GB2532256A

GB2532256A - Container closure assembly with vent

Info

Publication number: GB2532256A
Application number: GB1420189.1A
Authority: GB
Inventors: Milner King Roger
Original assignee: Beeson and Sons Ltd
Current assignee: Beeson and Sons Ltd
Priority date: 2014-11-13
Filing date: 2014-11-13
Publication date: 2016-05-18
Also published as: WO2016075471A1; GB201420189D0

Abstract

Gas is vented from within a container neck 12 (neck features are dashed lines in the cross-section) at least when the closure 16 (dotted lines in the cross-section) is in a venting position (fig 4D). The closure 16 has circumferentially overlapping screw thread segments 26 which engage lugs 20 in the container neck 12 and forms a seal 46, 48 when closed. When opening the closure 16, the lugs 20 can engage shoulder blocks 44 in the thread segments 26, which locks the closure in the venting position while under axial pressure (e.g. for safety), whereby recesses 34 adjacent the lugs 20 in the container neck 12 (see fig 4D) cooperate with the gaps between the threads 26 to allow the gas inside to escape. After venting, when there is no upwards axial pressure on the closure, the closure can drop down so lugs 20 disengage from shoulder blocks 44 (fig 4E) to allow further unscrewing of the closure (fig 4F). The neck may have a guide 64 to engage with the threads 26 of the closure to urge the closure away from the neck during unscrewing. Locking ribs 68 may cooperate with ramps 70 to prevent unwanted opening and there may be a tamper evident ring 56.

Description

CONTAINER CLOSURE ASSEMBLY WITH VENT

The present invention relates to improved container closure assemblies, and in particular to assemblies having a vent recess in the neck of the container.

Current commercially mass-produced beverage containers use threads on the container neck and cap of the continuous, helical type. The threads comprise a single, substantially continuous thread portion on the container neck with a low thread pitch angle. The low pitch angle is needed to ensure that the cap does not unscrew spontaneously. The low pitch angle also provides the necessary leverage to achieve an air tight compressive seal between the cap and the container neck when the cap is tightened on the container neck. The low pitch of the helical threads also generally means that the cap typically needs to be rotated through more than 360° to disengage it completely from the container neck. Unscrewing through more than 360° also provides gradual venting of pressure from inside the container, for example a carbonated beverage container, while the cap is being unscrewed and thereby reduces the risk of uncontrolled gas venting or missiling of the cap.

Drawbacks of these caps include the laborious rotation required to remove and resecure the cap on the neck and excessive use of moulded material to form long helical threads. A further problem is unreliable separation of tamper-evident rings from the cap skirt due to the low pitch angle of the threads. Also, venting is facilitated by repeated lining up of vent slits in the threads on the closure and the threads on the neck, resulting in a long and drawn out venting process.

GB-A-2 330 133 provides an improved closure assembly with a variable pitch segmented thread on the neck of the bottle and a venting groove in the neck to improve venting of the container when the closure is unscrewed. The variable pitch of the thread means that the closure can be removed safely with unscrewing through less than 360°. However, the position of the thread segments on the neck suffers from the drawback that the neck is less "kissable" by a user when a user drinks from the container.

WO-A-2005/058720 provides a further improved closure assembly in which the variable pitch segmented thread is on the inside of the closure, rather than the neck, so that the only protrusions on the neck are lugs to engage the thread segments. The thread segments also have longitudinal channels to aid venting. The drawback of these longitudinal vents is that they weaken the thread segments which can make the closure unstable under high pressures.

WO-A-2011/070326 provides as improvement of the closure assembly of WO-A-2005/058720. The inside of the cap comprises a spigot to contact the lugs on the neck of the container and lift the cap into a venting position.

The present invention aims to provide an improvement over prior assemblies to give a closure assembly that vents quickly and safely, and ensures that a tamper evident seal on the closure breaks before venting. The closure also uses less material and is simple to make thus lowering manufacturing and transportation costs.

Accordingly, in a first aspect the present invention provides a container closure assembly comprising; a container neck having an opening; a closure for the neck, the closure having a base portion and a skirt portion; a screw thread on the closure, the screw thread comprising a plurality of circumferentially overlapping thread segments, each thread segment having upper and lower thread surfaces; and lugs on the neck to engage the screw thread on the closure; and means for forming a seal between the neck and closure when the closure is screwed down on the neck; the closure further comprising a block to restrict rotation of the closure in an unscrewing direction beyond a venting position when the closure is under an axial pressure; wherein the neck and closure are constructed and arranged to provide a vent for venting gas from the container neck at least when the closure is in the venting position; and wherein the vent includes a recess in the neck located adjacent to one or more of the lugs on the neck.

The term "circumferentially overlapping" means that the thread segments on the closure are not bayonet-type thread segments, but extend around the container neck a sufficient distance so that a top portion of one thread segment overlaps a bottom portion of another thread segment for a finite angular distance around the closure skirt. A thread gap is defined between the overlapping regions of the thread segments on the closure. One of the lugs travels through this thread gap as the closure is screwed onto or off of the container neck. The thread gap provides a vent during unscrewing and it has been found that this thread gap may have a cross-section that is too small for gas venting in all circumstances. The present invention overcomes this difficulty by providing a recess in the container neck adjacent to one or more of the lugs on the neck to increase the rate of gas venting through the thread gap as the lug travels passed the thread gap when the closure is screwed off the container neck.

The term "venting position" means a position in which venting of gas from the container occurs and finishes but it is not the only position in which venting occurs. Venting also occurs as the lugs travel along the thread segments on the skirt of the container closure as the closure is screwed off the container neck.

A number of the features of the closure assembly have been described in WO-A-2005/058720 and WO-A-2011/070326, along with GB-A-2 330 133 in which the closer assembly is inverted, i.e. the thread segments are on the neck of the bottle.

The increased rate of venting from inside the container reduces the length of time that the closure is blocked at the venting position whilst venting takes place, without any loss of pressure safety.

The recess also provides the benefit that less material is used in preparing the closure which reduces manufacturing costs, and transportation costs due to the lighter weight of the assemblies.

Preferably, the vent recess is positioned on the neck such that it covers a thread gap between the closed position prior to venting and during unscrewing of the closure. This arrangement provides maximal increase in venting whilst also preventing distortion of the closure during venting.

Preferably, the recess comprises a substantially trapezoidal recess extending around the container neck. More preferably, the recess has upper and lower edges (upper being furthest away from the container) that have the same pitch as the part of the lower surface of the thread segment that is adjacent the thread gap.

More preferably, the recess has upper and lower edges having an angle in the range 8° to 19° relative to the longitudinal plane of the neck opening. Preferably, the recess extends around the neck in a range of 40° to 65°. Preferably, the recess has a cross sectional area in the range of 30 mm2 to 50 mm2 more preferably 35mm2 to 45mm2. Preferably, the recess has a depth towards the longitudinal axis of the container in the range of 0.25-0.55 mm.

Preferably, the circumferentially overlapping thread segments on the closure comprise a close plateau, an incline, and a vent plateau. The lugs rest on the close plateau when the closure is fully screwed onto the container neck and the lugs rest on the vent plateau when the closure is in the venting position. The incline region comprises a step of higher incline than that of the close plateau or the vent plateau that connects the two plateaux.

Preferably, the pitch of the upper surface of the close plateau is in the range 3° to 11°. Preferably, the pitch of the upper surface of the incline is in the range 15° to 35°. Preferably, the pitch of the upper surface of the vent plateau is in the range 3° to 11°.

Preferably the lugs on the neck, and the screw thread on the closure are arranged to permit axial displacement of the closure relative to the neck at least when the closure is at the venting position. Preferably, the block to restrict rotation of the closure in an unscrewing direction beyond a venting position when the closure is under an axial pressure is a shoulder at a distal end of the vent plateau on at least one of the thread segments. The shoulder engages with a lug on the neck when the closure is axially displaced in a direction emerging from the neck, for example by axial pressure from inside a pressurized container. More preferably, the lugs and the shoulder are arranged not to engage when the closure is axially displaced in a direction inwardly towards the neck at the venting position, for example when the closure is being screwed down onto the container neck.

In one embodiment, the screw thread on the closure has four thread segments and there are four lugs on the container neck to engage the thread segments on the closure to minimise the amount of rotation of the closure on the container neck that is required to achieve initial engagement of the lugs and the thread thereby making the assembly more child-and elderly-friendly. However, it will be understood that the number of thread segments and lugs required to minimise the amount of rotation of the closure neck will depend on the diameter of the closure neck.

Preferably, the closure can be moved from a fully released to a fully engaged position on the neck by a single smooth rotation through 360° or less, more preferably 180° or less, and most preferably about 90° or less.

Preferably, the lugs follow a substantially continuous, preferably substantially helical thread path for the whole of the rotation as the closure is screwed onto the container neck, although the pitch of the helix may vary. The continuous thread path renders the assembly easy to close by the elderly and infirm, or by children. Also, a continuous thread aids physically weak people to screw down against pressure from inside the container.

Preferably, the lugs are of substantially trapezoidal cross-section and extend around the neck in the range 25° to 40° Preferably, the means for forming a seal between the neck and closure when the closure is screwed down on the neck is the combination of a sealing skirt and an olive seal as described in more detail in international application WO 2010/086609. The seal comprises an olive seal and a sealing skirt on the base of the closure substantially concentric with the skirt portion of the closure and positioned to receive a lip of the closure neck. The closure maintains a seal and helps to prevent damage of the closure when axial forces, such as during the stacking of bottles, are applied to the closure in a direction towards the container. The depth of the bulb of the olive seal from the closure base and the length of the container neck that enters the seal are configured such that a constant seal is maintained even under varied temperature and internal pressure and when the base portion of the closure bulges under pressure from inside the container.

Preferably, the closure assembly further comprises a second block in the form of a shoulder at a distal end of the close plateau that blocks over-tightening of the closure. The provision of the block to prevent over-tightening of the closure on the container neck also helps to prevent damage of the threads and lugs by over tightening, and ensures that only the preferred length of the container neck enters the seal at the closed position.

Preferably, the closure assembly further comprises a tamper-evident ring that is frangibly joined to the skirt of the closure and engages a flange on the neck of the container in the closed position. Preferably, the depth of the bulb of the olive seal and the length of the container neck that is received in the seal in the closed position, along with the length and pitch of the close plateau are such that the frangible joining between the tamper-evident ring and the skirt of the closure breaks before the lugs pass from the close plateau to the incline of the screw thread on the neck. In other words, the frangible joining breaks before venting begins. Preferably, venting begins when the closure has been unscrewed by an angle in the range 30° to 40°.

Preferably, the assembly further comprises complementary locking means on the container neck and the closure that prevent unscrewing of the closure from the fully engaged and sealing position on the container neck until a minimum opening torque is applied. Most preferably, the locking means comprises a rib on one of the container neck or on the skirt portion of the closure, and a complementary locking ramp on the other of the container neck or the skirt portion of the container, wherein the locking rib abuts against a retaining edge of the locking ramp when the closure is fully engaged on the container neck.

The complementary locking means provide a number of important advantages. Firstly, they prevent accidental breaking off of the closure from the fully engaged and sealing position on the container neck and the closure. Furthermore, the locking means provide a positive "click" when the fully engaged and sealing position of the closure on the container neck is reached, thereby giving the user a positive indication of that position.

In a second aspect, the present invention provides a container closure assembly comprising; a container neck having an opening; a closure for the neck, the closure having a base portion and a skirt portion; a screw thread on the closure, the screw thread comprising a plurality of circumferentially overlapping thread segments, each thread segment having upper and lower thread surfaces; and lugs on the neck to engage the screw thread on the closure; and means for forming a seal between the neck and closure when the closure is screwed down on the neck; wherein the neck and closure are constructed and arranged to provide a vent for venting gas from the container neck at least when the closure is in the venting position; and wherein the neck comprises a guide positioned to engage with the lower thread surface of a circumferentially overlapping thread segment of the closure during unscrewing of the closure and urge the closure in a direction emerging from the container.

It will be understood that all of the preferred features of the first aspect, and the recess in the neck included in the vent, are preferred features of the second aspect also. Also, the container closure assembly of the first aspect may also comprise the guide of the second aspect.

Preferably, in both the first and second aspects, the guide has a top surface with a pitch the same as the lower surface of the incline which is preferably in the range 20° to 30°. Advantageously, the guide exerts an axial force against the lower surface of the thread segment on the closure when the closure is axially displaced in a direction emerging from the neck, for example by axial pressure from inside a pressurized container. Thus the upper surface of the thread segment is urged into contact with a lug as the lug moves through the thread gap between the overlapping regions of the thread segments on the closure thus forcing the lug onto the vent plateau. This is especially beneficial if the internal pressure of the closed container is low, or the beverage contains a still beverage and so there is minimal or no internal pressure to urge the closure into the stop position. The "stop position" being the position where the lug is on the vent plateau engaging the block at the distal end of the vent plateau. This is also known as the "safety position".

Advantageously, the urging force of the guide on the thread segment on the closure also provides displacement of the closure to aid breaking of the frangible joining between a tamper-evident ring and the skirt of the closure before venting occurs, i.e. whilst a part of the neck is still received in the sealing means.

It will be understood that the dimensions, angles and pitches of the parts of the assembly depend on the size (i.e. diameter) of the container neck.

Specific embodiments of the container closure assemblies according to the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which:-Figure 1 shows a side view of a bottle comprising the closure assembly with the closure screwed onto the neck; Figure 2 shows a side view of the bottle with the closure unscrewed showing the neck. The closure is shown in cross-section; Figure 3 shows a cross sectional view of the closure in the fully engaged position on the container neck.

Figures 4(A)-(F) show steps of the unscrewing procedure with the closure and container neck in plane projection. The base and skirt portions of the cap are not shown for clarity. The lugs, vent, guide and rib on the container neck are dashed for clarity.

Specifically, figure 4(A) shows a plane projection of the closure in the fully engaged position on the container neck.

Figure 4(B) shows a similar projection to Fig. 4(A), but with the cap in the part of the unscrewing sequence moving towards where venting begins.

Figure 4(C) shows a similar projection to Figs. 4(A) and (B), but further along in the unscrewing sequence where the lug begins to travel through the venting channel along the incline and venting is occurring.

Figure 4(D) shows a similar projection to Figs. 4(A), (B) and (C), but further along in the unscrewing sequence where the lug is in the safety position against the block in the venting position.

Figure 4(E) shows a similar projection to Figs. 4(A)-(D), but further along in the unscrewing sequence where the lug is in an unblocked screwing/unscrewing position.

Figure 4(F) shows a similar projection to Figs. 4(A)-(E), but further along in the unscrewing sequence where the cap is in an advanced unblocked position.

Referring to Figs 2 and 3, this embodiment is a container closure assembly especially adapted for a carbonated beverage container. It will be understood that the closure assembly is also applicable to containers with non-carbonated beverages, and other liquids.

The assembly includes a container neck 12 of a container for carbonated beverages, and a closure 14. Both the container neck and the closure are formed from plastics material. The container is preferably formed by blow molding of polyterephthalate as is conventionally known for carbonated beverages. The closure is preferably formed by injection molding of polyethylene. The closure comprises a base portion 16 and a skirt portion 18.

The inside of the closure 18 has a screw thread formed from four circumferentially overlapping thread segments 26 having an upper surface 28 and a lower surface 30. A substantially continuous, approximately helical thread gap 32 is defined between overlapping regions of the upper and lower surfaces 28, 30 on adjacent thread segments 26.

The thread segments on the inside of the closure have a close plateau 38, an incline 40 and a vent plateau 42. On the outside of the neck 12 are four lugs 20. The four lugs are equally circumferentially spaced around the neck and have a lower surface 22 with a relatively low pitch that corresponds to the upper surface of the close plateau 38 and an upper surface 24 with an intermediate pitch that corresponds with the lower surface 30 of the incline 40.

Vent recesses 34 are adjacent to the lugs on the container neck. As can be seen in Fig. 3 the recesses are positioned on the neck such that they cover the thread gap 32 on the inside of the closure in the closed position prior to venting and during unscrewing of the closure. The angles of the upper and lower edges 36,37 of the recess are the same pitch as the part of the lower surface 30 of the thread segment 26 that is adjacent the thread gap. The recess extends 45° around the neck.

At the distal end of the vent plateau 42 there is a shoulder 44 that acts as a safety block to restrict rotation of the closure in an unscrewing direction beyond a venting position on the vent plateau when the closure is under axial pressure from the gas released by the carbonated beverage in the container.

The container closure assembly comprises a means for forming a gas-tight seal in the form of olive seal 46 and sealing skirt 48 both of which are concentric with the skirt portion 18 of the closure. The seal is described in detail in WO 2010/086609. The seal has a depth 50 and the bulb is a depth 51 from the base of the container. A length 52 of the container neck is received in the seal in the closed position. The depth 51 of the bulb and the length 52 of the container neck received in the seal are such that a constant seal is maintained even under varied temperature and internal pressure and when the base portion of the closure bulges under pressure from inside the container.

The close plateau 38 has a second block 54 in the form of a shoulder at its distal end that blocks over-tightening of the closure. The block 54 is positioned to ensure that at the closed position, only length 52 of the neck 12 enters the sealing means 46,48.

The container closure assembly also comprises a tamper evident safety feature 56 that is joined to the skirt portion 18 of the closure 14 by frangible joints 58. The tamper-evident ring also comprises a plurality of integrally formed, flexible, radially inwardly projecting retaining tabs 60. In the closed position, tamper-evident band 56 engages flange 62 on the neck of the container. The length 52 of the neck enters into the seal 46,48 in the closed position, the depth 51 of the bulb of the olive seal and the pitch of the close plateau 38 are such that the frangible joining between the tamper-evident ring and the skirt of the closure breaks before the lugs pass from the close plateau to the incline of the screw thread on the neck i.e when venting takes place.

The container neck also comprises two diametrically opposite guides 64 proximal to the container. The guides 64 have a triangular shape and a top surface 66 with a pitch the same as the lower surface 30 of the incline of the thread segments 26 on the closure. The guides are positioned such that they engage with the lower thread surfaces 30 of the inclines 40 of thread segment 26 on the closure during unscrewing of the closure and urge the closure in a direction emerging from the container.

The container closure assembly also has complementary locking elements 68, 70 on the container neck and the closure to block unscrewing of the closure from the fully engaged position on the container neck unless a minimum screwing torque is applied. The locking elements comprise four equally radially spaced locking ribs 68 on the inside of the closure skirt 18, and four equally spaced retaining ramps 70 on the container neck. The ramps 70 comprise a radially sloped outer surface 72 and a radially projecting retaining edge 74 against which the rib 68 on the closure abuts when the closure is in the fully engaged position on the container neck.

In use, the closure 14 is secured onto the container neck 12 by screwing down in conventional fashion. The closure 14 can be moved from a fully disengaged position to a fully engaged position on the container neck 12 by rotation through about 90°. Whilst the closure is being screwed down, there is normally a net axial force applied by the user on the closure into the container neck, and accordingly the lugs 20 abut against and ride along the lower surface 30 of the thread segments 26 on the inside of the container skirt. The lugs 20 follow a substantially continuous path along a variable pitch helix. The lugs 20 and thread segments 26 are free-running, in other words there is substantially no frictional torque between the lugs and the thread segments until the full engaged position is neared. These features of a 90° closure rotation, substantially continuous thread path and free-running threads all make the closure extremely easy to secure on the neck, especially for elderly or arthritic persons, or children.

As the closure 14 nears the fully engaged position on the container neck 12, several things happen. Firstly, tamper-evident ring 56 starts to ride over flange 62 on the container neck. The retaining tabs 60 on the tamper-evident ring 56 flex radially outwardly to enable the tamper-evident ring to pass over the flange 62 without excessive radial stress on the frangible bridges 58.

Secondly, the locking ribs 68 on the closure skirt 12 ride up the outer ramped surface 72 of the retaining ramps 70 on the container neck. The gentle slope of the ramped surfaces 72, together with the resilience of the closure skirt 18, mean that relatively little radial torque is required to cause locking ribs 68 to ride up the ramped surfaces 72.

Thirdly, the initial contact between the seal 46,48 and the container neck results in a net axial force on the closure in a direction out of the container neck. This pushes the lugs 20 on the container neck out of contact with the lower surface 30 of the thread segments 26 on the closure skirt and into contact with the upper surface of the thread segments 26. Continued rotation of the closure cap in a screwing-down direction causes the lugs 20 to travel along the upper region until the final, fully engaged position where the lug is on the close plateau, shown in Figs. 3 and 4(A), is reached.

When the fully engaged position is reached the locking ribs 68 click over the top of the respective ramped surfaces 72 and into contact with the steep retaining surfaces of the ratchet ramps 70. At the same position, the ends of the lugs 20 come into contact with the shoulders 54 at the distal ends of the close plateaux 38 thereby blocking over tightening of the closure that could cause damage, and ensuring that only a length 52 of the container neck 12 enters the sealing means, which ensures that there is no venting of the container during unscrewing before the frangible joints on the tamper-evident ring break.

When the closure 14 is in the fully engaged position on the container neck 12, the lower surfaces 22 of the lugs 20 are in contact with the close plateau 38 of the thread segments 26 on the neck, as shown in Figs. 3 and 4(A). The lower surfaces 22 of the lugs 20 have a low pitch to match that of the upper surface of the close plateau 38, so as to maximise contact area between the thread segments, and thereby distribute the axial force exerted by the closure as evenly as possible around the container neck. Because of the low pitch of the close plateau 38, relatively little of the axial force emerging from the container neck due to pressure inside the container is cammed into unscrewing rotational force thus greatly reducing the tendency of the closure to unscrew spontaneously under pressure.

Also, in the fully engaged position vent recess 34 in the neck overlaps the thread gap on the inside of the closure and has a depth 76 meaning that the recess does not overlap the thread segments 26 on the skirt of the closure. This means that it does impact on the seal in the close position, and does not allow the sides of the closure to be compressed when the closure is gripped on the outside of the skirt portion.

Spontaneous unscrewing is also prevented by the contact between locking ribs 68 and the retaining edge 74 on the locking ramps 72. An important advantage is that the reduced tendency to unscrew spontaneously dues to the low pitch of the close plateaux 38 means the minimum opening torque of the locking elements 68, 70 can be reduced without risk of the closure blowing off spontaneously.

In use, the closure is removed from the container neck by simple unscrewing. An initial, minimum screwing torque is required to overcome the resistance of the locking elements 68, 70. Once this resistance has been overcome, essentially no torque needs to be applied by the user to unscrew the closure. The internal pressure inside the container exerts an axial force on the closure in a direction emerging from the mouth of the container, as a result of which the lugs 20 ride along the upper surface of the thread segments 26 as the closure is unscrewed.

The lugs 20 initially ride along the close plateau 38 to the position shown in Fig. 4(B). The lugs then move along the incline 40 onto the vent plateau 42 before coming into contact with blocking shoulder 44. In this position, shown in Fig. 4(D), further unscrewing of the closure is blocked whilst gas venting takes place and the axial force of the gas venting from the container against the base of the cap prevents the user from pushing the closure down such that the lug 20 is no longer in contact with the blocking shoulder 44. This is an important safety feature that prevents the closure from blowing off during unscrewing.

Venting of gas from the container begins as the lugs 20 move along the close plateaux 38, at about the position in between those shown in figures 4(B) and Fig 4(C). By this time, the pitch of close plateaux 38 and the length of the neck in the seal 52 are such that the closure has moved far enough axially to break the frangible joints 58 on the tamper-evident ring before venting occurs.

When the lug 20 reaches the provision shown in Fig 4(C), it blocks the thread gap 32 between the thread segments 26 on the neck and thus would block gas from venting. However, vent recesses 34 allow gas to vent whilst the lug 20 is in this position and thus the axial pressure on the container base from the gas venting from the container is maintained and the lug is forced down the incline 40 onto the vent plateau 42 where venting continues and finishes, as shown in Fig. 4(D).

During unscrewing, guide 64 comes into contact with the lower surfaces of incline 40 on the thread segment 26 on the skirt of the closure as shown in Fig. 4(B). The guide acts as a failsafe mechanism to ensure that the lug 20 remains in contact with the upper surface of the incline 40 and moves onto the vent plateau 42 into contact with the blocking shoulder 44. This is advantageous when the carbonation level of the beverage in the container is low and thus the axial pressure exerted on the closure that otherwise forces the lug 20 into contact with the incline 42 and eventually the blocking shoulder 44 is weak. The surface 66 of guide 64 has a pitch the same of the lower surface of incline 40 to ensure a smooth, constant, contact.

Once gas venting is complete so that there is no longer axial upward force on the closure, the closure can drop down so as to bring the lugs 20 into contact with the bottom surfaces 30 of the thread segments on the closure skirt 18, as shown in Fig 4(E). In this position, unscrewing can be continued to disengage the closure completely from the container neck as shown in Fig. 4(F).

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

Claims

Claims: 1. A container closure assembly comprising; a container neck having an opening; a closure for the neck, the closure having a base portion and a skirt portion; a screw thread on the closure, the screw thread comprising a plurality of circumferentially overlapping thread segments, each thread segment having upper and lower thread surfaces; and lugs on the neck to engage the screw thread on the closure; and means for forming a seal between the neck and closure when the closure is screwed down on the neck; the closure further comprising a block to restrict rotation of the closure in an unscrewing direction beyond a venting position when the closure is under an axial pressure; wherein the neck and closure are constructed and arranged to provide a vent for venting gas from the container neck at least when the closure is in the venting position; and wherein the vent includes a recess in the neck located adjacent to one or more of the lugs on the neck.
2. A container closure assembly according to claim 1, wherein the recess comprises a substantially trapezoidal recess extending around the container neck.
3. A container closure assembly according to claim 2, wherein the recess has upper and lower edges having an angle of 8° to 19° relative to the longitudinal axis of the neck.
4. A container closure assembly according to any preceding claim, wherein the recess extends around the neck in the range 40° to 65°.
5. A container closure assembly according to any preceding claim, wherein each circumferentially overlapping thread segment comprises a close plateau, an incline and a vent plateau.
6. A container closure assembly according to claim 5, wherein the pitch of the upper surface of the close plateau is in the range 3° to 11°.
7. A container closure assembly according to claim 5 or claim 6, wherein the pitch of the upper surface of the incline is in the range 15° to 35°.
8. A container closure assembly according to any one of claims 5 to 7, wherein the pitch of the upper surface of the vent plateau is in the range 3° to 11°.
9. A container closure according to any one of claims 5 to 8, wherein the block is a shoulder at a distal end of the vent plateau.
10. A container closure assembly according to any preceding claim, further comprising a second block in the form of a shoulder at a distal end of the close plateau that blocks over-tightening of the closure.
11. A container closure assembly according to any preceding claim, wherein the lugs are substantially trapezoidal and extend around the neck in a range 25 to 40°.
12. A container closure assembly according to any preceding claim, wherein the means for forming a seal comprises an olive seal and a sealing skirt on the base of the closure concentric with the skirt portion of the closure and positioned to receive a lip of the closure neck.
13. A container closure assembly according to any preceding claim, further comprising a tamper-evident ring that is frangibly joined to the skirt of the closure and engages a flange on the neck of the container in the closed position.
14. A container closure assembly according to claim 13, wherein the depth of the seal and a pitch of a close plateau are such that the frangible joining between the tamper-evident ring and the skirt of the closure breaks before the lugs pass from the close plateau to an incline of the screw thread on the closure.
15. A container closure assembly according to any preceding claim, wherein the neck comprises a guide positioned to engage with the lower thread surface of an incline portion of a circumferentially overlapping thread segment of the closure during unscrewing of the closure and urge the closure in a direction emerging from the container.
16. A container closure assembly according to claim 15, wherein the guide has a top surface with a pitch the same as the lower surface of the incline.
17. A container closure assembly comprising; a container neck having an opening; a closure for the neck, the closure having a base portion and a skirt portion; a screw thread on the closure, the screw thread comprising a plurality of circumferentially overlapping thread segments, each thread segment having upper and lower thread surfaces; and lugs on the neck to engage the screw thread on the closure; and means for forming a seal between the neck and closure when the closure is screwed down on the neck; wherein the neck and closure are constructed and arranged to provide a vent for venting gas from the container neck at least when the closure is in the venting position; and wherein the neck comprises a guide positioned to engage with the lower thread surface of a circumferentially overlapping thread segment of the closure during unscrewing of the closure and urge the closure in a direction emerging from the container.
18. A container closure substantially as herein described with reference to the accompanying figures.
19. A beverage container sealed with a closure assembly according to any preceding claim.
20. A beverage container according to claim 19 which contains a carbonated beverage.