Abstract:
This invention provides a self-supporting container ( 10; 110; 210; 310 ) having at least one wall ( 36; 336 ), a base ( 52; 152; 252; 352 ) and a top ( 50; 350 ). The top has a closable spout ( 54 ) whereby the container is suitable for storing and transporting materials such as a drinks and other liquids. The wall is made of plastics material and includes at least one wall air chamber ( 26; 226; 326 ). The base has at least one base air chamber ( 84, 86 ), the at least one base air chamber having a dimension (2d) which is greater than a dimension (w) of the base whereby the base of the container is concave. The concave shape of the base makes the container more stable in use. There is also provided a blank for making the container, and a method of manufacturing the container blank.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a container, to a container blank, and to a method of manufacturing the container. The invention relates in particular to a self-supporting closed container. 
         [0002]    The container is expected to have is primary utility for containing liquids such as beverages during their transportation and storage, and the following description will therefore relate primarily to such applications. However, the use of the container for some solids (such as granular solids) is not excluded. 
         [0003]    Directional and orientational terms such as “top” “bottom” “base” and “vertical”, for example, refer to the container in its normal orientation of use, as shown in  FIGS. 2 and 3 , unless otherwise stated. 
       BACKGROUND TO THE INVENTION 
       [0004]    Many different containers are available, some of which are open-topped. Examples of open-topped containers are disclosed in U.S. Pat. Nos. 4,585,755, 5,135,132 and 5,314,250. Each of those containers is self-supporting and derives some of its structural strength from one or more chambers which are filled with air. 
         [0005]    The present invention is directed to a closed container, i.e. a container which can fully enclose a material such as a liquid. Unless otherwise stated, the word “container” used in the remainder of this application refers to a closed container rather than an open-topped container such as those described in the above patents. 
         [0006]    With containers for liquids in particular, it is desirable that the containers are sufficiently rigid to be self-supporting, i.e. they do not collapse under their own weight when empty, or under the weight of the liquid when full. 
         [0007]    Some containers obtain at least some of their structural strength from the contained product, so that the containers are not self-supporting. Gelatinous liquids such as soups for example are often supplied within a pouch having a front wall, a rear wall and a base. The material from which the walls are made is of flexible plastics, and the material is sufficiently thick to allow the container to stand up when full of the soup. The material is not sufficiently thick to support its own weight when empty, however. Such containers are therefore not suitable for materials which may be consumed over a period of time, for example fruit juices or milk, for which the container should be self-supporting, i.e. sufficiently rigid to stand up regardless of the volume of product contained. 
         [0008]    Other containers are made from aluminium and glass, and whilst these containers are self-supporting they are not universally acceptable. Aluminium containers in particular are not preferred since they are not readily resealable, so that the contained material may not retain its optimum freshness once the container has been opened. Glass containers are self-supporting and can be resealable, but are typically too heavy for more widespread use. Both aluminium and glass containers must be transported empty from the container manufacturer to the product supplier, and that represents an oncost since the transporting vehicle will typically not be fully utilised. 
         [0009]    The weight of packaging is a factor in the cost of the product to the eventual customer. The weight of the packaging directly affects the cost of transportation, both from the container manufacturer to the product supplier, and from the product supplier to the retailer or customer. The product supplier will typically seek to reduce the weight of the packaging, and will also typically seek to avoid the under-utilisation of the vehicle delivering the empty containers. 
         [0010]    With wine, beer and other relatively expensive products, the additional cost due to the weight of the packaging and the under-utilisation of a transporting vehicle is not usually significant, and so aluminium and glass containers continue to be widely used. With other relatively less expensive products, and products which are particularly price-sensitive such as milk and fruit juices on the other hand, these additional costs are significant, and the suppliers of these products, and the retailers of these products, will usually seek to reduce the weight of the packaging, and also to avoid any unnecessary oncost due to under-utilisation of transport vehicles. 
         [0011]    The use of plastics and combinations of paper and plastics for the packaging of certain materials (including milk and fruit juices) has therefore become increasingly widespread. 
         [0012]    A commonly-used self-supporting container for fruit juices is made of carton board (such as that sold under the trade name “Tetra Brik”® for example). A carton board container comprises a vessel having a square cross-section in plan view with walls comprising a number of layers of different materials. Most of the structural strength is provided by a layer of card. The card is made waterproof by at least one layer of plastics. One or more additional layers are provided for specific purposes, for example a metallic layer to prevent the passage of oxygen through the wall whereby the shelf-life of the product is extended. 
         [0013]    Carton board containers are particularly beneficial in terms of space utilisation during transportation. Firstly, the container can be made and delivered to the user in a collapsed, substantially flat, condition, and it can be erected before being filled. Secondly, the filled container can be stacked alongside other similar containers during delivery to the retailer or customer, with relatively little wasted volume. 
         [0014]    Despite their advantages and widespread utilisation, carton board containers have a number of disadvantages. Firstly, they are necessarily made from a number of layers of different materials, which makes recycling a used container more difficult. Whilst many local authorities accept used carton board containers for recycling, they are rarely if ever separated into their primary components so that those components can be reused. 
         [0015]    In addition, the product supplier is required to have a dedicated machine to erect the container, the machine undertaking the necessary folding and gluing operations. The machine is necessarily complex and any breakdown may require the services of a dedicated technician as the machine may be significantly different to the other machines at the supplier&#39;s location. 
         [0016]    Self-supporting plastics containers are commonly used for liquids such as water and milk. Plastics containers are often used where oxygen migration is not a significant concern, and so these containers typically do not utilise a metallic layer. PE and PET are commonly used material for plastics containers of this type. It is not, however, typical to make the container lid from PET, so that the lids of PET containers in particular must be recycled separately from the remainder of the container. 
         [0017]    Self-supporting containers which obtain some of their structural strength from air-filled chambers are described in WO 2009/021329, U.S. Pat. No. 2,751,953, WO 80/02545, and also GB 2 333 085. 
       SUMMARY OF THE INVENTION 
       [0018]    The inventors have appreciated that a new container is required which seeks to avoid or reduce the above-stated disadvantages of the various known containers and is particularly (but not exclusively) suitable for use with liquids such as milk and fruit juices. The inventors have also sought to provide a container which weighs no more than, and ideally weighs less than, the known containers of similar volume. 
         [0019]    According to the first aspect of the present invention, there is provided a self-supporting container having at least one wall, a base and a top, the top having a closable spout, the wall being made of plastics material and including at least one wall air chamber, the base having at least one base air chamber, said at least one base air chamber having a dimension which is greater than the dimension of the base whereby the base of the container is concave. 
         [0020]    In the present invention it is the air within the wall air chamber and the base air chamber which provides the structural strength necessary for the container to be self-supporting. Accordingly, when the container is empty the air chamber(s) can also be empty, whereupon the container is not self-supporting and can be collapsed for transportation, whereby the utilisation of the transportation vehicle can be maximised. 
         [0021]    The provision of at least one base air chamber having a dimension which is greater than the dimension of the base creates a base with an “over-centre” feature, i.e. a tendency to be concave or convex rather than flat. It can be arranged that the filling machine ensures that the base is concave, whereby the erected container rests upon the periphery of its base rather than the whole of its base, and is thereby more stable. 
         [0022]    Preferably, the container is substantially rectangular (ideally square) in plan view, with four walls. Preferably there is one wall air chamber, or there are two wall air chambers, defining each of the four corners of the container. More than two wall air chambers can be used at each corner if desired, but that is expected to be disadvantageous. Specifically, embodiments utilising a single air chamber at each corner have the additional advantage of increasing the available area of each of the walls of the container which is suitable for the application of printed labels and product information. 
         [0023]    According to a second aspect of the invention, there is provided a self-supporting container having at least one wall, a base and a top, the top having a closable spout, the wall being made of plastics material and including a plurality of air chambers, the container having means to permit the deflation of some of the air chambers during emptying of the container. 
         [0024]    Embodiments of the invention according to the second aspect have advantages as containers for use with particular industrial materials. With some industrial materials it is desirable to avoid the material coming into contact with air. The containers for those materials are usually emptied by the application of a reduced (vacuum) pressure applied to the container spout. The container is designed to collapse as its contents are transferred to a machine for subsequent processing. It is, however, a known concern that the collapsing container might not be completely emptied. Thus, a container which collapses in an uncontrolled manner may sometimes trap some of the material and prevent its removal. Depletion devices are commonly introduced into the containers so as to ensure that the collapse of the container is controlled and all of the material may be emptied. 
         [0025]    The present invention can avoid the requirement for separate depletion devices. By arranging for the collapse of some, but not all, of the air chambers (and in particular not all of the air chambers in the walls of the container), the container can partially collapse as its contents are emptied, but can retain enough structural rigidity to reduce or avoid the likelihood of some of the material becoming trapped. 
         [0026]    Two separate air networks can be provided, both of which networks can be inflated to provide the container with structural support during transportation. When the container has been connected to the machine for emptying its contents, the first air network can be opened or released to allow the container to collapse as the contents are emptied, but the second air network can be maintained so as to provide sufficient structural rigidity to ensure complete emptying. In one embodiment, the air chambers defining one side wall of the container are connected together as the second air network, and the remaining air chambers are connected together as the first air network. 
         [0027]    In some embodiments of the various aspects of the present invention therefore, all of the air chambers are interconnected in a single air network. There is therefore only the need to undertake one inflation operation for all of the air chambers. In other embodiments the air chambers are arranged in two (or more) separate air networks which must be inflated (and deflated) separately. 
         [0028]    According to a third aspect of the invention, there is provided a self-supporting container having at least one wall, a base and a top, the wall being made of plastics material and including at least one air chamber, the container having a spout assembly with a first passageway adapted to permit material to be introduced into and removed from the container and a valve to permit the inflation of the at least one air chamber. 
         [0029]    Preferably, the valve includes disabling means adapted to open the valve. The disabling means can be operated to allow air to flow out of the air chamber(s) when the container has been emptied. 
         [0030]    According to a fourth aspect of the invention, there is provided a self-supporting container having at least one wall, a base and a top, the top having a closable spout, the wall being made of plastics material and including at least one air chamber, the top being made of a two-layer material, the spout having a passageway to permit a material to be introduced into and removed from the container and a base plate surrounding the passageway, the base plate being located between parts of each layer of material in the top of the container. 
         [0031]    In one method of manufacturing a container according to the fourth aspect, the spout is fixed to one layer of wall material before the second layer of wall material. Specifically, a first layer of wall material is provided, and an opening in made through the layer (which will provide the filling opening). A substantially rigid spout is fixed by way of its base plate to the first layer, with the passageway of the spout aligned with the opening. A second layer of wall material is then laid over the first layer of wall material, the second layer of wall material having a corresponding opening to surround the passageway. The second layer of material is fixed to the base plate of the spout whereby the spout is secured between the two layers. In embodiments in which the spout is part of a spout assembly which also provides the inflation valve, the base plate can include a passageway communicating with the air chamber(s) whereby air can be introduced between the layers of wall material. 
         [0032]    Ideally, the wall(s), base and top of the container are made from a polyolefin such as polyethylene of polypropylene, or from polyester, all of which are known to be suitable as packaging materials. The spout or spout assembly can also be made from the same material, whereby the container is made from a single material and is ideally suited to recycling. 
         [0033]    It will be understood that for some contained materials such as milk, for which the shelf life is relatively short, the migration of oxygen through the plastics walls of the container will be so slow that the shelf life is unaffected. Some containers will therefore not require an additional (usually metallic) layer to reduce or prevent the passage of oxygen. With materials which have a longer shelf-life, such as fruit juices for example, a metallised layer to reduce or prevent the passage of oxygen may be required, and whilst this will reduce the recyclability of the empty container, it will not avoid its weight-saving advantages over the known containers. 
         [0034]    As above indicated, the wall(s) of the container are ideally made from a two-ply sheet of plastics material. The regions of the sheet which will form the respective air chambers are separated from the regions of the sheet which will not form air chambers by seams which join the two layers together. 
         [0035]    The present invention therefore also provides a blank for the container, the blank comprising two layers of plastics material formed with seams joining selected parts of the layers together. The blank can be folded and respective parts of the folded blank joined together whereby to make a (collapsed or flattened) container suitable for transportation to the user. The user can simply pump air into the air chamber(s) whereby to erect the container prior to (or preferably at the same time as) filling with material. 
         [0036]    Preferably, the seams are formed by a welding operation, so that the use of other materials such as adhesives is avoided. This facilitates recycling of the container since it can comprise a single material. 
         [0037]    When the container has been emptied by the customer, it can be deflated (e.g. punctured), whereupon it will lose its structural strength and can be collapsed so as to minimise the volume for subsequent transportation. Preferably, the container can include a weakened zone such as a tear strip or the like to facilitate deflation when empty. 
         [0038]    The fact that air is compressible adds a further advantage to the present invention, in that the container can be squeezed and will return to its erect shape when released. This is advantageous for gelatinous products such as soups and the like, allowing their easier removal from the container. 
         [0039]    The fact that a layer of air surrounds part of the product can also have an insulating effect, which can be beneficial during transportation of a chilled product from the retailer to the customer&#39;s home, for example. Again, the use of separate air networks can be utilised, the first network comprising the interconnected air chambers which provide the structural support for the container, the second network comprising the wall(s) which are inflated to provide insulation. The use of separate air networks is desired since the pressure within the second (insulation) network should typically be lower than the pressure within the first (structural support) network. 
         [0040]    According to a fifth aspect of the present invention there is provided a collapsible container having four walls, a base and a top, the base and the top being substantially rectangular, the top having a closable spout, at least one air chamber defining each corner of the container between adjacent walls, the walls, base and top being of two-layer material, the collapsible container having fold lines whereby to define the form of the container when collapsed, there being at least one fold line in an opposing pair of walls whereby the opposing walls are folded inwardly in the collapsed container. 
         [0041]    A collapsible container which can be folded in such a fashion is often called a “gusseted bag” (or is often said to utilise “side gussets”), and is known to be used with containers. The layers of material forming the base and top are secured together (as by welding) to define the required shape of the container, and further fold lines can be provided for the base and top, whereby parts of the base and top can be folded inwardly or outwardly in order to provide a substantially flat bag ready for erection and subsequent filling with material. Gusseted bags can readily be erected into a container having a substantially flat base and substantially flat sides. The present inventors are apparently the first to utilise the benefits of a gusseted bag arrangement for an inflatable container, and in particular for a container having walls, top and base made of two-layer (or two-ply) material. 
         [0042]    The top of the collapsed container can be readily accessible so that the filling spout and the inflation valve can be accessed and the container can readily be erected (by inflation) at the same time as it is filled. 
         [0043]    Embodiments of the invention can use one or more of the above aspects, as desired. 
         [0044]    Whilst reference is made herein to “air chambers”, it will be understood that the chamber(s) can be filled with a gas other than air if desired. 
     
    
     
       BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
         [0045]    The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: 
           [0046]      FIG. 1  shows a blank for the container according to the present invention; 
           [0047]      FIG. 2  shows a perspective view from above of an erected container according to the present invention; 
           [0048]      FIG. 3  shows a perspective view from below of the container of  FIG. 2 ; 
           [0049]      FIG. 4  shows a more detailed view of the top of the container; 
           [0050]      FIG. 5 . shows a sectional view of part of the top of the container; 
           [0051]      FIG. 6  shows a side view of the spout assembly of the container; 
           [0052]      FIG. 7  shows a perspective view from below of the spout assembly of  FIG. 6 ; 
           [0053]      FIG. 8  shows a perspective view from above of the spout assembly of  FIG. 6 ; 
           [0054]      FIG. 9  shows a sectional view through the spout assembly of  FIG. 6 ; 
           [0055]      FIG. 10  shows a sectional view of the valve member of the spout assembly; 
           [0056]      FIG. 11  shows a sectional view of an alternative spout assembly; 
           [0057]      FIG. 12  shows a perspective view from below of part of an alternative embodiment of container according to the present invention; 
           [0058]      FIG. 13  shows a sectional view of part of the base of the container of  FIG. 12 ; 
           [0059]      FIG. 14  shows a blank for an alternative container according to the present invention; 
           [0060]      FIG. 15  shows a perspective view from below of part of a container produced from the blank of  FIG. 14 ; 
           [0061]      FIG. 16  shows a sectional view of the container of  FIG. 15 ; 
           [0062]      FIG. 17  shows a collapsed container according to the present invention; and 
           [0063]      FIG. 18  shows a blank for another alternative container according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0064]    The container  10  shown in  FIG. 2  is constructed from a blank  12  shown in  FIG. 1 . The blank  12  comprises a two-ply polypropylene sheet, i.e. sheet comprising two layers of polypropylene, one of the layers overlying the other. The two layers are joined together by a number of seams  14   a - i , the seams being created by a welding process or the like which is known to adhere two layers of polypropylene together. In other embodiments the blank comprises a two-ply sheet of another polyolefin material, such as polyethylene. 
         [0065]    The structure of the erected container shown in  FIG. 2  is dependent upon the arrangement of the seams  14 , as will be explained below. Whilst many of the seams  14  are interconnected, they will be described separately below according to their function. 
         [0066]    The seam  14   a  defines the outer wall of an annular valve chamber  16 , and the seam  14   b  defines the inner wall of the annular valve chamber. The seams  14   c  define the walls of a passage  20  connecting the valve chamber  16  to a top chamber  22 . 
         [0067]    The top chamber  22  is defined by a top seam  14   d  and a lower seam  14   e , and by respective parts of two side seams  14   f.    
         [0068]    The top seam  14   d  is continuous, as are the side seams  14   f . The side seams  14   f  are connected to a bottom seam  14   g  which is also continuous. 
         [0069]    The lower seam  14   e  is not continuous, and has a number of gaps  24 . Each of the gaps  24  is provided to permit air to pass from the top chamber  22  into a respective wall air chamber  26 . The sides of each air chamber  26  are defined by longitudinal seams  14   h , the top of each air chamber is defined by a part of the lower seam  14   e , and the bottom of each air chamber  26  is defined by a part of the upper seam  14   i  of the bottom chamber  30 . 
         [0070]    The bottom chamber  30  is defined by the upper seam  14   i , the bottom seam  14   g , and respective parts of the side seams  14   f . The upper seam  14   i  has gaps  32  corresponding to the gaps  24  in the lower seam  14   e.    
         [0071]    It will therefore be understood that when air is introduced into the annular valve chamber  16  the air can pass through the passage  20  and into the top chamber  22 , through each of the gaps  24  into the respective air chambers  26 , and through the gaps  32  into the bottom chamber  30 . The top chamber  22 , the air chambers  26  and the bottom chamber  30 , can therefore all be filled with air, to the pressure required, in one step. 
         [0072]    The longitudinal seams  14   h  separate the air chambers  26  from first regions  34  and second regions  36  which do not become filled with air. 
         [0073]    It will be understood that the blank  12  can be made from two continuous layers of polypropylene material, i.e. the seams  14   a - i  can be welded and the layers cut to form the blank  12 , in a substantially continuous operation. 
         [0074]    In order to create the container  10 , the blank  12  is folded and the side edge  40  is welded or otherwise secured onto the side edge  42 . The top panel  44  and the bottom panel  46  are also folded and welded or otherwise secured to form the top  50  of the container and the base  52  of the container respectively. 
         [0075]    It will be understood that as the top panel  44  is folded, and the bottom panel  46  is folded, the top  50  and base  52  of the container will have multiple sheets of polypropylene. In some embodiments the salvage (i.e. the excess parts of the top panel  44  and bottom panel  46 ) is removed prior to being secured together, so that the top wall  50  and the base  52  comprise substantially a single (two-ply) sheet, so that the weight of the container  10  is minimised. 
         [0076]    In order to avoid outwardly-directed welded joints which might make the container  10  less stable in use, at least the base  52  can be welded from the inside, if desired. 
         [0077]    It will be understood that in the erected container shown in  FIGS. 2 and 3  two air chambers  26  define each of the vertical corners of the container. The (narrower) first regions  34  are bent to provide the corners of the container, whereas the (wider) second regions  36  are substantially flat and provide much of the side walls of the container. 
         [0078]    A spout assembly or gland  54  is mounted to the top  50  of the container  10 . In this embodiment the spout assembly  54  is made of polypropylene to match the material of the blank  12 , and thereby facilitate recycling of a used container. The spout assembly  54  is, however, of considerably thicker material than the sheet making up the blank  12 , so that it is substantially rigid. 
         [0079]    The spout assembly  54  is shown in more detail in  FIGS. 4-10 , and comprises a base plate  56  which can be welded or otherwise secured to the material at the top  50  of the container. Ideally, the base plate  56  is secured between the two layers of polypropylene which lie within the seam  14   b  defining the inner edge of the annular valve chamber  16 , whereby the annular valve chamber  16  surrounds the fill passageway  60  and the valve passageway  62 . 
         [0080]    Though not shown in  FIG. 1 , the blank  12  includes further seams defining a passage  58  (see  FIG. 5 ) whereby the valve passageway  62  can communicate with the annular valve chamber  16 . If desired, in other embodiments the valve passageway  62  can overlie the enlarged part  28  of the annular valve chamber  16  (see  FIG. 1 ) whereby air can pass directly into the valve chamber. 
         [0081]    The base plate  56  carries a fill tube  64  which defines the fill passageway  60 , and has a screw thread  66  whereby to accept a screw cap  70 , in known fashion. The base plate  56  also carries a valve tube  72  which defines the valve passageway  62 . The valve tube  72  locates a valve member  74  as described in more detail below. 
         [0082]    It will be understood that during the process of manufacturing the container  10 , a section of the polypropylene material lying within the inner seam  14   b  is removed, and the border of the removed material is welded or otherwise secured to the base plate  56  surrounding the fill passageway  60 , so that the fill passageway  60  opens into the interior of the erected container. 
         [0083]    Whilst it would be possible to fill the container  12  with the chosen material by way of the base  52  (with the base panel  46  being closed and secured after filling), in the present embodiment it is desired that the container  10  is filled by way of the spout assembly  54 , and specifically by way of the fill tube  64 . Ideally, the filling machine includes means to hold the fill tube  64  during filling of the container, and also includes means to pump air into the valve tube  72 . Accordingly, a filling machine can pump air into the air chambers  22 ,  26  and  30  of the container  10  whereby to erect the container, at substantially the same time as the container is being filled with product. 
         [0084]    The added complexity of the means to pump air into the valve tube  72  is relatively minor compared to a machine required to erect a carton board container, and is not likely to be a barrier to users. In addition, it is likely to take far less time to fill the air chambers  22 ,  26 ,  30  with air than it is to fill the container  12  with liquid, so that the inflation step will not impact adversely upon the filling process. 
         [0085]    The valve member  74  is located in the “open” position shown in  FIGS. 5 ,  6  and  9  as air is being pumped into the air chambers  22 ,  26 ,  30 , air being able to pass through the openings  78  in the valve member  74 . When the required air pressure within the air chambers  22 ,  26 ,  30  has been reached, the valve member is pressed into the valve tube  72 , to the “closed” position shown in  FIG. 10 , sealing the air within the air chambers  22 ,  26 ,  30  and maintaining the self-supporting structural rigidity of the container  10 . 
         [0086]      FIG. 11  shows an alternative embodiment of spout assembly  154  (without the screw cap) in which the fill tube  164  is manufactured as a separate component to the base plate  156 . These components are secured together by complementary formations  80 . The advantage of such an arrangement is that the screw cap does not need to be screwed onto the fill tube  164  after the container has been filled, this being a relatively slow operation. Instead, the fill tube  164  and its pre-fitted screw cap can be pressed into position after the container has been filled. 
         [0087]      FIGS. 12 and 13  show the bottom part of an alternative container  110 , made from an alternative design of blank. The top part of the container  110  is not shown, but may be similar to the top part of the container  10  for example. In the container  110  the base  152  has base air chambers  82  in addition to the bottom chamber  130 . The base air chambers  82  are connected to the bottom chamber  130  by respective gaps in the bottom seam of the blank. The base air chambers  82  provide a more rigid base, and help to define the structure of the container  110  when the air chambers are filled. In a particularly preferred embodiment, the salvage of the bottom panel of the blank is welded after the air chambers  22 ,  26 ,  130  and  82  have been filled which will secure the base in its erected condition. 
         [0088]    It will be understood that the top  50  of the container  10  can be gabled or substantially flat, or made as a single continuous panel, as desired, depending upon the form of the blank and the folding and welding steps. 
         [0089]    An alternative design of blank  212  for producing a container is shown in  FIG. 14 , and the bottom of a container  210  which is produced from the blank is shown in  FIGS. 15 and 16 . The container  210  which is produced from the blank  212  has several similarities with the container  10 , namely four walls (which are substantially vertical in use), a top including a spout assembly, and a base. 
         [0090]    The blank  212  differs from the blank  12  in providing only a single air chamber  226  for each of the (vertical) corners of the container. Thus, in this embodiment the annular valve chamber  216  is connected to the top chamber  220 , which in turn is connected to the bottom chamber  230  by way of only four air chambers  226 . 
         [0091]    The blank  212  also differs from the blank  12  in having base air chambers which will provide the structure of the base  252  (somewhat similar to the blank used to form the container  110  of  FIGS. 12 and 13 ). Specifically, the bottom chamber  230  is connected to two primary base air chambers  84  and two secondary base air chambers  86 . As shown in  FIG. 15 , in the erected container  210  (in which the edges  240  and  242  have been secured together) the respective primary base air chambers  84  lie on opposed sides of the base  252 , and the respective secondary base air chambers  86  lie on opposed sides of the base, between the primary base air chambers  84 . 
         [0092]    Importantly, the dimension d of the primary base air chambers  84  is slightly greater than half of the dimension w which is the width of the base  252  (inside the bottom chamber  230 ) of the erected container. When the edges  88  of the primary base air chambers  84  are secured together the combined dimension 2d of the primary base air chambers exceeds the width w of the erected container. When the primary base air chambers  84  are filled with air they are not able to lie in a common plane, i.e. the base  252  is not flat, but instead the primary base air chambers  84  tend to push the base inwards (concave) or outwards (convex). It can be arranged that the machine which fills the air chambers (and which is ideally the machine which also fills the container with product), will drive (and hold) the base in its concave position. 
         [0093]    The secondary base air chambers  86  act to lock the primary base air chambers  84  in position, i.e. they enhance the “over-centre” arrangement. It is arranged in particular that the force with which the primary and second base air chambers  84 , 86  tend to maintain the concave position will exceed the weight of the contents which seeks to push the base  252  towards its convex position. 
         [0094]    It will be noted that the annular valve chamber  216  is larger than the annular valve chamber  16  relative to the width w of the base (and top). The blank  212  therefore provides a container with a relatively larger spout assembly. It could be arranged in an alternative embodiment that the spout assembly spans substantially all of the top of the container, which is desirable when the contained product is a solid which does not readily flow, for example breakfast cereals such as corn flakes. 
         [0095]    The blank  212  also differs from the blank  12  in providing notches  90  in the bottom chamber  230 . When the container is erected from the blank  212  the notches  90  lie at the respective outer corners of the base  252 . The reduction in the cross-section of the bottom chamber  230  at each corner serves to “flatten” the base, i.e. it removes excess material which might otherwise fold or buckle at the corners. 
         [0096]    As shown in  FIGS. 15 and 16 , the erected container  210  will rest upon the bottom chamber  230 , the bottom chamber  230  providing the junction between the walls and base of the erected container. The container therefore rests upon the periphery of its base rather than the whole of its base (similar to a wine bottle). It will be much easier to ensure that the periphery of the base is substantially flat than the whole of the base, with the result that the erected container  210  is more stable. In addition, since the contact area upon which the erected container  210  rests is relatively small, less care needs to be taken over the seams of the base  252 , as only those seams which lie within the contact area affect the stability of the container. 
         [0097]    Another alternative blank  312  for producing a container is shown in  FIG. 17 . The blank  312  differs from the blanks  12  and  212  in having two separate air networks. The air networks are both designed to be filled by way of the spout assembly (not shown), and so the blank  312  has two separate valve air chambers  316   a ,  316   b , each having its own enlarged part  328   a  and  328   b  which can be connected to a respective valve tube. The spout assembly therefore has two separate valve openings, perhaps similar to the valve openings  62  (and two separate valves), one for each of the air networks. 
         [0098]    The valve chamber  316   a  communicates with the top chamber  322  and wall air chambers  326  in a similar fashion to the blanks  12  and  212 . The air chambers  326  communicate with the bottom chamber  330  (and hence to the base air chambers  384  and  386 ) by way of a single gap  332  in the upper seam  314   i.    
         [0099]    An additional seam  314   h  is provided between the upper seam  314   i  and the air chambers  326 , and an additional seam  314   j  is provided inside the seam  314   f . The chambers formed between the seams  314   f  and  314   j , and between the seams  314   i  and  314   h , comprise conduits of a second air network. The seam  314   h  has openings  92  therethrough, each of the openings  92  communicating with a respective wall panel  336 . Air can therefore be delivered through the valve chamber  316   b  into the second air network which includes the wall panels  336 . 
         [0100]    The blank  312  is suitable for producing an insulating container, with the first air network being filled with higher-pressure air so as to provide the structure of the container, and the second air network being filled with lower pressure air so as to provide an insulating layer for the wall panels. 
         [0101]    It will be understood that the configuration of the first air network and the second air network can be varied by varying the configuration of the seams on the blank. In one alternative embodiment the first air network is filled with air to inflate three of the four walls of the container and perhaps also the base, whilst the second air network is filled with air to inflate the fourth wall. Such an embodiment would avoid the requirement for a depletion device when used for a product which should not come into contact with air, the first air network being deflated as the container is emptied, the second air network being maintained so as to avoid total collapse of the container and avoid the potential trapping of some of the product. 
         [0102]    The blank  312  also shows another feature, which serves to form a collapsed container  310  of  FIG. 18 . After forming of the blank  312 , and prior to folding of the blank, fold lines  94  and  96  are formed therein. The fold lines  94  are formed to fold inwardly (i.e. down into the paper as drawn, whereas the fold lines  96  are formed to fold outwardly (i.e. up from the paper as drawn). Following connection of the edges  340  and  342 , and the folding and welding of the top panel  344  and the bottom panel  346  to form the top  350  and base  352  respectively of the container  310 , the container may be folded into the gusseted bag shown in  FIG. 18   
         [0103]    It will be understood that the blanks  12  and  212  can also be modified to provide two separate air networks, and/or to provide a gusseted bag, if desired. In fact, the features which are shown for each blank  12 ,  212 ,  312  are generally interchangeable so as to provide a blank having all of the desired features of the resulting container. 
         [0104]    A means for deflating the container is shown in  FIG. 1 . A weakened section  38  of one or both of the layers of polypropylene are provided at a chosen location of the container. In this embodiment the weakened section  38  is provided in the top chamber  22 , but it will be understood that it could be provided in alternative locations such as the base or one of the walls, as desired. A strip of material  48  is secured adjacent to the weakened section  38 , and in this embodiment lies between the two sheets of polypropylene, so that a part of the strip  48  lies within the top chamber  22 , and a part lies outside the top chamber. When the container has been erected a part of the outer layer of polypropylene (within the top panel  44 ) is removed to expose the end of the strip  48  and allow the tear strip to be gasped by the user. When the container has been emptied and it is desired to deflate the container the strip may be pulled to tear or rupture the weakened section  38 , and allow the escape of air. 
         [0105]    It will be understood that a tear strip such as  48  and a weakened section such as  38  can be used in the other embodiments (and blanks) described herein. In containers having two air networks, a single tear strip can span both of the air networks so that they are deflated together, or separate tear strips can be provided for each air network, whereby the separate air networks can be deflated separately. 
         [0106]    In other embodiments a strip of material similar to the strip  48  is adhered to one of the layers of polypropylene adjacent to the weakened section  38 , i.e. the tear strip does not lie between the two sheets of polypropylene. In yet other alternative embodiments the tear strip is extended to project beyond the top panel  44 , so that it is not necessary to remove a part of the top panel in order to expose the tear strip. 
         [0107]    It will be understood that the container does not need to be square in plan view, but could instead be oblong. Other shapes such as triangular, hexagonal or cylindrical could be provided if desired, but rectangular shapes are preferred because they minimise the volume of wasted space during transportation. 
         [0108]    Tests undertaken by the inventors have demonstrated that whilst the air chambers add thickness to the walls of the container, the detrimental effect upon the transportation utilisation (when full) is minor. Thus, a one litre container (such as the container  10 ) having a footprint identical to that of a one litre carton board container would need to only a few millimetres taller that the carton board container. This difference in height is a small disadvantage compared to the weight, processing and recycling advantages of the containers of the present invention. The increase in height over a corresponding carton board container would be less for larger-volume containers in which the footprint is larger. A container according to the present invention is both lighter and more space efficient than the known HDPE plastics containers used for milk.