GB2221450A

GB2221450A - Tray-type lidded cartons

Info

Publication number: GB2221450A
Application number: GB8917260A
Authority: GB
Inventors: Gordon David Edwards
Original assignee: CMB Packaging UK Ltd; Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1988-08-05
Filing date: 1989-07-28
Publication date: 1990-02-07
Also published as: GB8917260D0; GB8818642D0

Abstract

In a tray-type lidded carton made of a plastic coated board material and having a lid (15) heat sealed to an out-turned peripheral flange (14), the lid is formed with a single continuous score (16) on its under surface only, closely spaced inwards from the peripheral heat-sealed region (17), the upper surface of the lid being free from scores. The lid (15) is formed at one corner with a projecting tab (18) and with a score (19) on its under surface extending across the base of the tab (18), so that lifting the tab initiates delamination of the lid along the heat sealed region (17). The score (16) then enables the lid (15) to be torn off the carton. <IMAGE>

Description

TRA-PE LIDDED CARTONS This invention relates to tray-type lidded cartons made of a plastic-coated board material, such as are used for packaging processed foods which are sold ready for cooking or reheating in either a conventional oven or a microwave oven.

The invention is particularly concerned with such cartons which have a peripheral out-turned flange to which a lid of similar plastic-coated material is secured by heat-sealing the plastic coating of a peripheral region of the lid to the plastic coating of the upper surface of the flange.

To provide for the removal of the lid after cooking, it is known to form the lid with scores in its upper and lower surfaces, so that it can readilly be fractured by thumb pressure at an appropriate point and then torn off. This arrangement has the disadvantages that, if the carton is well filled, it can be difficult to press in the appropriate part of the lid sufficiently to start the fracture and when the fracture is made the contents may spurt out. Even when the carton is not so full, the operator's thumb may inadvertently enter the liquid contents and, if they have just been cooked, may be burnt thereby. Furthermore, the lid is liable to be broken inadvertently by comparatively small top loads, so that the contents of the carton can be spilt in transit.There is also a risk that the liquid contents may penetrate through the lower score into the fibre material of the board and cause leakage or staining.

In some cases, the score in the op surface of the lid has been staggered outwardly with respect to the score in the inner surface. This makes it somewhat more difficult to open the lid, since the plastic coatings on the upper and lower surfaces will only tear along the scores and opening of the lid thus requires delamination of the board material in the narrow region between the staggered scores, so the lid does have the advantage of increased strength for supporting top loads.

It has also been proposed to separate the plastic coating on the top surfaces of the flanges from the plastic coating on the remainder of the inside of the carton by means of scores, so that no score is required in the lid but it can be opened by delamination of the board material of the flanges. This has the disadvantage that it is difficult to initiate the opening of the lid.

According to the present invention, in a tray-typed lidded carton made of a plastic-coated board material and having a peripheral out-turned flange to which a lid of similar plastic-coated material is secured by heat-sealing the plastic coating of a peripheral region of the lid to the plastic coating of the upper surface of the flange, the lid is formed with a single continuous score on its under surface only, running adjacent to but spaced from the inner edge of the peripheral heat-sealed region, the upper surface of the lid being free from scores, and the lid is formed at one corner with a tab projecting outwardly beyond the heat-sealed region and with a score on its under surface extending across the base of the tab, the two scores both penetrating through the plastic coating on the under surface of the lid, so that lifting the tab initiates delamination of the lid and enables it to be torn off the carton by delamination of the whole of the peripheral heat-sealed region.

This arrangement provides convenient and easy opening of the lid while retaining much of its strength and ability to resist top loads. The single continuous score on the under surface of the lid does not interrupt the plastic coating on the upper surface and so does not seriously weaken the lid. On lifting the tab, the board material of the lid commences to delaminate along the peripheral regions which are heat-sealed to the flanges while the continuous score ensures that the heatsealed plastic on the under surface of the lid in the peripheral region separates from the plastic coating on the main part of the lid.

To improve the initiation of the delamination, it is preferable that the score extending across the base of the tab also extends part-way around the corner of the lid.

Preferably the single continuous score on the under surface of the lid is formed at the corner adjacent the tab with a sharply angled corner portion to assist initiation of separation of the plastic coating of the heat-sealed peripheral region from the rest of the lid.

The single continuous score on the under surface of the lid is normally formed at each corner other than that adjacent the tab with a rounded corner portion, but it may alternatively be formed with a diagonal corner portion to provide a reinforcing shoulder.

The lid may be initially formed separate from the carton and secured to the flange by heat-sealing all around the periphery of the lid and carton. Alternatively, the lid may be hinged to the carton along one side and secured to the flange by heat-sealing around the remaining sides of the lid and carton.

The plastic coating on the board material may be of a polyester, such as polyethylene terephthalate, particularly where the carton is to be used for foods which are to be cooked or reheated at temperatures up to 2400C.

Alternatively it may be of polypropylene or polyethylene where the food does not require heating above approximately 180 0C.

A specific embodiment of the invention will now be described in more detail by way of example and with reference to the accompanying drawings, in which: Figure 1 is a perspective view from above of a tray-type carton, Figure 2 is a plan view from above of a lid for the carton of Figure 1, Figure 3 is a perspective view from above of the carton with the lid secured thereon, and Figure 4 shows the carton of Figure 3 with the lid partially opened.

As seen in Figure 1, the tray-type carton 10 has a floor 11, four upwardly diverging side walls 12 and a peripheral outturned flange 14 extending all around the top of the tray.

Figure 2 illustrates a lid 15 for the carton of Figure 1.

Like the carton, the lid 15 is made of a plastic-coated board material, preferably a white board. A coating of heatsealable polyethylene terephthalate is provided on the inside of the carton 10 and hence on the upper surface of the flange 14, and on the under surface of the lid 15. The other surfaces have a conventional clay coating. A single continuous score 16 is formed on the under surface of the lid 15 running adjacent to, but spaced from, the inner edge of a peripheral region 17 which corresponds in dimensions to the flange 14 of the carton and is to be heat-sealed thereto. The upper surface of the lid 15 is free from scores.

The lid is formed at one corner with a tab 18 projecting outwardly beyond the peripheral region 17. A score 19 on the under surface of the lid extends across the base of the tab 18 and also extends part way around the corner of the lid as shown at 20. The adjacent corner of the score 16 is formed with a sharply angled corner portion 21. At each of the other Y J corners, the score 16 is formed with a diagonal corner portion 22. It would alternatively be possible to form the score 16 with diagonal corner portions to provide reinforcing shoulder portions (not shown).

Figure 3 shows the lid 15 secured to the carton by heatsealing the plastic coating of the peripheral region 17 on the under surface of the lid to the plastic coating of the upper surface of the flange 14. It will be seen that the tab 18 projects and is easily grasped for opening the lid.

As shown in Figure 4, when the tab 18 is grasped and pulled upwards, it initiates delamination of the board material of the lid in the peripheral region 17. The angled portion 21 of the score 16 assists initiation of the separation of the plastic coating of the heat-sealed peripheral region 17 from the rest of the lid and further tearing continues down the score 16 to enable the lid to be removed entirely from the carton 1.0.

The invention is equally applicable to tray-type cartons having hinged lids, i.e. in which the lid is hinged to the carton along one side and is secured to the flange by heatsealing around the remaining sides of the lid and carton.

In either case, removal of the lid is facilitated while the lid retains a substantial amount. of strength to resist top loads.

Claims

1. A tray-type lidded carton made of a plastic-coated board material and having a peripheral out-turned flange to which a lid of similar plastic-coated material is secured by heat-sealing the plastic coating of a peripheral region of the lid to the plastic coating of the upper surface of the flange, wherein the lid is formed with a single continuous score on its under surface only, running adjacent to but spaced from the inner edge of the peripheral heat-sealed region, the upper surface of the lid being free from scores, and the lid is formed at one corner with a tab projecting outwardly beyond the heat-sealed region and with a score on its under surface extending across the base of the tab, the two scores both penetrating through the plastic coating on the under surface of the lid, so that lifting the tab initiates delamination of the lid and enables it to be torn off the carton by delamination of the whole of the peripheral heat-sealed region.

2. A tray-type carton according to claim 1 wherein the score extending across the base of the tab also extends part-way around the corner of the lid.

3. A tray-type carton according to claim 1 or 2 wherein the single continuous score on the under surface of the lid is formed at the corner adjacent the tab with a sharply angled corner portion to assist initiation of separation of the plastic coating of the heat-sealed peripheral region from the rest of the lid.

4. A tray-type carton according to any one of the preceding claims wherein the single continuous score on the under surface of the lid is formed at each corner other than that adjacent the tab with a diagonal corner portion to provide a reinforcing shoulder.

5. A tray-type carton according to any one of the preceding claims wherein the lid is initially formed separate from the carton and is secured to the flange by heat-sealing all around the periphery of the lid and carton.

6. A tray-type carton according to any one of claims 1 to 4, wherein the lid is hinged to the carton along one side and is secured to the flange by heat-sealing around the remaining sides of the lid and carton.

7. A tray-type carton according to any one of the preceding claims wherein the plastic coating on the board material is of a polyester.

8. A tray-type carton according to claim 7 wherein the plastic coating is of polyethylene terephthalate.

9. A tray-type carton according to any one of claims 1 to 6 wherein the plastic coating on the board material is of polypropylene or polyethylene.

10. A tray-type carton made of a plastic-coated board material and having a peripheral out-turned flange to which a lid of similar plastic-coated material is secured by heat-sealing the plastic coating of a peripheral region of the lid to the plastic coating of the upper surface of the flange, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.