GB2321053A - Screw cap with liner - Google Patents

Abstract

A screw cap 320, which has a predetermined orientation when fully tightened onto a container neck 312, has a liner 340 and a pair of annular beads 327, 328 which define a recess 323 on the underside of the cap. When the cap is fully tightened onto the container, the liner is resiliently deformed into the recess to provide a seal for the container neck. The annular beads may have V-shaped cross-sections with included angles of at least 90‹, and may be positioned so that the outer bead 328 is radially outward from the outer surface of the container neck, and the inner bead 327 is radially inward from the inner surface of the container neck. The beads may be rounded and the outer bead may be taller than the inner bead, both heights preferably being within the range 0.7 - 0.8 mm. The liner may be made from a relatively incompressible material such as card, and may be retained within the screw cap by lugs 329. In a preferred embodiment, the cap and container are polygonal and have cooperating stops to ensure correct alignment.

Description

CLOSURE WITH WAD SUPPORT BEADS The present invention relates to a closure and, in particular, to a closure of plastics material having features moulded on its underside which are adapted to support a card wad in a resilient fashion when the wad is contacted from beneath by a container rim during use.

Dry particulate consumer goods, such as coffee, are most frequently sold in packages which are a combination of a glass container and a moulded plastics closure. The closure is provided with a sealing wad on its underside and, when a closure is applied for the first time to a filled container, the wad is lightly glued to the rim of the container neck. Typically, that surface of the wad destined for engagement with the rim of the container neck has a foil covering. This ensures a seal of high integrity. When the closure is removed for the first time, the foil covering separates from the wad so that the container remains sealed until the foil is ruptured. In the case of goods such as coffee, this helps to preserve the richness of aroma that is released whenever a new jar is opened.

The surviving portion of the wad is retained in the closure and helps to seal the container against moisture ingress during the subsequent shelf life of the container contents. Of course, the sealing effect is not as comprehensive as that provided by the glued foil covering. However, without a wad, degradation of the container contents can be quite rapid, so it is generally recognised in the art that a wad is desirable for re-sealing.

In a conventional arrangement, the jar and closure are both circular in cross-section. The neck finish of the container is provided with an external screw thread, which may be a single or a multi-start thread, and the closure is provided with a depending skirt having a complimentary thread formation on its radially inner surface. In such an arrangement, the closure is rotated on the neck finish of the jar so that the respective threads engage and the closure then tightens as the wad retained on its underside compresses against the top of the neck finish, or container rim.

As indicated above, typical containers for dry particulate beverage goods are formed from glass. For glass containers, the distance between the rim and the start of the thread is subject to considerable variation from one unit to another during production. Typically, such containers have a tolerance in excess of 0.5 mm.

Whenever a closure is applied to a neck finish, its final orientation depends on the position of the glass thread within its height tolerance, i.e. how far the thread in the closure is engaged before the closure becomes fully tightened.

The tolerance band which must be designed into the closure for achievement of a fully tightened condition on a glass neck finish is not normally important because the closure, like the container, is round and does not require a specific orientation in its end position.

Nowadays, however, some suppliers of coffee or the like are changing to non-circular containers, particularly for their top of the range brands. Where the packaging style combines a non-circular container with a non-circular closure, there is a desire to achieve precise alignment between the container and its closure in the fully-tightened condition for maximum aesthetic effect.

Similarly, if the closure or container has an embossed logo or other design that requires alignment with a feature on the other component, final orientation of the closure relative to the container can be important.

In order to achieve such alignment, stops are normally provided on the neck finish against which the closure threads engage, thereby orienting the closure in its stop position. In such circumstances, a compressible wadding material is required that allows compression of the wad by an amount which is at least equal to the tolerance band of the glass neck thread height and its stop formation. This ensures that the wadding material is compressed against the rim of the neck finish in order to obtain a good seal. The wadding material normally used in such an arrangement is expanded polyethylene, which has a compressibility of 0.7 - 0.8 mm. This is adequate to compensate for the usual degree of variation in neck thread heights of glass containers. By contrast, a conventional card wad has a compressibility of only 0.1 mm.

The disadvantage of using expanded polyethylene wadding is that it is relatively expensive, costing in the region of 60% more than conventional card wadding. In view of the fact that a cost saving of roughly 8% per unit could be achieved if closures could be fitted with a conventional card wad, suppliers would rather use a card wad in preference to expanded polyethylene.

However, they are unable to do so for closures having a predetermined radial orientation at the stop position because card lacks the necessary degree of compressibility for achieving a reliable seal over the range of tolerances likely to be encountered with glass neck finishes.

It is therefore an object of the present invention to provide a closure adapted to assume a predetermined orientation relative to a container in the fully closed condition which is able to use a wad formed of a substantially incompressible material. It is a further object of the invention to provide a closure which is more economical to manufacture than prior art closures by virtue of its suitability for use with relatively cheaper wad means. It is also an object of the invention to provide a closure that uses a substantially incompressible wad which is mounted in such a way that it behaves as if it were compressible.

The invention is a closure of the type adapted for releasable engagement with a container neck by rotation relative thereto wherein said closure and said container have fixed radial orientations relative to each other in a fully closed condition thereof, said closure comprising a cap portion, an annular skirt portion and wad means disposed on the underside of said cap portion, characterised in that said cap portion is provided on its underside with a pair of raised annular beads defining a recess therebetween into which said wad means is resiliently deformable.

Preferably, the outermost of said pair of raised annular beads has a diameter at least as great as the outside diameter of a container rim to which the closure is secured in use. Similarly, the innermost of said pair of raised annular beads preferably has a diameter no greater than the inside diameter of the container rim. Most preferably, the diameter of the outermost raised annular formation slightly exceeds the outside diameter of the container rim and the diameter of the innermost raised annular formation is slightly less than the inside diameter of the container rim. In such an arrangement, as the container rim approaches the underside of the closure, it encounters the wad means and deforms it into the recess between the two raised annular beads. The degree of deformation is dependent on the degree of variation in the neck finish of the container, that is to say on the tolerance range of the neck thread height and its stop.

Best results are achieved with raised annular beads having a substantially V-shaped cross-section, the "V" having an included angle of 900 or more. The included angles and radii at the crests and roots of the raised annular beads can be critical to the ease with which a closure can be ejected from the mould during manufacture, for reasons which will be explained in more detail below.

Closures which are designed for use with a wad are formed with wadretaining features on the wall forming the interior surface of the skirt portion.

It is desirable to mould these wad-retaining formations with a sharp corner where they adjoin the skirt wall and with a flat "top" surface substantially parallel to and facing the closure underside. In order to achieve this geometry, it is necessary to employ a collapsing core during the moulding process.

However, use of a collapsing core is generally understood by persons skilled in the art to be incompatible with the provision of raised beads on the underside of the closure. The raised beads are susceptible to damage or deformation during the action of the core collapse.

Preferably, the outer slope of the outermost raised bead forms an angle of 35-550 relative to the underside of the closure. More preferably, this angle lies in the range 40-500, even more preferably 43-470, the most preferred angle being 450. The inner slope of this bead preferably forms an angle of 20-400 relative to the underside of the closure. More preferably, this angle lies in the range 25-350, even more preferably 28-320, the ideal angle being 300.

The slopes of the innermost raised bead are preferably equal in angle relative to the underside of the closure. Advantageously, the angles of these slopes are in the range 35-550, more preferably in the range 40-500, even more preferably 43-470 and ideally 450.

The separation between the adjacent crests of the innermost and outermost raised annular beads may be determined with reference to the thickness of the container neck onto which the closure is applied in use. The critical dimension here is the thickness of the container neck at its rim.

Preferably, the separation between the adjacent crests of the raised annular beads is such that the recess defined between them has a flat portion at its root which is at least equal to the thickness of the container neck at its rim.

The dimension of the flat portion may be up to 50% greater than this so that the card wad means can be deformed into the recess without creasing.

The height of the raised annular beads is chosen so that the card wad means may be deformed into the recess defined between them by an amount which corresponds to the compressibility of an expanded plastics wad.

Typically, the height of the raised annular beads lies in the range 0.6 - 1.0 mm, though a preferred range is 0.7 - 0.8 mm. Preferably, the outermost raised annular bead is marginally higher than the innermost raised annular bead, so that the wad is contacted firstly by the outermost bead when the closure is re-applied to a container. It has been found that this difference in height between the innermost and outermost annular beads is helpful in preventing creasing of the card wad means. Such creasing should be avoided because it reduces the resilience of the wad and therefore compromises the effectiveness of the seal which the wad is intended to provide. Radiused corners at the crests and roots of the annular beads also assist in the avoidance of creasing.

Preferably, the radii fall in the range 0.05 to 0.30 mm, though a preferred range is 0.15 to 0.20 mm.

The invention will now be described by way of example only with reference to the drawings, in which: Figure 1 is a perspective view of a multi-sided closure in accordance with the invention and a similarly-configured container; Figure 2 is an enlarged cross-sectional view through a portion of a first embodiment of a closure in accordance with the invention; Figure 3, views (a) and (b), are partial cross-sectional views through a closure in accordance with a first embodiment of the invention showing deflection of a wad by the rim of a container, and Figure 4 is an enlarged cross-sectional view through a portion of a second embodiment of a closure in accordance with the invention.

Referring now to Figure 1, there is shown a glass container 10 intended for the storage of coffee or the like. The container 10 comprises a body portion 11 having six sides 16 and a neck 12. Rim 13 of the neck 12 defines a mouth 14 through which the container contents may be dispensed in use.

On its radially external surface, neck 1 2 is provided with a raised screw thread formation 15 having a radial stop 15a.

Closure 20 comprises a top portion 21 and a depending annular skirt 22 which includes a complementary screw thread formation (not shown) on its radially inner surface. Like the container body, the closure skirt 22 is a six-sided structure and the sides 26 are intended to sit in register with the sides 16 of the container 10 when the closure 20 is fully tightened.

In the fully-tightened condition, the radial stop 1 5a of the thread formation engages the closure thread and arrests relative rotation between the container 10 and the closure 20 at a mutually predetermined orientation to achieve alignment of the respective container and closure sides 16 and 26.

In the illustrated embodiment, only a single-start thread is shown, but it will be understood by persons skilled in the art that the underlying principles of the invention are equally applicable to arrangements having multiple start threads. Also, the invention may be adapted to closures of the snap-on/twistoff type.

Figure 2 is an enlarged cross-sectional view through part of a first embodiment of a closure in accordance with the present invention. In particular, the Figure shows a closure 220, the underside of which has a pair of raised annular beads 227 and 228 formed thereon. Between the beads 227 and 228 is an annular land region 223, the purpose of which is explained in greater detail below. The left hand side of the Figure shows the upper portion of the annular skirt 222 in the region above the internal thread (not shown).

A series of wad retaining lugs 229 is arranged around the skirt inner periphery for holding a wad in position adjacent the closure underside.

In the embodiment shown, inner annular bead 227 is symmetrically formed in the shape of an inverted "V". The included angle at the crest of the bead is 900 and the slope of each of its sides forms an angle of 450 with the underside of the closure 220. The crest of inner annular bead 227 has a radius of 0.15 mm and the radii at its root where it meets the closure underside are both 0.20 mm. Outer annular bead 228 is also in the form of an inverted "V", but is not symmetrical. Its radially inner slope forms an angle of 300 with the closure underside, whilst its radially outer slope lies at 450 to the closure underside. The crest of outer annular bead 228 has a radius of 0.15 mm and the radii at its root where it joins the closure underside are 0.20 mm.

Inner annular bead 227 is 0.7 mm in height, whilst outer annular bead 228 is slightly larger at 0.8 mm. This difference in height means that, in use, the wad is urged by the rim of a container against the outer annular bead slightly before it contacts the inner annular bead. This assists resilient distortion of the wad without causing creasing. The respective diameters of the inner annular bead 227 and the outer annular bead 228 are r and R, where r is O to 5 mm less than the bore diameter of the container mouth and R is O to 5 mm greater than the external diameter of the container neck. The annular land region 223 is substantially equal to the thickness of the container rim to which the closure is intended to be applied in use.

Turning now to Figure 3, each of views (a) and (b) show the interaction between a wad 340 and the rim 313 of a container neck 312. Part of closure 320 is illustrated in cross-section, with thread 325 shown on the radially inner surface of annular skirt 322. Wad 340 is retained adjacent the underside of closure 320 by wad retaining lugs 329, one of which is shown in section in each view. When the closure is fully tightened, the wad is pushed out of contact with the wad supports 329 by the container rim 313 and into engagement with the underside of the closure 320.

The clearance between the wad retaining lugs 329 and the closure underside is exaggerated in these views. In practice, the upper surface of the wad retaining lugs 329 would be much nearer to the closure underside, allowing only minimal axial movement of the wad 340.

View (a) of Figure 3 shows an arrangement in which the distance d between the container rim 313 and the start of the thread 315 on the container neck 312 is at the minimum tolerance value. In this situation, the container rim 313 deflects the wad 340 only slightly in the fully-tightened condition.

View (b) of Figure 3 shows an arrangement in which the distance d between the container rim 313 and the start of the thread 315 on the container neck 31 2 is at the maximum tolerance value. In such an arrangement, the container rim 313 deflects the wad 340 much more so that its upper surface just comes into contact with the underside of the closure 320 in the annular land region 323 between the inner and outer raised annular beads 327 and 328. Of course, the majority of containers have neck finishes which fall between these two extremes of tolerance.

Figure 4 is an enlarged cross-sectional view through another embodiment of a closure in accordance with the invention. The arrangement is very similar to that discussed above in relation to Figure 2 and equivalent features in the two embodiments have been given corresponding reference numerals, save that the reference numerals in Figure 4 have been increased by 200. The only difference in this second embodiment lies in the configuration of the outer annular bead 428. Rather than being an inverted "V" shape, outer annular bead 428 is formed with only one sloping surface, on its radially inner side. At the level of its maximum height 428my", the bead profile continues in a plane parallel with the underside of the closure 420 to form a shelf 430. The outer radial limit of shelf 430 is bounded by axial wall 431, the diameter of which is slightly less than the internal diameter of the closure skirt 422. This arrangement is possible because the closure no longer needs to be as flexible as the Figure 2 embodiment at the junction between the closure top 421 and the skirt 422 for ease of removal from the mould. The Figure 2 embodiment, having an undercut region defined by the radially outer slope of the outer annular bead 228, needs to be relatively flexible to facilitate its ejection from the mould.

Although the invention has been particularly described above with reference to illustrative embodiments, it will be understood by persons skilled in the art that variations are possible without departing from the scope of the claims which follow.

Claims (21)

1. A closure of the type adapted for releasable engagement with a container neck by rotation relative thereto wherein said closure and said container have fixed radial orientations relative to each other in a fully closed condition thereof, said closure comprising a cap portion, an annular skirt portion and wad means disposed on the underside of said cap portion, characterised in that said cap portion is provided on its underside with a pair of raised annular beads defining a recess therebetween into which said wad means is resiliently deformable.

2. A closure as claimed in claim 1 wherein the outermost of said pair of raised annular beads has a diameter at least as great as the outside diameter of a container rim to which the closure is secured in use.

3. A closure as claimed in claim 1 or claim 2 wherein the innermost of said pair of raised annular beads has a diameter no greater than the inside diameter of said container rim.

4. A closure as claimed in any preceding claim wherein at least one of the raised annular beads has a substantially V-shaped cross-section, the "V" having an included angle of 900 or more.

5. A closure as claimed in claim 4 wherein the outermost raised annular bead has a non-symmetrical V-shaped cross-section, the radially outer slope forming an angle of 35-550 relative to the underside of the closure and the radially inner slope forming an angle of 20-400 relative to the underside of the closure.

6. A closure as claimed in claim 5 wherein the outermost raised annular bead has a radially outer slope forming an angle of 40-500 relative to the underside of the closure and a radially inner slope forming an angle of 25-350 relative to the underside of the closure.

7. A closure as claimed in claim 6 wherein the outermost raised annular bead has a radially outer slope forming an angle of 43-470 relative to the underside of the closure and a radially inner slope forming an angle of 28-320 relative to the underside of the closure.

8. A closure as claimed in claim 7 wherein the outermost raised annular bead has a radially outer slope forming an angle of 450 relative to the underside of the closure and a radially inner slope forming an angle of 300 relative to the underside of the closure.

9. A closure as claimed in any one of claims 4 to 8 wherein the slopes of the innermost raised annular bead are equal in angle relative to the underside of the closure in the range 35-550.

10. A closure as claimed in claim 9 wherein the slopes of the innermost raised annular bead are in the range 40-500.

11. A closure as claimed in claim 10 wherein the slopes of the innermost raised annular bead are in the range 43-470.

1 2. A closure as claimed in claim 11 wherein the slopes of the innermost raised annular bead are 450.

13. A closure as claimed in any preceding claim wherein the height of the raised annular beads lies in the range 0.6 - 1.0 mm.

14. A closure as claimed in claim 13 wherein the height of the raised annular beads lies in the range 0.7 - 0.8 mm.

15. A closure as claimed in any preceding claim wherein the height of the outermost raised annular bead is greater than the height of the innermost raised annular bead.

16. A closure as claimed in any preceding claim wherein radiused corners are provided at the crests and roots of the annular beads.

17. A closure as claimed in claim 1 6 wherein the radii fall in the range 0.05 to 0.30 mm.

18. A closure as claimed in claim 1 7 wherein the radii fall in the range 0.15 to 0.20 mm.

19. A closure as claimed in any preceding claim wherein the space between adjacent crests of the raised annular beads defines a land region, the radial dimension of which is at least equal to the thickness of said container rim.

20. A closure as claimed in claim 19 wherein the radial dimension of the land region is up to 50% greater than the thickness of said container rim.

21. A closure substantially as described herein with reference to Figures 1 to 3 or with reference to Figures 1 and 4 of the drawings.