GB2510796A

GB2510796A - Plastics container

Info

Publication number: GB2510796A
Application number: GB201217021A
Authority: GB
Inventors: Mark Hobley
Original assignee: Nampak Plastics Europe Ltd
Current assignee: Nampak Plastics Europe Ltd
Priority date: 2012-09-24
Filing date: 2012-09-24
Publication date: 2014-08-20
Also published as: GB201217021D0

Abstract

A blow moulded plastics container 10 is provided for storing liquid such as milk, the container comprising a blow moulded body defining a chamber for storing liquid, a base 18 for standing the body in an upright manner, and a part line 20. The base defines a recess 22 extending co-linear with the part line. A rib (30, fig 2a) is formed along a portion of the part line within the recess, the rib extending outwardly within the recess, and a ratio of the width of the rib to the height of the rib along a substantial length of the rib is between about 0.8:1 and about 1.2:1. The rib may have a first end, a second end and a centre portion, and may define at least one shoulder (32, fig 1b) adjacent the rib at the first end and/or the second end of the rib. Two further recesses 34 may be provided each extending substantially perpendicular to the recess 22. The recesses 34 may be substantially tear-drop shaped, each having a narrow end 34a proximal the recess 22. A mould and a method of producing a base is also provided.

Description

Plastics container The present invention relates to a plastics container, more particularly, but not exclusively, to a blow moulded plastics container of the kind commonly used for transporting or storing milk.

It is known to package milk in plastics containers for retail through supermarkets and the like.

There is a desire to make such plastics containers as lightweight as possible, whilst ensuring that they remain fit for purpose in delivering the product in good condition for consumers.

Such plastics containers are usually manufactured by a blow moulding process, wherein a parison is clamped in a two part mould and inflated so that it takes on the shape of a cavity within the mould. The process creates a seam around the blown container -referred to commonly as the part line', since it corresponds to the position at which the two parts of the mould come together to form the mould cavity.

It is known to form a rib along the part line at the underside of the container, to provide improved structural strength. However, the moulding process may result in a rib of hollow structure, particularly if the parison is of reduced plastics content (i.e. for the purpose of producing a lightweight container). This is undesirable, since any hollow region may ultimately define a weak point of the container. The container is thus more likely to split under pressure of liquid held within the container at the rib than elsewhere.

There is a need for an improved plastics container.

According to one aspect of the invention, there is provided a blow moulded plastics container for storing liquid such as milk, as set forth in claim 1.

In exemplary embodiments, the ratio of width to height may be between 0.9:1 and 1.1:1. The above ratios have been found to provide significant improvements in structural integrity of the container, with a ratio is 1:1 perceived to provide optimum results.

In exemplary embodiments, the width of the nb may be between 0.8mm and 1.7mm.

I

In exemplary embodiments, the recess defines a concavity on the underside of the container and the rib defines a convex formation within the concavity. Preferably, the rib does not project beyond the concavity.

In exemplary embodiments, at least one shoulder is formed adjacent the rib a the first and/or second end of the nb. The provision of a shoulder has been found to increase the structural integrity of the rib, further reducing tendency for splitting to occur. The or each shoulder may be between 50% and 80% of the height of the rib at the respective end of the rib, e.g. between 60% and 70% of the height of the rib. io

According to another aspect of the invention, there is provided a blow moulded plastics container for storing liquid such as milk, as set forth in claim 9.

This configuration has been found to be particularly effective in improving the structural iS integrity of the underside of the container. In particular, the provision of a shoulder has been found to increase the structural integrity of the rib, reducing tendency for splitting to occur.

The or each shoulder may be between 50% and 80% of the height of the rib at the respective end of the rib, e.g. between 60% and 70% of the height of the rib.

In exemplaiy embodiments, the recess defines a concavity on the underside of the container and the rib defines a convex formation within the concavity. Preferably, the nb does not project beyond the concavity.

According to a further aspect of the invention, there is provided a Now moulded plastics container for storing liquid such as milk, as set forth in claim 17. The height of the rib at the first end and/or second is lower than the height of the rib at the centre portion.

This configuration has been found to be particularly effective in improving the structural integrity of the underside of the container. In particular, this configuration has been found to reduce the tendency for hollow regions to be formed along the rib during the blow moulding process, particularly at the ends of the ribs.

The rib being lower at its ends than at the centre provides the benefit of there being more plastic at each end of the rib, whilst retaining the required rib height. Increased amounts of plastic at the rib ends leads to a more robust part line along the base of the container.

According to another aspect of the present invention there is provided a blow moulded lO plastics container for storing liquid such as milk, as set forth in claim 23. The depth of the recess is shallower at the first and/or second end of the rib than at the centre portion.

This configuration has been found to be particularly effective in improving the structural integrity of the underside of the container. In particular, this configuration has been found to iS reduce the tendency for hollow regions to be formed along the rib during the blow moulding process, particularly at the ends of the ribs. An increase in material is provided at the ends of the rib due to the decreased height difference at the rib ends, creating a more robust part line at the rib ends.

In exemplaiy embodiments the height of the rib at the centre portion is the same as at the first and second ends. The height of the rib may be uniform along its length.

According to a yet further aspect of the invention, there is provided a method of producing a plastics container for storing liquid such as milk, the method comprising the step of providing a mould tool configured so that blow moulding plastics in the mould tool results in a container as set forth in any one of the above aspects; and blow moulding plastics in said mould tool.

Other aspects and features of the invention will be apparent from the claims and following description of embodiments, made by way of example, with reference to the following drawings, in which: Figure Ia is a plan view of the underside of a plastics container; Figure lb is a partial enlarged view of the view of Figure la; Figure 2a is a perspective view of the underside of the plastics container of Figures la and i0 Ib; Figure 2b is a partial enlarged view of the view of Figure 2a; Figure 3 is a partial side view of the plastics container of Figures la to 2b; iS Figure 4 is a partial cross-sectional view of the plastics container of Figures Ia to 3; Figure 5a is perspective view of part of a mould tool for the plastics container of Figures Ia to 4; Figure Sb is a partial enlarged view of the mould tool part of Figure 5; Figure Ga is a plan view of the underside of a plastics container; Figure 6b is a partial enlarged view of Figure 6a; Figure 7 is a partial side view of the plastics container of Figures 6a to Gb; Figure 8 is a partial cross-sectional view of the plastics container of Figures Ga to 7; Figure 9a is perspective view of part of a mould tool for the plastics container of Figures 6a to 8; and Figure 9b is a partial enlarged view of the mould tool part of Figure 9a.

Referring firstly to Figures Ia to 4, a blow moulded plastics container is indicated generally at 10, which takes the form of a blow moulded body 12 defining an internal chamber 14 (e.g. see Figure 4) for storing liquid.

Figures la to 4 are concerned with only the underside of the container, which defines a base 16 for resting the container 10 in an upright condition. However, in terms of general construction, the container may be of the kind defined in the following published patent applications, the content of which is incorporated by reference: W020 11131920, W0201105 1694, W020l0043890. Hence, although not illustrated, the container 10 may include a handle, e.g. formed as an integral part of the body 12. Furthermore, it will be understood that the container 10 will include a neck extending from the body 12, the neck defining an open passageway which communicates with the chamber 14 and through which the container 10 may be filled with, and emptied of, liquid. The passageway may be covered with a seal and/or lid to close the chamber 14. In exemplary embodiments, the container is a centre neck container, wherein the open passageway is concentric with a central axis of the body 12.

It will be understood that the moulding process for the blow-moulded container 10 involves clamping a parison between two parts of a moirld tool and inflating the parison so that it takes on the shape of a cavity within the tool. This results in the formation of a part line 20 which bisects the body 12 of the container 10, in this embodiment diagonally (from one corner to another) of the footprint of the body 12.

An elongate concavity or recess 22 is formed in the base 16 of the body 12, co-linear with the part line 20. The recess 22 defines first and second ends 26a, 26b, separated by an intermediate or centre portion 24. In this embodiment, the ends 26a, 26b of the recess 22 are rounded and are wider than the centre portion 24. Hence, the recess 22 is substantially dog-bone shaped as viewed in Figure 1.

In this embodiment, the recess 22 is substantially V-shaped in cross-section, as can be seen most clearly in Figure 3.

A rib 30 is formed within the recess 22, in particular at the base of the recess 22 (i.e. at the apex of the V in the embodiment of Figures Ia to 4). The rib 30 extends co-linear with the part line 20 and a longitudina' axis of the recess 22. The rib 30 projects outwardly with respect to the underside of the container, as can be seen most clearly in Figure 3. However, the rib does not project beyond the concavity of the recess, so that the container 10 can rest on the base 18 without interference from the rib 30. In this embodiment, the recess 22 is deeper than the rib 30 is high, and extends substantially the full length of the recess 22.

In the illustrated embodiment, the nb 30 has a height of approximately 1mm (distance y on Figure 2b) and a width of approximately 1mm (distance x on Figure 2b), so that the proportion of width to height of the rib 30 is approximately 1:1. The proportion of width to height of the rib 30 may in other embodiments be between 0.8:1 to 1.2:1, or between 0.6:1 to 1.4:1.

The proportion of the width to height within the above ranges is in contrast to prior art containers, where the width to height ratio is often closer to 1:2 (i.e. the height of the rib is always substantially greater than the width of the rib). By controfling the ratio of width to height. the degree of stretch of the parison at this critical region is less than in the prior art, with the advantage of the container 10 being less likely to split or leak at the rib 30. The proportion of 1:1 in particular has been found to make the rib 30 more compact and stronger.

The depth of the recess is non-uniform along its length. lii particular. the recess 22 is shallower at the first and second ends 26a, 26b than in the centre portion 24. This provides greater material thickness at the recess ends 26a, 26b. strengthening the part line area.

In the region where the nb 30 extends within the ends 26a, 26b of the recess 22, shoulders 32 are formed on either side of the rib 30. The shoulders 32 provide support to the rib 30, increasing structural integrity of the container and so decreasing the likelihood of splitting or leaking at the rib 30.

The shoulders 32 are in this embodiment approximately two thirds the height of the rib 30.

That is, the shoulders 32 of this embodiment are approximately 0.66mm high. In aliernative embodiments the shoulders 32 may be equal th height to the rib 30, or may be more or less than two thirds the height of the rib 30.

The base 16 defines two further recesses 34, each extending substantially perpendicular to the recess 22. The recesses 34 are substantially tear-drop shaped, each having a narrow end 34a proximal the recess 22.

A suitably shaped mould tool is used for manufacturing the container 10. A base block 40 of such a mould tool is shown in Figures Sa and Sb. The base block 40 is configured for clamping against a corresponding symmetrical base block (not shown) at a first side 40a. The base block 40 defines a cavity 41 in which the base 16 is formed, with protrusions 42 configured to produce the recesses 22, 34. The rib 30 is formed in an indentation 44 along the first side 40a, with recesses 46 configured to produce the shoulders 32.

An exemplary method of producing the container 10 is produced as follows. A two part mould tool (not shown) including two base blocks 40 is provided. A parison is clamped between the two parts of the mould tool, with its lower end between the base blocks 40. The parison is inflated so that it takes on the shape of the mould tool, including the shape of the cavity 41. The resulting container 10 is released from the mould tool.

Another embodiment is shown in Figures 6a to 9b. Features corresponding to those of the first embodiment have been given corresponding reference numbers with the additional prefix "1". Only features that differ from those of the first embodiment are discussed in depth.

With reference to Figures 6a to 8, it can be seen that the rib 130 is stepped at the ends of the recess 122. In particular, the end portions l3Oa, l3Ob of the rib 130 have a height lower than the height of the rib 130 at a centre portion 131 of the rib 130. That is, where the rib 130 extends within the ends l26a, l26b of the recess 122, the iib 130 projects to a lesser extent than within the central portion 124 of the recess 122.

This configuration has been found to provide support to and increase the structural integrity of the rib 130. The likelihood of splitting and/or leakage from the container 110 at the underside 116 is thus decreased.

The rib 130 being stepped allows more plastic to be retained at the rib ends 130a, 130b and reduces the likelihood of hollow regions occurring along the rib during the blow moulding process, and so reduces the likelihood of failure due to splitting of a hollow region or insufficient plastic thickness.

In this embodiment, as in the previous embodiment, the main portion (i.e. centre portion 131) of the rib 130 is approximately 1mm in height from the apex of the recess 122. The stepped end portions I 30a. I 30b are approximately one third of the height of the centre portion 131, i.e. approximately 0.33mm in height. In alternative embodiments the end portions 130a, 130b may be more or less than one third of the height of the centre portion 131. As in the previous embodiment, the proportion of width to height of centre portion 131 is approxirnatdy 1:1. The proportion of width to height of the centre portion 131 may in other embodiments be between 0.8:1 to 1.2:1, or between 0.6:1 to 1.4:1.

In an altemative embodiment (not shown), the rib 130 is stepped at one end of the recess 122 only. In one embodiment (not shown) the rib 130 is stepped only at an end of the recess 122 opposite a side of the container 110 upon which a handle (not shown) is provided. Formation of the handle can lead to stretching of the parison at this end of the recess 122 in particular during manufacture. The rib 120 being stepped at this end provides a smaller rib profile requiring tess stretching of the parison. The likefihood of failure due to splitting (e.g. as a result of insufficient plastic thickness) is thus advantageously reduced.

A base block 140 suitably shaped for manufacture of the container 110 is shown in Figures 9a and 9b. The base block 140 defines a cavity 141 in which the base 118 is formed. The indentation 144 defines stepped shallower end portions 148 configured to provide the stepped end portions 130a, 130b.

In an alternative embodiment the stepped rib 130 may be supported by shoulders, either at the end portions 30a, 30b, 130a, 130b andlor at the centre portion 131.

The above embodiments provide a lightweight container 10, 110 with improved structural integrity.

Claims

Claims 1. A blow moulded plastics container for storing liquid such as milk, the container comprising: a blow moulded body defining a chamber for storing Uquid, a base for standing the body in an upright manner, and a part line, wherein the base defines a recess extending co-linear with the part line, wherein a rib is formed along a portion of part line within the recess, the rib extending outwardly within the recess; and wherein a ratio of the width of the rib to the height of the rib along a substantial length of the rib is between about 0.8:1 and about 1.2:1.
2. A blow moulded plastics container according to claim 1 wherein the ratio of the width of a main portion of the rib to the height of the main portion of the rib is between about 0.9:1 andabouti.i:1.
3. A blow moulded plastics container according to claim I or claim 2 wherein the rib has a first end, a second end and a centre portion, and wherein the recess is shallower at the first and/or second end of the rib than at the centre portion.
4. A blow moulded plastics container according to claim 3 wherein the height of the rib at the centre portion is the same as at the first and second ends.
5. A blow mouded plastics container according to claim 3 or claim 4 wherein the height of the rib is uniform along its length.
6. A blow moulded plastics container according to any preceding claim wherein the rib has a first end, a second end and a centre portion, and wherein the recess defines at least one shoulder adjacent the rib at the first andlor second end of the rib.
7. A blow moulded plastics container according to claim 6 wherein the or each shoulder is between about 50% and about 80% of the maximum height of the rib, e.g. between about 60% and about 70% of the maximum height of the rib.
8. A blow moulded plastics container according to any of claims 1 to 7 wherein the rib has a first end, a second end and a centre portion, and wherein the height of the rib is decreased at the first andlor second end in relation to the centre portion.
9. A blow moulded plastics container for storing liquid such as milk, the container compnsing: a blow moulded body defining a chamber for storing liquid, a base for standing the body in an upright manner, and a part line, wherein the base defines a recess extending co-linear with the part line, lO wherein a rib is formed along a portion of part line within the recess, the rib extending outwardly within the recess; and wherein the rib has a first end, a second end and a centre portion, and defines at least one shoulder adjacent the rib at the first and/or second end of the rib.iS
10. A blow moulded plastics container according to claim 9 wherein the or each shoulder is between about 50% and about 80% of the maximum height of the rib, e.g. between about 60% and about 70% of the maximum height of the rib.
11. A blow moulded plastics container according to claim 9 or claim 10 wherein the rib has a first end, a second end and a centre portion, and wherein the recess is sha1ower at the first and/or second end of the rib than at the centre portion.
12. A blow moulded plastics container according to claim 11 wherein the height of the rib at the centre portion is the same as at the first and second ends.
13. A blow moulded plastics container according to claim 11 or claim 12 wherein the height of the rib is uniform along its length.
14. A blow moulded plastics container according to any of claims 9 to 13 wherein a ratio of the width of the rib to the height of the rib along a substantial length of the rib is between about 0.8:1 and about 1.2:1.
15. A blow moulded plastics container according to claim 14 wherein the ratio of the width of a main portion of the rib to the height of the main portion of the rib is between about 0.9:1 and about 1.1:1.
16. A blow moulded p'astics container according to any of claims 9 to 15 wherein the height of the nb is decreased at the first andlor second end in relation to the centre portion.
17. A blow moulded plastics container for storing liquid such as milk, the container compnsing: a blow moulded body defining a chamber for storing liquid, a base for standing the body in an upright manner, and a part line, wherein the base defines a recess extending co-linear with the part fine, wherein a rib is formed along a portion of part line within the recess, the rib extending outwardly within the recess; and wherein the rib has a first end, a second end and a centre portion, and the height of the rib is decreased at the first and/or second end in relation to the centre portion.
18. A blow moulded plastics container according to claim 17 wherein a ratio of the width of the rib to the height of the rib along a substantial length of the rib is between about 0.8:1 andaboutl.2:l.
19. A blow moulded plastics container according to claim 18 wherein the ratio of the width of a main portion of the rib to the height of the main portion of the rib is between about 0.9:1 and about 1.1:1.
20. A blow moulded plastics container according to any of claims 17 to 19 wherein the recess is shallower at the first and/or second end of the rib than at the centre portion.
21. A blow moulded plastics container according to any of claims 17 to 20 wherein the recess defines at least one shoulder adjacent the rib at the first and/or second end of the rib.
22. A blow mo&ded plastics container according to claim 21 wherein the or each shoulder is between about 50% and about 80% of the maximum height of the rib, e.g. between about 60% and about 70% of the maximum height of the rib.
23. A blow moulded plastics container for storing liquid such as milk, the container comprising: a blow moulded body defining a chamber for storing liquid, a base for standing the body in an upright manner, and a part line, wherein the base defines a recess extending co-linear with the part line, wherein a rib is foimed along a portion of part line within the recess, the nb extending outwardly within the recess; and wherein the rib has a first end, a second end and a centre portion, and the recess is lO shallower at the first and/or second end of the rib than at the centre portion.
24. A blow moirlded plastics container according to claim 23 wherein the recess defines at least one shoulder adjacent the rib at the first and/or second end of the rib.iS
25. A blow moulded plastics container according to claim 24 wherein the or each shoulder is between about 50% and about 80% of the maximum height of the rib, e.g. between about 60% and about 70% of the maximum height of the rib.
26. A blow moulded plastics container according to any preceding claim wherein the rib extends along at least a substantial length of the recess.
27. A blow moulded plastics container according to any preceding claim wherein the part line bisects the recess.
28. A blow moulded container according to any preceding claim wherein the recess has first and/or second ends which are wider than a centre portion of the recess.
29. A mould tool configured for producing a plastics container in accordance with any one of claims ito 8.
30. A mould tool configured for producing a plastics container in accordance with any one of claims 9 to 16.
31. A mould tool configured for producing a plastics container in accordance with any one of claims 17 to 22.
32. A mould tool configured for producing a plastics container in accordance with any one of claims 23 to 28.
33. A method of producing a plastics container for stonng liquid such as milk, the method comprising the step of providing a mould tool configured so that blow moulding plastics in the mould tool results in a container according to any one of claims 1 to 8, 9 to 16, 17 to 22, or 23 to 28; and blow moulding plastics in said mould tool.
34. A blow moulded plastics container or mould tool substantially as described herein andlor with reference to the accompanying drawings.