EP0362250A1

EP0362250A1 - Plastics food containers

Info

Publication number: EP0362250A1
Application number: EP19880904575
Authority: EP
Inventors: Peter Reginald 4 Colne Place Clarke
Original assignee: R CLARKE AND CO MOULDS Ltd
Current assignee: R CLARKE AND CO MOULDS Ltd
Priority date: 1987-05-22
Filing date: 1988-05-20
Publication date: 1990-04-11
Also published as: GB8712162D0; WO1988009142A1; AU1785488A; GB2205064A

Abstract

Le récipient (10) pour aliments décrit comprend plusieurs compartiments séparés (12) servant de plats et on le produit en formant un flan. Le flan est constitué par un flan façonné moulé par injection et comporte des parties élargies qui, dans le récipient formé (10), définissent des nervures de renforcement (22) dans les âmes (18) entre les compartiments adjacents (12) du récipient (10).The described food container (10) comprises several separate compartments (12) serving as dishes and is produced by forming a blank. The blank consists of a shaped injection molded blank and has enlarged parts which, in the formed container (10), define reinforcing ribs (22) in the cores (18) between the adjacent compartments (12) of the container ( 10).

Description

PLASTICS FOOD CONTAINERS

The invention relates to food containers made of a plastics material and is particularly concerned with containers for containing prepared meals and which have separate dished compartments to keep the different components of the meal separate during transportation and preparation. Such containers are used for frozen meals and also for meals served on board aircraft.

The conventional manner of constructing such a food container is to form it from a flat sheet. The term "forming" is used here to include any process by which the sheet is stretched or deformed into the shape of a mould, for example by air pressure, vacuum or mechanical pressure. The sheet is initially flat and in selecting the thickness of the sheet one must consider several factors such as the depth of the compartments and the weight of the blank, the latter affecting the cost of the container. It is desirable to use the minimum thickness of sheet which affords sufficient strength in the corners of the dished compartments, which undergo the most deformation during the forming process, but this would mean that the webs between the compartment would be weak and would permit the container to flex.

The present invention seeks to provide a food container wherein increased rigidity is achieved in the moulded container while making economical use of the plastics material.

According to the present invention, there is provided a food container comprising a plurality of separate dished compartments and produced by forming a blank, wherein the blank is a shaped injection moulded blank and includes thickened portions which in the formed container define reinforcement ribs in the webs between adjacent compartments of the container. Preferably, the blank is formed from non-crystalline poly(ethylen terephthalate) plastics material (herein referred to as P.E.T.) and the formed container is at least partly crystallised during or after the forming the process.

P.E.T. has been used in the packaging of food because of its strength and its chemically inert character. However, hitherto P.E.T. has only been formed from extruded plastics sheet blanks. It has however been found, surprisingly, that it is possible to inject mould the blanks for containers and by so doing it is possible to provide additional rigidity in selected areas, without increasing the overall thickness of the blank.

P.E.T. has the property that it changes in crystal structure when heated to a certain temperature and upon such crystallisation its physical properties are changed significantly. In particular, the strength is improved and this changed is also accompanied by a change in the appearance of the material.

Temperature control at all stages in the moulding and forming processes is therefore of importance and it is possible to mould by injection a blank which is amorphous and which can be formed into a container of the desired shape prior to heat being applied to crystallise the plastics material.

The blank may be formed with varying thickness to reinforce the parts which undergo the most deformation during the forming process. It is also possible to shape the blank so that containers of other than rectangular section can be formed without the wastage that result from using an extruded sheet material.

It is convenient to form the blanks with loops which can later be bent to form handles for the container. P.E.T. is a particularly difficult material to cut and any cutter used wears rapidly. A further advantage of the use of individual moulded blanks as opposed to cutting flat blanks from an extruded sheet is that this problem can be circumvented.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which :

Figure 1 shows a plan view of the underside of a first embodiment of the invention.

Figure 2 is a section along line I-I in Figure 1, and

Figures 3 and 4 show views similar to Figure 1 of two further embodiments of the invention.

Figure 1 shows a circular container 10 with three individual dished compartments 12 each extending over approximately 120°. The compartments 12 have sloping side walls 14 and a base 16 and are separated from one another by webs 18.

Even though the rim of the container 10 is formed with a lip 20, there is a tendency for the container to flex along the webs especially when it is full and has been softened during the warming of the food. To strengthen the container, ribs 22 are formed along the webs 18 to reduce the tendency to flex.

To manufacture the container, a circular blank is formed by injection moulding of P.E.T. which contains the ribs 22 and such other thickened portions, as may be required. For example, the sides 14 and in particular the corners of the container undergo significant deformation during the forming process and may be thickened to provide additional strength in the finished articles at these vulnerable locations.

The blank is next transferred after cooling to a forming mould, where the rim of the blank is held firm and pressure is applied to the regions of the blank which are to form the dished compartments 12 to deform the material of the blank into a female mould of the desired shape. The pressure required to stretch the P.E.T. material can be a positive gas pressure, a vacuum, mechanical pressure exerted by a male mould member, or a combination of these.

After or during the formation of the blank, it is heated to bring about at least partial crystallisation. It is preferred to separate the crystallisation process from the forming process in order to increase the yield of the forming mould.

The embodiment of Figure 3 differs from that described above in that the container 10' has only two compartments 12' and in that it is provided with two carrying handles 24 which initially lie in the plane of the blank and which are bent upwards when carrying the full container.

Figure 4 shows an embodiment which differs only in shape from the embodiment of Figure 1, the container 10" being rectangular and the compartments 12" being of difference sizes. Here again, carrying handles can be provided if desired.

In the use of the container for prepacked meals, the different compartments are used for the different courses or for different parts of the same course. After placing the food in the various compartments, these are sealed by means of a foil which is adhered to the webs 18 and the rim 20. The foil is peeled back or punctured after the meal has been heated, thus permitting a hot meal to be processed and transported without risk of spillage. This is of course of particular advantage in the aircraft industry and is also value in packaging of convenience foods.

The formation of the container from an injection moulded blank has the advantages of not requiring blanks to be cut from a sheet, a process which presents problems when the plastics material is P.E.T.. Furthermore, one is not constrained in the shape of the container by the need to minimise wastage in the extruded sheet and in this respect the provision of a handle as proposed in the embodiment of Figure 3 would be wholly impracticable if the blanks were to be cut from sheet material.

Claims

1. A food container comprising a plurality of separate dished compartments and produced by forming a blank, wherein the blank is a shaped injection moulded blank and includes thickened portions which in the formed container define reinforcement ribs in the webs between adjacent compartments of the container.

2. A container as claimed in Claim 1, wherein the blank is formed from non-crystalline poly(ethylen terephthalate) plastics material and the formed container is at least partly crystallised during or after the forming process.

3. A container as claimed in claim 1 or 2, wherein the blank is formed with varying thickness to reinforce the parts which undergo the most deformation during the forming process.

4. A container as claimed in any preceding claim, wherein the contour of the container is non-rectangular.

5. A container as claimed in any preceding claim, wherein the blank includes loops which can be bent out of the plane of the blank to form carrying handles for the container.