EP0387133A1 - Tray-type package with a thermally produced interior coating - Google Patents

Abstract

The tray-type package comprises, on the inside and in each corner, a corner panel (28) which inclines towards the bottom of the tray by approaching the centre of the said bottom, the said corner panel being inclined at an obtuse angle with respect to the bottom and to the walls (24, 36) which define the corner. <IMAGE>

Description

The present invention relates to a packaging tray of semi-rigid material, for example corrugated cardboard, the inner walls of which are intended to be coated, by thermoforming, with a film of thermoplastic material. Such trays are commonly used to package wet foodstuffs in a modified gas atmosphere, for their preservation.

An example of a tray of this type is known from European patent EP 0 192 537. This tray is of the type produced from a blank, comprising a substantially rectangular bottom on the sides of which are articulated two longitudinal walls provided with edge panels. intended to be folded to double the longitudinal walls, and two transverse walls provided with entablatures intended to extend parallel to the bottom and towards the inside of the mounted tray. Once assembled, the plate is waterproofed by a protective film which is applied without discontinuity on its internal faces. To produce such a coating, the tray is placed in the mounted state inside a mold, then a strip of film of thermoplastic material is placed above the opening of the mold. A cover is applied to the opening of the mold, the edges of the film strip then being applied against the upper faces of the entablatures, the film is then heated to bring it to its softening temperature, then by application of pressing, blowing or sucking the film towards the inside of the tray.

The edges of the film then adhere to the upper faces of the entablatures, while its central part expands until it comes to be applied against the lower faces of the entablatures and against the side walls and the bottom of the plate. The tray is then closed by means of a tight seal in thermoplastic material.

However, it has been found that the coating film in thermoplastic material is subjected to a significant stretching especially in the angles formed by the walls and the bottom, and this all the more that the plate is high. In these areas, the film undergoes strong thinning and risks tearing during or after thermoforming. If the film breaks, the gas inside the tray escapes and the food is no longer in a conditioned atmosphere. In addition, the external humidity or that which results from the exudation of the foodstuffs can gain the cardboard through the holes and tears in the film, rapidly reducing its resistance to stacking.

The present invention aims to remedy these drawbacks and it relates to a packaging tray provided with means which make it possible to reduce as much as possible the stretching of the thermoplastic film in the angles formed by the walls and the bottom.

The packaging according to the invention is of the aforementioned type and is characterized in that it internally comprises, in the corners, corner panels which tilt at an obtuse angle on the bottom while advancing towards the center of the latter, and which are also inclined at an obtuse angle relative to the bottom and to the longitudinal and transverse walls defining the corners.

Due to the exclusive presence of obtuse angles in the corners, the thermoplastic film stretches less than in the case where the side walls are perpendicular to each other and to the bottom.

In the case of an externally rectangular tray, the corner panels are in the shape of a triangle having a base applied to the bottom.

In the case where the tray is rectangular on the outside with cutaway corners, the corner panels are trapezoidal, the large base of which rests on the bottom, and the small base of which coincides with the upper side of the cutaway .

Said corner panels can be made in one piece with the starting blank of the tray. In this Indeed, each ledge is extended at each of its two ends by a triangular or trapezoidal corner panel. The corner panels can themselves be extended by end flaps intended to be applied to a transverse wall of the tray, thereby locking the ledges and the corner panels.

• la figure 1 représente un flan étalé à plat, destiné à réaliser un plateau pourvu de panneaux de coin trapézoïdaux, dans le cas d'un panneau à coins tronqués;
• la figure 2 montre en perspective le plateau de la figure 1 à l'état semi-monté;
• la figure 3 est une vue en perspective partielle d'une autre forme de réalisation de plateau avec panneaux de coin triangulaires, dans le cas d'un panneau à coins non tronqués ; et
• la figure 4 est une vue en perspective partielle d'un plateau de même type que celui de la figure 1, mais dans lequel les panneaux de coin sont raportés.

We will now describe, by way of nonlimiting example, two embodiments of packaging trays according to the invention, with reference to the appended drawings in which:

• FIG. 1 shows a blank spread out flat, intended to produce a tray provided with trapezoidal corner panels, in the case of a panel with truncated corners;
• Figure 2 shows in perspective the tray of Figure 1 in the semi-assembled state;
• Figure 3 is a partial perspective view of another embodiment of the tray with triangular corner panels, in the case of a panel with non-truncated corners; and
• Figure 4 is a partial perspective view of a tray of the same type as that of Figure 1, but in which the corner panels are reported.

The description which follows will be made with regard to a rectangular-shaped packaging tray provided with two entablatures, but as will be seen, the invention applies to trays of all shapes, for example triangular, square or polygonal, with or without entablatures.

With reference to FIG. 1, the starting blank 10 is made of single or double thickness corrugated cardboard. It comprises a rectangular bottom 12 truncated at its corners 13 and on which are hinged by fold lines 15, 17 two longitudinal walls 14, 16 and two transverse walls 18, 20. The corrugations 11 of the carton are oriented parallel to the width of the background 12.

On the longitudinal walls are articulated, by double fold lines 22, ledges 24, 26 intended to be folded over the longitudinal walls to form double thickness walls.

Each ledge, for example 24, is extended at its ends by foldable corner panels 28, of trapezoidal shape, the small base 30 and the large base 32 of which extend substantially in the longitudinal direction. The small base 30 is on the inside of the corner panel and has substantially the same length as the corner 13.

The corner panels 28 are articulated on the ledge by a fold line 34 and are themselves extended by end flaps 36 articulated on the corner panels by fold lines 38.

The transverse walls 18, 20 are extended at each of their ends by a foldable rectangular panel 44 having substantially the same width as the truncated corner 13 and which is followed by an end flap 46 foldable along a line 47. The transverse walls carry along their longitudinal side entablatures 48, 49 foldable along fold lines 50. These entablatures are provided at their ends with locking tabs 52 intended to penetrate into slots 54 cut between the double drawdown lines 22. The ledges 24, 26 have, on their free edges, protrusions 53 capable of fitting into slots 55 cut out on the bottom, along the fold lines 15.

To shape the packaging plate, we first erect perpendicular to the bottom 12, the transverse walls 18, 20. We then erect all of the longitudinal walls 14, 16 and their edges 24, 26 perpendicular to the bottom 12, then the folds are folded over the longitudinal walls, taking care to insert the end flaps 46 between the longitudinal walls 14, 16 and the folds. The corner panels 28 are then found in the corners defined by the longitudinal and transverse walls, while the end flaps 36 are internally lining the transverse walls. Entablatures 48, 49 are then folded horizontally and their locking tabs 52 are inserted into the slots 54.

It will be noted in FIG. 2 that the corner panels 28 are inclined up and down as they approach the center of the bottom 12 and form obtuse angles with the bottom, the longitudinal walls and the end flaps 36. The lower corners of the plate formed at the junction between the base 32 of the panel and the bottom 12 have therefore been significantly brought closer to the center of said bottom with respect to the outer corners which have been represented in FIG. 2 in dashed lines. As a result, during the thermoforming of a coating film of thermoplastic material, it will be much less stretched in the region of the bottom and in the lower corners under the entablatures than it would have been if it hadn’t there was no corner sign. The risks of tearing of the film are therefore practically eliminated.

It is true that by making inclined corner panels, we sacrifice the stacking resistance of the tray compared to the case where the walls would have been vertical over the entire length of the tray, but we significantly gain on the security of the seal .

In the vicinity of the corners of the bottom 12 are incised tabs 56 capable of being raised relative to the plane of the bottom to serve as stops for the corner panels. This lifting is automatically carried out in the mold which is used to thermoform the packaging tray.

The packaging tray of Figure 3 differs from that of Figure 2 in that its corners are not truncated. It therefore comprises corner panels 58 of triangular shape. Here too, the stretch to which the coating film is subjected during thermoforming will be considerably reduced in the corners of the tray.

In the embodiment of FIG. 4, the panels 60, which occupy the same positions on the blank as the corner panels had, are now rectangular and are applied exactly on the sides 44. The corner panels 28 are at present constituted by independent parts that are inserted into the corners of the tray and which hold in place either by wedging effect between the entablatures, the tongue 56 and the side walls, or by gluing to these walls.

Likewise, the triangular corner panels of FIG. 3 may be constituted by independent added parts.

Naturally, the interior lining is thermoformed once the added corner panels have been put in place.

Claims (7)

1. Packaging tray of the type produced from a blank (10), comprising a substantially rectangular bottom (12) on the sides of which are articulated two longitudinal walls (14, 16) provided with overlay panels (24, 26) intended to be folded to double the longitudinal walls, and two transverse walls (18, 20) provided with entablatures (48) intended to extend parallel to the bottom and towards the inside of the mounted tray, characterized in that it includes internally in the corners, corner panels (28; 58) which tilt at an obtuse angle on the bottom (12) approaching the center of said bottom and which are also inclined at an obtuse angle on the longitudinal and transverse walls (14, 16, 18, 20) which define the corners. 2. Packaging tray of rectangular outer shape according to claim 1, characterized in that the corner panels (58) are in the shape of a triangle, the base of which is applied to the bottom (12) and the top of which relative to said base. coincides with the upper corner defined by two adjacent side walls. 3.- Packing tray of rectangular external shape with cut sides (44) in the corners, according to claim 1, characterized in that the corner panels (28) are trapezoidal, including the large base (32) rests on the bottom (12), and whose small base (30) coincides with the upper side of a cutaway (44). 4. Packaging tray according to one of the preceding claims, characterized in that the corner panels (28; 58) are made in the same blank as that of the packaging. 5. Packaging tray according to one of claims 1 to 4, characterized in that each ledge (24, 26) is extended at each of its two ends by a corner panel (28; 58) in the shape of a triangle or trapezium, said corner panel itself extending by an end flap (36) intended to be applied on the transverse walls (18, 20) of the plate. 6. Packaging tray according to one of claims 1 to 3, characterized in that the corner panels (28; 58) are constituted by independent parts attached to the tray. 7. Packaging tray according to the preceding claims, characterized in that on the bottom (12) of the blank are incised lugs (56) serving as a stop for the corner panels.

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