AU2021201723A1 - Plastic container - Google Patents

Abstract

The invention relates to a blow-moulded plastic container having a body (1) defining an internal volume of the container, the body comprising: a base panel (5) having four corners and a rectangular base perimeter (15) ; and four generally rectangular side panels (2a, 2b, 2c, 2d) extending upwards from the base panel (5) to form sides of the container body (1). Each side panel (2a, 2b, 2c, 2d) includes: a base edge (6a, 6b, 6c, 6d) that joins integrally with the base panel (5) along the rectangular base perimeter (15), two vertical side edges that are integrally joined with respective adjacent side panels, and a top edge, wherein the top edge of each of the side panels merge to form an upper body portion (10) that defines an outlet (4) of the container. At least one of the side panels, and preferably two, three or four of the side panels, includes at least one integral deformation (8a, 8b, 8c, 8d). (Fig. 6) 4/9 4 2b 8 b 6b 8c 6c 8d 6a 2a FIG. 6

Description

4/9

4 2b

8b 6b

8c

6c

8d 6a 2a

FIG. 6

PLASTIC CONTAINER FIELD OF INVENTION

[0001] The present invention relates to the field of plastic containers, particularly blow moulded containers.

[0002] In one form, the invention relates to lightweight plastic containers for retail sale of milk or other liquids.

[0003] It will be convenient to hereinafter describe the invention in relation to milk containment, however it should be appreciated that the present invention is not limited to that use only and can be used for a wide range of consumable liquids and non-consumable industrial liquids.

BACKGROUND ART

[0004] Plastic milk containers, typically made of high density polyethylene (HDPE), low density polyethylene (LDPE) or polyester (PETE) have been in use since the 1960s when they largely replaced glass bottles. While glass bottles were reusable, light weight plastic bottles are designed for single use and plastic recycling.

[0005] A wide variety of milk bottle designs are available. Some have a round cross section while others have a square or rectangular cross-section to maximize shipping and storage efficiency.

[0006] Plastic milk containers are typically manufactured by the blow moulding process. Large scale industrial production of blow-moulded products was well established by the 1950s. Blow moulding begins with melting plastic and forming it into a parison. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass. The parison is clamped into a mold and air blown in to push the plastic outward to match the container mold. Once the plastic has cooled and hardened the mold is opened up and the container is ejected.

[0007] Designers of moulds for blow-moulded bottles have to consider and balance a wide range of competing parameters including the physical characteristics of the plastic, consumer expectations and legislative compliance requirements. Further challenges are presented with respect to the blow moulding process because the bottle moulds have a number of features such as flat walls, rounded edges, corners, handles and a neck and the parison will interact and stretch differently as it comes into contact with each of these features.

[0008] Typical blow-moulded plastic containers of the prior art are described in US patent application 2011/0215104, US patent 8,517,195, and Australian Design registration 201817395.

[0009] It is well established fact that the plastic thickness in the finished container is a function of the amount of stretch from the molten parison. This fact has been well documented in numerous scholastic articles that describe the blow moulding process. One such article of note is "Mathematical Modelling of the Blow Moulding Process" - M E Ryan &A Dutta, Polymer and Engineering Science, Vol 22, No.17 (1982).

[0010] Ryan & Dutta describe mathematical modelling and equations relating to the blow moulding process. Specifically, they consider the numerous, complex interactions between the molten plastic parison and the mold that produces the bottle. A soft plastic parison can stretch only a short distance before it begins thinning and if it thins too fast, the parison splits and the moulding fails. This is particularly likely to happen at the corner regions, that is, at the furthest distance of travel for the blown plastic where the plastic is concomitantly thinnest.

[0011] One of the problems associated with milk containers of the prior art, is structural weakness which leads to deficiencies such as rolling, creasing or buckling when the container is under load stress such as when filling or capping load is applied. This is particularly evident when the container is stacked. Lack of rigidity of blow-moulded plastic milk bottles and their tendency to deform under load is a longstanding problem as described in patents from the 1970's such as US patent 4,127,206 and US patent 3,708,082. Efforts continue to be made to improve the strength to weight ratio of the containers.

[0012] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

SUMMARY OF INVENTION

[0013] An object of the present invention is to provide an improved portable liquid container, such as a milk container.

[0014] A further object of the present invention is to alleviate at least one disadvantage associated with the related art.

[0015] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

[0016] In a first aspect of embodiments described herein there is provided a blow moulded plastic container having a body comprising: - four rectangular side panels, each panel including a base edge and two vertical side edges integral with adjacent panels, the top edges of the panels merging to form an upper body that defines an outlet for the container, - a base having four corners, and a rectangular base perimeter that is integral with the base edges of the side panels, wherein at least one panel, preferably two, three or four side panels includes at least one integral deformation.

[0017] Typically, the body is elongate, having a longitudinal axis, and is intended to be generally vertical during use and/or storage. The body may include an integral handle to facilitate lifting and carrying the container and pouring out the contents.

[0018] At least one panel, preferably two, three or four side panels includes an integral deformation. Relative to the plane of the panel, the deformation may be generally concave, or convex, or a combination thereof. The panel bearing a deformation may have second, or subsequent deformations. Sufficient deformations may be included to form a type of corrugation.

[0019] In at least one embodiment, therefore, the invention provides a blow-moulded plastic container having a body defining an internal volume of the container, the body comprising: a base panel having four corners and a rectangular base perimeter; and four generally rectangular side panels extending upwards from the base panel to form sides of the container body. Each side panel includes: a base edge that joins integrally with the base panel along the rectangular base perimeter, two vertical side edges that are integrally joined with respective adjacent side panels, and a top edge, wherein the top edge of each of the side panels merge to form an upper body that defines an outlet of the container. At least one of the side panels, and preferably two, three or four of the side panels, includes at least one integral deformation.

[0020] In a preferred embodiment, the at least one integral deformation has a three dimensional profile and is desirably in the form of a depression or indentation (i.e. concave feature) or alternatively a protrusion (i.e. convex feature), formed in the at least one of the side panels during blow-moulding and configured to strengthen or reinforce the side panel. Thus, in a preferred embodiment, the deformation may comprise an indentation or recess formed in an outer surface of the at least one side panel. For example, the deformation is preferably a curved concave shape or so-called 'scallop' shape. The deformation may alternatively be more like a groove, furrow or corrugation.

[0021] Preferably, the at least one deformation is formed in the at least one side panel at a location intermediate of, and preferably approximately equidistant from, two adjacent corners of the base panel. The at least one deformation is preferably generally elongate in the vertical direction. It may have any of a variety of shapes or profiles.

[0022] In a preferred embodiment, the base edge of each side panel curves with a base radius in a plane generally perpendicular to a primary face of the side panel. The base radius of the base edge is preferably in the range of about 3 mm to about 20 mm, and more preferably in the range of about 5 mm to about 12 mm.

[0023] In a preferred embodiment, the at least one deformation is formed in the base edge of the respective side panel, and preferably commences or has a lowermost extent in the base edge (i.e. without extending into the base panel), and extends upwardly from the base edge. That is, the deformation in each of the side panels is typically located in or extends into the base edges of the side panel. The deformations may be integral with the base perimeter but preferably do not extend into the rectangular base. That is, the deformation(s) is/are preferably substantially entirely or entirely located in and/or upwardly of the base edge of the side panel - i.e. in and/or upwardly of that region at which a side panel transitions to the base of the container. This may thus differentiate the container of the present invention from analogous bottles or containers of the prior art which often have deformations extending into the base.

[0024] In a preferred embodiment, the at least one deformation has a height, a width and a depth. The height is preferably at least equal to a base radius of the base edge, more preferably in the range of one to three times the base radius, and most preferably one to two times the base radius. The depth is preferably at least equal to about 0.1 times the base radius, and more preferably at least 0.15 times the base radius; e.g. the depth is, for example, in the range of 0.2 to 0.5 times the base radius. The width of the deformation is preferably in the range of about 0.5 to about 2 times the base radius.

[0025] In a preferred embodiment, at least about 10% of the volume of the deformation is located in the base edge of the respective side panel, and preferably up to about 25 %

of the volume of the deformation is located in the base edge.

[0026] Preferably the deformation is located where the plastic of the container panels or walls is naturally thick. Typically, the plastic of the container panels or walls is thick at a distance from the corners of the container. As such, each deformation is preferably located spaced from or intermediate of the corners of the container, more preferably equidistant from a pair of adjacent corners of the base panel.

[0027] In a preferred embodiment, the at least one side panel may include a plurality of deformations. That is, each side panel may include two, three or even more deformations, and these deformations need not necessarily all have the same shape.

[0028] Without wishing to be bound by theory it is believed that the deformation tends to interrupt the bottom radius of the container and resist rolling of the base in response to vertical load.

[0029] The location of the deformation in the side panel takes advantage of the natural flow of the molten plastic during the blow moulding process. The molten plastic naturally thins in proximity to the corners of the base of the mould. In the present invention, the deformations are positioned mid-way between corners in regions of the side panels that are naturally thicker due to their close proximity to the molten parison. This also allows minimum necessary thickness limits to be maintained in the corners and makes use of geometric features that provide strength in areas where the material is thicker.

[0030] By comparison, prior art containers have deformations located at the corners of the base, interrupting the flow of molten plastic, creating thinner and weaker areas in the base corners and negating the strength benefits imparted by other geometric features.

[0031] Thus, the present invention aims to strike a balance between the thickness of the container plastic and the geometry of the container. During manufacture, the molten plastic is allowed to flow towards the corners as smoothly as possible, by locating geometric features such as the deformations where the plastic is naturally thickest.

[0032] In another aspect of embodiments described herein there is provided a method of blow moulding a plastic container of the present invention, the method comprising the steps of: - locating a parison formed of a thermoplastic resin within a mould, preferably between two halves of a mould, and closing the mould, wherein the interior surfaces of the mould define a desired shape of the container, - heating and inflating the parison to contact the interior surfaces of the closed mould, - allowing the thermoplastic resin to solidify, and

- opening the mould and ejecting the solidified thermoplastic resin in the shape of the container, wherein the container has at least one deformation in at least one side panel, preferably two, three or four side panels.

[0033] In a preferred embodiment, the method of blow-moulding the plastic container described above is an extrusion blow-moulding method comprising steps of: - heating a thermoplastic resin to a molten state, and - extruding the molten resin through a die head to form a parison, before the step of locating the parison within the mould.

[0034] Thus, in at least one embodiment, the method of blow-moulding the plastic container of the invention described above comprises steps of: - heating a thermoplastic resin to a molten state, - extruding the molten resin through a die head to form a parison, - locating the parison between two halves of a mould then closing the mould halves together, the interior surfaces of the mould defining the shape of the container, - inflating the parison to contact all interior surfaces of the closed mould, - allowing the plastic to solidify, and - opening the mould halves and ejecting the solidified plastic in the shape of the container having at least one deformation in at least one side panel, preferably two, three or four side panels.

[0035] In one embodiment the container of the present invention has a liquid, brimful capacity of 2026 to 2064 mIs per ASTM D2911, a weight of 36 to 43 grams and height of 261 to 263 mm. The footprint is square, typically between 95 x 95 mm and 97 x 97 mm. These dimensions would usually be recognised by consumers as the size of container in which they buy 2 litres of milk. However the person skilled in the art will recognise that the present invention is not limited to milk containers and could be applied to any convenient volume container for holding a range of materials.

[0036] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0037] In essence, embodiments of the present invention stem from the realization that including a deformation in two or more side panels, instead of the base panel, provides a container of improved structural integrity with high top load resistance and less prone to base rolling. When the container is under vertical load, this design feature can reduce vertical deformation of the container with less base radius roll and thus transfers the load to the vertical faces with greater (better) top load strength. This further enables a reduction in container weight while retaining top load strength.

[0038] Advantages provided by the present invention comprise the following: • vertical load force applied to the container is imparted to the side panels so the container base transition radius is less prone to rolling, * the container has a stiffer, more resilient structure, * the container is lightweight, but crush resistant, * the container is better able to withstand loads applied during manufacture, such as loads applied during the filling and capping process, and * less blowouts (thin spot holes) in the moulding production due to the avoidance of forming thin spots.

[0039] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, in which like reference signs designate like parts and in which:

FIG. 1 illustrates a perspective view of a lower part of a conventional container;

FIG. 2 illustrates a contour map of the material thickness of the lower part of the container depicted in FIG. 1;

FIG. 3 illustrates the load-reaction behaviour of the base edge of the container depicted in FIG. 1;

FIG. 4 illustrates the manner in which the base edge of the container depicted in FIG. 1 deforms when loading is applied through the vertical container side walls;

FIG. 5 illustrates deformations of a container base that includes scallop shaped deformations, when loading is applied through the vertical container walls;

FIG. 6 illustrates in perspective view, the base edges of a container according to the present invention that includes concave scallop shaped deformations;

FIG. 7 illustrates a top view of the container of FIG. 6 showing the top surface including the port and handle;

FIG. 8 illustrates a bottom view of the container of FIG. 6, showing the base edges that includes scallop shaped concave deformations and a substantially planar base panel.

FIG. 9 illustrates a side view of the container of FIG. 6 showing the side edge and handle;

FIG 10 is a plot of a load-displacement curve illustrating top applied load (kg) against vertical displacement (mm) for the container of FIG. 6; and

FIG. 11 is an isometric view of another embodiment of a container according to the present invention.

[0041] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate particular embodiments of the invention and together with the description serve to explain the principles of the invention. Other embodiments of the invention and many of the attendant advantages will be appreciated as they become better understood with reference to the following detailed description.

[0042] The reference signs used to describe various features of the embodiment of the container of the present invention depicted in the drawings are set out in the following table:

1 container body 10 upperbody 2a,2b,2c,2d side panels 11 vertical side edge of side panels 2b/2c 3 handle 12 vertical side edge of side panels 2c/2d 4 opening 13 vertical side edge of side panels 2d/2a base panel 6a,6b,6c,6d base edge of 15 base perimeter side panels 2a-2d 7 base ridge 16a,16b,16c,16d corners 8a,8b,8c,8d concave deformation of 17a,17b,17c,17d base radius side panels 2a-2d 9 vertical side edge of 18a,18b,18c,18d pair of concave side panels 2a/2b deformations in side panels 2a-2d

DETAILED DESCRIPTION

[0043] In general, for plastic containers produced by blow moulding the plastic thickness is a function of the amount of stretch in the molten plastic parison. As mentioned above, with reference to the article by Ryan & Dutta, particular effects are associated with blowing into a corner from a round tube of molten plastic (parison).

[0044] An example of typical geometry as outlined in the Ryan & Dutta article would be a section through the base of a container as depicted in FIG. 1. To achieve an acceptable level of thickness in the corners of the container a relatively large corner radius would be required. The minimum thickness permissible must be sufficient to resist crush in the thin regions. For lighter weight containers larger corner radii may be required.

[0045] Utilising the equations outlined in Ryan & Dutta, a contour map of the material thickness in an illustrative container can be produced as shown in FIG. 2. The contour map shows thicker regions in the centres of the main panels (300) and the base edge intermediate adjacent corners (200). The thickness reduces towards the corners with the minimum thickness evident in the diagonal corners (100a, 100b, 100c, 100d).

Loading of Containers

[0046] An important loading requirement for a milk container is associated with the vertical compression strength. Sufficient vertical compression strength is required to resist vertical forces imparted by filling and capping loads and/or due to vertical stacking.

[0047] The load-reaction behaviour of the base region of a typical container of the prior art is shown in FIG. 3. FIG. 3 illustrates a force applied through vertical container walls and the resultant reaction occurring at the contact line through the tangent point of the base radius. For lighter weight bottles minimum thickness limits require a larger base perimeter radius.

[0048] A consequence of this is that there is a significant amount of offset through the centre of the base radius in a bending moment around the top edge of the radius. The larger the radius, the greater the moment. The total reaction load is calculated from the perimeter of the region in contact with the floor. The resultant stress in the material is the total reactionary force/thickness x perimeter (F/A). The resultant deflection and illustration of the manner in which the side panel deforms from the loading is shown in FIG. 4.

[0049] The force applied to the upper edge at A results in the base radius rolling. The inner radius edge at B is then under radial compression due to the lateral displacement generated by the base rotation. This rolling promotes a pinching effect at the diagonal corners of the base with final corner crush. Alternatively, a localised buckle could occur in the base radius. The peak vertical deformation before the load is taken by the vertical wall is the dimension from the floor to position A.

[0050] The present invention reduces the amount of base radius roll by introducing a structural design feature in the form of a three-dimensional profile feature or deformation (8a, 8b, 8c, 8d), such as a scallop or corrugation (or multiple scallops or corrugations), in the vertical side panel. This design feature is positioned to reduce the amount of vertical deflection in the base radius and thus acts to transfer the load to the vertical faces. The deformation(s) is/are positioned in the side panel, not the base panel, in such a manner that it/they does/do not reduce the contact of the base perimeter (15) with the floor. FIG. 5 illustrates the difference in deflection generated in a container according to the invention (e.g. as shown in FIG. 6). That is, the position C where the tapered face (dashed line) meets the base radius results in less vertical deflection. Although this structural feature could potentially cause localised thinning of the plastic of the side panel, it can be viable if located in regions that are naturally thicker than necessary minimum thickness limits.

Preferred Embodiment

[0051] An example of a container according to the invention is shown in FIG. 6. In this case, the container has a container body 1 comprising a base panel 5 having four corners and a rectangular base perimeter 15, and four generally rectangular side panels 2a, 2b, 2c, 2d which extend upwards from the base panel 5 to form sides of the container body 1. Each side panel (2a, 2b, 2c, 2d includes a respective base edge 6a, 6b, 6c, 6d that joins integrally with the base panel 5 along the rectangular base perimeter 15, opposite vertical side edges that are integrally joined with respective adjacent side panels, and a top edge, wherein the top edges of each of the side panels 2a, 2b, 2c, 2d merge to form an upper body 10 that defines an outlet 4 of the container. Each of the side panels 2a, 2b, 2c, 2d includes a deformation (8a, 8b, 8c, 8d) having a three-dimensional profile in the form of a depression or indentation (i.e. concave feature) configured to strengthen or reinforce the side panel. Thus, each deformation (8a, 8b, 8c, 8d) comprises an indentation formed in an outer surface of the respective side panel (2a, 2b, 2c, 2d) in the shape of a scallop. The scalloped deformations (8a, 8b, 8c, 8d) are positioned intermediate adjacent corners of the base (5) approximately centrally of the base edge (6a, 6b, 6d, 6d) of the side panels

(2a, 2b, 2c, 2d) to take structural advantage of the beam of thicker material that runs up the centre of the side panels. The container of FIG. 6 is further illustrated in a side view (FIG. 9) a bottom view (FIG. 8) and a top view (FIG. 7).

[0052] Fig. 9 depicts an x-axis and a y-axis for this embodiment of the container, which is taller than it is wide. The longitudinal axis of the container in this embodiment is parallel with the y-axis when the container is vertical, such as during storage in a refrigerator. For purposes of description herein, the terms "upper," "lower," "right," "left," "rear," "front," "vertical," "horizontal," "interior," "exterior," and derivatives thereof shall relate to the invention as oriented in FIG. 9. However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary.

[0053] FIGS. 6 to 9 show the plastic container body (1) having four rectangular side panels (2a, 2b, 2c, and 2d), each including a base edge (6a, 6b, 6c and 6d). Pairs of adjacent side panels (2a, 2b, 2c, and 2d) share vertical side edges. That is, panels 2a and 2b meet at vertical side edge 9; panels 2b & 2c meet at vertical side edge 11; panels 2c and 2d meet at vertical side edge 12; panels 2d and 2a meet at vertical side edge 13. Panel 2b includes the label face (14) to which is adhered the label for identification of the contents of the container, relevant specifications and vendor details. The top of the side panels (2a, 2b, 2c, 2d) merge to form the upper body (10) including a threaded neck that defines an outlet (4) for the container. A handle (3) is integral with the upper body (10). The neck is typically threaded to receive a lid, for example, a 38 mm snap screw lid.

[0054] The base edges (6a, 6b, 6c, 6d) of the four rectangular side panels (2a, 2b, 2c, 2d) are joined to and are integral with the periphery of the base panel (5) via a base or fillet radius. The base panel (5) has a concave diagonal seam ridge (7) that extends from a first corner to a second corner. In this embodiment, the base edges (6a, 6b, 6c, 6d) each include a corresponding deformation (8a, 8b, 8c, 8d) that is generally scallop shaped. The deformations (8a, 8b, 8c, 8d) do not extend into the area defined by the base panel (5), that is, they form part of, but do not extend past the base perimeter (15). The deformations in the shape of scallops (8a, 8b, 8c, 8d) are positioned in the centre of the side panels (2a, 2b, 2c, 2d) to take structural advantage of the thickest part of the panels. When the base panel (5) is positioned flat upon a surface such that the container (1) stands upright, the amount of contact between the base perimeter (15) and the surface is not reduced by the presence of the deformations.

[0055] Each scallop-shaped deformation (8a, 8b, 8c, 8d) seen in FIG. 6 and FIG. 9 is generally elongate and has a generally 'tear-drop' or 'pear' shape in which it is wider at the bottom and tapers upwardly to be narrower at the top. The deformation could, however, have a range of shapes and could be generally straight-sided. Each deformation (8a, 8b, 8c, 8d) has a height, a width, and a depth. The height (i.e. vertical extent) is at least equal to the base radius of the base edge (6a, 6b, 6c, 6d), and is preferably in the range of about one to three times the base radius, e.g. about double the base radius. The depth of each deformation (8a, 8b, 8c, 8d) - i.e. into the indentation or recess - is at least about 0.2 times the base radius, and the width of the deformation (i.e. across the side panel) is in the range of 1 to 2 times the base radius. The base radius of the base edge (6a, 6b, 6c, 6d) in this embodiment is in the range of about 6 mm to about 10 mm; e.g. about 8 mm.

[0056] The structural integrity of the container of the present invention is illustrated by the load-displacement curve of FIG. 10 generated from a plot of top applied load (y-axis; kg) against vertical displacement (x-axis; mm) for three 2 litre blow-moulded milk containers of shape analogous to the container of the present invention. The steeper curves with lower top applied load (y-axis) correspond to two prior art containers comprising 37 grams and 41.5 grams respectively of plastic. The remaining curve with higher (better) top applied load (y-axis) corresponds to a container of the present invention having a single deformation in each side panel as per the depiction in Fig. 6.

[0057] The comparison of the various structural responses was carried out using computer simulation (Finite Element analysis). Finite Element Analysis is a good way to compare different structures because small differences caused by process variability (e.g. humidity, blow rate operator etc.) can be removed or ignored. Warpage, typically in the form of cooling or shrinkage from the differing thickness was included in the analyses. So, when simulations are carried out and comparisons are made, they are representative of a typical moulded article. Warpage simulation in the finite element analysis model is important as it adds a geometry defect for determination of buckle points and realistic representation of the predicted failure mode and failure load.

Further Embodiment

[0058] Another example of an embodiment of a container according to the present invention is shown in an isometric view in FIG. 11. The shape of the container is similar to the container shown in FIG. 6 except that in this case, there is a pair of scallop shaped deformations (18a, 18b, 18c, 18d) positioned intermediate adjacent corners, in the centre of the base edge (6a, 6b, 6d,6d) of each of the side panels (2a, 2b, 2c, 2d) to take structural advantage of the beam of thicker material that runs up the centre of the side panels. In a further variation, each of the side panels (2a, 2b, 2c, 2d) could optionally include three or more deformations (18a, 18b, 18c, 18d), and these need not necessarily all have the same shape.

[0059] Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by persons of ordinary skill in the art that a variety of alternative and/or equivalent implementations exist. It should be appreciated that each exemplary embodiment is an example only and is not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0060] It will also be appreciated that the terms "comprise", "comprising", "include", "including", "contain", "containing", "have", "having", and any variations thereof, as used throughout this document are, unless the context requires otherwise, intended to be understood in an inclusive (i.e. non-exclusive) sense, such that the process, method, device, apparatus, or system described herein is not limited to those features, integers, parts, elements, or steps recited but may include other features, integers, parts, elements, or steps not expressly listed and/or inherent to such process, method, device, apparatus, or system. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects. In addition, reference to positional terms, such as "lower" and "upper", used in the above description are to be taken in context of the embodiments depicted in the figures, and are not to be taken as limiting the invention to the literal interpretation of the term but rather as would be understood by the skilled addressee in the appropriate context.

[0061] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures. For example, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface to secure wooden parts together, in the environment of fastening wooden parts, a nail and a screw are equivalent structures.

Claims (13)

1. A blow-moulded plastic container having a body defining an internal volume of the container, the body comprising: a base panel having four corners and a rectangular base perimeter; and four generally rectangular side panels extending upwards from the base panel to form sides of the container body, wherein each side panel includes: a base edge that joins integrally with the base panel along the rectangular base perimeter, two vertical side edges that are integrally joined with respective adjacent side panels, and a top edge, wherein the top edge of each of the side panels merge to form an upper body portion that defines an outlet of the container; wherein at least one of the side panels, and preferably two, three or four of the side panels, includes at least one integral deformation.

2. A blow-moulded plastic container according to claim 1, wherein the at least one integral deformation has a three-dimensional profile, preferably in the form of a depression or indentation (i.e. concave feature) or a protrusion (i.e. convex feature) formed in the at least one of the side panels during blow-moulding and configured to strengthen or reinforce the side panel.

3. A blow-moulded plastic container according to claim 1 or claim 2, wherein the at least one deformation is formed in the at least one side panel at a location intermediate of, and preferably approximately equidistant from, two adjacent corners of the base panel.

4. A blow-moulded plastic container according to any one of the preceding claims, wherein the base edge of each side panel curves with a base radius in a plane generally perpendicular to a primary face of the side panel, wherein the at least one deformation is formed in the base edge of the respective side panel, and preferably commences or has a lowermost extent in the base edge (i.e. without extending into the base panel), and extends upwardly from the base edge.

5. A blow-moulded plastic container according to any one of the preceding claims, wherein the at least one deformation has a height, a width and a depth, wherein the height is at least equal to a base radius of the base edge, preferably in the range of one to three times the base radius, and more preferably one to two times the base radius, and wherein the depth is at least equal to about 0.1 times the base radius, preferably at least 0.15 times the base radius.

6. A blow-moulded plastic container according to claim 5, wherein the width of the at least one deformation is in the range of 0.5 to 2 times the base radius.

7. A blow-moulded plastic container according to any one of claims 4 to 6, wherein the base radius of the base edge is in the range of about 3 mm to about 20 mm, and preferably about 5 mm to about 12 mm.

8. A blow-moulded plastic container according to any one of claims 4 to 7, wherein at least about 10% of the volume of the deformation is located in the base edge of the side panel, and preferably up to about 25 % of the volume.

9. A blow-moulded plastic container according to any one of the preceding claims, wherein the base edge comprises thicker material than the remainder of the side panels and the deformation is located in said thicker material.

10. A blow-moulded plastic container according to any one of the preceding claims, wherein, when the container is upright with the base perimeter contacting a surface, the amount of contact of the base perimeter with the surface is not reduced by the presence of the deformation(s).

11. A method of blow-moulding a plastic container of any one of claims 1 to 10, the method comprising steps of: - locating a parison formed of a thermoplastic resin within a mould, preferably between two halves of a mould, and closing the mould, wherein the interior surfaces of the mould define a shape of the container, - inflating the parison to contact the interior surfaces of the closed mould, - allowing the thermoplastic resin to solidify, and - opening the mould and ejecting the solidified thermoplastic resin in the shape of the container, wherein the container has at least one deformation in at least one side panel, preferably two, three or four side panels.

12. A method of blow-moulding a plastic container according to claim 11, wherein the method is an extrusion blow-moulding method comprising steps of: - heating a thermoplastic resin to a molten state, and - extruding the molten resin through a die head to form a parison, before the step of locating the parison within the mould.

13. A method of blow moulding the plastic container of any one of claims 1 to 10, the method comprising steps of: - heating a thermoplastic resin to a molten state, - extruding the molten resin through a die head to form a parison, - locating the parison between two halves of a mould then closing the mould halves together, the interior surfaces of the mould defining the shape of the container, - inflating the parison to contact all interior surfaces of the closed mould, - allowing the plastic to solidify, and - opening the mould halves and ejecting the solidified plastic in the shape of the container having at least one deformation in at least one side panel, preferably two, three or four side panels.