Container Closure Assembly With Pressure Seal

Abstract

The invention provides a container closure assembly comprising: a container neck (10) having side walls defining an opening at one end thereof and a lip (14) extending around the opening; a cap (12) for said neck, the cap having a base portion (22) and a threaded skirt portion (24); a first screw thread (16) on the neck; a second screw thread (26) on an inner surface of the threaded skirt of the cap; said first and second screw threads being configured to enable a user to secure, remove and resecure the cap into a sealing position on the neck by rotation of the cap on the neck; a sealing plug (52) extending from said base portion of the cap inside and substantially concentric with said threaded skirt portion of the cap, wherein the sealing plug is an olive sealing plug for forming a seal against an inside surface of the container neck when the cap is secured on the container neck; and a sealing skirt (54) extending from said base portion of the cap intermediate said sealing plug and said threaded skirt portion of the cap and substantially concentric with said sealing plug and said threaded skirt portion of the cap, wherein said cap can be displaced towards said neck from said sealing position by application of an axial force without rotation of the cap on the neck and substantially without plastic deformation of the cap.

Claims

1. A container closure assembly comprising: a container neck having side walls defining an opening at one end thereof and a lip extending around the opening; a cap for said neck, the cap having a base portion and a threaded skirt portion; a first screw thread on the neck; a second screw thread on an inner surface of the threaded skirt of the cap; said first and second screw threads being configured to enable a user to secure, remove and resecure the cap into a sealing position on the neck by rotation of the cap on the neck; a sealing plug extending from said base portion of the cap inside and substantially concentric with said threaded skirt portion of the cap, wherein the sealing plug is an olive sealing plug for forming a seal against an inside surface of the container neck when the cap is secured on the container neck; and a sealing skirt extending from said base portion of the cap intermediate said sealing plug and said threaded skirt portion of the cap and substantially concentric with said sealing plug and said threaded skirt portion of the cap, and wherein said cap can be displaced towards said neck from said sealing position by application of an axial force without rotation of the cap on the neck and substantially without plastic deformation of the cap.

2. A container closure assembly according to claim 1, wherein the displacement from said sealing position is a resilient displacement.

3. A container closure assembly according to any preceding claim, wherein no part of the cap contacts the top surface of the container lip at the sealing position.

4. A container closure assembly according to any preceding claim, wherein the container lip is substantially fully radiused in longitudinal cross-section.

5. A container closure assembly according to any preceding claim, wherein the inner and/or the outer surfaces of the container neck adjoining the lip is slightly tapered

6. A container closure assembly according to any preceding claim, wherein the sealing skirt has a radial thickness at half-height equal to from about 40% to about 80% of the radial thickness of the sealing plug measured at the same height.

7. A container closure assembly according to any preceding claim, wherein a region of the radially inner surface of the sealing skirt is concave for engagement with an outer surface of the container neck proximate to said lip when the cap is secured on the container neck.

8. A container closure assembly according to any preceding claim, wherein the inside diameter of the sealing skirt at half-height is from about 0.05 mm to about 0.5 mm less than the outside diameter of the container neck.

9. A container closure assembly according to any preceding claim, wherein an outer surface of the sealing skirt does not abut against an internal surface of the threaded skirt or the cap base when the cap is in the secured and sealing position on the neck.

10. A container closure assembly according to any preceding claim, wherein at least one circumferential sealing rib is provided in said concave region of said sealing skirt.

11. A container closure assembly according to claim 10, wherein at least one said circumferential sealing rib has a substantially triangular cross-section.

12. A container closure assembly according to claim 11, wherein at least one of the sealing ribs has a height in the range of from about 10 to about 250 micrometers.

13. A container closure assembly according to any preceding claim, wherein the cap is a low-profile cap having an axial height from the top of the base to the bottom of the threaded skirt, but excluding any tamper-evident ring attached to the cap, of from about 10 mm to about 15 mm.

14. A container closure assembly according to any preceding claim, wherein the cap can be secured and resecured on the container neck by a single smooth rotation through 360 or less, preferably through 180 or less, and more preferably through about 90.

15. A container closure assembly according to any preceding claim, wherein the first and second threads are multiple start threads.

16. A container closure assembly according to any preceding claim, wherein the first and second threads are substantially continuous helical threads.

17. A container closure assembly according to any preceding claim, wherein the container and cap further comprise complementary locking elements on the container neck and the cap that block or resist unscrewing of the cap from the fully secured position on the container neck until a predetermined minimum opening torque is applied.

18. A container closure assembly according to claim 17, wherein said complementary locking elements comprise first and second locking projections on the container neck and the threaded cap skirt, and either said first locking projection is located longitudinally overlapping with and circumferentially spaced from an upper end of a first thread segment, or said second locking projection is located longitudinally overlapping with and circumferentially spaced from a lower end of a second thread segment, whereby the said first or second locking projection defines an extension of the thread path defined by the thread segments on the neck or the cap.

19. A container closure assembly according to any preceding claim, further comprising a projecting stop surface on one of the container neck and the cap skirt for abutment against a second stop or a thread on the other of the container neck or the cap to block over-tightening of the cap beyond a predetermined angular sealing position of the cap on the container neck.

20. A container closure assembly according to any preceding claim, wherein the torque required to secure the cap in a sealing position on the container neck is from about 0.7 Nm to about 0.9 Nm.

21. A beverage container sealed with a container closure assembly according to any preceding claim.

22. A beverage container according to claim 21 which contains a carbonated beverage.

Description

[0063] Embodiments of the present invention will now be described further by way of example with reference to the accompanying drawings, in which:

[0064] FIG. 1 shows a partial longitudinal cross-section through a container closure assembly according to the invention with the cap shown immediately prior to application to the neck;

[0065] FIG. 2 shows a view partially in longitudinal cross-section and partially in elevation of the container closure assembly of FIG. 1, with the cap in the fully secured and sealing position on the container neck; and

[0066] FIG. 3 shows a partial longitudinal cross-section through the top region of the neck of a container closure assembly according to the invention

[0067] Referring to FIGS. 1 and 2, this embodiment is a container closure assembly especially adapted for a carbonated beverage container. Many features of this assembly resemble those of the assembly described and claimed in our International Patent Applications WO95/05322 and WO97/21602 and WO99/19228. However, it is important to note that the threads on the closure and the neck are reversed in the present invention relative to the closure assemblies described in those applications. That is to say, the earlier patent specifications describe in detail assemblies having short thread segments in the closure skirt and longer thread segments on the neck, whereas the present invention provides only short thread segments on the neck and longer thread segments on the closure skirt.

[0068] The assembly according to this embodiment includes a container neck 10 of a container for carbonated beverages, and a closure 12. Both the container neck and the closure are formed from plastics material, but the container neck could also be made from glass. The container is preferably formed by injection moulding and blow moulding of polyethylene terephthalate in the manner conventionally known for carbonated beverage containers. The closure is preferably formed by injection moulding or compression moulding of polyethylene. The container neck has a cylindrical inner surface 13 terminating in rounded lip 14.

[0069] Referring to FIG. 3, an embodiment of the lip region of the container neck is shown in more detail. The neck has an internal surface 80, an outside surface 82, and a radiused lip 84. A region 86 of the internal surface adjacent to the radiused lip 84 is tapered at an angle of approximately 16 degrees. A region 88 of the outside surface adjacent to the radiused lip 84 is tapered at an angle of approximately 9 degrees. These regions of taper provide that there is a less abrupt increase in screwing torque when the sealing plug and sealing skirt of the cap come into engagement with the neck as the sealing position of the cap on the neck is approached.

[0070] On the container neck 10 there is provided a four-start first screw thread made up of four first thread segments 16, as shown in FIG. 2. The first thread segments 16 are short thread segments extending about 33 around the neck and having a lower surface 18 with relatively low pitch of about 6 and an upper surface 20 with intermediate pitch of about 13.5. The first thread segments present a substantially trapezoidal cross-section along the axis of the neck.

[0071] Referring to FIGS. 1 and 2, the closure 12 comprises a base portion 22 and a skirt portion 24. The closure skirt 24 is provided with a second screw thread formed from four elongate second thread segments 26, each having a lower thread surface 30 and an upper thread surface 32. (The term upper in this context means closer to the base of the closure, i.e. further from the open end of the closure). The upper and lower second thread surfaces 30, 32 give the thread segments substantially trapezoidal side edges that are complementary to the shape of the first thread segments. A substantially continuous, approximately helical thread path for the first thread segments is defined between adjacent second thread segments 26.

[0072] A feature of this assembly is the profiling of the upper surfaces 32 of the second thread segments 26, which is described in more detail in our International patent application WO97/21602. The upper thread surfaces 32 in a first, upper region have a substantially constant pitch of only about 6. The upper region adjoins an intermediate region having a substantially constant, much higher pitch of about 25. The average pitch of the helical thread path defined by the second thread segments 26 is 13.5.

[0073] The second thread segments 26 also include a pressure safety feature similar to that described and claimed in our International Patent Application WO95/05322. Briefly, the lowermost portion of the second thread segment 26 defines a step 38 to abut against a first end 40 of the first thread segments 16 and block unscrewing of the closure 12 from the neck 10 when the said first thread segments 16 are in abutment with the upper surface 32, i.e. when there is a net force on the closure in an axial direction out of the container neck. A third region of the upper surfaces 32 of the second thread segments situated adjacent to the step 38 also has a low pitch of about 6.

[0074] The container and closure assembly is also provided with complementary locking elements 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 unscrewing torque is applied. These locking elements comprise four equally radially spaced first locking projections 44 on the container neck, and four equally radially spaced second locking projections 46 on the inside of the closure skirt 24. The projections on the container neck are located at the bottom of the thread, where they are least noticeable to a person drinking directly from the container neck. The locking projections 46 on the closure skirt are located level with, and radially spaced by about 2 mm from, the bottom of the threads 26 on the skirt. The locking projections on the closure skirt 24 are formed as a continuation of the closure thread segments 26, whereby the thread segments 16 on the neck 10 can pass smoothly past the locking projections on the neck as the cap is secured on the neck.

[0075] Each of the locking projections 44,46 is substantially in the form of a triangular prism having its long axis aligned with the axis of the closure assembly. The height of each locking projection is about 1.5 mm, and the base width is about 1.5 mm. This ensures that the projections have sufficient strength to snap over each other without permanent deformation.

[0076] Each of the second thread segments 26 includes a longitudinally upwardly projecting portion 48 that defines a longitudinal stop surface against which a second end 50 of one of the first thread segments 16 may abut when the closure is fully secured on the neck to block overtightening of the closure on the neck.

[0077] The cap comprises a cylindrical sealing plug 52. The cap further comprises a cylindrical sealing skirt 54 that is substantially concentric with the sealing plug. The sealing plug 52 and the sealing skirt 54 are concentric with the threaded skirt 24 and located inside the threaded skirt 24 for sealing abutment against opposite sides of the container neck proximate to the container lip 14.

[0078] The sealing plug 52 is an olive sealing plug having a bulbous projection 56 on the radially outer surface thereof that forms a seal against the inside surface of the container neck in use.

[0079] The sealing skirt 54 has a concave region 58 on its radially inner surface. Two small circumferential sealing ribs 60 of substantially triangular cross-section project inwardly from the concave region. The circumferential sealing ribs on the sealing skirt have a substantially equilateral triangular cross-section, and are approximately 150 micrometers high, in the unstressed state. However, they deform when pressed against the harder material (glass or PET) of the container neck to form the pressure-tight seal. The small dimensions of the sealing ribs 60 enable a pressure tight seal to be achieved without substantial force having to be applied to the sealing skirt to form the seal.

[0080] The container closure assembly according to this embodiment also comprises a tamper-evident safety feature. This comprises a tamper-evident ring 66 that is initially formed integrally with the skirt 24 of the container closure 12 and joined thereto by frangible bridges 64. The tamper-evident ring 66 comprises a plurality of integrally formed, flexible, radially inwardly pointing retaining tabs 70. A circumferential retaining bead 72 is provided on the container neck 10. Ratchet projections (not present in this embodiment) may also be provided on the container neck below the circumferential retaining bead 72 and radially spaced around the container neck to block rotation of the tamper-evident ring 66 on the container neck 10 in an unscrewing direction. However, it may be preferred to smooth or omit the ratchet projections in order to improve user-friendliness of the neck finish. The structure and operation of the tamper-evident ring feature are as described and claimed in our International Patent Application WO94/11267.

[0081] In use, the closure 12 is secured onto the container neck 10 by screwing down in conventional fashion. There are four thread starts, and the closure 12 can be moved from a fully disengaged position to a fully engaged position on the container neck 10 by rotation through about 90. It can be seen that the thread segments 16 on the neck initially ride past the upper end of the locking projections 46 on the closure skirt, and are thereby guided into a helical thread path. In other words, the locking projections 46 on the skirt 24 define an initial extension of the helical thread path followed by the thread segments 16 on the neck. In this way, the locking projections on the skirt do not interfere or block the free running of the threads.

[0082] When 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 first thread segments 16 on the neck abut against and ride along the lower surfaces 30 of the second thread segments 26 on the closure. It can thus be seen that the first thread segments 16 follow a substantially continuous path along a variable pitch helix. The first and second threads are free-running, which is to say that there is substantially no frictional torque between the thread segments until the fully engaged position is neared. These features of multiple thread starts, a 90 closure rotation, substantially continuous thread path, and free-running threads, all make the closure extremely easy to secure on the container neck, especially for elderly or arthritic persons, or children.

[0083] As the closure nears the fully engaged position on the container neck 10, several things happen. Firstly, the tamper-evident ring 66 starts to ride over the retaining bead 72 on the container neck. The retaining tabs 70 on the tamper-evident ring 66 flex radially outwardly to enable the tamper-evident ring to pass over the retaining bead 72 without excessive radial stress on the frangible bridges 64.

[0084] Secondly, the initial abutment between the sealing plug 52 and sealing skirt 54 in the container closure base and the sealing lip 14 on the container neck results in a net axial force on the closure in a direction out of the container neck. This pushes the thread segments 16 out of abutment with the lower surfaces 30 of the projecting portions of the second thread segments 26 and into abutment with the upper surfaces 32 of the projecting portions of the second thread segments 20. More specifically, it brings the first thread segments 16 into abutment with the upper regions 34 of upper thread surfaces 32. Continued rotation of the closure in a screwing-down direction causes the first thread segments 16 to travel along the upper regions 34 until the final, fully engaged position shown in FIGS. 1 and 4 is reached. The low pitch of the upper surfaces 34 means that this further rotation applies powerful leverage (camming) to compress the sealing plug 52 and sealing skirt 54 against the container lip 14 in order to achieve an effective gas-tight seal. The concave inner surface 58 of the sealing skirt 54 conforms to the curved container lip 14 to form an effective seal without substantial deformation of the sealing skirt 54.

[0085] Thirdly, as the fully closed position is reached, the locking projections 46 on the closure skirt flex and ride over the complementary locking projections 44 on the container neck. At the fully closed position, the complementary locking projections remain in abutment, such that the closure skirt is still slightly deformed. The resilient restoring force exerted by the closure skirt is leveraged by the projections 44,46 into a closing torque on the assembly, which helps to ensure that sufficiently strong sealing force is applied to the various sealing surfaces of the assembly. It will be appreciated that this effect, coupled with the relatively large size of the projections 44,46, enables effective sealing to be achieved even if the locking projections 44,46 are not moulded to a very high tolerance.

[0086] Finally, as the fully engaged position of the closure 12 on the container neck 10 is reached or passed, the second ends 76 of the first thread segments 16 may come into abutment with the stop shoulders 50 projecting from the second thread segments 26, thereby blocking further tightening of the closure that could damage the threads and/or distort the sealing fins and ribs on the closure.

[0087] When the closure 12 is in the fully engaged position on the container neck 10, the lower surfaces 18 of the first thread segments 16 abut against the upper regions 34 of the upper thread surfaces 32 of the projecting portions of the second thread segments 26, as shown in FIG. 2. The lower surface 18 of the first thread segments 16 has a low pitch to match that of the upper regions 34, so as to maximise the contact area between the projecting portions in the regions 34, and thereby distribute the axial force exerted by the closure as evenly as possible around the container neck. Because of the low pitch in the regions 34, relatively little of the axial force emerging from the container neck due to pressure inside the container is converted into unscrewing rotational force by the abutment between the thread surfaces in this position. This greatly reduces the tendency of the closure to unscrew spontaneously under pressure. Spontaneous unscrewing is also prevented by the abutment between the first and second locking projections 44, 46. An advantage of the assembly is that the reduced tendency to unscrew spontaneously due to the low pitch of the thread in the lower regions 34 means that the minimum opening torque of the locking projections 44, 46 can be reduced without risk of the closure blowing off spontaneously. This makes the closure easier to remove by elderly or arthritic people, or by children, without reducing the pressure safety of the closure.

[0088] In the fully engaged and sealing position, the cap is secured on the container neck as shown in FIG. 2. Both the sealing skirt 20 and the sealing plug 24 are radially slightly flexible to engage the sealing lip. The bulbous projection on the sealing plug and the circumferential sealing ribs on the sealing skirt engage opposite sides of the sealing lip 5, and pinch the lip between them to form a highly effective seal. The overall effect is to provide a sealing jaw for gripping the top of the container neck.

[0089] In use, the closure is removed from the container neck by simple unscrewing. An initial, minimum unscrewing torque is required to overcome the resistance of the locking projections 44, 46. 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 first thread segments 16 ride along the upper surfaces 32 of the second thread segments 26 as the closure is unscrewed. The first thread segments 16 initially ride along the upper regions 34, and then along the steeply pitched intermediate regions 36 of the upper surface of the second thread segments 20. The first thread segments 16 then come into abutment with lower projecting portion 38 of the second thread segments 26. In this position, further unscrewing of the closure is blocked while gas venting takes place along the thread paths. It should also be noted that, in this intermediate gas venting position, the first thread segments 16 abut primarily against the region 42 of the upper surface of the second thread segments 26. The low pitch of this region 42 results in relatively little of the axial force on the closure being converted into unscrewing rotational torque, thereby reducing the tendency of the closure to override the pressure safety feature and blow off.

[0090] Once gas venting from inside the container neck is complete so that there is no longer axial upward force on the closure, the closure can drop down so as to bring the thread segments 16 into abutment with the lower surfaces 30 of the second thread segments 26. In this position, unscrewing can be continued to disengage the closure completely from the container neck.

[0091] The sealing arrangement in the assemblies according to the present invention enables the cap to be secured and resecured on the container neck without the need for high torque or low pitched threads to force a seal. It can be seen that the assembly according to the invention provides at least two circumferential seals having a high sealing pressure over the whole range of temperature and pressure normally encountered in carbonated beverage containers. It can further be seen that the cap is suitable for application to container necks having rounded top lips, such as glass container necks and plastic container necks having a rounded lip to assist drinking directly from the neck. The drawbacks associated with the use of soft sealing liners in the cap are eliminated, in particular the caps according to the present invention can be resecured on the container neck repeatedly, without damage or loss of effectiveness.

[0092] The performance of the container closure assembly according to this embodiment applied to a PET carbonated beverage container was studied under extended storage at 38 C. (high temperature/pressure test). The assembly met the most rigorous industry standard, set by the current Bericap closure according to WO98/35881, but with lower and more controllable opening and closing torque than the Bericap closure. Furthermore, the assembly according to the present invention significantly outperformed the closure of WO2007/057706 in this test.

[0093] 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.

[0094] All patent publications referred to in the foregoing specification are thereby incorporated by reference in their entirety.