U.S. patent application number 13/146782 was filed with the patent office on 2012-02-16 for container closure assembly with pressure seal.
This patent application is currently assigned to Beeson and Sons Limited. Invention is credited to Roger Milner King.
Application Number | 20120037589 13/146782 |
Document ID | / |
Family ID | 40469361 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120037589 |
Kind Code |
A1 |
King; Roger Milner |
February 16, 2012 |
CONTAINER CLOSURE ASSEMBLY WITH PRESSURE SEAL
Abstract
A container closure assembly includes a container neck having an
opening at one end, a lip extending around the opening; a cap for
said neck, the cap having a base portion and a threaded skirt; a
screw thread on the neck; a screw thread on an inner surface of the
threaded skirt of the cap; the screw threads enabling a user to
secure, remove and resecure the cap into a sealing position on the
neck; an olive sealing plug extending from the cap inside and
substantially concentric with said threaded skirt portion of the
cap, the sealing plug forming a seal against an inside surface of
the neck; and a sealing skirt extending from said base of the cap
intermediate said sealing plug and said threaded skirt portion of
the cap and 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.
Inventors: |
King; Roger Milner;
(Buckinghamshire, GB) |
Assignee: |
Beeson and Sons Limited
Buckinghamshire
GB
|
Family ID: |
40469361 |
Appl. No.: |
13/146782 |
Filed: |
January 28, 2010 |
PCT Filed: |
January 28, 2010 |
PCT NO: |
PCT/GB2010/000140 |
371 Date: |
October 14, 2011 |
Current U.S.
Class: |
215/329 |
Current CPC
Class: |
B65D 41/0471 20130101;
B65D 1/0246 20130101; B65D 2401/20 20200501; B65D 41/0421
20130101 |
Class at
Publication: |
215/329 |
International
Class: |
B65D 41/04 20060101
B65D041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2009 |
GB |
0901572.8 |
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 claim 1, 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 claim 1, wherein the
container lip is substantially fully radiused in longitudinal
cross-section.
5. A container closure assembly according to claim 1, 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 claim 1, wherein the
sealing skirt has a radial thickness at half-height equal to from
about 40% to about 80% of radial thickness of the sealing plug
measured at the same height.
7. A container closure assembly according to claim 1, 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 claim 1, 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 claim 1, 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 claim 1, 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 claim 1, 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 claim 1, wherein the
cap can be secured and resecured on the container neck by a single
smooth rotation through 360.degree. or less, preferably through
180.degree. or less, and more preferably through about
90.degree..
15. A container closure assembly according to claim 1, wherein the
first and second threads are multiple start threads.
16. A container closure assembly according to claim 1, wherein the
first and second threads are substantially continuous helical
threads.
17. A container closure assembly according to claim 1, 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 claim 1, 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 claim 1, 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 claim 1.
22. A beverage container according to claim 21 which contains a
carbonated beverage.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to improved seals for
container closure assemblies. The invention is especially
applicable to the sealing of containers in substantially gas-tight
and liquid-tight fashion, such as the sealing of carbonated and
non-carbonated beverage containers.
[0003] It is well known to provide beverage containers of glass,
paper, card, metal or plastic having a screw top that can be
resecured on the bottle neck. It is desirable to provide such
containers with a screw top cap assembly that provides an airtight
and liquid-tight seal to retain the quality of the beverage both
during initial transport and storage, and after partial consumption
of the contents when the cap has been resecured onto the container
neck.
[0004] The present invention relates to improved seals for
container closure assemblies. The invention is especially
applicable to the sealing of containers in substantially gas-tight
and liquid-tight fashion, such as the sealing of carbonated and
non-carbonated beverage containers.
[0005] It is well known to provide beverage containers of glass,
paper, card, metal or plastic having a screw top that can be
resecured on the bottle neck. It is desirable to provide such
containers with a screw top cap assembly that provides an airtight
and liquid-tight seal to retain the quality of the beverage both
during initial transport and storage, and after partial consumption
of the contents when the cap has been resecured onto the container
neck.
[0006] Certain existing container and cap assemblies make use of an
elastomeric liner in the base of the cap. This liner is pressed
against the lip of the bottle neck when the cap is screwed firmly
onto the bottle neck, and the compression between the soft,
deformable liner and the lip of the container provides a tight
seal. Unfortunately, the manufacture and insertion of the liner
into the cap are relatively costly additional process steps.
Furthermore, care must be taken not to over-tighten such caps onto
the container neck, since the liner can become brittle or damaged
if excessive pressure is applied thereto.
[0007] It is also known to provide a cylindrical plug seal
projecting downwardly from the base of the cap, such that the plug
forms an interference fit with an inner surface of the bottle neck
close to the lip of the bottle. Effective sealing by such plug
seals requires the cap to be screwed down very tightly on the
container neck in order to deform the base of the cap and thereby
force the plug radially outwardly into a tight sealing engagement
with the container neck. It is very often the case that such caps
are under-tightened, especially by children and elderly users.
Furthermore, a sufficient sealing force can only be achieved by the
use of threads on the cap and the neck having a low pitch, such
that the cap torque applied to the cap is leveraged into a very
strong downward sealing force between the lip of the container and
the cap base.
[0008] Certain existing container and cap assemblies make use of an
elastomeric liner in the base of the cap. This liner is pressed
against the lip of the bottle neck when the cap is screwed firmly
onto the bottle neck, and the compression between the soft,
deformable liner and the lip of the container provides a tight
seal. Unfortunately, the manufacture and insertion of the liner
into the cap are relatively costly additional process steps.
Furthermore, care must be taken not to over-tighten such caps onto
the container neck, since the liner can become brittle or damaged
if excessive pressure is applied thereto.
[0009] It is also known to provide a cylindrical plug seal
projecting downwardly from the base of the cap, such that the plug
forms an interference fit with an inner surface of the bottle neck
close to the lip of the bottle. Effective sealing by such plug
seals requires the cap to be screwed down very tightly on the
container neck in order to deform the base of the cap and thereby
force the plug radially outwardly into a tight sealing engagement
with the container neck. It is very often the case that such caps
are under-tightened, especially by children and elderly users.
Furthermore, a sufficient sealing force can only be achieved by the
use of threads on the cap and the neck having a low pitch, such
that the cap torque applied to the cap is leveraged into a very
strong downward sealing force between the lip of the container and
the cap base.
[0010] 2. Description of Related Art
[0011] WO02/42171 describes a container closure assembly
comprising: a sealing plug extending from the base portion of the
cap inside and substantially concentric with the skirt portion of
the cap, wherein the sealing plug comprises a plurality of
circumferential sealing ribs on an outer surface of the sealing
plug for engagement with the inner surface of the container neck
when the cap is secured on the container neck; at least one
flexible sealing fin between the sealing plug and the cap skirt for
engagement with the lip of the container when the cap is secured on
the container neck; and at least one circumferential sealing rib on
an inner surface of the cap skirt for engagement with an outer
surface of the container neck proximate to the lip when the cap is
secured on the container neck. In use, the lip of the container
neck is pinched between the ribs on the outer surface of the
sealing plug and the sealing rib on the inner surface of the cap
skirt to form a pressure-tight seal.
[0012] WO2007/057706 describes a container closure assembly
comprising: a sealing plug extending from the base portion of the
cap inside and substantially concentric with the threaded skirt
portion of the cap, wherein the sealing plug comprises two or more
longitudinally spaced circumferential sealing ribs on an outer
surface of the sealing plug for engagement with an inner surface of
the container neck proximate to the lip when the cap is secured on
the container neck. The cap further comprises a sealing skirt
extending from the base portion of the cap intermediate the sealing
plug and the threaded skirt portion of the cap and substantially
concentric with the sealing plug and the threaded skirt portion of
the cap, wherein the sealing skirt comprises two or more
longitudinally spaced circumferential sealing ribs on an inner
surface of the sealing skirt for engagement with an outer surface
of the container neck proximate to the lip when the cap is secured
on the container neck. In use two of the sealing ribs on the
sealing plug are located at substantially the same longitudinal
distances from the base portion of the cap as a two of the
circumferential sealing ribs on the sealing skirt, whereby the lip
of the container neck is pinched between the sealing ribs on the
cap plug and the sealing skirt at two or more longitudinally spaced
locations when the cap is in the secured position on the container
neck.
[0013] Sealing arrangements for plastic container closures are also
known that make use of a sealing olive extending from the base of
the cap that forms an interference fit inside the container neck
for sealing against an inside surface of the container neck
proximate to the lip of the container neck. The sealing olive is a
sealing plug that is characterized by having a smooth, bulbous
circumferential projection (when viewed in longitudinal
cross-section) on its radially outer surface. The olive seal is
robust, easy to mould, and can maintain a good seal even when the
base of the cap is distorted (domed) by pressure from inside the
container. However, the olive seal on its own is not sufficient to
provide a good, pressure-tight seal on carbonated beverage
containers.
[0014] U.S. Pat. No. 5,871,111 and WO-A-9944896, US-A-20040060893,
US-A-20020158037, GB-A-2131774, EP-A-0076778, WO-A-2007132254,
US-A-20010027957 and WO2008012426 show arrangements in which a
sealing olive or sealing plug is used together with one or more
circumferential sealing ribs on the base of the cap that abut
against the top of the container neck in the sealing position.
[0015] In a further development of closures of this type,
WO98/35881 describes container closures in which a sealing olive is
used together with a highly flexible sealing skirt that deforms to
cover the lip of the container neck when the cap is secured on the
neck. The contact area between the sealing skirt and the neck is
quite large in the sealing position, which reduces problems caused
by defects or dirt on the lip. Caps of this type, manufactured by
Bericap GmbH, probably represent the most effective sealing caps on
the market. However, the large contact area between the sealing
skirt and the container neck in the sealing position results in an
undesirably high sealing and opening torque. Furthermore,
over-tightening of the cap can result in damage to the sealing
skirt. WO2008/012426 describes a similar cap with an olive seal and
a relatively short sealing skirt. However it appears that this cap
further requires an elastomeric liner in the base of the cap and a
further sealing rib near the bottom of the cap in order to produce
a satisfactory seal.
BRIEF SUMMARY OF THE INVENTION
[0016] The present inventors have found that the above sealing
arrangements in which a portion of the cap abuts directly against
the top of the container lip present a problem, which is that the
application of an axial force on the cap to displace it further
towards the neck from the fully closed and sealing position results
in permanent deformation and damage to the cap and impaired
subsequent sealing. This excess axial displacement of the cap
towards the neck can occur not only as a result of over-tightening
of the cap on the neck (which can generally be prevented by means
of suitable thread stops) but also as a result of the weight of
superimposed containers when the containers are stacked, as is
commonplace in the storage and transport of, for example, beverage
containers.
[0017] A need remains for a screw-top container and cap arrangement
that can provide an effective seal without the need for a liner,
and also without the need for a strong axial sealing force between
the container neck and the cap, and which furthermore is tolerant
of high axial forces applied to the cap when it is in the closed
and sealing position on the neck, for example the weight of
superimposed containers when the containers are stacked.
[0018] The present invention provides 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; and 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, 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.
[0019] Generally, the seal between the cap and the neck is
maintained during said displacement. The ability to displace the
cap by axial force provides improved performance of the closure
assembly when containers equipped with the assembly are stacked so
that the assemblies at the bottom of the stack are subjected to
axial force due to the superimposed containers. Suitably, the
displacement is a resilient displacement, whereby the closure tends
to spring back to substantially the original sealing position when
the axial force is removed even in the absence of any external
restoring force such as pressure inside the container. This
resilience can be primarily due to the elastic flexure of the
sealing skirt. It goes without saying that the prior art closure
assemblies currently in use, as described above, do not have this
property, as they all require direct abutment between the top of
the container lip and the cap at the sealing position that blocks
further axial movement of the cap towards the neck under axial
force and/or results in permanent, plastic deformation of the cap
under the axial force that impairs the sealing properties of the
assembly both during and after the axial force is applied.
Suitably, the axial displacement of the cap in the assemblies of
the present invention takes place substantially or completely
without plastic (permanent) deformation of the cap. Suitably, the
resilient axial deformation may be at least 0.1 mm, more suitably
from about 0.2 mm to about 2 mm, typically from about 0.5 mm to
about 1 mm. Suitably, the axial force may be from about 1N to about
1000N, for example from about 10N to about 100N.
[0020] In order to allow for the above axial displacement, the
assemblies according to the invention suitably have a clearance
(gap) between the top of the container lip and the axially adjacent
point on the cap at the sealing position. Suitably, the clearance
between the topmost point of the lip and the axially adjacent point
on the base of the closure at the sealing position (in the absence
of external applied axial force) should be at least about 0.1 mm,
suitably about 0.2 mm to about 2 mm, for example about 0.5 mm to
about 1 mm. Suitably no part of the cap should contact the top
surface of the container lip at the sealing position. The term "top
surface" in this context refers to any portion of the lip that is
inclined (in longitudinal cross-section) at an angle of more than
about 45 degrees to the main axis of the assembly, preferably about
30 degrees to the main axis of the assembly.
[0021] Suitably, 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. Such a concave sealing skirt is well adapted to
slide around the side of the lip to maintain effective sealing
during the axial displacement.
[0022] The combination of olive sealing plug and concave sealing
skirt is new, and provides surprisingly improved sealing at low
sealing forces, in addition to the improved performance when
subjected to axial force at the sealing position.
[0023] Suitably, the neck is molded in one piece from thermoplastic
material, such as polyethylene terephthalate. The neck may form
part of a beverage container, such as a molded plastic or glass
carbonated beverage bottle.
[0024] Suitably, the container lip is substantially fully radiused
in longitudinal cross-section. That is to say, the longitudinal
cross-section of the lip surface presents a substantially
continuous curve extending from the inside surface of the neck to
the outside surface of the neck, so that the top of the lip is
rounded, not flat. More suitably, the surface of the lip is shaped
substantially as a segment of a circle in cross-section, for
example it may be substantially semi-circular. The rounded lip
provides for easy and comfortable drinking directly from the
container neck. It is a further advantage of the present invention
that the sealing arrangement is effective to provide a
pressure-tight seal on a rounded container lip by engagement of the
concave inner surface of the sealing skirt on the rounded surface
of the lip.
[0025] Suitably, the inner and/or the outer surfaces of the
container neck adjoining the lip are slightly tapered. That is to
say, the internal diameter of the neck adjacent to the bottom of
the lip may be slightly tapered inwardly providing a substantially
conical surface wherein the internal diameter decreases slightly
with increasing distance from the junction with the (radiused part
of) the lip. Suitably, this region of taper extends for an axial
distance from about 1 mm to about 10 mm, for example about 2 mm to
about 5 mm. so that the olive seal abuts against the tapered inside
surface as the sealing position is approached when screwing the cap
onto the neck. Similarly, the outer diameter of the neck adjacent
to the bottom of the lip may be slightly tapered outwardly so that
the outer diameter increases slightly with increasing distance from
the junction with the (radiused part of) the lip. Suitably, this
region of taper extends for an axial distance from about 1 mm to
about 10 mm, for example about 2 mm to about 5 mm, so that the
sealing skirt abuts against the tapered inside surface as the
sealing position of the cap on the neck is approached. The angle of
each taper, measured in longitudinal cross-section, is suitably
independently from about 1 degree to about 30 degrees, more
suitably from about 5 degrees to about 20 degrees from the
longitudinal axis of the assembly. The slight taper of the neck
below the lip results in a more constant torque being required to
secure the cap on the neck close to the sealing position. In other
words, there is a less abrupt increase in screwing torque as the
sealing plug and sealing skirt first engage the neck.
[0026] The assembly according to the invention further comprises a
cap having a base portion and a threaded skirt portion. The cap is
suitably molded in one piece from thermoplastic material, for
example by injection molding or by compression molding. The cap
includes a sealing plug and a sealing skirt depending from the base
of the cap, as defined above.
[0027] The sealing plug is suitably in the form of a tube,
typically projecting perpendicularly downwardly from the base of
the cap and preferably substantially concentric with the threaded
skirt and coaxial with the longitudinal axis of the cap. The height
of the sealing plug (measured from the inside surface of the base
of the cap) is suitably from about 1 mm to about 5 mm, for example
about 1.5 mm to about 2.5 mm. The sealing plug is normally molded
integrally with the base of the cap. The mean thickness of the
tubular wall of the sealing plug is suitably from about 0.5 mm to
about 2 mm, for example about 0.7 mm to about 1.2 mm. This gives
the sealing plug the right degree of resilience and strength for
the desired sealing function.
[0028] The sealing plug is in the form of an olive seal. That is to
say, the plug has a circumferentially projecting radially outer
surface having a bulbous shape (when viewed in longitudinal
cross-section). The bulbous projection has a substantially smooth,
continuous surface and a height suitably from about 10% to about
50% of the radial thickness of the plug. The minimum radius of
curvature of the bulbous projection is suitably no less than about
the mean radial thickness of the plug. Suitably, the minimum radius
of curvature of the bulbous projection is from about 0.5 mm to
about 1 mm. Such olive sealing plugs are relatively tolerant of
small axial displacements of the plug, for example caused by doming
of the cap base under pressure from inside the container, without
loss of sealing effectiveness.
[0029] The container closure in the assembly according to the
present invention further comprises a circumferential sealing
skirt. The sealing skirt is separate and radially spaced from the
threaded cap skirt that engages the thread on the outside of the
container neck. Suitably, the sealing skirt is substantially
tubular, and projects downwardly from the base of the cap
intermediate the cap skirt and the sealing plug. The sealing skirt
is preferably substantially concentric with the threaded skirt and
the sealing plug, and coaxial with the longitudinal axis of the
cap. The height of the sealing skirt is suitably from about 1 mm to
about 5 mm, for example about 1.5 mm to about 2.5 mm. The height of
the sealing skirt in certain embodiments (measured from the inside
surface of the cap adjacent to the inside surface of the sealing
skirt) is at least about 50%, for example at least about 75% of the
height of the sealing plug. The sealing skirt is normally molded
integrally with the base of the cap. The mean thickness of the
tubular wall of the sealing skirt is suitably from about 0.5 mm to
about 2 mm, for example about 0.7 mm to about 1.2 mm. This gives
the sealing skirt the right degree of resilience and strength for
the desired sealing function.
[0030] The sealing skirt in the arrangement of the present
invention is suitably relatively thick relative to its height, and
undergoes relatively little deformation upon sealing when compared
to the sealing skirt of, for example, WO98/35881. Suitably, the
sealing force applied by the skirt is provided by the resilience of
the skirt itself, not by abutment of the outside of the sealing
skirt against the inside of the threaded skirt or the cap base as
taught in WO98/35881. The relatively thick and resilient sealing
skirt is less likely to be damaged by repeated use, in particular
by over-tightening. Suitably, the sealing skirt has a radial
thickness at half-height (said height of the sealing skirt being
measured from the base of the radially inner surface of the sealing
skirt) equal to from about 40% to about 80% of the radial thickness
of the sealing plug measured at the same height. Suitably, the
sealing skirt has a radial thickness at half-height (said height of
the sealing skirt being measured from the base of the radially
inner surface of the sealing skirt) equal to from about 20% to
about 50% of the height of the sealing skirt, for example from
about 25% to about 40% of said height.
[0031] Suitably, 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. For example, it may be from
about 0.1 mm to about 0.25 mm less than the outside diameter of the
container neck. In other words, the inside diameter of the sealing
skirt is only slightly less than the outside diameter of the
container neck proximate to the rounded lip, whereby the skirt is
only slightly deformed in the sealing position. However, the
resilience of the sealing skirt is sufficient for a slight
deformation to produce a strong sealing force against the lip.
Moreover, the resilience of the sealing skirt allows the skirt to
flex outwardly without plastic deformation and without loss of
sealing effectiveness when the cap is forced axially downwardly
beyond the normal sealing position by an external force, for
example the weight of another container stacked on top of the
assembly. The same resilience of the sealing skirt restores the
original sealing position of the cap when the external axial force
is removed.
[0032] The sealing effectiveness of the sealing skirt may be
further enhanced by providing at least one circumferential sealing
rib in said concave region of said sealing skirt. Suitably, there
are two of the sealing ribs on the sealing skirt, but in some
embodiments there could be from 3 to 10 of the ribs, and for
example 4 to 6 ribs.
[0033] Suitably, at least one of the sealing ribs has a
substantially triangular cross-section when the cap is viewed in
longitudinal cross-section, for example substantially equilateral
triangular. Suitably, the contact angle between the sides of the
sealing ribs and the radially inside surface of the sealing skirt
is from about 30 degrees to about 75 degrees, for example from
about 45 degrees to about 60 degrees. This enables the sealing
force to be concentrated in the tip of the sealing rib to maximize
sealing effectiveness. Suitably, at least one of the sealing ribs
has a height in the range of 10 to 250 micrometers, more suitably
20 to 150 micrometers, for example 50 to 150 micrometers. The
height is defined as the maximum distance that the sealing rib
projects above the adjacent surface of the sealing skirt, when the
cap is viewed in longitudinal cross-section. Such micro sealing
ribs are especially effective to concentrate the sealing force and
achieve an effective seal with a substantially smooth sealing
surface on the container neck. Furthermore, such micro ribs are
especially easy to mold in high-speed cap molding equipment, and to
bump off the mold mandrel of the equipment after molding.
[0034] An advantage of using multiple sealing ribs on the sealing
skirt is that the plurality of sealing ribs may have more than one
dimension in order to optimize sealing. For example, the size of
the sealing rib closest to the base of the cap may be greater than
the size of the sealing rib remote from the base of the cap. This
allows the sealing rib closest to the base of the cap (i.e. closest
to the lip of the container) to deform more that the sealing rib
furthest from the base of the cap.
[0035] The use of multiple circumferential sealing ribs on the
sealing skirt, which has a degree of radial flexibility, allows a
pressure-tight seal to be formed between the container neck and the
cap without application of excessive force to the cap, and without
any need for a sealing liner in the base of the cap. Accordingly,
the caps in the assemblies according to the present invention
suitably do not include a liner, i.e. they are linerless caps.
Furthermore, the cap assemblies do not require, and preferably do
not include, any sealing elements on the cap other than the olive
seal plug and the sealing skirt. In particular, as previously
explained, and in contrast to almost all prior art closure
assemblies for carbonated beverages, the assemblies according to
the present invention do not require, and normally do not have, any
sealing elements abutting against the top of the lip.
[0036] Suitably, the cap is a low-profile cap having an axial
height from the top of the base to the bottom of the threaded skirt
(i.e. excluding any tamper-evident ring attached to the bottom of
the threaded skirt), of from about 10 mm to about 15 mm, for
example about 12 mm to about 14 mm. The sealing arrangement of the
present invention is especially suitable for use with low-profile
caps, because the minimal distortion of the sealing skirt during
sealing makes it possible to arrange the sealing skirt and plug so
that they axially overlap the top of the threads on the cap skirt
without interfering with the running of those threads.
[0037] It has been found that the assemblies according to the
invention provide excellent sealing of carbonated beverage
containers even under high pressure/high temperature conditions
such as storage at 38.degree. C. This is because the distortion
(doming) of the base of the cap leverages increased sealing force
onto the sealing skirt, while the olive seal on the inside of the
container neck is more tolerant of deformation of the cap base
compared to the sealing plugs described in WO02/42171 and
WO2007/057706. However, the arrangements according to the present
invention maintain the advantages of robustness, resistance to
over-tightening, ease of molding, and low sealing/opening torque of
those prior art assemblies.
[0038] The container closure assembly according to the present
invention is especially suitable for use in conjunction with thread
arrangements that are quick and easy to secure and resecure,
wherein the cap can be secured and resecured on the container neck
by a single smooth rotation through 360.degree. or less, more
suitably 180.degree. or less, and most suitably about
90.degree..
[0039] Suitably, the first and second threads may be multiple start
threads such as two-start threads or three-start threads, and more
suitably they are four-start threads. This further assists securing
of the cap on the neck, since the user needs to rotate the cap less
in order to find a thread start. Suitably, the threads are
substantially free-running or parallel threads. That is to say, the
threads on the cap and the neck slide past each other freely
without forming an interference fit between the thread segments on
the cap and the neck. However, the present invention is also
applicable to embodiments in which the first and second threads may
be more conventional, single-start, low-pitch continuous
threads.
[0040] Suitably, the first and second threads are continuous
helical threads. That is to say, they are not bayonet-type threads
that require a stepped motion of the cap to secure the cap on the
neck, but rather they define a substantially continuous helical
thread path having a thread gradient (pitch) less than 90 degrees
substantially throughout. Suitably the threads have a mean thread
pitch of from 5.degree. to 25.degree., more suitably from
10.degree. to 20.degree.. Typically, the minimum vertical
displacement of the cap between the fully secured position on the
container neck and a fully disengaged position of the cap on the
neck of from about 2 mm to about 10 mm, for example from about 4 mm
to about 8 mm.
[0041] Steeply pitched threads provide advantages in terms of ease
of use and more reliable separation of tamper-evident rings from
the cap skirt. However, it will be appreciated that such steeply
pitched threads result in a relatively small leverage of rotational
force applied to the cap into downward force on the cap, and it is
a feature of the sealing arrangement according to the invention
that it can provide a reliable pressure-tight seal without strong
downward force being applied to the cap as in previous sealing
arrangements.
[0042] Suitably, the torque required to secure the cap in a sealing
position on the container neck is less than 1.2 Nm, more suitably
less than 1 Nm and most suitably from about 0.7 to about 0.9 Nm.
This is the torque required to engage the complementary locking
arrangement (where present) at the sealing position, and/or
otherwise the force required to substantially eliminate gas leakage
at normal carbonated beverage pressure differentials.
[0043] It is an advantage of the assemblies according to the
present invention that they can provide a pressure tight seal
without the need for additional circumferential flexible sealing
fins between the sealing plug and the sealing skirt of the kind
described in WO02/42171.
[0044] In certain embodiments, the container closure assembly
according to the invention, the container further comprises
mutually engageable elements on the neck and the closure to block
or restrict rotation of the closure in an unscrewing direction
beyond an intermediate position when the closure is under axial
pressure in a direction emerging from the container neck. This is
the so-called pressure safety feature that is intended to prevent
the closure unscrewing uncontrollably or missiling as it is removed
from a container neck under pressure. Preferably, the pressure
safety feature is as described in WO95/05322, WO97/21602 and
WO99/19228.
[0045] In these embodiments, the first and second screw threads are
constructed and arranged to permit axial displacement of the
closure relative to the neck at least when the closure is at the
said intermediate position, and preferably the engageable elements
are adapted to engage each other when the closure is axially
displaced in a direction emerging from the neck, for example by
axial pressure from inside the pressurized container. More
preferably, the mutually engageable elements are constructed and
arranged not to mutually engage each other when the closure is
axially displaced in a direction inwardly towards the neck at the
intermediate position, for example when the closure is being
screwed down onto the container neck.
[0046] Preferably, the mutually engageable elements comprise a step
or recess formed in the lower surface of one of the second screw
thread segments to provide a first abutment surface against which a
second abutment surface on one of the first screw thread segments
abuts to block or restrict rotation of the closure in an unscrewing
direction at the said intermediate position when the closure is
under axial pressure in a direction emerging from the container
neck, but which allows easy removal of the closure when the
container is not unduly pressurized.
[0047] More preferably, the second thread segment comprises a first
thread portion having a first longitudinal cross section and a
second thread portion having a second longitudinal cross section
narrower than the first cross section, whereby the first thread
segment abuts against the second thread portion. The relatively
broad first cross section is preferably adjacent to the
circumferentially overlapping region of the second thread segments,
resulting in a relatively narrow thread gap in that region.
[0048] Preferably, the first and second threads on the container
neck and closure are variable pitch threads, preferably as
described in WO97/21602. Preferably, the pitch of an unscrewing
thread path defined by the first and the second thread segments is
relatively lower in a first region and relatively higher in a
second region displaced from the first region in an unscrewing
direction. The pitch of the thread path in the first region is
preferably substantially constant. The first region normally
includes the position at which the closure is sealed on the
container neck. Preferably, the first region extends for
20.degree.-40.degree. about the circumference of the container neck
or the closure skirt. Preferably, the pitch of the lower thread
surface in the first region is in the range of 1.degree. to
12.degree., more preferably 2.degree. to 8.degree..
[0049] Preferably, the second region is adjacent to the first
region of the thread path. Preferably, the pitch of the helical
thread path in the second region is substantially constant, and the
second region preferably extends for 15.degree. to 35.degree. about
the circumference of the container neck or the closure skirt.
Preferably, the pitch of the thread path in the second region is in
the range of 15.degree. to 35.degree..
[0050] The use of a variable pitch thread renders it easier to
combine fast-turn threads having a steep average pitch that are
elderly- and child-friendly with pressure safety. A problem that
could arise with fast-turn threads is that they are steeply
pitched, which results in a tendency to back off from the fully
secured position on the container neck when the container is
pressurized. This problem can be overcome by using bayonet-type
threads, but the use of bayonet-type threads results in a number of
different problems, as described above. In contrast, the variable
pitch threads solve the problem of backing off of the closure under
pressure, whilst retaining all of the advantages of continuous,
fast-turn threads.
[0051] Preferably, the helical unscrewing thread path further
comprises a third region adjacent to the second region, wherein the
third region has a relatively low pitch. Preferably, the third
region has a relatively constant pitch, preferably in the range 1
to 12.degree., more preferably 2 to 8.degree.. The third region
preferably includes the position of the closure on the container
neck when the closure is blocked at the intermediate gas venting
position. The relatively low pitch of the third region reduces the
tendency of the closure to override the blocking means at high gas
venting pressures.
[0052] Suitably, the container and cap assemblies according to the
present invention comprise complementary locking elements on the
container neck and the cap that block or resist unscrewing of the
cap from the sealing position on the container neck until a
predetermined minimum opening torque is applied. For example, the
locking elements may comprise a longitudinal locking rib on one of
the container neck or the skirt portion of the cap, and a
complementary locking ramp on the other of the container neck and
the skirt portion of the cap, the locking rib abutting against the
retaining edge of the locking ramp when the cap is fully secured on
the container neck.
[0053] In certain embodiments, the first and second locking
projections (side catches) longitudinally overlap the first and/or
the second thread segments when the cap is in said fully engaged
position on the container neck. In other words, the first and
second locking projections are not located entirely above or below
the threads (the terms above and below refer to relative positions
along the longitudinal axis of the assembly), but are located, at
least in part, circumferentially in-between the threads. The side
catches are preferably located adjacent to an end of the threads.
This enables the entire thread assembly to be made more compact in
the longitudinal (vertical) direction, thereby reducing the total
amount of molding material needed to make the assembly, and the
space taken up by the assembly. In certain embodiments, it also
enables the neck thread to be made more suitable for consumption
directly from the neck.
[0054] Typically, the first and second locking elements are
situated near the lower end of the threads when the cap is fully
secured on the container. Preferably, the first and/or second
locking projections do not extend below the lower edge of the first
or second thread segments when the cap is in said fully engaged
position on the container neck. The term "lower" refers to the part
of the neck thread furthest from the opening of the container neck.
In such assemblies, the locking projections are preferably located
substantially completely circumferentially between the threads and
not above or below the threads. Preferably, the locking projections
on the neck are not joined at the lower edge to a circumferential
flange or shoulder (e.g. the shoulder used to retain a
tamper-evident band), thereby enhancing the flexibility of the
locking projections and enhancing the "click-to-close" noise.
[0055] Further to the aforesaid, at least one, and preferably both
of the complementary locking projections on the neck and/or the cap
is substantially separate from the thread segments and can flex
substantially independently of the thread segments in order to
provide the snap-fitting and clearly audible click as the fully
secured position of the cap on the neck is reached. In general, a
radially innermost vertex of the second locking element on the cap
skirt rides over a radially outermost vertex of the first locking
element on the container neck as the fully secured position is
approached. The second locking element then rides back over the
outermost vertex of the first locking element when the cap is
removed from the secured position, for example when opening the
assembly.
[0056] At least one, and preferably both of the complementary
locking projections on the neck and/or the cap has a length in the
longitudinal direction (i.e. along the rotational axis of the cap
assembly) of from about 1 mm to about 6 mm, for example from about
2 mm to about 4 mm. At least one, and preferably both of the
complementary locking projections on the neck and/or the cap has a
height of from about 0.25 mm to about 2 mm, for example from about
0.5 mm to about 1.5 mm. In any case the height of the locking
projections is normally less than the average height of the
respective thread segments. At least one, and preferably both of
the complementary locking projections on the neck and/or the cap
has a maximum width (i.e. around the circumference of the neck or
cap skirt) of from about 0.5 mm to about 3 mm, for example from
about 1 mm to about 2 mm. At least one, and preferably both of the
complementary locking projections on the neck and/or the cap has a
ratio of the maximum height to the maximum width of at least about
0.5, more preferably at least 1, for example from about 1 to about
5.
[0057] In suitable embodiments, the first locking projection is
located longitudinally overlapping with and circumferentially
spaced from an upper end of a first thread segment. In other
embodiments, the second locking projection is located
longitudinally overlapping with and circumferentially spaced from a
lower end of a second thread segment. These latter embodiments are
preferred, since the first locking projections are then located
further from the opening of the container neck. The circumferential
spacing between the projections and the respective thread segments
in these embodiments is typically from about 1 mm to about 10 mm,
for example from about 1 mm to about 4 mm. In these embodiments,
the circumferentially spaced locking projections may abut against
the thread segments of the other assembly component as the assembly
is screwed together. That is to say, the circumferentially spaced
projections may define a part of the thread path on the cap or
neck. For example, in the case where there are relatively long
thread segments on the cap skirt defining a thread path for
relatively short thread segments on the container neck, the locking
projections on the cap skirt may be circumferentially spaced from
the lower end of the relatively long thread segments on the cap
skirt and may thereby define an extension at the start of the
thread path followed by the thread segments on the neck when the
cap is applied to the neck. This method of using the locking
projections to form an extension of the thread path on one of the
neck or the cap solves the problem of providing larger locking
projections that overlap with the threads, but do not interfere
with the running of the threads. The locking projections are
generally in the line of and, as it were, are extensions of the
thread path on one of the neck or the cap. Suitably, the locking
projections are as described in WO-A-2005058720.
[0058] The assemblies according to the present invention may
comprise more than one pair of complementary locking projections on
the container neck and the cap. Preferably there are at least two
such complementary pairs radially spaced around the neck and cap
skirt. There will normally be at least one pair for each thread
start, for example there may be four pairs radially spaced around
the neck and cap skirt.
[0059] The said sealing position of the cap on the neck is thus
normally the first rotational position in the screwing direction at
which the locking projections are in locking engagement, i.e.
normally in abutment.
[0060] Suitably, the locking projections on the neck and the cap
skirt are circumferentially positioned such that they are in
abutment when the cap is at the said sealing position on the
container neck. That is to say, the projection on the cap has
ridden over one side of, and is resting in abutment with the
opposite side of, the corresponding projection on the container
neck at said fully closed and sealing position. This ensures that
there is no play in the cap at said closed and sealing position
that could allow leakage from the seal. Preferably, when the
projections are in abutment at the closed and sealing position, the
cap skirt and/or the projections are still slightly distorted such
that a resilient force is exerted between the projections in
abutment. This resilient force is leveraged by the abutment into a
closing torque between the cap and the neck that urges the cap into
the fully closed and sealing position. This can ensure that the
respective sealing surfaces of the container neck and the cap are
automatically seated against each other, even though the cap may
not be screwed down especially tightly. Furthermore, the locking
projections allow for considerably lower manufacturing tolerances
in the molding of the assembly, since effective sealing is achieved
over a broader range of rotational sealing positions due to the
interaction between the locking projections and the radial
deformation of the cap skirt.
[0061] The advantages of locking projections that urge the cap into
the sealing position are discussed in detail in WO93/01098.
[0062] The complementary locking elements according to the present
invention provide a number of other important advantages, besides
urging the cap into the fully secured and sealing position as
described above. Firstly, they prevent accidental backing off of
the cap from the fully engaged and sealing position on the
container neck due to pressure from inside the container. These
elements enable more steeply pitched threads and free running
(parallel) threads to be used without risk of the cap unscrewing
spontaneously. The use of more steeply pitched threads in turn
makes it easier to remove and resecure the cap.
[0063] In some embodiments, the locking elements according to the
present invention may also provide a positive "click" when the
fully engaged and sealing position of the cap on the container neck
is reached, thereby giving the user a positive indication that the
cap is in the closed (sealed) position. This system also ensures
that exactly the right degree of compression is applied between the
container and cap to achieve an effective airtight seal.
[0064] Suitably, the container closure assembly according to the
present invention further comprises 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. The stop
elements act in conjunction with the locking arrangement to ensure
that exactly the right degree of screwing of the cap is achieved in
order to provide a pressure-tight seal with the sealing arrangement
of the present invention. The stop surfaces may be in abutment at
said sealing position of the cap on the neck, or they may be very
close to abutment, for example within less than about 2 mm,
suitably less than about 1 mm of abutment at said sealing position,
to allow for manufacturing tolerances.
[0065] Suitable locking and stop arrangements are described in
detail in WO 91/18799, WO 95/05322 and WO2005/058720.
[0066] The container closure assembly also suitably comprises a
tamper-evident safety feature. The safety feature preferably
includes a tamper-evident ring that is initially formed integrally
with the skirt of the container closure and joined to the lower
edge thereof by one or more frangible bridges. The tamper-evident
ring is retained on the container neck when the cap is removed from
the neck for the first time, suitably by abutment with the
underside of a circumferential retaining lip provided on the
container neck below the threads.
[0067] In certain embodiments, the tamper-evident ring comprises a
plurality of integrally formed, flexible, radially inwardly
pointing retaining tabs to retain the ring under the retaining lip.
In these embodiments, ratchet projections may also be provided on
the container neck below the circumferential retaining lip and
radially spaced around the container neck to block rotation of the
tamper-evident ring on the container neck in an unscrewing
direction and thereby assist separation of the tamper-evident ring
from the neck. The structure and operation of the tamper-evident
ring feature according to these embodiments may be as described and
claimed in our International Patent Publication WO94/11267.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0068] Embodiments of the present invention will now be described
further by way of example with reference to the accompanying
drawings, in which:
[0069] 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;
[0070] 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
[0071] FIG. 3 shows a partial longitudinal cross-section through
the top region of the neck of a container closure assembly
according to the invention
DETAILED DESCRIPTION OF THE INVENTION
[0072] 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.
[0073] 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 molding and
blow molding of polyethylene terephthalate in the manner
conventionally known for carbonated beverage containers. The
closure is preferably formed by injection molding or compression
molding of polyethylene. The container neck has a cylindrical inner
surface 13 terminating in rounded lip 14.
[0074] 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 .alpha. of approximately 16 degrees. A region
88 of the outside surface adjacent to the radiused lip 84 is
tapered at an angle .beta. 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.
[0075] 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.degree. around the neck and having a
lower surface 18 with relatively low pitch of about 6.degree. and
an upper surface 20 with intermediate pitch of about 13.5.degree..
The first thread segments present a substantially trapezoidal
cross-section along the axis of the neck.
[0076] 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.
[0077] 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.degree.. The upper
region adjoins an intermediate region having a substantially
constant, much higher pitch of about 25.degree.. The average pitch
of the helical thread path defined by the second thread segments 26
is 13.5.degree..
[0078] 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.degree..
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.degree.. 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.
[0087] 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.degree. 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.
[0088] 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.
[0089] 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.
[0090] 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 molded to a very high tolerance.
[0091] 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.
[0092] 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 maximize 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.
[0093] 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.
[0094] 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.
[0095] 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.
[0096] 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.
[0097] 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.degree. 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.
[0098] 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.
[0099] All patent publications referred to in the foregoing
specification are thereby incorporated by reference in their
entirety.
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