Method and apparatus for filling and sealing plastic containers
United States Patent [191 Cayton et al.  
 [ METHOD AND APPARATUS FOR FILLING AND SEALING PLASTIC CONTAINERS [75] Inventors: Kenneth Cayton, Welwyn Garden City; Grahame Melvin Reade, Wheathampstead, both of England [73] Assignee: Imperial Chemical Industries Limited, London, England [22] Filed: Mar. 15, 1973 [21] Appl. NO.: 341,605  
 [30] Foreign Application Priority Data Mar. 28, 1972 United Kingdom 14451/72 [52] US. Cl 53/22 B; 53/112 B [51] Int. Cl B65b 31/04 [58] Field of Search 53/22 B, 112 B [451 Apr. 15,1975  
 [56] References Cited UNITED STATES PATENTS 2,638,963 5/1953 Frederick 53/28 X 3,745,024 7/1973 Ford et al 53/22 B X Primary Examiner-Travis S. McGehee Attorney, Agent, or FirmCushman, Darby &amp; Cushman [57] ABSTRACT In a method of pressurizing and filling a plastics-film pouch through an aperture in its walls, and subsequently sealing a patch over the aperture, while the pouch is held with the aperture in sealing contact with a surface, the use of a surface of specified curvature for supporting the patch during sealing.  
 7 Claims, 8 Drawing Figures METHOD AND APPARATUS FOR FILLING AND SEALING PLASTIC CONTAINERS This invention relates to a method and apparatus for producing a package comprising a sealed flexible plastics container with contents&#39;including a gas at superatmospheric pressure.  
  The invention relates particularly to the filling and sealing of flexible plastics containers containing liquids under pressure, including liquids containing dissolved gases, such as beer and carbonated soft drinks, and liquids which are packed under pressure of a gas that is not soluble in the liquid, to give substantially rigid packs. It may be applied also to the packaging of solid articles, the pack being pressurized to make it rigid, usually for the purpose of protecting the contents or to improve the sale appeal of the pack, and to the packaging of particulate solids. The invention includes the fill ing of the container with gas alone under superatmospheric pressure.  
  In application Ser. No. 271,208 filed Dec. 7, 1972, we have described and claimed a method of producing a package comprising a sealed flexible plastics con tainer, with contents including a gas at 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 at super-atmospheric 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 and in gastight contact with said surface, 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 sealing the sealing strip to the wall of the container around said aperture, by applying heat if necessary.  
  The term over an orifice includes 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. The expression closed container&#34; means that the container is gas-tight, in respect of the pressure of gas to be reached within the container, except at the aperture provided for pressurizing 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. The term fully inflated means that the pressure inside the container is at least sufficient to enable 7 the container wall to be pneumatically held in substantially gas-tight contact with the surface.  
  When the container is to be filled with a liquid or particulate solid, this is preferably introduced through the aperture after the container has been inflated with gas. It may be introduced through the same orifice as the gas, or through a closely adjacent second orifice that is also covered by the aperture in the container, or through a second orifice spaced from the first orifice, to which the inflated container may be slid after it has been pressurized at the first orifice. When the package is to contain a solid article or articles these are preferably put into the container before it is closed, and the container is subsequently pressurized and sealed in the manner described.  
  The method of the invention is used with particular advantage in the packaging of beer and carbonated soft drinks in flexible plastics containers.  
  The invention of application Ser. No. 271,208 filed Dec. 7, 1972 further provides apparatus for performing a method as described, that includes a smooth surface having therein an orifice; means for supplying a sealing strip in such a 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 and in line with the orifice; means for supplying through the orifice a gas for inflating to superatmospheric pressure a plastics film container presented to said surface with an aperture in its wall located over said orifice; means for holding the container sufficiently under compression against said surface or surfaces to maintain a seal around said aperture, while it is slid along said surface or surfaces to bring said aperture into the path of said sealing strip and until the sealing strip covers and surrounds the aperture; and, if necessary, means for heat sealing the sealing strip around the aperture.  
  We have now found that, in heat-sealing the flexible sealing strip to the wall of the container around the filling aperture, the seal can be improved if the sealing strip and the container wall surrounding the aperture are supported during sealing upon a curved protrusion on the surface against which the inflated container is held. The seal may then be produced without any puckering of the container wall or of the sealing patch, and the seal much improved in strength and reliability.  
  In accordance with the present invention, therefore, a method as claimed in application Ser. No. 271,208 filed Dec. 7, 1972 is further characterized in that the flexible sealing strip and the container wall surrounding the aperture are supported, during the sealing of the strip to the wall of the container, upon a surface that follows effectively a convex curve across each and any diameter of the area supporting the portion of the strip that is to be sealed to the container and the container wall surrounding said portion.  
  In accordance with a further feature of the present invention, an apparatus as claimed in application Ser. No. 271,208 filed Dec. 7, 1972 is further characterized in that the part of the surface that supports the portion of the sealing strip that is to be sealed to the container, and the container wall surrounding said portion, during the sealing of the strip to the wall of the container, follows effectively a convex curve across each and any diameter thereof.  
  Whilst the supporting surface ideally follows a true curve across each and any diameter thereof, the surface may for ease of machining be shaped across at least one diameter as a series of flats giving the effect of a convex curve.  
  The invention will now be more particularly described by way of example with reference to the accompanying drawings, which illustrate the filling of plastics-film pouches with beer, and of which:  
  FIG. 1 is a side view, seen partly in section, of the filling and sealing apparatus;  
  FIGS. 2 to 6 show in more detail the shape of the surface upon which the flexible sealing strip is supported in the apparatus of FIG. 1;  
  FIG. 7 shows schematically the supply-lines for the beer and for carbon dioxide for pressurizing the pouches; and  
  FIG. 8 shows a plastics-film pouch suitable for use in the method of the invention.  
  In FIG. 1: l is a magazine of plastics-film tubular pouches to be filled; 2 is a block, suitably of stainless steel, constituting the pressurizing and filling head, provided with a smooth, flat front surface, 3, in which are a filling orifice, 4, and concentric with and surrounding the filling orifice, a pressurizing orifice 5; 6, 7 are a pair of blocks, again suitably of stainless steel, separated by a narrow gap, 8, suitably about 0.005 inch wide, and having their smooth, flat front faces level with that of block 2, the face of block 6 being contiguous with that of block 2. Through the gap 8 passes the leading end of a sealing tape; supplied from reel 9, the tape having a heat-sealable coating on the surface that faces the block 6. 10 is the heat-sealer block, whose front face is of a curved shape to be more particularly described, across which passes a heat-sealer element, 11. The heat-sealer block 10, which is of heat-insulating material such as a bonded fabric laminate, is separated from block by a narrow gap through which operates a retractable knife, 12. 13 is a chute into which filled packs are ejected.  
  Opposite the members just described are a pair of parallel rails, the upper of which is shown at 14, for supporting inflated packs pressed against them, and a rod, 15, parallel with the rails 14, upon which is driven a reciprocating cylinder, 16; to this cylinder are attached two pairs of vertically-spaced pawls for pushing the pressurized and filled packs to the right (as seen in the drawing), the upper pawls of the two pairs being shown at 17, 18. Also attached to cylinder 16 is a reciprocable vacuum-pad, 19, which may be advanced to take a plastics-film pouch, 20, from the magazine, and transfer it, on movement of the cylinder 16 to the right (as seen in the drawing), to a position against the pressurizing and filling block, 2.  
  The plastics-film pouches, which are closed by gastight seals except for a circular filling aperture in the wall of each, are accurately located in the magazine with their filling apertures in a predetermined position. Thus, when the apparatus is in operation, successive pouches may be indexed by the vacuum pad 19 to a position in which the filling aperture is opposite and adjacent to the orifices 4, 5 in the pressurizing and filling block 2. When the pouch has been indexed into this position, carbon dioxide is blown through orifice 5 into the pouch, and the vacuum pad is pushed back by the inflating pouch until the pouch comes into contact with the rails 14, while the vacuum is cutoff; the cylinder 16 is then returned to its original position, so that the vacuum pad is returned to a position opposite the pouch magazine, and the pawls 17 are brought past the inflated pack 21 to its rear side. Meanwhile when the pouch has been inflated to the desired pressure, as shown at 21, a metred quantity of beer is pumped into the pouch through orifice 4, as a jet, carbon dioxide being displaced as the pouch fills. When the flow of beer has stopped and excess has been bled from the feed (as will be later described), the cylinder 16 again advances to the right, and the filled pack 21 is pushed by pawls 17 past the sealing tape supply slot and on until its filling aperture is opposite the heat-sealer element 11; a pack in this position is shown at 22. As the pack advances, the leading end 23 of the sealing tape is carried forward upon the pack by frictional forces, and further tape is withdrawn from roll 9, until the tape covers and extends beyond the filling aperture. Thus, on arrival at the heat-sealer 11, the pack has a patch of sealing tape covering its filling aperture. When this movement of the cylinder 16 is complete, the heatsealer switches on, the knife 12 advances to cut the tape, and the tape becomes securely sealed as a patch over the filling aperture of the pack. Meanwhile, the cylinder 16 moves back, bringing pawls 18 past the pack shown at 22 to its rear side. At the next forward movement of cylinder 16, pawls l8 push the filled and sealed pack from the heat-sealer and on until it drops into chute 13. From the chute 13 the successive packs may pass to a sleeve-wrapping device.  
  The shape of the heat-sealer block 10 is shown in FIGS. 2 to 6 of which: FIG. 2 is a plan; FIGS. 3 and 4 are side and end views respectively; and FIGS. 5 and 6 are sections through A,A and B,B of FIG. 2, respectively. The pack approaches the heat-sealer blocks as shown in FIG. 2 from the left-hand side. In a particular example of a heat-sealer block as shown in FIGS. 2 to 6, and suitable for use in sealing a pack formed from a tubular-film pouch having a flat width of mm, the surface shape is produced by a transverse spherical curvature of 31.75 mm on which is imposed, longitudinally, a flat from the left-hand side as shown, at an angle of 8, and a flat from the right-hand side at an angle of 5, separated by a 0 flat 10 mm in length at the position of the heat-sealer element 11, the three flats giving an effective radius of curvature, from a line perpendicular to the center point of the 10 mm flat, of approximately 92.5 mm.  
 Suitable curvatures for heat-sealer blocks for sealing packs of different sizes may be determined by experiment. Generally, the larger the diameter of the pack, the larger are the preferred curvatures of the heatsealer block.  
  In FIG. 7 are shown schematically the supply lines for the carbon dioxide and beer. As previously indicated, the gas and beer are supplied to the pouches through concentric orifices; for simplification and clarity, however, the two supply systems are shown in FIG. 7 on separate sides of the pack. Both systems provide for any carbon dioxide and beer entering the pouches to be maintained in a substantially sterile condition.  
  In FIG. 7, 21 represents the pouch being pressurized and filled, 24 the line to the supply source of carbon dioxide. which is suitably maintained at a pressure of about 20 psi, and 25 the line to the beer supply, suitably maintained at a pressure of about 30 psi. For the carbon dioxide line 24, 26 is an on/off valve, 27 a nonreturn valve, and 28 the line to orifice 5 (FIG. 1); while 29 is a line to a drain, through non-return valve 30 and pressure-relief valve 31, the latter being set at 20 psi or other pressure desired in the filled pack. For the beer line 25: 36 is a non-return valve; 37 is a metering pump, suitably a diaphragm pump; 38 is an on/off valve and 39 a two-way valve; and 40 is a bleed line for beer remaining beyond valve 39 after a pack has been filled, this bleed line leading to a drain via on/off valve 41, non-return valve 42 and restrictor valve 43. In operation, the on/off valve 26 for the carbon dioxide is turned on for the initial inflation of the pouch, and remains on until just before the filled pack is moved from block 2 and slid along to be heat-sealed. When the pouch has been pressurized, the measured amount of beer is pumped into it through line 25. As the beer is fed into the pouch carbon dioxide is displaced through non-return valve 30 and pressure-relief valve 31. When filling is complete, and to prevent beer remaining in the line between valve 39 and the filling orifice from blowing out when the pack is moved, and wetting the surface of block 2 (FIG. 1), 2-way valve 39 is turned to its second position, and bleed valve 41 is turned on for a time sufficient to empty this remaining beer to the drain, which is at atmospheric pressure, an excessive pressure drop being prevented by restrictor valve 43.  
  In order to ensure that substantially sterile conditions may be maintained, the parts of lines 28 and 29 between the non-return valves 27 and 30 and the pressurizing orifice, and the part of line 25 between the twoway valve 39 and the filling orifice, are made as short as possible.  
  Although FIG. I has been described as a side view, the apparatus is in fact arranged during operation so that the surface 3 is in a downwardly facing position indined at a small angle to the horizontal. The container may then be sufficiently filled with the beer, but a gas space still left under the filling 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; it also facilitates heat sealing, since the loss of heat through the gas is much less than if a liquid were in contact with the film. The apparatus is suitably tilted until surface 3 is at an angle of about 45 to the horizontal.  
  In FIG. 8 is shown a plastics-film pouch suitable for use in the method of the invention. This is a preferred form of pouch produced in the manner described in our copending Application Ser. No. 311,154, filed Dec. 1, 1972, which describes a method of closing an open end of a plastics-film container that comprises forming an elongated heat-seal between the flat, opposed layers of the plastics film at or towards their edges and along the whole length of said open end, folding the end of the container over, inwardly of the seal, so that the heatseal lies wholly against the external surface of one wall of the container, and adhering the folded-over end in such position by means ofa strip offlexible material adhered over the edge region of the folded-over end, along substantially the whole length thereof, and extending beyond the inner edge of the heat-seal, and to the adjacent portion of the container wall. In the preferred method a reinforcing ribbon is first adhered to the outer side of the seal, extending beyond its edge, and the strip of flexible material extends over the fold of the folded-over end with its ends projecting beyond the sides of the container, the opposed edges of the strip being adhered one to the other in this region. In FIG. 8: 34 is the flat, empty plastics-film pouch; 35 is the filling aperture in its wall; 46 is the heat-sealed, folded-over end; 47 is the edge of the seal-reinforcing ribbon; and 48 is the strip of flexible material extending over the fold of the folded-over end, the projecting ends of the strip, adhered together, being shown at 49. When the pouch has been filled and sealed it assumes a cylindrical form over the major part of its length, but has chisel-shaped, or saddle-shaped, ends as indicated in the packs shown at 21, 22 in FIG. 1.  
  Various modifications may be made in the method and apparatus particularly described. For example, other methods may be used for presenting the pouches to the pressurizing and filling surface, or other arrangements may be made for sliding the filled packs from one station to the next. Or the filled packs may be slid longitudinally instead of transversely from the filling to the sealing station. The surfaces against which the packs are slid need not necessarily be flat, provided that they are sufficiently smooth to allow such sliding. They may, for example, form parts ofa cylindrical surface. For contents other than carbonated liquids, a gas other than carbon dioxide may be used, particularly nitrogen.  
  Types of plastics&#39;film pouches other than that particularly described may be used provided that they are of sufficient strength, are formed with gas-tight seals, and are provided with a filling aperture in their wall.  
  The nature of the plastics material forming the pouches will be chosen in accordance with the intended pressure to be enclosed or developed within the pack. For high pressures such as those exceeding 15 psi, pouches formed of biaxially oriented polyethylene terephthalate film are especially suitable, particularly when coated with a heat-scalable, gas-impermeable coating, for example a coating of vinyliden e chloride copolymer. The coating may be an external coating or an internal coating.  
  The adhesive used for sealing the filling aperture must also be chosen to suit the pressure it will have to withstand. Hot melt adhesives, particularly when used on a plastics film of the same type as used for the construction of the container, are generally preferred. Particularly suitable hot melt adhesives include those based on copolymers of two or all of the acids sebacic, terephthalic and isophthalic acid condensed with ethylene glycol. Hot melt adhesives based on ethylene/vinyl acetate copolymers are also suitable. It is also possible to use for sealing the filling aperture a sealing strip bearing a pressure sensitive adhesive coating effective at room temperature.  
  The filled packs are preferably provided with a sleeve of paper, foil or other flexible sheet material, preferably formed by wrapping or winding around substantially the whole of the cylindrical part of the pack a sheet or strip of the sheet material and securing it by means of an adhesive, such as a moisture-activated adhesive, applied at least to the edges of the sheet. If the sleeve is applied closely to the container while the contents are cold, subsequent slight expansion of the container results in the container walls being firmly supported by the sleeve. This gives added strength to the pack and also provides for its labelling and decoration. The sleeve may be extended at one end to form a stand. When pouches as shown in FIG. 8 are used, the sleeve preferably extends just over, the edge of the reinforcing strip 47 at each end of the pack, the ends of the adhered edges 48 of the strip being folded down upon the walls of the pack when they are covered by the sleeve. The finished pack then has a neat appearance, and can be made attractive by print applied to the sleeve.  
 We claim:  
  1. In a method of filling and sealing a flexible plastics container, closed by gas-tight seals except at a filling aperture in its wall, to produce a package having contents at superatmospheric pressure, by placing the container against a smooth surface with said aperture located over an orifice in said surface, said orifice being connected to a source of gas at superatmospheric pressure and said surface being of such smoothness that the aperture may be sealed thereby against the substantial escape of gas when the container is inflated and held with its apertured wall pressed against said surface, in-  
 flating the container by the introduction of gas through said orifice from said source of gas, and while holding the inflated container with said aperture in substantially gas-tight juxtaposition to said surface, sliding the container along, against and 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 sealing the sealing strip to the wall of the container around said aperture, while said container is substantially in gas-tight juxtaposition to said surface: the improvement consisting in that the container is slid along a surface on which the flexible sealing strip and-the container wall surrounding the aperture are held during the sealing of the strip to the wall of the container wherein the surface follows effectively a convex curve across each and any diameter of the area of the strip that is to be sealed to the container wall.  
  2. A method as claimed in claim 1 in which, after the container has been inflated by said gas, but before it is sealed,a liquid is introduced into the container through said aperture under pressure such that the major part of the gas is displaced by the liquid, while the displaced gas is concurrently withdrawn from the container.  
  3. A method as claimed in claim 2 in which the container is filled with a carbonated liquid.  
  4. In an apparatus for filling and sealing a flexible plastics container, said apparatus comprising a smooth surface having therein an orifice, means for supplying and means for supporting a sealing strip in such manner that it may be drawn from its source of supply along a path substantially continuous with said surface and in line with but in a direction away from said orifice, means for supplying through said orifice a gas for inflating to superatmospheric pressure a plastics-film container presented to said surface with a filling aperture in its wall located over said orifice, a support means for holding the container sufficiently under compression against said surface to maintain a substantially gas-tight seal around said aperture while the container is slid along said surface to bring said aperture into the path of said sealing strip and until the sealing strip covers and surrounds said aperture, and means for causing sealing of the sealing strip to the container wall: the improvement consisting in that the surface of said means for supporting the sealing strip follows effectively a convex curve across each and any diameter thereof.  
  5. An apparatus as claimed in claim 4 in which said orifice is connected through valves to a source of gas at superatmospheric pressure and to a source of liquid stored under superatmospheric pressure.  
  6. An apparatus as claimed in claim 4 that includes means for heating the convexly curved surface of said means for supporting the sealing strip, such that said surface constitutes a heat-sealer for said sealing strip.  
 7. In an apparatus comprising:  
 1. a smooth surface having an orifice therein;  
 2, first container moving means for moving a plasticsfilm container which is closed except for an aperture in a wall of the container into a position such that the aperture is in register with the orifice;  
 3. gas supply means for supplying to said orifice a gas under superatmospheric pressure whereby the container is inflated by the gas passing through said orifice and aperture into the container;  
 4. container support means for holding the inflated container under sufficient pressure against said smooth surface so as to maintain a substantially gas-tight seal around said aperture;  
 5. second container moving means for moving the inflated container between the container support means and the smooth surface so that the aperture is moved out of register with the orifice but so that the aperture remains in contact with the said smooth surface, thereby maintaining the inflation of the container;  
 6. sealing strip supply means for supplying a sealing strip in such a position that the sealing strip is engaged by the container wall and covers and surrounds the aperture;  
 7. sealing means having a sealing support surface for supporting the sealing strip and the surrounding portion of the container wall and causing sealing of the sealing strip to the container wall;  
 the improvement comprising a sealing support surface which follows effectively a convex curve across each and any diameter thereof.