Background Art United States patent specification 5,423,444 discloses a plastics closure for a container having an externally screw threaded neck, the closure including a top portion and an internally threaded skirt. The closure has an annular sealing rib which projects downwardly from the underside of the top portion. The rib includes a first substantially cylindrical portion contiguous with the underside of the top portion and lying adjacent to or abutting with the skirt, and a second, frusto-conical, portion contiguous with the end of the first portion distal to the underside of the top portion and extending radially inwardly to a circular free edge. During threaded attachment of the closure with the neck, the second, frusto-conical, portion will be engaged by a free end of the neck and folded back against the first, substantially cylindrical portion of the rib to form a gas tight seal between at least the outer surface of the neck of the container and the closure.

United States patent specification 5,609,263 discloses a variant of the above closure in which there is at the free end of the second portion of the rib a thick seal ring of substantially circular cross-sectional shape. The rib and the seal ring are dimensioned to engage the free end of the neck when the closure is threaded onto the neck such that when the neck is fully screwed into the closure its free end crushes the seal ring directly against the inside surface of the top portion of the closure.

International Patent Application No PCT/AU98/00510 (WO 99/03746) discloses still further variants of the closure described in US In one variant, the sealing rib of the closure has a third portion connected to the second portion at or adjacent its circular edge and extending generally in a direction away from the top portion. The third portion is substantially no thicker than the second portion and has a length longer than its thickness.

On attachment of this closure to a container, the third portion is positioned between the neck of the container and the underside of the top portion of the closure.

The present invention is directed to a sealing rib arrangement for closures that further improves the sealing ability of closures of the type identified in the abovementioned prior art.

Disclosure of the Invention Throughout this specification, including the claims, the word "comprise"and variants such as"comprises"and"comprising"are used in a non-exclusive sense.

According to a first aspect, the present invention relates to a closure suitable for attachment to a container having an opening defined by an end portion of the container, the closure comprising a top portion and a skirt portion depending from the top portion, an annular sealing rib projecting downwardly from an underside of the top portion, the rib comprising a first portion which is contiguous with the top portion and having an inner surface, which inner surface lies radially inwardly of the skirt portion, a radially inwardly extending second, frusto-conical, portion contiguous with the first portion and separated from the top portion by the inner surface of the first portion, a third portion connected to the second portion and extending generally in a direction away from the top portion to an end distal the top portion, and a fourth portion connected to the third portion at or adjacent the distal end of the third portion and also extending in a direction generally away from the top portion, the fourth portion having a thickness that is less than the thickness of the third portion.

In a preferred embodiment, the inner surface of the first portion has an internal diameter relative to the external diameter of the end portion of the container such that during attachment of the closure with the end portion of the container, the sealing rib will be engaged by the end portion of the container so folding the second portion towards at least the inner surface of the first portion of the rib, and with the third and fourth portions of the rib positioned between the end portion of the container and at least the top portion of the closure.

In a preferred embodiment, the underside of the top portion of the closure can have a nub extending downwardly from the underside and positioned radially inwardly of the sealing rib. The nub is preferably positioned such that during attachment of the closure with the end portion of the container, at least some of the fourth portion of the sealing rib abuts the nub and is positioned between the nub and the end portion of the container.

In a preferred embodiment, the nub comprises a continuous member having an inner and outer surface. The outer surface of the nub can also be substantially cylindrical. In another embodiment, one of or both the outer or inner surfaces of the nub can taper relatively towards or away from each other as the nub extends away from the top portion. The nub preferably extends downwardly from the top portion a length less than the length of the inner surface of the first portion of the sealing rib. The nub is also preferably positioned such that its outer surface, before attachment of the closure, is radially inward of the outer surface of the third portion of the sealing rib. In a still further embodiment, the thickness of the top portion of the closure between the outer surface of the nub and the inner surface of the first portion of the sealing rib can be greater than the thickness of the top portion inwardly of the nub.

The end portion of the container to be sealed by the present invention preferably has a free end, an outside, preferably cylindrical, surface and an inside. preferably cylindrical, surface, the inside surface defining a bore. The join between the free end and the inside surface and the join between the free end and the outside surface are each preferably smoothly curved and define respectively what are hereinafter called the inner and outer sealing radii of the end portion of the container. In a preferred embodiment, on commencement of attachment of the closure with the end portion, the free end of the container's end portion firstly engages the fourth portion of the sealing rib. The relative upward movement of the fourth portion and hence the third portion results in the second portion also being pushed upwardly.

As the second portion is pushed upwardly it moves about the fold provided by the line of meeting between the first and second portions and so moves towards the inner surface of the first portion.

Once the closure is attached to the end portion of a container having an inner sealing radius, the nub preferably serves to exert a substantially outward pressure against at least some of the fourth portion of the sealing rib such that it seals against at least the inner sealing radius. In one embodiment, the nub can provide sufficient outwardly directed pressure and the sealing rib is of a sufficient length such that the fourth portion of the sealing rib either also sealingly engages with the inside surface of the end portion or only sealingly engages with the inside surface. It will be appreciated that the degree of sealing engagement of the fourth portion with

the inside surface of the container will depend on a number of factors, including the relative length of the second, third and fourth portions and the wall thickness of the end portion of the container.

On attachment of the closure to the end portion of a container, the second portion preferably seals with at least the outside surface of the end portion of the container. In a preferred embodiment, on attachment, the third portion preferably seals with the end portion of the container from a position on the outside surface of the end portion about the outer sealing radius and on to at least the apex of the free end of the end portion. It has also been found that the presence of the third portion reduces the torque needed to unscrew a closure from a corresponding container to which it has been attached.

The closures are preferably provided with a screw thread on an inside surface of the skirt portion adapted to engage with a corresponding thread on an external surface of the end portion of the container. It is, however, possible for the container and the closure to be formed with other complementary attachment means. Such an arrangement could, for instance, comprise snap-on attachment means having a rib on the inside surface of the closure and a corresponding groove on the outside surface of the end portion of the container.

The inner surface of the first portion of the sealing rib is preferably substantially cylindrical. The first portion of the rib can comprise a thickening of the skirt portion in the region adjacent its connection to the top portion. By comprising such a thickening, the root of the second portion of the rib is moved inwardly of the part of the skirt portion having the screw thread or other attachment means.

In another embodiment, the first portion of the sealing rib is formed radially inwardly of the skirt portion with an annular space therebetween. In a still further embodiment, the first portion of the sealing rib can be in abutment with the skirt portion.

In yet a further embodiment, the first portion of the rib can have a thickness that increases as it extends in a direction away from the top portion of the closure. This thickening of the first portion serves to increase the force of the pressure of the rib against the outside surface of the end portion of the container on attachment of the closure to the end portion. The thickness of the first portion can increase at a uniform rate along the length of the first

portion away from the top portion, however, it could do so in a non-uniform mailler. The increase in the thickness of the first portion means that the inside surface and, where there is one, the outside surface, of the first portion will each not necessarily be exactly cylindrical. They may respectively taper slightly inwardly or outwardly relative to the axis of the closure in a direction away from the top portion of the closure.

The inner surface of the first portion serves to form an abutment towards which the second portion is moved or folded during attachment of the closure with the end portion of a container. Preferably, during attachment, the second portion will be folded back against the first portion such that it bears against the inner surface of the first portion. This will cause the second portion to bear more strongly against at least the outside surface of the end portion of the container and so form a better seal with at least the outside surface of the end portion.

The third portion of the sealing rib is preferably contiguous with an end of the second portion distal the first portion, though it may be spaced slightly radially outwardly from the end of the second portion. The third portion is preferably substantially no thicker than the second portion and further preferably has a length longer than its thickness. The third portion also preferably projects generally axially away from the top portion of the closure to the distal end of the third portion. The third portion is preferably substantially cylindrical and can have both a cylindrical inner surface and a cylindrical outer surface. The third portion can join the second portion in an angular disjunction or it may join it in a smooth angular transition from the generally radially inward direction of the second portion to a generally axial direction.

The fourth portion of the sealing rib is preferably contiguous with the distal end of the third portion. The fourth portion also preferably projects generally axially away from the top portion of the closure. The fourth portion also preferably has a length longer than its thickness. The fourth portion is preferably substantially cylindrical, having both a cylindrical inner surface and a cylindrical outer surface. In a preferred embodiment, the outer surface of the fourth portion is coincident with the outer surface of the third portion. In this embodiment, as the fourth portion has a thickness that is less than the third portion, the inner cylindrical surface of the fourth portion is radially outwardly offset from the inner surface of the third portion. In an

alternative embodiment, the cylindrical inner surface of the fourth portion is coincident with the cylindrical inner surface of the third portion, with the outer surface of the fourth portion being radially inwardly offset from the outer cylindrical surface of the third portion.

In another embodiment, the fourth portion can taper in thickness as it extends away from the distal end of the third portion. The taper of the fourth portion can be provided by the inner surface tapering towards a cylindrical outer surface, or by the outer surface tapering towards a cylindrical inner surface. or by both the inner and outer surfaces tapering towards each other.

Where the fourth portion does taper in thickness, the thickness of the fourth portion preferably decreases at a uniform rate along the length of the fourth portion away from the third portion, however, it could do so in a non- uniform manner.

The closure according to the present invention may be moulded from a synthetic plastics material. It is preferred that the closure is formed from a suitable grade of polyethylene or polypropylene. It is also preferred to form the closure in one piece. The closures could, however, be formed in two or more parts with at least the sealing rib formed separately from the top portion and the skirt portion.

It will be apparent to persons skilled in the art that numerous modifications may be made to the closure described in this specification without departing from the scope of the invention as earlier defined. The closure may, for instance, be provided with a tamper evident band adapted to provide an indication of removal or attempted removal of the closure from a container. The tamper evident band can extend from the skirt portion by connection through a plurality of frangible bridges.

As is described in Australian Patent No 668197, the contents whereof are incorporated herein by reference, the band can also comprise a generally cylindrical body portion and a segmented rib extending inwardly of the body portion and adapted to provide a lip having an inner free edge to engage under a retaining flange extending outwardly from the end portion of the container. The combine length of the segmented ribs can be equal to at least 50% of the internal circumference of the band and the segmented ribs are preferably separated from each other by a gap. Each of the rib segments can each have an upper surface facing generally towards the top portion of the closure and an underside facing generally away from the top portion,

with the inner surface of the band having a plurality of radially inward projections extending from above the free edge of the band and not extending beyond the inner free edge of the lip.

As is described in Australian Patent No 683598, the contents whereof are incorporated herein by reference, the upper surface of each rib segment extending inwardly of the body portion can be a compound surface and comprise a first surface contiguous with the body portion of the band, which surface slopes inwardly and downwardly away from the top portion, and a second surface which extends radially inwardly from the inner terminus of the first surface and has a slope angle substantially normal to the skirt portion of the closure.

As is described in US Patent No 5676269, the contents whereof are incorporated herein by reference, the tamper evident band can be joined to the skirt portion of the closure by a plurality of frangible bridges and at least one non-frangible bridge. The band can further have a substantially L- shaped slot extending through the side wall of the band, the horizontal leg of which terminates directly adjacent to or under the non-frangible bridge, and a weakened frangible region extending from the terminating end of the horizontal leg axially downwardly to the bottom of the band distal the frangible bridges.

Where the closure has a screw thread on the inner surface of the skirt portion, the thread can be continuous or formed of a series of thread segments. If formed from a series of thread segments, the thread segments can be arrange, starting from a first thread segment distal to the top, along a helical thread locus, as is described in Australian Patent No 668197. Each of the thread segments except the first can be formed with two substantially planar end surfaces that are inclined to the axis of the closure and face away from the top of the closure, that is they face in the direction that a mold core used to mold the closure was withdrawn. In this specification, the term "substantially planar surface"is used to describe a surface that is nearly actually planar or that is curved provided that it all faces in the defined direction. The first of the thread segments is preferably pointed at its end distal to its one adjacent thread segment to assist in mating the thread on the closure with a complementary thread on the end portion of a container.

The substantially planar ends of the thread segments can also be incline to a notional radial plane of the closure extending from the

longitudinal axis of the closure to the end of the respective thread segment such that the ends are incline to the cylindrical skirt by an angle that is less than the angle that the respective notional plane makes with that skirt.

To assist in the venting of any gas that may be present in the container, the spaces between the thread segments in adjacent turns of the thread can be aligned. A groove may also be provided on the inside surface of the skirt portion of the closure extending longitudinally thereof through the aligned spaces.

There also can be at the line of meeting of the first and second portions of the sealing rib, a weakened zone or annular region of weakness to assist even deformation of the second portion relative to the first as the closure is attached to a container as is described in Australian Patent No 637706, the contents whereof are incorporated herein by reference.

In a further aspect, the present invention comprises a container having an opening defined by an end portion of the container, the end portion being sealed by a closure as defined herein. The container can be a carbonated beverage container and is preferably formed from polyethylene terephthalate (PET).

In a further aspect, the present invention comprises a mold for forming a closure as defined in any one of the preceding claims. The mould can be used to form the closure using injection or rotary moulding. It will be appreciated by persons skilled in the art that other suitable techniques for forming the closure could also be utilised.

In yet a further aspect, the present invention comprises a method of applying a closure as defined herein to an end portion of a container, the method comprising the step of turning the closure onto the end portion of the container until the closure seals the container.

Brief Description of Drawings The following description of a preferred embodiment of the present invention is provided as an example of the invention and is described with reference to the accompanying drawings, in which:- Fig. 1 is a diametrical sectional view through a part of a closure according to the first aspect of the present invention ; and Figs. 2a-2d are diametrical sectional views through the part of the closure depicted in Fig. 1 depicting the action of the sealing rib on attachment of the closure to an end portion of a container.

Best Mode for Carrving Out the Invention The closure 10 shown in Fig. 1 is injection moulded from a synthetic plastics material in a suitable mould. The closure 10 comprises a circular top 11 and a depending skirt 12. The radially inner surface of the skirt 12 is provided with a screw thread (not visible) that is adapted to mate with a corresponding thread on the neck of a bottle 20 to which the closure 10 is adapted to be attached. While the embodiment of the closure depicted in the drawings is described herein as having a screw thread, other suitable means for attaching the closure to the bottle 20 would be immediately apparent to a person skilled in the art.

The radially outer surface of the skirt 12 carries a series of fine vertical ribs 13. The fine ribs 13 in the depicted embodiment terminate at the lower edge of the skirt 12 in a narrow circumferential rib (not visible).

A sealing rib 14 is provided on the underside of the top 11 of the closure 10. The rib 14 is continuous and annular. Seen in cross-section the rib 14 has four portions 15,16,17 and 18. The first portion 15 is contiguous with the top 11 and, in the depicted embodiment, comprises a thickening of the skirt 12 adjacent the top 11. It will be appreciated that the first portion 15 could be formed radially inward of the skirt 12 such that there is an annular space therebetween.

The inner surface 19 of the first portion 15 is substantially cylindrical, while the second portion 16 is frusto-conical in form and is of substantially constant thickness as it extends radially inwardly from its outer edge which is contiguous with the lower end of the first portion 15. While depicted as being of substantially constant thickness, it will be envisaged that the second portion 16 can taper slightly in thickness as it extends radially inwardly from its outer edge.

A sharp edge 21 is formed at the line of meeting between the first portion 15 and the second portion 16. This sharp edge 21 defines a line of weakness between the two portions for a purpose that will be described later in this specification. The third portion 17 is contiguous with the radially inner end of the second portion 16, the two joining in a curved transition zone 22. The transition zone 22 changes the direction of the third portion 17 so that it projects substantially in an axial direction away from the top 11 to its distal end 23. The third portion 17 has a cylindrical inner surface 24 and a cylindrical outer surface 25 and is of a substantially constant thickness.

Again, it could be readily envisaged that the third portion 17 could taper in thickness from the transition zone 22 to its distal end 23.

The fourth portion 18 of the sealing rib 14 is contiguous with the distal end 23 of the third portion 17 and, in the depicted embodiment, also projects in an axial direction away from the top 11. The depicted fourth portion is also substantially cylindrical having a cylindrical inner surface 26 and a cylindrical outer surface 27. The outer cylindrical surface 27 is coincident with the outer cylindrical surface 25 of the third portion 17. As the thickness of the fourth portion 18 is about half that of the third portion 17, the inner cylindrical surface 26 of the fourth portion 18 is offset radially outwardly from the inner surface 24 of the third portion 17.

The underside of top 11 of the closure 10 has a nub 28 extending downwardly from the underside and positioned radially inwardly of the sealing rib 14. The depicted nub 28 is continuous and has an inner surface 29 and an outer surface 31 that taper slightly towards each other. The nub 28 extends downwardly from the top 11 for a length less than the length of the inner surface 19 of the first portion 15 of the sealing rib 14. The nub 28 is also positioned such that its outer surface 31, before application of the closure 10 to the bottle 20, is radially inward of the outer surface 24 of the third portion 17 of the sealing rib 14.

As is depicted in the drawings, the thickness of the top 11 of the closure 10 between the outer surface 31 of the nub 28 and the inside surface 19 of the first portion 15 of the sealing rib 14 can be greater than the thickness of the top 11 inwardly of the inner surface 29 of the nub 28.

The bottle 20 to be sealed by the closure 10 has a neck having an end portion 40. In the depicted embodiment, the bottle 20 is a returnable polyethylene terephthalate (PET) bottle. Such bottles typically have a thicker end portion 40 than non-returnable PET bottles of similar capacity. The end portion 40 has a free end 41, an outside cylindrical surface 42 and an inside cylindrical surface 43, with the inside surface 43 defining a bore 43a (see Fig.

2a). The join between the free end 41 and the inside surface 43 and the join between the free end 41 and the outside surface 42, on the bottle 20 depicted in Figs. 2a-2d are each smoothly curved and define respectively inner and outer sealing radii 44,45 of the end portion 40 of the bottle 20. While the present closure 10 can seal bottles 20 having the end portion 40 depicted in Figs. 2a-2d. it will be readily appreciated that the closure 10 can seal bottles

having different end portion configurations, eg. no outer and no inner sealing radii, or only one of the outer or inner sealing radii.

As is seen in Figs. 2a-2d, when the closure 10 is applied to and turned onto the end portion 40 of a bottle 20, the free end 41 of the end portion 40 engages the free end of the fourth portion 18 and starts to push it relatively upwardly within the closure 10. The relative upward movement of the fourth portion 18 and hence the third portion 17 results in the second portion 16 also being pushed upwardly. As the second portion 16 is pushed upwardly it bends relative to the first portion 15 along the line of weakness defined by the sharp edge 21. This ensures that the folding back of the second portion 16 relative to the first portion 15 takes place generally evenly around the whole circumference of the rib 14. The folding back of the second portion 16, and with it the third portion 17, allows at least the fourth portion 18 to contact the end portion 40 in the region proximate the inner radius 44. As the closure 10 continues to be turned onto the bottle 20, the second portion 16 is folded back towards the inner surface 19 of the first portion 15 (see Fig. 2c). At about this time, the rib 14 also begins to abut the nub 28.

Once the closure 10 is fully turned onto the end portion 40, the sealing rib 14 is positioned between the end portion 40 and the underside of the top 11 of the closure 10. As is depicted in Fig. 2d, the second portion 16 has been folded, in this case, back into contact with the inner surface 19 of the first portion 15. The second portion, while folded back against the inside surface 19, also bears against the outer surface 42 and onto the outer sealing radius 45 of the end portion 40.

With the closure 10 fully engaged on the bottle 20, the nub 28 also exerts an outwardly directed pressure on the sealing rib 14 such that at least a portion of the fourth portion 18 is forced into sealing engagement with the inner sealing radius 44 of the end portion 40. Once the closure 10 is fully turned onto the end portion 40, a seal extends from the outer surface 42, over the outer sealing radius 45. at least a portion of the free end 41, and at least a portion of the inside radius 44 of the end portion 40.

In another embodiment, the nub 28 can provide sufficient outwardly directed pressure and the sealing rib 14 can be of a sufficient length such that the fourth portion 18 of the sealing rib 14 also sealing engages with the inside surface 43 of the end portion 40. It will be appreciated that the degree of

sealing engagement of the fourth portion 18 with the inside surface 43 of the end portion 40 will depend on a number of factors, including the relative length of the second, third and fourth portions and the wall thickness of the end portion 40. For example, it could be envisaged that the fourth portion only sealingly engages with the inside surface 43 of the end portion 40, with the other portions sealing with the remainder of the end portion 40 as described.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.