EP2338800A1

EP2338800A1 - Cardboard tray for foodstuffs, with strengthened edge, and relevant manufacturing process

Info

Publication number: EP2338800A1
Application number: EP09425530A
Authority: EP
Inventors: Anderlini Michelangelo
Original assignee: Cartonspecialist Srl
Current assignee: Cartonspecialist Srl
Priority date: 2009-12-23
Filing date: 2009-12-23
Publication date: 2011-06-29
Anticipated expiration: 2029-12-23
Also published as: ATE547333T1; EP2338800B1

Abstract

The cardboard tray for foodstuffs has an opening rim (8) in the shape of a flat ring and portions (4') carrying creases, which have reinforcing fillets fastened to said rim and reproducing its shape and are made of the same cardboard constituting the tray, as they are constituted of appendices of the cardboard of the rim of the cup-type container which form a single body with said cardboard along certain sections (8') of the outer edge of the rim which are free of creases.

The manufacturing process provides for the following phases:
- Obtaining by die cutting a first cardboard sheet (2) cut according to a contour (3) suitable for obtaining, by deep drawing and thermal forming, a tray (7) of a pre-determined shape, where the outer contours of portions (5) of the initial sheet (2) non destined for creasing happen to be formed like appendices (6;9) capable of superimposing themselves, by bending to the rim (8) of the trya opening at the end of the deep-drawing and thermal forming process.
- Backward bending, after the initial sheet (2) has been subjected to the creasing, deep-drawing and thermal forming phases, of the mentioned appendices (6;9) along the lines (8) belonging to the outer contour of the rim of the tray, until they superimposes themselves to said rim, that they are finally welded to.

Description

The object of the present invention is a cardboard food tray with a reinforced opening rim, and its manufacturing method.
The market for food containers used to package meats, vegetables, frozen items and food in general shows to be extremely variegated and diversified.
Among the various food trays, those made of cardboard, and in particular an ovenable cardboard, are enjoying increasing success. Thanks to their characteristics, the cardboard trays are in fact fitting the most demanding packaging requirements and can be used in freezers, in refrigerators and in ovens moreover they can be printed on their outer side.
There are at the moment two types of cardboard food trays on the market: normal thermally formed trays, and trays with a reinforced peripheral rim.
The normal thermally formed cardboard containers show a moderate rigidity on their peripheral portions, with specific regard to the square and rectangular forms. These containers can be used where the container's closing system does not require a particular rigidity of the rim (for instance, a sealing by thermal sealing, with lids made of cardboard and/or film). For closing systems that require a thermal shrinking film around the container or a high-traction wrapping film around the container, a simple thermally formed cardboard container proves to be too weak, and its rims and walls will deform.
In order to eliminate this disadvantage, certain reinforcing systems have been developed for the rim at the opening of the tray, rim that has generally the shape of a flat ring . According to some of these reinforcing systems, the peripheral rim of the tray is reinforced by a ring associated with the upper rim, that duplicates the outline of the same, or by associating a reinforcing element with the rim which is subdivided into a first portion capable of being stably associated with a portion of the board next to its connection with the walls, and into a second portion with the walls next to the rim; these two portions of the reinforcing element present a development that duplicates the rim and sides form, so as to define an additional surface or layer capable of allowing a stiffening of the area between the rim and the walls. An example of the mentioned reinforcing systems is schematically described in the following, with reference to the Figures 5-8, and in greater detail in the document WO 02/060768 A1 .
There are moreover other reinforcing systems that envision adding reinforcing segments to be coupled to the tray's upper or lower rim. An example of these latter reinforcing systems is schematically described in the following with reference to the Figures 9-12, and in greater detail in the document IT 1364833 .
The systems exemplified in the Figures 5-8 have, while on one side offering the advantage of stiffening the entire rim of the container, the disadvantage of wasting a lot of material. In order to produce the reinforcing elements, which are continuous and integrally follow the outline of the container rim, it becomes necessary to fully discard the internal portion of the same elements or to find an alternative usage of the same portions that is not always available because of their size or number.
A further disadvantage is the fact that the coupling of such a ring to the upper rim inhibits the thermal welding properties, of any heat sealable lid, when using a material similar to that of the container itself. Therefore, the containers obtained in this manner can be sealed easily only by using certain methods (for instance filming), but cannot be sealed by heat sealing. In This case users might be obliged to use different kinds of trays depending on the sealing system they need or use.
The systems of a type shown in the Figures 9-12 have the advantage of significantly cutting back on the consumption of material needed for the reinforcing action, but make it difficult to realize them at moderate costs because of the complexity of the operations to be carried out in order to apply the reinforcing element and permanently coupling it to the container.
In view of the mentioned drawbacks, the scope of the present invention is to realize a cardboard food tray with a reinforced opening rim and the relative manufacturing process, being capable of ensuring at least one of the following advantages:

The reinforcements allow a considerably reduced consumption of raw material and happen to be firmly fastened to the rim of the tray,
The reinforcements are achieved as a result of a manufacturing process of considerably reduced complexity and costs, and the emplacing and coupling the reinforcements to the proper positions is being facilitated;
The elements of the container's peripheral rim, which are most exposed to a risk of deforming, are provided with adequate stiffness;
The container thus obtained allows applying all different container closing systems (heat sealing, filming, etc.).

For this purpose, the tray and its relative manufacturing process are as characterized in the following claims 1 and 3.
The characteristics and advantages of the invention will be better evident from the following description relating to a few examples of embodiment of a non-limiting nature, made with reference to the enclosed figures, in which:

The Figures 1-3: show phases of the already known manufacturing process of cardboard tray fitted with a rim to be reinforced;
The Figure 4: is a perspective view of the tray of Figs. 3;
The Figures 5-8: show phases of the already known manufacturing process of the cardboard tray using a continuous cardboard ring reproducing the shape of the rim;
The Figures 9-12: show phases of the already known manufacturing process of the rim by using cardboard segments reproducing the shape of the rim;
The Figures 13-15: show a tray with a reinforced rim according to the invention:
The Figures 16-19: show phases of a first example of the manufacturing process according to the invention;
The Figures 21-24: show phases of a second example of the manufacturing process according to the invention;
The Figures 20, 25: are figures evidencing the reduced consumption of material needed to realize the reinforcement according to the invention.

Figs. 1-3 schematically show phases of the known manufacturing process of cardboard trays with a rim not reinforced.
In particular, Fig. 1 shows the cardboard utilized for manufacturing a cup-type container prior to the start of its fabrication. The contour "a" of the hatched portion stands to indicate the line along which, in a first working phase, the die cutting of the cardboard is to occur. The hatched lines inside the mentioned contour stand to indicate the areas "b" of the cardboard that will be subjected to a creasing suitable for favouring a subsequent deep drawing and thermal forming phase.
Figs. 2 shows the cardboard as it looks after the die cutting and creasing phase, while the Figures 3 and 4 show a top view and a prospective view, respectively, of the cup-type container as it looks at the end of the deep drawing and thermal forming phase.
The Figs. 5-8 show, in a very simplified form, the reinforcing process for the already known rim of the cup-type container of the Figs. 3 and 4, based on a continuous ring.
In particular, Fig. 5 shows the cardboard utilized for obtaining the reinforcement of the rim. The two hatched lines "c" stand to indicate the contours of the cardboard ring to be shaped by die-cutting.
Fig. 6 shows the portions of the initial cardboard (hatched parts) destined for scrapping, while Fig. 7 shows the ring "d" obtained by die-cutting the cardboard of Fig. 5. Finally, Fig. 8 shows a top view of a cup-type container after the application and welding of the ring on its rim.
The Figs. 9-12 are referring to phases of the already known process of reinforcing the rim while using cardboard segments reproducing the shape of the rim.
In particular, Fig. 9 shows the cardboard utilized for obtaining the reinforcement of the rim, where the hatched lines stand to indicate the contour of the cardboard segments to be obtained by die-cutting. Fig. 10 shows the portions of the initial cardboard (hatched parts) destined for scrapping, while Fig. 11 illustrates four segments "e" obtained pursuant to the mentioned die-cutting and as emplaced at the instant of their application on the board of the tray. Finally, Fig. 12 shows a top view of a tray after the application and welding of the segments on its rim.
The Figs. 13, 14 and 15 respectively illustrate a prospective view, a top view and a front view of a tray with a reinforced rim according to the invention. The tray according to the invention is, like the tray of Fig. 4, of a type produced according to the conventional method, which has a rim 8 of the opening in the shape of a flat ring, angular portions 4' fitted with creases, and reinforcing fillets 6', 9' fastened to its rim, and is characterized by the fact that the fillets are constituted of appendices of the same cardboard of the rim of the tray that form a single body with said cardboard along sections 8' of the outer contour of rim portions free of creases.
The tray with a reinforced rim as above essentially presents the following advantages:

The cup-type container thus obtained is compatible with all the closing systems for the same (thermal welding, filming,);
The presence of the rim sections 8', wherein the cardboard of the fillets forms a single body with the one of the rim, constitutes a useful method for joining the fillets to the rim, supplemental with respect to the means (gluing, thermal welding or other) used to fasten the fillets to the rim;
It becomes possible to produce the reinforcement of the rim with a considerably reduced need of scrapping than before;
It becomes possible to produce the reinforcement simultaneously with the cup-type containers manufacturing process, with only slight changes with respect to the traditional method.

The example of the Figs. 13-15 refers to the case in which it becomes necessary to produce a reinforcement on all four sides of the cup-type container. If, on the contrary, the cup-type container is to be used for closing systems with films primarily exercising pressure forces on the longest sides of the tray, the reinforcing fillets on the shorter sides may be missing.
The Figs. 16-19 shows the phases of a first manufacturing process of a tray with a reinforced rim according to the present invention. The example refers to the case where it suffices to produce a container with reinforced rims only along the two longer sides of tray, because a reinforcement limited to the mentioned two sides is adequate to withstand the pressure forces exercised on the rim of the majority of the films that close the openings of the tray.
As in the traditional technology process, the manufacturing process comprises the following phases:

Realizing, by die-cutting a sheet 1 of food approved cardboard, an initial sheet 2 of a cardboard cut according to a contour 3 and suitable for obtaining, by deep-drawing and thermal forming, a cup-type container (as per Fig. 19) of a predetermined shape (Fig. 16 shows the hatched outline both of the contour 3 of the portion to be cut out, as well as the internal areas 4 of said portion, to be subsequently subjected to creasing);
Creasing of the portions 4 of the mentioned initial sheet destined for a subsequent deep-drawing (Fig. 17 represents the initial sheet 2 with the portions 4 being creased);
Deep-drawing and thermal forming of said initial creased sheet, suitable for conferring the tray the pre-determined shape; and is characterized by the fact that:
The outer contour of two portions 5 of the initial sheet which are not destined for a creasing are conformed like appendices 6 in the shape of strips of a width matching the width of the rim 8 of the tray's opening, appendices suitable to be overlapped, by bending, on the rim at the end of the deep drawing and thermal forming phases;
After the initial sheet has been subjected to the creasing, deep-drawing and thermal forming phases, so as to obtain a cup-type container 7 of the pre-determined shape (Fig. 18), the mentioned appendices 6 are bent along lines 8' belonging to the outer contour of the rim 8, until they superimpose themselves on said rim, that they are finally welded to (for instance by gluing or thermal welding).

At the end of the process, a tray with a reinforced rim, as shown in Fig. 19, is obtained.
In order to ease the final bending of the appendices 6 along the mentioned lines 8' belonging to the outer contour of the tray, the same lines are incised in sections during the initial die-cutting phase.
The advantages of the process according to the invention are clearly evident from the foregoing description.
One of the evident advantages is a reduced consumption of raw material needed to achieve the reinforcement. This is evidenced by Fig. 20, where a continuous line represent the food-approved cardboard sheet needed to realize a traditional tray without a reinforced rim, and a hatched line indicates the slight widening needed to realize a cup-type container of the same dimensions but with a reinforced rim.
Other evident advantages are:

The structure is reinforced only in the sections needed;
The operations of positioning and coupling the reinforcing cardboard in its appropriate position are rendered simple and easy;
The shape of the initially die-cut cardboard allows providing, immediately and in a single piece, the rim reinforcing elements of the container, albeit without compromising the subsequent thermal forming operations of the same, and while guaranteeing that the reinforcing elements remained stiff, so as provide a maximum stiffening efficiency once they are coupled to the rim of the container;

The connection of the lateral extensions to the cardboard rim provided only in the sections that are not creased generates in the neighboring sections a gap free of material, that allows an easy forming of the die-cut item and keeps the flaps perfectly rigid;
The die-cut item thus designed can be achieved through a single die-cutting operation, and does not involve passages or operations in addition to the usual die-cutting/rope-finishing operations;
Being integral with the body of the container, the lateral extensions can be easily bent back to the desired position, both manually and automatically.

Figs. 21-24 show the phases of a second example of a manufacturing process of a tray with a reinforced rim according to this invention. The example refers to a case in which it is necessary to realize a tray with rims reinforced on all sides.
The manufacturing process is similar, with some obvious variants, to the previous one. The only variants are the provision of two additional appendices 9 on the initial sheet, and the likewise backward bending of these appendices on the rim of the cup-type container at the end of the deep-drawing phase.
Even for this second example, the consumption of raw material needed for obtaining a reinforcement is quite limited, as evidenced in Fig. 25, where a continuous line represents the food-approved cardboard sheet needed for realizing a traditional tray, and a hatched line indicates the slight widening needed to realize a tray of the same size but with a reinforced rim on all sides.
The invention has been previously described with reference to two preferred examples of embodiment. It is however evident that numerous other variants, substitutions and additions can be applied without thereby abandoning the spirit of the invention and its scope of protection, as defined by the claims to follow.
One of these obvious variants may concern the ways of bending back the reinforcing fillets on the rim of the tray. In fact, instead of being bent back toward the top until they superimpose themselves on the upper surface of the rim, as described in the previous examples, these fillets can in fact, in an entirely equivalent manner, be bent back toward the bottom, until they superimpose themselves on the back of the rim.

Claims

Cardboard tray for foodstuffs, fitted with an opening rim (8) in the shape of a flat ring and portions (4') with creases, where reinforcing fillets (6,9) are present fastened to the rim and reproducing its shape, characterized by the fact that said fillets (6',9) are made of the same cardboard of the container and are constituted of appendices of the rim which form a single body with the cardboard of the container along sections (8') of the outer edge of the rim that are free from creases.
Cardboard tray for foodstuffs according to claim 1, characterized by the fact that said fillets appear bent backward on the rim along the mentioned sections (8') of the outer edge of the rim.
Manufacturing process of a cardboard tray for foodstuffs, fitted with a reinforced opening rim (8) having the shape of a flat ring, comprising the following phases:
- Obtaining, by die cutting, an initial sheet (2) of a cardboard cut according to a contour (3) suitable for obtaining, by deep drawing and thermal forming, a cup-type container (7) of a pre-determined shape;

- Creasing of the portions (4) of said initial sheet destined for a subsequent deep-drawing process;

- Deep-drawing and thermal forming of said creased initial sheet, suitable for conferring the tray the said pre-determined shape;
characterized by the fact that:
- Portions (5) of the outer contour of the initial sheet (2) which are not destined for creasing are conformed like appendices (6;9) in the shape of strips of a width substantially equal to the width of the rim (8) of the container opening, said appendices being suitable to be overlapped, by bending, on the rim (8) at the end of the deep drawing and thermal forming phases;

- After the initial sheet (2) has been subjected to the creasing, deep-drawing and thermal forming phases, the mentioned appendices (6;9) are bent back along lines (8') belonging to the outer contour of the rim (8) until they superimpose themselves on said rim, that they are finally welded to.
Manufacturing process of a cardboard tray according to claim 3, characterized by the fact that the die-cutting of the initial sheet (2) also provides for an incision of the sheet in sections along the lines (8') along which the mentioned appendices are bent back in a subsequent phase.
Manufacturing process of a cardboard tray according to claim 3, in where the final welding of the appendices (6;9) on the rim (8) of the cup-type container occurs by gluing or thermal welding.