GB2375760A

GB2375760A - Container closure

Info

Publication number: GB2375760A
Application number: GB0208532A
Authority: GB
Inventors: Nigel Thompson
Original assignee: Alcoa Closure Systems International Inc
Current assignee: Closure Systems International Inc
Priority date: 2001-04-12
Filing date: 2002-04-12
Publication date: 2002-11-27
Anticipated expiration: 2022-04-12
Also published as: GB0208532D0; GB2375760B; HK1052674A1

Abstract

The present invention concerns a closure 2 for a container neck 10, the closure comprising: a crown 4 having a peripherally depending skirt 6; an annular channel 16 formed on the underside of the crown for receiving the container neck; and a resiliently deformable liner 12 disposed in the channel and having a substantially U-shaped sealing surface for forming a seal with the container neck; the channel being bounded radially inwardly by a protrusion 18 formed in the crown, the protrusion extending axially further from the crown than the part of the sealing surface which is nearest the crown; wherein the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion. A closure for a container, comprises a crown 4 having a peripherally depending skirt 6 and a resiliently deformable liner 12, the crown 4 underside having an annular protrusion formed thereon, and a hinge at or adjacent a radially inward transition from the protrusion to the crown 4.

Description

CONTAINER CLOSURE The present invention relates to closures for containers, and in particular to closures for sealing a container against leakage of liquid or gas under pressure.

It is known to provide screw-threaded closure caps having a liner formed on the underside of the crown of the cap. Such liners may be moulded into the cap interior, using injection moulding or other moulding processes and are generally formed of resiliently deformable material, thereby acting to improve the seal made with the upper rim of the neck of the container.

A problem with containers bearing such caps can occur when they are exposed to relatively high or low temperatures (such as experienced in hot or cold climates). In this respect, characteristics (such as flexibility) of the components of the container and closure can change with temperature, such changes potentially resulting in relative movement of such components. The integrity of the seal made between the container neck and the closure cap can be compromised when such components relate to the seal.

Further, when closures of this type are exposed to relatively high internal gas pressures relative to their surroundings, they will tend to dome upwards. This'doming'may cause the seal components to shift, again resulting in the potential for leakage of liquids and/or gases from the container.

An object of the present invention is to seek to alleviate such problems.

According to a first aspect of the present invention there is provided a closure for a container neck, the closure comprising: a crown having a peripherally depending skirt; an annular channel formed on the underside of the crown for receiving the container neck; and a resiliently deformable liner disposed in the channel and having a substantially Ushaped sealing surface for forming a seal with the container neck; the channel being bounded radially inwardly by a protrusion formed in the crown, the protrusion extending axially further from the crown than the part of the sealing surface which is nearest the crown; wherein the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion.

In this way, the point at which the protrusion meets the crown radially inward of the protrusion forms a hinge point. As such, should the closure experience forces that would tend to cause doming, then the central portion of the crown will be allowed to dome and the protrusion will remain isolated from the effects of doming.

In use of this arrangement, the protrusion formed in the crown extends into the inside of the container neck when the closure is in place.

In preferred embodiments, the liner extends at least from a position adjacent the skirt to a position radially inside the protrusion. Hence the liner is provided throughout the required area of sealing.

Conveniently, the liner covers the entire inward facing surface of the crown. A radially outer portion of the liner

adjacent an inner face of the skirt and a radially inner portion of the liner adjacent the radially outer face of the protrusion have an increased thickness. This increased thickness of the liner is provided to afford additional resilience for the seal between the container neck and the closure. In this connection, the outer portion of the liner adjacent the inner face of the skirt can thereby provide a primary seal with the rim of the container neck and the inner portion of the liner adjacent the outermost face of the protrusion can provide a secondary, or inner, seal with the rim of the container neck.

In normal operation of the closure, with the closure in place the liner is biassed against the container neck to ensure a reliable seal. Ordinarily, this biassing force would not be sufficient to alter the position of the container neck in the closure, due to the relative stiffness of the container neck.

However, when a container bearing such a closure is exposed to relatively high ambient temperatures, the walls of the container neck will become more flexible. As such they will tend to be urged radially inwardly by the biassing effect of the outer portion of the liner. Hence, as the container neck becomes warmer and more flexible, it will become more susceptible to inward movement, thereby potentially breaking the primary seal with the liner.

With the present invention however, if the interior dimension of the neck tries to shrink as a result of inward radial movement of the container neck wall, the protrusion provides a plug or stop resisting such inward movement and hence maintaining the primary seal.

Preferably, the radially outermost face of the protrusion is substantially planar and extends substantially axially of the crown. The radially innermost face of the protrusion is inclined, preferably at substantially 45 to the axial direction of the closure and so provides support to prevent tendency of the protrusion to bend inward. In this manner the protrusion forms an effective stop along its length to resist inward movement of the container neck. Coupled with a portion of liner of increased thickness between the container neck and the protrusion, the provision of an inner seal in that area is enhanced.

Preferably, the skirt is provided with a projection extending radially inwardly thereof and substantially adjacent the liner. The projection is arranged to retain the liner against the underside of the crown and provide support for the liner against the container neck. As such the liner can be held securely in position in preparation for reception of a container neck, whereupon the projection provides a profiled support for effective sealing. In this regard, the projection may be ramped.

In preferred embodiments, the skirt comprises a screw-thread on the inner face thereof, to co-operate with a screw thread on the container neck.

Preferably, the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion by around 10 to 20 %, and more particularly by substantially 15 %.

According to a second aspect of the present invention there is provided a closure for a container neck, the closure

comprising: a crown having a peripherally depending skirt; an annular channel formed on the underside of the crown for receiving the container neck; and a resiliently deformable liner disposed in the channel and having a substantially Ushaped sealing surface for forming a seal with the container neck ; the channel being bounded radially inwardly by a protrusion formed in the crown, the protrusion extending axially further from the crown than the part of the sealing surface which is nearest the crown; wherein the crown is formed with a hinge at or adjacent the radially inward transition from the protrusion to the crown for isolating the protrusion from movement of the central area of the crown.

The hinge may be formed as a thinning of the crown radially inward of the protrusion relative to the thickness of the crown radially outward of the protrusion.

In this manner doming of the crown is only permitted inward of the hinge, allowing components of the closure outward of the hinge to maintain their conformity. Hence, significant shifting of the seal components does not occur and leakage of liquids or gases from the container is inhibited.

According to a further aspect of the present invention there is provided a closure for a container, the closure comprising a crown having a peripherally depending skirt, and a resiliently deformable liner disposed on the underside of the crown, the crown underside having an annular protrusion formed thereon and spaced radially inwardly of the skirt and extending axially further from the crown than the underside of the liner in the radial space between the protrusion and the skirt, wherein the crown is formed with a hinge at or adjacent the radially inward transition from the protrusion

to the crown, for isolating the protrusion from movement of the central area of the crown.

The invention will now be described by way of example with reference to the accompanying drawings, in which :- Figure 1 is a diagrammatic partial cross-sectional view of one embodiment of the invention immediately before engagement with a container neck; and Figure 2 shows the closure of Figure 1, after engagement.

Referring to the Figures, the closure 2 comprises a crown 4 formed for example of a plastics material with a peripheral depending skirt 6. The skirt is provided with a plurality of vertically extending knurls 5 to assist in gripping of the closure.

The skirt has an inwardly directed radial projection 7 spaced axially downwardly of the crown 4 to locate a liner 12. The skirt further is provided with a screw thread 8.

The closure is adapted for co-operation with a neck 10 of a container, which neck is provided with a screw thread portion 9 to its exterior.

A channel 16 is formed in the underside of the crown 4 between the skirt 6 and an annular protrusion 18. The channel 16 is provided for receiving a top rim 11 of the neck 10. The rim 11 is adapted to be forced into contact with the liner 12 in the channel by operation of the screw thread 8.

The container neck 10 may be formed of glass, but the

invention is particularly effective in plastics beverage containers, for example those formed of PET.

The liner 12 is moulded within the interior of the closure and forms a substantially U-shaped sealing area including a radially outer portion 20 and a radially inner portion 21. It is formed of resiliently deformable material, for example plastics material such as non-PVC plastisols or elastomers conventional in the art.

The radially outer portion 20 of the liner is of increased thickness and is provided adjacent the skirt. This outer portion is provided with an inclined face 22 for receiving and engaging the neck rim 11. The radially inner portion 21 of the liner is also of increased thickness and is provided adjacent to the protrusion. The outer and inner portions 20 and 21 afford enhanced resilient capacity, in order to optimise sealing properties between the container neck and the closure.

The thickness of the liner should be taken as the shortest distance between the liner outer surface which is to engage the container neck and the inner surface of the closure which the liner overlies. Hence in the central area of the crown, this is a vertical dimension, whereas at the radially inner and outer portions 20 and 21 this is a radial dimension.

In the embodiment shown, the ratio of the thickness of the liner at the radially outer portion 20 to that at the central area of the crown is substantially 4.5 : 1, whereas the ratio of the thickness of the liner at the radially inner portion 21 to that at the central area of the crown in substantially 2.5 : 1.

The projection 7 is arranged to retain the outer portion of the liner against the underside of the crown and provide support for the liner against the container neck. As such the liner can be held securely in position in preparation for reception of a container neck, whereupon the projection provides a profiled support for effective sealing.

On operation of the screw threads 8,9, the rim 11 is urged into the channel 16 to form a seal against the liner 12. The protrusion 18 thus extends into the interior of the neck 10.

As can be seen in Figure 2, the closure is aligned such that on contact with the container neck the liner 12 deforms in the region of the outer portion 20, between the outer face of the rim 11 and the skirt 6. In this regard, a primary seal is formed between the outer portion 20 and outer face of the rim.

The ramped, shallow rotated"S"shaped profile of the projection 7 ensures the outer portion 20 deforms in a manner to provide a reliable seal with the container neck.

The outer face 19 of the protrusion 18 extends substantially axially of the crown 4 so as to provide a sealing surface along its length.

Should the interior of the neck 10 try to contract by way of inward movement of the wall of the neck, this will be resisted by the protrusion 18. The protrusion 18 is positioned such that it will act to resist inward movement of the container neck before the primary seal formed by the outer portion 20 at the outer face of the container neck is compromised. At the same time, a secondary or inner seal is enhanced between the protrusion and container neck.

The protrusion 18 is formed with a planer outer face 19 but an inclined radially inner face 25. The inclination of the inner face 25 of the protrusion is configured to maximise support to the protrusion against inwardly directed forces from the container neck.

The angle of inclination a of the inner face 25 is between 30 and 60 but more preferably is substantially 45 .

As shown, the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion. Thereby, a hinge is formed at or adjacent the radially inward transition from the protrusion to the crown. The hinge has the effect of isolating the protrusion from movement of the central area of the crown associated with doming.

As such any doming is limited to occur inwardly of said hinge.

Consequently such doming does not significantly compromise conformity of the seal components of the cap.

In this connection, the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion by around 10 to 20 %, but preferably by substantially 15 %. In practice this equates to a reduction from 1. 42 mm to 1. 2 mm for the example shown in the drawings.

Claims

Claims: 1. A closure for a container neck, the closure comprising: a crown having a peripherally depending skirt; an annular channel formed on the underside of the crown for receiving the container neck; and a resiliently deformable liner disposed in the channel and having a substantially U-shaped sealing surface for forming a seal with the container neck; the channel being bounded radially inwardly by a protrusion formed in the crown, the protrusion extending axially further from the crown than the part of the sealing surface which is nearest the crown; wherein the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion.
2. A closure as claimed in claim 1, in which a radially outermost face of the protrusion is substantially planar and extends substantially axially of the crown.
3. A closure as claimed in claim 1 or 2, in which the liner extends from a position adjacent the skirt to a position radially inside the protrusion.
4. A closure as claimed in claim 1 2 or 3, in which a portion of the liner adjacent the radially inner face of the skirt has an increased thickness.
5. A closure as claimed in any preceding claim, in which a portion of the liner adjacent the radially outer face of the protrusion has an increased thickness.

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6. A closure as claimed in any one of the preceding claims, in which the skirt is provided with a projection extending radially inwardly and arranged to retain the liner against the underside of the crown.
7. A closure as claimed in any one of the preceding claims, in which the skirt comprises a screw-thread on the inner face thereof.
8. A closure as claimed in any one of the preceding claims, in which a radially innermost face of the protrusion is inclined relative to the axial direction of the closure.
9. A closure as claimed in claim 7, in which the innermost face of the protrusion is inclined at substantially 45 to the axial direction of the closure.
10. A closure as claimed in any preceding claim, wherein the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion by substantially 10 to 20

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11. A closure as claimed in claim 10, wherein the thickness of the crown radially inward of and adjacent the protrusion is reduced relative to the thickness of the crown radially outward of the protrusion by substantially 15 %.
12. A closure for a container, the closure comprising a crown having a peripherally depending skirt, and a resiliently deformable liner disposed on the underside of the crown, the crown underside having an annular protrusion formed thereon and spaced radially inwardly of the skirt and extending

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axially further from the crown than the underside of the liner in the radial space between the protrusion and the skirt, wherein the crown is formed with a hinge at or adjacent the radially inward transition from the protrusion to the crown for isolating the protrusion from movement of the central area of the crown.
13. A closure as claimed in claim 10, wherein the hinge is formed as a thinning of the crown radially inward of the protrusion, relative to the thickness of the crown radially outward of the protrusion.
14. A closure substantially as hereinbefore described with reference to the accompanying drawings.