WO1997035773A2

WO1997035773A2 - Snap-on, twist-off container closure assemblies

Info

Publication number: WO1997035773A2
Application number: PCT/GB1997/000798
Authority: WO
Inventors: Roger Milner King
Original assignee: Beeson And Sons Limited
Priority date: 1996-03-22
Filing date: 1997-03-21
Publication date: 1997-10-02
Also published as: WO1997035773A3; GB2311285A; GB9606041D0; AU2037897A

Abstract

The invention provides snap-on, twist-off container closure assemblies including one or more of the following features: (1) a sealing plug on the closure for insertion into the container neck, said plug having an outer annular sealing recess or sealing rib for engagement with an annular sealing rib or sealing recess on the inside of the container neck to form a seal; (2) complementary first and second locking elements on the container neck and the closure which engage to resist twisting-off of the closure from the neck until a predetermined minimum opening torque is applied to the closure, the assembly further comprising an alignment means to align the first and second locking elements when the closure is snap-fitted onto the container neck; and (3) ramped first and second thread segments on the container neck and the closure to reduce the axial force required to snap the closure onto the container neck relative to the axial force required to snap the closure off the container neck; and (4) a sealing web on the container neck and a compressible sealing wad in the base of the closure to form a seal with the container neck after removal of the sealing web.

Description

SNAP-ON. TWIST-OFF CONTAINER CLOSURE ASSEMBLIES

The present invention relates to container closure assemblies in which the closure is preferably secured onto a container neck by snap-fitting, and is preferably removed from the container neck by twisting off.

Snap-on, twist-off container closure assemblies are known for certain consumer applications, in particular for one liter and two liter plastic milk bottles. The closures are preferably snap fitted on to the bottle necks, that is to say the closure caps are preferably secured on the bottle necks simply by placing the cap over the neck and then applying a moderate axial downward force to snap fit the cap onto the bottle neck. This simplifies securing of the cap onto the neck both after the initial filling of the container in a bottling plant, and also by the consumer after use. Since it is relatively less easy to pull a closure cap axially off a container neck to which it has been snap fitted, these container closure assemblies are provided with shallow threads that enable the cap to be removed by twisting off. Both ease of opening and ease of resecuring of the cap on the container neck are thereby achieved. Container closure assemblies of this general type are described in, for example, US-A-5307946.

Existing snap-on, twist-off container closure assemblies of the kind described above suffer from a number of drawbacks. These drawbacks arise because of a compromise between the need to achieve a strong, reliable securing of the closure on the container neck and the need to achieve snap-on capability.

The need to achieve snap-on capability usually requires that the retaining threads on the container neck and the closure cap are very shallow, which limits the axial sealing force that can be applied between the closure and the container neck by engagement of the retaining threads. It also limits the maximum force that can be applied between the closure and a tamper-evident ring attached to the closure and retained on the container neck to separate the tamper-evident ring from the closure. In practice, separation of the tamper-evident ring is often a problem with this kind of snap-on, twist-off container closure assembly.

A further problem is that the closure usually has to be made of a soft plastic material in order to have sufficient flexibility for snap-on operation. Such soft plastic material is prone to wear, and is difficult to manufacture to precise tolerances.

Finally, existing snap-on, twist-off container closure assemblies are prone to leak when used on containers for liquids, such as milk. This is due to a combination of factors, including the low axial sealing force achievable between the snap-on closure and the container, low tolerances in the manufacture of the container closure and neck due to the use of soft plastic materials, and a tendency of the closure to work loose (back off) from the container neck.

Accordingly, it is an object of the present invention to provide an improved snap-on, twist-off container closure assembly.

In a first aspect, the present invention provides a container closure assembly comprising: a container neck having first retaining means on an outer surface thereof and an inner annular sealing rib or sealing recess on an inner surface thereof; and a closure having a base portion and a skirt portion, said skirt portion bearing second retaining means complementary to said first retaining means to secure said closure on said container neck in a snap-on, twist- off fashion, and said closure further comprising a sealing plug extending from the base portion of the closure inside said skirt portion for insertion into the container neck, said sealing plug having an outer annular sealing recess or sealing rib on an outer surface thereof for engagement with said inner annular sealing rib or sealing recess to form a seal when said closure is fully secured on said container neck.

Here and elsewhere in the specification, the terms "inner" and "outer" and cognate expressions refer to radially inner and outer positions, relative to the longitudinal axis of the container closure assembly.

The container neck and closure are preferably of circular cross-section, but it is an advantage of the snap- on, twist-off container closure assemblies according to the present invention that they do not necessarily need to be circular.

The first and second retaining means on the container neck and the closure for retaining the closure on the container neck in a snap-on, twist-off fashion may, for example, comprise anchor shaped projections on the closure skirt portion for abutment against bumps spaced around the container neck to bump the closure off the container neck, as described in WO91/01925, the entire contents of which are expressly incorporated herein by reference. However, preferably, the first and second retaining means each comprise at least one thread segment, such that the thread segment on the closure skirt can be snapped over the thread segment on the container neck, and then abuts against the thread segment on the container neck to retain the closure on the container neck until the closure is twisted off. The use of such thread segments provides the advantage that the closure can be secured on the container neck either by snap fitting or by screwing the closure onto the container neck.

The closure further comprises a sealing plug depending from the base portion of the closure inside the skirt portion for insertion into the container neck to plug the container neck when the closure is fully secured on the container neck. The characterising feature of this aspect of the invention is that the sealing plug comprises an outer annular sealing recess or outer annular sealing rib on an outer surface thereof for engagement with an inner annular sealing rib or inner annular sealing recess on the container neck to form a seal when the closure is fully secured on the container neck. This seal is formed inside the neck of the container, and helps to reduce leakage of fluid from inside the container when the closure is fully secured on the container neck. The location of this seal inside the container neck is particularly advantageous, since it prevents leakage of fluid from inside the container into the closure, where it could cause contamination. The engagement between the sealing rib and the sealing recess also helps to hold the closure in the secured position on the container neck, and reduces the tendency of the closure to work loose.

Preferably, the above seal is formed between an inner annular sealing rib on the container neck and an outer annular sealing recess on the sealing plug of the closure.

Preferably, the annular sealing rib has a ramped cross- section, whereby less axial force is required to secure the closure on the container neck than is required to remove the closure from the container neck. In order to achieve this effect, the sealing rib should be ramped so that the upper surface of the sealing rib (viewed in cross-section) is inclined as a smaller angle to the longitudinal axis of the assembly than the lower surface of the sealing rib.

Here and elsewhere in the specification, the term "upper" and cognate expressions refer to the side of the container neck furthest from the container and closest to the mouth of the container neck, and to the side furthest from the closure base portion for features on the closure skirt. Conversely, the term "lower" and cognate expressions refer to the side of the container neck closest to the container body and furthest from the mouth of the container neck, and to the side of the closure skirt closest to the base portion of the closure and furthest from the open end of the closure.

Preferably, the annular sealing rib has a substantially triangular cross section, with the upper and lower sides of the triangle making respectively lesser and greater angles to the axis of the container closure assembly as described above. In other preferred embodiments, the annular sealing rib can have a trapezoidal cross-section, with the upper and lower (sloped, non-parallel) sides of the trapezoid making respectively greater and lesser angles to the longitudinal axis of the container closure assembly.

Preferably, the annular sealing recess that forms a seal with the ramped annular sealing rib also has a ramped cross- section, complementary to the ramped cross-section of the annular sealing rib.

The ramped cross-section of the annular sealing rib and annular sealing recess operates as a ratchet, whereby less axial force is required to engage the annular rib and recess when applying the closure to the container neck than is required to disengaged the annular sealing rib and sealing recess when removing the closure from the container neck. This reduces the tendency of the closure to back off from the container neck in use, whilst making the closure easier to snap onto the container neck even when both are made of relatively hard plastic materials.

Preferably, the container closure assembly according to the first aspect of the present invention further comprises a second, outer annular sealing rib or sealing recess on the container neck and a second, inner annular sealing recess or sealing surface or sealing rib on the inner surface of the closure to form a second seal between the container neck and the closure outside the container neck when the closure is fully engaged on the container neck. The second seal still further reduces the tendency of the fully secured container closure assembly to leak.

In a second aspect, the present invention provides a container closure assembly comprising: a container neck having first retaining means and at least one first locking element located on the outer surface of the container neck; and a closure having a base portion and a skirt portion, said skirt portion having second retaining means complementary to said first retaining means for securing the closure on the container neck in a snap-on, twist-off fashion; said skirt portion further bearing at least one second locking element which engages said first locking element when the closure is fully secured on the container neck, and which resists twisting-off of the closure from the neck until a predetermined minimum opening torque is applied to the closure, said container closure assembly further comprising an alignment means to enable alignment of the first and second locking elements when the closure is snap fitted onto the container neck.

The preferred first and second retaining means for this aspect of the invention are as specified above for the first aspect of the invention. In addition, preferred embodiments of the present invention according to the second aspect also comprise any or all of the features of the invention according to the first aspect.

Preferably, the first locking elements each comprise a projection on the container neck, preferably located below the first retaining means, and presenting a first longitudinal abutment surface. Furthermore, the second locking elements preferably each comprise an inward projection on the closure skirt preferably located above the second retaining means on the closure skirt, and presenting a second longitudinal abutment surface for abutting the first longitudinal abutment surface to resist twisting-off of the closure from its fully securing position on the container neck until the predetermined minimum opening torque is applied. Here and elsewhere in the specification, the term "longitudinal" implies extending generally in the direction of the longitudinal axis of the container closure assembly.

The provision of the locking elements on the container neck and the closure effectively prevents working loose of the closure from its fully secured position on the container neck, and thereby greatly reduces the tendency of this kind of closure assembly to leak in use. This reduced tendency of the closure to work loose is particularly necessary where relatively steeply pitched thread segments are used as the retaining means on the container neck and the closure, as may be desirable for the reasons set forth below.

It will be appreciated that the locking elements on the container neck and the closure could, for example, comprise a projection such as longitudinal locking rib or stud on the container neck or the closure skirt for engagement in a complementary locking recess in the container closure skirt or the container neck.

Preferably, the assembly is further provided with one or more stop elements. The stop element is preferably a radial projection on the container neck, preferably adjacent to the first locking element. The height and shape of the stop element are adapted to abut the second locking element to block further screwing down of the closure beyond the fully secured position of the closure on the neck, i.e. the position at which the closure is retained by the locking elements. This prevents damage to the threads and sealing surfaces by over-tightening of the closure on the neck.

A feature of the provision of the locking elements on the container neck and the closure is that the locking elements will only engage at certain angular positions of the container closure on the container neck. For this reason, the container closure assembly according to this aspect of the invention also comprises an alignment means to enable alignment of the first and second locking elements when the closure is snap fitted onto the container neck.

The alignment means may be as simple as a visual marker or a radially or axially projecting flange to enable the user (or a mechanical capping apparatus) to align the closure correctly on the container neck before snap-fitting. Preferably, a plurality of radially spaced alignment flanges are provided around the outside of the closure. In alternative preferred embodiments, the retaining means on the container closure and the container neck are configured and arranged so that snap-fitting is only possible at certain predetermined angular positions of the closure on the container neck at which engagement of the first and second locking elements is automatically achieved.

It is a preferred feature of the assemblies according to this aspect of the invention that the closure can be secured on the container neck either by snap-fitting or by twisting-on of the closure until the locking elements engage. It is envisaged that the closure will be snap- fitted onto the neck at the bottling^plant after filling of the container, using automated alignment means as indicated above. Once the container closure assembly has been opened for the first time, it is envisaged that the domestic user will normally resecure the closure on the container neck by twisting-on.

The accuracy of the alignment between the closure and the container neck required for snap-fitting of the closure onto the container neck in this aspect of the invention can be reduced by providing first and second locking elements with first and second longitudinal abutment surfaces as described above, in which the first and/or the second longitudinal abutment surface is inclined to the longitudinal axis of the container closure assembly, whereby snap-fitting of the closure onto the container neck with engagement of the first and second abutment surfaces is possible over a range of angular positions of the closure on the container neck.

The accuracy of molding required to achieve a tight seal between the closure and the container neck at the precise position where the locking elements engage can be reduced by the provision of ramped longitudinal abutment surfaces on the locking elements, as described in detail in our US patent no. 5,411,157, the entire content of which is expressly incorporated herein by reference. Briefly, the first (and preferably also the second) longitudinal abutment surface is inclined at an angle to the radius of the container neck, such that the first and second longitudinal abutment surfaces abut radially when the closure is at or near the sealing position on the neck. A radial restoring force is exerted between the locking elements by resilient deformation of the closure skirt, and this force is converted by the said abutment into a closure torque on the closure when it is at or near said sealing position.

In a third aspect, the present invention provides a container closure assembly comprising: a container neck bearing one or more first thread segments on an outer surface thereof; a closure comprising a base portion and a skirt portion, said skirt portion bearing one or more second thread segments complementary to said first thread segments for securing the closure on the container neck in a snap- on, twist-off fashion; said first thread segments and/or said second thread segments having a ramped cross-section to reduce the axial force required to snap the closure onto the container neck relative to the axial force required to snap the closure off the container neck.

Any one or more of the characterising or preferred features of container closure assemblies according to either or both of the first and second aspects of the present invention may be present in the container closure assemblies according to the third aspect of the present invention.

In the third aspect of the invention, the retaining means on the container neck and the closure skirt are first and second thread segments, at least some of which have a ramped longitudinal cross-section whereby less axial force is required to snap the closure onto the container neck than would be required to snap the closure off the container neck. That is to say, the first thread segments and/or the second thread segments have an upper surface that is inclined at a lesser angle to the longitudinal axis of the assembly than the lower surface of the thread segment. This allows the first and second thread segments to snap over each other in ratchet fashion.

Preferably, the ramped cross section is substantially triangular, with the side of the triangle closest to the respective mouth of the neck or the closure inclined at a smaller angle to the longitudinal axis of the closure than the side of the triangle furthest from the respective mouth of the neck or of the closure.

In alternative preferred embodiments, the ramped cross section is substantially trapezoidal, with the side of the trapezoid closest to the respective mouth of the neck or of the closure inclined at a smaller angle to the longitudinal axis of the assembly than the side of the trapezoid furthest from the respective mouth of the neck or of the closure.

Preferably, the side of the ramped cross-section closest to the respective mouth of the neck or of the closure is inclined at an angle of 10-30°, preferably about 20°, to the longitudinal axis of the assembly.

Preferably, the side of the ramped cross-section furthest from the respective mouth of the neck or of the closure is inclined at an angle of 60°-90°, preferably 65°- 85°, more preferably about 80°, to the longitudinal axis of the assembly.

Preferably, the first and second thread segments have one or more substantially parallel respective abutting surfaces. That is to say, the first and second thread segments preferably have respective, matching upper and lower surfaces that abut over a substantial part of their whole length when the closure is fully secured on the container neck. More preferably, the first and second thread segments have matching cross-sections. This maximises the contact area between the first and second thread portions, and thereby maximises the axial sealing force that can be applied without deforming the closure.

The provision of the thread segments having a ramped cross section means that a more reliable snap-on container closure assembly can be achieved without sacrificing ease of snap-fitting. For example, a harder plastic can be used for the closure than is conventional for this kind of assembly, thereby reducing the tendency of the closure to wear in use, or to work loose from the container neck in use.

For some applications it is preferable to have a sealing web extending across the top of the container neck and bonded thereto to seal the contents of the container. The sealing web is peeled off, flipped off or pierced when the assembly is opened for the first time. The sealing web prevents contamination of the container contents, prevents leakage from the filled assembly during transport and storage before use, and functions as a tamper-evident feature.

A drawback of sealing webs as described above is that they cannot normally provide a seal once the assembly _has been opened for the first time. It is thus necessary to have a secondary seal to provide sufficient sealing of the container when the closure is resecured on the neck. A further drawback of sealing webs as described above is that the webs are normally formed from relatively fragile plastics or metallized plastics membranes. As a result, the webs can be damaged by the closure when it is secured onto the container neck for the first time.

It is an object of a fourth aspect of the present invention to provide a snap-on, twist-off container closure assembly with a sealing web that overcomes the above drawbacks.

The fourth aspect of the present invention provides a container closure assembly comprising: a container neck having an opening and first retaining means located below the opening; a sealing web extending across the opening and bonded to the container neck around the opening to seal the container neck; a closure having a base portion and skirt portion, said skirt portion having second retaining means complementary to the first retaining means for securing the closure on the container neck in a snap-on, twist-off fashion; and a compressible sealing wad inside the base portion of the closure for forming a compression seal with the container neck around the opening both before and after the sealing web is removed from the container neck.

The compressible sealing wad provides a leak-tight secondary seal even after the sealing web has been removed. Clearly, in order for this to work, the compressible sealing wad needs to be sufficiently compressible to accommodate the sealing web before it is removed. To achieve this compressibility, the thickness of the sealing wad is preferably at least twice the thickness of the sealing web, and more preferably at least four times the thickness of the sealing web.

The snap-on characteristics of the assembly enable the closure to be secured onto the container neck for the first time without disturbing the sealing web. This can be further assured by providing a circumferential recess on the container neck immediately below the sealing web, so that there is a clearance between the sealing web and the closure skirt when the closure is secured onto the container neck for the first time.

The container closure assembly according to the fourth aspect of the present invention preferably also comprises one or more of the characterizing or preferred features of the assemblies according to the second or third aspects of the invention.

Preferably, the retaining means on the container closure assemblies according to all aspects of the present invention comprise eight first thread segments on the container neck and eight second thread segments on the skirt portion of the closure. Preferably, the thread segments on the container neck and the closure enable the closure to be moved from a fully secured position to a fully disengaged position on the container neck by relative rotation through about 90° or less, preferably by rotation through 45-90°. Preferably, this disengagement is achieved in a single smooth rotation, with the thread segments on the cap following a substantially continuous, substantially helical thread path defined by the thread segments on the container neck.

Preferably, at least one of the thread segments has upper and lower thread surfaces, wherein the pitch of the lower thread surface is relatively lower in a first region and relatively higher in a second region displaced from a first region in a unscrewing direction.

Such variable pitch threads are described in detail an_d claimed in our copending United Kingdom patent application no. 9525876.0, the entire content of which is expressly incorporated herein by reference. The purpose of providing the varying pitch on the lower thread surface is in order to combine the advantages of steeply pitched threads (fast opening, more reliable sealing, and more reliable separation of the tamper-evident ring from the closure) with the advantages of shallow pitched threads and bayonet threads (reduced tendency to back off from the fully secured position and less torque required to exert the strong axial sealing force between the closure and the container necks) . These objects are achieved by providing the variable pitch thread, which has a low effective pitch when the closure is at or near the fully secured position on the container neck, and a steep pitch when the closure has been partially unscrewed from the fully secured position on the container neck.

Preferably, the pitch of the lower thread surface in the first region, i.e. in the low pitch region close to the fully secured position on the container neck, is substantially constant. Preferably, the pitch of the lower thread surface in this region is in the range -5° to +ιo°, more preferably +1 to +7°.

Preferably, the second region is adjacent to the first region of the lower thread surface.

Preferably, the container closure assemblies according to the present invention further comprise a tamper-evident ring joined to the skirt portion of the closure and separable therefrom when the closure is removed from the container neck for the first time.

Preferably, the tamper-evident ring is formed in one piece with the closure and is snap-fitted onto the container neck together with the closure. Preferably, the tamper- evident ring is joined to the closure by integral, severable bridges.

Preferably, the container neck comprises an abutment means below the retaining means for the closure, and the tamper-evident ring comprises a collar and a plurality of inwardly and upwardly directed flexible tabs extending from the collar, the tabs being able to flex outwardly to allow the tamper-evident ring to be snap-fitted over the abutment means when the closure is secured on the container neck for the first time. The tabs then abut against the abutment means to block axial movement of the tamper-evident ring when the closure is removed from the container neck for the first time, thereby causing the tamper-evident ring to separate from the closure.

More preferably, the tamper-evident ring and container neck are as described in our patent application 094/11267, the entire content of which is expressly incorporated herein by reference.

The abutment means may comprise a circumferential lip extending around the container neck, and preferably also comprises ratchet projections below the circumferential lip to block rotation of the tamper-evident ring in an unscrewing direction. In particularly preferred embodiments, the abutment means comprises a plurality of recesses spaced around the container neck below the retaining means, such that the flexible tabs are received in the recesses when the closure is snap fitted onto the container neck for the first time. The recesses block both axial and rotational movement of the tabs and hence of the tamper-evident ring when the closure is unscrewed for the first time, and thereby ensure more reliable separation of the tamper-evident ring from the closure.

Moreover, it is more difficult for somebody who wishes to tamper with the contents of the container to remove the closure from such an assembly without separating the tamper- evident ring from the closure.

Specific embodiments of the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 shows in side elevation a closure with tamper- evident ring for use in a container closure assembly according to the present invention;

Figure 2 shows a bottom plan view of the closure of Figure 1;

Figure 3 shows a longitudinal cross-section through the closure of Figure l, together with a partially cut away side elevation view of a container neck onto which the closure is to be fitted in a container closure assembly according to the present invention;

Figure 4 shows a detail view of a longitudinal cross- section through a container closure assembly formed by fully securing together with the container neck and closure shown in Figure 3;

Figure 5 shows a detail of part of a longitudinal cross- section through the container neck and closure of Figure 3 as the closure and tamper-evident ring are being snap- fitted onto the container neck for the first time;

Figure 6 shows a detail of part of Figure 4;

Figure 7 shows a detail of part of Figure 5;

Figure 8 shows a detail view of a longitudinal cross- section through a second embodiment of the container closure assembly according to the present invention with the closure fully secured on the container neck for the first time; and

Figure 9 shows a similar view to that of Figure 8, but after the closure has been resecured on the container neck following opening of the assembly for the first time. Referring first to Figure 3, this embodiment of the container closure assembly according to the present invention comprises a container neck 1 and a closure 3. The container neck 1 is preferably formed integrally in one piece, and integrally in one piece with a container body, by blow moulding of a plastic material such as polyethylene terephthalate. The closure 3 is preferably formed integrally in one piece by injection moulding of a plastic material such as polyethylene.

The container neck 1 is provided on its outside surface with eight thread segments 5 for retaining the closure on the container neck. Each thread segment 5 has a ramped triangular longitudinal cross-section, as shown more clearly in Figures 4 and 5. The surface 7 of each thread segment 5 that is closest to the mouth of the container neck is inclined less steeply to the longitudinal axis of the assembly than the thread surface 9 that is located further from the mouth of the container neck and faces away from the mouth of the container neck.

The lower surface 9 of each thread segment 5 is profiled, with a first region 11 having a relatively low pitch of only about 2°, and a second region 13 have a much steeper pitch of around 8°.

Extending around the inside of the container neck near the top of the container neck there is a circumferential inner sealing rib 15. The sealing rib 15 also has a substantially ramped triangular cross-section, with an upper surface 17 that is inclined at a smaller angle to the longitudinal axis of the assembly than the lower surface 19 of the circumferential inner sealing rib 15, as shown more clearly in Figure 5.

A circumferential sealing recess 21 is also provided around the outside of the container neck close to the top of the container neck. A plurality of projecting first locking elements 23 are radially spaced around the outside of the container neck below the thread segments 5. Each locking element 23 comprises a near-tangential ramp surface 25 and a near- radial abutment surface 27. The abutment surface 27 is inclined at a slight angle to the longitudinal axis of the container closure assembly. The abutment surface 27 is also inclined at a slight angle to the radius of the container closure assembly that it intersects, i.e. the abutment surface 27 is radially ramped as described in US patent no. 5,411,157.

A plurality of stop elements 26 are spaced around the container neck adjacent to the first locking elements 23 and spaced therefrom in a screwing-down direction. The stop elements 26 project slightly radially further and more steeply than the locking elements 23, as shown more clearly in Fig. 10 below.

Finally, below the locking elements 23 and stop elements 26 are located a plurality of circumferentially spaced rectangular recesses 29 in the outside of the container neck for received the flexible tabs of the tamper-evident ring on the closure, as described in more detail below.

Referring now to Figures 1-3, the closure 3 comprises a base portion 31, a skirt portion 33 and a tamper-evident ring 35.

A total of eight thread segments 37 are spaced around the inside of the skirt portion 33 for engagement beneath the thread segments 5 of the container neck to secure the closure 3 on the container neck 1. The thread segments 37 have a substantially triangular ramped section, and profiled lower surfaces, substantially as described hereinbefore for the thread segments 5 on the container neck.

A cylindrical skirt 39 extends upwardly from the base 31 of the closure to form a cylindrical sealing plug for insertion into the inside of the container neck l. The sealing plug is tapered to assist insertion into the container neck. Near the lower end of the cylindrical skirt 39 there is provided a circumferential sealing recess for engagement with the interior circumferential sealing rib 15 on the container neck. The circumferential sealing recess 41 has a substantially triangular ramped cross-section complementary to that of the inner sealing rib 15 on the container neck.

A circumferential sealing rib 43 is also provided on the inside of the closure skirt portion near to the base of the closure for engagement with the circumferential sealing recess 21 on the container neck.

A plurality of second locking elements 45 are radially spaced around the inside of the closure skirt 33 above the thread segments 37. The second locking elements 45 each comprise a projection having a substantially tangential ramp surface 47 and a substantially radial abutment surface 49, the abutment surface 49 being inclined to the longitudinal axis of the assembly substantially as described hereinbefore for the first locking elements 23.

The relationship of the first and second locking elements 23,45 and the stop elements 26 when the closure is in the secured and sealing position on the neck is shown more clearly in Fig. 10. The points to note are: (1) the leading edge of the first locking element 23 on the neck is sloped at an angle to the neck radius and abuts a similarly sloped trailing edge of the second locking element 45 on the closure at said sealing position, whereby a radial restoring force exerted by the radially deformed closure skirt is cammed to a closing torque that helps to ensure a high sealing force between the container and closure, as described in more detail in US-A-5 11157 ; (2) the sloped leading and trailing edges described above enable the second locking element 45 to ride over the first locking element 23 when a predetermined opening torque is applied to the closure; and (3) the stop element 26 has a radial height greater than that of the first locking element 23, and has a trailing edge 28 parallel to a radius of the neck for abutting a similarly oriented leading edge of the second locking element 45, whereby it is extremely difficult to force the second locking element 45 over the stop element 26 when attempting to over-tighten the closure on the neck.

The tamper-evident ring 35 is formed integrally in one piece with the closure skirt 33, being joined thereto by frangible bridges 51. The tamper-evident ring 35 comprises a collar 53 and a plurality of flexible tabs projecting inwardly and downwardly from the collar. Recesses 57 are provided in the tamper-evident ring behind the flexible tabs 55 to allow the tabs 55 to flex outwardly, for example when the tamper-evident ring 35 is being snap-fitted onto the container neck 1.

A plurality of radial flanges 59 are provided on the outside of the skirt portion 33 of the closure to enable visual or mechanical alignment of the closure on the container neck.

In use, the closure 3 is snap fitted onto the container 1 as shown in Figure 5. The closure 3 having the tamper- evident ring 35 attached to the skirt portion 33 is aligned using the flange 51 so that the respective abutment surfaces 27,49 of the first and second locking elements are substantially in radial alignment. The closure 1 is then pressed directly down onto the container neck 1. The thread elements 5,37 ride over each other in ratchet fashion to achieve snap-fitting of the closure on the container neck. At the same time, the flexible tabs 55 flex outwardly to pass over the rim 61 before snapping into the recesses 29 on the container neck. The circumferential sealing ribs 15 and 41 likewise snap into the corresponding circumferential sealing recesses 41 and 21.

It is a further advantage of this embodiment of the invention that the closure may, alternatively, be fully secured on the container neck by screwing down, which may be preferably in some automated bottling plants.

In the fully secured position shown in Figure 4, the container closure assembly benefits from a double circumferential seal formed by the sealing ribs 15 and 43 and the circumferential sealing recesses 41 and 21. The ramped ratchet profile of the thread segments 5,37 means that a very much larger axial force would be required to lift the closure axially off the container neck than was required to snap fit the closure onto the container neck. At the same time, the abutment between the locking elements 23 and 45 ensures that there is no rotational working loose of the closure from the container neck until a predetermined minimum opening torque has been applied to the closure.

Referring now to the alternative embodiment shown in Figure's 8 and 9, the internal bore seal (plug seal) of the embodiment of Figures 1-8 has been replaced by a sealing web 70 of metallized thermoplastic film extending across the top of the container neck and thermally bonded thereto to form a liquid-tight and tamper-evident seal. A sealing wad 72 of soft plastics material is bonded to the inside of the base of the closure and is compressed against the sealing web 70 as shown.

A top portion 74 of the container neck immediately below the sealing web 72 is recessed to prevent contact between the sealing web 72 and the closure skirt when the closure is secured onto the container neck for the first time, and to assist flipping-off or peeling-off of the sealing web. This feature is described and claimed in our patent application GB-A-2257693, the entire content of which is expressly incorporated herein by reference. Preferably, the compressible sealing wad 72 is at least twice as thick, on average, as the sealing web 70, and more preferably at least four times as thick to provide sufficient compressibility.

In use, the closure is initially snap-fitted onto the container neck bearing the sealing web, as described above. The snap-fitting avoids exerting any twisting force on the sealing web that could tear or disrupt it. The firm abutment between the sealing wad 72 and the sealing web 70 provides a secure secondary seal. Once the assembly has been opened for the first time and the sealing web has been removed, the closure can be resecured on the neck by twisting-on, whereupon the sealing wad makes a reliable seal with the top of the container neck to prevent leakage as shown in Figure 9.

Accordingly, the container closure assemblies according to the present invention provide improved sealing and improved security relative to existing closures of this general type.

The above embodiments have been described by way of example only. Many other embodiments falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims

1. A container closure assembly comprising: a container neck having first retaining means on an outer surface thereof and an inner annular sealing rib or sealing recess on an inner surface thereof; and a closure having a base portion and a skirt portion, said skirt portion bearing second retaining means complementary to said first retaining means to retain said closure on said container neck in a snap-on, twist-off fashion, and said closure further comprising a sealing plug extending from the base portion of the closure inside said skirt portion for insertion into the container neck, said plug having an outer annular sealing recess or sealing rib on an outer surface thereof for engagement with said inner annular sealing rib or sealing recess to form a seal when said closure is fully secured on said container neck.

2. A container closure assembly according to claim 1 comprising an inner annular sealing rib on said container neck and an outer annular sealing recess on said sealing plug.

3. A container closure assembly according to claim 1 or 2, wherein said annular sealing rib has a ramped cross-section, whereby less axial force is required to secure the closure on the container neck than is required to remove the closure from the container neck.

4. A container closure assembly according to claim 3, wherein said annular sealing recess has a ramped cross- section complementary to the ramped cross-section of said annular sealing rib.

5. A container closure assembly according to any preceding claim, further comprising a second, outer annular sealing rib or sealing recess on the container neck and a second, inner annular sealing recess or sealing surface or sealing rib on an inner surface of the closure skirt to form a second seal between the container neck and the closure when the closure is fully engaged on the container neck.

6. A container closure assembly comprising: a container neck having first retaining means and at least one first locking element located on an outer surface of the container neck; and a closure having a base portion and a skirt portion, said skirt portion having second retaining means complementary to said first retaining means for securing the closure on the container neck in a snap-on, twist-off fashion; said skirt portion further bearing at least one second locking element which engages said first locking element when the closure is fully secured on the container neck, and which resists twisting-off of the closure from the neck until a predetermined minimum opening torque is applied to the closure, said container closure assembly further comprising an alignment means to enable alignment of the first and second locking elements when the closure is snap fitted onto the container neck.

7. A container closure assembly according to claim 6, wherein each said first locking element comprises a projection on the container neck presenting a first longitudinal abutment surface, and each said second locking element comprises an inward projection on the closure skirt portion, presenting a second longitudinal abutment surface for abutting the first longitudinal abutment surface to resist twisting-off of the closure from its fully secured position on the container neck.

8. A container closure assembly according to the claim 7, wherein said first and/or said second longitudinal abutment surface is inclined to the longitudinal axis of the container closure assembly, whereby snap-fitting of the closure onto the container neck with engagement of the first and second abutment surfaces is possible over a range of angular positions of the closure on the container neck.

9. A container closure assembly according to claim 6, 7 or 8, wherein the alignment means comprises a radially or axially projecting flange on the closure.

10. A container closure assembly according to claim 9, wherein the alignment means comprises a plurality of radially equidistant radially projecting flanges.

11. A container closure assembly according to any of Claims 6 to 9, further comprising at least one stop element on said container neck or said closure to prevent over-tightening of said closure on said neck.

12. A container closure assembly according to Claim 11, wherein said at least one stop element is located on said container neck adjacent to said first locking element, and blocks said over-tightening by abutment against said second locking element on said closure.

13. A container closure assembly comprising: a container neck having an opening and first retaining means located below said opening; a sealing web extending across said opening and bonded to the container neck around said opening to seal said container neck; a closure having a base portion and a skirt portion, said skirt portion having second retaining means complementary to said first retaining means for securing the closure on the container neck in a snap-on, twist-off fashion; and a compressible sealing wad inside the base portion of the closure for forming a compression seal with the container neck around said opening both before and after said sealing web is removed from the container neck.

14. A container closure assembly according to claim 13, wherein a recess is formed in the container neck immediately below said opening.

15. A container closure assembly according to claim 13 or 14, wherein the thickness of the compressible wad in the uncompressed state is at least four times the thickness of the sealing web.

16. A container closure assembly according to any preceding claim, wherein said first and second retaining means each comprise a plurality of thread segments to enable said closure to be removed from and applied to said container neck by rotation of the closure relative to the neck.

17. A container closure assembly according to claim 16, wherein said closure can be moved from a fully secured to a fully disengaged position on the container neck by a single smooth rotation through about 90° or less.

18. A container closure assembly comprising: a container neck bearing one or more first thread segments; a closure comprising a base portion and a skirt portion, said skirt portion bearing one or more second thread segments complementary to said first thread segments for securing the closure on the container neck in a snap-on, twist-off fashion; said first thread segments and/or said second thread segments having a ramped cross-section to reduce the axial force required to snap the closure onto the container neck relative to the axial force required to snap the closure off the container neck.

19. A container closure assembly according to claim 18, wherein the said ramped cross section is substantially triangular, with the side of the triangle closed to the respective mouth of the neck or the closure inclined at a smaller angle to the longitudinal axis of the assembly than the side of the triangle furthest from the respective mouth of the neck or of the closure.

20. A container closure assembly according to claim 18, wherein the said ramped cross section is substantially trapezoidal, with the side of the trapezoid closest to the respective mouth of the neck or of the closure inclined at a smaller angle to the longitudinal axis of the assembly than the side of the trapezoid furthest from the respective mouth of the neck or of the closure.

21. A container closure assembly according to any of claims 18, 19 or 20, wherein the first and second thread segments have one or more substantially parallel respective abutting surfaces.

22. A container closure assembly according any of claims 18 to 21 and also according to claim 16 or 17.

23. A container closure assembly according to any of claims 16 to 22, comprising eight of said first thread segments and eight of said second thread segments.

24. A container closure assembly according to any of claims 16 to 23, wherein at least one of said thread segments has upper and lower thread surfaces, and wherein the pitch of the lower thread surface is relatively lower in a first region and relatively higher in a second region displaced from the first region in an unscrewing direction.

25. A container closure assembly according to claim 24, wherein the pitch of the lower thread surface in the first region is substantially constant.

26. A container closure assembly according to any preceding claim, wherein the pitch of the lower thread surface in t_he first region is in the range -5° to +10°C.

27. A container closure assembly according to claim 26, wherein the pitch of the lower thread surface in the first region is in the range +1° to +7°.

28. A container closure assembly according to any of claims 24 to 27, wherein the second region is adjacent to the first region of the lower thread surface.

29. A container closure assembly according to any preceding claim, which further comprises a tamper-evident ring joined to the skirt portion of the closure and separable therefrom when the closure is removed from the container neck for the first time.

30. A container closure assembly according to claim 29, wherein the container neck further comprises an abutment means below said first retaining means, and the tamper- evident ring comprises a collar and a plurality of inwardly and downwardly directed flexible tabs, said tabs being able to flex outwardly to allow the tamper-evident ring to be slipped over the abutment means when the closure is secured on the container neck for the first time, and said tabs abutting against the abutment means to block axial movement of the tamper-evident ring when the closure is removed from the container neck for the first time, thereby causing the tamper-evident ring to separate from the closure.

31. A container closure assembly according to claim 30, wherein the abutment means comprises a circumferential lip extending around the container neck below said first retaining means.

32. A container closure assembly according to claim 30, wherein the abutment means comprises one or more window recesses in the container neck below the first retaining means for receiving said flexible tabs when the closure is fully secured on the container neck.

33. A container closure assembly substantially as hereinbefore described with reference to the accompanying drawings.