EP1502867A1

EP1502867A1 - Disposable plastic container

Info

Publication number: EP1502867A1
Application number: EP03017258A
Authority: EP
Inventors: Ian C. Grimbly; Clive B. Hammond
Original assignee: Cryovac LLC
Current assignee: Cryovac LLC
Priority date: 2003-07-30
Filing date: 2003-07-30
Publication date: 2005-02-02

Abstract

An open top, semi-rigid, plastic receptacle (100) capable to undergo a partial, reversible, and controlled collapse comprising a bottom (2) which can be wedge-shaped or flat and walls (3, 4) upstanding from said bottom and ending up in a continuous flange (5), wherein said walls comprise opposing parts flaring out from said bottom, each of said opposing parts containing hinge lines (6a, 6b), parallel one to the other and substantially orthogonal to the desired direction of the controlled collapse of the receptacle.

The open top receptacle of the invention allows the customer to easily and cleanly grasp the product loaded thereon, extracting it from the receptacle, if desired, by means of a controlled collapse of the receptacle walls, or to extract the product from the receptacle by sliding it over one of the receptacle walls following its collapse.

Description

The present invention relates to a disposable plastic container suitable for food packaging.
More particularly the present invention refers to an open top receptacle for food products made of plastic material and closeable either by film/sheet lidding or film wrapping, which receptacle is designed to be collapsible in a controlled manner to allow the consumer to have an easy access to the food products contained therein. This "controlled collapsibility" would allow the customer either to more easily extract the food from the container and, in case of fast food items, such as cold or hot sandwiches, to consume the food in situ if desired.
Actually the sandwich market is heavily dominated by the plastic thermoformed wedge packs, heat-sealed on the open top with a transparent plastic film. This is the most common packaging system for products like sandwiches that are seen in supermarkets, service stations, entertainment venues and other locations where it is important to display food and keep it fresh for at least 2-3 days. One of the problems with this type of packs is the difficulty met by the end users to remove the sandwich from the plastic receptacle without getting dirty. In order to avoid the filling falling out in transit, the triangular packs are in fact designed to be a close fit to the sandwich they contain, with the edges of the wedge that are specifically pinched in to keep the comers of the bread together. When the customer opens the pack and tries to somehow grasp the food product to draw it out, he inevitably ends up pushing his fingers in between the slices of bread and particularly when the sandwich contains a soft fill, or a grease, such as butter, or a creamy sauce such as mayonnaise, this step can hardly be performed cleanly.
The same type of problem is faced by the customers with those trays that contain food products that fill completely or almost completely the cavity of the tray, particularly if their consistency is soft, such as for instance meat loaves, pies, or rolls.
It is therefore desirable to provide an open top receptacle that may allow the customer to easily and cleanly grasp the product loaded thereon, extracting it from the receptacle, if desired, by means of a controlled collapse of the receptacle walls, or that may allow the customer to extract the product from the receptacle by sliding it over one of the receptacle walls following its collapse.
It is also desirable to provide such an open top receptacle that can be closed, once loaded with the product, by means of a heat-sealable lidding film or sheet, or by means of an integrated closure system.
It is further desirable to provide such an open top receptacle made of a heat resistant material so that the receptacle itself and the product contained therein will not be damaged or contaminated upon exposure to heat, be it accidental or intentional to heat, cook or thaw the product contained therein.
It is still yet further desirable to provide such an open top receptacle which can be easily and inexpensively made, e.g. by thermoforming.
These and other objects of the present invention can be achieved by providing an open-top, semi-rigid, plastic receptacle that allows the customer to easily and cleanly reach the food product contained therein by pressing down, manually, on the top flange of the receptacle causing the walls of the container to collapse in a predictable manner and thus exposing at least a portion of the packaged product.
The first object of the present invention is therefore an open top, semi-rigid, plastic receptacle capable to undergo a partial, reversible, and controlled collapse comprising a bottom and walls upstanding from said bottom and ending up in a continuous flange, wherein said walls comprise opposing parts flaring out from said bottom, each of said opposing parts containing hinge lines, parallel one to the other and substantially orthogonal to the desired direction of the controlled collapse of the receptacle.
In one embodiment of the invention the receptacle also comprises corrugation lines in the receptacle walls that connect the opposing parts comprising the hinge lines, said corrugation lines being parallel to the hinge lines. Said corrugation lines, if present, are preferably positioned in a band of the walls that can be defined isometrically to the band between the lowermost and the uppermost hinge lines in the hinge containing opposing walls.
In another embodiment of the invention the receptacle also comprises enhanced facets in the receptacle walls that connect the opposing parts comprising the hinge lines. Said facets protrude alternately outboard and inboard, are parallel to the hinge lines, and are positioned in a band of the walls that can be defined isometrically to the band between the lowermost and the uppermost hinge lines in the hinge containing opposing walls.
In one embodiment of the invention the receptacle also contains ribs, designed to give vertical stiffness to the receptacle walls above and below the collapsible section and lend rigidity to the receptacle bottom.
As used herein the term "semi-rigid" when referred to "receptacle" is intended to refer to a receptacle that is capable of supporting itself and that has a specific shape, size and volume but whose shape may be reversibly changed by the application of a small pressure, such as the pressure that can normally be exerted by the hand of an adult without undue effort.
The term "reversible" when referred to "collapse" is used herein to mean that when the application of pressure is discontinued the receptacle returns back essentially to its original moulded at rest state.
In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawings in which:
Fig. 1 is a perspective view (top-bottom) of one embodiment of a receptacle in accordance with the present invention;
Fig. 2 is a different perspective view (bottom-top) of the same receptacle of Fig. 1;
Fig. 3 is a perspective view (top-bottom) of a variant of the embodiment of Fig. 1
Fig. 4 is a different perspective view (bottom-top) of the same receptacle of Fig. 3.
Fig. 5 is a perspective view (top-bottom) of another embodiment of a receptacle in accordance with the present invention;
Fig. 6 is a different perspective view (bottom-top) of the same receptacle of Fig. 5 while Fig. 7 and Fig. 8 are side views of the same receptacle.
Fig. 9 is a perspective view (top-bottom) of a variant of the embodiment of Fig. 5;
Fig. 10 is a perspective view (bottom-top) of the receptacle of Fig. 9;
Fig. 11 is a perspective view (top-bottom) of another embodiment of a receptacle in accordance with the present invention;
Fig. 12 is a perspective view (bottom-top) of the receptacle of Fig. 11;
Fig. 13 is a perspective view (top-bottom) of a variant of the embodiment of Fig. 12; and
Fig. 14 is a perspective view (bottom-top) of the receptacle of Fig. 13.
The receptacle 100, shown in Fig. 1 and in Fig. 2, comprises a bottom 2, which in this embodiment is wedge-shaped, substantially upright sidewalls 3 laterally closing the wedge and creating the long sidewalls of the receptacle and flaring out sidewalls 4 that create the short sidewalls of the receptacle. A top flange 5 is the upper periphery of the receptacle and extends around its open top in a continuous unbroken manner, wherein 5a is the flange portion, which flares from sidewalls 4, and 5b is the flange portion that flares from sidewalls 3. Said top flange 5 is planar, i.e. it lies completely within a plane. In the case of the receptacle of this first embodiment that has a wedge-shaped bottom 2 and that is specifically designed for sandwich packaging, generally the package is stored on the shelves lying on one of the flaring out sidewalls 4 and in that case the plane of the flange 5 will be angularly disposed with respect to the plane of the flaring wall used to support the package. The receptacle 100 of Fig. 1 and 2 comprises on sidewalls 4 two hinge lines, 6a and 6b, that are formed by wave-shaped deformable folds. Said hinge lines are parallel one to the other and in this embodiment parallel to the top flange 5a. The distance 7 between these two hinge lines, as well as the distance between them and the bottom of the receptacle and the flange thereof, will suitably be selected depending on the length of sidewalls 4, on the angle between these sidewalls and the plane of the flange and mainly on the size of collapse desired. Instead of two hinge lines as in Fig. 1, there could be more than two, e.g. three, four, or more hinge lines. The width of these hinge lines, indicated in Fig.1 as 8, is very small, typically up to 5 mm, preferably up to 4 mm, more preferably up to 3 or even 2 mm. Wider hinges might be used but this will not improve collapsibility while it will increase the void volume within the receptacle and affect the external appearance of the receptacle that should be as smooth as possible to be appealing to the customers. In Fig.1 the two hinge lines 6a and 6b will divide the receptacle into three bands or sections, a lower section comprising the wedge-shaped bottom of the receptacle and up to the lower hinge line 6a, a middle section comprised between the two hinge lines 6a and 6b and a top section from the hinge line 6b to the receptacle flange 5. In the embodiment represented in Fig. 1 and in Fig. 2, along sidewalls 3, in the middle section, there are corrugation lines 9 that are aimed at precisely controlling that the direction of collapse of the receptacle sidewalls 4 be orthogonal to the hinge lines as well as to the corrugation lines. Finally the bottom section and/or the top section of the receptacle 100 comprise a plurality of ribs 10 to increase the vertical stiffness of sidewalls 3. Also, the receptacle in this Fig. 1 is provided with a separation (denesting) feature 11, that in this Figure is positioned in flange 5 at all the internal comers of the receptacle and is of identical shape. In particular in this Figure the denesting feature is a conic with negative draft in the sidewalls whose top edge is coincidental with the plane of the flange and protrudes outboard of the cavity. This separation feature however might also be positioned on only some of the corners and be of a shape different for each comer. Said separation feature 11 is useful to avoid the receptacles 100 telescoping into each other or otherwise locking together, when they are stacked.
For packaging sandwiches, typically two halves per pack, the standard dimensions of the receptacle 100, that will normally be symmetrical, with sidewalls 4 of the same length and an inner angle of the wedge-shaped bottom comprised between about 90° and about 120°, the length of sidewalls 4 will normally be comprised between 12 and 18 cm, typically about 14-16 cm, and their width will be generally comprised between 5 and 10 cm, typically about 6-8 cm. The two hinge lines may be positioned along sidewalls 4 at a distance of e.g. 4, 5, 6, cm and 8, 9,10 cm respectively from the flange. Their width may be about 2-3 mm. The corrugations lines 9 may be parallel flutes, furrows, ridges, crests or grooves that are formed in the side walls 3, i.e. in the side walls connecting the side walls comprising the hinge lines, in the middle section, i.e. in the virtual section of the receptacle side walls 3 comprised between the plane passing through hinge lines 6a and that passing through hinge lines 6b.
The width of the flange is not critical. If the receptacle is closed by heat-sealing a lidding film or sheet onto the flange, then the flange should be at least 3-4 mm wide. If the receptacle is closed by wrapping up, actually the flange may be even smaller than that. In such a case the receptacle will preferably have a flange structure that prevents splitting or tearing of the wrapping film on the edges of the receptacle itself. As an example, the edges of the flange may be rounded or curved downwards and slightly inwardly so that the wrapping film that will be stretched or shrunk over and around the receptacle will not be hit by sharp free edges of the flange structure.
In one embodiment of the present invention that is not illustrated here, a covering lid may be included and unitarily formed with the receptacle. In such an embodiment the lid and the receptacle are a single continuous piece of material formed simultaneously with a hinge, formed integrally therewith, which on deformation allows the covering lid to swing backwards and forwards on opening and closing the receptacle. With reference to the receptacle of Fig. 1, if present, said hinge articulatably linking the receptacle to its lid would be positioned along at least part of one end of flange 5a or 5b of the receptacle, and be flexible enough to allow closure of the receptacle by pivoting the lid around it. In such an embodiment the flange 5 of the receptacle and/or the mating surface in the pivotable lid may be provided with means to form a seal there between, such as a layer of an adhesive, or any of the snap fits commonly employed in this field.
The variant of this embodiment illustrated in Fig. 3 and Fig. 4 is a receptacle 100 wherein the side walls 4 contain three hinge lines of slightly different size, the intermediate one 6c being smaller that the other two 6a and 6b, and instead of the corrugation lines 9 of the receptacle 100 of Fig. 1 and Fig. 2, along the side walls 3 there are enhanced facets 12 protruding outboard and inboard so as to direct the fold in a predicted manner and with a minimal intrusion. The inboard migration of the long side walls during collapse of the receptacle will depend on distance between these facets as the collapse will be halted when the lower half 13a meets the upper half 13b. To prevent any detrimental effect on the content the distance between these facets 12 needs to be small.
The receptacle 200 of the embodiment illustrated in Fig. 5 and Fig. 6 essentially differs from the embodiment of Fig. 1 in that it has a flat bottom 22 instead of a wedge-shaped one. The products that can be packaged therein are typically processed meat (frankfurters, meat loaves, stuffed rolls, and the like) or bakery and the advantages for the end user are the same as seen above, i.e. the possibility of easily removing the product from the package. The flat bottom in the embodiment of Fig. 5 and Fig.6 has substantially a rectangular shape and sidewalls 23 and 24 are all slightly flaring out from the interconnecting flat bottom 22 and are ending in a flange 25, as illustrated in the side views of Fig. 7 and 8. There are several parallel hinge lines, indicated as 26 that run all around the sidewalls in a continuous manner. No separate corrugations lines are present and the control of the direction of collapse is obtained by the presence of the hinge lines all around the sidewalls. Ribs are not illustrated in the receptacle of Fig. 5 but they may well be added in the upper section of the sidewalls of the receptacle, in the area above the uppermost hinge line. In the embodiment illustrated in Fig. 5 there are two steps 27 in the upper part of the long sidewalls that, when the receptacle is brought into the collapsed status by pressing on the receptacle flange, allow finger access to capture the packaged product. The ways the receptacle of this embodiment can be closed are the same as for receptacle 100. In Fig. 9, a variant of the embodiment of Fig. 5 is illustrated, where the two steps in the long sidewalls, in this embodiment indicated by numeral 28, have a rounded and elongated shape. This configuration allows finger access and at the same time gives more stiffness to the upper part of the receptacle sidewalls, so that the pressure on the flange will not give any deformation of this portion of the receptacle but will be transmitted to the collapsible portion thereof. Fig. 10 illustrates the same receptacle from a different perspective view (bottom-top).
The embodiment illustrated in Fig. 11 represents a receptacle 300, having a flat bottom 32 with an octagonal shape. The receptacle has a succession of alternating longer (33) and shorter (34) sidewalls which contain alternating hinge lines 36, shaped as creases, wherein those along the short side walls, 36a, are intercalated with respect to those in the long side walls, 36b. The sidewalls end with a flange 35 that in this embodiment is structured with a double flange 37, that widens in one comer to form a tab 38. Said tab will facilitate opening of the package when closure of the receptacle is provided by a snap-on system. The cover in such a case will contain a tab not aligned with tab 38 and it will be removed by pulling the two tabs apart.
The receptacle illustrated in Fig. 13 and Fig. 14 is a variant of the receptacle 300 of Fig. 11 and 12, wherein the shape of the bottom is essentially that of a chamfered rectangle with long walls 33, short walls 34, and the inclined walls 39, giving the "chamfered" characteristics. Also in this case there are alternating undulations all along the walls (33, 34, and 39) and parallel to the flange, giving a concertina design.
The polymeric materials that can be used in the manufacture of the receptacle of the present invention can include any polymers that fulfill the purposes of the invention or which, with the addition of additives can be modified to fulfill the purposes of the invention. Polymers suitable include polyolefins, such as polypropylenes and polyethylenes, polyvinyl chloride, polyesters, co-polyesters, polyamides, co-polyamides, polystyrene, polystyrene copolymers, and the like polymers. It is also possible to use blends of suitable polymers, particularly when one of the components of the blend is used in a minor amount as an impact modifier to increase flexural modulus and crack resistance.
In one embodiment the polymeric material used for the receptacle is heat-resistant so that the food product packaged in the receptacle and the receptacle itself are not damaged or contaminated by any exposure to heat, such as by microwaving or by submersion of the closed receptacle in hot water. Examples of thermoplastic materials suitable for the manufacture of a microwaveable tray are e.g. polypropylene and propylene co-or ter-polymers, nylons, polystyrene, ethylene-styrene copolymers, polyesters, co-polyesters, polyethylene, particularly irradiated polyethylene, and blends thereof. As used herein, the term "microwaveable", when referred to the package unit according to the present invention, means that under the specific conditions that might be required for thawing, cooking, or re-heating the packaged product into a microwave oven, the packaging material is substantially not deformed (by melting or softening and re-shaping upon cooling) and does not release more than 60 ppm of global contaminants to the packaged food in contact therewith.
It is also possible to use multilayer polymeric structures, particularly if gas-barrier properties or improved sealability properties are desired.
Gas-barrier properties may be required e.g. to maintain a suitably modified or controlled atmosphere within the package that would prolong the shelf life of the packaged food product. In such a case the material used for the receptacle will comprise a gas-barrier layer, typically comprising ethylene-vinyl alcohol copolymers, nylons, or blends thereof, set in order to provide the materials with an Oxygen Transmission Rate (OTR) (evaluated by following the method described in ASTM D-3985 and using an OX-TRAN instrument by Mocon) lower than 250, preferably lower than 125 cm³/m².d.atm, when measured at 23 °C and 0 % of relative humidity.
Improved sealability properties may be required when e.g. the closure is provided by means of a lid heat-sealed to the receptacle flange and a hermetic seal is required (such as in MAP or vacuum packages). In such a case the material used for the receptacle may be a multilayer material comprising at least a heat-sealable resin, such as a polyethylene resin, used as the innermost layer (i.e. the skin or external layer of the receptacle which is closer to the food product), and a bulk layer of a polymer or polymer blend such as those indicated above.
The thermoplastic material used for the receptacle of the present invention may be transparent, either clear or colored, translucent, either clear or colored, or opaque.
The sheet used for the manufacture of the receptacle may be obtained by extrusion and in case of multilayer sheets by co-extrusion or by conventional lamination. The conversion of the sheet into the receptacle can be easily carried out by heating the thermoplastic sheet to its softening and then forcing the soft and flexible material against the contours of a mold by pneumatic means (by pulling a vacuum between the plastic and the mold and/or by forcing the material against the mold by the pressure of compressed air), mechanical means (plug, matched mold, etc.) or a combination of pneumatic and mechanical means.
The thickness of the sidewalls in the receptacle according to the present invention will generally be within the range of from about 30 µm to about 500 µm, preferably from about 50 µm to about 400 µm, even more preferably from about 50 µm to about 300 µm, most preferably from about 75 µm to about 250 µm. Wall thicknesses outside these ranges may be used and are intended to be encompassed within the present invention as long as the receptacle sidewalls fulfill the purposes hereof, and in particular remain collapsible upon application of the pressure that can normally be exerted by the hand of an adult without undue effort and have sufficient rigidity to maintain their shape in the absence of such an external force.
Thermoplastic materials suitable for the manufacture of the wrapping or lidding sheet or film include mono- and multi-layer films, oriented or non oriented, and, if oriented, heat-shrinkable or heat-set. Monolayer structures will typically comprise polyolefins (such as propylene-based polymers or, preferably cross-linked, polyethylene-based polymers) or polyesters. Multi-layer structures will comprise at least an outer sealing layer, generally an outer heat-sealing layer, and an outer abuse layer. These multi-layer structure may include additional inner layers, such as gas-barrier layers, if a gas-barrier package is desired, bulk layers, and tie layers, as known in the art.

Claims

An open top, semi-rigid, plastic receptacle capable to undergo a partial, reversible, and controlled collapse comprising a bottom and walls upstanding from said bottom and ending up in a continuous flange, wherein said walls comprise opposing parts flaring out from said bottom, each of said opposing parts containing hinge lines, parallel one to the other and substantially orthogonal to the desired direction of the controlled collapse of the receptacle.
The open top receptacle of claim 1 wherein the bottom is wedge-shaped.
The open top receptacle wherein the bottom is flat.
The open receptacle of claim 1 which comprises corrugation lines in the receptacle walls that connect the opposing parts comprising the hinge lines, said corrugation lines being parallel to the hinge lines and being preferably positioned in a band of the walls that can be defined isometrically to the band between the lowermost and the uppermost hinge lines in the hinge containing opposing walls.
The open receptacle of claim 1 which comprises enhanced facets in the receptacle walls that connect the opposing parts comprising the hinge lines, said facets protruding alternately outboard and inboard, being parallel to the hinge lines, and positioned in a band of the walls that can be defined isometrically to the band between the lowermost and the uppermost hinge lines in the hinge containing opposing walls.
The open receptacle of any of the preceding claims which contains ribs, designed to give vertical stiffness to the receptacle walls, above and below the collapsible section.
The receptacle of any of the preceding claims wherein the receptacle and a covering lid are a single continuous piece of material formed simultaneously with a hinge, formed integrally therewith, which on deformation allows the covering lid to swing backwards and forwards on opening and closing the receptacle.
The receptacle of any of the preceding claims wherein the polymeric material used for the receptacle is heat-resistant so that the food product packaged in the receptacle and the receptacle itself are not damaged or contaminated by any exposure to heat, such as by microwaving or by submersion of the closed receptacle in hot water.
The receptacle of any of the preceding claims wherein the polymeric material used for the receptacle has an Oxygen Transmission Rate lower than 250, preferably lower than 125 cm³/m².d.atm, when measured at 23 °C and 0 % of relative humidity.
The receptacle of any of the preceding claims which is manufactured by heating a thermoplastic flat sheet to its softening and then forcing the soft and flexible material against the contours of a mould by pneumatic means, mechanical means, or a combination of pneumatic and mechanical means.