GB1593072A

GB1593072A - Closures for containers

Info

Publication number: GB1593072A
Application number: GB52052/77A
Authority: GB
Original assignee: Metal Closures Ltd
Current assignee: Arconic Closure Systems International UK Ltd
Priority date: 1977-12-14
Filing date: 1977-12-14
Publication date: 1981-07-15
Also published as: ZA782344B; BE867558A

Description

(54) IMPROVEMENTS IN AND RELATING TO CLOSURES FOR CONTENDERS (71) We, METAL CLOSURES GROUP LIMITED, a British Company, of P.O. Box 32, Bromford Lane, West Bromwich, West Midlands B70 7HY, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to pressure resistant closures for containers and has particular reference to a closure having an improved pilfer proof or tamper proof seal or ring. At the same time, the invention has particular reference to a closure which is essentially formed from a one-piece moulding and incorporates the twin facilities of a pilfer proof or tamper proof seal and a pressure resistant seal.

Glass containers having a screw threaded type closure adapted to accommodate gasified goods such, for example, as lemonade, tonic water, soda water and the like, are generally well known. There is no indication to be provided on present such containers of any indication whether the goods have been adulterated or not, and, furthermore, there is frequently the occasion when a consumer purchases such goods and finds that the contents of the container are "flat", i.e. have lost, to a large extent, their gasified properties.

At the present time, these containers are generally provided with generally metal closures which have a sealing liner in the cap thereof so that on application of the closure to the bottle or container interaction of the screw thread between the closure and the container and also on the application of such top pressure as may be applied, draws the closure down on to the neck of the container so that the liner engages the rim of the container neck to deform the same and to effect a seal between the liner and the container neck itself.

The manufacture of such articles involves the formation of the closure and the insertion and/or formation of the liner in the closure itself. While this is a relatively simple operation, and has been practised for many years, the insertion of the liner is becoming increasingly more expensive and there is considerable advantage in the use of a plastics material itself to take up the slight imperfections of the container neck.

In our copending British Patent Application No: 50545/77 (Serial No. 1592960) there is provided a closure for a container the contents of which are pressurised, which closure comprises: a crown and a depending skirt, retaining means provided in or on said skirt and adapted to co-operate with the neck of the container to which the closure is to be applied, a flexible annular sealing ring extending from an internal surface of the closure and adapted to engage in sealing relationship with a container neck, and a support ring depending from the crown of the closure and disposed substantially concentrically within said sealing ring and arranged whereby when said closure is applied to a container neck, the extremity of the support ring abuts a surface of the sealing ring to restrain flexing of the sealing ring wherein the arrangement between the support ring and the sealing ring applied to a container neck is such that the pressurised contents of the container can permeate between the abutting support ring and the sealing ring to urge the sealing ring into further sealing engagement with the neck of the container to which the closure is applied.

With the desirability, however, of providing a pilfer proof seal, it then becomes that much more difficult to insert the liner into the closure.

Pilfer proof or tamper proof rings about the lower end of the skirt of the closure are generally well known and it has been proposed to provide such a ring with a tear strip or line of rupturable bridges defining a line of weakness between the skirt extension constituting the pilfer proof ring and the lowermost extremity of the skirt depending from the crown of the closure itself.

Hitherto, the interengagement between the pilfer proof ring portion on the one hand and the container neck on the other, has comprised an inwardly projecting barb or bead provided on the internal surface of the security ring adapted to snap over the corresponding security band or flange on the neck of the container so that once it is on, it is not possible to remove the closure without tearing the weakened portion between the pilfer proof ring portion and the closure or, in the alternative, removing the pilfer proof ring portion in to to, thus indicating clearly to a consumer that the contents of that particular container may well have been sampled.

The principal disadvantage of this arrangement is that, when applying such a pilfer proof ring/closure assembly to a container in the first instance, it is necessary to "snap over" the engaging bead or barb on the pilfer proof ring portion with a corresponding engaging portion on the neck of the container. To do this, the bead or barb which is usually of thicker section that the material of the rest of the pilferproof ring portion has to be stretched and the torque or force required to do this and to drive the thickened bead or barb over the engagement portion of the container neck is usually quite high.In general, it is a problem that the force required approaches or even exceeds that at which rupture of the weakened portion between the pilfer proof ring portion and the closure proper takes place and, in consequence, a number of containers have to be resealed as a result of failure of the pilfer proof ring portion during application of the closure.

According to the present invention, there is provided a pilfer proof closure for a container having an upstanding neck defining a dispensing opening and having a security band portion on the external neck surface, said closure comprising a crown portion adapted to overlay and close said dispensing opening, a skirt depending from the periphery of said crown portion including, on the internal surface of the skirt retaining means adapted to cooperate with corresponding means provided on the container neck, a flexible annular sealing ring depending from an internal surface of the closure and inclined inwardly towards the axis of the closure, said sealing ring being adapted to engage in sealing relationship with the container neck, a support ring depending from said crown portion and disposed substantially concentrically within said sealing ring to limit flexing of the sealing ring on application to a container neck and a skirt extension having a rupturable pilfer proof security portion which on application to the container neck enters over the security band portion on the container neck without rupture.

By "security band portion" as used herein in relation to the construction of the neck of a container is to be understood to include any bead, flange, rib, band or expanded portion or any groove, recess or slot which is adapted to engage a projection on the pilfer proof security portion for retention thereof against the action of closure removal.

The skirt extension preferably includes a plurality of tongue elements each hingedly connected with the skirt extension and adapted to extend inwardly thereof to engage the security band portion on the container neck and a rupturable portion disposed between the tongue elements and the closure skirt whereby removal of the closure from the container neck results in breaking of the rupturable portion to leave the skirt extension about the container neck thereby indicating that the container contents have been sampled.

On application of the closure to the container the tongue elements readily hinge upwards to pass over the cooperating means on the container neck without exertion of torque or force sufficient to break the rupturable portion.

The skirt extension may terminate at its lower extremity in an outwardly extending bead for strengthening purposes.

The plurality of tongues may be stamped, cut or otherwise formed juxtaposed the bead so that the extremity of the tongue extends upwardly and inwardly of the bead to hinge along the line juxtaposed the upper extremity of the bead.

The rupturable portion may comprise a plurality of circumferential splits extending around the skirt extension between the plane of the tongue elements and the plane defined by the lower extremity of the skirt of the container. The rupturable portion may further be associated with at least one axial line of weakness formed in the skin extrusion extending from the rupturable portion to the lower extremity thereof; a strengthening bridge may be provided juxtaposed said axial line of weakness across the rupturable portion whereby on removal of the closure from the container, the rupturable portion ruptures byt the strengthening bridge holds and causes further rupturing along the axial line of weakness so that the skirt extension is removed completely from the container neck.

This latter embodiment has some considerable advantage since the hinged nature of the tongue means that as the closure is withdrawn from the container neck the hinge line is drawn upwardly and the tongues pivot about the extremity of engagement with the cooperating portion on the container neck so that the hinge line is urged outwardly to expand the bead and assist tearing of any axial line of weakness.

As an alternative to the formation of the tongues and rupturable portion on the closure prior to application to a container, the pilfer proof closure may be applied to the container and the tongues and rupturable portion stamped or otherwise formed in situ on the container neck.

The invention further includes a method of closing a container which comprises applying a closure in accordance with the present invention and thereafter stamping out the tongues inwardly under the security band portion on the container neck either separately or simultaneously forming the lines of weakness constituting the rupturable portion. An axial line of weakness may be formed at the same time if desired.

The arrangement of the sealing ring and the support ring of the closure is preferably such that they urge the sealing ring into further sealing engagement with the neck of the container to which the closure is applied. The internal surface of the skirt juxtaposed the sealing ring may include an inwardly projecting annular bead which, when the closure is applied to the container, abuts the surface of the neck thereof juxtaposed the ring and serves to centre the closure on the container neck as the components are brought into sealing engagement and at the same time serves to take up and deform in response to any slight irregularity in the finish of the container neck per se.

The sealing ring may be a flexible annular ring extending inwardly from the crown and/or skirt of the closure and it is preferred that the sealing ring extends inwardly from the junction of the crown and the skirt to define a ring of generally frustoconical form which decreases in overall diameter with increasing spacing from the crown. The outer extremity of the ring on that portion adapted to engage the neck of the container may have an annular sealing member.

The annular sealing member may itself include a sealing surface adapted to engage the rim of the container neck and the sealing surface may carry one or more ribs each adapted to make line contact with the neck of the container.

The pressure of the contents of the container are arranged to act upon the sealing ring by permeating between the abutting surface of the support ring and the back of the sealing ring when the closure is in sealing engagement with the container. The imperfections between the sealing ring and the support ring are sufficient to allow pressure to build up in the annular space defined by the support ring, the crown, the skirt and the "back" of the sealing ring so that said additional pressure serves to urge the ring into further sealing engagement with the neck of the container. This additional sealing occurs by further flexing of the sealing ring into the low pressure area of the closure towards the skirt.

In an alternative embodiment of the present invention, the support ring may have one or more interruptions to allow pressurized gas to enter behind the ring in a manner described above.

At the same time, the inwardly directed annular bead engages the upper extremity of the container neck and serves to locate and centre the closure before maximum closure and sealing torque is finally applied.

The depth of the support ring is preferably selected so that the sealing ring is brought into abutting engagement therewith without the sealing surface being flexed at an angle such that the sealing surface passes through the perpendicular to the axis of the closure. With this arrangement the harder the closure is applied to the container, the greater is the sealing force applied directly to the sealing ring. Imperfections between the sealing ring and the support ring serve to allow permeation of pressurised gas into the annulus defined by the back of the sealing ring, adjacent portions of the skirt, and crown of the closure of the annular support ring thereby causing further flexing of the ring radially outwardly of the support ring to increase the sealing engagement one with the other.

In accordance with the preferred embodiment of the present invention, the higher the pressure of the contents the more effective the sealing of the sealing ring, while an interference fit is obtained between the annular bead and the neck of the container.

The invention described above provides the twin advantages of a one-piece plastics cap incorporating a pilfer proof or tamper proof security ring on the one hand and a built-in positive seal on the other. This is achieved without the considerable problem of providing an inner sealing liner into a closure havirg a skirt extension.

Following is a description by way of example only and with reference to the accompanying drawings of embodiments of closures in accordance with the present invention.

In the drawings: Figure 1 is a part section of the neck of the container to which the closure is to be employed; Figure 2 is a section of the closure in accordane with the present invention; Figure 3 is an elevation of part of the closure of Figure 2; Figure 3a is a diagrammatic view of part of a security ring of the closure of Figure 2; Figure 4 is a section on the line II-II of Figure 2; Figure 5 is a section of the closure of Figure 2 when applied to a container showing the sealing arrangement and the interengagement of the pilfer proof ring and the closure; Figure 6 is an alternative arrangement of the sealing assembly of Figure 2; Figure 7 is a section along the line 6-6 of Figure 6.

The upstanding neck 10 of a container shown in Figure 1 has a substantially smooth internal surface 11 and is substantially cylindrical to define a dispensing opening. The neck 10 terminates in an annular rim 12 and the external surface of the neck is provided with screw threads indicated at 13. A thickened security band 14 is provided below the threads 13 and provides an annular ridge 15 for engagement with the security ring of a closure to be applied to the container neck.

A closure has a substantially circular crown portion 110 and a depending cylindrical skirt 111, the outer cylindrical surface of which skirt is preferably knurled at 112 to assist manipulation by a user. The depending skirt 111 is provided on its inner surface with screw threads 113 adapted to co-operate with threads 13 provided on the container neck. The lower extremity 24 of cylindrical skirt 111 is provided with a depending cylindrical skirt extension security ring 25 which terminates at its lower end in an outwardly projecting annular bead 26. Juxtaposed the lower extremity 24 of cylindrical skirt 111 there is provided in the security ring 25 a circumferential line of slots 27 to define a line of weakness constituting a rupturable portion.

Towards the lower end of security ring 25 there is provided a plurality of circumferentially spaced tongues 28 hingedly connected to security ring 25 so that the tongues project inwardly of security ring 25 and upwardly thereof to provide an abutment surface 29. The tongues 28 are hingedly connected to the security ring 25 so that the tongues 28 can hinge outwardly to lie substantially in the plane of the security ring but have a residual bias inwardly to the position and attitude described above and as shown in Figure 2.

On application of such a closure to the container the closure together with the security ring is simply entered over the container neck and screwed on in the usual way. As each tongue enters over the security band 14, the inner extremity of tongue 28 engages the outer surface of the band and the tongue is hinged inwardly towards the plane of security ring 25. Progressive application of the closure to the container allows the tongue 28 to ride along the slightly inclined outer surface of the security band 14 until the extremity of tongue 28 is juxtaposed the engagement surface 15.The residual bias of the tongue 28 then allows the tongue to project inwardly as shown in Figure 2 so that an attempt to remove the closure will result in upward withdrawal of the security ring and to bring the abutment surface of the tongue into engagement with the ridge 15 of the security band 14 of the neck of the container. Continued application of torque to the closure would cause the tongue 28 to hinge outwardly about the abutment surface to splay bead 26 and to provide a downward resistance to removal of the closure. When the torque applied is greater than the residual strength of the rupturable portion defined by the line of weakness constituted by slots 27 is reached, the bridging portions between the slots will tear thus separating the closure from the security ring.Thus, unauthorised tampering with the closure will thus result in a clear indication to the consumer that the contents of the container may have been sampled.

In an alternative embodiment of the present invention an axial line of external or internal weakness 30 may be provided in the security ring 25 extending from a slot 27 to and through the annular bead 26. This line of weakness may be formed by a reduction in thickness by the provision of a groove 31 in one or other surfaces of the security ring (see Figure 3A). With this embodiment a strengthened bridge 32 may be provided adjacent axial line of weakness 30 so as to induce tearing of the line of weakness 30 as the closure is removed in order to remove the security ring with the closure. The security ring may then be torn off the closure once removed from the container neck and the closure reapplied to the container as required by the consumer.

The internal surface of the skirt 111 is provided with a screw thread 113 and the junction between an internal surface 114 of the skirt and the inner surface of the crown 115 is provided with a generally frusto-conical inwar inwardly directed flexible ring 116. The ring 116 juxtaposed the junction of internal surface 114 and inner surface 115 comprises a first flexible portion 117 and a second outer sealing member 118. The second outer sealing member 118 has a lower sealing surface 119 and an upper curved surface 120 merging continuously with a back surface 121. The upper curved surface 120 and the sealing surface 119 together define an annular extremity 122 of the ring and the lower sealing surface has an annular bead 123.

The crown of the closure constituted by disc 110 carries an annular support ring 124 generally concentric with the disc 110 and spaced inwardly of the junction of sealing ring 116 with the crown and the skirt. The annular support ring depends from the inner surface 115 of the crown and is generally trapezoidal in cross-section decreasing in cross-section in a direction downwardly and away from the crown. The annular support ring has a substantially annular surface 125 which is adapted to engage with and abut the back surface 121 of the sealing ring when the latter is flexed.

Towards the junction of the sealing member 117 with the skirt 111 there is provided in the surface of the skirt above the upper extremity of the thread 113 a radially inwardly directed bead 127 which is adapted to engage with and abut the periphery 128 of neck 10 juxtaposed the annular neck rim 12.

In use, the closure is applied to the neck 10 of the container by engaging the screw thread 113 on the internal surface of the skirt 111 with corresponding thread 13 on the external surface of neck 10. By screwing the closure onto the container neck 10 the extremity 122 of the sealing ring 116 is brought into contact with rim 12 defining the extremity of the container neck. Continued application of the closure results in flexing of the flexible portion 117 of the ring 116 to bring the lower sealing surface 119 into juxtaposition with rim 12 with the annular bead 123 carried by lower sealing surface 119 in abutting relationship with the juxtaposed portion of rim 12.

As the closure is screwed onto the container neck, the rim 12 enters within radially inwardly directed bead 127 until the outer surface abuts said bead 127. The closure is then located and centred by bead 127 as final tightening of the closure is completed. The closure is tightened down until the back surface 121 of the sealing ring 116 abuts the annular surface 125 of support ring 124 to positively urge the sealing ring into sealing engagement with the rim 12 of the neck 10 of the container.

In this condition, the generation of pressure within the container itself results in an increase in pressure within the container. The increase in pressure will tend to assist gas permeation between the annular support ring 124 and the sealing ring 116 to enter the annulus 140 and to exert pressure on the first flexible portion 117 and the back surface 121 of sealing ring 116 thus enhancing the sealing engagement between member 118 and the rim 12 of the container to which the closure is employed.

It will be appreciated that the flexible portion 117 of the sealing ring 116 is urged and flexed into the relatively low pressure area defined between the outer surface of the rim 12 of the container and the inner surface of the skirt carrying the threads 113.

The closure described above was attached to a test rig including a suitable neck and applied with a torque of 20 Ib/inches. A pressure of 160 Ibs. per square inch was applied to the inside of the container neck and was maintained for 2 minutes. The removal torque after release of the pressure was 11 to 12 Ib./ inches.

A container was filled with carbonised water and the above closure applied with a torque of 20 Ib./inches. The container was shaken continuously for 14 days and the container referred to above was then stored lying on its side for 80 days. In each case no leakage was noted.

It will be appreciated that the closure described above may be manufactured of any suitable resilient thermoplastics material and depending on the contents of the container, materials such as polypropylene and modified polyethylene have been found to be particularly successful. Closures manufactured in accordance with the present invention have been tested with water under laboratory conditions of pressures in excess of 50 Ib. per square inch without leaking. It will be appreciated, however, that the degree of pressure seal obtained is dependent on the nature of the plastics material employed, the nature of the contents of the container and the material and uniformity of the sealing surfaces of the container itself.

In the embodiments shown in Figures 5 and 6, the support ring 124 is provided with a number of gaps 125', which serve to provide means for the entry of pressure building up within the neck of the container to enter behind the sealing ring 116 as shown in Figure 6.

It will be appreicated that this facilitates the entry of pressurized gas behind the flexible sealing ring 116 to enhance the sealing thereof with the container rim.

WHAT WE CLAIM IS: 1. A pilfer-proof closure for a container having an upstanding neck defining a dispensing opening and with a security band portion on the external neck surface thereof, said closure comprising a crown portion adapted to overlay and close said dispensing opening, a skirt depending from the periphery of said crown portion including, on the internal surface of the skirt, retaining means adapted to cooperate with corresponding means provided on the container neck, a flexible annular sealing ring depending from the internal surface of the closure and inclined inwardly toward the axis thereof, said sealing ring being adapted to engage in sealing relationship with the container neck, a support ring depending from said crown portion and disposed substantially concentrically within the sealing ring to limit flexing of the sealing ring on application to a container neck and a skirt extension having a rupturable pilfer proof security portion which on application to the container neck enters over the security band portion on the neck without rupture.

2. A closure as claimed in claim 1 wherein the skirt extension includes a plurality of tongue elements each hingedly connected with the skirt extension and adapted to extend inwardly thereof to engage the security band portion on the container neck.

3. A closure as claimed in claim 2 wherein the rupturable portion is disposed between the tongue elements and the closure skirt, whereby removal of the closure from the container neck results in breakage of the rupturable portion to leave the skirt extension about the container neck thereby indicating that the container contents have been sampled.

4. A closure as claimed in any preceding claim wherein the skirt extension terminates at its lower edge in an outwardly extending bead.

5. A closure as claimed in claim 4 wherein the plurality of tongues are stamped, cut or otherwise formed juxtaposed the bead so that the extremity of each tongue extends upwardly and inwardly of the bead to hinge along the line juxtaposed the upper extremity of the bead.

6. A closure as claimed in claim 4 and claim 5 wherein the rupturable portion comprises a plurality of circumferential slits extending around the skirt extension and between the plane of the tongue elements and the plane defined by the lower extremity of the skirt to define a pilfer proof ring.

7. A closure as claimed in any preceding claim wherein the rupturable portion further includes at least one axial line of weakness extending between the peripheral line of weakness constituting the rupturable portion and the lower extremity of the skirt extension.

8. A closure as claimed in claim 7 when dependent on claims I, 2 and 4 to 6 wherein a strengthening bridge is provided juxtaposed the axial line of weakness across the rupturable portion whereby on removal of the closure from

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ring 116 abuts the annular surface 125 of support ring 124 to positively urge the sealing ring into sealing engagement with the rim 12 of the neck 10 of the container. In this condition, the generation of pressure within the container itself results in an increase in pressure within the container. The increase in pressure will tend to assist gas permeation between the annular support ring 124 and the sealing ring 116 to enter the annulus 140 and to exert pressure on the first flexible portion 117 and the back surface 121 of sealing ring 116 thus enhancing the sealing engagement between member 118 and the rim 12 of the container to which the closure is employed. It will be appreciated that the flexible portion 117 of the sealing ring 116 is urged and flexed into the relatively low pressure area defined between the outer surface of the rim 12 of the container and the inner surface of the skirt carrying the threads 113. The closure described above was attached to a test rig including a suitable neck and applied with a torque of 20 Ib/inches. A pressure of 160 Ibs. per square inch was applied to the inside of the container neck and was maintained for 2 minutes. The removal torque after release of the pressure was 11 to 12 Ib./ inches. A container was filled with carbonised water and the above closure applied with a torque of 20 Ib./inches. The container was shaken continuously for 14 days and the container referred to above was then stored lying on its side for 80 days. In each case no leakage was noted. It will be appreciated that the closure described above may be manufactured of any suitable resilient thermoplastics material and depending on the contents of the container, materials such as polypropylene and modified polyethylene have been found to be particularly successful. Closures manufactured in accordance with the present invention have been tested with water under laboratory conditions of pressures in excess of 50 Ib. per square inch without leaking. It will be appreciated, however, that the degree of pressure seal obtained is dependent on the nature of the plastics material employed, the nature of the contents of the container and the material and uniformity of the sealing surfaces of the container itself. In the embodiments shown in Figures 5 and 6, the support ring 124 is provided with a number of gaps 125', which serve to provide means for the entry of pressure building up within the neck of the container to enter behind the sealing ring 116 as shown in Figure 6. It will be appreicated that this facilitates the entry of pressurized gas behind the flexible sealing ring 116 to enhance the sealing thereof with the container rim. WHAT WE CLAIM IS:

1. A pilfer-proof closure for a container having an upstanding neck defining a dispensing opening and with a security band portion on the external neck surface thereof, said closure comprising a crown portion adapted to overlay and close said dispensing opening, a skirt depending from the periphery of said crown portion including, on the internal surface of the skirt, retaining means adapted to cooperate with corresponding means provided on the container neck, a flexible annular sealing ring depending from the internal surface of the closure and inclined inwardly toward the axis thereof, said sealing ring being adapted to engage in sealing relationship with the container neck, a support ring depending from said crown portion and disposed substantially concentrically within the sealing ring to limit flexing of the sealing ring on application to a container neck and a skirt extension having a rupturable pilfer proof security portion which on application to the container neck enters over the security band portion on the neck without rupture.

the container the rupturable portion ruptures but the strengthening bridge holds and causes further rupture along the axial line of weakness so that the skirt extension is removed from the container neck with the closure.

9. A closure as claimed in any one of claims 4 to 8 wherein the tongues and rupturable portion are formed in the skirt extension after the closure has been applied to a container.

10. A closure as claimed in any preceding claim wherein the sealing ring and support ring are disposed to urge the sealing ring into further sealing engagement with the neck of the container to which the closure is applied.

11. A closure as claimed in any one of the preceding claims wherein the internal surface of the skirt juxtaposed the sealing ring includes an inwardly projecting annular bead which, when the closure is applied to the container, abuts the surface of the neck juxtaposed the ring and serves to centre the closure on the container neck as the components are brought into sealing engagement.

12. A closure as claimed in any preceding claim wherein the sealing ring is a flexible annular ring extending inwardly from the crown and/or skirt of the closure.

13. A closure as claimed in claim 12 wherein the sealing ring extends inwardly from the junction of the crown and the skirt to define a ring of generally frustoconical form which decreases in overall diameter with increasing spacing from the crown.

14. A closure as claimed in claim 13 wherein the outer extremity of the ring on that portion adapted to engage the neck of the container has an additional annular sealing member.

15. A closure as claimed in claim 14 wherein the annular sealing member includes a sealing surface adapted to engage the rim of the container neck, said sealing surface carrying one or more ribs each adapted to make sealing contact with the neck of the container.

16. A closure as claimed in any one of claims 13 to 15 wherein the support ring is disposed concentrically within the sealing ring and adpated to abut the back of the sealing ring when the closure is in sealing engagement with the container.

17. A closure as claimed in any preceding claim wherein the dimension of the support ring is selected so that the sealing ring is brought into abutting engagement therewith without the sealing surface of the sealing ring being flexed at an angle such that the sealing surface passes through the perpendicular to the axis of the closure.

18. A closure as claimed in any preceding claim wherein the support ring has one or more interruptions to allow the pressurized gas to enter behind the ring to flex the sealing ring into the low-pressure area of the closure towards the skirt.

19. A closure as claimed in any one of claims 1 to 17 wherein the support ring is substantially continuous and wherein imperfections between the support ring and the sealing ring are such that pressurized gas from within the container permeates between the support and the sealing ring to urge the sealing ring into further sealing engagement with the neck of the container.

20. A closure as claimed in claim 1 and substantially as herein described with reference to and as illustrated in Figures 2 to 4, 5 and 6 of the accompanying drawings.

21. A method of closing a container which comprises applying a closure in accordance with claim 1 and thereafter stamping out in the skirt extension a plurality of tongue elements extending upwardly and inwardly from a bead at the lower extremity thereof so that the inner extremity of each tongue engages under a security band portion on the container neck.

22. A method as claimed in claim 21 wherein the rupturable portion is formed between the tongues and the skirt of the closure.

23. A method as claimed in claim 22 wherein a line of weakness defines the rupturable portion and is formed simultaneously with the formation of the tongue.

24. A method as claimed in claim 21 or claim 22 wherein a line of weakness define the rupturable portion and is formed after or before formation of the tongues.

25. A method as claimed in any one of claims 21 to 24 wherein an axial line of weakness is formed in the skirt extension extending from the rupturable portion ot the lower extremity thereof.

26. A method as claimed in any one of claims 21 to 25 and substantially as herein described with reference to the accompanying drawings.

27. In combination, a container having an upstanding neck defining a dispensing opening and having a security band portion on the external surface thereof and a closure as claimed in any one of claims 1 to 20.