ES2787648T3 - Reinforced base for plastic bottles or flasks - Google Patents

Abstract

A reinforced base [1] for a plastic bottle, said base comprising: (a) an annular edge [2] on which the bottle rests; (b) a concave dome [3] limited by said edge, with the concavity towards the outside of the body of the bottle; said dome having a total area and comprising three regions: (i) an external annular region [4], adjacent to said edge; (ii) a circular inner region [5], in the center of said dome; and (iii) an annular middle region [6], between said outer and inner regions; (c) a plurality of separate geometric configurations [7] in the form of closed polygonal or circular formations located in said mid-annular region of the dome; CHARACTERIZED IN THAT said inner circular region [5] comprises from 2.5% to 10% of the total area of the dome, said middle annular region [6] comprises from 60% to 90% of the total area of the dome and said annular region external (4) comprises from 7.5% to 30% of the total area of the dome (3) and is free of said geometric configurations (7).

Description

DESCRIPTION

Reinforced base for plastic bottles or flasks

Field of the invention

The present invention relates to a reinforced base for a plastic bottle according to the preamble of claim 1 and to a plastic bottle comprising said base. These bottles or flasks are, for example, those made of plastic material, obtained by injection, stretch and blow molding (ISBM) or other similar techniques intended to contain liquids under pressure, their bodies ending in their lower part in a reinforced bottom and in its upper part in an outlet to pour the liquid contents, which can be plugged in.

Background and prior art

It has been found in practice that prior art bottles or flasks intended to contain liquid and subject to very high total pressures have very high wall thicknesses, which increases raw material costs and reduces production rate, or restricts the geometry of your body wall. On the other hand, it was found that the higher the heat dissipation capacity of the bottom of the bottles or flasks, the higher the production rate of the bottles or flasks.

It is very important, for reasons of economy and minimization of environmental impact, to minimize the amount of material used to produce plastic bottles, especially those intended to contain beverages and which are generally considered to be single-use before recycling. However, bottles still need to be able to perform their function through the rigors 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 containers on a production line. A vacuum (or partial vacuum) is created within the bottle and then liquid can be dispensed into the evacuated interior, allowing rapid filling without the need to allow air to escape simultaneously. For traditional glass bottles, the requirement that the bottles can withstand this pressure differential during filling is easily met. For plastic bottles, and especially where you want to minimize the amount of material used to produce them, this requirement poses a greater challenge.

In addition, to give the bottles more structural stability when handling and transporting, it is common in the industry to pressurize the bottles after filling to make the filled package more rigid against external deformation forces. For non-carbonated beverages, this is often accomplished by introducing a small amount of liquid nitrogen into the bottle along with the contents, which results in a pressure increase as the liquid nitrogen increases in temperature. Consequently, the bottles must also be able to withstand the pressure inside them, after filling.

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

It is known to introduce reinforcing structures (e.g. ribs) into the side wall of plastic bottles to make them better able to withstand vacuum filling operations, and a plurality of such circumferential ribs are typically arranged in a relative relationship. spaced along the length of the bottle wall.

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

Document WO2013 / 156710 A1 discloses a plastic container, according to the preamble of claim 1, with a conical arc that extends to its base to define in cross section a star-shaped profile inscribed between two circles, where a ratio of the diameters of the two circles is greater than or equal to 0.7. The profile surrounds a circular inner region and is surrounded by an annular region which is in turn surrounded by a downward facing annular edge on which the bottle stands.

It is therefore among the objects of the present invention to provide a means by which champagne-type bases can be used in larger plastic bottles, while withstanding the required overpressure during production and transportation. It is also among the objects of the invention to be able to reduce the amount of material used in the manufacture of the bottle, thus reducing costs and environmental impact while preserving the desired technical properties.

The invention also has among its objects a reduction in the costs of raw materials, an increased production rate and making the geometry of the body independent of the geometry of the bottom. Therefore, the reinforced bottom according to the present invention has a configuration that allows a reduction in the thickness of the wall of the bottle or flask.

The reinforced bottom according to the present invention also allows an increase in the rate of production of bottles or flasks, since the configuration of the reinforced bottom allows greater heat dissipation and therefore a higher manufacturing rate is obtained. .

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

Summary of the invention

Accordingly, the invention provides a reinforced base for a plastic bottle as defined in claim 1. Optional features are set forth in the dependent claims.

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

The intervals 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 approximately 5%.

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

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

Said internal region of the dome comprises between 2.5% and 10% of the area of the dome and is preferably also free of said geometric configurations. By keeping this area free of geometric configurations, centering of the bottle preform in the mold prior to molding is facilitated.

In any aspect of the invention, it is particularly preferred that said geometric configurations occupy at least 30% of the area of said middle region of the dome. The provision of this density of geometric configurations makes it easier to provide the required additional strength to the bottle dome. In further preferred embodiments, the patterns occupy at least 35%, 40%, 45%, 50%, 55%, or even 60% of the area of said mid-dome region.

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

Such geometric configurations can be formed, for example, by including wall features that separate polygonal or circular features. However, it is particularly preferred that said geometric configurations comprise, or consist of, a split region. In this way, the thickness of the base wall can be kept more uniform along the base of the bottle and less material is used in its construction.

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

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

In any aspect of the invention, it is preferred that the polygonal or circular formations are sized such 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 can be offset over the radius of the middle annular region, allowing the forces to spread between the formations. As for a minimum size, it is preferred that said closing circle is not less than 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 probability of stress formation increases.

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

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

Preferably, said bottle comprises a wall extending from the edge 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 edge.

One skilled in the art can determine an appropriate degree of convexity by trial and error, to provide a balance between the vacuum strength properties of the convex wall portion and ease of molding. Clearly, a smaller radius of curvature would lead to increased resistance to vacuum forces, but would produce a more "bulbous" shape on the bottle wall, which may be more difficult to mold and may not conform to any aesthetic requirement. As a guide, the minimum radius of curvature should be greater than the distance between said first reinforcement and the edge. A radius equal to half that distance would give a wall section meeting the edge and reinforcement at right angles; A smoother transition is to be preferred. Where the distance between the edge 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> 1L. Preferably, r can be up to about 2L, that is, within the range of 0.5L <r <2L. More preferably, said wall is provided with a second circumferential reinforcement of this type and wherein said wall is of convex cross section between said first and second reinforcements.

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

Figure 13A-E illustrates a range of convexities that could 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 both ends of the wall portion is given by L. The relationships are as follows:

Fig 13A r = 0.5 L

Fig 13B r = 06 L

Fig 13C r = 08 L

Fig 13D r = 10 L

Fig 13E r = 20 L

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

It is particularly preferred that a maximum of two or three such reinforcements are employed on the bottle. The provision of the convex wall cross sections means that normally no more than this number is required, the additional reinforcements simply increasing the cost and complexity of the design.

For any such bottle, it is particularly preferred that the capacity of the bottle is one liter. This base design is intended to be appropriate for bottles having a capacity of at least 1, or 1.5, or 2, or 2.5, or 3, or even 5 liters.

Also described is a reinforced base for a plastic bottle, or a bottle comprising said base substantially as described herein with reference to and as illustrated in any appropriate combination of the accompanying drawings.

Brief description of the figures

The invention will be described with reference to the accompanying drawings, where:

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 bottom side plan views of the reinforced bottle bases of the invention;

Figures 8 and 9 are cross-sectional elevation 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 a reinforced bottom of another bottle or flask, not claimed;

Figure 12 is a plan view of the reinforced bottom of Figure 11; Y

Figure 13 illustrates a fan of convexities for a portion of the side wall of a bottle of the invention.

Description of the preferred embodiments

Figure 1 illustrates, in cross-sectional view, a reinforced base, generally indicated 1, for a plastic bottle, according to one embodiment of the invention. The side walls of the bottle are also illustrated. The check lines extending from the bottle and the base delineate the various sections of the bottle and the base. The base 1 has an annular edge 2 on which the bottle can rest, in use, and which connects the wall 8 of the bottle with 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, which is adjacent to the edge 3; a circular inner region 5, in the center of the dome; and an annular middle region 6 that lies between the outer 4 and inner 5 regions. The central region 6 is provided with a plurality of spaced geometric configurations 7 that serve to reinforce the dome 3.

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

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

Figure 4 illustrates, in plan view, the lower part of a reinforced bottle base 1 of the invention with geometric configurations 7 located in the middle annular region 6. In this embodiment, configurations 7 are circular in shape and all are of the Same size. It can be seen that the outer annular region 4 is free of geometric configurations. Some areas 10 of the mid-annular region 6 are also free from geometric configurations, and these can be conveniently used for marking, such as recycling information, mold numbering, and manufacturer logos.

Figures 5 and 6 illustrate, in plan view, the lower part of the 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 base of the bottle. These embodiments are of bottles that also have a convex wall portion 9 and this can also be seen in the illustrations. Items similar to the embodiments described above are similarly numbered.

In Figure 5, geometric configurations 7 in the form of square grooves are employed, while in the embodiment of Figure 6 the configurations are circular grooves.

Figure 7 illustrates, again in plan view, the underside of a particularly preferred embodiment of a reinforced base 1 of the invention. Again, items similar to those already described are similarly numbered. In this embodiment, the geometric configurations 7 are in the form of regular hexagonal grooves. Within the central region 5 of the dome the position of the injection molding point 11 for the bottle preform 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, in accordance with the invention and additional wall features for 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 from the base 1 to the neck region 14. In this embodiment, the reinforcement is in the form of a circumferential groove, or slot 15 in the side wall. 8 from the bottle.

The portion 16 of the wall 8 that lies between the edge 2 and the first circumferential reinforcement 13 is convex, bulbous in shape, forming an arcuate 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 than would otherwise be necessary to provide equivalent resistance to vacuum forces, allowing for a more simplified mold and greater opportunities for label placement.

In this embodiment, a second circumferential reinforcement 17 of this type is also provided, approximately midway between the base 1 and the neck region 14 of the bottle 12. Again, this reinforcement is in the form of a circumferential groove, 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 the second 17 circumferential stiffeners is also convex, bulbous in shape, forming a second arcuate structure to resist deformation in the face of an internal void.

The upper region 20 of the bottle is conical in shape.

Reinforced base performance

To demonstrate the performance of the reinforced base, Finite Element Analysis (FEA) was carried out to determine the stresses within the bottle and the base structure in the face of internal pressure.

Six base models were compared, two of which were embodiments of the present invention; the remaining four were more traditional in 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 grooves arranged on the central 6 and central 5 regions of the dome 3, while the outer annular region 4 is free of such geometric configurations.

Figure 10B is a model of a reinforced base 1 of the invention having regular hexagonal grooves arranged 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 10C 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 terminates near the edge 2 at the other end. Six other radial valleys 22 are found at the base, each of which communicates at one end with the concave dome 3 and extends over the edge 2 of the base at the other end.

Figure 10D is a model of a conventional petaloid base having six foot portions 23, each separated by valley regions 24 that extend toward the side wall of the bottle.

Figure 10E is a model of a stiffened base having an edge 2 and a dome 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 terminates near the edge 2 at the other end.

Figure 10F is a model of a stiffened base having a dome rim and region 3. A secondary dome 20 is provided in the center of the main dome. Five radial valleys 21 extend through the base, one end communicating with the secondary dome, and extending through the dome 3 and rim 2 and ending at the side wall 8 of the bottle. Five other radial secondary valleys 22 are provided, interspersed with the first valleys and extending at one end from a point within the main dome 3, through the edge 2 and into the side wall 8 of the bottle.

The designs are mentioned below as A - F.

FEA simulations were performed in each of these models, using parameters that represent a bottle made of PET (polyethylene terephthalate) that has a density of 1.336 g.cm-3, an elastic modulus of 2500 MPa, a Poisson's ratio of 0.4 and a yield strength of 106 MPa. The shape of the bottle attached to each base was as illustrated in Figures 8 and 9 and was simulated to have a volume of 1.5 liters. Simulations were carried out to evaluate the performance of the reinforced bases against a pressure inside the bottle of 100 and 150 kPa (1 bar and 1.5 bar respectively). In each case, the simulations assumed an identical mass of polymer (53.5 g).

The linear displacement of the bottle base after the 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 on 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 the petaloid designs. Even so, the champagne-style bases of the invention outperformed even the petaloid design.

As another comparison, an 850ml version of a champagne style PET plastic bottle was scaled using the improved base feature. The original 850 ml bottle, which has a base feature as illustrated in Figure 10E could be manufactured using a preform weight of 48 g and was able to withstand the required differential pressure of 150 kPa. If the bottle were scaled up to 1.5 liters in capacity using the same base design, the base design was shown to provide too much deflection when under pressure (see results table above). In contrast, the improved design B provided acceptable performance, with much lower base drift under pressure, using a preform weight of 52.9 g. The surface areas of the two bottle sizes were 600 cm2 and 870 cm2 for the 850 ml and 1500 ml bottles respectively. Therefore, the 1500ml bottle using an improved design had a PET usage of only 60.7 mg.cm2 as opposed to 74.9 mg.cm2 and still achieved the required pressure resistance, even in size larger.

Additional disclosure

Also disclosed but not part of the scope of the present invention, is a reinforced bottom for bottles or jars of plastic material, preferably obtained by injection stretch blow molding (ISBM) or other similar techniques, intended to contain liquids under pressure, which They comprise a body 8 that extends between a neck, in its upper part, and a reinforced bottom 1, in its lower part, said reinforced bottom 1 being adapted to withstand, without significant deformation, an internal pressure of up to 300 kPa, preferably of 100 kPa to 200 kPa, in addition to the weight of the liquid contained in said bottle or flask, which comprises an edge 2, made up of a substantially annular portion, which limits inside a dome 3 of generally concave shape, with the concavity facing the exterior of the flask or flask body, and extending towards the neck of the flask or flask along the body of the flask or bottle, wherein said dome 3 has a plural number of geometric configurations 7, which are defined by closed polygonal formations, and wherein said geometric configurations occupy at least 80 to 90% of the surface of said dome 3. Preferably, said polygonal formations 7 have a triangular cross section , quadrangular or rounded.

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

Also in any respect, it is preferred that the dome 3 is rounded.

The reinforced bottom comprises an edge whose wall is constituted by a substantially annular portion, which internally defines a concave dome, the concavity of which is towards the outside of the bottle or flask, the wall of said edge extending towards the neck along the wall of the bottle or body of the flask.

Said edge can have any suitable shape adapted to the shape of the bottle or flask and does not interfere with the geometry of the wall of the body of said bottle or flask.

Due to its high strength, the reinforced bottom provides greater dimensional stability to the bottle or flask.

In an embodiment that is not part of the present invention, the concave dome, limited by said edge, can be formed by a plurality of geometric configurations, delimited by closed polygonal formations. Said closed polygonal formations form ribs, which act as reinforcement and heat dissipation elements.

In an embodiment that is not part of the present invention, the closed polygonal formations define portions on their interior walls, which can be flat, convex or concave, according to the application of the bottle or flask or the pressure to which it is intended. to endure. Said closed polygonal formations preferably have a cross section, triangular, quadrangular, trapezoidal, rounded or any other suitable configuration.

The reinforced bottom is configured to allow the bottle or flask to carry, with an insignificant change in 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 B1 discloses a reinforced bottom. As can be seen in the drawings attached to this patent, the described reinforced bottom also has reinforcing ribs in a reduced number and that define geometric figures formed by open polygonal formations, whose bottom reinforcement capacity is much less than the reinforcement capacity of the present invention. Its heat dissipation capacity is also much less than the heat dissipation capacity of the reinforced bottom according to the present invention. Unlike the reinforced bottom of the present invention, the bottom of the bottle described in EP 1705124 B1 can only be used in extrusion blow molding (EBM).

Document EP 2133277 B1 describes a reinforced bottom for a bottle, which, although with respect to the pressure to withstand and the manufacturing speed, has 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 characteristic being of particular importance for the industry, in particular with regard to the production of bottles or flasks of plastic material.

The following characteristics are shown in the figures: The reinforced bottom 1 comprises an edge 2, constituted by a substantially annular portion with the shape shown in the figures, which delimits inside a rounded dome 3, generally concave, with the concavity towards the Outside of the body of the bottle 8, the upper wall of the rim 2 extends through the wall of the bottle or body of the flask 8. 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 inner wall portions of the hexagonal configurations 7, delimited by the ribs 25, can 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 the manufacturing process of the bottle 12, according to the present invention, due to the optimal dissipation achieved by the reinforced base 1, to be carried out at higher speeds than those that can be obtained. currently with the generality of the backgrounds of the prior art and / or allows the geometry of the body to be independent of the geometry of the bottom.

Claims (14)

1. A reinforced base [1] for a plastic bottle, said base comprising: (a) an annular edge [2] on which the bottle rests; (b) a concave dome [3] limited by said edge, with the concavity towards the outside of the body of the bottle; said dome having a total area and comprising three regions: (i) an annular outer region [4], adjacent to said edge; (ii) a circular inner region [5], in the center of said dome; Y (iii) an annular middle region [6], between said outer and inner regions; (c) a plurality of separate geometric configurations [7] in the form of closed polygonal or circular formations located in said mid-annular region of the dome; CHARACTERIZED WHY said inner circular region [5] comprises from 2.5% to 10% of the total area of the dome, said annular middle region [6] comprises from 60% to 90% of the total area of the dome and said external annular region (4) comprises from 7.5% to 30% of the total area of the dome (3) and is free of said geometric configurations (7). 2. A base according to claim 1 wherein each of said geometric configurations (7) is in the form of a tessellated regular polygon. 3. A base according to claim 2 wherein said polygon is a regular hexagon. 4. A base according to any preceding claim wherein said internal circular region (5) of the dome (3) is also free from said geometric configurations (7). 5. A base according to any preceding claim wherein said geometric configurations (7) occupy at least 30% of the area of said middle annular region (6) of the dome (3). A base according to any preceding claim, wherein said geometric configurations [7] are in the form of split regions [9]. A base according to claim 6 wherein said recessed regions [9] define recesses having a depth [A-A '] of at least 0.5 mm. 8. 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 (6). 9. A base according to any preceding claim wherein said edge (2) is curved in profile, having a radius of curvature of at least 1 mm. 10. A plastic bottle [12] comprising a reinforced base according to any preceding claim. A bottle according to claim 10 comprising a wall [8] extending from the edge [2] of the base to a neck region [14] at the top of the bottle; wherein said wall is provided with a circumferential reinforcement [13] to resist deformation of the bottle under vacuum and said wall is of convex cross section between said reinforcement and said edge. A bottle according to claim 11, wherein said wall (8) is provided with a second circumferential reinforcement [17] of this type and wherein said wall is of convex cross section between said first (13) and second ( 17) reinforcements. A bottle according to claim 11 or claim 12 wherein said reinforcement (13,17) is in the form of a groove [15, 18] in the wall of the bottle. 14. A bottle according to any one of claims 10 to 13 having a capacity of at least one liter.