GB2304097A

GB2304097A - Sealed pack

Info

Publication number: GB2304097A
Application number: GB9616496A
Authority: GB
Inventors: Daryl John Thompson
Original assignee: PENLEA PLASTICS Ltd
Current assignee: PENLEA PLASTICS Ltd
Priority date: 1995-08-12
Filing date: 1996-08-06
Publication date: 1997-03-12
Anticipated expiration: 2016-08-06
Also published as: GB9516562D0; GB2304097B; GB9616496D0; EP0758614A1

Description

2304097 Sealed Pack The pres6nt invention is a sealed pack in the form of

a container and a lid for the container. Such packs may be exemplified by, but are not limited to, transparent packs of this type used for transporting and/or displaying food products.

Some packs used for food products require to be secure against leakage of liquid from within the pack. For this purpose, the lid of the pack may be heat-sealed to the base. However, to simplify the assembling of the pack and at the same time to avoid the need for a substantial i in heat-sealing machinery, having continuous nvestment packs have been developed leakproof mechanical seals in the region of their circumference.

Leakproof seals of this latter consisted of a type have continuous projection on the lid or base of the pack inserted into a continuous channel on the base or lid. The projection and channel have been designed to be a very close fit together with the aim of preventing all passage of liquid past the seal. In practice, such close-fitting seals have given rise to two significant disadvantages. Firstly, it has been found that liquid tends to leach by capillary action past two closely-engaging plastics surfaces, in spite of the mechanical integrity of the seal. Secondly, when the contents of the pack are to be used, it has often proved difficult to separate the lid from the base, especially when the user has limited for gripping these two components, as capacity in the case of an arthritic user Quite apart from these disadvantages of such available "leakproof" packs, there is a need for a pack which is also proof against the passage of air or gas into or from the pack. For example, with some products, it is important to exclude air from the pack, while for others it is desirable to prevent outward loss of a gas required to protect or preserve the pack contents, or of a gaseous ripening agent.

An object of the present invention is to provide an improved pack, by means of which some at least of the disadvantages of prior packs are reduced or overcome, and which is devised to limit or prevent inward or outward passage of air or gas.

The pack according to the present invention 3 - comprises a container and a lid therefor, each of which is made of a resilient synthetic polymeric material, a continuously curved channel in the region of the circumference of either the lid or the container and a continuously curved projection in the region of the circumference of the other of the lid and the container and adapted to engage said channel, the surface of the projection which faces the channel when the two are engaged being flat and the innermost surface of the channel which faces the projection when the two are engaged also being flat, the height of the projection relative to the depth of the channel being such that said two surfaces abut each other closely when the proje ction and the channel are engaged, the lateral width of said projection surfacebeing less than the lateral width of said channel innermost surface, and the lateral width of said projection overall being greater than the lateral inner width of the channel at its widest point.

By virtue of the characteristics and relative dimensions of the projection and channel as specified above, it is possible to provide a pack in which leakage both of liquid and of gas into and from the pack according to the present invention is 4 minimised or, in practical terms, prevented.

The container and lid of the pack are each made of a resilient synthetic polymeric material but need not be made of the same material. The material must be at least to some extent resilient because the effectiveness of the seal depends upon relative distortion of the projection and the channel.

Suitable materials include polyvinyl chlorides (PVC's), polypropylenes and polystyrenes, if desired in dissimilar combinations, for example a PVC base with a polypropylene lid.

The projection may be located on the lid and the channel on the container or vice versa. In effect, the terms "lid" and "container" may be regarded as interchangeable, in the sense that a flat base with an upstanding lid may be inverted to form a deep container with a flat lid.

Both the projection and the channel must be continuously curved, without therefore having any angular changes of direction or any corners. However, the container and lid need not be generally circular but may be shaped to reflect the nature of the intended contents or for aesthetic reasons. Thus, while these two components may indeed be generally circular in plan, they may also be elliptical, or generally rectangular but with smoothly curving "corners", or any other continuously curved shape.

As specified above, the two interengaging surfaces of the projection and channel are both flat but the surface of the projection is narrower than that of the channel. As a result, a space is formed within the channel along each side of the projection. These two spaces each interrupt the face-to-face contact of the projection and channel and prevent leaching of liquid by capillary action between the surfaces. The assembling of the pack is easier than with prior available packs. By virtue of these foregoing features, opening of the pack when the contents are to be used is also significantly easier.

Because the overall width of the projection is greater than the maximum internal width of the channel, one or both of those features must distort to enable the channel to accommodate the projection. As indicated above, this necessary distortion contributes to the efficiency of the seal.

The invention will now be further described with reference to the accompanying drawings, which illustrate, by way of example only, the structure of the seal in one preferred embodiment of the sealed pack according to the present inventi-on and wherein:

The pack formed of both of which projection 10 the region of As shown in projection 10 increases slightly below projection and surface 13.

A continuous channel 14 is formed around the lid within the region of the outer perimeter 15 of the lid. As shown in Fig. 2, the cross-section Fig. 1 is a cross-sectional view of the projection on the base; Fig. 2 is a cross-sectional view of the channel on the lid; and Fig. 3 illustrates the features of Figs. 1 and 2 superimposed.

of which the seal is illustrated a PVC base and a polypropylene lid, are circular in plan. A continuous extends upwardly from the base within the outer perimeter 11 of the base. Fig. 1, the cross-section of the upwardly to a level 12 the mid-point of the height of the then reduces towards a flat top of the channel 14 increases away from the continuous opening 18 of the channel to a level 16 at about threequarters of the depth of the channel and then reduces towards a flat ihner surface 17.

The surface 13 of the projection 10 is narrower than the surface 17 of the channel 14. Thus, when the projection 10 is introduced into the channel via the opening 18 and the surfaces 13 and 17 abut each other, a space 19, 20 (Fig. 3) remains at each side of the projection.

Fig. 3 illustrates the relative dimensions of the projection 10 and the channel 14, with the projection being shown in broken line. As shown, the projection cannot fit within the channel without distortion, which in practice has been found to occur, although the precise position and distribution of the distortion has not yet been identified. However it is clear that the break line at 12 along the outsides of the projection 10 forms a continuous liquid barrier where it contacts the inner face of the channel 14 on both sides of the projection.

Thus, when the lid and container are assembled together, any liquid or gas which may tend to escape from the container must first, having entered the channel 14, pass the liquid barrier at 12 and then traverse the space 19. It must then pass in some way between the abutting surfaces 13 and 17, traverse the space 20 and finally pass the second liquid barrier at 12 on the radially outer side of the projection 10.

In experimental practice, it has been found that the illustrated seal is a very effective proof against transmission of liquid and gas. A pack containing a product packed in a chilled environment and left in an ambient area retained the expanding air until the seal eventually burst apart. Similarly, a pack which had been packed in a warm atmosphere and then chilled eventually imploded.

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Claims

1. A sealed pack comprising a container and a lid therefor, each of which is made of a resilient synthetic polymeric material, a continuously curved channel in the region of the circumference of either the lid or the container and a continuously curved projection in the region of the circumference of the other of the lid and the container and adapted to engage said channel, the surface of the projection which faces the channel when the two are engaged being flat and the innermost surface of the channel which faces the projection when the two are engaged also being flat, the height of the projection relative to the depth of the channel being such that said two surfaces abut each other closely when the projection and the channel are engaged, the lateral width of said projection surface being less than the lateral width of said channel innermost surface, and the lateral width of said projection overall being greater than the lateral inner width of the channel at its widest point.

2. A sealed pack as claimed in Claim 1, wherein the container and the lid are each made of polyvinyl chloride, polypropylene or polystyrene but need not be of the same material.

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3. A sealed pack as claimed in Claim 2, comprising a polyvinyl chloride base and a polypropylene lid.

4. A sealed pack as claimed in any of Claims 1 to 3, wherein the 'container and lid are, in plan, each generally circular, elliptical or generally rectangular with curved corners.

5. A sealed pack, substantially as hereinbefore described with reference to, and as in part illustrated in. the accompanying drawings.