Bottles and jars – Closures – Cap type
Patent
1997-02-12
1997-12-09
Shoap, Allan N.
Bottles and jars
Closures
Cap type
215343, 215320, B65D 4104
Patent
active
056950837
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a leaktight screw cap comprising a cup-shaped body comprising, on its lateral wall, a female thread interacting with a male thread of the neck of the container and on its bottom sealing means interacting with the neck of the container.
BACKGROUND OF THE INVENTION
Known leaktight caps of this type are generally one-part caps made from plastic. The plastics used most are polyethylene, that is to say a relatively flexible material and the more rigid polypropylene. In the case of beverages, polyethylene is generally used for non-carbonated or slightly carbonated beverages, whereas polypropylene is used for highly carbonated beverages on account of its better gas impermeability.
However, there exist numerous cases of packaging where the gas impermeability provided by caps made from polypropylene is still insufficient. This is the case during the packaging of products sensitive to the action of oxidation from oxygen in the air (fats, sauces, fruit juices), responsible for an organoleptic alteration which may rapidly render the product unsuitable for eating. This also applies to the preservation of the CO.sub.2 content of highly carbonated beverages. Another problem consists in the losses of aromas and of volatile substances from spices and essential oils. Finally, gas-impermeability defects lead to risks of picking up undesirable odours by a product such as the water in plastic bottles during storage or transport in a confined space.
In order to attempt to solve these problems, a leaktight cap has already been proposed, for example according to European Patent Application No 0,280,068, produced from an oxygen-permeable thermoplastic material, for example polypropylene, the bottom of which is internally covered with an oxygen-impermeable complex sheet (paper, chlorinated rubber, PVC), a plastisol seal being cast onto the said complex sheet. However, this cap is not always satisfactory, especially in the case of beverages, the complex sheet being in contact with the contents of the container which is made leaktight by the cap.
Moreover, it has already been proposed, for example by French Patent No. 1,197,200, to produce a leaktight screw cap from two cup-shaped shells fitted one into the other, the inner shell consisting of a flexible plastic and comprising, on its lateral wall, a female thread capable of interacting with a male thread of the neck of the container and, on its bottom sealing means which are capable of interacting with the neck of the container and the outer shell consisting of a hard plastic.
Both shells may therefore be produced in an optimal material taking into account the function which they have to fulfil in the cap. Thus, in order to obtain good sealing with respect to liquids, the use of polyethylene, that is to say a flexible and low-hardness material, is perfectly suitable for the inner shell which is in contact with the packaged product and with the neck of the container and which, on account of its flexibility, adapts well to defects which the container may also have. By contrast, the outer shell may be produced from a hard and rigid material exhibiting, moreover, good properties in terms of resistance to mechanical stresses which could jeopardise the sealing if they were exerted on a single-part cap made from a flexible plastic. However, the lower gas-impermeability of these caps formed from two shells is often not satisfactory.
SUMMARY OF THE INVENTION
The present invention is directed towards a leaktight cap of the type having two fitted shells which, whilst being of simple manufacture and of low cost, ensures both good sealing with respect to liquids and good gas-impermeability and can be used without problems for products of the greatest diversity.
In the leaktight cap in accordance with the invention, the gas impermeability is ensured solely or principally by a disk having a gas-barrier effect which is inserted between the bottom of the outer shell and the bottom of the inner shell.
Thus, the disk is imprisoned between the inner shell and the
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Hylton Robin A.
Rical S.A.
Shoap Allan N.
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