Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CLOSURE DEVICE FOR CONTAINERS
This invention relates to a closure device for
containers.
Closure devices for containers are commonly made
of natural materials such as cork. These are used for
temporarily sealing containers in order to prevent
spillage and to preserve the contents of the
container. They have a traditional appeal and are
effective. Very large quantities are used in wine
bottling and they are also used for other foodstuffs
and for other substances such as cosmetics. However,
they have the disadvantage of being relatively
expensive, are labour intensive to produce, are
subject to quality variations and can introduce
microorganisms and other impurities to the stored
substance. These disadvantages have been recognised
for some time and synthetic substitutes have been
developed using synthetic rubbers and plastics.
These, however, have the disadvantages of being more
expensive than natural materials, of not being readily
reusable, of not looking and feeling like natural
materials and of behaving differently to the natural
materials. Consumers notice these differences and are
put off, thus reducing the acceptability of these
substitutes in the marketplace. There is thus a need
for a synthetic closure which looks, feels and behaves
similarly to the natural material but with advantages
of low cost, consistent quality, and of being sterile.
In EP-A-0 496 194 there is described and claimed
a sealing closure for containers of liquids
; characterised in that it comprises a substantially
cylindrical plastic element, which may be made of
foamed polystyrene, in which an also substantially
cylindrical elastic insert, which may be of cork, is
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axially ~r~h~ e~. However, such a design of closure
appears potentially to have serious drawbacks from the
point of view of lack of sterility due to the presence
of the natural cork; from the point of view of
structural integrity; and from the point of view of
inadequate elastic behaviour. Also, although it is
stated in the description of the patent specification
that the production cost will be low, the complex
structure of the product would indicate the contrary.
There is therefore still a demand for a
satisfactory alternative to cork closures for
containers, and particularly for liquid containers
such as wine bottles.
According to the present invention there is
provided a closure device for a container comprising a
body of circular cross-section which is preferably
cylindrical and which is adapted to fit in an opening
in the container to seal said container said body
consisting essentially of moulded foamed closed-cell
polymer or copolymer preferably expanded polystyrene,
having a substantially uniform density of at least
0.03 g/cc.
It should be noted that the closure device of the
invention does not contain an insert of any other
2S material in its body.
The particularly preferred polymeric material of
the closure device of this invention is expanded
polystyrene. Expanded polystyrene is well known for
its very low density and it is extensively employed,
for example, in packaging applications in which the
expanded polystyrene used may typically have a density
of 0.016 g/cc. It is important to note, however, that
an essential novel feature of the present invention is
that the polymeric material used has a density of at
least 0.03 g/cc so that it is more comparable in
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density to cork which typically has a density of
around 0.1 g/cc although varying depending its source.
Also the increased density of the material renders it
more impermeable to gases and liquids. Thus, the
process conditions used for the production of moulded
expanded polystyrene closure devices of the present
invention are controlled, in known conventional
manner, to produce a final density of at least 0.03
g/ cc .
Although the preferred shape of the body of
closure device in accord with the invention is
substantially cylindrical it may for example be of
other shapes having a circular cross-section, for
example frustoconical. Also, the closure device may
have an enlarged end, that is an end which has a
larger diameter than the body of the closure device,
similar to that of the types of cork which are used
for sealing wines of the "Champagne" type in which the
enlarged end serves to provide an anchorage for a wire
fastening attached to the neck of the bottle to secure
the closure device against being forced out of the
mouth of the bottle by the internal pressure of the
gas in the bottle.
The closure device of the invention is inserted
into the opening of a container to prevent the
material held in the container escaping through the
container's opening when the closure is in place. It
also prevents outside contaminants such as gases,
moisture, bacteria or fungi from entering the
container through the opening. Through achieving an
air-tight seal, it maintains the material stored in
the container in as near perfect a condition as
possible.
The polymeric material of the closure is
desirably coloured to look like the natural material
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that it replaces and is also desirably surface-
textured or otherwise physically surface-treated with
the same end in view. It can also be painted and/or
be printed with information on its surface if
required.
The closure may be pressure treated in its
manufacture for example by rolling. It was originally
thought that this pressure treatment increased both
the elasticity and the density of only a surface layer
of the material. However it is now believed that the
pressure treatment increases the elasticity and
density of the whole body of the closure but that
there is no significant resulting change in the
uniformity of its density. This pressure treatment
enhances the closure's ability to press against the
walls of the container opening and thereby to seal it.
The closure may also be coated with a flexible
impervious coating such as polyurethane if an
additional degree of impermeability is required. The
closure may also be waxed. Additionally, any coating
composition used may contain colour so as to render
the closure device of similar colour to that of
natural cork.
A specific embodiment of the invention will now
be described by way of example with reference to the
accompanying drawing in which:
Figure 1 shows a perspective of the closure
device, in this case acting as a substitute for a cork
in a wine bottle.
Figure 2 shows the closure device in place in a
wine bottle.
Referring to the drawings, the closure device
comprises a cylinder of expanded polystyrene 1 of
substantially uniform density greater than 0.03 g/cc.
At such higher densities, the expanded polystyrene
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exhibits a greatly reduced permeability to gases and
water vapour, and to other fluids. Expanded
polystyrene is resistant to alcohol and is an approved
material for contact with foodstuffs. It is
biologically inert and acts as a barrier to the
ingress of bacteria and moulds. Also, as mentioned
above, at higher densities such as above 0.03 g/cc it
also compares favourably to cork in density and also
has a microstructure of similar appearance to that of
cork. The texture of its external surface 2 is
already very cork-like and this is desirably enhanced
by colouring and/or by physically treating the
surface, for example by shaving, sanding or texturing.
The frictional properties between high density
expanded polystyrene and glass compare favourably to
those between cork and glass. It should be noted
however that cork relies to some extent on absorption
of liquid from the contents of the container in order
to achieve its effectiveness in sealing whereas the
closure device of the present invention does not
absorb liquids to any significant degree.
As is well known in the art, expanded polystyrene
is conventionally produced by a bead process using a
suspension polymerisation technique. A blowing agent
such as for example about 6~ of a low boiling
petroleum ether fraction, e.g. n-pentane, is either
incorporated before polymerisation, or after
polymerisation the beads are impregnated under heat
and pressure. The beads are then processed by steam
moulding. The beads are first pre-foamed by heating
in a steam bath. This causes the beads to expand and
the expansion is continued until they reach an
appropriate level in the mould corresponding to the
desired density. This may be determined by a suitably
positioned thermocouple which is arranged to cause the
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steam to be switched off when this point is reached.
The expanded beads are then allowed to stand for 24
hours to allow them to cool to room temperature and to
allow air to diffuse into the cells so that the cells
equilibrate with outside conditions.
Then a steam moulding process is performed. The
beads are charged into a mould which is provided with
perforated walls to admit steam. The mould is
completely filled with the beads. Steam is then
passed into the mould causing the beads to swell
further and to weld with each other and take up the
shape of the mould.
When the bodies of the closure devices are to be
substantially cylindrical the mould itself may be in
the form of a plurality of cylinders which may be
interlinked each of which cylinders may be several
times the length of the closure devices to be
produced.
When moulding is complete the mouldings are taken
out of the moulds, trimmed, cut to length, printed,
textured, coated and waxed with paraffin wax, as
appropriate.
It should be understood of course that the above-
mentioned specific procedure can be varied in many
respects without departing from the scope of the
invention as hereinafter claimed.
The resulting closure devices can be inserted
directly into a container such as a bottle at this
stage if the mouldings are of sufficiently small
diameter. However, for greater pull strengths larger t
diameter mouldings are used which are reduced in size
by compression, e.g. by rolling, before being put into
a conventional cork inserter.
It should be mentioned that because expanded
polystyrene does not have the same elasticity as cork
= ~
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it is usually necessary to adjust conventional cork
inserters from a usual diameter of 16 mm for a
conventional cork closure to a diameter of say 18 mm
for the closure device of the present invention, to
allow for this di~ference in elasticity and
corresponding expansion.
As mentioned above, the closure device may be
pressure treated, for example by rolling, to improve
the elasticity of the polystyrene. The closure device
is compressed as it is pushed into a bottle 3 and
provides a seal against the glass. On withdrawal the
elasticity of the closure device creates a good
simulation of the sensation of a real cork being
removed from a bottle and allows the closure device to
be reinserted if required. The closure device retains
rigidity thus providing mechanical strength to prevent
the closure device from distorting through bending
when it is pushed into a bottle 4 and to provide
purchase for extraction devices. The high density
expanded polystyrene is practically impervious to
gases and fluid of the nature likely to be encountered
in wine. Additional protection can be given by
treating the ends and/or sides with a colourless
impermeable coating such as polyurethane 5.
As explained above, therefore, the closure device
of the invention thus consists essentially solely of
an expanded closed-cell polymer, preferably expanded
polystyrene, which has a substantially constant
density of greater than 0.03 g/cc throughout, and
which can be partially or wholly surface coated with
an impermeable sealing material for example with
polyurethane and/or a wax to prevent moisture and
gaseous movement through and around the closure
device.
