular but not exclusively for the channel 8 and its possible sections (same as for the rib 21) for the shape and geometric volume of the container. 1 and its cover 2, and where appropriate for the shape and number of corresponding protuberances 81 and recesses 23, clearances 22, teeth 111, etc.]

Claims (6)

Yo. Container, in particular suitable for containing food, the container comprises a container (1) which is made of plastic material and is hinged to a lid (2), the container (1) is provided with a polygonal base (4) and a wall continuous peripheral comprising a plurality of flat faces (5), the upper edge (6) of said peripheral wall delimits an opening and is provided with a polygonal peripheral edge (7) that extends radially outwards and is provided with a channel ( 8) capable of cooperating with a peripheral rib (21) of the lid (2) by engaging with the rib (21) in said channel (8), and the container also comprises an outer cover (40) that is made of a material made of cardboard or other material of biological origin, fits at least in the contact of the faces (5) of the container (1) and is fixed between the channel (8) and the part of said faces (5) near the edge (6). , the polygonal rib (21) and the channel (8) fit together so as to elastically engage through frictional contact of at least a part of their walls, except at the corners of the rib (21) of the cover (2). which have a free space (22) in their interior wall, therefore eliminating contact with the interior wall of the channel (8) in each corner region. 2. Container suitable for containing food according to claim 1, characterized in that the free space (22) is rounded. 3. Container suitable for containing food according to any of the preceding claims, characterized in that the channel (8) has, in each straight segment between the corner regions, at least one protuberance (81) projecting from its inner wall, projecting in the volume of the channel (8) and fits into a corresponding formed recess (23) made in the part of the rib (21) provided to engage therewith. 4. Container suitable for containing food according to the preceding claim, characterized in that the protuberance (81) takes the form of a ramp that begins at the edge of the inner wall of the channel (8) and extends to the bottom thereof, where the projection in the volume of channel (8) is at a maximum. 5. Method for manufacturing containers comprising a container and lid according to the preceding claims, characterized in that the method comprises the following steps: - insert the cover (40) made of cardboard or other material of biological origin into the cavity (100) of a thermoforming mold comprising a recess (101) that corresponds at least partially to the shape of the container (1); - placing said cover (40) made of cardboard or other material of biological origin in such a way that its upper peripheral edge protrudes from the recess (101) by a distance equal to the depth of the channel (8); - transporting a plastic film as a continuous web between the cavity (100) and a countermold of a thermoforming mold; - to close the thermoforming mold, move said cavity (100) and the countermold between themselves and the plastic film; - molding the plastic film after closing the cavity (100) and the countermold, moving at least one molding core of the countermold and simultaneously producing a positive pressure in the countermold and a negative pressure in the cavity (100). 6. A thermoforming mold cavity for implementing the method according to the preceding claim, characterized in that the edge of the recess (101) of the cavity (100) of the thermoforming mold comprises teeth (111) distributed over its periphery, whose teeth protrude from the recess (101) in a distance equal to the depth of the channel (8), and of whose teeth a first face is in the extension of the wall of the recess (101) that protrudes, and a second face opposite the first face has the shape of ramp starting from the upper edge of the tooth (111).