EP3154864A1

EP3154864A1 - Bottle and base

Info

Publication number: EP3154864A1
Application number: EP15727405.1A
Authority: EP
Inventors: Satvinder DHILLON; Christopher Clarke; Paulo Jose Ferreira CORREIA
Original assignee: Logoplaste Innovation Lab Lda; Lucozade Ribena Suntory Ltd
Current assignee: Suntory Holdings Ltd
Priority date: 2014-06-12
Filing date: 2015-06-08
Publication date: 2017-04-19
Anticipated expiration: 2035-06-08
Also published as: PL3154864T3; ES2787648T3; GB2527171A; EP3154864B1; DK3154864T3; WO2015189127A1; PT3154864T; GB201503354D0; GB2527171B

Abstract

A reinforced base(l) for a plastics bottle (12), having an annular rim (2)upon which the bottle rests; a concave dome (3) bounded by the rim, with the concavity facing the outside of the bottle body. The dome comprises three regions: (i) an outer (4), annular region, adjacent the rim; (ii) an in inner (5), circular region, at the centre of said dome; and (iii) a middle (6), annular region, between the outer and inner regions. A number of spaced apart geometrical configurations (7) in the form of closed polygonal or circular formations are located on middle annular region of the dome, whereas the outer annular region, which comprises at least 7.5% of the area of the dome, is free of said geometrical configurations. Variants with convex wall portions are also included.

Description

Bottle and Base

Field of the Invention

The present invention relates to improvements in bottles or flasks, in particular, those made of plastic material, obtained by Injection Stretch Blow Moulding (ISBM) or other similar techniques intended to contain liquids under pressure, their bodies ending at its lower part by a reinforced bottom and at its top portion by an outlet for pouring the liquid contents, which can be plugged. The invention relates in particular to improvements in the base of such bottles and also in the wall structure.

Background and Prior Art

It has been found in practice that the bottles or flasks intended to contain liquid and subject to very high total pressures of the prior art either present very high wall thicknesses, which increases the costs of raw materials and reduces the production rate, or constrain the geometry of the wall of its body. Moreover, it was found that the greater the heat dissipation capability from the bottom of the bottles or flasks the greater will be the production rate of the bottles or flasks.

It is very important, for reasons of economy and minimisation of environmental impact, to reduce as far as possible the amount of material used to produce plastic bottles, especially those destined to contain beverages and that are generally considered to be for single use before recycling. However, the bottles still need to be able to perform their function though the rigours of the processing systems to which they will be subjected. In many industries, including the beverage manufacturing industry, bottles are often filled under vacuum conditions to increase the fill rate of the containers on a production line. A vacuum (or partial vacuum) is created within the bottle, and liquid can then be dispensed into the evacuated interior, allowing rapid filling without needing to simultaneously allow air to escape. For traditional glass bottles, the requirement for the bottles to be able to withstand this pressure differential during filling is easily met. For plastic bottles, and especially where it is desired to minimise the amount of material used to produce them, this requirement poses more of a challenge.

In addition, to give the bottles more structural stability when being handled and transported, it is common in the industry to pressurise the bottles after filling to make the filled pack more rigid in the face of external deformation forces. For non-carbonated beverages, this is often carried out by introducing a small amount of liquid nitrogen into the bottle along with the contents, which leads to a pressure increase as the liquid nitrogen increases in temperature. Accordingly, the bottles also have to be able to withstand pressure within them, after filling.

It will be appreciated that the ability of a container, such as a bottle, to withstand vacuum and overpressure is not only dependent on the geometrical configuration of the bottle and materials of construction, but also on its absolute size. As bottle sizes increase for a given geometrical form, they become less able to withstand such pressure differentials. As a result, there is more design freedom in the shape of smaller bottles (e.g. those typically designed to hold less than about one litre of liquid) than there is for larger bottles (e.g. one litre and above). Whilst smaller bottles can be designed with so-called "champagne" bases (i.e. those having a shallow concave pontil, and an uninterrupted rim), these cannot currently be used for larger bottles that are manufactured in plastic, and a so-called petaloid base structure is often employed, or a reinforcing ring is placed around the base of the bottle, further increasing costs and environmental impact. However, for some uses, petaloid bases do not have the required aesthetic appeal.

It is known to introduce reinforcing structures (e.g. ribs) in the side wall of plastic bottles to make them more able to withstand vacuum filling operations, and a plurality of such circumferential ribs are typically disposed in a spaced-apart relationship down the length of the bottle wall.

US Patent 3468443 describes a plastic disposable bottle having a base adapted to resist internal pressure.

It is therefore amongst the objects of the present invention to provide a means by which champagne-type bases may be used on larger plastic bottles, whilst withstanding the overpressure required during production and transport. It is also amongst the objects of the invention to be able to reduce the amount of material used in manufacture of the bottle, thereby reducing costs and environmental impact whilst retaining the desired technical properties.

The invention also has amongst its aims a reduction in raw material costs, an increased production rate and making the body geometry independent from the bottom geometry.

Therefore, the reinforced bottom according to the present invention has a configuration that allows a reduction the wall thickness of the bottle or flask. The reinforced bottom according to the present invention also allows an increase in the bottle or flask production rate, since the configuration of the reinforced bottom allows a greater heat dissipation and, therefore, a higher manufacturing rate is obtained.

The reinforced bottom also allows complete freedom of the geometry of the bottle or flask body wall. This is especially so when the improved side wall features of the bottle are simultaneously employed.

Summary of the Invention

Accordingly, the invention provides a reinforced base for a plastics bottle, said base comprising: (a) an annular rim upon which the bottle rests; (b) a concave dome bounded by said rim, with the concavity facing the outside of the bottle body; said dome comprising three regions: (i) an outer, annular region, adjacent said rim; (ii) in inner, circular region, at the centre of said dome; and (iii) a middle, annular region, between said outer and inner regions; (c) a plurality of spaced apart geometrical configurations in the form of closed polygonal or circular formations located on said middle annular region of the dome; wherein said outer annular region comprises at least 7.5% of the area of the dome, and is free of said geometrical configurations.

The provision of the polygonal or circular formations add to the strength of the dome structure, whilst retaining the rim required of a champagne-style bottle base. Keeping the formations away from the abutment of the rim and the dome prevents deformation of the rim during manufacture, and when the bottle is under pressure.

Particularly preferred ranges for the area of each of the dome regions (as a percentage of the total dome area) are as follows:

Inner region: At least 2.5%, up to a maximum of 10%, preferably about 5%.

Middle region: At least 60%, up to a maxi8mum of 90%, preferably about 75%.

Outer region: At least 7.5%, up to a maximum of 30%, preferably about 30%.

Preferably said inner region of the dome comprises between 2.5% and 10% of the area of the dome, and is also free of said geometrical configurations. By keeping this area free of the geometrical configurations, centring of the bottle pre-form in the mould prior to moulding is facilitated. In any aspect of the invention, it is particularly preferred that said geometrical configurations occupy at least 30% of the area of said middle region of the dome. Provision of this density of geometrical configurations makes it easier to provide the required additional strength to the dome of the bottle. In further preferred embodiments, the configurations occupy at least 35%, 40%, 45%, 50%, 55% or even 60% of the area of said middle region of the dome.

In any aspect of the invention it is preferred that each of said geometrical configurations is in the form of a tessellating regular polygon. This makes it easier to pack the configurations onto the surface of the dome. There are only three tessellating regular polygons: the triangle, square and hexagon. Hexagonal polygons are particularly preferred, as they have the largest internal angle, of 120°, as opposed to 60° and 90° for triangles and squares respectively, which therefore reduces stress in the polymer material.

Such geometrical configurations may be formed by e.g. including wall features separating then polygonal or circular features. However, it is particularly preferred that said geometrical configurations comprise, or consist of, an indented region. In this way, the wall thickness of the base can be kept more even across the base of the bottle, and less material is used in its construction.

It is particularly preferred that the depth of said indented region is at least 0.5mm.

In other configurations, said geometrical configuration comprises a region surrounded by a wall.

In any aspect of the invention, it is preferred that the polygonal or circular formations are so sized that a circle enclosing each polygonal or circular formation has a diameter of less than 50% of the width of the middle annular region. In this way, at least about three of the formations may be spaced apart in an offset fashion over the radius of the middle annular region, allowing forces to be spread between the formations. As for a minimum size, it is preferred that said enclosing circle is no less that about 10% or 20% or 30% of the width of the middle annular region. For sizes smaller than this, the additional structural strength is low, but the likelihood of stress formation increases.

In any aspect of the invention it is particularly preferred that said rim is of a curved profile, having a radius of curvature of at least 1mm. This further reduces the stress on the base structure when exposed to pressure differentials. By contrast, the presence of a sharp corner, or a flat rim can readily lead to deformation under pressure.

Also included within the scope of the invention is a plastics bottle comprising a base as described herein.

Preferably, said bottle comprises a wall extending from the rim of the base to a neck region at the top of the bottle; wherein said wall is provided with a circumferential reinforcement to resist deformation of the bottle under vacuum and said wall is of convex cross-section between said reinforcement and said rim.

An appropriate degree of convexity may be determined by the skilled address by trial and error, in order to provide a balance between the vacuum-resisting properties of the convex wall portion, and the ease of moulding. Clearly, a smaller radius of curvature would lead to increased resistance to vacuum forces, but would produce a more "bulbous" shape to the bottle wall, which might be more difficult to mould, and might not suit any aesthetic requirements. As a guide, the minimum radius of curvature should be greater than the distance between said first reinforcement and the rim. A radius equal to half such a distance would give a wall section that meets the rim and reinforcement at right angles; a smoother transition is to be preferred. Where the distance between the rim and the first reinforcement is given by L, and the radius of curvature is r, it is preferable that r>0.5L, such as r>0.6L, or r>0.8L or r>lL. By preference r may be up to about 2L, i.e. within the range 0.5L<r<2L.

More preferably, said wall is provided with a second such circumferential reinforcement and wherein said wall is of convex cross-section between said first and second reinforcements.

Again, an appropriate degree of convexity may be chosen as above, related to the distance between the two circumferential reinforcements (i.e. defining L to be this separation distance).

Figure 13A-E illustrates a range of convexities that might be employed for the wall portions 16, 19 described in more detail below. The radius of curvature is given by r, and the distance between either end of the wall portion is given by L. The ratios are as follows:

Fig 13 A: r = 0.5 L

13B r = 0.6 L

13C r = 0.8 L 13D: r = 1.0 L

13E: r = 2.0 L

Such a reinforcement could comprise a thickening of the bottle wall, but, in either case, it is further preferred that said reinforcement is in the form of a groove, or valley in the bottle wall. This provides the required structural stability by virtue of the geometry without the need for additional plastics material for manufacturing the bottle.

It is particularly preferred that a maximum of two or three such reinforcements is employed on the bottle. The provision of the convex wall cross-sections mean that no more than this number is normally required, further reinforcements merely adding to the cost and complexity of the design.

For any such bottle, it is particularly preferred that the capacity of the bottle is one litre. It is envisaged that this base design will be appropriate for bottles having a capacity of at least 1 , or 1.5, or 2, or 2.5 or 3 or even 5 litres.

Also included within the scope of the invention is a reinforced base for a plastics bottle, or a bottle comprising such a base substantially as described herein with reference to and as illustrated any appropriate combination of the accompanying drawings.

Brief Description of the Figures

The invention will be described with reference to the attached drawings, in which:

Figure 1 is a cross-sectional view of a reinforced bottle base of the invention;

Figure 2 is an enlarged view of a portion of Figure 1 ;

Figures 3-7 are plan views of the underside of reinforced bottle bases of the invention;

Figures 8 and 9 are elevation and cross-sectional views of a bottle of the invention;

Figures 10A-10B are perspective views of reinforced bottle bases of the invention;

Figures 10C-10F are perspective views of reference alternative reinforced bottle bases;

Figure 11 is a perspective view of the bottle or flask reinforced bottom in accordance with an embodiment of the present invention;

Figure 12 is a plan view of the reinforced bottom of Figure 12; and

Figure 13 illustrates a range of convexities for a portion of side wall of a bottle of the invention. Description of Preferred Embodiments

Figure 1 illustrates, in cross-sectional view, a reinforced base, generally indicated by 1, for a plastics bottle, according to an embodiment of the invention. The side walls of the bottle are also illustrated. Tick lines extending from the bottle and base delineate the various sections of the bottle and base. The base 1 has an annular rim 2 on which the bottle can rest, in use, and which connects the wall 8 of the bottle to the rest of the base. The base 1 is provided with a concave dome 3 with the concavity facing the outside of the bottle. The dome 3 comprises three regions: an outer, annular region 4, that lies adjacent the rim 3; an inner, circular region 5, at the centre of the dome; and a middle, annular region 6 that lies between the outer 4 and inner 5 regions. The middle region 6 is provided with a plurality of spaced apart geometrical configurations 7 that serve to reinforce the dome 3.

A section of the middle region 6, bounded by the dashed circle, is illustrated in greater detail in Figure 2. It can be seen that, in this embodiment, the geometrical configurations 7 are in the form of indented regions 9. The indentations have a depth illustrated by the arrows A-A'. In preferred embodiments of the invention, the depth of the indentations is at least 0.5mm, typically between about 0.5mm and 3mm, for example about 1mm.

Figure 3 is a plan view of the underside of a reinforced bottle base 1 of the invention to illustrate the various regions of the structure. The figure illustrates the position of the rim 2, as well as the outer 4 and middle 6 annular regions, and the central circular region 5. The geometrical configurations are not illustrated, for clarity. It should be stressed that the regions do not denote physically separate parts of the bottle base, but merely serve to indicate where certain structural features should be located.

Figure 4 illustrates, in plan view, the underside of a reinforced bottle base 1 of the invention with geometrical configurations 7 located on the middle annular region 6. In this embodiment, the configurations 7 are circular in shape, and are all of the same size. It can be seen that the outer annular region 4 is free of geometrical configurations. Some areas 10 of the middle annular region 6 are also left free of geometrical configurations, and these may be conveniently used for placement of indicia, such as recycling information, mould numbering, and manufacturer's logos.

Figures 5 and 6 illustrate, in plan view, the underside of reinforced bottle bases 1 of the invention. The outer 4, inner 5 and middle 6 regions of the dome are indicated, as well as the rim 2 of the bottle base. These embodiments are of bottles that also have convex wall portion 9, and this can also be seen in the illustrations. Like elements to embodiments described above are similarly numbered.

In Figure 5, geometrical configurations 7 in the form of square indentations are employed, whilst in the embodiment of Figure 6 the configurations are circular indentations.

Figure 7 illustrates, again in plan view, the underside of a particularly preferred embodiment of a reinforced base 1 of the invention. Again, like elements to those already described are similarly numbered. In this embodiment, the geometrical comfigurations 7 are in the form of regular hexagonal indentations, within the centre region 5 of the dome the position of the injection mould point 11 for the bottle pre -form can also be seen.

Figures 8 and 9 illustrate, in elevation and cross-section respectively, an embodiment of a bottle of the invention, generally indicated by 12. The bottle 12 is provided with a reinforced base 1 , according to the invention and additional wall features to resist deformation of the bottle under vacuum. The bottle 12 is provided with a first circumferential reinforcement 13 located approximately one sixth of the way up the bottle from the base 1 to the neck region 14. In this embodiment, the reinforcement is in the form of a circumferential indentation, or groove 15 in the side wall 8 of the bottle.

The portion 16 of the wall 8 that lies between the rim 2 and the first circumferential reinforcement 13 is of a convex, bulbous shape, forming an arched structure. This allows that portion of the wall to resist deformation of the wall in the face of an internal vacuum in the bottle. This allows fewer reinforcements to be used that would otherwise be required to provide equivalent strength in the face of vacuum forces, allowing for a more simplified mould, and greater opportunities for label placement.

In this embodiment, a second such circumferential reinforcement 17 is also provided, approximately half way between the base 1 and the neck region 14 of the bottle 12. Again, this reinforcement is in the form of a circumferential indentation, or groove 18 in the side wall 8 of the bottle.

The portion 19 of the wall 8 that lies between the first 13 and second 17 circumferential reinforcements is also of a convex, bulbous shape, forming a second arched structure to resist deformation in the face of an internal vacuum.

The upper region 20 of the bottle is of conical shape. Performance of Reinforced Base

In order to demonstrate the performance of the reinforced base, finite element analysis (FEA) was carried out to determine stresses within the bottle and base structure in the face of internal pressure.

Six models of base were compared, two of which were embodiments of the present invention; the remaining four were of more traditional design. The designs are illustrated in Figures 10A-F.

Figure 10A is a model of a reinforced base 1 of the invention having regular hexagonal indentations disposed over the middle 6 and central 5 regions of the dome 3, whilst the outer annular region 4 is free of such geometrical configurations.

Figure 1 OB is a model of a reinforced base 1 of the invention having regular hexagonal indentations disposed only within the middle region 6 of the dome 3.

Figures 10C-10F are not embodiments of the invention, but represent alternative designs. The base of Figure IOC has a concave dome region 3 within which is a secondary concave dome 20 of smaller dimension. Six radial valleys 21 are located on the surface of the dome 3, each of which communicates at one end with the secondary concave dome 20, and ends short of the rim 2 at the other end. A further six radial valleys 22 are located on the base, each of which communicates at one end with the concave dome 3, and extending onto the rim 2 of the base at the other end.

Figure 10D is a model of a standard petaloid base having six feet portions 23, each separated by valley regions 24 extending into the side wall of the bottle.

Figure 10E is a model of a reinforced base having a rim 2, and a domed region 3. A secondary dome 20 is provided within the main dome. Six radial valleys 21 are located on the surface of the dome 3, each of which communicates at one end with the secondary concave dome 20, and ends short of the rim 2 at the other end.

Figure 1 OF is a model of a reinforced base having a rim, and a domed region 3. a secondary dome 20 is provided at the centre of the main dome. Five radial valleys 21 extend across the base, communicating at one end with the secondary dome, and extending across the dome 3 and rim 2 and terminating on the side wall 8 of the bottle. A further five radial secondary valleys 22 are provided, interspaced with the first valleys, and extending at one end from a point within the main dome 3, across the rim 2, and into the side wall 8 of the bottle.

The designs are referred to below as A - F.

FEA simulations were performed on each of these models, using parameters representing a bottle manufactured in PET (Polyethylene terephthalate) having a density of 1.336 g.cm^"3, an elastic Modulus of 2500 MPa, a Poisson Ratio of 0.4, and a yield stress of 106MPa. The bottle shape attached to each base was as illustrated in Figures 8 and 9, and simulated to have a volume of 1.51itres. Simulations were carried out to assess to performance of the reinforced bases in the face of a within-bottle pressure of lbar and 1.5bar (100 and 150 kPa

respectively). In each case, the simulations assumed an identical mass of polymer (53.5g).

The linear displacement of the base of the bottle following application of an internal pressure was used as a measure of performance, as this is often indicative of a loss of stability of the bottle when standing in its base. The following results were obtained:

It can be seen that the two embodiments of the invention (Designs A and B) each exhibited significantly lower displacements of the base under pressure than the alternative designs. The next best design in terms of displacement was the petaloid base of Design D. However, an object of the present invention was to allow a "champagne" style base to be employed in contrast to petaloid designs. Even so, the champagne style bases of the invention outperformed even the petaloid design.

As a further comparison, an 850ml version of a champagne-style PET plastics bottle was scaled up using the improved base feature. The original 850ml bottle, having a base feature as illustrated in Figure 10E could be manufactured using a preform weight of 48g, and was able to withstand the required pressure differential of 150kPa. If the bottle were scaled up to 1.51itres capacity using the same base design, it was shown that the base design provided too much deflection when under pressure (see results table above). By contrast, the improved design B provided acceptable performance, with a much lower base deflection under pressure, using a preform weight of 52.9g. The surface areas of the two sizes of bottle were 600 cm² and 870 cm² for the 850ml and 1500ml bottles respectively. Thus, the 1500ml bottle using the improved design had a PET use of only 60.7 mg.cm² as opposed to 74.9 mg.cm², and still achieved the required pressure resistance, even at the larger size.

Further Aspects of the Invention

Also disclosed is a reinforced bottom for bottles or flasks made of plastic material, obtained preferably by Injection Stretch Blow Molding (ISBM) or other similar techniques, intended to contain liquids under pressure, which comprise a body 8 which extends between a neck, at its top portion, and a reinforced bottom 1 , at its lower portion, said reinforced bottom 1 being adapted to support, without significant deformation, an internal pressure of up to 300 kPa, preferably from 100 kPa to 200 kPa, in addition to the weight of the liquid contained in said bottle or flask, characterized in that it comprises a rim 2, constituted by a substantially annular portion, which bounds inside it a dome 3, of generally concave shape, with the concavity facing the outside of the bottle or flask body, and which extends towards the neck of the bottle or flask throughout the bottle or flask body, in that said dome 3 has a plurality of geometrical configurations 7, which are defined by closed polygonal formations, and in that said geometrical configurations occupy, at least, 80 to 90% of the surface of said dome 3.

Preferably, the said polygonal formations 7 have a triangular, quadrangular or rounded cross section.

In any aspect of the invention it is preferred that the wall portions bounded by polygonal formations 7 are concave, convex or flat.

Also in any aspect of the invention, it is preferred that the dome 3 is rounded.

The reinforced bottom according to this invention comprises a rim whose wall is constituted by a substantially annular portion, which defines interiorly a concave dome, whose concavity faces the outside of the bottle or flask, the wall of said rim extending toward the neck throughout the wall of the bottle or flask body. Said rim can be of any suitable shape adapted to the shape of the bottle or flask, and does not interfere with the geometry of the body wall of said bottle or flask.

Due to its great resistance, the reinforced bottom provides enhanced dimensional stability to the bottle or flask.

The concave dome, bounded by said rim, is shaped by a plurality of geometrical configurations, bounded by closed polygonal formations. Said closed polygonal formations conform ribs, which act as reinforcing and heat dissipation elements.

Said closed polygonal formations define in its interior wall portions, which may be flat, convex or concave, according to the application of the bottle or flask or the pressure to which it is intended to support. Said closed polygonal formations preferably have a cross section, triangular, quadrangular, trapezoidal, rounded or any other suitable configuration.

The reinforced bottom in accordance with the present invention is configured to allow the bottle or flask bears, with a negligible change of shape and external volume, in addition to the weight of the liquid contained therein, an internal pressure of between up to 300 kPa, preferably from 100 kPa to 200 kPa.

EP 1705124 Bl discloses a reinforced bottom. As can be seen from the attached drawings to this patent, the described reinforced bottom further presents reinforcing ribs in a reduced number, and which define geometrical figures formed by open polygonal formations, which reinforcement capacity of the bottom is much lower than the reinforcement capacity of the present invention. Its heat dissipation capacity is also much lower than the heat dissipation capacity of the reinforced bottom in accordance with the present invention. Unlike the reinforced bottom of the present invention, the bottom of the bottle described in EP 1705124 Bl can only be used in Extrusion Blow Molding (EBM).

EP 2133277 B l discloses a reinforced bottom for a bottle, which, although in respect to the pressure to be supported and to manufacture rate, have a similar performance to the reinforced bottom of the present invention, the geometry of the reinforced bottom described in this patent determines the geometry of the body of the bottle or flask, this feature being of particular importance for the industry, in particular as regards the production of bottles or flasks of plastic material. The features and advantages of the present invention will now be explained in more detail on the basis of an embodiment as shown in the figures of the accompanying drawings, in which:

The reinforced bottom 1 comprises a rim 2, constituted by a substantially annular portion with the shape as shown in the figures, which delimits inside a rounded dome 3, generally concave, with the concavity facing the outside of the bottle body 8, the upper wall of the rim 2 extending throughout the wall of the bottle or flask 8 body. Said rim 2 allows said bottle to rest stably on a substantially horizontal surface.

The dome 3 has a plurality of hexagonal configurations 7, which are defined by ribs 25.

The portions of inner wall of the hexagonal configurations 7, bounded by the ribs 25, may be concave, convex or flat.

Said ribs 25 have a quadrangular cross-sectional shape. Said ribs 25 occupy at least 80 to 90% of the surface of said dome 3.

Said ribs 25 are intended to reinforce said bottom 1 and to allow optimum heat dissipation during the manufacturing process of said bottle.

The configuration of said reinforced bottom 1 also allows that the manufacturing process of the bottle 12, according to the present invention, due to the optimum dissipation achieved by the reinforced base 1 , is performed at higher rates than currently obtainable with generality of the bottoms of prior art and/or allows that the body geometry is independent from the bottom geometry.

Claims

1. A reinforced base for a plastics bottle, said base comprising:

(a) an annular rim upon which the bottle rests;

(b) a concave dome bounded by said rim, with the concavity facing the outside of the bottle body; said dome comprising three regions:

(i) an outer, annular region, adjacent said rim;

(ii) in inner, circular region, at the centre of said dome; and

(iii) a middle, annular region, between said outer and inner regions;

(c) a plurality of spaced apart geometrical configurations in the form of closed polygonal or circular formations located on said middle annular region of the dome; wherein said outer annular region comprises at least 7.5% of the area of the dome, and is free of said geometrical configurations.

2. A base according to Claim 1 wherein said inner region of the dome comprises between 2.5% and 10% of the area of the dome, and is also free of said geometrical configurations.

3. A base according to either Claiml or Claim 2 wherein said geometrical configurations occupy at least 30% of the area of said middle region of the dome.

4. A base according to any preceding claim wherein each of said geometrical configurations is in the form of a tessellating regular polygon.

5. A base according to Claim 4 wherein said polygon is a regular hexagon.

6. A base according to any preceding claim wherein said geometrical configurations comprise an indented region.

7. A base according to Claim 6 wherein the depth of said indented region is at least 0.5mm.

8. A base according to any of Claims 1 to 5 wherein said geometrical configuration comprise a region surrounded by a wall.

9. A base according to any preceding claim wherein a circle enclosing each polygonal or circular formation has a diameter of less than 50% of the width of the middle annular region.

10. A base according to any preceding claim wherein said rim is of a curved profile, having a radius of curvature of at least 1mm.

11. A plastics bottle comprising a base according to any preceding claim.

12. A bottle according to Claim 11 comprising a wall extending from the rim of the base to a neck region at the top of the bottle; wherein said wall is provided with a circumferential reinforcement to resist deformation of the bottle under vacuum and said wall is of convex cross-section between said reinforcement and said rim.

13. A bottle according to Claim 12, wherein said wall is provided with a second such circumferential reinforcement and wherein said wall is of convex cross-section between said first and second reinforcements.

14. A bottle according to either of Claim 12 or Claim 13 wherein said reinforcement is in the form of a groove in the bottle wall.

15. A bottle according to any of claims 11 to 14 having a capacity of at least one litre.

16. A reinforced base for a plastics bottle, or a bottle comprising such a base substantially as described herein with reference to and as illustrated any appropriate combination of the accompanying drawings.