IL30477A - Method of filling and sealing containers - Google Patents

Description

METHOF FOR FILEING ¾ND SEALING CONTAINERS o' a'o m»aq i 'i 'o no'u; P.2043b/20415/20 /20482/ 2087 /20873/ 1133/21144 This invention relates to a method of producing packages comprising filled containers of plastics film with contents under superatmospheric pressure, to packages so made, and to film containers for use in producing such packages.

The invention relates particularly to the filling and sealing of 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 or solid substances in plastics film containers made rigid by enclosing a gas or vapour 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 vapours of low boiling liquids, e.g. aerosol propellents.

The invention also relates to containers particularly suitable for use in making the packages, and to methods of producing the containers.

In accordance with the present invention, a method of producing a package comprising a filled and sealed flexible plastics container, with contents under superatmospheric pressure, comprises: locating an aperture in the wall of the closed container 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 in substantially gas-tight contact with' said surface; and, while said container is still fully inflated, sliding it along relative to said surface to bring that portion of the wall of the container which surrounds said 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 20872/20873/21133A '44 In the term "over an orifice" we include any case where the I 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. By the expression "a closed in respect of the pressure of gas to be reached within the package, except at the aperture provided for pressurising the container and at any further aperture in the wall of the container that may be held in gas-tight contact with a surface and sealed in similar manner to the aperture described. By the term "fully inflated" we mean that the pressure inside the package is at least sufficient to allow the container to be held in substantially gas-tight contact with the surface.

When the container is to be filled with a liquid, this is introduced through the aperture after the container has been inflated with gas. When the package is to contain a solid article or articles, these are put into the container before it is closed, and the container is subsequently pressurised and sealed in the manner described. Powders and other particulate solids may be fed into the container through the filling aperture.

The method of the invention is used with particular advantage in the packaging of beer and carbonated soft drinks in flexible plastics containers.

The pressurising and filling method of the invention will now be more particularly described by way of example with reference to Figures 1 and 2 of the accompanying drawings, which illustrate diagrammatically the use of the method for filling a container formed from a length of plastics lay-flat tubing, and closed by a bunched, ligatured neck at each end. A preferred form of such containers will be more particularly described hereinafter. . 20872/20873/2 133 211 Figure 1 is a diagrammatic elevation, seen from one side and partly in section, of a filling and sealing apparatus; and Figure 2 is a view of a section through Χ,Χ' of Figure 1 , seen from the direction A.

In Figure 1 : 1 is a brass block provided with a smooth, flat front surface, 2, in which are a first orifice, 3» through which passes a retractable tubular probe, 4, which is connected to a reservoir of beer stored under pressure of carbon dioxide, and a second orifice, 5t connected to the carbon dioxide above the beer. The beer reservoir. is located at a level a few feet higher than the orifice 3· The orifices 3 and 5 are close together. The lines to orifices 3 and 5 are provided with valves, 6 and 7 respectively. Below the brass block 1 is shown a heat sealing unit, the body, 8 , of which consists of an electrically insulating and heat resistant material, suitably of a hard, bonded asbestos block. The heat sealing unit has a front face, 9» contiguous with the front surface, 2 , of the brass block, except for a 0.005 in. gap provided to allow a continuous length of heat sealable tape, 10, to be fed between the brass block 1 and the heat sealing unit 8 , to pass down the face of the latter. 11 is the heating element, suitably of O.OOO5 inch thick stainless steel strip, connected at one end to a transformer terminal, 12, passing over and down the front face of the heat sealer 8 , and having its other end in close contact with a /8 inch thick brass strip, 13» which is connected to the other terminal of the transformer and held between the heat sealer 8 and a supporting block, 14. The .latter is also made of electrically insulating material. The front face of the brass strip 13 is level both with the front face 9 of the heat sealing unit and with the front face of the supporting block 14. A strip of glasscloth 2087 /20873/2 133/^*44 outer surface of the heat sealing element, to provide a non-stick surfaced A gate, ? is provided, formed of transparent material such as polymethyl methacr late, and mounted in a support so as to be slidable in a plane parallel with the front faces of the brass block 1 and heat sealer 80 The assembly comprising the brass block , heat sealer, 8 , and supporting block, 14, is slidably mounted on four rods (not shown) connected to the support (not shown) for the gate 15s s° that the assembly is adapted for relative motion towards and away from the gate 15° A stop is provided to limit the gap between the gate 15 and the front face, 9, of the block 1 » At 16 is shown a fully inflated plastics film container located in the apparatusβ This container is formed from a length of oriented, lay-flat plastics tubing, provided with gas-tight seals at each end and with a pressurising and filling aperture which, when the container is in the pressurising and filling position, is located over the two orifices 3 and 5» For clarity of illustration this aperture is shown at 17s but the gap between the gate 15 and the faces of the brass block 1 and heat sealing unit 8 is adjusted so that, when the container is fully inflated, the surface of the container surrounding the orifice is pressed flat against the surface of the brass block 1 „ In Figure 2 are shown : the front face, 2 , of the brass block 1 ; the apertures 3 and 5 » the gap, 18, through which the sealing tape, 10, is fed; the position of the heating element, 11 , beneath the PTFE-impregnated glasscloth covering the front face, 9, of the heat sealing unit; the front edge of the brass strip, 13; and the front face of the supporting block 14u In operation, the empty, flat container is placed between 20872/20873/211 /21144 being held initially somewhat apart from the gate) with its longitudinal axis parallel to that of the apparatus, and located so that the filling aperture is approximately opposite the two orifices, 3 sind 5· The container is then manoeuvered into position with the filling aperture located exactly over the orifices, use being made, as required, of the sliding movement of the gate. The main part of the apparatus is then released and returns to its position against the gate, with the container held between itself and the gate. The valve 7 is then opened, and the container is inflated and pressurised with the carbon dioxide, causing the gate and the main part of the apparatus to separate to the stop position. The stop will have been adjusted so that the gap between the sliding gate and the front face of the block 1 is sufficiently less than the diameter of the container when freely inflated to fully circular shape, for the wall of the container around the aperture to lie flat against the face 2 when the container is fully inflated in the apparatus. It has been found, surprisingly, that this provides a perfect seal, even against pressures as high, or higher than, 0 p.s.i. With the container thus inflated, and with the valve 7 still open, the probe 4 is inserted into the container. The valve, 6 , to the beer supply is then opened, and beer flows under its few feet of gravity head through the probe into the container, to fill it to the desired level. During the filling operation, the carbon dioxide is displaced back into the beer reservoir. The valve 6 is then closed. Because the gas pressure within the container is equal to the pressure above the beer supply, the beer does not froth. After valve 6 has been closed, the tubular probe 4 is withdrawn into the supply tube. Valve 7 is then closed, and the filled container is pulled down through the apparatus, together 20872/20873/2 133/ 144 into a position opposite the .beat sealing element, with the sealing strip and the polytetrafluoroethylene/glasseloth layer lying between it and the heat sealing element0 ¾e heat sealer is then brought into operation to seal the sealing strip around the aperture, and the filled, sealed container is drawn through and out cf the apparatus The sealing strip is cut above the sealo Although the apparatus as illustrated is shown in the vertical position, it is preferably inclined, for operation, to an angle approaching the horizontal, with the filling orifice above the filling aperture, so that the container may be sufficiently filled, but a gas space may still be left under the aperture until the aperture has been sealed. The presence of this gas space allows the surface of the container to be kept dry while the container is filled, and also facilitates heat sealing, since the thermal conductivity through the gas is much less than if a liquid were in contact with the film0 The apparatus is suitably tilted to an angle of about 20° to the horizontal With such an arrangement, the main part of the apparatus is preferably slidably mounted on rods attached to the support for the sliding gate It is then urged by gravity towards the gate, thus exerting pressure upon the container. On inflation of the container, the main part of the apparatus is pushed away from the gate to the stop position, at which the container is filled,, Alternatively, the main part of the apparatus may be fixed and the gate support slidably mounted on the connecting rods, and urged by springs towards the main part of the apparatus.

If desired, a band of sealable tape may be attached horizontally around the container, over the sealed aperture, to give added security.

The sealing strip may if desired comprise a carrier tape 2087 /20873/21 /21144 appropriately spaced apart for attachment to successive plastics film containers passing through the apparatuse The adhesive used for sealing the container must also be chosen to suit the pressure it will have to withstando Hot melt adhesives, particularly when used on a carrier strip of plastics film of the same type as used for the construction of the container, are generally preferred.. Hot melt adhesives based on ethylene/vinyl acetate copolymers are particularly suitable0 It is however within the scope of our invention to use a sealing strip bearing a pressure sensitive adhesive coating.

Various modifications may be made in the method and apparatus particularly described. For example, instead of the surfaces of the filling block and heat sealer being flat, they may form parts of a cylindrical surface, of circular or otherwise curved configuration. In this modification these surfaces should have a radius of curvature greater than that of the inflated container, so that there is a flattening effect on the wall of the container when pressed against the filling block. The holding surfaces of the sliding gate may be similarly curved.

It is also not essential for the container to be slipped in the direction of its longitudinal axis from the filling station to the sealing station. In another preferred form of the method of the invention, the filling and sealing stations, and the supply of sealing strip, may be so placed that the container may be slipped at right angles to its longitudinal axis from one station to another. Thus, for example, the process may be operated by means of a rotary apparatus providing a number of filling and sealing stations, so that a number of containers may be filled and sealed simultaneously. In such modifications of the method of the invention, 20872/20873/21133s 4 allow an additional length of sealable tape to be attached as a band around the container and the sealed aperture,. ° Irrespective of whether the containers are slipped from the filling station to the sealing station in the direction of their longitudinal axes or in a direction at right angles thereto, the empty containers may be fed continuously to the filling head*. The provision of the containers in a continuous length for feeding to the filling head is a separate feature of the invention which will be more particularly described hereinafter^ 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 unsuccessfulo In accordance with a further feature of the present invention, we provide a plastics film container suitable for use in making packages with contents under superatmospheric pressure by the method of the invention, the container being formed from a length of plastics tubular film closed at each end by a 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, and the container being provided with a filling aperture through the wall thereof» In referring to the "region of greater cross-sectional area" - ' sectional area than the adjacent region towards the contents of the oontainerv 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 pressurised. 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" β 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 if desired include a degree of systematic folding or twisting,, region is provided by additional material or layers attached to the outer I(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 be ond the intended 20872/20873/21133/211 4 position of the ligature, in respect of the contents, and preferably continuous with the outer seal. 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 containei'» 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 surfac 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 polyme s 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 20872/20873/2113 21144 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 provision 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 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, s is 20872/2087 / 1133/ 1 44 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 Figures 3 to 12 of the accompanying drawings, of which: Figures 3 and 5 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; Figure 4 is a section through the line A-A in Figure 3i Figure 6 shows a finished container with each end sealed and tied with a ligature; and Figures 7 to 12 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, Figure 11 being a section through line B-B of Figure 10.

In Figures to 6 : 19 represents a length of plastics tubular film and 20 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 Figures 3 and 4) at 21 ; 22 is a heat seal between the four layers of film so brought together; and 23 (Figures 5 and 6) 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 24. The container is provided with a filling aperture, shown at 25, which is formed before the second end of the tubing is closed. liquid containing a gas under pressure, by the method previously described. 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 Figures to represents a length of plastics tubular film, which is provided at each end with a layer, 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. A filling aperture is provided at The tubing is flattened at one end as shown at in Figure to seal together the opposed surfaces of the tape and form the bottom of the container. A ligature, shown at in Figures and 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, (Figures is optionally applied xipon the region, thickened by the tape, as shown in Figure and in cross-section in Figure The top of the container is then closed in the manner described for the bottom neck.

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: and the longitudinal draw ratio is then the product £ is from to preferably from to and the ratio x v_ is from to preferably from to 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 20872/20873/21133/ l 144 coating of a material highly impermeable to water vapour, 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% and 5% by weight of vinylidene chloride and up to 20 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 20872/20873/2113 21144 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 sleeve of an impermeable plastics material, such as vinylidene chloride polymer or copolymer, around substantially the whole of the cylindrical section of the container, after it has been filled.

The use of such a tubular sleeve around the container can provide a number of advantages, whether it be of a plastics material the same as or different from that of the container, or of another material. One particular advantage, especially for use at very high pressure, is that it may provide 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 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 may be formed by wrapping or winding round the cylindrical part of the container, after it has been filled, 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. When the sleeve is provided for the purpose of giving added resistance to f 72 20 73 21133/W 144 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 and the sleeve exerts a reinforcing action,, The sleeve, if made of a sufficiently stiff material, may if desired project at one end to the extremity of the container or beyond, to provide a free-standing support.

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 ¾'«ft 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 acka e which while bein ca able of withstandin hi h internal 20872/20873/ 13 21144 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 a 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 it 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 ut t in f H wv v n s w s f s r i s 72/20 73/21133/2 44 some advantage, since the end of the de-pressurised 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 filan 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 rti f 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 reinforcin 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, 3μβΐ -'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 tapei; 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 Figures 13 and 14 of the accompanying drawings, of which: Figure 13 shows the unopened container, and Figure 14 shows the container after opening.

In the figures : 33 represents the body of the container, which is suitabl formed of a length of biaxially oriented tubular film of polyethylene terephthalate 0.0008 inch thick; 3 are the ends of the container, which have been folded over a short distance from the edges and heat sealed, at 35» through the four film layers close to the cut ed es of the tubin 6 is a li aure closin the 72 20 73 1133 21144 container between the contents and the seal at a position immediately adjacent to the seal; and 37 is the level of liquid contents under superatmospheric pressure. 38 is a horse-shoe shaped piece of adhesive tape stuck to the dome of the container around a major part of its circumference. The sealing strip covering the filling aperture is shown at 39· 40, in Figure 14, shows a pouring spout produced by spontaneous failure of the seal 35 (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 horse-shoe shaped strip 38.

The heat seals 35, for the 0.0008 inch thick polyethylene terephthalte film, may be suitably formed by pressing the layers together at a temperature of 280°C for four seconds.

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 pressurised 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 two minutes a static pressure of 1 p.s.i. within the container, but will fail within two minutes when subjected to a static pressure within the range of 20872/20873/ 1133/21144 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 U-shaped metal clips of the kind illustrated at 31 in Figures 10 to,r12, 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 non-carbonated 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, fertilisers; 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, flavourings. The containers may also be used for packaging powders or other particulate solids or solid articles, the pack being pressurised to make it rigid and thus to protect the contents or to improve the sales appeal of the pack.

As indicated hereinbefore, the method of the invention may be operated as a continuous process, in which the containers are preferably fed successivel to the pressurisin and fillin 72 20 73 21133 1 44 head as a continuous strip of apertured tubular container units, sealed at both ends, from which individual units may be separated. The strip of such container units, which we provide as a further feature of this invention, is preferably formed by intermittently advancing a length of tubular plastics film, forming filling apertures through one wall of the tubular film at intervale spaced so as to provide an aperture to each desired container, and forming transverse heat seals between the walls of the flattened tubular film between the spaced apertures, to provide seals to close the ends of the containers. The transverse heat seals may be wide seals, which may each be divided by a transverse cut across the tubing to sever a single unit from the strip, thus providing a seal for the opposite ends of adjacent units; or they may be double linear seals, so that the tubing may be cut transversely between the two sealed areas of each double seal to separate the individual containers, sealed at both ends, from the strip. The transverse heat seals are preferably located so that each aperture is close to one end of the container.

The apertures may conveniently be formed in the wall of the tubular film while it lies against an internal mandrel„ They may be formed at any stage in the production of the tubular film in which an internal mandrel is used, and when a loss of internal pressure through the apertures is not detrimental to the process. In a preferred method, however, an isolated mandrel is enclosed in the tubular film for the purpose of providing the support for the film while it is being perforated.. If the tubular film is caused to travel vertically upwards or downwards, the mandrel can be held in the film above, say, a pair of nip rolls, without further support, or supported only by external guides or rollers in contact with the film or the m ndrel ma be he d in osition m neticall 72/20 73/21133/21144 The apertures may be formed by punching the tubular film against the mandrel, preferably by means of a tool heated to a temperature above the melting temperature of the plastics material. In a preferred method, however, they are formed by localised heating of the film by a jet of hot gas or a flame, the surrounding areas of the film being protected against melting, preferably by means of a shield between the hot gas or flame and the tubular film, apertured to allow the jet to be directed at the localised area of the tubular film.

Instead of the length of containers being made from plastics film, extruded in tubular form, they may be made from a strip of flat film, longitudinally folded and having its edges sealed together, preferably by a lapped sealo The apertures may be formed at a convenient stage during this operation, and the transverse seals formed after the longitudinal seal has been formed.

The method may be adapted to provide regions of greater cross-sectional area, as hereinbefore described, in the necks of the containers. This may be done, for example, by forming tucks in the film before heat sealing, so that more than two layers of film are included in the heat seal, or by feeding strips of plastics. material into the heat sealing region, so that they become included in the seal, or by forming crimped seals that are less compressible than the adjacent areas of the neck region of the containers.

The joined containers are ligatured at each end at some stage after the formation of the heat seals. They may be provided to the filling head as a continuous strip either with the ligatures already applied, or as a strip of flat containers, a ligaturing device then being provided for use in conjunction with the pressurising and filling device, to apply ligatures at both ends f the c n in rs i n f i . 20872/20873/21133/21144 station. It is generally preferred to adopt the latter method, since the strips. of flat containers can be more easily reeled arid stored than can strips ' of containers already ligatured.

If strips of the containers already ligatured are desired, however, the strips pf flat containers may be formed continuously from tubular plastics film in the manner described hereinbefore, and, after the heat seals have been formed, the heck regions of the containers may be bunched, and a ligature or similar closure applied to the bunched region a each side of the heat seal.

The pressurising and filling Operation may be continuously operated with the use of the strips of containers in varying manner. For example, it may be operated in such manner that the containers travel in one direction, parallel with their longitudinal axes, from the feeding. in of the containers to the release of the filled package. Or the containers may be fed to the pressurising head in a direction parallel to their longitudinal axes, severed from the length before or during the pressurising and filling step, and moved in a direction, transverse to their direction of feed, for the subsequent sealing operation.

In accordance with yet a further feature of our invention, we have found that the appearance and strength of the closure of the tubular containers may be improved, and other advantages obtained, if the neck is bunched in a particular way, instead of in a haphazard mariner.

In accordance with this feature of the present invention, a method of forming :the closures by bunching the tubular plastics film and applying a ligature, clip or like encircling closure device to the ' bunched. region, is characterised in that the tubing, before it is bunched, is curved across its width to 20872/20873/21133/2 144 until it is bunched, the curve being concave towards the axis of the bunch.

The tubing is preferably curved into a circular arc, preferably to a semi-circle or greater arc of a circle having as its axis the axis about which the tubing is bunched. The method is used with particular advantage as a continuous operation of producing plastics film containers from a length of plastics film in flattened, tubular form.

One preferred form of the method of this aspect of the invention will now be particularly described by way of example with reference to the Figure 5 of the accompanying drawings, which is a diagrammatic side elevation of a device for bunching, at spaced intervals, an intermittently advancing length of flattened tubular plastics film, to form containers closed at both ends in the manner described.

In the drawing, 41 represents a forming shoe having an upper surface of semi-circular form, equal in circumference to the width of the flattened tubing; 42 represents the advancing tubular film, which is curved longitudinally to semi-circular part cylindrical form upon the surface of the forming shoe, upon which it advances without creasing; 43 shows iris diaphragm gathering devices, which operate simultaneously to gather the film evenly, at 44, about the axis of the part-cylindrical surface of the forming shoe; 45 shows ligatures, which are applied to the bunched neck by suitable ligaturing devices of known type (not shown); and 46 represents a completed container unit, which retains a curved, boat-shaped form as it leaves the device. At 47, are shown heat seals and at 48 a filling aperture, previously formed in one wall of the flattened tubular film to provide a continuous strip of container units in the manner just described.. After removal from the ligaturing device, the tubing may be cut transversely between the paired ligatures, forming containers closed at both ends, suitable for filling with, for example, beer or another carbonated drink, by the method previously described,. The containers may alternatively be wound up or similarly collected for storage, and separated from the length as they are usedo The method of applying the ligatures in accordance with this aspect of the invention gives an additional advantage in the containers, in that the empty containers are substantially of the form of a flat bottomed boat, the flat surface of which may be very easily held against the flat surface of the pressuring and filling device hereinbefore described. The filling aperture is then appropriately located at one end of flat surface of the boat-shaped empty container, on the convex side thereof. The ligaturing method may be integrated with the filling operation, the string of containers being fed successively to the filling head, with their convex side towards the flat surface of the pressurising and filling device, and the containers being separated from the length immediately before filling, or after filling, as desired.

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 2-J inches, was provided at both ends with a closure in the manner described hereinbefore with reference to Figures 1 to 4 of the drawings. To seal the ends of the tubing, each end portion of the flattened tube was folded over along a 20872/20873/2 133/ 144- line parallel with, and about "/8 inch from, the end, and a heat seal /8 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°C, using a sealing cycle of 3 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. Before the ends of the container were closed, a circular aperture 7 / ·32 inch in diameter-was punched in one wall of the container, 2„5 inches from the position of the top seal, and the container was placed in a filling device as described hereinbefore with reference to Figures 1 and 2 of the drawings, with the aperture located over the carbon dioxide and beer inlet orifices. The beer supply was at a temperature of 70°.F and under a carbon dioxide pressure of l8 p0s,i and was located at a height of 4 ft. above the filling device. The stop setting the gap between the sliding gate and the main part of the apparatus was set to provide a gap of 1 /4 inches between the gate and the flat surfaces of the filling block and heat sealing unit. The apparatus was tilted so that the longitudinal axis of the container was at an angle of 20° to the horizontal, with the aperture located uppermost and at the top end of the container.

The container was first pressurised with the carbon dioxide and then filled with beer in the manner described hereinbefore. After the filling probe had been withdrawn, the sliding gate was moved downwards with the filled container and sealing strip, the surface of the container sliding upon the filling block, until the aperture was opposite the centre of the heat sealing element. An impulse 20872/ 0873/21133 21144 element, which was a 4 /8 x /8 x 0.0005 in, stainless steel strip. The filled, sealed container was withdrawn from the apparatus, and the sealing strip was trimmed off at each side of the sealo A length of the same sealing strip was heat sealed horizontally around the container, over the sealed aperture.

The sealing strip used was a strip of biaxially oriented film of polyethylene terephthalate, bearing a heat seal coating of 50 parts of ethylene/vinyl acetate copolymer (24 vinyl acetate) and 50 parts of polyterpene resin„ The filled pack was held at 70°F for 2 days, then at 40°F for days, and finally at 80°F for 2 days. At the end of this time the seal was intact, and the contents when tested ware indistinguishable from the same beer bottled at the same time in the conventional manner.

Further packs made and filled with beer in the same manner were stored for 14 days, during which time the storage temperature varied from 40° to 80°F. There was no leakage, and the beer, when sampled, was again found to be in excellent condition.

EXAMPLE 2 A container was made, filled with beer and sealed in the manner described in Example , except that the heat seals were made by means of an impulse sealer which reached a maximum temperature of 280°C, and the sealing cycle was of 4 seconds. After the filled pack had been removed from the filling and sealing apparatus, a horse-shoe shaped piece of adhesive tape was applied around the . dome of one closed end, as shown in Figure 10» When the beer had warmed up to room temperature (65°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 " "

Claims (1)

1. P o20413b/20 15/2041 /20482/ 0872/20873/21133/^1 1, A method of pr fecing a package comprising a filled and sealed flexible plastics container, with contents under superatmospheric pressure, that comprises; locating an aperture in the wall of the closed container 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 said container is still fully inflated, sliding it along relative to said surface to bring that portion of the wall of the container which surrounds said 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 said aperture.. 2„ A method as claimed in Claim 1 in which, after the container has been inflated by said gas, the major part of the gas is displaced by a liquid or particulate solid supplied under pressure,, 3· A method as claimed in Claim 2 in which the container is filled with beer or another carbonated liquid, the gas is supplied from and returned to a gas space in a reservoir for the liquid from which the liquid is fed by gravity to the container. 4» A method as claimed in Claim 2 or Claim 3 in which, the container is inclined at an angle approaching the horizontal, with the filling aperture on its uppermost side, for the filling and sealing operations. 5 · A method as claimed in any one of the preceding claims in which the process is operated continuously and the sealing strips are supplied as separate patches mounted on a carrier tapeo Go Apparatus for operating a method as claimed in any one of the preceding claims that includes a smooth surface having P.20413b/20415/20 (17/20482/ .. ; . 20872/20873/2 133*2144 therein an orifice connected to a source of gas under pressure; means for supplying a sealing strip in such manner that it may be drawn from its source of supply along a path on said surface, or on a second surface substantially continuous therewith, such that the longitudinal axis of said path lies on a line or arc passing through said orifice; means for . presenting a flattened, empty, tubular film container to said surface with a pre-determined point of its wall over said orifice, for inflation at said orifice through an aperture in- the container wall at said pre-determined point; means for sliding the. container,: whilst Iholding it. sufficiently under compression, against said surface to maintain a seal around P.204 3b/20415/2041,7/20482/ 20872/20873/21133/S 1 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 being sealed against egress of gas from the container, and the container being provided with a filling aperture in that part of the wall thereof which assumes a cylindrical form when the container is inflated. 10. A container as claimed in Claim 9, formed from a length of seamless tubular film. 11 . A container as claimed in Claim 9 or 10 formed from polyethylene terephthalate film that has been biaxially oriented to draw ratios such.that, where the circumferential draw ratio is x: 1 and the longitudinal draw ratio v_: 1 , then the product xy_ is from 7 to 16, preferably from 12 to 15» arid the ratio x/v_ is from 1.2 to 2.5, preferably from 1 .3 to 1 .8. 12. A container as claimed in any of Claims 9 to 11 , formed from plastics film having a coating of a polymer or copolymer of vinylidene chloride. 13. Containers as claimed in any one of Claims to 12 in which the capillaries leading through the bunched necks from inside the containers to the atmosphere are closed by a seal between the flattened walls of the neck of each 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 other encircling; closure, 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 3 p.s.i. to 30 p.s.i. 14. Containers as claimed in Claim 13 in which said seal is stronger over a major portion than over the remaining portion of P.20413b/20415/20417/20482/ 20872/20873/ 1133^14 15» A container as claimed in any one of Claims 9 to 14 in which the ligature is a covered wire ligature wound more than once round the bunched neck and having adjacent turns adhered together. 16. A method of forming containers as claimed in any one of Claims 9 to 15 that includes the steps of intermittently advancing a length of tubular plastics film, forming filling apertures through the wall of the tubular film at intervals spaced so as to. provide an aperture to each desired container, and forming transverse heat seals between the walls of the flattened tubular film and a further layer or layers of film or of another material, between the spaced apertures, to provide thickened seals to close the ends of the containers. 17. A method as claimed in Claim 16 in which the tubular film advanced to the sealing station passes an internal mandrel against which said filling apertures are formed in the wall of the tubular film. 18. A continuous strip of units, suitable for producing a container as claimed in Claim 16 or 17. as claimed in any of Claims 9 to 1 » whenever produced by a method/ 19. A continuous method of bunching and ligaturing the necks of container units formed in a continuous strip by a method as claimed in Claim 16 or 17» by bunching the tubular film to form a neck at positions adjacent to the heat seals and applying a ligature to the bunched neck, in which the strip of flattened container units, before it is bunched, is curved across its width to bring it to part-cylindrical form, and is held in such form until it is bunched, the curve being concave towards the axis of the bunch, and preferably being a semi-circular or greater arc of a circle having as its axis the axis about which the strip is bunched. 20 A continuous strip of ligatured containers as claimed in any one of Claims 9 to 15» whenever produced by a method as claimed p„20413b/20415/20417/20482/ A, 20872/20873/2 33/^^4 21. A package comprising a filled and sealed flexible plastics container with contents under superatmospheric pres£¾re, whenever produced by a method as claimed in any one of Claims 1 to 5· 22. A package as claimed in Claim 21 in which the flexible plastics container is a container as claimed in any one of Claims 9 to 15· 3 o A package as claimed in Claim 21 or 22 which contains beer or another carbonated drink. 24. A package as claimed in Claim 21 or 22 which contains an article, articles or a particulate solid and a gas under superatmospheric pressure. 25» A package comprising a filled and eealed container as claimed in Claim 13, with contents under superatmospheric pressure, in which means are provided over a major portion of the circumference of the filled container for preventing, initially or wholly, the creases in the dome of the container, below the bunched neck thereof, from being opened out by pressure of the escaping gas when the ligature or other encircling closure has been released. 26. A package as claimed in any one of Claims 21 to 25 in which the container is provided with a tubular sleeve, said sleeve having been formed by wrapping or winding around substantially the whole of the cylindrical part of the container a sheet or strip of flexible material and sealing it into tubular form by heat or adhesive. 27» A package as claimed in Claim 26 in which the container is 29.2.68· formed from polyethylene terephthalate film that is bxaxially oriented to draw ratios such that, where the circumferential draw ratio is x; 1 and the longitudinal draw ratio 21 , then the product £ is from 7 to 16 and the ratio /x exceeds 1 » S. HOROWITZ & CO.