U.S. patent number 3,620,774 [Application Number 04/749,497] was granted by the patent office on 1971-11-16 for plastics containers and packages.
This patent grant is currently assigned to Imperial Chemical Industries Limited, London, GB2. Invention is credited to Andrew George Ford, Ronald Augustus Hudson.
United States Patent |
3,620,774 |
|
November 16, 1971 |
PLASTICS CONTAINERS AND PACKAGES
Abstract
A plastics film container containing a gas under
superatmospheric pressure, e.g. beer or a soft drink, closed by a
ligature applied to the sealed, bunched neck below a thickened
region thereof.
Inventors: |
Andrew George Ford (Hitchin,
GB2), Ronald Augustus Hudson (Welwyn Garden, GB2) |
Assignee: |
Imperial Chemical Industries
Limited, London, GB2 (N/A)
|
Family
ID: |
25013991 |
Appl.
No.: |
04/749,497 |
Filed: |
August 1, 1968 |
Foreign Application Priority Data
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Aug 1, 1967 [GB3] |
|
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35,333/67 |
Aug 1, 1967 [GB3] |
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28,354/68 |
Aug 1, 1967 [GB3] |
|
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28,356/68 |
Aug 31, 1967 [GB3] |
|
|
39,820/67 |
Feb 29, 1968 [GB3] |
|
|
9,848/68 |
Jun 12, 1968 [GB3] |
|
|
27,902/68 |
|
Current U.S.
Class: |
426/106; 426/127;
383/71 |
Current CPC
Class: |
B65D
75/48 (20130101) |
Current International
Class: |
B65D
75/00 (20060101); B65D 75/48 (20060101); B65d
035/08 () |
Field of
Search: |
;99/171B,171S,171C,171LP
;229/63 ;53/14 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
639812 |
|
Apr 1, 1962 |
|
CA |
|
926159 |
|
May 1, 1963 |
|
GB3 |
|
Primary Examiner: Frank W. Lutter
Assistant Examiner: William L. Mentlik
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
1. A package comprising a length of biaxially oriented tubular
plastic film and contents therein under superatmospheric pressure,
the tubular film being closed at each end by a bunched neck of the
tubular film and an encircling closure applied as a tightly drawn
ligature about the bunched neck, said closure being disposed
between the body portion of the tubular film and the end portion of
the tubular film which end portion has a thickened region that is
of greater cross-sectional area than the region encompassed by the
encircling closure, and a seal at each end of the tubular film to
prevent egress of the contents of the package through
2. A package as claimed in claim 1 in which the plastic film is
biaxially
3. A package as claimed in claim 2 having a coating of vinylidene
chloride
4. A package as claimed in claim 1, having a tubular sleeve of the
same or a different plastic film disposed substantially around the
whole of the
5. A package as claimed in claim 1 in which the said thickened
region comprises additional material disposed at the inner surface
of the end
6. A package as claimed in claim 5 in which said additional
material is a flexible tape coated on both sides with adhesive and
applied around the
7. A package as claimed in claim 1 in which the said thickened
region comprises additional material applied to the outer surface
of the end
8. A package as claimed in claim 7 in which the additional layers
of
9. A package as claimed in claim 7 in which the thickened region
comprises the end of the flattened tubular film being folded over
upon itself and
10. A package as claimed in claim 7 in which the additional
material is
11. A package as claimed in claim 1 in which the thickened region
comprises the walls of the tubular film which are bunched and
sealed together by a
12. A package as claimed in claim 1, closed at each end by a
bunched neck
13. A package as claimed in claim 1, in which a continuous seal is
provided between the walls of the neck of the tubular film to seal
all capillaries
14. A package as claimed in claim 1 in which the tubular film is
closed at each end by the said bunched neck and a tubular sleeve of
flexible material is disposed around substantially the whole of the
cylindrical portion of the tubular film, said flexible material
being sealed or
15. A package as claimed in claim 1 in which the opposed inner
walls at both ends of the tubular film are sealed together in flat
contact and are gathered together to form a bunched neck, said neck
being closely held by an encircling closure device located between
the said seal and contents
16. A package as claimed in claim 1, having a filling aperture in
the cylindrical wall thereof sealed by a patch of flexible sheet
material
17. A package as claimed in claim 1 in which the film bears a
coating of a
18. A package as claimed in claim 1 in which the package is formed
of double walled tubing, the two walls being of the same or
different
19. A package as claimed in claim 1 in which the encircling closure
is a
20. A package as claimed in claim 1 which contains a carbonated
drink.
Description
This invention relates to packages comprising filled containers of
plastics film with contents under superatmospheric pressure, and to
the film containers for producing such packages.
The invention relates particularly to plastics film containers for
gas-containing liquids, such as beer and carbonated soft drinks,
and liquids packed under pressure of a gas. It may also be applied
to the packaging of articles of solid substances in plastics film
containers made rigid by enclosing a gas or vapor under pressure.
It may also be used in packaging gases, alone, or low boiling
liquids that generate pressure under normal storage conditions. In
the term "gas" we shall hereinafter include vapors of low boiling
liquids, e.g. aerosol propellants.
It has previously been proposed to package liquids in plastics film
containers closed by heat sealing. Such packages, however, have not
been satisfactory for applications in which the contents are under
relatively high pressures; even pressures as low as 3 p.s.i. cause
seal failures. Attempts to make a purely mechanical closure to
contain the pressures generated by carbonated drinks have also been
unsuccessful.
The present invention provides a plastics film container for
contents including a gas under superatmospheric pressure, the
container being closed by at least one bunched neck, with a
ligature or other encircling closure applied to the bunched neck
immediately below a region thereof that is of greater
cross-sectional area than the region encompassed by the encircling
closure, and all capillaries leading through the bunched neck from
inside the container to the atmosphere are sealed against egress of
gas from the container.
The invention further provides a package comprising a container as
described, sealed from the atmosphere and with contents including a
gas under superatmospheric pressure.
In referring to the "region of greater cross-sectional area" we
mean that this region of the bunched neck has a greater
cross-sectional area than the adjacent region, either through the
inclusion of additional material, or through this portion being
rendered less easily deformable by the force exerted towards it by
the ligature when the container is pressurized For example, the
increase in cross-sectional area may be brought about by strongly
crimping or embossing the film, particularly where it is sealed, as
will be more particularly described hereinafter, and thus is not
necessarily due to the presence of additional film or other
material in the region. For simplicity, the region of greater
cross-sectional area will be referred to hereinafter as the
"thickened" region, and the "ligature or other encircling closure"
will be referred to simply as the "ligature." By referring to the
position of the ligature as being immediately "below" the thickened
region, we mean that the ligature is immediately adjacent to the
thickened region and on the same side thereof as the contents of
the container. The neck of the container will generally be bunched
simply by gathering it together, with the ligature or by other
means. However, the closing of the neck may include a degree of
systematic folding or twisting.
In one preferred form of the closure, a thickened region is
provided by additional material or layers attached to the outer
surface of the container wall in the region to be thickened.
Methods of providing such additional layers include that of folding
over the end of the flattened container upon itself and sealing all
the layers of film together by heat and pressure or by adhesives,
before the neck is bunched or twisted. Another method is by
similarly sealing a separate strip or strips of material to the
outer surface of the container walls, a seal also being formed
between the inner surfaces of the container, beyond the intended
position of the ligature, in respect of the contents, and
preferably beneath the applied layers. We find that even a
relatively weak and brittle seal between the inner surfaces, such
as a heat seal formed between adjacent surfaces of oriented film of
polyethylene terephthalate without a heat-seal coating, is
sufficient to withstand the pressure of enclosed gas when the
ligature is in position. Additional material may otherwise be
attached to the outer surface of the container wall in the region
to be thickened by coating it on to the walls, or by depositing it
discontinuously thereon, as a melt or from a solution or
dispersion. Thus, hot melt compositions that will adhere to the
film may be used for this purpose.
Additional material to provide the thickened region may
alternatively be applied to the inside surface of the neck of the
container. For example, a tape of film or other flexible sheet
material may be bonded to the surface by heat sealing or by
adhesive, or a plastics material may be melt coated on to the
surface. The thickened region may further be provided by a layer of
self-adhesive material coated on to one or both of the opposed
surfaces of the film; for example, a wax, a low molecular weight
polymer, or other material normally solid but capable of melting at
a temperature below that at which the plastics film melts or
becomes unserviceable, may be coated upon the appropriate parts of
the film surface, or injected into the region of the closure.
Alternatively, as previously indicated, the thickened region may be
a heat-seal, crimped, embossed, or otherwise formed in such a way
that it is sufficiently less compressible than the adjacent regions
to resist the force of the internal pressure upon the ligature,
tending to push it along the bunched neck. The degree of
incompressibility required in the seal will of course depend in
part on the maximum pressure that will be developed in the package.
It will also depend on the limpness of the film. Thus, if the film
is of a limp sort, deep embossing on a wide seal is required to
effect the desired increase in cross-sectional area. The
provisional of a suitable seal will thus be a matter to be
determined by experiment for any particular use of the container
that may be envisaged. A further method of providing the thickened
region by means of a heat seal is that of cutting the bunched neck
just beyond the ligature by means of a hot knife, and pushing the
fused, cut edges towards the ligature so that, on cooling, the seal
serves to provide a thickened rim as well as to seal any
capillaries through the bunched neck.
In a further form of the container, a suitable thickened region of
the neck is provided by shrinking a portion of the walls of the
neck by locally heating the film to a sufficiently high
temperature. In this case the neck may be simultaneously or
separately sealed, by heat sealing or by an adhesive, to close any
capillaries that would otherwise remain through the bunched neck.
Here also the degree of shrinkage that is required to provide
sufficient thickening is a matter to be determined by
experiment.
In general, it is preferred to provide the thickened region by the
inclusion of additional material, rather than by the provision of a
suitably modified heat seal or by shrinkage of the container neck,
since the first method gives more reliable and consistent results,
particularly for relatively high pressures such as those generated
by beer and carbonated drinks.
The container is preferably a plastics film tube closed at each end
by a closure as described. The containers are preferably formed
without seams, but they may be formed with a seam or seams capable
of withstanding the pressure of enclosed gas. It will be
appreciated that internal pressures can be more easily withstood
by, for example, a lapped seam in the wall than by a seal that is
subject to a peeling force, as is the case with seals of the type
normally used for closing filled bags and similar containers.
If desired, a mechanical closure may be placed upon the thickened
region of the neck of the container, to provide additional security
to the closure.
Particular forms of the container of the present invention as so
far described will now be described by way of example with
reference to FIGS. 1 to 10 of the accompanying drawings, of
which:
FIGS. 1 and 3 show stages in the formation of a closure of a
preferred type at one end of a length of tubular plastics film from
which a container is to be formed, the thickened region of the neck
being provided by the inclusion of additional layers in the
seal;
FIG. 2 is a section through the line A-A in FIG. 1;
FIG. 4 shows a finished container with each end sealed and tied
with a ligature; and
FIGS. 5 to 10 show stages in the formation and filling of a
container with an alternative type of closure, in which the
thickened region is provided by an additional layer of film applied
round the inside surface of the container neck, FIG. 9 being a
section through line B-B of FIG. 8.
In FIGS. 1 to 4: 1 represents a length of plastics tubular film,
and 2 a fold by which an open end of the length has been turned
over upon the tubular film, the trimmed edges of the end being
shown (in FIGS 1 and 2) at 3; 4 is a heat seal between the 4 layers
of film so brought together; and 5 (FIGS. 3 and 4) is a ligature of
plastics coated wire which has been passed four times round the
bunched neck, immediately adjacent to the thickened region provided
by the four layers of film. The wire is pulled tight, and the ends
twisted together at 6.
One preferred method of filling the containers is that described in
our copending British application No. 9849/68. For this purpose,
the container is preferably supplied in flattened form, closed at
both ends, as shown in FIG. 4. The container is preferably provided
with an aperture, shown at 7, which is formed before the second end
of the tubing is closed. The container is then ready to be
pressurized and filled with a liquid containing a gas under
pressure, by the method described in the said application. The
aperture is preferably punched in the wall of the container by
means of a hot tool, or by a jet of hot air or a flame, so that the
edges of the aperture become slightly thickened.
In FIGS. 5 to 9: 8 represents a length of plastics tubular film,
which is provided at each end with a layer, 9, of tape (preferably
a plastics film tape) coated on both sides with a contact adhesive,
and adhered all round the inside surface of the ends of the tubing.
The tubing is flattened at one end as shown at 10 in FIG. 6, to
seal together the opposed surfaces of the tape and form the bottom
of the container. A ligature, shown at 11 in FIGS. 6, 7 and 8,
suitably of plastics coated wire, is then applied immediately above
the tape, and is drawn tight and has its ends twisted together. A
metal clip, 12 (FIGS. 8-10) is optionally applied upon the region,
13, thickened by the tape, as shown in FIG. 8, and in cross section
in FIG. 9. The tube thus closed at one end is then filled, for
example with a refrigerated carbonated liquid, suitably by the
method described in our copending British application No. 35334/67,
in which method the major part of the container is first brought to
its fully inflated state by the application of differential
pressure to the inner and outer surfaces of the container, and is
maintained in such inflated state during filling and sealing. The
top of the container is then closed in the manner described for the
bottom neck. In this case the operation must be carried out
quickly, before a large pressure is generated. The finished package
is shown in FIG. 10.
The containers are preferably formed of oriented tubular film of
polyethylene terephthalate. For the preferred tubular containers
already described the polyethylene terephthalate film is preferably
biaxially oriented in such manner that, where the circumferential
draw ratio is x:1 and the longitudinal draw ratio is y:1, then the
product xy is from 7 to 16, preferably from 12 to 15, and the ratio
x/y is from 1.2 to 2.5, preferably from 1.3 to 1.8. By selecting
draw ratios within this range, the thickness of film required to
contain a given maximum pressure within the containers may be kept
to a minimum, which gives an economic advantage. When the container
is to be used in the packaging of beer or other carbonated drinks,
it is preferably provided with a coating of a material highly
impermeable to water vapor, carbon dioxide and oxygen. Suitable
materials for such coatings include vinylidene chloride polymers
and copolymers, particularly copolymers of vinylidene chloride with
a lesser proportion of acrylonitrile, for example copolymers
containing between 80 percent and 95 percent by weight of
vinylidene chloride and up to 20 percent of acrylonitrile and, if
desired, small proportions of other monomers such as itaconic acid
or methacrylic acid. These polymeric materials are also
particularly suitable for forming gas impermeable coatings on films
other than polyethylene terephthalate which may be used for making
the containers. The coating may be applied to the inner or outer
surface of the tubular film; it is usually more convenient to coat
the outer surface. Such coatings have the additional advantage that
they form strong heat seals.
Materials other than polyethylene terephthalate films that may be
used for forming the containers include oriented or unoriented
nylon films and oriented films of polypropylene, polyvinyl
chloride, or copolymers of vinylidene chloride with minor
proportions of other monomers, for example vinyl chloride,
acrylonitrile or acrylic or methacrylic esters, the nature of the
material, at least as to the inner wall of the container, being
such as to have substantially no undesirable effect on the intended
contents of the container.
While it is generally preferred to use a coating on the plastics
film to provide the desired impermeability, the container may be a
double-walled tube of plastics material to which one wall
contributes high strength, and the other wall contributes a high
impermeability to gases, and improved heat sealability if desired.
Thus, for example, tubing having an outer wall of polyethylene
terephthalate and an inner wall of vinylidene chloride polymer or
copolymer may be used. Alternatively, a sufficient degree of
impermeability to gases may be provided in, say, a container of
polyethylene terephthalate film, by providing a tubular sleeve of
an impermeable plastics material around substantially the whole of
the cylindrical section of the container.
The use of a tubular sleeve around the container, of a material the
same as or different from the walls of the container, can provide a
number of further advantages. One particular advantage, especially
for use at very high pressure, is that it gives added strength
against radial stress, which is greater than the stress upon the
end sections of the filled tubular containers. Thus, the addition
of a tubular sleeve covering only the cylindrical portion will
allow the use for the container of thinner film, down to about half
the thickness, than would otherwise be needed to give a container
of adequate strength. Not only does this give a saving of material;
it also facilitates the closing of the container, since thin film
can be more easily closed by bunching or twisting than can thick
film, without capillaries being left through the closure. An
ancillary use of the sleeve is to enclose a label or decoration
between itself and the container, when the sleeve is transparent,
or to provide protection for print on the wall of the
container.
The sleeve, when in the form of plastics tubing, may be easily
placed in position by slipping it over the container before it is
filled. Alternatively, the sleeve may be formed by wrapping or
winding round the cylindrical part of the container a sheet or
strip of plastics film, paper, or other flexible material having
properties desired for the intended function of the sleeve, and
sealing it into tubular form by heat or adhesive. Thus, for
example, when the pack contents are carbonated drinks, these may be
chilled before being introduced into the pack, to reduce the
pressure they initially exert. The sheet material may then be
wrapped or spirally wound around the pack, and sealed while the
contents are still chilled. When the pack reaches room temperature
it expands so that the sleeve exerts a reinforcing action. The
sleeve may be extended at one end to form a stand.
When a close-fitting sleeve is placed upon the cylindrical part of
the container to provide increased bursting strength, and the
container is formed of polyethylene terephthalate film, it is often
preferred that the container be formed of film that is oriented to
a higher draw ratio in the longitudinal than in the circumferential
direction, while still having a product of draw ratios within the
range 7 to 16. This will give improved bursting strength in the two
ends of the container, which are not supported by the sleeve.
For opening the filled containers, they may be placed in a
supporting tube, preferably self-standing, for example of cardboard
(which may be reusable, or may be provided as a part of the
package), and opened by cutting off the top of the container,
preferably after pricking it to release the pressure, or by means
of a tear tape or similar opening device. When the container is
formed of polyethylene terephthalate film, and closed with a wire
ligature, one end of the ligature may be left of such length that
the wire, bared of its plastics coating, may be used to prick the
container to release the pressure before the container is opened.
Polyethylene terephthalate film does not run from pinholes and the
container does not burst during this operation. The slightly
explosive opening of the container may thus be avoided.
In a further embodiment of our invention, however, we provide a
package which, while being capable of withstanding high internal
pressures, is nevertheless conveniently opened.
In accordance with this embodiment of the invention, we provide a
package or container as already described, but in which a
continuous seal is provided between the walls of the neck of the
container to seal all capillaries through the bunched neck, and in
which at least a part of said seal is of such strength that it will
readily fail under pressure of the contents when the ligature is
released.
The failure of the seal may be due to a peeling apart of the film
layers at the seal, or to rupture of one or more of the film layers
in the region of the seal, where they may have been weakened by
sealing, when subjected to forces generated by the pressure within
the container when the ligature is released. The failure of the
seal results in the spontaneous (or readily assisted) opening of
the container when the ligature is released, and so avoids any
difficulty in opening that might otherwise arise in the absence of
special opening devices.
The seal, which is preferably a heat seal, should be of such
strength that it will readily fail spontaneously when the ligature
or other closure is removed, or will fail when a shock is applied,
for example by tapping the container upon a solid surface or by
handling the seal. Preferably the strength of the seal is such that
will fail spontaneously, or readily if a small shock is applied,
within about 10 seconds, preferably within 5 seconds, of release of
the ligature. The shock applied should not be so great or of such
nature as to cause the contents to spurt from the container. The
seal should preferably not be so strong throughout its length as to
prevent it from failing, or from being easily persuaded to fail, in
a reasonably short time, or to allow only a pin-hole failure to
develop and not propagate, so that pressure is lost slowly from the
container without a convenient emptying outlet being formed.
However, even a slow loss of pressure provides some advantage,
since the end of the depressurized container can subsequently be
cut off, or a tear tape may be provided for the purpose, and an
explosive "pop" is avoided. A very weak seal, such as the heat seal
obtained between oriented, heat-set polyester film without a heat
seal coating, is sufficient, in the presence of the ligature, to
hold fast against pressure of the contents, and will generally fail
spontaneously and almost immediately under pressure from the
contents when the ligature or other closure is removed.
The strength of the seal, if it be a heat seal, may be modified in
such ways as by varying the heating cycle in forming the seal, or
by adjusting the pressure applied. If desired, heat seal coatings
may be provided on the film surfaces to be sealed. The best
conditions for forming a heat seal which will give a desired
average interval between the removal of the closure and the failure
of the seal may be determined by experiment, for any particular
internal pressure desired in the container. Similarly, seals
provided by pressure sensitive adhesives may be adjusted to give a
desired bursting time, for example by selecting a suitable adhesive
and by adjusting the width of the seal.
In a preferred form of this embodiment of the invention, the seal
is stronger, or is reinforced, along a major portion of its length,
so that a minor portion of the bunched neck is blown out on
opening, at the position corresponding to the weaker section of the
seal, to a greater extent than the remaining portion. This forms a
spout or lip by which the container may be more conveniently
emptied. It gives the further advantage that the "pop" which occurs
on opening the container, and which may in some circumstances be
regarded as undesirable, is reduced in volume.
Methods of providing a seal which is stronger along a major portion
of its length include, in the case of seals that fail by peeling
apart, those of making a double linear seal along the major portion
of the width of the container, leaving a single seal over a short
distance at one end, or making a wedge-shaped seal, or a seal that
is wider along a major portion of its length than at one end
thereof, so that the seal peels apart only at the thinner end, or
progressively from the thinner end. Reinforced seals are usually
preferred, however, since they are more easily controlled to
provide a desired opening. Methods of reinforcing the seal include
those in which, over a major portion of the circumference of the
container, the creases in the dome at the end of the container,
just below the bunched neck, are initially or wholly prevented from
being opened out by pressure of the escaping gas. Thus, for
example, strips or shapes of flexible sheet material such as
adhesive tape, or a coating of a film forming material, may be
adhered to the creased film around the dome of the container after
filling. In a particularly preferred such method, an incomplete
circle or U-shaped portion of adhesive tape is adhered around the
dome. Such devices may form a part of the decoration or labelling
of the container.
One preferred form of this embodiment of the present invention will
now be described by way of example with reference to FIGS. 10 and
11 of the accompanying drawings, of which:
FIG. 11 shows the unopened container, and
FIG. 12 shows the container after opening.
In the FIGS.: 14 represents the body of the container, which is
suitably formed of a length of biaxially oriented tubular film of
polyethylene terephthalate 0.0008 inch thick; 15 are the ends of
the container, which have been folded over a short distance from
the edges and heat sealed, at 16, through the four film layers
close to the cut edges of the tubing; 17 is a ligature closing the
container between the contents and the seal at a position
immediately adjacent to the seal; and 18 is the level of liquid
contents under superatmospheric pressure. 19 is a horseshoe-shaped
piece of adhesive tape stuck to the dome of the container around a
major part of its circumference. 20, in FIG. 12, shows a pouring
spout produced by spontaneous failure of the seal 16 (in this case,
by rupture of the film immediately beside the seal), the failure
having occurred in the region between the two ends of the
horseshoe-shaped strip 19. The heat seals 16, for the 0.0008 inch
thick polyethylene terephthalate film, may be suitably formed by
pressing the layers together at a temperature of 280.degree. C. for
4 seconds.
FIG. 13 shows the tubular film container 30 with closures 31 and a
sleeve of flexible material 32 disposed around the cylindrical
portion of the tubular film container 30 and the sleeve is sealed
or adhered to the container 30.
FIG. 14 is an enlarged fragmentary cross section of a portion of
container 30 and shows the film 40 having a lapped seam which has
been heat sealed at 41.
FIG. 15 is an enlarged fragmentary cross section of a portion of
FIG. 13 having the closure removed therefrom for the sake of
clarity and shows the film 50 having a coating 51 on the outside
thereof.
The pressure within the filled containers will usually be at least
1 p.s.i., because such pressure is required to give sufficient
rigidity to the package when it is pressurized for this purpose.
When the internal pressure is due to the nature of the contents (a
carbonated drink, for example) it will generally be considerably in
excess of 1 p.s.i., for example up to 30 p.s.i. or even above, 60
p.s.i. for example, in hot weather.
Our invention therefore further comprises plastics film containers
for use in making a package according to the invention, the
containers each having a bunched neck closed by a ligature or like
removable closure device and by a seal beyond the closure device,
with respect to the interior of the container, at least a part of
the region of the seal having a strength, as shown by sampling,
such that, in the absence of the ligature or like closure upon said
neck, it will withstand for at least 2 minutes a static pressure of
1 p.s.i. within the container, but will fail within 2 minutes when
subjected to a static pressure within the range of from 3 p.s.i. to
30 p.s.i.
Containers intended for contents under a pressure as low as 1
p.s.i. may usefully be provided with a seal capable of withstanding
a static pressure of 3 p.s.i. or a little above, since such a seal
can be ruptured by shock waves applied to the contents, as, for
example, by tapping or compressing the package, or by handling the
seal. Containers with contents under relatively high pressure are
preferably provided with a seal that will fail readily at a lower
pressure, so that the containers will open spontaneously when the
ligature is removed. The strength of the seal will thus be adapted,
in practice, to a proposed use or uses of the container.
The ligature used for any of the containers of the invention is
preferably formed of plastics coated wire passed at least once
round the neck. If it is not sufficiently stiff to remain in place
when wound round the neck without loosening under pressure of the
contents, the ends of the ligature may be tied or twisted together,
or the ligature may be provided with an adhesive coating, in which
case the twist is not necessary, the ligature merely being passed
more than once round the neck, and the adjacent turns being adhered
together sufficiently to hold the ligature against loosening under
the internal pressure, but not strongly enough to make the ligature
difficult to unwind by hand. The adhesive coating may be a hot melt
adhesive, caused to adhere by the external application of heat or
by resistance heating applied through the wire; or it may be a
pressure sensitive adhesive or a tacky material of the type which
adheres to itself but does not adhere unduly to other materials.
Ligatures secured in this way are particularly useful for the
containers that are to be opened by removing the ligature.
Other types of ligature that may be used in accordance with the
invention include metal clips capable of gripping the bunched neck,
of types well known in the art and including, for example, U-shaped
metal clips of the kind illustrated at 12 in FIGS. 8 to 10,
although there placed upon, rather than below, the thickened region
of the neck.
The containers are particularly useful for retailing beer and other
gas-containing liquids, especially carbonated soft drinks, and for
the packaging of other pressure-generating liquids, for example
wines. They may also be used for the packaging of noncarbonated
liquids under pressure of a gas, to give substantially rigid packs.
Products that may be packed in such manner include: household
products, such as liquid detergents, liquid bleach, fabric
softeners, starch solutions, dry cleaning fluid, liquid waxes and
polishes, window cleaners, disinfectants, paints, varnishes,
linseed oil; adhesives; inks and other artists' materials; medical
and pharmaceutical liquids such as blood, sterile water, medicines
and alcohol; motor car products such as lubricating oil, thin oil,
battery liquid, polishes and shampoos; fire extinguishing liquids;
potable liquids such as milk and milk products, natural or
synthetic cream and cream products, fruit squash, fruit juices,
spirits; garden products such as insecticides, fungicides,
herbicides, fertilizers; toilet and cosmetic products such as nail
varnish, liquid shampoo, toilet water, hair setting lotion, hand
creams; and food products such as canned fruit and vegetables,
soups, ketchups, salad dressings, edible oils, salad oils, vinegar,
syrup, coffee essences, flavorings. The containers may also be used
for packaging solid articles, the pack being pressurized to make it
rigid and thus to protect the contents or to improve the sales
appeal of the pack. In this case, of course, the article or
articles are inserted before the second closure is applied, and the
package may, if desired, be pressurized by enclosing a little solid
CO.sub.2.
Our invention is further illustrated but in no way limited by the
following examples.
EXAMPLE 1
A 9 inch length of biaxially oriented lay-flat tubing of
polyethylene terephthalate, having a wall thickness of 0.0008 inch
and a flat width of 21/2 inches, was provided at one end with a
closure in the manner described hereinbefore with reference to
FIGS. 1 to 3 of the drawings. To seal the end of the tubing, the
end portion of the flattened tube was folded over along a line
parallel with, and about three-eighths inch from, the end, and a
heat seal one-eighth inch wide was formed between the four layers
of the folded portion, close to the fold and extending along the
whole length of this portion, from side to side of the tubing. The
excess film was trimmed off close to the seal. The seal was formed
by an impulse heat sealer which reached a maximum temperature of
about 280.degree. C., using a sealing cycle of 5 seconds. The
ligature, applied immediately below the heat seal, was of copper
wire, 0.02 inch in diameter and bearing a plastics coating 0.01
inch thick. At the open end of the tube, a layer of tape coated on
both sides with contact adhesive was applied round the inside
surface of the mouth, as shown in FIG. 4. The tube thus closed at
one end was opened out in a suction mould, as described in our
copending application No. 35334/67, and was filled with one-half
pint of beer chilled to a temperature of 2.degree. C. The top of
the container was then closed in the manner previously described
with reference to FIGS. 4 to 8 of the drawings, except that the
inner surfaces of the Scotch tape were caused to adhere by
pressure, and no clip was applied to the neck above the
ligature.
Packs filled with beer in this manner were stored for 14 days,
during which time the storage temperature varied from 40.degree. to
80.degree. F. There was no leakage, and the beer, then sampled, was
found to be in excellent condition.
EXAMPLE 2
A container was made and filled with beer in the manner described
in example 1, except that the heat seal at the bottom of the
container was made by means of an impulse sealer which reached a
maximum temperature of 280.degree. C., and the sealing cycle was of
4 seconds. After the container had been closed at the other end,
the container was inverted and a horseshoe-shaped piece of adhesive
tape was applied around the dome of the first closed end, as shown
in FIG. 10. When the beer had warmed up to room temperature
(65.degree. C.) the container was placed in a tubular cardboard
support, with the same end uppermost, and the ligature was removed.
Almost immediately the container opened spontaneously, as shown in
FIG. 9, with only a small "pop" and with the formation of a
convenient pouring lip.
As indicated hereinbefore, instead of the containers being filled
by the method described in the examples, they may be provided in
the form shown in FIG. 4 and filled through the filling aperture by
the method described in our copending British application No.
9849/68. The method comprises: locating the aperture over an
orifice in a substantially smooth surface, said orifice being
connected to a source of a gas under superatmospheric pressure;
inflating the container by the introduction of said gas while the
container wall surrounding said aperture is held substantially in
gas-tight contact with said surface; and, while the container is
still fully inflated, sliding it along relative to said surface to
bring that portion of the wall of the container which surrounds the
aperture into contact with a supported flexible sealing strip held
in substantially continuous relationship to said surface; and
applying heat if necessary to seal the sealing strip to the wall of
the container around the aperture. In the term "over an orifice" is
included any case where the container is located so that the
aperture covers the orifice, irrespective of whether the surface
containing the orifice is generally located above, beneath or
beside the container.
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