[0001] The invention relates to a container and closure cap therefor and in particular relates
to a container and closure cap of the type in which the cap is screwed onto the container
to a predetermined rotational orientation relative thereto.
[0002] It is frequently desired, typically for aesthetic reasons but also for some child
resistant closure latch mechanisms, to design threaded closures and containers with
non-round shapes or otherwise irregular protrusions intended to sit in alignment with
respect to each other when the package is in the closed and sealed position. One example
would be square shaped jars and caps for skin creams or other personal care products.
Another includes oval shaped double wall screw caps designed to lock onto oval child
resistant containers for medicines and other hazardous consumer products.
[0003] The stop to which such closures are tightened to provide alignment with the container
may be either or both of two general configurations. In the first instance, a radial
stop on the neck of the container is configured to interact with a cooperating stop,
either at the thread tail-out or on the skirt of the closure. In other cases, the
stop is implemented as the lower extremity of the closure skirt comes into the vertical
contact with a specially configured (squared off) shoulder on the container. The latter
is frequently used to eliminate any unsightly gap between the skirt of the closure
and the shoulder of the container. Again, in both cases, the positioning of the closure
against any surface other than the sealing surface creates a variability in the pressure
exerted against the sealing surface and results in either over-tightened closures,
which are difficult to remove, or loose closures which are not well sealed to the
container. Also the closure may have two or more aligned/stopped positions each corresponding
to one of the starts of a multi-start thread.
[0004] Due to minor variations in thread dimensions and the configurations of the sealing
components resulting from mass production tooling and processes, closure orientation
may vary by as much as 20 to 100 degrees relative to the container body when screwed
on and tightened to a particular sealing force. Conversely, when such closures are
screwed on to an orientation stop, the sealing force may vary from zero to an unacceptably
high value.
[0005] While there are many dimensions that can vary to cause the problem, the net result
of any combination of variations may be measured as a variation in the vertical dimension
between the inside roof of the closure and the sealing lip on the bottle when the
cap is brought to a particular orientation and stopped. The sealing lip itself may
very well be slightly irregular such that the sealing pressure varies around its circumference.
[0006] In the past, closures have been designed to overcome this problem by means of a special
sealing feature designed to telescope vertically with a cooperating feature on the
container neck, such as tight fitting plug sized to seal the bore of the container
neck over a range of depths of insertion. However, in many cases this technique will
not work for lack of a smooth controlled diameter on the bottle to seal against.
[0007] In other instances closures have been designed to use a relatively thick gasket resilient
through an appropriate range of compressibility to take up the variation and provide
sealing pressure within a suitable range. However, it is frequently desired to use
only a relatively thin gasket which may be combined with a thin film glued or heat
sealed across the mouth of the container to provide tamper evidence, improved barrier
properties and reduced cost.
[0008] The present invention seeks to improve on the prior art and provides a container
and closure cap therefor comprising: a container having an open-ended and externally
threaded cylindrical neck; a closure cap having an end wall and a cylindrical side
wall with an internal screw thread adapted to cooperate with the thread on the container
neck; and a flat liner disc located in the cap and adapted to form a seal with the
open end of the container neck and having a diameter substantially equal to the internal
diameter of the cylindrical side wall, the liner disc consisting of a circular radially
inner region and an annular radially outer region; a circular spacing means formed
on the end wall of the closure and having the inner region of the liner disc adhered
thereto, the spacing means defining an annular recess therearound such that the outer
region of the liner disc is spaced from the end wall of the cap; the arrangement being
such that the annular region of the liner is deflected resiliently into the annular
recess by engagement with the cylindrical neck of the container when the cap is screwed
onto the container.
[0009] In the arrangement of the present invention the liner disc is deflectected resiliently
within its elastic limit and can return to its original flat condition when the closure
cap is removed and flex again when the closure is re-applied.
[0010] Embodiments of the invention are described below with reference to the accompanying
drawings in which:
Figure 1 is an isometric view of a rectangular container with a closure cap fitted;
Figure 2 is a partial cross sectional view taken on the line II- II in Figure 1;
Figure 3 is an isomeric view of a cylindrical container with a closure cap fitted;
Figure 4 is a partial cross sectional view taken on the line IV-IV in Figure 3; and
Figure 5 is a view similar to that of Figure 4 but showing the liner deflected.
[0011] A generally rectangular container 1 is shown in Figure 1 having a generally rectangular
closure cap 2. The container and cap are of the type in which the cap is intended
to be screwed onto the container to a predetermined rotational orientation to form
a seal. As seen from Figure 2 the container has a body 3 and a cylindrical neck 4
connected to the body by a shoulder 5. The neck has an open end and is provided with
an external screw thread 7.
[0012] The cap 2 has an end wall 8, a rectangular outer wall 9 and a cylindrical inner wall
10 which is provided with an internal screw thread 11. The threads 7 and 11 are adapted
to enable the cap to be screwed onto the container so that the open end of the container
can form a seal with a thin and stiff flat liner disc 12 which is provided in the
cap for this purpose.
[0013] A circular plinth 13 is formed on the underside of the end wall 8 and is adhered
such as by glue to the circular radially inner region 121 of the liner so that the
annular radially outer region 122 of the liner disc is held spaced from the end wall
of the cap. The plinth 13 defines a recess 14 therearound. When the cap is screwed
onto the container, the outer region 122 of the liner disc 12 can deflect resiliently
into the recess 14. Because the inner region 121 of the liner is glued to the plinth
13 and thus held against bending, the outer region 122 is effectively mounted and
deflected in cantilever.
[0014] An alternative embodiment is shown in Figures 3-5 where the plinth is replaced by
a plurality of concentric rings 15. This aids cooling of the closure in the mould
and also helps liner adhesion since the glue can flow into the gaps between the rings.
Figure 4 shows a container and cap where the threads have been positioned such that
adequate sealing pressure is established just as the closure reaches an orientation
stop on the container. This is a "loosest fit" combination of tolerances and the liner
is only very slightly deflected. Figure 5 shows the liner deformation which may occur
when specimens having dimensions at the opposite ("tightest fit") extremes are tightened
to the same relative orientation.
[0015] The liner is typically of the type comprising a thin, stiff cardboard liner disc
of about 1 - 1.2 mm thickness which carries a thin aluminium membrane (not shown)
which can be induction heat sealed or otherwise attached to the open end of the neck
4 in known manner. The cardboard disc becomes separated from the membrane during the
heat sealing process. When the container is first opened, the membrane is torn out
and discarded but the cardboard disc remains in the cap for re-sealing the container.
Naturally a liner disc which does not carry on aluminium membrane may be used for
applications where this is not required.
[0016] The diameter of the liner disc 12 is such that it will completely cover the open
neck of the container but can nevertheless be placed in position for gluing to the
cap without being distorted. Thus it has a diameter substantially equal to the internal
diameter of the cylindrical side wall of the closure cap measured at the thread crests.
In one example, the diameter of the liner disc is 0.3 mm less than that of the cylindrical
side wall.
[0017] The external diameter of the neck of the container measured at the root of the threads
is only slightly less than the internal diameter of the cylindrical side wall so that
a good close fit is provided.
[0018] The diameter of the plinth 13 (or of the outer ring 15 in the case of the Figure
4 embodiment) may be varied according to design and liner material requirements. As
the plinth diameter increases, the angle through which the liner 12 must flex in order
to take up the same height variation increases. This changing of the angle through
which the liner material flexes causes a proportional change in the force against
the sealing lip of the bottle. ie the smaller the angle through which the material
has to flex, the lower the force required to flex it, and vice versa. This permits
tailoring of the sealing force to the optimum required for welding the IHS (induction
heat seal) type materials. In the case of liner materials that do not need welding,
it permits tailoring of the tightening force required to accommodate a range of liner
material stiffnesses.
1. A container and closure cap therefor comprising:
a container having an open-ended and externally threaded cylindrical neck;
a closure cap having an end wall and a cylindrical side wall with an internal screw
thread adapted to cooperate with the thread on the container neck; and
a flat liner disc located in the cap and adapted to form a seal with the open end
of the container neck and having a diameter substantially equal to the internal diameter
of the cylindrical side wall, the liner disc consisting of a circular radially inner
region and an annular radially outer region;
a circular spacing means formed on the end wall of the closure and having the inner
region of the liner disc adhered thereto, the spacing means defining an annular recess
therearound such that the outer region of the liner disc is spaced from the end wall
of the cap; the arrangement being such that the annular region of the liner is deflected
resiliently into the annular recess by engagement with the cylindrical neck of the
container when the cap is screwed onto the container.
2. A container and closure cap according to Claim 1, wherein the spacing means comprises
a circular plinth formed on the underside of the end wall of the cap.
3. A container and closure cap according to Claim 1, wherein the spacing means comprises
a plurality of concentric rings formed on the underside of the end wall of the cap.
4. A container and closure therefor substantially as described herein with reference
to the accompanying drawings