GB2501455A

GB2501455A - A Thermoformed Open-Topped Container.

Info

Publication number: GB2501455A
Application number: GB1116375.5A
Authority: GB
Inventors: Carl Petrie
Original assignee: Kobusch UK Ltd
Current assignee: Kobusch UK Ltd
Priority date: 2011-09-22
Filing date: 2011-09-22
Publication date: 2013-10-30
Anticipated expiration: 2031-09-22
Also published as: GB201116375D0; GB2501455B

Abstract

An open-topped container 1 e.g. a salad bowl has a bottom wall 2 with a raised plinth 6, the circumference of which is at least partially defined by a channel 7, a wall 9 of which extends downwardly from the plinth. Also claimed a mould system for thermoform manufacture of such a container comprising a male mould over which a single sheet of heated thermoformable material is formed, the lowermost section of the mould equating to the uppermost section of the container i.e. the container is thermoformed upside down. The container may be made from aPET, rPET, polypropylene, PVC and/or styrene. The channel may be 6-10mm deep and less than 3mm wide. The container may have an internal de-nesting feature comprising the wall 9 of the channel being angled to form an undercut structure and a locating groove 17, on which a similar container will rest when stacked (Figure 5).The container may have a hinged lid which is push-fit to close at a sealing flange 12, such that it is leak resistant.

Description

Improved thermoforming method and thermoformed containers The present invention provides an improved process for thermoforming containers and other materials, as well as equipment used during the process. The process uses an inverted mould system to allow more intricate formations to be produced. The invention also relates to novel containers that may be produced using the thermoforming process and equipment.

Currently a number of premium food products are packaged and merchandised in injection moulded containers. A common example of this is an injection moulded "salad bowl" which incorporates a pedestal base, generally having either a round or square footprint, with a raised plinth section. The plinth has the effect of raising the contents of the container which offers a very appealing method of presenting the contents of the container, for example a salad, to a potential customer. The containers are currently only utilised for premium products, as the costs associated with the required injection moulding process and tooling are high.

Furthermore, injection moulded bowls of this type cannot be manufactured from recycled polyethylene terephthalate (rPET) material as this material is not suitable for injection moulding. Many retailers now prefer containers which are manufactured in rPET material due to its environmental benefits when compared to other plastic materials.

A more cost effective process for producing containers suitable for packaging foodstuffs is thermoforming. In its most general sense thermoforming is a process whereby a single, usually thin, sheet of plastic is heated to a pliable forming temperature and formed to a specific desired shape by being forced into or against a mould before being cooled again to produce a container, or part thereof, having a uniform, generally very thin cross-sectional thickness. Unfortunately, current thermoform ing processes are not suitable for producing containers of the type described above, as the bowl design with a raised plinth cannot be formed from a flat sheet of material using conventional thermoforming moulds.

It would be desirable to be able to produce a container or bowl which has the presentational benefits of a raised internal plinth base but which avoids the excess costs associated with injection moulding the same. It would also be desirable if the container or bowl could be manufactured from rPET material due to the environmental benefits that this material confers when compared to other plastics materials such as those commonly used in the manufacture of injection moulded containers.

The present invention looks to obviate or mitigate one or more of the disadvantages associated with current processes for manufacturing containers such as bowls with a raised plinth base.

According to the first aspect of the present invention there is provided a container comprising a body portion, the body portion comprising a bottom wall and at least one side wall upstanding from the bottom wall thereby defining a cavity having an opening at an upper end thereof, characterised in that the bottom wall comprises a raised plinth, the circumference of which is at least partially defined by a channel, the wall of the channel extending downwardly from the raised plinth.

A particular benefit of such an arrangement is that items, such as foodstuffs, which are placed within the container are raised up on the raised plinth. This offers a particularly appealing presentation of the items in the container.

Preferably the container is a thermoformed container.

The channel comprises two side walls and a base wall. The external surfaces of the channel may form a visually appealing pedestal base section.

Optionally the pedestal base section extends from the lower edge of the one or more side walls.

II is preferable in such arrangements that the angle between the bottom wall and the pedestal base section side wall is substantially equal to or less than 90 degrees. In certain arrangements, the angle is less than 90 degrees and greater than 80 degrees. In this way, in the forming process, the formed container may more easily be removed from the mould.

The base wall of the channel provides the lowermost section of the container.

Preferably the distance between the side walls of the channel is approximately 3mm or less.

Preferably the depth of the channel is approximately 6-10mm.

Optionally the outer edge(s) of the raised plinth comprises a locating groove which comprises a first flange portion which extends downwards from the raised plinth at, or substantially at, right angles thereto, and a second flange portion configured to extend outward from the first flange portion on a plane substantially parallel to the plane of the raised plinth.

A benefit of such a locating flange configuration is that it aids with the stacking of multiple containers.

Preferably the inner wall of the channel comprises an undercut feature. A benefit of such a feature is that it aids de-nesting. Furthermore, and unusually, this de-nest feature is provided in the lower section of the container. More specifically, the de-nest feature is provided on the inner section of the lower section of the container. In this way, the de-nest feature will be hidden from view when the container is filled with a foodstuff.

In certain embodiments, the at least one side wall of the body portion is upstanding from the bottom wall at or substantially at right angles to the bottom wall.

In preferred embodiments, the angle between the bottom wall and the side wall is obtuse. In such embodiments, the width of the opening at the upper end of the cavity defined by the body portion is greater than the width of the bottom wall. In one particular embodiment the base has a circular footprint with an upstanding side wall that extends upwards to form a frustoconical container.

II is preferable in such arrangements that the angle between the bottom wall and the side wall is greater than 90 degrees.

It is preferable in such arrangements that the angle between the bottom wall and the side wall does not exceed 135 degrees.

Preferably the upper edge of the one or more side walls which defines an upper opening is provided with a sealing flange. Preferably the sealing flange radiates outwardly from the upper edge. At least a portion of the sealing flange extends outwards on a plane which is substantially parallel to the plane of the raised plinth.

A benefit of the present configuration is that the upper edge can be relatively smooth in profile and a complex de-nesting feature is not required at the upper edge, as the de-nesting feature can be incorporated and hidden in the lower section of the container.

The container may have any suitable footprint. For example, the container may have a circular, square, or rectangular footprint.

As the container is thermoformed, the bottom wall and one or more side walls are integrally formed from the same sheet of material.

The container may suitably be formed of a thermoformable polymer. More specifically, the thermoformable polymer may be one or more of aPET, rPET, polypropylene, polyvinylchloride (PVC) and/or styrene, or the like.

Most preferably the container is formed from rPET.

The container may be provided with a lid.

The lid may attach to the container by push fit.

More specifically the container and the lid may be hingedly connected.

Alternatively, the container and lid may be engaged by way of a push-fit arrangement. Preferably the closure between the lid and the second base portion is leak resistant.

The sealing flange may provide a surface to which a lid may be attached.

The sealing flange is generally configured to extend outwards from the upper edge of the side wall on a plane that is generally parallel to the plane of the plinth.

The opening in the upper end of the container may be provided with a film.

The film may be attached to the first flange portion of the sealing flange.

More specifically, a heat-activated film may provide a leak proof closure of the opening. By providing a film closure on the container, said container becomes air-tight and leak proof. Such arrangements are particularly suited to containing non-viscous fluids.

According to a second aspect of the present invention there is provided a mould system for use in the thermoform manufacture of the container of the first aspect, comprising a male mould body configured to produce the container of the first aspect when a thermoformable sheet of material is moulded over it.

Advantageously, by providing a male mould which is an inverted version of a typical mould used in a thermoforming process for the production of food containers, a single sheet of material can be used to form a container which has a raised plinth base.

Preferably the mould system comprises one or more moulds configured to the internal dimensions of the container of the first aspect characterised in that the lowermost section of the one or more moulds is configured to equate to the to the uppermost section of the container.

Most preferably the one or more moulds comprises one or more narrow ridges on their outer surface.

The benefit of such a mould configuration is that the ridges will result in narrow channels forming in the thermoformable material when the thermoformable material is formed over the mould.

The ridges generally comprise two ridge side walls which extend outward from the mould body and a ridge top wall which extends between the two ridge side walls. The external dimensions of the ridge are configured to match the internal dimensions of the channel that is required in the thermoformable material when forming a container. A preference is that the ridge side walls extend out from the mould body approximately 6- 10mm and the distance between the two side walls, i.e. the width of the ridge top wall, is approximately or less than 3mm.

It is preferred that the one or more moulds are positioned on a mould base. The mould base may be integral with the one or more moulds.

According to a third aspect of the present invention there is provided a method of manufacturing a container characterized in that a sheet of thermoformable material is heated to a pliable forming temperature and formed over a male mould system characterised in that the lowermost section of the one or more moulds is configured to equate to the uppermost section of the container.

Preferably the thermoformable material is formed over the mould system of the second aspect.

Preferably the thermoformable material is then cooled to produce the container of the first aspect.

Preferably the thermoformable material is rPET.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

In order to provide a better understanding of the present invention embodiments will be described, by way of example only, and with reference to the following drawings; Figure 1 shows a perspective view of a container in accordance with the first aspect of the present invention; and Figure 2 shows a perspective upside down view of a container in accordance with the first aspect of the present invention; and Figure 3a shows a plan view of a container in accordance with the first aspect of the present invention; and Figure 3b shows a side sectional view of a container in accordance with the first aspect of the present invention; and Figure 4 shows a side sectional view of the raised plinth and channel/base feature of a container in accordance with the first aspect of the present invention; and Figure 5 shows a side sectional view of portions of containers in accordance with the first aspect of the present invention in a stacked formation; and Figure 6 shows a side sectional view of a filled container in accordance with the first aspect of the present invention in a stacked formation; and Figure 7 shows a male multi-cavity mould system in accordance with the second aspect of the present invention and for use with the method of the third aspect.

While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof is shown by way of example in the drawings and will herein be described in detail. It should be understood that the drawings and detailed description thereof are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the invention as defined by the appended claims.

In the drawings, similar features are denoted by the same reference signs throughout.

Thermo formed container A container I according to one embodiment of the present invention is generally depicted in figure 1 (in use configuration), figure 2 (upside down/inverted) and figures 3a and 3b. The embodiment which is shown is that of a salad bowl, however it is understood that other containers could be formed based upon the same principles. The container is formed from a single sheet of material by a thermoforming process which will be described in more detail below. Whilst the embodiment shown does not depict a lid it will be readily understood that a lid could be provided for example in the form of a push fit plastic lid, a heat sealable film, an adhesive foil or any combination thereof. The lid will generally be formed from a separate sheet of material but could be formed integrally with the container 1 if required. This will typically occur when the lid and container have a hinged configuration.

In this embodiment the thermoformed container has a circular footprint (as shown best in figures 2 and 3a). The container comprises a circular bottom wall 2 and a side wall 3 upstanding therefrom thereby forming a bowl defining a cavity 4, having an open top area 5 at an upper end thereof. In this embodiment the side wall defines a frusto-conical container.

It will be understood that in alternative embodiments (not shown) the shape of the bottom wall could be varied and the number of side walls upstanding therefrom will be commensurate with the shape of the first base portion and, indeed, the container itself. For example, in embodiments wherein the bottom wall is square, there will be four side walls upstanding therefrom, one from each edge of the bottom wall, thereby defining a cuboidal or rectangular obloid shaped bowl.

In the present embodiment, and as best shown in figures 1 and 2, the angle (z) between the bottom wall 2 and the side wall 3 will be obtuse, forming a wider opening at the upper end of the cavity than is defined by the bottom wall of the container resulting in a frusto-conical container 1. It is preferable in such arrangements that the angle is between 90 degrees and l35degrees.

In alternative embodiments (not shown), the side wall(s) of the container may be upstanding from the bottom wall at, or substantially at, right angle(s) to the bottom wall. Where the base portion is circular as with the present embodiment, such a configuration of the side wall would result in a substantially cylindrical first base portion.

It is preferred that the bottom wall and side wall(s) are integrally formed.

The upper edge 11 of the side wall 3 is provided with a sealing flange 12.

The first flange portion 13 of the sealing flange 12 radiates or extends outwards from the side wall. A second flange portion 14 of the sealing flange 12 depends therefrom in generally a downward direction.

Advantageously the sealing flange 12 may provide a surface to which a lid (not shown) or film (not shown) may be attached. When a push fit type lid is used the multi part sealing flange 12 depicted is preferred, however if only a heat sealable film is used then the second flange portion 14 may be present to aid rigidity. It would also be readily understood that the sealing flange 12 can be omitted entirely in some embodiments.

The lower part of the container 1 is shown more clearly in figures 3b and 4. It can be seen that the bottom wall 2 comprises a raised plinth 6, the circumference of which is defined by a narrow, approximately or less than 3mm wide (a), channel 7 which is formed in the bottom wall 2. The channel 7 comprises an outer channel wall 8, an inner channel wall 9 and a base channel wall 15. The outer surface of the base channel wall 15 is the effective base of the container 1 on which the container 1 will stand. In the embodiment shown the outer channel wall 8 is integral with the side wall 3 of the container. It would however be evident that it would be possible to include a flange between the outer channel wall 8 and side wall 3 if preferred.

The raised plinth 6 of the shown embodiment is circular, however other appropriate cross sections could be used. For example if the footprint of the bottom wall was square it would be preferred, although not essential, for the cross section of the raised plinth 6 to also be square.

As is clearly depicted in figure 6, the raised plinth 6 allows the foodstuff 18 or other item that is placed inside the container 1 to be elevated away form the lower surface. To enable the raised plinth to be thermoformed out of a single sheet of material the narrow channel 7 is located around the perimeter of the raised plinth 6. By making the channel very narrow, 3mm or less for example, this prevents many foodstuff such as salad leaves from falling into it, thus giving an appealing method of presenting foodstuff to a consumer.

In usual circumstances it would not be possible to thermoform such a narrow channel 7 around the raised plinth 6. Further detail of how this problem is overcome in the present case are given below.

An additional benefit of the embodiment that is depicted in the attached figures, and particularly visible in figures 4 and 5, is that a de-nest feature is provided in the inner, lower portion of the container 1. By providing the de-nest feature on the inner of the lower portion, same is hidden from the consumer's view when the container is filled with a foodstuff. De-nest features allow containers to be stacked neatly together for transportation and packing but also to easily be separated when required. In most containers the de-nest feature is provided at the upper edge of a side wall, which can be unsightly and, from certain viewing angles, can partially obscure the view of the product within the container.

As mentioned above, the channel 7 comprises an outer channel wall 8, an inner channel wall 9 and a base channel wall 15. Whilst the inner surfaces of these walls form a channel 7, this same channel 7 acts as a pedestal base on which the container 1 can stand when considering the outer surfaces. The inner channel wall 9 is angled such that the outer surface of the same is configured to form an undercut feature 16. The undercut feature aids with de-nesting.

Furthermore, the outer edge of the raised plinth 6 is provided with a locating groove 17 (which in the embodiment shown is a locating ring, but could be of other appropriate circumference depending on the shape of the raised plinth 6). The locating groove 17 comprises a first locating flange 18 which extends downwards from the raised plinth 6, and a second locating flange 19 configured to extend outward from the first flange 18 on a plane substantially parallel to the plane of the raised flange 6. The angle (b) between the first locating flange 18 and the second locating flange 19 is substantially the same as the angle (b) between the inside surfaces of the inner channel wall 9 and base channel wall 15. This ensures that the inside corner 20 of the pedestal base easily locates on the locating ring 17 which results in easy stacking. This is shown in detail in figure 5.

Incorporation of de-nest features on the lower inside surfaces of the container 1 ensures that the feature is less visible to a consumer as the foodstuff 18 within the container will effectively hide the de-nest feature(s).

Thermoforming methods and mould systems therefore As mentioned briefly above, thermoforming is a process whereby a single, usually thin, sheet of plastic is heated to a pliable forming temperature and formed to a specific desired shape by being forced into or against a mould before being cooled again to produce a container, or part thereof, having a uniform, generally very thin cross-sectional thickness.

Typically, it would not be possible to use thermoforming to manufacture the container 1 described in the above embodiment, as the normal thermoforming process relies on pulling a sheet of thermoformable material, which has been heated to make it pliable, into a female mould.

This technique stretches the sheet of thermoformable material and thins it slightly as it reaches the face of the female mould. If the face of the female mould has the narrow channel indentations required to form the base channel 7 of the container 1 described herein, the thermoformable material cannot form properly into said channels due to the narrowness and depth (generally 6-10mm).

The present invention overcomes this problem by providing a mould system which comprises a mould tool 21, as is depicted in figure 7, where the moulds are inverted to form males moulds over which thermoformable material can be laid. The mould tool 21 has a substantially planar mould base 22 with one or more, in the shown embodiment there are six, mould bodies 23 extending therefrom. The mould bodies are configured such that the external shape and surface of a mould body 23 matches required internal configuration of the container 1.

More particularly, and as shown in one embodiment in figure 7, the lowermost section of each mould body 23 (i.e. the portion of the mould body 23 which is closest to the mould base 22) is configured to relate to the to the uppermost section of the container. The mould body 23 may extend partially into the mould base 22. In the embodiment depicted there is a sealing flange channel 24 at the lower end of each mould body 23, the inner wall 25 of which extends to become the outer mould wall 26. The outer mould wall extends upwards at a predetermined angle which is appropriate for the required side wall 3 of the container 1 that is to be formed. Generally, the angle at which the outer mould wall 26 extends from the mould base 22 is a supplementary angle to that which is required between the bottom wall 2 and the side wall 3 of the container 1 that the mould will be used to form (i.e. together they equate to 180 degrees).

Effectively, each mould 23 is an inverted or male mould.

As can be clearly seen in the depicted embodiment, the top of the mould body 23 comprises a ridge 27 which extends upwards from the upper edge of the outer mould wall 26, substantially at right angles to the surface plane of the mould base 22. The ridge comprises an inner ridge wall 29 and outer ridge wall 30, the distance between which is approximately or less than 3mm. It is the ridge 27 that will result in the formation of a channel 7 in a container formed using the mould tool 21. The ridge 27 defines the outer circumference of the lowered upper mould wall 28 and extends 6-10mm above the surface of the lowered upper mould wall. This configuration allows for the formation of a raised plinth 6 surrounded by a narrow channel 7 using thermoforming material such as rPET and thermoforming techniques.

In use, a single planar film or sheet of rPET (or other appropriate thermoformable material) is obtained. The material used may be slightly thicker than is typically utilised for thermoforming techniques making containers of this type as the use of a male mould system can result in further thinning of the thermoformable material than is seen with a female mould system. The planar film or sheet is heated to an appropriate temperature within a forming window". The forming window has a minimum temperature below which the material is not capable of thermoforming and a maximum temperature above which the material is heat damaged and becomes unsuitable. It will be understood that the actual temperatures of a forming window will be dependent upon the material being thermoformed. When the planar film or sheet material has been heated to a temperature within its forming window, it becomes pliable and capable of thermoforming. The planar film or sheet is heated to an appropriate temperature, using methods well known to those skilled in the art, and is pulled over the male mould bodies 23 on the mould tool 21 using known thermoforming techniques. The planar film forms or moulds to the shape of the mould body and, in particular, the film forms around the ridge 27 with a very good fit to form a container 1 with an narrow channel 7 formed on an inner surface. This differs significantly from prior art methods which use female moulds as it would not be possible to thermoform such a narrow channel on a female mould as the film would not form into a channel which had such dimensions.

Once the rPET film has been formed over the moulds the material is allowed to cool to form the shaped container 1. These steps will be well recognised to those skilled in the art of thermoforming containers. The container shaped rPET can then be removed from the mould and any excess material removed.

The resulting container offers the presentational benefits of an injection moulded product with the lower manufacturing costs of thermoforming.

Furthermore, the process allows manufacturers to use the more favoured rPET material in the production of high specification pedestal pots.

It will be evident to a skilled person that various modifications and improvements could be made to the abovementioned products and methods within the scope of the invention. Further modification can be made without departing from the scope of the invention herein intended.

For example, it would be readily understood that the footprint of the container and therefore the shape of the associated mould could be any appropriate shape.

Additionally the angles between the raised plinth and one or more side walls can be altered to provide different shapes and sizes of cavity.

Furthermore, whilst the preferred option is to utilise rPET to manufacture the containers described herein it is clear that other appropriate materials couldbeused.

The container may be also be provided with a sleeve, such as a cardboards sleeve which could be printed. Alternatively the container may be directly printed or embossed with information indicia or the like.

Claims

Claims 1. A container comprising a body portion, the body portion comprising a bottom wall and at least one side wall upstanding from the bottom wall thereby defining a cavity having an opening at an upper end thereof, characterised in that the bottom wall comprises a raised plinth, the circumference of which is at least partially defined by a channel, the wall of the channel extending downwardly from the raised plinth.
2. A container according to claim 1, wherein the container is a thermoformed container.
3. A container according to claim 1 or claim 2, wherein the channel comprises two side walls and a base wall.
4.A container according to any one of the preceding claims, wherein the external surfaces of the channel form a pedestal base section.
5. A container according to claim 4, wherein the pedestal base section extends from the lower edge of the one or more side walls.
6. A container according to claim 4 or claim 5, wherein the angle between the bottom wall and the pedestal base section side wall is substantially equal to or less than 90 degrees.
7. A container according to any one of the preceding claims, wherein the base wall of the channel provides the lowermost section of the container.
8. A container according to any one of the preceding claims, wherein the distance between the side walls of the channel is 3mm or less.
9. A container according to any one of the preceding claims, wherein the depth of the channel is between 6mm and 10mm.
10. A container according to any one of the preceding claims, wherein the outer edge(s) of the raised plinth comprises a locating groove which comprises a first flange portion which extends downwards from the raised plinth at, or substantially at, right angles thereto, and a second flange portion configured to extend outward from the first flange portion on a plane substantially parallel to the plane of the raised plinth.
11. A container according to any one of the preceding claims, wherein the inner wall of the channel comprises an undercut feature.
12. A container according to any one of the preceding claims, wherein the at least one side wall of the body portion is upstanding from the bottom wall at or substantially at right angles to the bottom wall.
13. A container according to any one of claims 1 to 11, wherein the angle between the bottom wall and the at least one side wall is obtuse.
14. A container according to claim 13, wherein the angle between the bottom wall and the at least one side wall is greater than 90 degrees.
15. A container according to claim 13 or claim 14, wherein the angle between the bottom wall and the at least one side wall does not exceed degrees.
16. A container according to any one of the preceding claims, wherein the upper edge of the one or more side walls which defines an upper opening is provided with a sealing flange.
17. A container according to claim 16, wherein the sealing flange radiates outwardly from the upper edge.
18. A container according to claim 16 or claim 17, wherein at least a portion of the sealing flange extends outwards on a plane which is substantially parallel to the plane of the raised plinth.
19. A container according to any one of the preceding claims, wherein the bottom wall and one or more side walls are integrally formed from the same sheet of material.
20. A container according to any one of the preceding claims, wherein the container is provided with a lid.
21. A container according to any one of the preceding claims, wherein the opening in the upper end of the container is provided with a film.
22. A mould system for use in the thermoform manufacture of the container according to any one of claims 1 to 21, the mould system comprising a male mould body configured to produce the container according to any one of claims 1 to 21 when a thermoformable sheet of material is moulded over it.
23. A mould system according to claim 22, comprising one or more moulds configured to the internal dimensions of the container according to any one of claims 1 to 21, the mould system being characterised in that the lowermost section of the one or more moulds is configured to equate to the to the uppermost section of the container.
24. A mould system according to claim 23, wherein the one or more moulds comprises one or more narrow ridges on their outer surface.
25. A mould system according to claim 24, wherein the ridges comprise two ridge side walls which extend outward from the mould body and a ridge top wall which extends between the two ridge side walls.
26. A mould system according to any one of claims 22 to 25, wherein the one or more moulds are positioned on a mould base.
27. A mould system according to claim 26, wherein the mould base is integral with the one or more moulds.
28. A method of manufacturing a container characterized in that a sheet of thermoformable material is heated to a pliable forming temperature and formed over a male mould system characterised in that the lowermost section of the one or more moulds is configured to equate to the uppermost section of the container.
29. A method according to claim 28, wherein the thermoformable material is formed over the mould system according to any one of claims 22 to 27.
30. A method according to claim 28, wherein, once formed, the thermoformable material is cooled to produce the container according to any one of claims ito 21.
31. A container substantially as hereindescribed with reference to the accompanying figures.
32. A mould system substantially as hereindescribed with reference toFigure 7 and the accompanying description.