WO2004052733A1

WO2004052733A1 - A container with a flexible bottom wall

Info

Publication number: WO2004052733A1
Application number: PCT/AU2003/001643
Authority: WO
Inventors: Andrew Lees; Edmund Fisher; Lance Gledhill; Peter Zelez
Original assignee: Amcor Limited
Priority date: 2002-12-09
Filing date: 2003-12-09
Publication date: 2004-06-24
Also published as: NZ541041A; AU2002953207A0

Abstract

A container for packaging foodstuffs that adhere to the walls of the container and form a seal therewith is disclosed. The container including: a bottom wall (11); a side wall (10); and a top wall (12). The side wall extends upwardly and outwardly of the bottom wall. The bottom wall includes a flexible portion (14) that can be pressed inwardly and move the foodstuff after the container is opened to at least in part separate the side wall and adhered foodstuff. This movement of the foodstuff allows the passage of air downwardly between the foodstuff and the side wall to facilitate release of the foodstuff from the container.

Description

A CONTAINER WITH FLEXIBLE A BOTTOM WALL

Field of the Invention

The present invention relates to a container for packaging foodstuffs.

The present invention relates particularly, although by no means exclusively, to a metal, typically steel, container for packaging foodstuffs.

Background of the Invention

Consumers are demanding increasing convenience in packaging, particularly in opening a package and removing a product from the package. This is especially true in respect of containers for packaging foodstuffs.

Improvements in technology for opening containers, such as metal cans, have been the focus of many developments and are commercially available in the form of many easy-open ends.

It is known to use internal coatings on the side and bottom walls of containers which are selected to reduce adhesion of a product to the container walls and thereby facilitate removal of a product from containers. Such coatings are commonplace and reasonably successful when the product has a low viscosity or has the consistency of a slurry. However, the coatings are often not successful with other types of product.

For example, when a metal can is hot filled with a product in its liquid state or in a very viscous state and takes up the contours of the can and, on cooling, forms a solid, conventional methods of release, such as the above-described coatings, tend not to be successful if the product is required to be removed in one piece.

Product release under these circumstances is difficult because the product and the filling method create a seal between the product and the bottom and side walls of the container and, as the product cools, the seal creates a vacuum between the product and the container bottom and side walls that restricts product removal and the forces required to dislodge the product can lead to product damage.

Such product release problems are not confined to products that are hot filled and can occur with any foodstuffs that adhere to the walls of a container and form a seal therewith.

Cheese is one example of a product that has product release difficulties from metal cans. Other examples include pate and fish paste.

It is an object of the present invention to provide a container for foodstuffs that adhere to the bottom and side walls of the container and form a seal therewith from which the foodstuffs can be more conveniently removed.

Summary of the Invention

According to the present invention there is provided a container for packaging foodstuffs that adhere to the walls of the container and form a seal therewith, the container including: a bottom wall; a side wall; and a top wall; wherein the side wall extends upwardly and outwardly of the bottom wall, and the bottom wall includes a flexible portion that can be pressed inwardly and move the foodstuff after the container is opened to at least in part separate the side wall and adhered foodstuff, and thereby allow the passage of air downwardly between the foodstuff and the side wall to facilitate release of the foodstuff from the container.

An advantage provided by the above-described container of the present invention is that the movementof the foodstuff in response to inward movement of the flexible portion enables a vacuum formed in the bottom region of the container to be released when a consumer wishes to remove the foodstuff and thereby facilitates removing the foodstuff from the container with only little or no damage.

Another advantage provided by the container of the present invention is that a plurality of the containers can be nested together.

The present invention relates particularly, although not exclusively, to foodstuffs that are filled into a container in a liquid or highly viscous state

(typically hot filled) and, when cooled, form a "soft" solid in the shape of the contours of the container. Such soft foodstuffs are particularly susceptible to forming a seal between the foodstuff and the bottom and side walls of the container that creates a vacuum in a bottom region of the container as the foodstuff cools that is likely to prevent the foodstuff being removed from a conventional container without being fragmented or broken.

It is preferred that the side wall extends upwardly and outwardly of the bottom wall at an angle in the range of 2° to 4° described between the side wall and an axis extending perpendicularly to a major plane of the bottom wall .

It is preferred that the side wall extends upwardly and outwardly of the bottom wall such that the inside diameter of the container increases up to 5 mm over a height ranging from 20 to 80 mm.

It is even more preferred that the inside diameter of the container increases up to 4 mm over a height ranging from 40 to 60 mm.

It is preferred that the flexible portion of the bottom wall has an outwardly projecting profile when the container is closed, whereby when the container is opened by removing the top wall of the container the flexible portion can be pressed inwardly and facilitate upward movement of the foodstuff and thereby removal of the foodstuff from the container.

It is even more preferred that the flexible portion be a panel having an outward convex shape when the container is closed, whereby when the container is opened by removing the top wall of the container the panel can be pressed inwardly so as to form an inward concave shape and facilitate upward movement of the foodstuff and thereby removal of the foodstuff from the container.

It is preferred that the flexible portion be formed so that the inward movement of the flexible portion is between 3 and 8 mm for containers ranging in height between 25 and 90 mm and having top wall diameters ranging from 50 to 100 mm.

It is preferred that the container include an annular rim at the junction of the side wall and the bottom wall, with the rim projecting below the flexible portion such that when the container is placed in a upright position, the container rests on the annular rim.

It is preferred that the rim be an annular trough formation extending around the perimeter of the bottom wall .

Preferably the trough formation includes an annular bottom panel and an inner panel that extends upwardly from an inner periphery of the bottom panel and integrally connects to the flexible portion of the bottom wall.

Preferably the opposite outer periphery of the bottom panel integrally connects to the side wall of the container.

It is preferred that the flexible panel include a chime that defines a flattened region centrally located of the bottom wall so that the panel remains above the rim when the flexible panel projects outwardly before being pressed inwardly.

It is preferred that the container further includes a base member positioned on the bottom wall of the container and extending substantially, typically at least 70%, across the bottom wall between the foodstuff and the bottom wall whereby the base member distributes upward force imparted by the flexible portion across the lower surface of the packaged foodstuff and facilitates uniform upward movement of the foodstuff. This is a particularly advantageous feature for some "soft" products that tend to deform, for example by bulging in the centre, in response to upward movement of the flexible portion with the seal between the foodstuff and the bottom and side walls of the container being largely unaffected by upward movement.

The base member may be of any suitable shape and construction bearing in mind that the purpose of the base member is to transfer upward force imparted by the flexible portion, preferably uniformly, across the lower surface of the packaged foodstuff to facilitate uniform upward movement of the foodstuff.

The container may include a non-stick or low adhesion coating applied to the walls of the container.

However, it is preferred that the container further includes a sleeve of a low friction material that is positioned between the side wall and the foodstuff.

The low friction material may be any suitable material. One suitable material is polypropylene.

It is preferred that the base member and the sleeve be integrally formed.

It is preferred that the force required to press the flexible portion inwardly to dislodge foodstuffs from the side wall when the container is open be no greater than the equivalent of 6kg.

It is even more preferred that the force required to press the flexible portion inwardly when the container is open be no greater than the equivalent of 5kg.

It is even more preferred that the force required to press the flexible portion inwardly when the container is open be no greater than the equivalent of 3kg.

It is preferred that the top wall be in the form of a removable lid.

It is preferred that the container be a two- piece construction in which the bottom and side walls are integrally formed from a first continuous sheet and the top wall is formed from a second sheet. It is even more preferred that the first and second sheets be made from a food grade steel.

Brief Description of the Drawings

The present invention is described further with reference to the accompanying drawings, of which:

Figures 1 and 2 which are cross sectional views of one embodiment a container for packaging foodstuffs in accordance with the invention; and

Figures 3 and 4 which are cross sectional views of another embodiment a container for packaging foodstuffs in accordance with the invention.

Detailed Description of the Embodiments

The container shown in Figures 1 and 2 includes a side wall 10, a bottom wall 11 and a top wall 12.

The side wall 10 and the bottom wall 11 are stamped from a single sheet of food grade steel . The top wall 12 is stamped from another sheet of steel so that the container is essentially a two-piece construction.

Although not apparent from the Figures, the top wall 12 may include a pre-scored lid having a pull ring or other suitable opening means for severing the lid from the top wall 12.

The side wall 10 extends upwardly and outwardly above the bottom wall 11 at an acute angle to the vertical, typically an acute angle of 2° to 4°. For instance, the inside diameter of a container may increase by up to 5 mm over a height ranging from 40 to 80 mm. The bottom wall 11 includes a rim in the form of an annular trough 13 interconnecting a central flexible portion 14 of the bottom wall 11 and the side wall 10.

The trough 13 includes a bottom engaging panel 15 and an inner panel 16 extending upwardly from an inner periphery of the bottom panel 15. The inner panel 16 is integrally connected to the flexible portion 14 of the bottom wall 11. The side wall 10 of the container is integrally connected to the outer periphery of the bottom panel 15 and thereby forms an outer panel of the trough 13.

As can best be seen in Figure 1, the annular trough 13 supports the container in a stable condition while the flexible portion 14 projects outwardly in a convex shape .

The flexible portion includes an annular chime 17 in the form of a flattened central section that prevents the flexible portion 14 engaging the surface below.

Figures 1 and 2 illustrate the flexible portion 14 of the bottom wall 11 in two alternative positions.

Specifically, Figure 1 illustrates the flexible portion 14 projecting outwardly in a convex-shape. The flexible portion 14 assumes this position when the container is closed and contains a foodstuff. In the event of a person wishing to remove the contents from the container, after removing the top wall 12 in part or in full and opening the container, a person presses the flexible portion 14 inwardly in the direction of arrow 20 until the flexible portion 14 forms a concave shape as shown in Figure 2.

As the flexible portion 14 is pressed inwardly, the foodstuff is forced upwardly within the container and is separated at least partially from the side wall 10 and thereby disrupts a seal between the foodstuff and the bottom and side walls 10, 11 and thus creates a passage for air toward the bottom wall 11. The container therefore allows a vacuum in the bottom region of the container to be released. As a result, the flexible portion 14 reduces the need to fragment or break a foodstuff in order to remove it from the container.

Separation of the foodstuff from the side wall 10 is assisted by the side wall extending outwardly and upwardly above the bottom wall 11. In other words, the side wall 10 and foodstuffs contained by the side wall 10 taper toward the bottom wall 11 of the container and upon upward movement of the foodstuff, a space is formed between the foodstuff and the side walls 10 to allow the passage of air toward the bottom wall 11.

In addition, non-stick or low adhesive lacquer may be applied to the surface of the side wall 10 and bottom wall 11 to assist in separating the foodstuff and the side wall 10.

The applicant has found that the embodiment shown in Figures 1 and 2 is a particularly suitable container for packaging foodstuffs that adhere to the walls of the container.

The embodiment shown in Figures 1 and 2 takes into account at least two sets of competing parameters that are discussed briefly below.

Firstly, it is desirable that the flexible portion 14 can be pressed inwardly with minimal force so that children and elderly people can remove foodstuff from the container. However, when foodstuffs packaged in the container are supplied in a hot state and a vacuum is created in the lower region of the container as the foodstuffs cool, the vacuum automatically creates an inward force on the flexible portion 14. It is therefore desirable that the flexible portion 14 has sufficient stiffness to resist flexing inwardly automatically upon cooling of a packaged product, yet be able to be pressed inwardly with only minimal force after the container is opened by removing the top wall thereof.

Secondly, as the depth or curvature of the convex flexible portion 14 increases, it is possible to press the flexible portion 14 further inwardly and thereby increase separation of the foodstuff from the walls of the container and thus provide a greater opportunity for air to pass to the bottom of the container. However, as the depth or curvature of the convex flexible portion 14 increases, the depth of the annular trough must also increase to ensure that the container can be seated in a stable condition on a flat surface. However, as the depth of the annular trough increases, so too does the likelihood of a vacuum being formed in trough.

The applicant has found that containers of the type shown in Figures 1 and 2 that have the following key dimensions perform very well in terms of releasing a packaged product, such as cheese, as one piece without damage. The key dimensions are Top Wall Diameter Dl, Necked-In Diameter D2, Side Wall Height H, and movement of the flexible portion 14. The dimensions Dl, d2, and H are marked on Figures 1 and 2.

The embodiment shown in Figures 3 and 4 is the same in terms of basic construction to the embodiment shown in Figures 1 an 2 and the same reference numerals are used to describe the same features.

The container shown in Figures 1 and 2 also includes an assembly of a base member 26 and a sleeve 28 extending upwardly and outwardly from the base member 26 and arranged to fit in the container as shown in the figures so that the assembly is between the bottom and side walls 10, 11 and the packaged foodstuff.

The assembly is formed from a low density polypropylene/ high density polypropylene mixture. This material was selected on the basis that it is a low friction material.

The purpose of the base member 26 is to transfer the upward force imparted by movement of the flexible portion 14 from the convex to the concave positions shown in Figures 3 and 4 uniformly across the lower surface of the packaged foodstuff and thereby facilitate uniform upward movement of the foodstuff. As is indicated above, this is a particularly advantageous feature for some

"soft" products, such as cheese, that tend to deform, for example by bulging in the centre, in response to upward movement of the flexible portion 14 with the seal between the foodstuff and the bottom and side walls 10, 11 of the container being largely unaffected.

The purpose of the sleeve 28 is to provide a low friction material in direct contact with the side wall 10. Whilst there will be a seal and therefore a vacuum formed between the sleeve 28 and the side wall 10 in the packaged product, the low friction material of the sleeve 28 promotes release of the packaged foodstuff from the container.

A person skilled in the art would appreciate that modifications may be made to the invention without departing from the spirit and scope of the invention.

For example, the flexible portion of the bottom wall is not limited to a pre-set convex shaped panel while the container is closed for storage and be any shape provided it can be pressed inwardly.

Claims

CLAIMS :

1. A container for packaging foodstuffs that adhere to the walls of the container and form a seal therewith, the container including: a bottom wall; a side wall; and a top wall; wherein the side wall extends upwardly and outwardly of the bottom wall, and the bottom wall includes a flexible portion that can be pressed inwardly and move the foodstuff after the container is opened to at least in part separate the side wall and adhered foodstuff, and thereby allow the passage of air downwardly between the foodstuff and the side wall to facilitate release of the foodstuff from the container.

2. The container defined in claim 1 wherein the side wall extends upwardly and outwardly of the bottom wall at an angle in the range of 2° to 4° described between the side wall and an axis extending perpendicularly to a major plane of the bottom wall.

3. The container defined in claim 1 or claim 2 wherein the side wall extends upwardly and outwardly of the bottom wall such that the inside diameter of the container increases up to 5 mm over a height ranging from 20 to 80 mm.

4. The container defined in claim 3 wherein the inside diameter of the container increases up to 5 mm over a height ranging from 25 to 90 mm.

5 The container defined in any one of the preceding claims wherein the flexible portion of the bottom wall has an outwardly projecting profile when the container is closed, whereby when the container is opened by removing the top wall of the container the flexible portion can be pressed inwardly and facilitate upward movement of the foodstuff and thereby removal of the foodstuff from the container.

6. The container defined in any one of the preceding claims wherein the flexible portion is a panel having an outward convex shape when the container is closed, whereby when the container is opened by removing the top wall of the container the panel can be pressed inwardly so as to form an inward concave shape and facilitate upward movement of the foodstuff and thereby removal of the foodstuff from the container.

7. The container defined in any one of the preceding claims wherein the flexible portion is formed so that the inward movement of the flexible portion is between 3 and 8 mm for containers ranging in height between 25 and 90 mm and having top wall diameters ranging from 50 to 100 mm.

8. The container defined in any one of the preceding claims includes an annular rim at the junction of the side wall and the bottom wall, with the rim projecting below the flexible portion such that when the container is placed in a upright position, the container rests on the annular rim.

9. The container defined in claim 8 wherein the rim is an annular trough formation extending around the perimeter of the bottom wall.

10. The container defined in claim 9 wherein the trough formation includes an annular bottom panel and an inner panel that extends upwardly from an inner periphery of the bottom panel and integrally connects to the flexible portion of the bottom wall .

11. The container defined in claim 9 wherein the opposite outer periphery of the bottom panel integrally connects to the side wall of the container.

12. The container de ined in any one of the preceding claims wherein the flexible panel includes a chime that defines a flattened region centrally located of the bottom wall so that the panel remains above the rim when the flexible panel projects outwardly before being pressed inwardly.

13. The container defined in any one of the preceding claims wherein the container further includes a base member positioned on the bottom wall of the container and extending substantially, typically at least 70%, across the bottom wall between the foodstuff and the bottom wall whereby the base member distributes upward force imparted by the flexible portion across the lower surface of the packaged foodstuff and facilitates uniform upward movement of the foodstuff.

14. The container defined in any one of the preceding claims further includes a sleeve of a low friction material that is positioned between the side wall and the foodstuff.

15. The container defined in claim 14 when the claim is dependent on claim 13 wherein the base member and the sleeve are integrally formed.

16. The container defined in any one of claims 1 to 13 includes a non-stick or low adhesion coating applied to the walls of the container.

17. The container defined in any one of the preceding claims wherein the force required to press the flexible portion inwardly to dislodge foodstuffs from the side wall when the container is open be no greater than the equivalent of 6kg.

18. The container defined in claim 17 wherein the force required to press the flexible portion inwardly when the container is open be no greater than the equivalent of 5kg.

19. The container defined in claim 18 wherein the force required to press the flexible portion inwardly when the container is open be no greater than the equivalent of 3kg.

20. The container defined in any one of the preceding claims in the form of a two-piece construction in which the bottom and side walls are integrally formed from a first continuous sheet and the top wall is formed from a second sheet.