Short title: Food packaging tub

The present invention relates to a food packaging tub comprising an opening with an opening edge; a bottom with a bottom edge; a side wall joined to the opening edge and the bottom edge comprising a side wall section converging in the direction of the bottom edge; and ribs for reinforcing the side wall.

A food packaging tub of this type is known in the prior art. This known food packaging tub is used commercially for packaging pieces of fresh pineapple.

The food packaging tub has an opening with a circular opening edge and a bottom with a circular bottom edge. A stacking edge is provided directly below the opening edge along the entire periphery. The stacking edge is formed by a widened section in the side wall. The widened section is of slightly conical shape and converges in the direction towards the opening edge. By means of the stacking edge below the opening edge, empty food packaging tubs can be stacked in a defined manner without the food packaging tubs becoming stuck to one another. The circular bottom edge has a smaller diameter than the circular opening edge. The side wall below the stacking edge converges in its entirety towards the bottom edge and near the bottom edge comprises a relatively strongly converging side wall section which is convex.

Fold-like ribs are arranged on the side wall and reinforce the side wall. The fold-like ribs are in the relatively strongly converging side wall section and originate from the bottom edge. The fold-like ribs face the opening edge and extend vertically up to approximately halfway along the side wall. The ribs form a fold due to the fact that their shape is wide at the bottom and gradually narrows in the direction of the opening edge. In this case, the ribs protrude further inwards near the bottom edge than further away from the bottom edge.

Furthermore, the bottom of the food packaging tub has a convex

surface which is situated on the inside.

In view of the use of the food packaging tub, it is important that the food packaging tub is sufficiently rigid. The known food packaging tub is used for packaging fresh products, such as fruit.

In order to preserve the fruit, the fruit is sterilized in the food packaging tub. During sterilization, the food packaging tubs with its contents are passed through a zone where a temperature of approximately 80° to 100 ⁰ C prevails. The food packaging tubs are sealed with a film under such high-temperature conditions. Then, the food packaging tub with its contents cools down to room temperature.

The process of cooling down the tub from the high temperature places specific demands on the food packaging tub. The food packaging tub has to be able to resist the pressure difference which occurs during cooling down. The cooling down process results in a reduced pressure in the food packaging tub, as a result of which, for example, the side wall of the food packaging tub could become dented, which is undesirable. The design of the known food packaging tub is therefore such that undesirable deformation is prevented. To this end, for example, the fold-like ribs are provided on the, relatively strongly converging convex section of the side wall.

In a stack of filled food packaging tubs, the food packaging tub is also loaded with a pressure load on the opening edge. The side wall

^■ of the food packaging tub has to be able to withstand buckling. The forces which are introduced via the opening edge result in reaction forces on the bottom edge. As the bottom edge has a relatively. small diameter, the forces on the opening edge and the bottom edge result in a moment on the side wall. In particular, this makes the section of the side wall which converges relatively strongly towards the bottom susceptible to buckling.

In order to improve the shelf life of the fresh products in the food packaging tub, the food packaging tub is made of a. multilayered film. The film comprises a layer of plastic material, which is suitable for packaging foods, for example polypropylene (PP) , and a

' layer which is not readily permeable to oxygen, for example ethylene vinyl acetate vinyl alcohol (EVOH) . The multilayered film which is

used for the production of the known food packaging tub has a thickness of at least 1400 μm. The thickness of the material also contributes to the rigidity of the food packaging tub.

The known food packaging tub has the disadvantage that it requires a substantial amount of material in order to produce a sufficiently rigid food packaging tub. The amount of material used to a large extent determines the cost price of the food packaging tub. In addition, the material used for the food packaging tub is detrimental to the environment.

It is an object of the present invention to at least partially overcome at least one of the abovementioned drawbacks and/or to provide a usable alternative. In particular, it is an object of the invention to provide a food packaging tub which achieves a saving in the amount of material used in order, in this way, to reduce the cost price and the impact on the environment.

This object is achieved by a food packaging tub as defined in claim 1. The food packaging tub comprises an opening with an opening edge, a bottom with a bottom edge and a side wall joined to the opening edge and the bottom edge and comprising a side wall section converging in the direction of the bottom edge. Furthermore, the food packaging tub comprises ribs for reinforcing the side wall.

Characteristic of the food packaging tub according to the invention is the fact that at least two ribs are at least partially deflected in a tangential direction, said ribs being deflected in opposite directions with respect to one another.

A centre axis through the opening and the bottom defines the axial direction. The side wall extends with a specific periphery around the axial centre axis. Said tangential direction corresponds to the peripheral direction. The food packaging tub may, for example, comprise a pattern of ribs having ribs with a curvature, as well as ribs without a curvature. The ribs may be deflected over the entire length or part of the length of the rib.

As at least two of the ribs are deflected, these ribs provide

increased rigidity to the side wall. When a load acts on the side wall, several ribs cooperate. Compared to the non-deflecting ribs, the deflected ribs extend over a larger part of the side wall, so that the side wall is reinforced over a larger surface area.

The rigidity of the food packaging tub is determined by the shape as well as the thickness of the material. Preferably, the food packaging tub is produced by therrαoforming. As a result, the ribs are incorporated in the side wall and the side wall has acquired a substantially uniform wall thickness. Now that the food packaging tub according to the invention has acquired an increased rigidity as a result of its shape, it is possible to reduce the amount of material required in order to produce the food packaging tub. Even with a reduced amount of material, the food packaging tub according to the invention thus still meets the requirements imposed with regard to rigidity. It has been found that, compared to the known food packaging tub, the food packaging tub according to the invention can be produced from a multilayered film having a thickness of at least 1200 μm instead of at least 1400 μm, which results in a considerable saving in material and thus also in a considerable cost saving.

Preferably, ribs which are positioned directly next to one another on the side wall in a tangential direction are at least partially ^■ bent towards one another. The side wall is loaded through the forces acting on the food packaging tub as a result of the filled food packaging tubs being stacked and the reduced pressure prevailing inside the food packaging tub. The ribs provided offer reinforcement in order to withstand the force acting on the tub. When the ribs situated next to one another are deflected towards one another in a tangential direction, the ribs will cooperate and offer resistance to a load acting on the side wall of the food packaging tub. In particular, the side wall section which converges relatively strongly can be reinforced considerably if the ribs deflect towards one another in a tangential direction. As a result, the side wall is able to withstand a greater force compared to ribs bent towards one another in a non-tangential direction before a dent is produced in the side wall as a result of, for example, reduced pressure within the food packaging tub.

In one preferred embodiment, at least two of the deflected ribs have a length and curvature such that they touch one another locally. As a result of these ribs touching one another locally, for example at the ends towards the opening edge, a certain interconnection is created between the ribs, which increases the rigidity of the side wall. The created increased rigidity results in a saving in material. In addition, the side wall has an increased rigidity relative to the bottom, so that deformations are more likely to be absorbed by the bottom. This makes the food packaging tub dimensionally stable for a relatively long period of time.

In a further preferred embodiment, at least two of the ribs are deflected in a tangential direction over the side wall in such a manner that these ribs cross one another at least once. As a result of the crossing of the ribs, a further interconnection is created between the various ribs over the side wall. Advantageously, this ensures that local loads acting on the side wall of the food packaging tub are absorbed by several ribs. The loads are distributed over several ribs.

In order to ensure that the side wall is reinforced in a uniform manner over the entire periphery, preferably at least eight deflected ribs are uniformly distributed over the periphery of the side wall. These ribs are preferably located near the bottom edge, as in particular the side wall section which is near the bottom edge is susceptible to buckling due to the fact that it converges relatively strongly. The ends of the ribs are uniformly distributed over the periphery, for example every 45° in the case of a circular bottom edge. This prevents any weak spots from occurring in the side wall, and in particular in the side wall section which converges relatively strongly.

In a further preferred embodiment of the food packaging tub according to the invention, the food packaging tub comprises a stacking edge. The deflected ribs extend from the bottom edge essentially up to the stacking edge which is positioned near the opening edge. Advantageously, the ribs which extend over the entire side wall from the bottom edge to the stacking edge reinforce the

entire side wall.

In a further preferred embodiment, the deflected ribs are located on the outside with respect to the side wall. Because the ribs are located on the outside, they offer relatively great resistance against forces which press the side wall inwards. Such forces occur, for example, as a result of the prevailing reduced pressure in a food packaging tub which has cooled down or of the reduced pressure in the food packaging tub due to transportation by aeroplane. In addition, the outwardly directed ribs offer more resistance to a pressure load on the opening edge of the food packaging tub as a result of, for example, stacking filled food packagings . Due to the ribs being directed outwards, the pressure forces will in particular be transmitted over the ribs instead of over the side wall sections located between the ribs. Thus, the ribs offer substantially more support in withstanding a pressure load on the opening edge. Due to the additional rigidity which the food packaging tub has acquired by the fact that the ribs are located on the outside, the food packaging tub can be produced using less material while still meeting the requirements which are imposed on food packaging tubs of this type.

Preferably, the ribs are shaped like folds, the ribs being wide near the bottom edge and tapering in the direction towards the opening edge. Thus, due to the relatively great width of the fold-like ribs, additional rigidity is achieved at locations where the side wall is subjected to relatively great loads, for example near the bottom edge in a strongly converging side wall section.

The fold-like ribs are distinguished by the fact that a folded edge is present. The folded edge is situated substantially in the centre of the fold-like rib. The presence of the folded edge increases the rigidity of the rib. The end of the fold-like rib turned towards the bottom edge has a width of at most 3 mm, for example, with the width of the fold-like rib decreasing along the folded edge in the direction of the opening edge.

Using the finite element method, it has been established that the theoretical buckling load has increased from 168 N to 224 N and

buckling only occurs at a theoretical reduced pressure of 0.30 bar, rather than 0.27 bar, with a food packaging tub according to the invention compared to the known food packaging tub with the same thickness of the material and ribs which are not deflected and are on the inside, as described above. Thus, it has been found that the theoretical buckling load is increased by approximately 30% and that the permitted theoretical reduced pressure is increased by approximately 10% with the same thickness of material.

As a result of the reinforcements in the food packaging tub according to the invention, it is possible to reduce the amount of material which is required to produce the latter, thereby reducing the cost price of the food packaging tub and the impact on the environment. It has been found that savings in material of between 5% and 30% are possible using the above measures.

Furthermore, the invention relates to a food packaging tub according to claim 18. It has been found to be advantageous to reinforce a food packaging tub according to the preamble of' claim 1 by means of ribs which are located on the outside with respect to the side wall. The ribs protrude on the outside of the food packaging tub. Due to the fact that the ribs are located on the outside, the food packaging tub is reinforced, as a result of which, advantageously, relatively little material is required in order to produce the food packaging tub. This food packaging tub may be reinforced further by means of reinforcement measures which are mentioned in this patent application. Thus, the ribs may be fold-like or the converging side wall section may be convex. The ribs may extend in a straight line in an axial direction, but also comprise a gradual curve in the peripheral direction.

In particular, the food packaging tub is a fruit packaging tub for packaging fresh products. This fruit packaging tub comprises a layer of material with an oxygen barrier layer in order to preserve the products. The ribs extend in a substantially straight line and at least partially along the side wall from the bottom edge to the opening edge.

Further preferred embodiments are defined in the other subclaims .

The invention will be discussed in more detail with reference to attached drawings which show a practical embodiment of the invention, but should not be viewed as being limiting, in which: Fig. 1 shows a bottom view of a food packaging tub according to the invention;

Fig. 2, subdivided into drawings 2a to 2g, shows a developed view of the ^' side wall for a food packaging tub according to the invention with various rib patterns; Fig. 3 shows a side view of the food packaging tub, in which the ribs form a reinforcement over a part of the side wall; and Fig. 4 shows a side view of the food packaging tub according to the preferred embodiment according to the invention.

Fig. 1 shows a bottom view of the food packaging tub 10- according to the invention. The food packaging tub has a circular opening edge Ia. The opening edge Ia has a larger diameter than the bottom edge 2a. The opening edge has a diameter which is between 70 mm and 100 mm. In a protrusion on a plane through the opening edge Ia, the bottom edge 2a is inside and substantially parallel with the opening edge Ia. Furthermore, the food packaging tub 10 has a side wall 4 with a local widening, as a result of which a stacking edge 3 is formed. The stacking edge 3 is near the opening edge Ia.

At least eight ribs 5 are provided in the side wall 4 which extend from the bottom edge 2a to the stacking edge 3.. The eight ribs ¹ 5 are distributed along the bottom edge 2a at regular intervals. With a division into eight parts and taking into account tolerances in dimensional accuracy for production, the angle α between two successive ribs 5 is at least 40° and at most 50°. The side wall 4 is uniformly reinforced by the at least eight ribs 5 along the periphery, so that there are no weak spots in the side wall 4.

The ribs 5 are shaped like folds. This means that the ribs are wide near the bottom edge 2a and taper in the direction of the stacking edge 3. The fold-like ribs 5 comprise an acute angle 5a which forms a folded edge. The acute angle 5a provides additional rigidity for the fold-like rib.

Fig. 1 shows that at least one rib 5 near the bottom edge 2a protrudes at least 3 mm with respect to the side wall. In the direction towards the opening edge Ia, the protrusion gradually decreases. As the food packaging tub is most susceptible to deformation near the bottom edge 2a, the food packaging tub is additionally reinforced near the bottom edge 2a by locally protruding ribs 5.

The ribs 5 are located on the outside with respect to the side wall 4, so that they offer more rigidity compared to ribs which are directed inwards. The increased rigidity resulting from the design of the food packaging tub according to the invention allows a reduction in the thickness of the material. This results in a food packaging tub which is made using less material while fulfilling the requirements prevailing with respect to the load-bearing capacity.

Fig. 2, subdivided into drawings 2a to 2g, shows various rib patterns in a developed view of the side wall for a food packaging tub according to the invention. The ribs deflect in a tangential direction.

Fig. 2a shows a developed view of the side wall for the food packaging tub according to the invention. The curved ribs 5 are indicated schematically, the ribs having a single curve " and , deflecting towards one another in a tangential direction. The single curve is gradual. The curve has no deflections. Measured along the bottom edge 2a, there is a distance ^λ a' and a distance ^λ b' between the ends of .the ribs. The distance ^λ a' is in this case smaller than the distance ^λ b' by a factor of at least two. In another embodiment, it is possible to provide ribs where no distance is present between the. ends of the ribs. The distance ^λ a' may be zero, so that two ribs together form a V-shape.

At the location of the dashed line, the side wall changes into a relatively strongly converging side wall section in the direction of the bottom edge 2a. The ribs 5 are situated on this relatively strongly converging side wall section because this side wall section is most susceptible to deformation.

Fig. 2b shows that adjacent ribs are deflected in opposite directions with respect to one another in a developed view of the side wall. Starting from the bottom edge 2a, the ribs are directed towards the opening edge Ia, .with a section tangentially deflecting near the end of the ribs 5. Since the ribs 5 fan out in opposite tangential directions, the ribs have a V-shape. In the converging side wall section, the surface area of the side wall between ribs extending only vertically would become ever larger in the axial direction towards the opening edge Ia. As a result of the V-shape of the ribs, the surface area of the side wall 4 between adjacent ribs is reduced, which results in a reinforcement of the side wall.

Fig. 2c shows a developed view of a food packaging tub according to the invention, in which ribs are provided in the side wall 4 and deflect tangentially. The neighbouring ribs 5 are positioned along the bottom edge in mirror-symmetrical fashion with respect to one another. The ribs 5 have multiple curves and comprise a first curve 5b ^' in such a manner that the ribs 5 deflect towards one another and cooperate when a force is transmitted. After a second curve 5c, the ribs extend further over the side wall 4. Of the double curve, in particular the first curve 5b is effective in reinforcing the side wall 4.

Fig. 2d diagrammatically shows an embodiment of the food packaging tub according to the invention in a developed view, in which the ribs 5 extend from the bottom edge 2a up to the stacking edge 3. Neither at the bottom edge, nor at the stacking edge do the ribs touch one another. As the ribs 5 extend over substantially the entire side wall and as the ribs are turned outwards, this embodiment of the food packaging tub according to the invention already achieves a considerable reinforcement, as a result of which the food packaging tub can be produced using less material while still meeting the requirements with respect to the occurring loads.

Fig. 2e diagrammatically shows, in a developed view of the food packaging tub, a further reinforcement compared to the food packaging tub shown in Fig. 2c. Fig. 2e shows that neighbouring ribs 5 touch one another near the bottom edge. Two ribs 5 on the side wall 4 meet near the bottom edge 2a in such a manner that the two

ribs together enclose a V-shape. In addition, the ribs 5 meet at the stacking edge 3. Due to the fact that the ribs touch one another, an interconnection is created by the various ribs. This provides

« additional reinforcement of the side wall.

In the developed view of the side wall from Fig. 2f, two ribs 5 directly adjacent to one another cross one another at least once. As a result of the ribs 5 crossing, the side wall 4 is divided further into side wall sections . Dividing the side wall 4 further leads to the resulting relatively small side wall sections offering higher resistance to reduced pressure which prevails inside the food packaging tub.

The interconnection of the ribs 5 shown in Figs. 2e and 2f is reminiscent of the gothic style of architecture, the buildings of which are characterized by pointed arches and cross vaults. The pointed arches and crossed ribs illustrated in Figs. 2e and 2f result in a reinforcement of the side wall 4 of the food packaging tub.

Fig. 2g, in a developed view of the side wall of the food packaging tub, shows a pattern of ribs, in which the ribs 5 cross one another at least twice. As a result, a fine-meshed interconnection of ribs is created on the side wall. The side wall 4 is divided into smaller side wall sections so that increased resistance can in particular be offered against a prevailing reduced pressure in the food packaging tub.

Fig. 3 diagrammatically shows, in a side view of the food packaging tub according to the invention, how the ^• ribs 5 are disposed in the relatively strongly converging side wall section 4a in the bottom part of the food packaging tub. In the case of a pressure load in a direction parallel to the centre axis of the food packaging tub, reaction forces will act on the bottom edge 2a, as a result of which a moment .will start to act on the relatively strongly converging side wall section 4a. This makes the side wall section 4a in particular susceptible to buckling. The side wall section 4a is of convex design, which already improves the rigidity compared to a side wall section which is purely conical. The convex shape has a

radius which is between at least 40 mm and at most 60 mm.

Preferably, the convex shape has a radius of at most 50 mm. Buckling is also counteracted by means of a pattern of ribs 5, as shown in Fig. 3. Neighbouring ribs 5 cross one another and their ends touch ribs situated at a distance. This results in an interconnection of ribs ^■ and the strongly converging side wall section 4a is divided into relatively small side wall areas. The relatively small side wall areas are relatively less susceptible, to deformation when the food packaging tub is subjected to a pressure load. The dashed line in Fig. 3 indicates the circular transition edge from the slightly conical side wall section 4b to the convex side wall section 4a. The relatively strongly converging side wall section adjoins the bottom edge 2a. The degree of convergence can be indicated by means of the vertex angle of an imaginary cone through the bottom edge 2a and the circular transition edge. In this case, the relatively strongly converging side wall section has a vertex angle of at least 30°.

The fact that the side wall section 4b above the circular transition edge remains substantially flat is an additional advantage. The flat, slightly conical side wall section 4b provides a space which is suitable, for example, , for applying a label or embossed brand

^■ logo. It should be noted that an embossed logo in the side wall section 4b also contributes to an increased rigidity.

The ribs 5 provided increase, the' rigidity of. the food packaging tub. so that a food packaging tub can be produced using less material while still .fulfilling the requirements which are imposed in connection with various load conditions .

Fig. 4 shows a side view of the preferred embodiment of the food packaging tub 10 according to the invention. In the preferred embodiment, many of the reinforcement measures already described above have been combined in one food packaging tub. Ribs are disposed over the entire side wall 4 between the bottom edge 2a and the stacking edge 3. The ribs 5 extend from the. bottom edge 2a up to

^■ the stacking edge 3, the ribs 5 near the bottom edge 2a being of wide design, for example at most 3 mm, and the width decreasing in a direction towards the stacking edge 3. The ribs 5 are ^' turned outwards with respect to the side wall 4. Near the bottom edge 2a,

the ribs 5 protrude outwards by at least 3 mm, with the protrusion of the ribs gradually decreasing in the direction towards the opening edge. As a result, the ribs 5 offer increased resistance compared to inwardly directed ribs when a reduced pressure occurs inside the food packaging tub. The ribs 5 of the food packaging tub form a certain pattern. In the pattern, neighbouring ribs cross one another twice, so that the side wall 4 is divided into side wall areas. These side wall areas offer increased rigidity to the entire side wall 4 as a result of the fact that they are bounded by sections of ribs 5. The ends of the neighbouring ribs 5 come together near the bottom edge 2a, thus creating V-shaped ribs. The various measures which have been taken in order to reinforce the side wall 4 result in a significant saving on the amount of material used to produce the food packaging tub.

The food packaging tub is used for packaging fresh products. To this end, a transparent multilayered film is preferably used during production by thermoforming, with a film layer on the inside forming a barrier to oxygen. The multilayered film has at least three layers, of which an inner film layer is not readily permeable to oxygen, which increases the storage life of the fresh products. A film made of ethylene vinyl acetate vinyl alcohol (EVOH) is particularly suitable as oxygen barrier layer. A suitable multilayered film is obtained by combining the oxygen barrier layer with layers of polypropylene (PP) . The resultant food packaging tub can be filled with food and be covered with a film or alternatively with a lid.

It has been found that, as a result of the relatively rigid shape, the food packaging tub as illustrated in Fig. 4 can be produced with a multilayered film thickness of at least 1000 μm, preferably at least 1200 μm, instead of the multilayered film thickness of at least 1400 μm which was required to produce the prior art food packaging tub described above. The saving in material produces an economic advantage and results in an environmentally friendly food packaging tub. In addition, the pattern of ribs as illustrated in Fig. 4 is advantageous when pineapple is packaged in the food packaging tub according to the invention, as the pattern of ribs is reminiscent of the exterior of a pineapple.

Many variants are possible in addition to the embodiments according to the invention illustrated in the figures. Thus, it is possible for example to use several ribs, as a result of which a more fine- meshed pattern is produced on the side wall. Further deformations and angles can be produced in the side wall in addition to the ribs in order to reinforce the side wall. Thus, it is possible to produce for example indentations or brand names in relief in the side wall, which improves the rigidity of the food packaging tub. It is also possible to add more material locally in order to reinforce the food packaging tub locally.

In a variant, it is also possible to arrange the pattern of ribs on the side wall of a food packaging tub with an oval or organically shaped opening edge.

Thus, a food packaging tub according to the invention has been produced which is suitable for use in circumstances where reduced pressure is created inside the food packaging tub as a result of sterilization or air transportation or where the opening edge is subjected to a pressure load due to the stacking, for example. As a result of the expedient arrangement of ribs on the side wall, the resultant food packaging tub according to the invention has acquired a rigidity which has been increased by the shape such that the amount of material required to produce the food packaging tub can be reduced. This results in an economically advantageous and environmentally friendly food packaging tub.