GB2479360A

GB2479360A - Petaloid Container Base with Reduced Diameter Contact Circle

Info

Publication number: GB2479360A
Application number: GB1005717A
Authority: GB
Inventors: Mikael Quasters
Original assignee: Petainer Lidkoeping AB
Current assignee: Petainer Lidkoeping AB
Priority date: 2010-04-06
Filing date: 2010-04-06
Publication date: 2011-10-12
Also published as: EP2555984B1; AU2011237887A1; PL2555984T3; WO2011124626A3; CN103003161B; GB2479451B; WO2011124626A2; ZA201208013B; RU2012147015A; CN103003161A; RU2598995C9; DK2555984T3; US20130062306A1; JP5641267B2; HUE033351T2; GB201005717D0; BR112012025471A2; PT2555984T; RU2598995C2; AU2011237887B2

Abstract

Petaloid base for a self-standing container 10 e.g. keg or bottle has a spheroidal, preferably hemispherical underlying base contour 14 and spheroidal, preferably ovoid foot projections 16 interrupting the base contour. Projections 16 may radiate from a central, polygonal, convex protrusion 18 in the base having longitudinal axes 20 extending outward and upwards in a conical formation from the central axis of the base. The intersection of the foot projection with the base 26 may be of concave cross section. Valleys 22 formed between the feet may extend from apices 24 of the polygonal protrusion and widen towards the outside of the base. The outermost edge of the foot formations may lie inwardly of the outer walls of the container, determined by a given ratio. The shape resists stress cracking, maximises capacity relative to the height of the container and reduces the surface area of the base and hence material usage.

Description

Self-standing container This invention relates to self-standing containers, more specifically to a petaloid base for such a container. Such containers may be blow-moulded of plastics material such as polyethylene terephthalate (PET).

Blow-moulded PET containers have long been used as bottles for beverages. More recently, they have been proposed for use as kegs for transporting, storing and dispensing beverages such as beer. An example of such a keg is disclosed in WO 2007/064277.

The example of WO 2007/064277 is given for background reference only: the broad concept of this invention is not limited to any particular use, material or method of manufacture of a container. However the invention has particular advantages in the context of thin-walled blow-moulded containers of the type apt to be manufactured from PET. It is in that context that the invention will be described in this specification.

Early PET containers had a plain hemispherical base and were rendered self-standing by the attachment of a separate base moulding to the base. Whilst a hemispherical base is simple, light and strong in isolation, the addition of a separate base moulding increases material and production costs and may hinder recycling.

To make a PET container self-standing without recourse to a separate base moulding, it is now well known to provide the container with an integrally-moulded petaloid base.

The term petaloid' refers to a multi-footed base shape whose feet are disposed in an angularly-spaced arrangement around the base, the resulting shape resembling the petals of a flower when viewed from under the container in use. The container usually has a cylindrical side wall of circular horizontal cross-section, in which case the feet typically lie on a contact circle that is concentric with, and whose diameter is smaller than, the circular cross-section of the side wall. The feet act together to provide a stable multi-point support for the container.

There is continual pressure in the art of containers to reduce material and production costs and to ease recycling. Not only has this led to the adoption of one-piece containers with petaloid bases, but efforts continue to improve the petaloid base so that containers can be produced more economically while still performing reliably during storage, transportation and use. It is particularly desirable to reduce the amount of material necessary to give the container sufficient integrity and stability for commercial use. Even a small saving of material per container has a massive effect on the cost of production when reproduced across potentially millions of containers.

It is against this background that the present invention has been devised. From one aspect, the invention resides in a petaloid base for a self-standing container, the base having a spheroidal underlying base contour and a plurality of spheroidal foot formations that interrupt and project from the underlying base contour to define a corresponding plurality of feet.

To maximise the capacity and strength of the container while minimising material usage, the underlying base contour is preferably substantially hemispherical. The contour may, for example, be that of an ablate spheroid whose polar axis coincides with a central axis of the base. For similar reasons, the foot formations are suitably elongate, such as ellipsoids or prolate spheroids. In preferred embodiments of the invention, the foot formations are ovoid (partially egg-shaped), in which case the contact points of the feet are most conveniently defined by the widest part of the cross-section of each foot formation being offset inwardly toward an inner end of the foot formation.

To define feet with minimal usage of material, the elongate foot formations preferably have respective longitudinal axes, which axes lie in planes extending radially from a central axis of the base. Those axes of the foot formations suitably extend outwardly and upwardly in conical relation from the central axis of the base.

Each foot formation may have an elliptical, preferably ovate intersection with the underlying base contour. To reduce stress concentration, the intersection is preferably of concave cross section.

To strengthen the base, the foot formations preferably radiate from a central protrusion. That protrusion may be approximately polygonal, with a number of sides corresponding to the number of foot formations.

The foot formations are suitably separated by valleys, that may for example radiate from apices of the polygonal protrusion. To minimise material usage, the valleys preferably widen moving outwardly across the base. Each valley may, for example, have an inner and an outer section and the walls of the valley may diverge more sharply in the outer section than in the inner section. However, the walls of the valley may diverge in both the inner and the outer sections of the valley.

In plan view, each foot formation may have an enlarged central region from which the foot formation tapers inwardly across an inner portion to an inner end. In that case, the inner portions of the foot formations suitably lie in segmented relation around the base.

To minimise material usage, it is preferred that in plan view, each foot formation tapers from the enlarged central region outwardly across an outer portion to an outer end of the foot formation.

The inventive concept extends to a container such as a keg or a bottle having the base of the invention.

In order that the invention may be more readily understood, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a plan view from underneath a container having a petaloid base in accordance with the invention; Figure 2 is a side view of the petaloid base of the container shown in Figure 1; and Figure 3 is a sectional side view through the petaloid base of the container shown in Figure 1; Figures 4(a), 4(b) and 4(c) are, respectively, an underneath plan view, a side view and a perspective view of a container having a base as shown in Figures 1 to 3, embodied in this example as a bottle of 0.33 litre capacity; Figures 5(a), 5(b) and 5(c) are, respectively, an underneath plan view, a side view and a perspective view of another container having a base as shown in Figures 1 to 3, embodied in this example as a keg of 20 litres capacity; and Figures 6(a), 6(b) and 6(c) are, respectively, an underneath plan view, a side view and a perspective view of another container having a base in accordance with the invention, embodied in this example as a bottle of 1.5 litres capacity, the base of this example being a variant having seven feet.

Referring firstly to Figures 1 and 2 of the drawings, a container 10 in this example of the invention comprises a hollow body of blow-moulded PET. The body of the container 10 is of circular horizontal section, the radius of that circle extending orthogonally from a central longitudinal axis 12 that extends centrally through the closed base 14 of the container 10. Above the base 14, but not shown in Figures 1 and 2, is a substantially cylindrical side wall surmounted by a neck portion. The side wall is integral with and terminates at its lower end in the base 14; in turn, the side wall is integral with and terminates at its upper end in the neck portion at the top of the container 10.

The fundamental or underlying shape of the base 14 is a slightly flattened hemisphere, that hemisphere being rotationally symmetrical about the central longitudinal axis 12 of the container 10. More generally, the underlying shape of the base 14 is an oblate spheroid, being a rotationally symmetric ellipsoid having a diameter on its polar axis (coinciding with the central longitudinal axis 12) that is shorter than the diameter of the equatorial circle whose plane bisects it. This approximately hemispherical shape maximises resistance to internal pressure, reduces stress concentrations to resist cracking, and also maximises internal volume while minimising material usage.

In accordance with the invention, the base 14 further includes integrally-moulded blister-like feet disposed in a petaloid arrangement around the base, the feet being defined in this example by five hollow ovoid foot formations 16 that radiate equi-angularly from a relatively shallow generally pentagonal convex protrusion 18 on the central longitudinal axis 12. More generally, the foot formations 16 are elongate ellipsoids in the form of prolate spheroids, a prolate spheroid being a spheroid whose diameter along its polar axis is greater than its equatorial diameter.

The polar axes 20 of the spheroidal foot formations 16 extend outwardly and upwardly in equi-angularly spaced radially-disposed planes from the central longitudinal axis 12 of the container 10. Thus, the polar axes 20 of the foot formations 16 (see Figure 2) lie on a virtual frusto-conical surface surrounding the central longitudinal axis 12.

Circumferentially adjacent pairs of foot formations 16 are separated by valleys 22 that radiate equi-angularly from the apices 24 of the pentagonal central protrusion 18. The valley floors follow the spheroidal shape of the base 14 and open at their outer ends to an outer portion of the base 14 that lies radially outwardly beyond the foot formations 16.

As shown in Figure 3, the convex central protrusion 18 has a radius of curvature rthat is smaller than the general radius of curvature R of the spheroidal base 14: thus R > r.

The foot formations 16 bulge outwardly from the underlying spheroidal contour of the base 14 by virtue of an ovoid convex wall. The convex wall of each foot formation 16 is surrounded by a concave transition zone 26 in the shape of an ovate ring. The transition zone 26 extends smoothly into the spheroidal wall of the base with a large radius of curvature to reduce stress concentration and hence to minimise stress cracking. The transition zones 26 of circumferentially adjacent foot formations 16 partially define the valley 22 between those foot formations 16.

Each foot formation 16 is generally elliptical (in this example, ovate) in underneath plan view, reaching a maximum width in an enlarged central region 28 between its inner end 30 and its outer end 32. Thus, each foot formation 16 tapers in opposite directions from the widest part of the central region 28: along an inner portion 34 moving inwardly toward the central longitudinal axis 12 to the inner end 30; and along an outer portion 36 moving outwardly away from the central longitudinal axis 12 to the outer end 32.

In underneath plan view, the inwardly-tapering inner portions 34 of the foot formations 16 fit closely between their neighbours around the circular base 14 like segments of an orange. These inner portions 34 of the foot formations 16 alternate with, and are separated by, narrow inner sections 38 of the valleys 22, which may be approximately parallel but, in this example, widen slightly as they extend outwardly from the pentagonal central protrusion 18. However where they extend outwardly into their outer sections 40 beyond the widest part of the foot formations 16, the valleys 22 widen near-exponentially between the tapering outer portions 36 of the foot formations 16 until they reach a maximum width between the outer ends 32 of adjacent foot formations 16.

Thus, moving along the valleys 22 from the central longitudinal axis 12 toward the outer diameter of the base 14, the gap between the foot formations 16 increases. In contrast, in a previously-known petaloid base such as that disclosed in EP 0671331, this gap decreases.

Viewed now from the side, the foot formations 16 extend to a level beyond -and thus, in use, below -the lowermost apex of the base 14 defined by the central pentagonal protrusion 18. The foot formations 16 all extend to the same level. Thus, at that level, each foot formation 16 defines a contact point 42 that will lie stably upon a flat support surface (not shown) orthogonal to the central longitudinal axis 12 of the container 10.

Figure 3 shows that the foot formations are somewhat egg-shaped with the widest part of their cross-sections offset slightly inwardly and downwardly toward their inner ends 30.

The contact points 42 of the foot formations 16 are equi-spaced around a contact circle centred on the central longitudinal axis 12 of the container 10. The diameter (x) of the contact circle relates to the side wall diameter (Dy) of the container 10 in a ratio as follows: Dy = k 0. 5x In accordance with the invention, k is preferably between 3.6 and 5.5, more preferably between 4.0 and 5.3, still more preferably between 4.2 and 5.0 and typically 4.7. This may be contrasted with typical PET bottles on the market whose corresponding ratio k is typically 2.5 to 3.5. The relatively large value for k in the invention stems from a relatively small value for x. This is advantageous because a small contact circle creates a small -and hence inherently stiff -diaphragm between the contact points 42.

The result is a central area within the contact circle between the contact points 42 of the foot formations 16 that is quite rigid and hence resistant to movement during internal pressure, up to burst pressure. The rigidity of the area within the contact circle is enhanced by the undulating wall section defined by the inner portions 34 of the foot formations 16, the valleys 22 between them, and the central protrusion 18.

Stiffness within the contact circle is important not just for a high burst pressure but also for stability. This is because the lowest point on the central longitudinal axis (the lowermost apex of the base 14 defined by the central pentagonal protrusion 18) will tend to be pushed down under internal pressure. If that lowest point moves so far as to contact a supporting surface in use, the container cannot rest stably on the contact points 42 of the foot formations 16. The stiffness of the base shape of the invention means that compared to previously known designs, the distance from the central apex of the base to a supporting surface is relatively small, to the benefit of stability and capacity relative to the height of the container.

Viewing any one foot formation 16 end-on (i.e. from the side of the container 10 looking inwardly towards the central longitudinal axis 12), the contour of that foot formation 16 describes a substantially constant convex radius between the concave radii of the transition zones 26 to each side. A conventional petaloid base typically has flatter surfaces defining a V-shaped valley between the feet, to the detriment of material usage and stress concentration.

The petaloid base of the invention may be applied to a wide range of containers such as bottles and kegs. Figures 4(a), 4(b) and 4(c) and Figures 5(a), 5(b) and 5(c) show a five-footed base of the invention applied, respectively, to a bottle 44 of 0.33 litre capacity, which may typically be used for carbonated soft drinks, and a keg 46 of 20 litres capacity, which may typically be used for beer. These drawings show features omitted from Figures 1 and 2, namely a substantially cylindrical side wall 48 surmounted by a neck portion 50. The side wall 48 is integral with and terminates at its lower end in the base 14; in turn, the side wall 48 is integral with and terminates at its upper end in the neck portion 50 at the top of the container 10.

Other variations of the invention are possible without departing from the inventive concept. For example, a variant of the base of the invention shown in Figures 6(a), 6(b) and 6(c) is applied to a bottle 52 of 1.5 litres capacity. This variant has seven foot formations 54 instead of five, with a generally heptagonal central protrusion 56 between them. Like the five-footed base variant, seven-footed base variants can be applied to any size of container, such as bottles of 0.33 litres, 0.5 litres, 1 litre, 1.5 litres or larger, and kegs of 20 litres or other capacities.

An odd number of feet is preferred for optimum stability, there being at least three feet (in which case the central protrusion is generally triangular) but preferably not more than seven feet; five or seven feet are considered optimal.

To put the invention into context but without limiting its broadest scope as defined in the claims, various dimensional characteristics will now be given by way of example.

Firstly, the table below sets out a volume comparison between a conventional base and a base in accordance with the invention, assuming in this instance that the base defines five feet. Volumes in the table are expressed in millilitres (ml). The volume refers to the internal volume of the base, defined as the portion of the container below the cylindrical side wall of the container. It will be noted that the base of the invention has a volume approximately five times greater than the volume of a conventional petaloid container base, to the benefit of compactness and material usage for a given container capacity.

Container with five feet Conventional base Base of the invention litre keg, dia 235 mm 128 (20%) 634 0.33 litre bottle, dia 60 mm 2.7 (18%) 15 0.5 litre bottle, dia 65 mm 3.5 (18%) 19 1.0 litre bottle, dia 80mm 6.5 (18%) 36 1.5 litre bottle, dia 95 mm 11(20%) 55 Secondly, the following dimensions help to define the base shape for each of the above capacities of container: Container with five feet Radius of underlying Radius of transition from base contour underlying base contour to side wall litre keg, dia 235 mm 135.0 mm 49.6 mm 0.33 litre bottle, dia 60 mm 34.5 mm 19.1 mm 0.5 litre bottle, dia 65 mm 37.4 mm 20.7 mm 1.0 litre bottle, dia 80 mm 46.0 mm 25.4 mm 1.5 litre bottle, dia 95 mm 54.6 mm 30.2 mm Container with five feet Radial projection of foot Diameter of contact formations beyond radius of circle underlying base contour litre keg, dia 235 mm 18.1 mm 99.9 mm 0.33 litre bottle, dia 60 mm 5.3 mm 28.6 mm 0.5 litre bottle, dia 65mm 5.5mm 31.0 mm 1.0 litre bottle, dia 80mm 7.1 mm 38.1 mm 1.5 litre bottle, dia 95 mm 8.4 mm 45.3 mm Container with five feet Length of foot formations Width of foot along polar axis* formations across polar axis* litre keg, dia 235 mm 80.2 mm 59.5 mm 0.33 litre bottle, dia 60 mm 22.9 mm 15.6 mm 0.5 litre bottle, dia 65 mm 24.8 mm 16.9 mm 1.0 litre bottle, dia 80 mm 30.6 mm 20.8 mm 1.5 litre bottle, dia 95 mm 36.3 mm 24.7 mm *Including transition zone Container with seven feet Radius of underlying Radius of transition from base contour underlying base contour to side wall litre keg, dia 235 mm 135.0 mm 49.6 mm 0.33 litre bottle, dia 60 mm 34.2 mm 18.9 mm 0.5 litre bottle, dia 65 mm 37.3 mm 20.7 mm 1.0 litre bottle, dia 80 mm 46.2 mm 25.6 mm 1.5 litre bottle, dia 95 mm 54.6 mm 30.2 mm Container with seven feet Radial projection of foot Diameter of contact formations beyond radius of circle underlying base contour litre keg, dia 235 mm 18.1 mm 99.9 mm 0.33 litre bottle, dia 60 mm 5.3 mm 28.5 mm 0.5 litre bottle, dia 65mm 5.8 mm 31.0 mm 1.0 litre bottle, dia 80 mm 7.2 mm 38.5 mm 1.5 litre bottle, dia 95 mm 8.4 mm 45.4 mm Container with seven feet Length of foot formations Width of foot along polar axis* formations across polar axis* litre keg, dia 235 mm 78.9 mm 54.8 mm 0.33 litre bottle, dia 60 mm 22.4 mm 14.0 mm 0.5 litre bottle, dia 65 mm 24.4 mm 15.3 mm 1.0 litre bottle, dia 80mm 30.3mm 19.0mm 1.5 litre bottle, dia 95 mm 35.7 mm 22.4 mm *Including transition zone Radius of transition zone Radius of transition zone (five feet) (seven feet) litre keg, dia 235 mm 12.0 mm 8.0 mm 0.33 litre bottle, dia 60mm 3.15mm 1.88mm 0.5 litre bottle, dia 65 mm 3.44 mm 2.05 mm 1.0 litre bottle, dia 80 mm 4.26 mm 2.54 mm 1.5 litre bottle, dia 95 mm 5.0 mm 3.0 mm For a base with five feet, the following ratios apply in these examples: For 20-litre keg: Length of foot formations along polar axis/width of foot formations across polar axis = 1.35 Diameter of contact circle/ width of foot formations across polar axis = 1.68 Radius of underlying base contour/diameter of side wall = 0.57 Radius of underlying base contour/radius of transition from underlying base contour to side wall = 2.72 Radial projection of foot formations beyond radius of underlying base contour/radius of underlying base contour 1.13 For bottles of various capacities: Length of foot formations along polar axis/width of foot formations across polar axis = 1.47 Diameter of contact circle/ width of foot formations across polar axis = 1.83 Radius of underlying base contour/diameter of side wall = 0.58 Radius of underlying base contour/radius of transition from underlying base contour to side wall = 1.81 Radial projection of foot formations beyond radius of underlying base contour/radius of underlying base contour = 1.15 Similarly, for a base with seven feet, the following ratios apply in these examples: For 20-litre keg: Length of foot formations along polar axis/width of foot formations across polar axis = 1.44 Diameter of contact circle/ width of foot formations across polar axis = 1.82 Radius of underlying base contour/diameter of side wall = 0.57 Radius of underlying base contour/radius of transition from underlying base contour to side wall = 2.72 Radial projection of foot formations beyond radius of underlying base contour/radius of underlying base contour 1.13 For bottles of various capacities: Length of foot formations along polar axis/width of foot formations across polar axis = 1.59 Diameter of contact circle/ width of foot formations across polar axis = 2.03 Radius of underlying base contour/diameter of side wall = 0.57 Radius of underlying base contour/radius of transition from underlying base contour to side wall = 1.8 Radial projection of foot formations beyond radius of underlying base contour/radius of underlying base contour 1.15 It will be apparent from the foregoing description that the improved petaloid base shape of the invention has various additional advantages. Its softly-curving shape with an absence of sharp radii is beneficial to resist stress cracking. Also, importantly, its surface area is less than equivalent known designs. Thus, for a given amount of resin, the invention allows a thicker wall and hence a stronger base. Alternatively it is possible to reduce weight and material usage while maintaining the strength of the base. A strong base is particularly important in applications where the containers are subjected to elevated internal pressure and/or elevated temperature, such as carbonated soft drinks, beer and hot-fill or pasteurised liquids.

Claims

Claims 1. A petaloid base for a self-standing container, the base having a spheroidal underlying base contour and a plurality of spheroidal foot formations that interrupt and project from the underlying base contour to define a corresponding plurality of feet.
2. The base of Claim 1, wherein the underlying base contour is an oblate spheroid whose polar axis coincides with a central axis of the base.
3. The base of Claim 1 or Claim 2, wherein the underlying base contour is substantially hemispherical.
4. The base of Claim 1 or Claim 2, wherein the foot formations are elongate ellipsoids.
5. The base of Claim 4, wherein the foot formations are prolate spheroids.
6. The base of Claim 4 or Claim 5, wherein the foot formations are ovoid.
7. The base of Claim 6, wherein the widest part of the cross-section of each foot formation is offset inwardly toward an inner end of the foot formation.
8. The base of any of Claims 4 to 7, wherein the foot formations have respective longitudinal axes, which axes lie in planes extending radially from a central axis of the base.
9. The base of Claim 8, wherein the axes of the foot formations extend outwardly in conical relation from the central axis of the base.
10. The base of any preceding claim, wherein each foot formation has an elliptical intersection with the underlying base contour.
11. The base of Claim 10, wherein the intersection is ovate.
12. The base of Claim 10 or Claim 11, wherein the intersection is of concave cross section.
13. The base of any preceding claim, wherein the foot formations radiate from a central protrusion.
14. The base of Claim 13, wherein the central protrusion is generally polygonal, with a number of sides corresponding to the number of foot formations.
15. The base of any preceding claim, wherein the foot formations are separated by valleys.
16. The base of Claim 15 when dependent from Claim 14, wherein the valleys radiate from apices of the polygonal protrusion.
17. The base of Claim 15 or Claim 16, wherein the valleys widen moving outwardly across the base.
18. The base of Claim 17, wherein each valley has an inner and an outer section and the walls of the valley diverge more sharply in the outer section than in the inner section.
19. The base of Claim 18, wherein the walls of the valley diverge in both the inner and the outer sections of the valley.
20. The base of any preceding claim, wherein in plan view, each foot formation has an enlarged central region that tapers inwardly across an inner portion to an inner end of the foot formation.
21. The base of Claim 20, wherein the inner portions of the foot formations lie in segmented relation around the base.
22. The base of Claim 20 or Claim 21, wherein in plan view, each foot formation tapers from the enlarged central region outwardly across an outer portion to an outer end of the foot formation.
23. A self-standing container having a base as defined in any preceding claim.
24. The container of Claim 23, wherein the foot formations of the base define respective contact points that together are spaced around a contact circle whose diameter (x) relates to a side wall diameter (Dy) of the container as: Dy = k 0. 5x where k is between 3.6 and 5.5.
25. The container of Claim 24, wherein k is between 4.0 and 5.3.
26. The container of Claim 25, wherein k is between 4.2 and 5.0.